To simulate Bellman-Ford Routing within OMNeT++ that has requires to executing a distance-vector routing protocol, which utilizes the Bellman-Ford algorithm to calculate the shortest paths among the nodes in a network. This protocol computes the finest path according to the hop count or other parameters and updates routing tables occasionally or once changes in the network topology happen.
Even though the INET Framework in OMNeT++ offers numerous routing protocols like RIP (Routing Information Protocol) that is rely on the Bellman-Ford algorithm, we can also execute a custom Bellman-Ford routing protocol if we require more control over the routing process.
The following is a step-by-step instruction on how to replicate Bellman-Ford Routing using OMNeT++ and INET framework:
Steps to Simulate Bellman Ford Routing Projects in OMNeT++
- Install OMNeT++ and INET Framework
- Download OMNeT++:
- Install OMNeT++ from the OMNeT++ official website.
- Install INET Framework:
- The INET Framework delivers routing protocols such as RIP that uses the Bellman-Ford algorithm.
- Clone the INET repository:
git clone https://github.com/inet-framework/inet.git
-
- Import the INET project into OMNeT++ through File > Import > Existing Projects into Workspace, and choose the inet directory.
- Construct the INET project by right-clicking on the inet project within OMNeT++ and choosing Build Project.
- Define the Network Topology in NED
Make a network in which nodes are communicate using distance-vector routing protocols such as RIP (which uses Bellman-Ford). We can be described the network using the NED (Network Description) file.
Example NED File for Bellman-Ford Routing (BellmanFordNetwork.ned):
package bellmanfordrouting;
import inet.node.inet.Router;
import inet.node.inet.StandardHost;
import inet.linklayer.ethernet.EthernetInterface;
network BellmanFordNetwork
{
submodules:
host1: StandardHost {
@display(“p=100,100”);
}
host2: StandardHost {
@display(“p=300,100”);
}
router1: Router {
@display(“p=200,150”);
}
router2: Router {
@display(“p=400,150”);
}
connections allowunconnected:
host1.ethg++ <–> EthernetInterface <–> router1.ethg++;
router1.ethg++ <–> EthernetInterface <–> router2.ethg++;
router2.ethg++ <–> EthernetInterface <–> host2.ethg++;
}
Explanation:
- StandardHost: Denotes end systems (hosts), which generate and receive traffic.
- Router: Signifies routers, which utilize the Bellman-Ford (distance-vector) routing algorithm to forward packets.
- EthernetInterface: Wired connections among the routers and hosts.
- Configure RIP (Bellman-Ford) in omnetpp.ini
In this instance, we will be used RIP (Routing Information Protocol) that uses the Bellman-Ford algorithm to compute the shortest paths. We can set up the routing protocol and network parameters within the omnetpp.ini file.
Example omnetpp.ini Configuration:
[General]
network = BellmanFordNetwork
sim-time-limit = 200s
# IP Address Configuration for Hosts and Routers
*.host1.ipv4.address = “10.0.0.1”
*.host1.ipv4.netmask = “255.255.255.0”
*.host2.ipv4.address = “10.0.0.2”
*.host2.ipv4.netmask = “255.255.255.0”
*.router1.ipv4.address = “10.0.0.3”
*.router1.ipv4.netmask = “255.255.255.0”
*.router2.ipv4.address = “10.0.0.4”
*.router2.ipv4.netmask = “255.255.255.0”
# Enable RIP (Bellman-Ford) on Routers
*.router1.hasRip = true
*.router1.ripRouter.routingTable = “RipRoutingTable”
*.router2.hasRip = true
*.router2.ripRouter.routingTable = “RipRoutingTable”
# Traffic Configuration (UDP Traffic Generation)
*.host1.numApps = 1
*.host1.app[0].typename = “UdpBasicApp”
*.host1.app[0].destAddresses = “10.0.0.2” # Send traffic to Host2
*.host1.app[0].destPort = 5000
*.host1.app[0].messageLength = 1024B
*.host1.app[0].sendInterval = exponential(1s)
*.host2.numApps = 1
*.host2.app[0].typename = “UdpSink” # Host2 is the UDP receiver
*.host2.app[0].localPort = 5000
# RIP Parameters (Bellman-Ford Algorithm)
*.**.ripRouter.updateInterval = 10s # Interval for RIP updates
*.**.ripRouter.timeoutInterval = 30s # Time before a route is declared invalid
*.**.ripRouter.holdDownInterval = 15s # Hold-down time for unreachable routes
Explanation:
- RIP Configuration: Allows RIP (which uses the Bellman-Ford algorithm) on routers router1 and router2. The routers utilize RIP to exchange routing data and update their routing tables.
- Traffic Generation: Host1 transmits UDP traffic to Host2 via the routers, and Host2 receives the traffic.
- RIP Parameters: Set up the update interval (how often routing information is exchanged), timeout interval, and hold-down period for managing the unreachable routes.
- Run the Simulation
- Build the Project:
- Right-click on the OMNeT++ project and choose Build Project to compile the simulation files.
- Run the Simulation:
- Right-click on omnetpp.ini and choose Run As > OMNeT++ Simulation.
- We can utilize the Qtenv graphical interface to observe the behaviour of RIP (Bellman-Ford) in action, in which routers are exchange routing data and then calculate shortest paths.
- Analyze the Results
When the simulation is complete, we can examine several performance parameters and network behaviour:
- Routing Table Convergence:
- Monitor how the routers update their routing tables according to the Bellman-Ford algorithm. Each router swapped routing updates with its neighbours to assess the shortest path to other nodes.
- Traffic Flow:
- Examine the flow of traffic from Host1 to Host2 and check that RIP effectively calculates the optimal route among them.
- RIP Control Traffic:
- Observe the control messages swapped among the routers, like RIP updates that encompass routing information.
- Route Stability:
- Verify how rapidly the routing tables converge after network initialization or topology changes (e.g., link failures or restorations).
- Performance Metrics:
- End-to-End Delay: Compute the time taken for packets to navigate the network.
- Throughput: Investigate the overall data throughput among the hosts.
- Packet Loss: Ascertain if any packets were lost because of the routing issues or link failures.
- Simulate Dynamic Network Conditions
We can be mimicked dynamic conditions to experiment how the Bellman-Ford algorithm (RIP) adjusts to network changes:
- Link Failures:
- Replicate a link failure by disabling a link among two routers and monitor how the routing tables adjust to the change.
# Simulate link failure by disabling the connection between router1 and router2
*.router1.ethg[1].disable = true
- Congestion:
- Launch numerous traffic flows to mimic network congestion and monitor how RIP manages congestion and reroutes traffic.
- Latency and Packet Loss:
- Launch delays or packet loss on particular links to experiment how RIP manages the network reliability issues.
- Extend the Simulation
- Test with Larger Topologies:
- Maximizes the amount of routers and hosts to make a more complex network and monitor how the Bellman-Ford algorithm scales with network size.
- Implement Custom Bellman-Ford Protocol:
- If we require more control or customization then we can execute the Bellman-Ford algorithm from scratch by making own C++ modules for routing and distance vector updates.
- Compare with Other Routing Protocols:
- Replicate other routing protocols such as OSPF (which uses link-state routing) and compare their performance with RIP (Bellman-Ford) such as convergence time, control traffic overhead, and path optimality.
This demonstration contained the simple method using instance coding for Bellman Ford Routing projects, which were simulated and extended, with more insights to be added.
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