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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 January 5, 2016 5 Expires: July 8, 2016 7 IPv6 Backbone Router 8 draft-ietf-6lo-backbone-router-00 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 July 8, 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 . . . . . . . . . . . . . . . . . . . . 10 62 5.1. Transaction ID . . . . . . . . . . . . . . . . . . . . . 10 63 5.2. Owner Unique ID . . . . . . . . . . . . . . . . . . . . . 11 64 5.3. The Enhanced Address Registration Option (EARO) . . . . . 11 65 6. Backbone Router Routing Operations . . . . . . . . . . . . . 14 66 6.1. Over the Backbone Link . . . . . . . . . . . . . . . . . 14 67 6.2. Over the LLN Link . . . . . . . . . . . . . . . . . . . . 15 68 7. BackBone Router Proxy Operations . . . . . . . . . . . . . . 17 69 7.1. Registration and Binding State Creation . . . . . . . . . 19 70 7.2. Defending Addresses . . . . . . . . . . . . . . . . . . . 21 71 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 72 9. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 22 73 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 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 . . . . . . . . . . . . . . . . . . . . 28 80 A.1. Requirements Related to Mobility . . . . . . . . . . . . 28 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 . . . . . . . . . . . 32 87 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 33 89 1. Introduction 91 Though in most cases, including Low-Power ones, IEEE802.11 92 [IEEE80211] is operated as a wireless extension to an Ethernet 93 bridged domain, the impact of radio broadcasts for IPv6 [RFC2460] 94 multicast operations, in particular related to the power consumption 95 of battery-operated devices, lead the community to rethink the plain 96 layer-2 approach and consider splitting the broadcast domain between 97 the wired and the wireless access links. To that effect, the current 98 IEEE802.11 specifications require the capability to perform ARP and 99 ND proxy [RFC4389] functions at the Access Points (APs), but rely on 100 snooping for acquiring the related state, which is unsatisfactory in 101 a lossy and mobile environments. 103 Without a proxy, any IP multicast that circulates in the bridged 104 domain ends up broadcasted by the Access Points to all STAs, 105 including Low-Power battery-operated ones. With an incorrect or 106 missing state in the proxy, a packet may not be delivered to the 107 destination, which may have operational impacts depending on the 108 criticality of the packet. 110 Some messages are lost for the lack of retries, regardless of their 111 degree of criticality; it results for instance that Duplicate Address 112 Detection (DAD) as defined in [RFC4862] is mostly broken over Wi-Fi 113 [I-D.yourtchenko-6man-dad-issues]. 115 On the other hand, IPv6 multicast messages are processed by most if 116 not all wireless nodes over the fabric even when very few if any of 117 the nodes is effectively listening to the multicast address. It 118 results that a simple Neighbor Solicitation (NS) message [RFC4861], 119 that is supposedly targeted to a very small group of nodes, ends up 120 polluting the whole wireless bandwidth across the fabric 121 [I-D.vyncke-6man-mcast-not-efficient]. 123 It appears that in a variety of Wireless Local Area Networks (WLANs) 124 and Wireless Personal Area Networks (WPANs), the decision to leverage 125 the broadcast support of a particular link should be left to Layer-3 126 based on the criticality of the message and the number of interested 127 listeners on that link, for the lack of capability to indicate that 128 criticality to the lower layer. To achieve this, the operation at 129 the Access Point cannot be a Layer-2 bridge operation, but that of a 130 Layer-3 router; the concept of MultiLink Subnet (MLSN) must be 131 reintroduced, with IPv6 backbone routers (6BBRs) interconnecting the 132 various links and routing within the subnet. For link-scope 133 multicast operations, a 6BBR participates to MLD on its access links 134 and a multicast routing protocol is setup between the 6BBRs over the 135 backbone of the MLSN. 137 As the network scales up, none of the approaches of using either 138 broadcast or N*unicast for a multicast packet is really satisfying 139 and the protocols themselves need to be adapted to reduce their use 140 of multicast. 142 One degree of improvement can be achieved by changing the tuning of 143 the protocol parameters and operational practices, such as suggested 144 in Reducing energy consumption of Router Advertisements 146 [I-D.ietf-v6ops-reducing-ra-energy-consumption] (RA). This works 147 enables to lower the rate of RA messages but does not solve the 148 problem associated with multicast NS and NA messages, which are a lot 149 more frequent in large-scale radio environments with mobile devices 150 which exhibit intermittent access patterns and short-lived IPv6 151 addresses. 153 In the context of IEEE802.15.4 [IEEE802154], the more drastic step of 154 considering the radio as a medium that is different from Ethernet 155 because of the impact of multicast, was already taken with the 156 adoption of Neighbor Discovery Optimization for IPv6 over Low-Power 157 Wireless Personal Area Networks (6LoWPANs) [RFC6775]. This 158 specification applies that same thinking to other wireless links such 159 as Low-Power IEEE802.11 (Wi-Fi) and IEEE802.15.1 (Bluetooth) 160 [IEEE802151], and extends [RFC6775] to enable proxy operation by the 161 6BBR so as to decouple the broadcast domain in the backbone from the 162 wireless links. The proxy operation can be maintained asynchronous 163 so that low-power nodes or nodes that are deep in a mesh do not need 164 to be bothered synchronously when a lookup is performed for their 165 addresses, effectively implementing the ND contribution to the 166 concept of a Sleep Proxy [I-D.nordmark-6man-dad-approaches]. 168 DHCPv6 [RFC3315] is still a viable option in Low power and Lossy 169 Network (LLN) to assign IPv6 global addresses. However, the IETF 170 standard that supports address assignment specifically for LLNs is 171 6LoWPAN ND [RFC6775], which is a mix of IPv6 stateless 172 autoconfiguration mechanism (SLAAC) [RFC4862] and a new registration 173 process for ND. This specification introduces a Layer-3 association 174 process based on 6LoWPAN ND that maintains a proxy state in the 6BBR 175 to keep the LLN nodes reachable and protect their addresses through 176 sleeping periods. 178 A number of use cases, including the Industrial Internet, require a 179 large scale deployment of monitoring sensors that can only be 180 realized in a cost-effective fashion with wireless technologies. 181 Mesh networks are deployed when simpler hub-and-spoke topologies are 182 not sufficient for the expected size, throughput, and density. 183 Meshes imply the routing of packets, operated at either Layer-2 or 184 Layer-3. For routing over a mesh at Layer-3, the IETF has designed 185 the IPv6 Routing Protocol over LLN (RPL) [RFC6550]. 6LoWPAN ND was 186 designed as a stand-alone mechanism separately from RPL, and the 187 interaction between the 2 protocols was not defined. This 188 specification details how periodic updates from RPL can be used by 189 the RPL root to renew the association of the RPL node to the 6BBR on 190 its behalf so as to maintain the proxy operation active for that 191 node. 193 This document suggests a limited evolution to [RFC6775] so as to 194 allow operation of a 6LoWPAN ND node while a routing protocol (in 195 first instance RPL) is present and operational. It also suggests a 196 more generalized use of the information in the ARO option of the ND 197 messages outside the strict LLN domain, for instance over a converged 198 backbone. 200 2. Applicability and Requirements Served 202 Efficiency aware IPv6 Neighbor Discovery Optimizations 203 [I-D.chakrabarti-nordmark-6man-efficient-nd] suggests that 6LoWPAN ND 204 [RFC6775] can be extended to other types of links beyond IEEE802.15.4 205 for which it was defined. The registration technique is beneficial 206 when the Link-Layer technique used to carry IPv6 multicast packets is 207 not sufficiently efficient in terms of delivery ratio or energy 208 consumption in the end devices, in particular to enable energy- 209 constrained sleeping nodes. The value of such extension is 210 especially apparent in the case of mobile wireless nodes, to reduce 211 the multicast operations that are related to classical ND ([RFC4861], 212 [RFC4862]) and plague the wireless medium. 