Communication Panel audio issues

Network Address Translation (NAT) binding timeout on User Datagram Protocol (UDP) media ports

NAT/firewall closes UDP port bindings during idle periods (for example overnight). In the first call of the day, the Real-time Transport Protocol (RTP) stream is sent to a now invalid NAT mapping, resulting in one-way or no audio.

To fix this:

• Enable RTP keep-alive on the AudioCodes SBC and/or SIP endpoints.
• Configure frequent enough NAT binding refreshes (for example, every 15-30 seconds).
• Use symmetric RTP if supported.

Codec mismatch or delayed negotiation

Codec negotiation failure or delay in Session Description Protocol (SDP) exchange on the first call may cause missing audio.

To fix this:

• Verify codec priorities and make sure common codecs (for example, G.711 and Opus) are aligned across systems.
• Make sure there's no asymmetric codec handling on the first session.

Session Border Controller (SBC) media session not properly initialized

The first media path may not get properly opened due to the SBC being in a dormant or idle state, or media anchoring not being fully active.

To fix this:

• Check if media-anchoring or early media support is properly configured.
• Enable media timeout settings or pre-establishment of RTP on the SBC.
• Ensure ICE/STUN/TURN is used if endpoints are WebRTC-based or behind NAT.

Ensure that the latest firmware is installed on the SBC

It is always a good practice to keep SBC firmware as up to date as possible.

General diagnostic steps to investigate the issue

• Check SBC syslog and trace files for the first call SIP and RTP behavior.

• Use tools like Wireshark or SBC's built-in trace tools to verify:

  • SDP negotiation
  • RTP stream establishment
  • NAT behavior