Peer-to-Peer Networks
+ an Introduction to JXTA [ECE 451/566] -Introduction to Parallel and Distributed Computing
Professor: Manish Parashar
Presented by Vincent Matossian
On December 12th2005
Outline
Part I : Introduction to Peer-to-Peer Computing ?Definitions
?Challenges
?Applications
Part II : Project JXTA Overview
?Introduction
?Architecture
?Protocols
Part I
-Introduction to P2P computing -
?A peer is a “network individual” that can send, receive, and process messages to and from other peers
?A peer-to-peer system is a “network society” where peers exchange messages that fulfill the goals of the network application. For example : File-sharing, Number-crunching, Instant messaging
Clay Shirky’s “is it P2P ?” test:
1)Does it treat variable connectivity and
temporary network addresses as the
norm
2)Does it give the nodes at the edges of
the network significant autonomy?
Client/Server : a picture
P2P is commonly contrasted with the client/server model Example:
The World Wide Web as we know it
Peer-to-Peer : a picture
Instant Messaging (ICQ)File-Sharing (Gnutella)
Distributed Computing (Seti@Home)
?Shared Resources ?Bidirectional Communications
Historical references
1970’s till early 1980’s
Internet starts off with a P2P architecture (ARPANet)
1990’s
Internet Architecture and Protocols undergo standardizations (Not truly P2P anymore)
Late 1990’s till now
P2P file-sharing applications are the most popular
applications on the Internet
P2P overlay networks become testbed for research on
future Internet
“True” Peer-to-Peer
? A true peer-to-peer application must implement only peering protocols that do not recognize the concepts of "server" and "client".
?Such “true” peer applications and networks are rare. Most networks and applications described as peer-to-peer actually contain or rely on some non-peer elements, such as DNS
–DNS is a Name-to-IP mapping system that is based
on a hierarchy of servers contacted for each
translation of Name to IP
Random Graph
?Random Graph vertices, edges, and connections between them are determined in some random way
?Erdos and Rényi(1960) showed that graphs larger than a certain size have a high probability of having that property
P2P as Random Graph ?
?Random graphs follow a Poisson distribution
that a node has degree k : z k e-k/k!
–Probability p
k
?Real networks seem to follow a power-law distribution –Probability of node k having degree k is 1/k
P2P and power-law networks ?Small World Phenomenon (Stanley Milgram, 1967)–theory that everyone in the world can be reached through a short chain of social acquaintances
?Watts and Strogatz define a mathematical model of the phenomenon (1998)
–show that the addition of a handful of random links can turn a disconnected network into a highly connected one. ?Barabasi defines the WWW as a scale-free network that has small-world properties
–Growth:Starting with a small initial number of nodes, in every time step, a new node is added. This new node is connected to
m existing nodes.
–Preferential Attachment: The probability for a newly added node to be connected to an existing node n depends on the
degree of n(number of connections from n to other nodes). The more connections n has, the more likely new nodes will connect to n.
?P2P could align with the WWW vision but it needs to overcome the lack of dynamicity
P2P technical challenges ?Discovery
–How to discover peers, content ?
?Messaging and Routing
–How to route messages efficiently ?
?Metadata/Interoperability
–How to encode information for platform independence ??Quality of Service
–How to guarantee levels of service ?
?Performance and scalability
–How to build a network system that can grow dynamically ??Security and Trust
–How to encode transmission and guarantee privacy of members ??Accountability
–How to police the peergroup ?
?Social/Legal Issues
–How to avoid infringing international laws (copyright, ownership…) ?
P2P application challenges ?Administration of peers
?Privacy/Anonymity and Security ?Trust
?Propagation of undesirable content ?Intellectual property
?Availability of content
?Firewall, NAT bypassing
?Group membership communication
P2P Benefits
?High availability of content ?Optimized use of network bandwidth ?Lowered cost of content distribution ?Leveraged computing power from every node in the network ?Unlimited scalability
P2P Application classes
Instant Messaging (ICQ, Jabber, …)
File Sharing (Napster-like, Gnutella-like, …)
Distributed Search Engines (OpenCola, Copernic, …)Group Collaboration (Groove, NetMeeting, …)Online Gaming
Distributed Computing (Seti@Home , Parabon, …)Distributed Storage (Chord, Past, Pastry)Wireless network Writeable Web
Licensed Media Distribution Intelligent Agent War applications
T r e n d
Centralized indexes and repositories
Central Napster server
(x y
z
.
m p
3, 1
28.1
.2.3
)
128.1.2.3
x
y z .m p 3
?1
28.1.
