[

900 B.C. 500 B.C. China has an Greek telegraph: organized trumpets, drums, postal service shouting, beacon for govern- fires, smoke sig­ment use. nals, mirrors.

200 B.C. Tipaa gazettes are circulated to Chinese offi­cials.

100 Roman couriers carry govern­ment mail across the empire.

700 B.C. 500 B.C. 1200 Homing Persia has a University of pigeons carry form of the Paris starts messages in Pony Express. messenger ancient service.

Greece.

1200 European monasteries communicate by letter system.

1560 legalized, regulated pri­vote postal systems grow in Europe.

1689 Newspapers ore printed, at first as unfolded "broadsides."

1819 Hans C. Oersted discovers thot a wire carrying an electric current deRects a magnetic needle, a dis­covery that eventually leads to the creation of the telegraph.

1839 John W. Draper and Samuel F. B. Marse phatagraph New Yorkers using a technique developed by Frenchman louis Jacques Mande Daguerre. Draper and Morse are the first Americans to use the process.

p A R T

How the Internet Works

c H A p T E R s CHAPTER 24 HOW LOCAL AREA NETWORKS WORK 314

CHAPTER 25 HOW PCS CONNECT TO THE INTERNET 324

CHAPTER 26 HOW THE INTERNET MOVES DATA 332

CHAPTER 27 HOW WE REACH EACH OTHER THROUGH THE NET 338

CHAPTER 28 HOW WIRELESS SETS PCS FREE 350

CHAPTER 29 HOW THE NET PROVIDES VIDEO AND AUDIO ON DEMAND 360

CHAPTER 30 HOW THE WORLD WIDE WEB WORKS 366

CHAPTER 31 HOW INTERNET SECURITY FIGHTS OFF PC INVADERS 378

t 1844 1860 1866 1877 1895 The First public telegram is sent, using On April 3 the Pony Express opens for Transatlantic coble The Firs! commercial telephone is intro- Guglielmo Marconi sends a system designed by Samuel Morse. business, pledging to "deliver the goods is finally completely duced and the First telephone line is a wireless signal using a Realizing the potential impact of this in 10 days or less." Its first route cor- successful. The coble instolled between Charlie William's directional antenna, creation, Morse sends the message, ries moil between St. Joseph, Missouri remains in use for electrical shop on Court Street in Boston prompting the develop­"What hath God wrought!" and San Francisco, California. almost 100 years. and his home about three miles away. ment of the radio.

J

111858 1861 11861 11876 11886 The First transatlantic telegraph coble is Coast-to-coast The lost Pony March Alexander Graham Bell transmits the Heinrich Rudolf Hertz,D completed and messages begin to How telegraph commu· Express run is First message ever sent by telephone: "Mr. of Megahertz (MHz) between the shores of America and nication begins in mode as the tele- Watson, come here, I wont you" to his assis- fame, proves that e1ec­Europe. However, the coble fails after the United Stoles. graph tokes over. tont, who was linked by wire and receiver to tricity is transmitted at 26 days because the voltage is too high. the sending device in Bell's office. the speed of light.

fi1

30sIw THE INTERNET WORKS

IT would be a lot easier to explain how the Internet works if you could hold it in your hand.

Hardware-real, tangible, with a weight and size-is always easier to understand because

you can see it and you can point with confidence to say this gizmo leads to that gadget, every

time. The Net is not just a single thing; it is an abstract system. To understand the significance

of this term, consider a less abstract system-your body.

The molecules that make up your body are not the same all your life. New molecules are

constantly being taken in as food, water, and air, and are recombined into different molecules

of muscle, blood, and bone. But no matter which molecules make up your hair and eyes and

fingers, at any moment, the structure of your body remains the same. Your heart doesn't refuse

to pump because new molecules of blood are created. If you remove some parts of your body,

the system continues to function; sometimes, as in the case of brain damage, transferring the

job of the missing parts to healthy parts of the brain.

As a system, the Internet is similar to a living organism. It grows, taking in new "molecules"

in the form of PCs and networks that attach themselves to the Net. Parts of the Internet commu­

nicate with other parts that then respond with some action, not unlike the muscle activity set off

by nerve impulses. You can think of the Internet as a network of networks. Amoeba-like smaller

networks can break off the Net and live independent lives. Unlike amoebas, those smaller net­

works can later rejoin the main body of the Net.

The Net is ephemeral. Some pieces-the supercomputers that form the backbone of the

Internet-are always there. The local area networks (LANs) found at countless businesses qual­

ify as individual organs in the Body Internet. But nothing is really fixed in place-hard-wired.

