    Internet Engineering Task Force (IETF)                S. Gundavelli, Ed.
    Request for Comments: 6909                                         Cisco
    Category: Standards Track                                        X. Zhou
    ISSN: 2070-1721                                          ZTE Corporation
                                                                 J. Korhonen
                                                              Renesas Mobile
                                                                    G. Feige
                                                                   R. Koodli
                                                                       Cisco
                                                                  April 2013

           IPv4 Traffic Offload Selector Option for Proxy Mobile IPv6

    Abstract

       This specification defines a new mobility option, the IPv4 Traffic
       Offload Selector option, for Proxy Mobile IPv6.  This option can be
       used by the local mobility anchor and the mobile access gateway for
       negotiating IPv4 traffic offload policy for a mobility session.
       Based on the negotiated IPv4 traffic offload policy, a mobile access
       gateway can selectively offload some of the IPv4 traffic flows in the
       access network instead of tunneling back to the local mobility anchor
       in the home network.

    Status of This Memo

       This is an Internet Standards Track document.

       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).  Further information on
       Internet Standards is available in 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/rfc6909.

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    Copyright Notice

       Copyright (c) 2013 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. Conventions and Terminology .....................................4
          2.1. Conventions ................................................4
          2.2. Terminology ................................................4
       3. Solution Overview ...............................................4
          3.1. IPv4 Traffic Offload Selector Option .......................6
          3.2. MAG Considerations .........................................8
          3.3. LMA Considerations .........................................9
       4. Protocol Configuration Variables ...............................11
       5. IANA Considerations ............................................11
       6. Security Considerations ........................................12
       7. Acknowledgements ...............................................12
       8. References .....................................................13
          8.1. Normative References ......................................13
          8.2. Informative References ....................................13

    1.  Introduction

       Mobile operators are expanding their network coverage by integrating
       various access technology domains (e.g., Wireless LAN, CDMA, and
       Long-Term Evolution (LTE)) into a common IP mobility core.  The Third
       Generation Partnership Project (3GPP) S2a Proxy Mobile IPv6 [TS23402]
       reference point, specified by the 3GPP system architecture, defines
       the protocol interworking for building such integrated multi-access
       networks.  In this scenario, the mobile node's IP traffic is always
       tunneled back from the mobile access gateway [RFC5213] in the access
       network to the local mobility anchor in the home network.  Currently,
       there is no mechanism for allowing some of the subscriber's IP flows
       to be offloaded in the access network.

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       With the exponential growth in mobile data traffic, mobile operators
       are exploring new ways to offload some of the IP traffic flows at the
       nearest access edge.  The offload is intended either for local
       service access in the access network or for Internet offload through
       the access network when there is an Internet peering point.  Not all
       IP traffic flows need to be routed back to the home network; the
       traffic that does not require IP mobility support can be offloaded at
       the mobile access gateway in the access network.  This approach
       allows efficient usage of the mobile packet core, which helps in
       lowering transport costs.  To identify the IP flows that need to be
       offloaded, the local mobility anchor in the home network can deliver
       the IP flow policy to the mobile access gateway in the access
       network.  It is up to an operator's discretion to classify the
       traffic for offload.  One operator might choose to offload everything
       except traffic (such as Voice over IP) that requires QoS services.
       Another might choose to offload only HTTP traffic.  This
       specification is only concerned with matching IP traffic against a
       given flow selector and classification of IP traffic for offloading
       purposes.  This approach has one limitation with respect to
       identifying encrypted traffic: IPsec-encrypted traffic with no
       visibility into the application payload cannot be selected for
       offload.

       This document defines a new mobility option, the IPv4 Traffic Offload
       Selector option (see Section 3.1), for Proxy Mobile IPv6 (PMIPv6).
       This option can be used by the local mobility anchor and the mobile
       access gateway for negotiating IPv4 traffic offload policy for a
       mobility session.  This IPv4 traffic offload policy identifies the
       flow selectors that can be used for selecting the flows that can be
       offloaded at the access edge.  Since the mobile node's IP address
       topologically belongs to the home network, the offloaded IPv4 traffic
       flows may need to be NAT [RFC2663] translated.  These offloaded flows
       will not have mobility support as the NAT becomes the anchor point
       for those flows.  However, when the traffic is offloaded for local
       service access as opposed to Internet offload, NAT translation may
       not be needed if the mobile access gateway is in the path for the
       return traffic.  The decision on when to apply NAT translation can be
       based on local configuration on the mobile access gateway.  There are
       better ways to address the offload problem for IPv6, and with the
       goal not to create a NAT66 requirement, this specification therefore
       does not address traffic offload support for IPv6 flows.

