Internet DRAFT - draft-ietf-mipshop-fmip-ptp

draft-ietf-mipshop-fmip-ptp






Network Working Group                                             F. Xia
Internet-Draft                                               B. Sarikaya
Intended status: Informational                                Huawei USA
Expires: June 17, 2013                                 December 14, 2012


Prefix Management for Mobile IPv6 Fast Handover on Point-to-Point Links
                     draft-ietf-mipshop-fmip-ptp-05

Abstract

   Mobile IPv6 Fast Handovers specification currently does not
   explicitly define prefix management over point-to-point links when a
   mobile node uses a prefix to formulate a new care-of-address.  In
   this document a mechanism is developed for a previous access router
   to request unique prefixes from a new access router, and in turn, the
   previous access router advertises the prefixes to the mobile node for
   a new care-of-address configuration.  Extensions to Mobile IPv6 Fast
   Handovers specification are also specified in this document.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 17, 2013.

Copyright Notice

   Copyright (c) 2012 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
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   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Prefix Management on Point-to-Point Links . . . . . . . . . . . 5
     4.1.  Predictive mode . . . . . . . . . . . . . . . . . . . . . . 5
     4.2.  Reactive Mode . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  HI and Hack Extensions  . . . . . . . . . . . . . . . . . . . . 7
     5.1.  HI Extension  . . . . . . . . . . . . . . . . . . . . . . . 7
     5.2.  HAck Extension  . . . . . . . . . . . . . . . . . . . . . . 7
     5.3.  Dedicated Prefix Option . . . . . . . . . . . . . . . . . . 7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   7.  IANA considerations . . . . . . . . . . . . . . . . . . . . . . 9
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 9
     9.2.  Informative references  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9



























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1.  Introduction

   Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568] aims at reducing the
   handover latency by reducing the time to configure a new care-of
   address (NCoA) for a mobile node(MN).  In FMIPv6, the MN formulates a
   prospective NCoA when it is still present on a link of a previous
   access router (PAR).

   [RFC4968] provides different IPv6 link models that are suitable for
   IEEE802.16 based networks and provides analysis of various
   considerations for each link model and the applicability of each link
   model under different deployment scenarios.  [RFC5121] specifies the
   addressing and operation of IPv6 over the IPv6 specific part of the
   packet convergence sublayer of IEEE Std 802.16e [802.16e], and point-
   to-point link model is recommended.  Also, 3GPP and 3GPP2 have
   adopted the point-to-point link model based on the recommendations in
   [RFC3314].

   In this document, we first explain the problems associated with
   FMIPv6 on point-to-point links followed by a detailed description of
   prefix management for FMIPv6 operation on point-to-point links.

   In Section 3 we describe why the point-to-point link address
   formation procedures are needed in FMIPv6, in Section 4 we define a
   procedure that a new access router (NAR) can use to dynamically
   assign unique prefixes in point-to-point links and in Section 5 we
   define necessary messages/options for the operation in Section 4.


2.  Terminology

   The terminology in this document is based on the definitions in
   [RFC5568], in addition to the ones specified in this section.

   point-to-point link model:  In this model, a set of layer 2 transport
      connections between a MN and an access router (AR) are treated as
      a single link.  Each link is allocated a separate, unique prefix
      or a set of unique prefixes by the AR.  Please refer to [RFC4968]
      for details.

   shared link model:  In this model, one or more prefixes are shared by
      mobile nodes for constructing their global IPv6 addresses.  Please
      refer to [RFC4968] for details.








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   dedicated prefix:  In point-to-point link model, a unique prefix used
      by a MN for formulating a NCoA while the MN is still on a PAR's
      link.



3.  Problem Statement

   The following are operations relating to prefix management as per
   [RFC5568]:

   o  Movement detection.  The protocol enables a MN to quickly detect
      that it has moved to a new subnet by providing the new access
      point and the associated subnet prefix information when the MN is
      still connected to its current subnet.  For instance, the MN may
      discover available access points using link-layer specific
      mechanisms (i.e., a "scan" in WLAN) and then request subnet
      information corresponding to one or more of those discovered
      access points.  The MN sends a Router Solicitation for Proxy
      Advertisement (RtSolPr) to its access router to resolve one or
      more Access Point Identifiers (AP-ID)to subnet-specific
      information.  In response, the access router sends a Proxy Router
      Advertisement (PrRtAdv) message containing one or more [AP-ID, AR-
      Info] tuples, which the MN can use in readily detecting movement:
      when attachment to an access point with AP-ID takes place, the MN
      knows the corresponding new router's coordinates including its
      prefix, IP address, and L2 address.  In this document, there is no
      changes to the movement detection procedure specified in
      [RFC5568].

   o  NCoA configuration.  AR-Info contains the access router's L2 and
      IP addresses, and the prefix valid on the interface to which the
      Access Point (identified by AP-ID) is attached.  With the prefix
      provided in the PrRtAdv message, the MN formulates a prospective
      NCoA.

