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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 Aalto/UTN-FRM 4 Updates: 6553, 6550, 8138 (if approved) M. Richardson 5 Intended status: Standards Track SSW 6 Expires: July 23, 2020 P. Thubert 7 Cisco 8 January 20, 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-34 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 July 23, 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 . . . . . . . . 20 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 . . . . . . . . 22 82 7.2. SM: Interaction between Leaf and Internet. . . . . . . . 23 83 7.2.1. SM: Example of Flow from RAL to Internet . . . . . . 23 84 7.2.2. SM: Example of Flow from Internet to RAL . . . . . . 24 85 7.2.3. SM: Example of Flow from RUL to Internet . . . . . . 25 86 7.2.4. SM: Example of Flow from Internet to RUL. . . . . . . 26 87 7.3. SM: Interaction between Leaf and Leaf . . . . . . . . . . 27 88 7.3.1. SM: Example of Flow from RAL to RAL . . . . . . . . . 27 89 7.3.2. SM: Example of Flow from RAL to RUL . . . . . . . . . 28 90 7.3.3. SM: Example of Flow from RUL to RAL . . . . . . . . . 29 91 7.3.4. SM: Example of Flow from RUL to RUL . . . . . . . . . 30 92 8. Non Storing mode . . . . . . . . . . . . . . . . . . . . . . 31 93 8.1. Non-Storing Mode: Interaction between Leaf and Root . . . 32 94 8.1.1. Non-SM: Example of Flow from RAL to root . . . . . . 33 95 8.1.2. Non-SM: Example of Flow from root to RAL . . . . . . 33 96 8.1.3. Non-SM: Example of Flow from root to RUL . . . . . . 34 97 8.1.4. Non-SM: Example of Flow from RUL to root . . . . . . 35 98 8.2. Non-Storing Mode: Interaction between Leaf and Internet . 36 99 8.2.1. Non-SM: Example of Flow from RAL to Internet . . . . 36 100 8.2.2. Non-SM: Example of Flow from Internet to RAL . . . . 37 101 8.2.3. Non-SM: Example of Flow from RUL to Internet . . . . 38 102 8.2.4. Non-SM: Example of Flow from Internet to RUL . . . . 39 103 8.3. Non-SM: Interaction between Leafs . . . . . . . . . . . . 40 104 8.3.1. Non-SM: Example of Flow from RAL to RAL . . . . . . . 40 105 8.3.2. Non-SM: Example of Flow from RAL to RUL . . . . . . . 42 106 8.3.3. Non-SM: Example of Flow from RUL to RAL . . . . . . . 43 107 8.3.4. Non-SM: Example of Flow from RUL to RUL . . . . . . . 44 108 9. Operational Considerations of supporting 109 RUL-leaves . . . . . . . . . . . . . . . . . . . . . . . . . 45 110 10. Operational considerations of introducing 0x23 . . . . . . . 46 111 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 47 113 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 50 114 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 115 14.1. Normative References . . . . . . . . . . . . . . . . . . 51 116 14.2. Informative References . . . . . . . . . . . . . . . . . 52 117 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 119 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 Type 151 of the RPL Option to make RFC8200 routers ignore this option when not 152 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 GUA or ULA, but could 248 use the link-local addresses) of each node. If the packet must 249 traverse multiple hops, then it must be decapsulated at each hop, and 250 then re-encapsulated again in a similar fashion. 252 Non-Storing Mode (Non-SM): RPL mode of operation in which the RPL- 253 aware-nodes send information to the root about its parents. Thus, 254 the root know the topology, then the intermediate 6LRs do not 255 maintain routing state so that source routing is needed. 257 Storing Mode (SM): RPL mode of operation in which RPL-aware-nodes 258 (6LRs) maintain routing state (of the children) so that source 259 routing is not needed. 261 Note: Due to lack of space in some figures (tables) we refers IPv6- 262 in-IPv6 as IP6-IP6. 264 3. RPL Overview 266 RPL defines the RPL Control messages (control plane), a new ICMPv6 267 [RFC4443] message with Type 155. DIS (DODAG Information 268 Solicitation), DIO (DODAG Information Object) and DAO (Destination 269 Advertisement Object) messages are all RPL Control messages but with 270 different Code values. A RPL Stack is shown in Figure 1. 272 +--------------+ 273 | Upper Layers | 274 | | 275 +--------------+ 276 | RPL | 277 | | 278 +--------------+ 279 | ICMPv6 | 280 | | 281 +--------------+ 282 | IPv6 | 283 | | 284 +--------------+ 285 | 6LoWPAN | 286 | | 287 +--------------+ 288 | PHY-MAC | 289 | | 290 +--------------+ 292 Figure 1: RPL Stack. 294 RPL supports two modes of Downward traffic: in storing mode (SM), it 295 is fully stateful; in non-storing mode (Non-SM), it is fully source 296 routed. A RPL Instance is either fully storing or fully non-storing, 297 i.e. a RPL Instance with a combination of storing and non-storing 298 nodes is not supported with the current specifications at the time of 299 writing this document. 301 4. Updates to RFC6553, RFC6550 and RFC8138 303 4.1. Updates to RFC6550: Advertising External Routes with Non-Storing 304 Mode Signaling. 306 Section 6.7.8. of [RFC6550] introduces the 'E' flag that is set to 307 indicate that the 6LR that generates the DAO redistributes external 308 targets into the RPL network. An external Target is a Target that 309 has been learned through an alternate protocol, for instance a route 310 to a prefix that is outside the RPL domain but reachable via a 6LR. 311 Being outside of the RPL domain, a node that is reached via an 312 external target cannot be guaranteed to ignore the RPL artifacts and 313 cannot be expected to process the [RFC8138] compression correctly. 314 This means that the RPL artifacts should be contained in an IP-in-IP 315 encapsulation that is removed by the 6LR, and that any remaining 316 compression should be expanded by the 6LR before it forwards a packet 317 outside the RPL domain. 319 This specification updates [RFC6550] to RECOMMEND that external 320 targets are advertised using Non-Storing Mode DAO messaging even in a 321 Storing-Mode network. This way, external routes are not advertised 322 within the DODAG and all packets to an external target reach the Root 323 like normal Non-Storing Mode traffic. The Non-Storing Mode DAO 324 informs the Root of the address of the 6LR that injects the external 325 route, and the root uses IP-in-IP encapsulation to that 6LR, which 326 terminates the IP-in-IP tunnel and forwards the original packet 327 outside the RPL domain free of RPL artifacts. In the other 328 direction, for traffic coming from an external target into the LLN, 329 the parent (6LR) that injects the traffic always encapsulates to the 330 root. This whole operation is transparent to intermediate routers 331 that only see traffic between the 6LR and the Root, and only the Root 332 and the 6LRs that inject external routes in the network need to be 333 upgraded to add this function to the network. 335 A RUL is a special case of external target when the target is 336 actually a host and it is known to support a consumed Routing Header 337 and to ignore a HbH header as prescribed by [RFC8200]. The target 338 may have been learned through as a host route or may have been 339 registered to the 6LR using [RFC8505]. IP-in-IP encapsulation MAY be 340 avoided for Root to RUL communication if the RUL is known to process 341 the packets as forwarded by the parent 6LR without decapsulation. 343 In order to enable IP-in-IP all the way to a 6LN, it is beneficial 344 that the 6LN supports decapsulating IP-in-IP, but that is not assumed 345 by [RFC8504]. If the 6LN is a RUL, the Root that encapsulates a 346 packet SHOULD terminate the tunnel at a parent 6LR unless it is aware 347 that the RUL supports IP-in-IP decapsulation. 349 A node that is reachable over an external route is not expected to 350 support [RFC8138]. Whether a decapsulation took place or not and 351 even when the 6LR is delivering the packet to a RUL, the 6LR that 352 injected an external route MUST uncompress the packet before 353 forwarding over that external route. 355 4.2. Updates to RFC6553: Indicating the new RPI Option Type. 357 This modification is required to be able to send, for example, IPv6 358 packets from a RPL-Aware-Leaf to a RPL-unaware node through Internet 359 (see Section 7.2.1), without requiring IPv6-in-IPv6 encapsulation. 361 [RFC6553] (Section 6, Page 7) states as shown in Figure 2, that in 362 the Option Type field of the RPL Option, the two high order bits must 363 be set to '01' and the third bit is equal to '1'. The first two bits 364 indicate that the IPv6 node must discard the packet if it doesn't 365 recognize the Option Type, and the third bit indicates that the 366 Option Data may change in route. The remaining bits serve as the 367 Option Type. 369 +-------+-------------------+----------------+-----------+ 370 | Hex | Binary Value | Description | Reference | 371 + Value +-------------------+ + + 372 | | act | chg | rest | | | 373 +-------+-----+-----+-------+----------------+-----------+ 374 | 0x63 | 01 | 1 | 00011 | RPL Option | [RFC6553] | 375 +-------+-----+-----+-------+----------------+-----------+ 377 Figure 2: Option Type in RPL Option. 379 This document illustrates that is is not always possible to know for 380 sure at the source that a packet will only travel within the RPL 381 domain or may leave it. 383 At the time [RFC6553] was published, leaking a Hop-by-Hop header in 384 the outer IPv6 header chain could potentially impact core routers in 385 the internet. So at that time, it was decided to encapsulate any 386 packet with a RPL Option using IPv6-in-IPv6 in all cases where it was 387 unclear whether the packet would remain within the RPL domain. In 388 the exception case where a packet would still leak, the Option Type 389 would ensure that the first router in the Internet that does not 390 recognize the option would drop the packet and protect the rest of 391 the network. 393 Even with [RFC8138] that compresses the IPv6-in-IPv6 header, this 394 approach yields extra bytes in a packet which means consuming more 395 energy, more bandwidth, incurring higher chances of loss and possibly 396 causing a fragmentation at the 6LoWPAN level. This impacts the daily 397 operation of constrained devices for a case that generally does not 398 happen and would not heavily impact the core anyway. 400 While intention was and remains that the Hop-by-Hop header with a RPL 401 Option should be confined within the RPL domain, this specification 402 modifies this behavior in order to reduce the dependency on IPv6-in- 403 IPv6 and protect the constrained devices. Section 4 of [RFC8200] 404 clarifies the behaviour of routers in the Internet as follows: "it is 405 now expected that nodes along a packet's delivery path only examine 406 and process the Hop-by-Hop Options header if explicitly configured to 407 do so". 409 When unclear about the travel of a packet, it becomes preferable for 410 a source not to encapsulate, accepting the fact that the packet may 411 leave the RPL domain on its way to its destination. In that event, 412 the packet should reach its destination and should not be discarded 413 by the first node that does not recognize the RPL Option. But with 414 the current value of the Option Type, if a node in the Internet is 415 configured to process the Hop-by-Hop header, and if such node 416 encounters an option with the first two bits set to 01 and conforms 417 to [RFC8200], it will drop the packet. Host systems should do the 418 same, irrespective of the configuration. 420 Thus, this document updates the Option Type of the RPL Option 421 [RFC6553], abusively naming it RPI Option Type for simplicity, to 422 (Figure 3): the two high order bits MUST be set to '00' and the third 423 bit is equal to '1'. The first two bits indicate that the IPv6 node 424 MUST skip over this option and continue processing the header 425 ([RFC8200] Section 4.2) if it doesn't recognize the Option Type, and 426 the third bit continues to be set to indicate that the Option Data 427 may change en route. The five rightmost bits remain at 0x3. This 428 ensures that a packet that leaves the RPL domain of an LLN (or that 429 leaves the LLN entirely) will not be discarded when it contains the 430 RPL Option. 