Each time you use your PC to connect with, say, a PC in Pittsburgh that maintains information

on Star Trek, you don't have to use the same phone lines, switching devices, and intermediate

networks to reach it. The route to Pittsburgh one time might run through Chicago; next time it

might run through Copenhagen. Without realizing it, you can bounce back and forth among

several networks from one end of the country to the other, across an ocean and back again,

until you reach your destination in cyberspace.

1901 1904 1920 1924 1925 Marconi sends a radio signal across the A~antic.

John Ambrose Fleming patents the first practical electron tube known as the Fleming Valve, based on Thomas Edison's patented Edison Effect.

~DKA of Pittsburgh begins operations by broadcasting the returns of the 1920 presidential election. Although lewel"than 1,000 radios are tuned to this station, this is generally recognized as the beginning of commer­cial radio broadcasting in the United States.

Pictures are trans-milled over telephone lines.

AT&T's Long Lines Department oHers the press an early facsimile service between New York, Chicago, and San Francisco.

1 1902 1 1909 1 1915 1 1923 1 1934

.­

Photoelectric In an event that will for- AT&T researchers complete the "A picture in your radio set." In New York City, The Communications scanning ever change the mean- first transcontinental calilrom Russian-born engineer Vladimir Zworykin demon- Act of 1934 is passed. It can send ing of the word "news," New York to San Francisco and strates his new invention, the iconoscope, which is the first eHort to regu­and receive a wireless telegraphic start experimentally transmitting he claims will make it possible to transmit pic- late the telephone indus­a picture. press message is sent. voice across the country via radio. tures-even moving pictures-through the oil". try at the !ederallevel.

OVERVIEW 309

It's a lot easier to say what you can get from the Net-infor­

mation of all kinds. Being a system without physical limitations,

it's theoretically possible for the Net to include all information on

all computers everywhere, which in this age means essentially

everything the human race knows, or thinks it knows. But

because the Net is such an ad-hoc system, exploring it can be a

challenge. And you don't always find exactly what you want.

Plenty of software tools make surfing the Net easier, but the

Internet itself has no overall design to help those using it. You're

pretty much on your own when you jump in with whatever soft­

ware you can find.

Despite the amorphous nature of the individual elements that make up the Internet, it

is possible to describe the structure of the Net-the system that always remains the

same even as the elements that make it up are changing from moment to moment. And

for that structure, we can thank Sputnik.

Tile Little Net That Grew It was 1957 and the Cold War was subzero. The Soviet Union launched the first satel­

lite, Sputnik, shaking the confidence of the United States in its scientific and technology

leadership. President Eisenhower created the Advanced Research Projects Agency

(ARPA) within the Department of Defense [DoD) to get the U.S. into space. That role was

replaced by NASA, and ARPA redefined itself as a sponsor of advanced research pro­

jects at various universities and contractors.

In late 1960, Paul Baran of the RAND Corporation wrote a series of technical

papers for the Pentagon analyzing the vulnerability of communications in case of a

Soviet nuclear attack. A part of the papers were two ideas that would have far greater

impact than anyone imagined. Baran said that military command messages and control

signals should be carried over a distributed network that has redundant connections in

1956subv Asample af the cable laid in 1956 by the C. S. Manarch, connecting the United Kingdom and Newfoundland. The vacuum tube was part of several repeaters that periodically boosted the signal on its transatlantic trip.

Courtesy of Lucent Technologies

19591958

1 1958 In an effort to jump-start strategic missile research projects, President Dwight D. Eisenhower creates the Advanced Research Projects Agency (ARPA) within the Department of Defense (DoD). ARPA is given direction over all U.S. space programs and advanced strategic missile research.

1­

The National Aeronautics and Spoce Administration (NASA) is enacted into law. Spoce programs and advanced strategic missile research are tronsferred to NASA. The ARPA budget is slashed to $150 million.

ARPA redefines its charter as a "high-risk, high-gain" research sponsor, and more closely aligns itself with advanced research projects being conducted at vari­ous universities scattered around the u.s.

The Internet is first conceived. Under the leadership of the Department of Defense's Advanced Research Project Agency (DARPA), it grows frem a paper architecture into a small net­work (ARPAnetl intended to promote the sharing of supercom­puters among researchers in the United States.

