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Darroudi 4 Intended status: Standards Track Universitat Politecnica de Catalunya 5 Expires: June 16, 2020 T. Savolainen 6 DarkMatter 7 M. Spoerk 8 Graz University of Technology 9 December 14, 2019 11 IPv6 Mesh over BLUETOOTH(R) Low Energy using IPSP 12 draft-ietf-6lo-blemesh-07 14 Abstract 16 RFC 7668 describes the adaptation of 6LoWPAN techniques to enable 17 IPv6 over Bluetooth low energy networks that follow the star 18 topology. However, recent Bluetooth specifications allow the 19 formation of extended topologies as well. This document specifies 20 mechanisms that are needed to enable IPv6 mesh over Bluetooth Low 21 Energy links established by using the Bluetooth Internet Protocol 22 Support Profile. This document does not specify the routing protocol 23 to be used in an IPv6 mesh over Bluetooth LE links. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on June 16, 2020. 42 Copyright Notice 44 Copyright (c) 2019 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 1.1. Terminology and Requirements Language . . . . . . . . . . 3 61 2. Bluetooth LE Networks and the IPSP . . . . . . . . . . . . . 3 62 3. Specification of IPv6 mesh over Bluetooth LE links . . . . . 4 63 3.1. Protocol stack . . . . . . . . . . . . . . . . . . . . . 4 64 3.2. Subnet model . . . . . . . . . . . . . . . . . . . . . . 5 65 3.3. Link model . . . . . . . . . . . . . . . . . . . . . . . 6 66 3.3.1. Stateless address autoconfiguration . . . . . . . . . 6 67 3.3.2. Neighbor Discovery . . . . . . . . . . . . . . . . . 6 68 3.3.3. Header compression . . . . . . . . . . . . . . . . . 7 69 3.3.4. Unicast and multicast mapping . . . . . . . . . . . . 8 70 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 72 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 73 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 74 8. Appendix A: Bluetooth LE connection establishment example . . 10 75 9. Appendix B: Node joining procedure . . . . . . . . . . . . . 12 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 77 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 78 10.2. Informative References . . . . . . . . . . . . . . . . . 14 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 81 1. Introduction 83 Bluetooth Low Energy (hereinafter, Bluetooth LE) was first introduced 84 in the Bluetooth 4.0 specification. Bluetooth LE (which has been 85 marketed as Bluetooth Smart) is a low-power wireless technology 86 designed for short-range control and monitoring applications. 87 Bluetooth LE is currently implemented in a wide range of consumer 88 electronics devices, such as smartphones and wearable devices. Given 89 the high potential of this technology for the Internet of Things, the 90 Bluetooth Special Interest Group (Bluetooth SIG) and the IETF have 91 produced specifications in order to enable IPv6 over Bluetooth LE, 92 such as the Internet Protocol Support Profile (IPSP) [IPSP], and RFC 93 7668, respectively. Bluetooth 4.0 only supports Bluetooth LE 94 networks that follow the star topology. In consequence, RFC 7668 was 95 specifically developed and optimized for that type of network 96 topology. However, the functionality described in RFC 7668 is not 97 sufficient and would fail to enable an IPv6 mesh over Bluetooth LE 98 links. This document specifies mechanisms that are needed to enable 99 IPv6 mesh over Bluetooth LE links. This document does not specify 100 the routing protocol to be used in an IPv6 mesh over Bluetooth LE 101 links. 103 1.1. Terminology and Requirements Language 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 107 document are to be interpreted as described in RFC 2119 [RFC2119]. 