ARPANET Pioneers Built an Unreliable Network...on Purpose

In the 1960s a small group of visionary computer scientists saw the computer's potential as a communication device. They envisioned a network that would allow researchers to share computing resources and ideas. At the same time the U.S. Department of Defense wanted a network that could function even if some connections were destroyed. They provided funds for the scientists to build ARPANET, for Advanced Research Projects Agency Network.

ARPANET was built on two unorthodox assumptions: (1) the network itself was unreliable, so it had to be able to overcome its own unreliability, and (2) all computers on the network would be equal in their ability to communicate with other network computers. In ARPANET there was no central authority, because that would make the entire network vulnerable to attack. Messages were contained in software "packets" that could travel independently by any number of different paths, through all kinds of computers, toward their destinations.

ARPANET grew quickly into an international network; its protocols became the standard computer communication language, allowing different computer networks to be linked. In 1990, having fulfilled its research mission, ARPANET was disbanded and spawned the Internet.

The Internet is an interconnected network of thousands of networks linking academic, research, government, and commercial institutions, other organizations, and individuals. The Internet is a technology, a tool, and a culture. It was originally designed by computer scientists for computer scientists, but today it's used by people in all walks of life all over the world.

 

Internet Services:

The Internet provides scientists, engineers, researchers, educators, students, business people, consumers, and others with a variety of services, including:

• Electronic mail (e-mail)
• Remote login (telnet)
• Transferring files (FTP)
• Newsgroups (Usenet)
• The World Wide Web

Counting Connections:

It's impossible to pin down the exact size of the Internet for several reasons:

• The Internet is growing too fast to track.
• The Internet is too decentralized to quantify.
• The Internet doesn't have hard boundaries.

Internet Protocols:

The protocols at the heart of the Internet are called TCP/IP (Transmission Control Protocol/Internet Protocol). They were developed as an experiment in internetworking&endash;connecting different types of networks and computer systems. The TCP/IP specifications were published as open standards, not owned by any company. They define how information can be transferred between machines and how machines on the network can be identified with unique addresses.

When a message is sent on the Internet, it is broken into packets that travel independently toward their destination where they're reassembled. This packet switching model is flexible and robust, allowing messages to get through even when part of the network is down.

Every host computer on the Internet has a unique IP address: a string of four numbers separated by dots. Every packet includes the IP address of the sending computer and the receiving computer.

Internet Access Options:

There are three common ways users can connect their computers to the Internet to take advantage of some or all Internet services:

• Direct (dedicated) connection, which provides the fastest, most reliable service.
• Dial-up terminal emulation, which provides limited service.
• Full-access dial-up connection, which is like a temporary direct connection.

Internet service providers generally offer several connection options at different prices. In some cities inexpensive or free access to the Internet is available through a freenet&endash;a local bulletin board system designed to provide community access to on-line forums, announcements, and services. Many computer networks, bulletin board systems, and on-line services provide varying degrees of Internet access through gateways. A gateway is a computer connected to two networks&endash;in this case, the Internet and an outside network&endash;that translates communication protocols and transfers information between the two.

Intranets and Extranets:

For many organizations, Internet protocols and software are more important than the Net itself. Members of these organizations communicate through intranets&endash;self-contained intraorganizational networks that are designed using the same technology as the Internet.

Some private TCP/IP networks are designed for outside use by customers, clients, and business partners of the organization. These networks, often called extranets, are typically for electronic commerce&endash;business transactions through electronic networks.

Working with Internet applications is different from working with word processors or spreadsheets because of the distributed nature of the Internet and the client/server model used by most Internet applications. In the client/server model, a client program asks for information and a server program fields the request and provides the requested information from databases and documents. Two different users might access the same server using completely different client applications with different user interfaces.

 

The UNIX Connection:

The Internet is heavily populated with computers running the UNIX operating system. UNIX, developed at Bell Labs in the time before PCs, allows a timesharing computer to communicate with several other computers or terminals at once. UNIX is the most widely available multiuser operating system today.

Until recently, some knowledge of UNIX was necessary for taking advantage of most Internet services; it's still necessary for a few services.

Internet Address:

The most popular reason for connecting to the Internet is electronic mail. You can send messages to anyone with an Internet link, provided you know his or her Internet address.

A person's e-mail address is made up of two parts separated by an "at" sign (@)&endash;the person's user name (login name), and the host name&endash;the name of the host computer or network where the user receives mail. Here's the basic form:

username@hostname

The host is named using what's called the domain name system (DNS)&endash;a system that translates the computer's numerical IP address into something that's easier for humans to read and remember. The DNS uses a string of names separated by dots to specify the exact Internet location of the host computer. The words in the domain name are arranged hierarchically from little to big.

