idnits 2.17.1 draft-ietf-6lo-nfc-11.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 1, 2018) is 2032 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC4291' is defined on line 692, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6Lo Working Group Y. Choi, Ed. 3 Internet-Draft Y-G. Hong 4 Intended status: Standards Track ETRI 5 Expires: April 4, 2019 J-S. Youn 6 Dongeui Univ 7 D-K. Kim 8 KNU 9 J-H. Choi 10 Samsung Electronics Co., 11 October 1, 2018 13 Transmission of IPv6 Packets over Near Field Communication 14 draft-ietf-6lo-nfc-11 16 Abstract 18 Near field communication (NFC) is a set of standards for smartphones 19 and portable devices to establish radio communication with each other 20 by touching them together or bringing them into proximity, usually no 21 more than 10 cm. NFC standards cover communications protocols and 22 data exchange formats, and are based on existing radio-frequency 23 identification (RFID) standards including ISO/IEC 14443 and FeliCa. 24 The standards include ISO/IEC 18092 and those defined by the NFC 25 Forum. The NFC technology has been widely implemented and available 26 in mobile phones, laptop computers, and many other devices. This 27 document describes how IPv6 is transmitted over NFC using 6LowPAN 28 techniques. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on April 4, 2019. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3 66 3. Overview of Near Field Communication Technology . . . . . . . 4 67 3.1. Peer-to-peer Mode of NFC . . . . . . . . . . . . . . . . 4 68 3.2. Protocol Stacks of NFC . . . . . . . . . . . . . . . . . 4 69 3.3. NFC-enabled Device Addressing . . . . . . . . . . . . . . 6 70 3.4. MTU of NFC Link Layer . . . . . . . . . . . . . . . . . . 6 71 4. Specification of IPv6 over NFC . . . . . . . . . . . . . . . 7 72 4.1. Protocol Stacks . . . . . . . . . . . . . . . . . . . . . 7 73 4.2. Link Model . . . . . . . . . . . . . . . . . . . . . . . 8 74 4.3. Stateless Address Autoconfiguration . . . . . . . . . . . 9 75 4.4. IPv6 Link Local Address . . . . . . . . . . . . . . . . . 9 76 4.5. Neighbor Discovery . . . . . . . . . . . . . . . . . . . 10 77 4.6. Dispatch Header . . . . . . . . . . . . . . . . . . . . . 11 78 4.7. Header Compression . . . . . . . . . . . . . . . . . . . 11 79 4.8. Fragmentation and Reassembly . . . . . . . . . . . . . . 12 80 4.9. Unicast and Multicast Address Mapping . . . . . . . . . . 12 81 5. Internet Connectivity Scenarios . . . . . . . . . . . . . . . 13 82 5.1. NFC-enabled Device Connected to the Internet . . . . . . 13 83 5.2. Isolated NFC-enabled Device Network . . . . . . . . . . . 14 84 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 85 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 86 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 87 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 88 9.1. Normative References . . . . . . . . . . . . . . . . . . 15 89 9.2. Informative References . . . . . . . . . . . . . . . . . 17 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 92 1. Introduction 94 NFC is a set of short-range wireless technologies, typically 95 requiring a distance of 10 cm or less. NFC operates at 13.56 MHz on 96 ISO/IEC 18000-3 air interface and at rates ranging from 106 kbit/s to 97 424 kbit/s [ECMA-340]. NFC always involves an initiator and a 98 target; the initiator actively generates an RF field that can power a 99 passive target. This enables NFC targets to take very simple form 100 factors such as tags, stickers, key fobs, or cards that do not 101 require batteries. NFC peer-to-peer communication is possible, 102 provided both devices are powered. NFC builds upon RFID systems by 103 allowing two-way communication between endpoints, where earlier 104 systems such as contactless smart cards were one-way only. It has 105 been used in devices such as mobile phones, running Android operating 106 system, named with a feature called "Android Beam". In addition, it 107 is expected for the other mobile phones, running the other operating 108 systems (e.g., iOS, etc.) to be equipped with NFC technology in the 109 near future. 