View source for Ns-3-Network-Simulator/C2/Network-performance-Analysis/English


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|| '''Visual Cue'''
|| '''Narration'''
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|| '''Slide:1'''

'''Welcome'''
|| Welcome to the spoken tutorial on '''Analyzing network performance in ns-3.'''
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'''Learning Outcomes'''
|| In this tutorial, we will learn to
* Use trace sources
* Create callback functions
* Connect trace sources to callback functions and
* Calculate network parameters using trace sources

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'''System Requirements'''
|| To record this tutorial, I am using
* '''Ubuntu''' '''Linux Operating system version''' '''22.04'''
* '''ns-3.38'''
* '''NetAnim '''visualizer tool

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'''Prerequisite'''

[https://spoken-tutorial.org/ https://spoken-tutorial.org]
|| To follow this tutorial,
* You must have basic knowledge of using Linux terminal

* You must know how to create  '''point-to-point '''network in '''ns-3'''
* For pre-requisite Linux and '''ns-3''' tutorials, please visit this website

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'''Code files'''
||
* The files used in this tutorial are provided in the '''Code files''' link
* Please download and extract the files
* Make a copy and then use them while practicing

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|| Show diagram''':'''

'''Point-to-Point network with two nodes'''
|| For this tutorial, we would be creating the following topology:
* A '''point-to-point''' network with address 10.1.1.0

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|| Open the file '''network_performance.cc '''in the text editor.
|| I have created the source file '''network_performance.cc''' for this program.

Now we will go through the source code in the text editor.

The source code contains the required functions to analyse network performance.
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|| Highlight '''double node0_trans_time'''
|| First we declare the variables.

These variables shall hold the network parameters.

'''node0_trans_time''' holds the transmission time for node 0.
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|| Highlight '''node1_rec_time'''
|| '''node1_rec_time '''holds the packet receiving time for node 1.
|- 
|| Highlight '''node0_rec_time'''
|| '''Node0_rec_time ''' is the time at which node 0 receives the echo packet from node 1.
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|| Highlight '''round_trip_time <nowiki>= 0.0</nowiki>'''
|| '''round_trip_time ''' holds the round-trip packet time.

That is, the time taken to go from node 0 to node 1 and return.
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|| Highlight '''total_delay = 0.0'''
|| '''total_delay ''' holds the sum of all delays.
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|| Highlight '''prop_delay = 6560.0'''
|| '''prop_delay ''' is the propagation delay of the channel.

It is set by us.
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|| Highlight '''throughput = 0.0'''
|| '''throughput '''holds the throughput of the network.

It is the rate of packet delivery.
|- 
|| Highlight '''trans_delay = 0.0'''
|| '''trans_delay '''holds''' '''the transmission delay of a packet.
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|| Highlight '''RxTraceClient(std::string context, Ptr<const Packet> p)'''
|| '''RxTraceClient '''is a '''callback function'''.

It is executed whenever the client receives a packet.

The first argument is the traced source.

We shall explain trace sources later in this tutorial.

Here the traced source is '''Rx'''.

The second argument is the packet received.
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|| Highlight '''node0_rec_time = Simulator::Now().GetSeconds()'''
|| In the function, we will update the value of '''node0_rec_time '''variable.

Here, we set the value of the current time.

The current time is found using the '''GetSeconds ''' method.
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|| Highlight''' round_trip_time'''
|| Similarly, we update the value of the '''round_trip_time '''variable.

We set it to the sum of transmission and reception time of packets.

These values are represented by '''node0_trans_time''' and '''node0_rec_time'''.

The '''node0_trans_time '''variable would be updated in the '''TxTraceClient '''function.
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|| Highlight '''round_cnt++'''
|| Next, we increment the value of the '''round_cnt''' variable by 1.

We do so, to keep a track of the number of round-trips.
|- 
|| Highlight '''TxTraceClient'''
|| '''TxTraceClient '''is a callback function.

It is executed whenever the client sends a packet.

The first argument is the traced source.

The second argument is the receive packet.
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|| Highlight '''node0_trans_time'''
|| In the function, we set the value of '''node0_trans_time.'''

The value is the time at which transmission starts.
|- 
|| Highlight '''RxTraceServer'''
|| The last callback function is '''RxTraceServer.'''

It is executed when the server node receives a packet.

The first argument is the traced source.

The second argument is the received packet.
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|| Highlight '''node1_rec_time = Simulator::Now().GetSeconds()'''
|| Here we set the receiving time to the current time in seconds.

