About Computer Network and Internet
(Also in Nepali and in other language.)
-Introduction to Computer Network
A Computer network can consist of two or more computers connected together. It is the interconnection of several computers so that they can communicate, share resources and transfer data and information. The largest form of computer networks is called Internet. So, the Internet is also called the networks of networks. In 1960's, the Advance Research Project Agency (ARPA) designed a computer network called "Advance Research Project Agency Network" (ARPANET) for the United
States department of defense. It was the first computer network in the world.
-Advantage of Computer Network
Computer network has several advantages. Some of the advantages of computer network are as follows:
- Data and information can be shared.
- Hardware devices such as printer, harddisk, modem, etc can be shared.
- Software programs and database can be shared.
- Data processing is economic.
- Data processing is faster.
-Disadvantage of Computer Network
Computer network has several disadvantages. Some of the disadvantages of computer network are as follows:
- Initial setup cost is expensive.
- Rapid spread of computer virus.
- There may be great security issues.
Types of Computer Network :
On the basis of size, physical and geographical division, computer network can be categorized into three types. They are:
- Local Area Network (LAN)
- Metro Politan Area Network (MAN)
- Wide Area Network (WAN)
1. Local Area Network (LAN):
This is a type of computer network which covers small fixed area such as a room, a building, an office or a school using wired media. By creating a LAN, we can share resources such as hardware, software and transfer information between the computers.
-Feature of Local Area Network:
- Local Area Network is limited to short distance.
- It is owned privately by a single organization or person.
- Data transmission rate in Local Area Network is faster.
- Wired transmission media is used in Local Area Network.
2. Metropolitan Area Network (MAN):
This is a type of computer network which covers large geographical area such as: an university, an entire city, a valley, a district, a zone or a whole country. This type of network is prepared by connecting several LANs in different locations, using wired or wireless media both.
-Feature of Metropolitan Area Network:
- Metropolitan Area Network covers a large area i.e. an entire metropolitan city.
- It uses wired or wireless transmission media both.
- It is owned by single or multiple organizations.
- Data transmission in MAN is slower than LAN and faster than WAN.
3. Wide Area Network (WAN):
This is the largest computer network in the world which is not restricted to a geographical location. It can interconnect networks throughout the world. The Internet is an example of WAN.
-Feature of Metropolitan Area Network:
- Wide Area Network covers a large geographical area such as countries, continent or world.
- Data transmission in Wide Area Network is slowest in comparison to LAN ans MAN.
- It is owned by multiple public organizations.
- It uses wireless communication technology for data transmission.
-Network Connecting Devices:
Some commonly used network connecting devices are Networking Interface Card (NIC), Hub, Switch, Router etc.
- Network Interface Card (NIC): NIC card is a network connecting device which is placed on the expansion slot of the motherboard. It provides a port on the back of the system unit to connect a computer in a network.
- Hub: This is a network connecting device used in Local Area Network (LAN). It is a simple device that joins multiple computers together.
- Switch: Switch is a network-connecting device that joins multiple computers together within one local area network (LAN). Switches also work nearly identical to hubs but they can identify the intended destination of the information that they receive.
- Router: It is an intellegent network connecting device that joins multiple wired or wireless networks together. Router can determine the best path for sending data and filtering broadcast traffic to the local segment.
-Transmission Media :
The media that are used to transfer data between the computers in the networks are called transmission media. There are two types of media used in the network. They are:
- Wired media (guided media)
- Wireless media (unguided media)
This is a type of transmission media which uses wire or physical path to transfer data. The wired media are of following types.
- Twisted-pair cable: Twisted-paired cable is the most commonly used transmission media. It consists of copper wires twisted into pairs with each wire insulated with plastic.
- Coaxial Cable: Coaxial cable is a type of guided media which consists of an electrical cable with an inner conductor surrounded by an insulating layer by conducting shield.
- Fiber-Optic Cable: This is the advanced and fastest cable that uses glass or plastic threads (fibers) to transmit data. It consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.
- Wireless media (unguided media):
This is a type of transmission media which uses radio signals or infrared signals for transmitting and receiving data. The commonly used wireless communication systems are as follow:
- Microwave System: In the microwave system, a high frequency radio signals are used to transfer data through the space.
- Communication Satellite: A communication satellite is an artificial satellite stationed in space for the purpose of telecommunications.
- Bluetooth Technology: Bluetooth technology is a wireless technology that connects electronic devices while they are close to each another. Bluetooth creates a personal area network (PAN) while transmitting data.
- Wi-Fi technology: Wi-Fi (Wireless Fidelity) is a popular wireless technology that uses radio waves to provide wireless high-speed network connections.
-Network Topologies:
Network topology is the interconnection pattern of computers in the network. It is the physical layout of the terminals, links and computers in the network. The common types of Network Topologies are described below.
- Bus topology
- Star topology
- Ring topology
- Mesh topology
- Bus topology: This is a type of network topology in which, all the computers are connected to a common cable called bus or trunk. In this network topology, if the common cable breaks, it affects the whole network.
- Advantage of bus topology.
- Bus topology use short length cable which decreases the installation cost.
- It is simple and easy to install and maintain.
- This topology is more flexible.
- In Bus topology there is Easy to add new nodes.
- Disadvantage of bus topology.
- The Entire network shuts down if there is a break in the main cable.
- Terminators are required at both ends of the backbone cable.
- Stand-alone system is not suitable in a large building.
- Star topology: This is a type of network topology in which all the computers are connected to a main computer called server which controls all the other computers. This is the most commonly used topology in LAN. In this network, if the central point(server) fails, the whole network fails but the failure of one computer doesn't affect the rest of the network.
- Advantage of Star topology.
