An implementation study of the AODV routing protocol
雅思作文批改---经典版 (16)
Some people think that universities should provide graduates with the knowledge and skills needed in the workplace. Others think that the true function of a university should be to give access to knowledge for its own sake, regardless of whether the course is useful to an employer. What, in your opinion, should be the main function of a university?In current society where acquiring a certificate in the university is apt to be essential to a successful life, what should be offered in the university has been encouraged to a controversy. Some people argue that universities should only impart skills and knowledge that can benefit graduates’ jobs. As far as I am concerned, I have to insist that universities should provide knowledge for its own sake and leave the free to the graduate to decide whether to use it in workplace or not.It is admitted that under the ever rising stress of employment, the knowledge and skills gained in the university is pivotal for better adapting to the occupation. In terms of some occupation, one’s study in the university would lay a solid and essential foundation for the future work. For example, without the advance programing language taught in the university, a website developer can never create attractive and widely used social websites such as Facebook. However, this does not mean that universities should only impart practical skills that can be used on work.The principle of university is to spread knowledge to every corner of the world, no matter it is job related or not. Universities should set up the more subjects the better to cover the most knowledge in the world. And students could be free to choose what ever they like in the university to engage in a deep study and maybe accordingly become an expert, but it is not a must that they have a career in the related field. It is the inculcation of knowledge that is the duty of universities, while whether using it in a career is the graduates’ decision.To sum up, in my opinion, universities should not only provide opportunities to acquire practical skills that are significant in work but also other knowledge that is also an important part of human civilization. 总点评：本篇文章得分: Good参考范文：In the midst of financial turmoil and massive layoffs, it is understandable that the majority of university students think of their future job security as a pressing priority. Accordingly, they tend to regard universities primarily as institutions where employment skills can be acquired.This is especially time when we consider the fact that the cost of tuition and fees has been rising each year, which means to many, pursuing higher education is very much like making a substantial investment. Thus, university students and their parents alike tend to expect reasonable rates of return that can be, to some degree, quantified by the job skills students possess. 让步Still, I wish to point out that merely equipping students with employment skills may defeat the very purpose of universities as educational institutions. Realistically, it would be very hard for university administrators and faculty to determine what technical skills and knowledge will be needed three or four years from now as the technology in many areas is updating itself on a daily basis. What willalso be at risk is the students' capacity to innovate because true innovations require thorough understanding of fundamental theories in the related fields rather than the ability to apply these theories in the workplace, which is exactly how we define the employment skill.The main function of universities, therefore, should be building core curricula that stress the fostering of employment skills while at the same time, providing students with electives on the theoretical aspects of their fields of interest which not only facilitates their grasp of job skills but ensures their capacity to apply these skills innovatively as well.。
Theimplementatio...
The implementation of the education promotion law of thePeople's Republic of ChinaThe implementation of the education promotion law of the People's Republic of China(on July 25, 2008 in sichuan province, the fourth session of the standing committee of the 11th people's congress by July 25, 2008 in sichuan province people's congress standing committee announced in no. 1 shall be implemented as of October 1, 2008)Article 1 these measures are formulated in accordance with the provisions of the education promotion law of the People's Republic of China and relevant laws and regulations, combined with the actual practice of sichuan province.Article 2 the term "social organizations or individuals other than state institutions, using the non-state fiscal funds within the administrative areas of sichuan province faces the society for schools and other institutions of education activities, these measures shall apply.Article 3 the local people's governments at or above the county level shall adhere to actively encourage, support, correct guidance, in accordance with the management policy, private education career will be incorporated into the national economic and social development of overall planning, classified guidance, rational allocation of education resources, promote the sustained and healthy development of non-governmental education.Article 4 private schools and public schools shall have equal legal status. The autonomy of running schools and other lawful rights and interests of private schools shall be protected by law.Article 5 the private school faculty in the teachers' qualification, title evaluation, post employment, business training, award, application of scientific research project and task, social activities, etc shall enjoy the same rights and public school teachers.Private schools shall be protected in accordance with the law faculty of salary, benefits, build system of faculty salary only door, on time full specified amount paid staff wages, and in accordance with the regulations to participate in all sorts of insurance and housing accumulation fund.The teachers of the private schools may participate in the insurance of the institution. The specific measures shall be formulated by the provincial people's government.Article 6. The private schools of educatees in entrance, transfer, examination and employment, selection, take advanced traffic tools, students to student loans, insurance, aspects and so on social activities enjoy the same public school with the same educatees equal rights.Article 7 the establishment of a private school shall be commensurate with the development of local economic and social development and the development of education and the layout ofthe school. Set the standard reference to the same level of the same kind of public schools.The establishment of a private school shall be subject to the following permissions:(1) the institutions of higher learning of education, as well as the above undergraduate and undergraduate courses, and the higher schools of the normal and medical specialty, education, shall be submitted for approval in accordance with the relevant provisions;(2) the higher vocational technical college (junior college) shall be subject to the examination and approval of the provincial people's government, and shall be reported to the administrative department of the state council education for the record;(3) the non-curricula higher education institutions by the people's governments of cities (state) according to the set standards promulgated by the administrative department of the provincial education examination and approval, submitted to the provincial education administrative departments for the record.(4) the general and secondary vocational schools and other secondary education institutions shall be examined and approved by the administrative department of the municipal (state), education, and reported to the administrative department of the provincial education for the record;(5) the ordinary junior middle school, elementary vocational school, primary school, nursery school and other education institutions by the education administrative departments at the county level for examination and approval, and reported to the city (state) administrative department of education for the record;(6) vocational training and vocational skills training schools, which are primarily vocational qualifications,Primary by county (city, area) for examination and approval of the administrative department for labor security, intermediate by city (state) for examination and approval of the administrative department for labor security, advanced by the provincial administrative departments of labor security and education at the same level for examination and approval of the administrative departments for the record;(7) sports, medicine and health care and other categories of medium and medium under the private schools of education by the relevant administrative departments according to the relevant provisions of the state audit consent to corresponding education administrative department for examination and approval.Article 8 the name of a private school shall comply with relevant laws and administrative regulations and reflect the school's categories, levels and administrative areas. The name of the foreign language used in registration shall be in accordance with the Chinese name of the approved registration.The school or university that has implemented the education of higher education, the name of the school that has implemented the education in the implementation of the education, and the school that has implemented the pre-school education. The implementation of the professional education shall be subject to the words of occupation and professional technology; The implementation of the non-academic education shall be labeled as supplementary education, special repair, further education, training and so on.Article 9 of the examination and approval authorities shall, in accordance with the law of the public about private schools set up by the examination and approval items, basis, conditions, procedures, time limit, a catalogue of need to submit application materials, etc. The application for establishment shall be decided in accordance with the law within the statutory time limit. The application for the establishment of multiple schools shall be accepted by the competent authorities at the top level and shall be subject to examination and approval.After the examination and approval decision is made by the examining and approving organ, the examination and approval decision shall be made to the applicant in the form of a book. If they agree to raise a set of approval, they shall issue a certificate of approval; If the parties do not agree to the raise, the reasons shall be given in writing. To approve the establishment of a school permit for the establishment of a school, and a certificate shall be applied to the school license. If the case is not approved, the reasons shall be given in writing.The approved private schools shall not be allowed to recruit students during the establishment.The civil affairs departments shall, in accordance with the relevant regulations and procedures, make public announcements according to relevant regulations and procedures.Article 10 the termination and liquidation of a private school shall be handled in accordance with relevant laws and regulations.Article 11 a private school shall carry out the responsibility of the principal under the leadership of the council, the board of directors or other forms of decision-making. The director, the director (or the chairman, the director), the list of the examination and approval authorities for the record. The legal representative of a private school shall be the chairman, the chairman or the principal. The private schools shall implement the democratic management system such as the congress of the staff and staff and the public administration of the school affairs. To