This Recommendation defines synchronization aspects in packet networks. It specifies the maximum network limits of jitter and wander that shall not be exceeded. It specifies the minimum equipment tolerance to jitter and wander that shall be provided at the boundary of these packet networks at TDM and synchronization interfaces. It also outlines the minimum requirements for the synchronization function of network elements. In particular@ two main issues are addressed in this Recommendation: the distribution of a synchronization network clock signal over a packet network (PNT domain)@ and the distribution of a service clock signal over a packet network (CES domain). NOTE ?C The application of the transport of SDH signals over packet networks is only partly covered and some aspects are for further study. The packet networks that are in the scope of this Recommendation are currently limited to the following scenarios: ?Ethernet [IEEE 802.3]@ [IEEE 802.1D]@ [IEEE 802.1ad]@ [IEEE 802.1Q] and [b-IEEE P802.1Qay] ?MPLS [IETF RFC 3031] and [ITU-T G.8110] ?T-MPLS [ITU-T G.8110.1] ? IP [IETF RFC 791] and [IETF RFC 2460] The physical layer that is relevant to this Recommendation is the Ethernet media types as defined in [IEEE 802.3]. Other physical layers can be relevant and may be addressed in a future version of this Recommendation.