Nortel Networks 3500, NTRN10AN manual Timing sources and timing distribution

Operation, administration, and maintenance (OAM) features 2-155

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
	BITS Stratum-3
		or better
NE	NE	VTX-series or
		STX Module
Clock
(a) Internal timing	(b) External timing
NE	NE	VTX-series or
		STX Module
(c) Transport line timing	(d) Tributary line timing
Legend
= Primary Data flow	= Synchronization Timing
= Tributary Data flow	= External Synchronization Reference

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.

Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004