Yahoo and IPv6

Kevin Oberman oberman at
Mon May 9 16:34:12 UTC 2011

> From: Valdis.Kletnieks at
> Date: Mon, 09 May 2011 12:25:55 -0400
> On Mon, 09 May 2011 18:16:20 +0300, Arie Vayner said:
> > Actually, I have just noticed a slightly more disturbing thing on the Yahoo
> > IPv6 help page...
> > 
> > I have IPv6 connectivity through a HE tunnel, and I can reach IPv6 services
> > (the only issue is that my ISP's DNS is not IPv6 enabled), but I tried to
> > run the "Start IPv6 Test" tool at and
> > it says:
> > "We detected an issue with your IPv6 configuration. On World IPv6 Day, you
> > will have issues reaching Yahoo!, as well as your other favorite web sites.
> The *really* depressing part is that it says the same thing for me, on a *known*
> working IPv6 network.
> And then when I retry it a few minutes later, with a tcpdump running, it works.
> And then another try says it failed, though tcpdump shows it seems to work.
> For what it's worth, the attempted download  file is:
> % wget
> --2011-05-09 11:44:39--
> Resolving 2001:4998:f00d:1fe::2000, 2001:4998:f00d:1fe::2002, 2001:4998:f00d:1fe::2003, ...
> Connecting to|2001:4998:f00d:1fe::2000|:80... connected.
> HTTP request sent, awaiting response... 200 OK
> Length: unspecified [image/png]
> Saving to: `eye-test.png.1'
>     [ <=>                                   ] 2,086       --.-K/s   in 0s      
> 2011-05-09 11:44:39 (154 MB/s) - `eye-test.png.1' saved [2086]
> Looking at the Javascript that drives the test, it appears the *real* problem
> is that they set a 3 second timeout on the download - which basically means
> that if you have to retransmit either the DNS query or the TCP SYN, you're
> dead as far as the test is concerned.

I have talked to Yahoo engineers about this and they say that their
testing has shown that, if it takes more than 3 seconds for a site to
load, they start to lose significant traffic. Hence the 3 second

Sadly, I'm afraid that they have a point, but at the same time I suspect
that they are assuring failure for almost everyone. A 5 second timeout
would probably be more reasonable, but is probably unacceptable to Yahoo
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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