IS-IS reference

Vijay Gill wrath at
Tue Sep 14 19:28:32 UTC 1999

On Tue, 14 Sep 1999, Dave Cooper wrote:

> 1. if you are going to scale a large national backbone, limit as much
> as you can in your IGP. the less fluctation in flooding protocols, the
> better.  and since most backbones run on a single area (on the main 
> IGP process) or level-2 only, then fluctuations cause headaches for
> all participating routers. this is especially so when you have a 
> full layer-2 mesh or a full MPLS mesh.

A full mpls mesh should not be a problem as instantiated LSP's are
probably not going to be in your igp.  Running an IGP over an (opaque) LSP
adds a lot to your complexity without delivering any major benefits. 

You can add hierarchy to your topology obviating a need for a full mesh at
the L2 level.

Hierarchy can solve almost any scaling issue.  Hierarchy in BGP through
confederations/RR, hierarchy in your IGP and hierarchy in your physical
circuit layout.


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