2.3x y z .m p 3 ?
Napster
163.15.22.45
Pros and Cons
Cons
?Single point of failure
?Scalability
?Free-riding
?Abandoned because of legal issues
Pros
?Performance ?
Access control
Flooding broadcast of queries Gnutella
xyz.mp3 ?
x y z.m p3
Pros and Cons
Pros
?True P2P ?Legal ?Performance in small networks ?Scalability ?Fault tolerance Cons
?Performance in large networks
?Security
?Free-riding ?Reliability ?Availability
Outline The statements: This paper is going to discuss the liberalism that rooted in Isabel Archer’s mind—the heroin in the portrait of a lady.But sometimes she seems to go against her liberalism after marriage with Gilbert Osmond. 1. Introduction 2. The Maturity of Isabel Archer 3.Isabel's View of liberty 3.1 Liberty of Mind 3.1.1 Isabel's Attitude toward Life 3.1.2 Isabel's Attitude toward Love and Marriage 3.2 Liberty of Behaviours 3.2.1 Isabel's Refusal to Ideal Suitors—Goodwood and Warburton 3.2.2 Isabel's Choice to Marry Gilbert Osmond 4. Paradoxs in Isabel's View of Liberalism 4.1 Request for Liberty Versus Social Limitation 4.2 Love of Liberty Versus Fear of Liberty 4.3 Preservation of Dignity Versus Acceptance of Mistakes 5. Conclusion
Outline Thesis statement: like coins have two sides, giving students grades has advantages and disadvantages, say it is useful, imperfect, and harmful. I.Giving students grades is useful A.It can help students work hard. 1.My classmate, Sun didn’t want studying very much, when he was twelve years’old. But after my teacher, Miss Zhang told him that his grade in class is low, Sun began did his best to study. B.It can let students to know their disadvantages. https://www.doczj.com/doc/205531285.html,st year, my grade in our class was always high, but this year, my grade got lower. After my analysis, I know finally, I don’t have a good way to study. C.It let students who have high grade become more confident. 1.My classmate, King has a high grade in class, so he is very confident to study, and he becomes more and more successful. II.On the other hand, the disadvantages far overweight the advantages, because giving students grade is not perfect. A.It can’t reflect students’ comprehensive abilities.
样例：Persuasive Speech Outline 2011级国贸1班王红交稿时间2012.10.26 Independent travel is the best way of tourism Specific Purpose: To persuade my audience that independent travel is the best way of tourism. Central Idea: Independent travel is the best way of tourism because of three merits----more freedom, arranging the travel according to your needs, and experiencing a more authentic life when traveling by yourself. Introduction I. II. ? II.For packaged travel most of you must have experienced a lot, out with your parents. But now, as a college student I could say that independent travel must be the best way of IV. ?It is a self-arranged travel, which means you have to book the tickets and hotel V. So today, I will show you three of the independent travel to explain why it is the best way of tourism. Body I. A. 2.Or if somewhere is attractive enough, you can choose to stay longer to enjoy the beautiful scenery. (Transition: Actually, freedom is just a beginning. The second one is truly the most exciting one.) II. A.Packaged travel often has a which may contain many B.And also you can change your route randomly.
