Re: [v6ops] Looking for info on IGP choices in production dual-stack networks

Philip Matthews <> Fri, 05 June 2015 14:27 UTC

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Subject: Re: [v6ops] Looking for info on IGP choices in production dual-stack networks
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[Reformatting and excerpting my original message and Mark's reply  due to some technical issues]

On 2015-06-04, at 22:54 , Mark ZZZ Smith wrote:
>> Victor and I are looking for information on the IGP combinations people are running in their dual-stack networks. We are gathering this information so we can document in our Design Choices draft which IGP choices are known to work well (i.e., people actually run this combination in production networks without issues). The draft will not name names, but just discuss things in aggregate: for example, "there are 5 large production networks that run OSPF for IPv4 and IS-IS for IPv6, thus that combination is judged to work well".
> I don't think this is really a good thing to be stating in such abstract terms, that is, at the IGP protocol level. I'd think the successful co-existence or not of IGPs, assuming the protocols themselves aren't broken (e.g., by using the same field value id for two different things), is  implementation dependent, and dependent on which specific revision of the implementation a network has chosen to deploy, and how that network has chosen to deploy it. For example, a literally perfect implementation of OSPF + IS-IS might be "judged to work badly" if deployed badly (by, for example, putting too many routers in the backbone area, overloading control plane resources.) 
> I'm wondering a bit what the fundamental question trying to be being answered is? Is it to try to capture some information on the current popularity of various IGPs used to carrying IPv6 routes, and how popular the use of a single IGP to carry both IPv4 and IPv6 routes is?   What particular question or questions would the reader have that this text is trying to provide an answer for?
> Regards,
> Mark.

In the draft we have a table that lists the various combinations of IGPs for IPv4 and IPv6 and gives a few properties for each combination that people might want to consider when selecting a combination. The idea is to give people with less IPv6 knowledge some guidance and perhaps some reassurance when selecting a combination. 

One of the columns in the table is called "Known to work well".  Originally, Victor and I populated this based on our own experiences and biases, without consulting others.  However, in mid-April Mikael Abrahamsson commented on this table, noting that he has actually run one of the combinations that we marked as "not known to work well".  So Victor and I decided that we should be more scientific in populating this column.  Hence this survey of what people actually run.

Do you think the draft should NOT contain this type of information?  I can say that I have found the responses so far to be very interesting, even though it has been just a day so far.

Or do you have a suggestion for something else useful to say about each combination?  Victor and I feel it might be nice to add more information about each combination, but we don't have any ideas yet on what the "more information" should be.  We would love to hear from anyone who has a suggestion.

- Philip