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Versions: 00 01 02 draft-ietf-tcpm-converters

MPTCP Working Group                                       O. Bonaventure
Internet-Draft                                                  Tessares
Intended status: Experimental                               M. Boucadair
Expires: May 3, 2018                                              Orange
                                                              B. Peirens
                                                                Proximus
                                                                  S. Seo
                                                           Korea Telecom
                                                            A. Nandugudi
                                                                Tessares
                                                        October 30, 2017


                          0-RTT TCP Converter
                 draft-bonaventure-mptcp-converters-02

Abstract

   This document specifies an application proxy, called Transport
   Converter, to assist the deployment of Multipath TCP.  This proxy is
   designed to avoid inducing extra delay when involved in a network-
   assisted connection (that is, 0-RTT).  This specification assumes an
   explicit model, where the proxy is explicitly configured on hosts.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2018.

Copyright Notice

   Copyright (c) 2017 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



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   (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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Applicability Scope  . . . . . . . . . . . . . . . . . . . . .  5
   3.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Sample Examples of Converter-Assisted Multipath TCP
           Connections  . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Sample Example of Incoming Converter-Assisted
           Multipath TCP Connection . . . . . . . . . . . . . . . . . 11
     3.3.  Differences with SOCKSv5 . . . . . . . . . . . . . . . . . 12
   4.  The Converter Protocol . . . . . . . . . . . . . . . . . . . . 15
     4.1.  The Fixed Header . . . . . . . . . . . . . . . . . . . . . 15
     4.2.  Transport Converter TLVs . . . . . . . . . . . . . . . . . 15
       4.2.1.  Connect TLV  . . . . . . . . . . . . . . . . . . . . . 16
       4.2.2.  Extended TCP Header TLV  . . . . . . . . . . . . . . . 18
       4.2.3.  Error TLV  . . . . . . . . . . . . . . . . . . . . . . 18
       4.2.4.  The Bootstrap TLV  . . . . . . . . . . . . . . . . . . 21
       4.2.5.  Supported TCP Options TLV  . . . . . . . . . . . . . . 21
   5.  Interactions with middleboxes  . . . . . . . . . . . . . . . . 23
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
     6.1.  Privacy & Ingress Filtering  . . . . . . . . . . . . . . . 24
     6.2.  Authorization  . . . . . . . . . . . . . . . . . . . . . . 24
     6.3.  Denial of Service  . . . . . . . . . . . . . . . . . . . . 24
     6.4.  Traffic Theft  . . . . . . . . . . . . . . . . . . . . . . 25
     6.5.  Multipath TCP-specific Considerations  . . . . . . . . . . 25
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
     8.1.  Contributors . . . . . . . . . . . . . . . . . . . . . . . 28
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 29
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32










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1.  Introduction

   Transport protocols like TCP evolve regularly [RFC7414].  TCP has
   been improved in different ways.  Some improvements such as changing
   the initial window size or modifying the congestion control scheme
   can be applied independently on clients and servers.  Other
   improvements such as Selective Acknowledgements [RFC2018] or large
   windows [RFC7323] require a new TCP option or to change the semantics
   of some fields in the TCP header.  These modifications must be
   deployed on both clients and servers to be actually used on the
   Internet.  Experience with the latter TCP extensions reveals that
   their deployment can require many years.  Fukuda reports in
   [Fukuda2011] results of a decade of measurements showing the
   deployment of Selective Acknowledgements, Window Scale and TCP
   Timestamps.  Trammel et al. provide in [ANRW17] measurements showing
   that TCP Fast Open [RFC7413] (TFO) is still not widely deployed.

   There are some situations where the transport stack used on clients
   (resp. servers) can be upgraded at a faster pace than the transport
   stack running on servers (resp. clients).  In those situations,
   clients would typically want to benefit from the features of an
   improved transport protocol even if the servers have not yet been
   upgraded and conversely.  In the past, Performance Enhancing Proxies
   have been proposed and deployed [RFC3135] as solutions to improve TCP
   performance over links with specific characteristics.

   Recent examples of TCP extensions include Multipath TCP [RFC6824] or
   TCPINC [I-D.ietf-tcpinc-tcpcrypt].  Those extensions provide features
   that are interesting for clients such as wireless devices.  With
   Multipath TCP, those devices could seamlessly use WLAN and cellular
   networks, for bonding purposes, faster handovers, or better
   resiliency.  Unfortunately, deploying those extensions on both a wide
   range of clients and servers remains difficult.

   This document specifies an application proxy, called Transport
   Converter (TC).  A Transport Converter is a function that is
   installed by a network operator to aid the deployment of TCP
   extensions and to provide the benefits of such extensions to clients.
   A Transport Converter supports one or more TCP extensions.  The
   Converter Protocol (CP) is an application layer protocol that uses a
   TCP port number (see IANA section).  The Transport Converter adheres
   to the main principles as drawn in [RFC1919].  In particular, the
   Converter achieves the following:

   o  Listen for client sessions;

   o  Receive from a client the address of the final target server;




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   o  Setup a session to the final server;

   o  Relay control messages and data between the client and the server;

   o  Perform access controls according to local policies.

   The main advantage of network-assisted converters is that they enable
   new TCP extensions to be used on a subset of the end-to-end path,
   which encourages the deployment of these extensions.  The Transport
   Converter allows the client and the server to directly negotiate some
   options between the endpoints.  This document focuses on Multipath
   TCP [RFC6824] and TCP Fast Open [RFC7413].  The support for other TCP
   extensions will be discussed in other documents.

   This document does not assume that all the traffic is eligible to the
   network-assisted conversion service.  Only a subset of the traffic
   will be forwarded to a converter according to a set of policies.
   Furthermore, it is possible to bypass the converter to connect to the
   servers that already support the required TCP extension.

   This document assumes that a client is configured with one or a list
   of transport converters.  Configuration means are outside the scope
   of this document.

