OSPF -vs- ISIS

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1

All,

Can anyone point me to information on what the top N service providers
are using for their IGP? I'm trying to build a case for switching from
OSPF to IS-IS. Those on this list who are currently running IS-IS, do
you find better scalability and stability running IS-IS than OSPF? I
understand that this question is a lot more complex than a simple yes
or no since factors like design and routing policy will certainly
affect the protocols behavior.

Any insights or experiences that you can share would be most helpful.

Thanks,

Daniel Evans
Alltel Communications

2

Why are you trying to build a case...? Would you already have
operational benefit from switching and are you building a case round
that and if not, why switch...? Switching IGP in a non-trivial network
isn't something you'd want to do unless you've got a clear motive and it
gives you some operational advantage...

Cheers,

3

Can anyone point me to information on what the top N service providers
are using for their IGP?

Can we expand this to include enterprise networks as well? The University
that I work for is planning to do a switch-over from OSPF to ISIS, but
I'd like to know if we're really a one off.

Eric :slight_smile:

4

Dan Evans wrote:

All,

Can anyone point me to information on what the top N service providers
are using for their IGP? I'm trying to build a case for switching from
OSPF to IS-IS. Those on this list who are currently running IS-IS, do
you find better scalability and stability running IS-IS than OSPF? I
understand that this question is a lot more complex than a simple yes
or no since factors like design and routing policy will certainly
affect the protocols behavior.

Any insights or experiences that you can share would be most helpful.

Thanks,

Daniel Evans
Alltel Communications

Daniel, in short, we've found ISIS to be slightly easier to maintain and run, with slightly more peace of mind in terms of securitiy than OSPF. Performance and stability wise, no major difference that was noticable.

For more information, see the talk by Dave Katz at http://www.nanog.org/mtg-0006/katz.html

Also, AOL's experience in switching from OSPF to ISIS is covered at http://www.nanog.org/mtg-0310/gill.html
the PDF on that page is actually an older version. The full version I used at NANOG is available at http://www.vijaygill.com/oi.pdf

/vijay

5

We're currently running OSPF. Believe me, I understand that switching
IGP's is not a simple undertaking. There are several benefits that I'm
looking at, some of which have already been mentioned in replies to my
original thread. Security is one, the other being IPv6 support. I'm
going to have to turn on another protocol in order to support IPv6. My
two choices are OSFPv3 or IS-IS. The decision then becomes, do I have
a single IGP protocol that maintains both IPv4 and IPv6 information,
or do I run two seperate (although closely related) protocols.

-Dan

6

Hi Daniel,

We wrote a draft some time back comparing the two protocols ISIS and OSPF.
It should address some of your doubts and concerns.

Here's a pointer to my local copy:

http://geocities.com/mnvbhatia/draft-bhatia-manral-diff-isis-ospf-00.txt

Thanks,
Manav

!> -----Original Message-----
!> From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]
!> On Behalf Of Dan Evans
!> Sent: Tuesday, June 21, 2005 7:35 PM
!> To: nanog@merit.edu
!> Subject: OSPF -vs- ISIS
!>
!>
!> All,
!>
!> Can anyone point me to information on what the top N service
!> providers
!> are using for their IGP? I'm trying to build a case for
!> switching from
!> OSPF to IS-IS. Those on this list who are currently running IS-IS, do
!> you find better scalability and stability running IS-IS than OSPF? I
!> understand that this question is a lot more complex than a simple yes
!> or no since factors like design and routing policy will certainly
!> affect the protocols behavior.
!>
!> Any insights or experiences that you can share would be most helpful.
!>
!> Thanks,
!>
!> Daniel Evans
!> Alltel Communications
!>
!>

7

Hi Manav,

Excellent Document!

I see that this document has expired. Are you folks thinking of
respinning a copy of this draft?

Thanks,
Abhishek