Competition Protects Consumers, Politicians Protect Themselves :: Politics Political Essays

Rivalry Protects Consumers, Politicians Protect Themselves Baltimore Sun political author H. L. Mencken once cautioned, The entire point of pragmatic legislative issues is to keep the people frightened, and consequently rambunctious to be directed to security, by threatening it with a perpetual arrangement of ogres, every one of them fanciful. As heros lawmakers at that point report a variety of government projects to protect an appreciative electorate from some ogre. For that security, citizens are compelled to hack up billions of dollars to back government organizations like the Federal Trade Commission (FTC), Consumer Product Safety Administration (CPSC), and the Food and Drug Administration (FDA). Would could it be that at last secures the customer? It's not government but rather rivalry - numerous makers contending with one another for our dollars. What spurs a market supervisor to have deals, present new items and administrations and unremittingly scan for different approaches to satisfy us and make us faithful clients? The simple answer is that the administrator looks for more prominent benefits, yet benefits can't be basically proclaimed in light of the fact that he has no capacity to constrain us to shop at his store. He should draw us into his store satisfying us more than our next best other option - his rival down the road. The life of the director and his workers, would be a lot simpler in the event that they could get lawmakers to express level playing field laws to secure buyers against vicious rivalry. A level playing field law may command that all food merchants charge similar costs, sell similar things, and give indistinguishable client administrations. That way rivalry would be diminished. At this moment your merchant and his workers realize that on the off chance that he charges significant expenses and offers low quality support, you will take your business somewhere else. That would bring about less business, lower benefits and perhaps chapter 11. Be that as it may, if the director and his representatives could convince legislators to sanction a level playing field law, it would be an alternate story. The indistinguishable standard applies to laborers. A few people think trade guilds, Occupational Safety and Health Administration (OSHA), and the lowest pay permitted by law laws ensure the specialist. Worker's guilds, OSHA guidelines and least wages laws do ensure the occupations and pay of certain laborers yet to the detriment of other specialists' employments and salary. Worker's organizations and many work laws are minimal in excess of a conspiracy against different specialists. Association pioneers contend that their entitlement to strike is their most incredible asset in their quest for higher wages and better working conditions.

Encyclopedia of Dating Customs and Wedding †MyAssignmenthelp.com

Question: Talk about the Encyclopedia of Dating Customs and Wedding. Answer: Presentation Each individual plans a wedding that can be associated with an amazing remainder and stands apart as the most essential day in all their years. The wedding is related with customs and feelings, and subsequently individuals attempt and give out their best when they anticipate marriage (Monger, 2013). In spite of the fact that the possibility of the wedding is age-old, it is seen that numerous new thoughts have been joined into the procedure to make it stand apart from the conventional wedding rehearses. Be that as it may, the new components have been incorporated at the same time, the typical highlights stay steady and have a significant influence in the whole wedding process. The report will concentrate on the new things in the wedding alongside the conventional practices that are yet predominant. New parts of the advanced wedding The advanced wedding is recorded with a lot of new fuses that flourish to make the marriage extraordinary and amazing in its appearance. The possibility of Event the executives and occasion structure in the wedding has had an extensive effect in making the wedding present day in its methodology. New thoughts are being made into the conventional procedure, and this amalgamation makes the occasion further energizing in the cutting edge times. A portion of the components that are engaged with the new wedding are- Goal wedding-The lady of the hour and grooms nowadays seek to marry in a totally new area and away from their home area. The occasion planning group plans for a wedding that is away from the circumstance of the families and the whole procedure of the marriage happens on that specific area. The families travel to the spot alongside the visitors, and the entire game plan is made on that new area (Durinec, 2013). That brings a demeanor of newness, and going for the wedding is such a perspective, that entices the lady of the hour and man of the hour. This is a development in the wedding business as it has lead to making the occasion increasingly agreeable and fascinating for the whole list if people to attend. The visitors are included simply like the family, and consequently every individual remembered for the procedure appreciates and acquires recollections forever. Evacuation of Patriarchal ideas The whole procedure of a dad parting with his girl to man as though he claimed her and is stubbornly dying the proprietorship to her better half is an exceptionally man centric thought. The idea has been created, and nowadays the procedure is loaded with affection, and it is apparent that the young lady isn't claimed by anybody and she is her very own individual character. The lady of the hour came in under the cloak so the husband to be couldn't see the face except if it was an ideal opportunity to kiss the lady. Such suppositions have been diminished, and the settings of such ceremonies have totally changed (Alam, 2014). The lady similarly appreciates the wedding and moves and beverages to have a fabulous time upon the arrival of the wedding, and no cultural weight or judgment is forced on the lady of the hour at early occasions. Amusement consolidating Disk Jockey for playing music and making the individuals move is novel and new. The diversion remainders in the cutting edge weddings have been turned high, and the visitors are made to appreciate each snapshot of the wedding. Beforehand individuals were concerned more with the wedding being taken well however this has changed with time and diversion has transformed into a major need for the coordinators (Sari et al., 2014). Pre-wedding shoots-The new thought of making a video and photo collection of the couple reporting their marriage in a sentimental style gives the wedding a truly necessary imaginative side. Spare the date recordings are made as the couple gives out the date of their wedding through that video and it stays with them perpetually displaying their affection for one another (Napompech, 2014). Customary practices The deep rooted conventional practices that are yet applicable to the wedding function and individuals offer significance to them as much as the new fuse. The custom of wearing a white dress in the wedding is age-old, and it is yet kept up. The lady of the hour wears the white dress, and it creates the impact of a fantasy scene at the wedding as the dresses are of pixie and princess structure. The wedding band contains jewel in it, and this is a convention that is drilled for quite a while and has its importance and use even today. The jewel mirrors the valuable bond that is made during the commitment, and it likewise exhibits the sparkle the couple may have in their marital life from that point after (Francis?Tan Mialon, 2015). The lady of the hour and husband to be leave in a vehicle after the wedding is finished and it has quite recently wedded composed on it. This act of the couple leaving the spot together after the marriage is over is age-old and has been at this point kept all the while. The vehicles that are employed for the couple to leave the wedding area are as per the topic of the wedding. For the most part, as it is a well established practice, the vintage vehicles are chosen by individuals so it loans a demeanor of sovereignty to the whole wedding. End To finish up, wedding days are one of the most critical days for individuals engaged with the procedure. The conventional practices are not totally deferred off, and new components are being added to it to make it fabulous and charming. The feelings and estimations of the individuals are spared with such practices, and subsequently it ensures that the substance of a wedding never blurs. The cutting edge marriage is much about brilliance and style, and it is the conventional traditions that keep the soul of the wedding alive. It is to be respected that individuals nowadays are slanted towards the loftiness of the occasion, and keeping in mind that doing so its quintessence gets some place disappeared if the conventional practices are not coordinated with them. Reference Alam, F. (2014). Inside the Wedding: A Critical Study of Relationships in The God of Small Things and Brick Lane.BANGLADESH RESEARCH FOUNDATION, 158. Recovered from: https://www.researchfoundbd.org/pictures/Vol.3-No.2-2014.pdf#page=171 Durinec, N. (2013). Goal weddings in the Mediterranean.Hospitality and Tourism Management-2013, 1. Recovered from: https://tiikm.com/distribution/ICOHT-2013-continuing book.pdf#page=12 Francis?Tan, A., Mialon, H. M. (2015). A Diamond Is Forever And Other Fairy Tales: The Relationship Between Wedding Expenses And Marriage Duration.Economic Inquiry,53(4), 1919-1930. Recovered from: https://pdfs.semanticscholar.org/e1c8/373b9d170fa5066451b9d60f08e41091c3b3.pdf Monger, G. (2013).Marriage Customs of the World: An Encyclopedia of Dating Customs and Wedding Traditions, [2 Volumes]. Abc-clio. ISBN 1598846647, 9781598846645 Napompech, K. (2014). Characteristics In?uencing Wedding Studio Choice.Journal of Applied Sciences,14(21), 2685-2694. Recovered from: https://docsdrive.com/pdfs/ansinet/jas/0000/65343-65343.pdf Sari, D., Ozkurt, N., Hamamci, S. F., Ece, M., Yalcindag, N., Akdag, An., Akdag, Y. (2014, October). Appraisal of clamor contamination sourced from amusement puts in Antalya, Turkey. InINTER-NOISE and NOISE-CON Congress and Conference Proceedings(Vol. 249, No. 7, pp. 1072-1077). Foundation of Noise Control Engineering. Recovered from: https://www.researchgate.net/profile/Nesimi_Ozkurt/distribution/280223778_Assessment_of_noise_pollution_sourced_from_entertainment_places_in_Antalya_Turkey/joins/55adfd5008aed9b7dcdb0878/Assessment-of-clamor contamination sourced-from-diversion places-in-Antalya-Turkey.pdf

