term paper on modem & internet by enamul & tanvir_ict_3rd batch_1st semester_2011

7/31/2019 Term Paper on Modem & Internet by Enamul & Tanvir_ICT_3rd Batch_1st Semester_2011

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COMILLA UNIVERSITYDepartment of ICT TERM PAPER ON MODEM AND INTERNET

Prepared For-

Khondokar Fida Hasan

Lecturer

Department of ICT

Prepared By-

Md. Enamul Haq

Class ID: 1109005

&

Md. Tanvir Ul Haque

Class ID: 1109017

Date of Submission: 25 April, 2012.



LETTER OF TRANSMITTAL

April 25, 2012

Khondokar Fida Hasan

Lecturer

Department of Information and Communication Technology

Subject : Submission of Term Paper Report.

Dear Sir,

By the grace of Almighty Allah, the most benevolent and merciful, your solitary help . We have

been successful to complete this report on the study of “Modem and Internet” that you have

asked to prepared.,

We have tried our best to make the report reliable within the given time period . We also tried to

discuss the topics elaborately and easily.

Though our intention was strong to make the report best and comprehensive . Neverthless,

some mistake might be occur, please notice these types of mistakes with sympathy. Your

suggestion and comments for the improvements of this report will be thankfully received and if

you need any quires about the study please call us.

Sincerely yours

Md. Enamul Haq &

Md. Tanvir Ul Haque



ACKNOWLEDGEMENT

Without the assist of dedicative and cognizant teacher a student cannot be able to nourish his

caliber forlorm . A conversant teacher nurture his learners judiciously through rendering them his

ultimate excellence . We are really greatful to our honourable course teacher of “Basic Electrical

Curcit” Khondokar Fida Hasan for providing us a chance to prepare a comprehensive term paper

report on “Modem and Internet”. To ensure our superior quality and prove our faculty this kind

of convention is really worth mentionable. We gratefully acknowledgement his relentless effort

for arranging such an aimable presentation program and helping us for preparing this term paper

report. Frome the core of our heart . We dedicating him our precious tribute and endless

homepage for helping us a lot so that we can prepare ourself properly. We hope in future also,we

will get his solitude indication that will help us to determine the apt route .



Introduction to the Modem and Internet Page# 01

History of Modem and Internet Page# 01

A brief discussion about Internet Page# 02-14

The World Wide Web

What is the World Wide Web?

Why do we use HTML?

How do I make a web page?Writing andPublishing

Hypertext and the Reader

Writing effective hypertexts

Good HTML Guidelines

Information Online

Evaluating Internet Resources

Searching Effectively

How Search Engines Work

Interactive Data on the Web

Further reading

Safe and Secure Surfing

Introduction to Security

Internet Wildlife

Defence Mechanismsr

Future Internet: where is cyberspace heading?

Trends in technology

ADSL and broadband communications

Bandwidth

Wireless technology

IPv6--the next generation



Ethics of the Internet

Advantages and disadvantages of internet

A brief discussion about Modem Page # 14-22

Modem at a Glance

Modem Types

What is Cable Modem and how it is work

Cable Modem Application

Typical Cable Systeem With Internet Access

Typical Cable Modem

The unified simulator and modem software model

How Fast Cable Modem Work

Cable Modem Service

Modem Selection Criteria

Cable Modem Standard

Relative Speed Comparisons

Telephone Modems(Fsk ,Psk,QAM)

Conclusion Page# 23

Bibliography Page# 24-25



INTRORUCTION TO MODEM AND INTERNET :

A modem is a device that modulates an analog carrier signal to encode digital information, and

also demodulates such a carrier signal to decode the transmitted information. The goal is to

produce a signal that can be transmitted easily and decoded to reproduce the original digital data.

Modems can be used over any means of transmitting analog signals, from light emitting diodesto radio. The most familiar example is a voice band modem that turns the digital data of a

personal computer into modulated electrical signals in the voice frequency range of a telephone

channel. These signals can be transmitted over telephone lines and demodulated by another

modem at the receiver side to recover the digital data. A modem (modulator-demodulator) is a

device that modulates an analog carrier signal to encode digital information, and also

demodulates such a carrier signal to decode the transmitted information.The goal is to produce a

signal that can be transmitted easily and decoded to reproduce the original digital data.

The Internet, sometimes called simply "the Net," is a worldwide system of computer networks -

a network of networks in which users at any one computer can, if they have permission, getinformation from any other computer .Today, the Internet is a public, cooperative, and self-

sustaining facility accessible to hundreds of millions of people worldwide. Physically, the

Internet uses a portion of the total resources of the currently existing public telecommunication

networks. Technically, internet is a common set of communication protocol for communication

between two computer on the network

A SHORT HISTORY OF MODEM AND INTERNET:

Digital modems developed from the need to transmit data for North American air defense during

the 1950s. In 1962, the first commercial modem was manufactured - the Bell 103 by AT&T. TheBell 103 was also the first modem with full-duplex transmission, frequency-shift keying or FSK,

and had a speed of 300 bits per second or 300 bauds .Two special men behind the modem:

Brent Townshend, the man who dreamed up the idea for 56K bit/sec modems. Robert Lucky

invented the automatic adaptive equalizer in 1965 at Bell Laboratories.

