Editing Explicit Congestion Notification (section)

===ECN support in IP by routers===
Since ECN marking in routers is dependent on some form of [[active queue management]], routers must be configured with a suitable queue discipline in order to perform ECN marking.

Cisco IOS routers perform ECN marking if configured with the [[Weighted random early detection|WRED]] queuing discipline since version 12.2(8)T.

Linux routers perform ECN marking if configured with one of the [[Random Early Detection|RED]] or GRED queue disciplines with an explicit ''ecn'' parameter, by using the [[Stochastic Fair Blue|sfb]] discipline, by using the [[CoDel]] Fair Queuing (fq_codel) discipline, or the CAKE<ref name=":0">{{cite arXiv|title=Piece of CAKE: A Comprehensive Queue Management Solution for Home Gateways|last1=Høiland-Jørgensen|first1=Toke|last2=Täht|first2=Dave|last3=Morton|first3=Jonathan|year=2018|class=cs.NI|eprint=1804.07617v2}}</ref> queuing discipline.

Modern BSD implementations, such as [[FreeBSD]], [[NetBSD]] and [[OpenBSD]], have support for ECN marking in the [[ALTQ]] queueing implementation for a number of [[queuing discipline]]s, notably [[Random Early Detection|RED]] and [[Blue (queue management algorithm)|Blue]]. [[FreeBSD]] 11 included [[CoDel]], PIE, FQ-CoDel and FQ-PIE [[queuing discipline]]s implementation in [[ipfw]]/dummynet framework with ECN marking capability.<ref>{{cite web|title=Import Dummynet AQM version 0.2.1 (CoDel, FQ-CoDel, PIE and FQ-PIE) to FreeBSD 11|url=https://svnweb.freebsd.org/base?view=revision&revision=300779|website=The FreeBSD Project, FreeBSD r300779|access-date=5 August 2016}}</ref>