circuit_and_packet_switching

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川大林峰计网第一次作业

I. Multiple Choice1.1In the following options, which does not define in protocol? ( D )A the format of messages exchanged between two or more communicating entitiesB theorder of messages exchanged between two or more communicating entities C the actions taken on the transmission of a message or other event D the transmission signals are digital signals or analog signals1.2In the following options, which is defined in protocol? ( A )A the actions taken on the transmission and/or receipt of a message or other eventB theobjects exchanged between communicating entities C the content in the exchanged messages D the location of the hosts1.3 Which of the following nodes belongs to the network core? ( C )A. a Web ServerB. a Host with Win2003 ServerC. a Router with NAT serviceD. a Supernode on Skype Network1.4 In the Internet, the equivalent concept to end systems is ( A ). A hostsB serversC clientsD routers1.5 In the Internet, end systems are connected together by ( C ). A copper wireB coaxial cableC communication linksD fiber optics1.6 End systems access to the Internet through its ( C ). A modemsB protocolsC ISPD sockets1.7 In the following options, which belongs to the network core? ( B ) A end systemsB routersC clientsD servers1.8 End systems, packet switches, and other pieces of the Internet, run ( D ) that control the sending and receiving of information within the Internet. A programs B processes C applications D protocols1.9 The protocols of various layers are called ( A ). A the protocol stack B TCP/IP C ISP D network protocol1.10 In the OSI reference model, the upper layers of the OSI model are, in correct order (D)a) Session, application, presentation b) Session, presentation, application c) Session, application, presentation, physical d) Application, presentation, session1.11 The lower layers of the OSI model are, in correct order( D )a) physical, system, network, logical b) physical, logical, network, system c) physical, transport, network, data link d) physical, data link, network, transport1.12 Which of the following protocol layers is not explicitly part of the Internet Protocol Stack? ___B______ A. application layer B. session layer C. data link layer D. transport layer1.13 The 5-PDU is called__D_ A. message B. segment C. datagram D. frame1.14 Transport-layer packets are called: BA. messageB. segmentC. datagramD. frame1.15 The units of data exchanged by a link-layer protocol are called ( A ). A FramesB SegmentsC DatagramsD bit streams1.16 There are two fundamental approaches to building a network core, ( B ) and packet switching. A electrical current switching B circuit switching C data switching D message switching1.17 There are two classes of packet-switched networks: ( B ) networks and virtualcircuit networks. A datagramB circuit-switchedC televisionD telephone1.18 ( A ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Store-and-forward transmissionB FDMC End-to-end connectionD TDM1.19 In ( C ) networks, the resources needed along a path to provide for communication between the end system are reserved for the duration of the communication session. A packet-switched B data-switched C circuit-switched D message-switched1.20 In ( A ) networks, the resources are not reserved; a session’s messages use the resources on demand, and as a consequence, may have to wait for access to communication link. A packet-switched B data-switched C circuit-switched D message-switched1.21 Which of the following option belongs to the circuit-switched networks? ( D ) A FDMB TDMC VC networksD both A and B1.22 In a circuit-switched network, if each link has n circuits, for each link used by the end-to-end connection, the connection gets ( A ) of the link’s bandwidth for the duration of the connection. A a fraction 1/n B all C 1/2D n times1.23 For ( C ), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot. A CDMA B packet-switched network C TDM D FDM1.24 The network that forwards packets according to host destination addresses is called ( D ) network. A circuit-switched B packet-switched C virtual-circuit D datagram1.25 The time required to propagate from the beginning of the link to the next router is ( C ). A queuing delay B processing delay C propagation delay D transmission delay1.26 Processing delay does not include the time to ( B ). A examine the packet’s header B wait to transmit the packet onto the link C determine where to direct the packet D check bit-error in the packet1.27 In the following four descriptions, which one is correct? ( C )A The traffic intensity must be greater than 1.B The fraction of lost packets increases as the traffic intensity decreases.C If the traffic intensity is close to zero, the average queuing delay will be close to zero.D If the traffic intensity is close to one, the average queuing delay will be close to one.1.28 Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( B ), A LR／a B La／R C Ra／L D LR／a1.29 and it should no greater than ( B ). A 2 B 1 C 0D -11.30 Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.) ( A ) A L/R1＋L/R2 B L/R1 C L/R2 D none of the above1.31 We are sending a 30 Mbit MP3 file from a source host to a destination host. Suppose there is only one link between source and destination and the link has a transmission rate of 10 Mbps. Assume that the propagation speed is 2 * 108 meters/sec, and the distance between source and destination is 10,000 km. Also suppose that message switching is used, with the message consisting of the entire MP3 file. How many bits will the source have transmitted when the first bit arrives at the destination? CA. 1 bitB. 30,000,000 bitsC. 500,000 bitsD. none of the above1.32 Access networks can be loosely classified into three categories: residential access, company access and ( B ) access. A cabled B wireless C campus D city area1.33 The following technologies may be used for residential access, except DA. HFCB. DSLC. Dial-up modemD. FDDI1.34 Which kind of media is not a guided media? ( D ) A twisted-pair copper wireB a coaxial cableC fiber opticsD digital satellite channelII. True or False1.35 There is no network congestion in a circuit switching network.False1.36 Consider an application that transmits data at a steady rate, and once this application starts, it will stay on for a relatively long period of time. According to the characteristic, a packet-switched network would be more appropriate for this application than a circuit-switched network.FalseIII. Please Answer Following Questions Briefly1.37 How many layers are there in the Internet protocol stack? What are they? What are the principal responsibilities of each of these layers?5层。

