1、 教学目标 教学内容Unit 4 Network Technique 教学目标教学目标 了解计算机网络的发展史 理解网络安全的相关理论 了解虚拟化技术 掌握电子商务的相关技术 了解目前已经广泛使用的局域网技术教学内容教学内容 Text 1 Evolution of computer networks Text 2 Network Security Text 3 Virtualization Technology Text 4 Electronic Commerce Text 5 LAN-CruisingText 1 Evolution of computer networks Main Con
2、tents Words and Expressions Exercises The term network can mean many different things.It can imply an interconnection of railway tracks for the rail network;highways and streets for transportation networks;telephone lines and switching centers for the phone network;coaxial lines for the cable televi
3、sion network;fiber lines for cable communications networks;or the interconnection of service centers,businesses,and so on to form a network.All of these configurations refer to the means to tie together various resources so that they may operate as a group,realizing the benefits of numbers,sharing,a
4、nd communications in such a group.Text 1 Evolution of computer networksText 1 Evolution of computer networksIn computer systems terminology of a network is a combination of interconnected computing equipment and programs used for moving information(and computations)between points(nodes)in the networ
5、k where it may be generated,processed,stored,or used in whatever manner is deemed appropriate.The interconnection may take on many forms,such as dedicated links,shared links,telephone lines,microwave links,and satellite links.Networks in this sense form a loose coalition of devices that share inform
6、ation.This was one of the first uses of a network,although it was not the last.Users found that the network could offer more than just information sharing;it could offer other services for remote job execution and ultimately distributed computing.Text 1 Evolution of computer networksThe earliest con
7、cept of a network was of a loose binding together of devices or resources for sharing.An early computer network that exhibited these traits was the ARPANET.ARPANET was first brought on-line in 1969 as a research tool to investigate long-haul network issues and to provide a tool for research and deve
8、lopment solutions.It has evolved into the Internet,connecting millions of computers over local area networks,metropolitan area networks,and other wide area networks.ARPANET provided the vehicle for early research into communications protocols dealing with congestion,control,routing,addressing,remote
9、 invocation,distributed computing,distributed operating systems and services,and many other areas.The reasons for using networks such as ARPANET were to provide greater availability and access to a wider range of devices.Early applications of computers dealt with performing engineering tasks and maj
10、or data processing functions.As the technology of computers changed,and as researchers and users alike added more and more applications,information access and manipulation took on greater emphasis.Earlier networks provided the necessary information exchange services but were limited to basically jus
11、t this service.The information availability stimulated more imaginative uses of this information.As this occurred and the technology of networks improved,new applications arose.These new applications not only used information exchange but also remote job execution.It began simply as sending a batch
12、job down the link to a less busy host,having the job completed there,and then shipping the results back to the originator.Text 1 Evolution of computer networksText 1 Evolution of computer networksThis sufficed for a while,but it still did not provide the real-time or interactive environments that us
13、ers were beginning to become accustomed to,including more advanced protocols and network operating systems to provide further services for remote job invocation and synchronization.The era of the local area network was coming.The wide area networks biggest shortfall was in throughput or turnaround t
14、ime for jobs and interprocessor communications.Because of the wide distances,delays of seconds were commonplace and caused added overhead in performing otherwise simple tasks.Network designers saw the need to provide another link in the network:the local area network.Local area networks began showin
15、g up on the networking landscape in the early to mid 1970s as mostly research activities in universities and government laboratories.It was not until Ethernet was released in the mid 1970s that LANs became more widely available.Since that time,numerous LAN designs have been produced to fit an extrem
16、ely wide spectrum of user requirements-for example,the fiber ring.Additionally,standards have evolved,providing basic LAN topologies and their services to a greater number of users.Text 1 Evolution of computer networksText 1 Evolution of computer networksLocal area networks are finding their way int
17、o all aspects of modern society.We find them in our homes through cable modems and phone modems,automobiles via wireless technologies,banking(e.g.,ATMs),schools via Internet connections,businesses,government,and industry.There are not too many aspects of information exchange and data processing in w
