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Thubert, Ed. 3 Internet-Draft Cisco Systems 4 Updates: 6550, 6775, 8505 (if approved) M. Richardson 5 Intended status: Standards Track Sandelman 6 Expires: 12 April 2021 9 October 2020 8 Routing for RPL Leaves 9 draft-ietf-roll-unaware-leaves-22 11 Abstract 13 This specification updates RFC6550, RFC6775, and RFC8505, to provide 14 routing services to RPL Unaware Leaves that implement 6LoWPAN ND and 15 the extensions therein. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on 12 April 2021. 34 Copyright Notice 36 Copyright (c) 2020 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 41 license-info) in effect on the date of publication of this document. 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. Code Components 44 extracted from this document must include Simplified BSD License text 45 as described in Section 4.e of the Trust Legal Provisions and are 46 provided without warranty as described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 52 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 53 2.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 5 54 2.3. References . . . . . . . . . . . . . . . . . . . . . . . 6 55 3. RPL External Routes and Dataplane Artifacts . . . . . . . . . 7 56 4. 6LoWPAN Neighbor Discovery . . . . . . . . . . . . . . . . . 8 57 4.1. RFC 6775 Address Registration . . . . . . . . . . . . . . 8 58 4.2. RFC 8505 Extended Address Registration . . . . . . . . . 8 59 4.2.1. R Flag . . . . . . . . . . . . . . . . . . . . . . . 9 60 4.2.2. TID, "I" Field and Opaque Fields . . . . . . . . . . 9 61 4.2.3. ROVR . . . . . . . . . . . . . . . . . . . . . . . . 9 62 4.3. RFC 8505 Extended DAR/DAC . . . . . . . . . . . . . . . . 10 63 4.3.1. RFC 7400 Capability Indication Option . . . . . . . . 10 64 5. Requirements on the RPL-Unware Leaf . . . . . . . . . . . . . 11 65 5.1. Support of 6LoWPAN ND . . . . . . . . . . . . . . . . . . 11 66 5.2. Support of IPv6 Encapsulation . . . . . . . . . . . . . . 12 67 5.3. Support of the HbH Header . . . . . . . . . . . . . . . . 12 68 5.4. Support of the Routing Header . . . . . . . . . . . . . . 12 69 6. Enhancements to RFC 6550 . . . . . . . . . . . . . . . . . . 12 70 6.1. Updated RPL Target Option . . . . . . . . . . . . . . . . 13 71 6.2. New Flag in the RPL DODAG Configuration Option . . . . . 14 72 6.3. Updated RPL Status . . . . . . . . . . . . . . . . . . . 15 73 7. Enhancements to draft-ietf-roll-efficient-npdao . . . . . . . 16 74 8. Enhancements to RFC 6775 and RFC8505 . . . . . . . . . . . . 17 75 9. Protocol Operations for Unicast Addresses . . . . . . . . . . 17 76 9.1. General Flow . . . . . . . . . . . . . . . . . . . . . . 18 77 9.2. Detailed Operation . . . . . . . . . . . . . . . . . . . 20 78 9.2.1. Perspective of the 6LN Acting as RUL . . . . . . . . 20 79 9.2.2. Perspective of the 6LR Acting as Border Router . . . 22 80 9.2.3. Perspective of the RPL Root . . . . . . . . . . . . . 26 81 9.2.4. Perspective of the 6LBR . . . . . . . . . . . . . . . 27 82 10. Protocol Operations for Multicast Addresses . . . . . . . . . 27 83 11. Security Considerations . . . . . . . . . . . . . . . . . . . 29 84 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 85 12.1. Fixing the Address Registration Option Flags . . . . . . 31 86 12.2. Resizing the ARO Status values . . . . . . . . . . . . . 31 87 12.3. New DODAG Configuration Option Flag . . . . . . . . . . 31 88 12.4. RPL Target Option Registry . . . . . . . . . . . . . . . 31 89 12.5. New Subregistry for the RPL Non-Rejection Status 90 values . . . . . . . . . . . . . . . . . . . . . . . . . 32 91 12.6. New Subregistry for the RPL Rejection Status values . . 32 92 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33 93 14. Normative References . . . . . . . . . . . . . . . . . . . . 33 94 15. Informative References . . . . . . . . . . . . . . . . . . . 35 95 Appendix A. Example Compression . . . . . . . . . . . . . . . . 36 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37 98 1. Introduction 100 The design of Low Power and Lossy Networks (LLNs) is generally 101 focused on saving energy, which is the most constrained resource of 102 all. Other design constraints, such as a limited memory capacity, 103 duty cycling of the LLN devices and low-power lossy transmissions, 104 derive from that primary concern. 106 The IETF produced the "Routing Protocol for Low Power and Lossy 107 Networks" [RFC6550] (RPL) to provide IPv6 [RFC8200] routing services 108 within such constraints. RPL belongs to the class of Distance-Vector 109 protocols, which, compared to link-state protocols, limit the amount 110 of topological knowledge that needs to be installed and maintained in 111 each node, and does not require convergence to avoid micro-loops. 113 To save signaling and routing state in constrained networks, RPL 114 allows a path stretch (see [RFC6687]), whereby routing is only 115 performed along a Destination-Oriented Directed Acyclic Graph (DODAG) 116 that is optimized to reach a Root node, as opposed to along the 117 shortest path between 2 peers, whatever that would mean in a given 118 LLN. This trades the quality of peer-to-peer (P2P) paths for a 119 vastly reduced amount of control traffic and routing state that would 120 be required to operate an any-to-any shortest path protocol. 121 Additionally, broken routes may be fixed lazily and on-demand, based 122 on dataplane inconsistency discovery, which avoids wasting energy in 123 the proactive repair of unused paths. 125 For many of the nodes, though not all, the DODAG provides multiple 126 forwarding solutions towards the Root of the topology via so-called 127 parents. RPL is designed to adapt to fuzzy connectivity, whereby the 128 physical topology cannot be expected to reach a stable state, with a 129 lazy control that creates the routes proactively, but may only fix 130 them reactively, upon actual traffic. The result is that RPL 131 provides reachability for most of the LLN nodes, most of the time, 132 but may not converge in the classical sense. 134 RPL can be deployed in conjunction with IPv6 Neighbor Discovery (ND) 135 [RFC4861] [RFC4862] and 6LoWPAN ND [RFC6775] [RFC8505] to maintain 136 reachability within a Non-Broadcast Multi- (NBMA) Multi-Link subnet. 138 In that mode, IPv6 addresses are advertised individually as Host 139 routes. Some nodes may act as Routers and participate in the 140 forwarding operations whereas others will only terminate packets, 141 acting as Hosts in the data-plane. In [RFC6550] terms, an IPv6 Host 142 [RFC8504] that is reachable over the RPL network is called a Leaf. 144 [USEofRPLinfo] introduces the terms RPL-Aware-Leaf (RAL) and RPL- 145 Unaware Leaf (RUL). A RAL is a Leaf that injects Host routes in RPL 146 to manage the reachability of its IPv6 addresses. Conversely, a RUL 147 does not participate to RPL and cannot inject routes. Section 5 148 details a Host-to-Router interface that the RUL needs to implement to 149 advertise its IPv6 addresses to a Router that supports this 150 specification. The document specifies how the Router injects those 151 addresses as Host routes in the RPL network on behalf of the RUL. 153 This specification leverages the Address Registration mechanism 154 defined in 6LoWPAN ND to enable a 6LoWPAN Node (6LN) acting as a RUL 155 to interface with a 6LoWPAN Router (6LR) that is RPL-Aware router, 156 and request that the router injects a Host route for the Registered 157 Address in RPL on its behalf. A RUL may be unable to participate 158 because it is very energy-constrained, or because it is unsafe to let 159 it inject routes in RPL, in which case using 6LowPAN ND as the 160 interface for the RUL limits the surface of the possible attacks and 161 optionally protects the address ownership. 163 The RPL Non-Storing Mode mechanism is used to extend the routing 164 state with connectivity to the RULs even when the DODAG is operated 165 in Storing Mode. The unicast packet forwarding operation by the 6LR 166 serving a RUL is described in section 4.1 of [USEofRPLinfo]. 168 Examples of possible RULs include lightly powered sensors such as 169 window smash sensor (alarm system), and kinetically powered light 170 switches. Other applications of this specification may include a 171 smart grid network that controls appliances - such as washing 172 machines or the heating system - in the home. Appliances may not 173 participate to the RPL protocol operated in the Smartgrid network but 174 can still interact with the Smartgrid for control and/or metering. 176 This document is organized as follows: 178 * Section 3 and Section 4 present salient aspects of RPL and 6LoWPAN 179 ND, respectively, that are leveraged in this specification to 180 provide connectivity to a RUL across a RPL network. 182 * Section 5 lists the expectations that a RUL needs to match in 183 order to be served by a RPL router that complies with this 184 specification. 186 * Section 6, Section 7, and Section 8 present the changes made to 187 [RFC6550], [EFFICIENT-NPDAO], [RFC6775] and [RFC8505]. 189 * Section 9 and Section 10 present the operation of this 190 specification for unicast and multicast flows, respectively, and 191 Section 11 presents associated security considerations. 