4.4.8 Time Sensitive Communication

The 5G System is extended to support Time sensitive communication as defined in IEEE P802.1Qcc [95].

5G System已扩展为支持IEEE P802.1Qcc[95]中定义的Time敏感通信。

In this Release of the specification, integration of 5G System with TSN networks that are based on IEEE TSN (IEEE P802.1Qcc [95]) is supported. IEEE TSN is a set of standards to define mechanisms for the time-sensitive (i.e. deterministic) transmission of data over Ethernet networks.

本规范版本支持5G System与基于IEEE TSN的TSN网络的集成。IEEE TSN是一组标准，用于定义Ethernet网上数据的time-sensitive（即确定性）传输机制。

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 System 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). 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:

5G System作为TSN网桥与外部网络集成。该“逻辑”TSN网桥包括TSN Translator功能，用于用户平面和控制平面的TSN System和5G System之间的互操作。5GS TSN转换器功能包括Device-side TSN转换器（DS-TT）和Network-side TSN转换器（NW-TT）。5GC和RAN中的5G System特定程序、无线通信链路等仍然对TSN网络隐藏。为了实现对TSN网络和5GS的透明性，5GS通过DS-TT和NW-TT提供TSN入向和出向端口。DS-TT和NW-TT可选支持：

- hold and forward functionality for the purpose of de-jittering;

- per-stream filtering and policing as defined in IEEE 802.1Q [98] clause 8.6.5.1.

DS-TT optionally supports link layer connectivity discovery and reporting as defined in IEEE 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 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 802.1AB [97] for discovery of Ethernet devices attached to DS-TT on behalf of DS-TT.

DS-TT可选地支持IEEE 802.1AB[97]中定义的链路层连接发现和报告，用于发现连接到DS-TT的Ethernet设备。NW-TT支持IEEE 802.1AB[97]中定义的链路层连接发现和报告，用于发现连接到NW-TT的Ethernet设备。如果DS-TT不支持链路层连接发现和报告，则NW-TT执行IEEE 802.1AB[97]中定义的链路层连接发现和报告，以代表DS-TT发现连接到DS-TT的Ethernet设备。

NOTE 1: If NW-TT performs link layer connectivity discovery and reporting on behalf of DS-TT, it is assumed that LLDP frames are transmitted between NW-TT and UE on the default QoS Flow. Alternatively, SMF can establish a dedicated QoS Flow matching on the Ethertype defined for LLDP (IEEE 802.1AB [97]).

注1：如果NW-TT代表DS-TT执行链路层连接发现和报告，则假定LLDP帧在默认QoS Flow上在NW-TT和UE之间传输。或者，SMF可以在为LLDP定义的Ethertype上建立专用QoS Flow匹配。

There are three TSN configuration models defined in IEEE P802.1Qcc [95]. Amongst the three models:

- fully centralized model is supported in this release of the specification;

- fully distributed model is not supported in this release of the specification;

- hybrid model is not supported in this Release of the specification.

NOTE 2: This release only supports interworking with TSN using IEEE 802.1Q [98] clause 8.6.8.4 based scheduled traffic and IEEE 802.1Q [98] clause 8.6.5.1 based per-stream filtering and policy.

注2：此版本仅支持使用基于调度流量的IEEE 802.1Q[98]第8.6.8.4条和基于per-stream过滤和策略的IEEE 802.1Q[98]第8.6.5.1条与TSN互通。