unctions for frequency synchronization based on the physical layer." ITU-T Recommendation, 2020. https://handle.itu.int/11.1002/1000/14240 "G.813: Timing characteristics of SDH equipment slave clocks (SEC)." ITU-T Recommendation, 2003, with Corrigenda 1 (2005) and Corrigenda 2 (2016). https://handle.itu.int/11.1002/1000/13084 "G.823: The control of jitter and wander within digital networks which are based on the 2048 kbit/s hier- archy." ITU-T Recommendation, 2000. https://www.itu.int/rec/T-REC-G.823-200003-I/en "G.8260: Definitions and terminology for synchronization in packet networks." ITU-T Recommendation, 2020. https://handle.itu.int/11.1002/1000/14206 "G.8261: Timing and synchronization aspects in packet networks." ITU-T Recommendation, Amendment 2, 2020. http://handle.itu.int/11.1002/1000/1420 "G.8261.1: Packet delay variation network limits applicable to packet-based methods (Frequency synchroniz- ation)." ITU-T Recommendation, Amendment 1, 2014. https://handle.itu.int/11.1002/1000/12190 "G.8262: Timing characteristics of synchronous equipment slave clock." ITU-T Recommendation, Amend- ment 1, 2020. https://handle.itu.int/11.1002/1000/14208 "G.8262.1: Timing characteristics of enhanced synchronous equipment slave clock." ITU-T Recommenda- tion, Amendment 1, 2019. https://handle.itu.int/11.1002/1000/14011 "G.8263: Timing characteristics of packet-based equipment clocks." ITU-T Recommendation, 2017. https://handle.itu.int/11.1002/1000/13320 "G.8265.1: Precision time protocol telecom profile for frequency synchronization." ITU-T Recommendation, Amendment 1, 2019. https://handle.itu.int/11.1002/1000/12193 "G.8271: Time and phase synchronization aspects of telecommunication networks." ITU-T Recommenda- tion, 2020. https://handle.itu.int/11.1002/1000/14209 "G.8271.1: Network limits for packet time synchronization with full timing support from the network." ITU- T Recommendation, Amendment 1, 2020. https://handle.itu.int/11.1002/1000/14210 "G.8271.2: Network limits for time synchronization in packet networks wit