Sterotypes and Diversity in American Research Paper

Sterotypes and Diversity in American - Research Paper Example Stories related by friends and families, narratives handed down from generations to generations, information from books and magazines, and depictions in movies and television allow individuals to formulate generalizations. Majority of these stereotypical generalizations are logically correct, however, in almost all cases, humanity is resorting to bigotry by assigning labels and categorizations about a person merely rooted in a stereotype, devoid of real facts. Through stereotyping, suppositions are made on a person or group with some individuality. Stereotypical biases are oftentimes derived from secondhand information (Grobman, 1990). Extensive and continuous circulation of stereotypes causes uncertainty between realism and fallacy for both the subject and doer (Prell, 2009). At the time the United States was experiencing remarkable changes in the nineteenth and twentieth centuries from enormous immigrant arrivals; modernization and industrial ascension; and the inclusion of women, races, and minorities in the labor force, American civilization developed preoccupations with inflexible and often vindictive cultural stereotypes in the fields of literature, arts, and the media (Prell, 2009). As portrayed in the movie industry, African-Americans are negatively stereotyped as intellectually incapable, idle, or violent. Consequently, with this type of pigeonholed films, injustice in opposition to African-Americans is promoted. Another example of media stereotype is how women, the physically perfect in particular, are constantly presented as weak, unintelligent and sexually immoral (Grobman, 1990). Fashion icons, sports figures, television and movie personalities are glamorously represented by the media as models of perfection. However, ethnic, gendered, and culture-rooted stereotypes are oftentimes impossibly achievable resulting in a great divide between genders boasted in the media and the â€Å"ordinary† sexes of society. Moreover, with the current trend o f humanity’s fixation for excellence, society is confronted with socio-cultural threats and loss of identity and ethnicity (McConnell, 2008). The dilemma frequently comes up once the ‘label’ twists from being a classifier into an insulting position for the subject, especially if the individual formulating the stereotype is a person of authority. At that juncture, it is not simply the human perception of stereotypes but the person who commands power, creates labels and holds egotistic interests that is at fault. When a stereotype is used for maneuvering an individual’s manner of judgment, it has to be classified if it is an instrument or an obstruction in the user’s opinion (Stewart, n.d.). This paper will provide an explanation as to why stereotypes are made. Advantages and disadvantages of negative stereotyping will be laid out to raise awareness on how it affects the social wellbeing of a stigmatized individual. A treatment plan in combating negat ive stereotypes through active participation of individuals, the media and the educational system, will likewise be presented. The Reasons behind Stereotypes Nowadays, the term 'stereotype' is perceived as a form of maltreatment and exploitation. Diverse groups, predominantly the black outcasts, inferior-to-men women and discriminated gays, are stereotyped in the mass media and in the

FDIC takes the Banks back Research Paper Example | Topics and Well Written Essays - 1500 words

FDIC takes the Banks back - Research Paper Example The following brief discussion will focus on the FDIC and its second mission, to reduce the economic disruptions caused by bank failures. Specifically, the role of the FDIC in the recent spate of bank closures will be examined. In conclusion the FDICs intervention in the bank failures will be critically analyzed to determine its impacts, or lack thereof, on the American economy during the recent economic crisis popularly known as the Great Recession. Written in the 1980s the FDIC official history described American banks as â€Å"more closely regulated than in any other nation.† (â€Å"The First Fifty Years†) In the quarter century since that volume was written the situation changed significantly. American banks underwent a comprehensive process of deregulation that climaxed during the former Republican administration. In 2007 Philip E Strahan summarized the effects of more than a decade of deregulation: â€Å"Interest rate ceilings on deposits were phased out in the early 1980s; state usury laws have been weakened because banks may now lend anywhere; and limits to banks’ ability to engage in other financial activities have been almost completely eliminated, as have restrictions on the geographical scope of banking.† He also praised the positive impacts of deregulation. It â€Å"allowed banks to offer better services to their customers at lower prices. As a result, the real economy—Main Street as it were—seems to have benefited† and â€Å"Overall economic growth accelerated following deregulation.† (Strahan, 2007) Strahan was a firm proponent of the stimulative effect of banking deregulation. He also saw its benefits being distributed throughout society and including, notably, Main Street. When Strahans remarks were published in the influential, Federal Reserve Bank of St. Louis Reviews July/August issue in 2007.

