Hi Community
I have an issue where we have a no audio issue for Delayed offer calls going to an SCCP 7940 phone (issue is happening with 7940/7960 and 7925 phones). We know those models are old, but I wanted to know if there is a workarround for my issue.
topology
IP Phone <-SCCP-> CUCM PBX <-SIP-> CUCM SME <-SIP-> CUBE
the CUBE sends early offer to the SME, all the rest of the flow is delayed offer
issue is that we recaive the invite in CUCM and all messages are normal, but the phone is not sending the StationInit indicating the RTP port number it will use so that the CUCM PBX can send it in the 200 OK, so this is causing the CUCM to send the 200 OK with a dummy port number 4000, then the phone is sending the port in the ack for the OpenReceive Channel, this causes the CUCM PBX to send an Invite to SME that then goes to the rest of the path all the way to the CUBE.
cisco stated the following:
With Delayed Offer on SIP leg, CUCM needs to offer media attributes which include codec support, IP and RTP port for media. In order to do so, CUCM initiates a similar process with the SCCP phone known as StationPortReq/PortResp before sending 200 OK response to SIP leg. If the phone is not capable to process StationPortReq/PortResp signals, CUCM does not know the RTP port of the phone and this process does not occur, hence CUCM responds to SIP leg with Port 4000(dummy) to the offer in SDP due to the real port is not known at that stage of the call. Then, when CUCM knows the port via OpenReceiveChannelACK message coming from the phone, the mid-call event takes place.
I understand that the phone models needs to be changed, but we are on the process of changing them. Thing is that I cannot change to early offer and I need them to work until we change them.
Anyone on the support site that can recommend a workarround for this situation with 7940/7960 and 7921/7925 phones?
All other models are working (7941,7942, 7945, 88XX, etc)
