1. THE INTERNET,
INTRANETS, AND
EXTRANETS

2. An Overview of
Telecommunications and Networks
 Telecommunications: the electronic
transmission of signals for communications
 Telecommunications medium: anything that
carries an electronic signal and interfaces
between a sending device and a receiving
device

3. 3
An Overview of
Telecommunications and Networks
(continued)
Elements of a Telecommunications System

4. 4
Transmission Media
Transmission Media Types

5. 5
Transmission Media (continued)
Transmission Media Types (continued)

6. 6
Telecommunications Devices
Common Telecommunications Devices

7. Networks
 Computernetwork: the communications
media, devices, and software needed to
connect two or more computer systems or
devices
 Networknodes: the computers and devices on
the networks

8. Basic Processing Strategies
 Centralized processing: all processing occurs
in a single location or facility
 Decentralized processing: processing devices
are placed at various remote locations
 Distributed processing: computers are placed
at remote locations but connected to each
other via a network

9. Terminal-to-Host, File Server, and
Client/Server Systems
 Connecting computers in distributed
information processing:
 Terminal-to-host: the application and database
reside on one host computer, and the user
interacts with the application and data using a
“dumb” terminal
 File server: the application and database reside
on the one host computer, called the file server
 Client/server: multiple computer platforms are
dedicated to special functions, such as database
management, printing, communications, and
program execution

10. 10
Terminal-to-Host, File Server, and
Client/Server Systems (continued)
Client/Server Connection

11. Network Types
 Personal area network (PAN)
 Local area network (LAN)
 Metropolitan area network (MAN)
 Wide area network (WAN)
 International network

12. 12
Network Types (continued)
A Typical LAN

13. Network Types (continued)
A Wide Area Network

14. Communications Software and
Protocols
 Communications software: software that
provides a number of important functions in a
network, such as error checking and data
security
 Network operating system (NOS)
 Network management software
 Communications protocol: a standard set of
rules that controls a telecommunications
connection

15. 15
Communications Software and
Protocols (continued)
Common Communications Protocols

16. 16
Communications Software and
Protocols (continued)
Common Communications Protocols (continued)

17. Use and Functioning of the
Internet
 Internet: a collection of interconnected
networks, all freely exchanging information
 ARPANET
 The ancestor of the Internet
 A project started by the U.S. Department of
Defense (DoD) in 1969
 Internet Protocol (IP): communication
standard that enables traffic to be routed from
one network to another as needed

18. How the Internet Works
 The Internet transmits data from one computer
(called a ho st) to another
 If the receiving computer is on a network to
which the first computer is directly connected,
it can send the message directly
 If the receiving computer is not on a network
to which the sending computer is connected,
the sending computer relays the message to
another computer that can forward it

19. The Internet
 The internet
 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

21. Internet
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
There are a variety of ways to access the Internet. It is also
possible to

22. 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., http://www.yorku.ca/

23. 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
net networking organizations

24. 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

25. Three Ways to Access the
Internet

26. 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

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

28. 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

30. What is VOIP ?
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.

31. 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

32. 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

33. WWW Terminology
 Home page
 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

34. WWW Terminology
 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

35. HTML
 “The” language of WWW pages
 Need we say more!!!

36. 36
The World Wide Web
 The Web, WWW or W3
 A menu-based system that uses the
client/server model
 Organizes Internet resources throughout the
world into a series of menu pages, or screens,
that appear on your computer
 Hypermedia: tools that connect the data on
Web pages, allowing users to access topics in
whatever order they want

37. 37
The World Wide Web
 Hypertext Markup Language (HTML): the
standard page description language for Web
pages
 HTML tags: codes that let the browser know
how to format the text on a Web page and
whether images, sound, and other elements
should be inserted

38. Search Engines
 Search engines
 A search tool for the Web (like card catalogs in
libraries)
 E.g.,
Google.com
Yahoo.com
Rediff.com

39. 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

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

41. 41
Developing Web Content
 Products that greatly simplify the creation of a
Web page
 For example: .NET platform
 Content management system (CMS)
 Web services

42. 42
Web Services
 Standards and tools that streamline and
simplify communication among Web sites for
business and personal purposes
 Can also be used to develop new systems to
send and receive secure messages between
healthcare facilities, doctors, and patients,
while maintaining patient privacy

43. Push Technology
 Push technology
 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

44. 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.

45. What is Push ?
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.

46. Push Mail
Probably the oldest and most widely used push technology is e-
mail.
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.

47. 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
 A network based on Web technologies that links
selected resources of the intranet of a company with
its customers, suppliers, or other business partners

48. What is Intranet ?
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.

49. What is Extranet ?
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.

50. Virtual Private Network (VPN)
 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

52. VPN
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.

53. Tunneling
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)

54. Internet Issues
 Management issues
 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

55. Privacy & Security
 Cryptography
 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

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

57. Firewalls
 Firewalls
 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

58. Firewall
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

59. Firewall
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.

60. Firewall
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.

61. Summary
 Telecommunications is the electronic
transmission of signals for communications
 A computer network consists of the
communications media, devices, and software
needed to connect two or more computer
systems or devices
 Ways of connecting computers in distributed
information processing: terminal-to-host, file
server, and client/server

62. Summary (continued)
 Network types: personal area network (PAN),
local area network (LAN), metropolitan area
network (MAN), wide area network (WAN),
and international network
 The Internet is a collection of interconnected
networks, all freely exchanging information
 Internet Protocol (IP) is a communication
standard that enables traffic to be routed from
one network to another as needed

63. Summary (continued)
 Uniform Resource Locator (URL) is an
assigned address on the Internet for each
computer
 An intranet is an internal corporate network
built using Internet and World Wide Web
standards and protocols
 An extranet is a network based on Web
technologies that links selected resources of a
company’s intranet with its customers,
suppliers, or other business partners