How to Start Centralized Routing Projects Using NS2

To stimulate a Centralized Routing project in NS2 has includes the build a replicate in which the routing decisions are generate through a central controller or server rather than via individual network nodes. In centralized routing, all routing decisions are calculated at the central place, and network nodes are simply the follow for procedures offers through this controller.

This kind of routing is often used in Software-Defined Networking (SDN) or other network environment in which a central entity such as a network controller has a global show for the network and can regulate the optimize the routes for data packets.

Here’s a step-by-step guide to help you get started with Centralized Routing in NS2:

Steps to Start Centralized Routing Projects Using NS2

  1. Install NS2

First, we require have a NS2 installed. If we haven’t installed it yet, follow for this step below:

  • For Linux (Ubuntu/Debian-based):

sudo apt update

sudo apt install ns2

sudo apt install nam

  • For Windows: we will require to use a virtual machine or Cygwin because NS2 does not natively helps for the Windows.

Once installed, validate through process:

ns

This should open the NS2 command-line interface.

  1. Understand Centralized Routing

In centralized routing, a central entity like a controller or a server calculate the routing paths and allocates the routing data for the nodes in a network. The nodes before use this data for sending the packets. This method is typical in SDN structures, in which the controller have done for visibility into the network topology and can build a informed routing decisions.

In NS2, we can execute the centralized routing in the following way:

  1. The centralized controller calculates the optimal paths according to the current network topology and congestion environments.
  2. The controller brings up-to-date every node by the optimize the routes.
  3. Every node tracks the procedures and transmit the packets accordingly.

This can be replicated through controlling the packet sending a behaviour in NS2 from a central entity such as using scripts or a simulation control mechanism.

  1. Set Up NS2 Simulation Environment

We replicate the centralized routing in NS2, follow these steps:

  1. Define the Network Topology: Build a configure for the nodes and connection that signify the network.
  2. Controller Setup: In centralized routing, the controller will gather the data from overall nodes for sample using link-state information or traffic data and calculate the optimal routes.
  3. Traffic Setup: State the traffic flows such as using agents like CBR, UDP, etc. which will follow the routes calculate through the centralized controller.
  1. Create the TCL Script for Centralized Routing

Here is a sample on how to replicate centralized routing in NS2. In this setting:

  • A centralized controller calculates the routes and bring up-to-date the nodes through the optimize the paths.
  • We replicate a simple network through a few nodes.

Example: Simple Centralized Routing in NS2

# Create the simulator object

set ns [new Simulator]

# Create nodes (e.g., 4 nodes in the network)

set n0 [$ns node]  ;# Node 0 (controller will calculate the route for this node)

set n1 [$ns node]  ;# Node 1

set n2 [$ns node]  ;# Node 2

set n3 [$ns node]  ;# Node 3

# Create links between nodes

$ns duplex-link $n0 $n1 10Mb 20ms DropTail

$ns duplex-link $n1 $n2 10Mb 20ms DropTail

$ns duplex-link $n2 $n3 10Mb 20ms DropTail

# Define centralized routing controller

# For simplicity, assume the controller computes and assigns routes manually

# Normally, the controller can use network topology or dynamic conditions to compute routes

# Example: Controller computes the route for node 0 (via n1, n2 to n3)

# In this case, we are statically assigning the path, but a real controller would be dynamic.

$ns node-config -routing-protocol DSR  ;# You can use DSR or another routing protocol for nodes

# Setup traffic flow from n0 to n3 (via n1, n2)

set udp1 [new Agent/UDP]

set sink1 [new Agent/Null]

$sink1 attach-agent $n3

$udp1 attach-agent $n0

# Setup constant bit rate (CBR) traffic for the flow

set cbr1 [new Application/Traffic/CBR]

$cbr1 set packetSize_ 512

$cbr1 set interval_ 0.1  ;# Set rate for CBR traffic (e.g., 10 packets per second)

$cbr1 attach-agent $n0

 

# Set up traffic flow from node n0 to n3 (via the route computed by the controller)

$ns connect $udp1 $sink1

# Define start and stop time for the traffic

$ns at 1.0 “$cbr1 start”

$ns at 5.0 “$cbr1 stop”

# Set up traces to observe the packet flow

$ns trace-all “centralized_output.tr”

$ns namtrace-all “centralized_output.nam”

# Run the simulation

$ns run

  1. Key Components of the TCL Script
  • Nodes and Links: The network topology is setting by four nodes connected by connections. This is a basic configure, and we can spread the further complex topologies.
  • Traffic Flows: The congestion is a setting to use the UDP and CBR (constant bit rate) traffic. This kind of traffic is often used in real-time applications.
  • Centralized Routing Control: In this sample, the routing is a static and determined by the TCL script. In a real centralized routing setting, the controller would dynamically calculate the paths according to the network environments, like as connection costs, load, or congestion.
  • Tracing: Suggest the files are ensured such as centralized_output.tr we track the packet flow and examine the routing behaviour. We can envision the replication using NAM such as centralized_output.nam.
  1. Simulate the Centralized Controller

In a real centralized routing situation, we would require a controller to calculate the routes and allocate to the nodes. In NS2, this can be replicated in various path:

  1. Static Route Assignment: We can manually allocate the routes in a script like in the above example, nevertheless this is not dynamic.
  2. Simulating a Controller’s Logic: Designed for dynamic behaviour, we can replicate the controller through periodically varying the routes according to network environments or link-state bring up-to-date. We would have a central node such as the controller which process a periodic function to bring up-to-date routes.
  3. Centralized Routing with Dynamic Path Calculation

In a real-world environment, the controller would calculate paths dynamically using a routing algorithm such as Dijkstra’s algorithm according to the network’s present state like as link status, traffic load, etc. We replicate this, you could:

  • Periodically update the routing tables of the nodes through new paths terms on the link-state data.
  • Implement a feedback mechanism from the nodes to the controller to report connection failures, congestion, or delays.

Here’s a plan on how the controller logic could be executed:

  • Link-State Exchange: Nodes are periodically transfer their link-state data to the controller.
  • Controller Path Calculation: The controller uses a procedure such as Dijkstra’s algorithm or another minimum-path procedure we calculate the routes.
  • Route Updates: The controller forwarding the updated routing data back to the nodes, that regulate their forwarding behaviour.
  1. Run and Analyze the Simulation

Once your script is ready, we can process for the replication and examine the behaviour of the network. Used the trace files and NAM and follow on the packet forwarding paths.

To see the trace outcomes:

nam centralized_output.nam

To analyze the trace file:

awk ‘{print $1, $2, $3}’ centralized_output.tr

  1. Extensions and Advanced Features
  • Dynamic Routing: Execute a dynamic controller which remeasures the paths based on network environments such as link failure, congestion is an important aspect of a further advanced the centralized routing replication.
  • Controller-to-Node Communication: Replicate the transmission among the controller and nodes using modify the protocols to alter the routing data.

From the demonstration we clearly deliver the significant information about Centralized Routing and the simulation process procedures, sample snippets and their explanation also provided to understand the concepts on how to run the results in ns2 tool. If clarification is needed, it will be included in an additional project manual.

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