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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 4919 == Outdated reference: A later version (-23) exists of draft-ietf-6lo-ap-nd-12 == Outdated reference: A later version (-44) exists of draft-ietf-roll-useofrplinfo-32 == Outdated reference: A later version (-18) exists of draft-ietf-roll-efficient-npdao-17 ** Downref: Normative reference to an Informational RFC: RFC 7102 -- Obsolete informational reference (is this intentional?): RFC 3315 (Obsoleted by RFC 8415) Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL P. Thubert, Ed. 3 Internet-Draft Cisco Systems 4 Updates: 6550, 8505 (if approved) M. Richardson 5 Intended status: Standards Track Sandelman 6 Expires: 18 June 2020 16 December 2019 8 Routing for RPL Leaves 9 draft-ietf-roll-unaware-leaves-08 11 Abstract 13 This specification extends RFC6550 and RFC8505 to provide unicast and 14 multicast routing services in a RPL domain to 6LNs that are plain 15 Hosts and do not participate to RPL, and enables the RPL Root to 16 proxy the EDAR/EDAC flow on behalf of the RULs and RANs in its DODAG. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on 18 June 2020. 35 Copyright Notice 37 Copyright (c) 2019 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 42 license-info) in effect on the date of publication of this document. 43 Please review these documents carefully, as they describe your rights 44 and restrictions with respect to this document. Code Components 45 extracted from this document must include Simplified BSD License text 46 as described in Section 4.e of the Trust Legal Provisions and are 47 provided without warranty as described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 53 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 2.2. References . . . . . . . . . . . . . . . . . . . . . . . 4 55 2.3. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 5 56 3. 6LoWPAN Neighbor Discovery . . . . . . . . . . . . . . . . . 7 57 3.1. RFC 6775 . . . . . . . . . . . . . . . . . . . . . . . . 7 58 3.2. RFC 8505 Extended ARO . . . . . . . . . . . . . . . . . . 7 59 3.2.1. R Flag . . . . . . . . . . . . . . . . . . . . . . . 8 60 3.2.2. TID, I Field and Opaque Fields . . . . . . . . . . . 8 61 3.2.3. ROVR . . . . . . . . . . . . . . . . . . . . . . . . 8 62 3.3. RFC 8505 Extended DAR/DAC . . . . . . . . . . . . . . . . 9 63 4. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 9 64 5. Updating RFC 8505 . . . . . . . . . . . . . . . . . . . . . . 10 65 6. Requirements on the RPL-Unware Leaf . . . . . . . . . . . . . 10 66 6.1. Support of 6LoWPAN ND . . . . . . . . . . . . . . . . . . 11 67 6.2. External Routes and RPL Artifacts . . . . . . . . . . . . 11 68 6.2.1. Support of the HbH Header . . . . . . . . . . . . . . 12 69 6.2.2. Support of the Routing Header . . . . . . . . . . . . 12 70 6.2.3. Support of IPv6 Encapsulation . . . . . . . . . . . . 12 71 7. Updated RPL Status . . . . . . . . . . . . . . . . . . . . . 13 72 8. Updated RPL Target option . . . . . . . . . . . . . . . . . . 14 73 9. Protocol Operations for Unicast Addresses . . . . . . . . . . 15 74 9.1. General Flow . . . . . . . . . . . . . . . . . . . . . . 15 75 9.1.1. In RPL Non-Storing-Mode . . . . . . . . . . . . . . . 15 76 9.1.2. In RPL Storing-Mode . . . . . . . . . . . . . . . . . 18 77 9.2. Detailed Operation . . . . . . . . . . . . . . . . . . . 18 78 9.2.1. By the 6LN . . . . . . . . . . . . . . . . . . . . . 19 79 9.2.2. By the 6LR . . . . . . . . . . . . . . . . . . . . . 20 80 9.2.3. By the RPL Root . . . . . . . . . . . . . . . . . . . 22 81 9.2.4. By the 6LBR . . . . . . . . . . . . . . . . . . . . . 23 82 10. Protocol Operations for Multicast Addresses . . . . . . . . . 23 83 11. Security Considerations . . . . . . . . . . . . . . . . . . . 25 84 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 85 12.1. New DODAG Configuration Option Flag . . . . . . . . . . 26 86 12.2. RPL Target Option Flags . . . . . . . . . . . . . . . . 26 87 12.3. New Subregistry for the RPL Non-Rejection Status 88 values . . . . . . . . . . . . . . . . . . . . . . . . . 26 89 12.4. New Subregistry for the RPL Rejection Status values . . 26 90 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 91 14. Normative References . . . . . . . . . . . . . . . . . . . . 27 92 15. Informative References . . . . . . . . . . . . . . . . . . . 29 93 Appendix A. Example Compression . . . . . . . . . . . . . . . . 30 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31 96 1. Introduction 98 The design of Low Power and Lossy Networks (LLNs) is generally 99 focused on saving energy, which is the most constrained resource of 100 all. Other design constraints, such as a limited memory capacity, 101 duty cycling of the LLN devices and low-power lossy transmissions, 102 derive from that primary concern. 104 The IETF produced the "Routing Protocol for Low Power and Lossy 105 Networks" [RFC6550] (RPL) to provide IPv6 [RFC8200] routing services 106 within such constraints. RPL belongs to the class of Distance-Vector 107 protocol, which, compared to link-state protocols, limits the amount 108 of topological knowledge that needs to be installed and maintained in 109 each node. 111 In order to operate in constrained networks, RPL allows a routing 112 stretch (see [RFC6687]), whereby routing is only performed along an 113 acyclic graph optimized to reach a Root node, as opposed to straight 114 along a shortest path between 2 peers, whatever that would mean in a 115 given LLN. This trades the quality of peer-to-peer (P2P) paths for a 116 vastly reduced amount of control traffic and routing state that would 117 be required to operate a any-to-any shortest path protocol. Finally, 118 broken routes may be fixed lazily and on-demand, based on dataplane 119 inconsistency discovery, which avoids wasting energy in the proactive 120 repair of unused paths. 122 In order to cope with lossy transmissions, RPL forms Direction- 123 Oriented Directed Acyclic Graphs (DODAGs) using DODAG Information 124 Solicitation (DIS) and DODAG Information Object (DIO) messages. For 125 most of the nodes, though not all, a 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 routes proactively but only fixes them when 130 they are used by actual traffic. 132 The result is that RPL provides reachability for most of the LLN 133 nodes, most of the time, but may not really converge in the classical 134 sense. RPL provides unicast and multicast routing services back to 135 RPL-Aware nodes (RANs). 137 A RAN will inject routes to itself using Destination Advertisement 138 Object (DAO) messages sent to either parent-nodes in Storing Mode or 139 to the Root indicating their parent in Non-Storing Mode. This 140 process effectively forms a DODAG back to the device that is a subset 141 of the DODAG to the Root with all links reversed. 143 RPL can be deployed as an extension to IPv6 Neighbor Discovery (ND) 144 [RFC4861][RFC4862] and 6LoWPAN ND [RFC6775][RFC8505] to maintain 145 reachability within a Non-Broadcast Multi-Access (NBMA) subnet. In 146 that mode, some nodes may act as Routers and participate to the 147 forwarding operations whereas others will only terminate packets, 148 acting as Hosts in the data-plane. In [RFC6550] terms, a Host that 149 is reachable over the RPL network is called a Leaf. 151 "When to use RFC 6553, 6554 and IPv6-in-IPv6" [USEofRPLinfo] 152 introduces the term RPL-Aware-Leaf (RAL) for a Leaf that injects 153 routes in RPL to manage the reachability of its own IPv6 addresses. 