A cousin to latency, Jitter is referred to as packet delay variation carrying voice or video data over a communications channel. Jitter happens when the RTP packet stream traverses the network (LAN, WAN, or Internet) because it has to share network capacity with other data.
Jitter can cause many participants to leave the phone call and either attempt to re-establish a connection or move to another form of communication. We often tend to ‘drop the call’ and quickly try to reconnect straight away. According to Cisco, the acceptable amount of Jitter time for a customer should be limited to 30ms. Jitter is more about pacing and a series of RTP packets that are coming in. When they appear in the right series in a good steady stream at regular intervals then you've got low jitter. Whether they come in interspersed intervals with holes, or if they appear out of order, then you've got a high jitter