18、hich a LAN cannot be found.Local area networks and their associated technologies represent one of the great growth areas of the 1990s and early 2000s.As more and more LANs become available,so will new products and uses for them.LANs are used to connect all personal computers in offices,classrooms,fa
19、ctory floors,retail establishments,and now even many homes.They are used in these environments to send memoranda,issue directives,schedule meetings,transmit documents,send e-mail,discover new information,and process large volumes of data concurrently at many sites.Text 1 Evolution of computer networ
20、ksLANs are used to link factory robots together with area and factory controllers.They provide sensor data,control data,and feedback to the control centers,while at the same time providing a vehicle to issue production changes and notices to users and robots alike.A fine example of a local area netw
21、ork providing diverse services to the users is seen in Walt Disney World.Disney uses LANs and computers to monitor all aspects of services,including fire protection,scheduling,ride management,on-line information,security,personnel services,and a plethora of other park management functions.Large bank
22、s,such as the World Bank,have adopted LANs as the means to interconnect their various local sites into smaller networks linked together by wide area networks.However,the LAN is not for everyone.Text 1 Evolution of computer networks Network evolution has not stopped there.As wireless technology has i
23、mproved,so has the interest in networking vendors to provide their services to users of these domains.Wireless networks began fairly quietly in the 1970s with the Aloha net as the foundation.Since then,wireless phone network development has opened the door for computer networks.Today one of the grea
24、t growth areas in networking will be in further developing wireless networks and integrating these into existing LAN and WAN networks to provide an even wider array of applications to the wireless cell phone community.Words and Expressionsinterconnection intknekn n.网络互连track trk n.【计算机】数据磁道cable kei
25、bl n.电缆coaxial kuksl adj.同轴传输线的transportation trnsp:tein n.运输，运输系统，运输工具fiber faib n.光纤configuration knfigjurein n.【计算机】配置terminology t:minldi n.用辞，术语microwave maikruweiv n.微波dedicated dedikeitid adj.【计算机】(装置、程序、系统等)专用的coalition kulin n.结合，合并，联合distributed distribju:tid vt.分布的，分布式的loose lu:s adj.宽松的，
26、不牢固的，不精确的Words and Expressionsbinding baindi n.1.捆绑；束缚；粘合；连接2.捆缚物；束缚物；连接物3.(滑雪屐上的)扣栓，(滑雪板上的)皮靴固定装置4.(如桌布、毯子等的)镶边，滚带5.(书籍的)装订；装帧；活页封面和封底、封皮ARPANET阿帕网investigate investigeit v.【计算机】研究long-haul lh:l;l:-adj.长远距的metropolitan metrplit()n n.大都市的居民，大主教，母国的居民adj.大都市的vehicle vi:ikl n.传播媒介，工具，手段，交通工具，车辆congest
27、ion kndestn n.【计算机】拥挤routing ru:ti;rau-n路由选择，路径选择invocation invukein【计算机】调用availability veilbiliti n.有效，有用，有益.Words and Expressionsmanipulation m，nipjulein n.处理emphasi emfsis n.强调，重点stimulate stimjuleit vt.刺激，激励，鼓舞batch bt n.批，成批，分批originator ridneit(r)n.创始人，发起人sufficed sfais v.足够，使.满足，合格synchroniza
28、tion sikrnaizein 同步化shortfall:tf:l n.不足之量，差额throughput ru:put n.【计算机】(计算机输入输出信息的)吞吐量，通过量，总处理能力turnaround t:nrand n.转变，突然好转Words and Expressionslandscape lndskeip n.风景，山水，风景画LANs abbr.局域网(local area networks)spectrum spektrm n.光谱，（比喻）范围，系列fiber faib n.纤维memoranda memrnd n.备忘录(便条)21世纪大英汉词典concurrently
29、 knkrntli adv.同时(兼)plethora pler n.过量，过剩vendor vend:n.厂商Aloha:luh:int.哈罗，欢迎，再见21世纪大英汉词典WAN wn(wide area network)广域网ExercisesI.True or false?If correct,write T in parentheses;Otherwise,write F.（）1.The term network can mean a same thing.（）2.Users found that the network could offer information sharing
30、only.（）3.The earliest concept of a network was of a loose binding together of devices or resources for sharing.（）4.An early computer network that exhibited these traits was the Internet.（）5.Because of the wide distances，delays of minutes were commonplace and caused added overhead in performing other
31、wise simple tasks.（）6.Local area networks began showing up on the networking landscape in the early to mid 1960s as mostly research activities in universities and government laboratories.（）7.We find wide area networks in our homes through cable modems and phone modems，automobiles via wireless techno
32、logies，banking(e.g.，ATMs)，schools via Internet connections，businesses，government，and industry.（）8.There are too many aspects of information exchange and data processing in which a LAN cannot be found.（）9.LANs are used to connect all personal computers in offices，classrooms，factory floors，retail esta
33、blishments，and now even many homes.（）10.Large banks，such as the World Bank，have adopted LANs as the means to interconnect their various local sites into smaller networks linked together by wide area networks.ExercisesII.Fill in the blanks with proper words.1._was first brought on-line in 1969 as a r
