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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6lo P. Thubert, Ed. 3 Internet-Draft cisco 4 Intended status: Standards Track March 18, 2016 5 Expires: September 19, 2016 7 IPv6 Backbone Router 8 draft-ietf-6lo-backbone-router-01 10 Abstract 12 This specification proposes an update to IPv6 Neighbor Discovery, to 13 enhance the operation of IPv6 over wireless links that exhibit lossy 14 multicast support, and enable a large degree of scalability by 15 splitting the broadcast domains. A higher speed backbone federates 16 multiple wireless links to form a large MultiLink Subnet. Backbone 17 Routers acting as Layer-3 Access Point route packets to registered 18 nodes, where an classical Layer-2 Access Point would bridge. 19 Conversely, wireless nodes register to the Backbone Router to setup 20 routing services in a fashion that is essentially similar to a 21 classical Layer-2 association. 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 September 19, 2016. 40 Copyright Notice 42 Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Applicability and Requirements Served . . . . . . . . . . . . 5 59 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 60 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 9 61 5. New Types And Formats . . . . . . . . . . . . . . . . . . . . 11 62 5.1. Transaction ID . . . . . . . . . . . . . . . . . . . . . 11 63 5.2. Owner Unique ID . . . . . . . . . . . . . . . . . . . . . 11 64 5.3. The Enhanced Address Registration Option (EARO) . . . . . 12 65 6. Backbone Router Routing Operations . . . . . . . . . . . . . 14 66 6.1. Over the Backbone Link . . . . . . . . . . . . . . . . . 14 67 6.2. Over the LLN Link . . . . . . . . . . . . . . . . . . . . 16 68 7. BackBone Router Proxy Operations . . . . . . . . . . . . . . 17 69 7.1. Registration and Binding State Creation . . . . . . . . . 20 70 7.2. Defending Addresses . . . . . . . . . . . . . . . . . . . 21 71 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 72 9. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 22 73 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 74 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 75 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 76 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 77 12.2. Informative References . . . . . . . . . . . . . . . . . 24 78 12.3. External Informative References . . . . . . . . . . . . 28 79 Appendix A. Requirements . . . . . . . . . . . . . . . . . . . . 29 80 A.1. Requirements Related to Mobility . . . . . . . . . . . . 29 81 A.2. Requirements Related to Routing Protocols . . . . . . . . 29 82 A.3. Requirements Related to the Variety of Low-Power Link 83 types . . . . . . . . . . . . . . . . . . . . . . . . . . 30 84 A.4. Requirements Related to Proxy Operations . . . . . . . . 31 85 A.5. Requirements Related to Security . . . . . . . . . . . . 31 86 A.6. Requirements Related to Scalability . . . . . . . . . . . 33 87 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 33 89 1. Introduction 91 Classical IPv6 Neighbor Discovery [RFC4862] operations are reactive 92 and rely heavily on multicast operations to locate a correspondent. 93 When this was designed, it was a natural match for the transparent 94 bridging operation of Ethernet. IEEE 802.11 Access Points IEEE802.11 95 [IEEE80211] effectively act as bridges, but, in order to protect the 96 medium, they do not implement transparent bridging. Instead, a so- 97 called association process is used to register proactively the MAC 98 addresses of the wireless STAs to the APs. Sadly, the IPv6 ND 99 operation was not adapted to match that model. 101 Though in most cases, including Low-Power ones, IEEE802.11 is 102 operated as a wireless extension to an Ethernet bridged domain, the 103 impact of radio broadcasts for IPv6 [RFC2460] multicast operations, 104 in particular related to the power consumption of battery-operated 105 devices, lead the community to rethink the plain layer-2 approach and 106 consider splitting the broadcast domain between the wired and the 107 wireless access links. To that effect, the current IEEE802.11 108 specifications require the capability to perform ARP and ND proxy 109 [RFC4389] functions at the Access Points (APs), but rely on snooping 110 for acquiring the related state, which is unsatisfactory in a lossy 111 and mobile environments. 113 Without a proxy, any IP multicast that circulates in the bridged 114 domain ends up broadcasted by the Access Points to all STAs, 115 including Low-Power battery-operated ones. With an incorrect or 116 missing state in the proxy, a packet may not be delivered to the 117 destination, which may have operational impacts depending on the 118 criticality of the packet. 120 Some messages are lost for the lack of retries, regardless of their 121 degree of criticality; it results for instance that Duplicate Address 122 Detection (DAD) as defined in [RFC4862] is mostly broken over Wi-Fi 123 [I-D.yourtchenko-6man-dad-issues]. 125 On the other hand, IPv6 multicast messages are processed by most if 126 not all wireless nodes over the fabric even when very few if any of 127 the nodes is effectively listening to the multicast address. It 128 results that a simple Neighbor Solicitation (NS) message [RFC4861], 129 that is supposedly targeted to a very small group of nodes, ends up 130 polluting the whole wireless bandwidth across the fabric 131 [I-D.vyncke-6man-mcast-not-efficient]. 133 It appears that in a variety of Wireless Local Area Networks (WLANs) 134 and Wireless Personal Area Networks (WPANs), the decision to leverage 135 the broadcast support of a particular link should be left to Layer-3 136 based on the criticality of the message and the number of interested 137 listeners on that link, for the lack of capability to indicate that 138 criticality to the lower layer. To achieve this, the operation at 139 the Access Point cannot be a Layer-2 bridge operation, but that of a 140 Layer-3 router; the concept of MultiLink Subnet (MLSN) must be 141 reintroduced, with IPv6 backbone routers (6BBRs) interconnecting the 142 various links and routing within the subnet. For link-scope 143 multicast operations, a 6BBR participates to MLD on its access links 144 and a multicast routing protocol is setup between the 6BBRs over the 145 backbone of the MLSN. 147 As the network scales up, none of the approaches of using either 148 broadcast or N*unicast for a multicast packet is really satisfying 149 and the protocols themselves need to be adapted to reduce their use 150 of multicast. 152 One degree of improvement can be achieved by changing the tuning of 153 the protocol parameters and operational practices, such as suggested 154 in Reducing energy consumption of Router Advertisements 155 [I-D.ietf-v6ops-reducing-ra-energy-consumption] (RA). This works 156 enables to lower the rate of RA messages but does not solve the 157 problem associated with multicast NS and NA messages, which are a lot 158 more frequent in large-scale radio environments with mobile devices 159 which exhibit intermittent access patterns and short-lived IPv6 160 addresses. 162 In the context of IEEE802.15.4 [IEEE802154], the more drastic step of 163 considering the radio as a medium that is different from Ethernet 164 because of the impact of multicast, was already taken with the 165 adoption of Neighbor Discovery Optimization for IPv6 over Low-Power 166 Wireless Personal Area Networks (6LoWPANs) [RFC6775]. This 167 specification applies that same thinking to other wireless links such 168 as Low-Power IEEE802.11 (Wi-Fi) and IEEE802.15.1 (Bluetooth) 169 [IEEE802151], and extends [RFC6775] to enable proxy operation by the 170 6BBR so as to decouple the broadcast domain in the backbone from the 171 wireless links. The proxy operation can be maintained asynchronous 172 so that low-power nodes or nodes that are deep in a mesh do not need 173 to be bothered synchronously when a lookup is performed for their 174 addresses, effectively implementing the ND contribution to the 175 concept of a Sleep Proxy [I-D.nordmark-6man-dad-approaches]. 177 DHCPv6 [RFC3315] is still a viable option in Low power and Lossy 178 Network (LLN) to assign IPv6 global addresses. However, the IETF 179 standard that supports address assignment specifically for LLNs is 180 6LoWPAN ND [RFC6775], which is a mix of IPv6 stateless 181 autoconfiguration mechanism (SLAAC) [RFC4862] and a new registration 182 process for ND. This specification introduces a Layer-3 association 183 process based on 6LoWPAN ND that maintains a proxy state in the 6BBR 184 to keep the LLN nodes reachable and protect their addresses through 185 sleeping periods. 187 A number of use cases, including the Industrial Internet, require a 188 large scale deployment of monitoring sensors that can only be 189 realized in a cost-effective fashion with wireless technologies. 