《信息通信網(wǎng)絡概論》chapter1-1.ppt

1、The Department of Radio Engineering,Introduction to Communication Networks,Chapter 1 Introduction,1.1 Evolution of Communication Networks and Key Technology 1.2 Types of Communication Networks 1.3 Topology of Communication Networks 1.4 Architecture and Standards 1.5 Quality of Service （QoS）,1.1 Evol

2、ution of Communication Networks Mathematical Theory of Communication: Nyquist Theorem in 1929 20世紀50年代、60年代半導體和集成電路的發(fā)展使數(shù)字通信得到發(fā)展 The first, large modern computer was built in A. 1945 -Digital Communication 1980s 1948 First commercial computer installed, the UNIVAC I 1958 First U.S. Communications sat

3、ellite sent into orbit 1959 FCC approves private microwave communications networks 1964 Packet switching network concept proposed by the Rand Corporation,Important Dates in the History of Data Communications (2),1966 IBMs binary synchronous (BISYNC or BSC) protocol announced 1969 ARPANET, first pack

4、et switching network (later to become the Internet), begins operation 1970 - the first practical optical fiber for communications was invented 1974 IBM announces its Systems Network Architecture (SNA) 1975 Personal computers introduced, the Altaire 8800 replaced terminals in many cases 1981 IBM PC i

5、ntroduced 1985 Cellular radio telephones are introduced 1990 World Wide Web is introduced 1993 Web search engines introduced 1995 The Internet grows to over four million host computers 1999 The Internet grows to over ten million host computers Etc.,1.1.2 Communication Network Construct and Key Techn

6、ologies,1. What Are Communication Networks? 2. Communication Network Construct 3. Key Technologies,1、 What Are Communication networks? （1）,What Are Communication networks? （2）,What Are Communication networks? （3）,What Are Communication Networks ? （4）,The Nodes: can be terminal entities, such as phon

7、e sets, computers, printers, file servers, or video monitors ; can also be communication device, such as switches, routers or repeaters.,Definition: A communication network is a set of nodes( terminal nodes or communication nodes ) that are interconnected to permit the exchange of information,2. Com

8、munication Network Construct（1）,Elements of communication networks: Terminal entity 、Communication devices、Communication Link、Protocol.,Link,nodes,Communication Network,A closer look at network structure:,network edge(end systems): hosts, terminals, etc network core: routers network of networks,Comm

9、unication Network Construct （2）,Terminal node: generate or use the information transmitted over the network. Perform some communication functions: at the very lest it have to receive or transmit information. Entities: such as phone sets, computers, printers, file servers, or video monitors .,Communi

10、cation node: Transport the information but do not generate or use it. Device: such as switch, routers, repeater,Communication Network Construct （3）,Communication Link: use to Connect node and node. composed by physical medium and Cooperate communication devices. communication devices: modem, send or

11、 receive device. Multiplex devices, etc. Wire or Wireless link : Optical fiber, copper wires, cable Radio waves, light wave etc. Protocol: define format, order of messages sent and received among network nodes, and actions taken on msg. transmission, receipt. (Detail1.3),3、Key TechnologySwitching Me

12、thod,Key technologies：Switch Technology, Transmission technology etc. mesh of interconnected the fundamental question: how is data transferred through network? circuit switching: dedicated circuit per call: telephone network packet-switching: data sent through network in discrete “chunks” Virtual ci

13、rcuit Switching Datagram switching message-switching,The Network Core,Key TechnologyMessage Switching,Message Switching（報文交換）:是以報文作為傳送單元采用存儲轉(zhuǎn)發(fā)機制的交換方式。,each end-end data stream as messages user A, B message share network resources each message uses full link bandwidth resources used as needed,resourc

14、e contention: aggregate resource demand can exceed amount available congestion: messages queue, wait for link use store and forward: messages move one hop at a time transmit over link wait turn at next link,Key Technology : Message Switching,Time,A,B,C,D,Queueing Delay,Transmission Delay,Header,Anal

