idnits 2.17.1 draft-thubert-6lo-routing-dispatch-03.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 : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC4944, but the abstract doesn't seem to directly say this. It does mention RFC4944 though, so this could be OK. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year (Using the creation date from RFC4944, updated by this document, for RFC5378 checks: 2005-07-13) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (January 19, 2015) is 3385 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) == Missing Reference: 'RFCthis' is mentioned on line 784, but not defined == Unused Reference: 'I-D.bormann-6lo-rpl-mesh' is defined on line 859, but no explicit reference was found in the text == Unused Reference: 'I-D.thubert-6lo-rpl-nhc' is defined on line 881, but no explicit reference was found in the text -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE802154' ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Downref: Normative reference to an Informational RFC: RFC 7102 ** Downref: Normative reference to an Informational RFC: RFC 7228 == Outdated reference: A later version (-02) exists of draft-bergmann-bier-ccast-00 == Outdated reference: A later version (-30) exists of draft-ietf-6tisch-architecture-04 == Outdated reference: A later version (-06) exists of draft-ietf-6tisch-tsch-05 == Outdated reference: A later version (-08) exists of draft-thubert-6lo-forwarding-fragments-02 == Outdated reference: A later version (-05) exists of draft-wijnands-bier-architecture-02 Summary: 3 errors (**), 0 flaws (~~), 9 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6lo P. Thubert, Ed. 3 Internet-Draft Cisco 4 Updates: 4944 (if approved) C. Bormann 5 Intended status: Standards Track Uni Bremen TZI 6 Expires: July 23, 2015 L. Toutain 7 IMT-TELECOM Bretagne 8 R. Cragie 9 ARM 10 January 19, 2015 12 A Routing Header Dispatch for 6LoWPAN 13 draft-thubert-6lo-routing-dispatch-03 15 Abstract 17 This specification provides a new 6LoWPAN dispatch type for use in 18 Route-over and mixed Mesh-under and Route-over topologies, that 19 reuses the encoding of the mesh type defined in RFC 4944 for pure 20 Mesh-under topologies. This specification also defines a method to 21 compress RPL Option (RFC6553) information and Routing Header type 3 22 (RFC6554), an efficient IP-in-IP technique and opens the way for 23 further routing techniques. This extends 6LoWPAN Transmission of 24 IPv6 Packets (RFC4944), and is applicable to new link-layer types 25 where 6LoWPAN is being defined. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on July 23, 2015. 44 Copyright Notice 46 Copyright (c) 2015 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 3. Updating RFC 4944 . . . . . . . . . . . . . . . . . . . . . . 5 64 4. General Format . . . . . . . . . . . . . . . . . . . . . . . 5 65 4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 6 66 4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 6 67 4.3. Placement of 6LoRH . . . . . . . . . . . . . . . . . . . 7 68 4.3.1. 6LoRH before Fragmentation Type and Header . . . . . 7 69 4.3.2. 6LoRH after Fragmentation Type and Header . . . . . . 7 70 5. The Routing Header type 3 (RH3) 6LoRH . . . . . . . . . . . . 8 71 6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 9 72 6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 10 73 6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 10 74 6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 11 75 7. The IP-in-IP 6LoRH . . . . . . . . . . . . . . . . . . . . . 13 76 8. The Mesh Header 6LoRH . . . . . . . . . . . . . . . . . . . . 14 77 9. The BIER 6LoRH . . . . . . . . . . . . . . . . . . . . . . . 15 78 10. Security Considerations . . . . . . . . . . . . . . . . . . . 17 79 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 80 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 81 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 82 13.1. Normative References . . . . . . . . . . . . . . . . . . 18 83 13.2. Informative References . . . . . . . . . . . . . . . . . 19 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 86 1. Introduction 88 The design of Low Power and Lossy Networks (LLNs) is generally 89 focused on saving energy, which is the most constrained resource of 90 all. The other constraints, such as the memory capacity and the duty 91 cycling of the LLN devices, derive from that primary concern. Energy 92 is often available from primary batteries that are expected to last 93 for years, or is scavenged from the environment in very limited 94 quantities. Any protocol that is intended for use in LLNs must be 95 designed with the primary concern of saving energy as a strict 96 requirement. 