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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL Working Group M. Robles 3 Internet-Draft UTN-FRM/Aalto 4 Updates: 6553, 6550, 8138 (if approved) M. Richardson 5 Intended status: Standards Track SSW 6 Expires: September 15, 2020 P. Thubert 7 Cisco 8 March 14, 2020 10 Using RPI Option Type, Routing Header for Source Routes and IPv6-in-IPv6 11 encapsulation in the RPL Data Plane 12 draft-ietf-roll-useofrplinfo-37 14 Abstract 16 This document looks at different data flows through LLN (Low-Power 17 and Lossy Networks) where RPL (IPv6 Routing Protocol for Low-Power 18 and Lossy Networks) is used to establish routing. The document 19 enumerates the cases where RFC6553 (RPI Option Type), RFC6554 20 (Routing Header for Source Routes) and IPv6-in-IPv6 encapsulation is 21 required in data plane. This analysis provides the basis on which to 22 design efficient compression of these headers. This document updates 23 RFC6553 adding a change to the RPI Option Type. Additionally, this 24 document updates RFC6550 defining a flag in the DIO Configuration 25 option to indicate about this change and updates [RFC8138] as well to 26 consider the new Option Type when the RPL Option is decompressed. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 15, 2020. 45 Copyright Notice 47 Copyright (c) 2020 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 64 2. Terminology and Requirements Language . . . . . . . . . . . . 5 65 3. RPL Overview . . . . . . . . . . . . . . . . . . . . . . . . 6 66 4. Updates to RFC6553, RFC6550 and RFC8138 . . . . . . . . . . . 7 67 4.1. Updates to RFC6550: Advertising External Routes with Non- 68 Storing Mode Signaling. . . . . . . . . . . . . . . . . . 7 69 4.2. Updates to RFC6553: Indicating the new RPI Option Type. . 8 70 4.3. Updates to RFC6550: Indicating the new RPI in the 71 DODAG Configuration option Flag. . . . . . . . . . . . . 11 72 4.4. Updates to RFC8138: Indicating the way to decompress with 73 the new RPI Option Type. . . . . . . . . . . . . . . . . 13 74 5. Sample/reference topology . . . . . . . . . . . . . . . . . . 14 75 6. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 16 76 7. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 19 77 7.1. Storing Mode: Interaction between Leaf and Root . . . . . 20 78 7.1.1. SM: Example of Flow from RAL to root . . . . . . . . 21 79 7.1.2. SM: Example of Flow from root to RAL . . . . . . . . 21 80 7.1.3. SM: Example of Flow from root to RUL . . . . . . . . 22 81 7.1.4. SM: Example of Flow from RUL to root . . . . . . . . 23 82 7.2. SM: Interaction between Leaf and Internet. . . . . . . . 24 83 7.2.1. SM: Example of Flow from RAL to Internet . . . . . . 24 84 7.2.2. SM: Example of Flow from Internet to RAL . . . . . . 26 85 7.2.3. SM: Example of Flow from RUL to Internet . . . . . . 26 86 7.2.4. SM: Example of Flow from Internet to RUL. . . . . . . 27 87 7.3. SM: Interaction between Leaf and Leaf . . . . . . . . . . 28 88 7.3.1. SM: Example of Flow from RAL to RAL . . . . . . . . . 28 89 7.3.2. SM: Example of Flow from RAL to RUL . . . . . . . . . 30 90 7.3.3. SM: Example of Flow from RUL to RAL . . . . . . . . . 31 91 7.3.4. SM: Example of Flow from RUL to RUL . . . . . . . . . 32 92 8. Non Storing mode . . . . . . . . . . . . . . . . . . . . . . 33 93 8.1. Non-Storing Mode: Interaction between Leaf and Root . . . 35 94 8.1.1. Non-SM: Example of Flow from RAL to root . . . . . . 36 95 8.1.2. Non-SM: Example of Flow from root to RAL . . . . . . 36 96 8.1.3. Non-SM: Example of Flow from root to RUL . . . . . . 37 97 8.1.4. Non-SM: Example of Flow from RUL to root . . . . . . 38 98 8.2. Non-Storing Mode: Interaction between Leaf and Internet . 39 99 8.2.1. Non-SM: Example of Flow from RAL to Internet . . . . 39 100 8.2.2. Non-SM: Example of Flow from Internet to RAL . . . . 40 101 8.2.3. Non-SM: Example of Flow from RUL to Internet . . . . 41 102 8.2.4. Non-SM: Example of Flow from Internet to RUL . . . . 42 103 8.3. Non-SM: Interaction between leaves . . . . . . . . . . . 43 104 8.3.1. Non-SM: Example of Flow from RAL to RAL . . . . . . . 43 105 8.3.2. Non-SM: Example of Flow from RAL to RUL . . . . . . . 46 106 8.3.3. Non-SM: Example of Flow from RUL to RAL . . . . . . . 48 107 8.3.4. Non-SM: Example of Flow from RUL to RUL . . . . . . . 49 108 9. Operational Considerations of supporting 109 RUL-leaves . . . . . . . . . . . . . . . . . . . . . . . . . 50 110 10. Operational considerations of introducing 0x23 . . . . . . . 51 111 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 52 113 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 55 114 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 56 115 14.1. Normative References . . . . . . . . . . . . . . . . . . 56 116 14.2. Informative References . . . . . . . . . . . . . . . . . 57 117 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59 119 1. Introduction 121 RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks) 122 [RFC6550] is a routing protocol for constrained networks. [RFC6553] 123 defines the RPL Option carried within the IPv6 Hop-by-Hop Header to 124 carry the RPLInstanceID and quickly identify inconsistencies (loops) 125 in the routing topology. The RPL Option is commonly referred to as 126 the RPL Packet Information (RPI) though the RPI is really the 127 abstract information that is defined in [RFC6550] and transported in 128 the RPL Option. RFC6554 [RFC6554] defines the "RPL Source Route 129 Header" (RH3), an IPv6 Extension Header to deliver datagrams within a 130 RPL routing domain, particularly in non-storing mode. 132 These various items are referred to as RPL artifacts, and they are 133 seen on all of the data-plane traffic that occurs in RPL routed 134 networks; they do not in general appear on the RPL control plane 135 traffic at all which is mostly Hop-by-Hop traffic (one exception 136 being DAO messages in non-storing mode). 138 It has become clear from attempts to do multi-vendor 139 interoperability, and from a desire to compress as many of the above 140 artifacts as possible that not all implementers agree when artifacts 141 are necessary, or when they can be safely omitted, or removed. 143 The ROLL WG analysized how [RFC2460] rules apply to storing and non- 144 storing use of RPL. The result was 24 data plane use cases. They 145 are exhaustively outlined here in order to be completely unambiguous. 146 During the processing of this document, new rules were published as 147 [RFC8200], and this document was updated to reflect the normative 148 changes in that document. 150 This document updates [RFC6553], changing the value of the Option 151 Type of the RPL Option to make [RFC8200] routers ignore this option 152 when not recognized. 154 A Routing Header Dispatch for 6LoWPAN (6LoRH)([RFC8138]) defines a 155 mechanism for compressing RPL Option information and Routing Header 156 type 3 (RH3) [RFC6554], as well as an efficient IPv6-in-IPv6 157 technique. 159 Since some of the uses cases here described, use IPv6-in-IPv6 160 encapsulation. It MUST take in consideration, when encapsulation is 161 applied, the RFC6040 [RFC6040], which defines how the explicit 162 congestion notification (ECN) field of the IP header should be 163 constructed on entry to and exit from any IPV6-in-IPV6 tunnel. 164 Additionally, it is recommended the reading of 165 [I-D.ietf-intarea-tunnels] that explains the relationship of IP 166 tunnels to existing protocol layers and the challenges in supporting 167 IP tunneling. 169 Non-constrained uses of RPL are not in scope of this document, and 170 applicability statements for those uses may provide different advice, 171 E.g. [I-D.ietf-anima-autonomic-control-plane]. 173 1.1. Overview 175 The rest of the document is organized as follows: Section 2 describes 176 the used terminology. Section 3 provides a RPL Overview. Section 4 177 describes the updates to RFC6553, RFC6550 and RFC 8138. Section 5 178 provides the reference topology used for the uses cases. Section 6 179 describes the uses cases included. Section 7 describes the storing 180 mode cases and section 8 the non-storing mode cases. Section 9 181 describes the operational considerations of supporting RPL-unaware- 182 leaves. Section 10 depicts operational considerations for the 183 proposed change on RPI Option Type, section 11 the IANA 184 considerations and then section 12 describes the security aspects. 186 2. Terminology and Requirements Language 188 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 189 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 190 "OPTIONAL" in this document are to be interpreted as described in BCP 191 14 [RFC2119] [RFC8174] when, and only when, they appear in all 192 capitals, as shown here. 194 Terminology defined in [RFC7102] applies to this document: LLN, RPL, 195 RPL domain and ROLL. 197 RPL Leaf: An IPv6 host that is attached to a RPL router and obtains 198 connectivity through a RPL Destination Oriented Directed Acyclic 199 Graph (DODAG). As an IPv6 node, a RPL Leaf is expected to ignore a 200 consumed Routing Header and as an IPv6 host, it is expected to ignore 201 a Hop-by-Hop header. It results that a RPL Leaf can correctly 202 receive a packet with RPL artifacts. On the other hand, a RPL Leaf 203 is not expected to generate RPL artifacts or to support IP-in-IP 204 encapsulation. For simplification, this document uses the standalone 205 term leaf to mean a RPL leaf. 207 RPL Packet Information (RPI): The abstract information that [RFC6550] 208 places in IP packets. The term is commonly used, including in this 209 document, to refer to the RPL Option [RFC6553] that transports that 210 abstract information in an IPv6 Hob-by-Hop Header. 212 RPL-aware-node (RAN): A device which implements RPL. Please note 213 that the device can be found inside the LLN or outside LLN. 215 RPL-Aware-Leaf(RAL): A RPL-aware-node that is also a RPL Leaf. 217 RPL-unaware-node: A device which does not implement RPL, thus the 218 device is not-RPL-aware. Please note that the device can be found 219 inside the LLN. 221 RPL-Unaware-Leaf(RUL): A RPL-unaware-node that is also a RPL Leaf. 223 6LoWPAN Node (6LN): [RFC6775] defines it as: "A 6LoWPAN node is any 224 host or router participating in a LoWPAN. This term is used when 225 referring to situations in which either a host or router can play the 226 role described.". In this document, a 6LN acts as a leaf. 228 6LoWPAN Router (6LR): [RFC6775] defines it as:" An intermediate 229 router in the LoWPAN that is able to send and receive Router 230 Advertisements (RAs) and Router Solicitations (RSs) as well as 231 forward and route IPv6 packets. 6LoWPAN routers are present only in 232 route-over topologies." 233 6LoWPAN Border Router (6LBR): [RFC6775] defines it as:"A border 234 router located at the junction of separate 6LoWPAN networks or 235 between a 6LoWPAN network and another IP network. There may be one 236 or more 6LBRs at the 6LoWPAN network boundary. A 6LBR is the 237 responsible authority for IPv6 prefix propagation for the 6LoWPAN 238 network it is serving. An isolated LoWPAN also contains a 6LBR in 239 the network, which provides the prefix(es) for the isolated network." 241 Flag Day: A transition that involves having a network with different 242 values of RPI Option Type. Thus the network does not work correctly 243 (Lack of interoperation). 245 Hop-by-Hop re-encapsulation: The term "Hop-by-Hop re-encapsulation" 246 header refers to adding a header that originates from a node to an 247 adjacent node, using the addresses (usually the Global Unicast 248 Address (GUA) or Unique Local Address (ULA) but could also use the 249 link-local addresses) of each node. If the packet must traverse 250 multiple hops, then it must be decapsulated at each hop, and then re- 251 encapsulated again in a similar fashion. 253 Non-Storing Mode (Non-SM): RPL mode of operation in which the RPL- 254 aware-nodes send information to the root about their parents. Thus, 255 the root knows the topology. Because the root knows the topology, 256 the intermediate 6LRs do not maintain routing state and source 257 routing is needed. 259 Storing Mode (SM): RPL mode of operation in which RPL-aware-nodes 260 (6LRs) maintain routing state (of the children) so that source 261 routing is not needed. 263 Note: Due to lack of space in some figures (tables) we refer to IPv6- 264 in-IPv6 as IP6-IP6. 266 3. RPL Overview 268 RPL defines the RPL Control messages (control plane), a new ICMPv6 269 [RFC4443] message with Type 155. DIS (DODAG Information 270 Solicitation), DIO (DODAG Information Object) and DAO (Destination 271 Advertisement Object) messages are all RPL Control messages but with 272 different Code values. A RPL Stack is shown in Figure 1. 274 +--------------+ 275 | Upper Layers | 276 | | 277 +--------------+ 278 | RPL | 279 | | 280 +--------------+ 281 | ICMPv6 | 282 | | 283 +--------------+ 284 | IPv6 | 285 | | 286 +--------------+ 287 | 6LoWPAN | 288 | | 289 +--------------+ 290 | PHY-MAC | 291 | | 292 +--------------+ 294 Figure 1: RPL Stack. 296 RPL supports two modes of Downward traffic: in storing mode (SM), it 297 is fully stateful; in non-storing mode (Non-SM), it is fully source 298 routed. A RPL Instance is either fully storing or fully non-storing, 299 i.e. a RPL Instance with a combination of storing and non-storing 300 nodes is not supported with the current specifications at the time of 301 writing this document. 303 4. Updates to RFC6553, RFC6550 and RFC8138 305 4.1. Updates to RFC6550: Advertising External Routes with Non-Storing 306 Mode Signaling. 308 Section 6.7.8. of [RFC6550] introduces the 'E' flag that is set to 309 indicate that the 6LR that generates the DAO redistributes external 310 targets into the RPL network. An external Target is a Target that 311 has been learned through an alternate protocol, for instance a route 312 to a prefix that is outside the RPL domain but reachable via a 6LR. 313 Being outside of the RPL domain, a node that is reached via an 314 external target cannot be guaranteed to ignore the RPL artifacts and 315 cannot be expected to process the [RFC8138] compression correctly. 316 This means that the RPL artifacts should be contained in an IP-in-IP 317 encapsulation that is removed by the 6LR, and that any remaining 318 compression should be expanded by the 6LR before it forwards a packet 319 outside the RPL domain. 