





Internet Engineering Task Force (IETF)                S. Gundavelli, Ed.
Request for Comments: 7629                                      K. Leung
Category: Experimental                                             Cisco
ISSN: 2070-1721                                              G. Tsirtsis
                                                                Qualcomm
                                                             A. Petrescu
                                                               CEA, LIST
                                                             August 2015


                   Flow-Binding Support for Mobile IP

Abstract

   This specification defines extensions to the Mobile IP protocol for
   allowing a mobile node with multiple interfaces to register a care-of
   address for each of its network interfaces and to simultaneously
   establish multiple IP tunnels with its home agent.  This essentially
   allows the mobile node to utilize all the available network
   interfaces and build a higher aggregated logical pipe with its home
   agent for its home address traffic.  Furthermore, these extensions
   also allow the mobile node and the home agent to negotiate IP traffic
   flow policies for binding individual flows with the registered care-
   of addresses.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7629.









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Copyright Notice

   Copyright (c) 2015 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   3
     2.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Example Call Flow . . . . . . . . . . . . . . . . . . . .   6
   4.  Message Extensions  . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Multipath Extension . . . . . . . . . . . . . . . . . . .   7
     4.2.  Flow-Binding Extension  . . . . . . . . . . . . . . . . .   9
     4.3.  New Error Codes for Registration Reply  . . . . . . . . .  12
   5.  Protocol Operation  . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  Mobile Node Considerations  . . . . . . . . . . . . . . .  12
     5.2.  Home Agent Considerations . . . . . . . . . . . . . . . .  14
   6.  Routing Considerations  . . . . . . . . . . . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  18
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19












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1.  Introduction

   With the ubiquitous availability of wireless networks based on
   different access technology types, mobile devices are now equipped
   with multiple wireless interfaces and have the ability to connect to
   the network using any of those interfaces.  For example, most mobile
   devices are equipped with Wi-Fi and LTE (Long Term Evolution)
   interfaces.  In many deployments, it is desirable for a mobile node
   to leverage all the available network interfaces and have IP mobility
   support for its IP flows.

   The operation defined in the Mobile IP protocol [RFC5944] allows a
   mobile node to continue to use its home address as it moves around
   the Internet.  Based on the mode of operation, there will be an IP
   tunnel that will be established between the home agent and the mobile
   node or between the home agent and the foreign agent where the mobile
   node is attached; see [RFC5944].  In both of these modes, there will
   only be one interface on the mobile node that is receiving the IP
   traffic from the home agent.  This approach of using a single access
   interface for routing all mobile node's traffic is not efficient and
   so there is a need to extend Mobile IP to concurrently use multiple
   access interfaces for routing the mobile node's IP traffic.  The goal
   is for efficient use of all the available access links to obtain
   higher aggregated bandwidth for the tunneled traffic between the home
   agent and the mobile node.

   This specification defines extensions to Mobile IPv4 protocol for
   allowing a mobile node with multiple interfaces to register a care-of
   address for each of its network interfaces and to simultaneously
   leverage all access links for the mobile node's IP traffic.
   Furthermore, this specification also defines extensions to allow the
   mobile node and the home agent to optionally negotiate IP flow
   policies for binding individual IP flows with the registered care-of
   addresses.

2.  Conventions and Terminology

2.1.  Conventions

   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].

2.2.  Terminology

   All the mobility-related terms used in this document are to be
   interpreted as defined in [RFC5944] and [RFC3753].  In addition, this
   document uses the following terms.



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   Binding Identifier (BID)

      It is an identifier assigned to a mobile node's binding.  A
      binding defines an association between a mobile node's home
      address and its registered care-of address.  When a mobile node
      registers multiple bindings with its home agent, each using a
      different care-of address, then each of those bindings are given a
      unique identifier.  Each of the binding identifiers will have a
      unique value that will be different from the identifiers assigned
      to the mobile node's other bindings.

   Flow Identifier (FID)

      It is an identifier for a given IP flow, uniquely identified by
      source address, destination address, protocol type, source port,
      destination port, Security Parameter Index, and other parameters
      as identified in [RFC6088].  In the context of this document, the
      IP flows associated with a mobile node are the IP flows using its
      home address.  For a mobile router, the IP flows also include the
      IP flows using the mobile network prefix [RFC6626].

