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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 RFC 5558

Network Working Group                                         F. Templin
Internet-Draft                                                S. Russert
Intended status: Informational                                     S. Yi
Expires: August 7, 2008                             Boeing Phantom Works
                                                        February 4, 2008


                        MANET Autoconfiguration
                   draft-templin-autoconf-dhcp-11.txt

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   This Internet-Draft will expire on August 7, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   Mobile Ad-hoc Networks (MANETs) connect routers on links with
   asymmetric reachability characteristics, and may also connect to
   other networks including the Internet.  Routers in MANETs must have a
   way to automatically provision IP addresses/prefixes and other
   information.  This document specifies mechanisms for MANET
   autoconfiguration; both IPv4 and IPv6 are discussed.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  MANET Autoconfiguration  . . . . . . . . . . . . . . . . . . .  6
     3.1.  MANET Router (MNR) Operation . . . . . . . . . . . . . . .  6
       3.1.1.  MANET Local Address (MLA) Configuration  . . . . . . .  6
       3.1.2.  MNBR List Discovery  . . . . . . . . . . . . . . . . .  7
       3.1.3.  VET Interface Configuration  . . . . . . . . . . . . .  7
       3.1.4.  Reachability Confirmation  . . . . . . . . . . . . . .  7
       3.1.5.  MNBR-Aggregated Address/Prefix Autoconfiguration . . .  8
       3.1.6.  Nomadic IPv6 Prefixes  . . . . . . . . . . . . . . . .  9
       3.1.7.  Self-Generated IPv6 Interface Identifiers  . . . . . .  9
       3.1.8.  Forwarding Packets to Off-MANET Destinations . . . . . 10
     3.2.  MANET Border Router (MNBR) Operation . . . . . . . . . . . 10
     3.3.  MANET Flooding . . . . . . . . . . . . . . . . . . . . . . 10
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   6.  Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Duplicate Address Detection (DAD) Considerations  . . 14
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
   Intellectual Property and Copyright Statements . . . . . . . . . . 18























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1.  Introduction

   Mobile Ad-hoc Networks (MANETs) connect MANET Routers (MNRs) on links
   with asymmetric reachability characteristics (see: [RFC2461], Section
   2.2).  MNRs may participate in a routing protocol over MANET
   interfaces to discover routes across the MANET using multiple Layer-2
   or Layer-3 forwarding hops if necessary.  MANETs may also connect to
   other networks including the Internet via MANET Border Routers
   (MNBRs), and MNRs may be multiple hops away from their nearest MNBR
   in some scenarios.  A MANET may be as simple as a small collection of
   MNRs (and their attached networks); a MANET may also contain other
   MANETs and/or be a subnetwork of a larger MANET.

   MANETs that comprise homogeneous link types can configure the routing
   protocol to operate as a sub-IP layer mechanism such that IP sees the
   MANET as an ordinary shared link the same as for a (bridged) campus
   LAN.  In that case, a single IP hop is sufficient to traverse the
   MANET without IP layer encapsulation.

   MANETs that comprise heterogeneous link types must instead (or, in
   addition) provide a routing service that operates as an IP layer
   mechanism to accommodate media types with dissimilar Layer-2 address
   formats and maximum transmission units (MTUs).  In that case,
   multiple IP hops may be necessary to traverse the MANET such that
   specialized autoconfiguration procedures are necessary to avoid
   multilink subnet issues [RFC4903].  In particular, we describe herein
   the use of a virtualized link that spans the MANET, to avoid the
   multilink subnet issues that arise when MANET interfaces are used
   directly by applications.

   Conceptually, a MNR embodies a router entity that connects its
   attached networks to MANETs and/or other networks including the
   Internet (see: Figure 1).  The router entity also connects to an
   imaginary Virtual Ethernet (VET) that sees the MANET as a fully-
   connected shared link.  For each distinct MANET to which they
   connect, MNRs discover a list of MNBRs that determines the MANET's
   identity.  An MNR (and its attached networks) is a "site" unto
   itself, therefore a MANET is a "site-of-sites".

