Active Queue Management (AQM) Based on Proportional Integral Controller Enhanced PIE) for Data-Over-Cable Service Interface Specifications (DOCSIS) Cable Modems
RFC 8034

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Internet Engineering Task Force (IETF)                          G. White
Request for Comments: 8034                                     CableLabs
Category: Informational                                           R. Pan
ISSN: 2070-1721                                            Cisco Systems
                                                           February 2017

                 Active Queue Management (AQM) Based on
          Proportional Integral Controller Enhanced (PIE) for
 Data-Over-Cable Service Interface Specifications (DOCSIS) Cable Modems

Abstract

   Cable modems based on Data-Over-Cable Service Interface
   Specifications (DOCSIS) provide broadband Internet access to over one
   hundred million users worldwide.  In some cases, the cable modem
   connection is the bottleneck (lowest speed) link between the customer
   and the Internet.  As a result, the impact of buffering and
   bufferbloat in the cable modem can have a significant effect on user
   experience.  The CableLabs DOCSIS 3.1 specification introduces
   requirements for cable modems to support an Active Queue Management
   (AQM) algorithm that is intended to alleviate the impact that
   buffering has on latency-sensitive traffic, while preserving bulk
   throughput performance.  In addition, the CableLabs DOCSIS 3.0
   specifications have also been amended to contain similar
   requirements.  This document describes the requirements on AQM that
   apply to DOCSIS equipment, including a description of the
   "DOCSIS-PIE" algorithm that is required on DOCSIS 3.1 cable modems.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8034.

White & Pan                   Informational                     [Page 1]
RFC 8034          PIE-Based AQM for DOCSIS Cable Modems    February 2017

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   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview of DOCSIS AQM Requirements . . . . . . . . . . . . .   3
   3.  The DOCSIS MAC Layer and Service Flows  . . . . . . . . . . .   4
   4.  DOCSIS-PIE vs. PIE  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Latency Target  . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Departure Rate Estimation . . . . . . . . . . . . . . . .   6
     4.3.  Enhanced Burst Protection . . . . . . . . . . . . . . . .   7
     4.4.  Expanded Auto-Tuning Range  . . . . . . . . . . . . . . .   7
     4.5.  Trigger for Exponential Decay . . . . . . . . . . . . . .   8
     4.6.  Drop Probability Scaling  . . . . . . . . . . . . . . . .   8
     4.7.  Support for Explicit Congestion Notification  . . . . . .   8
   5.  Implementation Guidance . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  DOCSIS-PIE Algorithm Definition  . . . . . . . . . .  11
     A.1.  DOCSIS-PIE AQM Constants and Variables  . . . . . . . . .  11
       A.1.1.  Configuration Parameters  . . . . . . . . . . . . . .  11
       A.1.2.  Constant Values . . . . . . . . . . . . . . . . . . .  11
       A.1.3.  Variables . . . . . . . . . . . . . . . . . . . . . .  12
       A.1.4.  Public/System Functions . . . . . . . . . . . . . . .  12
     A.2.  DOCSIS-PIE AQM Control Path . . . . . . . . . . . . . . .  13
     A.3.  DOCSIS-PIE AQM Data Path  . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

White & Pan                   Informational                     [Page 2]