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    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 the base Proxy Mobile IPv6 specifications
       [RFC5213] [RFC5844].  Additionally, this document uses the following
       terms:

       IP Flow

          IP flow [RFC5101] represents a set of IP packets that match a
          traffic selector (TS).  The selector is typically based on the
          source IP address, destination IP address, source port,
          destination port, and other fields in upper-layer headers.

       IP Traffic Offload

          IP traffic offload is the approach of selecting specific IP flows
          and routing them through the access network instead of tunneling
          them to the home network.  Offload can also be between two access
          networks (e.g., moving some of the traffic from LTE access to WLAN
          access).

    3.  Solution Overview

       Figure 1 illustrates the scenario where the mobile access gateway in
       an access network has enabled IPv4 traffic offload support for a
       mobility session.  The offload decision is based on the IPv4 traffic
       offload policy that it negotiated with the local mobility anchor in
       the home network.  For example, all the HTTP flows may be offloaded
       at the mobile access gateway, and all the other flows for that
       mobility session are tunneled back to the local mobility anchor.  The
       offloaded flows typically have to be NAT translated, and this
       specification does not impose any restrictions on the location of the
       NAT function.  It is possible for the NAT function to be co-located
       with the mobile access gateway or located somewhere at the edge of
       the access network.  When the NAT function is not co-located with the
       mobile access gateway, offloaded traffic flows must be delivered
       through the local access network between the mobile access gateway
       and the NAT function, for example, through a VLAN or a point-to-point
       link.  The exact means for this delivery are outside the scope of

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       this document.  If the offloaded IPv4 flows are for local service
       access and reverse traffic from the local service device can be
       routed to the mobile node through the mobile access gateway, the
       offloaded flows may be delivered directly to a local service device.

       The traffic selectors in the IPv4 traffic offload policy are used to
       classify the traffic, so it can be offloaded at the access network.
       These parameters include source IP address, destination IP address,
       TCP/UDP port numbers, and other fields.  The format of the IPv4
       binary traffic selector is specified in Section 3.1 of [RFC6088].

                                          _----_
                                        _(      )_
                     :-----------------( Internet )---------------:
                     |                  (_      _)                |
                     |                    '----'                  |
                     |                                            |
                     :                                            |
          (IPv4 Traffic Offload Point)                            |
                     :                                            |
                     |                                            |
          ........................................................|....
                     |                              |             |
          +--------+ |                   +---------------------+  |
          |  Local | |                   | Services requiring  |  |
          |Services| |                   | mobility, or service|  |
          +--------+ |                   | treatment           |  |
               |     |                   +---------------------+  |
               |   +---+                            |             |
               |   |NAT|                            |             |
               |   +---+                            |             |
               +-----|            _----_            |             |
                  +-----+       _(      )_       +-----+          |
          [MN]----| MAG |======(    IP    )======| LMA |----------
                  +-----+       (_      _)       +-----+  Internet
                                  '----'
                                     .
                                     .
              [Access Network]       .        [Home Network]
          ..........................................................

                 Figure 1: IPv4 Traffic Offload Support at the MAG

       Figure 2 explains the operational sequence of the Proxy Mobile IPv6
       protocol signaling message exchange between the mobile access gateway
       (MAG) and the local mobility anchor (LMA) for negotiating the IPv4
       traffic offload selectors.  The details related to DHCP transactions
       or Router Advertisements on the access link are not shown here as

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       that is not the key focus of this specification.  The use of IPv4
       Traffic Selector option in the Proxy Binding Update is for allowing
       the MAG to request the LMA for the IPv4 traffic offload policy.