电器电子英语词汇（C）_科技英语词汇

c to c transport 盒对盒薄片转移cable 电缆cable code 水线电码cable concentrator 集线器集中器cable connector 电缆连接器cable drum 电缆卷筒cable duct 电缆槽cable holder 电缆支架cable installation 电缆敷设cable interference 电缆干扰cable joint 电缆接头cable laying 电缆敷设cable locator 电缆探测器cable message 水线电报cable set 电缆附件cable shield 电缆包皮cable television 电缆电视cable terminating set 电缆终端cable transmission 电缆传输cablegram 水线电报cad 计算机辅助设计cad system 计算机辅助设计系统cad technique 计算机辅助设计技术cad tools 计算机辅助设计工具cad workstation 计算机辅助设计工拙cadmium 镉cage antenna 笼形天线cage dipole 笼形偶极子calcination 烧成calculagraph 计时器calibration test 校准试验call 呼叫call acceptance 呼叫接受call count 通话计数call finder 呼叫选择器call forward operation 呼叫转发电话call forwarding 呼叫转发电话call in operation 呼叫转发电话call indicator 呼叫指示器call sign 呼号call signal 呼叫信号call switch 呼叫转换开关call waiting 得等待call wire 呼叫线路callback 回叫called line 被叫线calling cord 呼叫塞绳calling device 呼叫装置calling key 呼叫键calling lamp 呼叫灯calling machine 铃龙calling plug 呼叫插塞calling relay 呼叫继电器calling subscriber 中用户calorimetric power measurement 热量计式功率测量法camber 挠曲camber free ceramics 无弯曲的陶瓷camera 照相机;摄像机camera alignment 摄像机导camera chain 摄像机系统camera lens 摄影机镜头camera signal 电视摄像机信号camera tube 电视摄像管camp 计算机辅助掩模制备camp on 得等待can 金属盒canal rays 阳极射线cancellation 熄灭cancelling 熄灭canonical form 标准形cap layer 保护层capacimeter 电容测量表capacitance 电容capacitance box 电容箱capacitance meter 电容测试器capacitive bridge 电容电桥capacitive coupling 电容性耦合capacitive diaphragm 电容性窗膜capacitive feedback 电容反馈capacitive iris 电容性窗膜capacitive load 电容性负载capacitive reactance 电容性电抗capacitive sawtooth generator 电容式锯齿波发生器capacitive strip 电容带capacitive susceptance 电容性电纳capacitive tuning 电容党capacitive unbalance 电容不平衡capacitive voltage divider 电容分压器capacitive window 电容性窗口capacitively loaded line 电容性负载线capacitor 电容器capacitor coupled fet logic 电容耦合式场效应晶体管逻辑capacitor network 电容气络capacitor parasitics 寄生电容器capacitor plate 电容偏板capacitor probe 电容式探针capacitor voltage characteristic 电容电压特性capacity 电容量capillary clogging 毛细管堵塞capless annealing 无覆盖退火capping 覆盖capping annealing 覆盖退火capping oxidation 覆盖氧化capping oxide 覆盖氧化物capstan 织轮capstan amplifier 转矩放大器capsulation 封装captive production 专用生产capture 捕获capture of particles 粒子俘获capture region 俘获区域capture time 捕获时间car radio 汽车收音机car receiver 汽车接收机carbon 碳carbon diaphragm 炭膜carbon dioxide laser 二氧化碳激光器carbon granule microphone 炭粒式话筒carbon mircrophone 炭精式话筒carbon resistor 碳电阻器carbonization 增碳carcinotron 返波管carcinotron oscillator 返波管振荡器card 卡cardioid diagram 心脏形曲线图cardioid microphone 心形传声器单向传声器cardioid pattern 心脏形曲线图cardioidal reception 心形方向图接收carrier 载波carrier amplitude 载波振幅carrier amplitude regulation 载波幅度蝶carrier balance 载波平衡carrier capture 载劣俘获carrier carrier interaction 载劣间相互酌carrier channel 载波信道carrier current telegraphy 载波电抱carrier density 载劣密度carrier dificiency 载劣耗尽carrier drift 载劣漂移carrier flutter 载波颤动carrier frequency 载波频carrier gas 载气carrier generation 载劣生成carrier heating 载劣加热carrier killer 载劣寿命扼杀剂carrier leak 载波泄漏carrier lifetime 载劣寿命carrier noise 载波噪音carrier pair generation 载劣对发生carrier recombination 载劣复合carrier socket 插座carrier spacing 载波间隔carrier storage 载劣存储carrier synchronization 载波同步carrier tape 带式载体carrier telegraphy 载波电抱carrier to noise ratio 载波信噪比carrier transfer 载劣传输carrier transfer device 载劣转移掐carrier transit time 载劣渡越时间carrier transmission 载波传输carrier transport 载劣输运cartridge 盒式磁带cascade 级联cascade amplifier 级联放大器cascade connected 级联的cascade connection 级联cascade image tube 级联摄象管cascade solar cell 级联太阳电池cascaded laser 级联激光器cascode 栅地阴地放大器共射共基放大器cascode amplifier 阴地栅地级联放大器涡尔曼放大器case 管壳casing 外壳cassegrain antenna 卡塞格伦天线cassette 箱cassette based transfer 盒式传送cassette loader 盒装载器cassette pitch 盒节距cassette sampling 向盒取样cassette station 向盒装卸台cassette to cassette approach 盒对盒装卸技术cassette to cassette coater 盒间装卸式涂敷器cassette to cassette feed 盒对盒装卸操作cassette to cassette handler 盒对盒装卸装置cassette to cassette operation 盒对盒装卸操作cassette to cassette wafer transport 盒对盒薄片转移casting 铸模casting resin 充填尸catalogue integrated circuit 集成电路样本catalogue microprocessor 微处理机样本catalytic oxidation 催化氧化cataphoresis pumping 电泳泵激cataphoretic laser 电泳激光器catcher 收注栅catcher resonator 收注栅catcher space 收注栅空间catchment area 积水面积cathode 阴极cathode bias 阴极偏压cathode coupled amplifier 阴极耦合放大器cathode current 阴极电流cathode dark space 阴极暗区cathode fall space 阴极电位降空间cathode follower 阴极跟随器cathode glow 阴板电辉cathode heater 阴极加热器cathode heater assembly 阴极加热器cathode heating time 阴极加热时间cathode modulation 阴极灯cathode poisoning 阴极中毒cathode ray 阴极射线cathode ray beam intensity modulation 阴极射线束强度灯cathode ray oscillograph 阴极射线示波器cathode ray storage tube 阴极射线存储管cathode ray tube 阴极射线管cathode spot 阴极斑点cathode spraying 阴极溅射cathode sputtering 阴极溅射cathodoluminescence 电子致发光cathodoluminescent display 阴极线发光显示器cation resin 阳离子交换尸cavity 空腔谐振器cavity adjustment 谐振腔蝶cavity filter 空腔滤波器cavity frequency meter 空腔频率计cavity laser 空腔激光器cavity length 谐振腔长度cavity linewidth 谐振谱线宽度cavity magnetron 空腔谐振磁控管cavity maser 共振腔脉泽cavity mirror 谐振腔反射镜cavity mode 空腔共振模cavity reflector 谐振腔反射镜cavity resonator 空腔共振器cavity stability 谐振腔稳定度cavity tuner 空腔党器cavity volume 空腔谐振棋积cavity wavemeter 谐振腔波长计ccd 电荷耦合掐ccd filter 电荷耦合掐滤波器ccd image array 电荷耦合掐成像阵列ccd imager 电荷耦合成像器ccd logic 电荷耦合掐逻辑ccd multiplexer 电荷耦合掐多路转换器ccd readout 电荷耦合读出设备ccd shift register 电荷耦合移位寄存器ccfl 电容耦合式场效应晶体管逻辑cci 电荷耦合成象器ccl 电荷耦合逻辑电路ccram 电荷耦合随机存取存储器cd 冲突检出cd amplifier 源输出放大器cdi 集电极扩散隔离cdip 陶瓷双列直插式外壳cell 电池cell array 单元阵列cell density 单元密度cell library 单元库cement 水泥cement bonding 粘合剂接合center 中心center frequency 中心频率center of a band 频带中心center to center spacing 中心间距centering 定中心centering control 准心蝶器居中蝶central antenna television 共用天线电视central battery system 共电制central exchange 电话总机central office 电话总机central processor unit 中央处埋机central telephone exchange 中央电话局centralized control 中心控制centre 电话总机centre holes 输送孔centrifuge 离心机centrifuge testing 离心机试验centring control 准心蝶器居中蝶cer dip 陶瓷双列直插式外壳ceramic and metal package 金属陶瓷外壳ceramic base 陶瓷衬底ceramic cap 陶瓷盖ceramic carrier 陶瓷芯片座ceramic dip 陶瓷双列直插式外壳ceramic encapsulated ic 陶瓷封装集成电路ceramic magnet 陶质磁体ceramic metallization 陶瓷金属化cerdip assembly 陶瓷双列直插式外壳组装cerdip package 陶瓷双列直插式外壳cerenkov losses 切伦科夫损失cerenkov radiation 切伦科夫辐射cerium 铈cerium glass 铈玻璃cermet 金属陶瓷材料cermet approach 金属陶瓷工艺cermet conductor 金属陶瓷导体cermet material 金属陶瓷材料cermet process 金属陶瓷工艺cesium 铯cesium antimonide photocathode 锑化铯光电阴极cesium atomic beam frequency standard 铯原子射束的频率标准cesium phototube 铯光电管chaff 箔条chain 电路chalcogenide glass 硫属化合物玻璃chalcogenide memory 硫族化合物存储器challenge 询问chamber wash 洗室channel 沟道;信道channel algorithm 通道算法channel amplifier 信道放大器channel balancing 通道平衡channel bank 通道纽channel capacity 信道容量channel conversion 信道变换channel current 沟道电流channel cutoff 沟道截止channel diffusion 沟道扩散channel electron multiplier 通道电子倍增器channel group 通道纽channel injection 沟道注入channel leakage 沟道漏电channel mobility 沟道载劣迁移率channel oxide 沟道区域氧化物channel phasing 通道定相channel pulse 推进脉冲channel region 沟道区域channel selector 信道选择器channel separating filter 信道分离滤波器channel separation 频道分隔channel stopper 沟道截断环channel stopper impurity 沟道截断环杂质channel stopper region 沟道截断区channel switching 通道转换channel type 沟道导电类型channeling 沟道酌chanstop 沟道截断环character code 字符码character display device 字符显示器character repertoire 字符集character set 字符集characteristic admittance 特性导纳characteristic frequencies 特盏率characteristic frequency 特盏率characteristic impedance 特件阻抗charactron 显象管charge 电荷charge carrier 载荷子charge carrier diffusion 载劣扩散charge carrier generation 载劣发生charge carrier injection 载劣注入charge carrier noise 载波噪音charge compensation 电荷补偿charge coupled array 电荷耦合掐阵列charge coupled cell 电荷耦合单元charge coupled circuit 电荷耦合集成电路charge coupled device 电荷耦合掐charge coupled fet 电荷耦合场效应晶体管结构charge coupled imager 电荷耦合成象器charge coupled logic 电荷耦合逻辑电路charge coupled memory 电荷耦合存储器charge coupled ram 电荷耦合随机存取存储器charge coupled register 电荷耦合寄存器charge depletion 载劣耗尽charge distribution 电荷分布charge injection device 电荷注入掐charge migration 电荷迁移charge packet 电荷包charge recombination center 截劣复合中心charge storage capacitor 电荷存储电容器charge storage diode 阶跃恢复二极管charge storage tube 电荷存储管charge transfer amplifier 电荷传输放大器charge transfer channel 电荷转移沟道charge transfer circuit 电荷传输集成电路charge transfer device 电荷转移掐charge transfer structure 电荷转移结构charge transit time 电荷渡越时间charge transport 电荷输送chargeable call 收费通话charged particle 带电粒子charged particle analyzer 带电粒子分析器charging indication 费用指示chatter 锯型边缘;接点振动音chebyshev filter 切比雪夫滤波器check 检查check test 检查试验checking 检查cheese antenna 盒形天线chemical affinity 化学亲合力chemical bond 化学键chemical deposition 化学淀积chemical durability 化学耐久性chemical etch polishing 化学腐蚀抛光chemical etchant 化学腐蚀剂chemical laser 化学激光器chemical pumping 化学激励chemical structure fault 化学结构缺陷chemical vapor deposition 化学汽相淀积chemical vapor deposition film 化学汽相淀积膜chemical vapor deposition reactor 化学汽相淀积反应器chemisorption 化学吸着chip 芯片chip and wire approach 芯片细线方法chip and wire hybrid ic 芯片细线混合电路chip approach 多片技术chip assember 片子装配器chip assembly 片子装配chip board 芯片板chip bonding 芯片焊接chip bonding pad 芯片焊盘chip capacitor 片状电容器chip carrier 芯片座chip carrier assembly 芯片载体组装chip component 片状元件chip density 芯片密度chip design 芯片设计chip dicing 切成小片chip diode 片状二极管chip edge 芯片边缘chip family 集成电路系列chip grid 芯片布置网chip holder 芯片座chip integrated circuit 片状集成电路chip layout 芯片布置布线图chip level complexity 芯片级致密度chip marking 芯片打标chip mounting 芯片组装chip mounting area 芯片安装面积chip on board process 基板上芯片装配工艺chip on tape 带式载体上的芯片chip placer 芯片装入机chip positioner 芯片定位器chip prober 芯片探测器chip processing 芯片处理chip profile 芯片剖面chip real estate 芯片有效面积chip resistor 片状电阻器chip set 芯片组chip set processor 多片处理机chip to header bond 芯片管座焊接chip trimming 片状电阻蝶chmos 互补高性能金属氧化物半导体结构choke 扼力choke coupling 扼力耦合choke joint 扼凉缘接头choke piston 扼令塞choked flange 阻波凸缝cholesteric liquid crystal 胆甾醇结构液晶chopped pulse 缩短脉冲chroma 色度chroma control 彩色强度蝶器chroma key 色度键chromatic aberration 色差chromatic channel 色度通道chromatron 彩色显象管chrome mask 铬掩模chrome master 铬掩模原版chrome photomask 铬掩模chrome plate 铬掩模chrominance 色度chrominance band 色度频带chrominance carrier reference 彩色载波基准频率chrominance channel 色度通道chrominance demodulation 色度信号解调chrominance demodulator 色度解调chrominance modulator 色度信号灯器chrominance signal 色度信号chrominance subcarrier 色度副载波chrominance subcarrier generator 色度副载波发生器chrominance synchronisation 彩色同步chromoscope 彩色显象管chronopotentiogram 测时电位图chronopotentiometry 计时电位测量法chronoscope 计时表cigfet 互补隔离栅场效应晶体管cil 电立入逻辑cipher 密码cipher mask 数码消隐ciphering 译成密码ciphony 密码电话circuit 电路circuit analysis 电路分析circuit closing connection 闭路接法circuit closing device 接通装置circuit component 电路元件circuit density 电路装配密度circuit design 电路设计circuit diagram 电路图circuit element 线路元件circuit engineering 电路技术circuit functional checkout 电路功能检查circuit interconnect pattern 电路互连图案circuit layout 电路布置图circuit orbit 圆形轨道circuit polarizer 圆偏振器circuit requirements 电路技术条件circuit simulation 电路模拟circuit switching 通道转换circuit technique 电路技术circuitry 电路图circular cavity 圆形空腔谐振器circular cross section 圆形截面circular guide 圆导轨circular polarization 圆偏振circular polarized wave 圆极化波circular ring laser 环形激光器circular scanning 圆扫描circular sweep 圆扫描circular waveguide 圆形波异管circularly polarized light 圆偏振光circularly polarized wave 圆极化波circulating beam 环柳circulating gas laser 循环式气体激光器circulating liquide laser 循环式液体激光器circulator 循环器circulator switch 循环平开关city exchange 市内电话交换局cl 闭合环路clad layer 镀层clad optical fiber 涂层光学纤维cladding 电镀cladding thickness 覆盖厚度clamp amplifier 箝位放大器clamp diode 箝位二极管clamp on 得等待clamp pulse 箝位脉冲clamping 电平固定clamping circuit 箝位电路clamping diode 箝压二极管class 100 clean environment 100级洁净环境class 100 clean room 100级洁净室class a amplifier a类放大器class a modulation 甲类灯class a modulator 甲类灯器class a operation a类运用class ab amplifier ab类放大器甲乙类放大器class ab operation ab类运用class b amplifier b类放大器class b modulation 乙类灯class b modulator 乙类灯器class b operation b类运用class c operation c类运用class d amplifier d类放大器classfication 分类classifier 分类机clean area 净化室clean audit 洁净度检测clean bench 洁净台clean machine 清洗装置clean room 净化室clean room compatibility 洁净室适合性clean room environment 洁净室环境clean room garment 洁净室工clean workstation 洁净工拙cleaner 清洗装置cleaning 清洗cleaning boat 清洗小舟cleanup 清洗clear back signal 话终信号clearing relay 话终继电器clearing signal 话终信号cleat 夹板cleavage 解理click filter 喀呖声滤波器clipper 限幅器clipper amplifier 限幅放大器clipper circuit 限制器限幅器;限幅器熄电路clipper diode 限幅二极管clipper tube 熄管clipping 限幅clipping level 限幅电平clock frequency 时钟频率clock pulse rate 时钟频率clock pulse source 时钟脉冲源clock rate 时钟频率close packed lattice 密集晶格close packing 密堆积closed circuit 闭合电路closed circuit cooling 闭路冷却closed