))) Primary timing PRTC/T-GM source End application a) PRTC/T-GM is deployed in the backhaul network Primary ((cp)) Backup timing timing source PRTC/T-GM source (((p))) End application b) PRTC/T-GM is deployed in the network connecting DU and RU Figure 10-34 Network PRTC Distributes Clock to DU and RUs Connected over Multiple Net- work Hops In this option, the nodes distributing the timing signal to the DU and RUs need to comply with the G.8275.1 PTP telecom profile with a minimum ITU-T G.8273.2 Class B performance as T-BC clocks. These network nodes also need to support the SyncE or eSyncE clock definition according to ITU-T G.8262 or G.8262.1. However, the DU or RU is not mandated to use the SyncE frequency source to achieve its own frequency synchronization and instead may use only PTP to achieve fre- quency as well as phase synchronization. As shown in suboption (b), if the network topology has a backup timing source, the DU and RUs can use the backup timing source to maintain longer holdover during a failure of the primary timing source. Features like APTS or BMCA are useful in such deployments. Option 3 The PRTC is directly connected to the RU as shown in Figure 10-35, which has two possibilities: The DU and RU receive clock from the same PRTC/T-GM. The DU and RU receive clock from different PRTC/T-GMs. Backup Primary timing Primary source for DU timing source timing for RU PRTC/T-GM source (((p))) Primary timing signal Secondary timing for RU source for DU End application a) PRTC/T-GM is deployed at RU, distributing clock to DU Primary Primary timing timing source PRTC/T-GM Backup source to RU for DU Primary timing source to RU End application b) PRTC/T-GM is deployed at RU, DU receives clock from network PRTC/T-GM Figure 10-35 Network PRTC Distributes Clock to DU and RUs Connected over Multiple Net- work Hops In this option, the nodes distributing the timing signal from the RUs to the DU need to comply with the G.8275.1 PTP telecom profile with a minimum ITU-T G.8273.2 Class B performance as T-BC clocks. 