Bba401 Slm Unit 02

Unit 2 Network Infrastructure forE-Commerce - I

Structure

2.1 Introduction

Objectives

2.2 Local Area Network (LAN)

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

2.4 Wide Area Network (WAN)

2.5 The Internet

2.6 TCP/IP Reference Model

2.7 Domain Names

2.8 Hyper Text Markup Language (HTML)

2.9 Simple Exercises in HTML

2.10 Summary

2.11 Glossary

2.12 Terminal Questions

2.13 Answers

References

2.1 Introduction

In the previous unit, you learnt about the definition and origin of e-commerce,

the history of the Internet, and the difference between e-commerce and traditional

business, among other topics. 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.

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Sikkim Manipal University Page No. 22

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)

2.2 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

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Metropolitan Area Network (MAN): Metropolitan Area Network or MAN (refer

to 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 fibre

optic, coaxial cable, etc.

Multi-tenantCustomers

CoreNetwork

Basestation

Basestation

RepeaterSMECustomer

ResidentialCustomer

SOHOCustomer

Figure 2.2 Metropolitan Area Network

Self-Assessment Questions

1. Fill in the blanks with appropriate words.

(a) With ______ it is possible for the connections to take place without

wires.

(b) Metropolitan Area Network connects the computer system, other

resources and some times local area network to a range from 5 to

______ km.

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2.3 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)


2. State whether the following statements are true or false.

(a) IEEE 802.3 is covered by small area (Local Area Network).

(b) The main disadvantages of the half-duplex are effectiveness and

space limitation.

2.4 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.

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Figure 2.3 Wide Area Network

Table 2.1 Wide Area Network

Parameter LAN MAN WAN

Area covered Covers small area i.e. within the building

Covers large area. But smaller than WAN

Covers large geographical area

Error rates Lowest Moderate Highest

Transmission speed

High speed Moderate speed Low speed

Equipment cost

Uses inexpensive equipment

Uses moderately expensive equipment

Uses most expensive equipment



(a) With MAN, the error rates are highest.

(b) LAN has low transmission speed.

2.5 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.

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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.

Activity 1

What is the biggest contribution of the Internet to human society? Write a

500 word essay on the topic.



(a) When two computers are connected over the ________, they can

exchange all types of information.

(b) The high-speed, fibre-optic cables (called backbones) through which

the bulk of the Internet data travels are owned by __________

companies.

2.6 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 represents

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are 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.

Client Gateway/(Internet) Host

Application layer

Presentation layer

Session layer

Transport layer

Network layer

Data link layer

Physical layer

Application layer

Presentation layer

Session layer

Transport layer

Network layer

Data link layer

Physical layer

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.

1. Application

2. Transport

3. Internet

Represents data to the user plus encoding and dialog control.

Support communication between diverse devices across diverse networks (using TCP/IP).

Determines the best path through the Network (using gateway).

Controls the hardware devices and media that make up the network. 4. Network Layer

Figure 2.5 TCP/IP Reference Model for Communication

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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 (host-

to-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.



(a) The builder of the TCP/IP protocol group created their own

architectural model to help describe its components and functions.

(b) The TCP/IP model has two layers that match six of the seven layers

in the OSI Reference Model.

2.7 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

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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.



(a) A domain name always contains_______ or more components.

(b) _______ represents educational intuitions.

2.8 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.

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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>

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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.

Item Name:

Item ID:

Number of Quantity:

(Submit)

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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.



(a) HTML is a method where ordinary text can be converted into

hypertext.

(b) The important aspect of web server development is application

gateway, more specifically, CGI.

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2.9 Simple Exercises in HTML

Basic exercises

1. Create a webpage that prints a name ‘Vijay’ to the screen.

Solution:<html>

<body>

<!— print name to the screen —>

Vijay

</body>

</html>

On Screen: Vijay

2. Create a webpage and set its title to ‘It is good to be home’ to the screen, and

set the title of the page to the current date.

Solution:<html>

<head>

<!—set the title of the page to the current date—>

<title>October 15, 2011</title>

</head>

<body>

<!—print a message—>

It is good to be home.

</body>

</html>

On screen: It is good to be home.

HTML Text exercise

3. Prints the name ‘Vijay’ in Tahoma font.

Solution:<html>

<body>

<font face=”Tahoma”>Vijay</font>

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</body>

</html>

On screen: Vijay

Would the World Wide Web function without HTML? Research the Internet

and give reasons to support your answer.

2.10 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.

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2.11 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

2.12 Terminal Questions

1. Discuss the importance of LAN.

2. What is Ethernet (IEEE 802.3)?

3. Explain the term ‘Wide Area Network’. How is it different from LAN?

4. What is the Internet?

5. Discuss the main features of the TCP/IP Reference Model.

6. What are domain names? Explain.

7. Why is Hyper Text Markup Language (HTML) important? Discuss.

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2.13 Answers

Answers to Self-Assessment Questions

1. (a) WLAN; (b) 50

2. (a) True; (b) True

3. (a) False; (b) False

4. (a) Internet; (b) Telephone

5. (a) True; (b) False

6. (a) Two; (b) Edu

7. (a) True; (b) True

Answers to Terminal Questions

1. Refer to Section 2.2







References

1. Turban, Efraim, Jae Kuy Lee and Michael Chung. 1999. Electronic

Commerce: A Managerial Perspective. Prentice Hall.

2. Whitley, David. 1998. E-commerce: Strategy, Technologies and

Applications. Tata McGraw-Hill.

Bba401 Slm Unit 02

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