The MPLS-OPS Archive

[Eric Osborne <eosborne@cisco.com>]

On Fri, Jan 23, 2004 at 07:31:49AM -0000, Sunil Menon K wrote:
> Hi all
> I work for a large ISP which currently has OSPF for IGP,running MPLS
> VPN and are headed for implementing QOS and Traffic Engineering and
> moving towards migrating to IPV6 and becoming a Tier 1 ISP.Since
> most Tier 1 ISPs are running IS IS as their IGP,I have been working
> on looking at IS IS in relation to OSPF to deciede if IS IS holds
> any significant advantages keeping mind two key aspects of
> convergence,scalability and support as the network grows.I have a
> few questions with regards to the same.

The difference between ISIS and OSPF is a lot like the difference
between SONET and SDH, but see inline

> 1.Does IS IS have the flexibility of supporting both v4 and V6 
> implementations?Is the same available with OSPFv2 aswell?

I'm not sure what development/standards are at; I know there's OSPFv3,
and ISIS should, if anything, be simpler to implement.

> 2.Does IS IS hold an edge over OSPF in anyway for Traffic 
> Engineering implementations?

There are some features that tend to ship for ISIS first and OSPF in
the next release, but if you aren't concerned with bleeding-edge, then
no.


> 3.With regards to the basic routing functionality ....can it be
>    safely said of IS IS as being more scalable with its support for
>    larger areas and a more strict hierarchy model?

Sure!  You can also say that the moon is made of cheese, up is down,
and bad is good..:)  

The persistent rumors of OSPF being less scalable are long due for
demise.  It's not true.  It used to be true, maybe 10 years ago, but
it's not any more.  They're largely identical in this respect.  

I'm not sure what 'a more strict hierarchy model' is.  Personally, I
never liked the l1->l2 automatic default stuff, but that's just me.


> 4.What in your opinion are the key benefits would a Tier 1 ISP stand to
> derieve from IS IS implementation of the two level hierarchial Link 
> state protocol.

The same ones as they'd get from an OSPF implementation of same...:)



eric

> 
> Any inputs and guidance on the same would be highly appriciated.
> 
> Thanks and Regards,
> Sunil.
> 
> 

-------
The MPLS-OPS Mailing List
Subscribe/Unsubscribe:  http://www.mplsrc.com/mplsops.shtml
Archive: http://www.mplsrc.com/mpls-ops_archive.shtml