Hello Kitty Singapore Essay

A person has many needs at any given time. Abraham Maslow sought to explain why people are driven by particular needs at particular times. According to him, human needs are arranged in a hierarchy (refer to Figure 1), from the most pressing to the least pressing. In order of importance, they are physiological needs, safety needs, social needs, esteem needs and self-actualization needs. The most basic level of needs must be satisfied first before desiring higher level needs. Therefore, having a Mctoy fulfils the forth level needs, called as ‘Esteem Needs’. Self-esteem is the desire for status, self-respect and prestige. Owning the series of Hello Kitty dolls has gained a sense of fulfilment to the individual because it is not that easy to get the limited edition toys at any time. Besides that, the ‘Kiasu’ attitude which is very popular among Singaporeans to have something which everyone else is having, regardless of whether it is of any use. The fear of losing out drives the feeling to fulfil their esteem needs, where they are happy knowing they too have one like others. In order to fulfil the esteem need, people are often engaged in either profession or hobby to gain recognition. For those who loves collecting dolls, use this hobby as a platform to gain recognition from others so that they will be praised. Thus, they feel that by owning the series of hello kitty dolls can make them gained recognition. How has McDonald’s created value to its consumers by offering Hello Kittty dolls in their Extra Value Meals? Marketing experts, Don Peppers and Martha Rogers say that ‘The only value a company will ever create is the value that comes from customers.’ Customer value is the relationship between the consumers perception of benefits they believe they will derive from a purchased compared to the price that will be paid. The total benefit package includes functional attributes of the product and related service attributes. Creating value not only transforms sales effectiveness, it also provides insulation from price pressure. There are many sales strategies, tactics and techniques for creating value for customers. McDonald’s has identified the benefits that consumers would gain from the promotion by creating a series of value to its customer through the promotion. The total value created to its consumers by McDonald’s comprises of four sources namely product, services, personnel and image. Firstly, the product (Hello kitty Dolls) were given as a premium to its loyal consumers at its cost price when consumer purchases the Extra Value Meal, rather than charging any extra amount for it. McDonalds has created value to its consumers by offering this product premium. In terms of service, McDonald’s has created value to its consumers an alternative way of getting the exclusive dolls, where these dolls can only be purchased through McDonald’s outlets during the limited period of time. This series of limited-edition toys will not be available as and when consumers want them. Thirdly, the satisfaction gained by consumers by owning these dolls. As the dolls were limited edition and were sold at cheaper price, McDonald’s has created the satisfaction feeling among its consumers when they own them. And finally image value is created to McDonald’s consumers where the consumers have the option to choose designs of their preferences during the one-month promotion. The image of ‘Kitty’ representing different cultures wedding costumes creates value to those owning them. Thus, McDonald’s has added up values from all the four sources mentioned above to successfully create values to its consumers through its ‘Hello Kitty’ Promotion. Recommendations and Conclusion Here are several alternatives that McDonald’s should have considered before carrying out the promotion to avoid such havoc from happening: 1) Study the consumer behaviour of Singaporeans 2) Periods of the promotion 3) Increase the number of toys offered for promotion In conclusion, the havoc caused from the ‘Hello Kitty’ Promotion in Singapore has not tarnished McDonald’s image in any aspect. This was proven when McDonald’s introduced another six sets of designs featured royal costumes around the world a year after, and the sales seem not to be declining. There was no repeat of the previous year’s frenzy as McDonald’s was prepared. Several precautions were taken such as limiting the number of dolls each customer can buy to four, and had more dolls in stock for panic buying. Besides that, to monitor and control the crowds, McDonald’s has hired security personnel and mobile squad officers to visit McDonald’s outlets.

What makes a good teacher

Teachers play a crucial role in the continues growth of society. The goal of every teacher is to pass his/her teachings to his/her students for their personal benefit. As a student I was assigned the task of analyzing and defining the differences of a teacher and a good one, comparing the virtues of a good teacher with many others things, and making clear what a good teacher is not. In order to understand what a good teacher is, first we need to analyze what is a teacher. A teacher is an individual who can be either male or female. A teacher is an adult who has mental ability. Teachers are individuals who have educated and prepared themselves such as going through a university degree, plus two years teachers college. Now, who is a great teacher? Being a good teacher does not ensure his or her to be a good one. Good teachers need to be wise people with enough experience and knowledge. Also, good teachers are patients and humorous with the main purpose that their teachings are easily understood by their students. Good teachers are sociable individuals who can interact with all their students in order to understand and respect their students` opinion. Good teachers could be compared with many things in this world. Good teachers are physiologists, as they are able to deduce their students’ problems. Good teachers are similar to parents given that they play a role model for students to become very successful in their future life. Good teachers are a great source of knowledge and experience. Good teachers are as coaches given that they encourage their students to achieve what they really want. In addition, good teachers can be considered as an encyclopedia because they have a broad knowledge, which they transmit to their students. By defining, what a good teacher is not, improve the understanding of a good teacher. Good teachers are not individuals who are only interested in making money because their commitment is to play an important role model for students. Good teachers are not magician; they cannot do miracles to incentive the students to study as the result depends on how eager the students have to meet their goals. In addition, good teachers are not robots because they also can get tired and have problems as students do. In conclusion, there are many differences between a teacher and a good one. However, the major task of a good teacher is to guide their students through the right path in order to make the students become successful in their future life. What Makes a Good Teacher What Makes a Good teacher? To teach or not to teach that is the question Teacher is not only a person, who should teach, it is a person who must lead the pupil on the way to the knowledge. Teacher shows the world and explain the laws of this world. He is often a tutor, a preceptor, a person that you respect. This profession is very hard and important. But, what makes a good teacher? There are many things which make a teacher great and they all can`t be defined. However i`ve always considered several of them essential.In my opinion a good teacher is someonewho first of all creates interest in studying,doesn`t underestimate the children,has equal expectations of siccess from everyone and last but not least likes his job. A good teavher always has a sense of purpose. He chooses very carefully the teaching programme and adjusts it to the needs of his students. Children always come first and that`s why the decision he makes are based on how they will affect them. He shares experience with other teachers and thus is always learning new things.It is very important for a teacher to be a good communicator. my mind, teacher is at first a man, a person and if he is a difficult person with inner problems, with bad character – he can’t be really good teacher because teacher works with people, not with machines. He should know how to socialize, how to help others. Good teacher must understand their pupils, their feelings. Teacher’s purpose is giving knowledge, but people don’t take knowledge easily, they want to convince themselves in necessity and importance of this information.Good teacher can make so that pupils let pass the studies throw their hearts. Most of all, it is very important for teacher to love his subject. His mood, opinion irrationally hands on his pupils. If person love something – his feelings, his example will be better than any words. So, what makes a good teacher? I think, a good teacher is a vocation, a gift of God bec ause sometimes a person have excellent qualities, wonderful character, loves his subject, but we can’t say that he is really good teacher. To be a good teacher is a talent and a miracle. What Makes a Good Teacher A person may be blessed with natural abilities, but through human nature, we desire personal connection and motivation. The movie Stand and Deliver told the story of a high school class that fell short of academic requirements. Jamie Escalante was a new, influential teacher who made an impact on inner city students by simply demonstrating interest and faith. Jamie showed attention to the students outside of the classroom and did not give them the opportunity to make excuses. Mr. Escalante cleverly manipulated his students into success with various techniques, a majority of which would help me thrive in math class.Angel was a student, first introduced as a trouble maker. As the audience realizes that there is more to Angel than his tough guy routine, so does Mr. Escalante. He is a compassionate grandson, taking care of his sickly grandmother. Angel showed up to Mr. Escalante’s house on Christmas Eve with his grandma, and although it was an act of resentment, they were welcomed in for dinner. Personally, when I was younger my grandpa was very sick; I would spend nights in the hospital with him and my family unable to complete homework assignments which ultimately set me behind in classes.However, like Mr. Escalante, my teachers understood that my life did not always revolve around the classroom. I had other responsibilities and worries on my mind. However, Mr. Escalante also did not allow his students to let their worried minds become excuses for their lack of success or sloppy work ethic. All Mr. Escalante asked of his students was ‘ganas’ or the desire to learn. He held them to a higher standard than they ever had been before which motivates me well because it gives me something to prove.I want to join the Navy after high school and a friend of my sister’s said that I do not have the desire for it. After I heard that, I became more encouraged than ever. Also no excuses were tolerated in his classroom which I believe is a fantastic tac tic. Students know exactly how to manipulate teachers, whether there is a sincere justification for something or just an excuse. When Angel is late to class, Mr. Escalante kicks him out, since his tardiness shows that Angel does not see the value in learning.Later, Angel again comes into class tardy, this time after being with his grandmother in the hospital. Although Angel’s excuse is genuine, Mr. Escalante does not accept it and asks Angel to leave. It is this attitude that inspires the students to attend class regularly and on time. In life, excuses get you nowhere except back where you started. Teachers who do not accept excuses are the ones who care about you enough to get you ready for the real world. Mr. Escalante was very successful. He started with a class of students who did not care about grades or math at all.However, through his tactics, within a few years, those same students passed the advanced placement calculus final. Mr. Brechlin, I will do better in math an d school in general if I am forced to be all I can be just as Jamie’s students were. I am a slacker†¦ and need to be pushed! Like Angel I do have personal and family issues and need help and guidance at times. However, as Mr. Escalante put it, when I’m getting hired for a job they will not want to hear my problems. In the real world, there are no such things as excuses, only my work ethic and ability to succeed.

