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TCP Extensions for Multipath Operation with Multiple Addresses
RFC 6824

Internet Engineering Task Force (IETF)                           A. Ford
Request for Comments: 6824                                         Cisco
Category: Experimental                                         C. Raiciu
ISSN: 2070-1721                             U. Politechnica of Bucharest
                                                              M. Handley
                                                       U. College London
                                                          O. Bonaventure
                                                U. catholique de Louvain
                                                            January 2013

     TCP Extensions for Multipath Operation with Multiple Addresses

Abstract

   TCP/IP communication is currently restricted to a single path per
   connection, yet multiple paths often exist between peers.  The
   simultaneous use of these multiple paths for a TCP/IP session would
   improve resource usage within the network and, thus, improve user
   experience through higher throughput and improved resilience to
   network failure.

   Multipath TCP provides the ability to simultaneously use multiple
   paths between peers.  This document presents a set of extensions to
   traditional TCP to support multipath operation.  The protocol offers
   the same type of service to applications as TCP (i.e., reliable
   bytestream), and it provides the components necessary to establish
   and use multiple TCP flows across potentially disjoint paths.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  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).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see 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/rfc6824.

Ford, et al.                  Experimental                      [Page 1]
RFC 6824                      Multipath TCP                 January 2013

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.

Table of Contents

   1. Introduction ....................................................4
      1.1. Design Assumptions .........................................4
      1.2. Multipath TCP in the Networking Stack ......................5
      1.3. Terminology ................................................6
      1.4. MPTCP Concept ..............................................7
      1.5. Requirements Language ......................................8
   2. Operation Overview ..............................................8
      2.1. Initiating an MPTCP Connection .............................9
      2.2. Associating a New Subflow with an Existing MPTCP
           Connection .................................................9
      2.3. Informing the Other Host about Another Potential Address ..10
      2.4. Data Transfer Using MPTCP .................................11
      2.5. Requesting a Change in a Path's Priority ..................11
      2.6. Closing an MPTCP Connection ...............................12
      2.7. Notable Features ..........................................12
   3. MPTCP Protocol .................................................12
      3.1. Connection Initiation .....................................14
      3.2. Starting a New Subflow ....................................18
      3.3. General MPTCP Operation ...................................23
           3.3.1. Data Sequence Mapping ..............................25
           3.3.2. Data Acknowledgments ...............................28
           3.3.3. Closing a Connection ...............................29
           3.3.4. Receiver Considerations ............................30

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