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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. 'G.9959' ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 over Networks of Resource-constrained Nodes (6lo) WG A. Brandt 3 Internet-Draft J. Buron 4 Intended status: Standards Track Sigma Designs 5 Expires: September 15, 2014 March 14, 2014 7 Transmission of IPv6 packets over ITU-T G.9959 Networks 8 draft-ietf-6lo-lowpanz-04 10 Abstract 12 This document describes the frame format for transmission of IPv6 13 packets and a method of forming IPv6 link-local addresses and 14 statelessly autoconfigured IPv6 addresses on ITU-T G.9959 networks. 16 Requirements Language 18 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 19 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 20 document are to be interpreted as described in [RFC2119]. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 15, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Terms used . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. G.9959 parameters to use for IPv6 transport . . . . . . . . . 4 59 2.1. Addressing mode . . . . . . . . . . . . . . . . . . . . . 4 60 2.2. IPv6 Multicast support . . . . . . . . . . . . . . . . . 4 61 2.3. G.9959 MAC PDU size and IPv6 MTU . . . . . . . . . . . . 5 62 2.4. Transmission status indications . . . . . . . . . . . . . 5 63 2.5. Transmission security . . . . . . . . . . . . . . . . . . 5 64 3. 6LoWPAN Adaptation Layer and Frame Format . . . . . . . . . . 6 65 3.1. Dispatch Header . . . . . . . . . . . . . . . . . . . . . 6 66 4. 6LoWPAN addressing . . . . . . . . . . . . . . . . . . . . . 7 67 4.1. Stateless Address Autoconfiguration of routable IPv6 68 addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 69 4.2. IPv6 Link Local Address . . . . . . . . . . . . . . . . . 8 70 4.3. Unicast Address Mapping . . . . . . . . . . . . . . . . . 8 71 4.4. On the use of Neighbor Discovery technologies . . . . . . 9 72 4.4.1. Prefix and CID management (Route-over) . . . . . . . 9 73 4.4.2. Prefix and CID management (Mesh-under) . . . . . . . 10 74 5. Header Compression . . . . . . . . . . . . . . . . . . . . . 11 75 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 76 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 77 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12 78 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 79 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 80 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 81 10.2. Informative References . . . . . . . . . . . . . . . . . 14 82 Appendix A. G.9959 6LoWPAN datagram example . . . . . . . . . . 14 83 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18 84 B.1. Changes since -00 . . . . . . . . . . . . . . . . . . . . 18 85 B.2. Changes since -01 . . . . . . . . . . . . . . . . . . . . 18 86 B.3. Changes since -02 . . . . . . . . . . . . . . . . . . . . 19 87 B.4. Changes since -03 . . . . . . . . . . . . . . . . . . . . 19 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 90 1. Introduction 92 The ITU-T G.9959 recommendation [G.9959] targets low-power Personal 93 Area Networks (PANs). This document defines the frame format for 94 transmission of IPv6 [RFC2460] packets as well as the formation of 95 IPv6 link-local addresses and statelessly autoconfigured IPv6 96 addresses on G.9959 networks. 98 The general approach is to adapt elements of [RFC4944] to G.9959 99 networks. G.9959 provides a Segmentation and Reassembly (SAR) layer 100 for transmission of datagrams larger than the G.9959 MAC PDU. 102 [RFC6775] updates [RFC4944] by specifying 6LoWPAN optimizations for 103 IPv6 Neighbor Discovery (ND) (originally defined by [RFC4861]). This 104 document limits the use of [RFC6775] to prefix and Context ID 105 assignment. An IID may be constructed from a G.9959 link-layer 106 address, leading to a "link-layer-derived IPv6 address". If using 107 that method, Duplicate Address Detection (DAD) is not needed. 108 Alternatively, IPv6 addresses may be assigned centrally via DHCP, 109 leading to a "non-link-layer-derived IPv6 address". Address 110 registration is only needed in certain cases. 