Re: [v6ops] Happy eyeballs suggestions, was: Re: Apple and IPv6, a few clarifications

Mark Andrews <marka@isc.org> Tue, 23 June 2015 00:33 UTC

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To: Iljitsch van Beijnum <iljitsch@muada.com>
From: Mark Andrews <marka@isc.org>
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In-reply-to: Your message of "Tue, 23 Jun 2015 02:12:35 +0200." <8A7D9143-A95E-4A54-A4E7-2D522EE4EEF2@muada.com>
Date: Tue, 23 Jun 2015 10:33:39 +1000
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Subject: Re: [v6ops] Happy eyeballs suggestions, was: Re: Apple and IPv6, a few clarifications
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In message <8A7D9143-A95E-4A54-A4E7-2D522EE4EEF2@muada.com>om>, Iljitsch van Beijnum writes:
> On 23 Jun 2015, at 2:06, Mark Andrews <marka@isc.org> wrote:
> 
> > For named (DNS) we just set IPV6_USE_MIN_MTU=1 for *both* TCP and
> > UDP.
> 
> So now application makers get to decide on TCP's segment size?
> 
> Fuck that.

Grow up.

Yes, application developers have applications that just don't work
with PMTUD.  IPV6_USE_MIN_MTU was add back at the turn of the century
for those applications.

For the DNS, where unless you are pipelining DNS queries at a server
or performing a zone transfer, all DNS transactions are less than
64K and 99.99999% are less than 4K the difference between 1280 and
1500 is a few of extra packets (for both UDP and TCP).  DNS also
has much tighter real life timing constraints than most applications.

Mark

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka@isc.org