One document matched: draft-ietf-tcpm-tcp-rfc4614bis-00.xml
<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!-- Section: Core Functionality -->
<!ENTITY RFC0793 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0793.xml'>
<!ENTITY RFC1122 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1122.xml'>
<!ENTITY RFC2460 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2460.xml'>
<!ENTITY RFC2873 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2873.xml'>
<!ENTITY RFC3390 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3390.xml'>
<!ENTITY RFC5681 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5681.xml'>
<!ENTITY RFC6093 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6093.xml'>
<!ENTITY RFC6298 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6298.xml'>
<!ENTITY RFC6691 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6691.xml'>
<!-- Subsection: Fundamental Changes -->
<!ENTITY RFC1323 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1323.xml'>
<!ENTITY RFC2675 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2675.xml'>
<!ENTITY RFC5482 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5482.xml'>
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
<!ENTITY RFC3042 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3042.xml'>
<!ENTITY RFC3168 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3168.xml'>
<!ENTITY RFC3465 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3465.xml'>
<!ENTITY RFC6582 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6582.xml'>
<!ENTITY RFC6633 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6633.xml'>
<!-- Subsection: SACK-Based Loss Recovery and Congestion Control -->
<!ENTITY RFC2018 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2018.xml'>
<!ENTITY RFC2883 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2883.xml'>
<!ENTITY RFC6675 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6675.xml'>
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
<!ENTITY RFC4015 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4015.xml'>
<!ENTITY RFC5682 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5682.xml'>
<!-- Subsection: Path MTU Discovery-->
<!ENTITY RFC1191 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1191.xml'>
<!ENTITY RFC1981 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1981.xml'>
<!ENTITY RFC4821 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4821.xml'>
<!-- Subsection: Header Compression -->
<!ENTITY RFC1144 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1144.xml'>
<!ENTITY RFC6846 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6846.xml'>
<!-- Subsection: Defending Spoofing and Flooding Attacks -->
<!ENTITY RFC4953 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4953.xml'>
<!ENTITY RFC4987 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4987.xml'>
<!ENTITY RFC5461 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5461.xml'>
<!ENTITY RFC5925 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5925.xml'>
<!ENTITY RFC5926 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5926.xml'>
<!ENTITY RFC5927 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5927.xml'>
<!ENTITY RFC5961 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5961.xml'>
<!ENTITY RFC6528 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6528.xml'>
<!-- Subsection: Architectural Guidelines -->
<!ENTITY RFC2140 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2140.xml'>
<!ENTITY RFC3124 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3124.xml'>
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
<!ENTITY RFC2861 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2861.xml'>
<!ENTITY RFC3540 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3540.xml'>
<!ENTITY RFC3649 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3649.xml'>
<!ENTITY RFC3742 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3742.xml'>
<!ENTITY RFC4782 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4782.xml'>
<!ENTITY RFC5562 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5562.xml'>
<!ENTITY RFC5690 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5690.xml'>
<!ENTITY RFC5827 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5827.xml'>
<!ENTITY RFC6069 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6069.xml'>
<!ENTITY RFC6928 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6928.xml'>
<!ENTITY RFC6937 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6937.xml'>
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
<!ENTITY RFC3522 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3522.xml'>
<!ENTITY RFC3708 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3708.xml'>
<!ENTITY RFC4653 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4653.xml'>
<!-- Subsection: Multipath TCP -->
<!ENTITY RFC6356 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6356.xml'>
<!ENTITY RFC6824 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6824.xml'>
<!-- Section: TCP Parameters at IANA -->
<!ENTITY RFC2780 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2780.xml'>
<!ENTITY RFC4727 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4727.xml'>
<!ENTITY RFC6335 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6335.xml'>
<!ENTITY RFC6994 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6994.xml'>
<!-- Section: Historic and Undeployed Extensions -->
<!ENTITY RFC0721 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0721.xml'>
<!ENTITY RFC1078 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1078.xml'>
<!ENTITY RFC1106 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1106.xml'>
<!ENTITY RFC1110 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1110.xml'>
<!ENTITY RFC1146 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1146.xml'>
<!ENTITY RFC1263 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1263.xml'>
<!ENTITY RFC1379 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1379.xml'>
<!ENTITY RFC1644 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1644.xml'>
<!ENTITY RFC1693 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1693.xml'>
<!ENTITY RFC1705 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1705.xml'>
<!ENTITY RFC6013 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6013.xml'>
<!ENTITY RFC6247 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6247.xml'>
<!-- Subsection: Foundational Works -->
<!ENTITY RFC0675 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0675.xml'>
<!ENTITY RFC0761 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0761.xml'>
<!ENTITY RFC0813 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0813.xml'>
<!ENTITY RFC0814 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0814.xml'>
<!ENTITY RFC0816 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0816.xml'>
<!ENTITY RFC0817 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0817.xml'>
<!ENTITY RFC0872 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0872.xml'>
<!ENTITY RFC0896 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0896.xml'>
<!ENTITY RFC0964 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0964.xml'>
<!-- Subsection: Architectural Guidelines -->
<!ENTITY RFC1958 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1958.xml'>
<!ENTITY RFC2914 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2914.xml'>
<!ENTITY RFC3439 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3439.xml'>
<!ENTITY RFC6182 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6182.xml'>
<!-- Subsection: Difficult Network Environments -->
<!ENTITY RFC2488 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2488.xml'>
<!ENTITY RFC2757 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2757.xml'>
<!ENTITY RFC2760 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2760.xml'>
<!ENTITY RFC3135 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3135.xml'>
<!ENTITY RFC3150 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3150.xml'>
<!ENTITY RFC3155 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3155.xml'>
<!ENTITY RFC3366 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3366.xml'>
<!ENTITY RFC3449 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3449.xml'>
<!ENTITY RFC3481 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3481.xml'>
<!ENTITY RFC3819 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3819.xml'>
<!-- Subsection: Guidance for Developing, Analyzing, and Evaluating TCP -->
<!ENTITY RFC4774 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4774.xml'>
<!ENTITY RFC5033 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5033.xml'>
<!ENTITY RFC5166 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5166.xml'>
<!ENTITY RFC6181 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6181.xml'>
<!ENTITY RFC6349 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6349.xml'>
<!-- Subsection: Implementation Advice -->
<!ENTITY RFC0794 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0794.xml'>
<!ENTITY RFC0879 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0879.xml'>
<!ENTITY RFC1071 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1071.xml'>
<!ENTITY RFC1624 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1624.xml'>
<!ENTITY RFC1936 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1936.xml'>
<!ENTITY RFC2525 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2525.xml'>
<!ENTITY RFC2923 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2923.xml'>
<!ENTITY RFC3360 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3360.xml'>
<!ENTITY RFC3493 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3493.xml'>
<!ENTITY RFC6056 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6056.xml'>
<!ENTITY RFC6191 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6191.xml'>
<!ENTITY RFC6429 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6429.xml'>
<!ENTITY RFC6897 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6897.xml'>
<!-- Subsection: Management Information Bases -->
<!ENTITY RFC1066 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1066.xml'>
<!ENTITY RFC1156 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1156.xml'>
<!ENTITY RFC1213 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1213.xml'>
<!ENTITY RFC2012 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2012.xml'>
<!ENTITY RFC2452 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2452.xml'>
<!ENTITY RFC4022 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4022.xml'>
<!-- Subsection: Tools and Tutorials -->
<!ENTITY RFC1180 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1180.xml'>
<!ENTITY RFC1470 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1470.xml'>
<!ENTITY RFC2398 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2398.xml'>
<!ENTITY RFC4614 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4614.xml'>
<!ENTITY RFC5783 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5783.xml'>
<!ENTITY RFC6077 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6077.xml'>
<!-- Subsection: Case Studies -->
<!ENTITY RFC0700 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0700.xml'>
<!ENTITY RFC0889 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.0889.xml'>
<!ENTITY RFC1337 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1337.xml'>
<!ENTITY RFC2415 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2415.xml'>
<!ENTITY RFC2416 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2416.xml'>
<!ENTITY RFC2884 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2884.xml'>
<!-- Informative References -->
<!ENTITY RFC1016 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.1016.xml'>
<!ENTITY RFC2026 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2026.xml'>
<!ENTITY RFC2474 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2474.xml'>
<!ENTITY RFC4340 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4340.xml'>
<!ENTITY RFC4341 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4341.xml'>
<!ENTITY rhee-tcpm-cubic SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-rhee-tcpm-cubic-02.xml'>
<!ENTITY sridharan-tcpm-ctcp SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-sridharan-tcpm-ctcp-02.xml'>
<!ENTITY leith-tcp-htcp SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-leith-tcp-htcp-06.xml'>
]>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<!-- For a complete list and description of processing instructions (PIs),
please see http://xml.resource.org/authoring/README.html. -->
<!-- Below are generally applicable Processing Instructions (PIs) that most I-Ds
might want to use. (Here they are set differently than their defaults in
xml2rfc v1.32) -->
<?rfc strict="yes" ?>
<!-- give errors regarding ID-nits and DTD validation -->
<!-- control the table of contents (ToC) -->
<?rfc toc="yes"?>
<!-- generate a ToC -->
<?rfc tocdepth="3"?>
<!-- the number of levels of subsections in ToC. default: 3 -->
<!-- control references -->
<?rfc symrefs="yes"?>
<!-- use symbolic references tags, i.e, [RFC2119] instead of [1] -->
<?rfc sortrefs="yes" ?>
<!-- sort the reference entries alphabetically -->
<!-- control vertical white space
(using these PIs as follows is recommended by the RFC Editor) -->
<?rfc compact="yes" ?>
<!-- do not start each main section on a new page -->
<?rfc subcompact="no" ?>
<!-- keep one blank line between list items -->
<!-- end of list of popular I-D processing instructions -->
<rfc ipr="trust200902" category="info" obsoletes="4614"
docName="draft-ietf-tcpm-tcp-rfc4614bis-00">
<!-- category values: std, bcp, info, exp, and historic
ipr values: full3667, noModification3667, noDerivatives3667
you can add the attributes updates="NNNN" and obsoletes="NNNN"
they will automatically be output with "(if approved)" -->
<!-- FRONT MATTER -->
<front>
<title abbrev="TCP Roadmap">A Roadmap for Transmission Control Protocol
(TCP) Specification Documents</title>
<author initials="M." surname="Duke" fullname="Martin Duke">
<organization abbrev='Boing'>>Boeing Research &
Technology</organization>
<address>
<postal>
<street>PO Box 3707, MC 7L-49</street>
<city>Seattle</city>
<region>WA</region>
<code>98124-2207</code>
</postal>
<phone>425-373-2852</phone>
<email>martin.duke@boeing.com</email>
</address>
</author>
<author initials="R." surname="Braden" fullname="Robert Braden">
<organization abbrev='ISI'>USC Information Sciences
Institute</organization>
<address>
<postal>
<street></street>
<city>Marina del Rey</city>
<region>CA</region>
<code>90292-6695</code>
</postal>
<phone>310-448-9173</phone>
<email>braden@isi.edu</email>
</address>
</author>
<author initials="W.M." surname="Eddy" fullname="Wesley M. Eddy">
<organization >MTI Systems</organization>
<address>
<postal>
<street>MS 500-ASRC; 21000 Brookpark Rd</street>
<city>Cleveland</city>
<region>OH</region>
<code>44135</code>
</postal>
<phone>216-433-6682</phone>
<email>wes@mti-systems.com</email>
</address>
</author>
<author initials="E." surname="Blanton" fullname="Ethan Blanton">
<organization />
<address>
<email>elb@psg.com</email>
</address>
</author>
<author initials="A." surname="Zimmermann" fullname="Alexander Zimmermann">
<organization>NetApp, Inc.</organization>
<address>
<postal>
<street>Sonnenallee 1</street>
<city>Kirchheim</city>
<code>85551</code>
<country>Germany</country>
</postal>
<phone>+49 89 900594712</phone>
<email>alexander.zimmermann@netapp.com</email>
</address>
</author>
<date month="August" year="2013" />
<!-- Meta-data Declarations -->
<area>Transport</area>
<workgroup>TCP Maintenance and Minor Extensions (TCPM) WG</workgroup>
<keyword>TCP Roadmap</keyword>
<abstract>
<t>This document contains a "roadmap" to the Requests for Comments
(RFC) documents relating to the Internet's Transmission Control
Protocol (TCP). This roadmap provides a brief summary of the
documents defining TCP and various TCP extensions that have
accumulated in the RFC series. This serves as a guide and quick
reference for both TCP implementers and other parties who desire
information contained in the TCP-related RFCs.</t>
</abstract>
</front>
<!-- MAIN MATTER -->
<middle>
<!-- Section: Introduction -->
<section title="Introduction">
<t>A correct and efficient implementation of the Transmission
Control Protocol (TCP) is a critical part of the software of most
Internet hosts. As TCP has evolved over the years, many distinct
documents have become part of the accepted standard for TCP. At
the same time, a large number of more experimental modifications to
TCP have also been published in the RFC series, along with
informational notes, case studies, and other advice.</t>
<t>As an introduction to newcomers and an attempt to organize the
plethora of information for old hands, this document contains a
"roadmap" to the TCP-related RFCs. It provides a brief summary of
the RFC documents that define TCP. This should provide guidance to
implementers on the relevance and significance of the
standards-track extensions, informational notes, and best current
practices that relate to TCP.</t>
<t>This document is not an update of RFC 1122 and is not a
rigorous standard for what needs to be implemented in TCP. This
document is merely an informational roadmap that captures,
organizes, and summarizes most of the RFC documents that a TCP
implementer, experimenter, or student should be aware of.
