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Multi Point Conferencing - Call Flow

Hi All

Wanted to confirm the call flow for multiconferencing callflow.. Im using polycom devices, though the technology looks the same..

with Point 2 point - we will have a H225/h245 from endpoint (VC terminal) to gatekeeper, and upon negotiation RTP session is established between the endpoints.. right ?

now with multipoint - again there would be h225/245 negotiation from endpoint to gatekeeper.. now with external MCU, there would be another H323 session between gatekeeper and MCU .. upon successful negotiation thro gatekeeper (CMA 5000), the GK forwards request to external MCU (RMX) and then MCU stitches the multipoint calls to a conference.. is that right ?



Everyone's tags (2)
Cisco Employee

Re: Multi Point Conferencing - Call Flow

That is correct in a point to point phone call the audio stream is directly between the two phones.  In the multipoint or conference scenario once the audio streams are setup, each device will transmit audio to the MCU or conference device, and then the conference device will duplicate the stream it receives and send it out to all the other phones.  Basically all audio is sent to the conference device and the conference device is what everyone listens to (the audio is sourced from).

Re: Multi Point Conferencing - Call Flow

Hi Joe

Thanks for the confirmation.

so with multipoint, the video endpoitns have RTP with the MCU. right ? would there be H.323 connection between end point and external MCU? or is the H323 only between video codecs & gatekeeper ? I see the external MCU has all devices mapped to it, but wanted to confirm if the call negotiation first happens with gatekeeper, and the GK inturn forwards it to MCU ?

I hope this is the same with IP/ISDN external MCU's like MGC 100 ??

Thanks again..


Cisco Employee

Re: Multi Point Conferencing - Call Flow

Right the endpoints send RTP directly to the MCU.  The next question about whether or not the endpoints have h323 to the MCU depends.  If the endpoints are registered to call manager the call manager has H323 traffic to/from the MCU but not the end points.  There also isn't H323 between the gatekeeper, the gatekeeper will just determine the IP of the end point to send the H225 SETUP to.

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