   This document is organized as follows.  We first provide a brief
   explanation of the operation of Transport Converters in Section 3.
   We compare them in Section 3.3 with SOCKS proxies that are already
   used to deploy Multipath TCP in cellular networks [IETFJ16].  We then
   describe the Converter Protocol in Section 4.  We then discuss the
   interactions with middleboxes (Section 5) and the security
   considerations (Section 6).




















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2.  Applicability Scope

   This specification is designed with Multipath TCP
   [RFC6824][I-D.ietf-mptcp-rfc6824bis] and TCP Fast Open [RFC7413] in
   mind.  That is, the specification draws how network-assisted
   Multipath TCP connections can be established even if the remote
   server is not Multipath TCP-capable without inducing extra connection
   delays (0-RTT proxy).  Further, the specification allows the client
   for end-to-end Multipath TCP connections with or without proxy
   involvement.  Assessing the applicability of the solution to other
   use cases and other TCP extensions such as [I-D.ietf-tcpinc-tcpcrypt]
   is outside the scope of this document.  Future documents are required
   to specify the exact behavior when the converter is deployed in other
   contexts than Multipath TCP.





































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3.  Architecture

   The architecture considers three types of endhosts:

   o  Client endhosts;

   o  Transport Converters;

   o  Server endhosts.

   It does not mandate anything on the server side.  The architecture
   assumes that new software will be installed on the Client hosts and
   on Transport Converters.  Further, the architecture allows for making
   use of TCP new extensions if those are supported by a given server.

   A Transport Converter is a network function that relays all data
   exchanged over one upstream connection to one downstream connection
   and vice versa.  A connection can be initiated from both interfaces
   of the transport converter (Internet-facing interface, client-facing
   interface).  The converter, thus, maintains state that associates one
   upstream connection to a corresponding downstream connection.  One of
   the benefits of this design is that different transport protocol
   extensions can be used on the upstream and the downstream
   connections.  This encourages the deployment of new TCP extensions
   until they are supported by many servers.

                        +------------+
      <--- upstream --->| Transport  |<--- downstream --->
                        | Converter  |
                        +------------+


     Figure 1: A Transport Converter relays data between pairs of TCP
                                connections

   Transport converters can be operated by network operators or third
   parties.  The Client is configured, through means that are outside
   the scope of this document, with the names and/or the addresses of
   one or more Transport Converters.  The packets belonging to the pair
   of connections between the Client and Server passing through a
   Transport Converter may follow a different path than the packets
   directly exchanged between the Client and the Server.  Deployments
   should minimize the possible additional delay by carefully selecting
   the location of the Transport Converter used to reach a given
   destination.

   A transport converter can be embedded in a standalone device or be
   activated as a service on a router.  How such function is enabled is



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   deployement-specific.

                 +-+    +-+    +-+
       Client -  |R| -- |R| -- |R| - - -  Server
                 +-+    +-+    +-+
                         |
                     Transport
                     Converter


     Figure 2: A Transport Converter can be installed anywhere in the
                                  network

   When establishing a connection, the Client can, depending on local
   policies, either contact the Server directly (e.g., by sending a TCP
   SYN towards the Server) or create the connection via a Transport
   Converter.  In the latter case, which is the case we consider in this
   document, the Client initiates a connection towards the Transport
   Converter and indicates the address and port number of the ultimate
   Server inside the connection establishment packet.  Doing so enables
   the Transport Converter to immediately initiate a connection towards
   that Server, without experiencing an extra delay.  The Transport
   Converter waits until the confirmation that the Server agrees to
   establish the connection before confirming it to the Client.

   The client places the destination address and port number of the
   target Server in the payload of the SYN sent to the Converter by
   leveraging TCP Fast Open [RFC7413].  In accordance with [RFC1919],
   the Transport Converter maintains two connections that are combined
   together.  The upstream connection is the one between the Client and
   the Transport Converter.  The downstream connection is between the
   Transport Converter and the remote Server.  Any user data received by
   the Transport Converter over the upstream (resp., downstream)
   connection is relayed over the downstream (resp., upstream)
   connection.

   At a high level, the objective of the Transport Converter is to allow
   the Client to use a specific extension, e.g.  Multipath TCP, on a
   subset of the end-to-end path even if the Server does not support
   this extension.  This is illustrated in Figure 3 where the Client
   initiates a Multipath TCP connection with the Converter (Multipath
   packets are shown with =) while the Converter uses a regular TCP
   connection with the Server.








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                            Transport
   Client                   Converter                       Server
        ======================>

                                    -------------------->

                                    <--------------------

        <======================
          Multipath TCP packets      Regular TCP packets

   Figure 3: Different TCP variants can be used on the Client-Converter
                   path and on the Converter-Server path

   Figure 4 illustrates the establishment of a TCP connection by the
   Client through a Transport Converter.  The information shown between
   brackets is part of the Converter protocol described later in this
   document.

   The Client sends a SYN destined to the Transport Converter.  This SYN
   contains a TFO Cookie and inside its payload the addresses and ports
   of the destination Server.  The Transport Converter does not reply
   immediately to this SYN.  It first tries to create a TCP connection
   towards the destination Server.  If this second connection succeeds,
   the Transport Converter confirms the establishment of the connection
   to the Client by returning a SYN+ACK and the first bytes of the
   bytestream contain information about the TCP Options that were
   negotiated with the final Server.  This information is sent at the
   beginning of the bytestream, either directly in the SYN+ACK or in a
   subsequent packet.  For graphical reasons, the figures in this
   section show that the Converter returns this information in the SYN+
   ACK packet.  An implementation could also place this information in a
   packet that it sent shortly after the SYN+ACK.

                            Transport
   Client                   Converter                       Server
        -------------------->
         SYN TFO [->Server:port]

                                    -------------------->
                                             SYN

                                    <--------------------
                                            SYN+ACK
        <--------------------
          SYN+ACK [ ]





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      Figure 4: Establishment of a TCP connection through a Converter

   The connection can also be established from the Internet towards a
   client via a transport converter.  This is typically the case when
   the client embeds a server (video server, for example).

