How to Calculate Network Maximum Deadline in NS2

To calculate the maximum deadline in ns2 is defined to the maximum allowable time within that the specific actions must be done like packet delivery or event completion. This idea is usually used in real-time networks like real-time multimedia applications, sensor networks, or vehicular networks in which the packets or events must be processed before a particular deadline to meet Quality of Service (QoS) requirements. The below are the procedures to compute the network maximum deadline in ns2:

Steps to Calculate Network Maximum Deadline in NS2

To compute the maximum deadline for a network, we generally requied to:

  1. Define the deadline (i.e., the maximum time permitted for a packet or event to reach its destination).
  2. Measure the time taken for each packet to travel from the source to the destination.
  3. Compare the actual transmission times with the clear deadline to regulate if packets encounter the deadline.
  4. Determine the maximum transmission time (or worst-case delay), that delivers an indication of the maximum network deadline the system can manage without missing the deadline.

Key Metrics for Deadline Evaluation:

  • End-to-End Delay: The time it takes for a packet to travel from the source to the destination.
  • Maximum Delay: The longest time any packet takes to extent its destination.
  • Deadline Misses: The number of packets that exceed the specified deadline.
  1. Set Up the NS2 Simulation:

Initially we want to configure an NS2 simulation in which packets are routed from a source node to a destination node. We can then state a deadline (e.g., 100 ms) and validate whether packets are delivered within this time.

Example TCL Script for Data Transmission:

# Create the simulator

set ns [new Simulator]

# Create two nodes: source and destination

set node_(0) [$ns node]

set node_(1) [$ns node]

# Create a duplex link between the nodes (1 Mbps bandwidth, 10ms delay)

$ns duplex-link $node_(0) $node_(1) 1Mb 10ms DropTail

# Attach UDP agents to nodes for sending and receiving data

set udp0 [new Agent/UDP]

set sink [new Agent/Null]

$ns attach-agent $node_(0) $udp0

$ns attach-agent $node_(1) $sink

$ns connect $udp0 $sink

# Set up CBR traffic on the UDP agent

set cbr0 [new Application/Traffic/CBR]

$cbr0 attach-agent $udp0

$cbr0 set packetSize_ 512        ;# Packet size in bytes

$cbr0 set rate_ 1Mb              ;# Transmission rate

# Start and stop the traffic

$ns at 1.0 “$cbr0 start”

$ns at 10.0 “$cbr0 stop”

# Enable tracing to capture packet transmission and reception

set tracefile [open out.tr w]

$ns trace-all $tracefile

# End simulation at time 12 seconds

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# End simulation at 12 seconds

$ns at 12.0 “finish”

In this simulation:

  • Packets are routed from node 0 to node 1 over a 1 Mbps link with a 10 ms delay.
  • We will estimate the time it takes for each packet to travel from node 0 to node 1, and compare it to a predefined maximum deadline (e.g., 100 ms).
  1. Trace File Analysis for Deadline Calculation:

Once the simulation is done, the trace file (out.tr) will log packet transmission and reception events. We can utilize the send (s) and receive (r) events to compute the end-to-end delay for each packet and validates if the deadline is encountered.

Example Trace File Entries:

s 2.000000000 _0_ AGT  — 512 cbr 0 0.0 1.0 1.0

r 2.010000000 _1_ AGT  — 512 cbr 0 0.0 1.0 1.0

s 3.000000000 _0_ AGT  — 512 cbr 1 0.0 2.0 2.0

r 3.010000000 _1_ AGT  — 512 cbr 1 0.0 2.0 2.0

  • s: Packet sent event.
  • r: Packet received event.
  • _0_ and _1_: Node IDs (source node _0_, destination node _1_).
  • 2.000000000: Time of the event in seconds.

Estimate the end-to-end delay, subtract the time when the packet was sent (s) from the time when it was received (r).

  1. Define a Maximum Deadline:

For this instance, let’s assume the maximum deadline for each packet is 100 ms (0.1 seconds). Any packet with an end-to-end delay greater than 100 ms will be deliberated to have missed the deadline.

  1. AWK Script to Calculate Maximum Delay and Deadline Misses:

We can use an AWK script to estimate the end-to-end delay for each packet and validates whether it go beyond the predefined deadline.

AWK Script to Calculate Maximum Delay:

BEGIN {

max_delay = 0;

missed_deadlines = 0;

deadline = 0.1;  # Maximum deadline in seconds (100 ms)

}

# Record the send time of each packet

$1 == “s” && $4 == “_0_” && $7 == “cbr” {

packet_time[$10] = $2;  # Store the send time indexed by packet ID

}

# Calculate the end-to-end delay when the packet is received

$1 == “r” && $4 == “_1_” && $7 == “cbr” {

delay = $2 – packet_time[$10];  # End-to-end delay

if (delay > max_delay) {

max_delay = delay;  # Update maximum delay

}

if (delay > deadline) {

missed_deadlines++;

print “Packet ” $10 ” missed the deadline. Delay: ” delay ” seconds”;

}

}

END {

print “Maximum Delay: ” max_delay ” seconds”;

print “Packets that missed the deadline: ” missed_deadlines;

}

  1. Running the AWK Script:

Save the AWK script as deadline.awk, and then executed it on the trace file created by NS2:

awk -f deadline.awk out.tr

The script will output:

  • The maximum end-to-end delay (which can be deliberated the maximum network deadline that can be supported without missing any deadlines).
  • The number of packets that missed the deadline.
  1. Interpreting Results:
  • Maximum Delay: This value denotes the worst-case delay in the network. we can give this as the maximum network deadline for real-time applications that the network can support.
  • Missed Deadlines: This shows you how many packets exceeded the predefined deadline (in this case, 100 ms). If many packets miss the deadline, the network can be inappropriate for applications with strict timing necessities.
  1. Conclusion:

To compute the maximum deadline in NS2:

  1. Set up the simulation with data transmission among nodes.
  2. Enable packet tracing to capture send and receive events.
  3. Analyze the trace file using AWK scripts to compute the end-to-end delay for each packet.
  4. Compare delays to the predefined deadline to classify packets that missed the deadline.
  5. Determine the maximum delay, that can be measured the network’s maximum supported deadline for real-time applications.

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