111 Considering the potential for exponential growth in the number of 112 heterogeneous air interface technologies, NFC would be widely used as 113 one of the other air interface technologies, such as Bluetooth Low 114 Energy (BT-LE), Wi-Fi, and so on. Each of the heterogeneous air 115 interface technologies has its own characteristics, which cannot be 116 covered by the other technologies, so various kinds of air interface 117 technologies would co-exist together. Therefore, it is required for 118 them to communicate with each other. NFC also has the strongest 119 ability (e.g., secure communication distance of 10 cm) to prevent a 120 third party from attacking privacy. 122 When the number of devices and things having different air interface 123 technologies communicate with each other, IPv6 is an ideal internet 124 protocols owing to its large address space. Also, NFC would be one 125 of the endpoints using IPv6. Therefore, this document describes how 126 IPv6 is transmitted over NFC using 6LoWPAN techniques. 128 [RFC4944] specifies the transmission of IPv6 over IEEE 802.15.4. The 129 NFC link also has similar characteristics to that of IEEE 802.15.4. 130 Many of the mechanisms defined in [RFC4944] can be applied to the 131 transmission of IPv6 on NFC links. This document specifies the 132 details of IPv6 transmission over NFC links. 134 2. Conventions and Terminology 136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 138 "OPTIONAL" in this document are to be interpreted as described in BCP 139 14 [RFC2119] [RFC8174] when, and only when, they appear in all 140 capitals, as shown here. 142 3. Overview of Near Field Communication Technology 144 NFC technology enables simple and safe two-way interactions between 145 electronic devices, allowing consumers to perform contactless 146 transactions, access digital content, and connect electronic devices 147 with a single touch. NFC complements many popular consumer level 148 wireless technologies, by utilizing the key elements in existing 149 standards for contactless card technology (ISO/IEC 14443 A&B and 150 JIS-X 6319-4). NFC can be compatible with existing contactless card 151 infrastructure and it enables a consumer to utilize one device across 152 different systems. 154 Extending the capability of contactless card technology, NFC also 155 enables devices to share information at a distance that is less than 156 10 cm with a maximum communication speed of 424 kbps. Users can 157 share business cards, make transactions, access information from a 158 smart poster or provide credentials for access control systems with a 159 simple touch. 161 NFC's bidirectional communication ability is ideal for establishing 162 connections with other technologies by the simplicity of touch. In 163 addition to the easy connection and quick transactions, simple data 164 sharing is also available. 166 3.1. Peer-to-peer Mode of NFC 168 NFC-enabled devices are unique in that they can support three modes 169 of operation: card emulation, peer-to-peer, and reader/writer. Peer- 170 to-peer mode enables two NFC-enabled devices to communicate with each 171 other to exchange information and share files, so that users of NFC- 172 enabled devices can quickly share contact information and other files 173 with a touch. Therefore, an NFC-enabled device can securely send 174 IPv6 packets to any corresponding node on the Internet when an NFC- 175 enabled gateway is linked to the Internet. 