unicast
termnetworking
Communication addressed to exactly one recipient.
Unicast is one-to-one delivery, the default for most traffic, in contrast to broadcast (to everyone on a segment), multicast (to a subscribed group), and anycast (to the nearest of many). The distinction shapes how efficiently traffic reaches its audience.
Unicast is one sender to one receiver, the default for essentially all traffic. It sits alongside broadcast, which reaches everyone on a segment, multicast, which reaches a subscribed group, and anycast, where many hosts share an address and the network delivers to the nearest.
The distinction is worth keeping straight because the failure modes differ completely. Unicast scales with the number of receivers, which is why streaming to a million people costs a million streams and why CDNs exist. Anycast is unicast from the sender's perspective and behaves differently under routing change, since the destination can move mid-conversation, which is fine for DNS and awkward for anything stateful.
Also known as: multicast, broadcast