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Versions: 00 01 02

   Individual Submission
   Internet Draft                                        Kyeong-Jin Lee
                                                         Jae-Hoon Jeong
                                                          Jung-Soo Park
                                                         Hyoung-Jun Kim
   <draft-leekj-nemo-ro-pd-02.txt>                                 ETRI
   Expires: August 2004                                16 February 2004


           Route Optimization for Mobile Nodes in Mobile Network
                        based on Prefix Delegation


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 except that the right to
   produce derivative works is not granted [1].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


Abstract

   This document describes how to support Route Optimization for the
   Mobile Nodes in IPv6 Mobile Network. The support is provided by
   Prefix Delegation. Mobile Router gets a prefix from an access router
   using Prefix Delegation protocol and advertises the delegated prefix
   to its subnet. Each Mobile Nodes makes its care-of address from the
   prefix and performs binding update. It allows the Mobile Nodes to
   communicate with correspondent nodes directly, avoiding ingress
   filtering.




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Conventions used in this document

   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 [2].


Table of Contents

   1. Terminology and Abbreviation..................................2
   2. Introduction..................................................2
   3. Protocol Overview.............................................3
   4. Neighbor Discovery extension : Delegated Prefix option format.6
   5. Mobile IPv6 extension : Process of Delegated Prefix option....7
   6. Handover Considerations.......................................7
   7. Security Considerations.......................................7
   8. Consideration for Optimization of DNS Name Resolution.........7
   9. Applicability Statements......................................7
   10. References....................................................8
   11. Authors' Addresses............................................8


1. Terminology and Abbreviation

   This document uses the terminology and abbreviation conformed to [1]
   [2] and [3] on the assumption that the reader is familiar with Mobile
   IPv6 and NEMO terminology. In addition, following terms are used:

     Delegated Prefix (DP)
        A prefix assigned to a site by a provider, from which the site
        may derive link prefixes [3]


2. Introduction

   NEMO Basic Support is to preserve session continuity using
   bidirectional tunnel between Mobile Router (MR) and the MRÆs HA. The
   support is reasonable for small-scale mobile network because MR MUST
   encapsulate and decapsulate all packets for Mobile Network Nodes.
   Specially, outbound packets MUST be tunneled in order to pass ingress
   filtering.

   The purpose of this document is to enable MNs behind the MR to
   perform Mobile IPv6 Route Optimization. This can reduce the overhead
   on MR because MR considers the packets of Local Fixed Nodes in the
   bidirectional tunnel between MR and HA.



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   When MR detects its movement, it runs Prefix Delegation (PD) protocol
   such as APD, RA-PD and DHCPv6 described in [5]-[7] respectively. If
   MRs become placed in multiple levels, the mobile network has
   hierarchical architecture. Most of the current PD protocols are
   designed for leaf network. How to extend PD protocol for hierarchical
   IPv6 network is outside the scope of this specification. For example,
   HPD (Hierarchical APD) protocol described in [10] is an extension of
   the APD protocol.

   Even when every AR on visited network does not support PD, there
   SHOULD be no problem in the communication between MN and CN. If this
   mechanism is disabled, all the Mobile Network Nodes (MNNs)
   communicate with CN by NEMO Basic Support. Therefore, it can provide
   Route Optimization for mobile nodes within mobile network according
   as the access network allows PD.

   This specification defines a new Neighbor Discovery Protocol option
   and modifies the operation of MR and MN to support route optimization.
   Fixed router in mobile network is not considered in this
   specification.


3. Protocol Overview

   This document assumes that all AR and MR support PD. Otherwise, only
   NEMO Basic Support [8] is provided to preserve session continuity and
   Route Optimization is disabled.

   Figure 1 shows a topology before two MRs move from home link to
   foreign link. When the MR1 and MR2 are at home link, each MR uses
   1:1:: and 2:1:: respectively as its own mobile network prefix.


















