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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'IPSP' ** Downref: Normative reference to an Informational RFC: RFC 4541 == Outdated reference: draft-ietf-6man-default-iids has been published as RFC 8064 -- Obsolete informational reference (is this intentional?): RFC 3633 (Obsoleted by RFC 8415) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6Lo Working Group J. Nieminen 3 Internet-Draft T. Savolainen 4 Intended status: Standards Track M. Isomaki 5 Expires: July 20, 2015 Nokia 6 B. Patil 7 AT&T 8 Z. Shelby 9 Arm 10 C. Gomez 11 Universitat Politecnica de Catalunya/i2CAT 12 January 16, 2015 14 Transmission of IPv6 Packets over BLUETOOTH(R) Low Energy 15 draft-ietf-6lo-btle-07 17 Abstract 19 Bluetooth Smart is the brand name for the Bluetooth low energy 20 feature in the Bluetooth specification defined by the Bluetooth 21 Special Interest Group. The standard Bluetooth radio has been widely 22 implemented and available in mobile phones, notebook computers, audio 23 headsets and many other devices. The low power version of Bluetooth 24 is a specification that enables the use of this air interface with 25 devices such as sensors, smart meters, appliances, etc. The low 26 power variant of Bluetooth is standardized since the revision 4.0 of 27 the Bluetooth specifications, although version 4.1 or newer is 28 required for IPv6. This document describes how IPv6 is transported 29 over Bluetooth low energy using 6LoWPAN techniques. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on July 20, 2015. 48 Copyright Notice 50 Copyright (c) 2015 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 1.1. Terminology and Requirements Language . . . . . . . . . . 3 67 2. Bluetooth Low Energy . . . . . . . . . . . . . . . . . . . . 3 68 2.1. Bluetooth LE stack . . . . . . . . . . . . . . . . . . . 4 69 2.2. Link layer roles and topology . . . . . . . . . . . . . . 5 70 2.3. Bluetooth LE device addressing . . . . . . . . . . . . . 5 71 2.4. Bluetooth LE packets sizes and MTU . . . . . . . . . . . 6 72 3. Specification of IPv6 over Bluetooth Low Energy . . . . . . . 6 73 3.1. Protocol stack . . . . . . . . . . . . . . . . . . . . . 7 74 3.2. Link model . . . . . . . . . . . . . . . . . . . . . . . 7 75 3.2.1. Stateless address autoconfiguration . . . . . . . . . 8 76 3.2.2. Neighbor discovery . . . . . . . . . . . . . . . . . 9 77 3.2.3. Header compression . . . . . . . . . . . . . . . . . 10 78 3.2.3.1. Remote destination example . . . . . . . . . . . 11 79 3.2.4. Unicast and Multicast address mapping . . . . . . . . 12 80 3.3. Internet connectivity scenarios . . . . . . . . . . . . . 12 81 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 82 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 83 6. Additional contributors . . . . . . . . . . . . . . . . . . . 14 84 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 85 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 86 8.1. Normative References . . . . . . . . . . . . . . . . . . 14 87 8.2. Informative References . . . . . . . . . . . . . . . . . 15 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 90 1. Introduction 92 Bluetooth low energy (LE) is a radio technology targeted for devices 93 that operate with coin cell batteries or minimalistic power sources, 94 which means that low power consumption is essential. Bluetooth LE is 95 an especially attractive technology for Internet of Things 96 applications, such as health monitors, environmental sensing, 97 proximity applications and many others. 99 Considering the potential for the exponential growth in the number of 100 sensors and Internet connected devices and things, IPv6 is an ideal 101 protocol due to the large address space it provides. In addition, 102 IPv6 provides tools for stateless address autoconfiguration, which is 103 particularly suitable for sensor network applications and nodes which 104 have very limited processing power or lack a full-fledged operating 105 system. 