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.