Does Minimalism Make You Complacent

Does Minimalism Make You Complacent I was explaining minimalism to a group of people at a dinner when a guy sporting a post-workday suit-and-tie combo peered at me skeptically when I told them I have no goals. Intrigue overtook his face. My life must’ve seemed so unrealistic to him since he was enmeshed in his corporate life. But that’s not his faultâ€"two years ago it seemed unrealistic to me too: in 2009 my goal-oriented life, obsessed with achievement and to-do lists, was no different from his. Then, his face still wrestling with doubt, he asked, “If you don’t have any goals, then aren’t you just being complacent?” “Yes,” I answered, “if by complacent  you mean content.” Minimalism has helped me become happier, has helped me get rid of life’s excess and be happy with what I have, has helped me live a more meaningful life: I can now focus on what’s important, and I don’t have to “achieve” to be happy. Sounds nice, doesnt it? Thats because it is. You can make the journey too: just decide it’s right for you and take action. Subscribe to The Minimalists via email.

Teaching Strategies For Learning Style Preferences

It is in this article that Beck matches three teaching strategies to learning style preferences. During which he attempts to link the 4MAT system, Dunn’s LSI, and the Renzulli Smith’s LSI to teaching strategies associated to display individual learning preferences linked to the brain’s hemispheres. The 4MAT system and Dunn’s LSI is teacher driven teaching strategies while the Renzulli Smith’s LSI allows student input into their teaching strategies. In linking the 4MAT system to teaching strategies, Beck further explores why certain teaching strategies are more successful and hemispheric appropriate when adapted to their individual natural tendencies. Student learning tendencies are associated with left- mode, right- mode, or multi- mode tendencies. Dunn s LSI includes a wide range of motivations that teachers should consider when determining individual learning styles that may include psychological and cognitive variables. However, Renzulli Smith’s LSI permits student to provide their input to list their favorite to least favorite activities. All three LSI have significance, but it is ultimately the teacher’s role to provide opportunities for each student to unharness their potential. The focus of this article was to perform research on the Preferred Teaching Approach Inventory (PTAI) including psychometric properties. This was performed to determine students preferred teaching styles impacted their personal learning styles. The research suggested thatShow MoreRelatedEducation Is Part Of Everyday Life1037 Words   |  5 Pageseducation and learn all aspect of life, learning must take place. Everyone is different and has individual styles of learning. Learning styles is defined as an individual’s mode of gaining knowledge, especially a preferred or best method (dictionary.com) Therefore, individual must have a better way of teaching others, and same goes to the person receiving the teaching. Learning is optimized by providing instructional method in means suitable for individual’s learning styles. The VARK questionnaire or knownRead MoreThe Objective Of Learning Styles966 Words   |  4 Pagesobjective of learning is to understand information intended to be learned. According to Brown (2000) learning styles is defined as the manner in which individuals perceive and process information in learning situations (Journal of Studies in Education, 2012). Depending on one s perspective, preferred learning styles help defined in multiple ways to get the most out of any learning or teaching experience. There are several ways to evaluate a person’s learning style, preference, and strategies that mayRead MoreThe Analysis : The Vark Questionnaire987 Words   |  4 PagesVARK Analyze Paper: The VARK Questionnaire According to Marcy (2001), â€Å"Learning styles† is a term used to refer to the way someone gathers, process, interprets, organizes, and thinks about information. However, each person has a different style or preference of learning, and being able to identify or understand someone’s learning styles is very important in the learning or teaching process. In the Fleming’s model, also known as VARK, an acronym stands for Visual, Auditory/aural, Read/write, andRead MoreAnalysis Paper : The Objective Of Learning1050 Words   |  5 Pagesobjective of learning is to understand information intended to be learned. According to Brown (2000) learning styles is defined as the manner in which individuals perceive and process information in learning situations (Journal of Studies in Education, 2012). Depending on one s perspective, preferred learning styles help defined in multiple ways to get the most out of any learning or teaching experience. There are several ways to evaluate a person’s learning style, preference, and strategies that mayRead MoreStudent Motivation And Academic Success1568 Words   |  7 Pagesacademic success of a student in college – motivation, learning preferences/styles, socioeconomic status, whether or not the student is a first generation college student, gender, and even race. With so many factors potentially contributing or hindering a student’s academic success in college; it is important for teachers to attempt to connect with students in the classroom. Adjusting instructional methods that focus on students’ learning preferences/styles can increase student motivation and can lead toRead MoreVark Assessment1111 Words   |  5 Pagesmaximum learning. The questionnaire consists of 16 questions which are aimed at isolating a learner’s preference to give them a better