34、esearch tool to investigate long-haul network issues and to provide a tool for research and development solutions.2._ has evolved into the Internet，connecting millions of computers over local area networks，metropolitan area networks，and other wide area networks.3._are finding their way into all aspe
35、cts of modern society.4.Large banks，such as the World Bank，have adopted _ as the means to interconnect their various local sites into smaller networks linked together by wide area networks.Text 2 Network Security Main Contents Words and Expressions Exercises Security is a broad topic and covers a mu
36、ltitude of sins.In its simplest form,it is concerned with making sure that nosy people cannot read,or worse yet,secretly modify messages intended for other recipients.It is concerned with people trying to access remote services that they are not authorized to use.It also deals with ways to tell whet
37、her that message purportedly from the IRS saying:Pay by Friday or else is really from the IRS and not from the Mafia.Security also deals with the problems of legitimate messages being captured and replayed,and with people trying to deny that they sent certain messages.Text 2 Network SecurityText 2 N
38、etwork SecurityNetwork security problems can be divided roughly into four closely intertwined areas:secrecy,authentication,nonrepudiation,and integrity control.Secrecy,also called confidentiality,has to do with keeping information out of the hands of unauthorized users.This is what usually comes to
39、mind when people think about network security.Authentication deals with determining whom you are talking to before revealing sensitive information or entering into a business deal.Nonrepudiation deals with signatures:How do you prove that your customer really placed an electronic order for ten milli
40、on left-handed doohickeys at 89 cents each when he later claims the price was 69 cents?Or maybe he claims he never placed any order.Finally,how can you be sure that a message you received was really the one sent and not something that a malicious adversary modified in transit or concocted?In the dat
41、a link layer,packets on a point-to-point line can be encrypted as they leave one machine and decrypted as they enter another.All the details can be handled in the data link layer,with higher layers oblivious to what is going on.This solution breaks down when packets have to traverse multiple routers
42、,however,because packets have to be decrypted at each router,leaving them vulnerable to attacks from within the router.Also,it does not allow some sessions to be protected(e.g.,those involving on-line purchases by credit card)and others not.Nevertheless,link encryption,as this method is called,can b
43、e added to any network easily and is often useful.Text 2 Network SecurityText 2 Network SecurityIn the network layer,firewalls can be installed to keep good packets and bad packets out.IP security also functions in this layer.In the transport layer,entire connections can be encrypted,end to end,that
44、 is,process to process.For maximum security,end-to-end security is required.Finally,issues such as user authentication and nonrepudiation can only be handled in the application layer.Since security does not fit neatly into any layer,it does not fit into any chapter of this book.For this reason,it ra
45、tes its own chapter.Text 2 Network SecurityIt is well documented that most security failures at banks,for example,are due to incompetent employees,lax security procedures,or insider fraud,rather than clever criminals tapping phone lines and then decoding encrypted messages.If a person can walk into
46、a random branch of a bank with an ATM slip he found on the street claiming to have forgotten his PIN and get a new one on the spot(in the name of good customer relations),all the cryptography in the world will not prevent abuse.In this respect,Ross Andersons book is a real eye-opener,as it documents
47、 hundreds of examples of security failures in numerous industries,nearly all of them due to what might politely be called sloppy business practices or inattention to security.Nevertheless,we are optimistic that as e-commerce becomes more widespread,companies will eventually debug their operational p
48、rocedures,eliminating this loophole and bringing the technical aspects of security to center stage again.Except for physical layer security,nearly all security is based on cryptographic principles.Words and ExpressionsRoss Anderson安德森，剑桥大学资讯安全工程讲师loom lu:m n.织布机v.朦胧地出现，隐约可见horizon hraizn n.地平线；视野；眼界
49、.pitfall pitf:l n.陷阱，诱惑，阴谋algorithm lgrim 算法sin sin n.罪，罪孽v.犯罪nosy nuzi adj.鼻子大的，好管闲事的，爱追问的recipient risipint n.接受者authorized:raizd adj.经认可的，审定的，经授权的21世纪大英汉词典purportedly p:p:tidli，p:p-，p:pt-ad.据称IRS abbr.Internal Revenue Service 美国国税局Mafia m:fi n.黑手党，秘密政党legitimate l iditimit a.合法的，正当的v.使合法malicious
50、 mlis a.怀恶意的，恶毒的Words and Expressionsperpetrator p:pitreit n.犯人，作恶之人outsmart autsm:t v.比.更聪明，打败adversary dvsri n.敌手，对手well-funded资金充足的thwart w:t a.横坐板v.反对，阻碍ad.横过perpetrate p:pitreit v.做，犯tapping tpi n.开孔(导出液体，放液，流出口，浇铸，抽头)insider insaid(r)n.内部的人，会员，知道内情的人grudge grd n.怨恨，恶意v.怀恨，嫉妒，吝惜intertwined int:
