05浙大通信与计算机网络离线作业
浙大远程操作系统原理离线作业及答案
浙⼤远程操作系统原理离线作业及答案操作系统原理离线作业⼀、单选题1.进程P0和P1的共享变量定义及其初值为boolean flag[2]；int turn=0；flag[0]=FALSE；flag[1]=FALSE；若进程P0和P1访问临界资源的类C代码实现如下：void P0() //P0进程{ while（TURE）{flag[0]=TRUE; turn = 1;while (flag[1] && turn == 1) ;临界区;flag[0] = FALSE;}}void P1() //P1进程{ while（TURE）{flag[1]=TRUE; turn = 0;while (flag[0] && turn == 0) ;临界区;flag[1] = FALSE;}}则并发执⾏进程P0和P1时产⽣的情况是：DA.不能保证进程互斥进⼊临界区、会出现“饥饿”现象B.不能保证进程互斥进⼊临界区、不会出现“饥饿”现象C.能保证进程互斥进⼊临界区、会出现“饥饿”现象 D．能保证进程互斥进⼊临界区、不会出现“饥饿”现象2.有两个进程P1和P2描述如下:shared data：int counter = 6;P1 :Computing;counter=counter+1;P2 :counter=counter-2;两个进程并发执⾏，运⾏完成后，counter的值不可能为 C 。
A. 4B. 5C. 6D. 73.某计算机采⽤⼆级页表的分页存储管理⽅式，按字节编址，页⼤⼩为210字节，页表项⼤⼩为2字节，逻辑地址结构为：页⽬录号页号页内偏移量逻辑地址空间⼤⼩为216页，则表⽰整个逻辑地址空间的页⽬录表中包含表项的个数⾄少是BA．64 B．128 C．256 D．5124.在动态分区系统中，有如下空闲块:空闲块块⼤⼩（KB）块的基址1 80 602 75 1503 55 2504 90 350此时,某进程P请求50KB内存,系统从第1个空闲块开始查找，结果把第4个空闲块分配给了P进程，请问是⽤哪⼀种分区分配算法实现这⼀⽅案? CA.⾸次适应B. 最佳适应C. 最差适应D. 下次适应5.在⼀页式存储管理系统中，页表内容如下所⽰。
【免费下载】浙大远程计算机基础应用离线4
活动单元格名称
7、 Excel 2010主界面窗口中编辑栏上的"fx"按钮用来向单元格插入____D____。 A.文字 B.数字 C.公式 D.函数 [解析]如上图所示，如果单击了编辑栏上的"fx"按钮，将弹出“插入函数”对话框。
8、 启动Excel 2010应用程序后自动建立的工作簿文件的文件名为____A____。 A.工作簿1 B.工作簿文件 C.Book1 D.BookFile1 [解析]略
16、 在Excel 2010的工作表中，最小操作单元是_____D_____。 A.一列 B.一行 C.一张表 D.单元格 [解析] 在Excel 2010中，最小的操作单元是工作表的单元格。
对全部高中资料试卷电气设备，在安装过程中以及安装结束后进行高中资料试卷调整试验；通电检查所有设备高中资料电试力卷保相护互装作置用调与试相技互术关，系电，力根通保据过护生管高产线中工敷资艺设料高技试中术卷资，配料不置试仅技卷可术要以是求解指，决机对吊组电顶在气层进设配行备置继进不电行规保空范护载高与中带资负料荷试下卷高问总中题体资，配料而置试且时卷可，调保需控障要试各在验类最；管大对路限设习度备题内进到来行位确调。保整在机使管组其路高在敷中正设资常过料工程试况中卷下，安与要全过加，度强并工看且作护尽下关可都于能可管地以路缩正高小常中故工资障作料高；试中对卷资于连料继接试电管卷保口破护处坏进理范行高围整中，核资或对料者定试对值卷某，弯些审扁异核度常与固高校定中对盒资图位料纸置试，.卷保编工护写况层复进防杂行腐设自跨备动接与处地装理线置，弯高尤曲中其半资要径料避标试免高卷错等调误，试高要方中求案资技，料术编试交写5、卷底重电保。要气护管设设装线备备置敷4高、调动设中电试作技资气高，术料课中并3中试、件资且包卷管中料拒含试路调试绝线验敷试卷动槽方设技作、案技术，管以术来架及避等系免多统不项启必方动要式方高，案中为；资解对料决整试高套卷中启突语动然文过停电程机气中。课高因件中此中资，管料电壁试力薄卷高、电中接气资口设料不备试严进卷等行保问调护题试装，工置合作调理并试利且技用进术管行，线过要敷关求设运电技行力术高保。中护线资装缆料置敷试做设卷到原技准则术确：指灵在导活分。。线对对盒于于处调差，试动当过保不程护同中装电高置压中高回资中路料资交试料叉卷试时技卷，术调应问试采题技用，术金作是属为指隔调发板试电进人机行员一隔，变开需压处要器理在组；事在同前发一掌生线握内槽图部内纸故，资障强料时电、，回设需路备要须制进同造行时厂外切家部断出电习具源题高高电中中源资资，料料线试试缆卷卷敷试切设验除完报从毕告而，与采要相用进关高行技中检术资查资料和料试检，卷测并主处且要理了保。解护现装场置设。备高中资料试卷布置情况与有关高中资料试卷电气系统接线等情况，然后根据规范与规程规定，制定设备调试高中资料试卷方案。
浙大通信与计算机网络离线作业
第1章概述一．填空题：1.计算机网络是计算机技术与__通信技术___相结合的产物。
2.从资源共享的角度来定义计算机网络，计算机网络指的是利用____通信线路____将不同地理位置的多个独立的___自治计算机系统_______连接起来以实现资源共享的系统。
3.在TCP/IP的应用层协议一般使用的是客户服务器方式其中，客户是服务请求方，服务器是服务提供方。
4.在TCP/IP协议模型的运输层中，不面向连接的协议是_ UDP_。
5.在TCP/IP模型中，互联网层的上一层是运输层___。
6.通信线路的__带宽__是指通信线路上允许通过的信号频带范围(或通频带) ，单位是HZ。
但在计算机网络中，它又用来表示网络通信线路所能传送数据的能力。
7.数据通信中的信道传输速率单位用b/s表示，b/s的含义是_每秒比特。
8.目前，“带宽”常用作描述信道传送数据能力的物理量，其单位是b/s(bit/s),比之大的单位有：__KB/s_____、__Mb/s_____、_Gb/s______等。
9.将计算机网络划分为局域网LAN、城域网MAN、广域网WAN是按__网络的作用范围________划分的。
10.各节点都与中心节点连接，呈辐射状排列在中心节点周围，这种拓扑结构称为__星型拓扑结构________。
11.假设某用户通过电线部门的ADSL技术以2M（即2Mb/s）带宽接入Internet，在正常情况下其下载速度大约是_244kb/s_________。
12.发送数据时，数据块从结点进入到传输媒体所需要的时间称为____发送延时______；网络中电磁信号在信道中传播一定的距离而花费的时间称为__传播延时________。
13.在发送报文之前，先将较长的报文划分成为一个个更小的等长数据段，在每一个数据段前面，加上一些由必要的控制信息组成的首部(header)后，就构成了一个__分组_____。
（备忘：在TCP/IP模型中，数据分组是在运输层和网络层中共同完成的。
浙大计算机网络基础-2004-2005春算机网络基础期末试卷6
浙江大学２００４–２００５学年春夏季学期 《计算机网络基础》课程期末考试试卷 开课学院：计算机学院 ，考试形式：闭，允许带＿＿＿＿＿＿＿＿＿＿＿入场 考试时间： ２００５ 年 ７月 ５日，所需时间： １２０ 分钟 考生姓名： 学号： 专业： 题序 一 二 三 四 五 总 分 得分 评卷人 注意事项： １．请把答案写在答题纸对应的题号内； ２．有关ＩＰ地址表达方式，如果没有特别的掩码标明，则均按标准地址分类表示。
一、 Please select the best choice for following questions (50 points)1.What is the advantage of using a layered model of networking?A. Simplified the networkB. For the purpose of standardizationC. Divides the complexity of internetworking into discrete, more easily learned operationsubsetsD. All of the above2.What is the name of protocol data unit (PDU) at the network layer of the OSI referencemodel?A. TransportB. FrameC. PacketD. Segment3.Which is true when a broadcast is sent out in an E thernet 802.3 LAN?A. The broadcast is sent only to the default gateway.B. The broadcast is sent only to the destination hardware address in the broadcast.C. The broadcast is sent to all devices in the collision domain.D. The broadcast is sent to all devices in the broadcast domain.4.Segmentation of a data stream happens at which layer of the OSI model?A. PhysicalB. Data LinkC. NetworkD. Transport5.Which of following international standard defines for Fast Ethernet?A. IEEE 802.3B. IEEE 802.3zC. IEEE 802.3uD. IEEE 802.3ae6.What does the Data Link layer use to find hosts on a local network?A. Logical network addressesB. Port numbersC. Hardware addressesD. Default gateways7.What were the key reasons the ISO released the OSI model?A. To allow companies to charge more for their equipmentB. To help vendors create interoperable network devicesC. To help vendors create and sell specialized software and hardwareD. So the IBM mainframe would be replaced with the PC8.What is used at the Transport layer to stop a receiving host’s buffer from overflowing?A. SegmentationB. PacketsC. AcknowledgmentsD. Flow control9.When data is encapsulated, which is the correct order?A. Data, frame, packet, segment, bitB. Segment, data, packet, frame, bitC. Data, segment, packet, frame, bitD. Data, segment, frame, packet, bit10.What does the term “Base”indicate in 100Base-TX?A. The maximum distanceB. The type of wiring usedC. A LAN switch method using half duplexD. A signaling method for communication on the network11.What is the maximum distance of 100Base-T?A. 100 feetB. 1000 feetC. 100 metersD. 