idnits 2.17.00 (12 Aug 2021) /tmp/idnits36069/draft-ietf-roll-useofrplinfo-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 18, 2016) is 2133 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'TO DO' is mentioned on line 274, but not defined ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) == Outdated reference: draft-ietf-6man-rfc2460bis has been published as RFC 8200 == Outdated reference: draft-ietf-6tisch-architecture has been published as RFC 9030 == Outdated reference: draft-ietf-roll-routing-dispatch has been published as RFC 8138 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL Working Group M. Robles 3 Internet-Draft Ericsson 4 Intended status: Informational M. Richardson 5 Expires: January 19, 2017 SSW 6 P. Thubert 7 Cisco 8 July 18, 2016 10 When to use RFC 6553, 6554 and IPv6-in-IPv6 11 draft-ietf-roll-useofrplinfo-06 13 Abstract 15 This document looks at different data flows through LLN (Low-Power 16 and Lossy Networks) where RPL (IPv6 Routing Protocol for Low-Power 17 and Lossy Networks) is used to establish routing. The document 18 enumerates the cases where RFC 6553, RFC 6554 and IPv6-in-IPv6 19 encapsulation is required. This analysis provides the basis on which 20 to design efficient compression of these headers. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on January 19, 2017. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology and Requirements Language . . . . . . . . . . . . 3 58 2.1. hop-by-hop IPv6-in-IPv6 headers . . . . . . . . . . . . . 4 59 3. Sample/reference topology . . . . . . . . . . . . . . . . . . 4 60 4. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7 61 5. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 8 62 5.1. Example of Flow from RPL-aware-leaf to root . . . . . . . 9 63 5.2. Example of Flow from root to RPL-aware-leaf . . . . . . . 10 64 5.3. Example of Flow from root to not-RPL-aware-leaf . . . . . 11 65 5.4. Example of Flow from not-RPL-aware-leaf to root . . . . . 12 66 5.5. Example of Flow from RPL-aware-leaf to Internet . . . . . 12 67 5.6. Example of Flow from Internet to RPL-aware-leaf . . . . . 13 68 5.7. Example of Flow from not-RPL-aware-leaf to Internet . . . 14 69 5.8. Example of Flow from Internet to non-RPL-aware-leaf . . . 14 70 5.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf . . 15 71 5.10. Example of Flow from RPL-aware-leaf to non-RPL-aware-leaf 16 72 5.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 18 73 5.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware- 74 leaf . . . . . . . . . . . . . . . . . . . . . . . . . . 19 75 6. Non Storing mode . . . . . . . . . . . . . . . . . . . . . . 20 76 6.1. Example of Flow from RPL-aware-leaf to root . . . . . . . 20 77 6.2. Example of Flow from root to RPL-aware-leaf . . . . . . . 21 78 6.3. Example of Flow from root to not-RPL-aware-leaf . . . . . 21 79 6.4. Example of Flow from not-RPL-aware-leaf to root . . . . . 22 80 6.5. Example of Flow from RPL-aware-leaf to Internet . . . . . 23 81 6.6. Example of Flow from Internet to RPL-aware-leaf . . . . . 23 82 6.7. Example of Flow from not-RPL-aware-leaf to Internet . . . 24 83 6.8. Example of Flow from Internet to non-RPL-aware-leaf . . . 25 84 6.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf . . 25 85 6.10. Example of Flow from RPL-aware-leaf to not-RPL-aware-leaf 26 86 6.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 27 87 6.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware- 88 leaf . . . . . . . . . . . . . . . . . . . . . . . . . . 28 89 7. Observations about the problem . . . . . . . . . . . . . . . 28 90 7.1. Storing mode . . . . . . . . . . . . . . . . . . . . . . 28 91 7.2. Non-Storing mode . . . . . . . . . . . . . . . . . . . . 29 92 8. 6LoRH Compression cases . . . . . . . . . . . . . . . . . . . 30 93 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 94 10. Security Considerations . . . . . . . . . . . . . . . . . . . 30 95 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30 96 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 97 12.1. Normative References . . . . . . . . . . . . . . . . . . 30 98 12.2. Informative References . . . . . . . . . . . . . . . . . 