Network Infrastructure for E-Commerce

Network Infrastructure for E-Commerce

 Structure

1 Introduction Objectives

2 Local Area Network (LAN)

3 Ethernet: IEEE 802.3: Local Area Network (LAN) Protocols

4 Wide Area Network (WAN)

5 The Internet

6 TCP/IP Reference Model

7 Domain Names

8 Hyper Text Markup Language (HTML)

9 Summary

10 Glossary

1 Introduction 

In this unit, you will be learning about the network
infrastructure for e-commerce, including topics such as Local Area Network
(LAN), Ethernet, Wide Area Network (WAN), the Internet, TCP/IP Reference
Model, Domain Names, and Hyper Text Markup Language (HTML).
You may know by now that that all the services of e-commerce work on
the Internet which is known as the ‘network of networks’. Computer network is
a collection of more than two computers, which are connected together to share
information and computer peripherals. The key word in the definition is ‘sharing’,
the main function of computer networking. The ability to share information
efficiently is what gives computer networking its power and appeal. Through
the efforts of all major factors involved—the sharing of time, talent, and
resource—the primary goal of computer networking is to reduce resources.

Objectives

After studying this unit, you should be able to:
• Give examples of the importance of Local Area Network (LAN)
• Generalize the workings of Ethernet (IEEE 802.3)
• Demonstrate the working of Wide Area Network (WAN)
• Summarize the importance of the Internet
• Evaluate the TCP/IP Reference Model
• Discuss the functioning of domain names
• Summarize the highlights of Hyper Text Markup Language (HTML)

2 Local Area Network (LAN)

A LAN (refer to Figure 2.1) covers only a limited geographically area ranging
from 0 to 2 Km, such as organizations, home, buildings. In a local area network,
nodes are connected in a network and operating systems are installed on them.
In this type of networking, generally, Cat 5 cable (8 wires) is used, meaning the
connection is done through wire. However, there is another option of connecting
LAN, which is WLAN, where connection is possible without wires. LAN stores
the system and application software that can be shared by the computers to
other computers and peripherals. Most LANs connect nodes and computers.
They have their own CPU for executing programs. The importance of LAN in an
organization is very high because users can easily communicate to each other
through LAN and they can share resources such as printers, memories, database
and other peripherals of network.

                                                     Figure 2.1 Local Area Network

Metropolitan Area Network (MAN): 

Metropolitan Area Network or MAN (referto Figure 2.2) occupies a larger area compared to LAN, such as a town or a university/organization premises (which is spread between 05 km to 20 km). It
incorporates a number of LANs to form a network. This bulky network comprises of an optical fibre setup. MAN connects the computer system, other resources and some times local area network to a range from 5 to 50 km, meaning it can effectively cover a town. It uses high speed data transfer mediums like fibreoptic, coaxial cable, etc.

Figure 2.2 Metropolitan Area Network

3 Ethernet: IEEE 802.3: 

Local Area Network (LAN) Protocols IEEE 802.3 is covered by a small area (Local Area Network). It refers to the family of Ethernet Protocols. There are two methods of process in Ethernet standard: first is half-duplex and second is a full-duplex mode. In the half duplex mode, data are transmitted using the popular Carrier-Sense Multiple Access/Collision Detection (CSMA /CD) protocol on a shared medium. The main disadvantages of the half-duplex are effectiveness and space limitation, in which the link distance is limited by the minimum MAC frame size. This restriction reduces the effectiveness drastically for high-rate transmission. Therefore, the carrier extension technique is used to make sure that the minimum frame size of 512 bytes in Gigabit Ethernet gets a reasonable link distance. Four data rates are currently defined for operation over optical fiber and twisted-pair cables. These are:
(i) 10 Mbps - 10Base-T Ethernet (IEEE 802.3)
(ii) 100 Mbps - Fast Ethernet (IEEE 802.3u)
(iii) 1000 Mbps - Gigabit Ethernet (IEEE 802.3z)
(iv) 10-Gigabit - 10 Gbps Ethernet (IEEE 802.3ae)

4 Wide Area Network (WAN)

A WAN (refer to Figure 2.3) crosses almost whole geographic areas, such as
nations. WANs often connect n number of smaller networks. Communication
medium of this networks are telephone line, satellite links, microwave, etc. In
other words, a Wide Area Network (WAN) is a bulky communication of network
that consists of a group of LANs and other different networks (refer to Table
2.1). WAN generally crosses a big geographical area, and can be used to connect
cities, states, or even countries.

                                                       Figure 2.3 Wide Area Network

 

                                                         Table 2.1 Wide Area Network

5 The Internet

The Internet is the network of networks or a means of connecting a computer or
network to any other computer or network in the world, through specific network
components and servers. When two computers are connected over the Internet,
they can exchange all types of information, such as video, computer programs,
text, graphics and voice.

