Diagnosing poor audio quality problem

Last Updated : Feb 07, 2024 |

Procedure

  1. Verify if a network assessment has ever been done and if the network remained unchanged after the assessment.

    If the assessment has been done or if the network remained unchanged, there might be a media module, IP telephone or network problem, or the IP telephone might have outdated software. If not, the network may not be compliant with the Avaya’s network requirements. If the problem cannot be resolved by using the procedures described below, an assessment or reassessment might need to be done, go to Step 2.

  2. Verify if the other IP Telephones on the same VLAN/subnet/floor experience the same problem.

    If other IP Telephones experience the problem, there may be a network problem, or multiple IP Telephones may have outdated firmware (see Software, firmware, and BIOS update or the Avaya Support Web site http://support.avaya.com).

  3. Verify if there is a separate VLAN or subnetwork used for voice.

    The customer can check this on the Ethernet switches.

  4. If there is a separate VLAN or subnetwork used for voice, check if the Ethernet switch connected to the media module is set to auto-negotiation.
  5. If there is no separate VLAN or subnetwork used for voice, check if the number of broadcast messages received are lower than 1000 messages per second (this is the number that can safely be handled by the IP telephone).
  6. Use the change ip-interface location command to check the ETHERNET OPTIONS settings.
  7. If the Auto field is set to y, go to Step 11.
  8. If the Auto field is set to n, change the setting to y (auto-negotiation enabled).

    If this is not possible, set the media module speed and duplex to match the switch port.

  9. Use the network management system or hook up a protocol analyzer to the network to check the number of messages.

    If this cannot be checked through the network management system, go to the subsequent steps first, as it takes a relatively large effort to hook up a protocol analyzer.

  10. If the number of messages are lower than 1000, go to Step 4.

    If not, there is a network problem. The customer should put the voice traffic (audio and signaling) on a separate VLAN with 802.1p priority 6 (the priority value reserved for voice and other real-time traffic).

  11. Verify if the Ethernet switch connected to the IP telephone transmitting in HDX mode by logging in to the Ethernet switch.

    The 4606, 4612, 4624, and 4630 IP Telephones are only capable of HDX transmission. The 4602 and 4620 IP Telephones do support full-duplex mode, but require that the Ethernet switch to which they are connected be set to autonegotiate mode.

  12. If the Ethernet switch is connected, refer to Verifying if 802.1p QoS and IP DiffServ are properly and consistently used in the switches, and routers. If not, change the switch setting to HDX (or auto for the 4602 or 4620). If this solves the problem, no further steps need to be taken.
  13. Verify if 802.1p QoS and IP DiffServ are properly and consistently used in the switches, routers, and the media module. Check if the call traverses a WAN link. Refer to Verifying if 802.1p QoS and IP DiffServ are properly and consistently used in the switches, and routers.
  14. Log on to the WAN routers and verify if the available bandwidth is sufficient to support voice.
    Note:

    Avaya recommends using G.729, which requires 24 Kbps (uncompressed, excluding Layer 2 overhead). IP packet fragmentation should be turned on when no DiffServ QoS facilities are available. On Avaya and Cisco routers it is possible to minimize bandwidth for audio usage by using the CRTP (compressed RTP).

  15. If the available bandwidth is sufficient, escalate the problem to your technical support representative.
  16. Check if the voice codec set to G.729 for calls across a WAN. Refer to, Verifying if the voice codec set to G.729 for calls across a WAN.
  17. If the voice codec is not set to G.729, change the voice codec to G.729 (which is a lower bandwidth encoder than G.711, but still provides high quality) by executing the change ip-codec-set command and by putting G.729 at the top of the codec list.

    If this solves the problem, no further steps need to be taken.

  18. Check if the end-to-end packet loss less than 1%. Refer to Packet loss analysis tools. If the loss is less than 1%, there is a network problem. The customer should explore the possibility to upgrade to a WAN link with the appropriate bandwidth and quality to ensure that it is compliant with the Avaya network requirements, possibly by establishing a new Service Level Agreement (SLA) with a network service provider. A network assessment or reassessment might need to be done. If the loss is more than 1%, there might still be a network problem. Escalate the problem to your technical support representative.