112 In addition to IPv6 application communication, the frame format 113 defined in this document may be used by IPv6 routing protocols such 114 as RPL [RFC6550] or P2P-RPL [RFC6997] to implement IPv6 routing over 115 G.9959 networks. 117 The encapsulation frame defined by this specification may optionally 118 be transported via mesh routing below the 6LoWPAN layer. Routing 119 protocol specifications are out of scope of this document. 121 1.1. Terms used 123 6LoWPAN: IPv6-based Low-power Personal Area Network 125 ABR: Authoritative Border Router ([RFC6775]) 127 AES: Advanced Encryption Scheme 129 EUI-64: Extended Unique Identifier 131 HomeID: G.9959 Link-Layer Network Identifier 133 IID: Interface IDentifier 135 MAC: Media Access Control 137 MTU: Maximum Transmission Unit 139 NodeID: G.9959 Link-Layer Node Identifier (Short Address) 141 PAN: Personal Area Network 143 PDU: Protocol Data Unit 145 SAR: Segmentation And Reassembly 146 ULA: Unique Local Address 148 2. G.9959 parameters to use for IPv6 transport 150 This chapter outlines properties applying to the PHY and MAC of 151 G.9959 and how to use these for IPv6 transport. 153 2.1. Addressing mode 155 G.9959 defines how a unique 32-bit HomeID network identifier is 156 assigned by a network controller and how an 8-bit NodeID host 157 identifier is allocated. NodeIDs are unique within the logical 158 network identified by the HomeID. The logical network identified by 159 the HomeID maps directly to an IPv6 subnet identified by one or more 160 IPv6 prefixes. 162 An IPv6 host MUST construct its link-local IPv6 address from the 163 link-layer-derived IID in order to facilitate IP header compression 164 as described in [RFC6282]. 166 A node interface MAY support the M flag of the RA message for the 167 construction of routable IPv6 addresses. If the M flag is not 168 supported, link-layer-derived addressing MUST be used. If the M flag 169 is supported, link-layer-derived addressing MUST be used if the M 170 flag is 0, while DHCPv6 address assignment MUST be used if the M flag 171 is 1. Nodes using DHCPv6 assigned IPv6 addresses MUST comply with 172 [RFC6775]. 174 A word of caution: since HomeIDs and NodeIDs are handed out by a 175 network controller function during inclusion, identifier validity and 176 uniqueness is limited by the lifetime of the logical network 177 membership. This can be cut short by a mishap occurring to the 178 network controller. Having a single point of failure at the network 179 controller suggests that deployers of high-reliability applications 180 should carefully consider adding redundancy to the network controller 181 function. 183 This warning applies to link-layer-derived addressing as well as to 184 non-link-layer-derived addressing deployments. 186 2.2. IPv6 Multicast support 188 [RFC3819] recommends that IP subnetworks support (subnet-wide) 189 multicast. G.9959 supports direct-range IPv6 multicast while subnet- 190 wide multicast is not supported natively by G.9959. Subnet-wide 191 multicast may be provided by an IP routing protocol or a mesh routing 192 protocol operating below the 6LoWPAN layer. Routing protocol 193 specifications are out of scope of this document. 195 IPv6 multicast packets MUST be carried via G.9959 broadcast. 197 As per [G.9959], this is accomplished as follows: 199 1. The destination HomeID of the G.9959 MAC PDU MUST be the HomeID 200 of the logical network 202 2. The destination NodeID of the G.9959 MAC PDU MUST be the 203 broadcast NodeID (0xff) 205 G.9959 broadcast MAC PDUs are only intercepted by nodes within the 206 logical network identified by the HomeID. 208 2.3. G.9959 MAC PDU size and IPv6 MTU 210 IPv6 packets MUST use G.9959 transmission profiles which support MAC 211 PDU payload sizes of 150 bytes or higher, i.e. profile R3 or higher. 212 (G.9959 profiles R1 and R2 only support MPDU payloads around 40 bytes 213 and the transmission speed is down to 9.6kbit/s) 215 [RFC2460] specifies that IPv6 packets may be up to 1280 octets. 