Particular comments or broad categorizations that this document
makes about individual mechanisms and behaviors are not to be taken
as definitive, nor should the content of this document alone
influence implementation decisions.</t>
<t>This roadmap includes a brief description of the contents of
each TCP-related RFC. In some cases, we simply supply the abstract
or a key summary sentence from the text as a terse description. In
addition, a letter code after an RFC number indicates its category
in the RFC series (see BCP 9 <xref target="RFC2026"/> for
explanation of these categories):
<list style="empty">
<t>S - Standards Track (Proposed Standard, Draft Standard,
or Internet Standard)</t>
<t>E - Experimental</t>
<t>I - Informational</t>
<t>H - Historic</t>
<t>B - Best Current Practice</t>
<t>U - Unknown (not formally defined)</t>
</list>
</t>
<t>Note that the category of an RFC does not necessarily reflect
its current relevance. For instance, RFC 5681 is nearly universally
deployed although it is only a Draft Standard. Similarly, some
Informational RFCs contain significant technical proposals for
changing TCP.</t>
<t>Finally, if an error in the technical content has been found
after publication of an RFC, this fact is indicated by the term
"(Errata)" in the headline of the RFC's description. The contents
of the errata can be found at the RFC editor home page
<xref target="Errata"/>.</t>
<t>This roadmap is divided into three main sections.
<xref target="must"/> lists the RFCs that describe absolutely
required TCP behaviors for proper functioning and interoperability.
Further RFCs that describe strongly encouraged, but non-essential,
behaviors are listed in <xref target="should"/>. Experimental
extensions that are not yet standard practices, but that potentially
could be in the future, are described in <xref target="may"/>.</t>
<t>The reader will probably notice that these three sections are
broadly equivalent to MUST/SHOULD/MAY specifications (per RFC
2119), and although the authors support this intuition, this
document is merely descriptive; it does not represent a binding
standards-track position. Individual implementers still need to
examine the standards documents themselves to evaluate specific
requirement levels.</t>
<t><xref target="iana"/> describes both the procedures that the
Internet Assigned Numbers Authority (IANA) uses and an RFC author
should follow when new TCP parameters are requested and finally
assigned.</t>
<t>A small number of older experimental extensions that have not
been widely implemented, deployed, and used are noted in
<xref target="history"/>. Many other supporting documents that are
relevant to the development, implementation, and deployment of TCP
are described in <xref target="support"/>.</t>
<t>A small number of fairly ubiquitous important implementation
practices that is not currently documented in the RFC series is
listed in <xref target="undocumented"/>.</t>
<t>Within each section, RFCs are listed in the chronological order
of their publication dates.</t>
</section>
<!-- Section: Core Functionality -->
<section title="Core Functionality" anchor="must">
<t>A small number of documents compose the core specification of
TCP. These define the required core functionalities of TCP's
header parsing, state machine, congestion control, and
retransmission timeout computation. These base specifications must
be correctly followed for interoperability.</t>
<t><list style="hanging">
<t hangText="RFC 793 S: "Transmission Control
Protocol", STD 7 (September 1981) (Errata)">
<vspace blankLines="1"/>
This is the fundamental TCP specification document
<xref target="RFC0793"/>. Written by Jon Postel as part of the
Internet protocol suite's core, it describes the TCP packet
format, the TCP state machine and event processing, and TCP's
semantics for data transmission, reliability, flow control,
multiplexing, and acknowledgment.</t>
<t>Section 3.6 of RFC 793, describing TCP's handling of the IP
precedence and security compartment, is mostly irrelevant
today. RFC 2873 changed the IP precedence handling, and the
security compartment portion of the API is no longer
implemented or used. In addition, RFC 793 did not describe any
congestion control mechanism. Otherwise, however, the majority
of this document still accurately describes modern TCPs. RFC
793 is the last of a series of developmental TCP
specifications, starting in the Internet Experimental Notes
(IENs) and continuing in the RFC series.</t>
<t hangText="RFC 1122 S: "Requirements for Internet Hosts -
Communication Layers" (October 1989)"><vspace blankLines="1"/>
This document <xref target="RFC1122"/> updates and clarifies
RFC 793, fixing some specification bugs and oversights. It
also explains some features such as keep-alives and Karn's and
Jacobson's RTO estimation algorithms <xref target="KP87"/><xref
target="Jac88"/><xref target="JK92"/>. ICMP interactions
are mentioned, and some tips are given for efficient
implementation. RFC 1122 is an Applicability Statement,
listing the various features that MUST, SHOULD, MAY, SHOULD
NOT, and MUST NOT be present in standards-conforming TCP
implementations. Unlike a purely informational "roadmap", this
Applicability Statement is a standards document and gives
formal rules for implementation.</t>
<t hangText="RFC 2460 S: "Internet Protocol, Version 6
(IPv6) Specification" (December 1998) (Errata)">
<vspace blankLines="1"/>
This document <xref target="RFC2460"/> is of relevance to TCP
because it defines how the pseudo-header for TCP's checksum
computation is derived when 128-bit IPv6 addresses are used
instead of 32-bit IPv4 addresses. Additionally, RFC 2675
describes TCP changes required to support IPv6
jumbograms.</t>
<t hangText="RFC 2873 S: "TCP Processing of the IPv4
Precedence Field" (June 2000) (Errata)">
<vspace blankLines="1"/>
This document <xref target="RFC2873"/> removes from the TCP
specification all processing of the precedence bits of the TOS
byte of the IP header. This resolves a conflict over the use
of these bits between RFC 793 and Differentiated Services
<xref target="RFC2474"/>.</t>
<t hangText="RFC 3390 S: "Increasing TCP's Initial
Window" (October 2002)"><vspace blankLines="1"/>
This document <xref target="RFC3390"/> specifies an increase in
the permitted initial window for TCP from one segment to three
or four segments during the slow start phase, depending on the
segment size.</t>
<t hangText="RFC 5681 S: "TCP Congestion Control"
(August 2009)"><vspace blankLines="1"/>
Although RFC 793 did not contain any congestion control
mechanisms, today congestion control is a required component of
TCP implementations. This document <xref target="RFC5681"/>
defines the current versions of Van Jacobson's congestion
avoidance and control mechanisms for TCP, based on his 1988
SIGCOMM paper <xref target="Jac88"/>.</t>
<t>A number of behaviors that together constitute what the
community refers to as "Reno TCP" are described in RFC 5681.
The name "Reno" comes from the Net/2 release of the 4.3 BSD
operating system. This is generally regarded as the least
common denominator among TCP flavors currently found running on
Internet hosts. Reno TCP includes the congestion control
features of slow start, congestion avoidance, fast retransmit,
and fast recovery.</t>
<t>RFC 1122 <xref target="RFC1122"/> mandates the
implementation of a congestion control mechanism, and RFC 5681
<xref target="RFC5681"/> details the currently accepted
mechanism. RFC 5681 differs slightly from the other documents
listed in this section, as it does not affect the ability of
two TCP endpoints to communicate; however, congestion control
remains a critical component of any widely deployed TCP
implementation and is required for the avoidance of congestion
collapse and to ensure fairness among competing flows.</t>
<t>RFC 2001 and RFC 2581 are the conceptual precursors of RFC
5681. The most important changes relative to RFC 2581 are:
<?rfc subcompact="yes"?>
<list style="format (%c)">
<t>The initial window requirements were changed to allow
larger Initial Windows as standardized in <xref
target="RFC3390"/>.</t>
<t>During slow start and congestion avoidance, the
usage of Appropriate Byte Counting <xref
target="RFC3465"/> is explicitly recommended.</t>
<t>The use of Limited Transmit <xref target="RFC3042"/>
is now recommended.</t>
</list>
<?rfc subcompact="no"?>
</t>
<t hangText="RFC 6093 S: "On the Implementation of the TCP
Urgent Mechanism" (January 2011)"><vspace blankLines="1"/>
This document <xref target="RFC6093"/> analyzes how current TCP
stacks process TCP urgent indications, and how the behavior of
widely deployed middleboxes affects the urgent indications
processing. Based on their investigation, the document updates
the relevant specifications such that they accommodate current
practice in processing TCP urgent indications. Finally, the
document raises awareness about the reliability of TCP urgent
indications in the Internet, and recommends against the use of
urgent mechanism.</t>
<t hangText="RFC 6298 S: "Computing TCP's Retransmission
Timer" (June 2011)"><vspace blankLines="1"/>
Abstract: "This document defines the standard algorithm
that Transmission Control Protocol (TCP) senders are required to
use to compute and manage their retransmission timer. It expands
on the discussion in section 4.2.3.1 of RFC 1122 and upgrades
the requirement of supporting the algorithm from a SHOULD to a
MUST." <xref target="RFC6298"/>. RFC 6298 is the successor
of RFC 2988, which changes the initial RTO from 3s to 1s.</t>
<t hangText="RFC 6691 I: "TCP Options and Maximum Segment
Size (MSS)" (July 2012)"> <vspace blankLines="1"/>
This document <xref target="RFC6691"/> clarifies what value to
use with the TCP Maximum Segment Size (MSS) option when IP and
TCP options are in use.</t>
</list></t>
</section>
<!-- Section: Recommended Enhancements -->
<section title="Recommended Enhancements" anchor="should">
<t>This section describes recommended TCP modifications that improve
performance and security. <xref target="fundamental"/> represents
fundamental changes to the protocol. <xref target="cc"/> lists
improvements in the congestion control and loss recovery mechanisms
specified in RFC 5681. <xref target="sack"/> describes further
refinements that make use of selective acknowledgments. <xref
target="spourious"/> describes algorithms that allows a TCP
sender to detect whether it has entered loss recovery
unnecessarily. <xref target="pmtud"/> compromises Path MTU
Discovery mechanisms. Header compression schemes for TCP/IP header
compression are listed in <xref target="compression"/>. Finally,
<xref target="antispoof"/> deals with the problem of preventing
forged segments and flooding attacks.</t>
<!-- Subsection: Fundamental Changes -->
<section title="Fundamental Changes" anchor="fundamental">
<t>RFC 1323 allows better utilization of high bandwidth-delay
product paths by providing some needed mechanisms for high-rate
transfers. RFC 2675 describes changes to TCP's semantic for
using IPv6 Jumbograms. RFC 5482 specifies the TCP User Timeout
Option.</t>
<t><list style="hanging">
<t hangText="RFC 1323 S: "TCP Extensions for High
Performance" (May 1992)"><vspace blankLines="1"/>
This document <xref target="RFC1323"/> defines TCP extensions
for window scaling, timestamps, and protection against wrapped
sequence numbers, for efficient and safe operation over paths
with large bandwidth-delay products. These extensions are
commonly found in currently used systems; however, they may
require manual tuning and configuration. One issue in this
specification that is still under discussion concerns a
modification to the algorithm for estimating the mean RTT
when timestamps are used. RFC 1072 and RFC 1185 are the
conceptual precursors of RFC 1323.</t>
<t hangText="RFC 2675 S: "IPv6 Jumbograms" (August
1999) (Errata)"><vspace blankLines="1"/>
IPv6 supports longer datagrams than were allowed in IPv4.