circuit television 闭路电视closed cycle 闭合环路closed loop 闭合环路closed shell 闭合壳层closed tube diffusion 闭管扩散closed tube oxidation diffusion system 闭管氧化扩散系统clover leaf aerial 苜蓿叶形天线clover leaf antenna 苜蓿叶形天线clutter 杂乱回波clutter noise 杂波噪声clutter reflections 地物反射cmis 互补型金属绝缘体半导体结构cml 电联关逻辑cml gate cml门电路cmos cmos结构cmos integrated circuit cmos集成电路cmos latchup cmos结构的闭锁cmos on sapphire 蓝宝石上互补金属氧化物半导体cmos on sapphire microprocessor 蓝宝石上互补金属氧化物半导体微处理机cmos on sapphire process 蓝宝石上互补金属氧化物半导体工艺cmos process cmos工艺cmosic cmos集成电路cmr 共横抑制cmrr 共模抑制比cmv 共模电压co channel interference 同波道干扰;同频道干扰co diffusion 同时扩散co3laser communication 二氧化碳激光通信coal microphone 炭精送话器coarse alignment 粗对准coarse tuning 粗调平直党coast station 海岸台coastal refraction 海岸折射coastal transmitter 海岸发射机coated optical fiber 涂层光学纤维coater 涂料器coating 覆盖coating composition 涂层成分coating striation 涂层条纹coaxial antenna 同轴天线coaxial attenuator 同轴衰减器coaxial cable 同轴电缆coaxial cavity 同轴空腔谐振器coaxial connector 同轴连接器coaxial filter 同轴滤波器coaxial line 同轴线coaxial line resonator 同轴线谐振器coaxial phase shifter 同轴移相器coaxial probe 同轴探针coaxial resonator 同轴谐振器coaxial short 同轴短路coaxial stub 同轴短线coaxial switch 同轴转换开关coaxial to waveguide transducer 同轴线波导管匹配变换器coaxial transmission line 同轴传输线coaxial tuner 同轴典器cockcroft walton accelerator 科克罗夫特沃尔顿加速器codan 载频控制的干扰抑制器code 符号code book 电码本code chip 代码单元code dictionary 电码本code division multiple access 分码多址访问code element 代码单元code message 编码信息code selector 选码器code signal 编码信号code translation 译码code unit 代码单元codec 编码译码器coded hologram 编码全息照相coded signal 编码信号coder 编码器coder decoder 编码译码器coding 编码coefficient of feedback 反馈系数coefficient of transparency 透玫数coevaporation 同时蒸发coherence measurement 相干性测量coherent acceleration 相干加速coherent amplification 相干放大coherent detector 相参检波器相干检波器coherent light 相干光线coherent light flux 相干光通量coherent light holography 相干光全息术coherent optical radiation 相干光辐射coherent optics 相干光学coherent oscillation of particles 粒子束相干振荡coherent pulse radar 相干脉冲雷达coherent radar 相干雷达coherent radiation 相干辐射coherent reception 相干接收coherent scattering 相干散射coherent scattering cross section 相干散射截面coherent signal 相干信号coherent sychrotron radiation 相干同步加速气射coherer 粉末检波器coil 绕纽coil aerial 环形天线coil antenna 环形天线coil getter 螺旋管吸气剂coin box 投币箱coin telephone 投币式公用电话coincidence analyzer 重合分析器coincidence circuit 重合电路coincidence gate 与电路coincident current selection 电霖合法cold carrier 冷载劣cold cathode 冷阴极cold cathode gaseous laser 冷阴极气体激光器cold cathode ionization gauge 冷阴极电离真空计cold cathode lamp 冷阴极管cold cathode thratron 冷阴极闸淋cold cathode tube 冷阴板电子管cold cathode valve 冷阴极管cold crucible technology 冷坩埚技术cold forming 冷模压cold measurement 冷测定cold processing technique 冷加工技术cold trap chiller 冷捕集器cold weld 冷焊collection efficiency 收集效率collective line 共用线collector 集电极collector base capacitance 集电极基极电容collector base diode 集电极基极二极管collector breakdown 集电极哗collector capacitance 集电极基极电容collector characteristic 集电极特性collector circuit 集电极电路collector current 集电极电流collector diffusion 集电极扩散collector diffusion isolation 集电极扩散隔离collector diffusion isolation technique 集电极扩散隔离技术collector electrode 集电极collector junction 集电极结collector junction capacitance 集电极结电容collector mask 集电极掩膜collector potential 集电极电位collector resistance 集电极电阻collector to base capacitance 集电极基极电容collector to base conductance 集电极基极电导collector to emitter conductance 集电极发射极电导collimation 视准collimator 准直仪collinear array 直排天线阵collision 碰撞collision broadening 碰撞展宽collision course indicator 航向防撞指示器collision cross section 碰撞横截面collision detection 冲突检出collision excitation 碰撞激发collision ionization 碰撞电离collision loss 碰撞损失collision number 碰撞数collisional heating 碰撞发热color balance 彩色平衡color balance control panel 彩色平衡控制盘color bar 彩条color bar generator 彩条信号发生器color bar signal 彩条信号color bar test pattern 彩条测试图color brilliance 彩色亮度color cathode ray tube 彩色阴极射线管color center formation 色中心形成color channel 彩色通路color coder 彩色编码器color contamination 彩色混杂color contrast 彩色对比度color control 色彩蝶color converter 彩色图象变换器color decoder 彩色信号解码器color difference information 色差信息color difference signal 色差信号color display device 彩色显示器color dividing electrode 彩色分离电极color dividing mask 彩色分离掩膜color flicker 彩色闪烁color hologram 彩色全息照相color holography 彩色全息照相术color image 彩色图象color image separation 彩色图象分离color information 彩色信息color killer 消色器color kinescope 彩色显象管color lock 彩色同步color matrix 彩色矩阵color modulator 彩色灯器color monitor 彩色监视器color noise 彩色信号杂波color overload 色过饱和color pattern 彩色测试图color pattern generator 彩色图样信号发生器color phase 彩色相位color pickup tube 彩色显象管color picture screen 彩色电视荧光屏color picture signal 彩色图象信号color picture tube 彩色显象管color picture tube of 110 110偏转角彩色显象管color primaries 基色color purity adjustment 色纯度蝶color purity coil 色纯度控制线圈color purity ring 色纯度蝶环color receiver 彩色电视接收机color reference signal 彩色基准信号color resolution 彩色分解力color stripe filter 彩条滤色器color subcarrier lock 彩色副载波锁相color synchronizing 彩色同步color television 彩色电视color television picture tube 彩色显象管color television receiver 彩色电视接收机color test signal 彩色测试信号color tv tube 彩色显象管colorimetry 比色法colour breakup 色乱colour centre 彩色中心colour matching 配色colour picture tube 彩色显象管colour sensation 色感觉colour sensitivity 感色灵敏度colpitts oscillator 考毕兹振荡器comb filter 梳形滤波器comb line 梳形线comb structure 梳状结构combination connector 通用终接机combination frequencies 组合频率combinational logic function 组合逻辑函数combined aerial 共用天线combiner amplifier 组合放大器command 命令common aerial 共用天线common base connection 共基极连接common cathode 共阴极common collector connection 共集电极连接common drain amplifier 源输出放大器common emitter connection 共发射极连接common mode rejection 共横抑制common mode rejection ratio 共模抑制比common mode voltage 共模电压communication 通信communication band 通信频带communication cable 通信电缆communication channel 通信信道communication engineering 通信工程学communication line 通信线路communication network 通信网络communication protocol 通信协议communication range 通信范围communication satellite 通信卫星communication satellite net 通信卫星系统communication security 通信保密communication system 通信系统community antenna 共用天线community television 集体电视commutation 换向commutation system 交换系统compact laser 小型激光器compaction 数据压缩compander 压伸器companding 压缩扩展comparator bridge 比较电桥compatibility 互换性compatible color television 兼容彩色电视compatible integrated circuit 兼容集成电路compensated impurity 补偿杂质compensated semiconductor 补偿半导体compensated video amplifier 视频补偿放大器compensating circuit 补偿电路compensating signals 补偿信号compensation 补偿compensation factor 补偿因数compensator bridge 补偿电桥complementary high performance mos 互补高性能金属氧化物半导体结构complementary insulated gate fet 互补隔离栅场效应晶体管complementary integrated circuit 互补集成电路complementary metal insulator semiconductor 互补型金属绝缘体半导体结构complementary mnos 互补金属氮化物氧化物半导体complementary mos cmos结构complementary transistor 互补晶体管complementary transistor logic 互补晶体管逻辑complementary ttl 互补晶体管晶体管逻辑电路complementary wavelength 互补色波长complete inversion 全反转completely reflecting mirror 全反射镜compliant lead 易弯曲的引线component 成分component density 元件密度component inserter 元件插入装置component integration 元件集成化component interconnect 元件间相互连接component layout 元件布置component manufacturing machinery 元件制造设备component mounting 元件装配component part 电路部件component reliability 元件可靠性composite board 复合板composite color signal 复合色信号composite gate 复合门composite gate mos structure 复合栅金属氧化物半导体结构composite layer 复合层composite material 合成材料composite picture signal 复合图象信号composite set 报话复合器composite substrate 复合衬底composite sync generator 复合同步信号发生器composite sync signal 复合同步信号composite transistor 复合晶体管composite wafer 多层薄片composition 成分compound 复合物compound glass 复合玻璃compound integration 多芯片集成电路compound semiconductor 化合物半导体compound semiconductor body 化合物半导体衬底compound semiconductor device 化合物半导体掐compound semiconductor interface 化合物半导体界面compound signal 复合信号compression 数据压缩compression system 压缩系统compressional heating 压缩加热compressor 压缩机computer 计算机computer aided customization 计算机辅助专用集成电路设计computer aided design 计算机辅助设计computer aided design facilities 计算机辅助设计工具computer aided design library 计算机辅助设计程序库computer aided design system 计算机辅助设计系统computer aided drafting 计算机辅助制图computer aided mask preparation 计算机辅助掩模制备computer conferencing 计算机会仪computer controlled laser 计算机控制激光器computer generated artwork 计算机生成原图computer hologram 计算机全息图computer mail 电子函政computer simulation 计算机模拟computer to computer communication 计算机间通信computerized design technique 计算机辅助设计技术computing machine 计算机computing technique 计算技术computor aided drawing 计算机辅助制图computor assisted design 计算机辅助设计concentration 浓度concentration gradient 浓度梯度concentration level 浓度级concentration profile 浓度分布曲线concentration ratio 浓度比率concentrator 集线器集中器condensation 数据压缩condensation nucleus 凝聚核condenser antenna 电容性天线condenser circuit 电容歧路condenser lens 聚束透镜condenser microphone 电容式话筒condenser transmitter 电容式话筒condenser voltage 电容歧压conditioned air 第的空气conductance 电导conductance band 导带conducting channel 导电沟道conducting film 导电膜conduction 导电conduction band 导带conduction electron density 导电电子密度conduction type 导电型conductive adhesive 导电粘合剂conductive coating 导电涂层conductive crossover 导线交叉conductive pattern 导电图conductivity 电导率conductivity modulation 电导率灯conductor 导线conductor insulator semiconductor fet 金属绝缘体半导体场效应晶体管conductor layer 导体层conductor paste 导体胶conductor paste system 导体膏系统conductor pattern 导线分布图conductor to hole spacing 导体孔间隔cone antenna 锥形天线configuration 配置confocal resonator 共焦谐振器congestion 超负荷conical horn 圆锥形喇叭conical resonator 圆锥形谐振器conical scanning 圆锥形扫描connecting device 连接装置connecting plug 塞子connection 连接connection diagram 接线图connection error 连接错误connection plug 塞子connection release 保险装置connection route 连接通路connector 插接器插头座constant current modulation 定疗constant current source 恒链constant luminance 恒定亮度constant voltage modulation 定压灯construction 结构contact annealing 接触式退火contact area 接触面积contact device 接触装置contact diffusion 电极孔形成扩散contact drop 接触电位差contact exposure 密接曝光contact gap 接触间隙contact hole 接触窗口contact hole opening 开接触孔contact lithography 接触光蚀刻contact mask printer 接触式掩模复制器contact opening 接触窗口contact pad 接触点contact photolithography 接触光蚀刻contact potential 接触电势contact potential barrier 接触势垒contact potential difference 接触电位差contact region 接触面积contact resistance 接触电阻contact scribing 接触式划片contact socket 接触座contact window 接触窗口contactless lithography 无接触光蚀刻contactless scribing 无接触划片contaminant 沾染物质contaminant free film 无沾污膜contamination 沾染物质continental code 国际电码continuous laser 连续工驻光器continuous layer 连续层continuous pump 连续激励continuous tuner 连续党器continuous wave doppler radar 连续波多普勒雷达continuous wave irradiation 连续波辐照continuous wave laser 连续波激光器continuous wave laser operation 连续波激光操作continuous wave mode 连续波运行continuous wave operation 连续波运行continuous wave radar 连续波雷达continuously operating laser 连续工驻光器continuously pumped laser 连续激励激光器continuously tunable laser 可连续党激光器contrast 对比contrast control 对比度第contrast control device 对比度第装置contrast dynamic range 对比度动态范围contrast range 对比度范围contrast ratio 对比度系数contrast threshold 对比阈control 控制control channel 控制信道control characteristic 控制特性control circuit 控制电路control circuit apparatus 控制电器control device 控制装置control diffusion 受控扩散control electrode 控制电极control gate 控制栅control grid 控制栅control of horizontal synchronization 行同步控制control of vertical synchronizing 场同步控制control track 控制声道control voltage 控制电压controlled atmosphere furnace 可控气氛炉controlled diode 控制二极管controlled junction depth 受控结深度controlled switch 受控开关controller 控制器第器;控制器convergence 会聚convergence circuit 会聚电路conversation 通话conversational mode 对话方式conversion 变换conversion efficiency 转换效率conversion integrated circuit 变换集成电路conversion loss 变换损耗converter 变换器converter tube 变换管conveyor dryer 传送带式干燥机coolant 冷却剂coolant fluid 冷却剂铃cooled photodetector 冷却式光电探测器cooler 冷却器cooling 冷却cooling circuit 冷却回路cooling fin 散热片cooling fluid 冷却液cooling jacket 冷却夹套cooling rate 冷却速率cooling system 冷却系统cooling water 冷却水cooling water circulation 冷水环流coordinate plotter 坐标绘图机coordinate sensitive photodetector 坐标敏感光电检测器coordinate table 坐标工专coordinatograph 坐标绘图机coplanar electrodes 共平面电极copper 铜copper clad laminate 敷铜箔叠层板copper filled adhesive 填铜粘合剂copper plated base material 镀铜的基体材料copying 复制cord circuit 塞绳电路cord circuit repeater 塞绳增音机cordless switchboard 无塞绳交换机core 磁心core logic 磁心逻辑coring 晶内偏析corner 弯曲软波导corner antenna 角反射旗线corner cube 角形反射器corner reflector 角形反射器corona 电晕放电corona discharge 电晕放电correcting amplifier 校正放大器correcting lens 校正透镜correcting signal 校正信号correction 校正correction of distortion 失真校正correction of phase 相位校正correction time 校正时间corrector circuit 校正电路corrosion 腐蚀corrosion stability 腐蚀稳定性corrugated mask 多孔障板。