   This document specifies mechanisms and operational practices for
   MANET autoconfiguration with multilink subnet avoidance.  Operation
   using standard DHCP
   [RFC2131][I-D.ietf-dhc-subnet-alloc][RFC3315][RFC3633] and neighbor
   discovery [RFC1256][RFC2461][RFC2462] mechanisms is assumed unless
   otherwise specified.  Both IPv4 [RFC0791] and IPv6 [RFC2460] are
   discussed.





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2.  Terminology

   The terminology in [I-D.ietf-autoconf-manetarch] and the normative
   references apply.  The following terms are defined within the scope
   of this document:

   subnetwork
      the same as defined in [RFC3819].

   egress/ingress interface
      the same as defined in ([RFC3753], Section 3).  Note that in some
      MANET scenarios, an interface may dynamically switch from being an
      ingress interface to being an egress interface, and vice-versa.

   Mobile Ad-hoc Network (MANET)
      a connected network region of MANET routers that maintain a
      routing structure among themselves over asymmetric reachability
      links (see: [RFC2461], Section 2.2).  A MANET may be as simple as
      a small collection of MNRs (and their attached networks); a MANET
      may also contain other MANETs and/or be a subnetwork of a larger
      MANET.  A MANET router (and its attached networks) is a site unto
      itself, and a MANET is therefore a site-of-sites.

      Further information on the characteristics of MANETs can be found
      in [RFC2501].

   MANET Router (MNR)
      a mobile router that forwards packets on behalf of both other MNRs
      over its MANET interfaces and networks attached on its ingress
      interfaces.  A MNR can also forward packets to other networks
      either directly via its egress interfaces or indirectly via an
      MNBR.  For the purpose of this specification, an MNR comprises a
      router entity, one or more host entities, and its attached
      ingress/egress/MANET interfaces (see: Figure 1).

   MANET Border Router (MNBR)
      an MNR that connects a MANET to other networks, including the
      Internet.  MNBRs that configure egress interfaces can delegate
      addresses/prefixes to other MNRs.

   MANET Interface
      a MANET Router's attachment to a link in a MANET.  A MANET
      interface is "neutral" in its orientation, i.e., it is inherently
      neither egress nor ingress.  In particular, a packet may need to
      traverse several MANET interfaces before it is forwarded via
      either an egress or ingress interface.





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   MANET Local Address (MLA)
      an address configured by an MNR that is unique within the MANET;
      it is used as an identifier for operating the routing protocol and
      may also be assigned to a MANET interface as a locator for packet
      forwarding within the scope of the MANET.

   Virtual Ethernet (VET)
      an imaginary shared link that connects all MNRs in a MANET.

   VET interface
      a MNR's attachment to a VET.  Each VET interface is configured
      over a set of underlying MANET interface(s) belonging to the same
      MANET.  The VET interface encapsulates each IP packet in an outer
      IP header then forwards it over an underlying MANET interface such
      that the TTL/HOP Limit in the inner IP header is not decremented
      as the packet traverses the MANET, i.e., the VET interface views
      the MANET as a unified shared link and presents an automatic
      tunneling abstraction.

   The following figure depicts the architectural model for a MANET
   router:
                              Egress Interfaces (to Internet)
                                      x   x        x
                                      |   |        |
             +------------------------+---+--------+----------+
             | Internal hosts         |   |        |          |    M
             |  and routers           |   |  ....  |          |    A
             |       ,-.    |     +---+---+--------+---+      |    N
             |      (H1 )---+     |                   /|      |    E
             |   |   `-'    |     |                I /*+------+--< T
             | . |  +---+   |     |                n|**|      |
             | . +--|R1 |---+-----+                t|**|      |    I
             | . |  +---+   |     |    Router    V e|**+------+--< n
             |   |   ,-.    |     |              E r|**|  .   |    t
             |      (H2 )---+     |    Entity    T f|**|  .   |    e
             |       `-'    |  .  |                a|**|  .   |    r
             |                 .  |                c|**|  .   |    f
             |       ,-.       .  |                e \*+------+--< a
             |      (Hn )---------+                   \|      |    c
             |       `-'          +---+---+--------+---+      |    e
             | Ingress Interfaces     |   |  ....  |          |    s
             | (to internal networks) |   |        |          |
             +------------------------+---+--------+----------+
                                      |   |        |
                                      x   x        x
                      Ingress Interfaces (to attached networks)