15、ogy: Postal service, telegraph network,Key TechnologyCircuit Switching,Circuit Switching(電路交換)是一種基于位置面向連接的交換方式，即在通信的兩個站點間需要建立一個物理通信通路；一旦建立，在整個通信過程中，該通路始終為通信雙方占用，因此，對用戶是透明的，信息以固定的數(shù)率傳輸； 當所有通信結(jié)束后，可以由任何一方釋放連接。電路交換要求每個站點必須有足夠的的內(nèi)部交換能力； 適用于大量數(shù)據(jù)傳輸?shù)膱龊稀?End-end resources reserved for “call” link bandwidth, sw

16、itch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required,Circuit Switching Delay,Circuit Establishment,Data Transmission,Circuit Termination,DATA,Circuit Switching Characteristic,電路交換的特點： 要在通信的用戶間建立專用的物理連接通路。（固定分配帶寬） 對傳送的信息無差錯控制措施。 對通信信息不作處理(信令除外)，而是原封不

17、動地傳送，用作低速數(shù)據(jù)傳送時不進行速率、碼型的變換。 用基于呼叫損失制的方法來處理業(yè)務流量，過負荷時呼損率增加，但不影響已建立的呼叫 電路交換的優(yōu)點： 時延確知，通信質(zhì)量有保證 控制簡單 電路交換的缺點： 呼叫建立需要時間 每個連接帶寬固定（不能適應不同速率的業(yè)務） 不傳信息時也占用資源（不適用于突發(fā)業(yè)務）,Key TechnologyPacket Switching (1),Packet-switching: store and forward behavior 34,Key TechnologyPacket Switching (2),分組交換（也稱包交換）：將用戶信息分成若干個小的數(shù)據(jù)單

18、元稱為分組（packet）或包。它采用存儲轉(zhuǎn)發(fā)技術(shù)，無需建立一條專用物理通信通路； 數(shù)據(jù)以分組形式傳輸，每個分組包括控制信息和用戶數(shù)據(jù)兩部分；為了保證分組能夠正確地傳送到目的地，每個分組必須攜帶一個用于指明該分組發(fā)往何地址信息和路由選擇、流量控制、擁塞控制等控制信息的分組頭。然后由交換機根據(jù)每個分組的地址標志，將他們轉(zhuǎn)發(fā)至目的地。,Key TechnologyPacket Switching (3),VC ( Virtual Circuit虛電路)所謂虛電路是面向連接的服務，在數(shù)據(jù)傳輸之前需要先建立一條邏輯鏈路；數(shù)據(jù)交換后，必須釋放這個連接。同一呼叫的數(shù)據(jù)分組只需標識邏輯電路號，并沿著虛電路按

19、序傳輸，提供可靠的報文服務。 它不同于電路交換中的物理連接，而是邏輯連接。 交換虛電路(SVC：Switched Virtual Circuit) 永久虛電路(PVC：Permanent Virtual Circuit),DG( Datagram 數(shù)據(jù)報)是無連接的服務，無需要預先建立連接，網(wǎng)絡隨時接受主機發(fā)送的分組；每個數(shù)據(jù)報需要標識出完整的目標地址；每個分組獨立的選擇路由，因此不能防止報文的丟失、重復或失序，它提供“盡最大努力交付”的服務，是一種不可靠的服務。,虛電路和數(shù)據(jù)報是分組交換兩種不同形式的服務。,Virtual Circuit,Datagram,H1,A,分組交換網(wǎng),B,D,E,

20、C,H5,H6,H4,H2,H3,H1 向 H5 發(fā)送分組,H2 向 H6 發(fā)送分組,注意分組路徑的變化！,結(jié)點交換機,注意分組的存儲轉(zhuǎn)發(fā)過程,H1,A,分組交換網(wǎng),B,D,E,C,H5,H6,H4,H2,H3,H1 向 H5 發(fā)送分組,結(jié)點交換機,主機,在結(jié)點交換機 A 暫存 查找轉(zhuǎn)發(fā)表 找到轉(zhuǎn)發(fā)的端口,在結(jié)點交換機 C 暫存 查找轉(zhuǎn)發(fā)表 找到轉(zhuǎn)發(fā)的端口,在結(jié)點交換機 E 暫存 查找轉(zhuǎn)發(fā)表 找到轉(zhuǎn)發(fā)的端口,最后到達目的主機 H5,Packet Switching Delay（1）,Packets experience delay on end-to-end path four sources

