《计算机网络》复习题及答案.doc

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1、Chapter 1 Computer Networks and the Internet1.The (A) is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world.A.public Internet B.IntranetC.switch net D.television net2.Which kind of media is not a guided media? (D)A.twisted-pair copp

2、er wire B.a coaxial cableC.fiber optics D.digital satellite channel3.Which kind of media is a guided media? (C)A.geostationary satellite B.low-altitude satelliteC.fiber optics D.wireless LAN4.The units of data exchanged by a link-layer protocol are called (A).A.Frames B.SegmentsC.Datagrams D.bit str

3、eams5.Which of the following option belongs to the circuit-switched networks? (D)A.FDM B.TDMC.VC networks D.both A and B6.(B)makes sure that neither side of a connection overwhelms the other side by sending too many packets too fast.A.Reliable data transfer B.Flow controlC.Congestion control D.Hands

4、haking procedure7.(A) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A.Store-and-forward transmission B.FDMC.End-to-end connection D.TDM8.Datagram networks and virtual-circuit networks differ in that (C).A.datag

5、ram networks are circuit-switched networks, and virtual-circuit networks are packet-switched networks.B.datagram networks are packet-switched networks, and virtual-circuit networks are circuit-switched networks.C.datagram networks use destination addresses and virtual-circuit networks use VC. number

6、s to forward packets toward their destination.D.datagram networks use VC. numbers and virtual-circuit networks use destination addresses to forward packets toward their destination.9.In the following options, which one is not a guided media? (D)A.twisted-pair wire B.fiber opticsC.coaxial cable D.sat

7、ellite10.Processing delay does not include the time to (B).A.examine the packets headerB.wait to transmit the packet onto the linkC.determine where to direct the packetD.check bit-error in the packet11.In the following four descriptions, which one is correct? (C)A.The traffic intensity must be great

8、er than 1.B.The fraction of lost packets increases as the traffic intensity decreases.C.If the traffic intensity is close to zero, the average queuing delay will be close to zero.D.If the traffic intensity is close to one, the average queuing delay will be close to one.12.The Internets network layer

9、 is responsible for moving network-layer packets known as (B) from one host to another.A.frame B.datagramC.segment D.message13.The protocols of various layers are called (A).A.the protocol stack B.TCP/IPC.ISP D.network protocol14.There are two classes of packet-switched networks: (A) networks and vi

10、rtual-circuit networks.A.datagram B.circuit-switchedC.television D.telephone15.Access networks can be loosely classified into three categories: residential access, company access and (B) access.A.cabled B.wirelessC.campus D.city areaQuestion 1617Suppose, a is the average rate at which packets arrive

11、 at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is (16: B ), and it should no greater than (17: B ).16. A.LRa 17.A.2 B.LaR B.1C.RaL C.0 D.LRa D.118.In the Internet, the equivalent concept to end systems is (A).A.hosts B.serversC.clients D.rout

12、ers19.In the Internet, end systems are connected together by (C).A.copper wire B.coaxial cableC.communication links D.fiber optics20.End systems access to the Internet through its (C).A.modems B.protocolsC.ISP D.sockets21.End systems, packet switches, and other pieces of the Internet, run (D) that c

13、ontrol the sending and receiving of information within the Internet.A.programs B.processesC.applications D.protocols22.There are many private networks, such as many corporate and government networks, whose hosts cannot exchange messages with hosts outside of the private network. These private networ

14、ks are often referred to as (C).A.internets B.LANC.intranets D.WAN23.The internet allows (D) running on its end systems to exchange data with each other.A.clients applications B.server applicationsC.P2P applications D.distributed applications24.The Internet provides two services to its distributed a

15、pplications: a connectionless unreliable service and (B) service.A.flow control B.connection-oriented reliableC.congestion control D.TCP25.It defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or rec

16、eipt of a message or other event. The sentence describes (B).A.Internet B.protocolC.intranet D.network26.In the following options, which does not define in protocol? (D)A.the format of messages exchanged between two or more communicating entitiesB.the order of messages exchanged between two or more

17、communicating entitiesC.the actions taken on the transmission of a message or other eventD.the transmission signals are digital signals or analog signals27.In the following options, which is defined in protocol? (A) A.the actions taken on the transmission and/or receipt of a message or other event B

18、.the objects exchanged between communicating entities C.the content in the exchanged messages D.the location of the hosts28.In the following options, which does not belong to the network edge? (B)A.end systems B.routersC.clients D.servers29.In the following options, which belongs to the network core

19、? (B)A.end systems B.routersC.clients D.servers30.In the following options, which is not the bundled with the Internets connection-oriented service? (B)A.reliable data transfer B.guarantee of the transmission timeC.flow control D.congestion-control31.An application can rely on the connection to deli

20、ver all of its data without error and in the proper order. The sentence describes (C).A.flow control B.congestion-controlC.reliable data transfer D.connection-oriented service32.It makes sure that neither side of a connection overwhelms the other side by sending toomany packets too fast. The sentenc

21、e describes (A).A.flow control B.congestion-controlC.connection-oriented service D.reliable data transfer33.It helps prevent the Internet from entering a state of gridlock. When a packet switch becomes congested, its buffers can overflow and packet loss can occur. The sentence describes (B).A.flow c

