计算机网络-第二次平时考试.doc

计算机网络平时考试试题（带答案）一、选择题1In the Ethernet frame structure, the Data field carries the ( ).A.IP datagram B.segment C.frame D.message2The units of data exchanged by a link-layer protocol are called ( ).A. Frames B. SegmentsC. Datagrams D. bit streams3The SYN segment is used for ( ).A.TCP connection setup B.TCP flow controlC.TCP congestion control D.Closing a TCP connection4The ( ) is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world. A. Internet B. Intranet C. switch net D. television net5The units of data exchanged by a link-layer protocol are called ( ).A. Frames B. SegmentsC. Datagrams D. bit streams6In Address：,（ ） indicates “host name”.A. www B. uzz C. edu D. cn 7. In the following options, which belongs to the network core? ( )A. end systems B. routers C. clients D. servers8The Internets connection-oriented service has a name, it is ( ).A.TCP B.UDP C.TCP/IP D.IP9There are two fundamental approaches to building a network core, ( ) and packet switching.A. electrical current switching B. circuit switchingC. data switching D. message switching10A ( ) protocol is used to move a datagram over an individual link.A. application-layer B. transport-layerC. network-layerD. link-layer11Services provided by transport layer include ( ).A.HTTP and FTP B.TCP and IP C.TCP and UDP D.ICMP 12IP addressing assigns an address to 50/29, the network address for this network is ( ).A.48 B. 50 C. D. 13IP belongs to ( ).layer? A.transport B.network C.data link D. physical 14Which of the following is correct? ( )A. No two adapters have the same MAC address.B. MAC broadcast address is FF-FF-FF-FF-FF-FF.C. A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes. ( ).D. All of the above15How many bits specify the IP protocol version in a datagram? ( ).A.1 bit B.2 bits C.4 bits D.8 bits16In the following applications, which one is a loss-tolerant application? A E-mail B file transfer C instant messaging D real-time audio18The Internet mail system has three components which they are ( ).A.user agent, SMTP, POP3 B.SMTP, POP3, IMAPC.user agent, SMTP, IMAP D.user agent, SMTP, mail server19DNS means ( ).A.Data Name System B.Data National SystemC.Domain Name System D.Domain National System20“/24”, where the /24 notation, sometimes known as a ( ).A. Subnet mask B. Networking addressC. Host addressD. None of above21Which of the following is not intra-AS routing protocol? ( )A. RIP B. OSPF C. IGRP D.BGP 22IP addressing assigns an address to 50/29, the network address for this network is ( ).A. 48 B. 50 C. D. 23IP Data-grams are rarely larger than ( ).A. 1500 bytes B. 65535 bytes C.500 bytes D.1024 bytes24Which of the following is correct? ( )A. No two adapters have the same MAC address.B. MAC broadcast address is FF-FF-FF-FF-FF-FF.C. A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes. D. All of the above25Which of the following is not belonging to channel partitioning protocols? ( )A.CSMA B.FDM C.CDMA D.TDM26. MAC address is ( ) bits long.A.32 B.48 C.128 D.6427The Internets connection-oriented service has a name, it is ( ).A.TCP B.UDP C.TCP/IP D.IP28In the LAN, ( ) protocol dynamically assign IP addresses to hosts.A.DNS B.ARP C.DHCP D.IP29Which layer provides host-to-host services? ( ).A. transport B. network C. data link D. physical30DHCP protocol is a four-step process: DHCP request. DHCP ACK. DHCP server discovery. DHCP server offer(s). The correct sequence is ( )A. B. C. D.31In the Ethernet frame structure, the CRC field is ( ) bytes.A.2B.4C.8D.3232Transport-layer protocols run in ( ).A.Servers B.Clients C.Routers D.End system33The maximum amount of data that can be grabbed and placed in a segment is limited by the( ).A. Maximum segment size (MSS)B. MTUC. ChecksumD. Sequence number34The internets network layer provides