The State of ECN Adoption in the Internet#

Danesh Zeynali, Max Planck Institute for Informatics

• Why: L4S and low-latency transport depend on ECN surviving end-to-end; this re-measures adoption a decade after the classic studies and finds a specific, named blocker.
• What: A revisiting and extension of the Bauer and Trammell ECN characterization studies: the majority of Internet service infrastructure is now ECN-aware, but a nontrivial fraction of hosts, routers and middleboxes bleach ECN bits — and many hyper-giants bleach along the path, with substantial implications for L4S. IPv6 endpoints and paths show stronger ECN support than IPv4.
• How: Active measurements covering endpoint support (handshake negotiation), network support (marking and bleaching on path), and a longitudinal view.
• Where applicable: Anyone counting on ECN or L4S — including teams whose lossless/low-latency DC designs assume ECN works beyond the fabric; the hyper-giant bleaching is the deployment blocker to watch.