31 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 101 1. Introduction 103 RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks) 104 [RFC6550] is a routing protocol for constrained networks. RFC 6553 105 [RFC6553] defines the "RPL option" (RPI), carried within the IPv6 106 Hop-by-Hop header to quickly identify inconsistencies (loops) in the 107 routing topology. RFC 6554 [RFC6554] defines the "RPL Source Route 108 Header" (RH3), an IPv6 Extension Header to deliver datagrams within a 109 RPL routing domain, particularly in non-storing mode. 111 These various items are referred to as RPL artifacts, and they are 112 seen on all of the data-plane traffic that occurs in RPL routed 113 networks; they do not in general appear on the RPL control plane 114 traffic at all which is mostly hop-by-hop traffic (one exception 115 being DAO messages in non-storing mode). 117 It has become clear from attempts to do multi-vendor 118 interoperability, and from a desire to compress as many of the above 119 artifacts as possible that not all implementors agree when artifacts 120 are necessary, or when they can be safely omitted, or removed. 122 An interim meeting went through the 24 cases defined here to discover 123 if there were any shortcuts, and this document is the result of that 124 discussion. This document should not be defining anything new, but 125 it may clarify what is correct and incorrect behaviour. 127 The related document A Routing Header Dispatch for 6LoWPAN (6LoRH) 128 [I-D.ietf-roll-routing-dispatch] defines a method to compress RPL 129 Option information and Routing Header type 3 [RFC6554], an efficient 130 IP-in-IP technique, and use cases proposed for the 131 [Second6TischPlugtest] involving 6loRH. 133 2. Terminology and Requirements Language 135 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 136 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 137 document are to be interpreted as described in RFC 2119 [RFC2119]. 139 Terminology defined in [RFC7102] applies to this document: LBR, LLN, 140 RPL, RPL Domain and ROLL. 142 2.1. hop-by-hop IPv6-in-IPv6 headers 144 The term "hop-by-hop IPv6-in-IPv6" header refers to: adding a header 145 that originates from a node to an adjacent node, using the addresses 146 (usually the GUA or ULA, but could use the link-local addresses) of 147 each node. If the packet must traverse multiple hops, then it must 148 be decapsulated at each hop, and then re-encapsulated again in a 149 similar fashion. 151 3. Sample/reference topology 153 A RPL network is composed of a 6LBR (6LoWPAN Border Router), Backbone 154 Router (6BBR), 6LR (6LoWPAN Router) and 6LN (6LoWPAN Node) as leaf 155 logically organized in a DODAG structure (Destination Oriented 156 Directed Acyclic Graph). 158 RPL defines the RPL Control messages (control plane), a new ICMPv6 159 [RFC4443] message with Type 155. DIS (DODAG Information 160 Solicitation), DIO (DODAG Information Object) and DAO (Destination 161 Advertisement Object) messages are all RPL Control messages but with 162 different Code values. A RPL Stack is showed in Figure 1. 164 RPL supports two modes of Downward traffic: in storing mode (RPL-SM), 165 it is fully stateful or an in non-storing (RPL-NSM), it is fully 166 source routed. A RPL Instance is either fully storing or fully non- 167 storing, i.e. a RPL Instance with a combination of storing and non- 168 storing nodes is not supported with the current specifications at the 169 time of writing this document. 171 +--------------+ 172 | Upper Layers | 173 | | 174 +--------------+ 175 | RPL | 176 | | 177 +--------------+ 178 | ICMPv6 | 179 | | 180 +--------------+ 181 | IPv6 | 182 | | 183 +--------------+ 184 | 6LoWPAN | 185 | | 186 +--------------+ 187 | PHY-MAC | 188 | | 189 +--------------+ 191 Figure 1: RPL Stack. 193 +---------+ 194 +---+Internet | 195 | +---------+ 196 | 197 +----+--+ 198 | DODAG | node:01 199 +---------+ Root +----------+ 200 | | 6LBR | | 201 | +----+--+ | 202 | | | 203 | | | 204 ... ... ... 205 | | | 206 +-----+-+ +--+---+ +--+---+ 207 |6LR | | | | | 208 +-----+ | | | | | 209 | | 11 | | 12 | | 13 +------+ 210 | +-----+-+ +-+----+ +-+----+ | 211 | | | | | 212 | | | | | 213 | 21 | 22 | 23 | 24 | 25 214 +-+---+ +-+---+ +--+--+ +- --+ +---+-+ 215 |Leaf | | | | | |Leaf| |Leaf | 216 | 6LN | | | | | | 6LN| | 6LN | 217 +-----+ +-----+ +-----+ +----+ +-----+ 219 Figure 2: A reference RPL Topology. 221 In Figure 2 is showed the reference RPL Topology for this document. 