runtime/network-tomography.mjs

// Application 2: Network Tomography / Packet Loss Counting
// Assign DSS weights to packet sequence numbers in multicast.
// Receiver reports aggregate of received weights.
// Sender determines EXACTLY how many packets arrived from the sum alone.

import { computeGreedySequence, buildCardinalityTable } from './greedy.mjs';

export function runNetworkTomographyDemo() {
  console.log('='.repeat(70));
  console.log('  NETWORK TOMOGRAPHY via DSS WEIGHTS');
  console.log('  Aggregate ACK reveals packet count in O(1)');
  console.log('='.repeat(70));
  console.log();

  const NUM_PACKETS = 15;
  const weights = computeGreedySequence(NUM_PACKETS);
  const table = buildCardinalityTable(weights);

  console.log(`Multicast stream: ${NUM_PACKETS} packets`);
  console.log(`DSS weights: [${weights.join(', ')}]`);
  console.log(`Total weight (all received): ${weights.reduce((a, b) => a + b, 0)}`);
  console.log(`Max weight: ${weights[NUM_PACKETS - 1]} (${Math.ceil(Math.log2(weights[NUM_PACKETS - 1] + 1))} bits per packet tag)`);
  console.log();

  // Simulate various loss patterns
  const scenarios = [
    { name: 'No loss', received: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14] },
    { name: '3 packets lost', received: [0,1,3,4,5,6,7,8,10,11,12,14] },
    { name: '7 packets lost', received: [0,2,5,6,9,11,13,14] },
    { name: 'Burst loss (middle)', received: [0,1,2,3,4,10,11,12,13,14] },
    { name: 'Only first arrived', received: [0] },
    { name: 'Total loss', received: [] },
  ];

  console.log('RECEIVER REPORTS:');
  console.log('-'.repeat(70));

  for (const scenario of scenarios) {
    const receivedWeights = scenario.received.map(i => weights[i]);
    const aggregateACK = receivedWeights.reduce((a, b) => a + b, 0);
    const detectedCount = aggregateACK === 0 ? 0 : (table.get(aggregateACK) ?? -1);

    console.log(`\n  ${scenario.name}:`);
    console.log(`    Received indices: [${scenario.received.join(',')}]`);
    console.log(`    Aggregate ACK value: ${aggregateACK}`);
    console.log(`    DSS Oracle: "${detectedCount} packets received"`);
    console.log(`    Actual: ${scenario.received.length} packets`);
    console.log(`    Correct: ${detectedCount === scenario.received.length ? 'YES' : 'NO'}`);
    console.log(`    Loss rate: ${((1 - scenario.received.length / NUM_PACKETS) * 100).toFixed(1)}%`);
  }

  console.log('\n' + '-'.repeat(70));
  console.log('\nPROTOCOL ADVANTAGE:');
  console.log('  Traditional ACK: Send bitmap of received packets (n bits)');
  console.log(`  DSS ACK: Send single integer (${Math.ceil(Math.log2(weights.reduce((a,b)=>a+b,0) + 1))} bits)`);
  console.log('  Savings: Constant-size ACK reveals reception COUNT instantly.');
  console.log('  Then targeted NACK for identity recovery within known cardinality.');
  console.log();

  return { weights, scenarios, table };
}