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Versions: (draft-boucadair-mptcp-dhc) 00

Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Standards Track                                  Orange
Expires: October 4, 2018                                        T. Reddy
                                                                   Cisco
                                                           April 2, 2018


                 DHCP Options for 0-RTT TCP Converters
                 draft-boucadair-tcpm-dhc-converter-00

Abstract

   Because of the lack of Multipath TCP (MPTCP) support at the server
   side, some service providers now consider a network-assisted model
   that relies upon the activation of a dedicated function called
   Converters.  Network-assisted MPTCP deployment models are designed to
   facilitate the adoption of MPTCP for the establishment of multi-path
   communications without making any assumption about the support of
   MPTCP by the communicating peers.  Converters located in the network
   are responsible for establishing multi-path communications on behalf
   of endpoints, thereby taking advantage of MPTCP capabilities to
   achieve different goals that include (but are not limited to)
   optimization of resource usage (e.g., bandwidth aggregation), of
   resiliency (e.g., primary/backup communication paths), and traffic
   offload management.

   This document focuses on the explicit deployment scheme where the
   identity of the Converters is explicitly configured on connected
   hosts.  This document specifies DHCP (IPv4 and IPv6) options to
   configure hosts with Converters parameters.

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

   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 https://datatracker.ietf.org/drafts/current/.




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   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 October 4, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  DHCPv6 Converter Option . . . . . . . . . . . . . . . . . . .   4
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  DHCPv6 Client Behavior  . . . . . . . . . . . . . . . . .   5
   4.  DHCPv4 Converter Option . . . . . . . . . . . . . . . . . . .   6
     4.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  DHCPv4 Client Behavior  . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  DHCP Server Configuration Guidelines . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   One of the promising deployment scenarios for Multipath TCP (MPTCP,
   [RFC6824]) is to enable a host or a Customer Premises Equipment (CPE)
   connected to multiple networks (e.g., DSL, LTE, WLAN) to optimize the



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   usage of such resources.  A deployment scenario relies on MPTCP
   Conversion Points (Converters).  A Converter terminates the MPTCP
   sessions established from a host/CPE, before redirecting traffic into
   a legacy TCP session.  Further Network-Assisted MPTCP deployment and
   operational considerations are discussed in
   [I-D.nam-mptcp-deployment-considerations].

   Figure 1 shows a deployment example of the Converters to assist
   establishing MPTCP connections.

  +------------+        _--------_    +----------------+
  |            |       (    LTE   )   |                |
  |   Host     +=======+          +===+  Backbone      |
  |            |       (_        _)   |   Network      |
  |            |         (_______)    |+--------------+|
  |            |       IP Network #1  ||   Converter  ||------> Internet
  |            |                      ||              ||
  |            |                      |+--------------+|
  |            |       IP Network #2  |                |
  |            |        _--------_    |                |
  |            |       (    DSL    )  |                |
  |            +=======+           +==+                |
  |            |       (_        _)   |                |
  +------------+        (_______)     +----------------+


                 Figure 1: "Network-Assisted" MPTCP Design

   [I-D.ietf-tcpm-converters] specifies the Converter as 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.

   [I-D.ietf-tcpm-converters] assumes the explicit mode that consists in
   configuring explicitly the reachability information of the
   Converter(s) on a host.

   This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options
   that can be used to configure hosts with Converter IP addresses.

   This specification assumes a Converter is reachable through one or
   multiple IP addresses.  As such, a list of IP addresses can be
   returned in the DHCP MPTCP option.  Also, it assumes the various
   network attachments provided to an MPTCP-enabled CPE are managed by
   the same administrative entity.






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2.  Terminology

   This document makes use of the following terms:

   o  Converter: a function that terminates a transport flow and relays
      all data received over it over another transport flow.  This
      element is located upstream in the network.  One or multiple
      Converters can be deployed in the network side.  The Converter
      achieves the following:

      *  Listen for client sessions;
      *  Receive from a client the address of the final target server;
      *  Setup a session to the final server;
      *  Relay control messages and data between the client and the
         server;
      *  Perform access controls according to local policies.

   o  DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC3315].
   o  DHCP client denotes a node that initiates requests to obtain
      configuration parameters from one or more DHCP servers.
   o  DHCP server refers to a node that responds to requests from DHCP
      clients.

