F.4 5GS interworking with TSN deployed in the transport network

23.5023GPPProcedures for the 5G System (5GS)Release 18TS

For 5GS to control the IEEE TSN features deployed in the transport network, the SMF/CUC interacts with the CNC in the transport network (TN CNC).

Figure F.4-1: 5GS Bridge information configuration

1. The UE establishes a PDU Session as described in clause 4.3.2.2.1.

2. During the PDU Session Establishment procedure, the SMF/CUC requests the UPF to assign the N3 tunnel information via N4 Session Establishment or Modification procedure. The SMF/CUC includes a TL-Container to the N4 Session Establishment or Modification request including a get-request to the TL-Container, as described in clause 5.28a.2 of TS 23.501 [2].

The UPF responds with a N4 Session Establishment or Modification response. If the UPF supports CN-TL, the UPF includes a TL-Container to the response. The TL-Container includes a get-response as described in clause 5.28a.2 of TS 23.501 [2]. The SMF/CUC stores the get-response.

3. During the PDU Session Establishment procedure, the SMF/CUC requests the NG-RAN to assign the N3 tunnel information by invoking the Namf_Communication_N1N2MessageTransfer request. The SMF/CUC includes a TL-Container to the N2 SM information in the request, the TL-Container contains a get-request as described in clause 5.28a.2 of TS 23.501 [2].

The NG-RAN responds with a N2 SM information. If the NG-RAN supports AN-TL, the NG-RAN includes a TL-Container to the N2 SM information. The TL-Container includes a get-response as described in clause 5.28a.2 of TS 23.501 [2]. The SMF/CUC stores the get-response.

4. The AF (TSCTSF, AF, NEF or TSN AF) invokes the Npcf_PolicyAuthorization_Create/Update request. This may be due to reception of Ntsctsf_QoSandTSCAssistance_Create/Update request by the TSCTSF as described in clause 4.15.6.6 or clause 4.15.6.6.a, or due to reception of 5GS Bridge configuration by the TSN AF as described in clause F.2. The TSN AF or TSCTSF determines the TSC Assistance Container for one or more TSC streams and sends them to the PCF.

5-6.When PCF receives the request, the PCF initiates an SM Policy Association Modification procedure. The PCF notifies the corresponding SMF/CUC via Npcf_SMPolicyControl_UpdateNotify message as described in clause 4.16.5.2. The PCF updates the PCC rule to the SMF/CUC. The PCC rule includes the 5GS QoS profile along with TSC Assistance Container.

SMF/CUC triggers the PDU Session Modification procedure as described in clause 4.3.3.2 to establish a QoS Flow to transfer the TSC streams.

7. During the PDU Session Modification procedure, the SMF/CUC provides the information received in PCC rules to the UPF via N4 Session Modification procedure. If the UPF does not support CN-TL, the SMF/CUC instructs the UPF to assign a distinct N3 tunnel end point address for the QoS Flow.

The UPF responds with a N4 Session Modification response.

8. During the PDU Session Modification procedure, the SMF/CUC provides the information received in PCC rules to the NG-RAN by invoking the Namf_Communication_N1N2MessageTransfer request. The SMF also determines the TSCAI for the QoS Flow(s) and sends the TSCAI along with the QoS profile(s) to the NG-RAN. If the NG-RAN does not support AN-TL, the SMF/CUC instructs the NG-RAN to assign a distinct N3 tunnel end point address for the QoS Flow.

The NG-RAN responds with a N2 SM information.

9. The SMF/CUC determines the merged stream requirements in the TSN UNI towards the TN CNC as described in Annex M of TS 23.501 [2]. The TN CNC uses the merged stream requirements as input to select respective path(s) and calculate schedules in TN.

10. Based on the results, the TN CNC provides a Status group that contains the merged end station communication-configuration back to the SMF/CUC.

11. [Optional] If the response from TN CNC includes InterfaceConfiguration, the SMF/CUC triggers the PDU Session Modification procedure as described in clause 4.3.3.2 to modify the QoS Flow to transfer the TSC streams.

12. [Optional] During the PDU Session Modification procedure, if the UPF supports CN-TL, the SMF/CUC invokes N4 Session Modification procedure and includes a TL-Container to the N4 Session Modification request including a set-request to the TL-Container as described in clause 5.28a.2 of TS 23.501 [2].

The UPF responds with a N4 Session Modification response. If the UPF supports CN-TL, the UPF includes a TL-Container to the response. The TL-Container includes a set-response as described in clause 5.28a.2 of TS 23.501 [2].

13. [Optional] During the PDU Session Modification procedure, if the NG-RAN supports AN-TL, the SMF/CUC invokes the Namf_Communication_N1N2MessageTransfer request. The SMF/CUC includes a TL-Container to the N2 SM information in the request, the TL-Container contains a set-request as described in clause 5.28a.2 of TS 23.501 [2]. The SMF/CUC may also update the TSCAI in the NG-RAN for the BAT in DL direction as described in clause 5.28a.2 of TS 23.501 [2], if the SMF/CUC received a TimeAwareOffset or AccumulatedLatency from TN CNC for a downlink stream (i.e. for a Talker in the UPF/CN-TL) in step 7.

