Internet DRAFT - draft-baek-nemo-nested-ro

draft-baek-nemo-nested-ro






NEMO Working Group                                               S. Baek
Internet-Draft                                                    J. Yoo
Expires: April 20, 2006                                          T. Kwon
                                               Seoul National University
                                                                 E. Paik
                                                                  M. Nam
                                                                      KT
                                                        October 17, 2005


         Routing Optimization in the same nested mobile network
                    draft-baek-nemo-nested-ro-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes a nested NEMO Route Opimization (NNRO)
   protocol for the communications between any two nodes in the same
   nested mobile network.  A nested NEMO Route Opimization message is
   used to exchange the routing information between two mobile network



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   nodes in the same nested mobile network.  The protocol is designed in
   a way such that the mobility of the entire nested mobile network is
   transparent to the nodes therein.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3

   3.  Overview of NNRO Operation . . . . . . . . . . . . . . . . . .  4

   4.  Changes to Existing Protocol . . . . . . . . . . . . . . . . .  4
     4.1   IPv6 Neighbor Discovery  . . . . . . . . . . . . . . . . .  4
     4.2   Conceptual Data Sturctures in Mobile Router  . . . . . . .  5

   5.  Message Formats for Route Optimization . . . . . . . . . . . .  6
     5.1   Nested NEMO Route Optimization Message . . . . . . . . . .  6

   6.  Operations of Mobile Routers . . . . . . . . . . . . . . . . .  8
     6.1   Sending NNRO Messages  . . . . . . . . . . . . . . . . . .  8
     6.2   Updating Forwading Table . . . . . . . . . . . . . . . . .  8
     6.3   Forwarding Packets . . . . . . . . . . . . . . . . . . . .  9

   7.  Design Considerations  . . . . . . . . . . . . . . . . . . . .  9
     7.1   Compatability with VMN . . . . . . . . . . . . . . . . . .  9
     7.2   Mobility Considerations  . . . . . . . . . . . . . . . . .  9

   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9

       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10

       Intellectual Property and Copyright Statements . . . . . . . . 12


















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1.  Introduction

   A mobile network (NEMO) is a network whose point of attachment to the
   Internet varies as it moves about [1, 2].  A mobile network consists
   of mobile routers (MRs) and mobile network nodes (MNNs).  When the
   mobile network changes its point of attachment, the MNNs can
   communicate with corresponding nodes without need to know about the
   movements.  To do this, all traffic to and from MNNs is forwarded
   through the bi-directional tunnel between the MR and MR's home agent
   (HA).  Therefore, sub-optimality occurs in the path between the two
   nodes [3].  When the mobile network is nested, this sub-optimality is
   amplified as all the traffic between two nodes should be routed
   through the HAs of the nested MRs.  Especially, when the two nodes
   are within a nested mobile network, the sub-optimality is notable
   although the two nodes are located within the same nested mobile
   network.  Besides, this sub-optimality causes the tunneling overhead.

   This document proposes a nested NEMO routing optimization (NNRO)
   protocol to improve the communication overhead between two MNNs
   within the same nested mobile network.  This protocol makes the
   traffic between two MNNs in the same nested NEMO to be routed
   directly without a traversing HAs of the nested MRs.

2.  Terminology

   MR

      mobile router.


   HA

      home agent.


   MNN

      mobile network node.  MNNs such as VMN and LFN are nodes in a
      mobile network.


   VMN

      visiting mobile node.  A VMN is temporarily attached to the MR's
      subnet by obtaining its CoA from the mobile network prefix.






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   LFN

      visiting mobile node. local fixed node.  This belongs to the
      mobile network and is unable to change its point of attachment.


3.  Overview of NNRO Operation

   An MR multicasts route optimization messages that contain reachable
   destinations and their path metrics to the MR's one hop neighbor MRs.
   The route optimization messages are transmitted by an IPv6 Link Local
   Multicast to the MR's lower MRs in ingress interface and by an
   unicast to the MR's upper MR in egress interface.  After the neighbor
   (lower and upper) MRs receive these route optimization messages, they
   transmit not only their own information of reachable destinations but
   also the received information from their neighbors.  Consquently, the
   information of mobile network prefixes is delivered to all of the MRs
   in the nested mobile network.