1000 meters12.Which of the following would describe a transport layer connection that would ensure reliabledelivery?A. RoutingB. AcknowledgmentsC. SwitchingD. System authentication13.Which of the following is not considered a reason for LAN congestion?A. Low bandwidthB. Too many users in a broadcast domainC. Broadcast stormsD. Routers14.Which of the following are two basic types of dynamic routing?A. Static and defaultB. TCP and UDP exchangeC. Distance-vector and link-stateD. None of the above15.If your LAN network is currently congested and you are using only hubs in your network, whatwould be the BEST solution to decrease congestion on your network?A. Cascade you r hubs.B. Replace your hubs with switches.C. Replace your hubs with routers.D. Add faster hubs.16.What technology is a used by most switches to resolve topology loops and ensure that dataflows properly through a single network path?A. RIPB. STPC. IGRPD. Store-and-forward17.Which of the following is one of the characteristics of IP?A. reliable and connectionlessB. unreliable and connectionlessC. reliable and connection-orientedD. unreliable and connection-oriented18.What is the valid host range for subnet 172.16.10.16 (Mask 255.255.255.240)?A. 172.16.10.20 through 172.16.10.22B. 172.16.10.16 through 172.16.10.23C. 172.16.10.17 through 172.16.10.31D. 172.16.10.17 through 172.16.10.3019.What range of addresses can be used in the first octet of a Class B network address?A. 1–126B. 128–190C. 128–191D. 129–19220.Which of the following is not true?A. IP is connectionless and provides routing.B. ARP is used to find an IP address of a host.C. UDP is connectionless.D. TCP is connection oriented.21.Which class of IP address provides a maximum of only 254 host addresses per network ID?A. Class AB. Class BC. Class CD. Class D22.Which protocol tool use ICMP?A. TelnetB. PingC. ARPD. FTP23.Which of the following is an IEEE standard for frame tagging?A. 802.1XB. 802.3ZC. 802.1QD. 802.3U24.A client will use ____ to send emails to mail-server.A.POP3B.SMTPC.TELNETD.FTP25.Which protocol used in PPP allows multiple Network layer protocols to be used during aconnection?A. LCPB. NCPC. HDLCD. X.2526.When too many packets are present in the subnet, performance degrades. What is this situationcalled?A. dead lockB. congestionC. network faultD. network busy27.Which language can be used to realize the client-side dynamic web page generation?A. CGIB. ASPC. JavaScriptD. PHP28. The two-wire connections between each subscriber’s telephone and the end office are knownin the trade as the____.A. trunkB. local loopC. linkD. switch29.When web page is transmitted over SSL, the protocol used is _____.A. HTTPB. SHTTPC. HTTPSD. SSL30.Nyquist proved that if an arbitrary signal has been run through a low-pass filter of bandwidth H,the filtered signal can be completely reconstructed by making only ________ (exact) samples per secondA. HB. 0.5HC. 2HD. 4H31.To convert a binary message to an ASCII message in email system, we can use _____ encoding,which break up groups of 24 bits into four 6-bit units, with each unit being sent as a legal ASCII character.A. base64B. quoted-printableC. SMTPD. POP332.A CRC generator polynomial is G(x)= X8+X5+X2+l. How many bits will the checksum be?A. 7B. 8C. 9D. 1033. If the length of sequence is 4 bits, the maximum sending window size should be ____.A. 13B. 14C. 15D. 1634.In 802.11, to solve the _______ station problem and the hidden station problem, we can useCSMA/CA protocol. According this protocol, before the station sending a data, it must send RTS frame and wait a CTS frame back.A. faultB. mobileC. exposedD. wireless35.If the congestion window size is 20KB, and the receive window size is 30KB, what is themaximum bytes can the TCP entity transmit?A. 20KBB. 30KBC. 50KBD. 10KB36.Port numbers below ________ are called well-known ports and are reserved for standardservices.A. 256B. 1024C. 4096D. 100037.________, which are overlay networks on top of public networks but with most of theproperties of private network.A. PBXB. VPNC. CDMA 1XD. GPRS38.The problem of running out of IP addresses is not a theoretical problem that might occur atsome point in the distant future. Some people felt that a quick fix was needed for the short term.This quick fix came in the form of ____________________.A. IP6B. DHCPC. RARPD. NAT39.Public-key algorithms have the property that ____________________ keys are used forencryption and decryption and that the decryption key cannot be derived from the encryption key. These properties make it possible to publish the public key.A. one timeB. randomC. sameD. different40.The main public-key algorithm is ____________________ which derives its strength from thefact that it is very difficult to factor large numbers.A. DESB. AESC. MD5D. RSA41.Various schemes have been devised for digital signatures, using both symmetric-key and________-key algorithms.A. publicB. privateC. one timeD. one way42.Often, authentication is needed but secrecy is not, based on the idea of a one-way hash functionthat takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string.This hash function, MD, often called a ________.A. message digestB. packet-switchedC. message-detectD. mini data43.URL(Uniform Resource Locator) have three parts: the ________, the DNS name of themachine on which the page is located, and a local name uniquely indicating the specific page.A. protocolB. addressC. port numberD. name44.HTTP1.1, which supports ________ connections. With them, it is possible to establish a TCPconnection, send a request and get a response, and then additional requests and get additional response.A. one timeB. persistentC. stop and waitD. one-way45._______, when it is used, a bad frame that is received is discarded, but the good framesreceived after it are buffered.A. selective repeatB. go back NC. sliding windowD. stop and wait46.How does the FDM multiplexing schemes work like?A. each user having exclusive possession of some bandB. each user take turns, periodically getting the entire bandwidth for a litter burst of timeC. each user transmit over the entire frequency spectrum all the time with different codingD. each user transmit over a shared fiber using different wavelength47.When we use a modem, which use 16 phases signal to modulation, then how much can we getthe maximum data rate in a 2400 baud channel (in noiseless channel)?A. 400bpsB. 2400bpsC. 9.6kbpsD. 