Nortel Networks OPTera Metro 3500 - Manual (Page 50)

2-12 Operation, administration, and maintenance (OAM) features
OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Lockout of working: prevents a protection switch of the working line
to the protection line.
Lockout of protection: prevents any of the channels from switching to
the protection line.
Automatically initiated BLSR switching requests
• Signal fail (SF)
— SF is a hard failure caused by a Loss of Signal, Loss of Frame, a line
BER exceeding a preselected threshold, a line AIS, or some other
protectable hard failure. All channels with the SF condition are
protected using the ring switch.
• Signal degrade (SD)
— SD is a soft failure caused by a BER exceeding a preselected threshold.
It can be used to detect gradual degradation of service to perform
preventive maintenance. All degraded lines are protected using the ring
switch.
• Reverse request (RR)
— RR is transmitted to the tail-end network element on the Short Path as
an acknowledgement for receiving the Short Path ring bridge request.
• Wait to restore (WTR)
— WTR is issued when working channels meet the restoral threshold after
an SD or SF condition. This request is used to maintain the current state
during the WTR period unless it is pre-empted by a higher priority
request.
When a failure occurs in the ring, the ring switches are performed by the nodes
immediately adjacent to the failed segment. It should be noted that a failed
segment may be a single span or many spans with multiple nodes.
For a 2-Fiber BLSR operating at an OC-48 rate, time slot numbers 1 through
24 at the multiplex input are reserved for working channels. Time slot number
‘X’ of the first fiber is protected using time slot number ‘X + 24’ of the second
fiber in the opposite direction, where X is an integer between 1 and 24.
Similarly, for a 2-Fiber BLSR operating at an OC-192 rate, time slot numbers
1 through 96 at the multiplex input are reserved for working channels. Time
slot number ‘X’ of the first fiber is protected using time slot number ‘X + 96’
of the second fiber in the opposite direction, where X is an integer between 1
and 96.
’Infinite wait-to-restore’ parameter
OPTera Metro 3500 allows users to provision an infinite wait-to-restore period
in BLSR-protected optical interfaces. This effectively allows users to
provision BLSRs to autonomously switch non-revertively.