怎样撰写英语的outline 好的outline对你撰写正文内容具有很强的指导作用。不管你要撰写的是什么类型的文章，outline都是非常必要（通常情况下也是必须的）。接下来的内容对撰写提纲有很大帮助。 1.明确文章的主旨。 一篇文章都有其所要表达主旨。选择一个最终主旨不仅能引导你主题的方向，还有助于你有逻辑的组织文章。比如你在写论文，写下能够概括文章主旨的中心思想，以帮助你确定主旨： ? 比较和对照两个事物。 ? 列出因果 ? 阐明或分析一个特殊方面 ? 列出单个或两者的论证 ? 提供证据并得出结论 ? 列出问题然后提供解决方案 2.收集辅助材料。 这些被收集来的材料可能来自引用他人成果、数据统计、理论、实验结果等。通过收集材料，明确这些材料使用，这些东西可能会体现在essay outline中。 3.决定如何安排辅助论证来支撑主旨。 举例：如果你在呈现一个历史概述，你可以按年代来排序；如果你在辩论文学方面内容，你可能要按主题排序；如果你处在某观点立场的两级徘徊时，你可以先列出和你立场有矛盾的证据，然后用反论证消除达到有说服力的结果。 4.撰写主题提纲或者句子提纲。 如果文章非常灵活多变，那么你可以用利用一些短语作为主题大纲；用句子大纲阐述细节。 ? 一般来说你可以尝试先用主题提纲来开始你的提纲撰写，然后再逐步转变成句子提纲。 5.确定主要类别。 根据文章的主旨和找到的辅助材料来决定把全文的大主题分散整理到不同逻辑类别。这些类别将会被标记成罗马数字来形成提纲的第一步。 ? 当写文章时，通常会用一个大点去代表一个段落：比如，一、文章的开头段，二、主体段落的第一段，等等。例如，如果描写飞机历史发展史的概论，每一个大点就该包括各个飞机历史上的时期。 6.确定论点。
Introduction to the Course --- Public Speaking Outline Specific purpose: To inform the students about the aspects of the course --- Public Speaking Central idea: The four aspects of this course include five purposes of opening the course, the way the course will be conducted and the teaching schedule, 14 requirements to ensure an effective result; and the evaluation and grading. Introduction I. First let me ask you three questions: A. A. Why do you choose this course B.What is a good speech C.What is the greatest obstacle if one wants to deliver a great speech II. As a veteran teacher of English I find Chinese students are reluctant to make a public speech. A.Chinese students are more likely to have stage fright because they are not or less trained. B.Public speech is a compulsory course in most of the American universities. III. For the next 30 minutes or so I’d like to talk about 4 things: the purposes of this course, the way the course will be conducted, the requirements you should meet and grading scheme. (Transition: Let’s start with the purposes of this course.) Body I. There are five main purposes to open this course.
Read the following passage carefully and compose a "topic outline" for it. Oceanography has been defined as “The application of all sciences to the study of the sea”. Before the nineteenth century, scientists with an interest in the sea were few and far between. Certainly Newton considered some theoretical aspects of it in his writings, but he was reluctant to go to sea to further this work. For most people the sea was remote, and with the exception of early intercontinental travelers or others who earned a living from the sea, there was little reason to ask many questions about it, let alone to ask what lay beneath the surface. The first time that the question 'What is at the bottom of the oceans?' had to be answered with any commercial consequence was when the laying of a telegraph cable from Europe to America was proposed. The engineers had to know the depth profile (起伏形状) of the route to estimate the length of cable that had to be manufactured. It was to Maury of the US Navy that the Atlantic Telegraph Company turned, in 1853, for information on this matter. In the 1840s, Maury had been responsible for encouraging voyages during which soundings (测深) were taken to investigate the depths of the North Atlantic and Pacific Oceans. Later, some of his findings aroused much popular interest in his book The Physical Geography of the Sea. The cable was laid, but not until 1866 was the connection made permanent and reliable. At the early attempts, the cable failed and when it was taken out for repairs it was found to be covered in living growths, a fact which defied contemporary scientific opinion that there was no life in the deeper parts of the sea. Within a few years oceanography was under way. In 1872 Thomson led a scientific expedition, which lasted for four years and brought home thousands of samples from the sea. Their classification and analysis occupied scientists for years and led to a five-volume report, the last volume being published in 1895.
