Freedom of Speech free essay sample

It is a right that should be practiced everywhere in the world, yet some countries in the world don’t. People must live in fear and be afraid to say anything. Only close friends share their opinions because they know it won’t be overheard by someone who will report it to the authorities. They can’t criticize their government when they make important decisions. Not having freedom of expression is holding them back. People have to pretend that everything that is being done by the authorities is splendid. With technology being part of our daily life expressing yourself has become even easier and lets you be heard by so many people. Not everyone but most of the people use social media as a way to connect with friends and colleagues. Websites like Facebook and Twitter are like worldwide public forum where something you say can be heard by hundreds or thousands of people, especially when there’s some heated debated going on about some hot topic. We will write a custom essay sample on Freedom of Speech or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Times like these are when you have to be careful what you say. Yes, it is a great right to express yourself freely but sometimes people forget that what they say can offend others and make them look bad in the long run. Alexandra Wallace is a perfect example. A UCLA student that last year posted a video on YouTube ranting about Asians being disrespectful at the library and using their cellphones. The video became famous within days and with it came the ridicule. Many people on YouTube made reply videos making fun of her. Found her Facebook and sent her threatening messages, emailing her and even calling her phone. A. Wallace withdrew from UCLA couple days later. This is a perfect example where you should think before you say something on social media. That brings up the idea about restricting the freedom of expression. What is the point of restricting it? It is going to be like we don’t have the freedom of expression then. If we do place restrictions, First Amendment should come with an asterisk after it and then you should go to the end of the page and find out what that asterisk means. You will end up reading tons of pages of â€Å"Terms and Conditions† like on some credit card application. Freedom of expression should not come with an asterisk after it; otherwise it should be renamed to something else and not include the word â€Å"freedom† in it. There is nothing â€Å"freedom† about it if there’s going to be restrictions on what and how you can express yourself. Instead, people should be reminded about something called common sense. There are things that are right to talk about and things that are frowned upon by the society. That is where there’s two big differences, when it is frowned upon to talk about something by government and when it is frowned upon by the society. When the government doesn’t want you to talk about something that is when you can face legal actions for what you say. When it is frowned upon by the society, you won’t face legal actions. Yes you may be made fun of but you won’t go to jail for it. You should use common sense and figure it out yourself if what you are about to say will turn out for good or bad. Freedom of Speech free essay sample Freedom of speech Freedom of speech  is the freedom to speak freely without  censorship. The synonymous term  freedom of expression  is sometimes used to indicate not only freedom of verbal speech but any act of seeking, receiving and imparting information or ideas, regardless of the medium used. In practice, the right to freedom of speech is not absolute in any country and the right is commonly subject to limitations, such as on hate speech.The right to freedom of speech is recognized as a  human right  under Article 19 of the  Universal Declaration of Human Rights  and recognized in  international human rights law  in the  International Covenant on Civil and Political Rights  (ICCPR). The ICCPR recognizes the right to freedom of speech as the right to hold opinions without interference. Everyone shall have the right to freedom of expression. Furthermore freedom of speech is recognized in European, inter-American and African regional human rights law. We will write a custom essay sample on Freedom of Speech or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page It is different from and not to be confused with the concept of  freedom of thought. The right to freedom of speech and expressionConcepts of freedom of speech can be found in early human rights documents  and the modern concept of freedom of speech emerged gradually during the  European Enlightenment(Voltaire). England’s  Bill of Rights 1689  granted freedom of speech in Parliament and the  Declaration of the Rights of Man and of the Citizen, adopted during the  French Revolution  in 1789, specifically affirmed freedom of speech as an inalienable right. The Declaration provides for freedom of expression in Article 11, which states that: The free communication of ideas and opinions is one of the most precious of the rights of man.Every citizen may, accordingly, speak, write, and print with freedom, but shall be responsible for such abuses of this freedom as shall be defined by law. Article 19 of the  Universal Declaration of Human Rights, adopted in 1948, s tates that: Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers. Today freedom of speech, or the freedom of expression, is recognized in international and regional  human rights law.The right is enshrined in Article 19 of the  International Covenant on Civil and Political Rights, Article 10 of the  European Convention on Human Rights, Article 13 of the  American Convention on Human Rights  and Article 9 of the  African Charter on Human and Peoples Rights. Based on  John Miltons arguments, freedom of speech is understood as a multi-faceted right that includes not only the right to express, or disseminate, information and ideas, but three further distinct aspects: * the right to seek information and ideas; * the right to receive information and ideas; the right to impart information and ideas. International, regional and national standards also recognize that freedom of speech, as the freedom of expression, includes any medium, be it orally, in written, in print, through the  Internet  or through art forms. This means that th e protection of freedom of speech as a right includes not only the content, but also the means of expression. Relationship to other rights The right to freedom of speech and expression is closely related to other rights, and may be limited when conflicting with other rights (seeLimitations on freedom of speech).The right to freedom of expression is also related to the  right to a fair trial  and court proceeding which may limit access to the search for information or determine the opportunity and means in which freedom of expression is manifested within court proceedings. As a general principle freedom of expression may not limit the  right to privacy, as well as the honor and reputation of others. However greater latitude is given when criticism of public figures is involved. The right to freedom of expression is particularly important for  media, which plays a special role as the bearer of the general right to freedom of expression for all.However,  freedom of the press  is not necessarily enabling freedom of speech. Judith Lichtenberg has outlined conditions in which freedom of the press may constrain freedom of speech, for example where the media suppresses information or stifles the diversity of voices inherent in freedom of speech. Lichtenberg argues that  freedom of the press  is simply a form of  property right  summed up by the principle no money, no voice. Origins and academic freedom Freedom of speech and expression has a long history that predates modern  international human rights instruments. It is thought that ancient  Athens’ democratic ideology  of free speech may have emerged in the late 6th or early 5th century BC. [12]  Two of the most cherished values of the  Roman Republic  were freedom of religion and freedom of speech. In  Islamic ethics, freedom of speech was first declared in the  Rashidun  period by the  caliph  Umar  in the 7th century AD. In the  Abbasid Caliphate  period, freedom of speech was also declared by al-Hashimi (a cousin of Caliph  al-Mamun) in a letter to one of the religious opponents he was attempting to  convert  through reason.According to George Makdisi and Hugh Goddard, the idea of  academic freedom in  universities  was modelled on Islamic custom as practiced in the medieval  Madrasah  system from the 9th century. Islamic influence was certainly discernible in the foundation of the first deliberately-planned university in Europe, the  University of Naples Federico II  founded by  Fred erick II, Holy Roman Emperor  in 1224. Starting in medieval times, Muslims began to refer to  Manichaeans,  apostates, pagans, heretics and those who antagonized Islam as zindiqs, the charge being punishable by death. As of the late 8th century the  Abbasid  caliphs  began to hunt down and exterminate freethinkers in large numbers, putting to death anyone on mere suspicion of being a  zindiq. Freedom of speech, dissent and truth Before the invention of the  printing press  a writing, once created, could only be physically multiplied by the highly laborious and error-prone process of manual copying out and an elaborate system of censorship and control over  scribes  existed. Printing allowed for multiple exact copies of a work, leading to a more rapid and widespread circulation of ideas and information (see  print culture).The origins of  copyright law  in most European countries lie in efforts by the  Roman Catholic Church  and governments to regulate and control the output of printers. In 1501  Pope Alexander VI  issued a Bill against the unlicensed printing of books and in 1559 the  Index Expurgatorius, or  List of Prohibited Books, was issued for the first time . The Index Expurgatorius is the most famous and long lasting example of bad books catalogues issued by the Roman Catholic Church, which assumed responsibility to control thoughts and opinions, and suppressed views that went against its doctrines.The Index Expurgatorius was administered by the  Roman Inquisition, but enforced by local government authorities, and went through 300 editions. Amongst others it banned or  censored  books written by  Rene Descartes,  Giordano Bruno,  Galileo Galilei,  David Hume,  John Locke,  Daniel Defoe,  Jean-Jacques Rousseau  and  Voltaire. While governments and church encouraged printing in many ways because it allowed for the dissemination of  Bibles  and government information, works of dissent and criticism could also circulate rapidly.As a consequence, governments established controls over printers across Europe, requiring them to have official licenses to trade and produce books. The notion that the expression of dissent or subversive views should be tolerated, not censured or punished by law, developed alongside the rise of  printing  and the  press. Areopagitica, published in 1644, was  John Miltons response to the  Parliament of Englandsre-introduction of government licensing of  printers, hence  publishers. [25]  Church authorities had previously ensured that Miltons  essay on the right to divorcewas refused a license for publication.In Areopagitica, published without a license,  Milton made an impassioned plea for freedom of expression and toleration of falsehood,  stating: Give me the liberty to know, to utter, and to argue freely according to conscience, above all liberties. Miltons defense of freedom of expression was grounded in a  Protestantworldview and he thought that the English people had the mission to work out the truth of the  Reformation, which would lead to the  enlightenment  of all people. But Milton also articulated the main strands of future discussions about freedom of expression.By defining the scope of freedom of expression and of harmful speech Milton argued against the principle of pre-censorship and in favor of tolerance for a wide range of views. As the menace of printing spread, governments established centralised control mechanism. The  French crown  repressed printing and the printer Etienne Dolet  was burned at the stake in 1546. In 1557 the  British Crownthought to stem the flow of seditious and heretical books by chartering theStationers Company. The ight to print was limited to the members of that guild, and thirty years later the  Star Chamber  was chartered to curtail the greate enormities and abuses of dyvers contentyous and disorderlye persons professinge the arte or mystere of pryntinge or selling of books. The right to print was restricted to two universities and to the 21 existing printers in the  city of London, which had 53printing presses. As the British crown took control of type founding in 1637 printers fled to the  Netherlands.Confrontation with authority made printers radical and rebellious, with 800 authors, printers and book dealers being incarcerated in the  Bastille  in Paris before it was stormed in 1789. succession of English thinkers developed the idea of a right to freedom of expression, starting with  John Milton  (1608–74), then  John Locke  (1632–1704) and culminating in  John Stuart Mill  (1806–1873). Locke established the  individual  as the unit of value and the bearer of rights to  life,  liberty,  property  and the  pursuit of happiness.It was the role of  Government  to protect these rights and this belief was first enshrined in the  US Constitution, with the  First Amendment  adding the guaran tee that Congress shall make no law.. . abridging the freedom of speech, or of the press. John Stuart Mill argued that human freedom is good and without it there can be no progress in science, law or politics, which according to Mill required free discussion of opinion. Mills  On Liberty, published in 1859 became a classic defence of the right to freedom of expression.Mill argued that  truth  drives out falsity, therefore the free expression of ideas, true or false, should not be feared. Truth is not stable or fixed, but evolves with time. Mill argued that much of what we once considered true has turned out false. Therefore views should not be prohibited for their apparent falsity. Mill also argued that free discussion is necessary to prevent the deep slumber of a decided opinion. Discussion would drive the onwards march of truth and by considering false views the basis of true views could be re-affirmed.In  Evelyn Beatrice Halls biography of  Voltaire, she coined the following phrase to illustrate Voltaires beliefs: I disapprove of what you say, but I will defend to the death your right to say it.   Halls quote is frequently cited to describe the principle of freedom of speech. In the 20th Century  Noam Chomsky  states that: If you believe in freedom of speech, you believe in freedom of speech for views you dont like. Stalin  and  Hitler, for example, were dictators in favor of freedom of speech for views they liked only. If youre in favor of freedom of speech, that means youre in favor of freedom of speech precisely for views you despise. Professor  Lee Bollinger  argues that the free speech principle involves a special act of carving out one area of social interaction for extraordinary self-restraint, the purpose of which is to develop and demonstrate a social capacity to control feelings evoked by a host of social encounters. Bollinger argues that  tolerance  is a desirable value, if not essential. However, critics argue that society should be concerned by those who directly deny or advocate, for example,  genocide.Democracy The notion of freedom of expression is intimately linked to political debate and the concept ofdemocracy. The norms on limiting freedom of expression mean that public debate may not be completely suppressed even in times of emergency. One of the most notable proponents of the link between freedom of speech and  democracy  is  Alexander Meiklejohn. He argues that the concept of democracy is that of self-government by the people. For such a system to work an informed electorate is necessary. In order to be appropriately knowledgeable, there must be no constraints on the free flow of information and ideas.According to Meiklejohn, democracy will not be true to its essential ideal if those in power are able to manipulate the electorate by withholding information and stifling criticism. Meiklejohn acknowledges that the desire to manipulate opinion can stem from the motive of seeking to benefit society. However, he argues, choosing manipulation negates, in its means, the democratic ideal. Eric Barendt  has called this defence of free speech on the grounds of democracy probably the most attractive and certainly the most fashionable free speech theory in modern Western democracies. Thomas I.Emerson expanded on this defence when he argued that freedom of speech helps to provide a balance between  stability  and  change. Freedom of speech acts as a safety valve to let off steam when people might otherwise be bent on  revolution. He argues that The principle of open discussion is a method of achieving a moral adaptable and at the same time more stable community, of maintaining the precarious balance between healthy cleavage and necessary consensus. Emerson furthermore maintains that Opposition serves a vital social function in offsetting or ameliorating (the) normal process of bureaucratic decay. Research undertaken by the  Worldwide Governance Indicators  project at the  World Bank, indicates that freedom of speech, and the process of accountability that follows it, have a significant impact in the quality of  governance  of a country. Voice and Accountability within a country, defined as the extent to which a countrys  citizens  are able to participate in selecting their  government, as well as freedom of expression,  freedom of association, and  free media is one of the six dimensions of governance that the Worldwide Governance Indicators measure for more than 200 countries. Social interaction and communityRichard Moon has developed the argument that the value of freedom of speech and freedom of expression lies with social interactions. Moon writes that by communicating an individual forms relationships and associations with others – family, friends, co-workers, church congregation, and countrymen. By entering into discussion with others an individual participates in the development of knowledge and in the direction of the community. Limitations According to the Freedom Forum Organization, legal systems, and society at large, recognize limits on the freedom of speech, particularly when freedom of speech conflicts with other values or rights.Limitations to freedom of speech may follow the harm principle or the offense principle, for example in the case of  pornography  or  hate speech. Limitations to freedom of speech may occur through legal sanction or social disapprobation, or both. In On Liberty (1859)  John Stuart Mill  argued that . .. there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered.   Mill argues that the fullest liberty of expression is required to push arguments to their logical limits, rather than the limits of social embarrassment.However, Mill also introduced what is known as the harm principle, in placing the following limitation on free expression: the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. In 1985  Joel Feinberg  introduced what is known as the offence principle, arguing that Mills harm principle does not provide sufficient protection against the wrongful behaviours of others.Feinberg wrote It is always a good reason in support of a proposed criminal prohibition that it would probably be an effective way of preventing serious offense (as opposed to injury or harm) to persons other th an the actor, and that it is probably a necessary means to that end.   Hence Feinberg argues that the harm principle sets the bar too high and that some forms of expression can be legitimately prohibited by law because they are very offensive. But, as offending someone is less serious than harming someone, the penalties imposed should be higher for causing harm.In contrast Mill does not support legal penalties unless they are based on the harm principle. Because the degree to which people may take offense varies, or may be the result of unjustified prejudice, Feinberg suggests that a number of factors need to be taken into account when applying the offense principle, including: the extent, duration and social value of the speech, the ease with which it can be avoided, the motives of the speaker, the number of people offended, the intensity of the offense, and the general interest of the community at large.The Internet and Information Society Jo Glanville, editor of the  Index on Censorship, states that the Internet has been a revolution for  ce nsorship  as much as for free speech. International, national and regional standards recognise that freedom of speech, as one form of freedom of expression, applies to any medium, including the  Internet. [8]  The  Communications Decency Act  (CDA) of 1996 was the first major attempt by the  United States Congress  to regulate  pornographic  material on the  Internet. In 1997, in the landmark  cyberlaw  case of  Reno v. ACLU, the  U. S.Supreme Court  partially overturned the law. Judge  Stewart R. Dalzell, one of the three federal judges who in June 1996 declared parts of the CDA unconstitutional, in his opinion stated the following: The Internet is a far more speech-enhancing medium than print, the village green, or the mails. Because it would necessarily affect the Internet itself, the CDA would necessarily reduce the speech available for adults on the medium. This is a constitutionally intolerable result. Some of the dialogue on the Internet surely tests the limits of conventional discourse.Speech on the Internet can be unfiltered, unpolished, and unconventional, even emotionally charged, sexually explicit, and vulgar – in a word, indecent in many communities. But we should expect such speech to occur in a medium in which citizens from all walks of life have a voice. We should also protect the autonomy that such a medium confers to ordinary people as well as media magnates. [. . . ] My analysis does not deprive the Government of all means of protecting children from the dangers of Internet communication.

