Introduction to TCP Congestion Control
TCP congestion control is a fundamental mechanism that prevents network congestion by dynamically adjusting the sending rate of data based on network conditions. It’s a vital aspect of reliable data transmission over the internet.
The Slow Start Algorithm
The slow start algorithm is the initial phase of TCP congestion control. It begins with a small initial congestion window (cwnd) and exponentially increases it with each acknowledged segment received. This allows the sender to quickly probe the network for available bandwidth.
// Simplified Slow Start Example
let cwnd = 1000; // Initial congestion window size
let interval = 100; // Send interval in milliseconds
function sendData() {
// ... (Simulate sending data) ...
console.log("Data sent: " + cwnd);
// Adjust cwnd based on acknowledgements (simplified here)
if (cwnd < 10000) {
cwnd += 500;
}
}
Additive Increase Multiplicative Decrease (AIMD)
After the slow start phase, AIMD takes over. The congestion window increases linearly (additive) with each acknowledgement, but decreases multiplicatively if packet loss is detected. This provides a balance between exploring available bandwidth and reacting to congestion.