193 2. Terminology 195 2.1. Requirements Language 197 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 198 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 199 "OPTIONAL" in this document are to be interpreted as described in BCP 200 14 [RFC2119] [RFC8174] when, and only when, they appear in all 201 capitals, as shown here. 203 2.2. Glossary 205 This document often uses the following acronyms: 207 AR: Address Resolution (aka Address Lookup) 208 ARQ: Automatic Repeat reQuest 209 6CIO: 6LoWPAN Capability Indication Option 210 6LN: 6LoWPAN Node (a Low Power Host or Router) 211 6LR: 6LoWPAN Router 212 (E)ARO: (Extended) Address Registration Option 213 (E)DAR: (Extended) Duplicate Address Request 214 (E)DAC: (Extended) Duplicate Address Confirmation 215 DAD: Duplicate Address Detection 216 DAO: Destination Advertisement Object (a RPL message) 217 DCO: Destination Cleanup Object (a RPL message) 218 DIS: DODAG Information solicitation (a RPL message) 219 DIO: DODAG Information Object (a RPL message) 220 DODAG: Destination-Oriented Directed Acyclic Graph 221 LLN: Low-Power and Lossy Network 222 NA: Neighbor Advertisement 223 NCE: Neighbor Cache Entry 224 ND: Neighbor Discovery 225 NS: Neighbor solicitation 226 RA: Router Advertisement 227 ROVR: Registration Ownership Verifier 228 RPI: RPL Packet Information 229 RAL: RPL-Aware Leaf 230 RAN: RPL-Aware Node (either a RPL Router or a RPL-Aware Leaf) 231 RUL: RPL-Unaware Leaf 232 TID: Transaction ID (a sequence counter in the EARO) 234 2.3. References 236 The Terminology used in this document is consistent with and 237 incorporates that described in "Terms Used in Routing for Low-Power 238 and Lossy Networks (LLNs)" [RFC7102]. A glossary of classical 239 6LoWPAN acronyms is given in Section 2.2. Other terms in use in LLNs 240 are found in "Terminology for Constrained-Node Networks" [RFC7228]. 241 This specification uses the terms 6LN and 6LR to refer specifically 242 to nodes that implement the 6LN and 6LR roles in 6LoWPAN ND and does 243 not expect other functionality such as 6LoWPAN Header Compression 244 [RFC6282] from those nodes. 246 "RPL", the "RPL Packet Information" (RPI), "RPL Instance" (indexed by 247 a RPLInstanceID) are defined in "RPL: IPv6 Routing Protocol for 248 Low-Power and Lossy Networks" [RFC6550]. The RPI is the abstract 249 information that RPL defines to be placed in data packets, e.g., as 250 the RPL Option [RFC6553] within the IPv6 Hop-By-Hop Header. By 251 extension, the term "RPI" is often used to refer to the RPL Option 252 itself. The DODAG Information solicitation (DIS), Destination 253 Advertisement Object (DAO) and DODAG Information Object (DIO) 254 messages are also specified in [RFC6550]. The Destination Cleanup 255 Object (DCO) message is defined in [EFFICIENT-NPDAO]. 257 This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware 258 Leaf (RAL) consistently with [USEofRPLinfo]. The term RPL-Aware Node 259 (RAN) is introduced to refer to a node that is either an RAL or a RPL 260 Router. As opposed to a RUL, a RAN manages the reachability of its 261 addresses and prefixes by injecting them in RPL by itself. 263 In this document, readers will encounter terms and concepts that are 264 discussed in the following documents: 266 Classical IPv6 ND: "Neighbor Discovery for IP version 6" [RFC4861] 267 and "IPv6 Stateless Address Autoconfiguration" [RFC4862], 269 6LoWPAN: "Problem Statement and Requirements for IPv6 over Low-Power 270 Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606] and 271 "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): 272 Overview, Assumptions, Problem Statement, and Goals" [RFC4919], 273 and 275 6LoWPAN ND: Neighbor Discovery Optimization for Low-Power and Lossy 276 Networks [RFC6775], "Registration Extensions for 6LoWPAN Neighbor 277 Discovery" [RFC8505], and "Address Protected Neighbor Discovery 278 for Low-power and Lossy Networks" [AP-ND]. 280 3. RPL External Routes and Dataplane Artifacts 282 Section 4.1 of [USEofRPLinfo] provides a set of rules detailed below 283 that must be followed for routing packets from and to a RUL. 285 A 6LR that acts as a border Router for external routes advertises 286 them using Non-Storing Mode DAO messages that are unicast directly to 287 the Root, even if the DODAG is operated in Storing Mode. Non-Storing 288 Mode routes are not visible inside the RPL domain and all packets are 289 routed via the Root. The RPL Root tunnels the packets directly to 290 the 6LR that advertised the external route, which decapsulates and 291 forwards the original (inner) packet. 293 The RPL Non-Storing MOP signaling and the associated IP-in-IP 294 encapsulated packets appear as normal traffic to the intermediate 295 Routers. The support of external routes only impacts the Root and 296 the 6LR. It can be operated with legacy intermediate Routers and 297 does not add to the amount of state that must be maintained in those 298 Routers. A RUL is an example of a destination that is reachable via 299 an external route that happens to be also a Host route. 301 The RPL data packets always carry a Hop-by-Hop Header to transport a 302 RPL Packet Information (RPI) [RFC6550]. So unless the RUL originates 303 its packets with an RPI, the 6LR needs to tunnel them to the Root to 304 add the RPI. As a rule of a thumb and except for the very special 305 case above, the packets from and to a RUL are always encapsulated 306 using an IP-in-IP tunnel between the Root and the 6LR that serves the 307 RUL (see sections 7 and 8 of [USEofRPLinfo] for details). 309 In Non-Storing Mode, packets going down carry a Source Routing Header 310 (SRH). The IP-in-IP encapsulation, the RPI and the SRH are 311 collectively called the "RPL artifacts" and can be compressed using 312 [RFC8138]. Appendix A presents an example compressed format for a 313 packet forwarded by the Root to a RUL in a Storing Mode DODAG. 315 The inner packet that is forwarded to the RUL may carry some RPL 316 artifacts, e.g., an RPI if the original packet was generated with it, 317 and an SRH in a Non-Storing Mode DODAG. [USEofRPLinfo] expects the 318 RUL to support the basic "IPv6 Node Requirements" [RFC8504]. In 319 particular the RUL is expected to ignore the RPL artifacts that are 320 either consumed or not applicable to a Host. 322 A RUL is not expected to support the compression method defined in 323 [RFC8138]. For that reason, the border router uncompresses the 324 packet before forwarding over an external route to a RUL 325 [USEofRPLinfo]. 327 4. 6LoWPAN Neighbor Discovery 329 4.1. RFC 6775 Address Registration 331 The classical "IPv6 Neighbor Discovery (IPv6 ND) Protocol" [RFC4861] 332 [RFC4862] was defined for serial links and transit media such as 333 Ethernet. It is a reactive protocol that relies heavily on multicast 334 operations for Address Discovery (aka Lookup) and Duplicate Address 335 Detection (DAD). 337 "Neighbor Discovery Optimizations for 6LoWPAN networks" [RFC6775] 338 adapts IPv6 ND for operations over energy-constrained LLNs. The main 339 functions of [RFC6775] are to proactively establish the Neighbor 340 Cache Entry (NCE) in the 6LR and to prevent address duplication. To 341 that effect, [RFC6775] introduces a new unicast Address Registration 342 mechanism that contributes to reducing the use of multicast messages 343 compared to the classical IPv6 ND protocol. 345 [RFC6775] defines a new Address Registration Option (ARO) that is 346 carried in the unicast Neighbor solicitation (NS) and Neighbor 347 Advertisement (NA) messages between the 6LoWPAN Node (6LN) and the 348 6LoWPAN Router (6LR). It also defines the Duplicate Address Request 349 (DAR) and Duplicate Address Confirmation (DAC) messages between the 350 6LR and the 6LoWPAN Border Router (6LBR). In an LLN, the 6LBR is the 351 central repository of all the Registered Addresses in its domain and 352 the source of truth for uniqueness and ownership. 354 4.2. RFC 8505 Extended Address Registration 356 "Registration Extensions for 6LoWPAN Neighbor Discovery" [RFC8505] 357 updates the behavior of RFC 6775 to enable a generic Address 358 Registration to services such as routing and ND proxy, and defines 359 the Extended Address Registration Option (EARO) as shown in Figure 1: 361 0 1 2 3 362 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 1 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 | Type | Length | Status | Opaque | 365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 | Rsvd | I |R|T| TID | Registration Lifetime | 367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 368 | | 369 ... Registration Ownership Verifier ... 370 | | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 Figure 1: EARO Option Format 375 4.2.1. R Flag 377 [RFC8505] introduces the R Flag in the EARO. The Registering Node 378 sets the R Flag to indicate whether the 6LR should ensure 379 reachability for the Registered Address. If the R Flag is not set, 380 then the Registering Node handles the reachability of the Registered 381 Address by other means. In a RPL network, this means that either it 382 is a RAN that injects the route by itself or that it uses another RPL 383 Router for reachability services. 385 This document specifies how the R Flag is used in the context of RPL. 386 A RPL Leaf that implements the 6LN functionality in [RFC8505] 387 requires reachability services for an IPv6 address if and only if it 388 sets the R Flag in the NS(EARO) used to register the address to a 6LR 389 acting as a RPL border Router. Upon receiving the NS(EARO), the RPL 390 Router generates a DAO message for the Registered Address if and only 391 if the R flag is set. 393 Section 9.2 specifies additional operations when R flag is set in an 394 EARO that is placed either in an NS or an NA message. 396 4.2.2. TID, "I" Field and Opaque Fields 398 When the T Flag is set, the EARO includes a sequence counter called 399 Transaction ID (TID), that is needed to fill the Path Sequence Field 400 in the RPL Transit Option. This is the reason why the support of 401 [RFC8505] by the RUL, as opposed to only [RFC6775] is a prerequisite 402 for this specification (more in Section 5.1). The EARO also 403 transports an Opaque field and an associated "I" field that describes 404 what the Opaque field transports and how to use it. 406 Section 9.2.1 specifies the use of the "I" field and the Opaque field 407 by a RUL. 409 4.2.3. ROVR 411 Section 5.3 of [RFC8505] introduces the Registration Ownership 412 Verifier (ROVR) field of variable length from 64 to 256 bits. The 413 ROVR is a replacement of the EUI-64 in the ARO [RFC6775] that was 414 used to identify uniquely an Address Registration with the Link-Layer 415 address of the owner but provided no protection against spoofing. 