IGP Comparison (Summary of Responses)

Niels Chr. Bank-Pedersen ncbp at bank-pedersen.dk
Wed Jan 6 07:55:26 UTC 1999

On Tue, Jan 05, 1999 at 09:13:18PM -0600, Sean Donelan wrote:
> randy at psg.COM (Randy Bush) writes:
> >> Most of the large ISPs in the US run IS-IS as their IP IGP.
> >> In europe a number of PTTs have chosen IS-IS as the IGP for their new
> >> IP Internet backbones. That might be an indication if IS-IS is dead.
> >
> >hypothesis: big isps talk less.  except a few loudmouths <g>, and when jhawk
> >gets pissed off <g^2>.
> I know why most of the older large ISPs use IS-IS, because it was the
> only option that worked at the time.  But now that some router vendors
> have come out with workable OSPF implementations, I've been wondering
> which road the new ISP competitors would take.  So far, they've been
> hiring all the engineering staff away from the older ISPs.  And then
> the engineers set up the new network with the same skills, meaning IS-IS.
> But what if you started from a clean slate...

I know of one new network planned by people originally most familiar with
OSPF that is now running IS-IS.  It did start out as OSPF allright, but
when you go beyond 200+ routers in area 0 within 6 months (and still
growing) you start wondering whether you shouldn't take a different
approach -- and thats when IS-IS comes in handy.

> If you didn't have an installed base, and didn't already know one or
> the other, which would you choose?  Or just punt, and use iBGP....

I guess it depends on how large you plan to get  :-)
 - and yes, I know, that OSPF scales quite well if you design it
carefully WRT areas, but so does IS-IS...

Another way to look at it would be that you could keep on making
sloppy networkdesign far longer in an IS-IS network than you could with
OSPF  ;)

> -- 
> Sean Donelan, Data Research Associates, Inc, St. Louis, MO
>   Affiliation given for identification not representation

/Niels Chr.

 Niels Christian Bank-Pedersen, NCB1-RIPE.
 Network Manager, Tele Danmark NET, IP-section.

 # rsh -l God universe.all find / -name '*windows*' -exec rm -rf {} \\;

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