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8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.3.3.3 Information flows
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.3.3.3.1 Root application and profile update notification
| If the MMTel Enabler Server interacts with the SEAL notification server to use the notification service, the Notification message specified in clause 17.3.2.4 applies to the Root application and profile update notification. The usage of the information elements in MMTel service is clarified as below:
- The identifier of the MMTel Enabler Client request DC application profiles works as VAL Application ID;
- The service identifier of MMTel Service in SEAL services works as VAL Service ID;
Besides the IEs specified in clause 17.3.2.4 of 3GPP TS 23.434 [6], the information elements included in Table 8.3.3.3.1-1 is also needed to be included in the Root application and profile update notification from the MMTel Enabler Server to the MMTel Enabler Client.
Table 8.3.3.3.1-1: Information elements in Root application and profile update notification
Information element
Status
Description
Immediate Indication
O
Indicates whether the operation is critical to UE, i.e. whether the Root application and profile need to be updated immediately. E.g. the update of Root application and profile is critical, if the available DC Application for the user is changed.
If the MMTel Enabler Server provides the notification service, only the information elements included in Table 8.3.3.3.1-1 are included in the Root application and profile update notification.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.3.3.3.2 Root application notification
| Table 8.3.3.3.2-1 describes information elements for the Root application notification from the MMTel Enabler Server to the MMTel Enabler Client.
Table 8.3.3.3.2-1: Information elements for Root application notification
Information element
Status
Description
Update Indication
M
Indicates whether the Root application is needed to be updated by the MMTel Enabler Client in the UE.
Root application version
O
The latest version of the Root application.
This IE presents only if the Root application is needed to be updated by the MMTel Enabler Client in the UE.
Root application (see NOTE)
O
The Root application provided by the MMTel service provider, e.g. layout, and/or home page etc. of the Data Channel Application list.
This IE is present if the update of the Root application in the UE is needed, i.e. the Root application version included in the Get Root application request is not equal to the latest version on the MMTel Enabler Server.
DC Application profile list
O
A list of DC application profiles available for this user. Each element in this list contains a DC application profile of this Data Channel Application.
The detailed information elements of DC application profile are listed in Table 8.3.2.3.4-2.
NOTE: The detailed information of this IE is implementation specific and out of scope of the present document.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.3.3.3.3 MMTel Enabler Client subscribes to the MMTel Enabler Server request
| Table 8.3.3.3.3-1 describes information elements for the MMTel Enabler Client subscribes to the MMTel Enabler Server request.
Table 8.3.3.3.3-1: Information elements for MMTel Enabler Client subscribes to
the MMTel Enabler Server request
Information element
Status
Description
MMTel Enabler Client ID
M
Identity of the requesting MMTel Enabler Client
MMTel Enabler Client version (see NOTE)
M
The version of MMTel Enabler Client.
Validity Duration
M
Indicates how long the subscription will last (i.e. subscription lifetime) as requested by the MMTel Enabler client.
NOTE: The MMTel service provider can provide the MMTel Enabler Client with different DC application profile list based on this IE.
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8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4 Application calling enablement
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.1 General
| The following clauses specify procedures and information flows for Application calling enablement.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2 Application calling service API with Data Channel capability
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.1 General
| The MMTel Enabler Server exposes the Application calling service API with Data Channel capability to the Applications in order to support establishing a call between Application and DCMTSI client.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.2 Procedure
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.2.1 Establishing an Application Call with Data Channel capability between non-IMS application and DCMTSI client
| Figure 8.4.2.2.1-1 illustrates the operation to establish an Application Call with Data Channel capability between non-IMS application and DCMTSI client.
Pre-conditions:
1. The Application is authorized to use Application calling service API provided by the MMTel Enabler Server.
2. The MMTel Enabler Server is authorized to use IMS DC capability APIs as defined in 3GPP TS 23.228 [3].
3. The MMTel Enabler Server is authorized to use OMA ThirdPartyCall API as specified in OMA-TS-REST_NetAPI_ThirdPartyCall [7].
Figure 8.4.2.2.1-1: Establishing a Application Call with Data Channel capability between non-IMS applications and DCMTSI client
1. The Application sends an Application Call with DC capability establishment request to the MMTel Enabler Server. The request message includes information elements as specified in clause 8.4.2.3.1.
2. Upon receiving the request, the MMTel Enabler Server validates if the requester is authorized for the request, if the requester is authorized then the MMTel Enabler Server can utilize the OMA Third Party Call API [7] to establish a Call session with audio and/or video media as specified in OMA-TS-REST_NetAPI_ThirdPartyCall and obtain the result of the Third-Party Call establishment. The MMTel Enabler Server may also obtains the IMS Session ID associated with the Third Party Call as specified in RFC 7989 [10], and handles the mapping between the OMA call session ID and the IMS session ID.
NOTE 1: The OMA call session ID attribute in the OMA Third Party Call API is generated by the entity implementing the OMA APIs, which is different from the IMS session ID.
3, The MMTel Enabler Server utilizes the DC update capability of the IMS core network to add DC media to the existing Application Call Session as specified in Annex AC of 3GPP TS 23.228 [3]. The IMS core network returns the update result.
3. The MMTel Enabler Server sends an Application Call establishment response to the Application. The response message includes information elements as specified in clause 8.4.2.3.2.
NOTE 2: In this release, the MMTel Enabler Server is deployed in the PLMN operator domain.
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8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.3 Information flows
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8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.3.1 Application Call establishment request
| The information elements of Application Call establishment request are as same as the elements in Table 8.4.3.3.1-1.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.2.3.2 Application Call establishment response
| The information elements of Application Call establishment response are as same as the elements in Table 8.4.3.3.2-1.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3 Third-Party Call service API with Data Channel capability
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.1 General
| The MMTel Enabler Server exposes the Third-Party Call service API with Data Channel capability to the Vertical service provider in order to support establishing a call between two UEs.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.2 Procedure
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.2.1 Establishing a Third-Party Call with Data Channel capability
| Figure 8.4.3.2.1-1 illustrates the operation to establish a Third-Party Call with Data Channel capability.
Pre-conditions:
1. The Vertical service provider is authorized to use Third-Party Call service API provided by the MMTel Enabler Server.
2. The MMTel Enabler Server is authorized to use the IMS DC capability APIs as defined in 3GPP TS 23.228 [3].
3. The MMTel Enabler Server is authorized to use OMA THIRD PARTY CALL API as specified in OMA-TS-REST_NetAPI_ThirdPartyCall [7].
Figure 8.4.3.2.1-1: Establishing a Third-Party Call with Data Channel capability
1. The Vertical service provider sends a Third-Party Call with DC capability establishment request to the MMTel Enabler Server. The request message includes information elements as specified in clause 8.4.3.3.1.
2. Upon receiving the request, the MMTel Enabler Server validates if the requester is authorized for the request, If the requester is authorized then the MMTel Enabler Server utilizes the OMA Third Party Call API [7] to establish a Third-Party Call session with audio and/or video media as specified in OMA-TS-REST_NetAPI_ThirdPartyCall and obtain the result of the Third Party Call establishment. The MMTel Enabler Server obtains IMS Session ID associated with the Third Party Call as specified in RFC 7989 [10],the OMA API call Session ID and handles the mapping between OMA call session ID and the IMS session ID
NOTE 1: The OMA call session ID attribute in the OMA Third Party Call API is generated by the entity implementing the OMA APIs, which is different from the IMS session Id.
3. the MMTel Enabler Server utilizes the DC update capability of the IMS core network to add DC media to the existing Third-Party Call Session as specified in 3GPP TS 23.228 [3], and the IMS core network returns the update result.
4. The MMTel Enabler Server sends a Third-Party Call with DC capability establishment response to the Vertical service provider. The response message includes information elements as specified in clause 8.4.3.3.2.
NOTE 2: In this release, the MMTel Enabler Server is deployed in the PLMN operator domain.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.3 Information flows
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.3.1 Third-Party Call with DC capability establishment request
| Table 8.4.3.3.1-1 describes information elements for the Third-Party Call with DC capability establishment request from the Application Server to the MMTel Enabler Server.
Table 8.4.3.3.1-1: Third-Party Call with DC capability establishment request
Information element
Status
Description
Related OMA API Element
Originating ID (see NOTE)
M
The identifier of the caller.
The first element in the participant list, which considered to denote the “A-Party” specified in OMA Third Party Call API [7].
Terminating ID (see NOTE)
M
The identifier of the callee.
The second element in the participant list, which considered to denote the “B-Party” specified in OMA Third Party Call API [7].
Media information
O
Identifier of one or more media type(s) which is expected to be used in the call, i.e. the media type(s) to be applied to the participants in the call session. In this IE, the media type(s) includes
a) audio;
b) video;
c) audio and video.
The detailed media information, e.g. the information included in the SDP of MMTel call session is negotiated by the underlying network.
If the parameter is absent, the media type(s) and detailed media information are all negotiated by the underlying network.
The mediaInfo of the CallSessionInformation specified in OMA Third Party Call API [7].
DC media information
O
Identifier of whether DC media is expected to be used in this call
N/A
Application Profile requested
O
The DC application profile expected to be used in this call
N/A
Notification information
M
The address where the call related notification, e.g. whether the call between UE A and UE B is established successfully or not, is sent to.
The callbackReference of the CallSessionInformation specified in OMA Third Party Call API [7].
NOTE: The Originating ID and Terminating ID may or may not be MSISDN based identifier, i.e. a private identifier in the Application domain. If Originating ID or Terminating ID is not MSISDN based identifier, the MMTel Enabler Server will translate it into a routable ID in the IMS domain and record the mapping relationship between the Originating ID/Terminating ID and the routable ID.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.3.3.2 Third-Party Call with DC capability establishment response
| Table 8.4.3.3.2-1 describes information elements for the Third-Party Call with DC capability establishment response from the Application Server to the MMTel Enabler Server.
Table 8.4.3.3.2-1: Third-Party Call with DC capability establishment response
Information element
Status
Description
Related OMA API Element
Call establishment result
M
Indication if the Call establishment is success or failure.
The HTTP response codes of the created call session as specified in OMA REST_NetAPI_Common [11].
Session ID (see NOTE 1)
O
The identifier of the call session.
The callSessionId as specified in OMA Third Party Call API [7].
Failure Cause (see NOTE 2)
O
The reason for failure
The Policy Exception and Service Exception fault as specified in OMA Third Party Call API [7].
Originating ID (see NOTE 3)
M
The identifier of the caller.
The first element in the participant list, which considered to denote the “A-Party” specified in OMA Third Party Call API [7].
Terminating ID (see NOTE 3)
M
The identifier of the callee.
The second element in the participant list, which considered to denote the “B-Party” specified in OMA Third Party Call API [7].
Media information
O
Identifier of one or more media type(s) which is expected to be used in the call, i.e. the media type(s) to be applied to the participants in the call session. In this IE, the media type(s) includes
a) audio;
b) video;
c) audio and video.
The detailed media information, e.g. the information included in the SDP of MMTel call session is negotiated by the underlying network.
If the parameter is absent, the media type(s) and detailed media information are all negotiated by the underlying network.
The mediaInfo of the CallSessionInformation specified in OMA Third Party Call API [7].
DC media information
O
Identifier of whether DC media is expected to be used in this call.
N/A
Application Profile requested
O
The DC application profile expected to be used in this call.
N/A
NOTE 1: This IE shall only be present when the Call establishment result is Success.
NOTE 2: This IE shall only be present when the Call establishment result is Failure.
NOTE 3: The Originating ID and Terminating ID may or may not be MSISDN based identifier, i.e. a private identifier in the Application domain. If Originating ID or Terminating ID is not MSISDN based identifier, the MMTel Enabler Server will translate it into a routable ID in the IMS domain and record the mapping relationship between the Originating ID/Terminating ID and the routable ID.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4 Establishing an Application Call with Data Channel capability (A2P)
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.1 Procedure
| Figure 8.4.4-1 illustrates the operation to establish an Application Call with Data Channel capability between the Application and the MMTel Enabler Server in order to add an A2P Data Channel to an existing IMS session of the user on UE1 in alignment with the A2P flow specified in 3GPP TS 23.228 [3].
Pre-conditions:
1. The Application can use DC (supports the media set information for DC) and is authorized to use the service API provided by the MMTel Enabler Server.
2. The MMTel Enabler Server is authorized to use IMS DC capability APIs as defined in 3GPP TS 23.228 [3].
3. The MMTel Enabler Server is authorized to use the NEF exposed IMS session management capabilities as specified in 3GPP TS 23.502 [12].
4. The MMTel Enabler Server is subscribed to the AEF (NEF) for IMS session events information e.g., media changes such as requested for the specific DC Application, for a list of users.
NOTE: How the IMS session ID is provided by the NEF exposure of IMS events in 3GPP TS 23.502 [12] is out of scope of this specification.
5. The DC Application Server is subscribed to the MMTel Enabler Server for events related to the DC application.
6. An IMS MMTel session is ongoing for User (UE1) with another user who requests the DC Application to provide some DC media to the user on UE1.
Figure 8.4.4-1: Establishing an Application Call with Data Channel capability
1. The DC Application server determines to add A2P application data channel(s) to an existing IMS session and sends request to MMTel Enabler Server. The request includes parameters such as the session ID, MDC2 endpoint, A2P type.
2. The MMTel Enabler Server requests an IMS session update to the NEF, providing the Session ID and MDC2 endpoint address. The NEF propagates the request to the IMS core which sets the media operation. The NEF sends the response to the MMTel Enabler to the IMS session Update request.
3. The MMTel Enabler Server sends the response to the DC Application Server including the Session ID for the Add media request.
4. Once the IMS system completed the media preparation for the IMS session, based on the notification from the IMS, the NEF sends an IMS session management notification request to the MMTel Enabler Server with MDC2 resource information for the Session ID.
5. The MMTel Enabler Server notifies the DC Application Server of the MDC2 resource information for the Session ID.
6. The DC Application Server responds (acknowledges) the MMTel Enabler Server notification.
7. The MMTel Enabler Server acknowledges the NEF notification.
Post-condition: The UE1 upon getting the updated IMS session information for the DC media proceeds to download the DC Application.
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8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.2 Information flows
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.2.1 Application Add Data Channel media to UE1 session (A2P) request
| Table 8.4.4.2.1-1: Application Add Data Channel media to UE1 session (A2P) request
Information element
Status
Description
Data Channel APPID
M
The identifier of the DC application.
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Media resource information
O
The media information to be passed via the Data Channel. It includes information described in 3GPP TS 23.502 [12] clause 5.2.6.40.
Application Profile requested
O
The DC application profile expected to be used in this call.
Notification address
M
The address where the call related notification, e.g. whether the call between UE A and UE B is established successfully or not, is sent to.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.2.2 Application Add Data Channel media to UE1 session (A2P) response
| Table 8.4.4.2.2-1: Application Add Data Channel media (A2P) response
Information element
Status
Description
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Result
M
Indicates the Notification of Application of DC media info (A2P) request was successful or failure.
> Cause
O
Indicates the cause of request failure.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.2.3 Notify Application of DC media info (A2P) request
| Table 8.4.4.2.3-1: Notify Application of DCH media info (A2P) request
Information element
Status
Description
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Notification address
M
The address where the call related notification, e.g. whether the call between UE A and UE B is established successfully or not, is sent to.
Media resource information
O
The media information to be passed via the Data Channel. It includes information described in 3GPP TS 23.502 [12] clause 5.2.6.40.
Application Profile requested
O
The DC application profile expected to be used in this call.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.4.2.4 Notify Application of DC media info (A2P) response
| Table 8.4.4.2.4-1: Notify Application of DC media info (A2P) response
Information element
Status
Description
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Result
M
Indicates the Notification of Application of DC media info (A2P) request was successful or failure.
> Cause
O
Indicates the cause of request failure.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5 Application calling service API with Data Channel capability
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5.1 Procedure
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5.1.1 Establishing an Application Call with Data Channel capability (P2A)
| Figure 8.4.5.1.1-1 illustrates the operation to establish an Application Call with Data Channel capability between a user (on UE1) and a Data Chanel (DC) Application via the MMTel Enabler Server.
Pre-conditions:
1. The Application can use DC (supports the media set information for DC) and is authorized to use the service API provided by the MMTel Enabler Server.
2. The MMTel Enabler Server is authorized to use IMS DC capability APIs as defined in 3GPP TS 23.228 [3].
3. The MMTel Enabler Server is authorized to use the NEF exposed IMS session management capabilities as specified in [8].
4. The MMTel Enabler Server is subscribed to the AEF (NEF) for IMS session events information for the specific DC Application (using the DCApplication Called party ID).
NOTE: How the IMS session ID is provided by the NEF exposure of IMS events in 3GPP TS 23.502 [12] is out of scope of this specification.
5. The DC Application Server is subscribed to the MMTel Enabler Server for events related to the DC application.
6. An IMS MMTel session is ongoing for User (UE).
Figure 8.4.5.1.1-1: Establishing a Application Call with Data Channel capability (P2A)
1. The user (on UE1) sends a request, via the 5GC and IMS, to add DC media for a specific DC Application.
2. The P2A session establishment is handled via 5GC and IMS system.
3. NEF notifies the MMTel Enabler Server of the new IMS session event for the DC Application.
4. The MMTel Enabler Server notifies the DC Application Server of the new request for DC media.
5. The DC Application Server accepts the request and provides the MDC2 media resource requested.
6. The MMTel Enabler Server utilizes the IMS session update capability exposed by the NEF [8] to request addition of the DC media to the existing IMS MMTel Call Session.
7. The NEF further interacts with the IMS system to request the DC media addition to the ongoing MMTel session and IMS further handles this as specified in Annex AC of 3GPP TS 23.228 [3].
Post-condition: The Application data channel is activated.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5.2 Information flows
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5.2.1 Notify DC Application of MDC2 media (P2A) request
| Table 8.4.5.2.1-1: Notify DC Application of MDC2 media (P2A) request
Information element
Status
Description
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Media resource information
O
The MDC2 media information requested by the UE1 to be sent over the Data Channel. It includes information described in 3GPP TS 23.502 [12] clause 5.2.6.40.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.4.5.2.2 Notify DC Application of MDC2 media (P2A) response
| Table 8.4.5.2.2-1: Notify DC Application of MDC2 media (P2A) response
Information element
Status
Description
Session ID
M
The session identifier of the session on which MMTel Enabler Server must add the new media.
