Contents

Section 4:Applications and Implications of Information and Communication Technology

Objective 4.1Use terms associated with data communication and networks

Objective 4.2Distinguish among Internet, intranet and extranet

Objective 4.3Explain concepts associated with the Internet

Objective 4.4Describe measures to secure data and maintain data integrity.

Objective 4.5Outline ways by which information can be misused.

Objective 4.6Describe appropriate hardware and software to meet the particular needs of a given application;

Objective 4.7Describe current and emerging technological trends;

Objective 4.8Assess the impact of Information Technology on job skills and careers;

Objective 4.9Describe the roles of various personnel in computer-related professionals;

Section 4:Applications and Implications of Information and Communication Technology

Objective 4.1Use terms associated with data communication and networks

Objective 4.2Distinguish among Internet, intranet and extranet

Data Communication

This is the transmission (movement) of data from one point to another for direct use or for further processing e.g. from one computer to another, from a cell phone to computer or vice-versa, or from a computer to fax machine.

Data communication systems are made up of hardware, software and communication facilities. They may span a small area or they may be set up over a global area. Data is moved through these systems via transmission channels or links. These channels are grouped according to their bandwidth. Bandwidthrefers to the volume of data that can be transmitted in a given time. There are three bandwidths:

  • Narrow-band channel transmits data at a slow speed of about 10 to 30 characters per second (cps). An example of this is the telegraph system
  • Voice-band channel transmits data at a rate of 1000 to 8000 cps. An example of this is the telephone line.
  • Broadbandchannel transmits large volumes of data at speeds of over 100 000 cps. An example of this is a communication satellite, fibre optic cables, coaxial cable, microwaves.

Transmission media

These are the ways and/or materials used to move data. Media can be cabled/wired or wireless. Cabled/wired media include:

  • Twisted pair cable: used for home networking where there is no great need for speed. It is a cheap convenient method of connecting computers and peripherals in a network.
  • Coaxial cable: used in medium-sized networks to transmit voice, video and data at moderate speeds.This is more expensive than twisted pair because the transmission capabilities are higher.
  • Fibre optic cable: used to transmit large volumes of digital data at extremely high speed virtually error-free. These are relatively expensive.

Wireless media includecommunications satellite, microwave links, infrared. Wireless network technology also called hot spot technologies refers to Bluetooth andWi-Fi. All of these are used to provide broadband.

Communications satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations.

Microwaves are radio waves that provide a high speed signal transmission. It is also called fixed wireless and involves sending signals from one microwave station to another. A microwave station is an earth-based reflective dish that contains the antenna, transceivers and other equipment necessary for microwave communications.

Infrared is a wireless transmission medium that sends signals using infrared light waves. Mobile computers and devices , such as mouse, printer, and smart phones often have IrDa ports that enables the transfer of data from one device to another using infrared light waves.

Hot spot is a wireless network that provides Internet connections to mobile computers and other devices. They are used by mobile users to check e-mail, browse the Web and access any service on the Internet.

Bluetooth is a standard developed by electronic manufacturers that allow any sort of electronic equipment (computers, digital video cameras, cell phones, PDAs, etc to automatically make their connections without wires, cables or any direct action from a user. One disadvantage of Bluetooth is it cannot transmit signals through walls and distances of over 3 meters.

Wi-Fi is short for wireless fidelity. It is a type of broadband Internet connection that uses radio signals to provide Internet connection to wireless computers and devices.

Communication modes

The lines that transmit data are also classified according to the direction in which data flows through them. There are three (3) types of lines:

  • A simplex line permits data to flow in only one direction. You can send data or receive data, but not both.
  • A half-duplex line can alternately send and receive data. That means that at any particular time you can either send data but not receive it, or receive data but not send it.
  • A full-duplex line can simultaneously send and receive data.

Networks

A network is group of two or more computers linked together so that they can share resources (hardware, software and data) and can communicate with one another. Computer networks maybe classified as one of the following:

  • Local Area Network (LAN)
  • Wide Area Network (WAN)
  • Metropolitan Network
  • Internet
  • Intranet
  • Extranet

Local Area Network (LAN)

LANs consists of a collection of microcomputers, such as in an office building, department or school that can share peripherals, files and programs and communicate with each other on the network. Each microcomputer that forms part of the network is connected either by cables or by a wireless link.

Benefits of a LAN are:

  • Hardware such as printers can be shared.
  • Storage facilities can be shared.
  • Software and data files can be shared by many users.
  • It is usually cheaper to buy one copy of a software application and pay license fee for several machines, than to buy individual packages for each computer.
  • Users can work together on a single document.
  • User can communicate using e-mail.

