RE: [pim] BSR update

["Venu Hemige" <venu.hemige at alcatel.com>]

John,

> 
> Yes, IFF one has not configured his network for redundancy.
> If I sound like a broken record, sorry.  I just want to be sure
> that forwarding a triggered BSM is not an option.  The cases it
> fixes are few while the potential for causing problems that we
> don't currently understand are many.
>

I agree the cases fixed by forwarding a triggered BSM are few. I also
agree that in a network configured for redundancy AND where there are
not multiple routers rebooting, there should be no issue with not
forwarding a triggered BSM. But I am yet to hear a case where it
actually causes a problem. 

The only example I have seen is Stig's example where there was a long
non-preferred path between A and C1. In that example, I would think
router B will have stale information even after the triggered (but not
forwarded) BSMs. I guess we are not concerned about fixing that (and
that scenario had some redundancy). If the triggered BSMs were also
forwarded, then even if there were scenarios where certain routers had
stale data, they should only be momentary since the BSM triggered by
router A to R1 should be forwarded to every router in the network.

Another problem I see with Stig's original example: Since router B has a
stale RP-SET even after R1 and R2 come up, it may or may not matter much
that all the other routers have the correct RP-SET. If the (*,G) Joins
have to go through router B, then we are not achieving the end objective
of faster convergence of multicast trees anyway. I believe the goal
should be to get the entire network to a consistent RP-SET as soon as
possible.

-Venu




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