AT&T NYC

alex at yuriev.com alex at yuriev.com
Tue Sep 3 12:33:17 UTC 2002


> > > > 
> > > > > > Has anybody mentioned the benefits of ISIS as an IGP to them.
> > > > > 
> > > > > Link-state protocols are evil, and when they break, they *really* break.
> > > > > I still do not see a compeling argument for not using BGP as your IGP.
> > > 
> > > Convergence time?
> > 
> > What is better - relatively long convergence time on affected routes or a
> > problem on unaffected route?  
> > 
> > Ask your customers. They do not care if someone else is having a problem.
> > They care that they dont. 
> 
> Do you run a decent sized network?

No, I have never touched a router in my life. 

> Convergence time in the order of that taken by BGP is not acceptable,
> things go crazy when traffic pours in and theres no routes to carry it.

This is a great blanked statement. What is convergence time?

> Other example, what about static dialup users, they dial up and wait a few
> minutes whilst their route is installed throughout BGP??

That is why their route is *nailed* via BGP to the router that *always*
provide connectivity to them. If they have to move, BGP injectors are your
friends. Takes seconds.

> > > > With link-state, one interface flap can mean doing SPF on every route.
> > > > If "every route" is only a couple hundred, rather than 100K, you fare
> > > 
> > > As you say disable synchronization and try and control the physical reach of
> > > your igp by some mechanism.. areas, summaries, ASes etc
> > 
> > Which is exactly what you are doing when you inject nailed routes into bgp.
> 
> No its not? I'm suggesting some level of order can help control the number of
> routers required to reconverge a network, I dont see the comparison with
> inserting routes in BGP which is how the routes get in not how they converge.

If you dont have a network wide meltdown due to IGP failure you wont need to
wait for entire network to come up. It is timing of discrete events.  Isn't
math grand.

Alex




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