To simulate Virtual Private Networks (VPNs) using NS2 has needs to generate a network topology in which the private communication among nodes is protected over a public or shared network (like the Internet). VPNs usually utilize tunnelling protocols, encryption, and access control mechanisms to make sure secure communication among geographically dispersed nodes.
Since NS2 does not directly support VPN protocols like IPSec or SSL/TLS, we can replicate VPN behaviour by designing secure tunnels, data encryption, and routing among private nodes over public infrastructure. To achieve the best simulation results, please provide us with all your research details. We will respond promptly with a concise explanation.
Here’s a guide to simulating VPN projects using NS2:
Steps to Simulate Virtual Private Networks Projects in NS2
- Install NS2
- Download and install NS2 from the official NS2 website.
- Ensure Tcl/Tk and other essential libraries are installed to execute simulation scripts and envision the outcomes using NAM (Network Animator).
- Understand Key Components of VPN Simulation
- VPN Gateways: These nodes (routers or firewalls) generate secure tunnels among private networks. They handle traffic encryption and decryption.
- Public Network: The infrastructure (e.g., the Internet) utilized to carry traffic among private networks across VPN tunnels.
- Private Networks: The internal networks of an organization or users that is associated through a VPN.
- Encryption Simulation: In NS2, we can replicate encryption overhead by adding latency to replicate an encryption and decryption processes.
- Define the VPN Topology
Generate a network with two private networks (each with several nodes), connected via VPN gateways over a public network (simulating the Internet).
Example OTcl Code for VPN Topology:
# Create a simulator instance
set ns [new Simulator]
# Define the topography (flat grid for the network)
set topo [new Topography]
$topo load_flatgrid 1000 1000
# Define VPN gateways (acting as VPN routers)
set vpn_gateway_1 [$ns node]
set vpn_gateway_2 [$ns node]
# Define nodes in private network 1 (connected to VPN gateway 1)
set priv_node_1_1 [$ns node]
set priv_node_1_2 [$ns node]
# Define nodes in private network 2 (connected to VPN gateway 2)
set priv_node_2_1 [$ns node]
set priv_node_2_2 [$ns node]
# Define the public network (simulating the Internet)
set public_router_1 [$ns node]
set public_router_2 [$ns node]
# Set up links between VPN gateways and public network
$ns duplex-link $vpn_gateway_1 $public_router_1 100Mb 50ms DropTail
$ns duplex-link $public_router_1 $public_router_2 100Mb 50ms DropTail
$ns duplex-link $vpn_gateway_2 $public_router_2 100Mb 50ms DropTail
# Set up links between private nodes and VPN gateways
$ns duplex-link $priv_node_1_1 $vpn_gateway_1 100Mb 10ms DropTail
$ns duplex-link $priv_node_1_2 $vpn_gateway_1 100Mb 10ms DropTail
$ns duplex-link $priv_node_2_1 $vpn_gateway_2 100Mb 10ms DropTail
$ns duplex-link $priv_node_2_2 $vpn_gateway_2 100Mb 10ms DropTail
In this example:
- Private networks are denoted by priv_node_1_1, priv_node_1_2 (connected to VPN gateway 1) and priv_node_2_1, priv_node_2_2 (connected to VPN gateway 2).
- The public network (Internet) is signifies by routers public_router_1 and public_router_2 with high-latency links between them.
- Simulate Encryption and Tunneling Overhead
We can replicate the encryption and decryption overhead by establishing additional latency on the links among the VPN gateways or by adapting packet processing times at the gateways.
Example: Simulate Encryption Overhead
# Function to simulate encryption delay in VPN gateway
proc vpn_encryption_delay {pkt} {
global ns
set delay [expr rand() * 10] ;# Simulate random encryption delay (e.g., 0-10 ms)
$ns at [$ns now] “handle_packet $pkt after_delay $delay”
}
# Function to simulate packet forwarding after encryption
proc handle_packet {pkt delay} {
global ns
puts “Packet $pkt forwarded after delay $delay ms”
# Forward the packet normally after the delay
}
This code replicates random encryption and decryption latency at the VPN gateways. We can call the vpn_encryption_delay function before forwarding packets via the VPN tunnel.
- Configure Routing for VPN
We can configure dynamic or static routing among the VPN gateways and private network nodes. Tunneling among VPN gateways is replicated by routing packets via the public network nodes (such as public_router_1 and public_router_2).
Example: Enable Dynamic Routing
# Enable dynamic routing protocol (Distance Vector Routing Protocol)
$ns rtproto DV
- Simulate Traffic between VPN Nodes
We can create traffic among nodes in private network 1 and private network 2 to replicate communication over the VPN. Traffic can be simulated using UDP or TCP agents.
