Computer Network

\omputers that are connected with one another for the purpose of communicating data electronically. An example of a network is the Internet, which connects millions of people all over the world. The computers use common communication protocols over digital interconnections to communicate with each other. A network set up by connecting two or more computers and other supporting hardware devices through communication channels is called a computer network. It enables computers to communicate with each other and to share commands, data, etc., including the hardware and software resources.

Besides physically connecting computer and communication devices, a network system serves the important function of establishing a cohesive architecture that allows a variety of equipment types to transfer information in a near-seamless fashion.

Uses of Computer Network

• It allows you to share resources such as printers, scanners, etc.
• You can share expensive software and database among network users.
• It facilitates communications from one computer to another computer.
• It allows the exchange of data and information among users through a network.

Popular Computer Networks

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

Local Area Network (LAN)

As the name suggests, the local area network is a computer network that operates in a small area, i.e., it connects computers in a small geographical area like within an office, company, school, or any other organization. So, it exists within a specific area, e.g. home network, office network, school network, etc.

A local area network may be a wired or wireless network or a combination of both. The devices in a LAN are generally connected using an Ethernet cable, which offers an interface to connect multiple devices like routers, switches, and computers. For example, using a single router, a few Ethernet cables, and computers, you can create a LAN at your home, office, etc. In this network, one computer may act as a server and other computers, which are part of the network, may serve as clients.

Topologies of LAN

Topology: It refers to the arrangement of computers (nodes) in a computer network. The main topologies of a local area network are as follows

As the name suggests, in a ring topology, the computers are connected in a circular and closed loop. The message in this topology moves only in one direction around the ring from one node to another node and is checked by each node for a matching destination address. So, the data keeps moving until it reaches its destination. All nodes are equal; a client-server relationship does not exist between them. As the nodes are in the form of a ring, if one node fails to transmit the data, the flow of communication is severed.

Star Topology

In this topology, all the computers are separately connected to a central node or connection point, which can be a server, a hub, a router, or a switch. This topology offers the advantage that if a cable does not work, only the respective node will suffer, and the rest of the nodes will work smoothly. All data or messages that one node sends to another pass through the central hub.

This topology is easy to design and implement as well as it is easy to add additional nodes to the central node. The major drawback of this topology is that it is prone to bottleneck or failure at the central connection point, i.e., failure at the central node will affect the entire communication.

Bus Topology

In this arrangement, the nodes (computers) are connected through interface connectors to a single communication line (central cable) that carries the message in both directions. The central cable to which all the nodes are connected is the backbone of the network. It is called a bus. The signal in this arrangement travels in both directions to all the machines until it finds the recipient machine. It is easy to set up than other topologies as it uses only a single central cable to establish the network.

Benefits of LAN

• It offers a higher operating speed than WAN and MAN.
• It is less expensive and easy to install and maintain.
• It perfectly fulfills the requirement of a specific organization, such as an office, school, etc.
• It can be wired or wireless or a combination of both.
• It is more secure than other networks as it is a small setup that can be easily taken care of.

Primary Functions of LAN

• Sharing of files: It allows you to share or transfer files from one computer to another computer within the LAN. For example, in a bank, it can be used to send a file with the details of transactions of a customer from the server to clients.
• Sharing of printers: It also allows shared access to a printer, file servers, etc. For example, ten computers that are connected through LAN can use a single printer, file server, fax machine, etc.
• Sharing of Computational capabilities: It allows the clients to access the computational power of a server, e.g., an application server as some applications which run on clients in a LAN may require higher computational capabilities.
• Mail and message-related services: It allows sending and receiving mails between computers of a LAN. You are required to have a mail server for this.
• Database services: It also allows storing and retrieving data with the help of a database server.

Metropolitan Area Network (MAN)

MAN is a high-speed network that spreads over a large geographical area such as a metro city or town. It is set up by connecting the local area networks using routers and local telephone exchange lines. It can be operated by a private company, or it may be a service provided by a company such as a local telephone company.

MAN is ideal for the people of a relatively large area who want to share data or information. It provides fast communication via high-speed carriers or transmission media such as copper, fiber optics, and microwaves. The commonly used protocols for MAN are X.25, Frame Relay, Asynchronous Transfer Mode (ATM), xDSL (Digital Subscriber Line), ISDN (Integrated Services Digital Network), ADSL (Asymmetrical Digital Subscriber Line), and more.

The area covered by MAN is larger than the LAN but smaller than a WAN. Its network ranges from 5 to 50 km. Furthermore, it also provides uplinks for connecting LANs to WANs and the internet. An organization can use a MAN to connect all of its LANs located at its different offices across the city.

Examples of MAN

• Cable TV Network
• Telephone service provides that provides high-speed DSL lines
• IEEE 802.16 or WiMAX
• Connected fire stations in a city
• Connected branches of a school in a city

Advantages of MAN

• Less Expensive: It is less expensive to set up a MAN and to connect it to a WAN.
• High Speed: The speed of data transfer is more than WAN.
• Local Emails: It can send local emails fast.
• Access to the Internet: It allows you to share your internet connection, and thus multiple users can have access to high-speed internet.
• Easy to set up: You can easily set up a MAN by connecting multiple LANs.
• High Security: It is more secure than WAN.

