Transcript What is the Internet?

What is the Internet?
 The Internet is a vast network that links together millions
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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 Internet
 In the 1960s, the United States government wanted to find
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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
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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 Internet
 The 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
 clients
 protocols
 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 Names
 IP 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
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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
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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 Management
 Who 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 Internet
 There 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 Online
 Once you have access to the Internet, there are several ways to get
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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
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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
Internet
 After 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 highcapacity, 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 URLs
 As 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 Services
 To 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 Services
 Internet 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
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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 Correspondence
 Services on the Internet that help people
communicate include:
 E-mail
 Usenet discussion groups
 Internet Relay Chat
 Instant 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
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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
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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,
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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 Files
 File Transfer Protocol (FTP) lets you transfer files on the
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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 email 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
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Internet, especially program files.
If you download a file from a site that doesn’t inspect files using up-todate 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
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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.