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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC0791' is defined on line 444, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) == Outdated reference: A later version (-08) exists of draft-templin-6man-rio-redirect-04 Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). 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: Informational October 16, 2017 5 Expires: April 19, 2018 7 IPv6 Prefix Delegation for Hosts 8 draft-templin-v6ops-pdhost-15.txt 10 Abstract 12 IPv6 prefixes are typically delegated to requesting routers which 13 then use them to number their downstream-attached links and networks. 14 This document considers the case when the requesting router is a node 15 that acts as a host on behalf of its local applications and as a 16 router on behalf of any downstream networks. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on April 19, 2018. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 54 3. Multi-Addressing Considerations . . . . . . . . . . . . . . . 6 55 4. Multi-Addressing Alternatives for Delegated Prefixes . . . . 7 56 5. MLD/DAD Implications . . . . . . . . . . . . . . . . . . . . 7 57 6. Dynamic Routing Protocol Implications . . . . . . . . . . . . 8 58 7. IPv6 Neighbor Discovery Implications . . . . . . . . . . . . 8 59 8. ICMPv6 Implications . . . . . . . . . . . . . . . . . . . . . 9 60 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 61 10. Security Considerations . . . . . . . . . . . . . . . . . . . 9 62 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 63 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 64 12.1. Normative References . . . . . . . . . . . . . . . . . . 10 65 12.2. Informative References . . . . . . . . . . . . . . . . . 11 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12 68 1. Introduction 70 IPv6 Prefix Delegation (PD) entails 1) the communication of a prefix 71 from a delegating router to a requesting router, 2) a representation 72 of the prefix in the delegating router's routing table, and 3) a 73 control messaging service between the delegating and requesting 74 routers to maintain prefix lifetimes. Following delegation, the 75 prefix is available for the requesting router's exclusive use and is 76 not shared with any other nodes. This document considers the case 77 when the requesting router is a node that acts as a host on behalf of 78 its local applications and as a router on behalf of any downstream 79 networks. The following paragraphs present possibilities for node 80 behavior upon receipt of a delegated prefix. 82 For nodes that connect downstream-attached networks (e.g., a 83 cellphone that connects a "tethered" Internet of Things (IoT) 84 network), a Delegating Router 'D' delegates a prefix 'P' to a 85 Requesting node 'R' as shown in Figure 1: 87 +---------------------+ 88 |Delegating Router 'D'| 89 | (Delegate 'P') | 90 +----------+----------+ 91 | 92 | Upstream link 93 | 94 +----------+----------+ 95 | Upstream Interface | 96 +---------------------+ 97 | | 98 | Requesting node 'R' | 99 | (Receive 'P') | 100 | | 101 +--+-+--+-+--+-----+--+ 102 |A1| |A2| |A3| ... |Aj| 103 +--+-+--+-+--+-----+--+ 104 | Downstream Interface| 105 +----------+----------+ 106 | 107 | Downstream link 108 | 109 X----+-------------+--------+----+---------------+---X 110 | | | | 111 +---++-+--+ +---++-+--+ +---++-+--+ +---++-+--+ 112 | |Ak| | | |Al| | | |Am| | | |A*| | 113 | +--+ | | +--+ | | +--+ | | +--+ | 114 | Host H1 | | Host H2 | | Host H3 | ... | Host Hn | 115 +---------+ +---------+ +---------+ +---------+ 117 <-------------- Downstream Network -------------> 119 Figure 1: Classic Routing Model 121 In this figure, when Delegating Router 'D' delegates prefix 'P', it 122 inserts 'P' into its routing table with Requesting node 'R' as the 123 next hop. Meanwhile, 'R' receives 'P' via an upstream interface and 124 sub-delegates 'P' to its downstream external (physical) and/or 125 internal (virtual) networks. 'R' assigns addresses 'A(*)' taken from 126 'P' to downstream interfaces, and Hosts 'H(i)' on downstream networks 127 assign addresses 'A(*)' taken from 'P' to their interface attachments 128 to the downstream link. 'R' then acts as a router between hosts 129 'H(i)' on downstream networks and correspondents reachable via other 130 interfaces. 'R' can also act as a host on behalf of its local 131 applications. 