Sender Control of Delayed Acknowledgments in TCP: Problem Statement, Requirements and Analysis of Potential Solutions
draft-gomez-tcpm-delack-suppr-reqs-01

Document Type Active Internet-Draft (individual)
Last updated 2020-03-26
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
TCPM Working Group                                              C. Gomez
Internet-Draft                                                       UPC
Intended status: Informational                              J. Crowcroft
Expires: September 27, 2020                      University of Cambridge
                                                          March 26, 2020

  Sender Control of Delayed Acknowledgments in TCP: Problem Statement,
            Requirements and Analysis of Potential Solutions
                 draft-gomez-tcpm-delack-suppr-reqs-01

Abstract

   TCP Delayed Acknowledgments (ACKs) allow reducing protocol overhead
   in many scenarios.  However, in some cases, Delayed ACKs may
   significantly degrade network and device performance in terms of link
   utilization, latency, memory usage and/or energy consumption.  This
   document presents the problem statement regarding sender control of
   Delayed ACKs in TCP.  The document discusses the scenarios and use
   cases in which sender control of Delayed ACKs offers advantages.
   Then, requirements for a potential solution are derived.  Finally, a
   number of potential solutions are discussed, based on the
   requirements, and also considering pros and cons in each case.

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 September 27, 2020.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents

Gomez & Crowcroft      Expires September 27, 2020               [Page 1]
Internet-Draft       Sender control of Delayed ACKs           March 2020

   (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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Problem statement: issues due to Delayed ACKs . . . . . . . .   3
     3.1.  Slow start  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  High bit rate environments and short data segments  . . .   4
     3.3.  IoT scenarios . . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  Beyond classic ACK transmission behavior  . . . . . . . .   4
   4.  Requirements for sender control of Delayed ACKs . . . . . . .   5
     4.1.  Sender-triggered mechanism  . . . . . . . . . . . . . . .   5
     4.2.  Per-segment granularity . . . . . . . . . . . . . . . . .   5
     4.3.  Header/Message overhead . . . . . . . . . . . . . . . . .   6
     4.4.  Support for enabling generic ACK ratios . . . . . . . . .   6
     4.5.  Middlebox traversal . . . . . . . . . . . . . . . . . . .   6
     4.6.  Safe return to normal Delayed ACKs operation  . . . . . .   6
     4.7.  Impact on existing TCP functionality  . . . . . . . . . .   7
     4.8.  Impact on future TCP development  . . . . . . . . . . . .   7
     4.9.  Avoidance of 'hacks'  . . . . . . . . . . . . . . . . . .   7
     4.10. Who is in control?  . . . . . . . . . . . . . . . . . . .   7
   5.  Potential solutions for sender control of Delayed ACKs  . . .   7
     5.1.  AckCC . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  TLP . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.3.  TCP ACK Pull (AKP) flag . . . . . . . . . . . . . . . . .   8
     5.4.  A new 'ACK Pull' TCP option . . . . . . . . . . . . . . .   9
     5.5.  Reuse of existing TCP header fields . . . . . . . . . . .   9
     5.6.  'Hacks' . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
Show full document text