





Internet Engineering Task Force (IETF)                            Z. Yan
Request for Comments: 8191                                         CNNIC
Category: Standards Track                                         J. Lee
ISSN: 2070-1721                                     Sangmyung University
                                                                  X. Lee
                                                                   CNNIC
                                                             August 2017


     Home Network Prefix Renumbering in Proxy Mobile IPv6 (PMIPv6)

Abstract

   In the basic Proxy Mobile IPv6 (PMIPv6) specification, a Mobile Node
   (MN) is assigned with a Home Network Prefix (HNP) during its initial
   attachment, and the MN configures its Home Address (HoA) with the
   HNP.  During the movement of the MN, the HNP remains unchanged to
   keep ongoing communications associated with the HoA.  However, the
   current PMIPv6 specification does not specify related operations when
   HNP renumbering has occurred (e.g., due to change of service provider
   or site topology, etc.).  In this document, a solution to support HNP
   renumbering is proposed, as an optional extension of the PMIPv6
   specification.

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 7841.

   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/rfc8191.














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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  HNP Renumbering Procedure . . . . . . . . . . . . . . . . . .   4
   4.  Session Connectivity  . . . . . . . . . . . . . . . . . . . .   6
   5.  Message Format  . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Other Issues  . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10




















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1.  Introduction

   At the time of writing, network managers prefer Provider-Independent
   (PI) addressing for IPv6 to attempt to minimize the need for future
   possible renumbering.  However, a widespread use of PI addresses will
   cause Border Gateway Protocol (BGP) scaling problems [RFC7010].  It
   is thus desirable to develop tools and practices that make IPv6
   renumbering a simpler process to reduce demand for IPv6 PI space
   [RFC6879].  In this document, we aim to support HNP renumbering when
   the HNP in PMIPv6 [RFC5213] is not a PI prefix.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Usage Scenarios

   There are a number of reasons why HNP renumbering support in PMIPv6
   is useful, and some scenarios are identified below:

   Scenario 1:  the HNP set used by a PMIPv6 service provider is
                assigned by a different Internet Service Provider (ISP),
                and then HNP renumbering MAY occur if the PMIPv6 service
                provider switches to a different ISP.

   Scenario 2:  multiple Local Mobility Anchors (LMAs) MAY be deployed
                by the same PMIPv6 service provider, and then each LMA
                MAY serve for a specific HNP set.  In this case, the HNP
                of an MN MAY change if the serving LMA is changed to
                another LMA that does not inherit the assigned HNP set
                [RFC6463].

   Scenario 3:  PMIPv6 HNP renumbering MAY be caused by the rebuilding
                of the network architecture as the companies split,
                merge, grow, relocate, or reorganize.  For example, the
                PMIPv6 service provider MAY reorganize its network
                topology.

   In Scenario 1, we assume that only the HNP is renumbered, while the
   serving LMA remains unchanged; this is the basic scenario considered
   in this document.  In Scenarios 2 and 3, more complex situations MAY
   result; for example, HNP renumbering MAY occur due to the switchover
   of a serving LMA.




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   In the Mobile IPv6 (MIPv6) protocol, when an HNP changes, the Home
   Agent (HA) will actively notify its MN about the new prefix, and then
   the renumbering of the Home Network Address (HoA) can be well
   supported [RFC6275].  In basic PMIPv6, the PMIPv6 binding is
   triggered by a Mobile Access Gateway (MAG), which detects the
   attachment of the MN.  A scheme is also needed for the LMA to
   immediately initiate the PMIPv6 binding state refreshment during the
   HNP renumbering process.  Although this issue is also mentioned in
   Section 6.12 of [RFC5213], the related solution has not been
   specified.

3.  HNP Renumbering Procedure

   When HNP renumbering happens in PMIPv6, the LMA MUST notify the MAG
   about the new HNP, and then the MAG MUST announce the new HNP to the
   attached MN accordingly.  Also, the LMA and the MAG MUST update the
   routing states for the HNP and the related addresses.  To support
   this procedure, [RFC7077] can be adopted; it specifies an
   asynchronous update from the LMA to the MAG about specific session
   parameters.  This document considers the following two cases:

   (1) HNP is renumbered under the same LMA

       In this case, the LMA remains unchanged as in Scenarios 1 and 3.
       The steps are shown in Figure 1.