establish and improve the management system of teaching, scientific research, personnel, finance and safety.Article 12 private schools shall appoint full-time presidents. The principal is under the same kind of public school standards, and the age is not more than 70 years old. The appointment or dismissal of the principal shall be decided by the school board, the board of directors or other forms of decision making and submitted to the examination and approval authorities for approval.Article 13 the implementation of higher education and secondary vocational and technical education in private schools of education, in addition to the regulations of the state, need approval, can according to the principle, training objectives and the market demand, to set up the professional, courses, independent and use teaching materials submitted to the examination and approval authorities for the record.Article 14 the privately-run schools shall enjoy the same enrollment right as the same kind of public schools at the same level.Article 22 the private schools set or adjust the charge to accept degree education pedagogue tuition and accommodation standards, it shall make a written application, in accordance with the school category and subordinate relations shall be reported to the education administrative department or the examination and approval by the administrative department of labor and social security, the price departments for approval, and the public.The private schools may, on their own, determine the fees and accommodation fees for the educatees who receive thenon-academic education, and report to the competent price authorities for the record.Article 23 the private schools in the recruitment of students, should be through a variety of forms of the public to the society fees, fee standards, and other related content, after the public shall not, without change.The private schools that implement the pre-school education shall be charged for the monthly or term basis. The private schools that implement the education degree of education shall be charged for the term or the academic year. The non-diploma education private school shall be charged for the semester or the academic year, which is less than one semester and shall be charged for the training period. Private schools may not charge for the academic year.If the educatee of a private school leaves the school for the withdrawal, transfer or other reasons, the school shall refund the corresponding fee according to the relevant provisions or the agreement between the two parties.Article 24 the establishment and improvement of the risk prevention system for private schools shall be established. The specific measures shall be formulated by the provincial people's government.Article 25 the supervision and administration of education, the supervision and administration of the people's governments at or above the county level, shall, in accordance with the law, supervise the public schools in accordance with the law and improve the quality of their schools.Build system of private school education information announcement, on a regular basis will be run by the local school running level and education quality of teaching evaluation is the evaluation results and other basic educational information announced to the public, the specific measures by the provincial administrative department of education andprovincial administrative departments of labor security, respectively.The administrative departments of education administrative departments of the people's governments at or above the county level and the administrative departments of labor security shall support the recruitment, examination and other work of the private schools.Article 26. The local people's governments at or above the county level shall set up special funds, used to fund the development of private education, rewards and recognition for outstanding contribution to the collective and individual.Article 27 of the state-owned enterprises and institutions can be idle housing and resources such as equipment and facilities in the form of state-owned assets investment andnon-governmental schools cooperation in running schools or priority in accordance with the lease or transfer for use in private schools.Article 28 the donors at private schools and investors are not required to obtain a reasonable return of private schools, shall enjoy equal to public schools of the tax and other preferential policies.The funders shall demand reasonable return of the private schools and enjoy the preferential tax policies stipulated by the state.The privately-run schools shall, in accordance with the law,carry out tax registration and, in accordance with the law, go through the formalities of cancellation of tax registration in accordance with the law.Article 29 citizens, legal persons or other organizations who donate property to private schools shall enjoy the preferential tax policies prescribed by the state.Article 30 the people's government at the county level with private schools entrusted to undertake part of its task of compulsory education, and shall, in accordance with the local implementation of the compulsory education of public school embrace standard education expenses for the corresponding education funds.The entrusted private schools shall receive fees for the students who are enrolled in the agreement, and shall be deducted from the cost of the disbursement of the funds.Article 31 the private schools shall carry out the same price policies as the same public schools in the areas of water, electricity and gas.Article 32 encourage financial institutions to support the development of education in accordance with the preferential policies of the state. The loan must be used for the development of mortgage loans made by the private schools for the development of such facilities as school enterprises.Article 33 the property rights of a private school shall be protected by law. The funders may, in accordance with therelevant provisions, make reasonable returns in the remaining balance of the school in accordance with the law, and the reasonable return for the development of the school shall be reinvested. Specific measures shall be carried out in accordance with the relevant provisions of the state.Article 34 the third paragraph of article 9 of the private schools violates these measures, the provisions of article 22, article 23, by the education administrative departments, administrative departments of labor security, price departments and other relevant administrative departments in accordance with the investigation.If the private school violates other provisions of these measures, it shall be handled according to relevant laws and regulations.Article 35 the management of the for-profit private training institutions registered with the administrative department for industry and commerce shall be carried out in accordance with the relevant provisions of the state.Article 36 the present measures shall go into effect as of October 1, 2008. On December 18, 1998, the sixth session of the standing committee of the 9th people's congress of sichuan province was abolished at the same time.。
足球进校园 英语作文
Football,as a beloved sport worldwide,has been increasingly integrated into educational institutions,not only for its entertainment value but also for the numerous benefits it brings to students physical and mental development.Heres an essay on how football has been introduced into schools and its impact on students.Title:The Integration of Football into School CurriculumsIn recent years,the concept of football in schools has gained significant traction globally. This initiative aims to foster a love for the sport among young learners and to use it as a tool for education and personal growth.The Benefits of Football in Schools1.Physical Fitness:Football is an excellent way to promote physical activity among students.Regular participation in football games and training sessions helps to improve cardiovascular health,strength,and flexibility.2.Teamwork and Social Skills:Playing football teaches students the importance of teamwork,communication,and collaboration.It helps them learn to work together towards a common goal,which is a valuable life skill.3.Discipline and Time Management:Football requires discipline and commitment. Students learn to manage their time effectively between studies and training,which is crucial for their future success.4.Coping with Pressure:Football matches often involve highpressure situations. Learning to perform under pressure and make quick decisions is a skill that can be applied in various aspects of life.5.Cultural Exchange:Football is a universal language that transcends cultural barriers.It allows students to connect with peers from different backgrounds,fostering a sense of global citizenship.Implementation Strategies1.Curriculum Integration:Schools can integrate football into their physical education curriculum,ensuring that all students have the opportunity to participate.2.Extracurricular Activities:Organizing football clubs and afterschool programs can provide additional opportunities for students who are interested in the sport.3.Professional Training:Hiring qualified coaches and providing professional training can enhance the quality of football education and inspire students to excel.4.Infrastructure Development:Investing in football fields and equipment is essential for providing a safe and conducive environment for students to play and practice.munity Engagement:Involving the local community in school football events can foster a sense of pride and support for the schools football program.Challenges and Solutions1.Balancing Academics and Sports:It is crucial to ensure that the introduction of football does not compromise students academic performance.Schools can achieve this by providing adequate support and guidance to students.2.Gender Inclusivity:Ensuring that both boys and girls have equal opportunities to participate in football is essential for promoting gender equality.3.Financial Constraints:Schools in resourcepoor settings may face challenges in funding football programs.Partnerships with local businesses,government support,and fundraising can help overcome these challenges.4.Safety Concerns:Proper safety measures and firstaid training for coaches and students are necessary to prevent injuries during football activities.ConclusionThe introduction of football into schools is a multifaceted initiative that offers a myriad of benefits to students.It not only enhances their physical wellbeing but also contributes to their social,emotional,and cognitive development.With careful planning and implementation,football in schools can become a powerful educational tool that shapes wellrounded individuals ready to face the challenges of the future.。
雅思大作文思路贯穿及表达