417 "Address Protected Neighbor Discovery for Low-power and Lossy 418 Networks" [AP-ND] leverages the ROVR field as a cryptographic proof 419 of ownership to prevent a rogue third party from registering an 420 address that is already owned and enable the 6LR to block traffic 421 that is not sourced at a owned address. 423 This specification does not address how the protection by [AP-ND] 424 could be extended for use in RPL. On the other hand, it adds the 425 ROVR to the DAO to build the proxied EDAR at the Root (see 426 Section 6.1), which means that nodes that are aware of the Host route 427 are also aware of the ROVR associated to the Target Address. 429 4.3. RFC 8505 Extended DAR/DAC 431 [RFC8505] updates the DAR/DAC messages into the Extended DAR/DAC to 432 carry the ROVR field. The EDAR/EDAC exchange takes place between the 433 6LR and the 6LBR. It is triggered by an NS(EARO) message from a 6LN 434 to create, refresh, and delete the corresponding state in the 6LBR. 435 The exchange is protected by the retry mechanism (ARQ) specified in 436 8.2.6 of [RFC6775], though in an LLN, a duration longer than the 437 RETRANS_TIMER [RFC4861] of 1 second may be necessary to cover the 438 Turn Around Trip delay between the 6LR and the 6LBR. 440 RPL [RFC6550] specifies a periodic DAO from the 6LN all the way to 441 the Root that maintains the routing state in the RPL network for the 442 lifetime indicated by the source of the DAO. This means that for 443 each address, there are two keep-alive messages that traverse the 444 whole network, one to the Root and one to the 6LBR. 446 This specification avoids the periodic EDAR/EDAC exchange across the 447 LLN. The 6LR turns the periodic NS(EARO) from the RUL into a DAO 448 message to the Root on every refresh, but it only generates the EDAR 449 upon the first registration, for the purpose of DAD, which must be 450 verified before the address is injected in RPL. Upon the DAO 451 message, the Root proxies the EDAR exchange to refresh the state at 452 the 6LBR on behalf of the 6LR, as illustrated in Figure 7. 454 4.3.1. RFC 7400 Capability Indication Option 456 "6LoWPAN-GHC: Generic Header Compression for IPv6 over Low-Power 457 Wireless Personal Area Networks (6LoWPANs)" [RFC7400] defines the 458 6LoWPAN Capability Indication Option (6CIO) that enables a node to 459 expose its capabilities in Router Advertisement (RA) messages. 461 [RFC8505] defines a number of bits in the 6CIO, in particular: 463 L: Node is a 6LR. 464 E: Node is an IPv6 ND Registrar -- i.e., it supports registrations 465 based on EARO. 466 P: Node is a Routing Registrar, -- i.e., an IPv6 ND Registrar that 467 also provides reachability services for the Registered Address. 469 0 1 2 3 470 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 1 471 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 472 | Type | Length = 1 | Reserved |D|L|B|P|E|G| 473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 474 | Reserved | 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 Figure 2: 6CIO flags 479 A 6LR that can provide reachability services for a RUL in a RPL 480 network as specified in this document MUST include a 6CIO in its RA 481 messages and set the L, P and E flags as prescribed by [RFC8505]. 483 5. Requirements on the RPL-Unware Leaf 485 This document provides RPL routing for a RUL. This section describes 486 the minimal RPL-independent functionality that the RUL needs to 487 implement to obtain routing services for its addresses. 489 5.1. Support of 6LoWPAN ND 491 To obtain routing services from a Router that implements this 492 specification, a RUL needs to implement [RFC8505] and set the "R" and 493 "T" flags in the EARO as discussed in Section 4.2.1 and 494 Section 4.2.3, respectively. Section 9.2.1 specifies new behaviors 495 for the RUL, e.g., when the R Flag set in a NS(EARO) is not echoed in 496 the NA(EARO), which indicates that the route injection failed. 498 The RUL is expected not to request routing services from a Router 499 that does not originate RA messages with a CIO that has the L, P, and 500 E flags all set as discussed in Section 4.3.1, unless configured to 501 do so. It is suggested that the RUL also implements [AP-ND] to 502 protect the ownership of its addresses. 504 A RUL that may attach to multiple 6LRs is expected to prefer those 505 that provide routing services. The RUL needs to register to all the 506 6LRs from which it desires routing services. 508 Parallel Address Registrations to several 6LRs should be performed in 509 a rapid sequence, using the same EARO for the same Address. Gaps 510 between the Address Registrations will invalidate some of the routes 511 till the Address Registration finally shows on those routes. 513 [RFC8505] introduces error Status values in the NA(EARO) which can be 514 received synchronously upon an NS(EARO) or asynchronously. The RUL 515 needs to support both cases and should refrain from using the address 516 when the Status Value indicates a rejection (see Section 6.3). 518 5.2. Support of IPv6 Encapsulation 520 Section 2.1 of [USEofRPLinfo] defines the rules for tunneling either 521 to the final destination (e.g., a RUL) or to its attachment Router 522 (designated as 6LR). To terminate the IP-in-IP tunnel, the RUL, as 523 an IPv6 Host, must be able to decapsulate the tunneled packet and 524 either drop the inner packet if it is not the final destination, or 525 pass it to the upper layer for further processing. Unless it is 526 aware by other means that the RUL can handle IP-in-IP properly, which 527 is not mandated by [RFC8504], the Root terminates the IP-in-IP tunnel 528 at the parent 6LR. It is thus not necessary for a RUL to support IP- 529 in-IP decapsulation. 531 5.3. Support of the HbH Header 533 A RUL is expected to process an Option Type in a Hop-by-Hop Header as 534 prescribed by section 4.2 of [RFC8200]. An RPI with an Option Type 535 of 0x23 [USEofRPLinfo] is thus skipped when not recognized. 537 5.4. Support of the Routing Header 539 A RUL is expected to process an unknown Routing Header Type as 540 prescribed by section 4.4 of [RFC8200]. This implies that the Source 541 Routing Header with a Routing Type of 3 [RFC6554] is ignored when the 542 Segments Left is zero, and the packet is dropped otherwise. 544 6. Enhancements to RFC 6550 546 This document specifies a new behavior whereby a 6LR injects DAO 547 messages for unicast addresses (see Section 9) and multicast 548 addresses (see Section 10) on behalf of leaves that are not aware of 549 RPL. The RUL addresses are exposed as external targets [RFC6550]. 550 Conforming to [USEofRPLinfo], an IP-in-IP encapsulation between the 551 6LR and the RPL Root is used to carry the RPL artifacts and remove 552 them when forwarding outside the RPL domain, e.g., to a RUL. 554 This document also synchronizes the liveness monitoring at the Root 555 and the 6LBR. The same value of lifetime is used for both, and a 556 single keep-alive message, the RPL DAO, traverses the RPL network. A 557 new behavior is introduced whereby the RPL Root proxies the EDAR 558 message to the 6LBR on behalf of the 6LR (more in Section 8), for any 559 Leaf node that implements the 6LN functionality in [RFC8505]. 561 Section 6.7.7 of [RFC6550] introduces the RPL Target Option, which 562 can be used in RPL Control messages such as the DAO message to signal 563 a destination prefix. This document adds the capabilities to 564 transport the ROVR field (see Section 4.2.3) and the IPv6 Address of 565 the prefix advertiser when the Target is a shorter prefix. Their use 566 is signaled respectively by a new ROVR Size field being non-zero and 567 a new "Advertiser address in Full" 'F' flag set, more in Section 6.1. 569 This specification defines the new "Root Proxies EDAR/EDAC" (P) flag 570 and encodes it in one of these reserved flags of the RPL DODAG 571 Configuration option, more in Section 6.2. 573 The RPL Status defined in section 6.5.1 of [RFC6550] for use in the 574 DAO-ACK message is extended to be placed in DCO messages 575 [EFFICIENT-NPDAO] as well. Furthermore, this specification enables 576 to carry the EARO Status defined for 6LoWPAN ND in RPL DAO and DCO 577 messages, embedded in a RPL Status, more in Section 6.3. 579 6.1. Updated RPL Target Option 581 This specification updates the RPL Target Option to transport the 582 ROVR that was also defined for 6LoWPAN ND messages. This enables the 583 RPL Root to generate the proxied EDAR message to the 6LBR. 585 The new 'F' flag is set to indicate that the Target Prefix field 586 contains the IPv6 address of the advertising node, in which case the 587 length of the Target Prefix field is 128 bits regardless of the value 588 of the Prefix Length field. If the 'F' flag is reset, the Target 589 Prefix field MUST be aligned to the next byte boundary after the size 590 (expressed in bits) indicated by the Prefix Length field. Padding 591 bits are reserved and set to 0 per section 6.7.7 of [RFC6550]. 593 With this specification the ROVR is the remainder of the RPL Target 594 Option. The size of the ROVR is indicated in a new ROVR Size field 595 that is encoded to map one-to-one with the Code Suffix in the EDAR 596 message (see table 4 of [RFC8505]). The ROVR Size field is taken 597 from the flags field, which is an update to the RPL Target Option 598 Flags IANA registry. 