Unicast, Multicast, Broadcast. What Does It Mean?
By Stephen Bucaro
Unicast, Multicast, and Broadcast are different network transmission methods.

Unicast is a transmission between a single sender and a single receiver
identified by a unique address over a network.

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 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 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: • Neighbor Discovery Protocol (NDP) • Pv6 Myths • TCP/IP Protocol Suite • IPv4 Datagram Fields • Internet Security and VPN Network Design • What Is Fabric Networking? • IPv6 Anycast Addresses • WAN Network Protocols - DSL, SONET, HDLC, DWDM, DLSW+ • A Simple Description of the IPv6 Header and Datagram • Session Border Controllers - More Than Just a Voice Firewall
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