107 RFC 4944 [RFC4944] specifies the transmission of IPv6 over IEEE 108 802.15.4. The Bluetooth LE link in many respects has similar 109 characteristics to that of IEEE 802.15.4. Many of the mechanisms 110 defined in the RFC 4944 can be applied to the transmission of IPv6 on 111 Bluetooth LE links. This document specifies the details of IPv6 112 transmission over Bluetooth LE links. 114 1.1. Terminology and Requirements Language 116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 118 document are to be interpreted as described in RFC 2119 [RFC2119]. 120 The terms 6LN, 6LR and 6LBR are defined as in [RFC6775], with an 121 addition that Bluetooth LE central and Bluetooth LE peripheral (see 122 Section 2.2) can both be either 6LN or 6LBR. 124 2. Bluetooth Low Energy 126 Bluetooth LE is designed for transferring small amounts of data 127 infrequently at modest data rates at a very low cost per bit. 128 Bluetooth Special Interest Group (Bluetooth SIG) has introduced two 129 trademarks, Bluetooth Smart for single-mode devices (a device that 130 only supports Bluetooth LE) and Bluetooth Smart Ready for dual-mode 131 devices (devices that support both Bluetooth and Bluetooth LE). In 132 the rest of the document, the term Bluetooth LE refers to both types 133 of devices. 135 Bluetooth LE was introduced in Bluetooth 4.0 and further enhanced in 136 Bluetooth 4.1 [BTCorev4.1]. Bluetooth SIG has also published 137 Internet Protocol Support Profile (IPSP) [IPSP], which includes 138 Internet Protocol Support Service (IPSS). The IPSP enables discovery 139 of IP-enabled devices and establishment of link-layer connection for 140 transporting IPv6 packets. IPv6 over Bluetooth LE is dependent on 141 both Bluetooth 4.1 and IPSP 1.0 or newer. 143 Devices such as mobile phones, notebooks, tablets and other handheld 144 computing devices which will include Bluetooth 4.1 chipsets will also 145 have the low-energy functionality of Bluetooth. Bluetooth LE will 146 also be included in many different types of accessories that 147 collaborate with mobile devices such as phones, tablets and notebook 148 computers. An example of a use case for a Bluetooth LE accessory is 149 a heart rate monitor that sends data via the mobile phone to a server 150 on the Internet. 152 2.1. Bluetooth LE stack 154 The lower layer of the Bluetooth LE stack consists of the Physical 155 (PHY) and the Link Layer (LL). The Physical Layer transmits and 156 receives the actual packets. The Link Layer is responsible for 157 providing medium access, connection establishment, error control and 158 flow control. The upper layer consists of the Logical Link Control 159 and Adaptation Protocol (L2CAP), Attribute Protocol (ATT), Generic 160 Attribute Profile (GATT) and Generic Access Profile (GAP) as shown in 161 Figure 1. The device internal Host Controller Interface (HCI) 162 separates the lower layers, often implemented in the Bluetooth 163 controller, from higher layers, often implemented in the host stack. 164 GATT and Bluetooth LE profiles together enable the creation of 165 applications in a standardized way without using IP. L2CAP provides 166 multiplexing capability by multiplexing the data channels from the 167 above layers. L2CAP also provides fragmentation and reassembly for 168 large data packets. 170 +-------------------------------------------------+ 171 | Applications | 172 +---------------------------------------+---------+ 173 | Generic Attribute Profile | Generic | 174 +--------------------+------------------+ Access | 175 | Attribute Protocol | Security Manager | Profile | 176 +--------------------+------------------+---------+ 177 | Logical Link Control and Adaptation Protocol | 178 - - -+-----------------------+-------------------------+- - - HCI 179 | Link Layer | Direct Test Mode | 180 +-------------------------------------------------+ 181 | Physical Layer | 182 +-------------------------------------------------+ 184 Figure 1: Bluetooth LE Protocol Stack 186 2.2. Link layer roles and topology 188 Bluetooth LE defines two GAP roles of relevance herein: the Bluetooth 189 LE central role and the Bluetooth LE peripheral role. A device in 190 the central role, which is called central from now on, has 191 