TFO support for Multipath TCP
draft-barre-mptcp-tfo-03

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Last updated 2018-05-29
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MPTCP Working Group                                             S. Barre
Internet-Draft                                                  G. Detal
Intended status: Informational                                  Tessares
Expires: November 30, 2018                                O. Bonaventure
                                                  UCLouvain and Tessares
                                                               C. Paasch
                                                                   Apple
                                                            May 29, 2018

                     TFO support for Multipath TCP
                        draft-barre-mptcp-tfo-03

Abstract

   TCP Fast Open (TFO) is a TCP extension that allows sending data in
   the SYN, instead of waiting until the TCP connection is established.
   This document describes what parts of Multipath TCP must be adapted
   to support it, and how TFO and MPTCP can operate together.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on November 30, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Barre, et al.           Expires November 30, 2018               [Page 1]
Internet-Draft              MPTCP TFO support                   May 2018

   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  TFO cookie request with MPTCP . . . . . . . . . . . . . . . .   3
   3.  Data sequence mapping under TFO . . . . . . . . . . . . . . .   4
   4.  Early context creation in server  . . . . . . . . . . . . . .   4
   5.  Using TFO to avoid useless MPTCP negotiations . . . . . . . .   5
   6.  Using TFO with MP_JOIN  . . . . . . . . . . . . . . . . . . .   6
   7.  Connection establishment examples . . . . . . . . . . . . . .   6
   8.  Middlebox interactions  . . . . . . . . . . . . . . . . . . .   8
   9.  Security considerations . . . . . . . . . . . . . . . . . . .   9
   10. Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  10
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   12. Informative References  . . . . . . . . . . . . . . . . . . .  10
   Appendix A.  Implementation status  . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   TCP Fast Open, described in [RFC7413], has been introduced with the
   objective of gaining one RTT before transmitting data.  This is
   considered a valuable gain as very short connections are very common,
   especially for HTTP request/response schemes.  MPTCP, on the other
   hand, has been defined in [I-D.ietf-mptcp-rfc6824bis] to add
   multipath support to TCP, where a TCP flow is divided in several TCP
   subflows.  Given that MPTCP can be applied transparently to any TCP
   socket, without the application knowing, it should be able to support
   TCP fast open when the application asks for it.

   When doing that, one important thing to examine is the option length
   consumed in segments that would carry both a TFO and an MPTCP option.
   The handling of MPTCP data sequence mappings must also be updated to
   take into account the data that is sent together with the SYN or the
   SYN+ACK.  A third issue to handle is the state creation in the
   server: TFO allows the server to create TCP state as soon as a SYN is
   received.  With MPTCP, even more state is created, and it may be
   useful to avoid this in a situation where MPTCP does not work but TFO
   does.

   The rest of this document is organized as follows:

   Section 2 describes the TFO cookie request, in the case of a
   Multipath TCP flow.  Section 3 proposes a way to map SYN data to the
   data sequence number space, while taking middleboxes into account.
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