Subject: [Insipid] Conference INSIPID backwards-compat call flows

From: Hadriel Kaplan <[email-masked]>
Date: Sat, 17 Aug 2013 10:09:14 -0400

This email is about the conferencing cases.

Note that as far as I'm aware, the INSIPID requirements document does NOT consider these call flows in-scope, in the sense that it says they're actually separate, distinct communication sessions. 

See section 3.2 in the requirements draft:
http://tools.ietf.org/html/draft-ietf-insipid-session-id-reqts-08#page-4

Regardless, below are the call flows...

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9.4. Single Focus Conferencing

   Multiple users call into a conference server (say, an MCU) to attend
   one of many conferences hosted on or managed by that server. Each
   user has to identify which conference they want to join, but this
   information is not necessarily in the SIP messaging.  It might be
   done by having a dedicated address for the conference or via an IVR,
   as assumed in this example. Each user in this example goes through a
   two-step process of signaling to gain entry onto their conference
   call.

      Session ID                Conference
         ---     Alice            Focus             Bob            Carol
                   |                |                |               |
                   |                |                |               |
         {A}       |----INVITE----->|                |               |
        {A;M1}     |<---200 OK------|                |               |
        {A;M1}     |-----ACK------->|                |               |
                   |<====RTP=======>|                |               |
        {A;M'}     |<---reINVITE----| (to change the |               |
        {A;M'}     |-----200 OK---->|   UUID to M')  |               |
        {A;M'}     |<-----ACK-------|                |               |
                   |                |                |               |
                   |                |                |               |
         {B}       |                |<----INVITE-----|               |
        {B;M2}     |                |-----200 OK---->|               |
        {B;M2}     |                |<-----ACK-------|               |
                   |                |<=====RTP======>|               |
        {B;M'}     | (to change the |----reINVITE--->|               |
        {B;M'}     |   UUID to M')  |<----200 OK-----|               |
        {B;M'}     |                |------ACK------>|               |
                   |                |                |               |
                   |                |                |               |
         {C}       |                |<--------------------INVITE-----|
        {C;M3}     |                |---------------------200 OK---->|
        {C;M3}     |                |<---------------------ACK-------|
                   |                |<=====================RTP======>|
        {C;M'}     | (to change the |--------------------reINVITE--->|
        {C;M'}     |   UUID to M')  |<--------------------200 OK-----|
        {C;M'}     |                |----------------------ACK------>|

                  Figure 4 - Single Focus Conference Bridge

---------------------------------------------------------------------------

9.5. Single Focus Conferencing using WebEx

   Alice, Bob and Carol call into same Webex conference.

      Session ID                Conference
         ---     Alice            Focus             Bob            Carol
                   |                |                |               |
                   |<** HTTPS *****>|                |               |
                   |  Transaction   |                |               |
                   |                |                |               |
         {M}       |<----INVITE-----|                |               |
        {M;A}      |-----200 OK---->|                |               |
        {M;A}      |<-----ACK-------|                |               |
                   |<=====RTP======>|                |               |
                   |                |                |               |
                   |                |<** HTTPS *****>|               |
                   |                |  Transaction   |               |
                   |                |                |               |
         {M}       |                |-----INVITE---->|               |
        {M;B}      |                |<----200 OK-----|               |
        {M;B}      |                |------ACK------>|               |
                   |                |<=====RTP======>|               |
                   |                |                |               |
                   |                |<****************** HTTPS *****>|
                   |                |                   Transaction  |
                   |                |                |               |
         {M}       |                |--------------------INVITE----->|
        {M;C}      |                |<-------------------200 OK------|
        {M;C}      |                |---------------------ACK------->|
                   |                |<====================RTP=======>|

                  Figure 5 - Single Focus Webex Conference

---------------------------------------------------------------------------

9.6. Cascading Conference Bridge Support for the Session ID

   To expand conferencing capabilities requires cascading conference
   bridges. A conference bridge, or MCU, needs a way to identify itself
   when contacting another MCU. RFC 4579 [RFC4579] defines the 'isfocus'
   Contact: header parameter just for this purpose.

      Session ID
         ---     MCU-1            MCU-2            MCU-3           MCU-4
                   |                |                |               |
         {M'}      |----INVITE----->|                |               |
        {M';J}     |<---200 OK------|                |               |
        {M';J}     |-----ACK------->|                |               |

          Figure 6 - MCUs Communicating Session ID UUID for Bridge

      Session ID
         ---     MCU-1            MCU-2            MCU-3           MCU-4
                   |                |                |               |
         {M'}      |----INVITE----->|                |               |
        {M';J}     |<---200 OK------|                |               |
        {M';J}     |-----ACK------->|                |               |
                   |                |                |               |
         {M'}      |---------------------INVITE----->|               |
        {M';K}     |<--------------------200 OK------|               |
        {M';K}     |----------------------ACK------->|               |
                   |                |                |               |
         {M'}      |-------------------------------------INVITE----->|
        {M';L}     |<------------------------------------200 OK------|
        {M';L}     |--------------------------------------ACK------->|

       Figure 7 - MCU Communicating Session ID UUID to More than One

-hadriel