4005-741-01 Advanced Computer Networks
Module 2. Discrete Event Simulation
Lecture Notes

Computer Science Course Library Packages

• Classes for building discrete event simulation programs
  • Package edu.rit.discretesim

• Classes for generating random numbers with various distributions
  • Package edu.rit.numeric.prob

• Classes for creating plots from within a program
  • Class edu.rit.numeric.plot.Plot
  • Class edu.rit.numeric.XYSeries
  • Class edu.rit.numeric.ListXYSeries

Example: Simulation of an M/M/1 Queue

• Class MM1 [source code]
  • Discrete event simulation of an unbounded FIFO M/M/1 queue
  • Mean arrival rate λ and mean service rate μ are command line arguments -- "knobs"
  • Measures mean wait time and mean queue length

• Class MM1v2 [source code]
  • Same as above, except . . .
  • Does several simulation runs with a series of λ values
  • Displays a plot of mean wait time versus λ

Example: Simulation of a Small Network

• Four routers connected in a bidirectional ring

• One host attached to each router

• Host 0 is a server, hosts 1-3 are clients
  

• Each host consists of one or more generators

• Traffic pattern
  • Host 1 → Host 0 packets, interarrival times exponentially distributed, mean arrival rate λ₁₀
  • Host 2 → Host 0 packets, interarrival times exponentially distributed, mean arrival rate λ₂₀
  • Host 3 → Host 0 packets, interarrival times exponentially distributed, mean arrival rate λ₃₀
  • Host 0 → Host 1 packets, interarrival times exponentially distributed, mean arrival rate λ₀₁
  • Host 0 → Host 2 packets, interarrival times exponentially distributed, mean arrival rate λ₀₂
  • Host 0 → Host 3 packets, interarrival times exponentially distributed, mean arrival rate λ₀₃

• All packets same size, all links same data rate, constant service rate μ
  

• Each router consists of one or more queues/servers
  • Each queue individually bounded at max packets

• Measurements
  • Mean delivery time for all packets
  • Mean drop fraction for all packets

• Classes
  • Class Packet [source code]
  • Class PacketFactory [source code]
  • Class Host [source code]
  • Class Router [source code]
  • Class DeliveryTimeMeter [source code]
  • Class Main01 [source code]

Advanced Computer Networks • 4005-741-01 • Fall Quarter 2009

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Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706

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Copyright © 2009 Alan Kaminsky. All rights reserved. Last updated 02-Oct-2009. Please send comments to ark­@­cs.rit.edu.