电路交换和分组交换（Circuitswitchingandpacketswitching）

电路交换和分组交换（Circuit switching and packet switching）Circuit switching and packet switchingCircuit switching technology is rarely used in data service networks, mainly because of the low efficiency and reliability of its resource utilization. Packet switching technology improves the efficiency of resource utilization by means of statistical multiplexing. Moreover, when line faults occur, packet switching technology can improve reliability by re routing retransmission. But the reality is that many of the line resources due to the lack of exchange ability is not used, the utilization rate of line resource use is often less than ten percent a year on average, the router downtime is less than 5 seconds, the probability of failure is very small. Therefore, the reasons for today's choice of switching technology do not make sense.On the other hand, packet switching is non connection oriented, and has inherent defects for some real-time transactions. Although there are a series of mitigation measures, such as resource reservation, it is not enough to solve the fundamental problem. Therefore, these business QoS problems are more complex. While circuit switching technology is connection oriented, it is suitable for real-time business, and its QoS problem is much simpler. At the same time, compared with packet switching technology, circuit switching technology is simple, inexpensive and easy to implement with hardware. And because it does not require buffers, and optical buffer technology seems to be far away, so it is easier to integrate with optical technology. Of course, the problem of traffic granularity mismatch between users of circuit switching technology and WDMis still to be solved. If you leave the existing facilities from scratch, it is believed that the possibility of choosing circuit switching technology is much greater. Here is an example that compares circuit switching techniques with packet switching techniques. Suppose a server connects with 100 users via a 1Mbit/s link, and the result is shown in table 1.Table 1 connection result table for 1Mbit/s link with 100 users:Circuit switched packet switchingBandwidth 1Mbit/s 10Kbit/sThe mean delay is 50s 100sThe maximum delay is 100s 100sCircuit switchingEach telephone is connected to the switch, and the switch uses the exchange method so that telephone users can communicate conveniently. Over the past more than 100 years, telephone switches have been switched over and over again, but circuit switching has always been the mode of exchange. When the number of telephones increases, the switches connected with each other are used to complete the exchange of the whole network. Note that this kind of switch uses circuit switching, and later packet switching uses the same telecommunications network, but different types of switches (of course, protocols are different).From the point of view of the distribution of communication resources, "switching" means dynamically allocating the resources of the transmission lines in some way.Before using the circuit switched call, dial the number to establish a connection: when dialing signaling through many switches to the called user connected to the switch, the switch to the telephone ringing of the user; the called user off hook and hook signals sent back to the calling user switches connected after the call is completed, then from the end to the caller on the establishment of a called terminal connection. Call process. After the call has been hung up, the hang up signaling tells these switches that the switch releases the physical path. This must be done through the three steps of "connection, communication, release, connection", called connection oriented. Circuit switching must be connection oriented.User to switch between called user line, dedicated to telephone users. Many users sharing between switches, called a relay line, with a large number of words, a word is on the phone users only take the road, all the time in the call, the two user calls always occupied fixed end to end transmission bandwidth.The mode of exchange for the purpose of circuit connection is circuit switching. In telephone networks, circuit switching is adopted. We can make a phone call to experience this mode of exchange. When you make a phone call, first pick up your phone and dial. After dialing, the switch will know who to talk to and who will establish the connection. When one party hangs up, the switch disconnects the lines,Get ready for each other to start a new call. Therefore, we can understand that the action of circuit switching is to establish (link) circuit in communication, and to remove (disconnect) circuit when communication is complete. As for communication, the contents of both sides are not related to the switching system.For example, suppose we have A, B, two cities, each city has a switch, and there are one thousand users, and two switches are connected by 100 trunks. So, if we say, "build a circuit between two users in A city", we mean connecting two user lines through the switches of A city. But when we say: set up a circuit between a user and a user of the B city of A, we refer to is by the subscriber line in A city by city of A connected to the switch between A and B, a trunk line, in the city of B switches connected to the subscriber line in B City the. Because of economic reasons, the relay lines are always much less than the subscriber lines and are shared by all users. Then, when we occupy a relay line, even if we do not transmit information, others can not use it, which is the most important drawback of circuit switching.In telephone communications, because the two sides of the speech are always talking and one is listening, the circuit idle time accounts for about 50%.What mechanism does the first generation of computer networks use?Circuit switchingCircuit switching is the process of communication to maintain the actual electronic circuit (physical circuit), after the establishment of this electronic circuit, the user always accounts forFixed transmission bandwidth from sender to receiverWhat are the disadvantages of the circuit switching mechanism?According to the principle of circuit switching, circuit switching will take up fixed bandwidth, which limits the traffic and the number of connections on the networkCircuit switching is often compared to packet switching. The main difference is that the communication lines of packet switching are not dedicated to the transmission of information between source and destination. The use of circuit switching is an ideal choice when data are required to be transmitted in sequence and at a constant rate. Therefore, when a real-time data is transmitted, such as audio and video, or when the quality of service (QOS) requirement is high, a circuit switched network is usually used. Packet switching is more efficient in data transmission, preventing delays and jitter in transport processes such as e-mail information and Web pagesPacket switching technology is in the development of computer technology to a certain extent, people in addition to direct telephone communication, through the realization of communication between computer and computer and computer terminal in the transmission line, the quality is not high, thenetwork technology is a single case, a switching technology came into being.Packet switching, also called packet switching, divides the data transmitted by the user into a certain length, each of which is called a packet. In front of each packet and a packet header, to indicate that the packet sent to any address, followed by the address of the packet switch according to each sign, they will be forwarded to the destination, a process called packet switching. Packet switched communications networks are called packet switched networks. In the light of the history of switching technology, data exchange has undergone the development of circuit switching, message switching, packet switching and integrated services digital exchange. Packet switching is essentially developed on the basis of store and forward. It has the advantages of circuit switching and message switching. Packet switching on-line adopts dynamic multiplexing technology to transfer data into many small segments according to a certain length. After each grouping is identified, a dynamic multiplexing technique is used on a physical line to deliver multiple data packets simultaneously. The data originating from the user is temporarily stored in the memory of the switch, and then forwarded in the network. At the receiving end, the packet header is removed, and the data fields are reassembled in sequence into full packets. Compared with circuit switching, packet switching has higher utilization ratio, less transmission delay and better interaction.In packet switching mode,Because packet switching can be carried out in packet mode, it is easy to implement inter - terminal communication at different rates and different procedures after switching processing. Packet switching is mainly characterized by:* the utilization of the line is high: packet switching carries out multiplexing of channels in the form of virtual circuits, realizes resource sharing, provides multiple logical channels on a physical line, and greatly improves the utilization of the line. Significantly reduce transmission costs.* different terminal can communicate with each other: the packet network provides the standard interface to the users in the X.25 protocol, the data packet in the network as a unit to store and forward, so that different rate of terminal protocol conversion function devices of different protocols are provided through network to achieve mutual communication.* the reliability of information transmission is high. When each packet is transmitted in the network, it uses the function of error check and retransmission between the node switches so that the bit error rate transmitted in the network is greatly reduced. Moreover, when the network fails, the routing mechanism in the network will automatically select a new route for the packet to avoid the point of failure and will not cause communication interruption.* packet multiplex communication: since each packet contains control information, a packet terminal can communicate with several user terminals at the same time, and send the same information to different users.* billing has nothing to do with transmission distance: network billing is long on time, information is charged, and it has nothing to do with the transmission distance. It is especially suitable for users who are not real-time and have little traffic.Packet switching network structure is usually composed of packet switching, network management center, remote concentrator, sub assembly and disassembly equipment, packet terminal / non packet terminal and transmission line and other basic equipment. Packet switching function:Provide basic services of the network: switching virtual circuits and permanent virtual circuits and other supplementary services, such as closed and user groups, network user identification, etc.. When communicating between end - to - end computers, routing and traffic control are performed. Can provide a variety of communication procedures, data forwarding, maintenance operations, fault diagnosis, billing and some network statistics.There is a user access mode:Dial-up network access: users use X.28 or X.32 procedures, and use a modem through a public telephone network (PSTN) to connect to a packet switched network.Private line users can rent telephone analog lines or digital data lines and adopt X.28 or X.25 rules. Easy access to CHINAPAC. CHINAPAC provides two basic business functions to users:Switched virtual circuit - a temporary logical connection between two users.Permanent virtual circuit - a permanent logical connection between two users. Once the user has turned on the machine, a permanent virtual circuit is automatically established.There is no link between the two host computers as a unique circuit connection. The source host will group the whole message one by one, while each of the host messages will be grouped togetherEach packet adds sufficient protocol information to enable them to be routed to the correct target hostWhat are the advantages of packet switching versus circuit switching?The messages sent by the packets do not take up fixed bandwidth and allow more connections to be built on the line。

10-Circuit-Packet

Physical Link Packet
X.25 - Physical
interface between station node link two ends are distinct
Data Terminal Equipment DTE (user equipment) Data Circuit-terminating Equipment DCE Circuit(node)
call control carried in separate logical connection multiplexing and switching at layer 2 no hop by hop error or flow control hence end to end flow and error control (if used) are done by higher layer
Data and Computer Communications
Chapter 10 – Circuit Switching and Packet Switching
Eighth Edition by William Stallings
Circuit Switching and Packet Switching
nonnon-blocking network
permits all stations to connect at once used for some data connections
Space Division Switch
3 Stage Space Division Switch
Time Division Switching
modern digital systems use intelligent control of space & time division elements use digital time division techniques to set up and maintain virtual circuits partition low speed bit stream into pieces that share higher speed stream individual pieces manipulated by control logic to flow from input to output

电子信息类专业英语(第三版)李白萍章 (11)

Unit11 Modern Switching Technique
Unit11 Modern Switching Technique
PassageA The Principles of Digital Switching PassageB Circuit Switching and Packet Switching PassageC ATM
Unit11 Modern Switching Technique
· Multiplexer (MUX). Multiplexer performs the multiplexing of the first order PCM signal. In the case of NEAX61, from the primary multiplexer (PMUX) 120 channels are obtained and from the secondary multiplexer (SMUX) 480 channels are obtained. The primary demultiplexer (PDMUX) and the secondary demultiplexer (SDMUX) perform the opposite operations.
Unit11 Modern Switching Technique
· Central Processor Subsystem. This subsystem performs by stored program control the digit analysis, the control of the speech path for the establishment of a call, the control of the Man-Machine interface, etc.