432 With the new Option Type, if an IPv6 (intermediate) node (RPL-not- 433 capable) receives a packet with an RPL Option, it should ignore the 434 Hop-by-Hop RPL Option (skip over this option and continue processing 435 the header). This is relevant, as it was mentioned previously, in 436 the case that there is a flow from RAL to Internet (see 437 Section 7.2.1). 439 This is a significant update to [RFC6553]. 441 +-------+-------------------+-------------+------------+ 442 | Hex | Binary Value | Description | Reference | 443 + Value +-------------------+ + + 444 | | act | chg | rest | | | 445 +-------+-----+-----+-------+-------------+------------+ 446 | 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)| 447 +-------+-----+-----+-------+-------------+------------+ 449 Figure 3: Revised Option Type in RPL Option. (*)represents this 450 document 452 Without the signaling described below, this change would otherwise 453 create a lack of interoperation (flag day) for existing networks 454 which are currently using 0x63 as the RPI Option Type value. A move 455 to 0x23 will not be understood by those networks. It is suggested 456 that RPL implementations accept both 0x63 and 0x23 when processing 457 the header. 459 When forwarding packets, implementations SHOULD use the same value as 460 it was received. This is required because, RPI Option Type can not 461 be changed by [RFC8200] - Section 4.2. It allows to the network to 462 be incrementally upgraded, and for the DODAG root to know which parts 463 of the network are upgraded. 465 When originating new packets, implementations SHOULD have an option 466 to determine which value to originate with, this option is controlled 467 by the DIO option described below. 469 The change of RPI Option Type from 0x63 to 0x23, makes all [RFC8200] 470 Section 4.2 compliant nodes tolerant of the RPL artifacts. There is 471 therefore no longer a necessity to remove the artifacts when sending 472 traffic to the Internet. This change clarifies when to use an IPv6- 473 in-IPv6 header, and how to address them: The Hop-by-Hop Options 474 Header containing the RPI MUST always be added when 6LRs originate 475 packets (without IPv6-in-IPv6 headers), and IPv6-in-IPv6 headers MUST 476 always be added when a 6LR find that it needs to insert a Hop-by-Hop 477 Options Header containing the RPL Option. The IPv6-in-IPv6 header is 478 to be addressed to the RPL root when on the way up, and to the end- 479 host when on the way down. 481 In the non-storing case, dealing with not-RPL aware leaf nodes is 482 much easier as the 6LBR (DODAG root) has complete knowledge about the 483 connectivity of all DODAG nodes, and all traffic flows through the 484 root node. 486 The 6LBR can recognize not-RPL aware leaf nodes because it will 487 receive a DAO about that node from the 6LR immediately above that 488 not-RPL aware node. This means that the non-storing mode case can 489 avoid ever using hop-by-hop re-encapsulation headers for traffic 490 originating from the root to the leafs. 492 The non-storing mode case does not require the type change from 0x63 493 to 0x23, as the root can always create the right packet. The type 494 change does not adversely affect the non-storing case. 496 4.3. Updates to RFC6550: Indicating the new RPI in the DODAG 497 Configuration Option Flag. 499 In order to avoid a Flag Day caused by lack of interoperation between 500 new RPI Option Type (0x23) and old RPI Option Type (0x63) nodes, this 501 section defines a flag in the DIO Configuration Option, to indicate 502 when then new RPI Option Type can be safely used. This means, the 503 flag is going to indicate the value of Option Type that the network 504 is using for the RPL Option. Thus, when a node join to a network 505 will know which value to use. With this, RPL-capable nodes know if 506 it is safe to use 0x23 when creating a new RPL Option. A node that 507 forwards a packet with an RPI MUST NOT modify the Option Type of the 508 RPL Option. 510 This is done using a DODAG Configuration Option flag which will 511 signal "RPI 0x23 enable" and propagate through the network. 512 Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP) 513 in the DIO Base Object. The flag is defined only for MOP value 514 between 0 to 6. For a MOP value of 7 or above, the flag MAY indicate 515 something different and MUST NOT be interpreted as "RPI 0x23 enable" 516 unless the specification of the MOP indicates to do so. 518 As stated in [RFC6550] the DODAG Configuration option is present in 519 DIO messages. The DODAG Configuration option distributes 520 configuration information. It is generally static, and does not 521 change within the DODAG. This information is configured at the DODAG 522 root and distributed throughout the DODAG with the DODAG 523 Configuration option. Nodes other than the DODAG root do not modify 524 this information when propagating the DODAG Configuration option. 526 Currently, the DODAG Configuration Option in [RFC6550] states: "the 527 unused bits MUST be initialize to zero by the sender and MUST be 528 ignored by the receiver". If the flag is received with a value zero 529 (which is the default), then new nodes will remain in RFC6553 530 Compatible Mode; originating traffic with the old-RPI Option Type 531 (0x63) value. If the flag is received with a value of 1, then the 532 option value for the RPL Option MUST be set to 0x23. 534 Bit number three of the flag field in the DODAG Configuration option 535 is to be used as shown in Figure 4 : 537 +------------+-----------------+---------------+ 538 | Bit number | Description | Reference | 539 +------------+-----------------+---------------+ 540 | 3 | RPI 0x23 enable | This document | 541 +------------+-----------------+---------------+ 543 Figure 4: DODAG Configuration Option Flag to indicate the RPI-flag- 544 day. 546 In case of rebooting, the node (6LN or 6LR) does not remember the RPI 547 Option Type, that is if the flag is set, so DIO messages sent by the 548 node would be set with the flag unset until a DIO message is received 549 with the flag set indicating the new RPI Option Type. The node sets 550 to 0x23 if the node supports this feature. 552 4.4. Updates to RFC8138: Indicating the way to decompress with the new 553 RPI Option Type. 555 This modification is required to be able to decompress the RPL Option 556 with the new Option Type of 0x23. 558 RPI-6LoRH header provides a compressed form for the RPL RPI [RFC8138] 559 in section 6. A node that is decompressing this header MUST 560 decompress using the RPI Option Type that is currently active: that 561 is, a choice between 0x23 (new) and 0x63 (old). The node will know 562 which to use based upon the presence of the flag in the DODAG 563 Configuration Option defined in Section 4.3. E.g. If the network is 564 in 0x23 mode (by DIO option), then it should be decompressed to 0x23. 566 [RFC8138] section 7 documents how to compress the IPv6-in-IPv6 567 header. 569 There are potential significant advantages to having a single code 570 path that always processes IPv6-in-IPv6 headers with no conditional 571 branches. 573 In Storing Mode, for the examples of Flow from RAL to RUL and RUL to 574 RUL comprise an IPv6-in-IPv6 and RPI compressed headers. The use of 575 the IPv6-in-IPv6 header is MANDATORY in this case, and it SHOULD be 576 compressed with [RFC8138] section 7. Figure 5 illustrates the case 577 in Storing mode where the packet is received from the Internet, then 578 the root encapsulates the packet to insert the RPI. In that example, 579 the leaf is not known to support RFC 8138, and the packet is 580 encapsulated to the 6LR that is the parent and last hop to the final 581 destination. 583 +-+ ... -+-+ ... +-+- ... -+-+- +-+-+-+ ... +-+-+ ... -+++ ... +-... 584 |11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP 585 |Page 1 |Type1 S=0| 6LoRH |6LoRH |LOWPAN_IPHC| UDP | hdr |Payld 586 +-+ ... -+-+ ... +-+- ... -+-+-.+-+-+-+-+ ... +-+-+ ... -+ ... +-... 587 <-4bytes-> <- RFC 6282 -> 588 No RPL artifact 590 Figure 5: RPI Inserted by the Root in Storing Mode 592 In Figure 5, the source of the IPv6-in-IPv6 encapsulation is the 593 Root, so it is elided in the IP-in-IP 6LoRH. The destination is the 594 parent 6LR of the destination of the inner packet so it cannot be 595 elided. It is placed as the single entry in an SRH-6LoRH as the 596 first 6LoRH. There is a single entry so the SRH-6LoRH Size is 0. In 597 that example, the type is 1 so the 6LR address is compressed to 2 598 bytes. It results that the total length of the SRH-6LoRH is 4 bytes. 599 Follows the RPI-6LoRH and then the IP-in-IP 6LoRH. When the IP-in-IP 600 6LoRH is removed, all the router headers that precede it are also 601 removed. The Paging Dispatch [RFC8025] may also be removed if there 602 was no previous Page change to a Page other than 0 or 1, since the 603 LOWPAN_IPHC is encoded in the same fashion in the default Page 0 and 604 in Page 1. The resulting packet to the destination is the inner 605 packet compressed with [RFC6282]. 607 5. Sample/reference topology 609 A RPL network in general is composed of a 6LBR, Backbone Router 610 (6BBR), 6LR and 6LN as leaf logically organized in a DODAG structure. 612 Figure 6 shows the reference RPL Topology for this document. The 613 letters above the nodes are there so that they may be referenced in 614 subsequent sections. In the figure, 6LR represents a full router 615 node. The 6LN is a RPL aware router, or host (as a leaf). 616 Additionally, for simplification purposes, it is supposed that the 617 6LBR has direct access to Internet and is the root of the DODAG, thus 618 the 6BBR is not present in the figure. 620 The 6LN leaves (RAL) marked as (F, H and I) are RPL nodes with no 621 children hosts. 623 The leafs marked as RUL (G and J) are devices which do not speak RPL 624 at all (not-RPL-aware), but uses Router-Advertisements, 6LowPAN DAR/ 625 DAC and efficient-ND only to participate in the network [RFC6775]. 626 In the document these leafs (G and J) are also referred to as an IPv6 627 node. 629 The 6LBR ("A") in the figure is the root of the Global DODAG. 631 +------------+ 632 | INTERNET ----------+ 633 | | | 634 +------------+ | 635 | 636 | 637 | 638 A | 639 +-------+ 640 |6LBR | 641 +-----------|(root) |-------+ 642 | +-------+ | 643 | | 644 | | 645 | | 646 | | 647 | B |C 648 +---|---+ +---|---+ 649 | 6LR | | 6LR | 650 +---------| |--+ +--- ---+ 651 | +-------+ | | +-------+ | 652 | | | | 653 | | | | 654 | | | | 655 | | | | 656 | D | E | | 657 +-|-----+ +---|---+ | | 658 | 6LR | | 6LR | | | 659 | | +------ | | | 660 +---|---+ | +---|---+ | | 661 | | | | | 662 | | +--+ | | 663 | | | | | 664 | | | | | 665 | | | I | J | 666 F | | G | H | | 667 +-----+-+ +-|-----+ +---|--+ +---|---+ +---|---+ 668 | RAL | | RUL | | RAL | | RAL | | RUL | 669 | 6LN | | 6LN | | 6LN | | 6LN | | 6LN | 670 +-------+ +-------+ +------+ +-------+ +-------+ 672 Figure 6: A reference RPL Topology. 674 6. Use cases 676 In the data plane a combination of RFC6553, RFC6554 and IPv6-in-IPv6 677 encapsulation are going to be analyzed for a number of representative 678 traffic flows. 680 This document assumes that the LLN is using the no-drop RPI Option 681 Type of 0x23. 683 The use cases describe the communication in the following cases: - 684 Between RPL-aware-nodes with the root (6LBR) - Between RPL-aware- 685 nodes with the Internet - Between RUL nodes within the LLN (e.g. see 686 Section 7.1.4) - Inside of the LLN when the final destination address 687 resides outside of the LLN (e.g. see Section 7.2.3). 689 The uses cases are as follows: 691 Interaction between Leaf and Root: 693 RAL to root 695 root to RAL 697 RUL to root 699 root to RUL 701 Interaction between Leaf and Internet: 703 RAL to Internet 705 Internet to RAL 707 RUL to Internet 709 Internet to RUL 711 Interaction between Leafs: 713 RAL to RAL 715 RAL to RUL 717 RUL to RAL 719 RUL to RUL 721 This document is consistent with the rule that a Header cannot be 722 inserted or removed on the fly inside an IPv6 packet that is being 723 routed. This is a fundamental precept of the IPv6 architecture as 724 outlined in [RFC8200]. 726 As the rank information in the RPI artifact is changed at each hop, 727 it will typically be zero when it arrives at the DODAG root. The 728 DODAG root MUST force it to zero when passing the packet out to the 729 Internet. The Internet will therefore not see any SenderRank 730 information. 