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rfc:rfc7389

Internet Engineering Task Force (IETF) R. Wakikawa Request for Comments: 7389 Softbank Mobile Category: Standards Track R. Pazhyannur ISSN: 2070-1721 S. Gundavelli

                                                                 Cisco
                                                            C. Perkins
                                                        Futurewei Inc.
                                                          October 2014
     Separation of Control and User Plane for Proxy Mobile IPv6

Abstract

 This document specifies a method to split the control plane (CP) and
 user plane (UP) for a network infrastructure based on Proxy Mobile
 IPv6 (PMIPv6).  Existing specifications allow a mobile access gateway
 (MAG) to separate its control and user plane using the Alternate
 Care-of Address mobility option for IPv6 or Alternate IPv4 Care-of
 Address option for IPv4.  However, the current specification does not
 provide any mechanism allowing the local mobility anchor (LMA) to
 perform an analogous functional split.  To remedy that shortcoming,
 this document specifies a mobility option enabling an LMA to provide
 an alternate LMA address to be used for the bidirectional user-plane
 traffic between the MAG and LMA.  With this new option, an LMA will
 be able to use an IP address for its user plane that is different
 than the IP address used for the control plane.

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/rfc7389.

Wakikawa, et al. Standards Track [Page 1] RFC 7389 PMIPv6 CP-UP Split October 2014

Copyright Notice

 Copyright (c) 2014 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 .....................................5
    2.1. Conventions ................................................5
    2.2. Terminology ................................................5
 3. Additional Fields in Conceptual Data Structures .................6
 4. LMA User-Plane Address Mobility Option ..........................6
 5. Protocol Configuration Variable .................................8
 6. IANA Considerations .............................................9
 7. Security Considerations .........................................9
 8. References .....................................................10
    8.1. Normative References ......................................10
    8.2. Informative References ....................................10
 Acknowledgements ..................................................12
 Authors' Addresses ................................................12

1. Introduction

 A Proxy Mobile IPv6 (PMIPv6) infrastructure comprises two primary
 entities: LMA (local mobility anchor) and MAG (mobile access
 gateway).  The interface between the MAG and LMA consists of the
 control plane and user plane.  The control plane is responsible for
 signaling messages between the MAG and LMA, such as the Proxy Binding
 Update (PBU) and Proxy Binding Acknowledgement (PBA) messages to
 establish a mobility binding.  In addition, the control-plane
 components in the MAG and LMA are also responsible for setting up and
 tearing down a bidirectional tunnel between the MAG and LMA.  The
 user plane is used for carrying the mobile node's IP traffic between
 the MAG and the LMA over the bidirectional tunnel.

Wakikawa, et al. Standards Track [Page 2] RFC 7389 PMIPv6 CP-UP Split October 2014

 Widely deployed mobility management systems for wireless
 communications require separation of IP transport for forwarding
 user-plane and control-plane traffic.  This separation offers more
 flexible deployment options for LMA and MAG entities in Proxy Mobile
 IPv6, as described in [MOBILE-SEPARATION].  To meet this requirement
 would also require that the control-plane functions of the LMA be
 addressable at a different IP address than the IP address assigned
 for the user plane.  However, PMIPv6 does not currently specify a
 mechanism for allowing the LMA to separate the control plane from the
 user plane.  The LMA is currently required to associate the IP
 address of the tunnel source with the target IP address for the
 control messages received from the MAG.
 The control-plane and user-plane components of a MAG or LMA are
 typically co-located in the same physical entity.  However, there are
 situations where it is desirable to have the control and user plane
 of a MAG or LMA in separate physical entities.  For example, in a
 WLAN (Wireless LAN) network, it may be desirable to have the control-
 plane component of the MAG reside on the Access Controller (also
 sometimes referred to as Wireless LAN Controller (WLC)) while the
 user-plane component of the MAG resides on the WLAN Access Point.
 This enables all the control-plane messages to the LMA to be
 centralized while the user plane would be distributed across the
 multiple Access Points.  Similarly, there is a need for either the
 control-plane or user-plane component of the LMA to be separated
 according to different scaling requirements or, in other cases, the
 need to centralize the control plane in one geographical location
 while distributing the user-plane component across multiple
 locations.  For example, as illustrated in Figure 1, the LMA and MAG
 could have one control session established for PMIPv6 control
 signaling while maintaining separate connectivity via Generic Routing
 Encapsulation (GRE) or IP-in-IP tunneling for forwarding user-plane
 traffic.

