cture and requirements for packet-based frequency distribution in telecom networks. It briefly describes examples of packet-based frequency distribution such as NTP and PTP. From the scope of the recommendation: This Recommendation describes the general architecture of frequency distribution using packet-based methods. The requirements and architecture form a base for the specification of other functionality needed to achieve packet-based frequency distribution in a carrier en- vironment. The architecture described covers the case where protocol interaction is at the end points of the network only, between a packet master clock and a packet slave clock. This recommendation therefore does not cover details of architectures where devices between the packet master and packet slave clocks participate in the timing solution. Included is discussion on these topics: Requirements for packet timing Architecture of packet-based frequency distribution, including redundancy and network partitioning Packet-based protocols for frequency distribution: PTP and NTP Security aspects G.8265 is informative and easy to read. More details on frequency distribution using packet timing are also provided in Appendix XII, "Basic principles of timing over packet networks" of G.8261, although it is a more mathematical treatment the subject. Link to recommendation: https://handle.itu.int/11.1002/1000/10910 G.8273: Framework of Phase and Time Clocks ITU-T G.8273 is a framework recommendation for phase and time clocks using packet-based meth- ods for transferring time/phase. This means that it puts the clock recommendations (the G.8273.x series) in perspective but does not contain a large amount of content about them. From the scope of the recommendation: 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 Recom- mendations. This Recommendation serves as 