Lucent DDM-2000 OC-3 User And Service Manual page 893

DLP-523
: Detailed Level Procedure
Page 11 of 30
Table E – BBF2B/BBF2C TGS/BBF4 TG3 Synchronization Provisioning
Topologies (Contd)
NE 1
External - Sync Out
External - Mult
External - Mult
NE 2
Line Timing - Sync Out
External - Mult
External - Sync Out
DDM-2000 OC-3 M
Issue 2, February 2000
Application Comments
Caution! This topology might create a timing
loop. In this topology the NE provisioned for
Line Timing will derive its timing and that of the
DS1 output reference from the NE provisioned
for External - Sync Out timing thus operating
synchronously with that respective NE. The
NE provisioned for External - Sync Out should
be reprovisioned for External - Mult to prevent
the timing loop existing in the actual
provisioning. If Synchronization Messaging is
enabled on both NE's, the DS1 output
reference on NE 1 will carry DS1 AIS and NE
2 will derive its timing and that of the DS1
output port from NE 1. If automatic
synchronization reconfiguration is supported
and enabled in a system, both NEs will
attempt to break the potential timing loop. NE
1 will attempt to break the loop by inserting
DS1 AIS on its DS1 output port. NE 2 will
attempt to switch to another line timing source,
if available, to prevent the timing loop.
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 bay to conserve ports on the BITS.
This topology is used to distribute network
timing to a target location from a location with
access to a synchronization reference. The
NE provisioned for External - Mult, is providing
timing to the NE provisioned for External -
Sync Out, which in turn generates a DS1
output reference regenerated from the optical
interface shared by both NE's. This DS1
output is used to provide a synchronization
reference to a BITS.
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