Wakikawa, et al. Standards Track [Page 3] RFC 7389 PMIPv6 CP-UP Split October 2014

                   MAG                    LMA
               +--------+              +--------+
 +------+      | MAG-CP |--------------| LMA-CP |        _----_
 |  MN  |      |        |    PMIPv6    |        |      _(      )_
 |      |----  +--------+              +--------+  ===( Internet )
 +------+          :                       :           (_      _)
               +--------+              +--------+        '----'
               | MAG-UP |--------------| LMA-UP |
               |        | GRE/IP-in-IP |        |
               +--------+    /UDP      +--------+
 MN: Mobile Node
 CP: Control Plane
 UP: User Plane
     Figure 1: Functional Separation of the Control and User Plane
 [RFC6463] and [RFC6275] enable separating the control and user plane
 in the MAG.  In particular, [RFC6463] defines the Alternate IPv4
 Care-of Address option, and [RFC6275] defines an Alternate Care-of
 Address option for IPv6.  The MAG may provide an Alternate Care-of
 Address in the PBU, and if the LMA supports this option, then a
 bidirectional tunnel is set up between the LMA address and the MAG's
 Alternate Care-of Address.  However, these documents do not specify a
 corresponding option for the LMA to provide an alternate tunnel
 endpoint address to the MAG.
 This specification therefore defines a new mobility option that
 enables a local mobility anchor to provide an alternate LMA address
 to be used for the bidirectional tunnel between the MAG and LMA, as
 shown in Figure 1.
 The LMA control-plane and the LMA user-plane functions are typically
 deployed on the same IP node, and in such a scenario, the interface
 between these functions is internal to the implementation.
 Deployments may also choose to deploy the LMA control-plane and the
 LMA user-plane functions on separate IP nodes.  In such deployment
 models, there needs to be a protocol interface between these two
 functions, but that is outside the scope of this document.  Possible
 options for such an interface include OpenFlow
 [OpenFlow-Spec-v1.4.0], Forwarding and Control Element Separation
 (ForCES) [RFC5810], use of routing infrastructure [STATELESS-UPLANE],
 and vendor-specific approaches.  This specification does not mandate
 a specific protocol interface and views this interface as a generic
 interface relevant more broadly for many other protocol systems in
 addition to Proxy Mobile IPv6.  When the LMA control-plane and the
 LMA user-plane functions are deployed on separate IP nodes, the
 requirement related to user-plane address anchoring (specified in

Wakikawa, et al. Standards Track [Page 4] RFC 7389 PMIPv6 CP-UP Split October 2014

 Section 5.6.2 of [RFC5213] and Section 3.1.3 of [RFC5844]) must be
 met by the node hosting the LMA user-plane functionality.  The LMA
 user-plane node must be a topological anchor point for the IP
 address/prefixes allocated to the mobile node.

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

 3GPP terms can be found in [RFC6459].  Other mobility-related terms
 used in this document are to be interpreted as defined in [RFC5213]
 and [RFC5844].  Additionally, this document uses the following terms:
 IP-in-IP
    IP-within-IP Encapsulation [RFC2473] [RFC4213].
 GRE
    Generic Routing Encapsulation [RFC1701].
 UDP Encapsulation
    Encapsulation mode based on UDP transport specified in [RFC5844].
 LMA Control-Plane Address (LMA-CPA)
    The IP address on the LMA that is used for sending and receiving
    control-plane traffic from the MAG.
 LMA User-Plane Address (LMA-UPA)
    The IP address on the LMA that is used for sending and receiving
    user-plane traffic from the MAG.
 MAG Control-Plane Address (MAG-CPA)
    The IP address on the MAG that is used for sending and receiving
    control-plane traffic from the LMA.