3.  Overview

   The illustration below in Figure 1 is an example scenario where a
   mobile node is connected to WLAN, LTE, and CDMA access networks.  The
   mobile node is configured with a home address, HoA_1, and has
   obtained the following care-of addresses [RFC5944]: CoA_1, from the
   WLAN network; CoA_2, from the LTE network; and CoA_3, from the CDMA
   network.

   The mobile node using the extensions specified in this document
   registers all three care-of addresses with its home agent.  The
   mobile node also establishes an IP tunnel with the home agent using
   each of its IP addresses, which results in three IP tunnels
   (Tunnel_1, Tunnel_2, and Tunnel_3) between the mobile node and the
   home agent.  Each of the tunnels represents an overlay routing path
   between the mobile node and the home agent and can be used for
   forwarding the mobile node's IP traffic.

   Furthermore, using the extensions specified in this document, the
   mobile node and the home agent can negotiate an IP flow policy.  The
   negotiated flow policy allows the mobile node and the home agent to
   determine the access network path for each of the mobile node's IP
   flows.







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   Flow_1 (SIP)
    |
    |Flow_2 (SSH)
    | |
    | |Flow_3 (HTTP)       _----_
    | | |         CoA_1  _(      )_ Tunnel_1
    | | |    .---=======(   Wi-Fi  )========\ Flow_1
    | | |    |           (_      _)          \
    | | |    |             '----'             \
    | | | +=====+          _----_              \  +=====+    _----_
    | | '-|     | CoA_2  _(      )_ Tunnel_2    \ |     |  _(      )_ --
    | '---| MN  |---====(   LTE    )=========-----| HA  |-( Internet )--
    '-----|     |        (_      _)      Flow_3 / |     |  (_      _) --
          +=====+          '----'              /  +=====+    '----'
           | |             _----_             /
    HoA_1--' |    CoA_3  _(      )_ Tunnel_3 /
             .------====(   CDMA   )========/ Flow_2
                         (_      _)
                           '----'

             Figure 1: Mobile Node (MN) with Multiple Tunnels
                          to the Home Agent (HA)

   The table below is an example of how the individual flows are bound
   to different care-of addresses registered with the home agent.

   +=========+===================+=====================================+
   | Flow ID |   Access Network  |           Description               |
   |  (FID)  |    Preferences    |                                     |
   +=========+===================+=====================================+
   | Flow_1  | Tunnel_1 / CoA_1  | All SIP flows over Wi-Fi (Preferred)|
   |         | Tunnel_2 / CoA_2  | If Wi-Fi is not available, use LTE  |
   |         |       <DROP>      | If Wi-Fi and LTE access networks are|
   |         |                   | not available, drop the flow        |
   +---------+-------------------+-------------------------------------+
   | Flow_3  | Tunnel_2 / CoA_2  | All HTTP flows over LTE (Preferred) |
   |         |       <DROP>      | If LTE not available, drop the flow |
   +---------+-------------------+-------------------------------------+
   | Flow_2  | Tunnel_3 / CoA_3  | All SSH flows over CDMA (Preferred) |
   |         | Tunnel_2 / CoA_2  | If CDMA not available, use LTE      |
   |         | Tunnel_1 / CoA_1  | If LTE not available, use Wi-Fi     |
   +---------+-------------------+-------------------------------------+

                 Figure 2: Example of an IP Traffic Policy







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3.1.  Example Call Flow

   Figure 3 is the call flow for the example scenario where a mobile
   node is connected to WLAN and LTE access networks.

      +-------+          +-------+          +-------+          +-------+
      |   MN  |          | WLAN  |          |  LTE  |          |  HA   |
      |       |          |Network|          |Network|          |       |
      +-------+          +-------+          +-------+          +-------+
         |                   |                  |                  |

   * MIP RRQ is sent using the IP address obtained from the WLAN Network

         |<--- (1) --------->|                  |                  |
         |                   |   RRQ (Multipath, Flow-Binding)     |
         |---- (2) ----------------------------------------------->|
         |                   |   RRP            |                  |
         |<--- (3) ------------------------------------------------|
         |              MIP Tunnel through WLAN Network            |
         |=====(4)===========*=====================================|