          MN    MAG(NAT)   LMA
          |------>|        |    1.  Mobile Node Attach
          |       |------->|    2.  Proxy Binding Update (IPv4TS)
          |       |<-------|    3.  Proxy Binding Acknowledgement (IPv4TS)
          |       |========|    4.  Tunnel/Route Setup
          |       +        |    5.  Installing the traffic offload rules
          |------>|        |    6.  IPv4 packet from mobile node
          |       +        |    7.  Offload rule applied (Tunnel/offload)
          |       |        |

               Figure 2: Exchange of IPv4 Traffic Offload Selectors

    3.1.  IPv4 Traffic Offload Selector Option

       A new mobility option, the IPv4 Traffic Offload Selector option (53),
       is defined for use in Proxy Binding Update (PBU) and Proxy Binding
       Acknowledgement (PBA) messages exchanged between a mobile access
       gateway and a local mobility anchor.  This option is used for
       carrying the IPv4 traffic offload policy.  This policy identifies the
       IPv4 traffic flow selectors that can be used by the mobile access
       gateway for enforcing the offload policy.

       The alignment requirement for this option is 4n.

       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     |   Length      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |M|                         Reserved                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  Traffic Selector Sub-option   ...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 3: IPv4 Traffic Offload Selector Option

       Type
          53

       Length
          8-bit unsigned integer indicating the length in octets of the
          option, excluding the type and length fields.

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       Offload Mode (M) Flag
          This field indicates the offload mode.

             If the (M) flag value is set to a value of (0), it is an
             indication that the IPv4 flow(s) that match the traffic
             selectors in the Traffic Selector sub-option [RFC6089] and that
             are associated to that mobility session have to be offloaded at
             the mobile access gateway.  All the other IPv4 flows associated
             with that mobility session and not matching the traffic
             selectors have to be tunneled to the local mobility anchor.

             If the (M) flag value is set to a value of (1), it is an
             indication that all the IPv4 flows associated to that mobility
             session except the IPv4 flow(s) matching the traffic selectors
             in the Traffic Selector sub-option have to be offloaded at the
             mobile access gateway.  All the IPv4 flows associated with that
             mobility session and matching the traffic selectors have to be
             tunneled back to the local mobility anchor.

       Reserved
          This field is unused for now.  The value MUST be initialized to 0
          by the sender and MUST be ignored by the receiver.

       Traffic Selector Sub-option
          The Traffic Selector sub-option includes the parameters used to
          match packets for a specific flow binding.  This is an optional
          sub-option when the IPv4 Traffic Selector option is carried in a
          Proxy Binding Update message but is a mandatory sub-option when
          the IPv4 Traffic Selector option is carried in a Proxy Binding
          Acknowledgement message.  The format of the Traffic Selector sub-
          option is defined in Section 4.2.1.4 of [RFC6089].  This sub-
          option includes a TS Format field, which identifies the format of
          the flow specification included in that sub-option.  The values
          for that field are defined in Section 3 of [RFC6088] and are
          repeated here for completeness.  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 that
          support is mandatory for this specification.  The text specified
          in this section takes precedence over what is specified in
          [RFC6088] and [RFC6089].

             1: IPv4 binary traffic selector

             2: IPv6 binary traffic selector (not used by this
             specification)

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    3.2.  MAG Considerations

       o  If the mobile access gateway is configured to enable IPv4 traffic
          offload support, then it includes the IPv4 Traffic Offload
          Selector option (Section 3.1) in the Proxy Binding Update message
          that it sends to the local mobility anchor.  Optionally, the
          mobile access gateway can also propose a specific offload policy.

          *  The mobile access gateway MAY choose not to propose any
             specific IPv4 traffic offload policy but request the local
             mobility anchor for the offload policy.  In this scenario, the
             IPv4 Traffic Offload Selector option that is carried in the
             Proxy Binding Update message does not include the Traffic
             Selector sub-option (see Section 3.1), and the (M) flag (see
             Section 3.1) in the option MUST be set to a value of (0).
             Including the IPv4 Traffic Offload Selector option in the Proxy
             Binding Update without the Traffic Selector sub-option serves
             as an indication that the mobile access gateway is not
             proposing any specific offload policy for that mobility
             session, but rather it makes a request to the local mobility
             anchor to provide the offload policy.

