2021 计算机网络（黄敏）(华南理工大学) 最新满分章节测试答案
本答案对应课程为:点我自动跳转查看
本课程起止时间为:2021-03-01到2021-08-01
本篇答案更新状态:已完结
【作业】Chapter 1- Introducation 第1章作业
1、 问题:What will the status code be in server-to-client response message when request msg not understood by server?A.200B.301C.400D.404
评分规则: 【 Answer:C
】
2、 问题:An application can rely on the connection to deliver of its data without error and
in the proper order. The sentence describes ( )?A. flow controlB. congestion controlC. reliable data transferD. connection-oriented service
评分规则: 【 Answer:C
】
3、 问题:Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses store-and-forward packet switch, what is the totally end-to-end delay to send a packet of length L? (Ignore queuing delay, propagation delay and processing delay)A. L/R1+L/R2B. L/R1C. L/R2D. none of the above
评分规则: 【 Answer:A
】
4、 问题:Suppose there is a change in the service (set of operations) provided by layer k. How does this impact services at layers k-1 and k+1?
评分规则: 【 The k+1 layer will be affected(3 points), because the services are provided by the lower to upper layer(3 points), such as k layer provided services to k+1 layer, and k layer’s service is provided by the k-1 layer. The similar answers also get the points.
】
5、 问题:Consider sending a packet from a source host to a destination host over a fixed route. List the delay components in the end-to-end delay. Which of these delays are constant and which are variable?
评分规则: 【 The delay components are processing delays (1 point), transmission delays (1 point) , propagation delays (1 point) , and queuing delays (1 point) . All of these delays are fixed, except for the queuing delays, which are variable.(2 points)The similar answers also get the points.
】
6、 问题:What is an application-layer message? A transport-layer segment? A network-layer datagram? A link-layer frame?
评分规则: 【 Application-layer message: data which an application wants to send and passed onto the transport layer; (2 point)transport-layer segment: generated by the transport layer and encapsulates application-layer message with transport layer header; (2 points)network-layer datagram: encapsulates transport-layer segment with a network-layer header; (2 point)link layer frame: encapsulates network-layer datagram with a link-layer header.(2 point)The similar answers also get the points.
】
7、 问题:Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three links, of rates R1 = 500 kbps, R2 = 2 Mbps, and R3 = 1 Mbps.a. Assuming no other traffic in the network, what is the throughput for the file transfer?b. Suppose the file is 4 million bytes. Dividing the file size by the throughput, roughly how long will it take to transfer the file to Host B?c. Repeat (a) and (b), but now with R2 reduced to 100 kbps.
评分规则: 【 Solution:a. 500 kbps (2 points)b. 64s (2 points)c. 100kbps (2 point); 320s (2 point)There is no calculation process, only half of the scores are obtained
】
8、 问题:What is the protocol?
评分规则: 【 Network protocol is a set of rules, standards or conventions established by data exchange in computer network.(2 points)Similar answers can also be scored.
】
9、 问题:What are the three elements of data transmission?
评分规则: 【 Source(transmitting device), sink (receiving device) and channel.2 points for each answer.
】
10、 问题:What is the process of encapsulation?
评分规则: 【 The data is transferred from the application layer to the next layer, which is encapsulated layer by layer, and each layer has a different name: (2 points)After the transmission layer, the TCP header is added to form the data segment (2points),Through the network layer, plus the IP header, data packets are formed (2points),After the data link layer, MAC header and a FCS verification data frame are added(2 points), the encapsulation is completed, and then the physical layer is transmitted through bit.(2 points)Similar answers can also be scored.
】
11、 问题:What are the similarities and differences between TCP service and UDP service?
评分规则: 【 1) TCP provides reliable transport service while UDP provides unreliable transport service.(2 points)2) TCP provides flow control and congestion control while UDP does not.(1 points)3) TCP is a connection-oriented service while UDP will not setup connection.(2 points)Similar answers can also be scored.
】
12、 问题:What are the layer names and functions on the iso-osi reference model.
评分规则: 【 Application layer:Provide interface for users.Presentation layer:Digital representation of data.Some specific functions can also be used.Session layer:Determine whether the network data will pass through the remote session, and have the synchronization function.Transport layer:Responsible for determining the port number, which is used to distinguish different applications.network layer:Responsible for providing logical address（IP）and selecting data path.Data-Link layer:Framing, using MAC address to access media, error detection and correction.Physical layer:Responsible for bit stream transmission, physical interface, electrical characteristics, etc.one point for each layer.Similar answers can also be scored.