   * MIP RRQ is sent using the IP address obtained from the LTE Network

         |<--- (5) ---------------------------->|                  |
         |                   |  RRQ (Multipath, Flow-Binding)      |
         |---- (6) ----------------------------------------------->|
         |                   |  RRP             |                  |
         |<--- (7) ------------------------------------------------|
         |              MIP Tunnel through LTE Access Network      |
         |=====(8)==============================*==================|
         |                                                         |
         *                                                         *
   (Policy-based Routing Rule)               (Policy-based Routing Rule)

            Figure 3: Multipath Negotiation - Example Call Flow

   o  (1): The mobile node attaches to the WLAN network and obtains the
      IP address configuration for its WLAN interface.

   o  (2)-(3): The mobile node sends a Registration Request (RRQ)
      [RFC5944] to the home agent through the WLAN network.  The message
      includes the Multipath (Section 4.1) and the Flow-Binding
      (Section 4.2) Extensions.  The home agent, upon accepting the
      request, sends a Registration Reply (RRP) [RFC5944]  with a value
      of (0) in the Code field of the Registration Reply.





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   o  (4): The mobile node and the home agent establish a bidirectional
      IP tunnel over the WLAN network.

   o  (5): The mobile node attaches to the LTE network and obtains the
      IP address configuration from that network.

   o  (6)-(7): The mobile node sends a Registration Request to the home
      agent through the LTE network.  The message includes the Multipath
      and the Flow-Binding Extensions.  The Flow-Binding Extension
      indicates that all HTTP flows need to be routed over the WLAN
      network and if the WLAN access network is not available, they need
      be routed over other access networks.  The negotiated policy also
      requires all voice-related traffic flows to be routed over the LTE
      network.  The home agent, upon accepting the request, sends a
      Registration Reply with a value of (0) in the Code field of the
      Registration Reply.

   o  (8): The mobile node and the home agent establish a bidirectional
      IP tunnel over the LTE network.  The negotiated traffic flow
      policy is applied.  Both the home agent and the mobile node route
      all the voice flows over the tunnel established through the LTE
      access network and the HTTP flows over the WLAN network.

4.  Message Extensions

   This specification defines the following new extensions to Mobile IP.

4.1.  Multipath Extension

   This extension is used for requesting multipath support.  It
   indicates that the sender is requesting the home agent to register
   the current care-of address listed in this Registration Request as
   one of the many care-of addresses through which the mobile node can
   be reached.  It is also for carrying the information specific to the
   interface to which the care-of address that is being registered is
   bound.

   This extension is a non-skippable extension and MAY be added by the
   mobile node to the Registration Request message.  There MUST NOT be
   more than one instance of this extension present in the message.
   This extension MUST NOT be added by the home agent to the
   Registration Reply.

   This extension should be protected using the Mobile-Home
   Authentication Extension [RFC5944].  As specified in Sections 3.2 and
   3.6.1.3 of [RFC5944], the mobile node MUST place this Extension
   before the Mobile-Home Authentication Extension in the registration
   messages so that this extension is integrity protected.



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   The format of this extension is as shown below.  It adheres to the
   long extension format described in [RFC5944].

        0                   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      |    Subtype    |           Length              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    If-ATT     |   If-Label    |   Binding ID  |B|O|  Reserved |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 4: Multipath Extension

   Type

      Type: Multipath-Extension-Type (154)

   Subtype

      This field MUST be set to a value of 1 (Multipath Extension).

   Length

      The length of the extension in octets, excluding Type, Subtype,
      and Length fields.  This field MUST be set to a value of 4.

   Interface Access-Technology Type (If-ATT)

      This 8-bit field identifies the Access Technology type of the
      interface through which the mobile node is connected.  The
      permitted values for this are from the Access Technology Type
      registry defined in [RFC5213].

   Interface Label (If-Label)

      This 8-bit field represents the interface label represented as an
      unsigned integer.  The mobile node identifies the label for each
      of the interfaces through which it registers a CoA with the home
      agent.  When using static traffic flow policies on the mobile node
      and the home agent, the label can be used for indexing forwarding
      policies.  For example, the operator may have a policy that binds
      an IP flow "F1" to any interface with the label "Blue".  When a
      registration through an interface matching the label "Blue" gets
      activated, the home agent and the mobile node establish an IP
      tunnel and the tunnel is marked with that label.  Both the home
      agent and the mobile node generate traffic rules for forwarding IP
      flow traffic "F1" through the mobile IP tunnel matching the label
      "Blue".  The permitted values for If-Label are 1 through 255.



