Various topologies can be used to broadcast LAN. One of them is bus topology.

In this topology at any instant one computer acts as master and it is allowed to transmit and the others are supposed to receive. When the bus is free any unit may start to transmit a message, the unit with the message of highest priority to be transmitted gains bus access.


If two or more nodes start transmitting messages at the same time a collision is created. To resolve this collision the arbitration mechanism is applied to decide which one will resend its packet first according to the priority of the packets. It is possible to have a centralized or distributed type of arbitration. The most popular example of bus topology is Ethernet. Ethernet operates on 10 or 100 Mbps. Computers on Ethernet can transmit whenever they want and if collision of their packets/messages takes place, then they wait random amount of time and then retransmit their packets.

Advantages

  • Simple and cheap.
  • Less amount of cable compared to other topologies.
  • If one computer fails it does not affect the rest of the computers.

Disadvantages

  • Difficult to install and reconfigure new devices.
  • If an error is produced in the communication line, it stops all transmissions in the network.