177 3.2. Protocol Stacks of NFC 179 IP can use the services provided by the Logical Link Control Protocol 180 (LLCP) in the NFC stack to provide reliable, two-way transport of 181 information between the peer devices. Figure 1 depicts the NFC P2P 182 protocol stack with IPv6 bindings to LLCP. 184 For data communication in IPv6 over NFC, an IPv6 packet MUST be 185 passed down to LLCP of NFC and transported to an Information (I) and 186 an Unnumbered Information (UI) Field in Protocol Data Unit (PDU) of 187 LLCP of the NFC-enabled peer device. LLCP does not support 188 fragmentation and reassembly. For IPv6 addressing or address 189 configuration, LLCP MUST provide related information, such as link 190 layer addresses, to its upper layer. The LLCP to IPv6 protocol 191 binding MUST transfer the SSAP and DSAP value to the IPv6 over NFC 192 protocol. SSAP stands for Source Service Access Point, which is a 193 6-bit value meaning a kind of Logical Link Control (LLC) address, 194 while DSAP means an LLC address of the destination NFC-enabled 195 device. 197 | | 198 | | Application Layer 199 | Upper Layer Protocols | Transport Layer 200 | | Network Layer 201 | | | 202 +----------------------------------------+ <------------------ 203 | IPv6-LLCP Binding | | 204 +----------------------------------------+ NFC 205 | | Logical Link 206 | Logical Link Control Protocol | Layer 207 | (LLCP) | | 208 +----------------------------------------+ <------------------ 209 | | | 210 | Activities | | 211 | Digital Protocol | NFC 212 | | Physical 213 +----------------------------------------+ Layer 214 | | | 215 | RF Analog | | 216 | | | 217 +----------------------------------------+ <------------------ 219 Figure 1: Protocol Stacks of NFC 221 The LLCP consists of Logical Link Control (LLC) and MAC Mapping. The 222 MAC Mapping integrates an existing RF protocol into the LLCP 223 architecture. The LLC contains three components, such as Link 224 Management, Connection-oriented Transport, and Connection-less 225 Transport. The Link Management component is responsible for 226 serializing all connection-oriented and connection-less LLC PDU 227 (Protocol Data Unit) exchanges and for aggregation and disaggregation 228 of small PDUs. This component also guarantees asynchronous balanced 229 mode communication and provides link status supervision by performing 230 the symmetry procedure. The Connection-oriented Transport component 231 is responsible for maintaining all connection-oriented data exchanges 232 including connection set-up and termination. The Connectionless 233 Transport component is responsible for handling unacknowledged data 234 exchanges. 236 3.3. NFC-enabled Device Addressing 238 According to NFC Logical Link Control Protocol v1.3 [LLCP-1.3], NFC- 239 enabled devices have two types of 6-bit addresses (i.e., SSAP and 240 DSAP) to identify service access points. The several service access 241 points can be installed on a NFC device. However, the SSAP and DSAP 242 can be used as identifiers for NFC link connections with the IPv6 243 over NFC adaptation layer. Therefore, the SSAP can be used to 244 generate an IPv6 interface identifier. Address values between 00h 245 and 0Fh of SSAP and DSAP are reserved for identifying the well-known 246 service access points, which are defined in the NFC Forum Assigned 247 Numbers Register. Address values between 10h and 1Fh SHALL be 248 assigned by the local LLC to services registered by local service 249 environment. In addition, address values between 20h and 3Fh SHALL 250 be assigned by the local LLC as a result of an upper layer service 251 request. Therefore, the address values between 20h and 3Fh can be 252 used for generating IPv6 interface identifiers. 254 3.4. MTU of NFC Link Layer 256 As mentioned in Section 3.2, an IPv6 packet MUST be passed down to 257 LLCP of NFC and transported to an Unnumbered Information Protocol 258 Data Unit (UI PDU) and an Information Field in Protocol Data Unit (I 259 PDU) of LLCP of the NFC-enabled peer device. 261 The information field of an I PDU contains a single service data 262 unit. The maximum number of octets in the information field is 263 determined by the Maximum Information Unit (MIU) for the data link 264 connection. The default value of the MIU for I PDUs is 128 octets. 