98 Controlling the amount of data transmission is one possible venue to 99 save energy. In a number of LLN standards, the frame size is limited 100 to much smaller values than the IPv6 maximum transmission unit (MTU) 101 of 1280 bytes. In particular, an LLN that relies on the classical 102 Physical Layer (PHY) of IEEE 802.14.5 [IEEE802154] is limited to 127 103 bytes per frame. The need to compress IPv6 packets over IEEE 104 802.14.5 led to the 6LoWPAN Header Compression [RFC6282] work 105 (6LoWPAN-HC). 107 Innovative Route-over techniques have been and are still being 108 developed for routing inside a LLN. In a general fashion, such 109 techniques require additional information in the packet to provide 110 loop prevention and to indicate information such as flow 111 identification, source routing information, etc. 113 For reasons such as security and the capability to send ICMP errors 114 back to the source, an original packet must not be tampered with, and 115 any information that must be inserted in or removed from an IPv6 116 packet must be placed in an extra IP-in-IP encapsulation. This is 117 the case when the additional routing information is inserted by a 118 router on the path of a packet, for instance a mesh root, as opposed 119 to the source node. This is also the case when some routing 120 information must be removed from a packet that will flow outside the 121 LLN. 123 As an example, the Routing Protocol for Low Power and Lossy Networks 124 [RFC6550] (RPL) is designed to optimize the routing operations in 125 constrained LLNs. As part of this optimization, RPL requires the 126 addition of RPL Packet Information (RPI) in every packet, as defined 127 in Section 11.2 of [RFC6550]. 129 The RPL Option for Carrying RPL Information in Data-Plane Datagrams 130 [RFC6553] specification indicates how the RPI can be placed in a RPL 131 Option for use in an IPv6 Hop-by-Hop header. This representation 132 demands a total of 8 bytes when in most cases the actual RPI payload 133 requires only 19 bits. Since the Hop-by-Hop header must not flow 134 outside of the RPL domain, it must be removed from packets that leave 135 the domain, and be inserted in packets entering the domain. In both 136 cases, this operation implies an IP-in-IP encapsulation. 138 ------+--------- ^ 139 | Internet | 140 | | Native IPv6 141 +-----+ | 142 | | Border Router (RPL Root) ^ | ^ 143 | | | | | 144 +-----+ | | | IPv6 in 145 | | | | IPv6 146 o o o o | | | + RPI 147 o o o o o o o o o | | | or RH3 148 o o o o o o o o o o | | | 149 o o o o o o o o o | | | 150 o o o o o o o o v v v 151 o o o o 152 LLN 154 Figure 1: IP-in-IP Encapsulation within the LLN 156 Additionally, in the case of the Non-Storing Mode of Operation (MOP), 157 RPL requires a Routing Header type 3 (RH3) as defined in the IPv6 158 Routing Header for Source Routes with RPL [RFC6554] specification, 159 for all packets that are routed down a RPL graph. With Non-Storing 160 RPL, even if the source is a node in the same LLN, the packet must 161 first reach up the graph to the root so that the root can insert the 162 RH3 to go down the graph. In any fashion, whether the packet was 163 originated in a node in the LLN or outside the LLN, and regardless of 164 whether the packet stays within the LLN or not, as long as the source 165 of the packet is not the root itself, the source-routing operation 166 also implies an IP-in-IP encapsulation at the root to insert the RH3. 168 6TiSCH [I-D.ietf-6tisch-architecture] specifies the operation of IPv6 169 over the TimeSlotted Channel Hopping [I-D.ietf-6tisch-tsch] (TSCH) 170 mode of operation of IEEE 802.14.5. The architecture requires the 171 use of both RPL and the 6lo adaptation layer framework ([RFC4944], 172 [RFC6282]) over IEEE 802.14.5. Because it inherits the constraints 173 on the frame size from the MAC layer, 6TiSCH cannot afford to spend 8 174 bytes per packet on the RPI. Hence the requirement for a 6LoWPAN 175 header compression of the RPI. 177 The type of information that needs to be present in a packet inside 178 the LLN but not outside of the LLN varies with the routing operation, 179 but there is overall a need for an extensible compression technique 180 that would simplify the IP-in-IP encapsulation, when needed, and 181 optimally compress existing routing artifacts found in LLNs. 183 This specification extends 6LoWPAN [RFC4944] and in particular reuses 184 the Mesh Header formats that are defined for the Mesh-under use cases 185 so as to carry routing information for Route-over use cases. The 186 specification includes the formats necessary for RPL and is 187 extensible for additional formats. 189 2. Terminology 191 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 192 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 193 "OPTIONAL" in this document are to be interpreted as described in 194 [RFC2119]. 