After reading this chapter, you should be able to:

• Describe the nature and function of local area networks and wide area networks
• Discuss the uses and implications of electronic mail, teleconferencing, and other forms of on-line communication
• Describe several ways people use information utilities and electronic bulletin boards
• Describe current and future trends in telecommunications and networking

Arthur C. Clarke's Magical Prophecy

Besides coining Clarke's laws, British writer Arthur C. Clarke has written more than 100 works of science fiction and nonfiction, including the film 2001: A Space Odyssey. But Clarke's most visionary work may be a paper published in 1945 in which he predicted the use of geostationary communication satellites&endash;satellites that match Earth's rotation so they can hang in a stationary position relative to the spinning planet below&endash;which would link the people of the world with a single communications network.

Telecommunication technology&endash;the technology of long-distance communication&endash;has come a long way since the War of 1812, and the world has changed dramatically as a result. The technological transformation has changed the popular definition of the word telecommunication, which today means long-distance electronic communication in a variety of forms.

 

 

LINKING UP: NETWORK BASICS

A computer network is any computer system that links together two or more computers. The reason networking is important revolves around the three essential components of every computer system: 

• Hardware. Networks allow people to share computer hardware, reducing costs and making it possible for more people to take advantage of powerful computer equipment.
• Software. Networks allow people to share data and software programs, increasing efficiency and productivity.
• People. Networks allow people to work together in ways that are otherwise difficult or impossible.

Basic Network Anatomy:

A network extends the range of computer electrical pulses, allowing them to travel to other computers. A computer may have a direct connection to a network or it might have remote access to a network through a phone line and a dial-up connection.

 

The Network Interface:

Personal computers communicate through serial ports with other computers. IBM-compatible PCs require a network interface card (NIC) containing the necessary serial port.

Communication À la Modem:

The telephone network is ideal for connecting remote computers, too, except it was designed to carry sound waves, not streams of bits. Before a digital signal&endash;a stream of bits&endash;can be transmitted over a standard phone line, it must be converted to an analog signal&endash;a continuous wave.

At the receiving end the analog signal first must be converted back into the bits representing the original digital message. Each of these tasks is performed by a modem (short for modulator/demodulator)&endash;a hardware device that connects a computer's serial port to a telephone line.

A modem converts a computer's digital signals into analog signals. The analog waves are transmitted through telephone lines to another modem, which converts them back into digital signals.

An internal modem is installed on a circuit board inside the computer's chassis. An external modem sits in a box linked to the computer's serial port. Both types use phone cables to connect to the telephone network through standard modular phone jacks.

Modems differ in their transmission speeds, measured in bits per second (bps).

Networks Near and Far:

A local area network (LAN) is a network in which the computers are close to each other, usually in the same building. Cables serve as information highways for transporting data between devices.

A typical local area network includes a collection of computers and peripherals; each computer and shared peripheral is an individual node on the network.

In a wireless network each computer has a tiny radio connected to its serial port so it can send and receive data through the air rather than through cables.

All computers on a LAN do not have to be the same brand, or use the same operating system. Most organizations depend on network administrators to take care of the behind-the-scenes details so others can focus on using the network.

A wide area network (WAN), as the name implies, is a network that extends over a long distance. Wide area networks are possible because of the web of telephone lines, microwave relay towers, and satellites that span the globe. Some WANs are private operations. Others are public or semipublic networks.

 

Communication Software:

Whether connected by cables, or a combination of modems and telephone lines, computers need some kind of communication software to interact.

To communicate with each other, two machines must follow the same protocol&endash;a set of rules for the exchange of data between a terminal and a computer or between two computers.

For users who work exclusively on a local area network, many communication tasks can be taken care of with a network operating system (NOS).

Some LANs follow a client/server model; others use a peer-to-peer model, in which every computer on the network can be both client and server.

Outside of a LAN, the most familiar type of communication software is the terminal program, which allows a personal computer to function as a terminal. This kind of program (sometimes called a terminal emulator) handles phone dialing, protocol management, and miscellaneous details necessary for making a personal computer and a modem work together.

