Nortel Networks OPTera Metro 3500 - Manual (Page 193)

Operation, administration, and maintenance (OAM) features 2-155
Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Tributary line timing
Tributary line timing is shown in Figure 2-49 on page 2-155 , example (d).
When using tributary line timing, a network element derives timing from a
received synchronous tributary signal. This signal is used in network elements
to synchronize the outgoing transport signals in all directions, and the
synchronous tributaries terminated by the network element. Sources of
tributary timing are OC-3, OC-3x4, OC-12, OC-48, DS1, and EC-1 facilities.
When the network element timing mode is set to Line Timing, the primary and
secondary timing references can be provisioned as OC-3, OC-12, OC-48, DS1,
and EC-1 facilities.
Note: DS1 facilities connected to a DSM module cannot be used as a
timing reference.
Figure 2-49
Flow of synchronization timing signals
EX1513p
Timing sources and timing distribution
The network elements in an OPTera Metro 3500 system can be integrated into
a synchronization timing architecture. This architecture is a timing reference
hierarchy that allows all network element timing to be referenced to an
accurate common timing source.
NE
NE NE
(b) External timing
(d) Tributary line timing
Clock
(a) Internal timing
NE
BITS Stratum-3
or better
(c) Transport line timing
VTX-series or
STX Module
Legend
= Primary Data flow
= Tributary Data flow
= Synchronization Timing
= External Synchronization Reference
VTX-series or
STX Module