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                               +---+
                               |CN |
                               +-+-+
                                 |
           +------+           +--+-----+                +------+
           |HA-MR1|-----------|Internet|----------------|HA-MR2|
           +---+--+           +--+-----+                +----+-+
               |1::              |                       2:: |
             +-+-+1           +--+-+                       +-+-+3
             |MR1|            | AR |                       |MR2|
             +-+-+2           +--+-+                       +-+-+4
               |1:1::            | 3::                 2:1:: |
         --+---+--+------+-  ----+---                 ---+---+--+--
           |      |      |                               |      |
         +-+-+5 +-+-+6 +-+-+7                          +-+-+8 +-+-+9
         |LMN|  |VMN|  |LFN|                           |LMN|  |VMN|
         +---+  +---+  +---+                           +---+  +---+


       Figure 1. Mobile router at home link

   Figure 2 shows a topology after two MRs move from home link to
   foreign link and each MR performs PD. First, MR1 detects movement and
   gets a prefix (3:1::) from AR. MR1 advertises the DP to its subnet by
   sending RA message with Delegated Prefix option. And then, MR2 moves
   to MR1's network. MR2 gets prefix (3:1:1::) from MR1 and advertises
   the prefix to its subnet.

   When each MN receives RA message with Delegated Prefix option, it
   processes the DP option preferentially: make CoA from the prefix and
   performs binding updates to HA and CN. In figure 2, CoA1 is used as a
   primary CoA, which is made from DP. This process is transparent to
   LFNs.

















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                               +---+
                               |CN |
                               +-+-+
                                 |
           +------+           +--+-----+                +------+
           |HA-MR1|-----------|Internet|----------------|HA-MR2|
           +---+--+           +--+-----+                +----+-+
               |1::              |                       2:: |
                              +--+-+
                              | AR |
                              +--+-+
                                 | 3::
                          --+----+------
                            |
                          +-+-+ HoA 1::1, CoA 3::1
                          |MR1| Delegated Prefix(DP) = 3:1::
                          +-+-+ Mobile Network Prefix(MNP) = 1:1::
                            |
                      --+---+--+------+--------+------
                        |      |      |        |
                      +-+-+  +-+-+  +-+-+    +-+-+ HoA  2::3
                      |LMN|  |VMN|  |LFN|    |MR2| CoA1 3:1::3
                      +---+  +---+  +---+    +-+-+ CoA2 1:1::3
                CoA1 3:1::5  3:1::6            |      DP = 3:1:1::
                CoA2         1:1::6     ---+---+--+-- MNP = 2:1::
                                           |      |
                                         +-+-+  +-+-+
                                         |LMN|  |VMN|
                                         +-+-+  +-+-+
                               CoA1    3:1:1::8  3:1:1::9
                               CoA2              2:1::9


       Figure 2. Prefix Delegation for Route Optimization

   After the PD, the routing table of routers is updated. It is possible
   because each router has information about delegated prefix.













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4. Neighbor Discovery extension : Delegated Prefix option format

   This specification defines a new option, the Delegated Prefix option,
   for the Neighbor Discovery protocol of IPv6. The option format is
   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     | Prefix Length |L|A| Reserved1 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Valid Lifetime                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Preferred Lifetime                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Reserved2                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +
       |                                                               |
       +                            Prefix                             +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 2. Delegated Prefix Option Format for Route Optimization


       Fields:

         Type         XXX [TBD: IANA]

         Prefix       Delegated Prefix. The Prefix Length field contains
                      the number of valid leading bits in the prefix.
                      The bits in the prefix after the prefix length
                      are reserved and MUST be initialized to zero by
                      the sender and ignored by the receiver

   The Delegated Prefix option provides mobile nodes with on-link prefix
   of access network and prefix for address autoconfiguration of CoA.
   The Delegated Prefix option appears in Router Advertisement packets
   and MUST be silently ignored for other messages.








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5. Mobile IPv6 extension : Process of Delegated Prefix option

   MN scans all options in received router advertisement message. To
   initiate Route Optimization MN operation MUST be extended as follows:

   (1)Process the new RA option, Delegated Prefix option: MN forms CoA
      using the prefix.
   (2)Use the CoA as primary CoA.

   MN performs registration procedure according to the Mobile IPv6
   protocol. Even if LMN is on home link, it SHOULD make new CoA using
   the DP and SHOULD perform binding updates to HA and CN. In this case,
   deregistration SHOULD NOT be performed.