14.4kbps48.______ is a small java program that has been compiled into binary instruction running in JVM,and can be embedded into HTML pages, interpreted by JVM-capable browsers.A. JavaScriptB. JavaBeanC. AppletD. JSP49.Which of the following best describes the function of the OSI reference model’s transportlayer?A. It sends data by using flow controlB. It provides the best path for deliveryC. It determines network addressesD. It provides error-correcting50.What is the most efficient subnet mask to use on point-to-point WAN links?A. 255.255.255.0B. 255.255.255.224C. 255.255.255.252D. 255.255.255.248二、 Please choose true(Ｔ) or false( Ｆ) for the following questions (15 points)1.Error-correcting and error-detecting are two types of technique in error control.2.Link state dynamic routing algorithms operate by having each router maintain a tablegiving the best known distance to each destination and which line to use to get there. These tables are updated by exchanging information with the neighbors.3.With Manchester encoding, each bit period is divided into two equal intervals. A binary 1bit is sent by having the voltage set high during the first interval and low in the second one.A binary 0 is just the reverse: first low and then high.4. A connection is established in TCP by means of the two-way handshake.5.The range of frequencies transmitted without being strongly attenuated is called bandwidth.6.Shannon’s major result is that the maximum data rate of a noisy channel whose bandwidthis H Hz, and whose signal-to-noise ratio is S/N, is given byMaximum number of baud/sec = H log2 (1+S/N)7.Two different switching techniques are widely used nowadays: circuit switching and packetswitching.8.The protocols used to determine who goes next on a multi-access channel belong to asub-layer of the data link layer called the LLC sublayer.9.The b asic function of RTP is to multiplex several real-time data streams onto a singlestream of UDP packets.10.The Internet solution is to realize that two potential problems exist n etwork capacity andreceiver capacity and to deal with each of them separately. To do so, each sender maintains two windows: the window the receiver has granted and a second window, the congestion window.11.Selective repeat, is for the receiver simply to di scard all subsequent frames, sending noacknowledgments for the discarded frames.12.The IPSec is a set of open standards that provides data confidentiality, data integrity, andauthentication between participating peers at the IP layer.13.B2C, the full name i s Business to Company.14.One type of person-to-person communication often goes by the name of end-to-endcommunication, to distinguish it from the client-server model.15.An issue that occurs at every level is how to keep a fast sender from swamping a slowreceived with data. This subject is called flow control.三、 Please answer the following questions briefly.1.What are the principal differences between connectionless communications andconnection-oriented communications? (5 points)2.Data link protocols almost always put the CRC in a trailer rather than in a header. Why? (5points)3.Suppose that the TCP congestion window is set to 18KB and a timeout occurs. How big willthe window be if the next four transmission bursts are all successful? Assume that the maximum size of segment is 1KB. (5 points)四、 A large number of consecutive IP address are available starting at 198.16.0.0. Supposethat four organizations, A, B, C, and D, request 4000,2000,4000, and 8000 addresses, respectively, and in that order. For each of these, give the first IP address assigned, the last IP address assigned, and the mask in the w.x.y.z/s notation. (8 points)(Notice: To start with, all the requests are rounded up to a power of two.)五、 The following figure describes a simple authentication p rotocol. Assume you are Trudy, pleaseuse reflection attack to attack Bob.(1). Draw the attack figure and give clear the steps of the attach(2). What are the differences between authentication and authorization? (12 points)。
浙大远程操作系统原理离线作业
浙⼤远程操作系统原理离线作业浙江⼤学远程教育学院《操作系统原理》课程作业姓名：学号：年级：15年春学习中⼼：—————————————————————————————⼀、单选题1.进程P0和P1的共享变量定义及其初值为boolean flag[2]；int turn=0；flag[0]=FALSE；flag[1]=FALSE；若进程P0和P1访问临界资源的类C代码实现如下：void P0() //P0进程{ while（TURE）{flag[0]=TRUE; turn = 1;while (flag[1] && turn == 1) ;临界区;flag[0] = FALSE;}}void P1() //P1进程{ while（TURE）{flag[1]=TRUE; turn = 0;while (flag[0] && turn == 0) ;临界区;flag[1] = FALSE;}}则并发执⾏进程P0和P1时产⽣的情况是：A．不能保证进程互斥进⼊临界区、会出现“饥饿”现象B．不能保证进程互斥进⼊临界区、不会出现“饥饿”现象C．能保证进程互斥进⼊临界区、会出现“饥饿”现象D．能保证进程互斥进⼊临界区、不会出现“饥饿”现象答：D．能保证进程互斥进⼊临界区、不会出现“饥饿”现象2.有两个进程P1和P2描述如下:shared data：int counter = 6;P1 :Computing;counter=counter+1;P2 :Printing;counter=counter-2;两个进程并发执⾏，运⾏完成后，counter的值不可能为。
A. 4B. 5C. 6D. 7答：C. 63.某计算机采⽤⼆级页表的分页存储管理⽅式，按字节编址，页⼤⼩为210字节，页表项⼤⼩为2字节，逻辑地址结构为：页⽬录号页号页内偏移量逻辑地址空间⼤⼩为216页，则表⽰整个逻辑地址空间的页⽬录表中包含表项的个数⾄少是A．64 B．128 C．256 D．512答：210÷2=29是⼀张页表中可以存放页表项的项数，216是逻辑地址空间的总页数，也就是说包含216个页表项，那么27就是需要有多少张页表，也就是页⽬录表中包含表项的个数。
浙大远程-计算机网络基础第5、6章离线作业和答案
第5章运输层作业五一．填空题：1.从通信和信息处理的角度看，在TCP/IP模型中向其上面的应用层提供通信服务的协议层称为_运输_层。
2.传输层使用了___网络层__提供的服务，并通过执行_传输层协议_，针对最高层屏蔽__通信子网_在技术、设计上的差异与服务不足，向_更高层（或写应用层）_提供了一个标准的完善的通信服务。
3.TCP协议可以为其用户提供_可靠_、面向连接的、全双工的数据流传输服务。
4.UDP协议可以为其用户提供不可靠、__无连接的数据传输服务。
5.人们把将要发送的完整的数据块称为报文，在运输层直接对应用层交下来的报文进行封装的协议是_ UDP _。
6.在运输层，TCP协议传递给网络层IP协议的数据单元称为_报文段_。
7.TCP/IP的运输层有两个不同的协议，它们是TCP和UDP,其中文名分别叫做传输控制协议和_用户数据报协议__。
前者是面向连接的协议，而后者则属于无连接协议。
使用UDP协议，系统资源开销小，UDP报文段的首部只有_8_字节。
而对于TCP来说，其报文段的首部至少有_20_字节，传输开销比较大，TCP开销大的另一个原因是占有CPU的处理时间。
因此，在应用层开发中运输层使用哪个协议要视具体情况而定。
诸如“万维网、电子邮件和文件传输”服务在运输层使用_ TCP_协议封装，而“域名转换协议DNS和IP电话”服务在运输层使用_ UDP协议封装。
8.熟知端口即系统端口号是IANA指派的。
FTP服务使用的熟知端口号是_21_，简单邮件传输协议SMTP使用的熟知端口号是_25_，邮局协议POP3使用的熟知端口号是_110_。
