One document matched: draft-ietf-tcpm-tcp-rfc4614bis-03.xml
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!-- Section: Core Functionality -->
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<!ENTITY RFC6691 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6691.xml'>
<!-- Subsection: Fundamental Changes -->
<!ENTITY RFC2675 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2675.xml'>
<!ENTITY ietf-tcpm-1323bis SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-tcpm-1323bis-17.xml'>
<!-- Subsection: Congestion Control Extensions -->
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<!-- Subsection: Loss Recovery Extensions -->
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<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
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<!-- Subsection: Path MTU Discovery-->
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<!-- Subsection: Defending Spoofing and Flooding Attacks -->
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<!ENTITY RFC5925 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5925.xml'>
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<!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 -->
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<!ENTITY RFC3124 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3124.xml'>
<!-- Subsection: Fundamental Changes -->
<!ENTITY ietf-tcpm-fastopen SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-tcpm-fastopen-05.xml'>
<!-- Subsection: Congestion Control and Loss Recovery Extensions -->
<!ENTITY RFC2861 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2861.xml'>
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<!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 RFC6928 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6928.xml'>
<!-- Subsection: Loss Recovery Extensions -->
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<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
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<!ENTITY RFC4653 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4653.xml'>
<!-- Subsection: TCP Timeouts -->
<!ENTITY RFC5482 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5482.xml'>
<!-- Subsection: Multipath TCP -->
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<!-- Section: TCP Parameters at IANA -->
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<!-- Section: Historic and Undeployed Extensions -->
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<!ENTITY RFC6247 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6247.xml'>
<!-- Subsection: Foundational Works -->
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<!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 RFC4774 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4774.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 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 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'>
<!ENTITY RFC4898 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4898.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 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 RFC2119 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
<!ENTITY RFC2474 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2474.xml'>
<!ENTITY RFC3758 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3758.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 RFC6115 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6115.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' ?>
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please see http://xml.resource.org/authoring/README.html. -->
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might want to use. (Here they are set differently than their defaults in
xml2rfc v1.32) -->
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<rfc ipr="trust200902" category="info" obsoletes="4614"
docName="draft-ietf-tcpm-tcp-rfc4614bis-03">
<!-- 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='F5'>F5 Networks</organization>
<address>
<postal>
<street>401 Elliott Ave W</street>
<city>Seattle</city>
<region>WA</region>
<code>98119</code>
</postal>
<phone>206-272-7537</phone>
<email> m.duke@f5.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" 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="December" 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 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 <xref
target="RFC1122"/> 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 <xref
target="RFC5681"/> is considered part of the required core
functionality of TCP, although the RFC 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
<xref target="RFC2119"/>), 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 are 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 (see <xref target="must"/>) 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 (see <xref target="must"/>), 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 (see
<xref target="fundamental"/>) 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 <xref target="must"/> and
Differentiated Services <xref target="RFC2474"/>.</t>
<t hangText="RFC 5681 S: "TCP Congestion Control"
(August 2009)"><vspace blankLines="1"/>
Although RFC 793 (see <xref target="must"/>) 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 5681 details the currently accepted congestion control