HRD Essay Example | Topics and Well Written Essays - 2250 words

HRD - Essay Example However, in accomplishing this particular objective of long-run sustainability, employee absenteeism rate is argued as a major challenge for Human Resource Managers (HRM) that is quite likely to result in declining productivity of the organisation, increasing conflicts amid the employees and hindered sustainability of the entire organisation (Cascio & Boudreau, 2010). Emphasising the severity of the effects of absenteeism, the discussion henceforth focuses on examining the issue on the basis of critical theoretical explanation. In this regard, various relevant theories have been considered in order to evaluate the factors that contribute towards the increasing the number of employees’ absenteeism rate in the modern day context. Employees’ Absenteeism Rate Employee absenteeism is often attributed as one of the most serious and challenging issues prevailing in organisations today. It is evident that employees are among the key assets for HRM in context to their operationa l efficiency and sustainability. Efficient and dedicated performances of the employees result in higher productivity, which further tends to have favourable impacts on the operations of the business. Conversely, inefficient performance of employees has often been observed to have led to lower productivity, which further contribute to a continuous decline in the company performance altogether. Absenteeism is viewed as a habitual pattern of absence deciphered by employees obstructing them from executing their responsibilities in the most effective manner. It is worth mentioning in this context that according to the modern managerial notion, high absenteeism rate of employees in workplace is often attributed as a by-product of poor work satisfaction owing to lack of motivation and morale (Cascio & Boudreau, 2010). To gain a comprehensive understanding on the increasing rate of employee absenteeism, certain relevant theories and concepts have been explained in the discussion below. Soci al Learning Theory of Employee Self-management Social Learning theory is a particular concept that has been applied in the workplace with the intention to encourage employees towards obtaining adequate learning experiences in their working process. This theory can be observed to be directly relevant with the behaviour and psychology of the employees. The theory basically states that people in the society learn mostly through their personal experiences that are acquired by their presences among others or through social interactions to be more precise. The theory further depicts that people in the society mainly learn by imitating or by observing the approach or actions of others. It is deemed that this theory have both positive and negative aspects associated with it in context to the workplace attitude of employees (French, 2011). According to Bandura (1971), employees in the workplace learn from others in a particular process, which includes attention, retention, reproduction and m otivation. Employees in the workplace is deemed to pay attention to what others do, often without judging the interpersonal differences or the after-effects of such a behaviour. As per the Social Learning theory, absenteeism habits of other employees might also be considered as a factor that attracts employees in the workplace and causes negative effects on their performances. As per this theory, the

Bretton Woods Institutions Essay Example | Topics and Well Written Essays - 1500 words

