Re: [DNSOP] opportunistic refresh and Happy Eyeballs

[Mikael Abrahamsson <[e-mail]>]

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: [e-mail]