CS526 F2003 Midterm Exam

Enter your CS Unix machine login and the first, middle, last initials followed by the last 4 digits of student ID as password (those without middle name, just use first and last initials followed by the last 4 digits of student ID as password) and submit the midterm before 11:59pm 11/15/2003.   You can work at home or at PC lab where you can access it through a web browser.  For multiple-choice questions, you must choose either yes or no for each answer.

After filled in the answers in the text areas and selected the answers, please print a copy of the web page with your answers before you hit the submit button. Note that "save file" menuitem does not save the data you enter. It only saves the HTML source file. Submit your answers by pressing the submit button at the end of this web page.  You will get a confirm web page with all your answers. Save or print  the answer confirmation web page for your record. If you have problem getting the confirm web page or submitting midterm answers using the web page, just email me the answers.

Your name:
Your login on CS UNIX machines:
Your password on CS UNIX machines:
Work/Home Phone number (option):

  1. Apache
    1. Web Server Configuration
      1. Why apache uses LoadModule directives to configure itself?
      2. Why modules are compiled as .so? Give a scenario where share object modules will have benefit to system performance?
      3. Why CS Unix Machines run the apache web server using the apache account instead of root?
      4. Assume the directory browsing feature was turned on. Suggest a way you can disable directory browsing on a particular directory.

    2. Cache Server Configuration
      1. Why we use CacheDirLevels directive to organize cached documents in different subdirectories (as opposed to flat files all in one directory)?

      2. When a client browser sent out http request with If-Modified-Since header, where does it get the value for that header?
      3. When a cache server receives a http request with If-Modified-Since header, should it go ahead forward to the original web server without additional processing? What it should do?


    3. Reverse Proxy Configuration
      1. In what way, the reverse proxy web server we set up for hw1 is similar to LVS web cluster . (short answer).

      2. What its major disadvantage compared with LVS-based web cluster? Also name one feature LVS has but apache reverse proxy does not.
    4. Access Control
      1. For the hw2 apache access control, the apache needs to check the .htaccess files in every directory along the path of the url. Does all the restriction on access apply equally or the last directory where the file located has higher priority?
      2. What is the reason of using -m option when use "htpasswd" command?
  2. Introduction to CDN
    1. Caching
      1. Name the different caching schemes that try to improve the content delivery system performance.
      2. Why Akamai's Edge Cache Server is called "Edge"? What the name refers to?
    2. ESI,

      3. What is the advantage of using ESI compared to using If-Modfied-Since header?

  3. LVS
    1. NAT.
      1. Can the real server running at different port number? Yes No
      2. Why the default gateway of the real server needs to point to the lvs?
    2. IP Tunnel
      1. What is the major advantage of using LVS IP Tunnel configuration?
      2. What is the main disadvantage of  using LVS IP Tunnel configuration, in terms of performance?

    3. Direct Routing
      Why it performs better than LVS NAT? 
    4. High Availability Issue.
      1. What is active-active configuration? Describe the simplest scheme to divide the load
      2. Name the utility you will use to check the health status of the server processes running on real servers. 
  4. Content Switching
    1. Why content switches is slow compared with layer 4 switches? Name 3 reasons.
    2. How can content switch do to speed up the processing?
    3. TCP Delayed Binding. in Page #50 of the handout. If CSEQ=3000, DSEQ=5000, SSEQ=9000, without modifying the sequence numbers, what will the client TCP layer do when receives the http response from the real server?
    4. Content Switching Rule Conflict Detection. Give an example of potential content switch rule conflict.

If you feel some of the questions are ambiguous, state the problem # and your assumptions on the answers.