Bretton Woods Institutions - Essay Example Many people regard these post-colonial institutions to help the developing countries. According to Anghie (2002), these institutions define the ‘unique’ relationship, which exists between international organizations and the Third World. These institutions have been developed, in order for technological advancement of different countries from the developing world, and to refine, reinforce, reproduce and manage the statehood of countries from the Third World (Tan, pp. 31, 2011). Although, established with the aim of reconstructing Europe, the World Bank has taken part in many development projects that have occurred in the Third World. World Bank has also provided different loans to these countries, in order for them to establish themselves properly (Chebucto, n.p, n.d). Although these organizations have been created under the UN charter; in practice, they are largely autonomous (Willis, pp. 36, 2005). These institutions, developed some 60 years ago were developed to put an end to the depression, caused by economic problems, as well as the war, and were a beacon of light for many, especially for the development countries. For this purpose, the paper seeks to examine the ways that the institutions have helped the poor countries (Daly, Farley, pp. 318, 2004). However, since there is large criticism surrounding these Bretton Woods Institutions, it is also imperative to discuss the extent that these organizations have been pro-poor over the years. Nonetheless, it is important to discuss the roles of these two sister organizations, before judging their actions. Although, they had been developed for different purposes, their roles have changed dramatically over the ensuing years. The World Bank seeks to provide development assistance. On the other hand, the International Monetary Fund (IMF) promotes monetary cooperation on an international level through surveying the countries, and lends to those countries, which have a negative position in Balance of Payme nts (BOP). However, their roles often overlap with each other, since they both seek to provide financial assistance, through one way or the other. For example, considering the actions of World Bank and IMF after the economic crisis in Latin America, one would notice that both these organizations help each other in their respective goals (Weiss, Daws, pp. 1, 2006). One can recognize that they have been active in working for the development for the poor through the ways that they have rapidly changed their roles. Aside from maintaining a fixed exchange rate system, which helped poor countries develop economically, the IMF also gave loans to countries, which had balance of payments problems. Most of these problems are experienced by countries, belonging to the Third World, and the repercussions of negative balance of payments are quite magnificent. Hence, in order to correct this situation, short-term loans were provided, during the 1950s. The World Bank sought to develop different cou ntries, by encouraging private investment to flow into the Third World, so that more development could occur in these countries (Weiss, Dawas, pp.5, 2006). Throughout the years, they kept adding more problems to their agenda, so that these problems could be solved. In 1988, the Multilateral Investment

Edgar Allan Poe Essay Example for Free

Edgar Allan Poe Essay Many poets and story writers write their stories based upon events and aspects of their life. They do this because it is so relatable and easy to write about because there is some truth in the words. Edgar Allan Poe is said to be one of these because his stories actually relate to his tragic, love stricken life. He is known to lead an overall depressing life that was full of loss and grief of loved ones. So because of this, Poe suffered most of his life. But although he had many misfortunes, he resorted to his passion of poetry to help him. Poe wrote many stories and poems that both reflected and represented his life. Stories such as Annabel Lee strongly show this as it is about the death of a loved women. Edgar Allan Poe was a mysterious man that accomplished many feats and went on to become one of the world’s most famous poets, although he also had a devastating life. On January 19th, 1809, Edgar Poe was born in Boston (â€Å"Edgar Allan Poe† Wikipedia). He began his tragic life at a young age of three years old when his mother died and father left him (â€Å"Edgar Allan Poe† Wikipedia). Then as an orphan, young Edgar was adopted by his uncle, a tobacco merchant, John Allan, and his wife Frances (â€Å"Edgar Allan Poe† Wikipedia). After years of school, Poe was admitted to the University of Virginia at only sixteen, but stayed for