 It is not helpful that the acronym SEC is reused in that way, but you need to be aware of it. Some older recommendations, such as G.813, will likely stay with the definition of SEC meaning the SDH equipment clock, whereas others (G.781 and G.8261, for example) use the new term because they apply across the different transport types. G.8262: Timing Characteristics of a Synchronous Equipment Slave Clock ITU-T G.8262 defines the Ethernet equipment clock for SyncE (or in newer language, the Ethernet version of the SEC). From the scope of the recommendation: Recommendation ITU-T G.8262 outlines requirements for timing devices used in synchron- izing network equipment that uses the physical layer to deliver frequency synchronization. This Recommendation defines the requirements for clocks, e.g., bandwidth, frequency ac- curacy, holdover and noise generation. This is the network clock in a packet network (for example, in a router that supports SyncE) that is equivalent to the SEC clock of G.813 (for physical/TDM). You should see that the limits are equi- valent, at least for Option I networks (based on E1/SDH). This recommendation includes the following main topics and appendixes: Frequency accuracy for an EEC in Option I and Option II networks Pull-in, hold-in, and pull-out ranges for both options Noise generation, noise tolerance, and noise transfer Transient response and holdover performance Synchronization input and output interfaces Appendix II, "Relationship between requirements contained in this Recommendation and other key synchronization-related Recommendations" Appendix III, "List of Ethernet interfaces applicable to synchronous Ethernet" Appendix IV, "Considerations related to synchronous Ethernet over 1000BASE-T and 10GBASE-T" The appendixes are quite important to understand, especially III and IV. If you are using older and slower Ethernet technologies in your network, do not assume your network will automatically sup- port SyncE. You may also need to address some issues when deploying SyncE over copper-ba