The American Idea

The notion of modernity is a concept that is employed to illustrate the state of being associated to modernism which, on the other hand, refers to a pattern of thought that confirms the influence of individuals to construct, enhance, and reform their environment. Further, the enlightenment project envisions the idea that new knowledge or understanding can be obtained which enables the clearness of perception.Hence, taken altogether, modernity in the context of the enlightenment considers the capacity of human beings to establish or reestablish their environment through the development of new wisdom and, more importantly, through the use of their reason or rationality. Jean Jacques Rousseau argued that the original state of man is one which is essentially free, or that freedom is originally humanity’s own. Moreover, he asserts that freedom has been lost but can yet be brought back through emancipation.In terms of modernity and the enlightenment, this emancipation can be taken b ack by using man’s rationality in order to clearly perceive what must be done so that individuals can reform their environment and, in the end, reclaim the freedom that they originally have. All these notions can be seen in Jose Marti’s Nuestra America specifically in the context of how he suggests that the Americans should act in order to reshape their environment and to eventually build a government that is uniquely their own and one that is devoid of foreign ideas and forms.There are quite several sharp notions in Nuestra America by Jose Marti, and all of these notions very well contribute to the revelation that with diversity comes the great possibility of acquiring an identity independent as it is from everything else outside. Although much of what is written verifies the idea that the creation of a government of the people surpasses that which is merely imitated, the role of the external elements can be argued as indispensable elements in the establishment of an identity.One of the central themes in Nuestra America is the idea of the formation of the government that is distinctive and proper to the Americans. Marti’s argument is grounded on the premise that a government that is shaped according to other nations or that which resembles or at least partly incorporates external elements from foreign nations will not be suitable for the people and for the entire nation. It can be observed that Marti firmly adheres to the principle of having an identity that is solidly based on what is natural to the people and to the rest of the country.What is natural supersedes those that are artificial. And what is essentially natural to America is ‘diversity’ in the truest sense of the word. Apparently, Marti makes it a point to bridge the issue with diversity to that of having a strong government structured according to the innate qualities of the American people. However, it fails to consider the fact that diversity also grants the sub stantial possibility of not actually unifying all the corners of the country into a single and identifiable sphere.What Marti does is to transcend this ‘diversity’ and patch all the different—albeit intrinsic—‘American’ elements into a unified concept that virtually quells, at least in theory, the force of other external factors. He does this at least in the sense of proposing an ‘ideological’ battle, one that treats ideas far superior than brute or physical force. Although Marti argues that bloodshed is inevitable, he also suggests that the ideas of man will have to take the core of the movement towards the establishment of an independent and unique government and that these ideas should come from the American people themselves and not from anybody else.In the opening parts of Marti’s work, it can be noted that he argues that men must unify themselves from the various ranks against the ‘seven-league giant’ thr ough the force of their ideas since ideas cannot be physically destroyed. While it is remains feasible that ideas cannot be destroyed in the physical sense and that while they can significantly proliferate and claim the victory of an entire nation, the role of sheer physical force in propelling such ideas towards certain goals cannot be denied.It should be noted that ideas have to be juxtaposed with physical and actual attempts of progressing towards a certain goal which, specifically in the context of Marti’s Nuestra America, is the creation of an American government in the strictest sense. By remaining as mere ideas contextualized solely on that rational or thinking part of human existence, ideas can hardly be a revolutionizing tool in altering the undesirable elements within the society.In another sense, there should be the ‘correspondence’ between such ideas and their physical or actual manifestation (Glennon and Johnson 2006). The absence of such a correspon dence may very well inhibit the ideas from ever reaching the desired outcomes, for what good is a prolific idea that is short of touching the actual existence of social problems and the reality of the clamoring for a physical government? Will ideas alone revolutionize a whole nation without even concretizing these ideas? Apparently, the answer to these questions is a resounding skepticism.History, at the least, tells one that most, if not all, of the changes or alterations in the society have, in one way or another, physical and actual movements which are strongly fastened to certain beliefs and ideologies (Merrill 1948). For instance, the American Revolution is considered to be founded on political and social ideologies that greatly contribute to the social movement during those times where the metaphorical ammunitions for artilleries are ideas that define what is being aimed at (Nelson 1965).Wars in Latin America are likewise strongly founded on the correspondence between ideologi es and the actual manifestation or enacting of these ideas (Thies 2005). Nevertheless, Marti also recognizes the notion that bloodshed is a strong coefficient of his proposed ideas of the unification of the American people and the establishment of a government solely their own and from their own.Marti strengthens to solidify his claim by suggesting that those who would seek the governance of America must focus on and attempt at identifying the reality of the nation and of the people—of the existing diversity that direly needs unification—in order to fulfill the idea that the spirit of the government is indeed the spirit that is truly derived from America and not from any other (Saldivar 1998).Hence, for those people seeking to identify what is being suggested to be identified must necessarily have the keen perception to not only feel what is real but to notice and extract the solutions for the reality of the social problems or, at least, of what is intended to be addre ssed. Otherwise, those