The internet has its root in the ARPANET system of the Advanced Research Project Agency of

the U.S. Department of Defence . ARPANET was the first WAN and had only four sites in 1969.

The Internet evoloved from the basic ideas of ARPANET for interconnecting computers, and

was initially used by research organization and universities to share and exchange information.

In 1989 , the U.S. Government lifted restrictions on the use of internet , and allowed it to beused for commercial purposeses as well.Since than , the Internet has rapidly grown to become

worlds largest network. It now interconnects more than 30000 networks, allowing more than 10

million computers , and more than 50000 million computers users in more than 150 countries all

around the world to communicate with each other. The Internet continues to grow at a rapid

pace.

http://en.wikipedia.org/wiki/Analog_signal

http://en.wikipedia.org/wiki/Digital_information

http://en.wikipedia.org/wiki/Signal_%28electronics%29

http://en.wikipedia.org/wiki/Light_emitting_diode

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Voice_band

http://en.wikipedia.org/wiki/Digital_data

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Electrical_signal

http://en.wikipedia.org/wiki/Voice_frequency

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/Telephone_lines

http://en.wikipedia.org/wiki/Telephone_lines

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/Voice_frequency

http://en.wikipedia.org/wiki/Electrical_signal

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Digital_data

http://en.wikipedia.org/wiki/Voice_band

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Light_emitting_diode

http://en.wikipedia.org/wiki/Signal_%28electronics%29

http://en.wikipedia.org/wiki/Digital_information

http://en.wikipedia.org/wiki/Analog_signal



A BRIEF DISCUSSION ABOUT INTERNET:

INTERNET SERVER , CLIANTS AND EXPONENTIAL GROWTH:The Internet, as a “network of networks”, consists of many computers, called server or host,

which are linked by communication lines. The administrators of these hosts may make

information or software stored on them publically available, so that others can view, downloador use the data. At the last count (Jul 2007), there were an estimated 489 million hosts connectedto the Internet. And hosts are increasing day by day.

Figure : Growth in number of Internet hosts

CONNECTION, PREMANENT OR DYNAMIC:

Clients may be permanently connected (often known as “always-on”), or may connect

dynamically when needed.A temporary, dynamic connection such as that provided by a modem

link needs to be connected each time the Internet is used, which can cause a delay. Modem links

also tend to be slower than dedicated digital links, because they use normal voice telephone lines

which are not designed to carry digital signals.Dedicated wiring for Internet traffic is most

commonly found in companies and other organisations, where a LAN is used to connect clients

and hosts together. Usually, this forms.an enclosed network which connects to the outside world

through a single point, which can be controlled and protected against intrusion and viruses.

Connection to this type of network is normally instantaneous and 'always-on'.

HOW DOES INFORMATION TRAVELS:

The Internet is based on packet-switched protocols. Information is carried in packets, which canbe imagined as small parcels being passed from computer to computer. Large chunks of data are

usually broken up into several smaller packets before being sent through the network. The

delivery mechanism, or protocol, that is used to encode the packet ensures safe transit, and



provides a way of reconstructing the data when it reaches its destination. The protocols used on

the Internet are referred to as TCP/IP, standing for Transmission Control Protocol Internet

protocol.

HOW FAST AND RELIABLE:

Another thing to look out for is the speed and reliability of the connection. This is partlydependent upon the speed of your modem and your computer, but also depends on your

ISPs(internet service provider) facilities too. Again it's worth shopping around to see which

service provides fastest access, and the quickest, most reliable connection. There are a number of websites that run independent tests and surveys on each of the major ISPs, so there's no shortage

of advice! It's also worth shopping around for extras, such as webspace and email boxes, domain

names, and even telephone deals. Remember, though, that if you use your ISP's email facilities,your email address will change each time you change your ISP; it's often better to have a

separate, permanent account from an independent email provider, such as Microsoft's hotmail

[http://www.hotmail.com/] or Google's gmail [http://mail.google.com/mail/help/intl/en/about.html].

WHO GOVERNS THE INTERNET:

This is a difficult question! The Internet grew as a collaborative network of researchers keen to

share their discoveries in a simple, accessible way. Because of this, there was no real need

to regulate or control the Internet; the information was already free and was of interest only to

other researchers, so it didn't need protection. But as the Internet has grown, it has become amore commercial, public entity, and some who use it now wish it to be governed and policed to

prevent certain types of abuse.

DOMAIN NAMES :

One form of control that is necessary (and possible) is the name service, which allocates Domain

Names on the Internet. These are unique names for subnetworks, which allow easier (human)

access to Internet addresses. So, instead of having to remember that Exeter's (numeric) addresses

all begin 144.173, you can just use .ex.ac.uk at the end of a name.

In the UK, these domain names (all ending in .uk) are managed by an organisation called

Nominet.UK . It delegates some UK addresses to other organisations, such as UKERNA

(for.ac.uk and .gov.uk addresses), but manages most itself.