       +-----+                +-----+                +-----+
       | MN  |                | MAG |                | LMA |
       +-----+                +-----+                +-----+
         |                      |                      |
         |                      |           Allocate new HNP
         |                      |                      |
         |                      |<------------- UPN ---|
         |                      |                      |
         |                      |                      |
         |                      |                      |
         |<-----RA/DHCP --------|                      |
         |                      |                      |
       Address configuration    |                      |
         |                      |                      |
         |            Update binding & routing states  |
         |                      |                      |
         |                      |--- UPA ------------->|
         |                      |                      |
         |                      |     Update binding & routing states
         |                      |                      |

             Figure 1: Signaling Call Flow for HNP Renumbering



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       o  When a PMIPv6 service provider renumbers the HNP set under the
          same LMA, the serving LMA SHOULD initiate the HNP renumbering
          operation.  The LMA allocates a new HNP for the related MN.

       o  The LMA sends the Update Notification (UPN) message to the MAG
          to update the HNP information.  If the Dynamic Host
          Configuration Protocol (DHCP) is used to allocate the address,
          the DHCP infrastructure MUST also be notified about the new
          HNP.

       o  Once the MAG receives this UPN message, it recognizes that the
          related MN has the new HNP.  Then, the MAG MUST notify the MN
          about the new HNP with a Router Advertisement (RA) message or
          allocate a new address within the new HNP through a DHCP
          procedure.

       o  After the MN obtains the HNP information through the RA
          message, it deletes the old HoA and configures a new HoA with
          the newly allocated HNP.

       o  When the new HNP is announced or the new address is configured
          to the MN successfully, the MAG MUST update the related
          binding and routing states.  Then, the MAG sends back the
          Update Notification Acknowledgement (UPA) message to the LMA
          for the notification of successful update of the HNP, related
          binding state, and routing state.  Then, the LMA updates the
          routing and binding information corresponding to the MN in
          order to replace the old HNP with the new one.

   (2) HNP renumbering is caused by the LMA switchover

       Since the HNP is assigned by the LMA, HNP renumbering MAY be
       caused by the LMA switchover, as in Scenarios 2 and 3.

       The LMA information is the basic configuration information of the
       MAG.  When the LMA changes, the related profile SHOULD be updated
       by the service provider.  In this way, the MAG initiates the
       binding registration to the MN's new LMA as specified in
       [RFC5213].  When HNP renumbering is caused in this case, the new
       HNP information is sent by the LMA during the new binding
       procedure.  Accordingly, the MAG withdraws the old HNP of the MN
       and announces the new HNP to the MN, similar to the case when the
       HNP is renumbered under the same LMA.








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4.  Session Connectivity

   HNP renumbering MAY cause the disconnection of the ongoing
   communications of the MN.  Basically, there are two modes to manage
   the session connectivity during HNP renumbering.

   (1)  Soft mode

        The LMA will temporarily maintain the state of the old HNP
        during the HNP renumbering (after the UPA reception) in order to
        redirect the packets to the MN before the MN reconnects the
        ongoing session and notifies the Correspondent Node (CN) about
        its new HoA.  This mode is aiming to reduce packet loss during
        HNP renumbering, but the binding state corresponding to the old
        HNP SHOULD be marked, for example, as transient binding
        [RFC6058].  Also, the LMA MUST stop broadcasting the routing
        information about the old HNP if the old HNP is no longer
        anchored at this LMA.

   (2)  Hard mode

        If HNP renumbering happens with the switchover of the LMA, hard
        mode is RECOMMENDED to keep the protocol simple.  In this mode,
        the LMA deletes the binding state of the old HNP after it
        receives the UPA message from the MAG, and the LMA silently
        discards the packets destined to the old HNP.

5.  Message Format

   (1)  UPN message

        In the UPN message sent from the LMA to the MAG, the
        notification reason is set to 2 (UPDATE-SESSION-PARAMETERS).
        Besides, the HNP Option [RFC5213] containing the new HNP and the
        Mobile Node Identifier Option [RFC4283] (which identifies the
        MN) are contained as Mobility Options of UPN.  The order of the
        HNP Option and Mobile Node Identifier Option in the UPN message
        is not mandated here.

   (2)  UPA message

        The MAG sends this message in order to acknowledge that it has
        received an UPN message with the (A) flag set and to indicate
        the status after processing the message.  If the MAG did not
        successfully renumber the HNP, which is required in the UPN
        message, the UPA message has the Status Code set to 128 (FAILED-
        TO-UPDATE-SESSION-PARAMETERS), and the subsequent operation of
        the LMA is PMIPv6 service provider specific.



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   (3)  RA message

        When the RA message is used by the MAG to advise the new HNP, it
        contains two Prefix Information Options [RFC4861] [RFC4862].  In
        the first Prefix Information Option, the old HNP is carried, and
        the related Preferred Lifetime is set to 0.  In the second
        Prefix Information Option, the new HNP is carried with the Valid
        Lifetime, and Preferred Lifetime set to larger than 0.

