Thursday, October 31, 2019
Strategic Organizational Culture Change Management Case Study
Strategic Organizational Culture Change Management - Case Study Example The final culture will be one in which everyone will focus on providing with error-free products and services according to the needs of the customer (Gregory H. Watson, 2007Page "Can it be said that Six Sigma is a culture" to which the obvious answer is "Yes." The reason is that Six Sigma is a concept-based metrics-driven, crisis-solving and project-tailored type of initiative. In addition Six Sigma connects performance to pay, has a proper vision, institutes a value, has distinct roles, is spread by way of knowledge transfer and calls for coaching by internal leaders. These are the reasons that make Six Sigma considerably control corporate culture (http://www. isixsigma.com/forum/ ask_dr_harry.aspToDo=view&questId=51&catId=9, retrieved 2nd October 2009). Gregory H. Watson, 2007, Strategic benchmarking reloaded with six sigma: improve your company's .., Jhon Wiley & sons Inc., Hoboken, New Jersey. http://www.isixsigma.com/forum/ask dr_harry.asp ToDo= view&questId=51&catId =9, retrieved 2nd October 2009.
Tuesday, October 29, 2019
Analyzing the pollution in rivers and lakes by using artificial neural Article
Analyzing the pollution in rivers and lakes by using artificial neural network, fuzzy logic, and regression methods - Article Example The basic approach is to train an ANN unit using a set of already known set of data to predict a similar future event. In this study feed forward ANN could be used to relate the DO measured at each location to predict the other quality parameters as reported. In this method, the (DO)i is considered as the input parameter to the input-neurons which would be passed into the hidden layer of neuron set after multiplying with a correction weight (kj). The main role of the hidden neuron is to add up the weighted sum received from the input set and combines it with a bias (bj) to determine a net value ( netj = ïÆ' ¥ (DO)i kj - bj ). This net value is passed into the output neuron which uses a non-linear function , say, f(net) = 1/ (1+e-net) to determine the output parameters BOD, NO3, NO2 and PO4 (Tayfur and Singh, 2006). The fuzzy logic approach for the prediction of dissolved oxygen level is based on the set of rules that is in built in the model. This process is undertaken in four different steps. Allocation of partial belonging to each input variable in the form of membership function , which takes up values from 0 to 1, is the first step. This process is referred as fuzzification. The allocation is based on intuition and linear triangular functions are the commonly adopted one. The fuzzy rule base is the next requirement to relate the input and the outputs using if-then logical relations. In the present work it could be either as - If BOD is low , NO3 is low and PO4 is low then DO is high - or If BOD is high, NO3 is high and PO4 is high then DO is low. Next is the fuzzy output subset construction by addition of all the fuzzy subsets. The fuzzy output function need to be converted to discrete form of results using defuzzifcation methods. Centre of gravity method (COG method) could be used to this process for the present situation (Tayfur and Singh, 2006, Chen et
Sunday, October 27, 2019
ÃÂcido ClorhÃÂdrico Y ÃÂcido Acético en Vinagre
à cido Clorhà drico Y à cido Acà ©tico en Vinagre Titulacià ³n de à ¡cido clorhà drico y à ¡cido acà ©tico en vinagre comercial con una base fuerte Propà ³sito Determinar el punto de equivalencia entre las reacciones NaOH (ac) + HCl (ac) à NaCl (ac) + H2O (l) y NaOH (ac) + HCH3COO (ac) à NaCH3COO (ac) + H2O (l), observando los cambios fà sicos en la titulacià ³n de las soluciones, utilizando un indicador (Fenolftaleà na o Anaranjado de metilo) y un pH metro. Antecedentes Debido a que en la prà ¡ctica 6 â€Å"Titulacià ³n de à ¡cido clorhà drico y à ¡cido acà ©tico en vinagre comercial con una base fuerte†se realizarà ¡ una titulacià ³n de dos sustancias que reaccionan en una neutralizacià ³n, se hace necesario conocer ambos conceptos. Existen sustancias que al diluirlas en agua (solvente) se disocian en sus iones. A à ©stas se les conoce como electrolitos, pues conducen electricidad. Aquellas que no se disocian en sus iones conformantes se les conoce como no electrolitos. En la prà ¡ctica se trabajarà ¡ con electrolitos, pues las sustancias utilizadas son bases y à ¡cidos que se disocian en sus iones OH- y H+ respectivamente, aumentando su concentracià ³n en el agua. El à ¡cido clorhà drico y el à ¡cido acà ©tico, cuando sean diluidos en agua aumentarà ¡n la concentracià ³n de protones H+, con lo que el pH de la disolucià ³n serà ¡ à ¡cido. Por el contrario el Hidrà ³xido de sodio es una base que acepta protones H+ disminuyendo la concentracià ³n en el solvente. Con ello el pH serà ¡ bà ¡sico. A las sustancias se les llama à ¡cidas cuando la concentracià ³n de protones de hidrà ³geno es mayor a 1 * 10 -7 ion por gramo por litro, neutra cuando es igual a 1*10-7 ion por gramo por litro, y bà ¡sica cuando es menor a 1 * 10 -7 ion por gramo por litro. Debido a que el valor de concentracià ³n de iones de hidrà ³geno los nà ºmeros son valores muy pequeà ±os, Sà ¶rensen los expresà ³ por logaritmos con signos positivos originando lo que conocemos como pH, que es una escala que expresa los exponentes de concentracià ³n de iones H+. Por lo tanto cuando hacemos que una disolucià ³n se vuelva à ¡cida su pH disminuye, y si al contrario se vuelve mà ¡s bà ¡sica su pH aumenta, tal como lo seà ±ala la siguiente escala: à cidas Neutras Bà ¡sicas 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Como se puede observar el HCl y el HCH3COO son à ¡cidos monoprà ³ticos, pues producen un protà ³n H+ por molà ©cula de à ¡cido. Caracterà sticas de las bases: Una propiedad especial es que son amargos y conducen corriente elà ©ctrica, ademà ¡s se ionizan liberando iones OH-. Caracterà sticas de los à ¡cidos: Entre los à ¡cidos tenemos dos grupos: Los hidrà ¡cidos formados por hidrà ³geno y no metales. Por ejemplo ClH (à cido clorhà drico). Por otro lado està ¡n los oxà ¡cidos, que son compuestos ternarios que se originan al combinar anhà dridos con agua. H2SO4 (à cido sulfà ºrico). La mayorà a son solubles en el agua. Tienen sabor picante (acre), y ademà ¡s actà ºan con los metales, liberando hidrà ³geno y formando sales. Los à ¡cidos y las bases se pueden clasificar en dà ©biles o fuertes. Ello depende de la facilidad con la que los à ¡cidos ceden protones y las bases aceptan protones. Un à ¡cido fuerte transfiere por completo sus protones, un à ¡cido dà ©bil se disocia parcialmente en agua. Una base fuerte es aquella que acepta por completo los protones que contiene el agua formando iones OH-. Por lo tanto la base dà ©bil los acepta parcialmente. Entre los seis à ¡cidos mà ¡s fuertes se encuentran uno utilizado en la prà ¡ctica, el à ¡cido clorhà drico, mientras que el à ¡cido acà ©tico es dà ©bil. Las bases fuertes son aquellas se componen de metales alcalinos o alcalinotà ©rreos. Por dicha razà ³n el NaOH es una base fuerte. Cuando disoluciones de una base y un à ¡cido se hacen reaccionar se origina una reaccià ³n de neutralizacià ³n, en la cual se produce una sal y agua. Se conoce como neutralizacià ³n pues al reaccionar disminuye los efectos de à ¡cido y de base. En la prà ¡ctica las reacciones NaOH (ac) + HCl (ac) à NaCl (ac) + H2O (l) y NaOH (ac) + HCH3COO (ac) à NaCH3COO (ac) + H2O (l), son de neutralizacià ³n, pues como se puede apreciar en ambas se formarà ¡n una sal y agua. Para determinar la concentracià ³n de H+ en las disoluciones de à ¡cidos respectivos se llevarà ¡ a cabo una titulacià ³n usando como titulante el Hidrà ³xido de sodio. Éste es un proceso a travà ©s del cual se determina la concentracià ³n de un soluto en combinacià ³n con una sustancia de concentracià ³n conocida. En à ©ste caso se desconoce la concentracià ³n de protones hidrà ³geno pero se conoce la concentracià ³n de Hidrà ³xido de sodio. El instrumento de medicià ³n serà ¡ el pHà metro, el cual es un dispositivo electrà ³nico que cuenta con dos electrodos que miden pequeà ±os voltajes especà ficos para à ¡cidos y bases. Conforme se agregue hidrà ³xido de sodio a la solucià ³n de à ¡cido clorhà drico y a la de à ¡cido acà ©tico se irà ¡ observando el momento en el que reaccionarà ¡n cantidades equivalentes de los reactivos. A ello se le conoce como punto de equivalencia y para conocer dicho punto se utilizarà ¡n dos indicadores: la fenolftaleà na y el anaranjado de metilo. Un indicador es una sustancia con elevado peso molecular, que cambian de color cuando entra en contacto con à ¡cido o base. El cambio de color seà ±alarà ¡ el punto final de la titulacià ³n el cual equivale al punto de equivalencia que se desea determinar. Para poder elegir el mejor indicador para cada parte de la prà ¡ctica, se debe basar en el punto de equivalencia y el rango de viraje de color de ambos. La fenolftaleà na es de color transparente en un medio à ¡cido y en medio bà ¡sico se torna rosado. En una titulacià ³n à ¡cido-base como la que se realizarà ¡ el punto final de la titulacià ³n ocurrirà ¡ cuando al agregar hidrà ³xido de sodio aparezca una coloracià ³n rosada pà ¡lida. Su viraje està ¡ en un rango de pH de 8 a 10. El anaranjado de metilo cambia de color en un intervalo de pH de 3.1 a 4.4, por debajo de 3.1 es su forma à ¡cida, con coloracià ³n roja. Por arriba de 4.4 es la conversià ³n completa a forma bà ¡sica y su coloracià ³n es amarilla, punto final de la titulacià ³n. No serà ¡ conveniente utilizar fenolftaleà na para la reaccià ³n del à ¡cido fuerte (HCl) y la base fuerte (NaOH), puesto que el pH en su punto de equivalencia es 7 pues todos sus iones estarà ¡n neutralizados y dicha sustancia cambia su coloracià ³n en un rango de 8 a 10 de la escala pH. En la segunda parte cuando reaccione el à ¡cido dà ©bil (HCH3COO) con la base fuerte (NaOH), si es conveniente usar la fenolftaleà na. Ello se debe a que cuando un à ¡cido dà ©bil reacciona con una base fuerte el protà ³n H+ se hidroliza. Por dicha razà ³n el pH del punto de equivalencia es mayor a 7. Es importante conocer que la hidrà ³lisis es un tipo de reaccià ³n, en la cual los iones reaccionan con agua para generar protones H+ o iones hidroxilo. Cuestionario Describa los siguientes conceptos: 1. Neutralizacià ³n: Es una reaccià ³n que se origina de la interaccià ³n entre una base y un à ¡cido, en la cual se contrarrestan sus efectos y se produce agua y una sal. La neutralizacià ³n ocurre de esta forma: H+ + OH- à H2O (l) 2. à cido: Sustancia que dona protones. 