Bus-topology

BUS-TOPOLOGY

A bus network uses a multi-drop transmission medium, all node on the network share a common bus and thus share communication. This allows only one device to transmit at a time. A distributed access protocol determines which station is to transmit. Data frames contain source and destination addresses, where each station monitors the bus and copies frames addressed to itself.

A bus topology connects each computer (nodes) to a single segment trunk (a communication line, typically coax cable, that is referred to as the 'bus'. The signal travels from one end of the bus to the other. A terminator is required at each to absorb the signal so as it does not reflect back across the bus. A media access method called CSMA/MA is used to handle the collision that occur when two signals placed on the wire at the same time. The bus topology is passive. In other words, the computers on the bus simply 'listen' for a signal; they are not responsible for moving the signal along.

Advantages: Failure of one of the station does not affect others.

Good compromise over the other two topologies as it allows relatively high rate of data tansmittion.

Well suited for temporary networks that must be set up in a hurry.

Easy to implement and extend.

Disadvantage: Require a network to detect when two nodes are transmitting at the same time.

Does not cope well with heavy traffic rates

Difficult to administer/troubleshoot.

Limited cable length and number of stations.

A cable brake can disable the entire network; no redundancy.

Maintenance cost may be higher in the long run.

Performance degrade as additional computers are added.