At the other end of the line, the communication software is usually built into the multiuser operating system of the host system. This software allows a timesharing computer to communicate with several other computers or terminals at once.

The Network Advantage:

Networks offer three big advantages for users:

• Networks allow people to share hardware, reducing costs and making it possible for more people to take advantage of powerful computer equipment.
• On a LAN, users can share printers, scanners, and modems. On a WAN, users can connect to powerful remote machines.
• Networks allow people to share data and software programs, increasing efficiency and productivity.

In a LAN, one or more computers can be used as file servers&endash;storehouses for software and data that are shared by several users.

Some companies offer site licenses or network licenses that reduce costs for multiple copies or remove restrictions on software copying and use at a network site.

Networks don't eliminate compatibility differences between different computer operating systems, but they can simplify data communication between machines. If users of different systems use programs with incompatible file formats, they need to use data translation software to read and modify each other's files.

Networks allow people to work together in ways that are difficult or impossible without network technology.

Some modern software applications can be classified as groupware&endash;programs designed to allow several networked users to work on the same documents at the same time.

Electronic mail (e-mail) systems allow users to send messages (mail) from one computer to another. Each user has a mailbox&endash;a storage area for messages. Users select a login name or screen name&endash;the one-word name they have chosen to identify the user on the screen. A user then enters a password&endash;a string of letters and numbers known only by the user&endash;and as it is typed only asterisks appear on the screen.

A variation of electronic mail is the teleconference&endash;an on-line meeting between two or more people. Many teleconferencing systems allow users to communicate in real time, just as they would by telephone. In a real-time teleconference, each participant sits at a computer or terminal, watching the meeting transcript scroll by on the screen and typing comments on the keyboard.

Participants of an asynchronous teleconference (sometimes called a delayed teleconference) share an electronic mailbox for messages related to the group's purposes.

The Postal Alternative:

For many organizations electronic communication is already reducing postal expenses because:

• E-mail is fast.
• E-mail doesn't depend on location.
• E-mail facilitates group communication.
• E-mail messages are digital data that can be edited and combined with other computer-generated documents.

Bypassing the Telephone:

Electronic mail and teleconferencing also offer advantages over telephones:

• On-line communication is less intrusive than the telephone.
• On-line communication allows time shifting.

Minimizing Meetings:

Teleconferences and e-mail offer several advantages for group decision making:

• Teleconferences and e-mail allow decisions to evolve over time.
• Teleconferences and e-mail make long-distance meetings possible.
• Teleconferences and e-mail emphasize the message over the messenger.

On-line Problems:

The most important problems introduced with on-line communication are:

• E-mail and teleconferencing are vulnerable to machine failures and human errors.
• E-mail can pose a threat to privacy.
• E-mail can be faked.
• E-mail works only if everybody plays.
• E-mail and teleconferencing filter out many "human" components of communication.

Electronic Bulletin Board Systems (BBSs):

An electronic bulletin board system (BBS) is a place for posting messages and reading messages left by others. BBS software allows the computer to receive, organize, and post messages in appropriate categories automatically.

Many BBSs operate without human supervision for long periods of time. The system operator, or sysop, is needed only for occasional maintenance and troubleshooting.

Many BBSs divide messages into categories called SIGs, for special interest groups.

In addition, many bulletin boards serve as repositories for public domain software and shareware&endash;two types of software that can be freely distributed without violating copyright laws.

BBS users can download software&endash;copy it from the BBS computer to their computers&endash;and upload software&endash;post it on the BBS so it's available for others. Software sharing can cause problems, including software piracy and viruses.

On-line Databases:

Many computer users use a modem to connect to on-line databases for instant answers.

Commercial On-line Services:

General-purpose commercial on-line information services allow users to send and receive information the way small BBSs do, but they're able to handle hundreds of users at a time. Services include the following:

• News
• Research
• Shopping
• Banking
• Games
• Bulletin boards
• Communication

Mail gateways link the major on-line utilities and networks to the Internet, making it possible for subscribers of competing services to send messages to each other.

