s net- work (RAN) front-haul network. The IEEE TSN Task Group has developed the IEEE 802.1CM- 2018 standard "Time-Sensitive Networking for front-haul," which enables the transport of time- sensitive front-haul traffic in the RAN by Ethernet networks. See the section "IEEE TSN" in "Chapter 4. Standards Development Organizations", for more details on TSN and TSN profiles. The IEEE 802. CM standard defines performance profiles that specify features, options, configura- tions, defaults, protocols, and procedures of Ethernet devices that are necessary to build networks capable of transporting radio traffic. Note that the RAN front-haul network uses TSN technologies in 802.1CM, but it does not use the 802.1AS PTP profile. The TSN Task Group is also working on two profiles where precise time synchronization plays an exceptional role: IEC/IEEE 60802: TSN Profile for Industrial Automation IEEE P802.1DG: TSN Profile for Automotive In-Vehicle Ethernet Communications The use cases and strict requirements in IEC/IEEE 60802 have triggered new work on an amend- ment for gPTP hot-standby services, meaning the ability to use independent backup GMs with mul- tiple domains. 7.5.1 IEC 62439-3 (2016) PTP Industry Profile (PIP) IEC 62439-3:2016 specifies two redundancy protocols (HSR and PRP) designed to provide seam- less recovery in case of a single failure in a network, either of a link or a network element. This re- dundancy is based on the parallel transmission of duplicated information using "doubly attached" network elements connected by one of these two methods (or a combination of them). Besides defining the PRP and HSR methods, on the topic of timing, the standard defines a PTP In- dustry Profile (PIP) to synchronize an industrial (Ethernet) network to sub-microsecond-level accur- acy. Two variants of the PIP profile are specified in Annex C of the standard: L3E2E (layer 3, end-to-end) for clocks operating on L3 networks with E2E delay measurement (from 1588-2008 Annex J.3) L2P2P (layer 2, peer-to-peer) for clocks operating 