How to Implement Network Packet Switching in NS2
To implement Network Packet Switching in NS2, we mimic how packets are forwarded via a network according to packet switching principles. In packet-switched networks, data is broken into smaller packets that are transmitting independently via the network. Each packet can take a diverse route, and the network dynamically decides how to forward each packet based on routing protocols.
In NS2, packet switching can be executed by generating a network topology of nodes and links and using routing protocols such as AODV (Ad hoc On-Demand Distance Vector) or DSDV (Destination-Sequenced Distance-Vector) to transmit the packets via the network.
Below is the brief approach to implement the Network Packet Switching in ns2:
Steps to Implement Network Packet Switching in NS2:
- Set up the Simulation Environment
Initially, describe the network nodes and links that will replicate the packet-switched network. This topology can contain routers, switches, and end-hosts (source and destination nodes).
Example TCL Script for Basic Setup:
# Create a simulator instance
set ns [new Simulator]
# Define link parameters (bandwidth and delay)
set bw 10Mb ;# Bandwidth for each link (10 Mbps)
set delay 10ms ;# Delay for each link
# Create network nodes
set node1 [$ns node] ;# Source node
set node2 [$ns node] ;# Intermediate router/switch
set node3 [$ns node] ;# Intermediate router/switch
set node4 [$ns node] ;# Destination node
# Create links between the nodes
$ns duplex-link $node1 $node2 $bw $delay DropTail
$ns duplex-link $node2 $node3 $bw $delay DropTail
$ns duplex-link $node3 $node4 $bw $delay DropTail
This topology denotes a simple network with a source node (node1), intermediate routers or switches (node2, node3), and a destination node (node4). The network links have a defined bandwidth and delay, that mimics real-world network conditions.
- Configure Traffic between Source and Destination
To replicate data transmission, setting up traffic flows using UDP or TCP agents. These agents will generate traffic that is divided into packets and transmitted via the network.
Example of Configuring Traffic between Nodes:
# Create UDP agent for the source node (sending packets)
set udp_src [new Agent/UDP]
$ns attach-agent $node1 $udp_src
# Create CBR traffic generator to simulate constant packet flow
set cbr_src [new Application/Traffic/CBR]
$cbr_src set packet_size_ 500 ;# Packet size in bytes
$cbr_src set rate_ 2Mb ;# Data rate (e.g., 2 Mbps)
$cbr_src attach-agent $udp_src
# Create a UDP sink at the destination node (receiving packets)
set null_sink [new Agent/Null]
$ns attach-agent $node4 $null_sink
# Connect source node to destination node via intermediate nodes (packet switching)
$ns connect $udp_src $null_sink
# Start and stop the traffic
$ns at 1.0 “$cbr_src start”
$ns at 10.0 “$cbr_src stop”
In this configuration:
- Node1 sends packets to Node4 using a UDP agent and CBR (Constant Bit Rate) traffic generator, that mimics a continuous flow of packets.
- The packets are transmitted via Node2 and Node3 before reaching Node4, representing packet switching in the network.
- Enable Routing Protocols for Packet Switching
Routing protocols are necessary for deciding how packets should be forwarded via the network. We can use a dynamic routing protocol such as AODV or DSDV to mimic packet switching. The routing protocol makes sure that each packet is forwarded to the correct next hop towards the destination.
Example of Enabling AODV for Routing:
# Enable AODV routing protocol
set val(rp) AODV
# Attach AODV routing protocol to all nodes in the network
for {set i 1} {$i <= 4} {incr i} {
set node [set node($i)]
$ns at 0.0 “$node set ragent [new Agent/AODV]”
}
With AODV, the network enthusiastically discovers routes as packets are routed. Each node will retain routing information to frontward packets to the suitable next hop.
- Simulate Packet Forwarding and Switching
Once the traffic and routing protocols are configured, the network can initiate forwarding packets according to the routing decisions made by the protocol. Each packet is forwarded independently; mimic a packet-switched network.
- Enable Tracing and Monitor Packet Switching
NS2 delivers tracing capabilities that permits to monitor how packets are forwarded across the network that has includes when they are received, dropped, or forwarded by diverse nodes. This is useful for understanding the packet-switching behaviour in the network.
Enable Trace Files:
# Enable tracing for the simulation
set tracefile [open “packet_switching_trace.tr” w]
$ns trace-all $tracefile
# Define a finish procedure to end the simulation and close the trace file
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exit 0
}
# Set the simulation end time
$ns at 20.0 “finish”
The trace file will capture events like packet transmissions, packet drops, and forwarding decisions made by the routing protocol that delivers insights into how packets are switched across the network.
- Run the Simulation
Execute the simulation to monitor on how packets are forwarded via the packet-switched network based on routing decisions.
# Run the simulation
$ns run
Example Complete TCL Script for Network Packet Switching Simulation
# Create a simulator instance
set ns [new Simulator]
# Define link parameters (bandwidth and delay)
set bw 10Mb
set delay 10ms
# Create network nodes
set node1 [$ns node] ;# Source node
set node2 [$ns node] ;# Intermediate router/switch
set node3 [$ns node] ;# Intermediate router/switch
set node4 [$ns node] ;# Destination node
# Create links between the nodes
$ns duplex-link $node1 $node2 $bw $delay DropTail
$ns duplex-link $node2 $node3 $bw $delay DropTail
$ns duplex-link $node3 $node4 $bw $delay DropTail
# Create UDP agent for the source node (sending packets)
set udp_src [new Agent/UDP]
$ns attach-agent $node1 $udp_src
# Create CBR traffic generator to simulate constant packet flow
set cbr_src [new Application/Traffic/CBR]
$cbr_src set packet_size_ 500
$cbr_src set rate_ 2Mb
$cbr_src attach-agent $udp_src
# Create a UDP sink at the destination node (receiving packets)
set null_sink [new Agent/Null]
$ns attach-agent $node4 $null_sink
# Connect source node to destination node via intermediate nodes (packet switching)
$ns connect $udp_src $null_sink
# Start and stop the traffic
$ns at 1.0 “$cbr_src start”
$ns at 10.0 “$cbr_src stop”
# Enable AODV routing protocol
set val(rp) AODV
for {set i 1} {$i <= 4} {incr i} {
set node [set node($i)]
$ns at 0.0 “$node set ragent [new Agent/AODV]”
}
# Enable tracing
set tracefile [open “packet_switching_trace.tr” w]
$ns trace-all $tracefile
# End simulation
$ns at 20.0 “finish”
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exit 0
}
# Run the simulation
$ns run
The above following demonstration will clearly show how to replicate and enforce the Network Packet Switching in ns2 tool that is used to transmit the packets via the network. More information will be shared regarding the Network Packet Switching.
If you need help with Network Packet Switching in NS2, feel free to send us the details of your project. We have plenty of resources to assist you. We specialize in routing protocols like AODV (Ad hoc On-Demand Distance Vector) and DSDV (Destination-Sequenced Distance-Vector) that could be relevant to your work. Just share your project information, and we’ll be happy to help!