四川大学计算机网络与通信期末考试-2007A(共6页).doc

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1、精选优质文档-倾情为你奉上四 川 大 学 期 末 考 试 试 题（A）（2006 2007 学年第 2 学期）课程号： 课序号：0 6 课程名称：计算机网络与通信 任课教师： 等 成绩：适用专业年级： 04 学生人数： 印题份数： 学号： 姓名：考 试 须 知四川大学学生参加由学校组织或由学校承办的各级各类考试，必须严格执行四川大学考试工作管理办法和四川大学考场规则。有考试违纪作弊行为的，一律按照四川大学学生考试违纪作弊处罚条例进行处理。四川大学各级各类考试的监考人员，必须严格执行四川大学考试工作管理办法、四川大学考场规则和四川大学监考人员职责。有违反学校有关规定的，严格按照四川大学教学事故认

2、定及处理办法进行处理。一、英译汉（10分）略1. PDA 2. RFC 3. IP 4.CIDR 5.URL6. CRC 7. CSMA/CD 8. ARQ 9. RIP 10.MSS 二、单项选择题 （每小题l分，共30分）1. DSL divides the communication link between the home and the ISP into three nonoverlapping frequency bands, a upstream channel is in _A_.A)50 kHz to 1MHz band B) 1MHz to 2MHz bandC)4 kH

3、z to 50kHz band D) 0 to 4kHz band2. As a data packet moves from the upper to the lower layers, headers are A .A) Added; B) subtracted; C) rearranged; D) modified3. What is the main function of the network layer? DA) node-to-node delivery; B) process-to-process message deliveryC) synchronization; D)

4、updating and maintenance of routing tables4. Which of the following is the default mask for the address 168.0.46.201? BA) 255.0.0.0; B) 255.255.0.0; C) 255.255.255.0; D) 255.255.255.2555. A router reads the address on a packet to determine the next hop. AA) IP ; B) MAC; C) source; D)ARP6 . Which dev

5、ice cant isolates the departmental collision domains. AA) Hub; B) switch; C) router; D) A and B7. Input port of a router dont perform _D_ functions.A) the physical layer functions B) the data link layer functionsC) lookup and forwarding function D) network management8. HTTP has a mechanism that allo

6、ws a cache to verify that its objects are up to date. The mechanism is DA) persistent connections B) cookies C) Web Caching D) conditional GET9. A protocol layer can be implemented in _D_.A) software B) hardware C) a combination of the software and hardware D) All of the above注：1试题字迹务必清晰，书写工整。 本题 4

7、页，本页为第 1 页 2 题间不留空，一般应题卷分开 教务处试题编号： 3务必用A4纸打印 10. A protocol has three important factors, they are_A_.A) syntax, semantics, order B) syntax, semantics, layerC) syntax, semantics, packet D) syntax , layer, packet 11. There are two broad classes of packet-switched networks: datagram networks and virtu

8、al-circuit networks. The virtual-circuit networks forward packets in their switches use _D_. A) MAC addresses B) IP addresses C) e-mail addresses D) virtual-circuit numbers12. TCP service model doesnt provide _D_service. A) reliable transport service B) flow control service C) congestion-control ser

9、vice D) guarantee a minimum transmission rate service.13. Usually elastic applications dont include_B_.A) Electronic mail B) Internet telephonyC) file transfer D) Web transfer 14. A user who uses a user agent on his local PC receives his mail sited in a mail server by using _B_ protocol.A)SMTP B) PO

10、P3C)SNMP D) FTP15. Considering sliding-window protocol, if the size of the transmitted window is N and the size of the receiving window is 1,the protocol is B A) stop-and-wait protocol B) Go-Back-N protocol C) selective Repeat protocol D) alternating-bit protocol16. which IP address is effective_B_.

11、A) 202,131,45,61 B) 126.0.0.1C) 192.268.0.2 D) 290.25.135.1217. if IP address is 202.130.191.33, subnet mask is 255.255.255.0,then subnet prefix is_D_ A) 202.130.0.0 B) 202.0.0.0 C) 202.130.191.33 D)202.130.191.018.The command Ping s implemented with _B_messagesA) DNS B) ICMPC) IGMP D) RIP19. Which

12、layer-function is mostly implemented in an adapter? _A_A) physical layer and link layer B) network layer and transport layerC)physical layer and network layer D) transport layer and application layer20. If a user brings his computer from Chengdu to Peking, and accesses Internet again. Now, _B_ of hi

13、s computer needs to be changed. A) MAC address B) IP addressC) e-mail address D) user address三、填空题 （每空1分，共22分(注意：所有填空题不能写中文，否则中文答案对的情况下扣0.5分) 1. link-layer address is variously called a LAN address, a MAC address, or a physical address.2 In the layered architecture of computer networking, n layer is

14、 the user of n-1 layer and the service provider of n+1 layer.A) n B) n+3 C) n+1D) n-1注：1试题字迹务必清晰，书写工整。 本题 4 页，本页为第 2 页 2 题间不留空，一般应题卷分开 教务处试题编号： 3务必用A4纸打印 AprocessingB3. Suppose that Host A has established a connection to a process in the server. Please fill in the segments containing data that the c