Wakikawa, et al. Standards Track [Page 5] RFC 7389 PMIPv6 CP-UP Split October 2014

 MAG User-Plane Address (MAG-UPA)
    The IP address on the MAG that is used for sending and receiving
    user-plane traffic from the LMA.  This address is also referred to
    as the Alternate Care-of Address.

3. Additional Fields in Conceptual Data Structures

 To support the capability specified in this document, the conceptual
 Binding Update List entry data structure maintained by the LMA and
 the MAG is extended with the following additional fields:
 o  The IP address of the LMA that carries user-plane traffic.
 o  The IP address of the LMA that handles control-plane traffic.

4. LMA User-Plane Address Mobility Option

 The LMA User-Plane Address mobility option is a new mobility header
 option defined for use with PBU and PBA messages exchanged between
 the LMA and the MAG.  This option is used for notifying the MAG about
 the LMA's user-plane IPv6 or IPv4 address.  There can be zero, one,
 or two instances of the LMA User-Plane Address mobility option
 present in the message.  When two instances of the option are
 present, one instance of the option must be for IPv4 transport, and
 the other instance must be for IPv6 transport.
 The LMA User-Plane Address mobility option has an alignment
 requirement of 8n+2.  Its format is as shown in Figure 2:
 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      |           Reserved            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +                                                               +
 |                                                               |
 .                                                               .
 +                     LMA User-Plane Address                    +
 |                                                               |
 +                                                               +
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        Figure 2: LMA User-Plane Address Mobility Option Format

Wakikawa, et al. Standards Track [Page 6] RFC 7389 PMIPv6 CP-UP Split October 2014

 Type
    59
 Length
    An 8-bit, unsigned integer indicating the length of the option in
    octets, excluding the Type and Length fields.
 Reserved
    This field is unused in this specification.  The value MUST be set
    to zero (0) by the sender and MUST be ignored by the receiver.
 LMA User-Plane Address
    Contains the 32-bit IPv4 address or the 128-bit IPv6 address of
    the LMA user plane.  When the LMA User-Plane Address mobility
    option is included in a PBU message, this field can be a zero-
    length field, or it can have a value of ALL_ZERO, with all bits in
    the 32-bit IPv4 address or the 128-bit IPv6 address set to zero.
 When including the LMA User-Plane Address mobility option in the PBU,
 the MAG must apply the following rules:
 o  When using IPv4 transport for the user plane, the IP address field
    in the option MUST be either a zero-length field or a 4-octet
    field with ALL_ZERO value.
 o  When using IPv6 transport for the user plane, the IP address field
    in the option MUST be either a zero-length field or a 16-octet
    field with ALL_ZERO value.
 When the LMA includes the LMA User-Plane Address mobility option in
 the PBA, the IP address field in the option MUST be set to the LMA's
 IPv4 or IPv6 address carrying user-plane traffic.
 o  When using IPv4 transport for the user plane, the IP address field
    in the option is the IPv4 address carrying user-plane traffic.
 o  When using IPv6 transport for the user plane, the IP address field
    in the option is the IPv6 address carrying user-plane traffic.
 The encapsulation mode that will be chosen for the user plane between
 the MAG and the LMA has to based on the considerations specified in
 [RFC5213] and [RFC5844].

Wakikawa, et al. Standards Track [Page 7] RFC 7389 PMIPv6 CP-UP Split October 2014

