ITU-T G.8273.2 (T-BC and T-TSC) One-Page Summary

Title: Timing characteristics of Telecom Boundary Clocks (T-BC) and Telecom Slave Clocks (T-TSC)


  • Clock specification for T-BC (boundary clock) and T-TSC (time slave clock) for full timing support architecture, including noise tolerance, noise generation, noise transfer, phase transients

  • Four clock types defined, classes A to D:

    • Class A intended for short chains (up to 10 clocks), to meet ±1.5µs overall requirement

    • Class B intended for long chains (up to 20 clocks) , to meet ±1.5µs overall requirement

    • Class C intended for long chains (up to 20 clocks), to meet ±130ns overall requirement

    • Class D intended for long chains, delivered over new interface types (e.g. FlexE, FlexO) with special provision for low-noise timing transmission


Key Contents

Noise Generation:

ParameterConditionsClass AClass BClass CClass D
Max |TE|Unfiltered, 1000s100ns70ns30ns-

0.1Hz low-pass filter,1000s

cTEAveraged over 1000s50ns20ns10ns-
dTEL MTIE0.1Hz low-pass filter, Const. temp, 1000s40ns40ns10ns-

0.1Hz low-pass filter, Var. temp, 10000s40ns40ns--
dTEL TDEV0.1Hz low-pass filter, Const. temp, 1000s4ns4ns2ns-
dTEH0.1Hz high-pass filter, Const. temp, 1000s70ns70ns--

Transfer Function:

Simplified Functional Model:

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