1. The Internet and the World Wide Web

2. Review From Week 1 Overview of eCommerce History of the Internet
Definition
Components
Comparison to Traditional Commerce
Why eCommerce: Unique features
Appropriateness of eCommerce
History of the Internet

3. Week Two Topics Technology Components Packet Switching
Protocols: TCP/IP, FTP, HTTP,
Purpose, use of various protocols
TCP/IP Architecture
IP Addresses, URLs, Domains
Publishing on the Web: In Depth
File Transfer Protocol

4. What is the Internet? A loosely configured global wide-area network.
Loosely configured = open architecture, no single control
Network = connection of computers
Wide Area = large geographical coverage

5. Factors Behind Growth
Primary technology factors behind growth discussed tonite:
The TCP/IP standard and packet switching.
The web-like ability to link from site to site enabled through HTML and HTTP.

6. A Model for Networking The world’s telephone companies were the early
models for networked computers because the
networks used leased telephone company lines.
Telephone companies at the time established a
single connection between sender and receiver
for each telephone call.
Once a connection was established, data traveled
along that path.

7. Circuit switching Telephone company switching equipment (both
mechanical and computerized) selected the
phone lines, or circuits, to connect in order to
create the path between caller and receiver.
This centrally controlled, single connection
model is known as circuit switching.
Using circuit switching does not work well for
sending data across a large network.
Point-to-point connections for each sender/
receiver pair is expensive and hard to manage.

8. A Different Approach
The Internet uses a less expensive and more easily
managed technique than circuit switching.
Files and messages are broken down into packets
that are labeled with codes that indicate their
origin and destination.
Packets travel from computer to computer along
the network until they reach their destination.
The destination computer reassembles the data
from the packets it receives.
This is called a packet switching network.

9. View of Packet Switching

10. Packet switching In a packet-switched network, each computer that
an individual packet encounters determines the
best way to move the packet to its destination.
Computers performing this determination are
called routers.
The programs that the computers use to determine
the path are called routing algorithms.
Utilizes Transmission Control Protocol/Internet Protocol
TCP/IP

11. Routing Messages

12. Benefits of Packet Switching
There are benefits to packing switching:
Long streams of data can be broken down into
small manageable data chunks, allowing the
small packets to be distributed over a wide
number of possible paths to balance traffic.
It is relatively inexpensive to replace damaged
data packets after they arrive, since if a data
packet is altered in transit only a single
packet must be retransmitted.

13. Protocols A protocol is a set of rules for the exchange of data across
communication lines.
Protocols need to handle the following tasks:
Format messages
Order Data in message
Compress message
Provide Error checking on message

14. Most Popular Internet Protocols
The most popular Internet protocols include:
TCP/IP: Transmission Control Protocol/Internet Protocol
FTP: File Transfer Protocol
HTTP: Hypertext Transfer Protocol
protocols: SMTP, POP, IMAP
Each protocol is used for a different purpose, but all of them are important.

15. TCP/IP The protocols that underlie the basic operation of
the Internet are TCP (transmission control
protocol) and IP (Internet protocol).
Establish rules about how data are moved across networks
and how network connections are established and
broken.

16. Purposes of Each TCP controls the assembly of a message into
smaller packets before it is transmitted over
the network. It also controls the reassembly
of packets once they reach their destination.
The IP protocol includes rules for routing
individual data packets from their source to
their destination. It also handles all addressing
details for each packet. More on addressing later.

17. TCP/IP Architecture

18. General Layer Properties
Full discussion of the TCP/IP Architecture beyond
the scope of this class.
Useful to understand where each protocol resides:
TCP operates in the transport layer.
IP operates in the Internet layer.
HTTP, SMTP, POP, IMAP and FTP operate in the
application layer.

19. File transfer protocol
FTP (file transfer protocol) is a part of TCP/IP
that allows files to be transferred between
computers connected using TCP/IP.
It uses the client/server model.
FTP permits files to be transferred in both
directions, that is, from the client to the server
or from the server to the client.
It can transfer files one at a time or many files
simultaneously.

20. Files types and FTP FTP allows the transfer of two types of files:
ASCII text: files containing only characters
available through the keyboard and containing
no formatting information.
Example: Files created using Notepad
Binary data: files containing word processed
documents, worksheets, graphics, etc.

21. Other Functions of FTP FTP has other useful functions:
Displaying remote and local computers’ directories
Changing the current client’s or server’s active
directories
Creating and removing local and remote directories.

22. Accessing with FTP There are two ways to access remote machines:
Full privilege FTP access: This requires that you
have an account on the remote computer and that
you supply your username and password.
Anonymous FTP: If you do not have an account
on the remote computer, you can type anonymous
as the username and your address as the
password and obtain limited access to the remote
computer.
You can use an FTP client program or Web browser
interface for FTP.

23. Browsing Through Files
Once you have logged into your account using FTP you can
browse through the files located in your account.
You do this by double clicking on the folders that appear.

24. FTP with a Browser To use a browser as an interface with FTP:
Type
This will bring up a window that prompts you
for your password.
Type in your password (being careful to type
it correctly) and hit enter.
The files in your main directory will appear. Note: Be sure to check that browser doesn’t store password. Look at Tools/Internet Options/Content/AutoComplete.

