Path: utzoo!attcan!uunet!decwrl!elroy.jpl.nasa.gov!usc!samsung!xylogics!bu.edu!bu-it!kwe
From: kwe@bu-it.bu.edu (Kent England)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Serious Routing Problems
Message-ID: <61787@bu.edu.bu.edu>
Date: 1 Aug 90 16:24:23 GMT
References: <9007311833.AA22548@nsipo.arc.nasa.gov> <61620@bu.edu.bu.edu>
Sender: news@bu.edu.bu.edu
Reply-To: kwe@bu-it.bu.edu (Kent England)
Organization: Boston University
Lines: 28

In article <9007311833.AA22548@nsipo.arc.nasa.gov>, 
medin@NSIPO.ARC.NASA.GOV ("Milo S. Medin", NASA ARC NSI Project Office) writes:
> 
> Kent, I'm a little confused here.  Line flapping should be fixed by
> having hystersis in the up/down line protocol.

	Yes, I was just wanting to point out that using the cisco
recommended settings for keepalive and update/holddown timers, a
20 second line outage will stimulate a route lossage of 4.5 minutes.

	I'm not faulting cisco for this, they have to recommend
*something* to their customers without knowing all details of
a particular situation.  There are trade-offs that I won't elaborate.
As I said, Chuck Hedrick has already posted details on
issues involved in shortening timers in IGRP for the bold-hearted
network managers out there that would like faster convergence.

> Because link-state protocols flood the topology information, and then
> the routers recompute the routing tables more or less in parallel,
> convergence can happen very quickly, and you also can do without
> the complicated holddowns and such needed to prevent route looping
> in vector-distance protocols.

	Right, I was just looking for demonstrated corroboration.
I must be belaboring the obvious, so let's move on to other topics
like expanded network addressing or open routing or S.I.N/dual IS-IS.

	--Kent