Indian Freedom Fighters Essay

Jawaharlal Nehru born on 14th November 1889 in Allahabad, was the first Prime Minister of India and a central figure in Indian politics for much of the 20th century. He emerged as the paramount leader of the Indian Independence Movement under Mahatma Gandhi and ruled India from its establishment as an independent nation in 1947 until his death in office in 1964. Nehru is considered to be the architect of the modern Indian nation-state; a sovereign, socialist, secular, and democratic republic. A committed nationalist since his teenage years, Nehru became a rising figure in Indian politics during the upheavals of the 1910s. He became the prominent leader of the Indian National Congress during the 1920s, and eventually of the entire Congress,. As Congress President, Nehru called for complete independence from Britain He was the principal author of the Indian Declaration of Independence (1929). As Prime Minister, Nehru set out to realise his vision of India. The Constitution of India was enacted in 1950, after which he embarked on an ambitious program of economic, social and political reforms. Chiefly, he oversaw India’s transition from a monarchy to a republic, while nurturing a plural, multi-party democracy. In foreign policy, Nehru took a leading role in Non-Alignment while projecting India as a regional hegemon in South Asia. Under Nehru’s leadership, the Congress emerged as a catch-all party, dominating national politics and winning consecutive elections in 1951, 1957, and 1962. He remained popular with the people of India in spite of political troubles in his final years and failure of leadership during Sino-Indian War. In India, his birthday is celebrated as Children’s Day. He died on may 27, 1964 in New Delhi. Gulzari Gulzarilal Nanda born on July 4 1898 in Sialkot, Pakistan, was an Indian politician and an economist with specialisation in labour problems. He was the interim Prime Minister of India twice for thirteen days each: the first time after the death of Prime Minister Jawaharlal Nehru in 1964, and the second time after the death of Prime Minister Lal Bahadur Shastri in 1966. The Government of India honoured Nanda with the Bharat Ratna award in 1997 Both his terms were uneventful, yet they were sensitive of period because of the potential danger to the country following Nehru’s death soon after a war with China in 1962 and Shastri’s death after a war with Pakistan  in 1965. He died on January 15 1998 in New Delhi. Lal Bahadur Shastri Lal Bahadur Shastri born on 2 October 1904 in Ramnagar, was the second Prime Minister of the Republic of India and a leader of the Indian National Congress party. Shastri joined the Indian independence movement in the 1920s. Deeply impressed and influenced by Mahatma Gandhi, he became a loyal follower, first of Gandhi, and then of Jawaharlal Nehru. Following independence in 1947, he joined the latter’s government and became one of Prime Minister Nehru’s principal lieutenants, first as Railways Minister (1951–56), and then in a variety of other functions, including Home Minister. Shastri was chosen as Nehru’s successor owing to his adherence to Nehruvian socialism Shastri as Prime Minister continued Nehru’s policies of non-alignment and socialism. He became a national hero following the victory in the Indo-Pakistan War of 1965. His slogan of â€Å"Jai Jawan Jai Kisan† (â€Å"Hail the soldier, Hail the farmer†) became very popular during the war and is remembered even today.[2] The war was formally ended in the Tashkent Agreement of 10 January 1966; he died the following day, still in Tashkent, Uzbekistan, of a heart attack on January 11 1966. Indira Gandhi Indira Priyadarshini Gandhi born on 19 November 1917, was the third Prime Minister of India and a central figure of the Indian National Congress party. Gandhi, who served from 1966 to 1977 and then again from 1980 until her assassination in 1984, is the second-longest-serving Prime Minister of India and the only woman to hold the office. As Prime Minister, Gandhi became known for her political ruthlessness and unprecedented centralisation of power. She presided over a period where India emerged with greater power than before to become the regional hegemon of South Asia with considerable political, economic, and military developments. Gandhi also presided over a state of emergency from 1975 to 1977 during which she ruled by decree and made lasting changes to the constitution of India. She was assassinated on 31 October, 1984, in the aftermath of Operation Blue Star. In 2001, Gandhi was voted the greatest Indian Prime Minister in a poll organised by India Today. She was also named â€Å"Woman of the Millennium† in a  poll organised by the BBC in 1999. Morarji Desai Morarji Desai born on 29 Feb 1896 in Valsad, was a notable Indian independence activist and the fourth Prime Minister of India from 1977 – 1979. He was also the first Prime Minister to head India’s first non-Congress Government. At foreign fronts, Desai holds international fame for his peace activism and made notable efforts to initiate peace between two-rival South Asian states, Pakistan and India. After India’s first nuclear explosion in 1974,Smiling Buddha, Desai helped restore friendly relations with China and Pakistan, and vowed to avoid armed conflict such as Indo-Pakistani war of 1971. Desai has the credible distinction of being the only Indian national to be conferred with Pakistan’s highest civilian award, Nishan-e-Pakistan, which was conferred on him by President Ghulam Ishaq Khan in 1990 in a colorful ceremony. Domestically, he played crucial role in Indian nuclear program after it was targeted by major nuclear powers after conducting a surprise test in 1974. Later, his policies promoted social, health and administrative reforms in the country. He died on 10 April 1995 in New Delhi. Charan Singh Chaudhuri Charan Singh , was the fifth Prime Minister of the Republic of India, serving from 28 July 1979 until 14 January 1980. Charan singh was born into a Jat family on December 23, 1902 in city Noorpur, Uttar Pradesh. Charan Singh entered politics as part of the Independence Movement. After independence he became particularly notable in the 1950s for opposing and winning a battle against Jawaharlal Nehru’s socialistic and collectivist land use policies, for the sake of the Indian Farmer, which endeared him to the agrarian communities throughout the nation, particularly in his native Uttar Pradesh. The leader of the Bharatiya Lok Dal, he was settled at the time for the largely honorary post of Deputy Prime Minister of India. During 1977 Lok Sabha Elections, there was not a single party, hence it was problem, which symbol has to be adopted Hence, a request was made to Chaudhary Charan Singh (Lok Dal) and he agreed to release his party-Lok Dal’s symbol â€Å"HALDHAR’. It was because of efforts of Raj Narain he later became Prime Minister in the year 1979. He was sworn in as Prime Minister with the support of just 64 MPs.Charan Singh died on 29 May 1987 in New  Delhi. He was survived by his wife, Gayatri Devi and five children. Rajiv Gandhi Rajiv Ratna Gandhi born on 20 August 1944 in Mumbai, was the sixth Prime Minister of India, serving from 1984 to 1989. He took office after the 1984 assassination of Prime Minister Indira Gandhi, his mother, to become the youngest Indian Prime Minister. For much of Rajiv’s childhood his grandfather Jawaharlal Nehru was prime minister. He became a professional pilot for the Indian Airlines. In 1968, he married Sonia Gandhi—and the couple settled down in Delhi to a domestic life with their children Rahul and Priyanka. Although for much of the 1970s his mother was prime minister, and his brother Sanjay wielded significant unofficial power, Rajiv remained apolitical. After Sanjay’s death in a plane crash in 1980, Rajiv reluctantly entered politics at the behest of Indira. The following year he became a member of the Lok Sabha . As part of his political grooming, Rajiv was made a general secretary of the Congress and given significant responsibility in organising the 1982 Asian Games. Rajiv Gandhi remained Congress President until the elections in 1991. While campaigning for the elections, he was assassinated by a suicide bomber from the Liberation Tigers of Tamil Eelam in May 21 1991 in Sriperumbudur. Rajiv Gandhi was awarded the highest civilian award by the government