          *  The mobile access gateway MAY choose to propose a specific IPv4
             traffic offload policy by including the Traffic Selector sub-
             option in the IPv4 Traffic Offload Selector option (see
             Section 3.1).  The specific details on how the mobile access
             gateway obtains the mobile node's IPv4 traffic offload policy
             are outside the scope of this document.  When this offload
             policy is included in the Proxy Binding Update message, it
             serves as a proposal to the local mobility anchor.  The local
             mobility anchor can override with its own offload policy, or it
             can agree to the proposed policy.  The offload policy has to be
             translated to a set of selectors that can be used to match the
             mobile node's IP flows, and these selectors have to be carried
             in the Traffic Selector sub-option.  The Traffic Selector sub-
             option MUST be constructed as specified in Section 4.2.1.4 of
             [RFC6089].  This sub-option includes a TS Format field, which
             identifies the format of the flow specification included in the
             sub-option.  The values for that field and the corresponding
             message format are defined in Section 3.1 of [RFC6088].
             Considerations from Section 3.1 apply with respect to setting
             the Offload Mode (M) flag.

       o  When sending a Proxy Binding Update either for Binding Lifetime
          Extension or for Binding De-Registration, the mobile access
          gateway SHOULD copy the IPv4 Traffic Offload Selector option from
          the initial Proxy Binding Update message.  Considerations from
          Sections 6.9.1.3 and 6.9.1.4 of [RFC5213] MUST be applied.

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       o  If the mobile access gateway is not configured to support IPv4
          traffic offload support as specified in this specification, but if
          the received Proxy Binding Acknowledgement message has the IPv4
          Traffic Offload Selector option, then the mobile access gateway
          MUST ignore the option and process the rest of the message as per
          [RFC5213].

       o  If there is no IPv4 Traffic Offload Selector option in the Proxy
          Binding Acknowledgement message received from the local mobility
          anchor, it is an indication that the local mobility anchor did not
          enable IPv4 traffic offload support for that mobility session.
          Upon accepting the Proxy Binding Acknowledgement message, the
          mobile access gateway SHOULD NOT enable IPv4 traffic offload
          support for that mobility session.

       o  If there is an IPv4 Traffic Offload Selector option in the Proxy
          Binding Acknowledgement message, then the mobile access gateway
          SHOULD enable IPv4 traffic offload support for that mobility
          session.  The mobility access gateway has to provision the data
          plane using the flow selectors present in the Traffic Selector
          sub-option.  The IPv4 flows matching the flow selectors have to be
          offloaded or tunneled back based to the local mobility anchor
          based on the value of the Offload Mode (M) flag (see Section 3.1).

    3.3.  LMA Considerations

       o  If the received Proxy Binding Update message does not include the
          IPv4 Traffic Offload Selector option (Section 3.1), then the local
          mobility anchor MUST NOT enable IPv4 traffic offload support for
          that mobility session, and the Proxy Binding Acknowledgement
          message that will be sent in response MUST NOT contain the IPv4
          Traffic Offload Selector option.

       o  If the Proxy Binding Update message includes the IPv4 Traffic
          Offload Selector option, but the local mobility anchor is not
          configured to support IPv4 traffic offload support, then the local
          mobility anchor will ignore the option and process the rest of the
          message as per [RFC5213].  This would have no effect on the
          operation of the rest of the protocol.

       o  If the Proxy Binding Update message has the IPv4 Traffic Offload
          Selector option and if the local mobility anchor is configured to
          support IPv4 traffic offload support, then the local mobility
          anchor MUST enable IPv4 traffic offload support for that mobility
          session.  The Proxy Binding Acknowledgement message that will be
          sent in response MUST include the IPv4 Traffic Offload Selector
          option.  The following considerations apply with respect to
          constructing the IPv4 Traffic Offload Selector option.

