Research Article Analysis Essay

This research article analysis is over the article Undergraduate student researchers, preferred learning styles, and basic science research: A winning combination which is published in the Clearing House Journal and written by Lori Woeste and Beverly Barham. This article can also be found in Week One Electronic Reserve Readings. In this analysis a summary of the article will be provided, the type of information discussed in the article will be given, as well as if the information in this article should be considered reliable and valid. Summary This article is based on basic science research and the role that a team dynamic has on a student. What studies have found is that while the technical portion of research can pose as a challenge, student researchers are often challenged with thriving in various team dynamics as well (Woeste & Barhamm, 2012). Woeste and Barham (2012) explains that understanding the preferred learning style of a student can pose as an advantage for mentors because it allows them to have a better understanding of how meet these challenges. In this article, the authors also chronicles the background of working alongside student researchers whom prefer different learning styles. The authors also correlate this information with how being well-informed on students’ preferred learning styles can contribute towards creating an environment enriched in positive learning experiences, which ultimately results in a winning combination for the team as a whole (Woeste & Barham, 2012). Type of Information The first section of the research paper introduces the two student researchers and his or her preferred learning style. Research student one  (SR1) had a preferred learning style of kinesthetic and research student two (SR2) had a preferred learning style of visual, with both agreeing that auditory was the least preferred learning style. According to Woeste and Barhman, â€Å"The nature of the basic science research required strict adherence to sterile technique, chemical hygiene protocols, quality control guidelines, and handling of microbiological specimens† (2012, pg. 64). Both research students were then asked to demonstrate various techniques needed in basic science research and both did so accordingly, displaying a throrough understanding and competence in the techniques required (Woeste & Barham, 2012). The next section chronicles the beginning of the project. After receiving a detailed plan from the grant application, the student researchers were asked to investigate and report the timing of adherence for bacteria to different substances (Woeste & Barham, 2012). Right away it was noticed that SR1 was experiencing difficulty starting anything new and although SR1 was able to take over once receiving help, there was a significant reoccurrence of the same issue (Woeste & Barham, 2012). However, after moving SR1 from the office space to the laboratory where he or she could have a hands-on approach to using instruments and protocols, SR1 displayed competence in the ability to begin and he or she began a great source of contribution by manipulating items to help in the creative part of the process (Woeste & Barham, 2012). By moving SR1 from the office to the laboratory, the student researcher was able to contribute as well as learn in a learning style that was best suited for his or her needs. While SR2 did not display the need for a hands-on approach to develop new ideas for various parts of the project, it was quickly noticed that SR2 required a need to write down all protocols and information in regard to the project (Woeste & Barham, 2012). Due to the fact that all research should be documented, SR2 was able to contribute to the documentation aspect of the research (Woeste & Barham, 2012). In the end, SR2 was also able to contribute in a manner that benefited the project as well as suited his or her preferred learning style just as SR1 was and together the two complemented one another. Since both students preferred auditory learning least, they were both given sample question that he or she may encounter during the presentation as a way to ease nerves and prepare. The next section of this article explains how SR1 and SR2 did during the  presentation. Both students answered questions and provided information in a manner that was in coherence with each of their learning styles. SR1 spoke with hand gestures, motions, and simulated steps in the laboratory while SR2 referred to the visual poster used in the delivery of the presentation to provide information and answer questions (Woeste & Barham, 2012). The last section of this article includes the conclusion and in findings that were discovered throughout this project. Throughout this project, the authors discovered that taking a learning-center approach, students are able to learn better and work together more efficiently because it attempts to â€Å"contextualize the construct of learning styles, with the ultimate goal of improving pedagogical practice† (Woeste & Barhman, 2012, p. 65). Reliability or Validity This article would be deemed as reliable and valid because of the source from which the information came, the citations and evidence used in the article, and credentials of the authors. The Clearing House is a journal of educational strategies, issues, and ideas through the use of peer-reviewed articles (Taylor and Francis Group, n.d.) The authors also used outside sources and citations from other journals as well as books that come from valid and peer-reviewed articles and information. Last, the authors have credentials in this field of work and study to accurately report and investigate the topic in which this article was about. Conclusion Providing an analysis on a research article requires much more depth and thought than simply reading the content in the article. A reader must begin with first understanding what the article is about and who the authors are and the source from which the article is coming from. Once a student has done this, an outline should be created of each section in the article and a summary should be developed. A summary will help the student to easily identify the main points in the article. After doing so, a highlight of each section should be done so that a quick, yet thorough understanding of the article can be assessed. If all steps are followed, students should be able to correctly present a research paper on articles and after time, improve his or her ability to do so. References Woeste, L. A., & Barham, B. J. (2007). Undergraduate student researchers, preferred learning styles, and basic science research: A winning combination. The Clearing House, 81(2), 63-66. Retrieved from http://search.proquest.com/docview/196879481?accountid=35812 Taylor and Francis Group. (n.d.). Genamics. Retrieved from http://journalseek.net/cgi-bin/journalseek/journalsearch.cgi?field=issn&query=0009-8655

Adolescence and Moral Development Essay

Two major reasons exist for studying moral development during adolescence. First, cognitive changes that occur during adolescence are related to moral development. Formal operational thinking allows the adolescent to interpret the social environment in new and different ways. Second, because adolescents are capable of devising new and idealistic social orders to which all are expected to conform, we may view them as moral philosophers. A number of researchers have noted other changes in moral development that point to the importance of adolescence as a transition stage in moral development. Unlike children, the adolescent is concerned with what is right as opposed to what is wrong. Also, adolescents become more preoccupied with personal and social moral codes. As they gain the competency to understand alternative points of view, they see that the moral codes are relative, not absolute. The above changes result in some conflict between moral conduct and moral thinking during adolescence. Early writing in the area of moral development was left to philosophers, who evolved three major doctrines of morality, each of which is represented in contemporary psychological theorizing. The â€Å"doctrine of the original sin† assumed that parental intervention was necessary to save the child’s soul. Current-day vestiges of this viewpoint may be found in theories of personality structure and the development of the conscience, or superego, which argue that the child internalizes parental standards of right and wrong. See more:  Perseverance essay The â€Å"doctrine of innate purity† argued that the child is basically moral, or pure, and that society, especially adults, are corrupting influences. This view is represented in the theorizing of Piaget, who argues that morality develops from the acquisition of autonomy emerging from the need to get along with peers. Moral thinking develops through peer-to-peer interactions that lead to an understanding of rules, according to Piaget. He also believes that parents do not allow autonomous thinking to develop because parent-child relationships are basically heteronomous, that is, the child is ruled by the parents. Therefore, the parents retard moral development. The last philosophical doctrine is the â€Å"tabula rasa† notion, which assumes that the child is neither innately pure nor corrupt but the product of environmental influences. The current-day representatives of this position are the learning theorists, who believe that development is the result of reinforcement and imitation  mechanisms. In addition to these differing philosophical and theoretical views regarding the origin of morality, we must keep in mind the distinctions between three concepts: systems of morality, moral behavior and moral character. Systems of morality are evidenced in the rules that guide social and interpersonal behavior. That includes rules that are written down and those that are not. This broad definition includes all types of social behaviors, not just those we consider moral behavior. Moral behaviors are those behaviors that are consistent with rules of morality. Like moral systems, moral behaviors include social behaviors of all types. This definition of moral behavior also includes behavior contrary to that expressed in moral code. Immoral behavior is simply a subclass of moral behavior. Moral character is a much more difficult concept to define. It is mostly hard to define due to the fact it involves an individual’s motives for behaving in a particular way. The basic problem in defining moral character is to determine those personality dimensions that determine it and vary as a function of it. Moral knowledge , socialization, empathy, autonomy, and moral judgement are the major concepts defining moral character. In order to have successful peer and adult relationships, the adolescent must learn the rules of the society and act in accordance to these rules. Individuals who successfully master these tasks are said to possess moral character. Among psychologists, the writings of Freud and Piaget have had the greatest impact on research in moral development. Following their early works, there was little written about moral development. In the last two or three decades, there has been considerable research and theorizing about the process underlying moral development. According to the principles of psychoanalytic theory, morality is part of the individual’s conscience, or superego. The acquisition of morality is explained by the information of the superego, which results from resolution of the Oedipal complex and identification with the same-sex parent. Society ensures its survival through this identification process by imposing its cultural standards, as represented by the parents’ behaviors, attitudes, aspirations, on the individual. Although the exact basis is unclear, Freud’s theorizing has stimulated considerable research into the effects of parental behavior on the child’s moral development. The major research concerns have centered on moral character , the consistency of moral behavior across situations, and the role of parental disciplinary techniques in shaping moral behavior.