who seek to eliminate the external or foreign elements seeping into American thoughts will utterly fail for lack of the capacity to transcend the blurring of the mind and of critical thinking.Such an attempt to identify the reality of the nation and of the people reinforces the idea that the better and fitting individuals to achieve such feat are those who are accustomed to America—and there can be no better person who does not only know much of America but acts and feels like America than the American. This goes to show that the foreigner cannot exactly feel the American reality, or that the foreign elements cannot entirely suffice to define the American experience although in some parts it may have something to do with it.Nevertheless, Marti’s Nuestra America clearly emphasizes the author’s strong attachment, at least in terms of the content of the literature, with the clamoring for a ‘pure’ American nation, a nation that is founded on American elements. Yet what is striking about Marti’s Nuestra America is the fact that it proposes for a unified government able to identify the reality of the nation, a unified government that is nonetheless rooted on a wide array of individuals or on a, roughly speaking, diversified society.It is indeed a widely held idea that the rest of America is diverse (Sullivan 1973), and that this entails the notion that a ‘unification’ of all the recognized and unrecognized sectors of the nations is a monumental task. While Marti champions his assertion that foreign ideas and forms have caused the delay in the rising of a logical structure of a government of America, he fails to note that the very diversity of America also has a role in such a delay.What he does in the article is to espouse the idea that such diversity can be committed towards the creation of a unique government and a unified people and to set aside or, at least, subtly put his hands off the lingering argument that this diversity may in fact be the one which will hinder the creation of an American government bereft of imported ideas and forms.Although native forces—‘forces’ not to be limited in the military sense—can keep at bay impending external or foreign forces from entering the layer that separates what is pure from what is alien, these same internal forces have a connection with the external forces in one way or another. Part of the evidence to this can be rooted from the argument that there is no such thing as a pure race that is distinct from the rest of the races since all of mankind emerged from a single ancestry otherwise known as Homo sapiens (McBrearty 1990).With the idea that all of humanity came from a single line of ancestry, by definition there can be no such thing as ‘race’ and that the demarcation between the American race and the ‘other’ races is dissolved. Technically, it may be true that mankind belongs to the same ancestry. Practically, there are staggering realities that ultimately create a wide space between socially constructed ‘races’ or equivalents thereof.Hence, although Jose Marti actually claims that there is no such thing as hatred for the other races because there are no races, he actually argues in Nuestra America that the people should consider the past, family and ancestral roots of the Americans and do away with what can be termed as ‘colonial inheritance’ for it entails things that are corrupt and defunct. By criticizing the ‘Parisians’ or ‘Madrileà ±os’, Marti actually draws the line between what is American from what is not.And in doing so, it cannot be avoided that Nuestra America in essence may contribute to the enlargement of the space that divides America from the imported ideas and forms and, thus, the treatment of these foreign entities as ‘others’. Marti’s work also appears to signify that America is indeed its own, and that what belongs to others is theirs as well which brings us back to what Marti’s work purports to address yet fails to meet—that there is no hatred among races because there is no such thing as ‘race’.Ironically, while Nuestra America echoes the clamoring for a unique government that is purely American by vanquishing the foreign or imported ideas that are imbibed into the society, it also establishes the idea of separating what is American from what is not if indeed a separation can ever be achieved at all, if not physically, at least ideologically. The fact that America and its people are diverse is a compelling reason to push the idea that the rest of America can hardly a government molded into a single, unified entity where opposition is inexistent or kept at a manageable level.Moreover, cultural relativism proclaims the idea that several values such as ethical values of rightness or wrongness may actually vary from culture to culture, and that cultural supremacy or the superiority of one culture from the other relatively varies as well on certain cultural perspectives (Schmidt 1955). From this, one can observe that Marti’s article conveys the idea that, by excluding anything that is foreign to the system of ideas of the American population, the American ideals are preferred over the foreign ones.Although there is no explicit mentioning that American ideals are far off better than imported ideas, by embracing American ideas in the formation of a unique government one actually albeit subliminally pursues the underlying assumption that what is native is more preferred since it applies better and fitting to the contextual nature of America and, therefore, is superior over the rest at least when put into the context of the formation of a unique government.Interestingly, cultural relativism tells us otherwise. The American attempt to furnish for themselves a unique government exclud es the assumption that imported ideas may also serve a contributive purpose in meeting such an end in replacement for defunct native ideas.While Nuestra America purports to assert for an American identity through its government and purely American ideas while straining foreign elements away from such a glaring feat, it also substantiates on the thesis of using the American diversity as a means towards unifying the whole, condensing them altogether into a single native label called ‘America’ without discussing much about the weakening force such a diversity may take with it.Nevertheless, Jose Marti nails the crucial point in his work—the great significance of ideas in the advancement of an American identity—by taking consideration the role of ideas in revolutionizing a nation flustered with unfamiliar or imported ideas. While it may be the case that ideas without corresponding actions are like vehicles without wheels, it certainly is the case that actions w ithout ideas are like violent storms which display their destructive might while leaving debris and rubbish after the winds and heavy rains abate.