                          Figure 1: MANET Router



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3.  MANET Autoconfiguration

3.1.  MANET Router (MNR) Operation

   MNRs configure egress interfaces that connect "upstream" toward fixed
   Internet infrastructure, ingress interfaces that connect "downstream"
   toward attached networks, and both MANET and VET interfaces that are
   "neutral" in the sense that the packets they forward may need to
   traverse several MANET hops before they are forwarded via either an
   egress or ingress interface.  MNRs also engage in the routing
   protocol over their MANET interfaces, and obtain addresses/prefixes
   and other autoconfiguration information using the mechanisms and
   operational practices specified in the following sections:

3.1.1.  MANET Local Address (MLA) Configuration

   Upon joining a MANET, each MNR first configures MANET Local Addresses
   (MLAs) that it will use for operating the routing protocol and/or
   assignment to MANET interfaces.

   IPv4 MLAs can be manually configured, administratively assigned,
   autoconfigured using DHCP or self-generated using a suitable pseudo-
   random IPv4 unique local address autoconfiguration mechanism.  Such a
   mechanism could be considered as a site-scoped equivalent to IPv4
   link-local addresses [RFC3927], and could delegate addresses out of a
   suitably large IPv4 prefix space such as the soon-to-be-reclassified
   240/4 space [I-D.fuller-240space].

   IPv6 MLAs can be manually configured, administratively assigned,
   autoconfigured using DHCP, autoconfigured using IPv6 StateLess
   Address AutoConfiguration (SLAAC) [RFC2462], or self-generated using
   IPv6 Unique Local Addresses (ULAs)
   [RFC4193][I-D.ietf-ipv6-ula-central].  IPv6 MLAs include interface
   identifiers that are either managed for uniqueness (e.g., see:
   [RFC4291], Appendix A) or self-generated using a suitable pseudo-
   random interface identifier generation mechanism (e.g.,
   Cryptographically Generated Addresses (CGAs) [RFC3972], IPv6 privacy
   addresses [I-D.ietf-ipv6-privacy-addrs-v2], etc.).

   When there is no manually/administratively assigned MLA, the choice
   of autoconfiguring an MLA using DHCP or self-generating one using
   some other mechanism is up to the MNR and may depend on the
   particular MANET deployment scenario.  DHCP-generated MLAs have the
   benefit of a "managed" avoidance of address collisions, while self-
   generated MLAs must be monitored for collisions with other nodes that
   might assign a duplicate.

   Since a MNR initially has no non-link-local addresses, DHCP



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   configuration of MLAs may require relay support from other MNRs that
   have already been autoconfigured within the MANET.  This means that
   MNRs with assigned MLAs should be prepared to relay another MNR's
   DHCP requests, e.g. to a site-scoped multicast address, to a unicast
   address(es), etc.

3.1.2.  MNBR List Discovery

   After configuring MLAs, the MNR next engages in any routing
   protocol(s) over its MANET interfaces and discovers the list of MNBRs
   (if any) on the MANET.  The list of MNBRs can be discovered through
   routing protocol information, or through an alternate discovery
   mechanism, e.g., per [RFC4214], Section 8.3.2.

   Identifying names/values for one or more MNBRs, and/or a set of
   address prefixes that they aggregate, serve as an identifier for the
   MANET.

3.1.3.  VET Interface Configuration

   The MNR configures a VET interface over a set of underlying MANET
   interfaces that represents a unified shared link for the MANET.  The
   VET interface autoconfigures a link-local address, e.g., an ISATAP
   link-local address ([RFC4214], Section 6.2) derived from an IPv4 MLA
   assigned to an underlying MANET interface, an IPv4 link local
   address[RFC3927], etc..  IP packets sent via the VET interface are
   encapsulated in an outer IP header then submitted to the IP
   forwarding engine for transmission on an underlying MANET interface.