INTERNET PROTOCOL ADDRESSES:

• System of unique numbers needed to find each host

• Managed by the Internet Assigned Numbers Authority (IANA) Every computer, server and other device that connects to the internet needs an address to be

found, and these need to be unique across the whole of the network. Managing to keep these

unique and ordered is the job of IANA, the Internet Assigned Numbers Authority.



WHO OWNS THE INTERNET:

This again is a difficult question. The individual networks and connections are owned by many

individual companies and organisations, and each makes the chunks it owns available to be used

to a greater or lesser extent creating the Internet as a whole. So, when you connect to your ISP

from home, you are effectively leasing a connection to their part of the network. They in turnwill lease connections to ISPs and network providers 'upstream', and so on. The core UK

network providers own and maintain a backbone of connections criss-crossing the country.

Other providers run connections to Europe and the United States, and so on. So when you sendan email from your computer in Exeter to your Aunt in Peru or your best friend travelling the

world and connecting in a cybercafe in Touva, the message is travelling via many networks

owned by many people, companies and government bodies. What's remarkableis that you're not charged by each company en route, since they all cooperate and allow (almost)

all traffic to pass through. Payment is made through the chain of ISPs by each ISP paying for its

right to connect higher up the chain, and agreeing to pass traffic through its own network. It's a

model that works well, though it is becoming more complex as the commercial value of

connectivity increases. The multiple ownership of the Internet also has implications for thesecurity of your messages, as your text will pass through many networks and may be readable by

any of them unless you take steps to safeguard it.

THE WORLD WIDE WEB:

• web servers, which store the web pages

• web documents, the pages themselves

•web clients, browsers of many types

The Web consists of many millions of internet-connected computers, each with information onthem that their owner has decided to share. These documents can be formed of anything from

plain text to multimedia or even 3D objects. These computers, called servers, deliver this

information over the Internet to client computers (such as your PC at home) using a protocol

called HTTP ( HyperText Transfer Protocol). The HTTP protocol is very simple; essentially it just provides a mechanism that allows a client to request a document, and a server to send that

document.As the web has become more and more popular, its capabilities have increased to

include such things as graphics, animations, scripts and even complete computer programs, allembedded into the pages of the documents. Essentially, the web is the easiest to use of all the

internet toolkit — this is partly why it has become so popular. Various mechanisms allow the

viewer to move around (navigate) the document easily. Clicking on a hyperlink moves you toanother part of the document, or to another document altogether.

THE WEB'S UNIQUE FEATURES:

• universal readership

• hyperlinks/hypertext/hypermedia

• authoring for computers and humans

• availability of information

• felxibility to adapt to new forms of media



# UNIVERSAL READERSHIP :

• a common format for information (HTML)

• a common access method (HTTP)

• a way to write content

• without having to worry about presentationAs the accessing of information stored on computers has become more widely accepted and

used,the number of methods, and hence the number of computer applications needed, has

multiplied.The web provides a way of integrating these methods and applications, using acommon interface to allow easy access to any information stored on any computer (provided you

are authorised to read it, of course).HTML or HyperText Markup Language, the language of the

web, was specifically designed to be easy to learn, and was based around the concept of markingtext functionally, to ensure a wide authorship. Thus, when the author wrote their document, they

would be able to concentrate on its

structure, and not worry about its presentation. As it has grown, the web has moved away from

this concept, becoming more complex and more graphical than originally envisioned, which has

led to many presentational features creeping into the HTML standard. Happily though, the corefunctions still lie beneath all the complexity, and allow more or less anyone to write their own

web pages quickly and easily, with a minimal set of software tools.

# HYPERTEXT AND HYPERMEDIA :

• linked documents create a “web of information”

• choice allows reader to choose path through text

• not a new idea - footnotes, bibliographies!

• technology has given links new power One of the most powerful features of the web is the ability to link documents together using

hyperlinks. On clicking a hyperlink (usually underlined), the browser tries to access the linked

The Web's unique features

1document, providing an almost instantaneous cross-referencing system. This creates a non-linear form of text, known as hypertext . Web pages can also contain multimedia content that can

also be hyperlinked, termed hypermedia. Many theorists believe that hyperlinks change the way

we view and read texts, and certainly the element of choice that hyperlinks give the reader createa

very different reading experience. The idea of hypertext has been around at least as long as

books have contained footnotes or external references/bibliographies, but the computer and theInternet make following hyperlinks instantaneous

# AUTHORING FOR COMPUTERS AND HUMANS:

• Hypertext Markup Language is designed to be many computer devices and “platforms” : easyfor humans to use to present information

• quick to author

• viewable onThough it may not seem so when you first see a raw web page, the language it is written in,

HTML,is designed to be easily read by humans, as well as computers. It was developed to make



sharing information easy, and to make it easy to write documents that would be displayed on

many types of computer. HTML can be interpreted at different levels, even in text-only mode.Now with devices such as mobile phones having Internet capabilities, the accessibility of web

information is even more important.