Result
M
Indicates the Notification of Application of DC media info (A2P) request was successful or failure.
> Cause
O
Indicates the cause of request failure.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.5 Multiple call control handling coordination among different Application Servers
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.5.1 General
| When receiving call control requests from multiple Application Servers, the MMTel Enabler Server provides call control handling consolidation and coordination.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.5.2 Procedure
| Figure 8.5.2-1 illustrates the procedure of multiple call control handling coordination among different Application Servers.
Pre-conditions:
1. The Application Servers and MMTel Enabler Server have mutually authenticated each other.
2. The call control handling policy (e.g. the priority of each Application Server) is pre-configured in MMTel Enabler Server.
3. Application Servers have completed call event subscription to MMTel Enabler Server and the MMTel Enabler Server subscribes the call event from NEF.
4. The MMTel Enabler Server is authorized to use NEF capability APIs as defined in 3GPP TS 23.502 [12].
Figure 8.5.2-1: Multiple call control handling coordination among different Application Servers
1. The NEF notifies the MMTel Enabler Server about an event in the IMS session for a user via Nnef_ImsSessionManagement_Notify call or via a Nnef_ImsEE_Notify, depending on the IMS session event that occurred, as described in 3GPP TS 23.502 [12] and based on the events defined in 3GPP TS 23.228 [3] in Table AA.2.4.4.5.
2. The MMTel Enabler Server checks which Application Server has subscribed this call event notification.
3. The MMTel Enabler Server sends Call event notification to Application Server(s) which has subscribed for this call event notification. The Call event notification request includes information elements as specified in Annex AA.2.4.2 of 3GPP TS 23.228 [3].
4-5. Application Servers receive call event notification and sends Call control request (e.g. create new call session, terminate call session or call control, etc.) based on its own service logic. The Call control request includes information elements as specified in Annex AA.2.4.3 or Annex AA.2.4.4 of 3GPP TS 23.228 [3].
6. The MMTel Enabler Server receives call control requests from different Application Servers.It checks whether these call control requests are contradictory or not and makes call control handling decision based on service policy and service priority (e.g. if no conflict happens, to decide call control request execution sequence; if conflict happens, to deny call control request from certain AS with lower priority, etc.).
7-8. The MMTel Enabler Server sends call control responses to each Application Server based on the call control handling decision including, whether the call control request is accepted or the failure reason if the call control request is not accepted. The call control response includes information elements as specified in Annex AA.2.4.3 or Annex AA.2.4.4 of 3GPP TS 23.228 [3].
9. The MMTel Enabler Server sends call control requests decided in step 6 from Application Servers (or permitted Application Servers in conflict scenario) to the NEF by returning Nnef_ImsSessionManagement_notify response and if applicable, to request the addition of DCH media to the ongoing IMS session via a Nnef_ImsSessionManagement_Update request to the NEF as defined in 3GPP TS 23.502 [12].
10. The MMTel Enabler Server sends the call control result notification request to the subscribed Application Servers in conflict scenario decided in step 6. The call control result notification includes information elements as specified in clause 8.5.3.1. The Application Server sends the corresponding control result notification response to the MMTel Enabler Server.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.5.3 Information flows
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 8.5.3.1 Call control result notification
| Table 8.5.3.1-1 describes information elements for call control result notification request from the MMTel Enabler Server to the Application server.
Table 8.5.3.1-1: Call control result notification request
Information element
Status
Description
Final result of the call control request
M
Indicates the final result of the call control request provided by the IMS
Media resource information set
O
If media resource information set is provided by IMS, include the media resource information set in this notification
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 9 Deployment Guideline
| |
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 9.1 General
| This clause describes deployments of the functional model specified in clause 6.
|
8d3dfbdf4c4d4401221ddf8bde92f8eb | 23.392 | 9.2 MMTel Enabler server deployed in PLMN operator domain
| The MMTel Enabler server is recommended to be deployed in the PLMN operator domain. Figure 9.2-1 illustrates the MMTel Enabler server deployed in PLMN operator domain.
Figure 9.2-1: MMTel Enabler server deployed in PLMN operator domain
The Application server can be deployed in PLMN operator domain or Application service provider domain and interacts with MMTel Enabler server via MMTel-2 reference point and MMTel-2e reference point respectively.The Application server deployed in PLMN operator domain, e.g. Application server 2 can only interact with the MMTel Enabler server deployed in the same PLMN operator domain, i.e. MMTel Enabler server 2. The Application server deployed in Application service provider domain, e.g. Application server 1, can interact with MMTel Enabler servers deployed in different PLMN operator domains, i.e. MMTel Enabler server 1 and MMTel Enabler server 2, based on business agreement between PLMN operator and Application service provider. In this case, the MMTel-2 reference point becomes MMTel-2e reference point.
The Controlling Application server can only be deployed in PLMN operator domain and interacts with MMTel Enabler server via MMTel-3 reference point. The Controlling Application server can only interact with the MMTel Enabler server deployed in the same PLMN operator domain.
NOTE: In this release, the MMTel Enabler Server is deployed in the PLMN operator domain.
Annex A:
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
2023-07
SA6#62-Ad Hoc-e
-
-
-
Proposed skeleton approved at S6#62-Ad Hoc-e
0.0.0
2023-07
SA6#62-Ad Hoc-e
Implemented pCRs approved in S6#62-Ad Hoc-e: S6a240100, S6a240101, S6a240102, S6a240103, S6a240282
Editorial changes by the rapporteur
0.1.0
2023-10
SA6#63
Implemented pCRs approved in S6#63: S6-244639, S6-244640, S6-244641, S6-244642, S6-244643, S6-244644
Editorial changes by the rapporteur
0.2.0
2023-11
SA6#64
Implemented pCRs approved in S6#64: S6-245625, S6-245626, S6-245627
Editorial changes by the rapporteur
0.3.0
2024-12
SA#106
SP-241697
Submitted to SA#106 for information
1.0.0
2025-02
SA6#65
Implemented pCRs approved in S6#65: S6-250072, S6-250074, S6-250077, S6-250078, S6-250079, S6-250150, S6-250372, S6-250373, S6-250374, S6-250375, S6-250376, S6-250379, S6-250380, S6-250381, S6-250382, S6-250383, S6-250384, S6-250549, S6-250550
Editorial changes by the rapporteur
1.1.0
2025-03
SA#107
SP-250194
Submitted to SA#107 for approval
2.0.0
2025-03
SA#107
SP-250194
MCC Editorial update for publication after TSG SA approval
19.0.0
2025-06
SA#108
SP-250612
0001
1
F
MMTel Enabler architecture fixes in section 6.2.1
19.1.0
2025-06
SA#108
SP-250612
0002
2
F
MMTel Enabler Server and Client descriptions update
19.1.0
2025-06
SA#108
SP-250612
0003
3
F
Multiple call control handling coordination multiple AS alignment with SA2
19.1.0
2025-06
SA#108
SP-250612
0006
2
F
Correction on DC application profiles downloading on UE
19.1.0
2025-06
SA#108
SP-250612
0007
F
Correction on MMTel Enabler Client request DC application profiles based on notification
19.1.0
2025-06
SA#108
SP-250612
0008
1
F
Corrections related to authentication aspect indicated in various procedures preconditions.
19.1.0
2025-06
SA#108
SP-250612
0009
1
F
Corrections related to Information elements across various procedures
19.1.0
2025-06
SA#108
SP-250612
0010
1
F
Update in abbreviations clause based on its usage in the procedures and other editorial corrections
19.1.0
2025-06
SA#108
SP-250612
0011
F
Update NOTE in the DC application profiles downloading procedure.
19.1.0
2025-06
SA#108
SP-250612
0012
F
Correction to the notification procedure
19.1.0
2025-06
SA#108
SP-250612
0013
1
F
Correction in Application Call with Data Channel capability procedure
19.1.0
2025-06
SA#108
SP-250612
0014
F
Remove DCAR related ENs in TS23.392
19.1.0
2025-06
SA#108
SP-250612
0016
1
F
Correction the figure in cl. 8.4.5
19.1.0
2025-06
SA#108
SP-250612
0017
1
F
Correction to cl. 8.4.4 and cl. 8.4.5
19.1.0
2025-09
SA#109
SP-251063
0020
1
F
Subscription request sent to the MMTel Enabler server
19.2.0
2025-09
SA#109
SP-251063
0021
F
Remove ENs regarding NEF exposure of IMS session management
19.2.0
2026-01
SA#110
SP-251487
0022
F
DC application and profile configuration request update
19.3.0
2026-01
SA#110
SP-251487
0023
1
F
Correction the figure in clause 8.2.3.2
19.3.0
|
b043aa03d2112b1c3a444522800f3b3a | 23.401 | 1 Scope
| The present document defines the Stage 2 service description for the Evolved 3GPP Packet Switched Domain - also known as the Evolved Packet System (EPS) in this document. The Evolved 3GPP Packet Switched Domain provides IP connectivity using the Evolved Universal Terrestrial Radio Access Network (E-UTRAN).
The specification covers both roaming and non-roaming scenarios and covers all aspects, including mobility between E-UTRAN and pre-E-UTRAN 3GPP radio access technologies, policy control and charging, and authentication.
The Radio Access Network functionality is documented only to the extent necessary to describe the overall system. TS 36.300 [5] contains the overall description of the Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN).
ITU-T Recommendation I.130 [3] describes a three-stage method for characterisation of telecommunication services, and ITU-T Recommendation Q.65 [4] defines Stage 2 of the method.
TS 23.402 [2] is a companion specification to this specification.
An Evolved Packet System architecture optimised for the support of Cellular IoT (Internet of Things) applications is also defined in this document.
The Evolved Packet System also provides support for the E-UTRAN to control a Dual Connectivity radio connection that uses a combination of E-UTRA and another radio access technology (e.g. NR). TS 36.300 [5] contains the overall description for Dual Connectivity.
Enhancements to support interworking of EPS with 5GS are captured in TS 23.501 [83] and TS 23.502 [84].
|
b043aa03d2112b1c3a444522800f3b3a | 23.401 | 2 References
| The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.402: "Architecture enhancements for non-3GPP accesses".
[3] ITU‑T Recommendation I.130: "Method for the characterization of telecommunication services supported by an ISDN and network capabilities of an ISDN".
[4] ITU‑T Recommendation Q.65: "The unified functional methodology for the characterization of services and network capabilities".
[5] 3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".
[6] 3GPP TS 23.203: "Policy and charging control architecture".
[7] 3GPP TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
[8] 3GPP TS 43.129: "Packet-switched handover for GERAN A/Gb mode; Stage 2".
[9] 3GPP TS 23.003: "Numbering, addressing and identification".
[10] 3GPP TS 23.122: "Non-Access-Stratum (NAS) functions related to Mobile Station in idle mode".
[11] 3GPP TS 43.022: "Functions related to MS in idle mode and group receive mode".
[12] 3GPP TS 25.304: "UE procedures in idle mode and procedures for cell re-selection in connected mode".
[13] 3GPP TS 23.246: "Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description".
[14] 3GPP TS 29.060: "GPRS Tunnelling Protocol (GTP) across the Gn and Gp interface".
[15] 3GPP TS 43.051: "GERAN Overall description - Stage 2".
[16] 3GPP TS 25.401: "UTRAN overall description".
[17] IETF RFC 1034 (1987): "Domain names – concepts and facilities" (STD 13).
[18] IETF RFC 4862: "IPv6 Stateless Address Autoconfiguration".
[19] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[20] Void.
[21] Void.
[22] 3GPP TS 25.413: "UTRAN Iu interface Radio Access Network Application Part (RANAP) signalling".
[23] 3GPP TS 44.064: "Mobile Station - Serving GPRS Support Node (MS-SGSN); Logical Link Control (LLC) Layer Specification".
[24] 3GPP TS 23.251: "Network Sharing; Architecture and functional description".
[25] IETF RFC 4039: "Rapid Commit Option for the Dynamic Host Configuration Protocol version 4 (DHCPv4)".
[26] IETF RFC 768: "User Datagram Protocol".
[27] 3GPP TS 23.221: "Architectural requirements".
[28] 3GPP TS 23.008: "Organization of subscriber data".
[29] 3GPP TS 23.078: "Customized Applications for Mobile network Enhanced Logic (CAMEL) Phase X; Stage 2".
[30] 3GPP TS 23.236: "Intra-domain connection of Radio Access Network (RAN) nodes to multiple Core Network (CN) nodes".
[31] IETF RFC 3588: "Diameter Base Protocol".
[32] IETF RFC 4861: "Neighbor Discovery for IP Version 6 (IPv6)".
[33] 3GPP TS 25.331: "Radio Resource Control (RRC); Protocol Specification".
[34] 3GPP TS 36.304: "Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) procedures in idle mode".
[35] IETF RFC 4960: "Stream Control Transmission Protocol".
[36] 3GPP TS 36.413: "Evolved Universal Terrestrial Access Network (E-UTRAN); S1 Application Protocol (S1AP)".
[37] 3GPP TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification".
[38] 3GPP TS 29.061: "Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN)".
[39] Void.
[40] 3GPP TS 33.102: "3G Security; Security architecture".
[41] 3GPP TS 33.401: "3GPP System Architecture Evolution: Security Architecture".
[42] 3GPP TS 48.018: "General Packet Radio Service (GPRS); Base Station System (BSS) - Serving GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP)".
[43] 3GPP TS 29.274: "3GPP Evolved Packet System (EPS); Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C); Stage 3".
[44] 3GPP TS 32.251: "Telecommunication management; Charging management; Packet Switched (PS) domain charging".
[45] 3GPP TS 24.007: "Mobile radio interface signalling layer 3; General aspects".
[46] 3GPP TS 24.301: "Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3".
[47] 3GPP TS 24.008: "Mobile Radio Interface Layer 3 specification; Core Network Protocols; Stage 3".
[48] 3GPP TS 23.041: "Technical realization of Cell Broadcast Service (CBS)".
[49] 3GPP TS 22.042: "Network Identity and Time Zone (NITZ) service description; Stage 1".
[50] Void.
[51] 3GPP TS 32.240: "Charging architecture and principles".
[52] 3GPP TS 23.228: "IP Multimedia Subsystem (IMS); Stage 2".
[53] 3GPP TS 24.285: "Allowed Closed Subscriber Group (CSG) List; Management Object (MO)".
[54] 3GPP TS 23.261: "IP flow mobility and seamless Wireless Local Area Network (WLAN) offload; Stage 2".
[55] IETF RFC 3168: "The Addition of Explicit Congestion Notification (ECN) to IP".
[56] 3GPP TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia Telephony; Media handling and interaction".
[57] 3GPP TS 23.271: "Functional stage 2 description of LCS".
[58] 3GPP TS 23.272: "Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2".
[59] 3GPP TS 23.107: "Quality of Service (QoS) concept and architecture".
[60] 3GPP TS 23.292: "IP Multimedia Subsystem (IMS) centralized services; Stage 2".
[61] 3GPP TS 29.303: "Domain Name System Procedures; Stage 3".
[62] IETF RFC 3376: "Internet Group Management Protocol, Version 3".
[63] IETF RFC 3810: "Multicast Listener Discovery Version 2 (MLDv2) for IPv6".
[64] IETF RFC 3927: "Dynamic Configuration of IPv4 Link-Local Addresses".
[65] IETF RFC 4291: "IP Version 6 Addressing Architecture".
[66] 3GPP TS 22.368: "Service Requirements for Machine-Type Communications (MTC); Stage 1".
[67] 3GPP TS 22.011: "Service Accessibility".
[68] 3GPP TS 22.153: "Multimedia priority service".
[69] 3GPP TS 24.368: "Non-Access Stratum (NAS) configuration Management Object (MO)".
[70] IETF RFC 6603: "Prefix Exclude Option for DHCPv6-based Prefix Delegation".
[71] 3GPP TS 23.002: "Network Architecture".
[72] 3GPP TS 23.007: "Restoration procedures".
[73] 3GPP TS 22.173: "IP Multimedia Core Network Subsystem (IMS) Multimedia Telephony Service and supplementary services; Stage 1".
[74] 3GPP TS 23.682: "Architecture enhancements to facilitate communications with packet data networks and applications".
[75] 3GPP TS 23.380: "IMS Restoration Procedures".
[76] 3GPP TS 36.423: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 Application Protocol (X2AP)".
[77] IETF RFC 5795: "The RObust Header Compression (ROHC) Framework".
[78] 3GPP TS 36.323: "Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification".
[79] 3GPP TS 29.128: "Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) interfaces for interworking with packet data networks and applications".
[80] 3GPP TS 22.101: "Service aspects; Service principles".
[81] 3GPP TS 23.167: "IP Multimedia Subsystem (IMS) emergency sessions".
[82] 3GPP TS 36.306: "Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio access capabilities".
[83] 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2".
[84] 3GPP TS 23.502: "Procedures for the 5G System; Stage 2".
[85] 3GPP TS 37.340: "Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Stage 2".
[86] 3GPP TS 29.002: "Mobile Application Part (MAP) specification".
[87] 3GPP TS 36.321: "Evolved Universal Terrestrial Radio Access -E-UTRA); Medium Access Control -MAC) protocol specification".
[88] 3GPP TS 23.503: "Policy and Charging Control Framework for the 5G System; Stage 2".
[89] 3GPP TS 38.331: "NR; Radio Resource Control (RRC); Protocol specification".
[90] 3GPP TS 38.401: "NG-RAN; Architecture description".
[91] 3GPP TS 29.674: "Interface between the UE radio Capability Management Function (UCMF) and the Mobility Management Entity (MME); Stage 3".
[92] 3GPP TS 36.410: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 general aspects and principles".
[93] 3GPP TS 38.300: "NR; NR and NG-RAN Overall Description; Stage 2".
[94] IETF RFC 8415: "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)".
[95] 3GPP TS 23.204: "Support of Short Message Service (SMS) over generic 3GPP Internet Protocol (IP) access; Stage 2".
[96] 3GPP TR 23.700‑29: "Study on Security and Privacy Aspects of 5G Satellite Access; Phase 3".
[97] 3GPP TS 22.261: "Service requirements for the 5G system; Stage 1".
|
b043aa03d2112b1c3a444522800f3b3a | 23.401 | 3 Definitions and abbreviations
| |
b043aa03d2112b1c3a444522800f3b3a | 23.401 | 3.1 Definitions
| For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
Disaster Condition: As defined in TS 22.261 [97].
Disaster Inbound Roamer: As defined in TS 22.261 [97].
Disaster Roaming: As defined in TS 22.261 [97].
MME Pool Area: An MME Pool Area is defined as an area within which a UE may be served without need to change the serving MME. An MME Pool Area is served by one or more MMEs ("pool of MMEs") in parallel. MME Pool Areas are a collection of complete Tracking Areas. MME Pool Areas may overlap each other.
MINT-EPS: As defined in TS 23.122 [10].
PLMN with Disaster Condition: A PLMN to which a Disaster Condition applies.
Serving GW Service Area: A Serving GW Service Area is defined as an area within which a UE may be served without need to change the Serving GW. A Serving GW Service Area is served by one or more Serving GWs in parallel. Serving GW Service Areas are a collection of complete Tracking Areas. Serving GW Service Areas may overlap each other.
PDN Connection: The association between a PDN represented by an APN and a UE, represented by one IPv4 address and/or one IPv6 prefix (for IP PDN Type) or by the UE Identity (for Non-IP and Ethernet PDN Types).
Default Bearer: The EPS bearer which is first established for a new PDN connection and remains established throughout the lifetime of the PDN connection.
Default APN: A Default APN is defined as the APN which is marked as default in the subscription data and used during the Attach procedure and the UE requested PDN connectivity procedure when no APN is provided by the UE.
eCall Only Mode: A UE configuration option that allows the UE to attach at EPS and register in IMS to perform only eCall Over IMS, and an IMS call to a non-emergency MSISDN or URI for test and/or terminal reconfiguration services. For a short period following either such call, an incoming call (e.g. callback from a PSAP or HPLMN operator) or other incoming session (e.g. for USIM reconfiguration) is possible. At other times when the UE is configured in this mode, the UE is required to refrain from any signalling to a network. Use of eCall Only Mode is configured in the USIM for the UE.
PDN Connection to the SCEF: The association between a UE, represented by the UE Identity, and a PDN represented by an APN to external packet data network via SCEF to allow transfer of Non-IP data. It includes establishment and persistence of T6 connection between MME and SCEF (see TS 29.128 [79]).
Emergency attached UE: A UE which only has bearer(s) related to emergency bearer service.
NOTE 1: The above term is equivalent to the term "attached for emergency bearer services" as specified in TS 24.301 [46].
LIPA PDN connection: a PDN Connection for local access (e.g. for IP or Ethernet access) for a UE connected to a HeNB.
en-gNB: As defined in TS 37.340 [85].
SIPTO at local network PDN connection: a PDN connection for SIPTO at local network for a UE connected to a (H)eNB.
Correlation ID: For a LIPA PDN connection, Correlation ID is a parameter that enables direct user plane path between the HeNB and L-GW.
SIPTO Correlation ID: For a SIPTO at local network PDN connection, SIPTO Correlation ID is a parameter that enables direct user plane path between the (H)eNB and L-GW when they are collocated.
Local Home Network: A set of (H)eNBs and L-GWs in the standalone GW architecture, where the (H)eNBs have IP connectivity for SIPTO at the Local Network via all the L-GWs.
Local Home Network ID: An identifier that uniquely identifies a Local Home Network within a PLMN.
Presence Reporting Area: An area defined within 3GPP Packet Domain for the purposes of reporting of UE presence within that area due to policy control and/or charging reasons. In the case of E-UTRAN, a Presence Reporting Area may consist in a set of neighbor or non-neighbor Tracking Areas, or eNodeBs and/or cells. There are two types of Presence Reporting Areas: "UE-dedicated Presence Reporting Areas" and "Core Network pre-configured Presence Reporting Areas" that apply to an MME pool.
RAN user plane congestion: RAN user plane congestion occurs when the demand for RAN resources exceeds the available RAN capacity to deliver the user data for a prolonged period of time.
NOTE 2: Short-duration traffic bursts is a normal condition at any traffic load level, and is not considered to be RAN user plane congestion. Likewise, a high-level of utilization of RAN resources (based on operator configuration) is considered a normal mode of operation and might not be RAN user plane congestion.
IOPS-capable eNodeB: an eNodeB that has the capability of IOPS mode operation, which provides local connectivity (e.g. for IP or Ethernet) and public safety services to IOPS-enabled UEs via a Local EPC when the eNodeB has lost backhaul to the Macro EPC or it has no backhaul to the Macro EPC.
IOPS network: an IOPS network consists of one or more eNodeBs operating in IOPS mode and connected to a Local EPC.
Local EPC: a Local EPC is an entity which provides functionality that eNodeBs in IOPS mode of operation use, instead of the Macro EPC, in order to support public safety services.
Macro EPC: the EPC which serves an eNodeB when it is not in IOPS mode of operation.
Nomadic EPS: a deployable system which has the capability to provide radio access (via deployable IOPS-capable eNodeB(s)), local connectivity (e.g. for IP or Ethernet) and public safety services to IOPS-enabled UEs in the absence of normal EPS
Multi-USIM UE: a UE with multiple USIMs, capable of maintaining a separate registration state with a PLMN for each USIM at least over 3GPP Access and supporting one or more of the features described in clause 4.3.33.
IOPS-enabled UE: is an UE that is configured to use networks operating in IOPS mode.
Cellular IoT: Cellular network supporting low complexity and low throughput devices for a network of Things. Cellular IoT supports IP, Ethernet and Non-IP traffic. Unless otherwise stated in this specification, Cellular IoT and all functionality applicable to Cellular IoT also apply to satellite access.
Narrowband-IoT: a 3GPP Radio Access Technology that forms part of Cellular IoT. It allows access to network services via E-UTRA with a channel bandwidth limited to 180 kHz (corresponding to one PRB). Unless otherwise indicated in a clause, Narrowband-IoT is a subset of E-UTRAN. Unless otherwise stated in this specification, Narrowband-IoT also includes satellite access.
LTE-M: a 3GPP RAT type Identifier used in the Core Network only, which is a sub-type E-UTRAN RAT type, and defined to identify in the Core Network the E-UTRAN when used by a UE indicating Category M in its UE radio capability. Unless otherwise stated in this specification, LTE-M also includes satellite access.
WB-E-UTRAN: in the RAN, WB-E-UTRAN is the part of E-UTRAN that excludes NB-IoT. In the Core Network, the WB-E-UTRAN also excludes LTE-M. Unless otherwise stated in this specification, WB-E-UTRAN also includes satellite access.
DCN-ID: DCN identity identifies a specific dedicated core network (DCN).
For the purposes of the present document, the following terms and definitions given in TS 23.167 [81] apply:
eCall Over IMS: See TS 23.167 [81].
RLOS attached UE: A UE is attached only for accessing Restricted Local Operator Services (see TS 23.221 [27]).
IAB-donor: For the purposes of this specification, this is a NR Secondary RAN node is further described in TS 37.340 [85] that supports Integrated access and backhaul (IAB) feature and provides connection to the core network to IAB-nodes. It supports the CU function of the CU/DU architecture for IAB defined in TS 38.401 [90].
IAB-node: A relay node that supports wireless in-band and out-of-band relaying of NR access traffic via NR Uu backhaul links. It supports the UE function and the DU function of the CU/DU architecture for IAB defined in TS 38.401 [90].
Feeder link: as defined in TS 36.300 [5].
Service link: as defined in TS 36.300 [5]
Store and Forward Satellite operation: An operation mode that provides to the UE a communication service when the serving satellite has a discontinuous connection to the ground network and such connection is not available when the satellite is interacting with the UE.
S&F Mode: The mode in which the RAN and core network entities perform Store and Forward Satellite operation.
NTN payload: as defined in TS 36.300 [5].
NTN Gateway: as defined in TS 36.300 [5].
|
b043aa03d2112b1c3a444522800f3b3a | 23.401 | 3.2 Abbreviations
| For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 [1].
5GS 5G System
AF Application Function
ARP Allocation and Retention Priority
AMBR Aggregate Maximum Bit Rate
CBC Cell Broadcast Centre
CBE Cell Broadcast Entity
CIoT Cellular IoT
CSG Closed Subscriber Group
CSG ID Closed Subscriber Group Identity
C-SGN CIoT Serving Gateway Node
CSS CSG Subscriber Server
DAPS Dual Active Protocol Stacks
DCN Dedicated Core Network
DeNB Donor eNode B
DL TFT DownLink Traffic Flow Template
DRX Discontinuous Reception
ECGI E-UTRAN Cell Global Identifier
ECM EPS Connection Management
ECN Explicit Congestion Notification
EMM EPS Mobility Management
eNodeB evolved Node B
EPC Evolved Packet Core
EPS Evolved Packet System
E-RAB E-UTRAN Radio Access Bearer
E-UTRAN Evolved Universal Terrestrial Radio Access Network
GBR Guaranteed Bit Rate
GUMMEI Globally Unique MME Identifier
GUTI Globally Unique Temporary Identity
GW Gateway
HeNB Home eNode B
HeNB GW Home eNode B Gateway
HFN Hyper Frame Number
IAB Integrated Access and Backhaul
IMEI/TAC IMEI Type Allocation Code
IOPS Isolated E-UTRAN Operation for Public Safety
IoT Internet of Things
ISR Idle mode Signalling Reduction
LAA Licensed Assisted Access
LBI Linked EPS Bearer Id
L-GW Local GateWay
LIPA Local IP Access
LWA LTE/WLAN Aggregation
LWIP LTE/WLAN Radio Level Integration with IPsec Tunnel
MBR Maximum Bit Rate
MINT Minimization of Service Interruption
MME Mobility Management Entity
MMEC MME Code
MTC Machine-Type Communications
MT-EDT Mobile Terminated Early Data Transmission
M-TMSI M-Temporary Mobile Subscriber Identity
NB-IoT Narrowband IoT
NR New Radio
NR-U New Radio Unlicensed
NTN Non-Terrestrial Network
OCS Online Charging System
OFCS Offline Charging System
OMC-ID Operation and Maintenance Centre Identity
P‑GW PDN Gateway
PCC Policy and Charging Control
PCRF Policy and Charging Rules Function
PRA Presence Reporting Area
PDCP Packet Data Convergence Protocol
PMIP Proxy Mobile IP
PSAP Public Safety Answering Point
PSM Power Saving Mode
PTI Procedure Transaction Id
QCI QoS Class Identifier
RACS UE Radio Capability Signalling optimization
RCAF RAN Congestion Awareness Function
RFSP RAT/Frequency Selection Priority
RLOS Restricted Local Operator Services
RN Relay Node
RUCI RAN User Plane Congestion Information
S&F Store and Forward
S‑GW Serving Gateway
S-TMSI S-Temporary Mobile Subscriber Identity
SDF Service Data Flow
SIPTO Selected IP Traffic Offload
TAC Tracking Area Code
TAD Traffic Aggregate Description
TAI Tracking Area Identity
TAU Tracking Area Update
TI Transaction Identifier
TIN Temporary Identity used in Next update
UCMF UE radio Capability Management Function
URRP-MME UE Reachability Request Parameter for MME
UL TFT UpLink Traffic Flow Template
ULR-Flags Update Location Request Flags
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4 Architecture model and concepts
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.1 General concepts
| Local breakout of traffic via the visited PLMN is supported, when network policies and user subscription allow it. Local breakout may be combined with support for multiple simultaneous PDN connections, described in clause 5.10.
CIoT EPS Optimisations provide improved support of small data transfer, described in clause 4.11.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2 Architecture reference model
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2.1 Non-roaming architecture
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Figure 4.2.1-1: Non-roaming architecture for 3GPP accesses
Figure 4.2.1-2: Non-roaming architecture for 3GPP accesses. Single gateway configuration option
NOTE 1: Also in this configuration option, S5 can be used between non collocated Serving Gateway and PDN Gateway.
NOTE 2: Additional interfaces for 2G/3G access are shown in TS 23.060 [7].
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2.2 Roaming architecture
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Figure 4.2.2-1: Roaming architecture for 3GPP accesses. Home routed traffic
NOTE 1: Additional interfaces/reference points for 2G/3G accesses are documented in TS 23.060 [7].
The figures 4.2.2-2 and 4.2.2-3 represent the Roaming with local breakout case with Application Function (AF) in the Home Network and in the Visited Network respectively. The concurrent use of AF's in the home network and AF's in the visited network is not excluded.
Figure 4.2.2-2: Roaming architecture for local breakout, with home operator's application functions only
NOTE 2: See TS 23.203 [6] for the role of and functions related to Home and Visited PCRF and S9/Rx reference points.
NOTE 3: In figure 4.2.2‑2, the control plane signalling and the user plane for accessing to Home Operator's services traverse over the SGi reference point via the Visited Operator's PDN.
Figure 4.2.2-3: Roaming architecture for local breakout, with visited operator's application functions only
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2.3 Reference points
| S1-MME: Reference point for the control plane protocol between E-UTRAN and MME.
S1-U: Reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter eNodeB path switching during handover. S1-U does not apply to the Control Plane CIoT EPS Optimisation.
S3: It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state. This reference point can be used intra-PLMN or inter-PLMN (e.g. in the case of Inter-PLMN HO).
S4: It provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunnelling.
S5: It provides user plane tunnelling and tunnel management between Serving GW and PDN GW. It is used for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.
S6a: It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS.
Gx: It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW.
S8: Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5.
S9: It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function.
S10: Reference point between MMEs for MME relocation and MME to MME information transfer. This reference point can be used intra-PLMN or inter-PLMN (e.g. in the case of Inter-PLMN HO).
S11: Reference point providing control plane between MME and Serving GW. In addition, in order to support Control Plane CIoT EPS Optimisation, the S11-U reference point provides user plane between MME and Serving GW.
S12: Reference point between UTRAN and Serving GW for user plane tunnelling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option.
S13: It enables UE identity check procedure between MME and EIR.
S17: It enables procedures for RACS between MME and UCMF.
SGi: It is the reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses.
Rx: The Rx reference point resides between the AF and the PCRF in the TS 23.203 [6].
NOTE 1: Except where stated otherwise, this specification does not make an explicit assumption as to whether an interface is intra-PLMN or inter-PLMN.
When data forwarding is used as part of mobility procedures different user plane routes may be used based on the network configuration (e.g. direct or indirect data forwarding). These routes can be between eNodeB and RNC, eNodeB and SGSN, RNC and S‑GW or between S‑GW and SGSN. Explicit reference points are not defined for these routes. These user plane forwarding routes can cross inter-PLMN boundaries (e.g. in the case of Inter-PLMN HO).
Protocol assumption:
- The S1-U is based on GTP-U protocol;
- The S3 is based on GTP protocol;
- The S4 and S11 are based on GTP protocol;
- The S5 is based on GTP protocol. PMIP variant of S5 is described in TS 23.402 [2];
- The S8 is based on GTP protocol. PMIP variant of S8 is described in TS 23.402 [2].
- S3, S4, S5, S8, S10 and S11 interfaces are designed to manage EPS bearers as defined in clause 4.7.2.
NOTE 2: Redundancy support on reference points S5 and S8 should be taken into account.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2.4 Warning System architecture
| Refer to TS 23.041 [48] and TS 23.002 [71] for the Warning System architecture.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.2.5 Radio Capability signalling optimization architecture
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Figure 4.2.5-1: RACS architecture
Figure 4.2.5-1 depicts the EPS architecture supporting RACS. RACS is further described in clause 5.11.3a. EPS architecture supporting provisioning of UCMF is described in TS 23.682 [74].
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3 High level functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.1 General
| The following list gives the logical functions performed within this system. Several functional groupings (meta functions) are defined and each encompasses a number of individual functions:
- Network Access Control Functions.
- Packet Routing and Transfer Functions.
- Mobility Management Functions.
- Security Functions.
- Radio Resource Management Functions.
- Network Management Functions.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2 Network access control functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.1 General
| Network access is the means by which a user is connected to the evolved packet core system.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.2 Network/Access network selection
| It is the means by which a UE selects a PLMN/Access network from which to gain connectivity. The network/access network selection procedure varies for different access technologies. For 3GPP access networks, the network selection principles are described in TS 23.122 [10]. For 3GPP access networks, the access network selection procedures are described in TS 36.300 [5], TS 43.022 [11] and TS 25.304 [12].
Architectural impacts stemming from support for network/access network selection procedures for non-3GPP access and between 3GPP access and non-3GPP accesses are described in TS 23.402 [2].
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.3 Authentication and authorisation function
| This function performs the identification and authentication of the service requester, and the validation of the service request type to ensure that the user is authorised to use the particular network services. The authentication function is performed in association with the Mobility Management functions.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.4 Admission control function
| The purpose of admission control is to determine if the requested resources are available, and then reserve those resources.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.5 Policy and Charging Enforcement Function
| This includes all the functionality of PCEF as defined by TS 23.203 [6]. The PCEF encompasses service data flow detection, policy enforcement and flow based charging functionalities as defined in TS 23.203 [6].
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.2.6 Lawful Interception
| Lawful interception is the action, performed by a network operator / access provider / service provider, of making available certain information and providing that information to a law enforcement monitoring facility.
4.3.2a Support for Dual Connectivity
Dual Connectivity involves two RAN nodes, i.e. Master and Secondary RAN nodes (see TS 36.300 [5] for the definitions), in providing radio resources to a given UE (with active radio bearers), while a single S1-MME termination point exists for an UE between a MME and the E-UTRAN. The E-UTRAN architecture and related functions to support Dual Connectivity with E-UTRAN is further described in TS 36.300 [5]. Dual Connectivity with E-UTRAN as Master RAN node and NR as Secondary RAN node is further described in TS 37.340 [85].
Dual connectivity defines "Master Cell Group (MCG) bearer" and "Secondary Cell Group (SCG) bearer" alternatives (see TS 36.300 [5]). For E-RABs configured as "MCG bearers" the U-plane termination points are maintained, whereas for E-RABs configured as "SCG bearers" it enables changing the U-plane termination point in the E-UTRAN by means of S1-MME signalling without changing the S1-MME termination point.