traditionally been able to manage multiple simultaneous connections 192 with a number of devices in the peripheral role, called peripherals 193 from now on. A peripheral is commonly connected to a single central, 194 but since Bluetooth 4.1 can also connect to multiple centrals. In 195 this document for IPv6 networking purposes the Bluetooth LE network 196 (i.e. a Bluetooth LE piconet) follows a star topology shown in the 197 Figure 2, where the router typically implements the Bluetooth LE 198 central role and nodes implement the Bluetooth LE peripheral role. 199 In the future mesh networking may be defined for IPv6 over Bluetooth 200 LE. 202 Node --. .-- Node 203 \ / 204 Node ---- Router ---- Node 205 / \ 206 Node --' '-- Node 208 Figure 2: Bluetooth LE Star Topology 210 In Bluetooth LE a central is assumed to be less constrained than a 211 peripheral. Hence, in the primary deployment scenario central and 212 peripheral will act as 6LoWPAN Border Router (6LBR) and a 6LoWPAN 213 Node (6LN), respectively. 215 In Bluetooth LE, direct communication only takes place between a 216 central and a peripheral. Hence, in a Bluetooth LE network using 217 IPv6, a radio hop is equivalent to an IPv6 link and vice versa. 219 2.3. Bluetooth LE device addressing 221 Every Bluetooth LE device is identified by a 48-bit device address. 222 The Bluetooth specification describes the device address of a 223 Bluetooth LE device as:"Devices are identified using a device 224 address. Device addresses may be either a public device address or a 225 random device address." [BTCorev4.1]. The public device addresses 226 are based on the IEEE 802-2001 standard [IEEE802-2001]. The random 227 device addresses are generated as defined in the Bluetooth 228 specification. These random device addresses have a very small 229 chance of being in conflict, as Bluetooth LE does not support random 230 device address collision avoidance or detection. 232 2.4. Bluetooth LE packets sizes and MTU 234 Optimal MTU defined for L2CAP fixed channels over Bluetooth LE is 27 235 bytes including the L2CAP header of four bytes. Default MTU for 236 Bluetooth LE is hence defined to be 27 bytes. Therefore, excluding 237 L2CAP header of four bytes, protocol data unit (PDU) size of 23 bytes 238 is available for upper layers. In order to be able to transmit IPv6 239 packets of 1280 bytes or larger, link layer fragmentation and 240 reassembly solution is provided by the L2CAP layer. The IPSP defines 241 means for negotiating up a link-layer connection that provides MTU of 242 1280 bytes or higher for the IPv6 layer [IPSP]. The link-layer MTU 243 is negotiated separately for each direction. Implementations that 244 require single link-layer MTU value SHALL use the smallest of the 245 possibly different MTU values. 247 3. Specification of IPv6 over Bluetooth Low Energy 249 Before any IP-layer communications can take place over Bluetooth LE, 250 Bluetooth LE enabled nodes such as 6LNs and 6LBRs have to find each 251 other and establish a suitable link-layer connection. The discovery 252 and Bluetooth LE connection setup procedures are documented by 253 Bluetooth SIG in the IPSP specification [IPSP]. In the rare case of 254 Bluetooth LE random device address conflict, the 6LBR can detect 255 multiple 6LNs with the same Bluetooth LE device address. The 6LBR 256 MUST have at most one connection for a given Bluetooth LE device 257 address at any given moment. This will avoid addressing conflicts 258 within a Bluetooth LE network. The IPSP depends on Bluetooth version 259 4.1, and hence both Bluetooth version 4.1, or newer, and IPSP version 260 1.0, or newer, are required for IPv6 communications. 262 Bluetooth LE technology sets strict requirements for low power 263 consumption and thus limits the allowed protocol overhead. 6LoWPAN 264 standards [RFC6775], and [RFC6282] provide useful functionality for 265 reducing overhead which can be applied to Bluetooth LE. This 266 functionality comprises of link-local IPv6 addresses and stateless 267 IPv6 address autoconfiguration (see Section 3.2.1), Neighbor 268 Discovery (see Section 3.2.2) and header compression (see 269 Section 3.2.3). 