These are known as Jumbograms, and use with TCP has
necessitated changes to the handling of TCP's MSS and Urgent
fields (both 16 bits). This document <xref target="RFC2675"/>
explains those changes. Although it describes changes to basic
header semantics, these changes should only affect the use
of very large segments, such as IPv6 jumbograms, which are
currently rarely used in the general Internet.</t>
<t>Supporting the behavior described in this document does
not affect interoperability with other TCP implementations
when IPv4 or non-jumbogram IPv6 is used. This document
states that jumbograms are to only be used when it can be
guaranteed that all receiving nodes, including each router
in the end-to-end path, will support jumbograms. If even a
single node that does not support jumbograms is attached to
a local network, then no host on that network may use
jumbograms. This explains why jumbogram use has been rare,
and why this document is considered a performance
optimization and not part of TCP over IPv6's basic
functionality.</t>
<t hangText="RFC 5482 S: "TCP User Timeout Option"
(June 2009)"><vspace blankLines="1"/>
As a local per-connection parameter the TCP user timeout
controls how long transmitted data may remain
unacknowledged before a connection is forcefully closed.
This document <xref target="RFC5482"/> specifies the TCP
User Timeout Option that allows one end of a TCP connection
to advertise its current user timeout value. This
information provides advice to the other end of the TCP
connection to adapt its user timeout accordingly.</t>
</list></t>
</section>
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
<section title="Congestion Control and Loss Recovery Extensions" anchor="cc">
<t>Two of the most important aspects of TCP are its congestion
control and loss recovery features. TCP traditionally treats
lost packets as indicating congestion-related loss, and cannot
distinguish between congestion-related loss and loss due to
transmission errors. Even when ECN is in use, there is a rather
intimate coupling between congestion control and loss recovery
mechanisms. There are several extensions to both features, and
more often than not, a particular extension applies to both. In
this sub-section, we group enhancements to either congestion
control, loss recovery, or both, which can be performed
unilaterally; that is, without negotiating support between
endpoints. In the next sub-section, we group the extensions
that specify or rely on the SACK option, which must be
negotiated bilaterally. TCP implementations should include the
enhancements from both sub-sections so that TCP senders can
perform well without regard to the feature sets of other hosts
they connect to. For example, if SACK use is not successfully
negotiated, a host should use the NewReno behavior as a fall
back.</t>
<t><list style="hanging">
<t hangText="RFC 3042 S: "Enhancing TCP's Loss Recovery
Using Limited Transmit" (January 2001)">
<vspace blankLines="1"/>
Abstract: "This document proposes Limited Transmit, a
new Transmission Control Protocol (TCP) mechanism that can
be used to more effectively recover lost segments when a
connection's congestion window is small, or when a large
number of segments are lost in a single transmission
window." <xref target="RFC3042"/> Tests from 2004 showed
that Limited Transmit was deployed in roughly one third of
the web servers tested <xref target="MAF04"/>.</t>
<t hangText="RFC 3168 S: "The Addition of Explicit
Congestion Notification (ECN) to IP" (September 2001)">
<vspace blankLines="1"/>
This document <xref target="RFC3168"/> defines a means for end
hosts to detect congestion before congested routers are forced
to discard packets. Although congestion notification takes
place at the IP level, ECN requires support at the transport
level (e.g., in TCP) to echo the bits and adapt the sending
rate. This document updates RFC 793 to define two
previously unused flag bits in the TCP header for ECN support.
RFC 3540 provides a supplementary (experimental) means for more
secure use of ECN, and RFC 2884 provides some sample results
from using ECN.</t>
<t hangText="RFC 3465 E: "TCP Congestion Control with
Appropriate Byte Counting (ABC)" (February 2003)">
<vspace blankLines="1"/>
This document <xref target="RFC3465"/> suggests that
congestion control use the number of bytes acknowledged
instead of the number of acknowledgments received. The ABC
mechanism behaves differently than the standard method when
there is not a one-to-one relationship between data
segments and acknowledgements. ABC still operates within
the accepted guidelines, but is more robust to delayed ACKs
and ACK-division <xref target="SCWA99"/><xref
target="RFC3449"/>.</t>
<t hangText="RFC 6633 S: "Deprecation of ICMP Source
Quench Messages" (May 2012)"><vspace blankLines="1"/>
This document <xref target="RFC6633"/> formally deprecates
the use of ICMP Source Quench messages by transport
protocols and provides a recommendation against the
implementation of <xref target="RFC1016"/>.</t>
<t hangText="RFC 6582 S: "The NewReno Modification to
TCP's Fast Recovery Algorithm" (April 2012)">
<vspace blankLines="1"/>
This document <xref target="RFC6582"/>
specifies a modification to the standard Reno fast recovery
algorithm, whereby a TCP sender can use partial
acknowledgments to make inferences
determining the next segment to send in situations where SACK
would be helpful but isn't available. Although it is only a
slight modification, the NewReno behavior can make a
significant difference in performance when multiple segments
are lost from a single window of data.</t>
<t>RFC 2582 and RFC 3782 are the conceptual precursors of RFC
6582. The main change in RFC 3782 relative to RFC 2582 was
to specify the Careful variant of NewReno's Fast Retransmit
and Fast Recovery algorithms and advace those two
algorithms from Experimental to Standards Track status. The
main change in RFC 6582 relative to RFC 3782 was to solve a
performance degradation that could occur if FlightSize on
Full ACK reception is zero.</t>
</list></t>
</section>
<!-- Subsection: SACK-Based Loss Recovery and Congestion Control -->
<section title="SACK-Based Loss Recovery and Congestion Control"
anchor="sack">
<t>The base TCP specification in RFC 793 provided only a simple
cumulative acknowledgment mechanism. However, a selective
acknowledgment (SACK) mechanism provides performance improvement in
the presence of multiple packet losses from the same flight, more
than outweighing the modest increase in complexity. A TCP should
be expected to implement SACK; however, SACK is a negotiated option
and is only used if support is advertised by both sides of a
connection.</t>
<t><list style="hanging">
<t hangText="RFC 2018 S: "TCP Selective Acknowledgment
Options" (October 1996) (Errata)"><vspace blankLines="1"/>
When more than one packet is lost during one round trip
time TCP may experience poor performance since a TCP sender
can only learn about a single lost packet per round trip
time from cumulative acknowledgments. This document
<xref target="RFC2018"/> defines the basic selective
acknowledgment (SACK) mechanism for TCP, which can help to
overcome these limitations. The receiving TCP returns SACK
blocks to inform the sender which data has been received.
The sender can then retransmit only the missing data
segments.</t>
<t hangText="RFC 2883 S: "An Extension to the Selective
Acknowledgement (SACK) Option for TCP" (July 2000)">
<vspace blankLines="1"/>
This document <xref target="RFC2883"/> extends RFC 2018.
It enables use of the SACK option to acknowledge duplicate
packets. With this extension, called DSACK, the sender is
able to infer the order of packets received at the
receiver, and therefore to infer when it has unnecessarily
retransmitted a packet.</t>
<t hangText="RFC 6675 S: "A Conservative Loss Recovery
Algorithm Based on Selective Acknowledgment (SACK) for
TCP" (August 2012)"><vspace blankLines="1"/>
This document <xref target="RFC6675"/> describes a
conservative loss recovery algorithm for TCP that is based
on the use of the selective acknowledgment (SACK) TCP
option <xref target="RFC2018"/>. The algorithm conforms to
the spirit of the congestion control specification in RFC
5681, but allows TCP senders to recover more effectively
when multiple segments are lost from a single flight of
data.</t>
<t>RFC 6675 is a revision of RFC 3517 to address several
situations that are not handled explicitly before. In
particular
<?rfc subcompact="yes"?>
<list style="format (%c)">
<t>it improves the loss detection in the event
that the sender has outstanding segments that are
smaller than SMSS.</t>
<t>it modifies the definition of a "duplicate
acknowledgment" to utilize the SACK information
in detecting loss.</t>
<t>it maintains the ACK clock under certain
circumstances involving loss at the end of the
window.</t>
</list>
<?rfc subcompact="no"?>
</t>
</list></t>
</section>
<!-- Subsection: Detection and Prevention of Spurious
Retransmissions -->
<section title="Detection and Prevention of Spurious
Retransmissions" anchor="spourious">
<t>Spurious retransmission timeouts are harmful to TCP
performance and multiple algorithms have been defined for
detecting when spurious retransmissions have occurred, and then
responding differently in order to recover performance. The
IETF defined multiple algorithms because there are tradeoffs in
whether or not certain TCP options need to be implemented, and
IPR status. The Standards Track documents in this section are
closely related to the Experimental documents in <xref
target="spourious-may"/> also addressing this topic.</t>
<t><list style="hanging">
<t hangText="RFC 4015 S: "The Eifel Response Algorithm
for TCP" (February 2005)"><vspace blankLines="1"/>
This document <xref target="RFC4015"/> describes the
response portion of the Eifel algorithm, which can be used
in conjunction with one of several methods of detecting when
loss recovery has been spuriously entered, such as the Eifel
detection algorithm in RFC 3522, the algorithm in RFC 3708,
or F-RTO in RFC 5682.</t>
<t>Abstract: "Based on an appropriate detection algorithm,
the Eifel response algorithm provides a way for a TCP sender
to respond to a detected spurious timeout. It adapts the
retransmission timer to avoid further spurious timeouts, and
can avoid - depending on the detection algorithm - the often
unnecessary go-back-N retransmits that would otherwise be
sent. In addition, the Eifel response algorithm restores the
congestion control state in such a way that packet bursts
are avoided."</t>
<t hangText="RFC 5682 S: "Forward RTO-Recovery (F-RTO):
An Algorithm for Detecting Spurious Retransmission Timeouts
with TCP" (September 2009)"><vspace blankLines="1"/>
The F-RTO detection algorithm <xref target="RFC5682"/>,
originally describes in RFC 4138, provides an option for
inferring spurious retransmission timeouts. Unlike some
similar detection methods (e.g. RFC 3522 and RFC 3708),
F-RTO does not rely on the use of any TCP options. The
basic idea is to send previously unsent data after the
first retransmission after a RTO. If the ACKs advance the
window, the RTO may be declared spurious.</t>
</list></t>
</section>
<!-- Subsection: Path MTU Discovery -->
<section title="Path MTU Discovery" anchor="pmtud">
<t>The MTUs supported by different links and tunnels within the
Internet can vary widely. Fragmentation of packets larger than
the supported MTU on a hop is undesirable. As TCP is the
segmentation layer for dividing an application's bytestream
into IP packet payloads, TCP implementations generally include
Path MTU Discovery (PMTUD) mechanisms in order to maximize the
size of segments they send, without causing fragmentation
within the network. Some algorithms may utilize signalling
from routers on the path that the MTU has been exceeded.</t>
<t><list style="hanging">
<t hangText="RFC 1191 S: "Path MTU Discovery"
(November 1990)"><vspace blankLines="1"/>
Abstract: "This memo describes a technique for
dynamically discovering the MTU of an arbitrary Internet
path. It specifies a small change to the way routers
generate one type of ICMP message. For a path that passes
through a router that has not been so changed, this
technique might not discover the correct path MTU, but it
will always choose a path MTU as accurate as, and in many
cases more accurate than, the path MTU that would be chosen
by current practice." <xref target="RFC1191"/></t>
<t hangText="RFC 1981 S: "Path MTU Discovery for IP
version 6" (August 1996)"><vspace blankLines="1"/>
Abstract: "This document describes Path MTU Discovery for
IP version 6. It is largely derived from RFC 1191, which
describes Path MTU Discovery for IP version 4."
<xref target="RFC1981"/></t>
<t hangText="RFC 4821 S: "Packetization Layer Path MTU
Discovery" (March 2007)"><vspace blankLines="1"/>
Abstract: "This document describes a robust method for
Path MTU Discovery (PMTUD) that relies on TCP or some other
Packetization Layer to probe an Internet path with
progressively larger packets. This method is described as
an extension to RFC 1191 and RFC 1981, which specify
ICMP-based Path MTU Discovery for IP versions 4 and 6,
respectively." <xref target="RFC4821"/></t>
</list></t>
</section>
<!-- Subsection: Header Compression -->
<section title="Header Compression" anchor="compression">
<t>Especially in streaming applications, the overhead of TCP/IP
headers could correspond to more then 50% of the total amount
of data sent. Such large overheads may be tolerable in wired
LANs where capacity is often not an issue, but are excessive
for WANs and wireless systems where bandwidth is scarce. Header
compressions schemes for TCP/IP like the RObust Header
Compression (ROHC) can significant compresses these overhead.
