IPv6 teredo blackout June 8th

Bernhard Schmidt berni at birkenwald.de
Wed Feb 2 21:09:11 CET 2011

On 02.02.2011 20:52, Bernhard Schmidt wrote:
> On 02.02.2011 11:05, Phil wrote:
> Hi Phil,
>> Some windows platforms have teredo enabled by default.
>> AAAA is preferred over A.
> Proper RFC3484 support (now present in all clients) prefers IPv4 over
> Teredo connectivity. So we should be safe here.

Note, this of course only stands true if the application does DNS "the 
right way" (calling getaddrinfo() with AF_UNSPEC and then using the 
returned list in order). If the application does any ordering itself, 
does seperate v6+v4 queries or does not use DNS at all (Bittorrent and 
SIP come to mind) all bets are off.

I recall a few years ago when an application vendor did exactly that. 
They dualstacked their servers delivering signature updates, but always 
preferred IPv6 in the update application. The joy in the community was 
quickly replaced by pain when nearby Teredo and 6to4 relays were flooded 
with traffic they could not handle.

Since the IPv6 day is mostly about Websites and all browsers are now 
fixed it should not be a problem.


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