600 The updated format is illustrated in Figure 3. It is backward 601 compatible with the Target Option in [RFC6550]. It SHOULD be used as 602 a replacement in new implementations in all MOPs in preparation for 603 upcoming Route Ownership Validation mechanisms based on the ROVR, 604 unless the device or the network is so constrained that this is not 605 feasible. 607 0 1 2 3 608 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 | Type = 0x05 | Option Length |ROVRsz |F|Flags| Prefix Length | 611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 | | 613 | Target Prefix (Variable Length) | 614 . . 615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 | | 617 ... Registration Ownership Verifier (ROVR) ... 618 | | 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 Figure 3: Updated Target Option 623 New fields: 625 ROVRsz (ROVR Size): Indicates the Size of the ROVR. It MAY be 1, 2, 626 3, or 4, indicating a ROVR size of 64, 128, 192, or 256 bits, 627 respectively. A value if 0 thus denotes a legacy Target Option. 629 F: 1-bit flag. Set to indicate that Target Prefix field contains an 630 address of prefix advertiser in full. 632 Registration Ownership Verifier (ROVR): This is the same field as in 633 the EARO, see [RFC8505] 635 6.2. New Flag in the RPL DODAG Configuration Option 637 The DODAG Configuration Option is defined in Section 6.7.6 of 638 [RFC6550]. Its purpose is extended to distribute configuration 639 information affecting the construction and maintenance of the DODAG, 640 as well as operational parameters for RPL on the DODAG, through the 641 DODAG. As shown in Figure 4, the Option was originally designed with 642 4 bit positions reserved for future use as Flags. 644 0 1 2 3 645 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 1 646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 647 | Type = 0x04 |Opt Length = 14| |P| | |A| ... | 648 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 649 <- Flags -> 651 Figure 4: DODAG Configuration Option (Partial View) 653 This specification defines a new flag "Root Proxies EDAR/EDAC" (P). 654 The 'P' bit is encoded in position 1 of the reserved Flags in the 655 DODAG Configuration Option (counting from bit 0 as the most 656 significant bit) and set to 0 in legacy implementations as specified 657 respectively in Sections 20.14 and 6.7.6 of [RFC6550]. 659 The 'P' bit is set to indicate that the Root performs the proxy 660 operation, which implies that it supports this specification and the 661 updated RPL Target Option (see Section 6.1). 663 Section 4.3 of [USEofRPLinfo] updates [RFC6550] to indicate that the 664 definition of the Flags applies to Mode of Operation (MOP) values 665 zero (0) to six (6) only. For a MOP value of 7, the Root is expected 666 to perform the proxy operation by default. 668 The RPL DODAG Configuration Option is typically placed in a DODAG 669 Information Object (DIO) message. The DIO message propagates down 670 the DODAG to form and then maintain its structure. The DODAG 671 Configuration Option is copied unmodified from parents to children. 672 [RFC6550] states that "Nodes other than the DODAG Root MUST NOT 673 modify this information when propagating the DODAG Configuration 674 option". Therefore, a legacy parent propagates the T Flag as set by 675 the Root, and when the T Flag is set, it is transparently flooded to 676 all the nodes in the DODAG. 678 6.3. Updated RPL Status 680 The RPL Status is defined in section 6.5.1 of [RFC6550] for use in 681 the DAO-ACK message and values are assigned as follows: 683 +---------+--------------------------------+ 684 | Range | Meaning | 685 +---------+--------------------------------+ 686 | 0 | Success/Unqualified acceptance | 687 +---------+--------------------------------+ 688 | 1-127 | Not an outright rejection | 689 +---------+--------------------------------+ 690 | 128-255 | Rejection | 691 +---------+--------------------------------+ 693 Table 1: RPL Status per RFC 6550 695 The 6LoWPAN ND Status was defined for use in the EARO, see section 696 4.1 of [RFC8505]. This specification enables to carry the 6LoWPAN ND 697 Status values in RPL DAO and DCO messages, embedded in the RPL Status 698 field. 700 To achieve this, the range of the EARO Status values is reduced to 701 0-63, which updates the IANA registry created for [RFC6775]. This 702 reduction ensures that the values fit within a RPL Status as shown in 703 Figure 5. See Section 12.2, Section 12.5, and Section 12.6 for the 704 respective IANA declarations. 706 0 1 2 3 4 5 6 7 707 +-+-+-+-+-+-+-+-+ 708 |E|A|StatusValue| 709 +-+-+-+-+-+-+-+-+ 711 Figure 5: RPL Status Format 713 This specification updates the RPL Status with subfields as indicated 714 below: 716 E: 1-bit flag. Set to indicate a rejection. When not set, a Status 717 Value of 0 indicates Success/Unqualified acceptance and other 718 values indicate "not an outright rejection" as per RFC 6550. 720 A: 1-bit flag. Indicates the type of the RPL Status Value. 722 Status Value: 6-bit unsigned integer. If the 'A' flag is set this 723 field transports a Status Value defined for IPv6 ND EARO. When 724 the 'A' flag is not set, the Status Value is defined for RPL. 726 When building a DCO or a DAO-ACK message upon an IPv6 ND NA or a EDAC 727 message, the RPL Root MUST copy the 6LoWPAN ND Status Code unchanged 728 in the RPL Status Value and set the 'A' flag. The RPL Root MUST set 729 the 'E' flag for all rejection and unknown Status Codes. The Status 730 Codes in range 1-10 [RFC8505] are all considered rejections. 732 Reciprocally, upon a DCO or a DAO-ACK message from the RPL Root with 733 a RPL Status that has the 'A' flag set, the 6LR MUST copy the RPL 734 Status Value unchanged in the Status field of the EARO when 735 generating an NA to the RUL. 737 7. Enhancements to draft-ietf-roll-efficient-npdao 739 [EFFICIENT-NPDAO] defines the DCO message for RPL Storing Mode only, 740 with a link-local scope. All nodes in the RPL network are expected 741 to support the specification since the message in processed hop by 742 hop along the path this is being cleaned up. 744 This specification extends the use of the DCO message to the Non- 745 Storing MOP, whereby the DCO is sent end-to-end by the Root directly 746 to the RAN that injected the DAO message for the considered target. 747 In that case, intermediate nodes do not need to support 748 [EFFICIENT-NPDAO]; they forward the DCO message as a plain IPv6 749 packet between the Root and the RAN. 751 This specification leverages the Non-Storing DCO between the Root and 752 the 6LR that serves as attachment Router for a RUL. A 6LR and a Root 753 that support this specification MUST implement the Non-Storing DCO. 755 8. Enhancements to RFC 6775 and RFC8505 757 This document updates [RFC6775] and [RFC8505] to reduce the range of 758 the ND Status Codes down to 64 values. 760 This document also changes the behavior of a 6LR acting as RPL Router 761 and of a 6LN acting as RUL in the 6LoWPAN ND Address Registration as 762 follows: 764 * If the RPL Root advertises the capability to proxy the EDAR/EDAC 765 exchange to the 6LBR, the 6LR refrains from sending the keep-alive 766 EDAR message. If it is separated from the 6LBR, the Root 767 regenerates the EDAR message to the 6LBR periodically, upon a DAO 768 message that signals the liveliness of the address. 770 * The use of the R Flag is extended to the NA(EARO) to confirm 771 whether the route was installed. 773 9. Protocol Operations for Unicast Addresses 775 The description below assumes that the Root sets the 'P' bit in the 776 DODAG Configuration Option and performs the EDAR proxy operation. 778 If the 'P' bit is reset, the 6LR MUST generate the periodic EDAR 779 messages and process the returned status as specified in [RFC8505]. 780 If the EDAC indicates success, the rest of the flow takes place as 781 presented but without the proxied EDAR/EDAC exchange. 783 Section 9.1 provides an overview of the route injection in RPL, 784 whereas Section 9.2 offers more details from the perspective of the 785 different nodes involved in the flow. 787 9.1. General Flow 789 This specification eliminates the need to exchange keep-alive 790 Extended Duplicate Address messages, EDAR and EDAC, all the way from 791 a 6LN to the 6LBR across a RPL mesh. Instead, the EDAR/EDAC exchange 792 with the 6LBR is proxied by the RPL Root upon the DAO message that 793 refreshes the RPL routing state. The first EDAR upon a new 794 Registration cannot be proxied, though, as it serves for the purpose 795 of DAD, which must be verified before the address is injected in RPL. 797 In a RPL network where the function is enabled, refreshing the state 798 in the 6LBR is the responsibility of the Root. Consequently, only 799 addresses that are injected in RPL will be kept alive at the 6LBR by 800 the RPL Root. Since RULs are advertised using Non-Storing Mode, the 801 DAO message flow and the keep alive EDAR/EDAC can be nested within 802 the Address (re)Registration flow. Figure 6 illustrates that, for 803 the first Registration, both the DAD and the keep-alive EDAR/EDAC 804 exchanges happen in the same sequence. 806 6LN/RUL <-ND-> 6LR <-RPL-> Root <-ND-> 6LBR 807 | | | | 808 | NS(EARO) | | | 809 |--------------->| | 810 | | Extended DAR | 811 | |--------------------------------->| 812 | | | 813 | | Extended DAC | 814 | |<---------------------------------| 815 | | DAO | | 816 | |------------->| | 817 | | | EDAR | 818 | | |------------------>| 819 | | | EDAC | 820 | | |<------------------| 821 | | DAO-ACK | | 822 | |<-------------| | 823 | NA(EARO) | | | 824 |<---------------| | | 825 | | | | 827 Figure 6: First RUL Registration Flow 829 This flow requires that the lifetimes and sequence counters in 830 6LoWPAN ND and RPL are aligned. 832 ITo achieve this, the Path Sequence and the Path Lifetime in the DAO 833 message are taken from the Transaction ID and the Address 834 Registration lifetime in the NS(EARO) message from the 6LN. 836 On the first Address Registration, illustrated in Figure 6 for RPL 837 Non-Storing Mode, the Extended Duplicate Address exchange takes place 838 as prescribed by [RFC8505]. If the exchange fails, the 6LR returns 839 an NA message with a negative status to the 6LN, the NCE is not 840 created, and the address is not injected in RPL. Otherwise, the 6LR 841 creates an NCE and injects the Registered Address in the RPL routing 842 using a DAO/DAO-ACK exchange with the RPL DODAG Root. 844 An Address Registration refresh is performed by the 6LN to maintain 845 the NCE in the 6LR alive before the lifetime expires. Upon the 846 refresh of a registration, the 6LR reinjects the corresponding route 847 in RPL before it expires, as illustrated in Figure 7. 849 6LN/RUL <-ND-> 6LR <-RPL-> Root <-ND-> 6LBR 850 | | | | 851 | NS(EARO) | | | 852 |--------------->| | | 853 | | DAO | | 854 | |------------->| | 855 | | | EDAR | 856 | | |------------------>| 857 | | | EDAC | 858 | | |<------------------| 859 | | DAO-ACK | | 860 | |<-------------| | 861 | NA(EARO) | | | 862 |<---------------| | | 864 Figure 7: Next RUL Registration Flow 866 This is what causes the RPL Root to refresh the state in the 6LBR, 867 using an EDAC message. In case of an error in the proxied EDAR flow, 868 the error is returned in the DAO-ACK using a RPL Status with the 'A' 869 flag set that imbeds a 6LoWPAN Status Value as discussed in 870 Section 6.3. 872 The 6LR may receive a requested DAO-ACK after it received an 873 asynchronous DCO, but the negative Status in the DCO supersedes a 874 positive Status in the DAO-ACK regardless of the order in which they 875 are received. Upon the DAO-ACK - or the DCO if one arrives first - 876 the 6LR responds to the RUL with an NA(EARO). 878 An issue may be detected later, e.g., the address moves to a 879 different DODAG with the 6LBR attached to a different 6LoWPAN 880 Backbone Router (6BBR), see Figure 5 in section 3.3 of [6BBR]. The 881 6BBR may send a negative ND status, e.g., in an asynchronous NA(EARO) 882 to the 6LBR. 884 [6BBR] expects that the 6LBR is collocated with the RPL Root, but if 885 not, the 6LBR MUST forward the Status Code to the originator of the 886 EDAR, either the 6LR or the RPL Root that proxies for it. The ND 887 Status Code is mapped in a RPL Status Value by the RPL Root, and then 888 back by the 6LR. 890 Figure 8 illustrates this in the case where the 6LBR and the Root are 891 not collocated, and the Root proxies the EDAR messages. 893 6LN/RUL <-ND-> 6LR <-RPL-> Root <-ND-> 6LBR <-ND-> 6BBR 894 | | | | | 895 | | | | NA(EARO) | 896 | | | |<------------| 897 | | | EDAC | | 898 | | |<-------------| | 899 | | DCO | | | 900 | |<------------| | | 901 | NA(EARO) | | | | 902 |<-------------| | | | 903 | | | | | 905 Figure 8: Asynchronous Issue 907 If the Root does not proxy, then the EDAC with a negative status 908 reaches the 6LR directly. In that case, the 6LR MUST clean up the 909 route using a DAO with a Lifetime of zero, and it MUST propagate the 910 status back to the RUL in a NA(EARO) with the R Flag not set. 912 The RUL may terminate the registration at any time by using a 913 Registration Lifetime of 0. This specification requires that the RPL 914 Target Option transports the ROVR. This way, the same flow as the 915 heartbeat flow is sufficient to inform the 6LBR using the Root as 916 proxy, as illustrated in Figure 7. 918 Any combination of the logical functions of 6LR, Root, and 6LBR might 919 be collapsed in a single node. 921 9.2. Detailed Operation 923 9.2.1. Perspective of the 6LN Acting as RUL 925 This specification does not alter the operation of a 6LoWPAN ND- 926 compliant 6LN/RUL, which is expected to operate as follows: 928 1. The 6LN obtains an IPv6 global address, either using Stateless 929 Address Autoconfiguration (SLAAC) [RFC4862] based on a Prefix 930 Information Option (PIO) [RFC4861] found in an RA message, or 931 some other means, such as DHCPv6 [RFC8415]. 933 2. Once it has formed an address, the 6LN registers its address and 934 refreshes its registration periodically, early enough within the 935 Lifetime of the previous Address Registration, as prescribed by 936 [RFC6775], to refresh the NCE before the lifetime indicated in 937 the EARO expires. It MUST set the T Flag. The TID is 938 incremented each time and wraps in a lollipop fashion (see 939 section 5.2.1 of [RFC8505], which is fully compatible with 940 section 7.2 of [RFC6550]). 942 3. As stated in section 5.2 of [RFC8505], the 6LN can register to 943 more than one 6LR at the same time. In that case, it uses the 944 same EARO for all of the parallel Address Registrations, with the 945 exception of the Registration Lifetime field and the setting of 946 the R flag that may differ. The 6LN SHOULD send the NS(EARO), if 947 any, that maintain a registration active (i.e., with a non-zero 948 Registration Lifetime) and ensure that one succeeds before it 949 sends an NS(EARO) that terminates another registration, to avoid 950 the churn related to transient route invalidation in the RPL 951 network. 953 4. Following section 5.1 of [RFC8505], a 6LN acting as a RUL sets 954 the R Flag in the EARO of its registration(s) for which it 955 requires routing services. If the R Flag is not echoed in the 956 NA, the RUL SHOULD attempt to use another 6LR. The RUL SHOULD 957 send the registration(s) with the R Flag set and ensure that one 958 succeeds before it sends the registrations with the flag reset. 959 In case of a conflict with the preceding rule on lifetime, the 960 rule on lifetime has precedence. 962 5. The 6LN may use any of the 6LRs to which it registered as the 963 default gateway. Using a 6LR to which the 6LN is not registered 964 may result in packets dropped at the 6LR by a Source Address 965 Validation function (SAVI) [RFC7039] so it is not recommended. 967 Even without support for RPL, the RUL may be configured with an 968 opaque value to be provided to the routing protocol. If the RUL has 969 knowledge of the RPL Instance the packet should be injected into, 970 then it SHOULD set the Opaque field in the EARO to the RPLInstanceID, 971 else it MUST leave the Opaque field to zero. 973 Regardless of the setting of the Opaque field, the 6LN MUST set the 974 "I" field to zero to signal "topological information to be passed to 975 a routing process", as specified in section 5.1 of [RFC8505]. 977 A RUL is not expected to produce RPL artifacts in the data packets, 978 but it may do so. For instance, if the RUL has minimal awareness of 979 the RPL Instance then it can build an RPI. A RUL that places an RPI 980 in a data packet MUST indicate the RPLInstanceID of the RPL Instance 981 where the packet should be forwarded. All the flags and the Rank 982 field are set to zero as specified by section 11.2 of [RFC6550]. 984 9.2.2. Perspective of the 6LR Acting as Border Router 986 As prescribed by [RFC8505], the 6LR generates an EDAR message upon 987 reception of a valid NS(EARO) message for the registration of a new 988 IPv6 address by a 6LN. If the initial EDAR/EDAC exchange succeeds, 989 then the 6LR installs an NCE for the Registration Lifetime. For the 990 registration refreshes, if the RPL Root has indicated that it proxies 991 the keep-alive EDAR/EDAC exchange with the 6LBR (see Section 6), the 992 6LR MUST refrain from sending the keep-alive EDAR. 994 If the R Flag is set in the NS(EARO), the 6LR SHOULD inject the Host 995 route in RPL, unless this is barred for other reasons, such as the 996 saturation of the RPL parents. The 6LR MUST use a RPL Non-Storing 997 Mode signaling and the updated Target Option (see Section 6.1). The 998 6LR MUST request a DAO-ACK by setting the 'K' flag in the DAO 999 message. Success injecting the route to the RUL's address is 1000 indicated by the 'E' flag set to 0 in the RPL status of the DAO-ACK 1001 message. 1003 The Opaque field in the EARO provides a mean to signal which RPL 1004 Instance is to be used for the DAO advertisements and the forwarding 1005 of packets sourced at the Registered Address when there is no RPI in 1006 the packet. 1008 As described in [RFC8505], if the "I" field is zero, then the Opaque 1009 field is expected to carry the RPLInstanceID suggested by the 6LN; 1010 otherwise, there is no suggested Instance. If the 6LR participates 1011 in the suggested RPL Instance, then the 6LR MUST use that RPL 1012 Instance for the Registered Address. 1014 If there is no suggested RPL Instance or else if the 6LR does not 1015 participate to the suggested Instance, it is expected that the 1016 packets coming from the 6LN "can unambiguously be associated to at 1017 least one RPL Instance" [RFC6550] by the 6LR. 1019 The DAO message advertising the Registered Address MUST be 1020 constructed as follows: 1022 1. The Registered Address is signaled as the Target Prefix in the 1023 updated Target Option in the DAO message; the Prefix Length is 1024 set to 128 but the 'F' flag is not set since the advertiser is 1025 not the RUL. The ROVR field is copied unchanged from the EARO 1026 (see Section 6.1). 1028 2. The 6LR indicates one of its global or unique-local IPv6 unicast 1029 addresses as the Parent Address in the RPL Transit Information 1030 Option (TIO) associated with the Target Option 1032 3. The 6LR sets the External 'E' flag in the TIO to indicate that it 1033 is redistributing an external target into the RPL network 1035 4. the Path Lifetime in the TIO is computed from the Registration 1036 Lifetime in the EARO. This operation converts seconds to the 1037 Lifetime Units used in the RPL operation. This creates the 1038 deployment constraint that the Lifetime Unit is reasonably 1039 compatible with the expression of the Registration Lifetime. 