5. Protocol Configuration Variable

 This specification defines the following configuration variable,
 which must be configurable (e.g., by the system management) on the
 LMA and MAG mobility entities.  The configured value for this
 protocol variable MUST survive server reboots and service restarts
 and MUST be the same for every LMA and MAG in the network domain
 supporting PMIPv6.
 Domain-wide-LMA-UPA-Support
       This variable indicates whether or not all the mobility
       entities in the PMIPv6 domain support the LMA User-Plane
       Address mobility option.
       When this variable on the MAG is set to zero (0), the MAG MUST
       indicate whether or not it supports this feature by including
       the LMA User-Plane Address mobility option in the PBU.  If the
       option is not present in the PBU, the LMA SHALL disable this
       feature for the mobility session corresponding to the PBU.
       Setting this variable to one (1) on the MAG indicates that
       there is domain-wide support for this feature and the MAG is
       not required to include the LMA User-Plane Address mobility
       option in the PBA.  In this case, the MAG MAY choose not to
       include the LMA User-Plane Address mobility option in the PBU.
       When this variable on the LMA is set to zero (0), the LMA MUST
       NOT include the LMA User-Plane Address mobility option in the
       PBA unless the MAG has indicated support for this feature by
       including the LMA User-Plane Address mobility option in the PBU
       message.
       Setting this variable to one (1) on the LMA indicates that
       there is domain-wide support for this feature and the LMA
       SHOULD choose to include this LMA User-Plane Address mobility
       option in the PBA even if the option is not present in the PBU
       message.
       On both the LMA and the MAG, the default value for this
       variable is zero (0).  This implies that the default behavior
       of a MAG is to include this option in the PBU, and the default
       behavior of an LMA is to include this option in a PBA only if
       the option is present in the PBU.

Wakikawa, et al. Standards Track [Page 8] RFC 7389 PMIPv6 CP-UP Split October 2014

6. IANA Considerations

 This specification defines a new mobility header option -- the LMA
 User-Plane Address mobility option.  The format of this option is
 described in Section 4.  The Type value 59 for this mobility option
 has been allocated by IANA in the "Mobility Options" registry at
 <http://www.iana.org/assignments/mobility-parameters>.

7. Security Considerations

 The Proxy Mobile IPv6 specification [RFC5213] requires the signaling
 messages between the MAG and the LMA to be protected using end-to-end
 security association(s) offering integrity and data origin
 authentication.  The Proxy Mobile IPv6 specification also requires
 IPsec [RFC4301] to be a mandatory-to-implement security mechanism.
 This document specifies an approach where the control-plane and user-
 plane functions of the MAG and LMA are separated and hosted on
 different IP nodes.  In such deployment models, the nodes hosting
 those respective control-plane functions still have to meet the
 [RFC5213] security requirement listed above; specifically, the Proxy
 Mobile IPv6 signaling messages exchanged between these entities MUST
 be protected using end-to-end security association(s) offering
 integrity and data origin authentication.  Furthermore, IPsec is a
 mandatory-to-implement security mechanism for the nodes hosting the
 control-plane function of the MAG and LMA.  Additional documents may
 specify alternative security mechanisms for securing Proxy Mobile
 IPv6 signaling messages.  The mobility entities in a Proxy Mobile
 IPv6 domain can enable a specific security mechanism based on either
 (1) static configuration or (2) dynamic negotiation (using any
 standard security negotiation protocols).
 As per the Proxy Mobile IPv6 specification, the use of IPsec for
 protecting the mobile node's user-plane traffic is optional.  This
 specification keeps the same requirement and therefore requires the
 nodes hosting the user-plane functions of the MAG and the LMA to have
 IPsec as a mandatory-to-implement security mechanism but make the use
 of IPsec optional for user-plane traffic protection.
 The LMA User-Plane Address mobility option defined in this
 specification is for use in PBU and PBA messages.  This option is
 carried like any other mobility header option as specified in
 [RFC5213].  Therefore, it inherits security guidelines from
 [RFC5213].

Wakikawa, et al. Standards Track [Page 9] RFC 7389 PMIPv6 CP-UP Split October 2014

 The IP address of the LMA user plane (the LMA-UPA), provided within
 the LMA User-Plane Address mobility option, MUST be a valid address
 under the administrative control associated with the LMA functional
 block.
 If the LMA user-plane and the LMA control-plane functions are hosted
 in different entities, any control messages between these two
 entities containing the LMA User-Plane Address mobility option MUST
 be protected using end-to-end security association(s) offering
 integrity and data origin authentication.

