Computer Network

Computer network




Definition: A computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users. A computer network allows sharing of resources and information among devices connected to the network.

Need of Computer Network

Computer networks can be used for several purposes:

1. Facilitating communications. Using a network, people can communicate efficiently and easily via e-mail, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.

2. Sharing hardware. In a networked environment, each computer on a network can access and use hardware on the network. Suppose several personal computers on a network each require the use of a laser printer. If the personal computers and a laser printer are connected to a network, each user can then access the laser printer on the network, as they need it.

3. Sharing files, data, and information. In a network environment, any authorized user can access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks.

4. Sharing software. Users connected to a network can access application programs on the network.

5. Data protection: You should know by now that it's vital to back up your computer data regularly. A network makes it easier to back up all of your company's data on an offsite server, or other backup systems.

6. Remote access: Having your own network allows greater mobility while maintaining the same level of productivity. With remote access in place, users are able to access the same files, data, and messages even when they're not in the office. This access can even be given to mobile handheld devices.

Types of networks

There are three basic types of networks:

1. LAN (Local Area Network)

2. MAN (Metropolitan Area Network)

3. WAN (Wide Area Network)

Local Area Network:

The Local Area Network is also referred as LAN. This system spans on a small area like a small office or home. The computer systems are linked with cables. In LAN system computers on the same site could be linked. The smallest home LAN can have exactly two computers; a large LAN can accommodate many thousands of computers. Many LANs are divided into logical groups called subnets. An Internet Protocol (IP) "Class A" LAN can in theory accommodate more than 16 million devices organized into subnets.

Advantages

High Speed: Data rates of currently available LANs cover a wide range. The slowest transfer data at around 100 kbps while the fastest have data rates of up to 100 mbps.

Low Cost: Many applications of LANs involve low cost microprocessors systems; it is desirable that connection of such systems to a LAN should be economic..

High reliability/Integrity: Since LAN is s set of multiple interconnected systems; it offers a good backup capability in the event of one or two systems failing in the network. This enhances the reliability and availability of the systems to users.

Installation flexibility: LAN offers flexibility in locating the equipment. Most computers on a LAN are physically placed at the user table, which is most convenient for working and improves productivity significantly.

Expandability: Unlike a large centralized system, a LAN may evolve with time. It may be put into operation with a small investment, and more systems.

East of Access: The connection pattern of a LAN is normally a simple topological form such as a ring or a tree and this has implications for the routing of packets on a LAN.

Metropolitan Area Networks:

The Metropolitan Area Networks connect multiple geographically nearby LANs to one another (over an area of up to a few dozen kilometres) at high speeds. Thus, a MAN lets two remote nodes communicate as if they were part of the same local area network. A MAN is made from switches or routers connected to one another with high-speed links (usually fibre optic cables). MAN is designed to extend over the entire city. It may be a single network as a cable TV network or it may be means of connecting a number of LANs into a larger network so that resources may be shared. MAN is wholly owned and operated by a private company or may be a service provided by a public company



Wide Area Network:

A Wide Area Network or WAN is a type of networking where a number of resources are installed across a large area such as multinational business. Through WAN offices in different countries can be interconnected. The best example of a WAN could be the Internet that is the largest network in the world. In WAN computer systems on different sites can be linked.



Some other types of networks are:

1. WLAN - Wireless Local Area Network

2. SAN - Storage Area Network, System Area Network, Server Area Network, Small Area Network

3. CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network

4. PAN - Personal Area Network



Wireless Local Area Network –

A LAN based on Wi-Fi wireless network technology.


Storage Area Network –

It connects servers to data storage devices through a technology like Fibre Channel. It links high-performance computers with high-speed connections in a cluster configuration


Campus Area Network –

A network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.


Personal Area Network (PAN) –

Personal Area Network is a computer network used for communication among computer and different information technological devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. A PAN may include wired and wireless connections between devices. The reach of a PAN typically extends to 10 meters.