On Jul 28, 2011, at 7:41 PM, Brian E Carpenter wrote:
Looking at a trace that I got from Geoff Huston a month or two ago,
there are 25486 IPv6 TCP sessions of which 10748 have a 6to4 source
That's surprisingly high, showing that the answer depends greatly on
the point of observation, and explains why operators really need
to try to run a decent 6to4 relay service as long as so many
such clients are observed. Which is why disabling 6to4 in clients
has to be the priority; it's far too soon to decommission the
Actually, it's why making hosts prefer IPv4 over 6to4 is the priority.
There's absolutely nothing wrong with using 6to4 if it's the best connectivity
to the destination that you have.
Also, this isn't a contest, we're on the same team, and we shouldn't be
competing against one another. The entire purpose of 6to4 is to allow people
to use IPv6 before they have native IPv6 connectivity, because we recognize
that the latter is in some cases very difficult to achieve end-to-end and faces
numerous barriers that vary from one situation to the next. That's why we have
so many technologies for layering IPv6 over IPv4.
IOW, 6to4's purpose is to be a gateway drug for native IPv6. And it can serve
that purpose even if at any given time only 1% are using it. The main thing is
to make sure that people who do try 6to4 find it attractive enough that they
want to upgrade to native IPv6. That means not using 6to4 in cases where it
will degrade performance compared to what people get already with IPv4, but it
doesn't mean disabling 6to4 entirely. It also means that DoS attacks on 6to4
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