I largely agree with Jonathan.
I even agree that an *ideal* solution will have the aggregated devices
aware that the aggregation is present. But I think it is also important
to be able to create such aggregations where only a subset of the
aggregated devices are aware of the aggregation. This is just a
recognition of the need to accommodate existing devices. It may be
suboptimal, but still more optimal than not having the aggregation at
all. For instance its easy to imagine this being orchestrated from one
"smart" device and a variety of "dumb" devices. So I see 3pcc as *one*
implementation, for which no additional standardization work is
required. There could be additional standardization work to communicate
the aggregation details among the cooperating devices.
Just in case it isn't obvious, the aggregation can occur at both ends of
the call too. That is all the more reason for aggregation at one end to
be hidden from the other end. The media may be disaggregated in
different ways at the two ends. If each end must be aware of what is
going on at the other end, then this becomes an O(n^2) problem.
Thanks,
Paul
Jonathan Rosenberg wrote:
Thanks for continuing to work this, Salvatore.
My main comment, as others have commented, is that the draft provides a
great set of use cases. However, it makes the fundamental assumption
that the right way to solve this is by having multiple dialogs from user
A to user B, and then have them correlated. I am *far* from convinced
this is the right solution.
So, focusing strictly on requirements, I'd like to see this document
retitled to something like, "Requirements for Supporting Disaggregated
Media", and keep the use cases, except delete the bits that suggest that
the problem is multiple dialogs. For example, in section 2.1, the first
two paragraphs are good, but the last two *assume* the multiple dialog
solution.
Other suggestions for similar use cases:
* voice/video from a deskphone and application sharing from PC
* voice from a deskphone and video to/from a TV attached to a set top
box with a camera
* the UI for the call on a mobile phone but the audio coming out of a
speakerphone in a room
There are lots more. I think the draft just should enumerate these.
The requirement, then, is a mechanism which allows these use cases. I
personally think that the solution should be *completely invisible* to
the far end of the call. In all cases, all of the various devices under
Alice's control (where Alice is the one with a multiplicity of devices)
need some kind of enhancement to make this work; I would very much like
to avoid the need for Bob to do *anything* to make this work. The reason
is simple: its much, much easier for a user to upgrade (or their provier
to upgrade) the devices under their control to get a feature that
benefits them, than it is to require *everyone else* to upgrade in order
to get a feature to work which benefits me.
The document has this requiremnt:
REQ3 UAs that do not implement the correlation mechanism and, thus,
do not understand the correlation information they received should
be able to handle the individual SIP dialogs that were supposed to
be correlated as well as possible. That is, the correlation
mechanism should not keep them from trying to handle the SIP
dialogs.
this is not nearly strong enough. I think the real requirement is:
REQ3: The mechanism should not require any changes to the far side of
the session.
I also don't think 3pcc is a particularly good solution either; besides
the issues raised in the threads about requiring one device to be
controller and the resulting complications, it also results in a really
suboptimal user experience because the slave phones think this is just a
normal call when its not. As a simple example, the caller ID on one of
the slave phones would probably show the controller and not the far end.
As another example, consider a PC doing video and audio on the
hardphone. What if the hardphone can also do video, and the user hits
the video button on the phone? Most likely this creates two video
streams. Ugh. Indeed, the hardphone would ideally indicate that there
already WAS video in progress, but on a PC. All of this means you can't
really just 'fool' the slave phone into sending media somewhere - you
really want it to be much smarter about this situation and be well aware
that there is disaggregated media.
Thanks,
Jonathan R.
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