WEEK ONEThe Concept of the Internet

Historical background of the Internet

Discuss Intranet and Extranet

WEEK TWOThe Economics, Social, Political, Educational and Cultural benefits of Internet

WEEK THREEVarious Internet services like:

Information search – (on last page)E-commerceE-mailFile Transfer Protocol (FTP)Bulletin Board ServiceAudio-Video CommunicationDigital LibraryWorld Wide WebTelnet and other services

WEEK FOURUnderstand the basic hardware required for Internet connectivity: Discuss MODEM and its functions

Explain the Data transfer rate of various MODEM

WEEK FIVEExplain the concept of Wireless Transmission and Bandwidth

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Discuss various wireless transmission media:VSATRadio etc

WEEK SIXDiscuss obstacle to effective Transmission

Discuss the Steps required to connect a PC to the Internet

WEEK SEVENDiscuss Problems of Telecommunication infrastructure in Nigeria: Technical know-how

WEEK EIGHTEconomic factors in Nigeria – Poverty level of the people; level of awareness

WEEK NINEThe government policies on Internet Access

Explain the concept of ISP and the need for it

WEEK TENExplain the economic effect of using local or foreign ISP

Describe Domain Name System (DNS) and its space

WEEK ELEVENExplain how to name servers in the DNSRevision

WEEK TWELVEEXAMINATION

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LECTURER: MR. M.A. ADEWUSI

THE CONCEPT OF THE INTERNET

Internet can be termed as the interconnection of the variety of networks and computers.

Internet makes use of the internet protocol and the transmission Control protocol. Internet

opened the doors of communication between the various stations. Internet facilitates

storing and transmission of large volumes of data. The internet is one of the most

powerful communication tools today.  

In the 1990’s internet gained popularity in the masses. People started becoming aware of

the uses of internet. Internet helped the people to organize their information and files in a

systematic order. Various researches were conducted on internet. Gopher was the first

frequently used hypertext interface.

In 1991, a network based implementation with respect to the hypertext was made. The

technology was inspired by many people. With the advent of the World Wide Web search

engine the popularity of internet grew on an extensive scale. Today, the usage of internet

is seen in science, commerce and nearly all the fields

There are various ways and means to access the internet. With the advancement in

technology people can now access internet services through their cell phones, play

stations and various gadgets. There are large numbers of internet service providers as

well.

With the development and the wide spread application of internet electronic mail people

from all across the globe come together and communication has become much easier than

ever before. Messages, in the form of Emails could be send in at any corner of the world

within fractions of seconds. Emails also facilitated mass communication (one sender

many receivers).

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Emails, video conferencing, live telecast, music, news, e-commerce are some of the

services made available due to internet.  Entertainment has taken new dimensions with

the increase of internet and all we see it's a continuous development and transformation.

THE WEB2.0 CONCEPT

"Web 2.0" refers to what is perceived as a second generation of web development and

web design. It is characterized as facilitating communication, information sharing,

interoperability, User-centered design[1] and collaboration on the World Wide Web. It has

led to the development and evolution of web-based communities, hosted services, and

web applications. Examples include social-networking sites, video-sharing sites, wikis,

blogs, mashups and folksonomies.

The term "Web 2.0" was coined by Darcy DiNucci in 1999. In her article "Fragmented Future," she writes[2]

The Web we know now, which loads into a browser window in essentially static screenfuls, is only an embryo of the Web to come. The first glimmerings of Web 2.0 are beginning to appear, and we are just starting to see how that embryo might develop. ... The Web will be understood not as screenfuls of text and graphics but as a transport mechanism, the ether through which interactivity happens. It will [...] appear on your computer screen, [...] on your TV set [...] your car dashboard [...] your cell phone [...] hand-held game machines [...] and maybe even your microwave.

Her arguments about Web 2.0 are nascent yet hint at the meaning that is associated with

it today.

The term is now closely associated with Tim O'Reilly because of the O'Reilly Media

Web 2.0 conference in 2004.[3][4] Although the term suggests a new version of the World

Wide Web, it does not refer to an update to any technical specifications, but rather to

cumulative changes in the ways software developers and end-users utilize the Web.

According to Tim O'Reilly:

Web 2.0 is the business revolution in the computer industry caused by the move to the

Internet as a platform, and an attempt to understand the rules for success on that new

platform.[5]

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However, whether it is qualitatively different from prior web technologies has been

challenged. For example, World Wide Web inventor Tim Berners-Lee called the term a

"piece of jargon"[6].

HISTORICAL BACKGROUNG OF THE INTERNET

1950

As early as 1950 work began on the defense system know as the Semi-Automatic

Ground Environment, or SAGE. This defense system was thought to be required to

protect the US mainland from the new Soviet long range bombers and missile carriers

such as the Tupolev. IBM, MIT and Bell Labs all worked together to build the SAGE

continental air defense network that became operational in 1959.

SAGE became the most advanced network in the world at the time of its creation and

consisted of early warning radar systems on land, sea, and even air courtesy of AWACS

planes. The network technology lead to more advanced systems and protocols that would

one day become the Internet, as well as common hardware items such as the mouse,

magnetic memory (tape), computer graphics, and the modem.

1957

In 1957 the USSR launched the first earth-orbiting artificial satellite and kicked off the

space race in a big way. The United States, suddenly fearful of Russian space platforms

armed with nuclear weapons, needed an agency designed to combat this menace. ARPA,

or Advanced Research Projects Agency, was founded in 1958 and was given the mission

of making the US the leader in science and technology. In 1972 ARPA was renamed the

Defense Advanced Research Projects Agency (DARPA). As of 1996 the agency is once

again called ARPA.

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ARPA hired J.C.R. Licklider in 1962 to become the Director of their Information

Processing Techniques Office (IPTO). Licklider’s works eventually lead to the field of

interactive computing, and is the foundation for the field of Computer Science in general.

Lickliders work with computer timesharing helped usher in the practical use of the

computer network.

1962 – Rise of the Modem and the Conceptual Internet

AT&T released the first commercially available modem, the Bell 103. The modem was

the first with full-duplex transmission capability and had a speed of 300 bits per second.

The first real conceptual plan of the Internet was being seen in a series of memos released

by J.C.R Licklider where he referred to a “Galactic Network” that connected all users and

data in the world. These memos grew from his first paper on the subject Man-Computer

Symbiosis released in 1960, although this early work covered human interaction with

computers and less about human to human communication. In 1962 the aptly named On-

Line Man Computer Communications was released and dealt with the concept of social

interaction through computer networks.

Birth of the World Wide Web

1992 – ISOC

Founded in 1992, The Internet Society (ISOC) is a non-profit organization that assists in

the development of Internet education, policy and standards. The organization has offices

in the U.S and Switzerland and works toward an Internet evolution that will benefit the

entire world.

ISOC is the home of organizations responsible for Internet infrastructure standards, the

Internet Engineering Task Force, and the Internet Architecture Board (IAB). ISOC is also

a clearinghouse for Internet education and information and a facilitator for Internet

activities all over the world. ISOC has run network training programs for developing

countries and assisted in the connecting of almost every country to the Internet.

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1994 - The Web Browser is Born

Jim Clark and Mark Andreessen founded Mosaic Communications in 1994. Andreessen

had been the leader of a software project at the University of Illinois called Mosaic, the

fist publically available web browser. Jim and Mark changed the name of Mosaic

Communications to Netscape Communications and their web browser was soon released

to a frantically growing market.

Netscape was the largest browser firm in the world very quickly and dominated the

market. Software releases seemed to come out monthly if not faster and it was these

Netscape offerings that lead to the term “internet time”. Business was moving faster

everyday. By 1995 Netscape had an 80% market share.

1995 - Windows 95 and the Browser Wars

Windows 95 was released by Microsoft and took the world by storm. The software giant

solidified its OS presence and began to make its way into homes across the world. A little

know program included with the OS was Internet Explorer, a web browser. Microsoft

wanted to challenge Netscape’s dominance in the browser market, and had the OS

platform to do it with. Netscape pushed the boundaries of browser technology and made

technological leaps forward on an almost daily basis. Netscape was considered the most

advanced browser available, and Microsoft had years of catching up to do. One key

difference however was Internet Explorer was free and Netscape was not. This was

difficult to overcome but Netscape pushed forward in what was now being called The

Browser Wars.

Although the term Browser Wars generally refers to the competition in the marketplace

of the various web browsers in the early and mid 90’s it is most commonly used in

reference to Internet Explorer and Netscape Navigator. Microsoft eventually captured

Netscape’s market share, and Netscape Navigator ceased to be. Firefox is now the

primary browser competitor to Internet Explorer.

1998 – ICANN is Formed

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ICANN is the Internet Corporation for Assigned Names and Numbers and is a not-for-

profit public benefit corporation. ICANN helps coordinate the unique identifiers ever

computer needs to be able to communicate via the Internet. It is by these identifiers

computers can find each other, and without them no communication would be possible.

ICAAN is dedicated to keeping the Internet the Internet secure, stable, and interoperable.

1999 – Y2K Looms

Y2K was short for “the year 2000 software problem” and was also called The

Millennium Bug. The problem has been the subject of many books and news reports, and

was discussed by Usenet users as early as 1985.

The heart of the problem was that it was thought that computer programs would produce

erroneous information or simply stop working because they stored years using only two

digits. This would mean the year 200 would be represented with 00 and appear to be the

year 1900 to the computer.

Government committees were set up to drive contingency plans around the Y2K issue

that would help mitigate damages caused to crucial infrastructure such as utilities,

telecommunication, banking and more. Although the failing of military systems was

discussed in public forums, the danger there was minimal as the closed systems were all

Y2K compliant. Public fears of the Y2K “disaster” grew as the date approached.

Although there was no Y2K disaster either due to concerted efforts or simply because

there never was a great danger, there were benefits to the issue such as the proliferation

of data back up systems and power contingency systems that protect businesses today.

One of the few Y2K incidents was the US timekeeper (USNO) reported the new year as

19100 on 01/01/2002

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2001 – HDTV over an IP Network

Level 3 Communications Inc and the University of Southern California successfully

demonstrate the first transmission of uncompressed real-time gigabit high-definition

television over an Internet Protocol optic network. This demonstration proved the

technology they were using would support high speed data steaming without packet

differentiation. Without the need of data packets, HDTV anywhere begins to be

discussed.

INTRANET AND EXTRANET

Introduction

A key requirement in today's business environment is the ability to communicate more

effectively, both internally with your employees and externally with your trading partners

and customers.

An intranet is a private - internal - business network that enables your employees to share

information, collaborate, and improve communications.

An extranet enables your business to communicate and collaborate more effectively with

selected business partners, suppliers and customers. An extranet can play an important

role in enhancing business relationships and improving supply chain management.

An intranet is a business' own private website. It is a private business network that uses

the same underlying structure and network protocols as the internet and is protected from

unauthorised users by a firewall.

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Intranets enhance existing communication between employees, and provide a common

knowledge base and storage area for everyone in your business. They also provide users

with easy access to company data, systems and email from their desktops.

Because intranets are secure and easily accessible via the internet, they enable staff to do

work from any location simply by using a web browser. This can help small businesses to

be flexible and control office overheads by allowing employees to work from almost any

location, including their home and customer sites.

Other types of intranet are available that merge the regular features of intranets with those

often found in software such as Microsoft Office. These are known as online offices or

web offices. Creating a web office will allow you to organise and manage information

and share documents and calendars using a familiar web browser function, which is

accessible from anywhere in the world.

Types of content found on intranets:

administrative - calendars, emergency procedures, meeting room bookings,

procedure manuals and membership of internal committees and groups

corporate - business plans, client/customer lists, document templates, branding

guidelines, mission statements, press coverage and staff newsletters

financial - annual reports and organisational performance

IT - virus alerts, tips on dealing with problems with hardware, software and

networks, policies on corporate use of email and internet access and a list of

online training courses and support

marketing - competitive intelligence, with links to competitor websites, corporate

brochures, latest marketing initiatives, press releases, presentations

human resources - appraisal procedures and schedules, employee policies,

expenses forms and annual leave requests, staff discount schemes, new vacancies

individual projects - current project details, team contact information, project

management information, project documents, time and expense reporting

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external information resources - route planning and mapping sites, industry

organisations, research sites and search engines.