Dual Connectivity also defines a "split bearer" alternative TS 36.300 [5]. The "split bearer" in the E-UTRAN is transparent to the core network entities (e.g. MME, S-GW etc.) with the exception of the CSG membership verification by the MME when the Secondary eNodeB is a hybrid access eNodeB.
The E-UTRAN uses the per-UE information supplied by the MME and local E-UTRAN configuration data to determine whether or not to use Dual Connectivity for that UE, and, on a per EPS bearer basis the E-UTRAN decides whether to use an MCG bearer or SCG bearer, and, whether or not that bearer is a "split bearer".
NOTE 1: Typically, the MME and SGW cannot determine whether the RAN termination point(s) for the S1-U interface are located on a Master RAN node that has multiple IP addresses, or, on a Secondary RAN node.
If the UE has indicated support for Dual Connectivity with NR and MME has an Access Restriction for NR for a UE (either signalled from the HSS, or, locally generated by VPLMN policy in the MME) then the MME shall signal this to the E-UTRAN as part of Handover Restriction List and to the UE in Attach and TAU Accept as defined in clauses 5.5.2.2.3, 5.5.2.4.3, 5.3.2.1, 5.3.3.1, 5.3.3.2 and D.3.6 respectively. An eNodeB supporting Dual Connectivity with NR checks whether the UE is allowed to use NR. If the UE is not allowed to use NR, the eNodeB shall not establish Dual Connectivity with NR as a secondary RAT.
The MME uses "UE support for dual connectivity with NR" for SGW and PGW selection when the UE indicates support for NR and there is no Access Restriction for NR for the UE.
An E-UTRAN cell, based on operator configuration, broadcasts whether it is capable of supporting dual connectivity with locally available NR secondary cell(s).
At inter-RAT handover from NR or GERAN/UTRAN, the Access Restriction for NR is either already in the MME's UE context, or, is obtained from the HSS during the subsequent Tracking Area Update procedure (i.e. not from the source AMF/SGSN or source RAN). In both inter-RAT handover cases, any NR Access Restriction is then signalled to the E-UTRAN.
NOTE 2: This signalling of the Access Restriction during the TAU after the inter-RAT handover procedure means that there is a small risk that NR resources are transiently allocated.
The eNodeB, at which the S1-MME terminates, performs all necessary S1-MME related functions (as specified for any serving eNodeB) such as mobility management, relaying of NAS signalling, E-RAB handling, etc. and manages the handling of user plane connection of S1-U.
Additional functional characteristics are:
- User location information reporting is based on the identity of the cell that is serving the UE and supported by the eNodeB terminating S1-MME. The cell identity of the Primary cell in the secondary RAN node may also be included, if available.
- Path update signalling for E-RABs configured as "SCG bearers" and Serving GW relocation cannot occur at the same time.
- During handover with dual connectivity, the requirement of forwarding "end marker" packets to target node is also applicable to secondary RAN node if it is the source node for S1-U bearer.
- After handover with data forwarding, the E-UTRAN initiated E-RAB modification procedure of clause 5.4.7 should not be initiated by the target eNodeB before "end marker" packet is received at the target RAN node or a timer in target eNodeB expires.
- Relaying function is not supported.
- CSG function may be supported if the Secondary eNodeB is a hybrid access eNodeB (see more details in clause 5.4.7 and in TS 36.300 [5]).
NOTE 3: A HeNB cannot be the Master eNodeB, i.e. a HeNB cannot initiate the Secondary eNodeB Addition procedure.
NOTE 4: A HeNB is not allowed to be the Secondary eNodeB if the HeNB is a closed access eNodeB.
- When the Secondary eNodeB is a hybrid access eNodeB, the Master eNodeB may ask CSG membership verification to the MME using E-RAB Modification Indication message (for SCG bearers) or UE Context Modification Indication (for split bearers) message. The MME shall determine the CSG membership based on the CSG Membership Information as specified in TS 36.300 [5] and shall respond to the Master eNodeB using respectively a E-RAB Modification Confirm or a UE Context Modification Confirm, but shall not update the User CSG Information in the Core Network.
- The LIPA function may be supported for the SCG bearer alternative, in the case that the Secondary eNodeB is a HeNB with a collocated L-GW (see more details in TS 36.300 [5]).
- "SIPTO at the Local Network with L-GW function collocated with the (H)eNB" function may be supported (see more details in TS 36.300 [5]):
- For the MCG and split bearer alternatives, if the Master eNodeB is collocated with a L-GW; and/or
- For the SCG bearer alternative, if the Secondary eNodeB is a (H)eNB with a collocated L-GW.
NOTE 5: LIPA or SIPTO at the Local Network PDN connection can be established if the SeNodeB has already been added before the UE requests establishment of the LIPA or SIPTO at the Local Network PDN connection.
NOTE 6: LIPA or SIPTO at the Local Network PDN connection can be established if the UE is in the coverage of the candidate SeNodeB when the UE requests establishment of the LIPA or SIPTO at the Local Network PDN connection, but the SeNodeB has not yet been added. In this case, there is a time gap between the moment when the PDN connection establishment is completed and the moment when the SeNodeB Addition procedure is completed.
- "SIPTO at the Local Network with stand-alone GW" function may be supported for the MCG, SCG, and split bearer alternatives if the Master and Secondary eNodeBs belong to the same LHN (see more detail in TS 36.300 [5]).
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.3 Packet routing and transfer functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.3.1 General
| A route is an ordered list of nodes used for the transfer of packets within and between the PLMN(s). Each route consists of the originating node, zero or more relay nodes and the destination node. Routing is the process of determining and using, in accordance with a set of rules, the route for transmission of a message within and between the PLMN(s).
The EPS is an IP network and uses the standard routing and transport mechanisms of the underlying IP network.
The Maximum Transfer Unit (MTU) size considerations in clause 9.3 of TS 23.060 [7] are also applicable to EPS.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.3.2 IP header compression function
| The IP header compression function optimises use of radio capacity by IP header compression mechanisms.
When Control Plane CIoT EPS Optimisation is supported for PDN connections of IP PDN Type, if the IP header compression based on ROHC framework IETF RFC 5795 [77] is implemented in the MME and the UE, the ROHC profiles defined in TS 36.323 [78] may be supported.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.3.3 Packet screening function
| The packet screening function provides the network with the capability to check that the UE is using the exact IPv4-Address and/or IPv6-Prefix that was assigned to the UE.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.3.4 IP Multicast Forwarding between a network accessed by LIPA and a UE
| The Home eNodeB L-GW should support IP forwarding of packets to multicast groups between the UE and the network accessed by LIPA.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.4 Security functions
| The security functions are described in clause 5.3.10.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5 Mobility management functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.1 General
| The mobility management functions are used to keep track of the current location of a UE.
Intra-RAT mobility for NB-IoT UEs is supported.
Inter-RAT idle mode mobility between NB-IoT and WB-EUTRAN/UTRAN/GERAN is supported. Tracking area list management as defined in clause 4.3.5.3 is required to ensure that at inter-RAT mobility, the UE performs a TAU or RAU procedure.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.2 Reachability Management for UE in ECM-IDLE state
| The location of a UE in ECM-IDLE state is known by the network on a Tracking Area List granularity. All cells of the Tracking Areas in which a UE in ECM-IDLE is currently registered needs to be taken into account for paging. The UE may be registered in multiple Tracking Areas. All the tracking areas in a Tracking Area List to which a UE is registered are served by the same serving MME.
An EMM-REGISTERED UE performs periodic Tracking Area Updates with the network after the expiry of the periodic TAU timer.
The MME may allocate long periodic TAU timer value to the UE according to clause 4.3.17.3.
If the UE is out of E-UTRAN coverage (including the cases when the UE is camped on GERAN/UTRAN cells) when its periodic TAU timer expires, the UE shall:
- if ISR is activated, start the E-UTRAN Deactivate ISR timer. After the E-UTRAN Deactivate ISR timer expires the UE shall deactivate ISR by setting its TIN to "P-TMSI".
- if ISR is activated and the UE is camping on a GERAN/UTRAN cell (or returns to coverage in GERAN/UTRAN) and the UE is EPS/IMSI attached, perform a LAU procedure in NMO II or a combined RA/LA update procedure in NMO I.
- when EMM-REGISTERED, perform a Tracking Area Update when it next returns to E‑UTRAN coverage. For UE using a RAN that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), if the UE knows how the E-UTRAN coverage varies with time based on information defined in TS 36.331 [37] (e.g. from the ephemeris data of a satellite access system that the UE is using) then the UE may deactivate its Access Stratum functions in order to optimise power consumption until coverage returns. Details are specified in TS 36.304 [34] and TS 24.301 [46].
If the UE is camped on an E‑UTRAN cell or is in ECM‑CONNECTED state when the UE's periodic RAU timer expires, the UE shall:
- if ISR is activated, start the GERAN/UTRAN Deactivate ISR timer. After the GERAN/UTRAN Deactivate ISR timer expires the UE shall deactivate ISR by setting its TIN to "GUTI".
- perform a Routing Area Update when it next returns to GERAN/UTRAN coverage.
If the UE is EPS attached only and either camps on an E UTRAN cell or is in ECM CONNECTED state when the UE's periodic LAU timer expires, the UE shall perform a Location Area Update procedure in NMO II or combined RA/LA update in NMO I when it next returns to GERAN/UTRAN coverage.
The E-UTRAN Deactivate ISR timer is stopped when the UE performs a successful Tracking Area Update or combined TA/LA Update; and the GERAN/UTRAN Deactivate ISR timer is stopped when the UE performs a successful Routing Area Update or combined RA/LA Update.
Expiry of the periodic TAU timer, or, the periodic RAU timer, or, the periodic LAU timer shall not cause the UE to change RAT.
The UE's periodic TAU timer is restarted from its initial value whenever the UE enters ECM‑IDLE mode and when the UE leaves the E‑UTRAN connection due to handover to GERAN/UTRAN. UTRAN RRC state transitions and GERAN GPRS STANDBY/READY state transitions shall have no other impact on the periodic TAU timer.
E‑UTRAN RRC state transitions shall have no impact on the periodic RAU timer or periodic LAU timer except that handover from GERAN/UTRAN to E‑UTRAN shall cause the periodic RAU timer to be started from its initial value.
Handover from E‑UTRAN to UTRAN/GERAN shall cause the periodic TAU timer to be started from its initial value.
Typically, the MME runs a mobile reachable timer. Whenever the UE enters ECM IDLE mode the timer is started with a value similar to the UE's periodic TAU timer. If this timer expires in the MME, the MME can deduce that the UE is not reachable. However, the MME does not know for how long the UE is not reachable, so, the MME shall not immediately delete the UE's bearers. Instead the MME should clear the PPF flag in the MME and start an Implicit Detach timer, with a relatively large value and if ISR is activated, at least slightly larger than the UE's E-UTRAN Deactivate ISR timer.
Tracking Area or RAT specific MME configuration can be used to support UEs using a RAN that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage).
NOTE 1: For example, if a satellite system only provides coverage to a UE for 20 minutes when a satellite passes, and the maximum time before a satellite passes any point on the earth is 10 hours, the MME could configure the periodic TAU timer and mobile reachable timer to be just greater than 20 minutes and the Implicit Detach timer to be greater than 10 hours to avoid unintended implicit detach due to coverage gap. Such configuration does not require MME to be aware of detailed coverage times for each UE or for different locations.
Further enhancements to handle discontinuous coverage for satellite access is provided in clause 4.13.8.2.
If MME has allocated an Active Time to the UE, then the MME starts the Active timer with the value of Active Time whenever the UE enters ECM IDLE mode. If this timer expires in the MME, the MME can deduce that the UE is not reachable and should clear the PPF flag in the MME.
With the PPF clear, the MME does not page the UE in E‑UTRAN coverage and shall send a Downlink Data Notification Reject message to the Serving GW when receiving a Downlink Data Notification message from the Serving GW. If the Implicit Detach timer expires before the UE contacts the network, then the MME can deduce that the UE has been 'out of coverage' for a long period of time and implicitly detach the UE as described in clause 5.3.8.3 "MME-initiated Detach procedure".
If the MME is requested to monitor Reachability for Data and the UE enters ECM-CONNECTED, the MME sends a Monitoring Report message to the address that was indicated in the related Monitoring Request as described in TS 23.682 [74].
When the MME applies General NAS level Mobility Management Congestion Control to a UE, the MME may need to adjust the mobile reachable timer and/or Implicit Detach timer (as clause 4.3.7.4.2.4).
NOTE 2: The SGSN has similar functionality as the MME.
NOTE 3: Alternative MME implementations are permitted, however, the externally visible MME behaviour should conform to the above description.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.3 Tracking Area list management
| Tracking Area list management comprises the functions to allocate and reallocate a Tracking Area Identity list to the UE. All the tracking areas in a Tracking Area List to which a UE is registered are served by the same serving MME.
The "tracking area list concept" is used with E-UTRAN. With this concept, when the UE registers with the network, the MME allocates a set (a "list") of tracking areas to the UE. By making the centre of this set of tracking areas close to the UE's current location, the chance of a UE rapidly making another tracking area update can be reduced.
When MME allocates TAI list for UE registered for Disaster Roaming service in EPS as specified in clause 4.14, the MME shall only consider TAIs covering the area with the Disaster Condition.
If SIPTO at local network with stand-alone GW, Serving GW relocation without mobility and ISR are supported in the core network the Tracking Area list should only contain either Tracking Areas inside one local network or inside the macro network. If the tracking area list covers both local network and macro network, the ISR shall not be activated if the UE is allowed to use SIPTO at local network.
The MME determines the RAT type the UE is camping on, i.e. NB-IoT or WB-E-UTRAN for terrestrial access and WB-E-UTRAN or NB-IoT RAT types for satellite access, based on the Tracking Area indicated in the INITIAL UE MESSAGE by the eNodeB.
To ensure a UE initiates tracking area updating procedure when performing inter-RAT mobility between NB-IoT and WB-E-UTRAN, the E-UTRAN shall be configured such that a Tracking Area does not contain both WB-E-UTRAN and NB-IoT cells, and, the MME shall not allocate a Tracking Area Identity list that contains both NB-IoT and WB-E-UTRAN Tracking Areas.
NOTE 1: It is assumed that a satellite either operates in S&F Mode or does not operate in S&F Mode at any given time, so that all the E-UTRAN cell(s), Tracking Area(s) or TAI list served by the onboard MME and onboard eNB are either operating in S&F mode or non S&F mode. The S&F cells and non S&F cells need to be using different Tracking Areas in order to trigger the UEs to perform Tracking Area Update.
To ensure the UE initiates tracking area update procedure when it moves to and from an MME that supports 15 EPS bearers per UE as defined in clause 4.12 to an MME that does not support 15 EPS bearers per MME and vice versa, the MME shall allocate a Tracking Area Identity list that provides homogenous support for 15 EPS bearers per UE.
Other features (e.g. User Plane CIoT EPS Optimisation, Supporting up to 15 EPS bearers per UE, satellite access) may require the MME to adapt how it creates the "list" of TAIs.
NOTE 2: This TAI list functionality is different to the SGSN behaviour in GERAN and UTRAN systems. In GERAN/UTRAN the UE is only registered in one Routeing Area at a time.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.4 Inter-eNodeB mobility anchor function
| The Inter-eNodeB Mobility Anchor is the functional entity that anchors the user plane for E-UTRAN mobility.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.5 Inter-3GPP mobility anchor function
| The Inter-3GPP Mobility Anchor is the functional entity that anchors the user plane for mobility between 3GPP 2G/3G access systems and the E-UTRA access system.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.6 Idle mode signalling reduction function
| The Idle mode Signalling Reduction (ISR) function provides a mechanism to limit signalling during inter-RAT cell-reselection in idle mode (ECM-IDLE, PMM-IDLE, GPRS STANDBY states).
NOTE 1: The Idle mode Signalling Reduction function is mandatory for E-UTRAN UEs that support GERAN and/or UTRAN and optional for core network. The UE's ISR capability in the UE Core Network Capability element is for test purpose.
The MME/SGSN activates ISR only if the Serving GW supports the ISR. How MME/SGSN determines a Serving GW supports ISR is implementation dependent.
ISR shall be activated by decision of the CN nodes and shall be explicitly signalled to the UE as "ISR activated" in the RAU and TAU Accept messages. The UE may have valid MM parameters both from MME and from SGSN. The "Temporary Identity used in Next update" (TIN) is a parameter of the UE's MM context, which identifies the UE identity that the UE shall indicate in the next RAU Request, TAU Request or Attach Request message. The TIN also identifies the status of ISR activation in the UE.
The TIN can take one of the three values, "P‑TMSI", "GUTI" or "RAT-related TMSI". The UE shall set the TIN when receiving an Attach Accept, a TAU Accept or RAU Accept message according to the rules in table 4.3.5.6-1.
Table 4.3.5.6-1: Setting of the TIN
Message received by UE
Current TIN value stored by UE
TIN value to be set by the UE when receiving message
Attach Accept via E-UTRAN
(never indicates "ISR Activated")
Any value
GUTI
Attach Accept via GERAN/UTRAN
(never indicates "ISR Activated")
Any value
P-TMSI
TAU Accept
not indicating "ISR Activated"
Any value
GUTI
TAU Accept
indicating "ISR Activated"
GUTI
P‑TMSI or RAT-related TMSI
GUTI
RAT-related TMSI
RAU Accept
not indicating "ISR Activated"
Any value
P‑TMSI
RAU Accept
indicating "ISR Activated"
P‑TMSI
GUTI or RAT-related TMSI
P‑TMSI
RAT-related TMSI
When "ISR Activated" is indicated by the RAU/TAU Accept message but the UE shall not set the TIN to "RAT-related TMSI" is a special situation. Here the UE has deactivated ISR due to special situation handling. By maintaining the old TIN value the UE remembers to use the RAT specific TMSI indicated by the TIN when updating with the CN node of the other RAT.
Only if the TIN is set to "RAT-related TMSI" ISR behaviour is enabled for the UE, i.e. the UE can change between all registered areas and RATs without any update signalling and it listens for paging on the RAT it is camped on. If the TIN is set to "RAT-related TMSI", the UE's P‑TMSI and RAI as well as its GUTI and TAI(s) shall remain registered with the network and shall remain valid in the UE.