mechanism, while RFC 1122 <xref target="must"/> mandates that
such a congestion control mechanism must be implemented. 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"/> (see <xref target="cc"/>).</t>
<t>During slow start and congestion avoidance, the
usage of Appropriate Byte Counting <xref
target="RFC3465"/> (see <xref target="cc"/>) is
explicitly recommended.</t>
<t>The use of Limited Transmit <xref target="RFC3042"/>
(see <xref target="lr"/>) 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. The document updates the relevant specifications
such that it accommodates 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 (see
<xref target="must"/>) and upgrades the requirement of
supporting the algorithm from a SHOULD to a MUST." <xref
target="RFC6298"/>. RFC 6298 updates RFC 2988 by changing
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: Strong Encouraged Enhancements -->
<section title="Strong Encouraged 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"/> and <xref
target="lr"/> list improvements over the congestion control and
loss recovery mechanisms as specified in RFC 5681 (see <xref
target="must"/>). <xref target="spurious"/> describes
algorithms that allow a TCP sender to detect whether it has entered
loss recovery spuriously. <xref target="pmtud"/> comprises Path MTU
Discovery mechanisms. Schemes for TCP/IP header compression are
listed in <xref target="compression"/>. Finally, <xref
target="antispoof"/> deals with the problem of preventing
preventing acceptance of forged segments and flooding attacks.</t>
<!-- Subsection: Fundamental Changes -->
<section title="Fundamental Changes" anchor="fundamental">
<t>RFCs 2675 and XXXX represent fundamental changes to TCP
by redefining how parts of the basic TCP header and options are
interpreted. RFC XXXX defines the Window Scale Option, which
re-interprets the advertised receive window. RFC 2675 specifies
that MSS option and urgent pointer fields with a value of
65,535 are to be treated specially.</t>
<t><list style="hanging">
<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 XXXX S: "TCP Extensions for High
Performance" (XXX 2014)"><vspace blankLines="1"/>
This document <xref target="I-D.ietf-tcpm-1323bis"/>
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. The predecessor of this document, RFC 1323,
was published in 1992, and is deployed in most TCP
implementations. This document includes fixes and
clarifications based on the gained deployment experience.
One specific issued addressed in this specification is a
recommendation how to modify the algorithm for estimating
the mean RTT when timestamps are used. RFC 1072, RFC 1185,
and RFC RFC 1323 are the conceptual precursors of RFC
XXXX.</t>
</list></t>
</section>
<!-- Subsection: Congestion Control Extensions -->
<section title="Congestion Control Extensions" anchor="cc">
<t>Two of the most important aspects of TCP are its congestion
control and loss recovery features. TCP 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 two sub-sections, we group enhancements to TCP's
congestion control, while the next sub-section focus on TCP's
loss recovery.</t>
<t><list style="hanging">
<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 (see <xref
target="must"/>) to define two previously unused flag
bits in the TCP header for ECN support. RFC 3540 (see <xref
target="cc-may"/>) provides a supplementary
(experimental) means for more secure use of ECN, and RFC
2884 (see <xref target="studies"/>) provides some sample
results from using ECN.</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 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 acknowledgments. ABC still operates within the
accepted guidelines, but is more robust to delayed ACKs and
ACK-division <xref target="SCWA99"/><xref
target="RFC3449"/>. ABC is recommended by RFC 5681 (see
<xref target="must"/>).</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 recommends against the implementation of
<xref target="RFC1016"/>.</t>
</list></t>
</section>
<!-- Subsection: Loss Recovery Extensions -->
<section title="Loss Recovery Extensions" anchor="lr">
<t>For the typical implementation of the TCP fast recovery
algorithm described in RFC 5681 (see <xref target="must"/>), a
TCP sender only retransmits a segment after a retransmit
timeout has occurred, or after three duplicate ACKs have
arrived triggering the fast retransmit. A single RTO might
result in the retransmission of several segments, while the
fast retransmit algorithm in RFC 5681 leads only to a single
retransmission. Hence, multiple losses from a single window of
data can lead to a performance degradation. Documents listed in
this section aim to improve the overall performance of TCP's
standard loss recovery algorithms. In particular, some of them
allows TCP senders to recover more effectively when multiple
segments are lost from a single flight of data.</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 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"/>.
Limited Transmit is recommended by RFC 5681 (see <xref
target="must"/>).</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 advance 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>
<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"/> (see <xref target="lr"/>).