of India, Bharat Ratna in 1991. V. P. Singh Vishwanath Pratap Singh born on 25 June 1931 in Allahabad, was the 7th Prime Minister of India. His initial ministry consisted of the following Cabinet ministers and their departments. The Cabinet was functional from the 2 December 1989 to 10 November 1990. Hence , he was ousted less than a year later. To hold unwieldy coalition together proved to be a formidable task. Additionally, Singh faced secessionist movements in the states of Punjab and Kashmir. The latter threatened to erupt into armed conflict with Pakistan in early 1990 and exacerbated Hindu-Muslim conflict in the country. Known as a consensus builder, skilled negotiator, and a person of strong will, Singh’s talents were considerable, but were stretched to their utmost and ultimately failed. Singh held the post as Prime Minister less than a year due to  pressures from political rivals and an electorate increasingly polarized along caste and religious lines. He died on November 10, 2006 in New Delhi. Chandra Shekhar Chandra Shekhar Singh born on 17 April 1927 in Ibrahimpatti, was the eighth Prime Minister of India. He became the eighth Prime Minister of India on 10 November 1990 as Congress decided to extend outside support to his government. The relationship crumbled quickly, as the Congress party accused him of spying on Rajiv Gandhi, their leader at that time.[3] The Congress Party then boycotted Parliament and as Shekhar’s faction only had 64 MPs, he resigned in a nationally televised address on 6 March 1991. He remained in office until national elections could be held later that year.[4]It was during these elections that Rajiv Gandhi was assassinated. Shekhar was known for abiding by the parliamentary conventions and was honoured with the inaugural Outstanding Parliamentarian Award in 1995.[3] Shekhar was a member of the Lok Sabha, India’s lower house of Parliament. He led the Samajwadi Janata Party. Starting in 1977, he won elections to the Lok Sabha eight times from Ballia constituency in eastern Uttar Pradesh. Chandra Shekhar suffered from multiple myeloma, a form of cancer of the plasma cell. He had been hospitalised for over three months by the date of his death, aged 80, in New Delhi on 8 July 2007 P. V. Narasimha Rao Pamulaparti Venkata Narasimha Rao born on 28 June 1921 in Vangara, Karimnagar, was an Indian lawyer, politician and freedom fighter[1] who served as the ninth Prime Minister of India from1991 to 1996. He led an important administration, overseeing a major economic transformation and several home incidents affecting national security of India.[3] Rao who held the Industries portfolio was personally responsible for the dismantling of the Licence Rajas this came under the purview of the Ministry of Commerce and Industry.[4] He is often referred to as the â€Å"Father of Indian Economic Reforms†.[5][6]Future prime ministers Atal Bihari Vajpayee and Manmohan Singh continued the economic reform policies pioneered by Rao’s government. Rao accelerated the dismantling of the License Raj, reversing the socialist policies of Rajiv Gandhi’s government. He employed Dr. Manmohan Singh as his Finance Minister to embark on historic economic  transition. With Rao’s mandate, Dr. Manmohan Singh launched India’s globalisation angle of the reforms that implemented the International Monetary Fund (IMF) policies to rescue the almost bankrupt nation from economic collapse.[4] Rao was also referred to as Chanakya for his ability to steer tough economic and political legislation through the parliament at a time when he headed aminority government.[7][8] Rao died on December 23, 2004 of a heart attack in New Delhi. He was cremated in Hyderabad.[10] He was a versatile personality with interests in a variety of subjects such as literature and computer software. He spoke 17 languages. H. D. Deve Gowda Haradanahalli Doddegowda Deve Gowda born 18 May 1933 in Haradanahalli was the 11th Prime Minister of India from 1996 to 1997 and the 14th Chief minister of the state of Karnataka from 1994 to 1996. He is an influential leader of the Vokkaliga community and is popularly known as â€Å"Mannina maga† (Son of the soil) for espousing the cause of the farmers.He is the National President of the Janata Dal (Secular) party. He earned his Diploma in Civil Engineering from Smt.L.V. Polytechnic, Hassan, Karnataka.[2] He married Smt. Chennamma and the couple have 4 sons and 2 daughters. His parents, Shri Dodde Gowda and Smt. Devamma were from a middle class agricultural background.[6] Hence, he was exposed to the hardships of farmers, early in his life and later became a champion of the farmers cause.[5] I.K. Gujral Inder Kumar Gujral was an Indian politician who served as the 12th Prime Minister of India from April 1997 to March 1998. Inder Kumar Gujral was born on 4 December 1919 to Avtar Narain and Pushpa Gujral in Jhelum, pakistan. He studied at D.A.V. College, Hailey College of Commerce and Forman Christian College University, Lahore. He also participated in the Indian independence movement and was jailed in 1942 during the Quit India Movement. As a student he became a member of the Communist Party of India. Gujral was admitted at Medanta Hospital in Gurgaon, Haryana, on 19 November 2012, after being diagnosed with a lung infection.[38] He had suffered a serious chest infection a few days before being admitted to the hospital[39] following more than a year of dialysis.[15] His health deteriorated in the hospital and was reported to be â€Å"very critical†. On 27 November, he fell unconscious  and his urine output system stopped working. Gujral died on 30 November 2012. The government of India declared a seven-day period of state mourning and cancelled official functions until 6 December. Atal Bihari Vajpayee Atal Bihari Vajpayee born 25 December 1924 in Gwalior, is an Indian statesman who served as the 10th Prime Minister of India, in three non-consecutive terms, first for 13 days in 1996, then for 13 months from 1998 to 1999 and then from 1999 to 2004 for a full five year term. A parliamentarian for over four decades, Vajpayee was elected to the Lok Sabha (the lower house of India’s Parliament) nine times, and twice to the Rajya Sabha (upper house). He is the only one to be elected from four different states at different times (Uttar Pradesh, Madhya Pradesh, Gujarat and Delhi.) He won his first election from Balrampur and later he moved to Lucknow, Uttar Pradesh, until 2009, when he retired from active politics due to health concerns. Vajpayee was among the founding members of the erstwhile Jana Sangh political party and had also been its President. He was also the Minister of External Affairs in the cabinet of Morarji Desai. Manmohan Singh Manmohan Singh is the 13th and current Prime Minister of India. A renowned economist, he is the only Prime Minister since Jawaharlal Nehru to return to power after completing a full five-year term, and the first non-Hindu to hold the office. Born on September 26, 1932 in Gah , Pakistan, Singh’s family migrated to India during its partition in 1947. He received a BA from Cambridge, and after obtaining his doctorate in economics from Oxford, Singh worked for the United Nations in 1966–69. He subsequently began his bureaucratic career when Lalit Narayan Mishra hired him as an advisor in the Ministry of Foreign Trade. Over the 70s and 80s, Singh held several key posts, in theGovernment of India such as Chief Economic Advisor (1972–76), Reserve Bank governor (1982–85) and Planning Commission head (1985–87). In 2004, when the Congress-led United Progressive Alliance (UPA) came to power, its chairperson Sonia Gandhi unexpectedly relinquished the premiership to Manmohan Singh. This Singh-led â€Å"UPA I† government executed several key legislations and projects, including the Rural Health  Mission, Unique Identification Authority, Rural Employment Guarantee scheme and Right to Information Act. In 2008, opposition to a historic civil nuclear agreement with the United States nearly caused Singh’s government to fall after Left Front parties withdrew their support. Although India’s economy grew rapidly under UPA I, its security was threatened by several terrorist incidents (including the 2008 Mumbai attacks) and the continuing Maoist insurgency.The 2009 general election saw the UPA return with an increased mandate, with Singh retaining the office of Prime Minister.

