計算機網絡題庫大連交通大學.doc

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Chapter 3 Transport Layer 1. A transport-layer protocol provides for logical communication between ____. A Application processes B Hosts C Routers D End systems 2. Transport-layer protocols run in ____. A Servers BClients CRouters DEnd systems 3. In transport layer, the send side breaks application messages into ____, passes to network layer.b5E2RGbCAP A Frames B Segments C Data-grams D bit streams 4. Services provided by transport layer include ____.p1EanqFDPw A HTTP and FTP B TCP and IP C TCP and UDP D SMTP 5. Which of the following services is not provided by TCP? DXDiTa9E3d A Delay guarantees and bandwidth guarantees B Reliable data transfers and flow controls C Congestion controls D In-order data transfers 6. These two minimal transport-layer services----____ and ____----are the only two services that UDP provides! RTCrpUDGiT A process-to-process data delivery, error checking B congestion control, reliable data transfer C flow control, congestion control D In-order data transfer, error checking 7. Port number’s scope is ____ to ____. A 0, 1023 B 0, 65535 C 0, 127 D 0,255 8. The port numbers ranging from ____to ____ are called well-known port number and are restricted.5PCzVD7HxA A 0, 1023 B 0, 65535 C 0, 127 D 0,255 9. UDP socket identified by two components, they are____.jLBHrnAILg A source IP addresses and source port numbers B source IP addresses and destination IP addresses C destination IP address and destination port numbersxHAQX74J0X D destination port numbers and source port numbers 10. TCP socket identified by a (an> ____. A 1-tuple B 2-tuple C 3-tuple D 4-tuple 11. Which of the following applications normally uses UDP services? LDAYtRyKfE A SMTP B Streaming multimedia C FTP D HTTP 18. Which of the following about TCP connection is not correct? Zzz6ZB2Ltk A It is a broadcast connection B It is a point-to-point connection C It is a pipelined connection D It is a full duplex connection 19. The SYN segment is used for____. A TCP connection setup B TCP flow control C TCP congestion control D Closing a TCP connection 20. The FIN segment is used for____. A TCP connection setup B TCP flow control C TCP congestion control D Closing a TCP connection 21. How does TCP sender perceive congestion? A Through a timeout event B Through a receiving duplicate ACK-s event C Both A and B D Either A or B 22. Extending host-to-host delivery to process-to-process delivery is called transport-layer____ and . dvzfvkwMI1 A multiplexing and de-multiplexing B storing and forwarding C forwarding and filtering D switching and routing 23. UDP is a ____ service while TCP is a connection-oriented service. rqyn14ZNXI A Connectionless B Reliable C Connection-oriented D In-order 24. The UDP header has only four fields, they are____. EmxvxOtOco A Source port number, destination port number, length and checksumSixE2yXPq5 B Source port number, destination port number, source IP and destination IP6ewMyirQFL C source IP, destination IP, source MAC address and destination MAC addresskavU42VRUs D source IP, destination IP, sequence number and ACK sequence numbery6v3ALoS89 25. There are two 16-bit integers: 1110 0110 0110 0110, 1101 0101 0101 0101. Their checksum is____. M2ub6vSTnP A 0100010001000011 B 1011101110111100 C 1111111111111111 D 1000000000000000 26. The maximum amount of data that can be grabbed and placed in a segment is limited by the____.0YujCfmUCw A Maximum segment size (MSS> B MTU C Checksum D Sequence number 27. The MSS is typically set by first determining the length of the largest link-layer frame that can be sent by the local sending host----the so-called____.eUts8ZQVRd A Maximum transmission unit (MTU> B MSS C Checksum D Sequence number 28. A File size of 500,000bytes, MSS equals 1000bytes. When we want to transmit this file with TCP, the sequence number of the first segment is 0, and the sequence number of the second segment is ____. sQsAEJkW5T A 1000 B 999 C 1001 D 500000 29. Because TCP only acknowledges bytes up to the first missing byte in the stream, TCP is said to provide____. GMsIasNXkA A Cumulative acknowledgements B Selective acknowledgements C 3 duplicate ACKs D positive ACKs 30. Provided α=0.125, current value of Estimated-RTT is 0.4s, Sample-RTT is 0.8s, then the new value of Estimated-RTT is ____s. TIrRGchYzg A 0.45 B 0.6 C 0.7 D 0.8 31. Provided RcvBuffer=20,LastByteRcvd=20,LastByteRead=15, then RcvWindow=____. 