   In the shared link mode, the PAR only needs to figure out what IPv6
   prefix is advertised by the NAR.  In most cases, there would only be
   a small set of adjacent NARs and the PAR would be able to obtain this
   information easily.  In the point-to-point link mode, the NAR has
   access to a pool of IPv6 prefixes and these prefixes are assigned
   dynamically to each mobile node's point-to-point link.  Therefore it
   becomes difficult for the PAR to figure out which IPv6 prefix is
   going to be assigned to a particular mobile node when point-to-point
   link mode is used.

   For the mobile node to configure an NCoA, the PAR sends a Proxy
   Router Advertisement to the mobile node.  This requires that for



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   point-to-point links, the PAR must first contact the NAR to for the
   dedicated prefix and then advertise the prefix to the mobile node.
   This is an extension to [RFC5568] to support point-to-point links.


4.  Prefix Management on Point-to-Point Links

   Upon the indication of handover from the PAR to the NAR, the PAR uses
   Handover Initiate (HI)/ Handover Acknowledge (HAck) message exchange
   to get a dedicated prefix from the NAR.  The PAR then sends this
   prefix in the PrRtAdv message to the MN as described in [RFC5568].
   In the PrRtAdv message, A-bit and L-bit must be turned on.  The MN
   thus uses this prefix for movement detection and NCoA configuration
   as per [RFC5568].

4.1.  Predictive mode

   New FMIPv6 message exchange is introduced for the PAR to ask for MN's
   dedicated prefix as shown in Figure 1.  The MN sends an RtSolPr
   message to the PAR to resolve one or more Access Point Identifiers to
   subnet-specific information.  The PAR in turn requests dedicated
   prefixes from the NAR through modified HI/HAck message exchange
   described in Section 5.  With the information provided in the PrRtAdv
   message, the MN formulates a prospective NCoA and sends an FBU
   message to the PAR.  The following operation is exactly the same as
   these specified in [RFC5568].

   Lifetime in Dedicated Prefix Option Section 5.3 is used to prevent
   prefix depletion because of erroneous movement in which the mobile
   node receives a dedicated prefix prior to a handover that it is
   moving to a new access point but it either moves to a different one
   or it aborts movement altogether.  Not until timeout of the prefix
   does the NAR release it.


















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     MN                    PAR                      NAR
      |                     |                        |
      |                     |                        |
      |------RtSolPr------->|                        |
      |                     |   HI(Prefix Request)   |
      |                     |----------------------->|
      |                     |                        |
      |                     |                        |
      |                     |  HAck(Prefix Response) |
      |                     |<-----------------------|
      |<-----PrRtAdv--------|                        |
      |                     |                        |No FBU
      |                     |                        |Release
      |                     |                        |Prefix
      |------FBU----------->|--------HI------------->|
      |                     |<------HAck-------------|
      |          <--FBack---|--FBack--->             |
    disconnect            forward                    |
      |                   packets===================>|
      |                     |                        |
      |                     |                        |
    connect                 |                        |
      |                     |                        |
      |--------- UNA ------------------------------->|
      |<=================================== deliver packets
      |                                              |


                        Figure 1: Prefix Signaling

   In some wireless networks, the handover control may reside in the
   network even though the decision to undergo handover may be mutually
   agreed between the MN and the network.  In such a case, the PAR can
   send an unsolicited PrRtAdv containing the link-layer address, IP
   address, and dedicated prefix of the mobile node when the network
   decides that a handover is imminent.  In this network-initiated
   handover scenario, there isn't explicit RtSolPr to trigger PAR to
   request a prefix and implementation specific trigger must be used by
   PAR to send HI message for prefix request.