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   Binding Identifier (BID)

      This 8-bit field is used for carrying the binding identifier.  It
      uniquely identifies a specific binding of the mobile node
      associated with this Registration Request.  Each binding
      identifier is represented as an unsigned integer.  The permitted
      values are 1 through 254.  The BID value of 0 and 255 are
      reserved.

   Bulk Re-registration Flag (B)

      The (B) flag, if set to a value of (1), notifies the home agent to
      update the binding lifetime of all the mobile node's bindings upon
      accepting this request.  The (B) flag MUST NOT be set to a value
      of (1) if the value of the Registration Overwrite Flag (O) flag is
      set to a value of (1).

   Registration Overwrite (O)

      The (O) flag, if set to a value of (1), notifies the home agent
      that upon accepting this request it should replace all of the
      mobile node's existing bindings with the new binding that will be
      created upon accepting this request.  The (O) flag MUST NOT be set
      to a value of (1) if the value of the Bulk Re-registration Flag
      (B) is set to a value of (1).  This flag MUST be set to a value of
      (0) in De-Registration requests.

   Reserved (R)

      This 6-bit field is unused for now.  The value MUST be initialized
      to (0) by the sender and MUST be ignored by the receiver.

4.2.  Flow-Binding Extension

   This extension contains information that can be used by the mobile
   node and the home agent for binding mobile node's IP flows to a
   specific multipath registration.  There can be more than one instance
   of this extension present in the message.

   This extension is a non-skippable extension and MAY be added to the
   Registration Request by the mobile node or by the home agent to the
   Registration Reply.

   This extension should be protected by Mobile-Home Authentication
   Extension [RFC5944].  As specified in Section 3.2 and 3.6.1.3 of
   [RFC5944], the mobile node MUST place this extension before the
   Mobile-Home Authentication Extension in the registration messages so
   that this extension is integrity protected.



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   The format of this extension is as shown below.  It adheres to the
   long extension format described in [RFC5944].

        0                   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      |    Subtype    |           Length              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Action     |  BID Count    |        ...   BID List   ...   ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   TS Format   |             Traffic Selector                  ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 5: Flow-Binding Extension

   Type

      Type: Multipath-Extension-Type (154)

   Subtype

      This field MUST be set to a value of 2 (Flow-Binding Extension).

   Length

      The length of the extension in octets, excluding Type, Subtype,
      and Length fields.

   Action

      The Action field identifies the traffic rule that needs to be
      enforced.  Following are the possible values.



















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   +---------+-------+-------------------------------------------------+
   |  Action | Value | Description                                     |
   +---------+-------+-------------------------------------------------+
   |  DROP   |   0   | Drop matching packets. A filter rule            |
   |         |       | indicating a drop action MUST include a single  |
   |         |       | BID byte, the value of which MAY be set to 255  |
   |         |       | by the sender and the value of which SHOULD be  |
   |         |       | ignored by the receiver.                        |
   +---------+-------+-------------------------------------------------+
   | FORWARD |   1   | Forward matching packets to the first BID in the|
   |         |       | list of BIDs the filter rule is pointing to.    |
   |         |       | If the first BID becomes invalid (i.e., the     |
   |         |       | corresponding CoA is de-registered), use the    |
   |         |       | next BID in the list.                           |
   +---------+-------+-------------------------------------------------+

              Figure 6: Action Rules for the Traffic Selector

   BID Count

      Total number of binding identifiers that follow this field.  The
      permitted values for this field are 1 through 8; each binding
      identifier is represented as an unsigned integer in a single octet
      field.  There is no delimiter between two binding identifier
      values; they are spaced consecutively.

   TS Format

      An 8-bit unsigned integer indicating the Traffic Selector (TS)
      Format.  The value (0) is reserved and MUST NOT be used.  When the
      value of the TS Format field is set to (1), the format that
      follows is the IPv4 Binary Traffic Selector specified in
      Section 3.1 of [RFC6088], and when the value of the TS Format
      field is set to (2), the format that follows is the IPv6 Binary
      Traffic Selector specified in Section 3.2 of [RFC6088].  The IPv6
      traffic selectors are only relevant when the mobile node registers
      IPv6 prefixes per [RFC5454].

