Shared Use of Experimental TCP Options
RFC 6994

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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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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