Education, which is perceived as the guidance for people to be well-mannered and well-educated, has a vital role to play in the shape of law-abiding citizens for the secure social stability and qualified workers (be) devoted to the social construction. Education can be divided into three levels, that is, primary education (elementary schools), secondary education (high schools) and tertiary education (universities or colleges). Along with the rapid social development, the cultivation of talented elites has been increasingly strengthened by both state governments and the public worldwide.Education should achieve five purposes for the social advance as follows.1.It should improve citizen's moral standard, which canensure the social security and stability.2.It should impart all sorts of information and skills rangingfrom theoretical knowledge such as common sense in science and humanities to practical know-how like how to manage sophisticated equipment. In addition, it should help student shape the independent and critical thinking, master analyzing and problem-solving skills,as well as have a good command of effective communication skills, and last but not least, it should stimulate students, adaptation to different social context.3.It should develop students,robust physical fitness, andinspire them to lead a healthy lifestyle, especially, in P.E.class, students could improve more good qualities such as cooperation / teamwork and competition, tolerance, as well as the sense of social responsibility and belonging.4.It should hone students,individual personality. Inparticular, it can encourage students to imagine wildly and mould their self-cultivation for their temperament, and also aesthetic appreciation can be established through creativity, originality, innovation, and novelty. 5.It should assist students in mastering practical techniquesand skills which is career-oriented, contributing to promising employment prospects.Thus, the implementation of education should accomplish its five functions in order to fulfill people's well-rounded development.Truly, education should help people make productive members in society by raising the awareness of law and practical skills catering for the social needs, whether mental labours such as professional doctors and lawyers (university)or manual labours like truck drivers and mechanics (vocational college).Education is not only a science, but also an art. Put another way, teachers have more than one role to play in modern classroom, acting as a designer for curriculums, a helper for students, an organizer for activities and a performer for attenders rather than a leader, whereas students are considered a centre, who are the determining factor in adjusting the new teaching approaches.Thanks to the state-of-the-art technological advance, great changes have taken place in the conduct of modern education, people are free to study anywhere, for example, in traditional classrooms, or in virtual space. The communication and interaction would be carried out whether in a face-to-face manner or not.In terms of the role of gender in learning efficiency and efficacy, it is strongly recommended that male and female students should share their characters or personalities, thinking mode and behaviours.The main objective or aim of education is not to teach what should be taught, but to learn how to learn more, so theprocess of learning may play a more significant role than the result of tests.Environment is termed as the living surroundings for both human race and the other species to co-exist for their respective sustainable development as well as the interactive balance of biological chain in biosphere in Nature.Unfortunately, human behaviours have posed a huge threat to the habitats for wild animals. To be more specific, there is a population burst in metropolises, traffic congestion and housing shortage are increasingly serious, and mass-produced manufacturing industry is in need of large quantities of resources, causing the depletion of precious energy and limited natural resources. Especially, urbanization and the new city planning like business movement from urban to rural areas could accelerate the complete disappearance of rainforest, where there are abundant resources, and more fossil fuels are overly exploited, contributing to the severe air pollution and the serious water contamination. Thus, global warming and El Nino are the main disastrous phenomena from which modern populations have suffered a lot.Faced with the disastrous catastrophe in natural environment, there should be a multilateral cooperation between developing countries and developed or industrialized countries worldwide. Also, both the administrative government, corporations and individual citizens should commit their responsibility to protect the environment and prevent the pollution as soon as possible in the near futureIn detail, the rational and feasible solutions are as follows;1.They should carry out global cooperation, reach the agreement, and set international standards for environmental protection.2.They should make out laws, and encourage low carbon economy.3.They should exploit renewable and green energy, and invest in energy-saving and eco-friendly technologies.4.They should promote environmentally-friendly products, and lead green consuming habits.5.They should raise public,s green awareness, and advocate low carbon lifestyle.When it comes to the air pollution, simply increasing the price of fossil fuels is plausible, but actually, the search for alternative methods and strategies to develop new and cleanenergy should be promulgated technologically. Plus, arousing the general public's awareness of environmental protection is also regarded socially essential.IIIL TECHNOLOGYTechnology, which attracts a heated concern worldwide, has become a main theme in the New Age. Indeed, whoever has mastered the core technological development surely has the opportunity to increase the efficiency and effectiveness in each sector in daily life, which may exert a far-reaching influence on their sustainable progress in the future.Modern technology has made a huge difference in two dimensions through chronological human history as follows.For one thing, high technology has changed modem people's communication style. The wide application of the Internet and mobile phones has made it possible for people to interchange beyond the spatial reach. Especially, it could facilitate the global interaction between different people with various social-economic backgrounds, contributing to the establishment of globalization. During this process, fashion, film industry and delicious cuisine have been popularized. However, this process may undermine local traditions more or less, particularly new-born babies and new generations are exposed to the international context, which may pose an obstacle to the transmission of traditional customs andcultures.For another, high technology has made great contributions to the modes of transportation. Certainly, the advent of new inventions (airplanes and private cars) has started a new channel for modern people to travel. Thanks to the appearance of modern transport, people could enjoy a long journey, which is a drive for the prosperity of global tourism, and a vehicle for the boom of international trade. Unluckily, the quality of the air and atmosphere has been devastatingly deteriorated. Both cars and planes impose an adverse limitation on the sustainable development of the planet which human beings and the other species rely on for their survival.Both communication and transportation have illustrated the conspicuous progress in human civilization, but the defects that they have brought should not be ignored. We are optimistic about the brand new lifestyle, while we are also should beware of the potential dangers.Technology provides modern people with a great variety of machines and devices, but they are simply regarded as the facilitating supplement rather than a dominant substitute, so on-line shopping vs shopping in store, long-distanceprogram vs. schooling, information about exotic culture and historical objects on TV and the Internet vs. a vivid and lively experience on spot should be complementary and compatible.Television, computers or the Internet, and mobile phones are the new items for modern people to enjoy their fast-paced life featured by the high efficiency. Children take delight in a world of online information, which could be conductive to the development of their intelligence and language skills. At the same time, they are suffering great pain and trouble from these high-tech products. Specifically, they are leading a sedentary life, causing their less fit and active physical condition; also, they spend less time on the face-to-face communication with peers and family members, which could be harmful for their social bonding and lead to the isolation and autism. Due to the exposure to the complex media with overwhelming information including certain violent images, teenagers are vulnerable to the menace and hazard, causing to the high rate of juvenile delinquency owing to their lack of judgment and parental guidance and guardianship.Culture is defined from many perspectives including dressing, cuisine, and architecture, festival and ideology (values, worldview, and outlook on life). In these disciplines, it is noteworthy that traditional and modern cultures co-exist in modern world.Tourists would prefer to visit historical sites to have an overall survey of geographical and natural sceneries as well as ethnical and national aromas in local regions. Museums and art galleries are a short-cut for them to interpret the atmosphere of culture.Tourism is an irreversible and inevitable trend in modern world. Thanks to the invention of modes of transportation, people are free to experience the exotic cultures in foreign communities in real time. Also, multiculturalism is a common phenomenon currently. Take China and USA as an illustration, both of them are abundant in cultural diversity and visitors are constantly enjoying the colourful folk cultures, and such kinds of societies possess the rich cultural treasures, which are of the historical and cultural value. Especially, tourism creates high employment rate and makesmore profits; and it popularizes and disseminates local cultures, and at the same time it may be a good chance to introduce foreign investment to local construction. However, modern tourism has also brought a certain number of disadvantages, the damage to the local environment and the disruption to local citizens, life. Global trip is regarded as an opportunity to present the economic integration and a trend for globalization, but, sometimes, it may contribute to the cultural bias and prejudice due to the misunderstanding and miscommunication resulting from quite different languages, mindsets and living habits. Confronted with this dilemma, schooling education and publicity on mass media should be advocated in order to eliminate the culture shock and establish culture fusion.State governments should assume hefty responsibilities, that is, to ensure national security, to stabilize the society, to enhance social welfare system, and to perfect the public facilities. Also, they should dominate various resources and make a rational agenda for national management. Especially, they should give top priority to investments on education, technology and basic human needs to guarantee public health, and then invest in entertainment and the establishment of recreational facilities to increase emotional well-being and enrich public cultural life.Owing to the levy on taxpayers, the administrative government should offer financial support in the social construction including science which caters for individual basically physical needs for life, as well as art which meets public emotional demands for pleasure.It is objectively proposed that the investment on science and art should strike to an interactive balance. That is to say, in the short run, the sectors regarding to public health should be focused on in a deliberate way initially; in the long run, the fields relating to ideology should also be considered.Governmental authorities of all the countries in the world should carry out the cooperative efforts to provide assistance to each other, lying the fact that some thorny problems like terrorism and climate change should be addressed as long as there is a joint endevour between nations. Due to the unbalanced distribution of various resources worldwide like the economic development, the cultivation of talents, the technological advance, the military power, the existence of natural resources and the increasing rate of population, there should be an interaction between nations in these aspects so as to establish the global village in harmony.。
学校制度英文短文
