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Re: [v6ops] An Update to Happy Eyeballs

Job Snijders <job@instituut.net> Wed, 22 March 2017 15:18 UTC

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From: Job Snijders <job@instituut.net>
Date: Wed, 22 Mar 2017 16:18:49 +0100
Message-ID: <CACWOCC8AJGFqcZWjgkhSFSsajQt0jGgM5h6VMHj4dqYp69POdQ@mail.gmail.com>
To: Lorenzo Colitti <lorenzo@google.com>
Cc: Fred Baker <fredbaker.ietf@gmail.com>, IPv6 Operations <v6ops@ietf.org>
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Subject: Re: [v6ops] An Update to Happy Eyeballs
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Perhaps of interest to this group:

https://blog.powerdns.com/2014/05/21/a-surprising-discovery-on-converting-ipv6-addresses-we-no-longer-prefer-getaddrinfo/

Kind regards,

Job

On Wed, Mar 22, 2017 at 4:15 PM, Lorenzo Colitti <lorenzo@google.com> wrote:
> On Thu, Mar 23, 2017 at 12:04 AM, Fred Baker <fredbaker.ietf@gmail.com>
> wrote:
>>
>> > I think it's extremely hard to argue that waiting for an A query when
>> > you have an AAAA in cache (or vice versa) is going to reduce latency or
>> > improve user experience. You can use getaddrinfo if you want, but you're
>> > going to pay the price in terms of latency. I wouldn't call that a best
>> > practice.
>>
>> I must be missing something. If you already know the AAAA, fine. If you're
>> using the resolver's cache, what API gets you an IPv6 address other than
>> getaddrinfo?
>
>
> You don't have to use getaddrinfo to do AAAA lookups. You can use your own
> code, or even pass binary blobs to res_send if you want.
>
> getaddrinfo is not very smart. It keeps trying until it has answers for
> everything you asked it to do, and then it returns everything. That means
> that if the A query is in cache and the AAAA query is not, then you have to
> wait for the AAAA query to succeed.
>
> I think the key point here is that integrating the DNS resolver retry loops
> with the connection attempts provide latency savings.
>
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> v6ops@ietf.org
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