What are the key takeaways from “TCP b : Additive Increase Multiplicative Decrease & 'Slow Start' - Computerphile” on Computerphile?

What is this episode about?

TCP remains the backbone of internet communication by balancing reliability with congestion control, despite being designed in the 1980s. While classroom models suggest a clean 'sawtooth' pattern of packet flow, real-world data reveals a much messier, complex reality where protocols must adapt to unpredictable network conditions without the ability to significantly change their rigid header structures.