How to Implement on Switching Protocols in NS2

To implement switching protocols in Network Simulator 2 (NS2) has several steps and it is difficult task in the reason of NS2 is mainly intended for network-layer (Layer 3) simulations, like routing protocols, and it doesn’t natively support Layer 2 (data link layer) protocols such as VLANs, STP (Spanning Tree Protocol), or MAC address learning, that are essential to switching. Nevertheless, we can mimic some simple switching behaviour or work around these issues in NS2 by focusing on the following contexts:

Step-by-Step Implementation:

Simulating a Basic Switch Behavior

Since NS2 does not directly support switching protocols that can mimic a simplified version of a switch by physically handling the packet forwarding according to MAC addresses, using static configurations. This technique will not fully mimic a real switch’s dynamic learning and STP operations, but it can design a simple packet forwarding behavior.

Using NS3 for Layer 2 Protocols

NS3 is the successor to NS2 which deliver the better support for Layer 2 protocol. If simulating Layer 2 protocols like VLANs, STP, or Ethernet switching is needed, consider using NS3.

Step-by-Step Guide to Simulating Basic Switching Behavior in NS2

Step 1: Set Up NS2

Make sure that NS2 is installed on the system.

Step 2: Create a Simple Network Topology

We can mimic a basic network in which the nodes are interconnected in a star topology, with one node acting as a switch that forwards packets among other nodes.

Create a New Tcl Script: Open a text editor and create a new file, for instance, simple_switching.tcl.
Set Up the Simulation Environment: Describe the simulator, configure the network topology, and setup the simple forwarding logic.

# Create a simulator object

set ns [new Simulator]

# Define options for the simulation

set val(chan) Channel/WirelessChannel ;# Channel type

set val(prop) Propagation/TwoRayGround ;# Propagation model

set val(netif) Phy/WirelessPhy ;# Network interface type

set val(mac) Mac/802_11 ;# MAC type

set val(ifq) Queue/DropTail/PriQueue ;# Interface Queue type

set val(ll) LL ;# Link layer type

set val(ant) Antenna/OmniAntenna ;# Antenna type

set val(ifqlen) 50 ;# Max packet in ifq

set val(nn) 5 ;# Number of nodes

set val(stop) 10.0 ;# Simulation time

set val(x) 500 ;# X dimension of topography

set val(y) 500 ;# Y dimension of topography

# Initialize the topology object

set topo [new Topography]

$topo load_flatgrid $val(x) $val(y)

# Create the God object

create-god $val(nn)

# Configure the nodes

$ns node-config -llType $val(ll) \

-macType $val(mac) \

-ifqType $val(ifq) \

-ifqLen $val(ifqlen) \

-antType $val(ant) \

-propType $val(prop) \

-phyType $val(netif) \

-channelType $val(chan) \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace ON \

-movementTrace ON

# Create nodes

for {set i 0} {$i < $val(nn)} {incr i} {

set node_($i) [$ns node]

$node_($i) random-motion 0

}

# Define node positions (optional, just for clarity)

$node_(0) set X_ 250.0; $node_(0) set Y_ 250.0 ;# Switch node

$node_(1) set X_ 150.0; $node_(1) set Y_ 250.0

$node_(2) set X_ 350.0; $node_(2) set Y_ 250.0

$node_(3) set X_ 250.0; $node_(3) set Y_ 150.0

$node_(4) set X_ 250.0; $node_(4) set Y_ 350.0

# Create links to simulate switch-like behavior

$ns duplex-link $node_(0) $node_(1) 1Mb 10ms DropTail

$ns duplex-link $node_(0) $node_(2) 1Mb 10ms DropTail

$ns duplex-link $node_(0) $node_(3) 1Mb 10ms DropTail

$ns duplex-link $node_(0) $node_(4) 1Mb 10ms DropTail

# Setup traffic sources

set udp [new Agent/UDP]

$ns attach-agent $node_(1) $udp

set null [new Agent/Null]

$ns attach-agent $node_(2) $null

$ns connect $udp $null

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set interval_ 0.1

$cbr start

# Setup simulation end

$ns at $val(stop) “stop”

$ns at $val(stop) “$ns nam-end-wireless $val(stop)”

$ns at $val(stop) “exit 0”

proc stop {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

}

# Run the simulation

$ns run

Step 3: Run the Simulation

Save the Tcl script (simple_switching.tcl).
Open a terminal and navigate to the directory in which we saved the Tcl script.
Execute the simulation using the following command:

ns simple_switching.tcl

This command will make trace files and optionally a network animation file (if enabled in script).

Step 4: Analyse the Results

Use trace files and the network animator (NAM) to evaluate the simple switching behaviour, that concentrates on packet forwarding and delivery.

Step 5: Visualize the Results (Optional)

If we have allows the network animator (NAM) in the script, we can visualize the simulation:

nam simple_switching.nam

This will launch the NAM window, in which we can see the network topology and the behaviour of the simulated switch.

Considerations and Limitations

Static Configuration: This technique needs manual setup and doesn’t enthusiastically learn MAC addresses as a real switch would.
No Support for Advanced Layer 2 Protocols: the simulation tool of ns2 can’t mimic the STP, VLANs, or dynamic MAC address learns natively.
NS3 for Advanced Layer 2 Simulation: If we need more accurate Layer 2 simulation like Ethernet switches, STP, VLANs, that deliberate using NS3 that delivers better support for such protocols.

Extending the Implementation

If we need a more realistic switching protocol simulation, consider:

Writing custom C++ code in NS2 to mimic Layer 2 behaviour.
Using NS3 or a dedicated network simulation tool that supports Layer 2 protocols.

The above are the complete step-by-step approach that was undertaken for switching protocols in ns2 simulator. More information will also be provided about how the switching protocols will be performed in other simulation tools.

To achieve optimal Switching Protocols in NS2, we offer guidance along with implementation results. You may contact us for customized services tailored to your needs.