265 The local and remote LLCs each establish and maintain distinct MIU 266 values for each data link connection endpoint. Also, an LLC MAY 267 announce a larger MIU for a data link connection by transmitting an 268 MIUX extension parameter within the information field. If no MIUX 269 parameter is transmitted, the default MIU value of 128 MUST be used. 270 Otherwise, the MTU size in NFC LLCP MUST be calculated from the MIU 271 value as follows: 273 MIU = 128 + MIUX. 275 According to [LLCP-1.3], Figure 2 shows an example of the MIUX 276 parameter TLV. Each of TLV Type and TLV Length field is 1 byte, and 277 TLV Value field is 2 bytes. 279 0 0 1 2 3 280 0 8 6 2 1 281 +--------+--------+----------------+ 282 | Type | Length | Value | 283 +--------+--------+----+-----------+ 284 |00000010|00000010|1011| MIUX | 285 +--------+--------+----+-----------+ 286 | <-------> | 287 0x000 ~ 0x7FF 289 Figure 2: Example of MIUX Parameter TLV 291 When the MIUX parameter is encoded as a TLV option, the TLV Type 292 field MUST be 0x02 and the TLV Length field MUST be 0x02. The MIUX 293 parameter MUST be encoded into the least significant 11 bits of the 294 TLV Value field. The unused bits in the TLV Value field MUST be set 295 to zero by the sender and ignored by the receiver. A maximum value 296 of the TLV Value field can be 0x7FF, and a maximum size of the MTU in 297 NFC LLCP is 2176 bytes including the 128 byte default of MIU. 299 4. Specification of IPv6 over NFC 301 NFC technology also has considerations and requirements owing to low 302 power consumption and allowed protocol overhead. 6LoWPAN standards 303 [RFC4944], [RFC6775], and [RFC6282] provide useful functionality for 304 reducing overhead which can be applied to NFC. This functionality 305 consists of link-local IPv6 addresses and stateless IPv6 address 306 auto-configuration (see Section 4.3), Neighbor Discovery (see 307 Section 4.5) and header compression (see Section 4.7). 309 4.1. Protocol Stacks 311 Figure 3 illustrates IPv6 over NFC. Upper layer protocols can be 312 transport layer protocols (TCP and UDP), application layer protocols, 313 and others capable running on top of IPv6. 315 | | Transport & 316 | Upper Layer Protocols | Application Layer 317 +----------------------------------------+ <------------------ 318 | | | 319 | IPv6 | | 320 | | Network 321 +----------------------------------------+ Layer 322 | Adaptation Layer for IPv6 over NFC | | 323 +----------------------------------------+ <------------------ 324 | IPv6-LLCP Binding | 325 | Logical Link Control Protocol | NFC Link Layer 326 | (LLCP) | | 327 +----------------------------------------+ <------------------ 328 | | | 329 | Activities | NFC 330 | Digital Protocol | Physical Layer 331 | RF Analog | | 332 | | | 333 +----------------------------------------+ <------------------ 335 Figure 3: Protocol Stacks for IPv6 over NFC 337 The adaptation layer for IPv6 over NFC SHALL support neighbor 338 discovery, stateless address auto-configuration, header compression, 339 and fragmentation & reassembly. 341 4.2. Link Model 343 In the case of BT-LE, the Logical Link Control and Adaptation 344 Protocol (L2CAP) supports fragmentation and reassembly (FAR) 345 functionality; therefore, the adaptation layer for IPv6 over BT-LE 346 does not have to conduct the FAR procedure. The NFC LLCP, in 347 contrast, does not support the FAR functionality, so IPv6 over NFC 348 needs to consider the FAR functionality, defined in [RFC4944]. 349 However, the MTU on an NFC link can be configured in a connection 350 procedure and extended enough to fit the MTU of IPv6 packet (see 351 Section 4.8). 353 This document does NOT RECOMMEND using FAR over NFC link due to 354 simplicity of the protocol and implementation. In addition, the 355 implementation for this specification SHOULD use MIUX extension to 356 communicate the MTU of the link to the peer as defined in 357 Section 3.4. 