Table 4.3.5.6-2: Temporary UE Identity that the UE shall indicate in Attach Request and TAU/RAU Request (as "old GUTI" or as "old P‑TMSI/RAI" information element)
Message to be sent by UE
TIN value: P-TMSI
TIN value: GUTI
TIN value: RAT-related TMSI
TAU Request
GUTI mapped from P‑TMSI/RAI
GUTI
GUTI
RAU Request
P-TMSI/RAI
P‑TMSI/RAI mapped from GUTI
P‑TMSI/RAI
Attach Request via E-UTRAN
GUTI mapped from P‑TMSI/RAI
GUTI
GUTI
Attach Request via GERAN/UTRAN
P‑TMSI/RAI
P‑TMSI/RAI mapped from GUTI
P‑TMSI/RAI
Table 4.3.5.6-2 shows which temporary identity the UE shall indicate in a Tracking or Routing Area Update Request or in an Attach Request message, when the UE stores these as valid parameters.
Situations may occur that cause unsynchronized state information in the UE, MME and SGSN. Such special situations trigger a deactivation of ISR locally in the UE.
The UE shall deactivate ISR locally by setting its TIN to the temporary identity of the currently used RAT in following special situations:
- Modification of any EPS bearer context or PDP context which was activated before the ISR is activated in the UE;
- At the time when the UE moves from E‑UTRAN to GERAN/UTRAN or moves from GERAN/UTRAN to E‑UTRAN by means other than PSHO, if any EPS bearer context or PDP context activated after the ISR was activated in the UE exists;
- At the time when the UE moves from GERAN/UTRAN to E‑UTRAN by means other than PSHO and CS to PS SRVCC, if the PDP contexts were suspended in GERAN and not successfully resumed before returning to E‑UTRAN;
- After updating either MME or SGSN about the change of the UE specific DRX parameters to guarantee that the other CN node is also updated;
- After updating either MME or SGSN about the change of the UE Core Network Capabilities to guarantee that the other CN node is also updated;
- E-UTRAN selection by a UTRAN-connected UE (e.g. when in URA_PCH to release Iu on UTRAN side);
- E-UTRAN selection from GERAN READY state;
- GERAN selection by an E-UTRAN-connected UE via Cell Change Order that is not for CS fallback;
- After a LAU procedure if the UE has CS fallback and/or SMS over SGs activated.
- For a UE that is IMS registered for voice, then after that UE moves from a Tracking Area List that supports IMS voice over PS sessions (see 4.3.5.8 for more information) to one that does not, and vice versa. It shall be possible, e.g. using Device Management or initial provisioning, to configure the UE to apply/not apply this particular exception.
NOTE 2: A UE moving between Tracking Area Lists that both support IMS voice over PS sessions, or that both do not support IMS voice over PS sessions, is unaffected by the above.
The UE shall deactivate ISR locally by setting its TIN to the temporary identity of the RAT that is still available to the UE in following special situations:
- After the RAT-specific Deactivate ISR timer expires, e.g. because the coverage of that RAT is lost or the RAT is no more selected by the UE (this may result also in implicit detach by SGSN or MME).
ISR shall be deactivated in the UE by the CN node using normal update signalling, i.e. by omitting the signalling of "ISR Activated", in following special situations:
- CN node change resulting in context transfer between the same type of CN nodes (SGSN to SGSN or MME to MME);
- Serving GW change;
- When the UE only has bearers related to emergency bearer service;
- When the UE is registered for RLOS service;
- TAU or RAU when UE moves over the border between local and macro network where SIPTO at local network with stand-alone GW and Serving GW relocation without mobility are supported in the core network.
- TAU or RAU when the network confirms to use PSM for the UE.
If tracking area list or routing area covers both local network and macro network, the ISR shall not be activated if the UE is allowed to use SIPTO at local network and Serving GW relocation without mobility are supported in the core network.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.7 Mobility Restrictions
| Mobility Restrictions comprises the functions for restrictions to mobility handling of a UE in E-UTRAN access. The Mobility Restriction functionality is provided by the UE, the radio access network and the core network.
Mobility Restriction functionality in state ECM-IDLE is executed in UE based on information received from the core network. Mobility Restriction functionality in state ECM-CONNECTED is executed in the radio network and the core network.
In state ECM-CONNECTED, the core network provides the radio network with a Handover Restriction List. The Handover Restriction List specifies roaming, area and access restrictions. If roaming restriction to GERAN or UTRAN access needs to be enforced, a MME that is connected to eNodeBs that may handover or invoke release with redirection to UTRAN or GERAN is configured with a list of HPLMN IDs that are permitted to access GERAN or UTRAN unless restricted by the UE individual access restriction information received from HSS.
For a UE requesting Disaster Roaming service in EPS, the UE is only allowed to receive services in the area with Disaster Condition as specified in clause 4.14. The other areas shall be considered as forbidden area for the UE attached for Disaster Roaming service in EPS.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.8 IMS voice over PS Session Supported Indication
| The serving PLMN shall send an indication toward the UE during the Attach procedure and Tracking Area Update procedures if an IMS voice over PS session is supported. The serving PLMN uses this indicator to indicate to the UE whether it can expect a successful IMS voice over PS session according to TS 22.173 [73] with a bearer that supports Conversational Voice as specified in TS 23.203 [6]. A UE with "IMS voice over PS" voice capability should take this indication into account when establishing voice over PS sessions (as specified in TS 23.221 [27]) as well as when determining whether to deactivate the special handling of ISR locally (as detailed in clause 4.3.5.6).
The serving PLMN provides this indication based e.g. on local policy, HPLMN, Voice Support Match Indicator, the SRVCC capability of the network and UE and/or extends of E-UTRAN/UTRAN coverage. The serving PLMN shall indicate to the UE that the UE can expect a successful IMS voice over PS session only if the MME is configured to know that the serving PLMN has a roaming agreement for IMS voice with the HPLMN of the UE. This indication is per TAI list.
On request by the HSS, the MME shall indicate the following:
- whether or not an IMS voice over PS Session is supported in the TA(s) that are registered for the UE ("IMS voice over PS Session Supported Indication"), together with the time of the last radio contact with the UE; and
- the current RAT type.
NOTE: In order to support routing of incoming IMS voice calls to the correct domain (PS or CS), the network-based T-ADS (see TS 23.292 [60] and TS 23.221 [27]) requires that there is homogeneous support/non-support of IMS voice over PS session for all registered TAs of the UE.
4.3.5.8A Homogenous Support of IMS Voice over PS Sessions Indication
The "Homogenous Support of IMS Voice over PS Sessions" indication is provided by the MME to the HSS, and can be used by the HSS to avoid requesting the serving nodes whether or not an IMS Voice over PS session according to TS 22.173 [73] with a bearer that supports Conversational Voice as specified in TS 23.203 [6] is supported. This indication is stored in the MME MM context.
The MME shall behave as follows whenever it sends a Update Location Request or a Notify Request message to the HSS:
- if "IMS Voice over PS Sessions" is supported homogeneously in all TAs in the serving MME for the UE, the MME shall include the "Homogenous Support of IMS Voice over PS Sessions" indication set to "Supported".
- if none of the TAs of the serving MME supports "IMS Voice over PS Sessions" for the UE, the MME shall include the "Homogenous Support of IMS Voice over PS Sessions" indication set to "Not supported".
- if "IMS Voice over PS Sessions" support is either non-homogeneous or unknown, the MME shall not include the "Homogenous Support of IMS Voice over PS Sessions" indication.
Regarding homogenous support/non-support of IMS Voice over PS session for all registered TAs of the UE, see clause 4.3.5.8.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.9 Voice domain preference and UE's usage setting
| If the UE supports CS fallback, or the UE is configured to support IMS voice, or both, the UE shall include the information element "Voice domain preference and UE's usage setting" in Attach Request, Tracking Area Update Request and Routing Area Update Request messages. The purpose of this information element is to signal to the network the UE's usage setting and voice domain preference for E-UTRAN. The UE's usage setting indicates whether the UE behaves in a voice centric or data centric way (as defined in TS 23.221 [27]). The voice domain preference for E‑UTRAN indicates whether the UE is configured as CS Voice only, CS Voice preferred and IMS PS Voice as secondary, IMS PS Voice preferred and CS Voice as secondary, or IMS PS Voice only (as defined in TS 23.221 [27]).
In this Release of the specifications, inter-RAT mobility to/from the NB-IoT RAT is not supported, and GBR bearers are not supported in the NB-IoT RAT. Hence the UE should not include the "Voice domain preference and UE's usage setting" IE when sending an Attach Request or Tracking Area Update Request on the NB-IoT RAT.
NOTE: Depending on operator's configuration, the UE's usage setting and voice domain preference for E‑UTRAN can be used by the network to choose the RFSP Index in use (see clause 4.3.6). As an example, this enables the enforcement of selective idle mode camping over GERAN/UTRAN for voice centric UEs relying on CS Fallback for voice support in E‑UTRAN.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.5.10 Preferred and Supported Network Behaviour
| A UE includes in a Preferred Network Behaviour indication the Network Behaviour the UE can support and what it would prefer to use.
The Preferred Network Behaviour includes this information:
- Whether Control Plane CIoT EPS Optimisation is supported.
- Whether User Plane CIoT EPS Optimisation is supported.
- Whether Control Plane CIoT EPS Optimisation is preferred or whether User Plane Plane CIoT EPS Optimisation is preferred.
- Whether S1-U data transfer is supported.
- Whether SMS transfer without Combined Attach is requested.
- Whether Attach without PDN Connectivity is supported.
- Whether header compression for Control Plane CIoT EPS Optimisation is supported.
If SMS transfer without Combined EPS Attach is requested by the UE, a supporting MME provides SMS transfer without the UE performing the combined EPS attach specified in TS 23.272 [58]. An MME connected to NB-IoT should support SMS transfer without the UE being required to perform a Combined Attach.This feature is only available to UEs that only support NB-IoT.
If S1-U data transfer is supported is indicated by the UE, the UE supports data transfer that is not subject to CIoT EPS Optimisations. If the UE indicates support of User Plane CIoT EPS Optimisation then it shall also indicate support of S1-U data transfer.
If Attach without PDN connection is supported, the UE need not establish a PDN connection as part of the Attach procedure and the UE and MME may at any time release all the PDN connections and remain EPS attached.
The MME indicates the network behaviour the network accepts in the Supported Network Behaviour information. This indication is per TAI List. The MME may indicate one or more of the following:
- Whether Control Plane CIoT EPS Optimisation is supported.
- Whether User Plane CIoT EPS Optimisation is supported.
- Whether S1-U data transfer is supported.
- Whether SMS transfer without Combined Attach is accepted.
- Whether Attach without PDN Connectivity is supported.
- Whether header compression for Control Plane CIoT EPS Optimisation is supported.
If the MME indicates support of User Plane CIoT EPS Optimisation then it shall also indicate support of S1-U data transfer. If the UE and MME indicate support for User Plane CIoT EPS Optimisation, MME sets the UE User Plane CIoT Support Indicator to "supported" in S1-AP messages as defined in TS 36.413 [36].
For NB-IoT UEs that only support Control Plane CIoT EPS Optimisation, the MME shall include support for Control Plane CIoT EPS Optimisation in NAS accept messages.
A UE that supports the NB-IoT shall always indicate support for Control Plane CIoT EPS Optimisation.
If the UE supports Control Plane CIoT EPS Optimisation, it may also indicate support for overhead reduction by setting "control plane CIoT EPS optimization with overhead reduction supported" indication as defined in TS 24.301 [46]. If the UE indicated support for Control Plane CIoT EPS Optimisation with overhead reduction and the MME supports and accepts Control Plane CIoT EPS Optimisation with overhead reduction, then the MME shall indicate "control plane CIoT EPS optimization with overhead reduction supported" as defined in TS 24.301 [46].
In a network that supports Dedicated Core Networks (see clause 5.19), the Preferred Network Behaviour indication from the UE may be used to influence policy decisions that can cause rerouting of the Attach or TAU from an MME to another MME.
Other CIoT EPS Optimisations include "Attach without PDN connection establishment"; "PDN type = non-IP"; and "UE connection to SCEF". These features are requested by implicit and explicit signalling described within the relevant clauses of this TS.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.6 Radio Resource Management functions
| Radio resource management functions are concerned with the allocation and maintenance of radio communication paths, and are performed by the radio access network. RRM includes both idle mode and connected mode. The RRM strategy in E-UTRAN may be based on user specific information.
To support radio resource management in E-UTRAN the MME provides the parameter 'Index to RAT/Frequency Selection Priority' (RFSP Index) to an eNodeB across S1. The RFSP Index is mapped by the eNodeB to locally defined configuration in order to apply specific RRM strategies. The RFSP Index is UE specific and applies to all the Radio Bearers. Examples of how this parameter may be used by the E-UTRAN:
- to derive UE specific cell reselection priorities to control idle mode camping.
- to decide on redirecting active mode UEs to different frequency layers or RATs.
To provide additional support to radio resource management in E-UTRAN, the MME may provide the parameter 'Additional RRM Policy Index' (ARPI) to an eNodeB across S1. The ARPI is mapped by the eNodeB to locally defined configuration in order to apply specific RRM strategies.
An example of how this parameter may be used by the E-UTRAN is:
- to prioritise the allocation of RAN resources to the set of UEs with the same ARPI.
The Serving PLMN can use the ARPI to carry information that is independent to the Reference SPID values documented in Informative Annex I of TS 36.300 [5].
The MME receives the subscribed RFSP Index and subscribed ARPI from the HSS (e.g., during the Attach procedure). For non-roaming subscribers the MME chooses the RFSP Index and ARPI in use according to one of the following procedures, depending on operator's configuration:
- the RFSP Index in use is identical to the subscribed RFSP Index, or
- the MME chooses the RFSP Index in use based on the subscribed RFSP Index, the locally configured operator's policies and the UE related context information available at the MME, including UE's usage setting and voice domain preference for E-UTRAN, if received during Attach and Tracking Area Update procedures (see clause 4.3.5.9).
NOTE: One example of how the MME can use the "UE voice capabilities and settings" is to select an RFSP value that enforces idle mode camping on 2G/3G for a UE acting in a "Voice centric" way and provisioned with "CS Voice preferred, IMS Voice as secondary", in order to minimize the occurrancy of RAT changes. Another example is the selection of an RFSP value that prevents idle mode camping on 2G for a UE provisioned with "IMS PS voice preferred, CS Voice as secondary" if other RATs supporting IMS Voice are available, as the UE would in such case always select the CS domain for its voice calls.
- the ARPI In Use is identical to the subscribed ARPI, or
- the MME chooses the ARPI in use based on the subscribed ARPI, the locally configured operator's policies and the UE related context information available at the MME.
For roaming subscribers the MME may alternatively choose the RFSP Index and ARPI in use based on the visited network policy, but can take input from the HPLMN into account (e.g., an RFSP Index value/ARPI value pre-configured per HPLMN, or a single RFSP Index value/single ARPI value to be used for all roamers independent of the HPLMN).
The MME forwards the RFSP Index and ARPI in use to the eNodeB across S1. The RFSP Index and ARPI in use is also forwarded from source eNodeB to target eNodeB when X2 is used for intra-E‑UTRAN handover, UE context retrieval, or, Dual Connectivity with a secondary RAN node.
The MME stores the subscribed RFSP Index and ARPI values received from the HSS and the RFSP Index and ARPI values in use. During the Tracking Area Update procedure, the MME may update the RFSP Index/ARPI value in use (e.g. the MME may need to update the RFSP Index/ARPI value in use if the UE related context information in the MME has changed). When the RFSP Index/ARPI value in use is changed, the MME immediately provides the updated RFSP Index/ARPI value in use to eNodeB by modifying an existing UE context or by establishing an new UE context in the eNodeB or by being configured to include the updated RFSP Index/ARPI value in use in the DOWNLINK NAS TRANSPORT message if the user plane establishment is not needed. During inter-MME mobility procedures, the source MME forwards both RFSP Index values and both ARPI values to the target MME. The target MME may replace the received RFSP Index and ARPI values in use with a new RFSP Index value in use or new ARPI value in use that is based on the operator's policies and the UE related context information available at the target MME.
The S1 messages that transfer the RFSP Index and ARPI to the eNodeB are specified in TS 36.413 [36]. Refer to TS 36.300 [5] for further information on E-UTRAN.
To support a RAN with a mixture of RAN nodes that support and do not support the ARPI, the MME sends the ARPI In Use in the S1 interface PATCH SWITCH ACKNOWLEDGEMENT and HANDOVER REQUEST messages.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7 Network management functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.1 General
| Network management functions provide mechanisms to support O&M functions related to the Evolved Packet System.
4.3.7.1a GTP-C signalling based Load and Overload Control
4.3.7.1a.1 GTP-C Load Control
GTP-C Load Control feature is an optional feature which allows a GTP control plane node to send its Load Control Information to a peer GTP control plane node which the receiving GTP control plane peer node uses to augment existing GW selection procedure (i.e. as described in "PDN GW Selection" and "Serving GW Selection" according to clauses 4.3.8.1, and 4.3.8.2 respectively). Load Control Information reflects the operating status of the resources of the originating GTP control plane node.
NOTE 1: How a node computes its Load Control Information is implementation dependent.
Where certain pre-condition as described in clause 12.2.4.1 of TS 29.274 [43], is applicable, an optional feature APN level load control may be supported and activated in the network. If this feature is activated, the PDN GW may convey the Load Control Information at APN level (reflecting the operating status of the resources at the APN level), besides at node level.
GTP-C Load Control feature allows the Serving GW to send its Load Control Information to the MME/SGSN.
GTP-C Load Control feature also allows the PDN GW to send its Load Control Information to the MME/SGSN via a Serving GW.
Upon receiving Load Control Information the MME/SGSN supporting GTP-C Load Control feature uses it according to clauses 4.3.8.1, and 4.3.8.2 for "PDN GW Selection" and "Serving GW Selection" respectively.
A node supporting GTP-C Load Control feature sends Load Control Information in any GTP control plane request or response message such that exchange of Load Control Information does not trigger extra signalling.
A node supporting GTP-C Load Control feature sends Load Control Information to a peer GTP control node based on whether local configuration allows for it.
A node supporting GTP-C Load Control feature may decide to send different values of Load Control Information on inter-network (roaming) and on intra-network (non-roaming) interfaces based on local configuration.
