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5.2.6.3.5 Target refresh request for a dialog
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When the P-CSCF receives from the UE a target refresh request for a dialog, the P-CSCF shall:
1) verify if the request relates to a dialog in which the originator of the request is involved:
a) if the request does not relates to an existing dialog in which the originator is involved, then the P-CSCF shall answer the request by sending a 403 (Forbidden) response back to the originator. The P-CSCF will not forward the request. No other actions are required; or
b) if the request relates to an existing dialog in which the originator is involved, then the P-CSCF shall continue with the following steps;
1A) remove its own SIP URI from the top of the list of Route header fields;
2) verify that the resulting list of Route header fields matches the list of Record-Route header fields constructed by inverting the order of the stored list of Record-Route header fields and removing its Record-Route header field value from the list. This verification is done on a per URI basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) return a 400 (Bad Request) response; the P-CSCF shall not forward the request, and shall not continue with the execution of steps 3 onwards; or
b) replace the Route header field value in the request with the list of Record-Route header fields constructed by inverting the order of the stored list of Record-Route header fields and removing its Record-Route header value from the list;
3) add its own address to the Via header field. The P-CSCF Via header field entry is built in a format that contains the port number of the P-CSCF where it awaits the responses to come, and either:
a) the P-CSCF FQDN that resolves to the IP address, or
b) the P-CSCF IP address;
4) void
5) for INVITE dialogs (i.e. dialogs initiated by an INVITE request), replace the saved Contact and CSeq header field values received in the request such that the P-CSCF is able to release the session if needed. If the Contact header field in the INVITE request contains a GRUU, the P-CSCF shall save the GRUU received in the Contact header field of the request and associate that GRUU with the UE contact address used during session establishment or with the registration flow and the associated UE contact address used during session establishment such that the P-CSCF is able to release the session if needed;
NOTE: The replaced Contact header field value is valid only if a 1xx or 2xx response will be received for the request. In other cases the old value is still valid.
6) if the P-CSCF inserted the header field parameters into the Feature-Caps header field of the initial request for the dialog then when the target refresh request is forwarded in the same direction, the P-CSCF shall insert the header field parameters with the same parameter values in the Feature-Caps header field; and
7) add a P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter;
before forwarding the request, based on the topmost Route header field, in accordance with the procedures of RFC 3261 [26].
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5.2.6.3.6 Responses to a target refresh request for a dialog
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When the P-CSCF receives a 1xx or 2xx response to the above request, the P-CSCF shall:
1) if a security association or TLS session exists, rewrite the address and port number of its own Record Route entry to the same value as for the response to the initial request for the dialog; and
2) replace the saved Contact header field value received in the response such that the P-CSCF is able to release the session if needed;
before forwarding the response to the UE in accordance with the procedures of RFC 3261 [26].
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5.2.6.3.7 Request for a standalone transaction
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When the P-CSCF receives from the UE the request for a standalone transaction, and a service route value list exists for the served user of the request, the P-CSCF shall:
1) remove its own SIP URI from the top of the list of Route header fields;
2) if the UE is performing the functions of an external attached network using static mode of operation:
i) select an I-CSCF and insert a Route header field with the URI of the I-CSCF as the topmost Route header field; otherwise
NOTE 1: The list of the I-CSCFs can be either obtained as specified in RFC 3263 [27A] or be provisioned in the P-CSCF.
ii) verify that the resulting list of Route header fields matches the list of URIs received in the Service-Route header field (during the last successful registration or reregistration). This verification is done on a per URI basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) return a 400 (Bad Request) response; the P-CSCF shall not forward the request, and shall not continue with the execution of steps 3 onwards; or
b) replace the preloaded Route header field value in the request with the one received during the last registration in the Service-Route header field of the 200 (OK) response;
NOTE 2: The P-CSCF can identify that a request is received from a UE performing the functions of an external attached network using static mode of operation by evaluating the TLS session or by other means.
3) if the 200 (OK) response to the last REGISTER request, which created or refreshed the binding of the contact address from which the request is received, has not contained a Feature-Caps header field, specified in RFC 6809 [190] with a "+g.3gpp.atcf" header field parameter, then:
a) if the P-CSCF is located in the visited network, and local policy requires the application of IBCF capabilities in the visited network towards the home network, select an IBCF in the visited network and add the URI of the selected IBCF to the topmost Route header field;
NOTE 3: It is implementation dependent as to how the P-CSCF obtains the address of the IBCF exit point.
3A) if the 200 (OK) response to the last REGISTER request, which created or refreshed the binding of the contact address from which the request is received, contained a Feature-Caps header field with a "+g.3gpp.atcf" header field parameter, then:
a) add the ATCF URI for originating requests, that the P-CSCF used to forward the last REGISTER request which created or refreshed the binding of the contact address from which the request is received, to the topmost Route header field;
3B) if the request is originated from a UE which the P-CSCF considers as privileged sender (including one which is also a UE performing the functions of an external attached network using static mode of operation), keep the P-Asserted-Identity header field unchanged if one was received, or include the originator of the request in the P-Asserted-Identity header field if no P-Asserted-Identity header field was received. In addition remove any P-Preferred-Identity header field, include the served user of the request in the P-Served-User header field as specified in RFC 5502 [133] and skip step 4) below;
NOTE 4: The P-CSCF determines if the UE is considered as privileged sender using the user-related policies provisioned to the P-CSCF (see subclause 5.2.1).
NOTE 5: The P-CSCF can retrieve the identity of the UE performing the functions of an external attached network from the subjectCommonName (CN) if it is not present in the subjectAltName in the certificates during the TLS session setup in accordance with the procedures of RFC 5280 [213] or by other means.
3D) if the request is originated from a UE performing the functions of an external attached network using static mode of operation and which the P-CSCF considers as is not a privileged sender, include the served user of the request in the P-Served-User header field as specified in RFC 5502 [133] and skip step 4) below;
4) remove any P-Preferred-Identity header field or P-Asserted-Identity header field, if present, and insert P-Asserted-Identity header fields the value identifying the served user of the request and the value of the alternative identity of the originator of the request, if identified (see subclause 5.2.6.3.1), including the display name if previously stored during registration, representing the served user of the request;
4A) if the identity of the served user of the request was taken from P-Preferred-Identity header field by matching a registered wildcarded public user identity, and the identity of the served user is not a distinct identity within the range of the wildcarded public user identity, include the wildcarded public user identity value in the P-Profile-Key header field as defined in RFC 5002 [97];
NOTE 6: The matching of distinct public user identities takes precedence over the matching of wildcarded public user identities.
4B) if a P-Private-Network-Indication header field is included in the request, check whether the information saved during registration or from configuration allows the receipt of private network traffic from this source. If private network traffic is allowed, the P-CSCF shall check whether the received domain name in any included P-Private-Network-Indication header field in the request is the same as the domain name associated with that saved information. If private network traffic is not allowed, or the received domain name does not match, then the P-CSCF shall remove the P-Private-Network-Indication header field;
4C) if the served user of the request is understood from information saved during registration or from configuration to always send and receive private network traffic from this source, insert a P-Private-Network-Indication header field containing the domain name associated with that saved information; and
4D) if the request comes from a UE performing the functions of an external attached network using static mode of operation add the "orig" parameter to the dialog request to indicate that this is an originating request; and
5) add a P-Charging-Vector header field with the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17] and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter. Based on local policy, the P-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier;
before forwarding the request, based on the topmost Route header field, in accordance with the procedures of RFC 3261 [26].
If the request comes from a UE performing the functions of an external attached network using static mode of operation:
- no response is received to the standalone SIP request and its retransmissions by the P-CSCF; or
- a 3xx response or 480 (Temporarily Unavailable) response is received,
the P-CSCF shall repeat the actions of the above bullets with a different I-CSCF.
If the P-CSCF fails to forward the standalone SIP request to any I-CSCF, the P-CSCF shall send back a 504 (Server Time-Out) response to the UE performing the functions of an external attached network, in accordance with the procedures in RFC 3261 [26].
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5.2.6.3.8 Responses to a request for a standalone transaction
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When the P-CSCF receives any response to the above request, the P-CSCF shall:
1) store the values received in the P-Charging-Function-Addresses header field;
before forwarding the response to the UE in accordance with the procedures of RFC 3261 [26].
NOTE: The P-CSCF can find the IMS communication service supported for the standalone transaction, as determined by the originating home network, in the topmost occurance of the "+g.3gpp.icsi-ref" header field parameter of the Feature-Caps header field(s) of 18x or 2xx response. The information can be used for charging purpose.
The P-CSCF shall forward the response to the UE using the mechanisms described in RFC 3261 [26] and RFC 3581 [56A], i.e. the P-CSCF shall send the response to the IP address indicated in the "received" header field parameter and, in case UDP is used, to the port indicated in the "rport" header field parameter (if present) of the Via header field associated with the UE. In case TCP is used, the P-CSCF shall use the TCP connection on which the REGISTER request was received for sending the response back to the UE.
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5.2.6.3.9 Subsequent request other than a target refresh request
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When the P-CSCF receives from the UE a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown), the P-CSCF shall:
1) verify if the request relates to a dialog in which the originator of the request is involved:
a) if the request does not relates to an existing dialog in which the originator is involved, then the P-CSCF shall answer the request by sending a 403 (Forbidden) response back to the originator. The P-CSCF will not forward the request. No other actions are required; or
b) if the request relates to an existing dialog in which the originator is involved, then the P-CSCF shall continue with the following steps;
1A) remove its own SIP URI from the top of the list of Route header fields;
2) verify that the resulting list of Route header fields matches the list of Record-Route header fields constructed by inverting the order of the stored list of Record-Route header fields and removing its Record-Route header field from the list. This verification is done on a per URI basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) return a 400 (Bad Request) response; the P-CSCF shall not forward the request, and shall not continue with the execution of steps 3 onwards; or
b) replace the Route header field value in the request with the list of Record-Route header fields constructed by inverting the order of the stored list of Record-Route header fields and removing its Record-Route header field from the list;
3) add a P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter; and
4) for INVITE dialogs, replace the saved CSeq header field value received in the request such that the P-CSCF is able to release the session if needed;
before forwarding the request (based on the topmost Route header field), in accordance with the procedures of RFC 3261 [26].
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5.2.6.3.10 Responses to a subsequent request other than a target refresh request
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Void
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5.2.6.3.11 Request for an unknown method that does not relate to an existing dialog
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When the P-CSCF receives from the UE the request for an unknown method (that does not relate to an existing dialog), and a service route value list exists for the served user of the request, the P-CSCF shall:
1) if the UE performing the functions of an external attached network using static mode of operation:
i) select an I-CSCF and insert a Route header field with the URI of the I-CSCF as the topmost Route header field; otherwise
NOTE 1: The list of the I-CSCFs can be either obtained as specified in RFC 3263 [27A] or be provisioned in the P-CSCF.
ii) verify that the list of URIs received in the Service-Route header field (during the last successful registration or reregistration) is included, preserving the same order, as a subset of the preloaded Route header fields in the received request. This verification is done on a per URI basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) return a 400 (Bad Request) response; the P-CSCF shall not forward the request, and shall not continue with the execution of steps 2 onwards; or
b) replace the Route header field value in the request with the one received during the last registration in the Service-Route header field of the 200 (OK) response;
NOTE 2: The P-CSCF can identify that a request is received from a UE performing the functions of an external attached network using static mode of operation by evaluating the TLS session or by other means.
2) if the 200 (OK) response to the last REGISTER request, which created or refreshed the binding of the contact address from which the request is received, has not contained a Feature-Caps header field, specified in RFC 6809 [190] with a "+g.3gpp.atcf" header field parameter, then:
a) if the P-CSCF is located in the visited network, and local policy requires the application of IBCF capabilities in the visited network towards the home network, then the P-CSCF shall select an IBCF in the visited network and add the URI of the selected IBCF to the topmost Route header field;
NOTE 3: It is implementation dependent as to how the P-CSCF obtains the address of the IBCF exit point.
2A) if the 200 (OK) response to the last REGISTER request, which created or refreshed the binding of the contact address from which the request is received, contained a Feature-Caps header field with a "+g.3gpp.atcf" header field parameter, then:
a) add the ATCF URI for originating requests, that the P-CSCF used to forward the last REGISTER request which created or refreshed the binding of the contact address from which the request is received, to the topmost Route header field;
2B) if the request is originated from a UE which the P-CSCF considers as privileged sender (including one which is also a UE performing the functions of an external attached network using static mode of operation), keep the P-Asserted-Identity header field unchanged if one was received, or include the originator of the request in the P-Asserted-Identity header field if no P-Asserted-Identity header field was received. In addition remove any P-Preferred-Identity header field, include the served user of the request in the P-Served-User header field as specified in RFC 5502 [133] and skip step 3) below;
NOTE 4: The P-CSCF determines if the UE is considered privileged sender using based on the user-related policies provisioned to the P-CSCF (see subclause 5.2.1).
NOTE 5: The P-CSCF can retrieve the identity of the UE performing the functions of an external attached network from the subjectCommonName (CN) if it is not present in the subjectAltName in the certificates during the TLS session setup in accordance with the procedures of RFC 5280 [213] or by other means.
2C) if the request is originated from a UE performing the functions of an external attached network using static mode of operation and which the P-CSCF considers as is not a privileged sender, include the served user of the request in the P-Served-User header field as specified in RFC 5502 [133] and skip step 3) below;
3) remove any P-Preferred-Identity header field or P-Asserted-Identity header field, if present, and insert a P-Asserted-Identity header fields the value identifying the originator of the request and the value of the alternative identity of the originator of the request, if identified (see subclause 5.2.6.3.1), including the display name if previously stored during registration, representing the served user of the request;
3A) if the identity of the served user of the request was taken from P-Preferred-Identity header field by matching a registered wildcarded public user identity, and the identity of the served user is not a distinct identity within the range of the wildcarded public user identity, include the wildcarded public user identity value in the P-Profile-Key header field as defined in RFC 5002 [97]; and
3B) if the request comes from a UE performing the functions of an external attached network using static mode of operation add the "orig" parameter to the dialog request to indicate that this is an originating request; and
4) add a P-Charging-Vector header field with the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17] and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter. Based on local policy, the P-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier;
NOTE 6: The matching of distinct public user identities takes precedence over the matching of wildcarded public user identities.
before forwarding the request, based on the topmost Route header field, in accordance with the procedures of RFC 3261 [26].
If the request comes from a UE performing the functions of an external attached network using static mode of operation:
- no response is received to the standalone SIP request and its retransmissions by the P-CSCF; or
- a 3xx response or 480 (Temporarily Unavailable) response is received,
the P-CSCF shall repeat the actions of the above bullets with a different I-CSCF.
If the P-CSCF fails to forward the unknown SIP request to any I-CSCF, the P-CSCF shall send back a 504 (Server Time-Out) response to the UE performing the functions of an external attached network using static mode of operation, in accordance with the procedures in RFC 3261 [26].
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5.2.6.3.12 Responses to a request for an unknown method that does not relate to an existing dialog
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NOTE: The P-CSCF can find the IMS communication service supported for the transaction, as determined by the originating home network, in the topmost occurance of the "+g.3gpp.icsi-ref" header field parameter of the Feature-Caps header field(s) of 18x or 2xx response. The information can be used for charging purpose.
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5.2.6.4 Requests terminated by the UE
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5.2.6.4.1 General for all requests
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The P-CSCF shall log all SIP requests destined for the UE that contain a "logme" Session-ID header field parameter based on local policy.
If the serving network supports PCRF based P-CSCF restoration and the Restoration-Info header field is included in the incoming request, and the P-CSCF has no binding for the identity in the Request-URI, the P-CSCF shall:
- initiate the PCRF based P-CSCF restoration procedure as specified in 3GPP TS 23.380 [7D] using the IMSI value contained in the Restoration-Info header field; and
- reject the request with a 404 (Not Found) response.
If the P-CSCF supports PCRF based P-CSCF restoration procedures, the P-CSCF shall remove the Restoration-Info header field, if included in the incoming request.
If the serving network supports HSS based P-CSCF restoration procedures and the P-CSCF has no binding for the identity in the Request-URI, the P-CSCF shall reject the request with a 404 (Not Found) response.
If the user-related policies provisioned to the P-CSCF (see subclause 5.2.1) do not indicate that the served UE is authorized to send early media, the P-CSCF shall not allow media flows in forward and backward direction before the 200 (OK) response to the initial INVITE is received. Based on operator policy the P-CSCF shall either remove the P-Early-Media header field or replace the value of the P-Early-Media header field with "inactive", if received from the terminating UE.
If the user-related policies provisioned to the P-CSCF (see subclause 5.2.1) indicate that the served UE is authorized to send early media, the P-CSCF shall not remove or modify the P-Early-Media header field if received in an UPDATE request.
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5.2.6.4.2 General for all responses
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When the P-CSCF receives, destined for the UE, a response sent on a dialog for which logging of signalling is in progress, the P-CSCF shall check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred then the P-CSCF shall stop treating the dialog as one for which logging of signalling is in progress, else the P-CSCF shall append a "logme" header field parameter to the SIP Session-ID header field if the parameter is missing and determine, by checking its trace configuration, whether to log the request.
If the user-related policies provisioned to the P-CSCF (see subclause 5.2.1) do not indicate that the served UE is authorized to send early media, the P-CSCF shall not allow media flows in forward and backward direction before the 200 (OK) response to the initial INVITE is received. Based on operator policy the P-CSCF shall either remove the P-Early-Media header field or replace the value of the P-Early-Media header field with "inactive", if received from the terminating UE.
If the user-related policies provisioned to the P-CSCF (see subclause 5.2.1) indicate that the served UE is authorized to send early media, the P-CSCF shall not remove or modify the P-Early-Media header field if received in a 18x provisional response.
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5.2.6.4.3 Initial request for a dialog
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When the P-CSCF receives, destined for the UE, an initial request for a dialog, prior to forwarding the request, the P-CSCF shall:
1) if an indication has been received from the PCRF that the signalling bearer to the UE is lost, and has not recovered, reject the request by sending 500 (Server Internal Error) response;
NOTE 1: The signalling bearer can be considered as recovered by the P-CSCF when the registration timer expires in P-CSCF and the user is de-registered from the IM CN subsystem, a new REGISTER request from the UE is received providing an indication to the P-CSCF that the signalling bearer to that user has become available or a P-CSCF implementation dependent function which discovers that the signalling bearer is available to the UE.
NOTE 2: The Retry-After header field value is set based on operator policy.
2) convert the list of Record-Route header field values into a list of Route header field values and save this list of Route header fields;
3) if the request is an INVITE request, save a copy of the Contact, CSeq and Record-Route header field values received in the request such that the P-CSCF is able to release the session if needed;
4) if a security association or TLS session exists, when adding its own SIP URI to the top of the list of Record-Route header fields and save the list, build the P-CSCF SIP URI in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
5) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is used, when adding its own SIP URI to the top of the list of Record-Route header fields and saving the list, build the P-CSCF URI in a format that contains an unprotected server port number where the P-CSCF expects subsequent requests from the UE;
6) if a security association or TLS session exists, when adding its own address to the top of the received list of Via header fields and save the list, build the P-CSCF Via header field entry in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
NOTE 3: The P-CSCF associates two ports, a protected client port and a protected server port, with each pair of security associations or TLS session. For details of the usage of the two ports see 3GPP TS 33.203 [19].
7) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled athentication is used, when adding its own address to the top of the received list of Via header fields and saving the list, build the P-CSCF Via header field entry in a format that contains an unprotected server port number where the P-CSCF expects responses to the current request from the UE;
7A) if the recipient of the request is understood from information saved during registration or from configuration to always send and receive private network traffic from this source, remove the P-Private-Network-Indication header field containing the domain name associated with that saved information;
8) store the values received in the P-Charging-Function-Addresses header field;
9) store the "icid-value" header field parameter and if present, the "orig-ioi" header field parameter received in the P-Charging-Vector header field;
10) if the request contains an "fe-identifier" header field parameter, based on local policy, store the content of the "fe-identifier" header field parameter of the P-Charging-Vector header field; and
11) save a copy of the P-Called-Party-ID header field;
before forwarding the request to the UE either in accordance with the procedures of RFC 3261 [26] or as specified in RFC 5626 [92].
If no security association exists between the P-CSCF and the UE performing the functions of an external attached network operating in static mode, the P-CSCF shall initiate a TLS session towards the UE performing the functions of an external attached network operating in static mode before sending the initial request in accordance with 3GPP TS 33.310 [19D].
NOTE 4: The P-CSCF can identify that a call is directed to a UE performing the functions of an external attached network operating in static mode by evaluating the Route header field, the Request URI or other means.
Once the TLS session is set up (using the certificates) the P-CSCF shall send the initial request for dialog over the secure connection to the UE performing the functions of an external attached network operating in static mode.
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5.2.6.4.4 Responses to an initial request for a dialog
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When the P-CSCF receives any 1xx or 2xx response to the above request, the P-CSCF shall:
0A) if the response is originated from a UE which the P-CSCF considers as privileged sender, remove any P-Preferred-Identity header field, and skip step 1) below;
NOTE: The P-CSCF determines if the UE is considered privileged sender using based on the user-related policies provisioned to the P-CSCF (see subclause 5.2.1).
1) remove any P-Preferred-Identity header field or P-Asserted-Identity header field, if present, and insert a P-Asserted-Identity header field with the saved public user identity from the P-Called-Party-ID header field that was received in the request, plus the display name if previously stored during registration, representing the originator of the response;
2) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request;
3) verify that the list of URIs received in the Record-Route header field of the request corresponding to the same dialog is included, preserving the same order, as a subset of the Record-Route header field list of this response. This verification is done on a per URI basis, not as a whole string.
If the verification fails, then the P-CSCF shall either:
a) discard the response; or
b) replace the Record-Route header field values with those received in the request, and if a security association or TLS session exists, add its own Record-Route entry with its own SIP URI with the port number where it awaits subsequent requests from the calling party. The P-CSCF shall include in the Record-Route header field either:
- the P-CSCF FQDN that resolves to its IP address; or
- the P-CSCF IP address.
The P-CSCF shall remove the "comp" SIP URI parameter from the Record-Route header field.
If the verification is successful, the P-CSCF shall rewrite its own Record-Route entry to its SIP URI in a format that contains the port number where it awaits subsequent requests from the calling party. The P-CSCF shall include in the Record-Route header field either:
a) the P-CSCF FQDN that resolves to its IP address; or
b) the P-CSCF IP address.
The P-CSCF shall remove the "comp" SIP URI parameter from the Record-Route header field;
When adding its SIP URI to the Record-Route header field, the P-CSCF shall also copy the flow token and the "ob" SIP URI parameter from the Route header field of the initial dialog-forming request destined for the UE to its SIP URI, if the Route header field contained these values;
4) store the dialog ID and associate it with the private user identity and public user identity involved in the session;
5) if the response corresponds to an INVITE request, save the Contact, To, From and Record-Route header field value received in the response such that the P-CSCF is able to release the session if needed. If the Contact header field in the response to the INVITE request contains a GRUU, the P-CSCF shall save the GRUU received in the Contact header field of the response and associate that GRUU with the contact address which was used to send the INVITE request or with the registration flow and the associated UE contact address which was used to send on which the INVITE request such that the P-CSCF is able to release the session if needed; and
6) include in the P-Charging-Vector header field:
- an "icid-value" header field parameter set to the value received in the request;
- the "orig-ioi" header field parameter, if received in the request; and
- a type 1 "term-ioi" header field parameter that identifies the sending network;
- if the P-CSCF has stored an "fe-identifier" header field parameter of the P-Charging-Vector header field, based on local policy, the stored "fe-identifier" header field parameter and include its own address or identifier in the "fe-addr" element of the "fe-identifier" header field parameter of the P-Charging-Vector header field.
before forwarding the response in accordance with the procedures of RFC 3261 [26].
When the P-CSCF receives any other response to the above request, the P-CSCF shall:
1) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If these lists do not match, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request; and
2) include in the P-Charging-Vector header field:
a) an "icid-value" header field parameter set to the value received in the request;
b) the "orig-ioi" header field parameter, if received in the request; and
c) a type 1 "term-ioi" header field parameter that identifies the sending network;
before forwarding the response in accordance with the procedures of RFC 3261 [26].
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5.2.6.4.5 Target refresh request for a dialog
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When the P-CSCF receives, destined for the UE, a target refresh request for a dialog, prior to forwarding the request, the P-CSCF shall:
1) if a security association or TLS session exists, add its own address to the top of the received list of Via header fields and save the list. The P-CSCF Via header field entry is built in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
NOTE 1: The P-CSCF associates two ports, a protected client port and a protected server port, with each pair of security associations or TLS session. For details of the usage of the two ports see 3GPP TS 33.203 [19].
2) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is used, when adding its own address to the top of the received list of Via header fields and saving the list, build the P-CSCF Via header field entry in a format that contains an unprotected server port number where the P-CSCF expects responses to the current request from the UE;
3) if a security association or TLS session exists, when adding its own SIP URI to the top of the list of Record-Route header fields and save the list, build the P-CSCF SIP URI in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
4) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is used, when adding its own SIP URI to the top of the list of Record-Route header fields and saving the list, build the P-CSCF URI in a format that contains an unprotected server port number where the P-CSCF expects subsequent requests from the UE;
5) for INVITE dialogs, replace the saved Contact and CSeq header field values received in the request such that the P-CSCF is able to release the session if needed;
6) if the request is destined to a UE performing the functions of an external attached network operating in static mode, send the request using the already established TLS session as described in subclause 5.2.6.4.3; and
NOTE 2: The replaced Contact header field value is valid only if a 1xx or 2xx response will be received for the request. In other cases the old value is still valid.
7) store the "orig-ioi" header field parameter received in the P-Charging-Vector header field if present;
before forwarding the request to the UE in accordance with the procedures of either RFC 3261 [26] or RFC 5626 [92].
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5.2.6.4.6 Responses to a target refresh request for a dialog
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When the P-CSCF receives a 1xx or 2xx response to the above request, the P-CSCF shall:
1) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request;
2) if a security association or TLS session exists, rewrite its own Record-Route entry to the same value as for the response to the initial request for the dialog and remove the "comp" SIP URI parameter;
3) replace the saved Contact header field value received in the response such that the P-CSCF is able to release the session if needed. If the Contact header field in the response to the target refresh request for a dialog contains a GRUU, the P-CSCF shall save the GRUU received in the Contact header field of the response and associate that GRUU with the contact address which was used to send the target refresh request or with the registration flow and the associated UE contact address which was used to send the target refresh request such that the P-CSCF is able to release the session if needed;
4) if the P-CSCF inserted the header field parameters into the Feature-Caps header field of the initial request for the dialog then when the response is forwarded in the same direction, the P-CSCF shall insert the header field parameters with the same parameter values in the Feature-Caps header field; and
5) include in the P-Charging-Vector header field:
- an "icid-value" header field parameter set to the value populated in the initial request for the dialog;
- the "orig-ioi" header field parameter, if received in the request; and
- a type 1 "term-ioi" header field parameter that identifies the sending network;
before forwarding the response in accordance with the procedures of RFC 3261 [26].
When the P-CSCF receives any other response to the above request, the P-CSCF shall:
1) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If the verification fails, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request; and
2) if a security association or TLS session exists, rewrite the IP address and the port number of its own Record-Route entry to the IP address and the port number where it awaits subsequent requests from the calling party and remove the "comp" SIP URI parameter;
3) include in the P-Charging-Vector header field:
a) an "icid-value" header field parameter set to the value populated in the initial request for the dialog;
b) the "orig-ioi" header field parameter, if received in the request; and
c) a type 1 "term-ioi" header field parameter that identifies the sending network;
before forwarding the response in accordance with the procedures of RFC 3261 [26].
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5.2.6.4.7 Request for a standalone transaction
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When the P-CSCF receives, destined for the UE, a request for a standalone transaction, or a request for an unknown method (that does not relate to an existing dialog), prior to forwarding the request, the P-CSCF shall:
1) if an indication has been received from the PCRF that the signalling bearer to the UE is lost, and has not recovered, reject the request by sending 500 (Server Internal Error) response;
NOTE 1: The signalling bearer can be considered as recovered by the P-CSCF when the registration timer expires in P-CSCF and the user is de-registered from the IM CN subsystem, a new REGISTER request from the UE is received providing an indication to the P-CSCF that the signalling bearer to that user has become available or a P-CSCF implementation dependent function which discovers that the signalling bearer is available to the UE.
NOTE 2: The Retry-After header field value is set based on operator policy.
2) if a security association or TLS session exists, add its own address to the top of the received list of Via header fields and save the list. The P-CSCF Via header field entry is built in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
NOTE 3: The P-CSCF associates two ports, a protected client port and a protected server port, with each pair of security associations or TLS session. For details of the usage of the two ports see 3GPP TS 33.203 [19].
3) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is used, when adding its own address to the top of the received list of Via header fields and saving the list, build the P-CSCF Via header field entry in a format that contains an unprotected server port number where the P-CSCF expects responses to the current request from the UE;
3A) if the recipient of the request is understood from information saved during registration or from configuration to always send and receive private network traffic from this source, remove the P-Private-Network-Indication header field containing the domain name associated with that saved information;
4) store the values received in the P-Charging-Function-Addresses header field;
5) store the "icid-value" header field parameter and if present, the "orig-ioi" header field parameter received in the P-Charging-Vector header field;
6) if the request contains an "fe-identifier" header field parameter, based on local policy, store the content of the "fe-identifier" header field parameter of the P-Charging-Vector header field; and
7) save a copy of the P-Called-Party-ID header field;
before forwarding the request to the UE either in accordance with the procedures of RFC 3261 [26] or as specified in RFC 5626 [92].
If no security association exists between the P-CSCF and the UE performing the functions of an external attached network operating in static mode, the P-CSCF shall initiate a TLS session towards the UE performing the functions of an external attached network operating in static mode before sending the standalone SIP request in accordance with 3GPP TS 33.310 [19D].
NOTE 4: The P-CSCF can identify that a call is directed to a UE performing the functions of an external attached network operating in static mode by evaluating the Route header field, the Request URI or other means.
Once the TLS session is set up (using the certificates) the P-CSCF shall send the standalone SIP request over the secure connection to the UE performing the functions of an external attached network operating in static mode.
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5.2.6.4.8 Responses to a request for a standalone transaction
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When the P-CSCF receives any response to the above request, the P-CSCF shall:
1) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If these lists do not match, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request;
1A) if the response is originated from a UE which the P-CSCF considers as privileged sender, remove any P-Preferred-Identity header field, and skip step 2) below;
NOTE: The P-CSCF determines if the UE is considered privileged sender using based on the user-related policies provisioned to the P-CSCF (see subclause 5.2.1).
2) remove any P-Preferred-Identity header field or P-Asserted-Identity header field, if present, and insert an P-Asserted-Identity header field with the saved public user identity from the P-Called-Party-ID header field of the request, plus the display name if previously stored during registration, representing the originator of the response; and
3) include in the P-Charging-Vector header field:
- an "icid-value" header field parameter set to the value received in the request;
- the "orig-ioi" header field parameter, if received in the request;
- a type 1 "term-ioi" header field parameter that identifies the sending network; and
- if the P-CSCF has stored an "fe-identifier" header field parameter of the P-Charging-Vector header field, based on local policy, the stored "fe-identifier" header field parameter and include its own address or identifier in the "fe-addr" element of the "fe-identifier" header field parameter of the P-Charging-Vector header field.
before forwarding the response in accordance with the procedures of RFC 3261 [26].
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5.2.6.4.9 Subsequent request other than a target refresh request
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When the P-CSCF receives, destined for the UE, a subsequent request for a dialog that is not a target refresh request (including requests relating to an existing dialog where the method is unknown), prior to forwarding the request, the P-CSCF shall:
1) if a security association or TLS session exists, add its own address to the top of the received list of Via header fields and save the list The P-CSCF Via header field entry is built in a format that contains the protected server port number of the security association or TLS session established from the UE to the P-CSCF and either:
a) the P-CSCF FQDN that resolves to the IP address of the security association or TLS session established from the UE to the P-CSCF; or
b) the P-CSCF IP address of the security association or TLS session established from the UE to the P-CSCF;
NOTE: The P-CSCF associates two ports, a protected client port and a protected server port, with each pair of security associations or TLS session. For details of the usage of the two ports see 3GPP TS 33.203 [19].
2) if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is used, when adding its own address to the top of the received list of Via header fields and saving the list, build the P-CSCF Via header field entry in a format that contains an unprotected server port number where the P-CSCF expects responses to the current request from the UE;
3) void;
4) for INVITE dialogs, replace the saved CSeq header field value received in the request such that the P-CSCF is able to release the session if needed;
5) if the request is destined to a UE performing the functions of an external attached network operating in static mode, send the request using the already established TLS session as described in subclause 5.2.6.4.3; and
6) store the "orig-ioi" header field parameter received in the P-Charging-Vector header field if present;
before forwarding the request to the UE either in accordance with the procedures of RFC 3261 [26] or as specified in RFC 5626 [92].
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5.2.6.4.10 Responses to a subsequent request other than a target refresh request
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When the P-CSCF receives any response to the above request, the P-CSCF shall:
1) verify that the list of Via header fields matches the saved list of Via header fields received in the request corresponding to the same dialog, including the P-CSCF Via header field value. This verification is done on a per Via header field value basis, not as a whole string. If these lists do not match, then the P-CSCF shall either:
a) discard the response; or
b) replace the Via header field values with those received in the request; and
2) include in the P-Charging-Vector header field:
a) an "icid-value" header field parameter set to the value received in the initial request for the dialog;
b) the "orig-ioi" header field parameter, if received in the request; and
c) a type 1 "term-ioi" header field parameter that identifies the sending network;
before forwarding the response in accordance with the procedures of RFC 3261 [26].
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5.2.6.4.11 Request for an unknown method that does not relate to an existing dialog
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Void.
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5.2.6.4.12 Responses to a request for an unknown method that does not relate to an existing dialog
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Void.
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5.2.7 Initial INVITE
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5.2.7.1 Introduction
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In addition to following the procedures for initial requests defined in subclause 5.2.6, initial INVITE requests also follow the procedures of this subclause.
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5.2.7.2 UE-originating case
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When the P-CSCF receives from the UE an INVITE request for which resource authorization procedure is required, if it receives from the IP-CAN (e.g. via PCRF) an indication that the requested resources for the multimedia session being established cannot be granted and this indication does not provide an acceptable bandwidth information:
- if the P-CSCF is unable to handle further requests from the UE (i.e. P-CSCF is overloaded by SIP requests), the P-CSCF shall return a 503 (Service Unavailable) response to the received INVITE request. Depending on local operator policy, the 503 (Service Unavailable) response may include a Retry-After header field; and
- if the P-CSCF is able to handle further requests from the UE (i.e. P-CSCF is not overloaded by SIP requests), the P-CSCF shall return a 500 (Server Internal Error) response to the received INVITE request. Depending on local operator policy, the 500 (Server Internal Error) response may include a Retry-After header field.
When the P-CSCF receives from the UE an INVITE request, the P-CSCF may require the periodic refreshment of the session to avoid hung states in the P-CSCF. If the P-CSCF requires the session to be refreshed, then the P-CSCF shall apply the procedures described in RFC 4028 [58] clause 8.
NOTE 1: Requesting the session to be refreshed requires support by at least one of the UEs. This functionality cannot automatically be granted, i.e. at least one of the involved UEs needs to support it.
The P-CSCF shall respond to all INVITE requests with a 100 (Trying) provisional response.
If received from the IP-CAN, the P-CSCF shall also include the access-network-charging-info parameter (e.g. received via the PCRF, over the Rx or Gx interfaces) in the P-Charging-Vector header field in the first request originated by the UE that traverses the P-CSCF, as soon as the charging information is available in the P-CSCF, e.g., after the local resource reservation is complete. Typically, this first request is an UPDATE request if the remote UA supports the "integration of resource management in SIP" extension or a re-INVITE request if the remote UA does not support the "integration of resource management in SIP" extension. See subclause 5.2.7.4 for further information on the access network charging information.
If:
- the UE is roaming;
- the P-CSCF is not in the home network; and
- an agreement exists with the home network operator (as identified by the bottom most URI in the list of URIs received in the Service-Route header field during the last successful registration or reregistration) to support Roaming Architecture for Voice over IMS with Local Breakout;
the P-CSCF may:
- insert into the request a Feature-Caps header field with the "+g.3gpp.trf" header field parameter as specified in RFC 6809 [190]. Based on local policy the P-CSCF shall insert the "+g.3gpp.trf" header field parameter with the parameter value set to the URI of the desired TRF; and
- if a TRF URI is included in the "+g.3gpp.trf" header field parameter and the P-CSCF supports indicating the traffic leg associated with a URI as specified in RFC 7549 [225] and if required by local policy, append an "iotl" SIP URI parameter with a value set to "homeA-visitedA" to the TRF URI.
If:
- the UE is roaming;
- the P-CSCF is not in the home network; and
- the visited network supports MRB functionality for the allocation of MRF resources and if an agreement exists with the home operator (identified by the bottom most URI in the list of URIs received in the Service-Route header field during the last successful registration or reregistration) to provide access to MRF resources from the visited network;
the P-CSCF may insert into the request a Feature-Caps header field with the "+g.3gpp.mrb" header field parameter, as specified in RFC 6809 [190]. Based on local policy the P-CSCF shall insert the "+g.3gpp.mrb" header field parameter with the parameter value set to the URI of the desired MRB.
The P-CSCF (IMS-ALG) shall transparently forward a received Contact header field towards the UE when the Contact header field contains a GRUU or a media feature tag indicating a capability for which the URI can be used.
NOTE 2: One example of such a media feature tag is the isfocus media feature tag where the URI in the Contact header field is used by conference services to transport the temporary conference identity that can be used when rejoining an ongoing conference.
NOTE 3: Various mechanisms can be applied to recognize the need for priority treatment (e.g., based on the dialled digits). The exact mechanisms are left to national regulation and network configuration.
Based on the alternative mechanism to recognize the need for priority treatment, the P-CSCF shall insert the temporarily authorised Resource-Priority header field with an appropriate namespace and priority value into the INVITE request.
If priority is supported and the MPS for Messaging indication in the user's subscription is set (enabled), and the SDP indicates a messaging session (the SDP contains m=message with MSRP protocol), the P-CSCF shall insert a Resource-Priority header field with the namespace and priority value from the reg-Event <rph> element in the <actions> element in the <registration> element into the INVITE request.
When the P-CSCF responds to the UE with a 500 (Server Internal Error) response after receiving an indication that radio/bearer resources are not available, then based on operator policy, the P-CSCF may include a Reason header field with a protocol value set to "FAILURE_CAUSE" and a "cause" header field parameter set to "1" as specified in subclause 7.2A.18.12.2 and a Response-Source header field with a "fe" header field parameter set to "<urn:3gpp:fe:p-cscf.orig>".
If the P-CSCF supports the in-call access update procedure and if a received response to the INVITE request contains a Feature-Caps header field with a g.3gpp.in-call-access-update feature capability indicator, the P-CSCF shall store the value of this feature capability indicator.