The NG-RAN responds with a N2 SM information. If the NG-RAN supports AN-TL, the NG-RAN includes a TL-Container to the N2 SM information. The TL-Container includes a set-response as described in clause 5.28a.2 of TS 23.501 [2].

Annex G (normative):
Support of GERAN/UTRAN access by SMF+PGW-C

This annex applies when the SMF+PGW-C is enhanced to support GERAN/UTRAN access via Gn/Gp interface as specified in Annex L of TS 23.501 [2].

NOTE 1: For the interface with the serving node of the UE, the SMF+PGW-C is assumed to behave as the Control Plane of the PGW described in Annex D of TS 23.401 [13].

SMF+PGW-C is selected by the SGSN using existing mechanism as specified in Annex A of TS 23.060 [56].

NOTE 2 If network deployment requires both SMF+PGW-C and legacy PGW, selection of SMF+PGW-C by SGSN can be achieved based on e.g. APN and optionally APN-OI Replacement as specified Annex A of TS 23.060 [56].

When a SMF+PGW-C is used for GERAN/UTRAN access, at PDP context activation, the SMF+PGW-C allocates a PDU Session ID (in the network range) and uses this PDU Session ID over SBI interface (e.g. N7).

The following procedures from TS 23.060 [56] are not supported when SMF+PGW-C is used for GERAN/UTRAN access:

– Network requested PDP Context Activation Procedure (clause 9.2.2.2 of TS 23.060 [56]).

– Secondary PDP Context Activation Procedure (clause 9.2.2.1.1 of TS 23.060 [56]).

– Network Requested Secondary PDP Context Activation Procedure using Gn (clause 9.2.2.1.3 of TS 23.060 [56]).

When SMF+PGW-C is used for GERAN/UTRAN access and interacts with PCF, the SMF+PGW-C uses SM policy association procedures as specified in clause 4.11.0a.2 with the following modification:

– The SMF+PGW-C performs mapping of QoS parameters as follows:

– The SMF+PGW-C maps the Release 99 QoS parameters received from Gn/Gp interface to EPS QoS parameters as specified in Annex E of TS 23.401 [13], which is then used to derive QoS parameters over N7 interface as specified in clause 4.11.0a.2.

– the SMF+PGW-C uses QoS parameters over N7 interface to derive EPS QoS parameters as specified in clause 4.11.0a.2, which is then mapped to Release 99 QoS parameters for Gn/Gp interface as specified in Annex E of TS 23.401 [13].

– For SM Policy Association Establishment Procedure, the SMF+PGW-C invokes Npcf_SMPolicyControl_Create Service operation taking input from the information elements received in Create PDP Context Request message (specified in TS 23.060 [79]), including mapping of QoS parameters as mentioned above as well as GERAN/UTRAN location management related information.

– For SM Policy Association Modification procedure initiated by the SMF+PGW-C, the SMF+PGW-C invokes Npcf_SMPolicyControl_Update Service operation taking input from the information elements received in Update PDP Context Request message (specified in TS 23.060 [79]), including mapping of QoS parameters as mentioned above, as well as GERAN/UTRAN location management related information.

– For SM Policy Association Modification procedure initiated by the PCF, the SMF+PGW-C may receive PCC Rules and PDU Session Policy Information. The SMF+PGW-C performs mapping of QoS parameters as mentioned above.

– For SM Policy Association Termination procedure, the SMF+PGW-C invokes Npcf_SMPolicyControl_Delete service operation (including GERAN/UTRAN location management related information) when receiving Delete PDP Context Request message (specified in TS 23.060 [79]).

– Even though N7 supports Ethernet PDU Session Type, as Ethernet PDN Type is not supported in GERAN/UTRAN, it is assumed that if the UE moves from E-UTRAN to GERAN/UTRAN, Ethernet PDN connections are released and thus no information related with Ethernet PDU Session Type shall be exchanged over N7 when a UE is served by GERAN/UTRAN.

– Even though GERAN/UTRAN specifications foresee other alternatives, the Bearer Binding is performed by the SMF+PGW-C acting as a PGW.

– Access Network Information reporting with a granularity of GERAN/UTRAN cell is supported over N7 and N5.

When the UE moves between E-UTRAN and GERAN/UTRAN, the SMF+PGW-C may invoke SM Policy Association Modification procedure based on the Policy Control Request Triggers as specified in TS 23.503 [20].

NOTE 3: Support for IP address preservation upon indirect mobility between 5GS and GERAN/UTRAN for PDN sessions established in EPC is described in clause 5.17.2.4 of TS 23.501 [2]. IP address preservation is not supported for direct mobility between 5GS and GERAN/UTRAN, nor for indirect mobility cases when the PDN session is established in 5GS or in GERAN/UTRAN.

NOTE 4: Usage of SMF+PGW-C to serve a PDP context requires no change to SGSN(s) (and thus to roaming partners in Home Routed roaming) as it is assumed that DNS records are properly configured to map APN to SMF+PGW-C acting as PGW.

Annex H (normative):
Support of EAP-based secondary authentication and authorization by DN-AAA over EPC