   Based on this information, the MRs in the nested mobile network
   construct forwarding tables for the mobile network prefixes in the
   nested mobile network.  Each forwarding table has entries, each of
   which contains the mobile network prefix, the path metric of the
   destination, the next hop, and the life time of the entry.  Before
   the MR forwards packets through the bi-directional tunnel, it
   searches the forwarding table.  If the MR finds out an entry that
   matches the destination of the packet, it forwards the packet to the
   next hop MR, not performing the bi-directional tunneling with its HA.
   Otherwise, the MR acts as specified in NEMO basic support protocol
   [2].

4.  Changes to Existing Protocol

   The proposed NNRO protocol requires some modifications for NEMO basic
   support protocol [2] and IPv6 Neighbor Discovery protocol [5].

4.1  IPv6 Neighbor Discovery

   A new flag (N) is included in the Router Advertisement Message to
   indicate to the MRs in the ingress interface whether the MR supports
   NNRO protocol in the same nested NEMO or not [5].










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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      |     Code      |          Checksum             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Cur Hop Limit |M|O|N| Reserved|       Router Lifetime         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                         Reachable Time                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          Retrans Timer                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |   Options ...
        +-+-+-+-+-+-+-+-+-+-+-+-


   Route Optimization in the same nested NEMO flag (N)

      The N flag is set to indicate to the MRs in the egress interface
      whether the sending MR supports the Route Opimization in the same
      neseted NEMO.

   For descriptions of the other fields in the message, see [5].

4.2  Conceptual Data Sturctures in Mobile Router

   An MR maintains a Forwarding Table, described in section 3.  The
   Forwarding Table is a data structure that records the reachability to
   the MNNs in the same nested mobile network.  There is one entry per
   each Mobile Network Prefix.

   Each Forwarding Table Entry (FTE) conceptually contains the following
   fields:

   o  The Mobile Network Prefix of the MRs in the same nested mobile
      network.  This field is used as the key for searching the
      Forwarding Table for the destination address of a packet being
      forwarded.


   o  The metric field is the cost at which the next hop MR can deliver
      packets to the destination.


   o  The next hop field is the address of the MR to which packets are
      forwarded.






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   o  A lifetime value, indicating the remaining lifetime for this FTE.
      The lifetime value is updated whenever NNRO messages are received.


5.  Message Formats for Route Optimization

5.1  Nested NEMO Route Optimization Message

   The Nested NEMO Route Optimization (NNRO) message is used by an MR to
   notify other MRs in the same nested NEMO of a recheability for the
   entries.  Each MR that supports nested NEMO Route Optimization has a
   process that sends and receives this NNRO message.

   The NNRO message will use a new MH Type value (say 11).  The format
   of the Message Data field in the Mobility Header is as follows [4]:



       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
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |D|R|P|         |  # of entries |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                Forwarding Table Entry 1 (20)                  ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                             ...                               ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                Forwarding Table Entry N (20)                  ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   where each Forwarding Table Entry (FTE) has the following format:












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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                    Mobile Network Prefix                      ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Prefix Length |    Metric     |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   Default (D)

      The Default (D) bit is set by the sending MR when it sends NNRO
      messages periodically.


   Request (R)

      The Request (R) bit is set by the sending MR to request that one
      hop neighbor MRs should send its whole FTE.


   Response (P)

      The Response (P) bit is set when the MR responds to the NNRO
      message with the R bit set.


   # of entries

      The number of entries indicates the number of entries in the NNRO
      message.


   Mobile Network Prefix

      A sixteen-byte field containing the Mobile Network Prefix.


   Prefix Length

      Eight-bit unsigned integer indicating the prefix length of the
      IPv6 prefix contained in the FTE.






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   Metric

      Eight-bit unsigned integer indicating the cost to reach that
      destination.


6.  Operations of Mobile Routers

6.1  Sending NNRO Messages

   The MR sends the NNRO messages to its ingress interface and its
   egress interface periodically.  When the MR sends NNRO messages to
   its ingress interface and its egress interface, the source IP address
   field of that packet is set to the HoA and the CoA of the MR,
   respectively.  When an MR starts its operation, there is only one
   entry in the Forwarding Table, which contains its own mobile network
   prefix.  As the NNRO messages from other MRs propagates, the number
   of entries FTE will be incremented.

   An MR updates its Forwarding Table as described in Section 6.2.  When
   the Forwarding Table is updated, the MR sends the NNRO message
   containing the updated FTEs immediately.

6.2  Updating Forwading Table

   Initially, an MR has an entry about its Mobile Network Prefix in the
   Forwarding Table.  This entry has the minimum Metric value.  When an
   MR receives the NNRO messages from its neighbor MRs, it updates its
   Forwarding Table based on the following criterion.

