After the complication of this chapter, students will be able to:
1. Define computer network and explain its importance
2. Explain the main components essential for the successful operation of a computer network.
3. Describe the network categories and network models.
4. Define Internet and the World Wide Web.
Concept: Sharing of information
The success of an organisation today will depends on its ability to deliver the services that it’s customers need. In today’s world of the ever fast moving information overload, computer networking is the essential element that any organization will need to incorporate if it is to succeed. It includes network media, such as a cable to carry network data; network adapter card to translate the data between the computer and the network media; a network operating system to enable a machine to participate in the network ; and a network protocol to control the network communications.
Computer networks provide tremendous benefits. The most important benefits are listed below:
1. It enables users to share and transfer files within the same network and save time.
2. It allows to share of network connected peripherals
3. It provides easier backup of data
4. It always to transfer sensitive files and software which is password protected to restrict access to unauthorized users.
5. It increases worker productivity and offer tremendous convenience.
The main components essential for the successful operation of a computer network can be divided into two types. They are hardware components and software components.
The hardware components in a network are:
# Computer System(called servers or clients)
A server serves information to computers that connect to a server, they can access programs, files and other information from the server. Common servers are web servers, mail servers, and LAN servers. A single computer can have several different server program running on it. Server provides centralized access and storage for resources that include applications, files, printers, or other hardware, and specialized services such as email.
A client is a network computer that utilizes the resources of other network computers, including other clients. The client computer has it’s own processor, memory, and storage, and can maintain some of its own resources and perform its own tasks and processing.
A network connectors is defined as a device that facilitates the connection or the interconnection of computers and other devices to the network. This connector facilitates the sharing of information and other resources. RJ45 is a standard type of connector for network cables. RJ45 connectors are most commonly seen with Ethernet cables and networks.
The network cables are the means by which data is transmitted between the sending and receiving devices in a network. There are several types of network cables. Some of the most common network cables are twisted pair cables, coaxial cables and fiber optic cables. These cables physically link the devices in a network.
Network Interface Card(NIC)
A network interface card is the card that physically makes the connection between the computer and the network cable. It provides a dedicated, full time connection to a network. It allows users to connect to each other either by using cables or wirelessly. These cards typically use an Ethernet connection and are available in 10, 100 and 1000 Base-T configurations. A 100 Base-T card can transfer data at 100 Mbps.
The software component required to run a computer network are of two types. They are:
# Network Operating System
A computer operating system referred to as Networking Operating System was designed with the sole purpose of supporting workstations, database, application, file and printer access sharing between multiple computers in a network. Certain standalone operating systems, such as Microsoft Windows NT and the and digital’s OpenVMS, come with multipurpose capabilities and can also as network operating systems. Some of the most well known network operating systems. Some of the most well-known network operating systems include Microsoft Windows Server 2003, Microsoft Windows Server 2008, Linux and Mac OS X.
# Network Protocol
Network Protocol is a set of rules or procedures for transmitting data between electronic devices, such as computers. It is necessary for all computers on a network to use the same protocol in order to communicate. These protocols are carried out by sending and receiving formatted instructions of data called packets. Some of the popular protocols are: TCP/IP, HTTP, POP3 and SMTP.
A network model is a design specifications for how the nodes on a network interact and communicate. The network model determines the degree to which communications and processing and centralized or distributed . There are three primary network models: centralized or hierarchical, client/server and peer-to-peer.
Centralized Computing Network
A Centralized Computing
Network is a network in
which a central host
computer performs data
processing and storage
on behalf of clients. Host computers typically run the UNIX operating system andcan process multiple jobs simultaneously. Centralized computing network provides high performance and centralized management, but it is also expensive to implement. Centralized computing network is also called host-based networks
A client/server network is a network in which one or more computers are designated as a server(s) and the other computers on the network, called clients, can requests services from the server. In a client/server environment, each computer still holds (or can still hold) its (or some) resources and files. Other computers can also access the resources stored in a computer, as in a peer-to-peer scenario. One of the particularities of a client/server network is that the files and resources are centralized. This means that a computer, the server, can hold them and other computers can access them. Since the server is always ON, the client machines can access the files and resources without caring whether a certain computer is ON. The client/server type of network also provides many other advantages such as centralized backup, intranet capability, internet monitoring, etc.