   (4)  DHCP message

        When the DHCP is used in PMIPv6 to configure the addresses for
        the MN, new IPv6 address or addresses (e.g., the HoA) will be
        generated based on the new HNP, and the related DHCP procedure
        is also triggered by the reception of the UPN message [RFC3315].

6.  Other Issues

   In order to maintain the reachability of the MN, the Domain Name
   System (DNS) resource record corresponding to this MN MAY need to be
   updated when the HNP of the MN changes [RFC3007].  However, this is
   beyond the scope of this document.

7.  Security Considerations

   The UPN and UPA messages in this document MUST be protected using
   end-to-end security association(s) offering integrity and data origin
   authentication as specified in [RFC5213] and [RFC7077].

   When HNP renumbering is triggered, a new HNP SHOULD be allocated to
   the MN.  The LMA MUST follow the procedure of PMIPv6 to make sure
   that only an authorized HNP can be assigned for the MN.  In this way,
   the LMA is ready to be the topological anchor point of the new HNP,
   which is for that MN's exclusive use.

   Per [RFC4862], if the Valid Lifetime in a Prefix Information Option
   is set to less than 2 hours in an unauthenticated RA, it is ignored.
   Thus, when the old HNP that is being deprecated is included in an RA
   from the MAG, the Valid Lifetime SHOULD be set to 2 hours (and the
   Preferred Lifetime set to 0) for an unauthenticated RA.  However, if
   the legality of the signaling messages exchanged between MAG and MN
   can be guaranteed, it MAY be acceptable to also set the Valid
   Lifetime to 0 for an unauthenticated RA.

8.  IANA Considerations

   This document does not require any IANA actions.




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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>.

   [RFC3007]  Wellington, B., "Secure Domain Name System (DNS) Dynamic
              Update", RFC 3007, DOI 10.17487/RFC3007, November 2000,
              <http://www.rfc-editor.org/info/rfc3007>.

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

   [RFC4283]  Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
              Chowdhury, "Mobile Node Identifier Option for Mobile IPv6
              (MIPv6)", RFC 4283, DOI 10.17487/RFC4283, November 2005,
              <http://www.rfc-editor.org/info/rfc4283>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <http://www.rfc-editor.org/info/rfc4862>.

   [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>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <http://www.rfc-editor.org/info/rfc6275>.

   [RFC6463]  Korhonen, J., Ed., Gundavelli, S., Yokota, H., and X. Cui,
              "Runtime Local Mobility Anchor (LMA) Assignment Support
              for Proxy Mobile IPv6", RFC 6463, DOI 10.17487/RFC6463,
              February 2012, <http://www.rfc-editor.org/info/rfc6463>.





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   [RFC7077]  Krishnan, S., Gundavelli, S., Liebsch, M., Yokota, H., and
              J. Korhonen, "Update Notifications for Proxy Mobile IPv6",
              RFC 7077, DOI 10.17487/RFC7077, November 2013,
              <http://www.rfc-editor.org/info/rfc7077>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <http://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [RFC6058]  Liebsch, M., Ed., Muhanna, A., and O. Blume, "Transient
              Binding for Proxy Mobile IPv6", RFC 6058,
              DOI 10.17487/RFC6058, March 2011,
              <http://www.rfc-editor.org/info/rfc6058>.

   [RFC6879]  Jiang, S., Liu, B., and B. Carpenter, "IPv6 Enterprise
              Network Renumbering Scenarios, Considerations, and
              Methods", RFC 6879, DOI 10.17487/RFC6879, February 2013,
              <http://www.rfc-editor.org/info/rfc6879>.

   [RFC7010]  Liu, B., Jiang, S., Carpenter, B., Venaas, S., and W.
              George, "IPv6 Site Renumbering Gap Analysis", RFC 7010,
              DOI 10.17487/RFC7010, September 2013,
              <http://www.rfc-editor.org/info/rfc7010>.


























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Acknowledgements

   The work of Jong-Hyouk Lee was supported by 'The Cross-Ministry Giga
   KOREA Project' grant from the Ministry of Science, ICT and Future
   Planning, Korea.

Authors' Addresses

   Zhiwei Yan
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing  100190
   China

   Email: yan@cnnic.cn


   Jong-Hyouk Lee
   Sangmyung University
   31, Sangmyeongdae-gil, Dongnam-gu
   Cheonan  31066
   Republic of Korea

   Email: jonghyouk@smu.ac.kr


   Xiaodong Lee
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing  100190
   China

   Email: xl@cnnic.cn


















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