3. Base: Sustancia que acepta protones. 4. à cido fuerte: Sustancia que dona protones y que se encuentra en disolucià ³n acuosa completamente como iones. 5. Base fuerte: Sustancia que acepta protones y que se encuentra en disolucià ³n acuosa completamente como iones. 6. à cido Dà ©bil: Sustancia que dona protones y que se encuentra en disolucià ³n acuosa parcialmente como iones. 7. Base dà ©bil: Sustancia que acepta protones y que se encuentra en disolucià ³n acuosa parcialmente como iones. 8. Punto de equivalencia: Punto en el cual reaccionan cantidades estequiomà ©tricamente equivalentes. Reacciones NaOH (ac) + HCl (ac) à NaCl (ac) + H2O(l) NaOH(ac) + HCH3COO(ac) à NaCH3COO (ac) + H2O(l)
Friday, October 25, 2019
Feminist Reading of The Yellow Wallpaper -- Feminism Feminist Women Cr
A Feminist Reading of The Yellow Wallpaper      In the late nineteenth century, after the American social and economic shift commonly referred to as the "Industrial Revolution" had changed the very fabric of American society, increased attention was paid to the psychological disorders that apparently had steamed up out of the new smokestacks and skyscrapers in urban populations (Bauer, 131). These disorders were presumed to have been born out of the exhaustion and "wear and tear" of industrial society (Bauer, 131-132). An obvious effect of these new disorders was a slew of physicians and psychiatrists advocating one sort of cure or another, although the "rest cure" popularized by the physician S. Weir Mitchell was the most embraced (Bauer, 131; Saur, 151-152). However, while the "rest cure" for men involved physical exercise and leisure activities, the cure for women was a suffocating slice of seclusion, bed rest, and no intellectual activity (Bauer, 131).         Charlotte Perkins Gilman, a renowned feminist and author, was one of the women affected with "...a severe and continuous nervous breakdown tending to melancholia..," which was commonly termed as "neurasthenia" (Gilman, 348-349). However, rather than cure her, Mitchell's "rest cure" nearly drove her insane. As a result of her maddening experience away from writing and almost all intellectual thought, she wrote her short story, "The Yellow Wallpaper" not "...to drive people crazy," but instead to "...save people from being driven crazy" (Gilman, 349). Although her purpose in writing the story is clear, one can not help but wonder if she was motivated solely by her protest to nineteenth century medical practice or by her protest to the legal and socia... ... Boston/New York: Bedford/St. Martin's, 1998. 130-132. Gilman, Charlotte Perkins. "The Yellow Wallpaper." The Yellow Wallpaper. Ed. Dale M. Bauer. Boston/New York: Bedford/St. Martin's, 1998. 41-58. Gilman, Charlotte Perkins. "Why I Wrote The Yellow Wallpaper?" The Yellow Wallpaper. Ed. Dale M. Bauer. Boston/New York: Bedford/St. Martin's, 1998. 348-349. Mitchell, S. Weir. "From Wear and Tear, or Hints for the Overworked." The Yellow Wallpaper. Ed. Dale M. Bauer. Boston/New York: Bedford/St. Martin's, 1998. 134-141. Saur, Prudence B. "From Maternity; A Book for Every Wife and Mother." The Yellow Wallpaper. Ed. Dale M. Bauer. Boston/New York: Bedford/St. Martin's, 1998. 151- 155. Williams, William C. "Old Doc Rivers." The Doctor Stories. Ed. Robert Coles. New York: New Directions Publishing Corporation, 1984. 13-41.
Thursday, October 24, 2019
Poverty Population Revised Essay
Believe it or not, more than a billion people worldwide subsists on less than one dollar per day. At the same time, the world is expected to have another three billion people by 2050, a majority of which are going to come from the poorest areas (Merrick, 2002).            Do poverty cause population growth? Or is it the other way around? This paper would look more closely at the relationship between poverty and population growth, and how to alleviate it.  *         *         *            The World Bank writes that poverty has many faces: It’s not having a job. Hunger. Not having access to medical services and schools. It’s fearing for the future. It’s surviving one day at a time. It’s powerlessness (World Bank, undated).            