How to Implement Network Aggregation in NS2

To implement the Network Aggregation within NS2 that refers to the method of combining several packets into a unique, larger packet to enhance the network efficiency by minimising overhead and reducing transmission time. This process is broadly used in the wireless sensor networks (WSNs) and ad hoc networks that bandwidth is frequently limited, and energy efficiency is a priority. We present stepwise approach on how to implement the network aggregation in NS2:

Step-by-Step Implementation:

  1. Understanding Network Aggregation
  • Packet Aggregation combines numerous small packets into one larger packet to minimise the transmission overhead.
  • Aggregation is especially helpful in networks in which nodes are make frequent small packets (e.g., in sensor networks) or once the aim is to minimise the number of transmissions.
  • In NS2, packet aggregation can replicate by executing a mechanism, which gathers several packets, aggregates them, and transfers the aggregated packet to the end.
  1. Approach to Simulate Network Aggregation in NS2
  • Aggregation Policy: Describe a policy for while packets should aggregate. For instance, based on a timer or the number of packets.
  • Modify the MAC Layer: Execute a custom packet aggregation mechanism at the MAC layer that gathers the packets before forwarding them.
  • Simulate Aggregated Packet Transmission: Aggregate a small packets into a larger packet, transmit it, then divide the packets back at the receiver.
  1. Steps to Implement Packet Aggregation in NS2

Step 1: Modify the MAC Layer to Implement Packet Aggregation

  1. Open the MAC Layer Script (mac-802_11.tcl):
    • In the simulation NS2, the MAC layer manages the transmission and reception of packets. We will change MAC layer to execute the packet aggregation.
  2. Define Aggregation Parameters:
    • Set a metrics like the maximum number of packets to combine and the maximum size of the aggregated packet.

# Define parameters for packet aggregation

set Mac/802_11/aggregation_threshold 5  ;# Aggregate up to 5 packets

set Mac/802_11/aggregation_timer 0.02   ;# Aggregate for up to 20 milliseconds

  1. Modify the Packet Transmission Logic:

We require to alter the packet transmission process in the MAC layer to gather packets, aggregate them, and then transfer a single large packet.

# Packet aggregation queue

set aggregated_packets {}

# Start packet aggregation

proc Mac/802_11::aggregate_packets { } {

global ns

set packet_count 0

set total_packet_size 0

set aggregation_threshold [Mac/802_11 set aggregation_threshold]

set aggregation_timer [Mac/802_11 set aggregation_timer]

set aggregated_packets {}

# Start aggregation timer

$ns at [expr $ns now + $aggregation_timer] “$self transmit_aggregated_packet”

}

# Aggregate packets based on threshold

proc Mac/802_11::enqueue_packet_for_aggregation {packet} {

global aggregated_packets

# Add the packet to the aggregation queue

lappend aggregated_packets $packet

# If aggregation threshold is reached, transmit aggregated packet

if {[llength $aggregated_packets] >= [Mac/802_11 set aggregation_threshold]} {

$self transmit_aggregated_packet

}

}

# Transmit the aggregated packet

proc Mac/802_11::transmit_aggregated_packet { } {

global aggregated_packets

if {[llength $aggregated_packets] == 0} {

return  ;# No packets to aggregate

}

# Create an aggregated packet (concatenate packet data)

set aggregated_packet [new Packet]

set total_packet_size 0

foreach pkt $aggregated_packets {

# Append each packet to the aggregated packet

set packet_size [$pkt size]

$aggregated_packet append $pkt

set total_packet_size [expr $total_packet_size + $packet_size]

}

# Set the size of the aggregated packet

$aggregated_packet set size $total_packet_size

# Transmit the aggregated packet

$self send $aggregated_packet

# Clear the aggregation queue

set aggregated_packets {}

}

Step 2: Modify the Packet Reception Logic to Handle Aggregated Packets

We want to change the packet reception process to divide the aggregated packet back into these original smaller packets at the receiver.

# Handle reception of aggregated packets

proc Mac/802_11::recv_aggregated_packet {aggregated_packet} {

# Get the size of the aggregated packet

set aggregated_size [$aggregated_packet size]

# Split the aggregated packet into original packets

while {$aggregated_size > 0} {

set original_packet [new Packet]

# Extract the original packet size

set original_size [extract_packet_size $aggregated_packet]

# Remove the original packet from the aggregated packet

$aggregated_packet remove $original_packet original_size

# Forward the original packet to the upper layers

$self recv $original_packet

# Update the size of the aggregated packet

set aggregated_size [expr $aggregated_size – $original_size]

}

}

Step 3: Define a TCL Simulation Script for Aggregation

We will require a TCL script, which configure a network, applies the packet aggregation at the MAC layer, and produces traffic.

