Network Working Group F. Templin, Ed. Internet-Draft Boeing Phantom Works Intended status: Informational October 14, 2008 Expires: April 17, 2009 Virtual Enterprise Traversal (VET) draft-templin-autoconf-dhcp-17.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 April 17, 2009. Abstract Enterprise networks connect routers over various link types, and may also connect to provider networks and/or the global Internet. Routers in enterprise networks must have a way to automatically provision IP addresses/prefixes and other information, and must also support post-autoconfiguration operations even for highly-dynamic networks. This document specifies a Virtual Enterprise Traversal (VET) abstraction for autoconfiguration and operation of routers in enterprise networks. Templin Expires April 17, 2009 [Page 1] Internet-Draft VET October 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Enterprise Characteristics . . . . . . . . . . . . . . . . . . 7 4. Autoconfiguration . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Enterprise-interior Interface Autoconfiguration . . . . . 9 4.2. VET Interface Autoconfiguration . . . . . . . . . . . . . 10 4.3. Enterprise Border Gateway Discovery and Enterprise Identification . . . . . . . . . . . . . . . . . . . . . . 10 4.4. Site-interior Interface Autoconfiguration . . . . . . . . 11 4.4.1. Autoconfiguration of IPv4 Addresses/Prefixes . . . . . 11 4.4.2. Autoconfiguration of IPv6 Addresses/Prefixes . . . . . 12 4.4.3. Prefix and Route Maintenance . . . . . . . . . . . . . 13 4.5. Portable and Self-Configured IP Prefixes . . . . . . . . . 13 5. Post-Autoconfiguration Operation . . . . . . . . . . . . . . . 13 5.1. Forwarding Packets to Destinations Outside of the Enterprise . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2. Enterprise-Local Communications . . . . . . . . . . . . . 14 5.3. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 15 5.4. Service Discovery . . . . . . . . . . . . . . . . . . . . 15 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . . 17 11.2. Informative References . . . . . . . . . . . . . . . . . . 18 Appendix A. Duplicate Address Detection (DAD) Considerations . . 19 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 23 Intellectual Property and Copyright Statements . . . . . . . . . . 24 Templin Expires April 17, 2009 [Page 2] Internet-Draft VET October 2008 1. Introduction Enterprise networks [RFC4852] connect routers over various link types (see: [RFC4861], Section 2.2). Certain Mobile Ad-hoc Networks (MANETs) [RFC2501] can be considered as a challenging example of an enterprise network, in that their topologies may change dynamically over time and that they may employ little/no active management by a centralized network administrative authority. These specialized characteristics for MANETs require careful consideration, but the same principles apply equally to other enterprise network scenarios. This document specifies a Virtual Enterprise Traversal (VET) abstraction for autoconfiguration and runtime operation of enterprise routers over various interface types, where addresses of different scopes may be assigned on various types of interfaces with diverse properties. Both IPv4 [RFC0791] and IPv6 [RFC2460] are discussed within this context. The use of standard DHCP [RFC2131][RFC3315] and neighbor discovery [RFC0826][RFC4861] mechanisms is assumed unless otherwise specified. Provider-edge Interfaces x x x | | | +--------------------+---+--------+----------+ E | | | | | n | I | | .... | | t | n +---+---+--------+---+ | e | t | +--------+ /| | r | e I x----+ | Host | I /*+------+--< p I | r n | |Function| n|**| | r n | n t | +--------+ t|**| | i t | a e x----+ V e|**+------+--< s e | l r . | E r|**| . | e r | f . | T f|**| . | f | V a . | +--------+ a|**| . | I a | i c . | | Router | c|**| . | n c | r e x----+ |Function| e \*+------+--< t e | t s | +--------+ \| | e s | u +---+---+--------+---+ | r | a | | .... | | i | l | | | | o +--------------------+---+--------+----------+ r | | | x x x Enterprise-edge Interfaces Figure 1: Enterprise Router Architecture Templin Expires April 17, 2009 [Page 3] Internet-Draft VET October 2008 Figure 1 above depicts the architectural model for an enterprise router. As shown in the figure, an enterprise router may have a variety of interface types including enterprise-edge, enterprise- interior, provider-edge, internal-virtual, as well as VET interfaces used for encapsulation of inner IP packets within outer IP headers. The different types of interfaces are defined, and the autoconfiguration mechanisms used for each type are specified. This architecture applies equally for MANET routers, in which enterprise- interior interfaces correspond to the wireless multihop radio interfaces typically associated with MANETs. Out of scope for this document is the autoconfiguration of provider interfaces, which must be coordinated in a manner specific to the service provider's network. The VET specification represents a functional superset of 6over4 [RFC2529] and ISATAP [RFC5214], and further supports additional encapsulations such as IPsec [RFC4301], SEAL [I-D.templin-seal], etc. The VET principles can be either directly or indirectly traced to the deliberations of the ROAD group in January 1992, and likely also to still earlier works. [RFC1955] captures the high-level architectural aspects of the ROAD group deliberations in a "New Scheme for Internet Routing and Addressing [ENCAPS] for IPNG". VET is related to the present-day activites of the IETF autoconf, dhc, ipv6, manet and v6ops working groups. 2. Terminology The mechanisms within this document build upon the fundamental principles of IP-within-IP encapsulation. 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. VET also supports the inclusion of "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 the normative references apply; the following terms are defined within the scope of this document: subnetwork the same as defined in [RFC3819]. Templin Expires April 17, 2009 [Page 4] Internet-Draft VET October 2008 enterprise the same as defined in [RFC4852]. site a logical and/or physical grouping of interfaces that connect a topological area less than or equal to the enterprise in scope. A site within an enterprise can be considered as an enterprise unto itself. Mobile Ad-hoc Network (MANET) a connected topology of mobile or fixed routers that maintain a routing structure among themselves over asymmetric reachability links (see: [RFC4861], Section 2.2), where a wide variety of MANETs share common properties with enterprise networks. Further information on MANETs can be found in [RFC2501]. enterprise/site/MANET throughout the remainder of this document, the term "enterprise" is used to collectively refer to any of enterprise/site/MANET, i.e., the VET mechanisms and operational principles apply equally to enterprises, sites and MANETs. enterprise router an Enterprise Interior Router, Enterprise Border Router, or Enterprise Border Gateway. For the purose of this specification, an enterprise router comprises a router function, a host function, one or more enterprise-interior interfaces and zero or more internal virtual, enterprise-edge, provider-edge and VET interfaces. Enterprise Interior Router (EIR) a fixed or mobile enterprise router that forwards packets over a set of enterprise-interior interfaces connected to the same enterprise. Enterprise Border Router (EBR) an EIR that connects edge networks to the enterprise, and/or connects multiple enterprises together. An EBR configures a seperate VET interface over each set of enterprise-interior interfaces that connect the EBR to each distinct enterprise, i.e., an EBR may configure mulitple VET interfaces - one for each distinct enterprise. All EBRs are also EIRs. Enterprise Border Gateway (EBG) an EBR that connects the enterprise to provider networks and can delegate addresses/prefixes to other EBRs within the enterprise. All EBGs are also EBRs. Templin Expires April 17, 2009 [Page 5] Internet-Draft VET October 2008 internal-virtual interface an EBR's attachment to an internal virual link (e.g., a loopback ). An internal-virtual interface is a special case of an enterprise-edge interface. enterprise-edge interface an EBR's attachment to a link (e.g., an ethernet, a wireless personal area network, etc.) on an arbitrarily-complex edge network that the EBR connects to an enterprise and/or to provider networks. By this definition, an internal-virtual interface that configures non-link-local addresses also qualifies as an enterprise-edge interface. provider-edge interface an EBR's attachment to the Internet, or to a provider network outside of the enterprise via which the Internet can be reached. enterprise-interior Interface a EIR's attachment to a link within an enterprise. An enterprise- interior interface is "neutral" in its orientation, i.e., it is inherently neither an enterprise-edge nor provider-edge interface. In particular, a packet may need to be forwarded over several enterprise-interior interfaces before it is forwarded via either an enterprise-edge or provider-edge interface. Enterprise Local Address (ELA) an enterprise-scoped IP address (e.g., an IPv6 Unique Local Address [RFC4193], an IPv4 privacy address [RFC1918], etc.) that is assigned to an enterprise-interior interface and unique within the enterprise. ELAs are used as identifiers for operating the routing protocol and/or locators for packet forwarding within the scope of the enterprise; ELAs are also used as *outer* IP addresses during encapsulation. Virtual Enterprise Traversal (VET) an abstraction that uses IP-in-IP encapsulation to span a multi- link enterprise in a single (inner) IP hop. VET interface an EBR's Non-Broadcast, Multiple Access interface used for Virtual Enterprise Traversal. The EBR configures a VET interface over a set of underlying enterprise-interior interface(s) belonging to the same enterprise. When there are multiple distinct enterprises (each with their own distinct set of enterprise-interior interfaces), the EBR configures a separate VET interface over each set of enterprise-interior interfaces, i.e., the EBR configures multiple VET interfaces. Templin Expires April 17, 2009 [Page 6] Internet-Draft VET October 2008 The VET interface encapsulates each inner IP packet in any mid- layer headers plus an outer IP header then forwards it on an underlying enterprise-interior interface such that the TTL/Hop Limit in the inner header is not decremented as the packet traverses the enterprise. The VET interface presents an automatic tunneling abstraction that represents the enterprise as a single IP hop. The following additional acronyms 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 3. Enterprise Characteristics Enterprises consist of links that are connected by enterprise routers as depicted in Figure 1. All enterprise routers also serve as Enterprise Interior Routers (EIRs) that typically participate in a routing protocol over enterprise-interior interfaces to discover routes that may include multiple Layer-2 or Layer-3 forwarding hops. Enterprise Border Routers (EBRs) are EIRs that connect edge networks and/or join multiple enterprises together, while Enterprise Border Gateways (EBGs) are EBRs that connect enterprises to provider networks. An enterprise may be as simple as a small collection of enterprise routers (and their attached edge networks); an enterprise may also contain other enterprises/sites and/or be a subnetwork of a larger enterprise. An enterprise may further encompass a set of branch offices connected to a home office over one or several service providers, e.g., through Virtual Private Network (VPN) tunnels. Enterprises 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 enterprise 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 enterprise without IP layer encapsulation. Enterprises that comprise heterogeneous link types and/or multiple IP subnets must also provide a routing service that operates as an IP Templin Expires April 17, 2009 [Page 7] Internet-Draft VET October 2008 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 enterprise such that specific autoconfiguration procedures are necessary to avoid multilink subnet issues [RFC4903]. In particular, we describe herein the use of IP-in-IP encapsulation to span the enterprise in a single (inner) IP hop in order to avoid the multilink subnet issues that arise when enterprise-interior interfaces are used directly by applications. Conceptually, an enterprise router (i.e, an EIR/EBR/EBG) embodies both a host function and router function. The host function supports global-scoped communications over any of the enterprise router's non- enterprise-interior interfaces according to the weak end system model [RFC1122] and also supports non-global-scoped communications over its enterprise-interior interfaces. The router function connects the enterprise router's attached edge networks to the enterprise and/or connects the enterprise to other networks including the Internet (see: Figure 1). In addition to other interface types, EBRs configure VET interfaces that view all other EBRs in an enterprise as single-hop neighbors, where the enterprise can also appear as a single IP hop within another enterprise. EBRs configure a separate VET interface for each distinct enterprise to which they connect, and discover a list of EBRs for each VET interface that can be used for forwarding packets to off-enterprise destinations. The following sections present the Virtual Enterprise Traversal approach. 4. Autoconfiguration EIRs configure one or more enterprise-interior interfaces and engage in routing protocols over those interfaces. They also configure zero or more provider-edge interfaces that connect the enterprise to a service provider, and zero or more enterprise-edge interfaces that attach edge networks to the enterprise. EIRs that configure enterprise-edge and/or provider-edge interfaces also act as EBRs, and configure a VET interface over a set of underlying enterprise-interior interfaces belonging to the same enterprise. (Note that an EBR may connect to multiple distinct enterprises, in which case it would configure multiple VET interfaces.) EIRs obtain addresses/prefixes and other autoconfiguration information using the mechanisms specified in the following sections. Templin Expires April 17, 2009 [Page 8] Internet-Draft VET October 2008 4.1. Enterprise-interior Interface Autoconfiguration When a EIR joins an enterprise, it first configures a unique IPv6 link-local address on each enterprise-interior interface that requires an IPv6 link-local capability and an IPv4 link-local address on each enterprise-interior 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. Next, the EIR configures an Enterprise Local Address (ELA) of the outer IP protocol version on each of its enterprise-interior interfaces and engages in any routing protocols on those interfaces. The EIR can configure an ELA via explicit management, DHCP autoconfiguration, pseudo-random self-generation from a suitably large address pool, or through an alternate autoconfiguration mechanism. DHCP configuration of ELAs may require support from relays within the enterprise that have already autoconfigured an ELA as well as an enterprise-wide multicast forwarding capability. For DHCPv6, relays that do not already know the ELA of a server relay requests to the 'All_DHCP_Servers' site-scoped IPv6 multicast group. For DHCPv4, relays that do not already know the ELA of a server relay requests to the site-scoped IPv4 multicast group address TBD (see: Section 6). DHCPv4 servers that delegate ELAs join the TBD multicast group and service any DHCPv4 messages received for that group. Self-generation of ELAs for IPv6 can be from a large IPv6 local-use address range, e.g., IPv6 Unique Local Addresses [RFC4193]. Self- generation of ELAs for IPv4 can be from a large IPv4 private address range, e.g., [I-D.fuller-240space]. When self-generation is used alone, the EIR must continuously monitor the ELAs for uniqueness, e.g., by monitoring the routing protocol, sending beacons, etc. (This continuous monitoring process is sometimes known as "in-service duplicate address detection"). A combined approach using both DHCP and self-generation is also possible. In this combined approach, the EIR first self-generates a temporary ELA which it will use only for the purpose of procuring an actual ELA from a DHCP server. Acting as a combined client/relay, the EIR then assigns the temporary ELA to an enterprise-interior interface, engages in the routing protocol and performs a relay- server exchange using the temporary ELA as an address for the relay. When the DHCP server delegates an actual ELA, the EIR abandons the Templin Expires April 17, 2009 [Page 9] Internet-Draft VET October 2008 temporary ELA, assigns the actual ELA to the enterprise-interior interface and re-engages in the routing protocol. Note that the range of ELAs delegated by a DHCP server must be disjoint from the range of ELAs used by the EIR for self-generation. 4.2. VET Interface Autoconfiguration EBRs configure a VET interface over a set of underlying enterprise- interior interfaces belonging to the same enterprise, where the VET interface presents a virtual view of all EBRs in the enterprise as single hop neighbors. 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 enterprise-interior interface. Further encapsulation details are specified in Section 5. When IPv6 and IPv4 are used as the inner/outer protocols (respectively), the EBR 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 ELA assigned to an underlying enterprise-interior interface, and need not be checked for uniqueness since the IPv4 ELA itself was already determined to be unique. Link- local address configuration for other inner/outer IP protocol combinations is through administrative configuration or through an unspecified alternate method. After the EBR configures a VET interface, it can communicate with other EBRs as single-hop neighbors. It can also confirm reachability of other EBRs through Neighbor Discovery (ND) and/or DHCP exchanges over the VET interface, or through other means such as information conveyed in the routing protocol. The EBR must be able to detect and recover from the loss of VET interface neighbors due to e.g., enterprise network partitions, node failures, etc. Mechanisms specified outside of this document 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. 4.3. Enterprise Border Gateway Discovery and Enterprise Identification After the EBR configures its VET interfaces, it next discovers a list of EBGs for each distinct enterprise to which it connects. The list can be discovered through information conveyed in the routing protocol or through the discovery mechanisms outlined in [RFC5214], Templin Expires April 17, 2009 [Page 10] Internet-Draft VET October 2008 Section 8.3.2. In particular, whether or not routing information is available the EBR can discover the list of EBGs by resolving an identifying name for the enterprise using an Enterprsie-local name resolution service (such as LLMNR [RFC4759] over the VET interface). In the absence of other identifying names, the EBR can resolve either the hostname "6over4" or the FQDN "6over4.example.com" (i.e., if an enterprise- specific suffix "example.com" is known) for multicast-capable enterprises. For non-multicast enterprises, the EBR can instead resolve the hostname "isatap" or the FQDN "isatap.example.com". Identifying names along with addresses of EBGs and/or the prefixes they aggregate serve as an identifier for the enterprise. 4.4. Site-interior Interface Autoconfiguration EBRs can acquire addresses and/or prefix delegations for assignment on enterprise-edge interfaces through autoconfiguration exchanges with EBGs over the VET interface. Site-interior interface autoconfiguration considerations are discussed in the following sections: 4.4.1. Autoconfiguration of IPv4 Addresses/Prefixes When IPv4 is used as the inner protocol, the EBR discovers the addresses of one or more EBGs 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 enterprise-edge interfaces. To perform the DHCPv4 prefix delegation exchange, a DHCPv4 client associated with the EBR's host function forwards a DHCPDISCOVER message with a Subnet Allocation option to a DHCPv4 relay associated with its router function, i.e., the EBR acts as both client and relay. The relay then forwards the message over the VET interface to the DHCPv4 server on an EBG. The forwarded DHCPDISCOVER will elicit a DHCPOFFER from the server containing IPv4 prefix delegations, and the EBR completes the delegation through a DHCPREQUEST/DHCPACK exchange. When the EBR receives IPv4 prefix delegations, it assigns the prefixes on enterprise-edge interfaces; it does not assign them on the VET interface nor on enterprise-interior interfaces. The EBR 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 enterprise-edge interfaces. Templin Expires April 17, 2009 [Page 11] Internet-Draft VET October 2008 4.4.2. Autoconfiguration of IPv6 Addresses/Prefixes When IPv6 is used as the inner protocol, the EBR sends unicast IPv6 Router Solicitation (RS) messages to EBGs 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 autoconfiguration is available. When the EBR 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 EBR receives an RA with the 'M' flag set to 1, the EBG that sent the RA also hosts a DHCPv6 server capable of delegating IPv6 prefixes (support for the EBG acting as a DHCPv6 relay may be considered in the future). If the RA also contains PIOs with the 'L' bit set to 0, the EBR can use them as hints of prefixes the server is willing to delegate. For example, an EBG can include a PIO with a prefix such as 2001:DB8::/48 as a hint of an aggregated prefix from which it is willing to delegate longer prefixes. Whether or not such hints are available, the EBR (acting as a requesting router) can use DHCPv6 prefix delegation [RFC3633] over a VET interface to obtain IPv6 prefixes from an EBG (acting as a delegating router). The EBR can then use the delegated prefixes for assignment and/or sub- delegation on its enterprise-edge interfaces; it can also act as an EBG on enterprises on which it is configured as a provider, and offer sub-delegations of the prefixes over a VET interface to other EBRs in those enterprises. The EBR obtains prefixes using either a 2-message or 4-message DHCPv6 exchange [RFC3315]. For example, to perform the 2-message exchange a DHCPv6 client associated with the EBR's host function forwards a Solicit message with an IA_PD option to a DHCPv6 relay associated with its router function, i.e., the EBR acts as both client and relay. The relay 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 EBR receives IPv6 prefix delegations, it assigns the prefixes on enterprise-edge interfaces only; it does not assign them on provider- edge, VET, or enterprise-interior interfaces (see: [RFC3633], Section 12.1). The EBR can also propose a specific prefix to the DHCPv6 server per Section 7 of [RFC3633], e.g., if a prefix delegation hint is available. The server will check the proposed prefix for consistency and uniqueness, then return it in the reply to the EBR if it was able to perform the delegation. The EBR can use mechanisms such as CGAs Templin Expires April 17, 2009 [Page 12] Internet-Draft VET October 2008 [RFC3972], IPv6 privacy address [RFC4941], etc. to self-generate addresses in conjunction with prefix delegation. 4.4.3. Prefix and Route Maintenance When DHCP prefix delegation is used, an EBG's DHCP server ensures that the delegations are unique within the enterprise and that its router function will forward IP packets over the VET interface to the EBR to which the prefix was delegated. The prefix delegation remains active as long as the EBR continues to issue renewals over the VET interface before the lease lifetime expires. The lease lifetime also keeps the delegation state active even if communications between the EBR and EBG is disrupted for a period of time (e.g., due to an enterprise network partition) before being reestablished (e.g., due to an enterprise network merge). Since the DHCP client and relay are co-resident on the same EBR, no special coordination is necessary for the EBG to maintain routing information. The EBG simply retains forwarding information base entries that identify the EBR as the next-hop toward the prefix via the VET interface, and issues ordinary redirects over the VET interface when necessary . 4.5. Portable and Self-Configured IP Prefixes Independent of any EBG-aggregated addresses/prefixes (see: Section 4.4), an EBR can retain portable IP prefixes (e.g., prefixes taken from a home network, IPv6 Unique Local Addresses (ULAs) [RFC4193][I-D.ietf-ipv6-ula-central], etc.) as it travels between visited enterprise networks as long it coordinates in some fashion, e.g., with a mapping agent, prefix aggregation authority, etc. EBRs can sub-delegate portable (and other self-configured) prefixes on networks connected on their enterprise-edge interfaces. Portable prefixes are not aggregated, redistributed or advertised by EBGs and can therefore travel with the EBR as it moves to new visited networks and/or configures peering arrangements with other nodes. Generation and coordination of portable (and other self-configured) prefixes can therefore occur independently of any other autoconfiguration considerations. 5. Post-Autoconfiguration Operation After a EIR has been autoconfigured, it participates in any routing protocols over enterprise-interior interfaces and forwards outer IP packets within the enterprise as for any ordinary router. Templin Expires April 17, 2009 [Page 13] Internet-Draft VET October 2008 EBRs can additionally engage in any inner IP routing protocols over enterprise-edge, provider-edge and VET interfaces interfaces, and can use those interfaces for forwarding inner IP packets to off- enterprise destinations. Note that these inner IP routing protocols are separate and distinct from any enterprise-interior routing protocols. The following sections discuss post-autoconfiguration operations: 5.1. Forwarding Packets to Destinations Outside of the Enterprise EBRs consult the inner IP forwarding table to determine the next hop address (e.g., the VET interface address of another EBR) for forwarding packets to destinations outside of the enterprise. When there is no forwarding information available, the EBR can discover the next-hop through FQDN or reverse lookup using the same name resolution services as for EBG discovery (see Section 4.3). For forwarding to next-hop addresses over VET interfaces that use IPv6-in-IPv4 encapsulation, EBRs determine the outer destination address through static extraction of the IPv4 address embedded in the next-hop ISATAP address. For other IP-in-IP encapsulations, determination of the outer destination address is through administrative configuration or through an unspecified alternate method. EBRs 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 EBR. After default and/or more-specific routes are discovered, the EBR can forward IP packets via a specific EBR as the next-hop router on the VET interface. When multiple default routers are available, the EBR can use default router preferences, routing protocol information, traffic engineering configurations, etc. to select the best exit router. 5.2. Enterprise-Local Communications When permitted by policy, pairs of EIRs that configure the endpoints of a communications session can avoid VET interface encapsulation by directly invoking the outer IP protocol using ELAs assigned to their enterprise-interior interfaces. For example, when the outer protocol is IPv4, a pair of communicating EIRs can use IPv4 ELAs for direct communications over their enterprise-interior interfaces without using the VET interface. Templin Expires April 17, 2009 [Page 14] Internet-Draft VET October 2008 5.3. Multicast In multicast-capable deployments, EIRs provide an enterprise-wide multicasting service such as Simplified Multicast Forwarding (SMF) [I-D.ietf-manet-smf] over their enterprise-interior interfaces such that outer IP multicast messages of site- or greater scope will be propagated across the enterprise. For such deployments, EBRs can also provide an inner IP multicast/broadcast capability over their VET interfaces through mapping of the inner IP multicast address space to the outer IP multicast address space. EBRs 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 other IP-in-IP encapsulations, mappings are established through administrative configuration or through an unspecified alternate method. For multicast-capable enterprises, use of the inner IP multicast service for operating the ND protocol over the VET interface is available but should be used sparingly to minimize enterprise-wide flooding. Therefore, EBRs should use unicast ND services over the VET interface instead of multicast whenever possible. 5.4. Service Discovery EIRs can peform enterprise-wide service discovery using 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 enterprise-interior interface. More scalable and efficient service discovery mechanisms are for further study. 6. IANA Considerations A Site-Local Scope IPv4 multicast group (TBD) for DHCPv4 server discovery is requested. The allocation should be taken from the 239.255.000.000-239.255.255.255 Site-Local Scope range in the IANA 'multicast-addresses' registry. 7. Security Considerations Security considerations for MANETs are found in [RFC2501]. Templin Expires April 17, 2009 [Page 15] Internet-Draft VET October 2008 Security concerns with tunneling along with recommendations that apply also to VET are found in [I-D.ietf-v6ops-tunnel-security-concerns] [RFC5214]. 8. 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. As for this document, these architectural principles also follow from earlier works articulated by the ROAD group deliberations of 1992. 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 proposals within the IETF have suggested similar mechanisms. 9. 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, Bob Hinden, Joe Macker, Thomas Narten, Alexandru Petrescu, John Spence, 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. 10. Contributors The following individuals have contributed to this document: Eric Fleischman (eric.fleischman@boeing.com) Thomas Henderson (thomas.r.henderson@boeing.com) Steven Russert (steven.w.russert@boeing.com) Seung Yi (seung.yi@boeing.com) Ian Chakeres (ian.chakeres@gmail.com) contributed to earlier versions of the document. 11. References Templin Expires April 17, 2009 [Page 16] Internet-Draft VET October 2008 11.1. Normative References [I-D.ietf-dhc-subnet-alloc] Johnson, R., "Subnet Allocation Option", draft-ietf-dhc-subnet-alloc-07 (work in progress), July 2008. [I-D.ietf-v6ops-tunnel-security-concerns] Hoagland, J., Krishnan, S., and D. Thaler, "Security Concerns With Tunneling", draft-ietf-v6ops-tunnel-security-concerns-00 (work in progress), July 2008. [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. [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. Templin Expires April 17, 2009 [Page 17] Internet-Draft VET October 2008 11.2. Informative References [I-D.cheshire-dnsext-multicastdns] Cheshire, S. and M. Krochmal, "Multicast DNS", draft-cheshire-dnsext-multicastdns-07 (work in progress), September 2008. [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-ipv6-ula-central] Hinden, R., "Centrally Assigned Unique Local IPv6 Unicast Addresses", draft-ietf-ipv6-ula-central-02 (work in progress), June 2007. [I-D.ietf-manet-smf] Macker, J. and S. Team, "Simplified Multicast Forwarding for MANET", draft-ietf-manet-smf-07 (work in progress), February 2008. [I-D.templin-seal] Templin, F., "The Subnetwork Encapsulation and Adaptation Layer (SEAL)", draft-templin-seal-23 (work in progress), August 2008. [RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC1955] Hinden, R., "New Scheme for Internet Routing and Addressing (ENCAPS) for IPNG", RFC 1955, June 1996. [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. Templin Expires April 17, 2009 [Page 18] Internet-Draft VET October 2008 [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 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. [RFC4852] Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D. Green, "IPv6 Enterprise Network Analysis - IP Layer 3 Focus", RFC 4852, April 2007. [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 A-priori uniqueness determination (also known as "pre-service DAD") for an ELA assigned on an enterprise-interior interface (such as specified in [RFC4862]) would require either flooding the entire enterprise or somehow discovering a link in the enterprise on which a node that configures a duplicate address is attached and performing a localized DAD exchange on that link. But, the control message Templin Expires April 17, 2009 [Page 19] Internet-Draft VET October 2008 overhead for such an enterprise-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 ELAs on enterprise-interior interfaces and employ a passive in-service DAD (e.g., one that monitors routing protocol messages for duplicate assignments). Pseudo-random IPv6 ELAs can be generated with mechanisms such as CGAs, IPv6 privacy addresses, etc. with very small probability of collision. Pseudo-random IPv4 ELAs 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 EBG- aggregated addresses/prefixes, while statistical properties for pseudo-random address self-generation can assure uniqueness for the ELAs assigned on an EIR's enterprise-interior interfaces. Still, an ELA delegation authority should be used when available, while a passive in-service DAD mechanism should be used to detect ELA duplications when there is no ELA delegation authority. Appendix B. Change Log (Note to RFC editor - this section to be removed before publication as an RFC.) Changes from -15 to 17: o title change to "Virtual Enterprise Traversal (VET)". o changed document focus from MANET-centric to the much-broader Enterprise-centric, where "Enterprise" is understood to also cover a wide range of MANET types. Changes from -14 to 15: o title change to "Virtual Enterprise Traversal (VET) for MANETs". o Address review comments Changes from -12 to 14: o title change to "The MANET Virtual Ethernet Abstraction". o Minor section rearrangement. Templin Expires April 17, 2009 [Page 20] Internet-Draft VET October 2008 o Clartifications on portable and self-configured prefixes. o Clarifications on DHCPv6 prefix delegation procedures. Changes from -11 to 12: 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. Templin Expires April 17, 2009 [Page 21] Internet-Draft VET October 2008 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: 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 Templin Expires April 17, 2009 [Page 22] Internet-Draft VET October 2008 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 Author's Address Fred L. Templin (editor) Boeing Phantom Works P.O. Box 3707 MC 7L-49 Seattle, WA 98124 USA Email: fltemplin@acm.org Templin Expires April 17, 2009 [Page 23] Internet-Draft VET October 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. 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. 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