109 The terms 6LoWPAN Node (6LN), 6LoWPAN Router (6LR) and 6LoWPAN Border 110 Router (6LBR) are defined as in [RFC6775], with an addition that 111 Bluetooth LE central and Bluetooth LE peripheral (see Section 2) can 112 both be adopted by a 6LN, a 6LR or a 6LBR. 114 2. Bluetooth LE Networks and the IPSP 116 Bluetooth LE defines two Generic Access Profile (GAP) roles of 117 relevance herein: the Bluetooth LE central role and the Bluetooth LE 118 peripheral role. A device in the central role, which is called 119 central from now on, has traditionally been able to manage multiple 120 simultaneous connections with a number of devices in the peripheral 121 role, called peripherals hereinafter. Bluetooth 4.1 (now deprecated) 122 introduced the possibility for a peripheral to be connected to more 123 than one central simultaneously, therefore allowing extended 124 topologies beyond the star topology for a Bluetooth LE network. In 125 addition, a device may simultaneously be a central in a set of link 126 layer connections, as well as a peripheral in others. On the other 127 hand, the IPSP enables discovery of IP-enabled devices and the 128 establishment of a link layer connection for transporting IPv6 129 packets. The IPSP defines the Node and Router roles for devices that 130 consume/originate IPv6 packets and for devices that can route IPv6 131 packets, respectively. Consistently with Bluetooth 4.1 and 132 subsequent Bluetooth versions (e.g. Bluetooth 4.2 [BTCorev4.2] or 133 subsequent), a device may implement both roles simultaneously. 135 This document assumes a mesh network composed of Bluetooth LE links, 136 where link layer connections are established between neighboring 137 IPv6-enabled devices (see Section 3.3.2, item 3.b)). The IPv6 138 forwarding devices of the mesh have to implement both IPSP Node and 139 Router roles, while simpler leaf-only nodes can implement only the 140 Node role. In an IPv6 mesh over Bluetooth LE links, a node is a 141 neighbor of another node, and vice versa, if a link layer connection 142 has been established between both by using the IPSP functionality for 143 discovery and link layer connection establishment for IPv6 packet 144 transport. 146 3. Specification of IPv6 mesh over Bluetooth LE links 148 3.1. Protocol stack 150 Figure 1 illustrates the protocol stack for IPv6 mesh over Bluetooth 151 LE links. There are two main differences with the IPv6 over 152 Bluetooth LE stack in RFC 7668: a) the adaptation layer below IPv6 153 (labelled as "6Lo for IPv6 mesh over Bluetooth LE") is now adapted 154 for IPv6 mesh over Bluetooth LE links, and b) the protocol stack for 155 IPv6 mesh over Bluetooth LE links includes IPv6 routing 156 functionality. 158 +------------------------------------+ 159 | Application | 160 +---------+ +------------------------------------+ 161 | IPSS | | UDP/TCP/other | 162 +---------+ +------------------------------------+ 163 | GATT | | IPv6 |routing| | 164 +---------+ +------------------------------------+ 165 | ATT | | 6Lo for IPv6 mesh over Bluetooh LE | 166 +---------+--+------------------------------------+ 167 | Bluetooth LE L2CAP | 168 - - +-------------------------------------------------+- - - HCI 169 | Bluetooth LE Link Layer | 170 +-------------------------------------------------+ 171 | Bluetooth LE Physical | 172 +-------------------------------------------------+ 174 Figure 1: Protocol stack for IPv6 mesh over Bluetooth LE links. 176 Bluetooth 4.2 defines a default MTU for Bluetooth LE of 251 bytes. 177 Excluding the L2CAP header of 4 bytes, a protocol data unit (PDU) 178 size of 247 bytes is available for the layer above L2CAP. (Note: 179 earlier Bluetooth LE versions offered a maximum amount of 23 bytes 180 for the layer atop L2CAP.) The L2CAP provides a fragmentation and 181 reassembly solution for transmitting or receiving larger PDUs. At 182 each link, the IPSP defines means for negotiating a link-layer 183 connection that provides an MTU of 1280 octets or higher for the IPv6 184 layer [IPSP]. The link-layer MTU is negotiated separately for each 185 direction. Implementations that require an equal link-layer MTU for 186 the two directions SHALL use the smallest of the possibly different 187 MTU values. 