Subject: Re: MPLS and IS-IS

From: "J. Noel Chiappa" <[email-masked]>
Date: Wed, 17 May 2000 17:14:30 -0400

> From: Curtis Villamizar <[email-masked]>

    > one timer for a one big ISIS-LSP is much friendlier to naive timer
    > implementations (such as linked lists of timer events) than a timer
    > for each OSPF-LSA.

Curtis, I seem to recall hearing that one protocol problem with OSPF, in
terms of scaling, was the way it "rolls over" the database slowly, to ensure
that any uncaught errors get flushed out. With the current routing table
sizes of 70K+ routes, and the relatively modest rollover time (which I think
is 30 minutes for the entire table, IIRC), that tends to cause a fairly high
update rate.

Of course, I don't think anyone (at the time these protocols were designed)
ever imagined in their wildest dreams (nightmares? :-) that they'd be
supporting routing tables with 70K+ entries, so it's not too surprising that
their are some scaling issues...

	Noel

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From: Dorian Kim <[email-masked]>
Date: Wed, 17 May 2000 17:20:20 -0400

> their are some scaling issues...

I doubt too many people's IGP is carrying 70+K routes. Most folks only
carry internal links and router loopbacks in their IGPs as this is the
only way to scale.

-dorian

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From: Dave Katz <[email-masked]>
Date: Wed, 17 May 2000 14:38:19 -0700 (PDT)

To my knowledge, the only people that have done this have not done it on
purpose.  It is quite educational to watch when it does happen.

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From: Dino Farinacci <[email-masked]>
Date: Wed, 17 May 2000 14:25:26 -0700

>> their are some scaling issues...

    Noel, no one in their right mind would carry 70K routes in their IGP. 
    For OSPF, it was a design goal to support this. For IS-IS, it was never
    intended to import OSI inter-domain routes into IS-IS. Yes, you can 
    configure many IS-IS implementations to do this, but no one would dare
    do it.

Dino