196 The Terminology used in this document is consistent with and 197 incorporates that described in `Terminology in Low power And Lossy 198 Networks' [RFC7102] and [RFC6550]. 200 The terms Route-over and Mesh-under are defined in [RFC6775]. 202 Other terms in use in LLNs are found in [RFC7228]. 204 The term "byte" is used in its now customary sense as a synonym for 205 "octet". 207 3. Updating RFC 4944 209 Section 5.1 of the IPv6 over IEEE 802.15.4 [RFC4944] specification 210 defines various Dispatch Types and Headers, and in particular a Mesh 211 Header that corresponds to a pattern 10xxxxxx and effectively 212 consumes one third of the whole 6LoWPAN dispatch space for Mesh-under 213 specific applications. 215 This specification reuses the Dispatch space for Route-over and mixed 216 operations. This means that a device that use the Mesh Header as 217 specified in [RFC4944] should not be placed in a same network as a 218 device which operates per this update. This is generally not a 219 problem since a network is classically either Mesh-under OR Route- 220 over. 222 A new implementation of Mesh-under MAY support both types of 223 encoding, and if so, it SHOULD provide a management toggle to enable 224 either mode and it SHOULD use this specification as the default mode. 226 4. General Format 228 The 6LoWPAN Routing Header (6LoRH) reuses the bit patterns that are 229 defined in [RFC4944] for the Mesh Header, specifically the Dispatch 230 Value Bit Pattern of 10xxxxxx. 231 It may contain source routing information such as a compressed form 232 of RH3, or other sorts of routing information such as the RPL RPI, 233 source and/or destination address, and is extensible for future uses, 234 with the given example of BIER bitmap encoding in Section 9. 236 There are two forms for 6LoRH: > Elective (6LoRHE) > Critical 237 (6LoRHC) 239 4.1. Elective Format 241 The 6LoRHE uses the Dispatch Value Bit Pattern of 101xxxxx. 242 A 6LoRHE may be ignored and skipped in parsing. 243 If it is ignored, the 6LoRHE is forwarded with no change inside the 244 LLN. 246 0 1 247 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 249 |1|0|1| Length | Type | | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 251 <-- Length --> 253 Figure 2: Elective 6LoWPAN Routing Header 255 Length: 256 Length of the 6LoRHE expressed in bytes, excluding the first 2 257 bytes. This is done to enable a node to skip a 6LoRH that it does 258 not support and/or cannot parse, for instance if the Type is not 259 known. 261 Type: 262 Type of the 6LoRHE 264 4.2. Critical Format 266 The 6LoRHC uses the Dispatch Value Bit Pattern of 100xxxxx. 267 A node which does not support the 6LoRHC Type MUST silently discard 268 the packet (note that there is no provision for the exchange of error 269 messages; such a situation should be avoided by judicious use of 270 administrative control and/or capability indications). 272 0 1 273 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 275 |1|0|0| TSE | Type | | 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 277 <-- Length implied by Type/TSE --> 279 Figure 3: Critical 6LoWPAN Routing Header 281 TSE: 282 Type Specific Extension. The meaning depends on the Type, which 283 must be known in all of the nodes. The interpretation of the TSE 284 depends on the Type field that follows. For instance, it may be 285 used to transport control bits, the number of elements in an 286 array, or the length of the remainder of the 6LoRHC expressed in a 287 unit other than bytes. 289 Type: 290 Type of the 6LoRHC 292 4.3. Placement of 6LoRH 294 One or more 6LoRHs MAY be placed in a 6LoWPAN packet and MUST always 295 be placed before the LOWPAN_IPHC [RFC6282]. A 6LoRH MAY be used in 296 conjunction with a Fragmentation Type and Header [RFC4944] in three 297 ways: > Before the Fragmentation Type and Header > Before and after 298 the Fragmentation Type and Header > After the Fragmentation Type and 299 Header 301 Headers are processed in order so if a 6LoRH is processed that is 302 sufficient to route a packet, then there is no need for the 303 intermediate node to process the packet further. 305 4.3.1. 6LoRH before Fragmentation Type and Header 307 | 6LoRH | Frag1 | IPHC | Payload Frag1 | 308 | 6LoRH | FragN | Payload Frag2 | 309 | 6LoRH | FragN | Payload Frag3 |... 311 If a 6LoRH is placed before a Fragmentation Type and Header, the 312 fragments can be routed individually. 314 4.3.2. 6LoRH after Fragmentation Type and Header 316 | Frag1 | 6LoRH | IPHC | Payload Frag1 | 317 | FragN | Payload Frag2 | 318 | FragN | Payload Frag3 |... 