3.  DHCPv6 Converter Option

3.1.  Format

   The DHCPv6 Converter option can be used to configure a list of IPv6
   addresses of a Converter.

   The format of this option is shown in Figure 2.  As a reminder, this
   format follows the guidelines for creating new DHCPv6 options
   (Section 5.1 of [RFC7227]).


















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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     OPTION_V6_CONVERT         |         Option-length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                         ipv6-address                          |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                         ipv6-address                          |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 2: DHCPv6 Converter option

   The fields of the option shown in Figure 2 are as follows:

   o  Option-code: OPTION_V6_CONVERT (TBA, see Section 6.1)
   o  Option-length: Length of the 'Converter IP Address(es)' field in
      octets.  MUST be a multiple of 16.
   o  Converter IPv6 Addresses: Includes one or more IPv6 addresses
      [RFC4291] of the Converter to be used by the TCP client.

      Note, IPv4-mapped IPv6 addresses (Section 2.5.5.2 of [RFC4291])
      are allowed to be included in this option.

   To return more than one Converters to the requesting DHCPv6 client,
   the DHCPv6 server returns multiple instances of OPTION_V6_CONVERT.
   Some guidelines for DHCP servers are elaborated in Appendix A.

3.2.  DHCPv6 Client Behavior

   Clients MAY request option OPTION_V6_CONVERT, as defined in
   [RFC3315], Sections 17.1.1, 18.1.1, 18.1.3, 18.1.4, 18.1.5, and 22.7.
   As a convenience to the reader, we mention here that the client
   includes requested option codes in the Option Request Option.

   The DHCPv6 client MUST be prepared to receive multiple instances of
   OPTION_V6_CONVERT; each instance is to be treated separately as it
   corresponds to a given Converter: there are as many Converters as
   instances of the OPTION_V6_CONVERT option.





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   If an IPv4-mapped IPv6 address is received in OPTION_V6_CONVERT, it
   indicates that the Converter has the corresponding IPv4 address.

   The DHCPv6 client MUST silently discard multicast and host loopback
   addresses [RFC6890] conveyed in OPTION_V6_CONVERT.

4.  DHCPv4 Converter Option

4.1.  Format

   The DHCPv4 Converter option can be used to configure a list of IPv4
   addresses of a Converter.  The format of this option is illustrated
   in Figure 3.

       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Code         |     Length    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | List-Length   |   List of     |
      +-+-+-+-+-+-+-+-+               |
      / Converter IPv4 Addresses      /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  ---
      | List-Length   |   List of     |   |
      +-+-+-+-+-+-+-+-+               |   |
      / Converter IPv4 Addresses      /   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |
      .             ...               . Optional
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |
      | List-Length   |   List of     |   |
      +-+-+-+-+-+-+-+-+               |   |
      / Converter IPv4 Addresses      /   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  ---


                     Figure 3: DHCPv4 Converter option

   The fields of the option shown in Figure 3 are as follows:

   o  Code: OPTION_V4_CONVERT (TBA, see Section 6.2);
   o  Length: Length of all included data in octets.  The minimum length
      is 5.
   o  List-Length: Length of the "List of Converter IPv4 Addresses"
      field in octets; MUST be a multiple of 4.
   o  List of Converter IPv4 Addresses: Contains one or more IPv4
      addresses of the Converter to be used by the TCP client.  The
      format of this field is shown in Figure 4.





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   o  OPTION_V4_CONVERT can include multiple lists of Converter IPv4
      addresses; each list is treated separately as it corresponds to a
      given Converter.

      When several lists of Converter IPv4 addresses are to be included,
      "List-Length" and "Converter IPv4 Addresses" fields are repeated.