271 A significant difference between IEEE 802.15.4 and Bluetooth LE is 272 that the former supports both star and mesh topology (and requires a 273 routing protocol), whereas Bluetooth LE does not currently support 274 the formation of multihop networks at the link layer. 276 3.1. Protocol stack 278 Figure 3 illustrates IPv6 over Bluetooth LE stack including the 279 Internet Protocol Support Service. UDP and TCP are provided as 280 examples of transport protocols, but the stack can be used by any 281 other upper layer protocol capable of running atop of IPv6. The 282 6LoWPAN layer runs on top of Bluetooth LE L2CAP layer. 284 +---------+ +----------------------------+ 285 | IPSS | | UDP/TCP/other | 286 +---------+ +----------------------------+ 287 | GATT | | IPv6 | 288 +---------+ +----------------------------+ 289 | ATT | | 6LoWPAN for Bluetooth LE | 290 +---------+--+----------------------------+ 291 | Bluetooth LE L2CAP | 292 - - +-----------------------------------------+- - - HCI 293 | Bluetooth LE Link Layer | 294 +-----------------------------------------+ 295 | Bluetooth LE Physical | 296 +-----------------------------------------+ 298 Figure 3: IPv6 over Bluetooth LE Stack 300 3.2. Link model 302 The concept of IPv6 link (layer 3) and the physical link (combination 303 of PHY and MAC) needs to be clear and the relationship has to be well 304 understood in order to specify the addressing scheme for transmitting 305 IPv6 packets over the Bluetooth LE link. RFC 4861 [RFC4861] defines 306 a link as "a communication facility or medium over which nodes can 307 communicate at the link layer, i.e., the layer immediately below 308 IPv6." 310 In the case of Bluetooth LE, 6LoWPAN layer is adapted to support 311 transmission of IPv6 packets over Bluetooth LE. The IPSP defines all 312 steps required for setting up the Bluetooth LE connection over which 313 6LoWPAN can function [IPSP], including handling the link-layer 314 fragmentation required on Bluetooth LE, as described in Section 2.4. 316 While Bluetooth LE protocols, such as L2CAP, utilize little-endian 317 byte orderering, IPv6 packets MUST be transmitted in big endian order 318 (network byte order). 320 This specification requires IPv6 header compression format specified 321 in RFC 6282 to be used [RFC6282]. It is assumed that the IPv6 322 payload length can be inferred from the L2CAP header length and the 323 IID value inferred from the link-layer address with help of Neighbor 324 Cache, if elided from compressed packet header. 326 Bluetooth LE connections used to build a star topology are point-to- 327 point in nature, as Bluetooth broadcast features are not used for 328 IPv6 over Bluetooth LE. 6LN-to-6LN communications, e.g. using link- 329 local addresses, need to be bridged by the 6LBR. The 6LBR ensures 330 address collisions do not occur (see Section 3.2.2). 332 After the peripheral and central have connected at the Bluetooth LE 333 level, the link can be considered up and IPv6 address configuration 334 and transmission can begin. 336 3.2.1. Stateless address autoconfiguration 338 At network interface initialization, both 6LN and 6LBR SHALL generate 339 and assign to the Bluetooth LE network interface IPv6 link-local 340 addresses [RFC4862] based on the 48-bit Bluetooth device addresses 341 (see Section 2.3) that were used for establishing underlying 342 Bluetooth LE connection. A 64-bit Interface Identifier (IID) is 343 formed from 48-bit Bluetooth device address by inserting two octets, 344 with hexadecimal values of 0xFF and 0xFE in the middle of the 48-bit 345 Bluetooth device address as shown in Figure 4. In the Figure letter 346 'b' represents a bit from Bluetooth device address, copied as is 347 without any changes on any bit. 349 |0 1|1 3|3 4|4 6| 350 |0 5|6 1|2 7|8 3| 351 +----------------+----------------+----------------+----------------+ 352 |bbbbbbbbbbbbbbbb|bbbbbbbb11111111|11111110bbbbbbbb|bbbbbbbbbbbbbbbb| 353 +----------------+----------------+----------------+----------------+ 355 Figure 4: Formation of IID from Bluetooth device adddress 357 The IID is then appended with prefix fe80::/64, as described in RFC 358 4291 [RFC4291] and as depicted in Figure 5. The same link-local 359 address SHALL be used for the lifetime of the Bluetooth LE L2CAP 360 channel. (After Bluetooth LE logical link has been established, it 361 is referenced with a Connection Handle in HCI. Thus possibly 362 changing device addresses do not impact data flows within existing 363 L2CAP channel. Hence there is no need to change IPv6 link-local 364 addresses even if devices change their random device addresses during 365 L2CAP channel lifetime). 