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,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
            Internet Protocol", RFC 4301, December 2005,
            <http://www.rfc-editor.org/info/rfc4301>.
 [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
            and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008,
            <http://www.rfc-editor.org/info/rfc5213>.
 [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
            Mobile IPv6", RFC 5844, May 2010,
            <http://www.rfc-editor.org/info/rfc5844>.

8.2. Informative References

 [MOBILE-SEPARATION]
            Wakikawa, R., Matsushima, S., Patil, B., Chen, B.,
            Joachimpillai, D., and H. Deng, "Requirements and use
            cases for separating control and user planes in mobile
            network architectures", Work in Progress,
            draft-wakikawa-req-mobile-cp-separation-00, November 2013.
 [OpenFlow-Spec-v1.4.0]
            Open Networking Foundation, "OpenFlow Switch
            Specification, Version 1.4.0", October 2013.
 [RFC1701]  Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic
            Routing Encapsulation (GRE)", RFC 1701, October 1994,
            <http://www.rfc-editor.org/info/rfc1701>.

Wakikawa, et al. Standards Track [Page 10] RFC 7389 PMIPv6 CP-UP Split October 2014

 [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
            IPv6 Specification", RFC 2473, December 1998,
            <http://www.rfc-editor.org/info/rfc2473>.
 [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
            for IPv6 Hosts and Routers", RFC 4213, October 2005,
            <http://www.rfc-editor.org/info/rfc4213>.
 [RFC5810]  Doria, A., Hadi Salim, J., Haas, R., Khosravi, H., Wang,
            W., Dong, L., Gopal, R., and J. Halpern, "Forwarding and
            Control Element Separation (ForCES) Protocol
            Specification", RFC 5810, March 2010,
            <http://www.rfc-editor.org/info/rfc5810>.
 [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
            in IPv6", RFC 6275, July 2011,
            <http://www.rfc-editor.org/info/rfc6275>.
 [RFC6459]  Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
            Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
            Partnership Project (3GPP) Evolved Packet System (EPS)",
            RFC 6459, January 2012,
            <http://www.rfc-editor.org/info/rfc6459>.
 [RFC6463]  Korhonen, J., Gundavelli, S., Yokota, H., and X. Cui,
            "Runtime Local Mobility Anchor (LMA) Assignment Support
            for Proxy Mobile IPv6", RFC 6463, February 2012,
            <http://www.rfc-editor.org/info/rfc6463>.
 [STATELESS-UPLANE]
            Matsushima, S. and R. Wakikawa, "Stateless user-plane
            architecture for virtualized EPC (vEPC)", Work in
            Progress, draft-matsushima-stateless-uplane-vepc-03,
            July 2014.

Wakikawa, et al. Standards Track [Page 11] RFC 7389 PMIPv6 CP-UP Split October 2014

Acknowledgements

 The authors of this document thank the NetExt Working Group for the
 valuable feedback on different versions of this specification.  In
 particular, the authors want to thank John Kaippallimalil, Sridhar
 Bhaskaran, Nirav Salot, Bruno Landais, Brian Carpenter, Pete Resnick,
 Stephen Farrell, and Brian Haberman for their valuable comments and
 suggestions to improve this specification.

Authors' Addresses

 Ryuji Wakikawa
 Softbank Mobile
 1-9-1, Higashi-Shimbashi, Minato-Ku
 Tokyo  105-7322
 Japan
 EMail: ryuji.wakikawa@gmail.com
 Rajesh S. Pazhyannur
 Cisco
 170 West Tasman Drive
 San Jose, CA  95134
 United States
 EMail: rpazhyan@cisco.com
 Sri Gundavelli
 Cisco
 170 West Tasman Drive
 San Jose, CA  95134
 United States
 EMail: sgundave@cisco.com
 Charles E. Perkins
 Futurewei Inc.
 2330 Central Expressway
 Santa Clara, CA  95050
 United States
 EMail: charliep@computer.org

Wakikawa, et al. Standards Track [Page 12]

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