214 This specification updates and generalizes 6LoWPAN ND to a broader 215 range of Low power and Lossy Networks (LLNs) with a solid support for 216 Duplicate Address Detection (DAD) and address lookup that does not 217 require broadcasts over the LLNs. The term LLN is used loosely in 218 this specification to cover multiple types of WLANs and WPANs, 219 including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE802.11AH and 220 IEEE802.15.4 wireless meshes, so as to address the requirements 221 listed in Appendix A.3 223 The scope of this draft is a Backbone Link that federates multiple 224 LLNs as a single IPv6 MultiLink Subnet. Each LLN in the subnet is 225 anchored at an IPv6 Backbone Router (6BBR). The Backbone Routers 226 interconnect the LLNs over the Backbone Link and emulate that the LLN 227 nodes are present on the Backbone using proxy-ND operations. This 228 specification extends IPv6 ND over the backbone to discriminate 229 address movement from duplication and eliminate stale state in the 230 backbone routers and backbone nodes once a LLN node has roamed. This 231 way, mobile nodes may roam rapidly from a 6BBR to the next and 232 requirements in Appendix A.1 are met. 234 This specification can be used by any wireless node to associate at 235 Layer-3 with a 6BBR and register its IPv6 addresses to obtain routing 236 services including proxy-ND operations over the backbone, effectively 237 providing a solution to the requirements expressed in Appendix A.4. 239 The Link Layer Address (LLA) that is returned as Target LLA (TLLA) in 240 Neighbor Advertisements (NA) messages by the 6BBR on behalf of the 241 Registered Node over the backbone may be that of the Registering 242 Node, in which case the 6BBR needs to bridge the unicast packets 243 (Bridging proxy), or that of the 6BBR on the backbone, in which case 244 the 6BBRs needs to route the unicast packets (Routing proxy). In the 245 latter case, the 6BBR may maintain the list of correspondents to 246 which it has advertised its own MAC address on behalf of the LLN node 247 and the IPv6 ND operation is minimized as the number of nodes scale 248 up in the LLN. This enables to meet the requirements in Appendix A.6 249 as long has the 6BBRs are dimensioned for the number of registration 250 that each needs to support. 252 In the context of the the TimeSlotted Channel Hopping (TSCH) mode of 253 [IEEE802154], the 6TiSCH architecture [I-D.ietf-6tisch-architecture] 254 introduces how a 6LoWPAN ND host could connect to the Internet via a 255 RPL mesh Network, but this requires additions to the 6LOWPAN ND 256 protocol to support mobility and reachability in a secured and 257 manageable environment. This specification details the new 258 operations that are required to implement the 6TiSCH architecture and 259 serves the requirements listed in Appendix A.2. 261 In the case of Low-Power IEEE802.11, a 6BBR may be collocated with a 262 standalone AP or a CAPWAP [RFC5415] wireless controller, and the 263 wireless client (STA) leverages this specification to register its 264 IPv6 address(es) to the 6BBR over the wireless medium. In the case 265 of a 6TiSCH LLN mesh, the RPL root is collocated with a 6LoWPAN 266 Border Router (6LBR), and either collocated with or connected to the 267 6BBR over an IPv6 Link. The 6LBR leverages this specification to 268 register the LLN nodes on their behalf to the 6BBR. In the case of 269 BTLE, the 6BBR is collocated with the router that implements the BTLE 270 central role as discussed in section 2.2 of [I-D.ietf-6lo-btle]. 272 3. Terminology 274 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 275 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 276 document are to be interpreted as described in [RFC2119]. 278 Readers are expected to be familiar with all the terms and concepts 279 that are discussed in "Neighbor Discovery for IP version 6" 280 [RFC4861], "IPv6 Stateless Address Autoconfiguration" [RFC4862], 281 "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): 282 Overview, Assumptions, Problem Statement, and Goals" [RFC4919], 283 Neighbor Discovery Optimization for Low-power and Lossy Networks 284 [RFC6775] and "Multi-link Subnet Support in IPv6" 285 [I-D.ietf-ipv6-multilink-subnets]. 287 Readers would benefit from reading "Multi-Link Subnet Issues" 288 [RFC4903], ,"Mobility Support in IPv6" [RFC6275], "Neighbor Discovery 289 Proxies (ND Proxy)" [RFC4389] and "Optimistic Duplicate Address 290 Detection" [RFC4429] prior to this specification for a clear 291 understanding of the art in ND-proxying and binding. 293 Additionally, this document uses terminology from 294 [I-D.ietf-roll-terminology] and [I-D.ietf-6tisch-terminology], and 295 introduces the following terminology: 297 LLN Low Power Lossy Network. Used loosely in this specification to 298 represent WLANs and WPANs. See [RFC4919] 300 Backbone This is an IPv6 transit link that interconnects 2 or more 301 Backbone Routers. It is expected to be deployed as a high 302 speed backbone in order to federate a potentially large set of 303 LLNS. Also referred to as a LLN backbone or Backbone network. 305 Backbone Router An IPv6 router that federates the LLN using a 306 Backbone link as a backbone. A BBR acts as a 6LoWPAN Border 307 Routers (6LBR) and an Energy Aware Default Router (NEAR). 309 Extended LLN This is the aggregation of multiple LLNs as defined in 310 [RFC4919], interconnected by a Backbone Link via Backbone 311 Routers, and forming a single IPv6 MultiLink Subnet. 313 Registration The process during which a wireless Node registers its 314 address(es) with the Border Router so the 6BBR can proxy ND for 315 it over the backbone. 317 Binding The state in the 6BBR that associates an IP address with a 318 MAC address, a port and some other information about the node 319 that owns the IP address. 321 Registered Node The node for which the registration is performed, 322 which owns the fields in the EARO option. 324 Registering Node The node that performs the registration to the 325 6BBR, either for one of its own addresses, in which case it is 326 Registered Node and indicates its own MAC Address as SLLA in 327 the NS(ARO), or on behalf of a Registered Node that is 328 reachable over a LLN mesh. In the latter case, if the 329 Registered Node is reachable from the 6BBR over a Mesh-Under 330 mesh, the Registering Node indicates the MAC Address of the 331 Registered Node as SLLA in the NS(ARO). Otherwise, it is 332 expected that the Registered Device is reachable over a Route- 333 Over mesh from the Registering Node, in which case the SLLA in 334 the NS(ARO) is that of the Registering Node, which causes it to 335 attract the packets from the 6BBR to the Registered Node and 336 route them over the LLN. 338 Registered Address The address owned by the Registered Node node 339 that is being registered. 341 Sleeping Proxy A 6BBR acts as a Sleeping Proxy if it answers ND 342 Neighbor Solicitation over the backbone on behalf of the 343 Registered Node whenever possible. This is the default mode 344 for this specification but it may be overridden, for instance 345 by configuration, into Unicasting Proxy. 347 Unicasting Proxy As a Unicasting Proxy, the 6BBR forwards NS 348 messages to the Registering Node, transforming Layer-2 349 multicast into unicast whenever possible. 351 Routing proxy A 6BBR acts as a routing proxy if it advertises its 352 own MAC address, as opposed to that of the node that performs 353 the registration, as the TLLA in the proxied NAs over the 354 backbone. In that case, the MAC address of the node is not 355 visible at Layer-2 over the backbone and the bridging fabric is 356 not aware of the addresses of the LLN devices and their 357 mobility. The 6BBR installs a connected host route towards the 358 registered node over the interface to the node, and acts as a 359 Layer-3 router for unicast packets to the node. The 6BBR 360 updates the ND Neighbor Cache Entries (NCE) in correspondent 361 nodes if the wireless node moves and registers to another 6BBR, 362 either with a single broadcast, or with a series of unicast 363 NA(O) messages, indicating the TLLA of the new router. 365 Bridging proxy A 6BBR acts as a bridging proxy if it advertises the 366 MAC address of the node that performs the registration as the 367 TLLA in the proxied NAs over the backbone. In that case, the 368 MAC address and the mobility of the node is still visible 369 across the bridged backbone fabric, as is traditionally the 370 case with Layer-2 APs. The 6BBR acts as a Layer-2 bridge for 371 unicast packets to the registered node. The MAC address 372 exposed in the S/TLLA is that of the Registering Node, which is 373 not necessarily the Registered Device. When a device moves 374 within a LLN mesh, it may end up attached to a different 6LBR 375 acting as Registering Node, and the LLA that is exposed over 376 the backbone will change. 