Nortel Networks 3500, NTRN10AN manual Protection hierarchy

Operation, administration, and maintenance (OAM) features 2-119

•Forced switch on working channel of a span. This switches traffic from the working channels on a span to the protection channels around the ring.

•Manual switch on a working channel of a span. This switches traffic from the working channels on a span to the protection channels around the ring.

In BLSR, squelching is the application of AIS-P to avoid misconnection when the source node or the destination node for connection is involved in a node failure, node isolation, or ring segmentation. Each node maintains a squelch table which holds the source and destination ID for each working connection that the node is terminating (adding/dropping) or passing through.

For BLSR configurations, Site Manager does not display squelch maps.

Protection hierarchy

Switch requests are not preempted. When a higher priority switch request is made, the lower priority switch request is dropped. If the higher priority switch request is released, the lower priority switch request is not reestablished.

Note: An exception to this is in the case of a Lockout of a working in a BLSR. The Lockout of the working optical interface pre-empts any pending forced or manual switches.

See Table 2-27for the protection request priority for circuit packs.

Table 2-27

Services protection priority

Circuit pack	Protection priority
DS1 (1:N, revertive) (see Note)	• Lockout
	• Forced
	• Autonomous (equipment failure)
	• Manual
DS3x3, DS3VTx12, DS3x12,	• Forced
DS3x12e, EC-1x3, EC-1x12, DSM	• Autonomous (equipment failure)
DS1x84 TM
	• Manual
(1+1 nonrevertive)
OC-3, OC-3x4, OC-12, OC-12x4,	• Forced
OC-48, OC-192 (UPSR, VT1.5,	• Autonomous (path failures)
STS-1, STS-3c, STS-12c, STS-24c,
	• Manual
STS-48c, path nonrevertive)

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