To simulate flow-based routing projects using NS2, we require concentrating on the routing mechanisms, which take into account the flow of traffic among the source and destination nodes. Flow-based routing protocols normally enhance the paths for each flow to attain targets such as load balancing, reducing congestion, or enhancing Quality of Service (QoS).
Here is how we can simulate a flow-based routing project within NS2 that utilizing a simple scenario in which the routing decisions are impacted by flow characteristics like bandwidth or delay.
Steps to Simulate Flow-Based Routing in NS2
- Install NS2
Make sure NS2 is installed on the machine. If we haven’t installed it, then we download it from the NS2 Official Website and follow the installation steps.
- Create a TCL Script for Flow-Based Routing
This script will configure a network with nodes, which replicate several traffic flows among diverse pairs of nodes. The routing protocol can be set to handle the traffic flows according to the metrics such as delay, bandwidth, or traffic load.
Example TCL Script for Flow-Based Routing Simulation:
# Create a new simulator object
set ns [new Simulator]
# Define trace and NAM files for analysis and visualization
set tracefile [open “flow_based_routing_trace.tr” w]
set namfile [open “flow_based_routing_simulation.nam” w]
$ns trace-all $tracefile
$ns namtrace-all $namfile
# Create network topology with nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
# Create links with different bandwidths and delays to simulate flow costs
$ns duplex-link $n0 $n1 2Mb 10ms DropTail ;# Link between n0 and n1
$ns duplex-link $n1 $n2 1Mb 20ms DropTail ;# Link between n1 and n2
$ns duplex-link $n2 $n3 1Mb 15ms DropTail ;# Link between n2 and n3
$ns duplex-link $n3 $n4 2Mb 10ms DropTail ;# Link between n3 and n4
$ns duplex-link $n0 $n2 1Mb 30ms DropTail ;# Alternative path: n0 to n2
$ns duplex-link $n1 $n3 1Mb 25ms DropTail ;# Alternative path: n1 to n3
# Enable flow-based routing (by default, routing considers shortest path but flow-based algorithms can be introduced)
for {set i 0} {$i < 5} {incr i} {
$ns at 0.0 “$n$i start-flow-routing”
}
# Define UDP agents for flows between different nodes
set udp0 [new Agent/UDP]
set udp1 [new Agent/UDP]
# Attach the UDP agents to source nodes
$ns attach-agent $n0 $udp0
$ns attach-agent $n1 $udp1
# Define CBR traffic generators for the flows
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 1Mb
$cbr0 attach-agent $udp0
set cbr1 [new Application/Traffic/CBR]
$cbr1 set packetSize_ 512
$cbr1 set rate_ 1Mb
$cbr1 attach-agent $udp1
# Attach UDP sink agents to destination nodes
set udp2 [new Agent/UDP]
set udp3 [new Agent/UDP]
$ns attach-agent $n3 $udp2
$ns attach-agent $n4 $udp3
# Connect source and destination for the flows
$ns connect $udp0 $udp2
$ns connect $udp1 $udp3
# Schedule the traffic flows
$ns at 1.0 “$cbr0 start”
$ns at 1.5 “$cbr1 start”
$ns at 4.5 “$cbr0 stop”
$ns at 4.8 “$cbr1 stop”
# Set up the finish procedure
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exit 0
}
# End the simulation at 5.0 seconds
$ns at 5.0 “finish”
# Run the simulation
$ns run
- Run the Simulation
We can save this script as flow_based_routing_simulation.tcl and then run it using NS2 with the below command:
ns flow_based_routing_simulation.tcl
- Visualize the Simulation Using NAM
We can open the NAM file made by the simulation to envision the network topology and the flow of traffic:
nam flow_based_routing_simulation.nam
- Analyze the Trace File
The trace file (flow_based_routing_trace.tr) will encompass details regarding the packet flows and routing decisions. We can examine:
- Which routes were selected for each flow.
- End-to-end delay for each flow.
- Packet delivery ratio and throughput for each flow.
- Modify the Simulation
- Flow Characteristics: Modify the bandwidth or delay of the links to replicate diverse routing behaviours relies on flow costs.
- More Flows: Insert more traffic flows among distinct nodes to mimic a more complex flow-based routing situation.
- Routing Protocol: Alter the routing protocol to launch flow-aware routing decisions, which enhance according to the current traffic loads or delay.
Optional Enhancements:
- QoS-Based Routing: Replicate routing that enhances rely on Quality of Service (QoS) parameters such as delay, jitter, and packet loss.
- Flow Congestion Control: Launch flow-based congestion control mechanisms, which reroute traffic when a certain link becomes congested.
In this entire simulation method, you can obtain the simulation and execution process regarding the Flow Based Routing offered in it using NS2 platform. We will ready to share the more information on this subject in another manual.
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