Re: To DAD or not to DAD?

[Bob Hinden <[e-mail]>]

Erik,

With no hats on.

> On Feb 18, 2015, at 11:46 AM, Erik Nordmark <[e-mail]> wrote:
> 
> 
> Hello,
> 
> Back in November the efficient-nd design team presented slides (http://www.ietf.org/proceedings/91/slides/slides-91-6man-11.pdf)
> and a document was produced on the DAD problems (https://datatracker.ietf.org/doc/draft-yourtchenko-6man-dad-issues/)
> 
> The key questions in the design team report was what to do about DAD. But we haven't had any discussion on this on the list and I'd like to get some feedback from the WG to we can move forward.
> 
> The slides offered these options:
> 1. Deprecate DAD - it is expensive and duplicates are not common

I think we know that duplicates are not common with IEEE EUI based IIDs.  In the case of duplicates at the L2 on a LAN, there is a bigger problem for the network operator to solve.  I don’t think DAD brings very much in this case.

> 2. Only send and receive DAD for manually configured addresses

I note we are in the process of moving away from IEEE EUI based IIDs to software generated pseudorandom numbers.  Lots of good reasons to do that, but I don’t think we know how well this new software will work in regard to duplicates.  It should work fine, but there will be bugs and possibly increased duplicates if different algorithms are chosen.  For this reason, I think that we should continue using DAD for software generated IIDs, at least until we get more operational experience.


> 3. Improve DAD
> 3a. Better at detecting duplicates (partition-join, etc)
> 3b. Less network and host impact (allow sleep schedule)
> 4. Do nothing a. aka go to the beach ;-)
> 
> The 3a vs. 3b implicitly refers to the list of issues in draft-yourtchenko-6man-dad-issues.

> 
> Given that the beach is kind of cold this time of year, we can remove the 4th choice from the list.
> More seriously, the WG needs to decide how to move forward with DAD.

I agree.

> 
> Would it be helpful to present draft-yourtchenko-6man-dad-issues in Dallas? Or can we have an email discussion without/prior to such a presentation?
> 

Yes, for both.

Thanks,
Bob


> Regards,
>    Erik
> 
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [e-mail]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------