STM32固件库使用手册的中文翻译版

该固态函数库通过校验所有库函数的输入值来实现实时错误检测。该动态校验提高了软件的鲁棒性。实时检测适合于用户应用程序的开发和调试。但这会增加了成本，可以在最终应用程序代码中移去，以。
因为该固件库是通用的，并且包括了所有外设的功能，所以应用程序代码的大小和执行速度可能不是最优的。对大多数应用程序来说，用户可以直接使用之，对于那些在代码大小和执行速度方面有严格要求的应用程序，该固件库驱动程序可以作为如何设置外设的一份参考资料，根据实际需求对其进行调整。
1.3.1 变量 ................................................................................................................................................ 28 1.3.2 布尔型 ............................................................................................................................................ 28 1.3.3 标志位状态类型 ........................................................................................................................... 29 1.3.4 功能状态类型 .............................................................................................................

复习题chapter1

计网作业1

Chapter I说明：括弧中红色标号为课本中对应的习题号（R-Review Questions, P-Problems）1.1，1.2节后的作业：1.(R1)What is the difference between a host and an end system? List the types of endsystems. Is a Web server an end system?Answer: There is no difference between a host and an end system.Type: PCs, workstations, Web servers, mail servers, Internet-connected PDAs, WebTVs, cellphone2.(R3)What is a client program? What is a server program? Does a server programrequest and receive services from a client program?Answer:3.(R4)List six access technologies. Classify each one as residential access, company access,or mobile access.Answer: (1)residential access :dial-up modem, DSL, HFC(2) company access :100 Mbps switched Enternet(3) mobile access :wireless LAN, cellular telephony4.(R8)Dial-up modems, HFC, and DSL are all used for residential access. For each of theseaccess technologies, provide a range of transmission rates and comment on whether the transmission rate is shared or dedicated.Answer:Dial-up modems :up to 56kbps direct access to router(often less),is dedicated.HFC : 30Mbps downstream ,is shared.DSL :up to 8Mbps downstream, is dedicated .5.(R10)Describe the most popular wireless Internet access technologies today. Compareand contrast them.Answer : There are two most popular wireless Internet access technologies today:a.Wireless LANIn a wireless LAN, wireless users transmit/receive packets to/from a base station (wireless access point) within a radius of a few ten s of meters. The base station is connected to the wired Internet and thus serves to connect wireless users to the wired network.b.wide-area wireless access networkpackets are transmitted over the same wireless infrastructure used for cellular telephony ,with the base station thus being managed by a telecommunications provider .This provides wireless access to users within a radius of tens of kilometers of the base station.6.删除1.3，1.4节后的作业：7.(R16)Consider sending a packet from a source host to a destination host over a fixedroute. List the delay components in the end-to-end delay. Which of these delays are constant and which are variable?Answer :The delay components are processing delays, transmission delays, propagation delays and queuing delays. All of these delays are fixed ,except for the queuing delays.8.(P2)Consider the circuit-switched network in Figure 1.8. Recall that there are n circuiton each link.A. What is the maximum numberof simultaneous connections that can bein progress at any one time in thisnetwork?B. Suppose that all connections arebetween the switch in theupper-left-hand corner and switch inthe lower-right-hand corner. What isthe maximum number of simultaneousthat can be in progress?Answer:A.there are n connectionsbetween each of the four pairsof adjacent switches. Thusgives a maximum of 4n connections.B.We can n connections passing through the switch in the upper-right handcorner and another n connections passing through the switch in the lower-left –hand corner ,giving a total of 2n connections.9.(P7)Suppose user share a 1Mbps link. Also suppose each user require 100 kbps whentransmitting, but each user transmits only 10 percent of the time. (See the discussion of statistical multiplexing in Section 1.3.)A. When circuit switching is used, how many users can be supported?B. For the remainder of this problem, suppose packet switching is used. Find the probability that a given user is transmitting.C. Suppose there are 40 users. Find the probability that at any given time, exactly n users are transmitting simultaneously. (Hint: Use the binomial distribution)D. Find the probability that there are 11 or more users transmitting simultaneously. Answer:A.10 users are supported.B.P = 0.1C.P(n users are transmitting simultaneously)=(0.1)^n*(1-0.1)^(40-n)D.P(11 or more users)==1-10.(P5)This elementary problem begins to explore propagation delay and transmissiondelay, two central concepts in data networking. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m meters, and suppose the propagation speed along the link is s meter/sec. Host A is send a packet of size L bits to Host B.a.Express the propagation delay, dprop, in term of m and s.dprop=m/s secondsb.Determine the transmission time of the packet, dtrans, in terms of L and R.dtrans=L/R secondsc.Ignoring processing and queuing delays, obtain an expression for end-to-end delay.=(m/s + L/R) secondsd.Suppose Host A begins to transmit the packet at time t=0. At time t=dtrans, where is the last bit of the packet?The bit is just leaving host A.e.Suppose dprop is greater than dtrans. At time t=dtrans, where is the first bit of thepacket?The first bit is in the link and has not reached host B.f.Suppose dprop is less than dtrans. At time t=dtrans, where is the first bit of the packet?The first bit has reached host B.g.Suppose s=2.5·108, L=100 bits, and R=28 kbps. Find the distance m so thatdprop equals dtrans.m = LS/R=100*(2.5*10^8)/28*10^3=893km11.(P13)Consider the queuing delay in a router buffer (preceding an outbound link.)Suppose all packets are L bits, the transmission rate is R bps, and that N packets simultaneously arrive at the buffer every LN/R seconds. Find the average queuing delay of a packet. (Hint: The queuing delay for the first packet is zero; for the second packet L/R; for the third packet 2L/R. The Nth packet has already been transmitted when the second batch of packet arrives.)It takes LN/R seconds to transmit the N packets .Thus ,the buffer is empty when a batch of N packets arrive.The first of the N packets has no queuing delay.The 2nd pachet has a queuing delay of L/Rseconds. The nth packet has a delay of (n-1)L/R seconds.The average delay is===12.(P18)Suppose two hosts, A and B, are separated by 10,000 kilometers and are connectedby a direct link of R=2 Mbps. Suppose the propagation speed over the link is 2.5·108 meters/sec..A.Calculate the bandwidth-delay product, R·dprop40000 bitsB.Consider sending a file of 400,000 bits from Host A to Host B. Suppose the file sentcontinuously as a large message. What is the maximum number of bits that will be in the link at any given time?40000 bitsC.Provide an interpretation of the bandwidth-delay product.The bandwidth-delay product of a link is the maximum number of bits that can be in the linkD.What is the width (in meters) of a bit in the link? Is it longer than a football field?1 bit is 250 meters long, which is longer than a football fieldE.Derive a general expression for the width of a bit in terms of the propagation speed s,the transmission rate R, and the length of the link m.s/R1.5，1.6，1.7节后的作业：13.(R23)What are the five layers in the Internet protocol stack? What are the principalresponsibilities of each of these layers?The five layers in the Internet protocol stack are –from top to bottom –the application layer, the network layer ,the link layer ,and the physical layer .For example, error control is often provided at more than one layer.14.(R24)Which layers in the Internet protocol stack does a router process? Which layersdoes a link-layer switch process? Which layers does a host process?Application-layer message: data which an application wants to send and passed onto the transport layer; transport-layer segment: generated by the transport layer and encapsulates application-layer message with transport layer header; network-layer datagram: encapsulates transport-layer segment with a network-layer header; link-layer frame: encapsulates network-layer datagram with a link-layer header.15.(R25)What is an application-layer message? A transport-layer segment? A network-layerdatagram? A link-layer frame?Routers process layers 1 through 3. (This is a little bit of a white lie, as modern routers sometimes act as firewalls or caching components, and process layer four as well.) Linklayer switches process layers 1 through 2. Hosts process all five layers.16.(P22)Suppose there is a 10 Mbps microwave link between a geostationary satellite andits base station on Earth. Every minute the satellite takes a digital photo and sends it to the base station. Assume a propagation speed of 2.4·108meters/sec.a.What is the propagation delay of link?b.What is the bandwidth-delay product, R·t prop?c.Let x denote the size of the photo. What is the minimum value of x for themicrowave link to be continuously transmitting?a. 35786*10^3/2.4*10^8=150msecb.10Mbps *150ms=1500000bitsc.600000000bits17. (P24)In modern packet-switched networks, the source host segments long,application-layer messages (for example, an image or music file) into smaller packets and sends the packets into the network. The receiver then reassembles the packets back into the original message. We refer to this process as message segmentation. Figure 1.24 illustrates the end-to-end transport of a message with and without message segmentation. Consider a message is 8·106 bits long that is to be sent from source to destination in Figure 1.24. Suppose each link in the figure is 2 Mbps. Ignore propagation, queuing, and processing delays.A. Consider sending the message form source to destination without message segmentation. How long does it take to move the message from the source host to the first packet switch? Keeping in mind that each switch uses store-and-forward packet switching, what is the total time to move the message from source host to destination host?B. Now suppose that the message is segmented into 4,000 packets, with each packet being 2,000 bits long. How long does it take to move the first packet from source host to the first switch? When the first packet is being sent from the first switch to the second switch, the second packet is being sent from the source host to the first switch. At what time will the second packet be fully received at the first switch?C. How long does it take to move the file from source host to destination host when message Segmentation is used? Compare this result with your answer in part (a) and comment.D. Discuss the drawback of message segmentation.a) Time to send message from source host to first packet switch =sec 5sec 105.1105.766=⨯⨯. With store-and-forward switching, the total time to move message from source host to destination host = sec 153sec 5=⨯hopsb) Time to send 1st packet from source host to first packet switch = .sec 1sec 105.1105.163m =⨯⨯. Time at which 2nd packet is received at the first switch= time at which 1st packet is received at the second switch =sec 2sec 12m m =⨯c) Time at which 1st packet is received at the destination host = .sec 33sec 1m hops m =⨯. After this, every 1msec one packet will be received; thus time at which last (5000th ) packet is received =sec 002.5sec 1*4999sec 3=+m m . It can be seen that delay in using messagesegmentation is significantly less (almost 1/3rd ).d) Drawbacks:i. Packets have to be put in sequence at the destination.ii. Message segmentation results in many smaller packets. Sinceheader size is usually the same for all packets regardless oftheir size, with message segmentation the total amount ofheader bytes is more.18. (P26) Consider sending a large file of F bits from Host A to Host B. There are two links (and one switch) between A and B, and the links are uncongested (that is no queuing delays). Host A segments the file into segments of S bits each and adds 40 bits of header to each segment, forming packets of L=40+S bits. Each link has a transmission rate of R bps. Find the value of S that minimizes the delay of moving the file from Host A to HostB. Disregard propagation delay.Time at which the 1st packet is received at the destination =240⨯+R S sec. After this, one packet is received at destination every RS 40+sec. Thus delay in sending the whole file = )1(40)40()1(240+⨯+=+⨯-+⨯+=SF R S R S S F R S delay To calculate the value of S which leads to the minimum delay,F S R SS S R F delay dS d 4001)401(02=⇒=++-⇒=19. 单项选择题（1）在OSI 参考模型的各层次中， D 的数据传送单位是报文。

