 as quality of service (QoS). The timing-aware device recognizes packets (such as PTP) that are transporting a timing signal and treats them specially. For a PTP-aware NE, this would include such features as being a boundary clock (BC) or a transparent clock (TC) for the profile of PTP being used. A packet network that contains only NE nodes that are PTP-aware connected by a transport that consists only of timing-aware devices is known as having full timing support and is often referred to as FTS. Packet networks that do not offer that level of support to transport timing are referred to having partial timing support (PTS), meaning that only a subset of the nodes understand and pro- cess PTP. Other elements in the network treat PTP messages just like any other layer 2 (L2) or layer 3 (L3) packet. Recall from "Chapter 8. ITU-T Timing Recommendations", that the ITU-T has defined network limits for phase/time synchronization based on both these use cases: G.8271.1 for the FTS case and G.8271.2 for PTS. There is also a recommended PTP telecom profile to support each of those use cases: G.8275.1, PTP over Ethernet (PTPoE) for FTS; and G.8275.2, PTP over IP (PTPoIP) for 11.1.1 Use Cases and Technology The most fundamental question to answer before designing a timing solution for a mobile network is, "What sort of mobile network is this design for?" The answer to that question should help the operator and the timing engineer decide upon the form of timing that is needed and the degree of accuracy it must deliver. The generation of mobile technology, the services enabled, the radio type, and the architecture of the RAN will determine whether only frequency is needed or whether the combined frequency, phase, and time synchronization is required. Chapter 10 covered the various flavors of LTE, LTE-A, and 5G networks and the type of timing they need in more detail. To summarize the basics, here are a few general rules (they all require frequency): All time division duplex (TDD) radios require phase/time. 5G radio or New Radi