The Internet poses a threat to many of these services because it offers similar services at lower cost.

Computer Networks Today: A Reality Check:

In spite of the hype, many networks today are besieged with problems: software failure, unfriendly interfaces, slow response, and others. These problems don't stop many people from spending hours each day on-line, but they discourage most people from becoming mouse potatoes.

Rules of Thumb: On-line Survival Tips

Whether you log onto a BBS, an information utility, or the Internet, you're using a relatively new communication medium with new rules. Here are some suggestions for successful on-line communication:

• If you're using a metered service, do your homework off-line.
• Let your system do as much of the work as possible.
• Store names and addresses in an on-line address book.
• Cross-check on-line information sources.
• Avoid information overload.

Alternative Communication Technologies

The following forms of telecommunication don't require users to type commands and messages.

Facsimile Transmission:

A facsimile (fax) machine is a fast and convenient tool for transmission of information stored in paper documents, such as typed letters, handwritten notes, photographs, drawings, book pages, and news articles.

A computer can send on-screen documents through a fax modem to a receiving fax machine. The fax modem translates the document into signals that can be sent over phone wires and decoded by the receiving fax machine.

A computer can also use a fax modem to receive transmissions from fax machines, treating the sending fax machine as a kind of remote scanner. Before a faxed document can be edited, it must be processed by optical character recognition (OCR) software.

Voice Mail and Computer Telephony:

A voice mail system is more than an answering device; it's a sophisticated messaging system with many of the advantages of e-mail.

Computer telephony software and hardware allow a personal computer to serve as a speakerphone, answering machine, and even as a voice mail system.

Video Teleconferencing:

A video teleconference allows people to communicate face to face over long distances by combining video and computer technology. Video teleconferencing comes to the desktop with video phones and video teleconferencing software.

 

Electronic Funds Transfer (EFT):

Money, like other digital information, can be transmitted through computer networks. That's why it's possible to withdraw cash from your checking account using an automated teller machine (ATM) at a bank, airport, or shopping mall thousands of miles from your home bank. An ATM is a specialized terminal linked to a bank's main computer through a commercial banking network.

Many people have paychecks deposited automatically in checking or savings accounts and have bills paid automatically out of those accounts.

Electronic funds transfer is one component of electronic commerce, or e-commerce&endash;commercial activity that takes place through networked computers.

Personal Digital Assistants (PDAs):

Many personal digital assistants (PDAs) combine cellular phone, fax modem, an electronic mailbox, a pager, and other communication equipment in a lightweight box. These devices are popular with a growing number of mobile professionals.

 

Converging Communication Technologies:

ISDN: The Integrated Services Digital Network, commonly called just ISDN, will link telephones, computers, fax machines, television, and even mail in a single digital system. ISDN is already available in a few cities, but most phone lines can't handle ISDN.

The main problem is bandwidth&endash;the quantity of information that can be transmitted through a channel in a given amount of time. The bandwidth bottleneck disappears when copper phone lines are replaced with high-capacity fiber optic cables. Fiber optic cables use light waves to carry information at blinding speeds.

 

Digital Communication Comes Home:

Integrated digital communication lines will eventually find their way into our homes, radically changing our lives in the process.

KEY TERMS

analog signal, asynchronous teleconference, automated teller machine (ATM)

bandwidth, bits per second (bps), bulletin board system (BBS), client/server model

communication satellite, communication software, delayed teleconference, digital signal, download

electronic commerce (e-commerce), electronic funds transfer (EFT), electronic mail (e-mail)

facsimile (fax), fax modem, fiber optic cable, file server

gateways, groupware, host system, ISDN, local area network (LAN), login name

modem, network, network license, network interface card (NIC), network operating system (NOS), node

on-line, on-line database, on-line information service

password, peer-to-peer model, personal digital assistant (PDA), port, protocol

real-time teleconference, server, site license

telecommunication, teleconference, telephony, terminal program, upload

video teleconference, voice mail, wide area network (WAN), wireless network

 Computer Literacy On-Line

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