《網(wǎng)絡原理-Computer-Networks》期末(A)試卷

1、精選優(yōu)質(zhì)文檔-傾情為你奉上上海應用技術學院20092010學年第1學期網(wǎng)絡原理 Computer Networks期末（A）試卷課程代碼: 學分: 考試時間: 分鐘課程序號: 6668,6780, 6666 班級： 學號： 姓名: 我已閱讀了有關的考試規(guī)定和紀律要求，愿意在考試中遵守考場規(guī)則，如有違反將愿接受相應的處理。題 號一二三四五六七八九十總 分得 分 試卷共 8 頁，請先查看試卷有無缺頁，然后答題。 I. Abbreviations: (10 points in total)The (everyday English) expansions of the following abbre

2、viations are wanted: A1-10.(1 point each, 10 points in total)A1. WAN = Wide Area NetworkA2. TCP = Transmission Control ProtocolA3. DNS = Domain Name System/ServiceA4. OSPF = Open Shortest Path FirstA5. SMTP = Simple Mail Transfer ProtocolA6. PPP = Point-to-Point ProtocolA7. GPS = Global Positioning

3、SystemA8. CSMA/CD = Carrier Sense Multiple Access with Collision DetectionA9. IP = Internet ProtocolA10. VLAN = Virtual LAN = Virtual Local Area NetworkII. Concepts: (30 points in total)Give the definition or description of the following concepts or names:B1-5 (6 points each, 30 points in total)B1.

4、What is the main task of the network layer (in the OSI reference model)? Solution (c5-P00)The network layer is concerned with getting packets from the source machine all the way to the destination machine.B3. We have studied many channel allocation methods. Please name three of them.B4. What approac

5、hes do we take to do error control? (or what mechanisms do we use to do error control?)B5. Please draw a figure to show the OSI Reference Model. Solution: （c1）P37B6. In Fig II-1, one of the 802.11 MAC sublayer protocol is illustrated and four stations, A, B, C, and D, are shown. Which of the last tw

6、o stations do you think is closest to A and why?III. Computation: (40 points in total)The process/procedure or explanation of computation and the correct results are all wanted. C1-5. (8 points each, 40 points in total).C1. The following character encoding is used in a data link protocol: A: ; B: ;

7、FLAG: ; ESC: Show the bit sequence transmitted (in binary) for the four-character frame: A ESC FLAG B Awhen each of the following framing methods is used:(a) Character count. (b) Flag bytes with byte stuffing.(c) Starting and ending flag bytes, with bit stuffing.C2. A bit stream is transmitted using

8、 the standard CRC method described in the text. The generator polynomial is x4+ x2+1. Show what code the receiver's end receives if the receiver's end will receive correct code.Solution:0 / 10101 the remainder is 1000So the receiver will receive 0C3. A router has the following (CIDR) entries

9、 in its routing table:Address/maskNext hop195.46.56.0/22Interface 0195.46.60.0/22Interface 1defaultRouter 1For each of the following IP addresses, what does the router do if a packet with that address arrives?a. 195.46.53.20b. 195.46.62.100c. 192.53.56.78SOLUTION: a. 53=B Because mask is 252(=B) sol

10、ution is =52So the router goes to Router 1 if a packet with address 195.46.53.20 arrives.b. 62=B Because mask is 252(=B) solution is So the router goes to Interface 1 if a packet with address 145.46.62.100 arrives.c. router 1 b/c 192.53.C4. A large number of consecutive IP address are available star

11、ting at 198.16.0.0. Suppose that 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. Solution(P478-40)To start w

12、ith, all the requests are rounded up to a power of two. The startingaddress, ending address, and mask are as follows: A: 198.16.0.0 198.16.15.255 written as 198.16.0.0/20B: 198.16.16.0 198.16.23.255 written as 198.16.16.0/21C: 198.16.32.0 198.16.47.255 written as 198.16.32.0/20D: 198.16.64.0 198.16.

13、95.255 written as 198.16.64.0/19C5. Consider building a CSMA/CD network running at 1 Gbps over a 1-km cable with no repeaters. The signal speed in the cable is 200,000 km/sec. What is the minimum frame size? Solution(P340-21) 對于1km 電纜，單程傳播時間為1/ =5×10-6 s，即5，來回路程傳播時間為2t =10。為了能夠按照CSMA/CD 工作，最小幀的

14、發(fā)射時間不能小于10。以1Gb/s 速率工作，10可以發(fā)送的比特數(shù)等于： 因此，最小幀是10 000 bit 或1250 字節(jié)長。 IV. Description: (20 points in total)a brief description with all principal points is wanted. D1-2. (10 points each, 20 points in total)D1. Two types of transmission technologies are in widespread use. They are broadcast links and poi

15、nt-to-point links. a) What do we mean by 'broadcast networks'? Give the definition or a brief description.p15Broadcast networks have a single communication channel that is shared by all the machines on the network. Short messages, called packets in certain contexts, sent by any machine are r

16、eceived by all the others.b) What do we mean by 'point-to-point networks'? Give the definition or a brief description.p15point-to-point networks consist of many connections between individual pairs of machines. To go from the source to the destination, a packet on this type of network may ha

17、ve to first visit one or more intermediate machines. Often multiple routes, of different lengths, are possible, so finding good ones is important in point-to-point networks.D2. The idea behind link state routing is simple and can be stated as five parts. What are the five parts or steps that each router must do?Solution:1).