321 This specification updates [RFC6550] to RECOMMEND that external 322 targets are advertised using Non-Storing Mode DAO messaging even in a 323 Storing-Mode network. This way, external routes are not advertised 324 within the DODAG and all packets to an external target reach the Root 325 like normal Non-Storing Mode traffic. The Non-Storing Mode DAO 326 informs the Root of the address of the 6LR that injects the external 327 route, and the root uses IP-in-IP encapsulation to that 6LR, which 328 terminates the IP-in-IP tunnel and forwards the original packet 329 outside the RPL domain free of RPL artifacts. In the other 330 direction, for traffic coming from an external target into the LLN, 331 the parent (6LR) that injects the traffic always encapsulates to the 332 root. This whole operation is transparent to intermediate routers 333 that only see traffic between the 6LR and the Root, and only the Root 334 and the 6LRs that inject external routes in the network need to be 335 upgraded to add this function to the network. 337 A RUL is a special case of external target when the target is 338 actually a host and it is known to support a consumed Routing Header 339 and to ignore a HbH header as prescribed by [RFC8200]. The target 340 may have been learned through as a host route or may have been 341 registered to the 6LR using [RFC8505]. IP-in-IP encapsulation MAY be 342 avoided for Root to RUL communication if the RUL is known to process 343 the packets as forwarded by the parent 6LR without decapsulation. 345 In order to enable IP-in-IP all the way to a 6LN, it is beneficial 346 that the 6LN supports decapsulating IP-in-IP, but that is not assumed 347 by [RFC8504]. If the 6LN is a RUL, the Root that encapsulates a 348 packet SHOULD terminate the tunnel at a parent 6LR unless it is aware 349 that the RUL supports IP-in-IP decapsulation. 351 A node that is reachable over an external route is not expected to 352 support [RFC8138]. Whether a decapsulation took place or not and 353 even when the 6LR is delivering the packet to a RUL, the 6LR that 354 injected an external route MUST uncompress the packet before 355 forwarding over that external route. 357 4.2. Updates to RFC6553: Indicating the new RPI Option Type. 359 This modification is required in order to be able to send, for 360 example, IPv6 packets from a RPL-Aware-Leaf to a RPL-unaware node 361 through Internet (see Section 7.2.1), without requiring IPv6-in-IPv6 362 encapsulation. 364 [RFC6553] (Section 6, Page 7) states as shown in Figure 2, that in 365 the Option Type field of the RPL Option, the two high order bits must 366 be set to '01' and the third bit is equal to '1'. The first two bits 367 indicate that the IPv6 node must discard the packet if it doesn't 368 recognize the Option Type, and the third bit indicates that the 369 Option Data may change in route. The remaining bits serve as the 370 Option Type. 372 +-------+-------------------+----------------+-----------+ 373 | Hex | Binary Value | Description | Reference | 374 + Value +-------------------+ + + 375 | | act | chg | rest | | | 376 +-------+-----+-----+-------+----------------+-----------+ 377 | 0x63 | 01 | 1 | 00011 | RPL Option | [RFC6553] | 378 +-------+-----+-----+-------+----------------+-----------+ 380 Figure 2: Option Type in RPL Option. 382 This document illustrates that it is not always possible to know for 383 sure at the source that a packet will only travel within the RPL 384 domain or may leave it. 386 At the time [RFC6553] was published, leaking a Hop-by-Hop header in 387 the outer IPv6 header chain could potentially impact core routers in 388 the internet. So at that time, it was decided to encapsulate any 389 packet with a RPL Option using IPv6-in-IPv6 in all cases where it was 390 unclear whether the packet would remain within the RPL domain. In 391 the exception case where a packet would still leak, the Option Type 392 would ensure that the first router in the Internet that does not 393 recognize the option would drop the packet and protect the rest of 394 the network. 396 Even with [RFC8138], where the IPv6-in-IPv6 header is compressed, 397 this approach yields extra bytes in a packet; this means consuming 398 more energy, more bandwidth, incurring higher chances of loss and 399 possibly causing a fragmentation at the 6LoWPAN level. This impacts 400 the daily operation of constrained devices for a case that generally 401 does not happen and would not heavily impact the core anyway. 403 While intention was and remains that the Hop-by-Hop header with a RPL 404 Option should be confined within the RPL domain, this specification 405 modifies this behavior in order to reduce the dependency on IPv6-in- 406 IPv6 and protect the constrained devices. Section 4 of [RFC8200] 407 clarifies the behaviour of routers in the Internet as follows: "it is 408 now expected that nodes along a packet's delivery path only examine 409 and process the Hop-by-Hop Options header if explicitly configured to 410 do so". 412 When unclear about the travel of a packet, it becomes preferable for 413 a source not to encapsulate, accepting the fact that the packet may 414 leave the RPL domain on its way to its destination. In that event, 415 the packet should reach its destination and should not be discarded 416 by the first node that does not recognize the RPL Option. But with 417 the current value of the Option Type, if a node in the Internet is 418 configured to process the Hop-by-Hop header, and if such node 419 encounters an option with the first two bits set to 01 and conforms 420 to [RFC8200], it will drop the packet. Host systems should do the 421 same, irrespective of the configuration. 423 Thus, this document updates the Option Type of the RPL Option 424 [RFC6553], abusively naming it RPI Option Type for simplicity, to 425 (Figure 3): the two high order bits MUST be set to '00' and the third 426 bit is equal to '1'. The first two bits indicate that the IPv6 node 427 MUST skip over this option and continue processing the header 428 ([RFC8200] Section 4.2) if it doesn't recognize the Option Type, and 429 the third bit continues to be set to indicate that the Option Data 430 may change en route. The rightmost five bits remain at 0x3(00011). 431 This ensures that a packet that leaves the RPL domain of an LLN (or 432 that leaves the LLN entirely) will not be discarded when it contains 433 the RPL Option. 435 With the new Option Type, if an IPv6 (intermediate) node (RPL-not- 436 capable) receives a packet with an RPL Option, it should ignore the 437 Hop-by-Hop RPL Option (skip over this option and continue processing 438 the header). This is relevant, as it was mentioned previously, in 439 the case that there is a flow from RAL to Internet (see 440 Section 7.2.1). 442 This is a significant update to [RFC6553]. 444 +-------+-------------------+-------------+------------+ 445 | Hex | Binary Value | Description | Reference | 446 + Value +-------------------+ + + 447 | | act | chg | rest | | | 448 +-------+-----+-----+-------+-------------+------------+ 449 | 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)| 450 +-------+-----+-----+-------+-------------+------------+ 452 Figure 3: Revised Option Type in RPL Option. (*)represents this 453 document 455 Without the signaling described below, this change would otherwise 456 create a lack of interoperation (flag day) for existing networks 457 which are currently using 0x63 as the RPI Option Type value. A move 458 to 0x23 will not be understood by those networks. It is suggested 459 that RPL implementations accept both 0x63 and 0x23 when processing 460 the header. 462 When forwarding packets, implementations SHOULD use the same value of 463 RPI Type as was received. This is required because the RPI Option 464 Type does not change en route ([RFC8200] - Section 4.2). It allows 465 the network to be incrementally upgraded and allows the DODAG root to 466 know which parts of the network have been upgraded. 468 When originating new packets, implementations SHOULD have an option 469 to determine which value to originate with, this option is controlled 470 by the DIO option described below. 472 The change of RPI Option Type from 0x63 to 0x23, makes all [RFC8200] 473 Section 4.2 compliant nodes tolerant of the RPL artifacts. There is 474 therefore no longer a necessity to remove the artifacts when sending 475 traffic to the Internet. This change clarifies when to use IPv6-in- 476 IPv6 headers, and how to address them: The Hop-by-Hop Options header 477 containing the RPI MUST always be added when 6LRs originate packets 478 (without IPv6-in-IPv6 headers), and IPv6-in-IPv6 headers MUST always 479 be added when a 6LR finds that it needs to insert a Hop-by-Hop 480 Options header containing the RPL Option. The IPv6-in-IPv6 header is 481 to be addressed to the RPL root when on the way up, and to the end- 482 host when on the way down. 484 In the non-storing case, dealing with not-RPL aware leaf nodes is 485 much easier as the 6LBR (DODAG root) has complete knowledge about the 486 connectivity of all DODAG nodes, and all traffic flows through the 487 root node. 489 The 6LBR can recognize not-RPL aware leaf nodes because it will 490 receive a DAO about that node from the 6LR immediately above that 491 not-RPL aware node. This means that the non-storing mode case can 492 avoid ever using Hop-by-Hop re-encapsulation headers for traffic 493 originating from the root to the leaves. 495 The non-storing mode case does not require the type change from 0x63 496 to 0x23, as the root can always create the right packet. The type 497 change does not adversely affect the non-storing case. 499 4.3. Updates to RFC6550: Indicating the new RPI in the DODAG 500 Configuration option Flag. 502 In order to avoid a Flag Day caused by lack of interoperation between 503 new RPI Option Type (0x23) and old RPI Option Type (0x63) nodes, this 504 section defines a flag in the DIO Configuration option, to indicate 505 when the new RPI Option Type can be safely used. This means, the 506 flag is going to indicate the value of Option Type that the network 507 will be using for the RPL Option. Thus, when a node joins to a 508 network will know which value to use. With this, RPL-capable nodes 509 know if it is safe to use 0x23 when creating a new RPL Option. A 510 node that forwards a packet with an RPI MUST NOT modify the Option 511 Type of the RPL Option. 513 This is done using a DODAG Configuration option flag which will 514 signal "RPI 0x23 enable" and propagate through the network. 515 Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP) 516 in the DIO Base Object. The flag is defined only for MOP value 517 between 0 to 6. For a MOP value of 7 or above, the flag MAY indicate 518 something different and MUST NOT be interpreted as "RPI 0x23 enable" 519 unless the specification of the MOP indicates to do so. 521 As stated in [RFC6550] the DODAG Configuration option is present in 522 DIO messages. The DODAG Configuration option distributes 523 configuration information. It is generally static, and does not 524 change within the DODAG. This information is configured at the DODAG 525 root and distributed throughout the DODAG with the DODAG 526 Configuration option. Nodes other than the DODAG root do not modify 527 this information when propagating the DODAG Configuration option. 529 Currently, the DODAG Configuration option in [RFC6550] states: "the 530 unused bits MUST be initialize to zero by the sender and MUST be 531 ignored by the receiver". If the flag is received with a value zero 532 (which is the default), then new nodes will remain in RFC6553 533 Compatible Mode; originating traffic with the old-RPI Option Type 534 (0x63) value. If the flag is received with a value of 1, then the 535 value for the RPL Option MUST be set to 0x23. 537 Bit number three of the flag field in the DODAG Configuration option 538 is to be used as shown in Figure 4 (which is the same as Figure 29 in 539 Section 11 and is shown here for convenience): 541 +------------+-----------------+---------------+ 542 | Bit number | Description | Reference | 543 +------------+-----------------+---------------+ 544 | 3 | RPI 0x23 enable | This document | 545 +------------+-----------------+---------------+ 547 Figure 4: DODAG Configuration option Flag to indicate the RPI-flag- 548 day. 550 In the case of reboot, the node (6LN or 6LR) does not remember the 551 RPI Option Type (i.e., whether or not the flag is set), so the node 552 will not trigger DIO messages until a DIO message is received 553 indicating the RPI value to be used. The node will use the value 554 0x23 if the network supports this feature 556 4.4. Updates to RFC8138: Indicating the way to decompress with the new 557 RPI Option Type. 559 This modification is required in order to be able to decompress the 560 RPL Option with the new Option Type of 0x23. 562 RPI-6LoRH header provides a compressed form for the RPL RPI; see 563 [RFC8138], Section 6. A node that is decompressing this header MUST 564 decompress using the RPI Option Type that is currently active: that 565 is, a choice between 0x23 (new) and 0x63 (old). The node will know 566 which to use based upon the presence of the flag in the DODAG 567 Configuration option defined in Section 4.3. E.g. If the network is 568 in 0x23 mode (by DIO option), then it should be decompressed to 0x23. 570 [RFC8138] section 7 documents how to compress the IPv6-in-IPv6 571 header. 573 There are potential significant advantages to having a single code 574 path that always processes IPv6-in-IPv6 headers with no conditional 575 branches. 577 In Storing Mode, the scenarios where the flow goes from RAL to RUL 578 and RUL to RUL include compression of the IPv6-in-IPv6 and RPI 579 headers. The use of the IPv6-in-IPv6 header is MANDATORY in this 580 case, and it SHOULD be compressed with [RFC8138] section 7. Figure 5 581 illustrates the case in Storing mode where the packet is received 582 from the Internet, then the root encapsulates the packet to insert 583 the RPI. In that example, the leaf is not known to support RFC 8138, 584 and the packet is encapsulated to the 6LR that is the parent and last 585 hop to the final destination. 587 +-+ ... -+-+ ... +-+- ... -+-+- +-+-+-+ ... +-+-+ ... -+++ ... +-... 