Re: [Sip] Comments to the TOTE draft

[Adam Roach <adam at nostrum.com>]

On 2/28/08 9:33 AM, Miguel Garcia wrote:
> Inline as well.
>
> Jonathan Rosenberg wrote:
>   
>>
>> How do you do pause with MSRP? Specifically, how does the receiver tell 
>> the sender to pause? How does the receiver cancel?
>>     
>
> Pause from receiver to sender: re-INVITE with SDP offer with the MSRP 
> media stream set to inactive.
>
> Cancel from receiver: re-INVITE with SDP offer setting the MSRP media 
> stream to port 0.
>   

This is getting off-topic, but I'm a bit concerned about using 
sledgehammers where screwdrivers are warranted.

For canceling a file transfer -- that is, a single MIME object -- you're 
better off using the approach described in section 10.5 of RFC 4975. 
Otherwise, you're running the risk of throwing out an ongoing IM session 
just because you don't want to complete a specific file transfer.

In the pause case, I agree that putting the MSRP stream on hold is a 
valid way to convey the semantics of, "I want you to pause everything 
inside this MSRP session," including the file transfer, but by no means 
limited to it. For most IM-related use cases, it would seem that this is 
very unlikely to be what the user expects, wants, or is even willing to 
put up with.

For example: imagine that we're in an IM session using a client designed 
as you propose above. You start sending me a 5 Mb file. A dialog box 
pops up on my screen that conveys the progress of this file; it contains 
two buttons: [Pause], and [Cancel]. I press the button marked "Pause," 
and the file stops arriving. And suddenly you stop responding to my 
instant messages. Perhaps I manage to guess that the IM session has 
frozen because I paused the file transfer. So, to fix this, I press 
[Cancel]. And the whole IM window just goes away.

/a
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