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5.2.7.3 UE-terminating case
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When the P-CSCF receives an INVITE request destined for the UE the P-CSCF may require the periodic refreshment of the session to avoid hung states in the P-CSCF. If the P-CSCF requires the session to be refreshed, then the P-CSCF shall apply the procedures described in RFC 4028 [58] clause 8.
NOTE 1: Requesting the session to be refreshed requires support by at least one of the UEs. This functionality cannot automatically be granted, i.e. at least one of the involved UEs needs to support it in order to make it work.
When the P-CSCF receives an initial INVITE request destined for the UE, it will have a list of Record-Route header fields. Prior to forwarding the initial INVITE request, the P-CSCF shall respond to all INVITE requests with a 100 (Trying) provisional response.
If received from the IP-CAN, the P-CSCF shall also include the access-network-charging-info parameter (e.g. received via the PCRF, over the Rx or Gx interfaces) in the P-Charging-Vector header field in the first request or reliable response originated by the UE that traverses the P-CSCF, as soon as the charging information is available in the P-CSCF e.g., after the local resource reservation is complete. When the P-CSCF sends the response including P-Charging-Vector header field, the P-CSCF shall set the "icid-value" header field parameter to the previously received value of "icid-value" header field parameter in the request. See subclause 5.2.7.4 for further information on the access network charging information.
The P-CSCF (IMS-ALG) shall transparently forward a received Contact header field towards the UE when the Contact header field contains a GRUU or a media feature tag indicating a capability for which the URI can be used.
NOTE 2: One example of such a media feature tag is the isfocus media feature tag where the URI in the Contact header field is used by conference services to transport the temporary conference identity that can be used when rejoining an ongoing conference.
If the P-CSCF supports the in-call access update procedure and if the received INVITE request contains a Feature-Caps header field with a g.3gpp.in-call-access-update feature capability indicator, the P-CSCF shall store the value of this feature capability indicator.
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5.2.7.4 Access network charging information
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The P-CSCF shall include the "access-network-charging-info" header field parameter within the P-Charging-Vector header field as described in subclause 7.2A.5.
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5.2.8 Call release
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5.2.8.1 P-CSCF-initiated call release
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5.2.8.1.1 Cancellation of a session currently being established
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Upon receipt of an indication that the signalling bearer is no longer available (e.g. an Rx interface message from PCRF), the P-CSCF shall cancel that dialog by applying the following steps:
1) if the P-CSCF serves the calling user of the session, send out a CANCEL request to cancel the INVITE request towards the terminating UE that includes:
a) if a cause or error code was received from the entity controlling radio/bearer resources, a Reason header field, with an appropriate protocol value in the protocol field, and the "cause" header field parameter set to the received cause or error code; and
b) if:
- no cause or error code was received from the entity controlling radio/bearer resources; or
- if the abort cause PS_TO_CS_HANDOVER was received over Rx from the entity controlling radio/bearer resources;
a Reason header field containing a 503 (Service Unavailable) status code according to the procedures described in RFC 3261 [26] and RFC 3326 [34A]; and
2) if the P-CSCF serves the called user of the session, send out a 500 (Server Internal Error) response to the received INVITE request. If a cause or error code was received from the entity controlling radio/bearer resources the P-CSCF shall include a Reason header field, with a protocol value set to "FAILURE_CAUSE" in the "protocol" header field parameter as described in subclause 7.2A.18.12.2, and the "cause" header field parameter set to "2" as described in subclause 7.2A.18.12.2.
Upon receipt of an indication that QoS or bearer resources are no longer available for a media negotiated in a multimedia session currently being established (e.g. an Rx interface message from PCRF) and if no SIP message removing the media for which resources are no longer available is received within an operator defined time after the reception of the indication, the P-CSCF shall:
1) cancel that dialog by responding to the original INVITE request with a 500 (Server Internal Error) response. If a cause or error code was received from the entity controlling radio/bearer resources the P-CSCF shall include a Reason header field, with a protocol value set to "FAILURE_CAUSE" in the "protocol" header field parameter as described in subclause 7.2A.18.12.2, and the "cause" header field parameter set to "1" as described in subclause 7.2A.18.12.2; and
2) by sending out a CANCEL request to the INVITE request towards the terminating UE that includes a Reason header field containing a 503 (Service Unavailable) status code according to the procedures described in RFC 3261 [26] and RFC 3326 [34A].
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5.2.8.1.2 Release of an existing session
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Upon:
1) receipt of an indication that the radio/bearer resources are no longer available for a media negotiated in a session (e.g. an Rx interface message from PCRF) and if no SIP message removing the media for which resources are no longer available is received within an operator defined time after the reception of the indication;
2) receipt of an indication that the signalling bearer is no longer available (e.g. an Rx interface message from PCRF); or
3) detecting that the SDP offer conveyed in a SIP response contained parameters which are not allowed according to the local policy (as specified in the subclause 6.2);
the P-CSCF shall release the respective dialog by applying the following steps:
1) if the P-CSCF serves the calling user of the session, then the P-CSCF shall generate a BYE request destined for the called user based on the information saved for the related dialog, including:
- a Request-URI, set to the stored Contact header field provided by the called user;
- a To header field, set to the To header field value as received in the 200 (OK) response for the initial INVITE request;
- a From header field, set to the From header field value as received in the initial INVITE request;
- a Call-ID header field, set to the Call-Id header field value as received in the initial INVITE request;
- a CSeq header field, set to the current CSeq value stored for the direction from the calling to the called user, incremented by one;
- a Route header field, set to the routeing information towards the called user as stored for the dialog;
- a Reason header field or Reason header fields that contains:
a) if a cause or error code was received from the entity controlling radio/bearer resources, an appropriate protocol value in the protocol field, and the "cause" header field parameter set to the received cause or error code;
b) if no cause or error code was received from the entity controlling radio/bearer resources, and if radio/bearer interface resources are no longer available, a 503 (Service Unavailable) response code;
c) if no cause or error code was received from the entity controlling radio/bearer resources, and if the signalling bearer is no longer available, a 503 (Service Unavailable) response code;
d) if no cause or error code was received from the entity controlling radio/bearer resources, and if a SDP offer conveyed in a SIP response contained parameters which are not allowed according to the local policy, a 488 (Not Acceptable Here) response code; and
e) if the abort cause PS_TO_CS_HANDOVER was received over Rx from the entity controlling radio/bearer resources, a 503 (Service Unavailable) response code;
- further header fields, based on local policy; and
- send the generated BYE requests towards the called user;
2) if the P-CSCF serves the calling user of the session and upon detecting that the SDP offer conveyed in a SIP response contained parameters which are not allowed according to the local policy (as specified in the subclause 6.2), then the P-CSCF shall generate an additional BYE request destined for the calling user based on the information saved for the related dialog, including:
- a Request-URI, set to a contact address obtained from the stored Contact header field if provided by the calling user. If the stored Contact header field contains either a public or a temporary GRUU, the P-CSCF shall set the Request-URI either to:
a) the stored UE IP address and the UE port associated with the respective GRUU, if the stored Contact header field contains either a public or a temporary GRUU and the bidirectional flow as defined in RFC 5626 [92] is not used for this session; or
b) the UE IP address and UE port associated with the bidirectional flow that the P-CSCF uses to send the in-dialog requests toward the UE as defined in RFC 5626 [92];
- a To header field, set to the From header field value as received in the initial INVITE request;
- a From header field, set to the To header field value as received in the 200 (OK) response for the initial INVITE request;
- a Call-ID header field, set to the Call-Id header field value as received in the initial INVITE request;
- a CSeq header field, set to the current CSeq value stored for the direction from the called to the calling user, incremented by one;
- a Route header field, set to the routeing information towards the calling user as stored for the dialog;
- a Reason header field that contains a 488 (Not Acceptable Here) response code;
- further header fields, based on local policy; and
- send the BYE request either:
a) to the contact address indicated in the Request-URI, if the dialog being released did not use the bidirectional flow to send the requests to the UE as defined in RFC 5626 [92]; or
b) over the same flow that the P-CSCF uses to send the in-dialog requests toward the UE as defined in RFC 5626 [92];
3) If the P-CSCF serves the called user of the session, then the P-CSCF shall generate a BYE request destined for the calling user based on the information saved for the related dialog, including:
- a Request-URI, set to the stored Contact header field provided by the calling user;
- a To header field, set to the From header field value as received in the initial INVITE request;
- a From header field, set to the To header field value as received in the 200 (OK) response for the initial INVITE request;
- a Call-ID header field, set to the Call-Id header field value as received in the initial INVITE request;
- a CSeq header field, set to the current CSeq value stored for the direction from the called to the calling user, incremented by one;
- a Route header field, set to the routeing information towards the calling user as stored for the dialog;
- a Reason header field or Reason header fields that contains:
a) if a cause or error code was received from the entity controlling radio/bearer resources, an appropriate protocol value in the protocol field, and the "cause" header field parameter set to the received cause or error code;
b) if no cause or error code was received from the entity controlling radio/bearer resources, and if radio/bearer interface resources are no longer available, a 503 (Service Unavailable) response code;
c) if no cause or error code was received from the entity controlling radio/bearer resources, and if a SDP offer conveyed in a SIP response contained parameters which are not allowed according to the local policy, a 488 (Not Acceptable Here) response code; and
d) if the abort cause PS_TO_CS_HANDOVER was received over Rx from the entity controlling radio/bearer resources, a 503 (Service Unavailable) response code;
- further header fields, based on local policy; and
- send the generated BYE requests towards the calling user;
4) if the P-CSCF serves the called user of the session and upon detecting that the SDP offer conveyed in a SIP response contained parameters which are not allowed according to the local policy (as specified in the subclause 6.2), then the P-CSCF shall generate an additional BYE request destined for the called user based on the information saved for the related dialog, including:
- a Request-URI, set to a contact address obtained from the stored Contact header field if provided by the called user. If the stored Contact header field contains either a public or a temporary GRUU, the P-CSCF shall set the Request-URI either to:
a) the stored UE IP address and the UE port associated with the respective GRUU, if the stored Contact header field contains either a public or a temporary GRUU and the bidirectional flow as defined in RFC 5626 [92] is not used for this session; or
b) the UE IP address and the UE port associated with the bidirectional flow that the P-CSCF uses to send the in-dialog requests toward the UE as defined in RFC 5626 [92];
- a To header field, set to the To header field value as received in the 200 (OK) response for the initial INVITE request;
- a From header field, set to the From header field value as received in the initial INVITE request;
- a Call-ID header field, set to the Call-Id header field value as received in the initial INVITE request;
- a CSeq header field, set to the current CSeq value stored for the direction from the calling to the called user, incremented by one;
- a Route header field, set to the routeing information towards the called user as stored for the dialog;
- a Reason header field that contains a 488 (Not Acceptable Here) response code;
- further header fields, based on local policy; and
- send the BYE request either:
a) to the contact address indicated in the Request-URI, if the dialog being released did not use t the bidirectional flow to send the requests to the UE as defined in RFC 5626 [92]; or
b) over the same flow that the P-CSCF uses to send the in-dialog requests toward the UE as defined in RFC 5626 [92].
Upon receipt of the 2xx responses for the BYE requests, the P-CSCF shall delete all information related to the dialog and the related multimedia session.
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5.2.8.1.3 Abnormal cases
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Upon receipt of a request on a dialog for which the P-CSCF initiated session release, the P-CSCF shall terminate this received request and answer it with a 481 (Call/Transaction Does Not Exist) response.
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5.2.8.1.4 Release of the existing dialogs due to registration expiration and deletion of the security association, IP association or TLS session
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If there are still active dialogs associated with the user after the security associations, IP association or TLS sessions were deleted, the P-CSCF shall discard all information pertaining to these dialogs without performing any further SIP transactions with the peer entities of the P-CSCF.
NOTE: If the interface between the P-CSCF and the IP-CAN is supported, the P-CSCF will also indicate (e.g. via the Rx or Gx interface) that the session has been terminated.
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5.2.8.2 Call release initiated by any other entity
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When the P-CSCF receives a 2xx response for a BYE request matching an existing dialog, then the P-CSCF shall delete all the stored information related to the dialog.
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5.2.8.3 Session expiration
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If the P-CSCF requested the session to be refreshed periodically, and the P-CSCF got the indication that the session will be refreshed, when the session timer expires, the P-CSCF shall delete all the stored information related to the dialog.
NOTE: If the interface between the P-CSCF and the IP-CAN is supported, the P-CSCF will also indicate to the IP-CAN (e.g. via the Rx or Gx interface), that the session has terminated.
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5.2.9 Subsequent requests
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5.2.9.1 UE-originating case
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The P-CSCF shall respond to all reINVITE requests with a 100 (Trying) provisional response.
For a reINVITE request or UPDATE request from the UE within the same dialog, the P-CSCF shall include the updated access-network-charging-info parameter from P-Charging-Vector header field when sending the SIP request to the S-CSCF. See subclause 5.2.7.4 for further information on the access network charging information.
For an ACK request from the UE sent on a dialog where a 200 (OK) has been received, the P-CSCF shall include the access-network-charging-info parameter from the P-Charging-Vector header field when updated access-network-charging-info is available when sending the ACK request to the S-CSCF. See subclause 5.2.7.4 for further information on the access network charging information.
If priority is supported, the P-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field value.
NOTE: A UE-initiated priority upgrade request directly from the UE to the P-CSCF is not supported using a special dial string as described in clause 4.11.
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5.2.9.2 UE-terminating case
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The P-CSCF shall respond to all reINVITE requests with a 100 (Trying) provisional response.
For a reINVITE request or UPDATE request destined towards the UE within the same dialog, when the P-CSCF sends 200 (OK) response (to the INVITE request or UPDATE request) towards the S-CSCF, the P-CSCF shall include the updated access-network-charging-info parameter in the P-Charging-Vector header field. See subclause 5.2.7.4 for further information on the access network charging information.
If priority is supported, the P-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field value and set the backwards indication accordingly.
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5.2.10 Emergency service
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5.2.10.1 General
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If the P-CSCF belongs to a network where the registration is not required to obtain emergency service, the P‑CSCF shall accept any unprotected request on the IP address and port advertised to the UE during the P-CSCF discovery procedure. The P-CSCF shall also accept any unprotected request on the same IP address and the default port as specified in RFC 3261 [26].
When the P-CSCF sends unprotected responses to the UE, it shall use the same IP address and port where the corresponding request was received.
The P-CSCF can handle emergency session and other requests from both a registered user as well as an unregistered user. Certain networks only allow emergency session from registered users.
NOTE 1: If only emergency setup from registered users is allowed, a request from an unregistered user is ignored since it is received outside of the security association, TLS session or IP association.
The P-CSCF can handle emergency session establishment within a non-emergency registration, i.e. one that did not contain the "sos" SIP URI parameter in the Contact header field of the 200 (OK) response.
If the network uses the Resource-Priority header field to control the priority of emergency calls, and the P-CSCF receives a REGISTER request containing an "sos" SIP URI parameter in the Contact header field, the P-CSCF shall, in addition to the normal handling of the REGISTER request, add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197] to the REGISTER request.
Upon receiving the 200 (OK) response to the REGISTER request that completes the emergency registration, as identified by the presence of the "sos" SIP URI parameter in the Contact header field of the 200 (OK) response, the P-CSCF shall not subscribe to the registration event package for any emergency public user identity specified in the REGISTER request.
Upon reception of a REGISTER request containing an "sos" SIP URI parameter in the Contact header field and not containing an Authorization header field, if:
1) the network supports IMS Services for roaming users in deployments without IMS-level roaming interfaces;
2) the UE is roaming;
3) there is no II-NNI to the HPLMN of the served user; and
4) the access type is not set to "3GPP-NR-ProSe-L3UNR";
NOTE 2: The P-CSCF can determine whether the UE is roaming by analysing the home network domain name of the user received in the Request-URI in the REGISTER request.
NOTE 3: The P-CSCF can know if II-NNI to the HPLMN of the served user is supported by analysing the home network domain name of the user received in the Request-URI in the REGISTER request.
or:
1) if required by operator policy; and
2) the UE is not roaming;
the P-CSCF:
1) shall not forward the REGISTER request; and
2) if the PCRF is used to retrieve the EPS-level identities (i.e., IMSI, IMEI(SV)) as specified in 3GPP TS 29.214 [13D] and IMSI is retrieved:
a) if the P-CSCF supports IMSI or IMEI verification upon reception of a REGISTER request without Authorization header;
i) if the IMSI derived from public user identity conveyed in To header is different from the IMSI received from PCRF, shall reject the REGISTER request by returning a 403 (Forbidden) response and shall not perform the rest of steps; and
NOTE 4: The P-CSCF can also derive IMSI from derived private user identity. The private user identity can be derived from the public user identity being registered by removing URI scheme and the following parts of the URI if present: port number, URI parameters, and To header field parameters.
ii) if the IMEI(SV) is retrieved from the PCRF and the TAC and SNR portions of the IMEI obtained from instance ID conveyed in Contact header field are different from the TAC and SNR portions of IMEI(SV) received from PCRF, reject the REGISTER request by returning a 403 (Forbidden) response and shall not perform the rest of steps;
b) if MSISDN is retrieved:
i) shall generate:
- a SIP URI with user=phone for the retrieved MSISDN; and
- a tel URI for the retrieved MSISDN;
and shall include the URIs in the associated set of implicitly registered public user identities bound to the contact address from which the REGISTER request was received; and
ii) shall treat the SIP URI with user=phone for the retrieved MSISDN as the default public user identity for requests received from the contact address from which the REGISTER request was received;
c) if MSISDN is not retrieved:
i) shall generate a temporary public user identity for the IMSI retrieved from the PCRF as specified in 3GPP TS 29.214 [13D] and shall include the temporary public user identity in the associated set of implicitly registered public user identities bound to the contact address from which the REGISTER request was received; and
ii) shall treat the temporary public user identity for the retrieved IMSI as the default public user identity for requests received from the contact address from which the REGISTER request was received; and
NOTE 5: In the case when MSISDN is not retrieved, if the temporary public user identity is not provisioned in the HSS or is provisioned in the HSS, but barred, then a PSAP callback is not possible.
d) shall send a 200 (OK) response for the REGISTER request. In the 200 (OK) response, the P-CSCF shall include a P-Associated-URI header field containing the list of the implicitly registered public user identities bound to the contact address from which the REGISTER request was received. The first URI in the list of public user identities will indicate the default public user identity.
The P-CSCF shall store a configurable list of local emergency service identifiers, i.e. emergency numbers (the emergency numbers that can be resolved in the network to which the P-CSCF belongs) and emergency service URNs (i.e. emergency service URNs identifying emergency services that can be resolved in the network to which the P-CSCF belongs). In addition to the configurable list of local emergency service identifiers, the P-CSCF shall store a configurable list of roaming partners' emergency service identifiers (i.e. the emergency service numbers or the emergency service URNs identifying emergency services, which can be resolved in the roaming partners' network). Each emergency number in a configurable list is mapped to an emergency service URN if the network is configured, for the emergency number, to:
- accept a received request including the emergency number; or
- reject, using a 380 (Alternative Service) response, a received request including the emergency number, and include in the response a Contact header field with the emergency service URN.
NOTE 6: The emergency service URN is common to all networks, although subtypes might either not necessarily be in use, or a different set of subtypes is in use in different networks.
Access technology specific procedures are described in each access technology specific annex to determine the originating network of the requests.
NOTE 7: Depending on local operator policy, the P-CSCF has the capability to reject requests relating to specific methods in accordance with RFC 3261 [26], as an alternative to the functionality described above.
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5.2.10.2 General treatment for all dialogs and standalone transactions excluding the REGISTER method – requests from an unregistered user
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If the P-CSCF receives an initial request for a dialog or standalone transaction, or an unknown method from an unregistered user on the IP address and the unprotected port advertised to the UE during the P-CSCF discovery or the SIP default port, the P-CSCF shall inspect the Request-URI independent of values of possible entries in the received Route header fields for emergency service identifiers. The P-CSCF shall consider the Request URI of the initial request as an emergency service identifier, if it is an emergency number or an emergency service URN in the list of local emergency service identifiers or in the list of roaming partners emergency service identifiers.
If the Request-URI is a service URN with a top-level service type of "sos" as specified in RFC 5031 [69] and the P-CSCF does not consider the Request URI of the initial request as an emergency service identifier, the P-CSCF may:
- remove the right most service identifier and re-inspect the Request-URI for emergency service identifiers; or
- set the Request-URI to an operator defined emergency service URN that matches one of the emergency service identifiers.
If the P-CSCF detects that the Request-URI of the initial request for a dialog or a standalone transaction, or an unknown method matches one of the emergency service identifiers, the P-CSCF:
1) shall include in the Request-URI an emergency service URN, i.e. a service URN with a top-level service type of "sos" in accordance with RFC 5031 [69]:
a) if the received Request-URI matches an emergency service URN, as received in the Request-URI from the UE; and
b) if the received Request-URI does not match an emergency service URN, as deduced from the Request-URI received from the UE;
NOTE 1: Bullet b) can happen if a request is received from a UE not following the procedures in the present document.
2) shall include a topmost Route header field set to the URI associated with an E-CSCF;
NOTE 2: How the list of E-CSCF is obtained by the P-CSCF is implementation dependent.
3) shall execute the procedure described in subclause 5.2.6.3.3, subclause 5.2.6.3.7, subclause 5.2.6.3.11 and subclause 5.2.7.2, as appropriate except for:
- verifying the preloaded route against the received Service-Route header field;
- routing to IBCF;
- removing the P-Preferred-Identity header field;
- inserting a P-Asserted-Identity header field; and
- inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field;
3A) void;
3B) where the network uses the Resource-Priority header field to control the priority of emergency calls, shall add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197];
4) if the P-CSCF detects that the UE is behind a NAT, and the UE's Via header field contains a "keep" header field parameter, shall add a value to the parameter, to indicate that it is willing to receive keep-alives associated with the dialog from the UE, as defined in RFC 6223 [143]; and
5) if required by operator policy (e.g. when the network supports IMS services for roaming users in deployments without IMS-level roaming interfaces), and the P-CSCF supports including EPS-level identities (i.e. IMSI, IMEI(SV)) and MSISDN in a request from an unregistered user:
a) shall attempt to retrieve from PCRF the EPS-level identities and MSISDN available for the IP-CAN session of the request:
b) if a Subscription-Id AVP(s) as specified in 3GPP TS 29.214 [13D] with an MSISDN, an IMSI or both is(are) retrieved:
i) shall remove from the request any P-Preferred-Identity header field;
ii) if an MSISDN is retrieved, shall insert in the request a P-Asserted-Identity header field set to a tel URI carrying the MSISDN; and
iii) if an IMSI is retrieved, shall insert in the request a P-Asserted-Identity header field set to a temporary public user identity derived from the IMSI, as defined in 3GPP TS 23.003 [3]; and
c) if a User-Equipment-Info-Type AVP or a User-Equipment-Info-Extension AVP as specified in 3GPP TS 29.214 [13D] with an IMEI(SV) is retrieved where the TAC and SNR portions are different from the TAC and SNR portions of the IMEI received in the "+sip.instance" header field parameter of the Contact header field of the request and if according to operator policy, shall reject the request with 403 (Forbidden) response.
When the P-CSCF receives any 1xx or 2xx response to the above requests, the P-CSCF shall execute the appropriate procedure for the type of request described in subclause 5.2.6.3.4, subclause 5.2.6.3.8, and subclause 5.2.6.3.12, except that the P-CSCF may rewrite the port number of its own Record-Route entry to an unprotected port where the P-CSCF wants to receive the subsequent incoming requests from the UE belonging to this dialog.
If the P-CSCF does not receive any response to the initial request for a dialog or standalone transaction or unknown method (including its retransmissions); or receives a 3xx response or 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method, the P-CSCF shall include a URI associated with a different E-CSCF in the topmost Route header field and forward the request.
When the P-CSCF received a subsequent request in the dialog from the UE, and the network uses the Resource-Priority header field to control the priority of emergency calls, the P-CSCF shall add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197].
When the P-CSCF receives a target refresh request from the UE for a dialog, the P-CSCF shall execute the procedure described in subclause 5.2.6.3.5, except for inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field.
When the P-CSCF receives from the UE subsequent requests other than a target refresh request (including requests relating to an existing dialog where the method is unknown), the P-CSCF shall execute the procedure described in subclause 5.2.6.3.9, except for inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field.
When the P-CSCF receives any 1xx or 2xx response to the above requests, the P-CSCF shall execute the appropriate procedure for the type of request described in subclause 5.2.6.3.5 or subclause 5.2.6.3.9.
5.2.10.2A General treatment for all dialogs and standalone transactions excluding the REGISTER method – requests to an unregistered user
When the P-CSCF receives, destined for the UE, a target refresh request for a dialog, prior to forwarding the request, the P-CSCF shall execute the procedure described in step 5, the paragraph of subclause 5.2.6.4.5.
When the P-CSCF receives a 1xx or 2xx response to the above request the P-CSCF shall execute the procedure described in subclause 5.2.6.4.6, except for inserting type 1 "orig-ioi" and "term-ioi" header field parameters in the P-Charging-Vector header field.
When the P-CSCF receives any other response to the above request the P-CSCF shall execute the procedure described in steps in the paragraph of subclause 5.2.6.4.6 describing when the P-CSCF receives any other response to a target request, except for inserting type 1 "orig-ioi" and "term-ioi" header field parameters in the P-Charging-Vector header field.
When the P-CSCF receives, destined for the UE, a subsequent request for a dialog that is not a target refresh request (including requests relating to an existing dialog where the method is unknown), prior to forwarding the request, the P-CSCF shall execute the procedure described in steps 3 and 4 of subclause 5.2.6.4.9 describing when a P-CSCF receives a subsequent request.
When the P-CSCF receives any other response to the above request the P-CSCF shall execute the procedure described in steps in the paragraph of subclause 5.2.6.4.10 describing when the P-CSCF receives any other response to a subsequent request, except for inserting type 1 "orig-ioi" and "term-ioi" header field parameters in the P-Charging-Vector header field.
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5.2.10.3 General treatment for all dialogs and standalone transactions excluding the REGISTER method after emergency registration
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If the P-CSCF receives an initial request for a dialog, or a standalone transaction, or an unknown method, for a registered user over the security association, TLS session, or IP association that was created during the emergency registration, as identified by the presence of the "sos" SIP URI parameter in the Contact header field of the 200 (OK) response, the P-CSCF shall inspect the Request-URI independent of values of possible entries in the received Route header fields for emergency service identifiers. The P-CSCF shall consider the Request URI of the initial request as an emergency service identifier, if it is an emergency number or an emergency service URN from the configurable lists that are associated with:
- the country of the operator to which the P-CSCF belongs to; and
- for inbound roamers, the country from which the UE is roaming from. The P-CSCF determines the country to which the UE is belonging to based on the content of the P-Assserted-Identity header field which contains the home network domain name in a SIP URI belonging to the user.
If the P-CSCF detects that the Request-URI of the initial request for a dialog, or a standalone transaction, or an unknown method does not match any one of the emergency service identifiers in the associated lists, the P-CSCF shall either:
- reject the request by returning a 403 (Forbidden) response to the UE; or
- if the Request-URI is a service URN with a top-level service type of "sos" as specified in RFC 5031 [69]:
1) the P-CSCF sets the Request-URI to an operator defined emergency service URN that matches one of the emergency service identifiers; or
2) remove the right most service identifier and re-inspect the Request-URI for emergency service identifiers.
If the P-CSCF detects that the Request-URI of the initial request for a dialog, or a standalone transaction, or an unknown method matches one of the emergency service identifiers in the associated lists, the P-CSCF shall:
1) include in the Request-URI an emergency service URN, i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69]:
a) if the received Request-URI matches an emergency service URN, as received from the UE in the Request-URI; and
b) if the received Request-URI does not match an emergency service URN, as deduced from the Request-URI received from the UE.
NOTE 1: Bullet b) can happen if a request is received from a UE not following the procedures in the present document.
1A) if the operator policy requires that emergency service requests are forwarded to the S-CSCF and the P-CSCF determines that the network to which the originating user is attached (see the IP-CAN specific annexes for the detailed procedure) is the network the P-CSCF is in and if the user is not roaming, then:
NOTE 2: The P-CSCF can know if the user is roaming by comparing the home network domain name of the user received in the Request-URI in the REGISTER request with its own domain name. If they are different the user is a roaming user.
a) execute the procedure described in subclause 5.2.6.3.3, subclause 5.2.6.3.7, subclause 5.2.6.3.11 and subclause 5.2.7.2, as appropriate except for routing to IBCF;
b) before the request is forwarded in the referenced procedures, include a bottom most Route header field set to the URI associated with an E-CSCF;
NOTE 3: It is implementation dependent as to how the P-CSCF obtains the list of E-CSCFs.
c) afterwards upon receipt of a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog from the UE, execute the procedure described in subclause 5.2.6.3.5 and subclause 5.2.6.3.9; and
d) afterwards upon receipt of any response from the UE to a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog, execute the procedure described in subclause 5.2.6.4.6 and subclause 5.2.6.4.10;
1B) if the condition for 1A) is not fulfilled then:
a) execute the procedure described in subclause 5.2.6.3.3, subclause 5.2.6.3.7, subclause 5.2.6.3.11 and subclause 5.2.7.2, as appropriate except for:
- verifying the preloaded route against the received Service-Route header field;
- routing to IBCF; and
- inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field;
b) before the request is forwarded in the referenced procedures, remove all Route header fields and include a Route header field set to the URI associated with an E-CSCF;
NOTE 4: It is implementation dependent as to how the P-CSCF obtains the list of E-CSCFs.
c) afterwards upon receipt of a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog from the UE, execute the procedure described in subclause 5.2.6.3.5 and subclause 5.2.6.3.9, except for inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field; and
d) afterwards upon receipt of any response from the UE to a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog, execute the procedure described in subclause 5.2.6.4.6 and subclause 5.2.6.4.10, except for inserting type 1 "orig-ioi" and "term-ioi" header field parameters in the P-Charging-Vector header field;
1C) if the request is from a UE that is not considered as privileged sender and if the alternative identity of the originator of the request was not identified (see subclause 5.2.6.3.1):
i) if the P-Asserted-Identity header field in the request to be sent contains a SIP URI and if a tel URI belongs to the set of implicitly registered public user identities that contains the SIP URI, add a second P-Asserted-Identity header field that contains the first tel URI of the implicitly registered public user identities; and
ii) if the P-Asserted-Identity header field in the request to be sent contains a tel URI, add a second P-Asserted-Identity header field that contains the first SIP URI of the implicitly registered public user identities that contains the tel URI;
2) if the request contains a Contact header field containing a GRUU the P-CSCF shall save the GRUU received in the Contact header field of the request and associate it with the UE IP address and UE port such that the P-CSCF is able to route target refresh request containing that GRUU in the Request-URI. The UE port used for the association is determined as follows:
- if IMS AKA or SIP digest with TLS is being used as a security mechanism, the UE protected server port for the security association on which the request was received; or
- if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled Authentication is being used as a security mechanism, the UE unprotected port on which the request was received;
3) where the network uses the Resource-Priority header field to control the priority of emergency calls, add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197]; and
4) if the P-CSCF supports calling number verification using signature verification and attestation information as specified in subclause 3.1 and if required by operator policy, the P-CSCF shall perform attestation of the user identity by inserting:
- a "verstat" tel URI parameter, specified in subclause 7.2A.20, to the tel URI or SIP URI with a user=phone parameter in the From header field or the P-Asserted-Identity header field;
- an Attestation-Info header field specified in subclause 7.2.18; and
- an Origination-Id header field, specified in subclause 7.2.19, set to a UUID identifying the P-CSCF which is configured based on local policy;
If the P-CSCF does not receive any response to an initial request for a dialog or standalone transaction or an unknown method sent to an E-CSCF (including its retransmissions); or receives a 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method sent to an E-CSCF, the P-CSCF shall include a URI, associated with a different E-CSCF, in the topmost Route header field and forward the request.
If the P-CSCF does not receive any response to an initial request for a dialog or standalone transaction or an unknown method sent to a S-CSCF (including its retransmissions); or receives a 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method sent to a S-CSCF, the P-CSCF shall include a URI, associated with a different E-CSCF, in the topmost Route header field of the initial request for a dialog or standalone transaction or an unknown method, and forward the request.
When the P-CSCF received a subsequent request in the dialog from the UE, and the network uses the Resource-Priority header field to control the priority of emergency calls, the P-CSCF shall add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197].
When the P-CSCF receives a target refresh request for a dialog with the Request-URI containing a GRUU the P-CSCF shall:
- obtain the UE IP address and UE port associated to the GRUU contained in the Request-URI and rewrite the Request-URI with that UE IP address and UE port; and
- perform the steps in subclause 5.2.6.4.5 for when the P-CSCF receives, destined for the UE, a target refresh request for a dialog.
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5.2.10.4 General treatment for all dialogs and standalone transactions excluding the REGISTER method - non-emergency registration
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If the P-CSCF receives an initial request for a dialog, or a standalone transaction, or an unknown method, for a registered user, and the request is:
a) understood from saved or included information to relate to private network traffic (see subclause 5.2.6.3), and operator policy requires the P-CSCF to detect an emergency session request relating to private network traffic; or
b) not understood from saved or included information to relate to private network traffic (see subclause 5.2.6.3);
then the P-CSCF shall inspect the Request-URI independent of values of possible entries in the received Route header fields for emergency service identifiers. The P-CSCF shall consider the Request URI of the initial request as an emergency service identifier, if it is an emergency numbers or an emergency service URN from the configurable lists that are associated with:
- the country of the operator to which the P-CSCF belongs to;
- for inbound roamers, the country from which the UE is roaming from. The P-CSCF determines the country to which the UE is belonging to based on the content of the P-Assserted-Identity header field which contains the home network domain name in a SIP URI belonging to the user; and
- the country of roaming partners, if the request originates from a different country then the country of the network to which the P-CSCF belongs to. Access technology specific procedures are described in each access technology specific annex to determine from which country and roaming partner the request was originated. If the country from which the request originates can not be determined all lists are associated.
If the P-CSCF detects that the Request-URI of the initial request for a dialog, or a standalone transaction, or an unknown method matches one of the emergency service identifiers in the associated lists, the P-CSCF shall:
0A) determine the geographical location of the UE. Access technology specific procedures are described in each access technology specific annex:
a) if the UE is roaming and the P-CSCF is in the home operator's network, or the SDP of the request describes CS media (see 3GPP TS 24.292 [8O]), then the P-CSCF:
I) shall reject the request as specified in subclause 5.2.10.5;
b) if the UE is roaming and the P-CSCF is in the same network where the UE is roaming, or the UE is not roaming, then the P-CSCF, depending on operator policies:
I) may reject the request as specified in subclause 5.2.10.5; or
II) may continue with the next steps;
NOTE 1: Roaming is when a UE is in a geographic area that is outside the serving geographic area of the home IM CN subsystem.
NOTE 2: Emergency service URN in the request-URI indicates for the network that the emergency call attempt is recognized by the UE.
1) include in the Request-URI an emergency service URN, i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69], if necessary. If information on the type of emergency service is known include a sub-service type. The entry in the Request-URI that the P-CSCF includes shall be:
- if the received Request-URI matches an emergency service URN, as received from the UE in the Request-URI; and
- if the received Request-URI does not match an emergency service URN, as deduced from the Request-URI received from the UE;
1A) if operator policy requires that emergency service requests are forwarded to the S-CSCF and the P-CSCF determines that the network to which the originating user is attached (see the IP-CAN specific annexes for the detailed procedure) is the network the P-CSCF is in then:
a) execute the procedure described in subclause 5.2.6.3.3, subclause 5.2.6.3.7, subclause 5.2.6.3.11 and subclause 5.2.7.2, as appropriate except for routing to IBCF;
b) before the request is forwarded in the referenced procedures, include a bottom most Route header field set to the URI associated with an E-CSCF;
NOTE 3: It is implementation dependent as to how the P-CSCF obtains the list of E-CSCFs.
c) afterwards upon receipt of a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog from the UE, execute the procedure described in subclause 5.2.6.3.5 and subclause 5.2.6.3.9; and
d) afterwards upon receipt of any response from the UE to a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog, execute the procedure described in subclause 5.2.6.4.6 and subclause 5.2.6.4.10;
1B) if the condition for 1A) is not fulfilled then:
a) execute the procedure described in subclause 5.2.6.3.3, subclause 5.2.6.3.7, subclause 5.2.6.3.11 and subclause 5.2.7.2, as appropriate except for:
- verifying the preloaded route against the received Service-Route header field;
- routing to IBCF; and
- inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field;
b) before the request is forwarded in the referenced procedures, remove all Route header fields and include a Route header field set to the URI associated with an E-CSCF;
NOTE 4: It is implementation dependent as to how the P-CSCF obtains the list of E-CSCFs.
c) afterwards upon receipt of a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog from the UE, execute the procedure described in subclause 5.2.6.3.5 and subclause 5.2.6.3.9, except for inserting a type 1 "orig-ioi" header field parameter in the P-Charging-Vector header field; and
d) afterwards upon receipt of any response from the UE to a target refresh request or a subsequent request other than a target refresh request (including requests relating to an existing dialog where the method is unknown) for a dialog, execute the procedure described in subclause 5.2.6.4.6 and subclause 5.2.6.4.10, except for inserting type 1 "orig-ioi" and "term-ioi" header field parameters in the P-Charging-Vector header field;
1C) if the request is from a UE that is not considered as privileged sender and if the alternative identity of the originator of the request was not identified (see subclause 5.2.6.3.1):
i) if the P-Asserted-Identity header field in the request to be sent contains a SIP URI and if a tel URI belongs to the set of implicitly registered public user identities that contains the SIP URI, add a second P-Asserted-Identity header field that contains the first tel URI of the implicitly registered public user identities; and
ii) if the P-Asserted-Identity header field in the request to be sent contains a tel URI, add a second P-Asserted-Identity header field that contains the first SIP URI of the implicitly registered public user identities that contains the tel URI;
2) if the request contains a Contact header field containing a GRUU the P-CSCF shall save the GRUU received in the Contact header field of the request and associate it with the UE IP address and UE port such that the P-CSCF is able to route target refresh request containing that GRUU in the Request-URI. The UE port used for the association is determined as follows:
- if IMS AKA or SIP digest with TLS is being used as a security mechanism, the UE protected server port for the security association on which the request was received; or
- if SIP digest without TLS is being used as a security mechanism, the UE unprotected port on which the request was received; and
3) where the network uses the Resource-Priority header field to control the priority of emergency calls, add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197].
If the P-CSCF does not receive any response to the initial request for a dialog or standalone transaction or an unknown method sent to an E-CSCF (including its retransmissions); or receives a 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method sent to an E-CSCF, the P-CSCF shall include a URI, associated with a different E-CSCF that has not been tried before for this initial request for the dialog or standalone transaction (including its retransmissions), in the topmost Route header field and forward the request.
If the P-CSCF does not receive any response to the initial request for a dialog or standalone transaction or an unknown method sent to a S-CSCF (including its retransmissions); or receives a 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method sent to a S-CSCF, the P-CSCF shall include a URI, associated with a different E-CSCF that has not been tried before for this initial request for the dialog or standalone transaction (including its retransmissions), in the topmost Route header field of the initial request for a dialog or standalone transaction or an unknown method, and forward the request.
