How to Implement ECMP Routing in NS2

To implement the Equal-Cost Multi-Path (ECMP) routing in Network Simulator 2 (NS2), we have to simulate several paths with equal costs amongst nodes and allocate traffic over those routes. Since the Ns2 doesn’t support ECMP, we have to achieve this by manually setting up numerous equal-cost routes and using multiple flows to replicate traffic splitting through those paths. Through this manual, you can implement the ECMP routing in ns2:

Steps to Implement ECMP Routing in NS2:

  1. Install and Set Up NS2

Make certain that you have installed the NS2 and check if its properly configured.

  1. Modify Tcl Script for ECMP Routing

We have to manually state the multiple equal-cost routes among the source and destination nodes to implement the ECMP in NS2. Start by configuring the numerous paths and balancing traffic over them.

Example Tcl Script for ECMP Routing:

# Create a new NS2 simulator instance

set ns [new Simulator]

# Create trace and NAM files for output

set tracefile [open “ecmp_trace.tr” w]

$ns trace-all $tracefile

set namfile [open “ecmp.nam” w]

$ns namtrace-all $namfile

# Define the network topology with 4 nodes

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

# Create duplex links between nodes with equal costs (bandwidth and delay)

$ns duplex-link $n0 $n1 1Mb 10ms DropTail

$ns duplex-link $n0 $n2 1Mb 10ms DropTail

$ns duplex-link $n1 $n3 1Mb 10ms DropTail

$ns duplex-link $n2 $n3 1Mb 10ms DropTail

# Enable static routing

$ns rtproto Manual

# Manually configure multiple equal-cost routes from n0 to n3

# Route 1: n0 -> n1 -> n3

$ns manual-route $n0 $n3 $n1 $n3

# Route 2: n0 -> n2 -> n3

$ns manual-route $n0 $n3 $n2 $n3

# Attach TCP agents to n0 and TCPSink agents to n3

set tcp0 [new Agent/TCP]

$ns attach-agent $n0 $tcp0

set sink [new Agent/TCPSink]

$ns attach-agent $n3 $sink

# Connect the agents

$ns connect $tcp0 $sink

# Create a CBR (Constant Bit Rate) traffic source

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $tcp0

$cbr set packetSize_ 512

$cbr set interval_ 0.05

# Start the CBR traffic at time 1.0 and stop at time 4.5

$ns at 1.0 “$cbr start”

$ns at 4.5 “$cbr stop”

# Define the end of the simulation at 5.0 seconds

$ns at 5.0 “finish”

# Procedure to finish the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam ecmp.nam &

exit 0

}

# Run the simulation

$ns run

  1. Key Components of the ECMP Tcl Script:
  • Static Routing (Manual): We restrict adaptive routing protocols and allow static routing using the $ns rtproto Manual command. This permits you to manually determine routing paths amongst nodes.
  • Equal-Cost Routes: We build two equal-cost routes from node n0 to node n3:
    • Route 1: n0 → n1 → n3
    • Route 2: n0 → n2 → n3
  • Traffic Generation: A TCP agent is included to n0, and a TCPSink agent is added to n3. A CBR (Constant Bit Rate) application is used to create traffic.
  • Traffic Splitting (Simulating ECMP): Although NS2 does not systematically split traffic over multiple paths; you can replicate ECMP by delivering multiple flows or modifying the script to substitute packet forwarding across the routes manually.
  1. Run the Simulation

You can execute the simulation with the given command, after the script is ready:

ns ecmp_simulation.tcl

This will produce a trace file (ecmp_trace.tr) and a NAM visualization file (ecmp.nam).

  1. Analyze the Results

Use the NAM (Network Animator) file to visualize the network topology and traffic:

nam ecmp.nam

In the NAM visualizer, you should monitor traffic being forwarded sideways both routes (via n1 and n2) from n0 to n3, replicating ECMP-like actions.

  1. Balancing Traffic Manually

To better simulate traffic splitting through multiple equal-cost paths, you can manually develop multiple flows or other packet forwarding amidst paths. Here are some techniques:

  • Create multiple CBR flows: Generate various CBR traffic sources and include them to different routes.
  • Use round-robin forwarding: Alternate the packet forwarding amongst paths by fine-tuning the source code.

For example, you could set up two CBR traffic sources, each sending traffic along a various path:

# Create two CBR traffic sources and alternate between paths

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $tcp0

set cbr2 [new Application/Traffic/CBR]

$cbr2 attach-agent $tcp0

# Route cbr1 via n1, and cbr2 via n2

$ns at 1.0 “$cbr1 start”

$ns at 2.5 “$cbr2 start”

Conclusion:

  • In NS2, ECMP routing can be simulated by manually stating multiple equal-cost routes between nodes and allocating traffic through these routes.
  • You can manually divide traffic across the existed routes by building multiple traffic flows or implementing a custom forwarding techniques.
  • While NS2 does not natively support automatic traffic splitting like ECMP, manual configuration offers a way to simulate these actions.

In this step-by-step procedure, we had completely delivered the instructions with samples snippets to implement the ECMP Routing using NS2 by manually defining the stating routing due to ns2 lacks the native support for ECMP. You can optimize the simulation by referring the evaluation’s outcomes. Reach out to ns2project.com for top-notch implementation advice on ECMP Routing in NS2. We offer exceptional project guidance tailored just for you.