367 10 bits 54 bits 64 bits 368 +----------+-----------------+----------------------+ 369 |1111111010| zeros | Interface Identifier | 370 +----------+-----------------+----------------------+ 372 Figure 5: IPv6 link-local address in Bluetooth LE 374 A 6LN MUST join the all-nodes multicast address. There is no need 375 for 6LN to join the solicited-node multicast address, since 6LBR will 376 know device addresses and hence link-local addresses of all connected 377 6LNs. The 6LBR will ensure no two devices with the same Bluetooth LE 378 device address are connected at the same time. Effectively duplicate 379 address detection for link-local addresses is performed by the 6LBR's 380 software responsible of discovery of IP-enabled Bluetooth LE nodes 381 and of starting Bluetooth LE connection establishment procedures. 382 This approach increases complexity of 6LBR, but reduces power 383 consumption on both 6LN and 6LBR at link establishment phase by 384 reducing number of mandatory packet transmissions. 386 After link-local address configuration, 6LN sends Router Solicitation 387 messages as described in [RFC4861] Section 6.3.7. 389 For non-link-local addresses a 64-bit IID MAY be formed by utilizing 390 the 48-bit Bluetooth device address. Alternatively, a randomly 391 generated IID (see Section 3.2.2) can be used instead, for example, 392 as discussed in [I-D.ietf-6man-default-iids]. The non-link-local 393 addresses 6LN generates must be registered with 6LBR as described in 394 Section 3.2.2. 396 Only if the Bluetooth device address is known to be a public address 397 the "Universal/Local" bit can be set to 1 [RFC4291]. 399 The tool for a 6LBR to obtain an IPv6 prefix for numbering the 400 Bluetooth LE network is out of scope of this document, but can be, 401 for example, accomplished via DHCPv6 Prefix Delegation [RFC3633] or 402 by using Unique Local IPv6 Unicast Addresses (ULA) [RFC4193]. Due to 403 the link model of the Bluetooth LE (see Section 2.2) the 6LBR MUST 404 set the "on-link" flag (L) to zero in the Prefix Information Option 405 [RFC4861]. This will cause 6LNs to always send packets to the 6LBR, 406 including the case when the destination is another 6LN using the same 407 prefix. 409 3.2.2. Neighbor discovery 411 'Neighbor Discovery Optimization for IPv6 over Low-Power Wireless 412 Personal Area Networks (6LoWPANs)' [RFC6775] describes the neighbor 413 discovery approach as adapted for use in several 6LoWPAN topologies, 414 including the mesh topology. Bluetooth LE does not support mesh 415 networks and hence only those aspects that apply to a star topology 416 are considered. 418 The following aspects of the Neighbor Discovery optimizations 419 [RFC6775] are applicable to Bluetooth LE 6LNs: 421 1. A Bluetooth LE 6LN SHOULD NOT register its link-local address. A 422 Bluetooth LE 6LN MUST register its non-link-local addresses with the 423 6LBR by sending a Neighbor Solicitation (NS) message with the Address 424 Registration Option (ARO) and process the Neighbor Advertisement (NA) 425 accordingly. The NS with the ARO option MUST be sent irrespective of 426 the method used to generate the IID. If the 6LN registers for a same 427 compression context multiple addresses that are not based on 428 Bluetooth device address, the 6LN and 6LBR will be unable to compress 429 IID and hence have to send IID bits inline. 431 2. For sending Router Solicitations and processing Router 432 Advertisements the Bluetooth LE 6LNs MUST, respectively, follow 433 Sections 5.3 and 5.4 of the [RFC6775]. 