The Only Place

The Only Place The Only Place The Only Place By Mark Nichol In spoken English, even the most careful speaker may casually misplace the modifier only in a sentence, as in â€Å"The meeting will only be held if the ordinance passes.† The intended meaning here is that whether the ordinance passes determines whether the meeting is to be held. Literally, however, the sentence indicates that the holding is the only action that will pertain to the meeting if the ordinance passes. (The meeting will not be recorded or reported on, for example, but if the ordinance fails, perhaps these and other things will occur in relation to the meeting.) As the parenthesized sentence before this one demonstrates, the meaning is changed depending the positioning of only: In the original sentence, the meeting is not conditional on the passage of the ordinance, though that is exactly what the speaker or writer means. Therefore, to accurately convey the meaning of the sentence, the word only should appear immediately after the word, phrase, or clause it modifies. Because a speaker can provide stress to the sentence, a listener is unlikely to misunderstand it, but a writer has no such advantage. Ambiguity is not inevitable when misplacing the modifier in written expression, but the careful writer makes the effort to produce a sentence that is syntactically sound. Here is another sentence best expressed with only positioned correctly: â€Å"Are we certain that participants only reside in those neighborhoods?† The significant point appears to be that the participants reside in those places but do not have any other connection to them. The intended meaning, however, is that the â€Å"we† are uncertain whether the participants live only in the specified locations and not in other places. This meaning is best conveyed by writing, â€Å"Are we certain participants reside only in those neighborhoods?† Note the difference in meaning when inserting the modifier only in various positions in the sentence â€Å"Smith said he could only confirm that nine demonstrators were taken into custody.† 1. Only Smith said he could confirm that nine demonstrators were taken into custody. (No one else made the claim that Smith could confirm the information.) 2. Smith only said he could confirm that nine demonstrators were taken into custody. (Smith didn’t say anything else.) 3. Smith said only he could confirm that nine demonstrators were taken into custody. (According to Smith, he is the only one who could confirm the information.) 4. Smith said he only could confirm that nine demonstrators were taken into custody. (Smith could not do anything else but potentially confirm the information.) 5. Smith said he could only confirm that nine demonstrators were taken into custody. (Smith could confirm the information but do nothing else about or to it.) 6. Smith said he could confirm only that nine demonstrators were taken into custody. (Smith could confirm nothing else but the information he provided.) 7. Smith said he could confirm that only nine demonstrators were taken into custody. (Smith was able to specify that nine demonstrators, not another quantity, were arrested, with the implication that other demonstrators were not arrested.) 8. Smith said he could confirm that nine only demonstrators were taken into custody. (This sentence seems to indicate, albeit ungrammatically, that the people arrested were only demonstrators and had no other occupation or pastime.) 9. Smith said he could confirm that nine demonstrators only were taken into custody. (The number of demonstrators arrested was only nine; unlike version number 7, this sentence does not necessarily imply additional demonstrators.) 10. Smith said he could confirm that nine demonstrators were only taken into custody. (The demonstrators were taken into custody, but nothing else pertaining to custody occurred to them.) 11. Smith said he could confirm that nine demonstrators were taken only into custody. (The demonstrators were not taken anywhere except into custody.) 12. Smith said he could confirm that nine demonstrators were taken into only custody. (The demonstrators were taken into a type of custody known as â€Å"only custody†; like version number 8, this sentence is not grammatically correct.) 13. Smith said he could confirm that nine demonstrators were taken into custody only. (Nothing else was done to the demonstrators besides taking them into custody.) The usual placement error for this type of sentence is â€Å"Smith said he could only confirm that nine demonstrators were taken into custody,† where only erroneously precedes the pertinent verb, suggesting that confirmation is all that could be done. However, the point that the stated item of information, and only that item, could be confirmed is correctly stated thus: â€Å"Smith said he could confirm only that nine demonstrators were taken into custody.† (Therefore, version 6 above is the only version suitable to express the intended meaning.) Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Style category, check our popular posts, or choose a related post below:How Many Tenses in English?20 Words Meaning "Being or Existing in the Past"Adverbs and Hyphens