# AVAILABILITY OF INFORMATION:• Information available 24/7

• Information often updated in real time

• Access for all on an equal basis The goal of a web server is to serve information to anyone who requests it; the web pages stored

on the server are made publically available. It's possible to restrict access to certain parts of the

Internet, or to those who have usernames and passwords, but it's not usual - most web sites areopen for all to read their contents. The use of the web as a public space to provoke discussion

or to provide otherwise difficult-to-publish information has been instrumental in its

popularity.Examples of this range from the subversive (terrorists or political groups publishing

propaganda) The Web's unique features to the more mundane (businesses publishing time-

critical data such as stock information or market prices).

# SURFACE AND DEEP WEB:

• Only a small part of the web is publicly accessible (the Surface Web)

• Much of the web is hidden inside intranets and commercial sites

• This “Deep Web” is often not searchable

• Deep web is possibly many times the size of surface web

With the rise of commerce on the Web, and the recognition of the market value that certain types

of information can command, parts of the Web have been loservices. A high proportion of this

Deep or Invisible Web is hidden from view, whether from you and I, or from search engines.

Estimates of the size of this deep Web vary, but most agree that it is many times the size of the

Surface Web, i.e. the web that is open and accessible to the public.

# FLEXIBILITY TO ADAPT TO NEW MEDIA:

• The HTTP protocol is media neutral

• HTML is text-only; other media items are stored separately

• The HTML language has evolved to embed new media types into web pages

The HTTP protocol was specifically designed from the outset to be media neutral, in thatthedocuments and data it transfers need not be in any particular format. As the document is

transferred, it is accompanied by a header which specifies a MIME type (more about MIME in

the section called “Using Email Attachments”), and this tells the browser viewing the item what

needs to be done to display (or play) the data.Similarly, the HTML language is designed to usethese media items by linking to them from within a web page. HTML has evolved over the years

to allow all kinds of media to be embedded;

from simple static images through video and animations, and even to 3D data.

HOW DOES THE WEB WORK?



• Web servers and web browsers communicate via HTTP

• HTTP ensures that all parts of the web page are delivered

• Web browser decides how these items are displayed

The backbone of the web is the network of webservers across the world. These are really just

computers that have a particular type of software running on them - software that knows how to

speak the HTTP protocol and knows which information stored on the computer should be madeaccessible through the web. It's possible to turn almost any computer into a webserver by

downloading and installing server software (the most popular is Apache, see

http://www.apache.org/), though it's not recommended unless you know what you're doing! Theweb browser is also particularly clever in the way it displays what it retrieves. Web pages are

written in HTML, and the browser knows how to display these correctly, whether you have a

huge flat screen or a tiny screen on a handheld device or phone. The HTML language gives thebrowser hints on how to display things, and the browser decides the final layout itself.

HOW DO WEB ADDRESSES WORK?• URIs and URLs

• breaking down a URL • aliases and redirects

The key to accessing all this information is the URI - the Uniform Resource Identifier.Each web page has a unique address, specified by its URL, which tells the client/browser how to

access the page. See the Wikipedia entry for URI [http://en.wikipedia.org/wiki/

.Uniform_resource_identifier].Take, for example: http://piglet.exeter.ac.uk/pallas/index.html

WHY DO WE USE HTML?

• compact and efficient language

• extensible to encompass new media formats

• standardised

# STANDARDISATION:• HTML language is well-defined by web standards

• W3C organises and ratifies these standards

• HTML is evolving into XHTML (eXtensible HTML)

• XHTML has stricter rules, but greater flexibility

# EASE OF USE:

• HTML designed to be simple and intuitive for humans

• HTML originally had little concept of presentation

• Designers have pushed HTML to have more presentational control

• XHTML moves presentation out to other more suitable languages

HOW DO I MAKE A WEB PAGE?GETTING STARTED:• Mark up text with tags

• Match the opening <tag> with a closing </tag>

http://piglet.exeter.ac.uk/pallas/index.html

http://piglet.exeter.ac.uk/pallas/index.html



• Nest the tags, don't overlap them

It's easy! Remember that all you're doing is marking up text --- adding marks to a text thatdescribe its structure or format. The markup is done using tags which are enclosed in angle-

brackets (lessthan and greater-than symbols). For example, <title> marks the beginning of the

title of a document. To mark the end of a structure, the corresponding close-tag is used, e.g.

</title>.To look at the marku

source from the Internet Explorer or Firefox menu. Here's an example of a truly minimalist web

page:

EXAMPLE : A MINIMALIST WEB PAGE<html><head>

<title>My first web page</title>

</head>

<body>

<h1>My First Web Page</h1><p>HTML is quite easy to learn.</p>

</body></html>

# DISCOVERING MORE TAGS

• learn by trial and error

• use the 'view source' command

• but always refer back to the standards

• there's lots of bad HTML around!

# VALIDATE!• Checks your X/HTML against the "Standard"

• Can give you clues to errors in your markup

• Can also be very confusing!