22、ontrol B.congestion-controlC.connection-oriented service D.reliable data transfer34.The Internets connection-oriented service has a name, it is (A).A.TCP B.UDPC.TCP/IP D.IP35.In the following options, which service does not be provided to an application by TCP? (C)A.reliable transport B.flow control

23、C.video conferencing D.congestion control36.The Internets connectionless service is called (B).A.TCP B.UDPC.TCP/IP D.IP37.In the following options, which does not use TCP? (B)A.SMTP B.internet telephoneC.FTP D.HTTP38.In the following options, which does not use UDP? (D)A.Internet phone B.video confe

24、rencingC.streaming multimedia D.telnet39.There are two fundamental approaches to building a network core, (B) and packet switching.A.electrical current switching B.circuit switchingC.data switching D.message switching40.In (C) networks, the resources needed along a path to provide for communication

25、between the end system are reserved for the duration of the communication session.A.packet-switched B.data-switchedC.circuit-switched D.message-switched41.In (A) networks, the resources are not reserved; a sessions messages use the resources on demand, and as a consequence, may have to wait for acce

26、ss to communication link.A.packet-switched B.data-switchedC.circuit-switched D.message-switched42.In a circuit-switched network, if each link has n circuits, for each link used by the end-to-end connection, the connection gets (A) of the links bandwidth for the duration of the connection.A.a fractio

27、n 1/n B.allC.1/2 D.n times43.For (C), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot.A.CDMA B.packet-switched networkC.TDM D.FDM44.(B) means that the switch must receive the entire packet before it can begin to transmit the first bit of the p

28、acket onto the outbound link.A.Queuing delay B.Store-and-forward transmissionC.Packet loss D.Propagation45.The network that forwards packets according to host destination addresses is called (D) network.A.circuit-switched B.packet-switchedC.virtual-circuit D.datagram46.The network that forwards pack

29、ets according to virtual-circuit numbers is called (C) network.A.circuit-switched B.packet-switchedC.virtual-circuit D.datagram47.In the following entries, which is not a kind of access network? (D)A.residential access B.company accessC.wireless access D.local access48.Suppose there is exactly one p

30、acket switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end delay to

31、send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.) (A)A.L/R1L/R2 B.L/R1C.L/R2 D.none of the above49.The time required to examine the packets header and determine where to direct the packet is part of the (B).A.queuing delay B.processing delayC.propagation del

32、ay D.transmission delay50.The time required to propagate from the beginning of the link to the next router is (C).A.queuing delay B.processing delayC.propagation delay D.transmission delay51.Consider sending a packet of 3000bits over a path of 5 links. Each link transmits at 1000bps. Queuing delays,

33、 propagation delay and processing delay are negligible. (6 points)(1).Suppose the network is a packet-switched virtual circuit network. VC setup time is 0.1 seconds. Suppose the sending layers add a total of 500 bits of header to each packet. How long does it take to send the file from source to des

34、tination?t=5*(3000+500)/1000+0.1=17.6s(2).Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose each packet has 200 bits of header. How long does it take to send the file?t=5*(3000+200)/1000=16s(3).Suppose that the network is a circuit-switched n

35、etwork. Further suppose that the transmission rate of the circuit between source and destination is 200bps. Assuming 0.02s setup time and 200 bits of header appended to the packet, how long does it take to send the packet?t=(3000+200)/200+0.02=16.02sChapter 2 Application Layer1.In the following four

36、 descriptions, which one is correct? A.In C/S architecture, clients communicate with each other directly.B.In C/S architecture, client has a fixed well-known address.C.In P2P architecture, peers communicate with each other directly.D.In P2P architecture, peer has a fixed well-known address.2.In the

37、context of a communication session between a pair of process, the process that initiates the communication is labeled as the , the process that waits to be contacted to begin the session is labeled as the .A.client process, server process B.sending process, receiving processC.input process, output p

38、rocess D.communicating process, connecting process3.A socket is the interface between within a host. A.the network layer and the link layerB.the link layer and the physical layerC.the application layer and the transport layerD.the transport layer and the network layer4.In the following applications,

39、 which one is a loss-tolerant application? A.E-mail B.file transfer C.instant messaging D.real-time audio5.In the following applications, which one is a bandwidth-sensitive application? A.E-mail B.web application C.real-time audio D.file transfer6.The service of TCP cant guarantee .A.delivery of all

40、 data without error B.delivery of all data in the proper orderC.the rate of delivery D.congestion control7.In the following applications, which one uses UDP? A.E-mail B.web application C.file transfer D.DNS8.In the following descriptions about HTTP, which one is not correct? A.HTTP uses non-persiste

41、nt connections in its default mode.B.HTTP uses TCP as its underlying transport protocol.C.HTTP is a stateless protocol.D.HTTP is client-server architecture.9.Suppose a web page consists of a base HTML file,5 JEPG images and a java applet,and also suppose HTTP uses persistent connection without pipelining,the total response time is .A.2RTT B.8RTT C.12 RTT D.14RTT10.In HTTP response message, if th