Let's have a little Focus
I figured I'd talk a little about the OCS conferencing architecture in this blog. The OCS Conf architecture consist of 3 main components: The focus, focus factory, and the MCUs. The Focus is the traffic cop. It is a conference state server that coordinates all aspects of a conference. The focus runs in the user services module on all FE servers. A separate instance is used for each "active" conference. The Focus is responsible for authenticating particpants for a conference, managing roles, managing conference state, calling for the MCUs, Maintaining SIP signaling between participants and MCUs, activating conferences, and accepting subscriptions to conference.
When a new media type is introduced into a conference the focus is responsible for calling the MCU and establishing connections for the new client and new media. This happens to all clients when new media is introduced.
The focus factory is used to create, delete, and modify meetings in the conference database. The focus factory receives a SIP SERVICE message with C3P cmds in payload from the client. The focus factory updates the database with a new meeting and sends the conference URI to the client.
There are 4 different MCU or conferencing servers for OCS:
- A/V
- Web Conferencing
- IM Conferencing
- Telephony Conferencing.
The A/V provides for multilparty audio and video mixing and relaying using RTP.
For IM the MCU provides for multiparty IM. Up to 100 participants.
For Web Conferencing this server component manages all aspects of the web conference including the ppts, document sharing, whiteboarding, app sharing, polling, q&a, etc. The web conferencing server using PSOM (Persistent Shared Object Model), a live meeting protocol, for operations including slide uploading to the web conference.
