On Apr 5, 2009, at 8:57 PM, Bruce Lowekamp wrote:
Bernard,
Thanks for the comments. Let me see if I can describe a scenario in
which behavior-discovery is useful.
First, we don't want to "go back to 3489." There were two problems
(well, there were a lot more problems, but I just want to talk about
two right now) in particular that we don't ever want to go back to:
- 3489 specified that an application would start up, characterize its
NAT, and work in that mode forever after
- 3489 specified that if you had a friendly NAT, you could query the
STUN server for your transport address and use that one address
At the same time, behavior-discovery is targeting applications for
which ICE doesn't necessarily make sense. For example, applications
that don't want to fall back to TURN, but have other options for how
to establish a connection. (whether this means indirect routing or
not needing the connection, or other reasons)
So let me try to go into more details on a potential P2P application.
When P2P node A starts up, it evaluates its NAT(s) relative to other
nodes already in the overlay. Let's say that its testing indicates
it's behind a good NAT, with endpoint-independent mapping and
filtering.
This is the where this whole line of thinking goes off the rails. How
would we run a test that would indicate the above? Many of the NATs
out there you can not make this determination without multiple IP
addresses behind the NAT. I have raised this objection at the
microphone multiple times in the WG and it is always meant with
roughly the same answer that is here "ah, there are some details that
are in the draft but we can explain how to do it in the next version
of the draft". The draft is now in IETF LC and we have not seen
details on how to do this that work even in an opportunistic way. The
WG has not even had a chance to comment on if the believe these
details would work or not.
Cullen <as individual contributor>
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