21、 of delay at each hop,nodal processing: check bit errors determine output link Queuing: time waiting at output link for transmission depends on congestion level of router,A,B,propagation,transmission,nodal processing,queuing,Packet Switching Delay （2）,Transmission delay: R= link bandwidth (bps) L= p

22、acket length (bits) time to send bits into link = L/R,Propagation delay: d = length of physical link s = propagation speed in medium (2x108 m/sec) propagation delay = d/s,Note: S and R are very different quantities!,Virtual Circuit Delay,Packet 1,Transmission time,Virtual Circuit Establishment,Packe

23、t 3,Datagram Delay,Virtual Circuit VS. Datagram (1),分組頭： DG方式的每個分組頭中要包含詳細的目的地址 VC方式由于預先已建立邏輯連接，分組頭中只要含有對應于所建立的VC的邏輯信道標識 選路： VC方式預先有建立過程，但一旦虛電路建立，在端到端之間所選定的路由上的各個交換節(jié)點都具有映象表，存放出入邏輯信道的對應關(guān)系，每個分組到來時只要查找映象表，而不需要進行復雜的選路。 DG方式則不需要有建立過程，但對每個分組都要獨立地進行選路。 分組順序： VC方式中，屬于同一呼叫的各個分組在同一條虛電路上傳送，分組會按原有順序到達終點，不會產(chǎn)生失序現(xiàn)象

24、。 DG方式中，各個分組由于是獨立選路，可以從不同的路由轉(zhuǎn)送，會引起失序,Virtual Circuit VS. Datagram (2),故障敏感性 VC方式對故障較為敏感，當傳輸鏈路或交換節(jié)點發(fā)生故障時可能引起虛電路的中斷，需要重新建立。 （有些分組網(wǎng)具有再連接功能，出現(xiàn)故障時可自動建立新的虛電路，并做到不丟失用戶數(shù)據(jù)） DG方式中各個分組可選擇不同路由，對故障的防衛(wèi)能力較強，從而可靠性較高。 應用 VC方式適用于較連續(xù)的數(shù)據(jù)流傳送，其持續(xù)時間應顯著地大于呼叫建立的時間，如文件傳送、傳真業(yè)務等。 DG方式則適用于面向事務的詢向響應型數(shù)據(jù)業(yè)務。,Datagram or VC network:

25、 why?,Internet data exchange among computers “elastic” service, no strict timing req. “smart” end systems (computers) can adapt, perform control, error recovery simple inside network, complexity at “edge” many link types different characteristics uniform service difficult,ATM evolved from telephony

26、human conversation: strict timing, reliability requirements need for guaranteed service “dumb” end systems telephones complexity inside network,Packet switching Vs. circuit switching,1 Mbit link each user: 100Kbps when “active” active 10% of time circuit-switching: 10 users packet switching: with 35

27、 users, probability 10 active less that .004,Packet switching allows more users to use network!,N users,1 Mbps link,A comparison of circuit switched and packet-switched networks.,Packet switching versus circuit switching More,Advantages in small packets Propagation delay plays important role in high

28、-speed communications, and it cannot be improved because it is constrained by the speed of light details in delay -1.5,Delay Comparison,采用存儲轉(zhuǎn)發(fā)方式的分組交換兼有電路交換和報文交換的優(yōu)點，它與報文交換的不同在于：分組交換將用戶要傳送的信息分割為若干個分組（packet），每個分組中有一個分組頭，含有可供選路的信息和其他控制信息。,3. Evolution and Trend of Communication Network（1）,Circuit Switc

29、hing & Telephone Period,Program Control Switch & Digital Transmit Period,Packet Switching & Digital Network Period,ISDN & Mobile Communication Period,始于19世紀末,始于20世紀60年代,始于20世紀70年代,始于20世紀80年代,NGN,I、 Message Switching & Telegraph Period,Telegraph Network Modern Telegraph Network：采用公用電信網(wǎng)，利用電報自動交換技術(shù)。,II

