To simulate the RPL (Routing Protocol for Low-Power and Lossy Networks) within NS2, which needs a few customization, as NS2 simulator doesn’t have native support for RPL such as it does for some other routing protocols (such as AODV, DSR, or DSDV). RPL protocol is generally used in IoT environments and it is specifically matched for networks with limited power, memory, and computational resources. To replicate RPL in NS2, we will require to either change NS2 to support RPL (using external modules) or utilize other simulators such as Cooja (part of Contiki OS) or NS3 that natively support RPL.
But, if we are set on using NS2 then here is a method to simulate RPL-like behavior by simulating its key aspects that containing DODAG (Destination Oriented Directed Acyclic Graph) construction, Rank, and Objective Function.
Steps to Simulate RPL-like Protocol in NS2
- Install NS2:
- Make sure that NS2 is appropriately installed on the system. We can download NS2 from NS2 official site or use a package manager if we are on Linux.
- Define the Network Topology:
- RPL normally operates within IoT-like networks with sensor nodes are communicating via a DODAG. Initially, we describe a basic network topology to mimic the routing process.
Example of a Simple Network Topology:
# Create a simulator object
set ns [new Simulator]
# Define nodes (IoT sensors)
set n0 [$ns node] ;# Root node (sink)
set n1 [$ns node] ;# Sensor node 1
set n2 [$ns node] ;# Sensor node 2
set n3 [$ns node] ;# Sensor node 3
set n4 [$ns node] ;# Sensor node 4
# Define links between the nodes
$ns duplex-link $n1 $n0 5Mb 10ms DropTail
$ns duplex-link $n2 $n1 5Mb 10ms DropTail
$ns duplex-link $n3 $n1 5Mb 10ms DropTail
$ns duplex-link $n4 $n2 5Mb 10ms DropTail
- Simulate DODAG Construction (RPL Feature):
- In RPL, nodes are form a DODAG (Destination Oriented Directed Acyclic Graph) rooted at a particular node that frequently called the sink or root node. The root shows the DODAG formation by propagating DIO (DODAG Information Object) messages, and other nodes join the DODAG according their rank.
Example: Simulating DODAG Formation
proc rpl_dodag_init {root_node} {
puts “Node $root_node initiating DODAG formation”
# Broadcast DIO message
broadcast_dio $root_node
}
proc broadcast_dio {node} {
puts “Node $node broadcasting DIO message to neighbors”
# Propagate DIO message to neighboring nodes
}
proc join_dodag {node parent} {
puts “Node $node joining DODAG with parent $parent”
# Join the DODAG based on parent node and rank
}
# Simulate DODAG formation starting from the root (n0)
$ns at 1.0 “rpl_dodag_init n0”
- Implement Rank and Objective Function (RPL Feature):
- RPL utilizes the concept of Rank to show the node’s location relative to the root in the DODAG. Each node computes its rank rely on an Objective Function (e.g., link quality, hop count, energy). The nodes choose the parent with the lowest rank.
Example: Simulating Rank Calculation
proc calculate_rank {node parent_rank} {
set rank [expr $parent_rank + 1] ;# Example: Rank increases by 1 for each hop
puts “Node $node has rank $rank”
return $rank
}
proc select_parent {node} {
puts “Node $node selecting the best parent based on rank”
# Select the parent with the lowest rank
}
# Simulate rank calculation for nodes joining the DODAG
$ns at 2.0 “join_dodag n1 n0”
$ns at 2.5 “join_dodag n2 n1”
- Simulate Traffic Flow:
- When the DODAG is built then we replicate traffic among the nodes. For RPL, the traffic normally flows upwards toward the root node (the sink), however we can also have downward traffic if required.
Example: Setting up Traffic Flow
# Create UDP agents for sensor data transmission
set udp1 [new Agent/UDP]
set udp2 [new Agent/UDP]
# Attach agents to nodes
$ns attach-agent $n3 $udp1
$ns attach-agent $n0 [new Agent/Null]
# Set up a CBR (Constant Bit Rate) traffic flow from node 3 to the sink (n0)
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 512
$cbr set interval_ 0.5
$cbr attach-agent $udp1
# Connect node 3 to sink (n0)
$ns connect $udp1 $null0
# Start the traffic at time 3.0s
$ns at 3.0 “$cbr start”
- Simulate Control Message Exchange (DIO, DAO, DIS):
- In RPL, nodes interchange control messages like DIO (for DODAG construction), DAO (Destination Advertisement Object) for downward routes, and DIS (DODAG Information Solicitation) once nodes request information from the root. These can be replicated with custom procedures.
Example: Simulating DAO Messages
proc send_dao {node parent} {
puts “Node $node sending DAO message to parent $parent”
# Simulate DAO message exchange to set up downward routes
}
# Simulate DAO transmission after DODAG formation
$ns at 4.0 “send_dao n4 n2”
- Run the Simulation:
- Set the simulation time and then we run the simulation.
Example: Running the Simulation
# Simulation will stop at 100 seconds
$ns at 100.0 “finish”
proc finish {} {
global ns
$ns flush-trace
puts “Simulation finished.”
exit 0
}
# Run the simulation
$ns run
- Trace and Analyze Results:
- When the simulation is finish then we can examine the trace file for parameters like routing efficiency, network traffic flow, and power consumption.
Example: Enabling Tracing
set tracefile [open rpl_simulation.tr w]
$ns trace-all $tracefile
We can then investigate the trace file to collect statistics like:
-
- Packet Delivery Ratio (PDR): How many packets successfully reach the root node (sink).
- End-to-End Delay: How long it takes for packets to attain the destination.
- Control Overhead: Amount of control messages exchanged (DIO, DAO, DIS).
- Energy Consumption (if energy model is implemented): Power consumed by each node for the period of the simulation.
Advanced RPL Simulation Ideas
- Energy Model:
- Execute an energy model for each node to replicate power consumption and monitor how the network performs under energy constraints.
- Mobility:
- Insert mobility to the nodes to learn how RPL manages dynamic topologies. It is specifically helpful for mobile IoT devices or sensor networks used in dynamic environments.
- Traffic Variations:
- Replicate distinct kinds of traffic patterns (e.g., periodic, event-driven, bursty) and monitor how RPL adjusts to changing traffic loads.
- Node Failures and Repairs:
- Mimic node or link failures and observe how the network heals itself by rebuilding the DODAG.
Example: Simulating Node Failure
# Simulate node 2 failure at 30 seconds
$ns at 30.0 “$ns rtmodel-at 30.0 down $n2 $n1”
- Multicast Traffic:
- RPL supports multicast routing. Replicate multicast data transmission and compute how the protocol manages it.
Metrics for RPL Performance Evaluation
- Packet Delivery Ratio (PDR): The ratio of the amount of packets effectively delivered to the destination.
- End-to-End Delay: The time taken for a packet to pass through from the source to the destination.
- Control Message Overhead: The amount of control packets (DIO, DAO, and DIS) exchanged for the period of the simulation.
- Energy Consumption: Assess the energy usage at each node and overall network lifetime.
- Convergence Time: The time it takes for the DODAG to become stable after network variations.
Using NS2, we performed comprehensive simulation steps with advanced concepts and metrics for RPL protocol projects to simulated and evaluated. We are equipped to extend the analysis with more informations as needed.
At phdprime.com, we are committed to being your reliable partner in achieving complete success. Our expertise in RPL Protocol Projects simulation using the ns2 tool is specifically designed to support your research needs. We specialize in various routing protocols, including AODV, DSR, and DSDV, ensuring you receive the best insights from our dedicated team.
