5.28.2 5GS Bridge configuration for TSN

The configuration information of 5GS Bridge as defined in clause 8.6.8.4 of IEEE Std 802.1Q [98], includes the following:

• Bridge ID of 5GS Bridge.
• Configuration information of scheduled traffic on ports of DS-TT and NW-TT:
• Egress ports of 5GS Bridge, e.g. ports on DS-TT and NW-TT;
• Traffic classes and their priorities.

NOTE 1: In this Release of the specification, scheduled traffic (clause 8.6.8.4 in IEEE Std 802.1Q [98]) is only supported with protected windows, (see clause Q.2 in IEEE Std 802.1Q [98]), therefore, it is enough to support AdminControlList, AdminBaseTime, AdminCycleTime and TickGranularity for the configuration of the 5GS.

The configuration information of 5GS Bridge as defined in IEEE Std 802.1Q [98], includes the following:

• Chassis ID of 5GS Bridge;
• Traffic forwarding information as defined in clause 8.8.1 of IEEE Std 802.1Q [98]:
• Destination MAC address and VLAN ID of TSN stream;
• Port number in the Port MAP as defined in clause 8.8.1 of IEEE Std 802.1Q [98].
• Configuration information per stream according to clause 8.6.5.1 of IEEE Std 802.1Q [98] including:
• Stream filters.
• Stream gates.

NOTE 2: In order to support clause 8.6.5.2.1 of IEEE Std 802.1Q [98], it is required to support the Stream Identification function as specified by IEEE Std 802.1CB [83].

The SMF report the MAC address of the DS-TT port of the related PDU Session to TSN AF via PCF. The association between the DS-TT MAC address, 5GS Bridge ID and port number on DS-TT is maintained at TSN AF and further used to assist to bind the TSN traffic with the UE's PDU session.

Two models are supported to configure 5GS QoS for TSN traffic:

• Based on the assumption that PSFP information is always provided by CNC: In this case the QoS Flows are setup based on the PSFP information provided by CNC;

NOTE 3: PSFP information may be provided by CNC if TSN AF has declared PSFP support to CNC. TSN AF indicates the support for PSFP to CNC only if each DS-TT and NW-TT of the 5GS bridge has indicated support of PSFP.

• Without requiring PSFP information provided by the CNC.: In this case, pre-configured QoS Flows are used and configured e.g. during PDU session establishment as described in clause 5.28.4. Additional QoS Flows are setup as necessary based on the PSFP, if available, as described in this clause.

When PSFP information is available, TSN AF identifies the ingress and egress port for the TSN stream as described in Annex I and determines the DS-TT port MAC address(es) identifying the corresponding PDU session(s) carrying the TSN stream. Flow direction of a TSN stream is determined as follows: if the ingress port is a DS-TT port, then the Flow direction is UL; otherwise if the ingress port(s) is (are) NW-TT port, the Flow direction is DL. Flow direction is part of the TSCAI as defined in clause 5.27.2.

The TSN AF uses the stream filter instances of PSFP information to derive the service data flow for TSN streams. The TSN AF uses the Priority values in the stream filter instances in PSFP information (if available) as defined in clause 8.6.5.2.1 of IEEE Std 802.1Q [98], the 5GS bridge delay information (see clause 5.27.5) and may additionally use scheduled traffic information as defined in clause 8.6.8.4 of IEEE Std 802.1Q [98], to derive the TSN QoS information (i.e. priority and delay) for a given TSN stream or flow of aggregated TSN streams as specified in clause 5.28.4.

The TSN AF identifies the egress port(s) for the TSN stream using local configuration or static filtering entry that matches the TSN stream. If the TSN AF determines that the TSN stream is for UE-UE communication (i.e. ingress and egress ports are in DS-TTs), the TSN AF divides the stream into one uplink stream and one or more downlink streams and provides the streams on AF Session basis to the PCF(s). The SMF applies local switching as specified in clause 5.8.2.13 or clause 5.8.2.5.3 in order to enable UPF locally forward uplink stream from one PDU session as downlink stream in another PDU session.

When CNC configures the PSFP information to the TSN AF, TSN AF determines the TSC Assistance Container as described in clause 5.27.2. The TSN AF associates the TSN QoS information and TSC Assistance Container (if available) with the corresponding service data flow description and provides to the PCF and the SMF as defined in clause 6.1.3.23 of TS 23.503 [45].

NOTE 4: When the TSN stream priority information from PSFP is not available (priority value in stream filters is set to wild card), in certain configurations it can be possible to use the scheduled traffic information as defined in clause 8.6.8.4 of IEEE Std 802.1Q [98] to derive the Priority of the TSN stream. For example, when there is a single downlink stream for a given DS-TT port, it can be possible to determine the affected DS-TT port in the downlink and the associated TSN stream priority based on the scheduled traffic information of the affected egress port and to derive an estimated MDBV based on the gate open interval and the assumed ingress port bitrate.

If TSN AF provides PSFP and/or scheduled traffic information to DS-TT and NW-TT then DS-TT and NW-TT execute on this information relative to the time base of the TSN GM clock (identified by the TSN time domain number received in PMIC).

NOTE 5: Configuration of TSN time domain number via PMIC is optional for NW-TT. NW-TT can instead be pre-configured with the single time domain that is used by the CNC for bridge configuration and reporting.