on DNS records

As I promised last week, I've substantially developed a draft (and some
code) to look more closely at whether a DNS record can be helpful. 
Before I get it out there, I wanted to check goals.  The situation is
this: there is a 2.0-enabled client and it must determine whether or not
the other end can speak 2.0.  Gabriel and Willy have already shown us
that it can be done INSIDE the protocol at the expense of one roundtrip,
but at the risk of a proxy doing the wrong thing (a classic case being
that it allows an Upgrade: header but then barfs all over the upgrade). 
So let's state our goals:

1.  Keep latency down.

  * First, is this a reasonable goal?
  * Can it reasonably be done better than what Willy & Gabriel have laid
    out?

2.  Transport Protocol Discovery

  * Some have suggested that it would be useful to do HTTP over UDP or
    SCTP.  Is that something that is a reasonable goal?

3.  Handle the case where multiple instances of the same application
protocol reside on the same host, but on different ports.

  * Is this a reasonable goal?

4.  No new URI schema

  * Address the 'side of the bus' problem.
  * Is this a reasonable goal?


Does this about cover it?  I claim we can solve all four, but not easily
with SRV.

Eliot