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Introduction to Internet

10.1 INTRODUCTION

In the present age of information Technology, use of Internet is

becoming quite popular for accessing information on any topic

of your interest. It also provides tremendous opportunities to

students; researchers and professionals for getting information

on matters related to academic and professional topics and lot

more. In the present world, most of the people who have

computers around themselves use Internet to access information

from the World Wide Web, exchange messages & documents and

e-services.

10.2 OBJECTIVES

After going through this lesson you would be able to:

l define Internet

l list different types of Internet connections

l explain various services provided by Internet

l download files

l send and receive e-mail

l be acquainted with the terminologies used in Internet

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Introduction to Internet :: 243

10.3 WHAT IS INTERNET?

The Internet or simply the Net is a worldwide network of computer

networks. It is an interconnection of large and small networks

around the globe.

10.4 APPLICATIONS OF INTERNET

With the help of Internet you can:

l Exchange messages using e-mail (Electronic mail).

l Transfer files as well as software.

l Browse through information on any topic on web.

l Communicate in real time (chat) with others connected to

the Internet.

l Search databases of government, individuals and

organizations.

l Read news available from leading news groups.

l Send or receive animation and picture files from distant

places.

l Set up a site with information about your company’s

products and services.

10.5 GETTING INTERNET CONNECTION ON YOUR

COMPUTER

Any terminal to activate internet

services on it require a internet

connection from a Internet

Service Provider. To have a

connection one needs to contact

the Internet Service Providers.

There are several Internet

Service Providers (ISP) in each

locality. There are some nominal

charges that you need to pay to

the ISP for the installation of the connection and for the rent (either

monthly or annually). Depending on the requirement you can

Fig. 10.1

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choose any one of the available options. If you need a high speed

dedicated network then you can opt for a high bandwidth

broadband or leased line connection.

If you need to have connection on a single PC then you choose a

low bandwidth or dialup connection . For small services at your

hand you can even have mobile phones connected to your

Internet. There are many ways to get connected to the Internet.

You can get internet connection in any of the following ways:-

1. through dial-up connection : user is supposed to get

connected to the internet after dialing up the number used

for connection. This is useful if your network is either

confined to small group of computers or for a single PC.

2. through leased lines: in this a dedicated line is laid

specifically for connection.

3. though broadband: in this you can get a broadband

connection which provides a high bandwidth for the internet

connection. This also provides a good speed.

These days even wireless connections are available. For this you

need to have a Wi Fi card attached to your computer which can

be useful if you do not have proper place to lay down the wires.

To connect to the Internet you need a PC (personal computer)

with requisite software including a browser, a telephone

connection or a leased line, and a modem, which allows the PC

to communicate with other computers.

10.5.1 Types of Internet Connections

(a) Dial-up

This is the most common basic type of connection available from

ISPs (Internet Server Providers). In Dial-up connection, you use

your computer, dial a phone number (provider by ISP) to get

connected to server at Providers end through which you access

Internet. It means you are not directly connected to Internet; you

access the Internet through an Internet Service Provider.

(b) ISDN (Integrated Services Digital Network)

The process of connecting to server to access Internet is almost

same as Dial-up, but it offers connectivity through the use of

Introduction to Internet :: 245

digital phone lines instead of Analog. It offers Internet connectivity

at speeds of up to 128 Kbps, allows the user to receive or make

calls simultaneously on the same line. ISDN comes through a

regular telephone wire from the telephone pole on the street. The

line combines two 64 Kbps channels to offer 128 Kbps bandwidth

broken into three bands: One band for the ringing signal of your

phone, one band for your telephone conversation, and one band

for data transfer.

(c) Leased Line Connection (Direct Internet Access)

A “permanent connection” between a computer system (single

CPU or LAN, and the Internet). It is generally used by larger

institutions, corporate and government agencies. It involves

establishing your own Internet gateway (connection) and payment

to have a direct full time line with the network. Your computers,

in effect, become part of the Net. The main advantage of this

connection is that: it is on line – 24 hrs a day, seven days a week,

(24x7) and provides faster access.

Dedicated links are established through an internet service

provider who places a computer-controlled router (message

director) at your site. A router is used to connect your local

network to the Internet, allow all the members of network to have

complete access to Internet.

(d) DSL (Digital Subscriber Line or Dedicated Service Line)

Broadband Connection

DSL, an “always-on’ data connection is becoming widely available

these days. It can provide an excellent Internet connection. It

connects your home or office to the Internet through the same

telephone wire that comes from telephone pole on the street. Like

ISDN, with DSL, user can make and receive telephone calls while

connected to the Internet. The difference between DSL and dial-

up / ISDN is that a DSL Internet connection uses a high-speed

dedicated circuit filtering out standard phone calls and Internet

signals.

10.6 HOW DOES INTERNET WORK?

The thing that characterizes the Internet is how data are

transferred from one computer to another. Did you ever wonder

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what magical things go on behind the scenes that results in a web

page being displayed on your screen seconds after you request

it? How does the data moves from one side of the world to the

other?