understanding of what is most effective for their retention of information being taught. According to the Vark questionnaire, there are four types of dominant learning styles; Visual, Aural, Read/Write and Kinesthetic. Additionally, Vark introduces a sub category of learning called multimodal. (Fleming, 2011) If the learner has a preference for Aural style of learningRead MoreEducational Advancement : Preferred Learning Style And Strategies1092 Words   |  5 PagesAdvancement: Preferred Learning Style and Strategies Learning transpires while an individual changes behavior, conduct, psychological processing, or emotional functioning as a consequence of introduction to new awareness, knowledge or experience. Precisely, a person’s learning style denotes the better approach, in which the learner captivates processes, understands comprehends and retains and recalls information. Learning style is also an individual s distinctive ways and method, learning a well-known onRead MoreEssay Vark Learning Styles1105 Words   |  5 PagesVARK Analysis Learning Style Scott T. Holman Grand Canyon University: NRS-429 June 17, 2014 VARK Analysis Learning Style Learning style is defined as an individual’s natural or habitual pattern of acquiring and processing information in learning situations (James, 1995). Most educational researchers and theorists generally agree that students learn in different ways (Tzu-Chien, 2009). There are many models that address learning styles including Davis A. Kolbs model based on ExperientialRead MoreEssay about Vark Learning Style Analysis1006 Words   |  5 PagesRunning head: VARK LEARNING STYLE ANALYSIS VARK Learning Style Analysis Kathleen Nash Grand Canyon University NRS-429V, Family Centered Health Promotion July 22, 2012 VARK Learning Style Analysis The VARK learning preference tool provides individuals with information that they can utilize to enhance their learning process by helping them to study more effectively and efficiently. The VARK tool consists of a questionnaire that the learner takes to identify which senses the individualRead MoreRelationship Between Learning Styles And Academic / Workplace Environment Essay1242 Words   |  5 PagesTHE RELATIONSHIP BETWEEN LEARNING STYLES AND ACADEMIC/WORKPLACE ENVIRONMENT 1. Learning styles: Learning styles refer to the different ways that people process and retain information and they serve as an indicator of the learning method that each student prefers. The learning styles theories/models that we will discuss about in this report are the Neil Fleming’s Visual-Auditory-Read/Write-Kinesthetic model and David Kolb’s Experiential Learning model. a. Visual-Auditory-Read/Write-Kinesthetic model:

Effective And Efficient Use Of Investment Tax Incentives

Executive Summary It has been observed from past experiences that there is ample room for effective and efficient use of investment tax incentives in Australia. It was found that tax incentives are does not make much impact on changing the investment climate and many times tax incentives turned out to be redundant – that is, investment would have been undertaken even without the incentives. The fiscal cost of tax incentives can be high, reducing opportunities for other required spending like on infrastructure, education and health care or any other sector. Effective and efficient use of tax incentives for small businesses requires careful tax designed. Many times government use income tax exemptions to attract investment or persuade for joint ventures to attract investments. Good infrastructure, long term effective policies, economic stability etc. are important for bringing investment. There is a need of have correct taxation policy to really have a great impact on domestic small business. Good governance of tax incentives is critical for small business growth. Transparency is necessity of time to facilitate accountability, providing opportunities for opening business or for extracting information for rent seekers and to curtail corruption. There are many stakeholders involved in the tax incentive proposal approval but the best in the ministry of finance that enforced and monitored by the tax administration. To grant tax incentives it should be based on rules rather thanShow MoreRelatedTax Reform For Small Businesses1433 Words   |  6 PagesExecutive Summary Tax reform is the crucial component in Government’s policy agenda so as to frame more employment, production, and opportunities. It is mostly initiated for the improvement of levy policy in order to implement social as well as the economic benefits. 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For these reasons, the nation’s historic buildings need to be preserved and restored to their original glory. More state and city governments should follow the federal government’s lead and provide tax incentives to encourage builders to remodel, and thus preserve historic buildings, preventing the demolition of iconic landmarks. A historic building is any place with historical context. The word â€Å"historic† is defined by Merriam Webster Dictionary asRead MoreA Summary On The Executive Summary1422 Words   |  6 PagesThe most efficient methods which are used in the reduction of emissions related to carbon are giving most of the business incentives which are aimed at reducing the activities which lead to the production of more carbon to the atmosphere. This is the efficient method to be used rather than using the command and control method whereby the governments regulate what the individual firms emit or what technology they are using. 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Critical Study of Apoptosis and “programmed cell death” Free Essays