320 If a 6LoRH is placed after a Fragmentation Type and Header, the 321 fragments cannot be individually routed and the whole IPv6 packet 322 needs to be reassembled at every LLN hop, unless a fragment 323 forwarding technique, such as discussed in LLN Fragment Forwarding 324 and Recovery [I-D.thubert-6lo-forwarding-fragments], is used. 326 5. The Routing Header type 3 (RH3) 6LoRH 328 The Routing Header type 3 (RH3) 6LoRH (RH3-6LoRH) is a Critical 329 6LoWPAN Routing Header that provides a compressed form for the RH3, 330 as defined in [RFC6554] for use by RPL routers. Routers that need to 331 forward a packet with a RH3-6LoRH are expected to be RPL routers and 332 expected to support this specification. If a non-RPL router receives 333 a packet with a RPI-6LoRH, this means that there was a routing error 334 and the packet should be dropped so the Type cannot be ignored. 336 0 1 337 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+ 339 |1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+ 342 Size indicates the number of compressed addresses 344 Figure 4: The RH3-6LoRH 346 The values for the RH3-6LoRH Type are an enumeration, 0 to 4. The 347 form of compression is indicated by the Type as follows: 349 +-----------+-----------+ 350 | Type | Size Unit | 351 +-----------+-----------+ 352 | 0 | 1 | 353 | 1 | 2 | 354 | 2 | 4 | 355 | 3 | 8 | 356 | 4 | 16 | 357 +-----------+-----------+ 359 Figure 5: The RH3-6LoRH Types 361 In the case of a RH3-6LoRH, the TSE field is used as a Size, which 362 encodes the number of hops minus 1; so a Size of 0 means one hop, and 363 the maximum that can be encoded is 32 hops. (If more than 32 hops 364 need to be expressed, a sequence of RH3-6LoRH can be employed.) 366 The next Hop is indicated in the first entry of the first RH3-6LoRH. 367 Upon reception, the entry is checked whether it refers to the 368 processing router itself. If it so, the entry is removed from the 369 RH3-6LoRH and the Size is decremented. If the Size is now zero, the 370 whole RH3-6LoRH is removed. If there is no more RH3-6LoRH, the 371 processing node is the last router on the way, which may or may not 372 be collocated with the final destination. 374 The last hop in the last RH3-6LoRH is the last router prior to the 375 destination in the LLN. So even when there is a RH3-6LoRH in the 376 frame, the address of the final destination is in the LoWPAN_IPHC 377 [RFC6282]. 379 If some bits of the first address in the RH3-6LoRH can be derived 380 from the final destination is in the LoWPAN_IPHC, then that address 381 may be compressed, otherwise is is expressed in full. Next addresses 382 only need to express the delta from the previous address. 384 All addresses in a RH3-6LoRH are compressed in a same fashion, down 385 to the same number of bytes per address. In order to get different 386 forms of compression, multiple consecutive RH3-6LoRH must be used. 388 6. The RPL Packet Information 6LoRH 390 [RFC6550], Section 11.2, specifies the RPL Packet Information (RPI) 391 as a set of fields that are to be added to the IP packets for the 392 purpose of Instance Identification, as well as Loop Avoidance and 393 Detection. 395 In particular, the SenderRank, which is the scalar metric computed by 396 an specialized Objective Function such as [RFC6552], indicates the 397 Rank of the sender and is modified at each hop. The SenderRank 398 allows to validate that the packet progresses in the expected 399 direction, either upwards or downwards, along the DODAG. 401 RPL defines the RPL Option for Carrying RPL Information in Data-Plane 402 Datagrams [RFC6553] to transport the RPI, which is carried in an IPv6 403 Hop-by-Hop Options Header [RFC2460], typically consuming eight bytes 404 per packet. 406 With [RFC6553], the RPL option is encoded as six Octets; it must be 407 placed in a Hop-by-Hop header that consumes two additional octets for 408 a total of eight. In order to limit its range to the inside the RPL 409 domain, the Hop-by-Hop header must be added to (or removed from) 410 packets that cross the border of the RPL domain. 412 The 8-bytes overhead is detrimental to the LLN operation, in 413 particular with regards to bandwidth and battery constraints. These 414 bytes may cause a containing frame to grow above maximum frame size, 415 leading to Layer 2 or 6LoWPAN [RFC4944] fragmentation, which in turn 416 cause even more energy spending and issues discussed in the LLN 417 Fragment Forwarding and Recovery 418 [I-D.thubert-6lo-forwarding-fragments]. 420 An additional overhead comes from the need, in certain cases, to add 421 an IP-in-IP encapsulation to carry the Hop-by-Hop header. This is 422 needed when the router that inserts the Hop-by-Hop header is not the 423 source of the packet, so that an error can be returned to the router. 424 This is also the case when a packet originated by a RPL node must be 425 stripped from the Hop-by-Hop header to be routed outside the RPL 426 domain. 