189 Note that this specification allows using different MTUs in different 190 links. If an implementation requires use of the same MTU on every 191 one of its links, and a new node with a smaller MTU is added to the 192 network, a renegotiation of one or more links can occur. In the 193 worst case, the renegotiations could cascade network-wide. In that 194 case, implementers need to assess the impact of such phenomenon. 196 Similarly to RFC 7668, fragmentation functionality from 6LoWPAN 197 standards is not used for IPv6 mesh over Bluetooth LE links. 198 Bluetooth LE's fragmentation support provided by L2CAP is used when 199 necessary. 201 3.2. Subnet model 203 For IPv6 mesh over Bluetooth LE links, a multilink model has been 204 chosen, as further illustrated in Figure 2. As IPv6 over Bluetooth 205 LE is intended for constrained nodes, and for Internet of Things use 206 cases and environments, the complexity of implementing a separate 207 subnet on each peripheral-central link and routing between the 208 subnets appears to be excessive. In this specification, the benefits 209 of treating the collection of point-to-point links between a central 210 and its connected peripherals as a single multilink subnet rather 211 than a multiplicity of separate subnets are considered to outweigh 212 the multilink model's drawbacks as described in [RFC4903]. 214 / 215 .--------------------------------. / 216 / 6LR 6LN 6LN \ / 217 / \ \ \ \ / 218 | \ \ \ | / 219 | 6LN ----- 6LR --------- 6LR ------ 6LBR ----- | Internet 220 | <--Link--> <---Link--->/<--Link->/ | | 221 \ / / / \ 222 \ 6LN ---- 6LR ----- 6LR / \ 223 '--------------------------------' \ 224 \ 226 <------------ Subnet -----------------><---- IPv6 connection --> 227 to the Internet 229 Figure 2: Example of an IPv6 mesh over a Bluetooth LE network 230 connected to the Internet 232 One or more 6LBRs are connected to the Internet. 6LNs are connected 233 to the network through a 6LR or a 6LBR. A prefix is used on the 234 whole subnet. 236 IPv6 mesh over Bluetooth LE links MUST follow a route-over approach. 237 This document does not specify the routing protocol to be used in an 238 IPv6 mesh over Bluetooth LE links. 240 3.3. Link model 242 3.3.1. Stateless address autoconfiguration 244 6LN, 6LR and 6LBR IPv6 addresses in an IPv6 mesh over Bluetooth LE 245 links are configured as per section 3.2.2 of RFC 7668. 247 Multihop DAD functionality as defined in section 8.2 of RFC 6775 and 248 updated by RFC 8505, or some substitute mechanism (see section 249 3.3.2), MAY be supported. 251 3.3.2. Neighbor Discovery 253 'Neighbor Discovery Optimization for IPv6 over Low-Power Wireless 254 Personal Area Networks (6LoWPANs)' [RFC6775], subsequently updated by 255 'Registration Extensions for IPv6 over Low-Power Wireless Personal 256 Area Network (6LoWPAN) Neighbor Discovery' [RFC8505], describes the 257 neighbor discovery functionality adapted for use in several 6LoWPAN 258 topologies, including the mesh topology. The route-over 259 functionality of RFC 6775 and RFC 8505 MUST be supported. 261 The following aspects of the Neighbor Discovery optimizations for 262 6LoWPAN [RFC6775],[RFC8505] are applicable to Bluetooth LE 6LNs: 264 1. A Bluetooth LE 6LN SHOULD register its non-link-local addresses 265 with its routers by sending a Neighbor Solicitation (NS) message with 266 the Extended Address Registration Option (EARO) and process the 267 Neighbor Advertisement (NA) accordingly. Note that in some cases 268 (e.g. very short-lived connections) it may not be worthwhile for a 269 6LN to send an NS with EARO for registering its address. The EARO 270 option includes a Registration Ownership Verifier (ROVR) field 271 [RFC8505]. In the case of Bluetooth LE, by default the ROVR field is 272 filled with the 48-bit device address used by the Bluetooth LE node 273 converted into 64-bit Modified EUI-64 format [RFC4291]. Optionally, 274 a cryptographic ID (see [I-D.ietf-6lo-ap-nd] MAY be placed in the 275 ROVR field. If a cryptographic ID is used, address registration and 276 multihop DAD formats and procedures defined in [I-D.ietf-6lo-ap-nd] 277 MUST be used, unless an alternative mechanism offering equivalent 278 protection is used. As per RFC 8505, a 6LN MUST NOT register its 279 link-local address. 