Benefits of intranets and extranets

Your organization’s' efficiency can be improved by using your intranet for:

publishing - delivering information and business news as directories and web

documents

document management - viewing, printing and working collaboratively on

office documents such as spreadsheets

training - accessing and delivering various types of e-learning to the user's

desktop

workflow - automating a range of administrative processes

front-end to corporate systems - providing a common interface to corporate

databases and business information systems

email - integrating intranet content with email services so that information can be

distributed effectively

The main benefits of an intranet are:

better internal communications - corporate information can be stored centrally

and accessed at any time

sharing of resources and best practice - a virtual community can be created to

facilitate information sharing and collaborative working

improved customer service - better access to accurate and consistent information

by your staff leads to enhanced levels of customer service

reduction in paperwork - forms can be accessed and completed on the desktop,

and then forwarded as appropriate for approval, without ever having to be printed

out, and with the benefit of an audit trail

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It is a good idea to give your intranet a different image and structure from your customer-

facing website. This will help to give your internal communications their own identity

and prevent employees confusing internal and external information.

BENEFITS OF INTERNET IN RELATION TO:

ECONOMICS: The most often cited reasons for communities establishing their

own local access networks are for reasons of economic development and the requirement

for local businesses to have high-speed Internet services. The system requirements were

that it must provide broadband virtual private networks (VPN) and high-speed Internet

access for municipal facilities, emergency and public services, businesses and industrial

spaces.

One of the more recent studies on the economic impact of mass market broadband was

conducted on a range of communities across the United States comparing indicators of

economic activity that included employment wages and industry mix (Lehr, Osorio,

Gillett and Sirbu, 2004).  In those U.S. communities where broadband had been deployed

since December 1999, the researchers found that between 1998 and 2002, these

communities experienced more rapid growth in employment, number of businesses

overall, and businesses in IT- intensive sectors. 

As noted by the authors, “… the early results presented here suggest that the assumed (and oft-touted) economic impacts of broadband are both real and measurable.”[7] 

The major reason that access to high-speed Internet access is believed to benefit local

communities, particularly in rural areas, is the impact that it has on increasing the

competitiveness of businesses by increasing productivity, extending their market reach

and reducing costs.  Until recently, there has been little research done on attempting to

analyse and document the underlying reasons why businesses are positively impacted by

high-speed Internet access. There are two studies, one from Cornwall, England and the

other from British Columbia, Canada, which have shown remarkably similar results.

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Cornwall is a relatively isolated area that is provided with high-speed Internet access by

actnow, a public-private partnership that was established in 2002 by Cornwall Enterprise

to promote economic development in the region.  In April 2005, an online survey of

companies that were served by actnow was undertaken.  The main findings of the study

were:

“Their answers suggest that broadband is generally benefiting enterprises, individuals, the Cornish economy, society and the natural environment by, for example, extending market reach and impact, making organisational working practices more efficient, enabling staff to work flexibly, and substituting travel and meetings with electronic communication. In particular:

Over 94% of respondents report positive overall impacts from broadband, with 68% stating that they are highly positive.

A large majority of respondents feel that broadband has positive impacts on business performance (91%), relationships with customers (87%), and the job satisfaction and skills of staff (74%).

90% of respondents expect to get continued benefits – and 45% considerable benefits - from broadband.” [8]

 The Peace River and South Silmilkameen regions are located in remote parts of British

Columbia, Canada. The area is served by the Peace Region Internet Society which is a

not for profit organisation established in 1994 to provide affordable access to the Internet

for individuals, businesses, and organizations in the Peace Region of Northern British

Columbia. In 2005, an online survey of customers was undertaken to measure the

economic impact of high-speed Internet access in these communities.  The major findings

were:

 “For most businesses in the communities we studied, broadband is an important factor in remaining competitive. Broadband allows businesses to be more productive, to identify and respond to opportunities faster, and to meet the expectations of customers, partners, and suppliers.

 

Over 80 per cent of business respondents reported that broadband positively affected their businesses. Over 18 per cent stated they could not operate without broadband;

62 per cent of businesses say productivity has gone up with a majority citing an increase of more than 10 per cent;

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Many businesses reported increased revenue and/or decreased costs due to broadband connectivity.”[9]

The two studies show a high degree of similarity in the responses with businesses in both

areas demonstrating that high-speed Internet access has positively impacted their

businesses, through increased productivity and overall efficiencies. The research

demonstrates that high-speed Internet connectivity is important to ensure that businesses

in rural and remote areas remain competitive and without it, they would be at a severe

competitive disadvantage. 

POLITICAL: Theoretical Background: Inclusion in or Exclusion from the

Political System? Some years ago Dick Morris, one of Bill Clintons spin doctors, saw the

United States on the way from James Madison towards Thomas Jefferson, from

representative democracy to direct democracy, with the Internet serving as a catalyst

(Morris 1999). Al Gore and others tried to "re-invent governance" by means of the

Internet, thus creating some sort of "new Athenian age" of democracy (Gore 1995).

Today such enthusiasm seems somehow exaggerated. The Internet fell short of many

expectations not only economically. Now we have the chance to take a restrained look at

the Internet to calculate costs and benefits from online communication - even in the field

of politics. First we want to specify the three levels on which an impact of the Internet in

this field may be considered: • a macro-level approach considers the use of the Internet

by states ("e-governance"). • a meso-level approach considers the use of the Internet by

political organizations ("virtual parties") • a micro-level approach considers the use of the

Internet by individual citizens ("e- democracy") In our presentation we deal only with

micro-level consequences of Internet usage. Our focus is on the individual activities

people take to communicate politically. This includes reception of political media as well

as talks about politics and showing of ones own opinion in public (in a demonstration for

example). What are the common assumptions about consequences of internet usage on

political communication? The literature provides a first position that ascribes a

"mobilizing function" to the Internet (Schwartz 1996; Rheingold 1994, Grossman 1995).

This position expects a higher frequency and a higher intensity in political

communication among Internet users than among non-users. It expects also that the

Internet may include even those parts of the population who can’t be reached by

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traditional channels of political communication. The public and scientific discussion is

dominated by this "hypothesis of inclusion": The Internet intensifies political

communication and thus leads to a growing integration of citizens into the political

system.

EDUCATIONAL: The internet provides a powerful resource for learning, as

well as an efficient means of communication. Its use in education can provide a number

of specific learning benefits, including the development of:

independent learning and research skills, such as improved access to subject learning

across a wide range of learning areas, as well as in integrated or cross-curricular

studies; and

communication and collaboration, such as the ability to use learning technologies to

access resources, create resources and communicate with others.

Access to resources

The internet is a huge repository of learning material. As a result, it significantly expands

the resources available to students beyond the standard print materials found in school

libraries. It gives students access to the latest reports on government and non-government

websites, including research results, scientific and artistic resources in museums and art

galleries, and other organisations with information applicable to student learning. At

secondary schooling levels, the internet can be used for undertaking reasonably

sophisticated research projects.

The internet is also a time-efficient tool for a teacher that expands the possibilities for

curriculum development.

Learning depends on the ability to find relevant and reliable information quickly and

easily, and to select, interpret and evaluate that information. Searching for information

on the internet can help to develop these skills. Classroom exercises and take-home

assessment tasks, where students are required to compare and contrast website content,

are ideal for alerting students to the requirements of writing for different audiences, the

purpose of particular content, identifying bias and judging accuracy and reliability. Since

many sites adopt particular views about issues, the internet is a useful mechanism for

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developing the skills of distinguishing fact from opinion and exploring subjectivity and

objectivity.

Communication and collaboration

The internet is a powerful tool for developing students’ communication and collaboration

skills. Above all, the internet is an effective means of building language skills. Through

email, chat rooms and discussion groups, students learn the basic principles of

communication in the written form. This gives teachers the opportunity to incorporate

internet-based activities into mainstream literacy programs and bring diversity to their

repertoires of teaching strategies. For example, website publishing can be a powerful

means of generating enthusiasm for literacy units, since most students are motivated by

the prospect of having their work posted on a website for public access.

Collaborative projects can be designed to enhance students’ literacy skills, mainly

through email messaging with their peers from other schools or even other countries.

Collaborative projects are also useful for engaging students and providing meaningful

learning experiences. In this way, the internet becomes an effective means of advancing

intercultural understanding. Moderated chat rooms and group projects can also provide

students with opportunities for collaborative learning.

Numerous protocols govern use of the internet. Learning these protocols and how to

adhere to them helps students understand the rule-based society in which they live and to

treat others with respect and decency. The internet also contributes to students’ broader

understanding of information and communication technologies (ICT) and its centrality to

the information economy and society as a whole.

Culture: Two definitions

1: High culture

The best literature, art, music, film that exists. Societies are often ‘defined’ by their high

culture.

Problem: who decides what is best – are there any timeless rules?

2: Culture as lived experience

Culture is the ordinary, everyday social world around us.

Is there a single culture?

• In the early part of the 20th century people would talk about “national culture”

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• With the rise of global media and the deregulation of information flows people

are more likely to talk about “cultures” within a nation based on age, ethnicity, interests,

gender.

• There are many cultures and an individual may belong to more than one….

• A key issue is that some groups may have more “power” than others to effect

people’s lives...

HARDWARE REQUIREMENT FOR INTERNET CONNECTIVITY

The term modem is an acronym of “modulator-demodulator”. In simple words, a modem

enables users to connect their computer to internet. It also enables to transmit and receive

data across the internet. It is the key that unlocks doors of the world of the Internet for the

user. The modems can be of various types. They may be hardware, software or controller

less. The most widely used modems are hardware modems. There are mainly three types

of hardware modems. All three types of modems work the same way. However, each has

its advantages and disadvantages. Here, we discuss them…

The oldest and simplest type of hardware modems are external modems. In fact, they are

the earliest modems that have been in use for more then 25 years. As the name suggest,

they reside outside the main computer. Therefore, they are easy to install, as the computer

need not be opened. They connect to a computer's serial port through a cable. On other

hand, the telephone line is plugged in a socket on the modem. Advantage of an external

modem is that the external modems have their own power supply. The modem can be

turned off to break an online connection quickly without powering down the computer.

Another advantage is that by having a separate power supply is that it does not drain any

power from the computer. The Main disadvantage is that the external modems are more

expensive then the internal modems.

On other hand, Internal modems come installed in the computer you buy. Internal

modems are integrated into the computer system mostly installed in the motherboard.

Hence, do not need any special attention. Internal modems are activated when you run a

dialer program to access internet. The internal modem can be turned off when you exit

the program. This can be very convenient. The major disadvantage with internal modems

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is their location. When you want to replace an internal modem you have to go inside the

computer case to change it. Internal modems usually cost less than external modems, but

the price difference is usually small.

The third significant type of hardware modem is the PC Card modem. These modems are

mainly designed for portable computers. They come in size of a credit card and could be

fitted into the PC Card slot on notebook and handheld computers. These modem cards are

removable when the modem is no longer needed. Most notably, except for their size, PC

Card modems combine the characteristics of both external and internal modems. The PC

card modems are plugged directly into an external slot in the portable computer. There is

no cable requirement like external modems. The only other requirement is the telephone

line connection. The only disadvantage is that running a PC Card modem while the

portable computer is operating on battery power drastically decreases the life of your

batteries. The portable computer need tp power the PC card modems. This is fine unless

the computer is battery operated.

Overall, you may have an external, an internal modem or a PC modem card as per your

requirements. The modem you choose should be depend upon how your computer is

configured and your preferences on accessing internet.

History

News wire services in 1920s used multiplex equipment that met the definition, but the

modem function was incidental to the multiplexing function, so they are not commonly

included in the history of modems.

Modems grew out of the need to connect teletype machines over ordinary phone lines

instead of more expensive leased lines which had previously been used for current loop-

based teleprinters and automated telegraphs. George Stibitz connected a New Hampshire

teletype to a computer in New York City by a subscriber telephone line in 1940.