217 G.9959 provides Segmentation And Reassembly for payloads up to 1350 218 octets. IPv6 Header Compression [RFC6282] improves the chances that 219 a short IPv6 packet can fit into a single G.9959 frame. Therefore, 220 section Section 3 specifies that [RFC6282] MUST be supported. With 221 the mandatory link-layer security enabled, a G.9959 R3 MAC PDU may 222 accommodate 6LoWPAN datagrams of up to 130 octets without triggering 223 G.9959 Segmentation and Reassembly. Longer 6LoWPAN datagrams will 224 lead to the transmission of multiple G.9959 PDUs. 226 2.4. Transmission status indications 228 The G.9959 MAC layer provides native acknowledgement and 229 retransmission of MAC PDUs. The G.9959 SAR layer does the same for 230 larger datagrams. A mesh routing layer may provide a similar feature 231 for routed communication. An IPv6 routing stack communicating over 232 G.9959 may utilize link-layer status indications such as delivery 233 confirmation and Ack timeout from the MAC layer. 235 2.5. Transmission security 237 Implementations claiming conformance with this document MUST enable 238 G.9959 shared network key security. 240 The shared network key is intended to address security requirements 241 in the home at the normal security requirements level. For 242 applications with high or very high requirements on confidentiality 243 and/or integrity, additional application layer security measures for 244 end-to-end authentication and encryption may need to be applied. 245 (The availability of the network relies on the security properties of 246 the network key in any case) 248 3. 6LoWPAN Adaptation Layer and Frame Format 250 The 6LoWPAN encapsulation formats defined in this chapter are carried 251 as payload in the G.9959 MAC PDU. IPv6 header compression [RFC6282] 252 MUST be supported by implementations of this specification. 254 All 6LoWPAN datagrams transported over G.9959 are prefixed by a 255 6LoWPAN encapsulation header stack. The 6LoWPAN payload follows this 256 encapsulation header stack. Each header in the header stack contains 257 a header type followed by zero or more header fields. An IPv6 header 258 stack may contain, in the following order, addressing, hop-by-hop 259 options, routing, fragmentation, destination options, and finally 260 payload [RFC2460]. The 6LoWPAN header format is structured the same 261 way. Currently only one payload option is defined for the G.9959 262 6LoWPAN header format. 264 The definition of 6LoWPAN headers consists of the dispatch value, the 265 definition of the header fields that follow, and their ordering 266 constraints relative to all other headers. Although the header stack 267 structure provides a mechanism to address future demands on the 268 6LoWPAN adaptation layer, it is not intended to provide general 269 purpose extensibility. 271 An example of a complete G.9959 6LoWPAN datagram can be found in 272 Appendix A. 274 3.1. Dispatch Header 276 The dispatch header is shown below: 278 0 1 2 3 279 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 281 | 6LoWPAN CmdCls| Dispatch | Type-specific header | 282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 284 Figure 1: Dispatch Type and Header 286 6LoWPAN CmdCls: 6LoWPAN Command Class identifier. This field MUST 287 carry the value 0x4F [G.9959]. The value specifies that the 288 following bits are a 6LoWPAN encapsulated datagram. Non-6LoWPAN 289 protocols MUST ignore the contents following the 6LoWPAN Command 290 Class identifier. 292 Dispatch: Identifies the header type immediately following the 293 Dispatch Header. 295 Type-specific header: A header determined by the Dispatch Header. 297 The dispatch value may be treated as an unstructured namespace. Only 298 a few symbols are required to represent current 6LoWPAN 299 functionality. Although some additional savings could be achieved by 300 encoding additional functionality into the dispatch byte, these 301 measures would tend to constrain the ability to address future 302 alternatives. 304 Dispatch values used in this specification are compatible with the 305 dispatch values defined by [RFC4944] and [RFC6282]. 307 +------------+------------------------------------------+-----------+ 308 | Pattern | Header Type | Reference | 309 +------------+------------------------------------------+-----------+ 310 | 01 1xxxxx | 6LoWPAN_IPHC - Compressed IPv6 Addresses | [RFC6282] | 311 +------------+------------------------------------------+-----------+ 312 All other Dispatch values are unassigned in this document. 314 Figure 2: Dispatch values 316 6LoWPAN_IPHC: IPv6 Header Compression. Refer to [RFC6282]. 318 4. 