Jonathan Swift’s style of writing Essay

Many critics like William Deans Howells; T.S. Eliot etc. have called Jonathan Swift the greatest writer of prose like T.S. Eliot says that â€Å"Swift, the greatest writer of English prose, and the greatest man who has ever written great English prose.† But there are reasons for this greatness. One of the main reasons is that Swift wrote in a very plain and downright style. He didn’t use any embellishments. At times, when Swift was writing serious stuff this same plain style appears dry but when writing humorously, this same plainness gives his wit a singular edge. Swift didn’t use ornate or rhetorical language; he said what he had to in simply without any affectation as Hugh Blair says â€Å"His style is of the plain and simple kind; free of all affectation, and all superfluity; perspicuous, manly and pure.† Look more:  jonathan swift satire essay And at times, his style appears so simple that its seems like anybody with a little sense of writing could write like him but in this same simple ness of manner lies Swift’s greatness like Scott says â€Å"Swift’s style seems so simple that one would think any child might write as he does, and yet if we try we find to our own despair that it is impossible.† This same simplicity of style in Gulliver’s Travels corresponds to the naivetà © and simplicity of Gulliver. Another important feature of Swift’s prose is that he uses the common touch. In other words, everybody can understand his language that is why even children can read his books with so much enjoyment. Also, Swift addresses people as rational and political beings, making them his equals. For example, in Drapier’s Letters Swift uses the same language of the class which he is addressing i.e. rough and shrewd. Swift doesn’t write long  sentences or speeches or difficult words. And he familiarizes with the people by using their own simple and at times coarse language. Invention or imagination is an aspect witch makes Swift one of the greatest English writers. J.J. Hogan says â€Å"One of Swift’s greatest outlets, of course, was invention.† Although Swift has used many non-sensical and imaginary words, but these imaginary words have an underlying meaning. For example, Lindalino indicates â€Å"Dublin†, Nardac when broken down in German Narr (meaning fool) and doch (meaning still) turns into ‘still a fool’. Hekinah Degul can be translated, on grounds of similarity of sound, turns into ‘What in the devil’. Glumdalclitch can be divided into French ‘grand’ and Latin ‘altrix’ which in turn is combined to produce the meaning ‘enormous nurse’. The word Grildrig can be translated into ‘Girl-thing’ or ‘doll’. Swift also uses onomatopoeic words for example, Gulliver, Lilliput, Brobdingnag, Houyhnhnms, Yahoos etc. The name Lilliput suggest something small like in the word little, Brobdingnag suggest something, which is big. The same way Houyhnhnms (pronounced Whinnims) sounds just like the neighing of a horse and Yahoo is the sound that people make when they are liberated. Even the names that Swift gives to characters are onomatopoeic like Gulliver which is similar in sound to gullible, the emperor’s name in Lilliput Golbasto Momaren Evlame Gurdilo Shefin Mully Ully Gue shows a little bit of the inflated nature of the emperor and the last part Mully Ully Gue sounds ridiculous after such a long, inflated name. And Swift tries to give meaning to these same words to create a sense of authenticity for example, in voyage II, Gulliver is described as being as big as a splacknuck. So, although some words sound totally non-sensical there, is, infact some sense and meaning behind them. There are a few other ways in which Swift’s writing is so remarkable. One of them is that is that Swift creates authenticity through the use of archaic language (like the language used in the Old Testament) for example after his long nap, Gulliver says that he awaked after a long nap. Also, Swift goes into very minute detail of anything that he’s describing. Like he describes  the exact latitude, longitude, dates, naval details, details about clothing, manners, etc. At times, these same details are very disgusting like he describes how he had to disburden himself in Lilliput or the beggars in Brobdingna, but these same disgusting details create realism. One of the most prominent features of Swift’s writing is his satire, which is described by Jacques Barzun as more deadly than a trap. His satire is very bitter, it isn’t gentle at all. But the best thing about his satire is that he’s satirizing the society through somebody as naà ¯ve and gentle as Gulliver. Swift most corrosive satire is on women and politicians, although, at times he does satirize other people like the scientists in Voyage III of Gulliver’s Travels or the religious members through The Tale of a Tub. Swift commonly uses situational satire to criticize or when he excessively praises someone, it’s a strategy of irony and Swift manipulates this praise for his own satiric ends. So the main reasons why Swift’s prose is plain perfection is that he writes in a simple manner, uses common language, he uses imaginary and non-sensical words and gives authenticity to these words, the use of archaic language to give authenticity, the description of everything up to the minutest detail and the way in which Swift uses satire.

