AT&T NYC

Tue Sep 3 09:24:44 UTC 2002

On Mon, 2 Sep 2002 alex at yuriev.com wrote:

> > 
> > > 
> > > > > 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? 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.

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

> > > 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.

Steve

> So, why do you need IGP such as OSPF again?
> 
> Alex
> 
> 