scope:

This Recommendation specifies minimum requirements for time and phase synchronization devices used in synchronizing network equipment, which operates in the network architecture as defined in [ITU-T G.8271] and [ITU-T G.8275]. It supports time and/or phase synchronization distribution for packet-based networks. The telecom transparent clock (T-TC) must be operating in end-to-end transparent clock (TC) mode.

This Recommendation assumes operation within the framework specified in [ITU-T G.8273], and that the physical layer reference chain behaviors given in [ITU-T G.803] and [ITU-T G.8261] are followed. It is also assumed that the network limits given in [ITU-T G.8271.1] are met and that the profile given in [ITU-T G.8275.1] is applied.

This Recommendation allows for proper network operation when a network equipment clock is timed from another network equipment clock or a higher quality clock.

This Recommendation defines the minimum requirements for transparent clocks. These requirements apply under normal environmental conditions specified for the equipment.

Guidelines for testing are described in Appendix I.

This version of the Recommendation focuses on syntonized T-TCs with frequency reference provided by the physical layer based on ITU-T G.8262 EEC-Option 1 (and ITU-T G.813 SEC-Option 1 as the requirements are identical). ITU-T G.8262 EEC-Option 2 and ITU-T G.813 SEC-Option 2 are for further study. A T-TC without a frequency reference provided by the physical layer is for further study.

NOTE - This Recommendation does not modify the physical layer reference chain behaviour, according to [ITU-T G.803] and [ITU-T G.8261]. This Recommendation does not exclude the use of other physical layer clocks (e.g., ITU-T G.812 Type I) within the frequency transport network. The equipment specification of a T-TC assisted by a physical layer equipment clock, other than ITU-T G.8262 Option 1, such as ITU-T G.812 Type I, is for further study.