Explore the intricacies of the Transmission Control Protocol (TCP) in this comprehensive 50-minute conference talk from SREcon19 Asia/Pacific. Delve into TCP's architecture, design principles, and core mechanisms, including the 3-way handshake, sliding window, reliability, and congestion control. Examine various enhancements and extensions proposed over the years to improve protocol efficiency. Learn about potential speed and efficiency improvements achievable through parameter tuning. Gain insights into advanced topics such as TCP slow start, fast retransmission, fast recovery, and loss recovery enhancements. Discover the impact of factors like bandwidth delay product, buffers, and congestion control algorithms on site speed improvements. Conclude with an introduction to modern protocols like QUIC and SCTP.