Troubleshooting: Call Quality Specifics

Topics Covered: Choppy Audio, One Way Audio, Delayed Audio, Static and Echo

Common Causes

Jitter/Latency - Frequently caused by saturation on a node or circuit with the exception of WAN Transit time (Latency); or incorrect QoS prioritization settings.
Packet Loss - The WAN or LAN is dropping packets.
Discards - These occur when the receiving end cannot interpret the contents of the SIP packet. Causes include incorrectly configured ports, duplex mismatch between nodes, faulty routes, SIP header manipulation, or saturation on nodes.

Jitter/Latency/Packet Loss -

Determine where the packet loss or latency is occurring with a diagnostic tool like PingPlotter. This will monitor out to a host and give trace route details including packet loss on each hop.
Run the diagnostic tool for a few minutes to determine the condition of the transport.
Perform a speed test to determine if the circuit is saturated.
You will typically see packet degradation over the transport, so you will want to engage the transport.
If packet loss or latency is detected on internal hops, then the issue might be on the internal
In this case, check log data for port errors.
If needed, add Jitter Buffers to network nodes or endpoints.

-Packet Loss

Contact the ISP for WAN packet loss.
Check the internal network for LAN packet loss.
Discards - If a port is saturated or not setup properly you will see discards on that interface.
Determine if SIP heater manipulation is occurring. This can cause packets to be discarded by Simplicity network.
Run a PCAO
Check the ISP gateway device, the firewall, and the edge device. If SIP ALG and/or SIP Transformation is enabled, this can cause SIP header manipulation.

Common Causes

Tx/ Rx Issue- This refers to a problem where transmit and/or receive packets are not flowing correctly across the network. For example, if you make an outbound call and cannot hear the other party, but they can hear you - this would indicate a problem on the receive (Rx) end.
Hardware/Analog Issue - A problem with a specific device such as a desk phone, softphone, or headset.
Packet Loss - This is more likely to cause choppy audio, but excessive packet loss in one direction can also result in one way audio.

Troubleshooting Steps/Solutions

Tx/ Rx Issue- If either party cannot not hear the other party, first determine which side of the call has lost audio:
- - Setup a capture on the edge of the network to check outbound traffic flow.
  - If outbound traffic flow is normal, contact Simplicity Support.
  - If outbound traffic flow is not normal, check the local network.
    - Setup a capture on the LAN to identify where the traffic is getting lost.

-Hardware/Analog Issue

Have the user try a different communication method. For example, if they are using a headset, have them use the speakerphone or handset instead.
Test the phone at another working location. If the problem travels with the hardware, it might need to be replaced.

Packet Loss

Common Causes

Troubleshooting Steps/Solutions

Determine where the jitter or latency is occurring. Most often these problems are coming from the WAN and must be resolved with the ISP.

Common Causes

Hardware Issues - A problem with a specific device such as a headset, desk phone, handset coil, or connector.
Interference - This usually causes white noise on cordless or analog phones.
Cable Degradation - Common with IP to analog devices.

Troubleshooting Steps/Solutions

Hardware Issues

Make test calls using different methods to determine which hardware component is causing the problem. For example make calls using the headset, handset, and speakerphone.
Check each device’s volume level.
Test with a lower volume to see if that resolves the problem.
Test each device from a known working location.

Interference

Make sure cordless base stations are not located near infrastructure devices (such as large electrical equipment).
Cable Degradation - Use cable testers onsite to verify the integrity cable runs.