   The procedure described in Figure 4 assumes that the Client has
   obtained a TFO Cookie from the Transport Converter.  This is part of
   the Bootstrap procedure which is illustrated in Figure 5.  The Client
   sends a SYN with a TFO Request option to obtain a valid cookie from
   the Converter.  The Converter replies with a TFO cookie in the SYN+
   ACK.  Once this connection has been established, the Client sends a
   Bootstrap message to request the list of TCP options supported by the
   Transport Converter.  Thanks to this procedure, the Client knows
   which TCP options are supported by a given Transport Converter.

                            Transport
   Client                   Converter                       Server
        -------------------->
         SYN TFO(empty)

        <--------------------
          SYN+ACK TFO(cookie)

        -------------------->
            [Bootstrap]

        <--------------------
          [Supported TCP Options]



   Figure 5: Bootstrapping a Client connection to a Transport Converter

   Note that the Converter may rely on local policies to decide whether
   it can service a given requesting client.  That is, the Converter may
   not return a cookie for that client.

   Also, the Converter may behave in a Cookie-less mode when appropriate
   means are enforced at the converter and the network in-between to
   protect against attacks such as spoofing and SYN flood.  Under such
   deployments, the use of TFO is not required.

3.1.  Sample Examples of Converter-Assisted Multipath TCP Connections

   As an example, let us consider how such a protocol can help the
   deployment of Multipath TCP [RFC6824].  We assume that both the
   Client and the Transport Converter support Multipath TCP, but



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   consider two different cases depending
   whether the Server supports Multipath TCP or not.  A Multipath TCP
   connection is created by placing the MP_CAPABLE (MPC) option in the
   SYN sent by the Client.

   Figure 6 describes the operation of the Transport Converter if the
   Server does not support Multipath TCP.

                            Transport
   Client                   Converter                    Server
        -------------------->
        SYN, MPC [->Server:port]

                                    -------------------->
                                          SYN, MPC

                                    <--------------------
                                            SYN+ACK
        <--------------------
          SYN+ACK,MPC [ ]

        -------------------->
            ACK,MPC
                                    -------------------->
                                             ACK


      Figure 6: Establishment of a Multipath TCP connection through a
                                 Converter

   The Client tries to initiate a Multipath TCP connection by sending a
   SYN with the MP_CAPABLE option (MPC in Figure 6).  The SYN includes
   the address and port number of the final Server and the Transport
   Converter attempts to initiate a Multipath TCP connection towards
   this Server.  Since the Server does not support Multipath TCP, it
   replies with a SYN+ACK that does not contain the MP_CAPABLE option.
   The Transport Converter notes that the connection with the Server
   does not support Multipath TCP and returns the TCP Options received
   from the Server to the Client.

   Figure 7 considers a Server that supports Multipath TCP.  In this
   case, it replies to the SYN sent by the Transport Converter with the
   MP_CAPABLE option.  Upon reception of this SYN+ACK, the Transport
   Converter confirms the establishment of the connection to the Client
   and indicates to the Client that the Server supports Multipath TCP.
   With this information, the Client has discovered that the Server
   supports Multipath TCP natively.  This will enable it to bypass the
   Transport Converter for the next Multipath TCP connection that it



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   will initiate towards this Server.

                            Transport
   Client                   Converter                       Server
        -------------------->
        SYN, MPC [->Server:port]

                                    -------------------->
                                          SYN, MPC

                                    <--------------------
                                            SYN+ACK, MPC
        <--------------------
          SYN+ACK, MPC [ MPC supported ]

        -------------------->
            ACK, MPC
                                    -------------------->
                                             ACK, MPC

      Figure 7: Establishment of a Multipath TCP connection through a
                                 converter

3.2.  Sample Example of Incoming Converter-Assisted Multipath TCP
      Connection

   An example of an incoming converter-assisted Multipath TCP connection
   is depicted in Figure 8.  In order to support incoming connections
   from remote hosts, the client may use PCP [RFC6887] to instruct the
   converter to create dynamic mappings.  Those mappings will be used by
   the converter to intercept an incoming TCP connection destined to the
   client and convert it into a Multipath TCP connection.



















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                        Transport
   H1                   Converter                       Remote Host
                                   <-------------------
                                     SYN

        <-------------------
       SYN, MPC[Remote Host:port]

        --------------------->
               SYN+ACK, MPC
                                   --------------------->
                                           SYN+ACK

                                   <---------------------
                                              ACK
        <-------------------
                 ACK, MPC


      Figure 8: Establishment of an Incoming TCP Connection through a
                                 Converter

3.3.  Differences with SOCKSv5

   The description above is a simplified description of the Converter
   protocol.  At a first glance, the proposed solution could seem
   similar to the SOCKS v5 protocol [RFC1928].  This protocol is used to
   proxy TCP connections.  The Client creates a connection to a SOCKS
   proxy, exchanges authentication information and indicates the
   destination address and port of the final server.  At this point, the
   SOCKS proxy creates a connection towards the final server and relays
   all data between the two proxied connections.  The operation of an
   implementation based on SOCKSv5 is illustrated in Figure 9.


















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   Client                     SOCKS Proxy                  Server
        -------------------->
                SYN
        <--------------------
              SYN+ACK
        -------------------->
                ACK

        -------------------->
        Version=5, Auth Methods
        <--------------------
              Method
        -------------------->
            Auth Request (if "No auth" method negotiated)
        <--------------------
            Auth Response
        -------------------->
        Connect Server:Port            -------------------->
                                              SYN

                                       <--------------------
                                            SYN+ACK
        <--------------------
             Succeeded

        -------------------->
               Data1
                                       -------------------->
                                              Data1

                                       <--------------------
                                              Data2
        <--------------------
                 Data2

     Figure 9: Establishment of a TCP connection through a SOCKS proxy
                          without authentication

   The Converter protocol also relays data between an upstream and a
   downstream connection, but there are important differences with
   SOCKSv5.

