QUIC Loss Detection and Congestion Control
draft-ietf-quic-recovery-26
QUIC J. Iyengar, Ed.
Internet-Draft Fastly
Intended status: Standards Track I. Swett, Ed.
Expires: 24 August 2020 Google
21 February 2020
QUIC Loss Detection and Congestion Control
draft-ietf-quic-recovery-26
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
(https://mailarchive.ietf.org/arch/search/?email_list=quic).
Working Group information can be found at https://github.com/quicwg
(https://github.com/quicwg); source code and issues list for this
draft can be found at https://github.com/quicwg/base-drafts/labels/-
recovery (https://github.com/quicwg/base-drafts/labels/-recovery).
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-
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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 24 August 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
Iyengar & Swett Expires 24 August 2020 [Page 1]
Internet-Draft QUIC Loss Detection February 2020
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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 . . . . . . . . . . . 9
5. Loss Detection . . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Acknowledgement-based Detection . . . . . . . . . . . . . 10
5.1.1. Packet Threshold . . . . . . . . . . . . . . . . . . 11
5.1.2. Time Threshold . . . . . . . . . . . . . . . . . . . 11
5.2. Probe Timeout . . . . . . . . . . . . . . . . . . . . . . 12
5.2.1. Computing PTO . . . . . . . . . . . . . . . . . . . . 12
5.3. Handshakes and New Paths . . . . . . . . . . . . . . . . 13
5.3.1. Sending Probe Packets . . . . . . . . . . . . . . . . 14
5.3.2. Loss Detection . . . . . . . . . . . . . . . . . . . 15
5.4. Handling Retry Packets . . . . . . . . . . . . . . . . . 15
5.5. Discarding Keys and Packet State . . . . . . . . . . . . 15
6. Congestion Control . . . . . . . . . . . . . . . . . . . . . 16
6.1. Explicit Congestion Notification . . . . . . . . . . . . 16
6.2. Slow Start . . . . . . . . . . . . . . . . . . . . . . . 17
6.3. Congestion Avoidance . . . . . . . . . . . . . . . . . . 17
6.4. Recovery Period . . . . . . . . . . . . . . . . . . . . . 17
6.5. Ignoring Loss of Undecryptable Packets . . . . . . . . . 17
6.6. Probe Timeout . . . . . . . . . . . . . . . . . . . . . . 18
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