The algorithm conforms to the spirit of the congestion
control specification in RFC 5681 (see <xref
target="must"/>), 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="spurious">
<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
concerns about IPR status. The Standards Track documents in
this section are closely related to the Experimental documents
in <xref target="spurious-may"/> also addressing this
topic.</t>
<t><list style="hanging">
<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
(see <xref target="lr"/>). 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. A
TCP sender could then use this information to detect
spurious retransmissions (see <xref target="RFC3708"/>.</t>
<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 (see <xref
target="spurious-may"/>), the algorithm in RFC 3708
(see <xref target="spurious-may"/>), or F-RTO in RFC 5682
(see <xref target="spurious"/>).</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 described in RFC 4138, provides an option for
inferring spurious retransmission timeouts. Unlike some
similar detection methods (e.g. RFC 3522 in <xref
target="spurious-may"/> and RFC 3708 in <xref
target="spurious-may"/>), 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 signaling 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 (see
<xref target="pmtud"/>), 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 (see <xref target="pmtud"/>) and
RFC 1981 (see <xref target="pmtud"/>), 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 compression schemes for TCP/IP like "RObust Header
Compression (ROHC) can significantly compress this 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 from 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 reset (send RST)
spoofing attacks. The document analyzes 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 analyzes 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"/> (see <xref
target="antispoof"/>).</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) <xref target="RFC5925"/>
(see <xref target="antispoof"/>) 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, 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 (see <xref
target="must"/>).</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 experimental RFC
is a proposal for a new protocol capability or service, i.e., it
requires a new TCP option code point, the implementation and
experimentation should follows <xref target="RFC6994"/> (see <xref
target="iana"/>), which describes how the experimental TCP
option code points 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 (see <xref
target="architectural-may"/>). 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. 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: Fundamental Changes -->
<section title="Fundamental Changes" anchor="fundamental-may">
<t>Like the standard documents listed in
<xref target="fundamental"/> there newly exist also experimental
RFCs that represent fundamental changes to TCP. One example is
TCP Fast Open that deviates from the standard TCP semantics
of <xref target="RFC0793"/>.</t>
<t><list style="hanging">
<t hangText="RFC XXX E: "TCP Fast Open" (XXX
2014)"><vspace blankLines="1"/>
This document <xref target="I-D.ietf-tcpm-fastopen"/>
describes TCP Fast Open that allows data to be carried in
the SYN and SYN-ACK packets and consumed by the receiver
during the initial connection handshake. It saves up to one
RTT compared to the standard TCP, which requires a
three-way handshake to complete before data can be
exchanged.</t>
</list></t>
</section>
<!-- Subsection: Congestion Control Extensions -->
<section title="Congestion Control Extensions" anchor="cc-may">
<t>TCP congestion control has been an extremely active research
area for many years (see RFC 5783, <xref target="tools"/>), as
it determines the performance of many applications that use
TCP. A number of experimental RFCs address issues with flow
start-up, overshoot, and steady-state behavior in the basic RFC
5681 (see <xref target="must"/>) algorithms. In this
sub-sections, enhancements to TCP's congestion control are
listed. The next sub-section focus on TCP's loss recovery.</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 (see <xref target="must"/>), 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"/>
(see <xref target="cc"/>) 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 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 (see <xref target="cc"/>), to 10
segments with a fallback to the existing recommendation
when performance issues are detected.</t>
</list></t>
</section>
<!-- Subsection: Loss Recovery Extensions -->
<section title="Loss Recovery Extensions" anchor="lr-may">
<t><list style="hanging">
<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 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="spurious-may">
<t>In addition to the Standards Track extensions to deal with
spurious retransmissions in <xref target="spurious"/>,
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: TCP Timeouts -->
<section title="TCP Timeouts" anchor="timeouts">
<t>Besides the well known retransmission timeout the TCP
standard <xref target="RFC0793"/> defines two more timeouts:
the user timeout and the time-wait timeout. This section lists
documents that deals with TCP's various timouts.</t>
<t><list style="hanging">
<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: 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 simultaneously 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="architectural-supp" format="counter"/>, <xref
target="development" format="counter"/>, and <xref
target="tcpimpl" format="counter"/> provide some additional
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 (see <xref
target="iana"/>).</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 code points can concurrently support
multiple TCP extensions, even within the same connection. It
creates an IANA registry for extensions to the experimental