281 If the 6LN registers for a same compression context multiple 282 addresses that are not based on Bluetooth device address, the header 283 compression efficiency will decrease. 285 2. For sending Router Solicitations and processing Router 286 Advertisements the Bluetooth LE hosts MUST, respectively, follow 287 Sections 5.3 and 5.4 of [RFC6775], and Section 5.6 of [RFC8505]. 289 3. The router behavior for 6LRs and 6LBRs is described in Section 6 290 of RFC 6775, and updated by RFC 8505. However, as per this 291 specification: a) Routers SHALL NOT use multicast NSs to discover 292 other routers' link layer addresses. b) As per section 6.2 of RFC 293 6775, in a dynamic configuration scenario, a 6LR comes up as a non- 294 router and waits to receive a Router Advertisement for configuring 295 its own interface address first, before setting its interfaces to be 296 advertising interfaces and turning into a router. In order to 297 support such operation in an IPv6 mesh over Bluetooth LE links, a 6LR 298 first uses the IPSP Node role only. Once the 6LR has established a 299 connection with another node previously running as a router, and 300 receives a Router Advertisement from that router, the 6LR configures 301 its own interface address, it turns into a router, and it runs as an 302 IPSP Router. A 6LBR uses the IPSP Router role since the 6LBR is 303 initialized. See an example in the Appendix. 305 4. Border router behavior is described in Section 7 of RFC 6775, and 306 updated by RFC 8505. 308 RFC 6775 defines substitutable mechanisms for distributing prefixes 309 and context information (section 8.1 of RFC 6775), as well as for 310 Duplicate Address Detection across a route-over 6LoWPAN (section 8.2 311 of RFC 6775). RFC 8505 updates those mechanisms and the related 312 message formats. Implementations of this specification MAY support 313 the features described in sections 8.1 and 8.2 of RFC 6775, as 314 updated by RFC 8505, unless some alternative ("substitute") from some 315 other specification is supported by the implementation. 317 3.3.3. Header compression 319 Header compression as defined in RFC 6282 [RFC6282], which specifies 320 the compression format for IPv6 datagrams on top of IEEE 802.15.4, is 321 REQUIRED as the basis for IPv6 header compression on top of Bluetooth 322 LE. All headers MUST be compressed according to RFC 6282 [RFC6282] 323 encoding formats. 325 To enable efficient header compression, when the 6LBR sends a Router 326 Advertisement it MAY include a 6LoWPAN Context Option (6CO) [RFC6775] 327 matching each address prefix advertised via a Prefix Information 328 Option (PIO) [RFC4861] for use in stateless address 329 autoconfiguration. Note that 6CO is not needed for context-based 330 compression when a single prefix is used in the network. 332 The specific optimizations of RFC 7668 for header compression, which 333 exploited the star topology and ARO (note that the latter has been 334 updated by EARO as per RFC 8505), cannot be generalized in an IPv6 335 mesh over Bluetooth LE links. Still, a subset of those optimizations 336 can be applied in some cases in such a network. These cases comprise 337 link-local interactions, non-link-local packet transmissions 338 originated by a 6LN, and non-link-local packets intended for a 6LN 339 that are originated or forwarded by a neighbor of that 6LN. For the 340 rest of packet transmissions, context-based compression MAY be used. 342 When a device transmits a packet to a neighbor, the sender MUST fully 343 elide the source IID if the source IPv6 address is the link-local 344 address based on the sender's Bluetooth device address (SAC=0, 345 SAM=11). The sender also MUST fully elide the destination IPv6 346 address if it is the link-local address based on the neighbor's 347 Bluetooth device address (DAC=0, DAM=11). 