This Recommendation specifies the maximum network limits of phase and time error that shall not be exceeded. It specifies the minimum equipment tolerance to phase and time error that shall be provided at the boundary of packet networks at phase and time synchronization interfaces. It also outlines the minimum requirements for the synchronization function of network elements. This Recommendation addresses the case of time and phase distribution across a network with packet-based method with full timing support to the protocol level from the network. The physical layer (PHY) that is relevant to this specification is the Ethernet media type as defined in [IEEE 802.3-2015].