TCP Congestion Window

Animate cwnd slow-start and congestion avoidance with loss events (sawtooth).

About this tool

This teaching model starts with cwnd = 1. Slow Start doubles cwnd once per RTT until ssthresh; Congestion Avoidance then adds one segment per RTT. Choose one reproducible loss event. A timeout sets cwnd to 1 and resumes Slow Start; three duplicate ACKs halve ssthresh and continue in Congestion Avoidance. It is a Reno-style illustration, not a packet-level TCP implementation.