计算机网络实验报告一.docx

1、计算机网络实验报告一计算机网络实验报告一班级：智能1401 * 学号：*一、HTTP1. The Basic HTTP GET/response interaction实验步骤：1.Start up your web browser.2. Start up the Ethereal packet sniffer, as described in the Introductory lab (but dontyet begin packet capture). Enter “http” (just the letters, not the quotation marks)in the displa

2、y-filter-specification window, so that only captured HTTP messageswill be displayed later in the packet-listing window. (Were only interested in theHTTP protocol here, and dont want to see the clutter of all captured packets).3. Wait a bit more than one minute (well see why shortly), and then begin

3、Etherealpacket capture.4. Enter the following to your browserhttp:/gaia.cs.umass.edu/ethereal-labs/HTTP-ethereal-file1.htmlYour browser should display the very simple, one-line HTML file.5. Stop Ethereal packet capture. 实验结果：1. Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is

4、 theserver running? 结果：我的浏览器HTTP的版本是1.1，服务器的HTTP版本是1.12. What languages (if any) does your browser indicate that it can accept to theserver? 结果：浏览器可以接受的语言版本：zh-Hans-CN,zh-Hans;q=0.8,en-US;q=0.5,en;q=0.33. What is the IP address of your computer? Of the gaia.cs.umass.edu server?结果：电脑的IP地址为192.168.1.8

5、 服务器IP为: 128.119.245.124. What is the status code returned from the server to your browser?结果：状态代码是200（请求成功）5. When was the HTML file that you are retrieving last modified at the server?结果：Last-Modified: Tue, 18 Apr 2017 05:59:01 GMTrn6. How many bytes of content are being returned to your browser?结

6、果：返回到浏览器的内容的字节1267. By inspecting the raw data in the packet content window, do you see any headerswithin the data that are not displayed in the packet-listing window? If so, nameone 通过检查数据包内容窗口中的原始数据，您会看到任何标题在数据包列表窗口中未显示的数据中？ 如果是这样，找出一个。结果：没有。2. The HTTP CONDITIONAL GET/response interaction实验步骤： St

7、art up your web browser, and make sure your browsers cache is cleared, asdiscussed above. Start up the Ethereal packet sniffer Enter the following URL into your browserhttp:/gaia.cs.umass.edu/ethereal-labs/HTTP-ethereal-file2.htmlYour browser should display a very simple five-line HTML file. Quickly

8、 enter the same URL into your browser again (or simply select the refreshbutton on your browser) Stop Ethereal packet capture, and enter “http” in the display-filter-specificationwindow, so that only captured HTTP messages will be displayed later in thepacket-listing window. (Note: If you are unable

9、 to run Ethereal on a live network connection, you canuse the http-ethereal-trace-2 packet trace to answer the questions below; seefootnote 1. This trace file was gathered while performing the steps above on oneof the authors computers.) 实验结果：8. Inspect the contents of the first HTTP GET request fro

10、m your browser to theserver. Do you see an “IF-MODIFIED-SINCE” line in the HTTP GET?结果：第一次HTTP GET没有看到“IF-MODIFIED-SINCE”9. Inspect the contents of the server response. Did the server explicitly return thecontents of the file? How can you tell?检查服务器响应的内容。 服务器是否显式返回文件的内容？ 你怎么知道？结果：返回内容：10. Now inspec

11、t the contents of the second HTTP GET request from your browser tothe server. Do you see an “IF-MODIFIED-SINCE:” line in the HTTP GET? Ifso, what information follows the “IF-MODIFIED-SINCE:” header?客户端第二次请求此URL时，根据 HTTP 协议的规定，浏览器会向服务器传送 If-Modified-Since 报头结果：有“IF-MODIFIED-SINCE:”，内容是：If-Modified-Si

12、nce: Sat, 22 Apr 2017 05:59:01 GMTrn11. What is the HTTP status code and phrase returned from the server in response tothis second HTTP GET? Did the server explicitly return the contents of the file?Explain. 答案：状态码和相应状态信息的值为302 Moved Temporarily。代表的意思是新的URL应该被视为临时性的替代。3. Retrieving Long Documents实验步

13、骤： Start up your web browser, and make sure your browsers cache is cleared, asdiscussed above. Start up the Ethereal packet sniffer Enter the following URL into your browserhttp:/gaia.cs.umass.edu/ethereal-labs/HTTP-ethereal-file3.htmlYour browser should display the rather lengthy US Bill of Rights.