   Traffic Selector

      A variable-length opaque field for including the traffic
      specification identified by the TS Format field.  It identifies
      the traffic selectors for matching the IP traffic and binding them
      to specific binding identifiers.







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4.3.  New Error Codes for Registration Reply

   This document defines the following error code values for use by the
   home agent in the Code field of the Registration Reply.

   MULTIPATH_NOT_ALLOWED (Multipath Support not allowed for this mobile
   node): 152

   INVALID_FB_IDENTIFIER (Invalid Flow-Binding Identifier): 153

5.  Protocol Operation

5.1.  Mobile Node Considerations

   o  The mobile node should register a care-of address for each of the
      connected interfaces that it wishes to register with the home
      agent.  It can do so by sending a Registration Request to the home
      agent through each of those interfaces.

   o  Each of the Registration Requests that is sent includes the care-
      of address of the respective interface.  The Registration Request
      has to be routed through the specific interface for which the
      registration is sought for.  Some of these interfaces may be
      connected to networks with a configured foreign agent on the link,
      and in such foreign-agent-based registrations, the care-of address
      will be the IP address of the foreign agent.

   o  A Multipath Extension (Section 4.1) reflecting the interface
      parameters is present in each of the Registration Requests.  This
      serves as an indication to the home agent that the Registration
      Request is a Multipath registration and the home agent will have
      to register this care-of address as one of the many care-of
      addresses through which the mobile node's home address is
      reachable.

   o  If the mobile node is configured to exchange IP flow policy to the
      home agent, then the Flow-Binding Extension (Section 4.2)
      reflecting the flow policy can be included in the message.
      Otherwise, the Flow-Binding Extension will not be included.

   o  The mobile node, upon receiving a Registration Reply with the Code
      value set to MULTIPATH_NOT_ALLOWED, MAY choose to register without
      the Multipath Extension specified in this document.  This implies
      the home agent has not enabled multipath support for this mobile
      node and hence multipath support MUST be disabled on the mobile
      node.





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   o  The mobile node, upon receiving a Registration Reply with the Code
      value set to INVALID_FB_IDENTIFIER, MUST re-register that specific
      binding with the home agent.

   o  The mobile node at any time can extend the lifetime of a specific
      care-of address registration by sending a Registration Request to
      the home agent with a new lifetime value.  The message MUST be
      sent as the initial multipath registration and must be routed
      through that specific interface.  The message MUST include the
      Multipath Extension (Section 4.1) with the value in the Binding ID
      field set to the binding identifier assigned to that binding.
      Alternatively, the home agent can send a single Registration
      Request with the Bulk Re-registration Flag (B) set to a value of
      (1).  This serves as a request to the home agent to update the
      registration lifetime of all the mobile node's registrations.

   o  The mobile node can, at any time, de-register a specific care-of
      address by sending a Registration Request to the home agent with a
      lifetime value of (0).  The message must include the Multipath
      Extension (Section 4.1) with the value in the Binding ID field set
      to the binding identifier assigned to that binding.
      Alternatively, the home agent can send a single Registration
      Request with the Bulk Re-registration Flag (B) set to a value of
      (1) and a lifetime value of (0).  This serves as a request to the
      home agent to consider this request as a request to de-register
      all the mobile node's care-of addresses.

   o  The mobile node can, at any time, update the parameters of a
      specific registration by sending a Registration Request to the
      home agent.  This includes a change of care-of address associated
      with a previously registered interface.  The message must be sent
      as the initial multipath registration and must be routed through
      that specific interface.  The message must include the Multipath
      Extension (Section 4.1) with the value in the Binding ID field set
      to the binding identifier assigned to that binding, and the
      Overwrite Flag (O) flag MUST be set to a value of (1).

   o  The mobile node, upon receiving a Registration Reply with the Code
      value set to 0 (registration accepted), will establish a Mobile IP
      tunnel to the home agent using that care-of address.  When using a
      foreign agent care-of address, the tunnel is between the home
      agent and the foreign agent.  The tunnel encapsulation type and
      any other parameters are based on the registration for that path.
      If there is also an exchange of flow policy between the mobile
      node and the home agent, with the use of Flow-Binding Extensions,
      then the mobile node must set up the forwarding plane that matches
      the flow policy.




