t the DU site (one could be +100, and the other be -100). The offset is unlikely to be that large, since both receivers are quite close to each other and, most likely, are tracking the same satellites under very similar atmospheric conditions. However, it is theoretically possible that they can diverge by up to 200 ns. According to vendors of GNSS chipsets, a more realistic number might be 30-40% of that, but there is no guarantee. This means that the requirement for a phase alignment of +65 ns or +130 ns may not be possible with the GNSS at each site, simply because the Class A PRTC is not accurate enough. In that case, it may be better to use PTP than separate GNSS receivers. It is for this reason that the ITU-T defined a new class of PRTC, known as the Class B PRTC, that offers an accuracy of 40 ns rather than 100 ns. To achieve that, the vendors are adopting techniques to improve the recovered accur- acy from the satellite systems, including dual-band and multi-constellation receivers. For larger networks, an increasing number of hops will introduce more time error than separate GNSS receivers, and using a PTP-aware FTS design may not meet the very tight CRAN packet FH timing requirements. Depending on the topology and budget, the better solution might be GNSS (where there are more hops in the FH) or PTP (where there are fewer). The exact dividing line will depend on the level of T-BC performance of the nodes and the timing error in the transport system. It is this exact scenario that led to the adoption of the Class C accuracy requirement for the T-BC in G.8273.2. Note that throughout this chapter, the term SyncE is used to refer to both the SyncE (G.8262) and eSyncE (G.8262.1) recommendations for physical transport of frequency in a packet network. The use of SyncE is widely accepted and the adoption of eSyncE is gaining momentum; within a couple of years, eSyncE will be the default option. Currently, the requirement to use eSyncE over SyncE is most important in the FH networks in combination with Class C T