154 In contrast, a RPL-Unaware Leaf (RUL) designates a Leaf does not 155 participate to RPL at all. A RUL is a plain Host that needs an 156 interface to its RPL Router to obtain routing services over the LLN. 158 This specification enables a RUL that is a 6LoWPAN Node (6LN) to 159 announce itself as a Host to its 6LoWPAN Router (6LR) in the 6LoWPAN 160 ND Address Address Registration, and to request that the 6LR injects 161 the relevant routing information for the Registered Address in the 162 RPL domain on its behalf. The unicast packet forwarding operation by 163 the 6LR serving a 6LN that is a RPL Leaf is described in 164 [USEofRPLinfo]. 166 Examples of routing-agnostic 6LN may include lightly-powered sensors 167 such as window smash sensor (alarm system), and kinetically powered 168 light switches. Other application of this specification may include 169 a smart grid network that controls appliances - such as washing 170 machines or the heating system - in the home. Appliances may not 171 participate to the RPL protocol operated in the Smartgrid network but 172 can still receive control packet from the Smartgrid. 174 2. Terminology 176 2.1. BCP 14 178 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 179 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 180 "OPTIONAL" in this document are to be interpreted as described in BCP 181 14 [RFC2119][RFC8174] when, and only when, they appear in all 182 capitals, as shown here. 184 2.2. References 186 The Terminology used in this document is consistent with and 187 incorporates that described in Terms Used in Routing for Low-Power 188 and Lossy Networks (LLNs). [RFC7102]. 190 A glossary of classical 6LoWPAN acronyms is given in Section 2.3. 192 The term "byte" is used in its now customary sense as a synonym for 193 "octet". 195 "RPL", the "RPL Packet Information" (RPI), "RPL Instance" (indexed by 196 a RPLInstanceID)are defined in "RPL: IPv6 Routing Protocol for 197 Low-Power and Lossy Networks" [RFC6550] . The DODAG Information 198 Solicitation (DIS), Destination Advertisement Object (DAO) and DODAG 199 Information Object (DIO) messages are also specified in [RFC6550]. 200 The Destination Cleanup Object (DCO) message is defined in 201 [EFFICIENT-NPDAO]. 203 This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware 204 Leaf (RAL) consistently with [USEofRPLinfo]. The term RPL-Aware Node 205 (RAN) is introduced to refer to a node that is either a RAL or a RPL 206 Router. As opposed to a RUL, a RAN manages the reachability of its 207 addresses and prefixes by injecting them in RPL by itself. 209 Other terms in use in LLNs are found in Terminology for 210 Constrained-Node Networks [RFC7228]. 212 Readers are expected to be familiar with all the terms and concepts 213 that are discussed in 215 * "Neighbor Discovery for IP version 6" [RFC4861], 217 * "IPv6 Stateless Address Autoconfiguration" [RFC4862], 219 * "Problem Statement and Requirements for IPv6 over Low-Power 220 Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], 222 * "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): 223 Overview, Assumptions, Problem Statement, and Goals" [RFC4919], 225 * "Neighbor Discovery Optimization for Low-power and Lossy Networks" 226 [RFC6775], and 228 * "Registration Extensions for IPv6 over Low-Power Wireless Personal 229 Area Network (6LoWPAN) Neighbor Discovery" [RFC8505]. 231 2.3. Glossary 233 This document often uses the following acronyms: 235 AR: Address Resolution (aka Address Lookup) 237 6LBR: 6LoWPAN Border Router 238 6LN: 6LoWPAN Node (a Low Power Host or Router) 240 6LR: 6LoWPAN Router 242 (E)ARO: (Extended) Address Registration Option 244 (E)DAR: (Extended) Duplicate Address Request 246 (E)DAC: (Extended) Duplicate Address Confirmation 248 DAD: Duplicate Address Detection 250 DAO: Destination Advertisement Object (a RPL message) 252 DCO: Destination Cleanup Object (a RPL message) 254 DIS: DODAG Information Solicitation (a RPL message) 256 DIO: DODAG Information Object (a RPL message) 258 DODAG: Destination-Oriented Directed Acyclic Graph 260 LLN: Low-Power and Lossy Network 262 NA: Neighbor Advertisement 264 NCE: Neighbor Cache Entry 266 ND: Neighbor Discovery 268 NS: Neighbor Solicitation 270 RA: Router Advertisement 272 ROVR: Registration Ownership Verifier 274 RPI: RPL Packet Information (the abstract information RPL places in 275 data packets as the RPL Option within the IPv6 Hop-By-Hop Header, 276 and by extension the RPL Option itself) 278 RAL: RPL-Aware Leaf 280 RAN: RPL-Aware Node (either a RPL Router or a RPL-Aware Leaf) 282 RUL: RPL-Unaware Leaf 284 TID: Transaction ID (a sequence counter in the EARO) 286 3. 6LoWPAN Neighbor Discovery 288 3.1. RFC 6775 290 The "IPv6 Neighbor Discovery (IPv6 ND) Protocol" suite [RFC4861] 291 [RFC4862] was defined for transit media such a Ethernet, and relies 292 heavily on multicast operations for address discovery and duplicate 293 address detection (DAD). "Neighbor Discovery Optimizations for 294 6LoWPAN networks" [RFC6775] (6LoWPAN ND) adapts IPv6 ND for 295 operations over energy-constrained LLNs. In particular, 6LoWPAN ND 296 introduces a unicast Host Registration mechanism that contributes to 297 reducing the use of multicast messages that are present in the 298 classical IPv6 ND protocol. 300 6LoWPAN ND defines a new Address Registration Option (ARO) that is 301 carried in the unicast Neighbor Solicitation (NS) and Neighbor 302 Advertisement (NA) messages between the 6LoWPAN Node (6LN) and the 303 6LoWPAN Router (6LR). 6LoWPAN ND also defines the Duplicate Address 304 Request (DAR) and Duplicate Address Confirmation (DAC) messages 305 between the 6LR and the 6LoWPAN Border Router (6LBR). In an LLN, the 306 6LBR is the central repository of all the Registered Addresses in its 307 domain. 309 The main functions of [RFC6775] are to proactively establish the 310 Neighbor Cache Entry in the 6LR and to avoid address duplication. 311 There is no concept of registering the address for an external 312 service. 314 3.2. RFC 8505 Extended ARO 316 "Registration Extensions for 6LoWPAN Neighbor Discovery" [RFC8505] 317 updates the behavior of RFC 6775 to enable a generic Address 318 Registration to services such as routing and ND proxy, and defines 319 the Extended Address Registration Option (EARO) as shown in Figure 1: 321 0 1 2 3 322 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 1 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | Type | Length | Status | Opaque | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | Rsvd | I |R|T| TID | Registration Lifetime | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | | 329 ... Registration Ownership Verifier ... 330 | | 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 Figure 1: EARO Option Format 335 3.2.1. R Flag 337 [RFC8505] introduces the "R" flag in the EARO. The Registering Node 338 sets the "R" flag to indicate whether the 6LR should ensure 339 reachability for the Registered Address, e.g., by means of routing or 340 proxying ND. If the "R" flag is not set, then the Registering Node 341 is expected to be a RAN that handles the reachability of the 342 Registered Address by itself. 344 This document specifies how the "R" flag is used in the context of 345 RPL. A 6LN operates as a RUL for an IPv6 address iff it sets the "R" 346 flag in the EARO used to register the address. The RPL Router 347 generates a DAO message for the Registered Address upon an NS(EARO) 348 iff the "R" flag in the EARO is set. Conversely, this document 349 specifies the behavior of a RPL Router acting as 6LR that depends on 350 the setting of the "R" flag in the EARO. 352 3.2.2. TID, I Field and Opaque Fields 354 The EARO also includes a sequence counter called Transaction ID 355 (TID), which maps to the Path Sequence Field found in Transit Options 356 in RPL DAO messages. This is the reason why the support of [RFC8505] 357 by the RUL as opposed to only [RFC6775] is a prerequisite for this 358 specification (more in Section 6.1). The EARO also transports an 359 Opaque field and an "I" field that describes what the Opaque field 360 transports and how to use it. Section 9.2.1 specifies the use of the 361 "I" field and of the Opaque field by a RUL. 363 3.2.3. ROVR 365 Section 5.3. of [RFC8505] introduces the Registration Ownership 366 Verifier (ROVR) field of variable length from 64 to 256 bits. The 367 ROVR is a replacement of the EUI-64 in the ARO [RFC6775] that was 368 used to identify uniquely an Address Registration with the Link-Layer 369 address of the owner, but provided no protection against spoofing. 