190 Mesh networks are deployed when simpler hub-and-spoke topologies are 191 not sufficient for the expected size, throughput, and density. 193 Meshes imply the routing of packets, operated at either Layer-2 or 194 Layer-3. For routing over a mesh at Layer-3, the IETF has designed 195 the IPv6 Routing Protocol over LLN (RPL) [RFC6550]. 6LoWPAN ND was 196 designed as a stand-alone mechanism separately from RPL, and the 197 interaction between the 2 protocols was not defined. This 198 specification details how periodic updates from RPL can be used by 199 the RPL root to renew the association of the RPL node to the 6BBR on 200 its behalf so as to maintain the proxy operation active for that 201 node. 203 This document suggests a limited evolution to [RFC6775] so as to 204 allow operation of a 6LoWPAN ND node while a routing protocol (in 205 first instance RPL) is present and operational. It also suggests a 206 more generalized use of the information in the ARO option of the ND 207 messages outside the strict LLN domain, for instance over a converged 208 backbone. 210 2. Applicability and Requirements Served 212 Efficiency aware IPv6 Neighbor Discovery Optimizations 213 [I-D.chakrabarti-nordmark-6man-efficient-nd] suggests that 6LoWPAN ND 214 [RFC6775] can be extended to other types of links beyond IEEE802.15.4 215 for which it was defined. The registration technique is beneficial 216 when the Link-Layer technique used to carry IPv6 multicast packets is 217 not sufficiently efficient in terms of delivery ratio or energy 218 consumption in the end devices, in particular to enable energy- 219 constrained sleeping nodes. The value of such extension is 220 especially apparent in the case of mobile wireless nodes, to reduce 221 the multicast operations that are related to classical ND ([RFC4861], 222 [RFC4862]) and plague the wireless medium. 224 This specification updates and generalizes 6LoWPAN ND to a broader 225 range of Low power and Lossy Networks (LLNs) with a solid support for 226 Duplicate Address Detection (DAD) and address lookup that does not 227 require broadcasts over the LLNs. The term LLN is used loosely in 228 this specification to cover multiple types of WLANs and WPANs, 229 including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE802.11AH and 230 IEEE802.15.4 wireless meshes, so as to address the requirements 231 listed in Appendix A.3 233 The scope of this draft is a Backbone Link that federates multiple 234 LLNs as a single IPv6 MultiLink Subnet. Each LLN in the subnet is 235 anchored at an IPv6 Backbone Router (6BBR). The Backbone Routers 236 interconnect the LLNs over the Backbone Link and emulate that the LLN 237 nodes are present on the Backbone using proxy-ND operations. This 238 specification extends IPv6 ND over the backbone to discriminate 239 address movement from duplication and eliminate stale state in the 240 backbone routers and backbone nodes once a LLN node has roamed. This 241 way, mobile nodes may roam rapidly from a 6BBR to the next and 242 requirements in Appendix A.1 are met. 244 This specification can be used by any wireless node to associate at 245 Layer-3 with a 6BBR and register its IPv6 addresses to obtain routing 246 services including proxy-ND operations over the backbone, effectively 247 providing a solution to the requirements expressed in Appendix A.4. 249 The Link Layer Address (LLA) that is returned as Target LLA (TLLA) in 250 Neighbor Advertisements (NA) messages by the 6BBR on behalf of the 251 Registered Node over the backbone may be that of the Registering 252 Node, in which case the 6BBR needs to bridge the unicast packets 253 (Bridging proxy), or that of the 6BBR on the backbone, in which case 254 the 6BBRs needs to route the unicast packets (Routing proxy). In the 255 latter case, the 6BBR may maintain the list of correspondents to 256 which it has advertised its own MAC address on behalf of the LLN node 257 and the IPv6 ND operation is minimized as the number of nodes scale 258 up in the LLN. This enables to meet the requirements in Appendix A.6 259 as long has the 6BBRs are dimensioned for the number of registration 260 that each needs to support. 262 In the context of the the TimeSlotted Channel Hopping (TSCH) mode of 263 [IEEE802154], the 6TiSCH architecture [I-D.ietf-6tisch-architecture] 264 introduces how a 6LoWPAN ND host could connect to the Internet via a 265 RPL mesh Network, but this requires additions to the 6LOWPAN ND 266 protocol to support mobility and reachability in a secured and 267 manageable environment. This specification details the new 268 operations that are required to implement the 6TiSCH architecture and 269 serves the requirements listed in Appendix A.2. 271 In the case of Low-Power IEEE802.11, a 6BBR may be collocated with a 272 standalone AP or a CAPWAP [RFC5415] wireless controller, and the 273 wireless client (STA) leverages this specification to register its 274 IPv6 address(es) to the 6BBR over the wireless medium. In the case 275 of a 6TiSCH LLN mesh, the RPL root is collocated with a 6LoWPAN 276 Border Router (6LBR), and either collocated with or connected to the 277 6BBR over an IPv6 Link. The 6LBR leverages this specification to 278 register the LLN nodes on their behalf to the 6BBR. In the case of 279 BTLE, the 6BBR is collocated with the router that implements the BTLE 280 central role as discussed in section 2.2 of [I-D.ietf-6lo-btle]. 282 3. Terminology 284 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 285 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 286 document are to be interpreted as described in [RFC2119]. 288 Readers are expected to be familiar with all the terms and concepts 289 that are discussed in "Neighbor Discovery for IP version 6" 290 [RFC4861], "IPv6 Stateless Address Autoconfiguration" [RFC4862], 291 "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): 292 Overview, Assumptions, Problem Statement, and Goals" [RFC4919], 293 Neighbor Discovery Optimization for Low-power and Lossy Networks 294 [RFC6775] and "Multi-link Subnet Support in IPv6" 295 [I-D.ietf-ipv6-multilink-subnets]. 297 Readers would benefit from reading "Multi-Link Subnet Issues" 298 [RFC4903], ,"Mobility Support in IPv6" [RFC6275], "Neighbor Discovery 299 Proxies (ND Proxy)" [RFC4389] and "Optimistic Duplicate Address 300 Detection" [RFC4429] prior to this specification for a clear 301 understanding of the art in ND-proxying and binding. 303 Additionally, this document uses terminology from 304 [I-D.ietf-roll-terminology] and [I-D.ietf-6tisch-terminology], and 305 introduces the following terminology: 307 LLN Low Power Lossy Network. Used loosely in this specification to 308 represent WLANs and WPANs. See [RFC4919] 310 Backbone This is an IPv6 transit link that interconnects 2 or more 311 Backbone Routers. It is expected to be deployed as a high 312 speed backbone in order to federate a potentially large set of 313 LLNS. Also referred to as a LLN backbone or Backbone network. 315 Backbone Router An IPv6 router that federates the LLN using a 316 Backbone link as a backbone. A BBR acts as a 6LoWPAN Border 317 Routers (6LBR) and an Energy Aware Default Router (NEAR). 319 Extended LLN This is the aggregation of multiple LLNs as defined in 320 [RFC4919], interconnected by a Backbone Link via Backbone 321 Routers, and forming a single IPv6 MultiLink Subnet. 323 Registration The process during which a wireless Node registers its 324 address(es) with the Border Router so the 6BBR can proxy ND for 325 it over the backbone. 327 Binding The state in the 6BBR that associates an IP address with a 328 MAC address, a port and some other information about the node 329 that owns the IP address. 331 Registered Node The node for which the registration is performed, 332 which owns the fields in the EARO option. 334 Registering Node The node that performs the registration to the 335 6BBR, either for one of its own addresses, in which case it is 336 Registered Node and indicates its own MAC Address as SLLA in 337 the NS(ARO), or on behalf of a Registered Node that is 338 reachable over a LLN mesh. In the latter case, if the 339 Registered Node is reachable from the 6BBR over a Mesh-Under 340 mesh, the Registering Node indicates the MAC Address of the 341 Registered Node as SLLA in the NS(ARO). Otherwise, it is 342 expected that the Registered Device is reachable over a Route- 343 Over mesh from the Registering Node, in which case the SLLA in 344 the NS(ARO) is that of the Registering Node, which causes it to 345 attract the packets from the 6BBR to the Registered Node and 346 route them over the LLN. 348 Registered Address The address owned by the Registered Node node 349 that is being registered. 351 Sleeping Proxy A 6BBR acts as a Sleeping Proxy if it answers ND 352 Neighbor Solicitation over the backbone on behalf of the 353 Registered Node whenever possible. This is the default mode 354 for this specification but it may be overridden, for instance 355 by configuration, into Unicasting Proxy. 