TCP and Stream Control Transmission Protocol (SCTP) RTO Restart
RFC 7765

Document Type RFC - Experimental (February 2016; No errata)
Last updated 2016-02-11
Replaces draft-hurtig-tcpm-rtorestart
Stream IETF
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Stream WG state Submitted to IESG for Publication Aug 2013
Document shepherd Michael Scharf
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IESG IESG state RFC 7765 (Experimental)
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Responsible AD Martin Stiemerling
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IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                         P. Hurtig
Request for Comments: 7765                                  A. Brunstrom
Category: Experimental                               Karlstad University
ISSN: 2070-1721                                               A. Petlund
                                           Simula Research Laboratory AS
                                                                M. Welzl
                                                      University of Oslo
                                                           February 2016

    TCP and Stream Control Transmission Protocol (SCTP) RTO Restart

Abstract

   This document describes a modified sender-side algorithm for managing
   the TCP and Stream Control Transmission Protocol (SCTP)
   retransmission timers that provides faster loss recovery when there
   is a small amount of outstanding data for a connection.  The
   modification, RTO Restart (RTOR), allows the transport to restart its
   retransmission timer using a smaller timeout duration, so that the
   effective retransmission timeout (RTO) becomes more aggressive in
   situations where fast retransmit cannot be used.  This enables faster
   loss detection and recovery for connections that are short lived or
   application limited.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7765.

Hurtig, et al.                Experimental                      [Page 1]
RFC 7765                TCP and SCTP RTO Restart           February 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  RTO Overview and Rationale for RTOR . . . . . . . . . . . . .   4
   4.  RTOR Algorithm  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Applicability . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Spurious Timeouts . . . . . . . . . . . . . . . . . . . .   7
     5.3.  Tracking Outstanding and Previously Unsent Segments . . .   8
   6.  Related Work  . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  SCTP Socket API Considerations  . . . . . . . . . . . . . . .  10
     7.1.  Data Types  . . . . . . . . . . . . . . . . . . . . . . .  10
     7.2.  Socket Option for Controlling the RTO Restart Support
           (SCTP_RTO_RESTART)  . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

Hurtig, et al.                Experimental                      [Page 2]
RFC 7765                TCP and SCTP RTO Restart           February 2016

1.  Introduction

   TCP and SCTP use two almost identical mechanisms to detect and
   recover from data loss, specified in [RFC6298] and [RFC5681] for TCP
   and [RFC4960] for SCTP.  First, if transmitted data is not
   acknowledged within a certain amount of time, a retransmission
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