Bernadette Proctor, citing census data figures from 1993 writes that 39.3 million people were officially poor in the United States, 15.1% of that were earning a below the poverty level income. This means that while most of these people worked, there were still not earning enough for their daily needs. The situation was not any better in 2002, with 34.6 million American still living below the poverty level. Lynette Clemetson at the New York Times quotes liberal economists as saying that any increase in poverty in the country was â€Å"too high†considering that the U.S. is viewed as a very prosperous country (Clemetson, 2003).            Outside the United States, statistics on poverty paints a grimmer picture that affects far more people in a far devastating degree.  Anup Shah says that there is a distinguished disparity in income, with 80% of the world’s people living in countries where there is widening differences in income between the rich and the poor. In fact, only 5% of the world’s total income are generated by almost half of the world’s population (Shah, 2008).            Out of 2.2 billion children in the world, 1 out of 2 are living in poverty, 1 in 3 do not have adequate homes, 1 in 5 do not have access to safe water, while 1 in 7 have no access to health services. Many more do not have access to education and proper nutrition (Shah, 2008).            Worldwide, a billion people are illiterate. Diseases like HIV/AIDS and malaria claim millions of lives. People have no access to clean, potable water (Shah, 2008). Causes            While it is difficult to pinpoint exact and complete causes of poverty, the Earth Institute at Columbia University lists three causes of poverty: the social and economic displacement due to civil wars, or local conflicts affecting million of people; the inequitable distribution of land and wealth, and man-made policies like inadequate access credit assistance and adoption of unsustainable technologies (The Earth Institute at Columbia University, undated).            Anup Shah asks the empirical questions regarding the causes of poverty. It could be personal, like wrong decisions made, laziness, or it could be a matter of governance and public policy. Shah, however, looks deeper into the global causes.            Structural adjustment policies have caused cutbacks in vital human services like health and education worldwide. Ironically, the policies have been instituted by the World Bank and the International Monetary Fund as loan and repayment conditions.  Shah also blames globalization in developing nations, after these countries opened their economies and found themselves competing with more powerful and industrialized nations. It became a battle of who could provide cheaper wages, resources and lower standards, and has worsened poverty and inequality for most people. Shah also mentions corruption as a cause of poverty (2008).            The Doors to Diplomacy Project, sponsored by the U.S. State Department and Global Schoolnet, agrees but adds that overpopulation is another major cause. The project defines overpopulation as the situation of having big numbers of people in too little space, with too few resources (2006).            Rapid population growth worsens inequality, impedes economic growth, and exacerbates poverty (Alonzo et. al., 2004). Poverty is caused by many contributing factors, and thus is seen as a complex phenomenon. While rapid and unsustainable growth alone cannot fully explain poverty, it can help worsen the poverty situation in any given area (Alonzo et. al., 2004).            Researchers at the University of the Philippines, citing a 2004 study that used data on 80 countries, states that a growing population exerts a â€Å"negative and significant†effect on the growth of the economy (Alonzo et. al., 2004). A Vicious Cycle            Debates on population, poverty and its causes are very similar to the childhood question: which came first the chicken or the egg? Thomas Merrick writes that the popular view in the 60s and 70s held that fertility decline would show population growth and eventually poverty came under fire in the 80s and the 90s (2002).            Merrick, however, clarifies that recent studies and thinking have shown that demographic trends do play a role in poverty studies. Merrick states that the potential benefits of a lower population, however, rests on the timing and degree of demographic change, the focus of economic policies, the social and economic status of women.            There are two contrasting views about population and poverty. One says that higher population growth results in poverty, so lower fertility is the key to alleviating poverty (Merrick, 2002).            The other holds that economic policies determine poverty reduction, disagreeing that family planning is all you need. This view argues that poverty causes the people to want more children because they can help around the house and take care of their parents in old age (Merrick, 2002).            