Charlotte’s Web

Charlotte’s Web tells a tale about the miracle of an ordinary pig. It is a narrative that embraces the values of friendship and loyalty. These values are communicated through the element of fantasy and through the eyes of a child. In this way, the audience looks deep within themselves to be able to capture its true essence. In this film, animals are given the ability to speak our language and rationalize in situations they may encounter.With that, they communicate to us that in some way animals and humans think, act, and feel the same. This heartfelt film begins with an interesting encounter of Fern, juvenile yet strong-willed lass, and Wilbur, some radiant and terrific pig. This touching beginning did not fail to get our attention and absorb ourselves to the series of events that follow. In that moment, Fern saves Wilbur from death and takes the responsibility of taking care of him. Fern demonstrates to us Justice.She tells us that Justice is what every being deserves despite appearance, ability, and any other traits. Moreover, Fern symbolized equality. After the Arable’s residence, let us recollect on the events when Wilbur was moved to the barn. I would say the barn may be associated to our society. It is the place where stereotypes are formed and where the foundation of friendship is observed. For instance, the other animals inside the barn judges Charlotte, a spider, based on her looks. They see her scary and intimidating.On the other hand, Wilbur takes the time to know Charlotte and eventually watch their friendship blossom. Through Charlotte’s guidance, we see Wilbur’s personality and knowledge progress. Her character in this account is very important. She serves as the instrument to open ourselves to miracles; miracles that are brought by friendship. I focused on the points: Friendship and Youth communicated by the characters of Fern, Wilbur, and Charlotte. Fern and Wilbur were the images of Youth that flaunt a free-spirited attitude and innocence.They react to certain situations based on their feelings as they seem to look at things in its simplest way. While Charlotte, exhibits the foundation of Friendship. It is Loyalty. She showed her dedication and willingness to spare Wilbur’s life even during the darkest hour of her days. I guess it is healthy to think as a child once in a while and see the essence of the little things through the simplest ways. To be able to savour the sweetness of youth and friendship. Charlotte’s Web Charlotte web the novel is a warm-hearted, classic children's novel. The center theme of the novel is about on true friendship and loyalty. The movie, although released in 2006, the proved to be true to the memorable and popular book. The story in the novel as well in the movie remains the same. But the main difference between reading the novel against watching the movie is, movie will eliminate the imagination of the landscape or the character and it will convert it into the beautiful manner.The feeling is stronger in the movie, which will impact to the children directly. The setting in the movie that has been shown is realistic and features a landscape that is recognizable to children. Charlotte web is a story of about a friendship. The novel which takes place mainly at the farm. The book as well as the movie has also begun with Fern and her father where Fern preventing her father from killing pig. The scene it self in the movie shows love of for the animal and children would more identify the meaning of the scene. Charlotte web follows a friendship from its beginning to its end, from all the steps in between.In novel Wilbur and Fern's friendship, or Wilbur and Charlotte friendship, and trace the way it grows and changes over the course of the story. The Charlotte web is reflects many of the quality such as power of helping others, reflection on friendship, love for any living creature etc. In the movie, when Fern takes too much take care of Wilbur her family sent Wilbur to the Uncle homer's barn. Even in that Fern frequently visited Wilbur. Wilbur was not thrilled to be in the new barn and felt like stranger. But in the mean time Wilbur had friend with Charlotte, a grey spider.In the movie the work of the spider shown beautifully, by cleverly working and weaving words like ‘TERRIFIC',RADIANT' in her web in an effort to describe Wilbur. In the book children would never understood how the words appeared in the spider's web. There were small differences a s well between novel and movies. In the book there were no mention of a particular setting while in the movie there were a specific setting created like Somerset County. Another difference at the beginning of the movie was when Fern sneaked Wilbur in her shirt and then took him to school.The screenwriters also gave some of the minor characters changes like they included a horse named Eke, who is not present in the book. His purpose in the film is often for humor and to get a laugh. These minor differences makes watching the movie more enjoyable than novel. The film version of the Charlotte web is entertaining because of the good screenplay and visual effects. Children would feel more connected to the film because of the excellent visual effects, landscape, animal talking and much of the added humor in the film. Children would easily connected to the film and identify the meaning of story from the film. Charlotte’s Web Ravdeep Singh EAC273 Prof: Priti Sharma 6 October 2012 Maternal Love A love that a mother can give to a child is something what is priceless. A mother is always helpful and supportive to her child in every stage of a child life like the Charlotte’s and Fern’s love for Wilbur. She build from her baby from her birth to an infant, childhood and then to adulthood. She also built the child’s confidence and encourages what the child wants to do in their life. She develops a child to be mature enough so that the child can stand in front of the world. The flame of ‘maternal love’ can be easily seen in ‘Charlotte’s Web’.A mother cannot be the only one who gives birth to the child but she can be the one who takes care of a child and raise him/her up. She always holds the child hands at ever different stages of the child’s life from her childhood, to the adulthood, and even at the old age. A child will always remain a child for their parents. A mother will first feed her child and then have her food. â€Å"But Fern couldn’t eat until her pig had had a drink of milk† (White 5). Fern too was a child but she takes care of Wilbur like a mother that shows us the maternal love of Fern.From the time she took responsibilities of Wilbur; she feeds Wilbur two times a day by her own hands and she also teaches Wilbur how to suck milk from the bottle just as mother do with the child. â€Å"But I am going to save you, and I want you to quiet down immediately† (White 51). This phrase describe Charlotte’s maternal love for Wilbur as Charlotte promise Wilbur to help him from being killed and live his life happily. Charlotte stops him from crying in the way a mother would stop her child when he/she is crying or might be fighting for life. A mother loves his child more than anything in the same way as â€Å"Fern loved Wilbur more than anything.She loved to stroke him, to feed him, to put him to bedâ₠¬  (White 8). This phrase explains the mother love and care for her child. â€Å"Won’t he be cold at night? † (9), â€Å"It relieved her mind to know that her baby would sleep covered up, and would stay warm† (9). Fern as a mother is protective and careful mother. She wants to make Wilbur comfortable and protect him from the cold night. This shows passionate love of a mother. â€Å"Sometimes, on these journeys, Wilbur would get tired, and fern would pick him up and put him in the carriage alongside the doll† (White 10), â€Å"Fern come almost every day to visit him. † (15). hese above phrases also describe the undying love of a mother. A mother takes care of a child when he/she is not comfortable walking, sleeping, and eating. When a child is away from her mother like a child is send to his hostel and mother wants to go and see whether his child is in a safe way. Charlotte helps Wilbur to build confidence in him. ‘Run around! † command ed Charlotte. â€Å"I want to see you in action, to see if you are radiant† (White 100). A mother’s feeling came into action as she was motivating and helping trying to show how radiant he was. Charlotte even boosts his energy by saying â€Å"Now back again, faster! † (White100).Wilbur obeyed what Charlotte was saying; in the same way as a child would obey to his parents. â€Å"I shall go too,† she said, softly. â€Å"I have decided to go with Wilbur. He may need me. We can’t tell what may happen at the Fair Grounds† (White 122). Charlotte gets agree to go with Wilbur because she does not that Wilbur should get scared and lose his confidence looking at many people around him. Charlotte’s was worried so she goes with Wilbur that would not make him feel alone and helpless. â€Å"It means I’m showing up feeling my age. I’m not young any more, Wilbur. But I don’t want you to worry about me. This is your big day today † (White 146).Charlotte at her old and ending age of her life still was encouraging Wilbur and is giving confident to him. A mother will act in a way as Charlotte’s acted at her end stage of her life. In a nutshell, â€Å"E. B. White† showing and expressing different themes in â€Å"Charlotte’s Web† book but â€Å"maternal love† and characters of Charlotte and Fern have impressed me a lot. It shows me how a mother takes care of her child fern raised Wilbur at his childhood, and how Charlotte was supportive to Wilbur throughout the time they met. So as it is said â€Å"Love of a mother is priceless†. Work Cited E. B. White. (1952). Charlotte's Web. New York: HarperCollins.

Argumentative Assignment Example | Topics and Well Written Essays - 750 words

Argumentative - Assignment Example In this paper therefore I will be summarising the arguments of both sides on the sticky abortion discourse. America’s constitution has legalised abortion; it may not be in our Bill of Rights or even the constitution itself but privacy is a right well enumerated. In the case of Roe vs. Wade of 1973 the Supreme Court ruled in favour of abortion in the 1st trimester. Following the ruling, more than thirty five million individuals in America have procured legal abortions. Today well over twenty four percent of America’s pregnancies are terminated and out of these, forty-percent are abortions by teenagers. But just because the act of abortion is now legal in America doest necessarily mean it the right thing to do. It will be remembered that over one hundred fifty years ago, slavery was legal but the truth remains that it was inhumane and has been right (Rosenthal, 2007). According to the thinking of the pro-choice group, the mother’s right of choosing must come before any other thing including even human life. There argument is strongly based on the fact that every woman has a right to chose what to do with their bodies and refer to the Roe vs. Wade, 1973 case. They also invoke issues to with the physical safety of mothers; where a mother’s life is put to danger by the pregnancy the abortion should be preferred. The prochoice group also believes abortion is justifiable where the pregnancy was conceived out of rape or incest. Their narrative is that a child conceived out rape may keep reminding the mother of the horrible incident while that conceived of incest may suffer mental retardation or be handicapped. Above all the pro-choice argument on abortion is hinged on the mother’s basic human rights. By arguing that the women’s right of choice should be respected they invoke also issues of privacy as was the court ruling in Roe vs. Wade case. Privacy is

E-Business Paper Essay Example | Topics and Well Written Essays - 1000 words

E-Business Paper - Essay Example Amazon.com was the first company to move book retailing online. In less than a decade, it has become one of the most recognizable brands on earth. It expanded from being a book retailer to a virtual marketplace where all sorts of buyers and sellers of rare, used, and collectible items found a platform. Today it offers even online auctions including toys, music, DVDs, house ware, and a variety of other products and it is the world’s most customer-centric company. It sells virtually anything to more than 38 million customers (Success story, 2002). By selling a wide range of products it has been able build customer loyalty and by 2005, has 50 million loyal customers (Evans, 2005). One of the main advantages of moving online is the use of sophisticated software that brings in constant innovation. This enhances the customer experience as the software can remember details and sends the shopping cart smoothly and swiftly to the check-out (Evans, 2005). The software also remembers the shipping address and the credit card details. Being online allows fro reviews and recommendations from readers. The key to Amazon.com’s success is the strong customer focused approach. They use technology to constantly improvise and innovate. They work hard to refine the technology, which allows them to make recommendations that make shopping more convenient and enjoyable (Customer Success, 2006). Amazon.com uses the SAS technology to analyze the results of their ongoing efforts to improve personalization. Multi-threading allows amazon.com to apply multiple processors to complex analytic tasks. They constantly evaluate the new product page layouts and new search technology. It is their ‘technology base that allows customers to find, discover and glean out of hundreds of millions of products, those that really interest them (Success story, 2000). Data warehousing allows them to manage growth (Success story). Their