357 Unicasting Proxy As a Unicasting Proxy, the 6BBR forwards NS 358 messages to the Registering Node, transforming Layer-2 359 multicast into unicast whenever possible. 361 Routing proxy A 6BBR acts as a routing proxy if it advertises its 362 own MAC address, as opposed to that of the node that performs 363 the registration, as the TLLA in the proxied NAs over the 364 backbone. In that case, the MAC address of the node is not 365 visible at Layer-2 over the backbone and the bridging fabric is 366 not aware of the addresses of the LLN devices and their 367 mobility. The 6BBR installs a connected host route towards the 368 registered node over the interface to the node, and acts as a 369 Layer-3 router for unicast packets to the node. The 6BBR 370 updates the ND Neighbor Cache Entries (NCE) in correspondent 371 nodes if the wireless node moves and registers to another 6BBR, 372 either with a single broadcast, or with a series of unicast 373 NA(O) messages, indicating the TLLA of the new router. 375 Bridging proxy A 6BBR acts as a bridging proxy if it advertises the 376 MAC address of the node that performs the registration as the 377 TLLA in the proxied NAs over the backbone. In that case, the 378 MAC address and the mobility of the node is still visible 379 across the bridged backbone fabric, as is traditionally the 380 case with Layer-2 APs. The 6BBR acts as a Layer-2 bridge for 381 unicast packets to the registered node. The MAC address 382 exposed in the S/TLLA is that of the Registering Node, which is 383 not necessarily the Registered Device. When a device moves 384 within a LLN mesh, it may end up attached to a different 6LBR 385 acting as Registering Node, and the LLA that is exposed over 386 the backbone will change. 388 Primary BBR The BBR that will defend a Registered Address for the 389 purpose of DAD over the backbone. 391 Secondary BBR A BBR to which the address is registered. A Secondary 392 Router MAY advertise the address over the backbone and proxy 393 for it. 395 4. Overview 397 An LLN node can move freely from an LLN anchored at a Backbone Router 398 to an LLN anchored at another Backbone Router on the same backbone 399 and conserve any of the IPv6 addresses that it has formed, 400 transparently. 402 | 403 +-----+ 404 | | Other (default) Router 405 | | 406 +-----+ 407 | 408 | Backbone Link 409 +--------------------+------------------+ 410 | | | 411 +-----+ +-----+ +-----+ 412 | | Backbone | | Backbone | | Backbone 413 | | router | | router | | router 414 +-----+ +-----+ +-----+ 415 o o o o o o 416 o o o o o o o o o o o o o o 417 o o o o o o o o o o o o o o o 418 o o o o o o o o o o 419 o o o o o o o 421 LLN LLN LLN 423 Figure 1: Backbone Link and Backbone Routers 425 The Backbone Routers maintain an abstract Binding Table of their 426 Registered Nodes. The Binding Table operates as a distributed 427 database of all the wireless Nodes whether they reside on the LLNs or 428 on the backbone, and use an extension to the Neighbor Discovery 429 Protocol to exchange that information across the Backbone in the 430 classical ND reactive fashion. 432 The Address Registration Option (ARO) defined in [RFC6775] is 433 extended to enable the registration for routing and proxy Neighbor 434 Discovery operations by the 6BBR, and the Extended ARO (EARO) option 435 is included in the ND exchanges over the backbone between the 6BBRs 436 to sort out duplication from movement. 438 Address duplication is sorted out with the Owner Unique-ID field in 439 the EARO, which is a generalization of the EUI-64 that allows 440 different types of unique IDs beyond the name space derived from the 441 MAC addresses. First-Come First-Serve rules apply, whether the 442 duplication happens between LLN nodes as represented by their 443 respective 6BBRs, or between an LLN node and a classical node that 444 defends its address over the backbone with classical ND and does not 445 include the EARO option. 447 In case of conflicting registrations to multiple 6BBRs from a same 448 node, a sequence counter called Transaction ID (TID) is introduced 449 that enables 6BBRs to sort out the latest anchor for that node. 450 Registrations with a same TID are compatible and maintained, but, in 451 case of different TIDs, only the freshest registration is maintained 452 and the stale state is eliminated. 454 With this specification, Backbone Routers perform ND proxy over the 455 Backbone Link on behalf of their Registered Nodes. The Backbone 456 Router operation is essentially similar to that of a Mobile IPv6 457 (MIPv6) [RFC6275] Home Agent. This enables mobility support for LLN 458 nodes that would move outside of the network delimited by the 459 Backbone link attach to a Home Agent from that point on. This also 460 enables collocation of Home Agent functionality within Backbone 461 Router functionality on the same backbone interface of a router. 462 Further specification may extend this be allowing the 6BBR to 463 redistribute host routes in routing protocols that would operate over 464 the backbone, or in MIPv6 or the Locator/ID Separation Protocol 465 (LISP) [RFC6830] to support mobility on behalf of the nodes, etc... 467 The Optimistic Duplicate Address Detection [RFC4429] (ODAD) 468 specification details how an address can be used before a Duplicate 469 Address Detection (DAD) is complete, and insists that an address that 470 is TENTATIVE should not be associated to a Source Link-Layer Address 471 Option in a Neighbor Solicitation message. This specification 472 leverages ODAD to create a temporary proxy state in the 6BBR till DAD 473 is completed over the backbone. This way, the specification enables 474 to distribute proxy states across multiple 6BBR and co-exist with 475 classical ND over the backbone. 477 5. New Types And Formats 479 5.1. Transaction ID 481 The specification expects that the Registered Node can provide a 482 sequence number called Transaction ID (TID) that is incremented with 483 each re-registration. The TID essentially obeys the same rules as 484 the Path Sequence field in the Transit Information Option (TIO) found 485 in RPL's Destination Advertisement Object (DAO). This way, the LLN 486 node can use the same counter for ND and RPL, and a 6LBR acting as 487 RPL root may easily maintain the registration on behalf of a RPL node 488 deep inside the mesh by simply using the RPL TIO Path Sequence as TID 489 for EARO. 491 When a Registered Node is registered to multiple BBRs in parallel, it 492 is expected that the same TID is used, to enable the 6BBRs to 493 correlate the registrations as being a single one, and differentiate 494 that situation from a movement. 496 If the TIDs are different, the resolution inherited from RPL sorts 497 out the most recent registration and other ones are removed. The 498 operation for computing and comparing the Path Sequence is detailed 499 in section 7 of [RFC6550] and applies to the TID in the exact same 500 fashion. 502 5.2. Owner Unique ID 504 The Owner Unique ID (OUID) enables to differentiate a real duplicate 505 address registration from a double registration or a movement. An ND 506 message from the 6BBR over the backbone that is proxied on behalf of 507 a Registered Node must carry the most recent EARO option seen for 508 that node. A NS/NA with an EARO and a NS/NA without a EARO thus 509 represent different nodes and if they relate to a same target then 510 they reflect an address duplication. The Owner Unique ID can be as 511 simple as a EUI-64 burn-in address, if duplicate EUI-64 addresses are 512 avoided. 514 Alternatively, the unique ID can be a cryptographic string that can 515 can be used to prove the ownership of the registration as discussed 516 in Address Protected Neighbor Discovery for Low-power and Lossy 517 Networks [I-D.sarikaya-6lo-ap-nd]. 519 In any fashion, it is recommended that the node stores the unique Id 520 or the keys used to generate that ID in persistent memory. 521 Otherwise, it will be prevented to re-register after a reboot that 522 would cause a loss of memory until the Backbone Router times out the 523 registration. 525 5.3. The Enhanced Address Registration Option (EARO) 527 With the ARO option defined in 6LoWPAN ND [RFC6775], the address 528 being registered and its owner can be uniquely identified and matched 529 with the Binding Table entries of each Backbone Router. 531 The Enhanced Address Registration Option (EARO) is intended to be 532 used as a replacement to the ARO option within Neighbor Discovery NS 533 and NA messages between a LLN node and its 6LoWPAN Router (6LR), as 534 well as in Duplicate Address Request (DAR) and the Duplicate Address 535 Confirmation (DAC) messages between 6LRs and 6LBRs in LLNs meshes 536 such as 6TiSCH networks. 