Protection Hierarchy - Nortel NTRN10AN Planning Manual

• 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 2-27
Table 2-27
Services protection priority
Circuit pack
DS1 (1:N, revertive) (see Note)
DS3x3, DS3VTx12, DS3x12,
DS3x12e, EC-1x3, EC-1x12, DSM
DS1x84 TM
(1+1 nonrevertive)
OC-3, OC-3x4, OC-12, OC-12x4,
OC-48, OC-192 (UPSR, VT1.5,
STS-1, STS-3c, STS-12c, STS-24c,
STS-48c, path nonrevertive)
Planning and Ordering Guide—Part 1 of 2 NTRN10AN
Operation, administration, and maintenance (OAM) features 2-119
for the protection request priority for circuit packs.
Protection priority
• Lockout
• Forced
• Autonomous (equipment failure)
• Manual
• Forced
• Autonomous (equipment failure)
• Manual
• Forced
• Autonomous (path failures)
• Manual
Rel 12.1 Standard Iss 1 Apr 2004