In order to maintain a disciplined and harmonious educational environment, schools have established a set of regulations that students are expected to follow. These regulations are designed to promote academic excellence, personal growth, and social development. This essay will discuss the importance of school regulations and their impact on students' lives.First and foremost, school regulations serve as a guide for students to follow. They provide clear guidelines on how students should behave, dress, and interact with others. By adhering to these regulations, students can create a positive and respectful atmosphere that fosters learning and growth.One of the most important aspects of school regulations is the emphasis on discipline. Discipline is essential for students to develop self-control and self-motivation. When students are disciplined, they are more likely to focus on their studies and achieve academic success. Additionally, discipline helps students learn to respect authority and adhere to societal norms.Another critical role of school regulations is to ensure the safety and well-being of students. Schools have implemented various safety measures, such as fire drills, bullying prevention policies, and access control systems. These measures help protect students from potential harm and create a secure environment where they can thrive.School regulations also promote academic integrity. By prohibiting cheating, plagiarism, and other forms of academic dishonesty, schools encourage students to develop their critical thinking and problem-solving skills. This not only enhances their academic performance but also prepares them for the challenges they will face in their future careers.Furthermore, school regulations help students develop good citizenship skills. By promoting respect, kindness, and cooperation, these regulations encourage students to be responsible members of their school community. This sense of responsibility extends beyond the school gates, enabling students to contribute positively to society as they grow older.Despite the benefits of school regulations, some students may find them restrictive. However, it is essential to understand that these regulations are in place for a reason. By adhering to them, students can create a more supportive and inclusive learning environment for everyone.To help students understand and comply with school regulations, schools often hold orientation sessions for new students and conduct regular reminders through assemblies, newsletters, and announcements. Teachers also play a crucial role in enforcing these regulations by setting a positive example and addressing any violations promptly and fairly.In conclusion, school regulations are an essential component of a well-rounded educational experience. They provide students with guidelines on how to behave, promote discipline and safety, ensure academic integrity, and foster good citizenship skills. While some students may view these regulations as restrictive, they ultimately serve to create a more supportive and inclusive learning environment for everyone. By adhering to these regulations, students can develop into responsible, successful, and well-rounded individuals.。
Authenticated Routing
Authenticated Routing for Ad Hoc Networks Kimaya Sanzgiri,Daniel LaFlamme,Bridget Dahill,Brian Neil Levine,Member,IEEE,Clay Shields,Member,IEEE,and Elizabeth M.Belding-Royer,Member,IEEEAbstract—Initial work in ad hoc routing has considered only the problem of providing efficient mechanisms forfinding paths in very dynamic networks,without considering security.Because of this,there are a number of attacks that can be used to manipulate the routing in an ad hoc network.In this paper,we describe these threats,specifically showing their effects on ad hoc on-demand dis-tance vector and dynamic source routing.Our protocol,named au-thenticated routing for ad hoc networks(ARAN),uses public-key cryptographic mechanisms to defeat all identified attacks.We de-tail how ARAN can secure routing in environments where nodes are authorized to participate but untrusted to cooperate,as well as environments where participants do not need to be authorized to participate.Through both simulation and experimentation with our publicly available implementation,we characterize and eval-uate ARAN and show that it is able to effectively and efficiently discover secure routes within an ad hoc network.Index Terms—Ad hoc networks,secure routing.I.I NTRODUCTIONS ECURING protocols for mobile ad hoc networks presents unique challenges due to characteristics such as lack of pre-deployed infrastructure,centralized policy and control.In this paper,we make a number of contributions to the design of se-cure ad hoc routing protocols.1First,we describe exploits that are possible against ad hoc routing protocols.We show specifi-cally that two protocols that are under consideration by the In-ternet Engineering Task Force(IETF)for standardization,ad hoc on-demand distance vector(AODV)[2]and dynamic source routing(DSR)[3],although efficient in terms of network perfor-mance,are replete with securityflaws.Second,we define and distinguish the heterogeneous environments that make use of ad hoc routing and differ in their assumed predeployment and security requirements.This approach is important because sat-isfying a tighter set of security requirements than an application requires is unwarranted and wasteful of resources.Manuscript received October17,2003;revised October15,2004.This work was supported in part by the National Science Foundation under Award ANI-522564,Award ANI-0335302,and Award EIA-0080199,in part by an Air Force Office of Scientific Research(AFOSR)Multidisciplinary University Research Initiative(MURI)Grant,and in part by the U.S.Department of Justice,Office of Justice Programs under Grant2000-DT-CX-K001.Contents are solely the responsibility of the authors and do not necessarily represent the official views of the Department of Justice(DoJ)or National Science Foundation(NSF).K.Sanzgiri and E.M.Belding-Royer are with the Department of Computer Science,University of California,Santa Barbara,CA93106USA(e-mail: kimaya@).Flamme,B.Dahill,and B.N.Levine are with the Department of Com-puter Science,University of Massachusetts,Amherst,MA01060USA.C.Shields is with the Department of Computer Science,Georgetown Univer-sity,Washington,DC20057USA.Digital Object Identifier10.1109/JSAC.2004.8425471This paper represents many refinements and extensions to our original work from IEEE ICNP2002[1].Third,we propose a secure routing protocol,authenticated routing for ad hoc networks(ARAN),that detects and protects against malicious actions by third parties and peers.ARAN in-troduces authentication,message integrity,and nonrepudiation to routing in an ad hoc environment as a part of a minimal se-curity policy.We detail how ARAN can be used in two environments: where mobile users are federated and can be precertified(e.g., on a campus)though remain untrusted;and where they are unknown to each other and cannot be precertified(e.g.,a “rooftop”access point).To our knowledge,ARAN is thefirst proposal for securing ad hoc routing for rooftop networks. We analyze the security of ARAN and evaluate its net-work performance through measurement of both our publicly available implementation and extensive simulations.Wefind that although there is a greater performance cost to ARAN as compared to DSR or AODV,the increase in cost is minimal and outweighed by the increased security.This paper is organized as follows.Section II presents an overview of recent work on ad hoc network security.Section III describes the security exploits possible in ad hoc routing proto-cols.Three ad hoc environments and the security requirements of any ad hoc network are defined in Section IV.Section V presents our secure ad hoc routing protocol,ARAN.A secu-rity analysis of ARAN is provided in Section VI,while Section VII evaluates ARAN through implementation and simulations. Finally,Section VIII offers concluding remarks.II.B ACKGROUNDSeveral proposed ad hoc routing protocols,for example [2]–[6],have security vulnerabilities and exposures that easily allow for routing attacks.While these vulnerabilities are common to many protocols,in this paper,we focus on two protocols that are under consideration by the IETF for stan-dardization:AODV[2]and DSR[3].The fundamental differences between ad hoc networks and standard Internet protocol(IP)networks necessitate the devel-opment of new security services.This point has been recog-nized,and several researchers have examined security problems in ad hoc networks.Numerous solutions have been proposed for providing a secure and reliable certification authority in ad hoc networks[7]–[10].Another problem that has received attention is that of stimulating cooperation among nodes in an ad hoc network and addressing malicious packet dropping[11]–[16]. Strategies used include detecting and punishing noncooperating nodes,rewarding nodes for forwarding packets,concealing the true destination of packets from intermediate nodes,and using redundant data transmissions over multiple paths.0733-8716/$20.00©2005IEEEThe issue of secure routing in particular has received signif-icant attention.Hu et al.have proposed ARIADNE[17],a se-cure version of DSR.ARIADNE can use predeployed pairwise symmetric keys or predeployed asymmetric cryptography for authentication.The former is more efficient,but requires shared secrets between communicating nodes,which may not always be feasible to establish.A third option for ARIADNE is the TESLA authentication scheme,which is also based on asym-metric encryption,thus requiring a certification authority or pre-deployed keys.TESLA requires that packets are delayed by the longest round-trip time(RTT)in the network before they are sent(thus route creation incurs this delay in both request and response phases).Chu et al.developed a secure proactive routing protocol based on DSDV[6]called SEAD[18],which is also based on public-key signed hash chains.SAODV[19],an early attempt to secure the AODV routing protocol,has numerous security vulnerabilities.For instance,it allows a malicious intermediate node to spoof its identity,ille-gally modify the hop count on route request messages,and fab-ricate route error messages.The use of security parameters,such as the trust level of a node in a hierarchical organization,as a routing metric is pro-posed in[20].To secure the scheme,the authors suggest that all nodes at the same level of trust should share a common se-cret.This is not very practical,and has many key-management issues.In an alternative scheme,Papadimitratos et al.