H3C Technologies H3C SecPath F1000-E - Manual (Page 6)

5
• Multimedia and streaming applications, such as Internet TV, Internet 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 other point-to-multipoint data distribution applications.
Multicast Models
Based on how the receivers treat the multicast sources, there are three multicast models: any-source
multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).
ASM model
In the ASM model, any sender sends information to a multicast group as a multicast source, and numbers
of receivers join a multicast group identified by a group address and obtain multicast information
addressed to that multicast group. In this model, receivers are not aware of the positions of the multicast
sources in advance. However, they can join or leave the multicast group at any time.
SFM model
The SFM model is derived from the ASM. From the view of a sender, the two models have the same
multicast membership architecture.
The SFM model functionally extends the ASM model: In the SFM model, the upper layer software checks
the source address of received multicast packets and permits or denies multicast traffic from specific
sources. Therefore, receivers receive the multicast data from only part of the multicast sources. From the
view of a receiver, multicast sources are not all valid: they are filtered.
SSM model
In practice, users may be interested in the multicast data from only certain multicast sources. The SSM
model provides a transmission service that allows users to specify the multicast sources they are interested
in at the client side.
The radical difference between the SSM model and the ASM model is that in the SSM model, receivers
already know the locations of the multicast sources by some other means. In addition, the SSM model
uses a multicast address range that is different from that of the ASM/SFM model, and dedicated
multicast forwarding paths are established between receivers and the specified multicast sources.
Multicast Architecture
IP multicast addresses the following questions:
• Where does the multicast source transmit information to? (multicast addressing)
• What receivers exist on the network? (host registration)
• Where is the multicast source the receivers need to receive multicast data from? (multicast source
discovery)
• How is information transmitted to the receivers? (multicast routing)
IP multicast is an end-to-end service. The multicast architecture involves the following four parts:
1. Addressing mechanism: Information is sent from a multicast source to a group of receivers through
a multicast address.