To simulate Bellman-Ford Routing within NS2, we require utilizing a Distance Vector Routing (DVR) protocol, as Bellman-Ford is the fundamental algorithm used by DVR. The Bellman-Ford algorithm computes the shortest path by iterating via all the nodes within the network and if a shorter path is discovered then updating the distance to the terminus.
The simulation platform NS2 supports Distance Vector Routing (such as RIP) by default, and we can replicate Bellman-Ford routing by leveraging this functionality. Below is a basic approach on how to simulate Bellman-Ford Routing projects in NS2:
Steps to Simulate Bellman-Ford Routing in NS2
- Install NS2
Make sure that NS2 is installed on the machine. If we haven’t installed it then we can download it from the NS2 Official Website and install it.
- Create the TCL Script for Bellman-Ford Simulation
We will make a network topology and configure nodes to communicate utilizing a Distance Vector Routing protocol (which internally uses Bellman-Ford). The TCL script describes the network topology, then sets up the routing protocol, and configures traffic flows.
Example TCL Script for Bellman-Ford Simulation:
# Create a simulator instance
set ns [new Simulator]
# Define a trace file and nam file for analysis and visualization
set tracefile [open “bellmanford_trace.tr” w]
set namfile [open “bellmanford_simulation.nam” w]
$ns trace-all $tracefile
$ns namtrace-all $namfile
# Create network nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
# Create duplex links between the nodes (bandwidth and delay)
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
$ns duplex-link $n2 $n3 1Mb 10ms DropTail
$ns duplex-link $n3 $n4 1Mb 10ms DropTail
$ns duplex-link $n0 $n3 1Mb 20ms DropTail
# Set up Distance Vector Routing (which uses Bellman-Ford)
for {set i 0} {$i < 5} {incr i} {
$ns at 0.0 “$n$i start-dv-routing”
}
# Create a UDP agent and attach it to node 0 (source)
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
# Create a traffic generator (CBR) for the UDP agent
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 1Mb
$cbr0 attach-agent $udp0
# Attach a UDP sink to the destination node (n4)
set udp1 [new Agent/UDP]
$ns attach-agent $n4 $udp1
# Connect the source and the destination
$ns connect $udp0 $udp1
# Schedule the traffic to start and stop
$ns at 1.0 “$cbr0 start”
$ns at 4.5 “$cbr0 stop”
# Set up the finish procedure
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exit 0
}
# Schedule the end of the simulation
$ns at 5.0 “finish”
# Run the simulation
$ns run
- Run the Simulation
Here, we can save the above script as bellmanford_simulation.tcl, and then run it in NS2:
ns bellmanford_simulation.tcl
- Visualize the Simulation with NAM
We need to open the .nam file made by the simulation in NAM to envision the network topology and how packets are forwarded based on the Bellman-Ford algorithm:
nam bellmanford_simulation.nam
- Analyze the Trace File
The trace file (bellmanford_trace.tr) includes the details of packet exchanges, routing decisions, and protocol behaviour. We can investigate this file to learn:
- Packet delivery ratio.
- End-to-end delay.
- Routing table updates (distance vector updates).
- Performance metrics such as throughput and routing efficiency.
- Modify the Topology
- We can insert more nodes and links to maximize the complexity of the topology.
- Alter link delays and bandwidths to experiment how Bellman-Ford adapts to diverse network conditions.
- Replicate link failures by disabling a link after a particular time to check how Bellman-Ford reroutes the traffic.
Optional Enhancements:
- Route Updates: We can print out the routing table updates at distinct time intervals to monitor how the Bellman-Ford algorithm recalculates the distances when new data is received.
- Comparison: Relate the Bellman-Ford’s performance with other routing algorithms, like Link-State Routing (which uses Dijkstra’s algorithm).
- Packet Loss and Link Failures: Replicate packet loss and link failures to experiment the Bellman-Ford’s robustness.
Through this given technique, we had successfully illustrated the Bellman Ford Routing projects, which was simulated and examined with the help of NS2 tool. These projects focused on how to calculate the shortest path by iterating through all the nodes in the network by using Bellman-Ford algorithm. We can ready to provide additional information of this project over another simulation manual.
To effectively simulate Bellman-Ford routing projects using the NS2 tool, we are prepared to provide you with comprehensive guidance. Please share all relevant details of your project, and we will assist you in achieving optimal results. Additionally, you can receive expert advice on Distance Vector Routing, including protocols like RIP, for your projects.