1962

1 1960 In a series of papers written for the Pentagon about the vulnerability of the military command and control system to nuclear attack, Paul Baran of the RAND Corporation introduces two revolutionary ideas that define a packet-switched network: Command ond control messages should be carried on a distributed network with redundant connections to intelligent nodes, and each messoge should be broken into blocks and sent along a distributed network using a heuristic routing doctrine capable of routing itself along a damaged network.

_3_1_0__: THE INTERNET WORKS

Opti( Fiber Glass rods are placed in adraw lower and then super-healed, allowing miles of hair-lhin optic fiber 10 be drown and spooled. The fiber allows light to corry far more information than electricity running over capper wires.

AT&T places the first commercial communications satellite (Telstor I) into orbit.

Paul Boron of RAND develops the idea of distributed, pocket-switching networks.

The first local area network (LAN) is devel­oped at Lawrence Livermore Lobs.

At a meeting of ARPA members, Lorry Roberts, Network Project Manager, presents the concept of on ARPA network to connect and shore research among its various sites.

BBN's Roy Tomlinson creates the first software allowing email to be sent between computers. Email quickly becomes the net­work', most popular application.

19621962

1962 Joseph Licklider and Wesley Clark publish "On-Line Man Computer Communication:' discussing their "Galactic Network" concept that would allow people to access data from any site connected through a vast network.

case a missile took out part of the system. The best way to do this

would be to break each message into blocks and send each block

separately over that network, avoiding any parts that aren't working.

A specific distributed military network was never built, but a few

years later ARPA began looking for a way its members could distrib­

ute messages and data among themselves so they could take advan­

tage of each other's research. They came up with the idea of a

distributed network called ARPAnet, built around something called

interface message processor (IMP), which connected computers at

university research centers. IMP also incorporated a technology

called TCPliP, developed at the National Science Foundation.

Standing for transmission control protocol/Internet protocol, TCPliP

calls for breaking up messages and data into packets to which

addressing information, error correction code, and identification are

added. The packets can all travel to their destination over the distrib­

uted network, and a computer on the other end checks for mistakes

and pieces them together in the right order. In 1969, computers at

universities allover the country were linked to ARPAnet. The first let­

ter sent over the new network was an "L" sent from UCLA to the

Stanford Research Institute.

The ARPAnet continued to expand until, in 1972, it connected

23 host sites. By 1975, one new installation was being added each

month. Meanwhile, other types of networks, such as the Computer

Science Network (CSNET), designed to be a less expensive version of ARPAnet, sprang up

across the country. In 1974, researcher Bob Kahn and Yint Cerf came up with the idea of

a "network of networks" that would let dissimilar networks communicate with one another.

By 1982, different networks were adopting TCPliP as their communications standard, and

the term "Internet" was used for the first time. A year later, a gateway was set up between

CSNET and ARPAnet using TCPliP as a common standard so people on the two networks

could communicate with each other.

1964 19721967

1965 Thomas Merrill and Lawrence Roberts set up the first WAN (wide area network) between MIT's Lincoln Lab TX-2 and System Development Corporation's Q-32 in California.

1969 ARPANET IMP #2 is installed at the Stanford Research Institute, Menlo Pork, California, and connected to SRI's SDS-940 Timesharing system and IMP #1. Several days later, Chorley Kline, on undergraduate stu­dent at UCLA, becames the first user of the ARPAnet when he types the letter "L" il1to the Sigmo-7 and it is received on the SRI system.

OVERVIEW 311

A high-speed 156Kbps) backbone was built by the NSF to connect five supercomputing centers.

All the transmission time wasn't used, so the NSF agreed to let local networks connect to each other

through the backbone. The Internet was born, even if people didn't realize it yet. For years, the

Internet was the territory of colleges and defense contractors. As the Internet grew, many of the

people who nursed it through its infancy were dismayed when, in 1991, the NSF lifted restrictions

on the commercial use of the Net. The first time someone sent out advertising over the Internet-a

practice destined to earn the name spam-reactions among Internet purists were angry and vocal.