732 Despite being legal to leave the RPI artifact in place, an 733 intermediate router that needs to add an extension header (e.g. RH3 734 or RPL Option) MUST still encapsulate the packet in an (additional) 735 outer IP header. The new header is placed after this new outer IP 736 header. 738 A corollary is that an RH3 or RPL Option can only be removed by an 739 intermediate router if it is placed in an encapsulating IPv6 Header, 740 which is addressed TO the intermediate router. When it does so, the 741 whole encapsulating header must be removed. (A replacement may be 742 added). This sometimes can result in outer IP headers being 743 addressed to the next hop router using link-local address. 745 Both the RPL Option and the RH3 headers may be modified in very 746 specific ways by routers on the path of the packet without the need 747 to add and remove an encapsulating header. Both headers were 748 designed with this modification in mind, and both the RPL RH3 and the 749 RPL Option are marked mutable but recoverable: so an IPsec AH 750 security header can be applied across these headers, but it can not 751 secure the values which mutate. 753 The RPI MUST be present in every single RPL data packet. 755 Prior to [RFC8138], there was significant interest in removing the 756 RPI for downward flows in non-storing mode. The exception covered a 757 very small number of cases, and causes significant interoperability 758 challenges, yet costed significant code and testing complexity. The 759 ability to compress the RPI down to three bytes or less removes much 760 of the pressure to optimize this any further 761 [I-D.ietf-anima-autonomic-control-plane]. 763 The earlier examples are more extensive to make sure that the process 764 is clear, while later examples are more concise. 766 The uses cases are delineated based on the following requirements: 768 The RPIhas to be in every packet that traverses the LLN. 770 - Because of the previous requirement, packets from the Internet 771 have to be encapsulated. 773 - A Header cannot be inserted or removed on the fly inside an IPv6 774 packet that is being routed. 776 - Extension headers may not be added or removed except by the 777 sender or the receiver. 779 - RPI and RH3 headers may be modified by routers on the path of 780 the packet without the need to add and remove an encapsulating 781 header. 783 - An RH3 or RPL Option can only be removed by an intermediate 784 router if it is placed in an encapsulating IPv6 Header, which is 785 addressed to the intermediate router. 787 - Non-storing mode requires downstream encapsulation by root for 788 RH3. 790 The uses cases are delineated based on the following assumptions: 792 This document assumes that the LLN is using the no-drop RPI Option 793 Type (0x23). 795 - Each IPv6 node (including Internet routers) obeys [RFC8200] RFC 796 8200, so that 0x23 RPI Option type can be safely inserted. 798 - All 6LRs obey RFC 8200 [RFC8200]. 800 - The RPI is ignored at the IPv6 dst node (RUL). 802 - In the uses cases, we assume that the RAL supports IP-in-IP 803 encapsulation. 805 - In the uses cases, we dont assume that the RUL supports IP-in-IP 806 encapsulation. 808 - Non-constrained uses of RPL are not in scope of this document. 810 - Compression is based on [RFC8138]. 812 - The flow label [RFC6437] is not needed in RPL. 814 7. Storing mode 816 In storing mode (SM) (fully stateful), the sender can determine if 817 the destination is inside the LLN by looking if the destination 818 address is matched by the DIO's Prefix Information Option (PIO) 819 option. 821 The following table (Figure 7) itemizes which headers are needed in 822 each of the following scenarios. It indicates if the IPv6-in-IPv6 823 header that is added, must be addressed to the final destination (the 824 RAL node that is the target(tgt)), to the "root", or the 6LR parent 825 of a leaf. 827 In cases where no IPv6-in-IPv6 header is needed, the column states as 828 "No". If the IPv6-in-IPv6 header is needed is a "must". 830 In all cases the RPI is needed, since it identifies inconsistencies 831 (loops) in the routing topology. In all cases the RH3 is not needed 832 because it is not used in storing mode. 834 In each case, 6LR_i are the intermediate routers from source to 835 destination. "1 <= i <= n", n is the number of routers (6LR) that 836 the packet goes through from source (6LN) to destination. 838 The leaf can be a router 6LR or a host, both indicated as 6LN. The 839 root refers to the 6LBR (see Figure 6). 841 +---------------------+--------------+------------+------------------+ 842 | Interaction between | Use Case |IPv6-in-IPv6| IPv6-in-IPv6 dst | 843 +---------------------+--------------+------------+------------------+ 844 | | RAL to root | No | No | 845 + +--------------+------------+------------------+ 846 | Leaf - Root | root to RAL | No | No | 847 + +--------------+------------+------------------+ 848 | | root to RUL | No | No | 849 + +--------------+------------+------------------+ 850 | | RUL to root | must | root | 851 +---------------------+--------------+------------+------------------+ 852 | | RAL to Int | No | No | 853 + +--------------+------------+------------------+ 854 | Leaf - Internet | Int to RAL | must | RAL (tgt) | 855 + +--------------+------------+------------------+ 856 | | RUL to Int | must | root | 857 + +--------------+------------+------------------+ 858 | | Int to RUL | must | 6LR | 859 +---------------------+--------------+------------+------------------+ 860 | | RAL to RAL | No | No | 861 + +--------------+------------+------------------+ 862 | | RAL to RUL | No | No | 863 + Leaf - Leaf +--------------+------------+------------------+ 864 | | RUL to RAL | must | root/RAL(tgt) | 865 + +--------------+------------+------------------+ 866 | | RUL to RUL | must | root/6LR | 867 +---------------------+--------------+------------+------------------+ 869 Figure 7: Table of IPv6-in-IPv6 encapsulation in Storing mode. 871 7.1. Storing Mode: Interaction between Leaf and Root 873 In this section is described the communication flow in storing mode 874 (SM) between, 876 RAL to root 878 root to RAL 880 RUL to root 882 root to RUL 884 7.1.1. SM: Example of Flow from RAL to root 886 In storing mode, RFC 6553 (RPI) is used to send RPL Information 887 instanceID and rank information. 889 In this case the flow comprises: 891 RAL (6LN) --> 6LR_i --> root(6LBR) 893 For example, a communication flow could be: Node F (6LN) --> Node D 894 (6LR_i) --> Node B (6LR_i)--> Node A root(6LBR) 896 The RAL (Node F) inserts the RPI, and sends the packet to 6LR (Node 897 D) which decrements the rank in the RPI and sends the packet up. 898 When the packet arrives at 6LBR (Node A), the RPI is removed and the 899 packet is processed. 901 No IPv6-in-IPv6 header is required. 903 The RPI can be removed by the 6LBR because the packet is addressed to 904 the 6LBR. The RAL must know that it is communicating with the 6LBR 905 to make use of this scenario. The RAL can know the address of the 906 6LBR because it knows the address of the root via the DODAGID in the 907 DIO messages. 909 The Table 1 summarizes what headers are needed for this use case. 911 +-------------------+---------+-------+----------+ 912 | Header | RAL src | 6LR_i | 6LBR dst | 913 +-------------------+---------+-------+----------+ 914 | Added headers | RPI | -- | -- | 915 | Modified headers | -- | RPI | -- | 916 | Removed headers | -- | -- | RPI | 917 | Untouched headers | -- | -- | -- | 918 +-------------------+---------+-------+----------+ 920 Table 1: SM: Summary of the use of headers from RAL to root 922 7.1.2. SM: Example of Flow from root to RAL 924 In this case the flow comprises: 926 root (6LBR) --> 6LR_i --> RAL (6LN) 928 For example, a communication flow could be: Node A root(6LBR) --> 929 Node B (6LR_i) --> Node D (6LR_i) --> Node F (6LN) 931 In this case the 6LBR inserts RPI and sends the packet down, the 6LR 932 is going to increment the rank in RPI (it examines the instanceID to 933 identify the right forwarding table), the packet is processed in the 934 RAL and the RPI removed. 936 No IPv6-in-IPv6 header is required. 938 The Table 2 summarizes what headers are needed for this use case. 940 +-------------------+----------+-------+---------+ 941 | Header | 6LBR src | 6LR_i | RAL dst | 942 +-------------------+----------+-------+---------+ 943 | Added headers | RPI | -- | -- | 944 | Modified headers | -- | RPI | -- | 945 | Removed headers | -- | -- | RPI | 946 | Untouched headers | -- | -- | -- | 947 +-------------------+----------+-------+---------+ 949 Table 2: SM: Summary of the use of headers from root to RAL 951 7.1.3. SM: Example of Flow from root to RUL 953 In this case the flow comprises: 955 root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 957 For example, a communication flow could be: Node A (6LBR) --> Node B 958 (6LR_i) --> Node E (6LR_i) --> Node G (RUL) 960 As the RPI extension can be ignored by the RUL, this situation is 961 identical to the previous scenario. 963 The Table 3 summarizes what headers are needed for this use case. 965 +-------------------+----------+-------+----------------------+ 966 | Header | 6LBR src | 6LR_i | RUL (IPv6 dst node) | 967 +-------------------+----------+-------+----------------------+ 968 | Added headers | RPI | -- | -- | 969 | Modified headers | -- | RPI | -- | 970 | Removed headers | -- | -- | -- | 971 | Untouched headers | -- | -- | RPI (Ignored) | 972 +-------------------+----------+-------+----------------------+ 974 Table 3: SM: Summary of the use of headers from root to RUL 976 7.1.4. SM: Example of Flow from RUL to root 978 In this case the flow comprises: 980 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR) 982 For example, a communication flow could be: Node G (RUL) --> Node E 983 (6LR_1)--> Node B (6LR_i)--> Node A root(6LBR) 984 When the packet arrives from IPv6 node (Node G) to 6LR_1 (Node E), 985 the 6LR_1 will insert a RPI, encapsulated in a IPv6-in-IPv6 header. 986 The IPv6-in-IPv6 header is addressed to the root (Node A). The root 987 removes the header and processes the packet. 989 The Figure 8 shows the table that summarizes what headers are needed 990 for this use case where the IPv6-in-IPv6 header is addressed to the 991 root (Node A). 993 +-----------+------+--------------+-----------------+------------------+ 994 | Header | RUL | 6LR_1 | 6LR_i | 6LBR dst | 995 | | src | | | | 996 | | node | | | | 997 +-----------+------+--------------+-----------------+------------------+ 998 | Added | -- | IP6-IP6(RPI) | | -- | 999 | headers | | | | | 1000 +-----------+------+--------------+-----------------+------------------+ 1001 | Modified | -- | -- | IP6-IP6(RPI) | -- | 1002 | headers | | | | | 1003 +-----------+------+--------------+-----------------+------------------+ 1004 | Removed | -- | -- | | IP6-IP6(RPI) | 1005 | headers | | | | | 1006 +-----------+------+--------------+-----------------+------------------+ 1007 | Untouched | -- | -- | -- | -- | 1008 | headers | | | | | 1009 +-----------+------+--------------+-----------------+------------------+ 1011 Figure 8: SM: Summary of the use of headers from RUL to root. 1013 7.2. SM: Interaction between Leaf and Internet. 1015 In this section is described the communication flow in storing mode 1016 (SM) between, 1018 RAL to Internet 1020 Internet to RAL 1022 RUL to Internet 1024 Internet to RUL 1026 7.2.1. SM: Example of Flow from RAL to Internet 1028 RPL information from RFC 6553 may go out to Internet as it will be 1029 ignored by nodes which have not been configured to be RPI aware. 1031 In this case the flow comprises: 1033 RAL (6LN) --> 6LR_i --> root (6LBR) --> Internet 1035 For example, the communication flow could be: Node F (RAL) --> Node D 1036 (6LR_i)--> Node B (6LR_i)--> Node A root(6LBR) --> Internet 1038 No IPv6-in-IPv6 header is required. 