• Important for checking usability and disability access

# COPYRIGHT AND THE WEB:• Copyright applies as much to Web as to print

• Be especially careful of using copyright images

• Always acknowledge your sources

• If in doubt, try to find copyright-free imagesCopyright is a hazy issue on the Internet — mainly because the law has not adapted yet to cope

with the new medium. Test cases regarding copyright violation are few, and are often too

specific to be applied as precedents across the board. Copyright of images is a particular

problem. It's very easy to download a graphic that would suit the page you're creating andinclude it in your own pages. There have been many projects and proposals to include digital

watermarks or copy protection into images, but none has proved



• Have they published other works in this area?

• If not, are they representing a responsible body which has some authority in the subject area?

• Has the information been edited or peer-reviewed by some authority?

# PAGE AND SITE INTEGRITY• Is the page part of a coherent website?

• Does the address (URL) indicate that the site has the authority it claims for itself? • Does the page metadata (see the section called “Metadata”) correspond to other evidence?

EVALUATING AUTHORITY BY COMPUTER:• Computers need to recognise useful/reliable information too

• Looking at how many pages link back to a page

• Looking at how many citations a page has

• Looking at the structure of the page

• And many other ways of determining authority....

• New discipline of “e-Science”

#SEARCHING EFFECTIVELY• Why is searching the web so difficult?

• No complete catalogue • The web is too large to catalogue comprehensively

• The web grows and changes too quickly

# SEARCH STRATEGIES• Search strategies require a number of techniques:

• Grazing - casually following links, almost at random

• Skimming - scanning large amounts of material very quickly

• Deep searching - delving deep into a particular website

• We also use a variety of tools

• Search engines

• Hubs and authorities

• Meta-search engines

# CHOOSING A SEARCH ENGINE• Google is still the most comprehensive and accurate

• Still worth considering others

• Specialist search engines - Google Scholar, etc.

• Localised versions often available

# FILTERING SEARCH RESULTS• Use as specific a search term as possible

• Reduces “false positives”

• Use the search term logic effectively

• Learn boolean logic if used by the search engine

• Learn how to select exact/approximate matches

# USING META-SEARCH ENGINES• Feeds your search terms to many search engines

• Aggregates results and presents most likely matches



• Can run in background or in batch mode

# HUBS AND AUTHORITIES• Authorities contain reliable, definitive information

• Hubs link to these, through human-edited listings

• Common model in the Academic domains • Some hubs can become authorities themselves (e.g. parts of Wikipedia [http://

www.wikipedia.org/])

HOW SEARCH ENGINES WORK• Complex algorithms to rate and rank pages by some criteria

• Database of cached pages to search through

#SPIDERS, WEBCRAWLERS, ETC.• Software that crawls the web, following hyperlinks

• Visited pages are indexed, catalogued and/or cached

• Systematic revisits keep the information fresh • Ranking and rating algorithms are closely guarded secrets

• e.g. Google's PageRank, using backlinks etc to rate a page

• How do we measure a page's “authority” or “usefulness”?

# METADATA• Added information to help search-engines

• See Example 6.1, “Meta tags in an HTML document”

• May contain information about authorship, contents, etc.

• Many different schemes, though standards are emerging

• The “Semantic Web” - the next generation of the web?

# INTERACTIVE DATA ON THE WEB• Not all data held on the web is in static HTML

• Many web pages now generated automatically from databases, etc.

• Sometimes difficult to search - the “Invisible Web”

• Some allow data creation - e.g. online banking, flickr, myspace

# UP-TO-DATE INFORMATION• Web is suited to dynamic and time-dependent data

• Applications such as product information, stock control, etc.

• Shopping sites benefit from this approach

# FEEDBACK• In e-commerce, keeping the customer informed is key

• Order status and parcel tracking

• Customer reviews

• Promotes confidence and shows off good customer service

• Can backfire - customer problems can also be highlighted

http://www.wikipedia.org/

http://www.wikipedia.org/



# PREFERENCES AND ADAPTIVE PAGES• Tracking of shopper's or user's habits

• Analysis of these habits to provide customised information

• Can increase multiple purchases and impulse-buys

• Customised homepages and portals

# COLLABORATIVE KNOWLEDGE• Feedback can be turned into more useful “knowledge”

• Information gathered from users can be faster, cheaper, easier, but...

• Issues with reliability and authenticity

• Issues with impartiality on controversial topics

• Problems with vandalism, abuse (and possibly libel)

• Need to gain “critical mass” of interested users

Example: Wikipedia

#ONLINE DATA AND PRIVACY

• Online data is easily propagated and abused • Concerns over security of sensitive information

• User tracking can be serious invasion of privacy

# INTRODUCTION TO SECURITY• Malicious software existed almost from the first computers

• Networks allow malicious software to spread more easily

• Broadband allows new threats to your computer

• “Always-on” allows sustained attacks

• “Static IP” allows discontinuous attacks

# INTERNET WILDLIFE• A look at some types of attack

• Pop-ups and pop-unders

• Adware and spyware

• Email scams and spam

• Denial of service (DoS)

• Viruses

• Worms

• Rootkits and Trojans

• Phishing

# DEFENCE MECHANISMS• Apply patches and update programs regularly

• Keep passwords secure; don't “recycle” them

• Keep digital signatures and certificates safe

• Use secure hardware - biometrics

• Secure your network from intruders

ADSL AND BROADBAND COMMUNICATION:



One of the most significant changes in the way we use the Internet is just around the corner.