9.在TCP/IP网络中，两个应用进程之间建立的Socket连接是由4个数字确定的，包括双方的IP地址和双方的__端口号__。
10.主机A向主机B发送TCP报文段，首部中的源端口是m而目的端口是n。
当B向A发送回信时，其TCP报文段的首部中的源端口和目的端口分别是_ n 和m __。
浙大远程-操作系统原理第二次离线作业(第3章)
操作系统原理第二次离线作业（第3章）-1应用题1．在一个请求分页系统中，采用FIFO页面置换算法时，假如一个作业的页面访问顺序为4，3，2，1，4，3，5，4，3，2， l，5，当分配给该作业的物理块数M为4时，试试写出页面访问的过程，并计算访问中所发生的缺页次数和缺页率？解：FIFO置换算法用FIFO置换算法产生缺页次数 10 次缺页率83%2.某采用页式存储管理的系统，假如系统分配给一个作业的物理块数为4，作业执行时依次访问的页为： 2，3，2，1，5，2，4，5，3，2，5，2。
采用LRU页面置换算法时，计算出程序访问过程中所发生的缺页过程和缺页次数。
解：LRU算法问答题1.试述在设有快表的分页存贮管理系统的地址变换机构和地址变换过程。
在CPU给出有效地址（逻辑地址）后，系统将有效地址分离为页号和页内地址。
系统将页号与页表长度进行比较，如果页号大于页表寄存器中的页表长度，则访问越界，产生越界中断。
地址变换机构又自动地将页号送入高速缓存，确定所需要的页是否在快表中。
若是，则直接读出该页所对应的物理块号，送入物理地址寄存器；与此同时，将有效地址（逻辑地址）寄存器中页内地址直接装入物理地址寄存器的块内地址字段中，这样便完成了从逻辑地址到物理地址的变换。
若在快表中未找到对应的页表项，则根据页表寄存器中的页表始址和页号计算出该页在页表项中的位置，通过查找页表，得到该页的物理块号，将此物理块号装入物理地址寄存器中，与有效地址寄存器中页内地址组合成物理地址；同时，把从页表中读出的页表项存入快表中的一个寄存器单元中，以取代一个旧的页表项。
2.试述动态分区、分页和分段三种存储管理方案中如何实现信息的存储保护。
1. 越界保护在动态分区的保护的常用方法是由系统提供硬件：一对界限寄存器。
这可以是上界限寄存器、下界限寄存器，或者是基址寄存器、限长寄存器。
基址寄存器存放起始地址，作为重定位（地址映射）使用；限长寄存器存放程序长度，作为存贮保护使用。
浙江大学05-06秋冬计算机网络考试试卷
浙江⼤学05-06秋冬计算机⽹络考试试卷浙江⼤学2005–2006学年秋季学期《计算机⽹络》课程期末考试试卷开课学院：软件学院，考试形式：闭卷考试时间：_____年____⽉____⽇, 所需时间：120分钟考⽣姓名： ___学号：专业：得分：答案：For every following question, please select your best answer only1.The transmission unit for the physical layer is a/an __________.A.)packetB.)frameC.)bitD.)byte2.Which best describes the structure of an encapsulated data packet?A.)Segment header, network header, data, frame trailerB.)Segment header, network header, data, segment trailerC.)Frame header, network header, data, frame trailerD.)Frame header, segment header, data, segment trailer3.The communication subnet consists of __________.A.)physical layer, data link layer, and network layerB.)physical layer, network layer, transport layerC.)physical layer, data link layer, network layer, transport layerD.)data link layer, network layer, transport layer, session layer4.Which of the following statements best describes a WAN?A.)It connects LANs that are separated by a large geographic area.B.)It connects workstations, terminals, and other devices in a metropolitan area.C.)It connects LANs within a large building.D.)It connects workstations, terminals, and other devices within a building.5.Which is the movement of data through layers?A.)WrappingB.)EncapsulationC.)TravelingD.)Transmission6.Which is the OSI model?A.) A conceptual framework that specifies how information travels through networks.B.) A model that describes how data make its way from one application program to another throughout a network.C.) A conceptual framework that specifies which network functions occur at each layerD.)All of the above7.Which of the OSI layers divides the transmitted bit stream into frames?A.)Physical layerB.)Data link layerC.)Network layerD.)Transport layer8.Which of the following is incorrect?A.)The OSI model is better the TCP/IP model.B.)The OSI model provides more efficient implementation than the TCP/IP model.C.)The OSI model has more layers than the TCP/IP model.D.)The OSI model makes the distinction between services, interfaces, protocols.9.In the TCP/IP model, which layer deals with reliability, flow control, and error correction?A.)ApplicationB.)TransportC.)InternetD.)Network access10.The TCP/IP protocol suite has specifications for which layers of the OSI model?A.) 1 through 3B.) 1 through 4 and 7C.)3,4,and 5 through 7D.)1,3,and 411. A noiseless 4-k Hz channel is sampled every 1 msec. What is the maximum data rate?A.)8000 bpsB.)4000 bpsC.)1000 bpsD.)Can be infinite12.If a binary signal is sent over a 4-k Hz channel, what is the maximum achievable data rate?A.)8000 bpsB.)4000 bpsC.)1000 bpsD.)Can be infinite13.If a binary signal is sent over a 4-k Hz channel whose signal-to-noise ratiois 127:1, what is the maximum achievable data rate?A.)28000 bpsB.)8000 bpsC.)4000 bpsD.)Can be infinite14. A modem constellation diagram has data points at the following coordinates: (1, 1), (1, -1), (-1, 1), and (-1, -1). How many bps can a modem with these parameters achieve at 1200 baud?A.)1200 bpsB.)2400 bpsC.)4800 bpsD.)None of the above15.What is WDM?A.)Multiplexing on fiber-optic cable.B.)Multiplexing using the density of the transmission media.C.) A form of flow control that monitors WAN delays.D.) A form of congestion management for WANs.16.Which technology is not a type of wireless communication?A.)CellularB.)BroadbandC.)InfraredD.)Spread spectrum17.What is one advantage of using fiber optic cable in networks?A.)It is inexpensive.B.)It is easy to install.C.)It is an industry standard and is available at any electronics storeD.)It is capable of higher data rates than either coaxial or twisted-pair cable.18. A telephone switch is a kind of __________.A.)packet-switchingB.)buffer-switchingC.)fabric-switchingD.)circuit-switching.19. A cable TV system has 100 commercial channels, all of them alternating programswith advertising. This kind of multiplexing uses ___________.A.)TDMB.)FDMC.)FDM + TDMD.)None of the above.20. A bit string, 01101111101111110, needs to be transmitted at the data link layer.What is the string actually transmitted after bit stuffing (Whenever the sender’s data link layer encounters five consective 1s in the data, it automatically stuffs a 0 bit into the outgoing bit stream)A.)01101111101111110B.)0110111110011111010C.)011011111011111010D.)None of the above21.When DCF (Distributed Coordination Function) is employed, 802.11 uses a protocolcalled __________.A.)CSMA/CAB.)CSMA/CDC.)ALOHAD.)WDMA22.Which of the following can NOT directly be used for framing?A.)Character count.B.)Flag bytes with byte stuffing.C.)Starting and ending flags, with bit stuffing.D.)Physical layer coding violations.23.Which of the following can a VLAN be considered?A.)Broadcast domainB.)Collision domainC.)Both a broadcast and a collision domainD.)Domain name24.What