428 This specification defines an IPinIP-6LoRH in Section 7 for that 429 purpose, but it must be noted that stripping a 6LoRH does not require 430 a manipulation of the packet in the LOWPAN_IPHC, and thus, if the 431 source address in the LOWPAN_IPHC is the node that inserted the 432 IPinIP-6LoRH then this alone does not mandate an IPinIP-6LoRH. 434 As a result, a RPL packet may bear only a RPI-6LoRH and no IPinIP- 435 6LoRH. In that case, the source and destination of the packet are 436 located in the LOWPAN_IPHC. 438 As with [RFC6553], the fields in the RPI include an 'O', an 'R', and 439 an 'F' bit, an 8-bit RPLInstanceID (with some internal structure), 440 and a 16-bit SenderRank. 442 The remainder of this section defines the RPI-6LoRH, a Critical 443 6LoWPAN Routing Header that is designed to transport the RPI in 444 6LoWPAN LLNs. 446 6.1. Compressing the RPLInstanceID 448 RPL Instances are discussed in [RFC6550], Section 5. A number of 449 simple use cases will not require more than one instance, and in such 450 a case, the instance is expected to be the global Instance 0. A 451 global RPLInstanceID is encoded in a RPLInstanceID field as follows: 453 0 1 2 3 4 5 6 7 454 +-+-+-+-+-+-+-+-+ 455 |0| ID | Global RPLInstanceID in 0..127 456 +-+-+-+-+-+-+-+-+ 458 Figure 6: RPLInstanceID Field Format for Global Instances 460 For the particular case of the global Instance 0, the RPLInstanceID 461 field is all zeros. This specification allows to elide a 462 RPLInstanceID field that is all zeros, and defines a I flag that, 463 when set, signals that the field is elided. 465 6.2. Compressing the SenderRank 467 The SenderRank is the result of the DAGRank operation on the rank of 468 the sender; here the DAGRank operation is defined in [RFC6550], 469 Section 3.5.1, as: 471 DAGRank(rank) = floor(rank/MinHopRankIncrease) 473 If MinHopRankIncrease is set to a multiple of 256, the least 474 significant 8 bits of the SenderRank will be all zeroes; by eliding 475 those, the SenderRank can be compressed into a single byte. This 476 idea is used in [RFC6550] by defining DEFAULT_MIN_HOP_RANK_INCREASE 477 as 256 and in [RFC6552] that defaults MinHopRankIncrease to 478 DEFAULT_MIN_HOP_RANK_INCREASE. 480 This specification allows to encode the SenderRank as either one or 481 two bytes, and defines a K flag that, when set, signals that a single 482 byte is used. 484 6.3. The Overall RPI-6LoRH encoding 486 The RPI-6LoRH provides a compressed form for the RPL RPI. Routers 487 that need to forward a packet with a RPI-6LoRH are expected to be RPL 488 routers and expected to support this specification. If a non-RPL 489 router receives a packet with a RPI-6LoRH, this means that there was 490 a routing error and the packet should be dropped so the Type cannot 491 be ignored. 493 Since the I flag is not set, the TSE field does not need to be a 494 length expressed in bytes. The field is fully reused for control 495 bits so as to encode the O, R and F flags from the RPI, and the I and 496 K flags that indicate the compression that is taking place. 498 The Type for the RPI-6LoRH is 5. 500 The RPI-6LoRH is immediately followed by the RPLInstanceID field, 501 unless that field is fully elided, and then the SenderRank, which is 502 either compressed into one byte or fully in-lined as the whole 2 503 bytes. The I and K flags in the RPI-6LoRH indicate whether the 504 RPLInstanceID is elided and/or the SenderRank is compressed and 505 depending on these bits, the Length of the RPI-6LoRH may vary as 506 described hereafter. 508 0 1 2 509 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+ 511 |1|0|0|O|R|F|I|K| 6LoRH Type=5 | Compressed fields | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+ 514 Figure 7: The Generic RPI-6LoRH Format 516 O, R, and F bits: 517 The O, R, and F bits as defined in [RFC6550], Section 11.2. 519 I bit: 520 If it is set, the Instance ID is elided and the RPLInstanceID 521 is the Global RPLInstanceID 0. If it is not set, the octet 522 immediately following the type field contains the RPLInstanceID 523 as specified in [RFC6550] section 5.1. 525 K bit: 526 If it is set, the SenderRank is be compressed into one octet, 527 and the lowest significant octet is elided. If it is not set, 528 the SenderRank, is fully inlined as 2 octets. 530 In Figure 8, the RPLInstanceID is the Global RPLInstanceID 0, and the 531 MinHopRankIncrease is a multiple of 256 so the least significant byte 532 is all zeros and can be elided: 534 0 1 2 535 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 |1|0|0|O|R|F|1|1| 6LoRH Type=5 | SenderRank | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 I=1, K=1 541 Figure 8: The most compressed RPI-6LoRH 543 In Figure 9, the RPLInstanceID is the Global RPLInstanceID 0, but 544 both bytes of the SenderRank are significant so it can not be 545 compressed: 547 0 1 2 3 548 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 1 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 |1|0|0|O|R|F|1|0| 6LoRH Type=5 | SenderRank | 