This Recommendation describes the general architecture of time and phase distribution using packet-based methods. This version of the Recommendation focuses on the distribution of time and phase using the standard for precision time protocol (PTP) [IEEE 1588]. The requirements and architecture form a base for the specification of other functionalities that are needed to achieve packet-based time and phase distribution in a carrier environment. The architecture described covers the case where protocol interaction is at all nodes, between a packet master clock and a packet slave clock or only a subset of the nodes between a packet master clock and a packet slave clock. Details of the necessary profiles are described in other Recommendations.