359 The NFC link between two communicating devices is considered to be a 360 point-to-point link only. Unlike in BT-LE, an NFC link does not 361 support a star topology or mesh network topology but only direct 362 connections between two devices. Furthermore, the NFC link layer 363 does not support packet forwarding in link layer. Due to this 364 characteristics, 6LoWPAN functionalities, such as addressing and 365 auto-configuration, and header compression, need to be specialized 366 into IPv6 over NFC. 368 4.3. Stateless Address Autoconfiguration 370 An NFC-enabled device (i.e., 6LN) performs stateless address 371 autoconfiguration as per [RFC4862]. A 64-bit Interface identifier 372 (IID) for an NFC interface is formed by utilizing the 6-bit NFC LLCP 373 address (see Section 3.3). In the viewpoint of address 374 configuration, such an IID SHOULD guarantee a stable IPv6 address 375 because each data link connection is uniquely identified by the pair 376 of DSAP and SSAP included in the header of each LLC PDU in NFC. 378 Following the guidance of [RFC7136], interface identifiers of all 379 unicast addresses for NFC-enabled devices are 64 bits long and 380 constructed by using the generation algorithm of random (but stable) 381 identifier (RID) [RFC7217] (see Figure 4). 383 0 1 3 4 6 384 0 6 2 8 3 385 +---------+---------+---------+---------+ 386 | Random (but stable) Identifier (RID) | 387 +---------+---------+---------+---------+ 389 Figure 4: IID from NFC-enabled device 391 The RID is an output which MAY be created by the algorithm, F() with 392 input parameters. One of the parameters is Net_IFace, and NFC Link 393 Layer address (i.e., SSAP) MAY be a source of the NetIFace parameter. 394 The 6-bit address of SSAP of NFC is easy and short to be targeted by 395 attacks of third party (e.g., address scanning). The F() can provide 396 secured and stable IIDs for NFC-enabled devices. In addition, an 397 optional parameter, Network_ID MAY be used to increase the randomness 398 of the generated IID. 400 4.4. IPv6 Link Local Address 402 Only if the NFC-enabled device address is known to be a public 403 address, the "Universal/Local" bit be set to 1. The IPv6 link-local 404 address for an NFC-enabled device is formed by appending the IID, to 405 the prefix FE80::/64, as depicted in Figure 5. 407 0 0 0 1 408 0 1 6 2 409 0 0 4 7 410 +----------+------------------+----------------------------+ 411 |1111111010| zeros | Interface Identifier | 412 +----------+------------------+----------------------------+ 413 | | 414 | <---------------------- 128 bits ----------------------> | 415 | | 417 Figure 5: IPv6 link-local address in NFC 419 The tool for a 6LBR to obtain an IPv6 prefix for numbering the NFC 420 network is can be accomplished via DHCPv6 Prefix Delegation 421 ([RFC3633]). 423 4.5. Neighbor Discovery 425 Neighbor Discovery Optimization for 6LoWPANs ([RFC6775]) describes 426 the neighbor discovery approach in several 6LoWPAN topologies, such 427 as mesh topology. NFC does not support a complicated mesh topology 428 but only a simple multi-hop network topology or directly connected 429 peer-to-peer network. Therefore, the following aspects of RFC 6775 430 are applicable to NFC: 432 o When an NFC-enabled device (6LN) is directly connected to a 6LBR, 433 an NFC 6LN MUST register its address with the 6LBR by sending a 434 Neighbor Solicitation (NS) message with the Address Registration 435 Option (ARO) and process the Neighbor Advertisement (NA) 436 accordingly. In addition, if DHCPv6 is used to assign an address, 437 Duplicate Address Detection (DAD) MAY not be required. 439 o When two or more NFC 6LNs(or 6LRs) meet, there MAY be two cases. 440 One is that they meet with multi-hop connections, and the other is 441 that they meet within a sigle hop range (e.g., isolated network). 442 In a case of multi-hops, all of 6LNs, which have two or more 443 connections with different neighbors, MAY be a router for 444 6LR/6LBR. In a case that they meet within a single hop and they 445 have the same properties, any of them can be a router. When the 446 NFC nodes are not of uniform category (e.g., different MTU, level 447 of remaining energy, connectivity, etc.), a performance- 448 outstanding device can become a router. Also, they MUST deliver 449 their MTU information to neighbors with NFC LLCP protocols during 450 connection initialization. The router MAY also communicate other 451 capabilities which is out of scope of this document. 