14、 Stop Ethereal packet capture, and enter “http” in the display-filter-specificationwindow, so that only captured HTTP messages will be displayed. (Note: If you are unable to run Ethereal on a live network connection, you canuse the http-ethereal-trace-3 packet trace to answer the questions below; se

15、efootnote 1. This trace file was gathered while performing the steps above on oneof the authors computers.) 实验结果：12. How many HTTP GET request messages were sent by your browser?结果：2个GET请求13. How many data-containing TCP segments were needed to carry the single HTTPresponse?需要多少数据包含TCP片段来承载单个HTTP响应？

16、结果：4个14. What is the status code and phrase associated with the response to the HTTP GETrequest?答案：状态码和短语是200 OK：表示请求成功，信息包含在响应的报文中。15. Are there any HTTP status lines in the transmitted data associated with a TCPinduced “Continuation”? 结果：有，对于一个大的HTML文件会被TCP分为若干个独立的包。4. HTML Documents with Embedded

17、 Objects实验步骤： Start up your web browser, and make sure your browsers cache is cleared, asdiscussed above. Start up the Ethereal packet sniffer Enter the following URL into your browserhttp:/gaia.cs.umass.edu/ethereal-labs/HTTP-ethereal-file4.htmlYour browser should display a short HTML file with two

18、 images. These twoimages are referenced in the base HTML file. That is, the images themselves arenot contained in the HTML; instead the URLs for the images are contained in thedownloaded HTML file. As discussed in the textbook, your browser will have toretrieve these logos from the indicated web sit

19、es. Our publishers logo isretrieved from the web site. The image of our books cover isstored at the manic.cs.umass.edu server. Stop Ethereal packet capture, and enter “http” in the display-filter-specificationwindow, so that only captured HTTP messages will be displayed. (Note: If you are unable to

20、run Ethereal on a live network connection, you canuse the http-ethereal-trace-4 packet trace to answer the questions below; seefootnote 1. This trace file was gathered while performing the steps above on oneof the authors computers.) 实验结果：16. How many HTTP GET request messages were sent by your brow

21、ser? To whichInternet addresses were these GET requests sent?结果：浏览器一共发出了4个HTTP GET请求，目的IP如图所示17. Can you tell whether your browser downloaded the two images serially, orwhether they were downloaded from the two web sites in parallel? Explain. 浏览器在下载这两个图片时，是串行下载还是并行下载？请解释结果：是并下载。因为两个图片是连续请求,并没有等第个图片请

22、求得到回复后才继续第二次请求。5.HTTP Authentication实验步骤： Make sure your browsers cache is cleared, as discussed above, and close downyour browser. Then, start up your browser Start up the Ethereal packet sniffer Enter the following URL into your browserhttp:/gaia.cs.umass.edu/ethereal-labs/protected_pages/HTTP-eth

23、ereal-file5.htmlType the requested user name and password into the pop up box. Stop Ethereal packet capture, and enter “http” in the display-filter-specificationwindow, so that only captured HTTP messages will be displayed later in thepacket-listing window. (Note: If you are unable to run Ethereal o

24、n a live network connection, you canuse the http-ethereal-trace-5 packet trace to answer the questions below; seefootnote 1. This trace file was gathered while performing the steps above on oneof the authors computers.) 实验结果：18. What is the servers response (status code and phrase) in response to th

25、e initialHTTP GET message from your browser?对于浏览器发出的最初的HTTPGET请求，服务器的响应是什么？结果：401 Unauthorized(XX)19. When your browsers sends the HTTP GET message for the second time, whatnew field is included in the HTTP GET message? 当浏览器发出第二个HTTP GET请求时，在HTTP GET报文中包含了哪些新的字段？结果：出现新字段：Authorization: Basic MTEyMzo

26、yMzEzrnCredentials: 1123:2313（用户名及密码）第一次请求：第二次请求：二、TCP实验步骤：1. Capturing a bulk TCP transfer from your computer to a remoteServer2. A first look at the captured trace3. TCP Basics实验结果：1. What is the IP address and TCP port number used by your client computer(source) to transfer the file to gaia.cs.um

27、ass.edu? What is the IP address and portnumber used by gaia.cs.umass.edu to receive the file.答：clientcomputer: IPaddress:10.63.236.170TCPportnumber:60813Gaia.cs.umass.edu: IPaddress:128.119.245.12TCPportnumber:802. What is the sequence number of the TCP SYN segment that is used to initiate theTCP co

28、nnection between the client computer and gaia.cs.umass.edu? What is itin the segment that identifies the segment as a SYN segment?答：第一次握手：Sequence number: 0 (relative sequence number), SYN被置位，SYN=1第二次握手：Sequence number: 0，Acknowledgment number: 1，SYN=1第三次握手：Sequence number: 1，Acknowledgment number:

29、1，SYN=03. What is the sequence number of the SYNACK segment sent by gaia.cs.umass.eduto the client computer in reply to the SYN? What is the value of theACKnowledgement field in the SYNACK segment? How did gaia.cs.umass.edudetermine that value? What is it in the segment that identifies the segment a

30、s aSYNACK segment?答：由上一个题目可知，三次握手的过程中，第二次握手SYNACK Sequence number: 0，Acknowledgment number: 1，SYN=1；第三次握手ACK Sequence number: 1，Acknowledgment number: 1，SYN=0，其中Acknowledgment number = 上一个Sequence numbe+1。实验结果和理论一致。4. What is the sequence number of the TCP segment containing the HTTP POSTcommand? No

31、te that in order to find the POST command, youll need to dig intothe packet content field at the bottom of the Ethereal window, looking for asegment with a “POST” within its DATA field.答：TCP segment data (481 bytes)5. Consider the TCP segment containing the HTTP POST as the first segment in theTCP connection. What are the sequence numbers of the first six segments in theTCP connection (including the segment containing the HTTP POST)? At whattime wa