   Considerations for setting the VET interface Maximum Transmission
   Unit (MTU) are discussed in [RFC4213].

3.1.4.  Reachability Confirmation

   After the MNR configures a VET interface, it can confirm reachability
   of MNRs/MNBRs and (in the case of IPv6) discover prefixes associated
   with the VET.  The MNR can confirm reachability by sending/receiving
   ordinary ND messages and/or issuing DHCP requests over the VET
   interface.  It can also confirm reachability through information
   conveyed in the routing protocol itself, or through some other means
   associated with the particular MANET subnetwork technology.

   Out of scope for this document are specific mitigations for the loss
   of MNRs/MNBRs due to e.g., network partitions, node failures, etc.
   Mechanisms such as routing protocol information, bidirectional
   forward detection, detection of network attachment, neighbor
   discovery hints of forward progress, short beaconing/polling
   intervals, etc. are candidates for further study.



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3.1.5.  MNBR-Aggregated Address/Prefix Autoconfiguration

   After the MNR discovers MNBRs, it can acquire MNBR-aggregated
   addresses/prefixes using either IPv6 Stateless Address
   AutoConfiguration (SLAAC) or DHCP.  These addresses/prefixes are
   delegated by specific MNBRs, and may be:

   o  global-scope and provider aggregated

   o  global-scope and provider-independent

   o  global-scope and 6to4 [RFC3056]

   o  unique-local scope and centrally administrated

   o  unique-local scope and locally assigned

   o  other non-link-local scope

   The following subsections discuss IPv6 SLAAC and DHCP address/prefix
   autoconfiguration considerations:

3.1.5.1.  IPv6 SLAAC

   For IPv6, MNRs can autoconfigure addresses on the VET interface based
   on Prefix Information Options in received RAs, i.e., the same as for
   ordinary IPv6 links (see: Section 3.2).

3.1.5.2.  DHCP Address/Prefix Autoconfiguration

   When DHCP is used, a DHCP client associated with the MNR's host
   entity forwards a DHCP DISCOVER (DHCPv4) or Solicit (DHCPv6) request
   to a DHCP relay associated with its router entity to request IP
   address/prefix delegations for assignment on ingress interfaces
   (i.e., the MNR acts as both DHCP client and relay).  The relay
   function then forwards the request to the unicast addresses of one or
   more MNBRs, to a site-scoped multicast address, or to another known
   DHCP server within the MANET.

   For DHCPv6, the MNR's relay function writes an address from the VET
   interface in the "peer-address" field and also writes an address from
   the prefix associated with the VET in the "link-address" field (if a
   prefix is available).  The MNR can also (or, instead) use DHCPv6
   prefix delegation [RFC3633] to obtain addresses/prefixes via MNBRs
   for assignment and/or further sub-delegation on networks connected on
   its ingress interfaces.  (Note that the MNR can obtain /128 prefixes
   using DHCP prefix delegation the same as for any IPv6 prefix.)




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   For DHCPv4, the MNR's relay function writes an address from a MANET
   interface in the 'giaddr' field.  If necessary to identify the MNR's
   ingress interface, the relay also includes a link selection sub-
   option [RFC3527] with an address from the prefix associated with the
   VET (if a prefix is available).  The MNR can also (or, instead) use
   DHCPv4 prefix delegation [I-D.ietf-dhc-subnet-alloc] to obtain
   addresses/prefixes via MNBRs for further assignment and/or further
   sub-delegation on networks connected on its ingress interfaces.
   (Note that the MNR can obtain /32 prefixes using DHCP prefix
   delegation the same as for any IPv4 prefix.)

   The DHCP request will elicit a DHCP reply from a server with IP
   address/prefix delegations that are aggregated by one or more MNBRs.
   When addresses are delegated, the MNR assigns the resulting addresses
   to an ingress interface, i.e., it does not assign the addresses on
   the VET interface or an underlying MANET interface.  When prefixes
   are delegated, the MNR can assign and/or further sub-delegate them to
   networks connected on its ingress interfaces.

   The DHCP server ensures IP address/prefix delegations that are unique
   within the MANET.  By assigning these IP addresses/prefixes only on
   ingress interfaces there is no requirement for the MNR to perform
   Duplicate Address Detection (DAD) for them over its MANET and VET
   interfaces (but see Appendix A for further DAD considerations).

3.1.6.  Nomadic IPv6 Prefixes

   Independent of any MNBR-aggregated addresses/prefixes (see:
   Section 3.1.5), MNRs can self-generate IPv6 Unique Local Address
   (ULA) prefixes [RFC4193][I-D.ietf-ipv6-ula-central] and sub-delegate
   them on networks connected on their ingress interfaces.  Similarly, a
   MNR can carry IPv6 prefixes (e.g., taken from a home network) as it
   travels between MANETs as long it coordinates in some fashion with a
   prefix aggregation authority.

   Such nomadic-use IPv6 prefixes are not aggregated, redistributed or
   advertised by MNBRs and can therefore travel with the MNR as it moves
   to new MANETs and/or configures peering arrangements with MNRs in
   other MANETs.  Generation of nomadic IPv6 prefixes can therefore
   occur independently of any other MNR autoconfiguration
   considerations.

3.1.7.  Self-Generated IPv6 Interface Identifiers

   MNR's can self-generate IPv6 interface identifiers such as specified
   for CGAs [RFC3972], IPv6 privacy address
   [I-D.ietf-ipv6-privacy-addrs-v2], etc.




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   For MNBR-aggregated address/prefix autoconfiguration (see:
   Section 3.1.5), the MNR can propose a self-generated address to the
   DHCPv6 server which will delegate the address to the MNR for
   assignment on an ingress interface if the proposed address is unique.

3.1.8.  Forwarding Packets to Off-MANET Destinations

   MNRs use the VET interface to forward IP packets to off-MANET
   destinations.

   For IPv6, MNRs can discover default router preferences and more-
   specific routes per [RFC4191] by sending unicast Router Solicitations
   over the VET interface to elicit Router Advertisements from MNBRs.
   MNRs/MNBRs should therefore include default router preferences and/or
   more-specific routes in their Router Advertisements.

   Once default routers and/or more-specific routes are discovered, the
   MNR can forward the packets via the VET interface with an MLA for an
   MNR/MNBR as the destination in the outer IP header.  When multiple
   MNR/MNBRs are available as next-hop routers on the VET interface, the
   MNR can use default router preferences, traffic engineering
   configurations, etc. to select the best exit router.

3.2.  MANET Border Router (MNBR) Operation

   MNBRs connect networks on ingress interfaces to the MANET, and may
   also connect the MANET to other networks that lead toward the
   Internet over egress interfaces.  This latter category of MNBRs can
   also delegate addresses/prefixes to other MNRs on the MANET.

   MNBRs send ordinary ND messages such as IPv6 RA messages with Route
   Information Options [RFC4191] to other MNRs over the VET interface.
   MNBRs that delegate addresses/prefixes for the MANET can also include
   link specific parameters, default router lifetimes, default router
   preferences, and Prefix Information Options for SLAAC on the VET
   interface in the IPv6 RA messages they send.

   For DHCPv6, MNBRs that delegate addresses/prefixes act as DHCP relays
   and/or servers for DHCP requests/replies.  (For DHCPv4, MNBRs may
   only act as DHCP servers, since the MLA address in the 'giaddr' field
   is not routable outside the scope of the MANET.)

3.3.  MANET Flooding

   MANETs that operate routing as an IP layer service should deploy a
   multicast flooding service (e.g., Simplified Multicast Forwarding
   (SMF) [I-D.ietf-manet-smf]) so that site-scoped multicast messages
   will be propagated across the MANET.



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4.  IANA Considerations

   A site-scoped IPv4 multicast group for: "All-MANET-Routers", or:
   "All-Site-Routers" is requested, e.g., to support MANET flooding for
   site-scoped service discovery (see: Section 3.3).


5.  Security Considerations

   Threats relating to MANET routing protocols also apply to this
   document.


6.  Related Work

   The authors acknowledge the work done by Brian Carpenter and Cyndi
   Jung in [RFC2529] that introduced the concept of intra-site automatic
   tunneling.  This concept was later called: "Virtual Ethernet" and
   investigated by Quang Nguyen under the guidance of Dr. Lixia Zhang.

   Telcordia has proposed DHCP-related solutions for the CECOM MOSAIC
   program.  The Naval Research Lab (NRL) Information Technology
   Division uses DHCP in their MANET research testbeds.  Various IETF
   AUTOCONF working group proposals have suggested similar mechanisms.


7.  Acknowledgements

   The following individuals gave direct and/or indirect input that was
   essential to the work: Jari Arkko, Teco Boot, Emmanuel Bacelli, James
   Bound, Thomas Clausen, Eric Fleischman, Bob Hinden, Joe Macker,
   Thomas Narten, Alexandru Petrescu, Jinmei Tatuya, Dave Thaler, and
   others in the IETF AUTOCONF and MANET working groups.  Many others
   have provided guidance over the course of many years.


8.  Contributors

   Thomas Henderson (thomas.r.henderson@boeing.com) contributed to this
   document.  Ian Chakeres (ian.chakeres@gmail.com) contributed to
   earlier versions of the document.


9.  References







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9.1.  Normative References

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              September 1981.

   [RFC1256]  Deering, S., "ICMP Router Discovery Messages", RFC 1256,
              September 1991.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              December 1998.

   [RFC2462]  Thomson, S. and T. Narten, "IPv6 Stateless Address
              Autoconfiguration", RFC 2462, December 1998.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, November 2005.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC4214]  Templin, F., Gleeson, T., Talwar, M., and D. Thaler,
              "Intra-Site Automatic Tunnel Addressing Protocol
              (ISATAP)", RFC 4214, October 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.







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9.2.  Informative References

   [I-D.fuller-240space]
              Fuller, V., "Reclassifying 240/4 as usable unicast address
              space", draft-fuller-240space-00 (work in progress),
              September 2007.

   [I-D.ietf-autoconf-manetarch]
              Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc
              Network Architecture", draft-ietf-autoconf-manetarch-07
              (work in progress), November 2007.

   [I-D.ietf-dhc-subnet-alloc]
              Johnson, R., "Subnet Allocation Option",
              draft-ietf-dhc-subnet-alloc-06 (work in progress),
              November 2007.

   [I-D.ietf-ipv6-privacy-addrs-v2]
              Narten, T., "Privacy Extensions for Stateless Address
              Autoconfiguration in IPv6",
              draft-ietf-ipv6-privacy-addrs-v2-05 (work in progress),
              October 2006.

   [I-D.ietf-ipv6-ula-central]
              Hinden, R., "Centrally Assigned Unique Local IPv6 Unicast
              Addresses", draft-ietf-ipv6-ula-central-02 (work in
              progress), June 2007.

   [I-D.ietf-manet-smf]
              Macker, J. and S. Team, "Simplified Multicast Forwarding
              for MANET", draft-ietf-manet-smf-06 (work in progress),
              November 2007.

   [RFC2501]  Corson, M. and J. Macker, "Mobile Ad hoc Networking
              (MANET): Routing Protocol Performance Issues and
              Evaluation Considerations", RFC 2501, January 1999.

   [RFC2529]  Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
              Domains without Explicit Tunnels", RFC 2529, March 1999.

   [RFC3527]  Kinnear, K., Stapp, M., Johnson, R., and J. Kumarasamy,
              "Link Selection sub-option for the Relay Agent Information
              Option for DHCPv4", RFC 3527, April 2003.

   [RFC3753]  Manner, J. and M. Kojo, "Mobility Related Terminology",
              RFC 3753, June 2004.

   [RFC3819]  Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,



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              Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
              Wood, "Advice for Internet Subnetwork Designers", BCP 89,
              RFC 3819, July 2004.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              May 2005.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4903]  Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
              June 2007.


Appendix A.  Duplicate Address Detection (DAD) Considerations

   Pre-service DAD for an MLA assigned on a MANET interface (such as
   specified in [RFC2462]) would require either flooding the entire
   MANET or somehow discovering a link in the MANET on which a node that
   configures a duplicate address is attached and performing a localized
   DAD exchange on that link.  But, the control message overhead for
   such a MANET-wide DAD would be substantial and prone to false-
   negatives due to packet loss and node mobility.  An alternative to
   pre-service DAD is to autoconfigure pseudo-random MLAs on MANET
   interfaces and employ a passive in-service DAD (e.g., one that
   monitors routing protocol messages for duplicate assignments).

   Pseudo-random IPv6 MLAs can be generated with mechanisms such as
   CGAs, IPv6 privacy addresses, etc. with very small probability of
   collision (but, IPv6 ULAs also provide an additional 40 pseudo-random
   bits in the prefix).  Pseudo-random IPv4 MLAs can be generated
   through random assignment from a suitably large IPv4 prefix space,
   e.g., the soon-to-be-reclassified 240/4 space [I-D.fuller-240space].

   Statistical properties for pseudo-random address self-generation can
   assure uniqueness for the MLAs assigned on a MNR's MANET interfaces,
   and consistent operational practices can assure uniqueness for MNBR-
   aggregated addresses/prefixes.  However, a passive in-service DAD
   mechanism should still be used to detect duplicates that were
   assigned through other means, e.g., manual configuration.







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Appendix B.  Change Log

   (Note to RFC editor - this section to be removed before publication
   as an RFC.)

   Changes from -10 to 11:

   o  removed the transparent/opaque VET portal abstractions.

   o  removed routing header as an option for MANET exit router
      selection.

   o  included IPv6 SLAAC as an endorsed address configuration mechanism
      for the VET interface.

   Changes from -08 to -09:

   o  Introduced the term "VET".

   o  Changed address delegation language to speak of "MNBR-aggregated"
      instead of global/local.

   o  Updated figures 1-3.

   o  Explained why a MANET interface is "neutral".

   o  Removed DHCPv4 "MLA Address option".  Now, MNBRs can only be
      DHCPv4 servers; not relays.

   Changes from -07 to -08:

   o  changed terms "unenhanced" and "enhanced" to "transparent" and
      "opaque".

   o  revised MANET Router diagram.

   o  introduced RFC3753 terminology for Mobile Router; ingress/egress
      interface.

   o  changed abbreviations to "MNR" and "MNBR".

   o  added text on ULAs and ULA-Cs to "Self-Generated Addresses".

   o  rearranged Section 3.1.

   o  various minor text cleanups

   Changes from -06 to -07:



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   o  added MANET Router diagram.

   o  added new references

   o  various minor text cleanups

   Changed from -05 to -06:

   o  Changed terms "raw" and "cooked" to "unenhanced" and "enhanced".

   o  minor changes to preserve generality

   Changed from -04 to -05:

   o  introduced conceptual "virtual ethernet" model.

   o  support "raw" and "cooked" modes as equivalent access methods on
      the virutal ethernet.

   Changed from -03 to -04:

   o  introduced conceptual "imaginary shared link" as a representation
      for a MANET.

   o  discussion of autonomous system and site abstractions for MANETs

   o  discussion of autoconfiguration of CGAs

   o  new appendix on IPv6 StateLess Address AutoConfiguration

   Changes from -02 to -03:

   o  updated terminology based on RFC2461 "asymmetric reachability"
      link type; IETF67 MANET Autoconf wg discussions.

   o  added new appendix on IPv6 Neighbor Discovery and Duplicate
      Address Detection

   o  relaxed DHCP server deployment considerations allow DHCP servers
      within the MANET itself

   Changes from -01 to -02:

   o  minor updates for consistency with recent developments

   Changes from -00 to -01:





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   o  new text on DHCPv6 prefix delegation and multilink subnet
      considerations.

   o  various editorial changes


Authors' Addresses

   Fred L. Templin
   Boeing Phantom Works
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124
   USA

   Email: fltemplin@acm.org


   Steven W. Russert
   Boeing Phantom Works
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124
   USA

   Email: steven.w.russert@boeing.com


   Seung Yi
   Boeing Phantom Works
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124
   USA

   Email: seung.yi@boeing.com


















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Full Copyright Statement

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