On Tue, 15 Aug 2017, Ted Lemon wrote:
If it's a commonly-used name, isn't this a one-time event, though? The
happy eyeballs client asks for A and AAAA, gets A because it was in the
cache, but AAAA also winds up in the cache, and then because it's a
commonly used name, neither record ever goes stale again.
That was the assumtion by a lot of people who aren't DNS experts
(including me). Mark Andrews brought up that this might be a more frequent
issue that people think.
Also there is the issue that as the TTL becomes 0 and the RR is now no
longer in cache, next question will trigger a lookup and if the
authoritative nameserver is 400ms RTT away, then during these 400ms a lot
of clients might only use IPv4 with current RFC6555bis proposal.
So there are two things here I see:
1. Opportunistically refresh RRs before they expire. I've been told some
resolvers do this already.
2. Tie together A and AAAA so that if one is asked for, make sure there is
an up-to-date of the second one as well, at least make sure it doesn't
expire even if it's infrequently used. I guess this means take into
account A questions when deciding whether to refresh that AAAA you might
have?
--
Mikael Abrahamsson email: swm...@swm.pp.se
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