This Recommendation defines time and phase synchronization aspects in packet networks. It specifies the suitable methods to distribute the reference timing signals that can be used to recover the phase synchronization and/or time synchronization according to the required quality. It also specifies the relevant time and phase synchronization interfaces and related performance. The packet networks that are in the scope of this Recommendation are currently limited to the following scenarios: ? Ethernet ([IEEE 802.3] and [IEEE 802.1Q]). ? MPLS ([IETF RFC 3031] and [ITU-T G.8110]). ? IP ([IETF RFC 791] and [RFC 2460]). The physical layers that are relevant to this specification are the Ethernet media types@ as defined in [IEEE 802.3]