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Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Standards Track                                  Orange
Expires: October 20, 2017                                 April 18, 2017


      RADIUS Extensions for Network-Assisted Multipath TCP (MPTCP)
                    draft-boucadair-mptcp-radius-04

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 MPTCP
   Conversion Point (MCP).  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.  MCPs 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 specifies a new Remote Authentication Dial-In User
   Service (RADIUS) attributes that carry the IP addresses that will be
   returned to authorized users to reach one or multiple MCPs.

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 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




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   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 20, 2017.

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
   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  MPTCP RADIUS Attributes . . . . . . . . . . . . . . . . . . .   4
     2.1.  MPTCP-MCP-IPv4  . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  MPTCP-MCP-IPv6  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Sample Use Case . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  Table of Attributes . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   One of the promising deployment scenarios for Multipath TCP (MPTCP,
   [RFC6824]) is to enable a Customer Premises Equipment (CPE) that is
   connected to multiple networks (e.g., DSL, LTE, WLAN) to optimize the
   usage of such resources, see for example [RFC4908].

   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.  This deployment scenario relies on
   MPTCP proxies located on both the CPE and network sides (Figure 1).



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   MPTCP proxies are responsible for establishing multi-path
   communications on behalf of endpoints, thereby taking advantage of
   MPTCP capabilities to optimize resource usage to achieve different
   goals that include (but are not limited to) bandwidth aggregation,
   primary/backup communication paths, and traffic offload management.

  +------------+        _--------_    +----------------+
  |            |       (    LTE   )   |                |
  |   CPE      +=======+          +===+  Backbone      |
  |  (MCP)     |       (_        _)   |   Network      |
  |            |         (_______)    |+--------------+|
  |            |       IP Network #1  || Concentrator ||------> Internet
  |            |                      ||    (MCP)     ||
  |            |                      |+--------------+|
  |            |       IP Network #2  |                |
  |            |        _--------_    |                |
  |            |       (    DSL    )  |                |
  |            +=======+           +==+                |
  |            |       (_        _)   |                |
  +-----+------+        (_______)     +----------------+
        |
  ---- LAN ----
        |
    end-nodes

         Figure 1: Network-Assisted MPTCP: Reference Architecture

   Within this document, an MPTCP Conversion Point (MCP) refers to a
   functional element that is responsible for aggregating the traffic
   originated by a group of CPEs.  This element is located in the
   network.  One or multiple MCPs can be deployed in the network to
   assist MPTCP-enabled CPEs to establish MPTCP connections via their
   available network attachments.  On the uplink path, the MCP
   terminates the MPTCP connections received from its customer-facing
   interfaces and transforms these connections into legacy TCP
   connections [RFC0793] towards upstream servers.  On the downlink
   path, the MCP turns the legacy server's TCP connection into MPTCP
   connections towards its customer-facing interfaces.

   This document specifies two new Remote Authentication Dial-In User
   Service (RADIUS, [RFC2865]) attributes that carry the MCP IP address
   list (Section 2).  In order to accommodate both IPv4 and IPv6
   deployment contexts, and given the constraints in Section 3.4 of
   [RFC6158], two attributes are specified.  Note that one or multiple
   IPv4 and/or IPv6 addresses may be returned to a requesting CPE.  A
   sample use case is described in Section 3.





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   This document assumes that the MCP(s) reachability information can be
   stored in Authentication, Authorization, and Accounting (AAA) servers
   while the CPE configuration is usually provided by means of DHCP
   ([RFC2131][RFC3315]).  Further Network-Assisted MPTCP deployment and
   operational considerations are discussed in
   [I-D.nam-mptcp-deployment-considerations].

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

   This document adheres to [RFC8044] for defining the new attributes.

2.  MPTCP RADIUS Attributes

2.1.  MPTCP-MCP-IPv4

   Description

      The RADIUS MPTCP-MCP-IPv4 attribute contains the IPv4 address of
      an MCP that is assigned to a CPE.

      Because multiple MCP IP addresses may be provisioned to an
      authorised CPE (that is a CPE entitled to solicit the resources of
      an MCP to establish MPTCP connections), multiple instances of the
      MPTCP-MCP-IPv4 attribute MAY be included; each instance of the
      attribute carries a distinct IP address.

      Both MPTCP-MCP-IPv4 and MPTCP-MCP-IPv6 attributes MAY be present
      in a RADIUS message.

      The MPTCP-MCP-IPv4 Attribute MAY appear in a RADIUS Access-Accept
      packet.  It MAY also appear in a RADIUS Access-Request packet as a
      hint to the RADIUS server to indicate a preference, although the
      server is not required to honor such a hint.

      The MPTCP-MCP-IPv4 Attribute MAY appear in a CoA-Request packet.