Developmental Delays and Trauma Essay

Developmental delays is when your child does not reach their developmental milestones at the projected times. It is an ongoing major or minor delay in the course of development. Developmental delays can have many different causes. There are many types of Developmental delays in children; they include problems with language or speech, vision, movement (motor skills), social, emotional and cognitive skills (van der Kolk, 1995). Developmental delays are easily distinguished if you pay close attention to the development and milestone periods contained by children; for example if you notice a child having a low attention span, they can’t stay still, they’re highly active and energetic all the time, that’s perhaps due to attention-deficit hyperactivity disorder, known as ADHD. There are so many different things that can cause developmental delays and children aren’t always born with developmental delays. Although, developmental delays can be genetic or born with , there are times when trauma at different ages can cause developmental delays such as a child being abused and suffering brain trauma, concussion, which could cause memory lost. Or there could be an accident and a child or adult undergo serious injuries to the spine, eyes, etc. Spinal injuries can be of damage to you motor skills. Spinal injuries or brain injuries if serious can lead to you basically having to start over as if you were a baby learning to walk, read, jump, or talk. The Shaken baby syndrome also can be a trauma that can cause brain injuries. There are numerous of things that have major components to play in developmental delays. Trauma definitely plays a one of those major parts in developmental delays. There are a number of Trauma’s that can cause development delays. It doesn’t always have to be abuse or accidents. Trauma can be caused by divorce, neglect, bullying, sports injuries, or even bad relationship breaks up. These types of trauma are called psychological trauma. Psychological  traumas effects are mostly emotional and it isn’t always permanent. Psychological trauma causes anger, irritability; mood swings, guilt, hopeless, anxiety, withdrawing, and disconnected to name a few. For divorce, Feldman says (2011) ch ildren and adults may experience depression, and disturbances and phobias and these things last from 6 months up until 2 years. Feldman states children whose parents are divorcing blames themselves for the breakup. He also states, evidence shows that twice as many children of divorced parents enter psychological counseling (Feldman, 2011). Children under the age 18 suffer 40% more anxiety as a result of divorce (van der Kolk, 1995). About 10-15 percent of students are bullied one time or the other (Feldman, 2011) and almost 85% of girls and 80% of boys are being bullied (Feldman, 2011). Those who are bullied lack social skills, cry easy (Feldman, 2011), and they experience depression, stress, anger, etc. Prayer and meditation help brain activity. Mediation to the mind is like an aerobic exercise to the body. Studies have also shown that meditation promotes mindfulness, decreased stress, insomnia, illnesses, depression, anxiety and panic. Spiritual connection brings comfort and healing to trauma. Researchers are learning the parts of the brain that are responsible for the spiritual thoughts, prayer and meditation. In one of our presentations his week, Dr. Jeanne Brooks stated that we have a spir itual part in our brain (2014). There are good and bad parts to everyone, I believe the good part is the spiritual part in everyone. For example, we’ve all seen cartoons in which there was a devil on one shoulder and an angel on the other. The shoulder with the angel is the part of us, the part of our brain or conscious that’s spiritual. References Brooks, Jeanne Dr. â€Å"Divorce and Stress† video presentation. LUO (2014) Feldman, R.S. (2014). Development across the Life Span (7th edition) Namka,, L. (2001). Children who are traumatized by bullying. alk, Trust and Feel Therapeutics., p. 18. Van Der Kolk, an der Kolk, B. (1995). developmental trauma disorder : Towards a rational diagnosis for children with complex trauma histories.

Music and Color which ones positively affect men and women, which ones Essay

Music and Color which ones positively affect men and women, which ones negatively affect them - Essay Example However, there are currently no books on this topic, and educators and parents are often forced to rely on news reports and websites that sometimes present the information in a biased and sketchy fashion. As a result, there is a great deal of confusion about the benefits of music listening and instruction. Music has been touted to cure backache, asthma, obesity, writer’s block, alcoholism, schizophrenia, prejudice, heart disease, drug addiction, headaches, and AIDS. Claims have been made that music makes bread rise better and improves the taste of beer. In Florida it’s now the law that all childcare facilities receiving state aid include at least half an hour of music exposure every day. The governors of both Tennessee and Georgia give newborns in their states classical music CDs. An Indiana obstetrician even markets a device that administers music in-utero. Clearly, most of these claims are unsubstantiated, despite the (usually) good intentions of their supporters. Unf ortunately, the exaggerated claims that have often accompanied the research have caused some academicians to be skeptical of any research suggesting the benefits of music. Although music is important in its own right, a book that systematically reviews what is known about the power of music to influence non-musical domains is necessary for scientists and laypeople alike’.(Sabattical , 2 ) ‘Color conveys meanings in two primary ways - natural associations and psychological symbolism. No, it’s not mind control. The truth of the matter is that people are comfortable when colors remind them of similar things. For example, a soft shade of blue triggers associations with the sky and a psychological sense of calm. Successful design requires an awareness of how and why colors communicate meaning. The source of these meanings can be quite conspicuous, such as those found in nature — red is the color of blazing fire

The Relationship between Induced Abortions Article

The Relationship between Induced Abortions - Article Example This could mean that a person who started out as ertophilic could turn into erotophobic during the process of the abortion. After an exhaustive literature review the authors "question" for their research was to find out whether there was a correlation between pregnancy and abortion and increased sexual problems and to find out whether a group of women who have chosen abortion are already thinking negatively about the abortion before they have it as opposed to "non-pregnant comparison group". The methods employed and detailed explanation of how they conducted the study. The researchers used two groups. The termination of pregnancy group (TOP) showed 98 women who were present in an NHS Clinic/hospital for the first trimester medical (34%) or a surgical (68%) abortion. A two-month follow-up was conducted with 44 women (46%). The demographics of the group showed that 91% were Caucasian and they ranged between 16 and 41 years old. About 33% had some college, 79% were currently in a relationship and 60% had no children. Both groups were given several questionnaires that provided information. They received the Sexual Opinion Survey (SOS) and the Golombok Rust Inventory of Sexual Satisfaction (GRISS) and each was to assess a different aspect of their theories. The women were asked to answer the GRISS three times: once to understand sexual problems, again two months into their pregnancy (they did this retrospectively) and a final time to test sexual problems that they encountered during the time in which they were pregnant. Seven weeks after their abortion they were sent a follow-up questionnaire through the mail. The questionnaire was timed seven weeks out to make sure women had already passed through their discomfort and were again having sexual relations. This post questionnaire was used to ask about changes in their relationship; they were also asked to complete the GRISS and the SOS again to ask about sexual problems that they may have experienced two months after the abortion.  Ã‚  

Twelve Characteristics of Effective Early Childhood Teachers Essay

Twelve Characteristics of Effective Early Childhood Teachers - Essay Example Good teachers strive to read and learn the latest research and instrumental techniques so as to skill their student. They will also be well trained with appropriate developmental characteristics of the age group. Nevertheless, they should develop the love of learning among the students by building on their natural curiosity. They should understand the role of play in young children. They thus provide the necessary equipment (Colker, 2008). It is also essential for them to come up with designs that enable students to develop both large and small motor functions. Good early childhood teachers will use nonbias tools of assessment to monitor the performance of their students. It is tremendously beneficial for them to have excellent classroom management skills with proper rules so as to enhance discipline among students. Lastly they should create an environment whereby students are able to appreciate each other’s differences (Colker,

Comparison of Two Recovery Room Warming Methods for Hypothermla Coursework

Comparison of Two Recovery Room Warming Methods for Hypothermla Patlents Who Had Undergone Spinal Surgery - Coursework Example Highlighting the differences and the essence of the research results, findings and conclusions can also be considered to play a major role in a research article analysis. With the above information in hand, this paper will analyze the research article namely The Comparison of Two Recovery Room Warming methods for Hypothermia Patients Who Had Undergone Spinal Surgery. The key element of this research article concerns the concept of homeostasis, whereby the human body is able to maintain a relative equilibrium state under fluctuating environmental (temperature) conditions. Thus, the human body is able to regulate the body temperature with the assistance of the hypothalamus. This research article also makes a detailed study on the time needed to reach the specified temperature by the hypothermia patients who have undergone spinal surgery. The efficiency of two major warming methods such as the warm cotton blankets and a radiant warmer for the patients in a post anesthetic care unit is c ompared in the article. The analysis of this research article can be centered on the evaluation of the validity of the results which in turn depends on the research plan measurement, data collection and analysis process. Thus, the research plan measurement can be further classified into fragments such as cases, observations, variables and unit of analysis. In this article, the cases that are taken for research were of the hypothermia patients who had undergone the spinal surgery. These patients were kept under observation with respect to their body temperatures. The variables implemented in this case would be the different types of warming methods. Hence, the research had a concrete plan on which the data collection, analysis and interpretation of the results were built up effectively. The other vital area to be focused would be the data collection process. â€Å"This study was conducted according to a quasi-experimental design. Data was collected from a medical referral centre in northern Taiwan.† (Yang, Lee, Chu, Su, Ho and Fan 2). Thus, the data collection process included selecting the study samples from patient group in Taiwan, who are older than eighteen years, also who were under general anesthesia during the course of the surgery as well as those who were conscious and able to communicate. Above all, the other parameters that were included in the process of data collection were selecting the patients who had had no fever for seventy two hours before carrying out the study, had an operation time of about three to six hours, and patients who had a tympanic temperature of about 34 to 35 degrees Celsius. Thus, based on the above criteria, the sample data were collected and the effectiveness of the warming devices on these patients was studied. After the completion of the data collection process, the next step would be data analysis and arriving at conclusions and results. The basic framework of the data analysis would be to measure the efficiency of the warming equipments with respect to the rewarming time required for the patients who had undergone the spinal surgery. â€Å"The data were analyzed using SPSS version 17 software for Windows and significance level was set at p

Russia Essay Example | Topics and Well Written Essays - 500 words - 2

Russia - Essay Example The site is beloved by Russians and visitors around the world; hence, making it a valuable example of a cultural landscape (Moscow.Info). From the observations, the Cathedral Square represents a rich cultural history of the Russian Republic. It symbolizes the rule of Tsarist. It was constructed by Ivan the Great. Additionally, the area acts as a center of power, coronation, and an assembly for the nobles, as well as different ceremonial rituals. The Kremlin wall is a vast enclosure of the buildings contained within the Kremlin. The wall creates an impression of a small city. The Grand Kremlin Palace hosts cultural performances from the Kremlin Ballet. The buildings in the Moscow Kremlin link the country to its legendary past (Geographia). The towers and domes of the St. Basil Cathedral have an important cultural history. At first, eight domes were constructed, representing the eight attacks on Kazan. The different colors and shapes of the cathedral are unique and unmatched anywhere in the world; thus, making it a cultural heritage of the Russian people. The bronze statue commemorates Dmitry Pozharsky and Kuzma Minin, who led a volunteer army against the Polish invasion in the 16th and 17th Century. From the above accounts, it is evident the St. Basil’s Cathedral is one of the cultural landscapes of Russia (Sacred-Destinations) The apartment blocks are unique; hence, they are part of the cultural landscape of the Russian Republic. The construction of these apartment blocks epitomizes the communal living advocated by the Soviet ideology (Obrazkova) The mosque is located in downtown St. Petersburg, and has a cultural and historical meaning to the Muslim community of Russia. The construction of the structure began in 1910; hence, the mosque has been in existence for more than 100 years (Admin). Cultural landscapes are of great importance to any country. They represent the identity of a people and the manner in which humankind co-existed in a given

American history Research Paper Example | Topics and Well Written Essays - 250 words

American history - Research Paper Example s abolished more than one hundred and fifty years ago, the legacy of slavery continues to have important ramifications on the lives of African-Americans today. Accordingly, African-Americans have lower-life expectancies than their white counterparts and the insidious legacy of slavery has many ramifications. Seeking to understand the paradox of American liberty and a shameful legacy of slavery, Edmund S. Morgan does an excellent job highlighting an oft-ignored aspect of American history with ramifications on the lives of Americans today (see Williams and Tucker 2000; Morgan 3-13 ). Seeking to highlight the American history of slavery, Edmund S. Morgan demonstrates that while the United States evolved during the concept of freedom and liberty from colonial Britain, to a large extent â€Å"Americans bought their independence with slave labor† (3). Many of the founders – paternally referred to as the Fathers of Independence – were slaveholders themselves and their concept of freedom pertained only to a certain class of people. Most often, their notions of freedom were limited and excluded non-whites, women and those without property. Thus, this concept of freedom, so engrained in the American psyche and so much a part of the American historical narrative, was a limited sort of freedom which was inherently exclusionary and certainly not universal. Furthermore, when Thomas Jefferson, the world-renowned spokesperson for American freedom and liberty, discussed the abolition of slavery, â€Å"he found it inconceivable that the freed slaves should be allowed to remain in the country..† (8). Exploring racial discrimination in both England and the American colonies during the late period of British rule in the Americas, Morgan argues that the dual and polarizing concepts of slavery and freedom were both â€Å"intertwined and interdependent, the rights of Englishmen supported on the wrongs of Africans...The American Revolution only made the contradictions more

