2022年2022年计算机网络作业题 2.pdf

《2022年2022年计算机网络作业题 2.pdf》由会员分享，可在线阅读，更多相关《2022年2022年计算机网络作业题 2.pdf（7页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、1 计算机网络作业题(2011 年 12 月版 ) 第一章1. Consider sending a packet of F bits over a path of Q links. Each link transmits at R bps. The network is lightly loaded so that there are no queuing delays. Propagation delay is negligible. a. Suppose the network is a packet-switched virtual-circuit network. Denote th

2、e VC setup time by tsseconds. Suppose the sending layers add a total of h bits of header to the packet. How long does it take to send the file from source to destination? b. Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose each packet has 2h

3、 bits of header. How long does it take to send the packet? c. Finally, suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between source and destination is R bps. Assuming ts setup time and h bits of header appended to the packet, how lo

4、ng does it take to send the packet? 1、a. ts+(F+h)/R*Q b.(F+2h)/R*Q c.C.ts+(F+h)/R 6. This elementary problem begins to explore propagation delay and transmission delay, two central concepts in data networking. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the tw

5、o hosts are separated by m meter, and suppose the propagation speed along the link is s meters/sec. Host A is to send a packet of size L bits to Host B. a. Express the propagation delay, dprop, in terms of m and s. b. Determine the transmission time of the packet, dtrans, in terms of L and R. c. Ign

6、oring processing and queuing delays, obtain an expression for the end-to-end dealy. d. Suppose Host A begins to transmit the packet at time t= 0. At time t=dtrans, where is the last bit of the packet? e. Suppose dprop is greater than dtrans. At time t= dtrans, where is the first bit of the packet? f

7、. Suppose dprop is less than dtrans. At time t=dtrans, where is the first bit of the packet? g. Suppose s=2.5108, L=100bits, and R=28kbps. Find the distance m so that dprop equals dtrans. 2、a)m/s b)L/R c)m/s+ L/R d)Interface of host A e)s*dtrans=s*L/R f)Host B g)m/s= L/R= m=8.928*105第二章1. In the fol

8、lowing figure, Alice sends an e-mail to Bob, and Bob gives a reply to Alice. If Alice and Bob both use mail user agent, please write what protocol is used in procedure ? If both Alice and Bob use Web browser, what protocol is used in procedure ? （1） SMTP; POP3 or IMAP; SMTP; SMTP; POP3 or IMAP; SMTP

9、 Alice Bob Alice s mail server Bob s mail server 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 1 页，共 7 页 - - - - - - - - - 2 （2） HTTP; HTTP; SMTP; SMTP; HTTP; HTTP 2. A client requests a Web page http:/ a server through IE browser. The version of HTTP is 1.1 and def

10、ault connection is persistent connection. The page is supported in Chinese. Please write the request message. If the server gives a reply to the client, the response message is created at 8:00:00 on 27-09-2011, and the object is modified at 00:00:00 on 18-09-2011. Please write the response message.

11、The known-conditions are: server is apache/2.0.40; the object is a text file and consists 1796 bytes. If there is a proxy server between the client and the Web server, how does the proxy server check the page it caches is newer or older? （1）GET /jwzx/index.do HTTP/1.1 Host: Connection: Keep-Alive Us

12、er-agent: Mozilla/4.0 Accept-language: zh-cn （2）HTTP/1.1 200 OK Date: Tue, 27 Sep 2011 08:00:00 GMT Server: Apache/2.0.40 Content-Length: 1796 Content-Type: text/html Last-Modified: Sun, 18 Sep 2011 00:00:00 GMT （3）the proxy server uses conditional GET GET /jwzx/index.do HTTP/1.1 Host: If-modified-s

13、ince: Sun, 18 Sep 2011 00:00:00 GMT 第三章1. Consider a TCP connection between Host A and Host B. Suppose that the TCP segments traveling from Host A to Host B have source port number x and destination port number y. What are the source and destination port numbers for the segments traveling from Host

14、B to Host A? Source port number is y, destination port number is x. 2. True of False? (1) Host A is sending Host B a large file over a TCP connection. Assume Host B has no data to send Host A. Host B will not send acknowledgments to Host A because Host B can not piggyback the acknowledgments on data