Currently, home users mostly dial into an ISP using some kind of modem or terminal adapter,and are charged for the time spent connected through telephone charges. Moreover, the data

transfer rate is severely limited, to around 43Kbps (up to 56Kbps with compression) per

telephone line. However, the technology called ADSL (Asynchronous Digital Subscriber Line)

provides apermanent, high-bandwidth connection over existing copper cable (phone lines). It works by

using a much higher frequency signal--which means it can also carry voice signals at the same

time--and by using this higher frequency primarily in one direction.

BANDWIDTThere are also implications rising from the speed of an ADSL connection. It's possible thatbandwidths will rise well over the 1Mbps level, and this will have a significant effect on our use

of the Internet, and on the infrastructure of the net in general. As bandwidths increase, more

multimedia applications will become viable and popular. We already have audio and video

conferencing, though it can be poor quality and temperamental. With higher bandwidths, more

information can be sent, thus giving increased picture and sound quality, or more participants perconference. With 1-2 Mbps, it's possible to have multi-way telephone quality audio

conferences,or point-to-point video at around 10 frames per second.There are also implicationsrising from the speed of an ADSL connection. It's possible that bandwidths will rise well over

the 1Mbps level, and this will have a significant effect on our use of the Internet, and on the

infrastructure of the net in general. As bandwidths increase, more multimedia applications will

become viable and popular. We already have audio and video conferencing, though it can bepoor quality and temperamental. With higher bandwidths, more information can be sent, thus giving increased picture and sound quality, or more participants per

conference. With 1-2 Mbps, it's possible to have multi-way telephone quality audio conferences,or point-to-point video at around 10 frames per second.

WIRELESS TECHNOLOGY:A little further off in the future lies the promise of truly wireless technology. It's already possibleto plug your laptop or PDA into a mobile phone and download your email. It's even possible to

buy email-capable mobile phones. The web has also been adapted for mobile use, in the form of

WAP (Wireless Application Protocol). This uses an HTML-like language called WML (WirelessMarkup Language) to provide pages of information in a compiled, compressed form, designed to

download quickly over the limited bandwidth of mobiles. With the next generation of phones

(3G), WML will become completely obsolete as the bandwidth required for true web access willbe available.

WI-FI TECHNOLOGY : Wireless has already taken off in the form of `WiFi' (or 802.11a/b/g) devices, which have amedium range of around 20m, and are mainly used to connect PCs, laptops or PDAs to a broadband link. Common uses are in Cybercafes and Universities (alas not here yet, despite

lobbying IT Services!), especially in locations where wired connections would be impractical..

IPV6--THE NEXT GENERATION:Many of these problems, and others besides, have been troubling Internet gurus for some time.



Their solutions have been fed into a new specification for the basic protocols of Internet data

transfer, known as IPv6 (version 6) or IPng (next generation). The most significant change in thisnew standard is the way computers are addressed. Internet addresses are specified using what's

called a `dotted quad', four 8-bit numbers (0-255) that uniquely specify each IPconnected

computer or device. As the Internet grows, the limited range of these numbers (there's a

theoretical maximum of around 4,000 million addresses, though a high proportion unavailabledue to the subdivisions into domains) will cause problems when allocating new addresses. As

more computers, PDAs and even household devices (yes, you can already buy an

InternetCulturalconnected refrigerator!) are linked to the net, we'll need many more addresses.So the proposal

is to use four sixteen-bit numbers, which will give around 18 million million million addresses(2

to the power 64), which should last a little while at least!

#Ethics of the InternetPerhaps the biggest unanswered question of all concerns the ethical use of the Internet, and how

we allow the freedom that the Internet has offered us, whilst protecting the vulnerable and

preventing abuse.For example, current debates are discussing the role of the Internet in theincreasing number of convictions relating to child pornography. Is the Internet facilitating this

increase? Or is itincreasing the rate of convictions because it allows the participants to be traced more easily?

This leads us into questions of anonymity and privacy: It's now very difficult to be completely

anonymous on the Internet, though it often feels as though we are. We have also sacrificed

thisanonymity (through government legislation) to allow this level of protection.There are manyquestions such as this which need to be asked; we'll be examining these in the “ConceptualIssues in Cyberspace” module

USE AND ABUSAGE OF INTERNET: Following are the advantages provided by the Internet:

1. Information The biggest benefit offered by the Internet is information. It functions as a

valuable resource of information. You can find any type of information on any subject

with the help of the search engines like Yahoo and Google.2. Communication The primary goal of the Internet is communication. It has done

extremely well in this field, however the development process is still going on to make it

more dependable and quick. By sending an e-mail, we can contact a person who isphysically present thousand miles away within the fraction of a second’s time.

3. Entertainment Internet functions as a popular medium of entertainment. A wide variety of

entertainment including video games, music, movies, chat room, news and others can be

accessed through the Internet.