Discuss the contributions of iron technology to the process of state Essay

Discuss the contributions of iron technology to the process of state formation in Bantu Africa - Essay Example Generally, the highlight of the state formation process in Bantu Africa was in the rate of growth, where within a very short time frame, the people had occupied a very wide area of land. Starting from Cross River region around Nigeria and Cameroon border, the people had by 1000 B.C expanded into Lake Victoria and later to southwest and south (Dubrulle, 2002). Wagner (2006) has explained that one important factor that could be accounted for the rapid process of state formation is the social and economic changes that involved other tribes tying up with the Bantu people as they moved along through interracial marriages. Regardless of the argument made for the social and economic changes that made the process of state formation possible and rapid, one aspect of growth factor that cannot be overlooked is the role of iron technology. Iron technology can be explained as the smelting of iron through the use of advantaged mechanisms in ensuring that the irons are refined into usable tools and equipment (Dubrulle, 2002). Generally, iron technology did not develop among Bantu Africa as an isolated trade. Rather, it came as a necessity to help in the boost of agricultural growth, which was identified as a major economic viability for the people. Agricultural growth in itself was also dependent on the fact that population was growing at a rate that was very high. Due to this high rate of population growth, it was necessary for the people to find a means of feeding themselves. But the old forms of tools made from stones, bones and woods were found not to be durable and strong enough to help them achieve this purpose. To this end, the people fell on iron technology for the production of various farm tools that were deemed to be more durable. Examples of such tools are axes, arrows, knifes, spears and hoes. Though the original intent was not iron technology as a trade, iron technology would eventually become the catalyst behind which Bantu Africa would

Unit 3 Discussion Board Essay Example | Topics and Well Written Essays - 500 words - 6

Unit 3 Discussion Board - Essay Example Every product goes through a particular life cycle and the strategy that must be applied will differ in each instance. For instance, during the early stages, company strategy must focus upon achieving competitiveness through judicious pricing, heavy marketing and expenses on R&D. During the later declining stage of the product life cycle, the emphasis is on broadening the product line and avoiding price cuts.(Wasson, 1974). On the basis of a product’s market share and growth based upon its life cycle, the BCG places the product portfolio of a Company into four different quadrants of a matrix, with the relative market share of the product ranked along the X axis and product growth ranked along the Y axis. Businesses in each quadrant will have significantly different tendencies to consume or generate cash. The appliances division of my Company has been placed in the upper right quadrant of the matrix, which represents the wildcat or question mark. This suggests that the division has a negative cash flow, requiring â€Å"large cash inputs that it cannot generate itself.† (Henderson, 1979, p166). Wildcat ventures are often fledgling operations and offer the promise of future generation of revenue. The major aspect to be addressed in the case of the appliances division is thus market share. Since the products may typically have a low market share because they are not well known, the recommended strategy would be to introduce a competitive price for the product as compared to similar products already in the market. It is also recommended that an aggressive advertising and promotional campaign is implemented, in order to increase sales of the product and improve its market share. In the event the market share of the product does not improve, then it may turn into a â€Å"dog† or become unproductive, and before that happens it is better to sell off the products or close up the division. Woo and Cooper (1980) have points

'How does interprofessional working impact on professional Essay

'How does interprofessional working impact on professional responsibility and accountability in the clinical setting' - Essay Example e we don’t work alone in the clinical setting, we interact and work together with other professionals who exert influence to each other’s own accountabilities and responsibilities. This paper will discuss the impact of inter-professional working on professional responsibility and accountability in the clinical setting with reference to my own clinical experience. It will address the importance of maintaining a healthy inter-professional working environment to promote a collaborative approach to safe and effective healthcare delivery. This paper will explore how professionals work together in promoting quality care delivery, the value systems in the scope of practice. In almost any healthcare setting, two or more professionals (of different professions) work together in the clinical setting. The nurse depends on the doctor in prescription of medications; the doctor needs the nurses’ help in carrying out his orders, and the nurse needs other professionals to lessen her load. Inter-professional collaboration is inevitable as we depend with each other in performing our own duties for better patient outcomes. Preparation for inter-professionalism begins at student years (Morison, Johnston and Stevenson, 2010). In the clinical setting, we professionals are not independent with each other. How we work with other healthcare team members influences our own professional accountabilities and responsibilities, like how the nurse’s accountability intertwines the unlicensed assistive personnel’s (UAP) accountability when the task is delegated by her to him. Our own accountabilities and responsibilities are dependent to each other as well while working as a team. Inter-professional work impacts our professional accountabilities and responsibilities, which can either, be positive or negative influence to ours. An example of a positive influence is my experience in transferring a patient from the chair to the bed. The nurse asked for my help in assisting the patient

Level 6 Diploma in Careers Guidance and Development Essay - 1

Level 6 Diploma in Careers Guidance and Development - Essay Example Reflective practice involves the ability to reflect on an action in order to take part in a continuous learning process that defines the traits of a professional practice. Reflective practice can also represent a criterion of paying attention to the practical theories and values that inform the everyday action through looking through the reflexively and reflectively practice. This leads to insight development. Reflective practice is a vital tool in professional practice-based learning settings where people learn out of their own experiences, instead of learning from a knowledge transfer, and a formal teaching. This means that reflective practice is the most crucial individual source of professional improvement and development. In this respect, the idea of reflective practice has obtained a huge take-up especially in the development of a practitioner’s profession in areas of health care and education. This means that reflective practice surrounds the issue of lifelong learning where one practitioner analyses different experiences so as to learn out of them. In this case, reflective practice promotes the professionals that are independent and continuously take part in situations of reflection that they come across in their world of profession. However, critics hold that reflection is time consuming and an annoying interruption to learners. It is noted that learners can end up becoming somewhat more anxious and introspective concerning their actions. Moreover, the lack of experience by learners can adversely affect the quality of reflective practice they adopt. This explains why there is need for continued evaluation of assumptions, beliefs, as well as hypothesis against the existing data on reflective practice. Needless to say, there is need to ensure that there is justification of the reflective learning design, and measurement of process, which need to focus upon the reflective

The Roman Empire Research Paper Example | Topics and Well Written Essays - 750 words

The Roman Empire - Research Paper Example Circuses on the other hand were centers that hosted sports such as horse races. The first and perhaps the biggest circus in the Roman Empire was the Circus Maximus. This circus stood between Palatine Hill and the Aventine. The circus had an attractive shape that made it suitable for hosting chariot races while at the same time providing good grounds for spectators to watch the field events while standing on the hillsides. Gill demonstrates that Circus Maximus served important purposes as it hosted yearly celebration of popular and important events in the empire. Circus Maximus in Rome: Courtesy of Gill, About.com As one way of ensuring defense of the empire and protecting it from the barbarian intrusion, the empire constructed big walls along its borders. One such defense walls were in Ostia, a harbor city in Rome. Ostia borders Tiber River, about 30 km to the west of Rome. Gill indicates that the King Ancus Martius was the founder of the wall of Ostia with sole aim of guarding the m outh of Tiber River, which had plenty deposits of salt. Gill reiterates that Ostia also hosted the ancient navy who found it strategically located due to its nearness to the river where training became easy. In the period of the late Republic, the significance of Ostia increased particularly when it became a commercial center of the Empire. The bordering river made it easy for transportation of goods and services in and out of the empire. All the aforementioned advantages of Ostia made it reasonable for the rulers to build the wall to strengthen defense. The remains of the wall of Ostia. Courtesy of Gill (2012). About.com Another wall that surrounded Rome was the Hadrian’s Wall located towards northern England. Gill explains that the Hadrian’s was formed one of the best walls of Rome having been constructed by the Roman Emperor to help prevent the northerners from reaching the Roman Britain. Hadrian’s Wall: Courtesy of Gill (2012). About.com According to Gill, t he Servian Wall constituted one of the defensive walls constructed to protect the Roman Empire. Servius Tullius was the Roman King who initiated building of the wall during the sixth century B.C. The wall stretched from Tiber to Capitol Hill then to Quirinal and extended to the valley Pincian to Esquiline. Gill unveils that the Servian Wall had twelve gates, specifically purposed to promote defense of the emperor. Servian Wall: Courtesy of Gill (2012). About.com As described by Gill, the Roman Empire had good sanitation earmarked by the construction of proper sewer systems. Gill points that one of the most remarkable sewer systems in ancient Roman Empire was the Cloaca Maxima built in the 6th or 7Th century B.C. Tarquinius Priscus was the Roman king who initiated the construction of the Cloaca Maxima. The main purpose for the construction of the sewer was to help drain marshes and house effluents into Tiber River. Gill clarifies that the sewer system drained wastes particularly from Viminal, Esquiline and Quirinal. It was because of this enhanced sewer system that areas surrounding the hills became inhabitable and even offered space for the forum Romanum. Cloaca Maxima (Great Sewer system): Courtesy of Gill (2012). About.com Roman Forum was a space organized to house and hosts various organs of governments and even serves as religious and business centers. The Forum also served as center for holding forums for public politics. The establishment of the forum became easy due to the availability of ridges connecting Quirinal with Capitoline Hill, and the

A quel point la perscution des minorits refltait-elle la volont des Essay

A quel point la perscution des minorits refltait-elle la volont des forces d'occupation et quel point refltait-el - Essay Example La zone non occupee de la [France] et l'assistance necessaires administration economique.2 Il y avait des problemes majeurs. Les deux Francais et Britanniques ont combattu pour l'independance de la France. "Dans la campagne de 1940 les Francais se sont battus courageusement, mais ... [l]es Britanniques ont combattu beaucoup plus obstinement ... ».3 Pour donner un peu de contexte, l'Allemagne avait acquis une partie de la France qui a ete envahie par les gens.  «En occupant la moitie nord du pays et toute la cote Atlantique, l'Allemagne s'est approprie le partie la plus riche et le plus peuple de la France metropolitaine ».4 En raison de l'oppression de son peuple, la reputation de Vichy est a jamais ternie. "L'histoire de Vichy, en cette epoque, abonde en pareils trompe-l'?il ».5 A la defense du peuple juif, les combats ont a l'Est. "Par consequent, au cours de la plupart des annees de combats sur le front de l'Est (ou la majeure partie de l'armee allemande a ete engage), les conditions sont devenues de plus en plus semblables a celles sur le front occidental dans la Premiere Guerre mondiale ».6 Il semblait que beaucoup de gens meprisaient les Juifs, c'etait un sentiment populaire et a la mode d'epouser a l'epoque. "Meme apres la guerre, Xavier Vallat revendiquee, avec quelque raison, que l'anti-semitisme de Vichy avait reflechi volonte populaire. Dans les registres tenus par l'administration francaise au cours de 1940-1944 il ya des signes evidents de l'antipathie populaire pour les Juifs, en particulier pour les refugies juifs etrangers ... ... repandre sur les Juifs d'origine francaise ainsi  ».7 Pendant ce temps, le cerveau se cache derriere la disparition du peuple juif etait Adolf Hitler-autrichien d'origine juive, vilipende les juifs et les exalte la race aryenne ci-dessus toutes les autres races. "Tout le monde sait Adolf Hitler. Notions du Troisieme Reich et la Seconde Guerre mondiale, [assurer] la  «Fuhrer » un endroit sur [dans l'hist oire]. Mais la situation varie considerablement dans l'histoire de cet homme.†8 Allemands voulaient eliminer totalement le peuple juif. "[L'Allemand] Armee et la Marine ... [A] l'avantage de la situation ... nouvelle [s] de faire valoir leurs interets.†9 Les gitans ont ete un autre peuple qui ont ete persecutes par les Allemands. "Si les ambitions allemandes en France concernees les moyens de maximiser l'exploitation de l'economie francaise dans l'interet de l'Allemagne, Vichy a saisi l'occasion fournie par la conquete allemande de realiser un [efficace] purge de la societe francaise, et un remodelage de la France a son image ».10 La persecution de toute personne consideree comme anormale a ete facilement acceptee par la societe francaise. Cette  «purge » de la societe francaise etait en effet l'un qui comprend un secteur important de personnes-des personnes handicapees, les personnes qui avaient des malformations congenitales, et cetera. Personne n'a ete epargne p ar le grand filet et le mal qui a ete coule pour tous ceux qui ont regarde differemment, agi differemment, ou ont vecu d'une maniere differente que le reste de la dynamique de la societe.Le francais de la