6LoWPAN addressing 320 IPv6 addresses are autoconfigured from IIDs which are again 321 constructed from link-layer address information to save memory in 322 devices and to facilitate efficient IP header compression as per 323 [RFC6282]. 325 A NodeID is mapped into an IEEE EUI-64 identifier as follows: 327 IID = 0000:00ff:fe00:YYXX 329 Figure 3: Constructing a compressible IID 331 where XX carries the G.9959 NodeID and YY is a one byte value chosen 332 by the individual node. The default YY value MUST be zero. A node 333 MAY use other values of YY than zero to form additional IIDs in order 334 to instantiate multiple IPv6 interfaces. The YY value MUST be 335 ignored when computing the corresponding NodeID (the XX value) from 336 an IID. 338 The method of constructing IIDs from the link-layer address obviously 339 does not support addresses assigned or constructed by other means. A 340 node MUST NOT compute the NodeID from the IID if the first 6 bytes of 341 the IID do not comply with the format defined in Figure 3. In that 342 case, the address resolution mechanisms of RFC 6775 apply. 344 4.1. Stateless Address Autoconfiguration of routable IPv6 addresses 346 The IID defined above MUST be used whether autoconfiguring a ULA IPv6 347 address [RFC4193] or a globally routable IPv6 address [RFC3587] in 348 G.9959 subnets. 350 4.2. IPv6 Link Local Address 352 The IPv6 link-local address [RFC4291] for a G.9959 interface is 353 formed by appending the IID defined above to the IPv6 link local 354 prefix FE80::/64. 356 The "Universal/Local" (U/L) bit MUST be set to zero in keeping with 357 the fact that this is not a globally unique value [EUI64]. 359 The resulting link local address is formed as follows: 361 10 bits 54 bits 64 bits 362 +----------+-----------------------+----------------------------+ 363 |1111111010| (zeros) | Interface Identifier (IID) | 364 +----------+-----------------------+----------------------------+ 366 Figure 4: IPv6 Link Local Address 368 4.3. Unicast Address Mapping 370 The address resolution procedure for mapping IPv6 unicast addresses 371 into G.9959 link-layer addresses follows the general description in 372 Section 7.2 of [RFC4861]. The Source/Target Link-layer Address 373 option MUST have the following form when the link layer is G.9959. 375 0 1 376 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 378 | Type | Length=1 | 379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 | 0x00 | NodeID | 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 | Padding | 383 +- -+ 384 | (All zeros) | 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 Figure 5: IPv6 Unicast Address Mapping 389 Option fields: 391 Type: The value 1 signifies the Source Link-layer address. The value 392 2 signifies the Destination Link-layer address. 394 Length: This is the length of this option (including the type and 395 length fields) in units of 8 octets. The value of this field is 396 always 1 for G.9959 NodeIDs. 398 NodeID: This is the G.9959 NodeID the actual interface currently 399 responds to. The link-layer address may change if the interface 400 joins another network at a later time. 402 4.4. On the use of Neighbor Discovery technologies 404 [RFC4861] specifies how IPv6 nodes may resolve link layer addresses 405 from IPv6 addresses via the use of link-local IPv6 multicast. 406 [RFC6775] is an optimization of [RFC4861], specifically targeting 407 6LoWPAN networks. [RFC6775] defines how a 6LoWPAN node may register 408 IPv6 addresses with an authoritative border router (ABR). Mesh-under 409 networks MUST NOT use [RFC6775] address registration. However, 410 [RFC6775] address registration MUST be used if the first 6 bytes of 411 the IID do not comply with the format defined in Figure 3. 413 4.4.1. Prefix and CID management (Route-over) 415 In route-over environments, IPv6 hosts MUST use [RFC6775] address 416 registration. A node implementation for route-over operation MAY use 417 RFC6775 mechanisms for obtaining IPv6 prefixes and corresponding 418 header compression context information [RFC6282]. RFC6775 Route-over 419 requirements apply with no modifications. 