133 This document also considers the case when 'R' does not have any 134 downstream interfaces, and can use 'P' solely for its own internal 135 addressing purposes. In that case, 'R' assigns 'P' to a virtual 136 interface (e.g., a loopback) that fills the role of a downstream 137 interface. 139 'R' can then function under the weak end system (aka "weak host") 140 model [RFC1122][RFC8028] by assigning addresses taken from 'P' to a 141 virtual interface as shown in Figure 2: 143 +---------------------+ 144 |Delegating Router 'D'| 145 | (Delegate 'P') | 146 +----------+----------+ 147 | 148 | Upstream link 149 | 150 +----------+----------+ 151 | Upstream Interface | 152 +---------------------+ 153 | | 154 | Requesting node 'R' | 155 | (Receive 'P') | 156 | | 157 +--+-+--+-+--+-----+--+ 158 |A1| |A2| |A3| ... |An| 159 +--+-+--+-+--+-----+--+ 160 | Virtual Interface | 161 +---------------------+ 163 Figure 2: Weak End System Model 165 'R' could instead function under the strong end system (aka "strong 166 host") model [RFC1122][RFC8028] by assigning IPv6 addresses taken 167 from 'P' to an upstream interface as shown in Figure 3: 169 +---------------------+ 170 |Delegating Router 'D'| 171 | (Delegate 'P') | 172 +----------+----------+ 173 | 174 | Upstream link 175 | 176 +----------+----------+ 177 | Upstream Interface | 178 +--+-+--+-+--+-----+--+ 179 |A1| |A2| |A3| ... |An| 180 +--+-+--+-+--+-----+--+ 181 | | 182 | Requesting node 'R' | 183 | (Receive 'P') | 184 | | 185 +---------------------+ 186 | Virtual Interface | 187 +---------------------+ 189 Figure 3: Strong End System Model 191 The major benefit for a node managing a delegated prefix in either 192 the weak or strong end system models is multi-addressing. With IPv6 193 PD-based multi-addressing, the node can configure an unlimited supply 194 of addresses to make them available for local applications without 195 requiring coordination with other nodes on upstream interfaces. 197 The following sections present considerations for nodes that employ 198 IPv6 PD mechanisms. 200 2. Terminology 202 The terminology of the normative references apply, and the terms 203 "node", "host" and "router" are the same as defined in [RFC8200]. 205 The following terms are defined for the purposes of this document: 207 shared prefix 208 an IPv6 prefix that may be advertised to more than one node on the 209 link, e.g., in a Router Advertisement (RA) message Prefix 210 Information Option (PIO) [RFC4861]. The router that advertises 211 the prefix must consider the prefix as on-link so that the IPv6 212 Neighbor Discovery (ND) address resolution function will identify 213 the correct neighbor for each packet. 215 individual prefix 216 an IPv6 prefix that is advertised to exactly one node on the link, 217 where the node may be unaware that the prefix is individual and 218 may not participate in prefix maintenance procedures. The router 219 that advertises the prefix can consider the prefix as on-link or 220 not on-link. In the former case, the router performs address 221 resolution so that it only forwards those packets that match one 222 of the node's configured addresses so that the node will not 223 receive unwanted packets. In the latter case, the router can 224 simply forward all packets matching the prefix to the node. An 225 example individual prefix service is documented in 226 [I-D.ietf-v6ops-unique-ipv6-prefix-per-host]. 228 delegated prefix 229 an IPv6 prefix that is explicitly delegated to a node for its own 230 exclusive use, where the node is an active participant in prefix 231 delegation and maintenance procedures. The router that delegates 232 the prefix simply forwards all packets matching the prefix to the 233 node. An example IPv6 PD service is the Dynamic Host 234 Configuration Protocol for IPv6 (DHCPv6) [RFC3315][RFC3633]. An 235 alternative service based solely on IPv6 ND messaging has also 236 been proposed [I-D.pioxfolks-6man-pio-exclusive-bit]. 238 3. Multi-Addressing Considerations 240 IPv6 allows nodes to assign multiple addresses to a single interface. 