1040 e.g., a Lifetime Unit of 0x4000 maps the most significant byte of 1041 the Registration Lifetime to the Path Lifetime. 1043 In that operation, the Path Lifetime must be rounded, if needed, 1044 to the upper value to ensure that the path has a longer lifetime 1045 than the registration. 1047 Note that if the Registration Lifetime is 0, then the Path 1048 Lifetime is also 0 and the DAO message becomes a No-Path DAO, 1049 which cleans up the routes down to the RUL's address; this also 1050 causes the Root as a proxy to send an EDAR message to the 6LBR 1051 with a Lifetime of 0. 1053 5. the Path Sequence in the TIO is set to the TID value found in the 1054 EARO option. 1056 Upon receiving or timing out the DAO-ACK after an implementation- 1057 specific number of retries, the 6LR MUST send the corresponding 1058 NA(EARO) to the RUL. Upon receiving an asynchronous DCO message, if 1059 a DAO-ACK is pending then the 6LR MUST wait for the DAO-ACK to send 1060 the NA(EARO) and deliver the status found in the DCO, else it MUST 1061 send an asynchronous NA(EARO) to the RUL immediately. 1063 The 6LR MUST set the R Flag in the NA(EARO) back if and only if the 1064 'E' flag is reset, indicating that the 6LR injected the Registered 1065 Address in the RPL routing successfully and that the EDAR proxy 1066 operation succeeded. 1068 If the 'A' flag in the RPL Status is set, the embedded Status Value 1069 is passed back to the RUL in the EARO Status. If the 'E' flag is 1070 also set, the registration failed for 6LoWPAN ND related reasons, and 1071 the NCE is removed. 1073 An error injecting the route causes the 'E' flag to be set. If the 1074 error is not related to ND, the 'A' flag is not set. In that case, 1075 the registration succeeds, but the RPL route is not installed. So 1076 the NA(EARO) is returned with a positive status but the R Flag not 1077 set, which means that the 6LN obtained a binding but no route. 1079 If the 'A' flag is not set in the RPL Status of the DAO-ACK, then the 1080 6LoWPAN ND operation succeeded, and an EARO Status of 0 (Success) 1081 MUST be returned to the 6LN. The EARO Status of 0 MUST also be used 1082 if the 6LR did not attempt to inject the route but could create the 1083 binding after a successful EDAR/EDAC exchange or refresh it. 1085 If the 'E' flag is set in the RPL Status of the DAO-ACK, then the 1086 route was not installed and the R flag MUST NOT be set in the 1087 NA(EARO). The R flag MUST NOT be set if the 6LR did not attempt to 1088 inject the route. 1090 In a network where Address Protected Neighbor Discovery (AP-ND) is 1091 enabled, in case of a DAO-ACK or a DCO indicating transporting an 1092 EARO Status Value of 5 (Validation Requested), the 6LR MUST challenge 1093 the 6LN for ownership of the address, as described in section 6.1 of 1094 [AP-ND], before the Registration is complete. This flow, illustrated 1095 in Figure 9, ensures that the address is validated before it is 1096 injected in the RPL routing. 1098 If the challenge succeeds, then the operations continue as normal. 1099 In particular, a DAO message is generated upon the NS(EARO) that 1100 proves the ownership of the address. If the challenge failed, the 1101 6LR rejects the registration as prescribed by AP-ND and may take 1102 actions to protect itself against DoS attacks by a rogue 6LN, see 1103 Section 11. 1105 6LN 6LR Root 6LBR 1106 | | | | 1107 |<--------------- RA ---------------------| | | 1108 | | | | 1109 |------ NS EARO (ROVR=Crypto-ID) -------->| | | 1110 | | | | 1111 |<- NA EARO(status=Validation Requested) -| | | 1112 | | | | 1113 |----- NS EARO and Proof-of-ownership -->| | 1114 | |--------- EDAR ------->| 1115 | | | 1116 | |<-------- EDAC --------| 1117 | | | 1118 | | | | 1119 | |-- DAO --->| | 1120 | | |-- EDAR -->| 1121 | | | | 1122 | | |<-- EDAC --| 1123 | |<- DAO-ACK-| | 1124 | | | | 1125 |<----------- NA EARO (status=0)----------| | | 1126 | | | | 1127 ... 1128 | | | | 1129 |------ NS EARO (ROVR=Crypto-ID) -------->| | | 1130 | |-- DAO --->| | 1131 | | |-- EDAR -->| 1132 | | | | 1133 | | |<-- EDAC --| 1134 | |<- DAO-ACK-| | 1135 |<----------- NA EARO (status=0)----------| | | 1136 | | | | 1137 ... 1139 Figure 9: Address Protection 1141 The 6LR may at any time send a unicast asynchronous NA(EARO) with the 1142 R Flag reset to signal that it stops providing routing services, and/ 1143 or with the EARO Status 2 "Neighbor Cache full" to signal that it 1144 removes the NCE. It may also send a final RA, unicast or multicast, 1145 with a Router Lifetime field of zero, to signal that it stops serving 1146 as Router, as specified in section 6.2.5 of [RFC4861]. This may 1147 happen upon a DCO or a DAO-ACK message indicating the path is already 1148 removed; else the 6LR SHOULD remove the Host route to the 6LN using a 1149 DAO message with a Path Lifetime of zero. 1151 A valid NS(EARO) message with the R Flag not set and a Registration 1152 Lifetime that is not zero signals that the 6LN wishes to maintain the 1153 binding but does not require the routing services from the 6LR (any 1154 more). Upon this message, if, due to previous NS(EARO) with the R 1155 Flag set, the 6LR was injecting the Host route to the Registered 1156 Address in RPL using DAO messages, then the 6LR MUST invalidate the 1157 Host route in RPL using a DAO with a Path Lifetime of zero. It is up 1158 to the Registering 6LN to maintain the corresponding route from then 1159 on, either keeping it active via a different 6LR or by acting as a 1160 RAN and managing its own reachability. 1162 9.2.3. Perspective of the RPL Root 1164 A RPL Root MUST set the 'P' bit in the RPL DODAG Configuration Option 1165 of the DIO messages that it generates (see Section 6) to signal that 1166 it proxies the EDAR/EDAC exchange and supports the Updated RPL Target 1167 option. 1169 Upon reception of a DAO message, for each updated RPL Target Option 1170 (see Section 6.1) that creates or updates an existing RPL state, the 1171 Root MUST notify the 6LBR by using a proxied EDAR/EDAC exchange. If 1172 if the RPL Root and the 6LBR are integrated, an internal API can be 1173 used. 1175 The EDAR message MUST be constructed as follows: 1177 1. The Target IPv6 address from the RPL Target Option is placed in 1178 the Registered Address field of the EDAR message; 1180 2. the Registration Lifetime is adapted from the Path Lifetime in 1181 the TIO by converting the Lifetime Units used in RPL into units 1182 of 60 seconds used in the 6LoWPAN ND messages; 1184 3. the TID value is set to the Path Sequence in the TIO and 1185 indicated with an ICMP code of 1 in the EDAR message; 1187 4. The ROVR in the RPL Target Option is copied as is in the EDAR and 1188 the ICMP Code Suffix is set to the appropriate value as shown in 1189 Table 4 of [RFC8505] depending on the size of the ROVR field. 1191 Upon receiving an EDAC message from the 6LBR, if a DAO is pending, 1192 then the Root MUST send a DAO-ACK back to the 6LR. Else, if the 1193 Status in the EDAC message is not "Success", then it MUST send an 1194 asynchronous DCO to the 6LR. 1196 In either case, the EDAC Status is embedded in the RPL Status with 1197 the 'A' flag set. 1199 The proxied EDAR/EDAC exchange MUST be protected with a timer of an 1200 appropriate duration and a number of retries, that are 1201 implementation-dependent, and SHOULD be configurable since the Root 1202 and the 6LBR are typically nodes with a higher capacity and 1203 manageability than 6LRs. Upon timing out, the Root MUST send an 1204 error back to the 6LR as above, either using a DAO-ACK or a DCO, as 1205 appropriate, with the 'A' and 'E' flags set in the RPL status, and a 1206 RPL Status Value of of "6LBR Registry Saturated" [RFC8505]. 1208 9.2.4. Perspective of the 6LBR 1210 The 6LBR is unaware that the RPL Root is not the new attachment 6LR 1211 of the RUL, so it is not impacted by this specification. 1213 Upon reception of an EDAR message, the 6LBR acts as prescribed by 1214 [RFC8505] and returns an EDAC message to the sender. 1216 10. Protocol Operations for Multicast Addresses 1218 Section 12 of [RFC6550] details the RPL support for multicast flows. 1219 This support is not source-specific and only operates as an extension 1220 to the Storing Mode of Operation for unicast packets. Note that it 1221 is the RPL model that the multicast packet is passed as a Layer-2 1222 unicast to each of the interested children. This remains true when 1223 forwarding between the 6LR and the listener 6LN. 1225 "Multicast Listener Discovery Version 2 (MLDv2) for IPv6" [RFC3810] 1226 provide an interface for a listener to register to multicast flows. 1227 In the MLD model, the Router is a "querier", and the Host is a 1228 multicast listener that registers to the querier to obtain copies of 1229 the particular flows it is interested in. 1231 The equivalent of the first Address Registration happens as 1232 illustrated in Figure 10. The 6LN, as an MLD listener, sends an 1233 unsolicited Report to the 6LR. This enables it to start receiving 1234 the flow immediately, and causes the 6LR to inject the multicast 1235 route in RPL. 1237 This specification does not change MLD but will operate more 1238 efficiently if the asynchronous messages for unsolicited Report and 1239 Done are sent by the 6LN as Layer-2 unicast to the 6LR, in particular 1240 on wireless. 1242 The 6LR acts as a generic MLD querier and generates a DAO with the 1243 Multicast Address as the Target Prefix as described in section 12 of 1244 [RFC6550]. As for the Unicast Host routes, the Path Lifetime 1245 associated to the Target is mapped from the Query Interval, and set 1246 to be larger to account for variable propagation delays to the Root. 1248 The Root proxies the MLD exchange as a listener with the 6LBR acting 1249 as the querier, so as to get packets from a source external to the 1250 RPL domain. 