Transcript The Internet - Penn State University

Lesson 2
Chapter 3
The Internet, Intranets, and
Extranets
Learning Objectives
Define how the Internet works
Describe the services associated with the
Internet
Describe the World Wide Web
Define the terms intranet and extranet and
discuss how organizations use them
Identify who is using the Web to conduct
business
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The Internet
(Figure 7.1)
The Internet
transmits data
from one
computer
(called a host)
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to another.
Internet Networks
Linked networks that work
much the same way -- they
pass data around in packets,
each of which carries the
addresses of its sender and
receiver.
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Use and Functioning of the
Internet
Interconnected networks
Global though US is the largest user
Internet Protocol (IP)
Research for a faster Internet
 Internet2 (I2)
 Next Generation Internet (NGI)
 Corporate efforts
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How the Internet Works
Hosts with Uniform Resource Locator (URL)
Routers forward packets to other networks
Internet Protocol Stack (TCP/IP)


Internet Protocol (IP)
Transport Control Protocol (TCP)
Backbones

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One of the Internet’s high-speed, long distance
communications links.
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How the Internet Works
Uniform Resource Locator (URL)
http://www.whitehouse.gov
World Wide Web
Hypertext
transfer protocol
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Domain category
Host Network Name
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The Internet is Based on the
Client-Server Model
In client/server computing, processes are divided
between the client and the server. This relationship is
based on a series of requests and responses.
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
Client: Requests services or information from
another computer (the server computer).

Server: Responds to the client's request by sending
the results of the request back to the client
computer.
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Client - Server Computing
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The Client-Server Model
This diagram illustrates the relationship between client and server
computers. The client requests information; the server processes
the request and sends a response back to the client.
CLIENT
SERVER
REQUEST
Client
Program
RESPONSE
Server
Program
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Send Request
Process Request
Read Results
Send Back Results
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Examples of Client Server
Transactions
FTP (file transfer protocol) - An FTP client program
contacts an FTP server and requests the transfer of a file;
the FTP server responds by transferring the file to the
client.
WWW (World Wide Web) - In this case the client
program is a browser. A browser requests the contents of
a web page and displays the results on the user's
computer.
E-MAIL - A mail client program enables the user to
interact with a server in order to access, read and send
electronic mail messages.
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Packets: The Internet “Letter”
To:
Destination:
From:
Instruction Fields:
Data
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What is a Packet?
A packet is a single unit, or "package", of data that is
sent across a network. Data is broken into packets
before it is sent across the Internet. Types of data
that are sent across the Internet using packets
include:
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
E-mail messages

Files, via File Transfer Protocol (FTP)

Web pages, via the World Wide Web (WWW)
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Parts of the Packet
The HEADER of a
packet contains both
the originating and
destination IP
(Internet Protocol)
address. The header
also contains coding
to handle transmission
errors and keep
packets flowing.
Routers use the data in
the header to get the
packet to the correct
address and to
reassemble it at the
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destination.
To:
Destination:
From:
Instruction Fields:
Data
The DATA portion
of the packet
contains the e-mail
text, the web page
information, or the
contents of the
file.
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Transmission Control
Protocol/Internet Protocol
(TCP/IP )
TCP/IP is a collection of protocols, or rules,
that govern the way data travels from one
machine to another across networks.
The Internet is based on TCP/IP.
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Internet Protocol
Determines
Breaks
how much data can fit into a single packet
the data into packets.
Places header information into the packet, enabling
the packet to be forwarded from router to router until it
reaches the final destination..

