Re: draft-ietf-sip-info-events-00: CANCEL???

All,

IMHO allowing CANCEL of INFO requests is a bad idea, it introduces a 
RACE condition that any CANCEL will generally loose. It also introduces 
semantic issues: what does it mean to cancel a given INFO event? For 
INVITE it somewhat intuitively means stop ringing the phone and signal 
to the callee that the call was aborted, it is not generally clear what 
CANCEL for a generic INFO event would mean. For example, an INFO event 
might trigger some action that is not "undoable" (e.g. a gaming move in 
a multiplayer game, the final digit of a 4-digit access code, ... )

I do have a question regarding the - somewhat hypothetical - scenario of 
a mid-dialog INVITE being CANCELed: How does that affect the INFO 
negotiation mechanism state? I guess from a UAS perspective the 
UAC-provided Send-Info and Recv-Info in the INVITE should be reverted 
back to the last known values, and for the UAC the 487 response should 
cause it to revert to the previous state?

Regards,
Jeroen

[email protected] wrote:
>    From: Paul Kyzivat <[email protected]>
>
>    I have a question regarding the following paragraph:
>
>        A UAC MAY CANCEL an INFO request.  A UAS receiving a CANCEL for an
>        INFO request SHOULD respond to the INFO with a "487 Request
>        Cancelled" response unless the UAC has already sent a final response.
>        The UAS then MUST ignore future INFO requests.
>
>    Why would the CANCEL affect *future* info requests???
>
> I'm sure we *don't* want CANCEL to affect future INFO requests.  That
> adds another bit of state that has to be remembered, and I'm sure it
> will cause some weird complications.  (Among other things, what is it
> to "ignore" an INFO request?  What response code is that?)
>
> Dale
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