prentice hallhigh performance tcp/ip networking, hassan-jain chapter 4 tcp/ip network simulation
TRANSCRIPT
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Chapter 4
TCP/IP Network Simulation
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Why Use
Simulation
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Systematic
Simulation
Study
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Systematic Simulation Study
Pre-software stage Define problem/objective Design network model and select fixed parameters Select performance metrics Select variable parameters
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Systematic Simulation Study (Cont.)
Software stageModel constructionSimulation configurationSimulation execution/Data collectionResult presentation
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Types of
Simulation
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Types of simulations
Continuos vs. discrete event Terminating vs. steady state Synthetic vs. trace-driven
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Trace-Driven Simulations
Actual network traces can be used as simulation input
Results can be more convincing
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Validation and Verification
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Simulation Validation and Verification
Validation: Make sure that the assumptions are realistic
Verification: Make sure that the model implements assumptions correctly
Guidelines to followLook for “surprise” in outputEmploy analytical modelingCompare with real network data
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Confidence Level Analysis
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Confidence Level (cont.)
Confidence level in steady-state simulation
Fixed length simulation
Adaptive length simulation
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Self Similar Traffic
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Simulation Tools
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Classification of Simulation Tools GPPL: General Purpose Programming Language PSL: “Plain” Simulation Language SP: Simulation Package p110, Fig. 4.7
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Ns class hierarchy
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Reference network for TCP simulation with background traffic
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Sequence No. vs. time
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Average throughput vs buffer size
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Single FTP with trace-driven “star wars movie” internet traffic
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
TCP throughput vs time
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TCP packet delay vs time
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
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
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Modeling hierarchy in OPNET
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Screen shot of a network-level modeling in OPNET
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Screen shot of a node-level modeling in OPNET
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Screen shot of a process-level modeling in OPNET
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Editing pad of state executives for process modeling in OPNET
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Link editor dialog box to set parameters of a point to point link object
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Packet editor to specify or edit details of TCP header fields
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Packet Editor to specify or edit details of TCP header
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Probe Editor to collect seven different types of statistics
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Simulation Tool showing two different simulation sequences
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Main menu of Analysis Tool
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Network model for RED gateway
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Evolution of buffer occupancy under FIFO and RED
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Network model for fairness evolution
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Average TCP/UDP throughput under FIFO
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Average TCP/UDP throughput under RED
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Average TCP/UDP throughput under WFQ
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Selecting the Right Tool
Built-in libraries Credibility User-Friendliness Technical support Level of Details Resource consumption Cost
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
NS vs. OPNET
Both have emerged as de facto “standard” for simulating TCP/IP networks
P143, Table 4.6
Prentice HallHigh Performance TCP/IP Networking, Hassan-Jain
Packet delay vs link capacity