Introduction Apoptosis in the hair follicle is programmed cell death, which occurs at a point during the cell cycle, when a sequence of programmed events causes the cells to be eliminated without the release of waste and harmful substances into the surrounding vicinity. Control of apoptosis is crucial to development of new and recycling of old cells within the body as over stimulation of apoptosis can be fatal, causing extreme tissue damage- examples of which are cancer sufferers. In this review we will discuss evidence from scientific experiments which investigate regulators of apoptosis and what really controls apoptosis in the hair follicle. We will write a custom essay sample on Critical Study of Apoptosis and â€Å"programmed cell death† or any similar topic only for you Order Now Apoptosis within the hair follicle cycle is controlled by many molecular processes and elements, of which include cytokines, tumor necrosis factor receptors, bcl-2 family gene products and ICE proteases (Soma et al., 1998). Apoptosis occurs during the catagen stage of follicle cycling which can also be known as the regression stage, and begins with initiation of receptors to their binding sites. This is specifically the binding of receptors that are rich in extracellular cysteine usually needed for binding, and intracellular compartments specific for signalling (Botchkareva et al., 2006). These receptors- also known as death receptors initiate the beginning of apoptosis, signalling via the mitochondrial membrane and setting in motion adapter molecules complementary to their apoptotic receptors (APO1/Fas receptor or tumor necrosis factor receptor- TNFR). Others include tyrosine kinase receptors- such as nerve growth factor (NGF), and p75 receptor- ‘p75NTR signalling is criticall y important for apoptosis in the regressing ORS and, therefore, for its shortening during catagen’ ( Botchkarev et al.,2000). These signals are conveyed into the cell via a cascade of enzymes known as caspases, which subsequently lead to the next stages of apoptosis. Investigations into apoptosis show that ‘physiological and pathological catagen is noticeably characterised by an up-regulation of ICE expression and an apparent inversion of the Bcl-2/Bax ratio in all epithelial follicle regions that undergo involution during catagen.’(Linder et al., 1997) This refers to intracellular and extracellular molecules located around the hair follicle, which show some control of the progression of cell death, when subjected to variation. The investigation proved that apoptosis within follicular keratinocytes in a normal state or diseased state occurred after a significant reduction in the Bcl-2/Bax ratio, which in turn caused activation of ICE proteases and eventually activation of endonucleases (Linder et al., 1997). This indicates that Bcl-2 and Bax ratios to an extent control apoptosis when down regulated, and then cause a domino effect to upregulate ICE proteases known as the caspase family, to eventually cause DNA to be cleaved into small er fragments, cell shrinkage and rounding, breakdown of the cytoskeleton and membrane blebbing. Caspases are the final inducer of apoptosis from physiological or pathological stimulation, and therefore play a major role in control of apoptosis, by remaining as an inactive form when apoptosis is not required, but becoming activated by the down regulation of the Bcl-2/Bax family of receptors, when apoptosis is required to take place. Caspases are mediators of apoptosis, and are defined and separated into two groups. The first group are the ‘instigators’ and begin the cascade, the second group are the ‘terminators’ which are activated by the instigators and cause the activation of other enzymes within the cell. The caspase family consists of caspase-8, caspase-10 and caspase-3, which act to activate the intrinsic pathway, and to link the extrinsic to the intrinsic pathway by releasing cytochrome c, a process which is primarily controlled by a family of proteins known as the Bcl-2 proteins. These are expressed in the epithelium, surrounding mesenchyme, a nd follicular papilla of the adult hair follicle throughout the cycle (Stenn et al., 1994). The release of cytochrome c ultimately forms a holoenzyme known as the apotosome, which is formed by the apoptosis initiator enzyme procaspase-9, and its adaptor molecule Apaf-1(Botchkareva et al., 2006). These apoptosomes then cleave and activate the procaspase into caspase-9, which subsequently turns on effector caspase-3. Caspase-3 is a major proteolytic enzyme, with the ability to defragment a wide range of molecules and substrates within the cell. The activation of caspase-3 then leads to the cell fragmentation and phagocytosis stages of hair follicle apoptosis. References http://www.nature.com/jid/journal/v126/n2/full/5700007a.html http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1858357/pdf/amjpathol00024-0099.pdf http://endo.endojournals.org/cgi/content/full/146/3/1214 http://www.fasebj.org/content/14/13/1931.long http://www.fasebj.org/content/15/9/1592.full.pdf http://www.applepoly.com/studies/Analysis_of_Apoptotic_Cell_Death_in_Human_Hair_Follicles.pdf How to cite Critical Study of Apoptosis and â€Å"programmed cell death†, Essay examples

