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Wednesday, 14 September 2016

Topologies, Types of Topologies

NETWORK TOPOLOGIES

There are Five  basic configurations used to connect computers they are the

Bus         -:-           Ring       -:-           Star        -:-           Mesh    -:-           Tree



Bus topology

Bus Topology is the type of network. It was widely used in the 1980’s. In Bus Topology The configuration is like that every computer (node) shares the networks total bus capacities. In this configuration adding more computers will reduce the access speed on the network. Each computer communicates to other computers on the network independently this is referred to as PEER-TO-PEER networking.


How a Bus Peer to Peer Network Works?

All computers on a network have a distinct address just like your house does. A message would be send from one computer with the address of another computer attached to the message. The message is broadcasted to all the computers on the network until the addressed PC accepts the message.


How it worked

The type of wires used for Bus Networks in the 80’s was called Thick net and Thin net. A Thick net cable (very large about 1 inch in diameter usually yellow was hung around a room). Thin net cables were connected to the PC’s NIC and a Transceiver. The Transceiver was tapped into the Thick net cable To stop the message from bouncing back and forward down the wire (known as signal bounce) both ends of the network are terminated with 50Ω resistors.


Problems

One of the main problems with this type of network is that it is not very fault tolerant, a break or defect in the bus would affect the whole network.

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Ring Topology

In Ring topology each node is connected to the two nearest nodes so the entire network forms a circle. Data only travels in one direction on a Ring network.



How this Topology works.

A node has information to send to another computer on the network so it sends the information out on the network to the PC it is connected to, if the information is for this PC (the recipients NIC address is attached to the message, which is like putting an address on an envelope) then the PC accepts the data otherwise it passes the information on to the next PC by repeating the data back out on the line. This method of repeating the data helps keep the integrity of the data readable by other computers.


How it Works

As it is better to have computers take turns using the connecting Data cable, Ring topologies incorporated a system called Token passing. In this topology, to transmit on the wire your computer must have control of the token or wait for the token to be free. Larger Token Ring networks use multiple tokens.


Problems and Solutions

The drawback to this type of topology is that a single malfunctioning workstation can disable the whole network. To make sure all the information is sent the receiving PC sends the token back to the sending PC after it has received all the data. If the sending PC is finished sending it passes the token to the next PC. This type of network was also widely used in the 1980’s. This type of network used Thin net cable joining nodes. In the mid 1980’s Thin net cable was replaced by Category 3 Ethernet cable capable of handling up to 10Mbps.

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Star Topology

In a Star topology every node is connected through a central device such as a Hub, Switch or Router. Compared to a Ring or Bus topology a Star topology requires that more thought be put into its setup




The Good and Bad of a Star Network

The upside of a star network is that if any one cable fails then only the node connected on that cable would be affected. Another positive point to this type of network is that it is very simple to join two star networks together by connecting their central devices to each other. As each computer is connected to a central device (Hub) the location of the Hub must be made as central as possible, so as to reduce cable lengths. The drawback to this type of topology is if a central device was to fail then all computers connected to that device would not be able to see the network. 

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Mesh Topology



Mesh topology can be defined as: It is the type of a network as Star, Ring and other topologies but in this topology every and each computer node is directly connected with each and every computer nodes present in the network. This network occur through cables it means network cables. In Mesh Topology The connection occur through Cables are some how like that in this each and every node of computer in the Network is directly connected to the each and every computer present in the network. or in The Topology.

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Tree Topology


A tree topology is the combination of characteristics of bus and star topologies.  It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies is the topology that allow for the expansion of an existing network, it also  enable schools to configure a network to meet their needs.
Bus, Mesh Topology, Network Topology, Ring Topology, Star Topology, Topologies, Topology, 

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