ECSE4963: Experimental Networking Exam 1

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ECSE-4963 Experimental Networking Exam 1

• Time 60 min (strictly enforced)
• Points 50
• YOUR NAME
• Be brief, but DO NOT omit necessary detail
• Note Simply copying text directly from the
  slides or notes will not earn (partial) credit.
  Brief, clear and consistent explanation will.

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• I. Quick questions on probability/experiment
  design
• 1. 5 pts What is the difference between the
  cumulative distribution function (CDF) and
  probability density function (pdf)? State one
  purpose where CDF is easier to work with than the
  pdf ?(hint mean vs median)

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• I. 10 pts Show (derive) that if two random
  variables are independent I.e. P(XY) P(X)P(Y)
  they are uncorrelated I.e. E(XY) E(X)E(Y) ,
  but the reverse is not true.

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• 2. 10 pts Given n6 random RTT samples (in
  ms)
• 31, 42, 28, 51, 28, 40
• Find sample mean (xbar), sample standard
  deviation (s), 90 confidence interval (CI) 95
  CI for the population mean

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• II. 10 pts Experiment Design Analyze the 23
  design
• Quantify all the main effects and all
  interactions 5 pts
• Quantify percentages of variations explained
  3 pts
• Sort the variables in the order of decreasing
  importance 2 pts

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• 15 pts DESIGN WALK-THROUGH We learnt about
  animation, simulation (ns-2), graphing tools, and
  click modular router toolkit. Assume that you are
  given the following design problem to design a
  new error resilience protocol for overlay
  networks that involves a mix of forward error
  correction (FEC) and automatic repeat request
  (ARQ) to be implemented at the IP-layer (I.e.
  layer 3).
• Discuss the design issues and tradeoffs for this
  problem 4 pts
• Walk me through how you would systematically use
  the above tools (in the right sequence) to help
  design and incrementally refine your design. 5
  pts
• What metrics would you use to test/validate your
  protocol explain why your set of metrics is a
  complete and meaningful set. 3 pts
• What set of workloads would you use to test such
  a system explain why it is meaningful, and yet
  helps you make quick progress in your design
  process. 3 pts

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