Critical Study of Apoptosis and “programmed cell death” Free Essays

Introduction Apoptosis in the hair follicle is programmed cell death, which occurs at a point during the cell cycle, when a sequence of programmed events causes the cells to be eliminated without the release of waste and harmful substances into the surrounding vicinity. Control of apoptosis is crucial to development of new and recycling of old cells within the body as over stimulation of apoptosis can be fatal, causing extreme tissue damage- examples of which are cancer sufferers. In this review we will discuss evidence from scientific experiments which investigate regulators of apoptosis and what really controls apoptosis in the hair follicle. We will write a custom essay sample on Critical Study of Apoptosis and â€Å"programmed cell death† or any similar topic only for you Order Now Apoptosis within the hair follicle cycle is controlled by many molecular processes and elements, of which include cytokines, tumor necrosis factor receptors, bcl-2 family gene products and ICE proteases (Soma et al., 1998). Apoptosis occurs during the catagen stage of follicle cycling which can also be known as the regression stage, and begins with initiation of receptors to their binding sites. This is specifically the binding of receptors that are rich in extracellular cysteine usually needed for binding, and intracellular compartments specific for signalling (Botchkareva et al., 2006). These receptors- also known as death receptors initiate the beginning of apoptosis, signalling via the mitochondrial membrane and setting in motion adapter molecules complementary to their apoptotic receptors (APO1/Fas receptor or tumor necrosis factor receptor- TNFR). Others include tyrosine kinase receptors- such as nerve growth factor (NGF), and p75 receptor- ‘p75NTR signalling is criticall y important for apoptosis in the regressing ORS and, therefore, for its shortening during catagen’ ( Botchkarev et al.,2000). These signals are conveyed into the cell via a cascade of enzymes known as caspases, which subsequently lead to the next stages of apoptosis. Investigations into apoptosis show that ‘physiological and pathological catagen is noticeably characterised by an up-regulation of ICE expression and an apparent inversion of the Bcl-2/Bax ratio in all epithelial follicle regions that undergo involution during catagen.’(Linder et al., 1997) This refers to intracellular and extracellular molecules located around the hair follicle, which show some control of the progression of cell death, when subjected to variation. The investigation proved that apoptosis within follicular keratinocytes in a normal state or diseased state occurred after a significant reduction in the Bcl-2/Bax ratio, which in turn caused activation of ICE proteases and eventually activation of endonucleases (Linder et al., 1997). This indicates that Bcl-2 and Bax ratios to an extent control apoptosis when down regulated, and then cause a domino effect to upregulate ICE proteases known as the caspase family, to eventually cause DNA to be cleaved into small er fragments, cell shrinkage and rounding, breakdown of the cytoskeleton and membrane blebbing. Caspases are the final inducer of apoptosis from physiological or pathological stimulation, and therefore play a major role in control of apoptosis, by remaining as an inactive form when apoptosis is not required, but becoming activated by the down regulation of the Bcl-2/Bax family of receptors, when apoptosis is required to take place. Caspases are mediators of apoptosis, and are defined and separated into two groups. The first group are the ‘instigators’ and begin the cascade, the second group are the ‘terminators’ which are activated by the instigators and cause the activation of other enzymes within the cell. The caspase family consists of caspase-8, caspase-10 and caspase-3, which act to activate the intrinsic pathway, and to link the extrinsic to the intrinsic pathway by releasing cytochrome c, a process which is primarily controlled by a family of proteins known as the Bcl-2 proteins. These are expressed in the epithelium, surrounding mesenchyme, a nd follicular papilla of the adult hair follicle throughout the cycle (Stenn et al., 1994). The release of cytochrome c ultimately forms a holoenzyme known as the apotosome, which is formed by the apoptosis initiator enzyme procaspase-9, and its adaptor molecule Apaf-1(Botchkareva et al., 2006). These apoptosomes then cleave and activate the procaspase into caspase-9, which subsequently turns on effector caspase-3. Caspase-3 is a major proteolytic enzyme, with the ability to defragment a wide range of molecules and substrates within the cell. The activation of caspase-3 then leads to the cell fragmentation and phagocytosis stages of hair follicle apoptosis. References http://www.nature.com/jid/journal/v126/n2/full/5700007a.html http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1858357/pdf/amjpathol00024-0099.pdf http://endo.endojournals.org/cgi/content/full/146/3/1214 http://www.fasebj.org/content/14/13/1931.long http://www.fasebj.org/content/15/9/1592.full.pdf http://www.applepoly.com/studies/Analysis_of_Apoptotic_Cell_Death_in_Human_Hair_Follicles.pdf How to cite Critical Study of Apoptosis and â€Å"programmed cell death†, Essay examples

Violence, Terror and the Crisis of the State an Example of the Topic History Essays by

Violence, Terror and the Crisis of the State Although this article is already dated, it is not yet obsolete. It contains interesting nuggets of political insights that may be built upon by political scientists and understand how the state and social problems interact. The author explores the process of nation-building and looks at how new global communities were created all over the world, thanks to the increasing assertion of ethnic peoples of their right to self-government. Since the state has the monopoly of force, the application of such force in the society over people who seek self-government and independence raises important questions as to the legitimacy of using such force. The author also mentioned the predictions of other writers that more peoples will seek to become independent from states and governments and establish their own states even while economic and cultural globalization is on-going. Need essay sample on "Violence, Terror and the Crisis of the State" topic? We will write a custom essay sample specifically for you Proceed The author explored the various roots of violence, how it permeates daily life, as well as the anthropological studies of violence while drawing upon the history of colonized countries in the world, and she also looked at the warrior class or group (the military) responsible for enforcing the state's monopoly of force. Nagengast also looked at political violence and terrorism, which prior to 2001 was an interesting but not the big problem that it is now. She also looked at the concepts of "state"and "nation"before finally making the connection between state, nation and hegemony. While the article may appear long, Nagengast succeeds in defining and making her reader understand the basics of what she was presenting in the article so that the issue of violence in the context of the state and nation could be addressed more fully. The central question that Nagengast's article addressed, however, is the issue of self-determination of people who consider themselves to belong in the same ethnicity. College Students Very Often Tell Us: Who wants to write essay for me? Professional writers recommend: Essaylab.Com Offers A Top-Quality Academic Essay Academic Writing Services Essay Writing Service Cheap Custom Writing Service Cheap Essay Writing She explained the processes that peoples of different ethnicities face after the end of the colonial period of history. In this context, she also explained how the United Nations recognized the right of peoples for self-determination. However, in most cases where the sate has the monopoly of force, it tends to use violence as a necessary means to keep its borders and keep people from separating from its established boundaries. While the question of identity, ethnicity and self-determination rage in the minds of certain segments of the population of a state, the state can and may use the power of force to impose its will on these people seeking to secede and form their own state. Nagengast does not believe that the world is moving towards a world government. Rather, she argues that more and more nation-states will emerge. History has been re-written since 1994 and so many small nation-states have emerged since then and the world continues to deal with the issues of ethnic people wanting to become independent from governments and states that they do not identify with. Perhaps, this trend will continue in the near future, unless some other new phenomenon occurs that will start the process towards reunification of previous sovereign states-just like the moves toward unity displayed by major European countries through the European Union. In such a case, then, the world may then become a collection of state unions more than just a scattering of nation-states. Reference Journal article "Violence, Terror, and the Crisis of the State" Carole Nagengast

