363-206-285
Transmission and Synchronization Interfaces
5-34 Issue 3 June 2001
Table 5-2 summarizes the DDM-2000 OC-3 synchronization modes for the current
software release.
Synchronization Messaging 5
SONET synchronization messaging is used to communicate the quality of
subnetwork timing, internal timing status, and timing states throughout a
subnetwork. Transitions to and from holdover or between OC-N references, for
shelf timing, and to and from DS1 AIS, for the DS1 Output, are based on
synchronization messages received over the OC-N line from which the DDM-2000
system is extracting timing.
In ring networks with synchronization messaging, the TG circuit pack allows line
timing and automatic switching from either of the two ring optical interfaces or
function unit C.
The DDM-2000 OC-3 and OC-12 Multiplexers provide a synchronization
messaging feature to ensure the integrity of network synchronization during both
normal and abnormal conditions. Through the use of synchronization messaging,
the current quality of the timing source can be conveyed from one DDM-2000 OC-3
Multiplexer to the next.
NOTE:
If the DDM-2000 is used in a multi-vendor environment, certain
synchronization options may need to be exercised. If used to provide or
receive line-timing with a non-Lucent SONET multiplexer, the DDM-2000 S1
Byte synchronization messaging must be enabled. This allows the flow of
sync messages between the two SONET multiplexers.
This capability allows the DDM-2000 OC-3 and OC-12 Multiplexers to automatically
change their timing reference in order to always maintain the highest quality timing
Table 5-2. DDM-2000 OC-3 Synchronization
Application
Ring
R13.0
Free-Running X
Line Timing X
External Timing X
DS1 Sync Output X
Synchronization Messaging X
Line Timing from Fn-C X
Automatic Synchronization
Reconfiguration
X
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