Content for  TS 23.501  Word version:  18.0.0

The 5G System can be extended to support the following:

1. Integration as a bridge in an IEEE 802.1 Time Sensitive Networking (TSN). The 5GS bridge supports the Time sensitive communication as defined in IEEE 802.1 Time Sensitive Networking (TSN) standards. The architecture is described in clause 4.4.8.2.
   This Release supports of the specification, integration of the 5G System with IEEE 802.1 TSN networks that apply the fully centralized configuration model as defined in IEEE Std 802.1Qcc [95]. IEEE TSN is a set of standards to define mechanisms for the time-sensitive (i.e. deterministic) transmission of data over Ethernet networks.
2. Enablers for AF requested support of Time Synchronization and/or some aspects of Time Sensitive Communication. The architecture is described in clause 4.4.8.3.
3. Enablers for interworking with TSN network deployed in the transport network. This option can be used simultaneously with either option a) or b). The architecture is described in clause 5.28a. The interworking is applicable when the transport network deploys the fully centralized configuration model as defined in IEEE Std 802.1Qcc [95].

The 5G System is integrated with the external network as a TSN bridge. This "logical" TSN bridge (see Figure 4.4.8.2-1) includes TSN Translator functionality for interoperation between TSN Systems and 5G System both for user plane and control plane. 5GS TSN translator functionality consists of Device-side TSN translator (DS-TT) and Network-side TSN translator (NW-TT). The TSN AF is part of 5GC and provides the control plane translator functionality for the integration of the 5GS with a TSN network, e.g. the interactions with the CNC. 5G System specific procedures in 5GC and RAN, wireless communication links, etc. remain hidden from the TSN network. To achieve such transparency to the TSN network and the 5GS to appear as any other TSN Bridge, the 5GS provides TSN ingress and egress ports via DS-TT and NW-TT. DS-TT and NW-TT optionally support:

• hold and forward functionality for the purpose of de-jittering;
• per-stream filtering and policing as defined in clause 8.6.5.1 of IEEE Std 802.1Q [98].

DS-TT optionally supports link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to DS-TT. NW-TT supports link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to NW-TT. If a DS-TT does not support link layer connectivity discovery and reporting, then NW-TT performs link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to DS-TT on behalf of DS-TT.

This clause describes the architecture to enable Time Sensitive Communication AF requested time sensitive communication and time synchronization services. The Time Sensitive Communication and Time Synchronization related features that are supported based on AF request are described in clauses 5.27.1 and 5.27.2, respectively. Figure 4.4.8.3-1 shows the architecture to support Time Sensitive Communication and Time Synchronization services. As shown in Figure 4.4.8.3-1, to support Time Synchronization service based on IEEE Std 802.1AS [104] or IEEE Std 1588 [126] for Ethernet or IP type PDU Sessions, the DS-TT, NW-TT and Time Sensitive Communication and Time Synchronization Function (TSCTSF) are required in order to support the features in IEEE Std 802.1AS [104] or IEEE Std 1588 [126] as described in clause 5.27. The NEF exposes 5GS capability to support Time Synchronization service as described in clause 5.27.1.8. TSCTSF controls the DS-TT(s) and NW-TT for the (g)PTP based time synchronization service. In addition, TSCTSF supports TSC assistance container related functionalities.

UPF/NW-TT distributes the (g)PTP messages as described in clause 5.27.1. When the UPF supports one or more NW-TT(s), there is one-to-one association between an NW-TT and the network instance or between an NW-TT and network instance together with DNN/S-NSSAI in the UPF. When there are multiple network instances within a UPF, each network instance is considered logically separate. The network instance for the N6 interface (clause 5.6.12) may be indicated by the SMF to the UPF for a given PDU Session during PDU Session establishment procedure. UPF allocates resources based on the Network Instance and S-NSSAI and it is supported according to TS 29.244. DNN/S-NSSAI may be indicated by the SMF together with the network instance to the UPF for a given PDU Session during PDU Session establishment procedure.