Local Area Networks in Bus

Generalities and Characteristics

Bus LANs use a multipoint configuration, that is, all stations are connected to the same transmission medium, so a bus topology is a particular case of a tree topology.

In a Bus LAN, the information emitted by a station travels the entire bus bidirectionally until it reaches its destination, which indicates that this information can be intercepted by any station on the network. It includes, at both ends of the bus, devices called terminators whose function is to avoid possible bounces of the signal, that is, it absorbs or eliminates the signal.

The cable on which all the elements of a Bus LAN are connected or "hanged" is called "Cable Backbone". All the stations are directly connected to the bus through taps (connection sockets), the configuration of the line or the bus with the stations is full duplex, which allows the transmission and sending of the data simultaneously between them and therefore in all network.

The medium access protocol used is called CSMA/CD (Call Sense Multiple Access Collision Detection), which is based on each station monitoring or listening to the medium to determine if it is available so that the station can send its message. Otherwise, it waits for the bus to be free to be able to transmit.

The signal power of the emitter in a Bus LAN must be strong enough to transmit to all the other stations and enough not to saturate the emitter circuit, that is, the signal must be balanced, this is determined taking into account the combinations of stations taken 2 by 2, that is, for n stations the number of combinations is n * (n-1).