The Evolution of TCP Transport Protocols#

Geoff Huston

• Why: Congestion-control fundamentals cut across everything the PM touches — from lossless/DC fabrics to internet transport — and the shift from loss-based control to BBR (with ECN being reconsidered) changes how buffers should be sized and how traffic behaves on your network.
• What: A look at the fundamental feedback-loop problem in packet networking: various TCP flow control protocols, their relationship with network buffers, the reconsideration of explicit congestion notification, and the growth of BBR (from abstract only).
• How: Analysis of the design space of sender/receiver feedback loops — loss-based, delay/ECN-based, and model-based (BBR) — and how each interacts with buffer sizing in the network.
• Where applicable: Universal — every operator's queue/buffer behaviour is affected. Especially relevant as BBR-driven senders (large content/CDN players) increasingly set the tone for how paths are used.