Network topology refers to the physical layout of the network i.e. the locations of the computers and how the cable is run between them. To select the right topology for how the network will be used is very important. Each topology has its own strength and weaknesses.
The choice of a topology for installing a computer network depends upon a combination of factors such as, reliability, performance of the system, number of nodes and geographical distribution of the system.
The main 2 types are
Bus Topology & Peer to Peer Topology
Peer to Peer topology consists of Star topology and Ring topology.
Bus Topology
It is often used when network installation is small, simple or temporary. On a typical bus network the cable is just 1 or more wires with no active electronics to amplify the signal or pass it along from computer to computer. This makes the bus a passive topology. When 1 computer send a signal up the wire all the computers receive the information but only one with the address that matches accepts the information, the rest disregard the message.
Advantages:
1) Easy to use and to understand.
2) Requires least amount of cable to connect the computers together. It is therefore less expensive than other cabling arrangements.
3) It is easy to extend a bus; two cables can be joined into 1 longer cable with a BNC, Barrel connector making a longer cable and allowing more computers to join the network.
Disadvantages:
1) Heavy network traffic can slow a bus considerably as only 1 computer can send a message at a time.
2) It is difficult to troubleshoot the bus. A cable break or loose connector causes reflection and stops all the activity.
Star Topology
In this kind of topology all the cables run from the computers to the central location where they are all connected by a device called hub or switch. Each computer on a star network communicates with a central device that resends the message either to each computer or only to the destination computer, e.g. if it is a hub then it will send to all and if it is a switch then it will send to only destination computer.When network expansion is expected and when the greater reliability is needed, star topology is the best.
Advantages:
1) It is easy to modify and add new computers without disturbing the rest of the network.
2) The center of the star network is a good place to diagnose the faults.
3) Single computer failure does not necessarily bring down the whole star network.
Disadvantages:
1) If the central device fails the whole network fails to operate.
2) Star networking is expensive because all network cables must be pulled to one central point, requires more cable than other network topologies.
Ring Topology
In this type each computer is connected to the next computer with the last one connected to the first. Each retransmits what it receives from the previous computer. The message flows around the ring in one direction. The ring network does not subject to signal loss problem as a bus network experiences. There is no termination because there is no end to the ring.
Advantages:
1) Each node has equal access.
2) Capable of high speed data transfer.
Disadvantages:
1) Failure of one computer on the ring can affect the whole network.
2) Difficult to troubleshoot the network.
Topologies remain an essential part of network design speculation. But understanding these can help you to get the deeper knowledge of the elements like hub, switch etc.
By: Deepti Pawar
