Say "Thank you" to Bill...

Bernhard Schmidt berni+ipv6 at
Sun Apr 1 14:01:59 CEST 2007

On Sun, Apr 01, 2007 at 02:08:30PM +0000, Max Tulyev wrote:

Hi Max,

> >
> >
> Thank you, nice reading ;)
> Am I understand correctly Server helps to chose a Relay?

Generally no, except in a few corner cases (globally anycasted
destination for example).

The usual case would be: When Teredo client C (behind NAT) tries to
contact the native destination D it sends an ICMPv6 echo request to the
destination D through its own configured Teredo server S. S forwards the
packet like any other packet to D. D replies back with ICMPv6 echo reply
and sends it to the nearest Teredo relay R (all Teredo relays advertise
2001::/32 in BGP). R cannot contact C directly because C is behind
NAT/Firewall/whatever, so it tags the packet with its own IPv4 address
and forwards it to the Teredo server S the client is connected to. S
can forward the packet to C because it has an existing state already.
Now C can contact R from its side and start communication with D.

So unless you try to contact a globally anycasted destination where the
nodes use different relays for the way back, the Teredo server is not
involved in the relay selection.

> We are going to establish layer2 channel to Frankfurt to get native and
> shortest V6 instead of tunnels. It takes some time, of course.

Good news. I hope this will be "real" upstream and not another free

> > I would not dare to run any "interactive services" (I consider
> > webbrowsing interactive) on that either.
> Browsing working fine, by the way. SSH have a significant lags.

I'm involved with satellite communication, which has 500-550ms RTT, not
that much more than my current path to you. Of course that affects IPv4
as well, and I can tell you that most webpages are not that nice to use
anymore with that latency.

> We are continue investigation. Only is clear - disabling IPv6 in hosting
> stops complains and gets sites back visible, and this happens with Vista
> and XP enabled V6 clients.

You could have installed a local Teredo relay, this setup (local
content, Teredo clients accessing it) is one of the cases where that
makes sense


More information about the ipv6-ops mailing list