      The MPTCP-MCP-IPv4 Attribute MAY appear in a RADIUS Accounting-
      Request packet.

      The MPTCP-MCP-IPv4 Attribute MUST NOT appear in any other RADIUS
      packet.

   Type




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      TBA (see Section 6).

   Length

      6

   Data Type

      The attribute MPTCP-MCP-IPv4 is of type ip4addr (Section 3.3 of
      [RFC8044]).

   Value

      This field includes an IPv4 address (32 bits) of the MCP.

      The MPTCP-MCP-IPv4 attribute MUST NOT include multicast and host
      loopback addresses [RFC6890].  Anycast addresses are allowed to be
      included in an MPTCP-MCP-IPv4 attribute.

2.2.  MPTCP-MCP-IPv6

   Description

      The RADIUS MPTCP-MCP-IPv6 attribute contains the IPv6 address of
      an MCP that is assigned to a CPE.

      Because multiple MCP IP addresses may be provisioned to an
      authorised CPE (that is a CPE entitled to solicit the resources of
      an MCP to establish MPTCP connections), multiple instances of the
      MPTCP-MCP-IPv6 attribute MAY be included; each instance of the
      attribute carries a distinct IP address.

      Both MPTCP-MCP-IPv4 and MPTCP-MCP-IPv6 attributes MAY be present
      in a RADIUS message.

      The MPTCP-MCP-IPv6 Attribute MAY appear in a RADIUS Access-Accept
      packet.  It MAY also appear in a RADIUS Access-Request packet as a
      hint to the RADIUS server to indicate a preference, although the
      server is not required to honor such a hint.

      The MPTCP-MCP-IPv6 Attribute MAY appear in a CoA-Request packet.

      The MPTCP-MCP-IPv6 Attribute MAY appear in a RADIUS Accounting-
      Request packet.

      The MPTCP-MCP-IPv6 Attribute MUST NOT appear in any other RADIUS
      packet.




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   Type

      TBA (see Section 6).

   Length

      18

   Data Type

      The attribute MPTCP-MCP-IPv6 is of type ip6addr (Section 3.9 of
      [RFC8044]).

   Value

      This field includes an IPv6 address (128 bits) of the MCP.

      The MPTCP-MCP-IPv6 attribute MUST NOT include multicast and host
      loopback addresses [RFC6890].  Anycast addresses are allowed to be
      included in an MPTCP-MCP-IPv6 attribute.

3.  Sample Use Case

   This section does not aim to provide an exhaustive list of deployment
   scenarios where the use of the RADIUS MPTCP-MCP-IPv6 and MPTCP-MCP-
   IPv4 attributes can be helpful.  Typical deployment scenarios are
   described, for instance, in [RFC6911].

   Figure 2 shows an example where a CPE is assigned an MCP.  This
   example assumes that the Network Access Server (NAS) embeds both
   RADIUS client and DHCPv6 server capabilities.




















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         CPE                             NAS                      AAA
     DHCPv6 client                    DHCPv6 server              server
          |                                |                        |
          |---------DHCPv6 Solicit-------->|                        |
          |                                |----Access-Request ---->|
          |                                |                        |
          |                                |<----Access-Accept------|
          |                                |    MPTCP-MCP-IPv6      |
          |<-------DHCPv6 Advertisement----|                        |
          |        (OPTION_V6_MPTCP)       |                        |
          |                                |                        |
          |---------DHCPv6 Request-------->|                        |
          |                                |                        |
          |<---------DHCPv6 Reply----------|                        |
          |       (OPTION_V6_MPTCP)        |                        |

                       DHCPv6                          RADIUS

                     Figure 2: Sample Flow Example (1)

   Upon receipt of the DHCPv6 Solicit message from a CPE, the NAS sends
   a RADIUS Access-Request message to the AAA server.  Once the AAA
   server receives the request, it replies with an Access-Accept message
   (possibly after having sent a RADIUS Access-Challenge message and
   assuming the CPE is entitled to connect to the network) that carries
   a list of parameters to be used for this session, and which include
   MCP reachability information (namely a list of IP addresses).

   The content of the MPTCP-MCP-IPv6 attribute is then used by the NAS
   to complete the DHCPv6 procedure that the CPE initiated to retrieve
   information about the MCP it has been assigned.

   Upon change of the MCP assigned to a CPE, the RADIUS server sends a
   RADIUS CoA message [RFC5176] that carries the RADIUS MPTCP-MCP-IPv6
   attribute to the NAS.  Once that message is accepted by the NAS, it
   replies with a RADIUS CoA ACK message.  The NAS replaces the old MCP
   with the new one.