Merrick also cites recent research that have found that when fertility declines, there is increased personal savings and investment becomes possible. The scenario also gives rise to the situation wherein there are more workers responsible for fewer children. Merrick, however, recognizes that this benefit is temporary, and soon, there will be a situation, when the opposite is true, more retirees will be depending on the working class.            Merrick also says that a higher population growth increases poverty by retarding the growth of the economy, and worsening the distribution of additional income created by the growth (Merrick, 2002). Government Policy            Clemetson puts it succinctly: the policy shifts that resulted in the reduction of benefits and welfare structure for the poor are to blame. Peter Timmer agrees. Timmer writes that the different views on the private and social returns of having many children paves the way for government interventions, hopefully something that extends beyond the simple family planning schemes to broader economic development policies (Timmer, 1994).            Timmer advocates for learning more about the dynamic behavior of poor households within the context of their environments. This would lead to a sound policy that can break into the vicious cycle of worsening poverty and declining productivity (Timmer, 1994). Timmer suggests economic development policies that addresses nutrition, health, and education, as well as policies that bring about a reduction in â€Å"income poverty†can help alleviate poverty (Timmer, 1994).            Timmer also says that it would be wise to raise domestic food production, which addresses nutrition further, and also offers a way to control food prices and income distribution by increasing access to food (Timmer, 1994).            Merrick adds that family planning alone will not necessarily reduce poverty. What’s needed to alleviate poverty is the combination of slower population growth, sound economic development, and the reduction of gender inequality (Merrick, 2002).            Public policy should promote the woman’s right to choose for herself how many children she wants to bear and when. Public policy should inform and educate– and perhaps, subsidize –women about fertility regulation (Merrick, 2002). Empowering Women            At the heart of the debate including poverty, public policy, and population growth, there is one common thread: empowering women. The United Nations Population Fund explains that poor women who do not have access to family planning services will not be able to participate in income generating activities because they cannot time or space their children adequately. A woman who is empowered to choose their family size will slow population growth and help alleviate poverty. The UNFPA reiterates that reproductive health, women’s empowerment and equal right can help break the poverty cycle (United Nations Population Fund, 2004).            Empowering women also extends to getting paid employment and education. The Population Problem: Theory and Evidence as cited by Atanu Dey in his essay The Population-Poverty Trap, states that the lack of education and subsequent paid employment can hinder a woman from making decisions on her own, for herself. Both imparts a degree of self-confidence (Dey, 2004).            *         *         *            More than a billion people are scarcely surviving worldwide. Another two billion are not much better off. Poverty is taking countless of lives, and making countless more miserable. Whatever the reasons, poverty and its eradication, or at least, alleviation should be top of anybody’s list. A growing body research have pointed to population growth as one of its leading causes. A vicious cycle is apparent: population growth causes poverty, poverty causes population growth.            This time, two things are clearer. Public policy should be formulated only after a thorough understanding of poverty and its causes in a particular locale and milieu, and that policy should take to heart the role and importance of women if it should even go near succeeding.            In effect, the way to combat poverty is to put in policies and programs at the grassroots level that would curb the rapid growth of population, coupled with sound public policy and the active and informed participation (coming from education) of women. Without any one of these elements, any measure will be doomed to fail. Alonzo, R., Balisacan, A., Canlas, D., Capuno, J., Clarete, R., Danao, R., de Dios, E., Diokno, B., Esguerra, E., Fabella, R., Bautista, S., Kraft, A., Medalla, F., Mendoza, M.N., Monsod, S., Paderanga, C., Pernia, E., Quimbo, S., Sicat, G., Solon, O., Tan E., and Tecson G. (2004). Population and Poverty: The Real Score. University of the Philippines School of Economics. Retrieved on 14 April 2008. Causes of Poverty. (2006). Doors to Diplomacy Project. Retrieved on 15 April 2008. Clemetson, Lynette. (2003). More American in Poverty in 2002, Census Study Says. New York Times. Retrieved on 14 April 2008. Dey, Atanu. (2004). The Population-Poverty Trap. Retrieved on 14 April 2008. Focus on global poverty. The Earth Institute at Columbia Univeristy. Retrieved on 14 April 2008. Merrick, Thomas W. (2002). Population and Poverty: New Views on an Old Controvery. International Family Planning Perspectives, Vol. 28, No. 1. Retrieved on 14 April 2008. Poverty, Population and Development. (2004). United Nations Population Fund. Retrieved on 14 April 2008. Proctor, Bernadette. Poverty: Population Profile of the United States. U.S. Census Bureau.  