[21]propose the secure routing protocol(SRP);however,this is vulnerable to attacks such as fabricated route error messages.Routing security in sensor networks has been analyzed in[22].The wormhole attack against secure ad hoc routing protocols is studied and a solution is presented in[23],though imple-menting the solution requires specialized hardware to achieve a high degree of clock synchronization.Awerbuch et al.design a flooding-free reactive routing protocol based on Swarm Intelli-gence and the distributed reinforcement learning paradigm[24], which is secure against a dynamic Byzantine adversarial model. Finally,intrusion detection techniques for ad hoc networks have been studied[25],[26].Our work differs from other work in that we do not assume any hardware modifications or synchronized clocks,and only minimal advance keying from a trusted authority.We also ac-count for the costs of distributing cryptographic material instead of assuming it is predeployed.In comparison against related work(e.g.,[17],[27]),ARAN has higher computational costs at each node,which has impli-cations for power costs and latency.However,the dominant en-ergy cost of wireless networking on handheld devices is the idle system with an idle radio[28];the costs of ARAN’s cryptog-raphy represent a small price in comparison.ARAN’s compu-tational delays are comparable to the mandatory authentication delays required by TESLA[27],a hash-chain-based approach to security.TESLA mandates delays equal to twice the diam-eter RTT of the network in addition to processing delays,even if the path is between direct neighbors.TABLE IV ULNERABILITIES OF AODV,DSR,ANDARANIII.E XPLOITS A GAINST E XISTING P ROTOCOLS Several popular ad hoc routing protocols allow for many dif-ferent types of attacks.In this section,we classify and briefly describe modification,impersonation,and fabrication exploits against ad hoc routing protocols.Detailed descriptions of the at-tacks can be found in our previous work[1].In addition,several attacks are possible in the forwarding operation.Data packets can be dropped,replayed,or redirected.In Section V,we pro-pose a protocol that is not exploitable in these ways.Our focus is on vulnerabilities and exposures that result from the specification of the ad hoc routing protocol,and not from problems with IEEE802.11.Additionally,denial-of-service at-tacks based on noncooperation and packet dropping,or resource depletion by aggressive route requestflooding,are possible in all ad hoc routing protocols.We do not deal with the issue of en-suring protocol compliance,and look only at security problems arising from manipulation of the network routing.The attacks presented below are described in terms of the AODV and DSR protocols,which we use as representatives of ad hoc on-demand protocols.Table I provides a summary of each protocol’s vulnerability to the following exploits.A.Attacks Using ModificationMalicious nodes can cause redirection of network traffic and DoS attacks by altering control messagefields or by forwarding routing messages with falsified values.Below,we briefly de-scribe several modification attacks against AODV and DSR. 1)Redirection by Modified Route Sequence Num-bers:Protocols such as AODV and DSDV assign mono-tonically increasing sequence numbers to routes toward specific destinations.A route with a higher sequence number is pre-ferred over one with a lower sequence number.Thus,in AODV, any node may divert traffic through itself by advertising a route to a node with a destination sequence num greater than the authentic value.2)Redirection With Modified Hop Counts:In AODV,a redi-rection attack is possible by modification of the hop countfield in route discovery messages.When routing decisions cannot be made by other metrics,AODV uses the hop countfield to deter-mine a shortest path.Malicious nodes can increase the chances they are included on a newly created route by resetting the hopcountfield of the route request(RREQ)to zero.Similarly,by setting the hop countfield of the RREQ to infinity,created routes will tend to not include the malicious node.Such an attack is most threatening when combined with spoofing,described in Section III-B.3)Denial-of-Service With Modified Source Routes:DSR utilizes source routes,thereby explicitly stating routes in data packets.These routes lack any integrity checks and a simple denial-of-service attack can be launched in DSR by altering the source routes in packet headers,such that the packet can no longer be delivered to the destination.4)Tunneling:Ad hoc networks have an implicit assumption that any node can be located adjacent to any other node.A tun-neling attack is where two or more nodes collaborate to encapsu-late and exchange messages along existing data paths.Such col-laborating nodes can pretend to be neighbors,and falsely repre-sent the length of available paths by preventing honest interme-diate nodes from correctly incrementing the path length metric. It is also possible that instead of tunneling through existing multi-hop routes,the malicious nodes can use a long-range di-rectional wireless link or a wired link between them.Such a link gives the attackers an unfair advantage toward occurring on the shortest delay route between a source and destination.This has been referred to as the wormhole attack in recent literature[17], [23].However,if the malicious nodes truly lie on the shortest delay path,it could be argued that the selection of this path is not a subversion of the routing protocol.A mechanism for de-fending against wormhole attacks is presented in[23].B.Attacks Using ImpersonationSpoofing occurs when a node misrepresents its identity in the network,such as by altering its medium access control(MAC) or IP address in outgoing packets,and is readily combined with other attacks,such as those based on modification.The advan-tage of spoofing is that the attack cannot be traced back to the malicious node.C.Attacks Using FabricationFabrication attacks involve the generation of false routing messages.Such attacks can be difficult to verify as invalid con-structs,especially in the case of fabricated error messages that claim a neighbor cannot be contacted.1)Falsifying Route Errors in AODV and DSR:In AODV and DSR,if the destination node or an intermediate node along an active path moves,the node upstream of the link break broad-casts a route error message to all active upstream neighbors. This message causes the corresponding route to be invalidated in all upstream nodes.A denial-of-service attack can be launched by continually sending route error messages indicating a broken link on the route,thereby preventing the source from communi-cating with the destination.2)Route Cache Poisoning in DSR:In DSR,a node over-hearing any packet may add the routing information contained in that packet’s header to its own route cache,even if that node is not on the path from source to destination.An attacker could easily exploit this method of learning routes and poison route caches by transmitting packets containing invalid routes in their headers.IV.S ECURITY R EQUIREMENTS OF A D H OC N ETWORKS Applications for ad hoc networks include military operations, emergency rescue missions,and simple provisioning of wire-less network access,such as at a conference or in a classroom. In this section,we classify ad hoc networks into three distinct environments that differ in security needs and assumed prede-ployment.These classes are defined because it is difficult to con-struct a single secure ad hoc routing protocol to suit the needs of many heterogeneous wireless applications.The lower secu-rity requirements of some environments do not justify use of costly protocols that satisfy stricter security policies.The envi-ronments defined in this section enable us to clearly state where we expect to apply our secure protocol.A good secure routing algorithm prevents each of the exploits presented in Section III;it must ensure that no node can prevent successful route discovery and maintenance between any other nodes other than by nonparticipation.We define a set of three discrete ad hoc wireless environ-ments:open,managed-open and managed-hostile.These differ not only in the level of security needed,but also in that some have opportunity for exchange of security parameters before the nodes are deployed.In sum,all secure ad hoc routing protocols must satisfy the following requirements to ensure that path discovery from source to destination functions correctly in the presence of malicious adversaries.1)Route signaling cannot be spoofed.2)Fabricated routing messages cannot be injected into thenetwork.3)Routing messages cannot be altered in transit,exceptaccording to the normal functionality of the routing protocol.4)Routing loops cannot be formed through malicious action.5)Routes cannot be redirected from the shortest path bymalicious action.These requirements help define an open environment along with the following distinction:all nodes can be considered authorized.This scenario might exist,for example,for a user walking through an urban environment or driving on a highway. Managed-open environments are accordingly distinguished by an additional requirement.6)Unauthorized nodes must be excluded from route compu-tation and discovery.This requirement does not preclude the fact that authenticated peers may act maliciously as well.Additionally,we assume that the managed-open environment has the opportunity for predeployment or exchange of public keys,session keys,or certificates.We expect mobile nodes in this environment reside within some common context or geo-graphic proximity.Such an ad hoc network might be formed by peers at a conference,or students on a campus.We define a managed-hostile environment to have require-ments listed above,as well as the following.7)The network topology must neither be exposed to adver-saries nor to authorized nodes by the routing messages.A managed-hostile environment is formed,for example,by mil-itary nodes in a battle environment,or perhaps by emergencyresponse crews in a disaster area.In such an environment,nodes are deployed by a common source.Consequently,there may be opportunity for predeployed exchange of security parameters.The distinguishing security threat of the managed-hostile envi-ronment is that every node is vulnerable to physical capture and take-over of equipment,where hostile entities can then pose as friendly entities at a compromised node.Therefore,exposure of node location from the routing protocol messages is not de-sirable,else adversaries may gain an opportunity to annihilate users.In Section V ,we present the ARAN protocol,which meets the needs of the managed-open and open environments.It does not provide a solution to the managed-hostile environment because it exposes the routing topology.V .A UTHENTICATED R OUTING FOR A D H OC N ETWORKS (ARAN)In this section,we detail the operation of ARAN.ARAN uses cryptographic certi ficates to prevent most of the attacks pre-sented in Section III and detect erratic behavior.ARAN consists of a preliminary certi fication process followed by a route instantiation process that guarantees end-to-end authentication.The protocol is simple compared to most nonsecured ad hoc routing protocols,and does not include routing optimizations present in the latter.It should be noted that these optimizations are the chief cause of most exploits listed in Section III.Route discovery in ARAN is accomplished by a broadcast route discovery message from a source node that is replied to by the destination node.The routing messages are authenticated end-to-end and only authorized nodes participate at each hop between source and destination.A.Certi fication of Authorized NodesARAN uses cryptographic certi ficates to bring authenti-cation,message-integrity and nonrepudiation to the route discovery process.ARAN,therefore,requires the use of a trusted certi ficateserver ,whose public key is known to all valid nodes (or multiple servers may be used [10]).Nodes use these certi ficates to authenticate themselves to other nodes during the exchange of routing messages.The use of public keys and certi ficates is common in many secure ad hoc routing protocols,but most assume the existence of such information without any explicit description of how it is transmitted.While ARAN may appear more expensive,it is in part because we ac-count for the distribution of the cryptographic keying material.In managed-open environments,keys are a priori generated and exchanged through an existing,perhaps out-of-band,rela-tionshipbetween and each node.Before entering the ad hoc network,each node must request a certi ficatefrom .Each node receives exactly one certi ficate after securely authenticating its identityto .Details of how certi ficates are revoked are ex-plained in Section V-G.Section V-H describes the certi fication process for open environments.A node receives a certi ficate from as follows:(1)TABLE IIT ABLE OF V ARIABLES AND N OTATIONThe certi ficate contains the IP address of ,the publickey of,a timestamp of when the certi ficate was created,and a time at which the certi ficate expires.Table II summarizes our notation.These variables are concatenated and signed by .All nodes must maintain fresh certi ficates with the trusted server.B.Authenticated Route DiscoveryThe goal of end-to-end authentication is for the source to verify that the intended destination was reached.The source trusts the destination to select the return path.The source node begins route