   A first difference is that the Converter protocol leverages the TFO
   option [RFC7413] to exchange all control information during the
   three-way handshake.  This reduces the connection establishment delay
   compared to SOCKS that requires two or more round-trip-times before
   the establishment of the downstream connection towards the final
   destination.  In today's Internet, latency is a important metric and



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   various protocols have been tuned to reduce their latency
   [I-D.arkko-arch-low-latency].  A recently proposed extension to SOCKS
   also leverages the TFO option [I-D.olteanu-intarea-socks-6].

   A second difference is that the Converter protocol explicitly takes
   the TCP extensions into account.  By using the Converter protocol,
   the Client can learn whether a given TCP extension is supported by
   the destination Server.  This enables the Client to bypass the
   Transport Converter when the destination supports the required TCP
   extension.  Neither SOCKS v5 [RFC1928] nor the proposed SOCKS v6
   [I-D.olteanu-intarea-socks-6] provide such a feature.

   A third difference is that a Transport Converter will only accept the
   connection initiated by the Client provided that the downstream
   connection is accepted by the Server.  If the Server refuses the
   connection establishment attempt from the Transport Converter, then
   the upstream connection from the Client is rejected as well.  This
   feature is important for applications that check the availability of
   a Server or use the time to connect as a hint on the selection of a
   Server [RFC6555].































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4.  The Converter Protocol

   We now describe in details the messages that are exchanged between a
   Client and a Transport Converter.  The Converter Protocol (CP)
   leverages the TCP Fast Open extension defined in [RFC7413].

   The Converter Protocol uses a 32 bits long fixed header that is sent
   by both the Client and the Transport Converter.  This header
   indicates both the version of the protocol used and the length of the
   CP message.

4.1.  The Fixed Header

   The Fixed Header is used to exchange information about the version
   and length of the messages between the Client and the Transport
   Converter.  The Client and the Transport Converter MUST send the
   fixed-sized header shown in Figure 10 as the first four bytes of the
   bytestream.

                           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
      +---------------+---------------+-------------------------------+
      |  Version      |  Total Length |          Reserved             |
      +---------------+---------------+-------------------------------+

        Figure 10: The fixed-sized header of the Converter protocol

   The Version is encoded as an 8 bits unsigned integer value.  This
   document specifies version 1.  The Total Length is the number of 32
   bits word, including the header, of the bytestream that are consumed
   by the Converter protocol messages.  Since Total Length is also an 8
   bits unsigned integer, those messages cannot consume more than 1020
   bytes of data.  This limits the number of bytes that a Transport
   Converter needs to process.  A Total Length of zero is invalid and
   the connection MUST be reset upon reception of such a header.  The
   Reserved field MUST be set to zero in this version of the protocol.

4.2.  Transport Converter TLVs

   The Converter protocol uses variable length messages that are encoded
   using a TLV format to simplify the parsing of the messages and leave
   room to extend the protocol in the future.  A given TLV can only
   appear once on a connection.  If two or more copies of the same TLV
   are exchanged over a Converter connection, the associated TCP
   connections MUST be closed.  All fields are encoded using the network
   byte order.

   Five TLVs are defined in this document.  They are listed in Table 1.



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          +------+------+----------+---------------------------+
          | Type | Hex  | Length   | Description               |
          +------+------+----------+---------------------------+
          | 1    | 0x1  | 1        | Bootstrap TLV             |
          |      |      |          |                           |
          | 10   | 0xA  | Variable | Connect TLV               |
          |      |      |          |                           |
          | 20   | 0x14 | Variable | Extended TCP Header TLV   |
          |      |      |          |                           |
          | 21   | 0x15 | Variable | Supported TCP Options TLV |
          |      |      |          |                           |
          | 30   | 0x1E | Variable | Error TLV                 |
          +------+------+----------+---------------------------+

             Table 1: The TLVs used by the Converter protocol

   To use a given Transport Converter, a Client MUST first obtain a
   valid TFO cookie from it.  This is the bootstrap procedure during
   which the Client opens a connection to the Transport Converter with
   an empty TFO option.  According to [RFC7413], the Transport Converter
   returns its cookie in the SYN+ACK.  Then the Client sends a Bootstrap
   TLV and the Transport Converter replies with the Supported TCP
   Options TLV that lists the TCP options that it supports (section
   Section 4.2.5).

   With the TFO Cookie of the Transport Converter, the Client can
   request the establishment of connections to remote servers with the
   Connect TLV (see Section 4.2.1).  If the connection can be
   established with the final server, the Transport Converter replies
   with the Extended TCP Header TLV and returns an Error TLV inside a
   RST packet (see section Section 4.2.3).

4.2.1.  Connect TLV

   This TLV (Figure 11) is used to request the establishment of a
   connection via a Transport Converter.

   The 'Remote Peer Port' and 'Remote Peer IP Address' fields contain
   the destination port and IP address of the target server for an
   outgoing connection towards a server located on the Internet.  For
   incoming connections destined to a client serviced via a Converter,
   these fields convey the source port and IP address.

   The Remote Peer IP Address MUST be encoded as an IPv6 address.  IPv4
   addresses MUST be encoded using the IPv4-Mapped IPv6 Address format
   defined in [RFC4291].

   The optional 'TCP Options' field is used to specify how specific TCP



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   Options should be advertised by the Transport Converter to the final
   destination of a connection.  If this field is not supplied, the
   Transport Converter MUST use the default TCP options that correspond
   to its local policy.

