Transcript Chapter 2 - Faculty of Computer Science and Information Technology

Chapter 2
Infrastructure for Electronic
Commerce
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Learning Objectives
In this chapter, you will learn about:
• The general structure of the network
• Protocols of electronic commerce and email
• Internet utility programs
• Popular Internet applications
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Learning Objectives
• This history and use of Web markup
languages
• Web client and server architecture
• Differences and similarities between the
Internet, intranets, and extranets
• Cost and bandwidth of connecting to the
Internet
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E-commerce Technology
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The Internet
Database software
Network switches and hubs
Encryption hardware and software
Multimedia support
World Wide Web
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Packet-Switched Networks
• Circuit switching is used in telephone
communication.
• The Internet uses packet switching.
• Packet switching needs the computers
called routers and the programs called
routing algorithms
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ARPANET
• ARPANET is the earliest packet-switched
network.
• This wide area network used the Network
Control Protocol (NCP).
• A protocol is a collection of rules for
formatting, ordering, and error-checking
data sent across a network.
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Open Architecture of ARPANET
• Independent networks should not require any
internal changes in order to be connected to the
network.
• Packets that do not arrive at their destinations
must be retransmitted from their source network.
• The router computers do not retain information
about the packets that they handle.
• No global control exists over the network.
Click to see Figure 2-1
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The TCP/IP Protocol
• The Transmission Control Protocol (TCP) and the
Internet Protocol (IP) are the two protocols that
support the Internet operation.
• TCP controls the assembly of a message into
smaller packets before it is transmitted over the
Internet.
• The IP protocol includes rules for routing
individual data packets from their source to their
destination.
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TCP/IP Architecture
TCP/IP Protocol layers (from the highest to
the lowest):
• Application
• Transport
• Internet
• Network Interface
• Hardware
Click to see Figure 2-2
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IP Address
• Internet addresses are based on a 32-bit
number called an IP address.
• IP addresses appear as a series of up to four
separate numbers delineated by a period.
• An address such as 126.204.89.56 uniquely
identifies a computer connected to the
Internet.
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Domain Names
• A Uniform Resource Locator (URL)
consists of names and abbreviations that are
much easier to remember than IP addresses.
• The HTTP protocol defines how an Internet
resource is accessed.
• An address such as www.microsoft.com is
called a domain name.
Click to see Figure 2-3
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HTTP
• Hypertext Transfer Protocol (HTTP) is responsible
for transferring and displaying Web pages.
• A user’s Web browser opens an HTTP session and
sends a request for a Web page to a remote server.
• In response, the sever creates an HTTP response
message that is sent back to the client’s Web
browser.
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SMTP, POP, and IMAP
• E-mail is sent across the Internet is
managed and stored by mail servers.
• Simple Mail Transfer Protocol (SMTP) is
the standard for e-mail client program.
• Post Office Protocol (POP) is the standard
for e-mail server program.
• The Interactive Mail Access Protocol
(IMAP) is a newer e-mail protocol.
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FTP
• The File Transfer Protocol (FTP)
implements a mechanism to transfer files
between TCP/IP-connected computers.
• FTP transfers both binary and ASCII text.
• Full privilege FTP allows remote uploading
and downloading files.
• Anonymous FTP allows you to log on as a
guest.
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Internet Utility Programs
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Finger
Ping
Tracert
Other route-tracing programs
Click to see Figure 2-4:
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Internet Applications
Three representative Internet applications:
• Electronic mail
• Telnet
• FTP
Click to see Figure 2-6:
Click to see Figure 2-7:
Click to see Figure 2-8:
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Overview of Markup Languages
• SGML is a rich meta language that is useful
for defining markup languages.
• HTML is particularly useful for displaying
Web pages.
• XML defines data structures for electronic
commerce.
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Standard Generalized Markup
Language
• The ISO adopted SGML standard in 1986.
• SGML is nonproprietary and platformindependent.
• SGML supports user-defined tags and
architecture to complement the required
richness of documents.
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Hypertext Markup Language
• Tim Berners-Lee invented HTML.
• HTML is a document production language
that includes a set of tags that define the
format and style of a document.
• HTML is based on SGML.
• HTML is an instance of one particular
SGML document type – Document Type
Definition (DTD).