HSBC Culture Essay

It is necessary to underline that organizational culture plays crucial role for employees’ motivation, job commitment, productivity, and overall working atmosphere. Therefore, HSBC culture promotes believes of honesty, teamwork, and integrity. HSBC culture is based on the following principles and values: highest personal standards of integrity, truth and fair dealing, quality and competence, minimum bureaucracy, quick decision-making, group interest ahead the personal ones, sustainable development and many others. For example, from the very start of the recruitment process HSBC leadership claims that right values are the most important criterion along with excellent leadership skills and good grades. Moreover, HSBC is open to provide changes and innovations. HSBC tends to seek new approach to dealing with routines and problems, and constructive feedback is highly appreciated and encouraged. (Hargett 2007) Moreover, HSBC provides flexible working patterns, disability care and care for elderly, as well as in-house employee assistance. Therefore, employees have an opportunity to solve health and divorce problems. HSBC culture is rewarding, vibrant, stimulating, and tends to prevent arrogance and coldness in banking sphere. HSBC culture promotes professional development and training. For example, professional trainers will provides staff with necessary interpersonal skills, problem-solving and decision-making techniques, personal grooming, time and planning management, etc. From the beginning of working process all employees have free access to on-line course and professional literature. HSBC offers variety. In other words, there are many things to discover and many people to learn from. HSBC has diverse personnel. (Wig 2007) HSBC culture strongly emphasizes the role of collective management and teamwork stating that these principles are the core of future success. Nevertheless, each team member is responsible for particular tasks. The working atmosphere is friendly – people are ready to help each other. Moreover, many employees are real critical and creative thinkers – they are open to new ideas. For example, HSBC consider critical thinking the vital component of decision-making process and business as a whole. Critical thinking gives experts and employees an opportunity to develop new fresh solutions to problems. It gives the possibility to enjoy analyzing data and information and then to develop opinions and conclusions. One more positive moment is that HSBC encourages striking the right balance meaning that people have enough time for social life. The Head of HSBC Human Resources states: â€Å"The day I stop smiling coming to and going from work is the day I know I have to stop working†. (Where to Work 2002) HSBC culture is driven by understanding traditions, needs of individuals, job commitments, etc. Furthermore, the company tries to be committed to all individual needs. It is necessary to outline that women comprise large component of company’s market and the company is trying to make service available and affordable for every community. Company’s success and achievements are seen worldwide. HSBC tends to understand better local people and to provide employees with right information to offer necessary services and to reinforce brand. HSBC developed unique way f tailoring services – it can â€Å"offer an enhanced level of service than other local practitioners operating in multicultural countries and this facet, therefore, offers significant competitor advantage†, as one of the HSBC leaders says. (Wig 2007) HSBC culture is also based on the principles of gender diversity and no discriminated I observed in this filed. HSBC finds it impossible to leave women out of the equation. HSBC tries to achieve gender split 50/50, and it is a good sign of pleasant culture. According to corporate culture, women are encouraged actively to be promoted from the first managerial rung of the ladder to the next steps. HSBC developed â€Å"Women’s Development Program† to attract women to enhanced roles. Bank organization is more balanced and more adaptable to new situations. For example, HSBC proclaims cultural diversity stating that respect for every individual will promote loyalty and tolerance in employees. (Where to Work 2002) The next moment to admit is that HSBC culture is defined as confident rather than brash. Bank organization isn’t organization which tends to shout from the rooftops. The main principles of corporate culture are modesty, honesty, openness, kindness, and knowledge. The next principle is multicultural staff. For example, in London, the board managers and managers of all layers are representatives of different races and ethnical backgrounds. HSBC positions itself as the world’s local bank. HSBC tend to find the best practices and make personnel acquainted with them. HSBC culture is described by collective management and teamwork rather than individual work. Collective management is presented at all levels of bank organization. It is possible to say that thousands of bank offices are, actually, one office. No other organization can say that their workers in London are chatting with partners in New York discussing ways of handling procedures. (Wig 2007) Finally, HSBC culture represents a strong set of values and believes. It promotes the overall sense of responsibility, provides recommendations how to act in everyday life and how make everyday decision. HSBC tends to assist employees both at work and in personal life. Further, HSBC supports straightforwardness and honesty in relations with customers. HSBC fulfills all responsibilities to customers, colleagues, shareholders, wider operational communities, and shareholders. Moreover, HSBC has a long-standing commitment to education that goes back well over a hundred years. It is known that organization supports educational projects and has deep commitment to the environment. (Hargett 2007) References A Better Environment For Business. Available from [Accessed 13 November 2007] Hargett, J. (2007). HSBC Holdings to Join in Financial Write-Down Parade. Available from [Accessed 13 November 2007] HSBC Bank. (2002). Available from [Accessed 13 November 2007] Where to Work. (2002). Available from [Accessed 13 November 2007] Wig, S. (2007). HSBC Careers. Available from http://hsbc.com.sg/sg/career/mdp/testim_swati.htm