378 Primary BBR The BBR that will defend a Registered Address for the 379 purpose of DAD over the backbone. 381 Secondary BBR A BBR to which the address is registered. A Secondary 382 Router MAY advertise the address over the backbone and proxy 383 for it. 385 4. Overview 387 An LLN node can move freely from an LLN anchored at a Backbone Router 388 to an LLN anchored at another Backbone Router on the same backbone 389 and conserve any of the IPv6 addresses that it has formed, 390 transparently. 392 | 393 +-----+ 394 | | Other (default) Router 395 | | 396 +-----+ 397 | 398 | Backbone Link 399 +--------------------+------------------+ 400 | | | 401 +-----+ +-----+ +-----+ 402 | | Backbone | | Backbone | | Backbone 403 | | router | | router | | router 404 +-----+ +-----+ +-----+ 405 o o o o o o 406 o o o o o o o o o o o o o o 407 o o o o o o o o o o o o o o o 408 o o o o o o o o o o 409 o o o o o o o 411 LLN LLN LLN 413 Figure 1: Backbone Link and Backbone Routers 415 The Backbone Routers maintain an abstract Binding Table of their 416 Registered Nodes. The Binding Table operates as a distributed 417 database of all the wireless Nodes whether they reside on the LLNs or 418 on the backbone, and use an extension to the Neighbor Discovery 419 Protocol to exchange that information across the Backbone in the 420 classical ND reactive fashion. 422 The Address Registration Option (ARO) defined in [RFC6775] is 423 extended to enable the registration for routing and proxy Neighbor 424 Discovery operations by the 6BBR, and the Extended ARO (EARO) option 425 is included in the ND exchanges over the backbone between the 6BBRs 426 to sort out duplication from movement. 428 Address duplication is sorted out with the Owner Unique-ID field in 429 the EARO, which is a generalization of the EUI-64 that allows 430 different types of unique IDs beyond the name space derived from the 431 MAC addresses. First-Come First-Serve rules apply, whether the 432 duplication happens between LLN nodes as represented by their 433 respective 6BBRs, or between an LLN node and a classical node that 434 defends its address over the backbone with classical ND and does not 435 include the EARO option. 437 In case of conflicting registrations to multiple 6BBRs from a same 438 node, a sequence counter called Transaction ID (TID) is introduced 439 that enables 6BBRs to sort out the latest anchor for that node. 440 Registrations with a same TID are compatible and maintained, but, in 441 case of different TIDs, only the freshest registration is maintained 442 and the stale state is eliminated. 444 With this specification, Backbone Routers perform ND proxy over the 445 Backbone Link on behalf of their Registered Nodes. The Backbone 446 Router operation is essentially similar to that of a Mobile IPv6 447 (MIPv6) [RFC6275] Home Agent. This enables mobility support for LLN 448 nodes that would move outside of the network delimited by the 449 Backbone link attach to a Home Agent from that point on. This also 450 enables collocation of Home Agent functionality within Backbone 451 Router functionality on the same backbone interface of a router. 452 Further specification may extend this be allowing the 6BBR to 453 redistribute host routes in routing protocols that would operate over 454 the backbone, or in MIPv6 or the Locator/ID Separation Protocol 455 (LISP) [RFC6830] to support mobility on behalf of the nodes, etc... 457 The Optimistic Duplicate Address Detection [RFC4429] (ODAD) 458 specification details how an address can be used before a Duplicate 459 Address Detection (DAD) is complete, and insists that an address that 460 is TENTATIVE should not be associated to a Source Link-Layer Address 461 Option in a Neighbor Solicitation message. This specification 462 leverages ODAD to create a temporary proxy state in the 6BBR till DAD 463 is completed over the backbone. This way, the specification enables 464 to distribute proxy states across multiple 6BBR and co-exist with 465 classical ND over the backbone. 467 5. New Types And Formats 469 5.1. Transaction ID 471 The specification expects that the Registered Node can provide a 472 sequence number called Transaction ID (TID) that is incremented with 473 each re-registration. The TID essentially obeys the same rules as 474 the Path Sequence field in the Transit Information Option (TIO) found 475 in RPL's Destination Advertisement Object (DAO). This way, the LLN 476 node can use the same counter for ND and RPL, and a 6LBR acting as 477 RPL root may easily maintain the registration on behalf of a RPL node 478 deep inside the mesh by simply using the RPL TIO Path Sequence as TID 479 for EARO. 481 When a Registered Node is registered to multiple BBRs in parallel, it 482 is expected that the same TID is used, to enable the 6BBRs to 483 correlate the registrations as being a single one, and differentiate 484 that situation from a movement. 486 If the TIDs are different, the resolution inherited from RPL sorts 487 out the most recent registration and other ones are removed. The 488 operation for computing and comparing the Path Sequence is detailed 489 in section 7 of [RFC6550] and applies to the TID in the exact same 490 fashion. 492 5.2. Owner Unique ID 494 The Owner Unique ID (OUID) enables to differentiate a real duplicate 495 address registration from a double registration or a movement. An ND 496 message from the 6BBR over the backbone that is proxied on behalf of 497 a Registered Node must carry the most recent EARO option seen for 498 that node. A NS/NA with an EARO and a NS/NA without a EARO thus 499 represent different nodes and if they relate to a same target then 500 they reflect an address duplication. The Owner Unique ID can be as 501 simple as a EUI-64 burn-in address, if duplicate EUI-64 addresses are 502 avoided. 504 Alternatively, the unique ID can be a cryptographic string that can 505 can be used to prove the ownership of the registration as discussed 506 in Address Protected Neighbor Discovery for Low-power and Lossy 507 Networks [I-D.sarikaya-6lo-ap-nd]. 509 In any fashion, it is recommended that the node stores the unique Id 510 or the keys used to generate that ID in persistent memory. 511 Otherwise, it will be prevented to re-register after a reboot that 512 would cause a loss of memory until the Backbone Router times out the 513 registration. 515 5.3. The Enhanced Address Registration Option (EARO) 517 With the ARO option defined in 6LoWPAN ND [RFC6775], the address 518 being registered and its owner can be uniquely identified and matched 519 with the Binding Table entries of each Backbone Router. 521 The Enhanced Address Registration Option (EARO) is intended to be 522 used as a replacement to the ARO option within Neighbor Discovery NS 523 and NA messages between a LLN node and its 6LoWPAN Router (6LR), as 524 well as in Duplicate Address Request (DAR) and the Duplicate Address 525 Confirmation (DAC) messages between 6LRs and 6LBRs in LLNs meshes 526 such as 6TiSCH networks. 528 An NS message with an EARO option is a registration if and only if it 529 also carries an SLLAO option. The AERO option also used in NS and NA 530 messages between Backbone Routers over the backbone link to sort out 531 the distributed registration state, and in that case, it does not 532 carry the SLLAO option and is not confused with a registration. 534 The EARO extends the ARO and is recognized by the setting of the TID 535 bit. A node that supports this specification MUST always use an EARO 536 as a replacement to an ARO in its registration to a router. This is 537 harmless since the TID bit and fields are reserved in [RFC6775] are 538 ignored by a legacy router. A router that supports this 539 specification answers to an ARO with an ARO and to an EARO with an 540 EARO. 542 This specification changes the behavior of the peers in a 543 registration flows. To enable backward compatibility, a node that 544 registers to a router that is not known to support this specification 545 MUST behave as prescribed by [RFC6775]. Once the router is known to 546 support this specification, the node MUST obey this specification. 