A peer-to-peer Network is a group of computers that functions both as a client and a server. All clients on the network are equal in terms of providing and using resources and users are authenticated by each individual workstation. Computers in a peer to peer network run the same networking protocols and software. Peer network are also often situated physically near to each other, typically in homes, small businesses, or schools. Some peer networks, however, utilize the internet and are geographically dispersed worldwide. Peer-to-peer networks are easy and inexpensive to implement.
a computer network or data network is a telecommunications network that allows computer to exchange data. The size and complexity of a network may vary from just two computers connected together to a chain of a few hundred computers of different types of spread around te world. Thus, networks vary in size, complexity and geographical spread. The entire computer network can be classified into three categories depending on:
1.Local Area Network
2.Metropolitan Area Network
3.Wide Area Network
Local Area Network (LAN)
Local Area Network (LAN) is a group of computers and associated devices that share a common communications line or wireless link. Typically, connected devices share the resources of a single processor or server within a small geographic area. This network may be in one room or group of buildings. It consists of a communications channel, networked computers and devices, a network interface card and a network operating system. The major benefit of a local area network is that it can help to reduce cost by allowing people and computers to share expensive resources. LANS also provide users with access to shared programs data files, improving workflow, productivity and communication within an organization.
A wireless local area network links two or more devices using some wireless distribution method, and usually providing a connection through an access point to the wider internet.
Metropolitan Area Network
Metropolitan Area Network is a large computer network that spans a Metropolitan area or campus. It’s Geographic scope for between a WAN and LAN. MANs provide internet connectivity for LANs in a metropolitan region, and connect them to wider area networks like the internet. This internet is used as link between office buildings in a city. They typically use wireless infrastructure or optical fiber connections to link their sites. Cellular phone networks are the good examples of such networks.
Wide Area Network
Wide area network (WAN) is a geographically dispersed telecommunications network. This network may be across the town, between different cities, countries or continents. Typically, it employs communication circuits such as long-distance telephone wires, microwaves and satellites. It consists of two or more LANs connected by routers that ensure that data, instructions and information are delivered to the correct destination. The internet is the single largest global wide area network.
- Short cable length and simple wiring layout.
- Low installation cost.
- Easy to add a new node.
- Well suited for temporary or small networks,
- Easy to implement and extend
- Initially less expensive than other topologies
Facts Corner: The purpose of the terminator is to absorb signals so that they do not reflect back down the line.
- Difficult to administer/ trouble shoot
- If problem occurs on the backbone “cable”, the entire network will go down.
- All computers in the network must have good communication and decision-making capability.
- Performance degrades as additional computers are added or on heavy traffic.
- Limited cable length and number of stations.
- Maintenance costs may be higher in the long run.
Physical Ring Topology
A ring topology is a network topology in which network nodes are connected in a continuous circle. In a ring network layout, all of the computer are connected to one another in a circle. The data passes from one computer to the next one and then all the way around the ring layout until it reaches the destination computer. The information on a ring network travels in one direction only either clockwise or anti-clockwise direction.
- The cost per node is less compared to other topologies. The amount of cable required is also lesser.
- Short cable connection causes an increase in network reliability.
- Using optical fibers offers the possibility of very high speed transmission.
- A failure in any of the nodes can affect the entire network.
- Difficult to diagnose faults.
- Network reconfiguration is difficult.
Physical Star Topology
Star network is a network topology in which all nodes (workstation or other devices) are directly connected to a common central computer. Every workstation is indirectly connected to every other through the central computer. In some star network, the central computer can also operate as a workstation. Star network are usually the layout of choice in schools and offices because they tend to be the most reliable of the topologies.
- Star network are very reliable. If one connection fails, it does not affect other users.
- Very few data collisions as each workstation has its own cables to the server.
- Good security – no workstation can interact with another without going through the server first.
- The most expensive network layout to install because of the amount of cables needed
- Installing the network usually needs experts to set it up.
- Extra hardware such as hubs and switches may be needed.
- If the server crashes or stops working then nobody will be able to access their files or use the network.
Facts corner: A workstation is a computer that’s designed for professional use by a single user.
The internet is the most powerful, global data communications system making it the greatest invention of science because of its wide range of benefits and uses in the world today. The influence of this technology can be found in almost every walk of life. It is a collection of millions of computers all over the world. It allows access to a vast amount of information. It is a massive public spider web of computer connections. There are many organizations, corporation, governments, schools, private citizens and service providers that all own pieces of the infrastructure, but there is no one body that owns it all. There are assign IP addresses and domain names, such as the National Science Foundation, the Internet Engineering Task Force, ICANN, Inter NIC and the Internet Architecture Board. The internet is the world’s largest computer network and it is called network of networks.
The major services provided by the Internet are listed below:
- Allows user to communicate using online chat.
- Allows downloading free computer software and other programs available.
- Allows playing the multimedia games, listening to music and watching movies.
- Sends files, data and information through electronic mail.
- Acts as a virtual market place where people can advertise and order their products.
- Facilities rapid interactive communication.
- Facilities the exchange of huge volumes of data.
- Facilities the establishment of professional contact.
- Facilities access to different sources, of information, which is continously up- dated.
- Facilitates management of companies information system.
- Easier to access information from millions of web sites using search engines.
World Wide Web
The World Wide Web (WWW) is the information store of the Internet. It contains a large collection of linked text, image, sound, and video files. The World Wide Web consists of all the public web sites connected to the internet worldwide, including the client devices (such as computers and cell phones) that access Web content. The World Wide Web is often referred to as the web. The advantages of WWW are listed below:
- It is the fastest medium for transferring information.
