How to Implement SDN in ns2

To implement the Software-Defined Networking (SDN) in ns2 has several steps and basically it is a network architecture that decouples the control plane from the data plane that permits for centralized management of the network via a software-based controller. Executing the SDN in ns2 is difficult because ns2 was not originally considered with SDN in mind. Since, we can approximate an SDN-like environment in ns2 by emulated the centralized control and dynamic network reconfiguration. The following are the procedures to implement the SDN in ns2:

Step-by-Step Implementation:

Step 1: Understand the Limitations

In the NS2 lacks built-in support for SDN controllers, OpenFlow, or similar protocols. Hence, simulating SDN in ns2 needs a approximating SDN features, such as:

  1. Centralized Controller: We can simulate a controller by using a script or a node that generates routing decisions dynamically.
  2. Dynamic Routing: execute the dynamic changes to routing tables based on predefined conditions or inputs from the “controller.”
  3. Flow Management: To mimic flow-based routing by controlling packet forwarding decisions.

Step 2: Create the Tcl Script

The given below is a simple Tcl script that emulates an SDN-like environment by dynamically controlling routing decisions from a centralized “controller.”

Example Tcl Script for Simulating SDN in ns2

# Create a simulator object

set ns [new Simulator]

# Define the network topology

set n0 [$ns node]  # Source node

set n1 [$ns node]  # Intermediate node 1

set n2 [$ns node]  # Intermediate node 2

set n3 [$ns node]  # Destination node

# Create links between nodes (representing data plane connections)

$ns duplex-link $n0 $n1 10Mb 10ms DropTail

$ns duplex-link $n1 $n2 10Mb 10ms DropTail

$ns duplex-link $n2 $n3 10Mb 10ms DropTail

# Create a centralized controller (simulated as a script)

proc sdn_controller {} {

global ns n0 n1 n2 n3

# Initially set up routing via n1 to n2 to n3

$ns rtproto Static

$n0 add-route-to $n3 0 $n1 0

$n1 add-route-to $n3 0 $n2 0

# Simulate a condition to change the route dynamically

# For example, after 5 seconds, route traffic directly from n0 to n2 to n3

$ns at 5.0 “dynamic_route_change”

}

# Define a procedure to dynamically change the route

proc dynamic_route_change {} {

global ns n0 n1 n2 n3

# Clear the old route

$n0 delete-route-to $n3

# Add a new route directly from n0 to n2 to n3

$n0 add-route-to $n3 0 $n2 0

}

# Define agents and traffic

set tcp [new Agent/TCP]

$ns attach-agent $n0 $tcp

set sink [new Agent/TCPSink]

$ns attach-agent $n3 $sink

$ns connect $tcp $sink

set ftp [new Application/FTP]

$ftp attach-agent $tcp

$ftp start

# Schedule the SDN controller to start

$ns at 0.1 “sdn_controller”

# Define a finish procedure to end the simulation

proc finish {} {

global ns

$ns halt

exit 0

}

# Schedule the end of the simulation

$ns at 10.0 “finish”

# Run the simulation

$ns run

Step 3: Run the Tcl Script

Save the script with a .tcl extension, like sdn_simulation.tcl. Run the script using the following command in terminal:

ns sdn_simulation.tcl

Step 4: Analyse the Simulation

This script emulates a basic SDN-like environment in which the routing decisions are dynamically handled by a centralized “controller.” The controller adjusts the routing paths during the simulation to reflect a dynamic response to network conditions.

Script Explanation

  • Centralized Controller: The sdn_controller procedure emulates an SDN controller that starts sets up static routes and then enthusiastically changes them based on a condition.
  • Dynamic Routing: The dynamic_route_change procedure is called after 5 seconds to variation the routing path that implements the characteristics of an SDN controller reconfiguring the network.
  • Flow Management: Even though this sample uses simple routing changes, we could expand it to handle the flows more precisely by controlling packet forwarding based on flow identifiers.

Customization

  • More Complex Topologies: Extend the network topology to contain the more nodes and links that emulate a more complex SDN-managed network.
  • Advanced Routing Policies: Execute more sophisticated routing policies in the controller, like load balancing or QoS-based routing.
  • Flow Table Simulation: Mimic the flow tables at each node by enthusiastically updating routing entries based on incoming flows.
  • Failure Handling: Replicate the link or node failures and demonstrate how the SDN controller retransmits the traffic in response.

Limitations

  • Simplified SDN Model: This script delivers a simplified and abstracted model of SDN. It does not fully capture the complexity of real SDN systems, like OpenFlow, or the communication among control and data planes.
  • No True SDN Protocols: This replication does not contains SDN-specific protocol such as OpenFlow. As an alternative, it uses simple routing table manipulations.
  • Limited Scalability: The script is intended for small-scale simulations and it involve important adaptation for more complex or larger-scale SDN environments.

In this page, we know how to execute and validate the outcomes for Software-Defined Networking by using the ns2 tool that effectively manages the network performances. We will plan to extend the information how the Software-Defined Networking performs in other simulation tool.

For support with implementation, please reach out to us at ns2project.com. We provide guidance in network analysis for your Satellite Communication project utilizing ns2tool, ensuring the sharing of optimal results. Our team comprises leading experts in the SDN platform.