If the P-CSCF:
- does not receive any response to this initial request for a dialog or standalone transaction or an unknown method (including its retransmissions); or receives a 3xx response or 480 (Temporarily Unavailable) response to an initial request for a dialog or standalone transaction or an unknown method, and if all E-CSCFs have been tried before for this initial request for the dialog or standalone transaction (including its retransmissions), the P-CSCF shall reject this request as specified in subclause 5.2.10.5;
- receives:
1) any 4xx response other than a 480 (Temporarily Unavailable) response;
2) any 5xx response;
3) any 6xx response,
and the entry in the Request-URI as received from the UE is not in accordance with RFC 5031 [69], then the P-CSCF shall reject this request as specified in subclause 5.2.10.5.
If the P-CSCF receives from the IP-CAN (e.g. via PCRF) an indication that the requested resources for the multimedia session being established cannot be granted and the entry in the Request-URI as received from the UE is not in accordance with RFC 5031 [69], then the P-CSCF shall:
- send a CANCEL request to cancel the request forwarded to the selected E-CSCF; and
- reject this request as specified in subclause 5.2.10.5.
When the P-CSCF received a subsequent request in the dialog from the UE, and the network uses the Resource-Priority header field to control the priority of emergency calls, the P-CSCF shall add a Resource-Priority header field containing a namespace of "esnet" as defined in RFC 7135 [197].
When the P-CSCF receives a target refresh request for a dialog with the Request-URI containing a GRUU the P-CSCF shall:
- obtain the UE IP address and UE port associated to the GRUU contained in the Request-URI and rewrite the Request-URI with that UE IP address and UE port; and
- perform the steps in subclause 5.2.6.4 for when the P-CSCF receives, destined for the UE, a target refresh request for a dialog.
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5.2.10.5 Abnormal and rejection cases
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If the IM CN subsystem to where the P-CSCF belongs to is not capable to handle emergency sessions or due to local policy does not handle emergency sessions or only handles certain type of emergency session request or does not support emergency sessions for either the geographical location of the UE is located or the IP-CAN to which the UE is attached, or the SDP of the request describes CS media (see 3GPP TS 24.292 [8O]), or for reasons described in subclause 5.2.10.4, the P-CSCF shall not forward the initial request for a dialog or standalone transaction or an unknown method. The P-CSCF:
I) shall reject the request by returning a 380 (Alternative Service) response;
II) if:
- support for the 3GPP IM CN subsystem XML body as described in subclause 7.6 in the Accept header field is not indicated, the P-CSCF shall assume that the UE supports version 1 of the 3GPP XML Schema for the IM CN subsystem XML; or
- if both the "sv" and "schemaversion" parameters are present, then the P-CSCF shall ignore the value of the "schemaversion" parameter;
III) shall include in the 380 (Alternative Service) response:
a) a Content-Type header field with the value set to associated MIME type of the 3GPP IM CN subsystem XML body as described in subclause 7.6.1;
b) a P-Asserted-Identity header field set to the value of the SIP URI of the P-CSCF included in the Path header field during the registration of the user whose UE sent the request causing this response (see subclause 5.2.2.1); and
c) if required by operator policy implementing national regulatory requirements, a Contact header field with an emergency service URN (i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69]). If a type of emergency service can be deduced from the Request-URI received from the UE and if required by operator policy implementing national regulatory requirements, the P-CSCF shall include in the emergency service URN a sub-service type deduced from the Request-URI received from the UE; and
NOTE 1: If the Request-URI identifies an emergency service with a type of emergency service, and the 380 (Alternative Service) response does not contain a Contact header field with an emergency service URN or contains a Contact header field with an emergency service URN which does not include a sub-service type, and if, upon reception of the response, the UE performs the emergency call attempt in the IM CN subsystem, then the emergency call attempt in the IM CN subsystem can be misrouted.
IV) shall include an IM CN subsystem XML body with the following elements:
a) an <ims-3gpp> element with the "version" attribute set to "1" and with an <alternative-service> child element, set to the parameters of the alternative service;
i) a <type> child element, set to "emergency" (see table 7.6.2) to indicate that it was an emergency call;
ii) a <reason> child element, set to an operator configurable reason; and
iii) an <action> child element, set to "emergency-registration" (see table 7.6.3) if the P-CSCF is accordingly configured by the operator.
NOTE 2: Emergency service URN in the request-URI indicates for the network that the emergency call attempt is recognized by the UE.
NOTE 3: Some networks only allow session requests with a Request-URI containing an emergency service URN, i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69].
Upon reception of a REGISTER request containing an "sos" SIP URI parameter in the Contact header field and containing an Authorization header field, if:
1) the network supports IMS Services for roaming users in deployments without IMS-level roaming interfaces;
2) required by operator policy;
3) the UE is roaming; and
4) there is no II-NNI to the HPLMN of the served user;
NOTE 4: The P-CSCF can determine whether the UE is roaming by analysing the home network domain name of the user received in the Request-URI in the REGISTER request.
NOTE 5: The P-CSCF can know if II-NNI to the HPLMN of the served user is supported by analysing the home network domain name of the user received in the Request-URI in the REGISTER request.
or:
1) if required by operator policy; and
2) the UE is not roaming;
the P-CSCF:
1) if the P-CSCF supports GPRS-IMS-Bundled authentication, shall reject the request by returning a 420 (Bad Extension) response in which the Unsupported header field contains the value "sec-agree"; and
2) if the P-CSCF does not support GPRS-IMS-Bundled authentication, shall reject the request by returning a 403 (Forbidden) response.
When the P-CSCF responds 420 (Bad Extension) or 403 (Forbidden) response, if required by operator policy implementing national regulatory requirements (i.e., the network support an emergency session for an unregistered user as described in subclause 5.2.10.2), the P-CSCF shall include:
1) a Content-Type header field with the value set to associated MIME type of the 3GPP IM CN subsystem XML body as described in subclause 7.6.1;
2) a Content-Disposition header field with a disposition type "render" value and a "handling" header field parameter with an "optional" value, as described in RFC 3261 [26];
3) a P-Asserted-Identity header field set to the value of the SIP URI of the P-CSCF; and
4) a 3GPP IM CN subsystem XML body containing:
a) an <ims-3gpp> element with the "version" attribute set to "1" and with an <alternative-service> child element, set to the parameters of the alternative service:
i) a <type> child element, set to "emergency" (see table 7.6.2) to indicate that it was an emergency call;
ii) a <reason> child element, set to an operator configurable reason; and
iii) an <action> child element, set to "anonymous-emergencycall" (see table 7.6.3) if the P-CSCF is accordingly configured by the operator.
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5.2.11 Void
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5.2.12 Resource sharing
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The P-CSCF supporting resource sharing shall perform the actions defined in access technology specific annexes.
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5.2.13 Priority sharing
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The P-CSCF supporting priority sharing shall perform the actions defined in access technology specific annexes.
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5.2.14 Access update
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This subclause specifies procedures for the P-CSCF to inform the S-CSCF and any AS as applicable that the UE has changed access and possibly PLMN. This includes access update when the UE is not in a call and an in-call access update procedure when the access change happens when the UE is involved in an IMS session.
If the P-CSCF is aware that the UE has changed PLMN, and the P-CSCF has a policy to require a different encryption for the new PLMN than what the UE currently uses, the P-CSCF shall send a MESSAGE request towards the S-CSCF populated as follows:
1) the Request-URI set to the URI of the S-CSCF as received in the Service-Route header field during the registration of the served UE;
2) a From header field set to the FQDN of the P-CSCF sending the request;
3) a To header field, set to the same value as the Request-URI;
4) a P-Asserted-Identity header field set to the default public user identity of the served user;
5) a P-Charging-Vector header field with the "icid-value" header field parameter populated with the ICID value used for the dialog related to the access change and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter;
6) a P-Access-Network-Info header field including network-provided location information;
7) a P-Visited-Network-ID header field; and
8) based on network configuration a Handover-Info header field, defined in subclause 7.2.15, set to "authentication-needed";
When the UE is in a call,if the P-CSCF supports the in-call access update procedure, has received the g.3gpp.in-call-access-update feature-capability indicator during session set-up, and determines that the UE has changed access or PLMN, then the P-CSCF shall generate a MESSAGE request populated as follows:
1) the Request URI set to the stored value of the g.3gpp.in-call-access-update feature-capability indicator;
2) a From header field set to the FQDN of the P-CSCF sending the request;
3) a To header field, set to the same value as the Request-URI;
4) a P-Asserted-Identity header field set to the default public user identity of the served user;
5) a P-Charging-Vector header field with the "icid-value" header field parameter populated with the ICID value used for the dialog related to the access change and a type 1 "orig-ioi" header field parameter. The P-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The P-CSCF shall not include the type 1 "term-ioi" header field parameter;
6) a P-Access-Network-Info header field including network-provided location information;
7) a P-Visited-Network-ID header field; and
8) if the MESSAGE request is to be sent via the S-CSCF, a Route header field with the S-CSCF address as received in the Service-Route header field during registration.
If the procedure above leads to a re-authentication from the user and no encryption of the signalling is used, the P-CSCF shall after a successful re-authentication, i.e. on receipt of the 200 (OK) response to the REGISTER request, send a MESSAGE request populated as above and including a Handover-Info header field set to "handover-completed".
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5.3 Procedures at the I-CSCF
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5.3.0 General
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When sending a failure response to any received request, depending on operator policy, the I-CSCF may insert a Response-Source header field with an "fe" header field parameter constructed with the URN namespace "urn:3gpp:fe", the fe-id part of the URN set to "i-cscf" and optionally an appropriate fe-param part of the URN set in accordance with subclause 7.2.17.
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5.3.1 Registration procedure
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5.3.1.1 General
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During the registration procedure the I-CSCF shall behave as a stateful proxy.
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5.3.1.2 Normal procedures
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When the I-CSCF receives a REGISTER request, the I-CSCF shall verify whether or not it has arrived from a trusted domain. If the request has not arrived from a trusted domain, the I-CSCF shall complete the processing of the request by responding with 403 (Forbidden) response. Otherwise, the I-CSCF starts the user registration status query procedure to the HSS as specified in 3GPP TS 29.228 [14].
NOTE 1: The I-CSCF can find out whether the request arrived from a trusted domain or not, from the procedures described in 3GPP TS 33.210 [19A].
NOTE 2: Different UEs, each with its own private user identity, can register the same shared public user identity. Registrations of all public user identities belonging to these UEs are directed to the same S-CSCF as described in 3GPP TS 29.228 [14].
If the REGISTER request does not include an Authorization header field and private user identity, the I-CSCF shall derive the private user identity from the public user identity being registered, contained in the To header field, by removing URI scheme and the following parts of the URI if present: port number, URI parameters, and To header field parameters.
If priority is supported and the I-CSCF received a REGISTER request containing Resource-Priority header field, the I-CSCF shall give priority over other registrations.
Prior to performing the user registration query procedure to the HSS, the I-CSCF decides which HSS to query, possibly as a result of a query to the Subscription Locator Functional (SLF) entity as specified in 3GPP TS 29.228 [14]. As a result of the query the I-CSCF gets the Redirect-Host AVP.
If the user registration status query response from the HSS includes a valid SIP URI, the I-CSCF shall:
1) replace the Request-URI of the received REGISTER request with the SIP URI received from the HSS in the Server-Name AVP;
2) optionally include in the P-User-Database header field defined in RFC 4457 [82]:
a) either the received Redirect-Host AVP value; or
b) the HSS Group ID using the form "aaa://hss.5gc.gid.<GID>.invalid", if the HSS Group ID is received following procedures in clause X.3; and
3) forward the REGISTER request to the indicated S-CSCF.
NOTE 3: The P-User-Database header field can be included only if the I-CSCF can assume (e.g. based on local configuration) that the receiving S-CSCF will be able to process the header field.
If the user registration status query response from the HSS includes a list of capabilities, the I-CSCF shall:
1) select a S-CSCF that fulfils the indicated mandatory capabilities – if more than one S-CSCFs fulfils the indicated mandatory capabilities the S-CSCF which fulfils most of the possibly additionally indicated optional capabilities;
2) replace the Request-URI of the received REGISTER request with the URI of the S-CSCF;
3) optionally, include in the P-User-Database header field defined in RFC 4457 [82]:
a) either the received Redirect-Host AVP value; or
b) the HSS Group ID using the form "aaa://hss.5gc.gid.<GID>.invalid", if the HSS Group ID is received following procedures in clause X.3; and
4) forward the REGISTER request to the selected S-CSCF.
NOTE 4: The P-User-Database header field can be included only if the I-CSCF can assume (e.g. based on local configuration) that the receiving S-CSCF will be able to process the header field.
NOTE 5: It is important that the I-CSCF does not alter the Via header field for requests and responses sent in the direction from the UE to the S-CSCF in the case of GPRS-IMS-Bundled authentication
When the I-CSCF receives a 2xx response to a REGISTER request, the I-CSCF shall forward the 2xx response to the P-CSCF.
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5.3.1.3 Abnormal cases
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In the case of SLF query, if the SLF does not send HSS address to the I-CSCF, the I-CSCF shall send back a 403 (Forbidden) response to the UE.
If the HSS sends a negative response to the user registration status query request, the I-CSCF shall send back a 403 (Forbidden) response.
If the user registration status query procedure cannot be completed, e.g. due to time-out or incorrect information from the HSS, the I-CSCF shall send back a 480 (Temporarily Unavailable) response to the UE.
If a selected S-CSCF:
- does not respond to the REGISTER request and its retransmissions by the I-CSCF; or
- sends back a 3xx response or 480 (Temporarily Unavailable) response to a REGISTER request;
and:
- the REGISTER request did not include an "integrity-protected" header field parameter in the Authorization header field;
- the REGISTER request did include an "integrity-protected" header field parameter in the Authorization header field with a value set to "no" in the Authorization header field;
- the REGISTER request did include an "integrity-protected" header field parameter in the Authorization header field with a value set to other than "no" and the I-CSCF supports S-CSCF restoration procedures; or
- the REGISTER request did not include an Authorization header field and the I-CSCF supports S-CSCF restoration procedures;
then:
- if the I-CSCF has received the list of capabilities from the HSS, the I-CSCF shall select a new S-CSCF as described in subclause 5.3.1.2, based on the capabilities indicated from the HSS. The newly selected S-CSCF shall not be one of any S-CSCFs selected previously during this same registration procedure; or
- if the I-CSCF has received a valid SIP URI from the HSS because the S-CSCF is already assigned to other UEs sharing the same public user identity, it will request the list of capabilities from the HSS and, on receiving these capabilities, the I-CSCF shall select a new S-CSCF as described in subclause 5.3.1.2, based on the capabilities indicated from the HSS. The newly selected S-CSCF shall not be one of any S-CSCFs selected previously during this same registration procedure.
NOTE 1: Checking for the inclusion of the Authorization header field is necessary to prevent S-CSCF reselection in the case of GPRS-IMS-Bundled authentication or NASS-IMS bundled authentication when no Authorization header field is present in case I-CSCF does not support S-CSCF restoration procedures.
NOTE 2: In case the S-CSCF does not respond, the I-CSCF can apply a pre-configured timer based on local policy before re-selecting a new S-CSCF.
When forwarding the REGISTER request to the new S-CSCF, the I-CSCF includes the SIP URI parameter "scscf-reselection" to the Request-URI of the REGISTER request.
If a selected S-CSCF does not respond to a REGISTER request and its retransmissions by the I-CSCF and none of the conditions specified above in this case are fulfilled, the I-CSCF shall send back a or 504 (Server Time-Out) response to the user, in accordance with the procedures in RFC 3261 [26].
If the I-CSCF cannot select a S-CSCF which fulfils the mandatory capabilities indicated by the HSS, the I-CSCF shall send back a 600 (Busy Everywhere) response to the user.
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5.3.2 Initial requests
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5.3.2.1 Normal procedures
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The I-CSCF may behave as a stateful proxy for initial requests.
Upon receipt of a request, the I-CSCF shall perform the originating procedures as described in subclause 5.3.2.1A if the topmost Route header field of the request contains the "orig" parameter. Otherwise, the I-CSCF shall continue with the rest of the procedures of this subclause.
When the I-CSCF receives a request, the I-CSCF shall verify whether it has arrived from a trusted domain or not. If the request has arrived from a non trusted domain, then the I-CSCF shall remove all P-Charging-Vector header fields and all P-Charging-Function-Addresses header fields the request may contain.
NOTE 1: The I-CSCF can find out whether the request arrived from a trusted domain or not, from the procedures described in 3GPP TS 33.210 [19A].
For all SIP transactions identified:
- if priority is supported, as containing an authorised Resource-Priority header field, or, if such an option is supported, relating to a dialog which previously contained an authorised Resource-Priority header field;
the I-CSCF shall give priority over other transactions or dialogs. This allows special treatment of such transactions or dialogs. If priority is supported, the I-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field or backwards indication value.
NOTE 2: The special treatment can included filtering, higher priority processing, routeing, call gapping. The exact meaning of priority is not defined further in this document, but is left to national regulation and network configuration.
The I-CSCF shall discard the P-Profile-Key header field, if the I-CSCF receives the P-Profile-Key header field in a SIP request or response.
When the I-CSCF receives, destined for a served user or a PSI, an initial request for a dialog or standalone transaction the I-CSCF shall:
1) if the Request-URI includes:
a) a pres: or an im: URI, then translate the pres: or im: URI to a public user identity and replace the Request-URI of the incoming request with that public user identity; or
b) a SIP-URI that is not a GRUU and with the user part starting with a + and the "user" SIP URI parameter equals "phone" then replace the Request-URI with a tel-URI with the user part of the SIP-URI in the telephone-subscriber element in the tel-URI, and carry forward the tel-URI parameters that may be present in the Request-URI; or
c) a SIP URI that is a GRUU, then obtain the public user identity or an identity of the UE that represents the functionality within the UE that performs the role of registrar from the Request-URI and use it for location query procedure to the HSS. When forwarding the request, the I-CSCF shall not modify the Request-URI of the incoming request;
NOTE 3: SRV records have to be advertised in DNS pointing to the I-CSCF for pres: and im: queries.
2) remove its own SIP URI from the topmost Route header field, if present; and
3) check if the domain name of the Request-URI matches with one of the PSI subdomains configured in the I-CSCF. If the match is successful, the I-CSCF resolves the Request-URI by an internal DNS mechanism into the IP address of the AS hosting the PSI and does not start the user location query procedure. Otherwise, the I-CSCF will start the user location query procedure to the HSS as specified in 3GPP TS 29.228 [14] for the called PSI or user, indicated in or derived from the Request-URI. Prior to performing the user location query procedure to the HSS, the I-CSCF decides which HSS to query, possibly as a result of a query to the Subscription Locator Functional (SLF) entity as specified in 3GPP TS 29.228 [14].
When the I-CSCF receives any response to such a request, the I-CSCF shall store the value of the "term-ioi" header field parameter received in the P-Charging-Vector header field, if present.
NOTE 4: A received "term-ioi" header field parameter will be a type 3 IOI if received from an AS hosting a PSI or a type 2 IOI if received from the S-CSCF of the served user. The type 3 IOI identifies the service provider from which the response was sent and the type 2 IOI identifies the network from which the response was sent.
When the I-CSCF receives an INVITE request, the I-CSCF may require the periodic refreshment of the session to avoid hung states in the I-CSCF. If the I-CSCF requires the session to be refreshed, then the I-CSCF shall apply the procedures described in RFC 4028 [58] clause 8.
NOTE 5: Requesting the session to be refreshed requires support by at least one of the UEs. This functionality cannot automatically be granted, i.e. at least one of the involved UEs needs to support it.
In case the I-CSCF is able to resolve the Request-URI into the IP address of the AS hosting the PSI, then the I-CSCF shall:
1) store the value of the "icid-value" header field parameter received in the P-Charging-Vector header field and retain the "icid-value" header field parameter in the P-Charging-Vector header field. If no P-Charging-Vector header field was found, then insert the P-Charging-Vector header field with the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17]. The I-CSCF shall insert a type 3 "orig-ioi" header field parameter in place of any received "orig-ioi" header field parameter. The I-CSCF shall set the type 3 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The I-CSCF shall not include the type 3 "term-ioi" header field parameter. Based on local policy, the I-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier; and
2) forward the request directly to the AS hosting the PSI.
Upon successful user location query, when the response contains the URI of the assigned S-CSCF, or the URI of an AS hosting the PSI, the I-CSCF shall:
1) insert the URI received from the HSS as the topmost Route header field;
2) store the value of the "icid-value" header field parameter received in the P-Charging-Vector header field and retain the P-Charging-Vector header field in the P-Charging-Vector header field. If no "icid-value" header field parameter was found, then insert the P-Charging-Vector header field with the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17];
2A) based on local policy, add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier;
3) optionally, include in the P-User-Database header field defined in RFC 4457 [82]:
a) either the received Redirect-Host AVP value; or
b) the HSS Group ID using the form "aaa://hss.5gc.gid.<GID>.invalid", if the HSS Group ID is received following procedures in clause X.3;
3A) if the Wildcarded Identity value is received from the HSS in the Wildcarded-Identity AVP and the I-CSCF supports the SIP P-Profile-Key private header extension, include the wildcarded identity value in the P-Profile-Key header field defined in RFC 5002 [97]; and
4) forward the request based on the topmost Route header field.
NOTE 6: The P-User-Database header field can be included only if the I-CSCF can assume (e.g. based on local configuration) that the receiving S-CSCF will be able to process the header field.
Upon successful user location query, when the response contains information about the required S-CSCF capabilities, the I-CSCF shall:
1) if overlap signalling using the multiple-INVITEs method is supported as a network option, and if the I-CSCF receives an INVITE request outside an existing dialog with the same Call ID and From header as a previous INVITE request during a certain period of time, route the new INVITE to the same next hop as the previous INVITE request; otherwise
2) select a S-CSCF according to the method described in 3GPP TS 29.228 [14];
3) insert the URI of the selected S-CSCF as the topmost Route header field value;
4) execute the procedure described in step 2 and 3 in the above paragraph (upon successful user location query, when the response contains the URI of the assigned S-CSCF);
5) optionally, include in the P-User-Database header field defined in RFC 4457 [82]:
a) either the received Redirect-Host AVP value; or
b) the HSS Group ID using the form "aaa://hss.5gc.gid.<GID>.invalid", if the HSS Group ID is received following procedures in clause X.3;
6) if the Wildcarded Identity value is received from the HSS in the Wildcarded-Identity AVP and the I-CSCF supports the SIP P-Profile-Key private header extension, include the wildcarded identity value in the P-Profile-Key header field as defined in RFC 5002 [97]; and
NOTE 7: A Wildcarded Identity can be either a PSI or a public user identity.
7) forward the request to the selected S-CSCF.
NOTE 8: The P-User-Database header field can be included only if the I-CSCF can assume (e.g. based on local configuration) that the receiving S-CSCF will be able to process the header field.
Upon an unsuccessful user location query when the response from the HSS indicates that the user does not exist, and if the Request-URI is a tel URI containing a public telecommunications number as specified in RFC 3966 [22], the I-CSCF may support a local configuration option that indicates whether or not request routeing is to be attempted. If the local configuration option indicates that request routeing is to be attempted, then the I-CSCF shall perform one of the following procedures based on local operator policy:
1) forward the request to the transit functionality for subsequent routeing; or
2) invoke the portion of the transit functionality that translates the public telecommunications number contained in the Request-URI to a routeable SIP URI, and process the request based on the result, as follows:
a) if the translation fails, the request may be forwarded to a BGCF or any other appropriate entity (e.g. a MRFC to play an announcement) in the home network, or the I-CSCF may send an appropriate SIP response to the originator, such as 404 (Not Found) or 604 (Does not exist anywhere). When forwarding the request to a BGCF or any other appropriate entity, the I-CSCF shall leave the original Request-URI containing the tel URI unmodified:
i) if overlap signalling using the multiple-INVITEs method is supported as a network option, and if the I-CSCF receives an INVITE request outside an existing dialog with the same Call ID and From header as a previous INVITE request during a certain period of time, the I-CSCF shall route the new INVITE to the same next hop as the previous INVITE request; and
ii) additional procedures apply if the I-CSCF supports NP capabilities and these capabilities are enabled by local policy, and the database used for translation from an international public telecommunications number to a SIP URI also provides NP data (for example, based on the PSTN Enumservice as defined by RFC 4769 [114] or other appropriate data bases). If the above translation from an international public telecommunications number to a SIP URI failed, but NP data was obtained from the database, then the I-CSCF shall replace the tel-URI in the Request-URI with the obtained NP data, prior to forwarding the request to the BGCF or other appropriate entity. The URI is updated by the I-CSCF by adding the NP parameters defined by RFC 4694 [112] to the tel-URI in the Request-URI: an "npdi" tel-URI parameter is added to indicate that NP data retrieval has been performed, and if the number is ported, an "rn" tel-URI parameter is added to identify the ported-to routeing number. The I-CSCF shall perform these procedures if the tel-URI in the received Request-URI does not contain an "npdi" tel-URI parameter. In addition, the I-CSCF may, based on local policy, perform these procedures when the tel-URI in the received Request-URI contains an "npdi" tel-URI parameter indicating that the NP data has been previously obtained; or
NOTE 9: The I-CSCF might need to replace NP data added by a previous network if the previous network's NP database did not contain the local ported data for the called number. When the I-CSCF replaces the tel URI in the Request-URI with the obtained NP data, all tel URI parameters in the received Request-URI will be replaced by the obtained NP data.
b) if this translation succeeds, then replace the Request-URI with the routeable SIP URI and process the request as follows:
- determine the destination address (e.g. DNS access) using the URI placed in the topmost Route header field if present, otherwise based on the Request-URI. If the destination requires interconnect functionalities (e.g. the destination address is of an IP address type other than the IP address type used in the IM CN subsystem), the I-CSCF shall:
i) if the I-CSCF supports indicating the traffic leg as specified in RFC 7549 [225] and required by local policy, append the "iotl" SIP URI parameter set to "homeA-homeB" to the Request-URI; and
ii) forward the request to the destination address via an IBCF in the same network;
- if network hiding is needed due to local policy, put the address of the IBCF to the topmost Route header field;
- route the request based on SIP routeing procedures; and
- if overlap signalling using the multiple-INVITE method is supported as a network option, and if the I-CSCF receives an INVITE request outside an existing dialog with the same Call ID and From header as a previous INVITE request during a certain period of time, route the new INVITE to the same next hop as the previous INVITE request.
Upon an unsuccessful user location query when the response from the HSS indicates that the user does not exist, and if local operator policy does not indicate that request routeing is to be attempted, then, the I-CSCF shall return an appropriate unsuccessful SIP response. Upon an unsuccessful user location query when the response from the HSS indicates that the user does not exist, and if if the Request-URI is a SIP URI, the I-CSCF shall also return an appropriate unsuccessful SIP response. This response may be a 404 (Not found) or 604 (Does not exist anywhere) in the case the user is not a user of the home network.
Upon an unsuccessful user location query when the response from the HSS indicates that the user is not registered and no services are provided for such a user, the I-CSCF shall return an appropriate unsuccessful SIP response. This response may be a 480 (Temporarily unavailable) response if the user is recognized as a valid user, but is not registered at the moment and it does not have services for unregistered users.
When the I-CSCF receives an initial request for a dialog or standalone transaction, that contains a single Route header field pointing to itself, the I-CSCF shall determine from the entry in the Route header field whether it needs to do HSS query. In case HSS query not is needed, then the I-CSCF shall:
1) remove its own SIP URI from the topmost Route header field; and
2) route the request based on the Request-URI.
When the I-CSCF receives an initial request for a dialog or standalone transaction containing more than one Route header field, the I-CSCF shall:
1) remove its own SIP URI from the topmost Route header field; and
2) forward the request based on the topmost Route header field.
NOTE 10: In accordance with SIP the I-CSCF can add its own routeable SIP URI to the top of the Record-Route header field to any request, independently of whether it is an initial request. The P-CSCF will ignore any Record-Route header field that is not in the initial request of a dialog.
When the I-CSCF receives a response to an initial request (e.g. 183 (Session Progress) response or 2xx response), the I-CSCF shall store the values from the P-Charging-Function-Addresses header field, if present. If the next hop is outside of the current network, then the I-CSCF shall remove the P-Charging-Function-Addresses header field prior to forwarding the message.
When the I-CSCF receives any response to the initial request for a dialog or standalone transaction containing a "term-ioi" header field parameter in the P-Charging-Vector header field from the AS hosting the PSI, the I-CSCF shall:
1) remove all received "orig-ioi" and "term-ioi" header field parameters from the forwarded response;
2) insert the stored "orig-ioi" header field parameter if received in the request; and
3) insert a type 2 "term-ioi" header field parameter. The "term-ioi" header field parameter is set to a value that identifies the sending network of the response.
When the I-CSCF, upon sending an initial INVITE request to the S-CSCF, receives a 305 (Use Proxy) response from the S-CSCF, the I-CSCF shall forward the initial INVITE request to the SIP URI indicated in the Contact field of the 305 (Use Proxy) response, as specified in RFC 3261 [26].
5.3.2.1A Originating procedures for requests containing the "orig" parameter
The procedures of this subclause apply for requests received at the I-CSCF when the topmost Route header field of the request contains the "orig" parameter.
The I-CSCF shall verify for all requests whether they arrived from a trusted domain or not. If the request arrived from a non trusted domain, then the I-CSCF shall respond with 403 (Forbidden) response.
If the request arrived from a trusted domain, the I-CSCF shall perform the procedures below.
NOTE 1: The I-CSCF can find out whether the request arrived from a trusted domain or not, from the procedures described in 3GPP TS 33.210 [19A].
For all SIP transactions identified:
- if priority is supported, as containing an authorised Resource-Priority header field, or, if such an option is supported, relating to a dialog which previously contained an authorised Resource-Priority header field;
the I-CSCF shall give priority over other transactions or dialogs. This allows special treatment of such transactions or dialogs. If priority is supported, the I-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field or backwards indication value.
NOTE 2 The special treatment can include filtering, higher priority processing, routeing, call gapping. The exact meaning of priority is not defined further in this document, but is left to national regulation and network configuration.
If the I-CSCF receives the P-Profile-Key header field in a SIP request or response the I-CSCF shall discard the P-Profile-Key header field.
When the I-CSCF receives an initial request for a dialog or standalone transaction the I-CSCF will start the user location query procedure to the HSS as specified in 3GPP TS 29.228 [14] for the calling user, indicated in either:
1) the P-Served-User header field, if included in the request; or
2) the P-Asserted-Identity header field, if the P-Served-User header field is not included in the request.
Prior to performing the user location query procedure to the HSS, the I-CSCF decides which HSS to query, possibly as a result of a query to the Subscription Locator Functional (SLF) entity as specified in 3GPP TS 29.228 [14].
When the I-CSCF receives an INVITE request, the I-CSCF may require the periodic refreshment of the session to avoid hung states in the I-CSCF. If the I-CSCF requires the session to be refreshed, the I-CSCF shall apply the procedures described in RFC 4028 [58] clause 8.
NOTE 3: Requesting the session to be refreshed requires support by at least one of the UEs. This functionality cannot automatically be granted, i.e. at least one of the involved UEs needs to support it.
When the response for user location query contains information about the required S-CSCF capabilities, the I-CSCF shall select a S-CSCF according to the method described in 3GPP TS 29.228 [14].
If the user location query was successful, the I-CSCF shall:
1) insert the URI of an AS hosting the PSI, or the URI of the S-CSCF - either received from the HSS, or selected by the I-CSCF based on capabilities - as the topmost Route header field appending the "orig" parameter to the URI of the S-CSCF;
2) store the value of the "icid-value" header field parameter received in the P-Charging-Vector header field and retain the "icid-value" header field parameter in the P-Charging-Vector header field. If no P-Charging-Vector header field was found, then insert the P-Charging-Vector header field with the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17];
2A) based on local policy, add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier;
3) optionally, include in the P-User-Database header field defined in RFC 4457 [82]:
a) either the received Redirect-Host AVP value; or
b) the HSS Group ID using the form "aaa://hss.5gc.gid.<GID>.invalid", if the HSS Group ID is received following procedures in clause X.3;
4) if a wildcarded identity value is received from the HSS in the Wildcarded-Identity AVP and the I-CSCF supports the SIP P-Profile-Key private header extension, include the wildcarded public user identity value in the P-Profile-Key header field as defined in RFC 5002 [97]; and
5) forward the request based on the topmost Route header field.
NOTE 4: The P-User-Database header field can be included only if the I-CSCF can assume (e.g. based on local configuration) that the receiving S-CSCF will be able to process the header field.
Upon an unsuccessful user location query, the I-CSCF shall return an appropriate unsuccessful SIP response. This response may be a 404 (Not found) response or 604 (Does not exist anywhere) response in the case the user is not a user of the home network.
When the I-CSCF receives any response to the above request, and forwards it to AS, the I-CSCF shall:
- store the values from the P-Charging-Function-Addresses header field, if present. If the next hop is outside of the current network, then the I-CSCF shall remove the P-Charging-Function-Addresses header field prior to forwarding the message; and
- insert a P-Charging-Vector header field containing the type 3 "orig-ioi" header field parameter, if received in the request, and a type 3 "term-ioi" header field parameter in the response. The I-CSCF shall set the type 3 "term-ioi" header field parameter to a value that identifies the sending network of the response and the type 3 "orig-ioi" header field parameter is set to the previously received value of type 3 "orig-ioi" header field parameter.
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5.3.2.2 Abnormal cases
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In the case of SLF query, if the SLF does not send HSS address to the I-CSCF, the I-CSCF shall send back a 404 (Not Found) response to the UE.
Upon successful user location query, when the response contains the URI of the assigned S-CSCF, if the I‑CSCF is unable to contact the assigned S-CSCF, as determined by one of the following:
- the S-CSCF does not respond to the service request and its retransmissions by the I-CSCF; or
- by unspecified means available to the I-CSCF;
and:
- the I-CSCF supports S-CSCF restoration procedures;
then:
- the I-CSCF shall explicitly request the list of capabilities from the HSS and, on receiving these capabilities, the I-CSCF shall select a new S-CSCF, based on the capabilities indicated from the HSS. The newly selected S-CSCF shall not be one of any S-CSCFs selected previously during this same terminating procedure. Re-selection shall be performed until SIP transaction timer expires as specified in RFC 3261 [26]. When forwarding the request to the new S-CSCF, the I-CSCF includes the SIP URI parameter "scscf-reselection" to the Request-URI of the request.
NOTE 1: These procedures do not prevent the usage of unspecified reliability or recovery techniques above and beyond those specified in this subclause.
Upon successful user location query, when the response contains information about the required S-CSCF capabilities, if the I-CSCF is unable to contact a selected S-CSCF, as determined by one of the following:
- the S-CSCF does not respond to the service request and its retransmissions by the I-CSCF; or
- by unspecified means available to the I-CSCF;
then:
- the I-CSCF shall select a new S-CSCF, based on the capabilities indicated from the HSS. The newly selected S‑CSCF shall not be one of any S-CSCFs selected previously during this same terminating procedure. Re-selection shall be performed until SIP transaction timer expires as specified in RFC 3261 [26]. When forwarding the request to the new S-CSCF, the I-CSCF includes the SIP URI parameter "scscf-reselection" to the Request-URI of the request.
NOTE 2: These procedures do not prevent the usage of unspecified reliability or recovery techniques above and beyond those specified in this subclause.
If the I-CSCF receives a negative response to the user location query, the I-CSCF shall send back a 404 (Not Found) response.
If the I-CSCF receives a CANCEL request and if the I-CSCF finds an internal state indicating a pending Cx transaction with the HSS, the I-CSCF:
- shall answer the CANCEL request with a 200 (OK) response; and
- shall answer the original request with a 487 (Request Terminated) response.
NOTE 3: The I-CSCF will discard any later arriving (pending) Cx answer message from the HSS.
With the exception of 305 (Use Proxy) response, the I-CSCF may recurse on a 3xx response only when the domain part of the URI contained in the 3xx response is in the same domain as the I-CSCF. For the same cases, if the URI is an IP address, the I-CSCF shall only recurse if the IP address is known locally to be a address that represents the same domain as the I-CSCF.
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5.3.3 Void
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5.3.3.1 Void
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5.3.3.2 Void
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5.3.5 Subsequent requests
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When the I-CSCF receives a subsequent request, the I-CSCF shall verify whether it has arrived from an entity within the trust domain or not. If the request has not arrived from an entity within the trust domain, then the I-CSCF shall remove all P-Charging-Vector header fields, if present.
If no P-Charging-Vector header field was found in the received subsequent request, then insert the P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog.
When the I-CSCF receives any response to the subsequent request, the I-CSCF shall store the value of the "term-ioi" header field parameter received in the P-Charging-Vector header field, if present.
When the I-CSCF receives a subsequent request directly forwarded to the AS hosting the PSI, the I-CSCF shall insert a type 3 "orig-ioi" header field parameter in place of any received "orig-ioi" header field parameter, if the received request including a P-Charging-Vector header field. The I-CSCF shall set the type 3 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The I-CSCF shall not include the type 3 "term-ioi" header field parameter.
When the I-CSCF receives any response to the subsequent request from the AS hosting the PSI, if the received response containing a "term-ioi" header field parameter in the P-Charging-Vector header field, the I-CSCF shall:
1) remove all received "orig-ioi" and "term-ioi" header field parameters from the forwarded response;
2) insert the stored "orig-ioi" header field parameter if received in the request; and
3) insert a type 2 "term-ioi" header field parameter. The "term-ioi" header field parameter is set to a value that identifies the sending network of the response.
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5.4 Procedures at the S-CSCF
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5.4.0 General
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Where the S-CSCF provides emergency call support, the procedures of subclause 5.4.8 shall be applied first.
Upon
1) a third-party registration due to initial registration on behalf of a served public user identity; or
2) a trigger to an AS for an unregistered public user identity and there is no IP address of that AS associated with that public user identity stored;
the S-CSCF shall store the IP address of the AS and associate the IP address with the public user identity and the AS SIP URI along with all URI parameters.
When sending a failure response to any received request, depending on operator policy, the S-CSCF may insert a Response-Source header field with an "fe" header field parameter constructed with the URN namespace "urn:3gpp:fe", the fe-id part of the URN set to "s-cscf" and optionally an appropriate fe-param part of the URN set in accordance with subclause 7.2.17. A S-CSCF when sending a failure response will add in the URN the "side" header field parameter set to:
- "orig" for a UE-originating case; and
- "term" for a UE-terminating case.