Last Updated 8 February 2008. Retrieved on 14 April 2008. Shah, Anup. (2008). Poverty Facts and Stats. Retrieved on 15 April 2008. Shah, Anup. (2008). Causes of Poverty. Retrieved on 15 April 2008. Timmer, C. Peter. (1994). Population, poverty and politics. The American Economic Review Vol. 84. No. 2. pp 261. Understanding Poverty. World Bank. Retrieved on 14 April 2008.
Wednesday, October 23, 2019
DHCP
ENGINEERING MANAGEMENT Course EMP-5116 Issues in the Management and Operation of Communication Prepared by Student Number Submitted To KAMRUL KHAN 7025417 Dr. Serban Gheorghe Term Report (FALL 2012) December 13, 2012 The main purpose of using DHCP is to assign unique IP address to the computers in a network. This protocol is widely used by the ISPs to let their customers join the internet with less effort. It is also used by the enterprises to reduce workload and simplify the network management. (1) (2) 1. 1 History of DHCP Before DHCP was developed a protocol named Bootstrap Protocol (BOOTP) was developed for similar functionality as DHCP. Later in 1993, DHCP was introduced for the first time with the release of RFC 1531 as an extension to the BOOTP. The main reason behind extending BOOTP was that manual intervention was required to add configuration information for each client. Furthermore, BOOTP had no mechanism to reclaim disused IP addresses. Within a short period of time, DHCP became popular among the IT community. In 1997 another update of DHCP was released through RFC 2131. RFC 3315 defined the DHCPv6 specification. RFC 3633 was released with a prefix delegation mechanism for DHCPv6. RFC 3736 mechanism to provide configuration information to clients configured using stateless address auto configuration was added as an extension. (1) 1. A brief overview A database of available IP addresses and configuration information is maintained by the DHCP server. When a client requests the DHCP server for configuration information, the DHCP server checks the subnet in which DHCP client is connected, and then sends back the client with appropriate configuration information. 2 Typically IP addresses distributed to clients are assigned f or limited interval by the server. DHCP clients are responsible for renewing their IP address before that interval has expired. If they are unable to renew it by the expiration interval, they must stop using the address. Both IPv4 and IPv6 are supported by DHCP. Even if a client does not use DHCP for acquiring IP address, it can still be used to obtain other configuration information. (1) 2 2. 1 DHCP and Its operation DHCP Protocol Overview The major component of DHCP is the DHCP server and clients. Basic task of server is to assign IP address to the clients. The DHCP client makes a request to a DHCP server that may or may reside on different subnet. The server distributes IP address, subnet mask and default gateway to a host. Other configuration parameters such as name servers and netbios configuration can also be included. The IP assignment process is called â€Å"binding†or â€Å"lease†. The word â€Å"lease†is used as the client leases an IP address for a particular amount of time. This implies, after a certain period of time client must relinquish the IP address. The DHCP client side works combining six basic states. These states are: Initializing Selecting Requesting Binding Renewing Rebinding These states will be discussed in details in the next chapters of this paper. (3) 3 2. 2 DHCP Lease As discussed before DHCP lease is the process of associating IP address and client. The address leased by the client expires after certain period of time. Two timers are maintained by the client to manage this expiration process. Which are, 1. Renewing time T1 2. Rebinding Time T2 Renewing time T1 means the client will get a new lease from a server. Rebinding is the extension of lease. Typically renewing time is set to half of the renewing time. (4) 2. 3 DHCP Messages and Client States DHCP has several messages for establishing server to client communications. All DHCP instruction or updates are carried through these messages. The basic messages defined for DHCP are, DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK, DHCPNAK, DHCPDECLINE, DHCPRELEASE, and DHCPINFORM. All these messages are effectively used during different states of DHCP. Purpose and flow of these messages in different DHCP states are discussed in the following sections. (4) 2. 