30、、Circuit Switching & Telephone Period,PSTN ( Public Switched Telephone Network公眾電話網(wǎng)):為公眾提供電話業(yè)務而建立和經(jīng)營的電信網(wǎng). 公眾電話網(wǎng)包括本地電話網(wǎng)、長途電話網(wǎng)和國際電話網(wǎng)。 無線通信網(wǎng),、Program Control Switch & Digital Transmit Period,骨干網(wǎng):由模擬向數(shù)字網(wǎng)轉(zhuǎn)變，數(shù)字技術(shù)和計算機技術(shù)在網(wǎng)絡中廣泛使用： 數(shù)字傳輸技術(shù)：基于PCM技術(shù)的數(shù)字傳輸設備，提高長途信號傳輸質(zhì)量，降低傳輸成本。 交換技術(shù)：數(shù)字交換設備，提高交換速度和可靠性。 模擬程控交換機： 1965

31、年5月美國開通了第一個程控交換機（ESS No.1）。 數(shù)字程控交換機： 1970年法國開通了第一個數(shù)字程控交換機（E10） 業(yè)務數(shù)據(jù)化 傳真網(wǎng)：（利用電話通信網(wǎng)完成傳真的發(fā)送與接收）, 、 Packet Switching & Digital Network Period,DDN (Digital Data Network）、X.25、 FR(Frame Relay) 、ATM (Asynchronous Transfer Mode) and Internet Network。 Computer Network：LAN, MAN, WAN.,Packet Switching & Digita

32、l Network Period - - Internet,互連網(wǎng)技術(shù) ：在不同類型的網(wǎng)絡之間進行信息傳輸 19691983 研究試驗階段 19831994 因特網(wǎng)在教育科研領(lǐng)域廣泛使用的 實用階段 1994現(xiàn)在 商業(yè)化發(fā)展階段 IP網(wǎng)絡特點：技術(shù)簡單，可擴展性好，靈活性高 存在問題：傳輸效率低，無法保證服務質(zhì)量,、ISDN & Mobile Communication Period,Broadband，Mobile，Integration，Intelligent Core/Backbone Network :Optical Technology CATV ( Cable Television

33、） CCSN (Common Channel Signaling Network) ：CCS No.7 (Common Channel signaling No.7) 。 Synchronous Network：SDH management network ：TMN ( Telecommunication Management Network),ISDN & Mobile Communication Period - Broadband,ISDN(Integrated Services Digital Network)：能夠提供端端數(shù)字連接，支持包括話音和非話在內(nèi)的多種電信業(yè)務 N-ISDN:

34、 傳輸速率和交換模式限制了具有更高速率和可變速率業(yè)務的提供，已不能適應未來通信網(wǎng)發(fā)展的需要。 B-ISDN：以光纖作為傳輸媒介，以信元作為傳輸交換的基本單位，利用虛通路與虛通道實現(xiàn)資源共享。采用ATM技術(shù)和光纖通信技術(shù)的ISDN,Broadband Access Network,Wire Broadband Access Network ： 電纜接入XDSL：DSL技術(shù)按上行和下行速率的是否相同，可分為速率對稱型和速率非對稱型兩種。如果用戶下載的數(shù)據(jù)量比較大，采用速率非對稱型DSL技術(shù)（非對稱數(shù)字用戶線路XDSL ）。X表示A/H/S/C/I/V/RA等不同的數(shù)據(jù)調(diào)制實現(xiàn)方法，使數(shù)據(jù)或多媒體信息可以更高速地在銅質(zhì)雙絞線上傳送，避免擁塞。 Broadband optical Fiber Access Network Wireless Broadband Access Network：WLAN，WiMAX, WCDMA, etc. 多媒體 語音、數(shù)據(jù)、圖象要在同一網(wǎng)絡中傳輸和共享 移動性 用戶終端在運動中保持通信,ISDN