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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin, Ed. 3 Internet-Draft Boeing Research & Technology 4 Intended status: Standards Track January 18, 2011 5 Expires: July 22, 2011 7 Virtual Enterprise Traversal (VET) 8 draft-templin-intarea-vet-22.txt 10 Abstract 12 Enterprise networks connect hosts and routers over various link 13 types, and often also connect to provider networks and/or the global 14 Internet. Enterprise network nodes require a means to automatically 15 provision addresses/prefixes and support internetworking operation in 16 a wide variety of use cases including Small Office, Home Office 17 (SOHO) networks, Mobile Ad hoc Networks (MANETs), ISP networks, 18 multi-organizational corporate networks and the interdomain core of 19 the global Internet itself. This document specifies a Virtual 20 Enterprise Traversal (VET) abstraction for autoconfiguration and 21 operation of nodes in enterprise networks. 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on July 22, 2011. 40 Copyright Notice 42 Copyright (c) 2011 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 59 3. Enterprise Network Characteristics . . . . . . . . . . . . . . 11 60 4. Autoconfiguration . . . . . . . . . . . . . . . . . . . . . . 13 61 4.1. Enterprise Router (ER) Autoconfiguration . . . . . . . . . 13 62 4.2. VET Border Router (VBR) Autoconfiguration . . . . . . . . 15 63 4.2.1. VET Interface Initialization . . . . . . . . . . . . . 15 64 4.2.2. Potential Router List (PRL) Discovery . . . . . . . . 15 65 4.2.3. Provider-Aggregated (PA) EID Prefix 66 Autoconfiguration . . . . . . . . . . . . . . . . . . 16 67 4.2.4. Provider-(In)dependent (PI) EID Prefix 68 Autoconfiguration . . . . . . . . . . . . . . . . . . 18 69 4.3. VET Border Gateway (VBG) Autoconfiguration . . . . . . . . 18 70 4.4. VET Host Autoconfiguration . . . . . . . . . . . . . . . . 19 71 5. Internetworking Operation . . . . . . . . . . . . . . . . . . 20 72 5.1. Routing Protocol Participation . . . . . . . . . . . . . . 20 73 5.1.1. PI Prefix Routing Considerations . . . . . . . . . . . 20 74 5.2. Default Route Configuration and Selection . . . . . . . . 21 75 5.3. Address Selection . . . . . . . . . . . . . . . . . . . . 21 76 5.4. Next Hop Determination . . . . . . . . . . . . . . . . . . 22 77 5.5. VET Interface Encapsulation/Decapsulation . . . . . . . . 23 78 5.5.1. Inner Network Layer Protocol . . . . . . . . . . . . . 23 79 5.5.2. Mid-Layer Encapsulation . . . . . . . . . . . . . . . 23 80 5.5.3. SEAL Encapsulation . . . . . . . . . . . . . . . . . . 23 81 5.5.4. Outer UDP Header Encapsulation . . . . . . . . . . . . 24 82 5.5.5. Outer IP Header Encapsulation . . . . . . . . . . . . 24 83 5.5.6. Decapsulation . . . . . . . . . . . . . . . . . . . . 25 84 5.6. Mobility and Multihoming Considerations . . . . . . . . . 25 85 5.7. Neighbor Coordination on VET Interfaces using SEAL . . . . 26 86 5.7.1. Router Discovery . . . . . . . . . . . . . . . . . . . 28 87 5.7.2. Neighbor Unreachability Detection . . . . . . . . . . 28 88 5.7.3. Redirect Function . . . . . . . . . . . . . . . . . . 29 89 5.8. Neighbor Coordination on VET Interfaces using IPsec . . . 30 90 5.9. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 30 91 5.9.1. Multicast over (Non)Multicast Enterprise Networks . . 30 92 5.9.2. Multicast Over Multicast-Capable Enterprise 93 Networks . . . . . . . . . . . . . . . . . . . . . . . 31 94 5.10. Service Discovery . . . . . . . . . . . . . . . . . . . . 32 95 5.11. VET Link Partitioning . . . . . . . . . . . . . . . . . . 32 96 5.12. VBG Prefix State Recovery . . . . . . . . . . . . . . . . 32 97 5.13. Support for Legacy ISATAP Services . . . . . . . . . . . . 32 98 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33 99 7. Security Considerations . . . . . . . . . . . . . . . . . . . 33 100 8. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 33 101 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 34 102 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 34 103 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35 104 11.1. Normative References . . . . . . . . . . . . . . . . . . . 35 105 11.2. Informative References . . . . . . . . . . . . . . . . . . 36 106 Appendix A. Duplicate Address Detection (DAD) Considerations . . 41 107 Appendix B. Anycast Services . . . . . . . . . . . . . . . . . . 41 108 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 42 109 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 45 111 1. Introduction 113 Enterprise networks [RFC4852] connect hosts and routers over various 114 link types (see [RFC4861], Section 2.2). The term "enterprise 115 network" in this context extends to a wide variety of use cases and 116 deployment scenarios. For example, an "enterprise" can be as small 117 as a Small Office, Home Office (SOHO) network, as complex as a multi- 118 organizational corporation, or as large as the global Internet 119 itself. Internet Service Provider (ISP) networks are another example 120 use case that fits well with the VET enterprise network model. 121 Mobile Ad hoc Networks (MANETs) [RFC2501] can also be considered as a 122 challenging example of an enterprise network, in that their 123 topologies may change dynamically over time and that they may employ 124 little/no active management by a centralized network administrative 125 authority. These specialized characteristics for MANETs require 126 careful consideration, but the same principles apply equally to other 127 enterprise network scenarios. 129 This document specifies a Virtual Enterprise Traversal (VET) 130 abstraction for autoconfiguration and internetworking operation, 131 where addresses of different scopes may be assigned on various types 132 of interfaces with diverse properties. Both IPv4/ICMPv4 133 [RFC0791][RFC0792] and IPv6/ICMPv6 [RFC2460][RFC4443] are discussed 134 within this context (other network layer protocols are also 135 considered). The use of standard DHCP [RFC2131] [RFC3315] is assumed 136 unless otherwise specified. 138 Provider-Edge Interfaces 139 x x x 140 | | | 141 +--------------------+---+--------+----------+ E 142 | | | | | n 143 | I | | .... | | t 144 | n +---+---+--------+---+ | e 145 | t | +--------+ /| | r 146 | e I x----+ | Host | I /*+------+--< p I 147 | r n | |Function| n|**| | r n 148 | n t | +--------+ t|**| | i t 149 | a e x----+ V e|**+------+--< s e 150 | l r . | E r|**| . | e r 151 | f . | T f|**| . | f 152 | V a . | +--------+ a|**| . | I a 153 | i c . | | Router | c|**| . | n c 154 | r e x----+ |Function| e \*+------+--< t e 155 | t s | +--------+ \| | e s 156 | u +---+---+--------+---+ | r 157 | a | | .... | | i 158 | l | | | | o 159 +--------------------+---+--------+----------+ r 160 | | | 161 x x x 162 Enterprise-Edge Interfaces 164 Figure 1: Enterprise Router (ER) Architecture 166 Figure 1 above depicts the architectural model for an Enterprise 167 Router (ER). As shown in the figure, an ER may have a variety of 168 interface types including enterprise-edge, enterprise-interior, 169 provider-edge, internal-virtual, as well as VET interfaces used for 170 encapsulating inner network layer protocol packets for transmission 171 over outer IPv4 or IPv6 networks. The different types of interfaces 172 are defined, and the autoconfiguration mechanisms used for each type 173 are specified. This architecture applies equally for MANET routers, 174 in which enterprise-interior interfaces typically correspond to the 175 wireless multihop radio interfaces associated with MANETs. Out of 176 scope for this document is the autoconfiguration of provider 177 interfaces, which must be coordinated in a manner specific to the 178 service provider's network. 180 Enterprise networks require a means for supporting both Provider- 181 (In)dependent (PI) and Provider-Aggregated (PA) addressing. This is 182 especially true for enterprise network scenarios that involve 183 mobility and multihoming. The VET specification provides adaptable 184 mechanisms that address these and other issues in a wide variety of 185 enterprise network use cases. 187 The VET framework builds on a Non-Broadcast Multiple Access (NBMA) 188 [RFC2491] virtual interface model in a manner similar to other 189 automatic tunneling technologies [RFC2529][RFC5214]. VET interfaces 190 support the encapsulation of inner network layer protocol packets 191 over IP networks (i.e., either IPv4 or IPv6). VET is also compatible 192 with mid-layer encapsulation technologies including IPsec [RFC4301], 193 and supports both stateful and stateless prefix delegation. 195 VET and its associated technologies (including the Subnetwork 196 Encapsulation and Adaptation Layer (SEAL) [I-D.templin-intarea-seal]) 197 are functional building blocks for a new Internetworking architecture 198 based on the Internet Routing Overlay Network (IRON) 199 [I-D.templin-iron] and Routing and Addressing in Networks with Global 200 Enterprise Recursion (RANGER) [RFC5720] [I-D.russert-rangers]. Many 201 of the VET principles can be traced to the deliberations of the ROAD 202 group in January 1992, and also to still earlier initiatives 203 including NIMROD [RFC1753] and the Catenet model for internetworking 204 [CATENET] [IEN48] [RFC2775]. The high-level architectural aspects of 205 the ROAD group deliberations are captured in a "New Scheme for 206 Internet Routing and Addressing (ENCAPS) for IPNG" [RFC1955]. 208 VET is related to the present-day activities of the IETF INTAREA, 209 AUTOCONF, DHC, IPv6, MANET, and V6OPS working groups, as well as the 210 IRTF RRG working group. 212 2. Terminology 214 The mechanisms within this document build upon the fundamental 215 principles of IP encapsulation. The term "inner" refers to the 216 innermost {address, protocol, header, packet, etc.} *before* 217 encapsulation, and the term "outer" refers to the outermost {address, 218 protocol, header, packet, etc.} *after* encapsulation. VET also 219 accommodates "mid-layer" encapsulations including the Subnetwork 220 Encapsulation and Adaptation Layer (SEAL) [I-D.templin-intarea-seal], 221 IPsec [RFC4301], etc. 223 The terminology in the normative references apply; the following 224 terms are defined within the scope of this document: 226 Virtual Enterprise Traversal (VET) 227 an abstraction that uses encapsulation to create virtual overlays 228 for transporting inner network layer packets over outer IPv4 and 229 IPv6 enterprise networks. 231 enterprise network 232 the same as defined in [RFC4852]. An enterprise network is 233 further understood to refer to a cooperative networked collective 234 of devices within a structured IP routing and addressing plan and 235 with a commonality of business, social, political, etc., 236 interests. Minimally, the only commonality of interest in some 237 enterprise network scenarios may be the cooperative provisioning 238 of connectivity itself. 240 subnetwork 241 the same as defined in [RFC3819]. 243 site 244 a logical and/or physical grouping of interfaces that connect a 245 topological area less than or equal to an enterprise network in 246 scope. From a network organizational standpoint, a site within an 247 enterprise network can be considered as an enterprise network unto 248 itself. 250 Mobile Ad hoc Network (MANET) 251 a connected topology of mobile or fixed routers that maintain a 252 routing structure among themselves over links that often have 253 dynamic connectivity properties. The characteristics of MANETs 254 are described in [RFC2501], Section 3, and a wide variety of 255 MANETs share common properties with enterprise networks. 257 enterprise/site/MANET 258 throughout the remainder of this document, the term "enterprise 259 network" is used to collectively refer to any of {enterprise, 260 site, MANET}, i.e., the VET mechanisms and operational principles 261 can be applied to enterprises, sites, and MANETs of any size or 262 shape. 264 VET link 265 a virtual link that uses automatic tunneling to create an overlay 266 network that spans an enterprise network routing region. VET 267 links can be segmented (e.g., by filtering gateways) into multiple 268 distinct segments that can be joined together by bridges or IP 269 routers the same as for any link. Bridging would view the 270 multiple (bridged) segments as a single VET link, whereas IP 271 routing would view the multiple segments as multiple distinct VET 272 links. VET links can further be partitioned into multiple logical 273 areas, where each area is identified by a distinct set of border 274 nodes. 276 VET links configured over non-multicast enterprise networks 277 support only Non-Broadcast, Multiple Access (NBMA) services; VET 278 links configured over enterprise networks that support multicast 279 can support both NBMA and native multicast services. All nodes 280 connected to the same VET link appear as neighbors from the 281 standpoint of the inner network layer. 283 Enterprise Router (ER) 284 As depicted in Figure 1, an Enterprise Router (ER) is a fixed or 285 mobile router that comprises a router function, a host function, 286 one or more enterprise-interior interfaces, and zero or more 287 internal virtual, enterprise-edge, provider-edge, and VET 288 interfaces. At a minimum, an ER forwards outer IP packets over 289 one or more sets of enterprise-interior interfaces, where each set 290 connects to a distinct enterprise network. 292 VET Border Router (VBR) 293 an ER that connects edge networks to VET links and/or connects 294 multiple VET links together. A VBR is a tunnel endpoint router, 295 and it configures a separate VET interface for each distinct VET 296 link. All VBRs are also ERs. 298 VET Border Gateway (VBG) 299 a VBR that connects VET links to provider networks. A VBG may 300 alternately act as "half-gateway", and forward the packets it 301 receives from neighbors on the VET link to another VBG on the same 302 VET link. All VBGs are also VBRs. 304 VET host 305 any node (host or router) that configures a VET interface for 306 host-operation only. Note that a node may configure some of its 307 VET interfaces as host interfaces and others as router interfaces. 309 VET node 310 any node (host or router) that configures and uses a VET 311 interface. 313 enterprise-interior interface 314 an ER's attachment to a link within an enterprise network. 315 Packets sent over enterprise-interior interfaces may be forwarded 316 over multiple additional enterprise-interior interfaces within the 317 enterprise network before they reach either their final 318 destination or a border router/gateway. Enterprise-interior 319 interfaces connect laterally within the IP network hierarchy. 321 enterprise-edge interface 322 a VBR's attachment to a link (e.g., an Ethernet, a wireless 323 personal area network, etc.) on an arbitrarily complex edge 324 network that the VBR connects to a VET link and/or a provider 325 network. Enterprise-edge interfaces connect to lower levels 326 within the IP network hierarchy. 328 provider-edge interface 329 a VBR's attachment to the Internet or to a provider network via 330 which the Internet can be reached. Provider-edge interfaces 331 connect to higher levels within the IP network hierarchy. 333 internal-virtual interface 334 an interface that is internal to a VET node and does not in itself 335 directly attach to a tangible link, e.g., a loopback interface. 337 VET interface 338 a VET node's attachment to a VET link. VET nodes configure each 339 VET interface over a set of underlying enterprise-interior 340 interfaces that connect to a routing region spanned by a single 341 VET link. When there are multiple distinct VET links (each with 342 their own distinct set of underlying interfaces), the VET node 343 configures a separate VET interface for each link. 345 The VET interface encapsulates each inner packet in any mid-layer 346 headers followed by an outer IP header, then forwards the packet 347 on an underlying interface such that the Time to Live (TTL) - Hop 348 Limit in the inner header is not decremented as the packet 349 traverses the link. The VET interface therefore presents an 350 automatic tunneling abstraction that represents the VET link as a 351 single hop to the inner network layer. 353 Provider Aggregated (PA) prefix 354 a network layer protocol prefix that is delegated to a VET node by 355 a provider network. 357 Provider-(In)dependent (PI) address/prefix 358 a network layer protocol prefix that is delegated to a VET node by 359 an independent prefix registration authority. 361 Routing Locator (RLOC) 362 a public-scope or enterprise-local-scope IP address that can 363 appear in enterprise-interior and/or interdomain routing tables. 364 Public-scope RLOCs are delegated to specific enterprise networks 365 and routable within both the enterprise-interior and interdomain 366 routing regions. Enterprise-local-scope RLOCs (e.g., IPv6 Unique 367 Local Addresses [RFC4193], IPv4 privacy addresses [RFC1918], etc.) 368 are self-generated by individual enterprise networks and routable 369 only within the enterprise-interior routing region. 371 ERs use RLOCs for operating the enterprise-interior routing 372 protocol and for next-hop determination in forwarding packets 373 addressed to other RLOCs. End systems can use RLOCs as addresses 374 for end-to-end communications between peers within the same 375 enterprise network. VET interfaces treat RLOCs as *outer* IP 376 addresses during encapsulation. 378 Endpoint Interface iDentifier (EID) 379 a public-scope network layer address that is routable within 380 enterprise-edge and/or VET overlay networks. In a pure mapping 381 system, EID prefixes are not routable within the interdomain 382 routing system. In a hybrid routing/mapping system, EID prefixes 383 may be represented within the same interdomain routing instances 384 that distribute RLOC prefixes. In either case, EID prefixes are 385 separate and distinct from any RLOC prefix space, but they are 386 mapped to RLOC addresses to support packet forwarding over VET 387 interfaces. 389 VBRs participate in any EID-based routing instances and use EID 390 addresses for next-hop determination. End systems can use EIDs as 391 addresses for end-to-end communications between peers either 392 within the same enterprise network or within different enterprise 393 networks. VET interfaces treat EIDs as *inner* network layer 394 addresses during encapsulation. 396 Note that an EID can also be used as an *outer* network layer 397 address if there are nested encapsulations. In that case, the EID 398 would appear as an RLOC to the innermost encapsulation. 400 The following additional acronyms are used throughout the document: 402 CGA - Cryptographically Generated Address 403 DHCP(v4, v6) - Dynamic Host Configuration Protocol 404 ECMP - Equal Cost Multi Path 405 FIB - Forwarding Information Base 406 ICMP - either ICMPv4 or ICMPv6 407 IP - either IPv4 or IPv6 408 ISATAP - Intra-Site Automatic Tunnel Addressing Protocol 409 NBMA - Non-Broadcast, Multiple Access 410 ND - Neighbor Discovery 411 PIO - Prefix Information Option 412 PRL - Potential Router List 413 PRLNAME - Identifying name for the PRL 414 RIB - Routing Information Base 415 RIO - Route Information Option 416 SCMP - SEAL Control Message Protocol 417 SEAL - Subnetwork Encapsulation and Adaptation Layer 418 SLAAC - IPv6 StateLess Address AutoConfiguration 419 SNS/SNA - SEAL Neighbor Solicitation/Advertisement 420 SRS/SRA - SEAL Router Solicitation/Advertisement 422 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 423 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 424 document are to be interpreted as described in [RFC2119]. When used 425 in lower case (e.g., must, must not, etc.), these words MUST NOT be 426 interpreted as described in [RFC2119], but are rather interpreted as 427 they would be in common English. 429 3. Enterprise Network Characteristics 431 Enterprise networks consist of links that are connected by Enterprise 432 Routers (ERs) as depicted in Figure 1. ERs typically participate in 433 a routing protocol over enterprise-interior interfaces to discover 434 routes that may include multiple Layer 2 or Layer 3 forwarding hops. 435 VET Border Routers (VBRs) are ERs that connect edge networks to VET 436 links that span enterprise networks. VET Border Gateways (VBGs) are 437 VBRs that connect VET links to provider networks. 439 Conceptually, an ER embodies both a host function and router 440 function, and supports communications according to the weak end- 441 system model [RFC1122]. The router function engages in the 442 enterprise-interior routing protocol on its enterprise-interior 443 interfaces, connects any of the ER's edge networks to its VET links, 444 and may also connect the VET links to provider networks (see 445 Figure 1). The host function typically supports network management 446 applications, but may also support diverse applications typically 447 associated with general-purpose computing platforms. 449 An enterprise network may be as simple as a small collection of ERs 450 and their attached edge networks; an enterprise network may also 451 contain other enterprise networks and/or be a subnetwork of a larger 452 enterprise network. An enterprise network may further encompass a 453 set of branch offices and/or nomadic hosts connected to a home office 454 over one or several service providers, e.g., through Virtual Private 455 Network (VPN) tunnels. Finally, an enterprise network may contain 456 many internal partitions that are logical or physical groupings of 457 nodes for the purpose of load balancing, organizational separation, 458 etc. In that case, each internal partition resembles an individual 459 segment of a bridged LAN. 461 Enterprise networks that comprise link types with sufficiently 462 similar properties (e.g., Layer 2 (L2) address formats, maximum 463 transmission units (MTUs), etc.) can configure a subnetwork routing 464 service such that the inner network layer sees the underlying network 465 as an ordinary shared link the same as for a (bridged) campus LAN 466 (this is often the case with large cellular operator networks). In 467 that case, a single inner network layer hop is sufficient to traverse 468 the underlying network. Enterprise networks that comprise link types 469 with diverse properties and/or configure multiple IP subnets must 470 also provide an enterprise-interior routing service that operates as 471 an IP layer mechanism. In that case, multiple inner network layer 472 hops may be necessary to traverse the underlying network such that 473 care must be taken to avoid multi-link subnet issues [RFC4903]. 475 In addition to other interface types, VET nodes configure VET 476 interfaces that view all other nodes on the VET link as neighbors on 477 a virtual NBMA link. VET nodes configure a separate VET interface 478 for each distinct VET link to which they connect, and discover 479 neighbors on the link that can be used for forwarding packets to off- 480 link destinations. VET interface neighbor relationships may be 481 either unidirectional or bidirectional. 483 A unidirectional neighbor relationship is typically established and 484 maintained as a result of network layer control protocol messaging in 485 a manner that parallels IPv6 neighbor discovery [RFC4861]. A 486 bidirectional neighbor relationship is typically established and 487 maintained as result of a short transaction between the neighbors 488 carried by a reliable transport protocol such as TCP. The protocol 489 details of the transaction are out of scope for this document, and 490 indeed need not be standardized as long as both neighbors observe the 491 same specifications. 493 For each distinct VET link , a trust basis must be established and 494 consistently applied. For example, for VET links configured over 495 enterprise networks in which VBRs establish symmetric security 496 associations, mechanisms such as IPsec [RFC4301] can be used to 497 assure authentication and confidentiality. In other enterprise 498 network scenarios, asymmetric securing mechanisms such as SEcure 499 Neighbor Discovery (SEND) [RFC3971] may be necessary. Still other 500 enterprise networks may find it sufficient to employ additional 501 encapsulations (e.g., SEAL [I-D.templin-intarea-seal]) that include a 502 simple per-packet nonce to detect off-path attacks. 504 Finally, for VET links configured over enterprise networks with a 505 centralized management structure (e.g., a corporate campus network, 506 an ISP network, etc.), a hybrid routing/mapping service can be 507 deployed using a synchronized set of VBGs. In that case, the VBGs 508 can provide a "default mapper" [I-D.jen-apt] service used for short- 509 term packet forwarding until route-optimized paths can be 510 established. For VET links configured over enterprise networks with 511 a distributed management structure (e.g., disconnected MANETs), peer- 512 to-peer coordination between the VET nodes themselves without the 513 assistance of VBGs may be required. Recognizing that various use 514 cases will entail a continuum between a fully centralized and fully 515 distributed approach, the following sections present the mechanisms 516 of Virtual Enterprise Traversal as they apply to a wide variety of 517 scenarios. 519 4. Autoconfiguration 521 ERs, VBRs, VBGs, and VET hosts configure themselves for operation as 522 specified in the following subsections. 524 4.1. Enterprise Router (ER) Autoconfiguration 526 ERs configure enterprise-interior interfaces and engage in any 527 routing protocols over those interfaces. 529 When an ER joins an enterprise network, it first configures an IPv6 530 link-local address on each enterprise-interior interface that 531 requires an IPv6 link-local capability and configures an IPv4 link- 532 local address on each enterprise-interior interface that requires an 533 IPv4 link-local capability. IPv6 link-local address generation 534 mechanisms include Cryptographically Generated Addresses (CGAs) 535 [RFC3972], IPv6 Privacy Addresses [RFC4941], StateLess Address 536 AutoConfiguration (SLAAC) using EUI-64 interface identifiers 537 [RFC4291] [RFC4862], etc. The mechanisms specified in [RFC3927] 538 provide an IPv4 link-local address generation capability. 540 Next, the ER configures one or more RLOCs and engages in any routing 541 protocols on its enterprise-interior interfaces. The ER can 542 configure RLOCs via administrative configuration, pseudo-random self- 543 generation from a suitably large address pool, DHCP 544 autoconfiguration, or through an alternate autoconfiguration 545 mechanism. 547 Pseudo-random self-generation of IPv6 RLOCs can be from a large 548 public or local-use IPv6 address range (e.g., IPv6 Unique Local 549 Addresses [RFC4193]). Pseudo-random self-generation of IPv4 RLOCs 550 can be from a large public or local-use IPv4 address range (e.g., 551 [RFC1918]). When self-generation is used alone, the ER continuously 552 monitors the RLOCs for uniqueness, e.g., by monitoring the 553 enterprise-interior routing protocol. (Note however that anycast 554 RLOCs may be assigned to multiple enterprise-interior interfaces; 555 hence, monitoring for uniqueness applies only to RLOCs that are 556 intended as unicast.) 558 DHCP autoconfiguration of RLOCs uses standard DHCP procedures, and 559 ERs acting as DHCP clients SHOULD include Authentication options in 560 their DHCP messages [RFC3118] [RFC3315]. In some enterprise network 561 scenarios (e.g., MANETs that include links with asymmetric 562 reachability properties), DHCP operation may require support from 563 multiple relays. This may lead to considerable DHCP message relaying 564 until a server is located, but the DHCP Authentication Replay 565 Detection vector provides relays with a means for avoiding message 566 duplication. 568 In all scenarios, the amount of DHCP relaying required can be 569 significantly reduced if each relay has a way of contacting a DHCP 570 server directly. In particular, if the relay can discover the 571 unicast addresses for one or more servers (e.g., by discovering the 572 unicast RLOC addresses of VBGs as described in Section 4.2.2) it can 573 forward DHCP requests directly to the unicast address(es) of the 574 server(s). If the relay does not know the unicast address of a 575 server, it can forward DHCP requests to a site-scoped DHCP server 576 multicast address if the enterprise network supports site-scoped 577 multicast services. For DHCPv6, relays can forward requests to the 578 site-scoped IPv6 multicast group address 'All_DHCP_Servers' 579 [RFC3315]. For DHCPv4, relays can forward requests to the site- 580 scoped IPv4 multicast group address 'All_DHCPv4_Servers', which 581 SHOULD be set to 239.255.2.1 unless an alternate multicast group for 582 the enterprise network is known. DHCPv4 servers that delegate RLOCs 583 SHOULD therefore join the 'All_DHCPv4_Servers' multicast group and 584 service any DHCPv4 messages received for that group. 586 A combined approach using both DHCP and self-generation is also 587 possible when the ER configures both a DHCP client and relay that are 588 connected, e.g., via a pair of back-to-back connected Ethernet 589 interfaces, a tun/tap interface, a loopback interface, inter-process 590 communication, etc. The ER first self-generates an RLOC taken from a 591 temporary addressing range used only for the bootstrapping purpose of 592 procuring an actual RLOC taken from a delegated addressing range. 593 The ER then engages in the enterprise-interior routing protocol and 594 performs a DHCP exchange as above using the temporary RLOC as the 595 address of its relay function. When the DHCP server delegates an 596 actual RLOC address/prefix, the ER abandons the temporary RLOC and 597 re-engages in the enterprise-interior routing protocol using an RLOC 598 taken from the delegation. 600 Alternatively (or in addition to the above), the ER can request RLOC 601 prefix delegations via an automated prefix delegation exchange over 602 an enterprise-interior interface and can assign the prefix(es) on 603 enterprise-edge interfaces. Note that in some cases, the same 604 enterprise-edge interfaces may assign both RLOC and EID addresses if 605 there is a means for source address selection. In other cases (e.g., 606 for separation of security domains), RLOCs and EIDs are assigned on 607 separate sets of enterprise-edge interfaces. 609 In some enterprise network scenarios (e.g., MANETs that include links 610 with asymmetric reachability properties), assignment of RLOCs on 611 enterprise-interior interfaces as singleton addresses (i.e., as 612 addresses with /32 prefix lengths for IPv4, or as addresses with /128 613 prefix lengths for IPv6) MAY be necessary to avoid multi-link subnet 614 issues. 616 4.2. VET Border Router (VBR) Autoconfiguration 618 VBRs are ERs that configure and use one or more VET interfaces. In 619 addition to the ER autoconfiguration procedures specified in 620 Section 4.1, VBRs perform the following autoconfiguration operations. 622 4.2.1. VET Interface Initialization 624 VBRs configure a separate VET interface for each VET link, where each 625 VET link spans a distinct sets of underlying links belonging to the 626 same enterprise network. All nodes on the VET link appear as single- 627 hop neighbors from the standpoint of the inner network layer protocol 628 through the use of encapsulation. 630 The VBR binds each VET interface to one or more underlying 631 interfaces, and uses the underlying interface addresses as RLOCs to 632 serve as the outer source addresses for encapsulated packets. The 633 VBR then assigns a link-local address to each VET interface if 634 necessary. When IPv6 and IPv4 are used as the inner/outer protocols 635 (respectively), the VBR can autoconfigure an IPv6 link-local address 636 on the VET interface using a modified EUI-64 interface identifier 637 based on an IPv4 RLOC address (see Section 2.2.1 of [RFC5342]). 638 Link-local address configuration for other inner/outer protocol 639 combinations is through administrative configuration, random self- 640 generation (e.g., [RFC4941], etc.) or through an unspecified 641 alternate method. 643 4.2.2. Potential Router List (PRL) Discovery 645 After initializing the VET interface, the VBR next discovers a 646 Potential Router List (PRL) for the VET link that includes the RLOC 647 addresses of VBGs. The PRL can be discovered through administrative 648 configuration, information conveyed in the enterprise-interior 649 routing protocol, an anycast VBG discovery message exchange, a DHCP 650 option, etc. In multicast-capable enterprise networks, VBRs can also 651 listen for advertisements on the 'rasadv' [RASADV] multicast group 652 address. 654 When no other information is available, the VBR can resolve an 655 identifying name for the PRL ('PRLNAME') formed as 656 'hostname.domainname', where 'hostname' is an enterprise-specific 657 name string and 'domainname' is an enterprise-specific Domain Name 658 System (DNS) suffix [RFC1035]. The VBR discovers 'PRLNAME' through 659 administrative configuration, the DHCP Domain Name option [RFC2132], 660 'rasadv' protocol advertisements, link-layer information (e.g., an 661 IEEE 802.11 Service Set Identifier (SSID)), or through some other 662 means specific to the enterprise network. The VBR can also obtain 663 'PRLNAME' as part of an arrangement with a private-sector PI prefix 664 vendor (see: Section 4.2.4). 666 In the absence of other information, the VBR sets the 'hostname' 667 component of 'PRLNAME' to "isatapv2" and sets the 'domainname' 668 component to an enterprise-specific DNS suffix (e.g., "example.com"). 669 Isolated enterprise networks that do not connect to the outside world 670 may have no enterprise-specific DNS suffix, in which case the 671 'PRLNAME' consists only of the 'hostname' component. (Note that the 672 default hostname "isatapv2" is intentionally distinct from the 673 convention specified in [RFC5214].) 675 After discovering 'PRLNAME', the VBR resolves the name into a list of 676 RLOC addresses through a name service lookup. For centrally managed 677 enterprise networks, the VBR resolves 'PRLNAME' using an enterprise- 678 local name service (e.g., the DNS). For enterprises with no 679 centralized management structure, the VBR resolves 'PRLNAME' using 680 Link-Local Multicast Name Resolution (LLMNR) [RFC4795] over the VET 681 interface. In that case, all VBGs in the PRL respond to the LLMNR 682 query, and the VBR accepts the union of all responses. 684 4.2.3. Provider-Aggregated (PA) EID Prefix Autoconfiguration 686 VBRs that connect their enterprise networks to a provider network 687 obtain Provider-Aggregated (PA) EID prefixes through stateful and/or 688 stateless autoconfiguration mechanisms. The stateful and stateless 689 approaches are discussed in the following subsections. 691 4.2.3.1. Stateful Prefix Delegation 693 For IPv4, VBRs acquire IPv4 PA EID prefixes through administrative 694 configuration, an automated IPv4 prefix delegation exchange, etc. 696 For IPv6, VBRs acquire IPv6 PA EID prefixes through administrative 697 configuration or through DHCPv6 Prefix Delegation exchanges with an 698 VBG acting as a DHCP relay/server. In particular, the VBR (acting as 699 a requesting router) can use DHCPv6 prefix delegation [RFC3633] over 700 the VET interface to obtain prefixes from the VBG (acting as a 701 delegating router). The VBR obtains prefixes using either a 702 2-message or 4-message DHCPv6 exchange [RFC3315]. 704 To perform the 2-message exchange, the VBR's DHCPv6 client function 705 can send a Solicit message with an IA_PD option either directly or 706 via the VBR's own DHCPv6 relay function (see Section 4.1). The VBR's 707 VET interface then forwards the message using VET encapsulation (see: 708 Section 5.4) to a VBG which either services the request or relays it 709 further. The forwarded Solicit message will elicit a Reply message 710 from the server containing prefix delegations. The VBR can also 711 propose a specific prefix to the DHCPv6 server per Section 7 of 712 [RFC3633]. The server will check the proposed prefix for consistency 713 and uniqueness, then return it in the Reply message if it was able to 714 perform the delegation. 716 After the VBR receives IPv4 and/or IPv6 prefix delegations, it can 717 provision the prefixes on enterprise-edge interfaces as well as on 718 other VET interfaces configured over child enterprise networks for 719 which it acts as an VBG. The VBR can also provision the prefixes on 720 enterprise-interior interfaces to service directly-attached hosts on 721 the enterprise-interior link. 723 The prefix delegations remain active as long as the VBR continues to 724 renew them via the delegating VBG before lease lifetimes expire. The 725 lease lifetime also keeps the delegation state active even if 726 communications between the VBR and delegating VBG are disrupted for a 727 period of time (e.g., due to an enterprise network partition, power 728 failure, etc.). Note however that if the VBR abandons or otherwise 729 loses continuity with the prefixes, it may be obliged to perform 730 network-wide renumbering if it subsequently receives a new and 731 different set of prefixes. 733 Stateful prefix delegation for non-IP protocols is out of scope. 735 4.2.3.2. Stateless Prefix Delegation 737 When IPv6 and IPv4 are used as the inner and outer protocols, 738 respectively, a stateless IPv6 PA prefix delegation capability is 739 available using the mechanisms specified in [RFC5569][RFC5969]. VBRs 740 can use these mechanisms to statelessly configure IPv6 PA prefixes 741 that embed one of the VBR's IPv4 RLOCs. 743 Using this stateless prefix delegation, if the IPv4 RLOC changes the 744 IPv6 prefix also changes and the VBR is obliged to renumber any 745 interfaces on which sub-prefixes from the delegated prefix are 746 assigned. This method may therefore be most suitable for enterprise 747 networks in which IPv4 RLOC assignments rarely change, or in 748 enterprise networks in which only services that do not depend on a 749 long-term stable IPv6 prefix (e.g., client-side web browsing) are 750 used. 752 Stateless prefix delegation for other protocol combinations is out of 753 scope. 755 4.2.4. Provider-(In)dependent (PI) EID Prefix Autoconfiguration 757 VBRs can acquire Provider (In)dependent (PI) prefixes to facilitate 758 multihoming, mobility and traffic engineering without requiring site- 759 wide renumbering events. These PI prefixes are made available to 760 VBRs through a prefix delegation authority that may or may not be 761 associated with a specific ISP. 763 VBRs that connect major enterprise networks (e.g., large 764 corporations, academic campuses, ISP networks, etc.) to a parent 765 enterprise network and/or the global Internet can acquire short PI 766 prefixes (e.g., an IPv6 ::/20, an IPv4 /16, etc.) through a 767 registration authority such as the Internet Assigned Numbers 768 Authority (IANA) or a major regional Internet registry. VBRs that 769 connect small enterprise networks (e.g., SOHO networks, MANETs, etc.) 770 to a parent enterprise network can acquire longer PI prefixes through 771 arrangements with a PI prefix delegation vendor. 773 After a VBR receives PI prefixes, it can sub-delegate portions of the 774 prefixes on enterprise-edge interfaces, on child VET interfaces for 775 which it is configured as a VBG and on enterprise-interior interfaces 776 to service directly-attached hosts on the enterprise-interior link. 777 The VBR can also sub-delegate portions of its PI prefixes to 778 requesting routers connected to child enterprise networks. These 779 requesting routers consider their sub-delegated portions of the PI 780 prefix as PA, and consider the delegating routers as their points of 781 connection to a provider network. 783 4.3. VET Border Gateway (VBG) Autoconfiguration 785 VBGs are VBRs that connect VET links configured over child enterprise 786 networks to provider networks via provider-edge interfaces and/or via 787 VET links configured over parent enterprise networks. A VBG may also 788 act as a "half-gateway", in that it may need to forward the packets 789 it receives from neighbors on the VET link via another VBG connected 790 to the same VET link. This arrangement is seen in the IRON 791 [I-D.templin-iron] client/server/relay architecture, in which a 792 server "half-gateway" is a VBG that forwards packets with off-link 793 destinations via a relay "half-gateway" VBG that connects the VET 794 link to the provider network. 796 VBGs autoconfigure their provider-edge interfaces in a manner that is 797 specific to the provider connections, and they autoconfigure their 798 VET interfaces that were configured over parent VET links using the 799 VBR autoconfiguration procedures specified in Section 4.2. For each 800 of its VET interfaces connected to child VET links, the VBG 801 initializes the interface the same as for an ordinary VBR (see 802 Section 4.2.1). It then arranges to add one or more of its RLOCs 803 associated with the child VET link to the PRL. 805 VBGs configure a DHCP relay/server on VET interfaces connected to 806 child VET links that require DHCP services. VBGs may also engage in 807 an unspecified anycast VBG discovery message exchange if they are 808 configured to do so. Finally, VBGs respond to LLMNR queries for 809 'PRLNAME' on VET interfaces connected to VET links that span child 810 enterprise networks with a distributed management structure. 812 4.4. VET Host Autoconfiguration 814 Nodes that cannot be attached via a VBR's enterprise-edge interface 815 (e.g., nomadic laptops that connect to a home office via a Virtual 816 Private Network (VPN)) can instead be configured for operation as a 817 simple host on the VET link. Each VET host performs the same 818 enterprise interior interfaces RLOC configuration procedures as 819 specified for ERs in Section 4.1. The VET host next performs the 820 same VET interface initialization and PRL discovery procedures as 821 specified for VBRs in Section 4.2, except that it configures its VET 822 interfaces as host interfaces (and not router interfaces). Note also 823 that a node may be configured as a host on some VET interfaces and as 824 an VBR/VBG on other VET interfaces. 826 A VET host may receive non-link-local addresses and/or prefixes to 827 assign to the VET interface via DHCP exchanges and/or through 828 information conveyed in Router Advertisements (RAs). If prefixes are 829 provided, however, there must be assurance that either 1) the VET 830 link will not partition, or 2) that each VET host interface connected 831 to the VET link will configure a unique set of prefixes. VET hosts 832 therefore depend on DHCP and/or RA exchanges to provide only 833 addresses/prefixes that are appropriate for assignment to the VET 834 interface according to these specific cases, and depend on the VBGs 835 within the enterprise keeping track of which addresses/prefixes were 836 assigned to which hosts. 838 When the VET host solicits a DHCP-assigned EID address/prefix over a 839 (non-multicast) VET interface, it maps the DHCP relay/server 840 multicast inner destination address to the outer RLOC address of a 841 VBG that it has selected as a default router. The VET host then 842 assigns any resulting DHCP-delegated addresses/prefixes to the VET 843 interface for use as the source address of inner packets. The host 844 will subsequently send all packets destined to EID correspondents via 845 a default router on the VET link, and will discover more-specific 846 routes based on any redirect messages it receives. 848 5. Internetworking Operation 850 Following the autoconfiguration procedures specified in Section 4, 851 ERs, VBRs, VBGs, and VET hosts engage in normal internetworking 852 operations as discussed in the following sections. 854 5.1. Routing Protocol Participation 856 ERs engage in any RLOC-based routing protocols over enterprise- 857 interior interfaces to exchange routing information for forwarding IP 858 packets with RLOC addresses. VBRs and VBGs can additionally engage 859 in any EID-based routing protocols over VET, enterprise-edge and 860 provider-edge interfaces to exchange routing information for 861 forwarding inner network layer packets with EID addresses. Note that 862 any EID-based routing instances are separate and distinct from any 863 RLOC-based routing instances. 865 VBR/VBG routing protocol participation on non-multicast VET 866 interfaces uses the NBMA interface model, e.g., in the same manner as 867 for OSPF over NBMA interfaces [RFC5340]. (VBR/VBG routing protocol 868 participation on multicast-capable VET interfaces can alternatively 869 use the standard multicast interface model, but this may result in 870 excessive multicast control message overhead.) 872 VBRs can use the list of VBGs in the PRL (see: Section 4.2.1) as an 873 initial list of neighbors for EID-based routing protocol 874 participation. VBRs can alternatively use the list of VBGs as 875 potential default routers instead of engaging in an EID-based routing 876 protocol instance. In that case, when the VBR forwards a packet via 877 a default router it may receive a redirect message indicating a 878 different VBR as a better next hop. 880 5.1.1. PI Prefix Routing Considerations 882 VBRs that connect large enterprise networks to the global Internet 883 advertise their EID PI prefixes directly into the Internet default- 884 free RIB via the Border Gateway Protocol (BGP) [RFC4271] the same as 885 for a major service provider network. VBRs that connect large 886 enterprise networks to provider networks can instead advertise their 887 EID PI prefixes into the providers' routing system(s) if the provider 888 networks are configured to accept them. 890 VBRs that connect small enterprise networks to provider networks 891 obtain one or more PI prefixes and register the prefixes with a 892 serving VBG in the PI prefix vendor's network (e.g., through a 893 vendor-specific short http(s) transaction). The PI prefix vendor 894 network then acts as a virtual "home" enterprise network that 895 connects its customer small enterprise networks to the Internet 896 routing system. The customer small enterprise networks in turn 897 appear as mobile components of the PI prefix vendor's network, i.e., 898 the customer networks are always "away from home". 900 Further details on routing for PI prefixes is discussed in "The 901 Internet Routing Overlay Network (IRON)" [I-D.templin-iron] and "Fib 902 Suppression with Virtual Aggregation" [I-D.ietf-grow-va]. 904 5.2. Default Route Configuration and Selection 906 Configuration of default routes in the presence of VET interfaces 907 must be carefully coordinated according to the inner and outer 908 network protocols. If the inner and outer protocols are different 909 (e.g., IPv6 within IPv4) then default routes of the inner protocol 910 version can be configured with next-hops corresponding to default 911 routers on a VET interface while default routes of the outer protocol 912 version can be configured with next-hops corresponding to default 913 routers on an underlying interface. 915 If the inner and outer protocols are the same (e.g., IPv4 within 916 IPv4), care must be taken in setting the default route to avoid 917 ambiguity. For example, if default routes are configured on the VET 918 interface then more-specific routes could be configured on underlying 919 interfaces to avoid looping. In a preferred method, however, 920 multiple default routes can be configured with some having next-hops 921 corresponding to (EID-based) default routers on VET interfaces and 922 others having next-hops corresponding to (RLOC-based) default routers 923 on underlying interfaces. In that case, special next-hop 924 determination rules must be used (see: Section 5.4). 926 5.3. Address Selection 928 When permitted by policy and supported by enterprise-interior 929 routing, VET nodes can avoid encapsulation through communications 930 that directly invoke the outer IP protocol using RLOC addresses 931 instead of EID addresses for end-to-end communications. For example, 932 an enterprise network that provides native IPv4 intra-enterprise 933 services can provide continued support for native IPv4 communications 934 even when encapsulated IPv6 services are available for inter- 935 enterprise communications. In other enterprise network scenarios, 936 the use of EID-based communications (i.e., instead of RLOC-based 937 communications) may be necessary and/or beneficial to support address 938 scaling, transparent Network Address Translator (NAT) traversal, 939 security domain separation, site multihoming, traffic engineering, 940 etc. . 942 VET nodes can use source address selection rules (e.g., based on name 943 service information) to determine whether to use EID-based or RLOC- 944 based addressing. The remainder of this section discusses 945 internetworking operation for EID-based communications using the VET 946 interface abstraction. 948 5.4. Next Hop Determination 950 VET nodes perform normal next-hop determination via longest prefix 951 match, and send packets according to the most-specific matching entry 952 in the FIB. If the FIB entry has multiple next-hop addresses, the 953 VBR selects the next-hop with the best metric value. If multiple 954 next hops have the same metric value, the VET node can use Equal Cost 955 Multi Path (ECMP) to forward different flows via different next-hop 956 addresses, where flows are determined, e.g., by computing a hash of 957 the inner packet's source address, destination address and flow label 958 fields. 960 If the VET node has multiple default routes of the same inner and 961 outer protocol versions, with some corresponding to EID-based default 962 routers and others corresponding to RLOC-based default routers, it 963 must perform source address based selection of a default route. In 964 particular, if the packet's source address is taken from an EID 965 prefix the VET node selects a default route configured over the VET 966 interface; otherwise, it selects a default route configured over an 967 underlying interface. 969 As a last resort when there is no matching entry in the FIB (i.e., 970 not even default), VET nodes can discover neighbors within the 971 enterprise network through on-demand name service queries for the EID 972 prefix taken from a packet's destination address (or, by some other 973 inner address to outer address mapping mechanism). For example, for 974 the IPv6 destination address '2001:DB8:1:2::1' and 'PRLNAME' 975 "isatapv2.example.com" the VET node can perform a name service lookup 976 for the domain name: 977 '0.0.1.0.0.0.8.b.d.0.1.0.0.2.ip6.isatapv2.example.com'. 979 Name-service lookups in enterprise networks with a centralized 980 management structure use an infrastructure-based service, e.g., an 981 enterprise-local DNS. Name-service lookups in enterprise networks 982 with a distributed management structure and/or that lack an 983 infrastructure-based name service instead use LLMNR over the VET 984 interface. 986 When LLMNR is used, the VBR that performs the lookup sends an LLMNR 987 query (with the prefix taken from the IP destination address encoded 988 in dotted-nibble format as shown above) and accepts the union of all 989 replies it receives from neighbors on the VET interface. When a VET 990 node receives an LLMNR query, it responds to the query IFF it 991 aggregates an IP prefix that covers the prefix in the query. If the 992 name-service lookup succeeds, it will return RLOC addresses (e.g., in 993 DNS A records) that correspond to neighbors to which the VET node can 994 forward packets. 996 5.5. VET Interface Encapsulation/Decapsulation 998 VET interfaces encapsulate inner network layer packets in any 999 necessary mid-layer headers and trailers (e.g., IPsec [RFC4301], 1000 etc.) followed by a SEAL header (if necessary) followed by an outer 1001 UDP header (if necessary) followed by an outer IP header. Following 1002 all encapsulations, the VET interface submits the encapsulated packet 1003 to the outer IP forwarding engine for transmission on an underlying 1004 interface. The following sections provide further details on 1005 encapsulation: 1007 5.5.1. Inner Network Layer Protocol 1009 The inner network layer protocol sees the VET interface as an 1010 ordinary network interface, and views the outer network layer 1011 protocol as an ordinary L2 transport. The inner- and outer network 1012 layer protocol types are mutually independent and can be used in any 1013 combination. Inner network layer protocol types include IPv6 1014 [RFC2460] and IPv4 [RFC0791], but they may also include non-IP 1015 protocols such as OSI/CLNP [RFC0994][RFC1070][RFC4548]. 1017 5.5.2. Mid-Layer Encapsulation 1019 VET interfaces that use mid-layer encapsulations encapsulate each 1020 inner network layer packet in any mid-layer headers and trailers as 1021 the first step in a potentially multi-layer encapsulation. 1023 5.5.3. SEAL Encapsulation 1025 Following any mid-layer encapsulations, VET interfaces that use SEAL 1026 add a SEAL header as specified in [I-D.templin-intarea-seal]. 1027 Inclusion of a SEAL header must be applied uniformly between all 1028 neighbors on the VET link. Note that when a VET interface sends a 1029 SEAL-encapsulated packet to a neighbor that does not use SEAL 1030 encapsulation, it may receive an ICMP "port unreachable" or "protocol 1031 unreachable" depending on whether/not an outer UDP header is 1032 included. 1034 SEAL encapsulation is used on VET links that require path MTU 1035 mitigations due to encapsulation overhead and/or mechanisms for VET 1036 interface neighbor coordination. When SEAL encapsulation is used, 1037 the VET interface sets the 'Next Header' value in the SEAL header to 1038 the IP protocol number associated with either the mid-layer 1039 encapsulation or the IP protocol number of the inner network layer 1040 (if no mid-layer encapsulation is used). The VET interface sets the 1041 other fields in the SEAL header as specified in 1042 [I-D.templin-intarea-seal]. 1044 5.5.4. Outer UDP Header Encapsulation 1046 Following any mid-layer and/or SEAL encapsulations, VET interfaces 1047 that use UDP encapsulation add an outer UDP header. Inclusion of an 1048 outer UDP header must be applied uniformly between all neighbors on 1049 the VET link. Note that when a VET interface sends a UDP- 1050 encapsulated packet to a neighbor that does not recognize the UDP 1051 port number, it may receive an ICMP "port unreachable" message. 1053 VET interfaces use UDP encapsulation on VET links that may traverse 1054 NATs and/or legacy networking gear (e.g., Equal Cost MultiPath (ECMP) 1055 routers, Link Aggregation Gateways (LAGs), etc.) that only recognize 1056 well-known network layer protocols. When UDP encapsulation is used, 1057 the VET interface encapsulates the mid-layer packet in an outer UDP 1058 header then sets the UDP port numbers as specified for the outermost 1059 mid-layer protocol (e.g., IPsec [RFC3947][RFC3948], etc.) 1061 When SEAL [I-D.templin-intarea-seal] is used as the outermost mid- 1062 layer protocol, the VET interface sets the UDP destination port 1063 number to the value reserved for SEAL and sets the UDP source port 1064 number according to whether the next hop neighbor relationship is 1065 bidirectional or unidirectional. For bidirectional neighbors, the 1066 VET interface sets the UDP source port to a constant value so that 1067 return packets will correctly traverse any NATs in the path. For 1068 unidirectional neighbors, the VET interface sets the UDP source port 1069 to a hash calculated over the inner network layer {destination, 1070 source} values or (optionally) over the inner network layer {dest 1071 addr, source addr, protocol, dest port, source port} values. The VET 1072 interface uses a hash function of its own choosing, but it MUST be 1073 consistent in the manner in which the hash is applied. 1075 For VET links configured over IPv4 enterprise networks, the VET 1076 interface sets the UDP checksum field to zero. For VET links 1077 configured over IPv6 enterprise networks, considerations for setting 1078 the UDP checksum are discussed in [I-D.ietf-6man-udpzero]. 1080 5.5.5. Outer IP Header Encapsulation 1082 Following any mid-layer, SEAL and/or UDP encapsulations, the VET 1083 interface adds an outer IP header. Outer IP header construction is 1084 the same as specified for ordinary IP encapsulation (e.g., [RFC2003], 1085 [RFC2473], [RFC4213], etc.) except that the "TTL/Hop Limit", "Type of 1086 Service/Traffic Class" and "Congestion Experienced" values in the 1087 inner network layer header are copied into the corresponding fields 1088 in the outer IP header. The VET interface also sets the IP protocol 1089 number to the appropriate value for the first protocol layer within 1090 the encapsulation (e.g., UDP, SEAL, IPsec, etc.). When IPv6 is used 1091 as the outer IP protocol, the VET interface sets the flow label value 1092 in the outer IPv6 header the same as described in 1093 [I-D.carpenter-flow-ecmp]. 1095 5.5.6. Decapsulation 1097 When a VET interface receives an encapsulated packet, it retains the 1098 outer headers and processes the SEAL header as specified in 1099 [I-D.templin-intarea-seal]. 1101 Next, if the packet will be forwarded from the receiving VET 1102 interface into a forwarding VET interface, the VET node copies the 1103 "TTL/Hop Limit", "Type of Service/Traffic Class" and "Congestion 1104 Experienced" values in the outer IP header received on the receiving 1105 VET interface into the corresponding fields in the outer IP header to 1106 be sent over the forwarding VET interface (i.e., the values are 1107 transferred between outer headers and *not* copied from the inner 1108 network layer header). This is true even if the packet is forwarded 1109 out the same VET interface that it arrived on, and necessary to 1110 support diagnostic functions (e.g., traceroute) and avoid looping. 1112 During decapsulation, when the next-hop is via a non-VET interface, 1113 the "Congestion Experienced" value in the outer IP header is copied 1114 into the corresponding field in the inner network layer header. 1116 5.6. Mobility and Multihoming Considerations 1118 VBRs that travel between distinct enterprise networks must either 1119 abandon their PA prefixes that are relative to the "old" network and 1120 obtain PA prefixes relative to the "new" network, or somehow 1121 coordinate with a "home" network to retain ownership of the prefixes. 1122 In the first instance, the VBR would be required to coordinate a 1123 network renumbering event on its attached networks using the new PA 1124 prefixes [RFC4192][RFC5887]. In the second instance, an adjunct 1125 mobility management mechanism is required. 1127 VBRs can retain their PI prefixes as they travel between distinct 1128 network points of attachment as long as they continue to refresh 1129 their PI prefix to RLOC address mappings with their serving VBG as 1130 described in [I-D.templin-iron]. (When the VBR moves far from its 1131 serving VBG, it can also select a new VBG in order to maintain 1132 optimal routing.) In this way, VBRs can update their PI prefix to 1133 RLOC mappings in real time and without requiring an adjunct mobility 1134 management mechanism. 1136 The VBGs of a multihomed enterprise network participate in a private 1137 inner network layer routing protocol instance (e.g., via an interior 1138 BGP instance) to accommodate network partitions/merges as well as 1139 intra-enterprise mobility events. 1141 5.7. Neighbor Coordination on VET Interfaces using SEAL 1143 VET interfaces that use SEAL use the SEAL Control Message Protocol 1144 (SCMP) as specified in Section 4.5 of [I-D.templin-intarea-seal] to 1145 coordinate reachability, routing information, and mappings between 1146 the inner and outer network layer protocols. SCMP directly parallels 1147 the IPv6 Neighbor Discovery (ND) [RFC4191][RFC4861] and ICMPv6 1148 [RFC4443] protocols, but operates from within the tunnel and supports 1149 operation for any combinations of inner and outer network layer 1150 protocols. 1152 VET and SEAL are specifically designed for encapsulation of inner 1153 network layer payloads over outer IPv4 and IPv6 networks as a link 1154 layer. VET interfaces that use SCMP therefore require a new Source/ 1155 Target Link-Layer Address Option (S/TLLAO) format that encapsulates 1156 IPv4 addresses as shown in Figure 2 and IPv6 addresses as shown in 1157 Figure 3: 1159 0 1 2 3 1160 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1162 | Type = 2 | Length = 1 | Reserved | 1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1164 | IPv4 address (bytes 0 thru 3) | 1165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1167 Figure 2: SCMP S/TLLAO Option for IPv4 RLOCs 1169 0 1 2 3 1170 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1172 | Type = 2 | Length = 3 | Reserved | 1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1174 | Reserved | 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1176 | IPv6 address (bytes 0 thru 3) | 1177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1178 | IPv6 address (bytes 4 thru 7) | 1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1180 | IPv6 address (bytes 8 thru 11) | 1181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1182 | IPv6 address (bytes 12 thru 15) | 1183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1185 Figure 3: SCMP S/TLLAO Option for IPv6 RLOCs 1187 In addition, VET interfaces that use SCMP use a modified version of 1188 the Route Information Option (RIO) (see: [RFC4191]) formatted as 1189 shown in Figure 4: 1191 0 1 2 3 1192 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1194 | Type = 24 | Length | Prefix Length | AF |Prf|Resvd| 1195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1196 | Route Lifetime | 1197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1198 | Prefix (Variable Length) | 1199 . . 1200 . . 1201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1203 Figure 4: SCMP Route Information Option Format 1205 In this modified format, the VET interface sets the Route Lifetime 1206 and Prefix fields in the RIO option the same as specified in 1207 [RFC4191]. It then sets the fields in the header as follows: 1209 o the 'Type', 'Prf', and 'Resvd' fields are set the same as 1210 specified in [RFC4191]. 1212 o the 'Length' field is set to 1, 2, or 3 as specified in [RFC4191]. 1213 It is instead set to 4 if the 'Prefix Length' is greater than 128 1214 and set to 5 if the 'Prefix Length' is greater than 192 (e.g., in 1215 order to accommodate longer prefixes of non-IP protocols). 1217 o the 'Prefix Length' field ranges from 0 to 255. The 'Prefix' 1218 field is 0, 8, 16, 24 or 32 octets depending on the Length, and 1219 the embedded prefix MAY be up to 255 bits in length. 1221 o bits 24 - 26 are used to contain an 'Address Family (AF)' value 1222 that indicates the embedded prefix protocol type. This document 1223 defines the following values for AF: 1225 * 000 - IPv4 1227 * 001 - IPv6 1229 * 010 - OSI/CLNP NSAP 1231 The following subsections discuss VET interface neighbor coordination 1232 using SCMP: 1234 5.7.1. Router Discovery 1236 VET hosts and VBRs can send SCMP Router Solicitation (SRS) messages 1237 to one or more VBGs in the PRL to receive solicited SCMP Router 1238 Advertisements (SRAs). 1240 When an VBG receives an SRS message on a VET interface, it prepares a 1241 solicited SRA message. The SRA includes Router Lifetimes, Default 1242 Router Preferences, PIOs and any other options/parameters that the 1243 VBG is configured to include. If necessary, the VBG also includes 1244 Route Information Options (RIOs) formatted as specified above. 1246 The VBG finally includes one or more SLLAOs formatted as specified 1247 above that encode the IPv6 and/or IPv4 RLOC unicast addresses of its 1248 own enterprise-interior interfaces or the enterprise-interior 1249 interfaces of other nearby VBGs. 1251 5.7.2. Neighbor Unreachability Detection 1253 VET nodes perform Neighbor Unreachability Detection (NUD) on VET 1254 interface neighbors by monitoring hints of forward progress enabled 1255 by SEAL mechanisms as evidence that a neighbor is reachable. First, 1256 when data packets are flowing, the VET node can periodically set the 1257 A bit in the SEAL header of data packets to elicit SCMP responses 1258 from the neighbor. Secondly, when no data packets are flowing, the 1259 VET node can send periodic probes such as SCMP Neighbor Solicitation 1260 (SNS) messages for the same purpose. 1262 Responsiveness to routing changes is directly related to the delay in 1263 detecting that a neighbor has gone unreachable. In order to provide 1264 responsiveness comparable to dynamic routing protocols, a reasonably 1265 short neighbor reachable time (e.g., 5sec) SHOULD be used. 1267 Additionally, a VET node may receive outer IP ICMP "Destination 1268 Unreachable; net / host unreachable" messages from an ER on the path 1269 indicating that the path to a neighbor may be failing. The node 1270 SHOULD first check the packet-in-error to obtain reasonable assurance 1271 that the ICMP message is authentic. If the node receives excessive 1272 ICMP unreachable errors through multiple RLOCs associated with the 1273 same FIB entry, it SHOULD delete the FIB entry and allow subsequent 1274 packets to flow through a different route (e.g., a default route with 1275 a VBG as the next hop). 1277 5.7.3. Redirect Function 1279 A VET node (i.e., the redirectee) may receive a redirect message when 1280 it forwards packets over a VET interface to a neighboring VET node 1281 (i.e., the redirector). The redirector will forward the packet and 1282 return an SCMP Redirect message if necessary to inform the redirectee 1283 of a better next hop. 1285 The SCMP Redirect message is formatted the same as for ordinary 1286 ICMPv6 redirect messages (see Section 4.5 of [RFC4861]), except that 1287 the Destination and Target Address fields are unnecessary and 1288 therefore omitted. The format of the SCMP Redirect message is shown 1289 in Figure 5 1290 0 1 2 3 1291 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 | Type = 137 | Code = 0 | Checksum | 1294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1295 | Reserved | 1296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1297 | Options ... 1298 +-+-+-+-+-+-+-+-+-+-+-+- 1300 Figure 5: SCMP Redirect Message Format 1302 The redirector then adds any necessary Options to the Redirect 1303 message. It first includes one or more TLLAOs (see above) that 1304 include RLOCs corresponding to better next hops. The redirector next 1305 includes an RIO that contains a prefix from its FIB that covers the 1306 destination address of the original packet. 1308 Following the RIO option, the redirector includes any other necessary 1309 options (e.g., SEND options) followed by a Redirected Header option 1310 containing the leading portion of the packet that triggered the 1311 redirect as the final option in the message. The redirector then 1312 encapsulates the Redirect message the same as for any other SCMP 1313 message and sends it to the redirectee. 1315 When the redirectee receives the Redirect, it first authenticates the 1316 message then uses the EID prefix in the RIO with its respective 1317 lifetime to update its FIB. The redirectee also caches the IPv4 or 1318 IPv6 addresses in TLLAOs as the layer 2 addresses of potential next- 1319 hops for the prefix. 1321 The redirectee retains the FIB entry created as a result of receipt 1322 of an SCMP Redirect until the route lifetime expires, or until the 1323 redirected target neighbor becomes unreachable. In this way, RLOC 1324 liveness detection parallels IPv6 Neighbor Unreachability Detection. 1326 5.7.3.1. Correspondent Node Redirection 1328 When a mobile VET node moves to a new network point of attachment, it 1329 leaves short-term forwarding information with its former network 1330 point of attachment. Thereafter, any existing correspondents that 1331 attempt to contact the mobile node via the former network point of 1332 attachment will be redirected to the new network point of attachment. 1334 In this way, mobile VET nodes need not inform correspondents of a 1335 mobility event, since the correspondents will soon receive redirects 1336 from the network. 1338 5.8. Neighbor Coordination on VET Interfaces using IPsec 1340 VET interfaces that use IPsec encapsulation use the Internet Key 1341 Exchange protocol, version 2 (IKEv2) [RFC4306] to manage security 1342 association setup and maintenance. IKEv2 provides a logical 1343 equivalent of the SCMP in terms of VET interface neighbor 1344 coordinations; for example, IKEv2 also provides mechanisms for 1345 redirection [RFC5685] and mobility [RFC4555]. 1347 IPsec additionally provides an extended Identification field and 1348 integrity check vector; these features allow IPsec to utilize outer 1349 IP fragmentation and reassembly with less risk of exposure to data 1350 corruption due to reassembly misassociations. On the other hand, 1351 IPsec entails the use of symmetric security associations and hence 1352 may not be appropriate to all enterprise network use cases. 1354 5.9. Multicast 1356 5.9.1. Multicast over (Non)Multicast Enterprise Networks 1358 Whether or not the underlying enterprise network supports a native 1359 multicasting service, the VET node can act as an inner network layer 1360 IGMP/MLD proxy [RFC4605] on behalf of its attached edge networks and 1361 convey its multicast group memberships over the VET interface to a 1362 VBG acting as a multicast router. Its inner network layer multicast 1363 transmissions will therefore be encapsulated in outer headers with 1364 the unicast address of the VBG as the destination. 1366 5.9.2. Multicast Over Multicast-Capable Enterprise Networks 1368 In multicast-capable enterprise networks, ERs provide an enterprise- 1369 wide multicasting service (e.g., Simplified Multicast Forwarding 1370 (SMF) [I-D.ietf-manet-smf], Protocol Independent Multicast (PIM) 1371 routing, Distance Vector Multicast Routing Protocol (DVMRP) routing, 1372 etc.) over their enterprise-interior interfaces such that outer IP 1373 multicast messages of site-scope or greater scope will be propagated 1374 across the enterprise network. For such deployments, VET nodes can 1375 optionally provide a native inner multicast/broadcast capability over 1376 their VET interfaces through mapping of the inner multicast address 1377 space to the outer multicast address space. In that case, operation 1378 of link-or greater-scoped inner multicasting services (e.g., a link- 1379 scoped neighbor discovery protocol) over the VET interface is 1380 available, but SHOULD be used sparingly to minimize enterprise-wide 1381 flooding. 1383 VET nodes encapsulate inner multicast messages sent over the VET 1384 interface in any mid-layer headers (e.g., UDP, SEAL, IPsec, etc.) 1385 followed by an outer IP header with a site-scoped outer IP multicast 1386 address as the destination. For the case of IPv6 and IPv4 as the 1387 inner/outer protocols (respectively), [RFC2529] provides mappings 1388 from the IPv6 multicast address space to a site-scoped IPv4 multicast 1389 address space (for other encapsulations, mappings are established 1390 through administrative configuration or through an unspecified 1391 alternate static mapping). 1393 Multicast mapping for inner multicast groups over outer IP multicast 1394 groups can be accommodated, e.g., through VET interface snooping of 1395 inner multicast group membership and routing protocol control 1396 messages. To support inner-to-outer multicast address mapping, the 1397 VET interface acts as a virtual outer IP multicast host connected to 1398 its underlying interfaces. When the VET interface detects that an 1399 inner multicast group joins or leaves, it forwards corresponding 1400 outer IP multicast group membership reports on an underlying 1401 interface over which the VET interface is configured. If the VET 1402 node is configured as an outer IP multicast router on the underlying 1403 interfaces, the VET interface forwards locally looped-back group 1404 membership reports to the outer IP multicast routing process. If the 1405 VET node is configured as a simple outer IP multicast host, the VET 1406 interface instead forwards actual group membership reports (e.g., 1407 IGMP messages) directly over an underlying interface. 1409 Since inner multicast groups are mapped to site-scoped outer IP 1410 multicast groups, the VET node MUST ensure that the site-scoped outer 1411 IP multicast messages received on the underlying interfaces for one 1412 VET interface do not "leak out" to the underlying interfaces of 1413 another VET interface. This is accommodated through normal site- 1414 scoped outer IP multicast group filtering at enterprise network 1415 boundaries. 1417 5.10. Service Discovery 1419 VET nodes can perform enterprise-wide service discovery using a 1420 suitable name-to-address resolution service. Examples of flooding- 1421 based services include the use of LLMNR [RFC4795] over the VET 1422 interface or multicast DNS (mDNS) [I-D.cheshire-dnsext-multicastdns] 1423 over an underlying interface. More scalable and efficient service 1424 discovery mechanisms (e.g., anycast) are for further study. 1426 5.11. VET Link Partitioning 1428 A VET link can be partitioned into multiple distinct logical 1429 groupings. In that case, each partition configures its own distinct 1430 'PRLNAME' (e.g., 'isatapv2.zone1.example.com', 1431 'isatapv2.zone2.example.com', etc.). 1433 VBGs can further create multiple IP subnets within a partition, e.g., 1434 by sending SRAs with PIOs containing different IP prefixes to 1435 different groups of VET hosts. VBGs can identify subnets, e.g., by 1436 examining RLOC prefixes, observing the enterprise-interior interfaces 1437 over which SRSs are received, etc. 1439 In the limiting case, VBGs can advertise a unique set of IP prefixes 1440 to each VET host such that each host belongs to a different subnet 1441 (or set of subnets) on the VET interface. 1443 5.12. VBG Prefix State Recovery 1445 VBGs retain explicit state that tracks the inner network layer 1446 prefixes delegated to VBRs connected to the VET link, e.g., so that 1447 packets are delivered to the correct VBRs. When a VBG loses some or 1448 all of its state (e.g., due to a power failure), client VBRs must 1449 refresh the VBG's state so that packets can be forwarded over correct 1450 routes. 1452 5.13. Support for Legacy ISATAP Services 1454 VBGs can support legacy ISATAP services according to the 1455 specifications in [RFC5214]. In particular, VBGs can configure 1456 legacy ISATAP interfaces and VET interfaces over the same sets of 1457 underlying interfaces as long as the PRLs and IPv6 prefixes 1458 associated with the ISATAP/VET interfaces are distinct. 1460 Legacy ISATAP hosts acquire addresses and/or prefixes in the same 1461 manner and using the same mechanisms as described for VET hosts in 1462 Section 4.4 above. 1464 6. IANA Considerations 1466 There are no IANA considerations for this document. 1468 7. Security Considerations 1470 Security considerations for MANETs are found in [RFC2501]. 1472 The security considerations found in 1473 [RFC2529][RFC5214][I-D.nakibly-v6ops-tunnel-loops] also apply to VET. 1475 SEND [RFC3971] and/or IPsec [RFC4301] can be used in environments 1476 where attacks on the neighbor coordination protocol are possible. 1477 SEAL [I-D.templin-intarea-seal] provides a per-packet identification 1478 that can be used to detect source address spoofing. 1480 Rogue neighbor coordination messages with spoofed RLOC source 1481 addresses can consume network resources and cause VET nodes to 1482 perform extra work. Nonetheless, VET nodes SHOULD NOT "blacklist" 1483 such RLOCs, as that may result in a denial of service to the RLOCs' 1484 legitimate owners. 1486 VBRs and VBGs observe the recommendations for network ingress 1487 filtering [RFC2827]. 1489 8. Related Work 1491 Brian Carpenter and Cyndi Jung introduced the concept of intra-site 1492 automatic tunneling in [RFC2529]; this concept was later called: 1493 "Virtual Ethernet" and investigated by Quang Nguyen under the 1494 guidance of Dr. Lixia Zhang. Subsequent works by these authors and 1495 their colleagues have motivated a number of foundational concepts on 1496 which this work is based. 1498 Telcordia has proposed DHCP-related solutions for MANETs through the 1499 CECOM MOSAIC program. 1501 The Naval Research Lab (NRL) Information Technology Division uses 1502 DHCP in their MANET research testbeds. 1504 Security concerns pertaining to tunneling mechanisms are discussed in 1505 [I-D.ietf-v6ops-tunnel-security-concerns]. 1507 Default router and prefix information options for DHCPv6 are 1508 discussed in [I-D.droms-dhc-dhcpv6-default-router]. 1510 An automated IPv4 prefix delegation mechanism is proposed in 1511 [I-D.ietf-dhc-subnet-alloc]. 1513 RLOC prefix delegation for enterprise-edge interfaces is discussed in 1514 [I-D.clausen-manet-autoconf-recommendations]. 1516 MANET link types are discussed in [I-D.clausen-manet-linktype]. 1518 The LISP proposal [I-D.ietf-lisp] examines encapsulation/ 1519 decapsulation issues and other aspects of tunneling. 1521 Various proposals within the IETF have suggested similar mechanisms. 1523 9. Acknowledgements 1525 The following individuals gave direct and/or indirect input that was 1526 essential to the work: Jari Arkko, Teco Boot, Emmanuel Bacelli, Fred 1527 Baker, James Bound, Scott Brim, Brian Carpenter, Thomas Clausen, 1528 Claudiu Danilov, Chris Dearlove, Remi Despres, Gert Doering, Ralph 1529 Droms, Washam Fan, Dino Farinacci, Vince Fuller, Thomas Goff, David 1530 Green, Joel Halpern, Bob Hinden, Sascha Hlusiak, Sapumal Jayatissa, 1531 Dan Jen, Darrel Lewis, Tony Li, Joe Macker, David Meyer, Gabi 1532 Nakibly, Thomas Narten, Pekka Nikander, Dave Oran, Alexandru 1533 Petrescu, Mark Smith, John Spence, Jinmei Tatuya, Dave Thaler, Mark 1534 Townsley, Ole Troan, Michaela Vanderveen, Robin Whittle, James 1535 Woodyatt, Lixia Zhang, and others in the IETF AUTOCONF and MANET 1536 working groups. Many others have provided guidance over the course 1537 of many years. 1539 10. Contributors 1541 The following individuals have contributed to this document: 1543 Eric Fleischman (eric.fleischman@boeing.com) 1544 Thomas Henderson (thomas.r.henderson@boeing.com) 1545 Steven Russert (steven.w.russert@boeing.com) 1546 Seung Yi (seung.yi@boeing.com) 1547 Ian Chakeres (ian.chakeres@gmail.com) contributed to earlier versions 1548 of the document. 1550 Jim Bound's foundational work on enterprise networks provided 1551 significant guidance for this effort. We mourn his loss and honor 1552 his contributions. 1554 11. References 1556 11.1. Normative References 1558 [I-D.templin-intarea-seal] 1559 Templin, F., "The Subnetwork Encapsulation and Adaptation 1560 Layer (SEAL)", draft-templin-intarea-seal-26 (work in 1561 progress), January 2011. 1563 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1564 September 1981. 1566 [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, 1567 RFC 792, September 1981. 1569 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1570 Requirement Levels", BCP 14, RFC 2119, March 1997. 1572 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1573 RFC 2131, March 1997. 1575 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1576 (IPv6) Specification", RFC 2460, December 1998. 1578 [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: 1579 Defeating Denial of Service Attacks which employ IP Source 1580 Address Spoofing", BCP 38, RFC 2827, May 2000. 1582 [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP 1583 Messages", RFC 3118, June 2001. 1585 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 1586 and M. Carney, "Dynamic Host Configuration Protocol for 1587 IPv6 (DHCPv6)", RFC 3315, July 2003. 1589 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 1590 Host Configuration Protocol (DHCP) version 6", RFC 3633, 1591 December 2003. 1593 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 1594 Neighbor Discovery (SEND)", RFC 3971, March 2005. 1596 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1597 RFC 3972, March 2005. 1599 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1600 More-Specific Routes", RFC 4191, November 2005. 1602 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1603 Architecture", RFC 4291, February 2006. 1605 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 1606 Message Protocol (ICMPv6) for the Internet Protocol 1607 Version 6 (IPv6) Specification", RFC 4443, March 2006. 1609 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1610 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1611 September 2007. 1613 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1614 Address Autoconfiguration", RFC 4862, September 2007. 1616 [RFC5342] Eastlake, D., "IANA Considerations and IETF Protocol Usage 1617 for IEEE 802 Parameters", BCP 141, RFC 5342, 1618 September 2008. 1620 11.2. Informative References 1622 [CATENET] Pouzin, L., "A Proposal for Interconnecting Packet 1623 Switching Networks", May 1974. 1625 [I-D.carpenter-flow-ecmp] 1626 Carpenter, B. and S. Amante, "Using the IPv6 flow label 1627 for equal cost multipath routing and link aggregation in 1628 tunnels", draft-carpenter-flow-ecmp-03 (work in progress), 1629 October 2010. 1631 [I-D.cheshire-dnsext-multicastdns] 1632 Cheshire, S. and M. Krochmal, "Multicast DNS", 1633 draft-cheshire-dnsext-multicastdns-13 (work in progress), 1634 January 2011. 1636 [I-D.clausen-manet-autoconf-recommendations] 1637 Clausen, T. and U. Herberg, "MANET Router Configuration 1638 Recommendations", 1639 draft-clausen-manet-autoconf-recommendations-00 (work in 1640 progress), February 2009. 1642 [I-D.clausen-manet-linktype] 1643 Clausen, T., "The MANET Link Type", 1644 draft-clausen-manet-linktype-00 (work in progress), 1645 October 2008. 1647 [I-D.droms-dhc-dhcpv6-default-router] 1648 Droms, R. and T. Narten, "Default Router and Prefix 1649 Advertisement Options for DHCPv6", 1650 draft-droms-dhc-dhcpv6-default-router-00 (work in 1651 progress), March 2009. 1653 [I-D.ietf-6man-udpzero] 1654 Fairhurst, G. and M. Westerlund, "IPv6 UDP Checksum 1655 Considerations", draft-ietf-6man-udpzero-02 (work in 1656 progress), October 2010. 1658 [I-D.ietf-dhc-subnet-alloc] 1659 Johnson, R., Kumarasamy, J., Kinnear, K., and M. Stapp, 1660 "Subnet Allocation Option", draft-ietf-dhc-subnet-alloc-11 1661 (work in progress), May 2010. 1663 [I-D.ietf-grow-va] 1664 Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and 1665 L. Zhang, "FIB Suppression with Virtual Aggregation", 1666 draft-ietf-grow-va-03 (work in progress), August 2010. 1668 [I-D.ietf-lisp] 1669 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 1670 "Locator/ID Separation Protocol (LISP)", 1671 draft-ietf-lisp-09 (work in progress), October 2010. 1673 [I-D.ietf-manet-smf] 1674 Macker, J. and S. Team, "Simplified Multicast Forwarding", 1675 draft-ietf-manet-smf-10 (work in progress), March 2010. 1677 [I-D.ietf-v6ops-tunnel-security-concerns] 1678 Krishnan, S., Thaler, D., and J. Hoagland, "Security 1679 Concerns With IP Tunneling", 1680 draft-ietf-v6ops-tunnel-security-concerns-04 (work in 1681 progress), October 2010. 1683 [I-D.jen-apt] 1684 Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and 1685 L. Zhang, "APT: A Practical Transit Mapping Service", 1686 draft-jen-apt-01 (work in progress), November 2007. 1688 [I-D.nakibly-v6ops-tunnel-loops] 1689 Nakibly, G. and F. Templin, "Routing Loop Attack using 1690 IPv6 Automatic Tunnels: Problem Statement and Proposed 1691 Mitigations", draft-nakibly-v6ops-tunnel-loops-03 (work in 1692 progress), August 2010. 1694 [I-D.russert-rangers] 1695 Russert, S., Fleischman, E., and F. Templin, "RANGER 1696 Scenarios", draft-russert-rangers-05 (work in progress), 1697 July 2010. 1699 [I-D.templin-iron] 1700 Templin, F., "The Internet Routing Overlay Network 1701 (IRON)", draft-templin-iron-17 (work in progress), 1702 January 2011. 1704 [IEN48] Cerf, V., "The Catenet Model for Internetworking", 1705 July 1978. 1707 [RASADV] Microsoft, "Remote Access Server Advertisement (RASADV) 1708 Protocol Specification", October 2008. 1710 [RFC0994] International Organization for Standardization (ISO) and 1711 American National Standards Institute (ANSI), "Final text 1712 of DIS 8473, Protocol for Providing the Connectionless- 1713 mode Network Service", RFC 994, March 1986. 1715 [RFC1035] Mockapetris, P., "Domain names - implementation and 1716 specification", STD 13, RFC 1035, November 1987. 1718 [RFC1070] Hagens, R., Hall, N., and M. Rose, "Use of the Internet as 1719 a subnetwork for experimentation with the OSI network 1720 layer", RFC 1070, February 1989. 1722 [RFC1122] Braden, R., "Requirements for Internet Hosts - 1723 Communication Layers", STD 3, RFC 1122, October 1989. 1725 [RFC1753] Chiappa, J., "IPng Technical Requirements Of the Nimrod 1726 Routing and Addressing Architecture", RFC 1753, 1727 December 1994. 1729 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 1730 E. Lear, "Address Allocation for Private Internets", 1731 BCP 5, RFC 1918, February 1996. 1733 [RFC1955] Hinden, R., "New Scheme for Internet Routing and 1734 Addressing (ENCAPS) for IPNG", RFC 1955, June 1996. 1736 [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, 1737 October 1996. 1739 [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor 1740 Extensions", RFC 2132, March 1997. 1742 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1743 IPv6 Specification", RFC 2473, December 1998. 1745 [RFC2491] Armitage, G., Schulter, P., Jork, M., and G. Harter, "IPv6 1746 over Non-Broadcast Multiple Access (NBMA) networks", 1747 RFC 2491, January 1999. 1749 [RFC2501] Corson, M. and J. Macker, "Mobile Ad hoc Networking 1750 (MANET): Routing Protocol Performance Issues and 1751 Evaluation Considerations", RFC 2501, January 1999. 1753 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 1754 Domains without Explicit Tunnels", RFC 2529, March 1999. 1756 [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, 1757 February 2000. 1759 [RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., 1760 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 1761 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 1762 RFC 3819, July 2004. 1764 [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic 1765 Configuration of IPv4 Link-Local Addresses", RFC 3927, 1766 May 2005. 1768 [RFC3947] Kivinen, T., Swander, B., Huttunen, A., and V. Volpe, 1769 "Negotiation of NAT-Traversal in the IKE", RFC 3947, 1770 January 2005. 1772 [RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. 1773 Stenberg, "UDP Encapsulation of IPsec ESP Packets", 1774 RFC 3948, January 2005. 1776 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 1777 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 1778 September 2005. 1780 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1781 Addresses", RFC 4193, October 2005. 1783 [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms 1784 for IPv6 Hosts and Routers", RFC 4213, October 2005. 1786 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 1787 Protocol 4 (BGP-4)", RFC 4271, January 2006. 1789 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1790 Internet Protocol", RFC 4301, December 2005. 1792 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 1793 RFC 4306, December 2005. 1795 [RFC4548] Gray, E., Rutemiller, J., and G. Swallow, "Internet Code 1796 Point (ICP) Assignments for NSAP Addresses", RFC 4548, 1797 May 2006. 1799 [RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol 1800 (MOBIKE)", RFC 4555, June 2006. 1802 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 1803 "Internet Group Management Protocol (IGMP) / Multicast 1804 Listener Discovery (MLD)-Based Multicast Forwarding 1805 ("IGMP/MLD Proxying")", RFC 4605, August 2006. 1807 [RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local 1808 Multicast Name Resolution (LLMNR)", RFC 4795, 1809 January 2007. 1811 [RFC4852] Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D. 1812 Green, "IPv6 Enterprise Network Analysis - IP Layer 3 1813 Focus", RFC 4852, April 2007. 1815 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 1816 June 2007. 1818 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 1819 Extensions for Stateless Address Autoconfiguration in 1820 IPv6", RFC 4941, September 2007. 1822 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 1823 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 1824 March 2008. 1826 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 1827 for IPv6", RFC 5340, July 2008. 1829 [RFC5569] Despres, R., "IPv6 Rapid Deployment on IPv4 1830 Infrastructures (6rd)", RFC 5569, January 2010. 1832 [RFC5685] Devarapalli, V. and K. Weniger, "Redirect Mechanism for 1833 the Internet Key Exchange Protocol Version 2 (IKEv2)", 1834 RFC 5685, November 2009. 1836 [RFC5720] Templin, F., "Routing and Addressing in Networks with 1837 Global Enterprise Recursion (RANGER)", RFC 5720, 1838 February 2010. 1840 [RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering 1841 Still Needs Work", RFC 5887, May 2010. 1843 [RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 1844 Infrastructures (6rd) -- Protocol Specification", 1845 RFC 5969, August 2010. 1847 Appendix A. Duplicate Address Detection (DAD) Considerations 1849 A priori uniqueness determination (also known as "pre-service DAD") 1850 for an RLOC assigned on an enterprise-interior interface would 1851 require either flooding the entire enterprise network or somehow 1852 discovering a link in the network on which a node that configures a 1853 duplicate address is attached and performing a localized DAD exchange 1854 on that link. But, the control message overhead for such an 1855 enterprise-wide DAD would be substantial and prone to false-negatives 1856 due to packet loss and intermittent connectivity. An alternative to 1857 pre-service DAD is to autoconfigure pseudo-random RLOCs on 1858 enterprise-interior interfaces and employ a passive in-service DAD 1859 (e.g., one that monitors routing protocol messages for duplicate 1860 assignments). 1862 Pseudo-random IPv6 RLOCs can be generated with mechanisms such as 1863 CGAs, IPv6 privacy addresses, etc. with very small probability of 1864 collision. Pseudo-random IPv4 RLOCs can be generated through random 1865 assignment from a suitably large IPv4 prefix space. 1867 Consistent operational practices can assure uniqueness for VBG- 1868 aggregated addresses/prefixes, while statistical properties for 1869 pseudo-random address self-generation can assure uniqueness for the 1870 RLOCs assigned on an ER's enterprise-interior interfaces. Still, an 1871 RLOC delegation authority should be used when available, while a 1872 passive in-service DAD mechanism should be used to detect RLOC 1873 duplications when there is no RLOC delegation authority. 1875 Appendix B. Anycast Services 1877 Some of the IPv4 addresses that appear in the Potential Router List 1878 may be anycast addresses, i.e., they may be configured on the VET 1879 interfaces of multiple VBRs/VBGs. In that case, each VET router 1880 interface that configures the same anycast address must exhibit 1881 equivalent outward behavior. 1883 Use of an anycast address as the IP destination address of tunneled 1884 packets can have subtle interactions with tunnel path MTU and 1885 neighbor discovery. For example, if the initial fragments of a 1886 fragmented tunneled packet with an anycast IP destination address are 1887 routed to different egress tunnel endpoints than the remaining 1888 fragments, the multiple endpoints will be left with incomplete 1889 reassembly buffers. This issue can be mitigated by ensuring that 1890 each egress tunnel endpoint implements a proactive reassembly buffer 1891 garbage collection strategy. Additionally, ingress tunnel endpoints 1892 that send packets with an anycast IP destination address must use the 1893 minimum path MTU for all egress tunnel endpoints that configure the 1894 same anycast address as the tunnel MTU. Finally, ingress tunnel 1895 endpoints should treat ICMP unreachable messages from a router within 1896 the tunnel as at most a weak indication of neighbor unreachability, 1897 since the failures may only be transient and a different path to an 1898 alternate anycast router quickly selected through reconvergence of 1899 the underlying routing protocol. 1901 Use of an anycast address as the IP source address of tunneled 1902 packets can lead to more serious issues. For example, when the IP 1903 source address of a tunneled packet is anycast, ICMP messages 1904 produced by routers within the tunnel might be delivered to different 1905 ingress tunnel endpoints than the ones that produced the packets. In 1906 that case, functions such as path MTU discovery and neighbor 1907 unreachability detection may experience non-deterministic behavior 1908 that can lead to communications failures. Additionally, the 1909 fragments of multiple tunneled packets produced by multiple ingress 1910 tunnel endpoints may be delivered to the same reassembly buffer at a 1911 single egress tunnel endpoint. In that case, data corruption may 1912 result due to fragment misassociation during reassembly. 1914 In view of these considerations, VBGs that configure an anycast 1915 address should also configure one or more unicast addresses from the 1916 Potential Router List; they should further accept tunneled packets 1917 destined to any of their anycast or unicast addresses, but should 1918 send tunneled packets using a unicast address as the source address. 1920 Appendix C. Change Log 1922 (Note to RFC editor - this section to be removed before publication 1923 as an RFC.) 1925 Changes from -14 to -15: 1927 o new insights into default route configuration and next-hop 1928 determination 1930 Changes from -13 to -14: 1932 o fixed Idnits 1934 Changes from -12 to -13: 1936 o Changed "VGL" *back* to "PRL" 1938 o More changes for multi-protocol support 1940 o Changes to Redirect function 1942 Changes from -11 to -12: 1944 o Major section rearrangement 1946 o Changed "PRL" to "VGL" 1948 o Brought back text that was lost in the -10 to -11 transition 1950 Changes from -10 to -11: 1952 o Major changes with significant simplifications 1954 o Now support stateless PD using 6rd mechanisms 1956 o SEAL Control Message Protocol (SCMP) used instead of ICMPv6 1958 o Multi-protocol support including IPv6, IPv4, OSI/CLNP, etc. 1960 Changes from -09 to -10: 1962 o Changed "enterprise" to "enterprise network" throughout 1964 o dropped "inner IP", since inner layer may be non-IP 1966 o TODO - convert "IPv6 ND" to SEAL SCMP messages so that control 1967 messages remain *within* the tunnel interface instead of being 1968 exposed to the inner network layer protocol engine. 1970 Changes from -08 to -09: 1972 o Expanded discussion of encapsulation/decapsulation procedures 1974 o cited IRON 1976 Changes from -07 to -08: 1978 o Specified the approach to global mapping using virtual aggregation 1979 and BGP 1981 Changes from -06 to -07: 1983 o reworked redirect function 1985 o created new section on VET interface encapsulation 1987 o clarifications on nexthop selection 1989 o fixed several bugs 1991 Changed from -05 to -06: 1993 o reworked VET interface ND 1995 o anycast clarifications 1997 Changes from -03 to -04: 1999 o security consideration clarifications 2001 Changes from -02 to -03: 2003 o security consideration clarifications 2005 o new PRLNAME for VET is "isatav2.example.com" 2007 o VET now uses SEAL natively 2009 o EBGs can support both legacy ISATAP and VET over the same 2010 underlying interfaces. 2012 Changes from -01 to -02: 2014 o Defined CGA and privacy address configuration on VET interfaces 2016 o Interface identifiers added to routing protocol control messages 2017 for link-layer multiplexing 2019 Changes from -00 to -01: 2021 o Section 4.1 clarifications on link-local assignment and RLOC 2022 autoconfiguration. 2024 o Appendix B clarifications on Weak End System Model 2025 Changes from RFC5558 to -00: 2027 o New appendix on RLOC configuration on VET interfaces. 2029 Author's Address 2031 Fred L. Templin (editor) 2032 Boeing Research & Technology 2033 P.O. Box 3707 MC 7L-49 2034 Seattle, WA 98124 2035 USA 2037 Email: fltemplin@acm.org