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Anderson-Jacobsen brand Bell 101 dataset 110 baud RS-232 modem, in original wood

chassis

Mass-produced modems in the United States began as part of the SAGE air-defense

system in 1958, connecting terminals at various airbases, radar sites, and command-and-

control centers to the SAGE director centers scattered around the U.S. and Canada.

SAGE modems were described by AT&T's Bell Labs as conforming to their newly

published Bell 101 dataset standard. While they ran on dedicated telephone lines, the

devices at each end were no different from commercial acoustically coupled Bell 101,

110 baud modems.

In the summer of 1960, the name Data-Phone was introduced to replace the earlier term

digital subset. The 202 Data-Phone was a half-duplex asynchronous service that was

marketed extensively in late 1960. In 1962, the 201A and 201B Data-Phones were

introduced. They were synchronous modems using two-bit-per-baud phase-shift keying

(PSK). The 201A operated half-duplex at 2000 bit/s over normal phone lines, while the

201B provided full duplex 2400 bit/s service on four-wire leased lines, the send and

receive channels running on their own set of two wires each.

The famous Bell 103A dataset standard was also introduced by Bell Labs in 1962. It

provided full-duplex service at 300 baud over normal phone lines. Frequency-shift keying

was used with the call originator transmitting at 1070 or 1270 Hz and the answering

modem transmitting at 2025 or 2225 Hz. The readily available 103A2 gave an important

boost to the use of remote low-speed terminals such as the KSR33, the ASR33, and the

IBM 2741. AT&T reduced modem costs by introducing the originate-only 113D and the

answer-only 113B/C modems.

The Carterfone decision

The Novation CAT acoustically coupled modem

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For many years, the Bell System (AT&T) maintained a monopoly in the United States on

the use of its phone lines, allowing only Bell-supplied devices to be attached to its

network. Before 1968, AT&T maintained a monopoly on what devices could be

electrically connected to its phone lines. This led to a market for 103A-compatible

modems that were mechanically connected to the phone, through the handset, known as

acoustically coupled modems. Particularly common models from the 1970s were the

Novation CAT and the Anderson-Jacobson, spun off from an in-house project at the

Lawrence Livermore National Laboratory. Hush-a-Phone v. FCC was a seminal ruling in

United States telecommunications law decided by the DC Circuit Court of Appeals on

November 8, 1956. The District Court found that it was within the FCC's authority to

regulate the terms of use of AT&T's equipment. Subsequently, the FCC examiner found

that as long as the device was not physically attached it would not threaten to degenerate

the system. Later, in the Carterfone decision, the FCC passed a rule setting stringent

AT&T-designed tests for electronically coupling a device to the phone lines. AT&T

made these tests complex and expensive, so acoustically coupled modems remained

common into the early 1980s.

In December 1972, Vadic introduced the VA3400. This device was remarkable because it

provided full duplex operation at 1200 bit/s over the dial network, using methods similar

to those of the 103A in that it used different frequency bands for transmit and receive. In

November 1976, AT&T introduced the 212A modem to compete with Vadic. It was

similar in design to Vadic's model, but used the lower frequency set for transmission. It

was also possible to use the 212A with a 103A modem at 300 bit/s. According to Vadic,

the change in frequency assignments made the 212 intentionally incompatible with

acoustic coupling, thereby locking out many potential modem manufacturers. In 1977,

Vadic responded with the VA3467 triple modem, an answer-only modem sold to

computer center operators that supported Vadic's 1200-bit/s mode, AT&T's 212A mode,

and 103A operation.

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The Smartmodem and the rise of BBSes

US Robotics Sportster 14, 400 Fax modem (1994)

The next major advance in modems was the Smartmodem, introduced in 1981 by Hayes

Communications. The Smartmodem was an otherwise standard 103A 300-bit/s modem,

but was attached to a small controller that let the computer send commands to it and

enable it to operate the phone line. The command set included instructions for picking up

and hanging up the phone, dialing numbers, and answering calls. The basic Hayes

command set remains the basis for computer control of most modern modems.

Prior to the Hayes Smartmodem, modems almost universally required a two-step

process to activate a connection: first, the user had to manually dial the remote number on

a standard phone handset, and then secondly, plug the handset into an acoustic coupler.

Hardware add-ons, known simply as dialers, were used in special circumstances, and

generally operated by emulating someone dialing a handset.

With the Smartmodem, the computer could dial the phone directly by sending the modem

a command, thus eliminating the need for an associated phone for dialing and the need

for an acoustic coupler. The Smartmodem instead plugged directly into the phone line.

This greatly simplified setup and operation. Terminal programs that maintained lists of

phone numbers and sent the dialing commands became common.

The Smartmodem and its clones also aided the spread of bulletin board systems (BBSs).

Modems had previously been typically either the call-only, acoustically coupled models

used on the client side, or the much more expensive, answer-only models used on the

server side. The Smartmodem could operate in either mode depending on the commands

sent from the computer. There was now a low-cost server-side modem on the market, and

the BBSs flourished.

21

Softmodem (dumb modem)

Main article: Softmodem

Apple's GeoPort modems from the second half of the 1990s were similar. Although a

clever idea in theory, enabling the creation of more-powerful telephony applications, in

practice the only programs created were simple answering-machine and fax software,

hardly more advanced than their physical-world counterparts, and certainly more error-

prone and cumbersome. The software was finicky and ate up significant processor time,

and no longer functions in current operating system versions.

Almost all modern modems also do double-duty as a fax machine as well. Digital faxes,

introduced in the 1980s, are simply a particular image format sent over a high-speed

(commonly 14.4 kbit/s) modem. Software running on the host computer can convert any

image into fax-format, which can then be sent using the modem. Such software was at

one time an add-on, but since has become largely universal.

A PCI Winmodem/Softmodem (on the left) next to a traditional ISA modem (on the

right). Notice the less complex circuitry of the modem on the left.

A Winmodem or Softmodem is a stripped-down modem that replaces tasks traditionally

handled in hardware with software. In this case the modem is a simple digital signal

processor designed to create sounds, or voltage variations, on the telephone line.

Softmodems are cheaper than traditional modems, since they have fewer hardware

components. One downside is that the software generating the modem tones is not

simple, and the performance of the computer as a whole often suffers when it is being

used. For online gaming this can be a real concern. Another problem is lack of portability

such that other OSes (such as Linux) may not have an equivalent driver to operate the

modem. A Winmodem might not work with a later version of Microsoft Windows, if its

driver turns out to be incompatible with that later version of the operating system.

22

Narrowband/phone-line dialup modems

A standard modem of today contains two functional parts: an analog section for

generating the signals and operating the phone, and a digital section for setup and

control. This functionality is actually incorporated into a single chip, but the division

remains in theory. In operation the modem can be in one of two "modes", data mode in

which data is sent to and from the computer over the phone lines, and command mode in

which the modem listens to the data from the computer for commands, and carries them

out. A typical session consists of powering up the modem (often inside the computer

itself) which automatically assumes command mode, then sending it the command for

dialing a number. After the connection is established to the remote modem, the modem

automatically goes into data mode, and the user can send and receive data. When the user

is finished, the escape sequence, "+++" followed by a pause of about a second, is sent to

the modem to return it to command mode, and the command ATH to hang up the phone

is sent.

The commands themselves are typically from the Hayes command set, although that term

is somewhat misleading. The original Hayes commands were useful for 300 bit/s

operation only, and then extended for their 1200 bit/s modems. Faster speeds required

new commands, leading to a proliferation of command sets in the early 1990s. Things

became considerably more standardized in the second half of the 1990s, when most

modems were built from one of a very small number of "chip sets". We call this the

Hayes command set even today, although it has three or four times the numbers of

commands as the actual standard.

23

Increasing speeds (V.21 V.22 V.22bis)

A 2400 bit/s modem for a laptop.

The 300 bit/s modems used frequency-shift keying to send data. In this system the stream

of 1s and 0s in computer data is translated into sounds which can be easily sent on the

phone lines. In the Bell 103 system the originating modem sends 0s by playing a

1070 Hz tone, and 1s at 1270 Hz, with the answering modem putting its 0s on 2025 Hz

and 1s on 2225 Hz. These frequencies were chosen carefully, they are in the range that

suffer minimum distortion on the phone system, and also are not harmonics of each other.

In the 1200 bit/s and faster systems, phase-shift keying was used. In this system the two

tones for any one side of the connection are sent at the similar frequencies as in the 300

bit/s systems, but slightly out of phase. By comparing the phase of the two signals, 1s and

0s could be pulled back out, for instance if the signals were 90 degrees out of phase, this

represented two digits, "1, 0", at 180 degrees it was "1, 1". In this way each cycle of the

signal represents two digits instead of one. 1200 bit/s modems were, in effect, 600

symbols per second modems (600 baud modems) with 2 bits per symbol.

Voiceband modems generally remained at 300 and 1200 bit/s (V.21 and V.22) into the

mid 1980s. A V.22bis 2400-bit/s system similar in concept to the 1200-bit/s Bell 212

signalling was introduced in the U.S., and a slightly different one in Europe. By the late

1980s, most modems could support all of these standards and 2400-bit/s operation was

becoming common.

24

For more information on baud rates versus bit rates, see the companion article List of

device bandwidths.

Increasing speeds (one-way proprietary standards)

Many other standards were also introduced for special purposes, commonly using a high-

speed channel for receiving, and a lower-speed channel for sending. One typical example

was used in the French Minitel system, in which the user's terminals spent the majority of

their time receiving information. The modem in the Minitel terminal thus operated at

1200 bit/s for reception, and 75 bit/s for sending commands back to the servers.

Three U.S. companies became famous for high-speed versions of the same concept.

Telebit introduced its Trailblazer modem in 1984, which used a large number of 36 bit/s

channels to send data one-way at rates up to 18,432 bit/s. A single additional channel in

the reverse direction allowed the two modems to communicate how much data was

waiting at either end of the link, and the modems could change direction on the fly. The

Trailblazer modems also supported a feature that allowed them to "spoof" the UUCP "g"

protocol, commonly used on Unix systems to send e-mail, and thereby speed UUCP up

by a tremendous amount. Trailblazers thus became extremely common on Unix systems,

and maintained their dominance in this market well into the 1990s.

U.S. Robotics (USR) introduced a similar system, known as HST, although this supplied

only 9600 bit/s (in early versions at least) and provided for a larger backchannel. Rather

than offer spoofing, USR instead created a large market among Fidonet users by offering

its modems to BBS sysops at a much lower price, resulting in sales to end users who

wanted faster file transfers. Hayes was forced to compete, and introduced its own 9600-

bit/s standard, Express 96 (also known as "Ping-Pong"), which was generally similar to

Telebit's PEP. Hayes, however, offered neither protocol spoofing nor sysop discounts,

and its high-speed modems remained rare.

4800 and 9600 (V.27ter, V.32)

Echo cancellation was the next major advance in modem design. Local telephone lines

use the same wires to send and receive, which results in a small amount of the outgoing

signal bouncing back. This signal can confuse the modem. Is the signal it is "hearing" a

data transmission from the remote modem, or its own transmission bouncing back? This

was why earlier modems split the signal frequencies into answer and originate; each

25

modem simply didn't listen to its own transmitting frequencies. Even with improvements

to the phone system allowing higher speeds, this splitting of available phone signal

bandwidth still imposed a half-speed limit on modems.

Echo cancellation got around this problem. Measuring the echo delays and magnitudes

allowed the modem to tell if the received signal was from itself or the remote modem,

and create an equal and opposite signal to cancel its own. Modems were then able to send

at "full speed" in both directions at the same time, leading to the development of 4800

and 9600 bit/s modems.

Increases in speed have used increasingly complicated communications theory. 1200 and

2400 bit/s modems used the phase shift key (PSK) concept. This could transmit two or

three bits per symbol. The next major advance encoded four bits into a combination of

amplitude and phase, known as Quadrature Amplitude Modulation (QAM). Best

visualized as a constellation diagram, the bits are mapped onto points on a graph with the

x (real) and y (quadrature) coordinates transmitted over a single carrier.