7EqZcWLZNX A 14 B 15 C 16 D 10 32. TCP service does not provide____. A Reliable data transfer B Flow control C Delay guarantee D Congestion control 33. There are two states in TCP congestion control, which are ____.lzq7IGf02E A slow start and congestion avoidance B safe start and congestion avoidance C slow start and congestion abandon D safe start and congestion abandon 34. The transport-layer protocol provides logical communication between ____, and the network-layer protocol provides logical communication ____.zvpgeqJ1hk A hosts, processes B processes, hosts C threads, processes D processes, threads 36. If an application developer chooses ____ protocol, then the application process is almost directly talking with IP. NrpoJac3v1 A HTTP B RIP C CSMA/CD D UDP 37. ____ maintains connection-state in the end systems. This connection state includes receive and send buffers, congestion-control parameters, and sequence and acknowledgment number parameters. 1nowfTG4KI A UDP B TCP C DNS D HTTP 38. The host that initiates the session in the Internet is labeled as ____.fjnFLDa5Zo A server B user agent C client D router 39. With TCP there is no _____ between sending and receiving transport-layer entities. tfnNhnE6e5 A flow control B handshaking C.congestion control D VC setup 40. The Internet’s ____ service helps prevent the Internet from entering a state of gridlock. HbmVN777sL A datagram B congestion control C sliding window D timeout event 41. Connection setup at the transport layer involves ____. V7l4jRB8Hs A server B only the two end systems C client D router 42. A ____layer protocol provides for logical communication between applications. 83lcPA59W9 A transport B application C networking D MAC 43. In static congestion window, if it satisfies W*S/R > RTT + S/R, the Latency is ____.mZkklkzaaP A W*S/R – ( RTT+ S/R> B 2RTT + O/R C 2RTT + O/R + (k-1>[W* S/R- (RTT + S/R>] D 2RTT + S/R 44. The receive side of transport layer reassembles segments into messages, passes to ____layer. AVktR43bpw A Application B Networking C Physical D MAC 45. In the following four options, which one is correct?ORjBnOwcEd A The variations in the SampleRTT are smoothed out in the computation of the EstimatedRTT2MiJTy0dTT B The timeout should be less than the connection’s RTTgIiSpiue7A C Suppose that the last SampleRTT in a TCP connection is equal to 1 sec. Then the current value of TimeoutInterval will necessarily be≥1 secuEh0U1Yfmh D Suppose that the last SampleRTT in a TCP connection is equal to 1 sec. Then the current value of TimeoutInterval will necessarily be≤1 secIAg9qLsgBX 46. The port number used by HTTP is ____. A 80 B 25 C 110 D 53 47. The port number used by SMTP is ____. A 80 B 25 C 110 D 53 48. The port number used by pop3 is ____. A 80 B 25 C 110 D 53 49. The port number used by DNS is ____. A 80 B 25 C 110 D 53 50. The port number used by FTP is ____. A 20 and 21 B 20 C 21 D 53 51. A UDP socket identified by a ____ tuple(s>. A 2 B 4 C 1 D 3 52. A TCP socket identified by a ____ tuple(s>. A 2 B 4 C 1 D 3 53. A TCP socket does not include____. A Source MAC address B Source port number C Destination IP address D Destination port number 54. Which of following about UDP is not correct. A It is a reliable data transfer protocol B It is connectionless C no handshaking between UDP sender, receiver D it is a best effort service protocol 55. DNS uses ____ service. A TCP B UDP C Both TCP and UDP D None of above 56. Which of following about UDP is correct? A Finer application-level control over what data is sent, and when WwghWvVhPE B No connection establishment (which can add delay>, so no delay for establish a connectionasfpsfpi4k C No connection state (so, UDP can typically support many active clients>ooeyYZTjj1 D Large packet header overhead (16-B> 57. Streaming media uses a ____ service normally. A TCP B UDP C Both TCP and UDP D None of above 58. The UDP header has only ____ fields. A 2 B 4 C 1 D 3 59. Which of the following does not included in UDP header. BkeGuInkxI A Source port number B Destination port number C Checksum D Sequence number 60. Which of the following is not a pipelining protocol. PgdO0sRlMo A Rdt1.0 B Go-Back-N C Selective repeat D TCP 61. In the following four descriptions about MSS and MTU, which one is not correct? 3cdXwckm15 A The MSS is the maximum amount of application-layer data in the segmenth8c52WOngM B The MSS is the maximum size of the TCP segment including headersv4bdyGious C The MSS is typically set by MTU D The MTU means the largest link-layer frame 62. 