Lucent Technologies FiberReach DDM-2000 User Manual

363-206-305
Transmission and Synchronization
5-18
Issue 3 June 2000
the other DDM-2000 FiberReach Multiplexers are line-timed in a counterclockwise
direction. The sync quality unknown (SQU) message is sent to indicate where
timing is traceable to an external BITS and where it is valid to be used. The timing
looped back (TLB) message is sent on the interface that is being used as the line
timing reference and, thus, where using that timing would create a timing loop.
Synchronization messaging and automatic synchronization have both been
enabled for this network.
In Figure 5-8b, a fiber has been cut between sites A and B. Immediately, the DDM-
2000 FiberReach Multiplexer at site B enters holdover and sends out the internal
clock (IC) message to site C. The DDM-2000 FiberReach Multiplexer at site B
cannot switch to line time from site C because it is receiving the TLB message on
that interface.
Figure 5-8. Synchronization Reconfiguration — Access Ring (Sheet 1 of 3)
PRS
Traceable
BITS
PRS
Traceable
BITS
Sync Flow
a) Before Failure
SQU
Site A
Site B
Site C
SQU
SQU
SQU
TLB
TLB
TLB
SQU
SQU
Site D
Site C
SQU
SQU
TLB
TLB
IC
b) Failure Occurs,
Site B Changes Message
DDM-2000
FiberReach
DDM-2000
FiberReach
Site B
DDM-2000
FiberReach
DDM-2000
FiberReach
DDM-2000
FiberReach
Site D
DDM-2000
FiberReach
DDM-2000
OC-3 or
SLC®-2000
ARM Shelf
DDM-2000
OC-3 or
SLC-2000
ARM Shelf
Site A
SQU
tpa 843629/01

Lucent Technologies FiberReach DDM-2000 Specifications

General

Brand	Lucent Technologies
Model	FiberReach DDM-2000
Category	Multiplexer
Language	English