The new V.27ter and V.32 standards were able to transmit 4 bits per symbol, at a rate of

1200 or 2400 baud, giving an effective bit rate of 4800 or 9600 bits per second. The

carrier frequency was 1650 Hz. For many years, most engineers considered this rate to be

the limit of data communications over telephone networks.

Error correction and compression

Operations at these speeds pushed the limits of the phone lines, resulting in high error

rates. This led to the introduction of error-correction systems built into the modems,

made most famous with Microcom's MNP systems. A string of MNP standards came out

in the 1980s, each increasing the effective data rate by minimizing overhead, from about

75% theoretical maximum in MNP 1, to 95% in MNP 4. The new method called MNP 5

took this a step further, adding data compression to the system, thereby increasing the

data rate above the modem's rating. Generally the user could expect an MNP5 modem to

transfer at about 130% the normal data rate of the modem. MNP was later "opened" and

became popular on a series of 2400-bit/s modems, and ultimately led to the development

of V.42 and V.42bis ITU standards. V.42 and V.42bis were non-compatible with MNP

but were similar in concept: Error correction and compression.

26

Another common feature of these high-speed modems was the concept of fallback,

allowing them to talk to less-capable modems. During the call initiation the modem

would play a series of signals into the line and wait for the remote modem to "answer"

them. They would start at high speeds and progressively get slower and slower until they

heard an answer. Thus, two USR modems would be able to connect at 9600 bit/s, but,

when a user with a 2400-bit/s modem called in, the USR would "fall back" to the

common 2400-bit/s speed. This would also happen if a V.32 modem and a HST modem

were connected. Because they used a different standard at 9600 bit/s, they would fall

back to their highest commonly supported standard at 2400 bit/s. The same applies to

V.32bis and 14400 bit/s HST modem, which would still be able to communicate with

each other at only 2400 bit/s.

Breaking the 9.6k barrier

In 1980 Gottfried Ungerboeck from IBM Zurich Research Laboratory applied powerful

channel coding techniques to search for new ways to increase the speed of modems. His

results were astonishing but only conveyed to a few colleagues. Finally in 1982, he

agreed to publish what is now a landmark paper in the theory of information coding. By

applying powerful parity check coding to the bits in each symbol, and mapping the

encoded bits into a two dimensional "diamond pattern", Ungerboeck showed that it was

possible to increase the speed by a factor of two with the same error rate. The new

technique was called "mapping by set partitions" (now known as trellis modulation).

Error correcting codes, which encode code words (sets of bits) in such a way that they are

far from each other, so that in case of error they are still closest to the original word (and

not confused with another) can be thought of as analogous to sphere packing or packing

pennies on a surface: the greater two bit sequences are from one another, the easier it is to

correct minor errors.

The industry was galvanized into new research and development. More powerful coding

techniques were developed, commercial firms rolled out new product lines, and the

standards organizations rapidly adopted to new technology. The "tipping point" occurred

with the introduction of the SupraFAXModem 14400 in 1991. Rockwell had introduced a

new chipset supporting not only V.32 and MNP, but the newer 14, 400 bit/s V.32bis and

the higher-compression V.42bis as well, and even included 9600 bit/s fax capability.

27

Supra, then known primarily for their hard drive systems, used this chipset to build a low-

priced 14, 400 bit/s modem which cost the same as a 2400 bit/s modem from a year or

two earlier (about US$300). The product was a runaway best-seller, and it was months

before the company could keep up with demand.

V.32bis was so successful that the older high-speed standards had little to recommend

them. USR fought back with a 16, 800 bit/s version of HST, while AT&T introduced a

one-off 19, 200 bit/s method they referred to as V.32ter (also known as V.32 terbo), but

neither non-standard modem sold well.

V.34 / 28.8k and 33.6k

An ISA modem manufactured to conform to the V.34 protocol.

Any interest in these systems was destroyed during the lengthy introduction of the 28,

800 bit/s V.34 standard. While waiting, several companies decided to "jump the gun" and

introduced modems they referred to as "V.FAST". In order to guarantee compatibility

with V.34 modems once the standard was ratified (1994), the manufacturers were forced

to use more "flexible" parts, generally a DSP and microcontroller, as opposed to purpose-

designed "modem chips".

Today the ITU standard V.34 represents the culmination of the joint efforts. It employs

the most powerful coding techniques including channel encoding and shape encoding.

From the mere 4 bits per symbol (9.6 kbit/s), the new standards used the functional

equivalent of 6 to 10 bits per symbol, plus increasing baud rates from 2400 to 3429, to

create 14.4, 28.8, and 33.6 kbit/s modems. This rate is near the theoretical Shannon limit.

28

When calculated, the Shannon capacity of a narrowband line is Bandwidth * log2(1

+ Pu / Pn), with Pu / Pn the signal-to-noise ratio. Narrowband phone lines have a

bandwidth from 300-3100 Hz, so using Pu / Pn = 10,000: capacity is approximately

36 kbit/s.

Without the discovery and eventual application of trellis modulation, maximum

telephone rates would have been limited to 3429 baud * 4 bit/symbol == approximately

14 kilobits per second using traditional QAM.

Using digital lines and PCM (V.90/92)

In the late 1990s Rockwell and U.S. Robotics introduced new technology based upon the

digital transmission used in modern telephony networks. The standard digital

transmission in modern networks is 64 kbit/s but some networks use a part of the

bandwidth for remote office signaling (eg to hang up the phone), limiting the effective

rate to 56 kbit/s DS0. This new technology was adopted into ITU standards V.90 and is

common in modern computers. The 56 kbit/s rate is only possible from the central office

to the user site (downlink) and in the United States, government regulation limits the

maximum power output to only 53.3 kbit/s. The uplink (from the user to the central

office) still uses V.34 technology at 33.6k.

Later in V.92, the digital PCM technique was applied to increase the upload speed to a

maximum of 48 kbit/s, but at the expense of download rates. For example a 48 kbit/s

upstream rate would reduce the downstream as low as 40 kbit/s, due to echo on the

telephone line. To avoid this problem, V.92 modems offer the option to turn off the

digital upstream and instead use a 33.6 kbit/s analog connection, in order to maintain a

high digital downstream of 50 kbit/s or higher. (See November and October 2000 update

at http://www.modemsite.com/56k/v92s.asp ) V.92 also adds two other features. The first

is the ability for users who have call waiting to put their dial-up Internet connection on

hold for extended periods of time while they answer a call. The second feature is the

ability to "quick connect" to one's ISP. This is achieved by remembering the analog and

digital characteristics of the telephone line, and using this saved information to reconnect

at a fast pace.

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Using compression to exceed 56k

Today's V.42, V.42bis and V.44 standards allow the modem to transmit data faster than

its basic rate would imply. For instance, a 53.3 kbit/s connection with V.44 can transmit

up to 53.3*6 == 320 kbit/s using pure text. However, the compression ratio tends to vary

due to noise on the line, or due to the transfer of already-compressed files (ZIP files,

JPEG images, MP3 audio, MPEG video). [2] At some points the modem will be sending

compressed files at approximately 50 kbit/s, uncompressed files at 160 kbit/s, and pure

text at 320 kbit/s, or any value in between. [3]

In such situations a small amount of memory in the modem, a buffer, is used to hold the

data while it is being compressed and sent across the phone line, but in order to prevent

overflow of the buffer, it sometimes becomes necessary to tell the computer to pause the

datastream. This is accomplished through hardware flow control using extra lines on the

modem–computer connection. The computer is then set to supply the modem at some

higher rate, such as 320 kbit/s, and the modem will tell the computer when to start or stop

sending data.

Compression by the ISP

As telephone-based 56k modems began losing popularity, some Internet Service

Providers such as Netzero and Juno started using pre-compression to increase the

throughput & maintain their customer base. As example, the Netscape ISP uses a

compression program that squeezes images, text, and other objects at the server, just prior

to sending them across the phone line. The server-side compression operates much more

efficiently than the "on-the-fly" compression of V.44-enabled modems. Typically website

text is compacted to 4% thus increasing effective throughput to approximately 1300

kbit/s. The accelerator also pre-compresses Flash executables and images to

approximately 30% and 12%, respectively.

The drawback of this approach is a loss in quality, where the graphics become heavily

compacted and smeared, but the speed is dramatically improved such that web pages load

in less than 5 seconds, and the user can manually choose to view the uncompressed

images at any time. The ISPs employing this approach advertise it as "DSL speeds over

regular phone lines" or simply "high speed dial-up".

30

FUNCTIONSIn addition to converting digital signals into analog signals, the modems carry out many

other tasks. Modems minimize the errors that occur while the transmission of signals.

They also have the functionality of compressing the data sent via signals. Modems also

do the task of regulating the information sent over a network.

Error Correction: In this process the modem checks if the information they

receive is undamaged. The modems involved in error correction divide the

information into packets called frames. Before sending this information, the

modems tag each of the frames with checksums. Checksum is a method of

checking redundancy in the data present on the computer. The modems that

receive the information, verify if the information matches with checksums, sent

by the error-correcting modem. If it fails to match with the checksum, the

information is sent back.

Compressing the Data: For compressing the data, it is sent together in many bits.

The bits are grouped together by the modem, in order to compress them.

Flow Control: Different modems vary in their speed of sending signals. Thus, it

creates problems in receiving the signals if either one of the modems is slow. In

the flow control mechanism, the slower modem signals the faster one to pause, by

sending a 'character'. When it is ready to catch up with the faster modem, a

different character is sent, which in turn resumes the flow of signals.

WiFi and WiMax

Wireless data modems are used in the WiFi and WiMax standards, operating at

microwave frequencies.

WiFi is principally used in laptops for Internet connections (wireless access point) and

wireless application protocol (WAP).

Mobile modems and routers

Modems which use mobile phone lines (GPRS,UMTS,HSPA,EVDO,WiMax,etc.), are

known as Cellular Modems. Cellular modems can be embedded inside a laptop or

appliance, or they can be external to it. External cellular modems are datacards and

cellular routers. The datacard is a PC card or ExpressCard which slides into a

31

PCMCIA/PC card/ExpressCard slot on a computer. The most famous brand of cellular

modem datacards is the AirCard made by Sierra Wireless. (Many people just refer to all

makes and models as "AirCards", when in fact this is a trademarked brand name.)

Nowadays, there are USB cellular modems as well that use a USB port on the laptop

instead of a PC card or ExpressCard slot. A cellular router may or may not have an

external datacard ("AirCard") that slides into it. Most cellular routers do allow such

datacards or USB modems, except for the WAAV, Inc. CM3 mobile broadband cellular

router. Cellular Routers may not be modems per se, but they contain modems or allow

modems to be slid into them. The difference between a cellular router and a cellular

modem is that a cellular router normally allows multiple people to connect to it (since it

can "route"), while the modem is made for one connection.

Most of the GSM cellular modems come with an integrated SIM cardholder (i.e, Huawei

E220, Sierra 881, etc.) The CDMA (EVDO) versions do not use SIM cards, but use

Electronic Serial Number (ESN) instead.

The cost of using a cellular modem varies from country to country. Some carriers

implement "flat rate" plans for unlimited data transfers. Some have caps (or maximum

limits) on the amount of data that can be transferred per month. Other countries have "per

Megabyte" or even "per Kilobyte" plans that charge a fixed rate per Megabyte or

Kilobyte of data downloaded; this tends to add up quickly in today's content-filled world,

which is why many people are pushing for flat data rates. See : flat rate.

The faster data rates of the newest cellular modem technologies

(UMTS,HSPA,EVDO,WiMax) are also considered to be "Broadband Cellular Modems"

and compete with other Broadband modems below.

DATA RATE TRANSFER

The speed at which a modem can transfer information, usually given in bits per second

(bps). The higher the data transfer rate, the faster the modem, but the more it costs. A

faster modem can save you money by cutting down on your long-distance charges. Three

common speeds for modems are 9,600 bps, 14,400 bps, and 28,800 bps.