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Extensible Markup Language
• XML is a descendant of SGML.
• XML allows designers to easily describe and
deliver structured data from any application in a
standard, consistent way.
• XML can be embedded within an HTML
document.
• XML allows you to create your own customized
markup language.
Click to see Figure 2.9
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HTML Tags
• An HTML document contains both document
content and tags.
• The tags are the HTML codes inserted in a
document to specify the format on screen.
• Each tag is enclosed in brackets (< >).
• Most tags are two-sided – opening and closing
tags.
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HTML Links
• Hyperlinks are bits of text that connect the current
document to:
– Another location in the same document
– Another document on the same host machine
– Another document on the Internet
• Hyperlinks are created using the HTML anchor
tag.
• Two popular link structures:
– Linear hyperlink structure
– Hierarchical hyperlink structure
Click to see Figure 2-14:
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HTML Version History
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HTML version 1.0 was introduced in 1991.
HTML 2.0 was released in Sept. 1995.
HTML 3.2 was introduced in 1997.
HTML 4.0 was released by W3C in Dec.
1997.
• HTML 4.01 was released in Dec. 1999.
• XHTML 1.0 became a W3C
recommendation in Jan. 2000.
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HTML Editors
• Low end editor displays HTML code on the screen
and allow you to insert HTML tag pairs by
clicking selected buttons.
• High end editor are Web site builder programs,
they provide a rich environment that displays the
Web page, not the HTML code.
• Microsoft FrontPage and Macromedia
Dreamweaver are examples of Web site builders.
Click to see Figure 2-15:
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Web Clients and Severs
• Your PC is a Web client in a worldwide
client/server network.
• Web software is platform-neutral.
• Computers that are connected to the Internet
and contain documents made publicly
available are called Web servers.
Click to see Figure 2-16:
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Web Client/Server Architecture
• Client/server architecture may be used on LANs,
WANs, and the Web.
• The server’s workload is heavy, it needs to be
high-ended computers with lots of disk capacity,
fault-tolerant processors, and ample memory.
• The term thin client describes a client’s relatively
low workload, compared with that of a server.
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Two-Tier Client/Server
• A two-tier architecture is one in which only a
client (tier 1) and a server (tier 2) are involved in
the requests and the responses that flow between
them over the Internet.
• A typical request message from a client to a server
consists of three major parts:
– A request line
– Optional request headers
– An optional entity body
Click to see Figure 2-17:
Click to see Figure 2-18:
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Three-Tier Client/Server
• A three-tier architecture builds on the
traditional two-tier approach.
• The first tier is the client, the second tier is
the Web server, and the third tier consists of
applications and their databases.
• A Common Gateway Interface (CGI) is a
protocol which allows Web servers to
interact dynamically with clients.
Click to see Figure 2-19:
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Intranets
• An intranet is a Web-based private network that
hosts Internet applications on a LAN.
• Intranets are an extremely popular and low-cost
way to distribute corporate information.
• The intranet infrastructure includes a TCP/IP
network, Web authoring software, Web server
hardware and software, Web clients, and a firewall
server.
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Intranet Benefits
• Increased, less expensive, environmentally
friendly internal communication.
• Low acquisition and deployment costs.
• Low maintenance costs.
• Increased information accessibility.
• Timely, current information availability.
• Easy information publication, distribution,
and training.
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Extranets
• Extranets connect companies with suppliers
or other business partners.
• An extranet can be: a public network, a
secure (private) network, or a virtual private
network (VPN).
• Extranets provide the private infrastructure
for companies to coordinate their purchase
and communications with one another.
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Extranets
• A public network extranet exists when an
organization allows the public to access its intranet
from any public network.
• A private network is a private, leased-line
connection between two companies that physically
connects their intranets to one another.
• A VPN extranet is a network that uses public
networks and their protocols to send sensitive data
to partners, customers, suppliers, and employees
using a system called “tunneling”.
Click to see Figure 2-20:
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Internet Connectivity
• Internet Service Providers (ISPs) provide Internet
access services to other businesses.
• Ways to connect to an ISP:
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Dial-up connection
DSL connection
ISDN connection
Cable connection
T1 connection
T3 connection
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