Queue Protection to Preserve Low Latency
draft-briscoe-docsis-q-protection-00

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Transport Area Working Group                             B. Briscoe, Ed.
Internet-Draft                                                  G. White
Intended status: Informational                                 CableLabs
Expires: January 9, 2020                                    July 8, 2019

                Queue Protection to Preserve Low Latency
                  draft-briscoe-docsis-q-protection-00

Abstract

   This informational document defines and explains the specification of
   the queue protection algorithm used in DOCSIS 3.1.  It is believed
   this algorithm will be useful in scenarios other than DOCSIS.  A
   shared low latency queue relies on the non-queue-building behaviour
   of every traffic flow using it.  However, some flows might not take
   such care, either accidentally or maliciously.  If a queue is about
   to exceed a threshold level of delay, the queue protection algorithm
   can rapidly detect the flow(s) most likely to be responsible.  It can
   then prevent selected packets of these flows (or whole flows) from
   harming the queuing delay of other traffic in the low latency queue.

Status of This Memo

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   This Internet-Draft will expire on January 9, 2020.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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Briscoe & White          Expires January 9, 2020                [Page 1]
Internet-Draft  Queue Protection to Preserve Low Latency       July 2019

   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Document Roadmap  . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Approach - In Brief . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Mechanism . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Policy  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Necessary Flow Behaviour  . . . . . . . . . . . . . . . . . .   6
   4.  Pseudocode Walk-Through . . . . . . . . . . . . . . . . . . .   7
     4.1.  Input Parameters, Constants and Variables . . . . . . . .   8
     4.2.  Queue Protection Data Path  . . . . . . . . . . . . . . .   9
   5.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Rationale: Blame for Queuing, not for Rate in Itself  . .  14
     5.2.  Rationale for Aging the Queuing Score . . . . . . . . . .  17
     5.3.  Rationale for Normalized Queuing Score  . . . . . . . . .  17
     5.4.  Rationale for Policy Conditions . . . . . . . . . . . . .  18
   6.  Limitations . . . . . . . . . . . . . . . . . . . . . . . . .  20
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   9.  Comments Solicited  . . . . . . . . . . . . . . . . . . . . .  21
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  21
     11.2.  Informative References . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

1.  Introduction

   This informational document defines and explains the specification of
   the queue protection (QProt) algorithm used in DOCSIS 3.1
   [DOCSIS3.1].  It is believed this algorithm will be useful in
   scenarios other than DOCSIS.

   Low queuing delay depends on hosts sending their data smoothly either
   at low rate or responding to explicit congestion notifications (ECN).
   So low latency is something hosts create themselves, not something
   the network gives them.  Therefore, there is no incentive for flows
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