5.26 Support of Time Sensitive Communications and Time Synchronization (for 5GC)

29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.26.1 General

The SMF may request the UPF to measure and report the clock drift between the TSN time and 5GS time for one or more TSN time domains (see clause 5.27.2 of 3GPP TS 23.501 [28]), by provisioning one or more Clock Drift Control Information IE(s) in a PFCP Association Setup Request or a PFCP Association Update Request, with the following information:

– TSN Time Domain Number IE(s), identifying the TSN working time domain(s), e.g. PTP (Precision Time Protocol) "domainNumber", for which clock drift needs to be measured and reported (see clause 5.27.1.3 of 3GPP TS 23.501 [28]). This may be present if the Configured Time Domain IE is omitted. The SMF may omit the Time Domain Number IE in the request; if neither the Time Domain Number IE nor the Configured Time Domain IE is included, the UPF shall report the clock drift for all Time domains the UPF is connected to;

– Configured Time Domain IE with the CTDI (Configured Time Domain Indicator) flag set to "1", to indicate that clock drift needs to be measured and reported for the Time Domain Number configured in the NW-TT(s). This may be present if the Time Domain Number IE is omitted;

– the requested Clock Drift Information, indicating a request to report when the Time Offset Reporting Threshold is exceeded and/or when the cumulative RateRatio Reporting Thresholds is exceeded;

– the Time offset reporting threshold (i.e. the maximum time offset between the TSN time and 5G system time), if Time Offset Reporting is requested;

– the Cumulative rateRatio measurement threshold (i.e. related to cumulative rateRatio calculated at NW-TT)), if Cumulative RateRatio Reporting is requested.

If so requested, when detecting either of the clock drift offset triggers exceeding the defined threshold, the UPF shall send a PFCP Node Report Request to the SMF, including one or more Clock Drift Reports, with the corresponding TSN Time Domain Number(s), measurement information and Network Instance (if available) and the combination of DNN and S-NSSAI (if available).

5.26.2 5GS Bridge management

5GS Bridge information reporting is defined in Annex F.1 of 3GPP TS 23.502 [29]; this procedure enables the SMF to report 5GS Bridge/User Plane Node information of a PDU session established for Time Sensitive Communication (TSC) to the TSN AF or TSCTSF via the PCF.

Identities of 5GS Bridge/User Plane Node and UPF/NW-TT ports may be pre-configured in the UPF based on deployment. When establishing the PFCP session for the PDU session for TSC, the SMF shall provide the Network Instance IE and it may provide the APN/DNN IE and S-NSSAI IE to the UPF to enable the UPF to respond with the proper User Plane Node ID or Bridge ID based on configuration information associated with the network instance or DNN and S-NSSAI pair. The 5GS User Plane Node IE shall contain the Bridge ID in case of IEEE TSN.

In order to establish a PDU Session for TSC, the SMF shall send a PFCP Session Establishment Request to the UPF to establish the corresponding PFCP session as specified in this specification. Additionally, the SMF shall request the UPF to allocate the port number for DS-TT and provide the related 5GS User Plane Node by including the Create Bridge Info for TSC IE with the Bridge Information Indication (BII) bit set to "1", in the PFCP Session Establishment Request. If so requested, the UPF shall provide corresponding information to the SMF in the Created Bridge Info for TSC IE in the PFCP Session Establishment Response message.

NOTE: The port number for DS-TT and Bridge ID are not meant to be used in PDRs.

5.26.3 Transfer of 5GS bridge and port management information

5GS User Plane Node and port information configuration is defined in clause 5.28.3 of 3GPP TS 23.501 [28] and in Annex F of 3GPP TS 23.502 [29]; this procedure enables the SMF to relay transparently bridge and/or port related information between the TSN AF or TSCTSF and the NW-TT (and DS-TT).

Port management information shall be transferred between the SMF and UPF in a Port Management Information Container (PMIC). If the NW-TT supports several ports, and port management information needs to be sent for several ports, a separate PMIC shall be used for each port.

User Plane Node management information shall be transferred between the SMF and UPF in a User Plane Node Management Information Container (UMIC).

The SMF and UPF may send a PMIC or a UMIC using PFCP session related procedures of any PFCP session associated with the 5GS bridge.

The SMF may provide NW-TT related UMIC and/or PMIC(s) to the UPF by sending a PFCP Session Modification Request to the UPF including the TSC Management Information IE.

For a PDU session established for TSC, the UPF may send NW-TT related UMIC and/or PMIC(s) to the SMF by sending a PFCP Session Modification Response or a PFCP Session Report Request including the TSC Management Information IE.

The details of the User Plane Node and Port Management Container communication between NW-TT and TSN AF or TSCTSF is defined in the 3GPP TS 24.539 [63].

5.26.4 Reporting clock drift between External and 5GS times from UPF to SMF

The SMF may request the UPF to measure and report the clock drift between the external time and 5GS time for one or more external time domains (see clause 5.27.2.4 of 3GPP TS 23.501 [28]), by provisioning one or more Clock Drift Control Information IE(s) in a PFCP Association Setup Request or a PFCP Association Update Request, with the following information:

– Time Domain Number IE(s), identifying the working time domain(s), e.g. PTP (Precision Time Protocol) "domainNumber", for which clock drift needs to be measured and reported. This may be present if the Configured Time Domain IE is omitted. The SMF may omit the Time Domain Number IE in the request; if neither the Time Domain Number IE nor the Configured Time Domain IE is included, the UPF shall report the clock drift for all Time domains the UPF is connected to;

– the requested Clock Drift Information, indicating a request to report when the Time Offset Reporting Threshold is exceeded and/or when the cumulative RateRatio Reporting Thresholds is exceeded;

– the Time offset reporting threshold (i.e. the maximum time offset between the external time and 5G system time), if Time Offset Reporting is requested;

– the Cumulative rateRatio measurement threshold (i.e. related to cumulative rateRatio calculated at NW-TT)), if Cumulative RateRatio Reporting is requested.

If so requested, when detecting either of the clock drift offset triggers exceeding the defined threshold, the UPF shall send a PFCP Node Report Request to the SMF, including one or more Clock Drift Reports, with the corresponding Time Domain Number(s), measurement information and Network Instance (if available) and the combination of DNN and S-NSSAI (if available).