Control of Bit-Level Synchronization within a Distributed Digital PBX(8-13)

One of the most difficult functions to control on a distributed basis is the flow of timing and bit level synchronization. In a distributed PBX, in which all nodes derive their timing from a single node over the shortest path through the system, control is typically complex and requires a centralized dynamic data base of system status. Complex communication is generally required to perform synchronization protection switching and restoration, and synchronization reconfiguration. Such complexity is particularly important for PBX systems because of the expectation of minimal error rates within the PBX. When one or more nodes of a distributed system fail, a flood of messages to control the reconfiguration of timing flow generally result - the last thing an ailing system needs.