Wide Area Network (WAN)

WAN extends over a large geographical area. It is not confined to an office, school, city, or town and is mainly set up by telephone lines, fiber optic, or satellite links. It is mostly used by big organizations like banks and multinational companies to communicate with their branches and customers across the world. Although it is structurally similar to MAN, it is different from MAN in terms of its range, e.g., MAN covers up to 50 Kms, whereas WAM covers distances larger than 50 Km, e.g., 1000km or more.

A WAN works by using TCP/IP protocol in combination with networking devices such as switches, routers, firewalls, and modems. It does not connect individual computers; rather, they are designed to link small networks like LANs and MANs to create a large network. The internet is considered the largest WAN in the world as it connects various LANs and MANs through ISPs.

The computers are connected to the wide-area network through public networks, such as telephone systems, leased lines or satellites. The users of a WAN do not own the network as it is a large setup connecting the remote computer systems. However, they are required to subscribe to a service provided by a telecommunication provider to use this network.

Advantages of a WAN

• Large Network Range: It spans a large geographical area of 2000 km or more, e.g., from one country to another country.
• Centralized data: It allows your different office branches to use your head office server for retrieving and sharing data. Thus, you don’t need to buy email servers, file servers, backup servers, etc.
• Get updated files and data: It provides an ideal platform for companies who need a live server for their employees to exchange updated files within seconds.
• High bandwidth: It offers high bandwidth than a normal broadband connection. Thus, it can increase the productivity of your company by offering uninterrupted data transfer and communication.
• Workload Distribution: It helps distribute your workload to other locations. You can hire employees in different countries and assign them to work from your office.

According to Area

1. Personal Area Network (PAN)

The smallest and most basic type of network, a PAN is made up of a wireless modem, a computer or two, phones, printers, tablets, etc., and revolves around one person in one building. These types of networks are typically found in small offices or residences and are managed by one person or organization from a single device.

2. Local Area Network (LAN)

We’re confident that you’ve heard of these types of networks before – LANs are the most frequently discussed networks, one of the most common, one of the most original, and one of the simplest types of networks. LANs connect groups of computers and low-voltage devices together across short distances (within a building or between a group of two or three buildings in close proximity to each other) to share information and resources. Enterprises typically manage and maintain LANs.

Using routers, LANs can connect to wide area networks (WANs, explained below) to rapidly and safely transfer data.

3. Wireless Local Area Network (WLAN)

Functioning like a LAN, WLANs make use of wireless network technology, such as Wi-Fi. Typically seen in the same types of applications as LANs, these types of networks don’t require that devices rely on physical cables to connect to the network.

4. Campus Area Network (CAN)

Larger than LANs, but smaller than metropolitan area networks (MANs, explained below), these types of networks are typically seen in universities, large K-12 school districts or small businesses. They can be spread across several buildings that are fairly close to each other so users can share resources.

5. Metropolitan Area Network (MAN)

These types of networks are larger than LANs but smaller than WANs – and incorporate elements from both types of networks. MAN span an entire geographic area (typically a town or city, but sometimes a campus). Ownership and maintenance is handled by either a single person or a company (a local council, a large company, etc.).

6. Wide Area Network (WAN)

Slightly more complex than a LAN, a WAN connects computers together across longer physical distances. This allows computers and low-voltage devices to be remotely connected to each other over one large network to communicate even when they’re miles apart.

The Internet is the most basic example of a WAN, connecting all computers together around the world. Because of a WAN’s vast reach, it is typically owned and maintained by multiple administrators or the public.

7. Storage-Area Network (SAN)

As a dedicated high-speed network that connects shared pools of storage devices to several servers, these types of networks don’t rely on a LAN or WAN. Instead, they move storage resources away from the network and place them into their own high-performance network. SANs can be accessed in the same fashion as a drive attached to a server. Types of storage-area networks include converged, virtual and unified SANs.

8. System-Area Network (also known as SAN)

This term is fairly new within the past two decades. It is used to explain a relatively local network that is designed to provide high-speed connection in server-to-server applications (cluster environments), storage area networks (called “SANs” as well), and processor-to-processor applications. The computers connected on a SAN operate as a single system at very high speeds.

9. Passive Optical Local Area Network (POLAN)

As an alternative to traditional switch-based Ethernet LANs, POLAN technology can be integrated into structured cabling to overcome concerns about supporting traditional Ethernet protocols and network applications such as PoE (Power over Ethernet). A point-to-multipoint LAN architecture, POLAN uses optical splitters to split an optical signal from one strand of single-mode optical fiber into multiple signals to serve users and devices.

10. Enterprise Private Network (EPN)

These types of networks are built and owned by businesses that want to securely connect their various locations to share computer resources.

11. Virtual Private Network (VPN)

By extending a private network across the Internet, a VPN lets its users send and receive data as if their devices were connected to the private network – even if they’re not. Through a virtual point-to-point connection, users can access a private network remotely.