Controlled Delay Active Queue Management

Document Type Replaced Internet-Draft (individual in tsv area)
Last updated 2014-10-27 (latest revision 2014-03-03)
Replaced by draft-ietf-aqm-codel, draft-aqm-codel
Stream IETF
Intended RFC status Informational
Expired & archived
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Stream WG state (None)
Document shepherd No shepherd assigned
IESG IESG state Replaced by draft-ietf-aqm-codel, draft-aqm-codel
Telechat date
Responsible AD Martin Stiemerling
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The "persistently full buffer" problem has been discussed in the IETF community since the early 80's [RFC896]. The IRTF's End-to-End Working Group called for the deployment of active queue management (AQM) to solve the problem in 1998 [RFC2309]. Despite the awareness, the problem gotten worse as by Moore's Law growth in memory density fueled an exponential increase in buffer pool size. Efforts to deploy AQM have been frustrated by difficult configuration and negative impact on network utilization. The full buffer problem, recently christened "bufferbloat"[TSVBB2011, BB2011] has become increasingly important throughout the Internet but particularly at the consumer edge. To address bufferbloat, this document describes a general framework for controlling excessived delay in networks called Controlled Delay (CoDel) designed to work in modern networking environments as a part of the solution to bufferbloat [CODEL2012]. CoDel consists of an estimator, a setpoint, and a control loop and can be deployed in the Internet without configuration. CoDel comprises some major technical innovations and has been made available as open source so that the framework can be applied by the community to a range of problems. It has been implemented in Linux (and available in the Linux distribution) and deployed in some networks at the consumer edge. In addition, the framework has been successfully applied in other ways. Note: Code Components extracted from this document must include the license as included with the code in Section 5.


Kathleen Nichols (
Van Jacobson (

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