10-Circuit-Packet

In Channel Signaling（随路信令）
• Use same channel for signaling and call（使用相同的信道传输信令和呼叫信息）
— Requires no additional transmission facilities
• Inband（带内信令）
— Uses same frequencies as voice signal（和语音信号使用相同的频率） — Can go anywhere a voice signal can — Impossible to set up a call on a faulty speech path
— Estaenerally on demand（按照用户的需求建立连接） Handle and acknowledge requests（处理和响应用户的连接请求） Determine if destination is free（确定目的站是否空闲） construct path（建立通路）
Public Circuit Switched Network
Telecomms Components
• Subscriber（用户）
— Devices attached to network
• Subscriber line（用户线）
— Local Loop（本地回路） — Subscriber loop（用户回路） — Connection to network — Few km up to few tens of km
Location of Signaling
• Subscriber to network
—Depends on subscriber device and switch（取决于用户设备和交换机）

packetswitching名词解释

packetswitching名词解释Packet switching（数据包交换）是一种网络通信数据传输技术。

它将数据分割成多个较小的数据包，发送到目标地点，并通过网络的不同路径进行传输，再在目标地点重新组装成完整的数据。

1. Packet switching is the method used in computer networks to transmit data in the form of packets.数据包交换是计算机网络中传输数据的方法。

2. In packet switching, the data is divided into packetsof fixed size for transmission.在数据包交换中，数据被划分为固定大小的数据包进行传输。

3. Each packet in packet switching contains a header that includes the source and destination addresses.数据包交换中的每个数据包都包含一个头部，其中包括源地址和目标地址。

4. Unlike circuit-switching, packet switching allows multiple connections to share the same physical network links.与电路交换不同，数据包交换允许多个连接共享相同的物理网络链路。

5. Packet switching is more efficient than circuit-switching for transmitting bursty data traffic.对于传输突发性数据流量，数据包交换比电路交换更高效。

6. The Internet uses packet switching as its primary communication method.互联网使用数据包交换作为其主要通信方法。

计算机网络英文题库附答案chapter定稿版

计算机网络英文题库附答案c h a p t e r精编W O R D版IBM system office room 【A0816H-A0912AAAHH-GX8Q8-GNTHHJ8】Chapter 1 Computer Networks and the Internet 1．The ( ) is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world.ppt3A public InternetB IntranetC switch netD television net2．Which kind of media is not a guided media ( )A twisted-pair copper wireB a coaxial cableC fiber opticsD digital satellite channel3．Which kind of media is a guided media ( )A geostationary satelliteB low-altitude satelliteC fiber opticsD wireless LAN4．The units of data exchanged by a link-layer protocol are called ( ).A FramesB SegmentsC DatagramsD bit streams5．Which of the following option belongs to the circuit-switched networks ( )A FDMB TDMC VC networksD both A and B6．( )makes sure that neither side of aconnection overwhelms the other side bysending too many packets too fast.A Reliable data transferB Flow controlC Congestion controlD Handshaking procedure7．( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Store-and-forward transmissionB FDMC End-to-end connectionD TDM8．Datagram networks and virtual-circuit networks differ in that ( ).A datagram networks are circuit-switchednetworks, and virtual-circuit networks arepacket-switched networks.B datagram networks are packet-switchednetworks, and virtual-circuit networks arecircuit-switched networks.C datagram networks use destinationaddresses and virtual-circuit networks useVC. numbers to forward packets towardtheir destination.D datagram networks use VC. numbersand virtual-circuit networks use destinationaddresses to forward packets toward theirdestination.9．In the following options, which one is not a guided media ( )A twisted-pair wireB fiber opticsC coaxial cableD satellite10．Processing delay does not include the time to ( ).A examine the packet’s headerB wait to transmit the packet onto the linkC determine where to direct the packetD check bit-error in the packet11．In the following four descriptions, which one is correct ( )A The traffic intensity must be greaterthan 1.B The fraction of lost packets increases asthe traffic intensity decreases.C If the traffic intensity is close to zero,the average queuing delay will be close tozero.D If the traffic intensity is close to one, theaverage queuing delay will be close to one.12．The Internet’s network layer isresponsible for moving network-layerpackets known as ( ) from one host toanother.A frameB datagramC segmentD message13．The protocols of various layers are called ( ).A the protocol stackB TCP/IPC ISPD network protocol14．There are two classes of packet-switched networks: ( ) networks and virtual-circuitnetworks.A datagramB circuit-switchedC televisionD telephone15．Access networks can be loosely classified into three categories: residential access,company access and ( ) access.A cabledB wirelessC campusD city areaQuestion 16～17Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( 16 ), and it should no greater than ( 17 ).16．A LR／aB La／RC Ra／LD LR／a 17．A 2B 1C 0D -118．In the Internet, the equivalent concept to end systems is ( ).A hostsB serversC clientsD routers19．In the Internet, end systems are connected together by ( ).A copper wireB coaxial cableC communication linksD fiber optics20．End systems access to the Internet through its ( ).A modemsB protocolsC ISPD sockets21．End systems, packet switches, and other pieces of the Internet, run ( ) that controlthe sending and receiving of informationwithin the Internet.A programsB processesC applicationsD protocols22．There are many private networks, such as many corporate and government networks,whose hosts cannot exchange messageswith hosts outside of the private network.These private networks are often referredto as ( ).A internetsB LANC intranetsD WAN23．The internet allows ( ) running on its end systems to exchange data with each other.A clients applicationsB server applicationsC P2P applicationsD distributed applications24．The Internet provides two services to its distributed applications: a connectionlessunreliable service and () service.A flow controlB connection-oriented reliableC congestion controlD TCP25．It defines the format and the order of messages exchanged between two or morecommunicating entities, as well as theactions taken on the transmission and/orreceipt of a message or other event. Thesentence describes ( ).A InternetB protocolC intranetD network26．In the following options, which does not define in protocol ( )A the format of messages exchangedbetween two or more communicatingentitiesB the order of messages exchangedbetween two or more communicatingentitiesC the actions taken on the transmission ofa message or other eventD the transmission signals are digitalsignals or analog signals27．In the following options, which is defined in protocol ( )A the actions taken on the transmissionand/or receipt of a message or othereventB the objects exchanged between communicating entitiesC the content in the exchanged messagesD the location of the hosts28．In the following options, which does not belong to the network edge ( )A end systemsB routersC clientsD servers29．In the following options, which belongs to the network core ( )A end systemsB routersC clientsD servers30．In the following options, which is not the bundled with the Internet’s connection-oriented service( )A reliable data transferB guarantee of the transmission timeC flow controlD congestion-control31．An application can rely on the connection to deliver all of its data without error andin the proper order. The sentencedescribes ( ).A flow controlB congestion-controlC reliable data transferD connection-oriented service32．It makes sure that neither side of aconnection overwhelms the other side bysending too many packets too fast. Thesentence describes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer33．It helps prevent the Internet from enteringa state of gridlock. When a packet switchbecomes congested, its buffers canoverflow and packet loss can occur. Thesentence describes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer34．The Internet’s connection-oriented service has a name, it is ( ).A TCPB UDPC TCP/IPD IP 35．In the following options, which service does not be provided to an application by TCP( )A reliable transportB flow controlC video conferencingD congestion control36．The Internet’s connectionless service is called ( ).A TCPB UDPC TCP/IPD IP37．In the following options, which does not use TCP()A SMTPB internet telephoneC FTPD HTTP38．In the following options, which does not use UDP( )A Internet phoneB video conferencingC streaming multimediaD telnet39．There are two fundamental approaches to building a network core, ( ) and packetswitching.A electrical current switchingB circuit switchingC data switchingD message switching40．In ( ) networks, the resources needed along a path to provide forcommunication between the end systemare reserved for the duration of thecommunication session.A packet-switchedB data-switchedC circuit-switchedD message-switched41．In ( ) networks, the resources are not reserved; a session’s messages use theresources on demand, and as aconsequence, may have to wait for accessto communication link.A packet-switchedB data-switchedC circuit-switchedD message-switched42．In a circuit-switched network, if each link has n circuits, for each link used by theend-to-end connection, the connectiongets ( ) of the link’s bandwidth for theduration of the connection.A a fraction 1/nB allC 1/2D n times43．For ( ), the transmission rate of a circuit is equal to the frame rate multiplied by thenumber of bits in a slot.A CDMAB packet-switched networkC TDMD FDM 44．( ) means that the switch must receive the entire packet before it can begin totransmit the first bit of the packet onto theoutbound link.A Queuing delayB Store-and-forward transmissionC Packet lossD Propagation45．The network that forwards packetsaccording to host destination addresses iscalled ( ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram46．The network that forwards packetsaccording to virtual-circuit numbers iscalled ( ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram47．In the following entries, which is not a kind of access network()A residential accessB company accessC wireless accessD local access48．Suppose there is exactly one packet switch between a sending host and a receivinghost. The transmission rates between thesending host and the switch and betweenthe switch and the receiving host are R1and R2, respectively. Assuming that theswitch uses store-and-forward packetswitching, what is the total end-to-enddelay to send a packet of length L (Ignorequeuing delay, propagation delay, andprocessing delay.) ( )A L/R1＋L/R2B L/R1C L/R2D none of the above49．The time required to examine thepacket’s header and determine where todirect the packet is part of the ( ).A queuing delayB processing delayC propagation delayD transmission delay50．The time required to propagate from the beginning of the link to the next router is( ).A queuing delayB processing delayC propagation delayD transmission delay51．Consider sending a packet of 3000bits over a path of 5 links. Each link transmits at 1000bps. Queuing delays, propagation delay and processing delay are negligible. (6 points) (1).Suppose the network is a packet-switched virtual circuit network. VC setup time is 0.1 seconds. Suppose the sending layers add a total of 500 bits of header to each packet. How long does it take to send the file from source to destination?(2).Suppose the network is a packet-switched datagram network and a connectionless serviceis used. Now suppose each packet has 200 bitsof header. How long does it take to send the file?(3).Suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between sourceand destination is 200bps. Assuming 0.02s setuptime and 200 bits of header appended to the packet, how long does it take to send the packet?So lution:(1).t=5*(3000+500)/1000+0.1=17.6s( 2).t=5*(3000+200)/1000=16s( 3).t=(3000+200)/200+0.02=16.02s。