15、. (2) The size of the TCP RcvWindow never changes throughout the duration of the connection.(3) Suppose Host A is sending Host B a large file over a TCP connection. The number of unacknowledged bytes that A sends cannot exceed the size of the receive buffer. (4) Suppose Host A is sending a large fil

16、e to Host B over a TCP connection. If the sequence number for a segment of this connection is m, then the sequence number for the subsequent segment will necessarily be m+1. (5) The TCP segment has a field in its header for RcvWindow . (6) Suppose that the last SampleRTTin a TCP connection is equal

17、to 1 sec. Then the current value of TimeoutInterval for the connection will necessarily be1 sec. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 2 页，共 7 页 - - - - - - - - - 3 (7) Suppose Host A sends over a TCP connection to Host B one segment with sequence number 38

18、and 4 bytes of data. In this same segment the acknowledgment number is 42. (8) Consider congestion control in TCP. When the timer expires at the sender, the threshold is set to one half of its previous value. 3. Suppose Host A sends two TCP segments back to back to Host B over a TCP connection. The

19、first segment has sequence number 90; the second has sequence number 110. (1) How much data is in the first segment? 20 bytes (2) Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgment that Host B sends to Host A, what will be acknowledgment number? 90 4. S

20、uppose you have the following six 16-bit bytes: 01010000 11001101, 00110011 01100110, 0001001001001000, please compute the 16-bit checksum. 0110100110000100 习题课1. congestion window 计算2. Latency.计算（静态）3. checksum 计算参考第三版教材P291：27 题， P293：3437 题第四章1. There is a host A in the Internet. Its IP address i

21、s 210.100.89.204/20. Please answer the following questions: (1) Network address. (2)Broadcast address. (3) What is the subnet mask? (4) The fist host IP address. (5) The last host IP address. (6) How many hosts are there in the network? Solution: (1) 210.100.80.0 (2)210.100.95.255 (3) 255.255.240.0

22、(4) 210.100.80.1 (5) 210.100.95.254 (6) 232-20=212=4094 2. For the given topology of the network, use Dijstras shortest path algorithm to compute the shortest path from A to all network nodes. Give a shortest path tree and nod e A s routing table.1 E A B D C F 1 2 5 2 2 1 5 3 2 1 1 E A B D C F 1 2 2

23、 1 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 3 页，共 7 页 - - - - - - - - - 4 ND(B),p(B) D(C),p(C) D(D),p(D) D(E),p(E) D(F),p(F) A 5,A 2,A 1,A 2,A AD 2,D 2,A 2,A 4,D ADC 2,D 2,A 4,D/4,C ADCE 2,D 3,E ADCEB 3,E ADCEBF 第五章1. Please write the typical features of the fo

24、llowing popular interconnection devices at traffic isolation, plug and play, optimal routing and cut-through.hubs;routers;link-layer switches Routers Switches Hubs Traffic isolateion Yes Yes No Plug-and-play No Yes Yes Optimal routing Yes No No Cut-through No Yes Yes 2. There are two nodes going to

25、communicate with each other. The sender and the receiver agree on a generator G as 1001. Consider the piece of data, D=10111000, that the sending node wants to send to the receiving node. Suppose the two communicating nodes use CRC method detecting errors.Please write the bit-stream that the sending

26、 node transmits to the link.Assume the receiving node receives the value 10111000110, what does the receiving node will do? Is the bit-stream correct or not? Answers:1 0 1 0 1 1 0 11 0 0 1)1 0 1 1 1 0 0 0 0 0 0 1 0 0 1 1 0 1 0 1 0 0 1 1 1 0 0 1 0 0 1 1 0 1 0 1 0 0 1 1 1 0 0 1 0 0 1 1 0 1 R101,so the

27、 bit-stream that the sending node transmits to the link is 10111000101 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 4 页，共 7 页 - - - - - - - - - 5 1 0 1 0 1 1 0 11 0 0 1)1 0 1 1 1 0 0 0 1 1 0 1 0 0 1 1 0 1 0 1 0 0 1 1 1 0 0 1 0 0 1 1 0 1 1 1 0 0 1 1 0 1 0 1 0 0 1 1