349 When a 6LN transmits a packet, with a non-link-local source address 350 that the 6LN has registered with EARO in the next-hop router for the 351 indicated prefix, the source address MUST be fully elided if it is 352 the latest address that the 6LN has registered for the indicated 353 prefix (SAC=1, SAM=11). If the source non-link-local address is not 354 the latest registered by the 6LN, then the 64 bits of the IID SHALL 355 be fully carried in-line (SAC=1, SAM=01) or if the first 48 bits of 356 the IID match with the latest address registered by the 6LN, then the 357 last 16 bits of the IID SHALL be carried in-line (SAC=1, SAM=10). 359 When a router transmits a packet to a neighboring 6LN, with a non- 360 link-local destination address, the router MUST fully elide the 361 destination IPv6 address if the destination address is the latest 362 registered by the 6LN with EARO for the indicated context (DAC=1, 363 DAM=11). If the destination address is a non-link-local address and 364 not the latest registered, then the 6LN MUST either include the IID 365 part fully in-line (DAM=01) or, if the first 48 bits of the IID match 366 to the latest registered address, then elide those 48 bits (DAM=10). 368 3.3.4. Unicast and multicast mapping 370 The Bluetooth LE Link Layer does not support multicast. Hence, 371 traffic is always unicast between two Bluetooth LE neighboring nodes. 372 If a node needs to send a multicast packet to several neighbors, it 373 has to replicate the packet and unicast it on each link. However, 374 this may not be energy efficient, and particular care must be taken 375 if the node is battery powered. A router (i.e. a 6LR or a 6LBR) MUST 376 keep track of neighboring multicast listeners, and it MUST NOT 377 forward multicast packets to neighbors that have not registered as 378 listeners for multicast groups the packets belong to. 380 4. IANA Considerations 382 There are no IANA considerations related to this document. 384 5. Security Considerations 386 The security considerations in RFC 7668 apply. 388 IPv6 mesh over Bluetooth LE links requires a routing protocol to find 389 end-to-end paths. Unfortunately, the routing protocol may generate 390 additional opportunities for threats and attacks to the network. 392 RFC 7416 [RFC 7416] provides a systematic overview of threats and 393 attacks on the IPv6 Routing Protocol for Low-Power and Lossy Networks 394 (RPL), as well as countermeasures. In that document, described 395 threats and attacks comprise threats due to failures to authenticate, 396 threats due to failure to keep routing information, threats and 397 attacks on integrity, and threats and attacks on availability. 398 Reported countermeasures comprise confidentiality attack, integrity 399 attack, and availability attack countermeasures. 401 While this specification does not state the routing protocol to be 402 used in IPv6 mesh over Bluetooth LE links, the guidance of RFC 7416 403 is useful when RPL is used in such scenarios. Furthermore, such 404 guidance may partly apply for other routing protocols as well. 406 The ROVR can be derived from the Bluetooth device address. However, 407 such a ROVR can be spoofed, and therefore, any node connected to the 408 subnet and aware of a registered-address-to-ROVR mapping could 409 perform address theft and impersonation attacks. Use of Address 410 Protected Neighbor Discovery [I-D.ietf-6lo-ap-nd] provides protection 411 against such attacks. 413 6. Contributors 415 Carlo Alberto Boano (Graz University of Technology) contributed to 416 the design and validation of this document. 