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Versions: 00 01                                                         
Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Experimental                                     Orange
Expires: June 11, 2017                                  December 8, 2016


                         TCP Capability Option
               draft-boucadair-tcpm-capability-option-01

Abstract

   This document defines an experimental TCP option that can be used to
   negotiate a set of options that are supported by two TCP endpoints.
   The main motivation for designing this option is the optimization of
   the option space for SYN segments.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 11, 2017.

Copyright Notice

   Copyright (c) 2016 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
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Applicability . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  TCP Capability Option . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   TCP ([RFC0793]) can be extended by defining new options.  Because of
   the presence of NATs, firewalls, and other types of flow-aware
   service functions between two TCP endpoints, means to ensure that
   both endpoints support a given option, and that the paths used to
   forward traffic between them do not involve nodes that strip or alter
   the content of the options.  This is actually achieved by negotiating
   the support of a given option during the 3WHS stage.

   Typically, an option is included in the SYN message to inform the
   remote TCP peer that the originating TCP peer is "X"-capable (that
   is, it supports feature "X").  Upon receipt of the SYN message, and
   if no intermediary node has stripped that option, the remote peer
   will echo that option in a SYN/ACK if and only if it is also "X"-
   capable.  Feature "X" can then be used if the SYN/ACK message that is
   received by the originating peer still carries the "X"-capable; the
   option must then be included in the ACK.

   For example, several TCP extensions have been designed with this
   design rationale in mind, e.g., SYN-EOS
   [I-D.touch-tcpm-tcp-syn-ext-opt], EDO [I-D.ietf-tcpm-tcp-edo], SACK
   Permitted [RFC2018], MP_CAPABLE [RFC6824], etc.  In the meantime, and
   given the limited TCP option space, it becomes more challenging to
   include all options in a single SYN message.

   Several solutions have been proposed to solve that problem (e.g.,
   [I-D.touch-tcpm-tcp-syn-ext-opt]) by means of generating a companion
   TCP message.  This document proposes a solution that aims to optimize
   the required option space to facilitate the insertion of several "X"-
   capable options.







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1.1.  Applicability

   The option is primarily designed for network configurations where the
   path between the TCP endpoints is managed (e.g., an MPTCP endpoint
   embedded in the CPE and the remote MPTCP endpoint is located in the
   network side; the paths between these endpoints are managed by the
   same administrative entity such as in
   [I-D.boucadair-mptcp-natfwfree-profile]).

   A flow-aware device that removes the option will disable all the
   options that were included in the TCP Capability option.  This is not
   supposed in the target deployment context for this option.

   Some middleboxes may allow the TCP Capability option to pass through,
   but the individual options may be blocked.  This is not supposed in
   the target deployment context for this option as those flow-aware
   functions are managed.

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  TCP Capability Option

   The format of the TCP Capability option is shown in Figure 1.  The
   option follows the format defined in [RFC0793].

    +--------+--------+--------+--------+
    |  Kind  | Length |  Kind 1| Kind 2 |
    +--------+--------+--------+--------+
    :       ....      |Kind n-1| Kind n |
    +-------....------+--------+--------+

                                 Figure 1

   "Kind" is to be assigned by IANA (see Section 4).

   In order to conduct experiments with this option, a format that
   adheres to [RFC6994] is used (see Figure 2).  ExID MUST be set to
   0x0CA0 (3232).









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    +--------+--------+--------+--------+
    |  Kind  | Length |       ExID      |
    +--------+--------+--------+--------+
    : Kind 1 | Kind 2 |       ...       :
    +-------....------+-----------------+

                                 Figure 2

   "Kindi" carries the code point of an option that a TCP endpoint
   supports and which it would like to negotiate with the remote peer.
   One or multiple "Kindi" fields may be included.

   An endpoint that wishes to enable the capabilities associated with
   one or multiple TCP options must include the corresponding "Kind"
   codes in a TCP Capability option, which is included in the initial
   SYN.  If the remote peer supports at least one of the options carried
   in the TCP Capability option, it replies with a SYN/ACK that includes
   the TCP Capability option and which only carries the code points of
   the options it supports.  These values are then echoed in the ACK
   message the originating peer sends back to the remote peer.

   When replying to a SYN message that includes a TCP Capability option,
   the remote peer should preserve the same order of the "Kindi" fields
   (of course, those that are not supported won't be included).

3.  Security Considerations

   The security considerations are to be completed.

4.  IANA Considerations

   IANA is requested to record the following identifier in the "TCP
   Experimental Option Experiment Identifiers (TCP ExIDs)" registry:

   Value         Description               Reference
   0x0CA0    TCP Capability Option      [This document]

5.  References

5.1.  Normative References

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <http://www.rfc-editor.org/info/rfc793>.







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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC6994]  Touch, J., "Shared Use of Experimental TCP Options",
              RFC 6994, DOI 10.17487/RFC6994, August 2013,
              <http://www.rfc-editor.org/info/rfc6994>.

5.2.  Informative References

   [I-D.boucadair-mptcp-natfwfree-profile]
              Boucadair, M., Jacquenet, C., Seite, P., Bonaventure, O.,
              and D. Lingli, "An MPTCP Profile for NAT- and Firewall-
              Free Networks: Network-Assisted MPTCP Deployments", draft-
              boucadair-mptcp-natfwfree-profile-00 (work in progress),
              July 2015.

   [I-D.ietf-tcpm-tcp-edo]
              Touch, J. and W. Eddy, "TCP Extended Data Offset Option",
              draft-ietf-tcpm-tcp-edo-06 (work in progress), June 2016.

   [I-D.touch-tcpm-tcp-syn-ext-opt]
              Touch, J. and T. Faber, "TCP SYN Extended Option Space
              Using an Out-of-Band Segment", draft-touch-tcpm-tcp-syn-
              ext-opt-05 (work in progress), October 2016.

   [RFC2018]  Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP
              Selective Acknowledgment Options", RFC 2018,
              DOI 10.17487/RFC2018, October 1996,
              <http://www.rfc-editor.org/info/rfc2018>.

   [RFC6824]  Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
              "TCP Extensions for Multipath Operation with Multiple
              Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
              <http://www.rfc-editor.org/info/rfc6824>.

Authors' Addresses

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com






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   Christian Jacquenet
   Orange
   Rennes  35000
   France

   Email: christian.jacquenet@orange.com













































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