NS STRUCTURE

NS STRUCTURE
● NS is an object oriented discrete­event simulator
* Simulator maintains list of events and executes one event after another
* Single thread of control: no locking or race conditions


● Back end is C++ event scheduler
* Protocols mostly
* Fast to run, more control


● Front end is oTCL
* Creating scenarios, extensions to C++ protocols
* fast to write and change

WHY TWO LANGUAGE? (TCL & C++)
• C++: Detailed protocol simulations require systems programming language  
* byte manipulation, packet processing, algorithm implementation
* Run time speed is important
* Turn around time (run simulation, find bug, fix bug, recompile, re-run) is slower


• Tcl: Simulation of slightly varying parameters or configurations
* quickly exploring a number of scenarios
* iteration time (change the model and re -run) is more important