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How to Implement Overlay Topology in OMNeT++

To implement an overlay topology in OMNeT++ has contains to generate a logical network on top of an existing physical network. An “Overlay networks” are usually used in scenarios such as peer-to-peer (P2P) networks, virtual private networks (VPNs), and content delivery networks (CDNs), where the logical connections among the nodes do not directly map to the physical connections.

The given below are the procedures on how to implement the overlay topology in OMNeT++:

Step-by-Step Implementation:

  1. Set up OMNeT++ and INET Framework
  • Make sure that OMNeT++ and the INET framework are installed and configured correctly on the suystem. The INET framework delivers the essential modules for emulating the different network topologies that contains overlay networks.
  1. Define the Physical Topology in a NED File
  • First, describe the underlying physical network topology. This will be the foundation on which the overlay network is built.

Example:

package overlayTopologyExample;

import inet.node.inet.Router;

import inet.node.inet.StandardHost;

network PhysicalNetwork

{

parameters:

int numNodes = default(6);  // Number of nodes in the physical network

submodules:

router[numNodes]: Router {

parameters:              @display(“p=200+300*cos(pi/2+i*2*pi/numNodes),200+300*sin(pi/2+i*2*pi/numNodes)”);

}

node[numNodes]: StandardHost {

parameters:             @display(“p=400+300*cos(pi/2+i*2*pi/numNodes),400+300*sin(pi/2+i*2*pi/numNodes)”);

}

connections allowunconnected:

// Connect each node to its corresponding router

for i=0..numNodes-1 {

node[i].ethg++ <–> Eth10G <–> router[i].ethg++;

}

// Create a physical backbone by connecting routers

for i=0..numNodes-2 {

router[i].ethg++ <–> Eth10G <–> router[i+1].ethg++;

}

router[numNodes-1].ethg++ <–> Eth10G <–> router[0].ethg++;

}

  • In this example:
    • Router signifies the routers in the physical network.
    • StandardHost symbolizes the end devices connected to the network.
    • The physical topology connects each node to a router, with routers forming a ring topology.
  1. Define the Overlay Topology in the Same or another NED File
  • Now, describe the logical overlay connections on top of the physical topology. This overlay network will connect nodes that may not be directly connected in the physical topology.

Example:

network OverlayNetwork extends PhysicalNetwork

{

connections:

// Overlay connections between nodes

node[0].pppg++ <–> Ppp <–> node[3].pppg++;

node[1].pppg++ <–> Ppp <–> node[4].pppg++;

node[2].pppg++ <–> Ppp <–> node[5].pppg++;

node[0].pppg++ <–> Ppp <–> node[5].pppg++;

}

  • In this example:
    • The OverlayNetwork extends the PhysicalNetwork by adding extra logical connections among nodes that may not be physically connected.
    • These logical connections form the overlay network.
  1. Configure the Nodes in OMNeT++ INI File
  • In the omnetpp.ini file, configure the properties of the nodes has contains IP addresses, routing, and the applications they will run.

Example:

network = overlayTopologyExample.OverlayNetwork

# Configure IP addresses

*.router[*].ipv4.arp.typename = “GlobalArp”

*.node[*].ipv4.arp.typename = “GlobalArp”

*.node[*].ppp[0].ipv4.address = “10.0.0.x”

*.node[*].ppp[0].ipv4.netmask = “255.255.255.0”

# Example application setup: node[0] communicates with node[3] via overlay connection

*.node[0].numApps = 1

*.node[0].app[0].typename = “UdpBasicApp”

*.node[0].app[0].destAddresses = “10.0.0.4”  # IP address of node[3]

*.node[0].app[0].destPort = 5000

*.node[0].app[0].messageLength = 1024B

*.node[0].app[0].sendInterval = 1s

*.node[3].numApps = 1

*.node[3].app[0].typename = “UdpSink”

*.node[3].app[0].localPort = 5000

  • In this example:
    • node[0] is configured to send UDP packets to node[3] through the overlay connection.
    • node[3] is configured to receive and process the packets.
  1. Configure Routing Protocols
  • Depending on the complexity of overlay topology, we need to configure routing protocols to handle how information is forwarded among the nodes.

Example:

*.router[*].hasOspf = true

*.node[*].hasOspf = true

  • This configuration enables OSPF on all routers and nodes that permits dynamic routing across both the physical and overlay networks.
  1. Run the Simulation
  • After setting up the network topology and configuration compile and run the simulation in OMNeT++. We need to see nodes interacting through both physical and overlay connections.
  1. Analyze the Results
  • Use OMNeT++’s built-in tools to visualize and assess the network traffic. Investigate how information is routed through the overlay network, how the overlay and physical layers communicate, and how the network manages traffic.
  1. Enhancements and Variations
  • Dynamic Overlay Creation: To execute a dynamic overlay creation mechanism where nodes create and tear down overlay connections based on network conditions or particular application requirements.
  • Application-Specific Overlays: To emulate diverse applications running on the overlay network like P2P file sharing, and evaluate their performance.
  • Fault Tolerance: Introduce failures in the physical network and monitor how the overlay network maintains communication.

Example Files

  1. PhysicalNetwork.ned: Outlines the underlying physical network.
  2. OverlayNetwork.ned: Extends the physical network with overlay connections.
  3. omnetpp.ini: Contains configuration settings for the simulation.

We demonstrate how the overlay topology will simulate the network scenario and how to execute and analyse the outcomes using the OMNeT++. Additional specific details about how the overlay topology will perform in other simulation scenarios. Connect with our developers to discover the best simulation and project ideas for Overlay Topology in the OMNeT++ program. We also offer implementation support, so feel free to share your details with us, and we’ll help you out!

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