Subject: Questions regarding LER's

From: Zappacosta Rolando Jorge <[email-masked]>
Date: Thu, 9 Aug 2001 12:35:17 -0300

Hi all. I've a question that may sound dumb for almost everybody of you;
I've been thinking about the answers but I want to be sure I'm right.
The question is wether it's necesary (or at least better) to run BGP on the
LER's under the following scenarios:
Common Assumptions: in each of the scenarios supposse I've an MPLS network
running OSPF as IGP and that the routers are able to impose labels to OSPF
learned routes.
SCENARIO 1: The LER's have no other routers beyond them, i.e. I've only
directly connected networks with hosts and *no any router* outside the core.
Of course I won't see outside OSPF adjacencies, so IGP doesn't really
matter.
I think it's unnecesary BGP just because I can't figure out any advantage
using it. I will just let the routers impose labels learned through OSPF
here.
SCENARIO 2: The LER's are seeing just a few same area OSPF routers outside.
Here, I think the only advantage will be an inferior convergence time in
case a link failure inside the core, but it would be almost unperceptible.
So it doesn't care so much.
SCENARIO 3: The LER's have a lot of routers outside. So, I think here it is
highly recomendable to run BGP, no matter the outside OSPF routers are or
are not from the same area. This will increase the convergence time in case
of failures and decrease the memory and CPU usage in the inside routers to
hold the routes and links status.

Am I right? Any comments?

Thanks a lot in advance,

Rolando J. Zappacosta
Gerencia Laboratorios - DER
Reconquista 179
Ciudadela (B1702FCC)
Pcia. de Buenos Aires - ARGENTINA
Tel: +54-11-4332-8360
Fax: +54-11-4303-5586 Ext: 6005