Cell Phones Research Paper Example | Topics and Well Written Essays - 750 words

Cell Phones - Research Paper Example The main reasons for this monumental change over such a short, time are the abilities that science and technology has conferred to modern phones, particularly mobile devices. Today, a phone has acquired such a wide variety of uses that a phone without the ability to call, while it would be dysfunctional, would still be a viable communication device. On the other hand, a 1990s phone would be useless if one could not make or receive calls on it. While the early phones were expensive gadgets and the reserve for the rich and educated, today they can be owned by almost anyone and one needs only the most basic education to use a phone. Mobile phone companies are competing to see whose device can hold and use the most applications and offer the best services other than calling. One can use their mobile phone to browse the internet, and as such access pertinent information from virtually anywhere in the world, provided they have a good signal. As a result, millions of people many of them you ths spend hundreds of hours every week using their phones on nonverbal interaction and social networking, indeed, the time spent making phone calls pales in comparison to the time spent on Facebook, tweeter, instant messaging or in related activities. Many mobile phones offer the user a capacity to do any of these activities especially the smart phones, described as â€Å"clever gadgets,† which are more than just phones, (McKendrick, 2011). This is because of their many features that transcend what ordinary mobile phones can do including a variety of user friendly applications that allow users to carry out a range of tasks such as; reading EBooks, teleconferencing, reading, and creating emails. Mobile phones can also be used in time of emergencies; to call for help, or look for directions when one is lost because some of them have gotten applications like Google maps, which enable users to look for direction, and pinpoint their current location. Furthermore, mobile companies use the technology to help the police trace lost people or criminals by tracing their signals. Indeed a lost person can be traced even if their phone is switched off (Siegel, 2008). Other security futures include sending distress messages without having to make a phone call, for instance with some Samsung phones one only need to press the volume key thrice, and a discrete text is sent to a pre-determined number notifying the recipient that the sender is in danger. Mobile devices are also used as/alongside baby monitors, using certain IPhones applications parents use their Smartphone to keep an â€Å"eye† on their infants. For instance, one can use an application that automatically sends a message to their phone whenever the child makes noise or cries (Associated Press, 2009). A more rudimentary albeit expensive tactic, which can be used, is to leave one phone in the baby crib with an active connection to another phone, possibly with a headpiece so one can listen to the baby w ithout being present. Mobiles phones today have an immense entertainment role and are competing with mainstream media such as Television and radios. Several phone types allow one to listen to radio and watch television on the move. Teens and young adults (13-24) are the leading users of mobile devices for these functions (chiff.com

Writer's Autobiography Assignment Example | Topics and Well Written Essays - 750 words