453 o For sending Router Solicitations and processing Router 454 Advertisements, the NFC 6LNs MUST follow Sections 5.3 and 5.4 of 455 [RFC6775]. 457 4.6. Dispatch Header 459 All IPv6-over-NFC encapsulated datagrams are prefixed by an 460 encapsulation header stack consisting of a Dispatch value followed by 461 zero or more header fields. The only sequence currently defined for 462 IPv6-over-NFC is the LOWPAN_IPHC header followed by payload, as 463 depicted in Figure 6. 465 +---------------+---------------+--------------+ 466 | IPHC Dispatch | IPHC Header | Payload | 467 +---------------+---------------+--------------+ 469 Figure 6: A IPv6-over-NFC Encapsulated 6LOWPAN_IPHC Compressed IPv6 470 Datagram 472 The dispatch value may be treated as an unstructured namespace. Only 473 a single pattern is used to represent current IPv6-over-NFC 474 functionality. 476 +------------+--------------------+-----------+ 477 | Pattern | Header Type | Reference | 478 +------------+--------------------+-----------+ 479 | 01 1xxxxx | 6LOWPAN_IPHC | [RFC6282] | 480 +------------+--------------------+-----------+ 482 Figure 7: Dispatch Values 484 Other IANA-assigned 6LoWPAN Dispatch values do not apply to this 485 specification. 487 4.7. Header Compression 489 Header compression as defined in [RFC6282], which specifies the 490 compression format for IPv6 datagrams on top of IEEE 802.15.4, is 491 REQUIRED in this document as the basis for IPv6 header compression on 492 top of NFC. All headers MUST be compressed according to RFC 6282 493 encoding formats. 495 Therefore, IPv6 header compression in [RFC6282] MUST be implemented. 496 Further, implementations MAY also support Generic Header Compression 497 (GHC) of [RFC7400]. 499 If a 16-bit address is required as a short address, it MUST be formed 500 by padding the 6-bit NFC link-layer (node) address to the left with 501 zeros as shown in Figure 8. 503 0 1 504 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 506 | Padding(all zeros)| NFC Addr. | 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 Figure 8: NFC short address format 511 4.8. Fragmentation and Reassembly 513 IPv6-over-NFC fragmentation and reassembly (FAR) for the payloads is 514 NOT RECOMMENDED in this document as discussed in Section 3.4. The 515 NFC link connection for IPv6 over NFC MUST be configured with an 516 equivalent MIU size to fit the MTU of IPv6 Packet. The MIUX value is 517 0x480 in order to fit the MTU (1280 bytes) of a IPv6 packet if NFC 518 devices support extension of the MTU. However, if the NFC device 519 does not support extension, IPv6-over-NFC uses FAR with default MIU 520 (128 bytes), as defined in [RFC4944]. 522 4.9. Unicast and Multicast Address Mapping 524 The address resolution procedure for mapping IPv6 non-multicast 525 addresses into NFC link-layer addresses follows the general 526 description in Section 7.2 of [RFC4861], unless otherwise specified. 528 The Source/Target link-layer Address option has the following form 529 when the addresses are 6-bit NFC link-layer (node) addresses. 531 0 1 532 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 534 | Type | Length=1 | 535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 536 | | 537 +- Padding (all zeros) -+ 538 | | 539 +- +-+-+-+-+-+-+ 540 | | NFC Addr. | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 Figure 9: Unicast address mapping 545 Option fields: 547 Type: 549 1: for Source Link-layer address. 551 2: for Target Link-layer address. 553 Length: 555 This is the length of this option (including the type and 556 length fields) in units of 8 octets. The value of this field 557 is 1 for 6-bit NFC node addresses. 559 NFC address: 561 The 6-bit address in canonical bit order. This is the unicast 562 address the interface currently responds to. 564 The NFC Link Layer does not support multicast. Therefore, packets 565 are always transmitted by unicast between two NFC-enabled devices. 