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24-port NWay Ethernet Switch User’s Guide
Switch Management and Operating Concepts 103
Multicasting
Multicasting is a group of protocols and tools that enable a single
source point to send packets to groups of multiple destination
points with persistent connections that last for some amount of
time. The main advantage to multicasting is a decrease in the
network load compared to broadcasting.
Multicast Groups
There are three types of IP v4 addresses: unicast, broadcast, and
multicast. Unicast addresses are used to transmit messages
from a single network device to another, single network device.
Broadcast packets are sent to all devices on the subnetwork.
Multicast defines a group of network devices or computers that
will receive the multicast packets. The members of this group
are not necessarily on the same subnetwork. Multicast
addresses are used to send multicast packets to the group
members.
Multicast Addressing
Class D IP addresses are assigned to a group of network devices
that comprise a multicast group. The four most significant four
bits of a Class D
A Class D IP address is assigned to a group of nodes defining a
multicast group. The most significant four bits of Class D
addresses are set to “1110”. The 28-bit number following these
four bits is called “multicast group ID”. Some of the Class D
addresses are registered with the Internet Assigned Numbers
Authority (IANA) for special purposes. The block of multicast