NCERT Computer: Chapter 5 – Data Communication and Networking Part 5

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Network Topologies

Network topology is the arrangement of the various elements of a computer network.

As we have seen earlier, topology is the geometric arrangement of the computers in a network. Common topologies include star, ring and bus.

Star Network

Frequently used to connect one or more small computers or peripheral devices to a large host computer or CPU.

Many organizations use the star network or a variation of it in a time-sharing system, in which several users are able to share a central processor.

This image shows Star Network

Image of Star Network

This image shows Star Network

Fig. Star Topology

In a time-sharing setup, each terminal receives a fixed amount of the CPU's time, called a time slice.

Star network is frequently used in a LAN to connect several microcomputers to a central unit that works as a communications controller.

The message is routed through the central communications controller. Another common use of the star network is the feasibility of connecting several microcomputers to a mainframe computer that allows access to an organization's database.

Access and control of star network typically is maintained by a polling system. Polling means that the central computer or communications controller "polls" or asks each device in the network if it has a message to send and then allows each in turn to transmit data.

Ring Network

A ring - can be as simple as a circle or point-to-point connections of computers at dispersed locations, with no central host computer or communications controller. That is, all of the nodes are connected in a closed loop.

This image shows Ring Topology

Image of Ring Topology

This image shows Ring Topology

Fig. Ring Topology.

Access and control of ring networks are typically maintained by a "token-passing" system.

A Token-Ring network as shown resembles a merry-go-round.

Bus Network

Bus networks are similar to ring network that the ends are not connected. All communications are carried on a common cable or bus and are available to each device on the network.

Access and control of bus networks are typically maintained by a method called contention, whereby if a line is unused, a terminal or device can transmit its message at will, but if two or more terminals initiate messages simultaneously, they must stop and transmit again at different interval

This image shows Bus network

Image of Bus Network

This image shows Bus network

Fig. Bus network