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NETLMM Working Group                                          K. Weniger
Internet-Draft                                                  G. Velev
Expires: October 22, 2007                                      Panasonic
                                                          April 20, 2007


         Proxy Mobile IPv6 and Mobile IPv6 interworking issues
              draft-weniger-netlmm-pmipv6-mipv6-issues-00

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Copyright Notice

   Copyright (C) The IETF Trust (2007).














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Abstract

   This document discusses issues that may arise if Proxy Mobile IPv6
   and Mobile IPv6 are used together.  Solutions for those issues are
   currently out of scope.  The purpose of this document is to agree on
   a comprehensive list of interworking issues and to trigger the
   discussion of solutions.


Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  List of PMIPv6-MIPv6 interworking issues . . . . . . . . . . .  5
     3.1.  Issue #1: Mobility mode selection  . . . . . . . . . . . .  5
     3.2.  Issue #2: MIPv6 de-registration Binding Update deletes
           PMIPv6 binding cache entry . . . . . . . . . . . . . . . .  5
     3.3.  Issue #3: Race condition between Binding Update and
           Proxy Binding Update messages  . . . . . . . . . . . . . .  5
     3.4.  Issue #4: Mismatch of binding cache lookup key . . . . . .  6
     3.5.  Issue #5: Use of wrong home agent or LMA after handover  .  6
     3.6.  Issue #6: Redirection attack against mobile nodes
           outside PMIP domain due to compromised MAG . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 12





















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1.  Terminology

   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 [1].

   Furthermore, the terminology defined in [2] and [3] is used.












































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2.  Introduction

   The NETLMM WG is standardizing Proxy Mobile IPv6 [3], a Mobile IPv6-
   based protocol for localized mobility management.  This protocol
   allows the network to manage the mobility of mobile nodes, e.g., to
   enable IP mobility of nodes that do not implement Mobile IPv6.  There
   are various scenarios, in which Mobile IPv6 (MIPv6) [2] and Proxy
   Mobile IPv6 (PMIPv6) can be used together.  In [4], the following
   interworking scenarios are presented:

   1.  PMIPv6 and MIPv6 are used in a hierarchical manner.  In this
       scenario, a mobile node's MIPv6-CoA equals the MN-HoA.

   2.  Transitioning between PMIPv6 and MIPv6.  In this scenario, a
       mobile node's MIPv6-HoA equals the MN-HoA.  Home agent and LMA
       are co-located.

   3.  Other co-existence of PMIPv6 and MIPv6 nodes in the same network,
       where neither MIPv6-CoA nor MIPv6-HoA equals MN-HoA.  The home
       agent and LMA are typically co-located in this scenario and a
       mobility session of a specific mobile node is handled either
       exclusively by MIPv6 or exclusively by PMIPv6.

   This draft intends to document all issues that may arise in any of
   these interworking scenarios.  Issues specific to extensions of
   PMIPv6 or MIPv6 like IPv4 support, route optimization, MONAMI6 or
   NEMO etc. are currently out of scope of this document.  Solutions for
   the issues are currently out of scope as well and may be specified in
   future versions of this document or in a companion document.
   However, note that some of the interworking issues may be solvable by
   (pre-)configuration or may be handled at system-level by other SDOs.




















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3.  List of PMIPv6-MIPv6 interworking issues

3.1.  Issue #1: Mobility mode selection

   This issue can arise in all interworking scenarios. [3] discusses
   that a MAG shall be able to announce the visited prefix to a MIPv6-
   enabled node instead of the home prefix, so that the mobile node can
   use MIPv6 to manage the mobility by itself.  The issue is how the MAG
   can figure out which prefix to announce.

3.2.  Issue #2: MIPv6 de-registration Binding Update deletes PMIPv6
      binding cache entry

   When the mobile node moves from a MIPv6 foreign network to the PMIPv6
   home domain in scenario 2, the MAG registers the mobile node at the
   LMA by sending a Proxy Binding Update.  Subsequently, the LMA updates
   the mobile node's binding cache entry with the MAG address and the
   MAG emulates the mobile node's home link.  Upon detection of the home
   link, the mobile node will send a de-registration Binding Update to
   its home agent.  According to [2], the home agent would delete the
   binding cache entry after accepting the de-registration Binding
   Update, i.e., it would delete the proxy binding cache entry that was
   just established by the MAG.  Hence, packets arriving at the LMA and
   destined for the mobile node would not be forwarded to the mobile
   node anymore.

3.3.  Issue #3: Race condition between Binding Update and Proxy Binding
      Update messages

   There are two variants of this issue, which apply to scenario 1 and
   2, respectively.  The fundamental reason for this issue is that MIPv6
   and PMIPv6 use different mechanisms for handling re-ordering of
   registration messages and that they are sent by different entities.
   Whereas Binding Update messages are ordered by a sequence numbers and
   sent by the mobile node, Proxy Binding Update messages are ordered by
   a timestamp option and sent by MAGs.

