How to Implement hierarchical routing in OMNeT++

To implement the hierarchical routing in OMNeT++ comprises to making a simulation where the network is separated into many hierarchical levels, like domains or clusters, with routing decisions being made at each level. This approach helps to handle large-scale networks more effectively by decreasing the complexity of routing tables and controlling the scope of routing information propagation.

Step-by-Step Implementations:

Step 1: Set Up OMNeT++ and INET Framework

1. Install OMNeT++:
   • Make certain that OMNeT++ is installed on the system. Download it from the  OMNeT++
2. Install the INET Framework:
   • Download and install the INET Framework, which provides a whole set of network protocol models. INET can be downloaded from the INET GitHub repository.

Step 2: Create a New OMNeT++ Project

1. Create the Project:
   • Open OMNeT++ and make a new OMNeT++ project by File > New > OMNeT++ Project.
   • Name the project like HierarchicalRouting and set up the project directory.
2. Set Up Project Dependencies:
   • Make sure the project references the INET Framework by right-clicking on your project in the Project Explorer, directing to Properties > Project References, and verifying the INET project.

Step 3: Define the Network Topology

1. Create a NED File:
   • Describe the network topology using the NED language. The topology must involve numerous hierarchical levels, like local domains or clusters, each with its own routing protocols.

Example:

network HierarchicalNetwork

{

submodules:

// Level 1 – Core Routers

coreRouter1: Router;

coreRouter2: Router;

// Level 2 – Aggregation Routers

aggRouter1: Router;

aggRouter2: Router;

aggRouter3: Router;

aggRouter4: Router;

// Level 3 – Edge Routers / Hosts

edgeRouter1: Router;

edgeRouter2: Router;

edgeRouter3: Router;

edgeRouter4: Router;

connections:

// Core Routers Interconnection

coreRouter1.ethg++ <–> Eth10Gbps <–> coreRouter2.ethg++;

// Aggregation Routers to Core Routers

aggRouter1.ethg++ <–> Eth1Gbps <–> coreRouter1.ethg++;

aggRouter2.ethg++ <–> Eth1Gbps <–> coreRouter1.ethg++;

aggRouter3.ethg++ <–> Eth1Gbps <–> coreRouter2.ethg++;

aggRouter4.ethg++ <–> Eth1Gbps <–> coreRouter2.ethg++;

// Edge Routers to Aggregation Routers

edgeRouter1.ethg++ <–> Eth100Mbps <–> aggRouter1.ethg++;

edgeRouter2.ethg++ <–> Eth100Mbps <–> aggRouter2.ethg++;

edgeRouter3.ethg++ <–> Eth100Mbps <–> aggRouter3.ethg++;

edgeRouter4.ethg++ <–> Eth100Mbps <–> aggRouter4.ethg++;

}

1. Configure Network Parameters:
   • Set up the required link parameters like bandwidth, delay, and packet loss to mimic a realistic hierarchical network setting.

Step 4: Implement the Hierarchical Routing Protocol

1. Define the Routing Modules:
   • Build new modules in NED for the hierarchical routing protocol. These modules will manage routing decisions at each level of the hierarchy.

Example (in NED):

simple HierarchicalRouting

{

parameters:

@display(“i=block/network2”);

gates:

inout lowerLayerIn;

inout lowerLayerOut;

}

1. Implement Hierarchical Routing Logic in C++:
   • To implement the routing logic for each level of the hierarchy. It will include managing routing tables, exchanging routing information within and between levels, and verifying routes based on the hierarchical structure.

Example (C++ implementation):

#include <map>

#include “inet/common/INETDefs.h”

#include “inet/networklayer/contract/IRoutingTable.h”

#include “inet/networklayer/ipv4/IPv4RoutingTable.h”

class HierarchicalRouting : public cSimpleModule

{

private:

std::map<std::string, std::string> localRoutingTable;  // For routing within the local domain

std::map<std::string, std::string> globalRoutingTable;  // For routing between domains

IRoutingTable *routingTable;

protected:

virtual void initialize() override;

virtual void handleMessage(cMessage *msg) override;

void updateLocalRoutingTable();

void updateGlobalRoutingTable();

};

