CS526 S2005 Midterm Exam

Enter your CS Unix machine login and the last 4 digits of student ID as password and submit the midterm before 11:59pm 3/8/2005.   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 (last four digits of your SID):

  1. Apache
    1. Web Server Configuration
      1. Specify the barebone httpd.conf that specifies a web server listens to port 8080 with web pages located at /var/apache/html.
      2. What directive is used to load Dynamic Shared Object (DSO)? What the two parameters needed for the directive?
      3. 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 out http request with If-Modified-Since header, where does it get the value for that header?

      2. When a cache server receives a http request with If-Modified-Since header, what it should do?


    3. Reverse Proxy
      1. What are the two main differences between the reverse proxy based cluster and LVS-NAT based cluster?

      2. What are the two main differences between Reverse Proxy based cluster and LVS-Tunnel based cluster?
    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 .htaccess of the last directory where the file located has higher priority, i.e., take precedence?
      2. What is the reason of using -m option when use "htpasswd" command?
      3. What is the major advantage of using client certifcate authentication vs. the basic authentication (login and password)?
    5. If virtual hosting means hosting a customer's web site, DNS, mail, which of the three hosting techniques can handle such virtual hosting?

  2. Introduction to CDN and Locally Distributed Web-Server System.
    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?
      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
      In page 270 of Cardellini's paper, three main classes of local distributed architectures are identified. To what class does LVS belong?

  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. Scheduling. Give a simple scenario where weighted round robin is more suitable than simple round robin.

    3. Direct Routing
      List two reasons why DR-based cluster performs better than NAT-based cluster? 

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