How to Implement Network scheduling in NS2

To implement Network scheduling in NS2 has needs to follow the steps that includes to execute algorithms that handles on how data packets are routed via the network, make sure efficient use of resources and fair allocation of bandwidth. We can execute the network scheduling in NS2 at different layers, like the MAC layer or queue management.

Here is a guide to implement network scheduling in NS2:

Step-by-Step Implementation:

  1. Understand the Types of Scheduling

Before implementing scheduling in NS2, it is significant to know the different types of scheduling that can be implemented:

  • First Come First Serve (FCFS): Packets are processed in the order they arrive.
  • Priority Queueing (PQ): Diverse queues for different priority packets, with higher priority packets processed first.
  • Weighted Fair Queueing (WFQ): Make sure fair distribution of bandwidth among flows.
  • Deficit Round Robin (DRR): Allocates bandwidth equally between all queues in a round-robin fashion.
  • Earliest Deadline First (EDF): Prioritizes packets with the closest deadline.
  1. Modify Queue Scheduling in NS2

In NS2, queue management is a significant part of implementing network scheduling. The queue is responsible for holding packets before they are routed. We can adapt the behaviour of these queues to execute different scheduling algorithms.

Example of First Come First Serve (FCFS)

The default NS2 configuration usually uses a simple FCFS or DropTail queue. We can set it in simulation:

# Set FCFS queue

set val(ifq) Queue/DropTail/PriQueue

Example of Priority Queueing (PQ)

In NS2, Priority Queueing (PQ) can be executed by attaching different queues with diverse priority levels to nodes. Higher-priority packets are served before lower-priority packets. Here’s an instance of configuring priority queues:

# Create a priority queue

set pq [new Queue/DropTail/PriQueue]

$pq set queue_limit_ 100 ;# Set the queue limit to 100 packets

# Set different priorities for packets

set highPriority [new Queue/DropTail]

set lowPriority [new Queue/DropTail]

# Attach high priority queue to higher priority class

$pq set queue_class_1_ $highPriority

$pq set queue_class_2_ $lowPriority

# Attach priority queue to the node

$node_(0) attach $pq

In this sample, the Queue/DropTail/PriQueue object is used, and different traffic types can be allocated to different priority levels.

  1. Implement Weighted Fair Queueing (WFQ)

Weighted Fair Queueing (WFQ) make certain that multiple queues are served fairly based on the assigned weights. To executed WFQ, we need to handle numerous queues and assign them weights according to their priority. Here’s an example:

# Create WFQ

set wfq [new Queue/DropTail/PriQueue]

# Create different queues with different weights

set q1 [new Queue/DropTail]

set q2 [new Queue/DropTail]

# Assign queues to different priority classes

$wfq set queue_class_1_ $q1

$wfq set queue_class_2_ $q2

# Assign weights (priority)

$q1 set weight_ 2 ;# Higher weight for higher priority

$q2 set weight_ 1 ;# Lower weight for lower priority

# Attach the weighted fair queue to a node

$node_(1) attach $wfq

This code allocates different weights to queues, that make sure that higher-weighted queues get more bandwidth.

  1. Deficit Round Robin (DRR) Scheduling

Deficit Round Robin (DRR) is a common scheduling algorithm for fair queuing. Each queue is distributed a quantum (a number of bytes), and packets are sent in a round-robin fashion, using the quantum to control how much data each queue can send.

Though NS2 does not have a direct implementation of DRR, we can replicate DRR-like behaviour using a weighted round-robin scheme by enthusiastically adapting the queue weights.

# Create DRR-like scheduling

set drq [new Queue/DropTail/PriQueue]

# Create queues

set queue1 [new Queue/DropTail]

set queue2 [new Queue/DropTail]

# Set quantum for each queue

$queue1 set quantum_ 1500 ;# Bytes

$queue2 set quantum_ 1000 ;# Bytes

# Attach queues to the DRR scheduler

$drq set queue_class_1_ $queue1

$drq set queue_class_2_ $queue2

# Attach DRR to the node

$node_(2) attach $drq

This is a simple representation of DRR, in which we manually set the quantum for each queue.

