Transcript Document 7368111

Chapter 10
Inside the Internet
and the Web
 2002 Prentice Hall
Origins
1969: ARPANET (Advanced Research Projects
Agency NETwork)
Computer Scientists envisioned a need for efficient
sharing of resources and ideas.
Military strategists wanted a network that could
function if some connections were destroyed.
ARPANET was used by hundreds of military and
university users until 1990.
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The Internet:
A Network of Networks
The Internet is an interconnected network of
thousands of networks linking academic, research,
government, and commercial institutions.
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Internet Services
The Internet provides scientists, engineers, educators,
students, business people, and others with a variety of
services such as:
 Electronic mail (send/receive mail messages)
 Remote login (Telnet - access to other computers)
 Transferring files (FTP - accessing archives of data)
 Newsgroups (Usenet - on-line public discussions)
 World Wide Web (a collection of multimedia
documents)
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Counting Connections
Today, the Internet connects computers to about
every country in the world. However, the Internet
is:
 growing too fast to measure its growth
 too decentralized to quantify
 a network with no hard boundaries
One agency, www.internic.net, does perform some
Management functions
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Internet Protocols
The language at the heart of the Internet is
TCP/IP…

Transmission Control Protocol/Internet Protocol
– Define how information can be transferred between
machines and how machines on the network can be
identified with unique addresses.
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Internet Protocols
TCP breaks messages into packets
 Each packet has all the information needed to travel
from network to network
 Host systems called Routers determine how to route
transmissions
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Internet Protocols
IP is the address for the packets
 Each Internet host computer has a unique IP Address
 Each address is comprised of four sets of numbers
separated by periods, such as 123.23.168.22
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Internet Access Options
Direct (dedicated) Connection
(T1 or T3 lines)
 Computer has its own IP address and
is attached to a LAN
 No need to dial up
 Files are stored on your computer
 Response time is quick
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Internet Access Options
Dialup Connections
 limited connection using a modem
 slowest speeds
Broadband Connections:
 DSL (Digital Service Line) service is newer, faster, and
cheaper than the older ISDN and allows sharing of
telephone lines
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Internet Access Options
Other types of Broadband Connections:
 Cable Modem Connection
– allow Internet connections using shared TV cables
– Carry increased privacy and security risks
 Satellite Connections
– provides connections using DirecTV satellite dishes
 Wireless Broadband: Wi-Fi
– Uses short-range radio waves
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Internet Access Options
Internet Service Providers (ISPs)
 local ISPs provide connections through
local telephone lines
 national ISPs offer connections on a
nationwide scale
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Internet Addresses
E-mail addresses are made up
of two parts separated by an
at(@) sign:
 User name@host name
 Example: [email protected]
The host is named using DNS (domain name system),
which translates IP addresses into a string of names.
“Each person on the “Internet” has a unique e-mail “address” created
by having a squirrel run across a computer keyboard.”
Dave Barry
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Internet Addresses
An Internet address includes:
[email protected]
 username is the person’s “mailbox”
 hostname is the name of the host computer
and is followed by one or more domains
separated by periods:
– host.subdomain.domain
– host.domain
– host.subdomain.subdomain.domain
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Internet Addresses
Top level domains include:
 .edu - educational sites
 .com - commercial sites
 .gov - government sites
 .mil - military sites
 .net - network administration sites
 .org - nonprofit organizations
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Internet Addresses
Examples:
[email protected]
[email protected]
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User President whose mail
is stored on the host
whitehouse in the
government domain
User hazel_filbert at the
server for Lane County,
Oregon, k-12 school
district
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Inside the World Wide Web
WWW is a distributed browsing and searching
system developed at CERN
System was designed to give Internet documents
unique addresses
HTML language was created for encoding and
displaying documents
Browser software was built for viewing documents
from remote locations
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Browsing the Web
Web site Jargon:
Web pages are made up of text and images
A Web site is a collection of web pages
A Home page is the main entry to a Web site
A Web browser like Netscape Communicator or Internet
Explorer allows you to explore the Web by clicking links
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Browsing the Web
Hyperlinks (links) are
words or pictures that
act as buttons, allowing
you to go to another
Web page
Links are typically underlined or
displayed in a different color
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More on Browsing the Web
More Web site Jargon
Links allow you to locate information without
knowing its exact location (it may move from
time to time)
Back and Forward buttons let you retrace your
steps
Bookmarks and Favorites can be set up to mark
your favorite Web locations
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Web Addresses
A typical URL (Uniform Resource
Locator) looks like this:
http://www.prenhall.com.beekman
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Web Addresses
Dissecting Web Page address:
Path to the host
http://
www.vote-smart.org/
Protocol for Web pages
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help/database.html
Resource Page
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Searching the Web
Search engines
 produce a list of pages that match a keyword
 they are built around a database that catalogs
Web locations based on content
Directory or Subject Tree
 A hierarchical catalog of Web sites
Natural Language
 Ask questions
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“The ability to
ask the right
question is more
than half the
battle of finding
the answer.”
Thomas J.
Watson
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Search Engines
Search engines help find information when you
type a query using keywords.
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Search Engines
Directory/subject tree
engines offer a menu of
subject choices
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Search Engines
Ask questions in a Natural Language Search Engine
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Portals
Portals offer quick and easy access to a variety
of services such as e-mail, chat,maps, news,
shopping, etc.
Examples of consumer portals include
 Yahoo!, Excite, Lycos, Alta Vista, Netscape
Netcenter, Snap
 Specialized portals target specific industries and
economic sectors
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