566 Even in the case where a 6LBR is attached to multiple 6LNs, the 6LBR 567 cannot do a multicast to all the connected 6LNs. If the 6LBR needs 568 to send a multicast packet to all its 6LNs, it has to replicate the 569 packet and unicast it on each link. 571 5. Internet Connectivity Scenarios 573 As two typical scenarios, the NFC network can be isolated and 574 connected to the Internet. 576 5.1. NFC-enabled Device Connected to the Internet 578 One of the key applications of using IPv6 over NFC is securely 579 transmitting IPv6 packets because the RF distance between 6LN and 580 6LBR is typically within 10 cm. If any third party wants to hack 581 into the RF between them, it must come to nearly touch them. 582 Applications can choose which kinds of air interfaces (e.g., BT-LE, 583 Wi-Fi, NFC, etc.) to send data depending on the characteristics of 584 the data. 586 Figure 10 illustrates an example of an NFC-enabled device network 587 connected to the Internet. The distance between 6LN and 6LBR is 588 typically 10 cm or less. If there is any laptop computers close to a 589 user, it will become the a 6LBR. Additionally, when the user mounts 590 an NFC-enabled air interface adapter (e.g., portable NFC dongle) on 591 the close laptop PC, the user's NFC-enabled device (6LN) can 592 communicate with the laptop PC (6LBR) within 10 cm distance. 594 ************ 595 6LN ------------------- 6LBR -----* Internet *------- CN 596 | (dis. 10 cm or less) | ************ | 597 | | | 598 | <-------- NFC -------> | <----- IPv6 packet ------> | 599 | (IPv6 over NFC packet) | | 601 Figure 10: NFC-enabled device network connected to the Internet 603 Two or more LNs MAY be connected with a 6LBR, but each connection 604 uses a different subnet. The 6LBR is acting as a router and 605 forwarding packets between 6LNs and the Internet. Also, the 6LBR 606 MUST ensure address collisions do not occur and forwards packets sent 607 by one 6LN to another. 609 5.2. Isolated NFC-enabled Device Network 611 In some scenarios, the NFC-enabled device network may transiently be 612 a simple isolated network as shown in the Figure 11. 614 6LN ---------------------- 6LR ---------------------- 6LN 615 | (10 cm or less) | (10 cm or less) | 616 | | | 617 | <--------- NFC --------> | <--------- NFC --------> | 618 | (IPv6 over NFC packet) | (IPv6 over NFC packet) | 620 Figure 11: Isolated NFC-enabled device network 622 In mobile phone markets, applications are designed and made by user 623 developers. They may image interesting applications, where three or 624 more mobile phones touch or attach each other to accomplish 625 outstanding performance. In an isolated NFC-enabled device network, 626 when two or more LRs MAY be connected with each other, and then they 627 are acting like routers, the 6LR MUST ensure address collisions do 628 not occur. 630 6. IANA Considerations 632 There are no IANA considerations related to this document. 634 7. Security Considerations 636 When interface identifiers (IIDs) are generated, devices and users 637 are required to consider mitigating various threats, such as 638 correlation of activities over time, location tracking, device- 639 specific vulnerability exploitation, and address scanning. 641 IPv6-over-NFC is, in practice, not used for long-lived links for big 642 size data transfer or multimedia streaming, but used for extremely 643 short-lived links (i.e., single touch-based approaches) for ID 644 verification and mobile payment. This will mitigate the threat of 645 correlation of activities over time. 647 IPv6-over-NFC uses an IPv6 interface identifier formed from a "Short 648 Address" and a set of well-known constant bits (such as padding with 649 '0's) for the modified EUI-64 format. However, the short address of 650 NFC link layer (LLC) is not generated as a physically permanent value 651 but logically generated for each connection. Thus, every single 652 touch connection can use a different short address of NFC link with 653 an extremely short-lived link. This can mitigate address scanning as 654 well as location tracking and device-specific vulnerability 655 exploitation. 