通信网络选择题100+答案

1、1 The information to be communicated in a data communications system is the _.A、 Medium B、Protocol C、Transmission D、Message D2Communication between a computer and a keyboard involves _ transmission.A、simplex B、half-duplex C、full-duplex D、automatic A3. _ refers to the structure or format of the data,

2、 meaning the order in which they are presented.A、Semantics B、Timing C、Syntax D、none of the above C4. The host-to-host delivery of the entire message is the responsibility of the _ layer.A、Network B、Transport C、Application D、Physical A5. In OSI/RM, the _ layer lie between the transport layer and the

3、application layer.A、data link and network B、session and presentation C、session and network D、presentation and network B6. When data are transmitted from device A to device B, the header from As layer 4 is read by Bs _ layer.A、Physical B、Data link C、Transport D、None of the above C7. Why was the OSI m

4、odel developed?A、Manufacturers disliked the TCP/IP protocol suite.B、The rate of data transfer was increasing exponentiallyC、Standards were needed to allow any two systems to communicateD、None of the above C8. In the OSI model, encryption and decryption are functions of the _ layer.A、transport B、pres

5、entation C、session D、application B9. _ is a process-to-process protocol that adds only port addresses, checksum error control, and length information to the data from the upper layer.A、 TCP B、UDP C、IP D、None of the above B10. The physical, data link, and network layers are the _ support layers.A、 us

6、er B、network C、both (a) and (b) D、none of the above A11. The _ product defines the number of bits that can fill the link.A、bandwidth-period B、frequency-amplitude C、bandwidth-delay D、delay-amplitude C12. _ encoding has a transition at the beginning of each 0 bit.A、RZ B、Manchester C、Differential Manch

7、ester D、None of the above C13. If the baud rate is 400 for a QPSK signal, the bit rate is _ bps.A、100 B、400 C、800 D、1600 C 14. In _ transmission, the frequency of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal. The peak amplitude and phase o

8、f the carrier signal remain constant, but as the amplitude of the information signal changes, the frequency of the carrier changes correspondingly.A、AM B、PM C、FM D、none of the above C15. _ can be applied when the bandwidth of a link (in hertz) is greater than the combined bandwidths of the signals t

9、o be transmitted.A、TDM B、FDM C、Both (a) or (b) D、Neither (a) or (b) B 16. A _ network is made of a set of switches connected by physical links, in which each link is divided into n channels.A、line-switched B、frame-switched C、circuit-switched D、none of the above C17. In _, each packet is treated inde

10、pendently of all others.A、datagram switching B、circuit switching C、frame switching D、none of the above A18. The _ address in the header of a packet in a datagram network normally remains the same during the entire journey of the packet.A、source B、destination C、local D、none of the above B 19In cyclic

11、 redundancy checking, the divisor is _ the CRC.A、The same size as B、one bit less than C、one bit more than D、None of the above C20We add r redundant bits to each block to make the length n = k + r. The resulting n-bit blocks are called _.A、datawords B、codewords C、blockwords D、none of the above B21To

12、guarantee correction of up to 5 errors in all cases, the minimum Hamming distance in a block code must be _.A. 5 B、6 C、11 D、none of the above C22In a Go-Back-N ARQ, if the window size is 63, what is the range of sequence numbers?A. 0 to 63 B、0 to 64 C、1 to 63 D、1 to 64 A23In Go-Back-N ARQ, if frames

13、 4, 5, and 6 are received successfully, the receiver may send an ACK _ to the sender.A、5 B、6 C、7 D、none of the above C 24In _ framing, we need a delimiter (flag) to define the boundary of two frames.A、fixed-size B、variable-size C、standard D、none of the above B 25In _ protocols, we use _.A、character-

14、oriented; byte stuffing B、character-oriented; bit stuffingC、bit-oriented; character stuffing D、none of the above A 26_ control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgment.A、Flow B、Error C、Transmission D、None of the abov

15、e A 27The _Protocol has both flow control and error control.A、Stop-and-Wait B、Go-Back-N ARQ C、Selective-Repeat ARQ D、both (b) and (c) D 28The Stop-And-Wait ARQ, Go-Back-N ARQ, and the Selective Repeat ARQ are for _ channels.A、noisy B、noiseless C、either (a) or (b) D、neither (a) nor (b) A 29In Go-Back

16、-N ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the send window must be _A、15 B、16 C、31 D、1 C30The vulnerable time for CSMA is the _propagation time.A、the same as B、two times C、three times D、None of the above A31In the _method, after the station finds the line id

