Telcobridges - Session Border Controllers
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One Way Audio/ No Audio Problems

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One Way Audio/ No Audio Problems Empty One Way Audio/ No Audio Problems

Post by Admin Wed Jan 02, 2019 2:41 am

One-way Audio/No Audio is a common VoIP problem. It is one of the most frequent support questions we receive. There are many possible causes.

  • Outdated firmware in routers, VoIP phones, Firewalls, etc. can cause one-way audio. Ensure you have the latest updates for all the devices in the call path.
  • Firewall mistakenly blocking RTP, be sure firewalls configured correctly
  • Particularly if NAT is involved in the call path, configuration of the various devices may be a problem. Please click here for NAT configuration on Telcobridges devices
  • Another reason for one way audio is having your system set to offering unsupported codecs within your other SIP systems.  

    • Please check the following link for TB supported codecs; Voice Codecs
    • Check if the codecs are configured correctly in the SDP; Profile SDP Description

  • Just as each side of a call must send RTP within the same codec, each side must also have the same phase timing (or ptime value).  Profile SDP Description
  • Configured RTP port ranges can cause a problem too. Check FreeSBC and endpoints (Clients, SIP Trunks) are using correct RTP ports. RTP Port Range
  • High one-way packet loss. If sufficient packet loss occurs in one direction on a call, that half of the conversion may break down, but not cause the entire call to drop. Packet loss can occur due to a number of reasons:

    • High utilization on a link with no QoS.
    • Misconfigured interface: Half-duplex or duplex mismatch.
    • Underperforming network devices.
    • Cabling faults.  

  • Wrong threshold configuration under SBC Advanced parameter can cause FreeSBC to block RTP-Audio by the firewall due to thresholds. You can see the following error in your call trace;
    ** Data path error;
    -Blocking all packets due to  excessive packets/bandwidth from network
    Please double check your thresholds configuration from;
    SBC -> Advanced parameters

Please check the following wiki for more troubleshooting steps; FreeSBC Troubleshooting Guide


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Registration Date : 2017-11-27

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