To simulate the Dijkstra’s Link-State Routing Algorithm using OMNeT++, which has requires to contain modeling a network in which each router uses link-state information to calculate the shortest paths to all other routers. The routers swap the link-state advertisements (LSAs) to build a topology map of the network, and Dijkstra’s algorithm is utilized to estimate the shortest path trees according to this topology.
In the INET framework for OMNeT++, we can be mimicked link-state routing using the OSPF (Open Shortest Path First) protocol that is rely on Dijkstra’s algorithm. OSPF is a broadly used link-state routing protocol, which computes the shortest path for each node using Dijkstra’s algorithm.
We will instruct you through the step-by-step procedure to simulating Dijkstra’s Link-State Routing (via OSPF) in OMNeT++:
Steps to Simulate Dijkstra’s Link-State Projects in OMNeT++
Step 1: Install OMNeT++ and INET Framework
Make certain that OMNeT++ and the INET framework are installed. INET offers built-in support for OSPF that executes Dijkstra’s algorithm for link-state routing.
- Download OMNeT++: OMNeT++ official website
- Download INET Framework: INET Framework
Step 2: Define the Network Topology in the NED File
We require to describe a network with routers and hosts. For each router will be utilized OSPF to compute the shortest paths to all other routers within the network using Dijkstra’s algorithm.
Here’s an instance NED file for a simple network, which supports link-state routing:
network LinkStateNetwork
{
submodules:
host1: StandardHost {
@display(“p=100,200”);
}
host2: StandardHost {
@display(“p=500,200”);
}
router1: Router {
@display(“p=200,300”);
}
router2: Router {
@display(“p=300,300”);
}
router3: Router {
@display(“p=400,300”);
}
connections:
host1.ethg++ <–> Eth100M <–> router1.ethg++;
router1.ethg++ <–> Eth100M <–> router2.ethg++;
router2.ethg++ <–> Eth100M <–> router3.ethg++;
router3.ethg++ <–> Eth100M <–> host2.ethg++;
}
In this topology:
- host1 and host2 are the end devices.
- router1, router2, and router3 will use OSPF to calculate the shortest paths.
Step 3: Enable OSPF (Link-State Routing) in INET Framework
To replicate Dijkstra’s link-state routing, set up OSPF as the routing protocol for each router. OSPF uses Dijkstra’s algorithm to evaluate the shortest paths according to the link-state data collected from other routers.
Step 3.1: Assign IP Addresses
In the omnetpp.ini file, allocate an IP addresses to each host and router in the network.
[Config LinkStateNetworkSimulation]
network = LinkStateNetwork
sim-time-limit = 100s
# Assign IPv4 addresses to hosts and routers
*.host1.ipv4.config = “manual”
*.host1.ipv4.addresses = “10.0.0.1/24”
*.host2.ipv4.config = “manual”
*.host2.ipv4.addresses = “10.0.3.1/24”
*.router1.ipv4.config = “manual”
*.router1.ipv4.addresses = “10.0.0.254/24 10.0.1.1/24”
*.router2.ipv4.config = “manual”
*.router2.ipv4.addresses = “10.0.1.254/24 10.0.2.1/24”
*.router3.ipv4.config = “manual”
*.router3.ipv4.addresses = “10.0.2.254/24 10.0.3.254/24”
In this configuration:
- host1 has the IP address 10.0.0.1/24.
- host2 has the IP address 10.0.3.1/24.
- router1, router2, and router3 have two interfaces, each connected to a distinct subnet.
Step 3.2: Enable OSPF on the Routers
Allow OSPF as the routing protocol for each router to execute the link-state routing using Dijkstra’s algorithm.
# Enable OSPF on all routers
*.router1.hasOspf = true
*.router1.routingTable.ospfRouterID = “1.1.1.1”
*.router1.routingTable.ospfAreaID = “0.0.0.0”
*.router1.interfaceTable[0].ospfInterfaceType = “broadcast”
*.router1.interfaceTable[1].ospfInterfaceType = “broadcast”
*.router2.hasOspf = true
*.router2.routingTable.ospfRouterID = “2.2.2.2”
*.router2.routingTable.ospfAreaID = “0.0.0.0”
*.router2.interfaceTable[0].ospfInterfaceType = “broadcast”
*.router2.interfaceTable[1].ospfInterfaceType = “broadcast”
*.router3.hasOspf = true
*.router3.routingTable.ospfRouterID = “3.3.3.3”
*.router3.routingTable.ospfAreaID = “0.0.0.0”
*.router3.interfaceTable[0].ospfInterfaceType = “broadcast”
*.router3.interfaceTable[1].ospfInterfaceType = “broadcast”
# Enable OSPF debug logging (optional)
*.router1.routingTable.ospfDebug = true
*.router2.routingTable.ospfDebug = true
*.router3.routingTable.ospfDebug = true
Step 4: Simulate Traffic Between Hosts
To experiment the routing functionality, mimic UDP traffic among the host1 and host2.
