计算机网络复习计网试卷

1、诚信应考,将带来严重！华南理工大学期末 Computer Networks A 试卷注意事项：1.2.3请将密封线内填写清楚；请直接答在试卷上(注：选择题形式：闭卷；所有请填入题目前面的表格中)；时间 120 分钟。4. 本试卷共五大题，满分 100 分,题号12345总分得分评卷人1. Select the correct choice.(30 scores, every one is 2 scores)NO.123456789101112131415solution(1) It is the architecture for TCP/IP protocol stack, which one

2、 below doesnt belong tothe application layer ()?A.NETdo HTTP,)B.ICMPC. POPD. SMTPFTP, SMTP and POP3 run on top of TCP rathern UDP?(2) Why(A. Reliable daC. Real-timeransferB. ThroughputD. Security(3) Supe Host A wants to send a file to Host B, there are three links betn A toB, and the rates of the th

3、ree links are respectively R1=2 Mbps, R2= 1Mbps, andR3= 4 Mbps. If no any other traffiche network, what is the throughput forthe file transfer? ()A. 2 MbpsB. 1 MbpsC. 4 MbpsD. 7Mbps(4) Supe an application generates cks of 120 bytes of data every second, andTCP segment and then an IP datagram(noeach

4、ck gets encapsulated in aoptions fields).What percentage of each datagram will contain application data?(A. 80%)B. 75%C. 60%D.25%(5) The job of delivering the data in a transport-layer segment to the correct socket iscalled().学号学院专业座位号( 密 封 线 内 不 答 题 )密封线A. DemultiplexingC. TDMB. MultiplexingD. FDM(

5、6) Consider sending a 999 byte datagramo a links an MTU of 500 bytes ,(A.B.C.D.)fragments are created with offset field value 0,500, respectivelyfragments are created with offset field value 0, 480, 960, respectively3 fragments are created with offset field value 0, 60, 120, respectively None of the

6、se above(7) About the encapsulation relationships of segment、datagram and frame, which ofthe following is correct?()A.Segment is encapsulated within the frame, and the frame isencapsulatedwithhe datagram.B.Datagram is encapsulated within the Segment, and theSegment isencapsulated withhe frame.C.Segm

7、ent is encapsulated within the datagram, and thedatagram isencapsulated withhe frame.D. Frame is encapsulated withhe datagram, and the datagram is encapsulatedwithhe segment.(8) TCP has which of the following characteristics: ()A. Flow controlC. Congestion control(9) What is the ICMP used forB. Conn

8、ection establishmentD. All of the above？ ()A. Error reportingB. Used by(10) A taking-turns MAC protocolC. A and BD. None above.has which of the following characteristics:()A. there is no single pofailureit does not generate collisthere is no master nodeall of the above(11) In the Ethernet two-layer

9、switches, how is the forwarding table established?()A. Manual configurationC. Routing algorithmB. Self-learningD. Destination address learning(12) Which are the error detection and correction techniques used often in link layer?()A. CRCB. ChecksumC. Parity checksD. None of the above(13) In routing a

10、mong ASs, which of the following ies dominants? ()A. Routing PolicyC. Current congestion levelsB. Geographical distance betn Asshe ASsD. Number of ASs traversed(14) An ARP query packet is encapsulated in ()a link-layer frame addressed to a specific adaptera link-layer broadcast framean IP datagramno

11、ne of the above(15) Two important reasonst theernet is)anized as a hierarchy of networksfor the pures of routing are (A. Least cost andum free circuit availabilityMessage complexity and speed of convergenceScale and administrative autonomyLink cost changes and link failure2. Fill the bl. (10 scores,

12、 every blis 1 score )(1)The task of the data link layer is providing daransmisservibetn; The task of the network layer is providing datatransmisservibetn; and the task of transportlayer is providing daransmisservinetworkbetn.(2)Thetwokeyfunctionsof.layerare and(3)Two routing protocols have been used

13、extensively for routing within anautonomous systemheernet: RIP protocol and protocol.(4)The header of IP datagram has a field, when the value of the fieldis 0, the datagram transmitted will be discarded.(5)RIP advertisements typically announce the number of hops to variousdestination;BGPupdates,onth

14、eotherhand,announcetheto the various destinations.TCP provides a service to its application to eliminate the sibility of the sender overwhelming the receiver.(6)(7)The tool (d)t can be used to determine the number of hops to adestination and the round trip time (RTT) for each hop is .3.Judge the fol

