Coding and congestion control in transport
draft-irtf-nwcrg-coding-and-congestion-04

Document Type Active Internet-Draft (nwcrg RG)
Authors Nicolas Kuhn  , Emmanuel Lochin  , Fran├žois Michel  , Michael Welzl 
Last updated 2020-10-30
Replaces draft-kuhn-coding-congestion-transport
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NWCRG                                                            N. Kuhn
Internet-Draft                                                      CNES
Intended status: Informational                                 E. Lochin
Expires: May 3, 2021                                                ENAC
                                                               F. Michel
                                                               UCLouvain
                                                                M. Welzl
                                                      University of Oslo
                                                        October 30, 2020

               Coding and congestion control in transport
               draft-irtf-nwcrg-coding-and-congestion-04

Abstract

   Forward Erasure Correction (FEC) is a reliability mechanism that is
   distinct and separate from the retransmission logic in reliable
   transfer protocols such as TCP.  Using FEC coding can help deal with
   transfer tail losses or with networks having non-congestion losses.
   However, FEC coding mechanisms should not hide congestion signals.
   This memo offers a discussion of how FEC coding and congestion
   control can coexist.  Another objective is to encourage the research
   community to also consider congestion control aspects when proposing
   and comparing FEC coding solutions in communication systems.

   This document is the product of the Coding for Efficient Network
   Communications Research Group (NWCRG).  The scope of the document is
   end-to-end communications: FEC coding for tunnels is out-of-the scope
   of the document.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2021.

Kuhn, et al.               Expires May 3, 2021                  [Page 1]
Internet-Draft            Coding and congestion             October 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Separate channels, separate entities  . . . . . . . . . . . .   4
   3.  FEC above the transport . . . . . . . . . . . . . . . . . . .   6
     3.1.  Flowchart . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Discussion  . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  FEC within the transport  . . . . . . . . . . . . . . . . . .   8
     4.1.  Flowchart . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Discussion  . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  FEC below the transport . . . . . . . . . . . . . . . . . . .   9
     5.1.  Flowchart . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.2.  Discussion  . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Fairness, redundacy rate and congestion signals . . . . . . .  10
     6.1.  Fairness, a policy concern  . . . . . . . . . . . . . . .  10
     6.2.  Fairness and impact on non-coded flows  . . . . . . . . .  11
       6.2.1.  FEC above the transport . . . . . . . . . . . . . . .  11
       6.2.2.  FEC within the transport  . . . . . . . . . . . . . .  11
       6.2.3.  FEC below the transport . . . . . . . . . . . . . . .  11
     6.3.  Congestion control and recovered symbols  . . . . . . . .  11
       6.3.1.  FEC above the transport . . . . . . . . . . . . . . .  11
       6.3.2.  FEC within the transport  . . . . . . . . . . . . . .  12
       6.3.3.  FEC below the transport . . . . . . . . . . . . . . .  12
     6.4.  Interactions between congestion control and coding rates   12
       6.4.1.  FEC above the transport . . . . . . . . . . . . . . .  12
       6.4.2.  FEC within the transport  . . . . . . . . . . . . . .  12
       6.4.3.  FEC below the transport . . . . . . . . . . . . . . .  13
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