Unicast Definition

A unicast is a transmission over a network from one host (i.e., computer on the network) to another.

This contrasts with a broadcast, which is the simultaneous transmission of a single message to all hosts on a broadcast domain (i.e., a part of the network). It also contrasts with a multicast, which is the sending of a message just to a select list of hosts on the network.

Unicasts are still the dominant form of transmission on LANs (local area networks) and the Internet. HTTP (hypertext transfer protocol) and TCP/IP (transmission control protocol/Internet protocol) are among the many network protocols that use unicasting.

It can be much more efficient with regard to bandwidth conservation to use multicasting for situations in which large numbers of hosts want to receive large files at the same time, for example for downloading video files.

Another, older, term for unicast is point-to-point communication.

Created October 21, 2005.
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