Questions and Answers Assignment Example | Topics and Well Written Essays - 250 words

Questions and Answers - Assignment Example The misuse of hard liquor is itself a social harm, with additional economic costs as well as increased health consequences in the long-term (Mathurin & Deltenre, 2009). For parents sending their teenagers off to college, the survey results are but a sobering reminder that not all activities in college are caged in slide rules and long hours at the library. Noteworthy, such negative publicity informs public opinion, whether true or falls, on the type of policies operationalized in such institutions. The study deviates a little from the survey rankings and so seeks to determine whether there is any relationship/connection between a student’s gender and binge drinking in such institutions of higher learning. To get the answers sought after, the study will sample opinions of students on whether such negative partying has any relationship with one’s gender. The study will utilize a sample size of 100 students, with each selected using simple random sampling

Older Adulthood Essay Example | Topics and Well Written Essays - 250 words

Older Adulthood - Essay Example This means that some diseases and health defects associated with old age can be prevented or at least reduced if proper care is taken. I will advocate for routine medical checkup for me and my friends so that these many complications are avoided in future. For example, it has come to my attention that avoiding exposure to environmental toxins and other hazards and also getting faster access to healthcare can avoid these complications. For a successful transition into old age, I will from now henceforth advice those with old age to accept the change, be sociable and also employ spiritual faith. Older adults require religious support and spiritual nourishment to enable them cope as I have just realized. Another way of coping is by keeping old and retired people busy by volunteering. This enable them overcome depression associated with old age, widowhood or caring for a sick partner. Having family members visit the old is refreshing to them (Kail and Cavanaugh 519). Old people are sometimes neglected or abused. This is not good as they require as minimum stress as possible. I have a changed opinion about old age, and will from now on emphasize on love and care for the old people. From this class, I have learnt of better ways of caring for and helping the older people. I have also gained an insight that can enable me advice old people into successful transition to old age. Plus, it has changed my view on old age. Old is

Access and Availability of dental care to Paediatric special needs Research Proposal

Access and Availability of dental care to Paediatric special needs patients in Saudi Arabia - Research Proposal Example The general oral hygiene of these chidlren were also found to be very low (Al-Banyan, Echeverri, Narendran and Keene, 2000, p.43). This study had recommended an oral health program to be implemented through the educational institutions (Al-Banyan, Echeverri, Narendran and Keene, 2000, p.43). Further studies to identify the specific factors leading to the problem was also suggested by this study (Al-Banyan, Echeverri, Narendran and Keene, 2000, p.43). Al-Malik and Rehbini (2006) have also pointed to the high level of caries in children in Saudi Arabia as compared to children in other countries and called for immediate intervention through school intervention programs. Especially when it comes to special needs patients like children with autism, the negative behavior of such children towards treatment or any similar problems in case of other special needs groups, will limit their access to and availability of dental care and treatment (Murshid, 2005). It is this existing research highl ights along with the case studies displaying the high prevalence of oral problems among special needs children that was witnessed while working with them that prompted this researcher to explore further in this area of study. Though the research works mentioned above have exhibited that there is a high level of oral health problems in children with special needs in Saudi Arabia, none of them have thrown light upon to what extent this problems gets addressed. It is not revealed whether these children have access to and availability of appropriate and efficient dental care in the present context in Saudi Arabia. Only by assessing the lacuna that is there, further steps can be taken to address the oral health needs of these special needs children. Hence this researcher is of the belief that this study on the access and availability of dental care to special needs children in Saudi Arabia can add valuable