17、le it sends or refrain from sending based on the outcome of a random number generator. If the line is busy, it tries again.A、non-persistent B、1-persistent C、p-persistent D、None of the above C32In _ methods, no station is superior to another station and none is assigned the control over another.A、ran

18、dom access B、controlled access C、channelization D、none of the above A33In _, a station monitors the medium after it sends a frame to see if the transmission was successful. If so, the station is finished. If, however, there is a collision, the frame is sent again.A、CSMA/CA B、CSMA/CD C、either (a) or

19、(b) D、both (a) and (b) B34If an Ethernet destination address is 07:01:02:03:04:05, then this is a _ address.A、unicast B、multicast C、broadcast D、any of the above B35Which of the following could not be an Ethernet multicast destination?A、77:7B:6C:DE:10:00 B、9B:AA:C1:23:45:32 C、AC:56:21:1A:DE:F4 D、C3:3

20、2:21:21:4D:34 C 36The _ sub-layer is responsible for the operation of the CSMA/CD access method and framing. A、LLC B、MAC C、MII D、None of the above B 37In _, autonegotiation allows two dvices to negotiate the mode or data rate of operation.A、Standard Ethernet B、Fast Ethernet C、Gigabit Ethernet D、Ten-

21、Gigabit Ethernet B 38The first address assigned to an organization in classless addressing _.A、must be a power of 4 B、must be evenly divisible by the number of addressesC、must belong to one of the A, B, or C classes D、None of the above B 39An organization is granted a block; one address is 2.2.2.64/

22、20. The organization needs 10 subnets. What is the subnet prefix length?A、/20 B、/24 C、/25 D、/26 B 40In a block, the prefix length is /24; what is the mask? _A、255.255.255.0 B、255.255.242.0 C、255.255.0.0 D、None of the above A 41In IPv4, what is the value of the total length field in bytes if the head

23、er is 28 bytes and the data field is 400 bytes? A、428 B、427 C、407 D、107 A 42An IPv4 datagram is fragmented into three smaller datagrams. Which of the following is true?A、The do not fragment bit is set to 1 for all three datagrams.B、The more fragment bit is set to 0 for all three datagrams.C、The iden

24、tification field is the same for all three datagrams.D、The offset field is the same for all three datagrams. C 43In IPv4, what is needed to determine the number of the last byte of a fragment?A、Identification number B、Offset number C、Total length D、(b) and (c) D 44The term _ means that IP provides n

25、o error checking or tracking. IP assumes the unreliability of the underlying layers and does its best to get a transmission through to its destination, but with no guarantees.A、reliable delivery B、connection-oriented delivery C、best-effort delivery D、none of the above C 45The IPv4 header field forme

26、rly known as the service type field is now called the _ field.A、IETF B、checksum C、differentiated services D、none of the above C46A _ address is an internetwork address with universal jurisdiction.A、physical B、logical C、both a and b D、none of the above B47If the sender is a host and wants to send a p

27、acket to another host on the same network, the logical address that must be mapped to a physical address is _.A、the destination IP address in the datagram headerB、the IP address of the router found in the routing tableC、either a or b D、none of the above A48If the sender is a host and wants to send a

28、 packet to another host on another network, the logical address that must be mapped to a physical address is _.A、the destination IP address in the datagram headerB、the IP address of the router found in the routing tableC、either a or b D、none of the above B49The sender is a router that has received a

29、 datagram destined for a host on another network. The logical address that must be mapped to a physical address is _.A、the destination IP address in the datagram headerB、the IP address of the router found in the routing tableC、either a or b D、none of the above B50The sender is a router that has rece

30、ived a datagram destined for a host on the same network. The logical address that must be mapped to a physical address is _.A、the destination IP address in the datagram headerB、the IP address of the router found in the routing tableC、either a or b D、none of the above 51 The _ is the physical path ov

31、er which a message travels.A、Protocol B、Medium C、Signal D、All the above B52A television broadcast is an example of _ transmission.B、 simplex B、half-duplex C、full-duplex D、automatic A53. _ defines how a particular pattern to be interpreted, and what action is to be taken based on that interpretation.