538 An NS message with an EARO option is a registration if and only if it 539 also carries an SLLAO option. The AERO option also used in NS and NA 540 messages between Backbone Routers over the backbone link to sort out 541 the distributed registration state, and in that case, it does not 542 carry the SLLAO option and is not confused with a registration. 544 The EARO extends the ARO and is recognized by the setting of the TID 545 bit. A node that supports this specification MUST always use an EARO 546 as a replacement to an ARO in its registration to a router. This is 547 harmless since the TID bit and fields are reserved in [RFC6775] are 548 ignored by a legacy router. A router that supports this 549 specification answers to an ARO with an ARO and to an EARO with an 550 EARO. 552 This specification changes the behavior of the peers in a 553 registration flows. To enable backward compatibility, a node that 554 registers to a router that is not known to support this specification 555 MUST behave as prescribed by [RFC6775]. Once the router is known to 556 support this specification, the node MUST obey this specification. 558 When using the EARO option, the address being registered is found in 559 the Target Address field of the NS and NA messages. This differs 560 from 6LoWPAN ND [RFC6775] which specifies that the address being 561 registered is the source of the NS. 563 The reason for this change is to enable proxy-registrations on behalf 564 of other nodes in Route-Over meshes, for instance to enable that a 565 RPL root registers addresses on behalf LLN nodes that are deeper in a 566 6TiSCH mesh. In that case, the Registering Node MUST indicate its 567 own address as source of the ND message and its MAC address in the 568 Source Link-Layer Address Option (SLLAO), since it still expects to 569 get the packets and route them down the mesh. But the Registered 570 Address belongs to another node, the Registered Node, and that 571 address is indicated in the Target Address field of the NS message. 573 One way of achieving all the above is for a node to first register an 574 address that it owns in order to validate that the router supports 575 this specification, placing the same address in the Source and Target 576 Address fields of the NS message. The node may for instance register 577 an address that is based on EUI-64. For such address, DAD is not 578 required and using the SLLAO option in the NS is actually more 579 amenable with older ND specifications such as ODAD [RFC4429]. 581 Once that first registration is complete, the node knows from the 582 setting of the TID in the response whether the router supports this 583 specification. If this is verified, the node may register other 584 addresses that it owns, or proxy-register addresses on behalf some 585 another node, indicating those addresses being registered in the 586 Target Address field of the NS messages, while using one of its own, 587 already registered, addresses as source. 589 The format of the EARO option is as follows: 591 0 1 2 3 592 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 1 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Type | Length = 2 | Status | Reserved | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | Reserved |T| TID | Registration Lifetime | 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | | 599 + Owner Unique ID (EUI-64 or equivalent) + 600 | | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 Figure 2: EARO 605 Option Fields 607 Type: 609 Length: 2 611 Status: OK=0; Duplicate=1; Full=2; Moved=3; Removed=4; 613 Reserved: This field is unused. It MUST be initialized to zero by 614 the sender and MUST be ignored by the receiver. 616 T: One bit flag. Set if the next octet is a used as a TID. 618 TID: 1-byte integer; a transaction id that is maintained by the node 619 and incremented with each transaction. it is recommended that the 620 node maintains the TID in a persistent storage. 622 Registration Lifetime: 16-bit integer; expressed in minutes. 0 623 means that the registration has ended and the state should be 624 removed. 626 Owner Unique Identifier: A globally unique identifier for the node 627 associated. This can be the EUI-64 derived IID of an interface, 628 or some provable ID obtained cryptographically. 630 6. Backbone Router Routing Operations 632 | 633 +-----+ 634 | | Other (default) Router 635 | | 636 +-----+ 637 | /64 638 | Backbone Link 639 +-------------------+-------------------+ 640 | /64 | /64 | /64 641 +-----+ +-----+ +-----+ 642 | | Backbone | | Backbone | | Backbone 643 | | router | | router | | router 644 +-----+ +-----+ +-----+ 645 o N*/128 o o o M*/128 o o P*/128 646 o o o o o o o o o o o o o o 647 o o o o o o o o o o o o o o o 648 o o o o o o o o o o 649 o o o o o o o 651 LLN LLN LLN 653 Figure 3: Routing Configuration in the ML Subnet 655 6.1. Over the Backbone Link 657 The Backbone Router is a specific kind of Border Router that performs 658 proxy Neighbor Discovery on its backbone interface on behalf of the 659 nodes that it has discovered on its LLN interfaces. 661 The backbone is expected to be a high speed, reliable Backbone link, 662 with affordable and reliable multicast capabilities, such as a 663 bridged Ethernet Network, and to allow a full support of classical ND 664 as specified in [RFC4861] and subsequent RFCs. In other words, the 665 backbone is not a LLN. 667 Still, some restrictions of the attached LLNs will apply to the 668 backbone. In particular, it is expected that the MTU is set to the 669 same value on the backbone and all attached LLNs, and the scalability 670 of the whole subnet requires that broadcast operations are avoided as 671 much as possible on the backbone as well. Unless configured 672 otherwise, the Backbone Router MUST echo the MTU that it learns in 673 RAs over the backbone in the RAs that it sends towards the LLN links. 675 As a router, the Backbone Router behaves like any other IPv6 router 676 on the backbone side. It has a connected route installed towards the 677 backbone for the prefixes that are present on that backbone and that 678 it proxies for on the LLN interfaces. 680 As a proxy, the 6BBR uses an EARO option in the NS-DAD and the 681 multicast NA messages that it generates on behalf of a Registered 682 Node, and it places an EARO in its unicast NA messages if and only if 683 the NS/NA that stimulates it had an EARO in it. 685 When possible, the 6BBR SHOULD use unicast or solicited-node 686 multicast address (SNMA) [RFC4291] to defend its Registered Addresses 687 over the backbone. In particular, the 6BBR MUST join the SNMA group 688 that corresponds to a Registered Address as soon as it creates an 689 entry for that address and as long as it maintains that entry, 690 whatever the state of the entry. The expectation is that it is 691 possible to get a message delivered to all the nodes on the backbone 692 that listen to a particular address and support this specification - 693 which includes all the 6BBRs in the MultiLink Subnet - by sending a 694 multicast message to the associated SNMA over the backbone. 696 The support of Optimistic DAD (ODAD) [RFC4429] is recommended for all 697 nodes in the backbone and followed by the 6BBRs in their proxy 698 activity over the backbone. With ODAD, any optimistic node MUST join 699 the SNMA of a Tentative address, which interacts better with this 700 specification. 702 This specification allows the 6BBR in Routing Proxy mode to advertise 703 the Registered IPv6 Address with the 6BBR Link Layer Address, and 704 attempts to update Neighbor Cache Entries (NCE) in correspondent 705 nodes over the backbone, using gratuitous NA(Override). This method 706 may fail of the multicast message is not properly received, and 707 correspondent nodes may maintain an incorrect neighbor state, which 708 they will eventually discover through Neighbor Unreachability 709 Detection (NUD). Because mobility may be slow, the NUD procedure 710 defined in [RFC4861] may be too impatient, and the support of 711 [RFC7048] is recommended in all nodes in the network. 713 Since the MultiLink Subnet may grow very large in terms of individual 714 IPv6 addresses, multicasts should be avoided as much as possible even 715 on the backbone. Though it is possible for plain hosts to 716 participate with legacy IPv6 ND support, the support by all nodes 717 connected to the backbone of [I-D.nordmark-6man-rs-refresh] is 718 recommended, and this implies the support of [RFC7559] as well. 720 6.2. Over the LLN Link 722 As a router, the Nodes and Backbone Router operation on the LLN 723 follows [RFC6775]. Per that specification, LLN Hosts generally do 724 not depend on multicast RAs to discover routers. It is still 725 generally required for LLN nodes to accept multicast RAs 726 [I-D.ietf-v6ops-reducing-ra-energy-consumption], but those are rare 727 on the LLN link. Nodes are expected to follow the Simple Procedures 728 for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) 729 to assert movements, and to support the Packet-Loss Resiliency for 730 Router Solicitations [RFC7559] to make the unicast RS more reliable. 