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CS526 S2006 Midterm Exam

Enter your CS Unix machine login and the student ID as password and submit the midterm before 11:59pm 3/15/2006.   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 and an email 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 (your SID):

  1. Apache
    1. Web Server Configuration
      1. Specify a barebone httpd.conf that specifies a web server listening to port 8080 and serving web pages located in /var/apache/html directory.
      2. Why CS Unix Machines run the apache web server using the apache account instead of root?

    2. Cache Server Configuration
      1. When a client browser sends a http request with the If-Modified-Since header, where does it get the value for that header?

      2. When a cache server receives a http request, it is required to check with the original web server to see if the local cached copy is old. This may cause a long round trip delay. How Akami's Edge Server Side Include (ESI) technique addresses and improves this? Hint: http://cs.uccs.edu/~chow/pub/conf/pdcat/tutorial.ppt#11.


    3. Reverse Proxy
        4. List the two main differences between the apache reverse proxy based cluster and LVS-NAT based cluster.

    4. Access Control
      1. Which http header carries the authentication realm info to a web browser? Which http header carries the login and password in uuencode format back to the web server?
        Hint: http://cs.uccs.edu/~cs401/doc/authentication.ppt
      2. What is the reason of using -s option when use "htpasswd" command as opposed to using the default?
    5. If virtual hosting means hosting a customer's web server, email server, and streaming server, which of the three hosting techniques we covered can handle such virtual hosting?

  2. Introduction to CDN and Locally Distributed Web-Server System.
    1. Caching
      1. Name the four 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?
      3. Given the same processing power and connection bandwidth, explain the main reason why the edge cache server will typically perform better than the mirror server.
    2. Taxonomy of Locally Distributed Web-Server System
      1. In page 270 of Cardellini's paper, three main classes of locally distributed architectures are identified. To what class does LVS belong?
      2. One technique to improve web cluster performance is through the web page rewrite. The set of web pages to be served by the cluster are divided and loaded into different web servers of the cluster. The links and embedded references in those web pages are modified accordingly to reflect where they are saved. This technique allows a user to access a web page directly on a real web server without having to go through a load balancer. To what class of locally distributed architectures, does this web page rewrite architecture belong?

  3. LVS
    1. LVS-NAT.
      1. Can the real servers run at different port numbers than that known to the client? Yes No
      2. What is the default gateway configured on each real server?
    2. LVS-Tunnel.
      What is the major advantage of a LVS-Tunnel configuration compared with the other two LVS configurations?

    3. LVS-Direct Routing
      List two reasons why DR-based cluster performs better than NAT-based cluster?
       
  4. LCS
    1. List two reasons why a content switch has more processing overhead than the LVS?

    2. What is TCP delayed binding? Why a LVS cluster does not have to address this problem?
    3. Name two ways to improve TCP delayed binding.

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