Autobiography Example Essay Example for Free

Autobiography Example Essay My name is Gelliza Z. Quiambao, and I am currently in college studying education. I was born on 12th of September year 1996, four o’clock in the afternoon, in Jose Payumo Memorial Hospital. My parents are Gilbert and Josephine and I have two brothers who are Gil Joseph and Gianni. I started studying when I was three. My grandparents are the ones who served as my babysitter since my parents weren’t home for work, so my granddad enrolled me in a Daycare Center. You may not believe this but my grandma told me that I always sleep and cry in school. After that, my parents enrolled me in Kindergarten then to Elementary. I was only five years old when I was on the first grade. Had to say, I was the youngest but I’m subsequent. Â  My elementary days are incredibly awesome. I gained many friends; I achieved honors and awards, academic and sports, specifically chess. It’s been quite jaded studying six years on the same school but it’s totally fine with me because I have friends to laugh with, have fun with, and learn with. In 2008, I graduated from elementary and became a high school freshman in Bataan Peninsula State University. It’s great that I found true friends that same year, and it’s quite funny how I always wanted a sister and God gave me nine super cool and amazing friends that actually treated me like a sister. I had so much fun with them. We went hiking on a mountain. It’s really unforgettable because we took a ride on a horse. It’s my sophomore year in 2009, and the best moment that I remembered back there is when we ditched class. Yeah, I know it’s not a really good thing to do but, best moments come from worst ideas, right? We cleaned the faculty room as our punishment. We did it for three months. In 2010, I fell in love with music. It’s like, my world revolves around music. There’s something about the songs that I can somehow relate myself into the lyrics. I learned so much from it. Also this year is when I fell in love with a boy. Honestly, it wasn’t a pretty story. I fell deeply in love with him then when we broke up; it’s like my worst nightmare ever. But I learned that maybe we’re not really meant to be together. Then, I realized that the fact between ‘boy love’ and ‘boy hate’ is the belief that whatever happens, I’ll be fine. Good friends, competitive teachers and one wonderful family are the ones who mold me for who I am today. Everything good I have inside of me, I get from them. Â  I experienced lots of challenges that test my skills and personality. All those challenges and problems that I’ve been through leaves a wonderful lesson. Good days gave me happiness, bad days gave me experiences, which are both essential to life. Success keeps me growing and failures make me humble. Right now, I’m studying very well so if I finished college, I can have a good job in order for me to help my family and raise the style of living that we have now with Gods grace and guidance. Just always remember that, life is like a roller coaster. It has ups and downs. But it’s your choice to scream or just enjoy the ride.

Video game industry

Video game industry Sony Computer Entertainment Ltd. Versus Nintendo Ltd. For many years, video game industry has played a key role in the growth of economics of some counties. Both Sony Computer Entertainment (SCE) and Nintendo are two representatives of this industry and they also are the main competitors in this fierce market. Previous research has shown that SCE had dominated the video game console market since Playstation2 launched with 138 million unit sales (Plunkett, 2009). Nintendo however occupy much marketing share after their new generation game console Wii and Nintendo Dual Screen (NDS) succeeded in this industry. This essay will compare and contrast SCE and Nintendo in several aspects and this paper which based on secondary resources without exclusive information. Therefore, it will begin via discussing the characteristics of product produced by these two companies, subsequently a discussion concerning price factors between the products of two corporations, for examples the development cost and price of software. Finally, this essay will focu s on the marketing share and sales. Nintendo is a multinational corporation founded on 23 September, 1889 by Fusajiro Yamauchi which producing handmade hanafuda cards. Then the company had tried several small businesses before they developed into a video game company, for example as a cab company and love hotel (Nintendo, 2009a). Consequently, Takenaka (2007) points out Nintendo became Japans third most valuable listed company by developing game console and software, with a market value of over 85 billion USD. Nintendo on the other hand is the majority owner of the Seattle Mariners, a Major League Baseball team. Unlike Nintendo, SCE is a wholly-owned subsidiary of Sony which was established on 16 November, 1993 for handling the Research and Development, production and sales of both hardware and software for Playstation (SCE, 2009). SCE currently has three main headquarters around the world: Japan which controls operations in Asia; USA and UK response to control operation in North America and Europe respectively. SCE and Nintendo have their own way to innovating for making their product attractive in order to surviving in the competitive market. Therefore, according to the announcements about new consoles of SCE in 2004 and 2006, Playstation Portable (PSP) and Playstation3 has launched in 12 December 2004 and 11 November 2006 respectively. People were amazed about the high technology in the hardware of the two consoles, for instance, PS3 has built-in Blu-Ray Disc (BD) player and cell processor, and PSP has UMD disc player and 3D image processor. BD is the new standard of disc which has enough space to save the high definition media files. As a result, the software launched for PS3 and PSP, particularly video games evolved by fantastic screen. Unlike SCE, Nintendo did not invest much to develop disruptive technology in order to improving the hardware but creating new game style. The product features of Wii are the motion sensitive remote and NDS with touch screen and internal microphone. There fore, most of software launched on Nintendo console has bring the features in full play. For instance, the Wii Fit is the education program about Yoga and it is suitable for people who want learn yoga at home, especially ladies. Furthermore, My Word Coach DS and SekainoGohan Shaberu DS are the software for teaching user language and cooking respectively. While, Nintendos product no matter consoles and software are considerably cheaper than SCEs. The significant brand image of SONY and the costly latest technology for consoles determine SCEs product is expensive. There were two hardware configurations announced for PS3 in E3 2006: a 20GB model and a 60GB model, initially priced at 499 USD and 599 USD respectively (IGN, 2006). Furthermore, PSP is the first venture of SCE in the pocket game console market with price skimming strategy too. The price of the base model in first announcement of it was 19800 yen about 181 USD in 2004 (IGN, 2004). Then, in accordance with appendix 1(Curmudgeon Gamer, 2007), the table reveals the comparison of the average game price between DS and PSP in Mid-Nov 2006 and Mid-Apr 2007 respectively. The trends of average game price for PSP and DS both were experienced a decreased during that period of time. Besides, the average game price of PSP is more expensive than DS by 2-3 USD per game. However the price of Nintendos consoles wii and NDS are much lower than PS3 and PSP. Compared with PS3, the Wii launched in United States in November 2006 at 249.99 USD nearly half of PS3 (Sanders and Casamassina, 2006). Moreover, according to Harris (2004) Nintendo announced the NDS would be released in North America in November, 2004 for 149.99 USD. Nintendo already had occupied much more marketing share than SCE with the successful strategy and the attractive features of consoles. Although SCE had invested significant mount of money for developing their new generation game console. Sony released its life-to-date sales for the PS3 and PSP. As of June 30, 2009, the high-powered and relatively high-priced console had sold 23.8 million units worldwide since its November 2006 launce. (Thorsen, 2009: no page) Thorsen (2009), also cited in the Game Spot, The PSP, which launched in 2004 (Japan) and 2005 (all other territories), had sold 55.9 million units as of the end of Sonys last fiscal quarter. On the contrary, Nintendo (2009b, pp9) reported NDS and Wii had sold 107.75 million units and 52.62.million units since it launched to the June, 09 respectively. Moreover, appendix 2 illustrates the sales of the four game consoles in the three main markets (Japan, United Kingdom and United States). To sum up, the purpose of this essay is to highlight some main differences and similarities between SCE and Nintendo, it has been seen that even though SCE and Nintendo produce the same types of products, they have the different way on designing their products and expanding their business. In terms of evaluating the circumstance of the two corporations it has emerged from the discussion above that Nintendo occupied much more market share and it is in a stronger financial position than SCE. Given the current economic climate, Nintendo therefore is the video game development company which would suffer the least economic loss. References Brightman.J (2008) Wii U.S. installed base now leads Xbox 360 by almost 2 million (Online) Retrieved from http://www.gamedaily.com/articles/news/wii-us-installed-base-now-leads-xbox-360-by-almost-2-million [Assessed 24 October 2009] Curmudgeon Gamer (2007) Nintendo DS vs. Sony PSP: game pricing update (Online) Retrieved from http://curmudgeongamer.com/2007/04/nintendo-ds-vs-sony-psp-game-pricing.html [Assessed 22 October 2009] Famistu (2009) Revenue of Japan video game industry was almost 582.61 billion yens (In Japanese) (Online) Retrieved from http://www.famitsu.com/game/news/1221045_1124.html [Assessed 24 October 2009] Harris.C (2004) Official Nintendo DS launch details (Online) Retrieved from http://uk.ds.ign.com/articles/549/549919p1.html [Assessed 23 October 2009] IGN (2004) Japanese price and date set (Online) Retrieved from http://uk.psp.ign.com/articles/560/560947p1.html [Assessed 22 October 2009] IGN (2006) E3 2006: The final word on playstation (Online) Retrieved from http://uk.ps3.ign.com/articles/709/709973p1.html [Assessed 22 October 2009] Kiyoshi Takenaka (2007) UPDATE 2-Nintendo sets $85 bln high score, thanks to Wii, DS (Online) Retrieved from http://www.reuters.com/article/companyNewsAndPR/idUST30751820071015 [Assessed 10 November 2009] Martin, M (2009) Console installed base reaches 22m in UK (Online) Retrieved from http://www.gamesindustry.biz/articles/console-installed-base-reaches-22m-in-uk [Assessed 24 October 2009] Nintendo (2009a) Company History (In Japanese) (Online) Retrieved from: http://www.nintendo.co.jp/corporate/outline/index.html [Assessed 21 October 2009] Nintendo (2009b) Consolidated Financial Highlights pp9 (Online) Retrieved from http://www.nintendo.co.jp/ir/pdf/2009/090730e.pdf#page=23 [Assessed 24 October 2009] Plunkett, L (2009) Sony talks Playstation lifetime sales, PSN revenue (Online) Retrieved from: http://kotaku.com/5340392/sony-talk-playstation-lifetime-sales-psn-revenue [Assessed 21 October 2009] Sanders, K and Casamassina, M (2006) US Wii price, launch date revealed (Online) Retrieved from http://uk.wii.ign.com/articles/732/732669p1.html [Assessed 23 October 2009] SCE (2009) Company Profile (Online) Retrieve from: http://www.scei.co.jp/corporate/index_e.html [Assessed 21 October 2009] SCE (2004) PSP enters the market on December 12, 2004 at 19,800 Yen in Japan (Online) Retrieved from http://www.scei.co.jp/corporate/release/pdf/041027ae.pdf [Assessed 22 October 2009] SCE (2006) Playstation3 Launches on November 11, 2006 in Japan (Online) Retrieved from http://www.scei.co.jp/corporate/release/pdf/060509ae.pdf [Assessed 22 October 2009] Thorsen.T (2009) PS3 sales almost 24 million, PSP near 56 million (Online) Retrieved from: http://uk.gamespot.com/news/6214693.html?om_act=convertom_clk=newstoptag=newstop;title;5 [Assessed 24 October 2009]

