Why it matters:
Packet drops and jitter can greatly reduce the quality of a VoIP call. When troubleshooting VoIP call quality issues the following items should be looked at.
- Interface errors
- Buffer errors
- Interface congestion
- Link congestion
- Round Trip delay
A simple ping test can be used to exams the round trip delay (latency). The round trip delay should not exceed 300ms ideally much less. Ideally the delay (latency) should be consistent; as to not introduce jitter or variance in the delay.
In a Cisco environment the show interface and show interface stats command can be used to examine the other counters.
A network analyzer can also be used to greatly reduce the amount of time troubleshooting such issues. For example a Path Analysis test can be used to gather all the stats along with ping times from the two end points in 1 simple test.