   The first variant of the issue can occur in scenario 2.  Let's assume
   the mobile performs a handover from a MAG1 to a MAG2 in its PMIP home
   domain and shortly thereafter the mobile node moves out of the PMIP
   domain to an AR, where it configures a new MIPv6-CoA and sends a
   Binding Update message to its home agent.  If now the Proxy Binding
   Update message from MAG2 is delayed so that it reaches the LMA after
   the Binding Update, the binding cache entry at the LMA would wrongly
   point to MAG2.  Unless a new Binding Update is sent by the mobile
   node, packets are not forwarded to the mobile node, since the mobile
   node has already left MAG2.  This may result in a significant packet
   loss.  A similar situation can occur if the mobile node moves from



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   one AR to another and shortly thereafter enters the PMIP home domain.

   A second variant of this issue can occur in scenario 1.  When the
   mobile node enters a PMIP domain, it may configure a MIPv6-CoA and
   register this at its home agent before the Proxy Binding Update sent
   by the MAG reaches the LMA.  This can happen, e.g., if the home
   prefix is announced to the mobile node before the MAG sends the
   corresponding Proxy Binding Update.  In such case, packets arriving
   at the LMA are not forwarded to the mobile node until the Proxy
   Binding Update is received at the LMA, which may result in some
   packet loss.

3.4.  Issue #4: Mismatch of binding cache lookup key

   MIPv6 uses the home address as lookup key for the binding cache,
   whereas PMIPv6 uses the NAI as lookup key.  In some situations, the
   LMA may not even know the mobile node's home address.  Hence, the LMA
   or home agent in scenario 2 may not be able to update the same
   binding cache entry when receiving both Binding Update and Proxy
   Binding Update messages.  Consequently, two different binding cache
   entries for the same node may be created by the LMA or home agent,
   which may result in ambiguous forwarding entries and significant
   packet loss.

3.5.  Issue #5: Use of wrong home agent or LMA after handover

   This issues can arise in scenario 2 when multiple home agents and
   LMAs are deployed on the home link.  If the mobile node moves from a
   MIPv6 foreign network to the PMIP home domain, the MAG must send the
   Proxy Binding Update to the particular LMA that is co-located with
   the home agent which maintains the active binding cache entry of the
   mobile node.  If a different LMA is assigned to the MAG, packets
   addressed to the mobile node's home address do not reach the mobile
   node anymore.  Similarly, if the mobile node moves from the PMIP home
   domain to a MIPv6 foreign network, the mobile node must send the
   Binding Update to the particular home agent that is co-located with
   the LMA which maintains the active proxy binding cache entry of the
   mobile node.  If the mobile node selects a different home agent,
   packets addressed to the mobile node's home address do not reach the
   mobile node.

3.6.  Issue #6: Redirection attack against mobile nodes outside PMIP
      domain due to compromised MAG

   A MAG authorized to update the LMA's binding cache entry can update
   the entry of any mobile node registered at this LMA by sending a
   Proxy Binding Update with the mobile node's NAI.  In deployment
   scenarios where an authorized MAG can be compromised by an attacker,



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   the attacker can redirect traffic for any mobile node in the PMIP
   domain to itself.  Note that the mobile node does not need to be
   attached to the compromised MAG to allow this attack, i.e., this can
   be an off-path attack.  In scenario 2, this threat is extended to
   MIPv6, because an authorized MAG must be able to modify a MIPv6
   binding cache entry.  Consequently, a compromised MAG can redirect
   traffic to itself which is destined for mobile nodes located outside
   the PMIP domain.











































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4.  Security Considerations

   This document only discusses issues that arise when combining two
   protocols.  It does not propose any new mechanisms that require
   security considerations.














































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5.  Acknowledgements

   We would like to thank everybody that contributed to compiling the
   list of issue presented in this document.  Many of the issues were
   presented by Gerardo Giaretta at the MIP6 WG during IETF#68 in
   Prague.  The scenarios and some of the issues were mentioned by the
   authors of [3] and [4] in their documents or on the mailing list.












































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6.  References

6.1.  Normative References

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

   [2]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
        IPv6", RFC 3775, June 2004.

   [3]  Gundave, S., Leung, K., Devarapalli, V., Chowdhury, K., and B.
        Patil, "Proxy Mobile IPv6", draft-ietf-netlmm-proxymip6-00 (work
        in progress), April 2007.

6.2.  Informative References

   [4]  Devarapalli, V., Gundave, S., Chowdhury, K., and A. Muhanna,
        "Proxy Mobile IPv6 and Mobile IPv6 interworking",
        draft-devarapalli-netlmm-pmipv6-mipv6-00 (work in progress),
        April 2007.































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Authors' Addresses

   Kilian A. Weniger
   Panasonic R&D Center Germany
   Monzastr. 4c
   Langen  63225
   Germany

   Email: kilian.weniger@eu.panasonic.com


   Genadi Velev
   Panasonic R&D Center Germany
   Monzastr. 4c
   Langen  63225
   Germany

   Email: genadi.velev@eu.panasonic.com

































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Full Copyright Statement

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