PPT Slide
(1) The call agent (CA) sends Notification Request messages (RQNT) to both gateways (GW1 & GW2) to look for an off hook event (hd).
(2) An off hook event (hd) is detected by gateway #1 (GW1), in turn sending a Notify message (NTFY) to the call agent (CA).
(3) The call agent (CA) sends a Create Connection message (CRCX) to gateway #1 (GW1) to create an RTP session, and returns its Local
Connection Descriptor for the endpoint (P1).
(4) The call agent (CA) sends a Notification Request message (RQNT) to gateway #2 (GW2) to signal the endpoint (P2) to start ringing.
<At this point the endpoint (P2) at gateway #2 (GW2) is ringing>
(5) An off hook event (hd) is detected by gateway #2 (GW2), and in turn sends a Notify message (NTFY) to the call agent (CA).
(6) The call agent (CA) sends a Create Connection message (CRCX) with the Remote Connection Descriptor of endpoint (P1)
to gateway #2 (GW2) to create the other RTP session.
(7) The call agent (CA) sends a Modify Connection message (MDCX) with the Remote Connection Descriptor of gateway #2 (GW2)
to gateway #1 (GW1) to modify the first RTP session.
<At this point, ringing is removed and there is an established audio path between the two phones (P1 & P2).
(8) The call agent (CA) sends a Notification Request message (RQNT) to both gateways (GW1 & GW2) to look for an on hook event (hu).
(9) An on hook event is detected by one of the gateways (GW1 in this case), in turn sending a Notify message (NTFY) to the call agent (CA).
(10) The call agent (CA) sends a Delete Connection messages (DLCX) to both gateways (GW1 & GW2).