371 "Address Protected Neighbor Discovery for Low-power and Lossy 372 Networks" [AP-ND] leverages the ROVR field as a cryptographic proof 373 of ownership to prevent a rogue third party from misusing the 374 address. [AP-ND] adds a challenge/response exchange to the [RFC8505] 375 Address Registration and enables Source Address Validation by a 6LR 376 that will drop packets with a spoofed address. 378 This specification does not address how the protection by [AP-ND] 379 could be extended to RPL. On the other hand, it adds the ROVR to the 380 DAO to build the proxied EDAR at the Root, which means that nodes 381 that are aware of the Host route to the 6LN are now aware of the 382 associated ROVR as well. 384 3.3. RFC 8505 Extended DAR/DAC 386 [RFC8505] updates the periodic DAR/DAC exchange that takes place 387 between the 6LR and the 6LBR using Extended DAR/DAC messages. The 388 Extended Duplicate Address messages can carry a ROVR field of 389 variable size. The periodic EDAR/EDAC exchange is triggered by a 390 NS(EARO) message and is intended to create and then refresh the 391 corresponding state in the 6LBR for a lifetime that is indicated by 392 the 6LN. Conversely, RPL [RFC6550] specifies a periodic DAO from the 393 6LN all the way to the Root that maintains the routing state in the 394 RPL network for a lifetime that is indicated by the source of the 395 DAO. This means that there are two periodic messages that traverse 396 the whole network to indicate that an address is still reachable, one 397 to the Root and one to the 6LBR. 399 This specification saves the support of RPL in a 6LN called a RUL and 400 avoids an extraneous periodic flow across the LLN. The RUL only 401 needs to perform a [RFC8505] Address Registration to the 6LR. The 402 6LR turns it into a DAO message to the Root on behalf of the RUL. 403 Upon the new DAO, the Root proxies the EDAR exchange to the 6LBR on 404 behalf of the 6LR. This is illustrated in Figure 5. 406 4. Updating RFC 6550 408 This document specifies a new behavior whereby a 6LR injects DAO 409 messages for unicast addresses (see Section 9) and multicast 410 addresses (see Section 10) on behalf of leaves that are not aware of 411 RPL. The Targets are exposed as External addresses. An IP-in-IP 412 encapsulation that terminates at the border 6LR is used to remove RPL 413 artifacts and compression techniques that may not be processed 414 correctly outside of the RPL domain. 416 This document also synchronizes the liveness monitoring at the Root 417 and the 6LBR. A same value of lifetime is used for both, and a 418 single heartbeat message, the RPL DAO, traverses the RPL network. A 419 new behavior is introduced whereby the RPL Root proxies the EDAR 420 message to the 6LBR on behalf of the 6LR (more in Section 5), for any 421 6LN, RUL or RAN. 423 RPL defines a configuration option that is registered to IANA in 424 section 20.14. of [RFC6550]. This specification defines a new flag 425 "Root Proxies EDAR/EDAC" (P) that is encoded in one of the reserved 426 control bits in the option. The new flag is set to indicate that the 427 Root performs the proxy operation and that all nodes in the network 428 must refrain from renewing the 6LBR state directly. The bit position 429 of the "P" flag is indicated in Section 12.1. 431 Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP) 432 in the DIO Base Object. The new "P" flag is defined only for MOP 433 value between 0 to 6. For a MOP value of 7 or above, the flag MAY 434 indicate something different and MUST NOT be interpreted as "Root 435 Proxies EDAR/EDAC" unless the specification of the MOP indicates to 436 do so. 438 The RPL Status defined in section 6.5.1. of [RFC6550] for use in the 439 DAO-Ack message is extended to be used in the DCO messages 440 [EFFICIENT-NPDAO] as well. Furthermore, this specification enables 441 to use a RPL Status to transport the IPv6 ND Status defined for use 442 in the EARO, more in Section 7. 444 Section 6.7. of [RFC6550] introduces the RPL Control Message Options 445 such as the RPL Target Option that can be included in a RPL Control 446 Message such as the DAO. Section 8 updates the RPL Target Option to 447 optionally transport the ROVR used in the IPv6 Registration (see 448 Section 3.2.3) so the RPL Root can generate a full EDAR Message. 450 5. Updating RFC 8505 452 This document updates [RFC8505] to introduce a keep-alive EDAR 453 message and a keep-alive NS(EARO) message. The keep-alive messages 454 are used for backward compatibility, when the DAO does not transport 455 a ROVR as specified in Section 8. The keep-alive messages have a 456 zero ROVR field and can only be used to refresh a pre-existing state 457 associated to the Registered Address. More specifically, a keep- 458 alive message can only increase the lifetime and/or increment the TID 459 of the existing state in a 6LBR. 461 Upon the renewal of a 6LoWPAN ND Address Registration, this 462 specification changes the behavior of a RPL Router acting as 6LR for 463 the Address Registration as follows. If the Root indicates the 464 capability to proxy the EDAR/EDAC exchange to the 6LBR then the 6LR 465 refrains from sending an EDAR message; if the Root is separated from 466 the 6LBR, the Root regenerates the EDAR message to the 6LBR upon a 467 DAO message that signals the liveliness of the Address. 469 6. Requirements on the RPL-Unware Leaf 471 This document provides RPL routing for a RUL, that is a 6LN acting as 472 an IPv6 Host and not aware of RPL. Still, a minimal RPL-independent 473 functionality is required from the RUL in order to obtain routing 474 services from the 6LR. 476 6.1. Support of 6LoWPAN ND 478 In order to obtain routing services from a RPL 6LR, a RUL MUST 479 implement [RFC8505] and set the "R" flag in the EARO option. 481 The RUL MUST register to all the 6LRs from which it expects to get 482 routing services. The Address Registrations SHOULD be performed in a 483 rapid sequence, using the exact same EARO for a same Address. Gaps 484 between the Address Registrations will invalidate some of the routes 485 till the Address Registration finally shows on those routes as well. 487 [RFC8505] introduces error Status values in the NA(EARO) which can be 488 received synchronously upon an NS(EARO) or asynchronously. The RUL 489 MUST support both cases and refrain from using the Registered Address 490 as specified by [RFC8505] depending on the Status value. 492 A RUL SHOULD support [AP-ND] to protect the ownership of its 493 addresses. 495 6.2. External Routes and RPL Artifacts 497 Section 4.1. of [USEofRPLinfo] provides a set of rules that MUST be 498 followed when forwarding packets over an external route: 500 RPL data packets are often encapsulated using IP-in-IP and in Non- 501 Storing Mode, packets going down will carry an SRH as well. RPL data 502 packets also typically carry a Hop-by-Hop Header to transport a RPL 503 Packet Information (RPI) [RFC6550]. These additional headers are 504 called RPL artifacts. 