Manage customer

Customer service is crucial in the automotive industry, especially given the sheer amount of choice consumers have today. A customer who has a bad experience with a brand has plenty of others to choose from. The same is true with dealers-there might be another store selling and servicing the same brand Just a few miles away. A bad experience in the service department–the department that Is generally the most profitable for a dealership–or on the sales floor can chase customers away.By Implementing customer feedback strategies, the organization will be able to discover he company's strengths and potential weaknesses, as set by the actual customer. Reacting on the feedback In a timely and appropriate manner will Increase revenues and customer satisfaction. Although a customer feedback programs will be an added cost In the beginning, long term It will save money for the organization, as It costs far more money to get new customer's than keep a satisfied, existing customers . Understanding what customers think of the organization will Improve service delivery and quality of products leading to business sustainability.Customers should be the centre of the approach. Whatever he says and asks from you, it should be immediately responded to. Be kind and show to them that you are always willing to answer their queries and help them in any way. Make them feel important and greatly valued. To meet customer needs it is necessary to understand why customers purchase and to match both products and services and the selling style of the organization with customer needs. You need to know who your customers are, where they come from and what their buying intentions are.

Answering Question Number One

Go Ahead Enterprises started as a company and made itself famous through its unique metal toys. The company was able to establish a national reputation for their product.   Its strength lies in having a manufacturing plant which produces the toys. However, as competition intensified, the company thinkers decided to overhaul the system and to go for more profit. This re-invention of the company was successful but only for a time. The atmosphere changed and soon the company found itself wondering where to start again.   Go Ahead Enterprises evolved from a manufacturing organization into a marketing one. This made the significant over-turn of the company, which sadly, was an unforeseen suicidal path. The company reduced its number of employees and moved to the city where it could market toys. It has stopped manufacturing its own metal toys. It sold its manufacturing plant. This decision was a critical one since the company never realized its important resource- the plant itself. Having a manufacturing plant is one key for sustainability.   Plus, the company is sure that each metal toy manufactured is at its best. Quality is assured. The demands or orders for the products can be handled easily since Go Ahead Enterprises supervises its own operation. Selling the manufacturing plant was an unwise move. Losing a great deal number of people is also critical since they are the company’s best asset. Letting go of competent and trained staff or employees is a loss to the company, too. People are one great resource that brings additional investments and profit. However, cutting knowledgeable and skilled employees off from the company may also result to downfall. The company’s big bosses’ decision to source instead of manufacturing its own metal toys became a major disappointment in the long run. Go Ahead Enterprises created a niche for itself in the market. Changing the position of that niche affects the company. What Go Ahead Enterprises did was to create another niche for itself by turning into a marketing company. It used to produce metal toys under its brand name.   But since the big bosses decided to make a complete overhaul, the company lost its niche as the manufacturer of metal toys. The company leaders’ decision was enough to ruin the company unintentionally.   On organisational level, they have induced the change. What they failed to see is the long-term effect of that decision. They saw profits coming in like never before. But an initial success is not a guarantee of future sustainability and growth. The company leaders never saw that right and noble decisions may sometime lead to a bitter path.   They should have seen the consequences first before jumping to conclusion and endanger the company’s growth, position in the market and quality of products. On the other hand, environmental factors do play a big part. Globalization floods the market with cheap products. This resulted to steeping competition and fight for consumers’ favor. Globalization made the market more diversified with more choices and alternatives. The consumers are left confused, bewildered and happy. The consumers are happy because influx of goods means affordability. They get to choose the products which suit their purse. Yet, cheap goods are sometimes made of inferior quality. Satisfaction is still an issue. There are consumers who still opt to buy branded products even if it is priced higher than the usual ones. Better to spend much than to be sorry, so they say. Go Ahead Enterprises banked on globalisation and joined the bandwagon to keep itself on top of the game. It imitated other companies which are also changing their company’s course to accommodate changes. The environmental change brought by globalization has transformed, but not necessarily improved Go Ahead Enterprises. Losing the company’s niche, its manufacturing plant and its key people brought the company lower than what it used to be. Go Ahead should have maintained its manufacturing and strengthened its niche in the market. The leaders should have come up with more strategies rather than adopting a strategic plan, which in the end, brought more harm than profit. The company must focus on its vision and keep the main thing â€Å"the main thing† (Hybels 2002). In this case, Go Ahead Enterprises' fate will be on its feet again if it will re-align its strength, assets, priorities, and focus on the main thing. It may not be money or profit but company reputation and sustainability. List of References Hybels, B. 2002, Courageous Leadership, Zondervan Publishing, Michigan.                     

Commuity health hazards Essay Example | Topics and Well Written Essays - 250 words

Commuity health hazards - Essay Example An analysis on the health risk is as follows. Cancer risk score was at 70%: non cancer risk score 100%: air released of recognized carcinogen 70%: air released of recognized development toxicants 70%: air released of reproductive toxicants 80%. From this review, it is clear that the region is facing a health threat from the environment pollutants (Pollution ReportCard, 2005). The collaborative on health and the environment is one organization involved in raising awareness on environmental health hazards. It does this by involving of the public in a dialogue to know the environmental problems facing the community and possible ways of solving the hazards (Health and the Enviroment, 2010). There also exist state laws that are responsible for monitoring the flow of waste products from industries. For example, there is the clean water act, which requires that, surface water be of high quality so as to ensure the safety of fish and wildlife population, and Safe drinking water for human consumption. Nurses also play a crucial role; they classify the health hazards, educate the public on the environmentally related diseases like lung cancer, and publish journals on environmental hazards and how they affect human health in the home, workplace, community, and globally (Maurer, Smith, & Leake, 2008). Maurer, A. F., Smith, C. M., & Leake, P. (2008). Environmental Health Risks: At Home, at Work, and in the Community, 4th ed. In A. F. Maurer, C. M. Smith, & P. Leake, Community/Public Health Nursing: Health for Families and Populations. Amsterdam: Elsevier - Health Sciences Division. Population ReportCard. (2005). Retrieved September 28, 2011, from Scorecard: The Pollution Information Site:

Communications Best Practices When Identifying Critical Infrastructur Research Paper

