[AusNOG] OSPF vs ISIS - Which do you prefer & why?

[Diogo Montagner]

Personal opinion certainly weights in a lot.

I dont fully agree with the points made in the article. I think he missed
some technical points in his comments.

About this topic, a good reading is Jeff Doyle's book:
https://www.amazon.com/OSPF-Choosing-Large-Scale-Networks/dp/0321168798

These days, if you use MPLS as infrastructure of transport, you can easily
pick either one.

In terms of resources, as the article pointed out, both rely on SPF
algorithm. Hence, what dictates how resource hungry they will be is your
network design.

I personally prefer ISIS over OSPF because of the following:

- easier to use, configure and operate in a dual-stack environment,
especially if you use MPLS TE.

- the TLV mechanism make it a very flexible routing protocol. Although this
point can be argued against (how many protocol changes have we seen till
today ?), we don't know what changes might come into this area. I rather
prefer to deal with SW upgrades to support new TLVs than replacing an
entire IGP for another existing or new one.

On item #1 above, you can easily avoid that if you use MPLS.

One advantage I see on OSPF is its DR/BDR design compared to DIS.

At the end, what really matters is the network design. Both OSPF and ISIS
will fit well in a good network design. One or another may save you some
headches in a poor network design. But that may not last long .....

My 2c.

Thanks

On Thursday, 1 September 2016, Paul Wilkins <paulwilkins369 at gmail.com>
wrote:

> All I can say is that redistribution between IGPs is never the right
> answer. OSPF works and is generally well understood.
>
> Kind regards
>
> Paul Wilkins
>
> On 1 September 2016 at 22:25, Michael Bullut <main at kipsang.com
> <javascript:_e(%7B%7D,'cvml','main at kipsang.com');>> wrote:
>
>> Greetings Team,
>>
>> ​While I haven't worked with IS-IS before but the only disadvantage I've
>> encountered with OSPF is that it is resource intensive on the router it is
>> running on which is why only one instance runs on any PE & P device on an
>> ISP network. OSPF is pretty good in handling the core network routing while
>> BGP & EGP handle the last-mile routing between PE & CE devices. BGP & EGP
>> can run on top of OSPF. I came across this *article*
>> <https://routingfreak.wordpress.com/2011/03/05/why-providers-still-prefer-is-is-over-ospf-when-designing-large-flat-topologies/>
>> when scrolling the web a while back and I still want to find out if am the
>> only one who thinks its a matter of choice between the two. Although there
>> isn't distinct 1:1 argument, it's good we discuss it here and figure out
>> why one prefer one over the other *(consider a huge flat network)**.* What
>> say you ladies and gentlemen?
>>
>> Warm regards,
>>
>> Michael Bullut.
>>
>> ---
>>
>> *Cell:*
>> *+254 723 393 114.**Skype Name:* *Michael Bullut.*
>> *Twitter:*
>> * @Kipsang <http://twitter.com/Kipsang/>*
>> *Blog: http://www.kipsang.com/ <http://www.kipsang.com/>*
>> *E-mail:* *main at kipsang.com
>> <javascript:_e(%7B%7D,'cvml','main at kipsang.com');>*
>>
>> *---*
>>
>> _______________________________________________
>> AusNOG mailing list
>> AusNOG at lists.ausnog.net
>> <javascript:_e(%7B%7D,'cvml','AusNOG at lists.ausnog.net');>
>> http://lists.ausnog.net/mailman/listinfo/ausnog
>>
>>
>

-- 
./diogo -montagner
JNCIE-SP 0x41A
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ausnog.net/pipermail/ausnog/attachments/20160902/1abb98a0/attachment.html>