An Argument for Increasing TCP's Initial Congestion Window Again
11 days ago
- #TCP
- #Networking
- #Performance
- Google increased TCP's initial congestion window from 1 to 10 in 2011 to improve web performance.
- Modern internet traffic, especially web pages and API calls, suffers from slow initial congestion window settings.
- TCP's initial congestion window affects how much data can be sent at the start of a connection, impacting load times.
- Google's 2011 adjustment allowed 85% of assets to load in one round trip, but modern web bloat requires further changes.
- Increasing the initial congestion window too much risks causing congestion and bufferbloat.
- Google's BBR congestion control algorithm helps by monitoring congestion rather than packet loss.
- Recommendations include increasing the initial congestion window to 20-40 and adopting BBR for web servers.
- QUIC, Google's HTTP over UDP protocol, bypasses TCP congestion issues but is often disabled by enterprises.
- TCP tuning remains important for legacy devices and networks that disable QUIC.
- A careful increase in TCP's initial congestion window, paired with BBR, can improve modern internet performance.