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          *  The local mobility anchor can obtain the offload policy from
             the local configuration store or from a network function such
             as AAA (Authentication, Authorization, and Accounting) or PCRF
             (Policy and Charging Rule Function).  The offload policy has to
             be translated to a set of selectors that can be used to match
             the mobile node's IP flows, and these selectors have to be
             carried in the Traffic Selector sub-option.  The Traffic
             Selector sub-option MUST be constructed as specified in Section
             4.2.1.4 of [RFC6089].  Considerations from Section 3.1 apply
             with respect to the Offload Mode (M) flag setting.

          *  If the Proxy Binding Update message includes a specific IPv4
             traffic offload policy proposal in the form of the Traffic
             Selector sub-option [RFC6089], then the local mobility anchor
             MAY choose to agree to that request by including the same IPv4
             traffic offload policy in the Proxy Binding Acknowledgement
             message.  This implies the local mobility anchor has agreed to
             the IPv4 traffic offload policy provided by the mobile access
             gateway.  The local mobility anchor MAY also choose to override
             the request by including a different IPv4 traffic offload
             policy that it wants the mobile access gateway to enforce for
             that mobility session.  This is entirely based on the policy
             configuration on the local mobility anchor.

          *  The IPv4 traffic offload policy that is sent to the mobile
             access gateway has to be specific to the mobility session
             identified using the Mobile Node Identifier option [RFC5213].
             The offload policy MUST be specific to a mobile node's
             application traffic.  The traffic selectors have to match only
             the mobile node's application traffic and MUST NOT match any
             other mobile node's IP traffic.  Furthermore, control-plane
             traffic such as DHCP, Neighbor Discovery (ND), or any other IP
             traffic that is used for IP address configuration, mobility
             management, or other control-plane functions MUST NOT be
             subject to offload.

          *  The local mobility anchor MUST NOT make any changes to the
             mobile node's offload policy during the middle of a mobility
             session, as long as the mobile node continues to attach to the
             mobile access gateway that negotiated the offload policy.
             However, when the mobile node performs an inter-MAG handover,
             the new mobile access gateway may not be capable of supporting
             IP Traffic offload and in this scenario, the offload policy may
             change.  Therefore, the IPv4 Traffic Selector option with the
             Traffic Selector sub-option that is delivered during the
             initial mobility signaling MUST be the same as the one that is
             delivered as part of the mobility signaling related to lifetime
             extension from the same mobile access gateway.

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    4.  Protocol Configuration Variables

       This specification defines the following configuration variable that
       controls the IPv4 traffic offload support feature.  This
       configuration variable is internal to the system and has no bearing
       on interoperability across different implementations.

       The mobility entities, local mobility anchor, and the mobile access
       gateway have to allow these variables to be configured by the system
       management.  The configured values for these protocol variables have
       to survive server reboots and service restarts.

       EnableIPv4TrafficOffloadSupport

             This flag indicates whether or not IPv4 traffic offload support
             needs to be enabled.  This configuration variable is available
             at both the mobile access gateway and the local mobility
             anchor.  The default value for this flag is set to (0),
             indicating that IPv4 traffic offload support is disabled.

             When this flag on the mobile access gateway is set to a value
             of (1), the mobile access gateway has to enable IPv4 traffic
             offload support for all mobility sessions, by specifically
             requesting the IPv4 traffic offload policy from the local
             mobility anchor by including the IPv4 Traffic Offload Selector
             option in the Proxy Binding Update message.  If the flag is set
             to a value of (0), the mobile access gateway has to disable
             IPv4 traffic offload support for all mobility sessions.

             Similarly, when this flag on the local mobility anchor is set
             to a value of (1), the local mobility anchor has to enable IPv4
             traffic offload support.  If the local mobility anchor chooses
             to enable IPv4 traffic offload support when there is an offload
             policy specified for a mobile node, it has to deliver the IPv4
             traffic offload policy to the mobile access gateway by
             including the IPv4 Traffic Offload Selector option in the Proxy
             Binding Acknowledgement message.

    5.  IANA Considerations

       Per this specification, IANA has assigned a new mobility option: the
       IPv4 Traffic Offload Selector option (53).  This option is described
       in Section 3.1.  The Type value for this option has been assigned
       from the same numbering space as allocated for the other mobility
       options [RFC6275].