548 When using the EARO option, the address being registered is found in 549 the Target Address field of the NS and NA messages. This differs 550 from 6LoWPAN ND [RFC6775] which specifies that the address being 551 registered is the source of the NS. 553 The reason for this change is to enable proxy-registrations on behalf 554 of other nodes in Route-Over meshes, for instance to enable that a 555 RPL root registers addresses on behalf LLN nodes that are deeper in a 556 6TiSCH mesh. In that case, the Registering Node MUST indicate its 557 own address as source of the ND message and its MAC address in the 558 Source Link-Layer Address Option (SLLAO), since it still expects to 559 get the packets and route them down the mesh. But the Registered 560 Address belongs to another node, the Registered Node, and that 561 address is indicated in the Target Address field of the NS message. 563 One way of achieving all the above is for a node to first register an 564 address that it owns in order to validate that the router supports 565 this specification, placing the same address in the Source and Target 566 Address fields of the NS message. The node may for instance register 567 an address that is based on EUI-64. For such address, DAD is not 568 required and using the SLLAO option in the NS is actually more 569 amenable with older ND specifications such as ODAD [RFC4429]. 571 Once that first registration is complete, the node knows from the 572 setting of the TID in the response whether the router supports this 573 specification. If this is verified, the node may register other 574 addresses that it owns, or proxy-register addresses on behalf some 575 another node, indicating those addresses being registered in the 576 Target Address field of the NS messages, while using one of its own, 577 already registered, addresses as source. 579 The format of the EARO option is as follows: 581 0 1 2 3 582 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 1 583 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 | Type | Length = 2 | Status | pref level | 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 | Reserved |T| TID | Registration Lifetime | 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 | | 589 + Owner Unique ID (EUI-64 or equivalent) + 590 | | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 Figure 2: EARO 595 Option Fields 597 Type: 599 Length: 2 601 Status: OK=0; Duplicate=1; Full=2; Moved=3; Removed=4; 603 Reserved: This field is unused. It MUST be initialized to zero by 604 the sender and MUST be ignored by the receiver. 606 T: One bit flag. Set if the next octet is a used as a TID. 608 TID: 1-byte integer; a transaction id that is maintained by the node 609 and incremented with each transaction. it is recommended that the 610 node maintains the TID in a persistent storage. 612 Registration Lifetime: 1-byte integer; expressed in minutes. 0 613 means that the registration has ended and the state should be 614 removed. 616 Owner Unique Identifier: A globally unique identifier for the node 617 associated. This can be the EUI-64 derived IID of an interface, 618 or some provable ID obtained cryptographically. 620 6. Backbone Router Routing Operations 622 | 623 +-----+ 624 | | Other (default) Router 625 | | 626 +-----+ 627 | /64 628 | Backbone Link 629 +-------------------+-------------------+ 630 | /64 | /64 | /64 631 +-----+ +-----+ +-----+ 632 | | Backbone | | Backbone | | Backbone 633 | | router | | router | | router 634 +-----+ +-----+ +-----+ 635 o N*/128 o o o M*/128 o o P*/128 636 o o o o o o o o o o o o o o 637 o o o o o o o o o o o o o o o 638 o o o o o o o o o o 639 o o o o o o o 641 LLN LLN LLN 643 Figure 3: Routing Configuration in the ML Subnet 645 6.1. Over the Backbone Link 647 The Backbone Router is a specific kind of Border Router that performs 648 proxy Neighbor Discovery on its backbone interface on behalf of the 649 nodes that it has discovered on its LLN interfaces. 651 The backbone is expected to be a high speed, reliable Backbone link, 652 with affordable and reliable multicast capabilities, such as a 653 bridged Ethernet Network, and to allow a full support of classical ND 654 as specified in [RFC4861] and subsequent RFCs. In other words, the 655 backbone is not a LLN. 657 Still, some restrictions of the attached LLNs will apply to the 658 backbone. In particular, it is expected that the MTU is set to the 659 same value on the backbone and all attached LLNs, and the scalability 660 of the whole subnet requires that broadcast operations are avoided as 661 much as possible on the backbone as well. Unless configured 662 otherwise, the Backbone Router MUST echo the MTU that it learns in 663 RAs over the backbone in the RAs that it sends towards the LLN links. 665 As a router, the Backbone Router behaves like any other IPv6 router 666 on the backbone side. It has a connected route installed towards the 667 backbone for the prefixes that are present on that backbone and that 668 it proxies for on the LLN interfaces. 670 As a proxy, the 6BBR uses an EARO option in the NS-DAD and the 671 multicast NA messages that it generates on behalf of a Registered 672 Node, and it places an EARO in its unicast NA messages if and only if 673 the NS/NA that stimulates it had an EARO in it. 675 When possible, the 6BBR SHOULD use unicast or solicited-node 676 multicast address (SNMA) [RFC4291] to defend its Registered Addresses 677 over the backbone. In particular, the 6BBR MUST join the SNMA group 678 that corresponds to a Registered Address as soon as it creates an 679 entry for that address and as long as it maintains that entry, 680 whatever the state of the entry. The expectation is that it is 681 possible to get a message delivered to all the nodes on the backbone 682 that listen to a particular address and support this specification - 683 which includes all the 6BBRs in the MultiLink Subnet - by sending a 684 multicast message to the associated SNMA over the backbone. 686 The support of Optimistic DAD (ODAD) [RFC4429] is recommended for all 687 nodes in the backbone and followed by the 6BBRs in their proxy 688 activity over the backbone. With ODAD, any optimistic node MUST join 689 the SNMA of a Tentative address, which interacts better with this 690 specification. 692 This specification allows the 6BBR in Routing Proxy mode to advertise 693 the Registered IPv6 Address with the 6BBR Link Layer Address, and 694 attempts to update Neighbor Cache Entries (NCE) in correspondent 695 nodes over the backbone, using gratuitous NA(Override). This method 696 may fail of the multicast message is not properly received, and 697 correspondent nodes may maintain an incorrect neighbor state, which 698 they will eventually discover through Neighbor Unreachability 699 Detection (NUD). Because mobility may be slow, the NUD procedure 700 defined in [RFC4861] may be too impatient, and the support of 701 [RFC7048] is recommended in all nodes in the network. 703 Since the MultiLink Subnet may grow very large in terms of individual 704 IPv6 addresses, multicasts should be avoided as much as possible even 705 on the backbone. Though it is possible for plain hosts to 706 participate with legacy IPv6 ND support, the support by all nodes 707 connected to the backbone of [I-D.nordmark-6man-rs-refresh] is 708 recommended, and this implies the support of [RFC7559] as well. 710 6.2. Over the LLN Link 712 As a router, the Nodes and Backbone Router operation on the LLN 713 follows [RFC6775]. Per that specification, LLN Hosts generally do 714 not depend on multicast RAs to discover routers. It is still 715 generally required for LLN nodes to accept multicast RAs 716 [I-D.ietf-v6ops-reducing-ra-energy-consumption], but those are rare 717 on the LLN link. Nodes are expected to follow the Simple Procedures 718 for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) 719 to assert movements, and to support the Packet-Loss Resiliency for 720 Router Solicitations [RFC7559] to make the unicast RS more reliable. 722 The Backbone Router acquires its states about the addresses on the 723 LLN side through a registration process from either the nodes 724 themselves, or from a node such as a RPL root / 6LBR (the Registering 725 Node) that performs the registration on behalf of the address owner 726 (the Registered Node). 728 When operating as a Routing Proxy, the router installs hosts routes 729 (/128) to the Registered Addresses over the LLN links, via the 730 Registering Node as identified by the Source Address and the SLLAO 731 option in the NS(EARO) messages. 733 In that mode, the 6BBR handles the ND protocol over the backbone on 734 behalf of the Registered Nodes, using its own MAC address in the TLLA 735 and SLLA options in proxyed NS and NA messages. It results that for 736 each Registered Address, a number of peer Nodes on the backbone have 737 resolved the address with the 6BBR MAC address and keep that mapping 738 stored in their Neighbor cache. 