Disadvantages of a LAN are:

  • The initial set costs are high
  • There is increased risk of data corruption. Since many users will be using the system, there is greater chance of data being corrupted or tampered with.
  • There is a greater risk from viruses because they easily spread between the computers that are part of the LAN.
  • If the file server fails, all workstations are affected and or work stored on shared hard disk drives will not be accessible; nor will it be possible to use networked printers, etc.
  • Networks can be complicated to maintain and may require a network manager. Additional costs may therefore be incurred.

Wide Area Network (WAN)

This network connects mainframes, LANs and PCs across a large geographical area such as a city, a country or the world using a combination of many types of media such a telephone lines, cables microwave links, satellite links. WANs are used mainly by universities, research centres and large organizations with branches in different countries.

Metropolitan Network (MAN)

This network connects LANs in a metropolitan area such as a city, state or town. It includes one or more LANs but covers a smaller geographical area than a WAN. It is usually managed by a single network provider that sells the service to users. Telephone companies and cable television operators provide connections to the MAN.

Intranet

This network is a micro-version of the Internet within a company or organization. It offers the same features of the global Internet but limited to a small area such as a factory site or an office. Authorized users within the company can use the company’s intranet to find information easily and quickly. The documents in the intranet have links to other documents in the network or outside the wider Internet. This network uses browsers and software just like those used on the Internet.

Extranet

This is an Intranet that allows limited access to it by people outside the company. A company may set up an extranet, for example, to provide technical support information to its customers based on products it sells or services it provides.

Objective 4.3Explain concepts associated with the Internet

The Internet

This is the world’s largest WAN. It is a network of networks that connects computers worldwide via a huge set of telecommunication links. The Internet does not have a central authority. No one is in charge of the Internet. There are organizations which develop technical aspects of the network and set standards for creating applications on it, but no one governing body or government is in control.

Advantages of the Internet

  • Vast volumes of information are available on virtually any topic.
  • Information can be updated regularly.
  • Much of the information is free.
  • It allows people to telecommute i.e. work from home using Internet facilities like e-mail, and keep in touch cheaply and quickly with friends and relatives.
  • It is convenient for many common chores e.g. booking flights and Internet banking.
  • It is easily accessible: all you need is a PC with modem and a phone line.

Disadvantages of the Internet

  • Lots of incorrect information is available; there is no authority to check the accuracy of Internet documents, etc.
  • It can be difficult to find exactly what you need because of the large volume of information available.
  • Computer viruses can easily be downloaded without the user realizing.
  • There are lots of undesirable websites on the Internet (pornography, racist, propaganda (half truths), etc.).
  • The security of computers and WAN/LAN systems connected to the Internet may be at risk from hackers.

For a basic connection to the Internet you need the following:

  • Computer hardware – a personal computer and modem
  • Communication link – a phone line or cable or satellite dish
  • An Internet Service Provider (ISP)
  • Computer software – facility to implement TCP/IP and an Internet browser.

Modem

A standard telephone line can transmit only analogue data, whereas data emitted from a computer is in a digital form. A modem (modulator/demodulator) is a device used to convert the digital data emitted from the computer into analogue data that can be transmitted over a telephone line. When the data gets to the other end of the line, a modem converts the analogue data back into digital data for the computer at that end of the line to process. The data transmitted can be sound, pictures, video or text. Modems can be external or internal (attached to the mother board). There are also different types of modems:

  • Integrated Services digital network (ISDN)
  • Asymmetric digital subscriber line (ADSL)
  • Cable modems

Internet Service Provider (ISP)

This is a company that has a direct connection to the Internet and gives users access to it, usually for a fee. The company usually has a small network that is linked via a high-speed communication link to a high-speed link that forms part of the Internet’s backbone (supercomputers and other large networks that make up the Internet worldwide).

TCP/IP

Computers on the Internet use a protocol called TCP/IP. This is a set of protocols used to transfer data from one computer to another over the Internet. A protocol is asset of rules that defines how computers interact or communicate with each other. TCP/IP is not designed for any specific type of computer so it enables hardware and operating systems software from different computers to communicate. E.g. an IBM computer can communicate with an Apple computer.