506 When IP-in-IP is used and the outer headers terminate at a 6LR down 507 the path (see Figure 9 for the compressed format in Storing Mode), 508 then the 6LR decapsulates the IP-in-IP and the packet that is 509 forwarded to the external destination is free of RPL artifacts - but 510 possibly an RPI if packet was generated by a RAN in the same RPL 511 domain as the destination RUL. 513 Non-Storing Mode DAO messages are used to signal external routes to 514 the Root, even if the DODAG is operated in Storing Mode. This 515 enables to advertise the 6LR that injects the route for use as tunnel 516 endpoint in the data path. 518 For all external routes, the Root should use an IP-in-IP tunnel to 519 that 6LR, with the RPL artifacts in the outer header to be stripped 520 by the 6LR. The IP-in-IP encapsulation may be avoided in Storing 521 Mode if the path to the external destination beyond the 6LR is known 522 to handle or ignore the RPL artifacts properly [RFC8200]. 524 A RUL is an example of a destination that is reachable via an 525 external (Host) route for which IP-in-IP tunneling may be avoided as 526 it ignores the RPI and the consumed SRH artifacts. The use of non- 527 Storing Mode signaling in Storing Mode and the associated IP-in-IP 528 encapsulation are transparent to intermediate Routers that only see 529 packets back and forth between the Root and the 6LR and do not need a 530 special support for external routes. 532 The RUL may not support IP-in-IP tunneling [RFC8504], so if IP-in-IP 533 is used, and unless the Root as a better knowledge, the tunnel should 534 terminate at the 6LR that injected the external route to the RUL. 536 Additionally, the RUL is not expected to support the compression 537 method defined in [RFC8138]. The 6LR that injected the route MUST 538 uncompress the packet before forwarding over an external route, even 539 when delivering to a RUL, even when it is not the destination in the 540 outer header of the incoming packet, unless configured to do 541 otherwise. 543 6.2.1. Support of the HbH Header 545 A RUL is expected to process an unknown Option Type in a Hop-by-Hop 546 Header as prescribed by section 4.2 of [RFC8200]. This means in 547 particular that an RPI with an Option Type of 0x23 [USEofRPLinfo] is 548 ignored when not understood. 550 6.2.2. Support of the Routing Header 552 A RUL is expected to process an unknown Routing Header Type as 553 prescribed by section 4.4 of [RFC8200]. This means in particular 554 that Routing Header with a Routing Type of 3 [RFC6553] is ignored 555 when the Segments Left is zero, and dropped otherwise. 557 6.2.3. Support of IPv6 Encapsulation 559 Section 2.1 of [USEofRPLinfo] sets the rules for forwarding IP-in-IP 560 either to the final 6LN or to a parent 6LR. In order to enable IP- 561 in-IP to the 6LN in Non-Storing Mode, the 6LN must be able to 562 decapsulate the tunneled packet and either drop the inner packet if 563 it is not the final destination, or pass it to the upper layer for 564 further processing. Unless it is aware that the RUL can handle IP- 565 in-IP properly, the Root that encapsulates a packet to a RUL 566 terminates the IP-in-IP tunnel at the parent 6LR . For that reason, 567 it is beneficial but not necessary for a RUL to support IP-in-IP. 569 7. Updated RPL Status 571 The RPL Status is defined in section 6.5.1. of [RFC6550] for use in 572 the DAO-Ack message and values are assigned as follows: 574 +---------+--------------------------------+ 575 | Range | Meaning | 576 +=========+================================+ 577 | 0 | Success/Unqualified acceptance | 578 +---------+--------------------------------+ 579 | 1-127 | Not an outright rejection | 580 +---------+--------------------------------+ 581 | 128-255 | Rejection | 582 +---------+--------------------------------+ 584 Table 1: RPL Status per RFC 6550 586 This specification extends the scope of the RPL Status to be used in 587 RPL DCO messages. Furthermore, this specification enables to carry 588 the IPv6 ND Status values defined for use in the EARO and initially 589 listed in table 1 of [RFC8505] in a RPL Status. Only EARO Status 590 values in the range 0-63 can be transported. 592 The resulting RPL Status is as follows: 594 0 595 0 1 2 3 4 5 6 7 596 +-+-+-+-+-+-+-+-+ 597 |E|A| Value | 598 +-+-+-+-+-+-+-+-+ 600 Figure 2: RPL Status Format 602 RPL Status subfields: 604 E: 1-bit flag. Set to indicate a rejection. When not set, a value 605 of 0 indicates Success/Unqualified acceptance and other values 606 indicate "not an outright rejection" as per RFC 6550. 608 A: 1-bit flag. Indicates the type of the Status value. 610 Status Value: 6-bit unsigned integer. If the 'A' flag is set this 611 field transports a Status value defined for IPv6 ND EARO. When 612 the 'A' flag is not set, the Status value is defined in a RPL 613 extension. 615 When building a DCO or a DAO-ACK message upon an IPv6 ND NA or a DAC 616 message, the RPL Root MUST copy the ARO Status unchanged in a RPL 617 Status with the 'A' bit set. Conversely the 6LR MUST copy the value 618 of the RPL Status unchanged in the EARO of an NA message that is 619 built upon a RPL Status with the 'A' bit set in a DCO or a DAO-ACK 620 message. 622 8. Updated RPL Target option 624 This specification updates the RPL Target option to transport the 625 ROVR as illustrated in Figure 3. This enables the RPL Root to 626 generate a full EDAR Message as opposed to a keep-alive EDAR that has 627 restricted properties. 629 The Target Prefix MUST be aligned to the next 4-byte boundary after 630 the size indicated by the Prefix Length. if necessary it is padded 631 with zeros. The size of the ROVR is indicated in a new ROVR Type 632 field that is encoded to map the CodePfx in the EDAR message (see 633 section 4.2 of [RFC8505]). 635 With this specification the ROVR is the remainder of the RPL Target 636 Option. The format is backward compatible with the Target Option in 637 [RFC6550] and SHOULD be used as a replacement. 639 0 1 2 3 640 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 1 641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 | Type = 0x05 | Option Length |ROVRsz | Flags | Prefix Length | 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | | 645 + + 646 | Target Prefix (Variable Length) | 647 . Aligned to 4-byte boundary . 648 . . 649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 650 | | 651 ... Registration Ownership Verifier (ROVR) ... 652 | | 653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 Figure 3: Updated Target Option 657 New fields: 659 ROVRsz: Indicates the Size of the ROVR. It MAY be 1, 2, 3, or 4, 660 denoting a ROVR size of 64, 128, 192, or 256 bits, respectively. 662 Registration Ownership Verifier (ROVR): This is the same field as in 663 the EARO, see [RFC8505] 665 9. Protocol Operations for Unicast Addresses 667 The description below assumes that the Root sets the "P" flag in the 668 DODAG Configuration Option and performs the EDAR proxy operation. 670 9.1. General Flow 672 This specification enables to save the exchange of Extended Duplicate 673 Address messages, EDAR and EDAC, from a 6LN all the way to the 6LBR 674 across a RPL mesh, for the sole purpose of refreshing an existing 675 state in the 6LBR. Instead, the EDAR/EDAC exchange is proxied by the 676 RPL Root upon a DAO message that refreshes the RPL routing state. 678 To achieve this, the lifetimes and sequence counters in 6LoWPAN ND 679 and RPL are aligned. In other words, the Path Sequence and the Path 680 Lifetime in the DAO message are taken from the Transaction ID and the 681 Address Registration lifetime in the NS(EARO) message from the 6LN. 683 In that flow, the RPL Root acts as a proxy to refresh the state in 684 the 6LBR. The proxy operation applies to both RUL and RAN. This 685 means that in a RPL network where the function is enabled, refreshing 686 the state in the 6LBR is the responsibility of the Root. 687 Consequently, only addresses that are injected in RPL will be kept 688 alive by the RPL Root. 690 In a same fashion, if an additional routing protocol is deployed on a 691 same network, that additional routing protocol may need to handle the 692 keep alive procedure for the addresses that it serves. 