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Ethereal Lab: HTTP

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Ethereal Lab: HTTP
1. The Basic HTTP GET/response interaction
No. Time Source Destination Protocol Info 1190 131.859385 128.238.245.34 128.119.245.12 HTTP GET /ethereal-labs/HTTP-ethereal-file1.html HTTP/1.1 Hypertext Transfer Protocol GET /ethereal-labs/HTTP-ethereal-file1.html HTTP/1.1\r\n Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, */*\r\n Accept-Language: en-us\r\n Accept-Encoding: gzip, deflate\r\n User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)\r\n Host: gaia.cs.umass.edu\r\n Connection: Keep-Alive\r\n \r\n
No. Time Source Destination Protocol Info 1192 131.875550 128.119.245.12 128.238.245.34 HTTP HTTP/1.1 200 OK (text/html) Hypertext Transfer Protocol HTTP/1.1 200 OK\r\n Date: Fri, 15 Oct 2004 18:13:19 GMT\r\n Server: Apache/2.0.40 (Red Hat Linux)\r\n Last-Modified: Fri, 15 Oct 2004 18:13:01 GMT\r\n ETag: "1bbf0-7e-60996540"\r\n Accept-Ranges: bytes\r\n Content-Length: 126\r\n Keep-Alive: timeout=10, max=100\r\n Connection: Keep-Alive\r\n Content-Type: text/html; charset=ISO-8859-1\r\n \r\n Line-based text data: text/html <html> Congratulations. You've downloaded the file http://gaia.cs.umass.edu/ethereal-labs/HTTP-ethereal-file1.html! </html>
Answer the following questions: 1. Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is the server running? Answer: Both are running HTTP 1.1 2. What languages (if any) does your browser indicate that it can accept to the server? Answer: Accept-Language: en-us

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3. What is the IP address of your computer? Of the gaia.cs.umass.edu server? Answer: My IP address is 128.238.245.34 and the server¨s is 128.119.245.12 4. What is the status code returned from the server to your browser? Answer: HTTP/1.1 200 OK (text/html) 5. When was the HTML file that you are retrieving last modified at the server? Answer: Last-Modified: Fri, 15 Oct 2004 18:13:01 GMT 6. How many bytes of content are being returned to your browser? Answer: Content-Length: 126 7. By inspecting the raw data in the packet content window, do you see any headers within the data that are not displayed in the packet-listing window? If so, name one. Answer: No all of the headers can be found in the raw data.
2. The HTTP CONDITIONAL GET/response interaction
No. Time Source Destination Protocol Info 72 6.592603 128.238.245.34 128.119.245.12 HTTP GET /ethereal-labs/HTTP-ethereal-file2.html HTTP/1.1 Frame 72 (403 bytes on wire, 403 bytes captured) Arrival Time: Oct 15, 2004 15:21:06.783195000 Time delta from previous packet: 6.592603000 seconds Time since reference or first frame: 6.592603000 seconds Frame Number: 72 Packet Length: 403 bytes Capture Length: 403 bytes Hypertext Transfer Protocol GET /ethereal-labs/HTTP-ethereal-file2.html HTTP/1.1\r\n Accept: */*\r\n Accept-Language: en-us\r\n Accept-Encoding: gzip, deflate\r\n User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)\r\n Host: gaia.cs.umass.edu\r\n Connection: Keep-Alive\r\n \r\n
No. Time Source Destination Protocol Info 74 6.608674 128.119.245.12 128.238.245.34 HTTP HTTP/1.1 200 OK (text/html) Frame 74 (739 bytes on wire, 739 bytes captured) Arrival Time: Oct 15, 2004 15:21:06.799266000 Time delta from previous packet: 0.016071000 seconds Time since reference or first frame: 6.608674000 seconds

