This Recommendation is a framework Recommendation for phase and time clocks for devices used in synchronizing network equipment that operate in the network architecture defined in [ITU-T G.8271]@ [ITU-T G.8275] and the ITU-T G.8271.x-series of Recommendations. This Recommendation serves as a framework for phase and time clocks defined in the ITU-T G.8273.x-series. It includes annexes with detailed testing and measurement methods of phase and time clocks.