To simulate Hot Potato Routing in MATLAB environment which is also known as deflection routing that is a technique utilized within networks in which packets are sent to the next hop without being queued. If several packets contend for the similar outgoing link then they are “deflected” or transmitted along alternative paths, which regardless of the optimality of the path, to prevent the congestion or buffer delays.
This is a general method in optical networks and high-speed interconnects in which queuing packets can lead to important latency. In this MATLAB simulation, if the ideal path is congested then we will design a network in which each node deflects packets.
Steps to Simulate Hot Potato Routing in MATLAB
- Define the Network Topology and Link Costs:
- Signify the network using an adjacency matrix. Each entry in the matrix denotes the cost among nodes, and a huge value like inf specifics no direct connection.
% Define the number of nodes and network area
numNodes = 6;
infCost = inf; % Large value representing no direct link
% Define the adjacency matrix for link costs (undirected graph)
linkCosts = [0 1 infCost 3 infCost 2;
1 0 1 infCost infCost infCost;
infCost 1 0 2 3 infCost;
3 infCost 2 0 infCost 2;
infCost infCost 3 infCost 0 1;
2 infCost infCost 2 1 0];
% Display the link costs for verification
disp(‘Network Link Costs:’);
disp(linkCosts);
- Initialize Packet Information and Network State:
- Describe the packets that containing its source and destination nodes. Also, introduce a traffic load matrix to keep trace of packet paths and identify the potential disagrees for each link.
% Define packets with source, destination, and current position
packets = [
1, 5; % Packet from Node 1 to Node 5
2, 4; % Packet from Node 2 to Node 4
3, 6; % Packet from Node 3 to Node 6
];
% Initialize matrix to track link utilization
linkUtilization = zeros(numNodes);
- Implement Dijkstra’s Algorithm to Find Optimal Paths:
- Calculate the shortest path from each node to every other node utilizing Dijkstra’s algorithm. This path will perform as an instruction, however it possibly diverged from if links are engaged.
function [distances, previous] = dijkstra(linkCosts, sourceNode)
numNodes = size(linkCosts, 1);
distances = inf(1, numNodes); % Distance vector
distances(sourceNode) = 0;
previous = -1 * ones(1, numNodes); % Previous node for path reconstruction
visited = false(1, numNodes);
for i = 1:numNodes
[~, u] = min(distances + inf * visited);
visited(u) = true;
% Update distances for each neighbor
for v = 1:numNodes
if linkCosts(u, v) < inf && ~visited(v)
alt = distances(u) + linkCosts(u, v);
if alt < distances(v)
distances(v) = alt;
previous(v) = u;
end
end
end
end
end
- Simulate Packet Forwarding with Hot Potato Routing:
- For each packet, attempt to send it along the shortest path to their destination. If the preferred link is previously in use (based on linkUtilization) then turn aside the packet to other neighbor with the succeeding lowest cost link.
% Initialize packet positions (current nodes)
packetPositions = packets(:, 1);
% Run routing simulation for a set number of time steps
maxSteps = 10;
for step = 1:maxSteps
disp([‘Time Step ‘, num2str(step)]);
newLinkUtilization = zeros(numNodes); % Reset for each step
% Process each packet individually
for p = 1:size(packets, 1)
currentNode = packetPositions(p);
destinationNode = packets(p, 2);
% Check if packet has reached its destination
if currentNode == destinationNode
disp([‘Packet ‘, num2str(p), ‘ reached its destination: Node ‘, num2str(destinationNode)]);
continue;
end
% Find shortest path from current node to destination
[distances, previous] = dijkstra(linkCosts, currentNode);
nextHop = previous(destinationNode);
% If optimal next hop link is occupied, select an alternate route
if newLinkUtilization(currentNode, nextHop) > 0
disp([‘Packet ‘, num2str(p), ‘ deflected at Node ‘, num2str(currentNode)]);
% Find alternate neighbors with lower link cost
neighbors = find(linkCosts(currentNode, 🙂 < inf);
deflected = false;
for n = 1:length(neighbors)
altNextHop = neighbors(n);
if altNextHop ~= nextHop && newLinkUtilization(currentNode, altNextHop) == 0
nextHop = altNextHop;
deflected = true;
break;
end
end
% If no alternate route, continue along original path
if ~deflected
disp([‘Packet ‘, num2str(p), ‘ has no alternate path, taking original next hop.’]);
end
end
% Move packet to next hop
packetPositions(p) = nextHop;
newLinkUtilization(currentNode, nextHop) = newLinkUtilization(currentNode, nextHop) + 1;
newLinkUtilization(nextHop, currentNode) = newLinkUtilization(nextHop, currentNode) + 1; % Undirected
end
% Update link utilization for next step
linkUtilization = newLinkUtilization;
end
- Display the Packet Paths and Deflections:
- Indicate the path taken by each packet and any deflections that happened, after the simulation ends.
disp(‘Final Packet Positions:’);
for p = 1:size(packets, 1)
fprintf(‘Packet from Node %d to Node %d final position: Node %d\n’, packets(p, 1), packets(p, 2), packetPositions(p));
end
- Visualize the Network and Packet Paths:
- Visualize the network topology and then display the paths each packet takes with any deflections.
% Define node positions for visualization
nodePositions = [10 10; 20 10; 20 20; 10 20; 15 25; 25 15];
figure;
hold on;
% Plot links
for i = 1:numNodes
for j = i+1:numNodes
if linkCosts(i, j) < infCost
plot([nodePositions(i, 1), nodePositions(j, 1)], [nodePositions(i, 2), nodePositions(j, 2)], ‘k–‘);
end
end
plot(nodePositions(i, 1), nodePositions(i, 2), ‘bo’); % Plot nodes
text(nodePositions(i, 1), nodePositions(i, 2), num2str(i), ‘VerticalAlignment’, ‘bottom’, ‘HorizontalAlignment’, ‘center’);
end
% Highlight initial and destination nodes for each packet
for p = 1:size(packets, 1)
sourceNode = packets(p, 1);
destinationNode = packets(p, 2);
plot(nodePositions(sourceNode, 1), nodePositions(sourceNode, 2), ‘go’, ‘MarkerSize’, 10, ‘MarkerFaceColor’, ‘g’);
plot(nodePositions(destinationNode, 1), nodePositions(destinationNode, 2), ‘ro’, ‘MarkerSize’, 10, ‘MarkerFaceColor’, ‘r’);
end
title(‘Network Topology with Hot Potato Routing’);
hold off;
Explanation of Key Components
- Dijkstra’s Algorithm for Path Calculation: Each packet discovers the best next hop utilizing Dijkstra’s shortest path algorithm however may not always utilize it because of the potential deflections.
- Link Utilization Tracking: Keeps follow of the present load on each link, which finding once deflections are required.
- Deflection Mechanism: If an intended link of packet is busy then it is deflected to an alternative neighbor that potentially leading to an extended path.
- Visualization: The network topology and packet routes are display how packets are deflected and the last paths they take.
Possible Extensions
- Dynamic Traffic Generation: Replicate the packet arrivals over time to monitor ongoing deflections and its influence on network performance.
- Performance Metrics: Calculate performance parameters such as the number of deflections, average path length, and latency to estimate the effectiveness of hot potato routing.
- Randomized Deflection: Rather than the next lowest-cost link, execute the random deflection to examine the influence on packet paths.
By applying MATLAB tool, we conducted an extensive simulation process of the Hot Potato Routing Projects, which were simulated and visualized in this manual. If needed, we can explore this project further and offer complete information.
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