code points.</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 deployment, or were found to be defective for
general use. Most of them are reclassified by <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 was not 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"/> proposes 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 acknowledgment" or NAK option. There is a comparison
of NAK and SACK methods, and early discussion of TCP over
satellite issues. RFC 1110 (see <xref target="history"/>)
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
(see <xref target="history"/>) 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, <xref target="history"/>.</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. RFC 1379 <xref
target="RFC1379"/> (see <xref target="history"/>) and RFC
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 (see <xref
target="architectural-may"/>), 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 specialized transport protocols
other than TCP, such as PR-SCTP <xref target="RFC3758"/>.</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. Later work on splitting
locator and identifier values is summarized well in <xref
target="RFC6115"/>, but no resulting changes to TCP have
occurred.</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 negotiate 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 a method to extent the option space after the
connection establishment.</t>
<t>Although RFC 6013 was published 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 advice can be found in
<xref target="tcpimpl"/>. RFCs that describe tools for testing and
debugging TCP implementations or that contain high-level tutorials
on the protocol are listed <xref target="tools"/>. The TCP
Management Information Bases are described in <xref
target="mibs"/>, 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 fundamental RFC 793 (see <xref
target="must"/>), 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 (see <xref
target="must"/>).</t>
<t hangText="RFC 761 H: "DoD standard Transmission
Control Protocol" (Januar 1980)">
<vspace blankLines="1"/>
This document <xref target="RFC0761"/> is the immediate
precursor of RFC 793 (see <xref target="must"/>). The
header format, the connection establishment including the
different connection states, and the overall API correspond
mostly to the final Standard RFC 793 (see <xref
target="must"/>).</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. Furthermore, it defined an algorithm for efficient
transmission of small packets that is today known as the
Nagle Algorithm.</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 (see
<xref target="must"/>). 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. Later work on TCP
has included several more aggressive mechanisms than Reno
TCP includes, and RFC 5033 (see <xref
target="development"/>) provides additional guidance on
use of such algorithms. The fundamental architectural
discussion in RFC 2914 remains valid, regarding the
standards process role in defining protocol aspects that
are critical to performance and avoiding congestion
collapse scenarios.</t>
<t hangText="RFC 3439 I: "Some Internet Architectural
Guidelines and Philosophy" (December 2002)">
<vspace blankLines="1"/>
This document <xref target="RFC3439"/> updates RFC 1958
(see <xref target="architectural-supp"/>) 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 impediment to efficient scaling.</t>
<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
with routers that do not understand the defined alternate
semantics.</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) (see <xref target="mptcp-may"/>). 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 (i.e., networks with low bandwidth and high
delay), 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 (see <xref target="pilc"/>)
and RFC 3155 (see <xref target="pilc"/>), and these
documents should be preferred where there is overlap
between them and RFC 2757 (see <xref target="pilc"/>).</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 (see <xref target="pilc"/>) 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.
RFC 3366 (see <xref target="pilc"/>) specifically focuses
on ARQ mechanisms, while RFC 3819 more widely covers
additional aspects of the underlying layers</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 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 (see <xref
target="architectural-supp"/>). 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 topics, the document discusses throughput, delay,
loss rates, response times, fairness and robustness for
challenging environments.</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>
<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) (see <xref
target="mptcp-may"/>). 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 (see <xref
target="tcpimpl"/>).</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 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 acknowledgments (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 (RFC XXXX, see <xref
target="fundamental"/>) 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) (see <xref
target="mptcp-may"/>) 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: 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
usable.</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 is on
end-host-based congestion control.</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) was a single monolithic MIB module,
called MIB-I, defined in RFC 1156. This evolved over time to
the MIB-II specification in RFC 1213, which obsoletes RFC 1156.
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. RFC 2012 was obsoleted by RFC 4022,
which is the primary TCP MIB document today. For current TCP
implementers, RFC 4022 should be supported.</t>
<t><list style="hanging">
<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. It is the
immediate successor of RFC 1158, with minor modifications.
