What is the Internet?The Internet is a vast network that links

together millions of computers around the world.In the 1960s, people were working on ideas that

later became the Internet.In 1969, the first four major computer centers in

the United States were linked.By 1973, the network was international.In 1983, the Internet protocols went online for

the first time.Two major groups worked on the development of

the Internet: the United States military and university researchers.

Invention of the InternetIn the 1960s, the United States government wanted

to find a way to communicate in the event of a disaster or military attack.

The military began to work on a system that would operate even if some communication connections were destroyed.

The Defense Advanced Research Projects Agency (DARPA) of the U.S. Department of Defense focused on computer networking and communications.

This research was led by MIT scientist J.C.R. Licklider.

In 1962, Licklider wrote about a “galactic network.”

Invention of the Internet cont.He and others envisioned a globally connected

network in which any computer could access any other computer and exchange data.

In 1968, this research led to a network of connected computer centers called the Advanced Research Projects Agency Network (ARPANET).

With the military’s leadership and funding, DARPA formed computing research centers at universities across the United States.

From 1969 through 1987, the number of computers on the network increased from four to more than 10,000.

These connections created the networks that became the Internet.

Organization of the InternetThe Internet is a global WAN, a network of

networks.It connects everything from single computers

to large networks.The Internet can even connect computers

that run different operating systems.This ability to share information with almost

any computer makes the Internet a powerful tool for communication.

Organization of the Internet cont.The Internet accomplishes Licklider’s

vision using three basic elements:servers clientsprotocols

Internet servers are the computers that provide services to other computers by way of the Internet.

These services include processing e-mail, storing Web pages, or helping send files from one computer to another.

Organization of the Internet cont.Internet clients are the computers that

request services from a server.When you connect to the Internet, the

computer you use is considered a client.The special sets of rules that allow clients

and servers to talk to one another are the protocols.

All Internet protocols are TCP/IP.

Organization of the Internet cont.TCP stands for Transmission Control Protocol.It defines how one Internet-connected

computer contacts another and exchanges information.

IP stands for Internet Protocol, which defines the Internet’s addressing scheme.

Each computer is uniquely identified by an Internet Protocol (IP) Address.

This is a four-part number separated by periods. Example:123.257.91.7

The administrator of the network to which your computer connects assigns your IP address.

Domain NamesIP addresses can be difficult to remember so a

simple naming system called the domain name system using letters as well as numbers was created.

A domain name identifies one or more IP addresses and is used to locate information on the Internet.

Example—An Internet server computer’s domain name might be whitehouse.gov, but its numeric IP address might be 206.166.48.45.

The domain name and the IP address are simply two ways to identify the same computer on the Internet.

Domain Names cont.Every domain name has a suffix that tells

which type of organization registered the name.

The most common domains are:.com (commercial).edu (education).org (nonprofit organizations).gov (government).mil (military).net (network organizations)These are called top-level domains.

Domain Names cont.There are also new top-level domain names

coming online to meet the growing demand for new classifications..biz (business).museum (arts and culture).pro (professionals).info (information services).name (individuals)

Domain Names cont.How do domain names work? Let’s say you

want your computer to access information stored on another computer. Your local ISP’s domain name server will contact the domain name server you are calling.

The information to identify both computers will be exchanged, and the contact will be made.

Domain Names cont.A special server called a Domain Name System (DNS)

server matches the domain name to the correct IP address.To get a domain name, you or your ISP must contact a

registering organization, which then contacts InterNIC. InterNIC is a service organization that maintains a central

database of domain names in the United States.Other countries maintain their own network information

centers.When you register a domain name, you pay a fee to keep it

in the database of domain names. If you do not pay the renewable registration fee, the

domain becomes available for someone else to register in his or her name.

Organization of the Internet cont.One amazing thing about the Internet is that you

can exchange information with computers that are different from your own.

When you connect to the Internet, you may connect to an Internet server on a Macintosh, a Windows PC, a Linux PC, a UNIX machine, or a mainframe computer.

A platform is a kind of computer that uses a certain type of processor and operating system, such as an Intel-based Windows PC.

Software or hardware is said to have cross-platform capability when it can run the same way on more than one platform.

Organization of the Internet cont.When you are using the Internet, you don’t

know which type of computer platform you are accessing, and it doesn’t make any difference to the tasks you are doing.

This is because all computers on the Internet use TCP/IP.

As a result, they all look and behave the same way online, regardless of their platform.

Organization of the Internet cont.Cross-platform compatibility is one of the major

reasons for the increasing popularity of private intranets.

