© 2008 Prentice-Hall, Inc. Slide 1. Chapter 8 Networking and Digital Communication © 2008 Prentice-Hall, Inc. Slide 2

© 2008 Prentice-Hall, Inc.Slide 1

Chapter 8Networking and Digital Communication


Describe the basic types of technology that make telecommunication possible.

Describe the nature and function of local area networks and wide area networks.

Discuss the uses and implications of email, instant messaging, blogging, teleconferencing, and other forms of online communication.


Explain how wireless network technology is transforming the ways people work and communicate.

Describe current and future trends in telecommunications and networking.


Clarke’s laws If an elderly but distinguished scientist says

that something is possible, he is almost certainly right, but if he says that it is impossible he is very probably wrong.

The only way to find the limits of the possible is to go beyond them into the impossible.

Any sufficiently advanced technology is indistinguishable from magic.


Arthur C. Clarke’s most famous work was the monumental 1968 film 2001: A Space Odyssey, in which he collaborated with movie director Stanley Kubrick.

Clarke’s most visionary work may be a paper published in 1945 in which he predicted the use of geostationary communications satellites—satellites that match the Earth’s rotation so they can hang in a stationary position relative to the spinning planet below, relaying wireless transmissions between locations on the planet.


A computer network is any system of two or more computers that are linked together.

How is networking important? People share computer hardware, thus reducing

costs. People share data and software programs, thus

increasing efficiency and production. People work together in ways that are otherwise

difficult or impossible.


Networks Near and Far In a local area network (LAN) computers are physically close to each other,

usually in the same building. Computers are linked within a building or

cluster of buildings. Each computer and peripheral is an individual

node on the network. Nodes are connected by cables, which may be

either twisted pair (copper wires) or coaxial cable.

In a wireless network each node has a tiny radio (or, less commonly, infrared) transmitter connected to its network port. Computers send and receive data through the air rather than through cables.


A metropolitan area network (MAN) links two or more LANs within a city. A wide area network (WAN) extends over a long distance.

Each networked LAN site is a node on the WAN. Data transmitted over common pathways called a backbone.


Communication frequently happens between LANs and WANs Routers: hardware devices or software programs that route

messages as they travel between networks Mesh networks: an alternative to today’s networks; rely on

centralized routers Used to set up small, temporary communication systems Example: emergency personnel use at fire scenes to coordinate

actions


“Pretty soon you’ll have no more idea of what computer you’re using than you have an idea of where your

electricity comes from.”—Danny Hillis, computer designer

Specialized Networks: From GPS to Financial Systems

Global Positioning System (GPS) GPS is a specialized network developed by

U.S. Department of Defense. It includes 24 satellites that circle the Earth. Each satellite contains a computer, an atomic

clock, and a radio. On the ground, a GPS receiver can use

signals broadcast by three or four visible

satellites to determine its position.


Networks that keep our global financial systems running: Automated Teller Machine (ATM): a specialized terminal linked to a bank’s main

computer through a commercial banking network


The Network Interface A network interface card (NIC) permits

direct network connection: Adds an additional serial port to the computer Controls the flow of data between the computer’s RAM

and the network cable

The most common types of networks today require some kind of Ethernet card or port in each computer. Ethernet is a popular networking architecture developed in 1976 at Xerox. Most newer PCs include an Ethernet port on the main circuit board, so they don’t

require NICs to connect to Ethernet networks.



Communication á la Modem

Modem: a hardware device that connects acomputer’s serial port to a telephone line (for remote access)

May be internal on the system board or external, sitting in a box linked to a serial port

Modem transmission speed measured in bits per second (bps) Transmit at 28,000 bps to 56.6K bps

Computers send digital signals. The modem (modulator/demodulator) converts the digital signals to

analog so that the message can be transmitted through telephone lines and converts it back on the other end.


Broadband connection—a connection with much greater bandwidth than modems have

DSL uses standard phone lines and is provided by phone companies in many areas.