 It is not possible for one to make an Internet. Still, organizations around
the world over collaborate in its functioning and development. The high-speed,
fibre-optic cables (called backbones) through which the bulk of the Internet
data travels are owned by telephone companies in their respective countries.
The Internet grew out of the Advanced Research Projects Agency’s Wide Area
Network (then called ARPANET) recognized by the US Department Of Defense
in 1960s for collaboration in military research among business and government
laboratories. Later universities and other US institutions connected to it. This
resulted in ARPANET growing beyond everyone’s expectations and acquiring
the name ‘Internet’. The development of hypertext based technology (called
World Wide web, WWW, or just the Web) provided means of displaying text,
graphics, and animations, and easy search and navigation tools that has triggered
the Internet’s explosive worldwide growth.

6 TCP/IP Reference Model

The builder of the TCP/IP protocol group created their own architectural model
to help describe its components and functions. This model goes by different
names, including the TCP/IP model, the DARPA model (after the agency that
was largely responsible for developing TCP/IP) and the DOD model (after the
United States Department of Defense, the “D” in “DARPA”).
In spite of the model you use to represent the function of a network—and
regardless of what you call that model—the functions that the model representsare pretty much the same. This means that the TCP/IP and the OSI models are
relatively same in nature even if they do not carve up the network functionality
pie in precisely the same way. There is a fairly natural correspondence between
the TCP/IP and OSI layers; it just isn’t always a ‘one-to-one’ relationship. Since
the OSI model is used so widely, it is common to explain the TCP/IP architecture
both in terms of the TCP/IP layers and the corresponding OSI layers.

                                              Figure 2.4 TCP/IP Layer Communications

 

Characteristics of Gateways

• Gateway routers are used to connect dissimilar LANs and perform all the
functions of bridges and routers. It operates as all seven layers of the
OSI Reference Model.
• Gateways provide full protocol conversion from one proprietary LAN
technology to another.
• Gateway uses higher layers of the OSI model, perhaps through layer 7,
the application layer.

                             Figure 2.5 TCP/IP Reference Model for Communication

 

The TCP/IP model (refer to Figure 2.5) has four layers that match six of
the seven layers in the OSI Reference Model. The TCP/IP model does not
address the physical layer, which is where network component and hardware
devices reside. The next three layers—network interface, the Internet and (hostto-
host) transport—correspond to layers 2, 3 and 4 of the OSI model. The TCP/
IP application layer conceptually ‘blurs’ the top three OSI layers. It is important
to note that some people consider certain aspects of the OSI session layer to
be possibly part of the TCP/IP host-to-host transport layer.

7 Domain Names

As numeric strings are hard to remember, which make up the IP address, all
servers on the Internet also have human-readable names, called domain names.
For instance, it is easier for us to remember www.sriram.ac.in than
134.45.56.178. An organization might block all access to certain domain names
or allow access only to specific domain names. A domain name always contains
two or more components separated by ‘dots’; for example microsoft.com,
tcs.co.in, etc. The last portion of the domain name is the top label domain name
and describes the type of organization. The major types of top label domain
names are:

com : represents commercial entities
org : represents miscellaneous organizations that do not fit any other
         category, such as non-profit group.
edu : represents educational institutions
net : represents organizations directly involved in Internet operations
gov : represents the United States Federal Government Entities
mil : represents the military of the United States

Country Codes: 

This is a two-letter abbreviation for a particular country; for

example ‘in’ represents India, ‘uk’ represents the United Kingdom, and ‘fr’
represents France.

8 Hyper Text Markup Language (HTML)

HTML is a method where ordinary text can be converted into hypertext. It is a
set of special codes included to control the layout and appearance of the text.
Technically, HTML is not a programming language. It combines instruction within
data to tell a display program called browser, how to render the data that the
document contains.
The following is the structure of HTML:
<html>
<head> about authors </head>
<title> First Page </title>
<body>
<h1> Hello this my Home page!
</body>
</html>

< HTML>: 

This tag defines the top most elements, identifying it as an HTML document.

<Head>:

 This tag contains information about your HTML file.

<Title>: 

This tag is nested within the head tag. It identifies your page to the
rest of the world. Output of tag is displayed on your browser’s title bar but does
not appear as part of the page.

<body>:

This is a body part of your HTML web page. Within this tag all the
various tag is used. Every tag has prespecified attributes and there possible
values.

Levels of Heading: 

Six different levels up to <h1>,<h2>,<h3>,<h4>,
<h5>,<h6>

Adding a comments:<! - - and ends with — >

Creating List: 

There are two types of list : ordered list and unordered list.

