View source for Ns-3-Network-Simulator/C3/Dynamic-Routing-Protocol/English

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|| '''Visual Cue'''
|| '''Narration'''
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|| '''Slide:1'''
|| Welcome to the spoken tutorial on '''Dynamic routing protocols in ns-3'''.
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'''Learning Objectives'''
|| In this tutorial, we will learn to
* Create a multi-path topology
* Schedule down times for links
* Implement '''OSPF''' dynamic routing

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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/'''
|| To follow this tutorial
* You must have basic knowledge of '''Linux ''' and '''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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'''What is OSPF Routing?'''
|| 
* '''Open Shortest Path First (OSPF) ''' is a link state routing protocol
* It determines the shortest path between the source and the destination

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|| Show diagram:

'''Network topology with 6 nodes and four paths'''
|| For this tutorial, we would be creating the following topology:
* The topology consists of 6 nodes
* Node 0 is the client node
* Node 5 is the server node
* There are four paths from client to server
* Each link is '''point-to-point '''connection 

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

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

The source code contains the required functions to implement '''OSPF dynamic routing.'''
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|| Highlight '''Config::SetDefault("ns3::Ipv4GlobalRouting::RespondToInterfaceEvents", BooleanValue(true))'''
|| Using the '''SetDefault ''' method, we first enable dynamic routing.

'''RespondToInterfaceEvents ''' enables the '''ns-3''' program to automatically change routes.
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|| Highlight 

'''NodeContainer p2pNodes'''

'''p2pNodes.Create(6)'''

|| The node container contains 6 nodes.
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|| Highlight''' stack.Install(p2pNodes);'''
|| Let’s install an internet stack on the nodes.
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|| Highlight '''NodeContainer n01, n02, n23, n14, n15, n45;'''
|| Next we create 6 more node containers. 

These containers are for the individual '''point-to-point''' networks.

The node containers are''' n01''', '''n02''', '''n23''',''' n34''', '''n14''',''' n15''' and '''n45'''.
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|| Highlight '''Address.SetBase'''
|| Then we assign base addresses to the '''point-to-point '''networks.
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|| Highlight '''10.1.1.0'''
|| The address of the network between node 0 and node 1 is 10.1.1.0.
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|| Highlight '''10.1.2.0'''
|| The address of the network between node 0 and node 2 is 10.1.2.0.

Similarly, the addresses for other networks are set.
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|| Highlight '''pointToPoint.Install(n01)'''
|| The '''Install''' method installs point-to-point channels on the nodes.

The nodes are node 0 and node 1 here.
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|| Highlight''' NetDeviceContainer nd01'''
|| The '''Install '''method returns an object of '''NetDeviceContainer''' class.

We store it in object nd01.
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|| Highlight''' Address.Assign(nd01)'''
|| The '''Assign '''method assigns '''IP addresses''' to the nodes.

The''' IP addresses''' are based on the network address..
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|| Highlight '''Ipv4InterfaceContainer i01'''
|| The '''Assign '''method returns an '''Ipv4InterfaceContainer''' object.

We store it in object i01.
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|| Highlight '''uint16_t port = 9'''
|| Next, we set the port number to 9.
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|| Highlight '''OnOffHelper onoff'''
|| Then we create '''OnOff applications '''to send packets.
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|| Highlight '''InetSocketAddress(i45.GetAddress(1), port)'''
|| Here we create a '''UDP socket''' on the remote destination node.

The socket is created on port 9 of node 5.

We get the '''IP address''' of node 5 using the i45 object.

The '''GetAddress '''method is used to get the address of the node with index 1.

Please note that the indexing is within the i45 interface.
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|| Highlight '''onoff.SetConstantRate(DataRate("2kbps"))'''
|| Then, we set the properties for the application.

The '''data rate '''is set to 2kbps.
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|| Highlight '''onoff.SetAttribute'''
|| The '''packet size''' is set to 50 bytes.
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|| Highlight '''ApplicationContainer apps = onoff.Install(p2pNodes.Get(0))'''
|| Create an application container.

Then, install the '''OnOff application '''on node 0.

Here the indexing is in the overall network.
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|| Highlight '''apps.Start(Seconds(1.0))'''
|| Set the start time for the apps to 1 second from the start of simulation.
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|| Highlight '''apps.Stop(Seconds(16.0))'''
|| Similarly set the stop time to 16 seconds from the start of simulation.
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|| Highlight '''Ipv4GlobalRoutingHelper '''
|| In order to get the routing tables, we create an '''Ipv4GlobalRoutingHelper '''object.

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|| Highlight '''Create<OutputStreamWrapper>'''
|| Then we create an output stream, with the class '''OutputStreamWrapper.'''

The '''OutputStreamWrapper '''encapsulates an output stream.
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|| Highlight '''global-routing.routes'''
|| The name of the output file is '''global-routing.routes.'''
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|| Highlight '''PrintRoutingTableAllAt'''
|| The '''PrintRoutingTableAllAt '''sets the time at which the routing tables are printed.
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|| Highlight '''Seconds (2)'''
|| We print the tables two times.

One at 2 seconds.
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|| Highlight '''Seconds (12)'''
|| The other at 12 seconds.
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|| Highlight '''routingStream'''
|| The routes are printed to the output stream created earlier.
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|| Only narration
|| We print the tables two times to observe the dynamic selection of routes.

Between the two prints, we shall make the shortest link down.