222 The numbers in or above the nodes are there so that they may be 223 referenced in subsequent sections. In the figure, a 6LN can be a 224 router or a host. The 6LN leafs marked as (21) and (25) are routers. 225 The leaf marked 6LN (24) is a device which does not speak RPL at all 226 (not-RPL-aware), but uses Router-Advertisements, 6LowPAN DAR/DAC and 227 efficient-ND only to participate in the network [RFC6775]. In the 228 document this leaf (24) is often named IPv6 node. The 6LBR in the 229 figure is the root of the Global DODAG. 231 This document is in part motivated by the work that is ongoing at the 232 6TiSCH working group. The 6TiSCH architecture 233 [I-D.ietf-6tisch-architecture] draft explains the network 234 architecture of a 6TiSCH network. 236 4. Use cases 238 In data plane context a combination of RFC6553, RFC6554 and IPv6-in- 239 IPv6 encapsulation is going to be analyzed for the following traffic 240 flows: 242 RPL-aware-leaf to root 244 root to RPL-aware-leaf 246 not-RPL-aware-leaf to root 248 root to not-RPL-aware-leaf 250 RPL-aware-leaf to Internet 252 Internet to RPL-aware-leaf 254 not-RPL-aware-leaf to Internet 256 Internet to not-RPL-aware-leaf 258 RPL-aware-leaf to RPL-aware-leaf 260 RPL-aware-leaf to not-RPL-aware-leaf 262 not-RPL-aware-leaf to RPL-aware-leaf 264 not-RPL-aware-leaf to not-RPL-aware-leaf 266 This document assumes a rule that a Header cannot be inserted or 267 removed on the fly inside an IPv6 packet that is being routed. A 268 fundamental precept of the IPv6 architecture as outlined in [RFC2460] 269 is that Extensions may not be added or removed except by the sender 270 or the receiver. 272 Note: current discussions on [I-D.ietf-6man-rfc2460bis] related to 273 extensions headers may affect some cases in this document (Ticket 274 nro. 9) in 6man. [TO DO]. 276 A second important thing is that packets with a Hop-by-Hop option 277 which are marked with option type 01 ([RFC2460] section 4.2) must be 278 discarded if received by a host or router which does not understand 279 that option. This means that in general, any packet that leaves the 280 RPL domain of an LLN (or leaves the LLN entirely) is likely to be 281 discarded if it still contains an [RFC6553] RPL Option Header known 282 as the RPI. 284 The combination of these two rules means that the arrangement of 285 headers must be done so that traffic intended to exit the RPL domain 286 can have the RPI option removed prior to leaving the RPL domain. 288 An intermediate router that needs to add a header must encapsulate 289 the packet in an (additional) outer IP header where the new header 290 can be placed. 292 This also means that a Header can only be removed by an intermediate 293 router if it is placed in an encapsulating IPv6 Header, and in that 294 case, the whole encapsulating header must be removed - a replacement 295 may be added. Further, an intermediate router can only remove such 296 an outer header if that outer header has the router as the 297 destination! 299 Both RPI and RH3 headers may be modified by routers on the path of 300 the packet without the need to add or remove an encapsulating header. 301 Both headers were designed with this modification in mind, and both 302 the RPL RH and the RPL option are marked mutable but recoverable, so 303 an IPsec AH security header can be applied across these headers, but 304 it may not secure all the values in those headers. 306 RPI should be present in every single RPL data packet. There is one 307 exception in non-storing mode: when a packet is going down from the 308 root. In a downward non-storing mode, the entire route is written, 309 so there can be no loops by construction, nor any confusion about 310 which forwarding table to use. There may be cases (such as in 311 6tisch) where the instanceID may still be needed to pick an 312 appropriate priority or channel at each hop. 314 The applicability for storing (RPL-SM) and non-Storing (RPL-NSM) 315 modes for the previous cases is showed as follows: 317 In the tables present in this document, the term "RPL aware leaf" is 318 has been shortened to "Raf", and "not-RPL aware leaf" has been 319 shortened to "~Raf" to make the table fit in available space. 321 The earlier examples are more extensive to make sure that the process 322 is clear, while later examples are more consise. 