// Cloudflare Blog · 12 May 2026

When "idle" isn't idle: how a Linux kernel optimization became a QUIC bug

We investigated a bug where CUBIC's congestion window became pinned at its minimum floor, causing a performance to plummet. The fix involved correctly measuring idle periods to distinguish RTT wait times from actual application idleness.

Cloudflare Blog

@cloudflare-blog · Esteban Carisimo

blog.cloudflare.com

Cloudflare Blog@cloudflare-blog