】
13、 问题:Make comparison between ISO-OSI reference model and TCP / IP reference model.
评分规则: 【 Similarity:Both OSI reference model and TCP/IP reference model adopt the concept of hierarchy (1 points ) and can provide two communication service mechanisms: connection oriented and connectionless;(1 points)Difference:Different requirements for reliability (the TCP/IP is higher).(1 points)The OSI model is designed before the development of the protocol, which is universal. TCP/IP is a set of protocols and then a model. (1 points)OSI model is only a theoretical model, and there is no mature product, and TCP/IP has become “the actual international standard”.1 points)Similar answers can also be scored.
】
14、 问题:What is peer to peer / virtual communication?
评分规则: 【 In order to transfer data packets from the source to the destination, each layer of the source OSI model must communicate with the peer layer of the destination, which is called peer layer communication.(2 points) In this process, the protocols of each layer exchange information between peers, which becomes protocol data unit (PDU). Located in each communication layer of the source computer, the PDU for that layer is used to communicate with the peer layer of the destination computer.(2 points)
】
15、 问题:What occasions are persistent and non-persistent connections suitable for?
评分规则: 【 Use a non-persistent connection for a single transmission(2 points), and use a persistent connection for multiple transmissions in a row(2 points).
】
【作业】Chapter 2 Application layer Chapter 2 homework
1、 问题:A process sends messages into, and receives messages from, the network through its ( )?A. SocketB. ProgramC. ClientD. Peer
评分规则: 【 Answer: A
】
2、 问题:Each URL has components, they are ( )A. transport protocol and object’s path nameB. host name and object’s path nameC. transport protocol and host nameD. client name and server name
评分规则: 【 Answer: B
】
3、 问题:In the following descriptions about persistent connection, which one is not correct?A. The server leaves the TCP connection open after sending a response.B. Each TCP connection is closed after the server sending one object.C. There are two versions of persistent connection: without pipelining and with pipelining.D. The default mode of HTTP uses persistent connection with pipelining.
评分规则: 【 Answer: B
】
4、 问题:In HTTP response message, if the Date: header ;one indicates the time Fri. 08 Aug. 2008 12:00:00 GMT, the Last-Modified: header line can not be ( ).A. Fri. 08 Aug. 2008 11:00:00 GMTB. Fri. 08 Aug. 2008 11:30:00 GMTC. Fri. 08 Aug. 2008 12:00:00 GMTD. Fri. 08 Aug. 2008 12:30:00 GMT
评分规则: 【 Answer: D
】
5、 问题:For a communication session between a pair of processes, which process is the client and which is the server?
评分规则: 【 Answer:The process which initiates the communication is the client;(5 points)the process that waits to be contacted is the server.(5 points)Similar answers can also be scored.
】
6、 问题:What information is used by a process running on one host to identify a process running on another host?
评分规则: 【 Answer:The IP address of the destination host and the port number of the socket in the destination process.(10 points)Similar answers can also be scored.
】
7、 问题:Why do HTTP, FTP, SMTP, and POP3 run on top of TCP rather than on UDP?
评分规则: 【 Answer: The applications associated with those protocols require that all application data be received in the correct order and without gaps.(7 points).TCP provides this service whereas UDP does not.(3 points)Similar answers can also be scored.
】
8、 问题:Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. What transport and application-layer protocols besides HTTP are needed in this scenario?
评分规则: 【 Answer:Application layer protocols: DNS and HTTP;(3 points for each)Transport layer protocols: UDP for DNS; TCP for HTTP.(3 points for each)
】
9、 问题:Briefly describe the process of ftp protocol from establishing a connection to transferring data.promote: How many connections will be established? Which port will be used? What if client whats to transfer more than one file?
评分规则: 【 Client contacts FTP server at port 21 (1 point), and authorized over control connection (1 point).Client sends commands over control connection (1 point) to browse remote directory and request to download files.When server receives file transfer command, it opens another TCP connection ( 1 point) to client as data connection (1 point) at port 20 (1 point).After transferring one file, server closes data connection (1 point). If there is another file transfer commend, server will open another TCP connection (1 point) to transfer file.
】
本文章不含期末不含主观题！！
本文章不含期末不含主观题！！
支付后可长期查看
有疑问请添加客服QQ 2356025045反馈
如遇卡顿看不了请换个浏览器即可打开
请看清楚了再购买哦，电子资源购买后不支持退款哦