   Figure 3 shows another example where a CPE is assigned an MCP, but
   the CPE uses DHCPv6 to retrieve a list of IP addresses of an MCP.











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        CPE                               NAS                      AAA
    DHCPv4 client                      DHCPv4 server              server
         |                                  |                        |
         |-----------DHCPDISCOVER---------->|                        |
         |                                  |----Access-Request ---->|
         |                                  |                        |
         |                                  |<----Access-Accept------|
         |                                  |    MPTCP-MCP-IPv4      |
         |<------------DHCPOFFER------------|                        |
         |         (OPTION_V4_MPTCP)        |                        |
         |                                  |                        |
         |------------DHCPREQUEST---------->|                        |
         |         (OPTION_V4_MPTCP)        |                        |
         |                                  |                        |
         |<-----------DHCPACK---------------|                        |
         |        (OPTION_V4_MPTCP)         |                        |

                       DHCPv4                         RADIUS

                     Figure 3: Sample Flow Example (2)

   Some deployments may rely on the mechanisms defined in [RFC4014] or
   [RFC7037], which allows a NAS to pass attributes obtained from a
   RADIUS server to a DHCP server.

4.  Security Considerations

   RADIUS-related security considerations are discussed in [RFC2865].

   MPTCP-related security considerations are discussed in [RFC6824] and
   [RFC6181].

   Traffic theft is a risk if an illegitimate MCP is inserted in the
   path.  Indeed, inserting an illegitimate MCP 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 an MCP should be enabled.

5.  Table of Attributes

   The following table provides a guide as what type of RADIUS packets
   that may contain these attributes, and in what quantity.









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   Access- Access- Access-  Challenge Acct. # Attribute
   Request Accept  Reject             Request
    0+      0+      0        0         0+      TBA MPTCP-MCP-IPv4
    0+      0+      0        0         0+      TBA MPTCP-MCP-IPv6

   CoA-Request CoA-ACK CoA-NACK #   Attribute
     0+          0       0        TBA MPTCP-MCP-IPv4
     0+          0       0        TBA MPTCP-MCP-IPv6

   The following table defines the meaning of the above table entries:

   0  This attribute MUST NOT be present in packet.
   0+ Zero or more instances of this attribute MAY be present in packet.

6.  IANA Considerations

   IANA is requested to assign two new RADIUS attribute types from the
   IANA registry "Radius Attribute Types" located at
   http://www.iana.org/assignments/radius-types:

      MPTCP-MCP-IPv4 (TBA)

      MPTCP-MCP-IPv6 (TBA)

7.  Acknowledgements

   Thanks to Alan DeKok for the comments.

8.  References

8.1.  Normative References

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

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <http://www.rfc-editor.org/info/rfc2865>.

   [RFC6158]  DeKok, A., Ed. and G. Weber, "RADIUS Design Guidelines",
              BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011,
              <http://www.rfc-editor.org/info/rfc6158>.






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   [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,
              <http://www.rfc-editor.org/info/rfc6890>.

   [RFC8044]  DeKok, A., "Data Types in RADIUS", RFC 8044,
              DOI 10.17487/RFC8044, January 2017,
              <http://www.rfc-editor.org/info/rfc8044>.

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,
              <http://www.rfc-editor.org/info/rfc793>.

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

   [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, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC4014]  Droms, R. and J. Schnizlein, "Remote Authentication Dial-
              In User Service (RADIUS) Attributes Suboption for the
              Dynamic Host Configuration Protocol (DHCP) Relay Agent
              Information Option", RFC 4014, DOI 10.17487/RFC4014,
              February 2005, <http://www.rfc-editor.org/info/rfc4014>.

   [RFC4908]  Nagami, K., Uda, S., Ogashiwa, N., Esaki, H., Wakikawa,
              R., and H. Ohnishi, "Multi-homing for small scale fixed
              network Using Mobile IP and NEMO", RFC 4908,
              DOI 10.17487/RFC4908, June 2007,
              <http://www.rfc-editor.org/info/rfc4908>.

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              DOI 10.17487/RFC5176, January 2008,
              <http://www.rfc-editor.org/info/rfc5176>.



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

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

   [RFC6911]  Dec, W., Ed., Sarikaya, B., Zorn, G., Ed., Miles, D., and
              B. Lourdelet, "RADIUS Attributes for IPv6 Access
              Networks", RFC 6911, DOI 10.17487/RFC6911, April 2013,
              <http://www.rfc-editor.org/info/rfc6911>.

   [RFC7037]  Yeh, L. and M. Boucadair, "RADIUS Option for the DHCPv6
              Relay Agent", RFC 7037, DOI 10.17487/RFC7037, October
              2013, <http://www.rfc-editor.org/info/rfc7037>.

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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