It performs well over links with significant error rates and
long round-trip times.</t>
<t><list style="hanging">
<t hangText="RFC 1144 S: "Compressing TCP/IP
Headers for Low-Speed Serial Links" (February 1990)">
<vspace blankLines="1"/>
This document <xref target="RFC1144"/> describes a method
for compressing the headers of TCP/IP datagrams to improve
performance over low speed serial links. The method
described in this document is limited in its handling of
TCP options and cannot compress the headers of SYNs and
FINs.</t>
<t hangText="RFC 6846 S: "RObust Header Compression
(ROHC): A Profile for TCP/IP (ROHC-TCP)"
January 2013)"><vspace blankLines="1"/>
From abstract: "This document specifies a RObust Header
Compression (ROHC) profile for compression of TCP/IP
packets. The profile, called ROHC-TCP, provides efficient
and robust compression of TCP headers, including frequently
used TCP options such as selective acknowledgments (SACKs)
and Timestamps." <xref target="RFC6846"/> RFC 6846 is the
successor of RFC 4996. It fixes a technical issue with the
SACK compression and clarifies other compression methods
used.</t>
</list></t>
</section>
<!-- Subsection: Defending Spoofing and Flooding Attacks -->
<section title="Defending Spoofing and Flooding Attacks" anchor="antispoof">
<t>By default, TCP lacks any cryptographic structures to
differentiate legitimate segments and those spoofed from malicious
hosts. Spoofing valid segments requires correctly guessing a
number of fields. The documents in this sub-section describe ways
to make that guessing harder, or to prevent it from being able to
affect a connection negatively.</t>
<t><list style="hanging">
<t hangText="RFC 4953 I: "Defending TCP Against Spoofing
Attacks" (July 2007)"><vspace blankLines="1"/>
This document <xref target="RFC4953"/> discusses the recently
increased vulnerability of long-lived TCP connections, such
as BGP connections, to resets (RSTs) spoofing attacks. The
document analyses the vulnerability, discussing proposed
solutions at the transport level and their inherent
challenges, as well as existing network level solutions and
the feasibility of their deployment.</t>
<t hangText="RFC 5461 I: "TCP's Reaction to Soft
Errors" (February 2009)"><vspace blankLines="1"/>
This document <xref target="RFC5461"/> describes a
non-standard but widely implemented modification to TCP's
handling of ICMP soft error messages that rejects pending
connection-requests when such error messages are received.
This behavior reduces the likelihood of long delays between
connection-establishment attempts that may arise in some
scenarios.</t>
<t hangText="RFC 4987 I: "TCP SYN Flooding Attacks and
Common Mitigations" (August 2007)">
<vspace blankLines="1"/>
This document <xref target="RFC4987"/> describes the
well-known TCP SYN flooding attack. It analyses and
discusses various countermeasures against these attacks,
including their use and trade-offs.</t>
<t hangText="RFC 5925 S: "The TCP Authentication
Option" (May 2010)"><vspace blankLines="1"/>
This document <xref target="RFC5925"/> describes the TCP
Authentication Option (TCP-AO), which is used to
authenticate TCP segments. TCP-AO obsoletes the TCP MD5
Signature option of RFC 2385. It supports the use of
stronger hash functions, protects against replays for
long-lived TCP connections (as used, e.g., in BGP and LDP),
coordinates key exchanges between endpoints, and provides a
more explicit recommendation for external key management.
Cryptographic algorithms for TCP-AO are defined in
<xref target="RFC5926"/>.</t>
<t hangText="RFC 5926 S: "Cryptographic Algorithms for
the TCP Authentication Option (TCP-AO)" (May 2010)">
<vspace blankLines="1"/>
This document <xref target="RFC5926"/> specifies the
algorithms and attributes that can be used in TCP
Authentication Option's (TCP-AO) current manual keying
mechanism and provides the interface for future message
authentication codes (MACs).</t>
<t hangText="RFC 5927 I: "ICMP attacks against
TCP" (July 2010)">
<vspace blankLines="1"/>
Abstract: "This document discusses the use of the
Internet Control Message Protocol (ICMP) to perform a
variety of attacks against the Transmission Control Protocol
(TCP). Additionally, this document describes a number of
widely implemented modifications to TCP's handling of ICMP
error messages that help to mitigate these issues."
<xref target="RFC5927"/></t>
<t hangText="RFC 5961 S: "Improving TCP's Robustness to
Blind In-Window Attacks" (August 2010)">
<vspace blankLines="1"/>
This document <xref target="RFC5961"/> describes minor
modifications to how TCP handles inbound segments. This
renders TCP connections, especially long-lived connections
such as H-323 or BGP, are less vulnerable to spoofed packet
injection attacks where the 4-tuple (the source and
destination IP addresses and the source and destination
ports) has been guessed.</t>
<t hangText="RFC 6528 S: "Defending Against Sequence
Number Attacks" (February 2012)"><vspace blankLines="1"/>
Abstract: "This document <xref target="RFC6528"/>
specifies an algorithm for the generation of TCP Initial
Sequence Numbers (ISNs), such that the chances of an
off-path attacker guessing the sequence numbers in use by a
target connection are reduced. This document revises (and
formally obsoletes) RFC 1948, and takes the ISN generation
algorithm originally proposed in that document to Standards
Track, formally updating RFC 793.</t>
</list></t>
</section>
</section>
<!-- Section: Experimental Extensions -->
<section title="Experimental Extensions" anchor="may">
<t>The RFCs in this section are still experimental, but they may
become proposed standards in the future. At least part of the
reason that they are still experimental is to gain more wide-scale
experience with them before a standards track decision is made.</t>
<t>At this point is worth mentioning that if the experimatal RFC
is a proposal for a new protocol capability or service, i.e., it
requires a new TCP option codepoint, the implemenation and
experimentation should follows <!--xref target="RFC6994"/--> (see
<xref target="iana"/>), which describes how the experimental TCP
option codepoints can concurrently support multiple TCP
extensions.</t>
<t>By their publication as experimental RFCs, it is hoped that the
community of TCP researchers will analyze and test the contents of
these RFCs. Although experimentation is encouraged, there is not
yet formal consensus that these are fully logical and safe
behaviors. Wide-scale deployment of implementations that use these
features should be well thought-out in terms of consequences.
</t>
<!-- Subsection: Architectural Guidelines -->
<section title="Architectural Guidelines" anchor="architectural-may">
<t>As multiple flows may share the same paths, sections of
paths, or other resources, the TCP implementation may benefit
from sharing information across TCP connections or other flows.
Some Experimental proposals have been documented and some
implementations have included the concepts.</t>
<t><list style="hanging">
<t hangText="RFC 2140 I: "TCP Control Block
Interdependence" (April 1997)"><vspace blankLines="1"/>
This document <xref target="RFC2140"/> suggests how TCP
connections between the same endpoints might share
information, such as their congestion control state. To some
degree, this is done in practice by a few operating systems;
for example, Linux currently has a destination cache.
Although this RFC is technically informational, the concepts
it describes are in experimental use, so we include it in
this section.</t>
<t hangText="RFC 3124 S: "The Congestion Manager"
(June 2001)"><vspace blankLines="1"/>
This document <xref target="RFC3124"/>, the Congestion
Manager, is a related proposal to RFC 2140. The idea behind
the Congestion Manager, moving congestion control outside of
individual TCP connections, represents a modification to the
core of TCP, which supports sharing information among TCP
connections as well. Although a Proposed Standard, some
pieces of the Congestion Manager support architecture have
not been specified yet, and it has not achieved use or
implementation beyond experimental stacks, so it is not
listed among the standard TCP enhancements in this
roadmap.</t>
</list></t>
</section>
<!-- Subsection: Congestion Control and Loss Recovery
Extensions -->
<section title="Congestion Control and Loss Recovery Extensions"
anchor="cc-may">
<t>TCP congestion control has been an extremely active research area
for many years, as it determines the performance of many
applications that use TCP. A number of experimental RFCs
address issues with flow startup, overshoot, and steady-state
behavior in the basic RFC 5681 algorithms.</t>
<t><list style="hanging">
<t hangText="RFC 2861 E: "TCP Congestion Window
Validation" (June 2000)"><vspace blankLines="1"/>
This document <xref target="RFC2861"/> suggests reducing the
congestion window over time when no packets are flowing.
This behavior is more aggressive than that specified in RFC
5681, which says that a TCP sender SHOULD set its congestion
window to the initial window after an idle period of an RTO
or greater.</t>
<t hangText="RFC 3540 E: "Robust Explicit Congestion
Notification (ECN) signaling with Nonces" (June 2003)">
<vspace blankLines="1"/>
This document <xref target="RFC3540"/> describes an optional
addition to ECN that protects against accidental or
malicious concealment of marked packets from the TCP
sender.</t>
<t hangText="RFC 3649 E: "HighSpeed TCP for Large
Congestion Windows" (December 2003)">
<vspace blankLines="1"/>
This document <xref target="RFC3649"/> proposes a
modification to TCP's congestion control mechanism for use
with TCP connections with large congestion windows, to allow
TCP to achieve a higher throughput in high-bandwidth
environments.</t>
<t hangText="RFC 3742 E: "Limited Slow-Start for TCP
with Large Congestion Windows" (March 2004)">
<vspace blankLines="1"/>
This document <xref target="RFC3742"/> describes a more
conservative slow-start behavior to prevent massive packet
losses when a connection uses a very large congestion
window.</t>
<t hangText="RFC 4782 E: "Quick-Start for TCP and
IP" (January 2007) (Errata)"><vspace blankLines="1"/>
This document <xref target="RFC4782"/> specifies the
optional Quick-Start mechanism for TCP. This mechanism
allows connections to use higher sending rates at the
beginning of the data transfer or after an idle period,
provided that there is significant unused bandwidth along
the path, and the sender and all of the routers along the
path approve this higher rate.</t>
<t hangText="RFC 5562 E: "Adding Explicit Congestion
Notification (ECN) Capability to TCP's SYN/ACK Packets"
(June 2009)"><vspace blankLines="1"/>
This document <xref target="RFC5562"/> describes an
experimental modification to ECN <xref target="RFC3168"/>
for the use of ECN in TCP SYN/ACK packets. This would allow
to ECN-mark rather than drop the TCP SYN/ACK packet at an
ECN-capable router, and to avoid the severe penalty of a
retransmission timeout for a connection when the SYN/ACK
packet is dropped.</t>
<t hangText="RFC 5690 I: "Adding Acknowledgement
Congestion Control to TCP" (February 2010)">
<vspace blankLines="1"/>
This document <xref target="RFC5690"/> describes a
congestion control mechanism for acknowledgment (ACKs)
traffic in TCP. The mechanism is based on the acknowledgment
congestion control of the Datagram Congestion Control
Protocol's (DCCP's) <xref target="RFC4340"/> Congestion
Control Identifier (CCID) 2 <xref target="RFC4341"/>.</t>
<t hangText="RFC 5827 E: "Early Retransmit for TCP and
SCTP" (April 2010)"><vspace blankLines="1"/>
This document <xref target="RFC5827"/> proposes the
"Early Retransmit" mechanism for TCP (and SCTP)
that can be used to recover lost segments when a
connection's congestion window is small. In certain special
circumstances, Early Retransmit reduces the number of
duplicate acknowledgments required to trigger fast
retransmit to recover segment losses without waiting for a
lengthy retransmission timeout.</t>
<t hangText="RFC 6069 E: "Making TCP more Robust to
Long Connectivity Disruptions (TCP-LCD)" (December
2010)"><vspace blankLines="1"/>
This document <xref target="RFC6069"/> describes how
standard ICMP messages can be used to disambiguate true
congestion loss from non-congestion loss caused by
connectivity disruptions. It proposes a reversion strategy
of TCP's retransmission timer that enables a more prompt
detection of whether or not the connectivity has been
restored.</t>
<t hangText="RFC 6928 E: "Increasing TCP's Initial
Window" (April 2013)"><vspace blankLines="1"/>
This document <xref target="RFC6928"/> proposes to increase
the TCP initial window from between 2 and 4 segments, as
specified in RFC 3390, to 10 segments with a fallback to
the existing recommendation when performance issues are
detected.</t>
<t hangText="RFC 6937 E: "Proportional Rate Reduction
for TCP" (May 2013)"><vspace blankLines="1"/>
This document <xref target="RFC6937"/> describes an
experimental Proportional Rate Reduction (PRR) algorithm as
an alternative to the widely deployed Fast Recovery
algorithm, to improve the accuracy of the amount of data
sent by TCP during loss recovery.</t>
</list></t>
</section>
<!-- Subsection: Detection and Prevention of Spurious
Retransmissions -->
<section title="Detection and Prevention of Spurious
Retransmissions" anchor="spourious-may">
<t>In addition to the Standards Track extensions to deal with
spurious retransmissions in <xref target="spourious"/>,
Experimental proposals have also been documented.</t>
<t><list style="hanging">
<t hangText="RFC 3522 E: "The Eifel Detection Algorithm
for TCP" (April 2003)"><vspace blankLines="1"/>
The Eifel detection algorithm <xref target="RFC3522"/>
allows a TCP sender to detect a posteriori whether it has
entered loss recovery unnecessarily by using the TCP
timestamp option to solve the ACK ambiguity.</t>
<t hangText="RFC 3708 E: "Using TCP Duplicate Selective
Acknowledgement (DSACKs) and Stream Control Transmission
Protocol (SCTP) Duplicate Transmission Sequence Numbers
(TSNs) to Detect Spurious Retransmissions" (February
2004)"> <vspace blankLines="1"/>
Abstract: "TCP and Stream Control Transmission Protocol
(SCTP) provide notification of duplicate segment receipt
through Duplicate Selective Acknowledgement (DSACKs) and
Duplicate Transmission Sequence Number (TSN) notification,
respectively. This document presents conservative methods
of using this information to identify unnecessary
retransmissions for various applications."
