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How to Implement distance vector routing in OMNeT++

To implement the Distance Vector Routing in OMNeT++, we have to figure out the best paths across the network by simulating a model in which their routers interchange routing information with their neighbors. The Distance Vector Routing algorithm is like the one used in protocols like RIP (Routing Information Protocol) which is based on the Bellman-Ford algorithm. Here’s a step-by-step guide to help you implement Distance Vector Routing in OMNeT++:

Step-by-Step Implementation:

Step 1: Set Up OMNeT++ and INET Framework

  1. Install OMNeT++:
    • Make sure that OMNeT++ is installed on your system.
  2. Install the INET Framework:
    • We can expand or use the library of network protocols and modules that are provided by INET. Install INET from the INET GitHub repository.

Step 2: Create a New OMNeT++ Project

  1. Create the Project:
    • Open OMNeT++ and create a new OMNeT++ project via File > New > OMNeT++ Project.
    • Name the project (like DistanceVectorRouting) and set up the project directory.
  2. Set Up Project Dependencies:
    • Make sure that the project references the INET Framework by right-clicking on the project in the Project Explorer, navigating to Properties > Project References, and checking the INET project.

Step 3: Define the Network Topology

  1. Create a NED File:
    • Use NED language to state the network topology which includes routers and links, where the routers will run the Distance Vector Routing protocol.

For instance:

network DistanceVectorNetwork

{

submodules:

router1: Router;

router2: Router;

router3: Router;

router4: Router;

connections:

router1.ethg++ <–> Eth10Mbps <–> router2.ethg++;

router2.ethg++ <–> Eth10Mbps <–> router3.ethg++;

router3.ethg++ <–> Eth10Mbps <–> router4.ethg++;

router4.ethg++ <–> Eth10Mbps <–> router1.ethg++;

}

  1. Configure Network Parameters:
    • Simulate the realistic network environment to build a essential link parameters like bandwidth, delay, and packet loss.

Step 4: Implement the Distance Vector Routing Protocol

  1. Define the Protocol Modules:
    • For the distance vector routing protocol, we have to create a new module in NED that will be a part of the router’s network layer.

Example (in NED):

simple DistanceVectorRouting

{

parameters:

@display(“i=block/network2”);

gates:

inout lowerLayerIn;

inout lowerLayerOut;

}

  1. Implement the Distance Vector Algorithm in C++:
    • Implement the Distance Vector Routing logic in a C++ class involves maintaining a routing table, exchanging routing information with neighbors, and updating routes based on received information.

Example (C++ implementation):

#include <map>

#include “inet/common/INETDefs.h”

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

class DistanceVectorRouting : public cSimpleModule

{

private:

struct RouteEntry {

int cost;

std::string nextHop;

};

std::map<std::string, RouteEntry> routingTable;  // Destination -> (Cost, Next Hop)

protected:

virtual void initialize() override;

virtual void handleMessage(cMessage *msg) override;

void sendRoutingUpdates();

void processRoutingUpdate(cMessage *msg);

void updateRoutingTable(const std::string& destination, int cost, const std::string& nextHop);

};

Define_Module(DistanceVectorRouting);

void DistanceVectorRouting::initialize() {

// Initialize the routing table with direct neighbors

// Assuming a direct mapping between interfaces and neighbors

for (int i = 0; i < gateSize(“lowerLayerOut”); i++) {

std::string neighbor = std::to_string(i + 1);

routingTable[neighbor] = {1, neighbor};  // Cost to direct neighbors is 1

}

// Send initial routing updates

sendRoutingUpdates();

}

void DistanceVectorRouting::handleMessage(cMessage *msg) {

if (msg->arrivedOn(“lowerLayerIn”)) {

processRoutingUpdate(msg);

}

}

void DistanceVectorRouting::sendRoutingUpdates() {

// Send routing table to all neighbors

for (int i = 0; i < gateSize(“lowerLayerOut”); i++) {

cMessage *update = new cMessage(“RoutingUpdate”);

// Package the routing table information into the message

// Example: Add the routing table entries to the message’s control info

for (auto &entry : routingTable) {

// Add each entry to the update message

// You may need a custom control info or message subclass

}

send(update, “lowerLayerOut”, i);