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 552 I=1, K=0 554 Figure 9: Eliding the RPLInstanceID 556 In Figure 10, the RPLInstanceID is not the Global RPLInstanceID 0, 557 and the MinHopRankIncrease is a multiple of 256: 559 0 1 2 3 560 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 1 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 |1|0|0|O|R|F|0|1| 6LoRH Type=5 | RPLInstanceID | SenderRank | 563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 I=0, K=1 566 Figure 10: Compressing SenderRank 568 In Figure 11, the RPLInstanceID is not the Global RPLInstanceID 0, 569 and both bytes of the SenderRank are significant: 571 0 1 2 3 572 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 1 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 |1|0|0|O|R|F|0|0| 6LoRH Type=5 | RPLInstanceID | Sender-... 575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 576 ...-Rank | 577 +-+-+-+-+-+-+-+-+ 578 I=0, K=0 580 Figure 11: Least compressed form of RPI-6LoRH 582 A typical packet in RPL non-storing mode going down the RPL graph 583 requires an IPinIP encapsulating the RH3, whereas the RPI is usually 584 omitted, unless it is important to indicate the RPLInstanceID. To 585 match this structure, an optimized IPinIP 6LoRH is defined in 586 Section 7. 588 7. The IP-in-IP 6LoRH 590 The IP-in-IP 6LoRH (IPinIP-6LoRH) is an Elective 6LoWPAN Routing 591 Header that provides a compressed form for the encapsulating IPv6 592 Header in the case of an IP-in-IP encapsulation. 594 An IPinIP encapsulation is used to insert a field such as a Routing 595 Header or an RPI at a router that is not the source of the packet. 596 In order to send an error back regarding the inserted field, the 597 address of the router that performs the insertion must be provided. 599 The encapsulation can also enable a router down the path removing a 600 field such as the RPI, but this can be done in the compressed form by 601 removing the RPI-6LoRH, so an IPinIP-6LoRH encapsulation is not 602 required for that sole purpose. 604 This field is not critical for routing so the Type can be ignored, 605 and the TSE field contains the Length in bytes. 607 0 1 2 608 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 610 |1|0|1| Length | 6LoRH Type 6 | Hop Limit | Encaps. Address | 611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 613 Figure 12: The IPinIP-6LoRH 615 The Length of an IPinIP-6LoRH is expressed in bytes and MUST be at 616 least 1, to indicate a Hop Limit (HL), that is decremented at each 617 hop. When the HL reaches 0, the packet is dropped per [RFC2460] 619 If the Length of an IPinIP-6LoRH is exactly 1, then the Encapsulator 620 Address is elided, which means that the Encapsulator is a well-known 621 router, for instance the root in a RPL graph. 623 If the Length of an IPinIP-6LoRH is strictly more than 1, then an 624 Encapsulator Address is placed in a compressed form after the Hop 625 Limit field. The value of the Length indicates which compression is 626 performed on the Encapsulator Address. For instance, a Size of 3 627 indicates that the Encapsulator Address is compressed to 2 bytes. 629 When it cannot be elided, the destination IP address of the IP-in-IP 630 header is transported in a RH3-6LoRH as the first address of the 631 list. 633 With RPL, the destination address in the IP-in-IP header is 634 implicitly the root in the RPL graph for packets going upwards, and 635 the destination address in the IPHC for packets going downwards. If 636 the implicit value is correct, the destination IP address of the IP- 637 in-IP encapsulation can be elided. 639 If the final destination of the packet is a leaf that does not 640 support this specification, then the chain of 6LoRH must be stripped 641 by the RPL/6LR router to which the leaf is attached. In that 642 example, the destination IP address of the IP-in-IP header cannot be 643 elided. 645 In the special case where the 6LoRH is used to route 6LoWPAN 646 fragments, the destination address is not accessible in the IPHC on 647 all fragments and can be elided only for the first fragment and for 648 packets going upwards. 650 8. The Mesh Header 6LoRH 652 The Mesh Header 6LoRH (MH-6LoRH) is an Elective 6LoWPAN Routing 653 Header that provides an alternate form for the Mesh Addressing Type 654 and Header defined in [RFC4944] with the same semantics. 656 The MH-6LoRH is introduced as replacement for use in potentially 657 mixed Route_Over and Mesh-under environments. LLN nodes that need to 658 forward a packet with a MH-6LoRH are expected to support this 659 specification. If a router that supports only Route-over receives a 660 packet with a MH-6LoRH, this means that there was a routing error and 661 the packet should be dropped, so the Type cannot be ignored. 