435 3.2.3. Header compression 437 Header compression as defined in RFC 6282 [RFC6282], which specifies 438 the compression format for IPv6 datagrams on top of IEEE 802.15.4, is 439 REQUIRED in this document as the basis for IPv6 header compression on 440 top of Bluetooth LE. All headers MUST be compressed according to RFC 441 6282 [RFC6282] encoding formats. 443 The Bluetooth LE's star topology structure and ARO can be exploited 444 in order to provide a mechanism for IID compression. The following 445 text describes the principles of IPv6 address compression on top of 446 Bluetooth LE. 448 The ARO option requires use of EUI-64 identifier [RFC6775]. In the 449 case of Bluetooth LE, the field SHALL be filled with the 48-bit 450 device address used by the Bluetooth LE node converted into 64-bit 451 Modified EUI-64 format [RFC4291]. 453 To enable efficient header compression, the 6LBR MUST include 6LoWPAN 454 Context Option (6CO) [RFC6775] for all prefixes the 6LBR advertises 455 in Router Advertisements for use in stateless address 456 autoconfiguration. 458 When a 6LN is sending a packet to or through a 6LBR, it MUST fully 459 elide the source address if it is a link-local address or a non-link- 460 local address 6LN has registered with ARO to the 6LBR for the 461 indicated prefix. That is, if SAC=0 and SAM=11 the 6LN MUST be using 462 the link-local IPv6 address derived from Bluetooth LE device address, 463 and if SAC=1 and SAM=11 the 6LN MUST have registered the source IPv6 464 address with the prefix related to compression context identified 465 with Context Identifier Extension. The destination IPv6 address MUST 466 be fully elided if the destination address is the same address to 467 which the 6LN has succesfully registered its source IPv6 address with 468 ARO (set DAC=0, DAM=11). The destination IPv6 address MUST be fully 469 or partially elided if context has been set up for the destination 470 address. For example, DAC=0 and DAM=01 when destination prefix is 471 link-local, and DAC=1 and DAM=01 with Context Identifier Extension if 472 compression context has been configured for the used destination 473 prefix. 475 When a 6LBR is transmitting packets to 6LN, it MUST fully elide the 476 source IID if the source IPv6 address is the one 6LN has used to 477 register its address with ARO (set SAC=0, SAM=11), and it MUST elide 478 the source prefix or address if a compression context related to the 479 IPv6 source address has been set up. The 6LBR also MUST elide the 480 destination IPv6 address registered by the 6LN with ARO and thus 6LN 481 can determine it based on indication of link-local prefix (DAC=0) or 482 indication of other prefix (DAC=1 with Context Identifier Extension). 484 3.2.3.1. Remote destination example 486 When a 6LN transmits an IPv6 packet to a remote destination using 487 global Unicast IPv6 addresses, if a context is defined for the 6LN's 488 global IPv6 address, the 6LN has to indicate this context in the 489 corresponding source fields of the compressed IPv6 header as per 490 Section 3.1 of RFC 6282 [RFC6282], and has to elide the full IPv6 491 source address previously registered with ARO. For this, the 6LN 492 MUST use the following settings in the IPv6 compressed header: CID=1, 493 SAC=1, SAM=11. In this case, the 6LBR can infer the elided IPv6 494 source address since 1) the 6LBR has previously assigned the prefix 495 to the 6LNs; and 2) the 6LBR maintains a Neighbor Cache that relates 496 the Device Address and the IID the device has registered with ARO. 497 If a context is defined for the IPv6 destination address, the 6LN has 498 to also indicate this context in the corresponding destination fields 499 of the compressed IPv6 header, and elide the prefix of or the full 500 destination IPv6 address. For this, the 6LN MUST set the DAM field 501 of the compressed IPv6 header as DAM=01 (if the context covers a 502 64-bit prefix) or as DAM=11 (if the context covers a full, 128-bit 503 address). CID and DAC MUST be set to CID=1 and DAC=1. Note that 504 when a context is defined for the IPv6 destination address, the 6LBR 505 can infer the elided destination prefix by using the context. 