Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer

Transcription

1 Part I: NS2 Basics Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared by y Teerwat Issariyakul

2 The Basics Part I: Outline Simulation of computer networks Tcl/OTcl Tutorial NS2 Fundamentals An introduction to NS2 Linkage Between en OTcl and C++ in NS2 Random Number Generators Event Driven Simulation in NS2 NS2 Main nnetwork Components by y Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared Teerwat Issariyakul

3 ss ar iy ak ul er w at I Pr ep ar ed by Te Simulation of Com Computer omp om Networks Textbook: k: T. Issariyaku Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer

4 Outline Computer Networks A Study of Computer Networks Time-Dependent Simulation Example Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared by y Teerwat Issariyakul

5 Computer Networks Computer + Networking Networking Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Pre repa pared ared by y Tee erwat rwat Issa sariya yakul

6 Computer Networks Generally, there are so many tasks Layering Concept: Separate functionality OSI Model - TCP/IP Model Application Presentation Session Transport Network Data Link Physical Application Transport Network Data Link Physical Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepa pa Dataarea red byy Teerwat Issariya yakul 6

7 A Study of Computer Networks Suppose you devise a great protocol. How do you show that tits it s great? Experiment: Put all routers together and dlet people use them Mathematic model: Model routers using a graph theory Simulation: :Use programming g (e.g., C++ or NS2) to represent routers Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared by y Teerwat Issariyakul

8 A Study of Computer Networks Pros Cons Experiment Realistic Expensive/ Sometime not possible Mathematic Insight Need to make Model assumptions Simulation Easy (Cheap) Used for verification Not much insight, sometimes need to make assumption Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepa pared e ed by y Tee erwat Issa sariyakul 8

9 Time-Dependent Simulation Most commonly-used Simulation proceeds chronologically. Two main types: Time-Driven Simulation byy Event-Driven Simulation Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared Teerwat Issariya yakul

10 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: erwat Issariyakul b a,b,c,d are eventsent 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 Prepared 10

11 Event-Driven Di nsimltin Simulation Observe every event. Each event provide a reference ence to the next event (e.g., using pointer) a b c Next_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 Prepared by btee erw Issariya nyakul 11

12 Example: Queuing System Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepared by ssariyakul

13 Example: Queuing System eer ssariyakul Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Prepa

14 Example: Queuing System Tee Issariyakul Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer P Prepa

15 Example: Queuing System Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer P ssariyakul

16 Summary Computer Networks = Computer + Networking A Study of Computer Networks Experimental Mathematical Model Simulation by Time-Dependent nt Simulation yt Time-Driven en Simulation Event-Driven Simulation Example: A queuing system Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer Preparepa ared Teerwat Issariyakul