663 The HopsLft field defined in [RFC4944] is encoded in the TSE, so this 664 specification doubles the potential number of hops vs. [RFC4944]. 666 The HopsLft value of 0x1F is reserved and signifies an 8-bit Deep 667 Hops Left field immediately following the Type, and allows a source 668 node to specify a hop limit greater than 30 hops. 670 0 1 671 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 673 |1|0|0| HopsLft |6LoRHType 8..11| originator address, final address | 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ 676 Figure 13: The MH-6LoRH 678 The V and F flags defined in [RFC4944] are encoded in the MH-6LoRH 679 Type as follows: 681 +-----------+-------+-------+ 682 | Type | V | F | 683 +-----------+-------+-------+ 684 | 8 | 0 | 0 | 685 | 9 | 0 | 1 | 686 | 10 | 1 | 0 | 687 | 11 | 1 | 1 | 688 +-----------+-------+-------+ 690 Figure 14: The MH-6LoRH Types 692 9. The BIER 6LoRH 694 (Note that the current contents of this section is a proof of concept 695 only; the details for this encoding need to be developed in parallel 696 with defining the semantics of a constrained version of BIER.) 698 The Bit Index Explicit Replication (BIER) 6LoRH (BIER-6LoRH) is an 699 Elective 6LoWPAN Routing Header that provides a variable-size 700 container for a BIER Bitmap. BIER can be used to route downwards a 701 RPL graph towards one or more LLN node, as discussed in the BIER 702 Architecture [I-D.wijnands-bier-architecture] specification. The 703 capability to parse the BIER Bitmap is necessary to forward the 704 packet so the Type cannot be ignored. 706 0 1 707 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+- ... -+ 709 |1|0|0| Size |6LoRHType12..19| Control Fields | bitmap | 710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+- ... -+ 712 Figure 15: The BIER-6LoRH 714 The Type for a BIER-6LoRH indicates the size of words used to build 715 the bitmap and whether the bitmap is operated as an uncompressed bit- 716 by-bit mapping, or as a Bloom filter. 718 In the bit-by-bit case, each bit is mapped in an unequivocal fashion 719 with a single addressable resource in the network. This may rapidly 720 lead to large bitmaps, and BIER allows to divide a network into 721 groups that partition the network so that a given bitmap is locally 722 significant to one group only. This specification allows to encode a 723 1-byte Group ID in the BIER-6LoRH Control Fields. 725 A Bloom Filter can be seen as a compression technique for the bitmap. 726 A Bloom Filter may generate false positives, which, in the case of 727 BIER, result in undue forwarding of a packet down a path where no 728 listener exists. 730 As an example, the Constrained-Cast [I-D.bergmann-bier-ccast] 731 specification employs Bloom Filters as a compact representation of a 732 match or non-match for elements in a large set. 734 In the case of a Bloom Filter, a number of Hash functions must be run 735 to obtain a multi-bit signature of an encoded element. This 736 specification allows to signal an Identifier of the Hash functions 737 being used to generate a certain bitmap, so as to enable a migration 738 scenario where Hash functions are renewed. A Hash ID is signaled as 739 a 1-byte value, and, depending on the Type, there may be up to 2 or 740 up to 8 Hash IDs passed in the BIER-6LoRH Control Fields associated 741 with a Bloom Filter bitmap, as follows: 743 +-----------+--------------+------------------+-----------+ 744 | Type | encoding | Control Fields | Word Size | 745 +-----------+--------------+------------------+-----------+ 746 | 12 | bit-by-bit | none | 32 bits | 747 | 13 | Bloom filter | 2* 1-byte HashID | 32 bits | 748 | 14 | bit-by-bit | none | 128 bits | 749 | 15 | Bloom filter | 8* 1-byte HashID | 128 bits | 750 | 16 | bit-by-bit | 1-byte GroupID | 128 bits | 751 +-----------+--------------+------------------+-----------+ 753 Figure 16: The BIER-6LoRH Types 755 In order to address a potentially large number of devices, the bitmap 756 may grow very large. Yet, the maximum frame size for a given MAC 757 layer may limit the number of bits that can be dedicated to routing. 758 The Size indicates the number of words in the bitmap minus one, so a 759 size of 0 means one word, a Size of 1 means 64 2 words, up to a size 760 of 31 which means 32 words. 762 10. Security Considerations 764 The security considerations of [RFC4944], [RFC6282], and [RFC6553] 765 apply. 767 Using a compressed format as opposed to the full in-line format is 768 logically equivalent and does not create an opening for a new threat 769 when compared to [RFC6550], [RFC6553] and [RFC6554]. 