3. 1 INIT The client tries to find a DHCP server by broadcasting DHCPDISCOVER message. It transitions to the SELECTING state. The server sends DHCPOFFER back to the client which is basically the choice of address and other parameters for the client. (5) 2. 3. 2 SELECTING In this state, client waits for DHCPOFFER message from any server. It selects the preferred offer and declares the selection by sending the DHCPREQUEST message. It transitions to the REQUESTING state. (5) 4 2. 3. 3 REQUESTING After sending the DHCPOFFER the client waits for the response from the server. Three different situations can occur. First, the most expected situation that, the server sends the acceptance of the request sent through DHCPACK. The client the starts the T1 and T2 timers and moves to the Bound state. Second, if the previously sent offer is no more available the server ill send a DHCPNAK message to deny the DHCPREQUEST. In this situation the client must return to the INIT state and start from the beginning. Third, server may send acceptance through DHCPACK however, the offer is no more acceptable to the client. Typically, this happens if the client finds the offered address is already been used somewhere else in the network. In this case client sends a DHCPDECLINE message and moves to the INIT state to start over. (4) 2. 3. 4 BOUND If lease assignment is successful the client goes to BOUND state. After timer T1 is expired the client sends a new DHCPREQUEST and moves to RENEWING state. 4) 2. 3. 5 RENEWING In this state client tries to extend of its lease by sending new DHCPREQUEST to the same server it took the lease from. Again three situations may be observed. First, the server may deny the request through DHCPNAK message. The client must return to INIT state and start from beginning in this situation. Second, if client does not get response from server, it will broadcast DHCPREQUEST after T2 is expired and move to the REINDING state. Third, server accepted the new request with the DHCPACK and the lease is extended. The client will again move back to BOUND state in this situation. 4) 5 2. 3. 6 REBINDING As discussed earlier, client moves to REBINDING state if T2 get expired in RENEWING state. Here, if client may get a DHCPACK response from the server if the request is approved. The client will then return to BOUND state extending the lease. Otherwise, the client gets a DHCPNAK response which indicates the refusal of request. In this case the client needs to move to the INIT state to start from beginning. (4) 2. 3. 7 INIT-REBOOT This state is for special case. If a client can find its previous DHCP configuration right after starting up, it moves to special INIT-REBOOT state. It sends a DHCPREQUEST message immediately from where it got the previous lease requesting to use the same old address and moves to the REBOOTING state. (4) 2. 3. 8 REBOOTING In REBOOTING state, client requests the server for allowing the client to continue with the previous address. Here, again two situations may occur. First, server may accept and send DHCPACK. Client will then reset timer T1 and T2 and continue with the previous address. Second, client may get a DHCPNAK message indicating the refusal of the request. Typically this kind of situation occurs when the client is turned off for very long time. The server may assign the address to other client. And as usual the only way left for the client is to go back to the INIT state and start from the beginning. (4) 2. 4 The Finite Client State Machine Finite State Machine (FSM) is a tool or method to describe a protocol. The behavior of a protocol is described by showing all the different states a device can be in, all possible transitions between individual states, events that cause transitions, and the actions that are performed as a response of an event. 6 The FSM can be used to describe the lease life cycle from the perspective of a DHCP client. The client begins its life cycle from the initial INIT state when no lease is acquired. It then travels through different states like, renews, rebinds and/or releases its IP address. The whole process can be described graphically using the FSM method. The below figure describe the FSM of DHCP client. (5) Figure 1: DHCP Client Finite State Machine 7 3 DCHP Server Vendors and Market Overview The ever increasing number of IP devices (Network endpoints, IP telephones, virtual servers, etc. ) is the main emerging factor of IP management and DCHP server market growth. In the past, the network admins had very limited options to pick up a DHCP/DNS solution. Sometimes, they used to write their own codes to manage DHCP/DNS in their network. However, now many vendors have come up with DHCP/DNS solutions. The integrated DNS/DHCP appliancebased offerings are proved to be more attractive to the consumers. (6) 3. 