Network Working Group F. Templin
Internet-Draft S. Russert
Intended status: Informational S. Yi
Expires: May 17, 2008 Boeing Phantom Works
November 14, 2007
MANET Autoconfiguration
draft-templin-autoconf-dhcp-10.txt
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Copyright (C) The IETF Trust (2007).
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 . . . . . . . . . . . . . 8
3.1.4. Reachability Confirmation . . . . . . . . . . . . . . 9
3.1.5. MNBR-Aggregated Address/Prefix Autoconfiguration . . . 9
3.1.6. Unique-local Address Autoconfiguration . . . . . . . . 11
3.1.7. Self-Generated IPv6 Interface Identifiers . . . . . . 11
3.1.8. Forwarding Packets to Off-MANET Destinations . . . . . 11
3.2. MANET Border Router (MNBR) Operation . . . . . . . . . . . 12
3.3. MANET Flooding . . . . . . . . . . . . . . . . . . . . . . 12
3.4. Changes to the Neighbor Discovery Model . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. IPv6 Neighbor Discovery (ND) and Duplicate
Address Detection (DAD) . . . . . . . . . . . . . . . 15
Appendix B. IPv6 StateLess Address AutoConfiguration (SLAAC) . . 16
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 20
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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 span an entire Autonomous System (AS)
or may be as simple as a small collection of MNRs (and their attached
networks). A MANET may contain other MANETs, and may also 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.
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
MNRs require specialized autoconfiguration procedures to avoid
multilink subnet issues [RFC4903].
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) via a virtual interface configured
over its MANET interfaces and used to avoid multilink subnet issues.
An "opaque" view of the VET sees the MANET as a fully-connected
shared link that connects all MNRs, while a "transparent" view sees
the MANET as a multilink site. 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).
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 span an entire
Autonomous System (AS) or only a small collection of MANET
routers, and a MANET may also 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. (Note that this
document considers the terms "MANET" and "site" as functional
equivalents.)
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 "upstream" networks (e.g., the
Internet) via egress interfaces, and delegates 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, and presents both opaque and transparent "portals" (see:
Figure 2 and Figure 3).
The opaque 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 opaque portal views the
MANET as a unified shared link. In this sense, the opaque portal
presents an automatic tunneling abstraction.
The transparent 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 transparent portal views the MANET as a multilink site.
Extended Neighbor Discovery (END) message
an IP Neighbor Discovery (ND) message [RFC1256] [RFC2461]
transmitted on the transparent portal of a VET interface with an
MLA of the underlying MANET interface as a source address and with
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:
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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 mobile networks)
Figure 1: MANET Router
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 mobile networks, and MANET interfaces that are
"neutral" in the sense that the packets they forward may need to
traverse several other MANET interfaces before they are forwarded via
either an egress or ingress interface. MNRs configure VET interfaces
and engage in the routing protocol over their MANET interfaces; they
also 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 for
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local communications within the MANET.
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.).
IPv4 MLAs can be manually configured, administratively assigned,
autoconfigured using DHCP or self-generated using an unspecified IPv4
unique local address configuration mechanism. (Such a mechanism
could be considered as a site-scoped equivalent to IPv4 link-local
addresses [RFC3927].)
When there is no manually configured/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. Note also that DHCP service for MLA
configuration may not be available in all MANETs.
Since a MNR initially has no non-link-local addresses, DHCP
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
information conveyed in the routing protocol, or through an alternate
discovery mechanism, e.g., per [RFC4214], Section 8.3.2.
The list of MNBRs serves as an identifier for the MANET. If the list
of MNBRs is NULL, an alternate token such as the Layer-2 address of
an ordinary MNR can serve as an identifier for the MANET.
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3.1.3. VET Interface Configuration
The MNR configures a VET interface for the MANET over the underlying
MANET interfaces.
The opaque portal of the VET interface configures a link-local
address that is assured to be unique among the VET interfaces of all
MNRs in the MANET, e.g., an ISATAP link-local address ([RFC4214],
Section 6.2) derived from the IPv4 MLA of an underlying MANET
interface. IP packets sent via the opaque portal are encapsulated in
an outer IP header then submitted to ip_output() for transmission on
an underlying MANET interface.
The transparent portal of the VET interface configures no addresses
itself, but rather provides IP with direct access to the underlying
MANET interfaces and their associated MLAs. IP packets sent via the
transparent portal are transmitted unencapsulated on an underlying
MANET interface, but may require an IPv4 source routing header
(likewise IPv6 routing header) or a subnetwork-specific encapsulation
to direct packets to specific MNBRs.
Figure 2 depicts the protocol stack model for the VET output routine,
and Figure 3 depicts the corresponding model for the VET input
routine:
+--------------------------------------------------+ |
| ip_output() | |
+--------------------------------------------------+ |
| vet_output() | |
| |
| _ transparent portal _ ___ opaque portal _____ | p
|/ \ / \| a
| - MANET intf already | - select MANET intf | c
| selected | - encapsulate in IP | k
| - insert routing hdr | - forward to MANET intf | e
| (if necessary) | via ip_output() | t
| - forward 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: vet_output()
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+--------------------------------------------------+ ^
| ip_input() | |
+--------------------------------------------------+ |
| vet_input() |
| | p
| _ transparent portal _ ___ opaque 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: vet_input()
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
END messages over the transparent portal, by sending/receiving
ordinary ND messages over the opaque portal, by issuing DHCP
requests, via reachability information conveyed in the routing
protocol itself, or through some other means associated with the
particular MANET subnetwork technology.
3.1.5. MNBR-Aggregated Address/Prefix Autoconfiguration
After the MNR discovers MNBRs, it can acquire MNBR-aggregated
addresses/prefixes using either DHCP or IPv6 Stateless Address
AutoConfiguration (SLAAC) (but see Appendix B for further
considerations on SLAAC). 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
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o other non-link-local scope
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 (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.)
For DHCPv4, the MNR's relay function writes an address from the VET
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. If the MANET
subnetwork uses a proactive routing protocol, the MNR can advertise
the delegated addresses/prefixes into the routing protocol during the
duration of the delegation lifetimes.
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 interfaces
or VET interfaces (but see Appendix A for further DAD
considerations).
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3.1.6. Unique-local Address Autoconfiguration
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. Note that in
some scenarios a MNR may not require any MNBR-aggregated address/
prefix assignments at all, and can use its own ULAs instead.
Self-generated unique-local addresses are portable and not aggregated
by MNBRs. The addresses can therefore travel with the MNR as it
moves to new MANETs and/or configures peering arrangements with MNRs
in other MANETs. Self-generation of unique-local addresses 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.
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
After the MNR configures IP addresses/prefixes, it can 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 opaque portal to elicit Router Advertisements
from MNBRs and other MNRs. MNRs/MNBRs should therefore send Router
Advertisements with default router preferences and/or more-specific
routes in response to unicast Router Solicitations. This matches the
operational framework established by ISATAP [RFC4214].
Once default routers and/or more-specific routes are discovered, the
MNR can either 1) forward the packets via the opaque portal with an
MLA for an MNR/MNBR as the destination in the outer IP header, or 2)
forward the packets via the transparent portal and insert an IPv4
source routing header (likewise IPv6 routing header) or a subnetwork-
specific encapsulation.
(For MANETs in which 'default' and/or more-specific routes are made
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available through the routing protocol, the MNR can optionally
forward IP packets to off-MANET destinations using the transparent
VET interface portal.)
3.2. MANET Border Router (MNBR) Operation
MNBRs connect the MANET to upstream networks over egress interfaces.
MNBRs send/receive END messages on the VET interface transparent
portal and/or send/receive ordinary ND messages on the opaque portal.
When stateful configuration is desired, MNBRs should set the M bit to
1 in the RA messages they send. (Stateless configuration is also
possible, but see: Appendix B for further considerations on using
SLAAC for MANET Autoconfiguration.)
For DHCPv6, MNBRs act as DHCP relays and/or servers for a MNR's 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.
3.4. Changes to the Neighbor Discovery Model
Ordinary link-scoped ND messages work as-normal over the VET
interface opaque portal, so ND operation over the opaque portal
requires no changes to the standard IP neighbor discovery protocols
specified in [RFC1256][RFC2461].
END messages over the VET interface transparent portal 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. 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).
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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
researched 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
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.
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[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.
[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.
9.2. Informative References
[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-05 (work in progress),
June 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.
Templin, et al. Expires May 17, 2008 [Page 14]
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[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., "Simplified Multicast Forwarding for MANET",
draft-ietf-manet-smf-05 (work in progress), June 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.,
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. 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
interfaces, but the primary requirement for link-locals seems to be
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for the purpose of uniquely identifying routers on the link. It is
therefore for further study as to whether MNRs should send RAs on
MANET interfaces (or even configure link local addresses on MANET
interfaces at all), since the transparent view of the MANET appears
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 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 link-local addresses 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.
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.
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. MNRs that
receive such messages could then self-generate an address from the
prefix and assign it to the VET interface, 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 other
partitions and address duplication could result. Further study on
DAD implications for SLAAC in MANETs is required.
Appendix C. Change Log
(Note to RFC editor - this section to be removed before publication
as an RFC.)
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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:
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:
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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:
o new text on DHCPv6 prefix delegation and multilink subnet
considerations.
o various editorial changes
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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
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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