363-206-285 Detailed Level Procedure: DLP-513
Issue 2, February 2000 Page 3 of 20
DDM-2000 OC-3 MULTIPLEXER
BBF2 TGS
7.
NOTE:
The timing mode of all nodes should be checked before the system is
placed in service. Improper timing modes may cause the system to act
unpredictably or cause a service interruption (for example, if all nodes are
set to line timed mode).
NOTE:
The BBF2 TGS timing mode may be provisioned as
Free Running
,
DS1
External
,or
Line Timed
. In free-running mode, the BBF2 TGS gets timing
from an oscillator on the BBF2 TGS. In external timing, the BBF2 TGS
gets timing from an external DS1 reference input. In line-timed mode, the
BBF2 TGS gets timing from an OLIU from a reference clock recovered
fromthereceivedOC-3lineratesignal.
NOTE:
Table B depicts all the possible timing topologies which can be
encountered on adjacent network elements (NE) with some comments or
cautionary notes on their application.
Table B – 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
inasystem,theNE2systemwillattempttoswitchto
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.
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