28、1 R011, R 0, so the bit-stream has bit-error. 3. Draw lines. CSMA/CD random access protocols FDM point-to-point link channel partitioning protocols slotted ALOHA PPP protocol CDMA broadcast link taking-turns protocols polling protocol TDM Token-passing protocol Answer:TCP connection and tear down In

29、 the following figure, there is a client initiates a TCP connection to server via packet. The connection is established after the client receives packet. Suppose the client find it has no data need to send. The client sends packet to close the TCP connection. Please write down the Sequence number an

30、d Acknowledgment number of each packet. Notice the special bit of each packet. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 5 页，共 7 页 - - - - - - - - - 6 In the following figure, there is a client and a server communicating with each other. The connection is establ

31、ished via packet . Reliable data transfer works with Packet . Packet is sent from server to close the TCP connection. Suppose, packet carries 10 bytes data, and packet has payload 20 bytes. Packet carries 10 bytes data, and packet has no payload. Suppose, packet carries 10 bytes data, and packetcarr

32、ies 10 bytes data. Packet and packet has no payload. The time-sequence diagram is shown on right, and the Sequence number of packet is 179, the Sequence number of packet is 531. Please write down the Sequence number and Acknowledgment number of each packet.计算机网络复习大纲CH1 Computer Networks and the Inte

33、rnet 1什么是协议，网络应用有哪几种工作模式，通信的双方如何定义角色2电路交换网的几种类型，分组交换网的几种类型，什么是带宽3分组交换的设备都有哪些4网络接入的方法大致有几种类型，可用的物理媒体有哪些5分组在网络中所经历的各种时延分别在什么位置发生，每种时延是由什么引起的，分组丢失在哪里发生？6网络上的流通强度应该满足什么条件？CH2 Application Layer 1应用层进程之间通信，如何对进程进行寻址2HTTP的工作原理，持久连接和非持久连接是如何工作的；两种工作方式在请求页面时，需要多少个RTT ？3HTTP报文格式：请求报文和响应报文，条件get 报文的作用及其响应报文；We

34、b cache的作用4FTP的工作原理5邮件系统的组成部分，SMTP 工作原理，邮件格式，MIME ，邮件访问协议有哪些？6DNS的功能，工作原理，DNS层次结构CH3 Transport Layer 1传输层提供的服务2多路复用、多路分解分别表示什么意思3TCP 、UDP报文段格式中各字段的含义，checksum 计算4TCP的可靠数据传输是如何实现的名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 6 页，共 7 页 - - - - - - - - - 7 5TCP timer的超

35、时间隔如何设置及设置依据6TCP连接的 3 次握手过程与TCP连接断开的过程7TCP流量控制中接收窗口是如何取值的，又是如何通知发送方的？8TCP拥塞控制算法（Reno） ，TCP延迟计算（静态）CH4 The Network Layer 1网络层提供的服务2网络层有哪些主要功能？2工作在网络层的网络设备是什么，由哪些部分组成，有哪些功能，处理的数据单位及依据3IPv4 数据报格式及编址涉及的计算，获取地址的方法4ICMP协议的功能5IPv6 数据报格式的变化，编址的变化及地址位数的变化6LS选路算法7RIP、OSPF 、BGP协议CH5 The Link Layer and Local Ar

36、ea Networks 1链路层提供的服务2网络链路的几种类型3适配器的定义、功能4奇偶校验、CRC检测5多址访问协议有哪几种类型？6什么是局域网7MAC 编址、 ARP工作原理； DHCP 工作原理8Ethernet链路层帧的结构，CSMA/CD 原理9Ethernet技术，网段的划分；在10BaseT 网络中使用hub 及双绞线连接两台主机，这两台主机之间的最大距离；在其他网络中，使用hub、switch连接两台主机，这两台主机之间的最大距离。10工作在链路层的设备是什么，有哪些功能，处理的数据单位及依据；工作在物理层的设备是什么，有哪些功能，处理的数据单位又是什么名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 7 页，共 7 页 - - - - - - - - -