[arin-ppml] ARIN-prop-127: Shared Transition Space for IPv4 Address Extension

George, Wes E [NTK] Wesley.E.George at sprint.com
Mon Jan 24 16:05:20 EST 2011


> -----Original Message-----
> From: Owen DeLong [mailto:owen at delong.com]
> Sent: Monday, January 24, 2011 2:54 PM
> To: George, Wes E [NTK]
> Cc: Joel Jaeggli; arin-ppml at arin.net
> Subject: Re: [arin-ppml] ARIN-prop-127: Shared Transition Space for
> IPv4 Address Extension
> 
> That's a pretty good argument for having a defined block that people
> can
> adjust the 6to4 routers to know about. 
Arguably, anycast 6to4 is
> moderately
> broken in a wide variety of circumstances anyway. I don't think it's
> quite
> as bad as Lorenzo would have us all believe, but, there are definite
> problems.
> 

[WES] sigh. We've gone round the circle again. If we could update those
boxes to understand that this block isn't a valid external address to use
for 6to4, we could also update them to do real IPv6, or to use class E
space, or 6RD, or DSLite, etc, etc.
The only thing that I can think of that makes this less broken would be if
the CGN box is smart enough to serve as an ALG for 6to4 packets (not just a
6to4 relay) and locally terminate them so that it can send real IPv6 packets
between itself and the destination, or otherwise rewrite the 6to4 packet
headers and track the state so that 6to4 actually works properly with the
external address. But I haven't heard of any vendors peddling that
particular hack yet, nor are any of the usual suspects generating a draft in
IETF for it (that I know of).

The idea here is that regardless of what anyone thinks about it, to quote
Brian Carpenter, "the toothpaste is out of the tube now." That is, we're
stuck with 6to4, and we're better off trying to make it work better for
those who are using it than to continue treating it as a completely
second-class citizen, because ultimately it is still a means to increase
IPv6 deployment in places where it otherwise wouldn't exist. Most of the
brokenness is because there aren't enough properly run 6to4 relays close
enough to the sources and sinks of traffic. Only a small percentage is due
to broken implementations that try to do 6to4 with 1918 addresses or the
like. Last I heard, Brian was working on a draft to make some
recommendations about how to make 6to4 suck less, but if Comcast's
experiences with 6to4 are any indication, simply saying "eh, 6to4 is broken
anyway" is a cop-out.

Wes George
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