QUIC Loss Detection and Congestion Control
draft-ietf-quic-recovery-24

Document Type Active Internet-Draft (quic WG)
Last updated 2019-11-04
Replaces draft-iyengar-quic-loss-recovery
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QUIC                                                     J. Iyengar, Ed.
Internet-Draft                                                    Fastly
Intended status: Standards Track                           I. Swett, Ed.
Expires: May 7, 2020                                              Google
                                                       November 04, 2019

               QUIC Loss Detection and Congestion Control
                      draft-ietf-quic-recovery-24

Abstract

   This document describes loss detection and congestion control
   mechanisms for QUIC.

Note to Readers

   Discussion of this draft takes place on the QUIC working group
   mailing list (quic@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/search/?email_list=quic [1].

   Working Group information can be found at https://github.com/quicwg
   [2]; source code and issues list for this draft can be found at
   https://github.com/quicwg/base-drafts/labels/-recovery [3].

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 7, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Iyengar & Swett            Expires May 7, 2020                  [Page 1]
Internet-Draft             QUIC Loss Detection             November 2019

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Design of the QUIC Transmission Machinery . . . . . . . . . .   5
     3.1.  Relevant Differences Between QUIC and TCP . . . . . . . .   5
       3.1.1.  Separate Packet Number Spaces . . . . . . . . . . . .   6
       3.1.2.  Monotonically Increasing Packet Numbers . . . . . . .   6
       3.1.3.  Clearer Loss Epoch  . . . . . . . . . . . . . . . . .   6
       3.1.4.  No Reneging . . . . . . . . . . . . . . . . . . . . .   7
       3.1.5.  More ACK Ranges . . . . . . . . . . . . . . . . . . .   7
       3.1.6.  Explicit Correction For Delayed Acknowledgements  . .   7
   4.  Estimating the Round-Trip Time  . . . . . . . . . . . . . . .   7
     4.1.  Generating RTT samples  . . . . . . . . . . . . . . . . .   7
     4.2.  Estimating min_rtt  . . . . . . . . . . . . . . . . . . .   8
     4.3.  Estimating smoothed_rtt and rttvar  . . . . . . . . . . .   8
   5.  Loss Detection  . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Acknowledgement-based Detection . . . . . . . . . . . . .  10
       5.1.1.  Packet Threshold  . . . . . . . . . . . . . . . . . .  10
       5.1.2.  Time Threshold  . . . . . . . . . . . . . . . . . . .  10
     5.2.  Probe Timeout . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  Computing PTO . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Handshakes and New Paths  . . . . . . . . . . . . . . . .  12
       5.3.1.  Sending Probe Packets . . . . . . . . . . . . . . . .  13
       5.3.2.  Loss Detection  . . . . . . . . . . . . . . . . . . .  14
     5.4.  Handling Retry Packets  . . . . . . . . . . . . . . . . .  14
     5.5.  Discarding Keys and Packet State  . . . . . . . . . . . .  14
   6.  Congestion Control  . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  Explicit Congestion Notification  . . . . . . . . . . . .  15
     6.2.  Slow Start  . . . . . . . . . . . . . . . . . . . . . . .  16
     6.3.  Congestion Avoidance  . . . . . . . . . . . . . . . . . .  16
     6.4.  Recovery Period . . . . . . . . . . . . . . . . . . . . .  16
     6.5.  Ignoring Loss of Undecryptable Packets  . . . . . . . . .  16
     6.6.  Probe Timeout . . . . . . . . . . . . . . . . . . . . . .  16
     6.7.  Persistent Congestion . . . . . . . . . . . . . . . . . .  17
     6.8.  Pacing  . . . . . . . . . . . . . . . . . . . . . . . . .  18
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