1 / 50

Chapter 4

Chapter 4. TCP/IP Network Simulation. Objectives. Appreciate the role of simulation in performance evaluation of TCP/IP networks Acquire the knowledge needed to conduct steady state simulation Master basic skills for analyzing confidence level Describe types of simulation tools available

yuri
Download Presentation

Chapter 4

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 4 TCP/IP Network Simulation

  2. Objectives • Appreciate the role of simulation in performance evaluation of TCP/IP networks • Acquire the knowledge needed to conduct steady state simulation • Master basic skills for analyzing confidence level • Describe types of simulation tools available • Familiarize with the capabilities of popular simulation tools

  3. Contents • Why use simulation • Systematic simulation study • Types of simulations • Simulation validation and verification • Confidence level of simulation results • Simulation with self similar traffic • Simulation tools

  4. Why Use Simulation

  5. Why Use Simulation • Predict performance for proposed network • Allow performance evaluation under a wide variety of network conditions • Compare alternative architectures under identical and repeatable conditions • Produce results closer to reality • Validate analytical results

  6. Systematic Simulation Study

  7. Systematic Simulation Study • Pre-software stage • Define problem/objective • Design network model and select fixed parameters • Select performance metrics • Select variable parameters

  8. Systematic Simulation Study (Cont.) • Software stage • Model construction • Simulation configuration • Simulation execution/Data collection • Result presentation

  9. Types of Simulation

  10. Types of simulations • Continuos vs. discrete event • Terminating vs. steady state • Synthetic vs. trace-driven

  11. Steady State • If we are interested in asymptotic behavior of a network system, we cannot use terminating simulations • Must continue until it reaches steady state

  12. Trace-Driven Simulations • Actual network traces can be used as simulation input • Results can be more convincing

  13. Validation and Verification

  14. Simulation Validation and Verification • Validation: Make sure that the assumptions are realistic • Verification: Make sure that the model implements assumptions correctly • Guidelines to follow • Look for “surprise” in output • Employ analytical modeling • Compare with real network data

  15. Confidence Level Analysis

  16. Confidence Level • Relative precision formula for 95% confidence (see Eq. 4.8, pp. 84) • Confidence level in terminating simulation • Repeat the entire simulation many times with different random numbers (or seeds) • p105, Fig. 4.4

  17. Confidence Level (cont.) • Confidence level in steady-state simulation • Fixed length simulation • Adaptive length simulation

  18. Self Similar Traffic

  19. Self Similar Traffic • Poisson model does not capture the burstiness of TCP/IP traffic • TCP/IP traffic usually exhibits self similar property • Generated by superimposing many ON/OFF sources with Pareto distribution

  20. Simulation Tools

  21. Classification of Simulation Tools • GPPL: General Purpose Programming Language • PSL: “Plain” Simulation Language • SP: Simulation Package • p110, Fig. 4.7

  22. NS Simulator • Developed by UC Berkeley • Public domain SP • Object-oriented • Written in C++ and object-oriented tcl (Otcl) • Network components are represented by classes

  23. Ns class hierarchy

  24. Reference network for TCP simulation with background traffic

  25. Sequence No. vs. time

  26. Average throughput vs buffer size

  27. Single FTP with trace-driven “star wars movie” internet traffic

  28. TCP throughput vs time

  29. TCP packet delay vs time

  30. OPNET • Developed by OPNET Technologies Inc. • Commercial SP • Object-oriented • Totally menu-driven package • Built-in model libraries contain most popular protocols and applications • Simulation task made easy

  31. Modeling hierarchy in OPNET

  32. Screen shot of a network-level modeling in OPNET

  33. Screen shot of a node-level modeling in OPNET

  34. Screen shot of a process-level modeling in OPNET

  35. Editing pad of state executives for process modeling in OPNET

  36. Link editor dialog box to set parameters of a point to point link object

  37. Packet editor to specify or edit details of TCP header fields

  38. Packet Editor to specify or edit details of TCP header

  39. Probe Editor to collect seven different types of statistics

  40. Simulation Tool showing two different simulation sequences

  41. Main menu of Analysis Tool

  42. Network model for RED gateway

  43. Evolution of buffer occupancy under FIFO and RED

  44. Network model for fairness evolution

  45. Average TCP/UDP throughput under FIFO

  46. Average TCP/UDP throughput under RED

  47. Average TCP/UDP throughput under WFQ

  48. Selecting the Right Tool • Built-in libraries • Credibility • User-Friendliness • Technical support • Level of Details • Resource consumption • Cost

  49. NS vs. OPNET • Both have emerged as de facto “standard” for simulating TCP/IP networks • P143, Table 4.6

  50. Packet delay vs link capacity

More Related