Negotiating the Maximum Number of Multipath TCP (MPTCP) Subflows
draft-boucadair-mptcp-max-subflow-01

Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Experimental                                     Orange
Expires: June 9, 2016                                   December 7, 2015

    Negotiating the Maximum Number of Multipath TCP (MPTCP) Subflows
                  draft-boucadair-mptcp-max-subflow-01

Abstract

   This document specifies an experimental Multipath TCP (MPTCP) option
   that is meant to negotiate the maximum number of subflows that can be
   established and maintained for a given MPTCP connection.  The purpose
   is to minimize any possible performance degradation that can be
   induced by a possibly large number of establishment requests for
   additional subflows if the remote endpoint is not appropriately
   dimensioned to handle such requests.

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].

Status of This Memo

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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Experiment Goals  . . . . . . . . . . . . . . . . . . . .   3
   2.  Maximum Subflows MPTCP Option (MP_MAXSUBFLOW) . . . . . . . .   3
   3.  Behavior  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   This document specifies a Multipath TCP (MPTCP, [RFC6824]) option
   that is meant to indicate to a remote peer the maximum number of
   subflows that can be established within a single MPTCP connection.
   If the remote peer honors the indication provided in this option, any
   performance degradation induced by a possibly abusive setup of
   additional subflows that exceed the said maximum becomes unlikely.

   This document adheres to [I-D.bonaventure-mptcp-exp-option].

   This option targets mainly MPTCP deployments within a single
   administrative domain such as those MPTCP designs meant to achieve
   load-balancing, for example.  The use of this option contributes to
   the harmonization of node configuration within an administrative
   domain, so that an optimal number of subflows is maintained by
   involved nodes independently of their actual performance
   capabilities.  This option can be used for other deployment
   scenarios.  It is out of scope of this document to identify an
   exhaustive list of such scenarios.

   Section 3.4 of [I-D.ietf-mptcp-experience] includes a discussion on
   the MPTCP session manager issues

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1.1.  Experiment Goals

   Experiments based upon the MPTCP option described in this document
   are meant to help operators refine their MPTCP design and operational
   procedures, by tweaking some MPTCP parameters such as the number of
   subflows to be associated with a given MPTCP connection.
   Experimenting with this MPTCP option should also help assess whether
   this option can be used to propagate MPTCP-related optimization
   parameters (derived from the number of concurrent subflows associated
   to each MPTCP connection) that can be configured in a node that is
   responsible for aggregating MPTCP connections established with
   upstream nodes.

2.  Maximum Subflows MPTCP Option (MP_MAXSUBFLOW)

   This option follows the shared experimental format defined in
   [I-D.bonaventure-mptcp-exp-option] (see Figure 1).

                            1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +---------------+---------------+-------+-----------------------+
       |     Kind      |    Length     |Subtype| Flags |  Experiment   |
       +---------------+---------------+-------+-------+---------------+
       | Id. (16 bits) |              Maximum Sub-Flows                |
       +---------------+-----------------------------------------------+

                          Figure 1: Option Format

   The meaning of "Kind", "Length", "Subtype", and "Flags" (especially
   'S' and 'U' flags) are exactly the same as defined in
   [I-D.bonaventure-mptcp-exp-option].

   Experiment ID (to be assigned, see Section 5).

   The "Maximum Sub-Flows" field indicates the number of maximum
   concurrent subflows that can be maintained by a given MPTCP endpoint
   for each MPTCP connection established by or with this endpoint.  The
   value of this field MUST be strictly greater than zero.

3.  Behavior

   The option defined in Section 2 MAY be used by a TCP endpoint to
   indicate to its corresponding peer the maximum number of subflows
   that it can maintain per MPTCP connection.

   If two peers (T1 and T2) indicate the maximum number of concurrent
   subflows per connection they can maintain, then they MUST NOT

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   maintain more than "MIN(MAX_SUBFLOW(T1), MAX_SUBFLOW(T2))" concurrent
   subflows.

   The absence of the MP_MAXSUBFLOW option in an MPTCP control message
   issued by a MPTCP endpoint is an indication that this endpoint can
   instantiate any number of subflows per MPTCP connection.

4.  Security Considerations

   MPTCP-related security considerations are documented in [RFC6824] and
   [RFC7430].

5.  IANA Considerations

   This document requests IANA to assign an experiment ID for
   MP_MAXSUBFLOW as per [I-D.bonaventure-mptcp-exp-option].

6.  References

6.1.  Normative References

   [I-D.bonaventure-mptcp-exp-option]
              Bonaventure, O., benjamin.hesmans@uclouvain.be, b., and M.
              Boucadair, "Experimental Multipath TCP option", draft-
              bonaventure-mptcp-exp-option-00 (work in progress), June
              2015.

   [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>.

   [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>.

6.2.  Informative References

   [I-D.ietf-mptcp-experience]
              Bonaventure, O., Paasch, C., and G. Detal, "Use Cases and
              Operational Experience with Multipath TCP", draft-ietf-
              mptcp-experience-03 (work in progress), October 2015.

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   [RFC7430]  Bagnulo, M., Paasch, C., Gont, F., Bonaventure, O., and C.
              Raiciu, "Analysis of Residual Threats and Possible Fixes
              for Multipath TCP (MPTCP)", RFC 7430,
              DOI 10.17487/RFC7430, July 2015,
              <http://www.rfc-editor.org/info/rfc7430>.

Authors' Addresses

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com

   Christian Jacquenet
   Orange
   Rennes  35000
   France

   Email: christian.jacquenet@orange.com

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