241 [RFC7934] discusses options for multi-addressing as well as use cases 242 where multi-addressing may be desirable. Address configuration 243 options for multi-addressing include StateLess Address 244 AutoConfiguration (SLAAC) [RFC4862], DHCPv6 address configuration 245 [RFC3315], manual configuration, etc. 247 Nodes configure addresses from a shared or individual prefix and 248 assign them to the upstream interface over which the prefix was 249 received. When the node assigns the addresses, it is required to use 250 Multicast Listener Discovery (MLD) [RFC3810] to join the appropriate 251 solicited-node multicast group(s) and to use the Duplicate Address 252 Detection (DAD) algorithm [RFC4862] to ensure that no other node 253 configures a duplicate address. 255 In contrast, a node that configures addresses from a delegated prefix 256 can assign them without invoking MLD/DAD on an upstream interface, 257 since the prefix has been delegated to the node for its own exclusive 258 use and is not shared with any other nodes. 260 4. Multi-Addressing Alternatives for Delegated Prefixes 262 When a node receives a delegated prefix, it has many alternatives for 263 provisioning the prefix to its local interfaces and/or downstream 264 networks. [RFC7278] discusses alternatives for provisioning a prefix 265 obtained by a User Equipment (UE) device under the 3rd Generation 266 Partnership Program (3GPP) service model. This document considers 267 the more general case when the node receives a delegated prefix 268 explicitly provided for its own exclusive use. 270 When the node receives the prefix, it can distribute the prefix to 271 downstream networks and configure one or more addresses for itself on 272 downstream interfaces. The node then acts as a router on behalf of 273 its downstream networks and configures a default route via a neighbor 274 on an upstream interface. 276 The node could instead (or in addition) use portions of the delegated 277 prefix for its own multi-addressing purposes. In a first 278 alternative, the node can assign as many addresses as it wants from 279 the prefix to virtual interfaces. In that case, applications running 280 on the node can use the addresses according to the weak end system 281 model. 283 In a second alternative, the node can assign as many addresses as it 284 wants from the prefix to the upstream interface over which the prefix 285 was received. In that case, applications running on the node can use 286 the addresses according to the strong end system model. 288 In both of these latter two cases, the node assigns the prefix itself 289 to a virtual interface so that unused addresses from the prefix are 290 correctly identified as unreachable. The node then acts as a host on 291 behalf of its local applications even though neighbors on the 292 upstream link see it as a router. 294 5. MLD/DAD Implications 296 When a node configures addresses for itself from a shared or 297 individual prefix, it performs MLD/DAD by sending multicast messages 298 over upstream interfaces to test whether there is another node on the 299 link that configures a duplicate address. When there are many such 300 addresses and/or many such nodes, this could result in substantial 301 multicast traffic that affects all nodes on the link. 303 When a node configures addresses for itself from a delegated prefix, 304 it can configure as many addresses as it wants but does not perform 305 MLD/DAD for any of the addresses over upstream interfaces. This 306 means that the node can configure arbitrarily many addresses without 307 causing any multicast messaging over the upstream interface that 308 could disturb other nodes. 310 6. Dynamic Routing Protocol Implications 312 Nodes that receive delegated prefixes can be configured to either 313 participate or not participate in a dynamic routing protocol over the 314 upstream interface, according to the deployment model. When there 315 are many nodes on the upstream link, dynamic routing protocol 316 participation might be impractical due to scaling limitations, and 317 may also be exacerbated by factors such as node mobility. 319 Unless it participates in a dynamic routing protocol, the node 320 initially has only a default route pointing to a neighbor via an 321 upstream interface. This means that packets sent by the node over an 322 upstream interface will initially go through a default router even if 323 there is a better first-hop node on the link. 325 7. IPv6 Neighbor Discovery Implications 327 When a node receives a shared or individual prefix with "L=1" and has 328 a packet to send to an IPv6 destination within the prefix, it is 329 required to use the IPv6 ND address resolution function over the 330 upstream interface to resolve the link-layer address of a neighbor 331 that configures the address. When a node receives a shared or 332 individual prefix with "L=0" and has a packet to send to an IPv6 333 destination within the prefix, if the address is not one of the 334 node's own addresses it sends the packet to a default router since 335 "L=0" makes no statement about on-link or off-link properties of the 336 prefix [RFC4861]. 