only one semester because of lack of financial aid from Allan (Giordano). Angry with Allan, Poe decided to enlist into the army as a private (Giordano). There, he published his first book in 1827, â€Å"Tamerlane and Other Poems,† and his career as a writer spiraled outward from there (â€Å"Edgar Allan Poe† Wikipedia). Poe continued to write and publish small books, earned little money, and did what he could to get noticed. He soon had another book published and by this point, he had a great fan base and was considered a celebrity in Baltimore (â€Å"Edgar Allan Poe† Wikipedia). His readers felt his work was so unique and sometimes even asked for autographs from Poe. From this publicity, he was earning good money. But the good fortune didn’t last long and he was soon at the poverty level again and moved back and forth from New York to Virginia, submitting stories to and working for different magazines, getting small amounts of money here and there. Then, in 1841, while working for Grahams Magazine (â€Å"Edgar Allan Poe† NNBD), Poe wrote the first ever detective story, a murder mystery. It was titled â€Å"The Murders in the Rue Morgue† (Giordano). The public had never seen this kind of story so it immediately became famous and Edgar’s fame rose even higher. Poe had created a whole new topic in literature and some agree that this was his greatest contribution to world literature. In the next several years, Poe lost his wife Virginia but continued writing novels and stories in his grief (â€Å"Edgar Allan Poe† Gale). This is said to be a basis for inspirations for his stories such as Annabel Lee and others (â€Å"Edgar Allan Poe† Wikipedia). He once said â€Å"The death of a beautiful woman is unquestionably the most poetical topic in the world. † (LeVert 12). When not further loved, Poe tried to commit suicide in Boston (â€Å"Edgar Allan Poe† NNBD). In this state of depression, Poe wrote the poem â€Å"Annabel Lee† using his favorite theme, the grief a man feels when he loses women (â€Å"Edgar Allan Poe† Wikipedia). Poe died on the October 7th due to complications related to a brain lesion (Giordano). This was the end of the tragic life of poet Edgar Allan Poe. Edgar Allan Poe led an influential but very rough life. He was usually in need of money despite his fame, but wrote a total of 30 books alongside starting a whole new genre of writing. This author/poet wrote some of the best stories and poems and although he wasn’t so lucky in the events of his life, he will always be remembered as a great influence on American Literature. One of the stories Poe wrote relating to the â€Å"death of a beautiful women† was Annabel Lee wrote in 1849, approximately 5 months before his death. This makes sense because throughout his life, Poe had lost many women to death in his life including his mother and his only wife Virginia, who died two years prior to the poem being written (â€Å"Edgar Allan Poe† Wikipedia). There has been debate on who this tragic story is about but most believe that is was truly written for Virginia, who he had married when she was 13 years old and died in 1847 (Giordano). This is supported by the fact that Virginia was Edgar’s only marriage, and the only one of his girlfriends that had died (â€Å"Edgar Allan Poe† Wikipedia). Also, in the poem, the narrator says that he fell in love with â€Å"Annabel Lee† when they were children and he did make her his wife (â€Å"Edgar Allan Poe† Wikipedia). The famous poem is about, again, the death of a beautiful woman named Annabel Lee and the eternal love after death he fells for her. The narrator says that â€Å"even winged seraphs of heaven coveted her and me† meaning that even the angels in heaven were jealous of the love he and Annabel shared (Giordano). Like Poe’s love for Virginia, the narrator expresses great loss and sadness when she dies, losing his one true love. As also implied in the poem, he sits by her grave at night just to be near his loved one. This shows the divine love he had for â€Å"Annabel Lee† (Giordano). Annabel Lee is a prose poem written in the first person and was first published in Sartain’s Union Magazine. As it was so close to his date of death, it was his very last completed poem (â€Å"Edgar Allan Poe† Wikipedia). Edgar Allan Poe had a great impact in the poetry and the overall literature world. He was a very mysterious man who lived a tough life and went through several struggles including death of loved ones. But from these losses and hardships came the inspiration for incredible poems like â€Å"Annabel Lee†. He wrote some of the world’s best poems, short stories, and novels and in doing so introduced the first detective story to America. The inspiring work he produced will be read and cherished forever.