1252 Upon a DAO with a Target option for a multicast address, the RPL Root 1253 checks if it is already registered as a listener for that address, 1254 and if not, it performs its own unsolicited Report for the multicast 1255 address as sescribed in section 5.1 of [RFC3810]. The report is 1256 source independent, so there is no Source Address listed. 1258 6LN/RUL 6LR Root 6LBR 1259 | | | | 1260 | unsolicited Report | | | 1261 |------------------->| | | 1262 | | | | 1263 | | DAO | | 1264 | |-------------->| | 1265 | | DAO-ACK | | 1266 | |<--------------| | 1267 | | | | 1268 | | | unsolicited Report | 1269 | | |---------------------->| 1270 | | | | 1272 Figure 10: First Multicast Registration Flow 1274 The equivalent of the registration refresh is pulled periodically by 1275 the 6LR acting as querier. Upon the timing out of the Query 1276 Interval, the 6LR sends a Multicast Address Specific Query to each of 1277 its listeners, for each Multicast Address, and gets a Report back 1278 that is mapped into a DAO one by one. Optionally, the 6LR MAY send a 1279 General Query, where the Multicast Address field is set to zero. In 1280 that case, the multicast packet is passed as a Layer-2 unicast to 1281 each of the interested children. . 1283 Upon a Report, the 6LR generates a DAO with as many Target Options as 1284 there are Multicast Address Records in the Report message, copying 1285 the Multicast Address field in the Target Prefix of the RPL Target 1286 Option. The DAO message is a Storing Mode DAO, passed to a selection 1287 of the 6LR's parents. 1289 Asynchronously to this, a similar procedure happens between the Root 1290 and a router such as the 6LBR that serves multicast flows on the Link 1291 where the Root is located. Again the Query and Report messages are 1292 source independent. The Root lists exactly once each Multicast 1293 Address for which it has at least one active multicast DAO state, 1294 copying the multicast address in the DAO state in the Multicast 1295 Address field of the Multicast Address Records in the Report message. 1297 This is illustrated in Figure 11: 1299 6LN/RUL 6LR Root 6LBR 1300 | | | | 1301 | Query | | | 1302 |<-------------------| | | 1303 | Report | | | 1304 |------------------->| | | 1305 | | DAO | | 1306 | |-------------->| | 1307 | | DAO-ACK | | 1308 | |<--------------| | 1309 | | | Query | 1310 | | |<-------------------| 1311 | | | Report | 1312 | | |------------------->| 1313 | | | | 1315 Figure 11: Next Registration Flow 1317 Note that any of the functions 6LR, Root and 6LBR might be collapsed 1318 in a single node, in which case the flow above happens internally, 1319 and possibly through internal API calls as opposed to messaging. 1321 11. Security Considerations 1323 It is worth noting that with [RFC6550], every node in the LLN is RPL- 1324 aware and can inject any RPL-based attack in the network. This 1325 specification isolates edge nodes that can only interact with the RPL 1326 Routers using 6LoWPAN ND, meaning that they cannot perform RPL 1327 insider attacks. 1329 The LLN nodes depend on the 6LBR and the RPL participants for their 1330 operation. A trust model must be put in place to ensure that the 1331 right devices are acting in these roles, so as to avoid threats such 1332 as black-holing, (see [RFC7416] section 7), Denial-Of-Service attacks 1333 whereby a rogue 6LR creates a high churn in the RPL network by 1334 advertising and removing many forged addresses, or bombing attack 1335 whereby an impersonated 6LBR would destroy state in the network by 1336 using the "Removed" Status code. 1338 This trust model could be at a minimum based on a Layer-2 Secure 1339 joining and the Link-Layer security. This is a generic 6LoWPAN 1340 requirement, see Req5.1 in Appendix of [RFC8505]. 1342 In a general manner, the Security Considerations in [RFC7416] 1343 [RFC6775], and [RFC8505] apply to this specification as well. 1345 The Link-Layer security is needed in particular to prevent Denial-Of- 1346 Service attacks whereby a rogue 6LN creates a high churn in the RPL 1347 network by constantly registering and deregistering addresses with 1348 the R Flag set in the EARO. 1350 [AP-ND] updated 6LoWPAN ND with the called Address-Protected Neighbor 1351 Discovery (AP-ND). AP-ND protects the owner of an address against 1352 address theft and impersonation attacks in a Low-Power and Lossy 1353 Network (LLN). Nodes supporting th extension compute a cryptographic 1354 identifier (Crypto-ID), and use it with one or more of their 1355 Registered Addresses. The Crypto-ID identifies the owner of the 1356 Registered Address and can be used to provide proof of ownership of 1357 the Registered Addresses. Once an address is registered with the 1358 Crypto-ID and a proof of ownership is provided, only the owner of 1359 that address can modify the registration information, thereby 1360 enforcing Source Address Validation. [AP-ND] reduces even more the 1361 attack perimeter that is available to the edge nodes and its use is 1362 suggested in this specification. 1364 Additionally, the trust model could include a role validation to 1365 ensure that the node that claims to be a 6LBR or a RPL Root is 1366 entitled to do so. 1368 The Opaque field in the EARO enables the RUL to suggest a 1369 RPLInstanceID where its traffic is placed. This opens to attacks 1370 where a RPL instance would be reserved for critical traffic, e.g., 1371 with a specific bandwidth reservation, that the additional traffic 1372 generated by a rogue may disrupt. This may be alleviated by 1373 traditional access control mechanisms where the 6LR shapes the 1374 incoming traffic from the 6LN. 1376 At the time of this writing, RPL does not have a Route Ownership 1377 Validation model whereby it is possible to validate the origin of an 1378 address that is injected in a DAO. This specification makes a first 1379 step in that direction by allowing the Root to challenge the RUL via 1380 the 6LR that serves it. 1382 [EFFICIENT-NPDAO] introduces the ability for a rogue common ancestor 1383 node to invalidate a route on behalf of the target node. In that 1384 case, the RPL Status in the DCO has the 'A' flag not set, and a 1385 NA(EARO) is returned to the 6LN with the R flag not set. This 1386 encourages the 6LN to try another 6LR. If a 6LR exists that does not 1387 use the rogue common ancestor, then the 6LN will eventually succeed 1388 gaining reachability over the RPL network in spite of the rogue node. 1390 12. IANA Considerations 1392 12.1. Fixing the Address Registration Option Flags 1394 Section 9.1 of [RFC8505] creates a Registry for the 8-bit Address 1395 Registration Option Flags field. IANA is requested to rename the 1396 first column of the table from "ARO Status" to "Bit number". 1398 12.2. Resizing the ARO Status values 1400 Section 12 of [RFC6775] creates the Address Registration Option 1401 Status Values Registry with a range 0-255. 1403 This specification reduces that range to 0-63, see Section 6.3. 1405 IANA is requested modify the Address Registration Option Status 1406 Values Registry so that the upper bound of the unassigned values is 1407 63. This document should be added as a reference. The registration 1408 procedure does not change. 1410 12.3. New DODAG Configuration Option Flag 1412 This specification updates the Registry that was created for 1413 [RFC6550] as the registry for "DODAG Configuration Option Flags" and 1414 updated as the registry for "DODAG Configuration Option Flags for MOP 1415 0..6" by [USEofRPLinfo], by allocating one new Flag as follows: 1417 +---------------+----------------------------+-----------+ 1418 | Bit Number | Capability Description | Reference | 1419 +---------------+----------------------------+-----------+ 1420 | 1 (suggested) | Root Proxies EDAR/EDAC (P) | THIS RFC | 1421 +---------------+----------------------------+-----------+ 1423 Table 2: New DODAG Configuration Option Flag 1425 12.4. RPL Target Option Registry 1427 Section 20.15 of [RFC6550] creates a Registry for the 8-bit "RPL 1428 Target Option Flags" field. IANA is requested to reduce the size of 1429 the field in the Registry to 4 bits. Section 6.1 also defines a new 1430 entry in the Registry as follows: 1432 +---------------+--------------------------------+-----------+ 1433 | Bit Number | Capability Description | Reference | 1434 +---------------+--------------------------------+-----------+ 1435 | 1 (suggested) | Advertiser address in Full (F) | THIS RFC | 1436 +---------------+--------------------------------+-----------+ 1438 Table 3: RPL Target Option Registry 1440 12.5. New Subregistry for the RPL Non-Rejection Status values 1442 This specification creates a new Subregistry for the RPL Non- 1443 Rejection Status values for use in the RPL DAO-ACK and DCO messages 1444 with the 'A' flag reset, under the RPL registry. 1446 * Possible values are 6-bit unsigned integers (0..63). 1448 * Registration procedure is "IETF Review" [RFC8126]. 1450 * Initial allocation is as indicated in Table 4: 1452 +-------+--------------------------+-------------------+ 1453 | Value | Meaning | Reference | 1454 +-------+--------------------------+-------------------+ 1455 | 0 | Unqualified acceptance | THIS RFC | 1456 +-------+--------------------------+-------------------+ 1457 | 1 | No routing-entry for the | [EFFICIENT-NPDAO] | 1458 | | indicated Target found | | 1459 +-------+--------------------------+-------------------+ 1461 Table 4: Acceptance values of the RPL Status 1463 12.6. New Subregistry for the RPL Rejection Status values 1465 This specification creates a new Subregistry for the RPL Rejection 1466 Status values for use in the RPL DAO-ACK and DCO messages with the 1467 'A' flag reset, under the RPL registry. 