732 The Backbone Router acquires its states about the addresses on the 733 LLN side through a registration process from either the nodes 734 themselves, or from a node such as a RPL root / 6LBR (the Registering 735 Node) that performs the registration on behalf of the address owner 736 (the Registered Node). 738 When operating as a Routing Proxy, the router installs hosts routes 739 (/128) to the Registered Addresses over the LLN links, via the 740 Registering Node as identified by the Source Address and the SLLAO 741 option in the NS(EARO) messages. 743 In that mode, the 6BBR handles the ND protocol over the backbone on 744 behalf of the Registered Nodes, using its own MAC address in the TLLA 745 and SLLA options in proxyed NS and NA messages. It results that for 746 each Registered Address, a number of peer Nodes on the backbone have 747 resolved the address with the 6BBR MAC address and keep that mapping 748 stored in their Neighbor cache. 750 The 6BBR SHOULD maintain, per Registered Address, the list of the 751 peers on the backbone to which it answered with it MAC address, and 752 when a binding moves to a different 6BBR, it SHOULD send a unicast 753 gratuitous NA(O) individually to each of them to inform them that the 754 address has moved and pass the MAC address of the new 6BBR in the 755 TLLAO option. If the 6BBR can not maintain that list, then it SHOULD 756 remember whether that list is empty or not and if not, send a 757 multicast NA(O) to all nodes to update the impacted Neighbor Caches 758 with the information from the new 6BBR. 760 The Bridging Proxy is a variation where the BBR function is 761 implemented in a Layer-3 switch or an wireless Access Point that acts 762 as a Host from the IPv6 standpoint, and, in particular, does not 763 operate the routing of IPv6 packets. In that case, the SLLAO in the 764 proxied NA messages is that of the Registering Node and classical 765 bridging operations take place on data frames. 767 If a registration moves from one 6BBR to the next, but the 768 Registering Node does not change, as indicated by the S/TLLAO option 769 in the ND exchanges, there is no need to update the Neighbor Caches 770 in the peers Nodes on the backbone. On the other hand, if the LLAO 771 changes, the 6BBR SHOULD inform all the relevant peers as described 772 above, to update the impacted Neighbor Caches. In the same fashion, 773 if the Registering Node changes with a new registration, the 6BBR 774 SHOULD also update the impacted Neighbor Caches over the backbone. 776 7. BackBone Router Proxy Operations 778 This specification enables a Backbone Router to proxy Neighbor 779 Discovery operations over the backbone on behalf of the nodes that 780 are registered to it, allowing any node on the backbone to reach a 781 Registered Node as if it was on-link. The backbone and the LLNs are 782 considered different Links in a MultiLink subnet but the prefix that 783 is used may still be advertised as on-link on the backbone to support 784 legacy nodes; multicast ND messages are link-scoped and not forwarded 785 across the backbone routers. 787 ND Messages on the backbone side that do not match to a registration 788 on the LLN side are not acted upon on the LLN side, which stands 789 protected. On the LLN side, the prefixes associated to the MultiLink 790 Subnet are presented as not on-link, so address resolution for other 791 hosts do not occur. 793 The default operation in this specification is Sleeping proxy which 794 means: 796 o creating a new entry in an abstract Binding Table for a new 797 Registered Address and validating that the address is not a 798 duplicate over the backbone 800 o defending a Registered Address over the backbone using NA messages 801 with the Override bit set on behalf of the sleeping node whenever 802 possible 804 o advertising a Registered Address over the backbone using NA 805 messages, asynchronously or as a response to a Neighbor 806 Solicitation messages. 808 o Looking up a destination over the backbone in order to deliver 809 packets arriving from the LLN using Neighbor Solicitation 810 messages. 812 o Forwarding packets from the LLN over the backbone, and the other 813 way around. 815 o Eventually triggering a liveliness verification of a stale 816 registration. 818 A 6BBR may act as a Sleeping Proxy only if the state of the binding 819 entry is REACHABLE, or TENTATIVE in which case the answer is delayed. 820 In any other state, the Sleeping Proxy operates as a Unicasting 821 Proxy. 823 As a Unicasting Proxy, the 6BBR forwards NS messages to the 824 Registering Node, transforming Layer-2 multicast into unicast 825 whenever possible. This is not possible in UNREACHABLE state, so the 826 NS messages are multicasted, and rate-limited to protect the medium 827 with an exponential back-off. In other states, The messages are 828 forwarded to the Registering Node as unicast Layer-2 messages. In 829 TENTATIVE state, the NS message is either held till DAD completes, or 830 dropped. 832 The draft introduces the optional concept of primary and secondary 833 BBRs. The primary is the backbone router that has the highest EUI-64 834 address of all the 6BBRs that share a registration for a same 835 Registered Address, with the same Owner Unique ID and same 836 Transaction ID, the EUI-64 address being considered as an unsigned 837 64bit integer. The concept is defined with the granularity of an 838 address, that is a given 6BBR can be primary for a given address and 839 secondary or another one, regardless on whether the addresses belong 840 to the same node or not. The primary Backbone Router is in charge of 841 protecting the address for DAD over the Backbone. Any of the Primary 842 and Secondary 6BBR may claim the address over the backbone, since 843 they are all capable to route from the backbone to the LLN node, and 844 the address appears on the backbone as an anycast address. 846 The Backbone Routers maintain a distributed binding table, using 847 classical ND over the backbone to detect duplication. This 848 specification requires that: 850 1. All addresses that can be reachable from the backbone, including 851 IPv6 addresses based on burn-in EUI64 addresses MUST be 852 registered to the 6BBR. 854 2. A Registered Node MUST include the EARO option in an NS message 855 that used to register an addresses to a 6LR; the 6LR MUST 856 propagate that option unchanged to the 6LBR in the DAR/DAC 857 exchange, and the 6LBR MUST propagate that option unchanged in 858 proxy registrations. 860 3. The 6LR MUST echo the same EARO option in the NA that it uses to 861 respond, but for the status filed which is not used in NS 862 messages, and significant in NA. 864 A false positive duplicate detection may arise over the backbone, for 865 instance if the Registered Address is registered to more than one 866 LBR, or if the node has moved. Both situations are handled 867 gracefully unbeknownst to the node. In the former case, one LBR 868 becomes primary to defend the address over the backbone while the 869 others become secondary and may still forward packets back and forth. 870 In the latter case the LBR that receives the newest registration wins 871 and becomes primary. 873 The expectation in this specification is that there is a single 874 Registering Node at a time per Backbone Router for a given Registered 875 Address, but that a Registered Address may be registered to Multiple 876 6BBRs for higher availability. 878 Over the LLN, and for any given Registered Address, it is REQUIRED 879 that: 881 de-registrations (newer TID, same OUID, null Lifetime) are 882 accepted and responded immediately with a status of 4; the entry 883 is deleted; 885 newer registrations (newer TID, same OUID, non-null Lifetime) are 886 accepted and responded with a status of 0 (success); the entry is 887 updated with the new TID, the new Registration Lifetime and the 888 new Registering Node, if any has changed; in TENTATIVE state the 889 response is held and may be overwritten; in other states the 890 Registration-Lifetime timer is restarted and the entry is placed 891 in REACHABLE state. 893 identical registrations (same TID, same OUID) from a same 894 Registering Node are not processed but responded with a status of 895 0 (success); they are expected to be identical and an error may be 896 logged if not; in TENTATIVE state, the response is held and may be 897 overwritten, but it MUST be eventually produced and it carries the 898 result of the DAD process; 900 older registrations (not(newer or equal) TID, same OUID) from a 901 same Registering Node are ignored; 902 identical and older registrations (not-newer TID, same OUID) from 903 a different Registering Node are responded immediately with a 904 status of 3 (moved); this may be rate limited to protect the 905 medium; 907 and any registration for a different Registered Node (different 908 OUID) are responded immediately with a status of 1 (duplicate). 