Local configuration may allow the VPLMN to decide whether or not to act upon Load Control Information sent from a peer GTP control plane node in the HPLMN.
NOTE 2: Refer to clause 12 of TS 29.274 [43] for the details, such as exact format of the Load Control Information, mechanisms to discover the support of the feature by the peer node, interfaces for which this feature is applicable, APN level load control, etc.
4.3.7.1a.2 GTP-C Overload Control
GTP-C Overload Control feature is an optional feature. Nodes using GTP control plane signalling may support communication of Overload Control Information in order to mitigate overload situation for the overloaded node through actions taken by the peer node(s). This feature is supported over S4, S11, S5 and S8 interfaces via GTPv2 control plane protocol.
A GTP-C node is considered to be in overload when it is operating over its nominal capacity resulting in diminished performance (including impacts to handling of incoming and outgoing traffic). Overload Control Information reflects an indication of when the originating node has reached such situation. This information, when transmitted between GTP-C nodes may be used to reduce and/or throttle the amount of GTP-C signalling traffic between these nodes. As such, the Overload Control Information provides guidance to the receiving node to decide actions which leads to mitigation towards the sender of the information.
NOTE 1: How a node determines its Overload Control Information is implementation dependent.
The Overload Control Information may convey information regarding the node itself and/or regarding specific APN(s) status. In order to mitigate overload,
- it shall be possible to signal control information about the overload of a GTP-C node (e.g. S-GW, P-GW);
- the PDN GW may detect overload for certain APNs, e.g. based on Diameter overload indication received from a PCRF or from an external AAA server, or e.g. based on shortage of resources for an APN (IP address pool). It shall be possible to signal appropriate control information about the APN status in addition to the mechanism described in clause 4.3.7.5.
For a given APN, the PDN GW shall either activate the congestion control by conveying the Overload Control Information at APN level or by conveying the "PDN GW back-off time" (as specified in clause 4.3.7.5), but not both at the same time, as specified in more detail in clause 12.3.8 of TS 29.274 [43].
GTP-C Overload Control feature allows the MME/SGSN to send its Overload Control Information to the PDN GW via Serving GW.
GTP-C Overload Control feature allows the Serving GW to send its Overload Control Information to the MME/SGSN and P-GW.
GTP-C Overload Control feature also allows the PDN GW to send its Overload Control Information to the MME/SGSN via a Serving GW.
GTP-C overload Control feature should continue to allow for preferential treatment of priority users (eMPS) and emergency services as per existing specifications.
An MME/SGSN may during ESM and EMM procedures apply certain restrictions towards GWs (Serving GW and/or PDN GW as applicable) that have indicated overload, e.g.:
- reject EPS Session Management requests from the UE (e.g. PDN Connectivity, Bearer Resource Allocation or Bearer Resource Modification Requests) with a Session Management back-off timer as described in clause 4.3.7.4.2;
- reject Mobility Management signalling requests from UEs (such as Attach, Detach, Service Request, Tracking Area Update) with a Mobility Management back-off timer (e.g. reject Service Request requiring to activate user plane bearers in an overloaded SGW) as described in clause 4.3.7.4.2;
- reject or accept requests for data transmission via Control Plane CIoT EPS Optimisation from UEs (e.g. Control Plane Service Request and ESM Data Transport or EMM Transport) with a Control Plane data back-off timer as described in clause 4.3.7.4.2.7;
- may reduce/throttle messages towards the GWs indicating overload status;
- other implementation specific mechanisms, which are outside the scope of 3GPP specifications.
A PDN GW may take the following actions for MME/SGSN which have indicated overload:
- Limit or completely block non-GBR dedicated bearer establishment;
- Limit or completely block all Dedicated Bearer establishments or modification, except QCI=1 bearers;
- Limit or completely block all Dedicated Bearer establishments, including the QCI=1 bearers;
- other implementation specific mechanisms, which are outside the scope of 3GPP specifications.
A node supporting GTP-C Overload Control feature sends Overload Control Information in any GTP control plane request or response message such that exchange of Overload Control Information does not trigger extra signalling.
The computation and transfer of the Overload Control Information shall not add significant additional load to the node itself and to its corresponding peer nodes. The calculation of Overload Control Information should not severely impact the resource utilization of the node.
Based on local policies/configuration, a GTP-C node may support Overload Control feature and act upon or ignore Overload Control Information in the VPLMN when received from HPLMN and in the HPLMN when received from VPLMN. When this feature is supported, a GTP-C node may decide to send different values of Overload Control Information on inter-network (roaming) and on intra-network (non-roaming) interfaces based on local policies/configuration.
NOTE 2: Refer to clause 12 of TS 29.274 [43] for the details, such as exact format of the Overload Control Information, mechanisms to discover the support of the feature by the peer node, interfaces for which this feature is applicable, APN level overload control, etc.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.2 Load balancing between MMEs
| The MME Load Balancing functionality permits UEs that are entering into an MME Pool Area to be directed to an appropriate MME in a manner that achieves load balancing between MMEs. This is achieved by setting a Weight Factor for each MME, such that the probability of the eNodeB selecting an MME is proportional to its Weight Factor. The Weight Factor is typically set according to the capacity of an MME node relative to other MME nodes. The Weight Factor is sent from the MME to the eNodeB via S1-AP messages (see TS 36.413 [36]). If a HeNB GW is deployed, the Weight Factor is sent from the MME to the HeNB GW.
NOTE 1: An operator may decide to change the Weight Factor after the establishment of S1-MME connectivity as a result of changes in the MME capacities. E.g., a newly installed MME may be given a very much higher Weight Factor for an initial period of time making it faster to increase its load.
NOTE 2: It is intended that the Weight Factor is NOT changed frequently. e.g. in a mature network, changes on a monthly basis could be anticipated, e.g. due to the addition of RAN or CN nodes.
In some networks, the eNodeB may be configured to select specific MME for UEs configured for low access priority with a different load balance to that used for MME selection for other UEs.
NOTE 3: The eNodeB can determine whether or not the "UE is configured for low access priority" from information received in the RRC establishment or RRC resume signalling.
When DCNs are used, load balancing by eNodeB is only performed between MMEs that belong to the same DCN within the same MME pool area, i.e. MMEs with the same PLMN and MMEGI value. When an MME serves multiple DCNs and one DCN is supported by multiple MMEs, in order to achieve load balancing across the MMEs of the same MME pool area supporting the same DCN, each DCN supported by this MME may have its own Weight Factor (Weight Factor per DCN). The Weight Factor per DCN is set according to the capacity of an MME node for a specific DCN relative to other MME nodes' capacity for that DCN within the same MME pool area. The eNodeB is provided with per DCN Weight Factors, if any, by the connected MMEs at the set-up of the S1 connection. The DCN Load Balancing functionality permits UEs that are entering into a pool area or being re-directed to an appropriate DCN to be distributed in a manner that achieves load balancing between the CN nodes of the same DCN. The eNodeB may be configured to select MME(s) from a specific CN for UEs configured for low access priority only for the case that no other information and configuration is available for selecting an MME from a specific DCN.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.3 Load re-balancing between MMEs
| The MME Load Re-balancing functionality permits UEs that are registered on an MME (within an MME Pool Area) to be moved to another MME.
NOTE 1: An example use for the MME Load Re-balancing function is for the O+M related removal of one MME from an MME Pool Area.
NOTE 2: Typically, this procedure should not be used when the MME becomes overloaded because the Load Balancing function should have ensured that the other MMEs in the pool area are similarly overloaded.
The eNodeBs may have their Load Balancing parameters adjusted beforehand (e.g. the Weight Factor is set to zero if all subscribers are to be removed from the MME, which will route new entrants to the pool area into other MMEs).
In addition the MME may off-load a cross-section of its subscribers with minimal impacts on the network and users (e.g. the MME should avoid offloading only the low activity users while retaining the high activity subscribers. Gradual rather than sudden off-loading should be performed as a sudden re-balance of large number of subscribers could overload other MMEs in the pool. With minimal impact on network and the user's experience, the subscribers should be off-loaded as soon as possible). The load re-balancing can off-load part of or all the subscribers.
To off-load ECM-CONNECTED mode UEs, the MME initiates the S1 Release procedure with release cause "load balancing TAU required" (clause 5.3.5). The S1 and RRC connections are released and the UE initiates a TAU but provides neither the S-TMSI nor the GUMMEI to eNodeB in the RRC establishment.
NOTE 3: Special care needs to be taken when offloading Relay Nodes. This is because there may be UEs connected to the RN and some of these UEs may be registered on other MMEs.
The MME should not release all S1 connections which are selected to be released immediately when offloading is initiated. The MME may wait until the S1 Release is performed due to inactivity. When the MME is to be offloaded completely the MME can enforce an S1 Release for all remaining UEs that were not offloaded by normal TAU procedures or by S1 releases caused by inactivity.
To off-load UEs which perform TA Updates or Attaches initiated in ECM-IDLE mode, the MME completes that procedure and the procedure ends with the MME releasing S1 with release cause "load balancing TAU required". The S1 and RRC connections are released and the UE initiates a TAU but provides neither the S-TMSI nor the GUMMEI to eNodeB in the RRC establishment.
When the UE provides neither the S-TMSI nor the GUMMEI in the RRC establishment, the eNodeB should select an MME based on the Weight Factors of the MMEs in the pool.
To off-load UEs in ECM-IDLE state without waiting for the UE to perform a TAU or perform Service request and become ECM‑CONNECTED, the MME first pages UE to bring it to ECM-CONNECTED state. If paging the UE fails and ISR is activated, the MME should adjust its paging retransmission strategy (e.g. limit the number of short spaced retransmissions) to take into account the fact that the UE might be in GERAN/UTRAN coverage.
Hardware and/or software failures within an MME may reduce the MME's load handling capability. Typically such failures should result in alarms which alert the operator/O+M system. Only if the operator/O+M system is sure that there is spare capacity in the rest of the pool, the operator/O+M system might use the load re-balancing procedure to move some load off this MME. However, extreme care is needed to ensure that this load re-balancing does not overload other MMEs within the pool area (or neighbouring SGSNs) as this might lead to a much wider system failure.
When the Dedicated Core Network (DCN) feature is used, the DCN load re-balancing functionality permits UEs that are registered on an MME in the DCN (within a pool area) to be moved to another MME in the same DCN in a manner that achieves load balancing between the CN nodes of the DCN and pool area. The DCN load re-balancing is triggered by the source MME (within a DCN). The details are as follows:
- If the UE is in ECM-IDLE state, the NAS Message Redirection procedure (see clause 5.19.1) is triggered at the next intra-MME Tracking Area Update Request enabling eNodeB to load balance between MMEs of the same DCN. To off-load UEs in ECM-IDLE state without waiting for the UE to perform a TAU or perform Service request, the MME first pages the UE to bring it to ECM-CONNECTED state and proceeds as described for the ECM-CONNECTED case below.
- If the UE is in ECM-CONNECTED state, the MME performs the GUTI reallocation procedure, includes the unchanged GUTI of the UE and a non-broadcast TAI to induce the UE to perform a TAU procedure, and forces the UE to go to ECM-IDLE state. During the subsequent TAU procedure the MME uses the NAS Message Redirection procedure (see clause 5.19.1) to redirect the UE to another MME within the same DCN.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4 MME control of overload
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.1 General
| The MME shall contain mechanisms for avoiding and handling overload situations. These can include the use of NAS signalling to reject NAS requests from UEs.
In addition, under unusual circumstances, the MME shall restrict the load that its eNodeBs are generating on it if it is configured to enable the overload restriction. This can be achieved by the MME invoking the S1 interface overload procedure (see TS 36.300 [5] and TS 36.413 [36]) to all or to a proportion of the eNodeB's with which the MME has S1 interface connections. To reflect the amount of load that the MME wishes to reduce, the MME can adjust the proportion of eNodeBs which are sent S1 interface OVERLOAD START message, and the content of the OVERLOAD START message.
The MME should select the eNodeBs at random (so that if two MMEs within a pool area are overloaded, they do not both send OVERLOAD START messages to exactly the same set of eNodeBs).
The MME may optionally include a Traffic Load Reduction Indication in the OVERLOAD START message. In this case the eNodeB shall, if supported, reduce the type of traffic indicated according the requested percentage (see TS 36.413 [36]).
NOTE 1: The MME implementation may need to take into account the fact that eNodeBs compliant to Release 9 and earlier version of the specifications do not support the percentage overload indication.
An MME supporting Control Plane CIoT EPS Optimisation may include an indication in the OVERLOAD START message indicating overload from data transfers via Control Plane CIoT EPS Optimisation.
Using the OVERLOAD START message, the MME can request the eNodeB to:
- reject RRC connection requests that are for non-emergency, non-exception reporting and non-high priority mobile originated services; or
NOTE 2: This blocks PS service and service provided by MSC following an EPS/IMSI attach procedure.
- reject new RRC connection requests for EPS Mobility Management signalling (e.g. for TA Updates) for that MME;
- only permit RRC connection requests for emergency sessions and mobile terminated services for that MME. This blocks emergency session requests from UEs with USIMs provisioned with Access Classes 11 and 15 when they are in their HPLMN/EHPLMN and from UEs with USIMs provisioned with Access Classes 12, 13 and 14 when they are in their home country (defined as the MCC part of the IMSI, see TS 22.011 [67]); or.
NOTE 3: The MME can restrict the number of responses to paging by not sending paging messages for a proportion of the events that initiate paging. As part of this process, the MME can provide preference for paging UEs with Emergency Bearer Services and terminations associated with MPS ARP.
- only permit RRC connection requests for high priority sessions, exception reporting and mobile terminated services for that MME;
- reject new RRC connection requests from UEs that access the network with low access priority;
- not accept RRC connection requests with RRC establishment cause "mo-data" or "delayTolerantAccess" from UEs that only support Control Plane CIoT EPS Optimisation.
NOTE 4: The RRC connection requests listed in this clause also include the request for RRC Connection Resume.
When rejecting an RRC connection request for overload reasons the eNodeB indicates to the UE an appropriate timer value that limits further RRC connection requests for a while.
An eNodeB supports rejecting of RRC connection establishments for certain UEs as specified in TS 36.331 [37]. Additionally, an eNodeB provides support for the barring of UEs configured for Extended Access Barring, as described in TS 22.011 [67]. These mechanisms are further specified in TS 36.331 [37]. If the UE is camping on NB-IoT, Extended Access Barring does not apply.
An eNodeB may initiate Extended Access Barring when:
- all the MMEs connected to this eNodeB request to restrict the load for UEs that access the network with low access priority; or
- requested by O&M.
If an MME invokes the S1 interface overload procedure to restrict the load for UEs that access the network with low access priority, the MME should select all eNodeBs with which the MME has S1 interface connections. Alternatively, the selected eNodeBs may be limited to a subset of the eNodeBs with which the MME has S1 interface connection (e.g. particular location area or where devices of the targeted type are registered).
During an overload situation the MME should attempt to maintain support for emergency bearer services (see clause 4.3.12) and for MPS (see clause 4.3.18).
When the MME is recovering, the MME can either:
- send OVERLOAD START messages with new percentage value that permit more traffic to be carried, or
- the MME sends OVERLOAD STOP messages.
to some, or all, of the eNodeB(s).
In addition, to protect the network from overload the MME has the option of rejecting NAS request messages which include the low access priority indicator before rejecting NAS request messages without the low access priority indicator (see clause 4.3.7.4.2 for more information).
NOTE 5: It cannot be guaranteed that voice services will be available for mobile terminated calls while the Mobility Management back-off timer is running. It is recommended, that UEs requiring voice services are not configured for low access priority.
In addition, for UEs that don't support the Service Gap Control feature (see clause 4.3.17.9), the MME may use "General NAS level Mobility Management control" as defined in clause 4.3.7.4.2.1.
4.3.7.4.1a Throttling of Downlink Data Notification Requests
Under unusual circumstances (e.g. when the MME load exceeds an operator configured threshold), the MME may restrict the signalling load that its SGWs are generating on it, if configured to do so.
The MME can reject Downlink Data Notification requests for non-priority traffic for UEs in idle mode or to further offload the MME, the MME can request the SGWs to selectively reduce the number of Downlink Data Notification requests it sends for downlink non-priority traffic received for UEs in idle mode according to a throttling factor and for a throttling delay specified in the Downlink Data Notification Ack message.
The SGW determines whether a bearer is to be subjected to the throttling of Downlink Data Notification Requests on the basis of the bearer's ARP priority level and operator policy (i.e. operator's configuration in the SGW of the ARP priority levels to be considered as priority or non- priority traffic). While throttling, the SGW shall throttle the Downlink Data Notification Requests for low and normal priority bearers by their priority. The MME determines whether a Downlink Data Notification request is priority or non-priority traffic on the basis of the ARP priority level that was received from the SGW and operator policy.
If ISR is not active for the UE, during the throttling delay, the SGW drops downlink packets received on all its non-priority bearers for UEs known as not user plane connected (i.e. the SGW context data indicates no downlink user plane TEID) served by that MME in proportion to the throttling factor, and sends a Downlink Data Notification message to the MME only for the non throttled bearers.
If ISR is active for the UE, during the throttling delay, the SGW does not send DDN to the MME and only sends the DDN to the SGSN. If both MME and SGSN are requesting load reduction, the SGW drops downlink packets received on all its non-priority bearers for UEs known as not user plane connected (i.e. the SGW context data indicates no downlink user plane TEID) in proportion to the throttling factors.
The SGW resumes normal operations at the expiry of the throttling delay. The last received value of the throttling factor and throttling delay supersedes any previous values received from that MME. The reception of a throttling delay restarts the SGW timer associated with that MME.
4.3.7.4.1b Throttling of NIDD Submit Requests
Under unusual circumstances (e.g. when the MME load exceeds an operator configured threshold), the MME may restrict NIDD Submit Request messages that its SCEFs are generating on it, if configured to do so.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2 NAS level congestion control
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.1 General
| NAS level congestion control contains the functions: "APN based congestion control" and "General NAS level Mobility Management control".
The use of the APN based congestion control is for avoiding and handling of EMM and ESM signalling congestion associated with UEs with a particular APN. Both UEs and network shall support the functions to provide APN based EMM and ESM congestion control.