421 4.4.2. Prefix and CID management (Mesh-under) 423 An implementation for mesh-under operation MUST use [RFC6775] 424 mechanisms for managing IPv6 prefixes and corresponding header 425 compression context information [RFC6282]. [RFC6775] Duplicate 426 Address Detection (DAD) MUST NOT be used, since the link-layer 427 inclusion process of G.9959 ensures that a NodeID is unique for a 428 given HomeID. 430 With this exception and the specific redefinition of the RA Router 431 Lifetime value 0xFFFF (refer to Section 4.4.2.3), the text of the 432 following subsections is in compliance with [RFC6775]. 434 4.4.2.1. Prefix assignment considerations 436 As stated by [RFC6775], an ABR is responsible for managing 437 prefix(es). Global routable prefixes may change over time. It is 438 RECOMMENDED that a ULA prefix is assigned to the 6LoWPAN subnet to 439 facilitate stable site-local application associations based on IPv6 440 addresses. A node MAY support the M flag of the RA message. If the 441 M flag is not supported, link-layer-derived addressing MUST be used. 442 If the M flag is supported, link-layer-derived addressing MUST be 443 used if the M flag is 0, while DHCPv6 address assignment MUST be used 444 if the M flag is 1. 446 4.4.2.2. Robust and efficient CID management 448 The 6LoWPAN Context Option (6CO) is used according to [RFC6775] in an 449 RA to disseminate Context IDs (CID) to use for compressing prefixes. 450 One or more prefixes and corresponding Context IDs MUST be assigned 451 during initial node inclusion. 453 When updating context information, a CID may have its lifetime set to 454 zero to obsolete it. The CID MUST NOT be reused immediately; rather 455 the next vacant CID should be assigned. Header compression based on 456 CIDs MUST NOT be used for RA messages carrying Context Information. 457 An expired CID and the associated prefix MUST NOT be reset but rather 458 retained in receive-only mode if there is no other current need for 459 the CID value. This will allow an ABR to detect if a sleeping node 460 without clock uses an expired CID and in response, the ABR MUST 461 return an RA with fresh Context Information to the originator. 463 4.4.2.3. Infinite prefix lifetime support for island-mode networks 465 Nodes MUST renew the prefix and CID according to the lifetime 466 signaled by the ABR. [RFC6775] specifies that the maximum value of 467 the RA Router Lifetime field MAY be up to 0xFFFF. This document 468 further specifies that the value 0xFFFF MUST be interpreted as 469 infinite lifetime. This value MUST NOT be used by ABRs. Its use is 470 only intended for a sleeping network controller; for instance a 471 battery powered remote control being master for a small island-mode 472 network of light modules. 474 5. Header Compression 476 IPv6 header compression [RFC6282] MUST be implemented according to 477 [RFC6282]. This section will simply identify substitutions that 478 should be made when interpreting the text of [RFC6282]. 480 In general the following substitutions should be made: 482 o Replace "802.15.4" with "G.9959" 484 o Replace "802.15.4 short address" with "" 486 o Replace "802.15.4 PAN ID" with "G.9959 HomeID" 488 When a 16-bit address is called for (i.e., an IEEE 802.15.4 "short 489 address") it MUST be formed by prepending an Interface label byte to 490 the G.9959 NodeID: 492 0 1 493 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 | Interface | NodeID | 496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 A transmitting node may be sending to an IPv6 destination address 499 which can be reconstructed from the link-layer destination address. 500 If the Interface number is zero (the default value), all IPv6 address 501 bytes may be elided. Likewise, the Interface number of a fully 502 elided IPv6 address (i.e. SAM/DAM=11) may be reconstructed to the 503 value zero by a receiving node. 505 64 bit 802.15.4 address details do not apply. 