A to Z Animal Profiles List By Common Name

A to Z Animal Profiles List By Common Name Animals (Metazoa) are a group of living organisms that includes more than one million identified species and many millions more that have yet to be named. Scientists estimate that the number of all animal species- those that have been named and those that have yet to be discovered- is between 3 and 30 million species. The following is an A to Z list of animal profiles available at this site, sorted alphabetically by common name: A Aardvark - Orycteropus afer - An arched-backed mammal with long ears. Adà ©lie penguin - Pygoscelis adeliae - A penguin that gathers in huge colonies. African elephant - Loxodonta africana - The largest living land animal. American beaver - Castor canadensis - One of two living species of beavers. American bison - Bison bison - The majestic herbivore of the Great Plains. American black bear - Ursus americanus -  One of three North American bears. American moose - Alces americanus -  The largest member of the deer family. Amphibians - Amphibia - The first land vertebrates. Amur leopard - Panthera pardus orientalis - One of the worlds most endangered cats. Animals - Metazoa - The high-level group to which all animals belong. Arctic wolf - Canis lupus arctos - A white-coated subspecies of the grey wolf. Arthropods - Arthropoda - A highly diverse group of invertebrates. Asian elephant - Elephas maximus - The elephants of  India and Southeast Asia. Atlantic puffin - Fratercula arctica - A small seabird of the North Atlantic. Atlantic white-sided dolphin - Lagenorhynchus acutus - A most colorful dolphin. Aye-aye - Daubentonia madagascariensis - An odd-looking prosimian of Madagascar. B Badger, European - Meles meles - The mustelids of  the British Isles, Europe, and Scandinavia. Baleen Whales - Mysticeti - Bar-headed goose - Anser indicus - Barn owls - Tytonidae - Bats - Chiroptera - Beaver, American - Castor canadensis - Birds - Aves - Birds of prey - Falconiformes - Bison, American - Bison bison - Black rhinoceros - Diceros bicornis - Black-footed ferret - Mustela nigripes - Blue-footed booby - Sula nebouxii - Blue whale - Balaenoptera musculus - Bobcat - Lynx rufus - Bornean orangutan - Pongo pygmaeus - Bottlenose dolphin - Tursiops truncatus - Brown bear - Ursus arctos - Burchells zebra - Equus burchellii - C Caecilians - Gymnophiona - California sea hare - Aplysia californica - Canada goose - Branta canadensis - Canids - Canidae - Caracal - Caracal caracal - Caribou - Rangifer tarandus - Carnivores - Carnivora - Cartilaginous fishes - Chondrichthyes - Cats - Felidae - Cetaceans - Cetacea - Cheetah - Acinonyx jubatus - Chordates - Chordata - Cichlids - Cichlidae - Cnidaria - Cnidaria - Common dolphin - Delphinus delphis - Common seal - Phoca vitulina - Crocodilians - Crocodilia - D Dugong - Dugong dugong - Dusky dolphin - Lagenorhynchus obscurus - E Echinoderms - Echinodermata - Eland antelope - Tragelaphus oryx - Elephants - Proboscidea - Eurasian lynx - Lynx lynx - European badger - Meles meles - European common toad - Bufo bufo - European robin - Erithacus rubecula - Even-toed ungulates - Artiodactyla - F Firefish - Pterois volitans - Frigatebirds - Fregatidae - Frogs and toads - Anura - G Galapagos land iguana - Conolophus subcristatus - Galapagos tortoise - Geochelone nigra - Gastropods, slugs, and snails - Gastropoda - Gavial - Gavialis gangeticus - Giant anteater - Myrmecophaga tridactyla - Giant panda - Ailuropoda melanoleuca - Giraffe - Giraffa camelopardalis - Golden-crowned sifaka - Propithecus tattersalli - Gorilla - Gorilla gorilla - Gray whale - Eschrichtius robustus - Great white shark - Carcharodon carcharias - Greater flamingo - Phoenicopterus ruber - Green poison dart frog - Dendrobates auratus - Green sea turtle - Chelonia mydas - H Hammerhead sharks - Sphyrnidae - Hares, rabbits, and pikas - Lagomorpha - Hawksbill sea turtle - Eretmochelys imbricata - Herons, storks, ibises, and spoonbills - Ciconiiformes - Hippopotamus - Hippopotamus amphibus - Hummingbirds - Trochilidae - Hyenas - Hyaenidae - I Insects - Insecta - Irrawaddy dolphin - Orcaella brevirostris - Ivory-billed woodpecker - Campephilus principalis - J Jellyfish - Scyphozoa - K Koala - Phascolarctos cinereus - Komodo Dragon - Varanus komodoensis - L Lava lizard - Microlophus albemarlensis - Leatherback sea turtle - Dermochelys coriacea - Lemurs, monkeys, and apes - Primates - Leopard - Panthera pardus - Lion - Panthera leo - Lionfish - Pterois volitans - Lizards, amphisbaenians, and snakes - Squamata - Lobe-finned fishes - Sarcopterygii - Loggerhead turtle - Caretta caretta - M Mammals - Mammalia - Manatees - Trichechus - Marine iguana - Amblyrhynchus cristatus - Marsupials - Marsupialia - Meerkat - Suricata suricatta - Mollusks - Mollusca - Monarch butterfly - Danaus plexippus - Moose, American - Alces americanus - Mountain lion - Puma concolor - Mustelids - Mustelidae - N Neandertal - Homo neanderthalensis - Nene goose - Branta sandvicensis - Newts and Salamanders - Caudata - Nine-banded armadillo - Dasypus novemcinctus - Northern cardinal - Cardinalis cardinalis - Northern gannet - Morus bassanus - Northern bottlenose whale - Hyperoodon ampullatus - O Ocelot - Leopardus pardalis - Odd-toed ungulates - Perissodactyla - Orca - Orcinus orca - Ostrich - Struthio camelus - Owls - Strigiformes - P Panda - Ailuropoda melanoleuca - Panther - Panthera onca - Pelicans and relatives - Pelicaniformes - Penguins - Sphenisciformes - Pigeon guillemot - Cepphus columba - Pigs - Suidae - Polar bear - Ursus maritimus - Primates - Primates - Pronghorn - Antilocapra americana - Przewalskis wild horse - Equus caballus przewalskii - R Rabbits, hares, and pikas - Lagomorpha - Ray-finned fishes - Actinopterygii - Red-eyed tree frog - Agalychnis callidryas - Red fox - Vulpes vulpes - Reindeer - Rangifer tarandus - Reptiles - Reptilia - Rhinoceros, black - Diceros bicornis - Rhinoceros, white - Ceratotherium simum - Rhinoceros iguana - Cyclura cornuta - Rodents - Rodentia - Rodriguez flying fox - Pteropus rodricensis - Roseate spoonbill - Platalea ajaja - Ruby-throated hummingbird - Archilochus colubris - S Scarlet ibis - Eudocimus ruber - Sharks, skates and rays - Elasmobranchii - Shoebill - Balaeniceps rex - Siberian tiger - Panthera tigris altaica - Skates and rays - Batoidea - Skunks and stink badgers - Mephitidae - Snails, slugs and nudibranchs - Gastropoda - Snow leopard - Panthera uncia - Somali wild ass - Equus asinus somalicus - Southern tamandua - Tamandua tetradactyla - Sponges - Porifera - Spectacled bear - Tremarctos ornatus - Squamates - Squamata - T Tapirs - Family Tapiridae - Tiger - Panthera tigris - Tinamous - Tinamiformes - Toothed Whales - Odontoceti - Tuataras - Sphenodontida - Tufted titmouse - Baeolophus bicolor - Turtles and tortoises - Chelonia Tytonidae - Barn owls - W Wandering albatross - Diomedea exulans - Waterfowl - Anseriformes - Whale shark - Rhincodon typus - White rhinoceros - Ceratotherium simum - X Xenarthrans - Xenarthra -

