A clocking mechanism with improved fault tolerance for synchronizing a distributed processing system includes a plurality of distributed clock sources. Each clock source may operate as a master clock for synchronizing the operations of the entire system or as a slave to an external clock while remaining available, in a backup capacity, to operate as a master clock in the event of a failure in the previous master clock. A clock selection mechanism is provided in each distributed switch element for selecting the best clock available to each switch element for synchronization. A failure recovery mechanism is provided with fast and automatic recovery in the event of a failure in a master clock. A data extraction mechanism is also provided capable of sampling a bit stream that is not phase-aligned, even in the presence of timing jitter and pulse width distortion, and having provisions for detecting a bit slip.