Name: (中文) Class: 1.5倍行距 Number: Date: Thesis Outline （小三，加粗，居中） Robinson Crusoe: A Middle-Class Hero （题目：四号，加粗，居中） （以下小四，1.5倍行距） Thesis Statement: The leading character in Robinson Crusoe embodied the values of the eighteenth century British middle class: individualism, adventurous spirits, utilitarianism and labor-worship. Outline: 1.Introduction 2.The 18th Century British Society 3.V alues of Middle Class and Robinson’s Heroic Image 3.1Individualism and Self-Reliance 3.1.1Rebellious Spirit 3.1.2Reluctance to Going Home 3.1.3Survival after Shipwreck 3.1.4Communication with God 3.2Exploration of Instinct and Adventurous Spirits 3.2.1Desires for Adventurous Spirits 3.2.2Slavery Adventure 3.2.3Exploring the Outside World 3.2.4Island Adventures 3.3Utilitarianism and Materialism
The spice of my life Outline Specificpurpose: To inform my audience about my experience living with my sister Central idea:To tell the story and feeling living with my sister. Introduction Eye contact Recently, China is about to carry out generally two-child policy. People have different views on the policy. Businesspersons discover new opportunities. Young parents are considering if they want a second child. How about you? Most of you are the only child. When you hear d the policy, are you happy your parents won’t want a second at this age? Or do you feel ashamed the policy carrying out so late? Slow down.But for me, as an older sister, my emotion is complex. I think of my experience living with my sister. She is like the spicy of my life.Today,according to my feeling I will divide the experience into four stages to share with you. (preview statement) (transition: let’s get down the first stage, sour) Body I. The first stage is my mother was pregnant, my feeling is sour. In other words, I was jealous of the little life. A.The reason why I hate younger sister 1. Before, I heard that if you had a younger sister or brother, all of your things would be shared. I believe it without doubt. 2.When my mother was pregnant, I was not allowed to be close to my mother, my
Speech Outline Step One – Preparation A.Topic:environment problems B.Audience:citizen C.Title of speech:What should we do with the environment problems? D.Purpose of speech:To make people ware the global environment problems, and encourage people to protect the environment. Step Two – Introduction Main point:The Paris agreement came into effect on November 4th ,2016. At present, the environment problems are becoming more and more serious. It is necessary to take measures to protect environment. It is the responsibility of citizen. Step Three – Body Main Idea 1 ?Idea: why do we need to pay attention to environmental problems? ?Details/Examples:The signing of the Paris agreement means the global environment is not optimistic. Environment problems will threaten the survival of human. Main Idea 2 ?Idea:What cause the environment pollution? ?Details/Examples: air pollution( haze,industry), water pollution(drainage), soil pollution(used battery) Main Idea 3 ?Idea: What should the government and citizen do? ?Details/Examples: government( make laws, financial support...) citizen(drive green, monitor government...)
有些同学11周可能没去上课，或者上课笔记没做完，下面是我在课堂上抄的笔记，希望对各位同学写outline有帮助！ 一、Outline的构成 Introduction –a formal presentation that leads to the main part of the essay. A good introduction gets the reader s’ attention and makes them want to read more. Thesis – a subject for a composition or essay, a statement put forward for consideration that is either proved or discussed against objections. Transition –a statement or two that shows the readers you are now talking about something else. Summary – a technique used usually in the conclusion of an essay that restates the author’s intentions without going into too much detail and highlights the major points the author wants to make in the written work. Conclusion –the end of the essay and often the part that readers remember most. It should be clear and avoid contradicting the points you have raised earlier in the essay. It’s your last chance to have the final say on the object. It should be clear and avoid using the same phrase. P.S. 在Transition中要避免使用first, second, third,………………