# Create a simulator instance

set ns [new Simulator]

# Define trace and nam files for output

set tracefile [open aggregation.tr w]

set namfile [open aggregation.nam w]

$ns trace-all $tracefile

$ns namtrace-all $namfile

# Define network topology

set topo [new Topography]

$topo load_flatgrid 1000 1000  ;# Simulation area: 1000×1000 meters

# Create the General Operations Director (GOD)

set god_ [create-god 10]  ;# 10 nodes in the network

# Set physical and MAC layer parameters

set Mac/802_11/aggregation_threshold 5

set Mac/802_11/aggregation_timer 0.02

# Define node parameters

set opt(chan)       Channel/WirelessChannel

set opt(prop)       Propagation/TwoRayGround

set opt(netif)      Phy/WirelessPhy

set opt(mac)        Mac/802_11

set opt(ifq)        Queue/DropTail/PriQueue

set opt(ll)         LL

set opt(ant)        Antenna/OmniAntenna

set opt(x)          1000

set opt(y)          1000

# Set number of nodes

set opt(nn) 10  ;# Number of nodes

# Create nodes and set initial positions

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

set node_($i) [$ns node]

$node_($i) random-motion 1  ;# Enable random motion for nodes

}

# Set up traffic generation

proc start_traffic {} {

global ns node_ opt

# Create UDP agents and attach them to nodes

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

set udp_($i) [new Agent/UDP]

set null_($i) [new Agent/Null]

$ns attach-agent $node_($i) $udp_($i)

$ns attach-agent $node_($i) $null_($i)

# Generate CBR traffic

set cbr_($i) [new Application/Traffic/CBR]

$cbr_($i) set packetSize_ 512

$cbr_($i) set interval_ 0.1

$cbr_($i) attach-agent $udp_($i)

# Connect UDP agents for communication between nodes

$ns connect $udp_($i) $null_($i)

}

}

# Start traffic at 1.0 second

$ns at 1.0 “start_traffic”

# Run the simulation

$ns at 100.0 “finish”

# End simulation procedure

proc finish {} {

global ns tracefile namfile

close $tracefile

close $namfile

$ns halt

}

# Run the simulation

$ns run

  1. Explanation of the Script
  • Aggregation Threshold: These threshold for aggregating packets is place to 5, meaning up to 5 packets are combined before sending. The aggregation timer is set to 20 milliseconds.
  • Packet Aggregation and Transmission: The aggregate_packets function gathers packets and aggregates them, when transmit_aggregated_packet transfers the aggregated packet.
  • Packet Reception: The recv_aggregated_packet function manages the reception of aggregated packets and divides them back into the original packets.
  • Traffic Generation: Constant Bit Rate (CBR) traffic is made among the nodes using UDP agents.
  1. Running the Simulation
  • We can save the modified mac-802_11.tcl file and the TCL script (aggregation.tcl).
  • Now, run the simulation using the below command:

ns aggregation.tcl

  1. Analyzing Results
  • To examine the trace file (aggregation.tr) to monitor the impacts of packet aggregation on network performance, after running the simulation.
  • We can liken the simulation outcomes with and without aggregation to monitor the effect on throughput, packet delivery ratio, and latency.
  1. Further Enhancements
  • Dynamic Aggregation: Execute dynamic aggregation schemes in which the aggregation threshold alters depends on network conditions such as traffic load or delay.
  • Aggregation with ARQ: Liken an aggregation including Automatic Repeat Request (ARQ) to make sure that reliable transmission.
  • Energy Efficiency: Estimate how aggregation enhances energy efficiency within wireless sensor networks by minimizing the number of transmissions.

Throughout this technique, we can obtain to understand more about how the Network Aggregation will be implemented with some examples. We offered the entire instructions of the execution and analyse of the Network aggregation in the NS2 simulation tool. You can customize the simulation as per your requirements. Reach out to ns2project.com for optimal Network Aggregation implementation results for your projects. Our developers are dedicated to offering exceptional project support. We prioritize the latest research methodologies to ensure you achieve the best outcomes for your initiatives.