Question
Consider the following string of ASCII characters that were captured by Wireshark when the browser sent an HTTP GET message (i.e., this is the actual content of an HTTP GET message). The characters <cr><lf> are carriage return and line-feed characters (that is, the italized character string <cr> in the text below represents the single carriage-return character that was con- tained at that point in the HTTP header). Answer the following questions, indicating where in the HTTP GET message below you find the answer.
GET /cs453/index.html HTTP/1.1<cr><lf>Host: gai a.cs.umass.edu<cr><lf>User-Agent: Mozilla/5.0 ( Windows;U; Windows NT 5.1; en-US; rv:1.7.2) Gec ko/20040804 Netscape/7.2 (ax) <cr><lf>Accept:ex t/xml, application/xml, application/xhtml+xml, text /html;q=0.9, text/plain;q=0.8,image/png,*/*;q=0.5 <cr><lf>Accept-Language: en- s,en;q=0.5<cr><lf>Accept- Encoding: zip,deflate<cr><lf>Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7<cr><lf>Keep-Alive: 300<cr> <lf>Connection:keep-alive<cr><lf><cr><lf>
a. What is the URL of the document requested by the browser?
b. What version of HTTP is the browser running?
c. Does the browser request a non-persistent or a persistent connection?
d. What is the IP address of the host on which the browser is running?
e. What type of browser initiates this message? Why is the browser type
needed in an HTTP request message?
Answer
a.The document request was http://gaia.cs.umass.edu/cs453/index.html. The Host : field indicates the server's name and /cs453/index.html indicates the file name.
b) The browser is running HTTP version 1.1, as indicated just before the first pair.
c) The browser is requesting a persistent connection, as indicated by the Connection: keep-alive.
d) This is a trick question. This information is not contained in an HTTP message anywhere. So there is no way to tell this from looking at the exchange of HTTP messages alone. One would need information from the IP datagrams (that carried the TCP segment that carried the HTTP GET request) to answer this question .
e) Mozilla/5.0. The browser type information is needed by the server to send different versions of the same object to different types of browsers.
Discussions
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a. What is the URL of the document requested by the browser?
The URL of the document is cs453/index.html.
b. What version of HTTP is the browser running?
The browser is running version 1.1 of HTTP.
c. Does the browser request a non-persistent or a persistent connection?
The browser requests a persistent connection. This is shown by the line “Connection:keep-alive.”
d. What is the IP address of the host on which the browser is running?
The IP address of the host on which the browser is running is gaia.cs.umass.edu.
e. What type of browser initiates this message? Why is the browser type
needed in an HTTP request message?
The type of browser that initiates this message is Mozilla 5.0 on Windows. The browser type is needed in an HTTP request message because different browsers may handle the same webpage differently, due to having different capabilities.
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