SyncE (Synchronous Ethernet)
SyncE is a physical layer based synchronization implementation for packet networks requiring frequency synchronization. SyncE was standardized by the ITU-T, in cooperation with IEEE, as three recommendations:
 1. ITU-T Rec. G.8261 that defines aspects about the architecture and the wander performance of SyncE networks
 2. ITU-T Rec. G.8262 that specifies Synchronous Ethernet clocks for SyncE
 3. ITU-T Rec. G.8264 that describes the specification of Ethernet Synchronization Messaging Channel (ESMC)