32

Modems are distinguished primarily by the maximum data rate they support. Data rates

can range from 75 bits per second up to 56000 and beyond. Data from the user (i.e.

flowing from the local terminal or computer via the modem to the telephone line) is

sometimes at a lower rate than the other direction, on the assumption that the user cannot

type more than a few characters per second.

Various data compression and error correction algorithms are required to support the

highest speeds. Other optional features are auto-dial (auto-call) and auto-answer which

allow the computer to initiate and accept calls without human intervention. Most modern

modems support a number of different protocols, and two modems, when first connected,

will automatically negotiate to find a common protocol (this process may be audible

through the modem or computer's loudspeakers). Some modem protocols allow the two

modems to renegotiate ("retrain") if the initial choice of data rate is too high and gives

too many transmission errors.

A modem may either be internal (connected to the computer's bus) or external ("stand-

alone", connected to one of the computer's serial ports). The actual speed of transmission

in characters per second depends not just the modem-to-modem data rate, but also on the

speed with which the processor can transfer data to and from the modem, the kind of

compression used and whether the data is compressed by the processor or the modem, the

amount of noise on the telephone line (which causes retransmissions), the serial character

format (typically 8N1: one start bit, eight data bits, no parity, one stop bit).

WIRELESS TRANSMISSION AND BANDWIDTH

The term "wireless" has become a generic and all-encompassing word used to describe

communications in which electromagnetic waves or RF (rather than some form of wire)

carry a signal over part or the entire communication path. Common examples of wireless

equipment in use today include:

Professional LMR (Land Mobile Radio) and SMR (Specialized Mobile Radio)

typically used by business, industrial and Public Safety entities

33

Consumer Two Way Radio including FRS (Family Radio Service), GMRS

(General Mobile Radio Service) and Citizens band ("CB") radios

The Amateur Radio Service (Ham radio)

Consumer and professional Marine VHF radios

Cellular telephones and pagers: provide connectivity for portable and mobile

applications, both personal and business.

Global Positioning System (GPS): allows drivers of cars and trucks, captains of

boats and ships, and pilots of aircraft to ascertain their location anywhere on

earth.

Cordless computer peripherals: the cordless mouse is a common example;

keyboards and printers can also be linked to a computer via wireless.

Cordless telephone sets: these are limited-range devices, not to be confused with

cell phones.

Satellite television: allows viewers in almost any location to select from hundreds

of channels.

Wireless gaming: new gaming consoles allow players to interact and play in the

same game regardless of whether they are playing on different consoles. Players

can chat, send text messages as well as record sound and send it to their friends.

Controllers also use wireless technology. They do not have any cords but they can

send the information from what is being pressed on the controller to the main

console which then processes this information and makes it happen in the game.

All of these steps are completed in milliseconds.

Wireless networking (i.e. the various types of unlicensed 2.4 GHz WiFi devices) is used

to meet many needs. Perhaps the most common use is to connect laptop users who travel

from location to location. Another common use is for mobile networks that connect via

satellite. A wireless transmission method is a logical choice to network a LAN segment

that must frequently change locations. The following situations justify the use of wireless

technology:

To span a distance beyond the capabilities of typical cabling,

To avoid obstacles such as physical structures, EMI, or RFI,

To provide a backup communications link in case of normal network failure,

34

To link portable or temporary workstations,

To overcome situations where normal cabling is difficult or financially

impractical, or

To remotely connect mobile users or networks.

Wireless communication can be via:

radio frequency communication,

microwave communication, for example long-range line-of-sight via highly

directional antennas, or short-range communication, or

infrared (IR) short-range communication, for example from remote controls or via

IRDA.

Applications may involve point-to-point communication, point-to-multipoint

communication, broadcasting, cellular networks and other wireless networks.

The term "wireless" should not be confused with the term "cordless", which is generally

used to refer to powered electrical or electronic devices that are able to operate from a

portable power source (e.g. a battery pack) without any cable or cord to limit the mobility

of the cordless device through a connection to the mains power supply. Some cordless

devices, such as cordless telephones, are also wireless in the sense that information is

transferred from the cordless telephone to the telephone's base unit via some type of

wireless communications link. This has caused some disparity in the usage of the term

"cordless", for example in Digital Enhanced Cordless Telecommunications.

In the last fifty years, wireless communications industry experienced drastic changes

driven by many technology innovations.

Early wireless workDavid E. Hughes, eight years before Hertz's experiments, induced electromagnetic waves

in a signaling system. Hughes transmitted Morse code by an induction apparatus. In

1878, Hughes's induction transmission method utilized a "clockwork transmitter" to

transmit signals. In 1885, T. A. Edison used a vibrator magnet for induction transmission.

In 1888, Edison deploys a system of signaling on the Lehigh Valley Railroad. In 1891,

Edison obtained the wireless patent for this method using inductance (U.S. Patent

465,971).

35

The demonstration of the theory of electromagnetic waves by Heinrich Rudolf Hertz in

1888 was important. The theory of electromagnetic waves were predicted from the

research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that

electromagnetic waves could be transmitted and caused to travel through space at straight

lines and that they were able to be received by an experimental apparatus. The

experiments were not followed up by Hertz. The practical applications of the wireless

communication and remote control technology were implemented by Nikola Tesla.

Bandwidth (Speed)

Wireless Network uses Transmitted signal rather then Wire (CAT5e/CAT6). There

are few parameters that are affecting Wireless Network communication that are not

an issue when using Wired Network. The two most important variables are Signal

Strength, Signal Stability.

Signal Strength is mainly depending on the Distance and the number and nature of

obstructions. Stability is affected by the presence of other signals in the air +

temporal changes in the environment.  As an example Computer movement and

orientation, people movement, electrical appliances “kinking in and out”, and other

interferences are constantly changing and affecting the signal in a temporal manner.

The general results are that Wireless Bandwidth (Speed) and Latency becomes

“None Stop” changeable variables.

Wireless Bandwidth (or “Speed”) of Wireless depends on what standard in use

(802.11b. 802.11g, etc.) and how much of the signal is available for processing.  The

smaller the signal the less bandwidth.

- VSAT

Short for very small aperture terminal, an earthbound station used in satellite

communications of data, voice and video signals, excluding broadcast television. A

VSAT consists of two parts, a transceiver that is placed outdoors in direct line of sight to

the satellite and a device that is placed indoors to interface the transceiver with the end

user's communications device, such as a PC. The transceiver receives or sends a signal to

a satellite transponder in the sky. The satellite sends and receives signals from a ground

station computer that acts as a hub for the system. Each end user is interconnected with

36

the hub station via the satellite, forming a star topology. The hub controls the entire

operation of the network. For one end user to communicate with another, each

transmission has to first go to the hub station that then retransmits it via the satellite to the

other end user's VSAT. VSAT can handle up to 56 Kbps.

- RADIO

Direct broadcast satellite, WiFi, and mobile phones all use modems to communicate, as

do most other wireless services today. Modern telecommunications and data networks

also make extensive use of radio modems where long distance data links are required.

Such systems are an important part of the PSTN, and are also in common use for high-

speed computer network links to outlying areas where fibre is not economical.

Even where a cable is installed, it is often possible to get better performance or make

other parts of the system simpler by using radio frequencies and modulation techniques

through a cable. Coaxial cable has a very large bandwidth, however signal attenuation

becomes a major problem at high data rates if a digital signal is used. By using a modem,

a much larger amount of digital data can be transmitted through a single piece of wire.

Digital cable television and cable Internet services use radio frequency modems to

provide the increasing bandwidth needs of modern households. Using a modem also

allows for frequency-division multiple access to be used, making full-duplex digital

communication with many users possible using a single wire.

Wireless modems come in a variety of types, bandwidths, and speeds. Wireless modems

are often referred to as transparent or smart. They transmit information that is modulated

onto a carrier frequency to allow many simultaneous wireless communication links to

work simultaneously on different frequencies.

Transparent modems operate in a manner similar to their phone line modem cousins.

Typically, they were half duplex, meaning that they could not send and receive data at the

same time. Typically transparent modems are polled in a round robin manner to collect

small amounts of data from scattered locations that do not have easy access to wired

infrastructure. Transparent modems are most commonly used by utility companies for

data collection.

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Smart modems come with a media access controller inside which prevents random data

from colliding and resends data that is not correctly received. Smart modems typically

require more bandwidth than transparent modems, and typically achieve higher data

rates. The IEEE 802.11 standard defines a short range modulation scheme that is used on

a large scale throughout the world.

OBSTACLES TO EFFECTIVE TRANSMISSION

While a message source may be able to deliver a message through a transmission

medium, there are many potential obstacles to the message successfully reaching the

receiver the way the sender intends.  The potential obstacles that may affect good

communication include:

Poor Encoding – This occurs when the message source fails to create the right

sensory stimuli to meet the objectives of the message.  For instance, in person-to-

person communication, verbally phrasing words poorly so the intended

communication is not what is actually meant, is the result of poor encoding.  Poor

encoding is also seen in advertisements that are difficult for the intended audience

to understand, such as words or symbols that lack meaning or, worse, have totally

different meaning within a certain cultural groups.  This often occurs when

marketers use the same advertising message across many different countries. 

Differences due to translation or cultural understanding can result in the message

receiver having a different frame of reference for how to interpret words, symbols,

sounds, etc.  This may lead the message receiver to decode the meaning of the

message in a different way than was intended by the message sender.

Poor Decoding – This refers to a message receiver’s error in processing the

message so that the meaning given to the received message is not what the source

intended.  This differs from poor encoding when it is clear, through comparative

analysis with other receivers, that a particular receiver perceived a message

differently from others and from what the message source intended.  Clearly, as we

noted above, if the receiver’s frame of reference is different (e.g., meaning of

words are different) then decoding problems can occur.  More likely, when it

comes to marketing promotions, decoding errors occur due to personal or

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psychological factors, such as not paying attention to a full television

advertisement, driving too quickly past a billboard, or allowing one’s mind to

wonder while talking to a salesperson.

Medium Failure – Sometimes communication channels break down and end up

sending out weak or faltering signals.  Other times the wrong medium is used to

communicate the message.  For instance, trying to educate doctors about a new

treatment for heart disease using television commercials that quickly flash highly

detailed information is not going to be as effective as presenting this information in

a print ad where doctors can take their time evaluating the information.

Communication Noise – Noise in communication occurs when an outside force in

someway affects delivery of the message.  The most obvious example is when loud

sounds block the receiver’s ability to hear a message.  Nearly any distraction to the

sender or the receiver can lead to communication noise.  In advertising, many

customers are overwhelmed (i.e., distracted) by the large number of advertisements

they encountered each day.  Such advertising clutter (i.e., noise) makes it difficult

for advertisers to get their message through to desired customers.

STEPS REQUIRED TO CONNECT PC TO INTERNET

General Guidelines

Use a Firewall

The most important step when setting up a new computer is to install a firewall

BEFORE you connect it to the Internet. Whether this is a hardware router/firewall or a

software firewall it is important that you have immediate protection when you are

connecting to the Internet. This is because the minute you connect your computer to the

Internet there will be remote computers or worms scanning large blocks of IP addresses

looking for computers with security holes. When you connect your computer, if one of

these scans find you, it will be able to infect your computer as you do not have the latest

security updates. You may be thinking, what are the chances of my computer getting

scanned with all the millions of computers active on the Internet. The truth is that your

chances are extremely high as there are thousands, if not more, computers scanning at

any given time. The best scolution is if you have a hardware router/firewall installed..

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This is because you will be behind that device immediately on turning on your computer

and there will be no lapse of time between your connecting to the Internet and being

secure. If a hardware based firewall is not available then you should use a software based

firewall. Many of the newer operating systems contain a built-in firewall that you should

immediately turn on. If your operating system does not contain a built-in firewall then

you should download and install a free firewall as there are many available. If you have a

friend or another computer with a cd rom burner, download the firewall and burn it onto a

CD so that you can install it before you even connect your computer to the Internet. We

have put together a tutorial on firewalls that you can read by clicking on the link below:

Disable services that you do not immediately need

Disable any non-essential services or applications that are running on your computer

before you connect to the Internet. When an operating system is not patched to the latest

security updates there are generally a few applications that have security holes in them.