Many organizations, such as schools, use computers that run on different platforms.

They may use computers running the Macintosh operating system in one part of the school; and computers running Windows in another.

These computers still need to share information.After the computers are connected with the

Internet’s TCP/IP protocols, the computers can exchange data and even control one another’s operations.

Internet ManagementWho owns the Internet?No specific organization or government does.The Internet is made up of many networks.Each network is managed by an organization,

school, company, or government.No one is in charge of the entire Internet.This provides both opportunities for growth

and problems.

Internet Management cont. Freedom of the Internet

One advantage to the open quality of the Internet is the ability to share information.

Because much of the Internet is available for public use, there is a lot of freedom to get information from the Internet as well as to add to it.

Anyone can make an idea or opinion accessible to anyone else. Pitfalls of the Internet

There are pitfalls to this open organization. People can post whatever point of view or information they want, even

if it can sometimes be misleading or false. It is up to the users of the Internet to think critically about the

information they find. Because the Internet is not managed and protected by a specific

government or agency, each individual has to figure out how to best use it.

The network developed from the ideas of the U.S. military and university researchers has now become a global, open system of communication and information.

Accessing the InternetThere are different ways to connect to the

Internet.The reasons for various options are availability,

location, speed, and price.Dialup—The least expensive way to get online is

to use a dialup connection between a standard phone line and a modem.

These connections are called “dialup” because your computer must connect to the Internet by using a telephone number to contact a server.

When the session is over, the connection is broken.

Accessing the Internet cont.Some Digital Subscriber Lines (DSL) require

a special telephone line.Integrated Services Digital Network (ISDN)

lines require a special ISDN adapter and modem.

As a result, both services cost more than regular phone service.

DSL and ISDN are not available in all areas.

Accessing the Internet cont.Cable television companies offer Internet

access through cable modems.This access is at speeds much faster than

dialup modems.You need a network card in your computer,

a cable modem, and cable access.Satellite access is also very fast for

downloading files to your computer, but it requires a phone line and a modem for sending files to outside users.

Getting OnlineOnce you have access to the Internet, there are several

ways to get online.Choices include Internet service providers and online

services.An Internet Service Provider (ISP) is a company that

provides a link from your computer to the Internet.For a fee, an ISP provides its subscribers with software, a

password, an access phone number, and a user-name.The username identifies who you are when you access the

Internet.An ISP does not guide you through the Internet—it only

provides an easy-to-use connection to it.You can use either a local ISP or a national ISP.

Getting Online cont.An online service connects your computer to the

Internet.Online services are businesses that provide tools

to help you navigate, or move to different parts of, the Internet.

Online services are not the Internet. They provide special software that you load onto

your computer.The software makes the connection to the service,

which then guides you through content and activities.

Three popular online services are America Online (AOL), Microsoft Network (MSN), and CompuServe.

Requesting Data on the InternetAfter connecting to the Internet you

request a Web page.Your request travels by local connections

to your ISP’s local point of presence or POP.

From there, your ISP sends your request to a regional backbone, that part of a network that transmits data.

The Internet backbone is made up of high-capacity, high-speed lines that carry billions of bits of data each second.

Requesting Data cont.Your Web page request then travels to a

national network access point, or NAP, which is like a freeway.

As your request nears its destination, it moves off the information freeway.

It travels back through the same cycle and the Web page you requested is displayed on your computer screen.

Dissecting URLsAs you read different materials, you’re

likely to see references to Web pages.The address for a Web page is called a

uniform resource locator, or URL.The browser breaks a URL, such as the

following one, into three parts:http://www.vote-smart.org/help/database.html

protocol (http) server name (www.vote-smart.org) folder and file name (help/database.html)

Dissecting URLs cont.Protocol—The first part of the URL

identifies the protocol that should be used to retrieve the Web page.

An http means that the file should be retrieved using hypertext transfer protocol (HTTP).

An ftp shows that the file should be retrieved with file transfer protocol, or FTP.

The second part of the URL identifies the domain name of the server in which the document is located.

Dissecting URLs cont.Folder and File Name—The last part of the

URL shows a specific resource’s file name and the folder in which the file is stored.

In some cases, a URL will include only the protocol and the server name, as in http://www.vote-smart.org.

This type of URL often takes you to the front page, also called the home page of the Web site.

Comparing Internet ServicesTo use the most popular Internet services, you’ll

need several client programs.You will need a Web browser to view Web

pages, a mail program to send and receive e-mail messages, and a newsgroup reader to access newsgroups.