Define_Module(HierarchicalRouting);

void HierarchicalRouting::initialize() {

routingTable = getModuleFromPar<IRoutingTable>(par(“routingTableModule”), this);

// Initialize local and global routing tables

updateLocalRoutingTable();

updateGlobalRoutingTable();

}

void HierarchicalRouting::handleMessage(cMessage *msg) {

// Handle incoming packets

if (msg->arrivedOn(“lowerLayerIn”)) {

// Determine the correct next hop based on hierarchical routing

std::string destination = “some_destination”;  // Extract destination from the message

if (localRoutingTable.find(destination) != localRoutingTable.end()) {

// Route within the local domain

send(msg, “lowerLayerOut”, routingTable->getInterfaceByName(localRoutingTable[destination].c_str())->getInterfaceId());

} else if (globalRoutingTable.find(destination) != globalRoutingTable.end()) {

// Route to another domain

send(msg, “lowerLayerOut”, routingTable->getInterfaceByName(globalRoutingTable[destination].c_str())->getInterfaceId());

} else {

// No route found, drop the packet

delete msg;

}

}

}

void HierarchicalRouting::updateLocalRoutingTable() {

// Populate the local routing table with routes within the local domain

localRoutingTable[“edgeRouter1”] = “eth0”;

localRoutingTable[“edgeRouter2”] = “eth1”;

// Add more entries as needed

}

void HierarchicalRouting::updateGlobalRoutingTable() {

// Populate the global routing table with routes to other domains

globalRoutingTable[“aggRouter3”] = “eth2”;

globalRoutingTable[“aggRouter4”] = “eth3”;

// Add more entries as needed

}

1. • Local Routing Table: Manage routing in a domain or cluster.
   • Global Routing Table: Handles routing among domains or clusters.
   • Routing Decision: When a packet arrives, the module determines whether the packet would be routed within the local domain or forwarded to any more domain based on the destination.
2. Integrate with the INET Framework:
   • Make sure the hierarchical routing module relates correctly with other layers in the protocol stack, especially the IP layer. We can need to interface with the IPv4RoutingTable module to handle routes in the INET framework.

Step 5: Set Up the Simulation

1. Configure the Simulation in omnetpp.ini:
   • Set up the simulation limits, like simulation time, network settings, and traffic patterns.

Example:

[General]

network = HierarchicalNetwork

sim-time-limit = 100s

# Enable scalar and vector recording for analysis

**.scalar-recording = true

**.vector-recording = true

# Application traffic configuration (if needed)

*.edgeRouter1.numApps = 1

*.edgeRouter1.app[0].typename = “UdpBasicApp”

*.edgeRouter1.app[0].destAddress = “edgeRouter4”

*.edgeRouter1.app[0].destPort = 5000

*.edgeRouter1.app[0].messageLength = 1024B

*.edgeRouter1.app[0].sendInterval = uniform(1s, 2s)

1. Traffic Configuration:
   • Set up application-level traffic between nodes to make network activity, triggering routing decisions across unlike hierarchical levels.

Step 6: Run the Simulation

1. Compile the Project:
   • Make sure everything is correctly implemented and compiled.
2. Run Simulations:
   • Implement the simulations using OMNeT++’s IDE or command line. Notice the behaviour of the hierarchical routing protocol, specifically how it handles traffic within and between domains.

Step 7: Analyze the Results

1. Monitor Routing Efficiency:
   • Calculate how helpfully the hierarchical routing protocol routes traffic within and across domains.
2. Evaluate Protocol Performance:
   • Evaluate key performance metrics like route optimality, update overhead, and network utilization.
   • Scalars and Vectors: Use OMNeT++ tools to record and analyse scalar and vector data. It may include tracking the number of routing updates, the total number of hops, and the time taken to grasp destinations.
3. Check for Issues:
   • Let see issues like routing loops or instability, especially under dynamic network conditions.

Step 8: Refine and Optimize the Protocol

1. Address Any Bugs or Inefficiencies:
   • If the protocol exhibits problems, think through refining the hierarchical structure or optimizing the routing algorithms.
2. Optimize for Performance:
   • Modify parameters like update intervals or routing table management to expand performance under numerous network conditions.
3. Re-Test:
   • Run the simulation again with the optimized protocol to justify improvements.

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