計(jì)算機(jī)網(wǎng)絡(luò)模擬題

1、-Computer networkinstructor: Wang Xia2015-6-15Computer networkMidterm ExaminationName:Student number:100minI.Choice(30*1).The () is a worldwidecomputer network, that is, a network that interconnects millions of computing devices throughout the world.A. InternetB.IntranetC. switch netD. television ne

2、tThe units of data exchanged by a link-layer protocol are called ( ).A. FramesB. SegmentsC. DatagramsD. bit streams() means that the switch must receive the entire packet before it can begin to transmit the firstbit of the packet onto the outbound link.A. Store-and-forward transmissionB. FDM C.End-t

3、o-end connectionD.TDMIn the following options, which one is not a guided(有線 ) media? ()A. twisted-pair wireB.fiber opticsC. coaxial cableD. satelliteDelay does not include ().A. Process delayB. propagation delayC. transmission delayD. control delayIn the following options, which belongs to the netwo

4、rk core? () A.end systemsB.routersC.clientsD.serversThe Internet s connection-oriented service has a name, it is ( ). A.TCPB.UDPC.TCP/IPD.IPThere are two fundamental approaches to building a network core, ( ) and packet switching. A.electrical current switchingB.circuit switchingC.data switchingD.me

5、ssage switchingA () protocol is used to move a datagram over an individual link.application-layerB.transport-layerC. network-layerD. link-layerWhich of the following protocols is not a link-layer protocol? ()A. EthernetB.PPPC.HDLCD.IPThe ARP protocol can translate () into (). ()A. host name, IP addr

6、essB. host name, MAC addressC. IP address, MAC addressD. broadcast address, IP addressIn CSMA/CD, the adapter waits some time and then returns to sensing the channel. In the following four times, which one is impossible? ()A.0 bit timesB. 512 bit times C. 1024 bit timesD. 1028 bit timesThe principal

7、 components of PPP include but not( ).A.framingB. physical-control protocolC.link-layer protocol D. network-layer protocolMAC address is () bits long.A.32B. 48C.128D. 64Which of the following is not belonging to channel partitioning protocols? () A.CSMAB.FDMC.CDMAD.TDMWhich of the following is corre

8、ct? ()A.No two adapters have the same MAC address.-Computer networkinstructor: Wang Xia2015-6-15C.A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes.D.All of the aboveIn the Ethernet frame structure, the Data field carries the ( ). A.IP datag

9、ramB.segmentC.frameD.message18A switch is a()device that acts on frame.A.physical-layerB.link-layerC.network-layerD.transport-layer19A router forwards a packet by examining the value of a field in the arriving packetthen using this value to index into the router s forwarding table,（ this ） value is?

10、A. destination IP addressB. source IP addressC. destination MAC addressD. source MAC addressWhich layer provides host-to-host services?（）A. transportB. networkC. data linkD. physicalIPV4 has a bit address?（）A. 48B. 16C. 32D. 64Data-grams are rarely larger than （?）A. 1500 bytesB. 65535 bytesC.500 byt

11、esD.1024 bytesICMP is used for ?（）A. Reliable data transferB. Error reportingC. Flow control D.Congestion controlIP addressing assigns an address to 50/29, the network address for this network is . （）A.48B. 50C. D. 25A switch works in layer?（）A. NetworkingB. Data linkC. ApplicationD. PhysicalThe int

12、ernet s network layer provides a single service-that is .（ ）A. Reliable data transfer B. Flow controlC. Congestion controlD. Best-effort-serviceWhich of the following is not a routing protocol?（）A. TCPB. RIPC. OSPFD.BGPIP address is identifier for .（）A. HostB. Router interfaceC. Both of aboveD. None

13、 of above“ /24” , where the /24 notation, sometimes known as a（ ）.A. Subnet maskB. Networking addressC. Host addressD. None of aboveWhich of the following is not intra-AS routing protocol?（）A. RIPB. OSPFC. IGRPD.BGPWhich layer-function is mostly implemented in an adapter? () A.physical layer and lin

14、k layerB. network layer and transport layerC.physical layer and network layerD. transport layer and application layerIn the following applications, which one is a loss-tolerant application?AE-mailBfile transferCinstant messagingDreal-time audioWhat is the main function of the network layer? ()A. nod

15、e-to-node deliveryB. process-to-process message deliveryC. synchronizationD.updating and maintenance of routing tablesAs a data packet moves from the upper to the lower layers, headers are( ) .A.AddedB.subtractedC.rearrangedD. modified In Address ： HYPERLINK / ,（） indicates“ host name ” .A. wwwB. uz

16、zC. eduD. Cn-Computer networkinstructor: Wang Xia2015-6-15The FIN segment is used for ().A. TCP connection setupB. TCP flow controlC. TCP congestion controlD. Closing a TCP connectionIf a user brings his computer from zaozhuang to beijing, and accesses Internet again. Now, ()of his computer needs to

17、 be changed.A.MAC addressB.IP addressC. e-mail addressD. user addressFill in the Blanks（20*1 ）。As a packet travels from one node to the subsequent node along the path, the packet suffers from several types of delays at each node along the path. The most important of these delays are the transmission

18、_delay, _ propagation_delay, _ processingdelay, and _ queuing_delay.The Internet mail system has three major components:User Agent, _ Mail Server_, and _ SMTP_.Historically, two routing protocols have been used extensively for routing within an autonomous system in the Internet:RIP protocol and _OSP