25. Creating Directories To create a directory on students.depaul.edu
using the browser interface:
Select File
Select New
Select Folder
Click on the folder and give it the name
you wish it to have.

26. Moving Files Once you have created a public_html directory, you
can move your HTML files into that directory.
In order to do that:
Open up the directory into which you wish to
move the file.
Open the folder where the file is located on your
local machine.
Select Edit/Copy or drag the file directly into the
directory.

27. HTTP HTTP (hypertext transfer protocol) is the protocol
responsible for transferring and displaying Web
pages.
It has continued to evolve since being introduced.
Like other Internet protocols, HTTP uses the client/
server model of computing. Thus, to understand
how HTTP works, we need to first discuss the
client/server model.

28. Client/Server model
In the client/server model there are two roles: the
client and the server.
The client process makes requests of the server.
The client is only capable of sending a request
to the server and then waiting for the reply.
The server satisfies the requests of the client. It
usually has access to a resource, such as data,
that the client wants. When the resource that
the client wants becomes available, it sends a
message to the client.
This model simplifies communication.

29. Client/Server Model

30. HTTP and Client/Server
With HTTP the client is the user’s Web browser
and the server is the Web server.
To open a session, the browser sends a request
to the server that holds the desired web page.
The server replies by sending back the page or an
error message if the page could not be found.
After the client verifies that the response sent was
correct, the TCP/IP connection is closed and
the HTTP session ends.
Each new page that is desired will result in a new
HTTP session and another TCP/IP connection.

31. One Page, Multiple Requests
If a Web page contains objects such as movies,
sound, or graphics, a client must make a
request for each object.
For example, a Web page containing a back-
ground sound and three graphics will result in
five separate server request messages to retrieve
the four objects plus the page itself.

32. Mail protocols Electronic mail is managed and stored by programs
and hardware collectively known as mail servers.
It is displayed and created using mail programs
such as Eudora, Pine, Unix mail, Outlook, Web interface mail programs.
Protocols are necessary for the mail programs to
construct requests to receive and for the
mail servers in downloading and/or deleting .
The protocols we will discuss use the client/
server model.

33. SMTP SMTP (simple mail transfer protocol) is used by
client mail programs to make requests about
mail delivery.
A wide variety of mail programs such as Eudora,
Unix mail, and PINE, use SMTP to send mail
to a mail server.
The SMTP specifies the exact format of a mail
message and describes how mail is to be
administered.

34. POP POP is responsible for retrieving e-mail from a server.
It requests that the mail server either retrieve
mail from the mail server and then delete it,
retrieve mail from the server without deleting
it, or simply ask whether new mail has come
but not retrieve it.
When is read, POP specifies that it must
be downloaded to your computer from the
server. Read is not kept on the server.

35. IMAP
IMAP (Internet Message Access Protocol) is a newer protocol that, like POP, can ask if there is new mail, download , and delete .
IMAP has capabilities that POP does not:
It defines how a client program asks a mail
server to present available mail.
It can allow you to manipulate and manage
without downloading it from the server.

36. Internet Addresses Internet addresses are represented in several ways,
but all the formats are translated to a 32-bit number
called an IP address; a function of Internet Protocol (IP)
The increased demand for IP addresses will soon
make 32-bit addresses too small, and they will be
replaced with 128-bit addresses (IP v6.0) in the near future.
How does increasing the number of bits in the address help
with increasing demand?

37. Dotted Quads IP numbers appear as a series of up to 4 separate
numbers delineated by a period.
Examples:
Each of the four numbers can range from 0 to 255, so
the possible IP addresses range from to

38. Elements of Internet Addressing

39. Domain Names Since IP numbers can be difficult for humans to
remember, domain names are associated with
each IP address.
Examples:
A domain name server is responsible for the mapping
between domain names and IP addresses.
Domain names and IP addresses are registered separately. Registering domain name doesn’t imply getting an IP address. IP address is from hosting service.

40. Uniform Resource Locator
People on the Web use a naming convention called the
uniform resource locator (URL).
A URL consists of at least two and as many as
four parts.
A simple two part URL contains the protocol
used to access the resource followed by the
location of the resource.
Example:
A more complex URL may have a file name
and a path where the file can be found.

41. Anatomy of an eMail Address
yahoo . com
Handle
Domain
Type
Host/Server

42. Domain types .com .edu .gov .mil .net .org .biz .info .aero .coop
Commercial organizations or businesses
.edu
Educational institutions
.gov
U.S. government agencies
.mil
U.S. military
.net
Network computers
.org
Nonprofit organizations and foundations
.biz
business firms
.info
information providers
.aero
Air transport industry
.coop
Cooperatives
.museum
Museums
.name
Individuals
.pro
Professionals

43. HTML HTML – Hypertext Markup Language
One of the languages with the parent SGML – Standard Generalized Markup Language
HTML provides Web page designers with a fixed set of markup “tags” that are used to format a Web page

44. HTML Example

45. HTML TOOLS