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5.2.  Home Agent Considerations

   The home agent, upon receiving a Registration Request from a mobile
   node with a Multipath Extension, should check if the mobile node is
   authorized for multipath support.  If multipath support is not
   enabled, the home agent MUST reject the request with a Registration
   Reply and with the Code set to MULTIPATH_NOT_ALLOWED.

   If the received Registration Request includes a Multipath Extension
   and additionally has the Bulk Re-registration (B) flag set to a value
   of (1), then the home agent MUST extend the lifetime of all the
   bindings associated with that mobile node.

   The home agent, upon receipt of a Registration Request with the Flow-
   Binding Extension, must process the extension and, upon accepting the
   flow policy, must set up the forwarding plane that matches the flow
   policy.  If the home agent cannot identify any of the binding
   identifiers, then it MUST reject the request with a Registration
   Reply and with the Code set to INVALID_FB_IDENTIFIER.

   If the received Registration Request includes a Multipath Extension
   and additionally has the Registration Overwrite (O) flag set to a
   value of (1), then the home agent MUST consider this as a request to
   replace all other mobile node's bindings with just one binding and
   that is the binding associated with this request.

6.  Routing Considerations

   When multipath registration is enabled for a mobility node, there
   will be multiple Mobile IP tunnels established between a mobile node
   and its home agent.  These Mobile IP tunnels appear to the forwarding
   plane of the mobile node as equal-cost, point-to-point links.

   If there is also an exchange of traffic flow policy between the
   mobile node and the home agent, with the use of Flow-Binding
   Extensions (Section 4.2), then the mobile node's IP traffic can be
   routed by the mobility entities as per the negotiated flow policy.
   However, if multipath is enabled for a mobility session without the
   use of any flow policy exchange, then both the mobile node and the
   home agent are required to have a pre-configured static flow policy.
   The specific details on the semantics of this static flow policy are
   outside the scope of this document.

   In the absence of any established traffic flow policies, most IP
   hosts support two alternative traffic load-balancing schemes, per-
   flow and per-packet load balancing [RFC2991].  These load-balancing
   schemes allow the forwarding plane to evenly distribute traffic on
   either a per-packet or per-flow basis, across all the available



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   equal-cost links through which a destination can be reached.  The
   default forwarding behavior of per-flow load balancing will ensure a
   given flow always takes the same path and will eliminate any packet
   re-ordering issues, and that is critical for delay-sensitive traffic,
   whereas the per-destination load-balancing scheme leverages all the
   paths much more effectively but with the potential issue of packet
   re-ordering on the receiver end.  This issue will be specially
   magnified when the access links have very different forwarding
   characteristics.  A host can choose to enable any of these
   approaches.  Therefore, this specification recommends the use of per-
   flow load balancing.

7.  IANA Considerations

   Per this document, the following IANA actions have been completed.

   o  Action 1: This specification defines two new Mobile IP extensions,
      the Multipath Extension and the Flow-Binding Extension.  The
      format of the Multipath Extension is described in Section 4.1, and
      the format of the Flow-Binding Extension is described in
      Section 4.2.  Both of these extensions are non-skippable
      extensions to the Mobile IPv4 header in accordance to the long
      extension format of [RFC5944].  Both of these extensions use a
      common Type value, Multipath-Extension (154), but are identified
      using different Subtype values.  The Type value 154 for these
      extensions has been allocated from the "Extensions to Mobile IP
      Registration Messages" registry at the URL
      <http://www.iana.org/assignments/mobileip-numbers>.  The field
      "Permitted for Notification Messages" for this extension MUST be
      set to "N".

   o  Action 2: This specification defines a new message subtype space,
      Multipath Extension subtype.  This field is described in
      Section 4.1.  The values for this subtype field are managed by
      IANA under the "Multipath Extension subtypes (Value 154)"
      registry.  This specification reserves the following Type values.
      Approvals of new Multipath Extension subtype values are to be made
      through IANA Expert Review [RFC5226].