418 7. Acknowledgements 420 The Bluetooth, Bluetooth Smart and Bluetooth Smart Ready marks are 421 registered trademarks owned by Bluetooth SIG, Inc. 423 The authors of this document are grateful to all RFC 7668 authors, 424 since this document borrows many concepts (albeit, with necessary 425 extensions) from RFC 7668. 427 The authors also thank Alain Michaud, Mark Powell, Martin Turon, 428 Bilhanan Silverajan, Rahul Jadhav and Pascal Thubert for their 429 comments, which helped improve the document. 431 Carles Gomez has been supported in part by the Spanish Government 432 Ministerio de Economia y Competitividad through projects 433 TEC2012-32531, TEC2016-79988-P and FEDER. 435 8. Appendix A: Bluetooth LE connection establishment example 437 This appendix provides an example of Bluetooth LE connection 438 establishment and use of IPSP roles in an IPv6 mesh over Bluetooth LE 439 links that uses dynamic configuration. The example follows text in 440 Section 3.3.2, item 3.b). 442 The example assumes a network with one 6LBR, two 6LRs and three 6LNs, 443 as shown in Figure 3. Connectivity between the 6LNs and the 6LBR is 444 only possible via the 6LRs. 446 The following text describes the different steps as time evolves, in 447 the example. Note that other sequences of events that may lead to 448 the same final scenario are also possible. 450 At the beginning, the 6LBR starts running as an IPSP Router, whereas 451 the rest of devices are not yet initialized (Step 1). Next, the 6LRs 452 start running as IPSP Nodes, i.e., they use Bluetooth LE 453 advertisement packets to announce their presence and support of IPv6 454 capabilities (Step 2). The 6LBR (already running as an IPSP Router) 455 discovers the presence of the 6LRs and establishes one Bluetooth LE 456 connection with each 6LR (Step 3). After establishment of those link 457 layer connections (and after reception of Router Advertisements from 458 the 6LBR), Step 4, the 6LRs start operating as routers, and also 459 initiate the IPSP Router role (note: whether the IPSP Node role is 460 kept running simultaneously is an implementation decision). Then, 461 6LNs start running the IPSP Node role (Step 5). Finally, the 6LRs 462 discover presence of the 6LNs and establish connections with the 463 latter (Step 6). 465 Step 1 466 ****** 467 6LBR 468 (IPSP: Router) 470 6LR 6LR 471 (not initialized) (not initialized) 473 6LN 6LN 6LN 474 (not initialized) (not initialized) (not initialized) 476 Step 2 477 ****** 478 6LBR 479 (IPSP: Router) 481 6LR 6LR 482 (IPSP: Node) (IPSP: Node) 484 6LN 6LN 6LN 485 (not initialized) (not initialized) (not initialized) 487 Step 3 488 ****** 490 6LBR 491 (IPSP: Router) 492 Bluetooth LE connection --> / \ 493 / \ 494 6LR 6LR 495 (IPSP: Node) (IPSP: Node) 497 6LN 6LN 6LN 498 (not initialized) (not initialized) (not initialized) 500 Step 4 501 ****** 503 6LBR 504 (IPSP: Router) 505 / \ 506 / \ 507 6LR 6LR 508 (IPSP: Router) (IPSP: Router) 510 6LN 6LN 6LN 511 (not initialized) (not initialized) (not initialized) 513 Step 5 514 ****** 516 6LBR 517 (IPSP: Router) 518 / \ 519 / \ 520 6LR 6LR 521 (IPSP: Router) (IPSP: Router) 523 6LN 6LN 6LN 524 (IPSP: Node) (IPSP: Node) (IPSP: Node) 526 Step 6 527 ****** 529 6LBR 530 (IPSP: Router) 531 / \ 532 / \ 533 6LR 6LR 534 (IPSP: Router) (IPSP: Router) 535 / \ / \ 536 / \ / \ 537 / \ / \ 538 6LN 6LN 6LN 539 (IPSP: Node) (IPSP: Node) (IPSP: Node) 541 Figure 3: An example of connection establishment and use of IPSP 542 roles in an IPv6 mesh over Bluetooth LE links. 544 9. Appendix B: Node joining procedure 546 This appendix provides a diagram that illustrates the node joining 547 procedure. First of all, the joining node advertises its presence in 548 order to allow establishing Bluetooth LE connections with neighbors 549 that already belong to a network. The latter typically run as a 6LR 550 or as a 6LBR. After Bluetooth LE connection establishment, the 551 joining node starts acting as a 6LN. 553 Figure 4 shows the sequence of messages that are exchanged by the 6LN 554 and a neighboring 6LR that already belongs to the network, after the 555 establishment of a Bluetooth LE connection between both devices. 