3com 5500-ei pwr Instruccion De Instalación

 

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As described in the previous sections, unicast is suitable for networks with sparsely distributed users, 

whereas broadcast is suitable for networks with densely distributed users. When the number of users 

requiring information is not certain, unicast and broadcast not efficient.  

Multicast solves this problem. When some users on a network require specified information, the 

multicast information sender (namely, the multicast source) sends the information only once. With 

multicast distribution trees established for multicast data packets through multicast routing protocols, 

the packets are duplicated and distributed at the nearest nodes, as shown in 

: 

Figure 1-3 Information transmission in the multicast mode  

Server

Host A

Host B

Host C

Host D

Host E

Packets for the multicast group

 

 

Assume that Hosts B, D and E need the information. To transmit the information to the right users, it is 

necessary to group Hosts B, D and E into a receiver set. The routers on the network duplicate and 

distribute the information based on the distribution of the receivers in this set. Finally, the information is 

correctly delivered to Hosts B, D, and E.  

The advantages of multicast over unicast are as follows:  

z 

No matter how many receivers exist, there is only one copy of the same multicast data flow on each 

link.  

z 

With the multicast mode used to transmit information, an increase of the number of users does not 

add to the network burden remarkably.  

The advantages of multicast over broadcast are as follows:  

z 

A multicast data flow can be sent only to the receiver that requires the data. 

z 

Multicast brings no waste of network resources and makes proper use of bandwidth.  

The following roles are involved in multicast transmission:  

z 

An information sender is referred to as a multicast source (“Source” in 

z 

Each receiver is a multicast group member (“Receiver” in