588 |11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP 589 |Page 1 |Type1 S=0| 6LoRH |6LoRH |LOWPAN_IPHC| UDP | hdr |Payld 590 +-+ ... -+-+ ... +-+- ... -+-+-.+-+-+-+-+ ... +-+-+ ... -+ ... +-... 591 <-4bytes-> <- RFC 6282 -> 592 No RPL artifact 594 Figure 5: RPI Inserted by the Root in Storing Mode 596 In Figure 5, the source of the IPv6-in-IPv6 encapsulation is the 597 Root, so it is elided in the IP-in-IP 6LoRH. The destination is the 598 parent 6LR of the destination of the inner packet so it cannot be 599 elided. It is placed as the single entry in an SRH-6LoRH as the 600 first 6LoRH. There is a single entry so the SRH-6LoRH Size is 0. In 601 that example, the type is 1 so the 6LR address is compressed to 2 602 bytes. It results that the total length of the SRH-6LoRH is 4 bytes. 603 Follows the RPI-6LoRH and then the IP-in-IP 6LoRH. When the IP-in-IP 604 6LoRH is removed, all the router headers that precede it are also 605 removed. The Paging Dispatch [RFC8025] may also be removed if there 606 was no previous Page change to a Page other than 0 or 1, since the 607 LOWPAN_IPHC is encoded in the same fashion in the default Page 0 and 608 in Page 1. The resulting packet to the destination is the inner 609 packet compressed with [RFC6282]. 611 5. Sample/reference topology 613 A RPL network in general is composed of a 6LBR, a Backbone Router 614 (6BBR), a 6LR and a 6LN as a leaf logically organized in a DODAG 615 structure. 617 Figure 6 shows the reference RPL Topology for this document. The 618 letters above the nodes are there so that they may be referenced in 619 subsequent sections. In the figure, 6LR represents a full router 620 node. The 6LN is a RPL aware router, or host (as a leaf). 621 Additionally, for simplification purposes, it is supposed that the 622 6LBR has direct access to Internet and is the root of the DODAG, thus 623 the 6BBR is not present in the figure. 625 The 6LN leaves (RAL) marked as (F, H and I) are RPL nodes with no 626 children hosts. 628 The leaves marked as RUL (G and J) are devices which do not speak RPL 629 at all (not-RPL-aware), but uses Router-Advertisements, 6LowPAN DAR/ 630 DAC and efficient-ND only to participate in the network [RFC6775]. 631 In the document these leaves (G and J) are also referred to as an 632 IPv6 node. 634 The 6LBR ("A") in the figure is the root of the Global DODAG. 636 +------------+ 637 | INTERNET ----------+ 638 | | | 639 +------------+ | 640 | 641 | 642 | 643 A | 644 +-------+ 645 |6LBR | 646 +-----------|(root) |-------+ 647 | +-------+ | 648 | | 649 | | 650 | | 651 | | 652 | B |C 653 +---|---+ +---|---+ 654 | 6LR | | 6LR | 655 +---------| |--+ +--- ---+ 656 | +-------+ | | +-------+ | 657 | | | | 658 | | | | 659 | | | | 660 | | | | 661 | D | E | | 662 +-|-----+ +---|---+ | | 663 | 6LR | | 6LR | | | 664 | | +------ | | | 665 +---|---+ | +---|---+ | | 666 | | | | | 667 | | +--+ | | 668 | | | | | 669 | | | | | 670 | | | I | J | 671 F | | G | H | | 672 +-----+-+ +-|-----+ +---|--+ +---|---+ +---|---+ 673 | RAL | | RUL | | RAL | | RAL | | RUL | 674 | 6LN | | 6LN | | 6LN | | 6LN | | 6LN | 675 +-------+ +-------+ +------+ +-------+ +-------+ 677 Figure 6: A reference RPL Topology. 679 6. Use cases 681 In the data plane a combination of RFC6553, RFC6554 and IPv6-in-IPv6 682 encapsulation are going to be analyzed for a number of representative 683 traffic flows. 685 This document assumes that the LLN is using the no-drop RPI Option 686 Type of 0x23. 688 The use cases describe the communication in the following cases: - 689 Between RPL-aware-nodes with the root (6LBR) - Between RPL-aware- 690 nodes with the Internet - Between RUL nodes within the LLN (e.g. see 691 Section 7.1.4) - Inside of the LLN when the final destination address 692 resides outside of the LLN (e.g. see Section 7.2.3). 694 The uses cases are as follows: 696 Interaction between Leaf and Root: 698 RAL to root 700 root to RAL 702 RUL to root 704 root to RUL 706 Interaction between Leaf and Internet: 708 RAL to Internet 710 Internet to RAL 712 RUL to Internet 714 Internet to RUL 716 Interaction between leaves: 718 RAL to RAL 720 RAL to RUL 722 RUL to RAL 724 RUL to RUL 726 This document is consistent with the rule that a Header cannot be 727 inserted or removed on the fly inside an IPv6 packet that is being 728 routed. This is a fundamental precept of the IPv6 architecture as 729 outlined in [RFC8200]. 731 As the rank information in the RPI artifact is changed at each hop, 732 it will typically be zero when it arrives at the DODAG root. The 733 DODAG root MUST force it to zero when passing the packet out to the 734 Internet. The Internet will therefore not see any SenderRank 735 information. 737 Despite being legal to leave the RPI artifact in place, an 738 intermediate router that needs to add an extension header (e.g. RH3 739 or RPL Option) MUST still encapsulate the packet in an (additional) 740 outer IP header. The new header is placed after this new outer IP 741 header. 743 A corollary is that an RH3 or RPL Option can only be removed by an 744 intermediate router if it is placed in an encapsulating IPv6 Header, 745 which is addressed TO the intermediate router. When it does so, the 746 whole encapsulating header must be removed. (A replacement may be 747 added). This sometimes can result in outer IP headers being 748 addressed to the next hop router using link-local address. 750 Both the RPL Option and the RH3 headers may be modified in very 751 specific ways by routers on the path of the packet without the need 752 to add and remove an encapsulating header. Both headers were 753 designed with this modification in mind, and both the RPL RH3 and the 754 RPL Option are marked mutable but recoverable: so an IPsec AH 755 security header can be applied across these headers, but it can not 756 secure the values which mutate. 758 The RPI MUST be present in every single RPL data packet. 760 Prior to [RFC8138], there was significant interest in creating an 761 exception to this rule and removing the RPI for downward flows in 762 non-storing mode. This exception covered a very small number of 763 cases, and caused significant interoperability challenges while 764 adding significant in the code and tests. The ability to compress 765 the RPI down to three bytes or less removes much of the pressure to 766 optimize this any further [I-D.ietf-anima-autonomic-control-plane]. 768 The earlier examples are more extensive to make sure that the process 769 is clear, while later examples are more concise. 771 The uses cases are delineated based on the following requirements: 773 The RPI has to be in every packet that traverses the LLN. 775 - Because of the above requirement, packets from the Internet have 776 to be encapsulated. 778 - A Header cannot be inserted or removed on the fly inside an IPv6 779 packet that is being routed. 781 - Extension headers may not be added or removed except by the 782 sender or the receiver. 784 - RPI and RH3 headers may be modified by routers on the path of 785 the packet without the need to add and remove an encapsulating 786 header. 788 - an RH3 or RPL Option can only be removed by an intermediate 789 router if it is placed in an encapsulating IPv6 Header, which is 790 addressed to the intermediate router. 792 - Non-storing mode requires downstream encapsulation by root for 793 RH3. 795 The uses cases are delineated based on the following assumptions: 797 This document assumes that the LLN is using the no-drop RPI Option 798 Type (0x23). 800 - Each IPv6 node (including Internet routers) obeys [RFC8200], so 801 that 0x23 RPI Option Type can be safely inserted. 803 - All 6LRs obey [RFC8200]. 805 - The RPI is ignored at the IPv6 dst node (RUL). 807 - In the uses cases, we assume that the RAL supports IP-in-IP 808 encapsulation. 810 - In the uses cases, we dont assume that the RUL supports IP-in-IP 811 encapsulation. 813 - For traffic leaving a RUL, if the RUL adds an opaque RPI then 814 the description of the RAL applies. 816 - The description for RALs applies to RAN in general. 818 - Non-constrained uses of RPL are not in scope of this document. 820 - Compression is based on [RFC8138]. 822 - The flow label [RFC6437] is not needed in RPL. 824 7. Storing mode 826 In storing mode (SM) (fully stateful), the sender can determine if 827 the destination is inside the LLN by looking if the destination 828 address is matched by the DIO's Prefix Information Option (PIO) 829 option. 831 The following table (Figure 7) itemizes which headers are needed in 832 each of the following scenarios. It indicates whether an IPv6-in- 833 IPv6 header must be added and what destination it must be addressed 834 to: (1) the final destination (the RAL node that is the target 835 (tgt)), (2) the "root", or (3) the 6LR parent of a RUL. 837 In cases where no IPv6-in-IPv6 header is needed, the column states as 838 "No". If the IPv6-in-IPv6 header is needed, the column shows "must". 840 In all cases, the RPI is needed, since it identifies inconsistencies 841 (loops) in the routing topology. In all cases, the RH3 is not needed 842 because it is not used in storing mode. 844 The leaf can be a router 6LR or a host, both indicated as 6LN. The 845 root refers to the 6LBR (see Figure 6). 847 +---------------------+--------------+------------+----------------+ 848 | Interaction between | Use Case |IPv6-in-IPv6|IPv6-in-IPv6 dst| 849 +---------------------+--------------+------------+----------------+ 850 | | RAL to root | No | No | 851 + +--------------+------------+----------------+ 852 | Leaf - Root | root to RAL | No | No | 853 + +--------------+------------+----------------+ 854 | | root to RUL | must | 6LR | 855 + +--------------+------------+----------------+ 856 | | RUL to root | must | root | 857 +---------------------+--------------+------------+----------------+ 858 | | RAL to Int | may | root | 859 + +--------------+------------+----------------+ 860 | Leaf - Internet | Int to RAL | must | RAL (tgt) | 861 + +--------------+------------+----------------+ 862 | | RUL to Int | must | root | 863 + +--------------+------------+----------------+ 864 | | Int to RUL | must | 6LR | 865 +---------------------+--------------+------------+----------------+ 866 | | RAL to RAL | No | No | 867 | Leaf - Leaf +--------------+------------+----------------+ 868 | | RAL to RUL | must(down) | 6LR | 869 | +--------------+------------+----------------+ 870 | | RUL to RAL | must(up) | root | 871 | | +------------+----------------+ 872 | | | must(down) | RAL | 873 | +--------------+------------+----------------+ 874 | | RUL to RUL | must(up) | root | 875 | | +------------+----------------+ 876 | | | must(down) | 6LR | 877 |---------------------+--------------+------------+----------------+ 879 Figure 7: Table of IPv6-in-IPv6 encapsulation in Storing mode. 881 7.1. Storing Mode: Interaction between Leaf and Root 883 In this section is described the communication flow in storing mode 884 (SM) between, 886 RAL to root 888 root to RAL 890 RUL to root 892 root to RUL 894 7.1.1. SM: Example of Flow from RAL to root 896 In storing mode, RFC 6553 (RPI) is used to send RPL Information 897 instanceID and rank information. 899 In this case the flow comprises: 901 RAL (6LN) --> 6LR_i --> root(6LBR) 903 For example, a communication flow could be: Node F (6LN) --> Node D 904 (6LR_i) --> Node B (6LR_i)--> Node A root(6LBR) 906 The RAL (Node F) inserts the RPI, and sends the packet to 6LR (Node 907 D) which decrements the rank in the RPI and sends the packet up. 908 When the packet arrives at 6LBR (Node A), the RPI is removed and the 909 packet is processed. 911 No IPv6-in-IPv6 header is required. 913 The RPI can be removed by the 6LBR because the packet is addressed to 914 the 6LBR. The RAL must know that it is communicating with the 6LBR 915 to make use of this scenario. The RAL can know the address of the 916 6LBR because it knows the address of the root via the DODAGID in the 917 DIO messages. 919 The Table 1 summarizes what headers are needed for this use case. 921 +-------------------+---------+-------+----------+ 922 | Header | RAL src | 6LR_i | 6LBR dst | 923 +-------------------+---------+-------+----------+ 924 | Added headers | RPI | -- | -- | 925 | Modified headers | -- | RPI | -- | 926 | Removed headers | -- | -- | RPI | 927 | Untouched headers | -- | -- | -- | 928 +-------------------+---------+-------+----------+ 930 Table 1: SM: Summary of the use of headers from RAL to root 932 7.1.2. SM: Example of Flow from root to RAL 934 In this case the flow comprises: 936 root (6LBR) --> 6LR_i --> RAL (6LN) 938 For example, a communication flow could be: Node A root(6LBR) --> 939 Node B (6LR_i) --> Node D (6LR_i) --> Node F (6LN) 940 In this case the 6LBR inserts RPI and sends the packet down, the 6LR 941 is going to increment the rank in RPI (it examines the RPLInstanceID 942 to identify the right forwarding table), the packet is processed in 943 the RAL and the RPI removed. 945 No IPv6-in-IPv6 header is required. 947 The Table 2 summarizes what headers are needed for this use case. 949 +-------------------+----------+-------+---------+ 950 | Header | 6LBR src | 6LR_i | RAL dst | 951 +-------------------+----------+-------+---------+ 952 | Added headers | RPI | -- | -- | 953 | Modified headers | -- | RPI | -- | 954 | Removed headers | -- | -- | RPI | 955 | Untouched headers | -- | -- | -- | 956 +-------------------+----------+-------+---------+ 958 Table 2: SM: Summary of the use of headers from root to RAL 960 7.1.3. SM: Example of Flow from root to RUL 962 In this case the flow comprises: 964 root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 966 For example, a communication flow could be: Node A (6LBR) --> Node B 967 (6LR_i) --> Node E (6LR_n) --> Node G (RUL) 969 6LR_i (Node B) represents the intermediate routers from the source 970 (6LBR) to the destination (RUL), 1 <= i <= n, where n is the total 971 number of routers (6LR) that the packet goes through from the 6LBR 972 (Node A) to the RUL (Node G). 974 The 6LBR will insert an RPI, encapsulated in a IPv6-in-IPv6 header. 