How to Implement Global Routing in NS2

To implement the Global Routing in Network Simulator 2 (NS2) which is direct approach, ns2 offers in-built support for global routing mechanisms. Based on the network topology, this routing uses central routing that has routes for every node in the network, permitting to find the best optimal path in ns2.

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In the below, we provide step-by-step guide on how to implement global routing in NS2:

Steps to Implement Global Routing in NS2:

  1. Install and Set Up NS2

Make certain that you have installed and configured the ns2 properly on your computer.

  1. Understanding Global Routing in NS2

By default, NS2 can allow global routing for wired topologies using the rtproto option. Global routing means that each node in the network knows the shortest path to every other node. This can be finished for static or wired networks where routes are predefined based on the topology.

  1. Modify Tcl Script for Global Routing

When you state your network in NS2, you can permit global routing with a simple command in your Tcl script. Follow the sample below of how to set up global routing in a simple wired topology:

Example of Tcl Script Using Global Routing:

# Create a new NS2 simulator instance

set ns [new Simulator]

# Create trace and NAM files

set tracefile [open “globalrouting_trace.tr” w]

$ns trace-all $tracefile

set namfile [open “globalrouting.nam” w]

$ns namtrace-all $namfile

# Define the network topology

# Create network nodes

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

# Create links between nodes

$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 $n0 $n3 1Mb 10ms DropTail

# Enable global static routing

$ns rtproto Static

# Attach a TCP agent to node n0 and a sink agent to node 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 traffic source

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $tcp0

$cbr set packetSize_ 500

$cbr set interval_ 0.1

# Schedule events for the traffic

$ns at 0.5 “$cbr start”

$ns at 4.5 “$cbr stop”

# Define the end of the simulation

$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 globalrouting.nam &

exit 0

}

# Run the simulation

$ns run

  1. Key Components of the Global Routing Tcl Script:
  • Simulator Object: The Simulator instance (set ns [new Simulator]) is used to configure the simulation environment.
  • Nodes: Nodes (n0, n1, n2, and n3) are generated using $ns node. These indicate the network components.
  • Links: Duplex links are stated amongst the nodes using $ns duplex-link $n0 $n1 1Mb 10ms DropTail, stating bandwidth, delay, and queuing discipline.
  • Global Routing: The command $ns rtproto Static allows global static routing, making sure that routing tables are estimated depends on the entire network topology.
  • Traffic Generation: A TCP agent is included to node n0 and a sink agent to node n3. A CBR (Constant Bit Rate) application creates traffic amongst them.
  • Simulation Termination: The simulation executes for 5 seconds, after which the technique finish flushes traces, closes files, and presents NAM (Network Animator) to visualize the simulation.
  1. Run the Simulation

After the script is ready, run the simulation with the given command in the terminal:

ns globalrouting_simulation.tcl

This will produce a trace file (globalrouting_trace.tr) and a NAM visualization file (globalrouting.nam).

  1. Analyze Results

You can evaluate the trace files and visualize the network in NAM:

nam globalrouting.nam

NAM will show the topology and envision how packets are routed amongst the nodes using the global routing table.

  1. Global Routing Behavior

With global routing enforced, NS2 computes and configures routing tables for all nodes at the starting of the simulation. Each node will have the shortest path to every other node according to the topology.

You can alter the topology or traffic patterns to monitor how global routing impacts the routing activities in various network configurations.

  1. Simulating Dynamic Topologies

If you want to simulate dynamic alterations in the network topology (for instance: link failures or new links being included), global routing may not automatically update its routes. In that case, you would need to either activate manual route recalculation or find dynamic routing protocols include OSPF or AODV.

In conclusion, we were provide the details on how to setup basic simulation, network topology and implement central routing for the execution of Global Routing in the Network simulation called ns2 including examples with codes.