                           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
      +---------------+---------------+-------------------------------+
      |     Type      |     Length    |      Remote Peer Port         |
      +---------------+---------------+-------------------------------+
      |                                                               |
      |         Remote Peer IP Address (128 bits)                     |
      |                                                               |
      |                                                               |
      +---------------------------------------------------------------+
      |                          TCP Options (Variable)               |
      |                              ...                              |
      +---------------------------------------------------------------+

                        Figure 11: The Connect TLV

   The 'TCP Options' field is a variable length field that carries a
   list of TCP Option fields (Figure 12).  Each TCP Option field is
   encoded as a block of 2+n bytes where the first byte is the TCP
   Option Type and the second byte is the length of the TCP Option as
   specified in [RFC0793].  The minimum value for the TCP Option Length
   is 2.  The TCP Options that do not include a length subfield, i.e.,
   option types 0 (EOL) and 1 (NOP) defined in [RFC0793] cannot be
   placed inside the TCP Options field of the Connect TLV.  The optional
   Value field contains the variable-length part of the TCP option.  A
   length of two indicates the absence of the Value field.  The TCP
   Options field always ends on a 32 bits boundary after being padded
   with zeros.

                           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
      +---------------+---------------+---------------+---------------+
      |  TCPOpt type  | TCPOpt Length | Value  (opt)  |  ....         |
      +---------------+---------------+---------------+---------------+
      |                             ....                              |
      +---------------------------------------------------------------+
      |                              ...                              |
      +---------------------------------------------------------------+

                     Figure 12: The TCP Options field

   If a Transport Converter receives a Connect TLV with a non-empty TCP
   Options field, it shall present those options to the destination peer



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   in addition to the TCP Options that it would have used according to
   its local policies.  For the TCP Options that are listed without an
   optional value, the Converter MUST generate its own value.  For the
   TCP Options that are included in the 'TCP Options' field with an
   optional value, it shall copy the entire option for use in the
   connection with the destination peer.  This feature is required to
   support TCP Fast Open.

4.2.2.  Extended TCP Header TLV

   The Extended TCP Header TLV is used by the Transport Converter to
   send to the Client the extended TCP header that was returned by the
   Server in the SYN+ACK packet.  This TLV is only sent if the Client
   sent a Connect TLV to request the establishment of a connection.

                           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
      +---------------+---------------+-------------------------------+
      |     Type      |     Length    |           Reserved            |
      +---------------+---------------+-------------------------------+
      |               Returned Extended TCP header                    |
      |                              ...                              |
      +---------------------------------------------------------------+

                  Figure 13: The Extended TCP Header TLV

   The Returned Extended TCP header field is a copy of the extended
   header that was received in the SYN+ACK by the Transport Converter.
   The Reserved field is set to zero by the transmitter and ignored by
   the receiver.

4.2.3.  Error TLV

   This optional TLV can be used by the Transport Converter to provide
   information about some errors that occurred during the processing of
   a request to convert a connection.  This TLV appears after the
   Converter header in a RST segment returned by the Transport Converter
   if the error is fatal and prevented the establishment of the
   connection.  If the error is not fatal and the connection could be
   established with the final destination, then the error TLV will be
   carried in the payload.

                           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
      +---------------+---------------+----------------+--------------+
      |     Type      |     Length    |    Error       |  Value       |
      +---------------+---------------+----------------+--------------+




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                         Figure 14: The Error TLV

   Different types of errors can occur while processing Converter
   protocol messages.  Each error is identified by a code represented as
   an unsigned integer.  Four classes of errors are defined:

   o  Message validation and processing errors (0<= error code < 31):
      returned upon reception of an an invalid message (including valid
      messages but with invalid or unknown TLVs).

   o  Client-side errors (32<= error code < 63): the Client sent a
      request that could not be accepted by the Converter (e.g.,
      unsupported operation).

   o  Converter-side errors (64<= error code <96) : problems encountered
      on the Converter (e.g., lack of ressources) which prevent it from
      fulfilling the Client's request.

   o  Errors caused by destination server (96<= error code < 127) : the
      final destination could not be reached or it replied with a reset
      message.

   The following errors are defined in this document:

   o  Unsupported Version (0): The version number indicated in the fixed
      header of a message received from a peer is not supported.  This
      error code MUST be generated by a Converter when it receives a
      request having a version number that it does not support.  The
      value field MUST be set to the version supported by the Converter.
      When multiple versions are supported by the converter, it includes
      the list of supported version in the value field; each version is
      encoded in 8 bits.  Upon receipt of this error code, the client
      checks whether it supports one of the versions returned by the
      Converter.  The highest common supported version MUST be used by
      the client in subsequent exchanges with the Converter.

   o  Malformed Message (1): This error code is sent to indicate that a
      message can not be successfully parsed.  To ease troubleshooting,
      the value field MUST echo the received message.  The Converter and
      the Client MUST send a RST containing this error upon reception of
      a malformed message.

   o  Unsupported Message (2): This error code is sent to indicate that
      a message type is not supported by the converter.  To ease
      troubleshooting, the value field MUST echo the received message.
      The Converter and the Client MUST send a RST containing this error
      upon reception of an unsupported message.




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   o  Not Authorized (32): This error code indicates that the Converter
      refused to create a connection because of a lack of authorization
      (e.g., administratively prohibited, authorization failure, etc.).
      The Value field is set to zero.  This error code MUST be sent by
      the Converter when a request cannot be successfully processed
      because the authorization failed.

   o  Unsupported TCP Option (33).  A TCP Option that the Client
      requested to advertise to the final Server is not supported by the
      Transport Converter.  The Value field is set to the type of the
      unsupported TCP Option.  If several unsupported TCP Options were
      specified in the Connect TLV, only one of them is returned in the
      Value.

   o  Resource Exceeded (64): This error indicates that the Transport
      Converter does not have enough resources to perform the request.
      This error MUST be sent by the Converter when it does not have
      sufficient resources to handle a new connection.

   o  Network Failure (65): This error indicates that the converter is
      experiencing a network failure to relay the request.  The
      converter MUST send this error code when it experiences forwarding
      issues to relay a connection.

   o  Connection Reset (96): This error indicates that the final
      destination responded with a RST packet.  The Value field is set
      to zero.

   o  Destination Unreachable (97): This error indicates that an ICMP
      destination unreachable, port unreachable, or network unreachable
      was received by the Converter.  The Value field contains the Code
      field of the received ICMP message.  This error message MUST be
      sent by the Converter when it receives an error message that is
      bound to a message it relayed previously.