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5.4.1 Registration and authentication
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5.4.1.1 Introduction
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The S-CSCF shall determine which authentication mechanism applies based on the contents of the REGISTER request and the authentication mechanism assigned in the HSS:
1) if the REGISTER request contains an Authorization header field with the "integrity-protected" header field parameter set to "no", the S-CSCF shall perform the initial registration procedures with IMS-AKA authentication described in subclauses 5.4.1.2.1 and 5.4.1.2.1A;
2) if the REGISTER request contains an Authorization header field with the "integrity-protected" header field parameter set to "yes", the S-CSCF shall perform the protected registration procedures with IMS-AKA as a security mechanism as described in subclause 5.4.1.2.2;
2A) if the REGISTER request contains an Authorization header field with the "integrity-protected" header field parameter set to "tls-connected" and with the "algorithm" header field parameter set to "AKAv2-SHA-256", and if the S-CSCF supports the IMS AKA using HTTP Digest AKAv2 without IPSec security association, the S-CSCF shall perform:
a) if the REGISTER request does not contain an authentication challenge response, the initial registration procedures for IMS-AKA authentication described in subclauses 5.4.1.2.1 and 5.4.1.2.1A; or
b) if the REGISTER request contains an authentication challenge response, the protected registration procedures with IMS-AKA as a security mechanism as described in subclause 5.4.1.2.2;
NOTE 1: 3GPP TS 33.203 [19] defines support of IMS AKA using http Digest AKAv2 without IPSec security association only for WebRTC.
3) if the REGISTER request does not contain an Authorization header field, then the S-CSCF shall identify the user by the public user identity as received in the To header field of the REGISTER request. The S-CSCF shall derive the private user identity from the public user identity being registered. The S-CSCF shall derive the private user identity by removing SIP URI scheme and the following parts of the SIP URI if present: port number, URI parameters, and To header field parameters or by alternative mechanisms to derive the private user identity if operator policy requires to do so. These alternative mechanisms are not defined in this version of the specification;
4) if the REGISTER request does not contain an Authorization header field and the access-type field in the P-Access-Network-Info header field indicated xDSL, Ethernet, or Fiber access, and containing the "network provided" header field parameter and the S-CSCF supports NASS-IMS-bundled authentication but does not support SIP digest, then the S-CSCF shall perform the initial registration procedures with NASS-IMS bundled authentication as a security mechanism as described in subclause 5.4.1.2.1D;
5) if the REGISTER request does not contain an Authorization header field and the access-type field in the P-Access-Network-Info header field indicates it is received from an IP-CAN different from 3GPP and containing the "network provided" header field parameter and the S-CSCF supports SIP digest but does not support NASS-IMS-bundled authentication, then the S-CSCF shall perform the initial registration procedures with SIP digest as a security mechanism as described in subclauses 5.4.1.2.1 and 5.4.1.2.1B;
6) if the REGISTER request does not contain an Authorization header field and there is no P-Access-Network-Info header field containing the "network provided" field or there is a P-Access-Network-Info header field indicating a 3GPP access network containing the "network provided", and the S-CSCF supports GPRS-IMS-Bundled authentication, the S-CSCF shall perform the initial registration procedures with GPRS-IMS-Bundled authentication described in subclause 5.4.1.2.1E;
7) if the REGISTER request does not contain an Authorization header field, and the P-Access-Network-Info header field indicates it is received from an access network other than 3GPP, xDSL, Ethernet or Fiber and containing the "network provided" header field parameter, and the S-CSCF supports SIP digest and NASS-IMS bundled authentication, the S-CSCF shall perform the initial registration procedures with SIP digest as a security mechanism as described in subclauses 5.4.1.2.1 and 5.4.1.2.1B:
8) if the REGISTER request does not contain an Authorization header field, and the P-Access-Network-Info header field indicates it is received from a xDSL, Ethernet or Fiber access network, and containing the "network provided" header field parameter, and the S-CSCF supports SIP digest and NASS-IMS bundled authentication, the S-CSCF sends an authentication request for the user to the HSS indicating that the authentication scheme is unknown as described in 3GPP TS 29.228 [14]:
- if the HSS responds with an authentication scheme of SIP digest, then the S-CSCF shall perform the initial registration procedures with SIP digest as a security mechanism as described in subclauses 5.4.1.2.1 and 5.4.1.2.1B; or
- if the HSS responds with an authentication scheme of NASS-IMS bundled authentication and the request was received from a P-CSCF in the home network and the P-CSCF is "TISPAN-enabled", then the S-CSCF shall perform the initial registration procedures with NASS-IMS bundled authentication as a security mechanism as described in subclause 5.4.1.2.1D;
9) if the REGISTER request contains an Authorization header field without an "integrity-protected" header field parameter, the S-CSCF shall send an authentication request for the user to the HSS indicating that the authentication scheme is unknown as described in 3GPP TS 29.228 [14]:
- if the HSS responds with an authentication scheme of NASS-IMS bundled authentication and the request was received from a P-CSCF is in the home network and the P-CSCF is "TISPAN-enabled", then the S-CSCF shall perform the initial registration procedures with NASS-IMS bundled authentication as a security mechanism as described in subclause 5.4.1.2.1D; or
- if the HSS responds with an authentication scheme of SIP digest, then the S-CSCF shall perform the initial registration procedures with SIP digest as a security mechanism as described in subclauses 5.4.1.2.1 and 5.4.1.2.1B;
10) if the REGISTER request contains an Authorization header field with the "integrity-protected" header field parameter set to "tls-pending", "tls-yes", "ip-assoc-pending" or "ip-assoc-yes", the S-CSCF shall perform the protected registration procedures for SIP digest described in subclause 5.4.1.2.2A;
11) if the REGISTER request contains an Authorization header field with the "integrity-protected" header field parameter set to "auth-done", the S-CSCF shall perform the protected registration procedures described in subclause 5.4.1.2.2E; and
12) if the REGISTER request contains a JSON Web Token with the "3gpp-waf" JSON Web Token claim or with the "3gpp-wwsf" JSON Web Token claim, as defined in RFC 7519 [235], and if the S-CSCF supports WebRTC, and if the S-CSCF has received authorization information about WAF or WWSF entities from the HSS, or per configuration, then the S-CSCF shall check whether the WAF or WWSF is not barred, as specified in 3GPP TS 33.203 [9] annex X. If the WAF or the WWSF is barred, the S-CSCF shall send a 403 (Forbidden) response to the REGISTER request.
NOTE 2: The S-CSCF needs to be configured to know which P-CSCFs are "TISPAN-enabled" and uses the Via header field to determine which P-CSCF forwarded the registration request.
The S-CSCF shall act as the SIP registrar for all UEs belonging to the IM CN subsystem and with public user identities.
Subclause 5.4.1.2 through subclause 5.4.1.7 define S-CSCF procedures for SIP registration that do not relate to emergency. All registration requests are first screened according to the procedures of subclause 5.4.8.2 to see if they do relate to an emergency registration.
For all SIP registrations identified:
- as relating to an emergency; or
- if priority is supported, as containing an authorised Resource-Priority header field;
the S-CSCF shall give priority over other registrations. This allows special treatment of such registrations.
NOTE 3: The special treatment can include filtering, higher priority processing, routeing, call gapping. The exact meaning of priority is not defined further in this document, but is left to national regulation and network configuration.
The S-CSCF shall support the use of the Path and Service-Route header field. The S-CSCF shall also support the Require and Supported header fields. The Path header field is only applicable to the REGISTER request and its 200 (OK) response. The Service-Route header field is only applicable to the 200 (OK) response of REGISTER. The S-CSCF shall not act as a redirect server for REGISTER requests.
The network operator defines minimum and maximum times for each registration. These values are provided within the S-CSCF.
The procedures for notification concerning automatically registered public user identities of a user are described in subclause 5.4.2.1.2.
If the S-CSCF supports HSS based P-CSCF restoration procedures, and receives a REGISTER request from a P-CSCF that the S-CSCF considers is in a non-working state, the S-CSCF shall consider this P-CSCF as being in a working state.
If the S-CSCF supports PCRF based P-CSCF restoration procedures, and receives a REGISTER request from a P-CSCF that the S-CSCF considers is in a non-working state, the S-CSCF shall consider this P-CSCF as being in a working state.
In case a device performing address and/or port number conversions is provided by a NA(P)T or NA(P)T-PT, the S-CSCF may need to modify the SIP signalling according to the procedures described in annex K if both a "reg-id" and "+sip.instance" header field parameter are present in the received Contact header field as described in RFC 5626 [92].
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5.4.1.2 Initial registration and user-initiated reregistration
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5.4.1.2.1 Unprotected REGISTER
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Any REGISTER request received unprotected by the S-CSCF without an Authorization header field, or with an Authorization header field having the "integrity-protected" header field parameter in the Authorization header field set to "no", or without an "integrity-protected" header field parameter is considered to be an initial registration. If such an initial registration contains a private user identity specifically reserved for IM CN subsystem registrations from an MSC Server enhanced for ICS as defined in 3GPP TS 23.003 [3], the S-CSCF shall respond with a 403 (Forbidden) response. The S‑CSCF shall consider this registration attempt as failed.
NOTE 1: For NASS-IMS bundled authentication and GPRS-IMS-Bundled Authentication there is no distinction between a protected and an unprotected REGISTER. There is only an unprotected REGISTER to consider.
NOTE 2: If IMS AKA or SIP digest with TLS are used as a security mechanism, a 200 (OK) final response to an initial registration will only be sent back after the S-CSCF receives a correct authentication challenge response in a REGISTER request that is sent integrity protected.
NOTE 3: A REGISTER with the registration expiration interval value equal to zero will always be received protected. However, it is possible that in error conditions a REGISTER with the registration expiration interval value equal to zero can be received unprotected. In that instance the procedures below will be applied.
Upon receipt of a REGISTER request that is part of an initial registration as outlined above, for a public user identity for which the maximum number of allowed simultaneously registration flows for the used UE (i.e. linked to the same private user identity and instance ID) is reached, if the REGISTER is adding a new registration flow, then the S-CSCF shall reject the REGISTER by generating a 403 (Forbidden) response. If not, the S-CSCF shall continue with the rest of the procedures of this subclause.
Upon receipt of a REGISTER request that is part of an initial registration as outlined above, for a user identity linked to a private user identity and instance ID/reg-id if available, that has previously registered one or more public user identities, the S-CSCF shall:
1) perform the procedure below in this subclause for receipt of a REGISTER request for a public user identity which is not already registered, for the received public user identity;
2) if the multiple registrations is not used and if the authentication that in step 1) has been successful, and there are public user identities (including the public user identity being registered, if previously registered) that belong to this user that have been previously registered with the same private user identity, and with an old contact address different from the one received in the REGISTER request, and the previous registrations have not expired, perform the network-initiated deregistration procedure (as described in subclause 5.4.1.5) for the previously registered public user identities belonging to this user including the public user identity being registered, if previously registered; and
3) if the multiple registrations is used (i.e., the "reg-id" header field parameter is included in the REGISTER request), and if the authentication that concludes the initial registration has been successful, and if the public user identity being registered has been previously registered with the same private user identity and the same "+sip.instance" and "reg-id" header field parameter values, and the previous registration has not expired:
a) identify the registration flow being replaced;
b) terminate any dialog, as specified in subclause 5.4.5.1.2, with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, associated with the registration flow being replaced; and
c) send a NOTIFY request to the subscribers to the registration event package for the public user identity indicated in the REGISTER request, as described in subclause 5.4.2.1.2.
NOTE 4: The way the S-CSCF identifies the dialogs associated with the registration flow being replaced is implementation specific.
NOTE 5: The S-CSCF will inform the HSS that the previously registered public user identities, excluding the public user identity being registered, have been deregistered.
NOTE 6: Contact related to emergency registration is not affected. S-CSCF is not able deregister contact related to emergency registration and will not delete that.
When S-CSCF receives a REGISTER request with the "integrity-protected" header field parameter in the Authorization header field set to "no" and a non-empty "response" Authorization header field parameter, the S-CSCF shall ignore the value of the "response" header field parameter.
Upon receipt of a REGISTER request that is part of an initial registration as outlined above, for a public user identity which is not already registered linked to the same private user identity and the "+sip.instance" and "reg-id" header field parameters, if available, the S-CSCF shall:
1) identify the user by the public user identity as received in the To header field and if the REGISTER request includes an Authorization header field, identify the private user identity as received in the "username" Authorization header field parameter of the REGISTER request;
2) check if the P-Visited-Network-ID header field is included in the REGISTER request, and if it is included identify the visited network by the value of this header field;
3) select an authentication vector for the user. If no authentication vector for this user is available, after the S-CSCF has performed the Authentication procedure with the HSS, as described in 3GPP TS 29.228 [14], the S-CSCF shall select an authentication vector as described in 3GPP TS 33.203 [19].
Prior to performing Authentication procedure with the HSS, the S-CSCF decides which HSS to query, possibly as a result of a query to the Subscription Locator Functional (SLF) entity as specified in 3GPP TS 29.228 [14] or use the value as received in the P-User-Database header field in the REGISTER request as defined in RFC 4457 [82];
NOTE 7: The HSS address received in the response to SLF query or as a value of P-User-Database header field can be used to address the HSS of the public user identity in further queries.
NOTE 8: At this point the S-CSCF informs the HSS, that the user currently registering will be served by the S-CSCF by passing its SIP URI to the HSS. This will be used by the HSS to direct all subsequent incoming initial requests for a dialog or standalone transactions destined for this user to this S-CSCF.
NOTE 9: When passing its SIP URI to the HSS, the S-CSCF may include in its SIP URI the transport protocol and the port number where it wants to be contacted.
4) store the "icid-value" header field parameter received in the P-Charging-Vector header field;
5) challenge the user by generating a 401 (Unauthorized) response for the received REGISTER request appropriate to the security mechanism in use;
6) send the so generated 401 (Unauthorized) response towards the UE, and if the URI in the first Path header field has an "ob" SIP URI parameter, include a Require header field with the option-tag "outbound" as described in RFC 5626 [92]; and
7) start timer reg-await-auth which guards the receipt of the next REGISTER request.
If the received REGISTER request indicates that the challenge sent previously by the S-CSCF to the UE was deemed to be invalid by the UE, the S-CSCF shall stop the timer reg-await-auth and proceed as described in the subclause 5.4.1.2.3.
5.4.1.2.1A Challenge with IMS AKA as security mechanism
On sending a 401 (Unauthorized) response to an unprotected REGISTER request, the S-CSCF shall populate the header fields as follows:
1) a WWW-Authenticate header field which transports:
a) a globally unique name of the S-CSCF in the "realm" header field parameter;
b) the RAND and AUTN parameters and optional server specific data for the UE in the "nonce" header field parameter;
c) if the REGISTER request contains an Authorization header field with an "integrity-protected" header field parameter set to the value "no":
- the security mechanism, in the "algorithm" header field parameter set to the value as received in the Authorization header field i.e. "AKAv2-SHA-256" or "AKAv1-MD5";
NOTE: The "AKAv1-MD5" algorithm is only supported for backward compatibility.
- the IK (Integrity Key) parameter for the P-CSCF in the "ik" header field parameter (see subclause 7.2A.1); and
- the CK (Cipher Key) parameter for the P-CSCF in the "ck" header field parameter (see subclause 7.2A.1); and
d) if the REGISTER request does contain an Authorization header field with the "algorithm" header field parameter set to "AKAv2-SHA-256", and if the S-CSCF supports the IMS AKA using HTTP Digest AKAv2 without IPSec security association:
- the security mechanism, which is "AKAv2-SHA-256" in the "algorithm" header field parameter.
The S-CSCF shall store the RAND parameter used in the 401 (Unathorized) response for future use in case of a resynchronisation. If a stored RAND already exists in the S-CSCF, the S-CSCF shall overwrite the stored RAND with the RAND used in the most recent 401 (Unauthorized) response.
5.4.1.2.1B Challenge with SIP digest as security mechanism
On sending a 401 (Unauthorized) response to an unprotected REGISTER request, the S-CSCF shall populate the header fields as follows:
1) for each supported digest algorithm the S-CSCF shall create a WWW-Authenticate header field as defined in RFC 7616 [286] and RFC 8760 [287], which transports:
- a protection domain in the "realm" header field parameter;
- a "nonce" header field parameter (generated by the S-CSCF);
- an "algorithm" header field parameter; and
- a "qop" header field parameter; if the qop value is not provided in the authentication vector, it shall contain the value "auth".
The S-CSCF shall include the WWW-Authenticate header fields to the 401 (Unauthorized) response in order of preference, starting with the most preferred algorithm.
5.4.1.2.1C Challenge with SIP digest with TLS as security mechanism
The procedures for subclause 5.4.1.2.1B apply.
NOTE: The S-CSCF is not able to distinguish between SIP Digest with TLS and SIP Digest without TLS for the case of an unprotected REGISTER request, therefore the procedures are the same for both.
5.4.1.2.1D Initial registration and user-initiated reregistration for NASS-IMS bundled authentication
Upon receipt of a REGISTER request that is determined to be NASS-IMS bundled authentication, for a user identity linked to a private user identity that has a registered public user identity but with a new contact address, the S-CSCF shall:
1) perform the procedure for receipt of a REGISTER request without the "integrity-protected" header field parameter in the Authorization header field or without the Authorization header field, for the received public user identity; and
2) if the Contact header field of the REGISTER request does not contain a "reg-id" header field parameter (i.e., the multiple registrations mechanism is not used), and the authentication has been successful, and there are public user identities (including the public user identity being registered, if previously registered) belonging to this user that have been previously registered with the same private user identity and with an old contact address different from the one received in the REGISTER request and if the previous registration have not expired:
a) terminate all dialogs, if any, associated with the previously registered public user identities (including the public user identity being registered, if previously registered), with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, as specified in subclause 5.4.5.1.2;
b) send a NOTIFY request, to the subscribers to the registration event package of the previously registered public user identities, that indicates that all previously registered public user identities (excluding the public user identity being registered) belonging to this user identified with its private user identity, have been deregistered, as described in subclause 5.4.2.1.2. For the public user identity being registered, the NOTIFY request contains the new contact information; and
NOTE 1: The last dialog to be terminated will be the dialog established by the UE subscribing to the reg event package. When sending the NOTIFY request to the UE over this dialog, the S-CSCF will terminate this dialog by setting in the NOTIFY request the Subscription-State header field to the value of "terminated".
c) delete all information associated with the previously registered public user identities.
NOTE 2: Contact related to emergency registration is not affected. The S-CSCF is not able to deregister contact related to emergency registration and will not delete it.
Upon receipt of a REGISTER request that is determined to be NASS-IMS bundled authentication, for a public user identity for which the maximum number of allowed simultaneously registration flows is for the used UE (i.e. linked to the same private user identity and instance ID) is reached, if the REGISTER is adding a new registration flow, then the S-CSCF shall reject the REGISTER by generating a 403 (Forbidden) response. If not, the S-CSCF shall continue with the rest of the procedures of this subclause;
Upon receipt of a REGISTER request without the "integrity-protected" header field parameter in the Authorization header field or without an Authorization header field, which is not for an already registered public user identity linked to the same private user identity, the S-CSCF shall:
1) identify the user by the public user identity as received in the To header field of the REGISTER request and if the Authorization header field is present, the private user identity as received in the Authorization header field of the REGISTER request. If the Authorization header field is not present, the S-CSCF shall derive the private user identity from the public user identity being registered by removing SIP URI scheme and the following parts of the SIP URI if present: port number, URI parameters, and To header field parameters;
2) check whether one or more Line-Identifiers previously received over the Cx interface, and stored as a result of a Authentication procedure with the HSS, are available for the user. If not, the S-CSCF performs the Authentication procedure with the HSS, as described in 3GPP TS 29.228 [14], in order to obtain these Line-Identifiers;
3) in the particular case where the S-CSCF received via the Cx interface one or more Line-Identifiers, compare each of Line-Identifiers with the "dsl-location", "eth-location" or "fiber-location" parameter of the P-Access-Network-Info header field (if present and if it includes the "network-provided" parameter):
- if one of these match, the user is considered authenticated, behave as described in step 5) to 11) of subclause 5.4.1.2.2;
- otherwise i.e. if these do not match, return a 403 (Forbidden) response to the REGISTER request; and
4) if no Line-Identifier is received over the Cx interface, send a 500 (Server Internal Error) response to the REGISTER request.
Upon receipt of a REGISTER request without the "integrity-protected" header field parameter in the Authorization header field or without an Authorization header field, for an already registered public user identity linked to the same private user identity, and for existing contact information, the S-CSCF shall behave as described in subclause 5.4.1.2.2F.
5.4.1.2.1E Initial registration and user-initiated reregistration for GPRS-IMS-Bundled authentication
Upon receipt of a REGISTER request without an Authorization header field, the S-CSCF shall:
1) identify the user by the public user identity as received in the To header field of the REGISTER request. The S-CSCF shall derive the private user identity from the public user identity being registered by removing URI scheme and the following parts of the URI if present: port number, URI parameters, and To header field parameters;
1A) if the maximum number of simultaneously registration flows allowed for the related public user identity for the used UE (i.e. linked to the same private user identity and instance ID) is reached, then the S-CSCF shall reject the REGISTER by generating a 403 (Forbidden) response. If not, the S-CSCF shall continue with the rest of the steps;
2) check if the P-Visited-Network-ID header field is included in the REGISTER request, and if it is included identify the visited network by the value of this header field;
3) check whether an IP address is stored for this UE. If no IP address (or prefix) is stored for the UE, query the HSS as described in 3GPP TS 29.228 [14] with the derived private user identity and the public user identity as input and store the received IP address (or prefix) of the UE; if the S-CSCF receives a prefix from the HSS, it will only check against prefixes otherwise it will check against the full IP address;
NOTE 1: At this point the S-CSCF informs the HSS, that the user currently registering will be served by the S‑CSCF by passing its SIP URI to the HSS. This will be indicated by the HSS for all further incoming requests to this user, in order to direct all these requests directly to this S-CSCF.
4) check whether a "received" header field parameter exists in the Via header field provided by the UE. If a "received" header field parameter exists, the S-CSCF shall compare the IP address recorded in the "received" header field parameter against the UE's IP address stored during registration. In case of IPv6 stateless autoconfiguration, the S-CSCF shall compare the prefix of the IP address recorded in the "received" header field parameter against the UE's IP address prefix stored during registration. If no "received" header field parameter exists in the Via header field provided by the UE, then the S-CSCF shall compare IP address recorded in the "sent-by" parameter against the stored UE IP address. In case of IPv6 stateless autoconfiguration, S-CSCF shall compare the prefix of the IP address recorded in the "sent-by" parameter against the UE's IP address prefix stored during registration. In any case, if the stored IP address (or prefix) and the (prefix of the) IP address recorded in the Via header field provided by the UE do not match, the S‑CSCF shall query the HSS as described in 3GPP TS 29.228 [14] with the derived private user identity and the public user identity as input and store the received IP address (or prefix) of the UE. If the stored IP address (or prefix) and the (prefix of the) IP address recorded in the Via header field provided by the UE still do not match the S-CSCF shall reject the registration with a 403 (Forbidden) response and skip the following steps;
5) after performing the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], store the following information in the local data:
a) the list of public user identities, including the registered own public user identity and its associated set of implicitly registered public user identities and wildcarded public user identities due to the received REGISTER request. Each public user identity is identified as either barred or non-barred;
b) all the service profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including initial Filter Criteria (the initial Filter Criteria for the Registered and common parts is stored and the unregisterd part is retained for possible use later - in the case the S-CSCF is retained if the user becomes unregistered);
c) if S-CSCF restoration procedures are supported, the restoration information if received as specified in 3GPP TS 29.228 [14]; and
d) if PCRF based P-CSCF restoration procedures are supported, all the user profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including the IMSI, if available;
NOTE 2: There might be more than one set of initial Filter Criteria received because some implicitly registered public user identities that are part of the same implicit registration set belong to different service profiles.
6) update registration bindings as follows:
a) bind to each non-barred registered public user identity all registered contact information including all header field parameters contained in the Contact header field and all associated URI parameters with the exception of the "pub-gruu" and "temp-gruu" header field parameters as specified in RFC 5627 [93], and store information for future use; and
b) if the Contact URI in the Contact header field does not contain a "bnc" URI parameter, then for each binding that contains a "+sip.instance" Contact header field parameter, assign a new temporary GRUU, as specified in subclause 5.4.7A.3;
NOTE 3: There might be more than one contact information available for one public user identity.
NOTE 4: The barred public user identities are not bound to the contact information.
7) check whether a Path header field was included in the REGISTER request and construct a list of preloaded Route header fields from the list of entries in the received Path header field. The S-CSCF shall preserve the order of the preloaded Route header fields and bind them either to the contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used) and the contact information that was received in the REGISTER request;
NOTE 5: If this registration is a reregistration or an initial registration (i.e., there are previously registered public user identities belonging to the user that have not been deregistered or expired), then a list of pre-loaded Route header fields will already exist. If multiple registration mechanism was not used, then the existing list of pre-loaded Route header fields is bound to a respective contact address of the UE. However, if multiple registration mechanism was used, then the existing list of pre-loaded Route header fields is bound to a registration flow and the associated contact address that was used to send the REGISTER request. In either case, the new list replaces the old list.
8) determine the duration of the registration by checking the registration expiration interval value in the received REGISTER request and bind it either to the respective contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used). Based on local policy, the S-CSCF may reduce the duration of the registration or send back a 423 (Interval Too Brief) response specifying the minimum allowed time for registration. The local policy can take into account specific criteria such as the used authentication mechanism to determine the allowed registration duration;
9) store the "icid-value" header field parameter received in the P-Charging-Vector header field;
9A) if an "orig-ioi" header field parameter is received in the P-Charging-Vector header field, store the value of the received "orig-ioi" header field parameter; and
NOTE 6: Any received "orig-ioi" header field parameter will be a type 1 IOI. The type 1 IOI identifies the network from which the request was sent.
10) create and send a 200 (OK) response for the REGISTER request as specified in subclause 5.4.1.2.2F.
When a user de-registers, or is de-registered by the HSS, the S-CSCF shall delete the IP address stored for the UE.
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5.4.1.2.2 Protected REGISTER with IMS AKA as a security mechanism
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Upon receipt of a REGISTER request with the "integrity-protected" header field parameter in the Authorization header field set to "yes" or to "tls-connected", the S-CSCF shall identify the user by the public user identity as received in the To header field and the private user identity as received in the Authorization header field of the REGISTER request, and:
If the maximum number of simultaneously registration flows allowed for the related public user identity for the used UE (i.e. linked to the same private user identity and instance ID) is reached, then the S-CSCF shall reject the REGISTER by generating a 403 (Forbidden) response. If not, the S-CSCF shall continue with rest of the procedures of this subclause;
In the case that there is no authentication currently ongoing for this user (i.e. no timer reg-await-auth is running):
1) check if the user needs to be re-authenticated.
The S-CSCF may require authentication of the user for any REGISTER request, and shall always require authentication for REGISTER requests received without the "integrity-protected" header field parameter in the Authorization header field set to "yes" or "tls-connected".
If the user needs to be re-authenticated, the S-CSCF shall proceed with the procedures as described for the unprotected REGISTER in subclause 5.4.1.2.1, beginning with step 3). If the user does not need to be re-authenticated, the S-CSCF shall proceed with the following steps in this paragraph; and
2) check whether a registration expiration interval value is included in the REGISTER request and its value. If the registration expiration interval value indicates a zero value, the S-CSCF shall perform the deregistration procedures as described in subclause 5.4.1.4. If the registration expiration interval value does not indicate zero, the S-CSCF:
- if the REGISTER request does not contain a "reg-id" header field parameter and the contact address indicated in the Contact header field was not previously registered, send a 403 (Forbidden) response to the UE; and
NOTE 1: New contact address is always registered via an initial registration.
3) check whether the public user identity received in the To header field is already registered. If it is not registered, the S-CSCF shall proceed beginning with step 4B below. Otherwise, the S-CSCF shall:
- send a 439 (First Hop Lacks Outbound Support) response to the UE, if the REGISTER request contains the "reg-id" Contact header field parameter and the "outbound" option tag in a Supported header field, but the first URI in the Path header field does not have an "ob" URI parameter; or
- otherwise proceed beginning with step 6 below.
In the case that a timer reg-await-auth is running for this user the S-CSCF shall:
1) check if the Call-ID of the request matches with the Call-ID of the 401 (Unauthorized) response which carried the last challenge. The S-CSCF shall only proceed further if the Call-IDs match;
2) stop timer reg-await-auth;
3) check whether an Authorization header field is included, containing:
a) the private user identity of the user in the "username" header field parameter;
b) if the "integrity-protected" header field parameter is set to "yes", the "algorithm" header field parameter set to "AKAv2-SHA-256" or "AKAv1-MD5";
c) if the "integrity-protected" header field parameter is set to "tls-connected", the "algorithm" header field parameter set to "AKAv2-SHA-256" if the S-CSCF supports the IMS AKA using HTTP Digest AKAv2 without IPSec security association; and
d) the authentication challenge response needed for the authentication procedure in the "response" header field parameter.
The S-CSCF shall only proceed with the following steps in this paragraph if the authentication challenge response was included;
4) check whether the received authentication challenge response and the expected authentication challenge response (calculated by the S-CSCF using XRES and other parameters as described in RFC 3310 [49] when AKAv1 is used or as described in RFC 4169 [227] when AKAv2 is used) match. The XRES parameter was received from the HSS as part of the Authentication Vector. The S-CSCF shall only proceed with the following steps if the challenge response received from the UE and the expected response calculated by the S-CSCF match;
4A) if the Contact header field of the REGISTER request does not contain a "reg-id" header field parameter (i.e., the multiple registrations mechanism is not used), and there are public user identities (including the public user identity being registered, if previously registered) that belong to this user that have been previously registered with the same private user identity, and with an old contact address different from the one received in the REGISTER request and if the previous registrations have not expired:
a) terminate all dialogs, associated with the previously registered public user identities (including the public user identity being registered, if previously registered), with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, as specified in subclause 5.4.5.1.2;
b) send a NOTIFY request, to the subscribers to the registration event package of the previously registered public user identities, that indicates that all previously registered public user identities (excluding the public user identity being registered) belonging to this user identified with its private user identity, have been deregistered, as described in subclause 5.4.2.1.2. For the public user identity being registered, the NOTIFY request contains the new contact information; and
NOTE 2: The last dialog to be terminated will be the dialog established by the UE subscribing to the reg event package. When sending the NOTIFY request to the UE over this dialog, the S-CSCF will terminate this dialog by setting in the NOTIFY request the Subscription-State header field to the value of "terminated".
c) delete all information associated with the previously registered public user identities;
NOTE 3: Contact related to emergency registration is not affected. The S-CSCF is not able to deregister contact related to emergency registration and will not delete it.
4B) if the REGISTER request contains the "reg-id" Contact header field parameter and the "outbound" option tag in a Supported header field, but the first URI in the Path header field does not have an "ob" URI parameter, send a 439 (First Hop Lacks Outbound Support) response to the UE;
5) after performing the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], store the following information in the local data:
a) the list of public user identities, including the registered own public user identity and its associated set of implicitly registered public user identities and wildcarded public user identities due to the received REGISTER request. Each public user identity is identified as either barred or non-barred;
b) all the service profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including initial Filter Criteria(the initial Filter Criteria for the Registered and common parts is stored and the unregistered part is retained for possible use later - in the case of the S-CSCF is retained if the user becomes unregistered);
c) if S-CSCF restoration procedures are supported, the restoration information if received as specified in 3GPP TS 29.228 [14]; and
d) if PCRF based P-CSCF restoration procedures are supported, all the user profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including the IMSI, if available;
NOTE 4: There might be more than one set of initial Filter Criteria received because some implicitly registered public user identities that are part of the same implicit registration set belong to different service profiles.
6) update registration bindings:
a) if the Contact URI in the Contact header field does not contains a "bnc" URI parameter, then bind to each non-barred registered public user identity all registered contact information including all header field parameters contained in the Contact header field and all associated SIP URI parameters, with the exception of the "pub-gruu" and "temp-gruu" header field parameters as specified in RFC 5627 [93], and store information for future use;
b) if the Contact URI in the Contact header field contains a "bnc" URI parameter, as a network option bind each non-barred registered public user identity to a contact address generated according to the procedures of RFC 6140 [191].
NOTE 5: It is assumed that when the Contact header field contains a "bnc" parameter, the associated public user identities obtained from the HSS are all of a form compatible with registration procedures as specified in RFC 6140 [191]; i.e. the set consists only of distinct public user identities contain global numbers in the international format or wildcarded public user identities representing multiple global numbers in the international format. The S-CSCF procedures for handling the error case where an associated public user identity is incompatible with RFC 6140 [191] is out of scope of this specification.
c) if the Contact URI in the Contact header field does not contain a "bnc" URI parameter, then for each binding that contains a "+sip.instance" Contact header field parameter, assign a new temporary GRUU, as specified in subclause 5.4.7A.3;
d) if the Contact header field of the REGISTER request contained a "+sip.instance" and a "reg-id" header field parameter, and the SIP URI in the Path header field inserted by the P-CSCF contained an "ob" SIP URI parameter header field, and:
- if the public user identity has not previously been registered with the same "+sip.instance" and "reg-id" Contact header field parameter values, then create the registration flow in addition to any existing registration flow; or
- if the public user identity has previously been registered with the same "+sip.instance" and "reg-id" header field parameter values, then determine whether the request refreshes or replaces an existing registration flow. If the request:
i) refreshes an existing registration flow, then the S-CSCF shall leave the flow intact; or
ii) replaces the existing registration flow with a new flow, then the S-CSCF shall:
a) terminate any dialog, as specified in subclause 5.4.5.1.2, with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, associated with the registration flow being replaced; and
b) send a NOTIFY request to the subscribers to the registration event package for the public user identity indicated in the REGISTER request, as described in subclause 5.4.2.1.2;
NOTE 6: The S-CSCF determines whether this REGISTER request replaces or refreshes an existing registration flow by examining the SIP URI in the Path header field inserted into the request by the P-CSCF (see subclause 5.2.2.1).
NOTE 7: The way the S-CSCF identifies the dialogs associated with the registration flow being replaced is implementation specific.
NOTE 8: There might be more than one contact information available for one public user identity.
NOTE 9: The barred public user identities are not bound to the contact information.
NOTE 10: Contact related to emergency registration is not affected. S-CSCF is not able deregister contact related to emergency registration and will not delete that.
7) check whether a Path header field was included in the REGISTER request and construct a list of preloaded Route header fields from the list of entries in the received Path header field. The S-CSCF shall preserve the order of the preloaded Route header fields and bind them either to the contact address of the UE or the registration flow and the associated contact address (if the multiple registration mechanism is used) and the contact information that was received in the REGISTER request;
NOTE 11: If this registration is a reregistration or an initial registration (i.e., there are previously registered public user identities belonging to the user that have not been deregistered or expired), then a list of pre-loaded Route header fields will already exist. If multiple registration mechanism was not used, then the existing list of pre-loaded Route header fields is bound to a respective contact address of the UE. However, if multiple registration mechanism was used, then the existing list of pre-loaded Route header fields is bound to a registration flow and the associated contact address that was used to send the REGISTER request. In either case, the new list replaces the old list.
8) determine the duration of the registration by checking the value of the registration expiration interval value in the received REGISTER request and bind it either to the respective contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used). Based on local policy, the S-CSCF may reduce the duration of the registration or send back a 423 (Interval Too Brief) response specifying the minimum allowed time for registration. The local policy can take into account specific criteria such as the used authentication mechanism to determine the allowed registration duration;
9) store the "icid-value" header field parameter received in the P-Charging-Vector header field;
10) if an "orig-ioi" header field parameter is received in the P-Charging-Vector header field, store the value of the received "orig-ioi" header field parameter; and
NOTE 12: Any received "orig-ioi" header field parameter will be a type 1 IOI. The type 1 IOI identifies the network from which the request was sent.
11) create and send a 200 (OK) response for the REGISTER request as specified in subclause 5.4.1.2.2F.
5.4.1.2.2A Protected REGISTER with SIP digest as a security mechanism
Upon receipt of a REGISTER request with the "integrity-protected" header field parameter in the Authorization header field set to "tls-pending", "tls-yes", "ip-assoc-pending", or "ip-assoc-yes", the S-CSCF shall identify the user by the public user identity as received in the To header field and the private user identity as received in the Authorization header field of the REGISTER request, and:
NOTE 1: Although the REGISTER request with the "integrity-protected" header field parameter set to "ip-assoc-pending" or "ip-assoc-yes" is handled as protected REGISTER request, the integrity of the request is actually not protected by SIP digest.
If the maximum number of simultaneously registration flows allowed for the related public user identity for the used UE (i.e. linked to the same private user identity and instance ID) is reached, then the S-CSCF shall reject the REGISTER by generating a 403 (Forbidden) response. If not, the S-CSCF shall continue with rest of the procedures of this subclause;
In the case that there is no authentication currently ongoing for this user (i.e. no timer reg-await-auth is running):
1) check if the user needs to be re-authenticated. The S-CSCF may require authentication of the user for any REGISTER request, and shall always require authentication for REGISTER requests received without the "integrity-protected" header field parameter in the Authorization header field set to "tls-yes".
If the user needs to be re-authenticated and the REGISTER did not include an Authorization header field with a digest response, the S-CSCF shall proceed with the authentication procedures as described for the initial REGISTER in subclause 5.4.1.2.1 and subclause 5.4.1.2.1B.
If the user needs to be re-authenticated and the REGISTER included an Authorization header field with a digest response, the S-CSCF shall proceed with the authentication procedures as described for the initial REGISTER in subclause 5.4.1.2.1 and subclause 5.4.1.2.1B and include the "stale" header field parameter with value "true" in the WWW-Authenticate header field.
In the case that a timer reg-await-auth is running for this user the S-CSCF shall:
1) check if the Call-ID of the request matches with the Call-ID of the 401 (Unauthorized) response which carried the last challenge. The S-CSCF shall only proceed further if the Call-IDs match;
2) stop timer reg-await-auth;
3) in the case the algorithm is "SHA-256", "SHA-512-256" or "MD5", check the following additional fields:
NOTE 2: The MD5 algorithm is only supported for backward compatibility.
- a "realm" header field parameter matching the "realm" header field parameter in the authentication challenge;
- an "algorithm" header field parameter which matches the "algorithm" header field parameter sent in the authentication challenge;
- "nonce" header field parameter matching the "nonce" header field parameter in the authentication challenge;
- a "cnonce" header field parameter; and
- a "nc" header field parameter.
The S-CSCF shall only proceed with the following steps in this paragraph if the authentication challenge response was included;
4) check whether the received authentication challenge response and the expected authentication challenge response match. The expected response is calculated by the S-CSCF as described in RFC 7616 [286] and RFC 8760 [287] using the H(A1) value provided by the HSS. If the received authentication challenge response and the expected authentication challenge response match, then the UE is considered authenticated. If the UE is considered authenticated, and if the "integrity-protected" header field parameter in the Authorization header field is set to the value "tls-pending" or "tls-yes", then the S-CSCF shall associate the registration with the local state of "tls-protected";
NOTE 3: The S-CSCF can have a local security policy to treat messages other than initial REGISTER requests, messages relating to emergency services, and error messages, differently depending on whether the registration is associated with the state "tls-protected".
