[Chapter-delegates] World IPv6 Day - on what Google, Yahoo and Facebook could do in a day.

[Marcin Cieslak]

On Fri, 29 Apr 2011, Sivasubramanian M wrote:

> Dear Marcin,
>
> IPv4 user => IPv4 page with "Oh, no you are on IPv4, alright, click here, we
> will take you to the usual facebook page" => facebook home page with IPv6
> day banner => usual experince

The problem is with this "click here" page - it would need to go to
IPv6-only DNS address (www.ipv6only.facebook.com) that would only
have an AAAA record and no A. (You need both for www.facebook.com
if you want do display IPv4 landing page).

Here's what happens with Windows Vista and 7: If there is no
IPv6 connectiviy by some other means (global IPv6 address
configured on one of the interfaces) - go ahead and try
to build a Teredo tunnel. You can see this in action on Windows
easily: go on IPv4 network with no IPv6 connectivity and
do "ping -6 www.isoc.org" or "ping -6 2001:41c8:20::19".
You will have to wait for ca. 20 seconds or more but then
you will be surprised to see ICMP packets coming back.
Congratulations, your Teredo tunnel is established.

It is probably possible to workaround this problem
by deploying a Teredo tunnel server within the content
provider's infrastructure, but I don't think we want
to have more tunnels. (Native IPv6 would be then
done between Teredo server and the website only,
which could be on the content privider LAN only).

I believe that MacOS X does not Teredo natively,
probably only 6to4 is attempted (and then you usually
hit the NAT barrier). One-year-old Opera 9 will
also attempt to build a 6to4 tunnel for you 
automatically, if the IPv6-enabled website is 
about to be reached.

//Marcin