The clock to drive TDM ports can be recovered from a TDM pseudowire using the Adaptive Clock Recovery (ACR) algorithm.
ACR recovers the TDM service clock based on the packet arrival rate and typically employed when no other clock is available in the network to achieve synchronization.
The adaptive clock recovery uses techniques to filter out the Packet Delay Variations (PDV) introduced in the packet stream by the PSN and recovers the TDM service clock.
The Wander and the Jitter budgets are defined by G.8261 deployment cases (case 1-a, 2-a, 2-b). Network deployments that differ from above cases require deriving the budgets based on the deployment model.
Limitations:
Only one TDM port can be timed using the clock recovered from the pseudowire.
The pseudowire can only time the TDM port that is attached as a service circuit.
The clock recovered from the pseudowire cannot be used as a system clock source for synchronization. This implies that the pseudowire recovered clock cannot be carried through Sync-E or PTP or BITS.
When configuring a SAToP pseudowire for clock recovery, the TDM payload bytes carried in pseudowire should be a multiple of 32.
Adaptive clock recovery cannot filter out the low frequency wander introduced by the ‘beating effect‘.
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