363-206-285 Detailed Level Procedure: DLP-503
Issue 2, February 2000 Page 2 of 10
DDM-2000 OC-3 MULTIPLEXER
Table A – BBF2 TGS Synchronization Provisioning Topologies
NE 1 NE 2 Application Comments
Free Running Free Running This topology is not supported. Both systems are operating
asynchronously from each other.
Free Running Line Timing This topology is allowed but results in having a SONET subnetwork
operating asynchronously with respect to other NE’s in the network.
The NE’s deriving timing off the NE provisioned for Free Running will be
synchronized to it but not to a PRS on the network. If automatic
synchronization reconfiguration is supported and enabled in a system,
the NE 2 system will attempt to switch to another better quality line
timing source, if available.
Free Running External - Mult This timing topology is not supported. The two network elements will be
operating asynchronously from each other.
External - Mult Line Timing This topology is used when one of the NE’s does not have access to an
external synchronous reference and needs to be synchronized to an NE
whose timing is traceable to a PRS. The NE provisioned for Line Timing
will derive its timing from the NE provisioned for External - Mult timing
thus operating synchronously with that respective NE. The NE
provisioned for External - Mult timing could use its DS1 output to
distribute its incoming DS1 timing reference to other shelves in the bay
to conserve ports on the BITS.
External - Mult External - Mult This topology is used when both NE’s have access to and are receiving
its timing from BITS clocks. The recommendation is to have these BITS
synchronized to references which are traceable to the same PRS. If
these guidelines are followed the subnetwork created by these two NE’s
would be operating synchronously. Note DDM-2000 systems are
designed to operate in pleisiochronous timing topologies. The DS1
output generated by each NE is regenerated from the input DS1 timing
reference and could be used to distribute this reference to other shelves
colocated in the same ba y to conserve ports on the BITS.
Line Timing Line Timing Caution! This topology creates a timing loop and it is not. supported.
The NE with access to an external timing reference traceable to a PRS,
if available, should be provisioned for External - Mult. If the reference
available is an optical reference provision to Line Timing with the proper
source using the set-sync command. If automatic synchronization
reconfiguration is supported and enabled in a system, both NEs will
attempt to switch to another line timing source, if available, to prevent a
timing loop.
Free Running Free Running This topology is not supported. Both systems are operating
asynchronously from each other.
Free Running Line Timing This topology is allowed but results in having a SONET subnetwork
operating asynchronously with respect to other NE’s in the network.
The NE’s deriving timing off the NE provisioned for Free Running will be
synchronized to it but not to a PRS on the network. If automatic
synchronization reconfiguration is supported and enabled in a system,
the NE 2 system will attempt to switch to another better quality line
timing source, if available.
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