Shared Use of Experimental TCP Options
RFC 6994
Internet Engineering Task Force (IETF) J. Touch
Request for Comments: 6994 USC/ISI
Category: Standards Track August 2013
ISSN: 2070-1721
Shared Use of Experimental TCP Options
Abstract
This document describes how the experimental TCP option codepoints
can concurrently support multiple TCP extensions, even within the
same connection, using a new IANA TCP experiment identifier. This
approach is robust to experiments that are not registered and to
those that do not use this sharing mechanism. It is recommended for
all new TCP options that use these codepoints.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6994.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Touch Standards Track [Page 1]
RFC 6994 Shared Use of Experimental TCP Options August 2013
Table of Contents
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................3
3. TCP Experimental Option Structure ...............................4
3.1. Selecting an ExID ..........................................5
3.2. Impact on TCP Option Processing ............................6
4. Reducing the Impact of False Positives ..........................7
5. Migration to Assigned Options ...................................7
6. Rationale .......................................................8
7. Security Considerations .........................................9
8. IANA Considerations .............................................9
9. References .....................................................10
9.1. Normative References ......................................10
9.2. Informative References ....................................10
10. Acknowledgments ...............................................11
1. Introduction
TCP includes options to enable new protocol capabilities that can be
activated only where needed and supported [RFC793]. The space for
identifying such options is small -- 256 values, of which 30 are
assigned at the time of this document's publication [IANA]. Two of
these codepoints (253, 254) are allocated to support experiments
[RFC4727]. These values are intended for testing purposes or for use
when an assigned codepoint is either not warranted or available,
e.g., based on the maturity status of the defined capability (i.e.,
Experimental or Informational, rather than Standards Track).
Here, the term "experimental TCP options" refers to options that use
the TCP experimental option codepoints [RFC4727]. Such experiments
can be described in an RFC of any status (e.g., Experimental,
Informational, etc.) and are intended to be used in controlled
environments and are allowed in public deployments (when not enabled
as default [RFC3692]). Nothing prohibits the deployment of multiple
experiments in the same environment -- controlled or public.
Further, some protocols are specified in Experimental or
Informational RFCs, which either include parameters or design choices
not yet understood or which might not be widely deployed [RFC2026].
Typically, these TCP options are not eligible to receive assigned
codepoints [RFC2780], so they need a way to share their use of the
experimental codepoints.
There is currently no mechanism to support shared use of the TCP
experimental option codepoints, either by different experiments on
different connections or for more than two experimental options in
the same connection. Experimental options 253 and 254 are already
deployed in operational code to support an early version of TCP
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