975 The IPv6-in-IPv6 header is addressed to the 6LR parent of the RUL 976 (6LR_n). The 6LR parent of the RUL removes the header and sends the 977 packet to the RUL. 979 The Figure 8 summarizes what headers are needed for this use case. 981 +-----------+---------+---------+---------+-----+ 982 | Header | 6LBR | 6LR_i | 6LR_n | RUL | 983 | | src | | | dst | 984 +-----------+---------+---------+---------+-----+ 985 | Added | IP6-IP6 | -- | -- | -- | 986 | headers | (RPI) | | | | 987 +-----------+---------+---------+---------+-----+ 988 | Modified | -- | IP6-IP6 | -- | -- | 989 | headers | | (RPI) | | | 990 +-----------+---------+---------+---------+-----+ 991 | Removed | -- | -- | IP6-IP6 | -- | 992 | headers | | | (RPI) | | 993 +-----------+---------+---------+---------+-----+ 994 | Untouched | -- | -- | -- | -- | 995 | headers | | | | | 996 +-----------+---------+---------+---------+-----+ 998 Figure 8: SM: Summary of the use of headers from root to RUL 1000 7.1.4. SM: Example of Flow from RUL to root 1002 In this case the flow comprises: 1004 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR) 1006 For example, a communication flow could be: Node G (RUL) --> Node E 1007 (6LR_1)--> Node B (6LR_i)--> Node A root(6LBR) 1009 6LR_i represents the intermediate routers from the source (RUL) to 1010 the destination (6LBR), 1 <= i <= n, where n is the total number of 1011 routers (6LR) that the packet goes through from the RUL to the 6LBR. 1013 When the packet arrives from IPv6 node (Node G) to 6LR_1 (Node E), 1014 the 6LR_1 will insert an RPI, encapsulated in a IPv6-in-IPv6 header. 1015 The IPv6-in-IPv6 header is addressed to the root (Node A). The root 1016 removes the header and processes the packet. 1018 The Figure 9 shows the table that summarizes what headers are needed 1019 for this use case where the IPv6-in-IPv6 header is addressed to the 1020 root (Node A). 1022 +-----------+------+--------------+----------------+-----------------+ 1023 | Header | RUL | 6LR_1 | 6LR_i | 6LBR dst | 1024 | | src | | | | 1025 | | node | | | | 1026 +-----------+------+--------------+----------------+-----------------+ 1027 | Added | -- | IP6-IP6(RPI) | | -- | 1028 | headers | | | -- | | 1029 +-----------+------+--------------+----------------+-----------------+ 1030 | Modified | -- | -- | IP6-IP6(RPI) | -- | 1031 | headers | | | | | 1032 +-----------+------+--------------+----------------+-----------------+ 1033 | Removed | -- | -- | --- | IP6-IP6(RPI) | 1034 | headers | | | | | 1035 +-----------+------+--------------+----------------+-----------------+ 1036 | Untouched | -- | -- | -- | -- | 1037 | headers | | | | | 1038 +-----------+------+--------------+----------------+-----------------+ 1040 Figure 9: SM: Summary of the use of headers from RUL to root. 1042 7.2. SM: Interaction between Leaf and Internet. 1044 In this section is described the communication flow in storing mode 1045 (SM) between, 1047 RAL to Internet 1049 Internet to RAL 1051 RUL to Internet 1053 Internet to RUL 1055 7.2.1. SM: Example of Flow from RAL to Internet 1057 In this case the flow comprises: 1059 RAL (6LN) --> 6LR_i --> root (6LBR) --> Internet 1061 For example, the communication flow could be: Node F (RAL) --> Node D 1062 (6LR_i)--> Node B (6LR_i)--> Node A root(6LBR) --> Internet 1064 6LR_i represents the intermediate routers from the source (RAL) to 1065 the root (6LBR), 1 <= i <= n, where n is the total number of routers 1066 (6LR) that the packet goes through from the RAL to the 6LBR. 1068 RPL information from RFC 6553 may go out to Internet as it will be 1069 ignored by nodes which have not been configured to be RPI aware. No 1070 IPv6-in-IPv6 header is required. 1072 On the other hand, the RAL may insert the RPI encapsulated in a IPv6- 1073 in-IPv6 header to the root. Thus, the root removes the RPI and send 1074 the packet to the Internet. 1076 No IPv6-in-IPv6 header is required. 1078 Note: In this use case, it is used a node as a leaf, but this use 1079 case can be also applicable to any RPL-aware-node type (e.g. 6LR) 1081 The Table 3 summarizes what headers are needed for this use case when 1082 there is no encapsulation. The Figure 10 summarizes what headers are 1083 needed when encapsulation to the root takes place. 1085 +-------------------+---------+-------+------+----------------+ 1086 | Header | RAL src | 6LR_i | 6LBR | Internet dst | 1087 +-------------------+---------+-------+------+----------------+ 1088 | Added headers | RPI | -- | -- | -- | 1089 | Modified headers | -- | RPI | -- | -- | 1090 | Removed headers | -- | -- | -- | -- | 1091 | Untouched headers | -- | -- | RPI | RPI (Ignored) | 1092 +-------------------+---------+-------+------+----------------+ 1094 Table 3: SM: Summary of the use of headers from RAL to Internet with 1095 no encapsulation 1097 +-----------+----------+--------------+--------------+--------------+ 1098 | Header | RAL | 6LR_i | 6LBR | Internet dst | 1099 | | src | | | | 1100 +-----------+----------+--------------+--------------+--------------+ 1101 | Added |IP6-IP6 | -- | -- | -- | 1102 | headers | (RPI) | | | | 1103 +-----------+----------+--------------+--------------+--------------+ 1104 | Modified | -- |IP6-IP6(RPI) | -- | -- | 1105 | headers | | | | | 1106 +-----------+----------+--------------+--------------+--------------+ 1107 | Removed | -- | -- |IP6-IP6(RPI) | -- | 1108 | headers | | | | | 1109 +-----------+----------+--------------+--------------+--------------+ 1110 | Untouched | -- | -- | -- | -- | 1111 | headers | | | | | 1112 +-----------+----------+--------------+--------------+--------------+ 1114 Figure 10: SM: Summary of the use of headers from RAL to Internet 1115 with encapsulation to the root (6LBR). 1117 7.2.2. SM: Example of Flow from Internet to RAL 1119 In this case the flow comprises: 1121 Internet --> root (6LBR) --> 6LR_i --> RAL (6LN) 1123 For example, a communication flow could be: Internet --> Node A 1124 root(6LBR) --> Node B (6LR_1) --> Node D (6LR_n) --> Node F (RAL) 1126 When the packet arrives from Internet to 6LBR the RPI is added in a 1127 outer IPv6-in-IPv6 header (with the IPv6-in-IPv6 destination address 1128 set to the RAL) and sent to 6LR, which modifies the rank in the RPI. 1129 When the packet arrives at the RAL the RPI is removed and the packet 1130 processed. 1132 The Figure 11 shows the table that summarizes what headers are needed 1133 for this use case. 1135 +-----------+----------+--------------+--------------+--------------+ 1136 | Header | Internet | 6LBR | 6LR_i | RAL dst | 1137 | | src | | | | 1138 +-----------+----------+--------------+--------------+--------------+ 1139 | Added | -- | IP6-IP6(RPI) | -- | -- | 1140 | headers | | | | | 1141 +-----------+----------+--------------+--------------+--------------+ 1142 | Modified | -- | -- | IP6-IP6(RPI) | -- | 1143 | headers | | | | | 1144 +-----------+----------+--------------+--------------+--------------+ 1145 | Removed | -- | -- | -- | IP6-IP6(RPI) | 1146 | headers | | | | | 1147 +-----------+----------+--------------+--------------+--------------+ 1148 | Untouched | -- | -- | -- | -- | 1149 | headers | | | | | 1150 +-----------+----------+--------------+--------------+--------------+ 1152 Figure 11: SM: Summary of the use of headers from Internet to RAL. 1154 7.2.3. SM: Example of Flow from RUL to Internet 1156 In this case the flow comprises: 1158 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet 1160 For example, a communication flow could be: Node G (RUL)--> Node E 1161 (6LR_1)--> Node B (6lR_i) --> Node A root(6LBR) --> Internet 1162 The node 6LR_1 (i=1) will add an IPv6-in-IPv6(RPI) header addressed 1163 to the root such that the root can remove the RPI before passing 1164 upwards. In the intermediate 6LR, the rank in the RPI is modified. 1166 The originating node will ideally leave the IPv6 flow label as zero 1167 so that the packet can be better compressed through the LLN. The 1168 6LBR will set the flow label of the packet to a non-zero value when 1169 sending to the Internet, for details check [RFC6437]. 1171 The Figure 12 shows the table that summarizes what headers are needed 1172 for this use case. 1174 +---------+-------+------------+-------------+-------------+--------+ 1175 | Header | IPv6 | 6LR_1 | 6LR_i | 6LBR |Internet| 1176 | | src | | [i=2,...,n] | | dst | 1177 | | node | | | | | 1178 | | (RUL) | | | | | 1179 +---------+-------+------------+-------------+-------------+--------+ 1180 | Added | -- |IP6-IP6(RPI)| -- | -- | -- | 1181 | headers | | | | | | 1182 +---------+-------+------------+-------------+-------------+--------+ 1183 | Modified| -- | -- |IP6-IP6(RPI) | -- | -- | 1184 | headers | | | | | | 1185 +---------+-------+------------+-------------+-------------+--------+ 1186 | Removed | -- | -- | -- | IP6-IP6(RPI)| -- | 1187 | headers | | | | | | 1188 +---------+-------+------------+-------------+-------------+--------+ 1189 |Untouched| -- | -- | -- | -- | -- | 1190 | headers | | | | | | 1191 +---------+-------+------------+-------------+-------------+--------+ 1193 Figure 12: SM: Summary of the use of headers from RUL to Internet. 1195 7.2.4. SM: Example of Flow from Internet to RUL. 1197 In this case the flow comprises: 1199 Internet --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1201 For example, a communication flow could be: Internet --> Node A 1202 root(6LBR) --> Node B (6LR_i)--> Node E (6LR_n) --> Node G (RUL) 1204 The 6LBR will have to add an RPI within an IPv6-in-IPv6 header. The 1205 IPv6-in-IPv6 is addressed to the 6LR parent of the RUL. 1207 Further details about this are mentioned in 1208 [I-D.ietf-roll-unaware-leaves], which specifies RPL routing for a 6LN 1209 acting as a plain host and not being aware of RPL. 1211 The 6LBR may set the flow label on the inner IPv6-in-IPv6 header to 1212 zero in order to aid in compression [RFC8138][RFC6437]. 1214 The Figure 13 shows the table that summarizes what headers are needed 1215 for this use case. 1217 +---------+-------+------------+--------------+-------------+-------+ 1218 | Header |Inter- | 6LBR | 6LR_i | 6LR_n | RUL | 1219 | | net | |[i=1,..,n-1] | | dst | 1220 | | src | | | | | 1221 | | | | | | | 1222 +---------+-------+------------+--------------+-------------+-------+ 1223 | Inserted| -- |IP6-IP6(RPI)| -- | -- | -- | 1224 | headers | | | | | | 1225 +---------+-------+------------+--------------+-------------+-------+ 1226 | Modified| -- | -- | IP6-IP6(RPI) | -- | -- | 1227 | headers | | | | | | 1228 +---------+-------+------------+--------------+-------------+-------+ 1229 | Removed | -- | -- | -- | IP6-IP6(RPI)| -- | 1230 | headers | | | | | | 1231 +---------+-------+------------+--------------+-------------+-------+ 1232 |Untouched| -- | -- | -- | -- | -- | 1233 | headers | | | | | | 1234 +---------+-------+------------+--------------+-------------+-------+ 1236 Figure 13: SM: Summary of the use of headers from Internet to RUL. 1238 7.3. SM: Interaction between Leaf and Leaf 1240 In this section is described the communication flow in storing mode 1241 (SM) between, 1243 RAL to RAL 1245 RAL to RUL 1247 RUL to RAL 1249 RUL to RUL 1251 7.3.1. SM: Example of Flow from RAL to RAL 1253 In [RFC6550] RPL allows a simple one-hop optimization for both 1254 storing and non-storing networks. A node may send a packet destined 1255 to a one-hop neighbor directly to that node. See section 9 in 1256 [RFC6550]. 1258 When the nodes are not directly connected, then in storing mode, the 1259 flow comprises: 1261 RAL src (6LN) --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> RAL 1262 dst (6LN) 1264 For example, a communication flow could be: Node F (RAL src)--> Node 1265 D (6LR_ia)--> Node B (6LR_x) --> Node E (6LR_id) --> Node H (RAL dst) 1267 6LR_ia (Node D) represents the intermediate routers from source to 1268 the common parent (6LR_x) (Node B), 1 <= ia <= n, where n is the 1269 total number of routers (6LR) that the packet goes through from RAL 1270 (Node F) to the common parent 6LR_x (Node B). 1272 6LR_id (Node E) represents the intermediate routers from the common 1273 parent (6LR_x) (Node B) to destination RAL (Node H), 1 <= id <= m, 1274 where m is the total number of routers (6LR) that the packet goes 1275 through from the common parent (6LR_x) to destination RAL (Node H). 1277 It is assumed that the two nodes are in the same RPL domain (that 1278 they share the same DODAG root). At the common parent (Node B), the 1279 direction flag ('O' flag) of the RPI is changed (from decreasing 1280 ranks to increasing ranks). 1282 While the 6LR nodes will update the RPI, no node needs to add or 1283 remove the RPI, so no IPv6-in-IPv6 headers are necessary. 1285 The Table 4 summarizes what headers are needed for this use case. 1287 +---------------+--------+--------+---------------+--------+--------+ 1288 | Header | RAL | 6LR_ia | 6LR_x (common | 6LR_id | RAL | 1289 | | src | | parent) | | dst | 1290 +---------------+--------+--------+---------------+--------+--------+ 1291 | Added headers | RPI | -- | -- | -- | -- | 1292 | Modified | -- | RPI | RPI | RPI | -- | 1293 | headers | | | | | | 1294 | Removed | -- | -- | -- | -- | RPI | 1295 | headers | | | | | | 1296 | Untouched | -- | -- | -- | -- | -- | 1297 | headers | | | | | | 1298 +---------------+--------+--------+---------------+--------+--------+ 1300 Table 4: SM: Summary of the Use of Headers from RAL to RAL 1302 7.3.2. SM: Example of Flow from RAL to RUL 1304 In this case the flow comprises: 1306 RAL src (6LN) --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> RUL 1307 (IPv6 dst node) 1309 For example, a communication flow could be: Node F (RAL)--> Node D 1310 --> Node B --> Node E --> Node G (RUL) 1312 6LR_ia represents the intermediate routers from source (RAL) to the 1313 common parent (6LR_x), 1 <= ia <= n, where n is the total number of 1314 routers (6LR) that the packet goes through from RAL to the common 1315 parent (6LR_x). 