Product Services And Branding Strategy Essay

Product Services And Branding Strategy Essay The term marketing mix was coined in 1953 by Neil Borden in his American Marketing Association presidential address. However this was actually a reformulation of an earlier idea by his associate, James Culliton, who in 1948 described the role of the marketing manager as a mixer of ingredients, who sometimes follows recipes prepared by others, sometimes prepares his own recipe as he goes along, sometimes adapts a recipe from immediately available ingredients, and at other times invents new ingredients no one else has tried.[1] A prominent marketer, E. Jerome McCarthy, proposed a Four P classification in 1960, which has seen wide use. The Four Ps concept is explained in most marketing textbooks and classes. -Definition: Marketing mix is the combination of elements that you will use to market your product. There are four elements: Product, Place, Price and Promotion. They are called the four Ps of the marketing mix Product A tangible object or an intangible service that is mass produced or manufactured on a large scale with a specific volume of units. Intangible products are service based like the tourism industry the hotel industry or codes-based products like cellphone load and credits. Typical examples of a mass produced tangible object are the motor car and the disposable razor. A less obvious but ubiquitous mass produced service is a computer operating system. Packaging also needs to be taken into consideration. Every product is subject to a life-cycle including a growth phase followed by an eventual period of decline as the product approaches market saturation. To retain its competitiveness in the market, product differentiation is required and is one of the strategy to differentiate from its competitors Level 1: Core Product. What is the core benefit your product offers?. Customers who purchase a camera are buying more then just a camera they are purchasing memories. Level 2 Actual Product: All cameras capture memories. The aim is to ensure that your potential customers purchase your one. The strategy at this level involves organisations branding, adding features and benefits to ensure that their product offers a differential advantage from their competitors. Level 3: Augmented product: What additional non-tangible benefits can you offer? Competition at this level is based around after sales service, warranties, delivery and so on. John Lewis a retail departmental store offers free five year guarantee on purchases of their Television sets, this gives their `customers the additional benefit of peace of mind over the five years should their purchase develop a fault. Product Decisions When placing a product within a market many factors and decisions have to be taken into consideration. These include: Product design: Will the design be the selling point for the organisation as we have seen with the iMAC, the new VW Beetle or the Dyson vacuum cleaner. Product quality: Quality has to consistent with other elements of the marketing mix. A premium based pricing strategy has to reflect the quality a product offers. Product features: What features will you add that may increase the benefit offered to your target market? Will the organisation use a discriminatory pricing policy for offering these additional benefits? Additional features should increase the benifit offered to your target market. The firm may decide to charge more for these additional features. Branding: One of the most important decisions a marketing manager can make is about branding. The value of brands in today ¿Ã‚ ½s environment is phenomenal. Brands have the power of instant sales, they convey a message of confidence, quality and reliability to their target market.In principles of marketing by philip Kotler and gary armstrong a brand is defined as a name, term, sign symbol or a combination of these, that identifies the marker or seller of the product. A brand must stand out and be recognizable, and should help the firm differentiate itself from its competitors. Brands have to be managed well, as some brands can be cash cows for organisations. In many organisations they are represented by brand managers, who have hugh resources to ensure their success within the market. A brand is a tool which is used by an organisation to differentiate itself from competitors. Ask yourself what is the value of a pair of Nike trainers without the brand or the logo? How does your perception change? Increasingly brand managers are becoming annoyed by  ¿Ã‚ ½copycat ¿Ã‚ ½ strategies being employed by supermarket food retail stores particular within the UK . Coca-Cola threatened legal action against UK retailer Sainsbury after introducing their Classic Cola, which displayed similar designs and fonts on their cans. Internet branding is now becoming an essential part of the branding strategy game. Recently within the UK banking industry we have seen the introduction of Internet banks such as cahoot.com and marbles.com the task by brand managers is to make sure that consumers understand that these brands are banks! The price is the amount a customer pays for the product. The business may increase or decrease the price of product if other stores have the same product pricing is one of the most important elements of the marketing mix. It is the only mix which generates a turnover for the organization. The remaining 3 ps are the varaible cost of the organisation. It costs to produce and design a product, it costs to distribute a product and it costs to promote a product. Pricing is diffiicult and must reflect supply and demand relationship. Pricing a product too high or too low could mean a loss of sales for the organisation. Pricing should take into consideration the following factors: 1.Fixed and variable costs. 2.Competition. 3.Company objectives 4.Proposed positioning strategies. 5.target group and willingness to pay. An organisation can adopt a number of pricing strategies among the following. 1.penetration price: Where the org sets a low price to increase sales and market share. 2.Skimming pricing: The org sets an initial high price and then slowly lowers the price to make the product available to a wider market. The objective is to skim profits of the market layer by layer. 3.Competition pricing: Setting a price in comparision with competitors.A firm has three options, price lower, price the same or price higher. 4.Product line pricing: Pricing different products within the same product range at different price points.The greater the features and benifits obtained the greater the consumer will pay. 5.Bundle pricing: the organisation bundles a group of products at a reduced price. 6.Psycological pricing: The seller will consider the psycology of the price and the positioning of the price within the market place. The seller with therefore charge 99p instead of  ¿Ã‚ ½1 or  ¿Ã‚ ½199 instead of  ¿Ã‚ ½200. 7.Premium pricing: The price set is high to reflect the exclusiveness of the product. 8.Optional pricing: The organisation sells optional extras along with the product to maximise its turnover. http://www.vodafone.com/etc/medialib/cr10/pdf.Par.17290.File.dat/vodafone_sustainability_report.pdf

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