694 On the first Address Registration, illustrated in Figure 4 and 695 Figure 6 for RPL Non-Storing and Storing Mode respectively, the 696 Extended Duplicate Address exchange takes place as prescribed by 697 [RFC8505]. Any of the functions 6LR, Root and 6LBR might be 698 collapsed in a single node. 700 When successful, the flow creates a Neighbor Cache Entry (NCE) in the 701 6LR, and the 6LR injects the Registered Address in RPL using DAO/DAO- 702 ACK exchanges all the way to the RPL DODAG Root. The protocol does 703 not carry a specific information that the Extended Duplicate Address 704 messages were already exchanged, so the Root proxies them anyway. 706 9.1.1. In RPL Non-Storing-Mode 708 In Non-Storing Mode, the DAO message flow can be nested within the 709 Address Registration flow as illustrated in Figure 4 and it is 710 possible to carry information such as an updated lifetime from the 711 6LBR all the way back to the 6LN. 713 6LN 6LR Root 6LBR 714 | | | | 715 | NS(EARO) | | | 716 |--------------->| | 717 | | Extended DAR | 718 | |--------------------------------->| 719 | | | 720 | | Extended DAC | 721 | |<---------------------------------| 722 | | DAO | | 723 | |------------->| | 724 | | | (keep-alive) EDAR | 725 | | |------------------>| 726 | | | EDAC | 727 | | |<------------------| 728 | | DAO-ACK | | 729 | |<-------------| | 730 | NA(EARO) | | | 731 |<---------------| | | 732 | | | | 733 (in case if an Error not reported in DAO-ACK) 734 | | | | 735 | | DCO | | 736 | |<-------------| | 737 | NA(EARO) | | | 738 |<---------------| | | 739 | | | | 741 Figure 4: First Registration Flow in Non-Storing Mode 743 An Address re-Registration is performed by the 6LN to maintain the 744 NCE in the 6LR alive before lifetime expires. Upon an Address re- 745 Registration, as illustrated in Figure 5, the 6LR redistributes the 746 Registered Address NS(EARO) in RPL. 748 6LN 6LR Root 6LBR 749 | | | | 750 | NS(EARO) | | | 751 |--------------->| | 752 | | DAO | | 753 | |------------->| | 754 | | | (keep-alive) EDAR | 755 | | |------------------>| 756 | | | EDAC | 757 | | |<------------------| 758 | | DAO-ACK | | 759 | |<-------------| | 760 | NA(EARO) | | | 761 |<---------------| | | 763 Figure 5: Next Registration Flow in Non-Storing Mode 765 This causes the RPL DODAG Root to refresh the state in the 6LBR with 766 an EDAC message or a keep-alive EDAC if the ROVR is not indicated in 767 the Target Option. In any case, the EDAC message sent in response by 768 the 6LBR contains the actual value of the ROVR field for that Address 769 Registration. In case of an error on the proxied EDAR flow, the 770 error SHOULD be returned in the DAO-ACK - if one was requested - 771 using a RPL Status with the 'A' flag set that imbeds a 6LoWPAN Status 772 value as discussed in Section 7. 774 If the Root could not return the negative Status in the DAO-ACK then 775 it sends an asynchronous Destination Cleanup Object (DCO) message 776 [EFFICIENT-NPDAO] to the 6LR placing the negative Status in the RPL 777 Status with the 'A' flag set. Note that if both are used in a short 778 interval of time, the DAO-ACK and DCO messages are not guaranteed to 779 arrive in the same order at the 6LR. 781 The 6LR may still receive a requested DAO-ACK even after it received 782 a DCO, but the negative Status in the DCO supercedes a positive 783 Status in the DAO-ACK regardless of the order in which they are 784 received. Upon the DAO-ACK - or the DCO if it arrives first - the 785 6LR responds to the RUL with a NA(EARO). If the RPL Status has the 786 'A' flag set, then the ND Status is extracted and passed in the EARO; 787 else, if the 'E' flag is set, indicating a rejection, then the status 788 4 "Removed" is used; else, the ND Status of 0 indicating "Success" is 789 used. 791 9.1.2. In RPL Storing-Mode 793 In RPL Storing Mode, the DAO-ACK is optional. When it is used, it is 794 generated by the RPL parent, which does not need to wait for the 795 grand-parent to send the acknowledgement. A successful DAO-ACK is 796 not a guarantee that the DAO has yet reached the Root or that the 797 keep-alive EDAR has succeeded. 799 6LN 6LR 6LR Root 6LBR 800 | | | | | 801 | NS(EARO) | | | | 802 |-------------->| | | | 803 | NA(EARO) | | | | 804 |<--------------| | | | 805 | | | | | 806 | | DAO | | | 807 | |-------------->| | | 808 | | DAO-ACK | | | 809 | |<--------------| | | 810 | | | | | 811 | | | DAO | | 812 | | |-------------->| | 813 | | | DAO-ACK | | 814 | | |<--------------| | 815 | | | | | 816 | | | | keep-alive EDAR | 817 | | | |---------------->| 818 | | | | EDAC(ROVR) | 819 | | | |<----------------| 820 | | | | | 821 (in case if an Error) 822 | | | | | 823 | | DCO | | 824 | |<------------------------------| | 825 | NA(EARO) | | | | 826 |<--------------| | | | 827 | | | | | 829 Figure 6: Next Registration Flow in Storing Mode 831 If the keep alive fails, the path is cleaned up asynchronously using 832 a DCO message [EFFICIENT-NPDAO] as illustrated in Figure 6 and 833 described in further details in Section 9.2.3. 835 9.2. Detailed Operation 836 9.2.1. By the 6LN 838 This specification does not alter the operation of a 6LoWPAN ND- 839 compliant 6LN, and a RUL is expected to operate as follows: 841 * The 6LN obtains an IPv6 global address, for instance using 842 autoconfiguration [RFC4862] based on a Prefix Information Option 843 (PIO) [RFC4861] found in a Router Advertisement message or by some 844 other means such as DHCPv6 [RFC3315]. 846 * Once it has formed an address, the 6LN (re)registers its address 847 periodically, within the Lifetime of the previous Address 848 Registration, as prescribed by [RFC6775] and [RFC8505]. 850 * A 6LN acting as a RUL sets the "R" flag in the EARO whereas a 6LN 851 acting as a RAN does not set the "R" flag as prescribed by 852 [RFC8505] section 5.1. 854 * Upon each consecutive Address Registration, the 6LN increases the 855 TID field in the EARO, as prescribed by [RFC8505] section 5.2. 857 * The 6LN can register to more than one 6LR at the same time. In 858 that case, it MUST use the same value of TID for all of the 859 parallel Address Registrations. 861 * The 6LN may use any of the 6LRs to which it register to forward 862 its packets. Using a 6LR to which the 6LN is not registered may 863 result in packets dropped at the 6LR by a Source Address 864 Validation function (SAVI). 866 Even without support for RPL, a RUL may be aware of opaque values to 867 be provided to the routing protocol. If the RUL has a knowledge of 868 the RPL Instance the packet should be injected into, then it SHOULD 869 set the Opaque field in the EARO to the RPLInstanceID, else it MUST 870 leave the Opaque field to zero. 872 Regardless of the setting of the Opaque field, the 6LN MUST set the 873 "I" field to zero to signal "topological information to be passed to 874 a routing process" as specified in section 5.1 of [RFC8505]. 876 A RUL is not expected to produce RPL artifacts in the data packets, 877 but it MAY do so. for instance, if the RUL has a minimal awareness of 878 the RPL Instance and can build an RPI. A RUL that places an RPI in a 879 data packet MUST indicate the RPLInstanceID that corresponds to the 880 RPL Instance the packet should be injected into. All the flags and 881 the Rank field are set to zero as specified by section 11.2 of 882 [RFC6550]. 