ollowing parameters contribute to the master selection process: Clock quality level (clockClass) PTSF status Local priority configured on the slave This profile is widely used in two use cases. The first is circuit emulation (CEM), whereby the leg- acy synchronous networks are replaced by packet transport and SyncE is not available. The second is the 3G and 4G mobile networks that need frequency synchronization but, again, SyncE is not an option. G.8275.1-Telecom Profile for Phase/Time Synchronization with Full Timing Support from the Network This recommendation defines a profile intended to be used to carry phase/time across a packet net- work in combination with a physical form of frequency (commonly SyncE). As shown in Figure 7- 13, this profile only applies to the topology that features full timing support from the network (every network element is a PTP clock). In this profile, the grandmaster clocks are known as Telecom Grandmasters (T-GM), the boundary clocks are known as Telecom Boundary Clocks (T-BC), and the slave clocks are known as Telecom Time Slave Clocks (T-TSC). There is also the ability to deploy (E2E) Telecom Transparent Clocks (T-TC). Using this profile over a network containing only PTP clocks allows the accuracy of the distributed time to be tightly controlled. That is because the performance limits of the T-BC and T-TSC clocks are specified in another recommendation (G.8273.2) and every node is processing PTP. This is not the case in G.8265.1 and not necessarily true for G.8275.2. It is not the profile itself that guarantees any performance because it merely describes the functions of the PTP. Other recommendations, such as those covering the clock characteristics and perform- ance and the E2E network topology, are concerned with performance. Chapter 8 covers the interac- tions between these various documents in more detail. The recommendation for this profile specifies the characteristics and behavior of the following clock types from G.8275: Telecom Grandmaster (T-GM): A 1588-2008 grandmas