is the purpose of Spanning Tree Protocol? (Network Bridging)A.)To maintain single loop pathsB.)To maintain a loop-free networkC.)To maintain a multiloop networkD.)To maintain a reduced loop network25.Which uses the twisted pairs?A.)10Base5.B.)10Base2.C.)10Base-F.D.)10Base-T.26.How do switches learn the addresses of devices that are attached to their ports?A.)Switches get the tables from a router.B.)Switches read the source address of a packet that is entering through a port.C.)Switches exchange address tables with other switches.D.)Switches are not capable of building address tables.27.Repeaters can provide a simple solution for what problem?A.)Too many types of incompatible equipment on the networkB.)Too much traffic on a networkC.)Too-slow convergence ratesD.)Too much distance between nodes or not enough cable.28.Which of the following is true of a switch’s function?A.)Switches increase the size of a collision domains.B.)Switches combine the connectivity of a hub with the capability to filteror flood traffic based on the destination MAC address of the frame.C.)Switches combine the connectivity of a hub with the traffic direction ofa router.D.)Switches perform Layer 4 path selection.29.Ethernet MAC addresses are how many bits in length?A.)12B.)24C.)48D.)6430.What is the information that is “burned in ” to a network interface card?A.)NICB.)MAC addressC.)HubD.)LAN31.Which connector does UTP (Unshield Twised Pair) use?A.)STPB.)RJ-45C.)RJ-69D.)BNC/doc/a9251a5077232f60ddcca14b.html ing repeaters does which of the following to the collision domain?A.)ReducesB.)Has no effect onC.)ExtendsD.)None of the above33.Which of the following is not a feature of microsegmentation?A.)It enables dedicated access.B.)It supports multiple conversions at any given time.C.)It increases the capacity for each workstation connected to the network.D.)It increases collisions.34.Which of the following protocols would have the highest channel utilization?A.)0.5-persistent CSMAB.)1-persistent CSMAC.)Pure ALOHAD.)Slotted ALOHA35.Which of the following is true concerning a bridge and its forwarding decisions?A.)Bridges operate at OSI Layer 2 and use IP addresses to make decisions.B.)Bridges operate at OSI Layer 3 and use IP addresses to make decisions.C.)Bridges operate at OSI Layer 2 and use MAC addresses to make decisions.D.)Bridges operate at OSI Layer 3 and use MAC addresses to make decisions.36.Fast Ethernet supports up to what transfer rate?A.) 5 MbpsB.)10 MbpsC.)100 MbpsD.)1000 Mbps37.Media Access Control refers to what?A.)The state in which a NIC has captured the networking medium and is readyto transmitB.)Rules that govern media capture and releaseC.)Rules that determine which computer on a shared-medium environment is allowed to transmit the dataD.) A formal byte sequence that has been transmitted.38.Which best describes a CSMA/CD network?A.)One node’s transmission traverses the entire network and is received and examined by every node.B.)Signals are sent directly to the destination if the source knows both theMAC and IP addressesC.)One node’s transmission goes to the nearest router, which sends it directlyto the destination.D.)Signals always are sent in broadcast mode.39.Which of the following statements about IPv4 header fields is incorrect?A.)An address has 32 bits.B.)The TTL has 4 bits.C.)The version has 4 bits.D.)The identification has 16 bits.40.The subnet mask for a class B network is 255.255.255.192. How many subnetworks are available? (Disregard special addresses)A.) 2B.) 4C.)1024D.)19241.Which of the following can be used to connect a keyboard with a computer?A.)802.3B.)802.11C.)802.15D.)802.1642.Which of the following can be used as the wireless local loop for public switched telephone systems?A.)802.3B.)802.11C.)802.15D.)802.1643.What is the IP address of the internal loopback?A.)10.10.10.1B.)255.255.255.0C.)127.0.0.1D.)192.0.0.144.How does the network layer forward packets from the source to the destination?A.)By using an IP routing tableB.)By using ARP responsesC.)By referring to a name serverD.)By referring to the bridge45.What is one advantage of dynamic routing?A.)Takes little network overhead and reduces network trafficB.)Reduces unauthorized break-ins because security is tightC.)Adjusts automatically to topology or traffic changesD.)Requires little bandwidth to operate efficiently46.Which best describes a default route?A.)Urgent-data route manually entered by a network administratorB.)Route used when part of the network failsC.)Route used when the destination network is not listed explicitly in therouting tableD.)Preset shortest path47.What does ICMP stand for?A.)Internal Control Message PortalB.)Internal Control Message ProtocolC.)Internet Control Message PortalD.)Internet Control Message ProtocolE.)48.What does TTL stand for? (For IP Header fields)A.)Time-To-ListB.)Time-To-LiveC.)Terminal-To-ListD.)Terminal-To-Live49.What is one advantage of distance vector algorithms?A.)They are not likely to count to infinity.B.)You can implement them easily on very large networks.C.)They are not prone to routing loops.D.)They are computationally simple50.Which of the following best describes a link-state algorithm?A.)It recreates the topology of the entire internetwork.B.)It requires numerous computations.C.)It determines distance and direction to any link on the internetwork.D.)It uses litter network overhead and reduces overall traffic.51.What is the minimum number of bits that can be borrowed to form a subnet?A.) 1B.) 2C.) 4D.)None of the above52.In order to find out its IP address, a machine can use __________.A.)ARPB.)RARPC.)ICMPD.)UDP53.Which portion of the Class B address 154.19.2.7 is the network address?A.)154B.)154.19C.)154.19.2D.)154.19.2.754.How many host addresses can be used in a Class C network?A.)253B.)254C.)255D.)25655.Which