Operation Manual – MulticastH3C S7500 Series Ethernet Switches Chapter 1 Multicast Overview1-2information, when a large number of users need this information, the server must sendmany pieces of information with the same content to the users. Therefore, the limitedbandwidth becomes the bottleneck in information transmission. This shows that unicastis not good for the transmission of a great deal of information.1.1.2 Information Transmission in the Broadcast ModeWhen you adopt broadcast, the system transmits information to all users on a network.Any user on the network can receive the information, no matter the information isneeded or not. Figure 1-2 shows information transmission in broadcast mode.SourceServerRReceiverReceivereceiverHost AHost BHost CHost DHost EPackets for all the networkFigure 1-2 Information transmission in the broadcast modeAssume that users B, D, and E need the information. The source server broadcasts thisinformation through routers, and users A and C on the network also receive thisinformation. The security and payment of the information cannot be guaranteed.As we can see from the information transmission process, the security and legal use ofpaid service cannot be guaranteed. In addition, when only a small number of users onthe same network need the information, the utilization ratio of the network resources isvery low and the bandwidth resources are greatly wasted.Therefore, broadcast is disadvantageous in transmitting data to specified users;moreover, broadcast occupies large bandwidth.1.1.3 Information Transmission in the Multicast ModeAs described in the previous sections, unicast is suitable for networks with sparselydistributed users, whereas broadcast is suitable for networks with densely distributed