884 9.2.2. By the 6LR 886 Also as prescribed by [RFC8505], the 6LR generates a DAR message upon 887 reception of a valid NS(EARO) message for the Address Registration of 888 a new IPv6 Address by a 6LN. If the Duplicate Address exchange 889 succeeds, then the 6LR installs an NCE. If the "R" flag was set in 890 the EARO of the NS message, and this 6LR can manage the reachability 891 of Registered Address, then the 6LR sets the "R" flag in the EARO of 892 the NA message that is sent in response. 894 From then on, the 6LN periodically sends a new NS(EARO) to refresh 895 the NCE state before the lifetime indicated in the EARO expires, with 896 TID that is incremented each time till it wraps in a lollipop fashion 897 (see section 5.2.1 of [RFC8505] which is fully compatible with 898 section 7.2 of [RFC6550]). As long as the R flag is set and this 899 Router can still manage the reachability of Registered Address, the 900 6LR keeps setting the "R" flag in the EARO of the response NA 901 message, but the exchange of Extended Duplicate Address messages is 902 skipped. 904 The Opaque field in the EARO hints the 6LR on the RPL Instance that 905 should be used for the DAO advertisements, and for the forwarding of 906 packets sourced at the registered address when there is no RPI in the 907 packet, in which case the 6LR MUST enacapsulate the packet to the 908 Root adding an RPI in the outer header. if the "I" field is not 909 zero, then the 6LR MUST consider that the Opaque field is zero. If 910 the Opaque field is not set to zero, then it should carry a 911 RPLInstanceID for the Instance suggested by the 6LN. If the 6LR does 912 not participate to the associated Instance, then the 6LR MUST 913 consider that the Opaque field is zero. If the Opaque field is zero, 914 the 6LR is free to use the default RPL Instance (zero) for the 915 registered address or to select an Instance of its choice; else, that 916 is if the 6LR participates to the suggested Instance, then the 6LR 917 SHOULD use that Instance for the registered address. 919 The DAO message advertising the Registered Address MUST be 920 constructed as follows: 922 * The Registered Address is placed in a RPL Target Option in the DAO 923 message as the Target Prefix, and the Prefix Length is set to 128; 925 * RPL Non-Storing Mode is used, and the 6LR indicates one of its 926 global IPv6 unicast addresses as the Parent Address in the RPL 927 Transit Information Option (TIO) associated to the Target Option. 929 * the External 'E' flag in the TIO is set to indicate that the 6LR 930 redistributes an external target into the RPL network. 932 * the Path Lifetime in the TIO is computed from the Lifetime in the 933 EARO Option to adapt it to the Lifetime Units used in the RPL 934 operation. Note that if the lifetime is 0, then the 6LR generates 935 a No-Path DAO message that cleans up the routes down to the 936 Address of the 6LN; 938 * the Path Sequence in the TIO is set to the TID value found in the 939 EARO option; 941 Upon a successful NS/NA(EARO) exchange: if the "R" flag was set in 942 the EARO of the NS message, then the 6LR SHOULD inject the Registered 943 Address in RPL by sending a DAO message on behalf of the 6LN; else 944 the 6LR MUST NOT inject the Registered Address into RPL. 946 If a DAO-ACK is not requested, or has a Status that is not a 947 rejection, indicating the DAO was accepted respectively by a parent 948 in Storing Mode or by the Root in non-Storing Mode, the 6LR replies 949 with a NA(EARO) to the RUL with a Status of 0 (Success). 951 In case of a DAO-ACK or a DCO indicating a rejection and transporting 952 an EARO Status Value of 5 (Validation Requested) the 6LR challenges 953 the 6LN for ownership of the address, as described in section 6.1 of 954 [RFC8505]. If the challenge succeeds then the operations continue as 955 normal. In particular a DAO message is generated upon the NS(EARO) 956 that proves the ownership of the address. If the challenge failed 957 the 6LR MUST refrain from injecting the address in RPL and may take 958 actions to protect itself against DoS attacks by a rogue 6LN, see 959 Section 11 961 The other rejection codes indicate that the 6LR failed to inject the 962 address into the RPL network. If an EARO Status is transported, the 963 6LR MUST send a NA(EARO) to the RUL with that Status value. If for 964 any other reason the 6LR fails to inject the address into the RPL 965 network, the 6LR SHOULD send a NA(EARO) to the RUL with a Status of 2 966 (Out of Storage) which indicates a possibility to retry later. 967 Similarly, upon a DCO message indicating that the address of a RUL 968 should be removed from the routing table, the 6LR issues an 969 asynchronous NA(EARO) to the RUL with the embedded ND Status value. 971 If a 6LR receives a valid NS(EARO) message with the "R" flag reset 972 and the 6LR was redistributing the Registered Address due to previous 973 NS(EARO) messages with the flag set, then it MUST stop injecting the 974 address. It is up to the Registering Node to maintain the 975 corresponding route from then on, either keeping it active by sending 976 further DAO messages, or destroying it using a No-Path DAO. 978 9.2.3. By the RPL Root 980 In RPL Storing Mode of Operation (MOP), the DAO message is propagated 981 from child to parent all the way to the Root along the DODAG, 982 populating routing state as it goes. In Non-Storing Mode, The DAO 983 message is sent directly to the RPL Root. Upon reception of a DAO 984 message, for each RPL Target option that creates or updates an 985 existing RPL state: 987 * the Root notifies the 6LBR using an internal API if they are co- 988 located, or performs an EDAR/EDAC exchange on behalf of the 6LR if 989 they are separated. If the Target option transports a ROVR, then 990 the Root MUST use it to build a full EDAR message as the 6LR 991 would. Else, a keep-alive EDAR is used with the ROVR field set to 992 zero. 994 An EDAR message MUST be constructed as follows: 996 * The Target IPv6 address from in the RPL Target Option is placed in 997 the Registered Address field of the EDAR message and in the Target 998 field of the NS message, respectively; 1000 * the Registration Lifetime is adapted from the Path Lifetime in the 1001 TIO by converting the Lifetime Units used in RPL into units of 60 1002 seconds used in the 6LoWPAN ND messages; 1004 * the RPL Root indicates its own MAC Address as Source Link Layer 1005 Address (SLLA) in the NS(EARO); 1007 * the TID value is set to the Path Sequence in the TIO and indicated 1008 with an ICMP code of 1 in the EDAR message; 1010 * when present in the RPL Target option, the ROVR field is used as 1011 is in the EDAR and the ICMP Code Suffix is set to the appropriate 1012 value as shown in Table 4 of [RFC8505] depending on the length of 1013 the ROVR field. If it is not present the ROVR field in the EDAR 1014 is set to zero indicating that this is a keep-alive EDAR. 1016 Upon a Status value in an EDAC message that is not "Success", the 1017 Root SHOULD destroy the formed paths using either a DAO-ACK (in Non- 1018 Storing Mode) or a DCO downwards as specified in [EFFICIENT-NPDAO]. 1019 Failure to destroy the former path would result in Stale routing 1020 state and local black holes if the address belongs to another party 1021 elsewhere in the network. The RPL Status value that maps the 6LowpAN 1022 ND Status value MUST be placed in the DCO. 1024 9.2.4. By the 6LBR 1026 Upon reception of an EDAR message with the ROVR field is set to zero 1027 indicating a keep-alive EDAR, the 6LBR checks whether an entry exists 1028 for the and computes whether the TID in the DAR message is fresher 1029 than that in the entry as prescribed in section 4.2.1. of [RFC8505]. 1031 If the entry does not exist, the 6LBR does not create the entry, and 1032 answers with a Status "Removed" in the EDAC message. 