4. E-commerce E-commerce is the idea that is implemented for any form of commercial

strategy or business transactions that entails transmission of data from one corner of theworld to another. E-commerce has become a fantastic option through which you can shop

anything.



5. Formation of communities Internet helps in formation of communities or forums. Here a

number of people can participate in different types of debates and discussions, expresstheir views and gather valuable knowledge.

6. Services A variety of services are offered via Internet, for example job searching, online

banking, buying movie tickets, hotel reservations and consultation services etc. Whenyou avail these services offline, they become more expensive.

THE DISADVANTAGES OF INTERNT

FOLLOWING ARE THE DISADVANTAGES OF INTERNET:

1) Spamming: Spamming denotes distribution of unsolicited e-mails in large numbers. They aremeaningless and they unnecessarily block the whole system. These activities are treated as

illegal.

2) Theft of personal details While using the Internet, there is high probability that your personal

details like name, address and credit card number may be accessed by con artists and used for

fraudulent purposes.3) Pornography: Pornography is definitely harmful for your children. There are numerous

pornographic sites available over the Internet and watching any of those can have very badinfluence on the mental health of your children.

4) Virus threat Virus is a program that interrupts the usual operation of your personal computer

system. PCs linked to the Internet have high probability of virus attacks and as a result of this

your hard disk can crash, giving you a lot of trouble.

MODEM AT GLANCE:• The middlemen between the computer and the telephone system

•

Convert analog data suitable for transmission over a phone line to digital datasuitable for a computer (modulator/demodulator)

• Can be either an external device or an internal device that is installed in anexpansion slot inside a computer

A phone line connects to a modem or telephone using either an RJ-11 or older RJ-12

connectorThis modem converts digital to analog.



MODEM TYPES:

1. Telephone modem

2. Optical Modem (Optical fiber)3. Cable modem4. DSL Modem etC

What is a Cable Modem &how does it work :

• A Cable Modem is a digital modem that uses a coaxial cable connection forthe data transmission.

This data connection is received by a cable modem that decodes the signal into your PC

• A device for high speed data access via a CATV network

http://www.whatis.com/coaxialc.htm

http://www.whatis.com/coaxialc.htm



WHO MAKES CABLE MODEMS?

1. Bay Networks -- LANcity

2. Motorola3. Zenith

4. General Instruments

5. Hewlett-Packard6. Scientific Atlanta

7. Phasecom

CABLE MODEM APPLICATION:

TYPICAL CABLE SYSTEM WITH INTERNET ACCESS:

1. High-speeD 2. Conventional

CoppeR Co-ax Cable to homes

Internet

Backbone

Link



3. Optic 4. CableLinks System

to Head End

Neighbor-

Headhoods

A TYPICAL CABLE MODEM:

.Connects 1 single host computer

>Though some can connect dozens of hosts.Has its own IP address

>Though some share an IP address with the single connected host

.Operates at speeds from 1 megabit / second to 10 megabits / second

>Though some claim up to 30 megabits / sec

.Is bidirectional>Though some use “telco return”

HOW FAST CABLE MODEM WORK :Variable Bit Rate: Bandwidth on Demand

Asymmetric Configuration

o Downstream Transmission

Frequency Range: 50-860 MHz

Transmission Speed: up to 36 Mbps (3~10 Mbps realistic)

o Upstream Transmission

Frequency Range: 5-42 MHzTransmission Speed: up to 10 Mbps (200 Kbps ~ 2 Mbps realistic)

There are many cable modem brands, and some of the most common ones are from Com21,Motorola, Bay Networks, RCA, Cisco, Toshiba, 3Com, and Terayon. There are several popular

cable modem providers. A few of them are: @Home available at http://www.Home.Com,

Mediaone Express available at http://www.MediaoneExpress.com, and Road Runner, a serviceby Time Warner available at http://www.RR.Com.

CABLE MODEM SERVICE:

.On the Internet--Speed Kills

.Now, low-speed open access by telephone

.Soon, hi-speed closed access by cable modem

MODEM SELECTION CRITERIA:.Digital or analog signals

.Asynchronous or synchronous

http://www.home.com/

http://www.mediaonerr.com/

http://www.rr.com/

http://www.rr.com/

http://www.mediaonerr.com/

http://www.home.com/



.Speed

.Distance

.Type of line

.Cost

.Use compatible modems for both end

CABLE MODEM STANDARD:

IEEE 802.14 (in May 1994)MCNS/DOCSIS (USA mainly, in January 1996)

Multimedia Cable Network System (MCNS)

Data Over Cable Service Interface SpecificationDVB/DAVIC (Europe mainly)

European Digital Video Broadcast (DVB)/ Digital Audio Visual Council (DAVIC),

EuroDOCSIS

THE UNIFIED SIMULATOR AND MODEM SOFTWARE MODEL:



CABLE MODEM:

Internal

Modem



RELATIVE SPEED COMPARISONS:



• Cable modems run up to 10 megabits / sec

• ISDN = 128 kilobits / sec

• Dialup modem = 28.8 kbps (or 33.6 or 56)

ADSL

•

Asymmetric digital Subscriber Line:-ADSL is the current demanding of the phone companies for delivering advanced

digital

Services.It offers the promise of high Speed transmission.