19、F_protocol. AndRIP is a distance-vector protocol. And OSPFis a link-state protocol.A hub is a _ physical_-layer device, and switches arelink _-layer devices.True or false.IP address is associated with the host or router. SO one device only have one IP addressF.In C/S architecture, client has a fixed

20、 well-known address. FDNS resolves hostnames for hosts anywhere in the Internet.TAn ARP query sent to all over the Internet. F5 UDP is a kind of unreliable transmission layer protocol, so there is not any checksum field in U DP datagram header. FIP is a kind of reliable transmission protocol. FThe t

21、ransmission delay is a function of the distance between the two routers. F 8 RIP and OSPF are Intra-AS routing protocols.T9 7 is a C-class IP address. F10 Packet switching is suitable for real-time services, and offers better sharing of bandwidth than circuit switching. F11.Any protocol that perform

22、s handshaking between the communication entities before transferring dat a is a connection-oriented service.TIV. Translation. （共 10 題，每空 1 分，共10 分）IP(Internet Protocol)： Flow-control： FTP(File Transfer Protocol)： HTTP( Hyper-Text Transfer Protocol )： ISP(Internet Service Provider)： -Computer network

23、instructor: Wang Xia2015-6-15DNS(Domain Name System)： BGP(Border Gateway Protocol)： ARP (Address Resolution Protocol)： URL (Uniform Resource Locator)： CSMA/CD： Congestion-control： SMTP(Simple Mail Transfer Protocol)： Answer（ 4*5 ）；簡(jiǎn)述 CSMA/CD的工作原理。答：（ 1 ）當(dāng)一個(gè)站點(diǎn)想要發(fā)送數(shù)據(jù)的時(shí)候，先偵聽(tīng)信道是否空閑。（ 1 分）（ 2）如果信道忙，則等待，直

24、到信道空閑；如果信道空閑，站點(diǎn)就準(zhǔn)備好要發(fā)送的數(shù)據(jù)。（ 1 分）（ 3）發(fā)送數(shù)據(jù)的同時(shí)，繼續(xù)偵聽(tīng)網(wǎng)絡(luò)，若無(wú)沖突則繼續(xù)發(fā)送，直到發(fā)完全部數(shù)據(jù)。（ 4）若有沖突，則立即停止發(fā)送數(shù)據(jù)，并發(fā)送干擾信號(hào)；等待一個(gè)預(yù)定的隨機(jī)時(shí)間，且在總線為空閑時(shí)，再重新發(fā)送未發(fā)完的數(shù)據(jù)。（ 1 分）試述五層協(xié)議的網(wǎng)絡(luò)體系結(jié)構(gòu)的要點(diǎn)，包括各層的主要功能。簡(jiǎn)述傳輸層兩種主要協(xié)議的相同點(diǎn)和不同點(diǎn)。答：相同點(diǎn)：TCP 和 UDP 都是傳輸層協(xié)議；都具有分用和復(fù)用的功能；（ 1 分 ）不同點(diǎn)：TCP 是面向連接的可靠協(xié)議，UDP 面向無(wú)連接的不可靠協(xié)議；TCP 具有流量控制，擁塞控制功能， UDP 協(xié)議沒(méi)有；TCP 協(xié)議處理的數(shù)據(jù)

25、單元是數(shù)據(jù)段，而UDP 的是用戶數(shù)據(jù)報(bào)。（ 1 分）一個(gè)應(yīng)用程序用UDP ，到了 IP 層把數(shù)據(jù)報(bào)再劃分為4 個(gè)數(shù)據(jù)報(bào)片發(fā)送出去。結(jié)果前兩個(gè)數(shù)據(jù)報(bào)片丟失，后兩個(gè)到達(dá)目的站。過(guò)了一段時(shí)間應(yīng)用程序重傳UDP ，而 IP 層仍然劃分為4個(gè)數(shù)據(jù)報(bào)片來(lái)傳送。結(jié)果這次前兩個(gè)到達(dá)目的站而后兩個(gè)丟失。試問(wèn)：在目的站能否將這兩次傳輸?shù)?4 個(gè)數(shù)據(jù)報(bào)片組裝成為完整的數(shù)據(jù)報(bào)？為什么？（假定目的站第一次收到的后兩個(gè)數(shù)據(jù)報(bào)片仍然保存在目的站的緩存中。）答：不行。（1 分）畫(huà)出 TCP 的三次握手協(xié)議示意圖。用表格表述Ehternet幀格式。 Applications: (3*10)一個(gè)自治系統(tǒng)有5 個(gè)局域網(wǎng)，其連接圖如

26、圖所示，LAN2LAN5的主機(jī)數(shù)為： 91，151，23，15。該自治系統(tǒng)分配到的IP 地址快為134.138.118/23。試給出每一個(gè)局域網(wǎng)的地址LAN2 ： 91 個(gè)主機(jī)LAN3 ： 151 個(gè)主機(jī)LAN4 ： 23 個(gè)主機(jī)LAN5 ： 15 個(gè)主機(jī)-LAN1-Computer networkinstructor: Wang Xia2015-6-15塊（包括前綴）。（ 10 分）假定要傳送的報(bào)文共x（bit ），從源站到目的站共經(jīng)過(guò)k 段鏈路，每段鏈路的傳播時(shí)延為d（s），數(shù)據(jù)率為 C（bit/s ）。在電路交換時(shí)電路的建立時(shí)間為s（ s）。在分組交換時(shí)分組長(zhǎng)度為p（ bit ），且各結(jié)點(diǎn)的排隊(duì)等待時(shí)間可忽略不計(jì)。問(wèn)在怎樣的條件下，分組交換的時(shí)延比電路