1034 If the entry exists but is not fresher, the 6LBR does not update the 1035 entry, and answers with a Status "Success" in the EDAC message. 1037 If the entry exists and the TID in the DAR message is fresher, the 1038 6LBR updates the TID in the entry, and if the lifetime of the entry 1039 is extended by the Registration Lifetime in the DAR message, it also 1040 updates the lifetime of the entry. In that case, the 6LBR replies 1041 with a Status "Success" in the DAC message. 1043 The EDAC that is constructed is the same as if the keep-alive EDAR 1044 was a full EDAR, and includes the ROVR that is associated to the 1045 Address Registration. 1047 10. Protocol Operations for Multicast Addresses 1049 Section 12 of [RFC6550] details the RPL support for multicast flows. 1050 This support is not source-specific and only operates as an extension 1051 to the Storing Mode of Operation for unicast packets. Note that it 1052 is the RPL model that the multicast packet is passed as a Layer-2 1053 unicast to each if the interested children. This remains true when 1054 forwarding between the 6LR and the listener 6LN. 1056 "Multicast Listener Discovery (MLD) for IPv6" [RFC2710] and its 1057 updated version "Multicast Listener Discovery Version 2 (MLDv2) for 1058 IPv6" [RFC3810] provide an interface for a listener to register to 1059 multicast flows. MLDv2 is backwards compatible with MLD, and adds in 1060 particular the capability to filter the sources via black lists and 1061 white lists. In the MLD model, the Router is a "querier" and the 1062 Host is a multicast listener that registers to the querier to obtain 1063 copies of the particular flows it is interested in. 1065 On the first Address Registration, as illustrated in Figure 7, the 1066 6LN, as an MLD listener, sends an unsolicited Report to the 6LR in 1067 order to start receiving the flow immediately. Since multicast 1068 Layer-2 messages are avoided, it is important that the asynchronous 1069 messages for unsolicited Report and Done are sent reliably, for 1070 instance using an Layer-2 acknoledgement, or attempted multiple 1071 times. 1073 The 6LR acts as a generic MLD querier and generates a DAO for the 1074 multicast target. The lifetime of the DAO is set to be in the order 1075 of the Query Interval, yet larger to account for variable propagation 1076 delays. 1078 The Root proxies the MLD echange as listener with the 6LBR acting as 1079 the querier, so as to get packets from a source external to the RPL 1080 domain. Upon a DAO with a multicast target, the RPL Root checks if 1081 it is already registered as a listener for that address, and if not, 1082 it performs its own unsolicited Report for the multicast target. 1084 6LN 6LR Root 6LBR 1085 | | | | 1086 | unsolicited Report | | | 1087 |------------------->| | | 1088 | | | | 1089 | | DAO | | 1090 | |-------------->| | 1091 | | DAO-ACK | | 1092 | |<--------------| | 1093 | | | | 1094 | | | unsolicited Report | 1095 | | |------------------->| 1096 | | | | 1097 | | | | 1099 Figure 7: First Multicast Registration Flow 1101 An Address re-Registration is pulled by 6LR acting as querier. Note 1102 that the message may be sent unicast to all the known individual 1103 listeners. Upon a time out of the Query Interval, the 6LR sends a 1104 Query to each of its listeners, and gets a Report back that is mapped 1105 into a DAO, as illustrated in Figure 8: 1107 6LN 6LR Root 6LBR 1108 | | | | 1109 | Query | | | 1110 |<-------------------| | | 1111 | Report | | | 1112 |------------------->| | | 1113 | | DAO | | 1114 | |-------------->| | 1115 | | DAO-ACK | | 1116 | |<--------------| | 1117 | | | | 1118 | | | Query | 1119 | | |<-------------------| 1120 | | | Report | 1121 | | |------------------->| 1122 | | | | 1123 | | | | 1125 Figure 8: Next Registration Flow 1127 Note that any of the functions 6LR, Root and 6LBR might be collapsed 1128 in a single node, in which case the flow above happens internally, 1129 and possibly through internal API calls as opposed to messaging. 1131 11. Security Considerations 1133 The LLN nodes depend on the 6LBR and the RPL participants for their 1134 operation. A trust model must be put in place to ensure that the 1135 right devices are acting in these roles, so as to avoid threats such 1136 as black-holing, (see [RFC7416] section 7) or bombing attack whereby 1137 an impersonated 6LBR would destroy state in the network by using the 1138 "Removed" Status code. This trust model could be at a minimum based 1139 on a Layer-2 access control, or could provide role validation as 1140 well. This is a generic 6LoWPAN requirement, see Req5.1 in 1141 Appendix of [RFC8505]. 1143 The keep-alive EDAR message does not carry a valid Registration 1144 Unique ID [RFC8505] and it cannot be used to create a binding state 1145 in the 6LBR. The 6LBR MUST NOT create an entry based on a keep-alive 1146 EDAR that does not match an existing entry. All it can do is refresh 1147 the lifetime and the TID of an existing entry. 1149 At the time of this writing RPL does not have a zerotrust model 1150 whereby the it is possible to validate the origin of an address that 1151 is injected in a DAO. This specification makes a first step in that 1152 direction by allowing the Root to challenge the RUL by the 6LR that 1153 serves it. 1155 12. IANA Considerations 1157 12.1. New DODAG Configuration Option Flag 1159 This specification updates the Registry for the "DODAG Configuration 1160 Option Flags" that was created for [RFC6550] as follows: 1162 +------------+----------------------------+-----------+ 1163 | Bit Number | Capability Description | Reference | 1164 +============+============================+===========+ 1165 | 1 | Root Proxies EDAR/EDAC (P) | THIS RFC | 1166 +------------+----------------------------+-----------+ 1168 Table 2: New DODAG Configuration Option Flag 1170 12.2. RPL Target Option Flags 1172 Section 20.15 of [RFC6550] creates a registry for the 8-bit RPL 1173 Target Option Flags field. This specification reduces the field to 4 1174 bits. The IANA is requested to reduce the size of the registry 1175 accordingly. 1177 12.3. New Subregistry for the RPL Non-Rejection Status values 1179 This specification creates a new Subregistry for the RPL Non- 1180 Rejection Status values for use in RPL DAO-ACK and RCO Messages, 1181 under the ICMPv6 parameters registry. 1183 * Possible values are 6-bit unsigned integers (0..63). 1185 * Registration procedure is "Standards Action" [RFC8126]. 1187 * Initial allocation is as indicated in Table 3: 1189 +-------+------------------------+-----------+ 1190 | Value | Meaning | Reference | 1191 +=======+========================+===========+ 1192 | 0 | Unqualified acceptance | RFC 6550 | 1193 +-------+------------------------+-----------+ 1195 Table 3: Acceptance values of the RPL Status 1197 12.4. New Subregistry for the RPL Rejection Status values 1199 This specification creates a new Subregistry for the RPL Rejection 1200 Status values for use in RPL DAO-ACK and RCO Messages, under the 1201 ICMPv6 parameters registry. 1203 * Possible values are 6-bit unsigned integers (0..63). 1205 * Registration procedure is "Standards Action" [RFC8126]. 1207 * Initial allocation is as indicated in Table 4: 1209 +-------+-----------------------+---------------+ 1210 | Value | Meaning | Reference | 1211 +=======+=======================+===============+ 1212 | 0 | Unqualified rejection | This document | 1213 +-------+-----------------------+---------------+ 1215 Table 4: Rejection values of the RPL Status 1217 13. Acknowledgments 1219 The authors wish to thank Georgios Papadopoulos for their early 1220 reviews of and contributions to this document 1222 14. Normative References 1224 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1225 Requirement Levels", BCP 14, RFC 2119, 1226 DOI 10.17487/RFC2119, March 1997, 1227 . 