And equally futile. The Internet and the World Wide Web, a section of the Internet developed to lift it

out of its text-only origins into the world of graphics, sound, and video, had lives of their own. The

imp was out of the bottle, and today what started as a modest experiment in communicating is grow­,; ; ing at a rate of 100-200 percent a year. r

KEY CONCEPTS~ ADSL Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper wiring that transmit from 1.5Mbps to 9Mbps downstream (to the subscriber) and from 16Kbps to 800Kbps upstream, depending on line distance.

analog A signal that can toke on any value in a range.

asymmetrical Provides different data rates in the upstream and downstream directions, where upstream is the direction from the end-user to the network, and downstream is the direction from the network to the user.

bandwidth The capacity of a channel to carry information. Measured in hertz (kHz or MHz) for analog transmission media, and in bits per second (kbps or Mbps) for digital transmission media. Literally, the width of a band of electromagnetic frequencies being used to send data. Wider band­widths can deliver more information at the some time or send a given amount of data faster.

bridge A device that connects a local area net­work (LAN) to another local area network that uses the same protocol-for example, Ethernet to Ethernet or token ring to token ring.

broadband A term for high-speed, high-capac­ity Internet and data connections.

backbone The highest speed Internet or net­work routes, off which branch regional and local networks that make up the body of the Internet.

browser A PC program that displays informa­tion from the Internet.

channel A transmission path between two points. Channel usually refers to a one-way path, but when paths in the two directions of transmis­sion are always associated, the term channel can refer to this two-way path.

client A computer or software that depends on another computer-a server-for data, other pro­grams, or the processing of data. Part of a client­server network.

r 1974 Bob Kahn and Vint Cerf jointly author a paper that addresses the issue of joining dissimilar networks via a gateway to cre­ate a "network of networks"-the Internet.

1976 Queen Elizabeth 90es online with the First royal email message.

1979 Kevin MacKenzie sends the first ever emoticon in a message to the MsgGroup. The first is-j, meaning tongue-in-cheek.

1982 The First PC LAN is demonstrated at the National Computer Conference by Drew Major, Kyle Powell, and Dale Neibour. Their software would eventually became Novell's NetWare.

1 1973 Bob Metcalfe at Xerox's Palo Alto Research Center (PARe) devel­ops a means to manage communications between numerous computers connected to a high-speed conduit using a technique called carrier sense multiple access/collision detection (CSMA/CD). He calls this means of communicating Ethernet.

1 1978 Vint Cerf, Steve Crocker, and Danny Cohen create a plan to separate TCP's routing func­tions into a separate protocol called the Internet protocol (lP). Error handling and data­gram functions would remoin a part of TCP.

1 1983 Acellular­phone network is created.

1 1983 The Internet becomes a reality when the ARPAnet is split into military and civilian sections.

31~W THE INTERNET WORKS

distributed network A network in which cru­cial files are spread across several servers. This eases the demand that would be made on a single server while safeguarding data, because informa­tion is stored on multiple servers, usually overlap­ping so that all data is available in its entirety even if one or more of the servers crashes.

domain A group of computers on a network that are administered as a unit, usually by the same company or organization.

downstream Refers to "host to end-user" (receive, download) direction.

DSL Digital Subscriber Line (DSL) technology pro­vides a dedicated digital circuit between a resi­dence and a telephone company's central office, allowing high-speed data transportation over exist­ing twisted copper telephone lines.

dynamic IP addressing An IP address is assigned to the customer for the current session or some other ISP-specified amount of time.

email Electronic mail sent within a network or over the Internet.

firewall A security device that controls access from the Internet to a local network.

gateway Hardware and software that link two networks that work differently, such as a Novell and a Windows NT network.

GIF File extension for graphics interchange For­mat; a compressed, bitmapped graphics format often used on the Web for animated graphics.

HTML Hypertext Markup Language, the coding used to control the look of documents on the World Wide Web.

http Part of a URL that identifies the location as one that uses HTML.

hub A device where various computers on a net­work or networks on the Internet connect.

1985 1989

Internet A worldwide network with more than 100 million users that are linked for the exchange of data, news, conversation, and commerce. The Internet is decentralized; that is, no one person, organization, or country controls the Net or what is available through it.

IP (Internet provider) A computer system that provides access to the Internet. AOL, Concentric, and most phone companies are IPs. Also stands for Internet Protocol, a format for contents and addresses of packets of information sent over the Net. Part of TCPliP.

IP address An identifier for a computer or device on a TCPliP network. l\Jetworks using the TCPliP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255.

link Text or graphics on a Web page that lead you to other pages if you click on them.

local area network (LAN) A more or less self­contained network (that can connect to the Internet), usually in a single office or building.

network interface card (NIC) A expansion board that allows a PC to connect to a network. Most NICs are designed for a particular type of net­work.

peer-to-peer A network in which there is no central server. All PCs on the network are peers and can perform the duties of a host and client at the same time.

POTS Plain Old Telephone System; basic analog telephone service with no frills from digital technol­ogy.

router A device that routes data between net­works using IP addressing. Routers provide firewall security.