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      +=========================================================+
      |  0    | Reserved                                        |
      +=========================================================+
      |  1    | Multipath Extension                             |
      +=========================================================+
      |  2    | Flow-Binding Extension                          |
      +=========================================================+
      |       |                                                 |
      ~ 3-254 | Unassigned                                      ~
      |       |                                                 |
      +=========================================================+
      |  255  | Reserved                                        |
      +=========================================================+

   o  Action 3: This document defines new status code values,
      MULTIPATH_NOT_ALLOWED (152) and INVALID_FB_IDENTIFIER (153), for
      use by the home agent in the Code field of the Registration Reply,
      as described in Section 4.3.  These values have been assigned from
      the "Registration denied by the home agent" registry at
      <http://www.iana.org/assignments/mobileip-numbers>.

8.  Security Considerations

   This specification allows a mobile node to establish multiple Mobile
   IP tunnels with its home agent by registering a care-of address for
   each of its active roaming interfaces.  This essentially allows the
   mobile node's IP traffic to be routed through any of the tunnel paths
   based on a static or a dynamically negotiated flow policy.  This new
   capability has no impact on the protocol security.  Furthermore, this
   specification defines two new Mobile IP extensions, the Multipath
   Extension and the Flow-Binding Extension.  These extensions are
   specified to be included in Mobile IP control messages, which are
   authenticated and integrity protected as described in [RFC5944].
   Therefore, this specification does not weaken the security of the
   Mobile IP protocol and does not introduce any new security
   vulnerabilities.















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9.  References

9.1.  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>.

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, DOI 10.17487/RFC5213, August 2008,
              <http://www.rfc-editor.org/info/rfc5213>.

   [RFC5944]  Perkins, C., Ed., "IP Mobility Support for IPv4, Revised",
              RFC 5944, DOI 10.17487/RFC5944, November 2010,
              <http://www.rfc-editor.org/info/rfc5944>.

   [RFC6088]  Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
              "Traffic Selectors for Flow Bindings", RFC 6088,
              DOI 10.17487/RFC6088, January 2011,
              <http://www.rfc-editor.org/info/rfc6088>.

9.2.  Informative References

   [RFC2991]  Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
              Multicast Next-Hop Selection", RFC 2991,
              DOI 10.17487/RFC2991, November 2000,
              <http://www.rfc-editor.org/info/rfc2991>.

   [RFC3753]  Manner, J., Ed. and M. Kojo, Ed., "Mobility Related
              Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004,
              <http://www.rfc-editor.org/info/rfc3753>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC5454]  Tsirtsis, G., Park, V., and H. Soliman, "Dual-Stack Mobile
              IPv4", RFC 5454, DOI 10.17487/RFC5454, March 2009,
              <http://www.rfc-editor.org/info/rfc5454>.

   [RFC6626]  Tsirtsis, G., Park, V., Narayanan, V., and K. Leung,
              "Dynamic Prefix Allocation for Network Mobility for Mobile
              IPv4 (NEMOv4)", RFC 6626, DOI 10.17487/RFC6626, May 2012,
              <http://www.rfc-editor.org/info/rfc6626>.




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Acknowledgements

   We would like to thank Qin Wu, Shahriar Rahman, Mohana Jeyatharan,
   Yungui Wang, Hui Deng Behcet Sarikaya, Jouni Korhonen, Michaela
   Vanderveen, Antti Makela, Charles Perkins, Pierrick Seite, Vijay
   Gurbani, Barry Leiba, Henrik Levkowetz, Pete McCann, and Brian
   Haberman for their review and comments on this document.

Contributors

   This document reflects discussions and contributions from the
   following people:

   Ahmad Muhanna
   Email: asmuhanna@yahoo.com

   Srinivasa Kanduru
   Email: skanduru@gmail.com

   Vince Park
   Email: vpark@qualcomm.com

   Hesham Soliman
   Email: hesham@elevatemobile.com



























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Authors' Addresses

   Sri Gundavelli (editor)
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   United States

   Email: sgundave@cisco.com


   Kent Leung
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   United States

   Email: kleung@cisco.com


   George Tsirtsis
   Qualcomm

   Email: tsirtsis@qualcomm.com


   Alexandre Petrescu
   CEA, LIST
   CEA Saclay
   Gif-sur-Yvette , Ile-de-France  91191
   France

   Phone: +33169089223
   Email: alexandre.petrescu@cea.fr

















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