MGCP Call Flow with Early Media

[agentjoe141]

Hello All,

Hope you guys are going great,

Currently, I am Studying about MGCP. I have studied basics of MGCP Call flows and other configuration items. But  i am unable to find any documentation or expert note regarding MGCP Call flows with Early Media. If someone could please provide me the necessary details, that would be awesome.

Thanks

[Vivek Batra]

This small piece of information explains well about SDP exchange.

http://flylib.com/books/en/2.285.1.27/1/

[agentjoe141]

Hello Vivek,

Thanks for your response. But in case of an Early Media, could there be any possibility that during the CRCX message exchange from Call Agent the SDP Parameters are encapsulated within the CRCX message and then the RTP Stream opens, without MDCX Message ?

Please follow my diagram

My request is to please authenticate this Call Flow.

Thanks

[Mohammed al Baqari]

Hi,

Are you asking about MGCP ringback.

Ringback is provided to calling phone through voice-cut through. This is the case whether the calling phone is local to MGCP gateway or non-local (remote PSTN phone). During call setup, the RTP connection will be created in recvonly mode. However, after call answering, the connection will  be modified to sendrecv status.

[agentjoe141]

Hi Mohammed,

No, it is not about MGCP Ringback, I need to know the Call Flow during Early Offer in MGCP.

Thanks  :)

[Mohammed al Baqari]

Fine. MGCP is different that SIP or H323 where you have early offer (fast start) or delayed offer (slow start).

MGCP is gateway controlled protocol or client server. It has single mode which is controlled by CUCM. CUCM will send the first CRCX with SDP. CUCM won't negotiate with gateway. Instead, it will order the gateway.

You don't have VoIP dialpeers configured on MGCP gateway for negotiation. Hope this clarifies

[agentjoe141]

Hi Mohammed,

I am sorry, i want to know about the Call Flow in MGCP in "Early Media".

Thanks