657 Thus, this document does not RECOMMEND sending NFC packets over the 658 Internet or any unsecured network. 660 If there is a compelling reason to send/receive the IPv6-over-NFC 661 packets over the unsecured network, the deployment SHOULD make sure 662 that the packets are sent over secured channels. The particular 663 Security mechanisms are out of scope of this document. 665 8. Acknowledgements 667 We are grateful to the members of the IETF 6lo working group. 669 Michael Richardson, Suresh Krishnan, Pascal Thubert, Carsten Bormann, 670 Alexandru Petrescu, James Woodyatt, Dave Thaler, Samita Chakrabarti, 671 and Gabriel Montenegro have provided valuable feedback for this 672 draft. 674 9. References 676 9.1. Normative References 678 [LLCP-1.3] 679 "NFC Logical Link Control Protocol version 1.3", NFC Forum 680 Technical Specification , March 2016. 682 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 683 Requirement Levels", BCP 14, RFC 2119, 684 DOI 10.17487/RFC2119, March 1997, 685 . 687 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 688 Host Configuration Protocol (DHCP) version 6", RFC 3633, 689 DOI 10.17487/RFC3633, December 2003, 690 . 692 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 693 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 694 2006, . 696 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 697 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 698 DOI 10.17487/RFC4861, September 2007, 699 . 701 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 702 Address Autoconfiguration", RFC 4862, 703 DOI 10.17487/RFC4862, September 2007, 704 . 706 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 707 "Transmission of IPv6 Packets over IEEE 802.15.4 708 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, 709 . 711 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 712 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 713 DOI 10.17487/RFC6282, September 2011, 714 . 716 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 717 Bormann, "Neighbor Discovery Optimization for IPv6 over 718 Low-Power Wireless Personal Area Networks (6LoWPANs)", 719 RFC 6775, DOI 10.17487/RFC6775, November 2012, 720 . 722 [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 723 Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, 724 February 2014, . 726 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 727 Interface Identifiers with IPv6 Stateless Address 728 Autoconfiguration (SLAAC)", RFC 7217, 729 DOI 10.17487/RFC7217, April 2014, 730 . 732 [RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for 733 IPv6 over Low-Power Wireless Personal Area Networks 734 (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November 735 2014, . 737 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 738 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 739 May 2017, . 741 9.2. Informative References 743 [ECMA-340] 744 "Near Field Communication - Interface and Protocol (NFCIP- 745 1) 3rd Ed.", ECMA-340 , June 2013. 747 Authors' Addresses 749 Younghwan Choi (editor) 750 Electronics and Telecommunications Research Institute 751 218 Gajeongno, Yuseung-gu 752 Daejeon 34129 753 Korea 755 Phone: +82 42 860 1429 756 Email: yhc@etri.re.kr 758 Yong-Geun Hong 759 Electronics and Telecommunications Research Institute 760 161 Gajeong-Dong Yuseung-gu 761 Daejeon 305-700 762 Korea 764 Phone: +82 42 860 6557 765 Email: yghong@etri.re.kr 767 Joo-Sang Youn 768 DONG-EUI University 769 176 Eomgwangno Busan_jin_gu 770 Busan 614-714 771 Korea 773 Phone: +82 51 890 1993 774 Email: joosang.youn@gmail.com 775 Dongkyun Kim 776 Kyungpook National University 777 80 Daehak-ro, Buk-gu 778 Daegu 702-701 779 Korea 781 Phone: +82 53 950 7571 782 Email: dongkyun@knu.ac.kr 784 JinHyouk Choi 785 Samsung Electronics Co., 786 129 Samsung-ro, Youngdong-gu 787 Suwon 447-712 788 Korea 790 Phone: +82 2 2254 0114 791 Email: jinchoe@samsung.com