Cable modems provide fast network connections through cable television networks in many areas.

High-speed wireless connections can connect computers to networks using radio waves rather than wires.

Satellite dishes can deliver fast computer network connections as well as television programs.



Fiber Optic Connections

DSL and cable modems have nowhere near the bandwidth of the fiber optic cables that are replacing copper wires in the worldwide telephone network.

A fiber optic network can rapidly and reliably transmit masses of multimedia data at the same time that it’s handling voice messages.


Wireless Network Technology

A lightning-fast network connection to your desktop is of little use if you’re away from your desk most of the time; when bandwidth is less important than mobility and portability, wireless technology can provide practical solutions.

The fastest growing wireless LAN technology is known as Wi-Fi or 802.11b.


Bluetooth: another type of wireless technology Named for a Danish king who overcame his country’s religious differences Overcomes differences between mobile phones, handheld computers, and PCs, making

it possible for all of these devices to communicate with each other regardless of operating system


With Bluetooth it’s possible to create a personal area network (PAN)—a network that links a variety of personal electronic devices so they can communicate with each other.

Bluetooth technology is currently limited to simple device connectivity, but in the future it will open up all kinds of possibilities: A pacemaker senses a heart attack and notifies the victim’s

mobile phone to dial 911. A car radio communicates with parking-lot video cameras

to find out where spaces are available.


More examples of Bluetooth possibilities:

A pen scans business cards and sends the information to a PDA inside a briefcase.A medical wristband transmits an accident victim’s vital information to a doctor’s handheld computer.A cell phone tells you about specials on clothes that are available in your size as you walk past stores in a mall.


Communication Software

Protocol is a set of rules for the exchange of data between a terminal and a computer or between two computers.

Communication software establishes a protocol that is followed by the computer’s hardware.


Communication software takes many forms: Network operating system (NOS)

System handles communications among many workstations.

Client/server model One or more computers act as dedicated servers and all the

remaining computers act as clients. Peer-to-peer model

Every computer on the network is both client and server. Many networks are hybrids, using features of the

client/server and peer-to-peer models.


The Network Advantage

Why do people use networks?

Networks enable people to share computer hardware resources, reducing costs and enabling people to take advantage of powerful computer equipment.

Networks enable people to share data and software programs, increasing efficiency and productivity.

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

A Home Computer Network


Firewall/router

USB cable

DSL modem

Wireless laptop

Multiplayer games

Wireless access point


The Many Faces of Email

Email systems enable you to send and receive messages to others

on the network. Web-based email systems and many older UNIX-based programs require

that read and unread messages be stored in post office boxes or folders on the remote mail servers.

Many email messages are plain ASCII text.


Even if their software can display HTML mail, not all email users want HTML emails:HTML encoding can slow down an email program.An HTML email message can also carry a Web bug.

Most email programs can send and receive formatted word processor documents, pictures, and other multimedia files as attachments to messages.


Mailing Lists Mailing lists enable you to participate in email discussion groups on

special-interest topics.Subscribing to a busy list might mean receiving hundreds of messages

each day. To avoid being overwhelmed by incoming mail, many list members sign up to

receive them in daily digest form. Some lists are moderated to ensure that the quality of the discussion remains

high.


NewsgroupsNewsgroup: a public discussion on a particular subject

Notes are written to a central Internet site. Notes are redistributed through a worldwide newsgroup network called USENET. Listserv mail messages are delivered automatically to your mailbox, but you have

to seek out information in newsgroups. Mailing list messages are sent to a specific group of people, whereas newsgroup

messages are available for anyone to see.Moderated newsgroups contain only messages that have been filtered by

designated moderators.


Rules of Thumb: Online Survival Tips

Let your system do as much of the work as possible.Store names and addresses in computer-accessible

addressbook.Don’t share your email address.Don’t open suspicious attachments.Protect your privacy.Cross-check on-line information sources.Be aware and awake.Avoid information overload.


