Operation Manual – Multicast
H3C S3100 Series Ethernet Switches
Chapter 1 Multicast Overview
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III. SSM model
In the practical life, 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 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 multicast sources.
1.3 Multicast Architecture
The purpose of IP multicast is to transmit information from a multicast source to
receivers in the multicast mode and to satisfy information requirements of receivers.
You should be concerned about:
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Host registration: What receivers reside on the network?
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Technologies of discovering a multicast source: Which multicast source should
the receivers receive information from?
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Multicast addressing mechanism: Where should the multicast source transports
information?
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Multicast routing: How is information transported?
IP multicast is a kind of peer-to-peer service. Based on the protocol layer sequence
from bottom to top, the multicast mechanism contains addressing mechanism, host
registration, multicast routing, and multicast application:
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Addressing mechanism: Information is sent from a multicast source to a group of
receivers through multicast addresses.
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Host registration: A receiving host joins and leaves a multicast group dynamically
using the membership registration mechanism.
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Multicast routing: A router or switch transports packets from a multicast source to
receivers by building a multicast distribution tree with multicast routes.
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Multicast application: A multicast source must support multicast applications, such
as video conferencing. The TCP/IP protocol suite must support the function of
sending and receiving multicast information.
1.3.1 Multicast Address
As receivers are multiple hosts in a multicast group, you should be concerned about the
following questions:
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What destination should the information source send the information to in the
multicast mode?
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How to select the destination address?