1040 Note: In this use case, it is used a node as leaf, but this use case 1041 can be also applicable to any RPL-aware-node type (e.g. 6LR) 1043 The Table 4 summarizes what headers are needed for this use case. 1045 +-------------------+---------+-------+------+----------------+ 1046 | Header | RAL src | 6LR_i | 6LBR | Internet dst | 1047 +-------------------+---------+-------+------+----------------+ 1048 | Added headers | RPI | -- | -- | -- | 1049 | Modified headers | -- | RPI | -- | -- | 1050 | Removed headers | -- | -- | -- | -- | 1051 | Untouched headers | -- | -- | RPI | RPI (Ignored) | 1052 +-------------------+---------+-------+------+----------------+ 1054 Table 4: SM: Summary of the use of headers from RAL to Internet 1056 7.2.2. SM: Example of Flow from Internet to RAL 1058 In this case the flow comprises: 1060 Internet --> root (6LBR) --> 6LR_i --> RAL (6LN) 1062 For example, a communication flow could be: Internet --> Node A 1063 root(6LBR) --> Node B (6LR_1) --> Node D (6LR_n) --> Node F (RAL) 1065 When the packet arrives from Internet to 6LBR the RPI is added in a 1066 outer IPv6-in-IPv6 header (with the IPv6-in-IPv6 destination address 1067 set to the RAL) and sent to 6LR, which modifies the rank in the RPI. 1068 When the packet arrives at the RAL the RPI is removed and the packet 1069 processed. 1071 The Figure 9 shows the table that summarizes what headers are needed 1072 for this use case. 1074 +-----------+----------+--------------+--------------+--------------+ 1075 | Header | Internet | 6LBR | 6LR_i | RAL dst | 1076 | | src | | | | 1077 +-----------+----------+--------------+--------------+--------------+ 1078 | Added | -- | IP6-IP6(RPI) | -- | -- | 1079 | headers | | | | | 1080 +-----------+----------+--------------+--------------+--------------+ 1081 | Modified | -- | -- | IP6-IP6(RPI) | -- | 1082 | headers | | | | | 1083 +-----------+----------+--------------+--------------+--------------+ 1084 | Removed | -- | -- | -- | IP6-IP6(RPI) | 1085 | headers | | | | | 1086 +-----------+----------+--------------+--------------+--------------+ 1087 | Untouched | -- | -- | -- | -- | 1088 | headers | | | | | 1089 +-----------+----------+--------------+--------------+--------------+ 1091 Figure 9: SM: Summary of the use of headers from Internet to RAL. 1093 7.2.3. SM: Example of Flow from RUL to Internet 1095 In this case the flow comprises: 1097 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet 1099 For example, a communication flow could be: Node G (RUL)--> Node E 1100 (6LR_1)--> Node B (6lR_i) --> Node A root(6LBR) --> Internet 1102 The 6LR_1 (i=1) node will add an IPv6-in-IPv6(RPI) header addressed 1103 to the root such that the root can remove the RPI before passing 1104 upwards. The IPv6-in-IPv6 addressed to the root cause less 1105 processing overhead. In the intermindiate 6LR the rank in the RPI is 1106 modified. 1108 The originating node will ideally leave the IPv6 flow label as zero 1109 so that the packet can be better compressed through the LLN. The 1110 6LBR will set the flow label of the packet to a non-zero value when 1111 sending to the Internet, for details check [RFC6437]. 1113 The Figure 10 shows the table that summarizes what headers are needed 1114 for this use case. 1116 +---------+-------+------------+--------------+-------------+--------+ 1117 | Header | IPv6 | 6LR_1 | 6LR_i | 6LBR |Internet| 1118 | | src | | [i=2,...,n] | | dst | 1119 | | node | | | | | 1120 | | (RUL) | | | | | 1121 +---------+-------+------------+--------------+-------------+--------+ 1122 | Added | -- |IP6-IP6(RPI)| -- | -- | -- | 1123 | headers | | | | | | 1124 +---------+-------+------------+--------------+-------------+--------+ 1125 | Modified| -- | -- | IP6-IP6(RPI) | -- | -- | 1126 | headers | | | | | | 1127 +---------+-------+------------+--------------+-------------+--------+ 1128 | Removed | -- | -- | -- | IP6-IP6(RPI)| -- | 1129 | headers | | | | | | 1130 +---------+-------+------------+--------------+-------------+--------+ 1131 |Untouched| -- | -- | -- | -- | -- | 1132 | headers | | | | | | 1133 +---------+-------+------------+--------------+-------------+--------+ 1135 Figure 10: SM: Summary of the use of headers from RUL to Internet. 1137 7.2.4. SM: Example of Flow from Internet to RUL. 1139 In this case the flow comprises: 1141 Internet --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1143 For example, a communication flow could be: Internet --> Node A 1144 root(6LBR) --> Node B (6LR_i)--> Node E (6LR_n) --> Node G (RUL) 1146 The 6LBR will have to add an RPI within an IPv6-in-IPv6 header. The 1147 IPv6-in-IPv6 is addressed to the 6LR parent of the RUL. 1149 Further details about this are mentioned in 1150 [I-D.ietf-roll-unaware-leaves], which specifies RPL routing for a 6LN 1151 acting as a plain host and not being aware of RPL. 1153 The 6LBR may set the flow label on the inner IPv6-in-IPv6 header to 1154 zero in order to aid in compression [RFC8138][RFC6437]. 1156 The Figure 11 shows the table that summarizes what headers are needed 1157 for this use case. 1159 +---------+-------+------------+--------------+-------------+--------+ 1160 | Header |Inter- | 6LBR | 6LR_i | 6LR_n | RUL | 1161 | | net | |[i=1,..,n-1] | | dst | 1162 | | src | | | | | 1163 | | | | | | | 1164 +---------+-------+------------+--------------+-------------+--------+ 1165 | Inserted| -- |IP6-IP6(RPI)| | -- | -- | 1166 | headers | | | | | | 1167 +---------+-------+------------+--------------+-------------+--------+ 1168 | Modified| -- | -- | IP6-IP6(RPI) | -- | -- | 1169 | headers | | | | | | 1170 +---------+-------+------------+--------------+-------------+--------+ 1171 | Removed | -- | -- | | IP6-IP6(RPI)| -- | 1172 | headers | | | | | | 1173 +---------+-------+------------+--------------+-------------+--------+ 1174 |Untouched| -- | -- | -- | -- | -- | 1175 | headers | | | | | | 1176 +---------+-------+------------+--------------+-------------+--------+ 1178 Figure 11: SM: Summary of the use of headers from Internet to RUL. 1180 7.3. SM: Interaction between Leaf and Leaf 1182 In this section is described the communication flow in storing mode 1183 (SM) between, 1185 RAL to RAL 1187 RAL to RUL 1189 RUL to RAL 1191 RUL to RUL 1193 7.3.1. SM: Example of Flow from RAL to RAL 1195 In [RFC6550] RPL allows a simple one-hop optimization for both 1196 storing and non-storing networks. A node may send a packet destined 1197 to a one-hop neighbor directly to that node. See section 9 in 1198 [RFC6550]. 1200 When the nodes are not directly connected, then in storing mode, the 1201 flow comprises: 1203 RAL src (6LN) --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> RAL 1204 dst (6LN) 1205 For example, a communication flow could be: Node F (RAL src)--> Node 1206 D (6LR_ia)--> Node B (6LR_x) --> Node E (6LR_id) --> Node H (RAL dst) 1208 6LR_ia (Node D) are the intermediate routers from source to the 1209 common parent (6LR_x) (Node B). In this case, 1 <= ia <= n, n is the 1210 number of routers (6LR) that the packet goes through from RAL (Node 1211 F) to the common parent 6LR_x (Node B). 1213 6LR_id (Node E) are the intermediate routers from the common parent 1214 (6LR_x) (Node B) to destination RAL (Node H). In this case, 1 <= id 1215 <= m, m is the number of routers (6LR) that the packet goes through 1216 from the common parent (6LR_x) to destination RAL (Node H). 1218 It is assumed that the two nodes are in the same RPL Domain (that 1219 they share the same DODAG root). At the common parent (Node B), the 1220 direction of RPI is changed (from decreasing to increasing the rank). 1222 While the 6LR nodes will update the RPI, no node needs to add or 1223 remove the RPI, so no IPv6-in-IPv6 headers are necessary. 1225 The Table 5 summarizes what headers are needed for this use case. 1227 +---------------+--------+--------+---------------+--------+--------+ 1228 | Header | RAL | 6LR_ia | 6LR_x (common | 6LR_id | RAL | 1229 | | src | | parent) | | dst | 1230 +---------------+--------+--------+---------------+--------+--------+ 1231 | Added headers | RPI | -- | -- | -- | -- | 1232 | Modified | -- | RPI | RPI | RPI | -- | 1233 | headers | | | | | | 1234 | Removed | -- | -- | -- | -- | RPI | 1235 | headers | | | | | | 1236 | Untouched | -- | -- | -- | -- | -- | 1237 | headers | | | | | | 1238 +---------------+--------+--------+---------------+--------+--------+ 1240 Table 5: SM: Summary of the use of headers for RAL to RAL 1242 7.3.2. SM: Example of Flow from RAL to RUL 1244 In this case the flow comprises: 1246 RAL src (6LN) --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> RUL 1247 (IPv6 dst node) 1249 For example, a communication flow could be: Node F (RAL)--> Node D 1250 --> Node B --> Node E --> Node G (RUL) 1251 6LR_ia are the intermediate routers from source (RAL) to the common 1252 parent (6LR_x) In this case, 1 <= ia <= n, n is the number of routers 1253 (6LR) that the packet goes through from RAL to the common parent 1254 (6LR_x). 1256 6LR_id (Node E) are the intermediate routers from the common parent 1257 (6LR_x) (Node B) to destination RUL (Node G). In this case, 1 <= id 1258 <= m, m is the number of routers (6LR) that the packet goes through 1259 from the common parent (6LR_x) to destination RUL. The packet from 1260 the RAL goes to 6LBR because the route to the RUL is not injected 1261 into the RPL-SM. 1263 The Table 6 summarizes what headers are needed for this use case. 1265 +-----------------+---------+--------+------+--------+--------------+ 1266 | Header | RAL src | 6LR_ia | 6LBR | 6LR_id | RUL dst | 1267 +-----------------+---------+--------+------+--------+--------------+ 1268 | Added headers | RPI | -- | -- | -- | -- | 1269 | Modified | -- | RPI | RPI | RPI | -- | 1270 | headers | | | | | | 1271 | Removed headers | -- | -- | -- | -- | -- | 1272 | Untouched | -- | -- | -- | -- | RPI(Ignored) | 1273 | headers | | | | | | 1274 +-----------------+---------+--------+------+--------+--------------+ 1276 Table 6: SM: Summary of the use of headers for RAL to RUL 1278 7.3.3. SM: Example of Flow from RUL to RAL 1280 In this case the flow comprises: 1282 RUL (IPv6 src node) --> 6LR_ia --> 6LBR --> 6LR_id --> RAL dst (6LN) 1284 For example, a communication flow could be: Node G (RUL)--> Node E 1285 --> Node B --> Node A --> Node B --> Node D --> Node F (RAL) 1287 6LR_ia (Node E) are the intermediate routers from source (RUL) (Node 1288 G) to the root (Node A). In this case, 1 <= ia <= n, n is the number 1289 of routers (6LR) that the packet goes through from source to the 1290 root. 1292 6LR_id are the intermediate routers from the root (Node A) to 1293 destination RAL (Node F). In this case, 1 <= id <= m, m is the 1294 number of routers (6LR) that the packet goes through from the root to 1295 the destination RAL. 1297 The 6LR_ia (ia=1) (Node E) receives the packet from the RUL (Node G) 1298 and inserts the RPI (RPI1) encapsulated in a IPv6-in-IPv6 header to 1299 the root. The root removes the outer header including the RPI (RPI1) 1300 and inserts a new RPI (RPI2) addressed to the destination RAL (Node 1301 F). 