Communications Best Practices When Identifying Critical Infrastructures - Research Paper Example Public service agencies communication airwaves have inherent device connectivity challenges that must be overcome by an installation of a communication system that is capable of averting the challenges. The best connectivity infrastructure must be flanked by the general outline of the systems used in a region. Interference of communication lines by the relevant public safety agencies must be reduced to negligible levels, to facilitate an around the clock service delivery and at an emergency handling capacity. Wireless communication spectrum in use by the communication system in lace must demonstrate a capacity to handle the various safety surveillance systems without running out of reach. Wireless bands in use by various public safety services officials must create an internetworking capacity that is handled by the principle of interoperability discussed below. Using the CARVER matrix in the infrastructure level of safety assurance, it is possible for emergency handling systems to avert various deficiencies. The acronym represents six vital features that must be in place to contain disaster risks. Criticality, Accessibility, Recuperability, Vulnerability, Effect and Recognizability are used in various applications for systems analysis for the relevant application in question. In public security service agencies, the matrix is used to calculate the level of risk exposure to various dangers that face the system such as public buildings and other infrastructure. Corresponding application of the matrix values allows the assessment to formulate response options using the infrastructure’s capacity to handle the identified risks. Using the values, the infrastructure in question can be evaluated and weaknesses obtained thereon used to design and implement the appropriate response capacity that is missing. Interoperability in safety communica tion systems is a conglomeration of the best disaster response program, by facilitation of the appropriate connectivity to allow efficiency in managing disasters.  

Dementia Patient Care Plan Assignment Example | Topics and Well Written Essays - 1500 words

Dementia Patient Care Plan - Assignment Example Different diseases that directly affect the brain can lead to the development of dementia, with the major cause being Alzheimer disease. As much as scientists have not identified the exact reasons behind and process that individuals develop Alzheimer disease, it is evident that it results from the death of neurons (nerve cells) in the brain (Lu & Bludau, 2011). It is evident that a type of protein referred to as beta-amyloid and protein fiber masses form deposits within the brain of individuals with the disease. Peter* is an 86-year-old Navajo of American-Indian background. He lives with Maria*, his 80-year-old wife, in a ranch on the outskirts of Alaska. The couple solely depends on Peter’s retirement benefits that are not enough to cater for their needs. The government’s health insurance is limited; hence, the family’s expenses majorly lies in Peter’s healthcare. The couple never had children and has to be independent at old age. However, Peter cut-off his drinking habits after attending rehabilitation. In his heydays, he was a professional footballer right before he retired from football and joined the media as a sports reporter. During his football career, Peter was admitted to hospital for a concussion and a brain contusion after continuous complaints of losing balance and having blurred vision. Peter has faced ten driving under the influence (DUI) charges that led to him losing his driving license and attending a rehabilitation center. Peter’s wife has osteoporosis and is weak, an aspect that has made it difficult for her to take care of her husband. Peter has reported cases of increased confusion and forgetfulness. For example, he stated that he often looks for something when he is holding it in the hand, and forgets names of close people and places. Such occurrences have increased concerns for Peter that he could be developing Alzheimer’s disease.  

Project Report 3 Essay Example | Topics and Well Written Essays - 750 words

Project Report 3 - Essay Example It began in December 2007 and lasted 18 months which was the longest recession since World War 2. By observing the U.S Gross Domestic Production (GDP) and the employment data, we can conclude that the current state of the U.S economy is recovering from the recession. The GDP is an important variable because GDP represents the total dollar value of all goods and services which being produced in the period time. The GDP is also related to the real income, employment and industry production. These reasons are why GDP is an important indicator to a country’s economy state. By looking at the Quarter-to-Quarter growth in real GDP graph (Bureau of Economic Analysis) the GDP in the last two quarters of 2008 and the first two quarters of 2009 are negative. Especially the last quarter in 2008, the GDP is down by 9% which means the economy of U.S had dropped 9% in the over the last quarter of 2008. However, from the third quarter of 2009 the GDP had grown back to positive and it stayed p ositive from 2010 to 2012. By using the previous data we can conclude that the recession is over and the U.S economy is recovering now. The other important variable is the employment data. ... mic Analysis), we can easily tell the number of employees dropped from 127,383,000 to 121,078,000 during 2008 to 2009 which means there are about 6,000,000 people lost their job during 2008 to 2009. In 2011, the number of equivalent of employees bounced back to 121,757,000 which is a good sign for U.S economy. There are many factors which can cause the economic recession. The most common reason is the declining in GDP growth and it brings the high unemployment rate, inflation and other economic problems. The latest recession in 2008 is because of the bubble burst in housing price. In 2006 the housing price in U.S peaked too high and the price started falling since 2007. The homeowners and the people who invested in real estate were facing a huge loss. Comparing the current GDP to the GDP before recession, we can realize that the GDP before recession is slightly lower than the current GDP. Therefore, U.S economy is recovered from the recession which was started from 2008. However, by observing the gross domestic investment data (Bureau of Economic Analysis table 5.2.3), the gross domestic investment in 2011 is still lower than 2004 to 2008. We can assume that the U.S economy is not fully recovered because people cannot have that much money to invest comparing to the time before the recession. We compared the recession between 2001 and 2008. These two recessions are interesting because they are really close to us, and most of us should remember how it was, and what was happening at that time. There were few main reasons that why the U.S. economy was slipping into recession in 2001. One of the most memorable reasons was the terrorist attack; the terrorist attack bringing down a $10.2 trillion dollar economy is dramatic. Another main cause of 2001 recession was the crash

National Sales Tax Essay Example | Topics and Well Written Essays - 2500 words

National Sales Tax - Essay Example Among other things, the NST is not high enough to replace current revenues. The NST should remain a fringe argument against the federal income tax. The NST would replace a number of taxes levied by the federal government. Principal among them is the income tax. The income tax sprung into being with the adoption of the 16th Amendment in 1913 (McNulty and Daniel 7). The tax taxes all income, however derived. The income that is taxed is subject to certain exemptions, deductions and credits depending on the class of person involved or the activity involved. For example, there is an additional standard deduction for the elderly and the blind (McNulty and Daniel 4). Additionally, there is a greater standard deduction for married people over single people (McNulty and Daniel 3-4). The government discerns among people and activities to encourage certain social behaviors. As McNulty and Daniel put on page 23: The income tax raises revenue, subsidizes some people or activities, encourages or discourages behavior, redistributes wealth, stimulates or stabilizes the economy, maintains federalism and tackles social problems like pollution and urban decay. The income tax is progressive - a defining feature of the system. People fall into different tax brackets based on their income. Higher income brackets are subject to higher marginal tax rates. The end result is that higher income individuals pay on average a higher proportion of their income as tax (McNulty and Daniel 18). Progressive taxation represents a federal policy of wealth distribution of money from the wealthy to services for the rest of the populace (Posin and Tobin 18). The income tax does not discourage work. People will be motivated to work so long as their federal, state and local tax rates don't exceed 100% (McNulty and Daniel 20). The federal income tax system is far reaching, pursues policy goals in addition to raising revenue and attempts to be fair among the classes. The National Sales Tax Defined The NST is a simple way to generate revenue. 45 states and the District of Columbia already take advantage of sales and use taxes. Several proposals for a national sales tax has floated in the last couple of years. This discussion reflects the national sales tax defined in H.R. 3039, sponsored by Reps. Dan Schaefer (R-Colo.) and Billy Tauzin (R-La.) (Burton and Mastromarco). The NST would replace the individual and corporate income tax, transfer taxes, and most non-trust-fund excise taxes with a single 15 percent flat-rate tax on tangible goods and services sold at the retail level (Burton and Mastromarco). The sales tax would be exempted from intermediate levels of production. The NST defined here does not replace the payroll taxes providing revenue for Social Security and Medicare. (Burton and Mastromarco). There are a slew of items that would be taxed in addition to goods and services. Housing, financial intermediation services and government goods and services that are sold to the public would be taxed. Rent and home purchases would be taxed. Imports would be taxed. (Burton and Mastromarco). The NST proposal attempts to deal with the otherwise regressive aspects of the tax. All people would receive a rebate of the tax equaling the tax rate times the poverty line, allowing poor people to avoid paying the tax and everyone else to afford the necessities of

