issa sariyayakul ul part i: nspart i: ns2 basics tee ns2teerawat/publications/ns2/w01-network...
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Part I: NSPart I: NS22 BasicsBasicsPart I: NSPart I: NS22 BasicsBasicsPart I: NSPart I: NS2 2 BasicsBasicsPart I: NSPart I: NS2 2 BasicsBasics
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 1
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Part I: OutlineTh B i• The Basics– Simulation of computer networks– Tcl/OTcl Tutorial– Tcl/OTcl Tutorial
• NS2 FundamentalsNS2 Fundamentals– An introduction to NS2– Linkage Between OTcl and C++ in NS2– Random Number Generators– Event Driven Simulation in NS2
NS2 Main Network Components– NS2 Main Network Components
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 2
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Simulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer NetworksSimulation of Computer Networks
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 3
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Outline• Computer Networks
A Study of Computer Networks• A Study of Computer Networks• Time-Dependent Simulationp• Example
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 4
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Computer Networks• Computer + Networking
NetworkingNetworking
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 5
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Computer Networks• Generally, there are so many tasks• Layering Concept: SeparateLayering Concept: Separate
functionalityOSI M d l TCP/IP M d l– OSI Model - TCP/IP Model
Application
TSession
Presentation
T
Application
Data LinkNetwork
Transport
Data LinkNetwork
Transport
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.PhysicalData Link
PhysicalData Link
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A Study of Computer Networks• Suppose you devise a great protocol.
How do you show that it’s great?How do you show that it s great?– Experiment: Put all routers together
d l t l s thand let people use them– Mathematic model: Model routers using
h ha graph theory– Simulation: Use programming (e.g., C++ p g g ( g
or NS2) to represent routers
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 7
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A Study of Computer Networks
Pros Cons
Experiment Realistic Expensive/ Sometime not possible
M h i I i h N d kMathematic Model
Insight Need to make assumptions
Simulation •Easy (Cheap)•Used for verification
Not much insight, sometimes need to
k tiTextbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.
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Time-Dependent Simulation
• Most commonly-usedy• Simulation proceeds chronologically.
T i t• Two main types:– Time-Driven Simulation– Event-Driven Simulation
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 9
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Time-Driven Simulation• Observe the system at a fixed interval.• Event occurs within an interval is assumed to
occur at the end of the interval• Suppose an interval = � seconds. Then the
simulation proceeds as follows:
– a,b,c,d are eventsi d 2– a is assume to occurred at t= 2�
– b,c are assume to occurred at t=( 5� )• The simulation finishes at a pre specified time
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.
• The simulation finishes at a pre-specified time.10
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E nt D i n Sim l ti nEvent-Driven Simulationb• Observe every event.
• Each event provide a reference to the next event (e.g.,Each event provide a reference to the next event (e.g., using pointer)
a b cNext_event Next_event Next_event
• Simulation finishes– At a pre-specified time– When there is no more event
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.
When there is no more event
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Example: Queuing System
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 12
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Example: Queuing System
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 13
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Example: Queuing System
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 14
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Example: Queuing System
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 15
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Summary• Computer Networks = Computer + Networking• A Study of Computer NetworksA Study of Computer Networks
– Experimental– Mathematical Model– Mathematical Model– Simulation
Tim D p d t Sim l ti• Time-Dependent Simulation– Time-Driven Simulation
E D l– Event-Driven Simulation• Example: A queuing system
Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 16
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