Network Working Group F. Templin Internet-Draft S. Russert Intended status: Informational S. Yi Expires: December 31, 2007 Boeing Phantom Works June 29, 2007 MANET Autoconfiguration draft-templin-autoconf-dhcp-08.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 31, 2007. Copyright Notice 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 global- and/or local-scope IP addresses/prefixes. This document specifies mechanisms for MANET autoconfiguration. Both IPv4 and IPv6 are discussed. Templin, et al. Expires December 31, 2007 [Page 1] Internet-Draft MANET Autoconfiguration June 2007 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 . . . . . . . 7 3.1.2. MNBR List Discovery . . . . . . . . . . . . . . . . . 7 3.1.3. Virtual Ethernet Interface Configuration . . . . . . . 8 3.1.4. MNBR Reachability Confirmation . . . . . . . . . . . . 9 3.1.5. Global-scope Address Autoconfiguration . . . . . . . . 9 3.1.6. Local-scope Address Autoconfiguration . . . . . . . . 10 3.1.7. Self-Generated IPv6 Interface Identifiers . . . . . . 11 3.1.8. Packet Forwarding and Default MNBR Selection . . . . . 11 3.2. MANET Border Router (MNBR) Operation . . . . . . . . . . . 12 3.3. DHCP Server Extensions . . . . . . . . . . . . . . . . . . 12 3.4. MLA Encapsulation . . . . . . . . . . . . . . . . . . . . 12 3.5. MANET Flooding . . . . . . . . . . . . . . . . . . . . . . 13 3.6. Changes to the Neighbor Discovery Model . . . . . . . . . 13 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . . 15 Appendix A. IPv6 Neighbor Discovery (ND) and Duplicate Address Detection (DAD) . . . . . . . . . . . . . . . 16 Appendix B. IPv6 StateLess Address AutoConfiguration (SLAAC) . . 17 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . . . 20 Templin, et al. Expires December 31, 2007 [Page 2] Internet-Draft MANET Autoconfiguration June 2007 1. Introduction Mobile Ad-hoc Networks (MANETs) connect MANET Routers (MNRs) on links with asymmetric reachability characteristics (see: [RFC2461], Section 2.2). MNRs participate in a routing protocol over MANET interfaces to discover routes across the MANET using multiple 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 large as an Autonomous System (AS) or as small as a single MNR (and its attached networks). A MANET may contain other MANETs, and may also be a subnetwork of a larger MANET. MNRs must have a means to automatically provision global- and/or local-scope IP addresses/ prefixes plus other configuration information. 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 shared link via a "virtual ethernet" interface configured over its MANET interfaces (see: Figure 2 and Figure 3). An "opaque" view of this virtual ethernet 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, 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 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. This document specifies mechanisms and operational practices for MANET autoconfiguration. Operation using standard DHCP [RFC2131][RFC3315][RFC3633] and neighbor discovery [RFC1256][RFC2461][RFC2462] mechanisms is assumed unless otherwise specified. Both IPv4 [RFC0791] and IPv6 [RFC2460] are discussed. Templin, et al. Expires December 31, 2007 [Page 3] Internet-Draft MANET Autoconfiguration June 2007 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). MANET Interface a MANET Router's attachment to an asymmetric reachability link (see: [RFC2461], Section 2.2). A MANET interface is a "lateral" interface, i.e., it is inherently neither an ingress nor egress interface although it can sometimes exhibit characteristics of both. Mobile Ad-hoc Network (MANET) a connected network region of MANET routers that maintain a routing structure among themselves over MANET interfaces. A MANET may be as large as an Autonomous System (AS) or as small as a single MANET router, and 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 node that participates in a routing protocol on its MANET interface(s) and forwards packets on behalf of both other MNRs and "downstream" networks attached on its ingress interfaces. A MNR can also connect to "upstream" networks either directly on its egress interfaces or indirectly via MNBRs. 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 (including the Internet) over egress interfaces. Templin, et al. Expires December 31, 2007 [Page 4] Internet-Draft MANET Autoconfiguration June 2007 MANET Local Address (MLA) an IP unicast 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 an imaginary shared link that connects all MNRs in a MANET. MNRs attach to the virtual ethernet via an interface that is configured over underlying MANET interface(s) 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. 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 the MNR's virtual ethernet 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: Templin, et al. Expires December 31, 2007 [Page 5] Internet-Draft MANET Autoconfiguration June 2007 Egress Interfaces (to Internet) ^ ^ ^ | | | +------------------------+---+--------+----------+ | Internal hosts | | | | M | an routers | | .... | | A | ,-. | +---+---+--------+---+ | N | (H1 )---+ | | | E | | `-' | | +------+--< T | . | +---+ | | | | | . +--|R1 |---+-----+ | | I | . | +---+ | | Router +------+--< n | | ,-. | | | . | t | (H2 )---+ | Entity | . | e | `-' | . | | . | r | . | | . | f | ,-. . | +------+--< a | (Hn )---------+ | | c | `-' +---+---+--------+---+ | e | Ingress Interfaces | | .... | | s | (to internal networks) | | | | +------------------------+---+--------+----------+ | | | v v v Ingress Interfaces (to external networks) Figure 1: MANET Router 3. MANET Autoconfiguration 3.1. MANET Router (MNR) Operation The following sections specify autoconfiguration mechanisms and/or operational practices used by MNRs to support egress interfaces that connect "upstream" (i.e., toward fixed Internet infrastructure), ingress interfaces that connect "downstream" to internal and external networks (i.e., away from fixed Internet infrastructure), and MANET interfaces that connect the MNR "laterally" to other MNRs. Egress interfaces have addresses assigned or validated by other devices, ingress interface addresses are controlled by the MNR, and MANET interface addresses are coordinated with other MNRs. MNRs engage in the routing protocol on MANET interfaces, configure virtual ethernet interfaces, and obtain global- and/or local-scope addresses/prefixes using these mechanisms and practices. Templin, et al. Expires December 31, 2007 [Page 6] Internet-Draft MANET Autoconfiguration June 2007 3.1.1. MANET Local Address (MLA) Configuration Upon joining a MANET, each MNR first configures an MLA used for operating the routing protocol and/or for local communications within the MANET. IPv6 MLAs can be administratively assigned, dynamically configured using DHCP[RFC3315], autoconfigured using IPv6 StateLess Address AutoConfiguration (SLAAC) [RFC2462], or self-generated using IPv6 Unique Local Addresses (ULAs) [RFC4193][I-D.ietf-ipv6-ula-central]. The MLAs include interface identifiers that are either managed for uniqueness (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 administratively assigned, dynamically configured using DHCP [RFC2131] 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 administratively assigned MLA, the choice of attempting to dynamically configure an MLA using DHCP or self- generate one using some other mechanism is up to the MNR. 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. DHCP configuration of MLAs for both IPv4 and IPv6 requires relay support from other MNRs that have already been autoconfigured within the MANET. In particular, since a MNR presumably has no usable site- scoped addresses before configuring an MLA, it must send its DHCP requests to a link-scoped broadcast/multicast address and await a (relayed) address delegation reply from a server. This means that all MNRs should be prepared to act as DHCP relays on behalf of neighboring MNRs that have recently joining the MANET, and relay any link-scoped DHCP requests to either a site-scoped "All-DHCP-Servers" address or to one or more unicast addresses. 3.1.2. MNBR List Discovery After configuring MLAs, the MNR next engages in the routing protocol(s) over its MANET interfaces and discovers the list of MNBRs on the MANET. The list of MNBRs is discovered the same as for the ISATAP Potential Router List (PRL) initialization procedure Templin, et al. Expires December 31, 2007 [Page 7] Internet-Draft MANET Autoconfiguration June 2007 ([RFC4214], Section 8.3.2); it also 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.) 3.1.3. Virtual Ethernet Interface Configuration The MNR configures a virtual ethernet interface that connects all MNRs in the MANET over the underlying MANET interfaces. The opaque portal of the virtual ethernet interface configures a link-local address that is assured to be unique among the virtual interfaces of all MNRs in the MANET (e.g., an ISATAP link-local address configured per ([RFC4214], Section 6.2) and derived from a MANET interface's IPv4 MLA). 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 virtual ethernet interface configures no addresses itself, but rather provides IP with direct access to the underlying MANET interfaces and their associated addresses. IP packets sent via the transparent portal are transmitted unencapsulated on an underlying MANET interface, but may include an IPv4 source routing header (likewise IPv6 routing header) or a subnetwork-specific encapsulation. Figure 2 depicts the protocol stack model for the virtual ethernet output routine, and Figure 3 depicts the corresponding model for the virtual ethernet input routine: +--------------------------------------------------+ | | ip_output() | | +--------------------------------------------------+ | | virtual_ethernet_output() | | | | | _ transparent portal _ ___ opaque 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 Templin, et al. Expires December 31, 2007 [Page 8] Internet-Draft MANET Autoconfiguration June 2007 Figure 2: virtual_ethernet_output() +--------------------------------------------------+ ^ | ip_input() | | +--------------------------------------------------+ | | virtual_ethernet_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: virtual_ethernet_input() 3.1.4. MNBR Reachability Confirmation After the MNR configures a virtual ethernet interface, it can confirm reachability of MNBRs and (in the case of IPv6) discover prefixes associated with the MANET's virtual ethernet. (It can also discover IPv6 prefixes through a MANET-specific out-of-band service discovery protocol.) The MNR can confirm reachability by sending/receiving END messages over the transparent portal, by sending/receiving ordinary ND messages over the opaque portal, via reachability information conveyed in the routing protocol itself, or through some other means associated with the particular MANET subnetwork technology. The MNR can then configure global- or local-scope addresses as specified in the following sections: 3.1.5. Global-scope Address Autoconfiguration After the MNR discovers MNBRs, it can configure global-scope addresses/prefixes that are topologically correct for the MANET according to either DHCP or IPv6 Stateless Address AutoConfiguration (SLAAC) (but see Appendix B for further considerations on SLAAC). When DHCP is used, a DHCP client associated with (one of) the MNR's host entity(s) forwards a DHCP DISCOVER (DHCPv4) or Solicit (DHCPv6) request to a DHCP relay associated with its router entity to request IP address and/or prefix delegations. (In other words, the MNR acts as both DHCP client and relay.) The relay function then forwards the request to one or more MNBRs, to other known DHCP servers, or to a Templin, et al. Expires December 31, 2007 [Page 9] Internet-Draft MANET Autoconfiguration June 2007 site-scoped "All-DHCP-Servers" multicast address. For DHCPv6, the MNR'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 MNR can also use DHCP prefix delegation [RFC3633] to obtain global-scope prefixes for assignment and/or further sub- delegation on networks connected on its ingress interfaces. For DHCPv4, the MNR'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 MNR's ingress interface, the relay also includes a link selection sub-option [RFC3527] with an address from the prefix associated with the MANET's virtual ethernet (if a prefix is available). The MNR can also use a prefix delegation mechanism [I-D.ietf-dhc-subnet-alloc] to obtain prefixes for further assignment and/or further sub-delegation on networks connected on its ingress interfaces. The DHCP request will elicit a DHCP reply from a server with IP address/prefix delegations. When addresses are delegated, the MNR assigns the resulting addresses to an ingress interface, i.e., it does *not* assign the addresses on the virtual ethernet 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) over its MANET interfaces or virtual ethernet interface. See Appendix A for further DAD considerations. 3.1.6. Local-scope Address Autoconfiguration Independent of any global-scope addresses autoconfigured per Section 3.1.5, MNR's can self-generate IPv6 Unique Local Address (ULA) prefixes [RFC4193][I-D.ietf-ipv6-ula-central] and use them to assign addresses/prefixes on networks connected on its ingress interfaces. Note that in some scenarios a MNR may not require any global-scope address/prefix assignments at all, and can use ULAs instead. (This is particularly true for the use case of joining two Templin, et al. Expires December 31, 2007 [Page 10] Internet-Draft MANET Autoconfiguration June 2007 MANETs via either physical or virtual links.) Self-generated local-scope addresses are portable and not relative to the MNR's current MANET of attachment. The addresses can therefore travel with the MNR as it moves to new MANETs. Self-generation of local-scope addresses can therefore occur independently of any other MNR autoconfiguration considerations. 3.1.7. Self-Generated IPv6 Interface Identifiers MNR's can create self-generated IPv6 interface identifiers such as specified for CGAs [RFC3972], IPv6 privacy address [I-D.ietf-ipv6-privacy-addrs-v2], etc. For global-scope address autoconfiguration (see: Section 3.1.5, the MNR can propose 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. For local-scope address autoconfiguration (see: Section 3.1.6), the MNR simply assigns the address to an ingress interface, since it is the responsible delegation authority for its own local-scope prefixes. 3.1.8. Packet Forwarding and Default MNBR Selection After the MNR configures IP addresses/prefixes, it can forward IP packets to on- and off-MANET destinations. Packets can be forwarded to off-MANET destinations either by using any available MNBRs as egress gateways or by selecting specific MNBRs. For MANETs in which MNBRs can advertise a 'default' route that propagates throughout the routing protocol, the MNR can forward IP packets using the transparent 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 MNR wishes to select a specific MNBR as the egress gateway, the MNR can ensure that the packets will be forwarded through a specific MNBR by either 1) forwarding the packets via the opaque portal with an MLA for an MNBR as the destination address in the outer IP header, or 2) forwarding the packets via the transparent portal and inserting an IPv4 source routing header (likewise IPv6 routing header) or a subnetwork-specific encapsulation. Templin, et al. Expires December 31, 2007 [Page 11] Internet-Draft MANET Autoconfiguration June 2007 3.2. MANET Border Router (MNBR) Operation MNBRs connect the MANET to upstream networks over its egress interfaces. MNBRs send/receive END messages on the virtual ethernet transparent portal and/or ordinary ND messages on the opaque portal. When stateful configuration is desired, MNBRs should advertise prefixes in RA messages 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.) MNBRs act as DHCP relays and/or servers for a MNR's DHCP requests/ replies. For DHCPv4, when a MNBR 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 MNR's relay function. 3.3. DHCP Server Extensions No MANET autoconfiguration-specific extensions are required for DHCPv6 servers. 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). Note that this extension is only required for DHCPv4 servers that support global IPv4 address/prefix delegations for MNRs - see: Section 3.1.5. 3.4. MLA Encapsulation For DHCPv6, the MLA is encoded directly in the "peer-address" field of DHCPv6 requests/replies. For DHCPv4 delegation of global IPv4 addresses/prefixes, a new DHCPv4 option [RFC2132] called the 'MLA option' is required to encode an MLA for DHCP transactions that will traverse a MNBR, i.e., so that the MNBR has a MANET-relevant address to direct DHCPv4 replies to the correct MNR, which may be multiple IP hops away. The format of the DHCPv4 MLA option is given below: Code Len Ether Type MLA +-----+-----+-----+-----+-----+-----+--- | TBD | n | type | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+--- Templin, et al. Expires December 31, 2007 [Page 12] Internet-Draft MANET Autoconfiguration June 2007 Code a one-octet field that identifies the option type (see: Section 4). 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, MANETs that operate routing as an IP layer service must use a multicast flooding mechanism (e.g., Simplified Multicast Forwarding (SMF) [I-D.ietf-manet-smf]) so that site-scoped multicast messages will be propagated across the MANET. 3.6. Changes to the Neighbor Discovery Model Ordinary link-scoped ND messages work as-normal over the virtual ethernet 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 virtual ethernet 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 new DHCPv4 option code is requested for the DHCPv4 MLA Option in the IANA "bootp-dhcp-parameters" registry (TBD, based on use case analysis for global IPv4 address configuration per Section 3.1). 5. Security Considerations Threats relating to MANET routing protocols also apply to this document. Templin, et al. Expires December 31, 2007 [Page 13] Internet-Draft MANET Autoconfiguration June 2007 6. Related Work 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. 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. 7. 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. 8. Contributors Ian Chakeres (ian.chakeres@gmail.com) contributed to earlier versions of this 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. [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. Templin, et al. Expires December 31, 2007 [Page 14] Internet-Draft MANET Autoconfiguration June 2007 [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. [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., "Mobile Ad hoc Network Architecture", draft-ietf-autoconf-manetarch-03 (work in progress), June 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. [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. Templin, et al. Expires December 31, 2007 [Page 15] Internet-Draft MANET Autoconfiguration June 2007 [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. 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 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 Templin, et al. Expires December 31, 2007 [Page 16] Internet-Draft MANET Autoconfiguration June 2007 probability of collision. But, IPv6 ULAs also provide an additional 40 pseudo-random bits in the IPv6 address prefix. Statistical properties for pseudo-random address self-generation can assure uniqueness for the MLAs assigned on a MNR's MANET interfaces, and careful operational practices can assure uniqueness for global- and local-scope 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 MANET's virtual ethernet 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 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: Templin, et al. Expires December 31, 2007 [Page 17] Internet-Draft MANET Autoconfiguration June 2007 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: Templin, et al. Expires December 31, 2007 [Page 18] Internet-Draft MANET Autoconfiguration June 2007 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 Seung Yi Boeing Phantom Works P.O. Box 3707 MC 7L-49 Seattle, WA 98124 USA Email: seung.yi@boeing.com Templin, et al. Expires December 31, 2007 [Page 19] Internet-Draft MANET Autoconfiguration June 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Templin, et al. Expires December 31, 2007 [Page 20]