   New FTE:

      When an MR receives the FTE that is not in the its Forwarding
      Table, it inserts a new entry for that destination.


   Better Metric FTE :

      When an MR receives an entry with a better metric, it modifies the
      Metric and the Next Hop values of the existing entry.


   Otherwise :

      Otherwise, an MR ignores the FTE.

   When inserting the new entries or modifying the exsting entries, the
   MR sets the Next Hop to the source IPv6 address of the NNRO messages.



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6.3  Forwarding Packets

   When the MR receives a data packet, it searches the Forwarding Table
   to find out entries that matches the destination IPv6 address of the
   packet before the MR forwards the packet through the bi-directional
   tunnel.  If the MR finds out the matched entry, it forwards the
   packet to the MR Next Hop in the Forwarding Table without tunneling.
   Otherwise, the MR forwards the packet through the bi-directional
   tunnel based on the NEMO basic support protocol [2].

7.  Design Considerations

7.1  Compatability with VMN

   Besides communication between an LFN and another LFN in the same
   nested mobile network, the proposed NNRO protocol supports route
   opimization between an LFN and a VMN or between a VMN and another
   VMN.  VMNs conforms to Mobile IPv6 protocol [4].  According to Moble
   IPv6 protocol, a mobile node can establish optimal route through
   binding uptate directly to the correspondent node.  After the
   procedure of binding update to the correspondent node, the
   destination address of the packet is the CoA of the VMN using type 2
   routing header when the LFN sends packets to the VMN in the same
   nested mobile network.  Therefore, the MR used by the VMN can forward
   the packet to the VMN by searching the Forwarding Table.

7.2  Mobility Considerations

   If the entire nested mobile network moves together and changes its
   point of attachment, the additional operations in the nested mobile
   network are not needed.  The MRs in the nested mobile network are
   transparent to this movement.  However, if an MR in the nested mobile
   network goes away, the topology of the nested mobile network is
   changed, and  the Forwarding Table Entry of the MR in the other MRs
   will be deleted.

8.  References

   [1]  Ernst, T. and H. Lach, "Network Mobility Support Terminology",
        draft-ietf-nemo-terminology-03 (work in progress),
        February 2005.

   [2]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
        "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
        January 2005.

   [3]  Ng, C., "Network Mobility Route Optimization Problem Statement",
        draft-ietf-nemo-ro-problem-statement-01 (work in progress),



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        October 2005.

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

   [5]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
        for IP Version 6 (IPv6)", RFC 2461, December 1998.


Authors' Addresses

   Sungmin baek
   Seoul National University
   Multimedia and Mobile Communications Lab., Seoul National Univ.
   Shillim-dong, Kwanak-gu
   Seoul  151-744
   Korea

   Phone: +82-2-880-9147
   Fax:   +82-872-2045
   Email: smbaek@mmlab.snu.ac.kr
   URI:   http://mmlab.snu.ac.kr/~smbaek/


   Jinkyu Yoo
   Seoul National University
   Multimedia and Mobile Communications Lab., Seoul National Univ.
   Shillim-dong, Kwanak-gu
   Seoul  151-744
   Korea

   Phone: +82-2-880-9147
   Fax:   +82-872-2045
   Email: jkyoo@mmlab.snu.ac.kr
   URI:   http://mmlab.snu.ac.kr/~jkyoo/
















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   Taekyoung Kwon
   Seoul National University
   Multimedia and Mobile Communications Lab., Seoul National Univ.
   Shillim-dong, Kwanak-gu
   Seoul  151-744
   Korea

   Phone: +82-2-880-9105
   Fax:   +82-872-2045
   Email: tkkwon@snu.ac.kr
   URI:   http://mmlab.snu.ac.kr/~tk/


   Eunkyoung Paik
   KT
   Portable Internet Team, Convergence Business Unit, KT
   17 Woomyeon-dong, Seocho-gu
   Seoul  137-792
   Korea

   Phone: +82-2-526-5233
   Fax:   +82-2-526-5200
   Email: euna@kt.co.kr
   URI:   http://mmlab.snu.ac.kr/~eun/


   Minji Nam
   KT
   Portable Internet Team, Convergence Business Unit, KT
   17 Woomyeon-dong, Seocho-gu
   Seoul  137-792
   Korea

   Phone: +82-2-526-6121
   Fax:   +82-2-526-5200
   Email: mjnam@kt.co.kr
   URI:   http://mmlab.snu.ac.kr/~mjnam/














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