910 7.1. Registration and Binding State Creation 912 Upon a registration for a new address with an NS(EARO), the 6BBR 913 performs a DAD operation over the backbone placing the new address as 914 target in the NS-DAD message. The EARO from the registration MUST be 915 placed unchanged in the NS-DAD message, and an entry is created in 916 TENTATIVE state for a duration of TENTATIVE_DURATION. The NS-DAD 917 message is sent multicast over the backbone to the SNMA address 918 associated with the registered address. If that operation is known 919 to be costly, and the 6BBR has an indication from another source 920 (such as a NCE) that the Registered Address was present on the 921 backbone, that information may be leveraged to send the NS-DAD 922 message as a Layer-2 unicast to the MAC that was associated with the 923 Registered Address. 925 In TENTATIVE state: 927 o the entry is removed if an NA is received over the backbone for 928 the Registered Address with no EARO option, or with an EARO option 929 with a status of 1 (duplicate) that indicates an existing 930 registration for another LLN node. The OUID and TID fields in the 931 EARO option received over the backbone are ignored. A status of 1 932 is returned in the EARO option of the NA back to the Registering 933 Node; 935 o the entry is also removed if an NA with an ARO option with a 936 status of 3 (moved), or a NS-DAD with an ARO option that indicates 937 a newer registration for the same Registered Node, is received 938 over the backbone for the Registered Address. A status of 3 is 939 returned in the NA(EARO) back to the Registering Node; 941 o when a registration is updated but not deleted, e.g. from a newer 942 registration, the DAD process on the backbone continues and the 943 running timers are not restarted; 945 o Other NS (including DAD with no EARO option) and NA from the 946 backbone are not responded in TENTATIVE state, but the list of 947 their origins may be kept in memory and if so, the 6BBR may send 948 them each a unicast NA with eventually an EARO option when the 949 TENTATIVE_DURATION timer elapses, so as to cover legacy nodes that 950 do not support ODAD. 952 o When the TENTATIVE_DURATION timer elapses, a status 0 (success) is 953 returned in a NA(EARO) back to the Registering Node(s), and the 954 entry goes to REACHABLE state for the Registration Lifetime; the 955 DAD process is successful and the 6BBR MUST send a multicast 956 NA(EARO) to the SNMA associated to the Registered Address over the 957 backbone with the Override bit set so as to take over the binding 958 from other 6BBRs. 960 7.2. Defending Addresses 962 If a 6BBR has an entry in REACHABLE state for a Registered Address: 964 o If the 6BBR is primary, or does not support the concept, it MUST 965 defend that address over the backbone upon an incoming NS-DAD, 966 either if the NS does not carry an EARO, or if an EARO is present 967 that indicates a different Registering Node (different OUID). The 968 6BBR sends a NA message with the Override bit set and the NA 969 carries an EARO option if and only if the NS-DAD did so. When 970 present, the EARO in the NA(O) that is sent in response to the NS- 971 DAD(EARO) carries a status of 1 (duplicate), and the OUID and TID 972 fields in the EARO option are obfuscated with null or random 973 values to avoid network scanning and impersonation attacks. 975 o If the 6BBR receives an NS-DAD(EARO) that reflect a newer 976 registration, the 6BBR updates the entry and the routing state to 977 forward packets to the new 6BBR, but keeps the entry REACHABLE. 978 In that phase, it MAY use REDIRECT messages to reroute traffic for 979 the Registered Address to the new 6BBR. 981 o If the 6BBR receives an NA(EARO) that reflect a newer 982 registration, the 6BBR removes its entry and sends a NA(AERO) with 983 a status of 3 (moved) to the Registering Node, if the Registering 984 Node is different from the Registered Node. If necessary, the 985 6BBR cleans up ND cache in peers nodes as discussed in 986 Section 6.1, by sending a series of unicast to the impacted nodes, 987 or one broadcast NA(O) to all-nodes. 989 o If the 6BBR received a NS(LOOKUP) for a Registered Address, it 990 answers immediately with an NA on behalf of the Registered Node, 991 without polling it. There is no need of an EARO in that exchange. 993 o When the Registration-Lifetime timer elapses, the entry goes to 994 STALE state for a duration of STABLE_STALE_DURATION in LLNs that 995 keep stable addresses such as LWPANs, and UNSTABLE_STALE_DURATION 996 in LLNs where addresses are renewed rapidly, e.g. for privacy 997 reasons. 999 The STALE state is a chance to keep track of the backbone peers that 1000 may have an ND cache pointing on this 6BBR in case the Registered 1001 Address shows back up on this or a different 6BBR at a later time. 1002 In STALE state: 1004 o If the Registered Address is claimed by another node on the 1005 backbone, with an NS-DAD or an NA, the 6BBR does not defend the 1006 address. Upon an NA(O), or the stale time elapses, the 6BBR 1007 removes its entry and sends a NA(AERO) with a status of 4 1008 (removed) to the Registering Node. 1010 o If the 6BBR received a NS(LOOKUP) for a Registered Address, the 1011 6BBR MUST send an NS(NUD) following rules in [RFC7048] to the 1012 registering Node targeting the Registered Address prior to 1013 answering. If the NUD succeeds, the operation in REACHABLE state 1014 applies. If the NUD fails, the 6BBR refrains from answering the 1015 lookup. The NUD expected to be mapped by the Registering Node 1016 into a liveliness validation of the Registered Node if they are in 1017 fact different nodes. 1019 8. Security Considerations 1021 This specification expects that the link layer is sufficiently 1022 protected, either by means of physical or IP security for the 1023 Backbone Link or MAC sublayer cryptography. In particular, it is 1024 expected that the LLN MAC provides secure unicast to/from the 1025 Backbone Router and secure Broadcast from the Backbone Router in a 1026 way that prevents tempering with or replaying the RA messages. 1028 The use of EUI-64 for forming the Interface ID in the link local 1029 address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and 1030 address privacy techniques. This specification RECOMMENDS the use of 1031 additional protection against address theft such as provided by 1032 [I-D.sarikaya-6lo-ap-nd], which guarantees the ownership of the OUID. 1034 When the ownership of the OUID cannot be assessed, this specification 1035 limits the cases where the OUID and the TID are multicasted, and 1036 obfuscates them in responses to attempts to take over an address. 1038 9. Protocol Constants 1040 This Specification uses the following constants: 1042 TENTATIVE_DURATION: 800 milliseconds 1043 STABLE_STALE_DURATION: 24 hours 1045 UNSTABLE_STALE_DURATION: 5 minutes 1047 DEFAULT_NS_POLLING: 3 times 1049 10. IANA Considerations 1051 This document requires the following additions: 1053 Address Registration Option Status Values Registry 1055 +--------+----------------------------------------------------------+ 1056 | Status | Description | 1057 +--------+----------------------------------------------------------+ 1058 | 3 | Moved: The registration fails because it is not the | 1059 | | freshest. | 1060 | | | 1061 | 4 | Removed: The binding state was removed | 1062 +--------+----------------------------------------------------------+ 1064 IANA is required to change the registry accordingly 1066 Table 1: New ARO Status values 1068 11. Acknowledgments 1070 Kudos to Eric Levy-Abegnoli who designed the First Hop Security 1071 infrastructure at Cisco. 1073 12. References 1075 12.1. Normative References 1077 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1078 Requirement Levels", BCP 14, RFC 2119, 1079 DOI 10.17487/RFC2119, March 1997, 1080 . 1082 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1083 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 1084 December 1998, . 1086 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1087 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1088 2006, . 1090 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 1091 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 1092 . 1094 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1095 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1096 DOI 10.17487/RFC4861, September 2007, 1097 . 1099 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1100 Address Autoconfiguration", RFC 4862, 1101 DOI 10.17487/RFC4862, September 2007, 1102 . 1104 [RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for 1105 Detecting Network Attachment in IPv6", RFC 6059, 1106 DOI 10.17487/RFC6059, November 2010, 1107 . 1109 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1110 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1111 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1112 Low-Power and Lossy Networks", RFC 6550, 1113 DOI 10.17487/RFC6550, March 2012, 1114 . 