   There is no change of HA and CN operations.


6. Handover Considerations

   When a MR moves into another AR and detects movement, it SHOULD NOT
   return prefix delegated from the old AR immediately. It takes some
   time to find out whether the new AR supports PD or not. Moreover, MR
   can fail in PD for several reasons. Therefore, some considerations
   are needed for smooth handover.


7. Security Considerations

   Because the mechanism described in this document needs to exchange PD
   message between a MR and its AR, AAA MAY be used to authenticate MR.


8. Consideration for Optimization of DNS Name Resolution

   The optimization of DNS name resolution is possible if mobile router
   announces the address of local recursive DNS server as well as prefix
   information through RA message. The DNS server can exist either
   within mobile network or within access network. The address of
   recursive DNS server is delivered to mobile nodes through Recursive
   DNS Server option, one of RA options [10].


9. Applicability Statements

   Proposed mechanism in this draft is applicable to large, hierarchical
   and stable mobile network such as train or airplane because it takes
   some time to configure and update new CoA by prefix delegation
   protocol. Those mobile networks do not change its topology frequently


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   so it reduces time to be consumed for prefix delegation whenever the
   topology changes in the mobile network.


10. References

   [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP9,
       RFC 2026, October 1996.

   [2] Thierry Ernst, "Network Mobility Support Terminology", draft-
       ietf-nemo-terminology-00.txt, May 2003.

   [3] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6",
       draft-ietf-mobileip-ipv6-24.txt, June 2003.

   [4] J. Manner and M. Kojo, "Mobility Related Terminology", draft-
       ietf-seamoby-mobility-terminology-05.txt, Nov 2003.

   [5] Nathan Lutchansky, "IPv6 Router Advertisement Prefix Delegation
       Option", draft-lutchann-ipv6-delegate-option-00.txt, Aug 2002.

   [6] B. Haberman, "Automatic Prefix Delegation Protocol for Internet
       Protocol Version 6 (IPv6)", draft-haberman-ipngwg-auto-prefix-
       02.txt, Aug 2002.

   [7] O. Troan and R. Droms, "IPv6 Prefix Options for DHCPv6", draft-
       troan-dhcpv6-opt-prefix-delegation-00.txt, Aug 2002.

   [8] Vijay Devarapalli, Ryuji wakikawa, Alexandru Petrescu and Pascal
       Thubert, "Network Mobility (NEMO) Basic Support Protocol",
       draft-ietf-nemo-basic-support-02.txt, Dec 2003.

   [9] Jaehoon Jeong, Soohong D. Park, Luc Beloeil and Syam Madanapalli,
       "IPv6 DNS Discovery based on Router Advertisement", draft-jeong-
       dnsop-ipv6-dns-discovery-01.txt, Feb 2004.

   [10] Byung-Yeob Kim, Kyeong-Jin Lee, Jung-Soo Park and Hyoung-Jun Kim,
       "Hierarchical Prefix Delegation Protocol for Internet Protocol
       Version 6(IPv6)", draft-bykim-ipv6-hpd-01.txt, Feb 2004.


11. Authors' Addresses

   Kyeong-Jin Lee
   ETRI / PEC
   161 Gajong-Dong, Yusong-Gu
   Daejon 305-350
   Korea


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   Phone: +82 42 860 6484
   EMail: leekj@etri.re.kr

   Jae-Hoon Jeong
   ETRI / PEC
   161 Gajong-Dong, Yusong-Gu
   Daejon 305-350
   Korea

   Phone: +82 42 860 1664
   EMail: paul@etri.re.kr

   Jung-Soo Park
   ETRI / PEC
   161 Gajong-Dong, Yusong-Gu
   Daejon 305-350
   Korea

   Phone: +82 42 860 6514
   EMail: pjs@etri.re.kr

   Hyoung-Jun Kim
   ETRI / PEC
   161 Gajong-Dong, Yusong-Gu
   Daejon 305-350
   Korea

   Phone: +82 42 860 6576
   EMail: khj@etri.re.kr




















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