Instant Messaging and Teleconferencing:Real-Time Communication

Mailing lists and newsgroups are delayed or asynchronous communication. The sender and the recipients don’t have to be logged in at the same time.

Instant messaging (IM) has been possible since the days of text-only Internet access.

Newer, easier to use messaging systems from AOL, Microsoft, Yahoo, Apple, and others have turned instant messaging into one of the most popular Internet activities.


Online services also offer chat rooms—public or private virtual conference rooms where people with similar interests or motivations can type messages to each other and receive near instant responses.

Several IM programs make it possible to carry on two-way video teleconferences.


Computer Telephony

Voice mail is a messaging system with the ability to store, organize, and forward messages. An example of a growing trend toward computer telephony integration

(CTI) is the linking of computers and telephones to gain productivity.

It’s also possible to send voice signals through a LAN, a WAN, or the Internet, bypassing the phone companies (and their charges) altogether.

Handheld PDA computers use software to integrate the functions of a PDA, a phone, and an Internet terminal.


Computer Telephony

Internet Telephony has become a legitimate competitor to traditional phone companies.Voice over IP (VoIP) requires a broadband connection to carry your

call over the Internet.You can place a calling using either a traditional phone with an

adapter or an Internet-connected PC with a microphone headset and

appropriate software.


Computer Telephony

Advantages of VoIPCalls are less expensive if you already have a broadband connection.Calls are routed to you no matter where you are connected. VoIP phones integrate more easily with online address books, video

conference services, and other Internet services.


Computer Telephony

Disadvantages of VoIPCommunication is impossible during a power outage (most networks

are unusable).There is no 911 or directory assistance service available. Quality is suspect because there is no guarantee of packets being

delivered in a timely manner.


Social Networks and Information Sharing

Online communities such as MySpace and FacebookMassively multiplayer role playing games (MMORPG)Common information resources such as Flickr and Wikipedia


Email Issues

Problems with Spam – more than 50% of e-mails are unsolicited.Email and teleconferencing are vulnerable to machine failures, network

glitches, human errors, and security breaches.Email can be overwhelming.Email can pose a threat to privacy.


Don’t Get Hooked—Advice on Phishing

Examine the URL in the address bar.Re-examine the URL in the address bar.Look for the https prefix.Look for the padlock icon.Pay attention to pop-up warnings about fraudulent certificates.Make your own Web connection.


Cookies – Can be used by snoopers to get information about you Wireless issues of access, security, and privacy Perils of posting too much information on blogs and websites Internet Addiction – Some game players spend 40-80 hrs a week online Virtual Sweatshops


Digital Communication in Perspective

Many services we take for granted today—video rentals, cable TV, newspapers, and magazines, for example—will be transformed or replaced by digital high-bandwidth interactive delivery systems of the future.

At the same time, entirely new forms of communication are likely to emerge.

Telecommunications technology is rapidly changing our lives, and the changes will accelerate as the technology improves.

Networking is one of the most important trends in computing today. LANs are made up of computers that are close enough to be directly

connected with cables or wireless radio transmitters/receivers. Most LANs include shared printers and file servers.

WANs are made up of computers separated by considerable distance. Many computer networks are connected together through the Internet so

messages and data can pass back and forth among them. Some specialized networks, including global positioning systems and

financial systems serve unique functions.


Most computer networks today use the Ethernet architecture; an Ethernet port is a standard feature on most modern PCs.

Communication software takes care of the details of communication between machines—details like protocols that determine how signals will be sent and received.

Email, instant messaging, and teleconferencing are the most common forms of communication between people on computer networks.

It’s not clear how all of these emerging technologies will converge; what is clear is that the wireless revolution is far from over.


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© 2008 Prentice-Hall, Inc. Slide 1. Chapter 8 Networking and Digital Communication © 2008 Prentice-Hall, Inc. Slide 2