740 The 6BBR SHOULD maintain, per Registered Address, the list of the 741 peers on the backbone to which it answered with it MAC address, and 742 when a binding moves to a different 6BBR, it SHOULD send a unicast 743 gratuitous NA(O) individually to each of them to inform them that the 744 address has moved and pass the MAC address of the new 6BBR in the 745 TLLAO option. If the 6BBR can not maintain that list, then it SHOULD 746 remember whether that list is empty or not and if not, send a 747 multicast NA(O) to all nodes to update the impacted Neighbor Caches 748 with the information from the new 6BBR. 750 The Bridging Proxy is a variation where the BBR function is 751 implemented in a Layer-3 switch or an wireless Access Point that acts 752 as a Host from the IPv6 standpoint, and, in particular, does not 753 operate the routing of IPv6 packets. In that case, the SLLAO in the 754 proxied NA messages is that of the Registering Node and classical 755 bridging operations take place on data frames. 757 If a registration moves from one 6BBR to the next, but the 758 Registering Node does not change, as indicated by the S/TLLAO option 759 in the ND exchanges, there is no need to update the Neighbor Caches 760 in the peers Nodes on the backbone. On the other hand, if the LLAO 761 changes, the 6BBR SHOULD inform all the relevant peers as described 762 above, to update the impacted Neighbor Caches. In the same fashion, 763 if the Registering Node changes with a new registration, the 6BBR 764 SHOULD also update the impacted Neighbor Caches over the backbone. 766 7. BackBone Router Proxy Operations 768 This specification enables a Backbone Router to proxy Neighbor 769 Discovery operations over the backbone on behalf of the nodes that 770 are registered to it, allowing any node on the backbone to reach a 771 Registered Node as if it was on-link. The backbone and the LLNs are 772 considered different Links in a MultiLink subnet but the prefix that 773 is used may still be advertised as on-link on the backbone to support 774 legacy nodes; multicast ND messages are link-scoped and not forwarded 775 across the backbone routers. 777 ND Messages on the backbone side that do not match to a registration 778 on the LLN side are not acted upon on the LLN side, which stands 779 protected. On the LLN side, the prefixes associated to the MultiLink 780 Subnet are presented as not on-link, so address resolution for other 781 hosts do not occur. 783 The default operation in this specification is Sleeping proxy which 784 means: 786 o creating a new entry in an abstract Binding Table for a new 787 Registered Address and validating that the address is not a 788 duplicate over the backbone 790 o defending a Registered Address over the backbone using NA messages 791 with the Override bit set on behalf of the sleeping node whenever 792 possible 794 o advertising a Registered Address over the backbone using NA 795 messages, asynchronously or as a response to a Neighbor 796 Solicitation messages. 798 o Looking up a destination over the backbone in order to deliver 799 packets arriving from the LLN using Neighbor Solicitation 800 messages. 802 o Forwarding packets from the LLN over the backbone, and the other 803 way around. 805 o Eventually triggering a liveliness verification of a stale 806 registration. 808 A 6BBR may act as a Sleeping Proxy only if the state of the binding 809 entry is REACHABLE, or TENTATIVE in which case the answer is delayed. 811 In any other state, the Sleeping Proxy operates as a Unicasting 812 Proxy. 814 As a Unicasting Proxy, the 6BBR forwards NS messages to the 815 Registering Node, transforming Layer-2 multicast into unicast 816 whenever possible. This is not possible in UNREACHABLE state, so the 817 NS messages are multicasted, and rate-limited to protect the medium 818 with an exponential back-off. In other states, The messages are 819 forwarded to the Registering Node as unicast Layer-2 messages. In 820 TENTATIVE state, the NS message is either held till DAD completes, or 821 dropped. 823 The draft introduces the optional concept of primary and secondary 824 BBRs. The primary is the backbone router that has the highest EUI-64 825 address of all the 6BBRs that share a registration for a same 826 Registered Address, with the same Owner Unique ID and same 827 Transaction ID, the EUI-64 address being considered as an unsigned 828 64bit integer. The concept is defined with the granularity of an 829 address, that is a given 6BBR can be primary for a given address and 830 secondary or another one, regardless on whether the addresses belong 831 to the same node or not. The primary Backbone Router is in charge of 832 protecting the address for DAD over the Backbone. Any of the Primary 833 and Secondary 6BBR may claim the address over the backbone, since 834 they are all capable to route from the backbone to the LLN node, and 835 the address appears on the backbone as an anycast address. 837 The Backbone Routers maintain a distributed binding table, using 838 classical ND over the backbone to detect duplication. This 839 specification requires that: 841 1. All addresses that can be reachable from the backbone, including 842 IPv6 addresses based on burn-in EUI64 addresses MUST be 843 registered to the 6BBR. 845 2. A Registered Node MUST include the EARO option in an NS message 846 that used to register an addresses to a 6LR; the 6LR MUST 847 propagate that option unchanged to the 6LBR in the DAR/DAC 848 exchange, and the 6LBR MUST propagate that option unchanged in 849 proxy registrations. 851 3. The 6LR MUST echo the same EARO option in the NA that it uses to 852 respond, but for the status filed which is not used in NS 853 messages, and significant in NA. 855 A false positive duplicate detection may arise over the backbone, for 856 instance if the Registered Address is registered to more than one 857 LBR, or if the node has moved. Both situations are handled 858 gracefully unbeknownst to the node. In the former case, one LBR 859 becomes primary to defend the address over the backbone while the 860 others become secondary and may still forward packets back and forth. 861 In the latter case the LBR that receives the newest registration wins 862 and becomes primary. 864 The expectation in this specification is that there is a single 865 Registering Node at a time per Backbone Router for a given Registered 866 Address, but that a Registered Address may be registered to Multiple 867 6BBRs for higher availability. 869 Over the LLN, and for any given Registered Address, it is REQUIRED 870 that: 872 de-registrations (newer TID, same OUID, null Lifetime) are 873 accepted and responded immediately with a status of 4; the entry 874 is deleted; 876 newer registrations (newer TID, same OUID, non-null Lifetime) are 877 accepted and responded with a status of 0 (success); the entry is 878 updated with the new TID, the new Registration Lifetime and the 879 new Registering Node, if any has changed; in TENTATIVE state the 880 response is held and may be overwritten; in other states the 881 Registration-Lifetime timer is restarted and the entry is placed 882 in REACHABLE state. 884 identical registrations (same TID, same OUID) from a same 885 Registering Node are not processed but responded with a status of 886 0 (success); they are expected to be identical and an error may be 887 logged if not; in TENTATIVE state, the response is held and may be 888 overwritten, but it MUST be eventually produced and it carries the 889 result of the DAD process; 891 older registrations (not(newer or equal) TID, same OUID) from a 892 same Registering Node are ignored; 894 identical and older registrations (not-newer TID, same OUID) from 895 a different Registering Node are responded immediately with a 896 status of 3 (moved); this may be rate limited to protect the 897 medium; 899 and any registration for a different Registered Node (different 900 OUID) are responded immediately with a status of 1 (duplicate). 902 7.1. Registration and Binding State Creation 904 Upon a registration for a new address with an NS(EARO), the 6BBR 905 performs a DAD operation over the backbone placing the new address as 906 target in the NS-DAD message. The EARO from the registration MUST be 907 placed unchanged in the NS-DAD message, and an entry is created in 908 TENTATIVE state for a duration of TENTATIVE_DURATION. The NS-DAD 909 message is sent multicast over the backbone to the SNMA address 910 associated with the registered address. If that operation is known 911 to be costly, and the 6BBR has an indication from another source 912 (such as a NCE) that the Registered Address was present on the 913 backbone, that information may be leveraged to send the NS-DAD 914 message as a Layer-2 unicast to the MAC that was associated with the 915 Registered Address. 917 In TENTATIVE state: 919 o the entry is removed if an NA is received over the backbone for 920 the Registered Address with no EARO option, or with an EARO option 921 with a status of 1 (duplicate) that indicates an existing 922 registration for another LLN node. The OUID and TID fields in the 923 EARO option received over the backbone are ignored. A status of 1 924 is returned in the EARO option of the NA back to the Registering 925 Node; 927 o the entry is also removed if an NA with an ARO option with a 928 status of 3 (moved), or a NS-DAD with an ARO option that indicates 929 a newer registration for the same Registered Node, is received 930 over the backbone for the Registered Address. A status of 3 is 931 returned in the NA(EARO) back to the Registering Node; 933 o when a registration is updated but not deleted, e.g. from a newer 934 registration, the DAD process on the backbone continues and the 935 running timers are not restarted; 937 o Other NS (including DAD with no EARO option) and NA from the 938 backbone are not responded in TENTATIVE state, but the list of 939 their origins may be kept in memory and if so, the 6BBR may send 940 them each a unicast NA with eventually an EARO option when the 941 TENTATIVE_DURATION timer elapses, so as to cover legacy nodes that 942 do not support ODAD. 944 o When the TENTATIVE_DURATION timer elapses, a status 0 (success) is 945 returned in a NA(EARO) back to the Registering Node(s), and the 946 entry goes to REACHABLE state for the Registration Lifetime; the 947 DAD process is successful and the 6BBR MUST send a multicast 948 NA(EARO) to the SNMA associated to the Registered Address over the 949 backbone with the Override bit set so as to take over the binding 950 from other 6BBRs. 952 7.2. Defending Addresses 954 If a 6BBR has an entry in REACHABLE state for a Registered Address: 956 o If the 6BBR is primary, or does not support the concept, it MUST 957 defend that address over the backbone upon an incoming NS-DAD, 958 either if the NS does not carry an EARO, or if an EARO is present 959 that indicates a different Registering Node (different OUID). The 960 6BBR sends a NA message with the Override bit set and the NA 961 carries an EARO option if and only if the NS-DAD did so. When 962 present, the EARO in the NA(O) that is sent in response to the NS- 963 DAD(EARO) carries a status of 1 (duplicate), and the OUID and TID 964 fields in the EARO option are obfuscated with null or random 965 values to avoid network scanning and impersonation attacks. 967 o If the 6BBR receives an NS-DAD(EARO) that reflect a newer 968 registration, the 6BBR updates the entry and the routing state to 969 forward packets to the new 6BBR, but keeps the entry REACHABLE. 970 In that phase, it MAY use REDIRECT messages to reroute traffic for 971 the Registered Address to the new 6BBR. 973 o If the 6BBR receives an NA(EARO) that reflect a newer 974 registration, the 6BBR removes its entry and sends a NA(AERO) with 975 a status of 3 (moved) to the Registering Node, if the Registering 976 Node is different from the Registered Node. If necessary, the 977 6BBR cleans up ND cache in peers nodes as discussed in 978 Section 6.1, by sending a series of unicast to the impacted nodes, 979 or one broadcast NA(O) to all-nodes. 981 o If the 6BBR received a NS(LOOKUP) for a Registered Address, it 982 answers immediately with an NA on behalf of the Registered Node, 983 without polling it. There is no need of an EARO in that exchange. 985 o When the Registration-Lifetime timer elapses, the entry goes to 986 STALE state for a duration of STABLE_STALE_DURATION in LLNs that 987 keep stable addresses such as LWPANs, and UNSTABLE_STALE_DURATION 988 in LLNs where addresses are renewed rapidly, e.g. for privacy 989 reasons. 991 The STALE state is a chance to keep track of the backbone peers that 992 may have an ND cache pointing on this 6BBR in case the Registered 993 Address shows back up on this or a different 6BBR at a later time. 994 In STALE state: 996 o If the Registered Address is claimed by another node on the 997 backbone, with an NS-DAD or an NA, the 6BBR does not defend the 998 address. Upon an NA(O), or the stale time elapses, the 6BBR 999 removes its entry and sends a NA(AERO) with a status of 4 1000 (removed) to the Registering Node. 1002 o If the 6BBR received a NS(LOOKUP) for a Registered Address, the 1003 6BBR MUST send an NS(NUD) following rules in [RFC7048] to the 1004 registering Node targeting the Registered Address prior to 1005 answering. If the NUD succeeds, the operation in REACHABLE state 1006 applies. If the NUD fails, the 6BBR refrains from answering the 1007 lookup. The NUD expected to be mapped by the Registering Node 1008 into a liveliness validation of the Registered Node if they are in 1009 fact different nodes. 1011 8. Security Considerations 1013 This specification expects that the link layer is sufficiently 1014 protected, either by means of physical or IP security for the 1015 Backbone Link or MAC sublayer cryptography. In particular, it is 1016 expected that the LLN MAC provides secure unicast to/from the 1017 Backbone Router and secure Broadcast from the Backbone Router in a 1018 way that prevents tempering with or replaying the RA messages. 1020 The use of EUI-64 for forming the Interface ID in the link local 1021 address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and 1022 address privacy techniques. This specification RECOMMENDS the use of 1023 additional protection against address theft such as provided by 1024 [I-D.sarikaya-6lo-ap-nd], which guarantees the ownership of the OUID. 1026 When the ownership of the OUID cannot be assessed, this specification 1027 limits the cases where the OUID and the TID are multicasted, and 1028 obfuscates them in responses to attempts to take over an address. 1030 9. Protocol Constants 1032 This Specification uses the following constants: 1034 TENTATIVE_DURATION: 800 milliseconds 1036 STABLE_STALE_DURATION: 24 hours 1038 UNSTABLE_STALE_DURATION: 5 minutes 1040 DEFAULT_NS_POLLING: 3 times 1042 10. IANA Considerations 1044 This document requires the following additions: 1046 Address Registration Option Status Values Registry 1048 +--------+----------------------------------------------------------+ 1049 | Status | Description | 1050 +--------+----------------------------------------------------------+ 1051 | 3 | Moved: The registration fails because it is not the | 1052 | | freshest. | 1053 | | | 1054 | 4 | Removed: The binding state was removed | 1055 +--------+----------------------------------------------------------+ 1057 IANA is required to change the registry accordingly 1059 Table 1: New ARO Status values 1061 11. Acknowledgments 1063 Kudos to Eric Levy-Abegnoli who designed the First Hop Security 1064 infrastructure at Cisco. 1066 12. References 1068 12.1. Normative References 1070 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1071 Requirement Levels", BCP 14, RFC 2119, 1072 DOI 10.17487/RFC2119, March 1997, 1073 . 1075 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1076 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 1077 December 1998, . 1079 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1080 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1081 2006, . 1083 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 1084 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 1085 . 1087 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1088 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1089 DOI 10.17487/RFC4861, September 2007, 1090 . 1092 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1093 Address Autoconfiguration", RFC 4862, 1094 DOI 10.17487/RFC4862, September 2007, 1095 . 1097 [RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for 1098 Detecting Network Attachment in IPv6", RFC 6059, 1099 DOI 10.17487/RFC6059, November 2010, 1100 . 1102 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1103 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1104 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1105 Low-Power and Lossy Networks", RFC 6550, 1106 DOI 10.17487/RFC6550, March 2012, 1107 . 1109 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1110 Bormann, "Neighbor Discovery Optimization for IPv6 over 1111 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1112 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1113 . 1115 12.2. Informative References 1117 [I-D.chakrabarti-nordmark-6man-efficient-nd] 1118 Chakrabarti, S., Nordmark, E., Thubert, P., and M. 1119 Wasserman, "IPv6 Neighbor Discovery Optimizations for 1120 Wired and Wireless Networks", draft-chakrabarti-nordmark- 1121 6man-efficient-nd-07 (work in progress), February 2015. 