《computer networking》中英词汇对照表

Chapter 11.1Internet：因特网Computer network ：计算机网络Host: 主机End system: 终端系统Packet switching: 分组交换Route: 路径Internet service provider (ISP): 因特网服务提供商Protocol: 协议Transmission Control Protocol (TCP)：传输控制协议1.2Client: 客户端Server: 服务器Peer: 对等机Reliable data transfer: 可靠数据传输Flow control: 流量控制Congestion-control: 拥塞控制User Datagram Protocol (UDP): 用户数据报协议1.3Circuit switching: 电路交换/线路交换Packet switching: 分组交换Frequency-division multiplexing (FDM): 频分多路复用Time-division multiplexing (TDM): 时分多路复用Bandwidth: 带宽Time slot: 时隙Frame: 帧Message: 报文:Packet: 分组Store-and-forward: 存储转发Datagram network: 数据报网络Virtual-circuit network: 虚电路网络1.4Router: 路由器Modem: 调制解调器Local area network (LAN): 局域网Ethernet: 以太网Wireless LAN: 无线局域网Guided media: 导向型介质Unguided media: 非导向型介质Twisted-pair copper wire: 双绞线Unshielded twisted pair(UTP): 非屏蔽双绞线Coaxial cable: 同轴电缆Fiber optics: 光线/光缆1.6Nodal processing delay: 结点处理延迟Queuing delay: 排队延迟Transmission delay: 发送延迟Propagation delay: 传播延迟Traffic intensity: 流通强度End-to-end delay: 端到端延迟1.7Layer: 层次Protocol stack: 协议栈Application layer: 应用层Transport layer: 传输层Network layer: 网络层Link layer: 链路层Physical layer: 物理层Encapsulation: 封装Message: 报文Segment: 报文段Datagram: 数据报Frame: 帧Chapter 22.1Client-server architecture: 客户端－服务器体系结构；C/S结构P2P architecture: 对等结构Processes: 进程Socket: 套接字Application programming interface (API): 应用程序编程接口IP address: IP地址Prot number: 端口号Syntax: 语法Semantics: 语义Full-duplex: 全双工Handshaking: 握手Real-time application: 实时应用2.2The World Wide Web: 万维网HyperText Transfer Protocol (HTTP): 超文本传输协议Web page: 网页Object: 对象HyperText Markup Language (HTML): 超文本标记语言URL：统一资源定位符Browser: 浏览器Persistent connection: 持久连接Non-persistent connection: 非持久连接Round-trip time (RTT): 往返时间Without pipelining: 非流水线方式With pipelining: 流水线方式Web cache: web 缓存Proxy server: 代理服务器2.3File Transfer Protocol (FTP): 文件传输协议Control connection: 控制连接Data connection: 数据连接Out-of-band: 带外In-band: 带内2.4Electronic Mail: 电子邮件User agent: 用户代理Mail server: 邮件服务器Simple Mail Transfer Protocol (SMTP): 简单邮件传输协议Mailbox: 邮箱Multipurpose Internet Mail Extensions (MIME): 多用途因特网邮件扩展协议Post Office Protocol (POP): 邮局协议Internet Mail Access Protocol (IMAP): Internet 邮件访问协议2.5 Domain Name System (DNS): 域名系统Hostname: 主机名Host aliasing: 主机别名Mail server aliasing: 邮件服务器别名Load distribution: 负载分配Root DNS server: 根DNS服务器Top-Level Domain (TLD) servers: 顶级域DNS服务器Authoritative DNS servers: 授权DNS服务器；权威DNS服务器Local DNS server: 本地DNS服务器Database: 数据库Chapter 33.1Logical communication: 逻辑通讯3.2Multiplexing: 多路复用Demultiplexing: 多路分解Well-known port number: 众所周知的端口号3.3UDP segment: UDP报文段Checksum: 校验和；检查和Wrapped around: 回卷3.4Channel: 通道；信道Positive acknowledgement : 肯定应答Negative acknowledgement: 否定应答ARQ （automatic repeat request）: 自动重传请求Feedback: 反馈Retransmission: 重传Stop-and-wait protocol: 停止－等待协议Duplicate packets: 冗余分组Sequence number: 顺序号Timer: 定时器Alternating-bit protocol: 比特交替协议Utilization: 利用率Go-back-N (GBN): 回退N步Window size: 窗口大小Sliding-window protocol: 滑动窗口协议Cumulative acknowledgement: 累积确认Timeout: 超时Selective Repeat (SR): 选择重传3.5Connection-oriented: 面向连接Point-to-point: 点到点Three-way handshake: 三次握手Maximum segment size (MSS): 最大报文段大小Maximum transmission unit (MTU): 最大传输单元Piggybacked: 捎带Sample RTT: 样本RTTFast retransmit: 快速重传Selective acknowledgement: 选择确认Flow-control: 流量控制Receive window: 接收窗口3.7Congestion control: 拥塞窗口Self-clocking: 自定时的Additive-increase, multiplicative-decrease: 加性增，乘性减Slow star: 慢启动Congestion avoidance: 拥塞避免Threshold: 阈值Fast recovery: 快速恢复Bottleneck: 瓶颈Latency: 延迟Chapter 44.1Forwarding: 转发Routing: 路由Routing algorithm: 路由算法Forwarding table: 转发表Router: 路由器Jitter: 抖动Best-effort service: 尽力而为的服务4.2Virtual-circuit (VC) network: 虚电路网络Datagram network: 数据报网络Prefix: 前缀Longest prefix matching rule: 最长前缀匹配规则4.3Input port: 输入端口Switching fabric: 交换结构Routing processor: 路由处理器Crossbar: 交叉结构4.4Time-to-live (TTL) :生存时间Fragmentation: 分片；片段Dotted-decimal notation: 点分十进制表示法Subnet: 子网Subnet mask: 子网掩码Classless Interdomain Routing (CIDR): 无类别域际路由选择Dynamic Host Configuration Protocol （DHCP）：动态主机配置协议Plug-and-play: 即插即用Network address translation (NAT): 网络地址转换Internet Control Message Protocol (ICMP): 因特网控制报文协议Dual-stack: 双栈Tunneling: 隧道4.5Default router: 默认路由器Graph: 图A global routing algorithm : 全局路由算法A decentralized routing algorithm : 分布式路由算法Static routing algorithm: 静态路由算法Dynamic routing algorithm : 动态路由算法Link-State (LS): 链路状态Distance-Vector(DV): 距离向量Routing table: 路由表Autonomous system (AS): 自治系统Intra-autonomous system routing protocol: 自治系统内路由协议Inter-AS routing protocol: 自治系统间路由协议4.6Interior gateway protocol: 内部网关协议Routing Information Protocol (RIP): 路由信息协议Open Shortest Path First (OSPF): 开放最短路径优先协议Advertisement: 公告Hop: 跳Border Gateway Protocol (BGP): 边界网关协议4.7Broadcast: 广播Multicast: 多播Chapter 55.1Node: 结点Link: 链路Frame: 帧Medium access control (MAC): 介质访问控制Full-duplex: 全双工Half-duplex: 半双工Adapter: 适配器Network interface card (NIC): 网卡Interface: 接口5.2Parity check: 奇偶校验Odd: 奇数Even: 偶数Cyclic redundancy check (CRC): 循环冗余校验Polynomial: 多项式5.3Collide: 冲突Multiple access protocol: 多路访问协议Channel partitioning protocol: 信道划分协议Random access protocol: 随机访问协议Taking-turns protocol: 轮转协议Code division multiple access (CDMA): 码分多址访问Carrier sensing: 载波侦听Collision detection: 冲突检测Polling protocol: 轮询协议Token-passing protocol: 令牌传递协议Token: 令牌Local Area Network (LAN): 局域网Token-ring: 令牌环Fiber distributed data interface (FDDI): 光纤分布式数据接口Metropolitan Area Network (MAN): 城域网5.4Address Resolution Protocol (ARP): 地址解析协议Dynamic Host Configuration Protocol (DHCP): 动态主机配置协议5.5Ethernet: 以太网Preamble: 前导码Manchester encoding: 曼彻斯特编码5.6Hub: 集线器Collision domain: 冲突域Switch: 交换机Filtering: 过滤Forwarding: 转发Switch table: 交换表Self-learning: 自学习Plug-and-play devices: 即插即用设备Cut-through switching: 直通式交换5.7Point-to-point: (PPP): 点到点。

计算机网络英文题库(附答案)chapter1

Chapter 1 Computer Networks and the Internet1．The ( ) is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world.ppt3A public InternetB IntranetC switch netD television net2．Which kind of media is not a guided media? ( )A twisted-pair copper wireB a coaxial cableC fiber opticsD digital satellite channel3．Which kind of media is a guided media? ( )A geostationary satelliteB low-altitude satelliteC fiber opticsD wireless LAN4．The units of data exchanged by a link-layer protocol are called ( ).A FramesB SegmentsC DatagramsD bit streams5．Which of the following option belongs to the circuit-switched networks? ( )A FDMB TDMC VC networksD both A and B6．( )makes sure that neither side of a connection overwhelms the other side by sending too many packets too fast.A Reliable data transferB Flow controlC Congestion controlD Handshaking procedure7．( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Store-and-forward transmissionB FDMC End-to-end connectionD TDM8．Datagram networks and virtual-circuit networks differ in that ( ).A datagram networks are circuit-switched networks, andvirtual-circuit networks are packet-switched networks.B datagram networks are packet-switched networks, andvirtual-circuit networks are circuit-switched networks.C datagram networks use destination addresses and virtual-circuitnetworks use VC. numbers to forward packets toward theirdestination.D datagram networks use VC. numbers and virtual-circuit networksuse destination addresses to forward packets toward their destination. 9．In the following options, which one is not a guided media? ( )A twisted-pair wireB fiber opticsC coaxial cableD satellite10．Processing delay does not include the time to ( ).A examine the packet’s headerB wait to transmit the packet onto the linkC determine where to direct the packetD check bit-error in the packet11．In the following four descriptions, which one is correct? ( )A The traffic intensity must be greater than 1.B The fraction of lost packets increases as the traffic intensitydecreases.C If the traffic intensity is close to zero, the average queuing delaywill be close to zero.D If the traffic intensity is close to one, the average queuing delaywill be close to one.12．The Internet’s network layer is responsible for moving network-layer packets known as ( ) from one host to another.A frameB datagramC segmentD message13．The protocols of various layers are called ( ).A the protocol stackB TCP/IPC ISPD network protocol14．There are two classes of packet-switched networks: ( ) networks and virtual-circuit networks.A datagramB circuit-switchedC televisionD telephone15．Access networks can be loosely classified into three categories: residential access, company access and ( ) access.A cabledB wirelessC campusD city areaQuestion 16～17Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( 16 ), and it should no greater than ( 17 ).16． A LR／aB La／RC Ra／LD LR／a17．A 2B 1C 0D -118．In the Internet, the equivalent concept to end systems is ( ).A hostsB serversC clientsD routers19．In the Internet, end systems are connected together by ( ).A copper wireB coaxial cableC communication linksD fiber optics20．End systems access to the Internet through its ( ).A modemsB protocolsC ISPD sockets21．End systems, packet switches, and other pieces of the Internet, run ( ) that control the sending and receiving of information within theInternet.A programsB processesC applicationsD protocols22．There are many private networks, such as many corporate and government networks, whose hosts cannot exchange messages withhosts outside of the private network. These private networks are often referred to as ( ).A internetsB LANC intranetsD WAN23．The internet allows ( ) running on its end systems to exchange data with each other.A clients applicationsB server applicationsC P2P applicationsD distributed applications24．The Internet provides two services to its distributed applications: a connectionless unreliable service and () service.A flow controlB connection-oriented reliableC congestion controlD TCP25．It defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on thetransmission and/or receipt of a message or other event. The sentence describes ( ).A InternetB protocolC intranetD network26．In the following options, which does not define in protocol? ( )A the format of messages exchanged between two or morecommunicating entitiesB the order of messages exchanged between two or morecommunicating entitiesC the actions taken on the transmission of a message or other eventD the transmission signals are digital signals or analog signals模拟信号27．In the following options, which is defined in protocol? ( )A the actions taken on the transmission and/or receipt of a message orother eventB the objects exchanged between communicating entitiesC the content in the exchanged messagesD the location of the hosts28．In the following options, which does not belong to the network edge? ( )A end systemsB routersC clientsD servers29．In the following options, which belongs to the network core? ( )A end systemsB routersC clientsD servers30．In the following options, which is not the bundled with the Internet’s connection-oriented service? ( )A reliable data transferB guarantee of the transmission timeC flow controlD congestion-control31．An application can rely on the connection to deliver all of its data without error and in the proper order. The sentence describes ( ).A flow controlB congestion-controlC reliable data transferD connection-oriented service32．It makes sure that neither side of a connection overwhelms淹没压倒the other side by sending too many packets too fast. The sentencedescribes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer33．It helps prevent the Internet from entering a state of gridlock. When a packet switch becomes congested, its buffers can overflow and packet loss can occur. The sentence describes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer34．The Internet’s connection-oriented service has a name, it is ( ).A TCPB UDPC TCP/IPD IP35．In the following options, which service does not be provided to an application by TCP?( )A reliable transportB flow controlC video conferencingD congestion control36．The Internet’s connectionless service is called ( ).A TCPB UDPC TCP/IPD IP37．In the following options, which does not use TCP?( )A SMTPB internet telephoneC FTPD HTTP38．In the following options, which does not use UDP?( )A Internet phoneB video conferencingC streaming multimediaD telnet39．There are two fundamental approaches to building a network core, ( ) and packet switching.A electrical current switchingB circuit switchingC data switchingD message switching40．In ( ) networks, the resources needed along a path to provide for communication between the end system are reserved for the duration持续of the communication session.A packet-switchedB data-switchedC circuit-switchedD message-switched41．In ( ) networks, the resources are not reserved; a session’s messages use the resources on demand, and as a consequence, may have to wait for access to communication link.A packet-switchedB data-switchedC circuit-switchedD message-switched42．In a circuit-switched network, if each link has n circuits, for each link used by the end-to-end connection, the connection gets ( ) of thelink’s bandwidth for the duration of the connection.A a fraction 1/nB allC 1/2D n times43．For ( ), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot.A CDMAB packet-switched networkC TDMD FDM44．( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Queuing delayB Store-and-forward transmissionC Packet lossD Propagation45．The network that forwards packets according to host destination addresses is called ( ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram46．The network that forwards packets according to virtual-circuit numbers is called ( ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram47．In the following entries, which is not a kind of access network?( )A residential accessB company accessC wireless accessD local access48．Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2,respectively. Assuming that the switch uses store-and-forward packetswitching, what is the total end-to-end delay to send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.)( )A L/R1＋L/R2B L/R1C L/R2D none of the above49．The time required to examine the packet’s header and determine where to direct the packet is part of the ( ).A queuing delayB processing delayC propagation delayD transmission delay50．The time required to propagate from the beginning of the link to the next router is ( ).A queuing delayB processing delayC propagation delayD transmission delay51．Consider sending a packet of 3000bits over a path of 5 links. Each link transmits at 1000bps. Queuing delays, propagation delay and processing delay are negligible可以忽略的. (6 points)(1).Suppose the network is a packet-switched virtual circuit network. VC setup time is 0.1 seconds. Suppose the sending layers add a total of 500 bits of header to each packet. How long does it take to send the file from source to destination?(2).Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose each packet has 200 bits of header. How long does it take to send the file?(3).Suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between source and destination is 200bps. Assuming 0.02s setup time and 200 bits of header appended to the packet, how long does it take to send the packet?Solution: (1). t=5*(3000+500)/1 000+0.1=17.6s(2). t=5*(3000+200)/1 000=16s(3). t=(3000+200)/20 0+0.02=16.02s。

