Re: IPv6 transition architecture discussion

[Brian E Carpenter <brian@hursley.ibm.com>]

To add to what Keith said, which I fully agree with, let's be clear
that 6to4 was invented as a supplementary mechanism, for the case where
a user site wants to support IPv6 and its ISP doesn't, and where for
whatever practical reason a configured tunnel or tunnel broker
solution isn't applicable. 6to4 shouldn't dominate the debate. It happens
to be the youngest of the techniques in the V6OPS charter, so it's no
surprise that it has open questions. That doesn't prevent it from
working.

   Brian

Keith Moore wrote:
> 
> > Suggestions on how to deploy IPv6 from the operating
> > system perspective seem to be lacking. 6to4 looks like a good solution,
> > but it doesn't work behind NAT. In addition, people in this working
> > group have strongly advised against any wide deployment of 6to4 hosts.
> 
> I don't think there's consensus about that, only that there are some
> questions or problems associated with 6to4 on a host level that haven't
> been fully resolved.  Personally I find "host 6to4" essential both to
> provide access to machines at home (where a single host serves both
> as an IPv4 presence and as a v6 router) and to allow me to access my
> v6 hosts from v4-only net connections.  I'm really disappointed that so
> few host OSes support it.  For instance the lack of 6to4 support in 10.2
> probably means I'll end up running NetBSD on my new 1Ghz powerbook g4.
> 
> > Apple would like to ship a version of our operating system that does
> > everything it can to get an IPv6 address.
> 
> I'd love for MacOS to support 6to4, though I'm not sure that having
> it automagically enabled is a good idea.  (there's such a thing as
> a machine being too clever or having too high an opinion of its
> own cleverness)
> 
> > The vocal people in this working group say that 6to4 and
> > Teredo are bad solutions. They rightly point out that the few 6to4
> > relays will probably melt down or people will stop running them.
> 
> 6to4 works wonderfully if you have v4 connectivity (perhaps indirectly)
> and are talking to other 6to4 sites.  if you want to talk to other sites
> over v4, right now you generally need to set up an explicit tunnel for
> that.  the anycast based relay routers don't work well enough to be used,
> IMHO.  at least not right now.  attempts to talk to v6 sites typically
> time out (which is annoying because the v6 addresses are tried first -
> another thing which needs to be fixed)
> 
> > We look to the IETF for a solution because we can't solve this problem
> > alone. I get the impression from this working group that the working
> > group is of the opinion that the transition mechanism will not work and
> > we should just sit on our thumbs until the ISPs provide us IPv6
> > connectivity.
> 
> be assured that not everyone here shares that opinion.  IMHO we need
> to define a host profile for 6to4, and perhaps another one for NAT boxes
> that wish to support 6to4.  yes there are problems.  let's fix them.
> 
> > We were considering turning on 6to4 by
> > default when there are no routing advertisements. This working group
> > has dissuaded us from doing so. If we did turn on 6to4, we would want
> > to add some extra smarts to getaddrinfo to list IPv4 addresses first
> > when 6to4 is in use to reduce the load on the relays.
> 
> it turns out that you need the address ordering to be sensitive to both
> network configuration and to the particular application.  some apps will
> be v4 by default, others will be v6 default, others will be exclusively
> one or the other.
> 
> Keith