   Table 2 summarizes the different error codes.















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                +-------+------+-------------------------+
                | Error | Hex  | Description             |
                +-------+------+-------------------------+
                | 0     | 0x00 | Unsupported version     |
                |       |      |                         |
                | 1     | 0x01 | Malformed Message       |
                |       |      |                         |
                | 2     | 0x02 | Unsupported Message     |
                |       |      |                         |
                | 32    | 0x20 | Not Authorized          |
                |       |      |                         |
                | 33    | 0x21 | Unsupported TCP Option  |
                |       |      |                         |
                | 64    | 0x40 | Resource Exceeded       |
                |       |      |                         |
                | 65    | 0x41 | Network Failure         |
                |       |      |                         |
                | 96    | 0x60 | Connection Reset        |
                |       |      |                         |
                | 97    | 0x61 | Destination Unreachable |
                +-------+------+-------------------------+

                    Table 2: The different error codes

4.2.4.  The Bootstrap TLV

   The Bootstrap TLV is sent by a Client to request the TCP Extensions
   that are supported by a Transport Converter.  It is typically sent on
   the first connection that a Client establishes with a Transport
   Converter to learn its capabilities.  The Transport Converter replies
   with the Supported TCP Options TLV described in Section 4.2.5.

                           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
      +---------------+---------------+-------------------------------+
      |     Type      |     Length    |             Zero              |
      +---------------+---------------+-------------------------------+


                       Figure 15: The Bootstrap TLV

4.2.5.  Supported TCP Options TLV

   The Supported TCP Options TLV is used by a Converter to announce the
   TCP options that it supports.  Each supported TCP Option is encoded
   with its TCP option Kind listed in the TCP Parameters registry
   maintained by IANA.  TCP option Kinds 0, 1, and 2 defined in
   [RFC0793] are supported by all TCP implementations and thus cannot



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   appear in this list.  The list of supported TCP Options is padded
   with 0 to end on a 32 bits boundary.

                           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
      +---------------+---------------+-------------------------------+
      |     Type      |     Length    |           Reserved            |
      +---------------+---------------+-------------------------------+
      |     Kind #1   |     Kind #2   |           ...                 |
      +---------------+---------------+-------------------------------+
      /                              ...                              /
      /                                                               /
      +---------------------------------------------------------------+

                 Figure 16: The Supported TCP Options TLV




































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5.  Interactions with middleboxes

   The Converter protocol was designed to be used in networks that do
   not contain middleboxes that interfere with TCP.  We describe in this
   section how a Client can detect middlebox interference and stop using
   the Transport Converter affected by this interference.

   Internet measurements [IMC11] have shown that middleboxes can affect
   the deployment of TCP extensions.  In this section, we only discuss
   the middleboxes that modify SYN and SYN+ACK packets since the
   Converter protocol places its messages in such packets.

   Let us first consider a middlebox that removes the TFO Option from
   the SYN packet.  This interference will be detected by the Client
   during the bootstrap procedure shown in Figure 5.  A Client should
   not use a Transport Converter that does not reply with the TFO option
   during the Bootstrap.

   Consider a middlebox that removes the SYN payload after the bootstrap
   procedure.  The Client can detect this problem by looking at the
   acknowledgement number field of the SYN+ACK returned by the Transport
   Converter.  The Client should stop to use this Transport Converter
   given the middlebox interference.

   As explained in [RFC7413], some carrier-grade NATs can affect the
   operation of TFO if they assign different IP addresses to the same
   end host.  Such carrier-grade NATs could affect the operation of the
   TFO Option used by the Converter protocol.  See also the discussion
   in section 7.1 of [RFC7413].






















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6.  Security Considerations

6.1.  Privacy & Ingress Filtering

   The Converter may have access to privacy-related information (e.g.,
   subscriber credentials).  The Converter MUST NOT leak such sensitive
   information outside a local domain.

   Given its function and its location in the network, a Transport
   Converter has access to the payload of all the packets that it
   processes.  As such, it must be protected as a core IP router.

   Furthermore, ingress filtering policies MUST be enforced at the
   network boundaries [RFC2827].

   This document assumes that all network attachements are managed by
   the same administrative entity.  Therefore, enforcing anti-spoofing
   filters at these network ensures that hosts are not sending traffic
   with spoofed source IP addresses.

6.2.  Authorization

   The Converter protocol is intended to be used in managed networks
   where end hosts can be identified by their IP address.  Thanks to the
   Bootstrap procedure (Figure 5), the Transport Converter can verify
   that the Client correctly receives packets sent by the Converter.
   Stronger authentication schemes should be defined to use the
   Converter protocol in more open network environments.

   See below for authorization considerations that are specific for
   Multipath TCP.

6.3.  Denial of Service

   Another possible risk is the amplification attacks since a Transport
   Converter sends a SYN towards a remote Server upon reception of a SYN
   from a Client.  This could lead to amplification attacks if the SYN
   sent by the Transport Converter were larger than the SYN received
   from the Client or if the Transport Converter retransmits the SYN.
   To mitigate such attacks, the Transport Converter SHOULD rate limit
   the number of pending requests for a given Client.  It SHOULD also
   avoid sending to remote Servers SYNs that are significantly longer
   than the SYN received from the Client.  In practice, Transport
   Converters SHOULD NOT advertise to a Server TCP Options that were not
   specified by the Client in the received SYN.  Finally, the Transport
   Converter SHOULD only retransmit a SYN to a Server after having
   received a retransmitted SYN from the corresponding Client.




