What is jitter?
Jitter is the variation in packet delay, the difference in arrival times between packets. Learn its causes, impact on VoIP and gaming, and how to mitigate it.
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Jitter is the variation in packet delay, the difference in arrival times between consecutive packets in the same stream. When a link delivers one packet in 20 ms, the next in 45 ms, and another in 18 ms, that spread is jitter. Latency measures how long a packet is in transit, while jitter measures how much that time fluctuates. For real-time applications jitter is often more damaging than high latency alone, because it disrupts the steady flow of data.
How jitter is measured
Jitter is expressed in milliseconds and describes the dispersion of arrival times relative to the expected, even spacing between packets. RFC 3550 (RTP) and RFC 3393 (IPDV, IP Packet Delay Variation) define formal methods for calculating it. In practical network monitoring, jitter is most often the mean absolute difference in delay between adjacent packets, reported by active probes or RTCP statistics.
- RFC 3550 (RTP/RTCP) describes the smoothed interarrival jitter reported in RTCP packets.
- RFC 3393 defines IPDV as the delay difference between two selected packets.
- Well-engineered transit and peering links keep jitter in the single-digit milliseconds.
- For VoIP, jitter below 30 ms is recommended. Above 50 ms call quality degrades noticeably.
- A jitter buffer at the receiver smooths variation at the cost of added latency.
What causes jitter
Jitter arises wherever packets wait different amounts of time to be processed. The most common cause is queuing on congested links: as buffers fill, successive packets wait variable amounts of time. Added to this are route flaps, uneven traffic distribution across ECMP, router CPU load, and microbursts, short traffic peaks that fill a buffer faster than the link can drain it.
Impact on VoIP and gaming
Real-time applications expect an even stream of packets. In VoIP, excessive jitter outpaces what the receive buffer can smooth. You get gaps, clicks, and robotic audio, while packets that arrive too late are discarded as if lost. In online gaming, jitter shows up as rubber-banding and unpredictable response times, even when the average ping is low. A steady 40 ms ping serves a player better than one swinging between 20 and 80 ms.
How to mitigate jitter
Jitter is reduced by stabilizing the path and managing queues. QoS with priority queuing (such as LLQ/PQ) and DSCP EF marking for voice traffic gives real-time packets precedence before they get stuck in a buffer. Provisioning links with headroom, keeping paths short and predictable, and avoiding congested exchange points all help as well.
- Deploy QoS and DSCP marking so VoIP and gaming traffic bypass long queues.
- Keep link utilization below the threshold where queues start to build.
- Shorten and stabilize paths with direct peering instead of long transit routes.
- Size the jitter buffer to the application: too large adds delay, too small drops packets.
- Monitor jitter continuously with active probes and RTCP statistics.
Jitter and the AS202520 SkyPass network
AS202520 SkyPass engineers its network to keep paths short and predictable, which is the key to low jitter. Our PoPs in Warsaw and Wrocław and peering at Polish exchanges (THINX, TPIX, WRIX, 1-IX) shorten the path for domestic traffic, removing needless hops and detours abroad. AS202520's peering and IP transit services provide provisioned links and stable routing, and our public looking glass lets you verify the path and delay to your prefixes. For VoIP operators and gaming platforms, this means a stable, even packet stream.
Frequently asked questions
How does jitter differ from latency?
Latency is how long a packet takes to reach its destination; jitter is the variation in that time between consecutive packets. A link can have low latency yet high jitter if arrival times fluctuate widely.
What jitter level is acceptable for VoIP?
For VoIP telephony, jitter below 30 ms is recommended. Above 50 ms, call quality degrades noticeably. You get gaps and distortion, and late-arriving packets are discarded by the buffer.
Does a jitter buffer eliminate the problem?
A jitter buffer smooths variation by holding packets and replaying them evenly, but it does so at the cost of added latency. A buffer too small drops late packets, while one too large needlessly increases latency.
How does peering affect jitter?
Direct peering shortens the path and reduces the number of hops and congested points along the way, which stabilizes arrival times. A shorter, more predictable route generally means lower and more stable jitter.