Ordered List:

<ol>
<li> MS-Windows
<li> MS-Excel
<li> MS-Word
</ol>

Unordered List:

<ul>
<li> MS-Windows
<li> MS-Excel
<li> MS-Word
</ol>

Creating Definition Lists:

A glossary consists of three tag elements:
<dl>: Define the List
<dt>: Define term
<dd>: Define the definition

Inserting Images:

To insert images in your page use <img> tag as follows:
<img src=”flower.gif” height=”100" width=”100" border=”1">

Linking the HTML page:

To link one HTML to another use anchor tag as follows:
<a href = “first.html” > Click me </a>

Setting font size:

We can set font of text by using font tag as follows:
<font face=”Arial” size=”4" color=”red”>

Marquee tag:

This tag offers some movement from up, down, left, right of given text:
<marquee direction=”up” bgColor=”red” behavior=”scroll”> MY Moving Text
is displayed here </marquee>

Table tag:

Page layout on the web has to be set by using tables because HTML has no
method to set margin or columns.
Example:
<table border=”1" cellspacing=”6" cellpadding=”6"
width=”80%”>
<tr> <th> Roll no </th>
<th> Name </th>
</tr>
<tr> <td> 34 </td>
<td> Pooja </td>
</tr>
<tr> <td> 35 </td>
<td> Priya </td>
</tr>
</table>

Form tag:

Form tag is an important element for doing online business. Forms are necessary
for gathering user information, conducting surveys, or even providing interactive
services. Forms are supported by both client and server for successful
implementation. A number of features are available for building forms, including
text boxes, check boxes, radio buttons, submit buttons and text area. A user
can enter text, selects items from a list, check boxes, and then submit the
information to the server. A program on the server then interprets the data acts
on it appropriately, either by returning information in hypertext form, downloading
a file, or electronically notifying the company of your order.

The corresponding coding of above HTML form is given below:

<form method=”post” action=”/cgi-bin/purchase.asp”>

Item Name: <input type=”text” name=” item_name” value=” CD”> <br>
Item Code: <input type=”text” name=”code” value=”CD_Mos_2" > <br>
Number of Quantity: <input type=”text” name=” Qty” value=”4" > <br>
           <input type=”submit” value=”submit”>

Generating forms in HTML is only half the task. The harder part is to
decode the input data submitted from the form. All the programs use data
submitted from the form. All the programs that use data submitted from an
HTML form must conform to the specification called Common Gateway Interface
(CGI).
The important aspect of web server development is application gateway,
more specifically, CGI, which is a specification for communicating data between
an information server, in this case, Web server, and another application. CGI is
used wherever the web server needs to send or receive data from another
application, such as a database. A CGI script is a program that negotiates the
movement of data between the Web server and an outside application.
Use of CGI is to pass data, filled in by a user in an HTML form, from the
web server to a database. Data also can be returned to the user’s browser via
CGI. CGI scripts may be written in high level language such as C and Perl,
because they can run so many platforms.

9 Summary

Let us recapitulate the important concepts discussed in this unit:
• Computer network is a collection of more than two computers, which are
connected together to share information and computer peripherals.
• A LAN covers only a limited geographically area ranging from 0 to 2 Km,
such as organizations, home, buildings.
• MAN occupies a larger area compared to LAN, such as a town or a
university/organization premises (which is spread between 05 km to 20
km) is termed as Metropolitan Area Network or MAN.
• IEEE 802.3 is covered by small area (Local Area Network). It refers to the
family of Ethernet Protocols. We have two methods of process in Ethernet
standard: first is half-duplex and second is a full-duplex mode.
• A Wide Area Network (WAN) crosses almost whole geographic areas,
such as nations. Communication medium of this networks are telephone
line, satellite links, microwaves, etc.
• The Internet is the network of networks and a means of connecting a
computer or network to any other computer or network in world through
specific network components and servers.
• The builder of the TCP/IP protocol group created their own architectural
model to help describe its components and functions. This model goes
by different names, including the TCP/IP model, the DARPA model (after
the agency that was largely responsible for developing TCP/IP) and the
DOD model (after the United States Department of Defense, the “D” in
“DARPA”).
• HTML is a method where ordinary text can be converted into hypertext. It
is a set of special codes included to control the layout and appearance of
the text. Technically, HTML is not a programming language.

10 Glossary

• Computer network: 

Collection of more than two computers, which are
connected together to share information and computer peripherals

• LAN: 

Supplies networking capability to a group of computers in close
proximity to each other such as in an office building, a school, or a home

• MAN: 

Metropolitan Area Network; covers a wider area than LAN

• WAN: 

Network that crosses almost whole geographic area, such as nation
and all over world; WANs often connect n number of smaller networks

• The Internet: 

Network of networks and a means of connecting a computer
or network to any other computer or network in the world through specific
network components and servers

• HTML: 

Method where ordinary text can be converted into hypertext; it is
a set of special codes included to control the layout and appearance of
the text

• Protocol: 

A set of rules that control the way data is sent between
computers

• Architecture: 

The design and structure of a computer system