Networking / AV-IT
Unicast vs Multicast
01 — Definition
Two ways of carrying a stream. In unicast, the sender puts out a separate copy for each destination: simple, but bandwidth swells with the number of receivers. In multicast, it sends once towards a group and the network duplicates only where the paths diverge: ideal for one-to-many (sACN, NDI multicast, AES67). In exchange, multicast needs IGMP snooping on the switches, or it degrades into flooding every port like broadcast.
02 — In the field
Sending sACN to 40 nodes by unicast can choke the source; in multicast you send one stream that the switches replicate. But with no IGMP snooping, that multicast floods everything — enable snooping before you go multicast.
04 — Sources
- ANSI E1.31-2018 §9.1 — sACN dirige les univers en multicast, l'unicast reste possible sans découverte