Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 532)

502 Multi-Service IronWare Switching Configuration Guide
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Tuning MRP timers
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Example 3:
Preforwarding time = 10000ms
Hello time = 5000ms
Time to forwarding = 2 x preforwarding time = 20000ms
Post recovery mac table flush time = 3 x hello time = 15000ms
Full connectivity = Time to forwarding + Post recovery mac table flush time = 35000ms = 35secs
It can therefore be seen that the hello time should not be changed on the network unless there is
evidence of regular misses on the ring. Time to traverse the ring can be determined by running
MRP diagnostics.
Effect of the scale timer
Changing the scale timer has a significant effect on the operation of MRP and should be
considered for very high performance low latency networks where a very rapid failure detection and
recovery mode is required. Achieving this rapid detection and recovery requires very stable high
speed environments to prevent a high level of unnecessary topology changes in the environment.
The effect of setting the scale timer is that the time taken to move from blocking to preforwarding
and preforwarding to forwarding is (preforwarding value – the hello time). This is a significant
change to the operation of MRP in the default state which has been described in the previous
section.
Note: When setting the timer at the CLI the actual value used will be exactly half of the input value.
The examples that follow assume the corrected value.
Consider a break in the network that does not generate alarm RHP’s
Example 1(default values):
Preforwarding time = 300ms
Hello time = 100ms
Time to forwarding = preforwarding time – hello time = 200ms
Post recovery mac table flush time = 3 x hello time = 300ms
Full connectivity = Time to forwarding + Post recovery mac table flush time = 500ms = 0.5secs
Example 2:
Preforwarding time = 100ms
Hello time = 50ms
Time to forwarding = preforwarding time – hello time = 50ms
Post recovery mac table flush time = 3 x hello time = 150ms
Full connectivity = Time to forwarding + Post recovery mac table flush time = 200ms = 0.2secs