1123 [I-D.delcarpio-6lo-wlanah] 1124 Vega, L., Robles, I., and R. Morabito, "IPv6 over 1125 802.11ah", draft-delcarpio-6lo-wlanah-01 (work in 1126 progress), October 2015. 1128 [I-D.ietf-6lo-6lobac] 1129 Lynn, K., Martocci, J., Neilson, C., and S. Donaldson, 1130 "Transmission of IPv6 over MS/TP Networks", draft-ietf- 1131 6lo-6lobac-03 (work in progress), October 2015. 1133 [I-D.ietf-6lo-btle] 1134 Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., 1135 Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low 1136 Energy", draft-ietf-6lo-btle-17 (work in progress), August 1137 2015. 1139 [I-D.ietf-6lo-dect-ule] 1140 Mariager, P., Petersen, J., Shelby, Z., Logt, M., and D. 1141 Barthel, "Transmission of IPv6 Packets over DECT Ultra Low 1142 Energy", draft-ietf-6lo-dect-ule-03 (work in progress), 1143 September 2015. 1145 [I-D.ietf-6lo-nfc] 1146 Youn, J. and Y. Hong, "Transmission of IPv6 Packets over 1147 Near Field Communication", draft-ietf-6lo-nfc-02 (work in 1148 progress), October 2015. 1150 [I-D.ietf-6tisch-architecture] 1151 Thubert, P., "An Architecture for IPv6 over the TSCH mode 1152 of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work 1153 in progress), November 2015. 1155 [I-D.ietf-6tisch-terminology] 1156 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 1157 "Terminology in IPv6 over the TSCH mode of IEEE 1158 802.15.4e", draft-ietf-6tisch-terminology-06 (work in 1159 progress), November 2015. 1161 [I-D.ietf-bier-architecture] 1162 Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and 1163 S. Aldrin, "Multicast using Bit Index Explicit 1164 Replication", draft-ietf-bier-architecture-02 (work in 1165 progress), July 2015. 1167 [I-D.ietf-ipv6-multilink-subnets] 1168 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 1169 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 1170 progress), July 2002. 1172 [I-D.ietf-roll-terminology] 1173 Vasseur, J., "Terms used in Routing for Low power And 1174 Lossy Networks", draft-ietf-roll-terminology-13 (work in 1175 progress), October 2013. 1177 [I-D.ietf-v6ops-reducing-ra-energy-consumption] 1178 Yourtchenko, A. and L. Colitti, "Reducing energy 1179 consumption of Router Advertisements", draft-ietf-v6ops- 1180 reducing-ra-energy-consumption-03 (work in progress), 1181 November 2015. 1183 [I-D.nordmark-6man-dad-approaches] 1184 Nordmark, E., "Possible approaches to make DAD more robust 1185 and/or efficient", draft-nordmark-6man-dad-approaches-02 1186 (work in progress), October 2015. 1188 [I-D.nordmark-6man-rs-refresh] 1189 Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6 1190 Neighbor Discovery Optional Unicast RS/RA Refresh", draft- 1191 nordmark-6man-rs-refresh-01 (work in progress), October 1192 2014. 1194 [I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] 1195 Popa, D. and J. Hui, "6LoPLC: Transmission of IPv6 Packets 1196 over IEEE 1901.2 Narrowband Powerline Communication 1197 Networks", draft-popa-6lo-6loplc-ipv6-over- 1198 ieee19012-networks-00 (work in progress), March 2014. 1200 [I-D.sarikaya-6lo-ap-nd] 1201 Sarikaya, B. and P. Thubert, "Address Protected Neighbor 1202 Discovery for Low-power and Lossy Networks", draft- 1203 sarikaya-6lo-ap-nd-01 (work in progress), October 2015. 1205 [I-D.vyncke-6man-mcast-not-efficient] 1206 Vyncke, E., Thubert, P., Levy-Abegnoli, E., and A. 1207 Yourtchenko, "Why Network-Layer Multicast is Not Always 1208 Efficient At Datalink Layer", draft-vyncke-6man-mcast-not- 1209 efficient-01 (work in progress), February 2014. 1211 [I-D.yourtchenko-6man-dad-issues] 1212 Yourtchenko, A. and E. Nordmark, "A survey of issues 1213 related to IPv6 Duplicate Address Detection", draft- 1214 yourtchenko-6man-dad-issues-01 (work in progress), March 1215 2015. 1217 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1218 C., and M. Carney, "Dynamic Host Configuration Protocol 1219 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1220 2003, . 1222 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1223 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1224 DOI 10.17487/RFC3810, June 2004, 1225 . 1227 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1228 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1229 DOI 10.17487/RFC3971, March 2005, 1230 . 1232 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1233 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1234 . 1236 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 1237 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 1238 2006, . 1240 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 1241 DOI 10.17487/RFC4903, June 2007, 1242 . 1244 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1245 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1246 Overview, Assumptions, Problem Statement, and Goals", 1247 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1248 . 1250 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1251 Ed., "Control And Provisioning of Wireless Access Points 1252 (CAPWAP) Protocol Specification", RFC 5415, 1253 DOI 10.17487/RFC5415, March 2009, 1254 . 1256 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1257 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1258 2011, . 1260 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1261 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1262 DOI 10.17487/RFC6282, September 2011, 1263 . 1265 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 1266 Locator/ID Separation Protocol (LISP)", RFC 6830, 1267 DOI 10.17487/RFC6830, January 2013, 1268 . 1270 [RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability 1271 Detection Is Too Impatient", RFC 7048, 1272 DOI 10.17487/RFC7048, January 2014, 1273 . 1275 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 1276 Interface Identifiers with IPv6 Stateless Address 1277 Autoconfiguration (SLAAC)", RFC 7217, 1278 DOI 10.17487/RFC7217, April 2014, 1279 . 1281 [RFC7428] Brandt, A. and J. Buron, "Transmission of IPv6 Packets 1282 over ITU-T G.9959 Networks", RFC 7428, 1283 DOI 10.17487/RFC7428, February 2015, 1284 . 1286 [RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss 1287 Resiliency for Router Solicitations", RFC 7559, 1288 DOI 10.17487/RFC7559, May 2015, 1289 . 1291 12.3. External Informative References 1293 [IEEE80211] 1294 IEEE standard for Information Technology, "IEEE Standard 1295 for Information technology-- Telecommunications and 1296 information exchange between systems Local and 1297 metropolitan area networks-- Specific requirements Part 1298 11: Wireless LAN Medium Access Control (MAC) and Physical 1299 Layer (PHY) Specifications". 1301 [IEEE802151] 1302 IEEE standard for Information Technology, "IEEE Standard 1303 for Information Technology - Telecommunications and 1304 Information Exchange Between Systems - Local and 1305 Metropolitan Area Networks - Specific Requirements. - Part 1306 15.1: Wireless Medium Access Control (MAC) and Physical 1307 Layer (PHY) Specifications for Wireless Personal Area 1308 Networks (WPANs)". 1310 [IEEE802154] 1311 IEEE standard for Information Technology, "IEEE Standard 1312 for Local and metropolitan area networks-- Part 15.4: Low- 1313 Rate Wireless Personal Area Networks (LR-WPANs)". 1315 Appendix A. Requirements 1317 This section lists requirements that were discussed at 6lo for an 1318 update to 6LoWPAN ND. This specification meets most of them, but 1319 those listed in Appendix A.5 which are deferred to a different 1320 specification such as [I-D.sarikaya-6lo-ap-nd]. 1322 A.1. Requirements Related to Mobility 1324 Due to the unstable nature of LLN links, even in a LLN of immobile 1325 nodes a 6LoWPAN Node may change its point of attachment to a 6LR, say 1326 6LR-a, and may not be able to notify 6LR-a. Consequently, 6LR-a may 1327 still attract traffic that it cannot deliver any more. When links to 1328 a 6LR change state, there is thus a need to identify stale states in 1329 a 6LR and restore reachability in a timely fashion. 1331 Req1.1: Upon a change of point of attachment, connectivity via a new 1332 6LR MUST be restored timely without the need to de-register from the 1333 previous 6LR. 1335 Req1.2: For that purpose, the protocol MUST enable to differentiate 1336 between multiple registrations from one 6LoWPAN Node and 1337 registrations from different 6LoWPAN Nodes claiming the same address. 1339 Req1.3: Stale states MUST be cleaned up in 6LRs. 1341 Req1.4: A 6LoWPAN Node SHOULD also be capable to register its Address 1342 to multiple 6LRs, and this, concurrently. 