TCP Congestion Control
RFC 5681
| Document | Type |
RFC - Draft Standard
(September 2009; Errata)
Obsoletes RFC 2581
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5681 (Draft Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Lars Eggert | ||
| Send notices to | (None) | ||
Network Working Group M. Allman
Request for Comments: 5681 V. Paxson
Obsoletes: 2581 ICSI
Category: Standards Track E. Blanton
Purdue University
September 2009
TCP Congestion Control
Abstract
This document defines TCP's four intertwined congestion control
algorithms: slow start, congestion avoidance, fast retransmit, and
fast recovery. In addition, the document specifies how TCP should
begin transmission after a relatively long idle period, as well as
discussing various acknowledgment generation methods. This document
obsoletes RFC 2581.
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2009 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
Allman, et al. Standards Track [Page 1]
RFC 5681 TCP Congestion Control September 2009
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table Of Contents
1. Introduction ....................................................2
2. Definitions .....................................................3
3. Congestion Control Algorithms ...................................4
3.1. Slow Start and Congestion Avoidance ........................4
3.2. Fast Retransmit/Fast Recovery ..............................8
4. Additional Considerations ......................................10
4.1. Restarting Idle Connections ...............................10
4.2. Generating Acknowledgments ................................11
4.3. Loss Recovery Mechanisms ..................................12
5. Security Considerations ........................................13
6. Changes between RFC 2001 and RFC 2581 ..........................13
7. Changes Relative to RFC 2581 ...................................14
8. Acknowledgments ................................................15
9. References .....................................................15
9.1. Normative References ......................................15
9.2. Informative References ....................................16
1. Introduction
This document specifies four TCP [RFC793] congestion control
algorithms: slow start, congestion avoidance, fast retransmit and
fast recovery. These algorithms were devised in [Jac88] and [Jac90].
Their use with TCP is standardized in [RFC1122]. Additional early
work in additive-increase, multiplicative-decrease congestion control
is given in [CJ89].
Note that [Ste94] provides examples of these algorithms in action and
[WS95] provides an explanation of the source code for the BSD
implementation of these algorithms.
In addition to specifying these congestion control algorithms, this
document specifies what TCP connections should do after a relatively
long idle period, as well as specifying and clarifying some of the
issues pertaining to TCP ACK generation.
This document obsoletes [RFC2581], which in turn obsoleted [RFC2001].
This document is organized as follows. Section 2 provides various
definitions that will be used throughout the document. Section 3
provides a specification of the congestion control algorithms.
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