Implementation of New Computer Network

Implementation of New Computer Network Here we are going to implement an new computer network for this company that 25 employees have been working in. Suppose you want to build a computer network, one that has potential to grow to global proportions to support applications as diverse as teleconferencing, video-on-demand, electronic commerce, distributed computing, and digital libraries. What available technologies would serve as the underlying building blocks, and what kind of software architecture would you design t integrate these building blocks into an effective communication service? Suppose you want to build a computer network, one that has the potential togrow to global proportions and to support applications as diverse as teleconferencing, video-on-demand, electronic commerce, distributed computing, and digital libraries. What available technologies would serve as the underlying building blocks, and what kind of software architecture would you design to integrate these building blocks into an effective communication service? Answering this question is the overriding goal of — to describe the available building materials and then to show how they can be used to construct a network from the ground up. Before we can understand how to design a computer network, we should first agree on exactly what a computer network is. At one time, the term network meant the set of serial lines used to attach dumb terminals to mainframe computers. To some, the term implies the voice telephone network. To others, the only interesting network is the cable network used to disseminate video signals. The main thing these networks have in common is that they are specialized to handle one particular kind of data (keystrokes, voice, or video) and they typically connect to special-purpose devices (terminals, hand receivers, and television sets). What distinguishes a computer network from these other types of networks? Probably the most important characteristic of a computer network is its generality. Computer networks are built primarily from general-purpose programmable hardware, and they are not optimized for a particular application like making phone calls or delivering television signals. Instead, they are able to carry many different types of data, and they support a wide, and ever-growing, range of applications. This chapter looks at some typical applications of computer networks and discusses the requirements that a network designer who wishes to support such applications must be aware of. Once we understand the requirements, how do we proceed? Fortunately, we will not be building the first network. Others, most notably the community of researchers responsible for the Internet, have gone before us. We will use the wealth of experience generated from the Internet to guide our design. This experience is embodied in a network architecture that identifies the available hardware and software components and shows how they can be arranged to form a complete network system. To start us on the road toward understanding how to build a network, this chapter does four things. First, it explores the requirements that different applications and different communities of people (such as network users and network operators) place on the network. Second, it introduces the idea of a network architecture, which lays the foundation for the rest of the book. Third, it introduces some of the key elements in the implementation of computer networks. Finally, it identifies the key metrics that are used to evaluate the performance of computer networks. 1.1 APPLICATIONS Most people know the Internet through its applications: the World Wide Web, email, streaming audio and video, chat rooms, and music (file) sharing. The Web, for example, presents an intuitively simple interface. Users view pages full of textual and graphical objects, click on objects that they want to learn more about, and a corresponding new page appears. Most people are also aware that just under the covers, each selectable object on a page is bound to an identifier for the next page to be viewed. This identifier, called a Uniform Resource Locator (URL), is used to provide a way of identifying all the possible pages that can be viewed from your web browser. For example, http://www.cs.princeton.edu/~llp/index.html is the URL for a page providing information about one of this books authors: the string http indicates that the HyperText Transfer Protocol (HTTP) should be used to download the page, www.cs.princeton.edu is the name of the machine that serves the page, and /~llp/index.html uniquely identifies Larrys home page at this site. What most Web users are not aware of, however, is that by clicking on just one such URL, as many as 17 messages may be exchanged over the Internet, and this assumes the page itself is small enough to fit in a single message. This number includes up to six messages to translate the server name (www.cs.princeton.edu) into its Internet address (128.112.136.35), three messages to set up a Transmission Control Protocol (TCP) connection between your browser and this server, four messages for your browser to send the HTTP get request and the server to respond with the requested page (and for each side to acknowledge receipt of that message), and four messages to tear down the TCP connection. Of course, this does not include the millions of messages exchanged by Internet nodes throughout the day, just to let each other know that they exist and are ready to serve web pages, translate names to addresses, and forward messages toward their ultim ate destination. Another widespread application of the Internet is the delivery of streaming audio and video. While an entire video file could first be fetched from a remote machine and then played on the local machine, similar to the process of downloading and displaying a web page, this would entail waiting for the last second of the video file to be delivered before starting to look at it. Streaming video implies that the sender and the receiver are, respectively, the source and the sink for the video stream. That is, the source generates a video stream (perhaps using a video capture card), sends it across the Internet in messages, and the sink displays the stream as it arrives. There are a variety of different classes of video applications. One class of video application is video-on-demand, which reads a pre-existing movie from disk and transmits it over the network. Another kind of application is videoconferencing, which is in some ways the more challenging (and, for networking people, interesting) case because it has very tight timing constraints. Just as when using the telephone, the interactions among the participants must be timely. When a person at one end gestures, then that action must be displayed at the other end as quickly as possible. Too much delay makes the system unusable. Contrast this with video-on-demand where, if it takes several seconds from the time the user starts the video until the first image is displayed, the service is still deemed satisfactory. Also, interactive video usually implies that video is flowing in both directions, while a video-on-demand application is most likely sending video in only one direction. One pioneering example of a videoconferencing tool, developed in the early and mid-1990s, is vic. shows the control panel for a vic session. vic is actually one of a suite of conferencing tools designed at Lawrence Berkeley Laboratory and UC Berkeley. The others include a whiteboard application (wb) that allows users to send sketches and slides to each other, a visual audio tool called vat, and a session directory (sdr) that is used to create and advertise videoconferences. All these tools run on Unix—hence their lowercase names—and are freely available on the Internet. Many similar tools are available for other operating systems. It is interesting to note that while video over the Internet is still considered to be in its relative infancy at the time of this writing (2006), that the tools to support video over IP have existed for well over a decade. Although they are just two examples, downloading pages from the Web and participating in a videoconference demonstrate the diversity of applications that can be built on top of the Internet, and hint at the complexity of the Internets design. Starting from the beginning, and addressing one problem at time, the rest of this book explains how to build a network that supports such a wide range of applications. Chapter 9 concludes the book by revisiting these two specific applications, as well as several others that have become popular on todays Internet. 1.2 REQUIREMENTS We have just established an ambitious goal for ourselves: to understand how to build a computer network from the ground up. Our approach to accomplishing this goal will be to start from first principles, and then ask the kinds of questions we would naturally ask if building an actual network. At each step, we will use todays protocols to illustrate various design choices available to us, but we will not accept these existing artifacts as gospel. Instead, we will be asking (and answering) the question of why networks are designed the way they are. While it is tempting to settle for just understanding the way its done today, it is important to recognize the underlying concepts because networks are constantly changing as the technology evolves and new applications are invented. It is our experience that once you understand the fundamental ideas, any new protocol that you are confronted with will be relatively easy to digest. The first step is to identify the set of constraints and requirements that influence network design. Before getting started, however, it is important to understand that the expectations you have of a network depend on your perspective: An application programmer would list the services that his application needs, for example, a guarantee that each message the application sends will be delivered without error within a certain amount of time. A network designer would list the properties of a cost-effective design, for example, that network resources are efficiently utilized and fairly allocated to different users. A network provider would list the characteristics of a system that is easy to administer and manage, for example, in which faults can be easily isolated and whereitiseasytoaccountfor usage. This section attempts to distill these different perspectives into a high-level introduction to the major considerations that drive network design, and in doing so, identifies the challenges addressed throughout the rest of this book. 1.2.1 Connectivity Starting with the obvious, a network must provide connectivity among a set of computers. Sometimes it is enough to build a limited network that connects only a few select machines. In fact, for reasons of privacy and security, many private (corporate) networks have the explicit goal of limiting the set of machines that are connected. In contrast, other networks (of which the Internet is the prime example) are designed to grow in a way that allows them the potential to connect all the computers in the world. A system that is designed to support growth to an arbitrarily large size is said to scale. Using the Internet as a model, this book addresses the challenge of scalability. Links, Nodes, and Clouds Network connectivity occurs at many different levels. At the lowest level, a network can consist of two or more computers directly connected by some physical medium, such as a coaxial cable or an optical fiber. We call such a physical medium a link,and we often refer to the computers it connects as nodes. (Sometimes a node is a more specialized piece of hardware rather than a computer, but we overlook that distinction for the purposes of this discussion.) As illustrated in, physical links are sometimes limited to a pair of nodes (such a link is said to be point-to-point), while in other cases, more than two nodes may share a single physical link (such a link is said to be multiple-access). Whether a given link supports point-to-point or multiple-access connectivity depends on how the node is attached to the link. It is also the case that multiple-access links are often limited in size, in terms of both the geographical distance they can cover and the number of nodes they can connect. If computer networks were limited to situations in which all nodes are directly connected to each other over a common physical medium, then networks would either be very limited in the number of computers they could connect, or the number of wires coming out of the back of each node would quickly become both unmanageable and very expensive. Fortunately, connectivity between two nodes does not necessarily imply a direct physical connection between them—indirect connectivity may be achieved among a set of cooperating nodes. Consider the following two examples of how a collection of computers can be indirectly connected. shows a set of nodes, each of which is attached to one or more point- to-point links. Those nodes that are attached to at least two links run software that forwards data received on one link out on another. If organized in a systematic way, these forwarding nodes form a switched network. There are numerous types of switched networks, of which the two most common are circuit-switched and packet-switched. The former is most notably employed by the telephone system, while the latter is used for the overwhelming majority of computer networks and will be the focus of this book. The important feature of packet-switched networks is that the nodes in such a network send discrete blocks of data to each other. Think of these blocks of data as corresponding to some piece of application data such as a file, a piece of email, or an image. We call each block of data either a packet or a message, and for now we use these terms interchangeably; we discuss the reason they are not always the same in Section 1.2.2. Packet-switched networks typically use a strategy called store-and-forward. As the name suggests, each node in a store-and-forward network first receives a complete packet over some link, stores the packet in its internal memory, and then forwards the complete packet to the next node. In contrast, a circuit-switched network first establishes a dedicated circuit across a sequence of links and then allows the source node to send a stream of bits across this circuit to a destination node. The major reason for using packet switching rather than circuit switching in a computer network is efficiency, discussed in the next subsection. The cloud in distinguishes between the nodes on the inside that implement the network (they are commonly called switches, and their primary function is to store and forward packets) and the nodes on the outside of the cloud that use the network (they are commonly called hosts, and they support users and run application programs). Also note that the cloud in is one of the most important icons of computer networking. In general, we use a cloud to denote any type of network, whether it is a single point-to-point link, a multiple-access link, or a switched network. Thus, whenever you see a cloud used in a figure, you can think of it as a placeholder for any of the networking technologies covered in this book. A second way in which a set of computers can be indirectly connected is shown in . In this situation, a set of independent networks (clouds) are interconnected to form an internetwork, or internet for short. We adopt the Internets convention of referring to a generic internetwork of networks as a lowercase i internet, and the currently operational TCP/IP Internet as the capital I Internet. A node that is connected to two or more networks is commonly called a router or gateway, and it plays much the same role as a switch—it forwards messages from one network to another. Note that an internet can itself be viewed as another kind of network, which means that an internet can be built from an interconnection of internets. Thus, we can recursively build arbitrarily large networks by interconnecting clouds to form larger clouds. Just because a set of hosts are directly or indirectly connected to each other does not mean that we have succeeded in providing host-to-host connectivity. The final requirement is that each node must be able to state which of the other nodes on the network it wants to communicate with. This is done by assigning an address to each node. An address is a byte string that identifies a node; that is, the network can use a nodes address to distinguish it from the other nodes connected to the network. When a source node wants the network to deliver a message to a certain destination node, it specifies the address of the destination node. If the sending and receiving nodes are not directly connected, then the switches and routers of the network use this address to decide how to forward the message toward the destination. The process of determining systematically how to forward messages toward the destination node based on its address is called routing. This brief introduction to addressing and routing has presumed that the source node wants to send a message to a single destination node (unicast). While this is the most common scenario, it is also possible that the source node might want to broadcast a message to all the nodes on the network. Or a source node might want to send a message to some subset of the other nodes, but not all of them, a situation called multicast. Thus, in addition to node-specific addresses, another requirement of a network is that it supports multicast and broadcast addresses. The main idea to take away from this discussion is that we can define a network recursively as consisting of two or more nodes connected by a physical link, or as two or more networks connected by a node. In other words, a network can be constructed from a nesting of networks, where at the bottom level, the network is implemented by some physical medium. One of the key challenges in providing network connectivity is to define an address for each node that is reachable on the network (including support for broadcast and multicast connectivity), and to be able to use this address to route messages toward the appropriate destination node(s). 