  1. Implementing Custom Scheduling Algorithms in NS2

To execute more advanced or custom scheduling algorithms, that need to adjust the NS2’s C++ source code. For example, we can generate a new queue class in NS2 by expanding the existing queue classes (queue.h and queue.cc) and executing the custom logic for packet scheduling.

Here is an overview of how to add custom scheduling logic in C++:

  1. Define a new queue class by modifying the NS2 queue system:
    • Generate a new class like CustomQueue that come into from Queue/DropTail.

Example in C++:

class CustomQueue : public Queue {

public:

CustomQueue();

void enque(Packet* p);

Packet* deque();

void update_weights();

};

  1. Implement the scheduling algorithm logic inside the deque() and enque() methods.

Example logic for weighted round robin scheduling:

void CustomQueue::deque() {

// Logic to dequeue packets based on weights or priority

if (class1_weight > class2_weight) {

// Serve class1 first

} else {

// Serve class2

}

}

  1. Compile NS2 after modifying the queue files.
  2. Attach the new scheduling class in the TCL script:

# Attach custom queue to a node

set customQueue [new CustomQueue]

$node_(0) attach $customQueue

  1. Monitor and Analyse Scheduling Performance

After executing the scheduling algorithms, we need to observe and measure on how well they perform in terms of:

  • Throughput: The rate at which packets are successfully delivered.
  • Fairness: Whether the resources are distributed fairly between different flows or priorities.
  • Packet loss: The number of packets dropped because of buffer overflow or congestion.

We can permit the tracing in NS2 to log packet arrival times, departure times, and queue states. For example, enable trace files in the TCL script:

# Enable tracing for analysis

set tracefile [open “trace.tr” w]

$ns_ trace-all $tracefile

Use tools like AWK or Perl scripts to measure the trace files and estimate the parameters such as average delay, throughput, and packet loss to check the efficiency of scheduling algorithm.

Example TCL Script for Network Scheduling

Here’s a basic sample TCL script that will show you on how to set up a weighted fair queue in NS2:

# Set up the simulator

set ns [new Simulator]

# Define network parameters

set val(chan) Channel/WirelessChannel

set val(prop) Propagation/TwoRayGround

set val(netif) Phy/WirelessPhy

set val(mac) Mac/802_11

set val(ifq) Queue/DropTail/PriQueue

set val(ll) LL

set val(ant) Antenna/OmniAntenna

set val(x) 500

set val(y) 500

set val(rp) AODV ;# Routing protocol

# Create nodes

set node_(0) [$ns node]

set node_(1) [$ns node]

# Set up the weighted fair queue

set wfq [new Queue/DropTail/PriQueue]

set q1 [new Queue/DropTail]

set q2 [new Queue/DropTail]

# Set queue weights

$q1 set weight_ 2 ;# Higher weight

$q2 set weight_ 1 ;# Lower weight

# Attach queues to the WFQ scheduler

$wfq set queue_class_1_ $q1

$wfq set queue_class_2_ $q2

# Attach WFQ to a node

$node_(0) attach $wfq

# Simulation start

$ns run

  1. Run and Analyse the Simulation

Once we have executed the scheduling techniques in the TCL script or C++ code, execute the simulation:

ns your_script.tcl

After the replication, use the trace file to measure how the scheduling technique impacted the performance in terms of throughput, delay, packet loss, and fairness.

We had deliver the entire process that were able to support the execution process for how the network scheduling will performs and schedules the packets over the network by using ns2 tool and also we plan to deliver the additional information regarding this process in other simulation tools. We assist you in generating the most suitable thesis ideas and topics that align with your interests. For effective implementation results in network scheduling using the NS2 tool, you may contact the team at ns2project.com.