1. The Internet, Intranets, and Extranets
Chapter 7
The Internet, Intranets, and Extranets

2. The Internet The internet Internet networks A network of networks
The internet transmits data from one computer (called a host) 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
Schematic

4. Internet ‘Discussion’ (1)
A global network connecting millions of computers. As of 1999, the
Internet has more than 200 million users worldwide, and that number
is growing rapidly. More than 100 countries are linked into
exchanges of data, news and opinions.
Unlike online services, which are centrally controlled, the Internet is
decentralized by design. Each Internet computer, called a host, is
independent. Its operators can choose which Internet services to
use and which local services to make available to the global Internet
community. Remarkably, this anarchy by design works exceedingly

5. Internet ‘Discussion’ (2)
well.
There are a variety of ways to access the Internet. Most online
services, such as America Online, offer access to some Internet
services. It is also possible to gain access through a commercial
Internet Service Provider (ISP).
Note: York University’s CCS (Computer and Communications
Services) is an ISP.

6. How the Internet Works Transport control protocol (TCP)
A protocol that operates at the transport layer and is used in combination with IP by most Internet applications
Backbone
An Internet high-speed, long distance communications links (like a bus; wire that connects nodes)
Uniform resource locator (URL)
An assigned address on the Internet for each computer
E.g.,

7. Domain Affiliations Domain Affiliations arts
cultural and entertainment activities
com
business organizations
edu
educational sites
firm
businesses and firms
gov
government sites
info
information service providers
mil
military sites
nom
individuals
net
networking organizations
org
organizations
rec
recreational activities
store
businesses offering goods for purchase
web
entities related to World Wide Web activities

8. Access to the Internet LAN servers
Local servers can provide access to the Internet through normal connections (e.g., Ethernet)
Serial line internet protocol (SLIP) and Point-to-point protocol (PPP)
Communications protocol software that transmits packets over telephone lines, allowing dial-up access to the Internet
Connection via an on-line service
Examples are America Online and Microsoft Network. These services usually require sign-up procedures

9. Three Ways to Access the Internet
Schematic

11. Internet Service Providers
Internet service provider (ISP)
Any company that provides individuals or companies with access to the Internet
Thousands of providers including large communications companies
Need an account with the ISP and software that links with TCP/IP

12. ISP Examples 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.

13. Internet Services E-mail Telnet FTP Usenet and newsgroups Chat rooms
Internet phone
Internet videoconferencing
Content streaming

14. Selected Usenet Groups
alt.fan.addams.family alt.life.itself
alt.pets alt.fan.bevis-n-butthead
alt.autos.camaro alt.fan.leonardo-dicaprio
alt.cloning alt.history
alt.fan.u2 alt.music.blues
alt.sports.baseball.cinci-red alt.music.zz-top
alt.politics.socialism alt.sports.college.sec
alt.sports.soccer.european.uk

15. Internet Services Internet telephony Also called voice-over-IP (VOIP)
Technology that enables network managers to route phone calls and fax transmissions over the same network they use for data

17. VOIP ‘Discussion’
Internet telephony is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls. For users who have free, or fixed-price, Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. To date, however, Internet telephony does not offer the same quality of telephone service as direct telephone connections.
There are many Internet telephony applications available. Some, like CoolTalk and NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products.

18. Content Streaming Content streaming
A method for transferring multimedia files over the Internet so that the data stream of voice and pictures plays continuously, without a break, or very few of them
It also enables users to browse large files in real time

19. The World Wide Web World Wide Web
A collection of tens of thousands of independently-owned computers that work together as one in an Internet service

20. WWW Terminology Home page Hypermedia Hypertext markup language (HTML)
The cover page for a Web site that has graphics, titles, coloured text, etc.
Hypermedia
Tools that connect the data on Web pages, allowing users to access topics in whatever order they wish
Hypertext markup language (HTML)
The standard page description language for Web pages

21. Some Interesting Web Sites
Says who?
Library of Congress
PointCast
In-Box Direct
Online Career Center
New York Times
Project Gutenberg
Sportsline USA
White House
MIT Lab for Computer Science
The Wall Street Journal

22. WWW Terminology Web browser Web page Applet
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

23. HTML
“The” language of WWW pages
Need we say more!!!

24. Search Engines Search engines
A search tool for the Web (like card catalogs in libraries)
E.g.,
Altavista
Excite
Galaxy
Hotbot
Infoseek
Lycos
Webcrawler
Yahoo!

25. Java Java An object-oriented programming language
Developed by Sun Microsystems
Based on C++
Allows small programs -- applets -- to be embedded within an HTML document

26. Applets
Applets are small java programs that are downloaded from the server to the local machine

27. Push Technology Push technology E.g.,
Technology that enables users to automatically receive information over the Internet rather than searching for it using a browser
Also called Webcasting
E.g.,
PointCast
InterMind

28. Webcasting ‘Discussion’
Using the Internet, and the World Wide Web in particular, to
broadcast information. Unlike typical surfing, which relies on a pull
method of transferring Web pages, webcasting uses push
technologies.