1.2.2 Cost-Effective Resource Sharing As stated above, this book focuses on packet-switched networks. This section explains the key requirement of computer networks—efficiency—that leads us to packet switching as the strategy of choice. Given a collection of nodes indirectly connected by a nesting of networks, it is possible for any pair of hosts to send messages to each other across a sequence of links and nodes. Of course, we want to do more than support just one pair of communicating hosts—we want to provide all pairs of hosts with the ability to exchange messages. The question, then, is how do all the hosts that want to communicate share the network, especially if they want to use it at the same time? And, as if that problem isnt hard enough, how do several hosts share the same link when they all want to use it at the same time? To understand how hosts share a network, we need to introduce a fundamental concept, multiplexing, which means that a system resource is shared among multiple users. At an intuitive level, multiplexing can be explained by analogy to a timesharing computer system, where a single physical CPU is shared (multiplexed) among multiple jobs, each of which believes it has its own private processor. Similarly, data being sent by multiple users can be multiplexed over the physical links that make up a network. To see how this might work, consider the simple network illustrated in , where the three hosts on the left side of the network (senders S1S3) are sending data to the three hosts on the right (receivers R1R3) by sharing a switched network that contains only one physical link. (For simplicity, assume that host S1 is sending data to host R1, and so on.) In this situation, three flows of data—corresponding to the three pairs of hosts—are multiplexed onto a single physical link by switch 1 and then demultiplexed back into separate flows by switch 2. Note that we are being intentionally vague about exactly what a flow of data corresponds to. For the purposes of this discussion, assume that each host on the left has a large supply of data that it wants to send to its counterpart on the right. There are several different methods for multiplexing multiple flows onto one physical link. One common method is synchronous time-division multiplexing (STDM). The idea of STDM is to divide time into equal-sized quanta and, in a round-robin fashion, give each flow a chance to send its data over the physical link. In other words, during time quantum 1, data from S1 to R1 is transmitted; during time quantum 2, data from S2 to R2 is transmitted; in quantum 3, S3 sends data to R3. At this point, the first flow (S1 to R1) gets to go again, and the process repeats. Another method is frequency-division multiplexing (FDM). The idea of FDM is to transmit each flow over the physical link at a different frequency, much the same way that the signals for different TV stations are transmitted at a different frequency on a physical cable TV link. Although simple to understand, both STDM and FDM are limited in two ways. First, if one of the flows (host pairs) does not have any data to send, its share of the physical link—that is, its time quantum or its frequency—remains idle, even if one of the other flows has data to transmit. For example, S3 had to wait its turn behind S1 and S2 in the previous paragraph, even if S1 and S2 had nothing to send. For computer communication, the amount of time that a link is idle can be very large—for example, consider the amount of time you spend reading a web page (leaving the link idle) compared to the time you spend fetching the page. Second, both STDM and FDM are limited to situations in which the maximum number of flows is fixed and known ahead of time. It is not practical to resize the quantum or to add additional quanta in the case of STDM or to add new frequencies in the case of FDM. The form of multiplexing that we make most use of in this book is called statistical multiplexing. Although the name is not all that helpful for understanding the concept, statistical multiplexing is really quite simple, with two key ideas. First, it is like STDM in that the physical link is shared over time—first data from one flow is transmitted over the physical link, then data from another flow is transmitted, and so on. Unlike STDM, however, data is transmitted from each flow on demand rather than during a predetermined time slot. Thus, if only one flow has data to send, it gets to transmit that data without waiting for its quantum to come around and thus without having to watch the quanta assigned to the other flows go by unused. It is this avoidance of idle time that gives packet switching its efficiency. As defined so far, however, statistical multiplexing has no mechanism to ensure that all the flows eventually get their turn to transmit over the physical link. That is, once a flow begins sending data, we need some way to limit the transmission, so that the other flows can have a turn. To account for this need, statistical multiplexing defines an upper bound on the size of the block of data that each flow is permitted to transmit at a given time. This limited-size block of data is typically referred to as a packet, to distinguish it from the arbitrarily large message that an application program might want to transmit. Because a packet-switched network limits the maximum size of packets, a host may not be able to send a complete message in one packet. The source may need to fragment the message into several packets, with the receiver reassembling the packets back into the original message. In other words, each flow sends a sequence of packets over the physical link, with a decision made on a packet-by-packet basis as to which flows packet to send next. Notice that if only one flow has data to send, then it can send a sequence of packets back-to-back. However, should more than one of the flows have data to send, then their packets are interleaved on the link. depicts a switch multiplexing packets from multiple sources onto a single shared link. The decision as to which packet to send next on a shared link can be made in a number of different ways. For example, in a network consisting of switches interconnected by links such as the one in the decision would be made by the switch that transmits packets onto the shared link. (As we will see later, not all packet-switched networks actually involve switches, and they may use other mechanisms to determine whose packet goes onto the link next.) Each switch in a packet-switched network makes this decision independently, on a packet-by-packet basis. One of the issues that faces a network designer is how to make this decision in a fair manner. For example, a switch could be designed to service packets on a first-in-first-out (FIFO) basis. Another approach would be to transmit the packets from each of the different flows that are currently sending data through the switch in a round-robin manner. This might be done to ensure that certain flows receive a particular share of the links b andwidth, or that they never have their packets delayed in the switch for more than a certain length of time. A network that attempts to allocate bandwidth to particular flows is sometimes said to support quality of service (QoS), a topic that we return to in Chapter 6. Also, notice in that since the switch has to multiplex three incoming packet streams onto one outgoing link, it is possible that the switch will receive packets faster than the shared link can accommodate. In this case, the switch is forced to buffer these packets in its memory. Should a switch receive packets faster than it can send them for an extended period of time, then the switch will eventually run out of buffer space, and some packets will have to be dropped. When a switch is operating in this state, it is said to be congested. The bottom line is that statistical multiplexing defines a cost-effective way for multiple users (e.g., host-to-host flows of data) to share network resources (links and nodes) in a fine-grained manner. It defines the packet as the granularity with which the links of the network are allocated to different flows, with each switch able to schedule the use of the physical links it is connected to on a per-packet basis. Fairly allocating link capacity to different flows and dealing with congestion when it occurs are the key challenges of statistical multiplexing. 1.2.3 Support for Common Services While the previous section outlined the challenges involved in providing costeffective connectivity among a group of hosts, it is overly simplistic to view a computer network as simply delivering packets among a collection of computers. It is more accurate to think of a network as providing the means for a set of application processes that are distributed over those computers to communicate. In other words, the next requirement of a computer network is that the application programs running on the hosts connected to the network must be able to communicate in a meaningful way. When two application programs need to communicate with each other, there are a lot of complicated things that need to happen beyond simply sending a message from one host to another. One option would be for application designers to build all that complicated functionality into each application program. However, since many applications need common services, it is much more logical to implement those common services once and then to let the application designer build the application using those services. The challenge for a network designer is to identify the right set of common services. The goal is to hide the complexity of the network from the application without overly constraining the application designer. Intuitively, we view the network as providing logical channels over which application-level processes can communicate with each other; each channel provides the set of services required by that application. In other words, just as we use a cloud to abstractly represent connectivity among a set of computers, we now think of a channel as connecting one process to another. shows a pair of application-level processes communicating over a logical channel that is, in turn, implemented on top of a cloud that connects a set of hosts. We can think of the channel as being like a pipe connecting two applications, so that a sending application can put data in one end and expect that data to be delivered by the network to the application at the other end of the pipe. Thechallengeistorecognize what functionality the channels should provide to application programs. For example, does the application require a guarantee that messages sent over the channel are delivered, or is it acceptable if some messages fail to arrive? Is it necessary that messages arrive at the recipient process in the same order in which they are sent, or does the recipient not care about the order in which messages arrive? Does the network need to ensure that no third parties are able to eavesdrop on the channel, or is privacy not a concern? In general, a network provides a variety of different types of channels, with each application selecting the type that best meets its needs. The rest of this section illustrates the thinking involved in defining useful channels. Identifying Common Communication Patterns Designing abstract channels involves first understanding the communication needs of a representative collection of applications, then extracting their common communication requirements, and finally incorporating the functionality that meets these requirements in the network. One of the earliest applications supported on any networ Implementation of New Computer Network Implementation of New Computer Network Here we are going to implement an new computer network for this company that 25 employees have been working in. Suppose you want to build a computer network, one that has potential to grow to global proportions to support applications as diverse as teleconferencing, video-on-demand, electronic commerce, distributed computing, and digital libraries. What available technologies would serve as the underlying building blocks, and what kind of software architecture would you design t integrate these building blocks into an effective communication service? Suppose you want to build a computer network, one that has the potential togrow to global proportions and to support applications as diverse as teleconferencing, video-on-demand, electronic commerce, distributed computing, and digital libraries. What available technologies would serve as the underlying building blocks, and what kind of software architecture would you design to integrate these building blocks into an effective communication service? Answering this question is the overriding goal of — to describe the available building materials and then to show how they can be used to construct a network from the ground up. Before we can understand how to design a computer network, we should first agree on exactly what a computer network is. At one time, the term network meant the set of serial lines used to attach dumb terminals to mainframe computers. To some, the term implies the voice telephone network. To others, the only interesting network is the cable network used to disseminate video signals. The main thing these networks have in common is that they are specialized to handle one particular kind of data (keystrokes, voice, or video) and they typically connect to special-purpose devices (terminals, hand receivers, and television sets). What distinguishes a computer network from these other types of networks? Probably the most important characteristic of a computer network is its generality. Computer networks are built primarily from general-purpose programmable hardware, and they are not optimized for a particular application like making phone calls or delivering television signals. Instead, they are able to carry many different types of data, and they support a wide, and ever-growing, range of applications. This chapter looks at some typical applications of computer networks and discusses the requirements that a network designer who wishes to support such applications must be aware of. Once we understand the requirements, how do we proceed? Fortunately, we will not be building the first network. Others, most notably the community of researchers responsible for the Internet, have gone before us. We will use the wealth of experience generated from the Internet to guide our design. This experience is embodied in a network architecture that identifies the available hardware and software components and shows how they can be arranged to form a complete network system. To start us on the road toward understanding how to build a network, this chapter does four things. First, it explores the requirements that different applications and different communities of people (such as network users and network operators) place on the network. Second, it introduces the idea of a network architecture, which lays the foundation for the rest of the book. Third, it introduces some of the key elements in the implementation of computer networks. Finally, it identifies the key metrics that are used to evaluate the performance of computer networks. 1.1 APPLICATIONS Most people know the Internet through its applications: the World Wide Web, email, streaming audio and video, chat rooms, and music (file) sharing. The Web, for example, presents an intuitively simple interface. Users view pages full of textual and graphical objects, click on objects that they want to learn more about, and a corresponding new page appears. Most people are also aware that just under the covers, each selectable object on a page is bound to an identifier for the next page to be viewed. This identifier, called a Uniform Resource Locator (URL), is used to provide a way of identifying all the possible pages that can be viewed from your web browser. For example, http://www.cs.princeton.edu/~llp/index.html is the URL for a page providing information about one of this books authors: the string http indicates that the HyperText Transfer Protocol (HTTP) should be used to download the page, www.cs.princeton.edu is the name of the machine that serves the page, and /~llp/index.html uniquely identifies Larrys home page at this site. What most Web users are not aware of, however, is that by clicking on just one such URL, as many as 17 messages may be exchanged over the Internet, and this assumes the page itself is small enough to fit in a single message. This number includes up to six messages to translate the server name (www.cs.princeton.edu) into its Internet address (128.112.136.35), three messages to set up a Transmission Control Protocol (TCP) connection between your browser and this server, four messages for your browser to send the HTTP get request and the server to respond with the requested page (and for each side to acknowledge receipt of that message), and four messages to tear down the TCP connection. Of course, this does not include the millions of messages exchanged by Internet nodes throughout the day, just to let each other know that they exist and are ready to serve web pages, translate names to addresses, and forward messages toward their ultim ate destination. Another widespread application of the Internet is the delivery of streaming audio and video. While an entire video file could first be fetched from a remote machine and then played on the local machine, similar to the process of downloading and displaying a web page, this would entail waiting for the last second of the video file to be delivered before starting to look at it. Streaming video implies that the sender and the receiver are, respectively, the source and the sink for the video stream. That is, the source generates a video stream (perhaps using a video capture card), sends it across the Internet in messages, and the sink displays the stream as it arrives. There are a variety of different classes of video applications. One class of video application is video-on-demand, which reads a pre-existing movie from disk and transmits it over the network. Another kind of application is videoconferencing, which is in some ways the more challenging (and, for networking people, interesting) case because it has very tight timing constraints. Just as when using the telephone, the interactions among the participants must be timely. When a person at one end gestures, then that action must be displayed at the other end as quickly as possible. Too much delay makes the system unusable. Contrast this with video-on-demand where, if it takes several seconds from the time the user starts the video until the first image is displayed, the service is still deemed satisfactory. Also, interactive video usually implies that video is flowing in both directions, while a video-on-demand application is most likely sending video in only one direction. One pioneering example of a videoconferencing tool, developed in the early and mid-1990s, is vic. shows the control panel for a vic session. vic is actually one of a suite of conferencing tools designed at Lawrence Berkeley Laboratory and UC Berkeley. The others include a whiteboard application (wb) that allows users to send sketches and slides to each other, a visual audio tool called vat, and a session directory (sdr) that is used to create and advertise videoconferences. All these tools run on Unix—hence their lowercase names—and are freely available on the Internet. Many similar tools are available for other operating systems. It is interesting to note that while video over the Internet is still considered to be in its relative infancy at the time of this writing (2006), that the tools to support video over IP have existed for well over a decade. Although they are just two examples, downloading pages from the Web and participating in a videoconference demonstrate the diversity of applications that can be built on top of the Internet, and hint at the complexity of the Internets design. Starting from the beginning, and addressing one problem at time, the rest of this book explains how to build a network that supports such a wide range of applications. Chapter 9 concludes the book by revisiting these two specific applications, as well as several others that have become popular on todays Internet. 