By disabling services that you do not immediately need or plan to use you minimize the

risk of these security holes being used by a malicious user or piece of software.

Download the latest security updates

Now that you have a firewall and non-essential services disabled, it is time to connect

your computer to the Internet and download all the available security updates for your

operating system. By downloading these updates you will ensure that your computer is up

to date with all the latest available security patches released for your particular operating

system and therefore making it much more difficult for you to get infected with a piece of

malware.

Use an Antivirus Software

Many of the programs that will automatically attempt to infect your computer are worms,

trojans, and viruses. By using a good and up to date antivirus software you will be able to

catch these programs before they can do much harm. You can find a listing of some free

antivirus programs at the below link:

Browse through the various free antivirus programs at the above list and install one

before you connect to the Internet. Download it from another computer and burn it onto a

CD so that it is installed before you connect.

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Specific Steps for Windows 2000

Windows 2000 does not contain a full featured firewall, but does contain a way for you to

get limited security until you update the computer and install a true firewall. Windows

2000 comes with a feature called TCP filtering that we can use as a temporary measure.

To set this up follow these steps:

1. Click on Start, then Settings and then Control Panel to enter the control panel.

2. Double-click on the Network and Dial-up Connections control panel icon.

3. Right-click on the connection icon that is currently being used for Internet access

and click on properties. The connection icon is usually the one labeled Local

Area Connection

4. Double-click on Internet Protocol (TCP/IP) and then click on the Advanced

button.

5. Select the Options tab

6. Double-click on TCP/IP Filtering.

7. Put a checkmark in the box labeled Enable TCP/IP Filtering (All Adapters) and

change all the radio dial options to Permit Only.

8. Press the OK button.

9. If it asks to reboot, please do so.

After it reboots your computer will now be protected from the majority of attacks from

the Internet. Now immediately go to http://www.windowsupdate.com/ and download and

install all critical updates and service packs available for your operating system. Keep

going back and visiting this page until all the updates have been installed.

Once that is completed install an antivirus software and free firewall, and disable the

filtering we set up previously.

Specific Steps for Microsoft Windows XP

If you have recently purchased a computer and it came with XP Service Pack 2 installed,

then the firewall will be enabled by default and you will not have to do anything but

install a antivirus software and check for any new updates at

http://www.windowsupdate.com/.

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On the other hand, if this is an older computer, or you are re-installing one, then you

should follow these steps before you connect to the Internet:

1. Log into Windows XP with an administrator account.

2. Enable the Internet Connection Firewall by following the steps found in the

following tutorial link: Configuring Windows XP Internet Connection

Firewall

3. Once the firewall has been turned immediately go to www.windowsupdate.com

and download and install all critical updates and service packs available for your

operating system. Keep going back and visiting this page until all the updates

have been installed.

4. Once that is completed install an antivirus software and free firewall.

5. Disable the built in XP firewall.

Specific Steps for MAC OSX

Mac OSX has a built-in firewall that should be used before connecting to the Internet. To

turn this firewall on follow these steps:

1. Open up the System Preferences

2. Click on the Sharing icon

3. Click on the Firewall tab

4. Click on the Start button

5. Now the screen should show the status of the Firewall as On.

Now that the firewall is configured you should connect to the Internet and immediately

check for new updates from Apple by following these steps:

1. Choose System Preferences from the Apple Menu.

2. Choose Software Update from the View menu.

3. Click Update Now.

4. Select the items you want to install, then click Install.

5. Enter an Admin user name and password.

6. After the update is complete, restart the computer if necessary

Now install an antivirus software on your computer if one is not already.

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Specific Steps for Linux/UNIX

Almost all Linux distributions come with a built in firewall which is usually iptables.

Make sure that the firewall is starting automatically at boot up and is configured to deny

all traffic inbound to your computer except for the services you require like SSH.

Unfortunately iptables would require a tutorial all in its own, so I will refer you to this

already created tutorial:

Installing and Configuring iptables

Once the firewall is configured, go to the respective site for your Linux distribution and

immediately download and install any of the latest security updates that are available.

Windows is not the only operating system with security vulnerabilities and it is just as

important for Linux users to have an up to date operating system.

Conclusion

As you can see the most important step that should be done before connecting to the

Internet is to install a firewall and block all ports that you do not need open. This will

assure us that your computer will not become hacked by many of the worms and bots out

on the Internet. Once a firewall is installed, updating your computer and installing an

antivirus software are the next steps. Please follow these steps, as if it is not done, your

computer will ultimately get compromised and then further proliferate the infection of

others..

PROBLEMS OF TELECOMMUNICATION

Information technology is continually developing and in the last few years there has been

a rapid growth in electronic telecommunications to provide Internet and other network-

based services. Interest in using telecommunications to provide services to the public is

growing, with a number of pilot services being set up across the country to explore

market potential and/or stimulate demand.Administrations across Europe are now using

telecommunications technology to provide citizens with information (Hoare, 1998). The

British Government, for instance, has issued a directive that 25% of all civil service

communications must be on-line by 2002. This is intended to provide savings in

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paperwork and a streamlined service.An area of possible government assistance is to

provide the public with on-line information about welfare benefit entitlement. This may

have benefits for all members of society but could be of particular value for retired and

older members of the public, many of whom do not always claim their entitlement. It is

estimated in the UK, for example, that one million pensioners could be entitled to Income

Support that they are not claiming (Benefits Agency, 1998). To provide information to

the public, the Benefits Agency produces a website of over 1,000 pages for customers to

browse through which can be viewed at http://www.dss.gov.uk/ba. Yet while many

people are now connected to the Internet, and the EU average is 25 computers connected

per thousand people, (Lennon, 1999) the number of older or retired people using it is still

quite small. An indication of this is given by the results of the worldwide 10th Georgia

Tech web survey (GVU, 1999). The survey, conducted in 1998, received 5,022 responses

of which only 2.7% were from people who were 66 years of age and over.This raises the

key question of whether older people will be able to benefit from the promise of the

connected future, with information available electronically on tap, or whether they will

get left behind. This also represents a lost opportunity for suppliers as, according to Oftel

(the UK telephone watchdog organisation) and disability campaign groups, A growing

grey market containing millions of potential customers is being ignored in the telecoms

boom, Dawe (1998).

Domain Name System

The Domain Name System (DNS) is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. An often-used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, www.example.com translates to 192.0.32.10.

The Domain Name System makes it possible to assign domain names to groups of Internet users in a meaningful way, independent of each user's physical location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device. Internet domain names are easier to remember

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than IP addresses such as 208.77.188.166 (IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). People take advantage of this when they recite meaningful URLs and e-mail addresses without having to know how the machine will actually locate them.

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed, fault tolerant, and helped avoid the need for a single central register to be continually consulted and updated.

In general, the Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.

Other identifiers such as RFID tags, UPC codes, International characters in email addresses and host names, and a variety of other identifiers could all potentially utilize DNS.[1]

The Domain Name System also defines the technical underpinnings of the functionality of this database service. For this purpose it defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the Internet Protocol Suite (TCP/IP).

Overview

The Internet maintains two principal namespaces, the domain name hierarchy and the Internet Protocol (IP) address system.[3] The Domain Name System maintains the domain namespace and provides translation services between these two namespaces. Internet name servers and a communications protocol, implement the Domain Name System.[4] A DNS name server is a server that stores the DNS records, such as address (A) records, name server (NS) records, and mail exchanger (MX) records for a domain name and responds with answers to queries against its database.

History

The practice of using a name as a humanly more meaningful abstraction of a host's numerical address on the network dates back to the ARPANET era. Before the DNS was invented in 1983, each computer on the network retrieved a file called HOSTS.TXT from a computer at SRI (now SRI International).[5][6] The HOSTS.TXT file mapped names to numerical addresses. A hosts file still exists on most modern operating systems, either by default or through explicit configuration. Many operating systems use name resolution

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logic that allows the administrator to configure selection priorities for available DNS resolution methods.

The rapid growth of the network required a scalable system that recorded a change in a host's address in one place only. Other hosts would learn about the change dynamically through a notification system, thus completing a globally accessible network of all hosts' names and their associated IP addresses.

At the request of Jon Postel, Paul Mockapetris invented the Domain Name System in 1983 and wrote the first implementation. The original specifications appeared in RFC 882 and RFC 883 which were superseded in November 1987 by RFC 1034[2] and RFC 1035.[4] Several additional Request for Comments have proposed various extensions to the core DNS protocols.

In 1984, four Berkeley students—Douglas Terry, Mark Painter, David Riggle and Songnian Zhou—wrote the first UNIX implementation, which was maintained by Ralph Campbell thereafter. In 1985, Kevin Dunlap of DEC significantly re-wrote the DNS implementation and renamed it BIND—Berkeley Internet Name Domain. Mike Karels, Phil Almquist and Paul Vixie have maintained BIND since then. BIND was ported to the Windows NT platform in the early 1990s.

BIND was widely distributed, especially on Unix systems, and is the dominant DNS software in use on the Internet.[7] With the heavy use and resulting scrutiny of its open-source code, as well as increasingly more sophisticated attack methods, many security flaws were discovered in BIND. This contributed to the development of a number of alternative nameserver and resolver programs. BIND itself was re-written from scratch in version 9, which has a security record comparable to other modern Internet software.

The DNS protocol was developed and defined in the early 1980s and published by the Internet Engineering Task Force.

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Structure

The domain name space

The hierarchical domain name system, organized into zones, each served by a name server.

The domain name space consists of a tree of domain names. Each node or leaf in the tree has zero or more resource records, which hold information associated with the domain name. The tree sub-divides into zones beginning at the root zone. A DNS zone consists of a collection of connected nodes authoritatively served by an authoritative nameserver. (Note that a single nameserver can host several zones.)

Administrative responsibility over any zone may be divided, thereby creating additional zones. Authority is said to be delegated for a portion of the old space, usually in form of sub-domains, to another nameserver and administrative entity. The old zone ceases to be authoritative for the new zone.

Domain name formulation

The definitive descriptions of the rules for forming domain names appear in RFC 1035, RFC 1123, and RFC 2181. A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com.

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The right-most label conveys the top-level domain; for example, the domain name www.example.com belongs to the top-level domain com.

The hierarchy of domains descends from right to left; each label to the left specifies a subdivision, or subdomain of the domain to the right. For example: the label example specifies a subdomain of the com domain, and www is a subdomain of example.com. This tree of subdivisions may consist of 127 levels.

Each label may contain up to 63 characters. The full domain name may not exceed a total length of 253 characters.[8] In practice, some domain registries may have shorter limits.

DNS names may technically consist of any character representable in an octet (RFC 3696). However, the allowed formulation of domain names in the DNS root zone, and most other subdomains, uses a preferred format and character set. The characters allowed in a label are a subset of the ASCII character set, and includes the characters a through z, A through Z, digits 0 through 9, and the hyphen. This rule is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in case-independent manner. Labels may not start or end with a hyphen, nor may two hyphens occur in sequence.

A hostname is a domain name that has at least one IP address associated. For example, the domain names www.example.com and example.com are also hostnames, whereas the com domain is not.

Internationalized domain namesMain article: Internationalized domain name

The permitted character set of the DNS prevented the representation of names and words of many languages in their native alphabets or scripts. ICANN has approved the Punycode-based Internationalized domain name (IDNA) system, which maps Unicode strings into the valid DNS character set. In 2009 ICANN approved the installation of IDN country code top-level domains. In addition, many registries of the existing TLDs have adopted IDNA.

Name servers

The Domain Name System is maintained by a distributed database system, which uses the client-server model. The nodes of this database are the name servers. Each domain has at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it. The top of the hierarchy is served by the root nameservers, the servers to query when looking up (resolving) a top-level domain name (TLD).

Authoritative name server

An authoritative name server is a name server that gives answers that have been configured by an original source, for example, the domain administrator or by dynamic DNS methods, in contrast to answers that were obtained via a regular DNS query to

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another name server. An authoritative-only name server only returns answers to queries about domain names that have been specifically configured by the administrator.

