Average Packet End to End Delay Calculation

 

Suppose we run a simulation ,and obtain a trace file. We have to compute the average values of delay. Let’s define delay as the duration since a packet enters a queue of a beginning node until it it arrives at the ending node. The definition of beginning and ending nodes depends on the type of delay under consideration as follows:

Average delay is computed by :

 E(delay)= summation of all delay samples/ no. of samples

where a delay sample is delay associated with a packet. 

The key to collect delay sample is to record packet arrival time in an associative array variable, namely t_arr whose index is the packet unique ID. 

When a new packet enters a queue of a beginning node, the associated time is recorded in a variable $t_arr[pid], where pid is the packet unique ID. 

When a packet with the same unique ID arrives at an ending node, the delay is computed as “(current time) - $t_arr[pid]”. 

The delay same is accumulated in the variable $total_delay, and the number of samles is incremented by one.

At the end of the program, the average delay is computed and stored in a variable avg_delay.

A sample execution of the AWK script is shown below:

============ awk for delay =========

BEGIN {

fromNode=2; toNode=3;

num_samples = 0;

total_delay = 0;

}

/^\+/&&$3==fromNode&&$4==toNode {

t_arr[$12] = $2;

};

/^r/&&$3==fromNode&&$4==toNode {

if (t_arr[$12] > 0) {

num_samples++;

delay = $2 - t_arr[$12];

total_delay += delay;

};

};

END{

avg_delay = total_delay/num_samples;

print "Average queuing transmission delay is " avg_delay " seconds";

print "Measurement details:";

print " - Start when packets enter the node " fromNode;

print " - Until the packets arrive the node " toNode;

};

============ abbfile.awk =========

BEGIN {

src="0.0"; dst="3.0";

num_samples = 0;

total_delay = 0;

}

/^\+/&&$9==src&&$10==dst {

t_arr[$12] = $2;

};

/^r/&&$9==src&&$10==dst{

if (t_arr[$12] > 0) {

num_samples++;

delay = $2 - t_arr[$12];

total_delay += delay;

};

};

END{

avg_delay = total_delay/num_samples;

print "Average end-to-end transmission delay is " avg_delay " seconds";

print "Measurement details:";

print " - Since packets are created from the address " src;

print " - Until the packets are destroyed at the address " dst;

};

Enjoy. Happy Coding.