It obsoletes the MIB-I, defined in RFC 1156 (see <xref
target="mibs"/>).</t>
<t hangText="RFC 2012 S: "SNMPv2 Management Information
Base for the Transmission Control Protocol using SMIv2"
(November 1996)"><vspace blankLines="1"/>
In an update to RFC 1213 (see <xref target="mibs"/>), this
document <xref target="RFC2012"/> defines the TCP MIB by
splitting out the TCP-specific portions. It is now
obsoleted by RFC 4022 (see <xref target="mibs"/>).</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
(see <xref target="mibs"/>) by adding an IPv6-specific
connection table. The rest of RFC 2012 holds for any IP
version. RFC 2452 is now obsoleted by RFC 4022 (see <xref
target="mibs"/>).</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
(see <xref target="mibs"/>) and RFC 2452 (see <xref
target="mibs"/>) and specifies the current standard for
the TCP MIB that should be deployed.</t>
<t hangText="RFC 4898 S: "TCP Extended Statistics
MIB" (May 2007)"><vspace blankLines="1"/>
This document <xref target="RFC4898"/> describes extended
performance statistics for TCP. They are designed to use
TCP's ideal vantage point to diagnose performance problems
in both the network and the application.</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
Hazards in 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 a packet, 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"/> includes an alternate algorithm for
triggering fast retransmit <xref target="RFC5681"/>, 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 duplicate ACK 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
duplicate ACK 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"/>
(see <xref target="cc-may"/>), Limited Slow-Start <xref
target="RFC3742"/> (see <xref target="cc-may"/>), 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
Mark Allman, Yuchung Cheng, Ted Faber, Fairhurst, Sally Floyd,
Janardhan Iyengar, Reiner Ludwig, Pekka Savola, and Joe Touch for
their contributions, in particular. 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;
&RFC5681;
&RFC6093;
&RFC6298;
&RFC6691;
<!-- Subsection: Fundamental Changes -->
&RFC2675;
&ietf-tcpm-1323bis;
<!-- Subsection: Congestion Control Extensions -->
&RFC3168;
&RFC3465;
&RFC3390;
&RFC6633;
<!-- Subsection: Loss Recovery Extensions -->
&RFC2018;
&RFC3042;
&RFC6582;
&RFC6675;
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
&RFC2883;
&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: Fundamental Changes -->
&ietf-tcpm-fastopen;
<!-- Subsection: Congestion Control Extensions -->
&RFC2861;
&RFC3540;
&RFC3649;
&RFC3742;
&RFC4782;
&RFC5562;
&RFC5690;
&RFC6928;
<!-- Subsection: Loss Recovery Extensions -->
&RFC5827;
&RFC6069;
&RFC6937;
<!-- Subsection: Detection and Prevention of Spurious Retransmissions -->
&RFC3522;
&RFC3708;
&RFC4653;
<!-- Subsection: TCP Timeouts -->
&RFC5482;
<!-- 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;
&RFC4774;
&RFC6182;
<!-- Subsection: Difficult Network Environments -->
&RFC2488;
&RFC2757;
&RFC2760;
&RFC3135;
&RFC3150;
&RFC3155;
&RFC3366;
&RFC3449;
&RFC3481;
&RFC3819;
<!-- Subsection: Guidance for Developing, Analyzing, and Evaluating TCP -->
&RFC5033;
&RFC5166;
&RFC6181;
&RFC6349;
<!-- Subsection: Implementation Advice -->
&RFC0794;
&RFC0879;
&RFC1071;
&RFC1624;
&RFC1936;
&RFC2525;
&RFC2923;
&RFC3360;
&RFC3493;
&RFC6056;
&RFC6191;
&RFC6429;
&RFC6897;
<!-- Subsection: Management Information Bases -->
&RFC1156;
&RFC1213;
&RFC2012;
&RFC2452;
&RFC4022;
&RFC4898;
<!-- Subsection: Tools and Tutorials -->
&RFC1180;
&RFC1470;
&RFC2398;
&RFC5783;
&RFC6077;
<!-- Subsection: Case Studies -->
&RFC0700;
&RFC0889;
&RFC1337;
&RFC2415;
&RFC2416;
&RFC2884;
</references>
<!-- Informative References -->
<references title="Informative References">
&RFC1016;
&RFC2026;
&RFC2119;
&RFC2474;
&RFC3758;
&RFC4340;
&RFC4341;
&RFC6115;
&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 10:45:04 |