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ITU-T G.8273.2

2017 Edition, January 1, 2017

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Timing characteristics of telecom boundary clocks and telecom time slave clocks



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Description / Abstract:

This Recommendation specifies minimum requirements for time and phase synchronization devices used in synchronization network equipment that operates in the network architecture as defined in [ITU-T G.8271], [ITU-T G.8271.1] and [ITU-T G.8275]. It supports time and/or phase synchronization distribution for packet based networks.

This Recommendation allows for proper network operation for phase/time synchronization distribution when network equipment embedding a telecom boundary clock (T-BC) and telecom time slave clock (T-TSC) is timed from another T-BC or a telecom grandmaster (T-GM). The current version of this Recommendation addresses only the distribution of phase/time synchronization with the full timing support architecture defined in [ITU-T G.8275] and the related profile defined in [ITU-T G.8275.1]. The definition of a T-BC and the T-TSC for the future partial timing support architecture is for further study.

This Recommendation defines the minimum requirements for telecom boundary clocks and telecom time slave clocks in network elements. These requirements apply under the normal environmental conditions specified for the equipment. The current version of this Recommendation focuses on the case of physical layer frequency support. Requirements related to the case without physical layer frequency support (i.e., the pure PTP case) are for further study.

This Recommendation includes noise generation, noise tolerance, noise transfer and transient response for telecom boundary clocks and telecom time slave clocks.

This version of the Recommendation was developed based on the simulations done for time transport via precision time protocol (PTP) and frequency transport via [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.

The T-BC requirements are given in clauses 6 and 7 and the T-TSC requirements are given in annex C.

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-BC 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.