15、lient and server hosts can send to each other.Then Host A Host BIf Host A Host B Source port =13 Dest port =21 Sequence number=1235Acknowledgment number=67905SYN=0ACKReceive windowChecksumNIL 1000 bytes data From above figure ,the window size of the segments is 216.4.Suppose a user sitting in a home

16、 network behind host 10.0.0.1 requests a Web page on some Web server(port 80) with IP address 202.119.30.156,please according the NAT translation table at the NAT router,fill in datagram that include port numbers as well as IP addresses.（有IP缺端口号一个扣0.5分 ）NAT transtation tableWAN sideLAN side139.78.30

17、.10, 500110.0.0.1, 1024 Source addr=10.0.0.1,1024Dest addr=202.119.30.156,80S =139.78.30.10,5001Dddr=202.119.30.156,80S addr=202.119.30.156,80D addr=139.78.30.10,5001139.78.30.1010.0.0.4S addr=202.119.30.156,80D addr=10.0.0.1,102410.0.0.110.0.0.210.0.0.3Source port =21 Dest port =13 Sequence number=

18、6790Acknowledgment number=22355SYN=0ACKReceive windowChecksumNIL 1000 bytes data 5.Summary of reliable data transfer mechanisms and their use, as show below. Please fill in transfer mechanisms. MechanismUseChecksumUsed to detect bit errors in a transmitted packet.Sequencenumber Used for sequential n

19、umbering of packets of data flowing from sender to receiver.Acknowledgment（或ACK）Used by the receiver to tell the sender that a packet or set of packets has been received correctly.Countdown timerUsed to timeout/retransmit a packet, possibly because the packet (or its ACK)was lost .Window,pipelinling

20、The sender may be restricted to sending only packets with sequence numbers that fall within a given range.四、判断题（每小题1分，共10分）1. The services of TCPs reliable data transfer founded on the services of the unreliable data transfer. 2. Any protocol that performs handshaking between the communication entit

21、ies before transferring data is a connection-oriented service.3. HOL blocking occur in output ports of router.4. Socket is globally unique.5. SMTP require multimedia data to be ASCII encoded before transfer.6. The transmission delay is a function of the distance between the two routers. 7. IP addres

22、s is associated with the host or router. SO one device only have one IP address.8. In packet-switched networks, a sessions messages use the resources on demand, and Internet makes its best effort to deliver packets in a timely manner. 9. UDP is a kind of unreliable transmission layer protocol, so th

23、ere is not any checksum field in UDP datagram header. 10. Forwarding table is configured by both Intra and Inter-AS routing algorithm 五、计算题 (28 points)1. Consider the following network. With the indicated link costs, use Dijkstras shortest-path algorithm to compute the shortest path from V to all ne

24、twork nodes(8分)y421133241211wx925ustvzStepND(t),p(t)D(U),p(u)D(s),p(s)D(w),p(w)D(x),p(x)D(y),p(y)D(z),p(z)1v9,v5,v1,v3,v2,v2vw9,v4,w2,w2,v3vwx9,v4,w2,v4vwxy6,y4,w13,y5vwxyu6,y8,u13,y6vwxyut7,t8,t7vwxyuts8,t8vwxyutsz9So: the shortest path from v to t is vyt ; the shortest path from v to u is vwu; the

25、 shortest path from v to s is vyts. the shortest path from v to w is vwthe shortest path from v to x is vwx the shortest path from v to s is vy. the shortest path from v to z is vytznote:如果只有列表，没有最短路径的结论扣3分2. Suppose a ISP has been allocated the address block 202.115.168.0/24, now if the ISP wants t

26、o divide its address block into 6 equal-sized subnet address blocks, and each subnet could include 16 hosts.1) Please determine the length of subnet portion of address.(namely, how many bits should be extend?(2 分 ) 27位（扩展3位）2) Please write out the subnet 4#s network prefix(2分) and subnet mask.(2分)su

27、bnet 4#s network prefix ：202.115.168.128/27；subnet mask：255.255.255.2243) Please write out the subnet 4#s broadcast address.(2分)4#s broadcast address：202.115.168.1594) Please write out the subnet 4#s range of host address. （2分）the subnet 4#s range of host address.：202.115.168.129/27202.115.168.158/2

28、7 3. Consider sending a 3,000-byte datagram into a link that has an MTU of 1500bytes.Suppose the original datagram is stamped with the identification number 422 .Assuming a 20-byte IP header,How many fragments are generated? What are their characteristics?(10分)Fragment Bytes IDOffsetflag1st fragment1480 (1分) 422 (0.5分)0 (1分)1(0.5分)2st fragment1480 (1分)422 (1分)185 (1分)1（0.5分）3st fragment20 (1分)422 (1分)370 (1分)0(0.5分)注：1试题字迹务必清晰，书写工整。 本题 4 页，本页为第 4 页 2 题间不留空，一般应题卷分开 教务处试题编号： 3务必用A4纸打印 专心-专注-专业