Then, the next shortest link would be selected dynamically.

In this program, the network between nodes 1 and 5 will be set down.
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|| Highlight '''Ptr<Node> n1 = p2pNodes.Get(1)'''
|| Next we create a pointer to the node whose link would be set down.

In this case, it is node 1.
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|| Highlight '''n1->GetObject<Ipv4>'''
|| Then, we get the '''IPv4 '''class object for the node using the '''GetObject '''method.
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|| Highlight '''ipv4ifIndex1 = 1'''
|| Now we need to select the network that has to be set down.

A single node can be connected to multiple networks.

We need to specify the index of the network.

The network indexes start from 1.

For this tutorial, we are deactivating the link between nodes 0 and 1.

It is the first network for node 1.

Hence, the index is 1 here.
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|| Highlight '''Simulator::Schedule(Seconds(5), &Ipv4::SetDown, ipv41, ipv4ifIndex1)'''
|| Then, we schedule the down time for the network to 5 seconds.

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|| Highlight '''AnimationInterface anim'''
|| Next we create an '''AnimationInterface '''object for '''NetAnim '''animation.
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|| Highlight '''anim.SetConstantPosition'''
|| Then set the positions for the nodes using the '''SetConstantPosition '''function. 
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|| Highlight '''Simulator::Run()'''
|| The '''Run '''function is used to run the simulation
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|| Highlight '''Simulator::Destroy()'''
|| And '''Destroy '''function ends the simulation

Close the text editor.
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|| Press Ctrl,Alt and T keys
Type '''cd ns-allinone-3.38/ns-3.38 '''to navigate to the ns3 installation directory

Type '''mv ~/Downloads/DynamicRouting.cc scratch/DynamicRouting.cc '''

|| Now we will observe the simulation. 

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/DynamicRouting.cc'''
|| Run the command '''dot forward slash''' '''ns3 run space scratch forward slash DynamicRoutingprotocols dot cc.'''

'''DynamicRoutingprotocols dot cc '''is the name of the source file. 
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|| Keep the terminal open and show the output of the command 
|| After compilation, there is no output on the terminal.

We shall observe the routing tables in the routes file created earlier.
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|| Switch to file manager and open the '''ns-3.38 '''directory.

Select the '''global-routing.routes '''file.
|| The routes file is created in the same directory from which we run the simulation.

In this case, it is '''ns-3.38 '''directory.

In the directory, a file with the name '''global-routing.routes '''should appear.
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|| Open the '''global-routing.routes '''file.

Highlight '''Node: 0, Time: +2s'''

|| Open the file by double clicking on it.

In the file for each node, the following details are shown:
* The destination address
* The gateway
* The network mask
* Flags
* Metric
* Use
* Interface

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|| Highlight '''Destination '''and '''Gateway'''.
|| The destination address and the gateway are of interest to us.

These represent the possible paths that the packet can take.
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|| Hover over the table under node 0.
|| As configured earlier, the tables are printed two times.

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|| Highlight '''Time: +2s'''
|| Once at 2 seconds, and the next at 12 seconds.

At 5 seconds, the link between nodes 0 and 1 goes down.
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|| Scroll down and highlight '''Node: 0, Time: +12s'''
|| Hence, at 12 seconds, the routes are different.

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|| Hover over the table under node 0.
|| You may inspect the routing tables to see the difference.
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|| Type '''cd ~/ns-allinone-3.38/netanim '''to navigate to the '''netanim '''directory.
|| Now, to visualize 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 '''DynamicRouting.xml '''file.
|| In the file picker, navigate to the '''ns-3.38 '''directory.

Select the '''DynamicRouting.xml '''file.
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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.
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|| Hover the cursor over node 0.
|| We see the circles representing the nodes.

The packets go from node 0 to node 5, via node 1.
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|| Move the cursor over the link between node 0 and node 1.
|| The lines with arrows represent the transfer of packets.
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|| Move the cursor from node 0 to node 1. 

Then move the cursor from node 1 to node 5.

Move the cursor according to the arrows.
|| The packets go from node 0 to node 5, via node 1.
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|| Hover over the ‘'''Sim time’ '''slider on the toolbar.

Wait for it to cross 5 seconds.
|| After 5 seconds, the link between nodes 0 and 1 gets down.

Before the link was set down, path 0-1-5 was the shortest.

This route goes from nodes 2, 3 and 4.
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|| Hover the cursor over the arrows as they move from node 0 to node 5.

[https://en.wikipedia.org/wiki/Open_Shortest_Path_First https://en.wikipedia.org/wiki/Open_Shortest_Path_First]

|| As we can see, the packets automatically switch to the next available route.

The selection of paths is based on the '''OSPF protoco'''l.

To learn more about OSPF, please refer to this link

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'''Summary'''
|| This brings us to the end of the tutorial. Let us summarize.

In this tutorial, we have learnt to
* Create a multi-path topology
* Schedule down times for links
* Implement '''OSPF dynamic routing'''

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'''Assignment'''
|| As an assignment, please do the following:
* Modify the code for the below criteria.
* Make the link between node 1 and node 4 down at 5 seconds
* Generate an XML file for animation

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'''Assignment - Observation'''
|| In '''NetAnim''', you will observe the change in routes after 5 seconds.

The route from node 0 to node 5 through node 4 gets chosen automatically.
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'''About the Spoken Tutorial Project'''
|| The video at the following link summarizes 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'''
|| Please 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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