Using an IEEE 802.1AS network as a distributed IEEE 1588 boundary, ordinary, or transparent clock

IEEE 802.1AS includes a very specific profile of IEEE 1588 that only runs at layer 2 over networks that follow the IEEE 802 architecture. It has some significant performance and scalability advantages, but at the cost of not allowing non-PTP-aware devices. This paper describes how a network having a common source of time can act as a distributed IEEE 1588 boundary, ordinary, or transparent clock, allowing the network to transport synchronization between portions of an IEEE 1588 network domain, and do this for any number of domains simultaneously. The network that acts as a distributed clock can be a PTP network supporting a profile that is different from that of the domains whose timing it is transporting. As one example, an IEEE 802.1AS network can act as a distributed IEEE 1588 boundary, ordinary, or transparent clock. As part of the discussion, the paper also shows that an IEEE 1588 boundary clock and peer-to-peer transparent clock are functionally equivalent in the manner in which they transport synchronization, and that the principal difference between the two is that the former invokes a best master clock algorithm (either default or alternate) and implements the full PTP state machine, while the latter does not. The concepts of distributed BC, TC, and OC, and the equivalence of the BC and peer-to-peer TC may be considered a new way of looking at the transport of synchronization in a network based on IEEE 1588.