556 Initially, the 6LN sends an RS message (1). Then, the 6LR replies 557 with an RA, which includes the PIO (2). After discovering the non- 558 link-local prefix in use in the network, the 6LN creates its non- 559 link-local address, registers that address with EARO (3) in the 6LR, 560 and multihop DAD is performed (4). The next step is the transmission 561 of the NA message sent by the 6LR in response to the NS previously 562 sent by the 6LN (5). If the non-link-local address of the 6LN has 563 been successfully validated, the 6LN can operate as a member of the 564 network it has joined. 566 (1) 6LN ----(RS)-------> 6LR 567 (2) 6LN <---(RA-PIO)---- 6LR 568 (3) 6LN ----(NS-EARO)--> 6LR 569 (4) [Multihop DAD procedure] 570 (5) 6LN <---(NA)-------- 6LR 572 Figure 4: Message exchange diagram for a joining node 574 10. References 576 10.1. Normative References 578 [BTCorev4.2] 579 Bluetooth Special Interest Group, "Bluetooth Core 580 Specification Version 4.2", December 2014, 581 . 584 [IPSP] Bluetooth Special Interest Group, "Bluetooth Internet 585 Protocol Support Profile Specification Version 1.0.0", 586 December 2014, . 589 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 590 Requirement Levels", BCP 14, RFC 2119, 591 DOI 10.17487/RFC2119, March 1997, 592 . 594 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 595 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 596 2006, . 598 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 599 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 600 DOI 10.17487/RFC4861, September 2007, 601 . 603 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 604 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 605 DOI 10.17487/RFC6282, September 2011, 606 . 608 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 609 Bormann, "Neighbor Discovery Optimization for IPv6 over 610 Low-Power Wireless Personal Area Networks (6LoWPANs)", 611 RFC 6775, DOI 10.17487/RFC6775, November 2012, 612 . 614 [RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., 615 Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low 616 Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015, 617 . 619 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 620 Perkins, "Registration Extensions for IPv6 over Low-Power 621 Wireless Personal Area Network (6LoWPAN) Neighbor 622 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 623 . 625 10.2. Informative References 627 [BTCorev4.1] 628 Bluetooth Special Interest Group, "Bluetooth Core 629 Specification Version 4.1", December 2013, 630 . 633 [I-D.ietf-6lo-ap-nd] 634 Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 635 "Address Protected Neighbor Discovery for Low-power and 636 Lossy Networks", draft-ietf-6lo-ap-nd-12 (work in 637 progress), April 2019. 639 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 640 DOI 10.17487/RFC4903, June 2007, 641 . 643 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 644 and M. Richardson, Ed., "A Security Threat Analysis for 645 the Routing Protocol for Low-Power and Lossy Networks 646 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 647 . 649 Authors' Addresses 651 Carles Gomez 652 Universitat Politecnica de Catalunya 653 C/Esteve Terradas, 7 654 Castelldefels 08860 655 Spain 657 Email: carlesgo@entel.upc.edu 659 Seyed Mahdi Darroudi 660 Universitat Politecnica de Catalunya 661 C/Esteve Terradas, 7 662 Castelldefels 08860 663 Spain 665 Email: sm.darroudi@entel.upc.edu 667 Teemu Savolainen 668 DarkMatter LLC 670 Email: teemu.savolainen@darkmatter.ae 672 Michael Spoerk 673 Graz University of Technology 674 Inffeldgasse 16/I 675 Graz 8010 676 Austria 678 Email: michael.spoerk@tugraz.at