How to Calculate Network Recovery in NS2
To calculate Network recovery in NS2 has denotes to the process of evaluating how the network returns to normal performance after a failure, like a link or node going miserable and later being restored. Recovery has includes not only rerouting traffic however it also measuring how rapidly and efficiently the network resumes its pre-failure performance levels.
To estimate network recovery in NS2, we will concentrate on parameters like recovery time, throughput restoration, packet loss, and the recovery of delay and jitter in the network. Below is a detailed guide on how to simulate and calculate network recovery in NS2:
Step-by-Step Implementation:
- Define Network Recovery Metrics
When measuring network recovery, we will concentrate on several key parameters:
- Recovery time: The time it takes for the network to fully recover after the failure is resolved that is when a failed link or node is restored.
- Throughput restoration: How rapidly the network restores the normal data rate subsequently a failure is repaired.
- Packet loss during recovery: The number of packets lost in the course of the recovery process.
- Delay and jitter recovery: Time taken to restore normal packet delivery delay and variations in delay (jitter).
- Set up the Simulation in NS2
To replicate network recovery, we need to generate a scenario where:
- A failure happens like a link or node going down.
- The network fails over to a backup route.
- The failed link or node is restored, and the network recovers.
Here’s a sample of an NS2 simulation script in which a link failure happens, and the link is restored after a period:
# Create NS2 simulator instance
set ns [new Simulator]
# Open trace file for output
set tracefile [open out.tr w]
$ns trace-all $tracefile
# Define nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
# Create links (two paths: n0-n1-n2 and n0-n3-n2)
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
$ns duplex-link $n0 $n3 1Mb 10ms DropTail
$ns duplex-link $n3 $n2 1Mb 10ms DropTail
# Set up traffic (UDP traffic from n0 to n2)
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
set null0 [new Agent/Null]
$ns attach-agent $n2 $null0
$ns connect $udp0 $null0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0
# Schedule traffic start and stop
$ns at 0.5 “$cbr0 start”
$ns at 4.5 “$cbr0 stop”
# Introduce a link failure at 2.0 seconds and recovery at 3.5 seconds
$ns at 2.0 “$ns rtmodel-at 2.0 down $n0 $n1”
$ns at 3.5 “$ns rtmodel-at 3.5 up $n0 $n1”
# End simulation
$ns at 5.0 “finish”
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exit 0
}
# Run simulation
$ns run
In this example:
- The link among n0 and n1 goes down at 2.0 seconds, causing a failover.
- The link is restored at 3.5 seconds, initially recovery process.
- Capture Data from the Trace File
NS2 will create a trace file (out.tr) that logs network events such as packet enqueueing, dequeueing, transmission, and drops. We can measure this trace file to evaluate network activities in the course of and after the recovery process.
Key events to analyse:
- Packet transmission (-): Point toward successful transmission.
- Packet drop (d): Indicates packets lost for the period of the failure or recovery process.
- Queue events (+, -): Reflect the status of network queues before and after the recovery.
- Analyse Network Recovery Metrics
Recovery Time
The recovery time is the interval among the restoration of the failed link or node and the point at that normal traffic flow resumes. This can be estimated as the time among the restoration of the failed link (or node) and when traffic resumes over that link.
Here’s an AWK script to calculate the recovery time:
awk ‘
{
if ($1 == “d” && $3 == “0” && $4 == “1”) { # Detect when packets start dropping on failed link
failure_time = $2;
}
if ($1 == “-” && $3 == “0” && $4 == “1” && $2 >= 3.5) { # Detect when packets are successfully transmitted after recovery
recovery_time = $2;
if (failure_time != “”) {
net_recovery_time = recovery_time – failure_time;
print “Network Recovery Time:”, net_recovery_time, “seconds”;
exit;
}
}
}’ out.tr
This script:
- Identifies the time when the link recovers.
- Identifies when traffic successfully resumes on the restored link.
- Estimate the recovery time as the difference among these events.