Example: Simulate UDP Traffic between Private Networks
# Create UDP agents for communication between private networks
set udp0 [new Agent/UDP]
set null0 [new Agent/Null]
$ns attach-agent $priv_node_1_1 $udp0
$ns attach-agent $priv_node_2_1 $null0
$ns connect $udp0 $null0
# Create a CBR traffic generator for constant bit rate traffic
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 1Mb
$cbr0 attach-agent $udp0
# Start the traffic at time 1.0 seconds
$ns at 1.0 “$cbr0 start”
In this example, constant bit rate (CBR) traffic is created among priv_node_1_1 (in private network 1) and priv_node_2_1 (in private network 2) over the VPN tunnel.
- Run the Simulation
Save simulation script as vpn_simulation.tcl and execute the simulation using the NS2 command:
ns vpn_simulation.tcl
- Analyse the Results
NS2 creates trace files in the course of the simulation. These trace files includes data about packet transmissions, delays, drops, and more. We can utilize these trace files to measure key VPN parameters like:
- Throughput: The amount of data successfully routed over the VPN.
- Encryption Overhead: The delay added because of encryption and decryption at VPN gateways.
- Packet Loss: The number of packets dropped because of congestion or network failures.
Example: Analyze Trace Files Using Awk
awk -f analyze_trace.awk vpn_simulation.tr
- Visualize the Simulation Using NAM
We can utilize Network Animator (NAM) to envision the communication among nodes in private networks via VPN tunnels over the public network.
nam vpn_simulation.nam
- Advanced VPN Features to Simulate
We can prolong the VPN simulation to contain additional characteristics:
- Multiple Tunnels: Replicate multiple VPN tunnels among different pairs of private networks.
- IPSec Simulation: Incorporate more detailed encryption overheads and packet processing time for IPSec-like behaviour.
- QoS in VPN: Execute traffic prioritization and bandwidth guarantees for specific kinds of VPN traffic (such as VoIP).
- Network Failover: Replicate network failure and failover scenarios in which VPN gateways switch to backup routes.
Example VPN Simulation Script Outline
# VPN Simulation script using NS2
set ns [new Simulator]
set topo [new Topography]
$topo load_flatgrid 1000 1000 ;# Set up a flat grid
# VPN gateways (acting as VPN routers)
set vpn_gateway_1 [$ns node]
set vpn_gateway_2 [$ns node]
# Nodes in private network 1set priv_node_1_1 [$ns node]
set priv_node_1_2 [$ns node]
# Nodes in private network 2
set priv_node_2_1 [$ns node]
set priv_node_2_2 [$ns node]
# Public network (simulating the Internet)
set public_router_1 [$ns node]
set public_router_2 [$ns node]
# Set up links between VPN gateways and public routers
$ns duplex-link $vpn_gateway_1 $public_router_1 100Mb 50ms DropTail
$ns duplex-link $public_router_1 $public_router_2 100Mb 50ms DropTail
$ns duplex-link $vpn_gateway_2 $public_router_2 100Mb 50ms DropTail
# Set up links between private nodes and VPN gateways
$ns duplex-link $priv_node_1_1 $vpn_gateway_1 100Mb 10ms DropTail
$ns duplex-link $priv_node_1_2 $vpn_gateway_1 100Mb 10ms DropTail
$ns duplex-link $priv_node_2_1 $vpn_gateway_2 100Mb 10ms DropTail
$ns duplex-link $priv_node_2_2 $vpn_gateway_2 100Mb 10ms DropTail
# Enable dynamic routing
$ns rtproto DV
# Simulate UDP traffic from priv_node_1_1 to priv_node_2_1 over VPN
set udp0 [new Agent/UDP]
set null0 [new Agent/Null]
$ns attach-agent $priv_node_1_1 $udp0
$ns attach-agent $priv_node_2_1 $null0
$ns connect $udp0 $null0
# CBR traffic generator
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 1Mb
$cbr0 attach-agent $udp0
# Start traffic at 1.0 seconds
$ns at 1.0 “$cbr0 start”
# End simulation at 20 seconds
$ns at 20.0 “finish”
# Run the simulation
$ns run
Key Points:
- VPN Gateways: Replicate VPN routers that associate private networks via secure tunnels over a public network.
- Encryption Overhead: Replicate an encryption and decryption delays at VPN gateways.
- Traffic Simulation: Utilize UDP or TCP to replicate traffic among nodes in different private networks across the VPN tunnel.
- Dynamic Routing: Utilize routing protocols to handle communication among nodes via the VPN.
In this simulation setup, we offered the simple approaches that were demonstrated using the sample code snippets related to the virtual private network project which were simulated and evaluated through ns2 tool. Some specific details regarding this process will be provided later.
