Jitter is a variation in the delay of recieved data packets. When packets are sent, they are done so in a continuos stream and evenly spaced. Due to a variety of network issues, packets can become unevenly spaced or displaced. Two common causes of jitter are network congestion and route changes.
Jitter is especially important when discussing VoIP solutions. If packets are recieved out of order or unevenly spaced, it will severely affect the quality of your VoIP communications. Most companies will compensate for jitter with a QOS router. When a VoIP QOS router receives RTP audio streams, it uses a delay buffer, or queueing, before converting the packets back into an analog audio stream.
I addition to a QOS router, the type of internet connectivity you use to deliver VoIP is key to ensuring jitter does not cause quality issues. Most Tier 1 T1 carriers guarantee low jitter in their SLA.
