Changing the Default QUIC ACK Policy
draft-fairhurst-quic-ack-scaling-00

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Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                A. Custura
Intended status: Informational                                  T. Jones
Expires: July 31, 2020                            University of Aberdeen
                                                        January 28, 2020

                  Changing the Default QUIC ACK Policy
                  draft-fairhurst-quic-ack-scaling-00

Abstract

   On network paths where there is significant path asymmetry,
   acknowledgments of data receipt can reduce the efficient use of
   network capacity.  This effect occurs when the return capacity is
   significantly more constrained than the forward capacity, or the cost
   of transmission per packet is a significant component of the total
   transmission cost.  In these cases, reducing the ratio of
   acknowledgements to data can improve link utilization and reduce link
   transmission costs.

   This document proposes a change to the default acknowledgement policy
   of the QUIC transport protocol to improve performance over paths with
   appreciable asymmetry.

Status of This Memo

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

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   This Internet-Draft will expire on July 31, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Internet-Draft    Changing the Default QUIC ACK Policy      January 2020

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  ACK Ratio Impact on Asymmetric Paths  . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Adapting the ACK Ratio in Current Transport
           Specifications  . . . . . . . . . . . . . . . . . . . . .   3
     2.4.  Adapting the ACK Ratio in the Network . . . . . . . . . .   4
   3.  Updating the Default ACK Ratio for QUIC . . . . . . . . . . .   4
     3.1.  Considerations Updating the Default QUIC ACK Policy . . .   4
     3.2.  During Slow Start . . . . . . . . . . . . . . . . . . . .   5
     3.3.  After Slow Start  . . . . . . . . . . . . . . . . . . . .   6
     3.4.  When Encountering Loss/Congestion . . . . . . . . . . . .   6
     3.5.  Further Tuning of the ACK Policy  . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Summary of Recommended ACK Policy for TCP  . . . . .   8
   Appendix B.  Experiments Exploring an ACK Ratio of 1:10 . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The current design of QUIC currently proposes a default
   acknowledgement (ACK) ratio of 1:2 (at least one ACK for each 2 data
   packets) inspired by current recommendations for TCP, Appendix A,
   see.  This document proposes an increase in the ratio of ACK packets
   to data packets from 1:2 to 1:10 for QUIC flows, once a flow has
   exited slow start.

2.  Motivation

   When the characteristics of the forward and return paths are not
   symmetric, the transmission of ACKs can adversely impact either
   transport performance or the cost of sending data across a link.

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