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|| Highlight '''total_delay += (node1_rec_time - node0_trans_time)*1000'''
|| Then, we set the '''total_delay''' variable, which stores the total delay.

It is computed as the difference between two variables.

The first is the packet reception time of the server.

The second is the packet transmission time of the client.

The value is multiplied by 1000 to get the unit in milliseconds.
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|| Highlight '''trans_delay += ((node1_rec_time - node0_trans_time)*1000 - prop_delay/1000000)'''
|| Next, we compute the value of '''transmission delay'''.

We get it by subtracting the value of propagation delay from '''total delay'''.

The propagation delay value is in nanoseconds, hence we divide it by 1000000.

This converts it to milliseconds.
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|| Highlight '''pkt_cnt++'''
|| Next we increment the packet count.
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|| Highlight '''if (pkt_cnt == pkts)'''
|| Finally we compare the value of packet count to the total packets.

We do this to know when the last packet is received.

If this is the last packet, we print all the parameters.
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|| Highlight '''NS_LOG_UNCOND'''
|| Using the '''NS_LOG_UNCOND '''function, we print the parameters to the terminal.

We print the parameters:
* End-to-end delay
* Transmission delay
* Throughput
* Propagation delay (constant)

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|| Highlight '''total_delay/(p->GetSize()*pkts'''
|| '''Throughput '''is calculated as total delay divided by total data size.
|- 
|| Highlight '''nodes.Create(2)'''
|| Let’s move to the main function now.

For the topology, we create a '''point-to-point''' network with two nodes.
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|| Highlight '''SetDeviceAttribute'''
|| The '''data rate''' for the device is 100 Mbps.
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|| Highlight '''SetChannelAttribute'''
|| The '''propagation delay''' is set to 6560 nanoseconds.
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|| Highlight '''address.SetBase("10.1.1.0", "255.255.255.0")'''
|| The base address of the network is 10.1.1.0.
|- 
|| Highlight '''UdpEchoServerHelper echoServer(9)'''
|| Next we create a UDP echo server with port address 9.
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|| Highlight '''echoServer.Install(nodes.Get(1))'''
|| The echo server application is installed on the second node.

The index of the node is 1.
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|| Highlight '''serverApps.Start(Seconds(1.0))'''
|| Here we set the start time of the server applications to 1 second.

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|| Highlight '''serverApps.Stop(Seconds(10.0))'''
|| Similarly, we set the stop time to 10 seconds.

Both the times are from the start of the simulation.
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|| Highlight '''echoClient(interfaces.GetAddress(1), 9)'''
|| Then we create an echo client application with destination port 9.
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|| Highlight '''SetAttribute'''
|| Using the '''SetAttribute '''method we set the following attributes for the client.
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|| Highlight '''MaxPackets'''
|| The maximum number of packets is 10.
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|| Highlight '''Interval'''
|| The time interval between packet transmissions is 0.5 seconds.
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|| Highlight '''PacketSize'''
|| The packet size is 1024 bytes.
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|| Highlight '''echoClient.Install(nodes.Get(0))'''
|| The echo client application is installed on the first node.

The index of the node is 0.
|- 
|| Highlight '''clientApps.Start(Seconds(2.0))'''
|| The start time of the client apps is set to 2 seconds.
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|| Highlight '''clientApps.Stop(Seconds(10.0))'''
|| The stop time is 10 seconds.
|- 
|| Highlight '''Config::Connect'''
|| Using the connect method, we connect trace sources to callback functions.

These functions are also known as trace sinks.

A callback function is passed as an argument to another function. 

These are used in conjunction with trace sources.

'''Trace sources ''' are entities that signal events in an ns-3 program.

These events include packet transmission, change in window size etc.
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|| Highlight '''UdpEchoClient/Tx'''
|| This program uses three trace sources.

The first is the '''Tx''' trace source, of the '''UdpEchoClient '''class.

It traces the transmission of a packet by an echo client application.
|- 
|| Highlight '''UdpEchoClient/Rx'''
|| The second trace source is '''Rx''', of the '''UdpEchoClient '''class.

It traces the reception of a packet by an echo client application.
|- 
|| Highlight '''UdpEchoServer/Rx'''
|| The last trace source is '''Rx ''', of the '''UdpEchoServer '''class.

It traces the reception of a packet by an echo server application.
|- 
|| Highlight '''AnimationInterface anim ("network_performance.xml");'''

|| Next we create an '''AnimationInterface '''object, '''anim''', for '''NetAnim''' animation.

The parameter for the constructor is the name of the XML animation file.

It will be generated by the program after the simulation.

