Re: [DNSOP] Introducing draft-vavrusa-dnsop-aaaa-for-free

[Florian Weimer <[e-mail]>]

On 03/22/2016 12:45 AM, Marek Vavruša wrote:

> there was an interest in reducing latency for address record lookups.
> Me and Olafur wrote a draft on adding AAAA records to A answers and
> treating them as authoritative. This fixes latency issues with NS
> A/AAAA discovery in resolvers and improves caching for clients (AAAA
> already cached by the time client comes asking for it).
> 
> Comments, feedback and snarky remarks would be great!
> https://datatracker.ietf.org/doc/draft-vavrusa-dnsop-aaaa-for-free/

The glibc stub resolver already implements this draft in its response
processing by accident.  I was planning to fix that.

I don't see how this proposal reduces latency or server load.  We still
have to do dual A/AAAA queries.  In the majority of cases, there is no
AAAA record, so we have to wait for the second reply to arrive.

We could reduce server load by sending the AAAA query only after the A
response, but we'd have to send it in most cases because we cannot take
absence of an AAAA RRset as proof of its non-existence.

On the server side, doing AAAA lookups for all incoming A queries, on
top of A lookups, isn't free (although it should be fairly cheap because
the server at least knows where to send the AAAA query).

Florian