1303 The Figure 12 shows the table that summarizes what headers are needed 1304 for this use case. 1306 +-----------+------+---------+---------+---------+---------+---------+ 1307 | Header | RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id | RAL | 1308 | | src | | | | | dst | 1309 | | node | | | | | node | 1310 +-----------+------+---------+---------+---------+---------+---------+ 1311 | Added | -- | IP6-IP6 | -- | IP6-IP6 | -- | -- | 1312 | headers | | (RPI1) | | (RPI2) | | | 1313 | | | | | | | | 1314 +-----------+------+---------+---------+---------+---------+---------+ 1315 | Modified | -- | | IP6-IP6 | -- | IP6-IP6 | -- | 1316 | headers | | | (RPI1) | | (RPI2) | | 1317 | | | | | | | | 1318 +-----------+------+---------+---------+---------+---------+---------+ 1319 | Removed | -- | | -- | IP6-IP6 | -- | IP6-IP6 | 1320 | headers | | | | (RPI1) | | (RPI2) | 1321 | | | | | | | | 1322 +-----------+------+---------+---------+---------+---------+---------+ 1323 | Untouched | -- | | -- | -- | -- | -- | 1324 | headers | | | | | | | 1325 +-----------+------+---------+---------+---------+---------+---------+ 1327 Figure 12: SM: Summary of the use of headers from RUL to RAL. 1329 7.3.4. SM: Example of Flow from RUL to RUL 1331 In this case the flow comprises: 1333 RUL (IPv6 src node)--> 6LR_1--> 6LR_ia --> 6LBR --> 6LR_id --> RUL 1334 (IPv6 dst node) 1336 For example, a communication flow could be: Node G (RUL src)--> Node 1337 E --> Node B --> Node A (root) --> Node C --> Node J (RUL dst) 1339 Internal nodes 6LR_ia (e.g: Node E or Node B) is the intermediate 1340 router from the RUL source (Node G) to the root (6LBR) (Node A). In 1341 this case, "1 < ia <= n", n is the number of routers (6LR) that the 1342 packet goes through from the RUL to the root. 1344 6LR_id (Node C) are the intermediate routers from the root (Node A) 1345 to the destination RUL dst node (Node J). In this case, 1 <= id <= 1346 m, m is the number of routers (6LR) that the packet goes through from 1347 the root to destination RUL. 1349 The RPI is ignored at the RUL dst node. 1351 The 6LR_1 (Node E) receives the packet from the RUL (Node G) and 1352 inserts the RPI (RPI), encapsulated in an IPv6-in-IPv6 header 1353 directed to the root. The root removes the outer header including 1354 the RPI (RPI1) and inserts a new RPI (RPI2) addressed to the 6LR 1355 father of the RUL. 1357 The Figure 13 shows the table that summarizes what headers are needed 1358 for this use case. 1360 +---------+----+-------------+--------+---------+--------+-------+---+ 1361 | Header |RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id |6LR_n |RUL| 1362 | |src | | | | | |dst| 1363 | | | | | | | | | 1364 +---------+----+-------------+--------+---------+--------+-------+---+ 1365 | Added | -- |IP6-IP6(RPI1)| -- | IP6-IP6 | -- | -- | --| 1366 | Headers | | | | (RPI2) | | | | 1367 +---------+----+-------------+--------+---------+--------+-------+---+ 1368 |Modified | -- | -- |IP6-IP6 | -- |IP6-IP6 | -- | --| 1369 |headers | | | (RPI1) | | (RPI2) | | | 1370 +---------+----+-------------+--------+---------+--------+-------+---+ 1371 | Removed | -- | -- | -- | IP6-IP6 | -- |IP6-IP6| --| 1372 | headers | | | | (RPI1) | | (RPI2)| | 1373 +---------+----+-------------+--------+---------+--------+-------+---+ 1374 |Untouched| -- | -- | -- | -- | -- | -- | --| 1375 | headers | | | | | | | | 1376 +---------+----+-------------+--------+---------+--------+-------+---+ 1378 Figure 13: SM: Summary of the use of headers from RUL to RUL 1380 8. Non Storing mode 1382 In Non Storing Mode (Non-SM) (fully source routed), the 6LBR (DODAG 1383 root) has complete knowledge about the connectivity of all DODAG 1384 nodes, and all traffic flows through the root node. Thus, there is 1385 no need for all nodes to know about the existence of RPL-unaware 1386 nodes. Only the 6LBR needs to act if compensation is necessary for 1387 not-RPL aware receivers. 1389 The table (Figure 14) summarizes what headers are needed in the 1390 following scenarios, and indicates when the RPI, RH3 and IPv6-in-IPv6 1391 header are to be inserted. It depicts the target destination address 1392 possible to a 6LN (indicated by "RAL"), to a 6LR (parent of a 6LN) or 1393 to the root. In cases where no IPv6-in-IPv6 header is needed, the 1394 column states as "No". There is no expectation on RPL that RPI can 1395 be omitted, because it is needed for routing, quality of service and 1396 compression. This specification expects that is always a RPI 1397 Present. 1399 The leaf can be a router 6LR or a host, both indicated as 6LN 1400 (Figure 6). In the table (Figure 14) the (1) indicates a 6tisch case 1401 [RFC8180], where the RPI may still be needed for the instanceID to be 1402 available for priority/channel selection at each hop. 1404 +-----------------+--------------+-----+-----+------------+------------+ 1405 | Interaction | Use Case | RPI | RH3 |IPv6-in-IPv6|IPv6-in-IPv6| 1406 | between | | | | | dst | 1407 +-----------------+--------------+-----+-----+------------+------------+ 1408 | | RAL to root | Yes | No | No | No | 1409 + +--------------+-----+-----+------------+------------+ 1410 | Leaf - Root | root to RAL | Yes | Yes | No | No | 1411 + +--------------+-----+-----+------------+------------+ 1412 | | root to RUL | Yes | Yes | must | 6LR | 1413 | | | (1) | | | | 1414 + +--------------+-----+-----+------------+------------+ 1415 | | RUL to root | Yes | No | must | root | 1416 +-----------------+--------------+-----+-----+------------+------------+ 1417 | | RAL to Int | Yes | No | No | No | 1418 + +--------------+-----+-----+------------+------------+ 1419 | Leaf - Internet | Int to RAL | Yes | Yes | must | RAL | 1420 + +--------------+-----+-----+------------+------------+ 1421 | | RUL to Int | Yes | No | must | root | 1422 + +--------------+-----+-----+------------+------------+ 1423 | | Int to RUL | Yes | Yes | must | 6LR | 1424 +-----------------+--------------+-----+-----+------------+------------+ 1425 | | RAL to RAL | Yes | Yes | must | root/RAL | 1426 + +--------------+-----+-----+------------+------------+ 1427 | | RAL to RUL | Yes | Yes | must | root/6LR | 1428 + Leaf - Leaf +--------------+-----+-----+------------+------------+ 1429 | | RUL to RAL | Yes | Yes | must | root/RAL | 1430 + +--------------+-----+-----+------------+------------+ 1431 | | RUL to RUL | Yes | Yes | must | root/6LR | 1432 +-----------------+--------------+-----+-----+------------+------------+ 1434 Figure 14: Table that shows headers needed in Non-Storing mode: RPI, 1435 RH3, IPv6-in-IPv6 encapsulation. 1437 8.1. Non-Storing Mode: Interaction between Leaf and Root 1439 In this section is described the communication flow in Non Storing 1440 Mode (Non-SM) between, 1441 RAL to root 1443 root to RAL 1445 RUL to root 1447 root to RUL 1449 8.1.1. Non-SM: Example of Flow from RAL to root 1451 In non-storing mode the leaf node uses default routing to send 1452 traffic to the root. The RPI must be included since it contains the 1453 rank information, which is used to avoid/detect loops. 1455 RAL (6LN) --> 6LR_i --> root(6LBR) 1457 For example, a communication flow could be: Node F --> Node D --> 1458 Node B --> Node A (root) 1460 6LR_i are the intermediate routers from source to destination. In 1461 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1462 packet goes through from source (RAL) to destination (6LBR). 1464 This situation is the same case as storing mode. 1466 The Table 7 summarizes what headers are needed for this use case. 1468 +-------------------+---------+-------+----------+ 1469 | Header | RAL src | 6LR_i | 6LBR dst | 1470 +-------------------+---------+-------+----------+ 1471 | Added headers | RPI | -- | -- | 1472 | Removed headers | -- | -- | RPI | 1473 | Modified headers | -- | RPI | -- | 1474 | Untouched headers | -- | -- | -- | 1475 +-------------------+---------+-------+----------+ 1477 Table 7: Non-SM: Summary of the use of headers from RAL to root 1479 8.1.2. Non-SM: Example of Flow from root to RAL 1481 In this case the flow comprises: 1483 root (6LBR) --> 6LR_i --> RAL (6LN) 1485 For example, a communication flow could be: Node A (root) --> Node B 1486 --> Node D --> Node F 1487 6LR_i are the intermediate routers from source to destination. In 1488 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1489 packet goes through from source (6LBR) to destination (RAL). 1491 The 6LBR inserts an RH3, and a RPI. No IPv6-in-IPv6 header is 1492 necessary as the traffic originates with an RPL aware node, the 6LBR. 1493 The destination is known to be RPL-aware because the root knows the 1494 whole topology in non-storing mode. 1496 The Table 8 summarizes what headers are needed for this use case. 1498 +-------------------+----------+-----------+-----------+ 1499 | Header | 6LBR src | 6LR_i | RAL dst | 1500 +-------------------+----------+-----------+-----------+ 1501 | Added headers | RPI, RH3 | -- | -- | 1502 | Modified headers | -- | RPI, RH3 | -- | 1503 | Removed headers | -- | -- | RH3, RPI | 1504 | Untouched headers | -- | -- | -- | 1505 +-------------------+----------+-----------+-----------+ 1507 Table 8: Non-SM: Summary of the use of headers from root to RAL 1509 8.1.3. Non-SM: Example of Flow from root to RUL 1511 In this case the flow comprises: 1513 root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1515 For example, a communication flow could be: Node A (root) --> Node B 1516 --> Node E --> Node G 1518 6LR_i are the intermediate routers from source to destination. In 1519 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1520 packet goes through from source (6LBR) to destination (RUL). 1522 In 6LBR the RH3 is added, it is modified at each intermediate 6LR 1523 (6LR_1 and so on) and it is fully consumed in the last 6LR (6LR_n), 1524 but left there. As the RPI is added, then the IPv6 node which does 1525 not understand the RPI, will ignore it (following RFC8200), thus 1526 encapsulation is not necessary. 1528 The Figure 15 depicts the table that summarizes what headers are 1529 needed for this use case. 1531 +-----------+----------+--------------+----------------+----------+ 1532 | Header | 6LBR | 6LR_i | 6LR_n | RUL | 1533 | | src | i=(1,..,n-1) | | dst | 1534 | | | | | | 1535 +-----------+----------+--------------+----------------+----------+ 1536 | Added | RPI, RH3 | -- | -- | -- | 1537 | headers | | | | | 1538 +-----------+----------+--------------+----------------+----------+ 1539 | Modified | -- | RPI, RH3 | RPI, | -- | 1540 | headers | | | RH3(consumed) | | 1541 +-----------+----------+--------------+----------------+----------+ 1542 | Removed | -- | -- | | -- | 1543 | headers | | | | | 1544 +-----------+----------+--------------+----------------+----------+ 1545 | Untouched | -- | -- | -- | RPI, RH3 | 1546 | headers | | | | (both | 1547 | | | | | ignored) | 1548 +-----------+----------+--------------+----------------+----------+ 1550 Figure 15: Non-SM: Summary of the use of headers from root to RUL 1552 8.1.4. Non-SM: Example of Flow from RUL to root 1554 In this case the flow comprises: 1556 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR) dst 1558 For example, a communication flow could be: Node G --> Node E --> 1559 Node B --> Node A (root) 1561 6LR_i are the intermediate routers from source to destination. In 1562 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1563 packet goes through from source (RUL) to destination (6LBR). For 1564 example, 6LR_1 (i=1) is the router that receives the packets from the 1565 IPv6 node. 1567 In this case the RPI is added by the first 6LR (6LR1) (Node E), 1568 encapsulated in an IPv6-in-IPv6 header, and is modified in the 1569 following 6LRs. The RPI and the entire packet is consumed by the 1570 root. 1572 The Figure 16 shows the table that summarizes what headers are needed 1573 for this use case. 1575 +---------+----+-----------------+-----------------+-----------------+ 1576 | |RUL | | | | 1577 | Header |src | 6LR_1 | 6LR_i | 6LBR dst | 1578 | |node| | | | 1579 +---------+----+-----------------+-----------------+-----------------+ 1580 | Added | -- |IPv6-in-IPv6(RPI)| -- | -- | 1581 | headers | | | | | 1582 +---------+----+-----------------+-----------------+-----------------+ 1583 | Modified| -- | -- |IPv6-in-IPv6(RPI)| -- | 1584 | headers | | | | | 1585 +---------+----+-----------------+-----------------+-----------------+ 1586 | Removed | -- | -- | -- |IPv6-in-IPv6(RPI)| 1587 | headers | | | | | 1588 +---------+----+-----------------+-----------------+-----------------+ 1589 |Untouched| -- | -- | -- | -- | 1590 | headers | | | | | 1591 +---------+----+-----------------+-----------------+-----------------+ 1593 Figure 16: Non-SM: Summary of the use of headers from RUL to root 1595 8.2. Non-Storing Mode: Interaction between Leaf and Internet 1597 This section will describe the communication flow in Non Storing Mode 1598 (Non-SM) between: 1600 RAL to Internet 1602 Internet to RAL 1604 RUL to Internet 1606 Internet to RUL 1608 8.2.1. Non-SM: Example of Flow from RAL to Internet 1610 In this case the flow comprises: 1612 RAL (6LN) src --> 6LR_i --> root (6LBR) --> Internet dst 1614 For example, a communication flow could be: Node F (RAL) --> Node D 1615 --> Node B --> Node A --> Internet 1617 6LR_i are the intermediate routers from source to destination. In 1618 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1619 packet goes through from source (RAL) to 6LBR. 1621 This case is identical to storing-mode case. 1623 The IPv6 flow label should be set to zero to aid in compression 1624 [RFC8138], and the 6LBR will set it to a non-zero value when sending 1625 towards the Internet [RFC6437]. 