华南理工软件学院2015期末考试-计算机网络b卷

姓名 学号 学院 专业 座位号 ( 密 封 线 内 不 答 题 )密封线线_ _ 诚信应考,考试作弊将带来严重后果！ 华南理工大学期末考试Computer Networks试卷 (B)注意事项：1. 考前请将密封线内填写清楚； 2. 所有答案请答在答题纸上(注：选择题答案请填入题目前面的表格中)； 3考试形式：闭卷； 4. 本试卷共 5 大题，满分100分，考试时间120分钟。题 号12345总分得 分评卷人1. Select the correct choice. (30 scores, every one is 2 scores)NO.123456789101112131415solution(1) Suppose Host A wants to send a file to Host B . The path from Host A to Host B has three links , their rates R1=500 kbps , R2=250 kbps , and R3=1 Mbps . Assuming no other traffic in the network , what is the throughput for the file transfer ? ( ) A. 500 kbps B. 1 MbpsC. 250 kbpsD. 1.75 Mbps(2) The transfer of a web document from one host to another is : ( )A. loss-intolerant and time insensitiveB. loss-tolerant and time sensitiveC. loss-intolerant and time sensitive D. none of the above(3) Ethernet interface addresses ( )A. are assigned at manufacturing time. B. are assigned manually or by DNSC. are generated randomly and checked for uniqueness by broadcasting a messageD. share the same high order bits , which determine the network or subnet in an internetwork.(4) Based on TCP/IP architecture ,which of the following protocol belongs to data-link layer ? ( ) A. HTTP B. IP C. UDP D.PPP(5) Two important reasons that the Internet is organized as a hierarchy of networks for the purposes of routing are ( )A. Least cost and maximum free circuit availabilityB. Message complexity and speed of convergenceC. Scale and administrative autonomy D. Link cost changes and link failure(6) With an exterior routing protocol , which of the following issues generally dominate the routing decisions ? ( )A. Geographical distance between ASsB. PolicyC. Number of ASs traversedD. Current congestion levels in the ASs(7) Which range of port number are reserved for services that are commonly used by applications that run on serves ? ( ) A. 0 to 255. B. 0 to 1023.C. 1024 to 49151. D. 49152 to 65535.(8) Which information is contained in the header of Network Layer to help data delivery? ( )A. port number B. Device physical addressC. Destination hosts IP address D. Virtual connection identifier(9) In internet communication ,IP datagram will go through the source host and routers to reach the destination host , usually ( )A. both source host and routers all know the complete path to the destination host that will be reached by IP datagram. B. source host knows the complete path to destination host that will be reached by IP datagram , but none the intermediate routers. C. the intermediate routers know the complete path to destination host that will be reached by IP datagram , but none the source host. D. neither source host nor the intermediate routers know the complete path to destination host that will be reached by IP datagram.(10) Which combination of network id and subnet mask correctly identifies all IP address form 172.16.128.0 through 172.16.159.255 ? ( )A. 172.16.128.0 255.255.255.224B. 172.16.128.0 255.255.0.0C. 172.16.128.0 255.255.224.0D. 172.16.128.0 255.255.255.192(11) What happens when a node on an Ethernet network is creating a frame and it does not have the destination MAC address ? ( )A. The node drops the frame. B. The node sends out a layer 3 broadcast messages.C. The node sends a message directly to the router for the address.D. The node sends out an ARP request with the destination IP address.(12) Suppose an application generates chunks of 120 bytes of data every second, and each chunk gets encapsulated in a TCP segment and then an IP datagram(no options fields).What percentage of each datagram will contain application data? ( ) A. 80% B. 75% C. 60% D.25%(13) Which statement is true about the CSMA/CD access method that is used in Ethernet ? ( )A. when a device hears a carrier signal and transmits , a collision cannot occur. B. A jamming signal causes only devices that caused the collision to execute a back off algorithm.C. All network devices must listen before transmitting. D. Devices involved in a collision get priority to transmit after the back off period.(14) In the Ethernet two-layer switches, how is the forwarding table established? ( )A. Manual configuration B. Self-learningC. Routing algorithmD. Destination address learning(15) Consider sending a 999 byte datagram into a link that has an MTU of 500 bytes , ( )A. 2 fragments are created with offset field value 0,500, respectivelyB. 3 fragments ar