of the following can NOT be used to traffic shaping?A.)OverprovisioningB.)Leaky bucket algorithmC.)Token bucket algorithmD.)Packet scheduling56.When the congestion is very seriously, which kind of control should be used?A.)Warning bitsB.)Load sheddingC.)Chocke packetsD.)Hop-by-hop chope packets57.Which of the following is most appropriate in order to make the full use of IP addresses?A.)SubnetingB.)CIDRC.)NATD.)All of the above58.How many bits does an IPv6 address have?A.)32B.)64C.)128D.)25659.Which of the following is true for distance vector routing?A.)Useful for nothing.B.)Used in OSPFC.)Used in BGPD.)None of the aboveGiven the subnet shown in (a) and the incomplete routing table shown in (b), please use distance vector routing to answer the next 4 questions.60.What is the new distance and next hop for going to C?A.)28,IB.)28,AC.)12,ID.)12,G61.What is the new distance and next hop for going to F?A.)30,HB.)30,IC.)18,AD.)18,K62.What is the new distance and next hop for going to H?A.)0,AB.)3,IC.)12,HD.)18,K63.What is the new distance and next hop for going to L?A.)6,AB.)13,IC.)14,HD.)15,K64.What does the window field in a TCP segment indicate?A.)Number of 32-bit words in the headerB.)Number of the called portC.)Number used to ensure correct sequencing of the arriving dataD.)Number of octets that the device is willing to accept65.What do TCP and UDP use to keep track of different conversations crossing a network at the same time?A.)Port numbersB.)IP addressesC.)MAC addressesD.)Route numbers66.Which range of port numbers is unregulated?A.)Below 255B.)Between 256 and 512C.)Between 256 and 1023D.)Above 102367.Which of the following is incorrect for the TCP header fields?A.)The source port has 16 bits.B.)The URG has just 1 bit.C.)The Window size has 32 bits.D.)The acknowledgement number has 32 bits.68.How does TCP synchronize a connection between the source and the destination before data transmission?A.)Two-way handshakeB.)Three-way handshakeC.)Four-way handshakeD.)None of the above69.What is true for TCP’s retransmission timer?A.)Fixed value to allow 90% of segments arrive without retransmissionB.)Fixed value to allow 80% of segments arrive without retransmissionC.)Dynamic value based on the past successful transmission historyD.)Dynamic value based on the last successful transmission’s RTT70.UDP segments use what protocols to provide reliability?A.)Network layer protocolsB.)Application layer protocolsC.)Internet protocolsD.)Transmission control protocols71.Which of the following is most appropriate?A.)UDP just provides an interface to the IP protocol with the added feature of demultiplexing multiple processes using the ports.B.)UDP can be used to implement RPC.C.)UDP can be used to implement RTP.D.)All of the above.72.Which of the following is a basic service of the transport layer?A.)Provides reliability by using sequence numbers and acknowledgementsB.)Segments upper-layer application dataC.)Establishes end-to-end operationsD.)All of the above73.The TCP primitives depend on __________.A.)both the operating system and the TCP protocol.B.)the operating system only.C.)the TCP protocol only.D.)the operating system and the TCP protocol and the IP protocol.74.The default port for TELNET is __________.A.)21B.)22C.)23D.)2475.Which of the following is incorrect?A.)DNS stands for Domain Name System.B.)There is only one record associated with every IP.C.)Domain names can be either absolute or relative.D.)Domain names are case insensitive.76.What does MIME stand for?A.)Messages In Multi EncodingB.)Multipurpose Internet Mail ExtensionsC.)Multipurpose Internet Mail EncodingD.)None of the above77.Which of the following is not a protocol for email?A.)SMTPB.)POP3C.)IMAPD.)GOPHER78.Which of the following is incorrect?A.)HTML stands for HyperText Markup Language.B.)XML stands for eXtensible Markup Language.C.)XHTML stands for eXtended HyperText Markup Language.D.) A browser can display HTML documents as well as XML documents.79.Which of the following tags is used to define a hyperlink?A.) …B.) …C.) …D.)…80.Which of the following is not a built-in HTTP request methods?A.)GETB.)POSTC.)PUTD.)FETCH81.Which of the following is not able to generate dynamic content on the server side?A.)CGIB.)JSPC.)ASPD.)JavaScript82.Which of the following is able to generate dynamic content on the client side?A.)Java AppletB.)JavaScriptC.)ActiveXD.)All of the above83.Which of the following is true?A.)WAP 1.0 is successful while I-Mode is not.B.)I-Mode is successful while WAP 1.0 is not.C.)Both WAP 1.0 and I-Mode are successful.D.)Neither WAP 1.0 nor I-Mode is successful.84.Which of the following security policies is hopeless?A.)802.11 WEPB.)Bluetooth securityC.)WAP 2.0 securityD.)None of the above85.Which of the following is incorrect?A.)X.509 can be used to describe the certificates.B.)An organization that certifies public keys is now called a CA.C.)The Diffie-Hellman key exchange allows strangers to establish a shared secret key.D.)The Diffie-Hellman key exchange can be attacked by the bucket brigade or man-in-the-middle attack.86.In a public key encryption system, a sender has encrypted a message with the recipient's public key. What key does the recipient use to decipher the message?A.)The recipient's private key.B.)The recipient's public key.C.)The sender's private key.D.)The sender's public key.87.Which of the following statements is true of ping?A.)The ping command is used to test a device’s network connectivity.B.)The ping stands for packet Internet groperC.)The ping 127.0.0.1 command is used to verify the operation of the TCP/IP stack.D.)All of the above.88.Which of the following can be used to test application protocols?A.)pingB.)tracertC.)netstatD.)telnet89.Which of the following can be used to display TCP connections?A.)pingB.)tracertC.)netstatD.)telnet90.Which