1627 The Table 9 summarizes what headers are needed for this use case. 1629 +-------------------+---------+-------+------+----------------+ 1630 | Header | RAL src | 6LR_i | 6LBR | Internet dst | 1631 +-------------------+---------+-------+------+----------------+ 1632 | Added headers | RPI | -- | -- | -- | 1633 | Modified headers | -- | RPI | -- | -- | 1634 | Removed headers | -- | -- | -- | -- | 1635 | Untouched headers | -- | -- | RPI | RPI (Ignored) | 1636 +-------------------+---------+-------+------+----------------+ 1638 Table 9: Non-SM: Summary of the use of headers from RAL to Internet 1640 8.2.2. Non-SM: Example of Flow from Internet to RAL 1642 In this case the flow comprises: 1644 Internet --> root (6LBR) --> 6LR_i --> RAL dst (6LN) 1646 For example, a communication flow could be: Internet --> Node A 1647 (root) --> Node B --> Node D --> Node F (RAL) 1649 6LR_i are the intermediate routers from source to destination. In 1650 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1651 packet goes through from 6LBR to destination (RAL). 1653 The 6LBR must add an RH3 header. As the 6LBR will know the path and 1654 address of the target node, it can address the IPv6-in-IPv6 header to 1655 that node. The 6LBR will zero the flow label upon entry in order to 1656 aid compression [RFC8138]. 1658 The Table 10 summarizes what headers are needed for this use case. 1660 +-----------+----------+--------------+--------------+--------------+ 1661 | Header | Internet | 6LBR | 6LR_i | RAL dst | 1662 | | src | | | | 1663 +-----------+----------+--------------+--------------+--------------+ 1664 | Added | -- | IPv6-in-IPv6 | -- | -- | 1665 | headers | | (RH3,RPI) | | | 1666 | Modified | -- | -- | IPv6-in-IPv6 | -- | 1667 | headers | | | (RH3,RPI) | | 1668 | Removed | -- | -- | -- | IPv6-in-IPv6 | 1669 | headers | | | | (RH3,RPI) | 1670 | Untouched | -- | -- | -- | -- | 1671 | headers | | | | | 1672 +-----------+----------+--------------+--------------+--------------+ 1674 Table 10: Non-SM: Summary of the use of headers from Internet to RAL 1676 8.2.3. Non-SM: Example of Flow from RUL to Internet 1678 In this case the flow comprises: 1680 RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet 1681 dst 1683 For example, a communication flow could be: Node G --> Node E --> 1684 Node B --> Node A --> Internet 1686 6LR_i are the intermediate routers from source to destination. In 1687 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1688 packet goes through from source (RUL) to 6LBR, e.g. 6LR_1 (i=1). 1690 In this case the flow label is recommended to be zero in the IPv6 1691 node. As RPL headers are added in the IPv6 node packet, the first 1692 6LR (6LR_1) will add a RPI inside a new IPv6-in-IPv6 header. The 1693 IPv6-in-IPv6 header will be addressed to the root. This case is 1694 identical to the storing-mode case (see Section 7.2.3). 1696 The Figure 17 shows the table that summarizes what headers are needed 1697 for this use case. 1699 +---------+----+-------------+--------------+--------------+--------+ 1700 | Header |RUL | 6LR_1 | 6LR_i | 6LBR |Internet| 1701 | |src | | [i=2,..,n] | | dst | 1702 | |node| | | | | 1703 +---------+----+-------------+--------------+--------------+--------+ 1704 | Added | -- |IP6-IP6(RPI) | -- | -- | -- | 1705 | headers | | | | | | 1706 +---------+----+-------------+--------------+--------------+--------+ 1707 | Modified| -- | -- | IP6-IP6(RPI) | -- | -- | 1708 | headers | | | | | | 1709 +---------+----+-------------+--------------+--------------+--------+ 1710 | Removed | -- | -- | -- | IP6-IP6(RPI) | -- | 1711 | headers | | | | | | 1712 +---------+----+-------------+--------------+--------------+--------+ 1713 |Untouched| -- | -- | -- | -- | -- | 1714 | headers | | | | | | 1715 +---------+----+-------------+--------------+--------------+--------+ 1717 Figure 17: Non-SM: Summary of the use of headers from RUL to Internet 1719 8.2.4. Non-SM: Example of Flow from Internet to RUL 1721 In this case the flow comprises: 1723 Internet src --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node) 1725 For example, a communication flow could be: Internet --> Node A 1726 (root) --> Node B --> Node E --> Node G 1728 6LR_i are the intermediate routers from source to destination. In 1729 this case, "1 <= i <= n", n is the number of routers (6LR) that the 1730 packet goes through from 6LBR to RUL. 1732 The 6LBR must add an RH3 header inside an IPv6-in-IPv6 header. The 1733 6LBR will know the path, and will recognize that the final node is 1734 not an RPL capable node as it will have received the connectivity DAO 1735 from the nearest 6LR. The 6LBR can therefore make the IPv6-in-IPv6 1736 header destination be the last 6LR. The 6LBR will set to zero the 1737 flow label upon entry in order to aid compression [RFC8138]. 1739 The Figure 18 shows the table that summarizes what headers are needed 1740 for this use case. 1742 +----------+--------+------------------+-----------+-----------+-----+ 1743 | Header |Internet| 6LBR | 6LR_i | 6LR_n | RUL | 1744 | | src | | | | dst | 1745 +----------+--------+------------------+-----------+-----------+-----+ 1746 | Added | -- | IP6-IP6(RH3,RPI) | -- | -- | -- | 1747 | headers | | | | | | 1748 +----------+--------+------------------+-----------+-----------+-----+ 1749 | Modified | -- | -- | IP6-IP6 | -- | -- | 1750 | headers | | | (RH3,RPI) | | | 1751 +----------+--------+------------------+-----------+-----------+-----+ 1752 | Removed | -- | -- | -- | IP6-IP6 | -- | 1753 | headers | | | | (RH3,RPI) | | 1754 +----------+--------+------------------+-----------+-----------+-----+ 1755 |Untouched | -- | -- | -- | -- | -- | 1756 | headers | | | | | | 1757 +----------+--------+------------------+-----------+-----------+-----+ 1759 Figure 18: Non-SM: Summary of the use of headers from Internet to RUL 1760 [1] The last 6LR before the IPv6 node. 1762 8.3. Non-SM: Interaction between Leafs 1764 In this section is described the communication flow in Non Storing 1765 Mode (Non-SM) between, 1767 RAL to RAL 1769 RAL to RUL 1771 RUL to RAL 1773 RUL to RUL 1775 8.3.1. Non-SM: Example of Flow from RAL to RAL 1777 In this case the flow comprises: 1779 RAL src --> 6LR_ia --> root (6LBR) --> 6LR_id --> RAL dst 1781 For example, a communication flow could be: Node F --> Node D --> 1782 Node B --> Node A (root) --> Node B --> Node E --> Node H 1784 6LR_ia are the intermediate routers from source to the root In this 1785 case, 1 <= ia <= n, n is the number of routers (6LR) that the packet 1786 goes through from RAL to the root. 1788 6LR_id are the intermediate routers from the root to the destination. 1789 In this case, "1 <= ia <= m", m is the number of the intermediate 1790 routers (6LR). 1792 This case involves only nodes in same RPL Domain. The originating 1793 node will add a RPI to the original packet, and send the packet 1794 upwards. 1796 The originating node must put the RPI (RPI1) into an IPv6-in-IPv6 1797 header addressed to the root, so that the 6LBR can remove that 1798 header. If it does not, then additional resources are wasted on the 1799 way down to carry the useless RPI. 1801 The 6LBR will need to insert an RH3 header, which requires that it 1802 add an IPv6-in-IPv6 header. It should be able to remove the 1803 RPI(RPI1), as it was contained in an IPv6-in-IPv6 header addressed to 1804 it. Otherwise, there may be a RPI buried inside the inner IP header, 1805 which should get ignored. The root inserts a RPI (RPI2) alongside 1806 the RH3. 1808 Networks that use the RPL P2P extension [RFC6997] are essentially 1809 non-storing DODAGs and fall into this scenario or scenario 1810 Section 8.1.2, with the originating node acting as 6LBR. 1812 The Figure 19 shows the table that summarizes what headers are needed 1813 for this use case. 1815 +---------+-------+----------+------------+----------+------------+ 1816 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | RAL | 1817 | | src | | | | dst | 1818 +---------+-------+----------+------------+----------+------------+ 1819 | Added |IP6-IP6| | IP6-IP6 | -- | -- | 1820 | headers |(RPI1) | |(RH3-> RAL, | | | 1821 | | | | RPI2) | | | 1822 +---------+-------+----------+------------+----------+------------+ 1823 | Modified| -- | IP6-IP6 | -- | IP6-IP6 | -- | 1824 | headers | | (RPI1) | |(RH3,RPI) | | 1825 +---------+-------+----------+------------+----------+------------+ 1826 | Removed | -- | -- | IP6-IP6 | -- | IP6-IP6 | 1827 | headers | | | (RPI1) | | (RH3, | 1828 | | | | | | RPI2) | 1829 +---------+-------+----------+------------+----------+------------+ 1830 |Untouched| -- | -- | -- | -- | -- | 1831 | headers | | | | | | 1832 +---------+-------+----------+------------+----------+------------+ 1834 Figure 19: Non-SM: Summary of the use of headers for RAL to RAL. 1836 8.3.2. Non-SM: Example of Flow from RAL to RUL 1838 In this case the flow comprises: 1840 RAL --> 6LR_ia --> root (6LBR) --> 6LR_id --> RUL (IPv6 dst node) 1842 For example, a communication flow could be: Node F --> Node D --> 1843 Node B --> Node A (root) --> Node B --> Node E --> Node G 1845 6LR_ia are the intermediate routers from source to the root In this 1846 case, 1 <= ia <= n, n is the number of intermediate routers (6LR) 1848 6LR_id are the intermediate routers from the root to the destination. 1849 In this case, "1 <= ia <= m", m is the number of the intermediate 1850 routers (6LRs). 1852 As in the previous case, the RAL (6LN) will insert a RPI (RPI_1) 1853 header which must be in an IPv6-in-IPv6 header addressed to the root 1854 so that the 6LBR can remove this RPI. The 6LBR will then insert an 1855 RH3 inside a new IPv6-in-IPv6 header addressed to the last 6LR_id 1856 (6LR_id = m). 1858 The Figure 20 shows the table that summarizes what headers are needed 1859 for this use case. 1861 +-----------+---------+---------+---------+---------+---------+------+ 1862 | Header | RAL | 6LR_ia | 6LBR | 6LR_id | 6LR_m | RUL | 1863 | | src | | | | | dst | 1864 | | node | | | | | node | 1865 +-----------+---------+---------+---------+---------+---------+------+ 1866 | Added | IP6-IP6 | | IP6-IP6 | -- | -- | -- | 1867 | headers | (RPI1) | | (RH3, | | | | 1868 | | | | RPI2) | | | | 1869 +-----------+---------+---------+---------+---------+---------+------+ 1870 | Modified | -- | IP6-IP6 | -- | IP6-IP6 | | -- | 1871 | headers | | (RPI1) | | (RH3, | | | 1872 | | | | | RPI2) | | | 1873 +-----------+---------+---------+---------+---------+---------+------+ 1874 | Removed | -- | -- | IP6-IP6 | -- | IP6-IP6 | -- | 1875 | headers | | | (RPI1) | | (RH3, | | 1876 | | | | | | RPI2) | | 1877 +-----------+---------+---------+---------+---------+---------+------+ 1878 | Untouched | -- | -- | -- | -- | -- | -- | 1879 | headers | | | | | | | 1880 +-----------+---------+---------+---------+---------+---------+------+ 1882 Figure 20: Non-SM: Summary of the use of headers from RAL to RUL. 1884 8.3.3. Non-SM: Example of Flow from RUL to RAL 1886 In this case the flow comprises: 1888 RUL (IPv6 src node) --> 6LR_1 --> 6LR_ia --> root (6LBR) --> 6LR_id 1889 --> RAL dst (6LN) 1891 For example, a communication flow could be: Node G --> Node E --> 1892 Node B --> Node A (root) --> Node B --> Node E --> Node H 1894 6LR_ia are the intermediate routers from source to the root. In this 1895 case, 1 <= ia <= n, n is the number of intermediate routers (6LR) 1897 6LR_id are the intermediate routers from the root to the destination. 1898 In this case, "1 <= ia <= m", m is the number of the intermediate 1899 routers (6LR). 1901 This scenario is mostly identical to the previous one. The RPI 1902 (RPI1) is added by the first 6LR (6LR_1) inside an IPv6-in-IPv6 1903 header addressed to the root. The 6LBR will remove this RPI, and add 1904 it's own IPv6-in-IPv6 header containing an RH3 header and an RPI 1905 (RPI2). 