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RE: I-D ACTION:draft-zinin-microloop-analysis-00.txt

Subject: RE: I-D ACTION:draft-zinin-microloop-analysis-00.txt
From: "Don Fedyk"
Date: Fri, 15 Oct 2004 14:17:15 -0400
Hi Alex

In the draft:

>Type C:
> Installation of the new route is delayed by time DELAY_TYPEC.
> Until then, the router continues to use its old next-hops.

>DELAY_TYPEB and DELAY_TYPEC are two configurable constants. They
>should be configured with the same value on all routers in the net-
>work and such that following equation is true:
>DELAY_TYPEB > DELAY_TYPEC > fault-propagation-time
>where fault-propagation-time is the time it is expected to take
>routers in the network to propagate new link-state information, cal-
>culate the new SPT, check the safety condition of the neighbors, and
>install required FIB entries.
>Suggested default values for DELAY_TYPEB and DELAY_TYPEC are 4 and 2
>seconds correspondingly.

- I'm O.K. with DELAY_TYPEB timers at this length. 
- But I think DELAY_TYPEC > time for an immediate neighbor to install an
This value is probably not very long (in the order of 100msec). In my
understanding Delay_TYPEC starts ticking very close to the time that updates
are being sent from C to B (In the Figure 1 the immediate neighbor).   Once
B has its alternates in place, C can forward to B with no issues.  

So I suggest: 

DELAY_TYPEB > fault-propagation-time 
DELAY_TYPEC > time for an immediate neighbor to install an alternate.  I
suppose one could then ask: Could I live with no timer on C?  


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