A network topology refers to the interconnection of various nodes of a computer network. In other words, it defines the layout of the various devices that are part of the computer network.Topology is the virtual "shape" of the network, but it may not actually represent the actual physical design of the network that the various devices are connected to each other.
There are two types of network topologies: physical and logical.

A physical topology refers to the physical design of the computer network that includes the computers and other devices, their location and the various cables installed in the network.

A logical topology means the mode of flow of data in the network in contrast to its physical arrangement.

There are mainly six types of network topologies listed as under:

• bus
• star
• ring
• tree
• mesh
• hybrid

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.