1907 The Figure 21 shows the table that summarizes what headers are needed 1908 for this use case. 1910 +-----------+------+---------+---------+---------+---------+---------+ 1911 | Header | RUL | 6LR_1 | 6LR_ia | 6LBR | 6LR_id | RAL | 1912 | | src | | | | | dst | 1913 | | node | | | | | node | 1914 +-----------+------+---------+---------+---------+---------+---------+ 1915 | Added | -- | IP6-IP6 | -- | IP6-IP6 | -- | -- | 1916 | headers | | (RPI1) | | (RH3, | | | 1917 | | | | | RPI2) | | | 1918 +-----------+------+---------+---------+---------+---------+---------+ 1919 | Modified | -- | | IP6-IP6 | -- | IP6-IP6 | -- | 1920 | headers | | | (RPI1) | | (RH3, | | 1921 | | | | | | RPI2) | | 1922 +-----------+------+---------+---------+---------+---------+---------+ 1923 | Removed | -- | | -- | IP6-IP6 | -- | IP6-IP6 | 1924 | headers | | | | (RPI1) | | (RH3, | 1925 | | | | | | | RPI2) | 1926 +-----------+------+---------+---------+---------+---------+---------+ 1927 | Untouched | -- | | -- | -- | -- | -- | 1928 | headers | | | | | | | 1929 +-----------+------+---------+---------+---------+---------+---------+ 1931 Figure 21: Non-SM: Summary of the use of headers from RUL to RAL. 1933 8.3.4. Non-SM: Example of Flow from RUL to RUL 1935 In this case the flow comprises: 1937 RUL (IPv6 src node) --> 6LR_1 --> 6LR_ia --> root (6LBR) --> 6LR_id 1938 --> RUL (IPv6 dst node) 1940 For example, a communication flow could be: Node G --> Node E --> 1941 Node B --> Node A (root) --> Node C --> Node J 1943 6LR_ia are the intermediate routers from source to the root. In this 1944 case, 1 <= ia <= n, n is the number of intermediate routers (6LR) 1946 6LR_id are the intermediate routers from the root to the destination. 1947 In this case, "1 <= ia <= m", m is the number of the intermediate 1948 routers (6LR). 1950 This scenario is the combination of the previous two cases. 1952 The Figure 22 shows the table that summarizes what headers are needed 1953 for this use case. 1955 +---------+------+-------+-------+---------+-------+---------+------+ 1956 | Header | RUL | 6LR_1 | 6LR_ia| 6LBR |6LR_id | 6LR_m | RUL | 1957 | | src | | | | | | dst | 1958 | | node | | | | | | node | 1959 +---------+------+-------+-------+---------+-------+---------+------+ 1960 | Added | -- |IP6-IP6| -- | IP6-IP6 | -- | -- | -- | 1961 | headers | | (RPI1)| | (RH3, | | | | 1962 | | | | | RPI2) | | | | 1963 +---------+------+-------+-------+---------+-------+---------+------+ 1964 | Modified| -- | -- |IP6-IP6| -- |IP6-IP6| -- | -- | 1965 | headers | | | (RPI1)| | (RH3, | | | 1966 | | | | | | RPI2)| | | 1967 +---------+------+-------+-------+---------+-------+---------+------+ 1968 | Removed | -- | -- | -- | IP6-IP6 | -- | IP6-IP6 | -- | 1969 | headers | | | | (RPI1) | | (RH3, | | 1970 | | | | | | | RPI2) | | 1971 +---------+------+-------+-------+---------+-------+---------+------+ 1972 |Untouched| -- | -- | -- | -- | -- | -- | -- | 1973 | headers | | | | | | | | 1974 +---------+------+-------+-------+---------+-------+---------+------+ 1976 Figure 22: Non-SM: Summary of the use of headers from RUL to RUL 1978 9. Operational Considerations of supporting RUL-leaves 1980 Roughly half of the situations described in this document involve 1981 leaf ("host") nodes that do not speak RPL. These nodes fall into two 1982 further categories: ones that drop a packet that have RPI or RH3 1983 headers, and ones that continue to process a packet that has RPI and/ 1984 or RH3 headers. 1986 [RFC8200] provides for new rules that suggest that nodes that have 1987 not been configured (explicitly) to examine Hop-by-Hop headers, 1988 should ignore those headers, and continue processing the packet. 1989 Despite this, and despite the switch from 0x63 to 0x23, there may be 1990 hosts that are pre-RFC8200, or simply intolerant. Those hosts will 1991 drop packets that continue to have RPL artifacts in them. In 1992 general, such hosts can not be easily supported in RPL LLNs. 1994 There are some specific cases where it is possible to remove the RPL 1995 artifacts prior to forwarding the packet to the leaf host. The 1996 critical thing is that the artifacts have been inserted by the RPL 1997 root inside an IPv6-in-IPv6 header, and that the header has been 1998 addressed to the 6LR immediately prior to the leaf node. In that 1999 case, in the process of removing the IPv6-in-IPv6 header, the 2000 artifacts can also be removed. 2002 The above case occurs whenever traffic originates from the outside 2003 the LLN (the "Internet" cases above), and non-storing mode is used. 2004 In non-storing mode, the RPL root knows the exact topology (as it 2005 must be create the RH3 header), and therefore knows what the 6LR 2006 prior to the leaf. For example, in Figure 5, node E is the 6LR prior 2007 to the leaf node G, or node C is the 6LR prior to the leaf node J. 2009 traffic originating from the RPL root (such as when the data 2010 collection system is co-located on the RPL root), does not require an 2011 IPv6-in-IPv6 header (in either mode), as the packet is originating at 2012 the root, and the root can insert the RPI and RH3 headers directly 2013 into the packet, as it is formed. Such a packet is slightly smaller, 2014 but only can be sent to nodes (whether RPL aware or not), that will 2015 tolerate the RPL artifacts. 2017 An operator that finds itself with a lot of traffic from the RPL root 2018 to RPL-not-aware-leaves, will have to do IPv6-in-IPv6 encapsulation 2019 if the leaf is not tolerant of the RPL artifacts. Such an operator 2020 could otherwise omit this unnecessary header if it was certain of the 2021 properties of the leaf. 2023 As storing mode can not know the final path of the traffic, 2024 intolerant (that drop packets with RPL artifacts) leaf nodes can not 2025 be supported. 2027 10. Operational considerations of introducing 0x23 2029 This section describes the operational considerations of introducing 2030 the new RPI Option Type of 0x23. 2032 During bootstrapping the node gets the DIO with the information of 2033 RPI Option Type, indicating the new RPI in the DODAG Configuration 2034 Option Flag. The DODAG root is in charge to configure the current 2035 network to the new value, through DIO messages and when all the nodes 2036 are set with the new value. The DODAG should change to a new DODAG 2037 version. In case of rebooting, the node does not remember the RPI 2038 Option Type. Thus, the DIO is sent with a flag indicating the new 2039 RPI Option Type. 2041 The DODAG Configuration option is contained in a RPL DIO message, 2042 which contains a unique DTSN counter. The leaf nodes respond to this 2043 message with DAO messages containing the same DTSN. This is a normal 2044 part of RPL routing; the RPL root therefore knows when the updated 2045 DODAG Configuration Option has been seen by all nodes. 2047 Before the migration happens, all the RPL-aware nodes should support 2048 both values . The migration procedure it is triggered when the DIO 2049 is sent with the flag indicating the new RPI Option Type. Namely, it 2050 remains at 0x63 until it is sure that the network is capable of 0x23, 2051 then it abruptly change to 0x23. This options allows to send packets 2052 to not-RPL nodes, which should ignore the option and continue 2053 processing the packets. 2055 In case that a node join to a network that only process 0x63, it 2056 would produce a flag day as was mentioned previously. Indicating the 2057 new RPI in the DODAG Configuration Option Flag is a way to avoid the 2058 flag day in a network. It is recommended that a network process both 2059 options to enable interoperability. 2061 11. IANA Considerations 2063 This document updates the registration made in [RFC6553] Destination 2064 Options and Hop-by-Hop Options registry from 0x63 to 0x23 as shown in 2065 Figure 23. 2067 +-------+-------------------+------------------------+---------- -+ 2068 | Hex | Binary Value | Description | Reference | 2069 + Value +-------------------+ + + 2070 | | act | chg | rest | | | 2071 +-------+-----+-----+-------+------------------------+------------+ 2072 | 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)| 2073 +-------+-----+-----+-------+------------------------+------------+ 2074 | 0x63 | 01 | 1 | 00011 | RPL Option(DEPRECATED) | [RFC6553] | 2075 | | | | | |[RFCXXXX](*)| 2076 +-------+-----+-----+-------+------------------------+------------+ 2078 Figure 23: Option Type in RPL Option.(*)represents this document 2080 DODAG Configuration option is updated as follows (Figure 24): 2082 +------------+-----------------+---------------+ 2083 | Bit number | Description | Reference | 2084 +------------+-----------------+---------------+ 2085 | 3 | RPI 0x23 enable | This document | 2086 +------------+-----------------+---------------+ 2088 Figure 24: DODAG Configuration Option Flag to indicate the RPI-flag- 2089 day. 2091 12. Security Considerations 2093 The security considerations covered in [RFC6553] and [RFC6554] apply 2094 when the packets are in the RPL Domain. 2096 The IPv6-in-IPv6 mechanism described in this document is much more 2097 limited than the general mechanism described in [RFC2473]. The 2098 willingness of each node in the LLN to decapsulate packets and 2099 forward them could be exploited by nodes to disguise the origin of an 2100 attack. 2102 While a typical LLN may be a very poor origin for attack traffic (as 2103 the networks tend to be very slow, and the nodes often have very low 2104 duty cycles) given enough nodes, they could still have a significant 2105 impact, particularly if attack is targeting another LLN. 2106 Additionally, some uses of RPL involve large backbone ISP scale 2107 equipment [I-D.ietf-anima-autonomic-control-plane], which may be 2108 equipped with multiple 100Gb/s interfaces. 2110 Blocking or careful filtering of IPv6-in-IPv6 traffic entering the 2111 LLN as described above will make sure that any attack that is mounted 2112 must originate from compromised nodes within the LLN. The use of 2113 BCP38 [BCP38] filtering at the RPL root on egress traffic will both 2114 alert the operator to the existence of the attack, as well as drop 2115 the attack traffic. As the RPL network is typically numbered from a 2116 single prefix, which is itself assigned by RPL, BCP38 filtering 2117 involves a single prefix comparison and should be trivial to 2118 automatically configure. 2120 There are some scenarios where IPv6-in-IPv6 traffic should be allowed 2121 to pass through the RPL root, such as the IPv6-in-IPv6 mediated 2122 communications between a new Pledge and the Join Registrar/ 2123 Coordinator (JRC) when using [I-D.ietf-anima-bootstrapping-keyinfra] 2124 and [I-D.ietf-6tisch-dtsecurity-secure-join]. This is the case for 2125 the RPL root to do careful filtering: it occurs only when the Join 2126 Coordinator is not co-located inside the RPL root. 2128 With the above precautions, an attack using IPv6-in-IPv6 tunnels can 2129 only be by a node within the LLN on another node within the LLN. 2130 Such an attack could, of course, be done directly. An attack of this 2131 kind is meaningful only if the source addresses are either fake or if 2132 the point is to amplify return traffic. Such an attack, could also 2133 be done without the use of IPv6-in-IPv6 headers using forged source 2134 addresses. If the attack requires bi-directional communication, then 2135 IPv6-in-IPv6 provides no advantages. 2137 Whenever IPv6-in-IPv6 headers are being proposed, there is a concern 2138 about creating security issues. In the security section of 2139 [RFC2473], it was suggested that tunnel entry and exit points can be 2140 secured, via "Use IPsec". This recommendation is not practical for 2141 RPL networks. [RFC5406] goes into some detail on what additional 2142 details would be needed in order to "Use IPsec". Use of ESP would 2143 prevent RFC8183 compression (compression must occur before 2144 encryption), and RFC8183 compression is lossy in a way that prevents 2145 use of AH. These are minor issues. The major issue is how to 2146 establish trust enough such that IKEv2 could be used. This would 2147 require a system of certificates to be present in every single node, 2148 including any Internet nodes that might need to communicate with the 2149 LLN. Thus, "Use IPsec" requires a global PKI in the general case. 2151 More significantly, the use of IPsec tunnels to protect the IPv6-in- 2152 IPv6 headers would in the general case scale with the square of the 2153 number of nodes. This is a lot of resource for a constrained nodes 2154 on a constrained network. In the end, the IPsec tunnels would be 2155 providing only BCP38-like origin authentication! That is, IPsec 2156 provides a transitive guarantee to the tunnel exit point that the 2157 tunnel entry point did BCP38 on traffic going in. Just doing BCP38 2158 origin filtering at the entry and exit of the LLN provides a similar 2159 level amount of security without all the scaling and trust problems 2160 of using IPsec as RFC2473 suggested. IPsec is not recommended. 