[nsp] OSPF or IS-IS (specific scenario)

Gert Doering gert at greenie.muc.de
Sat Feb 28 07:03:50 EST 2004


On Thu, Feb 26, 2004 at 09:27:06PM -0700, Pete Kruckenberg wrote:
> I'm biased towards OSPF unless it won't work for this
> configuration. My particular concern is the mix of
> multicast, IPv6 and MPLS with BGP confederations and the
> possibility that OSPF might not be fully implemented for
> that mix (or less-stable/mature than IS-IS for any single
> protocol or combination of protocols).

One thing to point out here is that OSPF is "two completely different 
protocols for OSPF/IPv4 and OSPF/IPv6 that just share the name and the
underlying logic", while ISIS is "one protocol, one set of adjacencies, 
carrying LSAs for both IPv4 and IPv6".

This means that if all your routers do IPv4 and IPv6, IS-IS might be the
better choice (only one routing protocol to care for).  

If your IPv6 and IPv4 topologies are disjunct, you need to be really 
careful with IS-IS, as it will happily construct a shortest-path for
IPv6 routing across an IPv4-only router.  Multi-Topology IS-IS will 
fix that - or using separate routing protocols for v4 and v6.

I'm not really sure how MPLS adds to that mix (not having very much
experience with that).

> I'm also wondering if OSPF will continue to play catch-up
> with IS-IS (at least in IOS implementation) in terms of new
> features, advanced network capabilities, and implementation
> maturity. Will the lag time OSPF experienced in getting
> millisecond convergence time and IPv6 support relative to
> IS-IS continue to be the case in the future?

I can't speak for IOS development, but as far as I understand, both
protocol suites have mostly the same features (and stability) as of 
today.  But I'm alway willing to learn otherwise ;-)


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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de

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