计算机网络模拟题

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(有线 ) 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 题，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 ）；简述 CSMA/CD的工作原理。答：（ 1 ）当一个站点想要发送数据的时候，先侦听信道是否空闲。（ 1 分）（ 2）如果信道忙，则等待，直

24、到信道空闲；如果信道空闲，站点就准备好要发送的数据。（ 1 分）（ 3）发送数据的同时，继续侦听网络，若无冲突则继续发送，直到发完全部数据。（ 4）若有冲突，则立即停止发送数据，并发送干扰信号；等待一个预定的随机时间，且在总线为空闲时，再重新发送未发完的数据。（ 1 分）试述五层协议的网络体系结构的要点，包括各层的主要功能。简述传输层两种主要协议的相同点和不同点。答：相同点：TCP 和 UDP 都是传输层协议；都具有分用和复用的功能；（ 1 分 ）不同点：TCP 是面向连接的可靠协议，UDP 面向无连接的不可靠协议；TCP 具有流量控制，拥塞控制功能， UDP 协议没有；TCP 协议处理的数据

25、单元是数据段，而UDP 的是用户数据报。（ 1 分）一个应用程序用UDP ，到了 IP 层把数据报再划分为4 个数据报片发送出去。结果前两个数据报片丢失，后两个到达目的站。过了一段时间应用程序重传UDP ，而 IP 层仍然划分为4个数据报片来传送。结果这次前两个到达目的站而后两个丢失。试问：在目的站能否将这两次传输的 4 个数据报片组装成为完整的数据报？为什么？（假定目的站第一次收到的后两个数据报片仍然保存在目的站的缓存中。）答：不行。（1 分）画出 TCP 的三次握手协议示意图。用表格表述Ehternet帧格式。 Applications: (3*10)一个自治系统有5 个局域网，其连接图如

26、图所示，LAN2LAN5的主机数为： 91，151，23，15。该自治系统分配到的IP 地址快为134.138.118/23。试给出每一个局域网的地址LAN2 ： 91 个主机LAN3 ： 151 个主机LAN4 ： 23 个主机LAN5 ： 15 个主机-LAN1-Computer networkinstructor: Wang Xia2015-6-15块（包括前缀）。（ 10 分）假定要传送的报文共x（bit ），从源站到目的站共经过k 段链路，每段链路的传播时延为d（s），数据率为 C（bit/s ）。在电路交换时电路的建立时间为s（ s）。在分组交换时分组长度为p（ bit ），且各结点的排队等待时间可忽略不计。问在怎样的条件下，分组交换的时延比电路