Fig. 10.2

Here is what happens to a piece of data (e.g. a Web page) when

it is transferred over the Internet:

l It is broken into a lot of same-sized pieces (called

packets).

l A header is added to each packet that explains where it

came from, where it should end up and how it fits in with

the rest of the packets.

l Each packet is sent from computer to computer until it

finds its way to its destination. Each computer along the

way decides where next to send the packet. This could

depend on things like how busy the other computers are

when the packet was received. The packets may not all

take the same route.

l At the destination, the packets are examined. If there is

any packet missing or damaged, a message is sent asking

for that packet to be resent. This continues until all the

packets have been received intact.

l The packets are reassembled into their original form.

Each computer connected up to the Internet has a software called

TCP/IP (Transmission Control Protocol/Internet Protocol), which

is responsible for receiving, sending and checking packets. TCP/

IP is the ‘glue’ of the Internet.

What is the Internet? To explain what the Internet is, we’ll start from the bottom up.

What is a Network? Most of the time, PC users work on their own with their PC connected to nothing more exciting than a printer. However, it has always been possible to connect two PCs with a piece of wire so that they can communicate – usually just to transfer files.

This, in essence, is all a network is – two or more computers connected by a physical piece of wire. The connection between the two computers is then managed and operated by some special software.

Local Area Networks It makes sense, most often for financial reasons but also for others, to network groups of computers where they share a common workload. Networking computers means that the people using them can share files easily, send each other messages and share each other’s printers. This idea has developed into Local Area Networks (LANs). Nowadays most organisations have a local area network. LANs can be as small as just one shared office or as large as a whole city.

Wide Area Networks In some cases an organisation is spread over a large area, and you do not have the easy concentration of computing to provide a LAN for. In this instance computers may be connected by a Wide Area Network (WAN). The difference between a WAN and a LAN is partly one of scale (although this is relative) but also relates to the technology. With a LAN you will typically get a fast network that can network PC file servers. With a WAN the network will often be much slower and will usually involve some mainframe computer as the server rather than a PC.

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Combinations of Networks

LANs and WANs are not mutually exclusive. In fact they combine very well together. Many organisations now have both, where a WAN has been created by connecting up a series of LANs. A good example of this is the Academic Community. Every University has its own LAN providing email, printing, file sharing and other facilities. Then every University is connected to the Joint Academic Network (JANET) which is a WAN running the length of the country. Through JANET someone in Leeds can log into a mainframe computer in Southampton.

The Internet If you take the principle of small, locally-managed, networks connected up to form a larger network, which in turn is connected up to form a larger network, and so on, you get some idea of what the Internet is. Physically it is just a collection of LANs and WANs that have been connected up at a national and international level.

The Internet is more than this, however. It not only is the physical wire, but also how information is sent from one computer to another. Take the example of making a road journey. If you are sending someone in a car to go somewhere, you can do one of two things: • give them precise written details of how to get to their destination.

As they have no other means of finding their way they will have to stick to your instructions even if they can see roadworks ahead.

• give them a map and let them find their own way. If roadworks, or some other blockage occurs then the person can either read the map and work out a fresh route, or else follow the diversion signs.

Originally information on networks followed the first method – it was given precise instructions on how to reach its destination. However, if there was a hold-up, say a computer was switched off, the information was also held up until the hold-up cleared.

Now information is more intelligent and can work out its own route, so if there is a hold-up it will try and get through some other way. It’s all rather clever, and was invented by the American Defence Industry who asked “If someone dropped a very large bomb on our computer network, would it still function?”. The intelligent information transfer – a mechanism called the Internetworking Protocol (hence “Internet”) – means now that it can.

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What do you do with the Internet? Talk to other people

A traveller was very impressed by a hotel in Hong Kong. Upon arrival at the hotel from the airport, he checked in, and went to his room. When the TV was switched on there was a message waiting for him on the TV screen.

This system is available to everyone who uses the Internet. To get on to the Internet you have to have an identification unique to you called your username. Everyone who connects to the Internet has a username, and if you have their username and the name of the machine they log into you can send a message to that username and they will receive it when they next log in. This system is called Electronic Mail or email for short.

The basic concepts behind email parallel those of regular mail. You send mail to people at their particular addresses. In turn, they write to you at your email address. You can subscribe to the electronic equivalent of magazines and newspapers. If you have email you will almost certainly get electronic junk mail (or spam) as well.

Email has two distinct advantages over regular mail. The most obvious is speed. Instead of several days, your message can reach the other side of the world in hours, minutes or even seconds. The other advantage is that once you master the basics, you’ll be able to use email to access databases and file libraries as well as transfer files and programs.

Email also has advantages over the telephone. You send your message when it’s convenient for you. Your recipients respond at their convenience. No more frustration whilst you phone someone who’s out, then they phone you back whilst you’re out. And while a phone call across the country or around the world can quickly result in huge phone bills, email lets you exchange vast amounts of mail for only a few pennies – even if the other person is on the other side of the earth.

