ELECTRONIC COMMERCE ARCHITECTURE
Web Client-Server Architecture
As it was mentioned before, every computer in the Internet runs a TCP/IP
protocol. To an end user, the lower level protocols like TCP/IP on which
the Internet is built, is transparent. A user interacts with the Internet
through one of several client/server applications. An application (client)
running in one computer (client) requests a service from another
application (server) running in another computer. In this architecture, there
are two major classes of software that work together:
 Client Software: It usually resides on an end user’s computer and
typically requests services such as a Web page, database access, email, and ftp to the server. It does very little work.
 Server Software: It usually resides on another computer that interprets
requests from the client, processes them, access services from other
computers if needed, and returns the result to the client.
In Web-based client-server application, the client is the Web browser
(Internet Explorer, Netscape Navigator) and the server is the Web server
software (Internet Information Server, Apache Server).
In this section, we will discuss the two- and three-tier Web-based clientserver architecture. We will also discuss the markup languages used to
develop a Web page.
Copyright 2002: Mohammad A. Rob
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Two-Tier Client-Server
In a two-tier architecture the client is tier 1 and the server is tier 2. A twotier system directs communications between the client on the Internet such
as a Web browser and the Web server on the other end.
In this mode, typically a user types a URL in the browser’s address line
(and hits return) or clicks a link on a Web page. The browser then formats
the request into a proper HTTP message and passes to the Internet.
A Web server always listens to a particular port (port 80) for any incoming
HTTP message. When it receives a request, it establishes a connection
with the client computer. It locates the requested Web page and formats it
into an HTTP message, and sends it back to the browser. The connection
is then broken.
When the client receives the message, it recognizes that the page is written
in HTML-something it can interpret, and displays the formatted page. If the
page contains any graphics, another connection is made between the client
and the server.
Three-Tier Client Server Application
The three-tier builds on the two-tier approach. The first tier is the client, the
second tier is the server, and the third tier is typically a database
application running in different computer.
Electronic commercial sites often require a three-tier system with its own
hardware and software to keep track of customer purchases/preferences;
query inventory databases or updates their catalog. The database
services, which comprise the third tier, are often referred to as the backend
machines/programs.
When a client request a Web page from the server, the interprets it, and if it
is found that the Web server needs to get services from a database, it
accesses the database, collects necessary data, and returns the data
formatted in HTML to the client.
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E-Commerce Infrastructure
In general, an e-commerce system includes mainly three software
components that interact over the Internet: a browser, a Web server, and a
database server. This is illustrated in Fig. 1. These components create an
architecture that is commonly termed as a three-tier client-server
architecture. The browser is the client installed on a computer at home or
business. The Web server and the database server are installed on
computers in a merchant network.
The client searches for products through a URL or a link on a Web page
that is stored on the Web server. The Web server interacts with the
database server whenever a Web page finds any code that requires data
access from the database. Fig. 1 also illustrates that a merchant Web
server may interact with an Automatic Clearing House (ACH) computer for
an on-line credit card processing or with a computer in the shipping
company that delivers products for the merchant. These interactions
create a multi-tier architecture for the electronic commerce application.
A. Network Requirements
A merchant must have a presence on the Internet so that a client from
anywhere on the Internet can interact with the electronic shop set-up by the
merchant. The merchant also needs to interact with other third-party
companies through the Internet for order fulfillment. This sets up a multitier architecture as mentioned before and illustrated in Fig. 1.
Fig. 1 also illustrates the architecture of the internal network of a merchant.
The exact architecture of the network or the number of interconnected
networks is not important here, except that many computers can be
connected to a network and some of these computers can be used to
install necessary software for e-commerce application development.
B. Hardware Requirements
The hardware architecture for a typical e-commerce application is
illustrated in Fig. 2. Three PCs are identified with shaded rectangles that
are involved in a typical e-commerce application. Two are server-type PCs
and the third is a regular office PC.
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Once the PCs are available, a network administrator can connect them in
the available network nodes, install necessary operating system software,
and assign IP addresses to the computers. Typically, these PCs are
located in the server room or in close proximity of the network or lab
administrator. This arrangement allows the network administrator to
manage the PCs like any other network resource in a campus network.
C. Software Requirements
Several software components are required to develop and manage an ecommerce application. These include: a network operating system, a Web
server and a database server. Fig. 2 illustrates the software requirements
for an e-commerce application.
a. Network Operating System
A network operating system is necessary to manage the hardware,
software, and users of a network. Microsoft Windows NT operating system
is the most popular network operating system in a PC networking area and
it should be available in any university. As shown by the dark rectangles in
Fig. 2, the NT server should be installed in the server-type PCs, and the NT
client or Windows 95/98 should be installed in the other PC. This last PC is
typically used to manage the Web server and database server.
b. Web Server
The Web server is the most important software of an e-commerce
application that provides Web presence for a merchant. As shown in Fig.
2, the Web server software needs to be installed in a PC running the NT
Server. Microsoft Internet Information Server (IIS) is the choice for the
Web server, because it comes free with the Windows NT operating system
and is widely used in the industry. Thus it is readily available to a network
administrator.