Browser

In order to navigate (go through) the World Wide Web (WWW), you need a web browser. A web browser is a program that resides in your computer and enables you to find, retrieve, view and send hypertext and hypermedia documents over the web. Popular browsers are MS Internet Explorer and Mozilla Firefox. Some of the things you can do with a browser are:

  • View hundreds of millions of web pages from all over the world.
  • Send and receive email
  • Participate in conferences
  • Chat
  • Shop online
  • See and hear recorded broadcasts

Internet Protocol (IP) addresses

Each computer on the Internet has a unique address that identifies it as a node so that information can be sent to it. This unique address is really a number consisting of four sets of up to three digits each, separated by full stops, e.g. 196.361.232.4. Because this address is difficult for humans to remember, names are used to correspond to each IP address. The names are determined through the Domain Name System (DNS). The DNS divides the Internet into a series of domains which are further divided into sub-domains, and the sub-domains into lower level domains. The top-level domains are grouped into categories. Some of them are:

  • Educational institutions.edu
  • Commercial entities.com
  • Public organizations.org
  • Government bodies.gov
  • Military.mil

Using the different domains from top down, a computer’s (host’s) name is determined. The complete name of a computer on the Internet includes the computer’s name, all sub-organizations, the organization and the top – level domain.

E.g. shop.ASCD.org

Top-level domain

Sub-domain

Computer’s name

Internet Application (uses)

There are four main types of services available on the Internet:

  • Terminal emulation services
  • File access and transfer services
  • Communication services
  • The World Wide Web (WWW)

Terminal emulation services (TES)

These enable you to connect your computer to a remote host and use the services available as if your computer were a terminal of the remote computer (host).Some of the services accessible are online databases, library catalogues and chat services. A popular TES is Telnet. This is a program that allows you to access data and programs from a Telnet server. When connected to a Telnet site, your computer becomes a dumb terminal that can only send text-based messages to the Telnet site and allow you to view the results.

File access and transfer services

These allow you to locate and use electronic files stored on computers across the Internet.

File transfer protocol (FTP)

This is a set of rules for communicating over the Internet. An FTP program enables you to find an electronic file stored on a computer somewhere and download it (take a file from one computer on the Internet and copy it to a storage device on your computer). It also allows you to upload files (send files to other computers on the Internet). Some FTP sites are private and require you to pay to retrieve or store information on them.

Communication services

Electronic mail (e-mail)

This is the most popular and widely used service on the Internet. It enables users worldwide to send electronic messages (text, sound, video and graphics) to one individual or group of individuals, and receive messages from others. E-mail is much faster than regular mail. It is free since you do not pay to send the e-mail, you only pay for Internet access from your ISP. It is convenient, since you can access your at anytime and from anywhere as long as your have Internet access.

Email addresses

To send and /or receive e-mail, each user must have an e-mail address and an email program. The address is unique to the user and consists of two parts separated by the @(‘at’) symbol. The first partis the user name, which can be a real or made up name. The second part is the domain name (the location of the e-mail account on the Internet).

E.g. of an email

For an email to be sent and received, the following must be in place:

  • Mail server: this is the computer on the Internet that operates like the traditional post office- it receives incoming messages and delivers outgoing messages. It allocates a certain amount of storage space (called your mailbox). Users retrieve their mail by supplying their username and password.
  • Mail client: this is a program that enables you to read and compose e-mail messages, send e-mail and access e-mail from the server.

Electronic Discussion Forums

Mailing Lists

An electronic mailing list is a group of people using e-mail to communicate their views on common issues or interests. You subscribe to become part of the group. Not all groups are open to everyone. Some allow only professionals in a certain field. When you become a member of a group, you can send messages with comments or views on some matter that is being discussed. A copy of your message is then sent to all subscribers on the mailing list. Some mailing list only let subscribers receive messages but not send them e.g. a mailing list that sends a joke a day.

Newsgroups

A newsgroup enables a group of people with common interests to communicate with each other. A subscriber to a newsgroup posts a message which can vary from a few lines to a whole article. The other subscribers read the message and may or may not choose to reply.

The main difference between newsgroups and mailing lists is the method of communication. Mailing lists use e-mail to communicate with subscribers. Messages are sent to a subscriber’s e-mail address. Newsgroups post messages on the Internet for all the users to access. For you to be able to read and post messages to newsgroups, your computer must have newsreader software.

Bulletin Board System (BBS)

This is an Internet facility much like a newsgroup. It is dedicated to the exchange of messages. Most bulletin boards serve specific interests groups and are often free, although some may charge a membership or user fee. Everyone with access to the bulletin board can post and view messages on topics covered the board.

Chat

Chat is a service used by a group of people who share the same interests and wish to communicate with each other interactively, in real time. Three different ways of chatting are:

  1. Text-based Chat

Each user entering the chat room sees the comments being typed by other users in the chat room in real time. Everyone is notified when new users enter the discussion. Each user types his/her comments. They may also choose to talk to specific persons in the group. An example of a text-based program is ICQ.