1-5z Distributive application: Multicast makes multiple-point application possible.Application of multicastThe multicast technology effectively addresses the issue of point-to-multipoint data transmission. Byenabling high-efficiency point-to-multipoint data transmission, over an IP network, multicast greatlysaves network bandwidth and reduces network load.Multicast provides the following applications:z Applications of multimedia and flow media, such as Web TV, Web radio, and real-time video/audioconferencing.z Communication for training and cooperative operations, such as remote education.z Database and financial applications (stock), and so on.z Any point-to-multiple-point data application.Multicast ModelsBased 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)ASM modelIn the ASM model, any sender can become a multicast source and send information to a multicastgroup; numbers of receivers can join a multicast group identified by a group address and obtainmulticast information addressed to that multicast group. In this model, receivers are not aware of theposition of a multicast source in advance. However, they can join or leave the multicast group at anytime.SFM modelThe SFM model is derived from the ASM model. From the view of a sender, the two models have thesame multicast group membership architecture.Functionally, the SFM model is an extension of the ASM model. In the SFM model, the upper layersoftware checks the source address of received multicast packets so as to permit or deny multicasttraffic from specific sources. Therefore, receivers can receive the multicast data from only part of themulticast sources. From the view of a receiver, multicast sources are not all valid: they are filtered.SSM modelIn 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 theyare interested in at the client side.The radical difference between the SSM model and the ASM model is that in the SSM model, receiversalready know the locations of the multicast sources by some means. In addition, the SSM model uses amulticast address range that is different from that of the ASM model, and dedicated multicast forwardingpaths are established between receivers and the specified multicast sources.
