Transcript 10 pts - ECSE - Rensselaer Polytechnic Institute

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.}
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
1
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)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
2
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.
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
3
2. [10 pts] Given: n=6 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
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
4
II. [10 pts] Experiment Design: Analyze the 2^3 design
a)
Quantify all the main effects and all interactions [5 pts]
b)
Quantify percentages of variations explained [3 pts]
c)
Sort the variables in the order of decreasing importance [2 pts]
A1
A2
C1
C2
C1
C2
B1
90
20
100
20
B2
35
30
30
45
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
5
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
6
I.
a)
b)
c)
d)
[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]
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
7
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
8