      0     8     16    24    32    40    48
      +-----+-----+-----+-----+-----+-----+--
      |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 | ...
      +-----+-----+-----+-----+-----+-----+--
           IPv4 Address 1          IPv4 Address 2 ...

   This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.

         Figure 4: Format of the List of Converter IPv4 Addresses

   OPTION_V4_CONVERT is a concatenation-requiring option.  As such, the
   mechanism specified in [RFC3396] MUST be used if OPTION_V4_CONVERT
   exceeds the maximum DHCPv4 option size of 255 octets.

   Some guidelines for DHCP servers are elaborated in Appendix A.

4.2.  DHCPv4 Client Behavior

   To discover one or more Converters, the DHCPv4 client MUST include
   OPTION_V4_CONVERT in a Parameter Request List Option [RFC2132].

   The DHCPv4 client MUST be prepared to receive multiple lists of
   Converter IPv4 addresses in the same OPTION_V4_CONVERT; each list is
   to be treated as a separate Converter instance.

   The DHCPv4 client MUST silently discard multicast and host loopback
   addresses [RFC6890] conveyed in OPTION_V4_CONVERT.

5.  Security Considerations

   The security considerations in [RFC2131] and [RFC3315] are to be
   considered.

   Generic Convert security considerations are discussed in
   [I-D.ietf-tcpm-converters].

   MPTCP-related security considerations are discussed in [RFC6824].

   Means to protect the Converter against Denial-of-Service (DoS)
   attacks must be enabled.  Such means include the enforcement of
   ingress filtering policies at the boundaries of the network.  In



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   order to prevent exhausting the resources of the Converter by
   creating an aggressive number of simultaneous subflows for each MPTCP
   connection, the administrator should limit the number of allowed
   subflows per host for a given connection.

   Attacks outside the domain can be prevented if ingress filtering is
   enforced.  Nevertheless, attacks from within the network between a
   host and a Converter instance are yet another actual threat.  Means
   to ensure that illegitimate nodes cannot connect to a network should
   be implemented.

   Traffic theft is also a risk if an illegitimate Converter is inserted
   in the path.  Indeed, inserting an illegitimate Converter in the
   forwarding path allows to intercept traffic and can therefore provide
   access to sensitive data issued by or destined to a host.  To
   mitigate this threat, secure means to discover a Converter should be
   enabled.

6.  IANA Considerations

6.1.  DHCPv6 Option

   IANA is requested to assign the following new DHCPv6 Option Code in
   the registry maintained in http://www.iana.org/assignments/
   dhcpv6-parameters:

                                Option Name Value
                          ----------------- -----
                          OPTION_V6_CONVERT TBA

6.2.  DHCPv4 Option

   IANA is requested to assign the following new DHCPv4 Option Code in
   the registry maintained in http://www.iana.org/assignments/bootp-
   dhcp-parameters/:

         Option Name Value Data length Meaning
   ----------------- ----- ----------- ---------------------------------
   OPTION_V4_CONVERT TBA   Variable;   Includes one or multiple lists of
                           the minimum Converter IP addresses; each list
                           length is   is treated as a separate
                           5.          Converter.

7.  Acknowledgements

   Many thanks to Olivier Bonaventure for the feedback on this document.
   Olivier suggested to define the option as a name but that design
   approach was debated several times within the dhc wg.



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   Thanks to Dan Seibel, Bernie Volz, Niall O'Reilly, Simon Hobson, and
   Ted Lemon for the feedback on the dhc wg mailing list.

8.  References

8.1.  Normative References

   [I-D.ietf-tcpm-converters]
              Bonaventure, O., Boucadair, M., Peirens, B., Seo, S., and
              A. Nandugudi, "0-RTT TCP Convert Protocol", draft-ietf-
              tcpm-converters-01 (work in progress), March 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://www.rfc-editor.org/info/rfc2131>.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
              <https://www.rfc-editor.org/info/rfc2132>.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <https://www.rfc-editor.org/info/rfc3315>.