1317 6LR_id (Node E) represents the intermediate routers from the common 1318 parent (6LR_x) (Node B) to destination RUL (Node G). In this case, 1 1319 <= id <= m, where m is the total number of routers (6LR) that the 1320 packet goes through from the common parent (6LR_x) to destination 1321 RUL. 1323 In this case, the packet from the RAL goes to 6LBR because the route 1324 to the RUL is not injected into the RPL-SM. Thus, the RAL inserts an 1325 RPI (RPI1) addressed to the root(6LBR). The root removes the RPI1 1326 and inserts an RPI2 encapsulated to the 6LR parent of the RUL, which 1327 removes the RPI2 before pasing the packet to the RUL. 1329 The Figure 14 summarizes what headers are needed for this use case. 1331 +-----------+---------+---------+---------+---------+---------+------+ 1332 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | 6LR_m | RUL | 1333 | | src | | | | | dst | 1334 | | node | | | | | node | 1335 +-----------+---------+---------+---------+---------+---------+------+ 1336 | Added | | | IP6-IP6 | -- | -- | -- | 1337 | headers | RPI1 | -- | (RPI2) | | | | 1338 | | | | | | | | 1339 +-----------+---------+---------+---------+---------+---------+------+ 1340 | Modified | -- | | -- | IP6-IP6 | | -- | 1341 | headers | | RPI1 | | (RPI2) | -- | | 1342 | | | | | | | | 1343 +-----------+---------+---------+---------+---------+---------+------+ 1344 | Removed | -- | -- | | -- | IP6-IP6 | -- | 1345 | headers | | | RPI1 | | (RPI2) | | 1346 | | | | | | | | 1347 +-----------+---------+---------+---------+---------+---------+------+ 1348 | Untouched | -- | -- | -- | -- | -- | -- | 1349 | headers | | | | | | | 1350 +-----------+---------+---------+---------+---------+---------+------+ 1352 Figure 14: SM: Summary of the Use of Headers from RAL to RUL 1354 7.3.3. SM: Example of Flow from RUL to RAL 1356 In this case the flow comprises: 1358 RUL (IPv6 src node) --> 6LR_ia --> 6LBR --> 6LR_id --> RAL dst (6LN) 1360 For example, a communication flow could be: Node G (RUL)--> Node E 1361 --> Node B --> Node A --> Node B --> Node D --> Node F (RAL) 1363 6LR_ia (Node E) represents the intermediate routers from source (RUL) 1364 (Node G) to the root (Node A). In this case, 1 <= ia <= n, where n 1365 is the total number of routers (6LR) that the packet goes through 1366 from source to the root. 1368 6LR_id represents the intermediate routers from the root (Node A) to 1369 destination RAL (Node F). In this case, 1 <= id <= m, where m is the 1370 total number of routers (6LR) that the packet goes through from the 1371 root to the destination RAL. 1373 The 6LR_ia (ia=1) (Node E) receives the packet from the RUL (Node G) 1374 and inserts the RPI (RPI1) encapsulated in a IPv6-in-IPv6 header to 1375 the root. The root removes the outer header including the RPI (RPI1) 1376 and inserts a new RPI (RPI2) addressed to the destination RAL (Node 1377 F). 1379 The Figure 15 shows the table that summarizes what headers are needed 1380 for this use case. 1382 +-----------+------+---------+---------+---------+---------+---------+ 1383 | Header | RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id | RAL | 1384 | | src | | | | | dst | 1385 | | node | | | | | node | 1386 +-----------+------+---------+---------+---------+---------+---------+ 1387 | Added | -- | IP6-IP6 | -- | IP6-IP6 | -- | -- | 1388 | headers | | (RPI1) | | (RPI2) | | | 1389 | | | | | | | | 1390 +-----------+------+---------+---------+---------+---------+---------+ 1391 | Modified | -- | | IP6-IP6 | -- | IP6-IP6 | -- | 1392 | headers | | -- | (RPI1) | | (RPI2) | | 1393 | | | | | | | | 1394 +-----------+------+---------+---------+---------+---------+---------+ 1395 | Removed | -- | | -- | IP6-IP6 | -- | IP6-IP6 | 1396 | headers | | -- | | (RPI1) | | (RPI2) | 1397 | | | | | | | | 1398 +-----------+------+---------+---------+---------+---------+---------+ 1399 | Untouched | -- | -- | -- | -- | -- | -- | 1400 | headers | | | | | | | 1401 +-----------+------+---------+---------+---------+---------+---------+ 1403 Figure 15: SM: Summary of the use of headers from RUL to RAL. 1405 7.3.4. SM: Example of Flow from RUL to RUL 1407 In this case the flow comprises: 1409 RUL (IPv6 src node)--> 6LR_1--> 6LR_ia --> 6LBR --> 6LR_id --> RUL 1410 (IPv6 dst node) 1412 For example, a communication flow could be: Node G (RUL src)--> Node 1413 E --> Node B --> Node A (root) --> Node C --> Node J (RUL dst) 1415 Internal nodes 6LR_ia (e.g: Node E or Node B) is the intermediate 1416 router from the RUL source (Node G) to the root (6LBR) (Node A). In 1417 this case, 1 <= ia <= n, where n is the total number of routers (6LR) 1418 that the packet goes through from the RUL to the root. 6LR_1 refers 1419 when ia=1. 1421 6LR_id (Node C) represents the intermediate routers from the root 1422 (Node A) to the destination RUL dst node (Node J). In this case, 1 1423 <= id <= m, where m is the total number of routers (6LR) that the 1424 packet goes through from the root to destination RUL. 1426 The RPI is ignored at the RUL dst node. 1428 The 6LR_1 (Node E) receives the packet from the RUL (Node G) and 1429 inserts the RPI (RPI), encapsulated in an IPv6-in-IPv6 header 1430 directed to the root. The root removes the outer header including 1431 the RPI (RPI1) and inserts a new RPI (RPI2) addressed to the 6LR 1432 father of the RUL. 1434 The Figure 16 shows the table that summarizes what headers are needed 1435 for this use case. 1437 +---------+----+-------------+--------+---------+--------+-------+---+ 1438 | Header |RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id |6LR_n |RUL| 1439 | |src | | | | | |dst| 1440 | | | | | | | | | 1441 +---------+----+-------------+--------+---------+--------+-------+---+ 1442 | Added | -- |IP6-IP6(RPI1)| -- | IP6-IP6 | -- | -- | --| 1443 | Headers | | | | (RPI2) | | | | 1444 +---------+----+-------------+--------+---------+--------+-------+---+ 1445 |Modified | -- | -- |IP6-IP6 | -- |IP6-IP6 | -- | --| 1446 |headers | | | (RPI1) | | (RPI2) | | | 1447 +---------+----+-------------+--------+---------+--------+-------+---+ 1448 | Removed | -- | -- | -- | IP6-IP6 | -- |IP6-IP6| --| 1449 | headers | | | | (RPI1) | | (RPI2)| | 1450 +---------+----+-------------+--------+---------+--------+-------+---+ 1451 |Untouched| -- | -- | -- | -- | -- | -- | --| 1452 | headers | | | | | | | | 1453 +---------+----+-------------+--------+---------+--------+-------+---+ 1455 Figure 16: SM: Summary of the use of headers from RUL to RUL 1457 8. Non Storing mode 1459 In Non Storing Mode (Non-SM) (fully source routed), the 6LBR (DODAG 1460 root) has complete knowledge about the connectivity of all DODAG 1461 nodes, and all traffic flows through the root node. Thus, there is 1462 no need for all nodes to know about the existence of RPL-unaware 1463 nodes. Only the 6LBR needs to act if compensation is necessary for 1464 not-RPL aware receivers. 1466 The table (Figure 17) summarizes what headers are needed in the 1467 following scenarios, and indicates when the RPI, RH3 and IPv6-in-IPv6 1468 header are to be inserted. The last column depicts the target 1469 destination of the IPv6-in-IPv6 header: 6LN (indicated by "RAL"), 6LR 1470 (parent of a RUL) or the root. In cases where no IPv6-in-IPv6 header 1471 is needed, the column indicates "No". There is no expectation on RPL 1472 that RPI can be omitted, because it is needed for routing, quality of 1473 service and compression. This specification expects that an RPI is 1474 always present. The term "may(up)" means that the IPv6-in-IPv6 1475 header may be necessary in the upwards direction. The term 1476 "must(up)" means that the IPv6-in-IPv6 header must be present in the 1477 upwards direction. The term "must(down)" means that the IPv6-in-IPv6 1478 header must be present in the downward direction. 1480 The leaf can be a router 6LR or a host, both indicated as 6LN 1481 (Figure 6). In the table (Figure 17) the (1) indicates a 6tisch case 1482 [RFC8180], where the RPI may still be needed for the RPLInstanceID to 1483 be available for priority/channel selection at each hop. 1485 The root always have to encapuslate on the way down 1487 +--- ------------+-------------+-----+-----+--------------+----------+ 1488 | Interaction | Use Case | RPI | RH3 | IPv6-in-IPv6 | IP-in-IP | 1489 | between | | | | | dst | 1490 +----------------+-------------+-----+-----+--------------+----------+ 1491 | | RAL to root | Yes | No | No | No | 1492 | +-------------+-----+-----+--------------+----------+ 1493 | Leaf - Root | root to RAL | Yes | Yes | No | No | 1494 | +-------------+-----+-----+--------------+----------+ 1495 | | root to RUL | Yes | Yes | must | 6LR | 1496 | | | (1) | | | | 1497 | +-------------+-----+-----+--------------+----------+ 1498 | | RUL to root | Yes | No | must | root | 1499 +----------------+-------------+-----+-----+--------------+----------+ 1500 | | RAL to Int | Yes | No | may(up) | root | 1501 | +-------------+-----+-----+--------------+----------+ 1502 |Leaf - Internet | Int to RAL | Yes | Yes | must | RAL | 1503 | +-------------+-----+-----+--------------+----------+ 1504 | | RUL to Int | Yes | No | must | root | 1505 | +-------------+-----+-----+--------------+----------+ 1506 | | Int to RUL | Yes | Yes | must | 6LR | 1507 +----------------+-------------+-----+-----+--------------+----------+ 1508 | | RAL to RAL | Yes | Yes | may(up) | root | 1509 | | | | +--------------+----------+ 1510 | | | | | must(down) | RAL | 1511 | Leaf - Leaf +-------------+-----+-----+--------------+----------+ 1512 | | RAL to RUL | Yes | Yes | may(up) | root | 1513 | | | | +--------------+----------+ 1514 | | | | | must(down) | 6LR | 1515 | +-------------+-----+-----+--------------+----------+ 1516 | | RUL to RAL | Yes | Yes | must(up) | root | 1517 | | | | +--------------+----------+ 1518 | | | | | must(down) | RAL | 1519 | +-------------+-----+-----+--------------+----------+ 1520 | | RUL to RUL | Yes | Yes | must(up) | root | 1521 | | | | +--------------+----------+ 1522 | | | | | must(down) | 6LR | 1523 +----------------+-------------+-----+-----+--------------+----------+ 1525 Figure 17: Table that shows headers needed in Non-Storing mode: RPI, 1526 RH3, IPv6-in-IPv6 encapsulation. 1528 8.1. Non-Storing Mode: Interaction between Leaf and Root 1530 In this section is described the communication flow in Non Storing 1531 Mode (Non-SM) between, 1533 RAL to root 1534 root to RAL 1536 RUL to root 1538 root to RUL 1540 8.1.1. Non-SM: Example of Flow from RAL to root 1542 In non-storing mode the leaf node uses default routing to send 1543 traffic to the root. The RPI must be included since it contains the 1544 rank information, which is used to avoid/detect loops. 1546 RAL (6LN) --> 6LR_i --> root(6LBR) 1548 For example, a communication flow could be: Node F --> Node D --> 1549 Node B --> Node A (root) 1551 6LR_i represents the intermediate routers from source to destination. 1552 In this case, 1 <= i <= n, where n is the total number of routers 1553 (6LR) that the packet goes through from source (RAL) to destination 1554 (6LBR). 1556 This situation is the same case as storing mode. 1558 The Table 5 summarizes what headers are needed for this use case. 1560 +-------------------+---------+-------+----------+ 1561 | Header | RAL src | 6LR_i | 6LBR dst | 1562 +-------------------+---------+-------+----------+ 1563 | Added headers | RPI | -- | -- | 1564 | Modified headers | -- | RPI | -- | 1565 | Removed headers | -- | -- | RPI | 1566 | Untouched headers | -- | -- | -- | 1567 +-------------------+---------+-------+----------+ 1569 Table 5: Non-SM: Summary of the use of headers from RAL to root 1571 8.1.2. Non-SM: Example of Flow from root to RAL 1573 In this case the flow comprises: 1575 root (6LBR) --> 6LR_i --> RAL (6LN) 1577 For example, a communication flow could be: Node A (root) --> Node B 1578 --> Node D --> Node F 1580 6LR_i represents the intermediate routers from source to destination. 1581 In this case, 1 <= i <= n, where n is the total number of routers 1582 (6LR) that the packet goes through from source (6LBR) to destination 1583 (RAL). 1585 The 6LBR inserts an RH3, and an RPI. No IPv6-in-IPv6 header is 1586 necessary as the traffic originates with a RPL aware node, the 6LBR. 1587 The destination is known to be RPL-aware because the root knows the 1588 whole topology in non-storing mode. 1590 The Table 6 summarizes what headers are needed for this use case. 1592 +-------------------+----------+-----------+-----------+ 1593 | Header | 6LBR src | 6LR_i | RAL dst | 1594 +-------------------+----------+-----------+-----------+ 1595 | Added headers | RPI, RH3 | -- | -- | 1596 | Modified headers | -- | RPI, RH3 | -- | 1597 | Removed headers | -- | -- | RH3, RPI | 1598 | Untouched headers | -- | -- | -- | 1599 +-------------------+----------+-----------+-----------+ 1601 Table 6: Non-SM: Summary of the use of headers from root to RAL 1603 8.1.3. Non-SM: Example of Flow from root to RUL 1605 In this case the flow comprises: 1607 root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1609 For example, a communication flow could be: Node A (root) --> Node B 1610 --> Node E --> Node G (RUL) 1612 6LR_i represents the intermediate routers from source to destination. 1613 In this case, 1 <= i <= n, where n is the total number of routers 1614 (6LR) that the packet goes through from source (6LBR) to destination 1615 (RUL). 1617 In the 6LBR, the RH3 is added; it is then modified at each 1618 intermediate 6LR (6LR_1 and so on), and it is fully consumed in the 1619 last 6LR (6LR_n) but is left in place. When the RPI is added, the 1620 IPv6 node, which does not understand the RPI, will ignore it (per 1621 [RFC8200]); thus, encapsulation is not necessary. 1623 The Figure 18 depicts the table that summarizes what headers are 1624 needed for this use case. 1626 +-----------+----------+--------------+----------------+----------+ 1627 | Header | 6LBR | 6LR_i | 6LR_n | RUL | 1628 | | src | i=(1,..,n-1) | | dst | 1629 | | | | | | 1630 +-----------+----------+--------------+----------------+----------+ 1631 | Added | RPI, RH3 | -- | -- | -- | 1632 | headers | | | | | 1633 +-----------+----------+--------------+----------------+----------+ 1634 | Modified | -- | RPI, RH3 | RPI, | -- | 1635 | headers | | | RH3(consumed) | | 1636 +-----------+----------+--------------+----------------+----------+ 1637 | Removed | -- | -- | -- | -- | 1638 | headers | | | | | 1639 +-----------+----------+--------------+----------------+----------+ 1640 | Untouched | -- | -- | -- | RPI, RH3 | 1641 | headers | | | | (both | 1642 | | | | | ignored) | 1643 +-----------+----------+--------------+----------------+----------+ 1645 Figure 18: Non-SM: Summary of the use of headers from root to RUL 1647 8.1.4. Non-SM: Example of Flow from RUL to root 1649 In this case the flow comprises: 1651 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR) dst 1653 For example, a communication flow could be: Node G --> Node E --> 1654 Node B --> Node A (root) 1656 6LR_i represents the intermediate routers from source to destination. 