My outline (080703120 汤煜芳) A Paralysed Wilderness —The Appreciation and Analysis of Symbols in Araby Thesis statement:The symbols regarding the setting, religion and characters in Araby are ingeniously adopted, which manifests a stretch of paralysed wilderness typical of Dublin and contributes immensely to the success of the short story. Outline: 1. Introduction 2. Demonstration 2.1 Symbols regarding the setting 2.1.1 Blind alley in North Richmond Street—hopelessness, bleakness, and ignorance 2.1.2 Houses and gardens in the street—decay and gloom 2.1.3 Lamplight 2.1. 3.1 Lamplight in the street—spiritual decadence 2.1. 3.2 Lamplight in Araby fair—darkness and disillusionment 2.1.4 Araby bazaar—boy’s goal and social reality 2.2 Symbols involving religion 2.2.1 Dead priest and his abandoned belongings—collapse of the religious belief 2.2.2 The wild garden—spiritual paralysis 2.2.3 The chalice—boy’s yearning for beautiful love 2.3 Symbols concerning the characters 2.3.1 Mangan’s sister—boy’s pursuit of dream 2.3.2 Aunt and uncle of th e narrator “I”—short-sighted and indifferent people 3. Conclusion 1
Name: He Yaoxi Student number: 201428010415014 Course code: B-13 WRITING ASSIGNMENT #5 Essay Outline Title: Do all students benefit from studying oversea? Thesis Statement: Not all students benefit from studying oversea, on the contrary, it would bring a lot of problems. We should make a reasonable selection according to our own conditions and pursuits. Outline: Ⅰ. Introduction- Thesis statement: With globalization, more and more educated, talented, passionate young graduate students prefer to study oversea rather than staying home. In such a wave, we need to pose a question: Do all students benefit from studying oversea? My answer is no. Not all students benefit from studying oversea, on the contrary, it would bring a lot of problems. Therefore, we should make a reasonable selection according to our own conditions and pursuits. Ⅱ. Body Paragraph #1 Topic Sentence: Foreign life means students have to make changes for the entirely different environment, such as lifestyle, culture and language, ect.. A. Students may hardly adapted themselves to the new lifestyle; B. Students may hardly adapted themselves to the different culture; C. Students may hardly adapted themselves to the foreign language; Ⅲ. Body Paragraph #2 Topic Sentence: There are not many opportunities for foreign countries after the financial crisis. A. The financial crisis lead to loss of jobs for overseas-students; B. The financial crisis make difficult for overseas-students to apply the fund ; C. The financial crisis create a tumultuous social upheaval for overseas-students; Ⅳ. Body Paragraph #3 Topic Sentence: Oversea studying adds parental burden, and apprehension and homesickness for students. A. Oversea studying adds parental burden for affording the high tuitions; B. Oversea studying may bring mental issue as feeling homesick; C. Oversea studying sometimes may broken your relationship. Ⅴ. Conclusion Not all students benefit from studying oversea, it also may cause a lot of troubles.