1990 1991 1991 The National Science Foundation (NSF) creates a national, high-speed (56Kbps) "bockbone" network (NSFNET) connect­ing five supercomputing centers, most notably NCSA. NSF agrees to democratize the Net by allowing local networks to interconnect to the "backbone" and thereby each other.

The first gateways between private electronic mail carriers and the Internet are established. CompuServe is connected through Ohio State University and MCI is connected through the Corporation for National Research Initiative.

The num­ber of hosts exceeds 300,000.

The World Wide Web (WWW)is released by CERN.

Linus Torvalds announces Linux ver­sion 0.02.

1 1986 1 1988 1 1988 1 1990 1 1991 Albert Gore (D-TN) The NSFNET back­ The Internet Worm is A happy victim of its own The number of Internet hosts breaks 600,000. introduces the bone is upgraded to released by Robert unplanned, unexpected success, NSF lifts restrictions on the commercial use of the S 2594 Super­ Tl (l.544Mbps) and Morris Jr., affecting about ARPAnet is decommissioned, NSFNET bockbone. The NSFNET backbone is computer Network handles more than 75 6,000 of the 60,000 leaving only the vast network-of­ upgraded to T3 (44.736Mbpsl as traffic passes Study Act of 1986. million packets a day. hosts on the Internet. networks called the Internet. 1 trillion bytes ond 10 billion packets per month.

OVERVIEW 313

search engine A program that searches docu­ments located on the Internet for key words or phrases entered by a person browsing the Net. It returns a lists of sites, sometimes rated, related to the topic searched for. HotBot, Yahoo!, and Excite are examples of sites that provide search engines.

server Part of a network that supplies files and services to clients. A file server is dedicated to stor­ing files, and a print server provides printing for many PCs. A mail server handles mail within a net­work and with the Internet.

spam Electronic junk mail: Solicitations, usually to buy something, that are sent in email to hun­dreds or thousands of Internet users.

spiders Programs used by search engines to prowl the Web looking for new or changed pages. When a spider finds something new, it sends the information back to the search engine so it can update its index of subject matter and pages.

Istatic IP address An assigned IP address used to connect to the Internet. The IP address stays with the customer's computer.

I switch A device that provides communication I, channels among end-users. A circuit switch pro­vides dedicated paths.

11 A point-ta-point digital communications circuit with 25 channels, each of which carries 64,000r bits a second. The channels may be used for data or digitized voice.

TCP/IP Transmission Control Protocol/Internet Protocol; actually a collection of methods used to connect servers on the Internet and to exchange data. TCP/IP is a universal standard for connecting to the Net.

URL Uniform Resource Locator. A Web address expressed in English that takes a browser directly to a specific web page.

Usenet The world's largest system of on-going, online discussions by people who constitute news­groups.

Website A group of World Wide Web pages, including a home page with links that lead to other pages at that site or on other sites.

Webmaster The person who maintains a web­site.

wide area network (WAN) Wide area net­work; a single network that extends beyond the boundaries of one office or building.

World Wide Web A loose confederation of Internet servers that support documents formatted in a language called HTML (Hypertext Markup Language) that can include links to other servers, documents, graphics, audio, and video.

worm A virus that doesn't infect other pro­grams. It makes copies of itself, and infects more computers, often through network connections or as email attachments. A worm doesn't attach itself to legitimate programs as most types of viruses do, but it can still change or destroy other files like other types of virus do.

XML Extensible Markup Language. An advanced form of HTML, in which data is defined rather than simply formatted. For example, a browser could identify which numbers on a web page are prices and which are quantifiers, and act on that information.

1992 The number of InIemet hosts breaks 1 million.

1992 The first audio and video broadcasts toke place over a portion of the Internel known as the MBONE.

1994 The number of Internet hosts breaks 3 million.

1995 A team of programmers at Sun Microsystems release an Internet programming language called Java, which radically alters the way applications and informahon can be retrieved, displayed, and used over the Internet.

1997 In January, the number of Internet hosts breaks 16 million.

1 1992 The term "surf­ing the net" is coined by Jean Armour Polly.

1 1993 The White House and United Notions come online.

1 1994 The first cyberbonk, First Virtual, opens.

1 1994 Network Solutions, Inc. reports that it is registering domain names at the rate of 2,000 per month.

1 1996 As the Internet celebrates its 25th anniversary, the military strategies that inAuenced its birth beoome historical footnotes. Approximately 40 million people are connected to the Internet. More than $1 billion per year changes hands at Internet shopping molls, and Internet-related companies such as Netscape are the darlings of high-tech investors.