Hello All,
My question is probably quite simple as I am new to SIP but I have 2 questions in relation to 3PCC best practices with SIP :http://tools.ietf.org/html/rfc3725.
In all of the examples in this document, the controller initiates the session. My first query relates to the scenario whereby if a device acting as a controller receives an invite. If this called controlling device was aware of a number of local devices it wanted to use in the session I imagine that it could either parse the initial invite SDP, and send the updated or new SDP (with relevant SDP parts) to each of the respective devices e.g. m =audio is sent to speaker, whereas m=video is sent to display device. Or an alternative approach would be just to forward the initial invite SDP to all the devices and parse and edit the SDP "answer" back to the calling device. Are both of these approaches valid? Please see the flow below :
Audio / Video Device Controller Speaker Display Device
|
|
|
|
|(1) INV SDP (m=video, |
|
|
| m=audio ) | | |
| ------------> | | |
| | (audio) | |
audio/video SDP at controller | |
| 200 OK(Combined a/v SDP) | | |
| <------------------ | | |
| (7) ACK | | |
| --------------> | | |
| | (8) ACK | |
| | --------------> | |
| | | |
| | (9) ACK -------------------> |
====================================================================
==================================Media Flow========================
====================================================================
| |2)INV SDP m=audio | |
| | ------------> | | | |3)INV SDP m=video | |
| | -----------------------------------> | | | | |
| | (4) 200 OK answer1| || | (audio) | |
| |<------------------| |
| | |(5)200 OK answer2 |
| | | (video) |
| (6)Parsing and combining of | || | |(5)200 OK answer2 |
| | | (video) |
| |<--------------------------------------|
| | | |
| | | |
| | | |
| | | |
audio/video SDP at controller | |
| 200 OK(Combined a/v SDP) | | |
| <------------------ | | |
| (7) ACK | | |
| --------------> | | |
| | (8) ACK | |
| | --------------> | |
| | | |
| | (9) ACK -------------------> |
====================================================================
==================================Media Flow========================
====================================================================
I have a second question in relation to a scenario where a session involve multiple devices on both sides. A controller on "each" side of the communication would be required here. I am not certain how this scenario would work but I assume the calling controller would invite its local devices to a session first with no SDP, and use the capabilities of these devices in the "invite" to the called controller. The called controller could then use this description data to invite its respective local devices?
Calling Side Called Side
Camera Microphone Controller - A Controller - B Speaker Display Device
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|
|
|
|
|
| |(1)INV No SDP| | | |
| | <----- | | | |
| | | | | |
| (2)INV No SDP | | | |
| <------------- | | | |
| | | | | |
| |(3)200 OK | | | |
| | with Audio offer | | |
| | -------> | | | |
|(4)200 OK| | | | |
| with video offer | | | |
| --------------> | | | |
| | | | | |
| | (5)Combine offers at | | |
| | Controller | | |
| | | INV SDP | | |
| | (Combined SDP) | | |
| | | ----------------> | | |
| | | | | |
| | | (6)Parsing of SDP | |
| | | | | |
| | | | (7) 200 OK answer1| |
| | | | for audio | |
| | | | <------------- | |
| | | | | |
| | | | |(8)200 ok ans 2 |
| | | | | for video |
| | | | <------------------------------- |
| | | | | |
| | | | | |
| | | (9)Combination of answers | |
| | | from various devices | |
| | | 200 OK COMBined answers| |
| | | <--------------------------------- | |
| |(10)ACK Audio| | | |
| | <-------- | | | |
| (11)ACK Video | | | |
| <----------------- | | ACK |
| | | | ---------------------------> |
=====================================================================================
===========================================Media Flow================================
=====================================================================================
| |(1)INV No SDP| | | |
| | <----- | | | |
| | | | | |
| (2)INV No SDP | | | |
| <------------- | | | |
| | | | | |
| |(3)200 OK | | | |
| | with Audio offer | | |
| | -------> | | | |
|(4)200 OK| | | | |
| with video offer | | | |
| --------------> | | | |
| | | | | |
| | (5)Combine offers at | | |
| | Controller | | |
| | | INV SDP | | |
| | (Combined SDP) | | |
| | | ----------------> | | |
| | | | | |
| | | (6)Parsing of SDP | |
| | | |INV SDP m=audio | |
| | | | ------------> | | | | | |INV SDP m=video | |
| | | | --------------------------------> || | | | | |
| | | | (7) 200 OK answer1| |
| | | | for audio | |
| | | | <------------- | |
| | | | | |
| | | | |(8)200 ok ans 2 |
| | | | | for video |
| | | | <------------------------------- |
| | | | | |
| | | | | |
| | | (9)Combination of answers | |
| | | from various devices | |
| | | 200 OK COMBined answers| |
| | | <--------------------------------- | |
| |(10)ACK Audio| | | |
| | <-------- | | | |
| (11)ACK Video | | | |
| <----------------- | | ACK |
| | | | ---------------------------> |
=====================================================================================
===========================================Media Flow================================
=====================================================================================
Thanks in advance,
Niall
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