 important recommendations for many deployments of accurate phase and time synchronization carried over a packet network. It specifies the minimum require- ments for T-BC and T-TSC time and phase clocks when deployed with full timing support from the network. From the scope of the recommendation: 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 Recom- mendation focuses on the case of physical layer frequency support. Requirements related to the case without physical layer frequency support (i.e., the PTP only case) are for further study. This Recommendation includes noise generation, noise tolerance, noise transfer and transi- ent response for telecom boundary clocks and telecom time slave clocks. Note that the recommendation currently only applies to the case with "physical frequency support," meaning where PTP is deployed in combination with some physical method (commonly SyncE) for frequency transport. This recommendation includes the following main topics and appendixes: Physical layer frequency performance requirements. T-BC performance requirements with full timing support. It includes parameters for time error noise generation, constant time error (cTE), filtered dynamic time error (dTE), relative time er- ror (rTE), noise tolerance, and noise transfer. Transient response and holdover performance. Phase and time as well as frequency interfaces, defining the characteristics of the interfaces used to carry physical timing signals. There are some increased requirements for class C and D clocks. Appendix III, "Background to performance requirements of the T-BC and T-TSC" Appendix V, "Performance estimation for cascaded media converters acting as T-BCs and for T- BC chains" Appendix VIII, "Measurement of Relative Time Error between two T-BC output ports" (defines two new relative time error generation limits