OSPF vs IS-IS

Scott Morris swm at emanon.com
Fri Aug 12 07:56:49 CDT 2011


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The learning curve isn't that big IMHO.  However, it's all about comfort.

You should never design a network because "someone else does it this
way".  While you can certainly take ideas into account about the WHY
their network looks that way, you need to look at your own needs and
desires to figure out if they line up.

If everyone in your organization knows OSPF.  Why force the change?   if
you can't come up with a good reason, then that's a great reason not to
do it, unless there is something missing from OSPF that you need.

The funny thing is that most people learn ISIS in conjunction with what
you already know (OSPF) and what the similarities/differences are in
terms of thinking.

Look at your current design.  I'll assume that you have a reason for the
aspects of your network design that you currently have (as opposed to
someone else did it this way!).  What are they?  How will they translate
to ISIS?  Will they translate?  Do you care?

THAT kind of thing makes a good design for your company.

HTH,

Scott


 


On 8/12/11 8:23 AM, CJ wrote:
> You guys are making a lot of good points.
>
> I will check into the Doyle book to formulate an opinion. So, I am
> completely new to the SP environment and OSPF is what I have learned
because
> I have ever only had experience in the enterprise.
>
> It seems that from this discussion, IS-IS is still a real, very viable
> option. So, IS-IS being preferred...realistically, what is the learning
> curve?
>
>
> CJ
>
> On Fri, Aug 12, 2011 at 7:57 AM, jim deleskie <deleskie at gmail.com> wrote:
>
>> If a network is big enough big / complex enough that you really need
>> to worry about performance of mesh groups or tweaking areas then its
>> big enough that having a noc eng page you out at 2am when there is an
>> issue doesn't really scale. I'm all for ISIS, if I was to build a
>> network from scratch I'd likely default to it. I'm just say, new
>> features or performance aside the knowledge of your team under you
>> will have much more impact on how your network runs then probably any
>> other factor. I've seen this time and time again when 'new tech' has
>> been introduced into networks, from vendors to protocols. Most every
>> time with engineers saying we have smart people they will learn it /
>> adjust. Almost every case of that turned into 6 mts of crap for both
>> ops and eng while the ops guys became clueful in the new tech, but as
>> a friend frequently says Your network, your choice.
>>
>> -jim
>>
>> On Thu, Aug 11, 2011 at 7:12 PM, Jeffrey S. Young <young at jsyoung.net>
>> wrote:
>>>
>>> On 12/08/2011, at 12:08 AM, CJ <cjinfantino at gmail.com> wrote:
>>>
>>>> Awesome, I was thinking the same thing. Most experience is OSPF so it
>> only
>>>> makes sense.
>>>>
>>>> That is a good tip about OSPFv3 too. I will have to look more deeply
>> into
>>>> OSPFv3.
>>>>
>>>> Thanks,
>>>>
>>>> -CJ
>>>>
>>>> On Thu, Aug 11, 2011 at 9:34 AM, jim deleskie <deleskie at gmail.com>
>> wrote:
>>>>> Having run both on some good sized networks, I can tell you to run
>>>>> what your ops folks know best. We can debate all day the technical
>>>>> merits of one v another, but end of day, it always comes down to your
>>>>> most jr ops eng having to make a change at 2 am, you need to design
>>>>> for this case, if your using OSPF today and they know OSPF I'd say
>>>>> stick with it to reduce the chance of things blowing up at 2am when
>>>>> someone tries to 'fix' something else.
>>>>>
>>>>> -jim
>>>>>
>>>>> On Thu, Aug 11, 2011 at 10:29 AM, William Cooper <wcooper02 at gmail.com>
>>>>> wrote:
>>>>>> I'm totally in concurrence with Stephan's point.
>>>>>>
>>>>>> Couple of things to consider: a) deciding to migrate to either ISIS or
>>>>>> OSPFv3 from another protocol is still migrating to a new protocol
>>>>>> and b) even in the case of migrating to OSPFv3, there are fairly
>>>>>> significant changes in behavior from OSPFv2 to be aware of (most
>>>>>> notably
>>>>>> authentication, but that's fodder for another conversation).
>>>>>>
>>>>>> -Tony
>>> This topic is a 'once a month' on NANOG, I'm sure we could check
>>> the archives for some point-in-time research but I'm curious to learn
>>> if anyone maintains statistics?
>>>
>>> It would be interesting to see statistics on how many service providers
>> run
>>> either protocol. IS-IS has, for some years, been the de facto choice for
>> SP's
>>> and as a result the vendor and standardisation community 'used to'
>> develop
>>> SP features more often for IS-IS. IS-IS was, therefore, more 'mature'
>> than OSPF
>>> for SP's. I wonder if this is still the case?
>>>
>>> For me, designing an IGP with IS-IS is much easier than it is with OSPF.
>>> Mesh groups are far easier to plan (more straightforward) easier to
>> change
>>> than OSPF areas. As for junior noc staff touching much of anything to do
>>> with an ISP's IGP at 2am, wake me up instead.
>>>
>>> jy
>
>
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