Jitter is the variation in packet delay over time. If packets that should arrive evenly spaced arrive in bursts or at uneven gaps, the network has high jitter even when average latency looks acceptable.
Why it matters
Real-time applications need steady delivery. Voice and video calls use a jitter buffer to smooth arrival times, trading extra delay for continuity; when jitter exceeds the buffer you hear choppy audio or see frozen frames. Causes include congestion, bufferbloat, wireless interference and routes that change between packets.
Example
Ping times (ms): 20, 21, 20, 85, 22, 20The average is about 31 ms, yet the single 85 ms spike causes an audible glitch in a call. Tools such as mtr or ping report the standard deviation, a rough indicator of jitter.
Common mistakes
- Looking only at average latency and missing the variation.
- Enlarging the jitter buffer without realizing it adds conversation delay.
- Running calls over congested Wi-Fi when a cable would remove most of the problem.
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