- Firmware version: Any
- Model: U-Series & Gateways
The problem could be like:
- The gateway is interconnected with Cisco CUCM by SIP trunk. The one-way audio issue happens when the call is retrieved from hold by CUCM extension.
- One-way audio after call established.
In the case of One-way Audio after Hold Retrieve from Cisco CUCM Extension: PCAP log show the call flow is complete, but the TG didn't send RTP packets to the CUCM media server after hold retrieve.
The CUCM uses the Late Offer model in SDP negotiation that the TG could not handle it properly when the SDP audio connection IP changes. It's kind of issue due to the Asterisk version.
Add MTP on Cisco CUCM to let it use Early Offer model is SDP negotiation.