4A) if the REGISTER request contains the "reg-id" Contact header field parameter and the "outbound" option tag in a Supported header field, but the first URI in the Path header does not have an "ob" URI parameter, send a 439 (First Hop Lacks Outbound Support) response to the UE;
5) after performing the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], store the following information in the local data:
a) the list of public user identities, including the registered own public user identity and its associated set of implicitly registered public user identities and wildcarded public user identities due to the received REGISTER request. Each public user identity is identified as either barred or non-barred;
b) all the service profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including initial Filter Criteria(the initial Filter Criteria for the Registered and common parts is stored and the unregistered part is retained for possible use later - in the case of the S-CSCF is retained if the user becomes unregistered);
c) if S-CSCF restoration procedures are supported, the restoration information, if received, as specified in 3GPP TS 29.228 [14]; and
d) if PCRF based P-CSCF restoration procedures are supported, all the user profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including the IMSI, if available;
NOTE 4: There might be more than one set of initial Filter Criteria received because some implicitly registered public user identities that are part of the same implicit registration set belong to different service profiles.
6) update registration bindings:
a) if the Contact URI in the Contact header field does not contains a "bnc" URI parameter, then bind to each non-barred registered public user identity all registered contact information including all header field parameters contained in the Contact header field and all associated URI parameters, with the exception of the "pub-gruu" and "temp-gruu" header field parameters as specified in RFC 5627 [93], and store information for future use;
b) if the Contact URI in the Contact header field contains a "bnc" URI parameter, as a network option bind each non-barred registered public user identity to a contact address as specified in RFC 6140 [191].
NOTE 5: It is assumed that when the Contact header field contains a "bnc" parameter, the associated public user identities obtained from the HSS are all of a form compatible with registration procedures as specified in RFC 6140 [191]; i.e. the set consists only of distinct public user identities contain global numbers in the international format or wildcarded public user identities representing multiple global numbers in the international format. The S-CSCF procedures for handling the error case where an associated public user identity is incompatible with RFC 6140 [191] is out of scope of this specification.
c) if the Contact URI in the Contact header field does not contain a "bnc" URI parameter, then for each binding that contains a "+sip.instance" Contact header field parameter, assign a new temporary GRUU, as specified in subclause 5.4.7A.3;
d) if the Contact header field of the REGISTER request does not contain a "reg-id" header field parameter (i.e., the multiple registrations mechanism is not used), and there are public user identities (including the public user identity being registered, if previously registered) that belong to this user that have been previously registered with the same private user identity, and with an old contact address different from the one received in the REGISTER request and if the previous registrations have not expired:
- terminate all dialogs, associated with the previously registered public user identities (including the public user identity being registered, if previously registered), with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, as specified in subclause 5.4.5.1.2;
- send a NOTIFY request, to the subscribers to the registration event package of the previously registered public user identities, that indicates that all previously registered public user identities (excluding the public user identity being registered) belonging to this user identified with its private user identity, have been deregistered, as described in subclause 5.4.2.1.2. For the public user identity being registered, the NOTIFY request contains the new contact information; and
NOTE 6: The last dialog to be terminated will be the dialog established by the UE subscribing to the reg event package. When sending the NOTIFY request to the UE over this dialog, the S-CSCF will terminate this dialog by setting in the NOTIFY request the Subscription-State header field to the value of "terminated".
- delete all information associated with the previously registered public user identities;
NOTE 7: Contact related to emergency registration is not affected. The S-CSCF is not able to deregister contact related to emergency registration and will not delete it.
e) if the Contact header field of the REGISTER request contained a "+sip.instance" and a "reg-id" header field parameter, and the SIP URI in the Path header field inserted by the P-CSCF contained an "ob" SIP URI parameter header field, and:
- if the public user identity has not previously been registered with the same "+sip.instance" and "reg-id" Contact header field parameter values, then create the registration flow in addition to any existing registration flow; or
- if the public user identity has previously been registered with the same "+sip.instance" and "reg-id" header field parameter values, then determine whether the request refreshes or replaces an existing registration flow. If the request:
i) refreshes an existing registration flow, then the S-CSCF shall leave the flow intact; or
ii) replaces the existing registration flow with a new flow, then the S-CSCF shall:
a) terminate any dialog, as specified in subclause 5.4.5.1.2, with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, associated with the registration flow being replaced; and
b) send a NOTIFY request to the subscribers to the registration event package for the public user identity indicated in the REGISTER request, as described in subclause 5.4.2.1.2; and
f) store the used nonce as a valid nonce for this registration or registration flow (if multiple registration mechanism is used) for an operator configured duration.
NOTE 8: The S-CSCF determines whether this REGISTER request replaces or refreshes an existing registration flow by examining the SIP URI in the Path header field inserted into the request by the P-CSCF (see subclause 5.2.2.1).
NOTE 9: The way the S-CSCF identifies the dialogs associated with the registration flow being replaced is implementation specific.
NOTE 10: There might be more than one contact information available for one public user identity.
NOTE 11: The barred public user identities are not bound to the contact information.
NOTE 12: Contact related to emergency registration is not affected. S-CSCF is not able deregister contact related to emergency registration and will not delete that.
7) check whether a Path header field was included in the REGISTER request and construct a list of preloaded Route header fields from the list of entries in the received Path header field. The S-CSCF shall preserve the order of the preloaded Route header fields and bind them to either the contact address of the UE or the registration flow and the associated contact address (if the multiple registration mechanism is used) and contact information that was received in the REGISTER request;
NOTE 13: If this registration is a reregistration or an initial registration (i.e., there are previously registered public user identities belonging to the user that have not been deregistered or expired), then a list of pre-loaded Route header fields will already exist. If multiple registration mechanism was not used, then the existing list of pre-loaded Route header fields is bound to a respective contact address of the UE. However, if multiple registration mechanism was used, then the existing list of pre-loaded Route header fields is bound to a registration flow and the associated contact address that was used to send the REGISTER request. In either case, the new list replaces the old list.
8) determine the duration of the registration by checking the value of the registration expiration interval value in the received REGISTER request and bind it either to the respective contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used). Based on local policy, the S-CSCF may reduce the duration of the registration or send back a 423 (Interval Too Brief) response specifying the minimum allowed time for registration. The local policy can take into account specific criteria such as the used authentication mechanism to determine the allowed registration duration;
9) store the "icid-value" header field parameter received in the P-Charging-Vector header field;
10) if an "orig-ioi" header field parameter is received in the P-Charging-Vector header field, store the value of the received "orig-ioi" header field parameter; and
NOTE 14: Any received "orig-ioi" header field parameter will be a type 1 IOI. The type 1 IOI identifies the network from which the request was sent.
11) create and send a 200 (OK) response for the REGISTER request as specified in subclause 5.4.1.2.2F. The S-CSCF shall also store the nonce-count value in the received REGISTER request and include an Authentication-Info header field containing the fields described in RFC 7616 [286] and RFC 8760 [287] as follows:
- a "nextnonce" header field parameter if the S-CSCF requires a new nonce for subsequent authentication responses from the UE. In that case, the S-CSCF shall consider this nonce as a valid nonce for this registration or registration flow (if multiple registration mechanism is used) for an operator configured duration;
- a "qop" header field parameter matching the "qop" Authorization header field parameter sent by the UE;
- a "rspauth" header field parameter with a response-digest calculated as described in RFC 7616 [286] and RFC 8760 [287];
- a "cnonce" header field parameter matching the "cnonce" Authorization header field parameter sent by the UE; and
- a "nc" header field parameter matching the "nc" Authorization header field parameter sent by the UE.
5.4.1.2.2B Protected REGISTER with SIP digest with TLS as a security mechanism
The procedures for subclause 5.4.1.2.2A apply.
5.4.1.2.2C NASS-IMS bundled authentication as a security mechanism
There is no protected REGISTER when NASS-IMS bundled authentication is used as a security mechanism. The procedures of subclause 5.4.1.2.1D apply to all REGISTER requests.
5.4.1.2.2D GPRS-IMS-Bundled authentication as a security mechanism
There is no protected REGISTER when GPRS-IMS-Bundled authentication is used as a security mechanism. The procedures of subclause 5.4.1.2.1E apply to all REGISTER requests.
5.4.1.2.2E Protected REGISTER – Authentication already performed
The S-CSCF shall not perform authentication of the user for any REGISTER request with the "integrity-protected" header field parameter in the Authorization header set to "auth-done".
In this release of this document, when the registration procedure as specified in this subclause is performed, i.e., the REGISTER request contains the "integrity-protected" header field parameter in the Authorization header set to "auth-done", the S-CSCF shall not employ outbound registration as described in RFC 5626 [92].
Upon receipt of a REGISTER request with the "integrity-protected" header field parameter in the Authorization header set to "auth-done", the S-CSCF shall identify the user by the public user identity as received in the To header field and the private user identity as received in the Authorization header field of the REGISTER request.
In addition the S-CSCF shall check whether a registration expiration interval value is included in the REGISTER request and its value. If the registration expiration interval value indicates a zero value, the S-CSCF shall perform the deregistration procedures as described in subclause 5.4.1.4. If the registration expiration interval value does not indicate zero, the S-CSCF shall:
1) if the REGISTER request contains the "reg-id" header field parameter in the Contact header field, respond with a 403 (Forbidden) response to the REGISTER request; and
2) if there are public user identities (including the public user identity being registered, if previously registered) that belong to this user that have been previously registered with the same private user identity, and with an old contact address different from the one received in the REGISTER request and if the previous registrations have not expired:
a) terminate all dialogs, associated with the previously registered public user identities (including the public user identity being registered, if previously registered), with a status code 480 (Temporarily Unavailable) in the Reason header field of the BYE request, as specified in subclause 5.4.5.1.2;
b) send a NOTIFY request, to the subscribers to the registration event package of the previously registered public user identities, that indicates that all previously registered public user identities (excluding the public user identity being registered) belonging to this user identified with its private user identity, have been deregistered, as described in subclause 5.4.2.1.2. For the public user identity being registered, the NOTIFY request contains the new contact information; and
NOTE 1: The last dialog to be terminated will be the dialog established by the user (identified with its private user identity) subscribing to its own reg event package using the old contact address. When sending the NOTIFY request over this dialog, the S-CSCF will terminate this dialog by setting in the NOTIFY request the Subscription-State header field to the value of "terminated".
c) delete all information associated with the previously registered public user identities;
Subsequently, the S-CSCF shall check whether the public user identity received in the To header field is already registered. If it is not registered, the S-CSCF shall proceed beginning with step 1 below. Otherwise, the S-CSCF shall proceed beginning with step 2 below.
1) after performing the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], store the following information in the local data:
a) the list of public user identities, including the registered own public user identity and its associated set of implicitly registered public user identities and wildcarded public user identities due to the received REGISTER request. Each public user identity is identified as either barred or non-barred;
b) all the service profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including initial Filter Criteria(the initial Filter Criteria for the Registered and common parts is stored and the unregistered part is retained for possible use later - in the case of the S-CSCF is retained if the user becomes unregistered); and
c) if PCRF based P-CSCF restoration procedures are supported, all the user profile(s) corresponding to the public user identities being registered (explicitly or implicitly), including the IMSI, if available;
NOTE 2: There might be more than one set of initial Filter Criteria received because some implicitly registered public user identities that are part of the same implicit registration set belong to different service profiles.
2) update registration bindings:
a) if the Contact URI in the Contact header field does not contains a "bnc" URI parameter, then bind to each non-barred registered public user identity all registered contact information including all header parameters contained in the Contact header and all associated URI parameters, with the exception of the URI "pub-gruu" and "temp-gruu" parameters as specified in RFC 5627 [93], and store information for future use;
b) if the Contact URI in the Contact header field contains a "bnc" URI parameter, as a network option bind each non-barred registered public user identity to a contact address as specified in RFC 6140 [191].
NOTE 3: It is assumed that when the Contact header field contains a "bnc" parameter, the associated public user identities obtained from the HSS are all of a form compatible with registration procedures as specified in RFC 6140 [191]; i.e. the set consists only of distinct public user identities contain global numbers in the international format or wildcarded public user identities representing multiple global numbers in the international format. The S-CSCF procedures for handling the error case where an associated public user identity is incompatible with RFC 6140 [191] is out of scope of this specification.
c) if the Contact URI in the Contact header field does not contain a "bnc" URI parameter, then for each binding that contains a "+sip.instance" header field parameter, assign a new temporary GRUU, as specified in subclause 5.4.7A.3.
NOTE 4: There might be more than one contact information available for one public user identity.
NOTE 5: The barred public user identities are not bound to the contact information.
3) check whether a Path header was included in the REGISTER request and construct a list of preloaded Route headers from the list of entries in the received Path header field. The S-CSCF shall preserve the order of the preloaded Route header fields and bind them to the contact information that was received in the REGISTER request;
NOTE 6: If this registration is a reregistration or an initial registration (i.e., there are previously registered public user identities belonging to the user that have not been deregistered or expired), then a list of pre-loaded Route headers will already exist. The new list replaces the old list.
4) determine the duration of the registration by checking the value of the registration expiration interval value in the received REGISTER request. Based on local policy, the S-CSCF may reduce the duration of the registration or send back a 423 (Interval Too Brief) response specifying the minimum allowed time for registration. The local policy can take into account specific criteria such as the used authentication mechanism to determine the allowed registration duration;
5) store the "icid-value" header field parameter received in the P-Charging-Vector header;
6) if an "orig-ioi" header field parameter is received in the P-Charging-Vector header, store the value of the received "orig-ioi" header field parameter; and
NOTE 7: Any received "orig-ioi" header field parameter will be a type 1 IOI. The type 1 IOI identifies the network from which the request was sent.
7) create and send a 200 (OK) response for the REGISTER request as specified in subclause 5.4.1.2.2F.
5.4.1.2.2F Successful registration
If a 200 (OK) response is to be sent for a REGISTER request, the S-CSCF shall, in addition to any contents identified elsewhere in subclause 5.4.1.2, include:
a) the list of received Path header fields;
b) a P-Associated-URI header field containing the list of the registered distinct public user identity and its associated set of implicitly registered distinct public user identities. The first URI in the list of public user identities supplied by the HSS to the S-CSCF will indicate the default public user identity to be used by the S-CSCF. The public user identity indicated as the default public user identity must be a registered public user identity. The S-CSCF shall place the default public user identity as the first entry in the list of URIs present in the P-Associated-URI header field. The default public user identity will be used by the P-CSCF in conjunction with the procedures for the P-Asserted-Identity header field, as described in subclause 5.2.6.3. If the S-CSCF received a display name from the HSS for a public user identity, then the S-CSCF shall populate the P-Associated-URI header field entry for that public identity with the associated display name. The S-CSCF shall not add a barred public user identity to the list of URIs in the P-Associated-URI header field;
NOTE 1: The P-Associated-URI header field lists only the public user identity and its associated set of implicitly registered public user identities that have been registered, rather than the list of user's URIs that may be either registered or unregistered as specified in RFC 7315 [52]. If the registered public user identity which is not barred does not have any other associated public user identities or wildcarded public user identities, the P-Associated-URI header field lists only the registered public user identity itself. The P-Associated-URI header field does not list wildcarded public user identities.
c) a Service-Route header field containing:
A) the SIP URI identifying the S-CSCF containing an indication that subsequent requests routed via this service route (i.e. from the P-CSCF to the S-CSCF) was sent by the UE using either the contact address of the UE or the registration flow and the associated contact address (if the multiple registration mechanism is used) that has been registered and are treated as for the UE-originating case.
NOTE 2: This indication can e.g. be in a parameter in the URI, a character string in the user part of the URI or be a port number in the URI.
The S-CSCF shall use a different SIP URI for each registration. If the multiple registration mechanism is used, the S-CSCF shall also use a different SIP URI for each registration flow associated with the registration;
B) if network topology hiding is required a SIP URI identifying an IBCF as the topmost entry; and
NOTE 3: In accordance with the procedures described in RFC 3608 [38], an IBCF does not insert its own routable SIP URI to the Service-Route header field.
C) if
1) S-CSCF supports indicating the traffic leg associated with a URI as specified in RFC 7549 [225];
2) the UE is roaming;
3) the P-CSCF is not in the home network; and
4) required by local policy
then the S-CSCF may append an "iotl" SIP URI parameter with a value set to "visitedA-homeA" to the S-CSCF SIP URI in the Service-Route header field;
d) if the P-CSCF is in the same network as the S-CSCF a P-Charging-Function-Addresses header field containing the values received from the HSS. It can be determined if the P-CSCF is in the same network as the S-CSCF by the contents of the P-Visited-Network-ID header field included in the REGISTER request;
NOTE 4: The P-CSCF does not check the P-Charging-Function-Addresses header field, providing this header field to the visiting network could cause undefined charging behaviour.
e) a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the REGISTER request, a type 1 "term-ioi" header field parameter and the "icid-value" header field parameter. The S-CSCF shall set the type 1 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request;
f) a Contact header field listing all contact addresses for this public user identity, including all saved header field parameters and URI parameters (including all ICSI values and IARI values) received in the Contact header field of the REGISTER request,
g) GRUUs in the Contact header field. If the REGISTER request contained a Required or Supported header field containing the value "gruu" then for each contact address in the Contact header field that has a "+sip.instance" header field parameter:
i) add "pub-gruu" header field parameter containing the public GRUU representing (as specified in subclause 5.4.7A.2) the association between the public user identity from the To header field in the REGISTER request and the instance ID contained in the "+sip.instance" header field parameter;
ii) if the Contact URI in the Contact header field does not contain a "bnc" URI parameter, then add a "temp-gruu" header field parameters. containing the most recently assigned temporary GRUU representing (as specified in subclause 5.4.7A) the association between the public user identity from the To header field in the REGISTER request and the instance ID contained in the "+sip.instance" header field parameter; and
iii) if the S-CSCF supports RFC 6140 [191] and the Contact URI in the Contact header field contains a "bnc" URI parameter, then add a "temp-gruu-cookie" header field parameter containing a value generated as specified in RFC 6140 [191];
h) if the received REGISTER request contained both a "reg-id" and "+sip.instance" header field parameters in the Contact header field, and the first URI within the Path header field contains the "ob" SIP URI parameter a Require header field with the "outbound" option-tag as described in RFC 5626 [92];
NOTE 5: There might be other contact addresses available, that this UE or other UEs have registered for the same public user identity.
i) void
j) optionally, a Feature-Caps header field including the ICSI values contained in the service profile of the served user except the ones that require explicit support indication of capabilities by intermediary entities and that have not been indicated as supported according to RFC 6809 [190] for the corresponding registration or registration flow (if multiple registration mechanism is used);
k) if the home network supports calling number verification using signature verification and attestation information, as defined in subclause 3.1,a Feature-Caps header field, as specified in RFC 6809 [190], including the "+g.3gpp.verstat" header field parameter;
NOTE 6: If the network has indicated support for the calling number verification using signature verification and attestation information to a UE during registration, the network needs to perform calling number verification for all calls delivered to the registered contact address.
l) if the home network supports the response code 607 (Unwanted) as specified in RFC 8197 [254], a Feature-Caps header field including the "+sip.607" header field parameter; and
m) if the home network supports the data channel, a Feature-Caps header field, as specified in clause B.1.1 of 3GPP TS 24.186 [297], including the "+g.3gpp.datachannel" header field parameter.
and send the so created 200 (OK) response to the UE.
For all service profiles in the implicit registration set, the S-CSCF shall send a third-party REGISTER request, as described in subclause 5.4.1.7, to each AS that matches the Filter Criteria of the service profile from the HSS for the REGISTER event; and,
NOTE 7: If this registration is a reregistration, the Filter Criteria already exists in the local data.
NOTE 8: If the same AS matches the Filter Criteria of several service profiles for the event of REGISTER request, then the AS will receive several third-party REGISTER requests. Each of these requests will include a public user identity from the corresponding service profile.
The S-CSCF shall consider the public user identity being registered to be bound either to the contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used), as specified in the Contact header field, for the duration indicated in the registration expiration interval value.
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5.4.1.2.3 Abnormal cases - general
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In the case that the expiration timer from the UE is too short to be accepted by the S-CSCF, the S-CSCF shall:
- reject the REGISTER request with a 423 (Interval Too Brief) response, containing a Min-Expires header field with the minimum registration time the S-CSCF will accept.
On receiving a failure response to one of the third-party REGISTER requests, based on the information in the Filter Criteria the S-CSCF may:
- abort sending third-party REGISTER requests; and
- initiate network-initiated deregistration procedure.
If the Filter Criteria does not contain instruction to the S-CSCF regarding the failure of the contact to the AS, the S-CSCF shall not initiate network-initiated deregistration procedure.
In the case that the REGISTER request from the UE contains multiple SIP URIs which are different addresses as Contact header field entries, the S-CSCF shall store:
- the entry in the Contact header field with the highest value of the "q" header field parameter; or
- an entry decided by the S-CSCF based on local policy;
and include the stored entry in the 200 (OK) response.
In the case that the REGISTER request from the UE contains multiple SIP URIs which are the same addresses with the same value of the "q" Contact header field parameter, the S-CSCF shall not store multiple entries with the same "q" value but store one of the entries with the same "q" value based on local policy along with any entries that have different "q" values and include only the stored entries in the 200 (OK) response.
NOTE 1: The UE can register multiple SIP URIs in the Contact header field simultanously, provided they all contain the same IP address and port number. In this case the S-CSCF behaviour is as defined RFC 3261 [26] (i.e multiple Contact header field entries are bound to the public user identity in the To header field and are returned in the 200 (OK) response).
NOTE 2: If the timer reg-await-auth expires, the S-CSCF will consider the authentication to have failed. If the public user identity was already registered, the S-CSCF will leave it registered, as described in 3GPP TS 33.203 [19].
If the S-CSCF receives a new initial REGISTER request before the reg-await-auth timer expires, the S-CSCF shall:
1) stop the reg-await-auth timer; and
2) initiate the authentication procedures for initial registration as if there is no authentication currently ongoing for this user and send a 401 (Unauthorized) response containing a new challenge as described in subclause 5.4.1.
For any error response, the S-CSCF shall insert a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the REGISTER request, a type 1 "term-ioi" header field parameter and the "icid-value" header field parameter. The S-CSCF shall set the type 1 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request.
NOTE 3: Any previously received "orig-ioi" header field parameter will be a type 1 IOI. The type 1 IOI identifies the visited network of the registered user.
If the Contact header field in the REGISTER request from the UE contains an invalid Contact URI as defined in RFC 6140 [191] (e.g., the Contact URI contains both a "bnc" and "user" URI parameter) then the S-CSCF shall reject the REGISTER request with a 400 (Bad Request) response.
5.4.1.2.3A Abnormal cases – IMS AKA as security mechanism
In the case that the REGISTER request, that contains the authentication challenge response from the UE does not match with the expected REGISTER request (e.g. wrong Call-Id or authentication challenge response) and the request has the "integrity-protected" header field parameter in the Authorization header field set to "yes", the S-CSCF shall:
- send a 403 (Forbidden) response to the UE. The S‑CSCF shall consider this authentication attempt as failed. The S-CSCF shall not update the registration state of the subscriber.
NOTE 1: If the UE was registered before, it stays registered until the registration expiration time expires.
In the case that the REGISTER request from the UE containing an "auts" Authorization header field parameter, indicating that the SQN was deemed to be out of range by the UE), the S-CSCF will fetch new authentication vectors from the HSS. In order to indicate a resynchronisation, the S-CSCF shall include the value of the "auts" header field parameter received from the UE and the stored RAND, when fetching the new authentication vectors. On receipt of the new authentication vectors from the HSS, the S-CSCF shall either:
- send a 401 (Unauthorized) response to initiate a further authentication attempt, using these new vectors; or
- respond with a 403 (Forbidden) response if the authentication attempt is to be abandoned. The S-CSCF shall not update the registration state of the subscriber.
NOTE 2: If the UE was registered before, it stays registered until the registration expiration time expires.
NOTE 3: Since the UE responds only to two consecutive invalid challenges, the S-CSCF will send a 401 (Unauthorized) response that contains a new challenge only twice.
NOTE 4: In the case of an "auts" Authorization header field parameter being present in the REGISTER request, the "response" Authorization header field parameter in the same REGISTER request will not be taken into account by the S-CSCF.
In the case that the S-CSCF receives a REGISTER request with the "integrity-protected" header field parameter in the Authorization header field set to "yes", for which the public user identity received in the To header field and the private user identity received in the "username" Authorization header field parameter of the REGISTER request do not match to any registered user at this S-CSCF, if the S-CSCF supports S-CSCF restoration procedures, the S-CSCF shall behave as described in subclause 5.4.1.2.2, otherwise the S-CSCF shall:
- respond with a 500 (Server Internal Error) response to the UE.
NOTE 5: This error is not raised if there is a match on the private user identity, but no match on the public user identity.
5.4.1.2.3B Abnormal cases – SIP digest as security mechanism
In the case that the REGISTER request, that contains the authentication challenge response from the UE does not match with the expected REGISTER request (e.g. wrong Call-Id or authentication challenge response) and the request has the "integrity-protected" header field parameter in the Authorization header field set to either "tls-pending", "tls-yes", "ip-assoc-pending", or "ip-assoc-yes", the S-CSCF shall do one of the following:
- send a 403 (Forbidden) response to the UE. The S CSCF shall consider this authentication attempt as failed. The S-CSCF shall not update the registration state of the subscriber; or
- rechallenge the user by issuing a 401 (Unauthorized) response including a challenge as per the authentication procedures described in subclause 5.4.1.2.1B.
NOTE 1: If the UE was registered before, it stays registered until the registration expiration time expires.
In the case that the REGISTER request from the UE contains an invalid "nonce" Authorization header field parameter with a valid challenge response for that nonce (indicating that the client knows the correct username/password), or when the nonce-count value sent by the UE is not the expected value, the S-CSCF shall:
- send a 401 (Unauthorized) response to initiate a further authentication attempt with a fresh nonce and the "stale" header field parameter set to "true" in the WWW-Authenticate header field.
In the case that the S-CSCF receives a REGISTER request with the "integrity-protected" header field parameter in the Authorization header field set to "tls-pending", "tls-yes", "ip-assoc-pending", or "ip-assoc-yes", for which the public user identity received in the To header field and the private user identity received in the Authorization header field of the REGISTER request do not match to any registered or initial registration pending user at this S-CSCF, if the S-CSCF supports S-CSCF restoration procedures, the S-CSCF shall behave as described in subclause 5.4.1.2.2A, otherwise the S-CSCF shall:
- respond with a 500 (Server Internal Error) response to the UE.
NOTE 2: This error is not raised if there is a match on the private user identity, but no match on the public user identity.
5.4.1.2.3C Abnormal cases – SIP digest with TLS as security mechanism
The procedures for subclause 5.4.1.2.3B apply.
5.4.1.2.3D Abnormal cases – NASS-IMS bundled authentication as security mechanism
There are no abnormal cases for NASS-IMS bundled authentication.
5.4.1.2.3E Abnormal cases – GPRS-IMS-Bundled authentication as security mechanism
There are no abnormal cases for GPRS-IMS-Bundled authentication.
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5.4.1.3 Authentication and re-authentication
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Authentication and re-authentication is performed by the registration procedures as described in subclause 5.4.1.2.
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5.4.1.4 User-initiated deregistration
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5.4.1.4.1 Normal cases
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When S-CSCF receives a REGISTER request with the registration expiration interval value containing the value zero, the S-CSCF shall:
1) verify that the REGISTER request is associated with an existing registered contact or an existing flow or, if the S-CSCF restoration procedures are supported by this S-CSCF, attempt to restore a contact or flow from HSS associated with the REGISTER request. If no associated contact or flow exists then the S-CSCF shall send a 481 (Call Leg/Transaction Does Not Exist) response to the UE and skip the remaining procedures in this subclause;
2) if IMS AKA is in use as the security mechanism, check whether the "integrity-protected" header field parameter in the Authorization header field set to "yes", indicating that the REGISTER request was received integrity protected. The S-CSCF shall only proceed with the following steps if the "integrity-protected" header field parameter is set to "yes";
3) if SIP digest without TLS or SIP digest with TLS is in use as a security mechanism, check whether the "integrity-protected" header field parameter in the Authorization header field set to "tls-yes" or "ip-assoc-yes", indicating that the REGISTER request was received from a previously registered user. If the "integrity-protected" header field parameter is set to "tls-pending", "ip-assoc-pending" or is not present the S-CSCF shall ensure authentication is performed as described in subclause 5.4.1.2.1 (and consequently subclause 5.4.1.2.1B or 5.4.1.2.1C) if local policy requires. The S-CSCF shall only proceed with the following steps if the "integrity-protected" header field parameter is set to "tls-yes", "ip-assoc-yes", or the required authentication is successfully performed if required by local policy;
4) if NASS-IMS bundled authentication is in use as a security mechanism, only proceed with the following steps if the "integrity-protected" header field parameter in the Authorization header field does not exist or without an Authorization header field, and one or more Line-Identifiers previously received over the Cx interface, stored as a result of an Authentication procedure with the HSS, as described in 3GPP TS 29.228 [14], are available for the user;
4A) if the security mechanism as described in subclause 5.4.1.2.2E is in use, check whether the "integrity-protected" header field parameter in the Authorization header field set to "auth-done". The S-CSCF shall only proceed with the following steps if the "integrity-protected" header field parameter is set to "auth-done";
5) release all INVITE dialogs that include this user's contact addresses or the flows that are being deregistered, and where these dialogs were initiated by or terminated towards these contact addresses and the same public user identity found that was To header field that was received REGISTER request or with one of the implicitly registered public user identities by applying the steps listed in subclause 5.4.5.1.2;
6) examine the Contact header field in the REGISTER request, and:
a) if the value "*" is not included in the Contact header field and:
i) if the "reg-id" header field parameter is not included in the Contact header field, then:
- remove the binding (i.e. deregister) between the public user identity found in the To header field together with the implicitly registered public user identities and the contact addresses specified in the REGISTER request. The S-CSCF shall only remove the contact addresses that were registered by this UE;
ii) if the "reg-id" header field parameter and "+sip.instance" header field parameter are included in the Contact header field, and the UE supports multiple registrations (i.e. the "outbound" option tag is included in the Supported header field), then:
- remove the binding (i.e. deregister) between the public user identity indicated in the To header field (together with the associated implicitly registered public user identities) and the flow identified by the "reg-id" header field parameter;
7) if the S-CSCF receives a REGISTER request with the value "*" in the Contact header field and the value zero in the Expires header field, remove all contact addresses that were bound to the public user identity found in the To header field and have been registered by this UE identified with its private user identity;
8) for all service profiles in the implicit registration set send a third-party REGISTER request, as described in subclause 5.4.1.7, to each AS that matches the Filter Criteria of the service profile from the HSS for the REGISTER event;
9) if this is a deregistration request for the only public user identity currently registered with its associated set of implicitly registered public user identities (i.e. no other is registered) and there are still active multimedia sessions that includes this user's registered contact address, where the session was initiated by or terminated towards the contact with the registered contact address for that public user identity which is currently registered or with one of the implicitly registered public user identities, release only each of these multimedia sessions associated with the registered contact address by applying the steps listed in subclause 5.4.5.1.2. The S-CSCF shall only release dialogs associated to the multimedia sessions originated or terminated towards the registered user's contact address; and
10) send a 200 (OK) response to a REGISTER request that contains a list of Contact header fields enumerating all contacts and flows that are currently registered, and all contacts that have been deregistered. For each contact address and the flow that has been deregistered, the Contact header field shall contain the contact address and the "reg-id" header field parameter that identifies the flow, if a flow was deregistered, and the associated information, and the registration expiration interval value shall be set to zero.
If all public user identities of the UE are deregistered, then the S-CSCF may consider the UE and P-CSCF subscriptions to the reg event package cancelled (i.e. as if the UE had sent a SUBSCRIBE request with an Expires header field containing a value of zero).
If the Authorization header field of the REGISTER request contained an "integrity-protected" header field parameter set to the value "no", the S-CSCF shall apply the procedures described in subclause 5.4.1.2.1.
On completion of the above procedures in this subclause and of the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], for one or more public user identities, the S-CSCF shall:
1) update or remove those public user identities, their registration state and the associated service profiles from the local data; and
2) if all the contacts bound to the public user identities have been deregistered and there is no ongoing session due to the public user identities, then remove all the stored AS IP addresses which are associated with those public user identities.
Based on operators' policy the S-CSCF can request the HSS to either be kept or cleared as the S-CSCF allocated to this subscriber. If emergency contacts are still registered for this subscriber, the S-CSCF requests the HSS to be kept as the S-CSCF allocated to this subscriber.
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5.4.1.4.2 Abnormal cases - IMS AKA as security mechanism
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If case that the S-CSCF receives a REGISTER request with the "integrity-protected" header field parameter in the Authorization header set to "yes" or to "tls-connected", for which the public user identity received in the To header and the private user identity received in the Authorization header of the REGISTER request do not match to any registered user at this S-CSCF, if the S-CSCF supports S-CSCF restoration procedures as specified in 3GPP TS 23.380 [7D], the S-CSCF shall behave as described in subclause 5.4.1.4.1, otherwise the S-CSCF shall:
- respond with a 500 (Server Internal Error) response to the UE.
NOTE: This error is not raised if there is a match on the private user identity, but no match on the public user identity.
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5.4.1.4.4 Abnormal cases – SIP digest with TLS as security mechanism
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The procedures for subclause 5.4.1.4.2 apply.
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5.4.1.4.5 Abnormal cases – NASS-IMS bundled authentication as security mechanism
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There are no abnormal cases for NASS-IMS bundled authentication.
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5.4.1.4.6 Abnormal cases – GPRS-IMS-Bundled authentication as security mechanism
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There are no abnormal cases for GPRS-IMS-Bundled authentication.
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5.4.1.5 Network-initiated deregistration
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NOTE 1: A network-initiated deregistration event that occurs at the S-CSCF can be received from the HSS or can be an internal event in the S-CSCF.
For any registered public user identity, the S-CSCF can deregister:
- all contact addresses bound to the indicated public user identity (i.e. deregister the respective public user identity);
- some contact addresses bound to the indicated public user identity;
- a particular contact address bound to the indicated public user identity; or
- one or more registration flows and the associated contact address bound to the indicated public user identity, when the UE supports multiple registration procedure;
by sending a single NOTIFY request.
Prior to initiating the network-initiated deregistration for the only currently registered public user identity and its associated set of implicitly registered public user identities and wildcarded public user identities that have been registered either with the same contact address of the UE or the same registration flow and the associated contact address (if the multiple registration mechanism is used), i.e. there are no other public user identities registered either with this contact address or with this registration flow and the associated contact address (if the multiple registration mechanism is used), and there are still active multimedia sessions belonging either to this contact address or to this registration flow and the associated contact address (if the multiple registration mechanism is used), the S-CSCF shall release only multimedia sessions belonging to this contact address or to this registration flow and the associated contact address (if the multiple registration mechanism is used) as described in the following paragraph. The multimedia sessions for the same public user identity, if registered either with another contact address or another registration flow and the associated contact address (if the multiple registration mechanism is used) remain unchanged.
Prior to initiating the network-initiated deregistration while there are still active multimedia sessions that are associated with this user and contact, the S-CSCF shall release none, some or all of these multimedia sessions by applying the steps listed in subclause 5.4.5.1.2 under the following conditions:
- when the S-CSCF does not expect the UE to reregister a given public user identity and its associated set of implicitly registered public user identities that have been registered with respective contact address (i.e. S-CSCF will set the event attribute within the respective <contact> element to "rejected" for the NOTIFY request, as described below), the S-CSCF shall release all sessions that are associated with the registered contact address for the public user identities using the contact address that is being deregistered, which includes the implicitly registered public user identities.
- when the S-CSCF expects the UE to reregister a given public user identity and its associated set of implicitly registered public user identities that have been registered with respective contact address (i.e. S-CSCF will set the event attribute within the respective <contact> element to "deactivated" for the NOTIFY request, as described below), the S-CSCF shall only release sessions that currently include the user's contact address, where the session was initiated by or terminated towards the user with the contact address registered to one of the public user identities using the contact address that is being deregistered, which includes the implicitly registered public user identities.
When a network-initiated deregistration event occurs for one or more public user identities that are bound either to one or more contact addresses or registration flows and the associated contact addresses (if the multiple registration mechanism is used), the S-CSCF shall send a NOTIFY request to all subscribers that have subscribed to the respective reg event package. For each NOTIFY request, the S-CSCF shall:
1) set the Request-URI and Route header field to the saved route information during subscription;
2) set the Event header field to the "reg" value;
3) in the body of the NOTIFY request, include as many <registration> elements as many public user identities the S-CSCF is aware of the user owns;
4) set the aor attribute within each <registration> element to one public user identity:
a) set the <uri> sub-element inside each <contact> sub-element of each <registration> element to the respective contact address provided by the UE;
b) if the public user identity:
i) has been deregistered (i.e. all contact addresses and all registration flows and associated contact addresses bound to the indicated public user identity are removed) then:
- set the state attribute within the <registration> element to "terminated";
- set the state attribute within each <contact> element belonging to this UE to "terminated"; and
- set the event attribute within each <contact> element belonging to this UE to either "unregistered", or "deactivated" if the S-CSCF expects the UE to reregister or "rejected" if the S-CSCF does not expect the UE to reregister; or
NOTE 2: If the multiple registration mechanism is used, then the reg-id header field parameter will be included as an <unknown-param> element within each respective <contact> element.
NOTE 3: The UE will consider its public user identity as deregistered when the binding between the respective public user identity and all contact addresses and all registration flows and associated contact addresses (if the multiple registration mechanism is used) belonging to the UE have been removed.
ii) has been kept registered then:
I) set the state attribute within the <registration> element to "active";
II) set the state attribute within each <contact> element to:
- for the binding between the public user identity and either the contact address or a registration flow and associated contact addresses (if the multiple registration mechanism is used) to be removed set the state attribute within the <contact> element to "terminated", and event attribute element to either "unregistered", or "deactivated" if the S-CSCF expects the UE to reregister or "rejected" if the S-CSCF does not expect the UE to reregister; or
- for the binding between the public user identity and either the contact address or the registration flow and associated contact addresses (if the multiple registration mechanism is used) which remain unchanged, if any, leave the <contact> element unmodified, and if the contact has been assigned GRUUs and the Contact URI did not contain a "bnc" SIP URI parameter then set the <pub-gruu> and <temp-gruu> sub-elements of the <contact> element as specified in RFC 5628 [94] and include the <unknown-param> sub-element within each <contact> to any additional header field parameters contained in the Contact header field of the REGISTER request according to RFC 3680 [43]; and
NOTE 4: There might be more than one contact information available for one public user identity. When deregistering this UE, the S-CSCF will only modify the <contact> elements that were originally registered by this UE using its private user identity. The <contact> elements of the same public user identity, if registered by another UE using different private user identities remain unchanged.
5) add a P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog and a type 1 "orig-ioi" header field parameter. The S-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 1 "term-ioi" header field parameter.
The S-CSCF shall only include the non-barred public user identities in the NOTIFY request.
When sending a final NOTIFY request with all <registration> element(s) having their state attribute set to "terminated" (i.e. all public user identities have been deregistered or expired), the S-CSCF shall also terminate the subscription to the registration event package by setting the Subscription-State header field to the value of "terminated".
Also, for all service profiles in the implicit registration set the S-CSCF shall send a third-party REGISTER request, as described in subclause 5.4.1.7, to each AS that matches the Filter Criteria of the service profile from the HSS as if a equivalent REGISTER request had been received from the user deregistering that public user identity, or combination of public user identities.