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   Upon reception of a SYN that contains a valid TFO Cookie and a
   Connect TLV, the Transport Converter attempts to establish a TCP
   connection to a remote Server.  There is a risk of denial of service
   attack if a Client requests too many connections in a short period of
   time.  Implementations SHOULD limit the number of pending connections
   from a given Client.  Means to protect against SYN flooding attacks
   MUST also be enabled [RFC4987].

6.4.  Traffic Theft

   Traffic theft is a risk if an illegitimate Converter is inserted in
   the path.  Indeed, inserting an illegitimate Converter in the
   forwarding path allows traffic interception and can therefore provide
   access to sensitive data issued by or destined to a host.  Converter
   discovery and configuration are out of scope of this document.

6.5.  Multipath TCP-specific Considerations

   Multipath TCP-related security threats are discussed in [RFC6181] and
   [RFC6824].

   The operator that manages the various network attachments (including
   the Converters) can enforce authentication and authorization policies
   using appropriate mechanisms.  For example, a non-exhaustive list of
   methods to achieve authorization is provided hereafter:

   o  The network provider may enforce a policy based on the
      International Mobile Subscriber Identity (IMSI) to verify that a
      user is allowed to benefit from the aggregation service.  If that
      authorization fails, the Packet Data Protocol (PDP) context/bearer
      will not be mounted.  This method does not require any interaction
      with the Converter.

   o  The network provider may enforce a policy based upon Access
      Control Lists (ACLs), e.g., at a Broadband Network Gateway (BNG)
      to control the hosts that are authorized to communicate with a
      Converter.  These ACLs may be installed as a result of RADIUS
      exchanges, e.g.  [I-D.boucadair-mptcp-radius].  This method does
      not require any interaction with the Converter.

   o  A device that embeds the Converter may also host a RADIUS client
      that will solicit an AAA server to check whether connections
      received from a given source IP address are authorized or not
      [I-D.boucadair-mptcp-radius].

   A first safeguard against the misuse of Converter resources by
   illegitimate users (e.g., users with access networks that are not
   managed by the same provider that operates the Converter) is the



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   Converter to reject Multipath TCP connections received on its
   Internet-facing interfaces.  Only Multipath PTCP connections received
   on the customer-facing interfaces of a Converter will be accepted.
















































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7.  IANA Considerations

   This document requests the allocation of a reserved service name and
   port number for the converter protocol at https://www.iana.org/
   assignments/service-names-port-numbers/
   service-names-port-numbers.xhtml.

   This documents specifies version 1 of the Converter protocol.  Five
   types of Converter messages are defined:

   o  1: Bootstrap TLV

   o  10: Connect TLV

   o  20: Extended TCP Header TLV

   o  21: Supported TCP Options TLV

   o  30: Error TLV

   Furthermore, it also defines the following error codes:

                +-------+------+-------------------------+
                | Error | Hex  | Description             |
                +-------+------+-------------------------+
                | 0     | 0x00 | Unsupported version     |
                |       |      |                         |
                | 1     | 0x01 | Malformed Message       |
                |       |      |                         |
                | 2     | 0x02 | Unsupported Message     |
                |       |      |                         |
                | 32    | 0x20 | Not Authorized          |
                |       |      |                         |
                | 33    | 0x21 | Unsupported TCP Option  |
                |       |      |                         |
                | 64    | 0x40 | Resource Exceeded       |
                |       |      |                         |
                | 65    | 0x41 | Network Failure         |
                |       |      |                         |
                | 96    | 0x60 | Connection Reset        |
                |       |      |                         |
                | 97    | 0x61 | Destination Unreachable |
                +-------+------+-------------------------+

                    Table 3: The different error codes






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8.  Acknowledgements

   Although they could disagree with the contents of the document, we
   would like to thank Joe Touch and Juliusz Chroboczek whose comments
   on the MPTCP mailing list have forced us to reconsider the design of
   the solution several times.

   We would like to thank Raphael Bauduin and Stefano Secci for their
   help in preparing this draft.  Sri Gundavelli and Nandini Ganesh
   provided valuable feedback about the handling of TFO and the error
   codes.  Thanks to them.

   This document builds upon earlier documents that proposed various
   forms of Multipath TCP proxies [I-D.boucadair-mptcp-plain-mode],
   [I-D.peirens-mptcp-transparent] and [HotMiddlebox13b].

   From [I-D.boucadair-mptcp-plain-mode]:

   Many thanks to Chi Dung Phung, Mingui Zhang, Rao Shoaib, Yoshifumi
   Nishida, and Christoph Paasch for their valuable comments.

   Thanks to Ian Farrer, Mikael Abrahamsson, Alan Ford, Dan Wing, and
   Sri Gundavelli for the fruitful discussions in IETF#95 (Buenos
   Aires).

   Special thanks to Pierrick Seite, Yannick Le Goff, Fred Klamm, and
   Xavier Grall for their inputs.

   Thanks also to Olaf Schleusing, Martin Gysi, Thomas Zasowski, Andreas
   Burkhard, Silka Simmen, Sandro Berger, Michael Melloul, Jean-Yves
   Flahaut, Adrien Desportes, Gregory Detal, Benjamin David, Arun
   Srinivasan, and Raghavendra Mallya for the discussion.

8.1.  Contributors

   As noted above, this document builds on two previous documents.

   The authors of [I-D.boucadair-mptcp-plain-mode] were: - Mohamed
   Boucadair - Christian Jacquenet - Olivier Bonaventure - Denis
   Behaghel - Stefano Secci - Wim Henderickx - Robert Skog - Suresh
   Vinapamula - SungHoon Seo - Wouter Cloetens - Ullrich Meyer - Luis M.
   Contreras - Bart Peirens

   The authors of [I-D.peirens-mptcp-transparent] were: - Bart Peirens -
   Gregory Detal - Sebastien Barre - Olivier Bonaventure






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9.  References

9.1.  Normative References

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

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291,
              February 2006, <https://www.rfc-editor.org/info/rfc4291>.

   [RFC4987]  Eddy, W., "TCP SYN Flooding Attacks and Common
              Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,
              <https://www.rfc-editor.org/info/rfc4987>.

