6to4 status (again)

Max Tulyev maxtul at netassist.ua
Tue Feb 26 11:29:05 CET 2013

I believe you are using some kind of Linux/BSD box as 6to4 relay. So 
just launch tcpdump/ethereal/wireshark and see it ;)

We operate the 6to4 relay in Ukraine. There is 400mbps traffic, and it 
seems it hits maximum available CPU usage (dual QuadXeon L5420) during a 
peak time.

The most of the traffic is 6to4<->Teredo. The second position is for 
BitTorrent. But a 'good' traffic is significally increased too, as there 
is Facebook, Google, Yandex, Vkontakte enabled IPv6 by default.

I see the root of the problem is in algoritm chooses the IPv4/IPv6 
preference. Mostly it uses IPv6 if it is available, whatever IPv4 path 
enabled or not. So it used to connect two IPv4-enabled boxes CAN connect 
through IPv4 - through IPv4<->6to4<->teredo<->IPv4 path. It is not good 
at all, and should be explained good to all vendors.

May be it will be a good idea to block some kind of IPv6 traffic on the 
relay to force use IPv4 instead of chains of tunnels?

On 25.02.13 23:48, Kevin Day wrote:
> I know this was brought up in November, but I didn't see much of a consensus…
> We run one of the public 6to4 relays. Lately traffic to it has been growing very rapidly and I'm really not sure why. Other people shutting their public relays down? More AAAA records are making more people fall back to 6to4? Idiots using it for DDoS?
> For most of 2012 the usage averaged about 50-100mbps, but lately we're seeing sustained levels of 500mbps-900mbps. I'd rather not deploy 10GE on our 6to4 box just to handle the traffic growth.
> Has anyone here looked at public 6to4 usage recently and seen similar trends?
> Part of me is thinking we should just rate limit the box to something more reasonable. While it's still running, it'll be slow enough that hopefully people will move to a better transitional technology. My fear is that it will cause more "v6 sucks, it's so slow" and people shut it off without looking at why.

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