On completion of the above procedures for one or more public user identities linked to the same private user identity, the S-CSCF shall consider those public user identities and the associated implicitly registered public user identities which have no contact address or a registration flow and associated contact addresses (if the multiple registration mechanism is used) bound to them as deregistered. On completion of the S-CSCF Registration/deregistration notification procedure with the HSS, as described in 3GPP TS 29.228 [14], the S-CSCF shall:
1) update or remove those public user identities linked to the same private user identity, their registration state and the associated service profiles from the local data (based on operators' policy the S-CSCF can request of the HSS to either be kept or cleared as the S-CSCF allocated to this subscriber); and
2) if all the contacts bound to the public user identities have been deregistered and there is no ongoing session due to the public user identities, then remove all the stored AS IP addresses which are associated with those public user identities.
On the completion of the network-initiated de-registration by the HSS procedure, as described in 3GPP TS 29.228 [14], the S-CSCF shall remove:
1) those public user identities, their registration state and the associated service profiles from the local data; and
2) if all the contacts bound to the public user identities have been deregistered and there is no ongoing session due to the public user identities, then remove all the stored AS IP addresses which are associated with those public user identities.
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5.4.1.6 Network-initiated re-authentication
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The S-CSCF may request a subscriber to re-authenticate at any time, based on a number of possible operator settable triggers.
NOTE 1: Triggers for re-authentication include e.g. a current registration of the UE is set to expire at a predetermined time; one or more error conditions in the S-CSCF; the S-CSCF mistrusts the UE, the S-CSCF receives an access update requesting re-authentication as specified in subclause 5.2.14.
If the S-CSCF is informed that a private user identity needs to be re-authenticated, the S-CSCF shall generate a NOTIFY request on all dialogs which have been established due to subscription to the reg event package of that user. For each NOTIFY request the S-CSCF shall:
1) set the Request-URI and Route header field to the saved route information during subscription;
2) set the Event header field to the "reg" value;
3) in the body of the NOTIFY request, include as many <registration> elements as many public user identities the S-CSCF is aware of the user owns:
a) set the <uri> sub-element inside the <contact> sub-element of each <registration> element to the contact address provided by the UE;
b) set the aor attribute within each <registration> element to one public user identity;
c) set the state attribute within each <registration> element to "active";
d) set the state attribute within each <contact> element to "active";
e) set the event attribute within each <contact> element that was registered by this UE to "shortened";
f) set the expiry attribute within each <contact> element that was registered by this UE to an operator defined value; and
g) if the Contact URI did not contain a "bnc" SIP URI parameter then set the <pub-gruu> and <temp-gruu> sub-elements within each <contact> element as specified in subclause 5.4.2.1.2; and
NOTE 2: There might be more than one contact information available for one public user identity. The S-CSCF will only modify the <contact> elements that were originally registered by this UE using its private user identity. The S-CSCF will not modify the <contact> elements for the same public user identitity, if registered by another UE using different private user identity.
4) set a P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog and a type 1 "orig-ioi" header field parameter. The S-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 1 "term-ioi" header field parameter.
Afterwards the S-CSCF shall wait for the user to re-authenticate (see subclause 5.4.1.2).
NOTE 3: Network initiated re-authentication can occur due to internal processing within the S-CSCF.
The S-CSCF shall only include the non-barred public user identities in the NOTIFY request.
When generating the NOTIFY request, the S-CSCF shall shorten the validity of all registration lifetimes associated with this private user identity to an operator defined value that will allow the user to be re-authenticated.
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5.4.1.7 Notification of Application Servers about registration status
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During registration, the S-CSCF shall include the P-Access-Network-Info header fields (as received in the REGISTER request from the UE and the P-CSCF) and a P-Visited-Network-ID header field (as received in the REGISTER request from the UE) in the third-party REGISTER request sent towards the ASs, if the AS is part of the trust domain. If the AS is not part of the trust domain, the S-CSCF shall not include any P-Access-Network-Info header field or P-Visited-Network-ID header field. The S-CSCF shall not include a P-Access-Network-Info header field in any responses to the REGISTER request.
If the registration procedure described in subclauses 5.4.1.2, 5.4.1.4 or 5.4.1.5 (as appropriate) was successful, the S-CSCF shall send a third-party REGISTER request to each AS with the following information:
a) the Request-URI, which shall contain the AS's SIP URI;
b) the From header field, which shall contain the S-CSCF's SIP URI;
c) the To header field, which shall contain a non-barred public user identity belonging to the service profile of the processed Filter Criteria. It may be either a public user identity as contained in the REGISTER request received from the UE or one of the implicitly registered public user identities in the service profile, as configured by the operator;
NOTE 1: For the whole implicit registration set only one public user identity per service profile appears in the third-party REGISTER requests. Thus, based on third-party REGISTER requests only, the ASs will not have complete information on the registration state of each public user identity in the implicit registration set. The only way to have a complete and continuously updated information (even upon administrative change in subscriber's profile) is to subscribe to the reg event package.
d) the Contact header field, which shall contain the S-CSCF's SIP URI;
e) for initial registration and user-initiated reregistration (subclause 5.4.1.2), the registration expiration interval value, which shall contain the same value that the S-CSCF returned in the 200 (OK) response for the REGISTER request received from the UE;
f) for user-initiated deregistration (subclause 5.4.1.4) and network-initiated deregistration (subclause 5.4.1.5), the registration expiration interval value, which shall contain the value zero;
NOTE 2: The user can have one or more contacts registered after a third-party deregister. If an AS needs more detailed knowledge of the user registration status, the AS can subscribe to the reg event package.
g) for initial registration and user-initiated reregistration (subclause 5.4.1.2), a message body, if there is Filter Criteria indicating the need to include HSS provided data for the REGISTER event (e.g. HSS may provide AS specific data to be included in the third-party REGISTER) or if there is Filter Criteria indicating the need to include the contents of the incoming REGISTER request or the contents of the 200 (OK) response to the incoming REGISTER request in the body of the third-party REGISTER. The S-CSCF shall format the MIME body and set the value of the Content-Type header field to include the MIME type specified in subclause 5.4.1.7A;
NOTE 3: When the AS is outside the trust domain for any header field that is permitted in the REGISTER request received from the UE or final response to the REGISTER request received from the UE, including an Include Register Request or Include Register Response indication in the initial Filter Criteria would cause the incoming REGISTER request or 200 (OK) response to the incoming REGISTER request contents to be delivered to the AS revealing information that AS is not trusted to obtain. Include Register Request and Include Register Response indication is therefore not included in the initial Filter Criteria for an AS that exists outside the trust domain for any such header field.
h) for initial registration and user-initiated reregistration, the P-Charging-Vector header field, which shall contain the same "icid-value" header field parameter that the S-CSCF received in the REGISTER request from the UE. The S-CSCF shall insert a type 3 orig-ioi parameter in place of any received "orig-ioi" header field parameter and shall set the type 3 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 3 "term-ioi" header field parameter;
i) for initial registration and user-initiated reregistration, a P-Charging-Function-Addresses header field, which shall contain the values received from the HSS if the message is forwarded within the S-CSCF home network;
j) in case the received REGISTER request contained a P-User-Database header field and the AS belongs to the same operator as the S-CSCF, optionally a P-User-Database header field which shall contain the received value; and
k) void
l) if the S-CSCF supports using a token to identify the registration for initial registration and user initiated reregistration, a "+g.3gpp.registration-token" Contact header field parameter, as defined in subclause 7.9.7, set to a value identifying this registration among the set of registrations for the registered URI. The value shall be the same until the UE is deregistered.
NOTE 4: Setting the value of the registration-token to the same value as the S-CSCF will use for the "id" parameter identifying this contact in the "reg" event package allows the AS to retrieve the value using the "reg" event package.
For third-party REGISTER upon user-initiated reregistration, user-initiated deregistration or network-initiated deregistration, the S-CSCF shall send SIP REGISTER request towards the IP address associated with the corresponding registered public user identity stored as described in subclause 5.4.0.
When the S-CSCF receives any response to a third-party REGISTER request, the S-CSCF shall store the value of the "term-ioi" header field parameter received in the P-Charging-Vector header field, if present.
NOTE 5: Any received "term-ioi" header field parameter will be a type 3 IOI. The type 3 IOI identifies the service provider from which the response was sent.
If the S-CSCF fails to receive a SIP response or receives a 408 (Request Timeout) response or a 5xx response to a third-party REGISTER, the S-CSCF shall:
- if the default handling defined in the filter criteria indicates the value "SESSION_CONTINUED" as specified in 3GPP TS 29.228 [14] or no default handling is indicated, no further action is needed; and
- if the default handling defined in the filter criteria indicates the value "SESSION_TERMINATED" as specified in 3GPP TS 29.228 [14], initiate the network-initiated deregistration as described in subclause 5.4.1.5 for the currently registered public user identity and its associated set of implicitly registered non-barred public user identities bound to the contact(s) registered in the REGISTER request causing the third-party REGISTER request.
5.4.1.7A Including contents in the body of the third-party REGISTER request
If there is a service information XML element provided in the HSS Filter Criteria for an AS (see 3GPP TS 29.228 [14]), then in the third-party REGISTER request the S-CSCF shall:
- include in the message body the service information within the <service-info> XML which is a child XML element of an <ims-3gpp> element with the "version" attribute set to "1" element as described in subclause 7.6; and
- set the value of the content type to the MIME type specified in subclause 7.6.
If there is an Include Register Request XML element provided in the HSS Filter Criteria for an AS (see 3GPP TS 29.228 [14]), then in the third-party REGISTER request the S-CSCF shall:
- include in the message body the incoming SIP REGISTER request within a "message/sip" MIME body as defined in RFC 3261 [26]; and
- set the value of the content type to "message/sip".
If there is an Include Register Response XML element provided in the HSS Filter Criteria for an AS (see 3GPP TS 29.228 [14]), then in the third-party REGISTER request, the S-CSCF shall:
- include in the message body the 200 (OK) response to the incoming SIP REGISTER request within a "message/sip" MIME body as defined in RFC 3261 [26]; and
- set the value of the content type to "message/sip".
If there is more than one message body to be included in the third-party REGISTER request then in the third-party REGISTER request the S-CSCF shall:
- include a multipart message body and set the value of the Content-Type header field to "multipart/mixed" as specified in RFC 2046 [149] and RFC 5621 [150]; and
- set the Content-Type of the elements of the MIME body to the content type specified for the body.
If there is only one message body to be included in the third-party REGISTER request then the S-CSCF sets the Content-Type header field to the content type specified for the body.
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5.4.1.8 Service profile updates
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NOTE 1: The S-CSCF can receive an update of subscriber data notification on the Cx interface, from the HSS, which can affect the stored information about served public user identities. According to 3GPP TS 29.228 [14], the changes are guaranteed not to affect the default public user identity within the registration implicit set.
When receiving a Push-Profile-Request (PPR) from the HSS (as described in 3GPP TS 29.228 [14]), modifying the service profile of served public user identities, the S-CSCF shall:
1) if the modification consists in the addition of a new non-barred public user identity to an implicit set, or in the change of status from barred to non-barred for a public user identity already in the implicit set, add the public user identity to the list of registered, non-barred public user identities;
2) if the modification consists in the deletion of a public user identity while there are no active multimedia session belonging to this public user identity, or in the change of status from non-barred to barred of a public user identity in an implicit set, remove the public user identity from the list of registered, non-barred public user identities;
NOTE 2: As the S-CSCF checks the barring status of the public user identity on receipt of a initial request for a dialog, or a standalone transaction, the above procedures have no impact on transactions or dialogs already in progress and are effective only for new transactions and dialogs.
3) if the modification consists of deletion of a public user identity from an implicit registration set while there are active multimedia session belonging to this public user identity and contact, release these multimedia sessions as described in subclause 5.4.5.1.2 and after all multimedia sessions are released, remove the public user identity from the list of registered, non-barred public user identities; and
4) synchronize with the UE and IM CN entities, by either:
- performing the procedures for notification of the reg-event subscribers about registration state, as described in subclause 5.4.2.1.2; or
- triggering the UE to reregister, by:
a) depending on operator configuration, rejecting a request from the UE using a 504 (Server Time-out) response and indicating in the response that S-CSCF restoration procedures are supported, in accordance with subclause 5.4.3.2; or
b) shortening the life time of the current registration, as described in subclause 5.4.1.6, e.g. when a new trigger point of Register method is added in the iFCs.
NOTE 3: The UE procedure in response to receiving a rejection as described in item a) (see subclause 5.1.2A.1.6) is specified for UEs since 3GPP Rel-8.
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5.4.2 Subscription and notification
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5.4.2.1 Subscriptions to S-CSCF events
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5.4.2.1.1 Subscription to the event providing registration state
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When an incoming SUBSCRIBE request addressed to S-CSCF arrives containing the Event header field with the reg event package, the S-CSCF shall:
0) if the Request-URI of the SUBSCRIBE request contains a URI for which currently no binding exists, then send a 480 (Temporarily Unavailable) response indicating that the subscription was not successful and skip the remainder of the steps;
1) check if, based on the local policy, the request was generated by a subscriber who is authorised to subscribe to the registration state of this particular user. The authorized subscribers include:
- all public user identities this particular user owns, that the S-CSCF is aware of, and which are not-barred;
- all the entities identified by the Path header field (i.e. the P-CSCF to which this user is attached to or the IBCF which encrypted the Path header field); and
- all the ASs listed in the initial filter criteria that are part of the trust domain;
if the request is received from a subscriber which is not auhorized to subscribe to the registration state of this particular user, then send a 403 (Forbidden) response indicating that the subscription was not successful and skip the remainder of the steps;
NOTE 1: The S-CSCF finds the identity for authentication of the subscription in the P-Asserted-Identity header field received in the SUBSCRIBE request.
1A) if the Request-URI of the SUBSCRIBE request identifies a public user identity that was implicitly registered using the registration procedures defined in RFC 6140 [191] and performs the functions of an external attached network, and the registration is currently active, then skip the remainder of the procedure in this subclause and route the SUBSCRIBE request to the UE performing the functions of an externally attached network using the procedures defined in subclause 5.4.3.3;
1B) store the "icid-value" header field parameter received in the P-Charging-Vector header field;
2) store the value of the "orig-ioi" header field parameter received in the P-Charging-Vector header field if present;
NOTE 2: Any received "orig-ioi" header field parameter will be either a type 1 IOI or a type 3 IOI. The type 1 IOI identifies the sending network and the type 3 IOI identifies the service provider from which the request was sent.
3) generate a 200 (OK) response acknowledging the SUBSCRIBE request and indicating that the authorised subscription was successful as described in RFC 3680 [43] and RFC 6665 [28]. The S-CSCF shall populate the header fields as follows:
- an Expires header field, set to either the same or a decreased value as the Expires header field in SUBSCRIBE request;
- if the request originated from an ASs listed in the initial filter criteria, a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the SUBSCRIBE request, a type 3 "term-ioi" header field parameter and the "icid-value" header field parameter. The S-CSCF shall set the type 3 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request; and
- if the request originated from a public user identity this particular user owns, or any of the entities identified by the Path header field, a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the SUBSCRIBE request, a type 1 "term-ioi" header field parameter, and the "icid-value" header field parameter. The S-CSCF shall set the type 1 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request.
The S-CSCF may set the Contact header field to an identifier uniquely associated to the SUBSCRIBE request and generated within the S-CSCF, that may help the S-CSCF to correlate refreshes for the SUBSCRIBE dialog; and
NOTE 3: The S-CSCF could use such unique identifiers to distinguish between UEs, when two or more users, holding a shared subscription, register under the same public user identity.
4) determine the applicable private user identity as the private user identity included in a REGISTER request:
- which created (implicitly or explictly) a binding of the public user identity in the Request-URI of the SUBSCRIBE request to an contact address; and
- for which one of the following is true:
a) the 200 (OK) response to the REGISTER request contained the Service-Route header field with the S-CSCF URI matching the URI in the top Route header field of the SUBSCRIBE request (i.e. the SUBSCRIBE request originated by a served UE); or
b) the 200 (OK) response to the REGISTER request contained a Path header field with a URI matching the URI in the P-Asserted-Identity header field of the SUBSCRIBE request (i.e. the SUBSCRIBE request originated by a P-CSCF serving a UE).
NOTE 4: If the URI in the P-Asserted-Identity header field of the initial SUBSCRIBE request matches URIs of several Path header fields (e.g. the SUBSCRIBE request is originated by Rel-7 P-CSCF), the applicable private user identity is not determined.
Afterwards the S-CSCF shall perform the procedures for notification about registration state as described in subclause 5.4.2.1.2.
If the SUBSCRIBE request originated from an AS listed in the initial filter criteria, for any response that is not a 2xx response, the S-CSCF shall insert a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the SUBSCRIBE request, a type 3 "term-ioi" header field parameter and the "icid-value" header field parameter. The S-CSCF shall set the type 3 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request.
If the SUBSCRIBE request originated from a public user identity this particular user owns, or any of the entities identified by the Path header field, for any response that is not a 2xx response, the S-CSCF shall insert a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the SUBSCRIBE request, a type 1 "term-ioi" header field parameter and the "icid-value" header field parameter. The S-CSCF shall set the type 1 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and the "icid-value" header field parameter is set to the previously received value of "icid-value" header field parameter in the request.
When the S-CSCF receives a subscription refresh request for a dialog that was established by the UE subscribing to the reg event package, the S-CSCF shall accept the request irrespective if the user's public user identity specified in the SUBSCRIBE request is either registered or has been deregistered.
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5.4.2.1.2 Notification about registration state
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The UE can bind any one of its public user identities either to its contact address or to a registration flow and the associated contact address (if the multiple registration mechanism is used) via a single registration procedure. When multiple registrations mechanism is used to register a public user identity and bind it to a registration flow and the associated contact address, the S-CSCF shall generate a NOTIFY request that includes one <contact> element for each binding between a public user identity and a registration flow and the associated contact address.
NOTE 1: If the UE binds a given public user identity to the same contact address but several registration flows and the associated contact address (via several registrations), then the NOTIFY request will contain one <contact> element for each registration flow and the associated contact address. Each respective <contact> elements will contain the same contact address in the <uri> sub-element, but different value in the "id" attribute and different "reg-id" value included in the respective <unknown-param> element.
For every successful registration that creates a new binding between a public user identity and either its contact address or the registration flow and the associated contact address (if the multiple registration mechanism is used, the NOTIFY request shall always include a new <contact> element containing new value in the "id" sub-element, the state attribute set to "active", and event attribute set to either "registered" or "created".
Any successful registration (that creates a new binding between a public user identity and either its contact address or a registration flow and associated contact address) may additionally replace or remove one or more existing bindings. In the NOTIFY request, for each replaced or removed binding, the <contact> element shall have the state attribute set to "terminated" and the event attribute set to "unregistered", "deactivated", or "rejected".
NOTE 2: When multiple registrations mechanism is not used, if the UE registers new contact address then all registrations, if any, using an old contact address are deregistered, i.e. the new registration replaces the old registrations. Hence, for each deregistered public user identity, the NOTIFY request will have the state attribute within the <registration> element set to "terminated" and the state attribute in the <contact> element set to "terminated" and the event attribute set to "unregistered", "deactivated", or "rejected".
NOTE 3: If the UE uses a multiple registrations mechanism to bind a public user identity to a new registration flow the registration flow and the associated contact address, and if the new registration flow replaces an existing registration flow, then for the registration flow and the associated contact address being replaced, the respective <contact> element in the NOTIFY request will have the state attribute set to "terminated" and the event attribute set to "unregistered", "deactivated", or "rejected".
The S-CSCF shall send a NOTIFY request:
- when an event pertaining to the user occurs. In this case the NOTIFY request is sent on all dialogs which have been established due to subscription to the reg event package of that user; and
- as specified in RFC 6665 [28].
When sending a NOTIFY request, the S-CSCF shall not use the default filtering policy as specified in RFC 3680 [43], i.e. the S-CSCF shall always include in every NOTIFY request the state information of all registered public user identities of the user (i.e. the full state information).
NOTE 4: Contact information related to emergency registration is not included.
When generating NOTIFY requests, the S-CSCF shall not preclude any valid reg event package parameters in accordance with RFC 3680 [43].
For each NOTIFY request triggered by an event and on all dialogs which have been established due to subscription to the reg event package of that user, the S-CSCF shall:
1) set the Request-URI and Route header field to the saved route information during subscription;
2) set the Event header field to the "reg" value;
3) in the body of the NOTIFY request, include one <registration> elements for each public user identity that the S-CSCF is aware the user owns.
If the user shares one or more public user identities with other users, the S-CSCF shall include any contact addresses registered by other users of the shared public user identity in the NOTIFY request;
4) for each <registration> element:
a) set the aor attribute to one public user identity or if the public user identity of this <registration> element is a wildcarded public user identity, then choose arbitrarily a public user identity that matches the wildcarded public user identity and the service profile of the wildcarded public user identity and set the aor attribute to this public user identity;
NOTE 5: If the public user identity of this <registration> element is a wildcarded public user identity, the value of the aor attribute will not be used by the receiver of the NOTIFY.
b) set the <uri> sub-element inside each <contact> sub-element of the <registration> element to the contact address provided by the respective UE as follows:
I) if the aor attribute of the <registration> element contains a SIP URI and if the Contact URI did not contain a "bnc" SIP URI parameter, then for each contact address that contains a "+sip.instance" Contact header field parameter, include <pub-gruu> and <temp-gruu> sub-elements within the corresponding <contact> element. The S-CSCF shall set the contents of these elements as specified in RFC 5628 [94]; or
II) if the aor attribute of the <registration> element contains a tel-URI, determine its alias SIP URI and if the Contact URI did not contain a "bnc" SIP URI parameter then include a copy of the <pub-gruu> and <temp-gruu> sub-elements from that equivalent element;
c) if the respective UE has provided a display-name in a Contact header field, set the <display-name> sub-element inside the respective <contact> sub-element of the <registration> element to the value provided by the UE according to RFC3680 [43];
d) if the user owns a wildcarded public user identity then include a <wildcardedIdentity> sub-element as described in subclause 7.10.2;
e) if the public user identity set in step a):
I) has been deregistered either by the UE or the S-CSCF (i.e. upon the deregistration, there are no binding left between this public user identity and either a contact address or a registration flows and associated contact addresses that belong to this user) then:
- set the state attribute within the <registration> element to "terminated";
- set the state attribute within each <contact> element belonging to this user to "terminated"; and
- set the event attribute within each <contact> element to "deactivated", "expired", "unregistered", "rejected" or "probation" according to RFC 3680 [43].
If the public user identity has been deregistered for this user and this deregistration has already been indicated in the NOTIFY request, and no new registration for this user has occurred, its <registration> element shall not be included in the subsequent NOTIFY requests;
II) has been registered by the UE (i.e. the public user identity has not been previously bound either to a contact address or to a registration flow and the associated contact address (if the multiple registration mechanism is used)) then:
- set the <unknown-param> element to any additional header field parameters contained in the Contact header field of the REGISTER request according to RFC 3680 [43];
NOTE 6: If the multiple registration mechanism is used, then the reg-id header field parameter will be included as an <unknown-param> element.
- if the subscription contains, for the applicable private user identity (determined as described in subclause 5.4.2.1.1) and the public user identity, any of the policies described in subclause 7.10.3, then include the policy associated with the applicable private user identity and the public user identity using coding described in subclause 7.10.3;
- set the state attribute within the <registration> element to "active"; and:
- set the state attribute within the <contact> element belonging to this user to "active", include new value for the "id" attribute within the <contact> sub-element, and set the event attribute within this <contact> element to "registered";
NOTE 7: If this registration, that created new binding, additionally replaces or removes one or more existing registrations, then for the replaced or removed registrations the respective <registration> elements and <contact> elements will be modified accordingly.
III) has been reregistered (i.e. it has been previously registered) then:
- set the state attribute within the <registration> element to "active";
- if the subscription contains, for the applicable private user identity (determined as described in subclause 5.4.2.1.1) and the public user identity, any of the policies described in subclause 7.10.3, then include the policy associated with the applicable private user identity and the public user identity using coding described in subclause 7.10.3;
- set the <unknown-param> element to any additional header field parameters contained in the Contact header field of the REGISTER request according to RFC 3680 [43];
- for contact addresses to be registered: set the state attribute within the <contact> element to "active"; and set the event attribute within the <contact> element to "registered";
- for contact addresses to be reregistered, set the state attribute within the <contact> element to "active"; and set the event attribute within the <contact> element to "refreshed" or "shortened" according to RFC 3680 [43]; and
- for contact addresses that remain unchanged, if any, leave the <contact> element unmodified (i.e. the event attribute within the <contact> element includes the last event that caused the transition to the respective state);
IV) has been automatically registered or registered by the S-CSCF, and has not been previously automatically registered:
- set the <unknown-param> element to any additional header field parameters contained in the Contact header field of the REGISTER request according to RFC 3680 [43];
- set the state attribute within the <registration> element to "active";
- set the state attribute within the <contact> element to "active"; and
- set the event attribute within the <contact> element to "created"; or
V) is hosted (unregistered case) at the S-CSCF:
- set the state attribute within the <registration> element to "terminated";
- set the state attribute within each <contact> element to "terminated"; and
- set the event attribute within each <contact> element to "unregistered".
The S-CSCF shall also terminate the subscription to the registration event package by setting the Subscription-State header field to the value of "terminated"; and
NOTE 8: The value of "init" for the state attribute within the <registration> element is not used.
f) set the callid and cseq attributes for the <contact> as specified in RFC 3680 [43], and the first-cseq attribute as specified in RFC 5628 [94]; and
NOTE 9: Errata of RFC 5628 clarifies the usage of the first-cseq attribute of the <temp-gruu> element.
5) set the P-Charging-Vector header field with the "icid-value" header field parameter set to the value populated in the initial request for the dialog, and
- if the NOTIFY request is sent towards an AS listed in the initial filter criteria a type 3 "orig-ioi" header field parameter. The S-CSCF shall set the type 3 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 3 "term-ioi" header field parameter; and
- if the NOTIFY request is sent towards a public user identity this particular user owns, or any of the entities identified by the Path header field, a type 1 "orig-ioi" header field parameter. The S-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 1 "term-ioi" header field parameter.
NOTE 10: When sending a NOTIFY request to a subscriber subscribing or unsubscribing to the reg event package, or when the S-CSCF terminates the subscription, the event attribute within the <contact> element includes the last event that caused the transition to the respective state.
The S-CSCF shall only include the non-barred public user identities in the NOTIFY request.
EXAMPLE 1: If sip:user1_public1@home1.net is registered, the public user identity sip:user1_public2@home1.net can automatically be registered. Therefore the entries in the body of the NOTIFY request look like:
<?xml version="1.0"?>
<reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
xmlns:cp="urn:ietf:params:xml:ns:common-policy"
xmlns:eri="urn:3gpp:ns:extRegInfo:1.0"
version="0" state="full">
<registration aor="sip:user1_public1@home1.net" id="as9"
state="active">
<contact id="76" state="active" event="registered">
<uri>sip:[5555::aaa:bbb:ccc:ddd]</uri>
<unknown-param name="audio"/>
</contact>
</registration>
<registration aor="sip:user1_public2@home1.net" id="as10"
state="active">
<contact id="86" state="active" event="created">
<uri>sip:[5555::aaa:bbb:ccc:ddd]</uri>
<unknown-param name="audio"/>
</contact>
<cp:actions>
<eri:rph ns="wps" val="1"/>
<eri:privSender/>
</cp:actions>
</registration>
</reginfo>
EXAMPLE 2: If sip:user1_public1@home1.net is registered, the public user identity sip:ep_user1@home1.net can automatically be registered. sip:ep_user1@home1.net is a dedicated identity out of the related range indicated in the <wildcardedIdentity> element. Therefore the entries in the body of the NOTIFY request look like:
<?xml version="1.0"?>
<reginfo xmlns="urn:ietf:params:xmlns:reginfo"
xmlns:ere="urn:3gpp:ns:extRegExp:1.0"
version="0" state="full">
<registration aor="sip:user1_public1@home1.net" id="as10"
state="active">
<contact id="86" state="active" event="created">
<uri>sip:[5555::aaa:bbb:ccc:ddd]</uri>
</contact>
</registration>
<registration aor="sip:ep_user1@home1.net" id="as11"
state="active">
<contact id="86" state="active" event="created">
<uri>sip:[5555::aaa:bbb:ccc:ddd]</uri>
</contact>
<ere:wildcardedIdentity>sip:ep_user!.*!@home1.net
</ere:wildcardedIdentity>
</registration>
</reginfo>
When sending a final NOTIFY request with all <registration> element(s) having their state attribute set to "terminated" (i.e. all public user identities have been deregistered, expired or are hosted (unregistered case) at the S-CSCF), the S-CSCF shall also terminate the subscription to the registration event package by setting the Subscription-State header field to the value of "terminated".
When all of a UE's contact addresses have been deregistered (i.e. there is no <contact> element set to "active" for this UE), the S-CSCF shall consider subscription to the reg event package belonging to the UE cancelled (i.e. as if the UE had sent a SUBSCRIBE request with an Expires header field containing a value of zero).
The S-CSCF shall only include the non-barred public user identities in the NOTIFY request.
When the S-CSCF receives any response to the NOTIFY request, the S-CSCF shall store the value of the "term-ioi" header field parameter received in the P-Charging-Vector header field, if present.
NOTE 11: Any received "term-ioi" header field parameter will be a type 3 IOI if received from an AS or a type 1 IOI if received from a public user identity this particular user owns, or any of the entities identified by the Path header field. The type 3 IOI identifies the service provider from which the response was sent and the type 1 IOI identifies the network from which the response was sent.
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5.4.2.1.3 Void
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5.4.2.1.4 Void
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5.4.2.1A Outgoing subscriptions to load-control event
Based on operator policy, the S-CSCF may subscribe to the load-control event package with one or more target SIP entities. The list of target SIP entities is provisioned.
Subscription to the load-control event package is triggered by internal events (e.g. the physical device hosting the SIP entity is power-cycled) or through a management interface.
The S-CSCF shall perform subscriptions to the load-control event package to a target entity in accordance with RFC 6665 [28] and with RFC 7200 [201]. When subscribing to the load-control event, the S-CSCF shall:
1) Send a SUBSCRIBE request in accordance with RFC 6665 [28] and with RFC 7200 [201] to the target entity, with the following elements:
- an Expires header field set to a network specific value;
2) If the target entity is located in a different network and local policy requires the application of IBCF capabilities, forward the request to an IBCF acting as an exit point.
The S-CSCF shall automatically refresh ongoing subscription to the load-control event package either 600 seconds before the expiration time if the initial subscription was for greater than 1200 seconds, or when half of the time has expired if the initial subscription was for 1200 seconds or less.
The S-CSCF can terminate a subscription according to RFC 6665 [28].
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5.4.2.2 Other subscriptions
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Upon receipt of a NOTIFY request with the Subscription-State header field set to "terminated" and the S-CSCF has retained the SIP dialog state information for the associated subscription, once the NOTIFY transaction is terminated, the S-CSCF can remove all the stored information related to the associated subscription.
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5.4.3 General treatment for all dialogs and standalone transactions excluding requests terminated by the S-CSCF
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5.4.3.1 Determination of UE-originated or UE-terminated case
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Upon receipt of an initial request or a stand-alone transaction, the S-CSCF shall:
- perform the procedures for the UE-originating case as described in subclause 5.4.3.2 if the request makes use of the information for UE-originating calls, which was added to the Service-Route header field entry of the S-CSCF during registration (see subclause 5.4.1.2.2F), e.g. the message is received at a certain port or the topmost Route header field contains a specific user part or parameter; or,
- perform the procedures for the UE-originating case as described in subclause 5.4.3.2 if the topmost Route header field of the request contains the "orig" parameter. The S-CSCF shall remove the "orig" parameter from the topmost Route header field; or,
- perform the procedures for the UE-terminating case as described in subclause 5.4.3.3 if this information is not used by the request.
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5.4.3.2 Requests initiated by the served user
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For all SIP transactions identified:
- if priority is supported, as containing an authorised Resource-Priority header field or a temporarily authorised Resource-Priority header field, or, if such an option is supported, relating to a dialog which previously contained an authorised Resource-Priority header field;
the S-CSCF shall give priority over other transactions or dialogs. This allows special treatment of such transactions or dialogs. If priority is supported, the S-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field or backwards indication value.
NOTE 1: The special treatment can include filtering, higher priority processing, routeing, call gapping. The exact meaning of priority is not defined further in this document, but is left to national regulation and network configuration.
When the S-CSCF receives from the UE an initial request for a dialog, which contains a GRUU and an "ob" SIP URI parameter in the Contact header field, and multiple contact addresses have been registered for the specific GRUU, then for all subsequent in-dialog requests sent toward the UE's, the S-CSCF shall populate the Request-URI with the registered contact address from which the UE sent the initial request for the dialog.
NOTE 2: When a given contact address is registered, the S-CSCF can use a dedicated value in its Service-Route header field entry to identify the given contact address. When the S-CSCF receives an initial request for a dialog, the S-CSCF can find out from which contact address the initial request was sent by looking at the preloaded Route header field (constructed from the Service-Route header field returned in the response for the REGISTER request) which contains the entry of the S-CSCF.
When performing SIP digest without TLS, when the S-CSCF receives from the served user an initial request for a dialog or a request for a standalone transaction, the S-CSCF may perform the steps in subclause 5.4.3.6 to challenge the request based on local policy.
NOTE 3: If the user registration is associated with the state "tls-protected", then the execution of Proxy-Authorization as described in subclause 5.4.3.6 is still possible, although it is unlikely this would add additional security provided the P-CSCF is trusted. Thus, in most cases the state "tls-protected" will be reason for the S-CSCF to not desire Proxy-Authentication for this user.
NOTE 4: The option for the S-CSCF to challenge the request does not apply to a request from an AS acting as an originating UA.
When performing GPRS-IMS-Bundled authentication, when the S-CSCF receives from the served user an initial request for a dialog or a request for a standalone transaction, the S-CSCF shall check whether a "received" header field parameter exists in the Via header field provided by the UE. If a "received" header field parameter exists, S-CSCF shall compare the (prefix of the) IP address received in the "received" header field parameter against the UE's IP address (or prefix) stored during registration. If no "received" header field parameter exists in the Via header field provided by the UE, then S-CSCF shall compare the (prefix of the) IP address received in the "sent-by" parameter against the IP address (or prefix) stored during registration. If the stored IP address (or prefix) and the (prefix of the) IP address in the "received" Via header field parameter provided by the UE do not match, the S-CSCF shall reject the request with a 403 (Forbidden) response. In case the stored IP address (or prefix) and the (prefix of the) IP address in the "received" Via header field parameter provided by the UE do match, the S-CSCF shall proceed as described in the remainder of this subclause.
If the S-CSCF supports HSS based P-CSCF restoration, and receives a request from a P-CSCF that the S-CSCF considers is not reachable, the S-CSCF shall consider this P-CSCF as being reachable.
If the S-CSCF supports PCRF based P-CSCF restoration, and receives a request from a P-CSCF that the S-CSCF considers is in a not reachable, the S-CSCF shall consider this P-CSCF as being reachable.
When the S-CSCF receives from the served user or from a PSI an initial request for a dialog or a request for a standalone transaction, and the request is received either from a functional entity within the same trust domain or contains a valid original dialog identifier (see step 3) or the dialog identifier (From, To and Call-ID header fields) relates to an existing request processed by the S-CSCF, then prior to forwarding the request, the S-CSCF shall:
0) if the request is received from a P-CSCF that does not support the trust domain handling of the P-Served-User header field then remove any P-Served-User header fields;
1) determine the served user as follows:
a) if the request contains a P-Served-User header field then
i) determine the served user by taking the identity contained in a P-Served-User header field as defined in RFC 5502 [133]. Then check whether the determined served user is a barred public user identity. In case the said header field contains the served user identity is a barred public user identity for the user, then the S-CSCF shall reject the request by generating a 403 (Forbidden) response. Otherwise, the S-CSCF shall save the public user identity of the served user and continue with the rest of the steps;
NOTE 5: If the P-Served-User header field contains a barred public user identity, then the message has been received, either directly or indirectly, from a non-compliant entity which should have had generated the content with a non-barred public user identity.
b) if the request does not contain a P-Served-User header field then
i) determine the served user by taking the identity contained in one of the URI(s) of the P-Asserted-Identity header field. In case the determined served user is a barred public user identity, then the S-CSCF shall reject the request by generating a 403 (Forbidden) response. Otherwise, the S-CSCF shall save the public user identity of the served user and continue with the rest of the steps; and
ii) if the P-Asserted-Identity header field contains two URIs and the URI other than the determined served user is not an alias of the determined served user or is barred then act based on local policy, e.g. reject the request by generating a 403 (Forbidden) response or remove the URI not identifying the determined served user from the P-Asserted-Identity header field;
NOTE 6: If the P-Asserted-Identity header field contains a barred public user identity, then the message has been received, either directly or indirectly, from a non-compliant entity which should have had generated the content with a non-barred public user identity.
1A) if the Contact is a GRUU, but is not valid as defined in subclause 5.4.7A.4, then return a 4xx response as specified in RFC 5627 [93];
2) store the value of the "orig-ioi" header field parameter received in the P-Charging-Vector header field if present, and remove it from any forwarded request;
NOTE 7: Any received "orig-ioi" header field parameter will be either a type 1 IOI or a type 3 IOI. The type 1 IOI identifies the network from which the request was sent and the type 3 IOI identifies the service provider from which the request was sent (AS initiating a session on behalf of a user or a PSI);
3) check if an original dialog identifier that the S-CSCF previously placed in a Route header field is present in the topmost Route header field of the incoming request.
- If not present, the S-CSCF shall build an ordered list of initial filter criteria based on the public user identity of the served user (as determined in step 1) of the received request as described in 3GPP TS 23.218 [5].