An authoritative name server can either be a master server or a slave server. A master server is a server that stores the original (master) copies of all zone records. A slave server uses an automatic updating mechanism of the DNS protocol in communication with its master to maintain an identical copy of the master records.

Every DNS zone must be assigned a set of authoritative name servers that are installed in NS records in the parent zone.

When domain names are registered with a domain name registrar their installation at the domain registry of a top level domain requires the assignment of a primary name server and at least one secondary name server. The requirement of multiple name servers aims to make the domain still functional even if one name server becomes inaccessible or inoperable.[9] The designation of a primary name server is solely determined by the priority given to the domain name registrar. For this purpose generally only the fully qualified domain name of the name server is required, unless the servers are contained in the registered domain, in which case the corresponding IP address is needed as well.

Primary name servers are often master name servers, while secondary name server may be implemented as slave servers.

An authoritative server indicates its status of supplying definitive answers, deemed authoritative, by setting a software flag (a protocol structure bit), called the Authoritative Answer (AA) bit in its responses.[4] This flag is usually reproduced prominently in the output of DNS administration query tools (such as dig) to indicate that the responding name server is an authority for the domain name in question.[4]

Recursive and caching name server

In principle, authoritative name servers are sufficient for the operation of the Internet. However, with only authoritative name servers operating, every DNS query must start with recursive queries at the root zone of the Domain Name System and each user system must implement resolver software capable of recursive operation.

To improve efficiency, reduce DNS traffic across the Internet, and increase performance in end-user applications, the Domain Name System supports DNS cache servers which store DNS query results for a period of time determined in the configuration (time-to-live) of the domain name record in question. Typically, such caching DNS servers, also called DNS caches, also implement the recursive algorithm necessary to resolve a given name starting with the DNS root through to the authoritative name servers of the queried domain. With this function implemented in the name server, user applications gain efficiency in design and operation.

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The combination of DNS caching and recursive functions in a name server is not mandatory, the functions can be implemented independently in servers for special purposes.

Internet service providers typically provide recursive and caching name servers for their customers. In addition, many home networking routers implement DNS caches and recursors to improve efficiency in the local network.

DNS resolversSee also: resolv.conf

The client-side of the DNS is called a DNS resolver. It is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address.

A DNS query may be either a non-recursive query or a recursive query:

A non-recursive query is one in which the DNS server provides a record for a domain for which it is authoritative itself, or it provides a partial result without querying other servers.

A recursive query is one for which the DNS server will fully answer the query (or give an error) by querying other name servers as needed. DNS servers are not required to support recursive queries.

The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in the query headers.

Resolving usually entails iterating through several name servers to find the needed information. However, some resolvers function simplistically and can communicate only with a single name server. These simple resolvers (called "stub resolvers") rely on a recursive name server to perform the work of finding information for them.

Operation

Address resolution mechanism

Domain name resolvers determine the appropriate domain name servers responsible for the domain name in question by a sequence of queries starting with the right-most (top-level) domain label.

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A DNS recursor consults three nameservers to resolve the address www.wikipedia.org.

The process entails:

1. A system that needs to use the DNS is configured with the known addresses of the root servers. This is often stored in a file of root hints, which are updated periodically by an administrator from a reliable source.

2. Query one of the root servers to find the server authoritative for the top-level domain.

3. Query the obtained TLD DNS server for the address of a DNS server authoritative for the second-level domain.

4. Repeating the previous step to process each domain name label in sequence, until the final step which would, rather than generating the address of the next DNS server, return the IP address of the host sought.

The diagram illustrates this process for the host www.wikipedia.org.

The mechanism in this simple form would place a large operating burden on the root servers, with every search for an address starting by querying one of them. Being as critical as they are to the overall function of the system, such heavy use would create an insurmountable bottleneck for trillions of queries placed every day. In practice caching is used in DNS servers to overcome this problem, and as a result, root nameservers actually are involved with very little of the total traffic.

Circular dependencies and glue records

Name servers in delegations appear listed by name, rather than by IP address. This means that a resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred. Since this can introduce a circular dependency if the nameserver referred to is under the domain for which it is authoritative, it is occasionally necessary for the nameserver providing the delegation to also provide the IP address of the next nameserver. This record is called a glue record.

For example, assume that the sub-domain en.wikipedia.org contains further sub-domains (such as something.en.wikipedia.org) and that the authoritative name server for these

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lives at ns1.something.en.wikipedia.org. A computer trying to resolve something.en.wikipedia.org will thus first have to resolve ns1.something.en.wikipedia.org. Since ns1 is also under the something.en.wikipedia.org subdomain, resolving ns1.something.en.wikipedia.org requires resolving something.en.wikipedia.org which is exactly the circular dependency mentioned above. The dependency is broken by the glue record in the nameserver of en.wikipedia.org that provides the IP address of ns1.something.en.wikipedia.org directly to the requestor, enabling it to bootstrap the process by figuring out where ns1.something.en.wikipedia.org is located.

Record caching

Because of the large volume of requests generated in the DNS for the public Internet, the designers wished to provide a mechanism to reduce the load on individual DNS servers. To this end, the DNS resolution process allows for caching of records for a period of time after an answer. This entails the local recording and subsequent consultation of the copy instead of initiating a new request upstream. The time for which a resolver caches a DNS response is determined by a value called the time to live (TTL) associated with every record. The TTL is set by the administrator of the DNS server handing out the authoritative response. The period of validity may vary from just seconds to days or even weeks.

As a noteworthy consequence of this distributed and caching architecture, changes to DNS records do not propagate throughout the network immediately, but require all caches to expire and refresh after the TTL. RFC 1912 conveys basic rules for determining appropriate TTL values.

Some resolvers may override TTL values, as the protocol supports caching for up to 68 years or no caching at all. Negative caching, i.e. the caching of the fact of non-existence of a record, is determined by name servers authoritative for a zone which must include the Start of Authority (SOA) record when reporting no data of the requested type exists. The value of the MINIMUM field of the SOA record and the TTL of the SOA itself is used to establish the TTL for the negative answer.

Reverse lookup

The term reverse lookup refers to performing a DNS query to find one or more DNS names associated with a given IP address.

The DNS stores IP addresses in form of specially formatted names as pointer (PTR) records using special domains. For IPv4, the domain is in-addr.arpa. For IPv6, the reverse lookup domain is ip6.arpa. The IP address is represented as a name in reverse-ordered octet representation for IPv4, and reverse-ordered nibble representation for IPv6.

When performing a reverse lookup, the DNS client converts the address into these formats, and then queries the name for a PTR record following the delegation chain as for

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any DNS query. For example, the IPv4 address 208.80.152.2 is represented as a DNS name as 2.152.80.208.in-addr.arpa. The DNS resolver begins by querying the root servers, which point to ARIN's servers for the 208.in-addr.arpa zone. From there the Wikimedia servers are assigned for 152.80.208.in-addr.arpa, and the PTR lookup completes by querying the wikimedia nameserver for 2.152.80.208.in-addr.arpa, which results in an authoritative response.

Client lookup

DNS resolution sequence.

Users generally do not communicate directly with a DNS resolver. Instead DNS resolution takes place transparently in applications programs such as web browsers, e-mail clients, and other Internet applications. When an application makes a request that requires a domain name lookup, such programs send a resolution request to the DNS resolver in the local operating system, which in turn handles the communications required.

The DNS resolver will almost invariably have a cache (see above) containing recent lookups. If the cache can provide the answer to the request, the resolver will return the value in the cache to the program that made the request. If the cache does not contain the answer, the resolver will send the request to one or more designated DNS servers. In the case of most home users, the Internet service provider to which the machine connects will usually supply this DNS server: such a user will either have configured that server's address manually or allowed DHCP to set it; however, where systems administrators have configured systems to use their own DNS servers, their DNS resolvers point to separately maintained nameservers of the organization. In any event, the name server thus queried will follow the process outlined above, until it either successfully finds a result or does not. It then returns its results to the DNS resolver; assuming it has found a result, the resolver duly caches that result for future use, and hands the result back to the software which initiated the request.

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Broken resolvers

An additional level of complexity emerges when resolvers violate the rules of the DNS protocol. A number of large ISPs have configured their DNS servers to violate rules (presumably to allow them to run on less-expensive hardware than a fully compliant resolver), such as by disobeying TTLs, or by indicating that a domain name does not exist just because one of its name servers does not respond.[10]

As a final level of complexity, some applications (such as web-browsers) also have their own DNS cache, in order to reduce the use of the DNS resolver library itself. This practice can add extra difficulty when debugging DNS issues, as it obscures the freshness of data, and/or what data comes from which cache. These caches typically use very short caching times — on the order of one minute. Internet Explorer offers a notable exception: recent versions cache DNS records for half an hour.[11]

Other applications

The system outlined above provides a somewhat simplified scenario. The Domain Name System includes several other functions:

Hostnames and IP addresses do not necessarily match on a one-to-one basis. Many hostnames may correspond to a single IP address: combined with virtual hosting, this allows a single machine to serve many web sites. Alternatively a single hostname may correspond to many IP addresses: this can facilitate fault tolerance and load distribution, and also allows a site to move physical location seamlessly.

There are many uses of DNS besides translating names to IP addresses. For instance, Mail transfer agents use DNS to find out where to deliver e-mail for a particular address. The domain to mail exchanger mapping provided by MX records accommodates another layer of fault tolerance and load distribution on top of the name to IP address mapping.

E-mail Blacklists: The DNS system is used for efficient storage and distribution of IP addresses of blacklisted e-mail hosts. The usual method is putting the IP address of the subject host into the sub-domain of a higher level domain name, and resolve that name to different records to indicate a positive or a negative. A hypothetical example using blacklist.com,

o 102.3.4.5 is blacklisted => Creates 5.4.3.102.blacklist.com and resolves to 127.0.0.1

o 102.3.4.6 is not => 6.4.3.102.blacklist.com is not found, or default to 127.0.0.2

o E-mail servers can then query blacklist.com through the DNS mechanism to find out if a specific host connecting to them is in the blacklist. Today many of such blacklists, either free or subscription-based, are available mainly for use by email administrators and anti-spam software.

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Software Updates: many anti-virus and commercial software now use the DNS system to store version numbers of the latest software updates so client computers do not need to connect to the update servers every time. For these types of applications, the cache time of the DNS records are usually shorter.

Sender Policy Framework and DomainKeys, instead of creating their own record types, were designed to take advantage of another DNS record type, the TXT record.

To provide resilience in the event of computer failure, multiple DNS servers are usually provided for coverage of each domain, and at the top level, thirteen very powerful root servers exist, with additional "copies" of several of them distributed worldwide via Anycast.

Dynamic DNS (also referred to as DDNS) provides clients the ability to update their IP address in the DNS after it changes due to mobility, e.g.

Protocol details

DNS primarily uses User Datagram Protocol (UDP) on port number 53[12] to serve requests. DNS queries consist of a single UDP request from the client followed by a single UDP reply from the server. The Transmission Control Protocol (TCP) is used when the response data size exceeds 512 bytes, or for tasks such as zone transfers. Some operating systems, such as HP-UX, are known to have resolver implementations that use TCP for all queries, even when UDP would suffice.

DNS resource records

Further information: List of DNS record types

A Resource Record (RR) is the basic data element in the domain name system. Each record has a type (A, MX, etc.), an expiration time limit, a class, and some type-specific data. Resource records of the same type define a resource record set. The order of resource records in a set, returned by a resolver to an application, is undefined, but often servers implement round-robin ordering to achieve load balancing. DNSSEC, however, works on complete resource record sets in a canonical order.

When sent over an IP network, all records use the common format specified in RFC 1035 and shown below.

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RR (Resource record) fields

Field DescriptionLength (octets)

NAME Name of the node to which this record pertains. (variable)

TYPE Type of RR. For example, MX is type 15. 2

CLASS Class code. 2

TTLUnsigned time in seconds that RR stays valid, maximum is 2147483647.