Modest Proposal by Jonathan Swift Essay Example | Topics and Well Written Essays - 1500 words

Modest Proposal by Jonathan Swift - Essay Example Arguments are presented to raise awareness about a trivial matter in a light-hearted manner and this is where the piece becomes important for its humorous worth. Such arguments do not lack force but refuse to impose views on others and this is what Suzanne Britt’s essay is all about. In a Modest Proposal, Jonathan Swift highlights the subject of poverty in Ireland in very harsh and satirical manner. It is important to understand that there is a very clear line dividing humor and satire and Swift’s work is not humorous in any way. His language is abrasive and there is little use of compassion. Even if logic is applied, it is twisted around which makes it appear like reversed logic. There is nothing mild about his essay and while his main purpose was to draw attention to the extremes of poverty in Ireland and the growing population problem, his solution might appear to be an attack against the government instead of a concern for societal good. Such themes were usually Swift’s favorites as Fox tells us, â€Å"Recurrent famine, widespread poverty and misery amongst the native peasantry, the failure to create a more self-reliant economy, and the landlords moral complacency are the principal targets of Swift's anger.† There is too much politics in the essay, which is one reason the essay cannot be truly enjoyed. No serious facts or statistics have been used and thus the essay lacks objectivity. With the kind of harshness he employed, statistics were definitely needed to support his case. In the contrast, we can use the example of Suzanne Britt’s essay, Neat people vs. Sloppy people. This essay has made good refreshing use of humor. The author has tried to attract attention to the differences between the attitude of neat and sloppy people and has employed humor with such ease and precision that every person would love this piece.

Bahlawane discussion Essay Example for Free

Bahlawane discussion Essay Conclusion Taking in account the scheme of galactoglucan synthesis regulation (Fig. 4. 1) and the scheme of motility regulation (Fig. 4. 2) proposed in this study, we may try to follow the effect of such regulation paths in the life styles of the bacteria. The last one is named as free – living microorganism or as symbiont in the plant root. In the first case, the bacteria are exposed to dryness and nutrients starvation. At this stage, the biofilm production is a pre-requisite for survival. Therefore, the EPS’s biosynthesis has to be switched ON. As it is quite improbable that the cell density is high enough to activate the quorum sensing system, we can speculate that MucR plays a key role in activating the succinoglycan biosynthesis. Since the soil exhibits very low level of Pi, galactoglucan is, at this point produced through the activation via phoB and WggR. Upon biofilm formation, the cell density probably increases and could activate the quorum sensing system, allowing the bacteria to produce more galactoglucan and swarm towards better conditions. In such conformation, the cells present within the centre of the swarming population are non motile and synthesized EPS; thus the cells present at the migration front are highly motile but do not synthesized EPS. It would be interesting to clarify whether a cell differentiation, as proposed by Soto (Soto et al. , 2002), takes place at this stage. Finally, if the host is present in the next neighbourhood the chemotactic compounds, as well as the nutrients found in the rood exudates, will attract the bacteria. When approaching the root, the moisture increases, along with the nutrients availability; so that swarming motility will be replaced by swimming motility that decline progressively. Indeed, the bacteria attached to the root, increasing the cell density that may lead to the inhibition of flagella production via ExpR / QS. Instead, EPS are produced, allowing recognition between the plant and the microbe as well as the invasion of the new synthesized infection thread. Once within the root, the bacteria will differentiate to bacteroid and start fixing nitrogen. We tried to highlight in this thesis the relevance of exopolysaccharides and motility for an efficient symbiosis. Great advances have been made the last years, leading to the identification of the quorum sensing interaction with motility. We participate in inclusion of MucR, as new regulator of motility and ExpR as requisite for swarming. However, the full understanding of the influence of motility in symbiosis establishment will require finding out which signals are inducing mucR and exoR/ exoS. Moreover, some tests have to be implemented to investigate the symbiosis establishment in more realistic conditions. Indeed, the bacteria are usually directly inoculated to the root, so that motility, via swarming or swimming is not required. Acknowledgments First and foremost, I would like to thank Prof. Dr. Alfred Puhler, Chair of the Genetics department, for allowing me use the very good infrastructure that promotes a very pleasant and conducive atmosphere during my research using performant techniques. I am especially grateful to Prof. Dr. Anke Becker, my supervisor, for giving me the chance to come back to research. Without her advices, ideas and resources, this work would not be possible and achieved. Thus, I thank her too for the freedom she gave me, as well as her support to test new ideas and her great help by conceiving and writing the manuscripts that become the pillars of this manuscript. Within the laboratory members, I would like to thank first Dr. Birgit Baumgarth who introduced me to the lab and to the investigated organism. Then, special thanks to Dr.Matthew McIntosh for the quorum sensing – related work and his help for preparing the derived publication. Furthermore, I would like to deeply thank Dr. Natasha Pobigaylo for her friendship, her helpful discussions and for giving me courage when I am about to lose it. I thank Manuela Mayer, too, for the assistance in microarray hybridizations as well as Dr. Lisa Krol, Javier Serrania and Thomas Montfort for the everyday help in the lab. Finally, I would like to thank all Exopol group members for the support and advices. Least, I would like to thank my family for their unending and heartwarming support in many ways. Special thanks to Rachida Bendaou, my mother-in-law, for her support in caring my children during my research. I would like to thank my children, Ines, Soraya and Jasmine, for filling up my life with love and happiness. I would like to apologize for the bad mood and stress situations that are unfortunately connected with such a thesis. My heartfelt gratitude to my understanding and loving husband, Naoufal, for his moral and financial support, for believing in me and for sharing the passion for science with me. Resume In order to enter symbiosis with its legume partner, Sinorhizobium meliloti has to face continual changing conditions. It has more ability to adapt quickly to the situation than the ability to face it efficiently that makes the difference in term of symbiosis efficiency. For the first interactions with its host, motility is required by S. meliloti to move towards the chemotactic compounds released by its host when exopolysaccharides (EPSs) are required later on, for the attachment to the root as well as for the invasion of the infection thread, leading to the formation of the root nodule. We focused in this study the regulatory networks leading to the coordination of motility and EPS’s production in the strain Rm2011. Depending on the phosphate concentration encountered in the environment Rm2011 synthesizes two different exopolysaccharides (EPS). Galactoglucan (EPS II) is produced under phosphate starvation but also in the presence of extra copies of the transcriptional regulator WggR (ExpG) or as a consequence of a mutation in mucR. The galactoglucan biosynthesis gene cluster contains the operons wga (expA), wge (expE), wgd (expD), and wggR (expG). Two promoters, differentially controlled by WggR, PhoB, and MucR, were identified upstream of each of these operons. The proximal promoters of the wga, wge, and wgd transcription units were constitutively active when separated from the upstream regulatory sequences. Promoter activity studies and the positions of predicted PhoB and WggR binding sites suggested that the proximal promoters are cooperatively induced by PhoB and WggR. MucR was shown to strongly inhibit the distal promoters and bound to the DNA in the vicinity of the distal transcription start sites. An additional inhibitory effect on the distal promoter of the structural galactoglucan biosynthesis genes was identified as a new feature of WggR in a mucR mutant. Motility is organized in S. meliloti in a hierarchical cascade, with Class Ia genes, encoding the major regulator of motility VisNR; controlling the expression of the class Ib gene, rem, which encodes a central regulator, activating the expression of the downstream Class II and class III genes. We could demonstrate that MucR binds a DNA sequence upstream of rem, following a different mechanism as previously observed upon binding upstream of the wg genes. By this way, MucR inhibits rem expression as well as the expression of the Rem-regulated genes such as flaF and flgG. Furthermore, we addressed a balance of the swimming and swarming abilities of several S. meliloti strains derivatives of Rm2011. We could show that all strains, able to build flagella, were swimming on low viscosity agar plates. However, swarming over high viscosity agar plates required all a functional expR / sin locus, the ability to build flagellum and the production of exopolysaccharides. Finally, we propose a model for the coordination of motility and EPSs synthesis in S. meliloti.

