Jitter is the inconsistency in how long packets take to arrive. If one packet takes 20 milliseconds and the next takes 45, that variation is jitter. Real-time applications care about it far more than they care about raw speed, because audio and video have to be reassembled on a steady clock.
Endpoints hold arriving packets in a jitter buffer and play them out evenly. The buffer smooths variation at the cost of added delay, and it can only absorb so much — packets arriving outside the window are discarded, which is heard as clipped or robotic audio. Larger buffers hide more jitter and make conversations feel less responsive.
Queuing under congestion, mostly. When a link is saturated, packets wait for variable amounts of time. This is why voice quality on a shared connection degrades precisely when the office gets busy, and why the fix is usually prioritisation or a dedicated circuit rather than a larger shared plan.
For voice, jitter under about 30 milliseconds is generally comfortable and under 10 is good. Well-run networks measure it continuously rather than checking it after complaints, because jitter problems are intermittent by nature and hard to reproduce on demand.
Jitter is the variation in inter-arrival time between packets, not the delay itself, and it is usually reported as an average that flatters the connection. What degrades a call is the occasional large excursion, so a percentile figure is far more informative than a mean. Where voice quality is the concern, a MOS estimate that folds latency, jitter, and loss together describes the experience better than any of the three alone.
Jitter is the single most common cause of "the phones are bad" reports, and it is frequently misdiagnosed as insufficient bandwidth. Any organization moving voice onto its data connection should understand it before the migration rather than after.
Jitter is one of the specifications these comparisons turn on.
Describe the requirement and an engineer will tell you which service actually fits — without a rate card or a sales script in the way.
Service availability depends on location, network proximity, capacity, and engineering review. Share an address and we will confirm what can be delivered there.