Writer's Autobiography - Assignment Example The fact remains that there were many sources that influenced me to learn new languages. Back in school, I had students in my class from different parts of the world. Since I have always been a person who would like to be social and communicate to people, I was able to learn and grasp meanings of different languages. However, every language was very different from each other. But friend Francis who was a French student brought challenges for me. Every day, Francis and I were used to learn different words. This was quiet challenging for me because English was a common language that was spoken in our school and community but French was a very rare language. Later on, Francis gave me an idea that I should write small notes in French so that I could learn them and memorize for the rest of my life. In this ways, I was able to write in French which appeared impressive for my family members and other friends. Despite getting interested in learning French, I continued my learning patterns of English writing as well. Similarly, I became friends with a Muslim student in my class named Akbar. He was from Saudi Arabia that is considered as a primary origin of Arabic language. Akbar was less confident about his language for which he kept ignoring my request about helping me learn Arabic. But with the passage of time, he was able to share his experiences and reasons behind becoming less confident about his language. These reasons included racial discrimination and partiality in the neighborhood. But I made sure that Akbar was able to feel proud of his language. I always appreciated him and his language which is a truth in itself. I have always become inspired by Arabic language as I watched films involving Arabic characters. After a while, I started using a fusion manner of writing where French, English and Arabic would come in concordance. However, this way of writing bothered by teachers a lot but I knew that

Introduction to Comparative Politics Essay Example | Topics and Well Written Essays - 1000 words

Introduction to Comparative Politics - Essay Example However, the ignored internal dynamics within the Chinese and Russian economies do have a direct impact on the regime stability in these countries.3 A lopsided distribution of the national wealth, corruption and a marked regional in-equilibrium in terms of economic development, do have the potential of disturbing political stability in China.4 At the same time, the ongoing economic meltdown and the 2008 oil price crisis had a dwindling impact on the popular support enjoyed by the Russian regime. Both these countries have embarked on an era of economic growth. However, the inbuilt flaws inherent in the politico-economic setup of these nations and external influences and pressures, are making the regimes in these countries rethink their growth strategies. There is no denying the fact that the above discussed internal and external socio-economic issues are quiet pivotal to the regime stability in China and Russia. The seven year (1991-1998) economic transition from the Soviet style centralized economy to a free market economy in Russia was tragically marked by chaos and instability. In the years of Boris Yeltsin, the Russian GDP dwindled by almost 30 percent.5 The inflation rates soared to new heights, resting at 20 percent by the late 90s.6 This deprived the Russian masses of their savings and purchasing power. The quality of life of the Russian people deteriorated on all parameters.7 This dire situation was further aggravated by a massive capital flight from Russia.8 This economic fiasco had a direct bearing on the popular support enjoyed by President Boris Yeltsin. People soon started to get critical of one’s ill conceived and poorly executed economic policies. However, things started to improve in 1999, with the change of regime in Russia. An ambitious growth in GDP translating into increased real wages and better standards of living and lower levels of poverty, garnered ample supp ort for President Putin, till the dwindling of oil prices

Emaar Research Paper Example | Topics and Well Written Essays - 1500 words

Emaar - Research Paper Example It is composed of EMAAR’S resources and comprises of factors that it can effectively use in adapting to the changing external environment. Unlike external environment, the internal environmental factors are much within the control of the management of EMAAR Company (Crum and Palmatier, pg 23). The factors include: The emaars resources that are mainly tangible e.g. production or operation factors: like plants, equipments and machinery; marketing factors like sales force, channels of distribution; personnel/ labor relations e.g. employees and relations with the trade unions and financial factors e.g. funds available and their sources e.g. loans. Intangible such as location factors e.g. suitability of the present location, reputation, research and development. Emaars internal environment assessment hence helps pinpoint the company’s strengths and weaknesses with which it faces and counteracts challenges in the global markets. The strengths in the firm’s internal env ironment enable it to exploit environmental opportunities or to overcome the problems thereon, hence its capacity to successfully enter the market despite competition (Martz, Pg 49). Such assessment is based on two specific areas namely Physical resources and the personnel competencies (Crum and Palmatier, pg 63). ... Another important consideration is the degree of integration that exists within the operating units of EMAAR Company (Madura pg, 67). The company uses â€Å"Vertical Integration† that is the ownership of all the assets needed to produce the goods and services to customers. The company purchases the controlling interest of their suppliers so as to ensure that the materials are available when needed. They also use the â€Å"Vertical Integration† which is the ownership of the core technologies and the manufacturing capabilities needed to produce outputs coupled with dependence on outsources to produce all the inputs needed. Personnel Competencies, The Company examines these because they reflect their strengths and weaknesses, that is an outstanding Research and Developments departments leads to the high development of high state quality outstanding of the products (Madura pg,97). VALUE CHAIN ANALYSIS A complementary approach to the internal environment assessment used by E maar is the examination of the firm’s value chain. It is the way in which the primary support activities are combined to produce valuable goods and services and increase the profit margin. The primary activities in EMAARS value chain include: Inbound logistics; Concerned with the receiving, storing, material handling and warehouse activities. Operations, in which inputs are converted into products form by the performance activities like machining, assembling, testing and packaging. Marketing and Sales, the Company uses this to inform and encourage customers to buy products and services they produce. In addition, the Emaar Company determines its competitive scope which is the breadth of its target markets within the