Introduction To Beats Frequency Philosophy Essay

Introduction To Beats Frequency Philosophy Essay The sound of a beat frequency or beat wave is a fluctuating volume caused when you add two sound waves of slightly different frequencies together. If the frequencies of the sound waves are close enough together, you can hear a relatively slow variation in the volume of the sound. A good example of this can be heard using two tuning forks that are a few frequencies apart. A sound wave can be represented as a sine waves, and you can add sine waves of different frequencies to get a graphical representation of the waveform. When the frequencies are close together, they are enclosed in a beat envelope that modulates the amplitude or loudness of the sound. The frequency of this beat is the absolute difference of the two original frequencies Examples and applications of beat frequencies:- A good demonstration of beat frequencies can be heard in the animation below. A pure sound of 330 Hz is combined with 331 Hz to give a rather slow beat frequency of 1 Hz or 1 fluctuation in amplitude per second. When the 330 Hz sound is combined with a 340 Hz sound, you can hear the more rapid fluctuation at 10 Hz. Another example of beats:- When you fly in a passenger plane, you may often hear a fluctuating droning sound. That is a beat frequency caused by engine vibrations at two close frequencies. Application of beats:- A piano tuner will strike a key and then compare the note with a tuning fork. If the piano is slightly out of tune, he will be able to hear the beat frequency and then adjust the piano wire until it is at the same frequency as the tuning fork. If the piano is severely out of tune, it makes the job more difficult, because the beat frequency may be too fast to readily hear. Adding sine waves :- Although sound is a compression wave that travels through matter, it is more convenient to illustrate the sound wave as a transverse wave, similar to how a guitar string vibrates or how a water wave appears. The shape of such a wave for a single frequency is called a sine wave. Its fig isà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦ in fig:- Here Sine wave represents a single frequency of sound with constant amplitude When we add sound waves traveling in the same direction together, elements of the sine wave add or subtract, according to where they are in the waveform. we add the amplitude of each wave, point by point. Making a graphical representation of the sum of two waves can be done by hand, but that can be be tedious. Beat envelope:- If we add two waves of slightly different frequencies, the resulting amplitude will vary or oscillate at a rate that is the difference between the frequencies. That beat frequency will create a beat envelope around the original sine wave. In this figure beat envelope modulates the amplitude of the sound Since the frequencies of the two sounds are so close and we would hear a sound that is an average of the two. But we would also hear the modulation of the amplitude as a beat frequency, which is the difference between the initial frequencies. fb = | f1 à ¢Ã‹â€ Ã¢â‚¬â„¢ f2 | where fb is the beat frequency . f1 and f2 are the two sound frequency. | f1 à ¢Ã‹â€ Ã¢â‚¬â„¢ f2 | is the absolute value or positive (+) value of the difference . Examples:- For example, if we add a wave oscillating at 445 Hz with one that is at 450 Hz, the resulting frequency will be an average of the sum of the two waves. (445 Hz + 450 Hz)/2 = 447.5 Hz. This waveform is close to a sine wave, since the frequency are almost the same. The amplitude of volume of this combination will oscillate at the beat frequency of the difference between the two: (450 Hz 445 Hz) = 5 Hz. Now, if we add 440 Hz and 500 Hz notes, the resulting waveform will be a complex version of a sine wave and will sound like a fuzzy average of the two tones. The average frequency of this complex wave will be (440 Hz + 500 Hz)/2 = 470 Hz. Also, its beat frequency will be 60 Hz, which would sound like a very low-pitched hum instead of a fluctuating volume. When two sound waves of different frequency approach your ear, the alternating constructive and destructive interference causes the sound to be alternatively soft and loud a phenomenon which is called beatingor producing beats. The beat frequency is equal to the absolute value of the difference in frequency of the two waves. -:Applications of Beats:- -:Envelope of Beat Production:- Beats are caused by the interference of two waves at the same point in space. This plot of the variation of resultant amplitude with time shows the periodic increase and decrease for two sine waves. The image below is the beat pattern produced by a London police whistle, which uses two short pipes to produce a unique three-note sound. Sum and difference frequencies Interference and Beats:- Wave interference is the phenomenon that occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium. If two upward displaced pulses having the same shape meet up with one another while traveling in opposite directions along a medium, the medium will take on the shape of an upward displaced pulse with twice the amplitude of the two interfering pulses. This type of interference is known as constructive interference. If an upward displaced pulse and a downward displaced pulse having the same shape meet up with one another while traveling in opposite directions along a medium, the two pulses will cancel each others effect upon the displacement of the medium and the medium will assume the equilibrium position. This type of interference is known as destructive interference. The diagrams below show two waves one is blue and the other is red interfering in such a way to produce a resultant shape in a medium; the resultant is shown in green. In two cases (on the left and in the middle), constructive interference occurs and in the third case (on the far right, destructive interference occurs. But how can sound waves that do not possess upward and downward displacements interfere constructively and destructively? Sound is a pressure wave that consists of compressions and rarefactions. As a compression passes through a section of a medium, it tends to pull particles together into a small region of space, thus creating a high-pressure region. And as a rarefaction passes through a section of a medium, it tends to push particles apart, thus creating a low-pressure region. The interference of sound waves causes the particles of the medium to behave in a manner that reflects the net effect of the two individual waves upon the particles. For example, if a compression (high pressure) of one wave meets up with a compression (high pressure) of a second wave at the same location in the medium, then the net effect is that that particular location will experience an even greater pressure. This is a form of constructive interference. If two rarefactions (two low-pressure disturbances) f rom two different sound waves meet up at the same location, then the net effect is that that particular location will experience an even lower pressure. This is also an example of constructive interference. Now if a particular location along the medium repeatedly experiences the interference of two compressions followed up by the interference of two rarefactions, then the two sound waves will continually reinforce each other and produce a very loud sound. The loudness of the sound is the result of the particles at that location of the medium undergoing oscillations from very high to very low pressures. As mentioned in a previous unit, locations along the medium where constructive interference continually occurs are known as anti-nodes. The animation below shows two sound waves interfering constructively in order to produce very large oscillations in pressure at a variety of anti-nodal locations. Note that compressions are labeled with a C and rarefactions are labeled with an R. Now if two sound waves interfere at a given location in such a way that the compression of one wave meets up with the rarefaction of a second wave, destructive interference results. The net effect of a compression (which pushes particles together) and a rarefaction (which pulls particles apart) upon the particles in a given region of the medium is to not even cause a displacement of the particles. The tendency of the compression to push particles together is canceled by the tendency of the rarefactions to pull particles apart; the particles would remain at their rest position as though there wasnt even a disturbance