A
li
smission. By
cast greatly
Multicast supports the following applications:
ultimedia and flow media, such as Web TV, Web radio, and real-time video/audio
conferencing.
n.
tions (stock), and so on.
pplication.
Multicast Models
ASM model
model, any sender can become a multicast source and send information to a multicast
group. In this model, receivers are not aware of the
S
The SFM model is derived from the ASM model. From the view of a sender, the two models have the
ast group membership architecture.
ore, receivers can receive the multicast data from only part of the
S
rtain multicast sources.
The SSM model provides a transmission service that allows users to specify the multicast sources they
ide.
The radical difference between the SSM model and the ASM model is that in the SSM model, receivers
icast sources.
Multica
from a multicast source to receivers in the
multicast mode and to satisfy information requirements of receivers. You should be concerned about:
pp cation of multicast
The multicast technology effectively addresses the issue of point-to-multipoint data tran
r an IP network, multi
enabling high-efficiency point-to-multipoint data transmission, ove
saves network bandwidth and reduces network load.
z
Applications of m
z
Communication for training and cooperative operations, such as remote educatio
z
Database and financial applica
z
Any point-to-multiple-point data a
Based on the multicast source processing modes, there are three multicast models:
z
Any-source multicast (ASM)
z
Source-filtered multicast (SFM)
z
Source-specific multicast (SSM)
In the ASM
group; numbers of receivers can join a multicast group identified by a group address and obtain
multicast information addressed to that multicast
position of a multicast source in advance. However, they can join or leave the multicast group at any
time.
FM model
same multic
Functionally, the SFM model is an extension of the ASM model. In the SFM model, the upper layer
software checks the source address of received multicast packets so as to permit or deny multicast
traffic from specific sources. Theref
multicast sources. From the view of a receiver, multicast sources are not all valid: they are filtered.
SM model
In the practical life, users may be interested in the multicast data from only ce
are interested in at the client s
already know the locations of the multicast sources by some means. In addition, the SSM model uses a
multicast address range that is different from that of the ASM model, and dedicated multicast forwarding
paths are established between receivers and the specified mult
st Architecture
The purpose of IP multicast is to transmit information
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