- The Web gives users access to a vast array of document that are connected to each other by means of hypertext or hypermedia links.
- Web site can post your business services, location, phone, and e-mail for the public to view.
- Web site can provide customers with the tools needed to locate the exact product that they are looking for and the forms needed to purchase any item or service onine.
Facts corner: The development of the World Wide Web was begun in 1989 by Tim Berners- Lee and his colleagues at CERN, an international scientific organization based in Geneva, Switzerland.
Web Pages and Links
A web page or webpage is a document commonly written in Hyper Text Markup Language (HTML) that is accessible by entering a URL addresses and may contain text, graphics, and hyperlinks to other web pages and files. Every web page has a unique address called a URL (uniform resources locator). These Web pages are linked to one another. This type of linked pages is called hypertext. A number of Web pages, which are linked and referred to by a name or an address, form a Web site. A Web Site is hosted by corporate, government, college and private companies all over the world. Most Web sites have a main page that acts as a ‘doorway’ to the rest of the pages at the site. This main page is referred to as a ‘home page’. The home page is an index to other pages on that site that you can jump to by clicking an underlined hyperlink or an icon.
Searching for Information on the Web
The web search engine is a software system that is designed to search for information on the World Wide Web. The search results are generally presented in a line of results often referred to as search engine results pages (SERPs). The information may be a specialist prod in web pages, images, information, and other types of files. Web search engines are actually databases that contain a reference to thousands of resources. These databases are maintained by special programs called agents, spiders or bots. They automatically search for new information on the web and update the databases. A number of search engines are available on the internet and sometimes they are called web crawlers or web spiders. Some of the search engines are: Google, WebCrawler, Yahoo! and Alta Vista.
Are you going to use a search tool to locate some information? Here are a few tips that might help.
a. Start with the right tool. For general information, use an index like Yahoo. For specific a. information, use a search engine like Hotbot.
b. Be as precise as possible. Use specific keywords that relate directly to the topic.
c. Use multiple words. Use quotation marks to identify keywords.
d. Check your spelling.
e. Look only at the first page of search results. If necessary, try another search engine using ditferent key words.
Client: A network computer that utilizes the resources of other network computers.
Host: The most powerful type of computer on the network, that does all the processing for the user.
Protocol: A set of rules by which computers communicate with each other over network.
Server: A network computer that shares its resources and responds to requests from other networked computers.
Internet: A global collection of millions of computers of different types belonging to various networks.
Let Us Revise
- A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users.
- A network connector is defined as a device that facilitate the connection or the interconnection of computers and other devices to a network.
- A network operating system is an operating system designed for the sole purpose of supporting workstations, database sharing, application sharing and file and printer access sharing among multiple computers in a network.
- A client/ server network is a network in which one or more computers are designated as a server(s) and the other computers on the network, called clients, can request services from the server.
- Local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link.
- A ring topology is a network topology in which network nodes are connected in a continuous circle.
- Star network is a network topology in which all nodes (workstations or other devices) are directly connected to a common central computer.
- It is a collection of millions of computers all over the world. It allows access to a vast amount of information.
1. What is a computer network?
Ans: A computer is a group of computer systems and other computing hardware devices that are linked together through communication and resource-sharing among a wide range of users.
2. What are the benefits of a computer network?
Ans: The most important benefits are listed below:
- It enables users to share and transfer files within the same network and save time.
- It allows to share of networked connected peripherals.
- It provides easier backup of data.
3. What is Local Area Network?
Ans: Local Area Network (LAN) is a group of computers and associated devices that share a common communication line or wireless link.
4. What is the internet, and how did it begin?
Ans: The internet is a global collection of millions of computers of different types belonging to various networks. The life of internet began in 1969 when the United States Development of Defence starts a network called ARPAnet. In 1986, the National Science Foundation created NSFNET to connect research universities. These networks formed the basis for the worldwide system of computers, giving birth to the internet.
5. What is web surfing?
Ans: A user can click any of the links in a Web page and can move to another web page. From there, the user can visit another web page in a different web site and this process can repeat. The process of moving through different web pages is called web surfing.
6. What is URL?
Ans: URL (Uniform Resource Locator) is the address of particular information on the internet.
7. What is a browser? What are some of the most popular browsers?
Ans: A browser is a software program that runs on your computer and helps you access web pages. It provides a set of tools for viewing web pages and navigating from one web page to another. The most popular browsers are Mosaic, Netscape Navigator and Internet Explorer.
8. What is a search engine? What are some of the search engines available on the Web?
Ans: Search engines are web sites that allow the users to search information based on keywords or a combination of keywords. Some of the popular search engines are: HotBot, WebCrawler, Yahoo! and AltaVista.