To start with, it involves setting up a default Web site, a home directory,
and a default Web page. The Internet Service Manager, which is installed
with the IIS, is the administrative tool for the management and configuration
of the Internet Information Server. See Fig. 3.
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Upon installation, the IIS automatically creates a default Web site with a
home directory such as C:\Inetpub\wwwroot. The name of the Web site
can be changed, and more than one Web sites with different home
directories can also be created. Fig. 4 shows the IIS property sheet with
the Web Site tab, displaying the name of the web server. The network IP
address of the computer is the default IP address of the Web site.
Fig. 5 shows the Home directory setting of the IIS. As shown, the home
directory can be selected from a directory in the local Web server or it can
be changed to a directory in any computer within the network. If a user is
allowed to browse the Web site to search for a file in a folder instead of
typing the full path in the Web browser, "Directory Browsing Allowed”
should be checked.
Fig. 6 illustrates the property tab setting for selecting one or more default
documents for the Web site. As shown, the “Enable Default Document”
box needs to be checked and a default file name needs to be identified. In
order to allow any user of the Internet to access the Web site, “Allow
Anonymous Access” should be checked on the “Directory Security” tab, as
illustrated in Fig. 7.
Once the Web server is configured, a user within the network can type the
name of the computer in the address line of a Web browser (for example,
http://b3308-bpa.cl.uh.edu/isam5931) and the Web server will respond by
displaying the default Web page. On the other hand, a user anywhere on
the Internet (within the network or outside), can access the default page of
the Web server just by typing the IP address of the computer (for example,
http://129.7.30.129). To access the Web site through a domain name, the
network administrator can assign a name for the computer within the
domain and place an entry in the domain name server to identify the
computer associated with the IP address.
One of the best ways to learn about a Web server is to start with the
Microsoft Personal Web server for Windows 95, 98 or NT, which can be
downloaded free from the Microsoft site (may not be available anymore).
Personal Web server can be used to set-up and configure a Web site in a
local host. A book on the Microsoft Internet Information Server might be
useful to set-up and administer the Web server. The IIS help menu also
provides various features on Web administration and Web publishing.
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c. Database Server
Database is an essential component of an e-commerce application. It
holds information of the electronic merchandise and is accessed
concurrently by many users over the Internet. Thus a network database is
essential to develop a true e-commerce application.
A network database has a client portion and a server portion. The server
portion is installed in a computer that runs a server-side operating system
such as the Windows NT server. See Fig. 2. The client portion is installed
in one or more computers in the network running a client operating system
such as the Windows 95, 98, or NT client. The server contains the actual
database and database-management tools.
The client is used for operating and managing the database system from a
remote computer within a local network. Many databases can be created
in a single database server and many users can access and manipulate a
single database from multiple computers. Incidentally, the database server
can be installed in the same computer that runs the Web server. This
arrangement does not compromise the performance of the database or the
Web server in an application development environment.
Microsoft SQL Server is a popular network database, because most
networked PCs run on the Windows operating system. The graphical user
environment of the SQL Server is very simple to use. The SQL server also
comes free with the Windows NT operating system and a few other
Microsoft software bundles. The security of the SQL server is integrated
with the security of the Windows NT operating system. It allows a network
administrator to easily map a user’s database access permission to that of
the network permission.
When the SQL Server is installed, “Enterprise Manager” management tool
is automatically installed with both the server and client versions. Thus the
SQL server can be managed either from the server computer or from a
remote computer within the network.
In order to create a database for an e-commerce application, one typically
accesses the database server from a client computer. Thus the SQL
server client portion needs to be installed in the laboratory personal
computers. After installation, each client needs to register with the
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database server using a valid username of the SQL server. This is
performed through the “New SQL Server Registration” option in the
Enterprise Manager.
Browser
PC
Automatic
Clearing
House
Client
Internet
Shipping
Company
Web
Server
Gateway
Database
Server
PC
PC
PC
Merchant
Fig.1: Multi-tier client-server architecture of an electronic commerce
application
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Stored Web
Pages
NT Server
NT Client
Internet
Information
Server (IIS)
Visual Basic,
Enterprise
Manager
NT Server
Visual
InterDev,
Enterprise
Manager
SQL
Server
NT Client
Database
Administration
of IIS and
SQL Server
Microsoft
Management
Console
NT Client
Access,
Visual
InterDev
NT Client
Fig. 2: Hardware and software architecture of an electronic commerce application
development and management environment in a PC Network.
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Fig. 3. Internet Service Manger window for managing Microsoft
Internet Information Server
Fig. 4. Web Site property tab showing the Web site name and IP address
of the Web server. Note the name of the Web site is changed to
UHCLMISWeb.
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Fig. 5. Default home directory and various permissions of the Web
site as shown on the property sheet of the Internet Information
Server.
Fig. 6. Document tab setting of the IIS property window. The Web
server first looks for the Main.htm file, and if not found, it looks for the
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Default.htm file. Pressing Add button would allow another file to be
included in the default document list.
Fig. 7. Directory security tab of the Internet Information Server. Selection
of "Allow Anonymous Access" allows any user of the Internet to access the
Web site or a Web page.
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