Test your connectivity for World IPv6 Day

[Tore Anderson]

* Rémi Després

> Le 7 juin 2011 à 00:20, Tore Anderson a écrit :
> 
>> It's quite hard to discover the blackholes (and by extension fix
>> them) if you're defaulting to 1280.
> 
> Which blackholes? - With 1280, there isn't any related to MTU's.
> Right?

Wrong. The blackholes are still there. Masking the symptoms does not fix
the underlying problem.

>> In any case, the few users that have HE/SixXS/etc. tunnels can take
>> care of themselves. If it breaks, they get to keep both parts.
> 
> Too bad for IPv6!
> 
>> For real deployments, on the other hand ... well, I'm hoping no
>> serious ISP or content provider will willingly put their end users
>> or web sites behind MTU-impaired links or tunnels. Recipe for
>> disaster if you ask me.
> 
> What do you mean, precisely, by "MTU-impaired links or tunnels"?

If an ISP, a tunnel broker, or a concious tunnel-using end user are
using a link/tunnel that has a MTU lower than 1500 but where PMTUD does
not work reliably, that is their problem, not mine. I refuse to work
around their defective network by crippling the MTU for all my visitors.

What MTU do you recommend for IPv4 servers, by the way? 576 or 68?

-- 
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com/
Tel: +47 21 54 41 27