Hi John,
see in line my answers
thanks
/Sal
Elwell, John wrote:
-----Original Message-----
From: Salvatore Loreto [mailto:salvatore.loreto@xxxxxxxxxxxx]
Sent: 06 March 2009 12:57
To: Elwell, John
Cc: sipping@xxxxxxxx
Subject: Re:
I-DAction:draft-loreto-sipping-context-id-requirements-02.txt
Hi John,
thanks for your comments,
Elwell, John wrote:
<snip>
I agree that handling different media within a session on different
devices on the calling side and/or the called side is an interesting
scenario. However, I believe one of the requirements is as follows:
"REQx: It must be possible for a user participating in a multi-media
session to use different devices for different media,
without requiring
any special support at the peer UA, other than the need to support
different remote IP addresses for different media."
yes, you can use 3pcc mechanism to solve all the use cases
that is a fact.
Also the session mobility draft, in section 5.4.3 "Transfer
to multiple
devices"
http://tools.ietf.org/html/draft-shacham-sipping-session-mobil
ity-05#page-22
suggests the usage of 3pcc mechanism "/to overcame this problem/" that
"/there is currently no standard way to associate multiple
sessions as
part of a single call in SIP./"
And yes the 3pcc hides everything you do on your side to the peer UA.
Of course, using 3pcc make users want to use different device
"independent" from what you call "special support"
at the peer multimedia devices.
However there is the implicit requirement that the user has to have
among his device, at least one that support
3pcc and is able to behave as controller.
[JRE] Some special capabilities are required on both devices (e.g., the
audio device and the video device) to get them to collaborate including,
for example, sharing a common session ID. If you don't use 3PCC, you
need some other mechanism. Whatever mechanism we use between the two
devices, it should have minimum impact on the remote UA.
[Sal] I agree on the fact the the mechanism should have a "minimum"
impact on the remote UA.
Maybe we can say something about it in the requirements.
Moreover there is
an even more
strict requirement, the controller
must not leave the call for all the session time.
so lets say you are at your office and join a call using your mobile
phone for the audio, and your computer
for the video and the messaging part.
You can do that because the SIP UA on your computer probably
support the
3pcc, and then act as controller.
However if the call lasts too long and you have to go home,
but you want
continue to be involved in the call
only with the audio you cannot turn off your computer because
if you do
you will automatically thrown out
from the call; and if you leave the computer on, I am not
sure you will
then be able to hang up completely the
call using only your mobile phone and not the controller.
[JRE] Then you should transfer the call to your mobile before leaving
the office. We already have mechanisms for call transfer. The result of
transfer would be that all media that the mobile can support are
transferred to the mobile.
If you have two dialogs, as you propose, how would you deal with such
situations? For example, I am using audio on my mobile and from my
mobile I want to turn off video on my PC because I no longer require it?
This seems to require special communication between the two devices.
[Sal] that is a matter of solution.
However the required special communication
could be as simple as send a REFER triggering a BYE from your mobile to
your PC.
John
_______________________________________________
Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip
Use sip@xxxxxxxx for new developments of core SIP
