ECN2

ECN2 is a proposed extension to Explicit Congestion Notification (ECN) in IP networking. It is discussed as a way to improve signaling of intermediate network congestion and to enable end hosts to react faster and more accurately than with traditional ECN alone, without resorting to packet loss as the primary cue.

Conceptually, ECN2 would build on the existing ECN mechanism, which marks packets to indicate congestion rather than dropping them. ECN2 aims to provide more granular or robust congestion signaling, potentially through new signaling primitives, expanded codepoints, or cooperative behavior between routers and endpoints. Any practical implementation would require negotiation and widespread support along the forwarding path, while preserving backward compatibility so non-ECN2-capable nodes can ignore the additional signaling without breaking communication.

Development status and standardization efforts: ECN2 has appeared mainly in academic discussions, experimental protocols, and some interoperability studies. There is no widely adopted standard or production deployment as of now, and ECN2 remains outside conventional IETF standards tracks. Research work typically evaluates performance, interoperability with legacy ECN, and the complexity of deploying new signaling in diverse networks.

Potential benefits and considerations: If adopted, ECN2 could reduce retransmissions and improve throughput on congested paths, particularly in high-latency or lossy networks. Benefits depend on compatible congestion-control algorithms and consistent interpretation of the signaling. Challenges include ensuring interoperability with existing ECN implementations, securing the signaling against abuse, and managing incremental deployment across routers and endpoints.

See also: Explicit Congestion Notification, ECN, congestion control, network signaling.