Throughput Restoration
To estimate throughput restoration, we can evaluate throughput before, for the period of, and after the recovery. Throughput is estimated by summing up the number of successfully transferred packets over time.
Here’s an AWK script to estimate throughput before and after the recovery event:
awk ‘
{
if ($1 == “-” && $3 == “0” && $4 == “1” && $2 < 2.0) { # Before failure
packets_before++;
}
if ($1 == “-” && $3 == “0” && $4 == “1” && $2 >= 3.5) { # After recovery
packets_after++;
}
}
END {
print “Throughput Before Failure:”, packets_before / 2.0, “packets/sec”;
print “Throughput After Recovery:”, packets_after / (5.0 – 3.5), “packets/sec”;
}’ out.tr
Packet Loss During Recovery
To compute packet loss during recovery, we can sum the number of packet drop (d) events in the trace file for the duration of the recovery period.
Here’s an AWK script to summing up the number of dropped packets for the duration of recovery:
awk ‘
{
if ($1 == “d” && $3 == “0” && $4 == “1” && $2 >= 2.0 && $2 <= 3.5) { # During recovery period
packet_drops++;
}
}
END { print “Packet Loss During Recovery:”, packet_drops }’ out.tr
Delay and Jitter Recovery
We can evaluate delay as the difference among when a packet is sent and when it is received. To estimate the average delay and jitter (variations in delay), so we would require to monitor the sending and receiving times of each packet.
Here’s a basic AWK script to estimate average packet delay:
awk ‘
{
if ($1 == “+”) {
send_time[$7] = $2; # Record packet send time
}
if ($1 == “-” && $3 == “0” && $4 == “1”) {
if (send_time[$7] != “”) {
delay = $2 – send_time[$7]; # Calculate delay
total_delay += delay;
count++;
}
}
}
END { print “Average Delay:”, total_delay / count, “seconds” }’ out.tr
For jitter, we cab estimate the difference in delay among following packets and take the average:
awk ‘
{
if ($1 == “+”) {
send_time[$7] = $2; # Record packet send time
}
if ($1 == “-” && $3 == “0” && $4 == “1”) {
if (send_time[$7] != “”) {
delay = $2 – send_time[$7]; # Calculate delay
if (prev_delay != “”) {
jitter_sum += (delay – prev_delay > 0) ? delay – prev_delay : prev_delay – delay;
}
prev_delay = delay;
count++;
}
}
}
END { print “Average Jitter:”, jitter_sum / (count – 1), “seconds” }’ out.tr
- Post-Process and Visualize the Results
Once we have estimated recovery parameters like recovery time, throughput, packet loss, delay, and jitter, we can use tools such as Python or Excel to envision the outcomes.
Example Python Plot for Throughput Restoration:
import matplotlib.pyplot as plt
# Example throughput data
time = [1.0, 2.0, 3.0, 4.0, 5.0]
throughput = [1000, 500, 0, 1000, 1000] # Example data showing throughput drop and recovery
plt.plot(time, throughput, marker=’o’)
plt.title(‘Throughput Before and After Recovery’)
plt.xlabel(‘Time (seconds)’)
plt.ylabel(‘Throughput (packets/sec)’)
plt.grid(True)
plt.show()
Summary
To calculate network recovery in NS2:
- Simulate a failure and recovery: configure a simulation in which a link or node fails and is later restored.
- Capture trace data: Use the trace file to track packet transmissions, drops, and queue events in course of the recovery process.
- Calculate recovery metrics: utilize AWK scripts to estimate recovery time, throughput restoration, packet loss, and delay/jitter recovery.
- Visualize the results: Utilize Python or Excel to plot the recovery performance.
In this replication, we had obviously understood the computation procedures, sample snippets were given to implement the Network recovery with the help of ns2 tool. We also deliver further significant information regarding the Network recovery will be provided.
Contact ns2prject.com to learn more about your Network Recovery in NS2 tool. We’re here to provide you with innovative project ideas and topics. If you need help assessing your network performance, just share your parameter details with us, and we’ll be glad to assist you!