The MME may detect the NAS signalling congestion associated with the APN and start and stop performing the APN based congestion control based on criteria such as:
- Maximum number of active EPS bearers per APN;
- Maximum rate of EPS Bearer activations per APN;
- One or multiple PDN GWs of an APN are not reachable or indicated congestion to the MME;
- Maximum rate of MM signalling requests associated with the devices with a particular subscribed APN; and/or
- Setting in network management.
The MME may detect the NAS signalling congestion associated with the UEs belonging to a particular group. The MME may start and stop performing the group specific NAS level congestion control based on criteria such as:
- Maximum rate of MM and SM signalling requests associated with the devices of a particular group; and/or
- Setting in network management.
The MME may detect the NAS signalling congestion associated with the UEs that belong to a particular group and are subscribed to a particular APN. The MME may start and stop performing the APN and group specific NAS level congestion control based on criteria such as:
- Maximum number of active EPS bearers per group and APN;
- Maximum rate of MM and SM signalling requests associated with the devices of a particular group and a particular subscribed APN; and/or
- Setting in network management.
The MME should not apply NAS level congestion control for high priority access and emergency services.
With General NAS level Mobility Management control, the MME may also use the reject of NAS level Mobility Management signalling requests under general congestion conditions such as detecting congestion of one or several DCNs in an MME serving multiple DCNs.
In addition, for UEs that don't support the Service Gap Control feature (see clause 4.3.17.9), the MME may return a Mobility Management back-off timer to the UE in responses to requests where the intention is to send MO data or re-attach with PDN connectivity when the Service gap timer for the UE is running at the MME.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.2 APN based Session Management congestion control
| The APN based Session Management congestion control may be activated by MME due to e.g. congestion situation at MME, or by OAM at MME, or by a restart or recovery condition of a PDN GW, or by a partial failure or recovery of a PDN GW for a particular APN(s).
The MME may reject the EPS Session Management (ESM) requests from the UE (e.g. PDN Connectivity, or Bearer Resource Allocation Requests) with a Session Management back-off timer when ESM congestion associated with the APN is detected. If the UE provides no APN, then the MME uses the APN which is used in PDN GW selection procedure.
The MME may deactivate PDN connections belonging to a congested APN by sending the NAS Deactivate EPS Bearer Context Request message to the UE with a Session Management back-off timer. If Session Management back-off timer is set in the NAS Deactivate EPS Bearer Context Request message then the cause "reactivation requested" should not be set.
NOTE 1: UEs that don't support the Session Management back-off timer (including earlier release of UE) might contribute to increasing the signalling load in the MME by reattempting Session Management procedure.
The MME may store a Session Management back-off time per UE and APN when congestion control is active for an APN if a request without the low access priority indicator is rejected by the MME. The MME may immediately reject any subsequent request from the UE targeting to the APN before the stored Session Management back-off time is expired. If the MME stores the Session Management back-off time per UE and APN and the MME decides to send a Session Management Request message to a UE connected to the congested APN (e.g. due to decreased congestion situation), the MME shall clear the Session Management back-off time prior to sending any Session Management Request message to the UE.
NOTE 2: The above functionality is to diminish the performance advantage for UEs that do not support the NAS level back-off timer (e.g. pre-Rel‑10 UEs) compared to UEs that do support it.
Upon reception of the Session Management back-off timer in the EPS Session Management reject message or in the NAS Deactivate EPS Bearer Context Request message, the UE shall take the following actions until the timer expires:
- If APN is provided in the rejected EPS Session Management Request message or if the Session Management back-off timer is received in the NAS Deactivate EPS Bearer Context Request message, the UE shall not initiate any Session Management procedures for the congested APN. The UE may initiate Session Management procedures for other APNs.
- If APN is not provided in the rejected EPS Session Management Request message, the UE shall not initiate any Session Management requests of any PDN type without APN. The UE may initiate Session Management procedures for specific APN.
- Cell/TA/PLMN/RAT change do not stop the Session Management back-off timer.
- The UE is allowed to initiate the Session Management procedures for high priority access and emergency services even when the Session Management back-off timer is running.
- The UE is allowed to initiate Bearer Resource Modification procedure to report 3GPP PS Data Off status change when the EPS Session Management back off timer is running.
- If the UE receives a network initiated EPS Session Management Request message for the congested APN while the Session Management back-off timer is running, the UE shall stop the Session Management back-off timer associated with this APN and respond to the MME.
- If the UE is configured with a permission for overriding low access priority and the Session Management back-off timer is running due to a reject message received in response to a request with low access priority, the upper layers in the UE may request the initiation of Session Management procedures without low access priority.
The UE is allowed to initiate PDN disconnection procedure (e.g. sending PDN Disconnection Request) when the EPS Session Management back off timer is running.
NOTE 3: The UE does not delete the related Session Management back-off timer when disconnecting a PDN connection.
The UE shall support a separate Session Management back-off timer for every APN that the UE may activate.
To avoid that large amounts of UEs initiate deferred requests (almost) simultaneously, the MME should select the Session Management back-off timer value so that deferred requests are not synchronized.
The APN based Session Management congestion control is applicable to the NAS ESM signalling initiated from the UE in the control plane. The Session Management congestion control does not prevent the UE to send and receive data or initiate Service Request procedures for activating user plane bearers towards the APN(s) that are under ESM congestion control.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.3 APN based Mobility Management congestion control
| The MME may perform the APN based congestion control for UEs with a particular subscribed APN by rejecting Attach procedures with a Mobility Management back-off timer.
When congestion control is active for UEs with a particular subscribed APN, a Mobility Management back-off timer may be sent by the MME to UE.
If MME maintains the UE context, the MME may store the back-off time per UE if a request without the low access priority indicator is rejected by the MME. The MME may immediately reject any subsequent request from the UE before the stored back-off time is expired.
NOTE 1: The above functionality is to diminish the performance advantage for UEs that do not support the NAS level back-off timer (e.g. pre-Rel‑10 UEs) compared to UEs that do support it.
After rejecting Attach Requests, the MME should keep the Subscriber Data for some time. This allows for rejection of subsequent requests without HSS signalling when the congestion situation resulting from UEs with a particular subscribed APN persists.
NOTE 2: Prior to the reject of attach messages of a UE by the MME, Subscriber Data for a UE may be present at the MME because it was not deleted after the UE's detach. In this case when APN based congestion control is active for a particular APN in the MME, the first reject of an attach message by the MME for this UE, may be done without HSS signalling as well.
While the Mobility Management back-off timer is running, the UE shall not initiate any NAS request for Mobility Management procedures. However, the UE is allowed to initiate the Mobility Management procedures for high priority access and emergency services even when the Mobility Management back-off timer is running. While the Mobility Management back-off timer is running, the UE is allowed to perform Tracking Area Update if it is already in connected mode.
While the Mobility Management back-off timer is running, the UE configured with a permission for overriding low access priority is allowed to initiate the Mobility Management procedures without low access priority if the Mobility Management back-off timer was started due to a reject message received in response to a request with low access priority and the upper layers in the UE request to activate a PDN connection without low access priority or the UE has an activated PDN connection that is not with low access priority.
To avoid that large amounts of UEs initiate deferred requests (almost) simultaneously, the MME should select the Mobility Management back-off timer value so that deferred requests are not synchronized.
NOTE 3: When receiving the Mobility Management back-off timer the UE behaviour is not APN specific.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.4 General NAS level Mobility Management congestion control
| Under general overload conditions the MME may reject Mobility Management signalling requests from UEs. When a NAS request is rejected, a Mobility Management back-off timer may be sent by the MME and MME may store the back-off time per UE if a request without the low access priority indicator is rejected by the MME and if MME maintains the UE context. The MME may immediately reject any subsequent request from the UE before the stored back-off time is expired. While the Mobility Management back-off timer is running, the UE shall not initiate any NAS request for Mobility Management procedures except for Detach procedure and except for high priority access, emergency services, mobile terminated services and to inform of an unavailability period (see clause 4.13.8.2). After any such Detach procedure, the back-off timer continues to run. While the Mobility Management back-off timer is running, the UE is allowed to perform Tracking Area Update if it is already in connected mode. If the UE receives a paging request from the MME while the Mobility Management back off timer is running, the UE shall stop the Mobility Management back-off timer and initiate the Service Request procedure or the Tracking Area Update procedure as described in clause 5.3.3.0.
While the Mobility Management back-off timer is running, the UE configured with a permission for overriding low access priority is allowed to initiate the Mobility Management procedures without low access priority if the Mobility Management back-off timer was started due to a reject message received in response to a request with low access priority and the upper layers in UE request to establish a PDN connection without low access priority or the UE has an established PDN connection that is without low access priority.
While the Mobility Management back-off timer is running, the UE configured with permission for sending exception reporting is allowed to initiate the Control Plane Service Request procedure for exception reporting. If the Mobility Management back-off timer was started due to a reject message received in response to a request for exception reporting, the UE shall not initiate the Control Plane Service Request procedure for exception reporting while the Mobility Management back-off timer is running.
The Mobility Management back-off timer shall not impact Cell/RAT and PLMN change. Cell/RAT and TA change do not stop the Mobility Management back-off timer. The Mobility Management back-off timer shall not be a trigger for PLMN reselection. The back-off timer is stopped as defined in TS 24.301 [46] when a new PLMN that is not an equivalent PLMN is accessed.
To avoid that large amounts of UEs initiate deferred requests (almost) simultaneously, the MME should select the Mobility Management back-off timer value so that the deferred requests are not synchronized.
When the UE receives a handover command, the UE shall proceed with the handover procedure regardless of whether Mobility Management back-off timer is running.
The MME should not reject Tracking Area Update procedures that are performed when the UE is already in connected mode or when the UE is indicating unavailability period.
For idle mode inter CN node mobility, the MME may reject Tracking Area Update procedures and include a Mobility Management back off timer value in the Tracking Area Reject message.
If the MME rejects Tracking Area Update request or Service request with a Mobility Management back-off timer which is larger than the sum of the UE's periodic TAU timer plus the Implicit Detach timer, the MME should adjust the mobile reachable timer and/or Implicit Detach timer such that the MME does not implicitly detach the UE while the Mobility Management back-off timer is running.
NOTE: This is to minimize unneeded signalling after the Mobility Management back-off timer expires.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.5 Group specific NAS level congestion control
| The group specific NAS level congestion control applies to a specific group of UEs. Each group has a group identifier assigned.
A UE belongs to a group, if the corresponding group identifier is stored in the UE's subscription data in the HSS. A UE may belong to multiple groups and the MME may perform the Group specific NAS level congestion control to an UE as described below independent of whether Group specific NAS level congestion control is activated for one, multiple, or all groups the UE belongs to. The group identifier shall be stored per UE in the HSS and obtained by the MME as part of normal HSS signalling. A UE is not aware of a group subscription.
The group specific NAS level congestion control may be activated for Session Management signalling, or for Mobility Management signalling, or both. The group specific NAS level congestion control is activated based on operator policies.
When the group specific NAS level congestion control for Session Management signalling is active for a particular group, the MME's behaviour is similar to that in clause 4.3.7.4.2.2, with the following modifications:
- MME may apply ESM congestion control to all subscribed APNs for UEs that belong to this particular group.
NOTE: How the MME applies ESM congestion control to all subscribed APNs is left to Stage 3.
- The MME rejects the EPS Session Management (ESM) request(s) from the UE belonging to this particular group (e.g. PDN Connectivity, or Bearer Resource Allocation Requests) with a Session Management back-off timer.
When group specific NAS level congestion control for Mobility Management signalling is active for a particular group, the MME's behaviour is similar to that in clause 4.3.7.4.2.3, but applied to UEs subscribed to this particular group rather that subscribed to a particular APN.
Group specific NAS level congestion control is performed at the MME based on the UE's subscription information provided by the HSS. There is no impact on the UE, and hence, UE's behaviour as described in clauses 4.3.7.4.2.2 and 4.3.7.4.2.3 does not change.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.6 APN and group specific NAS level congestion control
| The APN and group specific NAS level congestion control is the intersection of APN specific NAS level congestion control and Group specific NAS level congestion control, i.e. it applies to a specific group of UEs with a particular subscribed APN. Each group of UEs has a group identifier assigned and stored in the HSS.
A UE may belong to multiple groups and the MME may perform the APN and group specific NAS level congestion control to an UE as described below independent of whether the APN and group specific NAS level congestion control is activated for one, multiple or all groups the UE belongs to. The group identifier(s) shall be stored per UE in the HSS and obtained by the MME as part of normal HSS signalling. A UE is not aware of the group identifier(s) that the UE belongs to.
The APN and group specific NAS level congestion control may be activated for Session Management signalling, or for Mobility Management signalling, or both. The APN and group specific NAS level congestion control is activated based on operator policies.
When the APN and group specific NAS level congestion control for Session Management signalling is activated for a UE belonging to a particular group and initiating signalling to a particular APN, the MME's behaviour is similar to that in clause 4.3.7.4.2.2, with the following modifications:
- The EPS Session Management (ESM) congestion control is applied to this particular APN, and for UEs belonging to this particular group,
- The MME may reject ESM requests from the UEs belonging to this particular group and attaching to this particular APN (e.g. PDN Connectivity, or Bearer Resource Allocation Requests) with a Session Management back-off timer. If the UE provides no APN, then the MME uses the APN which is used in PDN GW selection procedure.
- The MME may deactivate PDN connections of the UEs, belonging to this particular group and attaching to this particular APN, by sending the NAS Deactivate EPS Bearer Context Request message to the UE with a Session Management back-off timer.
When the APN and group specific NAS level congestion control for Mobility Management signalling is activated for a UE belonging to a particular group and with a particular subscribed APN, the MME's behaviour is similar to that in clause 4.3.7.4.2.3, but applied to UEs with this particular subscribed APN and belonging to this particular group.
APN and group specific NAS level congestion control is performed at the MME based on the UE's subscription information provided by the HSS. There is no impact on the UE, and hence, UE's behaviour described in clauses 4.3.7.4.2.2 and 4.3.7.4.2.3 does not change.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.4.2.7 Control Plane data specific NAS level congestion control
| Under overload conditions the MME may restrict requests from UEs for data transmission via Control Plane CIoT EPS Optimisation. A Control Plane data back-off timer may be returned by the MME (e.g.in Attach/TAU/RAU Accept messages, Service Reject message or Service Accept message). While the Control Plane data back-off timer is running, the UE shall not initiate any data transfer via Control Plane CIoT EPS Optimisation, i.e. the UE shall not send any Control Plane Service Request with ESM Data Transport or EMM Transport message (per UE and network capability) message as defined in TS 24.301 [46]. The MME shall store the Control Plane data back-off timer per UE and shall reject any further request (other than exception reporting and a response to paging) for data transmission via Control Plane Service Request or EMM Transport from that UE while the Control Plane data back-off timer is still running.
NOTE 1: The Control Plane data back-off timer does not affect any other mobility management or session management procedure.
NOTE 2: The Control Plane data back-off timer does not apply to user plane data communication.
If the UE is allowed to send exception reporting, the UE may initiate Control Plane Service Request or EMM Transport for exception reporting even if Control Plane data back-off timer is running.
The UE may respond with Control Plane Service Request without ESM Data Transport or EMM Transport but without user data to a paging even if the Control Plane data back-off timer is running.
If the MME receives a Control Plane Service Request or EMM Transport in response to paging, and the MME has a Control Plane data back-off timer running for the UE, and the MME is not overloaded, and MME decides to accept the Control Plane Service Request or EMM Transport, then the MME shall respond with Service Accept message without the Control Plane data back-off timer and stop the Control Plane data back-off timer. If the UE receives a Service Accept message without the Control Plane data back-off timer from the MME while the Control Plane data back-off timer is running, the UE shall stop the Control Plane data back-off timer. The Control Plane data back-off timer in the UE and the MME is stopped at PLMN change.
If the MME receives a Control Plane Service Request with ESM Data Transport message or EMM Transport with user data message, and decides to send the UE a Control Plane data back-off timer, the MME may decide to process the Control Plane Service Request with ESM Data Transport message or EMM Transport with user data message, i.e. decrypt and forward the data payload, or not based on the following:
- If the UE has additionally indicated in a NAS Release Assistance Information in the NAS PDU that no further Uplink or Downlink Data transmissions are expected, then the MME may process (integrity check/decipher/forward) the received Control Plane data packet, and send SERVICE ACCEPT to the UE with Control Plane data back-off timer. The UE interprets this as successful transmission of the Control Plane data packet and starts the Control Plane data back-off timer.
- For all other cases, the MME may decide to not process the received control plane data packet and sends SERVICE REJECT to the UE with Control Plane data back-off timer. The UE interprets this indication as unsuccessful delivery of the control plane data packet and starts the Control Plane data back-off timer. Then MME may take into consideration whether the PDN Connection is set to Control Plane only to make the decision whether to reject the packet and send SERVICE REJECT or move the PDN connection to user plane and process the data packet.
- Alternatively, if UE has not provided in the in Control Plane service request or EMM Transport the NAS Release Assistance Information, and the EPS bearer belongs to a PDN connection not set to Control Plane only, and UE supports User Plane CIoT Optimisation (or legacy S1-U), then the MME may initiate establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS Optimisation (according to the procedure defined in clause 5.3.4B.4). In this case MME may also return a Control Plane data back-off timer within the NAS message.
The MME only includes the Control Plane data back-off timer if the UE has indicated support for Control Plane data back-off timer in the Attach/TAU/RAU request.
NOTE 3: If the MME is overloaded or close to overload, but the UE has not indicated support for Control Plane data back-off timer, the MME can use other overload control mechanisms, e.g. mobility management back-off timer or use user plane data communication.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.7.5 PDN GW control of overload
| The PDN GW may provide mechanisms for avoiding and handling overload situations. These include the rejection of PDN connection requests from UEs.
The PDN GW may detect APN congestion and start and stop performing overload control based on criteria such as:
- Maximum number of active bearers per APN; and/or
- Maximum rate of bearer activations per APN.