1 Present Market Statistics According to the recent statistics, DHCP solutions along with DNS and IPAM (DDI) have been showing more than 20% consistent growth starting from 2009. In 2011, DDI market had an increment of 36% by generating $290 million. It is estimated that, by the end of 2012, the market will increase to $380 million with an increment of 29%. According to the statistics mentioned above it can clearly be stated that, the DDI market is promising and growing. (7) 3. 2 Market Segments In general, DDI( DNS, DHCP and IPAM) solutions can be categorized in three major segments, bundled offerings, overlay management solutions and managed services. These segments are described in the following sections. (7) 3. 2. 1 Bundled Offerings Bounded offerings are the fastest growing in DDI market. In bundled offerings, the DHCP and DNS services share an integrated database. Although, physical appliance forms are the dominating factor of bundled offerings, software or virtual services are also available. (7) 3. 2. 2 Overlay Management Solutions Overlay management solutions are free DHCP or DNS services. It is easier to deploy as it does not require replacement of DHCP/DNS infrastructure or integration with existing DNS server. It can add management capability to DNS or DHCP and IPAM functionality. (7) 8 3. 2. 3 Managed Services Managed service market is smaller comparing to other segments. According to recent statistics it is around 10% of the total spending of DDI solutions. 7) 3. 3 DDI Vendors Though DDI market is growing, some giant DDI vendors discontinued with their products due to slow revenue and other factors like increasing popularity of appliance based offerings. For example, Nortel used to be one of the market leaders in the field of DDI. However, they decided to discontinue their IP Address Domain Manager from the beginning of 2008. On the ot her hand, Infoblox and BlueCat are getting more popular with their integrated DNS/DHCP appliance based offerings. There are couple of â€Å"free DHCP solutions†available in the market. Among them, the Internet Software Consortium should be mentioned in the first place. Other than that the CMU DHCP server is also very popular (4). However, considering the market scopes and market segments it was found the commercial solutions are more promising. Therefore, in this report only the commercial solutions are briefly described. According to recent market analysis, seven companies were found to be prominent. Their overall rating based on product/service, customer feedback and business strategy is given in the chart below. (7) Figure 2 Market Scope for DDI Source: Gartner, April 2012 9 3. . 1 Alcatel-Lucent Alcatel-Lucent developed their DDI solution VitalQIP back in 1998. It has flexible deployment options with broad overlay solutions. The solution is highly capable with large enterprise network. However, some common features like the DHCP lease history is missing in VitalQIP. This can be considered as major drawback. (7) 3. 3. 2 BlueCat Networks BlueCat is a DDI pure-pla y vendor based on Toronto, Canada. They offer Adion family of integrated DNS and DHCP which can be used as an overlay to manage windows DNS and DHCP. It has strong network discovery and endpoint mapping ability. 7) 3. 3. 3 BT Diamond Diamond IP was released on 2007 by British Telecom. It is a highly scalable product. It is available through software, appliance or for virtual environment (VMWare). Diamond IP is present in all three market segment discussed before: Bundled offerings, overlay and managed services. (7) 3. 3. 4 EfficientIP EfficientIP is another pure-play DDI vendor based on France. They provide solutions as bundled or overlay. The main feature of EfficientIP is its template based architecture functionality which makes it very easy to automate the configuration and management of DNS/DHCP servers. 7) 3. 3. 5 InfoBlox InfoBlox is a California based company founded on 1999. They sell integrated DHCP/DNS solutions and overlay solutions for Microsoft Windows DHCP. Their solutions are available through appliance and virtual VMWare environment. One of the main features of InfoBlox is its grid functionality which makes the operation and management easier. (7) 10 3. 3. 6 Men & Mice Men &Mice is a Iceland based company founded at 1990. They do not sell any integrated DNS/DHCP appliance. They only sell software based overlay solutions for managing DNS/DHCP services from othe r vendors. 7) 3. 3. 7 Nixu Software A Finland based company founded on 1988. The DDI components of Nixu software are only available as software appliance. (7) 4 4. 1 Case Study: TYROLIT Delivers Resilient DNS and DHCP with BlueCat Networks Background TYROLIT is an Austria based company founded in 1919. It is one of the world's largest manufacturers of grinding, cutting, drilling dressing tools and machines for the construction industry. TYROLIT has base in 12 different countries with 4,500 employees at 27 production locations. TYROLIT’ has a
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