To simulate VLAN Trunking Protocol (VTP) in NS2 can be a difficult task because NS2 is mainly modelled for replicating network layer protocols, since VTP performs at the data link layer (Layer 2) and is certain to VLAN management on switches. But, we can design VLAN behaviour and contexts of trunking by replicating network segments that act as such VLANs and executing trunk-like behaviour in switches.
Overview of VTP and VLAN Simulation in NS2:
- VTP (VLAN Trunking Protocol): A Cisco proprietary protocol utilized to handle VLAN configuration via switches. VTP enable switches to distribute VLAN configuration information, minimizing the need to set up VLANs manually on each switch.
- VLAN Simulation: In NS2, we can replicate VLANs by set up virtual networks in which devices on different VLANs are separated from each other, except when they interact over a VLAN trunk.
Steps to Simulate VLAN Trunking Protocol (VTP)-Like Behaviour in NS2
- Install NS2
Make sure that we have NS2 is installed on the system.
- Simulating VLANs in NS2
While NS2 does not directly support Layer 2 VLAN protocols such as VTP, we can replicate VLAN characteristics by isolating nodes into different groups (VLANs) and associating them through “trunk links.” Here’s how we can set up a network that implements VLANs and VTP-like behavior.
- Create a TCL Script for VLAN Simulation
In this instance, we will generate a basic network with multiple VLANs (represented as groups of nodes) and trunk links associating the VLANs. We will replicate the features of VLANs by separating traffic in VLANs and using trunk links to permit communication among them.
Example TCL Script for VLAN Trunking Simulation:
# Create a simulator object
set ns [new Simulator]
# Define trace and NAM files for analysis and visualization
set tracefile [open “vtp_trace.tr” w]
set namfile [open “vtp_simulation.nam” w]
$ns trace-all $tracefile
$ns namtrace-all $namfile
# Create VLANs by grouping nodes
# VLAN 1: Nodes 0, 1, 2
# VLAN 2: Nodes 3, 4, 5
# Trunk link between VLANs
# Create nodes
set n0 [$ns node] ;# VLAN 1
set n1 [$ns node] ;# VLAN 1
set n2 [$ns node] ;# VLAN 1
set n3 [$ns node] ;# VLAN 2
set n4 [$ns node] ;# VLAN 2
set n5 [$ns node] ;# VLAN 2
# Create duplex links for VLAN 1
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
# Create duplex links for VLAN 2
$ns duplex-link $n3 $n4 1Mb 10ms DropTail
$ns duplex-link $n4 $n5 1Mb 10ms DropTail
# Create a trunk link between VLAN 1 and VLAN 2 via a switch (node s0)
set s0 [$ns node] ;# Switch with trunking
$ns duplex-link $n2 $s0 1Mb 10ms DropTail ;# Trunk link from VLAN 1 to switch
$ns duplex-link $n5 $s0 1Mb 10ms DropTail ;# Trunk link from VLAN 2 to switch
# Simulate trunking between VLANs
proc send-vlan-packet {src dst} {
global ns
$ns at 1.0 “$src setdest $dst”
}
# Create UDP agents for sending and receiving traffic
set udp0 [new Agent/UDP]
set udp1 [new Agent/UDP]
# Attach UDP agents to a node in each VLAN
$ns attach-agent $n0 $udp0 ;# Source in VLAN 1
$ns attach-agent $n4 $udp1 ;# Destination in VLAN 2
# Create a CBR (Constant Bit Rate) traffic generator
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 0.5Mb
$cbr0 attach-agent $udp0
# Connect the UDP agents across VLANs through the trunk
$ns connect $udp0 $udp1
# Schedule the traffic flow
$ns at 1.0 “$cbr0 start”
$ns at 4.5 “$cbr0 stop”
# Define the finish procedure
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exit 0
}
# End the simulation after 5 seconds
$ns at 5.0 “finish”
# Run the simulation
$ns run
- Run the Simulation
Save the script as vtp_simulation.tcl and execute it in NS2:
ns vtp_simulation.tcl
- Visualize the Simulation Using NAM
Open the .nam file created by the simulation to envision the VLAN trunking behaviour:
nam vtp_simulation.nam
- Analyse the Trace File
The trace file (vtp_trace.tr) will encompass detailed information about packet transmissions and communication via the VLANs. We need to evaluate:
- Traffic within each VLAN.
- How traffic is manage over the trunk link associating the VLANs.
- Modify the Simulation
- Add More VLANs: Incorporate additional VLANs and replicate trunking behaviour among multiple VLANs.
- Trunk Failure Simulation: Replicate failures on the trunk link to track on how traffic is impacted among VLANs.
- Dynamic VLAN Membership: Replicate VLAN membership changes, in which nodes switch among VLANs, implement VTP-like behavior.
Optional Enhancements:
- Simulate VTP Advertisements: Incorporate functionality for VTP-like advertisements in which VLAN configuration variations are propagated via switches such as when VLANs are ingress or egress).
- VLAN Tagging: Execute VLAN tagging and replicate on how traffic is managed in terms of VLAN tags over trunk links.
In this replication, we clearly expounded and established the sample of VLAN Trunking Protocol projects that are simulated by using ns2 tools. Also we outline the further information on how VLAN Trunking Protocol will perform in other tools in another manual.
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