OSPF vs ISIS - Which do you prefer & why?

Dragan Jovicic draganj84 at gmail.com
Thu Nov 10 15:21:16 UTC 2016

In my experience/personal opinion, compared to OSPF2/3, in a large ISP,

- has simpler and better, less bloated code. Think ISIS on Juniper. Think
FreeBSD vs Linux.
- is more modular to introduce new features.
- has certain knobs which makes it a bit more useful for ISP (LSP
lifetime/Max number of LSP fragments, etc).

This is for a large single L1/L2/backbone area. There are at least 2 design
options I would consider before switching to multi-area ISP design.

With that said I know of at least two of the largest ISPs tat use OSPF and
many use that favor ISIS so it really comes down to ISP's preference and
NOC willingness to learn new unfamiliar protocol.


On Thu, Nov 10, 2016 at 3:35 PM, Mark Tinka <mark.tinka at seacom.mu> wrote:

> On 10/Nov/16 14:30, Joel M Snyder wrote:
> >
> >
> > In a world where you are doing well-controlled Cisco/Juniper/etc
> > networks with fairly homogeneous code bases, the engineers get to have
> > this discussion.  When you have to link in devices for which routing
> > is not their primary reason to exist, your options narrow very
> > quickly. It's not ideal; that's just the way it is.
> Quagga's IS-IS implementation is a great example.
> Mark.

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