instantiation to destination by broadcasting to its neighbors a route discovery packet (RDP)(2)The RDP includes a packet type identi fier (“RDP ”),the IP ad-dress of the destination’s certi ficate ,and a nonce,all signed with ’s private key.Note that the RDP is only signed by the source and not encrypted,so the con-tents can be viewed publicly.The purpose of the nonce is to uniquely identify an RDP coming from a source.Each time performs route discovery,it monotonically increases the nonce.The nonce is 5bytes in size,and is thus large enough that it will not need to be recycled within the lifetime of the network.2Note that a hop count is not included with the message.When a node receives an RDP message,it sets up a reverse path back to the source by recording the neighbor from which it received the RDP.This is in anticipation of eventually re-ceiving a reply message that it will need to forward back to the source.The receiving node uses ’s public key,which it extracts from ’s certi ficate,to validate the signature and verify that ’s certi ficate has not expired.The receiving node also checks thetuple to verify that it has not already processed thisRDP;nodes do not forward messages with already-seen tuples.The receiving node signs the contents of the message,appends its own certi ficate,and forward broadcasts the message to each of its neighbors.The signature prevents spoo fing attacks that may alter the route or form loops.2If a source sends a new RDP every millisecond,with a 5byte nonce,it wouldtake more than 34years for the value to wrap around.Let be a neighbor that has receivedfrom the RDP broad-cast,which it subsequentlyrebroadcasts(3)Upon receiving theRDP,’sneighbor validates the signa-tures forboth ,the RDP initiator,and ,the neighbor it re-ceived the RDP from,using the certi ficates in theRDP.thenremoves ’s certi ficate and signature,records as its prede-cessor,signs the contents of the message originally broadcastby and appends its own certi ficate.then rebroadcasts theRDP(4)Each intermediate node along the path repeats the same stepsas .C.Authenticated Route SetupEventually,the message is received by thedestination,,who replies to the first RDP that it receives for a source and a given nonce.This RDP need not have traveled along the path with the least number of hops;the least-hop path may have a higher delay,either legitimately or maliciously manifested.In this case,however,a noncongested,nonleast-hop path is likely to be preferred to a congested least-hop path because of the re-duction in delay.Because RDPs do not contain a hop count or speci fic recorded source route,and because messages are signed at each hop,malicious nodes have no opportunity to redirect traf fic with the exploits we described in Section III.After receiving the RDP,the destination unicasts a reply (REP)packet back along the reverse path to the source.Let the first node that receives the REP sentby benode(5)The REP includes a packet type identi fier (“REP ”),the IP ad-dressof,the certi ficate belongingto and the nonce sentby .Nodes that receive the REP forward the packet back to the predecessor from which they received the original RDP.Each node along the reverse path back to the source signs the REP and appends its own certi ficate before forwarding the REP to the next hop.Let ’s next hop to the source benode(6)validates ’s signature on the received message,removes the signature and certi ficate,then signs the contents of the message and appends its own certi ficate before unicasting the REPto.(7)Each node checks the nonce and signature of the previous hop as the REP is returned to the source.This avoids attacks where malicious nodes instantiate routes by impersonation and replay of X ’s message.When the source receives the REP,it veri-fies the destination ’s signature and the nonce returned by the destination.D.Route MaintenanceARAN is an on-demand protocol.When no traf fic has oc-curred on an existing route for that route ’s lifetime,the route is simply deactivated in the route table.Data received on an in-active route causes nodes to generate an error (ERR)message.Nodes also use ERR messages to report links in active routes that are broken due to node movement.All ERR messages mustbe signed.For a route betweensourceanddestination ,anodegenerates the ERR message for itsneighbor asfollows:(8)This message is forwarded along the path toward the source without modi fication.A nonce ensures that the ERR message is fresh.It is extremely dif ficult to detect when ERR messages are fab-ricated for links that are truly active and not broken.However,the signature on the message prevents impersonation and en-ables nonrepudiation.A node that transmits a large number of ERR messages,whether the ERR messages are valid or fabri-cated,should be avoided.E.Responses to Erratic BehaviorErratic behavior can come from a malicious node,but it can also come from a friendly node that is malfunctioning.ARAN ’s response does not differentiate between the two and regards all erratic behavior as the same.Erratic behavior includes the use of invalid certi ficates,improperly signed messages,and misuse of route error messages.ARAN ’s response to erratic behavior is a local decision and the details are left to implementors.We discuss how susceptible ARAN is to this behavior in the next section.F .Potential OptimizationsAlthough we have speci fied the use of public certi ficates here,it is clear that intermediary nodes (and in our examples)can easily agree upon and exchange session keys using the certi fi-cates that authenticate their participation in route creation.Two nodes can easily share a symmetric key generated with their own private key and the public key of the other.A session key can last the duration of their juxtaposition and can be a symmetrickey,to reduce processing costs;equivalently,juxtaposed peers can create low-cost hash chains between themselves for authentication of future ing these optimizations would decrease computational overhead and power consump-tion.However,even if these optimizations are used,we require that sources and destinations must include full public-key sig-natures for end-to-end route discovery and setup messages.G.Key RevocationIn some environments with strict security criteria,the re-quired certi ficate revocation mechanism must be very reliable and expensive.Due to the desired low overhead in wireless networks and the lower standards of security sought in the managed-open and open environments,a best-effort immediate revocation service can be provided that is backed up by the use of limited-time certi ficates.。
活动举措英语作文
活动举措英语作文Title: Implementing Effective Measures for Activities。
In modern society, the implementation of effective measures for various activities is crucial for theirsuccess and impact. Whether it's organizing community events, educational workshops, or corporate seminars, the execution of well-thought-out plans can make a significant difference. Here, we delve into some essential strategies and approaches to ensure the success of activities.First and foremost, thorough planning is paramount. Before initiating any activity, a detailed plan outlining the objectives, target audience, resources needed, and timeline should be established. This plan acts as a roadmap, guiding the organizers through each stage of the activity and ensuring that all necessary components are addressed.Secondly, effective communication plays a vital role in the success of any activity. Clear and concisecommunication with all stakeholders, including participants, volunteers, sponsors, and the broader community, is essential. Utilizing various channels such as social media, email newsletters, and traditional advertising methods can help spread the word and generate interest in the activity.Furthermore, garnering support from stakeholders is crucial. Whether it's securing funding from sponsors, enlisting the help of volunteers, or gaining endorsement from local authorities, having the support of various stakeholders can enhance the credibility and reach of the activity. Building and nurturing these relationships is an ongoing process that requires transparency, trust, and mutual benefit.Moreover, incorporating innovative and engagingelements into the activity can significantly enhance its appeal and impact. This could involve integratinginteractive workshops, guest speakers, hands-on demonstrations, or multimedia presentations to captivate participants and provide them with valuable insights and experiences.Additionally, evaluating and adapting the activity based on feedback and outcomes is essential for continuous improvement. Collecting feedback from participants, volunteers, and other stakeholders allows organizers to identify strengths, weaknesses, and areas for enhancement. This feedback loop enables organizers to refine their approach and make informed decisions for future activities.In conclusion, the implementation of effective measures is critical for the success of activities across various domains. By meticulously planning, communicating effectively, garnering support from stakeholders, incorporating innovative elements, and evaluating outcomes, organizers can maximize the impact and value of their activities. Ultimately, these efforts contribute tobuilding vibrant communities, fostering learning and development, and creating memorable experiences for all involved.。
如何在大学开展道德教育英语作文
如何在大学开展道德教育英语作文How to Carry out Moral Education in CollegeIn today's fast-paced and competitive society, it is becoming increasingly important for college students to not only excel academically, but also to develop strong moral character. Therefore, the implementation of moral education in college is essential in shaping students to become responsible and ethical individuals. Here are some effective ways to carry out moral education in college:First and foremost, colleges should incorporate moral education into the curriculum. This can be done by offering courses that focus on ethical decision-making, social responsibility, and character development. By including moral education in the academic curriculum, students will have the opportunity to learn about important ethical principles and values that will guide their behavior both in and out of the classroom.In addition to formal classroom instruction, colleges should also provide opportunities for students to participate in extracurricular activities that promote moral development. This can include community service projects, leadership training, andpeer mentoring programs. By engaging in these activities, students will have the chance to apply the moral principles they have learned in real-life situations, thereby strengthening their moral character.Furthermore, colleges should foster a campus culture that values and promotes ethical behavior. This can be achieved by creating a code of conduct that outlines the expected standards of behavior for students, faculty, and staff. Colleges should also organize ethics workshops, seminars, and lectures to promote discussions and raise awareness about moral issues.Moreover, colleges should empower students to take responsibility for their own moral development. This can be done by encouraging students to reflect on their actions and decisions, and to seek guidance from mentors and counselors when faced with ethical dilemmas. By empowering students to take ownership of their moral growth, colleges can instill a sense of personal responsibility and integrity in their student body.Overall, the implementation of moral education in college plays a crucial role in shaping the character of students and preparing them to become ethical leaders in society. By incorporating moral education into the curriculum, providing opportunities for extracurricular activities, fostering a campusculture of ethics, and empowering students to take responsibility for their own moral development, colleges can effectively promote moral values and principles among their student body. It is through these efforts that colleges can instill a sense of ethics, integrity, and social responsibility in their students, shaping them to become responsible citizens and leaders of tomorrow.。