Schedule Hundreds of Social Messages With Bulk Social Upload

Schedule Hundreds of Social Messages With Bulk Social Upload Your marketing team produces hundreds  of social messages every month. (Which is AWESOME). But the process of manually uploadingpreviewingeditingAND scheduling hundreds of social messages Across 5 different social networks†¦ Using multiple social profiles†¦. Eats up HOURS of your team’s already-limited time. (Which is not-so-awesome). But what if you could bring that process down from hours†¦ to just a few minutes? 😠 Where you could quickly upload hundreds of social messages (with just a couple clicks)†¦ Easily preview and edit every  message†¦ (add finishing touches like images, links, and social profiles) AND then schedule those messages to send at the best time for your audience. Interested?! Introducing Bulk Social Upload from ! AKA the *new* way to upload, finalize, and schedule hundreds of social messagesin a matter of minutes. With Bulk Social Upload, you can: Quickly upload HUNDREDS of social messages to your calendar.  The days of spending hours manually uploading a month’s worth of social messages are officially over.  With Bulk Social Upload, you can upload up to 365 social messages to a new OR existing social campaign with just a couple clicks. Easily preview, edit AND schedule every social message.  Just because you upload messages in bulk, doesn’t mean you care any less about giving each message the attention it deserves. With Bulk Social Upload, you can easily preview and edit every message, and schedule it to send at the best time for your audience. And when Bulk Social Upload makes it this easy to get a month’s (!!!) worth of messages on your calendar†¦ You’re gonna wonder how you ever  lived without it. Let’s get into the deets! Schedule Hundreds of Social Messages With Bulk Social Upload In @Quickly Upload HUNDREDS Of Social Messages To Your Calendar Having to manually copy and paste†¦ Hundreds of social messages†¦ EVERY MONTH†¦ Well, it’s not fun. And it’s a total drain on your very  precious time. Luckily, thanks to Bulk Social Upload from The days of spending hours manually uploading a month’s worth of social messages are officially over. 🎉 With Bulk Social Upload, you can quickly upload up to 365 social messages to a new OR existing social campaign with just a couple clicks. With Bulk Social Upload in @, you can quickly upload up to 365 social messages to a newHeres a quick video for those visual learners out there: Not a visual learner? Keep readin to get the exact how-tos.🠤“ How To Upload Messages To A *New* Campaign Step 1:  Find the day you would like to start your new campaign, and hit the â€Å"+† sign in upper right hand corner of that date (or go straight for the large â€Å"+† sign in the upper right hand corner of the overall calendar view if you’re not sure of the start date at this point). Step 2: Select the â€Å"Upload† button in the upper right hand corner of the pop-up. Step 3:  Choose â€Å"Social Messages† as the type of content you would like to upload. Step 4:  Download the CSV template. Step 5:  Add your messages to the template! (Pro Tip: Double check that the columns in the spreadsheet have the correct info before you upload it in the next couple steps!) Step 6: Once you’ve got your messages ready to go, continue the upload process in and select â€Å"Create new social campaign† Step 7:  Give your new social campaign a name. Step 8:  Find and upload your completed CSV file to . Step 9: Once your messages are uploaded, select at least one social profile. (Pro Tip: You can choose as many as you’d like or just onewe just need to assign the messages to at least one profile for the upload to be successful). Step 10: Let it processand once it does, you’re ready to start previewing, editing, and scheduling your messages! But we’ll get to that part of the process in the next section. 😊 Before we jump ahead†¦ Let’s do a quick how-to if you want to upload messages to an  existing  social campaign! How To Upload Messages To An Existing Campaign Step 1:  Find the large â€Å"+† sign in the upper right hand corner of the overall calendar view. Step 2: Select the â€Å"Upload† button in the upper right hand corner of the pop-up. Step 3:  Choose â€Å"Social Messages† as the type of content you would like to upload. Step 4:  Download the CSV template. Step 5:  Add your messages to the template! (Pro Tip: Double check that the columns in the spreadsheet have the correct info before you upload it in the next couple steps!) Step 6: Once you’ve got your messages ready to go, continue the upload process in and click on â€Å"Select existing campaign† Step 7:  Find and select an existing social campaign. Step 8:  Find and upload your completed CSV file to . Step 9: Once your messages are uploaded, select at least one social profile. (Pro Tip: You can choose as many as you’d like or just onewe just need to assign the messages to at least one profile for the upload to be successful). Step 10: Let it processand once it does, you’re ready to start previewing, editing, and scheduling your messages! Speaking of which†¦ Head to the next section to learn how you can preview, edit, AND schedule every  social message in your campaign.

