To simulate an Exterior Gateway Protocols (EGPs), like BGP (Border Gateway Protocol) that includes constructing a network, which associates various autonomous systems (ASes) and executing the BGP protocol for routing among these systems. BGP is the most broadly utilized EGP, and replicating their behavior can support examine inter-domain routing, path selection, and policy enforcement within real-world Internet-like networks.
We can follow the below procedure on how to simulate an exterior gateway protocol (such as BGP) in MATLAB:
Steps to Simulate BGP in MATLAB
- Define Network Topology with Autonomous Systems
- BGP is utilized to route traffic amongst autonomous systems (ASes). Thus, network topology has to contain several ASes, with routers in each AS connected to routers within other ASes.
Example of describing several autonomous systems and the routers within them:
numAS = 3; % Number of autonomous systems
routersPerAS = [3, 2, 4]; % Number of routers in each AS
totalRouters = sum(routersPerAS); % Total number of routers in the network
% Define network topology: Routers within each AS and connections between ASes
adjacencyMatrix = inf(totalRouters); % Initialize with infinite distances
% Intra-AS connections (local routing within each AS)
adjacencyMatrix(1,2) = 1; adjacencyMatrix(2,1) = 1;
adjacencyMatrix(2,3) = 2; adjacencyMatrix(3,2) = 2;
adjacencyMatrix(4,5) = 1; adjacencyMatrix(5,4) = 1;
% Inter-AS connections (BGP peering links between ASes)
adjacencyMatrix(3,5) = 3; adjacencyMatrix(5,3) = 3; % Peering between AS1 and AS2
adjacencyMatrix(5,7) = 4; adjacencyMatrix(7,5) = 4; % Peering between AS2 and AS3
adjacencyMatrix(1,6) = 5; adjacencyMatrix(6,1) = 5; % Peering between AS1 and AS3
- Implement BGP Path Selection Logic
- BGP chooses routes according to the policies, which not simply the shortest path. A router selects a path to attain a destination network rely on AS-Path, Local Preference, MED (Multi-Exit Discriminator), and so on.
BGP path selection can be replicated utilizing the following rules:
- Shortest AS-Path.
- Highest local preference.
- Lowest MED (if applicable).
- Closest egress point in the AS (lowest IGP cost).
Example of BGP path selection:
function [selectedPath] = bgpPathSelection(paths)
% paths: A cell array where each entry is an AS-Path
if isempty(paths)
selectedPath = []; % No path available
return;
end
% Selection based on shortest AS-Path
pathLengths = cellfun(@length, paths);
[~, idx] = min(pathLengths);
selectedPath = paths{idx};
end
% Example paths (AS paths to destination)
paths = {[1, 2, 3], [1, 3], [1, 4, 3]};
selectedPath = bgpPathSelection(paths);
disp([‘Selected BGP path: ‘, num2str(selectedPath)]);
- Implement BGP Route Advertisement and Propagation
- BGP routers propagate routes amongst ASes by publicizing its optimal path to adjacent BGP peers. Every single router updates their routing table depends on the paths received from its neighbors.
Example of BGP route advertisement:
function [updatedTable] = bgpRouteAdvertisement(routingTable, neighborTable, neighborID, asPath)
% Update routing table based on received routes from neighbor
for i = 1:length(asPath)
if ~ismember(asPath(i), routingTable{neighborID}) % If the AS-Path is new
routingTable{neighborID} = [routingTable{neighborID}; asPath];
end
end
updatedTable = routingTable;
end
% Example routing tables for routers
routingTable = cell(totalRouters, 1); % Each router has a routing table
asPathFromNeighbor = [1, 2, 3]; % AS-Path received from a neighbor
% Update routing table of router 5 with the received AS-Path
routingTable = bgpRouteAdvertisement(routingTable, routingTable, 5, asPathFromNeighbor);
- BGP Route Convergence
- Routers persist to broadcast updates until the network attains the convergence, which intends that every routers need a stable view of the optimal paths to all destination.
Example of iterating over routers for route convergence:
function routingTables = bgpConvergence(adjacencyMatrix, routingTables, maxIterations)
for iter = 1:maxIterations
for router = 1:size(adjacencyMatrix, 1)
neighbors = find(adjacencyMatrix(router, 🙂 < inf);
for neighbor = neighbors
% Receive routing updates from each neighbor
asPathFromNeighbor = routingTables{neighbor};
routingTables = bgpRouteAdvertisement(routingTables, routingTables, router, asPathFromNeighbor);
end
end
end
end
% Run the BGP convergence process
maxIterations = 10;
routingTables = bgpConvergence(adjacencyMatrix, routingTable, maxIterations);
- Simulate Data Transmission Based on BGP Routing
- When the routing tables converge then we replicate the transmission of data amongst source and destination routers rely on the chosen BGP paths.
Example of simulating data transmission:
function path = bgpFindPath(routingTable, src, dst)
% Find the path from source to destination based on BGP routing table
if isempty(routingTable{src}) || isempty(routingTable{dst})
path = []; % No path found
return;
end
path = routingTable{src}; % Get the AS path from src router
end
srcRouter = 1; % Starting point
dstRouter = 7; % Destination
path = bgpFindPath(routingTable, srcRouter, dstRouter);
disp([‘BGP path from ‘, num2str(srcRouter), ‘ to ‘, num2str(dstRouter), ‘: ‘, num2str(path)]);
- Analyze and Visualize BGP Routing and Network Performance
- Examine and compute the performance using parameters like routing convergence time, path length, routing stability, and network throughput, after replicating the BGP routing and data transmission.
Example of analyzing the average path length:
totalPathLength = 0;
numPaths = 0;
for i = 1:totalRouters
for j = i+1:totalRouters
path = bgpFindPath(routingTable, i, j);
if ~isempty(path)
totalPathLength = totalPathLength + length(path);
numPaths = numPaths + 1;
end
end
end
avgPathLength = totalPathLength / numPaths;
disp([‘Average path length: ‘, num2str(avgPathLength)]);
Also, we can envision the network and BGP paths utilizing MATLAB’s plotting functions:
figure;
plot(nodePositions(:,1), nodePositions(:,2), ‘bo’); % Plot nodes
hold on;
for i = 1:size(adjacencyMatrix, 1)
for j = i+1:size(adjacencyMatrix, 2)
if adjacencyMatrix(i,j) < inf
plot([nodePositions(i,1), nodePositions(j,1)], …
[nodePositions(i,2), nodePositions(j,2)], ‘r-‘);
end
end
end
title(‘Network Topology with BGP Peering Links’);
Conclusion
Replicating an exterior gateway protocol such as BGP within MATLAB that contains:
- Describing a network including several autonomous systems (ASes).
- Executing the BGP routing logic such as route propagation, AS-path selection, and policy enforcement.
- Mimicking BGP route convergence to attain the stable routing tables.
- Replicating data transmission relies on the computed paths.
- Examining performance parameters such as path length, routing overhead, and convergence time.
We elaborated on the sequential method guiding the Exterior Gateway Protocol projects using MATLAB platform. Upon request, we are equipped to provide comprehensive insights and delve deeper into this topic.
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