case studies

munchdrabNetworking and Communications

Oct 30, 2013 (4 years and 2 months ago)

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Chapter 2

The Internet and the Web:

Infrastructure for

Electronic Commerce

Electronic Commerce

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Technology Overview


Internet is the most obvious technology
needed to conduct e
-
commerce


Other technologies are also required


Database software


Network switches and hubs


Encryption hardware and software


Multimedia support


Potential for business volume to double
in less than a year

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Objectives


General structure of the network of
networks supporting the Internet and e
-
commerce


Protocols that move commerce across
the Internet and send/receive e
-
mail


Internet utility programs to trace, locate,
and verify the status of Internet host
sites

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Objectives


Popular Internet applications, including
e
-
mail, Telnet, and FTP


History and use of Web markup
languages, including SGML, HTML,
and XML


HTML tags and links


Web client and server architectures and
the messages they send to each other

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Objectives


Differences and similarities between
internets, intranets, and extranets


Options for connecting to the Internet,
their cost and bandwidth tradeoffs

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Web Clients and Servers


Client computers typically request
services, including printing, information
retrieval, and database access


Servers are responsible for processing
the clients’ requests

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Client/Server Structure of the WWW

Figure 2
-
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Web Client/Server Communication


Two
-
Tier Client/Server


All communication takes place between
the client on the Internet and the target
server at the other end


Request message consists of:


A request line


Optional request headers


An optional entity body

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Message Flow Between a

Web Client and Server


Figure 2
-
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Web Client/Server Communication

Figure 2
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Three
-
Tiered Client/Server


First tier is the client


Second tier is the Web server


Third tier are the applications and their
databases






(Figure 2
-
19)

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Open Architecture


Independent networks should not
require any internal changes in order to
be connected to the network


Packets that do not arrive at their
destination must be retransmitted


Router computers do not retain
information about the packets


No global control exists over the
network

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The TCP/IP Internet Protocol


Set of protocols developed by Vincent
Cerf and Robert Kahn


Transmission Control Protocol (TCP)


Controls the assembly of a message into
smaller packets before transmission, and
reassembles them once received


Internet Protocol (IP)


Rules for routing packets from their source to
their destination


Replaced NCP as used by ARPANET

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IP Address and Domain Names


Appears as a series of up to four
separate numbers delineated by a
period, often referred to as a “Dotted
Quad”


Each of the numbers range from 0 to 255


First four numbers identify the network


Following numbers identify a node


Sample IP address: 126.204.89.56

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IP Address and Domain Names


Uniform Resource Locator (URL)


Easier to remember than IP address


Consists of names and abbreviations


Contains at least two parts


First part contains the protocol used


Second part contains the location of the
resource


http://www.adobe.com

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Other Internet Protocols


Hypertext Transfer Protocol (HTTP)


Responsible for transferring and displaying
Web pages


Simple Mail Transfer Protocol (SMTP)


Specifies the exact format of a mail
message


Post Office Protocol (POP)


Responsible for retrieving e
-
mail from a
mail server

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Other Internet Protocols


Interactive Mail Access Protocol (IMAP)


Latest protocol, may replace POP


Defines how a client program asks a mail
server to present available mail


Download only selected messages, instead of
all messages


View headers only


Create and manipulate mailboxes on the
server

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Other Internet Protocols


File Transfer Protocol (FTP)


Transfers files between TCP/IP
-
connected
computers


Uses client/server model


Transfers both binary and ASCII text


Displays and manipulates remote and
local computer file directories


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Internet Applications:


Electronic Mail


Began in the 1970s for use on the
ARPANET


Most popular form of business
communication


Can send documents, pictures, movies,
worksheets, or other important pieces
of information

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Markup Languages and

the Web



Standard Generalized Markup
Language (SGML)


Regulated ISO standard since 1986


Nonproprietary


Supports user
-
defined tags


Costly to set up


Expensive compared to HTML


Steep learning curve

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Markup Languages and

the Web



Hypertext Markup Language (HTML)


Based on SGML


Easier to learn and support


Supports commonly used text markup
features


Headings, title bars, bullets, lines, lists


Precise graphic positioning, tables, and frames


Standard language for Web pages

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Markup Languages and

the Web



Extensible Markup Language (XML)


Descendant of SGML


Defines which data to display, instead of
how a page is displayed


Describes a page’s actual content, unlike
HTML


Data
-
tracking capability

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XML Example

Figure 2
-
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Traditional vs. Hyperlinked Document Pages

Figure 2
-
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More about HTML


HTML tags


<tagname properties>Displayed
information affected by tag</tagname>


<B>best</B>
-

Bolds the word “best”


<P align=“right”>
-

Aligns text to the right


HTML code defines the formatting of
the page, but a page may look different
on two different browsers

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Web Page and Paragraph Tag

With Right
-
Align Property

Figure 2
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HTML Codes to Format Memo Page

Figure 2
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Internet Explorer Display of Memo Page

Figure 2
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More about HTML


HTML Links


Anchor tags used to link to text within the
same document, or on a distant computer


<A HREF=“address”>Visible link text</A>


<A HREF=
http://www.purdue.edu
>Purdue
University</A>


<A HREF=“#references”>References are
found here</A>


Text between the anchors appears as a
hyperlink

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Hyperlink Structures

Figure 2
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HTML Editors


Used to generate the HTML code


Simple text editors offer limited flexibility


Any word processor can be used


Web site builders offer more control


Microsoft FrontPage


Dreamweaver


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Networks


Local and long distance telephone
companies were early models in the
1950s


Single paths were created to connect
two parties together, called
circuit
switching

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Packet
-
Switched Networks


The Internet uses
Packet switching


Files and messages are broken down into
packets, which are electronically labeled
with their origin and destination


The destination computer collects the
packets and reassembles the data from
the pieces in each packet


Each computer the packet encounters
decides the best route towards its
destination

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Packet
-
Switched Network


and Message Packets

Figure 2
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Internets, Intranets, and Extranets


Intranets


Only selected individuals are allowed
access


Low
-
cost way to distribute corporate
information


Collect and group information for external
dissemination


Infrastructure requirements are usually in
place if PCs are on a LAN

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Internets, Intranets, and Extranets


Extranets


Connect companies with suppliers or other
business partners


Provide the infrastructure for the
coordination of purchases, EDI, and
communications


Use the Internet for communicating among
themselves

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Internets, Intranets, and Extranets


Public Network


An extranet that allows the public to
access its intranet


When two or more companies agree to
link their intranets using a public network
(such as the Internet)


Private Network


A leased
-
line connection that physically
connects two intranets

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Internets, Intranets, and Extranets


Virtual Private Network (VPN)


Uses public networks and protocols to
send sensitive data by using “tunneling” or
“encapsulation”
-

private passageways
through the Internet


Designed to save money and create a
competitive advantage by alliances formed
with cooperating companies


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Secure VPN Extranet

Figure 2
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Internet Connections Options and
Tradeoffs


Internet Service Providers (ISPs) offer
connection choices to their users


Plain Old Telephone Service (POTS)


Existing telephone lines with modems


Bandwidth of 56Kbps (56,000 bits per second)


Integrated Services Digital Network (ISDN)


Bandwidths up to 128Kbps


Asymmetric Digital Subscriber Line (ADSL)


Upload at 640Kbps, download up to 9Mbps

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Cable Modems



Same broadband coaxial cable that
serves cable television


Upstream bandwidths of 300
-
500 Kbps


Downstream bandwidths of 1.5Mbps