E-mail on the Internet:

Basic e-mail can be handled by a character-based program like PINE or (if you have a full Internet connection) a graphical client program like Eudora. Standard Internet mail messages are plain ASCII text. Formatted word processor documents, pictures, and other multimedia files usually need to be temporarily converted to ASCII using some kind of encoding scheme before they can be sent through Internet mail; these encoded documents are sent as attachments to text messages.

 

Mailing Lists:

Mailing lists (sometimes called listservs) allow you to participate in e-mail discussion groups on special-interest topics. Lists can be small and local, or large and global. Each group has a mailing address that looks like any Internet address.

Network News:

You can participate in special-interest discussions and debates without overloading your mailbox by taking advantage of the hundreds of Usenet newsgroups. These are public discussions that you can check into and out of whenever you want; all messages are posted on virtual bulletin boards for anyone to read. Newsgroups are organized hierarchically, with dot names like rec.music.makers.percussion and soc.culture.french. To explore network newsgroups, you need a client program that can serve as a news reader.

Real-time Communication:

Mailing lists and news groups are delayed, or asynchronous communication, because the sender and the recipient don't have to be logged in at the same time. The Internet offers programs for real-time communication, too. Text-based options include Talk, Internet Relay Chat (IRC), and MUD (Multi-User Dungeon) games.

The MBONE (Multicast Backbone) is a virtual network for exchange of audio and video material. Some programs allow you to carry on audio conversations; others allow two-way video teleconferences.

Rules of Thumb: Netiquette

The Internet is a new type of community that uses new forms of communication. Here are some guidelines for appropriate behavior or netiquette:

• Say what you mean, and say it with care.
• Keep it short and to the point.
• Proofread your messages before sending them.
• Learn the "nonverbal" language of the network.
• Avoid the lynch-mob mentality.
• Don't be a source of electronic junk mail.
• Lurk before you leap.
• Check your FAQs. FAQs are Frequently Asked Questions.
• Give something back.

Besides communication, the most popular use of the Internet is information discovery and retrieval.

Telnet and FTP:

To find and retrieve information located on remote Internet sites, Net explorers have traditionally used two software tools: remote login and file transfer. Remote login allows users to connect to hosts all over the world from just about anywhere. The protocol that makes remote login possible is called telnet, which is also the name of the UNIX command that's used for remote login and the name of a program that executes the Telnet command from directly connected Macintosh and Windows PCs.

The Internet's file transfer protocol, commonly called just FTP, can transfer files from remote sites to users' host computers. Many sites allow anonymous FTP so you can collect files without officially logging in.

Most files in net archives are compressed&endash;made smaller using special encoding schemes. Compression saves storage space on disks and saves transmission time when files are transferred through networks.

Other Data Mining Tools:

Tools like the ones listed here hide the networking details behind simple interfaces.

•  
• Gopher is a hierarchical menu system that allows you to explore file archives by choosing from numbered menu items or navigating through folders.
• Archie is a program that checks hundreds of FTP sites regularly and updates a database called an Archie server.
• Veronica and Jughead are two programs that do for Gopher servers what Archie does for FTP sites.
• WAIS (Wide Area Information Server) is a distributed database system in which data is spread among computers on the network.

The World Wide Web (WWW or Web) is a distributed browsing and searching system originally developed by CERN (European Laboratory for Particle Physics). Since it was introduced in 1993, it has become phenomenally popular as a system for exploring, viewing, and publishing multimedia documents on the net.

 

Browsing the Web:

At the heart of the WWW is the concept of hypermedia, first discussed in Chapter 7. A collection of related pages stored on the same server is called a Web site. A Web document, called a home page or a Web page, is typically made up of text, drawings, and photographs, like a page in a book. The best way to navigate and view Web pages is with a Web browser&endash;a client program like Netscape Navigator that allows you to explore the Web by clicking on "hot" words or pictures on home pages.

Browsers have Back and Forward buttons so you can retrace your steps as often as you like. Most browsers include tools for keeping personal lists&endash;called hot lists or bookmarks&endash;of favorite sites. Web search utilities can help you find pages by subject or key words.

Web Addresses:

The Web is built around a naming scheme that allows every information resource on the Internet to be referred to using a Uniform Resource Locator, or, as it's more commonly known, URL.

