radio equipment may embed some device, such as a "dumb" layer 2 switch that understands no PTP or SyncE. Because that device is embedded into a standalone piece of equipment, a cell site router might be required to turn the G.8275.1 signal it is receiving into G.8275.2 (PTPoIP) to "hop over" the PTP-unaware L2 switch. Another case might be that the PTP slave clock in the radio itself supports only G.8275.2 and not G.8275.1. Figure 11-10 illustrates what a typical deployment of this nature looks like. The timing signals may be carried from the PRTC+T-GM using the "best in class" G.8275.1 with SyncE and terminate at the last T-BC before the PTP-unaware segment begins. That T-BC performs a profile interworking function that terminates the G.8275.1 message flow and initiates a G.8275.2 flow to cross the PTP- unaware network. This capability is also referred to as multi-profile support because it features the ability to config- ure a T-BC with a different profile on each PTP port. PTP-aware PTP-aware PTP-unaware network network network PRTC / T-GM G.8275.2 Profile G.8275.2 slave clock G.8275.1 SyncE interworking Figure 11-10 Mixed Telecom Profile Deployment with Profile Interworking Profile interworking is not as simple as it sounds, although it is somewhat easier between the G.8275.1 and G.8275.2 profiles because they have a lot of commonality in the way they work and the PTP features they support. The section "Profiles" in Chapter 7 covers the ways that different PTP profiles vary and explains how complex it can be to do interworking between other combina- tions of PTP profiles. For example, there are different fields that must be translated as they are received on one slave port and transmitted out on another master port in a different profile. This is particularly the case for the fields in the Announce message, which require translation of values that depend on the profile. The most obvious field that needs translation is the domain number. Since the range of domain values for G.8275.1 is between 24-43, and the r