771 11. IANA Considerations 773 This document creates a IANA registry for the 6LoWPAN Routing Header 774 Type, and assigns the following values: 776 0..4 : RH3-6LoRH [RFCthis] 778 5 : RPI-6LoRH [RFCthis] 780 6 : IPinIP-6LoRH [RFCthis] 782 8..11 : MH-6LoRH [RFCthis] 784 12..16 : BIER-6LoRH [RFCthis] 786 12. Acknowledgments 788 The authors wish to thank Martin Turon, James Woodyatt and Ralph 789 Droms for constructive reviews to the design in the 6lo Working 790 Group. The overall discussion involved participants to the 6MAN, 791 6TiSCH and ROLL WGs, thank you all. Special thanks to the chairs of 792 the ROLL WG, Michael Richardson and Ines Robles, and Brian Haberman, 793 Internet Area A-D, and Adrian Farrel, Routing Area A-D, for driving 794 this complex effort across Working Groups and Areas. 796 13. References 798 13.1. Normative References 800 [IEEE802154] 801 IEEE standard for Information Technology, "IEEE std. 802 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 803 and Physical Layer (PHY) Specifications for Low-Rate 804 Wireless Personal Area Networks", 2015. 806 [ISA100.11a] 807 ISA/ANSI, "Wireless Systems for Industrial Automation: 808 Process Control and Related Applications - ISA100.11a-2011 809 - IEC 62734", 2011, . 812 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 813 Requirement Levels", BCP 14, RFC 2119, March 1997. 815 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 816 (IPv6) Specification", RFC 2460, December 1998. 818 [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 819 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 820 September 2011. 822 [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., 823 Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. 824 Alexander, "RPL: IPv6 Routing Protocol for Low-Power and 825 Lossy Networks", RFC 6550, March 2012. 827 [RFC6552] Thubert, P., "Objective Function Zero for the Routing 828 Protocol for Low-Power and Lossy Networks (RPL)", RFC 829 6552, March 2012. 831 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 832 Power and Lossy Networks (RPL) Option for Carrying RPL 833 Information in Data-Plane Datagrams", RFC 6553, March 834 2012. 836 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 837 Routing Header for Source Routes with the Routing Protocol 838 for Low-Power and Lossy Networks (RPL)", RFC 6554, March 839 2012. 841 [RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann, 842 "Neighbor Discovery Optimization for IPv6 over Low-Power 843 Wireless Personal Area Networks (6LoWPANs)", RFC 6775, 844 November 2012. 846 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 847 Lossy Networks", RFC 7102, January 2014. 849 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 850 Constrained-Node Networks", RFC 7228, May 2014. 852 13.2. Informative References 854 [I-D.bergmann-bier-ccast] 855 Bergmann, O., Bormann, C., and S. Gerdes, "Constrained- 856 Cast: Source-Routed Multicast for RPL", draft-bergmann- 857 bier-ccast-00 (work in progress), November 2014. 859 [I-D.bormann-6lo-rpl-mesh] 860 Bormann, C., "NHC compression for RPL Packet Information", 861 draft-bormann-6lo-rpl-mesh-02 (work in progress), October 862 2014. 864 [I-D.ietf-6tisch-architecture] 865 Thubert, P., Watteyne, T., and R. Assimiti, "An 866 Architecture for IPv6 over the TSCH mode of IEEE 867 802.15.4e", draft-ietf-6tisch-architecture-04 (work in 868 progress), October 2014. 870 [I-D.ietf-6tisch-tsch] 871 Watteyne, T., Palattella, M., and L. Grieco, "Using 872 IEEE802.15.4e TSCH in an IoT context: Overview, Problem 873 Statement and Goals", draft-ietf-6tisch-tsch-05 (work in 874 progress), January 2015. 876 [I-D.thubert-6lo-forwarding-fragments] 877 Thubert, P. and J. Hui, "LLN Fragment Forwarding and 878 Recovery", draft-thubert-6lo-forwarding-fragments-02 (work 879 in progress), November 2014. 881 [I-D.thubert-6lo-rpl-nhc] 882 Thubert, P. and C. Bormann, "A compression mechanism for 883 the RPL option", draft-thubert-6lo-rpl-nhc-02 (work in 884 progress), October 2014. 886 [I-D.wijnands-bier-architecture] 887 Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and 888 S. Aldrin, "Multicast using Bit Index Explicit 889 Replication", draft-wijnands-bier-architecture-02 (work in 890 progress), December 2014. 892 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 893 "Transmission of IPv6 Packets over IEEE 802.15.4 894 Networks", RFC 4944, September 2007. 896 Authors' Addresses 898 Pascal Thubert (editor) 899 Cisco Systems 900 Village d'Entreprises Green Side 901 400, Avenue de Roumanille 902 Batiment T3 903 Biot - Sophia Antipolis 06410 904 FRANCE 906 Phone: +33 4 97 23 26 34 907 Email: pthubert@cisco.com 909 Carsten Bormann 910 Universitaet Bremen TZI 911 Postfach 330440 912 Bremen D-28359 913 Germany 915 Phone: +49-421-218-63921 916 Email: cabo@tzi.org 917 Laurent Toutain 918 Institut MINES TELECOM; TELECOM Bretagne 919 2 rue de la Chataigneraie 920 CS 17607 921 Cesson-Sevigne Cedex 35576 922 France 924 Email: Laurent.Toutain@telecom-bretagne.eu 926 Robert Cragie 927 ARM Ltd. 928 110 Fulbourn Road 929 Cambridge CB1 9NJ 930 UK 932 Email: robert.cragie@gridmerge.com