Email is your connection to help – your Net lifeline. The Net can sometimes seem a frustrating place! No matter how hard you try, no matter where you look, you just might not be able to find the answer to whatever is causing you problems. But when you know how to use email, help is often just a few keystrokes away: you can ask your system administrator or a friend for help in an email message.

Even if you use the Internet for no other purpose, email makes getting a connection worthwhile all by itself. Very quickly you’ll find yourself writing to friends who are on the Internet, contacting colleagues interested in similar professional areas all round the world, discussing politics and asking for advice on how to use some of the software on your computer. It is very powerful and incredibly cheap.

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Many-to-Many Discussions Mailing Lists Mailing Lists can be used to share information via email with people who have a common interest.

An electronic mailing list is quite similar to a postal mailing list in that it is a method of distributing the same information to lots of different people. Mailing lists are typically used to discuss work with colleagues at other Universities, share news, collaborate on projects and publications, announce jobs and conferences and keep in touch with current developments in your subject area.

In order to get information from an email mailing list you need to subscribe − that is, you need to ask that your name be added to the list. Other people can then send information to you and others on the mailing list simply by posting a message to a single email address. These messages are then automatically forwarded on to all members of the list.

How Do You Find Mailing Lists?

There are a number of different services you can use for finding out about what mailing lists exist, and how you can join them.

The National Academic Mailing List Service (JISCmail) is based at the Information Technology Department, Rutherford Appleton Laboratory. It hosts a wide number of different mailing lists for the academic community in the UK. This service was formerly known as Mailbase at the University of Newcastle. To explore the mailing lists hosted by JISCmail you can connect to their home page on the web: http://www.jiscmail.ac.uk

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1.0 Introduction

The purpose of the networking guidelines are as follows:

to assist students in understanding the benefits of networking to help students place in context their current stage of networking

development in their school. to assist students in planning the next stage of network development

in their school. to provide standard networking ‘models’ and best practice to students

that will assist students in their network planning. This document includes information under the following main headings:

Introduction to Networking Advantages of Networking Types of Networks Models of networking appropriate to students NCTE recommendation to students Some relevant terms.

1.1. Basic of Networking A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other. Fig 1 gives an example of a network in a school comprising of a local area network or LAN connecting computers with each other, the internet, and various servers.

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Fig 1: Representation of Network in a school.

Broadly speaking, there are two types of network configuration, peer-to-peer networks and client/server networks. Peer-to-peer networks are more commonly implemented where less then ten computers are involved and where strict security is not necessary. All computers have the same status, hence the term 'peer', and they communicate with each other on an equal footing. Files, such as word processing or spreadsheet documents, can be shared across the network and all the computers on the network can share devices, such as printers or scanners, which are connected to any one computer.

Fig 2: Peer to Peer Networking Client/server networks are more suitable for larger networks. A central computer, or 'server', acts as the storage location for files and applications shared on the network. Usually the server is a higher than average

File and Print Server CD or Multimedia Servers

Other users, computers

Users computers

Cache, Proxy, Filtering, Firewall Server

Access to: Internet content & learning resources, Scoilnet etc Email communication

Modem or Router

School ‘Local Area Network’ (LAN)

Peer to Peer Network

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performance computer. The server also controls the network access of the other computers which are referred to as the 'client' computers. Typically, teachers and students in a school will use the client computers for their work and only the network administrator (usually a designated staff member) will have access rights to the server.

Fig 3: Client - Server Networking Table 1 provides a summary comparison between Peer-to-Peer and Client/Server Networks.

Peer-to-Peer Networks vs Client/Server Networks Peer-to-Peer Networks Client/Server Networks Easy to set up More difficult to set up Less expensive to install More expensive to install

Can be implemented on a wide range of operating systems

A variety of operating systems can be supported on the client computers, but the server needs to run an operating system that supports networking

More time consuming to maintain the software being used

Less time consuming to maintain the software being used (as most of

Other equipment

File Server

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(as computers must be managed individually)

the maintenance is managed from the server)

Very low levels of security supported or none at all. These can be very cumbersome to set up, depending on the operating system being used

High levels of security are supported, all of which are controlled from the server. Such measures prevent the deletion of essential system files or the changing of settings

Ideal for networks with less than 10 computers

No limit to the number of computers that can be supported by the network

Does not require a server Requires a server running a server operating system

Demands a moderate level of skill to administer the network

Demands that the network administrator has a high level of IT skills with a good working knowledge of a server operating system

Table 1: Peer-to-Peer Networks vs Client/Server Networks Components of a Network A computer network comprises the following components:

A minimum of at least 2 computers Cables that connect the computers to each other, although wireless

communication is becoming more common (see Advice Sheet 20 for more information)

A network interface device on each computer (this is called a network interface card or NIC)

A ‘Switch’ used to switch the data from one point to another. Hubs are outdated and are little used for new installations.

Network operating system software Structured Cabling The two most popular types of structured network cabling are twisted-pair (also known as 10BaseT) and thin coax (also known as 10Base2). 10BaseT cabling looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. Thin coax looks like the copper coaxial cabling that's often used to connect a Video Recorder to a TV.