Bus topology

A bus topology uses a single cable to connect all the devices used in the network. The single cable forms the backbone of the communication medium in which the devices are attached. To establish a communication, a signal originating from the source travels in both directions to all the machines connected on the bus cable until it finds the address of the device to which the data is to be delivered. If the destination device finds that the data is for its own address, then only it accepts the data. The topology consists of terminators at both ends so that the data does not continue bouncing to and fro.

Advantages of bus topology:

• If one of the station fails to operate, it does not affect the operation of other stations.
• It can be a good replacement against other topologies.
• It is very suitable for such networks which are more or less temporary and which are needed immediately.
• It is easy to implement and extend.

Disadvantages of bus topology: 

• Data collision may occur when two or more nodes are transmitting the data at the same time.
• It is not suitable if the traffic rates in the network is heavy.
• It is very difficult to manage and troubleshoot a bus topology.
• A fault in the cable may disable the whole network and it would be very difficult to find that fault.
• Maintenance cost can increase unexpectedly at the long run.
• Performance of the network is degraded when more computers are added to the network.

Bus topology

MAN (Metropolitan Area Network)
A MAN is a computer network that covers a geographical area that is larger than a LAN but smaller than a WAN,extending typically over a city. It is usually owned by a single entity like a government branch or a large organization.

CAN ( Campus Area Network)
A CAN is a computer network that spans multiple LANs but which is smaller than a MAN. It is mostly present in universities or a campus.

 SAN (Storage Area Network)
This type of computer network is used to connect the servers to the data storage devices for storing the data or accessing the data that was stored previously on the device.

VPN (Virtual Private Network)
A VPN is a network of computers in which some of the links between the various nodes have open connections or have virtual circuits of some larger network, typically the internet, rather than joining them with physical wires. In other words, a VPN uses the connections of the internet or some other intranet to form a private network, without actual physical connection among the devices that form the node. This allows secure communications through the internet, because the VPN can be made accessible only by authorised personnels.

PAN (Personal Area Network)
A personal area network is a network of computers and/or other devices like PDAs (Personal Digital Assistant), cell phones, telephones, fax, printers, scanners etc. This network can be used to transfer files, emails, calender appointments, digital photos, music, etc. A PAN may be constructed through wire or wirelessly, and it typically covers an area of about 10 meters.

On the basis of the area a network covers, it can be divided into the following types:

    *  LAN      -  Local Area Network
    *  WLAN  - Wireless Local Area Network
    *  MAN     - Metropolitan Area Network
    *  WAN     - Wide Area Network
    * SAN       -  Storage Area Network, System Area Network, Server Area Network, Small Area Network

    * CAN      - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network
    * PAN      - Personal Area Network
    * DAN      - Desk Area Network


The original categories of computer networks were only LAN, MAN and WAN. The other categories evolved during the advancements in the technology of computer networks.

LAN (Local Area Network)

A LAN is a network of computers and devices over a relatively short geographical area. An office building networked with computers,a school or college or a home usually contains a single LAN, though sometimes one building will contain a few small LANs (probably one per room), and occasionally a LAN will span a group of nearby buildings. In addition to operating in a limited space, LANs are also controlled by a single person or organization. A LAN also tend to use certain connectivity technologies, primarily Ethernet or Token Ring.

 WAN - Wide Area Network
A WAN  spans a large physical distance compared to a LAN. The internet is the largest and the most common example of a WAN, that spans the whole Earth. A WAN can be considered as a collection of several LANs that are dispersed throughout the whole world. The network device Router connects several LANs to form the WAN. The Router also maintains both a LAN address and a WAN address in IP networking.

WLAN  - Wireless Local Area Network
WLAN is also a type of LAN(local area network) based on wireless network technology mostly referred as Wi-Fi. In contrast to a LAN, in WLAN no wires are used; radio signals are the medium for communication. To access any wireless network around, wireless network cards must be installed in the system. The wireless cards are connected to the Wireless Routers for the purpose of communication among the computers.

A computer network is a combination of computers and other computer related devices connected by communications channels for the purpose of sharing files and resources among the users. The network may be of many types, with unique features of its own.
The primary objective of computer network is to share the files among various users. Among the various networks of computers, the internet is definitely the most important inventions of modern age. It is a huge source of information on any topic, it brought the era of emails and point to point communication through voice and video, allowing anyone to communicate with anyone else in the world; and it is also a great medium of new kind of business - the online business. Everyone in the world today depend so much on the computer networks and specially the internet, that it has become a part of our daily life.

fig: Computer Networks