1.2 REQUIREMENTS We have just established an ambitious goal for ourselves: to understand how to build a computer network from the ground up. Our approach to accomplishing this goal will be to start from first principles, and then ask the kinds of questions we would naturally ask if building an actual network. At each step, we will use todays protocols to illustrate various design choices available to us, but we will not accept these existing artifacts as gospel. Instead, we will be asking (and answering) the question of why networks are designed the way they are. While it is tempting to settle for just understanding the way its done today, it is important to recognize the underlying concepts because networks are constantly changing as the technology evolves and new applications are invented. It is our experience that once you understand the fundamental ideas, any new protocol that you are confronted with will be relatively easy to digest. The first step is to identify the set of constraints and requirements that influence network design. Before getting started, however, it is important to understand that the expectations you have of a network depend on your perspective: An application programmer would list the services that his application needs, for example, a guarantee that each message the application sends will be delivered without error within a certain amount of time. A network designer would list the properties of a cost-effective design, for example, that network resources are efficiently utilized and fairly allocated to different users. A network provider would list the characteristics of a system that is easy to administer and manage, for example, in which faults can be easily isolated and whereitiseasytoaccountfor usage. This section attempts to distill these different perspectives into a high-level introduction to the major considerations that drive network design, and in doing so, identifies the challenges addressed throughout the rest of this book. 1.2.1 Connectivity Starting with the obvious, a network must provide connectivity among a set of computers. Sometimes it is enough to build a limited network that connects only a few select machines. In fact, for reasons of privacy and security, many private (corporate) networks have the explicit goal of limiting the set of machines that are connected. In contrast, other networks (of which the Internet is the prime example) are designed to grow in a way that allows them the potential to connect all the computers in the world. A system that is designed to support growth to an arbitrarily large size is said to scale. Using the Internet as a model, this book addresses the challenge of scalability. Links, Nodes, and Clouds Network connectivity occurs at many different levels. At the lowest level, a network can consist of two or more computers directly connected by some physical medium, such as a coaxial cable or an optical fiber. We call such a physical medium a link,and we often refer to the computers it connects as nodes. (Sometimes a node is a more specialized piece of hardware rather than a computer, but we overlook that distinction for the purposes of this discussion.) As illustrated in, physical links are sometimes limited to a pair of nodes (such a link is said to be point-to-point), while in other cases, more than two nodes may share a single physical link (such a link is said to be multiple-access). Whether a given link supports point-to-point or multiple-access connectivity depends on how the node is attached to the link. It is also the case that multiple-access links are often limited in size, in terms of both the geographical distance they can cover and the number of nodes they can connect. If computer networks were limited to situations in which all nodes are directly connected to each other over a common physical medium, then networks would either be very limited in the number of computers they could connect, or the number of wires coming out of the back of each node would quickly become both unmanageable and very expensive. Fortunately, connectivity between two nodes does not necessarily imply a direct physical connection between them—indirect connectivity may be achieved among a set of cooperating nodes. Consider the following two examples of how a collection of computers can be indirectly connected. shows a set of nodes, each of which is attached to one or more point- to-point links. Those nodes that are attached to at least two links run software that forwards data received on one link out on another. If organized in a systematic way, these forwarding nodes form a switched network. There are numerous types of switched networks, of which the two most common are circuit-switched and packet-switched. The former is most notably employed by the telephone system, while the latter is used for the overwhelming majority of computer networks and will be the focus of this book. The important feature of packet-switched networks is that the nodes in such a network send discrete blocks of data to each other. Think of these blocks of data as corresponding to some piece of application data such as a file, a piece of email, or an image. We call each block of data either a packet or a message, and for now we use these terms interchangeably; we discuss the reason they are not always the same in Section 1.2.2. Packet-switched networks typically use a strategy called store-and-forward. As the name suggests, each node in a store-and-forward network first receives a complete packet over some link, stores the packet in its internal memory, and then forwards the complete packet to the next node. In contrast, a circuit-switched network first establishes a dedicated circuit across a sequence of links and then allows the source node to send a stream of bits across this circuit to a destination node. The major reason for using packet switching rather than circuit switching in a computer network is efficiency, discussed in the next subsection. The cloud in distinguishes between the nodes on the inside that implement the network (they are commonly called switches, and their primary function is to store and forward packets) and the nodes on the outside of the cloud that use the network (they are commonly called hosts, and they support users and run application programs). Also note that the cloud in is one of the most important icons of computer networking. In general, we use a cloud to denote any type of network, whether it is a single point-to-point link, a multiple-access link, or a switched network. Thus, whenever you see a cloud used in a figure, you can think of it as a placeholder for any of the networking technologies covered in this book. A second way in which a set of computers can be indirectly connected is shown in . In this situation, a set of independent networks (clouds) are interconnected to form an internetwork, or internet for short. We adopt the Internets convention of referring to a generic internetwork of networks as a lowercase i internet, and the currently operational TCP/IP Internet as the capital I Internet. A node that is connected to two or more networks is commonly called a router or gateway, and it plays much the same role as a switch—it forwards messages from one network to another. Note that an internet can itself be viewed as another kind of network, which means that an internet can be built from an interconnection of internets. Thus, we can recursively build arbitrarily large networks by interconnecting clouds to form larger clouds. Just because a set of hosts are directly or indirectly connected to each other does not mean that we have succeeded in providing host-to-host connectivity. The final requirement is that each node must be able to state which of the other nodes on the network it wants to communicate with. This is done by assigning an address to each node. An address is a byte string that identifies a node; that is, the network can use a nodes address to distinguish it from the other nodes connected to the network. When a source node wants the network to deliver a message to a certain destination node, it specifies the address of the destination node. If the sending and receiving nodes are not directly connected, then the switches and routers of the network use this address to decide how to forward the message toward the destination. The process of determining systematically how to forward messages toward the destination node based on its address is called routing. This brief introduction to addressing and routing has presumed that the source node wants to send a message to a single destination node (unicast). While this is the most common scenario, it is also possible that the source node might want to broadcast a message to all the nodes on the network. Or a source node might want to send a message to some subset of the other nodes, but not all of them, a situation called multicast. Thus, in addition to node-specific addresses, another requirement of a network is that it supports multicast and broadcast addresses. The main idea to take away from this discussion is that we can define a network recursively as consisting of two or more nodes connected by a physical link, or as two or more networks connected by a node. In other words, a network can be constructed from a nesting of networks, where at the bottom level, the network is implemented by some physical medium. One of the key challenges in providing network connectivity is to define an address for each node that is reachable on the network (including support for broadcast and multicast connectivity), and to be able to use this address to route messages toward the appropriate destination node(s). 1.2.2 Cost-Effective Resource Sharing As stated above, this book focuses on packet-switched networks. This section explains the key requirement of computer networks—efficiency—that leads us to packet switching as the strategy of choice. Given a collection of nodes indirectly connected by a nesting of networks, it is possible for any pair of hosts to send messages to each other across a sequence of links and nodes. Of course, we want to do more than support just one pair of communicating hosts—we want to provide all pairs of hosts with the ability to exchange messages. The question, then, is how do all the hosts that want to communicate share the network, especially if they want to use it at the same time? And, as if that problem isnt hard enough, how do several hosts share the same link when they all want to use it at the same time? To understand how hosts share a network, we need to introduce a fundamental concept, multiplexing, which means that a system resource is shared among multiple users. At an intuitive level, multiplexing can be explained by analogy to a timesharing computer system, where a single physical CPU is shared (multiplexed) among multiple jobs, each of which believes it has its own private processor. Similarly, data being sent by multiple users can be multiplexed over the physical links that make up a network. To see how this might work, consider the simple network illustrated in , where the three hosts on the left side of the network (senders S1S3) are sending data to the three hosts on the right (receivers R1R3) by sharing a switched network that contains only one physical link. (For simplicity, assume that host S1 is sending data to host R1, and so on.) In this situation, three flows of data—corresponding to the three pairs of hosts—are multiplexed onto a single physical link by switch 1 and then demultiplexed back into separate flows by switch 2. Note that we are being intentionally vague about exactly what a flow of data corresponds to. For the purposes of this discussion, assume that each host on the left has a large supply of data that it wants to send to its counterpart on the right. There are several different methods for multiplexing multiple flows onto one physical link. One common method is synchronous time-division multiplexing (STDM). The idea of STDM is to divide time into equal-sized quanta and, in a round-robin fashion, give each flow a chance to send its data over the physical link. In other words, during time quantum 1, data from S1 to R1 is transmitted; during time quantum 2, data from S2 to R2 is transmitted; in quantum 3, S3 sends data to R3. At this point, the first flow (S1 to R1) gets to go again, and the process repeats. Another method is frequency-division multiplexing (FDM). The idea of FDM is to transmit each flow over the physical link at a different frequency, much the same way that the signals for different TV stations are transmitted at a different frequency on a physical cable TV link. Although simple to understand, both STDM and FDM are limited in two ways. First, if one of the flows (host pairs) does not have any data to send, its share of the physical link—that is, its time quantum or its frequency—remains idle, even if one of the other flows has data to transmit. For example, S3 had to wait its turn behind S1 and S2 in the previous paragraph, even if S1 and S2 had nothing to send. For computer communication, the amount of time that a link is idle can be very large—for example, consider the amount of time you spend reading a web page (leaving the link idle) compared to the time you spend fetching the page. Second, both STDM and FDM are limited to situations in which the maximum number of flows is fixed and known ahead of time. It is not practical to resize the quantum or to add additional quanta in the case of STDM or to add new frequencies in the case of FDM. The form of multiplexing that we make most use of in this book is called statistical multiplexing. Although the name is not all that helpful for understanding the concept, statistical multiplexing is really quite simple, with two key ideas. First, it is like STDM in that the physical link is shared over time—first data from one flow is transmitted over the physical link, then data from another flow is transmitted, and so on. Unlike STDM, however, data is transmitted from each flow on demand rather than during a predetermined time slot. Thus, if only one flow has data to send, it gets to transmit that data without waiting for its quantum to come around and thus without having to watch the quanta assigned to the other flows go by unused. It is this avoidance of idle time that gives packet switching its efficiency. As defined so far, however, statistical multiplexing has no mechanism to ensure that all the flows eventually get their turn to transmit over the physical link. That is, once a flow begins sending data, we need some way to limit the transmission, so that the other flows can have a turn. To account for this need, statistical multiplexing defines an upper bound on the size of the block of data that each flow is permitted to transmit at a given time. This limited-size block of data is typically referred to as a packet, to distinguish it from the arbitrarily large message that an application program might want to transmit. Because a packet-switched network limits the maximum size of packets, a host may not be able to send a complete message in one packet. The source may need to fragment the message into several packets, with the receiver reassembling the packets back into the original message. In other words, each flow sends a sequence of packets over the physical link, with a decision made on a packet-by-packet basis as to which flows packet to send next. Notice that if only one flow has data to send, then it can send a sequence of packets back-to-back. However, should more than one of the flows have data to send, then their packets are interleaved on the link. depicts a switch multiplexing packets from multiple sources onto a single shared link. The decision as to which packet to send next on a shared link can be made in a number of different ways. For example, in a network consisting of switches interconnected by links such as the one in the decision would be made by the switch that transmits packets onto the shared link. (As we will see later, not all packet-switched networks actually involve switches, and they may use other mechanisms to determine whose packet goes onto the link next.) Each switch in a packet-switched network makes this decision independently, on a packet-by-packet basis. One of the issues that faces a network designer is how to make this decision in a fair manner. For example, a switch could be designed to service packets on a first-in-first-out (FIFO) basis. Another approach would be to transmit the packets from each of the different flows that are currently sending data through the switch in a round-robin manner. This might be done to ensure that certain flows receive a particular share of the links b andwidth, or that they never have their packets delayed in the switch for more than a certain length of time. A network that attempts to allocate bandwidth to particular flows is sometimes said to support quality of service (QoS), a topic that we return to in Chapter 6. Also, notice in that since the switch has to multiplex three incoming packet streams onto one outgoing link, it is possible that the switch will receive packets faster than the shared link can accommodate. In this case, the switch is forced to buffer these packets in its memory. Should a switch receive packets faster than it can send them for an extended period of time, then the switch will eventually run out of buffer space, and some packets will have to be dropped. When a switch is operating in this state, it is said to be congested. The bottom line is that statistical multiplexing defines a cost-effective way for multiple users (e.g., host-to-host flows of data) to share network resources (links and nodes) in a fine-grained manner. It defines the packet as the granularity with which the links of the network are allocated to different flows, with each switch able to schedule the use of the physical links it is connected to on a per-packet basis. Fairly allocating link capacity to different flows and dealing with congestion when it occurs are the key challenges of statistical multiplexing. 1.2.3 Support for Common Services While the previous section outlined the challenges involved in providing costeffective connectivity among a group of hosts, it is overly simplistic to view a computer network as simply delivering packets among a collection of computers. It is more accurate to think of a network as providing the means for a set of application processes that are distributed over those computers to communicate. In other words, the next requirement of a computer network is that the application programs running on the hosts connected to the network must be able to communicate in a meaningful way. When two application programs need to communicate with each other, there are a lot of complicated things that need to happen beyond simply sending a message from one host to another. One option would be for application designers to build all that complicated functionality into each application program. However, since many applications need common services, it is much more logical to implement those common services once and then to let the application designer build the application using those services. The challenge for a network designer is to identify the right set of common services. The goal is to hide the complexity of the network from the application without overly constraining the application designer. Intuitively, we view the network as providing logical channels over which application-level processes can communicate with each other; each channel provides the set of services required by that application. In other words, just as we use a cloud to abstractly represent connectivity among a set of computers, we now think of a channel as connecting one process to another. shows a pair of application-level processes communicating over a logical channel that is, in turn, implemented on top of a cloud that connects a set of hosts. We can think of the channel as being like a pipe connecting two applications, so that a sending application can put data in one end and expect that data to be delivered by the network to the application at the other end of the pipe. Thechallengeistorecognize what functionality the channels should provide to application programs. For example, does the application require a guarantee that messages sent over the channel are delivered, or is it acceptable if some messages fail to arrive? Is it necessary that messages arrive at the recipient process in the same order in which they are sent, or does the recipient not care about the order in which messages arrive? Does the network need to ensure that no third parties are able to eavesdrop on the channel, or is privacy not a concern? In general, a network provides a variety of different types of channels, with each application selecting the type that best meets its needs. The rest of this section illustrates the thinking involved in defining useful channels. Identifying Common Communication Patterns Designing abstract channels involves first understanding the communication needs of a representative collection of applications, then extracting their common communication requirements, and finally incorporating the functionality that meets these requirements in the network. One of the earliest applications supported on any networ

