To simulate Software Defined Networking (SDN) projects in NS2 has needs to alteration of the existing networking design to isolate the control plane that makes decisions about routing and forwarding from the data plane that forwards the actual data. In SDN, a centralized controller handles the network and makes routing decisions, since the switches and routers manage the actual data forwarding according to the controller’s instructions.
Since NS2 does not directly support SDN, it is possible to replicate SDN-like behaviour by adjusting the control logic or using custom scripts and extensions. There are some community-developed SDN patches for NS2 that enable the simulation of SDN components.
Here is an approach to simulate the Software Defined Networking in ns2
Key Components for Simulating SDN in NS2:
- SDN Controller: The central entity that makes network routing decisions.
- OpenFlow Switches/Routers: Network nodes (switches or routers) that forward data packets according to the instructions from the controller.
- Control Messages: Communication among the controller and switches (i.e., flow setup, policy enforcement).
- Traffic Flows: Data traffic among hosts, with flow rules dynamically set by the SDN controller.
Steps to Simulate SDN in NS2
- Install NS2: Make sure NS2 is installed on the system. we can install it using the following command:
sudo apt-get install ns2
Validate the installation:
ns -version
- Extend NS2 for SDN Capabilities: While NS2 does not directly support SDN concepts, there are a few ways to replicate SDN behavior:
- Custom Scripting: We can execute an SDN controller in Tcl or C++ by controlling the routing decisions dynamically.
- Community-Contributed SDN Patches: Utilize any available SDN patches or frameworks built on NS2.
- Manually Implementing Centralized Control: we can replicate centralized control over routing decisions by modifying routing techniques and injecting control messages dynamically.
- Basic SDN Simulation Using Custom Tcl Script: Below is an instance Tcl script that replicate an SDN-like behavior in which a centralized controller dynamically configure routes among switches according to traffic flow.
Example Tcl Script for Simulating SDN-Like Behavior in NS2
# Create a new simulator object
set ns [new Simulator]
# Open trace and NAM files for output
set tracefile [open sdn_out.tr w]
$ns trace-all $tracefile
set namfile [open sdn_out.nam w]
$ns namtrace-all $namfile
# Define nodes in the network (SDN switches and controller)
set sdn_controller [$ns node] ;# Centralized SDN controller
set switch_1 [$ns node] ;# Switch 1
set switch_2 [$ns node] ;# Switch 2
set switch_3 [$ns node] ;# Switch 3
set host_A [$ns node] ;# Host A (connected to Switch 1)
set host_B [$ns node] ;# Host B (connected to Switch 3)
# Define links between switches, controller, and hosts
$ns duplex-link $sdn_controller $switch_1 100Mb 10ms DropTail
$ns duplex-link $sdn_controller $switch_2 100Mb 10ms DropTail
$ns duplex-link $sdn_controller $switch_3 100Mb 10ms DropTail
$ns duplex-link $switch_1 $host_A 10Mb 5ms DropTail
$ns duplex-link $switch_3 $host_B 10Mb 5ms DropTail
$ns duplex-link $switch_1 $switch_2 10Mb 10ms DropTail
$ns duplex-link $switch_2 $switch_3 10Mb 10ms DropTail
# Define TCP traffic from Host A to Host B (dynamic routing via SDN controller)
set tcp [new Agent/TCP]
$ns attach-agent $host_A $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $host_B $sink
$ns connect $tcp $sink
# Create an FTP application to generate traffic on top of TCP
set ftp [new Application/FTP]
$ftp attach-agent $tcp
# Schedule FTP traffic to start at 1 second
$ns at 1.0 “$ftp start”
$ns at 5.0 “$ftp stop”
# Function to simulate the SDN controller dynamically setting up routes
proc setup_sdn_route {controller switch_1 switch_2 switch_3 host_A host_B} {
global ns
puts “Setting up SDN route dynamically”
# Here the SDN controller would send control messages to the switches
# Simulate this with print messages for now
puts “Controller: Configuring path from Host A to Host B via switches”
# Set up the route dynamically based on SDN controller decision
$ns rtmodel-at 1.5 “route-setup $switch_1 $switch_2 $switch_3”
# Direct packets between the host and destination via the chosen path
$ns at 1.6 “$switch_1 route-to $switch_2”
$ns at 1.7 “$switch_2 route-to $switch_3”
}
# Call the SDN controller’s route setup function
$ns at 1.0 “setup_sdn_route $sdn_controller $switch_1 $switch_2 $switch_3 $host_A $host_B”
# Define finish procedure to close trace files and run NAM
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam sdn_out.nam &
exit 0
}
# Schedule the simulation to end at 10 seconds
$ns at 10.0 “finish”
# Run the simulation
$ns run
Explanation of the Tcl Script:
- Simulator Object:
- The line set ns [new Simulator] initializes the NS2 simulation object.
- SDN Controller and Switches:
- The SDN controller (sdn_controller) perform as a centralized control entity, while the switches (switch_1, switch_2, switch_3) forward packets allowing to the controller’s instructions.
- Traffic Flows:
- TCP traffic is created from Host A (connected to switch_1) to Host B (connected to switch_3) over dynamically set routes.
- The FTP application simulates a file transfer between the hosts.
- Dynamic Route Setup (SDN Controller):
- The setup_sdn_route procedure replicate an SDN controller enthusiastically configure paths among switches. Here, it transmit routing instructions to the switches to forward traffic among Host A and Host B.
- Simulation End:
- The simulation terminates at 10 seconds, and the finish procedure closes files and introduces NAM for visualization.
- Running the Simulation:
Save the script as sdn_simulation.tcl and execute it using NS2:
ns sdn_simulation.tcl
After the simulation completes, open NAM to visualize the network:
nam sdn_out.nam
- Analysing the Results:
- The trace file (sdn_out.tr) contains comprehensive logs of packet transmissions, receptions, and the SDN controller’s route decisions. We need to measure the trace file for parameters like:
- Throughput
- Latency
- Packet Delivery Ratio
- Flow setup delay (time taken for the SDN controller to set up the route)
- Example AWK script to estimate throughput:
BEGIN {
packet_count = 0;
start_time = 0;
end_time = 0;
}
{
if ($1 == “r” && $4 == “AGT”) {
packet_count++;
if (start_time == 0) {
start_time = $2;
}
end_time = $2;
}
}
END {
duration = end_time – start_time;
throughput = (packet_count * 512 * 8) / (duration * 1000); # kbps
printf(“Throughput: %.2f kbps\n”, throughput);
}
Extending the Simulation:
- Implementing OpenFlow Behavior:
- Adjust the routing algorithm to replicate OpenFlow-like behavior in which flow rules are enthusiastically installed in switches in terms of the controller’s instructions.
- Realistic Network Topology:
- Replicate a more complex SDN topology with multiple switches, hosts, and controller failover.
- Traffic Engineering:
- Apply traffic engineering approaches in which the controller dynamically adapts routes in terms of network congestion, flow priorities, or available bandwidth.
- Security Policies:
- Execute security policies like access control or firewall rules implemented by the SDN controller.
- Controller Failover:
- Replicate controller redundancy and failover mechanisms, in which a secondary controller takes over in case of a controller failure.
In this code snippet we clearly explain how to run the scenario for software defined network in ns2 including the detailed simulation procedure, installation setup and their explanation related to software defined network that helps you to simulate the process. We plan to deliver more information related to software defined network.
The team at phdprime.com provides further information on SDN projects, so please share all of your information with us, and we will assist you in achieving the finest simulation results. We can complete your comparison analysis and provide you with the finest option.
