Shared Use of Experimental TCP Options
draft-ietf-tcpm-experimental-options-01

The information below is for an old version of the document
Document Type Active Internet-Draft (tcpm WG)
Last updated 2012-05-30
Replaces draft-touch-tcpm-experimental-options
Stream IETF
Intended RFC status Proposed Standard
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Responsible AD Wesley Eddy
Send notices to tcpm-chairs@tools.ietf.org, draft-ietf-tcpm-experimental-options@tools.ietf.org
TCPM Working Group                                             J. Touch
Internet Draft                                                 USC/ISI
Intended status: Proposed Standard                         May 30, 2012
Expires: November 2012

                  Shared Use of Experimental TCP Options
                draft-ietf-tcpm-experimental-options-01.txt

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on November 30, 2012.

Copyright Notice

   Copyright (c) 2012 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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   document must include Simplified BSD License text as described in

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   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.

Abstract

   This document describes how TCP option codepoints can support
   concurrent experiments using a magic number field. This mechanism
   avoids the need for a coordinated registry, and is backward-
   compatible with currently known uses.

Table of Contents

   1. Introduction...................................................2
   2. Conventions used in this document..............................3
   3. TCP Experimental Option Structure..............................3
      3.1. Reducing the Impact of False Positives....................5
      3.2. Migration to Assigned Options.............................6
   4. Security Considerations........................................6
   5. IANA Considerations............................................6
   6. References.....................................................6
      6.1. Normative References......................................6
      6.2. Informative References....................................7
   7. Acknowledgments................................................7

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 31 are
   assigned at the time this document was published [IANA]. Two of
   these codepoints are allocated to support experiments (253, 254)
   [RFC4727]. These numbers are intended for testing purposes, and
   implementations need to assume they can be used for other purposes,
   but this is often not the case.

   There is no mechanism to support shared use of the experimental
   option codepoints. Experimental options 253 and 254 are deployed in
   operational code to support an early version of TCP authentication.
   Option 253 is also documented for the experimental TCP Cookie
   Transaction option [RFC6013]. This shared use results in collisions
   in which a single codepoint can appear multiple times in a single
   TCP segment and each use is ambiguous.

   Other codepoints have been used without assignment, notably 31-32
   (TCP cookie transactions, as originally distributed and in its API

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   doc) and 76-78 (tcpcrypt) [Bi11][Si11]. Commercial products
   reportedly also use unassigned options 33 and 76-78 as well. Even
   though these uses are inappropriate, they can impact legitimate
   assignees.

   There are a variety of proposed approaches to address this issue.
   The first is to relax the requirements for assignment of TCP
   options, allowing them to be assigned more readily for protocols
   that have not been standardized through the IETF process [RFC5226].
   A second would be to assign a larger pool to options, and to manage
   their sharing through IANA coordination [Ed11].
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