- If present, the request has been sent from an AS in response to a previously sent request, an ordered list of initial filter criteria already exists and the S-CSCF shall not change the ordered list of initial filter criteria even if the AS has changed the P-Served-User header field or the P-Asserted-Identity header field;
NOTE 8: An original dialog identifier is sent to each AS invoked due to iFC evaluation such that the S-CSCF can associate requests as part of the same sequence that trigger iFC evaluation in priority order (and not rely on SIP dialog information that can change due to B2BUA AS). If the same original dialog identifier is included in more than one request from a particular AS (based on service logic in the AS), then the S-CSCF will continue the iFC evaluation sequence rather than build a new ordered list of iFC;
4) remove its own SIP URI from the topmost Route header field;
4A) if a reference location was received from the HSS at registration as part of the user profile and the request does not contain a message body with the content type application/pidf+xml in accordance with RFC 6442 [89] and does not contain a P-Access-Network-Info header field containing the "network-provided" parameter, the S-CSCF shall insert a P-Access-Network-Info header field constructed according to the reference location received from the HSS and containing the "network-provided" parameter. The access type information received from the HSS shall be mapped into the corresponding access-type parameter of the P-Access-Network-Info header field and the location information shall be mapped into the location parameter corresponding to the access-type parameter, i.e. into "dsl-location" parameter, "fiber-location" parameter or "eth-location" parameter;
4B) if there was an original dialog identifier present in the topmost Route header field of the incoming request and the request is received from a functional entity within the same trust domain and contains a P-Asserted-Service header field, continue the procedure with step 5;
4C) if the request contains a P-Preferred-Service header field, check whether the ICSI value contained in the P-Preferred-Service header field is part of the set of the subscribed services for the served user and determine, using operator-configured data, whether the contents of the request match the ICSI for the subscribed service. The operator-configured data used to determine if there is a matching between the request and the ICSI value may be based on any information in the request (e.g. SDP media capabilities, Content-Type header field, request method). Then:
a) if there is no match between the request and the ICSI value, as an operator option, the S-CSCF may reject the request by generating a 403 (Forbidden) response. Otherwise remove the P-Preferred-Service header field and continue with the rest of the steps; and
b) if there is a match between the request and the ICSI value, then include a P-Asserted-Service header field in the request containing the ICSI value contained in the P-Preferred-Service header field, remove the P-Preferred-Service header field, and continue the procedure with step 5;
4D) if the request does not contain a P-Preferred-Service header field, check, using operator-configured data, whether the contents of the request match a subscribed service for each and any of the subscribed services for the served user:
a) if not, as an operator option, the S-CSCF may reject the request by generating a 403 (Forbidden) response; and
b) if so, and if the request is related to an IMS communication service and the IMS communication service requires the use of an ICSI value then select an ICSI value for the related IMS communication service and include a P-Asserted-Service header field in the request containing the selected ICSI value; and
NOTE 9: If more than one ICSI values match the contents of the request, the S-CSCF selects an ICSI value based on local policy.
c) if so, and if the request is related to an IMS communication service and the IMS communication service does not require the use of an ICSI value then continue without including an ICSI value; and
d) if so, and if the request does not relate to an IMS communication service (or if the S-CSCF is unable to unambiguously determine the service being requested but decides to allow the session to continue) then continue without including an ICSI value;
5) check whether the initial request matches any unexecuted initial filter criteria. If there is a match, then the S-CSCF shall select the first matching unexecuted initial filter criteria from the ordered list of initial filter criteria and the S-CSCF shall:
a) insert the AS URI to be contacted into the Route header field as the topmost entry followed by its own URI populated as specified in the subclause 5.4.3.4;
NOTE 10: If the AS is accessed via an ISC gateway function, then the URI will be the address of the ISC gateway function.
b) if the S-CSCF supports the P-Served-User extension as specified in RFC 5502 [133] and RFC 8498 [239] insert P-Served-User header field populated with the served user identity as determined in step 1. If required by operator policy, the S-CSCF shall:
- if the associated session case is "Originating" as specified in 3GPP TS 29.228 [14], include the sescase header field parameter set to "orig" and the regstate header field parameter set to "reg";
- if the associated session case is "Originating_Unregistered" as specified in 3GPP TS 29.228 [14], include the sescase header field parameter set to "orig" and the regstate header field parameter set to "unreg";
- if the associated session case is "Originating_CDIV" as specified in 3GPP TS 29.228 [14], include the "orig-cdiv" header field parameter, defined in RFC 8498 [239]; and
c) if the AS is located outside the trust domain then the S-CSCF shall remove the access-network-charging-info parameter in the P-Charging-Vector header field from the request that is forwarded to the AS; if the AS is located within the trust domain, then the S-CSCF shall retain the access-network-charging-info parameter in the P-Charging-Vector header field in the request that is forwarded to the AS;
d) insert a type 3 "orig-ioi" header field parameter in place of any received "orig-ioi" header field parameters in the P-Charging-Vector header field. The S-CSCF shall set the type 3 "orig-ioi" header field parameter to a value that identifies the sending network of the request. The S-CSCF shall not include the type 3 "term-ioi" header field parameter;
e) remove the "transit-ioi" header field parameter, if received;
f) based on operator policy insert in a Relayed-Charge header field the value of the received "transit-ioi" header field parameter in the P-Charging-Vector header field;
g) based on local policy, the S-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier;
h) if the S-CSCF supports using a token to identify the registration and if a registration exists, insert a "+g.3gpp.registration-token" Feature-Caps header field parameter, as defined in subclause 7.9A.8, set to the same value as included in the "+g.3gpp.registration-token" Contact header field parameter of the third party REGISTER request sent to the AS when the UE registered; and
i) if an IP address associated with the served user and the AS SIP URI is stored as described in subclause 5.4.0 exists, then the S-CSCF forwards the SIP message to the IP address associated with the served user and the AS SIP URI;
NOTE 11: Depending on the result of processing the filter criteria the S-CSCF might contact one or more AS(s) before processing the outgoing Request-URI.
NOTE 12: An AS can activate or deactivate its own filter criteria via the Sh interface. As the S-CSCF checks initial filter criteria only on receipt of an initial request for a dialog, or a standalone transaction, a modified service profile will have no impact on transactions or dialogs already in progress and the modified profile will be effective only for new transactions and dialogs. If the S-CSCF receives a modification of the iFC during their execution, then it should not update the stored initial Filter Criteria until the iFC related to the initial request have been completely executed.
6) if there was no original dialog identifier present in the topmost Route header field of the incoming request store the value of the "icid-value" header field parameter received in the P-Charging-Vector header field and retain the "icid-value" header field parameter in the P-Charging-Vector header field. Optionally, the S-CSCF may generate a new, globally unique ICID and insert the new value in the "icid-value" header field parameter of the P-Charging-Vector header field when forwarding the message. If the S-CSCF creates a new ICID, then it is responsible for maintaining the two ICID values in the subsequent messaging. Based on local policy, the S-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier if not already available;
7) in step 5, if the initial request did not match any unexecuted initial filter criteria (i.e. the request is not forwarded to an AS):
a) remove the received "transit-ioi" from the P-Charging-Vector header field, if present;
b) insert a type 2 "orig-ioi" header field parameter into the P-Charging-Vector header field. The S-CSCF shall set the type 2 "orig-ioi" header field parameter to a value that identifies the sending network. The S-CSCF shall not include the type 2 "term-ioi" header field parameter; and
c) remove the Relayed-Charge header field, if present;
8) insert a P-Charging-Function-Addresses header field populated with values received from the HSS if the request does not contain a P-Charging-Function-Addresses header field and the message is forwarded within the S-CSCF home network, including towards AS;
9) if there was no original dialog identifier present in the topmost Route header field of the incoming request and if the served user is not considered a privileged sender then:
a) if the P-Asserted-Identity header field contains only a SIP URI and if the S-CSCF has knowledge that the SIP URI contained in the received P-Asserted-Identity header field is an alias SIP URI for a tel URI, add a second P-Asserted-Identity header field containing this tel-URI, including the display name associated with the tel URI, if available; and
b) if the P-Asserted-Identity header field contains only a tel URI, the S-CSCF shall add a second P-Asserted-Identity header field containing a SIP URI. The added SIP URI shall contain in the user part a "+" followed by the international public telecommunication number contained in tel URI, and user's home network domain name in the hostport part. The added SIP URI shall contain the same value in the display name as contained in the tel URI. The S-CSCF shall also add a "user" SIP URI parameter equals "phone" to the SIP URI;
NOTE 13: If tel URI is shared URI so is the alias SIP URI.
10) if the request is not forwarded to an AS and if the outgoing Request-URI is:
- a SIP URI with the user part starting with a + and the "user" SIP URI parameter equals "phone", and if configured per local operator policy, the S-CSCF shall perform the procedure described here. Local policy can dictate whether this procedure is performed for all domains of the SIP URI, only if the domain belongs to the home network, or not at all. If local policy indicates that the procedure is to be performed, then the S-CSCF shall translate the international public telecommunications number contained in the user part of the SIP URI (see RFC 3966 [22]) to a globally routeable SIP URI using either an ENUM/DNS translation mechanism with the format specified in RFC 6116 [24], or any other available database. Database aspects of ENUM are outside the scope of the present document. An S-CSCF that implements the additional routeing functionality described in annex I may forward the request without attempting translation. If an agreement exists between the home network and the visited network to support roaming architecture for voice over IMS with local breakout, the S-CSCF does not enable NP capabilities, and the S-CSCF decides to loopback the call to the visited network, the S-CSCF may forward the request without attempting translation. If a translation is in fact performed and it succeeds, the S-CSCF shall update the Request-URI with the globally routeable SIP URI either returned by ENUM/DNS or obtained from any other available database. If this translation fails, the request may be forwarded to a BGCF or any other appropriate entity (e.g. a MRFC to play an announcement) in the originator's home network or the S-CSCF may send an appropriate SIP response to the originator. When forwarding the request to a BGCF or any other appropriate entity, the S-CSCF shall leave the original Request-URI containing the SIP URI with "user" SIP URI parameter equals phone unmodified. If the request is forwarded, the S-CSCF shall remove the access-network-charging-info parameter from the P-Charging-Vector header field prior to forwarding the message;
- a SIP URI with a "user" SIP URI parameter equals "dialstring" and the domain name of the SIP URI belongs to the home network (i.e. the local number analysis and handling is either failed in the appropriate AS or the request has not been forwarded to AS for local number analysis and handling at all), either forward the request to any appropriate entity (e.g a MRFC to play an announcement) in the originator's home network or send an appropriate SIP response to the originator;
- a SIP URI with a local number (see RFC 3966 [22]) in the user part and a "user" SIP URI parameter equals "phone" and the domain name of the SIP URI belongs to the home network (i.e. the local number analysis and handling is either failed in the appropriate AS or the request has not been forwarded to AS for local number analysis and handling at all), either forward the request to to a BGCFor any appropriate entity (e.g a MRFC to play an announcement) in the originator's home network or send an appropriate SIP response to the originator;
- a tel URI containing a global number (see RFC 3966 [22]) in the international format, the S-CSCF shall translate the E.164 address to a globally routeable SIP URI using either an ENUM/DNS translation mechanism with the format specified in RFC 6116 [24], or any other available database. Database aspects of ENUM are outside the scope of the present document. An S-CSCF that implements the additional routeing functionality described in annex I may forward the request without attempting translation. If an agreement exists between the home network and the visited network to support roaming architecture for voice over IMS with local breakout, the S-CSCF does not enable NP capabilities, and the S-CSCF decides to loopback the call to the visited network, the S-CSCF may forward the request without attempting translation. If this translation is in fact performed and it succeeds, the S-CSCF shall update the Request-URI with the globally routeable SIP URI returned by ENUM/DNS or any other available database. If this translation fails, the request may be forwarded to a BGCF or any other appropriate entity (e.g a MRFC to play an announcement) in the originator's home network or the S-CSCF may send an appropriate SIP response to the originator. When forwarding the request to a BGCF or any other appropriate entity, the S-CSCF shall leave the original Request-URI containing the tel URI unmodified. If the request is forwarded, the S-CSCF shall remove the access-network-charging-info parameter from the P-Charging-Vector header field prior to forwarding the message;
- a tel URI containing a local number (see RFC 3966 [22]) (i.e. the local number analysis and handling is either failed in the appropriate AS or the request has not been forwarded to AS for local number analysis and handling at all), either forward the request to a BGCF or any other appropriate entity (e.g. a MRFC to play an announcement) in the originator's home network or send an appropriate SIP response to the originator;
- a pres URI or an im URI, the S-CSCF shall forward the request as specified in RFC 3861 [63]. In this case, the S-CSCF shall not modify the received Request-URI: and
- a service URN, e.g. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69]. In this case the S-CSCF shall not modify the received Request-URI.
NOTE 14: If there is no SIP-based transport found after applying the procedure specified in RFC 3861 [63], the S-CSCF can forward the request to a translating gateway.
Additional procedures apply if the S-CSCF supports NP capabilities and these capabilities are enabled by local policy, and the database used for translation from an international public telecommunications number to a SIP URI also provides NP data (for example, based on the PSTN Enumservice as defined by RFC 4769 [114] or other appropriate data bases). If the above translation from an international public telecommunications number to a SIP URI failed, but NP data was obtained from the database and there is no "npdi" parameter in the received request, then the S-CSCF shall, based on operator policy, replace the URI in the Request-URI with the obtained NP data, prior to forwarding the request to the BGCF or other appropriate entity. If the received request already contains a tel-URI "npdi" parameter, then the S-CSCF may update the URI with the obtained NP data. The URI is updated by the S-CSCF by adding NP parameters defined by RFC 4694 [112]. If the Request-URI is a tel-URI, then an "npdi" tel-URI parameter is added to indicate that NP data retrieval has been performed, and if the number is ported, an "rn" tel-URI parameter is added to identify the ported-to routeing number. If the Request-URI is in the form of a SIP URI user=phone, the "npdi" and "rn" tel-URI parameters are added as described above to the userinfo part of the SIP URI;
NOTE 15: When the S-CSCF replaces the tel-URI in the Request-URI with the obtained NP data, all tel URI parameters in the received Request-URI will be replaced by the obtained NP data.
10A) if the request is not forwarded to an AS and if local policy requires the application of additional routeing capabilities, as defined in annex I, the S-CSCF shall apply the additional routeing capabilities if they are locally available or forward the request to an entity that implements the additional routeing capabilities;
10B) if an agreement exists between the home network and the visited network to support Roaming Architecture for Voice over IMS with Local Breakout then continue with the following steps. Otherwise continue with step 11. If:
- the top most Route header contains an indication that this is the UE-originating case;
NOTE 16: This indication can e.g. be in a URI parameter, a character string in the user part of the URI or can be a port number in the URI added by the S-CSCF during the registration in the Service-Route header field.
- the UE is roaming (as identified by the P-Visited-Network-ID header field value in the original REGISTER request); and
- the request is an INVITE request;
determine if loopback routeing is applicable for this request using local policy, and save this decision for subsequent processing along with the following information:
a) any URI representing the TRF address preference received from the visited network; and
b) the ICID received in the request.
In addition, the S-CSCF shall also include in the request a Feature-Caps header field with the "+g.3gpp.home-visited" header field parameter according to RFC 6809 [190] with the "+g.3gpp.home-visited" header field parameter set to the identifier of the visited network received in the P-Visited-Network-ID header field in the original registration request;
10C) if the request is an INVITE request, then determine whether loopback is applied for this request. The information saved in step 10B, and the presence or absence of the Feature-Caps header field with the "+g.3gpp.home-visited" header field parameter in the received INVITE request are taken into account in making this decision:
a) if loopback routeing is not to be performed for this request remove any "+g.3gpp.trf" header field parameter or "+g.3gpp.home-visited" header field parameter from the Feature-Caps header field of the outgoing request;
b) if loopback routeing is applied for this request;
i) remove all entries in the Route header field;
ii) if a "+g.3gpp.trf" header field parameter with a parameter value containing a valid URI, is included in the Feature-Caps header field of the request, insert the URI in a Route header field;
iii) if a "+g.3gpp.trf" header field parameter, with a parameter value containing a valid URI is not included in the Feature-Caps header field of the request, insert a locally configured TRF address, associated with the visited network for this call, in the Route header field;
iv) remove any "+g.3gpp.home-visited" header field parameter from the Feature-Caps header field of the outgoing request;
v) insert the "+g.3gpp.loopback" header field parameter as specified in subclause 7.9A.4 in the Feature-Caps header field of the request, in accordance with the RFC 6809 [190]. If providing the identifier of the home network is supported by the S-CSCF and the visited network, the S‑CSCF may based on operator agreement insert the "+g.3gpp.loopback" header field parameter set to the identifier of the home network;
vi) if included in the incoming request, remove the "+g.3gpp.trf" header field parameter from the Feature-Caps header field from the outgoing request;
vii) remove a type 2 "orig-ioi" header field parameter that was added in step 7 from the P-Charging-Vector header field and insert a type 1 "orig-ioi" header field parameter into the P-Charging-Vector header field. The S-CSCF shall set the type 1 "orig-ioi" header field parameter to a value that identifies the network in which the S-CSCF resides. The S-CSCF shall not include the "term-ioi" header field parameter; and
viii) if the S-CSCF supports indicating the traffic leg associated with a URI as specified in RFC 7549 [225] and if an "iotl" SIP URI parameter is not included in the TRF URI in the Route header field and if required by local policy, append an "iotl" URI parameter with a value set to "homeA-visitedA" to the URI in the Route header field; and
c) if the final decision on loopback routeing is deferred to a subsequent entity in the home network, the BGCF, then the S-CSCF includes, if absent, in the request a Feature-Caps header field with the "+g.3gpp.home-visited" header field parameter, with the parameter value set to the identifier of the visited network received in the P-Visited-Network-ID header field in the original registration request. The S-CSCF is expected to know by means of network configuration that such a subsequent entity exists; and
NOTE 17: The subsequent entity in the home network, the BGCF, will remove the "+g.3gpp.home-visited" header field parameter from the Feature-Caps header field when a final routeing decision is taken.
11) determine the destination address (e.g. DNS access) using the URI placed in the topmost Route header field if present, otherwise based on the Request-URI. If the destination requires interconnect functionalities (e.g. the destination address is of an IP address type other than the IP address type used in the IM CN subsystem), the S-CSCF shall forward the request to the destination address via an IBCF in the same network;
12) if network hiding is needed due to local policy, put the address of the IBCF to the topmost Route header field;
13) in case of an initial request for a dialog:
a) determine the need for GRUU processing. GRUU processing is required if:
- an original dialog identifier that the S-CSCF previously placed in a Route header field is not present in the topmost Route header field of the incoming request (this means the request is not returning after having been sent to an AS), and
- the contact address contains a GRUU that was either assigned by the S-CSCF that is valid as specified in subclause 5.4.7A.4 or a temporary GRUU self assigned by the UE based on the "temp-gruu-cookie" header parameter provided to the UE;
NOTE 18: The procedures for determining that a URI is a temporary GRUU assigned by the UE are specified in subclause 7.1.2.3 of RFC 6140 [191].
b) if GRUU processing is not required and the initial request originated from a served user, then determine the need to record-route for other reasons:
- if the request is routed to an AS which is part of the trust domain, the S-CSCF shall decide, based on operator policy, whether to record-route or not. The decision is configured in the S-CSCF using any information in the received request that may otherwise be used for the initial filter criteria. If the request is record-routed the S-CSCF shall create a Record-Route header field containing its own SIP URI;
- if the request is a SUBSCRIBE request and routed elsewhere, the S-CSCF shall decide, based on operator policy, whether to record-route or not. The decision is configured in the S-CSCF using any information in the received request (e.g. event package name). If the request is record-routed the S-CSCF shall create a Record-Route header field containing its own SIP URI; or
NOTE 19: Some subscriptions to event packages (e.g. presence) can result in virtually persistent subscriptions and if the S-CSCF Record-Routes this can prevent reassignment of the S-CSCF.
NOTE 20: If the S-CSCF does not Record-Route the initial SUBSCRIBE request, it will not be possible to perform SIP digest authentication of SIP requests sent inside the SIP dialog related to the associated subscription.
- if the request not a SUBSCRIBE request and is routed elsewhere, create a Record-Route header field containing its own SIP URI;
NOTE 21: For requests originated from a PSI the S-CSCF can decide whether to record-route or not based on operator policy.
c) if GRUU processing is required, the S-CSCF shall create a Record-Route header field containing its own SIP URI;
d) if GRUU processing is required, the S-CSCF shall save an indication that GRUU-routeing is to be performed for in-dialog requests that reach the S-CSCF because of the Record-route header field added in step c);
NOTE 22: The manner of representing the GRUU-routeing indication is a private matter for the S-CSCF. The indication is used during termination processing of in-dialog requests to cause the S-CSCF to replace a Request-URI containing a GRUU with the corresponding registered contact address. It can be saved using values in the Record-Route header field, or in dialog state.
14) based on the destination user (Request-URI), remove any P-Access-Network-Info header field and the access-network-charging-info parameter in the P-Charging-Vector header field prior to forwarding the message;
14A) if the request is not routed to an AS, to a BGCF or to an entity that implements the additional routeing functionality, remove the P-Served-User header field prior to forwarding the request;
14B) if the S-CSCF supports indicating the traffic leg as specified in RFC 7549 [225], the request is not routed to an AS, to a BGCF or to an entity that implements the additional routeing functionality, loopback routeing is not to be performed for this request, required by local policy and the Request-URI contains a SIP URI, append the "iotl" SIP URI parameter set to "homeA-homeB" to the Request-URI;
15) route the request based on SIP routeing procedures;
16) if the request is an INVITE request, save the Contact, CSeq and Record-Route header field values received in the request such that the S-CSCF is able to release the session if needed;
17) if the request contains a "logme"parameter in the Session-ID header field, treat this dialog as one for which logging is in progress and log SIP signalling for this dialog according to its trace configuration;
18) if the S-CSCF supports using a token to identify the registration and if the request is not forwarded to an AS, remove the "+g.3gpp.registration-token" Feature-Caps header field parameter, defined in subclause 7.9A.8, if received in the request; and
19) if the received request is an INVITE request or a MESSAGE request and the S-CSCF supports calling number verification using signature verification and attestation information as specified in subclause 3.1, the S-CSCF shall based on local policy perform attestation of the user identity by inserting:
- a "verstat" tel URI parameter, specified in subclause 7.2A.20, to the tel URI or SIP URI with a user=phone parameter in the From header field or the P-Asserted-Identity header field;
an Origination-Id header field, specified in subclause 7.2.19, set to a UUID identifying the S-CSCF which is configured based on local policy and requirements from national regulation: and
- an Attestation-Info header field, specified in subclause 7.2.18, set to the value "A".
When the S-CSCF receives, an initial request for a dialog or a request for a standalone transaction, from an AS acting on behalf of an unregistered user, the S-CSCF shall:
1) execute the procedures described in the steps 1, 2, 3, 4, 4B, 4C, 4D, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 in the above paragraph (when the S-CSCF receives, from a registered served user, an initial request for a dialog or a request for a standalone transaction).
NOTE 23: When the S-CSCF does not have the user profile, before executing the actions as listed above, it initiates the S-CSCF Registration/deregistration notification procedure, as described in 3GPP TS 29.228 [14]; with the purpose of downloading the relevant user profile (i.e. for unregistered user) and informs the HSS that the user is unregistered. The S-CSCF will assess triggering of services for the unregistered user, as described in 3GPP TS 29.228 [14]. When requesting the user profile, and the request received by the S-CSCF contains a P-Profile-Key header field, the S-CSCF can include the header field value in S-CSCF Registration/deregistration notification. If the response from the HSS includes a Wildcarded Public Identity AVP, and if the request received by the S-CSCF did not include a P-Profile-Key header field, the S-CSCF uses the AVP value to set the P-Profile-Key header field before forwarding the request to an AS.
When the S-CSCF receives a request initiated by the served user for which the S-CSCF does not have the user profile or does not trust the data that it has (e.g. due to restart), the S-CSCF shall attempt to retrieve the user profile from the HSS. If the S-CSCF receives a Diameter result code of DIAMETER_UNABLE_TO_COMPLY as defined in 3GPP TS 29.228 [14], the S-CSCF supports S-CSCF restoration procedures, and the Request-URI of the request does not match an emergency service URN, i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69], then the S-CSCF shall:
I) reject the request by returning a 504 (Server Time-out) response to the UE;
II) assume that the UE supports version 1 of the XML Schema for the 3GPP IM CN subsystem XML body if support for the 3GPP IM CN subsystem XML body as described in subclause 7.6 in the Accept header field is not indicated; and
III) include in the 504 (Server Time-out) response:
- a Content-Type header field with the value set to associated MIME type of the 3GPP IM CN subsystem XML body as described in subclause 7.6.1;
- a P-Asserted-Identity header field set to the value of the SIP URI of the S-CSCF included in the Service-Route header field (see subclause 5.4.1.2.2F) during the registration of the user whose UE sent the request causing this response; and
- a 3GPP IM CN subsystem XML body:
a) an <ims-3gpp> element with the "version" attribute set to "1" and with an <alternative-service> child element, set to the parameters of the alternative service;
i) a <type> child element, set to "restoration" (see table 7.6.2) to indicate that S-CSCF restoration procedures are supported;
ii) a <reason> child element, set to an operator configurable reason; and
iii) an <action> child element, set to "initial-registration" (see table 7.6.3).
NOTE 24: These procedures do not prevent the usage of unspecified reliability or recovery techniques above and beyond those specified in this subclause.
Depending on operator configuration (see subclause 5.4.1.8), when the S-CSCF receives a request with a Request-URI that does not match an emergency service URN, i.e. a service URN with a top-level service type of "sos" as specified in RFC 5031 [69], the request initiated by the served user for which the S-CSCF has modified but not synchronized the service profile for the served user and the S-CSCF supports S-CSCF restoration procedures, then the S-CSCF shall reject the request as described in items I), II) and III).
If the S-CSCF:
a) fails to receive a SIP response within a configurable time; or
b) receives a 408 (Request Timeout) response or a 5xx response from the AS without previously receiving a 1xx response to the original SIP request, and without previously receiving a SIP request from the AS that contained the same original dialog identifier as the original request;
the S-CSCF shall:
- if the default handling defined in the filter criteria indicates the value "SESSION_CONTINUED" as specified in 3GPP TS 29.228 [14] or no default handling is indicated, execute the procedure from step 5; and
- if the default handling defined in the filter criteria indicates the value "SESSION_TERMINATED" as specified in 3GPP TS 29.228 [14], either forward the received response or, if the request is an initial INVITE request, send a 408 (Request Timeout) response or a 5xx response towards the served UE as appropriate (without verifying the matching of filter criteria of lower priority and without proceeding for further steps).
If the S-CSCF receives any final response from the AS, the S-CSCF shall forward the response towards the served UE (without verifying the matching of filter criteria of lower priority and without proceeding for further steps).
When the S-CSCF receives any response to the above request containing a Relayed-Charge header field, and the next hop is not an AS, the S-CSCF shall remove the Relayed-Charge header field from the forwarded response.
When the S-CSCF receives any response to the above request, the S-CSCF may:
1) apply any privacy required by RFC 3323 [33] and RFC 3325 [34] to the P-Asserted-Identity header field.
NOTE 25: The P-Asserted-Identity header field would normally only be expected in 1xx or 2xx responses.
NOTE 26: The optional procedure above is in addition to any procedure for the application of privacy at the edge of the trust domain specified by RFC 3325 [34].
When the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If logging is in progress for this dialog, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred then stop treating this as a dialog for which logging is in progress, else the S-CSCF shall append a "logme" header field parameter to the SIP Session-ID header field if the parameter is missing and determine, by checking its trace configuration, whether to log the response.
When the S-CSCF receives any response to the above request containing a "term-ioi" header field parameter in the P-Charging-Vector header field, the S-CSCF shall:
1) store the value of the received "term-ioi" header field parameter if present;
2) remove all received "orig-ioi", "term-ioi" and "transit-ioi" header field parameters from the forwarded response;
3) include the stored "orig-ioi" header field parameter if received in the request;
4) include a type 1 "term-ioi" header field parameter if next hop is not an AS, or a type 3 "term-ioi" header field parameter. The "term-ioi" header field parameter is set to a value that identifies the sending network of the response
NOTE 27: Any received "term-ioi" header field parameter will be a type 2 IOI, if received from an S-CSCF, or type 3 IOI, if received from an AS, or type 1 IOI if the S-CSCF performed loopback routeing for this request. A type 2 IOI identifies the sending network of the response, a type 3 IOI identifies the sending service provider of the response, and a type 1 IOI identifies the visited network of the served user.
5) based on operator policy include any received "transit-ioi" header field parameter, from the P-Charging-Vector header field, in a Relayed-Charge header field, if the next hop is an AS.
When the S-CSCF receives any 1xx or 2xx response to the initial request for a dialog, if the response corresponds to an INVITE request, the S-CSCF shall save the Contact and Record-Route header field values in the response in order to be able to release the session if needed.
When the S-CSCF receives any 1xx or 2xx response to an initial request for a dialog or a request for a standalone transaction, if the response is forwarded within the S-CSCF home network and not to an AS, the S-CSCF shall insert a P-Charging-Function-Addresses header field populated with values received from the HSS.
When the S-CSCF, upon sending an initial INVITE request that includes an IP address in the SDP offer (in "c=" parameter), receives an error response indicating that the IP address type is not supported, (e.g., the S-CSCF receives the 488 (Not Acceptable Here) with 301 Warning header field indicating "incompatible network address format"), the S-CSCF shall either:
- fork the initial INVITE request to the IBCF; or
- process the error response and forward it using the Via header field.
NOTE 28: If the S-CSCF knows that the originating UE supports both IPv6 and IPv4 addresses simultaneously, the S-CSCF will forward the error response to the UE using the Via header field. The present version of the specification does not specify how the S-CSCF determines whether the UE supports both IPv6 and IPv4 addressing simultaneously.
When the S-CSCF receives from the served user a target refresh request for a dialog, prior to forwarding the request the S-CSCF shall:
0A) if the dialog is related to an IMS communication service determine whether the contents of the request (e.g. SDP media capabilities, Content-Type header field) match the IMS communication service as received as the ICSI value in the P-Asserted-Service header field in the initial request. As an operator option, if the contents of the request do not match the IMS communication service the S-CSCF may reject the request by generating a status code reflecting which added contents are not matching. Otherwise, continue with the rest of the steps;
1) remove its own URI from the topmost Route header field;
2) create a Record-Route header field containing its own SIP URI;
3) for INVITE dialogs (i.e. dialogs initiated by an INVITE request), save the Contact and CSeq header field values received in the request such that the S-CSCF is able to release the session if needed;
4) in case the request is routed towards the destination user (Request-URI) or in case the request is routed to an AS located outside the trust domain, remove the access-network-charging-info parameter in the P-Charging-Vector header field;
5) route the request based on the topmost Route header field; and
6) if the request was sent on a dialog for which logging of signalling is in progress, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred then stop logging of signalling, else determine, by checking its trace configuration, whether to log the response.
When the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If logging is in progress for this dialog, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred then stop logging of signalling, else determine, by checking its trace configuration, whether to log the response.
When the S-CSCF receives any 1xx or 2xx response to the target refresh request for an INVITE dialog, the S-CSCF shall replace the saved Contact header field values in the response such that the S-CSCF is able to release the session if needed.
If the S-CSCF inserted in the initial request for the dialog the header field parameters into the Feature-Caps header field then the S-CSCF shall include the header field parameters with the same parameter values into the Feature-Caps header field in any target refresh request for the dialog, and in each 1xx or 2xx response to target refresh request sent in the same direction.
When the S-CSCF receives from the served user a subsequent request other than a target refresh request for a dialog, prior to forwarding the request the S-CSCF shall:
1) remove its own URI from the topmost Route header field;
2) in case the request is routed towards the destination user (Request-URI) or in case the request is routed to an AS located outside the trust domain, remove the access-network-charging-info parameter in the P-Charging-Vector header field; and
3) route the request based on the topmost Route header field; and
4) if the request was sent on a dialog for which logging of signalling is in progress, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred, stop logging of signalling, else determine, by checking its trace configuration, whether to log the request.
When the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If logging is in progress for this dialog, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred then stop logging of signalling, else determine, by checking its trace configuration, whether to log the response.
With the exception of 305 (Use Proxy) responses, the S-CSCF shall not recurse on 3xx responses.
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.3.3 Requests terminated at the served user
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For all SIP transactions identified:
- if priority is supported, as containing an authorised Resource-Priority header field or a temporarily authorised Resource-Priority header field, or, if such an option is supported, relating to a dialog which previously contained an authorised Resource-Priority header field;
the S-CSCF shall give priority over other transactions or dialogs. This allows special treatment for such transactions or dialogs. If priority is supported, the S-CSCF shall adjust the priority treatment of transactions or dialogs according to the most recently received authorized Resource-Priority header field or backwards indication value.
NOTE 1: The special treatment can include filtering, higher priority processing, routeing, call gapping. The exact meaning of priority is not defined further in this document, but is left to national regulation and network configuration.
When the S-CSCF receives, destined for a registered served user, an initial request for a dialog or a request for a standalone transaction, and the request is received either from a functional entity within the same trust domain or contains a valid original dialog identifier or the dialog identifier (From, To and Call-ID header fields) relates to an existing request processed by the S-CSCF, then prior to forwarding the request, the S-CSCF shall:
1) check if an original dialog identifier that the S-CSCF previously placed in a Route header field is present in the topmost Route header field of the incoming request.
- If present, the request has been sent from an AS in response to a previously sent request.
- If not present, it indicates that the request is visiting the S-CSCF for the first time and in this case the S-CSCF shall determine the served user by taking the identity contained in the Request-URI. If the Request-URI is a temporary GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.3, then take the public user identity that is associated with the temporary GRUU to be the served user identity. Then check whether the determined served user identity is a barred public user identity. In case the served user identity is a barred public user identity for the user, then the S-CSCF shall reject the request by generating a 404 (Not Found) response. Otherwise, the S-CSCF shall save the Request-URI from the request, the served user identity and the public user identity of the served user and continue with the rest of the steps;
NOTE 2: An original dialog identifier is sent to each AS invoked due to iFC evaluation such that the S-CSCF can associate requests as part of the same sequence that trigger iFC evaluation in priority order (and not rely on SIP dialog information that can change due to B2BUA AS). If the same original dialog identifier is included in more than one request from a particular AS (based on service logic in the AS), then the S-CSCF will continue the iFC evaluation sequence rather than build a new ordered list of iFC;
2) remove its own URI from the topmost Route header field;
2A) if there was no original dialog identifier present in the topmost Route header field of the incoming request build an ordered list of initial filter criteria based on the public user identity in the Request-URI of the received request as described in 3GPP TS 23.218 [5].
3) if there was an original dialog identifier present in the topmost Route header field of the incoming request then check whether the Request-URI matches the saved Request-URI. The Request-URI and saved Request-URI are considered a match:
a) if the canonical forms of the two Request-URI are equal to the saved value of the Request-URI;
b) if the Request-URI is a GRUU (public or temporary) and the saved value of the Request-URI is a GRUU (public or temporary) and both GRUUs represent the same public user identity or represent public user identities that are alias SIP URIs of each other; or
c) if the Request-URI is an alias SIP URI of the saved value of the Request-URI.
NOTE 3: The canonical form of the Request-URI is obtained by removing all URI parameters (including the user-param), and by converting any escaped characters into unescaped form. The alias SIP URI is defined in subclause 3.1.
If there is no match, then the S-CSCF shall decide whether to trigger the originating services to be executed after retargeting. The decision is configured in the S-CSCF and may use any information in the received request that is used for the initial filter criteria or an operator policy. The S-CSCF shall decide either to:
a) stop evaluating current iFC. In that case, if the request is an INVITE request, save the Contact, CSeq and Record-Route header field values received in the request such that the S-CSCF is able to release the session if needed, forward the request based on the topmost Route header field or if not available forward the request based on the Request-URI (routeing based on Request-URI is specified in steps 2, 7 and 10 through 14a from subclause 5.4.3.2) and skip the following steps; or
b) stop evaluating current iFC and build an ordered list of iFC with the originating services to be executed after retargeting as described in 3GPP TS 23.218 [5] criteria based on the public user identity of the served user and start the evaluation of that iFC as described in subclause 5.4.3.2 starting at step 4B of subclause 5.4.3.2;
NOTE 4: The S-CSCF assesses triggering of services for the originating services after retargeting means it evaluates IFCs with a SessionCase set to ORIGINATING_CDIV, as defined in 3GPP TS 29.228 [14]. If the P-Served-User extension specified in RFC 5502 [133] is supported, the S-CSCF uses the "orig-cdiv" header field parameter defined in RFC 8498 [239].
NOTE 5: The identity of the served user can be obtained from the History-Info header field (see RFC 7044 [66]) or the P-Served User header field as specified in RFC 5502 [133]. The served user can be a public user identity, a public GRUU, or a temporary GRUU. It needs to be ensure, that all ASs in the iFC can determine the served user correctly.
NOTE 6: The S-CSCF determines whether to apply a) or b) based on information in the initial Filter Criteria.
3A) if the Request-URI is a GRUU, but is not valid as defined in subclause 5.4.7A.4, then return a 4xx response as specified in RFC 5627 [93];
3B) if the Request-URI contains a public GRUU and the saved value of the Request-URI is a temporary GRUU, then replace the Request-URI with the saved value of the Request-URI;
3C) if the request contains a P-Asserted-Service header field check whether the IMS communication service identified by the ICSI value contained in the P-Asserted-Service header field is allowed by the subscribed services for the served user:
a) if so, continue from step 4; and
b) if not, as an operator option, the S-CSCF may reject the request by generating a 403 (Forbidden) response. Otherwise, remove the P-Asserted-Service header field and continue with the rest of the steps;
3D) if the request does not contain a P-Asserted-Service header field check if the contents of the request matches a subscribed service (e.g. SDP media capabilities, Content-Type header field) for each and any of the subscribed services for the served user:
a) if not, as an operator option, the S-CSCF may reject the request by generating a 403 (Forbidden) response. Otherwise, continue with the rest of the steps; and
b) if so, and if the request is related to an IMS communication service and the IMS communication service requires the use of an ICSI value then include a P-Asserted-Service header field in the request containing the ICSI value for the related IMS communication service, and use it as a header field in the initial request when matching initial filter criteria in step 4; and
c) if so, and if the request is related to an IMS communication service and the IMS communication service does not require the use of an ICSI value then continue without including an ICSI value; and
d) if so, and if the request does not relate to an IMS communication service (or if the S-CSCF is unable to unambiguously determine the service being requested but decides to allow the session to continue) then continue without inclding an ICSI value;
4) check whether the initial request matches any unexecuted initial filter criteria based on the public user identity of the served user in the priority order and apply the filter criteria on the SIP method as described in 3GPP TS 23.218 [5] subclause 6.5. If there is a match, then the S-CSCF shall select the first matching unexecuted initial filter criteria and:
a) if the Request-URI is a temporary GRUU as defined in subclause 5.4.7A.3, then replace the Request-URI with the public GRUU that is associated with the temporary GRUU (i.e. the public GRUU representing the same public user identity and instance ID as the temporary GRUU);
b) insert the AS URI to be contacted into the Route header field as the topmost entry followed by its own URI populated as specified in the subclause 5.4.3.4;
c) if the S-CSCF supports the P-Served-User extension as specified in RFC 5502 [133], insert the P-Served-User header field populated with the served user identity as determined in step 1. If required by operator policy, the S-CSCF shall:
- if the associated session case is "Terminating" as specified in 3GPP TS 29.228 [14], include the sescase header field parameter set to "term" and the regstate header field parameter set to "reg";
- if the associated session case is "Terminating_Unregistered" as specified in 3GPP TS 29.228 [14], include the sescase header field parameter set to "term" and the regstate header field parameter set to "unreg";
d) insert a type 3 "orig-ioi" header field parameter replacing any received "orig-ioi" header field parameter in the P-Charging-Vector header field. The type 3 "orig-ioi" header field parameter identifies the sending network of the request message. The S-CSCF shall not include the type 3 "term-ioi" header field parameter;
e) based on local policy, the S-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or identifier if not already available;
f) remove the "transit-ioi" header field parameter, if received;
g) based on operator policy insert a Relayed-Charge header field containing the value of the received "transit-ioi" header field parameter in the P-Charging-Vector header field; and
h) if an IP address associated with the served user and the AS SIP URI is stored as described in subclause 5.4.0 exists, then the S-CSCF forwards the SIP message to the IP address associated with the served user and the AS SIP URI;
NOTE 7: Depending on the result of the previous process, the S-CSCF can contact one or more AS(s) before processing the outgoing Request-URI.