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Packet Switching Example
Hi Bob!
Hi Bob!
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Packet Switching Example
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
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Hi Bob!
Hi Bob!
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Packet Switching Example
Hi Bob!
Router
Hi Bob!
Router
Router
192.233.123.154
Hi Bob!
Hi Bob!
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Packet Switching Example
Hi Bob!
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Packet Switching Example
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
Hi Bob!
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Hi Bob!
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U.S. Top-Level Domain Affiliations
Affiliation ID
arts
com
edu
firm
gov
info
mil
nom
net
org
rec
store
web
net 3
Chapter
Affiliation
cultural and entertainment activities
business organizations
educational sites
businesses and firms
government sites
information service providers
military sites
individuals
networking organizations
organizations
recreational activities
businesses offering goods for purchase
entities related to World Wide Web activities
networking organizations
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Accessing the Internet
Fig 7.2
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Internet Service Providers
(ISPs)
Provide Internet access to account
holders
Monthly fee varies
Some are free
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Internet Service Providers
Internet Service Provider
Web Address
AT&T WorldNet Service
Digex, Inc.
GTE Internetworking
IBM Internet Connection
MCI Internet
NetCom On-Line Communication Services
PSINet, Inc.
Sprint Internet Services
Uunet Technologies, Inc.
www.att.com
www.digex.net
www.gte.net
www.ibm.net
www.mci2000.com
www.netcom.com
www.psinet.com
www.sprint.net
www.us.uu.net
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Internet Services
E-mail (Electronic mail)
Can include images, attachments, or
HTML
 Routed by gateways and routers

Telnet: remote login
FTP: file transfer
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Internet Services
Chat rooms: allow interactive
conversations
Instant Messaging: online, real-time
communication over the Internet
Videoconferencing
Internet phone
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Internet Services
Content streaming: transfers multimedia
files continuously so users can view
them in real-time
Music, radio & video
3-D Internet sites
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The World Wide Web
The WWW is Just a
Part of the Internet
The World Wide Web, also referred to as the WWW
and "the Web," is the universe of information
available via hypertext transfer protocol (HTTP).
The World Wide Web and HTTP:



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allow you to create "links" from one piece of information to
another;
can incorporate references to sounds, graphics, and movies,
etc.;
"understand" other Internet protocols, such as ftp, gopher,
and telnet.
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WWW Pages use Hyperlinks
The Web presents information as a series of "documents," often
referred to as web pages, that are prepared using the Hypertext
Markup Language (HTML).
Using HTML, the document's author can specially code sections
of the document to "point" to other information resources. These
specially coded sections are referred to as hypertext links. Users
viewing the webpage can select the hypertext link and retrieve or
connect to the information resource that the link points to.
Library Catalog
Webpage
Software
Repository
(ftp)
link
link
gopher site w/
link
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(telnet)
images & sounds
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The World Wide Web
A collection of tens of thousands of independently-owned
computers that work together as one in an Internet service.
Uses a menu-based approach and hyperlink technology in a
client/server topology.
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Home Page
The cover page
for a Web site
that has
graphics, titles,
and black and
blue text.
Hypermedia
Tools that connect
the data on Web
pages, allowing
users to access
topics in whatever
order they wish.
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Uniform Resource Locators (URL)
Identify Sources of Data on The Internet
A URL identifies a particular Internet resource. e.g. a Web page,
a gopher server, a library catalog, an image, or a text file.
URLs represent a standardized addressing scheme for Internet
resources. The basic structure of a URL is hierarchical moving
from left to right:
protocol://server-name.domain-name.top-level domain:
port/directory/filename
Examples:
http://www.healthyway.com:8080/exercise/mtbike.html
gopher://gopher.state.edu/
ftp://ftp.company.com/
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Several Interesting Web Sites
Library of Congress
PointCast
In-Box Direct
Online Career Center
New York Times
Project Gutenberg
Sportsline USA
White House
MIT CS Lab
The Wall Street Journal
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http://lcweb.loc.gov
http://www.pointcast.com
http://www.netscape.com
http://occ.com
http://www.nytimes.com
http://www.gutenberg.org
http://www.sportsline.com
http://www.whitehouse.gov
http://www.lcs.mit.edu
http://www.wsj.com
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Web Terminology
Web Server: Computer that stores web pages.
Web Browser
 Software that creates a unique hypermedia-based
menu on your computer screen and provides a
graphical interface to the Web.
Web Page
 A screen of information sent to a requesting user
and presented through a browser.
Applet
 A small program embedded in Web pages
Search engines

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Programs to find web pages of interest.
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Internet Services
Shopping on the Web
Bots: web search tools
Web Auctions
Office on the web
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Webcasting
aka Push Technology
Consolidates information according to a
user’s profile & displays in the browser
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Intranets and Extranets
Intranet

An internal corporate network built using Internet
and World Wide Web standards and products that
allows employees of an organization to gain access
to corporate information.
Extranet

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A network based on Web technologies that links
selected resources of the intranet of a company with
its customers, suppliers, or other business partners.
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Questions?
Chapter 3
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