CptS 464/564 Homework #3

 

Given: Wednesday, November 28, 2001

Due: Wednesday, December 12, 2001 at the beginning of class                    

Max points: 150 points for 464, 325 points for 564.

Weight: 5% of final grade

 

Note: This homework should not be handwritten, but must be done with a word processor.

 

1)   [20 points]  Rate Monotonic Scheduling

Fill in the schedule below with how a rate monotonic scheduler would allocate time slots to the following task table:

Task

Period

TWCET

1

2

1

2

10

2

3

20

6

Text Box:            


2)    [30 points] Security versus Fault Tolerance

As mentioned in the text and in lecture, handling security is harder than fault tolerance, where the emphasis is generally on handling benign and accidental failures.  The two reasons given were:

  1. Direct causes of failures (attacks) are deliberate
  2. Successful attacks often made possible by unintentional and dormant faults (vulnerabilities) made by designers

For each of these reasons, explain in a few brief but well-considered paragraphs how this makes handling security more difficult.  To get full credit, an answer must show good insight.

 

3)   [75 points 464; 150 points 564] Security Properties

The three main security properties discussed in class and the text were:

·        Confidentiality

·        Integrity

·        Availability.

Devise an interesting and realistic distributed application scenario, using an existing application or making one up, where it goes through three plausible modes or phases of operation.  In each phase it should have different CIA requirements that make sense, given the mode and application. 

Write up a page or so total, explaining

·        What each mode is, what its CIA requirements are for that mode, and, most importantly, why these requirements are appropriate for this mode.  The requirements for a given mode and property (e.g., availability) should be from {High, Medium, Low}.

To get full credit, your writeup should have an innovative application (different from anyone else’s) and should have cogent and compelling and interesting modes and reasons why the different CIA levels are required at each mode.  You don’t have to be as good a writer as Tom Clancy at this stuff, but if its poorly written you will suffer a bit, too.  464 is graded easier than 564 on this.

564 students, do the same, but for two different applications.

Note: if you are a non-US citizen, we promise we will not tell your government that you are working with the CIA!  J

4)   [100 points; 564 only] Distributed Quality of Service

QoS middleware needs to integrate disparate information (QoS meta-data) over different “elements” (for lack of a better term)

  1. Providers
  2. Locations

3.      Times

The QoS slides (slide 21) and the paper (section 4.2) give different examples of entities from each of these 3 elements.  For each element, pick 3 examples (the slides give plenty) and then for each example, write a short paragraph describing QoS meta-data that could be provided (describing QoS requirements/constraints, resources available, etc) and how it could affect QoS or resource allocation decisions.

For example, you could choose (see the slides)

1.      Providers: application program (client), remote object, network management information

  1. Locations: client host, remote object host, network (you could even subdivide network locations into multiple ones if you liked)

3.      Times: application initialization, contract setup, change in network conditions

5)    [25 points] The Semantic Web

Describe a distributed application today, and how it might be able to take advantage of  the semantic web concepts.  Or describe a new application made possible by them.  Your example should be a half or full page in length, and insightful and compelling to get full credit (564 graded tougher than 464 here), and the application (not just its description) should be different from any other student’s.