1229 [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast 1230 Listener Discovery (MLD) for IPv6", RFC 2710, 1231 DOI 10.17487/RFC2710, October 1999, 1232 . 1234 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1235 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1236 DOI 10.17487/RFC3810, June 2004, 1237 . 1239 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1240 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1241 Overview, Assumptions, Problem Statement, and Goals", 1242 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1243 . 1245 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1246 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1247 DOI 10.17487/RFC4861, September 2007, 1248 . 1250 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1251 Address Autoconfiguration", RFC 4862, 1252 DOI 10.17487/RFC4862, September 2007, 1253 . 1255 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1256 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1257 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1258 Low-Power and Lossy Networks", RFC 6550, 1259 DOI 10.17487/RFC6550, March 2012, 1260 . 1262 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 1263 Power and Lossy Networks (RPL) Option for Carrying RPL 1264 Information in Data-Plane Datagrams", RFC 6553, 1265 DOI 10.17487/RFC6553, March 2012, 1266 . 1268 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1269 Bormann, "Neighbor Discovery Optimization for IPv6 over 1270 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1271 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1272 . 1274 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1275 Writing an IANA Considerations Section in RFCs", BCP 26, 1276 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1277 . 1279 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 1280 "IPv6 over Low-Power Wireless Personal Area Network 1281 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 1282 April 2017, . 1284 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1285 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1286 May 2017, . 1288 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1289 (IPv6) Specification", STD 86, RFC 8200, 1290 DOI 10.17487/RFC8200, July 2017, 1291 . 1293 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1294 Perkins, "Registration Extensions for IPv6 over Low-Power 1295 Wireless Personal Area Network (6LoWPAN) Neighbor 1296 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1297 . 1299 [AP-ND] Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 1300 "Address Protected Neighbor Discovery for Low-power and 1301 Lossy Networks", Work in Progress, Internet-Draft, draft- 1302 ietf-6lo-ap-nd-12, 10 April 2019, 1303 . 1305 [USEofRPLinfo] 1306 Robles, I., Richardson, M., and P. Thubert, "Using RPL 1307 Option Type, Routing Header for Source Routes and IPv6-in- 1308 IPv6 encapsulation in the RPL Data Plane", Work in 1309 Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-32, 1310 4 November 2019, . 1313 [EFFICIENT-NPDAO] 1314 Jadhav, R., Thubert, P., Sahoo, R., and Z. Cao, "Efficient 1315 Route Invalidation", Work in Progress, Internet-Draft, 1316 draft-ietf-roll-efficient-npdao-17, 30 October 2019, 1317 . 1320 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 1321 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 1322 2014, . 1324 15. Informative References 1326 [RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem 1327 Statement and Requirements for IPv6 over Low-Power 1328 Wireless Personal Area Network (6LoWPAN) Routing", 1329 RFC 6606, DOI 10.17487/RFC6606, May 2012, 1330 . 1332 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1333 C., and M. Carney, "Dynamic Host Configuration Protocol 1334 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1335 2003, . 1337 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1338 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1339 DOI 10.17487/RFC6282, September 2011, 1340 . 1342 [RFC6687] Tripathi, J., Ed., de Oliveira, J., Ed., and JP. Vasseur, 1343 Ed., "Performance Evaluation of the Routing Protocol for 1344 Low-Power and Lossy Networks (RPL)", RFC 6687, 1345 DOI 10.17487/RFC6687, October 2012, 1346 . 1348 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 1349 Constrained-Node Networks", RFC 7228, 1350 DOI 10.17487/RFC7228, May 2014, 1351 . 1353 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 1354 and M. Richardson, Ed., "A Security Threat Analysis for 1355 the Routing Protocol for Low-Power and Lossy Networks 1356 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 1357 . 1359 [RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power 1360 Wireless Personal Area Network (6LoWPAN) Paging Dispatch", 1361 RFC 8025, DOI 10.17487/RFC8025, November 2016, 1362 . 1364 [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node 1365 Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, 1366 January 2019, . 1368 Appendix A. Example Compression 1370 Figure 9 illustrates the case in Storing Mode where the packet is 1371 received from the Internet, then the Root encapsulates the packet to 1372 insert the RPI and deliver to the 6LR that is the parent and last hop 1373 to the final destination, which is not known to support [RFC8138]. 1374 The difference with the format presented in Figure 19 of [RFC8138] is 1375 the addition of a SRH-6LoRH before the RPI-6LoRH to transport the 1376 destination address of the outer IPv6 header. 1378 +-+ ... -+-+ ... +-+- ... -+-+ ... -+-+-+ ... +-+-+ ... -+ ... +-... 1379 |11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP 1380 |Page 1 |Type1 S=0| 6LoRH | 6LoRH |LOWPAN_IPHC| UDP | hdr |Payld 1381 +-+ ... -+-+ ... +-+- ... -+-+ ... -+-+-+ ... +-+-+ ... -+ ... +-... 1382 <-4bytes-> <- RFC 6282 -> 1383 No RPL artifact 1385 Figure 9: Encapsulation to Parent 6LR in Storing Mode 1387 In Figure 9, the source of the IP-in-IP encapsulation is the Root, so 1388 it is elided in the IP-in-IP 6LoRH. The destination is the parent 1389 6LR of the destination of the inner packet so it cannot be elided. 1390 In Storing Mode, it is placed as the single entry in an SRH-6LoRH as 1391 the first 6LoRH. Since there is a single entry so the SRH-6LoRH Size 1392 is 0. In this particular example, the 6LR address can be compressed 1393 to 2 bytes so a Type of 1 is used. It results that the total length 1394 of the SRH-6LoRH is 4 bytes. 1396 In Non-Storing Mode, the encapsulation from the Root would be similar 1397 to that represented in Figure 9 with possibly more hops in the SRH- 1398 6LoRH and possibly multiple SRH-6LoRHs if the various addresses in 1399 the routing header are not compressed to the same format. Note that 1400 on the last hop to the parent 6LR, the RH3 is consumed and removed 1401 from the compressed form, so the use of Non-Storing Mode vs. Storing 1402 Mode is indistinguishable from the packet format. 1404 Follows the RPI-6LoRH and then the IP-in-IP 6LoRH. When the IP-in-IP 1405 6LoRH is removed, all the Router headers that precede it are also 1406 removed. 1408 The Paging Dispatch [RFC8025] may also be removed if there was no 1409 previous Page change to a Page other than 0 or 1, since the 1410 LOWPAN_IPHC is encoded in the same fashion in the default Page 0 and 1411 in Page 1. The resulting packet to the destination is the inner 1412 packet compressed with [RFC6282]. 1414 Authors' Addresses 1416 Pascal Thubert (editor) 1417 Cisco Systems, Inc 1418 Building D, 45 Allee des Ormes - BP1200 1419 06254 Mougins - Sophia Antipolis 1420 France 1422 Phone: +33 497 23 26 34 1423 Email: pthubert@cisco.com 1425 Michael C. Richardson 1426 Sandelman Software Works 1428 Email: mcr+ietf@sandelman.ca 1429 URI: http://www.sandelman.ca/