Here the name of the file is '''network_performance.xml'''.
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|| Highlight '''anim.SetConstantPosition'''
|| Then set the positions for the nodes using the '''SetConstantPosition ''' function. 
|- 
|| Highlight '''Simulator::Run()'''
|| The '''Run '''function is used to run the simulation.
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|| Highlight '''Simulator::Destroy()'''
|| The '''Destroy ''' function ends the simulation.

Close the text editor.
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|| Press Ctrl, Alt and T keys simultaneously.

Type '''cd ns-allinone-3.38/ns-3.38 '''to navigate to the ns3 installation directory

Type '''mv ~/Downloads/network_performance.cc scratch/network_performance.cc '''to move the source file to '''scratch '''directory.
|| Now we will observe the simulation. 

Open a terminal by pressing Ctrl, Alt and T keys simultaneously.

Using the '''cd '''command, navigate to the installation directory of '''ns-3'''.

Go to the '''ns-3.38''' directory.

Move your source file to the '''scratch ''' directory within the '''ns-3.38''' directory. 
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|| Type ./'''ns3 run scratch/network_performance.cc'''
|| Run the command '''dot forward slash ns3 run space scratch forward slash network '''underscore performance dot cc'''

'''network underscore performance '''is the name of the source file. 
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|| Keep the terminal open and show the output of the command 
|| After compilation, we get the network parameters. 

The parameters are
* '''End-to-end delay'''
* '''Transmission delay'''
* '''Throughput '''and
* '''Round trip time'''

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|| Type '''cd ~/ns-allinone-3.38/netanim'''
|| Now, to visualise the network, we will use NetAnim. 

Navigate to the '''netanim '''directory under '''ns-allinone-3.38.'''
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|| Type ./'''NetAnim'''
|| Now type '''dot forward slash NetAnim'''. 

The '''NetAnim'''' window will open.
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|| Click on the '''Open XML trace file '''icon on the top left corner of the window.
|| Click on the '''Open XML trace file ''' icon on the top left corner of the window.
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|| In the file picker, navigate to the '''ns-allinone-3.38/ns-3.38 '''directory and select the '''network_performance.xml '''file.
|| In the file picker, navigate to the '''ns-3.38 ''' directory.

Select the '''network_performance.xml ''' file.

The file would be generated by the program.

You can also download the file from '''Code Files''' section.
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|| On the toolbar, click on the '''Node Size '''drop down button, and select size 10.
|| On the toolbar, click on the '''Node Size ''' drop down button.

Select size 10.
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|| On the toolbar, click on the play button
|| On the toolbar, click on the play button to view the simulation.

We see the circles representing the nodes.

The lines with arrows represent the transfer of packets.
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|| Hover over node 0 and node 1 circles.
|| We see the packets moving from node 0 to node 1.
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'''Summary'''
|| This brings us to the end of the tutorial. 

Let us summarise.

In this tutorial, we have learnt to
* Use trace sources
* Create callback functions
* Connect trace sources to callback functions
* Calculate network parameters using trace sources

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'''Assignment'''
|| As an assignment, please do the following:
* Create a '''Point-to-Point '''network with 3 nodes
* Send packets from node 0 to node 2
* Calculate '''throughput ''' and''' transmission delay'''

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'''Assignment - Observation'''
|| In the terminal, you will get this output.

The values may vary depending on the network parameters.

These parameters include packet size, propagation delay and data rate.
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'''About the Spoken Tutorial Project'''
|| The video at the following link summarises the '''Spoken Tutorial project'''.

Please download and watch it.
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'''Spoken Tutorial Workshops''' 
|| The '''Spoken Tutorial Project''' team conducts workshops and gives certificates.

For more details, please write to us.
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'''Answers for THIS Spoken Tutorial'''
||Post your timed queries in this forum.
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'''FOSSEE Forum'''
|| For any general or technical questions on '''ns-3''', visit the''' FOSSEE forum''' and post your question.
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'''Acknowledgement'''
|| '''Spoken Tutorial''' Project was established by the '''Ministry of Education, Government of India'''.
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'''Acknowledgement'''
|| We thank '''Dr.Moyukh Laha''' from '''IIT Kharagpur''' for his domain support.

We would also like to thank '''Dr. R. Radha, Dr. X. Anita, and Dr. T. Subbulakshmi ''' from''' VIT, Chennai '''for their support.
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'''Thank You'''
|| This is''' Josiga, '''a FOSSEE summer fellow 2023, IIT Bombay signing off.


Thanks for joining.
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