32、A、Semantics B、Timing C、Syntax D、none of the above A54. The _ layer lies between the network layer and the application layer.A、Physical B、Data link C、Transport D、None of the above C55. Why was the OSI model developed?A、Manufacturers disliked the TCP/IP protocol suite.B、The rate of data transfer was i

33、ncreasing exponentiallyC、Standards were needed to allow any two systems to communicateD、None of the above C56. When a host on network A sends a message to a host on network B, which address does the router look at? A、Port B、Logical C、Physical D、Any of the above B57、_ provides full transport layer se

34、rvices to applications.A、TCP B、UDP C、ARP D、IP A58、A port address in TCP/IP is _ bits long.A、32 B、48 C、16 D、64 C59、The _ created a model called the Open Systems Interconnection, which allows diverse systems to communicate.A、OSI B、ISO C、IEEE D、None of the above B60、_ can impair a signal.A、Attenuation

35、B、Distortion C、Noise D、All of the above D61、Unipolar, bipolar, and polar encoding are types of _ encoding.A、line B、Manchester C、NRZ D、Manchester A62、In QAM, both _ of a carrier frequency are varied.A、frequency and amplitude B、phase and frequency C、amplitude and phase D、none of the above C 63、In _ tr

36、ansmission, the phase of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal.A、AM B、PM C、FM D、none of the above B64、_ can be achieved by using multiplexing; _ can be achieved by using spreading.A、Efficiency; privacy and antijamming B、Privacy and

37、antijamming; efficiencyC、Privacy and efficiency; antijamming D、Efficiency and antijamming; privacy A65、_ is designed to use the high bandwidth capability of fiber-optic cable.A、FDM B、TDM C、WDM D、None of the above C66Circuit switching takes place at the _ layer.A、data link B、physical C、network D、tran

38、sport B67In _ there are no setup or teardown phases.A、datagram switching B、circuit switching C、frame switching D、none of the above A68The network layer in the Internet is designed as a _ network.A、virtual-circuit B、datagram C、circuit-switched D、none of the above B69、In _ coding, we divide our messag

39、e into blocks, each of k bits, called _.A、 block; blockwords B、linear; datawords C、block; datawords D、none of the above C70For Stop-and-Wait ARQ, for 10 data packets sent, _ acknowledgments are needed. A、exactly 10 B、less than 10 C、more than 10 D、none of the above A71In _ framing, there is no need f

40、or defining the boundaries of frames.A、fixed-size B、variable-size C、standard D、none of the above A72Byte stuffing means adding a special byte to the data section of the frame when there is a character with the same pattern as the _.A、header B、trailer C、flag D、None of the above C73The Stop-And-Wait A

41、RQ, Go-Back-N ARQ, and the Selective Repeat ARQ are for _ channels.A、noisy B、noiseless C、either (a) or (b) D、neither (a) nor (b) C74Both Go-Back-N and Selective-Repeat Protocols use a _.A、sliding frame B、sliding window C、sliding packet D、None of the above B75In Go-Back-N ARQ, if 5 is the number of b

42、its for the sequence number, then the maximum size of the send window must be _A、15 B、31 C、16 D、1 B76In the Go-Back-N Protocol, if the size of the sequence number field is 8, the sequence numbers are in _ arithmetic,A、modulo-2 B、modulo- 8. C、modulo- 256 D、Any of the above C77In _ each station sends

43、a frame whenever it has a frame to send.A、pure ALOHA B、slotted ALOHA C、both (a) and (b) D、neither (a) nor (b) A78In pure ALOHA, the vulnerable time is _ the frame transmission time.A、the same as B、two times C、three times D、None of the above B79In the _method, a station that has a frame to send sense

44、s the line. If the line is idle, it sends immediately. If the line is not idle, it waits a random amount of time and then senses the line again.A、non-persistent B、1-persistent C、p-persistent D、None of the above A80In _, the chance of collision can be reduced if a station senses the medium before try

45、ing to use it.A、MA B、CSMA C、FDMA D、CDMA B81In _ methods, the stations consult one another to find which station has the right to send.A、random access B、controlled access C、channelization D、none of the above B82The IEEE 802.3 Standard defines _ CSMA/CD as the access method for first-generation 10-Mbp

46、s Ethernet.A、non-persistent B、1-persistent C、p-persistent D、None of the above B83Which of the following could not be an Ethernet unicast destination?A、B4:AA:C1:23:45:32 B、E6:56:21:1A:DE:F4 C、98:32:21:21:4D:34 D、A3:7B:6C:DE:10:00 D84The minimum frame length for 10-Mbps Ethernet is _bytes.A、320 B、640

47、C、680 D、None of the above D85Gigabit Ethernet access methods include _ mode.A、half-duplex B、full-duplex C、both (a) and (b) D、neither (a) nor (b) C86The purpose of the _ is to provide flow and error control for the upper-layer protocols that actually demand these servicesA、MAC B、LLC C、LLU D、None of the above B 87In the Ethernet frame, the