1344 A.2. Requirements Related to Routing Protocols 1346 The point of attachment of a 6LoWPAN Node may be a 6LR in an LLN 1347 mesh. IPv6 routing in a LLN can be based on RPL, which is the 1348 routing protocol that was defined at the IETF for this particular 1349 purpose. Other routing protocols than RPL are also considered by 1350 Standard Defining Organizations (SDO) on the basis of the expected 1351 network characteristics. It is required that a 6LoWPAN Node attached 1352 via ND to a 6LR would need to participate in the selected routing 1353 protocol to obtain reachability via the 6LR. 1355 Next to the 6LBR unicast address registered by ND, other addresses 1356 including multicast addresses are needed as well. For example a 1357 routing protocol often uses a multicast address to register changes 1358 to established paths. ND needs to register such a multicast address 1359 to enable routing concurrently with discovery. 1361 Multicast is needed for groups. Groups MAY be formed by device type 1362 (e.g. routers, street lamps), location (Geography, RPL sub-tree), or 1363 both. 1365 The Bit Index Explicit Replication (BIER) Architecture 1366 [I-D.ietf-bier-architecture] proposes an optimized technique to 1367 enable multicast in a LLN with a very limited requirement for routing 1368 state in the nodes. 1370 Related requirements are: 1372 Req2.1: The ND registration method SHOULD be extended in such a 1373 fashion that the 6LR MAY advertise the Address of a 6LoWPAN Node over 1374 the selected routing protocol and obtain reachability to that Address 1375 using the selected routing protocol. 1377 Req2.2: Considering RPL, the Address Registration Option that is used 1378 in the ND registration SHOULD be extended to carry enough information 1379 to generate a DAO message as specified in [RFC6550] section 6.4, in 1380 particular the capability to compute a Path Sequence and, as an 1381 option, a RPLInstanceID. 1383 Req2.3: Multicast operations SHOULD be supported and optimized, for 1384 instance using BIER or MPL. Whether ND is appropriate for the 1385 registration to the 6BBR is to be defined, considering the additional 1386 burden of supporting the Multicast Listener Discovery Version 2 1387 [RFC3810] (MLDv2) for IPv6. 1389 A.3. Requirements Related to the Variety of Low-Power Link types 1391 6LoWPAN ND [RFC6775] was defined with a focus on IEEE802.15.4 and in 1392 particular the capability to derive a unique Identifier from a 1393 globally unique MAC-64 address. At this point, the 6lo Working Group 1394 is extending the 6LoWPAN Header Compression (HC) [RFC6282] technique 1395 to other link types ITU-T G.9959 [RFC7428], Master-Slave/Token- 1396 Passing [I-D.ietf-6lo-6lobac], DECT Ultra Low Energy 1397 [I-D.ietf-6lo-dect-ule], Near Field Communication [I-D.ietf-6lo-nfc], 1398 IEEE802.11ah [I-D.delcarpio-6lo-wlanah], as well as IEEE1901.2 1399 Narrowband Powerline Communication Networks 1400 [I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] and BLUETOOTH(R) 1401 Low Energy [I-D.ietf-6lo-btle]. 1403 Related requirements are: 1405 Req3.1: The support of the registration mechanism SHOULD be extended 1406 to more LLN links than IEEE 802.15.4, matching at least the LLN links 1407 for which an "IPv6 over foo" specification exists, as well as Low- 1408 Power Wi-Fi. 1410 Req3.2: As part of this extension, a mechanism to compute a unique 1411 Identifier should be provided, with the capability to form a Link- 1412 Local Address that SHOULD be unique at least within the LLN connected 1413 to a 6LBR discovered by ND in each node within the LLN. 1415 Req3.3: The Address Registration Option used in the ND registration 1416 SHOULD be extended to carry the relevant forms of unique Identifier. 1418 Req3.4: The Neighbour Discovery should specify the formation of a 1419 site-local address that follows the security recommendations from 1420 [RFC7217]. 1422 A.4. Requirements Related to Proxy Operations 1424 Duty-cycled devices may not be able to answer themselves to a lookup 1425 from a node that uses classical ND on a backbone and may need a 1426 proxy. Additionally, the duty-cycled device may need to rely on the 1427 6LBR to perform registration to the 6BBR. 1429 The ND registration method SHOULD defend the addresses of duty-cycled 1430 devices that are sleeping most of the time and not capable to defend 1431 their own Addresses. 1433 Related requirements are: 1435 Req4.1: The registration mechanism SHOULD enable a third party to 1436 proxy register an Address on behalf of a 6LoWPAN node that may be 1437 sleeping or located deeper in an LLN mesh. 1439 Req4.2: The registration mechanism SHOULD be applicable to a duty- 1440 cycled device regardless of the link type, and enable a 6BBR to 1441 operate as a proxy to defend the registered Addresses on its behalf. 1443 Req4.3: The registration mechanism SHOULD enable long sleep 1444 durations, in the order of multiple days to a month. 1446 A.5. Requirements Related to Security 1448 In order to guarantee the operations of the 6LoWPAN ND flows, the 1449 spoofing of the 6LR, 6LBR and 6BBRs roles should be avoided. Once a 1450 node successfully registers an address, 6LoWPAN ND should provide 1451 energy-efficient means for the 6LBR to protect that ownership even 1452 when the node that registered the address is sleeping. 1454 In particular, the 6LR and the 6LBR then should be able to verify 1455 whether a subsequent registration for a given Address comes from the 1456 original node. 1458 In a LLN it makes sense to base security on layer-2 security. During 1459 bootstrap of the LLN, nodes join the network after authorization by a 1460 Joining Assistant (JA) or a Commissioning Tool (CT). After joining 1461 nodes communicate with each other via secured links. The keys for 1462 the layer-2 security are distributed by the JA/CT. The JA/CT can be 1463 part of the LLN or be outside the LLN. In both cases it is needed 1464 that packets are routed between JA/CT and the joining node. 1466 Related requirements are: 1468 Req5.1: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1469 the 6LR, 6LBR and 6BBR to authenticate and authorize one another for 1470 their respective roles, as well as with the 6LoWPAN Node for the role 1471 of 6LR. 1473 Req5.2: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1474 the 6LR and the 6LBR to validate new registration of authorized 1475 nodes. Joining of unauthorized nodes MUST be impossible. 1477 Req5.3: 6LoWPAN ND security mechanisms SHOULD lead to small packet 1478 sizes. In particular, the NS, NA, DAR and DAC messages for a re- 1479 registration flow SHOULD NOT exceed 80 octets so as to fit in a 1480 secured IEEE802.15.4 frame. 1482 Req5.4: Recurrent 6LoWPAN ND security operations MUST NOT be 1483 computationally intensive on the LoWPAN Node CPU. When a Key hash 1484 calculation is employed, a mechanism lighter than SHA-1 SHOULD be 1485 preferred. 1487 Req5.5: The number of Keys that the 6LoWPAN Node needs to manipulate 1488 SHOULD be minimized. 1490 Req5.6: The 6LoWPAN ND security mechanisms SHOULD enable CCM* for use 1491 at both Layer 2 and Layer 3, and SHOULD enable the reuse of security 1492 code that has to be present on the device for upper layer security 1493 such as TLS. 1495 Req5.7: Public key and signature sizes SHOULD be minimized while 1496 maintaining adequate confidentiality and data origin authentication 1497 for multiple types of applications with various degrees of 1498 criticality. 1500 Req5.8: Routing of packets should continue when links pass from the 1501 unsecured to the secured state. 1503 Req5.9: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for 1504 the 6LR and the 6LBR to validate whether a new registration for a 1505 given address corresponds to the same 6LoWPAN Node that registered it 1506 initially, and, if not, determine the rightful owner, and deny or 1507 clean-up the registration that is duplicate. 1509 A.6. Requirements Related to Scalability 1511 Use cases from Automatic Meter Reading (AMR, collection tree 1512 operations) and Advanced Metering Infrastructure (AMI, bi-directional 1513 communication to the meters) indicate the needs for a large number of 1514 LLN nodes pertaining to a single RPL DODAG (e.g. 5000) and connected 1515 to the 6LBR over a large number of LLN hops (e.g. 15). 1517 Related requirements are: 1519 Req6.1: The registration mechanism SHOULD enable a single 6LBR to 1520 register multiple thousands of devices. 1522 Req6.2: The timing of the registration operation should allow for a 1523 large latency such as found in LLNs with ten and more hops. 1525 Author's Address 1527 Pascal Thubert (editor) 1528 Cisco Systems, Inc 1529 Building D 1530 45 Allee des Ormes - BP1200 1531 MOUGINS - Sophia Antipolis 06254 1532 FRANCE 1534 Phone: +33 497 23 26 34 1535 Email: pthubert@cisco.com