4.2.  Reactive Mode

   In the reactive mode, there are two cases.

   o  In the first case, the MN receives the PrRtAdv message while still
      attached to the PAR.  The MN is then able to formulate NCoA before
      attaching to the NAR.  The MN and the NAR operate as per the
      procedures defined in [RFC5568].



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   o  In the second case, the MN does not receive a PrRtAdv before
      attaching to the NAR.  The MN can configure its IP address using
      stateless or stateful address configuration.  In the former case,
      the NAR should send un-solicited RA to expedite MN's address
      configuration.  Once NCoA formulation is finished, the MN operates
      according to [RFC5568].

   In both cases, the MN formulates NCoA from the dedicated prefix.
   Since the MN has already handed over to the NAR, this prefix is
   retained.


5.  HI and Hack Extensions

5.1.  HI Extension

   The Handover Initiate (HI),defined in [RFC5568], is a Mobility Header
   message sent by one Access Router to another to initiate the process
   of a MN's handover.

   In [RFC5568], the PAR uses a Code value of 0 when it processes an FBU
   with PCoA as source IP address, while uses a Code value of 1 when it
   processes an FBU whose source IP address is not PCoA.  A Code value
   is used for the dedicated prefix request.  Dedicated Prefix Option
   defined in Section 5.3 may be included as a hint for a requested
   preference.  The NAR may allocate a dedicated prefix based on the
   prefix preference in the option.  If the option is not included, the
   NAR allocates a prefix according to it's discretion.

5.2.  HAck Extension

   Handover Acknowledgment message defined in [RFC5568] is a Mobility
   Header message that must be sent as a reply to the Handover Initiate
   message.  In this document, HAck is extended as follows to respond to
   a dedicated prefix request:
   o  One new Code value is defined.  Here, a Code value is used for
      dedicated prefix response.
   o  Dedicated Prefix Option defined in Section 5.3 must be included
      for prefix delegation.

5.3.  Dedicated Prefix Option

   This option is of the form shown in Figure 2.








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       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     | Prefix Length | Reserved      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Lifetime                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                        Prefix                                 +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 2: Dedicated Prefix Option



     Type       The type of the option

     Length     The length of the option in units of 8 octets.

     Reserved
                must be set to zero by the sender and ignored by the
                receiver.

     Prefix Length
                8-bit unsigned integer.  The number of leading bits
                in the Prefix that are valid.  The value ranges from 0
                to 128.

     Lifetime   32-bit unsigned integer.  The length of time in seconds
                (relative to the time the packet is sent).  A value of
                all one bits (0xffffffff) represents infinity.

     Prefix     An IP address or a prefix of an IP address. A MN uses it
                to formulate a NCoA.



6.  Security Considerations

   Prefix management for FMIPv6 operation on point-to-point links uses
   two messages (HI/Hack) for prefix request and response.  These
   messages are secured using FMIPv6 security mechanisms and hence do



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   not introduce any new security threats and the security provided by
   FMIPv6 applies completely.


7.  IANA considerations

   None.


8.  Acknowledgements

   The authors would like to thank Heejin Jang, Daniel Park, Vijay
   Devarapalli, Rajeev Koodli, Subir Das, Spencer Dawkins, and Dirk Von-
   Hugo for valuable comments.


9.  References

9.1.  Normative References

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

   [RFC5568]  Koodli, R., "Mobile IPv6 Fast Handovers", RFC 5568,
              July 2009.

   [RFC5121]  Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
              Madanapalli, "Transmission of IPv6 via the IPv6
              Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
              February 2008.

9.2.  Informative references

   [802.16e]  Institute of Electrical and Electronics Engineer,
              "Amendment for Physical and Medium Access Control Layers
              for Combined Fixed and Mobile Operation in Licensed
              Bands",  IEEE 802.16e/D12.

   [RFC3314]  Wasserman, M., "Recommendations for IPv6 in Third
              Generation Partnership Project (3GPP) Standards",
              RFC 3314, September 2002.

   [RFC4968]  Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
              Based Networks", RFC 4968, August 2007.







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Authors' Addresses

   Frank Xia
   Huawei USA
   5340 Legacy Dr. Building 3
   Plano, TX  75024

   Phone: +1 972-509-5599
   Email: xiayangsong@huawei.com


   Behcet Sarikaya
   Huawei USA
   5340 Legacy Dr. Building 3
   Plano, TX  75024

   Phone: +1 972-509-5599
   Email: sarikaya@ieee.org

































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