CSci 555 / Neuman-Obraczka Fall 1998
Directions for completing exam
 

1. (50 points) Your company is building an electronic mall to be accessed over the Internet.  Your company plans to distinguish itself from its competitors by stressing the performance, reliability, security, and ease of use of your system.

An electronic mall provides services to its merchants, including the check modification. software to display and market their products, accept orders, clear payment for orders, and communicate with customers.  The infrastructure supporting these functions is implemented by the online mall, and shared by the merchants.  Data on orders is provided to the merchants for shipping, and depending on the merchant and the form of payment, payment for orders may be collected and cleared by the mall. Alternatively, payment information is passed on to the merchant for changed this sentence slightly.
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You have been asked to describe the features of your design that affect performance, reliability, security, and ease of use.  In the questions that follow, there is no single correct answer.  However, there are many answers that are wrong. Your answers should be plausible and you should argue why they are correct or likely, while avoiding answers that are clearly wrong.  Don't forget to consider the costs of particular features when considering the feasibility of your design.
 
• (10 points) Describe the components of the system from the user interface through order fulfillment.  Where are these components implemented, who controls each part of the system, and what software will be used?  What kinds of information will be maintained by the system and where will it be stored?  How might the ease of use requirement affect your answer?
• (20 points)Describe the techniques that you will use to improve the reliability, availability, and performance of the the system.  Describe the techniques in sufficient detail to show how each technique is applied and to which parts of the system.  What services will your system be dependent upon, and who controls those services? What kinds of failures will leave your system unavailable.  What are the costs or drawbacks of the steps you have taken.
• (20 points) Describe the methods used to protect your system, the users of the system, and the payment methods supported by the system.  Is there anything special about the high level structure of your system that improves its security, or that improves the performance of the components of the system supporting security? What measures might you take to improve the security of the system specifically for the end customer, and to promote user privacy?

• (50 points) The Next-Generation Internet will enable several next-generation multimedia applications.  Betting on the availability of this communication infrastructure, USC has hired your start-up company to design a virtual classroom system.  The system will enable fully interective classrooms accommodating local as well as remote students.  Students will be encouraged to purchase a relatively inexpensive notebook which they will use in class to download class notes and annotate them.  Classes (both audio and video) will be broadcast to remote sites and remote students will be able to ask questions and participate in class discussions.  Students enrolled in a class will be able to participate in fully interactive discussion sessions among themselves and the TA.  The system will also support assignment submission, posting of assignment and exam keys, and group projects.
• (20 points) Given the trends in kernel design discussed in class, which one would you choose to base the design of the system's kernel?  Why? Would you use the same kernel for all components of the system?  Justify.  What services would be provided by the kernel(s)? What services would be provided outside of the kernel?  Justify.
• (20 points) For each of the supported functions listed above: what is the corresponding file access/sharing pattern?  Where would the files be stored? If files are shared, how would maintain consistency?  Would you use caching? If so, would you cache all types of files?  Given the cache consistency mechanisms discussed in class, which one would you employ and why (discuss the tradeoffs in setting the parameters of the consistency mechanism of choice).  Would you use replication?  Would you replicate all types of files? How would you keep consistency among replicas?
• (10 points) Since disks are reasonably inexpensive, which function(s) supported by the system would justify the use of an array of disks? What would be the benefits and drawbacks of using an array of disks as opposed to replication?