time and phase) from a timing source to slave clocks at a RAN base station (BS) site: Using a GNSS receiver at RAN sites where time/phase is required. In previous generations of radio, a GNSS receiver would use short-run cables to give physical timing signals (to carry phase, time, and frequency) to the radio, but current generations of equipment use PTP and SyncE for this purpose. Using a PTP-unaware network with a packet-based method based on PTP (G.8275.2) carried "over the top" from the MSP core to the RAN BS. Using a combination of Ethernet physical layer (SyncE) for links combined with a packet-based method based on PTP (G.8275.1) carried on an FTS network. 11.4.1 Technology Splits Chapter 10 provides extensive coverage of the technology splits for RAN deployments. This section is simply intended to show how the different technology splits influence the timing design. The ba- sic principle for RAN timing is that normally both the DU and RU need synchronization, but the CU does not (only time of day to simplify operations). Of course, the RAN and radio team from the MSP can clarify the details of what their implementation really requires. The higher levels of the radio stack tend to be housed in the CU, the middle layers in the DU, and the lower layers in the RU. The point of demarcation between the various levels is defined by the split option and numbered from 1 (high in the stack) to 8 (low in the stack). The CU/DU demarca- tion is normally based on an option 2 split, and the two functions are interconnected by what is called the F1 interface, carried over the MH network (third and fourth cases depicted in Figure 11- 12). The CU side of that split requires no phase synchronization, but the DU side does. For this reason, it makes sense to introduce the timing signals at the site of the DU because this is the first component in the RAN chain that requires it. You can place a PRTC and T-GM higher the network and carry the signals through the BH network, but the number of hops to the DU quickly consumes the p