507 6. IANA Considerations 509 This document makes no request of IANA. 511 Note to RFC Editor: this section may be removed on publication as an 512 RFC. 514 7. Security Considerations 516 The method of derivation of Interface Identifiers from 8-bit NodeIDs 517 preserves uniqueness within the logical network. However, there is 518 no protection from duplication through forgery. Neighbor Discovery 519 in G.9959 links may be susceptible to threats as detailed in 520 [RFC3756]. G.9959 networks may feature mesh routing. This implies 521 additional threats due to ad hoc routing as per [KW03]. G.9959 522 provides capability for link-layer security. G.9959 nodes MUST use 523 link-layer security with a shared key. Doing so will alleviate the 524 majority of threats stated above. A sizeable portion of G.9959 525 devices is expected to always communicate within their PAN (i.e., 526 within their subnet, in IPv6 terms). In response to cost and power 527 consumption considerations, these devices will typically implement 528 the minimum set of features necessary. Accordingly, security for 529 such devices may rely on the mechanisms defined at the link layer by 530 G.9959. G.9959 relies on the Advanced Encryption Standard (AES) for 531 authentication and encryption of G.9959 frames and further employs 532 challenge-response handshaking to prevent replay attacks. 534 It is also expected that some G.9959 devices (e.g. billing and/or 535 safety critical products) will implement coordination or integration 536 functions. These may communicate regularly with IPv6 peers outside 537 the subnet. Such IPv6 devices are expected to secure their end-to- 538 end communications with standard security mechanisms (e.g., IPsec, 539 TLS, etc). 541 8. Privacy Considerations 543 IP addresses may be used to track devices on the Internet, which in 544 turn can be linked to individuals and their activities. Depending on 545 the application and the actual use pattern, this may be undesirable. 546 To impede tracking, globally unique and non-changing characteristics 547 of IP addresses should be avoided, e.g. by frequently changing the 548 global prefix and avoiding unique link-layer-derived IIDs in 549 addresses. 551 Some link layers use a 48-bit or a 64-bit link layer address which 552 uniquely identifies the node on a global scale regardless of global 553 prefix changes. The risk of exposing a G.9959 device from its link- 554 layer-derived IID is limited because of the short 8-bit link layer 555 address. 557 While intended for central address management, DHCPv6 address 558 assignment also decouples the IPv6 address from the link layer 559 address. 561 It should be noted that privacy and frequently changing address 562 assignment comes at a cost. Non-link-layer-derived IIDs require the 563 use of address registration and further, non-link-layer-derived IIDs 564 cannot be compressed, which leads to longer datagrams and increased 565 link layer segmentation. Finally, frequent prefix changes 566 necessitate more Context Identifier updates, which not only leads to 567 increased traffic but also may affect the battery lifetime of 568 sleeping nodes. 570 9. Acknowledgements 572 Thanks to the authors of RFC 4944 and RFC 6282 and members of the 573 IETF 6LoWPAN working group; this document borrows extensively from 574 their work. Thanks to Erez Ben-Tovim, Erik Nordmark, Kerry Lynn, 575 Michael Richardson, Tommas Jess Christensen for useful comments. 576 Thanks to Carsten Bormann for extensive feedback which improved this 577 document significantly. 579 10. References 581 10.1. Normative References 583 [G.9959] "G.9959 (02/12) + G.9959 Amendment 1 (10/13): Short range, 584 narrow-band digital radiocommunication transceivers", 585 February 2012. 587 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 588 Requirement Levels", BCP 14, RFC 2119, March 1997. 590 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 591 (IPv6) Specification", RFC 2460, December 1998. 593 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 594 Addresses", RFC 4193, October 2005. 596 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 597 Architecture", RFC 4291, February 2006. 599 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 600 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 601 September 2007. 603 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 604 "Transmission of IPv6 Packets over IEEE 802.15.4 605 Networks", RFC 4944, September 2007. 607 [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 608 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 609 September 2011. 611 [RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann, 612 "Neighbor Discovery Optimization for IPv6 over Low-Power 613 Wireless Personal Area Networks (6LoWPANs)", RFC 6775, 614 November 2012. 