Critical Analysis of Edvard Munchs The Scream Essay -- Visual Arts Pa

Critical Analysis of Edvard Munch's The Scream "The Scream", sometimes known as "The Cry" was painted by Edvard Munch in 1893. Some say Munch played a role in the development of German Expressionism, though the Norwegian painter turned down two offers to join the group, and preferred not to be classified, or 'put' into a category. This painting was part of Munch's "The Frieze of Life", a series of paintings each portraying a phase of life - as defined by Munch: Birth of Love, Blossoming and Dissolution of Love, Anguish of Life, and Death. The eleven paintings - "The Kiss", "Madonna", "Ashes", "Dance of Life", "Melancholy", "Red Virginia Creeper", "The Scream", "Death in the Sick-Room", "Puberty", "Moonlight", and "The Sick Child" - are as moving today as they were a hundred years ago when the motifs were first conceived. Munch finished "The Scream" in 1893. It was a work of great personal meaning to him. The painting was like the culmination of all the tragic and harrowing events in his life. When Munch was aged only five years old, his Mother died from Tuberculosis. Nine years later, his favourite sister Sophie dies from tuberculosis also, at the age of 15. Frequent illnesses prevent him from attending Technical college in Christiania (Oslo). In 1889, he is hit with perhaps the biggest blow so far: his beloved father dies. Munch wrote: "And I live with the dead ones; my mother, my sister, my grandfather, my father- he, especially. Every memory, every little thing, they all come back to me in flocks. I can see him again as I saw him for the last time four months ago, when he told me goodbye on the bench; we were a little bit shy, we didn't want to betray the pain that this separation was causing to us. How much we loved each other in spite of everything, how much he worried at night for me, for my life - because I couldn't share his faith" Therefore, it is not surprising that the mood of the painting is so haunting. Munch painted it surrounded by morbidity. The point in the painting where we see the figures, was a road on top of a hill looking over Christiania and the harbour. On one side of the hill was a psychiatric hospital where one of his sisters had been sent, and on the other side, an abattoir. Munch described the feeling he experienced in a diary entry in his literary diary in Nice, on the 22nd January 18... ...e influenced two German expressionist groups, Die Brà ¼ke and Die Blaue Reiter. He had two offers from Die Blaue Reiter to join them, but he turned both down. Painting was for Munch a personal experience, and he did not like to share it, or put his works into any grouping. The painting itself looks quite 'slapdash', as though it was rushed. The thick streaks of oil paint give the effect of a movement blur, like the world was swirling around the figure. It is hard to distinguish between the water and the land, difficult to recognize where the hills in the background stop and the sunset begins. "The Scream" is a painting full of emotion, full of character not understood at the time of its birth. It reflects Munch's life at that time, all the Death and anxiety that makes the painting so mysterious and haunting, whilst also lively. When I look at it, I feel I can hear the scream echoing from it. The screaming figure draws the attention of the onlooker, but other aspects of the painting are just as interesting. Whilst we cannot know what was going through Munch's mind when he painted"The Scream", we can guess that the painting evokes all the pain he was feeling.

