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The Internet, Intranets, &
Extranets
The Internet (1)
A collection of networks that pass data around in
packets, each of which carries the addresses of its
sender & receiver
Routers determine where each packet should be
sent & forward the packet appropriately
Transmission Control Protocol (TCP): A
protocol that together with the IP protocol is used by
most Internet applications (TCP/IP) (see Chapter 6)
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The Internet (2)
 Backbone: High-speed (>T1) long distance links
between routers
 Uniform Resource Locator (URL): An assigned
Internet address on the Web for each Web site,
e.g., http://www.ngi.gov
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Top-Level Domain Affiliations
(Extensions) on the Internet
.com
.edu
.gov
.mil
.net
.org
.ca
.uk
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Commercial organization
Educational organization
Governmental agency/organization
Military branch/agency
Networking organization
Not-for-profit organization
Canadian organization
United Kingdom organization
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Accessing the Internet
 LAN Servers
 Serial Line Internet Protocol (SLIP) & Pointto-Point Protocol (PPP)
 Communications protocol software that transmits
packets over telephone lines
 Dial-up access to the Internet
 Connection via On-Line Services, e.g., AOL,
Microsoft Network (MSN)
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Internet Service Providers (ISPs)
 A company that
provides individuals
or companies with
access to the Internet
 Thousands of
providers worldwide
 Need an account with
the ISP & software
that uses TCP/IP
 CN ISPs include
Sympatico, Escape,
etc.
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Internet Services (1)
World Wide Web: Information search & retrieval
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Internet Services (2)
 Voice Over IP (VOIP): Technology that enables
network managers to route phone calls & fax transmissions
over the same network they use for data; uses codec devices
to compress data/voice for transmission
 Content Streaming: A method of transferring
multimedia files over the Internet so that the data stream of
voice & pictures begins to play or can be read quickly,
rather than waiting for the entire file to download
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The World Wide Web (1)
A collection of independently owned computers that
work together as a single Internet service
 Home Page: The index page for a Web site that is
normally accessed first
 Hypermedia: Files & linkages (hyperlinks) that connect
the data on Web pages to other Web pages & URLs,
allowing users to access topics in whatever order they wish
 Hypertext Markup Language (HTML): The
standard programming language in which Web pages are
written
 Java: Object-oriented programming language from Sun
Microsystems based on C++ that allows small programs
(applets) to be embedded within an HTML document
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The World Wide Web (2)
 Web Browser: Applications software that
provides a graphical interface to the Web
 Web Page: A file, typically written in HTML, that
is presented through a browser
 Applet: A small program embedded within a Web
page, normally written in Java or Javascript
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Intranets & Extranets
 Intranet: An internal corporate network that uses
Internet & Web standards to allow employees to
access corporate information
 Extranet: A network based on Web technologies
that links an organization with its customers,
suppliers, & business partners (not available to the
public)
 Firewall: Hardware or software that functions
between an internal network & the outside world
& limits access in & out of the internal network
based on the organization’s access policy
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Internet Issues
 Management Issues
 No centralized governing body for the Internet
 Capacity & reliability may vary among ISPs/carriers
 Service Bottlenecks
 Phenomenal growth has left a service void
 Providers underestimate computing power needed (e.g.,
AOL crashed three times in one month last year)
 Reconciling router addresses needed to transverse the
network
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Net Issues - Privacy & Security (1)
Encryption &
Decryption
The conversion of a
message into a
secret code.
Digital
Signature
An encryption
technique used for
online financial
transactions.
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Net Issues - Privacy & Security (2)
 Firewalls: Look only at packet header
 Assured Pipeline: Looks at the entire request for
data & then determines whether the request is
valid
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Case for discussion
US West Communications, pp. 331-332
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