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 ____.J0bm4qMpJ9 A multiplexing B de-multiplexing C forwarding D routing 63. In the following four descriptions about the relationship between the transport layer and the network layer, which one is not correct? XVauA9grYP A The transport-layer protocol provides logical communication between hostsbR9C6TJscw B The transport-layer protocol provides logical communication between processespN9LBDdtrd C The services that a transport-layer protocol can provide are often constrained by the service model of the network-layer protocolDJ8T7nHuGT D A computer network may make available multiple transport protocolsQF81D7bvUA 64. Suppose the following three 8-bit bytes: 01010101, 01110000, 01001100. What’s the 1s complement of the sum of these 8-bit bytes? 4B7a9QFw9h A 00010001 B 11101101 C 00010010 D 10001000 65. The following four descriptions about multiplexing and de-multiplexing, which one is correct? ix6iFA8xoX A A UDP socket is identified by a two-tuples consisting of a source port number and a destination port number.wt6qbkCyDE B If two UDP segment have different source port number, they may be directed to the same destination process.Kp5zH46zRk C If two TCP segments with different source port number, they may be directed to the same destination process.Yl4HdOAA61 D If two TCP segments with same destination IP address and destination port number, they must be the same TCP connection.ch4PJx4BlI 66. UDP and TCP both have the fields except ____. A source port number B destination port number C checksum D receive window 67. If we define N to be the window size, base to be the sequence number of the oldest unacknowledged packet, and next-seq-num to be the smallest unused sequence number, then the interval [nextseqnum,base+N-1] corresponds to packet that ____.qd3YfhxCzo A can be sent immediately B have already been transmitted and acknowledged C cannot be used D have been sent but not yet acknowledged 68. Which of the following about TCP is not correct? E836L11DO5 A It is a connectionless protocol B Point-to-point protocol C Reliable, in-order byte steam protocol D Pipelined protocol 69. Which of the following about TCP is not correct? S42ehLvE3M A It is a connectionless protocol B full duplex data transfer protocol C connection-oriented protocol D flow controlled protocol 70. The maximum amount of data that can be grabbed and placed in a segment is limited by the ____. 501nNvZFis A Maximum segment size (MSS> B MTU C Sequence number D Check sum 71. The MSS is typically set by first determining the length of the largest link-layer frame that can be sent by the local sending host (the so-called____>, and then will fit into a single link-layer frame. jW1viftGw9 A Maximum segment size (MSS> B MTU C Sequence number D Check sum 72. The MSS is the maximum amount of ____layer data in the segment, not the maximum size of the TCP segment including headers.xS0DOYWHLP A Application B Transport C Networking D Link 73. Which of the following field is not used for connection setup and teardown?LOZMkIqI0w A Sequence number B TST C SYN D FIN 74. ____ is the byte stream number of first byte in the segment. ZKZUQsUJed A Sequence number B ACK number C Checksum D port number 75. ____ is the byte sequence numbers of next byte expected from other side. dGY2mcoKtT A Sequence number B ACK number C Checksum D port number 76. Because TCP only acknowledges bytes up to the first missing byte in the stream, TCP is said to provide ____ acknowledgements.rCYbSWRLIA A Cumulative B Selective C Single D Negative 77. Fast retransmit means in the case that ____ duplicate ACK-s are received, the TCP sender resend segment before timer expires.FyXjoFlMWh A 3 B 4 C 5 D 6 78. TCP____ means sender won’t overflow receiver’s buffer by transmitting too much, too fast. TuWrUpPObX A Flow control B Congestion control C Reliable data transfer D Connection-oriented service 79. TCP provides flow control by having the sender maintain a variable called the ____. 7qWAq9jPqE A Receive window B Congestion window C Sliding window D buffer 80. How does TCP sender perceive congestion? A Timeout B 3 duplicate ACK-s C Both A and B D None of above 81. Transport protocols run in ____. A Servers B Clients C Routers D End systems 82. Which of the following services is not provided by TCP? llVIWTNQFk A Delay guarantees and bandwidth guarantees B Reliable data transfers and flow controls C Congestion controls D In-order data transfers 83. Which service does UDP not provide? A multiplexing B de-multiplexing C error-detection B error-correction 84. There are three major events related to data transmission and retransmission in the TCP sender, which one is not in it?yhUQsDgRT1 A data received from application above B de-multiplexing segment C timer timeout D ACK receipt 85. Which of the following applications normally uses UDP services?MdUZYnKS8I A SMTP B Streaming multimedia C FTP D HTTP 86. Which of the following about TCP connection is not correct?09T7t6eTno A It is