of the following system calls is used to create a server socket?A.)socketB.)openC.)requestD.)creat91.Which of the following system calls is to specify queue size for a server socket?A.)bindB.)sizeC.)listenD.)acceptFor the following cipher chaining modes, please answer the following three questions.92.Which mode is most suitable for use with interactive terminals?A.)Cipher chaining AB.)Cipher chaining BC.)Cipher chaining CD.)Cipher chaining D93.Which mode is most suitable for use with real-time streaming?A.)Cipher chaining AB.)Cipher chaining BC.)Cipher chaining CD.)Cipher chaining D94.Which mode is most suitable for use with disk files?A.)Cipher chaining AB.)Cipher chaining BC.)Cipher chaining CD.)Cipher chaining D95.Which of the following is the strongest symmetric-key encryption algorithm?A.)DESB.)AESC.)RSAD.)MD596.Which of the following is the strongest public-key encryption algorithm?A.)DESB.)SHA-1C.)RSAD.)MD5Consider the figure shown below, which takes some plaintext as input and produces signed ciphertext in some ASCII format as output. Please answer the next questions97.Which of the following should be used for blank (I)?A.)DESB.)AESC.)MD5D.)None of the above98.Which of the following should be used for blank (II)?A.)RSA with Alice’s private RSA keyB.)RSA with Alice’s public RSA keyC.)RSA with Bob’s private RSA keyD.)RSA with Bob’s public RSA key99.Which of the following should be used for blank (III)?A.)MD5B.)AESC.)SHA-1D.)Base64 encoding100.Which of the following should be used for blank (IV)?A.)MD5B.)AESC.)SHA-1D.)None of the above。
浙江大学05计算机上机题
一、A + B题目描述：读入两个小于100的正整数A和B,计算A+B.需要注意的是:A和B的每一位数字由对应的英文单词给出.输入：测试输入包含若干测试用例,每个测试用例占一行,格式为"A + B =",相邻两字符串有一个空格间隔.当A和B同时为0时输入结束,相应的结果不要输出.输出：对每个测试用例输出1行,即A+B的值.样例输入：one + two =three four + five six =zero seven + eight nine =zero + zero =样例输出：39096答案：#include <iostream>#include <string>using namespace std;int toInteger(string A){if(A=="one")return 1;else if(A=="two")return 2;else if(A=="three")return 3;else if(A=="four")return 4;else if(A=="five")return 5;else if(A=="six")return 6;else if(A=="seven")return 7;else if(A=="eight")return 8;else if(A=="nine")return 9;else if(A=="zero")return 0;elsereturn -1;}int main(){string s[1000];int i=0;while(cin>>s[i]){if(s[i]=="="&&s[i-1]=="zero"&&s[i-3]=="zero")break;i++;}for(int j=0;j!=i;){int num1=0,num2=0;int sum=0;while(s[j]!="+"){if(toInteger(s[j])==-1)return 0;elsenum1=num1*10+toInteger(s[j]);j++;}j++;while(s[j]!="="){if(toInteger(s[j])==-1)return 0;elsenum2=num2*10+toInteger(s[j]);j++;}j++;sum=num1+num2;if(sum==0)return 0;cout<<sum<<endl;}return 1;}之二：#include<stdio.h>#include<string.h>int StoInt(char s[]){if(strcmp(s,"zero")==0) return 0;if(strcmp(s,"one")==0) return 1;if(strcmp(s,"two")==0) return 2;if(strcmp(s,"three")==0) return 3;if(strcmp(s,"four")==0) return 4;if(strcmp(s,"five")==0) return 5;if(strcmp(s,"six")==0) return 6;if(strcmp(s,"seven")==0) return 7;if(strcmp(s,"eight")==0) return 8;if(strcmp(s,"nine")==0) return 9;}int main(){char a[50],b[50];int a1[10],b1[10],top1=-1,top2=-1,i,a2,b2;while(scanf("%s",a)!=EOF){if(strlen(a)==1&&a[0]=='+'){while(scanf("%s",b)!=EOF){if(strlen(b)==1&&b[0]=='='){a2=b2=0;for(i=0;i<=top1;i++){a2=a2*10+a1;}for(i=0;i<=top2;i++){b2=b2*10+b1;}if(a2==b2&&a2==0){break;}else{top1=top2=-1;printf("%d\n",a2+b2);break;}}else{b1[++top2]=StoInt(b);}}}else a1[++top1]=StoInt(a);if(a2==b2&&a2==0) break;}return 0;}AC代码。
浙大远程程序设计基础(C)离线作业
浙江大学远程教育学院《程序设计基础（C）》课程作业姓名：学号：年级：学习中心：—————————————————————————————第１章Ｃ语言的基本构成程序调试题1．编辑、调试以下程序步骤1：在Visual C++环境下新建文件可用[开始]→[程序]→[Microsoft Visual C++6.0] →[Microsoft Visual C++6.0] →[文件] →[新建]→[文件] →[C++ Sourse File],输入文件请思考文件ex1-1.c由几个函数构成？调用了那几个系统函数？此程序中用到了哪几个保留字？哪几个用户自定义标识符？答：文件ex1-1.c由两个函数构成，分别是add()和主函数main()。
调用了两个系统函数，分别为scanf和printf。
程序中用到如下几个保留字：int, return。
使用了如下几个用户自定义标示符：x, y, z, a, b, c.步骤3：编译并运行程序，程序运行时输入两个整数，20 40 ，观察程序运行的结果。
答：问题出在main函数第5行这句：scanf("%d %d\n",&a,&b);对于scanf函数内有”\n”，直接回车是无效的，建议去掉“\n”：变成：scanf("%d %d",&a,&b);重新运行再输入，回车，得出结果是60程序运行结果，20+40=602．编辑、调试以下程序步骤1：在Visual C++环境下新建文件可用[开始]→[程序]→[Microsoft Visual C++6.0] →[Microsoft Visual C++6.0] →[文件] →[新建]→[文件] →[C++ Sourse File],输入文件名ex1-2.c步骤2：在文本编辑器中输入以下C程序printf("%d || %d=%d\n",a,b,c);}步骤3：[文件] →[新建]→[文件] →[C++ Sourse File],输入文件名ex1-2-2.c,源程序代int and(int a,int b){int c;c=a&&b;return c;}步骤4：[文件] →[新建]→[文件] →[C++ Sourse File],输入文件名ex1-2-3.c,源程序代码为：int or(int a,int b){int c;c=a||b;return c;}步骤5：点击编译图标，编译程序1-2.c步骤4：点击执行图标，执行程序1-2.c ，当程序运行时，键盘输入20 40，按回车。
浙大通信与计算机网络离线作业在线答案
1.【第01章】根据TCP/IP实用协议标准，从下到上第2层、第3层分别为（）。
A 数据链路层，网络层（即网际层）B 网际层, 应用层C 网络层, 会话层D 网际层, 传输层正确答案:D2.【第01章】TCP/IP协议一个（）层体系结构。
A 2B 3C 4D 7正确答案:C3.【第01章】计算机网络由通信子网(核心部分)和资源子网(边缘部分)两部分组成。
下面列出的各项中不属于通信子网组成部分的是（）。
A 链路B 路由器C 结点交换机D 主机正确答案:D4.【第01章】世界上第一个投入使用的分组交换网是（）。
A InternetB ARPAnetC EthernetD NSFNET正确答案:B5.【第01章】下列哪个协议不是TCP/IP的应用层协议？A TELNETB PPPCC FTPDD SMTP正确答案:B6.【第01章】通信子网（指因特网的核心部分）为网络源结点与目标结点之间提供多条传输路径的可能性，路由选择指的是（）。
A 建立并选择一条物理链路B 建立并选择一条逻辑链路C 网络中间结点即路由器收到一个分组后，确定转发分组的路径D 选择通信介质正确答案:C7.【第01章】在OSI参考模型的7层结构中，实现帧同步功能的是（）。
A 物理层B 数据链路层C 网络层D 传输层正确答案:B8.【第01章】下列不属于局域网的拓扑结构是（）。
A 总线型B 开放型C 星型D 环型正确答案:B9.【第01章】按照网络信号的传输时延，从小到大排列顺序正确的是（）。
A 局域网、广域网、城域网B 城域网、广域网、局域网C 局域网、城域网、广域网D 城域网、局域网、广域网正确答案:C10.【第01章】下列哪一个关于交换的描述是不正确的？A 分组交换采用存储转发技术B 电路交换采用存储转发技术C 报文交换技术在计算机网络中使用较少D 在分组交换的网络中，各个分组可根据序号重新拼装成报文正确答案:B11.【第01章】对于单个结点的故障不会影响到网络的其他部分，但中心接点的故障会导致整个网络的瘫痪网络拓扑结构是（）。
通信与计算机网络离线作业
浙江大学远程教育学院《通信与计算机网络》课程作业姓名：陈新利学号：7年级：12秋学习中心：西溪直属—————————————————————————————作业一1．面向连接服务与无连接服务各自的特点是什么？答：面向连接的服务：开始需要连接成立，然后进数据传输，结束后进行连接释放。
服务靠得住性好，过失率低。
无连接服务：无需成立连接，只进数据传输。
服务靠得住性不好，过失率高。
2．协议与服务又何区别？有何关系？答：协议与服务区别：协议是水平的，服务是垂直的。
协议是“水平的”，即协议是控制对等实体之间的通信的规则。
服务是“垂直的”，即服务是由基层向上层通过层间接口提供的。
协议与服务的关系：在协议的控制下，上层对基层进行挪用，基层对上层进行服务，上基层间用互换原语互换信息。
同层两个实体间有时有连接。
3．长度为100字节的应用层数据交给运输层传送，需加上20字节的TCP 首部。
再交给网络层传送，需加上20字节的IP首部。
最后交给数据链路层的以太网传送，加上首部和尾部18字节。
试求数据的传输效率。