NOTE 8: If the Request-URI of the received terminating request contains a temporary GRUU, then step 4 replaces the Request-URI with the associated public GRUU before invoking the AS, and step 3B restores the original temporary GRUU when the request is returned from the AS.
NOTE 9: An AS can activate or deactivate its own filter criteria via the Sh interface. As the S-CSCF checks initial filter criteria only on receipt of an initial request for a dialog, or a standalone transaction, a modified service profile will have no impact on transactions or dialogs already in progress and the modified profile will be effective only for new transactions and dialogs. If the S-CSCF receives a modification of the iFC during their execution, then it should not update the stored initial Filter Criteria until the iFC related to the initial request have been completely executed.
5) if there was no original dialog identifier present in the topmost Route header field of the incoming request insert a P-Charging-Function-Addresses header field, if not present, populated with values received from the HSS if the message is forwarded within the S-CSCF home network, including towards AS;
6) if there was no original dialog identifier present in the topmost Route header field of the incoming request store the value of the "icid-value" header field parameter received in the P-Charging-Vector header field and retain the "icid-value" header field parameter in the P-Charging-Vector header field;
7) if there was no original dialog identifier present in the topmost Route header field of the incoming request:
- store the value of the "orig-ioi" header field parameter received in the P-Charging-Vector header field, if present;
- remove received "orig-ioi", "term-ioi" and "transit-ioi" header field parameters from the forwarded request if next hop is not an AS; and
- include a type 1 "orig-ioi" header field parameter if next hop is not an AS;
NOTE 10: Any received "orig-ioi" header field parameter will be a type 2 IOI. or type 3 IOI. A type 2 IOI identifies the sending network of the request message, a type 3 IOI identifies the sending service provider of the request message.
7A) if there was an original dialog identifier present in the topmost Route header field of the incoming request:
- store the value of the "orig-ioi" header field parameter received in the P-Charging-Vector header field, if present;
- remove the received "orig-ioi" header field parameter if next hop is not an AS;
- include a type 1 "orig-ioi" header field parameter if next hop is not an AS;
- based on local policy, the S-CSCF shall add an "fe-addr" element of the "fe-identifier" header field parameter to the P-Charging-Vector header field with its own address or if not already available; and
- remove any received Relayed-Charge header field if next hop is not an AS;
NOTE 11: Any received "orig-ioi" header field parameter will be a type 3 IOI. A type 3 IOI identifies the sending service provider of the request message.
8) in the case:
i) there are no Route header fields in the request; and
ii) there are bindings saved during registration or reregistration as described in subclause 5.4.1.2 which are not marked as created by an emergency registration as described in subclause 5.4.8.2;
then, create a target set of potential routes from the list of preloaded routes associated with the bindings in item 8) ii), as follows:
a) if the Request-URI contains a valid GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that does not contain a "bnc" URI parameter, then the target set is determined by following the procedures for Request Targeting specified in RFC 5627 [93], using the public user identity and instance ID derived from the GRUU using the procedures of subclause 5.4.7A;
b) if the Request-URI contains a valid public GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that contains a "bnc" URI parameter then the target set is determined by following the procedures for routeing of public GRUUs specified in RFC 6140 [191].
NOTE 12: The procedures for Request Targeting for public GRUUs in subclause 7.1.1 of RFC 6140 [191] involve copying the "sg" SIP URI parameter from the Public GRUU into the Request-URI along with the bound registered Contact Address.
NOTE 13: In this release of the specification, use of preloaded routes saved during registration or reregistration which created or refreshed bindings marked as created by an emergency registration is out of scope.
c) if the Request-URI contains a temporary GRUU not assigned by the S-CSCF but that contains "temp-gruu-cookie" information provided by the S-CSCF to the UE in a "temp-gruu-cookie" header field parameter as specified in RFC 6140 [191] then the target set is determined by following the procedures for Request Targeting for temporary GRUUs specified in RFC 6140 [191]; or
NOTE 14: The procedures for obtaining the "temp-gruu-cookie" information from the temporary GRUU and for routeing of temporary GRUUs are specified in subclause 7.1.2.3 of RFC 6140 [191].
d) if the Request-URI contains a public user identity or a GRUU not assigned by the S-CSCF, then the target set is all the registered contacts saved for the destination public user identity;
9) if necessary perform the caller preferences to callee capabilities matching according to RFC 3841 [56B] to the target set;
NOTE 15: This might eliminate entries and reorder the target set.
NOTE 16: The S-CSCF performs caller preferences to callee capabilities matching also to select among multiple targets set to a single instance-id, when the UE has registered multiple registration flows.
10) in case there are no Route header fields in the request:
a) if there is more than one route in the target set determined in steps 8) and 9) above:
- if the fork directive in the Request-Disposition header field was set to "no-fork", use the contact with the highest qvalue parameter to build the target URI. In case no qvalue parameters were provided, the S-CSCF shall decide locally what contact address to be used to build the target URI;
- if the fork directive in the Request-Disposition header field was not set to "no-fork", fork the request or perform sequential search based on the relative preference indicated by the qvalue parameter of the Contact header field in the REGISTER request, as described in RFC 3261 [26]. In case no qvalue parameters were provided, then the S-CSCF determine the contact address to be used to build the target URI as directed by the Request-Disposition header field as described in RFC 3841 [56B]. If the Request-Disposition header field is not present, the S-CSCF shall decide locally whether to fork or perform sequential search among the contact addresses;
- in case that no route is chosen, return a 480 (Temporarily unavailable) response or another appropriate unsuccessful SIP response and terminate these procedures; and
- per the rules defined in RFC 5626 [92], the S-SCSF shall not populate the target set with more than one contact with the same public user identity and instance-id at a time. If a request for a particular public user identity and instance-id fails with a 430 response, the S-CSCF shall replace the failed branch with another target with the same public user identity and instance-id, but a different reg-id;
b) If no "Loose-Route Indication" indicating the HSS requires the loose-route mechanism as described in 3GPP TS 29.228 [14] has been received, in the service profile of the served public user identity, from the HSS during registration, build the Request-URI with the contents of the target URI determined in the previous step, otherwise the Request-URI is retained as received;
c) insert a P-Called-Party-ID SIP header field containing the contents of the Request-URI (if no "Loose-Route Indication" indicating the HSS requires the loose-route mechanism as described in 3GPP TS 29.228 [14] has been received, in the service profile of the served public user identity, from the HSS during registration, then exclude "rn" tel-URI parameter and "npdi" tel-URI parameter as defined in RFC 4694 [112]) received in the request unless the Request-URI contains a temporary GRUU in which case insert the public GRUU in the P-Called-Party-ID;
d) build the Route header field with the Path values from the chosen route and if "Loose-Route Indication" indicating the HSS requires the loose-route mechanism as described in 3GPP TS 29.228 [14] has been received, in the service profile of the served user identity, from the HSS during registration and the selected contact address was not registered as described in RFC 5626 [92], add the content of the target URI determined in step a), as last URI of the route. If the selected contact address was registered as described in RFC 5626 [92], the target URI determined in step a) is not added to the Route header field; and
e) save the Request-URI and the total number of Record-Route header fields as part of the dialog request state.
NOTE 17: For each initial dialog request terminated at a served user two pieces of state are maintained to assist in processing GRUUs: the chosen contact address to which the request is routed; and the position of an entry for the S-CSCF in the Record-Route header field that will be responsible for GRUU translation, if needed (the position is the number of entries in the list before the entry was added). The entry will be added in step 5) of the below procedures for handling S-CSCF receipt any 1xx or 2xx response to the initial request for a dialog. The S-CSCF can record-route multiple times, but only one of those (the last) will be responsible for gruu translation at the terminating end.
11) if the request is an INVITE request, save the Contact, CSeq and Record-Route header field values received in the request such that the S-CSCF is able to release the session if needed;
12) optionally, apply any privacy required by RFC 3323 [33] and RFC 3325 [34] to the P-Asserted-Identity header field and privacy required by RFC 7044 [66]. The S-CSCF shall not remove any priv-value from the Privacy header field;
NOTE 18: keeping the priv-value in the Privacy header field is necessary to indicate to the UE that the public user identity was not sent because of restriction. Although RFC 3323 [33] states that when a privacy service performs one of the functions corresponding to a privacy level listed in the Privacy header field, it SHOULD remove the corresponding priv-value from the Privacy header field, there is no harm that the S-CSCF does not remove the priv-values as there will be no other entity that would perform the privacy service after the S-CSCF.
NOTE 19: The optional procedure above is in addition to any procedure for the application of privacy at the edge of the trust domain specified by RFC 3325 [34].
13) in case of an initial request for a dialog, either:
- if the request is routed to an AS which is part of the trust domain, the S-CSCF shall decide, based on operator policy, whether to record-route or not. The decision is configured in the S-CSCF using any information in the received request that may otherwise be used for the initial filter criteria. If the request is record-routed the S-CSCF shall create a Record-Route header field containing its own SIP URI; or
- if the request is routed elsewhere, create a Record-Route header field containing its own SIP URI;
13A) if the request is routed towards the UE remove the P-User-Database header field and P-Served-User header field if present;
13B) void
13C) if the request was sent on a dialog for which logging of signalling is in progress, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred, stop treating the dialog as one for which logging of signalling is in progress, else append a "logme" header field parameter to the SIP Session-ID header field if the parameter is missing and determine, by checking its trace configuration, whether to log the request;
13D) if the request is routed towards the UE,
- the S-CSCF supports indicating the traffic leg as specified in RFC 7549 [225];
- the UE is roaming; and
- required by local policy;
then:
- if the bottommost Route header field does not contain the "tokenized-by" header field parameter and an "iotl" SIP URI parameter is not already included, append an "iotl" SIP URI parameter set to "homeB-visitedB" to the URI of the bottommost Route header field; and
- if the bottommost Route header field contains the "tokenized-by" header field parameter and an "iotl" SIP URI parameter is not already included, append an "iotl" SIP URI parameter set to "homeB-visitedB" to the URI of the second Route header field from the bottom;
NOTE 20: The bottommost Route header field contains an "iotl" SIP URI parameter if the P‑CSCF added the "iotl" SIP URI parameter in the Path header field during registration and if the visited network does not apply topology hiding. The second Route header field from the bottom contains an "iotl" SIP URI parameter if the P‑CSCF added the "iotl" SIP URI parameter in the Path header field during registration and if the visited network applied topology hiding.
13E) if the S-CSCF supports HSS based P-CSCF restoration and the S-CSCF considers the P-CSCF, identified by the bottommost Route header field, is not reachable:
- reject the request with a 480 (Temporarily Unavailable) response; and
- initiate the HSS based P-CSCF restoration procedure towards the served user as specified in 3GPP TS 23.380 [7D];
13F) if the S-CSCF supports PCRF based P-CSCF restoration procedures, insert a Restoration-Info header field including the IMSI value contained in the user profile of the registered served user as a quoted string defined in 3GPP TS 29.228 [14];
NOTE 21: If PCRF based P-CSCF restoration procedure is operated between the home network and the visited network, the operator policy depends on an agreement with the visited network operator.
13G) if the S-CSCF supports PCRF based P-CSCF restoration procedures,
- the request contains a topmost Route header field pointing to a P-CSCF, and
- the S-CSCF considers the P-CSCF is in a non-working state,
remove all entries in the Route header field and add a Route header field set to the URI associated with an alternative P-CSCF; and
NOTE 22: How the SIP URI of the alternative P-CSCF is obtained by the S-CSCF is implementation dependent. The S-CSCF can make sure that selected P-CSCF support the PCRF based P-CSCF restoration procedures based on local configuration.
NOTE 23: It is implementation dependent as to how the S-CSCF determines the P-CSCF is in non-working state.
14) forward the request based on the topmost Route header field.
If the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If the response contains a "logme" header field parameter in the SIP Session-ID header field then log the response based on local policy.
If the S-CSCF supports HSS based P-CSCF restoration and
a) receives a 404 (Not Found) response;
b) fails to receive any SIP response from a P-CSCF serving a non-roaming user within a configurable time; or
NOTE 24: The configurable time needs to be less than timer B and timer F.
c) receives a 408 (Request Timeout) response or a 504 (Server Time-out) response:
- including a Restoration-Info header field defined in subclause 7.2.11 set to "noresponse"; and
- the "+g.3gpp.ics" Contact header field parameter with a value set to "server" was not included in the REGISTER request when the UE registered;
NOTE 25: If this Contact header field parameter is not included the S-CSCF can deduce that the P-CSCF did not respond to the request.
the S-CSCF shall:
- send a 480 (Temporarily Unavailable) response;
- initiate the HSS based P-CSCF restoration procedure towards the served user as specified in 3GPP TS 23.380 [7D]; and
- if b) or c) above applied consider the P-CSCF as not reachable.
If the S-CSCF supports PCRF based P-CSCF restoration and receives a 404 (Not Found) response, the S-CSCF shall consider the P-CSCF to be in a non-working state and shall initiate the PCRF based P-CSCF restoration procedure towards the served user as specified in 3GPP TS 23.380 [7D].
If the S-CSCF:
a) fails to receive a SIP response within a configurable time; or
b) receives a 408 (Request Timeout) response or a 5xx response from the AS without previously receiving a 1xx response to the original SIP request, and without previously receiving a SIP request from the AS that contained the same original dialog identifier as the original request;
the S-CSCF shall:
- if the default handling defined in the filter criteria indicates the value "SESSION_CONTINUED" as specified in 3GPP TS 29.228 [14] or no default handling is indicated, execute the procedure from step 4; and
- if the default handling defined in the filter criteria indicates the value "SESSION_TERMINATED" as specified in 3GPP TS 29.228 [14], either forward the received response or, if the request is an initial INVITE request, send a 408 (Request Timeout) response or a 5xx response towards the originating UE as appropriate (without verifying the matching of filter criteria of lower priority and without proceeding for further steps).
If the S-CSCF receives any final response from the AS, the S-CSCF shall forward the response towards the originating UE (without verifying the matching of filter criteria of lower priority and without proceeding for further steps).
When the S-CSCF receives any response to the above request and forwards it to an AS, the S-CSCF shall remove any "orig-ioi", "term-ioi" and "transit-ioi" header field parameter if received in a P-Charging-Vector header field, insert a P-Charging-Vector header field containing the "orig-ioi" header field parameter, if received in the request, a type 3 "term-ioi" header field parameter, and based on operator option insert a Relayed-Charge header field in the response. The S-CSCF shall set the type 3 "term-ioi" header field parameter to a value that identifies the sending network of the response, the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter and include in the Relayed-Charge header field the received "transit-ioi" header field parameter from the P-Charging-Vector header field.
NOTE 26: Any received "term-ioi" header field parameter will be a type 1 IOI or a type 3 IOI. The type 1 IOI identifies the network from which the response was sent and the type 3 IOI identifies the service provider from which the response was sent.
When the S-CSCF receives, destined for an unregistered served user or a statically pre-configured PSI, an initial request for a dialog or a request for a standalone transaction, the S-CSCF shall:
1) Void.
2) execute the procedures described in 1, 2, 3, 3C, 3D, 4, 5, 6, 7, 11, 13, 13B, 13C and 14 in the above paragraph (when the S-CSCF receives, destined for the registered served user, an initial request for a dialog or a request for a standalone transaction).
3) In case that no more AS needs to be contacted, then S-CSCF shall return an appropriate unsuccessful SIP response. This response may be a 480 (Temporarily unavailable) and terminate these procedures.
NOTE 27: When the S-CSCF does not have the user profile, before executing the actions as listed above, it initiates the S-CSCF Registration/deregistration notification procedure, as described in 3GPP TS 29.228 [14]; with the purpose of downloading the relevant user profile (i.e. for unregistered user) and informs the HSS that the user is unregistered. The S-CSCF will assess triggering of services for the unregistered user, as described in 3GPP TS 29.228 [14]. When requesting the user profile the S-CSCF can include the information in the P-Profile-Key header field in S-CSCF Registration/deregistration notification. When requesting the user profile, and the request received by the S-CSCF contains a P-Profile-Key header field, the S-CSCF can include the header field value in S-CSCF Registration/deregistration notification. If the response from the HSS includes a Wildcarded Public Identity AVP, and if the request received by the S-CSCF did not include a P-Profile-Key header field, the S-CSCF uses the AVP value to set the P-Profile-Key header field before forwarding the request to an AS.
Prior to performing S-CSCF Registration/Deregistration procedure with the HSS, the S-CSCF decides which HSS to query, possibly as a result of a query to the Subscription Locator Functional (SLF) entity as specified in 3GPP TS 29.228 [14] or use the value as received in the P-User-Database header field in the initial request for a dialog or a request for a standalone transaction as defined in RFC 4457 [82]. The HSS address received in the response to SLF query can be used to address the HSS of the public user identity with further queries.
If the HSS indicates to the S-CSCF that there is already another S-CSCF assigned for the user, the S-CSCF shall return a 305 (Use Proxy) response containing the SIP URI of the assigned S-CSCF received from the HSS in the Contact header field.
When the S-CSCF receives any response to the above request containing a Relayed-Charge header field, and the next hop is not an AS, the S-CSCF shall remove the Relayed-Charge header field.
When the S-CSCF receives any 1xx or 2xx response to the initial request for a dialog (whether the user is registered or not), the S-CSCF shall:
1) if the response corresponds to an INVITE request, save the Contact and Record-Route header field values in the response such that the S-CSCF is able to release the session if needed;
2) if the response is not forwarded to an AS (i.e. the response is related to a request that was matched to the first executed initial filter criteria):
a) remove the received "transit-ioi" header field parameter if present and insert a type 2 "term-ioi" header field parameter in the P-Charging-Vector header field of the outgoing response. The type 2 "term-ioi" header field is set to a value that identifies the sending network of the response and the "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter. Values of "orig-ioi" and "term-ioi" header field parameters in the received response are removed; and
b) if the S-CSCF supports using a token to identify the registration, remove the "+g.3gpp.registration-token" Feature-Caps header field parameter, defined in subclause 7.9A.8, if received in the response;
3) in case the served user is not considered a privileged sender then:
a) if the P-Asserted-Identity header field contains only a SIP URI and in the case where the S-CSCF has knowledge that the SIP URI contained in the received P-Asserted-Identity header field is an alias SIP URI for a tel URI, the S-CSCF shall add a second P-Asserted-Identity header field containing this tel URI, including the display name associated with the tel URI, if available; and
b) if the P-Asserted-Identity header field contains only a tel URI, the S-CSCF shall add a second P-Asserted-Identity header field containing a SIP URI. The added SIP URI shall contain in the user part a "+" followed by the international public telecommunication number contained in tel URI, and user's home network domain name in the hostport part. The added SIP URI shall contain the same value in the display name as contained in the tel URI. The S-CSCF shall also add a "user" SIP URI parameter equals "phone" to the SIP URI;
4) in case the response is sent towards the originating user, the S-CSCF may retain the P-Access-Network-Info header field based on local policy rules and the destination user (Request-URI);
5) save an indication that GRUU routeing is to be performed for subsequent requests sent within this same dialog if:
a) there is a record-route position saved as part of the initial dialog request state; and
b) the contact address in the response is a valid GRUU assigned by the S-CSCF as specified in subclause 5.4.7A.4 or a temporary GRUU self assigned by the UE based on the "temp-gruu-cookie" header field parameter provided to the UE;
6) if the S-CSCF supports using a token to identify the registration and if a registration exists, add a "+g.3gpp.registration-token" Feature-Caps header field parameter, as defined in subclause 7.9A.8, set to the same value as included in the "+g.3gpp.registration-token" Contact header field parameter of the third party REGISTER request sent to the AS when the UE registered; and
NOTE 28: There could be several responses returned for a single request, and the decision to insert or modify the Record-Route needs to be applied to each. But a response might also return to the S-CSCF multiple times as it is routed back through AS. The S-CSCF will take this into account when carrying out step 5) to ensure that the information is stored only once.
7) if the response is forwarded within the S-CSCF home network and not to an AS, insert a P-Charging-Function-Addresses header field populated with values received from the HSS.
When the S-CSCF receives a response to a request for a standalone transaction (whether the user is registered or not), then:
1) in case the served user is not considered a privileged sender then:
a) if the P-Asserted-Identity header field contains only a SIP URI and in the case where the S-CSCF has knowledge that the SIP URI contained in the received P-Asserted-Identity header field is an alias SIP URI for a tel URI, the S-CSCF shall add a second P-Asserted-Identity header field containing this tel URI, including the display name associated with the tel URI, if available; and
b) if the P-Asserted-Identity header field contains only a tel URI, the S-CSCF shall add a second P-Asserted-Identity header field containing a SIP URI. The added SIP URI shall contain in the user part a "+" followed by the international public telecommunication number contained in tel URI, and user's home network domain name in the hostport part. The added SIP URI shall contain the same value in the display name as contained in the tel URI. The S-CSCF shall also add a "user" SIP URI parameter equals "phone" to the SIP URI; and
2) in case the response is forwarded to an AS that is located within the trust domain, the S-CSCF shall retain the access-network-charging-info parameter in the P-Charging-Vector header field; otherwise, the S-CSCF shall remove the access-network-charging-info parameter in the P-Charging-Vector header field.
When the S-CSCF receives the 200 (OK) response for a standalone transaction request, the S-CSCF shall:
1) insert a P-Charging-Function-Addresses header field populated with values received from the HSS if the message is forwarded within the S-CSCF home network, including towards an AS;
1A) if the S-CSCF supports using a token to identify the registration and if a registration exists, add a "+g.3gpp.registration-token" Feature-Caps header field parameter, as defined in subclause 7.9A.8, set to the same value as included in the "+g.3gpp.registration-token" Contact header field parameter of the third party REGISTER request sent to the AS when the UE registered;
1B) if the S-CSCF supports using a token to identify the registration in case the response is not forwarded to an AS the S-CSCF shall remove the "+g.3gpp.registration-token" Feature-Caps header field parameter, defined in subclause 7.9A.8, if received in the response; and
2) if the response is not forwarded to an AS (i.e. the response is related to a request that was matched to the first executed initial filter criteria), remove the received "orig-ioi", "term-ioi" and "transit-ioi" header field parameter if present and insert a type 2 "term-ioi" header field parameter in the P-Charging-Vector header field of the outgoing response. The type 2 "term-ioi" header field parameter is set to a value that identifies the sending network of the response and the type 2 "orig-ioi" header field parameter is set to the previously received value of "orig-ioi" header field parameter.
NOTE 29: If the S-CSCF forked the request of a stand alone transaction to multiple UEs and receives multiple 200 (OK) responses, the S-CSCF will select and return only one 200 (OK) response. The criteria that the S-CSCF employs when selecting the 200 (OK) response is based on the operator's policy (e.g. return the first 200 (OK) response that was received).
When the S-CSCF receives, destined for a served user, a target refresh request for a dialog, prior to forwarding the request, the S-CSCF shall:
0) if the dialog is related to an IMS communication service determine whether the contents of the request (e.g. SDP media capabilities, Content-Type header field) match the IMS communication service as received as the ICSI value in the P-Asserted-Service header field in the initial request. As an operator option, if the contents of the request do not match the IMS communication service the S-CSCF may reject the request by generating a status code reflecting which added contents are not matching. Otherwise, continue with the rest of the steps;
1) if the incoming request is received on a dialog for which GRUU routeing is to be performed and the Request-URI is not the GRUU for this dialog, then return a response of 400 (Bad Request).
2) if the incoming request is received on a dialog for which GRUU routeing is to be performed and the Request-URI contains the GRUU for this dialog then:
i) if the Request-URI contains a valid GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that does not contain a "bnc" URI parameter, then perform the procedures for Request Targeting specified in RFC 5627 [93], using the public user identity and instance ID derived from the Request-URI, as specified in subclause 5.4.7A;
ii) if the Request-URI contains a valid public GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that contains a "bnc" URI parameter then the target set is determined by following the procedures for routeing of public GRUUs specified in RFC 6140 [191]. or
NOTE 30: The procedures for Request Targeting for public GRUUs in subclause 7.1.1 of RFC 6140 [191] involve copying the "sg" SIP URI parameter from the Public GRUU into the Request-URI along with the bound registered Contact Address.
iii) if the Request-URI contains a temporary GRUU not assigned by the S-CSCF but that contains "temp-gruu-cookie" information provided by the S-CSCF to the UE in a "temp-gruu-cookie" header field parameter as specified in RFC 6140 [191] then the target set is determined by following the procedures for routeing of temporary GRUUs specified in RFC 6140 [191];
NOTE 31: The procedures for obtaining the "temp-gruu-cookie" information from the temporary GRUU and for routeing of temporary GRUUs are specified in subclause 7.1.2.3 of RFC 6140 [191].
iv) if no contact can be selected, return a response of 480 (Temporarily Unavailable);
3) remove its own URI from the topmost Route header field;
4) for INVITE dialogs (i.e. dialogs initiated by an INVITE request), save the Contact and CSeq header field values received in the request such that the S-CSCF is able to release the session if needed;
5) create a Record-Route header field containing its own SIP URI;
5A) void
5B) if the request was sent on a dialog for which logging of signalling is in progress, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred, stop treating the dialog as one for which logging of signalling is in progress, else append a "logme" header field parameter to the SIP Session-ID header field if the parameter is missing and determine, by checking its trace configuration, whether to log the request; and
6) forward the request based on the topmost Route header field.
When the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If the response contains a "logme" header field parameter in the SIP Session-ID header field then log the response based on local policy.
When the S-CSCF receives any 1xx or 2xx response to the target refresh request for a dialog (whether the user is registered or not), the S-CSCF shall:
1) for INVITE dialogs, replace the saved Contact header field values in the response such that the S-CSCF is able to release the session if needed; and
2) in case the response is forwarded to an AS that is located within the trust domain, the S-CSCF shall retain the access-network-charging-info parameter in the P-Charging-Vector header field; otherwise, the S-CSCF shall remove the access-network-charging-info parameter in the P-Charging-Vector header field.
When the S-CSCF receives, destined for the served user, a subsequent request other than target refresh request for a dialog, prior to forwarding the request, the S-CSCF shall:
1) if the incoming request is received on a dialog for which GRUU routeing is to be performed and the Request-URI is not the GRUU for this dialog, then return a response of 400 (Bad Request).
2) if the incoming request is received on a dialog for which GRUU routeing is to be performed and the Request-URI contains the GRUU for this dialog then:
i) if the Request-URI contains a valid GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that does not contain a "bnc" URI parameter, then perform the procedures for Request Targeting specified in RFC 5627 [93], using the public user identity and instance ID derived from the Request-URI, as specified in subclause 5.4.7A;
ii) if the Request-URI contains a valid public GRUU assigned by the S-CSCF as defined in subclause 5.4.7A.4 that contains a "bnc" URI parameter then the target set is determined by following the procedures for routeing of public GRUUs specified in RFC 6140 [191]; or
NOTE 32: The procedures for Request Targeting for public GRUUs in subclause 7.1.1 of RFC 6140 [191] involve copying the "sg" SIP URI parameter from the Public GRUU into the Request-URI along with the bound registered Contact Address.
iii) if the Request-URI contains a temporary GRUU not assigned by the S-CSCF but that contains "temp-gruu-cookie" information provided by the S-CSCF to the UE in a "temp-gruu-cookie" header field parameter as specified in RFC 6140 [191] then the target set is determined by following the procedures for routeing of temporary GRUUs specified in RFC 6140 [191].
NOTE 33: The procedures for obtaining the "temp-gruu-cookie" information from the temporary GRUU and for routeing of temporary GRUUs are specified in subclause 7.1.2.3 of RFC 6140 [191].
iv) if no contact can be selected, return a response of 480 (Temporarily Unavailable).
3) remove its own URI from the topmost Route header field;
3A) void
3B) if the request was sent on a dialog for which logging of signalling is in progress, check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. If a stop trigger event has occurred, stop treating the dialog as one for which logging of signalling is in progress, else append a "logme" header field parameter to the SIP Session-ID header field if the parameter is missing and determine, by checking its trace configuration, whether to log the request; and
4) forward the request based on the topmost Route header field.
When the S-CSCF receives any response to the above request, the S-CSCF shall:
1) If the response contains a "logme" header field parameter in the SIP Session-ID header field then log the response based on local policy.
When the S-CSCF receives a response to a a subsequent request other than target refresh request for a dialog, in case the response is forwarded to an AS that is located within the trust domain, the S-CSCF shall retain the access-network-charging-info parameter from the P-Charging-Vector header field; otherwise, the S-CSCF shall remove the access-network-charging-info parameter from the P-Charging-Vector header field.
With the exception of 305 (Use Proxy) responses, the S-CSCF shall not recurse on 3xx responses.
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.3.4 Original dialog identifier
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The original dialog identifier is an implementation specific token that the S-CSCF encodes into the own S-CSCF URI in a Route header field, prior to forwarding the request to an AS. This is possible because the S-CSCF is the only entity that creates and consumes the value.
The token may identify the original dialog of the request, so in case an AS acting as a B2BUA changes the dialog, the S-CSCF is able to identify the original dialog when the request returns to the S-CSCF. In a case of a standalone transaction, the token indicates that the request has been sent to the S-CSCF from an AS in response to a previously sent request. The token can be encoded in different ways, such as e.g., a character string in the user-part of the S-CSCF URI, a parameter in the S‑CSCF URI or port number in the S-CSCF URI.
The S-CSCF shall ensure that the value chosen is unique so that the S-CSCF may recognize the value when received in a subsequent message of one or more dialogs and make the proper association between related dialogs that pass through an AS.
An original dialog identifier is sent to each AS invoked due to iFC evaluation such that the S-CSCF can associate requests as part of the same sequence that trigger iFC evaluation in priority order (and not rely on SIP dialog information that may change due to B2BUA AS).
NOTE: If the same original dialog identifier is included in more than one request from a particular AS (based on service logic in the AS), then the S-CSCF will continue the iFC evaluation sequence. If the AS wants iFC evaluation to start from the beginning for a request, then AS should not include an original dialog identifier;
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.3.5 Void
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.3.6 SIP digest authentication procedures for all SIP request methods initiated by the UE excluding REGISTER
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.3.6.1 General
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When the S-CSCF receives from the UE a request (excluding REGISTER), and SIP digest without TLS or SIP digest with TLS is supported and in use for this UE, the S-CSCF may perform the following steps if authentication of SIP request methods initiated by the UE excluding REGISTER is desired:
1) The S-CSCF shall identify the user by the public user identity as received in the P-Asserted-Identity header field;
2) If the public user identity does not match one of the registered public user identities, and the public user identity does not match one of the registered wildcarded public user identities, the S-CSCF may reject the request with a 400 (Bad Request) response or silently discard the request;
3) If the request does not contain a Proxy-Authorization header field or the Proxy-Authorization header field does not contain a digest response, the S-CSCF shall:
a) challenge the user by generating a 407 (Proxy Authentication Required) response for the received request, including a Proxy-Authenticate header field as defined in RFC 7616 [286] and RFC 8760 [287], which includes:
- a "realm" header field parameter;
- a "nonce" header field parameter, with a newly generated value by the S-CSCF;
- an "algorithm" header field parameter; and
- a "qop" header field parameter; if the qop value is not provided in the authentication vector, it shall have the value "auth".
The challenge parameters, with the exception of the "nonce" header field parameter, shall be the same as the ones used for the last successful registration.
NOTE 1: The usage of the same parameters for authentication of non-registration SIP requests requires the storage of these parameters during authentication of REGISTER requests, as retrieval of authentication vectors is only specified for REGISTER requests.
NOTE 2: If these parameters are not locally stored in the S-CSCF, i.e. when the S-CSCF has restarted, and the S-CSCF supports restoration as specified in 3GPP TS 23.380 [7D], subclause 4.4.2, the S-CSCF can fetch these parameters from the HSS.
b) send the so generated 407 (Proxy Authentication Required) response towards the UE;
c) retain the nonce and initialize the corresponding nonce count to a value of 1; and
d) start timer request-await-auth.
4) If the request contains a Proxy-Authorization header field, the S-CSCF shall:
a) check whether the Proxy-Authorization header field contains:
- the private user identity of the user in the "username" header field parameter;
- an "algorithm" header field parameter value which matches the "algorithm" header field parameter in the authentication challenge (i.e. "SHA-256", "SHA-512-256" or "MD5");
- a "response" header field parameter with the authentication challenge response;
- a "realm" header field parameter matching the "realm" header field parameter in the authentication challenge;
- "nonce" header field parameter matching a nonce that is deemed valid by the S-CSCF for the related registration or registration flow (i.e. a nonce that was set in a a Proxy-Authenticate header field of a 407 (Proxy Authentication Required) response to a non-REGISTER request for which the associated validity duration has not expired or in a WWW-Authenticate header field of a 401 (Unauthorized) response to a REGISTER request for which the associated validity duration has not expired, a nonce sent in a "nextnonce" header field parameter sent in a Authentication-Info header field of a 200 OK (OK) to REGISTER request ) or if an authentication is ongoing for this request (i.e. a associated "req-await-auth" is running) matching the nonce that was sent in a Proxy-Authenticate header field of the 407 (Proxy Authentication Required) response to this request;
NOTE 3: The related registration flow or registration is identified by the couple instance-id and reg-id if the multiple registration mechanism is used or by contact address if not.
- a "uri" header field parameter matching the SIP Request-URI;
- a "cnonce" header field parameter; and
- a "nc" header field parameter with a value that equals the nonce-count expected by the S-CSCF. The S-CSCF may choose to accept a nonce-count which is greater than the expected nonce-count. If the S-CSCF uses this nonce-count and authentication is successful and the S-CSCF increments it for any subsequent authentication responses.
If any of the above checks do not succeed, the S-CSCF shall proceed as described in subclause 5.4.3.6.2, and skip the remainder of this procedure; and
b) check whether the received authentication challenge response and the expected authentication challenge response match. The S-CSCF shall compute the expected digest response as described in RFC 7616 [286] and RFC 8760 [287] using the H(A1) value contained within the authentication vector, and other digest parameters (i.e. nonce, cnonce, nc, qop).
In the case where the digest response does not match the expected digest response calculated by the S-CSCF, the S-CSCF shall consider the authentication attempt as failed and do one of the following:
1) rechallenge the user by issuing a 407 (Proxy Authentication Required) response including a challenge as per procedures described in this subclause; or
2) reject the request by issuing a 403 (Forbidden) response; or
3) reject the request without sending a response.
In the case where the digest response matches the expected digest response calculated by the S-CSCF, the S-CSCF shall:
1) consider the identity of the user verified and the request authenticated and continue with the procedures as described in subclause 5.4.3;
2) if the used nonce was not considered valid before the authentication succed (i.e a "req-await-auth" was running), add this nonce to the list of the valid nonces for the related registration or registration flow (if multiple registration mechanism is used) for an operator configured duration; and
3) stop the related "request-await-auth" running if any.
If the timer request-await-auth expires, the S-CSCF shall consider the authentication to have failed.
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24.229
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5.4.3.6.2 Abnormal cases
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In the case that SIP digest is used and the request from the UE contains an invalid "nonce" Authorization header field parameter with a valid challenge response for that nonce (indicating that the client knows the correct username/password), or when the "nonce-count" Authorization header field parameter value sent by the UE is not the expected value, or when the Proxy-Authorization header field does not include the correct parameters, the S-CSCF shall:
- send a 407 (Proxy Authentication Required) response to initiate a further authentication attempt with a fresh nonce and the "stale" header field parameter set to "true" in the Proxy-Authenticate header field.
When the S-CSCF cannot forward an initial incoming request to an Application Server due to overload control mechanism, it shall either
- if the default handling defined in the filter criteria indicates the value "SESSION_CONTINUED" as specified in 3GPP TS 29.228 [14] or no default handling is indicated, execute the procedure from step 5 in subclause 5.4.3.2 or from step 4 in subclause 5.4.3.3 depending on the type of request; and
- if the default handling defined in the filter criteria indicates the value "SESSION_TERMINATED" as specified in 3GPP TS 29.228 [14], reject the request as specified in RFC 7339 [199] and RFC 7200 [201] (without verifying the matching of filter criteria of lower priority and without proceeding for further steps).
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d3a3ac3f64ab68e4fcef5ea9a665f70a
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24.229
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5.4.4 Call initiation
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24.229
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5.4.4.1 Initial INVITE
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When the S-CSCF receives an INVITE request, either from the served user or destined to the served user, the S-CSCF may require the periodic refreshment of the session to avoid hung states in the S-CSCF. If the S-CSCF requires the session to be refreshed, the S-CSCF shall apply the procedures described in RFC 4028 [58] clause 8.
NOTE 1: Requesting the session to be refreshed requires support by at least one of the UEs. This functionality cannot automatically be granted, i.e. at least one of the involved UEs needs to support it.
For interworking with a visiting network, where the P-CSCF of the visiting network does not support priority but it is intended or required to give users of that P-CSCF priority in the home network, the S-CSCF in the home network shall recognize the need for priority treatment if such detection is not alternately provided via an IBCF in the home network.
NOTE 2: Various mechanisms can be applied to recognize the need for priority treatment (e.g., based on the dialled digits). The exact mechanisms are left to national regulation and network configuration.
When an S-CSCF interworks with a visiting network that does not support priority, and the S-CSCF recognizes the need for priority treatment, the S-CSCF shall insert the temporarily authorised Resource-Priority header field with appropriate namespace and priority value in the INVITE request.
When the S-CSCF receives an initial INVITE request destined for the served user, the S-CSCF shall either:
a) examine the SDP offer (the "c=" parameter) to detect if it contains an IP address type that is not supported by the IM CN subsystem; or
NOTE 3: The S-CSCF can, based on local policy, assume that a UE supports the IP address type of the SDP offer for media if it is identical to the address type of a contact that the UE has registered.
b) process the initial INVITE request without examining the SDP.
NOTE 4: If the S-CSCF knows that the terminating UE supports both IPv6 and IPv4 addressing simultaneously, the S-CSCF will forward the initial INVITE request to the UE without examining the SDP. The present version of the specification does not specify how the S-CSCF determines whether the UE supports both IPv6 and IPv4 addressing simultaneously.
NOTE 5: If the SDP offer contained an IP address type that is not supported by the IM CN subsystem, the S-CSCF will receive the 488 (Not Acceptable Here) response with 301 Warning header field indicating "incompatible network address format".
Subsequently, when the S-CSCF detects that the SDP offer contained an IP address type that is not supported by the IM CN subsystem (i.e., either case a) or b)), the S-CSCF shall either:
- return a 305 (Use Proxy) response to the I-CSCF with the Contact field containing the SIP URI of the IBCF, or
- forward the initial INVITE request to the IBCF. When forwarding the initial INVITE request, the S-CSCF shall not insert its SIP URI into the Record-Route header field.
If overlap signalling using the multiple-INVITE method is supported as a network option, several INVITE requests with the same Call ID and the same From header field (including "tag" header field parameter) can be received outside of an existing dialog. Such INVITE requests relate to the same call. If the S-CSCF receives an INVITE request from the served user outside an existing dialog with the same Call ID and From header field as a previous INVITE request during a certain period of time, it shall route the new INVITE request to the same next hop as the previous INVITE request.
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24.229
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5.4.4.2 Subsequent requests
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