1469 * Possible values are 6-bit unsigned integers (0..63). 1471 * Registration procedure is "IETF Review" [RFC8126]. 1473 * Initial allocation is as indicated in Table 5: 1475 +-------+-----------------------+-----------+ 1476 | Value | Meaning | Reference | 1477 +-------+-----------------------+-----------+ 1478 | 0 | Unqualified rejection | THIS RFC | 1479 +-------+-----------------------+-----------+ 1481 Table 5: Rejection values of the RPL Status 1483 13. Acknowledgments 1485 The authors wish to thank Ines Robles, Georgios Papadopoulos and 1486 especially Rahul Jadhav and Alvaro Retana for their reviews and 1487 contributions to this document. 1489 14. Normative References 1491 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1492 Requirement Levels", BCP 14, RFC 2119, 1493 DOI 10.17487/RFC2119, March 1997, 1494 . 1496 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1497 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1498 DOI 10.17487/RFC3810, June 2004, 1499 . 1501 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1502 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1503 DOI 10.17487/RFC4861, September 2007, 1504 . 1506 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1507 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1508 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1509 Low-Power and Lossy Networks", RFC 6550, 1510 DOI 10.17487/RFC6550, March 2012, 1511 . 1513 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1514 Bormann, "Neighbor Discovery Optimization for IPv6 over 1515 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1516 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1517 . 1519 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 1520 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 1521 2014, . 1523 [RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for 1524 IPv6 over Low-Power Wireless Personal Area Networks 1525 (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November 1526 2014, . 1528 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1529 Writing an IANA Considerations Section in RFCs", BCP 26, 1530 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1531 . 1533 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1534 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1535 May 2017, . 1537 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1538 (IPv6) Specification", STD 86, RFC 8200, 1539 DOI 10.17487/RFC8200, July 2017, 1540 . 1542 [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node 1543 Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, 1544 January 2019, . 1546 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1547 Perkins, "Registration Extensions for IPv6 over Low-Power 1548 Wireless Personal Area Network (6LoWPAN) Neighbor 1549 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1550 . 1552 [AP-ND] Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 1553 "Address Protected Neighbor Discovery for Low-power and 1554 Lossy Networks", Work in Progress, Internet-Draft, draft- 1555 ietf-6lo-ap-nd-23, 30 April 2020, 1556 . 1558 [USEofRPLinfo] 1559 Robles, I., Richardson, M., and P. Thubert, "Using RPI 1560 Option Type, Routing Header for Source Routes and IPv6-in- 1561 IPv6 encapsulation in the RPL Data Plane", Work in 1562 Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-41, 1563 21 September 2020, . 1566 [EFFICIENT-NPDAO] 1567 Jadhav, R., Thubert, P., Sahoo, R., and Z. Cao, "Efficient 1568 Route Invalidation", Work in Progress, Internet-Draft, 1569 draft-ietf-roll-efficient-npdao-18, 15 April 2020, 1570 . 1573 15. Informative References 1575 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1576 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1577 Overview, Assumptions, Problem Statement, and Goals", 1578 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1579 . 1581 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1582 Address Autoconfiguration", RFC 4862, 1583 DOI 10.17487/RFC4862, September 2007, 1584 . 1586 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 1587 Power and Lossy Networks (RPL) Option for Carrying RPL 1588 Information in Data-Plane Datagrams", RFC 6553, 1589 DOI 10.17487/RFC6553, March 2012, 1590 . 1592 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 1593 Routing Header for Source Routes with the Routing Protocol 1594 for Low-Power and Lossy Networks (RPL)", RFC 6554, 1595 DOI 10.17487/RFC6554, March 2012, 1596 . 1598 [RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem 1599 Statement and Requirements for IPv6 over Low-Power 1600 Wireless Personal Area Network (6LoWPAN) Routing", 1601 RFC 6606, DOI 10.17487/RFC6606, May 2012, 1602 . 1604 [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., 1605 "Source Address Validation Improvement (SAVI) Framework", 1606 RFC 7039, DOI 10.17487/RFC7039, October 2013, 1607 . 1609 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 1610 Constrained-Node Networks", RFC 7228, 1611 DOI 10.17487/RFC7228, May 2014, 1612 . 1614 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 1615 "IPv6 over Low-Power Wireless Personal Area Network 1616 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 1617 April 2017, . 1619 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1620 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1621 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1622 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1623 . 1625 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1626 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1627 DOI 10.17487/RFC6282, September 2011, 1628 . 1630 [RFC6687] Tripathi, J., Ed., de Oliveira, J., Ed., and JP. Vasseur, 1631 Ed., "Performance Evaluation of the Routing Protocol for 1632 Low-Power and Lossy Networks (RPL)", RFC 6687, 1633 DOI 10.17487/RFC6687, October 2012, 1634 . 1636 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 1637 and M. Richardson, Ed., "A Security Threat Analysis for 1638 the Routing Protocol for Low-Power and Lossy Networks 1639 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 1640 . 1642 [RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power 1643 Wireless Personal Area Network (6LoWPAN) Paging Dispatch", 1644 RFC 8025, DOI 10.17487/RFC8025, November 2016, 1645 . 1647 [6BBR] Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 1648 Backbone Router", Work in Progress, Internet-Draft, draft- 1649 ietf-6lo-backbone-router-20, 23 March 2020, 1650 . 1653 Appendix A. Example Compression 1655 Figure 12 illustrates the case in Storing Mode where the packet is 1656 received from the Internet, then the Root encapsulates the packet to 1657 insert the RPI and deliver to the 6LR that is the parent and last hop 1658 to the final destination, which is not known to support [RFC8138]. 1660 +-+ ... -+-+ ... +-+- ... -+-+ ... -+-+-+ ... +-+-+ ... -+ ... +-... 1661 |11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP 1662 |Page 1 |Type1 S=0| 6LoRH | 6LoRH |LOWPAN_IPHC| UDP | hdr |Payld 1663 +-+ ... -+-+ ... +-+- ... -+-+ ... -+-+-+ ... +-+-+ ... -+ ... +-... 1664 <-4 bytes-> <- RFC 6282 -> 1665 <- No RPL artifact ... 1667 Figure 12: Encapsulation to Parent 6LR in Storing Mode 1669 The difference with the example presented in Figure 19 of [RFC8138] 1670 is the addition of a SRH-6LoRH before the RPI-6LoRH to transport the 1671 compressed address of the 6LR as the destination address of the outer 1672 IPv6 header. In the [RFC8138] example the destination IP of the 1673 outer header was elided and was implicitly the same address as the 1674 destination of the inner header. Type 1 was arbitrarily chosen, and 1675 the size of 0 denotes a single address in the SRH. 1677 In Figure 12, the source of the IP-in-IP encapsulation is the Root, 1678 so it is elided in the IP-in-IP 6LoRH. The destination is the parent 1679 6LR of the destination of the inner packet so it cannot be elided. 1680 If the DODAG is operated in Storing Mode, it is the single entry in 1681 the SRH-6LoRH and the SRH-6LoRH Size is encoded as 0. The SRH-6LoRH 1682 is the first 6LoRH in the chain. In this particular example, the 6LR 1683 address can be compressed to 2 bytes so a Type of 1 is used. It 1684 results that the total length of the SRH-6LoRH is 4 bytes. 1686 In Non-Storing Mode, the encapsulation from the Root would be similar 1687 to that represented in Figure 12 with possibly more hops in the SRH- 1688 6LoRH and possibly multiple SRH-6LoRHs if the various addresses in 1689 the routing header are not compressed to the same format. Note that 1690 on the last hop to the parent 6LR, the RH3 is consumed and removed 1691 from the compressed form, so the use of Non-Storing Mode vs. Storing 1692 Mode is indistinguishable from the packet format. 1694 The SRH-6LoRHs are followed by RPI-6LoRH and then the IP-in-IP 6LoRH. 1695 When the IP-in-IP 6LoRH is removed, all the 6LoRH Headers that 1696 precede it are also removed. The Paging Dispatch [RFC8025] may also 1697 be removed if there was no previous Page change to a Page other than 1698 0 or 1, since the LOWPAN_IPHC is encoded in the same fashion in the 1699 default Page 0 and in Page 1. The resulting packet to the 1700 destination is the inner packet compressed with [RFC6282]. 1702 Authors' Addresses 1704 Pascal Thubert (editor) 1705 Cisco Systems, Inc 1706 Building D 1707 45 Allee des Ormes - BP1200 1708 06254 Mougins - Sophia Antipolis 1709 France 1711 Phone: +33 497 23 26 34 1712 Email: pthubert@cisco.com 1714 Michael C. Richardson 1715 Sandelman Software Works 1717 Email: mcr+ietf@sandelman.ca 1718 URI: http://www.sandelman.ca/