29. Push ‘Discussion’ (1)
In client/server applications, to send data to a client without
the client requesting it. The World Wide Web is based on a pull
technology where the client browser must request a Web page
before it is sent. Broadcast media, on the other hand, are push
technologies because they send information out regardless of
whether anyone is tuned in.
Increasingly, companies are using the Internet to deliver information
push-style. One of the most successful examples of this is
PointCast, which delivers customized news to users' desktops.

30. Push ‘Discussion’ (2)
Probably the oldest and most widely used push technology is .
This is a push technology because you receive mail whether you ask
for it or not -- that is, the sender pushes the message to the
receiver.

31. Business Use of the Web Uses:
Applications, , Product Display, Catalogs, Order placement
Products people are likely to buy on the Web
Software 77%
Books 67%
CDs 64%
Computer hardware 63%
Airline tickets 61%
Magazine subscriptions 53%
Concert/theater tickets 48%
Flowers 45%

32. Intranets and Extranets
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
A network based on Web technologies that links selected resources of the intranet of a company with its customers, suppliers, or other business partners

33. Intranet ‘Discussion’
A network based on TCP/IP protocols (an internet) belonging to an
organization, usually a corporation, accessible only by the
organization's members, employees, or others with authorization. An
intranet's Web sites look and act just like any other Web sites, but
the firewall surrounding an intranet fends off unauthorized access.
Like the Internet itself, intranets are used to share information.
Secure intranets are now the fastest-growing segment of the
Internet because they are much less expensive to build and manage
than private networks based on proprietary protocols.

34. Extranet ‘Discussion’
A new buzzword that refers to an intranet that is partially
accessible to authorized outsiders. Whereas an intranet resides
behind a firewall and is accessible only to people who are members
of the same company or organization, an extranet provides various
levels of accessibility to outsiders. You can access an extranet only
if you have a valid username and password, and your identity
determines which parts of the extranet you can view.
Extranets are becoming a very popular means for business partners
to exchange information.

35. Firewall
Firewall…
A device that sits between your internal network and the outside Internet and limits access into and out of your network based on your organization’s access policy

36. Virtual Private Network (VPN)
A secure connection between two points across the Internet
Tunneling
The process by which VPNs transfer information by encapsulating traffic in IP packets and sending the packets over the Internet
Schematic

38. VPN ‘Discussion’
Short for virtual private network, a network that is constructed by
using public wires to connect nodes. For example, there are a
number of systems that enable you to create networks using the
Internet as the medium for transporting data. These systems use
encryption and other security mechanisms to ensure that only
authorized users can access the network and that the data cannot
be intercepted.

39. Tunneling ‘Discussion’
A technology that enables one network to send its data via another
network's connections. Tunneling works by encapsulating a network
protocol within packets carried by the second network. For example,
Microsoft's PPTP technology enables organizations to use the
Internet to transmit data across a virtual private network (VPN). It
does this by embedding its own network protocol within the TCP/IP
packets carried by the Internet. (Note: PPTP = point-to-point tunneling
protocol)
Tunneling is also called encapsulation.

40. Internet Issues Management issues Service bottlenecks
No centralized governing body for the Internet
Service bottlenecks
Phenomenal growth has left a service void
Providers underestimating computing power needed
Reconciling router addresses needed to transverse the network

41. Privacy & Security Cryptography Encryption Digital Signature
The process of converting a message into a secret code and changing the encoded message back to regular text
Encryption
The original conversion of a message into a secret code
Digital Signature
An encryption technique used for online financial transactions

42. Encryption software running on sending computer
Have a nice day…
Encryption software running on sending computer
E%$&:”}{|…
Decryption software running on Receiving computer
Have a nice day…

43. Firewalls Firewalls Assured pipeline
A method of preventing unauthorized access between a company’s computers and the Internet (looks at the header of a packet)
Assured pipeline
An Internet security method that looks at the entire request for data and then determines whether the request is valid

44. Firewall ‘Discussion’ (1)
A system designed to prevent unauthorized access to or from a
private network. Firewalls can be implemented in both hardware and
software, or a combination of both. Firewalls are frequently used to
prevent unauthorized Internet users from accessing private
networks connected to the Internet, especially intranets. All
messages entering or leaving the intranet pass through the firewall,
which examines each message and blocks those that do not meet
the specified security criteria.

45. Firewall ‘Discussion’ (2)
There are several types of firewall techniques:
Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.
Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

46. Firewall ‘Discussion’ (3)
In practice, many firewalls use two or more of these techniques in
concert.
A firewall is considered a first line of defense in protecting private
information. For greater security, data can be encrypted.

47. End of Chapter 7
Chapter 8