Analysis of QoS Parameters

Analysis of QoS Parameters Chapter 3 3. Analysis of QoS Parameters 3.1 Introduction A Number of QoS [11] of parameters can be measured and monitored to determine whether a service level offered or received is being achieved. These parameters consist of the following 1. Network availability 2. Bandwidth 3. Delay 4. Jitter 5. Loss 3.1.1 Network Availability Network availability can have a consequential effect on QoS. Simply put, if the network is not available, even during short periods of time, the user or application may achieve unpredictable or undesirable performance (QoS) [11]. Network availability is the summation of the availability of many items that are used to create a network. These include network device redundancy, e.g. redundant interfaces, processor cards or power supplies in routers and switches, resilient networking protocols, multiple physical connections, e.g. fiber or copper, backup power sources etc. Network operators can increase their networks availability by implementing varying degrees of each item. 3.1.2 Bandwidth Bandwidth is one of the most important QoS parameter. It can be divided in to two types 1. Guaranteed bandwidth 2. Available bandwidth 3.1.2.1 Guaranteed bandwidth Network operators offer a service that provides minimum BW and burst BW in the SLA. Because the guaranteed BW the service costs higher as compare to the available BW service. So the service providers must ensure the special treatment to the subscribers who have got the guaranteed BW service. The network operator separates the subscribers by different physical or logical networks in some cases, e.g., VLANs, Virtual Circuits, etc. In some cases, the guaranteed BW service traffic may share the same network infrastructure with available BW service traffic. We often use to see the case at location where network connections are expensive or the bandwidth is leased from another service provider. When subscribers share the same network infrastructure, the subscribers of the guaranteed BW service must get the priority over the available BW subscribers traffic so that in times of networks congestion the guaranteed BW subscribers SLAs are met. Burst BW can be specified in terms of amount and du ration of excess BW (burst) above the guaranteed minimum. QoS mechanism may be activated to avoid or discard traffic that use consistently above the guaranteed minimum BW that the subscriber agreed to in the SLA. 3.1.2.2 Available bandwidth As we know network operators have fixed Bandwidth, but to get more return on the investment of their network infrastructure, they oversubscribe the BW. By oversubscribing the BW a user is subscribed to be no always available to them. This allows users to compete for available BW. They get more or less BW it depends upon the amount of traffic form other users on the network at any given time. Available bandwidth is a technique commonly used over consumer ADSL networks, e.g., a customer signs up for a 384-kbps service that provides no QoS (BW) guarantee in the SLA. The SLA points out that the 384-kbps is standard but does not make any guarantees. Under lightly loaded conditions, the 384-kbps BW will be available to the users but upon network loaded condition, this BW will not be available consistently. It can be noticed during certain times of the day when number of users access the network. 3.1.3 Delay Network delay is the transit time an application experiences from the ingress (entering) point to the egress (exit) point of the network. Delay can cause significant QoS issues with application such as Video conferencing and fax transmission that simply time-out and final under excessive delay conditions. Some applications can compensate for small amounts of delay but once a certain amount is exceeded, the QoS becomes compromised. For example some networking equipment can spoof an SNA session on a host by providing local acknowledgements when the network delay would cause the SNA session to time out. Similarly, VoIP gateways and phones provide some local buffering to compensate for network delay. There can be both fixed and variable delays. Examples of fixed delays are: Application based delay, e.g., voice codec processing time and IP packet creation time by the TCP/IP software stack Data transmission (queuing delay) over the physical network media at each network hop. Propagation delay across the network based on transmission distance Examples of variable delays are: †¢ Ingress queuing delay for traffic entering a network node †¢ Contention with other traffic at each network node †¢ Egress queuing delay for traffic exiting a network node 3.1.4 Jitter (Delay Variation) Jitter is the difference in delay presented by different packets that are part of the same traffic flow. High frequency delay variation is known as jitter and the low frequency delay variation is known as wander. Primary cause of jitter is basically the differences in queue wait times for consecutive packets in a flow and this is the most significant issue for QoS. Traffic types especially real time traffic such as video conferencing can not tolerate jitter. Differences in packet arrival times cause in the voice. All transport system exhibit some jitter. As long as jitter limits below the defined tolerance level, it does not affect service quality. 3.1.5 Loss Loss either bit errors or packet drops has a significant impact on VoIP services as compare to the data services. During the transmission of the voice, loss of multiple packets may cause an audible pop that will become irritating to the user. Now as compare to the voice transmission, in data transmission loss of single bit or multiple packets of information will not effect the whole communication and is almost never noticed by users. In case of real time video conferencing, consecutive packet loss may cause a momentary glitch (defect) on the screen, but the video then proceeds as before. However, if packet drops get increase, then the quality of the transmission degrades. For minimum quality rate of packet loss must be less than 5% and less then 1% for toll quality. When the network node will be congested, it will drop the packets and by this the loss will occur. TCP (Transmission Control Protocol) is one of the networking protocols that offer packets loss protection by the retransmission of packets that may have been dropped by the network. When network congestion will be increased, more packets will be dropped and hence there will be more TCP transmission. If congestion continues the network performance will obviously degrade because much of the BW is being used for the retransmission of dropped packets. TCP will eventually reduce its transmission window size, due to this reduction in window size smaller packets will be transmitted; this will eventually reduce congestion, resulting in fewer packets being dropped. Because congestion has a direct influence on packet loss, congestion avoidance mechanism is often deployed. One such mechanism is called Random Early Discard (RED). RED algorithms randomly and intentionally drop packets once the traff ic reaches one or more configured threshold. RED provides more efficient congestion management for TCP-based flows. 3.1.5.1 Emission priorities It determines the order in which traffic is transmitted as it exits a network node. Traffic with higher emission priority is transmitted a head of traffic with a lower emission priority. Emission priorities also determine the amount of latency introduced to the traffic by the network nodes queuing mechanism. For example, email which is a delay tolerant application will get the lower emission priority as compare to the delay sensitive real time applications such as voice or video. These delay sensitive applications can not be buffered but are being transmitted while the delay tolerant applications may be buffered. In a simple way we can say that emission priorities use a simple transmit priority scheme whereby higher emission priority traffic is always transmitted ahead of lower emission priority traffic. This is typically accomplished using strict priority scheduling (queuing) the downside of this approach is that low emission priority queues may never get services (starved) it there is always higher emission priority traffic with no BW rate limiting. A more detailed scheme provides a weighted scheduling approach to the transmission of the traffic to improve fairness, i.e., the lower emission priority traffic is transmitted. Finally, some emission priority schemes provide a mixture of both priority and weighted schedulers. 3.1.5.2 Discarded priorities Are used to determine the order in which traffic gets discarded. Due to the network congestion packets may be get dropped i.e., the traffic exceeds its prescribed amount of BW for some period of time. When the network will be congested, traffic with a higher discard priority will get drop as compare to the traffic with a lower discard priority. Traffic with similar QoS performance can be sub divided using discard priorities. This allows the traffic to receive the same performance when the network node is not congested. However, when the network node gets congested, the discard priority is used to drop the more suitable traffic first. Discard priorities also allow traffic with the same emission priority to be discarded when the traffic is out of profile. With out discard priorities traffic would need to be separated into different queues in a network node to provide service differentiation. This can be expensive since only a limited number of hardware queues (typically eight or less) are available on networking devices. Some devices may have software based queues but as these are increasingly used, network node performance is typically reduced. With discard priorities, traffic can be placed in the same queue but in effect the queue is sub divided into virtual queues, each with a different discard priority. For example if a product supports three discard priorities, then one hardware queues in effect provides three QoS Levels. Performance Dimension Application Bandwidth Sensitivity to Delay Jitter Loss VoIP Low High High Medium Video Conf High High High Medium Streaming Video on Demand High Medium Medium Medium Streaming Audio Low Medium Medium Medium Client Server Transaction Medium Medium Low High Email Low Low Low High File Transfer Medium Low Low High Table 3.1: Application performance dimensions (use histogram) Table 3.1 illustrates the QoS performance dimensions required by some common applications. Applications can have very different QoS requirements. As these are mixed over a common IP transport network, without applying QoS the network traffic will experience unpredictable behavior. 3.2 Categorizing Applications Networked applications can be categorized based on end user application requirements. Some applications are between people while other applications are a person and a networked device application, e.g., a PC and web server. Finally, some networking devices, e.g., router-to-router. Table 3.2 categorizes applications into four different traffic categories: 1. Network Control 2. Responsive 3. Interactive 4. Timely Traffic Category Example Application Network Control Critical Alarm, routing, billing ETC. Responsive Streaming Audio/Video, Client/Server Transaction Interactive VoIP, Interactive gaming, Video Conferencing Timely Email, Non Critical Table 3.2: Application Categorization 3.2.1 Network Control Applications Some applications are used to control the operations and administration of the network. Such application include network routing protocols, billing applications and QoS monitoring and measuring for SLAs. These applications can be subdivided into those required for critical and standard network operating conditions. To create high availability networks, network control applications require priority over end user applications because if the network is not operating properly, end user application performance will suffer. 