Yesterday's Windows update causes IPv4 to be default
dwing at cisco.com
Thu Nov 15 18:20:59 CET 2012
> -----Original Message-----
> From: Sander Steffann [mailto:sander at steffann.nl]
> Sent: Thursday, November 15, 2012 9:09 AM
> To: Dan Wing
> Cc: Mike Jones; Tassos Chatzithomaoglou; <ipv6-ops at lists.cluenet.de>
> Subject: Re: Yesterday's Windows update causes IPv4 to be default
> > The stability of ipv6.msftncsi.com 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
> ipv6.msftncsi.com'. Depending where the outage is the impact will be
> smaller/larger. It is still a very big step to go from
> 'ipv6.msftncsi.com is unreachable' to 'prefer IPv4 for all traffic for
> 30 days'.
Yep. And the corollary, the IPv6 path to ipv6.msftncsi.com 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
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.
To make sure that Windows 8 does not cause problems on
enterprise networks, the functionality has two safeguards:
* If the enterprise has provided specific routing information
to a particular destination, then Windows 8 will honor that
preference, regardless of the connectivity determined by
Windows. In enterprise environments, Windows assumes that
network administrators who configure such routes specifically
thought it was a good idea to use those routes.
* This change isn't implemented on networks with web proxies.
In these networks, the proxy provides connectivity to the
Internet; so end-to-end testing of IPv6 connectivity is
not useful. Instead, Windows 8 simply opens connections
to the proxy in the most efficient manner possible."
I have begged for a more technical document to no avail.
More information about the ipv6-ops