3Com Switch 8800 Advanced Software V5 Configuration Guide
494 CHAPTER 37: MULTICAST OVERVIEW
For a better understanding of the multicast concept, you can assimilate multicast
transmission to the transmission of TV programs, as shown in
Table 24.
n
■ A multicast source does not necessarily belong to a multicast group. Namely, a
multicast source is not necessarily a multicast data receiver.
■ A multicast source can send data to multiple multicast groups at the same
time, and multiple multicast sources can send data to the same multicast group
at the same time.
Advantages and
Applications of
Multicast
Advantages of multicast
Advantages of the multicast technique include:
■ Enhanced efficiency: reduces the CPU load of information sources and network
devices.
■ Optimal performance: reduces redundant traffic.
■ Distributive application: Enables point-to-multiple-point applications at the
price of the minimum network resources.
Applications of multicast
Applications of the multicast technique include:
■ Multimedia and streaming applications, such as Web TV, Web radio, and
real-time video/audio conferencing.
■ Communication for training and cooperative operations, such as distance
learning and telemedicine.
■ Data warehouse and financial applications (stock quotes).
■ Any point-to-multiple-point data distribution application.
Multicast Models Based on the multicast source processing modes, there are three multicast models:
■ Any-Source Multicast (ASM)
■ Source-Filtered Multicast (SFM)
■ Source-Specific Multicast (SSM)
Tabl e 24 An analogy between TV transmission and multicast transmission
Step TV transmission Multicast transmission
1 A TV station transmits a TV
program through a channel.
A multicast source sends
multicast data to a multicast
group.
2 A user tunes the TV set to the
channel.
A receiver joins the multicast
group.
3 The user starts to watch the
TV program transmitted by
the TV station via the channel.
The receiver starts to receive
the multicast data that the
source sends to the multicast
group.
4 The user turns off the TV set
or tunes to another channel.
The receiver leaves the
multicast group or joins
another group.