a single service-that is ( ).A. Reliable data transfer B. Flow controlC. Congestion control D. Best-effort-service35There are 6 flag fields. Which one is to indicate that the receiver should pass the data to the upper layer immediately? ( )A. PSH B. URG C. ACK D. RST36ICMP is used for ( ).A. Reliable data transfer B. Error reporting C. Flow control D.Congestion control37The FIN segment is used for ( ).A. TCP connection setup B. TCP flow controlC. TCP congestion control D. Closing a TCP connection38A transport-layer protocol provides for logical communication between ( ).A. Application processesB. Hosts C. RoutersD. End systems39Port numbers scope is ( ) to ( ). A. 0, 1023 B. 0, 65535 C. 0, 127 D. 0,25540“/24”, where the /24 notation, sometimes known as a( ).A. Subnet maskB. Networking addressC. Host addressD. None of above二、判断题1In CSMA/CD, one node listens to the channel before transmitting. T2In C/S architecture, client has a fixed well-known address. F3In P2P architecture, peers communicate with each other directly. T4Each TCP connection is closed after the server sending one object.5There are four steps in DHCP, the DHCP server can complete DHCP response.F6In full-duplex transmission(s), the nodes at both ends of a link may transmit packets at the same time. T7DNS resolves hostnames for hosts anywhere in the Internet. T8ARP resolves an IP address to a MAC address. T9In the broadcast packet of DHCP DISCOVER，source IP address is . T10The routing algorithm running within an autonomous system is called an intra-AS routing protocol. F11In CSMA/CD, one node listens to the channel before transmitting. TT12All of the Ethernet technologies provide connection-oriented reliable service to the network layer. F 13A router receives a packet, in which TTL=0, and the packet will be dropped. T14. Datagram networks are circuit-switched networks, and virtual-circuit networks are packet-switched networks. F15ARP resolves an IP address to a MAC address. T16If the traffic intensity is close to zero, the average queuing delay will be close to zero. T17A router receives a packet, in which TTL=0, and the packet will be dropped. T18The adapter is also called as NIC. T19Consider CRC error checking approach, the four bit generator G is 1011, and suppose that the data D is 10101010, then the value of R is 010. F20Hubs can interconnect different LAN technologies. F三、填空题1. Common Channel multiplexing technology includes _FDM_、_TDM_、_WDM_、_CDM_.2NIC works in _data link_ layer of Internet.3. _network_ layer provides host-to-host services, and _transport_ layer provides process-to-process services.4MAC address is _48_ bits, and IPV4 has a 32_ bit address.5The data transmission delay include: _propagation delay_、_transmission delay_、processing delay and queuing delay.6The port number used by HTTP is _80_；The port number used by SMTP is _25_；The port number used by DNS is _53_.7在TCP连接建立过程中，客户端向服务器发送一个连接请求的TCP报文，其中包含连接的初始序列号v和一个窗口大小，服务器收到报文后，向客户端发送一个请求确认的报文，其中包含它选择的初始序列号w确认号为_V+1_，和一个窗口大小。四简答题1比较TCP协议和UDP协议之间的异同点。2比较分组交换和电路交换之间的优缺点。3简述HTTP代理服务器的作用。4数据链路层的三个基本问题是什么？简单论述一下。5简述两种DNS服务器查询方式。6简单论述CSMA/CD的工作原理。7. 简述TCP的三次握手协议。五、应用题1一个自治系统有5个局域网，其连接图如图所示，LAN2LAN5的主机数为：93，147，23，20。该自治系统分配到的IP地址快为199.138.118/23。试给出每一个局域网的地址块（包括前缀）。（10分）2数据传输过程中，若接收方收到发送方送来的信息为10110011010，生成多项式为G（x）x4x31，接收方收到的数据是否是正确的？（请写出判断依据及推演过程）（5分）3用Ethereal工具捕获到如下数据包，请根据图的内容回答如下问题。（8分）（1）本次应用基于应用层的_协议，基于传输层的_协议。（2）上图中，数据包133是一个_数据包，134是一个_数据包，135是一个_数据包。（A. 连接接受 B. 连接确认 C. 连接请求）（3）查看Packet Detail窗口信息，可以看出：133数据包的源端口号为_，目的端口号为_，表示这是一个从_到_的数据包（填写Client或者Server）。（4）此数据包的传输层首部长度为_字节，其中固定首部长度为_字节，标识字段都有URG、ACK、PSH、RST、SYN、_共六种，其中数据包136的控制字段应为_=1 &_=1。4有如下的四个/24地址块，试进行最大可能的聚合。/24，/24，/24，/24。（8分）5现有五个站分别连接在三个局域网上，并且用两个透明网桥连接起来，如下图所示。每一个网桥的两个端口号都标明在图上。在一开始，两个网桥中的转发表都是空的。以后有以下各站向其他的站发送了数据帧，即H1