507 When a 6LBR receives an IPv6 packet sent by a remote node outside the 508 Bluetooth LE network, and the destination of the packet is a 6LN, if 509 a context is defined for the prefix of the 6LN's global IPv6 address, 510 the 6LBR has to indicate this context in the corresponding 511 destination fields of the compressed IPv6 header. The 6LBR has to 512 elide the IPv6 destination address of the packet before forwarding 513 it, if the IPv6 destination address is inferable by the 6LN. For 514 this, the 6LBR will set the DAM field of the IPv6 compressed header 515 as DAM=11. CID and DAC needs to be set to CID=1 and DAC=1. If a 516 context is defined for the IPv6 source address, the 6LBR needs to 517 indicate this context in the source fields of the compressed IPv6 518 header, and elide that prefix as well. For this, the 6LBR needs to 519 set the SAM field of the IPv6 compressed header as SAM=01 (if the 520 context covers a 64-bit prefix) or SAM=11 (if the context covers a 521 full, 128-bit address). CID and SAC are to be set to CID=1 and 522 SAC=1. 524 3.2.4. Unicast and Multicast address mapping 526 The Bluetooth LE link layer does not support multicast. Hence 527 traffic is always unicast between two Bluetooth LE nodes. Even in 528 the case where a 6LBR is attached to multiple 6LNs, the 6LBR cannot 529 do a multicast to all the connected 6LNs. If the 6LBR needs to send 530 a multicast packet to all its 6LNs, it has to replicate the packet 531 and unicast it on each link. However, this may not be energy- 532 efficient and particular care must be taken if the master is battery- 533 powered. In the opposite direction, a 6LN always has to send packets 534 to or through 6LBR. Hence, when a 6LN needs to transmit an IPv6 535 multicast packet, the 6LN will unicast the corresponding Bluetooth LE 536 packet to the 6LBR. The 6LBR will then forward the multicast packet 537 to other 6LNs. To avoid excess of unwanted multicast traffic being 538 sent to 6LNs, the 6LBR SHOULD implement MLD Snooping feature 539 [RFC4541]. 541 3.3. Internet connectivity scenarios 543 In a typical scenario, the Bluetooth LE network is connected to the 544 Internet as shown in the Figure 6. 546 6LN 547 \ ____________ 548 \ / \ 549 6LN ---- 6LBR ----- | Internet | 550 / \____________/ 551 / 552 6LN 554 <-- Bluetooth LE --> 556 Figure 6: Bluetooth LE network connected to the Internet 558 In some scenarios, the Bluetooth LE network may transiently or 559 permanently be an isolated network as shown in the Figure 7. 561 6LN 6LN 562 \ / 563 \ / 564 6LN --- 6LBR --- 6LN 565 / \ 566 / \ 567 6LN 6LN 569 <--- Bluetooth LE ---> 571 Figure 7: Isolated Bluetooth LE network 573 It is also possible to have point-to-point connection between two 574 6LNs, one of which being central and another being peripheral. 575 Similarly, it is possible to have point-to-point connections between 576 two 6LBRs, one of which being central and another being peripheral. 578 At this point in time mesh networking with Bluetooth LE is not 579 specified. 581 4. IANA Considerations 583 There are no IANA considerations related to this document. 585 5. Security Considerations 587 The transmission of IPv6 over Bluetooth LE links has similar 588 requirements and concerns for security as for IEEE 802.15.4. 589 Bluetooth LE Link Layer security considerations are covered by the 590 IPSP [IPSP]. 592 Bluetooth LE Link Layer supports encryption and authentication by 593 using the Counter with CBC-MAC (CCM) mechanism [RFC3610] and a 594 128-bit AES block cipher. Upper layer security mechanisms may 595 exploit this functionality when it is available. (Note: CCM does not 596 consume bytes from the maximum per-packet L2CAP data size, since the 597 link layer data unit has a specific field for them when they are 598 used.) 600 Key management in Bluetooth LE is provided by the Security Manager 601 Protocol (SMP), as defined in [BTCorev4.1]. 