Outline写作讲解 一般来说，outline提纲的写作模式如下： Example Outline Title 1. Introduction paragraph A. The background B. The thesis statement 2. Body paragraph(s) A. First major category of support ?supporting detail 1 ?supporting detail 2 …… B. Second major category of support ?supporting detail 1 ?supporting detail 2 …… C. Third major category of support ?supporting detail 1 ?supporting detail 2 …… 3. Conclusion ?review of the major categories of support ?the answer, solution, or final option What is it? An outline is a general plan of the material that is to be presented in a speech or a paper. The outline shows the order of the various topics, the relative importance of each, and the relationship between the various parts. Order in an Outline There are many ways to arrange the different parts of a subject. Sometimes, a chronological arrangement works well. At other times, a spatial arrangement is best suited to the material. The most common order in outlines is to go from the general to the specific. This means you begin with a general idea and then support it with specific examples（often also with a conclusion）.
撰写essay之前，好的outline对你撰写正文内容具有很强的指导作用。不管你要撰写的是什么类型的文章，outline 都是非常必要（通常情况下也是必须的）。接下来的内容对撰写提纲有很大帮助。 1.明确文章的主旨。 一篇文章都有其所要表达主旨。选择一个最终主旨不仅能引导你主题的方向，还有助于你有逻辑的组织文章。比如你在写论文，写下能够概括文章主旨的中心思想，以帮助你确定主旨： ?比较和对照两个事物。 ?列出因果 ?阐明或分析一个特殊方面 ?列出单个或两者的论证 ?提供证据并得出结论 ?列出问题然后提供解决方案 2.收集辅助材料。 这些被收集来的材料可能来自引用他人成果、数据统计、理论、实验结果等。通过收集材料，明确这些材料使用，这些东西可能会体现在essay outline中。 3.决定如何安排辅助论证来支撑主旨。 举例：如果你在呈现一个历史概述，你可以按年代来排序；如果你在辩论文学方面内容，你可能要按主题排序；如果你处在某观点立场的两级徘徊时，你可以先列出和你立场有矛盾的证据，然后用反论证消除达到有说服力的结果。 4.撰写主题提纲或者句子提纲。 如果文章非常灵活多变，那么你可以用利用一些短语作为主题大纲；用句子大纲阐述细节。 ?一般来说你可以尝试先用主题提纲来开始你的提纲撰写，然后再逐步转变成句子提纲。 5.确定主要类别。 根据文章的主旨和找到的辅助材料来决定把全文的大主题分散整理到不同逻辑类别。这些类别将会被标记成罗马数字来形成提纲的第一步。 ?当写文章时，通常会用一个大点去代表一个段落：比如，一、文章的开头段，二、主体段落的第一段，等等。例如，如果描写飞机历史发展史的概论，每一个大点就该包括各个飞机历史上的时期。 6.确定论点。 每个分类至少想两个论点，根据你文章的主旨和你之前收集的论据材料来选择你的分论点。这些分论点就是你提纲的第二个层级。一般它们是用英文字母标示的。（比如A、B、C 等等） ?让你的第二层级比你的第一层级缩进1.27到2.54厘米 ?还是用飞机发展史历史的例子，每一个分点就可以描写那个时代的发动机型号 7.根据需要确定中心论点的分论点。 如果有必要的话，你可以在中心论点上确定分论点。这么做会最大化你文章的逻辑性。再把这些分论点放在你提纲的第三层，并用阿拉伯数字标示。（1、2、3、4 等等） ?为了方便标识，你可以在下一层用小写罗马字符（i、 ii、 iii、 iv等等），接着用小写英文字母（a、b、 c、d等等），最后可以用回阿拉伯数字（1、2、3、4，等等） ?在写提纲时基本上不需要四个层级。如果出现这类状况，试着合并论点。
Euthanasia-the problem of when to die, and how Introduction: I.Introduce the U.S. state of Oregon's Death with Dignity Act in November 8, 1994. 2. II.Introduce the debates of “euthanasia” in 17th century. III.Today, I’ll inform you of some basic knowledge of euthanasia. IV.I’ll first explain what euthanasia is, and then classify it, and eventually move to the practice of it in reality. Body: I.The meaning and history of euthanasia. II.The classification of euthanasia. a)Active euthanasia and PAS i)Definition b)Passive euthanasia i)Definition III.The practice of it in reality. a)Active euthanasia and PAS b)Passive euthanasia Conclusion: 1.Preview. 2.Quotation. 3.What makes euthanasia so important and so contentious.
论文题目（英语） How To Treat Middle school Students' Errors in the Classroom ———————————————————————————————————————（以下部分用中文阐述） 一、意义简述（100字内） 古人说：“金无足赤，人无完人。”在学习过程中，每个学生多多少少都会不可避免地犯一些错误，通过学生的错误教师可以观察出他们在学习方面面临的问题和需要改进的地方。本文试图提出几条处理错误的方法，以改进教学实践。然而老师对待学生们的学习问题时所采取的措施不尽相同。基于上述情况，本文通过调查初中英语课堂上教师与学生的错误观及纠错方式。旨在提升教师的纠错方式，并促进中国教师与学生英语学习的共同进步。 二、文献综述（150字内） 本文将对以下问题作相应研究探讨： 1.研究中学生英语错误的必要性 2学生英语错误在当今的研究 3.范围界定：正确认识英语学习中”errors”和”mistakes”的区别 4.如何应对中学生英语学习中的错误 教学中只有正确对待学生的错误，才能更有效促进学生的学习和教师工作的开展，进而激发学生自主学习的欲望。 三、研究方法 1）理论基础（100字内） 错误分析法 1、罗列学生在学习过程中已发生或可能发生的错误。 2、分析发生错误的原因。
3、评价错误的后果。 2）研究问题或假设（150字内） 1. 学生们在课堂学习过程中可能出现那些错误？ 2. 教师应如何应对学生的不同错误？ 3）研究对象与研究方法、工具（如果是调查或课堂观察研究方法，注明研究工具，如自己设计还是采纳已有问卷表）（100字内） 以课堂观察的形式对中学生中英语学习者进行研究，课后对学生进行调查并及时记录 4）研究步骤（200字内） 1, 查阅相关书籍文献，收集可供参考的理论，依据，材料； 2. 联系所收集的理论，联系课堂观察中教师对学生学习错误的不同应对策略及效果，撰写教师应对学生错误的正确策略总结； 3. 指定整体论文框架，咨询导师吸收修改意见； 4. 撰写并修改论文； 5.导师终审并提交论文终稿； 6.论文开题答辩。 五、预期结论与研究局限性（150字） 预期结论：对学生英语错误的合在英语教学中具有重要地位。本文能够客观真实地指出，教师使用科学的、针对性的策略来解决学生英语学习错误能更有效地促进学生的英语学习。 研究局限性：调查范围有限，怕不够全面的反映问题。