1. Electronic Commerce Last Week
The Internet - a network of thousands of interconnected networks
Interconnected Backbone supported by NSPs
Access/Delivery sub-networks or ISPs
Thousands of government/private/institutional network
Internet Protocols
Packet-switched network
TCP/IP protocol
Link layer
Network layer
Transport layer
Application layer
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2. Electronic Commerce Last Week
Routing of data packets and routing table
IP address and classes of IP addresses
Subnet addressing
Domain name (
Domain name system (directory of domains names)
Uniform Resource Locator (
Other Internet protocols
FTP, SMTP, POP, Telnet
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3. Electronic Commerce This Week Internet utility programs
Finger, Ping, Tracert
Web Client-Server Architecture
Two-tier and three-tier architecture
Communication protocols in client-server architecture
HTTP protocol
Common Gateway Interface (CGI)
Application Programming Interface (API)
Database Gateways (ODBC, IDC, ADO)
Markup languages
SGML, HTML, XML
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4. Internet Utility Programs
TCP/IP supports a wide variety of utility programs that permit more convenient and efficient use of the Internet.
Some popular utility programs are
Finer
PING
Tracert
VisualRoute
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5. Internet Utility Programs
Finger
Finger is a utility program that runs on UNIX computers
It allows a user to obtain limited information about other network users from a remote computer
One can use a Finger command to determine which users are logged on to a particular network or gather some information about a particular user in the network:
userid of the user
Time the user is logged in
Name of the computer the user is logged in
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6. Internet Utility Programs
PING
PING (Packet InterNet Groper) tests connectivity between two Internet hosts and determine if a host is active on the network
It works by sending a packet to the specified address and waiting for a reply
It is primarily used by network administrators to troubleshoot Internet connection (whether a host is alive or not?)
It provides performance data about the connection between computers in the Internet, such as the number of hops it takes to reach a data packet from a sender to the receiver
Try ping or ping from the DOS prompt
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7. Internet Utility Programs
Tracert/VisualRoute
Tracert (TRACE RouTe) allows a user to trace the round trip path between his/her computer and another computer on the Internet.
It calculates and displays the number of hops between two computers and the time it takes to traverse the entire one way path between them.
The program works by sending a series of data packets to a particular destination IP address on the Internet. Each router on the path sends its IP address and the roundtrip time it took to reach it
A graphical traceroute program such as the VisualRoute displays a graphical view of the route of the data packet
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8. Web Client-Server Architecture
Introduction
Every computer in the Internet runs a TCP/IP protocol. To an end user, this lower level protocols is transparent
A user interacts with the Internet through one of several client/server applications
An application running in one computer (client) requests a service from another application running in another computer (server)
In this architecture, there are two major classes of software that work together:
Client software
Server software
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9. Web Client-Server Architecture
Client Software
It usually resides on an end user’s computer and typically requests services such as a Web page, database access, , 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.
It does most of the work
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10. Web Client-Server Architecture
Web-Based Client-Server Application:
The client is the Web browser (Internet Explorer, Netscape)
The server is the Web server software (Internet Information Server, Apache Server)
Two types of Web-based client-server applications architecture:
Two-tier client-server architecture
Three-tier client-server architecture
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11. Two-Tier Client-Server Architecture
A two-tier architecture is one in which a client (tier1) and a server (tier2) directs communications between them over the Internet
Steps of communication between a Web browser and Web server:
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 it to the Internet
A Web server always listens to a particular port (port 80) for any incoming HTTP message Continued..
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12. Two-Tier Client-Server Architecture
Steps of communication (continued):
When the server receives a request, it establishes a connection with the client computer, locates the requested Web page and formats it into an HTTP message
It then sends it back to the browser, and the connection is broken.
When the client receives the message, it recognizes that the page is written in HTML code-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
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13. Three-Tier Client-Server Architecture
The first tier is the client, the second tier is the server, and the third tier is typically a database or an application program running in a different computer.
From a software perspective, the three tires are: client processes - tier1, Web services - tier2, and data services - tier 3
From the hardware perspective, all three software could be in three different computers, or in two computers, or in one computer
The database services, which comprise the third tier, are often referred to as the backend machines/programs
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14. Three-Tier Client-Server Architecture
When a client request a Web page from the server, the server 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
Electronic commerce 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
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15. Communication Protocols in the Client-Server Architecture
HTTP protocol: Communication Between tier-1 and Tier-2:
Whether it is a two-tier or a three-tier client-server architecture, a common HTTP protocol is used to format a message sent between a client in tier-1 and server in tier-2
Communication protocols between tier-2 and tier-3:
Several protocols are used to communicate between the Web server and a database server.
Protocols supported by Web servers are:
Common Gateway Interface (CGI)
Application Programming Interface (API)
Open Database Connectivity (ODBC)
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16. Hypertext Transport Protocol (HTTP)
HTTP is a lightweight, stateless protocol that browsers and servers use to converse with each other.
There are only seven commands in the protocol. Two of these commands are: GET and POST. When a browser requests for a page from the Web server, it uses the GET command.
The HTTP is stateless because every request that a browser makes opens a new connection that is immediately closed after the document is returned. Thus the server cannot maintain state information about successive requests in a straightforward fashion.
This statelessness represents a substantial problem for electronic commerce applications, because an individual user is likely to have a series of related interactions (browsing catalog, select items, enter a payment information) within the application.
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17. Common Gateway Interface (CGI)
CGI is a standard way of interfacing backend applications with Web servers
It is program written in a high-level language such as C/C++, Visual Basic
A CGI program is executed when requested by a browser through an embedded call within a Web page
Web pages that contain forms filed with text boxes, option buttons, and list boxes supply information that CGI programs can use to manipulate databases, store information, or retrieve data
CGI is known as a server-side solution, because all the processing occurs in the Web server, not in the client computer
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18. Application Programming Interface (API)
A CGI program is called every time there is request of a Web page that contains a CGI program. This causes significant processing burden in a high-traffic Web server
Application Programming Interface or API is a set of protocols that uses “multithreading,” that is, it only invokes a single instance of the program to handle multiple user requests of the dynamic Web pages
API is more efficient than CGI, as CGI requires an individual program to be brought to the Web server memory when requested by multiple users
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19. Database Gateways
A database gateway eliminates the need of creating customized CGI program to access various databases produced by different vendors
Open database connectivity (ODBC) is a tool used by programs, including a Web page, to communicate with a database
Internet Database Connector (IDC) is a technology developed to access and manipulate data from a database
ActiveX Data Object (ADO) is another tool developed by Microsoft that is also used to access and manipulate data from a database.
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20. In-Class Work
Create an order processing database in Microsoft Access where a customer book order can be stored and the information can be used by the inventory personnel to fulfill the order.
The database should contain entities such as
customer, book, order
It should contain a order-entry form
It should also contain a report on the books ordered by customer and then by total amount
Any other enhancement!
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