Unicast, Multicast, Broadcast. What Does It Mean?
By Stephen Bucaro
Unicast, Multicast, and Broadcast are different network transmission methods.
![Unicast transmission Unicast transmission](images/unicast.jpg)
Unicast is a transmission between a single sender and a single receiver
identified by a unique address over a network.
![Multiple unicast transmissions Multiple unicast transmissions](images/multiple_unicast.jpg)
For video, even though multiple client computers might request the same video
at the same time, a separate unicast data stream is transmitted to each client computer.
![Multicast transmission Multicast transmission](images/multicast.jpg)
Multicast is a transmission between a single sender and multiple receivers
simultaneously. The clients that receive the multicast may have a common set of criteria,
or be specifically set up as a multicast group. A special kind of multicast, referred to as
"anycast" is a communication between any sender and the nearest receivers in a network.
![Broadcast transmission Broadcast transmission](images/broadcast.jpg)
Broadcast is a transmission from a single sender to all clients on the network.
Routers can be used to divide a network into separate broadcast domains. A broadcast is
then limited to a broadcast domain. The IP address 255.255.255.255 indicates a broadcast,
and this address is never forwarded by routers.
More Networking Protocols and Standards: • Network Routing Protocols - IGRP, EIGRP, OSPF, ISIS, BGP • Video - Data Link Layer of OSI Networking Model • Neighbor Discovery Protocol (NDP) • Networking and Internet Standards Organizations • OSI Transport Layer • OSI Network Model • Free eBook: IPv6 Addressing • Ports and Sockets • An Introduction to the Types of VPNs • IPv6 Flow Label Field
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