Please briefly elaborate on one of your extracurricular activities or Personal Statement - 1

Please briefly elaborate on one of your extracurricular activities or work experiences in the space below - Personal Statement Example My game improved and I ate free lunches for almost the entire summer! This is the type of challenge that best describes me. Other activities that I enjoy are downhill skiing and horseback riding. I am a novice a riding and am looking forward to improving. I have been told that I am too competitive by friends, but that is simply how I am wired. I never stoop to being a poor sport, and I have never lost a friend because of my competitive nature, so I guess I’m not too overbearing with my desire to always do my best. I am the sort of person that cannot relax by relaxing or giving something a half-effort. I relax by giving each challenge all of my effort and then enjoying the benefits of my hard work. This is why I love a good challenge. In the end, I’m a better more relaxed person because of the effort needed to overcome the

Risk assessment Essay Example | Topics and Well Written Essays - 2750 words

Risk assessment - Essay Example A risk based approach has been adopted for the development of a system for managing health, safety, and environmental risks. The system has been developed by benchmarking the system against international standards such as the ISO 2001. The components of the system include general requirements, SHE policy, planning, implementation and operation, measurement analysis and improvement, and management review. This section includes resources, roles, responsibility and authority. Competence, training and awareness have been addressed. Documentation, control of documents, operational control, and emergency preparedness and response have also been included. Probabilistic Risk Assessment (PRA) is an analytical method used to protect health and safety. The goal of PRA is to develop a method to predict concerns before they manifest in terms of loss, injury, or fatality. The calculation of risk involves mathematical representation and building model. Risk is related to the concept of safety, danger, hazard, loss, injury, death, toxicity, or peril. Risk is defined as , where ci is the consequence, and pi is the probability. Risk is expressed in terms of , average loss of life expectancy, or fatalities per 100000 persons per year (Ragheb, 2009). HSE (2007) has outlined five steps for the assessment of risks in the workplace. These include the identification of hazards; decision on who might be harmed and how; evaluation of risks and decision on precautions; recording of findings and implementation; and review of assessment and update as necessary. Sustainability in manufacturing includes product sustainability assessment, product design for sustainability, lifecycle issues in product design and manufacture, and product manufacture for societal impact. Product design and manufacture for societal impact includes personnel health, operational safety, security of personnel and systems, and work ethics. Manufacturing process should include environmentally conscious

