Re: [BLISS] I-D Action:draft-ietf-bliss-ach-analysis-02.txt

This looks pretty good to me. I wish I had had time to participate in 
the work. I have just a few comments:

- I have difficulty figuring out how to selectively deal with call 
waiting. If a UA could answer a call, even though it already has a call 
in progress, and would be willing to do so if needful, how can it defer 
to the proxy? Once it has rejected the call, it can't later answer it. 
And if the proxy, based on policy, later decides to present the call 
again, I don't see how the UA would know to answer it this time.

- What does it mean to be busy? (This is related to prior point.) Being 
on one call does not necessarily mean inability to take another. Nor 
does *not* being on a call mean you are not busy. In some cases it is 
literally possible to manage two calls simultaneously. (E.g. when they 
are IM sessions.) In other cases it is a matter of time division 
multiplexing between two sessions, so that the callers will realize they 
don't have full attention of the callee. Sorting this all out wold seem 
to be a complex policy problem, requiring a lot of data that won't 
easily be available to a proxy.

- rejection scope: It seems that there could be useful to have two 
different degrees of local rejection. As currently described in the 
draft it is proxy policy that determines if local rejection cancels 
delivery to other local UAs or not. But that could be something that 
might be desired as a per call option to the user on the UA. (The 
distinction between stopping only this extension from ringing, or 
stopping all extensions from ringing.)

	Thanks,
	Paul

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