3.2.2 Responsive applications Some applications are between a person and networked devices applications to be responsive so a quick response back to the sender (source) is required when the request is being sent to the networking device. Sometimes these applications are referred to as being near real time. These near real time applications require relatively low packet delay, jitter and loss. However QoS requirements for the responsive applications are not as stringent as real time, interactive application requirements. This category includes streaming media and client server web based applications. Streaming media application includes Internet radio and audio / video broadcasts (news, training, education and motion pictures). Streaming applications e.g. videos require the network to be responsive when they are initiated so the user doesnt wait for long time before the media begins playing. For certain types of signaling these applications require the network to be responsive also. For example with movie on deman d when a user changes channels or forward, rewinds or pause the media user expects the application to react similarly to the response time of there remote control. The Client / server web applications typically involve the user selecting a hyperlink to jump from one page to another or submit a request etc. These applications also require the network to be responsive such that once the hyperlink to be responsive such that once the hyperlink is selected, a response. This can be achieved over a best effort network with the help of broadband internet connection as compare to dial up. Financial transaction may be included in these types of application, e.g., place credit card order and quickly provide feedback to the user indicating that either the transaction has completed or not. Otherwise the user may be unsure to initiate a duplicate order. Alternatively the user may assume that the order was placed correctly but it may not have. In either case the user will not be satisfied with the network or applications performance. Responsive applications can use either UDP or TCP based transport. Streaming media applications typically use UDP because in UDP it would not be fruitful to retransmit the data. Web based applications are based on the hypertext transport protocol and always use TCP, for web based application packet loss can be managed by transmission control protocol (TCP) which retransmit lost packets. In case of retransmission of lost streaming media is sufficiently buffered. If not then the lost packets are discarded. This results in the form of distortion in media. 3.2.3 Interactive Applications Some applications are interactive whereby two or more people communicate or participate actively. The participants expect the real time response from the networked applications. In this context real time means that there is minimal delay (latency) and delay variations (jitter) between the sender and receiver. Some interactive applications, such as a telephone call, have operated in real time over the telephone companies circuit switched networks for over 100 years. The QoS expectations for voice applications have been set and therefore must also be achieved for packetized voice such as VoIP. Other interactive applications include video conferencing and interactive gaming. Since the interactive applications operate in real time, packet loss must be minimized. Interactive applications typically are UDP based (Universal Datagram Protocol) and hence cannot retransmit lost or dropped packets as with TCP based applications. However it would not be beneficial to retransmit the packets because interactive applications are time based. For example if a voice packet was lost. It doesnt make sense to retransmit the packet because the conservations between the sender and receiver have already progressed and the lost packet might be from part of the conversation that has already passed in time. 3.2.4 Timely Applications There are some applications which do not require real time performance between a person and networked devices application but do require the information to be delivered in a timely manner. Such example includes save and send or forward email applications and file transfer. The relative importance of these applications is based on their business priorities. These applications require that packets arrive with abounded amount of delay. For example, if an email takes few minutes to arrive at its destination, this is acceptable. However if we consider it in a business environment, if an email takes 10 minutes to arrive at its destination, this will often not acceptable. The same bounded delay applies to file transfer. Once a file transfer is initiated, delay and jitter are illogical because file transfer often take minutes to complete. It is important to note that timely applications use TCP based transport instead of UDP based transport and therefore packet loss is managed by TCP which r etransmit any lost packets resulting in no packet loss. By summarizing above paragraph we can say that timely applications expect the network QoS to provide packets with a bounded amount of delay not more than that. Jitter has a negligible effect on these types of applications. Loss is reduced to zero due to TCPs retransmission mechanism. 3.3 QoS Management Architecture We can divide QoS management architecture of VoIP into two planes: data plane and control plane. Packet classification, shaping, policing, buffer management, scheduling, loss recovery, and error concealment are involved in the mechanism of data plane. They implement the actions the network needs to take on user packets, in order to enforce different class services. Mechanisms which come in control plane are resource provisioning, traffic engineering, admission control, resource reservation and connection management etc. 3.3.1 Data Plane 3.3.1.1 Packet Forwarding It consists of Classifier, Marker, Meter, Shaper / Dropper. When a packet is received, a packet classifier is used to determine which flow or class the packet belongs to. Those packets belong to the same flow/class obey a predefined rule and are processed in an alike manner. The basic criteria of classification for VoIP applications could be IP address, TCP/UDP port, IP precedence, protocol, input port, DiffServ code points (DSCP), or Ethernet 802.1p class of service (CoS). Cisco supports several additional criteria such as access list and traffic profile. The purpose of the meter is to decide whether the packet is in traffic profile or not. The Shaper/Dropper drops the packets which crossed the limits of traffic profile to bring in conformance to current network load. A marker is used to mark the certain field in the packet, such as DS field, to label the packet type for differential treatment later. After the traffic conditioner, buffer is used for packet storage that waits for transmission. 3.3.1.2 Buffer Management and Scheduling Active queue management (RED) drops packets before the repletion of the queue can avoid the problem of unfair resource usage. Predictable queuing delay and bandwidth sharing can be achieved by putting the flows into different queues and treating individually. Schedulers of this type can not be scaled as overhead increases as the number of on-going traffic increases. Solution is class-based schedulers such as Constraint Based WFQ and static Priority which schedule traffic in a class-basis fashion. But for the individual flow it would be difficult to get the predictable delay and bandwidth sharing. So care must be taken to apply this to voice application which has strict delay requirements. 3.3.1.3 Loss Recovery We can classify loss recovery into two ways one is Active recovery and the other is Passive recovery. We have retransmission in Active recovery and Forward Error Correction (Adding redundancy) in passive recovery. Retransmission may not be suitable for VoIP because of it latency of packets increases. 3.3.2 Control Plane 3.3.2.1 Resource provisioning and Traffic Engineering Refers to the configuration of resources for applications in the network. In industry, main approach of resource provisioning is over provisioning, abundantly providing resources. Factors that make this attractive are cost of bandwidth and network planning, cost of bandwidth in the backbone is decreasing day by day and network planning is becoming simpler. 3.3.2.2Traffic Engineering It mainly focuses to keep the control on network means to minimize the over-utilization of a particular portion of the network while the capacity is available elsewhere in the network. The two methods used to provide powerful tools for traffic engineering are Multi-Protocol Label Switching (MPLS) and Constraint Based Routing (CBR). These are the mechanisms through which a certain amount of network resources can be reserved for the potential voice traffic along the paths which are determined by Constraint Based Routing or other shortest path routing algorithms. 3.3.2.3 Admission Control Admission control is used to limit the resource usage of voice traffic within the amount of the specified resources. There is no provision of admission control in IP networks so it can offer only best effort service. Parameter based Admission Control provides delay guaranteed service to applications which can be accurately described, such as VoIP. In case of bursty traffic, it is difficult to describe traffic characteristics which makes this type to overbook network resources and therefore lowers network utilization. To limit the amount of traffic over any period it uses explicit traffic descriptors (typical example is token bucket). Different algorithms used in parameter based admission control are: Æ’ËÅ" Ciscos resource reservation based (RSVP). Æ’ËÅ" Utilization based (compares with a threshold, based on utilization value at runtime it decides to admit or reject). Æ’ËÅ" Per-flow end-to-end guaranteed delay service (Computes bandwidth requirements and compares with available resource to make decision). Æ’ËÅ" Class-based admission control. 3.4 Performance Evaluation in VoIP applications 3.4.1 End-To-End Delay When End to End delay exceeds a certain value, the interactive ness becomes more like a half-duplex communication. There can be of two type of delay: 1) Delays due to processing and transmission of speech 2) Network delay (delay that is the result of processing with in the system) Network delay = Fixed part + variable part Fixed part depends upon the performance of the network nodes on the transmission path, transmission and propagation delay and the capacity of links between the nodes. Variable part is the time spent in the queues which depends on the network load. Queuing delay can be minimized by using the advanced scheduling mechanisms e.g. Priority queuing. IP packet delay can be reduced by sending shorter packets instead of longer packets. Useful technique for voice delay reduction on WAN is link fragmentation and interleaving. Fragment the lower packet into smaller packets and between those small packets VOICE packets are sent. 3.4.2 Delay Jitter Delay variation, also known as jitter, creates hurdle in the proper reconstruction of voice packets in their original sequential form. It is defined as difference in total end-to-end delay of two consecutive packets in the flow. In order to remove jitter, it requires collecting and storing packets long enough to permit the slowest packets to arrive in order to be played in the correct sequence. Solution is to employ a play out buffer at the receiver to absorb the jitter before outputting the audio stream. Packets are buffered until their scheduled play out time arrives. Scheduling a later deadline increases the possibility of playing out more packets and results in lower loss rate, but at the cost of higher buffering delay. Techniques for Jitter Absorption †¢ Setting the same play out time for all the packets for entire session or for the duration of each session. †¢ Adaptive adjusting of play out time during silence periods regarding to current network †¢ Constantly adapting the play out time for each packet, this requires the scaling of voice packets to maintain continued play out. 3.4.3 Frame Eraser (F.E) It actually happens at that time when the IP packet carrying speech frame does not arrive at the receiver side in time. There may be loss of single frame or a block of frames. Techniques used to encounter the frame erasure †¢ Forward Error Correction (requires additional processing) depends on the rate and distribution of the losses. †¢ Loss concealment (replaces lost frames by playing the last successfully received frame) effective only at low loss rate of a single frame. High F.E and delays can become troublesome because it can lead to a longer period of corrupt voice. The speech quality perceived by the listener is based on F.E levels that occur on the exit from the jitter buffer after the Forward Error Correction has been employed. To reduce levels of frame loss, Assured forwarding service helps to reduce network packet loss that occur because of full queues in network nodes. 