1116 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1117 Bormann, "Neighbor Discovery Optimization for IPv6 over 1118 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1119 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1120 . 1122 12.2. Informative References 1124 [I-D.chakrabarti-nordmark-6man-efficient-nd] 1125 Chakrabarti, S., Nordmark, E., Thubert, P., and M. 1126 Wasserman, "IPv6 Neighbor Discovery Optimizations for 1127 Wired and Wireless Networks", draft-chakrabarti-nordmark- 1128 6man-efficient-nd-07 (work in progress), February 2015. 1130 [I-D.delcarpio-6lo-wlanah] 1131 Vega, L., Robles, I., and R. Morabito, "IPv6 over 1132 802.11ah", draft-delcarpio-6lo-wlanah-01 (work in 1133 progress), October 2015. 1135 [I-D.ietf-6lo-6lobac] 1136 Lynn, K., Martocci, J., Neilson, C., and S. Donaldson, 1137 "Transmission of IPv6 over MS/TP Networks", draft-ietf- 1138 6lo-6lobac-04 (work in progress), February 2016. 1140 [I-D.ietf-6lo-btle] 1141 Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., 1142 Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low 1143 Energy", draft-ietf-6lo-btle-17 (work in progress), August 1144 2015. 1146 [I-D.ietf-6lo-dect-ule] 1147 Mariager, P., Petersen, J., Shelby, Z., Logt, M., and D. 1148 Barthel, "Transmission of IPv6 Packets over DECT Ultra Low 1149 Energy", draft-ietf-6lo-dect-ule-04 (work in progress), 1150 February 2016. 1152 [I-D.ietf-6lo-nfc] 1153 Youn, J. and Y. Hong, "Transmission of IPv6 Packets over 1154 Near Field Communication", draft-ietf-6lo-nfc-02 (work in 1155 progress), October 2015. 1157 [I-D.ietf-6tisch-architecture] 1158 Thubert, P., "An Architecture for IPv6 over the TSCH mode 1159 of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work 1160 in progress), November 2015. 1162 [I-D.ietf-6tisch-terminology] 1163 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 1164 "Terminology in IPv6 over the TSCH mode of IEEE 1165 802.15.4e", draft-ietf-6tisch-terminology-06 (work in 1166 progress), November 2015. 1168 [I-D.ietf-bier-architecture] 1169 Wijnands, I., Rosen, E., Dolganow, A., P, T., and S. 1170 Aldrin, "Multicast using Bit Index Explicit Replication", 1171 draft-ietf-bier-architecture-03 (work in progress), 1172 January 2016. 1174 [I-D.ietf-ipv6-multilink-subnets] 1175 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 1176 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 1177 progress), July 2002. 1179 [I-D.ietf-roll-terminology] 1180 Vasseur, J., "Terms used in Routing for Low power And 1181 Lossy Networks", draft-ietf-roll-terminology-13 (work in 1182 progress), October 2013. 1184 [I-D.ietf-v6ops-reducing-ra-energy-consumption] 1185 Yourtchenko, A. and L. Colitti, "Reducing energy 1186 consumption of Router Advertisements", draft-ietf-v6ops- 1187 reducing-ra-energy-consumption-03 (work in progress), 1188 November 2015. 1190 [I-D.nordmark-6man-dad-approaches] 1191 Nordmark, E., "Possible approaches to make DAD more robust 1192 and/or efficient", draft-nordmark-6man-dad-approaches-02 1193 (work in progress), October 2015. 1195 [I-D.nordmark-6man-rs-refresh] 1196 Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6 1197 Neighbor Discovery Optional Unicast RS/RA Refresh", draft- 1198 nordmark-6man-rs-refresh-01 (work in progress), October 1199 2014. 1201 [I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] 1202 Popa, D. and J. Hui, "6LoPLC: Transmission of IPv6 Packets 1203 over IEEE 1901.2 Narrowband Powerline Communication 1204 Networks", draft-popa-6lo-6loplc-ipv6-over- 1205 ieee19012-networks-00 (work in progress), March 2014. 1207 [I-D.sarikaya-6lo-ap-nd] 1208 Sarikaya, B. and P. Thubert, "Address Protected Neighbor 1209 Discovery for Low-power and Lossy Networks", draft- 1210 sarikaya-6lo-ap-nd-02 (work in progress), March 2016. 1212 [I-D.vyncke-6man-mcast-not-efficient] 1213 Vyncke, E., Thubert, P., Levy-Abegnoli, E., and A. 1214 Yourtchenko, "Why Network-Layer Multicast is Not Always 1215 Efficient At Datalink Layer", draft-vyncke-6man-mcast-not- 1216 efficient-01 (work in progress), February 2014. 1218 [I-D.yourtchenko-6man-dad-issues] 1219 Yourtchenko, A. and E. Nordmark, "A survey of issues 1220 related to IPv6 Duplicate Address Detection", draft- 1221 yourtchenko-6man-dad-issues-01 (work in progress), March 1222 2015. 1224 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1225 C., and M. Carney, "Dynamic Host Configuration Protocol 1226 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1227 2003, . 1229 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1230 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1231 DOI 10.17487/RFC3810, June 2004, 1232 . 1234 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1235 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1236 DOI 10.17487/RFC3971, March 2005, 1237 . 1239 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1240 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1241 . 1243 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 1244 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 1245 2006, . 1247 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 1248 DOI 10.17487/RFC4903, June 2007, 1249 . 1251 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1252 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1253 Overview, Assumptions, Problem Statement, and Goals", 1254 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1255 . 1257 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1258 Ed., "Control And Provisioning of Wireless Access Points 1259 (CAPWAP) Protocol Specification", RFC 5415, 1260 DOI 10.17487/RFC5415, March 2009, 1261 . 1263 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1264 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1265 2011, . 1267 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1268 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1269 DOI 10.17487/RFC6282, September 2011, 1270 . 1272 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 1273 Locator/ID Separation Protocol (LISP)", RFC 6830, 1274 DOI 10.17487/RFC6830, January 2013, 1275 . 1277 [RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability 1278 Detection Is Too Impatient", RFC 7048, 1279 DOI 10.17487/RFC7048, January 2014, 1280 . 1282 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 1283 Interface Identifiers with IPv6 Stateless Address 1284 Autoconfiguration (SLAAC)", RFC 7217, 1285 DOI 10.17487/RFC7217, April 2014, 1286 . 1288 [RFC7428] Brandt, A. and J. Buron, "Transmission of IPv6 Packets 1289 over ITU-T G.9959 Networks", RFC 7428, 1290 DOI 10.17487/RFC7428, February 2015, 1291 . 1293 [RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss 1294 Resiliency for Router Solicitations", RFC 7559, 1295 DOI 10.17487/RFC7559, May 2015, 1296 . 1298 12.3. External Informative References 1300 [IEEE80211] 1301 IEEE standard for Information Technology, "IEEE Standard 1302 for Information technology-- Telecommunications and 1303 information exchange between systems Local and 1304 metropolitan area networks-- Specific requirements Part 1305 11: Wireless LAN Medium Access Control (MAC) and Physical 1306 Layer (PHY) Specifications". 1308 [IEEE802151] 1309 IEEE standard for Information Technology, "IEEE Standard 1310 for Information Technology - Telecommunications and 1311 Information Exchange Between Systems - Local and 1312 Metropolitan Area Networks - Specific Requirements. - Part 1313 15.1: Wireless Medium Access Control (MAC) and Physical 1314 Layer (PHY) Specifications for Wireless Personal Area 1315 Networks (WPANs)". 1317 [IEEE802154] 1318 IEEE standard for Information Technology, "IEEE Standard 1319 for Local and metropolitan area networks-- Part 15.4: Low- 1320 Rate Wireless Personal Area Networks (LR-WPANs)". 1322 Appendix A. Requirements 1324 This section lists requirements that were discussed at 6lo for an 1325 update to 6LoWPAN ND. This specification meets most of them, but 1326 those listed in Appendix A.5 which are deferred to a different 1327 specification such as [I-D.sarikaya-6lo-ap-nd]. 1329 A.1. Requirements Related to Mobility 1331 Due to the unstable nature of LLN links, even in a LLN of immobile 1332 nodes a 6LoWPAN Node may change its point of attachment to a 6LR, say 1333 6LR-a, and may not be able to notify 6LR-a. Consequently, 6LR-a may 1334 still attract traffic that it cannot deliver any more. When links to 1335 a 6LR change state, there is thus a need to identify stale states in 1336 a 6LR and restore reachability in a timely fashion. 1338 Req1.1: Upon a change of point of attachment, connectivity via a new 1339 6LR MUST be restored timely without the need to de-register from the 1340 previous 6LR. 1342 Req1.2: For that purpose, the protocol MUST enable to differentiate 1343 between multiple registrations from one 6LoWPAN Node and 1344 registrations from different 6LoWPAN Nodes claiming the same address. 