1) what channel is used for sending status information back.
Async UDP
In-band escape sequences
...
(maybe this is something that you specify in your 'GET' request
if you're willing to accept them, and something that comes
back in the header if there's a place to recieve them)
2) What is the nature of the progress report:
percentage complete
amount of time remaining
X out of Y as Strata Rose indicated
I think we can manage to support all combinations of these,
optionally, in the protocol, and then see what actually gets
implemented and supported.