603 The IPv6 link-local address configuration described in Section 3.2.1 604 strictly binds the privacy level of IPv6 link-local address to the 605 privacy level device has selected for the Bluetooth LE. This means 606 that a device using Bluetooth privacy features will retain the same 607 level of privacy with generated IPv6 link-local addresses. 608 Respectively, device not using privacy at Bluetooth level will not 609 have privacy at IPv6 link-local address either. For non-link local 610 addresses implementations have a choice to support 611 [I-D.ietf-6man-default-iids]. 613 6. Additional contributors 615 Kanji Kerai, Jari Mutikainen, David Canfeng-Chen and Minjun Xi from 616 Nokia have contributed significantly to this document. 618 7. Acknowledgements 620 The Bluetooth, Bluetooth Smart and Bluetooth Smart Ready marks are 621 registred trademarks owned by Bluetooth SIG, Inc. 623 Samita Chakrabarti, Brian Haberman, Marcel De Kogel, Erik Nordmark, 624 Dave Thaler, and Victor Zhodzishsky have provided valuable feedback 625 for this draft. 627 Authors would like to give special acknowledgements for Krishna 628 Shingala, Frank Berntsen, and Bluetooth SIG's Internet Working Group 629 for providing significant feedback and improvement proposals for this 630 document. 632 8. References 634 8.1. Normative References 636 [BTCorev4.1] 637 Bluetooth Special Interest Group, "Bluetooth Core 638 Specification Version 4.1", December 2013. 640 [IPSP] Bluetooth Special Interest Group, "Bluetooth Internet 641 Protocol Support Profile Specification Version 1.0.0", 642 December 2014. 644 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 645 Requirement Levels", BCP 14, RFC 2119, March 1997. 647 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 648 Architecture", RFC 4291, February 2006. 650 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 651 "Considerations for Internet Group Management Protocol 652 (IGMP) and Multicast Listener Discovery (MLD) Snooping 653 Switches", RFC 4541, May 2006. 655 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 656 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 657 September 2007. 659 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 660 Address Autoconfiguration", RFC 4862, September 2007. 662 [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 663 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 664 September 2011. 666 [RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann, 667 "Neighbor Discovery Optimization for IPv6 over Low-Power 668 Wireless Personal Area Networks (6LoWPANs)", RFC 6775, 669 November 2012. 671 8.2. Informative References 673 [I-D.ietf-6man-default-iids] 674 Gont, F., Cooper, A., Thaler, D., and W. Will, 675 "Recommendation on Stable IPv6 Interface Identifiers", 676 draft-ietf-6man-default-iids-01 (work in progress), 677 October 2014. 679 [IEEE802-2001] 680 Institute of Electrical and Electronics Engineers (IEEE), 681 "IEEE 802-2001 Standard for Local and Metropolitan Area 682 Networks: Overview and Architecture", 2002. 684 [RFC3610] Whiting, D., Housley, R., and N. Ferguson, "Counter with 685 CBC-MAC (CCM)", RFC 3610, September 2003. 687 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 688 Host Configuration Protocol (DHCP) version 6", RFC 3633, 689 December 2003. 691 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 692 Addresses", RFC 4193, October 2005. 694 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 695 "Transmission of IPv6 Packets over IEEE 802.15.4 696 Networks", RFC 4944, September 2007. 698 Authors' Addresses 700 Johanna Nieminen 701 Nokia 703 Email: johannamaria.nieminen@gmail.com 705 Teemu Savolainen 706 Nokia 707 Visiokatu 3 708 Tampere 33720 709 Finland 711 Email: teemu.savolainen@nokia.com 713 Markus Isomaki 714 Nokia 715 Otaniementie 19 716 Espoo 02150 717 Finland 719 Email: markus.isomaki@nokia.com 721 Basavaraj Patil 722 AT&T 723 1410 E. Renner Road 724 Richardson, TX 75082 725 USA 727 Email: basavaraj.patil@att.com 728 Zach Shelby 729 Arm 730 Hallituskatu 13-17D 731 Oulu 90100 732 Finland 734 Email: zach.shelby@arm.com 736 Carles Gomez 737 Universitat Politecnica de Catalunya/i2CAT 738 C/Esteve Terradas, 7 739 Castelldefels 08860 740 Spain 742 Email: carlesgo@entel.upc.edu