338 When a node receives a delegated prefix, it acts as a simple host to 339 send Router Solicitation (RS) messages over upstream interfaces 340 (i.e., the same as described in Section 4.2 of [RFC7084]) but also 341 sets the "Router" flag to TRUE in its Neighbor Advertisement 342 messages. The node considers the upstream interfaces as non- 343 advertising interfaces [RFC4861], i.e., it does not send RA messages 344 over the upstream interfaces. The node further does not perform the 345 IPv6 ND address resolution function over upstream interfaces, since 346 the delegated prefix is explicitly not to be associated with an 347 upstream interface. 349 In all cases, the current first-hop router may send a Redirect 350 message that updates the node's neighbor cache so that future packets 351 can use a better first-hop node on the link. The Redirect can apply 352 either to a singleton destination address, or to an entire 353 destination prefix as described in [I-D.templin-6man-rio-redirect]. 355 8. ICMPv6 Implications 357 The Internet Control Message Protocol for IPv6 (ICMPv6) includes a 358 set of control message types [RFC4443] including Destination 359 Unreachable (DU). 361 According to [RFC4443], routers should return DU messages (subject to 362 rate limiting) with code 0 ("No route to destination") when a packet 363 arrives for which there is no matching entry in the routing table, 364 and with code 3 ("Address unreachable") when the IPv6 destination 365 address cannot be resolved. 367 According to [RFC4443], hosts should return DU messages (subject to 368 rate limiting) with code 3 to internal applications when the IPv6 369 destination address cannot be resolved, and with code 4 ("Port 370 unreachable") if the IPv6 destination address is one of its own 371 addresses but the transport protocol has no listener. 373 Nodes that obtain and manage delegated prefixes per this document 374 observe the same procedures as described for both routers and hosts 375 above. 377 9. IANA Considerations 379 This document introduces no IANA considerations. 381 10. Security Considerations 383 Security considerations for IPv6 Neighbor Discovery [RFC4861] and any 384 applicable PD mechanisms apply to this document. Nodes that receive 385 delegated prefixes do not perform DAD procedures on their upstream 386 interfaces, meaning that they cannot contribute to multicast 387 messaging congestion on the upstream link. Also, routers that 388 delegate prefixes keep only a single neighbor cache entry for each 389 prefix delegation recipient, meaning that the router's neighbor cache 390 cannot be subject to resource exhaustion attacks. 392 For shared and individual prefixes, if the router that advertises the 393 prefix considers the prefix as on-link the IPv6 ND address resolution 394 function will prevent unwanted IPv6 packets from reaching the node. 395 For delegated prefixes and individual prefixes that are not 396 considered on-link, the router delivers all packets that match the 397 prefix to the unicast link-layer address of the node (i.e., as 398 determined by resolution of the node's link-local address) even if 399 they do not match one of the node's configured addresses. In the 400 latter case, the node may receive unwanted IPv6 packets via an 401 upstream interface that do not match either a configured IPv6 address 402 or a transport listener. The node then drops the packets and 403 observes the "Destination Unreachable - Address/Port unreachable" 404 procedures discussed in Section 8. 406 The node may also receive IPv6 packets via an upstream interface that 407 do not match any of the node's delegated prefixes. In that case, the 408 node drops the packets and observes the "Destination Unreachable - No 409 route to destination" procedures discussed in Section 8. Dropping 410 the packets is necessary to avoid a reflection attack that would 411 cause the node to forward packets received from an upstream interface 412 via the same or a different upstream interface. 