![]() ![]() ![]() How to check really quick if the phones are sending / receiving RTP (audio). * Signalling issues, (call agent is not passing the correct ports or codec, or the communication is tagged as 'send only' or 'receive only') * RTP traffic is being misrouted, (by a route recently added / learned, or a VRF or WAN) * RTP traffic is being blocked or consumed by a FireWall, (FW), or another security device. Now, the possible causes for these issues are: * Then both phones open the audio channel and start transmitting and receiving RTP packets, please notice this Tx and Rx of audio packets (RTP Packets) is a point-to-point communication between the phones, the audio does NOT go through CUCM, (unless there is an MTP or CFB from the server itself involved), in case this is an external call the audio goes directly from the phone to the ingress / egress GW. * At this point you will see that the call is 'connected', (and it is at a signalling level), please notice this is just the phones talking to CUCM or the PBX. * If Phone B picks up the handset or press the speaker button then the call agent will ask both phones for the port they want to use to receive audio and will send that information to the other end. * The call agent indicates Phone B that there is an incoming call from Phone A. * The call agent, (CUCM, VCS, CME, or another PBX), receives a request from Phone A indicating that it wants to call Phone B. * OK, so here is a high level description of how this works: Sometimes the users even refer to these as "dropped calls" because they get a call, there is no audio and after a few seconds they hear reorder tone, (fast busy), this happens because the caller cannot hear the called phone and it's getting dead air and hang up, or maybe they can hear the other end, but realize that the called phone cannot hear them and hang up. ![]() So, first of all, you may get reports from end-users about one way or no way audio or maybe "ghost calls". If you are experiencing one-way or no-way / no audio issues, here is what you need to do to fix that easily.Īlso check and bookmark the main page of these 'how to' series which is continuously updated with Unified Collaboration Resources.Ĭnuche's One Stop, Unified Collaboration Tech Resources - Continuously updated.Ī one-way audio call is when you have a call between 2 phones (internal-internal or internal-external), and one of them cannot hear the other end.Ī no-way / no audio call is when you have a call between 2 phones (internal-internal or internal-external), and none of them can hear each other.īefore you start thinking about fixing that, you need to understand what is going on, how does it works, and what causes this problem. ![]()
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