TCP and Stream Control Transmission Protocol (SCTP) RTO Restart
RFC 7765
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
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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
timeout (RTO) occurs and the data is retransmitted. While the RTO is
based on measured round-trip times (RTTs) between the sender and
receiver, it also has a conservative lower bound of 1 second to
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