   [RFC3396]  Lemon, T. and S. Cheshire, "Encoding Long Options in the
              Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
              DOI 10.17487/RFC3396, November 2002,
              <https://www.rfc-editor.org/info/rfc3396>.

   [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>.

   [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>.

   [RFC6890]  Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
              "Special-Purpose IP Address Registries", BCP 153,
              RFC 6890, DOI 10.17487/RFC6890, April 2013,
              <https://www.rfc-editor.org/info/rfc6890>.



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8.2.  Informative References

   [I-D.nam-mptcp-deployment-considerations]
              Boucadair, M., Jacquenet, C., Bonaventure, O., Henderickx,
              W., and R. Skog, "Network-Assisted MPTCP: Use Cases,
              Deployment Scenarios and Operational Considerations",
              draft-nam-mptcp-deployment-considerations-01 (work in
              progress), December 2016.

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

   [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
              <https://www.rfc-editor.org/info/rfc7227>.

   [RFC7844]  Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
              Profiles for DHCP Clients", RFC 7844,
              DOI 10.17487/RFC7844, May 2016,
              <https://www.rfc-editor.org/info/rfc7844>.

   [RFC7969]  Lemon, T. and T. Mrugalski, "Customizing DHCP
              Configuration on the Basis of Network Topology", RFC 7969,
              DOI 10.17487/RFC7969, October 2016,
              <https://www.rfc-editor.org/info/rfc7969>.

Appendix A.  DHCP Server Configuration Guidelines

   DHCP servers that support the DHCP Converter option can be configured
   with a list of IP addresses of the Converter(s).  If multiple IP
   addresses are configured, the DHCP server MUST be explicitly
   configured whether all or some of these addresses refer to:

   1.  the same Converter: the DHCP server returns multiple addresses in
       the same instance of the DHCP Converter option.

   2.  distinct Converters : the DHCP server returns multiple lists of
       Converter IP addresses to the requesting DHCP client (encoded as
       multiple OPTION_V6_CONVERT or in the same OPTION_V4_CONVERT);
       each list refers to a distinct Converter.

   Precisely how DHCP servers are configured to separate lists of IP
   addresses according to which Converter they refer to is out of scope
   for this document.  However, DHCP servers MUST NOT combine the IP
   addresses of multiple Converters and return them to the DHCP client
   as if they were belonging to a single Converter, and DHCP servers



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   MUST NOT separate the addresses of a single Converter and return them
   as if they were belonging to distinct Converters.  For example, if an
   administrator configures the DHCP server by providing a Fully
   Qualified Domain Name (FQDN) for a Converter, even if that FQDN
   resolves to multiple addresses, the DHCP server MUST deliver them
   within a single server address block.

   DHCPv6 servers that implement this option and that can populate the
   option by resolving FQDNs will need a mechanism for indicating
   whether to query A records or only AAAA records.  When a query
   returns A records, the IP addresses in those records are returned in
   the DHCPv6 response as IPv4-mapped IPv6 addresses.

   Since this option requires support for IPv4-mapped IPv6 addresses, a
   DHCPv6 server implementation will not be complete if it does not
   query A records and represent any that are returned as IPv4-mapped
   IPv6 addresses in DHCPv6 responses.  The mechanism whereby DHCPv6
   implementations provide this functionality is beyond the scope of
   this document.

   For guidelines on providing context-specific configuration
   information (e.g., returning a regional-based configuration), and
   information on how a DHCP server might be configured with FQDNs that
   get resolved on demand, see [RFC7969].

Authors' Addresses

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com


   Christian Jacquenet
   Orange
   Rennes
   France

   Email: christian.jacquenet@orange.com










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   Tirumaleswar Reddy
   Cisco Systems, Inc.
   Cessna Business Park, Varthur Hobli
   Sarjapur Marathalli Outer Ring Road
   Bangalore, Karnataka  560103
   India

   Email: tireddy@cisco.com











































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