金融英语考试试题及答案
金融英语考试试题及答案金融英语是金融领域中不可或缺的一部分，对于从事金融行业的人士来说，掌握金融英语的知识非常重要。
为了帮助大家更好地备考金融英语考试，本文将为大家提供一些常见的金融英语考试试题及答案。
一、选择题1. What is the meaning of IPO?a) Initial Public Offeringb) International Purchase Orderc) Investment Portfolio Optimizationd) International Partnership Organization答案：a) Initial Public Offering2. What does the term "capital market" refer to?a) The market for physical capitalb) The market for financial assets with a maturity of less than a yearc) The market for financial assets with a maturity of more than a yeard) The market for real estate properties答案：c) The market for financial assets with a maturity of more than a year3. Which of the following is an example of a derivative?a) Stockb) Bondc) Optiond) Certificate of Deposit答案：c) Option4. What is the opposite of a deficit?a) Surplusb) Debtc) Liabilityd) Equity答案：a) Surplus5. What is the term for a loan that is secured by collateral?a) Unsecured loanb) Subordinated loanc) Secured loand) Revolving loan答案：c) Secured loan二、填空题1. The study of how individuals and institutions make financial decisions and how these decisions affect the allocation of resources is known as__________.答案：finance2. When a company issues shares for the first time and offers them to the public, it is called an ____________.答案：IPO (Initial Public Offering)3. The interest rate that a commercial bank charges its most creditworthy customers is known as the _________.答案：prime rate4. A financial instrument that represents ownership in a corporation is called a ___________.答案：stock5. The basic economic problem of having seemingly unlimited human wants in a world of limited resources is known as ________.答案：scarcity三、解答题1. Explain the concept of time value of money.答案：The time value of money refers to the idea that a dollar today is worth more than a dollar in the future. This is because money can be invested and earn interest over time. Therefore, receiving a dollar today ismore desirable than receiving the same amount in the future. The time value of money is an important concept in finance and is used to calculate the present value of future cash flows.2. What are the main functions of a central bank?答案：The main functions of a central bank include:- Monetary policy: Central banks are responsible for formulating and implementing monetary policy to control the money supply and interest rates in an economy. This is done to achieve specific macroeconomic objectives, such as price stability and economic growth.- Banker to the government: Central banks act as the government's bank and provide services such as managing the government's accounts, issuing government securities, and acting as a lender of last resort.- Banker to commercial banks: Central banks also provide banking services to commercial banks, including maintaining accounts, providing short-term loans, and overseeing the stability of the banking system.- Currency issuance: Central banks are responsible for issuing and circulating the national currency.- Financial stability: Central banks play a crucial role in maintaining financial stability and monitoring risks in the banking system.总结：本文为大家提供了一些常见的金融英语考试试题及答案。
Ad Hoc路由协议实现技术
Ad Hoc路由协议实现技术①张爱民，马志强，易晓蓉(总参谋部通信训练基地，宣化 075100）摘 要：针对目前的Ad-Hoc网络的研究大多在模拟环境进行的现状，对AODV路由协议实现展开了研究，提出了一种在Linux系统中基于Netfilter功能框架的AODV协议设计与实现方法。
搭建了以PXA310处理器和IEEE802.11b无线网卡为核心的硬件平台，完成了基于Netfilter功能框架的AODV路由协议的软件框架，实现了路由查询、更新和维护等过程。
对Ad-Hoc网络协议的实现具有较高的参考和实用价值。
关键词：Ad-Hoc；AODV路由协议；Linux系统；Netfilter功能框架；路由表Implementation of Ad Hoc Routing ProtocolZHANG Ai-Min, MA Zhi-Qiang, YI Xiao-Rong(Communication Training Base of PLA General Staff Headquarters, Xuanhua 075100, China)Abstract: The current Ad Hoc network researches are mainly based on simulated experiments. This paper is centered upon realization of AODV routing Protocol. A method on AODV routing Protocol of design and implementation based on Netfilter function framework is proposed. The hardware platform is founded based on PXA310 processor and IEEE802.11b wireless IEEE802.11b network card, a design of software based on the Netfilter function framework was accomplished, has achieved the major Processes such as the routing request, routing updating and maintenance, this design will be important worthiness for implementation of AODV routing protocol.Key words: Ad Hoc; AODV routing Protocol; Linux operation system; Netfilter function framework; routing table1引言Ad Hoc网络技术首先主要用于军事通信、救灾抢险和野外作业等领域中具有重要应用价值，路由协议是Ad Hoc网络研究的热点和难点问题，近些年来，人们己经提出20种以上的Ad Hoc网络路由协议，如：DSR、TOAR、AODV、DSDV、CGSR和ABR等，但具有原创性的路由协议不过几种。
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An Implementation Study of the AODV Routing ProtocolElizabeth M.RoyerDept.of Electrical&Computer Engineering University of California,Santa BarbaraSanta Barbara,CA93106eroyer@Charles E.Perkins Communications System Laboratory Nokia Research CenterMountain View,CA94043cperkins@Abstract(a) RREQ Broadcast(b) RREP Propagation andSubsequent RouteFig.2.Route Discovery Cycle.were necessary to the AODV protocol,while Section III-B de-scribes modifications needed in the Linux kernel.Plans for future work in the AODV implementation are discussed in Sec-tion IV.Finally,Section V concludes the paper.II.OVERVIEW OF AODVThe Ad hoc On-Demand Distance Vector(AODV)routing protocol provides unicast,broadcast,and multicast communi-cation in ad hoc mobile networks[5],[6],[7].AODV initiates route discovery whenever a route is needed by a source node, or whenever a node wishes to join a multicast group.Routes are maintained as long as they are needed by the source node or as long as the multicast group exists,and the routes are always loop-free through the use of sequence numbers.AODV nodes maintain a route table in which next hop routing information for destination nodes is stored.A.UnicastRoute discovery in AODV follows a route request/route re-ply query cycle.A source node in need of a route broadcasts a Route Request(RREQ)packet(Fig.2(a))across the network. Any node with a current route to the destination,including the destination itself,can respond to the RREQ by unicasting a Route Reply(RREP)to the source node.Once the source node receives the RREP,it can begin sending data packets along this route to the destination.Fig.2(b)illustrates the propagation of RREP messages back to the source node,and the subsequent route selected by the source node to the destination. Because nodes are moving,link breaks are likely to occur. When a link break in an active route occurs,the node upstream of the break broadcasts a Route Error(RERR)message con-taining a list of all the destinations which are now unreachable due to the loss of the link.The RERR is propagated back to the source node.Once the source node receives this message, it may reinitiate route discovery if it still needs the route.B.MulticastAs network nodes join a multicast group,a bi-directional shared tree composed of the multicast group members and intermediary nodes needed to connect the group members is created.Each multicast group has associated with it a group leader.The primary function of the group leader is to maintain and disseminate the multicast group sequence number.This sequence number is used in maintaining freshness of routing information for the multicast group.A node wishing to join a multicast group broadcasts a RREQ message with the joinflag set.Any node which is a member of the multicast tree can respond to this message by unicasting a RREP back to the originator of the RREQ.The node join-ing the group waits a discovery period,during which it collects RREPs.Any node forwarding a RREP must also keep track of its best route to the multicast tree.At the end of the dis-covery period,the requesting node selects the shortest route to the multicast tree,and unicasts the next hop along this route a Multicast Activation(MACT)message.When the next hop receives this message,it activates the link in its multicast route table.If this node is already a tree member,the new tree branch isfinalized.Otherwise,the next hop in turn unicasts a MACT message to the neighbor it has selected as its next hop towards the multicast group tree.Processing continues in this manner until a node that was already a member of the multicast tree is reached and the addition of the tree branch is complete.Further details about AODV multicast can be found in[7].III.MODIFICATIONSAODV has been implemented as a routing daemon in user space.The daemon communicates with the Linux kernel through the use of sockets.At initialization,AODV opens a UDP socket to the kernel.This socket is used for both the transmission and reception of AODV control messages.AODV has been issued port number654,and hence binds to this port when opening the socket.Other channels of communication include an IGMP socket for multicast,and a netlink socket for routing table updates.These sockets are described further in the following sections.During the development of the AODV implementation, many situations arose which required modifications to either the AODV protocol or the Linux kernel.Some of the changes were necessary due to simplifications made when simulating AODV,while others were needed because of incompatibilities between AODV and the Linux kernel.The following sections detail many of the modifications that were needed in the course of the implementation development.Fig.3.Gratuitous RREPs.A.Protocol ModificationsA.1The Route ReplyOne of the most basic changes made to AODV was the way in which RREP packets are forwarded.When a node receives a RREQ,it replies if it either is the destination,or if it has a cur-rent route to the destination.In the simulation,RREPs were originally unicast from the responding node to the source.As the RREP was propagated,intermediate nodes updated their route tables to include a route to the destination.In the imple-mentation,however,this does not work,because if the RREP is unicast from the responding node to the source,the interme-diate nodes use IP forwarding and do not process the packet. Hence the protocol needed to be changed so that RREPs are unicast on a hop-by-hop basis.Additionally,a Source IP Ad-dressfield was added to the RREP so that the ultimate destina-tion of the RREP would be retained.Another modification was made due to a discovery resulting from an implementation by Dan Ouchterlony et.al.