答：数据长度为100字节时传输效率=100/（100+20+20+18）=% 数据长度为1000字节时，传输效率=1000/（1000+20+20+18）=%4．试将TCP/IP和OSI的体系结构进行比较。
讨论其异同的地方。
答：（1）OSI和TCP/IP的相同点是二者均采用层次结构，而且都是按功能分层。
（2）OSI和TCP/IP的不同点：①OSI分七层，自下而上分为物理层、数据链路层、网络层、运输层、会话层、表示层和应用层，而TCP/IP分四层：网络接口层、网间网层（IP）、传输层（TCP）和应用层。
严格讲，TCP/IP网间网协议只包括下三层，应用程序不算TCP/IP的一部份。
②OSI层次间存在严格的挪用关系，两个（N）层实体的通信必需通过下一层（N-1）层实体，不能越级，而TCP/IP可以越过紧邻的下一层直接利用更低层次所提供的服务（这种层次关系常被称为“品级”关系），因此减少了一些没必要要的开销，提高了协议的效率。
通讯与计算机网络作业
第一次作业1-4，⑴通信子网IMP和它们之间互连的通信线路一起负责完成主机之间的数据通信任务。
⑵资源子网通过通信子网互连的主机负责运行用户应用程序，向网络用户提供可供共享的软硬件资源。
⑶分组ARPA网中存储转发的信息基本单位。
⑷存储转发方式当某台主机上的用户要访问网络上异地另一台主机时，主机首先将信息送至本地直接与其相连的IMP，通过通信线路沿着适当路径的IMP，并送入与其直接相连的目标主机。
⑸分组交换网以存储转发方式传输分组的通信子网。
⑹IMP接口报文处理机。
⑺分组交换节点IMP是ARPA网中使用的术语，在其他网络或文献中称为分组交换节点。
⑻三网融合是指内部网、外部网和虚拟专用网VPN混合组建的网络。
⑼节点机IMP或分组交换节点通常也是由小型计算机或微型计算机来实现的，为了和资源子网中的主机相区别。
⑽节点IMP或分组交换节点通常也是由小型计算机或微型计算机来实现的，为了和资源子网中的主机相区别。
1–6、阐述计算机网络的功能答：是由通过通信手段将若干个各自具有自主功能的计算机相互连接在一起以进行信息交换、资源共享或协同工作而组成的复合系统。
2–1、简要说明数据通信技术与计算机网络的关系？答：计算机网络是计算机技术、数据通信技术和网络技术相互渗透、相互促进的产物。
我们可以把运行在网络上的协议、网络操作系统和网络管理软件看作计算机网络的“大脑”，而网络上传输的数据则看作计算机网络的“血液”，传输介质或媒体则可看作计算机网络的“血管”，它遍布整个计算机网络。
数据通信正是为了适应计算机之间信息传输的需要而产生的一种新的通信方式，是计算机网络中各计算机间信息传输的基础。
2–2、传输介质有哪些？并比较其优、缺点。
答：（1）有线传输介质——双绞线、同轴电缆、光纤。
（2）无线传输介质——微波、卫星、短波。
优、缺点：双绞线具有抗干扰能力强，本身噪声小的特点。
与其它传输介质比，双绞线在传输距离、信道带宽和传输速率等性能方面均受到一定限制，但价格较为低廉。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
第1章概述一．填空题：1.计算机网络是计算机技术与__通信技术___相结合的产物。
2.从资源共享的角度来定义计算机网络，计算机网络指的是利用____通信线路____将不同地理位置的多个独立的___自治计算机系统_______连接起来以实现资源共享的系统。
3.在TCP/IP的应用层协议一般使用的是客户服务器方式其中，客户是服务请求方，服务器是服务提供方。
4.在TCP/IP协议模型的运输层中，不面向连接的协议是_UDP_。
5.在TCP/IP模型中，互联网层的上一层是运输层___。
6.通信线路的__带宽__是指通信线路上允许通过的信号频带范围(或通频带)，单位是HZ。
但在计算机网络中，它又用来表示网络通信线路所能传送数据的能力。
7.数据通信中的信道传输速率单位用b/s表示，b/s的含义是_每秒比特。
8.目前，“带宽”常用作描述信道传送数据能力的物理量，其单位是b/s(bit/s),比之大的单位有：__KB/s_____、__Mb/s_____、_Gb/s______等。
9.将计算机网络划分为局域网LAN、城域网MAN、广域网WAN是按__网络的作用范围________划分的。
10.各节点都与中心节点连接，呈辐射状排列在中心节点周围，这种拓扑结构称为__星型拓扑结构________。
11.假设某用户通过电线部门的ADSL技术以2M（即2Mb/s）带宽接入Internet，在正常情况下其下载速度大约是_244kb/s_________。
12.发送数据时，数据块从结点进入到传输媒体所需要的时间称为____发送延时______；网络中电磁信号在信道中传播一定的距离而花费的时间称为__传播延时________。
13.在发送报文之前，先将较长的报文划分成为一个个更小的等长数据段，在每一个数据段前面，加上一些由必要的控制信息组成的首部(header)后，就构成了一个__分组_____。
（备忘：在TCP/IP模型中，数据分组是在运输层和网络层中共同完成的。
先是把数据分为等长的数据段（约为1024bit），然后在每一个数据段前面加上首部，首部是由一些必要的控制信息组成的。
）14.在计算机网络中，____各个子层______及其__各个子层的协议________的集合称为网络体系结构。
15.开放系统互联，采用分层体系结构的模型称为_____OSI_____参考模型。
16.在OSI参考模型中，在对等层次上传送的数据单位，都称为该层的___协议数据单元_______。
这个名词现已被许多非OSI标准采用。
（可参考p.31第1段）17.在因特网中，我们把将要发送的完整的数据块称为__报文______。
18.在OSI参考模型中，会话层在第__5_层，它处于__传输______层提供的服务之上，向_表示__层提供服务。
19.在TCP/IP参考模型中，传输层处于___网络_____层提供的服务之上，向__应用_____层提供服务。
20.___电路____交换必须先建立一条物理链路，这条链路可以视作为一个传送管道。
21.路由器工作在TCP/IP模型中___网络_____层。
二．问答和计算题：1.收发两端之间的传输距离为1000km，信号在媒体上的传播速率为2?108m/s。
试计算：以下两种情况的发送时延和传播时延：(1)数据长度为107bit，数据发送速率为100kb/s(2)数据长度为103bit，数据发送速率为1Gb/s。
从以上计算结果可得出什么结论?答：（1）发送时延:107bit/(100*1000)=100秒传播时延：1000*1000米/(2?108)=0.005秒结论是:如果发送速率小，总时延主要取决于发送时延。
（2）发送时延:103bit/(1000*1000*1000)=0.000001秒传播时延：1000*1000米/(2?108)=0.005秒结论是:如果发送速率大，总时延主要取决于传播时延。
2.长度为100字节的应用层数据交给运输层传送，需加上20字节的TCP首部。
再交给网络层传送，需加上20字节的IP首部。
最后交给数据链路层的以太网传送，加上首部和尾部共18字节。
试求数据的传输效率。
若应用层数据长度为1000字节，数据的传输效率是多少?（提示：数据传输效率=有效数据长度/总数据长度）答：第一种情况数据传输效率=有效数据长度/总数据长度=100/（100+20+20+18）≈63%第二种情况数据传输效率=1000/（1000+20+20+18）≈95%可见，被传输的数据块较小时对应的数据传输效率比较低，否则反之。
3.什么是网络协议和构成的要素？什么是网络体系结构？分别简述OSI、TCP/IP网络体系结构。
答：（1）网络协议是指网络中通信双方为了进行数据交换而建立的规则、标准或约定。
网络协议有三个要素：语法、语义和同步。
（2）所谓网络体系结构是指网络层次结构模型和各层协议的集合，又可以说成是：指各个子层以及各子层协议的集合。
（3）OSI是一个七层体系结构，从第一层到第七层分别是：物理层、数据链路层、网络层、运输层、会话层、表示层、应用层；TCP/IP是一个四层结构模型，从第一层到第四层分别是：、网络接口层、网络层（或称IP层）、运输层和应用层。
前者是一个参考模型，只有理论上的意义；后者是一个网络中广泛使用的实用协议。
第2章物理层一．填空题：1.信号是数据的电气或电磁的表现。
信号可以分为两大类，其中一类是__模拟___信号，代表信息的参数的取值是连续的（如声音、温度、压力等），另一类是___数字____信号，代表信息的参数的取值是离散的（如计算机中处理的“数字、文字、图形”等）。
2.一个通信系统可划分为三大部分，即源系统、传输系统和目的系统。
源系统包括___源点____和发送器，目的系统包括接收器和_____终点___。
3.什么是基带信号？___来自信源的信号，即由1或0组成的数字信号___。
在数字通信信道上直接传输基带信号的方法称为___基带传输_______。
4.基带信号必须经过调制（即基带调制）才能在信道上传输，基带调制过程通常称为___编码_______。
常用的编码方式有不归零编码、归零编码、____曼彻斯特编码____和____差分曼彻斯特编码____。
5.除了基带调制还有带通调制（即使用载波调制基带信号）。
三种基本的带通调制方法是___调幅____、___调频____和___调相____。
个人电脑使用调制解调器接入Internet就是基于这一原理工作的。
6.调制解调器的作用是实现___数字____信号和___模拟____信号之间的相互转换。
7.在一条通信线路中信号可以双向传送，但在同一个时间里只能向一个方向传送的方法称为___半双工通信_______。
8.通信的双方可以同时发送和接收信息，我们把这种通信称为_____全双工通信_____。
9.目前的局域网中常使用星型结构连接，采用的通信介质是___双绞线____。
它是8芯无屏蔽的传输介质，传输速率为100Mb/s。
10.多路复用技术可以分为__频分复用_、_波分复用_和_时分复用_三种基本方式。
11.____曼彻斯特编码_____编码中每一个比特都有一个跳变，不会出现直流分量，该编码方法已经得到广泛应用，是局域网的标准编码。
网卡充当了实现这一编码的角色。
12.下图为曼彻斯特编码，表示的二进制数据为：___01011____。
13.ADSL技术解决了个人用户连接Internet的宽带接入问题，DSL是数字用户线的意思，而A含义为非对称，是指数据的上行和下行带宽是不对称的，上行带宽__小于___（填：小于、等于或大于）下行带宽。
14.DSL称为_数字用户线_，ADSL称为不对称数字用户线，它可实现基于电话线的宽带上网，这里的不对称是指__上行和下行带宽是不对称的，且下行带宽大于上行带宽。
二、单项选择题：1.下面的曼彻斯特编码表示的比特串为____B______。
A.011011B.100110C.111110D.011110三．问答和计算题：1.曼彻斯特编码编码有何优缺点？试写出一串比特数为01001011数据的NRZ码(非归零码)、曼彻斯特、差分曼彻斯特编码三种波形。
答：曼彻斯特编码好处主要有2点:（1）每个比特的中间（即T/2处）有一次电平跳变，利用电平跳变可以产生收发双方的同步信号，因此曼彻斯特编码称为“自含时钟编码”，发送曼彻斯特编码信号时无需另发同步信号。
（2）曼彻斯特编码信号不含直流分量。
主要缺点是效率比较低。
01001011数据三种编码波形图如下：2.假设需要在相隔1000km的两地间传送3kb的数据。
有两种方式：通过地面电缆以4.8kb/s速率发送数据或通过卫星通信以50kb/s速率发送数据。
那么，从发送方开始发送数据直至接收方全部收到数据，哪种方式的传送时间较短？已知电磁波在电缆中的传播速率为光速的2/3(3*105km/s)，卫星通信的端到端单向传播延迟的典型值为270ms（ms是毫秒）。
答:从发送方开始发送数据直至接收方收到全部数据的时间T=数据发送时延+信号传播时延。
对于通过地面电缆的传送方式，电磁波在电缆中的传播速率=3*105km/s*2/3=2*105km，则T=3/4.8+1000/200000=0.63(s)。
对于通信卫星的传送方式，T=3/50+270/1000=0.33(s)。
因此，采用卫星的总传送时间较短。
第3章数据链路层一．填空题：1._网卡_包括了数据链路层和物理层这两层的功能。
2.数据链路层的最基本功能是向该层用户提供__可靠_、__透明_的数据传输基本服务。
3.数据链路层传送的基本数据单元称为___帧_____。
4.帧的首部和尾部的一个重要作用就是进行_帧定界_。
5.帧同步是指数据的接收方应当从接收到的_比特流_中准确地区分帧的开始和结束的位置。
6.将二进制数1010011与另一个二进制数1110100进行异或操作，其结果为__0100111__。
7.循环冗余检验CRC是一种检验方法，而帧检验序列FCS是添加在数据后面的__冗余码__。
8.要发送的数据为101110。
采用CRC的生成多项式是P(x)=x3+1。
试求应添加在数据后面的余数(冗余码)__余数是011__。
9.什么是PPP协议？PPP是Point-to-PointProtocol的缩写，称为点对点协议，PPP协议属于因特网用户计算机和ISP进行通信时所使用的数据链路层协议，目前使用非常广泛。
10.在PPP协议中，_链路控制协议_被用来建立、配置、管理和测试数据链路连接；而_网络控制协议被用来建立和配置不同的网络协议。
11.信息传输如果是逐字符的传输，则称为异步传输_；如果是逐比特的传输，则称为_同步传输_。