1657 In this case, 1 <= i <= n, where n is the total number of routers 1658 (6LR) that the packet goes through from source (RUL) to destination 1659 (6LBR). For example, 6LR_1 (i=1) is the router that receives the 1660 packets from the IPv6 node. 1662 In this case, the RPI is added by the first 6LR (6LR_1) (Node E), 1663 encapsulated in an IPv6-in-IPv6 header, and modified in the 1664 subsequent 6LRs in the flow. The RPI and the entire packet are 1665 consumed by the root. 1667 The Figure 19 shows the table that summarizes what headers are needed 1668 for this use case. 1670 +---------+----+-----------------+-----------------+-----------------+ 1671 | |RUL | | | | 1672 | Header |src | 6LR_1 | 6LR_i | 6LBR dst | 1673 | |node| | | | 1674 +---------+----+-----------------+-----------------+-----------------+ 1675 | Added | -- |IPv6-in-IPv6(RPI)| -- | -- | 1676 | headers | | | | | 1677 +---------+----+-----------------+-----------------+-----------------+ 1678 | Modified| -- | -- |IPv6-in-IPv6(RPI)| -- | 1679 | headers | | | | | 1680 +---------+----+-----------------+-----------------+-----------------+ 1681 | Removed | -- | -- | -- |IPv6-in-IPv6(RPI)| 1682 | headers | | | | | 1683 +---------+----+-----------------+-----------------+-----------------+ 1684 |Untouched| -- | -- | -- | -- | 1685 | headers | | | | | 1686 +---------+----+-----------------+-----------------+-----------------+ 1688 Figure 19: Non-SM: Summary of the use of headers from RUL to root 1690 8.2. Non-Storing Mode: Interaction between Leaf and Internet 1692 This section will describe the communication flow in Non Storing Mode 1693 (Non-SM) between: 1695 RAL to Internet 1697 Internet to RAL 1699 RUL to Internet 1701 Internet to RUL 1703 8.2.1. Non-SM: Example of Flow from RAL to Internet 1705 In this case the flow comprises: 1707 RAL (6LN) src --> 6LR_i --> root (6LBR) --> Internet dst 1709 For example, a communication flow could be: Node F (RAL) --> Node D 1710 --> Node B --> Node A --> Internet 1712 6LR_i represents the intermediate routers from source to destination, 1713 1 <= i <= n, where n is the total number of routers (6LR) that the 1714 packet goes through from source (RAL) to 6LBR. 1716 In this case, the encapsulation from the RAL to the root is optional. 1717 The simplest case is when the RPI gets to the Internet (as the 1718 Table 7 shows it), knowing that the Internet is going to ignore it. 1720 The IPv6 flow label should be set to zero to aid in compression 1721 [RFC8138], and the 6LBR will set it to a non-zero value when sending 1722 towards the Internet [RFC6437]. 1724 The Table 7 summarizes what headers are needed for this use case when 1725 no encapsulation is used. The Table 8 summarizes what headers are 1726 needed for this use case when encapsulation to the root is used. 1728 +-------------------+---------+-------+------+----------------+ 1729 | Header | RAL src | 6LR_i | 6LBR | Internet dst | 1730 +-------------------+---------+-------+------+----------------+ 1731 | Added headers | RPI | -- | -- | -- | 1732 | Modified headers | -- | RPI | -- | -- | 1733 | Removed headers | -- | -- | -- | -- | 1734 | Untouched headers | -- | -- | RPI | RPI (Ignored) | 1735 +-------------------+---------+-------+------+----------------+ 1737 Table 7: Non-SM: Summary of the use of headers from RAL to Internet 1738 with no encapsulation 1740 +-----------+--------------+--------------+--------------+----------+ 1741 | Header | RAL src | 6LR_i | 6LBR | Internet | 1742 | | | | | dst | 1743 +-----------+--------------+--------------+--------------+----------+ 1744 | Added | IPv6-in-IPv6 | -- | -- | -- | 1745 | headers | (RPI) | | | | 1746 | Modified | -- | IPv6-in-IPv6 | -- | -- | 1747 | headers | | (RPI) | | | 1748 | Removed | -- | -- | IPv6-in-IPv6 | -- | 1749 | headers | | | (RPI) | | 1750 | Untouched | -- | -- | -- | -- | 1751 | headers | | | | | 1752 +-----------+--------------+--------------+--------------+----------+ 1754 Table 8: Non-SM: Summary of the use of headers from RAL to Internet 1755 with encapsulation to the root 1757 8.2.2. Non-SM: Example of Flow from Internet to RAL 1759 In this case the flow comprises: 1761 Internet --> root (6LBR) --> 6LR_i --> RAL dst (6LN) 1762 For example, a communication flow could be: Internet --> Node A 1763 (root) --> Node B --> Node D --> Node F (RAL) 1765 6LR_i represents the intermediate routers from source to destination, 1766 1 <= i <= n, where n is the total number of routers (6LR) that the 1767 packet goes through from 6LBR to destination (RAL). 1769 The 6LBR must add an RH3 header. As the 6LBR will know the path and 1770 address of the target node, it can address the IPv6-in-IPv6 header to 1771 that node. The 6LBR will zero the flow label upon entry in order to 1772 aid compression [RFC8138]. 1774 The Table 9 summarizes what headers are needed for this use case. 1776 +-----------+----------+--------------+--------------+--------------+ 1777 | Header | Internet | 6LBR | 6LR_i | RAL dst | 1778 | | src | | | | 1779 +-----------+----------+--------------+--------------+--------------+ 1780 | Added | -- | IPv6-in-IPv6 | -- | -- | 1781 | headers | | (RH3,RPI) | | | 1782 | Modified | -- | -- | IPv6-in-IPv6 | -- | 1783 | headers | | | (RH3,RPI) | | 1784 | Removed | -- | -- | -- | IPv6-in-IPv6 | 1785 | headers | | | | (RH3,RPI) | 1786 | Untouched | -- | -- | -- | -- | 1787 | headers | | | | | 1788 +-----------+----------+--------------+--------------+--------------+ 1790 Table 9: Non-SM: Summary of the use of headers from Internet to RAL 1792 8.2.3. Non-SM: Example of Flow from RUL to Internet 1794 In this case the flow comprises: 1796 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet 1797 dst 1799 For example, a communication flow could be: Node G --> Node E --> 1800 Node B --> Node A --> Internet 1802 6LR_i are the intermediate routers from source to destination, 1 <= i 1803 <= n, where n is the total number of routers (6LRs) that the packet 1804 goes through from the source (RUL) to the 6LBR, e.g., 6LR_1 (i=1). 1806 In this case the flow label is recommended to be zero in the IPv6 1807 node. As RPL headers are added in the IPv6 node packet, the first 1808 6LR (6LR_1) will add an RPI inside a new IPv6-in-IPv6 header. The 1809 IPv6-in-IPv6 header will be addressed to the root. This case is 1810 identical to the storing-mode case (see Section 7.2.3). 1812 The Figure 20 shows the table that summarizes what headers are needed 1813 for this use case. 1815 +---------+----+-------------+--------------+--------------+--------+ 1816 | Header |RUL | 6LR_1 | 6LR_i | 6LBR |Internet| 1817 | |src | | [i=2,..,n] | | dst | 1818 | |node| | | | | 1819 +---------+----+-------------+--------------+--------------+--------+ 1820 | Added | -- |IP6-IP6(RPI) | -- | -- | -- | 1821 | headers | | | | | | 1822 +---------+----+-------------+--------------+--------------+--------+ 1823 | Modified| -- | -- | IP6-IP6(RPI) | -- | -- | 1824 | headers | | | | | | 1825 +---------+----+-------------+--------------+--------------+--------+ 1826 | Removed | -- | -- | -- | IP6-IP6(RPI) | -- | 1827 | headers | | | | | | 1828 +---------+----+-------------+--------------+--------------+--------+ 1829 |Untouched| -- | -- | -- | -- | -- | 1830 | headers | | | | | | 1831 +---------+----+-------------+--------------+--------------+--------+ 1833 Figure 20: Non-SM: Summary of the use of headers from RUL to Internet 1835 8.2.4. Non-SM: Example of Flow from Internet to RUL 1837 In this case the flow comprises: 1839 Internet src --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1841 For example, a communication flow could be: Internet --> Node A 1842 (root) --> Node B --> Node E --> Node G 1844 6LR_i represents the intermediate routers from source to destination, 1845 1 <= i <= n, where n is the total number of routers (6LR) that the 1846 packet goes through from 6LBR to RUL. 1848 The 6LBR must add an RH3 header inside an IPv6-in-IPv6 header. The 1849 6LBR will know the path, and will recognize that the final node is 1850 not a RPL capable node as it will have received the connectivity DAO 1851 from the nearest 6LR. The 6LBR can therefore make the IPv6-in-IPv6 1852 header destination be the last 6LR. The 6LBR will set to zero the 1853 flow label upon entry in order to aid compression [RFC8138]. 1855 The Figure 21 shows the table that summarizes what headers are needed 1856 for this use case. 1858 +----------+--------+------------------+-----------+-----------+-----+ 1859 | Header |Internet| 6LBR | 6LR_i | 6LR_n | RUL | 1860 | | src | | | | dst | 1861 +----------+--------+------------------+-----------+-----------+-----+ 1862 | Added | -- | IP6-IP6(RH3,RPI) | -- | -- | -- | 1863 | headers | | | | | | 1864 +----------+--------+------------------+-----------+-----------+-----+ 1865 | Modified | -- | -- | IP6-IP6 | -- | -- | 1866 | headers | | | (RH3,RPI) | | | 1867 +----------+--------+------------------+-----------+-----------+-----+ 1868 | Removed | -- | -- | -- | IP6-IP6 | -- | 1869 | headers | | | | (RH3,RPI) | | 1870 +----------+--------+------------------+-----------+-----------+-----+ 1871 |Untouched | -- | -- | -- | -- | -- | 1872 | headers | | | | | | 1873 +----------+--------+------------------+-----------+-----------+-----+ 1875 Figure 21: Non-SM: Summary of the use of headers from Internet to 1876 RUL. 1878 8.3. Non-SM: Interaction between leaves 1880 In this section is described the communication flow in Non Storing 1881 Mode (Non-SM) between, 1883 RAL to RAL 1885 RAL to RUL 1887 RUL to RAL 1889 RUL to RUL 1891 8.3.1. Non-SM: Example of Flow from RAL to RAL 1893 In this case the flow comprises: 1895 RAL src --> 6LR_ia --> root (6LBR) --> 6LR_id --> RAL dst 1897 For example, a communication flow could be: Node F (RAL src)--> Node 1898 D --> Node B --> Node A (root) --> Node B --> Node E --> Node H (RAL 1899 dst) 1901 6LR_ia represents the intermediate routers from source to the root, 1 1902 <= ia <= n, where n is the total number of routers (6LR) that the 1903 packet goes through from RAL to the root. 1905 6LR_id represents the intermediate routers from the root to the 1906 destination, 1 <= id <= m, where m is the total number of the 1907 intermediate routers (6LR). 1909 This case involves only nodes in same RPL domain. The originating 1910 node will add an RPI to the original packet, and send the packet 1911 upwards. 1913 The originating node may put the RPI (RPI1) into an IPv6-in-IPv6 1914 header addressed to the root, so that the 6LBR can remove that 1915 header. If it does not, then the RPI1 is forwarded down from the 1916 root in the inner header to no avail. 1918 The 6LBR will need to insert an RH3 header, which requires that it 1919 add an IPv6-in-IPv6 header. It should be able to remove the 1920 RPI(RPI1), as it was contained in an IPv6-in-IPv6 header addressed to 1921 it. Otherwise, there may be an RPI buried inside the inner IP 1922 header, which should get ignored. The root inserts an RPI (RPI2) 1923 alongside the RH3. 1925 Networks that use the RPL P2P extension [RFC6997] are essentially 1926 non-storing DODAGs and fall into this scenario or scenario 1927 Section 8.1.2, with the originating node acting as 6LBR. 1929 The Figure 22 shows the table that summarizes what headers are needed 1930 for this use case when encapsulation to the root takes place. 1932 The Figure 23 shows the table that summarizes what headers are needed 1933 for this use case when there is no encapsulation to the root. 1935 +---------+-------+----------+------------+----------+------------+ 1936 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | RAL | 1937 | | src | | | | dst | 1938 +---------+-------+----------+------------+----------+------------+ 1939 | Added |IP6-IP6| | IP6-IP6 | -- | -- | 1940 | headers |(RPI1) | -- |(RH3-> RAL, | | | 1941 | | | | RPI2) | | | 1942 +---------+-------+----------+------------+----------+------------+ 1943 | Modified| -- | IP6-IP6 | -- | IP6-IP6 | -- | 1944 | headers | | (RPI1) | |(RH3,RPI) | | 1945 +---------+-------+----------+------------+----------+------------+ 1946 | Removed | -- | -- | IP6-IP6 | -- | IP6-IP6 | 1947 | headers | | | (RPI1) | | (RH3, | 1948 | | | | | | RPI2) | 1949 +---------+-------+----------+------------+----------+------------+ 1950 |Untouched| -- | -- | -- | -- | -- | 1951 | headers | | | | | | 1952 +---------+-------+----------+------------+----------+------------+ 1954 Figure 22: Non-SM: Summary of the Use of Headers from RAL to RAL with 1955 encapsulation to the root. 1957 +-----------+------+--------+---------+---------+---------+ 1958 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | RAL | 1959 +-----------+------+--------+---------+---------+---------+ 1960 | Inserted | RPI1 | -- | IP6-IP6 | -- | -- | 1961 | headers | | | (RH3, | | | 1962 | | | | RPI2) | | | 1963 +-----------+------+--------+---------+---------+---------+ 1964 | Modified | -- | RPI1 | -- | IP6-IP6 | -- | 1965 | headers | | | | (RH3, | | 1966 | | | | | RPI2) | | 1967 +-----------+------+--------+---------+---------+---------+ 1968 | Removed | -- | -- | -- | -- | IP6-IP6 | 1969 | headers | | | | | (RH3, | 1970 | | | | | | RPI2) | 1971 | | | | | | RPI1 | 1972 +-----------+------+--------+---------+---------+---------+ 1973 | Untouched | -- | -- | RPI1 | RPI1 | -- | 1974 | headers | | | | | | 1975 +-----------+------+--------+---------+---------+---------+ 1977 Figure 23: Non-SM: Summary of the Use of Headers from RAL to RAL 1978 without encapsulation to the root. 1980 8.3.2. Non-SM: Example of Flow from RAL to RUL 1982 In this case the flow comprises: 1984 RAL --> 6LR_ia --> root (6LBR) --> 6LR_id --> RUL (IPv6 dst node) 1986 For example, a communication flow could be: Node F (RAL) --> Node D 1987 --> Node B --> Node A (root) --> Node B --> Node E --> Node G (RUL) 1989 6LR_ia represents the intermediate routers from source to the root, 1 1990 <= ia <= n, where n is the total number of intermediate routers (6LR) 1992 6LR_id represents the intermediate routers from the root to the 1993 destination, 1 <= id <= m, where m is the total number of the 1994 intermediate routers (6LRs). 1996 As in the previous case, the RAL (6LN) may insert an RPI (RPI1) 1997 header which must be in an IPv6-in-IPv6 header addressed to the root 1998 so that the 6LBR can remove this RPI. The 6LBR will then insert an 1999 RH3 inside a new IPv6-in-IPv6 header addressed to the last 6LR_id 2000 (6LR_id = m) alongside the insertion of RPI2. 2002 If the originating node does not not put the RPI (RPI1) into an IPv6- 2003 in-IPv6 header addressed to the root. Then, the RPI1 is forwarded 2004 down from the root in the inner header to no avail. 