Yesterday's Windows update causes IPv4 to be default

Brian E Carpenter brian.e.carpenter at
Fri Nov 16 09:48:39 CET 2012

On 15/11/2012 17:20, Dan Wing wrote:
>> -----Original Message-----
>> From: Sander Steffann [mailto:sander at]
>> Sent: Thursday, November 15, 2012 9:09 AM
>> To: Dan Wing
>> Cc: Mike Jones; Tassos Chatzithomaoglou; <ipv6-ops at>
>> Subject: Re: Yesterday's Windows update causes IPv4 to be default
>> Hi,
>>> The stability of is quite good now.  I know of
>>> several probes checking it frequently, from different locations.
>> Ok, let's rephrase that to 'an outage somewhere between the user and
>>'. Depending where the outage is the impact will be
>> smaller/larger. It is still a very big step to go from
>> ' is unreachable' to 'prefer IPv4 for all traffic for
>> 30 days'.
> Yep.  And the corollary, the IPv6 path to works
> fine but the IPv6 path to $OTHER_DOMAIN is broken.
>> I hope the algorithm is better than it seems from this discussion. It
>> wouldn't be as bad if i.e. the result is cached for 30 minutes instead
>> of 30 days :-)
> The only official documentation from Microsoft is
> s-8.aspx
> the key section is
>    "Windows 8 performs the network connectivity test when you
>     first connect to a new network; it caches this information
>     and repeats the test every 30 days. The actual test for
>     connectivity is a simple HTTP GET to an IPv6-only server that
>     is hosted by Microsoft. (For standards buffs, this is
>     implemented between rules 5 and 6 of destination address
>     sorting in our implementation of RFC 3484.) Windows performs
>     a similar network connectivity test for IPv4 connectivity. If
>     both IPv4 and IPv6 are functioning, IPv6 will be preferred.

Incidentally, both the test URLs are Akamaized. That will
localize the connectivity test in an interesting way.


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