Network Topology

Topology refers to the physical layer and layout of a network of computers.

Bus Topology -- refers to a computer network that permits the connection of terminals along central cable. Its easy to add devices or delete them from the network. Bus topologies are most appropriate when the linked devices are physically close to one another. Ethernet - a commercial product of Xerox uses this kind of network. Ethernet uses CSMS/CD (Carrier Sense Multiple Access/Collision Detection) access method. To gain access to the network, a node with a message sent automatically requests network service from the network software. The request might give you a signal that the line is busy. In that case the node waits and tries again until the line is free.

Ring Topology -- is a computer network where the machines are connected in a closed loop, with no specific machine being the center of the network. Token Ring- IBM's ring type network. When one system routes a message to another system, its is passed around the ring until it reaches its destination address.

Star Topology -- a computer network where a central host computer is connected to a number of smaller computer systems. Arcnet uses star topology. Polling is commonly used in star based networks. Polling is when each terminal is polled in rotation to determine whether a message is ready to be sent. If a particular terminal has a message to be sent and the line is available, the front-end processor accepts the message and polls the next terminal.