Network Latency vs Jitter
Definition
Network latency is the time a packet takes to travel from source to destination, while jitter, or packet delay variation, is the variation of that time from one packet to the next. On a local network, latency usually stays well under 1 ms, and it rises when packets wait in switch queues. For audio over IP, jitter matters as much as average latency, because the latency set at the receiver must cover the slowest packets: in Dante, a packet that arrives later than the configured latency is discarded. Jitter comes mainly from queuing in switches under competing traffic and from the processing load of the sending and receiving devices.
In the field
A network with low average latency but high jitter can still cause Dante dropouts at a low latency setting, because only the late packets are lost; a network with 0.5 ms average latency and 2 ms of jitter, for example, drops audio at the 1 ms setting. Dante Controller shows the latency measured by each receiving device, and the usual remedies are to configure QoS or to raise the latency setting above the worst measured values.
Related lessons
Sources
- RFC 3393 : définition de la variation du délai des paquets IP (IPDV, gigue) · rfc-editor.org
- Audinate, Dante Controller User Guide, Latency : paquet arrivé après la latence configurée perdu ; réglages par nombre de sauts · dev.audinate.com
- Audinate/Yamaha, Dante Network Design Guide, QoS : la QoS donne la priorité à l'horloge et à l'audio Dante sur le trafic de fond · usa.yamaha.com