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Frame Number: 74 Packet Length: 739 bytes Capture Length: 739 bytes Hypertext Transfer Protocol HTTP/1.1 200 OK\r\n Date: Fri, 15 Oct 2004 19:21:11 GMT\r\n Server: Apache/2.0.40 (Red Hat Linux)\r\n Last-Modified: Fri, 15 Oct 2004 19:21:01 GMT\r\n ETag: "1bfef-173-53c94140"\r\n Accept-Ranges: bytes\r\n Content-Length: 371\r\n Keep-Alive: timeout=10, max=100\r\n Connection: Keep-Alive\r\n Content-Type: text/html; charset=ISO-8859-1\r\n \r\n Line-based text data: text/html <html> Congratulations again! Now you've downloaded the file lab2-2.html. <br> This file's last modification date will not change. <p> Thus if you download this multiple times on your browser, a complete copy <br> will only be sent once by the server due to the inclusion of the IN-MODIFIED-SINCE<br> field in your browser's HTTP GET request to the server. </html>
No. Time Source Destination Protocol Info 118 10.458581 128.238.245.34 128.119.245.12 HTTP GET /ethereal-labs/HTTP-ethereal-file2.html HTTP/1.1 Frame 118 (403 bytes on wire, 403 bytes captured) Arrival Time: Oct 15, 2004 15:21:10.649173000 Time delta from previous packet: 3.849907000 seconds Time since reference or first frame: 10.458581000 seconds Frame Number: 118 Packet Length: 403 bytes Capture Length: 403 bytes Hypertext Transfer Protocol GET /ethereal-labs/HTTP-ethereal-file2.html HTTP/1.1\r\n Accept: */*\r\n Accept-Language: en-us\r\n Accept-Encoding: gzip, deflate\r\n If-Modified-Since: Fri, 15 Oct 2004 19:21:01 GMT\r\n If-None-Match: "1bfef-173-53c94140"\r\n User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)\r\n Host: gaia.cs.umass.edu\r\n Connection: Keep-Alive\r\n \r\n

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No. Time Source Destination Protocol Info 119 10.471105 128.119.245.12 128.238.245.34 HTTP HTTP/1.1 304 Not Modified Frame 119 (243 bytes on wire, 243 bytes captured) Arrival Time: Oct 15, 2004 15:21:10.661697000 Time delta from previous packet: 0.012524000 seconds Time since reference or first frame: 10.471105000 seconds Frame Number: 119 Packet Length: 243 bytes Capture Length: 243 bytes Hypertext Transfer Protocol HTTP/1.1 304 Not Modified\r\n Date: Fri, 15 Oct 2004 19:21:14 GMT\r\n Server: Apache/2.0.40 (Red Hat Linux)\r\n Connection: Keep-Alive\r\n Keep-Alive: timeout=10, max=99\r\n ETag: "1bfef-173-53c94140"\r\n \r\n
Answer the following questions: 8. Inspect the contents of the first HTTP GET request from your browser to the server. Do you see an ^IF-MODIFIED-SINCE ̄ line in the HTTP GET? Answer: No 9. Inspect the contents of the server response. Did the server explicitly return the contents of the file? How can you tell? Answer: Yes because we can see the contents in the Line-based text data field. 10. Now inspect the contents of the second HTTP GET request from your browser to the server. Do you see an ^IF-MODIFIED-SINCE: ̄ line in the HTTP GET? If so, what information follows the ^IF-MODIFIED-SINCE: ̄ header? Answer: Yes. The information followed is: Fri, 15 Oct 2004 19:21:01 GMT\r\n which is the date of the last modification of the file from the previous get request. 11. What is the HTTP status code and phrase returned from the server in response to this second HTTP GET? Did the server explicitly return the contents of the file? Explain. Answer: The status code and phrase returned from the server is HTTP/1.1 304 Not
Modified. The server didn¨t return the contents of the file since the browser loaded it
from its cache.

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3. Retrieving Long Documents
Answer the following questions: 12. How many HTTP GET request messages were sent by your browser? Answer: There was 1 HTTP GET request message sent by my browser as seen in the screenshot. 13. How many data-containing TCP segments were needed to carry the single HTTP response? Answer: There were 4 data containing TCP segments containing 1064 ,1380 ,1380 and 679 bytes respectively for a total of 4500 bytes. 14. What is the status code and phrase associated with the response to the HTTP GET request? Answer: 200 OK 15. Are there any HTTP status lines in the transmitted data associated with a TCP induced ^Continuation ̄? Answer: No

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4. HTML Documents with Embedded Objects
Answer the following questions: 16. How many HTTP GET request messages were sent by your browser? To which Internet addresses were these GET requests sent? Answer: As you can see from the above screenshot there were 3 HTTP GET requests sent to the following Internet addresses: a. 128.119.245.12 b. 165.193.123.218 c. 134.241.6.82 17. Can you tell whether your browser downloaded the two images serially, or whether they were downloaded from the two web sites in parallel? Explain. Answer: By checking the TCP ports we can see if our files were downloaded serially or in parallel. In this case the 2 images were transmitted over 2 TCP connections therefore they were downloaded serially.

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5. HTTP Authentication
Answer the following questions: 18. What is the server¨s response (status code and phrase) in response to the initial HTTP GET message from your browser? Answer: Status code: 401 , Phrase: Authorization Required 19. When your browser¨s sends the HTTP GET message for the second time, what new field is included in the HTTP GET message? Answer: As seen in the screenshot the new field (highlighted) is Authorization.
Authorization: Basic ZXRoLXN0dWRlbnRzOm5ldHdvcmtz\r\n

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