I think this is more of an issue for Extensible Proxies than the
others.
I'm in complete agreement on the fault isolation issue. For other
things, while roles and responsibilities are ultimately important, binding
agreements on paper are perfectly acceptable (i.e., they do not
have to have an on-the-wire format).
I agree with this sentiment. I'm not trying to insist that the details
of such agreements be made a part of the protocol (though it would be
nice if we could do it, I suspect it would take a long time before we
could find a good way to encode the needs of real users into a protocol)
Keith