Operation Manual – MulticastH3C S3100 Series Ethernet Switches Chapter 1 Multicast Overview1-6III. SSM modelIn the practical life, users may be interested in the multicast data from only certainmulticast sources. The SSM model provides a transmission service that allows users tospecify 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 SSMmodel, 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 ofthe ASM model, and dedicated multicast forwarding paths are established betweenreceivers and the specified multicast sources.1.3 Multicast ArchitectureThe purpose of IP multicast is to transmit information from a multicast source toreceivers in the multicast mode and to satisfy information requirements of receivers.You should be concerned about:z Host registration: What receivers reside on the network?z Technologies of discovering a multicast source: Which multicast source shouldthe receivers receive information from?z Multicast addressing mechanism: Where should the multicast source transportsinformation?z Multicast routing: How is information transported?IP multicast is a kind of peer-to-peer service. Based on the protocol layer sequencefrom bottom to top, the multicast mechanism contains addressing mechanism, hostregistration, multicast routing, and multicast application:z Addressing mechanism: Information is sent from a multicast source to a group ofreceivers through multicast addresses.z Host registration: A receiving host joins and leaves a multicast group dynamicallyusing the membership registration mechanism.z Multicast routing: A router or switch transports packets from a multicast source toreceivers by building a multicast distribution tree with multicast routes.z Multicast application: A multicast source must support multicast applications, suchas video conferencing. The TCP/IP protocol suite must support the function ofsending and receiving multicast information.1.3.1 Multicast AddressAs receivers are multiple hosts in a multicast group, you should be concerned about thefollowing questions:z What destination should the information source send the information to in themulticast mode?z How to select the destination address?