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    6.  Security Considerations

       The IPv4 Traffic Offload Selector option defined in this
       specification is for use in Proxy Binding Update and Proxy Binding
       Acknowledgement messages.  This option is carried like any other
       mobility header option as specified in [RFC5213].  Therefore, it
       inherits from [RFC5213] its security guidelines and does not require
       any additional security considerations.  Carrying IPv4 traffic
       offload selectors does not introduce any new security
       vulnerabilities.

       When IPv4 traffic offload support is enabled for a mobile node, the
       mobile access gateway selectively offloads some of the mobile node's
       IPv4 traffic flows to the access network.  Typically, these offloaded
       flows get NAT translated, which essentially introduces certain
       vulnerabilities that are common to any NAT deployment.  These
       vulnerabilities and the related considerations have been well
       documented in the NAT specification [RFC2663].  There are no
       additional considerations above and beyond what has already been
       documented by the NAT specifications and that are unique to the
       approach specified in this document.

       The mobile node's home network may be equipped with firewall and
       other security devices to guard against any security threats.  When
       IPv4 traffic offload support is enabled, it potentially exposes the
       mobile node to some security risks in the access network.  This
       threat can be mitigated by deploying the security features both in
       the access network and in the home network.

       When IPv4 traffic offload support is enabled for a mobile node, some
       of the IP flows are sent through the home network, and some other IP
       flows are routed through the access network.  This potentially
       introduces some complexity with respect to enabling diagnostics or
       monitoring on the user traffic.  The tools that are used for such
       diagnostics have to be aware of the offload policy that in enabled in
       the network.

    7.  Acknowledgements

       The authors would like to thank Ahmad Muhanna, Basavaraj Patil,
       Carlos Bernardos, Eric Voit, Frank Brockners, Hidetoshi Yokota, Marco
       Liebsch, Mark Grayson, Pierrick Seite, Ryuji Wakikawa, Steve Wood,
       Barry Leiba, Sean Turner, Pete Resnick, Wesley Eddy, Mary Barnes,
       Vincent Roca, Ralph Droms, Scott Bradner, Stephen Farrell, Adrian
       Farrel, Benoit Claise, and Brian Haberman for all the reviews and
       discussions related to the topic of IPv4 traffic offload.

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    RFC 6909          IPv4 Traffic Offload Selector Option        April 2013

    8.  References

    8.1.  Normative References

       [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

       [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
                  and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

       [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
                  Mobile IPv6", RFC 5844, May 2010.

       [RFC6088]  Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
                  "Traffic Selectors for Flow Bindings", RFC 6088,
                  January 2011.

       [RFC6089]  Tsirtsis, G., Soliman, H., Montavont, N., Giaretta, G.,
                  and K. Kuladinithi, "Flow Bindings in Mobile IPv6 and
                  Network Mobility (NEMO) Basic Support", RFC 6089,
                  January 2011.

       [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
                  in IPv6", RFC 6275, July 2011.

    8.2.  Informative References

       [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
                  Translator (NAT) Terminology and Considerations",
                  RFC 2663, August 1999.

       [RFC5101]  Claise, B., "Specification of the IP Flow Information
                  Export (IPFIX) Protocol for the Exchange of IP Traffic
                  Flow Information", RFC 5101, January 2008.

       [TS23402]  3GPP, "Architecture enhancements for non-3GPP accesses",
                  2010.

    Gundavelli, et al.           Standards Track                   [Page 13]

    RFC 6909          IPv4 Traffic Offload Selector Option        April 2013

    Authors' Addresses

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

       EMail: sgundave@cisco.com

       Xingyue Zhou
       ZTE Corporation
       No.68 Zijinghua Rd
       Nanjing
       China

       EMail: zhou.xingyue@zte.com.cn

       Jouni Korhonen
       Renesas Mobile
       Porkkalankatu 24
       Helsinki  FIN-00180
       Finland

       EMail: jouni.nospam@gmail.com

       Gaetan Feige
       Cisco
       France

       EMail: gfeige@cisco.com

       Rajeev Koodli
       Cisco
       3650 Cisco Way
       San Jose, CA  95134
       USA

       EMail: rkoodli@cisco.com

    Gundavelli, et al.           Standards Track                   [Page 14]