}

}

void DistanceVectorRouting::processRoutingUpdate(cMessage *msg) {

// Extract the routing information from the received message

// Update the routing table based on the received data

std::string neighbor = “some_neigh”;  // Extracted from msg

int costToNeighbor = 1;  // Extracted from msg

for (auto &entry : routingTable) {

int newCost = costToNeighbor + entry.second.cost;

updateRoutingTable(entry.first, newCost, neighbor);

}

// Optionally, resend updates if the routing table was changed

sendRoutingUpdates();

delete msg;

}

void DistanceVectorRouting::updateRoutingTable(const std::string& destination, int cost, const std::string& nextHop) {

if (routingTable.find(destination) == routingTable.end() || routingTable[destination].cost > cost) {

routingTable[destination] = {cost, nextHop};

}

}

    • Routing Table: We have to trace the cost to reach every destination and next hop router by maintaining the routing table.
    • Periodic Updates: Periodically send routing updates to neighbors containing the current routing table.
    • Processing Updates: After receiving an update from a neighbor, it relates the received routes with the current routing table, if a cheaper path is found,it update and and propagate changes if necessary.
  2. Integrate with the INET Framework:
    • In the protocol stack, we have to make certain that Distance Vector Routing module interacts correctly with other layers, particularly in the IP layer. To maintain the routes in the INET framework, we need to interface with the IPv4RoutingTable module.

Step 5: Set Up the Simulation

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

Example:

network = DistanceVectorNetwork

sim-time-limit = 100s

# Enable scalar and vector recording for analysis

**.scalar-recording = true

**.vector-recording = true

# Application traffic configuration (if needed)

*.router1.numApps = 1

*.router1.app[0].typename = “UdpBasicApp”

*.router1.app[0].destAddress = “router4”

*.router1.app[0].destPort = 5000

*.router1.app[0].messageLength = 1024B

*.router1.app[0].sendInterval = uniform(1s, 2s)

  1. Traffic Configuration:
    • Build application-level traffic amongst nodes to generate network activity, which will initiate the transfer of routing information.

Step 6: Run the Simulation

  1. Compile the Project:
    • Make sure that everything is correctly executed and compiled.
  2. Run Simulations:
    • Use OMNeT++’s IDE or command line to implement the simulations. Observe the behavior of the routing protocol, especially how it converges to a stable state.

Step 7: Analyze the Results

  1. Monitor Convergence Time:
    • Measure the time it takes for the routing tables in all routers to stabilize (i.e., converge to a consistent state).
  2. Evaluate Protocol Performance:
    • Analyze key performance metrics like route optimality, update overhead, and network utilization.
    • Scalars and Vectors: Record and analyze scalar and vector data using OMNeT++. This can include tracking the count of routing updates, the total number of hops, and the time taken to reach destinations.
  3. Check for Issues:
    • Search for issues like routing loops or instability, which are common concerns with distance vector routing.

Step 8: Refine and Optimize the Protocol

  1. Address Any Bugs or Inefficiencies:
    • If the protocol exhibits problems like routing loops or slow convergence, consider generating enhancements like split horizon, route poisoning, or triggered updates.
  2. Optimize for Performance:
    • To optimize the performance under different network, we have to Fine-tune parameters like update intervals or damping mechanisms.
  3. Re-Test:
    • To validate the improvements, we have to run the simulation again with the optimized protocol.

Step 9: Document and Report Findings

  1. Document the Implementation:
    • Provide clear documentation of how the Distance Vector Routing protocol was implemented, including the key algorithms and data structures used.
  2. Report Performance Analysis:
    • Prepare a brief report of protocol’s performance like its convergence time, routing overhead, and network stability.
  3. Discuss Improvements:
    • For future enhancements, we had to propose the potential developments or optimizations.

In conclusion, we thoroughly concentrated on the implementation of distance vector algorithms, how to maintain the routing table for DVR using INET framework in the OMNeT++. If needed, we can also provide implementation of  this DVR for your project using omnet++  tool.

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