<xref target="RFC3708"/></t>
<t hangText="RFC 4653 E: "Improving the Robustness of
TCP to Non-Congestion Events" (August 2008)">
<vspace blankLines="1"/>
In the presence of non-congestion events, such as reordering
an out-of-order segment does not necessarily indicates a
lost segment and congestion. This document
<xref target="RFC4653"/> proposes to increase the threshold
used to trigger a fast retransmission from the fixed value
of three duplicate ACKs to about one congestion window of
data in order to disambiguate true segment loss from segment
reordering.</t>
</list></t>
</section>
<!-- Subsection: Multipath TCP -->
<section title="Multipath TCP" anchor="mptcp-may">
<t>MultiPath TCP (MPTCP) is an ongoing effort within the IETF
that allows a TCP connection to simultaneous use multiple
IP-addresses/interfaces to spread their data across several
subflows, while presenting a regular TCP interface to
applications. Benefits of this include better resource
utilization, better throughput and smoother reaction to
failures. The documents listed in this section specify the
Multipath TCP scheme, while the documents in Sections
<xref target="development" format="counter"/>,
<xref target="architectural-supp" format="counter"/> and
<xref target="tcpimpl" format="counter"/> provide some additinal
background information.</t>
<t><list style="hanging">
<t hangText="RFC 6356 E: "Coupled Congestion Control
for Multipath Transport Protocols" (August 2011)">
<vspace blankLines="1"/>
This document <xref target="RFC6356"/> presents a congestion
control algorithm for multipath transport protocols such as
Multipath TCP. It couples the congestion control algorithms
running on different subflows by linking their increase
functions, and dynamically controls the overall
aggressiveness of the multipath flow. The result is an
algorithm that is fair to TCP at bottlenecks while moving
traffic away from congested links.</t>
<t hangText="RFC 6824 E: "TCP Extensions for Multipath
Operation with Multiple Addresses" (January 2013)
(Errata)"><vspace blankLines="1"/>
This document <xref target="RFC6824"/> presents protocol
changes required to add multipath capability to TCP;
specifically, those for signaling and setting up multiple
paths ("subflows"), managing these subflows, reassembly of
data, and termination of sessions.</t>
</list></t>
</section>
</section>
<!-- Section: TCP Parameters at IANA -->
<section title="TCP Parameters at IANA" anchor="iana">
<t>RFCs listed here describes both the procedures that the Internet
Assigned Numbers Authority (IANA) uses when handling assignments
and the procedures an RFC author should follow when requesting
new TCP option codepoints.</t>
<t><list style="hanging">
<t hangText="RFC 2780 B: "IANA Allocation Guidelines For
Values In the Internet Protocol and Related Headers"
(March 2000)">
<vspace blankLines="1"/>
Abstract: "This memo provides guidance for the IANA to use in
assigning parameters for fields in the IPv4, IPv6, ICMP, UDP
and TCP protocol headers."<xref target="RFC2780"/></t>
<t hangText="RFC 4727 S: "Experimental Values"
(November 2006)">
<vspace blankLines="1"/>
This document <xref target="RFC4727"/> reserves both TCP
options 253 and 254 for experimentation purposes. When such
experiments are deployed in the Internet, they should follow
the additional requirements in RFC 6994.</t>
<t hangText="RFC 6335 B: "Internet Assigned Numbers
Authority (IANA) Procedures for the Management of the Service
Name and Transport Protocol Port Number Registry (August 2011)">
<vspace blankLines="1"/>
From abstract: "This document defines the procedures that the
Internet Assigned Numbers Authority (IANA) uses when handling
assignment and other requests related to the Service Name and
Transport Protocol Port Number registry."
<xref target="RFC6335"/></t>
<t hangText="RFC 6994 S: "Shared Use of Experimental TCP
Options (August 2013)">
<vspace blankLines="1"/>
This document <xref target="RFC6994"/> describes how the
experimental TCP option codepoints can concurrently support
multiple TCP extensions, even within the same connection. It
creates an IANA registry for extensions to the experimental
codepoints.</t>
</list></t>
</section>
<!-- Section: Historic and Undeployed Extensions -->
<section title="Historic and Undeployed Extensions" anchor="history">
<t>The RFCs listed here define extensions that have thus far failed
to arouse substantial interest from implementers and have never
seen widespread, or were found to be defective for general use. Most
of them are reclassifies by RFC 6247 <xref target="RFC6247"/> to
Historic status.</t>
<t><list style="hanging">
<t hangText="RFC 721 U: "Out-of-Band Control Signals in a
Host-to-Host Protocol" (September 1976): lack of interest">
<vspace blankLines="1"/>
RFC 721 <xref target="RFC0721"/> addresses the problem of
implementing a reliable out-of-band signal (interrupts) for use
in a host-to-host protocol. The proposal has not been included
in the final TCP specification.</t>
<t hangText="RFC 1078 U: "TCP Port Service Multiplexer
(TCPMUX)" (November 1988): lack of interest">
<vspace blankLines="1"/>
This document <xref target="RFC1078"/> propose a protocol to
contact multiple services on a single well-known TCP port using
a service name instead of a well-known number.</t>
<t hangText="RFC 1106 H: "TCP Big Window and NAK
Options" (June 1989): found defective">
<vspace blankLines="1"/>
This RFC <xref target="RFC1106"/> defined an alternative to the
Window Scale option for using large windows and described the
"negative acknowledgement" or NAK option. There is a comparison
of NAK and SACK methods, and early discussion of TCP over
satellite issues. RFC 1110 explains some problems with the
approaches described in RFC 1106. The options described in this
document have not been adopted by the larger community,
although NAKs are used in the SCPS-TP adaptation of TCP for
satellite and spacecraft use, developed by the Consultative
Committee for Space Data Systems (CCSDS).</t>
<t hangText="RFC 1110 H: "A Problem with the TCP Big
Window Option" (August 1989): deprecates RFC 1106">
<vspace blankLines="1"/>
Abstract: "The TCP Big Window option discussed in RFC 1106
will not work properly in an Internet environment which has
both a high bandwidth * delay product and the possibility of
disordering and duplicating packets. In such networks, the
window size must not be increased without a similar increase in
the sequence number space. Therefore, a different approach to
big windows should be taken in the Internet."
<xref target="RFC1110"/></t>
<t hangText="RFC 1146 H: "TCP Alternate Checksum
Options" (March 1990): lack of interest">
<vspace blankLines="1"/>
This document <xref target="RFC1146"/> defined more robust TCP
checksums than the 16-bit ones-complement in use today. A
typographical error in RFC 1145 is fixed in RFC 1146; otherwise,
the documents are the same.</t>
<t hangText="RFC 1263 I: "TCP Extensions Considered
Harmful" (October 1991): lack of interest">
<vspace blankLines="1"/>
This document <xref target="RFC1263"/> argues against
"backwards compatible" TCP extensions. Specifically mentioned
are several TCP enhancements that have been successful,
including timestamps, window scaling, PAWS, and SACK. RFC 1263
presents an alternative approach called "protocol evolution",
whereby several evolutionary versions of TCP would exist on
hosts. These distinct TCP versions would represent upgrades to
each other and could be header-incompatible. Interoperability
would be provided by having a virtualization layer select the
right TCP version for a particular connection. This idea did
not catch on with the community, while the type of extensions
RFC 1263 specifically targeted as harmful did become popular.
</t>
<t hangText="RFC 1379 H: "Extending TCP for Transactions
-- Concepts" (November 1992): found defective">
<vspace blankLines="1"/>
See RFC 1644.</t>
<t hangText="RFC 1644 H: "T/TCP -- TCP Extensions for
Transactions Functional Specification" (July 1994):
found defective"><vspace blankLines="1"/>
The inventors of TCP believed that cached connection state
could have been used to eliminate TCP's 3-way handshake, to
support two-packet request/response exchanges. RFCs 1379
<xref target="RFC1379"/> and 1644 <xref target="RFC1644"/> show
that this is far from simple. Furthermore, T/TCP floundered on
the ease of denial-of-service attacks that can result. One
idea pioneered by T/TCP lives on in RFC 2140, in the sharing of
state across connections.</t>
<t hangText="RFC 1693 H: "An Extension to TCP: Partial
Order Service" (November 1994): lack of interest">
<vspace blankLines="1"/>
This document <xref target="RFC1693"/> defines a TCP extension
for applications that do not care about the order in which
application-layer objects are received. Examples are
multimedia and database applications. In practice, these
applications either accept the possible performance loss
because of TCP's strict ordering or they use more specialized
transport protocols.</t>
<t hangText="RFC 1705 I: "Six Virtual Inches to the Left:
The Problem with IPng" (October 1994): lack of interest">
<vspace blankLines="1"/>
To overcome the exhaustion of the IP class B address space,
suggest this document <xref target="RFC1705"/> that a new
version of TCP (TCPng) needs to be developed and deployed.
It proposes that a globally unique address be assigned to
Transport layer to uniquely identify an internet host
without specifying any routing information.</t>
<t hangText="RFC 6013 E: "TCP Cookie Transactions
(TCPCT)" (January 2011): lack of interest">
<vspace blankLines="1"/>
This document <xref target="RFC6013"/> describes a method to
exchange a cookie (nonce) during the connection establishment
to negotiates elimination of receiver state. These cookies are
later used to inhibit premature closing of connections, and
reduce retention of state after the connection has
terminated.</t>
<t>Since the cookie pair is too large to fit with the other TCP
options in the 40 bytes of TCP option space, the document
further describes method to extent the option space after the
connection establishment.</t>
<t>Although the RFC 6013 is publish in 2011, the authors
of this document places it in this section of the roadmap
document due to two factors.
<?rfc subcompact="yes"?>
<list style="format (%c)">
<t>The authors are not aware of any wide deployment and
use of RFC 6013.</t>
<t>RFC 6013 uses experimental TCP option codepoints,
which prohibits a large scale deployment.</t>
</list>
<?rfc subcompact="no"?>
</t>
</list></t>
</section>
<!-- Section: Support Documents -->
<section title="Support Documents" anchor="support">
<t>This section contains several classes of documents that do not
necessarily define current protocol behaviors, but that are
nevertheless of interest to TCP implementers. <xref
target="foundation"/> describes several foundational RFCs that
give modern readers a better understanding of the principles
underlying TCP's behaviors and development over the years. <xref
target="architectural-supp"/> contains architectural guidelines
and principles for TCP architects and designers. The documents
listed in <xref target="pilc"/> provide advice on using TCP in
various types of network situations that pose challenges above
those of typical wired links. Guidance for developing, analyzing,
and evaluating TCP is given in <xref target="development"/>. Some
implementation notes and implementation advices can be found in
<xref target="tcpimpl"/>. The TCP Management Information Bases are
described in <xref target="mibs"/>. RFCs that describe tools for
testing and debugging TCP implementations or that contain
high-level tutorials on the protocol are listed <xref
target="tools"/>, and <xref target="studies"/> lists a number
of case studies that have explored TCP performance.</t>
<!-- Subsection: Foundational Works -->
<section title="Foundational Works" anchor="foundation">
<t>The documents listed in this section contain information
that is largely duplicated by the standards documents
previously discussed. However, some of them contain a greater
depth of problem statement explanation or other context.