616 10.2. Informative References 618 [EUI64] IEEE, "GUIIDELINES FOR 64-BIT GLOBAL IDENTIFIER (EUI-64) 619 REGISTRATION AUTHORITY", IEEE Std http:// 620 standards.ieee.org/regauth/oui/tutorials/EUI64.html, 621 November 2012. 623 [KW03] Elsevier's AdHoc Networks Journal, ""Secure Routing in 624 Sensor Networks: Attacks and Countermeasures", Special 625 Issue on Sensor Network Applications and Protocols vol 1, 626 issues 2-3", , September 2003. 628 [RFC3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global 629 Unicast Address Format", RFC 3587, August 2003. 631 [RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor 632 Discovery (ND) Trust Models and Threats", RFC 3756, May 633 2004. 635 [RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., 636 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 637 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 638 RFC 3819, July 2004. 640 [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., 641 Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. 642 Alexander, "RPL: IPv6 Routing Protocol for Low-Power and 643 Lossy Networks", RFC 6550, March 2012. 645 [RFC6997] Goyal, M., Baccelli, E., Philipp, M., Brandt, A., and J. 646 Martocci, "Reactive Discovery of Point-to-Point Routes in 647 Low-Power and Lossy Networks", RFC 6997, August 2013. 649 Appendix A. G.9959 6LoWPAN datagram example 651 This example outlines each individual bit of a sample IPv6 UDP packet 652 arriving to a G.9959 node from a host in the Internet via a PAN 653 border router. 655 In the G.9959 PAN, the complete frame has the following fields. 657 G.9959: 659 +------+---------+----------+---+-----+----------... 660 |HomeID|SrcNodeID|FrmControl|Len|SeqNo|DestNodeID| 661 +------+---------+----------+---+-----+----------+-... 663 6LoWPAN: 665 ...+--------------+----------------+-----------------------... 666 |6LoWPAN CmdCls|6LoWPAN_IPHC Hdr|Compressed IPv6 headers| 667 ...-------------+----------------+-----------------------+-... 669 6LoWPAN, TCP/UDP, App payload: 671 ...+-------------------------+------------+-----------+ 672 |Uncompressed IPv6 headers|TCP/UDP/ICMP|App payload| 673 ...------------------------+------------+-----------+ 675 The frame comes from the source IPv6 address 676 2001:0db8:ac10:ef01::ff:fe00:1206. The source prefix 677 2001:0db8:ac10:ef01/64 is identified by the IPHC CID = 3. 679 The frame is delivered in direct range from the gateway which has 680 source NodeID = 1. The Interface Identifier (IID) ff:fe00:1206 is 681 recognised as a link-layer-derived address and is compressed to the 682 16 bit value 0x1206. 684 The frame is sent to the destination IPv6 address 685 2001:0db8:27ef:42ca::ff:fe00:0004. The destination prefix 686 2001:0db8:27ef:42ca/64 is identified by the IPHC CID = 2. 688 The Interface Identifier (IID) ff:fe00:0004 is recognised as a link- 689 layer-derived address. 691 Thanks to the link-layer-derived addressing rules, the sender knows 692 that this is to be sent to G.9959 NodeID = 4; targeting the IPv6 693 interface instance number 0 (the default). 695 To reach the 6LoWPAN stack of the G.9959 node, (skipping the G.9959 696 header fields) the first octet must be the 6LoWPAN Command Class 697 (0x4F). 699 0 700 0 1 2 3 4 5 6 7 8 701 +-+-+-+-+-+-+-+-... 702 | 0x4F | 703 +-+-+-+-+-+-+-+-+-... 705 The Dispatch header bits '011' advertises a compressed IPv6 header. 707 0 1 708 0 1 2 3 4 5 6 7 8 9 0 709 +-+-+-+-+-+-+-+-+-+-+-... 710 | 0x4F |0 1 1 711 +-+-+-+-+-+-+-+-+-+-+-+-... 713 The following bits encode the first IPv6 header fields: 715 TF = '11' : Traffic Class and Flow Label are elided. 716 NH = '1' : Next Header is elided 717 HLIM = '10' : Hop limit is 64 719 0 1 720 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 722 | 0x4F |0 1 1 1 1 1 1 0| 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 725 CID = '1' : CI data follows the DAM field 726 SAC = '1' : Src addr uses stateful, context-based compression 727 SAM = '10' : Use src CID and 16 bits for link-layer-derived addr 728 M = '0' : Dest addr is not a multicast addr 729 DAC = '1' : Dest addr uses stateful, context-based compression 730 DAM = '11' : Use dest CID and dest NodeID to link-layer-derived addr 732 0 1 2 733 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 735 | 0x4F |0 1 1 1 1 1 0 1|1 1 1 0 0 1 1 1| 736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 738 Address compression context identifiers: 740 SCI = 0x3 741 DCI = 0x2 743 2 3 744 4 5 6 7 8 9 0 1 745 ...