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RDLENGTH Length of RDATA field. 2

RDATA Additional RR-specific data. (variable)

NAME is the fully qualified domain name of the node in the tree. On the wire, the name may be shortened using label compression where ends of domain names mentioned earlier in the packet can be substituted for the end of the current domain name.

TYPE is the record type. It indicates the format of the data and it gives a hint of its intended use. For example, the A record is used to translate from a domain name to an IPv4 address, the NS record lists which name servers can answer lookups on a DNS zone, and the MX record specifies the mail server used to handle mail for a domain specified in an e-mail address (see also List of DNS record types).

RDATA is data of type-specific relevance, such as the IP address for address records, or the priority and hostname for MX records. Well known record types may use label compression in the RDATA field, but "unknown" record types must not (RFC 3597).

The CLASS of a record is set to IN (for Internet) for common DNS records involving Internet hostnames, servers, or IP addresses. In addition, the classes CH (Chaos) and HS (Hesiod) exist. Each class is a completely independent tree with potentially different delegations of DNS zones.

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In addition to resource records defined in a zone file, the domain name system also defines several request types that are used only in communication with other DNS nodes (on the wire), such as when performing zone transfers (AXFR/IXFR) or for EDNS (OPT).

Wildcard DNS recordsMain article: Wildcard DNS record

The domain name system supports wildcard domain names which are names that start with the asterisk label, '*', e.g., *.example.[2][13] DNS records belonging to wildcard domain names specify rules for generating resource records within a single DNS zone by substituting whole labels with matching components of the query name, including any specified descendants. For example, in the DNS zone x.example, the following configuration specifies that all subdomains (including subdomains of subdomains) of x.example use the mail exchanger a.x.example. The records for a.x.example are needed to specify the mail exchanger. As this has the result of excluding this domain name and its subdomains from the wildcard matches, all subdomains of a.x.example must be defined in a separate wildcard statement.

X.EXAMPLE. MX 10 A.X.EXAMPLE.*.X.EXAMPLE. MX 10 A.X.EXAMPLE.*.A.X.EXAMPLE. MX 10 A.X.EXAMPLE.A.X.EXAMPLE. MX 10 A.X.EXAMPLE.A.X.EXAMPLE. AAAA 2001:db8::1

The role of wildcard records was refined in RFC 4592, because the original definition in RFC 1034 was incomplete and resulted in misinterpretations by implementers.[13]

Protocol extensions

The original DNS protocol had limited provisions for extension with new features. In 1999, Paul Vixie published in RFC 2671 an extension mechanism, called Extension mechanisms for DNS (EDNS) that introduced optional protocol elements without increasing overhead when not in use. This was accomplished through the OPT pseudo-resource record that only exists in wire transmissions of the protocol, but not in any zone files. Initial extensions were also suggested (EDNS0), such as increasing the DNS message size in UDP datagrams.

Dynamic zone updates

Dynamic DNS updates use the UPDATE DNS opcode to add or remove resource records dynamically from a zone data base maintained on an authoritative DNS server. The feature is described in RFC 2136. This facility is useful to register network clients into the DNS when they boot or become otherwise available on the network. Since a booting client may be assigned a different IP address each time from a DHCP server, it is not possible to provide static DNS assignments for such clients.

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Security issues

DNS was not originally designed with security in mind, and thus has a number of security issues.

One class of vulnerabilities is DNS cache poisoning, which tricks a DNS server into believing it has received authentic information when, in reality, it has not.

DNS responses are traditionally not cryptographically signed, leading to many attack possibilities; The Domain Name System Security Extensions (DNSSEC) modifies DNS to add support for cryptographically signed responses. There are various extensions to support securing zone transfer information as well.

Even with encryption, a DNS server could become compromised by a virus (or for that matter a disgruntled employee) that would cause IP addresses of that server to be redirected to a malicious address with a long TTL. This could have far-reaching impact to potentially millions of Internet users if busy DNS servers cache the bad IP data. This would require manual purging of all affected DNS caches as required by the long TTL (up to 68 years).

Some domain names can spoof other, similar-looking domain names. For example, "paypal.com" and "paypa1.com" are different names, yet users may be unable to tell the difference when the user's typeface (font) does not clearly differentiate the letter l and the numeral 1. This problem is much more serious in systems that support internationalized domain names, since many characters that are different, from the point of view of ISO 10646, appear identical on typical computer screens. This vulnerability is often exploited in phishing.

Techniques such as Forward Confirmed reverse DNS can also be used to help validate DNS results.

Domain name registration

The right to use a domain name is delegated by domain name registrars which are accredited by the Internet Corporation for Assigned Names and Numbers (ICANN), the organization charged with overseeing the name and number systems of the Internet. In addition to ICANN, each top-level domain (TLD) is maintained and serviced technically by an administrative organization, operating a registry. A registry is responsible for maintaining the database of names registered within the TLD it administers. The registry receives registration information from each domain name registrar authorized to assign names in the corresponding TLD and publishes the information using a special service, the whois protocol.

ICANN publishes the complete list of TLD registries and domain name registrars. Registrant information associated with domain names is maintained in an online database

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accessible with the WHOIS service. For most of the more than 240 country code top-level domains (ccTLDs), the domain registries maintain the WHOIS (Registrant, name servers, expiration dates, etc.) information. For instance, DENIC, Germany NIC, holds the DE domain data. Since about 2001, most gTLD registries have adopted this so-called thick registry approach, i.e. keeping the WHOIS data in central registries instead of registrar databases.

For COM and NET domain names, a thin registry model is used: the domain registry (e.g. VeriSign) holds basic WHOIS (registrar and name servers, etc.) data. One can find the detailed WHOIS (registrant, name servers, expiry dates, etc.) at the registrars.

Some domain name registries, often called network information centers (NIC), also function as registrars to end-users. The major generic top-level domain registries, such as for the COM, NET, ORG, INFO domains and others, use a registry-registrar model consisting of hundreds of domain name registrars (see lists at ICANN or VeriSign). In this method of management, the registry only manages the domain name database and the relationship with the registrars. The registrants (users of a domain name) are customers of the registrar, in some cases through additional layers of resellers.

ISP (Internet Service Provider)

Stands for "Internet Service Provider." In order to connect to the Internet, you need an ISP. It is the company that you (or your parents) pay a monthly fee to in order to use the Internet. If you use a dial-up modem to connect to your ISP, a point-to-point protocol (PPP) connection is established with another modem on the ISP's end. That modem connects to one of the ISP's routers, which routes you to the Internet "backbone." From there, you can access information from anywhere around the world. DSL and cable modems work the same way, except after you connect the first time, you are always connected.

ICT SPECIALISED TRAINING – WEB-TECH

SEARCH ENGINE

A web search engine is designed to search for information on the World Wide Web. The

search results are generally presented in a line of results often referred to as search

engine results pages (SERPs). The information may be a specialist in web pages, images,

information and other types of files. Some search engines also mine data available in

databases or open directories. Unlike web directories, which are maintained only by

human editors, search engines also maintain real-time information by running an

algorithm on a web crawler.

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A search engine operates in the following order:

1. Web crawling

2. Indexing

3. Searching

Web search engines work by storing information about many web pages, which they

retrieve from the HTML itself. These pages are retrieved by a Web crawler (sometimes

also known as a spider) — an automated Web browser which follows every link on the

site. Exclusions can be made by the use of robots.txt. The contents of each page are

then analyzed to determine how it should be indexed (for example, words can be

extracted from the titles, page content, headings, or special fields called meta tags).

Data about web pages are stored in an index database for use in later queries. A query

can be a single word. The purpose of an index is to allow information to be found as

quickly as possible. Some search engines, such as Google, store all or part of the source

page (referred to as a cache) as well as information about the web pages, whereas

others, such as AltaVista, store every word of every page they find. This cached page

always holds the actual search text since it is the one that was actually indexed, so it can

be very useful when the content of the current page has been updated and the search

terms are no longer in it. This problem might be considered to be a mild form of linkrot,

and Google's handling of it increases usability by satisfying user expectations that the

search terms will be on the returned webpage. This satisfies the principle of least

astonishment since the user normally expects the search terms to be on the returned

pages. Increased search relevance makes these cached pages very useful, even beyond

the fact that they may contain data that may no longer be available elsewhere.

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High-level architecture of a standard Web crawler

When a user enters a query into a search engine (typically by using keywords), the

engine examines its index and provides a listing of best-matching web pages according

to its criteria, usually with a short summary containing the document's title and

sometimes parts of the text. The index is built from the information stored with the data

and the method by which the information is indexed. As early as 2007 the Google.com

search engine has allowed one to search by date by clicking 'Show search tools' in the

leftmost column of the initial search results page, and then selecting the desired date

range. Most search engines support the use of the boolean operators AND, OR and NOT

to further specify the search query. Boolean operators are for literal searches that allow

the user to refine and extend the terms of the search. The engine looks for the words or

phrases exactly as entered. Some search engines provide an advanced feature called

proximity search which allows users to define the distance between keywords. There is

also concept-based searching where the research involves using statistical analysis on

pages containing the words or phrases you search for. As well, natural language queries

allow the user to type a question in the same form one would ask it to a human. A site

like this would be ask.com.

The usefulness of a search engine depends on the relevance of the result set it gives

back. While there may be millions of web pages that include a particular word or phrase,

some pages may be more relevant, popular, or authoritative than others. Most search

engines employ methods to rank the results to provide the "best" results first. How a

search engine decides which pages are the best matches, and what order the results

should be shown in, varies widely from one engine to another. The methods also change

over time as Internet usage changes and new techniques evolve. There are two main

types of search engine that have evolved: one is a system of predefined and

hierarchically ordered keywords that humans have programmed extensively. The other

is a system that generates an "inverted index" by analyzing texts it locates. This first

form relies much more heavily on the computer itself to do the bulk of the work.

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Most Web search engines are commercial ventures supported by advertising revenue

and, as a result, some employ ,the practice of allowing advertisers to pay money to have

their listings ranked higher in search results. Those search engines which do not accept

money for their search engine results make money by running search related ads

alongside the regular search engine results. The search engines make money every time

someone clicks on one of these ads.

References

1. ^ "Core Characteristics of Web 2.0 Services". http://www.techpluto.com/web-20-services/.

2. ^ DiNucci, D. (1999). "Fragmented Future". Print 53 (4): 32. 3. ^ a b c Paul Graham (November 2005). "Web 2.0".

http://www.paulgraham.com/web20.html. Retrieved on 2006-08-02. ""I first heard the phrase 'Web 2.0' in the name of the Web 2.0 conference in 2004.""

4. ^ a b c d e f Tim O'Reilly (2005-09-30). "What Is Web 2.0". O'Reilly Network. http://www.oreillynet.com/pub/a/oreilly/tim/news/2005/09/30/what-is-web-20.html. Retrieved on 2006-08-06.

5. ^ Tim O'Reilly (2006-12-10). "Web 2.0 Compact Definition: Trying Again". http://radar.oreilly.com/archives/2006/12/web_20_compact.html. Retrieved on 2007-01-20.

6. ^ a b c "developerWorks Interviews: Tim Berners-Lee". 2006-07-28. http://www.ibm.com/developerworks/podcast/dwi/cm-int082206txt.html. Retrieved on 2007-02-07.

7. Lehr, W., Osorio, C., Gillett, S., and Sirbu, M, (2005) “Measuring Broadband’s Economic Impact”, paper presented at the 33rd Research Conference on Communication, Information, and Internet Policy (TPRC), Arlington, VA, and revised as of October 4, 2005. http://itc.mit.edu/itel/docs/2005/MeasuringBB_EconImpact.pdf

8. James, P. and  Hopkinson, P., “SUSTAINABLE BROADBAND? -The Economic, Environmental and Social Impacts of Cornwall’s actnow Project, May 2005.http://www.sustainit.org/publications/files/87-EnvironmentalStudy-finalfullreport.doc 

9. Zilber, J., Schneider, D., and Djwa, P. “ You Snooze, You Lose: The Economic Impact of Broadband in the Peace River and South Similkameen Regions, September 2005. http://www.7thfloormedia.com/broadbandimpact

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10. http://en.wikipedia.org/wiki/Domain_Name_System

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