The FlowQueue-CoDel Packet Scheduler and Active Queue Management Algorithm
draft-ietf-aqm-fq-codel-06

Document Type Active Internet-Draft (aqm WG)
Last updated 2016-04-04 (latest revision 2016-03-18)
Replaces draft-hoeiland-joergensen-aqm-fq-codel
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Intended RFC status Experimental
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Document shepherd Wesley Eddy
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IESG IESG state RFC Ed Queue
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RFC Editor RFC Editor state MISSREF
AQM working group                                 T. Hoeiland-Joergensen
Internet-Draft                                       Karlstad University
Intended status: Experimental                                P. McKenney
Expires: September 19, 2016                  IBM Linux Technology Center
                                                                 D. Taht
                                                                Teklibre
                                                               J. Gettys

                                                              E. Dumazet
                                                            Google, Inc.
                                                          March 18, 2016

    The FlowQueue-CoDel Packet Scheduler and Active Queue Management
                               Algorithm
                       draft-ietf-aqm-fq-codel-06

Abstract

   This memo presents the FQ-CoDel hybrid packet scheduler/Active Queue
   Management algorithm, a powerful tool for fighting bufferbloat and
   reducing latency.

   FQ-CoDel mixes packets from multiple flows and reduces the impact of
   head of line blocking from bursty traffic.  It provides isolation for
   low-rate traffic such as DNS, web, and videoconferencing traffic.  It
   improves utilisation across the networking fabric, especially for
   bidirectional traffic, by keeping queue lengths short; and it can be
   implemented in a memory- and CPU-efficient fashion across a wide
   range of hardware.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 19, 2016.

Hoeiland-Joergensen, etExpires September 19, 2016               [Page 1]
Internet-Draft                  fq-codel                      March 2016

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Conventions used in this document . . . . . . . . . . . .   4
     1.2.  Terminology and concepts  . . . . . . . . . . . . . . . .   4
     1.3.  Informal summary of FQ-CoDel  . . . . . . . . . . . . . .   5
   2.  CoDel . . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Flow Queueing . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  The FQ-CoDel scheduler  . . . . . . . . . . . . . . . . . . .   7
     4.1.  Enqueue . . . . . . . . . . . . . . . . . . . . . . . . .   7
       4.1.1.  Alternative classification schemes  . . . . . . . . .   8
     4.2.  Dequeue . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Implementation considerations . . . . . . . . . . . . . . . .  10
     5.1.  Data structures . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Parameters  . . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  Interval  . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.2.  Target  . . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.3.  Packet limit  . . . . . . . . . . . . . . . . . . . .  11
       5.2.4.  Quantum . . . . . . . . . . . . . . . . . . . . . . .  12
       5.2.5.  Flows . . . . . . . . . . . . . . . . . . . . . . . .  12
       5.2.6.  Explicit Congestion Notification (ECN)  . . . . . . .  12
       5.2.7.  CE threshold  . . . . . . . . . . . . . . . . . . . .  13
     5.3.  Probability of hash collisions  . . . . . . . . . . . . .  13
     5.4.  Memory Overhead . . . . . . . . . . . . . . . . . . . . .  13
     5.5.  Per-Packet Timestamping . . . . . . . . . . . . . . . . .  14
     5.6.  Limiting queueing in lower layers . . . . . . . . . . . .  15
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