,單擊此處編輯母版標題樣式,單擊此處編輯母版文本樣式,第二級,第三級,第四級,第五級,*,*,汪 蕓,yunwangseu.edu,2004年2月,局域網(wǎng)與分布式處理,1,課程概況,主要內(nèi)容,-局域網(wǎng)技術：網(wǎng)絡體系結(jié)構，網(wǎng)絡各層協(xié)議，主要算法，根本設計方法,-分布計算：CORBA技術，容錯理論，分布算法,時間：40學時,參考書,-計算機網(wǎng)絡，Andrew Tanenbaum,third edition,清華大學出版社，1998,-CORBA技術及其應用，汪蕓，東南大學出版社，1999,-IP Routing Fundamentals,Mark A.Sportack,Cisco 系列叢書,清華大學出版社,1999,-High-Speed Networks and Internets Performance and Quality of Service(second edition),William Stallings,Prentice Hall,2002,-Introduction to Distributed Algorithms(second edition),Gerard Tel,電子工業(yè)出版社，2003,2,什么是計算機網(wǎng)絡？,3,計算機網(wǎng)絡,自主計算機的互聯(lián)集合,-三個根本要點：具有獨立計算能力的計算機，相互連接，能夠相互通信,網(wǎng)絡的優(yōu)勢,-便于溝通信息,-利用共享資源,-進行協(xié)作工作,4,計算機網(wǎng)絡續(xù),網(wǎng)絡面臨的問題,-從如何通信到如何可靠通信通信協(xié)議，容錯理論，平安理論等,-從如何傳輸數(shù)據(jù)到如何高速有效傳輸數(shù)據(jù)路由問題，糾錯問題，信號傳輸問題，可靠傳輸問題等,-從提供什么效勞到如何提供用戶友好效勞,-從如何構建網(wǎng)絡到如何應用網(wǎng)絡,5,什么是分布計算？,6,分布計算實例,E-learning,E-business,E-game,WWW applications,CSCW,Groupware,Mobile phone roaming,7,分布計算,Distributed Computing,Client/server Computing,P2P Computing,eg.SITHOME,Eg.HTTP,DCE,OO view of distributed computing,Eg.Java,J2EE,CORBA,DCOM,8,Motivation,Information exchange,Resource sharing,Increased reliability through replication,Increased performance through parallelization,Simplification of design through specialization,9,分布計算特點,位置透明性,效勞透明性,分布透明性,網(wǎng)絡透明性,協(xié)同工作,10,計算機網(wǎng)絡和分布計算的關系,各自的側(cè)重點不同,-計算機網(wǎng)絡側(cè)重于計算機之間的通信，分布計算側(cè)重于如何為一個共同目標而進行數(shù)據(jù)溝通,相互聯(lián)系,-分布計算環(huán)境通常是建立在計算機網(wǎng)絡根底上的,11,What Are Those“Hot Topics,Peer-to-peer systems.,Application-level multicast.,Overlay networks.,Gossip-based(epidemic)protocols.,Distributed file systems.,Security(e.g.,of all the above).,Solutions of the above for wireless networks.,12,第一章 網(wǎng)絡根底,13,1.1 A Communication Model,Source,Transmitter,Transmission System,Destination,Receiver,14,1.2 網(wǎng)絡的分類1,按照傳輸技術分：,播送式網(wǎng)絡和點到點網(wǎng)絡,播送式網(wǎng)絡：,-僅有一條通道,-多點接收,點到點網(wǎng)絡,Broadcast,multicast and unicast,15,網(wǎng)絡的分類2,按照連接距離和規(guī)?？梢苑譃椋?局域網(wǎng)，城域網(wǎng)和廣域網(wǎng),局域網(wǎng)：一般在10公里范圍內(nèi),城域網(wǎng)：覆蓋一個城市,廣域網(wǎng)：覆蓋整個地球,16,廣域網(wǎng),分為通信子網(wǎng)和資源子網(wǎng),通信子網(wǎng)是網(wǎng)絡中面向數(shù)據(jù)傳輸或者數(shù)據(jù)通信的局部資源集合,資源子網(wǎng)是網(wǎng)絡中面向數(shù)據(jù)處理的資源集合，由用戶的主機資源組成,廣域網(wǎng)通常由多個局域網(wǎng)組成,17,局域網(wǎng)和廣域網(wǎng)的關系,范圍,傳輸技術,-傳統(tǒng)局域網(wǎng)是播送式網(wǎng)絡,-廣域網(wǎng)主要采用分組交換加路由,拓撲結(jié)構,-局域網(wǎng)主要采用總線型、環(huán)型和星型,-廣域網(wǎng)主要采用層次結(jié)構網(wǎng)狀,18,網(wǎng)絡分類3,按照傳輸介質(zhì)可以分為：,-有線網(wǎng)絡,-無線網(wǎng)絡,19,1.3 拓撲結(jié)構(1),總線型,-,tap:hardware interfacing,-full-duplex operation between the station and the tap,-terminator:absorbs any signal,removing it from the bus,20,An Example,A,A,B,C,(a)C transmits frame addressed to A,A,A,B,C,(b)Frame is not addressed to B;B ignores it,21,An Example(Contd),A,A,B,C,(c)A receives the frame,-,no special action needs to be taken to remove frames from the medium,-,there needs to be some way of indicating for whom the transmission is intended,-a mechanism is needed to regulate transmission,22,Solution,Stations transmit in frames.,A frame=a frame header+a portion of the data,A frame header contains control information,e.g.addresses.,23,討論,Frame,packet,datagram,stream和message有什么不同？,24,拓撲結(jié)構2,環(huán)型,A closed loop,A set of repeaters:no buffering,only one direction,25,An Example,B,A,C,A,(a)C transmits frame addressed to A,B,A,C,A,(b)Frame is not addressed to B;B ignores it,26,An Example Contd),B,A,C,A,(c)A copies frame as it goes by,B,A,C,A,(d)C absorbs returning frame,27,討論,環(huán)型結(jié)構與總線型結(jié)構有什么相同點和不同點？,28,網(wǎng)絡拓撲3,星型,Central hub,switch,29,Central Node,To operate in a broadcast fashion,-A transmission of a frame from one station to the node is retransmitted on all of the outgoing links,To act as a frame switching device,-An incoming frame is buffered in the node and then retransmitted on an outgoing link to the destination station,30,討論,給出使用總線型、環(huán)型和星型拓撲結(jié)構的應用實例。,31,