Particularly, RFCs 813 - 817 (known as the "Dave Clark Five")
describe some early problems and solutions (RFC 815 only
describes the reassembly of IP fragments and is not included
in this TCP roadmap).</t>
<t><list style="hanging">
<t hangText="RFC 675 U: "Specification of Internet
Transmission Control Program" (December 1974)">
<vspace blankLines="1"/>
This document <xref target="RFC0675"/> is a very early
precursor of the infamous RFC 793 which already contained
the three-way handshake in its final form and the concept
of sliding windows for reliable data transmission. Apart
from that the segment layout is totally different and the
specified API differs from the latter RFC 793.</t>
<t hangText="RFC 761 H: "DoD standard Transmission
Control Protocol" (Januar 1980)">
<vspace blankLines="1"/>
This document <xref target="RFC0761"/> is the immediate
predecessor of RFC 793. The header format, the connection
establishment including the different connection states,
and the overall API correspond mostly the final Standard
RFC 793.</t>
<t hangText="RFC 813 U: "Window and Acknowledgement
Strategy in TCP" (July 1982)"><vspace blankLines="1"/>
This document <xref target="RFC0813"/> contains an early
discussion of Silly Window Syndrome and its avoidance and
motivates and describes the use of delayed
acknowledgments.</t>
<t hangText="RFC 814 U: "Name, Addresses, Ports, and
Routes" (July 1982)"><vspace blankLines="1"/>
Suggestions and guidance for the design of tables and
algorithms to keep track of various identifiers within a
TCP/IP implementation are provided by this document
<xref target="RFC0814"/>.</t>
<t hangText="RFC 816 U: "Fault Isolation and
Recovery" (July 1982)"><vspace blankLines="1"/>
In this document <xref target="RFC0816"/>, TCP's response
to indications of network error conditions such as timeouts
or received ICMP messages is discussed.</t>
<t hangText="RFC 817 U: "Modularity and Efficiency in
Protocol Implementation" (July 1982)">
<vspace blankLines="1"/>
This document <xref target="RFC0817"/> contains
implementation suggestions that are general and not
TCP specific. However, they have been used to develop TCP
implementations and describe some performance implications
of the interactions between various layers in the Internet
stack.</t>
<t hangText="RFC 872 U: "TCP-ON-A-LAN" (September
1982)"><vspace blankLines="1"/>
Conclusion: "The sometimes-expressed fear that using
TCP on a local net is a bad idea is unfounded."
<xref target="RFC0872"/> </t>
<t hangText="RFC 896 U: "Congestion Control in IP/TCP
Internetworks" (January 1984)"><vspace blankLines="1"/>
This document <xref target="RFC0896"/> contains some early
experiences with congestion collapse and some initial
thoughts on how to avoid it using congestion control in
TCP.</t>
<t hangText="RFC 964 U: "Some Problems with the
Specification of the Military Standard Transmission Control
Protocol" (November 1985)"><vspace blankLines="1"/>
This document <xref target="RFC0964"/> points out several
specification bugs in the US Military's MIL-STD-1778
document, which was intended as a successor to RFC 793.
This serves to remind us of the difficulty in specification
writing (even when we work from existing documents!).</t>
</list></t>
</section>
<!-- Subsection: Architectural Guidelines -->
<section title="Architectural Guidelines" anchor="architectural-supp">
<t>Some documents in this section contain architectural guidance
and concerns, while others specify TCP- and
congestion-control-related mechanisms that are broadly
applicable and have impacts on TCP's congestion control
techniques. Some of these documents are direct products of the
Internet Architecture Board (IAB), giving their guidance on
specific aspects of congestion control in the Internet.</t>
<t><list style="hanging">
<t hangText="RFC 1958 I: "Architectural Principles of
the Internet" (June 1996)"><vspace blankLines="1"/>
This document <xref target="RFC1958"/> describes the
underlying principles of the Internet architecture. It
provides guidelines for network systems design that have
proven useful in the evolution of the Internet.</t>
<t hangText="RFC 2914 B: "Congestion Control
Principles" (September 2000)"><vspace blankLines="1"/>
This document <xref target="RFC2914"/> motivates the use of
end-to-end congestion control for preventing congestion
collapse and providing fairness to TCP.</t>
<t hangText="RFC 3439 I: "Some Internet Architectural
Guidelines and Philosophy" (December 2002)">
<vspace blankLines="1"/>
This document <xref target="RFC3439"/> extents RFC 1958 by
outlining some philosophical guidelines for architects and
designers of Internet backbone networks. The document
describes the Simplicity Principle, which states that
complexity is the primary mechanism that impedes efficient
scaling.</t>
<t hangText="RFC 6182 I: "Architectural Guidelines for
Multipath TCP Development" (March 2011)">
<vspace blankLines="1"/>
Abstract: "This document outlines architectural
guidelines for the development of a Multipath Transport
Protocol, with references to how these architectural
components come together in the development of a Multipath
TCP (MPTCP). This document lists certain high-level design
decisions that provide foundations for the design of the
MPTCP protocol, based upon these architectural
requirements" <xref target="RFC6182"/></t>
</list></t>
</section>
<!-- Subsection: Difficult Network Environments -->
<section title="Difficult Network Environments" anchor="pilc">
<t>As the internetworking field has explored wireless,
satellite, cellular telephone, and other kinds of link-layer
technologies, a large body of work has built up on enhancing
TCP performance for such links. The RFCs listed in this
section describe some of these more challenging network
environments and how TCP interacts with them.</t>
<t><list style="hanging">
<t hangText="RFC 2488 B: "Enhancing TCP Over
Satellite Channels using Standard Mechanisms"
(January 1999)"><vspace blankLines="1"/>
From abstract: "While TCP works over satellite channels
there are several IETF standardized mechanisms that enable
TCP to more effectively utilize the available capacity of
the network path. This document outlines some of these TCP
mitigations. At this time, all mitigations discussed in
this document are IETF standards track mechanisms (or are
compliant with IETF standards)."
<xref target="RFC2488"/></t>
<t hangText="RFC 2757 I: "Long Thin Networks"
(January 2000)"><vspace blankLines="1"/>
Several methods of improving TCP performance over long thin
networks, such as geosynchronous satellite links, are
discussed in this document <xref target="RFC2757"/>. A
particular set of TCP options is developed that should work
well in such environments and be safe to use in the global
Internet. The implications of such environments have been
further discussed in RFC 3150 and RFC 3155, and these
documents should be preferred where there is overlap
between them and RFC 2757.</t>
<t hangText="RFC 2760 I: "Ongoing TCP Research Related
to Satellites" (February 2000)"><vspace blankLines="1"/>
This document <xref target="RFC2760"/> discusses the
advantages and disadvantages of several different
experimental means of improving TCP performance over
long-delay or error-prone paths. These include T/TCP,
larger initial windows, byte counting, delayed
acknowledgments, slow start thresholds, NewReno and
SACK-based loss recovery, FACK <xref target="MM96"/>, ECN,
various corruption-detection mechanisms, congestion
avoidance changes for fairness, use of multiple parallel
flows, pacing, header compression, state sharing, and ACK
congestion control, filtering, and reconstruction. Although
RFC 2488 looks at standard extensions, this document
focuses on more experimental means of performance
enhancement.</t>
<t hangText="RFC 3135 I: "Performance Enhancing
Proxies Intended to Mitigate Link-Related Degradations"
(June 2001)"><vspace blankLines="1"/>
From abstract: "This document is a survey of Performance
Enhancing Proxies (PEPs) often employed to improve degraded
TCP performance caused by characteristics of specific link
environments, for example, in satellite, wireless WAN, and
wireless LAN environments. Different types of Performance
Enhancing Proxies are described as well as the mechanisms
used to improve performance."
<xref target="RFC3135"/></t>
<t hangText="RFC 3150 B: "End-to-end Performance
Implications of Slow Links" (July 2001)">
<vspace blankLines="1"/>
From abstract: "This document makes performance-related
recommendations for users of network paths that traverse
"very low bit-rate" links....This recommendation may be
useful in any network where hosts can saturate available
bandwidth, but the design space for this recommendation
explicitly includes connections that traverse 56 Kb/second
modem links or 4.8 Kb/second wireless access links - both
of which are widely deployed."
<xref target="RFC3150"/></t>
<t hangText="RFC 3155 B: "End-to-end Performance
Implications of Links with Errors" (August 2001)">
<vspace blankLines="1"/>
From abstract: "This document discusses the specific TCP
mechanisms that are problematic in environments with high
uncorrected error rates, and discusses what can be done to
mitigate the problems without introducing intermediate
devices into the connection."
<xref target="RFC3155"/></t>
<t hangText="RFC 3366 B: "Advice to link designers on
link Automatic Repeat reQuest (ARQ)" (August 2002)">
<vspace blankLines="1"/>
From abstract: "This document provides advice to the
designers of digital communication equipment and link-layer
protocols employing link-layer Automatic Repeat reQuest
(ARQ) techniques. This document presumes that the
designers wish to support Internet protocols, but may be
unfamiliar with the architecture of the Internet and with
the implications of their design choices for the
performance and efficiency of Internet traffic carried over
their links." <xref target="RFC3366"/></t>
<t hangText="RFC 3449 B: "TCP Performance Implications
of Network Path Asymmetry" (December 2002)">
<vspace blankLines="1"/>
From abstract: "This document describes TCP performance
problems that arise because of asymmetric effects. These
problems arise in several access networks, including
bandwidth-asymmetric networks and packet radio subnetworks,
for different underlying reasons. However, the end result
on TCP performance is the same in both cases: performance
often degrades significantly because of imperfection and
variability in the ACK feedback from the receiver to the
sender.</t>
<t>The document details several mitigations to these
effects, which have either been proposed or evaluated in
the literature, or are currently deployed in networks."
<xref target="RFC3449"/></t>
<t hangText="RFC 3481 B: "TCP over Second (2.5G) and
Third (3G) Generation Wireless Networks" (February 2003)">
<vspace blankLines="1"/>
From abstract: "This document describes a profile for
optimizing TCP to adapt so that it handles paths including
second (2.5G) and third (3G) generation wireless networks."
<xref target="RFC3481"/></t>
<t hangText="RFC 3819 B: "Advice for Internet Subnetwork
Designers" (July 2004)"><vspace blankLines="1"/>
This document <xref target="RFC3819"/> describes how TCP
performance can be negatively affected by some particular
lower-layer behaviors and provides guidance in designing
lower-layer networks and protocols to be amicable to TCP.</t>
</list></t>
</section>
<!-- Subsection: Guidance for Developing, Analyzing, and Evaluating TCP -->
<section title="Guidance for Developing, Analyzing, and Evaluating TCP"
anchor="development">
<t>Documents in this section give general guidance for developing,
analyzing, and evaluating TCP. Some of the documents discuss for
example the properties of congestion control protocols that are
"safe" for Internet deployment, as well as how to measure the
properties of congestion control mechanisms and transport
protocols.</t>
<t><list style="hanging">
<t hangText="RFC 4774 B: "Specifying Alternate
Semantics for the Explicit Congestion Notification (ECN)
Field" (November 2006)"><vspace blankLines="1"/>
This document <xref target="RFC4774"/> discusses some of the
issues in defining alternate semantics for the ECN field,
and specifies requirements for a safe co- existence in an
Internet that may include routers that do not understand the
defined alternate semantics.</t>
<t hangText="RFC 5033 B: "Specifying New Congestion
Control Algorithms" (August 2007)">
<vspace blankLines="1"/>
This document <xref target="RFC5033"/> considers the
evaluation of suggested congestion control algorithms that
differ from the principles outlined in RFC 2914. It is
useful for authors of such algorithms as well as for IETF
members reviewing the associated documents.</t>
<t hangText="RFC 5166 I: "Metrics for the Evaluation of
Congestion Control Mechanisms" (March 2008)">
<vspace blankLines="1"/>
This document <xref target="RFC5166"/> discusses metrics
that needs to be considered when evaluating new or modified
congestion control mechanisms for the Internet. Among
others, the document discusses throughput, delay, loss
rates, response times, fairness and robustness for
challenging environments.</t>
<t hangText="RFC 6181 I: "Threat Analysis for TCP
Extensions for Multipath Operation with Multiple
Addresses" (March 2011)"><vspace blankLines="1"/>
This document <xref target="RFC6181"/> describes a threat
analysis for Multipath TCP (MPTCP). The document discusses
several types of attacks and provides recommendations for
MPTCP designers how to create an MPTCP specification that is
as secure as the current (single-path) TCP.</t>
<t hangText="RFC 6349 I: "Framework for TCP Throughput
Testing" (August 2011)"><vspace blankLines="1"/>
From abstract: "This document describes a practical
methodology for measuring end-to-end TCP throughput in a
managed IP network. The goal is to provide a better
indication in regard to user experience. In this
framework, TCP and IP parameters are specified to optimize
TCP throughput." <xref target="RFC6349"/></t>
</list></t>
</section>
<!-- Subsection: Implementation Advice -->
<section title="Implementation Advice" anchor="tcpimpl">
<t><list style="hanging">
<t hangText="RFC 794 U: "PRE-EMPTION"
(September 1981)"><vspace blankLines="1"/>
This document <xref target="RFC0794"/> discusses on a
high-level the realization of pre-emption in TCP.</t>
<t hangText="RFC 879 U: "The TCP Maximum Segment Size
and Related Topics" (November 1983)">
<vspace blankLines="1"/>
Abstract: "This memo discusses the TCP Maximum Segment
Size Option and related topics. The purposes is to clarify
some aspects of TCP and its interaction with IP. This memo
is a clarification to the TCP specification, and contains
information that may be considered as 'advice to
implementers'." <xref target="RFC0879"/></t>
<t hangText="RFC 1071 U: "Computing the Internet
Checksum" (September 1988) (Errata)">
<vspace blankLines="1"/>
This document <xref target="RFC1071"/> lists a number of
implementation techniques for efficiently computing the
Internet checksum (used by TCP).</t>
<t hangText="RFC 1624 I: "Computation of the
Internet Checksum via Incremental Update" (May 1994)">
<vspace blankLines="1"/>
Incrementally updating the Internet checksum is useful to
routers in updating IP checksums. Some middleboxes that
alter TCP headers may also be able to update the TCP
checksum incrementally. This document
<xref target="RFC1624"/> expands upon the explanation of the
incremental update procedure in RFC 1071.</t>
<t hangText="RFC 1936 I: "Implementing the Internet
Checksum in Hardware" (April 1996)">
<vspace blankLines="1"/>
This document <xref target="RFC1936"/> describes the
motivation for implementing the Internet checksum in
hardware, rather than in software, and provides an
implementation example.</t>
<t hangText="RFC 2525 I: "Known TCP Implementation
Problems" (March 1999)"><vspace blankLines="1"/>
From abstract: "This memo catalogs a number of known
TCP implementation problems. The goal in doing so is to
improve conditions in the existing Internet by enhancing
the quality of current TCP/IP implementations."
<xref target="RFC2525"/></t>
<t hangText="RFC 2923 I: "TCP Problems with Path
MTU Discovery" (September 2000)">
<vspace blankLines="1"/>
From abstract: "This memo catalogs several known
Transmission Control Protocol (TCP) implementation problems
dealing with Path Maximum Transmission Unit Discovery
(PMTUD), including the long-standing black hole problem,
stretch acknowlegements (ACKs) due to confusion between
Maximum Segment Size (MSS) and segment size, and MSS
advertisement based on PMTU."
<xref target="RFC2923"/></t>
<t hangText="RFC 3360 B: "Inappropriate TCP Resets
Considered Harmful" (August 2002)">
<vspace blankLines="1"/>
This document <xref target="RFC3360"/> is a plea that
firewall vendors not send gratuitous TCP RST (Reset)
packets when unassigned TCP header bits are used. This
practice prevents desirable extension and evolution of the
protocol and thus is potentially harmful to the future of
the Internet.</t>
<t hangText="RFC 3493 I: "Basic Socket Interface
Extensions for IPv6" (February 2003)">
<vspace blankLines="1"/>
This document <xref target="RFC3493"/> describes the de
facto standard sockets API for programming with TCP. This
API is implemented nearly ubiquitously in modern operating
systems and programming languages.</t>
<t hangText="RFC 6056 B: "Recommendations for
Transport-Protocol Port Randomization"
(December 2010)"><vspace blankLines="1"/>
This document <xref target="RFC6056"/> describes a number of
simple and efficient methods for the selection of the client
port number. It reduces the possibility of an attacker
guessing the correct five-tuple (Protocol,
Source/Destination Address, Source/Destination Port).</t>
<t hangText="RFC 6191 B: "Reducing the TIME-WAIT State
Using TCP timestamps" (April 2011)">
<vspace blankLines="1"/>
This document <xref target="RFC6191"/> describes the usage
of the TCP Timestamps option [JBB92] to perform heuristics
to determine whether or not to allow the creation of a new
incarnation of a connection that is in the TIME-WAIT
state.</t>
<t hangText="RFC 6429 I: "TCP Sender Clarification for
Persist Condition" (December 2011)">
<vspace blankLines="1"/>
This document <xref target="RFC6429"/> clarifies the actions
that a TCP can be taken on connections that are experiencing
the Zero Window Probe (ZWP) condition.</t>
<t hangText="RFC 6897 I: "Multipath TCP (MPTCP)
Application Interface Considerations" (March 2013)">
<vspace blankLines="1"/>
This document <xref target="RFC6897"/> characterizes the
impact that Multipath TCP (MPTCP) may have on applications.
It further discusses compatibility issues of MPTCP in
combination with non-MPTCP-aware applications. Finally, it
describes a basic API that is a simple extension of TCP's
interface for MPTCP-aware applications.</t>
</list></t>
</section>
<!-- Subsection: Management Information Bases -->
<section title="Management Information Bases" anchor="mibs">
<t>The first MIB module defined for use with Simple Network
Management Protocol (SNMP) (in RFC 1066 and its update, RFC
1156) was a single monolithic MIB module, called MIB-I. This
evolved over time to be MIB-II (RFC 1213). It then became
apparent that having a single monolithic MIB module was not
scalable, given the number and breadth of MIB data definitions
that needed to be included. Thus, additional MIB modules were
defined, and those parts of MIB-II that needed to evolve were
split off. Eventually, the remaining parts of MIB-II were also
split off, the TCP-specific part being documented in RFC
2012.</t>
<t>RFC 2012 was obsoleted by RFC 4022, which is the primary TCP
MIB document today. MIB-I, defined in RFC 1156, has been
obsoleted by the MIB-II specification in RFC 1213. For current
TCP implementers, RFC 4022 should be supported.</t>
<t><list style="hanging">
<t hangText="RFC 1066 H: "Management Information Base
for Network Management of TCP/IP-based Internets"
(August 1988)"><vspace blankLines="1"/>
This document <xref target="RFC1066"/> was the description
of the TCP MIB. It was obsoleted by RFC 1156.</t>
<t hangText="RFC 1156 S: "Management Information Base
for Network Management of TCP/IP-based Internets"
(May 1990)"><vspace blankLines="1"/>
This document <xref target="RFC1156"/> describes the
required MIB fields for TCP implementations, with minor
corrections and no technical changes from RFC 1066, which
it obsoletes. This is the standards track document for
MIB-I.</t>
<t hangText="RFC 1213 S: "Management Information Base
for Network Management of TCP/IP-based Internets:
MIB-II" (March 1991)"><vspace blankLines="1"/>
This document <xref target="RFC1213"/> describes the second
version of the MIB in a monolithic form. RFC 2012 updates
this document by splitting out the TCP-specific
portions.</t>
<t hangText="RFC 2012 S: "SNMPv2 Management Information
Base for the Transmission Control Protocol using SMIv2"
(November 1996)"><vspace blankLines="1"/>
This document <xref target="RFC2012"/> defined the TCP MIB,
in an update to RFC 1213. It is now obsoleted by RFC 4022.
</t>
<t hangText="RFC 2452 S: "IP Version 6 Management
Information Base for the Transmission Control Protocol"
(December 1998)"><vspace blankLines="1"/>
This document <xref target="RFC2452"/> augments RFC 2012 by
adding an IPv6-specific connection table. The rest of 2012
holds for any IP version. RFC 2012 is now obsoleted by RFC
4022.</t>
<t>Although it is a standards track document, RFC 2452 is
considered a historic mistake by the MIB community, as it
is based on the idea of parallel IPv4 and IPv6 structures.
Although IPv6 requires new structures, the community has
decided to define a single generic structure for both IPv4
and IPv6. This will aid in definition, implementation, and
transition between IPv4 and IPv6.</t>
<t hangText="RFC 4022 S: "Management Information Base
for the Transmission Control Protocol (TCP)"
(March 2005)"><vspace blankLines="1"/>
This document <xref target="RFC4022"/> obsoletes RFC 2012
and RFC 2452 and specifies the current standard for the
TCP MIB that should be deployed.</t>
</list></t>
</section>
<!-- Subsection: Tools and Tutorials -->
<section title="Tools and Tutorials" anchor="tools">
<t><list style="hanging">
<t hangText="RFC 1180 I: "TCP/IP Tutorial"
(January 1991) (Errata)"><vspace blankLines="1"/>
This document <xref target="RFC1180"/> is an extremely
brief overview of the TCP/IP protocol suite as a whole. It
gives some explanation as to how and where TCP fits in.</t>
<t hangText="RFC 1470 I: "FYI on a Network Management
Tool Catalog: Tools for Monitoring and Debugging TCP/IP
Internets and Interconnected Devices" (June 1993)">
<vspace blankLines="1"/>
A few of the tools that this document
<xref target="RFC1470"/> describes are still maintained and
in use today; for example, ttcp and tcpdump. However, many
of the tools described do not relate specifically to TCP and
are no longer used or easily available.</t>
<t hangText="RFC 2398 I: "Some Testing Tools for TCP
Implementors" (August 1998)"><vspace blankLines="1"/>
This document <xref target="RFC2398"/> describes a number
of TCP packet generation and analysis tools. Although some of
these tools are no longer readily available or widely used,
for the most part they are still relevant and useable.</t>
<t hangText="RFC 4614 I: "A Roadmap for Transmission
Control Protocol (TCP) Specification Documents"
(September 2006)"><vspace blankLines="1"/>
RFC 4614 <xref target="RFC4614"/> is the precursor of this
document.</t>
<t hangText="RFC 5783 I: "Congestion Control in the RFC
Series" (February 2010)"><vspace blankLines="1"/>
This document <xref target="RFC5783"/> provides an overview
of RFCs related to congestion control that have been
published so far. The focus of the document are on
end-host-based congestion control.</t>
<t hangText="RFC 6077 I: "Open Research Issues in
Internet Congestion Control" (January 2011)">
<vspace blankLines="1"/>
This RFC <xref target="RFC6077"/> summarizes the main open
problems in the domain of Internet congestion control. As a
good starting point for newcomers, the document describes
several new challenges that are becoming important as the
network grows, as well as some issues that have been known
for many years.</t>
</list></t>
</section>
<!-- Subsection: Case Studies -->
<section title="Case Studies" anchor="studies">
<t><list style="hanging">
<t hangText="RFC 700 U: "A Protocol Experiment"
(August 1974)"><vspace blankLines="1"/>
This document <xref target="RFC0700"/> presents a field
report about the deployment of a very early version of
TCP, the so-called INWN #39 protocol, which is originally
described by Cerf and Kahn in INWG Note #39
<xref target="CK73"/> to use a PDP-11 line printer via the
ARPANET.</t>
<t hangText="RFC 889 U: "Internet Delay Experiments"
(December 1983)"><vspace blankLines="1"/>
This document <xref target="RFC0889"/> is a status report
about experiments concerning the TCP retransmission timeout
calculation and also provides advices for implementers.</t>
<t hangText="RFC 1337 I: "TIME-WAIT Assassination
Hazardsin TCP" (May 1992)"><vspace blankLines="1"/>
This document <xref target="RFC1337"/> points out a problem
with acting on received reset segments while one is in the
TIME-WAIT state. The main recommendation is that hosts in
TIME-WAIT ignore resets. This recommendation might not
currently be widely implemented.</t>
<t hangText="RFC 2415 I: "Simulation Studies of
Increased Initial TCP Window Size" (September 1998)">
<vspace blankLines="1"/>
This document <xref target="RFC2415"/> presents results of
some simulations using TCP initial windows greater than 1
segment. The analysis indicates that user-perceived
performance can be improved by increasing the initial
window to 3 segments.</t>
<t hangText="RFC 2416 I: "When TCP Starts Up With Four
Packets Into Only Three Buffers" (September 1998)">
<vspace blankLines="1"/>
This document <xref target="RFC2416"/> uses simulation
results to clear up some concerns about using an initial
window of 4 segments when the network path has less
provisioning.<vspace blankLines="1"/></t>
<t hangText="RFC 2884 I: "Performance Evaluation of
Explicit Congestion Notification (ECN) in IP Networks"
(July 2000)"><vspace blankLines="1"/>
This document <xref target="RFC2884"/> describes
experimental results that show some improvements to the
performance of both short- and long-lived connections due to
ECN.</t>
</list></t>
</section>
</section>
<!-- Section: Undocumented TCP Features -->
<section anchor="undocumented" title="Undocumented TCP Features">
<t>There are a few important implementation tactics for the TCP
that have not yet been described in any RFC. Although this roadmap
is primarily concerned with mapping the TCP RFCs, this section is
included because an implementer needs to be aware of these
important issues.</t>
<t><list style="hanging">
<t hangText="Header Prediction"><vspace blankLines="1"/>
Header prediction is a trick to speed up the processing of
segments. Van Jacobson and Mike Karels developed the technique
in the late 1980s. The basic idea is that some processing time
can be saved when most of a segment's fields can be predicted
from previous segments. A good description of this was sent to
the TCP-IP mailing list by Van Jacobson on March 9, 1988:</t>
<t>"Quite a bit of the speedup comes from an algorithm that we
('we' refers to collaborator Mike Karels and myself) are
calling "header prediction". The idea is that if you're in the
middle of a bulk data transfer and have just seen acpacket, you
know what the next packet is going to look like: It will look
just like the current packet with either the sequence number or
ack number updated (depending on whether you're the sender or
receiver). Combining this with the "Use hints" epigram from
Butler Lampson's classic "Epigrams for System Designers", you
start to think of the tcp state (rcv.nxt, snd.una, etc.) as
"hints" about what the next packet should look like.</t>
<t>If you arrange those "hints" so they match the layout of a
tcp packet header, it takes a single 14-byte compare to see if
your prediction is correct (3 longword compares to pick up the
send & ack sequence numbers, header length, flags and
window, plus a short compare on the length). If the prediction
is correct, there's a single test on the length to see if
you're the sender or receiver followed by the appropriate
processing. E.g., if the length is non-zero (you're the
receiver), checksum and append the data to the socket buffer
then wake any process that's sleeping on the buffer. Update
rcv.nxt by the length of this packet (this updates your
"prediction" of the next packet). Check if you can handle
another packet the same size as the current one. If not, set
one of the unused flag bits in your header prediction to
guarantee that the prediction will fail on the next packet and
force you to go through full protocol processing. Otherwise,
you're done with this packet. So, the *total* tcp protocol
processing, exclusive of checksumming, is on the order of 6
compares and an add."</t>
<t hangText="Forward Acknowledgement (FACK)">
<vspace blankLines="1"/>
FACK <xref target="MM96"/> describes an alternate algorithm for
triggering fast retransmit, based on the extent of the SACK
scoreboard. Its goal is to trigger fast retransmit as soon as
the receiver's reassembly queue is larger than the DUPACK
threshold, as indicated by the difference between the forward
most SACK block edge and SND.UNA. This algorithm quickly and
reliably triggers fast retransmit in the presence of burst
losses -- often on the first SACK following such a loss. Such
a threshold based algorithm also triggers fast retransmit
immediately in the presence of any reordering with extent
greater than the DUPACK threshold. FACK is implemented in
Linux and turned on per default.</t>
<t hangText="Highspeed Congestion Control">
<vspace blankLines="1"/>
In the last decade significant research effort has been put
into experimental TCP congestion control modifications for
obtaining high throughput with reduced startup and recovery
times. Only few RFCs have been published on some of these
modifications, including HighSpeed TCP
<xref target="RFC3649"/>, Limited Slow-Start
<xref target="RFC3742"/>, and Quick-Start
<xref target="RFC4782"/> (see <xref target="cc-may"/>), but
high-rate congestion control mechanisms are still considered an
open issue in congestion control research. Some other schemes
have been published as Internet-Drafts, e.g. CUBIC
<xref target="I-D.rhee-tcpm-cubic"/> (the standard TCP
congestion control algorithm in Linux), Compound TCP
<xref target="I-D.sridharan-tcpm-ctcp"/>, and H-TCP
<xref target="I-D.leith-tcp-htcp"/> or have been discussed a
little by the IETF, but much of the work in this area has not
been adopted within the IETF yet, so the majority of this work
is outside the RFC series and may be discussed in other
products of the IRTF Internet Congestion Control Research Group
(ICCRG).</t>
</list></t>
</section>
<!-- Section: Security Considerations -->
<section title="Security Considerations">
<t>This document introduces no new security considerations. Each
RFC listed in this document attempts to address the security
considerations of the specification it contains.</t>
</section>
<!-- Section: IANA Considerations -->
<section title="IANA Considerations">
<t>This document contains no IANA considerations.</t>
</section>
<!-- Section: Acknowledgments -->
<section title="Acknowledgments">
<t>This document grew out of a discussion on the end2end-interest
mailing list, the public list of the End-to-End Research Group of
the IRTF, and continued development under the IETF's TCP
Maintenance and Minor Extensions (TCPM) working group. We thank
Joe Touch, Reiner Ludwig, Pekka Savola, Gorry Fairhurst, and Sally
Floyd for their contributions, in particular. The chairs of the
TCPM working group, Mark Allman and Ted Faber, have been
instrumental in the development of this document. Keith McCloghrie
provided some useful notes and clarification on the various
MIB-related RFCs.</t>
</section>
</middle>
<!-- BACK MATTER -->
<back>
<!-- Normative References -->
<references title="Normative References">
<!-- Section: Core Functionality -->
&RFC0793;
&RFC1122;
&RFC2460;
&RFC2873;
&RFC3390;
&RFC5681;
&RFC6093;
&RFC6298;
&RFC6691;
<!-- Subsection: Fundamental Changes -->
&RFC1323;
&RFC2675;
&RFC5482;
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
&RFC3042;
&RFC3168;
&RFC3465;
&RFC6582;
&RFC6633;
<!-- Subsection: SACK-Based Loss Recovery and Congestion Control -->
&RFC2018;
&RFC2883;
&RFC6675;
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
&RFC4015;
&RFC5682;
<!-- Subsection: Path MTU Discovery-->
&RFC1191;
&RFC1981;
&RFC4821;
<!-- Subsection: Header Compression-->
&RFC1144;
&RFC6846;
<!-- Subsection: Defending Spoofing and Flooding Attacks -->
&RFC4953;
&RFC4987;
&RFC5461;
&RFC5925;
&RFC5926;
&RFC5927;
&RFC5961;
&RFC6528;
<!-- Subsection: Architectural Guidelines -->
&RFC2140;
&RFC3124;
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
&RFC2861;
&RFC3540;
&RFC3649;
&RFC3742;
&RFC4782;
&RFC5562;
&RFC5690;
&RFC5827;
&RFC6069;
&RFC6928;
&RFC6937;
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
&RFC3522;
&RFC3708;
&RFC4653;
<!-- Subsection: Multipath TCP -->
&RFC6356;
&RFC6824;
<!-- Section: TCP Parameters at IANA -->
&RFC2780;
&RFC4727;
&RFC6335;
&RFC6994;
<!-- Section: Historic and Undeployed Extensions -->
&RFC0721;
&RFC1078;
&RFC1106;
&RFC1110;
&RFC1146;
&RFC1263;
&RFC1379;
&RFC1644;
&RFC1693;
&RFC1705;
&RFC6013;
&RFC6247;
<!-- Subsection: Foundational Works -->
&RFC0675;
&RFC0761;
&RFC0813;
&RFC0814;
&RFC0816;
&RFC0817;
&RFC0872;
&RFC0896;
&RFC0964;
<!-- Subsection: Architectural Guidelines -->
&RFC1958;
&RFC2914;
&RFC3439;
&RFC6182;
<!-- Subsection: Difficult Network Environments -->
&RFC2488;
&RFC2757;
&RFC2760;
&RFC3135;
&RFC3150;
&RFC3155;
&RFC3366;
&RFC3449;
&RFC3481;
&RFC3819;
<!-- Subsection: Guidance for Developing, Analyzing, and Evaluating TCP -->
&RFC4774;
&RFC5033;
&RFC5166;
&RFC6181;
&RFC6349;
<!-- Subsection: Implementation Advice -->
&RFC0794;
&RFC0879;
&RFC1071;
&RFC1624;
&RFC1936;
&RFC2525;
&RFC2923;
&RFC3360;
&RFC3493;
&RFC6056;
&RFC6191;
&RFC6429;
&RFC6897;
<!-- Subsection: Management Information Bases -->
&RFC1066;
&RFC1156;
&RFC1213;
&RFC2012;
&RFC2452;
&RFC4022;
<!-- Subsection: Tools and Tutorials -->
&RFC1180;
&RFC1470;
&RFC2398;
&RFC4614;
&RFC5783;
&RFC6077;
<!-- Subsection: Case Studies -->
&RFC0700;
&RFC0889;
&RFC1337;
&RFC2415;
&RFC2416;
&RFC2884;
</references>
<!-- Informative References -->
<references title="Informative References">
&RFC1016;
&RFC2026;
&RFC2474;
&RFC4340;
&RFC4341;
&rhee-tcpm-cubic;
&sridharan-tcpm-ctcp;
&leith-tcp-htcp;
<reference anchor="Errata" target="http://www.rfc-editor.org/errata.php">
<front>
<title>RFC Editor - RFC Errata</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="CK73">
<front>
<title>Towards Protocols for Internetwork Communication</title>
<author initials="V." surname="Cerf"/>
<author initials="R." surname="Kahn"/>
<date month="IFIP/TC6.1, NIC 18764, INWG 39, September" year="1973"/>
</front>
</reference>
<reference anchor="KP87">
<front>
<title>Round Trip Time Estimation</title>
<author initials="P." surname="Karn"/>
<author initials="C." surname="Partridge"/>
<date month="ACM SIGCOMM 1987 Proceedings, in ACM Computer
Communication Review, 17 (5), pp. 2-7, August" year="1987"/>
</front>
</reference>
<reference anchor="Jac88">
<front>
<title>Congestion Avoidance and Control</title>
<author initials="V." surname="Jacobson"/>
<date month="ACM SIGCOMM 1988 Proceedings, in ACM Computer
Communication Review, 18 (4), pp. 314-329, August" year="1988"/>
</front>
</reference>
<reference anchor="JK92">
<front>
<title>Congestion Avoidance and Control</title>
<author initials="V." surname="Jacobson"/>
<author initials="M." surname="Karels"/>
<date month="This paper is a revised version of [Jac88], that
includes an additional appendix. This paper has not been
traditionally published, but is currently available at
ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z." year="1992"/>
</front>
</reference>
<reference anchor="MAF04">
<front>
<title>Measuring the Evolution of Transport Protocols in the
Internet</title>
<author initials="A." surname="Medina"/>
<author initials="M." surname="Allman"/>
<author initials="S." surname="Floyd"/>
<date month="ACM Computer Communication Review, 35 (2), April"
year="2005"/>
</front>
</reference>
<reference anchor="SCWA99">
<front>
<title>TCP Congestion Control with a Misbehaving
Receiver</title>
<author initials="S." surname="Savage"/>
<author initials="N." surname="Cardwell"/>
<author initials="D." surname="Wetherall"/>
<author initials="T." surname="Anderson"/>
<date month="ACM Computer Communication Review, 29 (5), pp.
71-78, October" year="1999"/> </front>
</reference>
<reference anchor="MM96">
<front>
<title>Forward Acknowledgement: Refining TCP Congestion
Control</title>
<author initials="M." surname="Mathis"/>
<author initials="J." surname="Mahdavi"/>
<date month="ACM SIGCOMM 1996 Proceedings, in ACM Computer
Communication Review 26 (4), pp. 281-292, October"
year="1996"/>
</front>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-21 10:50:04 |