川大软院计网选择题答案Chapter1(含答案)

1.1 In the following options, which does not define in protocol? ( D )A the format of messages exchanged between two or more communicatingentitiesB the order of messages exchanged between two or more communicating entitiesC the actions taken on the transmission of a message or other eventD the transmission signals are digital signals or analog signals1.2 In the following options, which is defined in protocol? ( A )A the actions taken on the transmission and/or receipt of a message or other eventB the objects exchanged between communicating entitiesC the content in the exchanged messagesD the location of the hosts1.3 An application can rely on the connection to deliver all of its data without error and in the proper order. The sentence describes (C ).A flow controlB congestion-controlC reliable data transferD connection-oriented service1.4 The Internet’s connection-oriented service has a name, it is ( A ).A TCPB UDPC TCP/IPD IP1.5 The Internet’s connectionless service is called ( B ).A TCPB UDPC TCP/IPD IP1.6 Which of the following nodes belongs to the network core?CA. a Web ServerB. a Host with Win2003 ServerC. a Router with NAT serviceD. a Supernode on Skype Network1.7 In the Internet, the equivalent concept to end systems is ( )A.A hostsB serversC clientsD routers1.8 In the Internet, end systems are connected together by ( C ).A copper wireB coaxial cableC communication linksD fiber optics1.9 End systems access to the Internet through its (C ).A modemsB protocolsC ISPD sockets1.10 In the following options, which belongs to the network core? ( B )A end systemsB routersC clientsD servers1.11 End systems, packet switches, and other pieces of the Internet, run ( D ) that control the sending and receiving of information within the Internet.A programsB processesC applicationsD protocols1.12 The internet allows ( D ) running on its end systems to exchange data with each other.A clients applicationsB server applicationsC P2P applicationsD distributed applications1.13 The protocols of various layers are called ( A ).A the protocol stackB TCP/IPC ISPD network protocol1.14 In the OSI reference model, the upper layers of the OSI model are, in correct orderDA Session, application, presentationB Session, presentation, applicationC Session, application, presentation, physicalD Application, presentation, session1.15 The lower layers of the OSI model are, in correct orderDA physical, system, network, logicalB physical, logical, network, systemC physical, transport, network, data linkD physical, data link, network, transport1.16 The Internet Protocol (IP) generally corresponds to which OSI layer?AA Network (layer three)B Transport (layer four)C Data link (layer two)D Session (layer five)1.17 What layer of the OSI model is designed to perform error detection functions?BA PhysicalB Data linkC NetworkD transport1.18 Which of the following protocol layers is not explicitly part of the Internet Protocol Stack? _____B____A. application layerB. session layerC. data link layerD. transport layer1.19 The 5-PDU is called__A_A. messageB. segmentC. datagramD. frame1.20 The Internet’s network layer is responsible for moving network-layer packets known as B( ) from one host to another.A frameB datagramC segmentD message1.21 Transport-layer packets are called:BA. messageB. segmentC. datagramD. frame1.22 The units of data exchanged by a link-layer protocol are called ( A).A FramesB SegmentsC DatagramsD bit streams1.23 There are two fundamental approaches to building a network core, ( B ) and packet switching.A electrical current switchingB circuit switchingC data switchingD message switching1.24 Datagram networks and virtual-circuit networks differ in that ( C ).A datagram networks are circuit-switched networks, and virtual-circuit networksare packet-switched networks.B datagram networks are packet-switched networks, and virtual-circuit networksare circuit-switched networks.C datagram networks use destination addresses and virtual-circuit networks useVC. numbers to forward packets toward their destination.D datagram networks use VC. numbers and virtual-circuit networks usedestination addresses to forward packets toward their destination.1.25 (A ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Store-and-forward transmissionB FDMC End-to-end connectionD TDM1.26 In ( C ) networks, the resources needed along a path to provide for communication between the end system are reserved for the duration of the communication session.A packet-switchedB data-switchedC circuit-switchedD message-switched1.27 In ( A ) networks, the resources are not reserved; a session’s messages use the resources on demand, and as a consequence, may have to wait for access to communication link.A packet-switchedB data-switchedC circuit-switchedD message-switched1.28 In a circuit-switched network, if each link has n circuits, for each link used by the end-to-end connection, the connection gets ( A) of the link’s bandwidth for the duration of the connection.A a fraction 1/nB allC 1/2D n times1.29 For (C ), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot.A CDMAB packet-switched networkC TDMD FDM1.30 The network that forwards packets according to host destination addresses is called ( D) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram1.31 The network that forwards packets according to virtual-circuit numbers is called ( C ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram1.32 The time required to propagate from the beginning of the link to the next router is ( C).A queuing delayB processing delayC propagation delayD transmission delay1.33 Processing delay does not include the time to (B ).A examine the packet’s headerB wait to transmit the packet onto the linkC determine where to direct the packetD check bit-error in the packet1.34 In the following four descriptions, which one is correct? ( C)A The traffic intensity must be greater than 1.B The fraction of lost packets increases as the traffic intensity decreases.C If the traffic intensity is close to zero, the average queuing delay will be closeto zero.D If the traffic intensity is close to one, the average queuing delay will be closeto one.1.35 Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( B ),A LR／aB La／RC Ra／LD LR／a1.36 Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.) ( A )A L/R1＋L/R2B L/R1C L/R2D none of the above1.37 We are sending a 30 Mbit MP3 file from a source host to a destination host. Suppose there is only one link between source and destination and the link has a transmission rate of 10 Mbps. Assume that the propagation speed is 2 * 108 meters/sec, and the distance between source and destination is 10,000 km. Also suppose that message switching is used, with the message consisting of the entire MP3 file. How many bits will the source have transmitted when the first bit arrives at the destination?CA. 1 bitB. 30,000,000 bitsC. 500,000 bitsD. none of the above1.38 In the following entries, which is not a kind of access network?(D )A residential accessB company accessC wireless accessD local access1.39 The following technologies may be used for residential access, exceptDA. HFCB. DSLC. Dial-up modemD. FDDI1.40 Which kind of media is not a guided media? ( D)A twisted-pair copper wireB a coaxial cableC fiber opticsD digital satellite channel。

Circuit Switching and Packet Switching

Exercises
• • • • • •
电路交换分组交换报文交换子网信头目的地址
circuit switching packet switching message switching subnet header destination address
Exercises
误差控制存储转发方式突发性传输时延中间交换设备交换技术
Exercises
1. The switch ———— circuit switches, have no capability of ———— user's data on their way to the destination. A. calling, stored B. called, storing C. to call, to store D. be called, be stored
Exercises
3. The switching element is a computer ———— a message processor, with processing and storage capabilities. Message travels independently and asynchronously, ———— their own way from source to destination. A. to call, find B. calling, found C. referred to as, finding D. be called, sending
error control store-and-forward manner busty Transmission delay intermediate switching equipment switching technique

电路交换、存储转发包交换的概念

电路交换、存储转发包交换的概念英文回答：Circuit switching and packet switching are twodifferent methods of transmitting data in a network.Circuit switching is a method where a dedicated communication path is established between two devices for the duration of a communication session. This path remains open even if there is no data being transmitted, ensuring a continuous connection. In circuit switching, the network resources are reserved and allocated exclusively for the duration of the communication session. This method is commonly used in traditional telephone networks. The advantage of circuit switching is that it guarantees a constant and predictable bandwidth, but it is not efficient when there is a low utilization of the network resources.Packet switching, on the other hand, is a method where data is divided into small packets and transmittedindependently across the network. Each packet contains the source and destination addresses, as well as the actual data. These packets are then routed through the network using the most efficient path available at that moment. In packet switching, the network resources are shared among multiple users, and the packets can take different routes to reach the destination. This method is commonly used in modern computer networks, including the Internet. The advantage of packet switching is that it is more efficient in utilizing network resources, as packets can be routed dynamically based on the network conditions. However, it introduces some overhead due to the additional information included in each packet.存储转发包交换是一种基于包交换的网络传输方式。

电路交换与包交换区别与优缺点

电路交换和分组交换的区别及优缺点刘家宇20110801126 计算机科学与技术 1 班摘要：从传输技术来说，电话网是采用电路交换方式，即电话通信的电路一旦接通后，电话用户就占用了一个信道，无论用户是否在讲话，只要用户不挂断，信道就一直被占用着。

一般情况下，通信双方并不同时讲话，且讲话途中也会有停顿。

因此用电路交换方式时线路利用率很低，至少有50%以上的时间被浪费掉。

而因特网的信息传送是采用分组交换方式，所谓分组交换，是把数字化的信息，按一定的长度“分组”、打“包”，每个“包”加上地址标识和控制信息，在网络中以“存储—转发“的方式传送，即遇到电路有空就传送，并不占用固定的电路或信道，因此被称为是“无连接”的方式。

这种方式可以在一个信道上提供多条信息通路。

因此，利用因特网传送语音信息要比电话网传送语音的线路利用率提高许多倍。

本文主要目的就是简单阐述这两种交换技术的区别及优缺点。

关键词：电路交换;分组交换; 信息传输Abstract:From the transmission technologies, the use of the telephone network is a circuit switching mode, once the circuit switched telephone communication , the telephone user occupies one channel , whether the user is talking, as long as the user does not hang up , the channel has been occupied with . Under normal circumstances, the two sides did not speak at the same communication and speech on the way there will be a pause .Therefore, when using circuit-switched line utilization is very low, at least more than 50 % of the time is wasted . The information transfer is the use of the Internet packet exchange, the so-called packet switching, is the digital information , according to a certain length " grouping " fight " package" , each " package" together address identification and control information in the network in "Storage - forward" way to send that whenever you encounter circuit transmission, does not occupy a fixed circuit or channel , it is called a "no connection " approach. This way you can provide multiple information channels in a channel. Therefore, line utilization using the Internet to transmit voice information than the telephone network to transmit voice improved many times over. The main purpose of this paper is to briefly discusses the difference between these two switching technology and the advantages and disadvantages between them .Keywords:Circuit Switching ，Packet switching引言？1.电路交换每部电话都连接到交换机上，而交换机使用交换的方法，让电话用户之间可以很方便地通信。

电信英语词汇大全

of frame
code; A:
Alignment
of frame;
Z: Zero-
string
suppression
; P:
Polarity
G：产生帧码 conversion;
A：帧定位 A: Alarm;
Z：零串抑制 C: Clock
P：极性转换 recovery;
A：告警 C： H: Hunt
时钟恢复 during
H：帧同步重 reframe; O:
搜索 O：局 Office
信令
signaling GAZPACHO
GPRS
GPRS支持节 Support
点
Node
GSN
GSM Public
GSM公众陆地 Land Mobile
移动网
Network GSM PLMN
Enhanced
Data rate
Internet
Message
Internet消 Access
息接入协议 Protocol
IN
Switching
IN交换管理 Management
IP
IP 电话 telephony
IP
multicast
IP 组播技术 technology
IP-policy
IP策略语句 statement
IPX ISP IANA IMAP IN-SM
High
Density
3阶高密度双 Bipolar of
极性码
order 3 HDB3
four-wire
trunk
4线制干线 circuit
No.7
7号信令 signaling
A律