2006 The Figure 24 shows the table that summarizes what headers are needed 2007 for this use case when encapsulation to the root takes place. The 2008 Figure 25 shows the table that summarizes what headers are needed for 2009 this use case when no encapsulation to the root takes place. 2011 +-----------+---------+---------+---------+---------+---------+------+ 2012 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | 6LR_m | RUL | 2013 | | src | | | | | dst | 2014 | | node | | | | | node | 2015 +-----------+---------+---------+---------+---------+---------+------+ 2016 | Added | IP6-IP6 | | IP6-IP6 | -- | -- | -- | 2017 | headers | (RPI1) | -- | (RH3, | | | | 2018 | | | | RPI2) | | | | 2019 +-----------+---------+---------+---------+---------+---------+------+ 2020 | Modified | -- | IP6-IP6 | -- | IP6-IP6 | | -- | 2021 | headers | | (RPI1) | | (RH3, | -- | | 2022 | | | | | RPI2) | | | 2023 +-----------+---------+---------+---------+---------+---------+------+ 2024 | Removed | -- | -- | IP6-IP6 | -- | IP6-IP6 | -- | 2025 | headers | | | (RPI1) | | (RH3, | | 2026 | | | | | | RPI2) | | 2027 +-----------+---------+---------+---------+---------+---------+------+ 2028 | Untouched | -- | -- | -- | -- | -- | -- | 2029 | headers | | | | | | | 2030 +-----------+---------+---------+---------+---------+---------+------+ 2032 Figure 24: Non-SM: Summary of the use of headers from RAL to RUL with 2033 encapsulation to the root. 2035 +-----------+------+--------+---------+---------+---------+---------+ 2036 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | 6LR_n | RUL | 2037 | | src | | | | | dst | 2038 | | node | | | | | node | 2039 +-----------+------+--------+---------+---------+---------+---------+ 2040 | Inserted | RPI1 | -- | IP6-IP6 | -- | -- | -- | 2041 | headers | | | (RH3, | | | | 2042 | | | | RPI2) | | | | 2043 +-----------+------+--------+---------+---------+---------+---------+ 2044 | Modified | -- | RPI1 | -- | IP6-IP6 | -- | -- | 2045 | headers | | | | (RH3, | | | 2046 | | | | | RPI2) | | | 2047 +-----------+------+--------+---------+---------+---------+---------+ 2048 | Removed | -- | -- | -- | -- | IP6-IP6 | -- | 2049 | headers | | | | | (RH3, | | 2050 | | | | | | RPI2) | | 2051 +-----------+------+--------+---------+---------+---------+---------+ 2052 | Untouched | -- | -- | RPI1 | RPI1 | RPI1 | RPI1 | 2053 | headers | | | | | |(Ignored)| 2054 +-----------+------+--------+---------+---------+---------+---------+ 2056 Figure 25: Non-SM: Summary of the use of headers from RAL to RUL 2057 without encapsulation to the root. 2059 8.3.3. Non-SM: Example of Flow from RUL to RAL 2061 In this case the flow comprises: 2063 RUL (IPv6 src node) --> 6LR_1 --> 6LR_ia --> root (6LBR) --> 6LR_id 2064 --> RAL dst (6LN) 2066 For example, a communication flow could be: Node G (RUL)--> Node E 2067 --> Node B --> Node A (root) --> Node B --> Node E --> Node H (RAL) 2069 6LR_ia represents the intermediate routers from source to the root, 1 2070 <= ia <= n, where n is the total number of intermediate routers (6LR) 2072 6LR_id represents the intermediate routers from the root to the 2073 destination, 1 <= id <= m, where m is the total number of the 2074 intermediate routers (6LR). 2076 In this scenario the RPI (RPI1) is added by the first 6LR (6LR_1) 2077 inside an IPv6-in-IPv6 header addressed to the root. The 6LBR will 2078 remove this RPI, and add it's own IPv6-in-IPv6 header containing an 2079 RH3 header and an RPI (RPI2). 2081 The Figure 26 shows the table that summarizes what headers are needed 2082 for this use case. 2084 +----------+------+---------+---------+---------+---------+---------+ 2085 | Header | RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id | RAL | 2086 | | src | | | | | dst | 2087 | | node | | | | | node | 2088 +----------+------+---------+---------+---------+---------+---------+ 2089 | Added | -- | IP6-IP6 | -- | IP6-IP6 | -- | -- | 2090 | headers | | (RPI1) | | (RH3, | | | 2091 | | | | | RPI2) | | | 2092 +----------+------+---------+---------+---------+---------+---------+ 2093 | Modified | -- | | IP6-IP6 | -- | IP6-IP6 | -- | 2094 | headers | | -- | (RPI1) | | (RH3, | | 2095 | | | | | | RPI2) | | 2096 +----------+------+---------+---------+---------+---------+---------+ 2097 | Removed | -- | | -- | IP6-IP6 | -- | IP6-IP6 | 2098 | headers | | -- | | (RPI1) | | (RH3, | 2099 | | | | | | | RPI2) | 2100 +----------+------+---------+---------+---------+---------+---------+ 2101 |Untouched | -- | -- | -- | -- | -- | -- | 2102 | headers | | | | | | | 2103 +----------+------+---------+---------+---------+---------+---------+ 2105 Figure 26: Non-SM: Summary of the use of headers from RUL to RAL. 2107 8.3.4. Non-SM: Example of Flow from RUL to RUL 2109 In this case the flow comprises: 2111 RUL (IPv6 src node) --> 6LR_1 --> 6LR_ia --> root (6LBR) --> 6LR_id 2112 --> RUL (IPv6 dst node) 2114 For example, a communication flow could be: Node G --> Node E --> 2115 Node B --> Node A (root) --> Node C --> Node J 2117 6LR_ia represents the intermediate routers from source to the root, 1 2118 <= ia <= n, where n is the total number of intermediate routers (6LR) 2120 6LR_id represents the intermediate routers from the root to the 2121 destination, 1 <= id <= m, where m is the total number of the 2122 intermediate routers (6LR). 2124 This scenario is the combination of the previous two cases. 2126 The Figure 27 shows the table that summarizes what headers are needed 2127 for this use case. 2129 +---------+------+-------+-------+---------+-------+---------+------+ 2130 | Header | RUL | 6LR_1 | 6LR_ia| 6LBR |6LR_id | 6LR_m | RUL | 2131 | | src | | | | | | dst | 2132 | | node | | | | | | node | 2133 +---------+------+-------+-------+---------+-------+---------+------+ 2134 | Added | -- |IP6-IP6| -- | IP6-IP6 | -- | -- | -- | 2135 | headers | | (RPI1)| | (RH3, | | | | 2136 | | | | | RPI2) | | | | 2137 +---------+------+-------+-------+---------+-------+---------+------+ 2138 | Modified| -- | -- |IP6-IP6| -- |IP6-IP6| -- | -- | 2139 | headers | | | (RPI1)| | (RH3, | | | 2140 | | | | | | RPI2)| | | 2141 +---------+------+-------+-------+---------+-------+---------+------+ 2142 | Removed | -- | -- | -- | IP6-IP6 | -- | IP6-IP6 | -- | 2143 | headers | | | | (RPI1) | | (RH3, | | 2144 | | | | | | | RPI2) | | 2145 +---------+------+-------+-------+---------+-------+---------+------+ 2146 |Untouched| -- | -- | -- | -- | -- | -- | -- | 2147 | headers | | | | | | | | 2148 +---------+------+-------+-------+---------+-------+---------+------+ 2150 Figure 27: Non-SM: Summary of the use of headers from RUL to RUL 2152 9. Operational Considerations of supporting RUL-leaves 2154 Roughly half of the situations described in this document involve 2155 leaf ("host") nodes that do not speak RPL. These nodes fall into two 2156 further categories: ones that drop a packet that have RPI or RH3 2157 headers, and ones that continue to process a packet that has RPI and/ 2158 or RH3 headers. 2160 [RFC8200] provides for new rules that suggest that nodes that have 2161 not been configured (explicitly) to examine Hop-by-Hop headers, 2162 should ignore those headers, and continue processing the packet. 2163 Despite this, and despite the switch from 0x63 to 0x23, there may be 2164 hosts that are pre-RFC8200, or simply intolerant. Those hosts will 2165 drop packets that continue to have RPL artifacts in them. In 2166 general, such hosts can not be easily supported in RPL LLNs. 2168 There are some specific cases where it is possible to remove the RPL 2169 artifacts prior to forwarding the packet to the leaf host. The 2170 critical thing is that the artifacts have been inserted by the RPL 2171 root inside an IPv6-in-IPv6 header, and that the header has been 2172 addressed to the 6LR immediately prior to the leaf node. In that 2173 case, in the process of removing the IPv6-in-IPv6 header, the 2174 artifacts can also be removed. 2176 The above case occurs whenever traffic originates from the outside 2177 the LLN (the "Internet" cases above), and non-storing mode is used. 2178 In non-storing mode, the RPL root knows the exact topology (as it 2179 must create the RH3 header) and therefore knows which 6LR is prior to 2180 the leaf. For example, in Figure 6, Node E is the 6LR prior to leaf 2181 Node G, or Node C is the 6LR prior to leaf Node J. 2183 traffic originating from the RPL root (such as when the data 2184 collection system is co-located on the RPL root), does not require an 2185 IPv6-in-IPv6 header (in either mode), as the packet is originating at 2186 the root, and the root can insert the RPI and RH3 headers directly 2187 into the packet, as it is formed. Such a packet is slightly smaller, 2188 but only can be sent to nodes (whether RPL aware or not), that will 2189 tolerate the RPL artifacts. 2191 An operator that finds itself with a lot of traffic from the RPL root 2192 to RPL-not-aware-leaves, will have to do IPv6-in-IPv6 encapsulation 2193 if the leaf is not tolerant of the RPL artifacts. Such an operator 2194 could otherwise omit this unnecessary header if it was certain of the 2195 properties of the leaf. 2197 As storing mode can not know the final path of the traffic, 2198 intolerant (that drop packets with RPL artifacts) leaf nodes can not 2199 be supported. 2201 10. Operational considerations of introducing 0x23 2203 This section describes the operational considerations of introducing 2204 the new RPI Option Type of 0x23. 2206 During bootstrapping the node gets the DIO with the information of 2207 RPI Option Type, indicating the new RPI in the DODAG Configuration 2208 option Flag. The DODAG root is in charge to configure the current 2209 network to the new value, through DIO messages and when all the nodes 2210 are set with the new value. The DODAG should change to a new DODAG 2211 version. In case of rebooting, the node does not remember the RPI 2212 Option Type. Thus, the DIO is sent with a flag indicating the new 2213 RPI Option Type. 2215 The DODAG Configuration option is contained in a RPL DIO message, 2216 which contains a unique DTSN counter. The leaf nodes respond to this 2217 message with DAO messages containing the same DTSN. This is a normal 2218 part of RPL routing; the RPL root therefore knows when the updated 2219 DODAG Configuration option has been seen by all nodes. 2221 Before the migration happens, all the RPL-aware nodes should support 2222 both values . The migration procedure it is triggered when the DIO 2223 is sent with the flag indicating the new RPI Option Type. Namely, it 2224 remains at 0x63 until it is sure that the network is capable of 0x23, 2225 then it abruptly change to 0x23. This options allows to send packets 2226 to not-RPL nodes, which should ignore the option and continue 2227 processing the packets. 2229 In case that a node join to a network that only process 0x63, it 2230 would produce a flag day as was mentioned previously. Indicating the 2231 new RPI in the DODAG Configuration option Flag is a way to avoid the 2232 flag day in a network. It is recommended that a network process both 2233 options to enable interoperability. 2235 11. IANA Considerations 2237 This document updates the registration made in [RFC6553] Destination 2238 Options and Hop-by-Hop Options registry from 0x63 to 0x23 as shown in 2239 Figure 28. 2241 +-------+-------------------+------------------------+---------- -+ 2242 | Hex | Binary Value | Description | Reference | 2243 + Value +-------------------+ + + 2244 | | act | chg | rest | | | 2245 +-------+-----+-----+-------+------------------------+------------+ 2246 | 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)| 2247 +-------+-----+-----+-------+------------------------+------------+ 2248 | 0x63 | 01 | 1 | 00011 | RPL Option(DEPRECATED) | [RFC6553] | 2249 | | | | | |[RFCXXXX](*)| 2250 +-------+-----+-----+-------+------------------------+------------+ 2252 Figure 28: Option Type in RPL Option.(*)represents this document 2254 DODAG Configuration option is updated as follows (Figure 29): 2256 +------------+-----------------+---------------+ 2257 | Bit number | Description | Reference | 2258 +------------+-----------------+---------------+ 2259 | 3 | RPI 0x23 enable | This document | 2260 +------------+-----------------+---------------+ 2262 Figure 29: DODAG Configuration option Flag to indicate the RPI-flag- 2263 day. 2265 12. Security Considerations 2267 The security considerations covered in [RFC6553] and [RFC6554] apply 2268 when the packets are in the RPL Domain. 2270 The IPv6-in-IPv6 mechanism described in this document is much more 2271 limited than the general mechanism described in [RFC2473]. The 2272 willingness of each node in the LLN to decapsulate packets and 2273 forward them could be exploited by nodes to disguise the origin of an 2274 attack. 2276 While a typical LLN may be a very poor origin for attack traffic (as 2277 the networks tend to be very slow, and the nodes often have very low 2278 duty cycles), given enough nodes, LLNs could still have a significant 2279 impact, particularly if attack is targeting another LLN. 2280 Additionally, some uses of RPL involve large backbone ISP scale 2281 equipment [I-D.ietf-anima-autonomic-control-plane], which may be 2282 equipped with multiple 100Gb/s interfaces. 2284 Blocking or careful filtering of IPv6-in-IPv6 traffic entering the 2285 LLN as described above will make sure that any attack that is mounted 2286 must originate from compromised nodes within the LLN. The use of 2287 BCP38 [BCP38] filtering at the RPL root on egress traffic will both 2288 alert the operator to the existence of the attack, as well as drop 2289 the attack traffic. As the RPL network is typically numbered from a 2290 single prefix, which is itself assigned by RPL, BCP38 filtering 2291 involves a single prefix comparison and should be trivial to 2292 automatically configure. 