3.4.4 Out of Order Packet Delivery This type of problem occurs in the complex topology where number of paths exists between the sender and the receiver. At the receiving end the receiving system must rearrange received packets in the correct order to reconstruct the original speech signal. Techniques for OUT-OF-ORDER PACKET DELIVERY It is also done by Jitter buffer whose functionality now became †¢ Re-ordering out of order packets ( based on sequence number) †¢ Elimination of Jitter Analysis of QoS Parameters Analysis of QoS Parameters Chapter 3 3. Analysis of QoS Parameters 3.1 Introduction A Number of QoS [11] of parameters can be measured and monitored to determine whether a service level offered or received is being achieved. These parameters consist of the following 1. Network availability 2. Bandwidth 3. Delay 4. Jitter 5. Loss 3.1.1 Network Availability Network availability can have a consequential effect on QoS. Simply put, if the network is not available, even during short periods of time, the user or application may achieve unpredictable or undesirable performance (QoS) [11]. Network availability is the summation of the availability of many items that are used to create a network. These include network device redundancy, e.g. redundant interfaces, processor cards or power supplies in routers and switches, resilient networking protocols, multiple physical connections, e.g. fiber or copper, backup power sources etc. Network operators can increase their networks availability by implementing varying degrees of each item. 3.1.2 Bandwidth Bandwidth is one of the most important QoS parameter. It can be divided in to two types 1. Guaranteed bandwidth 2. Available bandwidth 3.1.2.1 Guaranteed bandwidth Network operators offer a service that provides minimum BW and burst BW in the SLA. Because the guaranteed BW the service costs higher as compare to the available BW service. So the service providers must ensure the special treatment to the subscribers who have got the guaranteed BW service. The network operator separates the subscribers by different physical or logical networks in some cases, e.g., VLANs, Virtual Circuits, etc. In some cases, the guaranteed BW service traffic may share the same network infrastructure with available BW service traffic. We often use to see the case at location where network connections are expensive or the bandwidth is leased from another service provider. When subscribers share the same network infrastructure, the subscribers of the guaranteed BW service must get the priority over the available BW subscribers traffic so that in times of networks congestion the guaranteed BW subscribers SLAs are met. Burst BW can be specified in terms of amount and du ration of excess BW (burst) above the guaranteed minimum. QoS mechanism may be activated to avoid or discard traffic that use consistently above the guaranteed minimum BW that the subscriber agreed to in the SLA. 3.1.2.2 Available bandwidth As we know network operators have fixed Bandwidth, but to get more return on the investment of their network infrastructure, they oversubscribe the BW. By oversubscribing the BW a user is subscribed to be no always available to them. This allows users to compete for available BW. They get more or less BW it depends upon the amount of traffic form other users on the network at any given time. Available bandwidth is a technique commonly used over consumer ADSL networks, e.g., a customer signs up for a 384-kbps service that provides no QoS (BW) guarantee in the SLA. The SLA points out that the 384-kbps is standard but does not make any guarantees. Under lightly loaded conditions, the 384-kbps BW will be available to the users but upon network loaded condition, this BW will not be available consistently. It can be noticed during certain times of the day when number of users access the network. 3.1.3 Delay Network delay is the transit time an application experiences from the ingress (entering) point to the egress (exit) point of the network. Delay can cause significant QoS issues with application such as Video conferencing and fax transmission that simply time-out and final under excessive delay conditions. Some applications can compensate for small amounts of delay but once a certain amount is exceeded, the QoS becomes compromised. For example some networking equipment can spoof an SNA session on a host by providing local acknowledgements when the network delay would cause the SNA session to time out. Similarly, VoIP gateways and phones provide some local buffering to compensate for network delay. There can be both fixed and variable delays. Examples of fixed delays are: Application based delay, e.g., voice codec processing time and IP packet creation time by the TCP/IP software stack Data transmission (queuing delay) over the physical network media at each network hop. Propagation delay across the network based on transmission distance Examples of variable delays are: †¢ Ingress queuing delay for traffic entering a network node †¢ Contention with other traffic at each network node †¢ Egress queuing delay for traffic exiting a network node 3.1.4 Jitter (Delay Variation) Jitter is the difference in delay presented by different packets that are part of the same traffic flow. High frequency delay variation is known as jitter and the low frequency delay variation is known as wander. Primary cause of jitter is basically the differences in queue wait times for consecutive packets in a flow and this is the most significant issue for QoS. Traffic types especially real time traffic such as video conferencing can not tolerate jitter. Differences in packet arrival times cause in the voice. All transport system exhibit some jitter. As long as jitter limits below the defined tolerance level, it does not affect service quality. 3.1.5 Loss Loss either bit errors or packet drops has a significant impact on VoIP services as compare to the data services. During the transmission of the voice, loss of multiple packets may cause an audible pop that will become irritating to the user. Now as compare to the voice transmission, in data transmission loss of single bit or multiple packets of information will not effect the whole communication and is almost never noticed by users. In case of real time video conferencing, consecutive packet loss may cause a momentary glitch (defect) on the screen, but the video then proceeds as before. However, if packet drops get increase, then the quality of the transmission degrades. For minimum quality rate of packet loss must be less than 5% and less then 1% for toll quality. When the network node will be congested, it will drop the packets and by this the loss will occur. TCP (Transmission Control Protocol) is one of the networking protocols that offer packets loss protection by the retransmission of packets that may have been dropped by the network. When network congestion will be increased, more packets will be dropped and hence there will be more TCP transmission. If congestion continues the network performance will obviously degrade because much of the BW is being used for the retransmission of dropped packets. TCP will eventually reduce its transmission window size, due to this reduction in window size smaller packets will be transmitted; this will eventually reduce congestion, resulting in fewer packets being dropped. Because congestion has a direct influence on packet loss, congestion avoidance mechanism is often deployed. One such mechanism is called Random Early Discard (RED). RED algorithms randomly and intentionally drop packets once the traff ic reaches one or more configured threshold. RED provides more efficient congestion management for TCP-based flows. 3.1.5.1 Emission priorities It determines the order in which traffic is transmitted as it exits a network node. Traffic with higher emission priority is transmitted a head of traffic with a lower emission priority. Emission priorities also determine the amount of latency introduced to the traffic by the network nodes queuing mechanism. For example, email which is a delay tolerant application will get the lower emission priority as compare to the delay sensitive real time applications such as voice or video. These delay sensitive applications can not be buffered but are being transmitted while the delay tolerant applications may be buffered. In a simple way we can say that emission priorities use a simple transmit priority scheme whereby higher emission priority traffic is always transmitted ahead of lower emission priority traffic. This is typically accomplished using strict priority scheduling (queuing) the downside of this approach is that low emission priority queues may never get services (starved) it there is always higher emission priority traffic with no BW rate limiting. A more detailed scheme provides a weighted scheduling approach to the transmission of the traffic to improve fairness, i.e., the lower emission priority traffic is transmitted. Finally, some emission priority schemes provide a mixture of both priority and weighted schedulers. 3.1.5.2 Discarded priorities Are used to determine the order in which traffic gets discarded. Due to the network congestion packets may be get dropped i.e., the traffic exceeds its prescribed amount of BW for some period of time. When the network will be congested, traffic with a higher discard priority will get drop as compare to the traffic with a lower discard priority. Traffic with similar QoS performance can be sub divided using discard priorities. This allows the traffic to receive the same performance when the network node is not congested. However, when the network node gets congested, the discard priority is used to drop the more suitable traffic first. Discard priorities also allow traffic with the same emission priority to be discarded when the traffic is out of profile. With out discard priorities traffic would need to be separated into different queues in a network node to provide service differentiation. This can be expensive since only a limited number of hardware queues (typically eight or less) are available on networking devices. Some devices may have software based queues but as these are increasingly used, network node performance is typically reduced. With discard priorities, traffic can be placed in the same queue but in effect the queue is sub divided into virtual queues, each with a different discard priority. For example if a product supports three discard priorities, then one hardware queues in effect provides three QoS Levels. Performance Dimension Application Bandwidth Sensitivity to Delay Jitter Loss VoIP Low High High Medium Video Conf High High High Medium Streaming Video on Demand High Medium Medium Medium Streaming Audio Low Medium Medium Medium Client Server Transaction Medium Medium Low High Email Low Low Low High File Transfer Medium Low Low High Table 3.1: Application performance dimensions (use histogram) Table 3.1 illustrates the QoS performance dimensions required by some common applications. Applications can have very different QoS requirements. As these are mixed over a common IP transport network, without applying QoS the network traffic will experience unpredictable behavior. 3.2 Categorizing Applications Networked applications can be categorized based on end user application requirements. Some applications are between people while other applications are a person and a networked device application, e.g., a PC and web server. Finally, some networking devices, e.g., router-to-router. Table 3.2 categorizes applications into four different traffic categories: 1. Network Control 2. Responsive 3. Interactive 4. Timely Traffic Category Example Application Network Control Critical Alarm, routing, billing ETC. Responsive Streaming Audio/Video, Client/Server Transaction Interactive VoIP, Interactive gaming, Video Conferencing Timely Email, Non Critical Table 3.2: Application Categorization 3.2.1 Network Control Applications Some applications are used to control the operations and administration of the network. Such application include network routing protocols, billing applications and QoS monitoring and measuring for SLAs. These applications can be subdivided into those required for critical and standard network operating conditions. To create high availability networks, network control applications require priority over end user applications because if the network is not operating properly, end user application performance will suffer. 