How to Implement Hierarchical Star Topology in OMNeT++

To implement the Hierarchical Star Topology in OMNeT++ has requires to include making a network, in a hierarchical manner multiple star networks are connected. In the topology, creating a hierarchy of star networks, smaller star networks are connected to bigger central nodes like switches or routers. It is generally used in scenarios where the networks want to be arranged in layers, like large enterprise network or campus networks.

Step-by-Step Implementations:

1. Set up OMNeT++ and INET Framework

• Make sure that OMNeT++ and the INET framework are installed and properly configured. The INET framework offers the required modules for mimicking different network topologies, containing hierarchical ones.

2. Define the Hierarchical Star Topology in a NED File

• Make a .ned file to describe the network topology. Smaller star networks are connected to higher-level star networks, usually through a central switch or router in a hierarchical star topology.

Example: A Hierarchical Star Topology with Two Levels

package hierarchicalStarTopologyExample;

import inet.node.inet.StandardHost;

import inet.node.ethernet.EtherSwitch;

network HierarchicalStarTopology

{

parameters:

int numSubStars = default(3);  // Number of sub-star networks

int numHostsPerSubStar = default(3);  // Number of hosts per sub-star network

submodules:

centralSwitch: EtherSwitch {

parameters:

@display(“p=300,200”);

}

subSwitch[numSubStars]: EtherSwitch {

parameters:

@display(“p=100+200*i,400”);

}

host[numSubStars][numHostsPerSubStar]: StandardHost {

parameters:

@display(“p=100+100*j+200*i,600”);

}

connections allowunconnected:

// Connect each sub-switch to the central switch

for i=0..numSubStars-1 {

subSwitch[i].ethg++ <–> EtherChannel <–> centralSwitch.ethg++;

}

// Connect hosts to their respective sub-switches

for i=0..numSubStars-1 {

for j=0..numHostsPerSubStar-1 {

host[i][j].ethg++ <–> EtherChannel <–> subSwitch[i].ethg++;

}

}

}

• Central Switch: The central switch links all the sub-star networks.
• Sub-switches: For a smaller star network each sub-switch serves as the central node
• Hosts: Hosts are connected to the sub-switches, forming individual star networks.

3. Configure the Nodes in OMNeT++ INI File

• Configure the properties of the nodes, like IP addresses, routing, and the applications they will run in the omnetpp.ini file,.

Example:

[General]

network = hierarchicalStarTopologyExample.HierarchicalStarTopology

# Configure IP addresses for the hosts

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

*.host[*][*].eth[0].ipv4.address = “10.0.x.y”

*.host[*][*].eth[0].ipv4.netmask = “255.255.255.0”

# Configure IP addresses for the switches (if needed)

*.centralSwitch.ipv4.arp.typename = “GlobalArp”

*.centralSwitch.eth[0].ipv4.address = “10.0.0.1”

*.centralSwitch.eth[0].ipv4.netmask = “255.255.255.0”

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

*.subSwitch[*].eth[0].ipv4.address = “10.0.x.1”

*.subSwitch[*].eth[0].ipv4.netmask = “255.255.255.0”

# Example application setup: host[0][0] communicates with host[2][2]

*.host[0][0].numApps = 1

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

*.host[0][0].app[0].destAddresses = “10.0.2.3”  # IP address of host[2][2]

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

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

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

*.host[2][2].numApps = 1

*.host[2][2].app[0].typename = “UdpSink”

*.host[2][2].app[0].localPort = 5000

• IP Addressing: Give IP addresses to each host in the network, make sure that each sub-star network has an only one subnet if required.
• Applications: Construct applications on the hosts to mimic network traffic across the hierarchical topology.

4. Implement Routing and Switching Logic

• Routing Protocols: If the hierarchical topology spans many subnets, we may want to configure routing among the subnets using dynamic routing protocols like OSPF or static routing.

Example: Enabling OSPF on all switches

*.centralSwitch.hasOspf = true

*.subSwitch[*].hasOspf = true

• Switching Logic: The EtherSwitch modules will manage Ethernet switching, allowing traffic to be routed among hosts in each star network and across the central switch.

5. Run the Simulation

• Compile and run the simulation in OMNeT++ after setting up the network topology and configuration. Monitor how traffic flows between hosts in various sub-star networks through the central switch and how the hierarchical topology handles various traffic patterns.

6. Analyze the Results

• To visualize and analyse the network traffic by using OMNeT++’s built-in tools. Observe how data is transmitted between hosts in various sub-star networks, how the central switch controls traffic aggregation, and how the hierarchical topology performs under several conditions.

7. Enhancements and Variations

• Scalability Testing: Hosts to test the scalability of the hierarchical star topology and rise the number of sub-star networks and analyse how the network manages increased traffic and node mass.
• Failure Scenarios: Present switch or link failures to see how the network performs and how resilient it is to disruptions.
• Load Balancing: Execute load balancing techniques if essential, to distribute traffic uniformly across the central switch and sub-switches.

Example Files

1. HierarchicalStarTopology.ned: Describes the hierarchical star topology.
2. omnetpp.ini: Encompasses configuration settings for the simulation.

In this notes, we had discussed about multiple star networks, to define hierarchical star topology and implement routing and switching logic is helps to execute Hierarchical Star Topology in OMNeT++. We will give additional data about this topic in various tool.

Reach out to the developers at omnet-manual.com for assistance with implementing and simulating Hierarchical Star Topology in the OMNeT++ tool. We’re here to help you with comparison analysis and project execution ideas—just send us a message!