   [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,
              <https://www.rfc-editor.org/info/rfc6824>.

   [RFC7413]  Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
              Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
              <https://www.rfc-editor.org/info/rfc7413>.

9.2.  Informative References

   [ANRW17]   Trammell, B., Kuhlewind, M., De Vaere, P., Learmonth, I.,
              and G. Fairhurst, "Tracking transport-layer evolution with
              PATHspider", Applied Networking Research Workshop 2017
              (ANRW17) , July 2017.

   [Fukuda2011]
              Fukuda, K., "An Analysis of Longitudinal TCP Passive
              Measurements (Short Paper)", Traffic Monitoring and
              Analysis. TMA 2011. Lecture Notes in Computer Science, vol
              6613. , 2011.

   [HotMiddlebox13b]
              Detal, G., Paasch, C., and O. Bonaventure, "Multipath in
              the Middle(Box)", HotMiddlebox'13 , December 2013, <http:/
              /inl.info.ucl.ac.be/publications/multipath-middlebox>.

   [I-D.arkko-arch-low-latency]
              Arkko, J. and J. Tantsura, "Low Latency Applications and
              the Internet Architecture",
              draft-arkko-arch-low-latency-01 (work in progress),
              July 2017.



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   [I-D.boucadair-mptcp-plain-mode]
              Boucadair, M., Jacquenet, C., Bonaventure, O., Behaghel,
              D., stefano.secci@lip6.fr, s., Henderickx, W., Skog, R.,
              Vinapamula, S., Seo, S., Cloetens, W., Meyer, U.,
              Contreras, L., and B. Peirens, "Extensions for Network-
              Assisted MPTCP Deployment Models",
              draft-boucadair-mptcp-plain-mode-10 (work in progress),
              March 2017.

   [I-D.boucadair-mptcp-radius]
              Boucadair, M. and C. Jacquenet, "RADIUS Extensions for
              Network-Assisted Multipath TCP (MPTCP)",
              draft-boucadair-mptcp-radius-05 (work in progress),
              October 2017.

   [I-D.ietf-mptcp-rfc6824bis]
              Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
              Paasch, "TCP Extensions for Multipath Operation with
              Multiple Addresses", draft-ietf-mptcp-rfc6824bis-09 (work
              in progress), July 2017.

   [I-D.ietf-tcpinc-tcpcrypt]
              Bittau, A., Giffin, D., Handley, M., Mazieres, D., Slack,
              Q., and E. Smith, "Cryptographic protection of TCP Streams
              (tcpcrypt)", draft-ietf-tcpinc-tcpcrypt-08 (work in
              progress), October 2017.

   [I-D.olteanu-intarea-socks-6]
              Olteanu, V. and D. Niculescu, "SOCKS Protocol Version 6",
              draft-olteanu-intarea-socks-6-00 (work in progress),
              June 2017.

   [I-D.peirens-mptcp-transparent]
              Peirens, B., Detal, G., Barre, S., and O. Bonaventure,
              "Link bonding with transparent Multipath TCP",
              draft-peirens-mptcp-transparent-00 (work in progress),
              July 2016.

   [IETFJ16]  Bonaventure, O. and S. Seo, "Multipath TCP Deployment",
              IETF Journal, Fall 2016 , n.d..

   [IMC11]    Honda, K., Nishida, Y., Raiciu, C., Greenhalgh, A.,
              Handley, M., and T. Hideyuki, "Is it still possible to
              extend TCP ?", Proceedings of the 2011 ACM SIGCOMM
              conference on Internet measurement conference , 2011.

   [RFC1919]  Chatel, M., "Classical versus Transparent IP Proxies",
              RFC 1919, DOI 10.17487/RFC1919, March 1996,



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              <https://www.rfc-editor.org/info/rfc1919>.

   [RFC1928]  Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and
              L. Jones, "SOCKS Protocol Version 5", RFC 1928,
              DOI 10.17487/RFC1928, March 1996,
              <https://www.rfc-editor.org/info/rfc1928>.

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

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <https://www.rfc-editor.org/info/rfc2827>.

   [RFC3135]  Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
              Shelby, "Performance Enhancing Proxies Intended to
              Mitigate Link-Related Degradations", RFC 3135,
              DOI 10.17487/RFC3135, June 2001,
              <https://www.rfc-editor.org/info/rfc3135>.

   [RFC6181]  Bagnulo, M., "Threat Analysis for TCP Extensions for
              Multipath Operation with Multiple Addresses", RFC 6181,
              DOI 10.17487/RFC6181, March 2011,
              <https://www.rfc-editor.org/info/rfc6181>.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555,
              April 2012, <https://www.rfc-editor.org/info/rfc6555>.

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,
              <https://www.rfc-editor.org/info/rfc6887>.

   [RFC7323]  Borman, D., Braden, B., Jacobson, V., and R.
              Scheffenegger, Ed., "TCP Extensions for High Performance",
              RFC 7323, DOI 10.17487/RFC7323, September 2014,
              <https://www.rfc-editor.org/info/rfc7323>.

   [RFC7414]  Duke, M., Braden, R., Eddy, W., Blanton, E., and A.
              Zimmermann, "A Roadmap for Transmission Control Protocol
              (TCP) Specification Documents", RFC 7414, DOI 10.17487/
              RFC7414, February 2015,
              <https://www.rfc-editor.org/info/rfc7414>.




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Internet-Draft             0-RTT TCP Converter              October 2017


Authors' Addresses

   Olivier Bonaventure
   Tessares

   Email: Olivier.Bonaventure@tessares.net


   Mohamed Boucadair
   Orange

   Email: mohamed.boucadair@orange.com


   Bart Peirens
   Proximus

   Email: bart.peirens@proximus.com


   SungHoon Seo
   Korea Telecom

   Email: sh.seo@kt.com


   Anandatirtha Nandugudi
   Tessares

   Email: anand.nandugudi@tessares.net





















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