OSPF -vs- ISIS

Tue Jun 21 16:50:59 UTC 2005

Thus spake "Mike Bernico" <mbernico at illinois.net>
> The State of Illinois converted to ISIS in 2002 from EIGRP and it
> has definitely been a good thing for us.  It's been operationally
> bullet proof, and simple to maintain.
>
> We typically get features faster than we would if we ran OSPF.
> For example, we have a desire in the future to use IPFRR.  Every
> indication from the vendor is that this feature will be available to
> ISIS first, most likely because of either the extensibility of ISIS
> or more likely because ISIS is in so many larger providers.

This points to something that's really unrelated to the minor technical
differences between the two protocols: how they're viewed by your vendor.

One vendor in particular sees ISIS as "an ISP protocol" and OSPF as "an
enterprise protocol".  Their implementation of the latter has often gotten
many enterprise-oriented features (e.g. dial-on-demand link support) that
the other didn't, whereas the former was known for reliability because the
coders were admonished to touch it rarely and test the heck out of every
change because screwing up might break the Internet.

The difference in stability is less apparent today, but the mindset is still
quite alive.  That means ISIS gets "ISP" features faster, and the code still
tends to be more solid than OSPF even though ISIS might now be getting
changes more frequently than it did in the past.

S

Stephen Sprunk      "Those people who think they know everything
CCIE #3723         are a great annoyance to those of us who do."
K5SSS                                             --Isaac Asimov