One Way Audio/ No Audio Problems

[Admin]

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• Outdated firmware in routers, VoIP phones, Firewalls, etc.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;
  

  Code:

  SBC -> Advanced parameters

  
  

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