TCP Congestion Control has been a research topic for over 30 years. Since the pioneering work of Jacobson and Karels in the 1980s, hundreds of researchers have sought to improve the avoidance and control of congestion in the Internet. Over time, new ideas such as using delay as well as packet loss to detect congestion have taken hold. This book walks through all the key approaches and gives the reader a framework to understand the big picture and ongoing challenges of congestion control.