川大软院计网选择题答案Chapter3

1、CHAPTER 3: TRANSPORT LAYER 1. A tran sport-layer protocol provides for logical com muni cati on betwee nC_. A. Routers B. Hosts C. Applicatio n processes D. E nd systems 2. Tra nsport-layer protocols run in _D_. A. Servers B. Clie nts C. Routers D. E nd systems 3.In transport layer, the send side br

2、eaks application messages intoB_, passes to n etwork layer. A. Frames B. Segme nts C. Data-grams D. bit streams 4.The receive side of tran sport layer reassembles segme nts into messages, passes to A layer. A. Applicatio n B. Networki ng C. Physical D. MAC 5.Services provided by tran sport layer in

3、clude _C_. A. HTTP and FTP B. TCP and IP C. TCP and UDP D. SMTP 6. Which of the following services is not provided by TCPD A. ln-o rder data tran sfers B. Reliable data tran sfers and flow con trols C. Con gestio n con trols D. Delay guara ntees and ban dwidth guara ntees 7. These two minimal transp

4、ort-layer services-A and-are the only two services that UDP provides A. process-to-process data delivery, error check ing B. c on gesti on con trol, reliable data tran sfer C. flow con trol, con gesti on con trol D. ln-o rder data tran sfer, error check ing 8. UDP offers which of the follow ing ben

5、efits relative to TCPC “in or A. UDP guara ntees that In dividual packets of a tran smissi on will arrive B. UDP supports a self-regulating “throttle fe”ture that prevents network saturati on C. UDP con sumes fewer computer resources by not mai ntai ning conn ecti on state D. None of the above 9. Wh

6、ich of the followi ng applicati ons n ormally uses UDP servicesB A. SMTP B. Streami ng multimedia C. FTP D. HTTP 10. The job of gathering data chunks, encapsulating each data chunk with header information to create segments and passing the segments to the network is called A . A. multiplexi ng B. de

7、-multiplex ing C. forwardi ng D. routi ng 11. This job of deliveri ng the data in a tran sport-layer segme nt to the correct socket is called B A.multiplexi ng B.de-multiplex ing C.forwardi ng D.routi ng 12.Port number s scope isB to. A.0, 1023 B.0, 65535 C.0, 127 D.0,255 13.The port nu mbers rangin

8、g fromC toare called well-k nown port nu mber and are restricted. A.0, 127 B.0, 65535 C.0, 1023 D.0,255 14. The UDP header has only four fields, they are A . A. Source port nu mber, desti nati on port nu mber, le ngth and checksum B. Source port number, destination port number, source IP and destina

9、tion IP C. source IP, desti nati on IP, source MAC address and dest in ati on MAC address D. source IP, dest in ati on IP, seque nee nu mber and ACK seque nee nu mber 15. The field of Length in UDP segment specifies the length ofB_. 16.W A. the UDP segme nt, not in clud ing the header B. the UDP seg

10、me nt, in clud ing the header C. the UDP segment s header D. the Length field Vhich of the followi ng about TCP conn ecti on is not correctA A. lt is a broadcast conn ecti on B. lt is a poin t-to-po int conn ecti on C. lt is a pipeli ned conn ecti on D. lt is a full duplex connection 17.ln the follo

11、wing four descriptions about MSS and MTU, which one is not correctC 18. A. The MSS is typically set by MTU B. The MSS is the maximum size of the TCP segment including headers C. The MSS is the maximum amount of application-layer data in the segment D. The MTU means the largest lin k-layer frame A is

12、 the byte stream nu mber of first byte in the segme nt. 19. A. Seque nee nu mber B. ACK number C. Checksum D. port nu mber B is the byte seque nee nu mbers of n ext byte expected from other side. A. Seque nee nu mber B. ACK number C. Checksum D. port nu mber 20.I n the following four options, which

13、one is correctD A. Suppose that the last SampleRTT in a TCP connection is equal to 1 sec. Then the curre nt value of Timeoutl nterval will n ecessarily be 1 sec D. The variations in the SampleRTT are smoothed out in the computation of the EstimatedRTT 21.There are two 16-bit integers: 1110 0110 0110

14、 0110, 1101 0101 0101 0101. Thei checksum is A . A. 011 B. 100 C. 111 D. 000 22.Suppose host A sends host B one TCP segment with sequenee number 418, ack no wledgeme nt nu mber 571, and 4 bytes of data. Then the seque nee nu mber in the ack no wledgeme nt to this segme nt isC A.422B. 418C. 571D. 575

15、 23.Because TCP on ly ack no wledges bytes up to the first missi ng byte in the stream, TCP is said to provide_D_. A. positive ACKs B. Selective ack no wledgeme nts C. 3 duplicate ACKs D. Cumulative ack no wledgeme nts 24.lf we define N to be the window size, base to be the sequenee number of the ol

16、dest un ack no wledged packet, and n ext-seq-num to be the smallest unused sequenee number, then the interval nextseqnum,base+N-1 corresponds to packet that A . A. ca n be sent immediately B. have already bee n tran smitted and ack no wledged C. ca nnot be used D. have bee n sent but not yet ack no

17、wledged 25.W Vhich of the follow ing is not a pipeli ning A. B. Go-Back-N C. Selective repeat D. TCP 26.What is the main differenee between stop-and-wait and pipelined reliable data 27.F tran sfer protocolB A.The pipelined protocol uses the NAK packets, whereas in the stop-and-wait protocol sen ders

18、 always wait for ACK packets. B. With the pipelined protocol, the sender can send several packets in row, whereas in the stop-a nd-wait protocol the sen der cannot send the packets in row. C. With the pipelined protocol, the receiver must send one ACK for severa packets (cumulative ACK), whereas in

19、the stop-and-wait protocol the receiver can not send the cumulative ACK. D. The pipelined protocol uses timeouts, whereas the stop-and-wait protocol does not use the timeout. :ast retra nsmit means in the case that D duplicate ACK-s are received, the TCP sen der rese nd segme nt before timer expires

20、. 28. A. 6 B. 5 C. 4 D. 3 B is a speed in g-match ing service-matchi ng the rate which the sen der is sending aga inst the rate at which the recei ving applicati on is read ing. A.c on gesti on con trol B. flow con trol C. slidi ng-wi ndow con trol D. variable con trol 29.TCPprovides flow control by

21、 having the sender maintain a variable called the _D_. A. buffer B. C on gesti on window C. Slidi ng win dow D. Receive win dow 3O.Provided RcvBuffer = 20, LastByteRcvd = 20, LastByteRead = 15, then RcvWindow=_B_. A. 14 B. 15 C. 16 D. 10 31.ln the follow ing four descriptio ns about TCP conn ecti on

22、 man ageme nt, which one is not correctD 32.H A.Either of the two processes participating in a TCPconnection can end the connection B. If the FIN bit is set to 1, it means that it wants to close the connection C. ln the first two step of the three-way handshake, the client and server ran domly choose an in itial seque nee nu mber D. In the three segments of the three-way handshake, the SYN bit must be set to 1 low does TCP sen der perceive con gesti onD A. Through a timeout eve nt B. Through a recei ving duplicate