Queuing Models in NS2

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M/M/1 is a system with poisson arrival time, servicing exponentially and a queue of unlimited capacity and type of FIFO Queue. This is the simplest queuing system.  NS2 supports various distributions like pareto, exponential, constant, unifrom, etc to handle the network dynamics and metrics. So it is very easy to test the given network link to monitor a given queue using any of these queuing models. The listing 3 and 4 are monitoring the link when DropTail queue is used with a capacity of finite and infinite. Listing 13.3 uses infinite capacity and Listing 13.4 uses Finite capacity The output screen shot is shown below the scripts for further understanding
Listing 3 – M/M/1 Queuing Model #new Simulator creation set ns [new Simulator] #trace file creation for capturing the UDP data set tf [open out.tr w] $ns trace-all $tf
#setting the exponential distribution param set lambda 30.0 set mu     33.0
#creation of nodes set n1 [$ns node] set n2 [$ns node] #The queue limit is 1Lakh as the capacity is infin…

Simple C Program

/* This program is written by T S Pradeep Kumar on 28th Sep 2010
This is to display Hello World to the display unit
*/
#include <stdio.h> //including the standard IO functions like printf(), scanf()
int main()
{
printf(“Hello World \n”);
return 0;
}
  1. stdio.h is the library which contains the printf(), scanf() and other standard IO functions, so before we use any function we need to include in our C program. Most of the compilers will take stdio.h automatically, even if we dont include in our program
  2. int main() {} is the main function
  3. printf(“Hello World\n”); printf() is the function which is printing to the display unit and it is displaying Hello World. Whatever is there inside the double quotes will displayed as it is in the monitor except the format specifiers or format codes (%d, %f, %c)
  4. return 0; is the final statement which returns the integer value 0 (this is just to make the compiler happy)
Here in the above program, you can see there are semi colons ;
Every C statement must end with a semicolon. If a statement is not completed, then there need not be a semicolon.

 T S Pradeep Kumar

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