Network Topology

Network Topology

DEFINITION:  A network topology refers to the layout of the computers and devices in a communications network.

There are two categories of network topology:

1) Physical topology                                       2) logical topology                                 

The arrangement of a cabling is the physical              The path that data travels  
 topology                                                                          between computers on a               

                                                                                          network is the logical topology.

Types of Network Topologies:

1) Star topology

All the computers and other devices on the network

connect to a central device, thus forming a star.

Two types of devices that provide a common central connection point to all the other devices on the network are a hub and a switch.

Hub / Switch

•The device that provides a common central connection point for other devices on a network.

•All data that transfers from one device to another passes through the hub or switch.

•The hub/switch takes a signal that comes from any device and passes it along to all the other
devices in the network. 

2)bus topology

A bus network consists of a single central cable (backbone), to which all computers and other devices connect.

•The bus is the physical cable that connects the computers and other devices.

•The bus in a bus network transmit data, instructions, and information  as a series of signal.

•Those signals are sent as electrical pulses that travel along the length of the cable in all
directions.

•Each devices is connected to the single bus cable through T-Connector.

•A terminator is required at each end of the bus cable to prevent the signal from bouncing
back and forth on the bus cable.

•When a sending device transmits data, the address of the receiving device is included with the

transmission.

•If the device address does not match the intended address for the data, the device ignores the
data.

•If the data does match the device address, the   data is accepted.

•All devices receive the data but only the receiving   device accept them.

3) ring topology

On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring.

•Data transmitted on a ring network travels from device to device around the entire ring, in
one direction  (clockwise or counterclockwise).

•Token passing is one method for sending data around a ring.

•Each device takes a turn sending and receiving information through the use of a token.

•The token along with any data is sent from the first device to the second device which extracts the data addressed to it and adds any data it wishes to send.

•Then second device passes the token and data to the third device, etc. until it comes
back around to the first device again.

•Only the device with the token is allowed to send data.

•All other devices must wait for the token to come to them.