Network Working Group                                         F. Templin
Internet-Draft                                                S. Russert
Intended status: Informational                               I. Chakeres
Expires: September 3, 2007                                         S. Yi
                                                    Boeing Phantom Works
                                                           March 2, 2007


                        MANET Autoconfiguration
                   draft-templin-autoconf-dhcp-07.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   Mobile Ad-hoc Networks (MANETs) consist of routers operating over
   multihop wireless links, and may or may not connect to other networks
   and/or the Internet.  Routers in MANETs must have a way to
   automatically provision local and global-use IP addresses/prefixes.
   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 (MR) Operation  . . . . . . . . . . . . . . .  6
     3.2.  MANET Border Router Operation  . . . . . . . . . . . . . .  9
     3.3.  DHCP Server Extensions . . . . . . . . . . . . . . . . . .  9
     3.4.  MLA Encapsulation  . . . . . . . . . . . . . . . . . . . . 10
     3.5.  MANET Flooding . . . . . . . . . . . . . . . . . . . . . . 10
     3.6.  Self-Generated Addresses . . . . . . . . . . . . . . . . . 10
     3.7.  Changes to the Neighbor Discovery Model  . . . . . . . . . 11
   4.  Operation with Multiple MBRs . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 12
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  IPv6 Neighbor Discovery (ND) and Duplicate
                Address Detection (DAD) . . . . . . . . . . . . . . . 14
   Appendix B.  IPv6 StateLess Address AutoConfiguration (SLAAC)  . . 15
   Appendix C.  Change Log  . . . . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
   Intellectual Property and Copyright Statements . . . . . . . . . . 18

























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1.  Introduction

   Mobile Ad-hoc Networks (MANETs) comprise links with asymmetric
   reachability characteristics (see: [RFC2461], Section 2.2) that
   connect MANET Routers (MRs).  MRs participate in a routing protocol
   to discover routes for forwarding packets across the MANET using
   multiple Layer-2 and/or Layer-3 hops if necessary.  MANETs may
   connect to other networks via MANET Border Routers (MBRs), and MRs
   may be multiple IP hops away from their nearest MBR in some
   scenarios.  A MANET may be as large as an Autonomous System (AS) or
   as small as an individual site.  A MANET may contain other MANETs
   and/or fixed networks, and a MANET may also be a subnetwork of a
   larger site.  MRs that connect downstream-attached links must have a
   means to automatically provision local and global-use IP addresses/
   prefixes and/or other configuration information.

   Conceptually, MRs embody a router entity linked to one or more host
   entities by virtual point-to-point interfaces (see: Figure 1).  The
   router entity also connects to an imaginary shared link (i.e., a
   "virtual ethernet") that connects all MRs in the MANET (see: Figure 2
   and Figure 3).  An "enhanced" view of this virtual ethernet sees the
   MANET as a fully-connected shared link that connects all MRs, while
   an "unenhanced" view sees the MANET as a multilink site.  For each
   MANET to which they connect, MRs discover a list of MBRs; this list
   determines the MANET's identity.  An MR (and its downstream-attached
   links) is a "site" unto itself, and a MANET is therefore a "site-of-
   sites".

   MANETs that comprise homogeneous link types can configure the routing
   protocol to operate as a sub-IP layer mechanism such that IP (i.e.,
   Layer-3) 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.

   MANETs that comprise heterogeneous link types must instead (or, in
   addition) provide a routing service that operates as a Layer-3
   mechanism based on MANET-local Addresses (MLAs) or other identifiers
   that are unique within the MANET to avoid issues associated with
   bridging 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.

   This document specifies mechanisms and operational practices for
   MANET autoconfiguration.  Operation using standard BOOTP/DHCP
   [RFC0951][RFC2131][RFC3315][RFC3633] and neighbor discovery
   [RFC0826][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:

   Mobile Ad-hoc Network (MANET)
      a connected network region that comprises MANET routers that
      maintain a routing structure among themselves over links with
      asymmetric reachability characteristics (see: [RFC2461], Section
      2.2).  A MANET may be as large as an Autonomous System (AS) or as
      small as an individual site, and may also be a subnetwork of a
      larger site.  A MANET router (and its downstream-attached links)
      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 (MR)
      a node that participates in a routing protocol over its MANET
      interface(s) and forwards packets on behalf of both other MRs and
      nodes on its other attached links.  Conceptually, an MR embodies a
      router entity linked to one or more host entities by virtual
      point-to-point interfaces, plus any other physical or virtual
      interfaces connected to other links (see: Figure 1).  For the
      purpose of this specification, an MR's host entity configures a
      DHCP client and its router entity configures a DHCP relay.

   MANET Border Router (MBR)
      an MR that connects the MANET to other networks.  For the purpose
      of this specification, MBRs are assumed to configure a DHCP relay
      and/or a DHCP server.

   MANET Local Address (MLA)
      a Layer-3 unicast address configured by an MR 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.
      For IPv6, Unique Local Addresses (ULAs)
      [RFC4193][I-D.jelger-autoconf-mla] provide a natural MLA
      mechanism.

   MANET Interface
      a MR's attachment to a link in a MANET.

   virtual ethernet
      an imaginary shared link that connects the MRs in a MANET.  MRs
      attach to the virtual ethernet via an interface configured over
      underlying MANET interface(s) that provides both enhanced and



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      unenhanced "portals" (see: Figure 2 and Figure 3).

      The enhanced portal encapsulates each IP packet in an outer IP
      header then sends it on 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 enhanced portal views the
      MANET as a unified shared link.

      The unenhanced portal sends each IP packet on an underlying MANET
      interface without further encapsulation such that the TTL/Hop
      Limit may be decremented as the packet traverses the MANET, i.e.,
      the unenhanced portal views the MANET as a multilink site.

   Extended Neighbor Discovery (END) message
      an IP Neighbor Discovery (ND) message [RFC1256] [RFC2461]
      transmitted on the unenhanced portal of the MR's virtual ethernet
      interface with an MLA of the underlying MANET interface as a
      source address and the destination address set to an MLA or a
      site-scoped multicast address.  The TTL/Hop Limit in END messages
      may be decremented as the message traverses the MANET.

   The following figure depicts the architectural model for a MANET
   router:

                    \ | /   \ | /       \ | /
                     \|/     \|/         \|/
                      |       |   ....    |
              +-------+-------+-----------+--------+
              |       |       |           |        |
       D I    |       |  MANET|Interfaces |        |    U I
       o n    |   +---+-------+-----------+---+    |    p n
       w t <--+---+                           +----+--> s t
       n e    |   |                           |    |    t e
       s r <--+---+       Router Entity       +----+--> r r
       t f  . | . |                           |  . | .  e f
       r a  . | . |                           |  . | .  a a
       e c  . | . +---+-------+-----------+---+  . | .  m c
       a e    |       |Virtual|P2P Intf's |        |      e
       m s    |     ,-+-.   ,-+-.       ,-+-.      |      s
              |    /Host \ /Host \     /Host \     |
              |   (Entity |Entity )...(Entity )    |
              |    \  1  / \  2  /     \  n  /     |
              |     `---'   `---'       `---'      |
              +------------------------------------+

                          Figure 1: MANET Router





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3.  MANET Autoconfiguration

   The following sections specify autoconfiguration mechanisms and
   operational practices that allow MRs to participate in the routing
   protocol and obtain addresses/prefixes for Intra-MANET and global
   Internet communications.

3.1.  MANET Router (MR) Operation

   Each MR configures MLAs used for operating the routing protocol
   and/or for assignment on MANET interfaces.  For IPv6 MANET
   interfaces, MLAs are generated using Unique Local Addresses
   [RFC4193][I-D.jelger-autoconf-mla] with interface identifiers that
   are either managed for uniqueness (e.g., per [RFC4291], Appendix A)
   or self-generated using a suitable random interface identifier
   generation mechanism that is compatible with EUI-64 format (e.g.,
   Cryptographically Generated Addresses (CGAs) [RFC3972], IPv6 privacy
   addresses [I-D.ietf-ipv6-privacy-addrs-v2], etc.).  For IPv4, MLAs
   are generated using a corresponding unique local address
   configuration mechanism.  (Such a mechanism could be considered as a
   site-scoped equivalent to IPv4 link-local addresses [RFC3927].)

   The MR next engages in the routing protocol over its MANET interfaces
   and discovers the list(s) of MBRs that identify the MANET(s).  The
   list of MBRs is discovered the same as for the ISATAP Potential
   Router List (PRL) initialization procedure [RFC4214].  One mechanism
   that can be used is Fully-Qualified Domainname (FQDN) lookup for an
   FQDN associated with the MANET (e.g., "isatap.example.com") using
   standard DNS, LLMNR [RFC4795], or node information queries [RFC4620].
   Other mechanisms include information learned from the routing
   protocol, a DHCP option, a DHCP vendor-specific option, or an
   unspecified alternate method.  If the list of MBRs is NULL, an
   alternate token (such as the IEEE MAC address of an ordinary MR) is
   used as an identifier for the MANET.

   For each MANET to which it attaches, the MR also configures a virtual
   ethernet interface over the underlying MANET interfaces connected to
   the MANET.  The enhanced portal of the virtual ethernet interface
   presents an opaque view to IP, and configures a link-local address
   that is assured to be unique among the virtual interfaces of all MRs
   in the MANET.  IP packets sent via the enhanced portal are
   encapsulated in an outer IP header then submitted to ip_output() for
   transmission on an underlying MANET interface.  The unenhanced portal
   of the virtual ethernet interface presents a transparent view to IP,
   and provides direct access to the underlying MANET interfaces and
   their associated addresses.  IP packets sent via the unenhanced
   portal are transmitted unencapsulated on an underlying MANET
   interface, but may include an IPv4 source routing header (likewise



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   IPv6 routing header) or a subnetwork-specific encapsulation.

   Figure 2 shows the protocol stack model for the virtual ethernet
   output routine, and Figure 3 shows the corresponding model for the
   virtual ethernet input routine:


       +--------------------------------------------------+   |
       |                   ip_output()                    |   |
       +--------------------------------------------------+   |
       |             virtual_ethernet_output()            |   |
       |                                                  |
       | _ unenhanced portal __   __ enhanced portal  ___ |   p
       |/                      \ /                       \|   a
       | - MANET intf already   | - select MANET intf     |   c
       |   selected by ULP      | - encapsulate in IP     |   k
       | - insert routing hdr   | - send to MANET intf    |   e
       |   (if necessary)       |   via ip_output()       |   t
       | - send directly to     +-------------------------+   s
       |   MANET intf           |       ip_output()       |
       +--------------+---------+----+-...-+--------------+   |
       | MANET Intf 0 | MANET Intf 1 | ... | MANET Intf n |   |
       |    (MLA 0)   |    (MLA 1)   | ... |    (MLA n)   |   |
       +--------------+--------------+-...-+--------------+   v

                    Figure 2: virtual_ethernet_output()


       +--------------------------------------------------+   ^
       |                    ip_input()                    |   |
       +--------------------------------------------------+   |
       |             virtual_ethernet_input()             |
       |                                                  |   p
       | _ unenhanced portal __   __ enhanced portal  ___ |   a
       |/                      \ /                       \|   c
       | - submit to ip_input() | - decapsulate packet    |   k
       |                        | - submit to ip_input()  |   e
       |                        +-------------------------+   t
       |                        |        ip_input()       |   s
       +--------------+---------+----+-...-+--------------+
       | MANET Intf 0 | MANET Intf 1 | ... | MANET Intf n |   |
       |    (MLA 0)   |    (MLA 1)   | ... |    (MLA n)   |   |
       +--------------+--------------+-...-+--------------+   |

                    Figure 3: virtual_ethernet_input()

   After the MR configures the virtual ethernet interface, it can
   confirm reachability of MBRs and (in the case of IPv6) discover



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   prefixes associated with the MANET's virtual ethernet.  It can
   confirm reachability by sending/receiving END messages over the
   unenhanced portal, by sending/receiving ordinary ND messages over the
   enhanced portal, via information conveyed in the routing protocol
   itself, or through some other means associated with the particular
   link technology.  For IPv6, prefixes can also be discovered through
   an out-of-band service discovery protocol.

   After the MR discovers MBRs, it can configure addresses/prefixes
   according to either DHCP or IPv6 Stateless Address AutoConfiguration
   (SLAAC) (but see Appendix B for further considerations on SLAAC).
   When DHCP is used, the DHCP client associated with (one of) the MR's
   host entity(s) forwards a DHCP DISCOVER (DHCPv4) or Solicit (DHCPv6)
   request to the DHCP relay associated with its router entity to
   request global IP address and/or prefix delegations (see also:
   Section 3.6).  The relay function then forwards the request to one or
   more MBRs, to other known DHCP servers, or to a site-scoped "All-
   DHCP-Servers" multicast address.

   For DHCPv6, the MR's relay function writes an address from the
   appropriate virtual ethernet interface portal in the "peer-address"
   field and also writes an address from the prefix associated with the
   virtual ethernet in the "link-address" field (if a prefix is
   available).  The MR can also use DHCP prefix delegation [RFC3633] to
   obtain prefixes for assignment and/or further sub-delegation on its
   downstream-attached links.

   For DHCPv4, the MR's relay function writes an address from the
   appropriate virtual ethernet interface portal in the 'giaddr' field
   and also includes the address in a DHCPv4 MLA option (see:
   Section 3.4).  If necessary to identify the MR's downstream-attached
   link, the relay also includes a link selection sub-option [RFC3527]
   with an address from the prefix associated with the virtual ethernet
   (if a prefix is available).  The MR can also use a suitable prefix
   delegation mechanism to obtain prefixes for further assignment and/or
   further sub-delegation on its downstream-attached links.

   The DHCP request will elicit a DHCP reply from a server with IP
   address/prefix delegations.  When addresses are delegated, the MR
   assigns the resulting addresses to the virtual point-to-point
   interface that connects its host and router entities, i.e., the
   addresses are *not* assigned on the virtual ethernet interface or an
   underlying MANET interface.  When prefixes are delegated, the MR can
   assign and/or further sub-delegate the prefixes to its downstream-
   attached links.  If the MANET uses a proactive routing protocol, the
   MR can advertise the delegated addresses/prefixes into the routing
   protocol during the duration of the delegation lifetimes.




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   The DHCP server ensures unique IP address/prefix delegations.  By
   assigning global IP addresses/prefixes only on downstream-attached
   interfaces there is no requirement for the MR to perform Duplicate
   Address Detection (DAD) over its virtual ethernet interface.  See
   Appendix A for further DAD considerations.

   After the MR configures global IP addresses/prefixes, it can send IP
   packets with global IP source addresses to on- and off-MANET
   destinations.  Packets can be sent to off-MANET destinations either
   by using any available MBRs as egress gateways or by selecting
   specific MBRs on a per-packet basis.  For MANETs in which MBRs can
   advertise a 'default' route that propagates throughout the routing
   protocol, the MR can send IP packets using the unenhanced virtual
   ethernet interface portal at the expense of extra TTL (IPv4) or Hop
   Limit (IPv6) decrementation.  For MANETs in which the routing
   protocol cannot propagate a default route, or when the MR wishes to
   select a specific MBR as the egress gateway, the MR can ensure that
   the packets will be forwarded through a specific MBR by either 1)
   sending the packets via the enhanced portal with an MLA for an MBR as
   the destination address in the outer IP header, or 2) sending the
   packets via the unenhanced portal and inserting an IPv4 source
   routing header (likewise IPv6 routing header) or a subnetwork-
   specific encapsulation.

3.2.  MANET Border Router Operation

   MBRs connect the MANET to other networks via their upstream-attached
   interfaces or via MANET interfaces connected to other MANETs.

   MBRs send END messages on the virtual ethernet unenhanced port and/or
   ordinary ND messages on the enhanced port.  When stateful
   configuration is desired, prefixes advertised in RA messages should
   be advertised as not to be used for on-link determination or
   StateLess Address AutoConfiguration (SLAAC) [RFC2462] by setting the
   'A', 'L' bits in Prefix Information Options to 0.  (But, see:
   Appendix B for further considerations on using SLAAC for MANET
   Autoconfiguration.)

   MBRs act as BOOTP/DHCP relays and/or servers for a MR's DHCP
   requests/replies.  For DHCPv4, when a MBR acting as a relay forwards
   a DHCP request that includes an MLA option, it writes its own address
   in the 'giaddr' field, i.e., it overwrites the value that was written
   into 'giaddr' by the MR's relay function.

3.3.  DHCP Server Extensions

   No MANET autoconfiguration-specific extensions are required for
   DHCPv6 servers.



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   DHCPv4 servers examine DHCPv4 requests for a DHCPv4 MLA option (see:
   Section 3.4).  If a DHCPv4 MLA option is present, the DHCPv4 server
   copies the option into the corresponding DHCPv4 reply message(s).

3.4.  MLA Encapsulation

   For DHCPv6, the MLA is encoded directly in the "peer-address" field
   of DHCPv6 requests/replies.

   For DHCPv4, a new DHCPv4 option [RFC2132] called the 'MLA option' is
   required to encode an MLA for DHCP transactions that will traverse a
   MBR, i.e., so that the MBR has a MANET-relevant address to direct
   DHCPv4 replies to the correct MR, which may be multiple Layer-3 hops
   away.  The format of the DHCPv4 MLA option is given below:

     Code  Len   Ether Type      MLA
   +-----+-----+-----+-----+-----+-----+---
   | TBD |  n  |    type   |  a1 |  a2 | ...
   +-----+-----+-----+-----+-----+-----+---

   Code
      a one-octet field that identifies the option type (see:
      Section 5).

   Len
      a one-octet field that encodes the remaining option length.

   Ether Type
      a type value from the IANA "ethernet-numbers" registry.

   MLA
      a variable-length MANET Local Address (MLA).

3.5.  MANET Flooding

   When multicast service discovery is required, Layer-3 MANETs that
   implement this specification must use a MANET flooding mechanism
   (e.g., Simplified Multicast Forwarding (SMF) [I-D.ietf-manet-smf]) so
   that site-scoped multicast messages can be propagated across multiple
   Layer-3 hops.

3.6.  Self-Generated Addresses

   MR's can self-generate an address (e.g., an IPv6 CGA [RFC3972], an
   IPv6 privacy address [I-D.ietf-ipv6-privacy-addrs-v2], etc.) then
   propose the address to the DHCP server.  If the DHCP server
   determines that the self-generated address is unique, it will
   delegate the address for the MR's use.



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3.7.  Changes to the Neighbor Discovery Model

   Ordinary link-scoped ND messages work as-normal over the virtual
   ethernet enhanced port, so ND operation over the enhanced port
   requires no changes to the standard IP neighbor discovery protocols
   specified in [RFC1256][RFC2461].

   END messages over the virtual ethernet unenhanced port must use a
   site-scoped unicast source address (i.e., an MLA) and an MLA or site-
   scoped multicast destination address such that the messages may be
   forwarded by a router and have their TTL/Hop Limit decremented on the
   path.  This means that END messages provide a site-scoped (and not
   link-scoped) discovery service which represents a departure from the
   link-scoped services specified in [RFC1256][RFC2461].


4.  Operation with Multiple MBRs

   For a set of MANETs and MBRs that attach to the same backbone
   network, MRs can retain their global IP address/prefix delegations as
   they move if the backbone network participates with the MBRs and MRs
   in a localized mobility management scheme, e.g., see:
   [I-D.templin-autoconf-netlmm-dhcp].

   For a set of MANETs and MBRs that attach to different backbone
   networks and/or serve different global IP prefixes from within the
   same network, MRs must configure new global IP addresses/prefixes as
   they change between different MBRs unless inter-MBR tunnels and
   routing protocol exchanges are supported, e.g., see:
   [I-D.russert-netlmm-hmap].

   Global mobility management mechanisms for MRs that configure new
   global IP addresses/prefixes as they move between different MBRs are
   beyond the scope of this document.


5.  IANA Considerations

   A new DHCP option code is requested for the DHCP MLA Option in the
   IANA "bootp-dhcp-parameters" registry.


6.  Security Considerations

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





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7.  Related Work

   Telcordia has proposed DHCP-related solutions for the CECOM MOSAIC
   program.  The virtual ethernet model was proposed by Quang Nguyen
   under the guidance of Dr. Lixia Zhang.  Various IETF AUTOCONF working
   group proposals have suggested similar mechanisms.


8.  Acknowledgements

   The following individuals gave direct and/or indirect input that was
   essential to the work: Jari Arkko, Emmanuel Bacelli, James Bound,
   Thomas Clausen, Joe Macker, Thomas Henderson, Bob Hinden, 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.

   The Naval Research Lab (NRL) Information Technology Division uses
   DHCP in their MANET research testbeds.


9.  References

9.1.  Normative References

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

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC0951]  Croft, B. and J. Gilmore, "Bootstrap Protocol", RFC 951,
              September 1985.

   [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.




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   [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.

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

9.2.  Informative References

   [I-D.ietf-autoconf-manetarch]
              Chakeres, I., "Mobile Ad hoc Network Architecture",
              draft-ietf-autoconf-manetarch-00 (work in progress),
              February 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-manet-smf]
              Macker, J., "Simplified Multicast Forwarding for MANET",
              draft-ietf-manet-smf-03 (work in progress), October 2006.

   [I-D.jelger-autoconf-mla]
              Jelger, C., "MANET Local IPv6 Addresses",
              draft-jelger-autoconf-mla-01 (work in progress),
              October 2006.

   [I-D.russert-netlmm-hmap]
              Russert, S. and F. Templin, "Hierarchical Mobility Anchor
              Points (HMAPs) for Network Localized Mobility  Mangement
              (NETLMM)", draft-russert-netlmm-hmap-00 (work in
              progress), February 2007.

   [I-D.templin-autoconf-netlmm-dhcp]



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              Templin, F., "Network Localized Mobility Management using
              DHCP", draft-templin-autoconf-netlmm-dhcp-04 (work in
              progress), October 2006.

   [I-D.thaler-autoconf-multisubnet-manets]
              Thaler, D., "Multi-Subnet MANETs",
              draft-thaler-autoconf-multisubnet-manets-00 (work in
              progress), February 2006.

   [I-D.thaler-intarea-multilink-subnet-issues]
              Thaler, D., "Issues With Protocols Proposing Multilink
              Subnets", draft-thaler-intarea-multilink-subnet-issues-00
              (work in progress), March 2006.

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

   [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.

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

   [RFC4620]  Crawford, M. and B. Haberman, "IPv6 Node Information
              Queries", RFC 4620, August 2006.

   [RFC4795]  Aboba, B., Thaler, D., and L. Esibov, "Link-local
              Multicast Name Resolution (LLMNR)", RFC 4795,
              January 2007.


Appendix A.  IPv6 Neighbor Discovery (ND) and Duplicate Address
             Detection (DAD)

   In terms of ND, existing standards [RFC2461][RFC4291] require that a
   node configure a link-local address on each of its IPv6-enabled



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   interfaces, but the primary requirement for link-locals seems to be
   for the purpose of uniquely identifying routers on the link.  It is
   therefore for further study as to whether MRs should send RAs on
   MANET interfaces (or even configure link local addresses on MANET
   interfaces at all), since the unenhanced view of the MANET is as a
   multilink peering point between distinct sites and not a unified
   link.

   In terms of DAD, 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 (remote) 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 link-local addresses can be generated with mechanisms
   such as CGAs, IPv6 privacy addresses, etc., but ULAs provide an
   additional 40/56 pseudo-random bits in the IPv6 address prefix.

   Statistical properties can assure uniqueness for the MLAs assigned on
   a MR's MANET interfaces, and careful operational practices can assure
   uniqueness for the global addresses/prefixes assigned on a MR's
   downstream-attached links (since the DHCP server assures unique
   assignments).  However, a passive in-service DAD mechanism should
   still be used to detect duplicates that were assigned via other
   means, e.g., manual configuration.


Appendix B.  IPv6 StateLess Address AutoConfiguration (SLAAC)

   For IPv6, the use of StateLess Address AutoConfiguration (SLAAC)
   [RFC2462] could be indicated by prefix information options in END
   and/or ordinary ND messages with the 'A' bit set to 1.  MRs that
   receive such messages could then self-generate an address from the
   prefix and assign it to the virtual point-to-point interface
   associated with the MANET's virtual ethernet, then use a passive in-
   service DAD approach to detect duplicates within the MANET.  But, if
   the MANET partitions, DAD might not be able to monitor the routing
   exchanges occurring in other partitions and address duplication could
   result.  Further study on DAD implications for SLAAC in MANETs is
   required.







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Appendix C.  Change Log

   Changes from -06 to -07:

   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:





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   o  minor updates for consistency with recent developments

   Changes from -00 to -01:

   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: fred.l.templin@boeing.com


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

   Email: steven.w.russert@boeing.com


   Ian D. Chakeres
   Boeing Phantom Works
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124
   USA

   Email: ian.chakeres@gmail.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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