a broadcast connection B It is a point-to-point connection C It is a pipelined connection D It is a full duplex connection 87. The SYN segment is used for____. A TCP connection setup B TCP flow control C TCP congestion control D Closing a TCP connection 88. Which service helps prevent the internet from entering a state of gridlock?e5TfZQIUB5 A reliable data transfer B flow control C congestion control D handshaking procedure 89. The Internet’s _____is responsible for moving packets from one host to another.s1SovAcVQM A application layer B transport layer C network layer D link layer 90. In the following applications, which one is a bandwidth-sensitive application?GXRw1kFW5s A E-mail B web application C real-time audio D file transfer 91. In the following applications, which one uses UDP?UTREx49Xj9 A E-mail B web application C file transfer D DNS 92. In the following four descriptions, which one is correct?8PQN3NDYyP A If one host’s transport layer uses TCP, then its network layer must use virtual-circuit network.mLPVzx7ZNw B Datagram network provides connection service C The transport-layer connection service is implemented in the routerAHP35hB02d D The network-layer connection service is implemented in the router as well as in the end system.NDOcB141gT 93. ____ is a speeding-matching service---matching the rate which the sender is sending against the rate at which the receiving application is reading.1zOk7Ly2vA A congestion control B flow control C sliding-window control D variable control 94. In the following four descriptions about Rcv-Window, which one is correct?fuNsDv23Kh A The size of the TCP RcvWindow never changes throughout the duration of the connectiontqMB9ew4YX B The size of the TCP RcvWindow will change with the size of the TCP RcvBufferHmMJFY05dE C The size of the TCP RcvWindow must be less than or equal to the size of the TCP RcvBufferViLRaIt6sk D Suppose host A sends a file to host B over a TCP connection, the number of unacknowledged bytes that A sends cannot exceed the size of the size of the RcvWindow.9eK0GsX7H1 95. There are 6 flag fields. Which one is to indicate that the receiver should pass the data to the upper layer immediately?naK8ccr8VI A PSH B URG C ACK D RST 96. Suppose the TCP receiver receives the segment that partially or completely fills in gap in received data, it will ____.B6JgIVV9ao A immediately send ACK B immediately send duplicate ACK C wait some time for arrival of another in-order segmentP2IpeFpap5 D send single cumulative 97. _____ imposes constrain on the rate at which a TCP sender can send traffic into the network.3YIxKpScDM A sliding window B congestion window C receive window D variable window 98. Flow control and congestion control are same at that they all limit the rate of the sender, but differ in that ____.gUHFg9mdSs A flow control limits its rate by the size of RcvWindow, but congestion control by the traffic on the linkuQHOMTQe79 B congestion control limits its rate by the size of RcvWindow, but flow control by the traffic on the linkIMGWiDkflP C flow control mainly is accomplished by the sender, but congestion control by the receiver.WHF4OmOgAw D flow control mainly is accomplished by the receiver, but congestion control by the link.aDFdk6hhPd 99. This job of delivering the data in a transport-layer segment to the correct socket is called ____.ozElQQLi4T A multiplexing B de-multiplexing C forwarding D routing 100. If we define N to be the window size, base to be the sequence number of the oldest unacknowledged packet, and next-seq-num to be the smallest unused sequence number, then the interval [base, nextseqnum-1] corresponds to packet that ____.CvDtmAfjiA A can be sent immediately B have already been transmitted and acknowledged C cannot be used D have been sent but not yet acknowledged 101. ____ are the two types of transport services that the Internet provides to the applications.QrDCRkJkxh A TCP and UDP B connection-oriented and connectionless service C TCP and IP D reliable data transfer and flow control 102. In the following descriptions about persistent connection, which one is not correct?4nCKn3dlMX A The server leaves the TCP connection open after sending a responseijCSTNGm0E B Each TCP connection is closed after the server sending one objectvfB1pxanfk C There are two versions of persistent connection: without pipelining and with pipeliningJbA9VhEou1 D The default mode of HTTP uses persistent connection with pipeliningX7Ahr18pJI 103. The field of Length in UDP segment specifies the length of ____.b3zqXLCqXo A the UDP segment, not including the header B the UDP segment, including the header C the UDP segment’s header D the Length fiel