[3].When an intermediate node sends a reply to the source,the destina-tion does not learn of that route to the source node because it has not received the route request.If all the route requests are answered by intermediate nodes and consequently the des-tination never receives a copy of the RREQ,it will never learn of a route to the source node.This can be detrimental if the source node wishes to establish a TCP connection.In order that the destination learns of routes to the source,a modifica-tion to AODV was made so that intermediate nodes respond-ing to RREQs by unicasting a RREP to the source node also send a gratuitous RREP to the destination informing it of the new route.The intermediate node places the destination IP ad-dress in the Source IP Addressfield of the RREP,and places the source IP address in the Destination IP Addressfield,since this is the node for which the route is offered.The intermedi-ate node enters its distance from the source in the HopCount field,and then unicasts this RREP to the destination.When the destination receives the RREP,it will know of a route to the source.Figure3illustrates an example of this process.In order to reduce the additional overhead incurred by the gratuitous RREP,we have added a Grat RREPflag to the RREQ.The source sets thisflag if the session is going to be run over TCP,or if the destination should receive the gratuitous RREP for any other reason.Otherwise,it leaves theflag unset.Nodes receiving the RREQ and responding with a RREP only transmit the gratuitous RREP to the destination if thisflag is set.A.2The DELETEPERIOD after reboot-ing before it responds to any routing messages.If it receives a data packet during this time,it sends a RERR for that desti-nation,since it no longer has the route.Additionally,it resets the waiting timer to the current time plus DELETEMEMBERSHIPLEA VEFig.4.Example Multicast Tree.multicast route table through the use of the MRT MFC socket option.AODV only issues this command once a MACT message activating the route has been received.Likewise, when a node leaves the multicast tree or when its route to the tree expires,a MRT MFC command is issued on the IGMP socket to invalidate this multicast table entry. Multicast route table entries in the kernel must be periodi-cally refreshed;otherwise,they expire and are deleted.AODV maintains a periodic timer for refreshing multicast route table entries.This refresh is also accomplished through the use of the IGMP socket.As nodes join a multicast group,a bi-directional shared tree is created which connects the multicast group members.When a node on the multicast tree receives a data packet destined for the multicast group,it processes the packet if it is a multicast group member.It then rebroadcasts the packet,regardless of whether it is a group member or just a router on the tree.The destination address of the data packet is the multicast group address.In the simulator version of AODV,when a node re-ceives a multicast data packet,it only processes the packet if the packet arrives from one of its next hops.In the course of the implementation development,however,we realized a sit-uation such as the one depicted in Figure4can arise.In the figure,the solid arrows indicate multicast tree links.Node E is connected to the multicast tree through node C.However, suppose node E is also within the transmission radius of node B,another node on the tree.When node B transmits multi-cast data packets,both nodes C and E receive them.We have modified the AODV protocol to enable multicast tree nodes to process multicast data packets if they are a member of the mul-ticast group,regardless of from whom they receive the packet. Hence,node E processes data packets it receives from node B or C.In this way,the multicast tree is used for ensuring that multicast group members are connected,but this increase in redundancy leads to a greater number of multicast data packets successfully delivered to the multicast group members.Loop-ing is prevented through the use of the IP Ident headerfield,as described in Section III-B.AODV had originally been designed so that there was a dif-ference in operation between a node wanting to join a multi-cast group,and a node needing tofind a route to the multicast group for the transmission of data packets to that group.In the former scenario,a node joining the group waits the full route discovery period after broadcasting a RREQ to receive RREPs from tree members.At the end of this discovery period,the node unicasts a MACT message to its selected next hop,and the branch is added on to the tree.On the other hand,when a node only needs a route to the tree but does not actually want to join the group,it broadcasts a RREQ and waits for reception of a RREP.After it receives thefirst RREP,it begins using that route(as in unicast AODV).If it later receives a better route,it then updates its routing table entry.While implementing the protocol,we realized that this ap-proach will not work for the case when the node is justfinding a route to the group.Because multicast traffic is by nature broadcast locally,neighboring nodes which forward a RREP to the source node will have no way of knowing whether they are selected as next hops for forwarding the multicast data to the multicast tree.Hence,when the source broadcasts the data, multiple neighboring nodes could potentially rebroadcast the packet,resulting in an inefficient use of the available band-width.We thus modified AODV so that when a node is dis-covering a route to the multicast group,it must wait the full discovery period,regardless of whether or not it wishes to join the group.At the end of this discovery period,the node uni-casts a MACT message to its selected next hop.A joinflag was added to the MACT message so that the node can in-dicate whether it is actually joining the multicast tree.Only nodes that receive this MACT message may rebroadcast mul-ticast data packets.This enables unnecessary broadcasts to be suppressed,and bandwidth is more efficiently utilized.A.5InterfacesMulti-homed devices were not originally taken into consid-eration in the design of the protocol.It was implicitly as-sumed that AODV would operate over single interface radios. However,because AODV should also operate smoothly over wired networks,and because it is likely that AODV will also be used with multi-homed radios,the consideration of inter-faces needed to be incorporated into the protocol design. When a node receives a RREQ,it needs to know upon which interface the packet arrived so that it will later know which in-terface to use to reach the source.Similarly,when a node re-ceives a RREP,the interface upon which the RREP arrived is needed so that the destination can later be reached.The same holds true for RERR and MACT messages.If a node has multi-ple interfaces,it is not necessary that a RERR be broadcast out of each of its interfaces;the RERR should only be transmitted on those interfaces that have a neighbor which uses the route. To enable AODV to maintain an association between destina-tions and outgoing interfaces,an interfacefield was added to routing table entries.B.Kernel ModificationsB.1IP RoutingWhen a packet arrives at a node’s IP-layer from the applica-tion layer,IP checks whether it has a route to the destination by consulting its routing table.If it has either a route or a default router,it forwards the packet.If neither of these ex-ists,IP informs the application that a route does not exist,and the session is aborted.In ad hoc routing,default routes typ-ically do not exist,except possibly for specific connections to an established infrastructure.Often,due to node mobility, and especially with on-demand protocols,a valid route is not known for a given destination.Instead of notifying the appli-cation,IP must be changed to notify the routing daemon that a route needs to be found for the destination.Linux’s netlink socket mechanism can be utilized so that IP sends a message to the AODV daemon,informing it to initiate route discovery for the destination.This prevents the session from aborting every time a route is not known.We have designed a mechanism through which IP may no-tify AODV of the need to initiate route discovery.Through the creation of a new netlink socket type,NETLINKIV.FUTURE WORKWe intend tofinish the Linux AODV implementa-tion and make it available at the AODV web site (/eroyer/aodv.html).We also want to make our netlink modificationsfit better with the in-tended overall(inferred)operation of the netlink facility in Linux.We also would like to apply the lessons we have learned with Linux to produce a FreeBSD implementation.Since netlink is not available with FreeBSD,we are likely to design a special device driver interface(/dev/aodv)with new ioctl()s replacing the Linux netlink functions.The basic controlflow,however,should otherwise remain identical.It would be nice to be able to produce a Windows implementa-tion,but so far we are hampered by the unavailability of source code or documented interfaces into the main Windows protocol stack.We also intend to upgrade our simulations with the new fea-tures motivated by the implementation lessons described in this paper.Then,it should be possible to run the full implementa-tion on networks containing a large number of simulated ad hoc nodes along with the nodes running the actual AODV im-plementation.This could give us valuable information towards selecting realistic and optimal values for the protocol parame-ters needed for any implementation of AODV.The method by which packets are stored during route dis-covery needs further improvements.We mightfind that it is possible to store pending packets in the memory of the AODV daemon.We might be able to devise application profiles that help to determine how long a packet should be stored before it goes stale and has to be discarded.Local feedback to the application is also possible in conjunction with such discard-ing operations.We may also determine that almost identical buffering operations are needed during any local repair oper-ations that may be carried out by intermediate routers along the path from source to destination.Again,any such buffering either at the source or the intermediate nodes should also be controllable according to any QoS parameters that have been associated with the route request.V.CONCLUSIONBecause protocol design is not yet an exact science,design-ers should take advantage of those tools which may aid them in validating the operation of their protocols.The use of design verification tools can aid in the examination of each possible usage case,and can validate the operation of a protocol in each of these situations.Because of the difficulty in enumerating all possible usage cases and node failure scenarios,these tools should be considered an important part of the protocol design process.Implementing a routing protocol is a crucial step in verify-ing the correct design and operation of the protocol.While simulation is necessary for ad hoc routing protocols in order to establish a set of repeatable test scenarios where small vari-ances can be made,certain assumptions and simplifications are often made in the simulation which do not hold true in a real world scenario.Hence it is essential to implement the protocol in order to ensure no over-simplifications are included in the final protocol specification.We have developed an implementation of the AODV routing protocol based on the simulation of this protocol.In the course of writing the implementation,some key changes needed to be made to both the protocol and the Linux kernel to enable AODV to operate correctly.As AODV continues to be refined, it is possible that further changes will be required,particu-larly when QoS operation is implemented.Additionally,tunnel management may also indicate the need for further modifica-tions.We look forward to the completion of the implementa-tion,the design of a testbed in which to test the implementa-tion,and interoperability testing with other existing implemen-tations.ACKNOWLEDGMENTThanks to Michael Speer for his help in designing the basic framework for using IGMP in the ad hoc networking environ-ment.References[1]S.H.Bae,S.-J.Lee,W.Su,and M.Gerla.The Design,Implementa-tion,and Performance Evaluation of the On-Demand Multicast Routing Protocol in Multihop Wireless Networks.IEEE Network,14(1):70–77, January/February2000.[2]K.Bhargavan,C.A.Gunter,and D.Obradovic.Fault Origin Adjudication.Proceedings of the Workshop on Formal Methods in Software Practice, Portland,OR,August2000.[3] F.Lilieblad,O.Mattsson,P.Nylund, D.Ouchter-lony,and A.Roxenhag.Personal Communication.http://fl.ssvl.kth.se/g4/madhoc/docs/techdoc.ps.[4] D.A.Maltz,J.Broch,and D.B.Johnson.Experiences Designing andBuilding a Multi-hop Wireless Ad hoc Testbed.Technical Report CMU, CMU School of Computer Science.[5] C.E.Perkins and E.M.Royer.Ad-hoc On-Demand Distance Vector Rout-ing.Proceedings of the IEEE Workshop on Mobile Computing Sys-tems and Applications,pages90–100,New Orleans,LA,February1999.[6] C.E.Perkins,E.M.Royer,and S.R.Das.Ad Hoc On Demand Dis-tance Vector(AODV)Routing.IETF Internet Draft,draft-ietf-manet-aodv-05.txt,March2000.(Work in Progress).[7] E.M.Royer and C.E.Perkins.Multicast Operation of the Ad-hocOn-Demand Distance Vector Routing Protocol.Proceedings of theACM/IEEE International Conference on Mobile Computing and Network-ing(MobiCom),pages207–218,Seattle,WA,August1999.。