passing through them. This is a form of destructive interference. Now if a particular location along the medium repeatedly experiences the interference of a compression and rarefaction followed up by the interference of a rarefaction and a compression, then the two sound waves will continually each other and no sound is heard. The absence of sound is the result of the par ticles remaining at rest and behaving as though there were no disturbance passing through it. Amazingly, in a situation such as this, two sound waves would combine to produce no sound. location along the medium where destructive interference continually occurs are known as nodes. Two Source Sound Interference:- A popular Physics demonstration involves the interference of two sound waves from two speakers. The speakers are set approximately 1-meter apart and produced identical tones. The two sound waves traveled through the air in front of the speakers, spreading our through the room in spherical fashion. A snapshot in time of the appearance of these waves is shown in the diagram below. In the diagram, the compressions of a wavefront are represented by a thick line and the rarefactions are represented by thin lines. These two waves interfere in such a manner as to produce locations of some loud sounds and other locations of no sound. Of course the loud sounds are heard at locations where compressions meet compressions or rarefactions meet rarefactions and the no sound locations appear wherever the compressions of one of the waves meet the rarefactions of the other wave. If we were to plug one ear and turn the other ear towards the place of the speakers and then slowly walk across the room pa rallel to the plane of the speakers, then you would encounter an amazing phenomenon. we would alternatively hear loud sounds as you approached anti-nodal locations and virtually no sound as you approached nodal locations. (As would commonly be observed, the nodal locations are not true nodal locations due to reflections of sound waves off the walls. These reflections tend to fill the entire room with reflected sound. Even though the sound waves that reach the nodal locations directly from the speakers destructively interfere, other waves reflecting off the walls tend to reach that same location to produce a pressure disturbance.) Destructive interference of sound waves becomes an important issue in the design of concert halls and auditoriums. The rooms must be designed in such as way as to reduce the amount of destructive interference. Interference can occur as the result of sound from two speakers meeting at the same location as well as the result of sound from a speaker meeting with sound reflected off the walls and ceilings. If the sound arrives at a given location such that compressions meet rarefactions, then destructive interference will occur resulting in a reduction in the loudness of the sound at that location. One means of reducing the severity of destructive interference is by the design of walls, ceilings, and baffles that serve to absorb sound rather than reflect it. The destructive interference of sound waves can also be used advantageously in noise reduction systems. Earphones have been produced that can be used by factory and construction workers to reduce the noise levels on their jobs. Such earphones capture sound from the environment and use computer technology to produce a second sound wave that one-half cycle out of phase. The combination of these two sound waves within the headset will result in destructive interference and thus reduce a workers exposure to loud noise. Musical Beats and Intervals:- Interference of sound waves has widespread applications in the world of music. Music seldom consists of sound waves of a single frequency played continuously. Few music enthusiasts would be impressed by an orchestra that played music consisting of the note with a pure tone played by all instruments in the orchestra. Hearing a sound wave of 256 Hz , would become rather monotonous (both literally and figuratively). Rather, instruments are known to produce overtones when played resulting in a sound that consists of a multiple of frequencies. Such instruments are described as being rich in tone color. And even the best choirs will earn their money when two singers sing two notes i.e., produce two sound waves that are an octave apart. Music is a mixture of sound waves that typically have whole number ratios between the frequencies associated with their notes. In fact, the major distinction between music and noise is that noise consists of a mixture of frequencies whose mathematical relati onship to one another is not readily discernible. On the other hand, music consists of a mixture of frequencies that have a clear mathematical relationship between them. While it may be true that one persons music is another persons noise (e.g., your music might be thought of by your parents as being noise), a physical analysis of musical sounds reveals a mixture of sound waves that are mathematically related. To demonstrate this nature of music, lets consider one of the simplest mixtures of two different sound waves two sound waves with a 2:1 frequency ratio. This combination of waves is known as an octave. A simple sinusoidal plot of the wave pattern for two such waves is shown below. Note that the red wave has two times the frequency of the blue wave. Also observe that the interference of these two waves produces a resultant (in green) that has a periodic and repeating pattern. One might say that two sound waves that have a clear whole number ratio between their frequencies interfere to produce a wave with a regular and repeating pattern. The result is music. Another easy example of two sound waves with a clear mathematical relationship between frequencies is shown below. Note that the red wave has three-halves the frequency of the blue wave. In the music world, such waves are said to be a fifth apart and represent a popular musical interval. Observe once more that the interference of these two waves produces a resultant (in green) that has a periodic and repeating pattern. It should be said again: two sound waves that have a clear whole number ratio between their frequencies interfere to produce a wave with a regular and repeating pattern; the result is music. Finally, the diagram below illustrates the wave pattern produced by two dissonant or displeasing sounds. The diagram shows two waves interfering, but this time there is no simple mathematical relationship between their frequencies (in computer terms, one has a wavelength of 37 and the other has a wavelength 20 pixels). We observe that the pattern of the resultant is neither periodic nor repeating (at least not in the short sample of time that is shown). It is clear: if two sound waves that have no simple mathematical relationship between their frequencies interfere to produce a wave, the result will be an irregular and non-repeating pattern. This tends to be displeasing to the ear. A final application of physics to the world of music pertains to the topic of beats. Beats are the periodic and repeating fluctuations heard in the intensity of a sound when two sound waves of very similar frequencies interfere with one another. The diagram below illustrates the wave interference pattern resulting from two waves (drawn in red and blue) with very similar frequencies. A beat pattern is characterized by a wave whose amplitude is changing at a regular rate. Observe that the beat pattern (drawn in green) repeatedly oscillates from zero amplitude to a large amplitude, back to zero amplitude throughout the pattern. Points of constructive interference (C.I.) and destructive interference (D.I.) are labeled on the diagram. When constructive interference occurs between two crests or two troughs, a loud sound is heard. This corresponds to a peak on the beat pattern (drawn in green). When destructive interference between a crest and a trough occurs, no sound is heard; this corres ponds to a point of no displacement on the beat pattern. Since there is a clear relationship between the amplitude and the loudness, this beat pattern would be consistent with a wave that varies in volume at a regular rate. The beat frequency refers to the rate at which the volume is heard to be oscillating from high to low volume. For exà ¢Ã¢â€š ¬Ã‚ ¦, if two complete cycles of high and low volumes are heard every second, the beat frequency is 2 Hz. The beat frequency is always equal to the difference in frequency of the two notes that interfere to