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Versions: 00 01                                                         
Autoconf Working Group                                         C. Jelger
Internet-Draft                                          Fraunhofer FOKUS
Expires: October 14, 2006                                 April 12, 2006


                       MANET Local IPv6 Addresses
                    draft-jelger-autoconf-mla-00.txt

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   This Internet-Draft will expire on October 14, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines how Unique Local IPv6 Unicast Addresses (RFC-
   4193) can be used in wireless mobile ad hoc networks (MANETs) as
   MANET Local IPv6 Addresses (MLAs).  MLAs are intended to be used
   inside a MANET and are not expected to be routable on the global
   Internet.  Each MANET node is expected to generate its MLA locally
   without any coordination with other MANET nodes.






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Table of Contents

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

   2.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 3

   3.  MANET Local IPv6 Addresses (MLAs) . . . . . . . . . . . . . . . 3
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.2.  Address generation  . . . . . . . . . . . . . . . . . . . . 4
     3.3.  Address scope . . . . . . . . . . . . . . . . . . . . . . . 4

   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5

   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 7




































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1.  Introduction

   This document defines a possible use of Unique Local IPv6 Unicast
   Addresses (ULAs)[1] as MANET Local IPv6 Addresses (MLAs) in wireless
   mobile ad hoc networks (MANETs).  MLAs are intended to be used inside
   a MANET and are not expected to be routable on the global Internet.
   Each MANET node is expected to generate its MLA locally, i.e. without
   any coordination with other MANET nodes.

   This extends the usage of ULAs to an extreme case where each MANET
   node is considered as being a site and subnet [1] by itself.  Since
   MANET routing is flat (i.e. it creates /128 host routes), MANET nodes
   do not necessarily need to share a network prefix for intra-MANET
   communications.  This loose addressing model allows to use a large
   fraction of the upper 64-bit part of IPv6 addresses in order to
   create addresses that are sufficiently random to avoid the use of
   duplicate address detection schemes for intra-MANET communications.


2.  Acknowledgements

   The idea of using Unique Local IPv6 Addresses as MANET Local
   Addresses has been originally discussed with a number of people
   including Ryuji Wakikawa, Francisco Ros, Robert Hinden, Brian
   Haberman and Guillaume Chelius.  Therefore the author of this
   document does not claim exclusive credit.  Also note that the
   formatting of this document is mostly inspired by [1].


3.  MANET Local IPv6 Addresses (MLAs)

3.1.  Format

   Strictly speaking, MLAs have the same format as ULAs.  The only
   difference with ULAs is that both the Global ID and Subnet ID fields
   are randomly generated.  This results in a merged 56-bit field called
   the Random ID.


     | 7 bits |1|        56 bits         |          64 bits           |
     +--------+-+------------------------+----------------------------+
     | Prefix |L|       Random ID        |        Interface ID        |
     +--------+-+------------------------+----------------------------+








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     Where:

       Prefix            FC00::/7 prefix to identify Local IPv6 unicast
                         addresses.

       L                 Set to 1. See [1] for details.

       Random ID         56-bit random identifier used to create a
                         globally unique address.

       Interface ID      64-bit Interface ID as defined in [2].

3.2.  Address generation

   To create an MLA for a given physical interface, a MANET node locally
   generates its Random ID in a random manner.  Since MANET routing is
   flat and creates /128 host routes, MANET nodes do not need to share a
   network prefix.  Hence the Random ID is used in addition to the
   Interface ID in order to create unique addresses (with a very high
   probability of uniqueness).  Using 56 bits gives around 7.2e+16
   possible values for the Random ID, hence drastically reducing the
   probability of an address collision if two nodes having the same
   Interface ID generate the same Random ID.

   The probability of an address collision is further reduced by the use
   of EUI-64 identifiers as Interface IDs.  EUI-64 that derive from
   EUI-48 (e.g.  IEEE 802 48-bit MAC addresses) are indeed expected to
   be globally unique, while randomly generated identifiers [3] have an
   extremely low collision probability (around 1.8e+19 possible values).

   Given the network size currently being considered within the MANET
   community (a few hundred nodes), and given the extremely large
   randomness of MLAs, a node must not necessarily check whether a
   generated MLA is unique.  The overhead of performing duplicate
   address detection (DAD) greatly superseeds its gain since the
   probability of address collisions is extremely low.

   Nevertheless, a passive DAD technique could be used in order to
   detect address collisions, eventhough such events are very unlikely
   to occur.  This extra mechanism is however out of the scope of this
   document.

3.3.  Address scope

   As Unique Local IPv6 Unicast Addresses, MANET Local Addresses have a
   global scope.  However MLAs are not globally routeable, and their use
   is restricted inside a MANET.  Since there does not exist any
   standardized definition of the boundaries of a MANET, we assume that



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   the use of MLAs is restricted to the set of MANET nodes (or routing
   instances) willing to route packets using MLAs.  This assumes that a
   MANET routing protocol should always be willing to route packets
   whose source and/or destination addresses are MLAs.

4.  References

   [1]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
        Addresses", RFC 4193, October 2005.

   [2]  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

   [3]  Narten, T. and R. Draves, "Privacy Extensions for Stateless
        Address Autoconfiguration in IPv6", RFC 3041, January 2001.




































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Author's Address

   Christophe Jelger
   Fraunhofer Institute FOKUS
   Kaiserin-Augusta-Allee 31
   Berlin  10589
   Germany

   Phone: +49 30 3463 7137
   Email: cje@fokus.fraunhofer.de









































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   Internet Society.




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