云南大学2015至2016学年上学期软件学院2014级
《计算机网络原理》期中考试试卷（闭卷）答案
满分：100分考试时间：100分钟任课教师：王世普
第一题答题卡：
第二题答题卡：
1．（1）is the protocol suite for the current Internet..
（1）A. NCP B. TCP/IP C.UNIX D.ACM
2．A GIF image is sent as email ,What is the content-type （2） .
（2）A．multipart/mixed B．multipart/image
C．image/JPEG D．image/gif
3．A user want to send some forms（表单）to Web server using HTTP protocol, the request line method is （3）.
（3）A．GET B．PA TCH C．MOVE D．POST
4．If a TCP segment carries data along with an acknowledgment, this technology is called （4）acknowledgment.
（4）A. backpacking B. piggybacking C. piggying D. mother’s help
5．TCP is a （5）transport layer protocol that ensure data to be exchanged reliably by（6）. So it requires set up connection before data exchanged by ( 7 )-way handshaking.
（5）A．connection B．connectionless C．join D．disconnection
（6）A．datagrams B．acknowledgements C．data D．segment
（7）A．one B．two C．three D．four
6．A user requests a Web page that consists of a basic HTML file and 5 JPEG image files. d trans denoting the time to transfer a file. The total time is (8) to request the Web page in
Nonpersistent connections mode?
（8）A. 6(2RTT+ d trans) B. 2RTT+6 d trans C. RTT+6 d trans D.6(RTT+ d trans)
7．Host A sends a TCP segment (Seq = 1, ACK = 111) to host B and Host B replies with a TCP segment (Seq = 111, ACK = 81). The payload length of the TCP segment from host A to host
B is ( 9 ) .
（9）A．80 bytes. B．81 bytes. C．82 bytes. D．unknown
8．As a data packet moves from the lower to the upper layers, header are （10）.
（10）A. modified B. added C. subtracted D. rearranged
二、判断正误（每个问题1分，共5分。正确的打“√”、错误的打“×”，请将判断结果填入第
二题答题卡）
1. The DNS defines a distributed, hierarchical database that provides only hostname to IP address
mappings.( × )
2. In SR protocol, sender only resends pkts for which ACK not received. ( √ ) 3．If sequence number is k bit, then the send window maximum size of GBN protocol is equal to 2k-1. ( √ ) 4．The UDP header checksum is recomputed at every routers. ( × ) 5．Suppose that the last SampleRTT in a TCP connection is equal to 1 sec. Then Timeout for the connection will necessarily be set to a value >= 1 sec. ( × )
三、回答下列问题（每个问题5分，共30分）
1．For a communication session between two hosts, which host is the client and which is the server?
要点：通信的发起者（请求者）是客户，通信的接受者（服务者）是服务器。2．What is the difference between persistent HTTP with pipelining and persistent HTTP without pipelining?
要点：前者在一个TCP连接期间可以传送多个WEB页面；后者在一个TCP 连接期间只能传送一个WEB页面。
3．What are the two types of services that the Internet provides to its applications? What are important characteristics of each of these services?
要点：面向连接的服务（连接管理、正确可靠、按序交互、流控制、拥塞控制）；无连接服务（不需建立连接、不可靠、每个报文独立传送，无流控制和拥塞控制）
4．Why is it said "out of band" (带外的) that FTP sends control information?