TELEPHONE MODEMS: .Telephone modems employ all three of the modulation techniques:

.FSK

.PSK

.QAM

.Because of the limitations of voice-grade telephone lines, these modems are restricted to abandwidth of about 3 kHz

The trend in modem design has been towards more sophisticated modulation schemes to achievethe maximum bit rate with available bandwidth

FSK MODEMS:.The first telephone modems used FSK and this technique is still used in specialized applications

such as the transmission of call-display information from the central computer to subscriber

telephones

PSK MODEMS:

.When faster data rates are needed than available with PSK, phase modulation is often used

.Most DPSK (delta phase-shift keying) systems use a four-phase system called quadrature phase-

shift keying (QPSK)

.The bit rate is twice the baud rate and is referred to as a dibit systemThe Bell 212A modem is an example of this type of modulation, capable of data rates up to 1200

bits per second

QAM MODEMS:

• Quadrature Amplitude Modulation (QAM) modems are capable of operating at

several different speeds, depending upon the quality of the connection

• Modem speeds using the ITU V.34 standard are capable of 33.6 kb/s, full duplex

• V.34 modems monitor line conditions and select the appropriate speeds for a

given noise level

56K MODEMS:



• The V.90 standards allow data transmissions up to a theoretical limit of 56 kb/s,but because of FCC requirements, the maximum allowable is 54 kb/s

• V.90 modems appear to exceed the Shannon Limit

• However, the higher rate is available only in the downstream direction and a

maximum of 33.6 kb/s is available in the upstream direction• Upper limits vary greatly according to line noise, distance from a telephone

substation, and availability of digital connections throughout the phone system

COMPETITION FOR CABLE MODEMS:

# FASTER MODEMS:

• 33.6K modem is about 16% faster than 28.8

• 56K modem would be about twice as fast

o …whenever it’s real

•

Even fast modems are only a fraction of speed of Etherneto Factor of several hundred

o Only in theory !Ethernet is shared

CONCLUTION : The Modem and Internet is a remarkable phenomenon. Essentially, it is just a large number of

computers connected together in such a way that communication between them is both reliable

and fast. Phrased in this way, it is wholly unremarkable. But the Modem and Internet is also thepeople who use it, to communicate and to share information, even to build relationships and

communities. It's a culture that has grown within a virtual space, and that has permeated many

aspects of our everyday lives. This module will provide an overview of the Modem and Internet,

from the mundane networking of computers to the new societies created within it.



BIBLIOGRAPHY:

http://www.wikipedia.org

http://www.answer.com

http://4shared.com

Vannevar Bush. 1945. “As We May Think”. Atlantic Monthly. 176. 101-108. Sven Birkerts. 1994. “The Gutenberg Elegies: The Fate of Reading in an Electronic

Age”.

Faber and Faber.

Barry Brown and Abigail Sellen. 2001. “Exploring User's Experiences of the Web”.

First

Monday. 6. 9. http://www.firstmonday.org/issues/issue6_9/brown/ . 2005-10-27.

Vinton Cerf. 1997. “A Brief History of the Internet”.

http://www.isoc.org/internet/history/ Cerf.shtml . 2006-06-22.

John December. 1996. “Living in Hypertext”. EJournal. V6. N3.

http://www.ucalgary.ca/

Ejournal/archive/v6n3/december/december.html . 2005-10-27.

Hubert L Dreyfus. 2001. On the Internet. Routledge. London.

Esther Dyson. 1997. Release 2.0: A design for living in the digital age. Viking.

London

Derek Foster. 1996. Community and Identity in the Electronic Village. 23-38. In

Internet

Culture

Paul Gilster. 1997. The Web Navigator. Wiley.

Preston Gralla. 1999. How the Internet Works. Millennium. Que. Indianapolis, IN.

Christoph Hölscher and Gerhard Strube. 2000. “Web Search Behavior of Internet

Experts and Newbies”. Computer Networks. 33. 337-346. Available from Elsevier

ScienceDirect via Athens

[http://www.library.ex.ac.uk/electronic/].

George P Landow. 1997. Hypertext 2.0: The Convergence of Contemporary Critical

Theory and Technology. Johns Hopkins University Press. Baltimore, OH. [Main Library:

1×NL, 2×SL

801.95 LAN].

John Naughton. 1999. “A Brief History of the Future: The Origins of the Internet”. Weidenfeld and Nicholson.

Rob Shields. 2000. Hypertext Links: The Ethic of the Index and its Space-TimeEffects. In

[Herman2000] .

David Whitehouse. 1999. The WWW is very big but not very wide. BBC News.http://

news.bbc.co.uk/1/hi/sci/tech/443754.stm . 2005-08-16.



Langdon Winner. 1995. “Who will we be in cyberspace?”. Network Observer. 2. 9.http://

polaris.gseis.ucla.edu/pagre/tno/september-1995.html . 2005-10-

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term paper on modem & internet by enamul & tanvir_ict_3rd batch_1st semester_2011

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