2162 An LLN with hostile nodes within it would not be protected against 2163 impersonation with the LLN by entry/exit filtering. 2165 The RH3 header usage described here can be abused in equivalent ways 2166 (to disguise the origin of traffic and attack other nodes) with an 2167 IPv6-in-IPv6 header to add the needed RH3 header. As such, the 2168 attacker's RH3 header will not be seen by the network until it 2169 reaches the end host, which will decapsulate it. An end-host should 2170 be suspicious about a RH3 header which has additional hops which have 2171 not yet been processed, and SHOULD ignore such a second RH3 header. 2173 In addition, the LLN will likely use [RFC8138] to compress the IPv6- 2174 in-IPv6 and RH3 headers. As such, the compressor at the RPL-root 2175 will see the second RH3 header and MAY choose to discard the packet 2176 if the RH3 header has not been completely consumed. A consumed 2177 (inert) RH3 header could be present in a packet that flows from one 2178 LLN, crosses the Internet, and enters another LLN. As per the 2179 discussion in this document, such headers do not need to be removed. 2180 However, there is no case described in this document where an RH3 is 2181 inserted in a non-storing network on traffic that is leaving the LLN, 2182 but this document should not preclude such a future innovation. It 2183 should just be noted that an incoming RH3 must be fully consumed, or 2184 very carefully inspected. 2186 The RPI, if permitted to enter the LLN, could be used by an attacker 2187 to change the priority of a packet by selecting a different 2188 RPLInstanceID, perhaps one with a higher energy cost, for instance. 2189 It could also be that not all nodes are reachable in an LLN using the 2190 default instanceID, but a change of instanceID would permit an 2191 attacker to bypass such filtering. Like the RH3, a RPI is to be 2192 inserted by the RPL root on traffic entering the LLN by first 2193 inserting an IPv6-in-IPv6 header. The attacker's RPI therefore will 2194 not be seen by the network. Upon reaching the destination node the 2195 RPI has no further meaning and is just skipped; the presence of a 2196 second RPI will have no meaning to the end node as the packet has 2197 already been identified as being at it's final destination. 2199 The RH3 and RPIs could be abused by an attacker inside of the network 2200 to route packets on non-obvious ways, perhaps eluding observation. 2201 This usage is in fact part of [RFC6997] and can not be restricted at 2202 all. This is a feature, not a bug. 2204 [RFC7416] deals with many other threats to LLNs not directly related 2205 to the use of IPv6-in-IPv6 headers, and this document does not change 2206 that analysis. 2208 Nodes within the LLN can use the IPv6-in-IPv6 mechanism to mount an 2209 attack on another part of the LLN, while disguising the origin of the 2210 attack. The mechanism can even be abused to make it appear that the 2211 attack is coming from outside the LLN, and unless countered, this 2212 could be used to mount a Distributed Denial Of Service attack upon 2213 nodes elsewhere in the Internet. See [DDOS-KREBS] for an example of 2214 such attacks already seen in the real world. 2216 If an attack comes from inside of LLN, it can be alleviated with SAVI 2217 (Source Address Validation Improvement) using [RFC8505] with 2218 [I-D.ietf-6lo-ap-nd]. The attacker will not be able to source 2219 traffic with an address that is not registered, and the registration 2220 process checks for topological correctness. Notice that there is an 2221 L2 authentication in most of the cases. If an attack comes from 2222 outside LLN IPv6-in- IPv6 can be used to hide inner routing headers, 2223 but by construction, the RH3 can typically only address nodes within 2224 the LLN. That is, a RH3 with a CmprI less than 8 , should be 2225 considered an attack (see RFC6554, section 3). 2227 Nodes outside of the LLN will need to pass IPv6-in-IPv6 traffic 2228 through the RPL root to perform this attack. To counter, the RPL 2229 root SHOULD either restrict ingress of IPv6-in-IPv6 packets (the 2230 simpler solution), or it SHOULD walk the IP header extension chain 2231 until it can inspect the upper-layer-payload as described in 2232 [RFC7045]. In particular, the RPL root SHOULD do [BCP38] processing 2233 on the source addresses of all IP headers that it examines in both 2234 directions. 2236 Note: there are some situations where a prefix will spread across 2237 multiple LLNs via mechanisms such as the one described in 2238 [I-D.ietf-6lo-backbone-router]. In this case the BCP38 filtering 2239 needs to take this into account, either by exchanging detailed 2240 routing information on each LLN, or by moving the BCP38 filtering 2241 further towards the Internet, so that the details of the multiple 2242 LLNs do not matter. 2244 13. Acknowledgments 2246 This work is done thanks to the grant given by the StandICT.eu 2247 project. 2249 A special BIG thanks to C. M. Heard for the help with the 2250 Section 4. Much of the redaction in that section is based on his 2251 comments. 2253 Additionally, the authors would like to acknowledge the review, 2254 feedback, and comments of (alphabetical order): Robert Cragie, Simon 2255 Duquennoy, Ralph Droms, Cenk Guendogan, Rahul Jadhav, Benjamin Kaduk, 2256 Matthias Kovatsch, Charlie Perkins, Alvaro Retana, Peter van der 2257 Stok, Xavier Vilajosana, Eric Vyncke and Thomas Watteyne. 2259 14. References 2261 14.1. Normative References 2263 [BCP38] Ferguson, P. and D. Senie, "Network Ingress Filtering: 2264 Defeating Denial of Service Attacks which employ IP Source 2265 Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, 2266 May 2000, . 2268 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2269 Requirement Levels", BCP 14, RFC 2119, 2270 DOI 10.17487/RFC2119, March 1997, 2271 . 2273 [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion 2274 Notification", RFC 6040, DOI 10.17487/RFC6040, November 2275 2010, . 2277 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 2278 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 2279 DOI 10.17487/RFC6282, September 2011, 2280 . 2282 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 2283 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 2284 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 2285 Low-Power and Lossy Networks", RFC 6550, 2286 DOI 10.17487/RFC6550, March 2012, 2287 . 2289 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 2290 Power and Lossy Networks (RPL) Option for Carrying RPL 2291 Information in Data-Plane Datagrams", RFC 6553, 2292 DOI 10.17487/RFC6553, March 2012, 2293 . 2295 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 2296 Routing Header for Source Routes with the Routing Protocol 2297 for Low-Power and Lossy Networks (RPL)", RFC 6554, 2298 DOI 10.17487/RFC6554, March 2012, 2299 . 2301 [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing 2302 of IPv6 Extension Headers", RFC 7045, 2303 DOI 10.17487/RFC7045, December 2013, 2304 . 2306 [RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power 2307 Wireless Personal Area Network (6LoWPAN) Paging Dispatch", 2308 RFC 8025, DOI 10.17487/RFC8025, November 2016, 2309 . 2311 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 2312 "IPv6 over Low-Power Wireless Personal Area Network 2313 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 2314 April 2017, . 2316 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2317 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2318 May 2017, . 2320 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2321 (IPv6) Specification", STD 86, RFC 8200, 2322 DOI 10.17487/RFC8200, July 2017, 2323 . 2325 [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node 2326 Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, 2327 January 2019, . 2329 14.2. Informative References 2331 [DDOS-KREBS] 2332 Goodin, D., "Record-breaking DDoS reportedly delivered by 2333 >145k hacked cameras", September 2016, 2334 . 2337 [I-D.ietf-6lo-ap-nd] 2338 Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 2339 "Address Protected Neighbor Discovery for Low-power and 2340 Lossy Networks", draft-ietf-6lo-ap-nd-13 (work in 2341 progress), January 2020. 2343 [I-D.ietf-6lo-backbone-router] 2344 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 2345 Backbone Router", draft-ietf-6lo-backbone-router-13 (work 2346 in progress), September 2019. 2348 [I-D.ietf-6tisch-dtsecurity-secure-join] 2349 Richardson, M., "6tisch Secure Join protocol", draft-ietf- 2350 6tisch-dtsecurity-secure-join-01 (work in progress), 2351 February 2017. 2353 [I-D.ietf-anima-autonomic-control-plane] 2354 Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic 2355 Control Plane (ACP)", draft-ietf-anima-autonomic-control- 2356 plane-21 (work in progress), November 2019. 2358 [I-D.ietf-anima-bootstrapping-keyinfra] 2359 Pritikin, M., Richardson, M., Eckert, T., Behringer, M., 2360 and K. Watsen, "Bootstrapping Remote Secure Key 2361 Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- 2362 keyinfra-34 (work in progress), January 2020. 2364 [I-D.ietf-intarea-tunnels] 2365 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2366 Architecture", draft-ietf-intarea-tunnels-10 (work in 2367 progress), September 2019. 2369 [I-D.ietf-roll-unaware-leaves] 2370 Thubert, P. and M. Richardson, "Routing for RPL Leaves", 2371 draft-ietf-roll-unaware-leaves-08 (work in progress), 2372 December 2019. 2374 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2375 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 2376 December 1998, . 2378 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2379 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2380 December 1998, . 2382 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2383 Control Message Protocol (ICMPv6) for the Internet 2384 Protocol Version 6 (IPv6) Specification", STD 89, 2385 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2386 . 2388 [RFC5406] Bellovin, S., "Guidelines for Specifying the Use of IPsec 2389 Version 2", BCP 146, RFC 5406, DOI 10.17487/RFC5406, 2390 February 2009, . 2392 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 2393 "IPv6 Flow Label Specification", RFC 6437, 2394 DOI 10.17487/RFC6437, November 2011, 2395 . 2397 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 2398 Bormann, "Neighbor Discovery Optimization for IPv6 over 2399 Low-Power Wireless Personal Area Networks (6LoWPANs)", 2400 RFC 6775, DOI 10.17487/RFC6775, November 2012, 2401 . 2403 [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and 2404 J. Martocci, "Reactive Discovery of Point-to-Point Routes 2405 in Low-Power and Lossy Networks", RFC 6997, 2406 DOI 10.17487/RFC6997, August 2013, 2407 . 2409 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 2410 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 2411 2014, . 2413 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 2414 and M. Richardson, Ed., "A Security Threat Analysis for 2415 the Routing Protocol for Low-Power and Lossy Networks 2416 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 2417 . 2419 [RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal 2420 IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) 2421 Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180, 2422 May 2017, . 2424 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 2425 Perkins, "Registration Extensions for IPv6 over Low-Power 2426 Wireless Personal Area Network (6LoWPAN) Neighbor 2427 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 2428 . 2430 Authors' Addresses 2432 Maria Ines Robles 2433 Aalto University, Finland/Uni. Tec. Nac.(UTN) - FRM, Argentina 2435 Email: mariainesrobles@gmail.com 2436 Michael C. Richardson 2437 Sandelman Software Works 2438 470 Dawson Avenue 2439 Ottawa, ON K1Z 5V7 2440 CA 2442 Email: mcr+ietf@sandelman.ca 2443 URI: http://www.sandelman.ca/mcr/ 2445 Pascal Thubert 2446 Cisco Systems, Inc 2447 Building D 2448 45 Allee des Ormes - BP1200 2449 MOUGINS - Sophia Antipolis 06254 2450 FRANCE 2452 Phone: +33 497 23 26 34 2453 Email: pthubert@cisco.com