Why Does TCP Use a Sliding Window?
Over high-latency networks, naive Stop-and-Wait throughput collapses because the physical pipe sits empty for most of the Round Trip Time (RTT).
⚡ The Bandwidth-Delay Product (BDP)
$$\text{BDP} = \text{Bandwidth} \times \text{RTT}$$
On a 10 Gbps transatlantic link with 100ms RTT, BDP = 125 MB! Stop-and-Wait wastes 99.9% of that capacity.
🧠 4 Buffer Window Zones
- Zone 1 (ACKed): Safe to discard from RAM.
- Zone 2 (In-Flight): Emitted, awaiting ACK.
- Zone 3 (Usable): Permitted to send immediately.
- Zone 4 (Blocked): Outside advertised window.
Read the full interactive visualizer on Binary Dose.
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