2294 There are some scenarios where IPv6-in-IPv6 traffic should be allowed 2295 to pass through the RPL root, such as the IPv6-in-IPv6 mediated 2296 communications between a new Pledge and the Join Registrar/ 2297 Coordinator (JRC) when using [I-D.ietf-anima-bootstrapping-keyinfra] 2298 and [I-D.ietf-6tisch-dtsecurity-zerotouch-join]. This is the case 2299 for the RPL root to do careful filtering: it occurs only when the 2300 Join Coordinator is not co-located inside the RPL root. 2302 With the above precautions, an attack using IPv6-in-IPv6 tunnels can 2303 only be by a node within the LLN on another node within the LLN. 2304 Such an attack could, of course, be done directly. An attack of this 2305 kind is meaningful only if the source addresses are either fake or if 2306 the point is to amplify return traffic. Such an attack, could also 2307 be done without the use of IPv6-in-IPv6 headers using forged source 2308 addresses. If the attack requires bi-directional communication, then 2309 IPv6-in-IPv6 provides no advantages. 2311 Whenever IPv6-in-IPv6 headers are being proposed, there is a concern 2312 about creating security issues. In the Security Considerations 2313 section of [RFC2473], it was suggested that tunnel entry and exit 2314 points can be secured by securing the IPv6 path between them. This 2315 recommendation is not practical for RPL networks. [RFC5406] goes 2316 into some detail on what additional details would be needed in order 2317 to "Use IPsec". Use of ESP would prevent [RFC8138] compression 2318 (compression must occur before encryption), and [RFC8138] compression 2319 is lossy in a way that prevents use of AH. These are minor issues. 2320 The major issue is how to establish trust enough such that IKEv2 2321 could be used. This would require a system of certificates to be 2322 present in every single node, including any Internet nodes that might 2323 need to communicate with the LLN. Thus, using IPsec requires a 2324 global PKI in the general case. 2326 More significantly, the use of IPsec tunnels to protect the IPv6-in- 2327 IPv6 headers would in the general case scale with the square of the 2328 number of nodes. This is a lot of resource for a constrained nodes 2329 on a constrained network. In the end, the IPsec tunnels would be 2330 providing only BCP38-like origin authentication! That is, IPsec 2331 provides a transitive guarantee to the tunnel exit point that the 2332 tunnel entry point did BCP38 on traffic going in. Just doing origin 2333 filtering per BCP 38 at the entry and exit of the LLN provides a 2334 similar level of security without all the scaling and trust problems 2335 related to IPv6 tunnels as discussed in RFC 2473. IPsec is not 2336 recommended. 2338 An LLN with hostile nodes within it would not be protected against 2339 impersonation with the LLN by entry/exit filtering. 2341 The RH3 header usage described here can be abused in equivalent ways 2342 (to disguise the origin of traffic and attack other nodes) with an 2343 IPv6-in-IPv6 header to add the needed RH3 header. As such, the 2344 attacker's RH3 header will not be seen by the network until it 2345 reaches the end host, which will decapsulate it. An end-host should 2346 be suspicious about an RH3 header which has additional hops which 2347 have not yet been processed, and SHOULD ignore such a second RH3 2348 header. 2350 In addition, the LLN will likely use [RFC8138] to compress the IPv6- 2351 in-IPv6 and RH3 headers. As such, the compressor at the RPL-root 2352 will see the second RH3 header and MAY choose to discard the packet 2353 if the RH3 header has not been completely consumed. A consumed 2354 (inert) RH3 header could be present in a packet that flows from one 2355 LLN, crosses the Internet, and enters another LLN. As per the 2356 discussion in this document, such headers do not need to be removed. 2357 However, there is no case described in this document where an RH3 is 2358 inserted in a non-storing network on traffic that is leaving the LLN, 2359 but this document should not preclude such a future innovation. It 2360 should just be noted that an incoming RH3 must be fully consumed, or 2361 very carefully inspected. 2363 The RPI, if permitted to enter the LLN, could be used by an attacker 2364 to change the priority of a packet by selecting a different 2365 RPLInstanceID, perhaps one with a higher energy cost, for instance. 2366 It could also be that not all nodes are reachable in an LLN using the 2367 default RPLInstanceID, but a change of RPLInstanceID would permit an 2368 attacker to bypass such filtering. Like the RH3, an RPI is to be 2369 inserted by the RPL root on traffic entering the LLN by first 2370 inserting an IPv6-in-IPv6 header. The attacker's RPI therefore will 2371 not be seen by the network. Upon reaching the destination node the 2372 RPI has no further meaning and is just skipped; the presence of a 2373 second RPI will have no meaning to the end node as the packet has 2374 already been identified as being at it's final destination. 2376 The RH3 and RPIs could be abused by an attacker inside of the network 2377 to route packets on non-obvious ways, perhaps eluding observation. 2378 This usage appears consistent with a normal operation of [RFC6997] 2379 and can not be restricted at all. This is a feature, not a bug. 2381 [RFC7416] deals with many other threats to LLNs not directly related 2382 to the use of IPv6-in-IPv6 headers, and this document does not change 2383 that analysis. 2385 Nodes within the LLN can use the IPv6-in-IPv6 mechanism to mount an 2386 attack on another part of the LLN, while disguising the origin of the 2387 attack. The mechanism can even be abused to make it appear that the 2388 attack is coming from outside the LLN, and unless countered, this 2389 could be used to mount a Distributed Denial Of Service attack upon 2390 nodes elsewhere in the Internet. See [DDOS-KREBS] for an example of 2391 such attacks already seen in the real world. 2393 If an attack comes from inside of LLN, it can be alleviated with SAVI 2394 (Source Address Validation Improvement) using [RFC8505] with 2395 [I-D.ietf-6lo-ap-nd]. The attacker will not be able to source 2396 traffic with an address that is not registered, and the registration 2397 process checks for topological correctness. Notice that there is an 2398 L2 authentication in most of the cases. If an attack comes from 2399 outside LLN IPv6-in- IPv6 can be used to hide inner routing headers, 2400 but by construction, the RH3 can typically only address nodes within 2401 the LLN. That is, an RH3 with a CmprI less than 8 , should be 2402 considered an attack (see RFC6554, section 3). 2404 Nodes outside of the LLN will need to pass IPv6-in-IPv6 traffic 2405 through the RPL root to perform this attack. To counter, the RPL 2406 root SHOULD either restrict ingress of IPv6-in-IPv6 packets (the 2407 simpler solution), or it SHOULD walk the IP header extension chain 2408 until it can inspect the upper-layer-payload as described in 2409 [RFC7045]. In particular, the RPL root SHOULD do [BCP38] processing 2410 on the source addresses of all IP headers that it examines in both 2411 directions. 2413 Note: there are some situations where a prefix will spread across 2414 multiple LLNs via mechanisms such as the one described in 2415 [I-D.ietf-6lo-backbone-router]. In this case the BCP38 filtering 2416 needs to take this into account, either by exchanging detailed 2417 routing information on each LLN, or by moving the BCP38 filtering 2418 further towards the Internet, so that the details of the multiple 2419 LLNs do not matter. 2421 13. Acknowledgments 2423 This work is done thanks to the grant given by the StandICT.eu 2424 project. 2426 A special BIG thanks to C. M. Heard for the help with the 2427 Section 4. Much of the redaction in that section is based on his 2428 comments. 2430 Additionally, the authors would like to acknowledge the review, 2431 feedback, and comments of (alphabetical order): Dominique Barthel, 2432 Robert Cragie, Simon Duquennoy, Ralph Droms, Cenk Guendogan, Rahul 2433 Jadhav, Benjamin Kaduk, Matthias Kovatsch, Charlie Perkins, Alvaro 2434 Retana, Peter van der Stok, Xavier Vilajosana, Eric Vyncke and Thomas 2435 Watteyne. 2437 14. References 2439 14.1. Normative References 2441 [BCP38] Ferguson, P. and D. Senie, "Network Ingress Filtering: 2442 Defeating Denial of Service Attacks which employ IP Source 2443 Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, 2444 May 2000, . 2446 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2447 Requirement Levels", BCP 14, RFC 2119, 2448 DOI 10.17487/RFC2119, March 1997, 2449 . 2451 [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion 2452 Notification", RFC 6040, DOI 10.17487/RFC6040, November 2453 2010, . 2455 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 2456 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 2457 DOI 10.17487/RFC6282, September 2011, 2458 . 2460 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 2461 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 2462 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 2463 Low-Power and Lossy Networks", RFC 6550, 2464 DOI 10.17487/RFC6550, March 2012, 2465 . 2467 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 2468 Power and Lossy Networks (RPL) Option for Carrying RPL 2469 Information in Data-Plane Datagrams", RFC 6553, 2470 DOI 10.17487/RFC6553, March 2012, 2471 . 2473 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 2474 Routing Header for Source Routes with the Routing Protocol 2475 for Low-Power and Lossy Networks (RPL)", RFC 6554, 2476 DOI 10.17487/RFC6554, March 2012, 2477 . 2479 [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing 2480 of IPv6 Extension Headers", RFC 7045, 2481 DOI 10.17487/RFC7045, December 2013, 2482 . 2484 [RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power 2485 Wireless Personal Area Network (6LoWPAN) Paging Dispatch", 2486 RFC 8025, DOI 10.17487/RFC8025, November 2016, 2487 . 2489 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 2490 "IPv6 over Low-Power Wireless Personal Area Network 2491 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 2492 April 2017, . 2494 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2495 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2496 May 2017, . 2498 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2499 (IPv6) Specification", STD 86, RFC 8200, 2500 DOI 10.17487/RFC8200, July 2017, 2501 . 2503 [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node 2504 Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, 2505 January 2019, . 2507 14.2. Informative References 2509 [DDOS-KREBS] 2510 Goodin, D., "Record-breaking DDoS reportedly delivered by 2511 >145k hacked cameras", September 2016, 2512 . 2515 [I-D.ietf-6lo-ap-nd] 2516 Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 2517 "Address Protected Neighbor Discovery for Low-power and 2518 Lossy Networks", draft-ietf-6lo-ap-nd-20 (work in 2519 progress), March 2020. 2521 [I-D.ietf-6lo-backbone-router] 2522 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 2523 Backbone Router", draft-ietf-6lo-backbone-router-19 (work 2524 in progress), March 2020. 2526 [I-D.ietf-6tisch-dtsecurity-zerotouch-join] 2527 Richardson, M., "6tisch Zero-Touch Secure Join protocol", 2528 draft-ietf-6tisch-dtsecurity-zerotouch-join-04 (work in 2529 progress), July 2019. 2531 [I-D.ietf-anima-autonomic-control-plane] 2532 Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic 2533 Control Plane (ACP)", draft-ietf-anima-autonomic-control- 2534 plane-24 (work in progress), March 2020. 2536 [I-D.ietf-anima-bootstrapping-keyinfra] 2537 Pritikin, M., Richardson, M., Eckert, T., Behringer, M., 2538 and K. Watsen, "Bootstrapping Remote Secure Key 2539 Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- 2540 keyinfra-38 (work in progress), March 2020. 2542 [I-D.ietf-intarea-tunnels] 2543 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2544 Architecture", draft-ietf-intarea-tunnels-10 (work in 2545 progress), September 2019. 2547 [I-D.ietf-roll-unaware-leaves] 2548 Thubert, P. and M. Richardson, "Routing for RPL Leaves", 2549 draft-ietf-roll-unaware-leaves-11 (work in progress), 2550 March 2020. 2552 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2553 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 2554 December 1998, . 2556 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2557 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2558 December 1998, . 2560 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2561 Control Message Protocol (ICMPv6) for the Internet 2562 Protocol Version 6 (IPv6) Specification", STD 89, 2563 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2564 . 2566 [RFC5406] Bellovin, S., "Guidelines for Specifying the Use of IPsec 2567 Version 2", BCP 146, RFC 5406, DOI 10.17487/RFC5406, 2568 February 2009, . 2570 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 2571 "IPv6 Flow Label Specification", RFC 6437, 2572 DOI 10.17487/RFC6437, November 2011, 2573 . 2575 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 2576 Bormann, "Neighbor Discovery Optimization for IPv6 over 2577 Low-Power Wireless Personal Area Networks (6LoWPANs)", 2578 RFC 6775, DOI 10.17487/RFC6775, November 2012, 2579 . 2581 [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and 2582 J. Martocci, "Reactive Discovery of Point-to-Point Routes 2583 in Low-Power and Lossy Networks", RFC 6997, 2584 DOI 10.17487/RFC6997, August 2013, 2585 . 2587 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 2588 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 2589 2014, . 2591 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 2592 and M. Richardson, Ed., "A Security Threat Analysis for 2593 the Routing Protocol for Low-Power and Lossy Networks 2594 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 2595 . 2597 [RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal 2598 IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) 2599 Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180, 2600 May 2017, . 2602 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 2603 Perkins, "Registration Extensions for IPv6 over Low-Power 2604 Wireless Personal Area Network (6LoWPAN) Neighbor 2605 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 2606 . 2608 Authors' Addresses 2610 Maria Ines Robles 2611 Universidad Tecno. Nac.(UTN)-FRM, Argentina / Aalto University, Finland 2613 Email: mariainesrobles@gmail.com 2614 Michael C. Richardson 2615 Sandelman Software Works 2616 470 Dawson Avenue 2617 Ottawa, ON K1Z 5V7 2618 CA 2620 Email: mcr+ietf@sandelman.ca 2621 URI: http://www.sandelman.ca/mcr/ 2623 Pascal Thubert 2624 Cisco Systems, Inc 2625 Building D 2626 45 Allee des Ormes - BP1200 2627 MOUGINS - Sophia Antipolis 06254 2628 FRANCE 2630 Phone: +33 497 23 26 34 2631 Email: pthubert@cisco.com