TELCOM 2120 – Network Performance
Homework 4 Spring 04
1. You are asked to determine the throughput performance of an ATM switch using two of the
ATM Forum Performance Benchmark Suite. Specifically you are asked to find a 90% confidence
interval with 5% relative precision on the Peak throughput and associated mean cell loss rate of
the switch for the following traffic scenarios.
1) Each input port has a multicast stream destined for the other output (i.e., (N-1) output)
ports
2) Each of the n input ports has a traffic source creating traffic destined for the same
output port (N to 1 stress test).
In each case the traffic source is a Variable Bit Rate connection with a maximum burst size of
50 cells. Describe a set of experiments you would conduct to achieve this. This is an open ended
problem with no one set answer as is the case in most real world experimental studies. Follow
the concepts of experimental design.
2. The 2k Factorial experimental design matrix below shows the results of a measurement study
on switched virtual circuit setup times in an operational multi-switch MAN ATM network. The
factors are
A: the number of hops between source and destination node (measured by number of
switches.)
B: the number of peer groups the switches organized into.
C: the number of destinations per source connection (amount of multicasting.)
For the factors the following level values were used
A: -1 level (1 hop) +1 level (5 hops)
B: -1 level (1 peer group) +1 level (2 peer groups)
C: -1 level (1 destination - unicast call) +1 level (4 multicast call)
The response variable is the call set up time - measured over an average of 10 experiments where
each experiment consisted of setting up and tearing down 400 switched virtual circuits.
A B C Call Set Up Time
(milliseconds)
-1 -1 -1 46.5
+1 -1 -1 240.7
-1 +1 -1 50.2
+1 +1 -1 590.0
-1 -1 +1 201.6
+1 -1 +1 1076.5
-1 +1 +1 880.4
+1 +1 +1 4449.0
(a) Determine the main effects and the interaction effects.
(b) Explain what you have observed based on values obtained in (a).
(c) Construct a regression model to predict a call set up time.