When performing overload control the PDN GW rejects PDN connection requests. When receiving the rejection from the PDN GW, the MME rejects the UE's PDN connection request as specified in clause 4.3.7.4.2. In addition the PDN GW may indicate a "PDN GW back-off time" for a specific APN to the MME. The MME should reject PDN connection requests, for the specific APN related to that PDN GW during the "PDN GW back-off time", by the means specified in clause 4.3.7.4.2. If a PDN GW indicates APN congestion by the "PDN GW back-off time" the MME may select another PDN GW of that APN instead of rejecting PDN connection requests unless there is already an existing PDN connection to the same APN for the UE, in which case, the MME shall reject PDN connection request.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.8 Selection functions
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.8.1 PDN GW selection function (3GPP accesses)
| The PDN GW selection function allocates a PDN GW that shall provide the PDN connectivity for the 3GPP access. The function uses subscriber information provided by the HSS and possibly additional criteria such as SIPTO/LIPA support per APN configured in the SGSN/MME, UE support for dual connectivity with NR, 15 EPS bearers support by the UE, CIoT EPS Optimisation(s) impacting PDN GW e.g. Non-IP support, Ethernet support, NB-IoT RAT support (for generation of accounting information), etc.
NOTE 1: Selection of PDN GWs optimised for different RATs (e.g. NB-IoT) can be achieved by the allocation of different APNs to subscribers allowed to use specific RATs and/or using the UE Usage Type.
The criteria for PDN GW selection may include load balancing between PDN GWs. When the PDN GW IP addresses returned from the DNS server include Weight Factors, the MME should use it if load balancing is required. The Weight Factor is typically set according to the capacity of a PDN GW node relative to other PDN GW nodes serving the same APN. For further details on the DNS procedure see TS 29.303 [61].
When the MME supports the GTP-C Load Control feature, it takes into account the Load Information received from the PDN GW in addition to the Weight Factors received from the DNS server to perform selection of an appropriate PDN GW.
NOTE 2: How Weight Factors can be used in conjunction with Load Information received via GTP control plane signalling is left up to Stage 3.
The PDN subscription contexts provided by the HSS contain:
- the identity of a PDN GW and an APN (PDN subscription contexts with subscribed PDN GW address are not used when there is interoperation with pre Rel‑8 2G/3G SGSN), or
- an APN and an indication for this APN whether the allocation of a PDN GW from the visited PLMN is allowed or whether a PDN GW from the home PLMN shall be allocated. Optionally an identity of a PDN GW may be contained for handover with non-3GPP accesses.
- optionally for an APN, an indication of whether SIPTO above RAN, or SIPTO at the Local Network, or both, is allowed or prohibited for this APN.
- optionally for an APN, an indication of whether LIPA is conditional, prohibited, or only LIPA is supported for this APN.
In the case of static address allocation, a static PDN GW is selected by either having the APN configured to map to a given PDN GW, or the PDN GW identity provided by the HSS indicates the static PDN GW.
The HSS also indicates which of the PDN subscription contexts is the Default one for the UE.
To establish connectivity with a PDN when the UE is already connected to one or more PDNs, the UE provides the requested APN for the PDN GW selection function.
If one of the PDN subscription contexts provided by the HSS contains a wild card APN (see TS 23.003 [9]), a PDN connection with dynamic address allocation may be established towards any APN requested by the UE. An indication that SIPTO (above RAN, at the local network, or both) is allowed or prohibited for the wild card APN allows or prohibits SIPTO for any APN that is not present in the subscription data.
If the HSS provides the identity of a statically allocated PDN GW, or the HSS provides the identity of a dynamically allocated PDN GW and the Request Type indicates "Handover", no further PDN GW selection functionality is performed. If the HSS provides the identity of a dynamically allocated PDN GW, the HSS also provides information that identifies the PLMN in which the PDN GW is located.
NOTE 3: The MME uses this information to determine an appropriate APN-OI and S8 protocol type (PMIP or GTP) when the MME and PDN GW are located in different PLMNs.
If the HSS provides the identity of a dynamically allocated PDN GW and the Request Type indicates "initial Request", either the provided PDN GW is used or a new PDN GW is selected. When a PDN connection for an APN with SIPTO-allowed is requested, the PDN GW selection function shall ensure the selection of a PDN GW that is appropriate for the UE's location. The PDN GW identity refers to a specific PDN GW. If the PDN GW identity includes the IP address of the PDN GW, that IP address shall be used as the PDN GW IP address; otherwise the PDN GW identity includes an FQDN which is used to derive the PDN GW IP address by using Domain Name Service function, taking into account the protocol type on S5/S8 (PMIP or GTP).
NOTE 4: Provision of a PDN GW identity of a PDN GW as part of the subscriber information allows also for a PDN GW allocation by HSS.
If the HSS provides a PDN subscription context that allows for allocation of a PDN GW from the visited PLMN for this APN and, optionally, the MME is configured to know that the visited VPLMN has a suitable roaming agreement with the HPLMN of the UE, the PDN GW selection function derives a PDN GW identity from the visited PLMN. If a visited PDN GW identity cannot be derived, or if the subscription does not allow for allocation of a PDN GW from the visited PLMN, then the APN is used to derive a PDN GW identity from the HPLMN. The PDN GW identity is derived from the APN, subscription data and additional information by using the Domain Name Service function. If the PDN GW identity is a logical name instead of an IP address, the PDN GW address is derived from the PDN GW identity, protocol type on S5/S8 (PMIP or GTP) by using the Domain Name Service function. The S8 protocol type (PMIP or GTP) is configured per HPLMN in MME/SGSN.
In order to select the appropriate PDN GW for SIPTO above RAN service, the PDN GW selection function uses the TAI (Tracking Area Identity), the serving eNodeB identifier, or TAI together with serving eNodeB identifier depending on the operator's deployment during the DNS interrogation as specified in TS 29.303 [61] to find the PDN GW identity. In roaming scenario PDN GW selection for SIPTO is only possible when a PDN GW in the visited PLMN is selected. Therefore in a roaming scenario with home routed traffic, PDN GW selection for SIPTO is not performed.
In order to select the appropriate GW for SIPTO at the local network service with a stand-alone GW (with S-GW and L-GW collocated), the PDN GW selection function uses the APN and the Local Home Network ID during the DNS interrogation as specified in TS 29.303 [61] to find the PDN GW identity. The Local Home Network ID is provided to the MME by the (H)eNB in every INITIAL UE MESSAGE and every UPLINK NAS TRANSPORT control message as specified in TS 36.413 [36]. The MME uses the Local Home Network ID to determine if the UE has left its current local network and if S-GW relocation is needed.
For SIPTO at the Local Network with L-GW function collocated with the (H)eNB the PDN GW selection function uses the L-GW address proposed by the (H)eNB in the S1-AP message, instead of DNS interrogation.
In order to select the appropriate L-GW for LIPA service, if permitted by the CSG subscription data and if the UE is roaming, the VPLMN LIPA is allowed, the PDN GW selection function uses the L-GW address proposed by HeNB in the S1-AP message, instead of DNS interrogation. If no L-GW address is proposed by the HeNB and the UE requested an APN with LIPA permissions set to "LIPA-only", the request shall be rejected. If no L-GW address is proposed by the HeNB and the UE requested an APN with LIPA permissions set to "LIPA-conditional", the MME uses DNS interrogation for PDN GW selection to establish a non-LIPA PDN connection. The PDN subscription context for an APN with LIPA permissions set to "LIPA-only" shall not contain a statically configured PDN address or a statically allocated PDN GW. A static PDN address or a static PDN GW address, if configured by HSS for an APN with LIPA permissions set to "LIPA-conditional", is ignored by MME when the APN is established as a LIPA PDN connection. When establishing a PDN connection for a LIPA APN, the VPLMN Address Allowed flag is not considered.
The PDN GW domain name shall be constructed and resolved by the method described in TS 29.303 [61], which takes into account any value received in the APN‑OI Replacement field for non-roaming or home routed traffic. Otherwise, or when the resolution of the above PDN GW domain name fails, the PDN GW domain name shall be constructed by the serving node using the method specified in Annex A of TS 23.060 [7] and clause 9 of TS 23.003 [9]. If the Domain Name Service function provides a list of PDN GW addresses, one PDN GW address is selected from this list. If the selected PDN GW cannot be used, e.g. due to an error, then another PDN GW is selected from the list. The specific interaction between the MME/SGSN and the Domain Name Service function may include functionality to allow for the retrieval or provision of additional information regarding the PDN GW capabilities (e.g. whether the PDN GW supports PMIP‑based or GTP-based S5/S8, or both).
NOTE 5: The APN as constructed by the MME/SGSN for PDN GW resolution takes into account the APN-OI Replacement field. This differs from the APN that is provided in charging data to another SGSN and MME over the S3, S10 and S16 interfaces as well as to Serving GW and PDN GW over the S11, S4 and S5/S8 interfaces, in that the APN-OI Replacement field is not applied. See clause 5.7.2 of the present document for more details.
If the UE provides an APN for a PDN, this APN is then used to derive the PDN GW identity as specified for the case of HSS provided APN if one of the subscription contexts allows for this APN.
If there is an existing PDN connection to the same APN used to derive the PDN GW address, the same PDN GW shall be selected.
As part of PDN GW selection, an IP address of the assigned PDN GW may be provided to the UE for use with host based mobility as defined in TS 23.402 [2], if the PDN GW supports host-based mobility for inter-access mobility towards accesses where host-based mobility can be used. If a UE explicitly requests the address of the PDN GW and the PDN GW supports host based mobility then the PDN GW address shall be returned to the UE.
When DCNs with dedicated PDN GWs are used, the DNS procedure (TS 29.303 [61]) for PDN GW selection may be used such that a PDN GW belonging to a DCN serving a particular category of UEs, e.g. identified by UE Usage Type, is selected. When UEs with the same UE Usage type are served by multiple DCNs, it shall also be possible to select the PDN GW belonging to the DCN serving the particular UE.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.8.2 Serving GW selection function
| The Serving GW selection function selects an available Serving GW to serve a UE. The selection bases on network topology, i.e. the selected Serving GW serves the UE's location and for overlapping Serving GW service areas, the selection may prefer Serving GWs with service areas that reduce the probability of changing the Serving GW. When SIPTO is allowed then it is also considered as a criterion for Serving GW selection, e.g. when the first PDN connection is requested. Other criteria for Serving GW selection should include load balancing between Serving GWs, UE support for dual connectivity with NR, CIoT EPS Optimisation(s) impacting Serving GW e.g. Non-IP support, Ethernet support, NB-IoT RAT support (for generation of accounting information), etc. When the Serving GW IP addresses returned from the DNS server include Weight Factors, the MME should use it if load balancing is required. The Weight Factor is typically set according to the capacity of a Serving GW node relative to other Serving GW nodes serving the same Tracking area. For further details on DNS procedure see TS 29.303 [61].
When the MME supports the GTP-C Load Control feature, it takes into account the Load Information received from the Serving GW in addition to the Weight Factors received from the DNS server to perform selection of an appropriate Serving GW.
NOTE 1: How Weight Factors can be used in conjunction with Load Information received via GTP control plane signalling is left up to Stage 3.
If a subscriber of a GTP only network roams into a PMIP network, the PDN GWs selected for local breakout support the PMIP protocol, while PDN GWs for home routed traffic use GTP. This means the Serving GW selected for such subscribers may need to support both GTP and PMIP, so that it is possible to set up both local breakout and home routed sessions for these subscribers. For a Serving GW supporting both GTP and PMIP, the MME/SGSN should indicate the Serving GW which protocol should be used over S5/S8 interface. The MME/SGSN is configured with the S8 variant(s) on a per HPLMN granularity.
If a subscriber of a GTP only network roams into a PMIP network, the PDN GWs selected for local breakout may support GTP or the subscriber may not be allowed to use PDN GWs of the visited network. In both cases a GTP only based Serving GW may be selected. These cases are considered as roaming between GTP based operators.
If combined Serving and PDN GWs are configured in the network the Serving GW Selection Function may preferably derive a Serving GW that is also a PDN GW for the UE.
In order to provide SIPTO at the local network service with stand-alone GW, the L-GW and Serving GW shall be co-located. The Serving GW selection function in the MME is used to ensure that the Serving GW is provided according to operator policy as described in clause 4.3.15a. When the L-GW is collocated with the (H)eNB, the Serving GW remains located in the mobile operator's core network.
The Domain Name Service function may be used to resolve a DNS string into a list of possible Serving GW addresses which serve the UE's location. The specific interaction between the MME/SGSN and the Domain Name Service function may include functionality to allow for the retrieval or provision of additional information regarding the Serving GW capabilities (e.g. whether the Serving GW supports PMIP-based or GTP-based S5/S8, or both). The details of the selection are implementation specific.
For handover from non-3GPP accesses in roaming scenario, the Serving GW selection function for local anchoring is described in TS 23.402 [2].
The Serving GW selection function in the MME is used to ensure that all Tracking Areas in the Tracking Area List belong to the same Serving GW service area.
When DCNs with dedicated Serving GWs are used, the DNS procedure (TS 29.303 [61]) for Serving GW selection may be used such that a Serving GW belonging to a DCN serving a particular category of UEs, e.g. identified by UE Usage Type, is selected. When UEs with the same UE Usage type are served by multiple DCNs, it shall also be possible to select the Serving GW belonging to the DCN serving the particular UE.
NOTE 2: Selection of Serving GWs optimised for different RATs (e.g. NB-IoT) can be achieved by using UE Usage Type and/or by using different TAIs for different RATs.
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b043aa03d2112b1c3a444522800f3b3a | 23.401 | 4.3.8.3 MME selection function
| The MME selection function selects an available MME for serving a UE. The selection is based on network topology, i.e. the selected MME serves the UE's location and for overlapping MME service areas, the selection may prefer MMEs with service areas that reduce the probability of changing the MME. When a MME/SGSN selects a target MME, the selection function performs a simple load balancing between the possible target MMEs. In networks that deploy dedicated MMEs/SGSNs for UEs configured for low access priority, the possible target MME selected by source MME/SGSN is typically restricted to MMEs with the same dedication.
When a MME/SGSN supporting DCNs selects a target MME, the selected target MME should be restricted to MMEs that belong to the same DCN. The DNS procedure may be used by the source CN node to select the target MME from a given DCN. If both low access priority and UE Usage Type parameter are used for MME selection, selection based on UE Usage type parameter overrides selection based on the low access priority indication.
When a MME supporting CIoT EPS Optimisation(s) selects a target MME, the selected MME should all support the CIoT EPS Optimisations applicable to the given UE's attachment. if the source MME is unable to find a target MME matching all CIoT EPS Optimisation(s) applicable to a given UE's attachment, then the source MME, based on implementation, selects a target MME which provides the CIoT EPS Optimisation(s) best applicable to that UE's attachment.
When an eNodeB selects an MME, the eNodeB may use a selection function which distinguishes if the GUMMEI is mapped from P-TMSI/RAI or is a native GUMMEI. The indication of mapped or native GUMMEI shall be signalled by the UE to the eNodeB as an explicit indication. The eNodeB may differentiate between a GUMMEI mapped from P‑TMSI/RAI and a native GUMMEI based on the indication signalled by the UE. Alternatively, the differentiation between a GUMMEI mapped from P-TMSI/RAI and a native GUMMEI may be performed based on the value of most significant bit of the MME Group ID, for PLMNs that deploy such mechanism. In this case, if the MSB is set to "0" then the GUMMEI is mapped from P-TMSI/RAI and if MSB is set to "1", the GUMMEI is a native one. Alternatively the eNodeB makes the selection of MME only based on the GUMMEI without distinguishing on mapped or native.
When an eNodeB selects an MME, the selection shall achieve load balancing as specified in clause 4.3.7.2.
When an eNodeB selects an MME, the selection shall consider the IAB support capability if the UE includes an IAB-Indication in the RRC connection establishment signalling as defined in TS 36.331 [37].
When the UE attempts to establish a signalling connection and the following conditions are met:
- the eNodeB serves more than one country (e.g. it supports E-UTRA satellite access); and
- the eNodeB knows in what country the UE is located; and
- the eNodeB is connected to MMEs serving different PLMNs of different countries; and
- the UE provides an S-TMSI or GUMMEI, which indicates an MME serving a different country to where the UE is currently located; and
- the eNodeB is configured to enforce selection of the MME based on the country the UE is currently located;
then the eNodeB shall select an MME serving a PLMN corresponding to the UE's current location. How the eNodeB selects the MME in this case is defined in TS 36.410 [92].
NOTE: When the UE accesses an eNodeB onboard a satellite (i.e. regenerative based satellite access), the eNodeB can be configured to select an MME supporting S1 Removal procedure defined in TS 36.413 [36].
When a satellite is operating in S&F Mode, the eNodeB is configured to enforce selection of the on-board MME supporting S&F Mode for every UE that accesses it.
When DCNs are deployed, to maintain a UE in the same DCN when the UE enters a new MME pool area, the eNodeB's NNSF should have configuration that selects, based on the MMEGIs or NRIs of neighbouring pool areas, a connected MME from the same DCN. Alternately, for PLMN wide inter-pool intra-RAT mobility, the operator may divide up the entire MMEGI and NRI value space into non-overlapping sets with each set allocated to a particular DCN. In this case all eNodeBs may be configured with the same MME selection configuration. If UE assisted DCN selection feature is supported and a DCN-ID is provided by the UE, the DCN-ID shall be used in the eNodeB for MME selection to maintain the same DCN when the serving MME is not available.
When selecting an MME for a UE that is using the NB-IoT RAT, and/or for a UE that signals support for CIoT EPS Optimisations in RRC signalling (as specified in TS 36.331 [37], for NB-IoT, UE indicates whether it supports "User Plane CIoT EPS Optimisation" and "EPS Attach without PDN Connectivity". And for WB-E-UTRAN, UE indicates whether it supports "Control Plane CIoT EPS Optimisation", "User Plane CIoT EPS Optimisation" and "EPS Attach without PDN Connectivity"), the eNodeB's MME selection algorithm shall select an MME taking into account the MME's support (or non-support) for the Release 13 NAS signalling protocol.
When DCN are deployed for the purpose of CIoT EPS Optimisation, UE included CIoT EPS Optimisation information in the RRC signalling, may depending on eNodeB configuration, be used to perform initial DCN selection.
When Restricted Local Operator Services feature is supported, a UE initiates access to Restricted Local Operator Services via RRC signalling as defined in TS 36.331 [37]. The UE included RLOS indication in RRC signalling may be used by the eNodeB to select an appropriate MME.
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