363-206-295
Transmission and Synchronization Interfaces
5-20 Issue 1 December 1997
Consider the access ring network in Figure 5-8. Under normal operation, the ring
has one DDM-2000 Multiplexer externally timed and the others line-timed in the
counterclockwise direction. If a fiber failure occurs between the first two
DDM-2000 Multiplexers, the automatic synchronization reconfiguration feature will
cause the DDM-2000 Multiplexers to change their line-timed directions to
clockwise. The result is that the ring is again operating synchronously. The ring
already provides self-healing restoration of the traffic, so it is especially important
to maintain synchronous operation during this type of failure to prevent service
degradation due to increased jitter and wander.
Figure 5-8. Synchronization Reconfiguration — Access Ring
PRS
Traceable
BITS
Normal
DDM-2000
DDM-2000
DDM-2000
PRS
Traceable
BITS
DDM-2000
DDM-2000
Sync Flow
DDM-2000 DDM-2000 DDM-2000
Failure/Reconfiguration
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