Queuing Models in NS2

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…

How to Write Makefile

Assume there are more number of source files to be compiled using a set of commands everytime is a tedious process. So there is a facility to compile everything at a stretch is by the use of a Makefile.
The makefile can be named as either “Makefile” or “makefile”.
Let me define four files for my simple application, create a new directory and store all the files given below
  • main.c  (which contains the main program)
  • sum.c (summing function is defined)
  • hello.c (print hello world)
  • function.h (function prototypes are declared)
int sum(int,int);
void print_hello();
#include “function.h”
void print_hello()
printf(“Hello World \n”);
#include “function.h”
int sum(int a, int b)
int c;
return c;
#include “function.h”
int main()
int a=10,b=20,c;
printf(“The sum of two numbers is %d “,c);
return 0;
There are different methods of compiling this file
Method 1: (gcc command based)
gcc main.c sum.c hello.c –o pradeep
once you execute the above command, an executable named pradeep is created and you can see the output by typing./pradeep
Method 2: using Makefile

The basic makefile is composed of:
This syntax applied to example would look like:
target: dependencies
[tab] system command
gcc main.c sum.c hello.c –o pradeep
to run this make file(the file name should be Makefile or makefile), execute the command
Method 3: using Makefile with dependencies
There may be a chance of using different targets in your makefile, this is because if you modify a single file in your project, you don’t have to recompile everything, only what you modified.
Here is an example
all: pradeep
hello: main.o sum.o hello.o
gcc main.o sum.o hello.o -o hello

main.o: main.c
gcc –c main.c

sum.o: sum.c
gcc –c sum.c

hello.o: hello.c
gcc –c hello.c

Method 4: using variables
CFLAGS=-c -Wall

all: hello
hello: main.o sum.o hello.o
$(CC) main.o sum.o hello.o -o hello

main.o: main.c
$(CC) $(CFLAGS) main.c

sum.o: sum.c
$(CC) $(CFLAGS) sum.c

hello.o: hello.c
$(CC) $(CFLAGS) hello.c

Method 5:
With this brief introduction to Makefiles, you can create some very sophisticated mechanism for compiling your projects.
CFLAGS=-c -Wall
SOURCES=main.c hello.c sum.c

$(CC) $(LDFLAGS) $(OBJECTS) -o $@

$(CC) $(CFLAGS) $< -o $@

If you understand this last example, you could adapt it to your own personal projects changing only 2 lines, no matter how many additional files you have !!!.
The above examples is tested only on linux and Windows also supports make utility (through nmake utility), the readers are advised to work on their own in Windows. the following link will show you the way to nmake utility

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