On 6to4 gateway and recommended MTU setting

[Ole Troan]

>>> Hello list,
>>> 
>>> was discussing best 6to4-relay interface MTU size with a friend and
>>> basically need more and wiser input.
>> 
>> 1280.
>> 
>> If you have anything else, you are being silly.
>> 
>> [..]
>>> A working PMTUd will resolve MTU problems, both on underlying IPv4 node
>>> <-> 6to4-gateway, but this isn't the issue at the moment.
>> 
>> Not in this case. PMTUd will resolve MTU problems on the layer that it
>> is running, thus IPv6. But that won't affect the IPv4 layer. Remember,
>> you are tunneling, thus both rules for IPv4 and IPv6 apply.
>> 
>> 
>> The better question is actually: why bother with 6to4?
>> 
>> Yes, it is a nice quick deployment strategy, but for anything long term,
>> go native... (or at least native addresses using 6rd or something).
> 
> 
> You know this not very easy is most of the situation. Let's suppose there are student and professors who are using IPv6 at the universities. They are using their own machines (laptops) to access IPv6 services, and they are getting to used some services in IPv6.
> But while they are at home they are using some broadband services (e.g. xDSL, cable, 3G-mobile etc.), where in most of cases no IPv6 service (and unfortunately no plan for it from telcos). How to access IPv6 service without IPv6 address:
> 
> - use 6to4 since good number of soho routers has some form of 6to4 support.
> - user teredo if the host system support it.
> 
> The research network is providing 6to4 relay and/or teredo relay announced via local IXs....
> 
> The tunnel broker might be another option.....

my assertions would be that unless IPv6 is supported in the network you connect to, you should not bother. and in fact do more damage to IPv6 deployment than good. by providing 'broken' IPv6 hosts, prohibiting content providers from enabling IPv6 on their services, and end users to disable IPv6.

see:
http://www.google.com/trends?q=disable+ipv6%2C+enable+ipv6
(and no it is not scientific, and I'm sure you could make google trends show anything you want, but it is quite funny even so). ;-)

cheers,
Ole