ECN++: Adding Explicit Congestion Notification (ECN) to TCP Control Packets
draft-ietf-tcpm-generalized-ecn-01

Document Type Active Internet-Draft (tcpm WG)
Last updated 2017-09-29
Replaces draft-bagnulo-tcpm-generalized-ecn
Stream IETF
Intended RFC status Experimental
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Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Obsoletes: 5562 (if approved)                                 B. Briscoe
Intended status: Experimental                                  CableLabs
Expires: April 1, 2018                                September 28, 2017

  ECN++: Adding Explicit Congestion Notification (ECN) to TCP Control
                                Packets
                   draft-ietf-tcpm-generalized-ecn-01

Abstract

   This document describes an experimental modification to ECN when used
   with TCP.  It allows the use of ECN on the following TCP packets:
   SYNs, pure ACKs, Window probes, FINs, RSTs and retransmissions.

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 April 1, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Bagnulo & Briscoe         Expires April 1, 2018                 [Page 1]
Internet-Draft                    ECN++                   September 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Experiment Goals  . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Document Structure  . . . . . . . . . . . . . . . . . . .   5
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Network (e.g. Firewall) Behaviour . . . . . . . . . . . .   6
     3.2.  Endpoint Behaviour  . . . . . . . . . . . . . . . . . . .   7
       3.2.1.  SYN . . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.2.2.  SYN-ACK . . . . . . . . . . . . . . . . . . . . . . .  11
       3.2.3.  Pure ACK  . . . . . . . . . . . . . . . . . . . . . .  13
       3.2.4.  Window Probe  . . . . . . . . . . . . . . . . . . . .  14
       3.2.5.  FIN . . . . . . . . . . . . . . . . . . . . . . . . .  14
       3.2.6.  RST . . . . . . . . . . . . . . . . . . . . . . . . .  15
       3.2.7.  Retransmissions . . . . . . . . . . . . . . . . . . .  15
       3.2.8.  General Fall-back for any Control Packet or
               Retransmission  . . . . . . . . . . . . . . . . . . .  16
   4.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.1.  The Reliability Argument  . . . . . . . . . . . . . . . .  16
     4.2.  SYNs  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
       4.2.1.  Argument 1a: Unrecognized CE on the SYN . . . . . . .  17
       4.2.2.  Argument 1b: Unrecognized ECT on the SYN  . . . . . .  19
       4.2.3.  Argument 2: DoS Attacks . . . . . . . . . . . . . . .  21
     4.3.  SYN-ACKs  . . . . . . . . . . . . . . . . . . . . . . . .  22
       4.3.1.  Response to Congestion on a SYN-ACK . . . . . . . . .  22
       4.3.2.  Fall-Back if ECT SYN-ACK Fails  . . . . . . . . . . .  23
     4.4.  Pure ACKs . . . . . . . . . . . . . . . . . . . . . . . .  23
       4.4.1.  Cwnd Response to CE-Marked Pure ACKs  . . . . . . . .  25
       4.4.2.  ACK Rate Response to CE-Marked Pure ACKs  . . . . . .  26
       4.4.3.  Summary: Enabling ECN on Pure ACKs  . . . . . . . . .  26
     4.5.  Window Probes . . . . . . . . . . . . . . . . . . . . . .  27
     4.6.  FINs  . . . . . . . . . . . . . . . . . . . . . . . . . .  28
     4.7.  RSTs  . . . . . . . . . . . . . . . . . . . . . . . . . .  28
     4.8.  Retransmitted Packets.  . . . . . . . . . . . . . . . . .  29
     4.9.  General Fall-back for any Control Packet  . . . . . . . .  30
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