Subject: [Fwd: Re: [Fwd: Re: The IPv6 Transitional Preference Problem]]

From: Denis Walker <[email-masked]>
Date: Thu, 17 Jun 2010 18:26:09 +0200

Hi

I pointed this issue to the DNS group at the RIPE NCC and their response
is below.

regards
Denis
Business Analyst
RIPE NCC Database Group

-------- Original Message --------
Subject: 	Re: [Fwd: Re: The IPv6 Transitional Preference Problem]
Date: 	Thu, 17 Jun 2010 16:53:53 +0200
From: 	Anand Buddhdev <[email-masked]>
To: 	Denis  <[email-masked]>
CC: 	
References: 	<[email-masked]>

It might be an issue with earlier versions of OS X, but on my Snow
Leopard (10.6.3) system, it's not an issue any more. Here's an example:

I type 'www.apnic.net' in my browser, and 2 DNS queries go out. I get
back a response with the A record first, and next I get back the
response with the AAAA record. However, my system does not ignore the
second response. It does make use of the AAAA record, and my browser
connects to APNIC's site over IPv6.

16:40:34.638265 IP 193.0.2.23.51663 > 193.0.19.6.53: 21148+ A?
www.apnic.net. (31)
16:40:34.641143 IP 193.0.19.6.53 > 193.0.2.23.51663: 21148 1/9/12 A
202.12.29.230 (491)
16:40:34.648670 IP 193.0.2.23.51652 > 193.0.19.6.53: 6434+ AAAA?
www.apnic.net. (31)
16:40:34.650519 IP 193.0.19.6.53 > 193.0.2.23.51652: 6434 1/9/12 AAAA
2001:dc0:2001:11::211 (503)

On 17/06/2010 16:28, Denis wrote:

> Hi
> 
> Does this affect us in any way with all the MAC machines we use
> here?
> 
> cheers denis
> 
> 
> -------- Original Message -------- Subject: 	Re: The IPv6
> Transitional Preference Problem Date: 	Thu, 17 Jun 2010 15:05:09
> +0100 From: 	Sabahattin Gucukoglu <[email-masked]> 
> Reply-To: 	Sabahattin Gucukoglu 
> <[email-masked]> To:
> [email-masked] References: 
> <[email-masked]> 
> <[email-masked]>
> 
> 
> 
> On 17 Jun 2010, at 13:30, Arnt Gulbrandsen wrote:
>> On 06/17/2010 01:38 PM, Sabahattin Gucukoglu wrote:
>>> Just in case someone here wants to take sides, have a look at
>>> this thread on the IPv6 discussion list at Apple: 
>>> http://lists.apple.com/archives/ipv6-dev/2010/Jun/msg00000.html 
>>> (the thread actually goes back earlier than that, but I can't be
>>> bothered going looking for it because I can't stand that awful
>>> PiperMail interface)
>> 
>> What I've never understood is why (almost) everyone tries addresses
>> in sequence instead of in parallel.
>> 
>> Even applications that routinely open two or more concurrent
>> connections to the server first try IPvX, then wait many seconds,
>> then try IPvY. Why not try both in parallel and use whatever
>> address answers first?
> 
> It's Apple we're talking about here.  Have a look at this for some
> nasty surprises: 
> http://www.fix6.net/archives/2010/03/06/the-strange-behavior-of-apples-mdnsresponder/
>
>  Admittedly this is just for DNS, but I think it illustrates the
> general problem, you can't win, you can't break even, and you can't
> even quit the game with this one.
> 
> Cheers, Sabahattin _______________________________________________ 
> Ietf mailing list [email-masked] 
> https://www.ietf.org/mailman/listinfo/ietf
> 
> 
>

---

From: Simon Perreault <[email-masked]>
Date: Thu, 17 Jun 2010 13:03:31 -0400

Please also refer to the results of the DNS64/NAT64 experiment that we
ran at IETF 77. Users of the service encountered a bug due to parallel
resolving in one particular operating system. We believe the bug is due
to that particular implementation. Parallel resolving is still a Good
Idea(TM), but this shows that implementing it correctly is not trivial.

See:
http://viagenie.ca/publications/2010-03-26-ietf-behave-nat64-experiment.pdf
http://www.ietf.org/proceedings/77/minutes/behave.txt

Hopefully it will be fixed by IETF 78... ;)

Simon
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