1346 Req1.3: Stale states MUST be cleaned up in 6LRs. 1348 Req1.4: A 6LoWPAN Node SHOULD also be capable to register its Address 1349 to multiple 6LRs, and this, concurrently. 1351 A.2. Requirements Related to Routing Protocols 1353 The point of attachment of a 6LoWPAN Node may be a 6LR in an LLN 1354 mesh. IPv6 routing in a LLN can be based on RPL, which is the 1355 routing protocol that was defined at the IETF for this particular 1356 purpose. Other routing protocols than RPL are also considered by 1357 Standard Defining Organizations (SDO) on the basis of the expected 1358 network characteristics. It is required that a 6LoWPAN Node attached 1359 via ND to a 6LR would need to participate in the selected routing 1360 protocol to obtain reachability via the 6LR. 1362 Next to the 6LBR unicast address registered by ND, other addresses 1363 including multicast addresses are needed as well. For example a 1364 routing protocol often uses a multicast address to register changes 1365 to established paths. ND needs to register such a multicast address 1366 to enable routing concurrently with discovery. 1368 Multicast is needed for groups. Groups MAY be formed by device type 1369 (e.g. routers, street lamps), location (Geography, RPL sub-tree), or 1370 both. 1372 The Bit Index Explicit Replication (BIER) Architecture 1373 [I-D.ietf-bier-architecture] proposes an optimized technique to 1374 enable multicast in a LLN with a very limited requirement for routing 1375 state in the nodes. 1377 Related requirements are: 1379 Req2.1: The ND registration method SHOULD be extended in such a 1380 fashion that the 6LR MAY advertise the Address of a 6LoWPAN Node over 1381 the selected routing protocol and obtain reachability to that Address 1382 using the selected routing protocol. 1384 Req2.2: Considering RPL, the Address Registration Option that is used 1385 in the ND registration SHOULD be extended to carry enough information 1386 to generate a DAO message as specified in [RFC6550] section 6.4, in 1387 particular the capability to compute a Path Sequence and, as an 1388 option, a RPLInstanceID. 1390 Req2.3: Multicast operations SHOULD be supported and optimized, for 1391 instance using BIER or MPL. Whether ND is appropriate for the 1392 registration to the 6BBR is to be defined, considering the additional 1393 burden of supporting the Multicast Listener Discovery Version 2 1394 [RFC3810] (MLDv2) for IPv6. 1396 A.3. Requirements Related to the Variety of Low-Power Link types 1398 6LoWPAN ND [RFC6775] was defined with a focus on IEEE802.15.4 and in 1399 particular the capability to derive a unique Identifier from a 1400 globally unique MAC-64 address. At this point, the 6lo Working Group 1401 is extending the 6LoWPAN Header Compression (HC) [RFC6282] technique 1402 to other link types ITU-T G.9959 [RFC7428], Master-Slave/Token- 1403 Passing [I-D.ietf-6lo-6lobac], DECT Ultra Low Energy 1404 [I-D.ietf-6lo-dect-ule], Near Field Communication [I-D.ietf-6lo-nfc], 1405 IEEE802.11ah [I-D.delcarpio-6lo-wlanah], as well as IEEE1901.2 1406 Narrowband Powerline Communication Networks 1407 [I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] and BLUETOOTH(R) 1408 Low Energy [I-D.ietf-6lo-btle]. 1410 Related requirements are: 1412 Req3.1: The support of the registration mechanism SHOULD be extended 1413 to more LLN links than IEEE 802.15.4, matching at least the LLN links 1414 for which an "IPv6 over foo" specification exists, as well as Low- 1415 Power Wi-Fi. 1417 Req3.2: As part of this extension, a mechanism to compute a unique 1418 Identifier should be provided, with the capability to form a Link- 1419 Local Address that SHOULD be unique at least within the LLN connected 1420 to a 6LBR discovered by ND in each node within the LLN. 1422 Req3.3: The Address Registration Option used in the ND registration 1423 SHOULD be extended to carry the relevant forms of unique Identifier. 1425 Req3.4: The Neighbour Discovery should specify the formation of a 1426 site-local address that follows the security recommendations from 1427 [RFC7217]. 1429 A.4. Requirements Related to Proxy Operations 1431 Duty-cycled devices may not be able to answer themselves to a lookup 1432 from a node that uses classical ND on a backbone and may need a 1433 proxy. Additionally, the duty-cycled device may need to rely on the 1434 6LBR to perform registration to the 6BBR. 1436 The ND registration method SHOULD defend the addresses of duty-cycled 1437 devices that are sleeping most of the time and not capable to defend 1438 their own Addresses. 1440 Related requirements are: 1442 Req4.1: The registration mechanism SHOULD enable a third party to 1443 proxy register an Address on behalf of a 6LoWPAN node that may be 1444 sleeping or located deeper in an LLN mesh. 1446 Req4.2: The registration mechanism SHOULD be applicable to a duty- 1447 cycled device regardless of the link type, and enable a 6BBR to 1448 operate as a proxy to defend the registered Addresses on its behalf. 1450 Req4.3: The registration mechanism SHOULD enable long sleep 1451 durations, in the order of multiple days to a month. 1453 A.5. Requirements Related to Security 1455 In order to guarantee the operations of the 6LoWPAN ND flows, the 1456 spoofing of the 6LR, 6LBR and 6BBRs roles should be avoided. Once a 1457 node successfully registers an address, 6LoWPAN ND should provide 1458 energy-efficient means for the 6LBR to protect that ownership even 1459 when the node that registered the address is sleeping. 1461 In particular, the 6LR and the 6LBR then should be able to verify 1462 whether a subsequent registration for a given Address comes from the 1463 original node. 1465 In a LLN it makes sense to base security on layer-2 security. During 1466 bootstrap of the LLN, nodes join the network after authorization by a 1467 Joining Assistant (JA) or a Commissioning Tool (CT). After joining 1468 nodes communicate with each other via secured links. The keys for 1469 the layer-2 security are distributed by the JA/CT. The JA/CT can be 1470 part of the LLN or be outside the LLN. In both cases it is needed 1471 that packets are routed between JA/CT and the joining node. 1473 Related requirements are: 1475 Req5.1: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1476 the 6LR, 6LBR and 6BBR to authenticate and authorize one another for 1477 their respective roles, as well as with the 6LoWPAN Node for the role 1478 of 6LR. 1480 Req5.2: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1481 the 6LR and the 6LBR to validate new registration of authorized 1482 nodes. Joining of unauthorized nodes MUST be impossible. 1484 Req5.3: 6LoWPAN ND security mechanisms SHOULD lead to small packet 1485 sizes. In particular, the NS, NA, DAR and DAC messages for a re- 1486 registration flow SHOULD NOT exceed 80 octets so as to fit in a 1487 secured IEEE802.15.4 frame. 1489 Req5.4: Recurrent 6LoWPAN ND security operations MUST NOT be 1490 computationally intensive on the LoWPAN Node CPU. When a Key hash 1491 calculation is employed, a mechanism lighter than SHA-1 SHOULD be 1492 preferred. 1494 Req5.5: The number of Keys that the 6LoWPAN Node needs to manipulate 1495 SHOULD be minimized. 1497 Req5.6: The 6LoWPAN ND security mechanisms SHOULD enable CCM* for use 1498 at both Layer 2 and Layer 3, and SHOULD enable the reuse of security 1499 code that has to be present on the device for upper layer security 1500 such as TLS. 1502 Req5.7: Public key and signature sizes SHOULD be minimized while 1503 maintaining adequate confidentiality and data origin authentication 1504 for multiple types of applications with various degrees of 1505 criticality. 1507 Req5.8: Routing of packets should continue when links pass from the 1508 unsecured to the secured state. 1510 Req5.9: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1511 the 6LR and the 6LBR to validate whether a new registration for a 1512 given address corresponds to the same 6LoWPAN Node that registered it 1513 initially, and, if not, determine the rightful owner, and deny or 1514 clean-up the registration that is duplicate. 1516 A.6. Requirements Related to Scalability 1518 Use cases from Automatic Meter Reading (AMR, collection tree 1519 operations) and Advanced Metering Infrastructure (AMI, bi-directional 1520 communication to the meters) indicate the needs for a large number of 1521 LLN nodes pertaining to a single RPL DODAG (e.g. 5000) and connected 1522 to the 6LBR over a large number of LLN hops (e.g. 15). 1524 Related requirements are: 1526 Req6.1: The registration mechanism SHOULD enable a single 6LBR to 1527 register multiple thousands of devices. 1529 Req6.2: The timing of the registration operation should allow for a 1530 large latency such as found in LLNs with ten and more hops. 1532 Author's Address 1534 Pascal Thubert (editor) 1535 Cisco Systems, Inc 1536 Building D 1537 45 Allee des Ormes - BP1200 1538 MOUGINS - Sophia Antipolis 06254 1539 FRANCE 1541 Phone: +33 497 23 26 34 1542 Email: pthubert@cisco.com