Internet Engineering Task Force                                  A. Ford
Internet-Draft                                                     Cisco
Intended status: Experimental                                  C. Raiciu
Expires: August 3, 2012                        University Politehnica of
                                                               Bucharest
                                                              M. Handley
                                               University College London
                                                          O. Bonaventure
                                                Universite catholique de
                                                                 Louvain
                                                        January 31, 2012


     TCP Extensions for Multipath Operation with Multiple Addresses
                   draft-ietf-mptcp-multiaddressed-06

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 provides the components necessary to establish and
   use multiple TCP flows across potentially disjoint paths.

Status of this Memo

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   This Internet-Draft will expire on August 3, 2012.



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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
   publication of this document.  Please review these documents
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   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  . . . . . . . . . . . . . . . . . . . . . .  6
     1.5.  Requirements Language  . . . . . . . . . . . . . . . . . .  7
   2.  Operation Overview . . . . . . . . . . . . . . . . . . . . . .  8
     2.1.  Initiating an MPTCP connection . . . . . . . . . . . . . .  8
     2.2.  Associating a new subflow with an existing MPTCP
           connection . . . . . . . . . . . . . . . . . . . . . . . .  9
     2.3.  Informing the other Host about another potential
           address  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     2.4.  Data transfer using MPTCP  . . . . . . . . . . . . . . . . 10
     2.5.  Requesting a change in a path's priority . . . . . . . . . 11
     2.6.  Closing an MPTCP connection  . . . . . . . . . . . . . . . 11
     2.7.  Notable features . . . . . . . . . . . . . . . . . . . . . 11
   3.  MPTCP Protocol . . . . . . . . . . . . . . . . . . . . . . . . 12
     3.1.  Connection Initiation  . . . . . . . . . . . . . . . . . . 13
     3.2.  Starting a New Subflow . . . . . . . . . . . . . . . . . . 17
     3.3.  General MPTCP Operation  . . . . . . . . . . . . . . . . . 21
       3.3.1.  Data Sequence Mapping  . . . . . . . . . . . . . . . . 23
       3.3.2.  Data Acknowledgements  . . . . . . . . . . . . . . . . 26
       3.3.3.  Closing a Connection . . . . . . . . . . . . . . . . . 27
       3.3.4.  Receiver Considerations  . . . . . . . . . . . . . . . 28
       3.3.5.  Sender Considerations  . . . . . . . . . . . . . . . . 29
       3.3.6.  Reliability and Retransmissions  . . . . . . . . . . . 30
       3.3.7.  Congestion Control Considerations  . . . . . . . . . . 31
       3.3.8.  Subflow Policy . . . . . . . . . . . . . . . . . . . . 32
     3.4.  Address Knowledge Exchange (Path Management) . . . . . . . 33
       3.4.1.  Address Advertisement  . . . . . . . . . . . . . . . . 34



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       3.4.2.  Remove Address . . . . . . . . . . . . . . . . . . . . 37
     3.5.  Fast Close . . . . . . . . . . . . . . . . . . . . . . . . 38
     3.6.  Fallback . . . . . . . . . . . . . . . . . . . . . . . . . 39
     3.7.  Error Handling . . . . . . . . . . . . . . . . . . . . . . 42
     3.8.  Heuristics . . . . . . . . . . . . . . . . . . . . . . . . 42
       3.8.1.  Port Usage . . . . . . . . . . . . . . . . . . . . . . 42
       3.8.2.  Delayed Subflow Start  . . . . . . . . . . . . . . . . 43
       3.8.3.  Failure Handling . . . . . . . . . . . . . . . . . . . 44
   4.  Semantic Issues  . . . . . . . . . . . . . . . . . . . . . . . 44
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 46
   6.  Interactions with Middleboxes  . . . . . . . . . . . . . . . . 47
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 50
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 50
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 51
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 52
   Appendix A.  Notes on use of TCP Options . . . . . . . . . . . . . 53
   Appendix B.  Control Blocks  . . . . . . . . . . . . . . . . . . . 54
     B.1.  MPTCP Control Block  . . . . . . . . . . . . . . . . . . . 55
       B.1.1.  Authentication and Metadata  . . . . . . . . . . . . . 55
       B.1.2.  Sending Side . . . . . . . . . . . . . . . . . . . . . 55
       B.1.3.  Receiving Side . . . . . . . . . . . . . . . . . . . . 56
     B.2.  TCP Control Blocks . . . . . . . . . . . . . . . . . . . . 56
       B.2.1.  Sending Side . . . . . . . . . . . . . . . . . . . . . 56
       B.2.2.  Receiving Side . . . . . . . . . . . . . . . . . . . . 56
   Appendix C.  Finite State Machine  . . . . . . . . . . . . . . . . 57
   Appendix D.  Changelog . . . . . . . . . . . . . . . . . . . . . . 57
     D.1.  Changes since draft-ietf-mptcp-multiaddressed-05 . . . . . 57
     D.2.  Changes since draft-ietf-mptcp-multiaddressed-04 . . . . . 58
     D.3.  Changes since draft-ietf-mptcp-multiaddressed-03 . . . . . 58
     D.4.  Changes since draft-ietf-mptcp-multiaddressed-02 . . . . . 58
     D.5.  Changes since