Network Working Group F. Templin, Ed. Internet-Draft S. Russert Intended status: Informational S. Yi Expires: October 5, 2008 Boeing Phantom Works April 3, 2008 MANET Autoconfiguration using Virtual Ethernet (VET) draft-templin-autoconf-dhcp-13.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 October 5, 2008. Abstract Mobile Ad-hoc Networks (MANETs) connect routers on links with asymmetric reachability characteristics, and may also connect to other networks including the Internet. Routers in MANETs must have a way to automatically provision IP addresses/prefixes and other information. This document specifies a Virtual Ethernet (VET) abstraction for autoconfiguration of routers in MANETs. Templin, et al. Expires October 5, 2008 [Page 1] Internet-Draft Virtual Ethernet April 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. MANET Autoconfiguration . . . . . . . . . . . . . . . . . . . 6 3.1. MANET Interface Autoconfiguration . . . . . . . . . . . . 6 3.2. MNBR/MNGW List Discovery . . . . . . . . . . . . . . . . . 7 3.3. VET Interface Autoconfiguration . . . . . . . . . . . . . 8 3.4. Ingress Interface Autoconfiguration . . . . . . . . . . . 8 3.4.1. Autoconfiguration of IPv4 Prefixes . . . . . . . . . . 9 3.4.2. Autoconfiguration of IPv6 Addresses/Prefixes . . . . . 9 3.4.3. Prefix and Route Maintenance . . . . . . . . . . . . . 11 3.5. Portable IP Prefixes . . . . . . . . . . . . . . . . . . . 11 3.6. Forwarding Packets to Off-MANET Destinations . . . . . . . 12 3.7. MANET-Local Communications . . . . . . . . . . . . . . . . 12 3.8. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 12 3.9. Service Discovery . . . . . . . . . . . . . . . . . . . . 13 3.10. Separation of IP Addressing Domains . . . . . . . . . . . 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. Duplicate Address Detection (DAD) Considerations . . 17 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 Intellectual Property and Copyright Statements . . . . . . . . . . 21 Templin, et al. Expires October 5, 2008 [Page 2] Internet-Draft Virtual Ethernet April 2008 1. Introduction Mobile Ad-hoc Networks (MANETs) connect MANET Routers (MNRs) on links with asymmetric reachability characteristics (see: [RFC4861], 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 via MANET Border Routers (MNBRs) and connect to the Internet via MANET Gateways (MNGWs). A MANET may be as simple as a small collection of MNRs (and their attached networks); a MANET may also contain other MANETs and/or be a subnetwork of a larger MANET. MANETs that comprise homogeneous link types within a single IP subnet can configure the routing protocol to operate as a sub-IP layer mechanism such that IP sees the MANET as an ordinary shared link the same as for a (bridged) campus LAN. In that case, a single IP hop is sufficient to traverse the MANET without IP layer encapsulation. MANETs that comprise heterogeneous link types and/or multiple IP subnets must also provide a routing service that operates as an IP layer mechanism, e.g., 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 specific autoconfiguration procedures are necessary to avoid multilink subnet issues [RFC4903]. In particular, we describe herein the use of a virtualized link that spans the MANET, to avoid the multilink subnet issues that arise when MANET interfaces are used directly by applications. Conceptually, a MNR embodies a router entity that connects its attached networks to MANETs and/or connects the MANET to other networks including the Internet (see: Figure 1). The router entity may also connect to an imaginary "Virtual Ethernet" that views other routers in the MANET as single-hop neighbors. For each distinct MANET to which they connect, MNRs discover a list of MNBRs that can be used for forwarding packets to off-MANET destinations. An MNR (and its attached networks) is a "site" unto itself, therefore a MANET is a "site-of-sites". This document specifies a Virtual EThernet (VET) abstraction using IP-in-IP encapsulation for MANET autoconfiguration with multilink subnet avoidance; both IPv4 [RFC0791] and IPv6 [RFC2460] are discussed within this context. Operation using standard DHCP [RFC2131][RFC3315] and neighbor discovery [RFC0826][RFC4861] mechanisms is assumed unless otherwise specified. Templin, et al. Expires October 5, 2008 [Page 3] Internet-Draft Virtual Ethernet April 2008 2. Terminology The terms "inner" and "outer" are used throughout this document to respectively refer to the innermost IP {address, protocol, header, packet, etc.} *before* encapsulation, and the outermost IP {address, protocol, header, packet, etc.} *after* encapsulation. (There may also be "mid-layer" encapsulations between the inner and outer layers, including IPSec [RFC4301], the Subnetwork Encapsulation and Adaptation Layer (SEAL) [I-D.templin-seal], etc.) 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]. Mobile Ad-hoc Network (MANET) a connected network region of MANET routers that maintain a routing structure among themselves over asymmetric reachability links (see: [RFC4861], Section 2.2). A MANET may be as simple as a small collection of routers (and their attached networks); a MANET may also contain other MANETs and/or be a subnetwork of a larger MANET. A MANET router (and its attached networks) is a site unto itself, and a MANET is therefore a site-of-sites. Further information on the characteristics of MANETs can be found in [RFC2501]. MANET Router (MNR) a mobile router that forwards packets over MANET interfaces. For the purpose of this specification, an MNR comprises a router entity, one or more host entities, one or more MANET interfaces and zero or more ingress/egress/VET interfaces (see: Figure 1). MANET Border Router (MNBR) an MNR that connects other networks to the MANET (via ingress interfaces) and/or connects the MANET to other networks, including the Internet (via egress interfaces). MNBRs also configure a VET interface for automatic tunneling across the MANET. All MNBRs are also MNRs. MANET Gateway (MNGW) a MNBR that connects the MANET to the Internet via egress interfaces and can delegate addresses/prefixes to other MNBRs. All MNGWs are also MNBRs. Templin, et al. Expires October 5, 2008 [Page 4] Internet-Draft Virtual Ethernet April 2008 egress/ingress interface the same as defined in ([RFC3753], Section 3). Note that in some MANET scenarios, an interface may dynamically switch from being an ingress interface to being an egress interface, and vice-versa. Addresses assigned to egress/ingress interfaces are used as *inner* IP addresses during encapsulation. MANET Interface a MNR'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. MANET Local Address (MLA) a MNR's IP address that is assigned to a MANET interface and unique within the MANET. MLAs are used as identifiers for operating the routing protocol and/or locators for packet forwarding within the scope of the MANET; MLAs are also used as *outer* IP addresses during encapsulation. Virtual Ethernet (VET) an imaginary shared link that connects all MNBRs in a MANET. VET interface a MNBR's attachment to a VET. The MNBR configures a VET interface over a set of underlying MANET interface(s) belonging to the same MANET. The VET interface encapsulates each inner IP packet in any mid-layer headers plus an outer IP header then forwards it on an underlying MANET interface such that the TTL/Hop Limit in the inner header is not decremented as the packet traverses the MANET. The VET interface presents an automatic tunneling abstraction that represents the MANET as a unified shared link. The following additional abbreviations are used throughout the document: CGA - Cryptographically Generated Address DHCP[v4,v6] - the Dynamic Host Configuration Protocol IP[v4,v6] - the Internet Protocol ISATAP - Intra-Site Automatic Tunnel Addressing Protocol ND - Neighbor Discovery PIO - Prefix Information Option RIO - Route Information Option RS/RA - IPv6 Neighbor Discovery Router Solicitation/Advertisement SEAL - Subnetwork Encapsulation and Adaptation Layer SLAAC - IPv6 StateLess Address AutoConfiguation Templin, et al. Expires October 5, 2008 [Page 5] Internet-Draft Virtual Ethernet April 2008 3. MANET Autoconfiguration Manet Autoconfiguration entails the configuration of addresses/ prefixes and other information for routers in MANETs. Figure 1 below depicts the conceptual model for a MNR: Egress Interfaces (to Internet) x x x | | | +------------------------+---+--------+----------+ | Internal hosts | | | | M | and routers | | .... | | A | ,-. | +---+---+--------+---+ | N | (H1 )---+ | /| | E | | `-' | | I /*+------+--< T | . | +---+ | | n|**| | | . +--|R1 |---+-----+ t|**| | I | . | +---+ | | Router V e|**+------+--< n | | ,-. | | E r|**| . | t | (H2 )---+ | Entity T f|**| . | e | `-' | . | a|**| . | r | . | c|**| . | f | ,-. . | e \*+------+--< a | (Hn )---------+ \| | c | `-' +---+---+--------+---+ | e | Ingress Interfaces | | .... | | s | (to internal networks) | | | | +------------------------+---+--------+----------+ | | | x x x Ingress Interfaces (to attached networks) Figure 1: MANET Router MNRs configure one or more MANET interfaces and engage in any MANET routing protocols over those interfaces. They also configure zero or more egress interfaces that connect the MANET to the Internet, and zero or more ingress interfaces (including internal virtual interfaces such as a loopback interface) that attach other networks to the MANET. MNRs that configure ingress/egress interfaces also act as MNBRs, and configure a VET interface over a set of underlying MANET interfaces belonging to the same MANET. MNRs obtain addresses/ prefixes and other autoconfiguration information using the mechanisms specified in the following sections: 3.1. MANET Interface Autoconfiguration When a MNR joins a MANET, it first configures a unique IPv6 link- local address on each MANET interface that requires an IPv6 link- Templin, et al. Expires October 5, 2008 [Page 6] Internet-Draft Virtual Ethernet April 2008 local capability and an IPv4 link-local address on each MANET interface that requires an IPv4 link-local capability. IPv6 link- local address generation mechanisms that provide sufficient uniqueness include Cryptographically Generated Addresses (CGAs) [RFC3972], StateLess Address AutoConfiguration (SLAAC) using EUI-64 interface identifiers [RFC4862], etc. The mechanisms specified in [RFC3927] provide an IPv4 link-local address generation capability, but with limited uniqueness properties. Next, the MNR configures a MANET Local Address (MLA) of the outer IP protocol version on each of its MANET interfaces and engages in any MANET routing protocols on those interfaces. The MNR can configure an MLA via explicit management, DHCP autoconfiguration, pseudo-random self-generation from a suitably large address pool, or through an alternate autoconfiguration mechanism. DHCP configuration of MLAs may require support from relays within the MANET that have already autoconfigured an MLA. For DHCPv6, relays that do not already know the MLA of a server relay requests to the 'All_DHCP_Servers' site-scoped IPv6 multicast group. For DHCPv4, relays that do not already know the MLA of a server relay requests to the IPv4 multicast group address TBD (see: Section 4). DHCPv4 servers that delegate MLAs join the TBD multicast group and service any DHCPv4 messages received for that group. Self-generation of MLAs for IPv6 can be from a large IPv6 local-use address range, e.g., IPv6 Unique Local Addresses [RFC4193]. Self- generation of MLAs for IPv4 can be from a large IPv4 private address range, e.g., 240/4 [I-D.fuller-240space]. When self-generation is used alone, the MNR must continuously monitor the self-generated MLAs through an in-service duplicate address detection mechanism, e.g., by monitoring the routing protocol. A combined approach using both DHCP and self-generation is also possible. In this combined approach, the MNR first self-generates a temporary MLA which it will use only for the purpose of procuring an actual MLA from a DHCP server. Acting as a combined client/relay, the MNR then uses the temporary MLA to engage in the routing protocol and performs a relay-server exchange using the temporary MLA as an address for the relay. When the DHCP server delegates an actual MLA, the MNR abandons the temporary MLA, assigns the actual MLA to the MANET interface and re-engages in the routing protocol. 3.2. MNBR/MNGW List Discovery After the MNR configures its MANET interfaces, it next discovers the list of MNBRs/MNGWs on the MANET. The list can be discovered through information conveyed in the routing protocol or through the discovery Templin, et al. Expires October 5, 2008 [Page 7] Internet-Draft Virtual Ethernet April 2008 mechanisms outlined in [RFC5214], Section 8.3.2. Identifying names/values for MNBRs/MNGWs (and/or the prefixes that they aggregate) serve as an identifier for the MANET. 3.3. VET Interface Autoconfiguration MNBRs configure a VET interface over a set of underlying MANET interfaces belonging to the same MANET, where the VET interface represents an attachment to a "virtual ethernet" that connects all MNBRs in the MANET. Inner IP packets forwarded over the VET interface are encapsulated in any mid-layer headers (e.g., IPsec, the SEAL header, etc.) followed by an outer IP header, then submitted to the outer IP forwarding engine for transmission on an underlying MANET interface. When IPv6 and IPv4 are used as the inner/outer protocols (respectively), the MNBR autoconfigures an ISATAP link-local address ([RFC5214], Section 6.2) on the VET interface to support packet forwarding and operation of the IPv6 neighbor discovery protocol. The ISATAP address embeds an IPv4 MLA assigned to an underlying MANET interface, and need not be checked for uniqueness since the IPv4 MLA itself was already determined to be unique. After the MNBR configures a VET interface, it can communicate with other MNBRs as on-link neighbors on the VET, i.e., it can confirm reachability of other MNBRs through Neighbor Discovery (ND) and/or DHCP exchanges over the VET interface. (The MNBR can also confirm reachability through information conveyed in the MANET routing protocol or through some other means associated with the specific MANET subnetwork technology.) The MNBR must be able to detect and recover from the loss of neighbors on the VET due to e.g., MANET partitions, node failures, etc. Mechanisms such as monitoring the routing protocol, ND beaconing/polling, DHCP renewals/leasequeries, upper layer protocol hints of forward progress, bidirectional forward detection, detection of network attachment, etc. can be used according to the particular deployment scenario. 3.4. Ingress Interface Autoconfiguration MNBRs can acquire addresses and/or prefix delegations for assignment on ingress interfaces through autoconfiguration exchanges with MNGWs over the VET interface. These prefixes may be: Templin, et al. Expires October 5, 2008 [Page 8] Internet-Draft Virtual Ethernet April 2008 o global-scope and provider aggregated o global-scope and provider-independent o global-scope and 6to4 [RFC3056] o unique-local scope and centrally administrated o unique-local scope and locally assigned o other non-link-local scope Ingress interface autoconfiguration considerations are discussed in the following sections: 3.4.1. Autoconfiguration of IPv4 Prefixes When IPv4 is used as the inner protocol, the MNBR discovers the addresses of one or more MNGWs that delegate IPv4 prefixes then performs a DHCPv4 prefix delegation exchange [I-D.ietf-dhc-subnet-alloc] over the VET interface to obtain IPv4 prefixes for assignment and/or sub-delegation on its ingress interfaces. To perform the DHCPv4 prefix delegation exchange, a DHCPv4 client function associated with the MNBR's host entity forwards a DHCPDISCOVER message with a Subnet Allocation option to a relay function associated with its router entity, i.e., the MNBR acts as both client and relay. The relay function then forwards the message over the VET interface to the DHCPv4 server on a MNGW. The forwarded DHCPDISCOVER will elicit a DHCPOFFER from the server containing IPv4 prefix delegations, and the MNBR completes the delegation through a DHCPREQUEST/DHCPACK exchange (again using the combined client/relay approach). When the MNBR receives IPv4 prefix delegations, it assigns the prefixes on ingress interfaces; it does not assign them on the VET interface or on MANET interfaces. The MNBR can also obtain /32 prefixes using DHCPv4 prefix delegation the same as for any IPv4 prefix, and can assign them as IPv4 addresses with /32 netmasks on ingress interfaces (including loopback interfaces). 3.4.2. Autoconfiguration of IPv6 Addresses/Prefixes When IPv6 is used as the inner protocol, the MNBR sends unicast IPv6 Router Solicitation (RS) messages to MNGWs over the VET interface to receive Router Advertisements (RAs) with Prefix Information Options (PIOs) and/or with the 'M' flag set to signify whether DHCPv6 Templin, et al. Expires October 5, 2008 [Page 9] Internet-Draft Virtual Ethernet April 2008 autoconfiguration is available. If the MNBR receives an RA containing PIOs with the 'A' and 'L' bits set to 1, it autoconfigures IPv6 addresses from the prefixes using SLAAC and assigns them to the VET interface. (When IPv4 is used as the outer IP protocol, the addresses are autoconfigured and assigned as ISATAP addresses the same as specified in [RFC5214].) When the MNBR receives an RA with the 'M' flag set to 1, the MNGW that sent the RA also hosts a DHCPv6 server capable of delegating IPv6 prefixes. If the RA also contains PIOs with the 'L' bit set to 0, the MNBR can use them as hints of prefixes the server is willing to delegate. For example, a MNGW can include a PIO with a prefix such as 2001::DB8::/64 as a hint of an aggregated prefix from which an MNBR can delegate a /128. Whether or not such hints are available, the MNBR can use DHCPv6 prefix delegation [RFC3633] to obtain IPv6 prefixes from the MNGW for assignment and/or sub- delegation on its ingress interfaces. The MNBR can obtain prefixes using either a 2-message or 4-message DHCPv6 exchange [RFC3315]. To perform the 2-message exchange, a DHCPv6 client function associated with the MNBR's host entity forwards a Solicit message with an IA_PD option to a relay function associated with its router entity, i.e., the MNBR acts as both client and relay. The relay function then forwards the message over the VET interface to the DHCPv6 server. The forwarded Solicit message will elicit a Reply from the server containing IPv6 prefix delegations. When the MNBR receives IPv6 prefix delegations, it assigns the prefixes on ingress interfaces; it does not assign them on the VET interface or on MANET interfaces. The MNBR can also obtain /128 prefixes using DHCPv6 prefix delegation the same as for any IPv6 prefix. When the MNBR receives a prefix delegation hint (see above) it can self-generate an address from the prefix using mechanisms such as CGAs [RFC3972], IPv6 privacy address [RFC4941], etc. without assigning the address to an interface. The MNBR can then perform a DHCPv6 prefix delegation exchange to propose the address as a /128 prefix to the DHCPv6 server per Section 7 of [RFC3633]. The server will check the proposed prefix for consistency and uniqueness, then return it in its reply to the MNBR if it was able to delegate the prefix. When no prefix delegation hints are available, the MNBR can self- generate an address using "prefix gleaning" from a /128 prefix generated by the DHCPv6 server. The MNBR first performs an ordinary DHCPv6 prefix delegation exchange with the server to obtain a server- generated /128 prefix delegation, then interprets the leading 64 bits of the /128 prefix as a /64 prefix delegation hint. As described in the previous paragraph, the MNBR then self-generates an address from Templin, et al. Expires October 5, 2008 [Page 10] Internet-Draft Virtual Ethernet April 2008 the /64 and proposes the resulting /128 prefix to the server, which will in turn delegate the prefix to the MNBR. (The MNBR can instead attempt "prefix substitution" in a 4-message DHCPv6 exchange by requesting its self-generated /128 prefix instead of the one advertised by the server, but some servers may find this confusing.) When the MNBR receives /128 prefix delegations, it can assign them as IPv6 addresses with /128 prefix lengths on ingress interfaces (including loopback interfaces). 3.4.3. Prefix and Route Maintenance When DHCP prefix delegation is used, the MNGW's DHCP server ensures that the delegations are unique within the MANET and that its routing function will forward IP packets over the VET interface to the MNBR to which the prefix was delegated. The prefix delegation remains active as long as the MNBR continues to issue renewals over the VET interface before the lease lifetime expires. The lease lifetime also keeps the delegation state active even if the link between the MNBR and MNGW is disrupted for a period of time (e.g., due to a MANET partition) before being reestablished (e.g., due to a MANET merge). Since the DHCP client and relay are co-resident on the same MNBR, no special coordination is necessary for the MNGW to maintain routing information. The MNGW simply retains forwarding information base entries that identify the MNBR as the next-hop toward the prefix via the VET interface, and issues redirects over the VET interface the same as for any link. 3.5. Portable IP Prefixes Independent of any MNGW-aggregated addresses/prefixes (see: Section 3.4), a MNBR can retain portable IP prefixes (e.g., taken from a home network) as it travels between visited networks as long it coordinates in some fashion, e.g., with a mapping agent, prefix aggregation authority, etc. MNBRs that use IPv6 as the inner protocol can also self-generate portable IPv6 Unique Local Address (ULA) prefixes [RFC4193][I-D.ietf-ipv6-ula-central] and sub-delegate them on networks connected on their ingress interfaces. Such portable prefixes are not aggregated, redistributed or advertised by MNGWs and can therefore travel with the MNBR as it moves to new visited networks and/or configures peering arrangements with other nodes. Generation and coordination of portable prefixes can therefore occur independently of any other autoconfiguration considerations. Templin, et al. Expires October 5, 2008 [Page 11] Internet-Draft Virtual Ethernet April 2008 3.6. Forwarding Packets to Off-MANET Destinations MNBRs forward IP packets to off-MANET destinations via the VET interface using another MNBR's address as the inner next-hop address. For IPv6-in-IPv4 encapsulation using an ISATAP next-hop address, determination of the outer destination address is through static extraction of the embedded IPv4 address. For other IP-in-IP encapsulations, determination of the outer destination address may require additional supporting mechanisms. MNBRs that use IPv6 as the inner protocol can discover default router preferences and more-specific routes [RFC4191] by sending an RS over the VET interface to elicit an RA from another MNBR. After default and/or more-specific routes are discovered, the MNBR can forward IP packets via a specific MNBR as the next-hop router on the VET interface. When multiple default routers are available on the VET interface, the MNBR can use default router preferences, traffic engineering configurations, etc. to select the best exit router. 3.7. MANET-Local Communications When permitted by policy, pairs of MNRs that configure the endpoints of a communications session can avoid VET encapsulation by directly invoking the outer IP protocol using MLAs assigned to their MANET interfaces. For example, when the outer protocol is IPv4 a pair of communicating MNRs can use IPv4 MLAs for direct communications over their MANET interfaces without using the VET interface. 3.8. Multicast In multicast-capable deployments, MNRs provide a MANET-wide multicasting service such as Simplified Multicast Forwarding (SMF) [I-D.ietf-manet-smf] over their MANET interfaces so that outer IP multicast messages of site- or greater scope will be propagated across the MANET. For these deployments, MNBRs can also provide an inner IP multicast capability over their VET interfaces through mapping of the inner IP multicast address space to the outer IP multicast address space. MNBRs encapsulate inner IP multicast messages sent over the VET interface in any mid-layer headers (e.g., IPsec, SEAL, etc.) plus an outer IP header with a site-scoped outer IP multicast address as the destination. For the case of IPv6 and IPv4 as the inner/outer protocols (respectively), [RFC2529] provides mappings from the IPv6 multicast address space to the IPv4 multicast address space. For multicast-capable MANETs, use of the inner IP multicast service for operating the ND protocol over the VET is available but should be Templin, et al. Expires October 5, 2008 [Page 12] Internet-Draft Virtual Ethernet April 2008 used sparingly to minimize MANET-wide flooding. Therefore, MNBRs should use unicast ND services over the VET interface instead of multicast whenever possible. 3.9. Service Discovery MANET-wide service discovery can be accommodated by a suitable name- to-address resolution service. Examples of flooding-based services include the use of LLMNR [RFC4759] over the VET interface or mDNS [I-D.cheshire-dnsext-multicastdns] over an underlying MANET interface. More scalable and efficient service discovery mechanisms for MANETs are for further study. 3.10. Separation of IP Addressing Domains When the inner and outer IP protocols are different (i.e., IPv6-in- IPv4 or IPv4-in-IPv6), the dual-stack orientation provides a natural separation between the inner and outer IP addressing domains, and separate default routes can be configured for each domain. When the inner and outer IP protocols are the same (i.e., IPv4-in- IPv4 or IPv6-in-IPv6) separation between inner and outer IP addressing domains can only be determined through the examination of IP prefixes (else, the inner and outer IP addressing domains would overlap). In that case, special configurations/mechanisms may be necessary to support unambiguous determination of when to encapsulate using the VET interface vs when to forward using a MANET interface. In certain use cases, comingling the inner and outer addressing domains directly over MANET interfaces and without invoking VET encapsulation may be acceptable. 4. IANA Considerations A site-scoped IPv4 multicast group (TBD) for DHCPv4 server discovery is requested. The group should be allocated from the IPv4 multicast site-local scope address block the same as for '239.255.2.2' (i.e., the IPv4 multicast group allocated for the 'rasadv' protocol [RASADV]). 5. Security Considerations Security considerations for MANETs are found in [RFC2501][I-D.ietf-autoconf-manetarch] and apply also to the mechanisms and procedures specified in this document. Security considerations for MANET routing protocols that may be used Templin, et al. Expires October 5, 2008 [Page 13] Internet-Draft Virtual Ethernet April 2008 within this context are found in their respective specifications. 6. Related Work The authors acknowledge the work done by Brian Carpenter and Cyndi Jung in [RFC2529] that introduced the concept of intra-site automatic tunneling. This concept was later called: "Virtual Ethernet" and investigated by Quang Nguyen under the guidance of Dr. Lixia Zhang. Telcordia has proposed DHCP-related solutions for the CECOM MOSAIC program. The Naval Research Lab (NRL) Information Technology Division uses DHCP in their MANET research testbeds. Various IETF AUTOCONF working group proposals have suggested similar mechanisms. 7. Acknowledgements The following individuals gave direct and/or indirect input that was essential to the work: Jari Arkko, Teco Boot, Emmanuel Bacelli, James Bound, Thomas Clausen, Eric Fleischman, Bob Hinden, Joe Macker, Thomas Narten, Alexandru Petrescu, Jinmei Tatuya, Dave Thaler, Michaela Vanderveen 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. [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. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. Templin, et al. Expires October 5, 2008 [Page 14] Internet-Draft Virtual Ethernet April 2008 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, 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. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, March 2008. 9.2. Informative References [I-D.cheshire-dnsext-multicastdns] Cheshire, S. and M. Krochmal, "Multicast DNS", draft-cheshire-dnsext-multicastdns-06 (work in progress), August 2006. [I-D.fuller-240space] Fuller, V., "Reclassifying 240/4 as usable unicast address space", draft-fuller-240space-02 (work in progress), March 2008. [I-D.ietf-autoconf-manetarch] Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc Network Architecture", draft-ietf-autoconf-manetarch-07 (work in progress), November 2007. [I-D.ietf-dhc-subnet-alloc] Johnson, R., "Subnet Allocation Option", draft-ietf-dhc-subnet-alloc-06 (work in progress), November 2007. [I-D.ietf-ipv6-ula-central] Templin, et al. Expires October 5, 2008 [Page 15] Internet-Draft Virtual Ethernet April 2008 Hinden, R., "Centrally Assigned Unique Local IPv6 Unicast Addresses", draft-ietf-ipv6-ula-central-02 (work in progress), June 2007. [I-D.ietf-manet-smf] Macker, J. and S. Team, "Simplified Multicast Forwarding for MANET", draft-ietf-manet-smf-07 (work in progress), February 2008. [I-D.templin-seal] Templin, F., "Subnetwork Encapsulation and Adaptation Layer", draft-templin-seal-03 (work in progress), February 2008. [RASADV] MSDN, "Remote Access Server Advertisement (RASADV) Protocol Specification, http://msdn2.microsoft.com/en-us/library/cc240334.aspx", March 2008. [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. [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via IPv4 Clouds", RFC 3056, February 2001. [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. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Templin, et al. Expires October 5, 2008 [Page 16] Internet-Draft Virtual Ethernet April 2008 Internet Protocol", RFC 4301, December 2005. [RFC4759] Stastny, R., Shockey, R., and L. Conroy, "The ENUM Dip Indicator Parameter for the "tel" URI", RFC 4759, December 2006. [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, June 2007. [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007. Appendix A. Duplicate Address Detection (DAD) Considerations Pre-service DAD for an MLA assigned on a MANET interface (such as specified in [RFC4862]) 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 intermittent connectivity. An alternative to pre-service DAD is to autoconfigure pseudo-random MLAs on MANET interfaces and employ a passive in-service DAD (e.g., one that monitors routing protocol messages for duplicate assignments). Pseudo-random IPv6 MLAs can be generated with mechanisms such as CGAs, IPv6 privacy addresses, etc. with very small probability of collision. Pseudo-random IPv4 MLAs can be generated through random assignment from a suitably large IPv4 prefix space, e.g., the soon- to-be-reclassified 240/4 space [I-D.fuller-240space]. Consistent operational practices can assure uniqueness for MNGW- aggregated addresses/prefixes, while statistical properties for pseudo-random address self-generation can assure uniqueness for the MLAs assigned on a MNR's MANET interfaces. Still, an MLA delegation authority should be used when available, while a passive in-service DAD mechanism should be used to detect MLA duplications when their is no MLA delegation authority. Appendix B. Change Log (Note to RFC editor - this section to be removed before publication as an RFC.) Changes from -11 to 12: Templin, et al. Expires October 5, 2008 [Page 17] Internet-Draft Virtual Ethernet April 2008 o title change to "MANET Autoconfiguration using Virtual Ethernet". o DHCP prefix delegation for both IPv4 and IPv6 as primary address delegation mechanism. o IPv6 SLAAC for address autoconfiguration on the VET interface. o fixed editorials based on comments received. Changes from -10 to 11: o removed the transparent/opaque VET portal abstractions. o removed routing header as an option for MANET exit router selection. o included IPv6 SLAAC as an endorsed address configuration mechanism for the VET interface. Changes from -08 to -09: o Introduced the term "VET". o Changed address delegation language to speak of "MNBR-aggregated" instead of global/local. o Updated figures 1-3. o Explained why a MANET interface is "neutral". o Removed DHCPv4 "MLA Address option". Now, MNBRs can only be DHCPv4 servers; not relays. Changes from -07 to -08: o changed terms "unenhanced" and "enhanced" to "transparent" and "opaque". o revised MANET Router diagram. o introduced RFC3753 terminology for Mobile Router; ingress/egress interface. o changed abbreviations to "MNR" and "MNBR". o added text on ULAs and ULA-Cs to "Self-Generated Addresses". Templin, et al. Expires October 5, 2008 [Page 18] Internet-Draft Virtual Ethernet April 2008 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: 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: Templin, et al. Expires October 5, 2008 [Page 19] Internet-Draft Virtual Ethernet April 2008 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 (editor) Boeing Phantom Works P.O. Box 3707 MC 7L-49 Seattle, WA 98124 USA Email: fltemplin@acm.org Steven W. Russert Boeing Phantom Works P.O. Box 3707 MC 7L-49 Seattle, WA 98124 USA Email: steven.w.russert@boeing.com Seung Yi Boeing Phantom Works P.O. Box 3707 MC 7L-49 Seattle, WA 98124 USA Email: seung.yi@boeing.com Templin, et al. Expires October 5, 2008 [Page 20] Internet-Draft Virtual Ethernet April 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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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. Templin, et al. Expires October 5, 2008 [Page 21]