+-+-+-+-+-+-+-+-... 746 | 0x3 | 0x2 | 747 ...+-+-+-+-+-+-+-+-... 749 IPv6 header fields: 750 (skipping "version" field) 751 (skipping "Traffic Class") 752 (skipping "flow label") 753 (skipping "payload length") 755 IPv6 header address fields: 757 SrcIP = 0x1206 : Use SCI and 16 LS bits of link-layer-derived address 759 (skipping DestIP ) - completely reconstructed from Dest NodeID and DCI 761 2 3 4 762 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 763 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 764 | 0x3 | 0x2 | 0x12 | 0x06 | 765 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 767 Hext header encoding for the UDP header: 769 Dispatch = '11110': Next Header dispatch code for UDP header 770 C = '0' : 16 bit checksupm carried inline 771 P = '00' : both src port and dest Port are carried in-line. 773 4 5 774 8 9 0 1 2 3 4 5 775 ...+-+-+-+-+-+-+-+-... 776 |1 1 1 1 0|0|0 0| 777 ...+-+-+-+-+-+-+-+-... 779 UDP header fields: 781 src Port = 0x1234 782 dest port = 0x5678 784 5 6 7 8 785 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 786 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 787 | 0x12 | 0x34 | 0x56 | 0x78 | 788 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-.. 790 (skipping "length") 791 checksum = .... (actual checksum value depends on 792 the actual UDP payload) 794 1 795 8 9 0 796 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 797 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 798 | (UDP checksum) | 799 ...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... 801 Add your own UDP payload here... 803 Appendix B. Change Log 805 B.1. Changes since -00 807 o Clarified that mesh-under routing may take place below the 6LoWPAN 808 layer but that specific mesh-under routing protocols are not 809 within the scope of this doc. 811 o Clarified that RFC6282 IPv6 Header Compression MUST be supported. 813 o Clarified the text of section 5.4 on the use of RFC6775 address 814 registration in mesh-under networks. 816 o Split 5.4.2 into multiple paragraphs. 818 B.2. Changes since -01 820 o Added this Change Log 822 o Editorial nits. 824 o Made IPv6 Header Compression mandatory. Therefore, the Dispatch 825 value "01 000001 - Uncompressed IPv6 Addresses" was removed from 826 figure 2. 828 o Changed SHOULD to MUST: An IPv6 host SHOULD construct its link- 829 local IPv6 address and routable IPv6 addresses from the NodeID in 830 order to facilitate IP header compression as described in 831 [RFC6282]. 833 o Changed SHOULD NOT to MUST NOT: Mesh-under networks MUST NOT use 834 [RFC6775] address registration. 836 o Changed SHOULD NOT to MUST NOT: [RFC6775] Duplicate Address 837 Detection (DAD) MUST NOT be used. 839 o Changed SHOULD NOT to MUST NOT: The CID MUST NOT be reused 840 immediately; 842 o Changed SHOULD NOT to MUST NOT: An expired CID and the associated 843 prefix MUST NOT be reset but rather retained in receive-only mode 845 o Changed LBR -> ABR 847 o Changed SHOULD to MUST: , the ABR MUST return an RA with fresh 848 Context Information to the originator. 850 o Changed SHOULD NOT to MUST NOT: This value MUST NOT be used by 851 ABRs. Its use is only intended for a sleeping network controller; 853 B.3. Changes since -02 855 o Editorial nits. 857 o Moved text to the right section so that it does not prohibit DAD 858 for Route-Over deployments. 860 o Introduced RA m flag support so that nodes may be instructed to 861 use DHCPv6 for centralized address assignment. 863 o Added example appendix: Complete G.9959 6LoWPAN datagram 864 composition with CID-based header compression 866 B.4. Changes since -03 868 o Corrected error in 6LoWPAN datagram example appendix: 64 hop limit 869 in comment => also 64 hop limit in actual frame format. 871 o Added section "Privacy Considerations" 873 Authors' Addresses 875 Anders Brandt 876 Sigma Designs 877 Emdrupvej 26A, 1. 878 Copenhagen O 2100 879 Denmark 881 Email: anders_brandt@sigmadesigns.com 883 Jakob Buron 884 Sigma Designs 885 Emdrupvej 26A, 1. 886 Copenhagen O 2100 887 Denmark 889 Email: jakob_buron@sigmadesigns.com