Do we train low-income students, and so limit their potential Essay

Do we train low-income students, and so limit their potential - Essay Example The main part played by engagement cannot be over-emphasized for the students whose achievements have been hurdled by limited experiences, resources as well as support and the conventional instructional practices have been identified as the main causes of increased risk of delays in students. Critical dissimilarities in achievement outcomes also favor the engaged students more than their disengaged counterparts who have the same level of ability. As the number of low-income students continues to increase, the number of low income students who complete their college their college education is significantly lower than those who come from high income families. â€Å"One explanation is simply that the rich have clearly gotten richer† (DeParle) Even though there are numerous challenges faced by the students who hail from low income families in regard to enrolment to colleges, the financial challenges they face can be mitigated through creation of policies that will reduce the costs these students have to incur. Decreased costs may reverse the fact that the low-income students are averse to debts and will try their best to avoid borrowing to go to college. High loans as well as the abhorrence to amass debts develop consequences that affect increased production in education. The students who have large loans have lower levels of persistence as compared with the ones who have considerably lower loans or no financial aid. Even the students who attend the less expensive community colleges are affected by the same phenomenon, as those who have loans are not as persistent in their education when compared to those who do not have loans. The low-income students also experience â€Å"under-matching, choosing a close or familiar sch ool instead of the best they can attend† (DeParle). When the needs of the students are not meant through

Subprime Mortgage Crisis Research Paper Example | Topics and Well Written Essays - 1750 words

Subprime Mortgage Crisis - Research Paper Example These numerous theories, which have come up to explain the root cause of the subprime crisis. Numerous experts and economists believe that a combination of factors resulted to the crisis (Lynnley 13). This study intends to examine the housing bubble as a major cause of the subprime crisis. Housing Bubble This study reveals that the present mortgage crisis started with the bursting of the U.S. housing bubble, which commenced in early 2001 and ascended to its peak in the year 2005. Essentially, a housing bubble can be defined as an economic bubble whose occurrence in both the local and international platforms in real markets id characterized by almost similar features. The housing bubble is defined by express rise in the valuations of real assets until untenable levels related to income and affiliated affordability indicators are reached (Lynnley 11). This situation leads to the decrease of home prices and debts related to mortgages, which are higher compared to the value of the assets . It is imperative to note that the housing bubble was discovered at the aftermath of the market correction that happened in the U.S in 2006. In 2007, Alan Greenspan, the former Chairman of the Federal Reserve Board indicated that, United States has been having a bubble in the housing sector (Muolo and Padilla 3-7). This came upon the realization that the house prices appeared to be overwhelmingly overvalued. The sentiments were echoed by the Richard Syron, the CEO Freddie Mac and concurred with the Yale University economist Robert Shiller who warned that the necessary correction of the bubble would be done in many years to come wit trillions of dollars being lost. This situation would lead to a double-digit decline in the home values. The housing bubble in relation to the historically low interest rates This study reveals that the majority of the experts and economists believe that the housing bubble in the United States of American was partially caused by the historical low intere st rates. It is imperative to note that the Federal Reserve Board had reduced the short-term interest rates by 5.5% (from 6.5% to as low as 1 %). This was a response of the collapse of the dot-com bubble (Muolo and Padilla 3-7). This happened in early the year 2000 and was followed by the ensuing recession in 2001; however, this response significantly endangered the housing bubble through the decrease in real long-term interest rates. It is essential to note that, the US mortgages rates are set in relation to Treasury bond yields of 10 years. These rates are influenced by the Federal funds rates. This study establishes that the Federal Reserve Board acknowledged the relevance of the connection amid lower interests’ rates, increased liquidity and the higher home values in relation to the general status of the economy. On the other hand, Greenspan disputes the claim that he engineered the housing bubble. Greenspan asserts that the Fed’s decline in rates contributed to th e inflation of the bubble. In 2007, Greenspan argued that, the housing bubble was not in any way related or linked to the Fed’s policy on interest rates, however, Greenspan pointed out on the international surplus in savings, which pushed down the interest rates

Religion and Grand Zoroastrian Nation Essay Example for Free

Religion and Grand Zoroastrian Nation Essay It fills my heart with joy unspeakable to rise in response to the warm and cordial welcome which you have given us. I thank you in the name of the most ancient order of monks in the world; I thank you in the name of the mother of religions; and I thank you in the name of the millions and millions of Hindu people of all classes and sects. My thanks, also to some of the speakers on this platform who, referring to the delegates from the Orient, have told you that these men from far-off nations may well claim the honour of bearing to different lands the idea of toleration. I am proud to belong to a religion which has taught the world both tolerance and universal acceptance. We believe not only in universal toleration, but we accept all religions as true. I am proud to belong to a nation, which has sheltered the persecuted, and the refugees of all religion and all nations of the earth. I am proud to tell you that we have gathered in our bosom the purest remnant of the Israelites, who came to southern India and took refuge with us in the very year in which their holy temple was shattered to pieces by Roman tyranny. I am proud to belong to the religion, which has sheltered and is still fostering the remnant of the grand Zoroastrian nation. I will quote to you, brethren, a few lines from a hymn which I remember to have repeated from my earliest boyhood, which is every day repeated by millions of human beings: ‘As the different streams having their sources in different places all mingle their water in the sea, so, O Lord, the different paths which men take through different tendencies various though they appear, crooked or straight, all lead to Thee’. Quoted from Siva Mahimnah Stotram 7. The present convention, which is one of the most august assemblies ever held, is in itself a vindication a declaration to the world of the wonderful doctrine preached in the Gita: ‘Whosoever comes to Me, through whatsoever form I reach him; all men are struggling through paths which in the end lead to Me’. Quoted from Geeta 4:11. Sectarianism, bigotry, and its horrible descendant, fanaticism, have long possessed this beautiful earth. They have filled the earth with violence, drenched it often and often with human blood, destroyed civilization, and sent whole nations to despair. Had it not been for these horrible demons, human society would be far more advanced  than it is now. But their time is come; and I fervently hope that the bell that tolled this morning in honour of this convention may be the death-knell of all fanaticism, of all persecutions with the sword or with the pen, and of all uncharitable feelings between persons wend ing their way to the same goal.

Analysing and Applying Business Process Reengineering

Analysing and Applying Business Process Reengineering In the first part of this assignment the meaning of business process reengineering (BPR) is analysed. In more details, it is outlined how business processes might be reengineered to improve company or organizational performance. The themes covered are: The importance of BPR in organizations The objectives of implementing BPR The specific techniques that can be used (like process mapping) The required training The possible problems in implementation (like resistance) As about the second part, a critical evaluation is made concerning the statement of McCabe (2004: 851): BPR does not challenge hierarchical authority, but instead attempts to reconfigure authority and power relations so as to obscure them through the language of consensus. In this section of the assignment it is critically evaluated the proposition that BPR in fact does very little to question the fundamental tenets of hierarchical control and in several important respects simply reinforces them. ANALYSIS OF PART 1. The term of BPR Today the business world is characterized by unpredictable changes, under the global competition and the customers demands. To be successful in such an environment, a firm must operate with speed, flexibility, low overheads and a clearly defined customer focus. The term business process reengineering (BPR) refers to an approach that is used by organizations seeking improvements in their business performance (Anonymous, 2007). The importance of BPR There is a series of driving forces, which trigger companies to undertake reengineering projects. These are customers, competition, change, cost, technology and shareholders and they lead to a requirement of new organizational structures and an alteration of the traditional way of doing business. Organizations consider BPR as an important tool of organizational improvement, as it helps them achieve the radical change necessary for todays volatile business environment. Additionally, BPR stresses the importance of linkages within an organisation. Though its structure integrated processes are generated concerning the nature of peoples jobs and how people are grouped and organized in the working environment. What is more, through BPR peoples jobs become multidimensional instead of narrow and traditional task orientation. When the concept of process is promoted in the BPR, cross boundary teamwork is incorporated and process shifts the goal focus on performance measurement and managerial r esponsibility from a function or responsibility center to an activity derivative process concept. So, BPR defines process teams as an important element in the business environment where work becomes multidimensional, substantive and more rewarding (Anonymous, 2007). It can be concluded that the importance of BPR is found at the fact that it is a dynamic tool for improving operations. BPR provides a process view of the organisation and a way of improving processes. Using this approach a company will be organized based on processes. As a result, processes are simplified, flows are improved and non value added work is eliminated (Schroeder, 2000). BPR is a complete life cycle approach. This provides the scope for problem identification and also solutions to implement the successful business operations. BPR can significantly improve cost, quality, service and speed simultaneously, so important results are provided to customers (Thyagarajan and Khatibi, 2004). It can be supported that organisations should focus on BPR for three key reasons: Firstly, there is much to be gained by improving business process. Secondly, business processes can be controlled and finally business processes are comparatively more important than production processes (Anonymous, 2007). The objectives of BPR BPR is a fundamental element in improving business performance and profitability. The BPR objectives refer to: improved operational performance, by closing performance gaps improved competencies, by closing skill and competency gaps reduced costs and manpower savings, by application of management analysis tools and techniques improved customer services or employee quality of life increased customer satisfaction increased productivity in the workplace continuous improvement of services quality delivered quality goods at competitive prices in a timely fashion (Anonymous, 2010a). The technical tools used in BPR There are different improvement techniques that can be adopted to analyse the BPR. These techniques enable the organization to understand, simplify and improve processes that already exist, not only to meet, but also to exceed the expectations of customers and provide a coordinating discipline for overall performance improvement (Anonymous, 2007). The selection of technical tools for BPR depends upon: (i) the nature of decision areas, (ii) the nature of data to be analysed, and (iii) the background of users. Table 1. The specific techniques that can be used in BPR Areas to be reengineered Techniques used in BPR BPR strategies Decision support system and Knowledge-based models Business process system design Analytical models such as queuing and simulations models Project management PERT/CPM and Flow Charts Reengineering business process Activity-based analysis and workflow model including flow chart Design of information system for reengineering business process Object-oriented models and programming Understanding of the business process system IDEF Models, EFQM Models, Petri-Net Models (Gunasekaran and Kobu, 2002). Process Mapping is a technique known as Process Charting or Flow Charting and is one of the oldest, simplest and most valuable techniques for streamlining work. It is one of the fastest ways to lower errors, increase productivity and affect customer service. It generally follows these steps: Choose a process. Assemble a team. Map out the way work is currently done. Identify problem areas. Brainstorm solutions. Evaluate action steps. Assign responsibilities. Create a master plan. Follow through. (Anonymous, 2010b). Process Mapping is an important tool in examining work flow and customer supplier relationships, which is the foundation for appropriate improvements. Additionally, it is a cost effective training tool for everyone interesting in increasing the efficiency of their organization and improving communication. (Damelio, 1996). Many organizations use this technique as a part of their reengineering projects, as it provides a variety of benefits (figure 1). Figure 1. The main benefits of implementing process mapping technique (Image available at the website http://www.google.gr, accessed 8-10-2010) The BPR training Implementing successfully BPR in an organisations environment is not an easy task, as the appeared changes require changes in attitudes and deep involvement of workforce both in individual and team level. As a result, the fact that a major aspect of BPR is human factor, it makes obvious that appropriate training is required in order to implement successfully BPR in the business environment. Companies should ensure that their employees are suitably motivated and the technology required for training is available in implementing BPR. Training is one of the most frequently used approaches to changing the organisations mindset. A company might offer the suitable training programs so as to effectively implement BPR processes (Daft, 2006) According to White (2010) business process reengineering education and training can come in a variety of ways, including: Learning more about process design at a graduate level. Using online continuing education options for further education. Attending seminars that cover various aspects of business process reengineering. The possible problems in BPR implementation Various radical changes occur when BPR takes place. Hammer and Champy (1993, cited in Anonymous, 2007) have listed the various kinds of changes that occur when a company re-engineers its business process. A shift from functional departments to process teams Job change A reversal of the power relationship: from superordinate to subordinate empowerment . Today markets are characterized by a high flow of information and companies face competitive business environments. Under this reality, organizations must follow effective strategies concerning change management (Robbins, 2001). BPR has to do with improving company or organizational performance, so its implementation requires the changes mentioned above often in a rapid way of implementation in attitudes and deep involvement of workforce both in individual and team level. These changes often refer to redefinition of charts structure and/ or redesign of the workforces roles and responsibilities. The new situation can bring resistance to change, so managers should examine carefully the way BPR implementation will take place. Managers should support understanding and trust concerning the new situation and minimize uncertainty within the workplace. The suggestions for dealing with the possible resistance to change are the following: Determining the goals of BPR implementation. Establishing a clear view about the changes that will occur in the workplace. Applying a direct communication method between managers and employees Checking the procedures of re-engineering, so as to deal with possible problems and find solutions. Focusing on performance measures and compensation shifts Enhancing customer focus as about value change Showing an appropriate management behaviour, through control and supervision Under these suggestions the changes in the business process, lob and structures, management and measurement systems, values and beliefs will result in a flatter organizational structure. As a consequence all the aspects (people, jobs, managers and values) are linked together and the organization will become more responsive in BPR implementation (Anonymous, 2007). ANALYSIS OF PART 2. In this section it will be critically evaluated the statement of McCabe (2004: 851): BPR does not challenge hierarchical authority, but instead attempts to reconfigure authority and power relations so as to obscure them through the language of consensus. In order to make this evaluation, it is essential to introduce the issue of hierarchical authority in an organizations environment. Hierarchical structures are present in most organizations today. Smaller organizations may have only two levels, while larger ones may have a vast number of levels. These structures are used as a method of communications and as the lines of authority. In an organizational environment, the hierarchy mainly apart of a singular/group of power at the top with subsequent levels of power beneath them. Members of such structures chiefly communicate with their immediate superior and with their immediate subordinates. Hierarchical authority structures are providing the opportunity for greater decision-making width for individuals and more flexible definitions of job activities. This is a challenge to existing organizational forms (Zhao, Rosson and Purao, 2007). In a hierarchical organisation employees are ranked at various levels within the organisation, each level is one above the other. At each stage in the chain, one person has a number of workers directly under them, within their span of control. A tall hierarchical organisation has many levels and a flat hierarchical organisation will only have a few (Anonymous, 2010d). At figure 2 a traditional hierarchy is given. Figure 2. A traditional hierarchy diagram (Hierarchical Organisation, available at the website http://www.learnmanagement2.com, accessed 18-10-2010) CHIEF EXECUTIVE MANAGER MANAGER MANAGER ASSISTANT MANAGER ASSISTANT MANAGER ASSISTANT MANAGER STAFF STAFF STAFF STAFF STAFF STAFF STAFF STAFF STAFF It is obvious that hierarchies within control systems are a clear need for business environments. Without some form of hierarchy, a low level of control can create numerous problems in an organization. There ate two kinds of control systems: flat and hierarchical. Hierarchical architectures have a more indirect coupling of perceptions to actions through a hierarchical control structure. Both kinds of control systems have benefits, but hierarchical structure can support faster learning and a better way to deal with resistance to change (Digney, 1998) Control is a fundamental managerial function. It is the process of regulating organizational activities so that actual performance conforms to expected organizational standards and goals and ensures that necessary corrective action is taken. In fact, control is ensuring work accomplishment according to plans. It is a process of ensuring that activities are producing desired results. We can support that control is an executive function involving three elements, i.e., standards, evaluative and corrective action. BPR is the latest wave in a series of management initiatives to increase managerial control (Gupta, 2010). According to the issues covered in the analysis of part one of this assignment, business process reengineering is proved to be a revolutionary, radical change approach to improving organizational performance through transformation. BPR methodologies aim for a flatter organizational structure, promoting the development of empowered process workers who are encouraged to use information technology in radically new ways to carry out business operations. In BPR approaches, empowerment is inflicted by leadership changing worker values and through the use of information technologies enables managerial control. Empowerment through BPR does not necessarily release control but does change the way control is exercised. Authority is still enforced through hierarchical control of culture. The reengineering approach polishes the management of power relations, when attempts are made to change traditional power structures and everyday power relations through the flattening of the hierarchy (Sayer an d Harvey, 1997). The introduction of reengineering introduces a new relationship of power in the form of a discipline which the reengineering sustains through discourse control. In this new situation any discipline comes with its structures, its hierarchies, its inspections, exercises and methods of training and conditioning (Foucault, 1980, p. 158). BPR is an approach that supports transformation with the notion of producing the flatter organization. Hierarchy and control are still promoted and within BPR, the emphasis lies on changing the formal patterns and using mechanisms of control to change the informal (Sayer and Harvey, 1997). BPR is a strong tool of managerial control. Controlling is the fourth function of management process (the other functions are planning, organizing and leading). Through BPR managers can identify whether the organization is on target towards its goals and can make better corrections if necessary. In BPR, information technology is generally considered as playing a role as enabler of new forms of organizing and collaborating. New information technology can help managers provide needed organizational control without strict top down constraints. A representative example is that of Cisco Systems: By using information technology to coordinate and monitor several aspects of operations, the company keeps tabs on employee and organizational performance without maintaining daily authoritarian control over workers. Cisco employees have amazing freedom to make decision and take actions, but they also know that top managers keep a close eye on what is going on throughout the company (Daft, 2006). Most businesses try to take advantage of BPR concerning dealing with the fundamental tenets of hierarchical control. BPR assumes radical redesign of business processes. Many processes simply can not be further improved in small steps and require a complete redesign in order to improve them in a major way. Hierarchical control is a fundamental element in this effort and managers who desire to organize around outcomes, have people processed their own information, put the decision point where the work is performed and build control into the process, should support the view that BPR can reinforce the fundamental tenets of hierarchical control. BPR is a management system of forced, speedy culture change, highly linked to hierarchical control. In fact it does very little to question the fundamental tenets of hierarchical control and in several important respects simply reinforces them. CONCLUSIONS Business Process Reengineering includes changes concerning both structures and procedures defined in a business environment. Human, organizational, technological dimensions that characterize an organization can change through BPR. Using this approach, organizations can seek improvements in their business performance. As it was analysed at the first part of this assignment, organizations consider BPR as an important tool of organizational improvement, as it helps them achieve the radical change necessary for todays volatile business environment. Additionally, BPR stresses the importance of linkages within an organization. What is more, through BPR peoples jobs become multidimensional instead of narrow and traditional task orientation. In result, the importance of BPR is found at the fact that it is a dynamic tool for improving operations. BPR is a fundamental element in improving business performance and profitability. The main BPR objectives refer to improved operational performance, improved competencies, reduced costs and manpower savings, improved customer services or employee quality of life, increased customer satisfaction, increased productivity in the workplace, continuous improvement of services quality and delivered quality goods at competitive prices in a timely fashion. There are different improvement techniques that can be adopted to analyse the BPR. Among them, Process Mapping is a technique known as Process Charting or Flow Charting and is one of the oldest, simplest and most valuable techniques for streamlining work. It is a cost effective training tool for everyone interesting in increasing the efficiency of their organization and improving communication and is highly preferred by enterprises today. Implementing successfully BPR in an organisations environment is not an easy task, as a major aspect of BPR is human factor. So, companies should ensure that their employees are suitably motivated and the technology required for training is available in implementing BPR. Various radical changes occur when BPR takes place, so managers should carefully examine the strategies in change management so as to achieve the best efficiency and deal appropriately with the possible resistance to change that BPR will bring. The second part included a critical evaluation of the statement of McCabe (2004: 851): BPR does not challenge hierarchical authority, but instead attempts to reconfigure authority and power relations so as to obscure them through the language of consensus. According to the relevant analysis, within control systems are a clear need for business environments. Without some form of hierarchy, a low level of control can create numerous problems in an organization. Hierarchical structure can support faster learning and a better way to deal with resistance to change, so BPR supports the management initiatives to increase managerial control. . In BPR approaches, empowerment is inflicted by leadership changing worker values and through the use of information technologies enables managerial control. Empowerment through BPR does not necessarily release control but does change the way control is exercised. Most businesses should try to take advantage of BPR concerning dealing with the fundamental tenets of hierarchical control. This is because BPR is a management system of forced, speedy culture change, highly linked to hierarchical control. In fact it does very little to question the fundamental tenets of hierarchical control and in several important respects simply reinforces them.

Mobile Ad Hoc Networks (MANETs)

Mobile Ad Hoc Networks (MANETs) Introduction What is Mobile Ad Hoc Network? With rapid development of wireless technology, the Mobile Ad Hoc Network (MANET) has emerged as a new type of wireless network. MANET is a collection of wireless mobile nodes (e.g. laptops) that dynamically function as a network without the use of any existing infrastructure and centralized administration. It is an autonomous system where each node operates not only as an end system but also as a router to forward packets for other nodes. Since the nodes in MANET move around, the wireless links break and re-establish frequently. Furthermore, most of mobile nodes are resource limited in computing capability and battery power and therefore traditional computing content routing protocols are not suitable for MANET. Several ad hoc routing protocols have been proposed for each node acting as router and maintaining routing information. There are many other applications of MANET. For examples, MANET can be used to provide emergency Services when the network is impaired due to the damaging of existing infrastructure [8]. Computer scientists have predicted a world of ubiquitous computing in which computers will be all around us, constantly performing mundane tasks to make our lives a little easier. These ubiquitous computers connect in mobile ad hoc mode and change the environment or react to the change of the environment where they are suited. MANET is also found useful in the so-called sensor dust network to coordinate the activities and reports of a large collection of tiny sensor devices which could offer detailed information about terrain or environmental dangerous conditions. Problem Statement and Motivation Most current ad hoc routing protocols assume that the wireless network is benign and every node in the network strictly follows the routing behavior and is willing to forward packets for other nodes. Most of these protocols cope well with the dynamically changing topology. However, they do not address the problems when misbehavior nodes present in the network.A commonly observed misbehavior is packet dropping. In a practical MANET, most devices have very limited computing and battery power while packet forwarding consumes a lot of such resources. Thus some of the mobile devices would not like to forward the packets for the benefit of others and they drop packets not destined to them. On the other hand, they still make use of other nodes to forward packets that they originate. These misbehaved nodes are very difficult to identify because we cannot tell that whether the packets are dropped intentionally by the misbehaved nodes or dropped due to the node having moved out of transmission range or other link error. Packet drop significantly decreases the network performance.Traditional security mechanisms are generally not suitable for MANET because: The network lacks central infrastructure to apply traditional security mechanism such as access control, authentication and trusted third party. Limited bandwidth, battery lifetime, and computation power prohibits the deployment of complex routing protocols or encryption algorithms. New security models or mechanisms suitable for MANET must be found. Network topologies and memberships are constantly changing. Thus new intrusion detection system and entity recognition mechanisms that are suitable for mobile ad hoc networks must be designed to avoid or mitigate the behavior to the networks. Trust management systems have been recently introduced as a security mechanism in MANET. In a trust management system, a communicating entity collects evidence regarding competence, honesty or security of other network participants with the purpose of making assessment or decisions regarding their trust relationships. Here trust Objective and Sub-tasks means the confidence of an entity on another entity based on the expectation that the other entity will perform a particular action important to the trustor, irrespective of the ability to monitor or control that other entity . For example, a trust-based routing protocol can collect the evidence of nodes misbehaving, form trust values of the nodes and select safest routes based on the trust metrics.Reputations systems are often seen as a derivation of trust management system. In the reputation system, an entity forms its trust on another entity based not only on the selfobserved evidence but also on the second hand information from third parties. One of the influential reputation systems is the DSR protocol. In the trust management system, reputation system and other trust-based systems, route selection is based on the sending nodes prior experience with other nodes in the network. Its opinions about how other entities are honest are constantly changing. Thus, we call the trust manag ement systems and their derivations as dynamic feedback mechanisms. The dynamic feedback mechanisms are usually applied on the current ad hoc routing protocols to rate the trust about other nodes in the network and make routing decisions based on the trust matrix, which is formed according to the evidence collected from previous interactions. By incorporating the dynamic feedback mechanism in the routing protocol, misbehaved nodes are identified and avoided to forward packets. In this way,misbehavior can be mitigated. Objective and Sub-tasks The primary objective of this thesis is to Investigate the state of the art of dynamic feedback mechanisms and protocols analyze, implement and evaluate DSR protocols to see how it improves the network performance and what are the side effects of introducing the mechanism to the mobile ad hoc network. Following tasks must be done to achieve the primary objective. Study the preliminary knowledge that is required to carry out the main tasks. For example, to understand DSR protocol one must have some knowledge of Bayesian analysis; to do performance analysis one must learn the methodologies of conducting performance analysis and processing simulation data. Investigate security issues of mobile ad hoc network and current dynamic feedback mechanisms or protocols that are used to solve or mitigate the issues. Investigate and learn how to use the network simulation tool. There are several popular network simulation tools available and we need to choose the one that best suits our needs. The selected network simulator should be studied so that we can use it as platform to implement protocol and conduct simulations. Analyze and implement the DSR protocol based on Dynamic Source Routing protocol (DSR); evaluate the network performance. Structure of the Report Since we have almost gone through the chapter one, we only briefly present the content of the subsequent chapters in this section. Preliminary Information State of the Art Analysis Design Implementation and Tests Performance Analysis Conclusion and Future Work Preliminary information we have introduced the MANET. This chapter presents other preliminary information and concepts that will be used in other parts of the thesis. Firstly four general modes of routing operations are introduced and compared. The DSR protocol, which is used as underlying routing protocol in the thesis, is explained in detail. Secondly Bayesian estimation and Beta function are explained to pave the way for the analysis of the reputation model of DSR in the chapter 4. Thirdly some techniques regarding simulation and performance analysis are presented. Finally, several popular network simulation tools are discussed and compared. Mobile Ad Hoc Network Routing Protocols Nowadays there are various routing protocols proposed for the MANET. The most popular ones are DSDV (Destination-Sequenced Distance Vector), TORA (Temporally- Ordered Routing Algorithm), DSR (Dynamic Source Routing) and AODV (Ad-hoc On Demand Distance Vector). These routing protocols can be categorized in different routing operation modes. Mode of Routing Operations These two modes concern whether or not nodes in an ad hoc network should keep track of routes to all possible destinations, or instead keep track of only those destinations of immediate interest Proactive protocols store route information even before it is needed. This kind of protocols has advantage that communications with arbitrary destination experience minimal delay. However it also suffers from the disadvantage that additional control traffic is needed to continually update stale route information. This could significantly increase routing overhead especially for the MANET where the links are often broken. Reactive protocols, on the contrary, acquire routing information only when it is actually needed. However, the latency of the communication increases tremendously especially when a node communicates to another at the first time. Source routing vs. Hop-by-hop routing These two modes concern whether the source node decides the route for a packet to be forwarded to the destination or the intermediate nodes are allowed to decide the next hop until the packet arrives at the destination. In the source routing protocols, the source node decides the route and puts the route information in the packet header. All the intermediate nodes forward the packet along the route faithfully. This kind of protocols has advantage that the intermediate nodes are not required to maintain the routing information. But it suffers from the disadvantage that the packet size grows because of source routing information carried in each packet. In the hop-by-hop routing protocols, it is sufficient for the source to know only how to get to the next hop and intermediate nodes find their own next-hops until the destination. In contrast to source routing protocols, hop-by-hop routing protocols do not increase packet size but they requires all the intermediate nodes to maintain rout ing information. Table 2-1 Categories of routing protocols has compared the performance of these four routing protocols . The results show that DSR has best throughput performance (above 95%) at all mobility rates and movement speeds. Thus we will use DSR as basic routing protocol in this thesis. The Dynamic Source Routing Protocol (DSR) John et al. proposed the dynamic source routing protocol (DSR) [1] which is a routing protocol for use in multi-hop wireless ad hoc networks of mobile nodes. DSR is an ondemand protocol, in which route are only discovered when data need to be transmitted to a node where no route has yet been discovered. The advantage of this on-demand routing protocol is that there are not any periodic routing advertisement and reducing the routing overhead. DSR is also a source routing protocol, allowing multiple routes to any destination and allows each sender to select and control the routes used in routing the packets. DSR is composed of the two main mechanisms: Route Discovery and Route Maintenance which are explained below. Route Discovery Route Discovery aims at finding routes from a source node to destination. Figure 2-1 illustrates the procedure of Route Discovery. When a source node S wants to send a data packet to some destination node D, it first searches its route cache to find whether there is a route to D. If there is no route to D, then S will initiate a Route Discovery and send out Route Request message which is propagated to all the nodes within its transmission range. At the mean time, it saves the data packet in its send buffer. The Route Request message contains the addresses of source node and destination node, a unique route request identifier and a route record which records all the intermediate nodes that this route request packet has traveled through. S appends itself to the beginning of the route record when it initiates the message. When a node receives the Route Request message, it compares the destination address in the message with its own address to judge whether itself is the destination node. If it is not, it will append its own address in the route record and propagate the message to other nodes. If the node is the destination node, it will send a Route Reply message to the source node and the message contains the source route record which is accumulated when the Route Request message is forwarded along its way to the destination. When the destination sends the Route Reply, if it uses MAC protocols such as IEEE 802.11 that require a bidirectional link, it just reverse the source route record and use it as route to send Route Reply to the source node. Otherwise it should find the route by searching its route cache or sending out a Route Request which piggybacks the Route Reply for the source node. When the source node receives the Route Reply message, it puts the returned route into its route cache. From t hen on all the packets destined to the same destination will use this route until it is broken. Route Maintenance Since the ad hoc network is dynamic and the topology of the network changes frequently, the existing routes maintained by nodes in their route cache are often broken. After forwarding a packet, a node must attempt to confirm the reachability of the next-hop node. If the node does not receive any confirmation from the next hop during a certain period of time, it will retransmit the packet. If after a maximum number of retransmission it still does not receive any confirmation, it will think the link to the next hop is broken and will send a Route Error message to the source node. DSR proposes three acknowledge mechanisms to confirm that data can flow over the link from that node to the next hop: Link-layer acknowledgement which is provided by MAC layer protocol such as IEEE 802.11. Passive acknowledgement in which a node hears the next-hop node forwarding the packet and thus confirms the reachability of the link. Network-layer acknowledgement in which a node sends an explicit acknowledgement request to its next-hop node. Passive Acknowledgement Passive Acknowledgement (PACK) is important in DSR protocol because it is used to detect whether the next hop forwards the packet or drops it. We explain it in detail in this section. Passive acknowledgement is used with the assumption that: Network links operates bi- directionally. The network interface is in the promiscuous mode. When a node taps a new packet in promiscuous mode after it originates or forwards a packet, it consider it as an acknowledgement of the first packet if both of following check success. The Source Address, Destination Address, Protocol, Identification, and Fragment Offset fields in the IP header of the two packets MUST match. If either packet contains a DSR Source Route header, both packets MUST contain one, and the value in the Segments Left field in the DSR Source Route header of the new packet MUST be less than that in the first packet. If no matched packet is found during PACK timeout, the node will consider the link between the next hop and itself is broken and will send Route Error message to the source node. Additional features DSR has additional features such as replying to route requests using cached routes, caching overheard routing information, packet salvaging and flow state extension and etc. We will introduce them in section 4.1 and discuss how they will impact the performance of network, how they will interact with DSR and whether they will be enabled in our simulation. Performance Analysis Techniques This section introduces the performance analysis techniques and methodologies that will be used in the performance evaluation. Factors and Primary Factors There are many parameters that will influence the simulation results and need to be carefully chosen in the simulations. Some parameters are chosen based on experience values or the conditions of the network we want to simulate. Others need to be tuned to optimize the network performance. We distinguish the two kinds of parameters as follows: Factors are the variables that affect the simulation result and have several alternatives. Normally they are decided based on experience. Primary factors are the factors whose effects need to be quantified. This kind of factors usually needs to be adjusted through simulation. Data Measurement The key step of the network performance analysis is to interpret the simulation result and summarize the characteristic of the network. To avoid the inaccurate simulation results due to an extreme scenario, we usually run simulations on several different scenarios. The data set of these simulations are called sample. A single number must be presented to give the key characteristic of the sample and this single number is called an average of the data. There are three alternatives to summarize a sample Mean is obtained by taking the sum of all observations and dividing this sum by the number of observations in the sample. Median is obtained by sorting the observations in an increasing order and taking the observation that is in the middle of series. If the number of the observations is even, the mean of the middle two values is used as a median. Mode is obtained by plotting a histogram and specifying the midpoint of the bucket where the histogram peaks. Confidence Interval for the Mean In our performance evaluation, the main objective is to compare the simulation results of DSR and Standard DSR to see whether there is any performance improvement. However, most simulation results are random in some degree due to the particularity of the node movement scenarios and we cannot tell whether the two systems are different. One way to minimize the random effect is to repeat the simulations with different scenarios as many times as possible and get a large sample space. Unfortunately, due to the time limitation we cannot conduct many simulations. points out that using confidence interval we can tell whether the two systems are different with smaller sample space. The confidence interval for the mean can be calculated using If the confidence intervals of the simulation results of the two systems have no overlap, then we can claim the two systems are different and one system is superior or inferior to the other. GloMoSims source and binary code can be downloaded only by academic institutions for research purposes. Commercial users must use QualNet, the commercial version of GloMoSim. OPNET Modeler OPNET Modeler is commercial network simulation environment for network modeling and simulation. It allows the users to design and study communication networks, devices, protocols, and applications with flexibility and scalability [30]. It simulates the network graphically and its graphical editors mirror the structure of actual networks and network components. The users can design the network model visually.The modeler uses object-oriented modeling approach. The nodes and protocols are modeled as classes with inheritance and specialization. The development language is C. Comparison When choosing a network simulator, we normally consider the accuracy of the simulator. Unfortunately there is no conclusion on which of the above three simulator is the most accurate one. David Cavin et al. has conducted experiments to compare the accuracy of the simulators and it finds out that the results are barely comparable [31]. Furthermore, it warns that no standalone simulations can fit all the needs of the wireless developers. It is more realistic to consider a hybrid approach in which only the lowest layers (MAC and physical layers) and the mobility model are simulated and all the upper layers (from transport to application layers) are executed on a dedicated hosts (e.g. cluster of machines). Although there is no definite conclusion about the accuracy of the three network simulators, we have to choose one of them as our simulation environment. We compare the simulators using some metrics and the results are summarized After comparing the three simulators, we decide to choose ns2 as network simulator in our thesis because Ns2 is open source free software. It can be easily downloaded and installed. The author of the thesis has used ns2 in another network related course and gotten familiar with the simulation. Ns2 uses TCL and C++ as development languages for which the author has some programming experience. The author of the DSR protocol has conducted simulation on GloMoSim and gotten performance results. We want to do the simulation on a different simulation to form comparison. State of the Art In this chapter we will introduce the start of the art security solutions in MANET with emphasis on dynamic feedback mechanisms. Firstly, we will present the general security issues/requirements of MANET to pave the way for the future investigation. Then we will discuss the state of the art security mechanisms for MANET such as payment system,trust management system, reputation system, etc. Finally, we will summarize all the security solutions we discussed in this chapter. Security Issues in Mobile Ad Hoc Network Due to lack of central infrastructural and wireless links susceptible to attacks, security in ad hoc network has inherent weakness. In section 1.2 we have discussed the reasons why mobile ad hoc network imposes security challenges that cannot be solved by traditional security mechanisms. In this section, we present the general security properties required by ad hoc network. Following are general security properties regarding ad hoc network Confidentiality: The confdiantiality property is to protect certain information from unauthorized disclosure. The information includes not only the application data that send over the routing protocol, but also the routing information itself as well as network topology and geographical location. Integrity: The integrity ensures that the transmitted message and other system asset are modified only by authorized parties. In the routing level, it requires all nodes in the network following correct routing procedure. The main challenge of ensuring integrity is that without central infrastructure and powerful computing capabilities, it is difficult to apply existing cryptography and key management systems. Availability: The availability property requires that the services or devices are exempt from denial of service, which is normally done by interruption, network or server overload. Typical examples or denial of service attack are radio jamming, in which a misbehaved node transmit radio to interference other nodes communications, and battery exhaustion, in which a misbehaved node interact with a node for no other purpose than to consume its battery energy. Authentication: The authentication property requires that the communication entitys identification is recognized and proved before communication starts. Access control: This property requires restricting resources, services or data to special identities according to their access rights or group membership. Non-repudiation: This property ensures that when data are sent from sender to receiver, the sender cannot deny that he has sent the data and the receiver cannot deny that he has received the data. Mobile nodes may conduct different misbehavior for different purposes. Po-Wah Yau classifies the misbehaved nodes into following categories. Failed nodes are simply those unable to perform an operation; this could be because power failure and environmental events. Badly failed nodes exhibit features of failed nodes but they can also send false routing messages which are a threat to the integrity of the network. Selfish nodes are typified by their unwillingness to cooperate as the protocol requires whenever there is a personal cost involved. Packet dropping is the main attack by selfish nodes. Malicious nodes aim to deliberately disrupt the correct operation of the routing protocol, denying network service if possible. These four types of misbehaved nodes actually can be categorized in two aspects: whether their misbehaviors are intentional or unintentional, and the severity of the results. Payment Systems Payment systems provide economic incentives for the cooperation in MANET. They consider that each node in MANET is its own authority and tries to maximize the benefits it gets from the network. Thus each node tends to be selfish, dropping packets not destined to them but make use of other nodes to forward their own packets. The purpose of payment systems is to encourage the cooperation within the MANET by economic incentives. There are several variations of payment systems proposed. Nuglets Nuglets is a virtual currency mechanism for charging (rewarding) server usage (provision). Nodes that use a service must pay for it (in nuglets) to nodes that provide the service. A typical service is packet forwarding which is provided by intermediate nodes to the source and the destination of the packet. Therefore either the source or the destination should pay for it. There are two models for charging for the packet forwarding service: the Packet Purse Model (PPM) and the Packet Trade Model (PTM). In the Packet Purse Model, the sender pays for the packet. It loads the packet with a number of nuglets when sending the packet. Each intermediate forwarding node acquires some nuglets from the packet that covers its forwarding costs. If a packet does not have enough nuglets to be forwarded, then it is discarded. If there are nuglets left in the packet once it reaches destination, the nuglets are lost. In the Packet Trade Model, the destination pays for the packet. Each intermediate node buys the packet from previous one for some nuglets and sells it to the next one for more nuglets until the destination buys it. Either of the two models has advantages and disadvantages. While the Packet Purse Model deters nodes from sending useless data and avoids the network overloading, the Packet Trade Model can lead to an overload of the network and the destination receives packets it does not want. On the other hand, in the Packet Purse Model it is difficult to estimate the number of nuglets th at are required to reach a given destination. But thePacket Purse Model does not need to consider this problem. To take advantages of the two models and avoid the disadvantages, a hybrid model is suggested. In this model, the sender loads the packet with some nuglets before sending it.The packet is handled according to the Packet Purse Model until it runs out of nuglets. Then it is handled according to the Packet Trade Model until the destination buys it. Counter To address the problems encountered by the nuglets approach such as difficulty in estimating pre-load nuglets and possible network overload, another payment approach based on credit counter is suggested. In this approach, the current state of each node is described by two variables b and c, where b is the remaining battery power and cstands for the value of its nuglet counter. More precisely, b is the number of packets that the node can send using its remaining energy and c is the number of packets a node canoriginate. A node can originate a number of packets N only when the condition c=N holds. When a node forwards a packet, nuglet counter c is increased by one and b is reduced by one. Thus in order to originate packets, each node must earn credits by forwarding packets. The counter solution requires tamper resistant hardware security module. Spirit S. Zhong et al. proposed Sprite [19], a credit-based system for MANET. As opposed to Nuglets or Counter they do not require tamper-proof hardware to prevent the fabrication of payment units. Instead, they introduce a central Credit Clearance Service (CCS). The basic scheme of the system is as follows. When a node receives a message the node keeps a receipt of the message and reports to the CCS when the node has a fast connection to Credit Clearance Service (CCS). The CCS then determines the charge and credits to each node involved in the transmission of a message, depending on the reported receipts of a message. In this scheme, the sender charges money. A node that has forwarded a message is compensated, but the credit that a node receives depends on whether or not its forwarding action is successful. Forwarding is considered successful if and only if the next node on the path reports a valid receipt to the CCS. Discussion on the Payment Systems The payment systems we describe in above sections either assumes a tamper resistant hardware module is available to ensure that the behavior of the node is not modified or requires a central authority server to determine the charge and credit to each node involved in the transmission of a message. Tamper resistant hardware may not be appropriate for most mobile devices because it demands advanced hardware solution and increases the cost of the devices. Lacking of central authority server is right the inherent property of MANET that causes security challenges so it is also not appropriate. Furthermore, all the approaches described above suffer from locality problems [20] that nodes in different locations of the network will have different chances for earning virtualcurrency, which may not be fair for all nodes. Usually nodes at the periphery of the network will have less chance to be rewarded. Reputation System Reputation systems have emerged as a way to reduce the risk entailed in interactions among total strangers in electronic marketplace. Centralized reputation systems have been adopted by many on-line electronic auctions such as eBay to collect and store reputation ratings from feedback providers in a centralized reputation database. Decentralized reputation systems used by MANET, on the other hand, do not use centralized reputation database. Instead, in these reputation systems, each node keeps the ratings about other node and updating the ratings by direct observation of the behaviorsof neighboring nodes or second hand information from other trusted nodes. Identifies three goals for reputation systems: To provide information to distinguish between a trust-worthy principal and an untrustworthy principals. To encourage principals to act in a trustworthy manner To discourage untrustworthy principals from participating in the service the reputation mechanism is present to protect. Most of the reputation systems in MANET are based on trust management system. Trust is such a subjective and dynamic concept that different entities can hold different opinions on it even while facing the same situation. Trust management system can work without reputation system. For example, a mobile node can form opinion about other nodes by direct experience with the nodes.We can unify reputation system and trust management system to dynamic feedback mechanisms. Former one is a global reputation system and mobile nodes share their own experiences of interaction with other nodes. The later one is a local reputation system in which mobile nodes rating the trustability of other nodes based on its own observation. DSR DSR is a reputation system aiming at coping with misbehavior in MANET. The idea is to detect the misbehaved nodes and isolate them fromcommunication by not using them for routing and forwarding and by not allowing the misbehaved nodes to use itself to forward packets. DSR stands for Cooperation Of Nodes: Fairness In Dynamic Ad-hoc Network. It usually works as an extension to on demand routing Mobile Ad Hoc Networks (MANETs) Mobile Ad Hoc Networks (MANETs) Introduction What is Mobile Ad Hoc Network? With rapid development of wireless technology, the Mobile Ad Hoc Network (MANET) has emerged as a new type of wireless network. MANET is a collection of wireless mobile nodes (e.g. laptops) that dynamically function as a network without the use of any existing infrastructure and centralized administration. It is an autonomous system where each node operates not only as an end system but also as a router to forward packets for other nodes. Since the nodes in MANET move around, the wireless links break and re-establish frequently. Furthermore, most of mobile nodes are resource limited in computing capability and battery power and therefore traditional computing content routing protocols are not suitable for MANET. Several ad hoc routing protocols have been proposed for each node acting as router and maintaining routing information. There are many other applications of MANET. For examples, MANET can be used to provide emergency Services when the network is impaired due to the damaging of existing infrastructure [8]. Computer scientists have predicted a world of ubiquitous computing in which computers will be all around us, constantly performing mundane tasks to make our lives a little easier. These ubiquitous computers connect in mobile ad hoc mode and change the environment or react to the change of the environment where they are suited. MANET is also found useful in the so-called sensor dust network to coordinate the activities and reports of a large collection of tiny sensor devices which could offer detailed information about terrain or environmental dangerous conditions. Problem Statement and Motivation Most current ad hoc routing protocols assume that the wireless network is benign and every node in the network strictly follows the routing behavior and is willing to forward packets for other nodes. Most of these protocols cope well with the dynamically changing topology. However, they do not address the problems when misbehavior nodes present in the network.A commonly observed misbehavior is packet dropping. In a practical MANET, most devices have very limited computing and battery power while packet forwarding consumes a lot of such resources. Thus some of the mobile devices would not like to forward the packets for the benefit of others and they drop packets not destined to them. On the other hand, they still make use of other nodes to forward packets that they originate. These misbehaved nodes are very difficult to identify because we cannot tell that whether the packets are dropped intentionally by the misbehaved nodes or dropped due to the node having moved out of transmission range or other link error. Packet drop significantly decreases the network performance.Traditional security mechanisms are generally not suitable for MANET because: The network lacks central infrastructure to apply traditional security mechanism such as access control, authentication and trusted third party. Limited bandwidth, battery lifetime, and computation power prohibits the deployment of complex routing protocols or encryption algorithms. New security models or mechanisms suitable for MANET must be found. Network topologies and memberships are constantly changing. Thus new intrusion detection system and entity recognition mechanisms that are suitable for mobile ad hoc networks must be designed to avoid or mitigate the behavior to the networks. Trust management systems have been recently introduced as a security mechanism in MANET. In a trust management system, a communicating entity collects evidence regarding competence, honesty or security of other network participants with the purpose of making assessment or decisions regarding their trust relationships. Here trust Objective and Sub-tasks means the confidence of an entity on another entity based on the expectation that the other entity will perform a particular action important to the trustor, irrespective of the ability to monitor or control that other entity . For example, a trust-based routing protocol can collect the evidence of nodes misbehaving, form trust values of the nodes and select safest routes based on the trust metrics.Reputations systems are often seen as a derivation of trust management system. In the reputation system, an entity forms its trust on another entity based not only on the selfobserved evidence but also on the second hand information from third parties. One of the influential reputation systems is the DSR protocol. In the trust management system, reputation system and other trust-based systems, route selection is based on the sending nodes prior experience with other nodes in the network. Its opinions about how other entities are honest are constantly changing. Thus, we call the trust manag ement systems and their derivations as dynamic feedback mechanisms. The dynamic feedback mechanisms are usually applied on the current ad hoc routing protocols to rate the trust about other nodes in the network and make routing decisions based on the trust matrix, which is formed according to the evidence collected from previous interactions. By incorporating the dynamic feedback mechanism in the routing protocol, misbehaved nodes are identified and avoided to forward packets. In this way,misbehavior can be mitigated. Objective and Sub-tasks The primary objective of this thesis is to Investigate the state of the art of dynamic feedback mechanisms and protocols analyze, implement and evaluate DSR protocols to see how it improves the network performance and what are the side effects of introducing the mechanism to the mobile ad hoc network. Following tasks must be done to achieve the primary objective. Study the preliminary knowledge that is required to carry out the main tasks. For example, to understand DSR protocol one must have some knowledge of Bayesian analysis; to do performance analysis one must learn the methodologies of conducting performance analysis and processing simulation data. Investigate security issues of mobile ad hoc network and current dynamic feedback mechanisms or protocols that are used to solve or mitigate the issues. Investigate and learn how to use the network simulation tool. There are several popular network simulation tools available and we need to choose the one that best suits our needs. The selected network simulator should be studied so that we can use it as platform to implement protocol and conduct simulations. Analyze and implement the DSR protocol based on Dynamic Source Routing protocol (DSR); evaluate the network performance. Structure of the Report Since we have almost gone through the chapter one, we only briefly present the content of the subsequent chapters in this section. Preliminary Information State of the Art Analysis Design Implementation and Tests Performance Analysis Conclusion and Future Work Preliminary information we have introduced the MANET. This chapter presents other preliminary information and concepts that will be used in other parts of the thesis. Firstly four general modes of routing operations are introduced and compared. The DSR protocol, which is used as underlying routing protocol in the thesis, is explained in detail. Secondly Bayesian estimation and Beta function are explained to pave the way for the analysis of the reputation model of DSR in the chapter 4. Thirdly some techniques regarding simulation and performance analysis are presented. Finally, several popular network simulation tools are discussed and compared. Mobile Ad Hoc Network Routing Protocols Nowadays there are various routing protocols proposed for the MANET. The most popular ones are DSDV (Destination-Sequenced Distance Vector), TORA (Temporally- Ordered Routing Algorithm), DSR (Dynamic Source Routing) and AODV (Ad-hoc On Demand Distance Vector). These routing protocols can be categorized in different routing operation modes. Mode of Routing Operations These two modes concern whether or not nodes in an ad hoc network should keep track of routes to all possible destinations, or instead keep track of only those destinations of immediate interest Proactive protocols store route information even before it is needed. This kind of protocols has advantage that communications with arbitrary destination experience minimal delay. However it also suffers from the disadvantage that additional control traffic is needed to continually update stale route information. This could significantly increase routing overhead especially for the MANET where the links are often broken. Reactive protocols, on the contrary, acquire routing information only when it is actually needed. However, the latency of the communication increases tremendously especially when a node communicates to another at the first time. Source routing vs. Hop-by-hop routing These two modes concern whether the source node decides the route for a packet to be forwarded to the destination or the intermediate nodes are allowed to decide the next hop until the packet arrives at the destination. In the source routing protocols, the source node decides the route and puts the route information in the packet header. All the intermediate nodes forward the packet along the route faithfully. This kind of protocols has advantage that the intermediate nodes are not required to maintain the routing information. But it suffers from the disadvantage that the packet size grows because of source routing information carried in each packet. In the hop-by-hop routing protocols, it is sufficient for the source to know only how to get to the next hop and intermediate nodes find their own next-hops until the destination. In contrast to source routing protocols, hop-by-hop routing protocols do not increase packet size but they requires all the intermediate nodes to maintain rout ing information. Table 2-1 Categories of routing protocols has compared the performance of these four routing protocols . The results show that DSR has best throughput performance (above 95%) at all mobility rates and movement speeds. Thus we will use DSR as basic routing protocol in this thesis. The Dynamic Source Routing Protocol (DSR) John et al. proposed the dynamic source routing protocol (DSR) [1] which is a routing protocol for use in multi-hop wireless ad hoc networks of mobile nodes. DSR is an ondemand protocol, in which route are only discovered when data need to be transmitted to a node where no route has yet been discovered. The advantage of this on-demand routing protocol is that there are not any periodic routing advertisement and reducing the routing overhead. DSR is also a source routing protocol, allowing multiple routes to any destination and allows each sender to select and control the routes used in routing the packets. DSR is composed of the two main mechanisms: Route Discovery and Route Maintenance which are explained below. Route Discovery Route Discovery aims at finding routes from a source node to destination. Figure 2-1 illustrates the procedure of Route Discovery. When a source node S wants to send a data packet to some destination node D, it first searches its route cache to find whether there is a route to D. If there is no route to D, then S will initiate a Route Discovery and send out Route Request message which is propagated to all the nodes within its transmission range. At the mean time, it saves the data packet in its send buffer. The Route Request message contains the addresses of source node and destination node, a unique route request identifier and a route record which records all the intermediate nodes that this route request packet has traveled through. S appends itself to the beginning of the route record when it initiates the message. When a node receives the Route Request message, it compares the destination address in the message with its own address to judge whether itself is the destination node. If it is not, it will append its own address in the route record and propagate the message to other nodes. If the node is the destination node, it will send a Route Reply message to the source node and the message contains the source route record which is accumulated when the Route Request message is forwarded along its way to the destination. When the destination sends the Route Reply, if it uses MAC protocols such as IEEE 802.11 that require a bidirectional link, it just reverse the source route record and use it as route to send Route Reply to the source node. Otherwise it should find the route by searching its route cache or sending out a Route Request which piggybacks the Route Reply for the source node. When the source node receives the Route Reply message, it puts the returned route into its route cache. From t hen on all the packets destined to the same destination will use this route until it is broken. Route Maintenance Since the ad hoc network is dynamic and the topology of the network changes frequently, the existing routes maintained by nodes in their route cache are often broken. After forwarding a packet, a node must attempt to confirm the reachability of the next-hop node. If the node does not receive any confirmation from the next hop during a certain period of time, it will retransmit the packet. If after a maximum number of retransmission it still does not receive any confirmation, it will think the link to the next hop is broken and will send a Route Error message to the source node. DSR proposes three acknowledge mechanisms to confirm that data can flow over the link from that node to the next hop: Link-layer acknowledgement which is provided by MAC layer protocol such as IEEE 802.11. Passive acknowledgement in which a node hears the next-hop node forwarding the packet and thus confirms the reachability of the link. Network-layer acknowledgement in which a node sends an explicit acknowledgement request to its next-hop node. Passive Acknowledgement Passive Acknowledgement (PACK) is important in DSR protocol because it is used to detect whether the next hop forwards the packet or drops it. We explain it in detail in this section. Passive acknowledgement is used with the assumption that: Network links operates bi- directionally. The network interface is in the promiscuous mode. When a node taps a new packet in promiscuous mode after it originates or forwards a packet, it consider it as an acknowledgement of the first packet if both of following check success. The Source Address, Destination Address, Protocol, Identification, and Fragment Offset fields in the IP header of the two packets MUST match. If either packet contains a DSR Source Route header, both packets MUST contain one, and the value in the Segments Left field in the DSR Source Route header of the new packet MUST be less than that in the first packet. If no matched packet is found during PACK timeout, the node will consider the link between the next hop and itself is broken and will send Route Error message to the source node. Additional features DSR has additional features such as replying to route requests using cached routes, caching overheard routing information, packet salvaging and flow state extension and etc. We will introduce them in section 4.1 and discuss how they will impact the performance of network, how they will interact with DSR and whether they will be enabled in our simulation. Performance Analysis Techniques This section introduces the performance analysis techniques and methodologies that will be used in the performance evaluation. Factors and Primary Factors There are many parameters that will influence the simulation results and need to be carefully