produce the beats. So if two sound waves with frequencies of 256 Hz and 254 Hz are played simultaneously, a beat frequency of 2 Hz will be detected. A common physics demonstration involves producing beats using two tuning forks with very similar frequencies. If a tine on one of two identical tuning forks is wrapped with a rubber band, then that tuning forks frequency will be lowered. If both tuning forks are vibrated together, then they produce sounds with slightly different frequencies. These sounds will interfere to produce detectable beats. The human ear is capable of detecting beats with frequencies of 7 Hz and below. A piano tuner frequently utilizes the phenomenon of beats to tune a piano string. She will pluck the string and tap a tuning fork at the same time. If the two sound sources the piano string and the tuning fork produce detectable beats then their frequencies are not identical. She will then adjust the tension of the piano string and repeat the process the beats can no longer be heard. As the piano string becomes more in tune with the tuning fork, the beat frequency will be reduced and approach 0 Hz. When beats are no longer heard, the piano string is tuned to the tuning fork; that is, they play the same frequency. The process allows a piano tuner to match the strings frequency to the frequency of a standardized set of tuning forks. Important Note:- Many of the diagrams on this page represent a sound wave by a sine wave. Such a wave more closely resembles a transverse wave and may mislead people into thinking that sound is a transverse wave. Sound is not a transverse wave, but rather a longitudinal wave. Nonetheless, the variations in pressure with time take on the pattern of a sine wave and thus a sine wave is often used to represent the pressure-time features of a sound wave. Whenever two wave motions pass through a single region of a medium simultaneously, the motion of the particles in the medium will be the result of the combined disturbance due to the two waves. This effect of superposition of waves, is also known as interference. The interference of two waves with respect to space of two waves traveling in the same direction, has been described in previous section. The interference can also occur with respect to time (temporal interference) due to two waves of slightly different frequencies, travelling in the same direction. An observer will note a regular swelling and fading or waxing and waning of the sound resulting in a throbbing effect of sound called beats. Number of beats heard per second Qualitative treatment:- Suppose two tuning forks having frequencies 256 and 257 per second respectively, are sounded together. If at the beginning of a given second, they vibrate in the same phase so that the compressions (or rarefactions) of the corresponding waves reach the ear together, the sound will be reinforced . Half a second later, when one makes 128 and the other  128*1/2 vibrations, they are in opposite phase, i.e., the compression of one wave combines with the rarefaction of the other and tends to produce silence. At the end of one second, they are again be in the same phase and the sound is reinforced. By this time, one fork is ahead of the other by one vibration. Thus, in the resultant sound, the observer hears maximum sound at the interval of one second. Similarly, a minimum loudness is heard at an interval of one second. As we may consider a single beat to occupy the interval between two consecutive maxima or minima, the beat produced in one second in this case, is one in each second. If the two tuning forks had frequencies 256 and 258, a similar analysis would show that the number of beats will be two per second. Thus, in general, the number of beats heard per second will be equal to the difference in the frequencies of the two sound waves. Analytical treatment:- Consider two simple harmonic sound waves each of amplitude A, frequencies f1 and f2 respectively, travelling in the same direction. Let y1 and y2 represent the individual displacements of a particle in the medium, that these waves can produce. Then the resultant displacement of the particle, according to the principle of superposition will be given by Y=y1+y2 This equation represents a periodic vibration of amplitude R and   frequency  . The amplitude and hence the intensity of the resultant wave, is a function of the time. The amplitude varies with a   frequency Since intensity (amplitude)2, the intensity of the sound is maximum in all these cases. For   to assume the above values like 0, p, 2p, 3p, 4p,. Thus, the time interval between two maxima or the period of beats = When the difference in the frequency of the two waves is small, the variation in intensity is readily detected on listening to it. As the difference increases beyond 10 per second, it becomes increasingly difficult to distinguish them. If the difference in the frequencies reaches the audible range, an unpleasant note of low pitch called the beat note is produced. The ability to hear this beat note is largely due to the lack of linearity in the response of the ear. Demonstration of beats:- Let two tuning forks of the same frequency be fitted on suitable resonance boxes on a table, with the open ends of the boxes facing each other. Let the two tuning forks be struck with a wooden hammer. A continuous loud sound is heard. It does not rise or fall. Let a small quantity of wax be attached to a prong of one of the tuning forks.. This reduces the frequency of that tuning fork. When the two forks are sounded again beats will be heard. Uses of beats:- The phenomenon of beats is used for tuning a note to any particular frequency. The note of the desired frequency is sounded together with the note to be tuned. If there is a slight difference in frequencies, then beats are produced. When they are exactly in unison, i.e., have the same frequency, they do not produce any beats when sounded together, but produce the same number of beats with a third note of slightly different frequency. Stringed musical instruments are tuned this way. The central note of a piano is tuned to a standard value using this method. The phenomenon of beats can be used to determine the frequency of a tuning fork. Let A and B be two tuning forks of frequencies fA (known) and fB (unknown). On sounding A and B, let the number of beats produced be n. Then one of the following equations must be true. fA fB = n à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. (i) or fB fA = n à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. (ii) To find the correct equation, B is loaded with a little wax so that its frequency decreases. If the number of beats increases, then equation (i) is to be used. If the number of beats decreases, then equation (ii) is to be used. Thus, knowing the value of fA and the number of beats, fB can be calculated. Sometimes, beats are deliberately caused in musical instruments in a section of the orchestra to create sound of a special tonal quality. The phenomenon of beats is used in detecting dangerous gases in mines. The apparatus used for this purpose consists of two small and exactly similar pipes blown together, one by pure air from a reservoir and the other by the air in the mine. If the air in the mine contains methane, its density will be less than that of pure air. The two notes produced by the pipes will then differ in the pitch and produce beats. Thus, the presence of the dangerous gas can be detected. The super heterodyne type of radio receiver makes use of the principle of beats. The incoming radio frequency signal is mixed with an internally generated signal from a local oscillator in the receiver. The output of the mixer has a carrier frequency equal to the difference between the transmitted carrier frequency and the locally generated frequency and is called the intermediate frequency. It is amplified and passed through a detector. This system enables the intermediate frequency signal to be amplified with less distortion, greater gain and easier elimination of noise Summary:- A beat frequency is the combination of two frequencies that are very close to each other. The sound you hear will fluctuate in volume according to the difference in their frequencies. You may often hear beat frequencies when objects vibrate. Beat frequencies can be graphically shown by adding two sine waves of different frequencies. The resulting waveform is a sine wave that has an envelope of modulating amplitude.

Analysis of QoS Parameters

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