The two most popular Web browsers, Netscape Navigator and Microsoft Internet Explorer, are available by themselves or in software suites that include other programs.

There are dozens of other browsers, written for every type of computer and operating system, to help you navigate the Internet and take advantage of online services.

Internet ServicesInternet portals provide organized subject

guides to Internet content.They usually offer search engines as well.A search engine is software that finds and

lists information that meets a specified search.

First, the search engine asks you to type a keyword into a blank field.

Then, the search engine will give you the results of that search.

Popular search engines include, Yahoo!, Excite, Google, and InfoSeek.

Internet Services cont.The World Wide Web is a huge collection of

hypertext documents called Web pages.In a hypertext document, certain words or

pictures can serve as hyperlinks.Hyperlinks are links to another document on the

web.Usually hyperlinks appear underlined, in a

different color, or highlighted. Sometimes there are buttons or images that can be

clicked.When you move your mouse over a hyperlink, the

pointer changes to an icon of a hand.You can click this hyperlink item to be transferred

to another document.

Internet Services cont.When you click a hyperlink, the Web browser

retrieves and displays the document connected to that hyperlink.

The URL tells where the document is located on the Internet and a hyperlink instructs the browser to go to the URL for that document.

Electronic CorrespondenceServices on the Internet that help people

communicate include:E-mailUsenet discussion groupsInternet Relay ChatInstant Messaging systems

For many Internet users, e-mail has replaced traditional mail and telephone services.

It is fast and easy and you can send a message to a whole group is just one step.

Electronic Correspondence cont.Usenet is an Internet discussion system that works

like a gigantic electronic bulletin board.It consists of thousands of newsgroups, or

discussion groups, in which users communicate by posting messages, called articles, on a particular topic.

This process creates a thread of discussion—a series of related messages.

To access Usenet, you use a Usenet client, sometimes called a newsreader.

The newsreader communicates with a Usenet server or a news server, also called a Network News Transport Protocol, or NNTP, server.

Electronic Correspondence cont.An Internet Relay Chat, or IRC, is an Internet

service that enables you to join chat groups, called channels, and have live conversations.

You need special chat software to find and join IRC channels.

Some IRCs cover a specific topic; others are gathering places for groups of friends.

Real-time chat groups are found on many Web sites.

Online services such as America Online are known for their chat features.

These forms of chat do not require special software.

Electronic Correspondence cont.Instant messaging (IM) allows you to create a

buddy list, or contact list, of people with whom you want to interact.

You can send and receive one-on-one live, or real-time messages to or from anyone on this list who is online.

Although not as popular, there are several other services that you may explore.

Multi-user dungeons (MUDs) offer chatting environments based on a theme.

Ping is a service often used to test whether Internet connections are working properly.

Telnet creates a virtual terminal, allowing you to control a remote computer.

Transferring FilesFile Transfer Protocol (FTP) lets you transfer files

on the Internet.With an FTP client, you can transfer files from an

FTP server to your computer in an operation called downloading.

In uploading, you transfer files from the client to the server.

FTP can transfer both text files and binary files.Binary files are program files, graphics, pictures,

music or video clips, and documents.Once you have stored a file on an FTP server, you

can distribute the URL so that your friends can also download the file from the server.

Transferring Files cont.One difference between using an FTP

server and e-mail to transfer files is that with FTP, the file stays on the server until you take it off.

With e-mail, a file that has been transferred will be lost once the e-mail message has been deleted.

E-mail is considered a more secure method because only the recipient of the e-mail message has access to the attached files.

File Transfer Safety It is important to exercise caution when downloading files

from the Internet, especially program files. If you download a file from a site that doesn’t inspect files

using up-to-date antivirus software, you could infect your computer with a virus.

A virus is a program created in order to damage computers and networks.

The damage caused my be minor or serious, such as altering or destroying data.

It is a good idea to check all downloaded files before saving them.

Most antivirus programs will do this for you automatically.You should update your antivirus program regularly so you

are more likely to be protected from the newest viruses.

File Transfer Safety cont.The larger a file is, the more time it takes to travel over a

network.File compression is a way of reducing file size so it can travel

more quickly over a network. If you are sending a large file, it is important to compress it. It can also be convenient to compress multiple files into one when

you are sending then to someone in an e-mail attachment.You will find that downloadable software is compressed to reduce

the amount of time it takes to download.Some compressed files are made to decompress automatically.Others must be decompressed using decompression software.The most widely used compression software for a Windows

system is WinZip.Macintosh computers use a program called StuffIt to compress

files and a utility called StuffIt Expander to decompress files.