Jitter is the difference in the time between the arrival of packets in an IP network. To compensate for jitter, VoIP endpoints contain a de-jitter buffer also called as a jitter buffer. Jitter buffers hold incoming packets for a specified duration so that voice samples can play at a normal rate to the user. In doing so, the jitter buffer also adds packet delay.
Excessive jitter can add to delay if the jitter still fits the size of the jitter buffer. Excessive jitter can also result in packet discard creating voice quality problems when the variation is greater than the jitter buffer size. The size of the static jitter buffers must be twice the largest statistical variance between packet arrivals. Dynamic jitter buffers give the best quality. However, the resizing algorithm of dynamic buffers must not result in adverse effects. Dynamic jitter buffering can exacerbate problems in an uncontrolled network. The network topology can also affect jitter. Multiple paths between endpoints with and routers enabled with load balancing can contribute significant amounts of jitter.
The following Avaya products have dynamic jitter buffers to minimize delay by automatically adjusting the jitter buffer size:
