Cisco 15327 - Manual (Page 441)

26-9
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 26 Configuring IEEE 802.17b Resilient Packet Ring
Configuring the Hold-off Timer
Figure 26-5 Each RPR-IEEE Node Responding to a Protection Event by Steering
You can modify many of the RPR-IEEE protection characteristics with the procedures in the following
sections.
Configuring the Hold-off Timer
You can delay the protection response to a failure event, such as a signal failure or signal degradation,
with the hold-off timer. When spans fail, the RPR protection switch may be triggered either by the
SONET/SDH error, or by RPR keepalive failure, whichever is detected first. The RPR protection switch
can be delayed by changing the Hold-off timer and the RPR keepalive-timer. These should be configured
according to the type of circuit
• If the TDM circuit is unprotected, then both these timers should be left at their default values. No
extra configuration is required in this case.
• When the TDM circuit is protected (e.g., path protection or BLSR), the RPR protection switch
should be delayed till the protection-switch at the TDM level has finished.
– For example : If it takes 60ms for the TDM protection switch to complete. Then both the hold
off timer and the RPR keepalive timer must be configured higher than 60 milliseconds. If either
of these timers is left at its default value, then it will trigger the RPR protection before TDM
protection is over.
Caution It TDM protection is configured along with RPR, and if the RPR protection switch kicks in before the
TDM protection switch over is complete, the system behavior is unpredictable/unstable.
Ringlet 1 (east)
Ringlet 0 (west)
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fiber break
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