# Simulate UDP traffic from host1 to host2
*.host1.numApps = 1
*.host1.app[0].typename = “UdpBasicApp”
*.host1.app[0].localAddress = “10.0.0.1”
*.host1.app[0].connectAddress = “10.0.3.1”
*.host1.app[0].sendInterval = 1s
*.host1.app[0].messageLength = 512B
*.host1.app[0].startTime = 10s
# Configure host2 to receive UDP traffic
*.host2.numApps = 1
*.host2.app[0].typename = “UdpSinkApp”
In this configuration:
- host1 makes UDP traffic and transmits it to host2.
- host2 receives the traffic as a sink.
Step 5: Run the Simulation
When we have configure the network topology and configured OSPF:
- Build and compile the project within OMNeT++.
- Run the simulation using the OMNeT++ GUI or from the command line.
- Observe OSPF behavior: Utilize the OMNeT++ GUI to envision packet flow, routing table updates, and OSPF message exchanges (such as link-state advertisements).
Step 6: Analyze Simulation Results
OMNeT++ makes .sca and .vec files encompassing simulation outcomes. We can be examined numerous key parameters related to link-state routing and OSPF performance:
- Shortest Path Calculation: Monitor how OSPF uses Dijkstra’s algorithm to estimate the shortest paths among the routers.
- Routing Table Updates: Monitor how routers update their routing tables according to the link-state information.
- End-to-End Delay: Compute the time it takes for packets to travel from host1 to host2 via the OSPF-calculated shortest path.
- Packet Delivery Ratio: Estimate the percentage of packets effectively delivered among the two hosts.
- Network Convergence Time: Examine how rapidly OSPF converges to a stable state after network changes.
We can be utilized OMNeT++’s built-in tools to envision these outcomes and better understand the effectiveness of Dijkstra’s algorithm in determining the shortest paths.
Step 7: Extend the Simulation
We can expand the simulation by testing with several configurations and scenarios:
7.1: Simulate Link Failures
Mimic link failures to monitor how OSPF recalculates the shortest paths and re-establishes routes utilizing Dijkstra’s algorithm.
# Simulate a link failure between router1 and router2 at 50 seconds
*.router1.interfaceTable[1].downAt = 50s
7.2: Modify OSPF Link Costs
Change the OSPF link costs to impact how Dijkstra’s algorithm computes the shortest paths. Higher-cost links are less favoured in the routing decisions.
# Set OSPF link costs
*.router1.interfaceTable[0].ospfCost = 10 # Higher cost
*.router1.interfaceTable[1].ospfCost = 1 # Lower cost
7.3: Add More Routers and Hosts
Extend the network by inserting more routers and hosts to mimic the larger networks. It will be permitted to observe how OSPF manages more complex topologies and how Dijkstra’s algorithm scales.
network LargerLinkStateNetwork
{
submodules:
host1: StandardHost;
host2: StandardHost;
router1: Router;
router2: Router;
router3: Router;
router4: Router; // Add more routers
router5: Router;
connections:
host1.ethg++ <–> Eth100M <–> router1.ethg++;
router1.ethg++ <–> Eth100M <–> router2.ethg++;
router2.ethg++ <–> Eth100M <–> router3.ethg++;
router3.ethg++ <–> Eth100M <–> router4.ethg++;
router4.ethg++ <–> Eth100M <–> router5.ethg++;
router5.ethg++ <–> Eth100M <–> host2.ethg++;
}
7.4: Simulate Network Congestion
Maximizes the traffic load and monitor how the shortest path alters actively when the network becomes congested.
# Increase traffic load to simulate congestion
*.host1.app[0].sendInterval = 0.1s # Increase message rate
Step 8: Visualize the Routing Process
OMNeT++ offers visualization tools to animate the packet flow and routing updates. It is especially helpful for knowing how OSPF estimates the shortest paths and adjusts to network changes.
Summary of Steps:
- Install OMNeT++ and INET Framework: Make certain the simulation environment is configure.
- Define Network Topology: Utilize a NED file to make a network of routers and hosts.
- Enable OSPF for Link-State Routing: Set up OSPF to replicate Dijkstra’s link-state algorithm.
- Simulate Traffic: Generate traffic among the hosts to experiment the routing.
- Run the Simulation: Monitor OSPF’s behaviour and how it calculates the shortest paths.
- Analyze Results: Estimate OSPF’s performance and routing decisions.
- Extend the Simulation: Testwith larger networks, link failures, and distinct OSPF configurations.
- Visualize the Routing Process: Utilize OMNeT++’s tools to monitor how OSPF adjusts to changes.
These basic techniques was illustrated through instance coding for Dijkstra’s link state projects, which were simulated, analysed, and vistualized via OMNeT++ tool. If you want more informations, we will be shared in forthcoming manual. phdprime.com offers exceptional guidance for Dijkstra’s Link State Projects utilizing OMNeT++ simulations. We encourage you to stay connected with us, as we are committed to providing you with the support you need for optimal results.
