Subject: Re: [Isis-wg] Questions

From: Danny McPherson <[email-masked]>
Date: Thu, 07 Feb 2002 18:23:43 -0700

> Currently I am working on ISIS and have two questions
> 1. In some old mail somebody described that a lot of ISPs 
> were using ISIS at that time (I guess it was in 99). Is it 
> still true? 

I actually did a survey a while back and found that of the 
largest 10 domestic ISPs ~7 used IS-IS, the remaining 3 used 
OSPF.  Of the ~70 networks I had knowledge of (either as a
result of direct involvement, directed queries or publicly 
solicited responses) ~15 used IS-IS while the rest used OSPF 
(minus a few stragglers using EIGRP or the like).

[Disclaimer:  "Largest 10" is purely in my mind, I did 
no customer counts, IP counts or the like in an attempt to 
qualify my employment of the phrase.]

It's quite reasonable to assume that the number of IS-IS 
ISP networks decreases substantially thereafter.  And I'm 
guessing there are very very few enterprises that employ 
IS-IS as their IP IGP -- for obvious reasons.

> Also do we know whether the use of ISIS among 
> ISPs has increased or decreased since then?

It really hasn't changed a whole lot since '99, other than 
the demise of lots of the "Broadband CLECs" and the like., 
of which a much greater amount of OSPF seemed to be deployed.  

> 2. I am looking for "A comparison between two routing protocols" 
> "OSPF and IS-IS" by R. Perlman. Where can I get it from?

I'm guessing you're talking about the great IGP Debate from 
"CONNEXIONS: The Interoperability Report", October 1991 Vol 
5, No. 10 (I had a copy on my bookshelf, if you're wondering 
:-).  Radia & Ross Callon discussed IS-IS and Mile Medin 
discussed OSPF. 

Of course, it's really dated and not of a great deal of use 
today, IMO.

A more useful reference is perhaps this:

 http://www.nanog.org/mtg-0006/katz.html

Reasons for all of the above have been hashed out here and on
other mailing lists for quite a while, so I'll not discuss
anything further here...

HTH,

-danny

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