The first part of the URL refers to the protocol that must be used to access information. It is most commonly http, for hypertext transfer protocol, the protocol used to transfer the Web's hypermedia documents across the net. The second part (the part following the //) is the address of the host containing the resource; it uses the same domain naming scheme used for e-mail addresses. The third part describes the path to the particular resource on the host&endash;the hierarchical nesting of directories (folders) that contain the resource.

Searching the Web:

If you're looking for a specific information resource but you don't know where in the Web it is, you might be able to find it using a search tool. Search tools fall into two broad categories: directories and search engines.

A directory (sometimes called an Internet index or a subject tree) is a hierarchical catalog of Web sites compiled by researchers. A search engine offers a much more complete database of what's on the Web because the database is compiled automatically.

Publishing on the Web:

Thousands of Internet users have created their own home pages using HTML (Hypertext Markup Language). An HTML document describes the format, layout, and logical structure of a hypermedia document. Many programs can generate HTML code automatically.

Some Web authoring programs work like WYSIWYG page layout programs used by desktop publishers.

From Hypertext to Multimedia:

Today we're seeing the emergence of true interactive multimedia on the web. Java, an object-oriented programming language developed by Sun Microsystems, is one tool that allows programmers to create true multimedia sites. Java promises to tear down the barriers between platforms by allowing developers to create programs that will run on all popular computers and operating systems.

Beyond HTML:

At its heart, HTML is still a static language designed for page layout, not programming. A new version of HTML, called dynamic HTML, adds more programming power to HTML by allowing HTML code to automatically modify itself under certain circumstances. Many experts expect HTML to soon be replaced by XML (extended markup language), which includes all of HTML's features plus many additional, powerful extensions.

For certain specialized applications, other alternatives to HTML already exist. VRML (virtual reality modeling language) allows Web page authors to create 3-D virtual worlds that can be easily viewed and explored with VRML-ready browsers.

Transcending HTML's limitations today is Java, an object-oriented programming language.

Push Technology:

The Web was built with pull technology&endash;browsers on client computers "pull" information from server machines. Many people prefer to have information delivered automatically to their desktop computers with push technology.

The Internet's rate of growth is so great that it raises questions about its ability to keep up; the amount of information transmitted may eventually be more than the Net can handle. The Internet is constantly being expanded to handle increased traffic, but the U.S. government no longer assumes primary responsibility for that expansion.

The commercialization of the Internet has opened a floodgate of new services to users. Unfortunately, commercialization has also brought electronic junk mail scams, get-rich-quick hoaxes, on-line credit-card thefts, e-mail forgery, digital child pornography pushing, and other sleazy activities.

Some of these problems have technological solutions looming on the horizon: digital cash and digital signatures should help prevent fraud.

Other problems are social problems that raise important political questions about human rights and censorship. The Internet's global reach and anarchical structure make it nearly impossible for governments to regulate it.

The Road to the Information Superhighway:

In the 1992 U.S. presidential election, candidates Bill Clinton and Al Gore campaigned for a National Information Infrastructure (NII) that would connect computers, telephones, televisions, and information appliances of all types.

The information superhighway, as it has come to be known, has captured the public imagination. Most analysts believe that the Internet will evolve into the information superhighway.

Cyberspace: The Electronic Frontier:

Science fiction writers suggest that tomorrow's networks may take us beyond the information superhighway of interactive TV and video phones into an artificial reality unlike anything we've seen before. This alternative reality has come to be known as cyberspace, a term coined by William Gibson in his visionary novel Neuromancer.

The Net today is a primitive cyberspace, but it's also a kind of electronic frontier populated by digital pioneers who are building the roads and towns that will someday be used by less adventurous settlers. The electronic frontier metaphor suggests that our expanding cyberspace has its share of social problems&endash;problems of computer crime and security that computer users, law enforcement agencies, and politicians are just beginning to understand.

asynchronous communication, attachment (e-mail), client/server model, compression, cyberspace

dial-up terminal emulation, direct (dedicated) connection, digital cash, extranet

FAQ (frequently asked question), freenet, FTP (file transfer protocol), full-access dial-up connection

gateway, home page, HTML (HyperText Markup Language), hypermedia

Information superhighway, Internet. Internet service provider, internetworking, intranet

Java , mailing list, National Information Infrastructure (NII), Net, netiquette, newsgroup, news reader

open standards, packet switching, pull technology, push technology, real-time communication, remote login

TCP/IP, telnet, UNIX, URL (Uniform Resource Locator)

Web authoring programs, Web browser, Web page, Web site, World Wide Web (WWW, W3, Web), XML

 Computer Literacy On-Line

Getting Started | TechInAction | MyITLab | Syllabus | Lecture Outline | Assignments | Glossary | Home | Videos