RACK-TLP: a time-based efficient loss detection for TCP
draft-ietf-tcpm-rack-09

Document Type Active Internet-Draft (tcpm WG)
Last updated 2020-07-13
Replaces draft-cheng-tcpm-rack
Stream IETF
Intended RFC status Proposed Standard
Formats plain text pdf htmlized (tools) htmlized bibtex
Stream WG state WG Document
Revised I-D Needed - Issue raised by WGLC
Document shepherd Michael Tüxen
IESG IESG state I-D Exists
Consensus Boilerplate Yes
Telechat date
Responsible AD (None)
Send notices to Martin Duke <martin.h.duke@gmail.com>, =?utf-8?q?Michael_T=C3=BCxen?= <tuexen@fh-muenster.de>
TCP Maintenance Working Group                                   Y. Cheng
Internet-Draft                                               N. Cardwell
Intended status: Standards Track                            N. Dukkipati
Expires: January 14, 2021                                         P. Jha
                                                             Google, Inc
                                                           July 13, 2020

        RACK-TLP: a time-based efficient loss detection for TCP
                        draft-ietf-tcpm-rack-09

Abstract

   This document presents the RACK-TLP loss detection algorithm for TCP.
   RACK-TLP uses per-segment transmit timestamp and selective
   acknowledgement (SACK) [RFC2018] and has two parts: RACK ("Recent
   ACKnowledgment") starts fast recovery quickly using time-based
   inferences derived from ACK feedback.  TLP ("Tail Loss Probe")
   leverages RACK and sends a probe packet to trigger ACK feedback to
   avoid the retransmission timeout (RTO) events.  Compared to the
   widely used DUPACK threshold approach, RACK-TLP detects losses more
   efficiently when there are application-limited flights of data, lost
   retransmissions, or data packet reordering events.  It is intended to
   be an alternative to the DUPACK threshold approach in
   [RFC5681][RFC6675].

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 January 14, 2021.

Copyright Notice

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

Cheng, et al.           Expires January 14, 2021                [Page 1]
Internet-Draft                    RACK                         July 2020

   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
   to this document.  Code Components extracted from this document must
   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  RACK-TLP high-level design  . . . . . . . . . . . . . . . . .   5
     3.1.  RACK: time-based loss inferences from ACKs  . . . . . . .   5
     3.2.  TLP: sending one segment to probe losses quickly with
           RACK  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  RACK-TLP: reordering resilience with a time threshold . .   6
       3.3.1.  Reordering design rationale . . . . . . . . . . . . .   6
       3.3.2.  Reordering window adaptation  . . . . . . . . . . . .   8
     3.4.  An Example of RACK-TLP in Action: fast recovery . . . . .   9
     3.5.  An Example of RACK-TLP in Action: RTO . . . . . . . . . .   9
     3.6.  Design Summary  . . . . . . . . . . . . . . . . . . . . .  10
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  Per-packet variables  . . . . . . . . . . . . . . . . . .  11
     5.2.  Per-connection variables  . . . . . . . . . . . . . . . .  12
   6.  RACK Algorithm Details  . . . . . . . . . . . . . . . . . . .  13
     6.1.  Upon transmitting a data segment  . . . . . . . . . . . .  13
     6.2.  Upon receiving an ACK . . . . . . . . . . . . . . . . . .  13
     6.3.  Upon RTO expiration . . . . . . . . . . . . . . . . . . .  19
   7.  TLP Algorithm Details . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Initializing state  . . . . . . . . . . . . . . . . . . .  20
     7.2.  Scheduling a loss probe . . . . . . . . . . . . . . . . .  20
     7.3.  Sending a loss probe upon PTO expiration  . . . . . . . .  21
     7.4.  Detecting losses by the ACK of the loss probe . . . . . .  22
       7.4.1.  General case: detecting packet losses using RACK  . .  22
       7.4.2.  Special case: detecting a single loss repaired by the
Show full document text