15、lowing questions as true or false. (10 scores, everyone is 1 scores)(1)When a user request a Wget consists of some text and two images. Forthis page, the cnt will send one request message and receive three response message.With a window size of 1, SR, GBN, and the alternating bit protocol are functi

16、onally equivalent.When using distance vector route algorithm, the complete network topology information must be known by a router.In a P2P file-sharing application, there is no notion of cnt and server sides of(2)(3)(4)a communication ses.(5)(6)(7)(8)All nodes connected to theernet must implement UD

17、P.Media Acs Control is a function of the data-link layer.s are delivered to receivers server using POP3 protocol.Both CIDR and NAT can lead to muaddress space.ore efficient use of the available IPv4(9)(10)Collis will not occur under CSMA/CD MAC protocol.When a TCP segment arrives to a host, the sock

18、et to which the segment isdirected depends on the destination port number and the destination IP address.NO.12345678910Solution(T or F)4. Answer the following questions briefly. (30 scores, every one is 6scores)(1)Consider sending a packet from a source host to a destination host over a fixed route.

19、Name the four factors of delay for the packet. Is the delay constant ? Why or why not? Identify which factor will most likely predominate (i.e. ,be thelargest factor ) for 1M Byte Packets in a flow on the following different links.a) 10 Mb/s LAN segment betn two PCshe same buildingb) 1 Mb/s geosynch

20、ronous-orbit salite (同步轨道and China) link betn the USc) on theernet betn the US and China(2)Name System (DNS) uses a distributed approach as oped to a singleusingserver. Why? Athe DNS. And ame a cme the cnt needs to find the IP address ofns a local DNS server, butt server does noveany addresses cache

21、d. What are the DNS serversIP address?t are queried (in order) to find the(3) Try to describe the main principles of reliable daransfer fBN as figure 1.Figure 1GBN window mechanism(4) Consider a subnet with prefix 4/26. Give anexanle of one IP erface in thisoftheformaddress(of form.)t can be assigne

22、d tonetwork.SupeanISPownstheblockofaddresses4/26. And supwith each block having the sae it wants to create four subnets from this block,mber of IP addresses. What are the prefixes(ofform a.b.c.d/x) for the four subnets?(5) As figure 2, supe Host A sends a datagram to Host B via router R. Please draw

23、up the source and destination MAC addresses, andsource and destination IPaddresseshe frame as required below:From A to the RFrom R to B.88-B2-2F-54-1A-0F74-29-9C-E8-FF-55AE6-E9-00-17-BB-4B1A-23-F9-CD-06-9B2111221020B12RFigure 249-BD-D2-C7-56-2ACC-49-DE-D0-AB-7D5. Comprehensive Questions (20 scores,

24、every one is 10 scores)(1) Consider the following network. With the indicated link costs, use Dijkstrasshortest palgorithm to compute the shortest path from x to all network nodes.While selecting the next node, if several nodes have the same min cost, select the onewith lowest id, (e.g., if t and v

25、have the same min cost, then select t).Figure 4Figure 3Please show how the algorithm works by filling out the following table.(2) Ame the following graph shows the behavior of a TCP congestion control,answer each question wishort discusjustifying your answer.a) Identify theervals of time when TCP sl

26、ow start is operating.b) Identify theervals of time when TCP congestion avoidance is operating.c)After 14th transmisround,is segment loss detected by a triple duplicate ACK orby a timeout? And which verthis information?of TCP protocol(Reno or Tahoe) is used base ond) During what transmisround is the

27、 50th segment?e) Aming a packet loss is detected after the 23rd round by the receipt of a tripleduplicate ACKs, what will be the values of the congestion window size and Threshold?诚信应考,将带来严重！华南理工大学期末 Computer Networks A 试卷6. Select the correct choice.(30 scores, every one is 2 scores)7. Fill the bl.

28、 (10 scores, every blis 1 score )(1)(2)(3)(4)(5)(6)(7)Adjacent nodes; hosts ; pro Forwarding , routing OSPFTTLsesSequence of ASs on the routes Flow controlTraceroute (Tracert)8. Judge the following questions as true or false. (10 scores,one is 1 scores)every9. Answer the following questions briefly.

29、 (30 scores, every one is 6scores)(1) nodal prosing delay, queuing delay, transmisdelay .Propagation delay.Itnot constant, and depends on the consgestion.a) transmisdelayb) propagation delayc) queuing delay学号学院专业座位号( 密 封 线 内 不 答 题 )密封线NO.12345678910Solution(T or F)FTTFTFFNO.123456789101112131415solutionBABBABCDCBBAABC(2) Why: A distributed hierarchy of server