414 In all cases, the node must decide whether or not to send DUs 415 according to the specific operational scenario. In trusted networks, 416 the node should send DU messages to provide useful information to 417 potential correspondents. In untrusted networks, the node can 418 refrain from sending DU messages to avoid providing sensitive 419 information to potential attackers. 421 11. Acknowledgements 423 This work was motivated by discussions on the v6ops list. Mark Smith 424 pointed out the need to consider MLD as well as DAD for the 425 assignment of addresses to interfaces. Ricardo Pelaez-Negro, Edwin 426 Cordeiro, Fred Baker, Naveen Lakshman, Ole Troan, Bob Hinden, Brian 427 Carpenter, Joel Halpern, Albert Manfredi and Dusan Mudric provided 428 useful comments that have greatly improved the document. 430 This work is aligned with the NASA Safe Autonomous Systems Operation 431 (SASO) program under NASA contract number NNA16BD84C. 433 This work is aligned with the FAA as per the SE2025 contract number 434 DTFAWA-15-D-00030. 436 This work is aligned with the Boeing Information Technology (BIT) 437 MobileNet program and the Boeing Research & Technology (BR&T) 438 enterprise autonomy program. 440 12. References 442 12.1. Normative References 444 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 445 DOI 10.17487/RFC0791, September 1981, 446 . 448 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 449 C., and M. Carney, "Dynamic Host Configuration Protocol 450 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 451 2003, . 453 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 454 Host Configuration Protocol (DHCP) version 6", RFC 3633, 455 DOI 10.17487/RFC3633, December 2003, 456 . 458 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 459 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 460 DOI 10.17487/RFC3810, June 2004, 461 . 463 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 464 Control Message Protocol (ICMPv6) for the Internet 465 Protocol Version 6 (IPv6) Specification", STD 89, 466 RFC 4443, DOI 10.17487/RFC4443, March 2006, 467 . 469 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 470 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 471 DOI 10.17487/RFC4861, September 2007, 472 . 474 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 475 Address Autoconfiguration", RFC 4862, 476 DOI 10.17487/RFC4862, September 2007, 477 . 479 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 480 (IPv6) Specification", STD 86, RFC 8200, 481 DOI 10.17487/RFC8200, July 2017, 482 . 484 12.2. Informative References 486 [I-D.ietf-v6ops-unique-ipv6-prefix-per-host] 487 Brzozowski, J. and G. Velde, "Unique IPv6 Prefix Per 488 Host", draft-ietf-v6ops-unique-ipv6-prefix-per-host-13 489 (work in progress), October 2017. 491 [I-D.pioxfolks-6man-pio-exclusive-bit] 492 Kline, E. and M. Abrahamsson, "IPv6 Router Advertisement 493 Prefix Information Option eXclusive Flag", draft- 494 pioxfolks-6man-pio-exclusive-bit-02 (work in progress), 495 March 2017. 497 [I-D.templin-6man-rio-redirect] 498 Templin, F. and j. woodyatt, "Route Information Options in 499 IPv6 Neighbor Discovery", draft-templin-6man-rio- 500 redirect-04 (work in progress), August 2017. 502 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 503 Communication Layers", STD 3, RFC 1122, 504 DOI 10.17487/RFC1122, October 1989, 505 . 507 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 508 Requirements for IPv6 Customer Edge Routers", RFC 7084, 509 DOI 10.17487/RFC7084, November 2013, 510 . 512 [RFC7278] Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6 513 /64 Prefix from a Third Generation Partnership Project 514 (3GPP) Mobile Interface to a LAN Link", RFC 7278, 515 DOI 10.17487/RFC7278, June 2014, 516 . 518 [RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi, 519 "Host Address Availability Recommendations", BCP 204, 520 RFC 7934, DOI 10.17487/RFC7934, July 2016, 521 . 523 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 524 Hosts in a Multi-Prefix Network", RFC 8028, 525 DOI 10.17487/RFC8028, November 2016, 526 . 528 Author's Address 530 Fred L. Templin (editor) 531 Boeing Research & Technology 532 P.O. Box 3707 533 Seattle, WA 98124 534 USA 536 Email: fltemplin@acm.org