Jitter is the variation in the arrival rate of packets at a destination point. Jitter is often caused by network congestion, timing drift, or route changes. Jitter is also measured in milliseconds (ms) (or thousandths of a second). Jitter greater than 30ms may result in packet drops thus impacting call-quality experiences.
Jitter simply refers to frequent changes in latency. In essence, the more that data packets within a conversation arrive at different times from one another, the higher the jitter. While you will always experience some latency, if you are regularly experiencing high jitter it means that the amount of latency you are experiencing changes frequently.
Data packets are transmitted at a certain speed. A sender sends packets to a receiver in millisecond intervals. Jitter occurs when this interval gets off track, leading to deviations or irregularities in runtime. The term "jitter” means fluctuation, oscillation, or a variation in frequency.
We measure jitter by making consecutive measures of latency, often using the RTT mentioned above, calculating the difference between the samples, then dividing by the number of samples (minus 1).
Here's an example:
macbook:~ hmerrett$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: icmpseq=0 ttl=56 time=976 ms
64 bytes from 8.8.8.8: icmpseq=1 ttl=56 time=475 ms
64 bytes from 8.8.8.8: icmpseq=2 ttl=56 time=361 ms
64 bytes from 8.8.8.8: icmpseq=3 ttl=56 time=473 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=56 time=391 ms
Here you can see 5 samples from a 3G connection. The average latency is 535.2 (add them, divide by 5). The jitter is calculated by taking the difference between samples.
976 to 475, diff = 501
475 to 361, diff = 114
361 to 473, diff = 112
473 to 391, diff = 82
If jitter is high, then you may want to increase your bandwidth. Usually, however, this comes at an additional charge. As an alternative, you can give higher priority to VoIP than to other data packets, such as emails.
The variation in the time between packets arriving, caused by network congestion, timing drift, or route changes. Typically, a jitter of 40ms or less is recommended. Perform the Jitter Speed Test.
