Editing Network congestion (section)

====Explicit Congestion Notification====
Another approach is to use [[Explicit Congestion Notification]] (ECN).<ref>RFC 3168 - The Addition of Explicit Congestion Notification (ECN) to IP</ref> ECN is used only when two hosts signal that they want to use it. With this method, a protocol bit is used to signal explicit congestion. This is better than the indirect congestion notification signaled by packet loss by the RED/WRED algorithms, but it requires support by both hosts.<ref>[http://citeseer.ist.psu.edu/bagal99comparative.html Comparative study of RED, ECN and TCP Rate Control (1999)]</ref><ref name="FloydRED"/>

When a router receives a packet marked as ECN-capable and the router anticipates congestion, it sets the ECN flag, notifying the sender of congestion. The sender should respond by decreasing its transmission bandwidth, e.g., by decreasing its sending rate by reducing the TCP window size or by other means.

The [[L4S]] protocol is an enhanced version of ECN which allows senders to collaborate with network devices to control congestion.<ref>{{Cite web |date=2023-06-14 |title=L4S |url=https://www.bell-labs.com/research-innovation/projects-and-initiatives/l4s/ |access-date=2025-01-31 |website=Nokia Bell Labs |language=en}}</ref>