Multicast Models; Multicast Architecture - HP FlexFabric 5700 Series Configuration Manual

Multicast models

Based on how the receivers treat the multicast sources, the multicast models include any-source multicast
(ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).
ASM model
In the ASM model, any multicast sources can send information to a multicast group. Receivers can join a
multicast group and get multicast information addressed to that multicast group from any multicast
sources. In this model, receivers do not know the positions of the multicast sources in advance.
SFM model
The SFM model is derived from the ASM model. To a multicast source, the two models appear to have
the same multicast membership architecture.
The SFM model functionally extends the ASM model. The upper-layer software checks the source address
of received multicast packets and permits or denies multicast traffic from specific sources. Therefore,
receivers can receive the multicast data from only part of the multicast sources. To a receiver, multicast
sources are not all valid, but are filtered.
SSM model
The SSM model provides a transmission service that enables multicast receivers to specify the multicast
sources in which they are interested.
In the SSM model, receivers have already determined the locations of the multicast sources. This is the
main difference between the SSM model and the ASM model. In addition, the ASM and SFM models use
a different multicast address range than the SSM model. Dedicated multicast forwarding paths are
established between receivers and the specified multicast sources.

Multicast architecture

IP multicast addresses the following issues:
Where should the multicast source transmit information to? (Multicast addressing.)
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• What receivers exist on the network? (Host registration.)
Where is the multicast source that will provide data to the receivers? (Multicast source discovery.)
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How is the information transmitted to the receivers? (Multicast routing.)
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IP multicast is an end-to-end service. The multicast architecture involves the following parts:
Addressing mechanism—A multicast source sends information to a group of receivers through a
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multicast address.
Host registration—Multicast receivers can join and leave multicast groups dynamically. This
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mechanism is the basis for management of group memberships.
Multicast routing—A multicast distribution tree (a forwarding path tree for multicast data on the
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network) is constructed for delivering multicast data from a multicast source to receivers.
• Multicast applications—A software system that supports multicast applications, such as video
conferencing, must be installed on multicast sources and multicast receivers. The TCP/IP stack must
support reception and transmission of multicast data.
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