chosen in the simulations. Some parameters are chosen based on experience values or the conditions of the network we want to simulate. Others need to be tuned to optimize the network performance. We distinguish the two kinds of parameters as follows: Factors are the variables that affect the simulation result and have several alternatives. Normally they are decided based on experience. Primary factors are the factors whose effects need to be quantified. This kind of factors usually needs to be adjusted through simulation. Data Measurement The key step of the network performance analysis is to interpret the simulation result and summarize the characteristic of the network. To avoid the inaccurate simulation results due to an extreme scenario, we usually run simulations on several different scenarios. The data set of these simulations are called sample. A single number must be presented to give the key characteristic of the sample and this single number is called an average of the data. There are three alternatives to summarize a sample Mean is obtained by taking the sum of all observations and dividing this sum by the number of observations in the sample. Median is obtained by sorting the observations in an increasing order and taking the observation that is in the middle of series. If the number of the observations is even, the mean of the middle two values is used as a median. Mode is obtained by plotting a histogram and specifying the midpoint of the bucket where the histogram peaks. Confidence Interval for the Mean In our performance evaluation, the main objective is to compare the simulation results of DSR and Standard DSR to see whether there is any performance improvement. However, most simulation results are random in some degree due to the particularity of the node movement scenarios and we cannot tell whether the two systems are different. One way to minimize the random effect is to repeat the simulations with different scenarios as many times as possible and get a large sample space. Unfortunately, due to the time limitation we cannot conduct many simulations. points out that using confidence interval we can tell whether the two systems are different with smaller sample space. The confidence interval for the mean can be calculated using If the confidence intervals of the simulation results of the two systems have no overlap, then we can claim the two systems are different and one system is superior or inferior to the other. GloMoSims source and binary code can be downloaded only by academic institutions for research purposes. Commercial users must use QualNet, the commercial version of GloMoSim. OPNET Modeler OPNET Modeler is commercial network simulation environment for network modeling and simulation. It allows the users to design and study communication networks, devices, protocols, and applications with flexibility and scalability [30]. It simulates the network graphically and its graphical editors mirror the structure of actual networks and network components. The users can design the network model visually.The modeler uses object-oriented modeling approach. The nodes and protocols are modeled as classes with inheritance and specialization. The development language is C. Comparison When choosing a network simulator, we normally consider the accuracy of the simulator. Unfortunately there is no conclusion on which of the above three simulator is the most accurate one. David Cavin et al. has conducted experiments to compare the accuracy of the simulators and it finds out that the results are barely comparable [31]. Furthermore, it warns that no standalone simulations can fit all the needs of the wireless developers. It is more realistic to consider a hybrid approach in which only the lowest layers (MAC and physical layers) and the mobility model are simulated and all the upper layers (from transport to application layers) are executed on a dedicated hosts (e.g. cluster of machines). Although there is no definite conclusion about the accuracy of the three network simulators, we have to choose one of them as our simulation environment. We compare the simulators using some metrics and the results are summarized After comparing the three simulators, we decide to choose ns2 as network simulator in our thesis because Ns2 is open source free software. It can be easily downloaded and installed. The author of the thesis has used ns2 in another network related course and gotten familiar with the simulation. Ns2 uses TCL and C++ as development languages for which the author has some programming experience. The author of the DSR protocol has conducted simulation on GloMoSim and gotten performance results. We want to do the simulation on a different simulation to form comparison. State of the Art In this chapter we will introduce the start of the art security solutions in MANET with emphasis on dynamic feedback mechanisms. Firstly, we will present the general security issues/requirements of MANET to pave the way for the future investigation. Then we will discuss the state of the art security mechanisms for MANET such as payment system,trust management system, reputation system, etc. Finally, we will summarize all the security solutions we discussed in this chapter. Security Issues in Mobile Ad Hoc Network Due to lack of central infrastructural and wireless links susceptible to attacks, security in ad hoc network has inherent weakness. In section 1.2 we have discussed the reasons why mobile ad hoc network imposes security challenges that cannot be solved by traditional security mechanisms. In this section, we present the general security properties required by ad hoc network. Following are general security properties regarding ad hoc network Confidentiality: The confdiantiality property is to protect certain information from unauthorized disclosure. The information includes not only the application data that send over the routing protocol, but also the routing information itself as well as network topology and geographical location. Integrity: The integrity ensures that the transmitted message and other system asset are modified only by authorized parties. In the routing level, it requires all nodes in the network following correct routing procedure. The main challenge of ensuring integrity is that without central infrastructure and powerful computing capabilities, it is difficult to apply existing cryptography and key management systems. Availability: The availability property requires that the services or devices are exempt from denial of service, which is normally done by interruption, network or server overload. Typical examples or denial of service attack are radio jamming, in which a misbehaved node transmit radio to interference other nodes communications, and battery exhaustion, in which a misbehaved node interact with a node for no other purpose than to consume its battery energy. Authentication: The authentication property requires that the communication entitys identification is recognized and proved before communication starts. Access control: This property requires restricting resources, services or data to special identities according to their access rights or group membership. Non-repudiation: This property ensures that when data are sent from sender to receiver, the sender cannot deny that he has sent the data and the receiver cannot deny that he has received the data. Mobile nodes may conduct different misbehavior for different purposes. Po-Wah Yau classifies the misbehaved nodes into following categories. Failed nodes are simply those unable to perform an operation; this could be because power failure and environmental events. Badly failed nodes exhibit features of failed nodes but they can also send false routing messages which are a threat to the integrity of the network. Selfish nodes are typified by their unwillingness to cooperate as the protocol requires whenever there is a personal cost involved. Packet dropping is the main attack by selfish nodes. Malicious nodes aim to deliberately disrupt the correct operation of the routing protocol, denying network service if possible. These four types of misbehaved nodes actually can be categorized in two aspects: whether their misbehaviors are intentional or unintentional, and the severity of the results. Payment Systems Payment systems provide economic incentives for the cooperation in MANET. They consider that each node in MANET is its own authority and tries to maximize the benefits it gets from the network. Thus each node tends to be selfish, dropping packets not destined to them but make use of other nodes to forward their own packets. The purpose of payment systems is to encourage the cooperation within the MANET by economic incentives. There are several variations of payment systems proposed. Nuglets Nuglets is a virtual currency mechanism for charging (rewarding) server usage (provision). Nodes that use a service must pay for it (in nuglets) to nodes that provide the service. A typical service is packet forwarding which is provided by intermediate nodes to the source and the destination of the packet. Therefore either the source or the destination should pay for it. There are two models for charging for the packet forwarding service: the Packet Purse Model (PPM) and the Packet Trade Model (PTM). In the Packet Purse Model, the sender pays for the packet. It loads the packet with a number of nuglets when sending the packet. Each intermediate forwarding node acquires some nuglets from the packet that covers its forwarding costs. If a packet does not have enough nuglets to be forwarded, then it is discarded. If there are nuglets left in the packet once it reaches destination, the nuglets are lost. In the Packet Trade Model, the destination pays for the packet. Each intermediate node buys the packet from previous one for some nuglets and sells it to the next one for more nuglets until the destination buys it. Either of the two models has advantages and disadvantages. While the Packet Purse Model deters nodes from sending useless data and avoids the network overloading, the Packet Trade Model can lead to an overload of the network and the destination receives packets it does not want. On the other hand, in the Packet Purse Model it is difficult to estimate the number of nuglets th at are required to reach a given destination. But thePacket Purse Model does not need to consider this problem. To take advantages of the two models and avoid the disadvantages, a hybrid model is suggested. In this model, the sender loads the packet with some nuglets before sending it.The packet is handled according to the Packet Purse Model until it runs out of nuglets. Then it is handled according to the Packet Trade Model until the destination buys it. Counter To address the problems encountered by the nuglets approach such as difficulty in estimating pre-load nuglets and possible network overload, another payment approach based on credit counter is suggested. In this approach, the current state of each node is described by two variables b and c, where b is the remaining battery power and cstands for the value of its nuglet counter. More precisely, b is the number of packets that the node can send using its remaining energy and c is the number of packets a node canoriginate. A node can originate a number of packets N only when the condition c=N holds. When a node forwards a packet, nuglet counter c is increased by one and b is reduced by one. Thus in order to originate packets, each node must earn credits by forwarding packets. The counter solution requires tamper resistant hardware security module. Spirit S. Zhong et al. proposed Sprite [19], a credit-based system for MANET. As opposed to Nuglets or Counter they do not require tamper-proof hardware to prevent the fabrication of payment units. Instead, they introduce a central Credit Clearance Service (CCS). The basic scheme of the system is as follows. When a node receives a message the node keeps a receipt of the message and reports to the CCS when the node has a fast connection to Credit Clearance Service (CCS). The CCS then determines the charge and credits to each node involved in the transmission of a message, depending on the reported receipts of a message. In this scheme, the sender charges money. A node that has forwarded a message is compensated, but the credit that a node receives depends on whether or not its forwarding action is successful. Forwarding is considered successful if and only if the next node on the path reports a valid receipt to the CCS. Discussion on the Payment Systems The payment systems we describe in above sections either assumes a tamper resistant hardware module is available to ensure that the behavior of the node is not modified or requires a central authority server to determine the charge and credit to each node involved in the transmission of a message. Tamper resistant hardware may not be appropriate for most mobile devices because it demands advanced hardware solution and increases the cost of the devices. Lacking of central authority server is right the inherent property of MANET that causes security challenges so it is also not appropriate. Furthermore, all the approaches described above suffer from locality problems [20] that nodes in different locations of the network will have different chances for earning virtualcurrency, which may not be fair for all nodes. Usually nodes at the periphery of the network will have less chance to be rewarded. Reputation System Reputation systems have emerged as a way to reduce the risk entailed in interactions among total strangers in electronic marketplace. Centralized reputation systems have been adopted by many on-line electronic auctions such as eBay to collect and store reputation ratings from feedback providers in a centralized reputation database. Decentralized reputation systems used by MANET, on the other hand, do not use centralized reputation database. Instead, in these reputation systems, each node keeps the ratings about other node and updating the ratings by direct observation of the behaviorsof neighboring nodes or second hand information from other trusted nodes. Identifies three goals for reputation systems: To provide information to distinguish between a trust-worthy principal and an untrustworthy principals. To encourage principals to act in a trustworthy manner To discourage untrustworthy principals from participating in the service the reputation mechanism is present to protect. Most of the reputation systems in MANET are based on trust management system. Trust is such a subjective and dynamic concept that different entities can hold different opinions on it even while facing the same situation. Trust management system can work without reputation system. For example, a mobile node can form opinion about other nodes by direct experience with the nodes.We can unify reputation system and trust management system to dynamic feedback mechanisms. Former one is a global reputation system and mobile nodes share their own experiences of interaction with other nodes. The later one is a local reputation system in which mobile nodes rating the trustability of other nodes based on its own observation. DSR DSR is a reputation system aiming at coping with misbehavior in MANET. The idea is to detect the misbehaved nodes and isolate them fromcommunication by not using them for routing and forwarding and by not allowing the misbehaved nodes to use itself to forward packets. DSR stands for Cooperation Of Nodes: Fairness In Dynamic Ad-hoc Network. It usually works as an extension to on demand routing