3.2.2 Responsive applications Some applications are between a person and networked devices applications to be responsive so a quick response back to the sender (source) is required when the request is being sent to the networking device. Sometimes these applications are referred to as being near real time. These near real time applications require relatively low packet delay, jitter and loss. However QoS requirements for the responsive applications are not as stringent as real time, interactive application requirements. This category includes streaming media and client server web based applications. Streaming media application includes Internet radio and audio / video broadcasts (news, training, education and motion pictures). Streaming applications e.g. videos require the network to be responsive when they are initiated so the user doesnt wait for long time before the media begins playing. For certain types of signaling these applications require the network to be responsive also. For example with movie on deman d when a user changes channels or forward, rewinds or pause the media user expects the application to react similarly to the response time of there remote control. The Client / server web applications typically involve the user selecting a hyperlink to jump from one page to another or submit a request etc. These applications also require the network to be responsive such that once the hyperlink to be responsive such that once the hyperlink is selected, a response. This can be achieved over a best effort network with the help of broadband internet connection as compare to dial up. Financial transaction may be included in these types of application, e.g., place credit card order and quickly provide feedback to the user indicating that either the transaction has completed or not. Otherwise the user may be unsure to initiate a duplicate order. Alternatively the user may assume that the order was placed correctly but it may not have. In either case the user will not be satisfied with the network or applications performance. Responsive applications can use either UDP or TCP based transport. Streaming media applications typically use UDP because in UDP it would not be fruitful to retransmit the data. Web based applications are based on the hypertext transport protocol and always use TCP, for web based application packet loss can be managed by transmission control protocol (TCP) which retransmit lost packets. In case of retransmission of lost streaming media is sufficiently buffered. If not then the lost packets are discarded. This results in the form of distortion in media. 3.2.3 Interactive Applications Some applications are interactive whereby two or more people communicate or participate actively. The participants expect the real time response from the networked applications. In this context real time means that there is minimal delay (latency) and delay variations (jitter) between the sender and receiver. Some interactive applications, such as a telephone call, have operated in real time over the telephone companies circuit switched networks for over 100 years. The QoS expectations for voice applications have been set and therefore must also be achieved for packetized voice such as VoIP. Other interactive applications include video conferencing and interactive gaming. Since the interactive applications operate in real time, packet loss must be minimized. Interactive applications typically are UDP based (Universal Datagram Protocol) and hence cannot retransmit lost or dropped packets as with TCP based applications. However it would not be beneficial to retransmit the packets because interactive applications are time based. For example if a voice packet was lost. It doesnt make sense to retransmit the packet because the conservations between the sender and receiver have already progressed and the lost packet might be from part of the conversation that has already passed in time. 3.2.4 Timely Applications There are some applications which do not require real time performance between a person and networked devices application but do require the information to be delivered in a timely manner. Such example includes save and send or forward email applications and file transfer. The relative importance of these applications is based on their business priorities. These applications require that packets arrive with abounded amount of delay. For example, if an email takes few minutes to arrive at its destination, this is acceptable. However if we consider it in a business environment, if an email takes 10 minutes to arrive at its destination, this will often not acceptable. The same bounded delay applies to file transfer. Once a file transfer is initiated, delay and jitter are illogical because file transfer often take minutes to complete. It is important to note that timely applications use TCP based transport instead of UDP based transport and therefore packet loss is managed by TCP which r etransmit any lost packets resulting in no packet loss. By summarizing above paragraph we can say that timely applications expect the network QoS to provide packets with a bounded amount of delay not more than that. Jitter has a negligible effect on these types of applications. Loss is reduced to zero due to TCPs retransmission mechanism. 3.3 QoS Management Architecture We can divide QoS management architecture of VoIP into two planes: data plane and control plane. Packet classification, shaping, policing, buffer management, scheduling, loss recovery, and error concealment are involved in the mechanism of data plane. They implement the actions the network needs to take on user packets, in order to enforce different class services. Mechanisms which come in control plane are resource provisioning, traffic engineering, admission control, resource reservation and connection management etc. 3.3.1 Data Plane 3.3.1.1 Packet Forwarding It consists of Classifier, Marker, Meter, Shaper / Dropper. When a packet is received, a packet classifier is used to determine which flow or class the packet belongs to. Those packets belong to the same flow/class obey a predefined rule and are processed in an alike manner. The basic criteria of classification for VoIP applications could be IP address, TCP/UDP port, IP precedence, protocol, input port, DiffServ code points (DSCP), or Ethernet 802.1p class of service (CoS). Cisco supports several additional criteria such as access list and traffic profile. The purpose of the meter is to decide whether the packet is in traffic profile or not. The Shaper/Dropper drops the packets which crossed the limits of traffic profile to bring in conformance to current network load. A marker is used to mark the certain field in the packet, such as DS field, to label the packet type for differential treatment later. After the traffic conditioner, buffer is used for packet storage that waits for transmission. 3.3.1.2 Buffer Management and Scheduling Active queue management (RED) drops packets before the repletion of the queue can avoid the problem of unfair resource usage. Predictable queuing delay and bandwidth sharing can be achieved by putting the flows into different queues and treating individually. Schedulers of this type can not be scaled as overhead increases as the number of on-going traffic increases. Solution is class-based schedulers such as Constraint Based WFQ and static Priority which schedule traffic in a class-basis fashion. But for the individual flow it would be difficult to get the predictable delay and bandwidth sharing. So care must be taken to apply this to voice application which has strict delay requirements. 3.3.1.3 Loss Recovery We can classify loss recovery into two ways one is Active recovery and the other is Passive recovery. We have retransmission in Active recovery and Forward Error Correction (Adding redundancy) in passive recovery. Retransmission may not be suitable for VoIP because of it latency of packets increases. 3.3.2 Control Plane 3.3.2.1 Resource provisioning and Traffic Engineering Refers to the configuration of resources for applications in the network. In industry, main approach of resource provisioning is over provisioning, abundantly providing resources. Factors that make this attractive are cost of bandwidth and network planning, cost of bandwidth in the backbone is decreasing day by day and network planning is becoming simpler. 3.3.2.2Traffic Engineering It mainly focuses to keep the control on network means to minimize the over-utilization of a particular portion of the network while the capacity is available elsewhere in the network. The two methods used to provide powerful tools for traffic engineering are Multi-Protocol Label Switching (MPLS) and Constraint Based Routing (CBR). These are the mechanisms through which a certain amount of network resources can be reserved for the potential voice traffic along the paths which are determined by Constraint Based Routing or other shortest path routing algorithms. 3.3.2.3 Admission Control Admission control is used to limit the resource usage of voice traffic within the amount of the specified resources. There is no provision of admission control in IP networks so it can offer only best effort service. Parameter based Admission Control provides delay guaranteed service to applications which can be accurately described, such as VoIP. In case of bursty traffic, it is difficult to describe traffic characteristics which makes this type to overbook network resources and therefore lowers network utilization. To limit the amount of traffic over any period it uses explicit traffic descriptors (typical example is token bucket). Different algorithms used in parameter based admission control are: Æ’ËÅ" Ciscos resource reservation based (RSVP). Æ’ËÅ" Utilization based (compares with a threshold, based on utilization value at runtime it decides to admit or reject). Æ’ËÅ" Per-flow end-to-end guaranteed delay service (Computes bandwidth requirements and compares with available resource to make decision). Æ’ËÅ" Class-based admission control. 3.4 Performance Evaluation in VoIP applications 3.4.1 End-To-End Delay When End to End delay exceeds a certain value, the interactive ness becomes more like a half-duplex communication. There can be of two type of delay: 1) Delays due to processing and transmission of speech 2) Network delay (delay that is the result of processing with in the system) Network delay = Fixed part + variable part Fixed part depends upon the performance of the network nodes on the transmission path, transmission and propagation delay and the capacity of links between the nodes. Variable part is the time spent in the queues which depends on the network load. Queuing delay can be minimized by using the advanced scheduling mechanisms e.g. Priority queuing. IP packet delay can be reduced by sending shorter packets instead of longer packets. Useful technique for voice delay reduction on WAN is link fragmentation and interleaving. Fragment the lower packet into smaller packets and between those small packets VOICE packets are sent. 3.4.2 Delay Jitter Delay variation, also known as jitter, creates hurdle in the proper reconstruction of voice packets in their original sequential form. It is defined as difference in total end-to-end delay of two consecutive packets in the flow. In order to remove jitter, it requires collecting and storing packets long enough to permit the slowest packets to arrive in order to be played in the correct sequence. Solution is to employ a play out buffer at the receiver to absorb the jitter before outputting the audio stream. Packets are buffered until their scheduled play out time arrives. Scheduling a later deadline increases the possibility of playing out more packets and results in lower loss rate, but at the cost of higher buffering delay. Techniques for Jitter Absorption †¢ Setting the same play out time for all the packets for entire session or for the duration of each session. †¢ Adaptive adjusting of play out time during silence periods regarding to current network †¢ Constantly adapting the play out time for each packet, this requires the scaling of voice packets to maintain continued play out. 3.4.3 Frame Eraser (F.E) It actually happens at that time when the IP packet carrying speech frame does not arrive at the receiver side in time. There may be loss of single frame or a block of frames. Techniques used to encounter the frame erasure †¢ Forward Error Correction (requires additional processing) depends on the rate and distribution of the losses. †¢ Loss concealment (replaces lost frames by playing the last successfully received frame) effective only at low loss rate of a single frame. High F.E and delays can become troublesome because it can lead to a longer period of corrupt voice. The speech quality perceived by the listener is based on F.E levels that occur on the exit from the jitter buffer after the Forward Error Correction has been employed. To reduce levels of frame loss, Assured forwarding service helps to reduce network packet loss that occur because of full queues in network nodes. 3.4.4 Out of Order Packet Delivery This type of problem occurs in the complex topology where number of paths exists between the sender and the receiver. At the receiving end the receiving system must rearrange received packets in the correct order to reconstruct the original speech signal. Techniques for OUT-OF-ORDER PACKET DELIVERY It is also done by Jitter buffer whose functionality now became †¢ Re-ordering out of order packets ( based on sequence number) †¢ Elimination of Jitter