automatic tunneling and v6 interoperation

[Pekka Savola <pekkas@netcore.fi>]

Hi,

Christian presented issues in the Unamanged connectivity possibilities in
Minneapolis on Wednesday.

There are multiple issues which I don't think came across clearly.  I hope
this mail helps in clarifying them.

1) the implication of economics to automatic tunneling mechanisms

Christian stated that tunnel brokers and similar mainly make sense (from 
economics perspective etc.) if the ISP [or maybe also a transit of the 
ISP, btw.] is providing the service.

However, what was not clearly noted that similar economics problem exists 
with automatic mechanisms as well.  For example, if you want to go from 
a Teredo host to {native,6to4} hosts, who is providing the relay service?  
Clearly, the ISP where the Teredo host resides is not, because then by 
definition they could deploy e.g. tunnel service instead.

2) the implication of "no relays" deployment to v6 interoperability

If there are no relays, note that every node a Teredo host needs to
communicate with has to implement and enable Teredo, as well as publicize
the Teredo addresses in the DNS in addition to the others, correct? 

(Similar would be equally applicable to no-relays deployment of 6to4, with
the difference that every site, not every node, would have one enabled
6to4 router and publicized addresses.)

3) lifespan of a solution

Solution like this must be supported for a long time, as long as there are 
people who go through NATs, unless their mechanisms are collectively 
everywhere replaced by something else.  That may or may not be reasonable, 
if you expect the implementation of the techniques in every node.

==> trying to summarize..

So, I don't think Teredo (or 6to4 for that matter, but it's slightly 
better from the second perspective) really solves the "economics of 
providing IPv6 service" -problem.  The only thing it seems to solve, to an 
extent, is a relatively smooth and direct IPv6 connectivity between Teredo 
hosts.  On the other hand, speaking to any other kind of nodes (e.g., 
6to4, native, ...) is riddled with identical problems as the IPv6 
deployment at ISPs.

It's best to be sure to understand the problems automatic tunneling
mechanisms try to solve.  Both Teredo and 6to4 seem reasonably usable if
used only between {6to4,6to4} and {Teredo,Teredo},
({native|tunnel-service,native|tunnel-service} being the first category).

But I guess the question is whether we want 3 separate IPv6 Internets, and 
reducing that would only be possible through the addition of the lowest 
common denominator, Teredo, everywhere? (The alternative is a network of 
relay systems, which don't make sense economically.)

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings