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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin 3 Internet-Draft S. Russert 4 Intended status: Informational S. Yi 5 Expires: May 17, 2008 Boeing Phantom Works 6 November 14, 2007 8 MANET Autoconfiguration 9 draft-templin-autoconf-dhcp-10.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on May 17, 2008. 36 Copyright Notice 38 Copyright (C) The IETF Trust (2007). 40 Abstract 42 Mobile Ad-hoc Networks (MANETs) connect routers on links with 43 asymmetric reachability characteristics, and may also connect to 44 other networks including the Internet. Routers in MANETs must have a 45 way to automatically provision IP addresses/prefixes and other 46 information. This document specifies mechanisms for MANET 47 autoconfiguration; both IPv4 and IPv6 are discussed. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 53 3. MANET Autoconfiguration . . . . . . . . . . . . . . . . . . . 6 54 3.1. MANET Router (MNR) Operation . . . . . . . . . . . . . . . 6 55 3.1.1. MANET Local Address (MLA) Configuration . . . . . . . 6 56 3.1.2. MNBR List Discovery . . . . . . . . . . . . . . . . . 7 57 3.1.3. VET Interface Configuration . . . . . . . . . . . . . 8 58 3.1.4. Reachability Confirmation . . . . . . . . . . . . . . 9 59 3.1.5. MNBR-Aggregated Address/Prefix Autoconfiguration . . . 9 60 3.1.6. Unique-local Address Autoconfiguration . . . . . . . . 11 61 3.1.7. Self-Generated IPv6 Interface Identifiers . . . . . . 11 62 3.1.8. Forwarding Packets to Off-MANET Destinations . . . . . 11 63 3.2. MANET Border Router (MNBR) Operation . . . . . . . . . . . 12 64 3.3. MANET Flooding . . . . . . . . . . . . . . . . . . . . . . 12 65 3.4. Changes to the Neighbor Discovery Model . . . . . . . . . 12 66 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 67 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 68 6. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 13 69 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 70 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13 71 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 72 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 73 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 74 Appendix A. IPv6 Neighbor Discovery (ND) and Duplicate 75 Address Detection (DAD) . . . . . . . . . . . . . . . 15 76 Appendix B. IPv6 StateLess Address AutoConfiguration (SLAAC) . . 16 77 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 16 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 79 Intellectual Property and Copyright Statements . . . . . . . . . . 20 81 1. Introduction 83 Mobile Ad-hoc Networks (MANETs) connect MANET Routers (MNRs) on links 84 with asymmetric reachability characteristics (see: [RFC2461], Section 85 2.2). MNRs may participate in a routing protocol over MANET 86 interfaces to discover routes across the MANET using multiple Layer-2 87 or Layer-3 forwarding hops if necessary. MANETs may also connect to 88 other networks including the Internet via MANET Border Routers 89 (MNBRs), and MNRs may be multiple hops away from their nearest MNBR 90 in some scenarios. A MANET may span an entire Autonomous System (AS) 91 or may be as simple as a small collection of MNRs (and their attached 92 networks). A MANET may contain other MANETs, and may also be a 93 subnetwork of a larger MANET. 95 MANETs that comprise homogeneous link types can configure the routing 96 protocol to operate as a sub-IP layer mechanism such that IP sees the 97 MANET as an ordinary shared link the same as for a (bridged) campus 98 LAN. In that case, a single IP hop is sufficient to traverse the 99 MANET. 101 MANETs that comprise heterogeneous link types must instead (or, in 102 addition) provide a routing service that operates as an IP layer 103 mechanism to accommodate media types with dissimilar Layer-2 address 104 formats and maximum transmission units (MTUs). In that case, 105 multiple IP hops may be necessary to traverse the MANET such that 106 MNRs require specialized autoconfiguration procedures to avoid 107 multilink subnet issues [RFC4903]. 109 Conceptually, a MNR embodies a router entity that connects its 110 attached networks to MANETs and/or other networks including the 111 Internet (see: Figure 1). The router entity also connects to an 112 imaginary Virtual Ethernet (VET) via a virtual interface configured 113 over its MANET interfaces and used to avoid multilink subnet issues. 114 An "opaque" view of the VET sees the MANET as a fully-connected 115 shared link that connects all MNRs, while a "transparent" view sees 116 the MANET as a multilink site. For each distinct MANET to which they 117 connect, MNRs discover a list of MNBRs that determines the MANET's 118 identity. An MNR (and its attached networks) is a "site" unto 119 itself, therefore a MANET is a "site-of-sites". 121 This document specifies mechanisms and operational practices for 122 MANET autoconfiguration with multilink subnet avoidance. Operation 123 using standard DHCP 124 [RFC2131][I-D.ietf-dhc-subnet-alloc][RFC3315][RFC3633] and neighbor 125 discovery [RFC1256][RFC2461][RFC2462] mechanisms is assumed unless 126 otherwise specified. Both IPv4 [RFC0791] and IPv6 [RFC2460] are 127 discussed. 129 2. Terminology 131 The terminology in [I-D.ietf-autoconf-manetarch] and the normative 132 references apply. The following terms are defined within the scope 133 of this document: 135 subnetwork 136 the same as defined in [RFC3819]. 138 egress/ingress interface 139 the same as defined in ([RFC3753], Section 3). 141 Mobile Ad-hoc Network (MANET) 142 a connected network region of MANET routers that maintain a 143 routing structure among themselves over asymmetric reachability 144 links (see: [RFC2461], Section 2.2). A MANET may span an entire 145 Autonomous System (AS) or only a small collection of MANET 146 routers, and a MANET may also be a subnetwork of a larger MANET. 147 A MANET router (and its attached networks) is a site unto itself, 148 and a MANET is therefore a site-of-sites. (Note that this 149 document considers the terms "MANET" and "site" as functional 150 equivalents.) 152 Further information on the characteristics of MANETs can be found 153 in [RFC2501]. 155 MANET Router (MNR) 156 a mobile router that forwards packets on behalf of both other MNRs 157 over its MANET interfaces and networks attached on its ingress 158 interfaces. A MNR can also forward packets to other networks 159 either directly via its egress interfaces or indirectly via an 160 MNBR. For the purpose of this specification, an MNR comprises a 161 router entity, one or more host entities, and its attached 162 ingress/egress/MANET interfaces (see: Figure 1). 164 MANET Border Router (MNBR) 165 an MNR that connects a MANET to "upstream" networks (e.g., the 166 Internet) via egress interfaces, and delegates addresses/prefixes 167 to other MNRs. 169 MANET Interface 170 a MANET Router's attachment to a link in a MANET. A MANET 171 interface is "neutral" in its orientation, i.e., it is inherently 172 neither egress nor ingress. In particular, a packet may need to 173 traverse several MANET interfaces before it is forwarded via 174 either an egress or ingress interface. 176 MANET Local Address (MLA) 177 an address configured by an MNR that is unique within the MANET; 178 it is used as an identifier for operating the routing protocol and 179 may also be assigned to a MANET interface as a locator for packet 180 forwarding within the scope of the MANET. 182 Virtual Ethernet (VET) 183 an imaginary shared link that connects all MNRs in a MANET. 185 VET interface 186 a MNR's attachment to a VET. Each VET interface is configured 187 over a set of underlying MANET interface(s) belonging to the same 188 MANET, and presents both opaque and transparent "portals" (see: 189 Figure 2 and Figure 3). 191 The opaque portal encapsulates each IP packet in an outer IP 192 header then sends it on an underlying MANET interface such that 193 the TTL/HOP Limit in the inner IP header is not decremented as the 194 packet traverses the MANET, i.e., the opaque portal views the 195 MANET as a unified shared link. In this sense, the opaque portal 196 presents an automatic tunneling abstraction. 198 The transparent portal sends each IP packet on an underlying MANET 199 interface without further encapsulation such that the TTL/Hop 200 Limit may be decremented as the packet traverses the MANET, i.e., 201 the transparent portal views the MANET as a multilink site. 203 Extended Neighbor Discovery (END) message 204 an IP Neighbor Discovery (ND) message [RFC1256] [RFC2461] 205 transmitted on the transparent portal of a VET interface with an 206 MLA of the underlying MANET interface as a source address and with 207 destination address set to an MLA or a site-scoped multicast 208 address. The TTL/Hop Limit in END messages may be decremented as 209 the message traverses the MANET. 211 The following figure depicts the architectural model for a MANET 212 router: 214 Egress Interfaces (to Internet) 215 x x x 216 | | | 217 +------------------------+---+--------+----------+ 218 | Internal hosts | | | | M 219 | and routers | | .... | | A 220 | ,-. | +---+---+--------+---+ | N 221 | (H1 )---+ | /| | E 222 | | `-' | | I /*+------+--< T 223 | . | +---+ | | n|**| | 224 | . +--|R1 |---+-----+ t|**| | I 225 | . | +---+ | | Router V e|**+------+--< n 226 | | ,-. | | E r|**| . | t 227 | (H2 )---+ | Entity T f|**| . | e 228 | `-' | . | a|**| . | r 229 | . | c|**| . | f 230 | ,-. . | e \*+------+--< a 231 | (Hn )---------+ \| | c 232 | `-' +---+---+--------+---+ | e 233 | Ingress Interfaces | | .... | | s 234 | (to internal networks) | | | | 235 +------------------------+---+--------+----------+ 236 | | | 237 x x x 238 Ingress Interfaces (to mobile networks) 240 Figure 1: MANET Router 242 3. MANET Autoconfiguration 244 3.1. MANET Router (MNR) Operation 246 MNRs configure egress interfaces that connect "upstream" toward fixed 247 Internet infrastructure, ingress interfaces that connect "downstream" 248 toward attached mobile networks, and MANET interfaces that are 249 "neutral" in the sense that the packets they forward may need to 250 traverse several other MANET interfaces before they are forwarded via 251 either an egress or ingress interface. MNRs configure VET interfaces 252 and engage in the routing protocol over their MANET interfaces; they 253 also obtain addresses/prefixes and other autoconfiguration 254 information using the mechanisms and operational practices specified 255 in the following sections: 257 3.1.1. MANET Local Address (MLA) Configuration 259 Upon joining a MANET, each MNR first configures MANET Local Addresses 260 (MLAs) that it will use for operating the routing protocol and/or for 261 local communications within the MANET. 263 IPv6 MLAs can be manually configured, administratively assigned, 264 autoconfigured using DHCP, autoconfigured using IPv6 StateLess 265 Address AutoConfiguration (SLAAC) [RFC2462], or self-generated using 266 IPv6 Unique Local Addresses (ULAs) 267 [RFC4193][I-D.ietf-ipv6-ula-central]. IPv6 MLAs include interface 268 identifiers that are either managed for uniqueness (e.g., see: 269 [RFC4291], Appendix A) or self-generated using a suitable pseudo- 270 random interface identifier generation mechanism (e.g., 271 Cryptographically Generated Addresses (CGAs) [RFC3972], IPv6 privacy 272 addresses [I-D.ietf-ipv6-privacy-addrs-v2], etc.). 274 IPv4 MLAs can be manually configured, administratively assigned, 275 autoconfigured using DHCP or self-generated using an unspecified IPv4 276 unique local address configuration mechanism. (Such a mechanism 277 could be considered as a site-scoped equivalent to IPv4 link-local 278 addresses [RFC3927].) 280 When there is no manually configured/administratively assigned MLA, 281 the choice of autoconfiguring an MLA using DHCP or self-generating 282 one using some other mechanism is up to the MNR and may depend on the 283 particular MANET deployment scenario. DHCP-generated MLAs have the 284 benefit of a "managed" avoidance of address collisions, while self- 285 generated MLAs must be monitored for collisions with other nodes that 286 might assign a duplicate. Note also that DHCP service for MLA 287 configuration may not be available in all MANETs. 289 Since a MNR initially has no non-link-local addresses, DHCP 290 configuration of MLAs may require relay support from other MNRs that 291 have already been autoconfigured within the MANET. This means that 292 MNRs with assigned MLAs should be prepared to relay another MNR's 293 DHCP requests, e.g. to a site-scoped multicast address, to a unicast 294 address(es), etc. 296 3.1.2. MNBR List Discovery 298 After configuring MLAs, the MNR next engages in any routing 299 protocol(s) over its MANET interfaces and discovers the list of MNBRs 300 (if any) on the MANET. The list of MNBRs can be discovered through 301 information conveyed in the routing protocol, or through an alternate 302 discovery mechanism, e.g., per [RFC4214], Section 8.3.2. 304 The list of MNBRs serves as an identifier for the MANET. If the list 305 of MNBRs is NULL, an alternate token such as the Layer-2 address of 306 an ordinary MNR can serve as an identifier for the MANET. 308 3.1.3. VET Interface Configuration 310 The MNR configures a VET interface for the MANET over the underlying 311 MANET interfaces. 313 The opaque portal of the VET interface configures a link-local 314 address that is assured to be unique among the VET interfaces of all 315 MNRs in the MANET, e.g., an ISATAP link-local address ([RFC4214], 316 Section 6.2) derived from the IPv4 MLA of an underlying MANET 317 interface. IP packets sent via the opaque portal are encapsulated in 318 an outer IP header then submitted to ip_output() for transmission on 319 an underlying MANET interface. 321 The transparent portal of the VET interface configures no addresses 322 itself, but rather provides IP with direct access to the underlying 323 MANET interfaces and their associated MLAs. IP packets sent via the 324 transparent portal are transmitted unencapsulated on an underlying 325 MANET interface, but may require an IPv4 source routing header 326 (likewise IPv6 routing header) or a subnetwork-specific encapsulation 327 to direct packets to specific MNBRs. 329 Figure 2 depicts the protocol stack model for the VET output routine, 330 and Figure 3 depicts the corresponding model for the VET input 331 routine: 333 +--------------------------------------------------+ | 334 | ip_output() | | 335 +--------------------------------------------------+ | 336 | vet_output() | | 337 | | 338 | _ transparent portal _ ___ opaque portal _____ | p 339 |/ \ / \| a 340 | - MANET intf already | - select MANET intf | c 341 | selected | - encapsulate in IP | k 342 | - insert routing hdr | - forward to MANET intf | e 343 | (if necessary) | via ip_output() | t 344 | - forward directly to +-------------------------+ s 345 | MANET intf | ip_output() | 346 +--------------+---------+----+-...-+--------------+ | 347 | MANET Intf 0 | MANET Intf 1 | ... | MANET Intf n | | 348 | (MLA 0) | (MLA 1) | ... | (MLA n) | | 349 +--------------+--------------+-...-+--------------+ v 351 Figure 2: vet_output() 353 +--------------------------------------------------+ ^ 354 | ip_input() | | 355 +--------------------------------------------------+ | 356 | vet_input() | 357 | | p 358 | _ transparent portal _ ___ opaque portal ____ | a 359 |/ \ / \| c 360 | - submit to ip_input() | - decapsulate packet | k 361 | | - submit to ip_input() | e 362 | +-------------------------+ t 363 | | ip_input() | s 364 +--------------+---------+----+-...-+--------------+ 365 | MANET Intf 0 | MANET Intf 1 | ... | MANET Intf n | | 366 | (MLA 0) | (MLA 1) | ... | (MLA n) | | 367 +--------------+--------------+-...-+--------------+ | 369 Figure 3: vet_input() 371 3.1.4. Reachability Confirmation 373 After the MNR configures a VET interface, it can confirm reachability 374 of MNRs/MNBRs and (in the case of IPv6) discover prefixes associated 375 with the VET. The MNR can confirm reachability by sending/receiving 376 END messages over the transparent portal, by sending/receiving 377 ordinary ND messages over the opaque portal, by issuing DHCP 378 requests, via reachability information conveyed in the routing 379 protocol itself, or through some other means associated with the 380 particular MANET subnetwork technology. 382 3.1.5. MNBR-Aggregated Address/Prefix Autoconfiguration 384 After the MNR discovers MNBRs, it can acquire MNBR-aggregated 385 addresses/prefixes using either DHCP or IPv6 Stateless Address 386 AutoConfiguration (SLAAC) (but see Appendix B for further 387 considerations on SLAAC). These addresses/prefixes are delegated by 388 specific MNBRs, and may be: 390 o global-scope and provider aggregated 392 o global-scope and provider-independent 394 o global-scope and 6to4 [RFC3056] 396 o unique-local scope and centrally administrated 398 o unique-local scope and locally assigned 399 o other non-link-local scope 401 When DHCP is used, a DHCP client associated with the MNR's host 402 entity forwards a DHCP DISCOVER (DHCPv4) or Solicit (DHCPv6) request 403 to a DHCP relay associated with its router entity to request IP 404 address/prefix delegations (i.e., the MNR acts as both DHCP client 405 and relay). The relay function then forwards the request to the 406 unicast addresses of one or more MNBRs, to a site-scoped multicast 407 address, or to another known DHCP server within the MANET. 409 For DHCPv6, the MNR's relay function writes an address from the VET 410 interface in the "peer-address" field and also writes an address from 411 the prefix associated with the VET in the "link-address" field (if a 412 prefix is available). The MNR can also (or, instead) use DHCPv6 413 prefix delegation [RFC3633] to obtain addresses/prefixes via MNBRs 414 for assignment and/or further sub-delegation on networks connected on 415 its ingress interfaces. (Note that the MNR can obtain /128 prefixes 416 using DHCP prefix delegation the same as for any IPv6 prefix.) 418 For DHCPv4, the MNR's relay function writes an address from the VET 419 interface in the 'giaddr' field. If necessary to identify the MNR's 420 ingress interface, the relay also includes a link selection sub- 421 option [RFC3527] with an address from the prefix associated with the 422 VET (if a prefix is available). The MNR can also (or, instead) use 423 DHCPv4 prefix delegation [I-D.ietf-dhc-subnet-alloc] to obtain 424 addresses/prefixes via MNBRs for further assignment and/or further 425 sub-delegation on networks connected on its ingress interfaces. 426 (Note that the MNR can obtain /32 prefixes using DHCP prefix 427 delegation the same as for any IPv4 prefix.) 429 The DHCP request will elicit a DHCP reply from a server with IP 430 address/prefix delegations that are aggregated by one or more MNBRs. 431 When addresses are delegated, the MNR assigns the resulting addresses 432 to an ingress interface, i.e., it does not assign the addresses on 433 the VET interface or an underlying MANET interface. When prefixes 434 are delegated, the MNR can assign and/or further sub-delegate them to 435 networks connected on its ingress interfaces. If the MANET 436 subnetwork uses a proactive routing protocol, the MNR can advertise 437 the delegated addresses/prefixes into the routing protocol during the 438 duration of the delegation lifetimes. 440 The DHCP server ensures IP address/prefix delegations that are unique 441 within the MANET. By assigning these IP addresses/prefixes only on 442 ingress interfaces there is no requirement for the MNR to perform 443 Duplicate Address Detection (DAD) for them over its MANET interfaces 444 or VET interfaces (but see Appendix A for further DAD 445 considerations). 447 3.1.6. Unique-local Address Autoconfiguration 449 Independent of any MNBR-aggregated addresses/prefixes (see: 450 Section 3.1.5), MNRs can self-generate IPv6 Unique Local Address 451 (ULA) prefixes [RFC4193][I-D.ietf-ipv6-ula-central] and sub-delegate 452 them on networks connected on their ingress interfaces. Note that in 453 some scenarios a MNR may not require any MNBR-aggregated address/ 454 prefix assignments at all, and can use its own ULAs instead. 456 Self-generated unique-local addresses are portable and not aggregated 457 by MNBRs. The addresses can therefore travel with the MNR as it 458 moves to new MANETs and/or configures peering arrangements with MNRs 459 in other MANETs. Self-generation of unique-local addresses can 460 therefore occur independently of any other MNR autoconfiguration 461 considerations. 463 3.1.7. Self-Generated IPv6 Interface Identifiers 465 MNR's can self-generate IPv6 interface identifiers such as specified 466 for CGAs [RFC3972], IPv6 privacy address 467 [I-D.ietf-ipv6-privacy-addrs-v2], etc. 469 For MNBR-aggregated address/prefix autoconfiguration (see: 470 Section 3.1.5), the MNR can propose a self-generated address to the 471 DHCPv6 server which will delegate the address to the MNR for 472 assignment on an ingress interface if the proposed address is unique. 474 3.1.8. Forwarding Packets to Off-MANET Destinations 476 After the MNR configures IP addresses/prefixes, it can forward IP 477 packets to off-MANET destinations. 479 For IPv6, MNRs can discover default router preferences and more- 480 specific routes per [RFC4191] by sending unicast Router Solicitations 481 over the VET interface opaque portal to elicit Router Advertisements 482 from MNBRs and other MNRs. MNRs/MNBRs should therefore send Router 483 Advertisements with default router preferences and/or more-specific 484 routes in response to unicast Router Solicitations. This matches the 485 operational framework established by ISATAP [RFC4214]. 487 Once default routers and/or more-specific routes are discovered, the 488 MNR can either 1) forward the packets via the opaque portal with an 489 MLA for an MNR/MNBR as the destination in the outer IP header, or 2) 490 forward the packets via the transparent portal and insert an IPv4 491 source routing header (likewise IPv6 routing header) or a subnetwork- 492 specific encapsulation. 494 (For MANETs in which 'default' and/or more-specific routes are made 495 available through the routing protocol, the MNR can optionally 496 forward IP packets to off-MANET destinations using the transparent 497 VET interface portal.) 499 3.2. MANET Border Router (MNBR) Operation 501 MNBRs connect the MANET to upstream networks over egress interfaces. 503 MNBRs send/receive END messages on the VET interface transparent 504 portal and/or send/receive ordinary ND messages on the opaque portal. 505 When stateful configuration is desired, MNBRs should set the M bit to 506 1 in the RA messages they send. (Stateless configuration is also 507 possible, but see: Appendix B for further considerations on using 508 SLAAC for MANET Autoconfiguration.) 510 For DHCPv6, MNBRs act as DHCP relays and/or servers for a MNR's DHCP 511 requests/replies. For DHCPv4, MNBRs may only act as DHCP servers, 512 since the MLA address in the 'giaddr' field is not routable outside 513 the scope of the MANET. 515 3.3. MANET Flooding 517 MANETs that operate routing as an IP layer service should deploy a 518 multicast flooding service (e.g., Simplified Multicast Forwarding 519 (SMF) [I-D.ietf-manet-smf]) so that site-scoped multicast messages 520 will be propagated across the MANET. 522 3.4. Changes to the Neighbor Discovery Model 524 Ordinary link-scoped ND messages work as-normal over the VET 525 interface opaque portal, so ND operation over the opaque portal 526 requires no changes to the standard IP neighbor discovery protocols 527 specified in [RFC1256][RFC2461]. 529 END messages over the VET interface transparent portal must use a 530 site-scoped unicast source address (i.e., an MLA) and an MLA or site- 531 scoped multicast destination address such that the messages may be 532 forwarded by a router and have their TTL/Hop Limit decremented on the 533 path. This means that END messages provide a site-scoped (and not 534 link-scoped) discovery service which represents a departure from the 535 link-scoped services specified in [RFC1256][RFC2461]. 537 4. IANA Considerations 539 A site-scoped IPv4 multicast group for: "All-MANET-Routers", or: 540 "All-Site-Routers" is requested, e.g., to support MANET flooding for 541 site-scoped service discovery (see: Section 3.3). 543 5. Security Considerations 545 Threats relating to MANET routing protocols also apply to this 546 document. 548 6. Related Work 550 The authors acknowledge the work done by Brian Carpenter and Cyndi 551 Jung in [RFC2529] that introduced the concept of intra-site automatic 552 tunneling. This concept was later called: "Virtual Ethernet" and 553 researched by Quang Nguyen under the guidance of Dr. Lixia Zhang. 555 Telcordia has proposed DHCP-related solutions for the CECOM MOSAIC 556 program. The Naval Research Lab (NRL) Information Technology 557 Division uses DHCP in their MANET research testbeds. Various IETF 558 AUTOCONF working group proposals have suggested similar mechanisms. 560 7. Acknowledgements 562 The following individuals gave direct and/or indirect input that was 563 essential to the work: Jari Arkko, Teco Boot, Emmanuel Bacelli, James 564 Bound, Thomas Clausen, Eric Fleischman, Bob Hinden, Joe Macker, 565 Thomas Narten, Alexandru Petrescu, Jinmei Tatuya, Dave Thaler, and 566 others in the IETF AUTOCONF and MANET working groups. Many others 567 have provided guidance over the course of many years. 569 8. Contributors 571 Thomas Henderson (thomas.r.henderson@boeing.com) contributed to this 572 document. Ian Chakeres (ian.chakeres@gmail.com) contributed to 573 earlier versions of the document. 575 9. References 577 9.1. Normative References 579 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 580 September 1981. 582 [RFC1256] Deering, S., "ICMP Router Discovery Messages", RFC 1256, 583 September 1991. 585 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 586 RFC 2131, March 1997. 588 [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor 589 Extensions", RFC 2132, March 1997. 591 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 592 (IPv6) Specification", RFC 2460, December 1998. 594 [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor 595 Discovery for IP Version 6 (IPv6)", RFC 2461, 596 December 1998. 598 [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address 599 Autoconfiguration", RFC 2462, December 1998. 601 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 602 and M. Carney, "Dynamic Host Configuration Protocol for 603 IPv6 (DHCPv6)", RFC 3315, July 2003. 605 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 606 Host Configuration Protocol (DHCP) version 6", RFC 3633, 607 December 2003. 609 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 610 More-Specific Routes", RFC 4191, November 2005. 612 [RFC4214] Templin, F., Gleeson, T., Talwar, M., and D. Thaler, 613 "Intra-Site Automatic Tunnel Addressing Protocol 614 (ISATAP)", RFC 4214, October 2005. 616 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 617 Architecture", RFC 4291, February 2006. 619 9.2. Informative References 621 [I-D.ietf-autoconf-manetarch] 622 Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc 623 Network Architecture", draft-ietf-autoconf-manetarch-07 624 (work in progress), November 2007. 626 [I-D.ietf-dhc-subnet-alloc] 627 Johnson, R., "Subnet Allocation Option", 628 draft-ietf-dhc-subnet-alloc-05 (work in progress), 629 June 2007. 631 [I-D.ietf-ipv6-privacy-addrs-v2] 632 Narten, T., "Privacy Extensions for Stateless Address 633 Autoconfiguration in IPv6", 634 draft-ietf-ipv6-privacy-addrs-v2-05 (work in progress), 635 October 2006. 637 [I-D.ietf-ipv6-ula-central] 638 Hinden, R., "Centrally Assigned Unique Local IPv6 Unicast 639 Addresses", draft-ietf-ipv6-ula-central-02 (work in 640 progress), June 2007. 642 [I-D.ietf-manet-smf] 643 Macker, J., "Simplified Multicast Forwarding for MANET", 644 draft-ietf-manet-smf-05 (work in progress), June 2007. 646 [RFC2501] Corson, M. and J. Macker, "Mobile Ad hoc Networking 647 (MANET): Routing Protocol Performance Issues and 648 Evaluation Considerations", RFC 2501, January 1999. 650 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 651 Domains without Explicit Tunnels", RFC 2529, March 1999. 653 [RFC3527] Kinnear, K., Stapp, M., Johnson, R., and J. Kumarasamy, 654 "Link Selection sub-option for the Relay Agent Information 655 Option for DHCPv4", RFC 3527, April 2003. 657 [RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology", 658 RFC 3753, June 2004. 660 [RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., 661 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 662 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 663 RFC 3819, July 2004. 665 [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic 666 Configuration of IPv4 Link-Local Addresses", RFC 3927, 667 May 2005. 669 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 670 RFC 3972, March 2005. 672 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 673 Addresses", RFC 4193, October 2005. 675 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 676 June 2007. 678 Appendix A. IPv6 Neighbor Discovery (ND) and Duplicate Address 679 Detection (DAD) 681 In terms of ND, existing standards [RFC2461][RFC4291] require that a 682 node configure a link-local address on each of its IPv6-enabled 683 interfaces, but the primary requirement for link-locals seems to be 684 for the purpose of uniquely identifying routers on the link. It is 685 therefore for further study as to whether MNRs should send RAs on 686 MANET interfaces (or even configure link local addresses on MANET 687 interfaces at all), since the transparent view of the MANET appears 688 as a multilink peering point between distinct sites, and not a 689 unified link. 691 In terms of DAD, pre-service DAD for an MLA assigned on a MANET 692 interface (such as specified in [RFC2462]) would require either 693 flooding the entire MANET or somehow discovering a link in the MANET 694 on which a node that configures a duplicate address is attached and 695 performing a localized DAD exchange on that link. But, the control 696 message overhead for such a MANET-wide DAD would be substantial and 697 prone to false-negatives due to packet loss and node mobility. An 698 alternative to pre-service DAD is to autoconfigure pseudo-random MLAs 699 on MANET interfaces and employ a passive in-service DAD (e.g., one 700 that monitors routing protocol messages for duplicate assignments). 701 Pseudo-random link-local addresses can be generated with mechanisms 702 such as CGAs, IPv6 privacy addresses, etc. with very small 703 probability of collision. But, IPv6 ULAs also provide an additional 704 40 pseudo-random bits in the prefix. 706 Statistical properties for pseudo-random address self-generation can 707 assure uniqueness for the MLAs assigned on a MNR's MANET interfaces, 708 and consistent operational practices can assure uniqueness for MNBR- 709 aggregated addresses/prefixes. However, a passive in-service DAD 710 mechanism should still be used to detect duplicates that were 711 assigned through other means, e.g., manual configuration. 713 Appendix B. IPv6 StateLess Address AutoConfiguration (SLAAC) 715 For IPv6, the use of StateLess Address AutoConfiguration (SLAAC) 716 [RFC2462] could be indicated by prefix information options in END 717 and/or ordinary ND messages with the 'A' bit set to 1. MNRs that 718 receive such messages could then self-generate an address from the 719 prefix and assign it to the VET interface, then use a passive in- 720 service DAD approach to detect duplicates within the MANET. But, if 721 the MANET partitions, DAD might not be able to monitor the other 722 partitions and address duplication could result. Further study on 723 DAD implications for SLAAC in MANETs is required. 725 Appendix C. Change Log 727 (Note to RFC editor - this section to be removed before publication 728 as an RFC.) 729 Changes from -08 to -09: 731 o Introduced the term "VET". 733 o Changed address delegation language to speak of "MNBR-aggregated" 734 instead of global/local. 736 o Updated figures 1-3. 738 o Explained why a MANET interface is "neutral". 740 o Removed DHCPv4 "MLA Address option". Now, MNBRs can only be 741 DHCPv4 servers; not relays. 743 Changes from -07 to -08: 745 o changed terms "unenhanced" and "enhanced" to "transparent" and 746 "opaque". 748 o revised MANET Router diagram. 750 o introduced RFC3753 terminology for Mobile Router; ingress/egress 751 interface. 753 o changed abbreviations to "MNR" and "MNBR". 755 o added text on ULAs and ULA-Cs to "Self-Generated Addresses". 757 o rearranged Section 3.1. 759 o various minor text cleanups 761 Changes from -06 to -07: 763 o added MANET Router diagram. 765 o added new references 767 o various minor text cleanups 769 Changed from -05 to -06: 771 o Changed terms "raw" and "cooked" to "unenhanced" and "enhanced". 773 o minor changes to preserve generality 775 Changed from -04 to -05: 777 o introduced conceptual "virtual ethernet" model. 779 o support "raw" and "cooked" modes as equivalent access methods on 780 the virutal ethernet. 782 Changed from -03 to -04: 784 o introduced conceptual "imaginary shared link" as a representation 785 for a MANET. 787 o discussion of autonomous system and site abstractions for MANETs 789 o discussion of autoconfiguration of CGAs 791 o new appendix on IPv6 StateLess Address AutoConfiguration 793 Changes from -02 to -03: 795 o updated terminology based on RFC2461 "asymmetric reachability" 796 link type; IETF67 MANET Autoconf wg discussions. 798 o added new appendix on IPv6 Neighbor Discovery and Duplicate 799 Address Detection 801 o relaxed DHCP server deployment considerations allow DHCP servers 802 within the MANET itself 804 Changes from -01 to -02: 806 o minor updates for consistency with recent developments 808 Changes from -00 to -01: 810 o new text on DHCPv6 prefix delegation and multilink subnet 811 considerations. 813 o various editorial changes 815 Authors' Addresses 817 Fred L. Templin 818 Boeing Phantom Works 819 P.O. Box 3707 MC 7L-49 820 Seattle, WA 98124 821 USA 823 Email: fred.l.templin@boeing.com 825 Steven W. Russert 826 Boeing Phantom Works 827 P.O. Box 3707 MC 7L-49 828 Seattle, WA 98124 829 USA 831 Email: steven.w.russert@boeing.com 833 Seung Yi 834 Boeing Phantom Works 835 P.O. 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