Site-directed mutagenesis of gene sequences in cells of plants, Essay

Site-directed mutagenesis of gene sequences in cells of plants, insects and animals can be achieved in situ used engineered zinc - Essay Example The ability to generate new DNA molecules and the process of inserting it into the genome to correct the diseases are the biomedical research nowadays. This type of modification of the cellular phenotype has become the back bone for the biomedical research. Knowing the position and the reading frame of the genes will help us to identify the nonsense mutants by the ochre suppressors. These non sense mutants are highlighted and this will help us for an efficient screening for silent mutants. The small oligonucleotides containing 7 nucleotides in length can be used to form stable duplexes with the single stranded DNA. (Jensen et al. 2011). These duplexes are stable even with a mismatch. This led to the introduction of oligonucleotide mutagenesis. The emergence of site directed mutagenesis as an analytical tool in the in the year 1985 was a mile stone in the field of molecular biology. (Herzog and Zolotukhin 2010). Site directed mutagenesis is widely used for the study of the protein fun ctions. The mutation at a defined site of the DNA leads to the change of an amino acid specific to a protein and this leads to the alteration of the protein molecules. Two methods of site directed mutagenesis can be used. The first one is overlapping method and the second one is called as whole round second round PCR. They create modified DNA sequences that are used to study the importance of the specific residues in protein structure and function. Protein engineering and altered protein substrate activity can be achieved using Site directed mutagenesis. PCR based Site directed mutagenesis is the most common method where the desired mutation is carried in one of the primer and annealed to the site of interest. Two cycles of PCR are carried out for insertion of mutation. (Lloyd 2005). Fig 1: Methods available to site specifically modify a genome target. (Herzog and Zolotukhin 2010). Zinc finger nuclease (ZFN) is a dimeric protein with each monomer having a zinc finger array (contains three or four zinc fingers). They are artificial restriction enzymes that have a lot of application in plants and animals. These zinc fingers (Cys 2 Hys 2) are arranged in the ? ? ? – fold ( beta- beta- alpha folding ) which is coordinated by the Zn+ ion and has the non specific cleavage site. (Gupta et al. 2011).These zinc finger arrays are bound to the cleavage site of the type II restriction endonuclease enzyme, Fok I. Fok l is responsible for the cleavage function of the Type II endonuclease. (Gupta et al. 2011).The dimerization of the cleavage domain is much essential for the enzyme activity. If the zinc finger array is engineered to bind to some specific site of the genome, then Fok l will perform the cutting action at that site. This double stranded break can be utilized for the site directed mutagenesis for protein engineering. This break is then repaired by using either homologous recombination (HR) or non-homologous end joining (NHEJ) technique. The HR requires ext ensive homology between the strands whereas NHEJ does not require any homology and the repair at the targeted site usually results in the mutation. (Herzog and Zolotukhin 2010). Because of this reason NHEJ is used in the site directed mutagenesis associated with the ZFNs. ZFN mediated gene modification will produce cell lines to contain biallelic knock outs. If ZFN targeted gene modificat

EMPHYSEMA Essay Example | Topics and Well Written Essays - 750 words

EMPHYSEMA - Essay Example The alveoli over-inflate and eventually burst and blend to form fewer larger air sacs, reducing the surface area over which gas exchange can take place. This significantly impairs oxygen and carbon dioxide exchange and the sufferer will have to breathe faster and heavier to compensate for this. Over the years the lungs also become less elastic as the tissue is destroyed due to chemical imbalance and this reduces their efficiency. (Wright, 2007) In fact, nearly 85% of all the cases found have been among cigarette smokers in their 50s or 60s, however, cigar and pipe smokers are also at risk. It has been found that tobacco smoke may damage the elastic fibers that make up the walls of the alveoli cells. This loss of elasticity leads to the retention of air in the lungs, expansion of the rib cage, and the flattening of the diaphragm. Normally, through contraction and relaxation, the diaphragm does most of the work when it comes to breathing. But when it remains flattened due to the effects of the smoke on the alveoli, muscles in the rib cage and abdomen take over the bulk of the work. Greater reliance on these muscles is a less efficient and more tiring way of breathing. (Lucey, 2003)   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Emphysema can also be contracted through genetics. An inherited deficiency of a protein known as alpha1-antitrypsin (ATT), which protects the lungs from destructive enzymes, also can cause emphysema, especially in people younger than fifty. Cases of hereditary emphysema are rare but are still a cause for concern.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  If a person is having difficulty in breathing or experiencing difficulty in tolerating even mild exercise, they should consult a doctor. The doctor will make a diagnosis of emphysema based on the following factors: the patients symptoms, medical history, results from lung function tests, findings on chest x-rays, and whether or not an increase in chest size has occurred.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  The most common symptoms of emphysema

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