- In this topology, installation and cable connection is so easy.
- Easier to detect faults and to remove parts in this topology.
- High data transmission is possible in star topology.
- If any of the local computers fail, the remaining portion of network is unaffected.
- Disadvantage of Star topology.
- If the hub or central device fails, nodes attached are disabled.
- More expensive than linear bus topologies because of the cost of the concentrators.
- This topology is difficult to expand.
- Ring topology: This is a type of topology in which one computer is connected with other, and so on to form a ring pattern. This network provides equal access for all computers so, if one of the computers fails, it impacts all the computers in the network.
- Advantage of Ring topology.
- Ring Topology works well where there is no central site computer system.
- Short cable connection which cause an increase in network reliability.
- Less chance of data collision because data travels in one direction only.
- Every computer has equal access facility in this topology.
- Disadvantage of Ring topology.
- Any communication path or node failure causes network failure in this topology.
- In ring topology, network configuration is difficult.
- Communication delay is directly proportional to the number of nodes in ring topology.
- Mesh topology: Mesh topology is special type of hybrid topologies in which all the computers are connected forming a mesh shape. It is completely connected network. Unlike other topologies, the messages in mesh topology are sent on a mesh network that can take any of several possible paths from source to destination.
- Mesh is a reliable topology because any link failure will not affect entire network.
- Each node of the network need not have individual routing capabilities in this topology.
- The Communication between two nodes of mesh topology is very fast.
- The failure of a device does not affect the data transmission to the destination device.
- This is one of expensive network system in term of linking cost.
- This topology is very difficult to install/setup.
- This topology is also difficult to reconfigure.
-Network Architecture:
Network architecture is an interaction behavior or model which defines how the computers on the network interact and communicate each other. The types of
Network architecture are:
- Client/Server Network architecture: This is a type of network architecture in which all the computers have distinctly defined role. One or more computer in the network acts as server which provides services to other computers called clients. Here, all the clients are dependent to the server for any type of communication.
- Peer-to-Peer Network architecture: A Peer-to-Peer network architecture is the type of network architecture in which all the computers act as both client and server i.e. all the computers can communicate independently. Each node can share the resources with other nodes in the network without server.
-Network Software: Network software is a group of programs which control and manage all the resources used in network. It is also called Network Operating
System (NOS). Novell Netware, Windows NT, Linux, etc Network Software.
-Introduction to Internet:
Internet is the most widely used technology in today's world. Today most of the people are using this technology all over the world. The Internet is a global networkof computers in which millions of computers are connected world wide. The billions of peoples throughout the world are using the Internet at the same time.
The Internet is formed by joining thousands of smaller networks such as LAN, WAN, and MAN throughout the world. Therefore, Internet is also called the network of networks. The Internet is a global network of computers in which thousands of smaller computers such as LAN, WAN and MAN are connected all over the world using TCP/IP.
-Terms Used in Internet :
There are lots of terms used in Internet. The commonly used terms are described below:
- World Wide Web (WWW): WWW is a system for finding document on the Internet. In the World Wide Web, millions of documents are linked with each other using HYPER TEXT links.
- Web Page: A webpage is a document that is connected to the World Wide Web. The webpages are created by using mark up language called Hyper Text Mark up language.
- Websites: A website is a collection WebPages that are related to each other by a certain topic. A website is like a book on the Internet, which provides information about any subject or topic.
- Home Pages: A home page is the very first page of a website. It is the first page that a browser opens when we access a website.
- URL (Uniform Resource Locator): Uniform Resource Locator is the address of a website or webpage on the Internet. Each website or webpage on the Internet has an unique address. Some examples of the URL are: Facebook (www.facebook.com), Youtube (www.youtube.com) etc.
- Web Browser: Web browser is a special type of software which are needed to access resources on the Internet. Internet Explorer, Mozilla Firefox, Google chrome etc are some examples of popular web browsing software.
- Downloading: The process of receiving and copying electronic information of any kind of data, files, software, MP3s, photos etc from the website to user's computer is called downloading.
- Uploading: The process of transferring data, file, programs etc from user's computer to World Wide Web is called the uploading.
- Chatting: Chatting is a service of the Internet that allows users to "talk" to one another in virtual real time. That means we can only chat with those people who are currently online.
- Internet Service Provider (ISP): Internet Service Provider is a company that provides Internet service to the user. Nepal Telecommunication (NTC), TP link, World link etc are some examples of ISPs.
- The E-mail: The electronic mail is an electronic transfer of messages, which can be sent from one computer to another computer through the Internet. It is very fast and reliable way of sending mail.
-Browsing the Websites on the Internet:
Opening the webpages on the World Wide Web using the web browser is called browsing. We can open any websites on the Internet from their URL using browsing
software. To open website on the Internet follow these steps:
Step 1: Open the Internet Explorer browser.
Step 2: Type the website address (URL) on the address bar of the browser window. Here type the address: google.com (example)
Step 3: Then click on the Go button or press Enter key.
-Search Engine:
Search engine is a special program that helps to search information and websites on the Internet. By using search engine we can search the resources without using
its URL. For example, to search the website of "public service commission", in the search engine then it will find its website. The commonly used search engines
are: GOOGLE, BING, YAHOO, ASK, ALTA VISTA, EXCITE etc.
-Using Search Engine:
Step 1: Open the browser such as Internet Explorer and type address of search engine on browser's address bar then press Enter key. Here type www.google.com
and press Enter key.
Step 2: Type word or phrase of word on Google search box.
Step 3: Click on 'Search' button or press Enter key. Here, type "Public service commission" and click on Search button or press Enter key. Then, the list of links
related to Public service commission will be displayed.
We can view different sites by clicking the links.
To be continued......
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