The Islamic Worldview

UNGS 2030 THE ISLAMIC WORLDVIEW SEMESTER 1 2012/2013 ASSIGNMENT #1 TITLE| WORLDVIEW:THE MEANINGS,NECESSITY AND ELEMENTS ACCORDING TO MUSLIM SCHOLARS| COURSE TITLE| THE ISLAMIC WORLVIEW| COURSE CODE| UNGS 2030| SUBMISSION DATE| 30 OCTOBER 2012| NAME| NURUL AMALINA BINTI MD ALI| MATRIC. NO| 1215762| SECTION| 2| LECTURER NAME| DR. MD YOUSUF ALI| ACKNOWLEDGEMENT Bismillahirrahmanirrahim Assalamualaikum, First and foremost, I would like to thank to my instructor of this assignment, Dr. Md Yousuf Ali who is my best lecturer of The Islamic Worldview subject for the valuable explanation, guidance and advice especially during lecture session. He inspired me greatly to work in this assignment. His willingness to motivate me contributed tremendously to my assignment. I also would like to thank him for showing me some example that related to the topic of my assignment about The Worldview in term of its meanings, necessity and elements according to Muslim scholars. Besides, an honourable mention goes to my family and friends for their understandings and supports on me in completing this assignment. Without helps of the particular that mentioned above, I would face many difficulties while doing this assignment. During complete this assignment, I faced many difficulties and challenging things especially midterm examination and Eid Adha Celebration was around the corner. I found the information that related to our topic through The Holy Quran, the Internet, magazine, reference book and people in surrounding. However, I had done and can overcome these problem by maximize my effort and pray to Him who is The Most Helpful to His servant. Alhamdulillah. THE MEANINGS THE MEANING OF WORLDVIEWS In this assignment, first and foremost, before us knowing about worldview in Islamic perspectives, we must know the introduction and definition of ‘Worldview’. Where is term come from? And where is it used? The word of ‘Worldview’ is come from many sources. Its meaning is defined by many of scholars either western scholars or Muslim scholars. One of them comes from German’s term which is called as â€Å"Weltanschauung. Meanwhile, in Arabic’s term it is refer as â€Å"Tasawur or Ru’yah al-Islam li al-Wujud â€Å",   *The Meaning of Worldview by Western Scholars In the end of 1700s, Friedrich Schilling who is the German philosopher defined that, worldview (Weltanschauung) is refer as â€Å"The self-realized productive and conscious way of apprehending an d interpreting the universe of beings†. After a century, about in 1868, â€Å"Weltanschauung† was known as â€Å"a comprehensive conception of the world especially from a specific point of view†. Based on German scholars perspectives defined that Worldview is comprises of set of attitudes on basic matters like the way people think about the world. *The Meaning of Worldview by Muslim Scholars Muslim scholars and thinkers started use the precept of â€Å"worldview† during modern period. This percept appeared in the works of a lot of Muslim scholars like Sheikh Badiuzaman Nursi (1877-1960) in â€Å"Rasa’il al Nur† (letters of light) and in some Iranian thinkers such as Ali Shari’ati (1933-1977), al-Mutahari Ayatullah Murtaza (fundamentals of Islamic thought: God, man and the universe), Sayed Husein Naser (1933-) in â€Å" Man and nature: the spiritual crisis in modern man†, â€Å"Islam and the plight of modern man†. Isma’il Raji al-Faruqi (933-1982) â€Å"cultural atlas of Islam†, â€Å"Tawhid: its implications for thought and life†, Muhammad Naqib al-Atas â€Å"Islam and secularism†. In Arabic literature Sayed Qutb (1906-1966) came in the first place in his â€Å"in the shade of the Qur’an† (Fi Zilal al-Qur’an) â€Å"The Islamic Perspective† â€Å"al-Tasawwur al-Islami† occupies a central position. In contemporary period, valuable works have been produced dealing with the issue from Islamic point of view by Sardar Ziauddin (Islamic civilization: history of sciences), Alam Shoudhury (economics) (The Islamic worldview: socio-scientific perspective), al-Messiri (Thought & Political science). The meaning of Worldview by Muslims’ approach stands that the worldview is made from the aspect of both al-Dunya and al-Akhirah, in which the Dunya-aspect must be related in a profound and inseparable way to the Akhirah-aspect which the Akhirah-aspect has ultimate and final significance. In other word, worldview is a set of attitudes on a wide range of fundamental matters. It has a comprehensive set of propositions about various aspects of the world around us and man’s place within it. It is also defined as a basic assumption about the way of thinking about the world, which provides a more or less coherent, though not necessarily accurate. A worldview is a profile of the way the people within a specified culture live, act, think, work and relate. At the same time, it can be act as a â€Å"map† or culture’s social, religious, economic and political views and relationships.THE MEANING OF ISLAMIC WORLDVIEWSBased on Syed Naquib Al-Attas, a great Muslim scholar, he mentioned that Islamic Worldviews is, â€Å"a vision of reality and truth that appears before our mind’s eye revealing what existance is all about†. â€Å"a metaphysical survey of the visible as well as the invisible worlds including the perspective of life as a whole†. According to Al-Attas, worldview is considered as vision of reality and truth (ru’yat  al-Islam  li  al-wujud) from the Islamic point of view. Another Muslim scholar, Professor Kamal Hassan ,Professor  Area of Specialization: Contemporary Islamic Thought IIUM, also stated that, Worldviews is a comprehensive conception of Allah,man and the universe and their relationship from Islamic perspectives. † The worldview of Islam encompasses both al-dunia and al-akhirah in which the dunia aspect must be inextricably linked to the akhirah aspect, and in which the akhirah aspect has ultimate and final significance. Hence, Islamic worldviews concern with this universe (world) and the hereafter or the Day of Judgment as far as Islamic nature of reality is concerned. The belief in dual worldviews has made Islam looks exceptional. Since these views are principally derived from the  Quran, this reflects that Islamic worldviews are identical to  Quranic  worldview. Unlike in the Western, their emphasizing is on logical reasoning as well as rationality. Due to this, Islam has distinguished itself from other available worldviews as mentioned by Khurshid  Ahmad as cited by   Mawdudi. For instances, the Western’s and Christian‘s worldviews are secular and religious respectively. Islamic worldview is about the seen and unseen matter like the universe, creator, prophethood, society, man, and hereafter. Amalgamation or historical concoction or any addition stories of various cultural values are not a worldview that is formed merely. Rather, it is a well established framework derived from the revelation and interpreted by Muslim scholars throughout Islamic history. Then, it is implement by Muslims today. This frame of reference provides us with correct and consistent answers to the ultimate questions pertinent to the issues of God, unseen, man, universe, and life. It also guides man as a vicegerent of Allah to the correct belief system, shari‘ah, and ethical values. THE NECESSITYTHE NECESSITY OF ISLAMIC WORLDVIEWWe all need a certain worldview, even if it is not made fully explicit, to interact with our world. There is a practical need to have at least an implicit and for that reason naive answer for each of the worldview questions. The Islamic worldview is more than a religion. In Islam, it covers all aspects of life for its followers. Many religious scholars treat the Islamic worldview as a monotheistic religion following five simple pillars of faith. In Islamic worldview, it has views about the words like astronomical, spiritual, physical, intellectual and many aspect of life. The outlook of life in this perceptive is highly emphasized which is show us the vision of life to achieve certain goal in world and the ultimate goal in hereafter. Islamic worldview is important in order to provide the Muslims with the true knowledge and explanation about the world seen and unseen as they are explained in the Quran. Quran is the best guidance for all questions about life. This revelation is restricted to deny. The answer from this revelation cannot change and make this worldview become stable due to have ultimate guidance. For instance, if we are question about something, we can refer to Quran to find the solution. This guidance also encourages us to get the answer through the learning and reading. In Surah Al-Alaq, Allah mentioned that: Another that, Islamic worldview helps us to interact with nature, individuals, peoples, nations, cultures and civilizations. It helps us to know them comprehensively and can plan neighborhood among them. After we have relation with certain culture, we have to recognize what is their ethnic and culture. This will helps us to correct our own values, perspectives, attitudes and behaviors. This perceptive guide and teach people the way and method how to achieve the main values of Islam in human life. We can differentiate which one is bad and good. In Islam, the aspects regarding our morality and virtues (akhlaq) are become one of necessity aspect of life although we are struggling to achieve a success in life. As an example, we need to cover aurah during working at workstation. Furthermore, this percept is purposed to establish the fundamental ethical precepts, such as justice, freedom, trust, and dignity of human life and existence. Some of worldview not emphasize ethical aspect very well. By this perception, it will formulate theories of politics, sociology, culture, etc.THE ELEMENTS THE ELEMENTS OF ISLAMIC WORLDVIEWThe fundamental elements of Islamic Worldview are the key terms of this perceptive. These elements act as integrating principles that place all our systems of meaning and standard of life and values in coherent order as a unified system forming the worldview. The highest principle of true reality as stated in Quran is focused on knowledge of the nature of God. The w orldview of Islam is characterized by an authenticity and finality that points to what is ultimate, and it projects a view of reality and truth that encompasses existence and life altogether in total perspective whose fundamental elements are permanently established. Quoted back of Syed Naquib Al Attas word,† A metaphysical survey of seen and unseen world including the perspective of life as a whole†. The element of worldview are include visible anfd visible things. They are: 1. The Nature of God This the supreme principle of Islamic Worldview. This all about the existence of God. 2. The Nature of Revelation- The Qur'an ; Prophethood This element are totally derived from Revelation, the change which is possible in this case is restricted to the manifestation of these elements in different units of time and space. 3. The Nature of Revealed Religion- Islam 4. The Nature of the World and Hereafter (dunya wal akhirah) 5. The Nature of Man The Psychology Of Human Soul (insan) 6. The Nature of Knowledge (‘ilm) As mentioned in Surah Al Alaq which is encourage us to seek knowledge. 7. The Nature of Adab (values and virtues) The aspects regarding our morality and virtues (ahlaq) are become one of necessity aspect of life although we are struggling to achieve a success in life. 8. The Nature of Freedom 9. The Nature of Happiness (sa'adah) 10. The True Meaning of Change, Development, and Progress 1. Concluding Remarks All of them are together with the key terms and concepts that they unfold, have profound bearing upon our ideas about change, development, and progress. These fundamental elements act as integrating principles that place all our system of meaning and standards of life and values in coherent order as a unified system forming the worldview and the supreme principle of true reality that is articulated by these fundamental elements is focused on knowledge of the nature of God as revealed in the Qur'an.CONCLUSIONIt is a high time that the initiative of integrating the Islamic worldview into the planning of neighbourhoods takes off in the Muslim world. Worldviews play the main role in the human being life. Its affect every single action of a man. Different worldviews will certainly shape different qualities of mankind which will eventually lead them to different end means of life as well. This distinction due to man’s aql (intellectual) which is very limited and sometime buyers (not fair). Worldview is a complex and a comprehensive perception. A worldview manifests itself in all aspects of life, social, political, economic, civilization etc. This complex includes the spiritual, cognitive, intellectual and behavioral abilities that Allah has endowed him. Thus, a worldview is at once a mean and a fruit of human spiritual, cognitive, and behavioral efforts. The worldview perceptive can be human-made as well as Revelation based precept. Islamic worldview is a collective and based on ummatic unified. A worldview is similar to any other human ideas which is it develops according to their accumulated knowledge, historical events, and human experience and then it is implemented by the people. However, as far as the Islamic worldview is concerned, the fact of change takes significantly a different position. Although we are busy to achieve world’s mission of life, hereafter’s goal become significant and our priority to achieve it.REFERENCES* Lecture Notes  © Department of General Studies IIUM,2007- 2008. * The Islamic Worldview: Glimpse on Studies and Definitions,Abdelaziz Berghout,Introduction to the Islamic Worldview,Study of Seleceted Essentials,IIUM Press (2010). * Basic Principles of Islamic Worldview ,Sayyid Qutb Islamic Pubns Intl (September 15, 2005). Vidal, C. (2008) Wat is een wereldbeeld? (What is a worldview? ). * David Naugle: Worldview: The History of a Concept (Eerdmans, 2002). * Merriam –Webster 1994 (Britannica Encyclopedia 2001). * Contribution Of The Islamic Worldview Towards Corporate Governance Mohamed Asri, Mohamed Fahmi Msc Accounting Sem 2   2003 IIUM. * http://wikipedia. com/worldview/ * http://www. allaboutworldview. org/is lamic-worldview. htm * http://izat2009. blogspot. com/worldview * http://ungss. blogspot. com * http://web. usm. my/islamicworldview/