Organizational Characteristics Essay Example for Free

Organizational Characteristics Essay This paper will describe the culture and the organizational characteristics of a chosen organization, Publix Supermarkets. Detailed throughout will be the common characteristics of the organization as it operates on a day to day basis. Specifically the system based on individual units, rules and norms expected of the associates and supervisors as well as the hierarchy will be established for the reader to garner a better understanding. Furthermore, the communication networks, organizational orientation, approaches to and by leadership members, as well as the decision making and communication procedures put forth by members of management will be analyzed. This paper will describe which 4 of these listed characteristics are most influenced by communication between members and levels of Publix Supermarkets. The author has been employed with this supermarket chain for more than 7 years and has ample knowledge and understanding on the organization as a whole. Common Characteristics of an Organization Publix Supermarkets is a grocery chain unlike many others for a variety of reasons. Founded in 1930 in Winter haven, Florida by George W. Jenkins, Publix is known for its customer first atmosphere and pleasurable shopping experience. The grocery chain whose motto states they will never knowingly disappoint their customers operates in Florida, Georgia, South Carolina, and Tennessee and currently has more than 1000 stores in operation (Publix.com). Jenkins’ supermarket chain has continued to grow on their customer friendly business sense. Publix has since become a Fortune 500 company and is privately held and owned by its employees. For as well as they treat their customers, the chain treats its associates and management staff just as well if not better. Publix workers who have been with the company a base number of years receive shares of stock for every 1000 hours worked, and can purchase more shares of stock at almost any time during a given year. The grocery chain is also well known for its high ranking employee benefits and treatment in the employment world. Rules/Norms (Written and Unwritten) Outside of the big green P logo, the Publix atmosphere is what customers relate to with the chain more than anything else. Communication with customers is a major asset in following proper Publix protocol. The smiling helpful associates, clean stores, and consumer friendly set up of product is where Publix truly prides itself as an organization. Each experience ends with a friendly cashier and bagger, and the bagger will always bring the customer to their vehicle and help load product into the car for them. Believe it or not this all relates to performance evaluations that are done quarterly, where associates are evaluated on their behavior amongst the customers. Customer intimacy is something Publix takes very seriously. The Publix image extends onto its associates as well. All employees are expected to show up to work on time and be clean shaven in full clean uniform attire. Each department and job class has their own specific uniform; however all include proper hygiene, reasonable hairstyling, and proper equipment to perform their tasks to better serve the shoppers. Publix is an organization that understands how to promote their brand by utilizing all available options to do so. Clean stores and clean happy associates promote the â€Å"Publix Way.† This plays a major role in nonverbal communication between Publix associates and their customers. Aside from dress code and customer relations, two major elements, there are many other standards Publix employees are held to. A good example of one unwritten Publix rule would be: communication between associates when out on the sales floor during business hours must be respectful, and if at all possible must include the customer. Also, outside from positive communication both verbal and nonverbal with customers and fellow associates employees are expected to communicate both effectively and respectfully with management teams as well. Hierarchy The Publix store level hierarchy is something that runs seemingly parallel in each department throughout the store. Each department and sub department have their chain of command as follows: part time associates, full time associates, assistant department manager, and department manager. The two major departments, grocery and customer service, have the most associates, in order to better supervise their employees there is a position called a team leader that fits into the hierarchy between the full time associates and the management team. Publix is a company that only promotes from within. This is a big selling point for associates and applicants alike. Knowing that the opportunity for advancement is always there is a major asset for the associates in the store. Communications between the different levels of the chain of command are fluid. The associates can go to their department managers, or team leaders, with any concern or idea. The department managers at store level then communicate with the store’s assistant manager and store manager about the associate’s ideas and concerns. Communication Networks The information Publix gathers through their retail channels is usually information based on product analysis and placement that they can pass down to the management teams at store levels to assess further. Ultimately the store will take the advice of corporate and try to taper the information in the way it works most effectively for each store. Each store can take the same information and depict it differently. Information about new products, events, or openings may not influence all stores, or influence them all at the same level. There are times, during major events like hurricanes, holidays, or back to school time, where Publix store level employees must take the information sent to them by corporate including sales figures and forecasts in order to build the proper displays and floor models for customers to browse. Having product out that customers take interest in can help drive sales. The communication between the different levels of Publix Supermarkets goes hand in hand with communication networks at the store level. Leadership Approaches A major tool in the line of communication at Publix is how they allow anyone who is willing to step up and be a leader, do so. When every associate feels that sense of empowerment in their employment it urges them to lead in a different way, work harder and do a better job to lead by example. Publix pushes their associates to be role models both in the stores, and in the community. The management teams are in place to ensure guidelines are followed, but showing quality leadership through positive communication means so much more. Communicating with leaders is always a situation associates take very seriously in any industry or business. This is no different in the retail world at Publix. Associates voice their concerns and feelings to their leaders, whether it be management, team leaders, or even fellow associates who take on the responsibility of leading a specific group. At Publix supermarkets the communication had with leadership is always something associates should come away from feeling they were heard out and understood, good virtue for any organization to sustain. Conclusion Publix through the years has become one of the most widely respected organizations in America. This is due to the quality product and customer service put out the grocery chain, but also playing a role in the respect factor is the culture of the organization. This of course starts at store level and works its way to the corporate ranks, and is in large part to do with positive, effective communication. Publix supermarkets are known throughout the world a company that is great to work for, just as much as they are to shop at. Through utilizing all of the common communication characteristics Publix has continued to promote a very associate friendly atmosphere through the years. The supermarket chain takes pride in the fact that each associate understands their value to their company and takes pride in hiring quality applicants. Publix utilizes its rules and norms, hierarchy, communication networks, and strong leadership approach in all day to day activities in order to remain a successful industry leader.

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