How to Calculate Network Application Response Time in NS2

To calculate the Network Application Response Time in the Network Simulator 2 (NS2), it denotes the time which takes for a request to be sent from a client to a server and for the server to react back to the client with a replies. The important metrics in applications are web browsing, database access and any client server model in which the prompt responses are essential for a good user experience.

It can be calculated by estimating the time variation amongst the request being sent from the client and the response being obtained at the client after the server processing. Use the given computational guide to implement this in the ns2 simulator:

Key Components of Application Response Time:

  1. Request Transmission Time: The time it takes for the request to reach the server from the client.
  2. Server Processing Time: The time it takes for the server to process the request and produce a response.
  3. Response Transmission Time: The time it takes for the reaction to reach the client from the server.
  4. Application Response Time: The total of these works.

Formula:

Application Response Time=Time of Response Reception−Time of Request Sent\text{Application Response Time} = \text{Time of Response Reception} – \text{Time of Request Sent}Application Response Time=Time of Response Reception−Time of Request Sent

Steps to Calculate Application Response Time in NS2:

  1. Set Up a Client-Server Simulation in NS2:

Simulate a client-server interaction by setting up two nodes: one indicating the client and the other denoting the server. A TCP connection can be used to mimic the request-response communication, where the client sends a request, and the server processes it and delivers back a response.

Example TCL Script for a Client-Server Simulation:

# Create the simulator

set ns [new Simulator]

# Create two nodes: client and server

set client [$ns node]

set server [$ns node]

# Create a duplex link between client and server (1 Mbps bandwidth, 10ms delay)

$ns duplex-link $client $server 1Mb 10ms DropTail

# Attach TCP agents to nodes for request-response communication

set tcp0 [new Agent/TCP]

set sink [new Agent/TCPSink]

$ns attach-agent $client $tcp0

$ns attach-agent $server $sink

$ns connect $tcp0 $sink

# Create FTP application to simulate client-server interaction

set ftp [new Application/FTP]

$ftp attach-agent $tcp0

# Start and stop FTP (to simulate request and response)

$ns at 1.0 “$ftp start”  ;# Request sent at 1.0 second

$ns at 5.0 “$ftp stop”   ;# Stop after 5 seconds (response received)

# Enable tracing to capture request-response events

set tracefile [open out.tr w]

$ns trace-all $tracefile

# End simulation after 6 seconds

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

$ns at 6.0 “finish”

  1. Trace File Overview:

The trace file (out.tr) produced by NS2 will contain events for both the request transmission and response reception. These events can be assessed to measure the Application Response Time.

Example Trace File Entries:

s 1.000000000 _0_ AGT  — 1000 ftp 0 0.0 1.0 1.0

r 1.010000000 _1_ AGT  — 1000 ftp 0 0.0 1.0 1.0

s 5.000000000 _1_ AGT  — 1000 ftp 0 0.0 2.0 2.0

r 5.010000000 _0_ AGT  — 1000 ftp 0 0.0 2.0 2.0

In this sample:

  • s: Sent packet (the request or response).
  • r: Received packet (the request or response).
  • 0 and 1: Node IDs (client _0_, server _1_).
  • 1.000000000: Time when the request was sent.
  • 5.010000000: Time when the response was received.
  1. Calculate Application Response Time:

In the trace file, the Application Response Time can be estimated by discovering the time difference amongst the request being sent from the client and the response being acquired by the client.

AWK Script to Calculate Application Response Time:

BEGIN {

request_time = 0;

response_time = 0;

}

# Record the time the request was sent from the client (_0_)

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

request_time = $2;  # Store the request sent time

}

# Record the time the response was received by the client (_0_)

$1 == “r” && $4 == “_0_” && $7 == “ftp” {

response_time = $2;  # Store the response reception time

}

END {

if (request_time > 0 && response_time > 0) {

app_response_time = response_time – request_time;

print “Application Response Time: ” app_response_time ” seconds”;

} else {

print “No complete request-response pair found!”;

}

}

This script:

  • Keep record of when the request is sent from the client and when the response is received by the client.
  • Computes the Application Response Time as the difference amidst these two events.
  1. Running the AWK Script:

Store the AWK script as app_response_time.awk, and execute it on the trace file designed by NS2:

awk -f app_response_time.awk out.tr

  1. Interpreting the Results:

The script will result the Application Response Time for the simulated client-server interaction.

Example output:

Application Response Time: 4.010000 seconds

This signifies that it took 4.01 seconds for the client to get a response after sending the request, which contains the transmission time, processing time, and return transmission time.

  1. Conclusion:

To calculate Application Response Time in NS2:

  1. Configure a client-server simulation using TCP connections to model request-response interactions.
  2. Enable tracing to capture the request sent and response received events.
  3. Assess the trace file using an AWK script to measure the time difference between when the request is sent and when the response is received.
  4. The outcome is the Application Response Time, which reflects the overall latency in the client-server interaction.

From this approach, we can thoroughly know how to calculate the network Application Response Time using ns2 tool and understands the concept behinds the client’s request and the server’s response for that. If you have any doubts about this computation, we will help you out of it.

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