324 5. Storing mode 326 In storing mode (fully stateful), the sender cannot determine whether 327 the destination is RPL-capable and thus would need an IP-in-IP 328 header. The IP-in-IP header needs to be addressed on a hop-by-hop 329 basis so that the last 6LR can remove the RPI header. Additionally, 330 The sender can determine if the destination is inside the LLN by 331 looking if the destination address is matched by the DIO's PIO 332 option. 334 The following table summarizes what headers are needed in the 335 following scenarios, and indicates when the IP-in-IP header must be 336 inserted on a hop-by-hop basis, and when it can target the 337 destination node directly. There are three possible situations: hop- 338 by-hop necessary (indicated by "hop"), or destination address 339 possible (indicated by "dst"). In all cases hop by hop can be used. 340 In cases where no IP-in-IP header is needed, the column is left 341 blank. 343 The leaf can be a router 6LR or a host, both indicated as 6LN. 345 +--------------+-------+-------+-----------+---------------+ 346 | Use Case | RPI | RH3 | IP-in-IP | IP-in-IP dst | 347 +--------------+-------+-------+-----------+---------------+ 348 | Raf to root | Yes | No | No | -- | 349 | root to Raf | Yes | No | No | -- | 350 | root to ~Raf | Yes | No | Yes | hop | 351 | ~Raf to root | Yes | No | Yes | root | 352 | Raf to Int | Yes | No | Yes | root | 353 | Int to Raf | Yes | No | Yes | raf | 354 | ~Raf to Int | Yes | No | Yes | root | 355 | Int to ~Raf | Yes | No | Yes | hop | 356 | Raf to Raf | Yes | No | No | -- | 357 | Raf to ~Raf | Yes | No | Yes | hop | 358 | ~Raf to Raf | Yes | No | Yes | dst | 359 | ~Raf to ~Raf | Yes | No | Yes | hop | 360 +--------------+-------+-------+-----------+---------------+ 362 Table 1: Headers needed in Storing mode: RPI, RH3, IP-in-IP 363 encapsulation 365 5.1. Example of Flow from RPL-aware-leaf to root 367 In storing mode, RFC 6553 (RPI) is used to send RPL Information 368 instanceID and rank information. 370 As stated in Section 16.2 of [RFC6550] a RPL-aware-leaf node does 371 not generally issue DIO messages; a leaf node accepts DIO messages 372 from upstream. (When the inconsistency in routing occurs, a leaf 373 node will generate a DIO with an infinite rank, to fix it). It may 374 issue DAO and DIS messages though it generally ignores DAO and DIS 375 messages. 377 In storing mode, RFC 6553 (RPI) is used to send RPL Information 378 instanceID and rank information. 380 In this case the flow comprises: 382 RPL-aware-leaf (6LN) --> 6LR --> 6LR,... --> root (6LBR) 384 As it was mentioned In this document 6LRs, 6LBR are always full- 385 fledge RPL routers. 387 The 6LN inserts the RPI header, and sends the packet to 6LR which 388 decrements the rank in RPI and sends the packet up. When the packet 389 arrives at 6LBR, the RPI is removed and the packet is processed. 391 The RPI header can be removed by the 6LBR because the packet is 392 addressed to the 6LBR. The 6LN must know that it is communicating 393 with the 6LBR to make use of this scenario. The 6LN can know the 394 address of the 6LBR because it knows the address of the root via the 395 DODAGID in the DIO messages. 397 +-------------------+-----+------+------+ 398 | Header | 6LN | 6LR | 6LBR | 399 +-------------------+-----+------+------+ 400 | Inserted headers | RPI | -- | -- | 401 | Removed headers | -- | -- | RPI | 402 | Re-added headers | -- | -- | -- | 403 | Modified headers | -- | RPI | -- | 404 | Untouched headers | -- | -- | -- | 405 +-------------------+-----+------+------+ 407 Storing: Summary of the use of headers from RPL-aware-leaf to root 409 5.2. Example of Flow from root to RPL-aware-leaf 411 In this case the flow comprises: 413 root (6LBR)--> 6LR --> RPL-aware-leaf (6LN) 415 In this case the 6LBR inserts RPI header and sends the packet down, 416 the 6LR is going to increment the rank in RPI (examines instanceID 417 for multiple tables), the packet is processed in 6LN and RPI removed. 419 No IP-in-IP header is required. 421 +-------------------+------+-------+------+ 422 | Header | 6LBR | 6LR | 6LN | 423 +-------------------+------+-------+------+ 424 | Inserted headers | RPI | -- | -- | 425 | Removed headers | -- | -- | RPI | 426 | Re-added headers | -- | -- | -- | 427 | Modified headers | -- | RPI | -- | 428 | Untouched headers | -- | -- | -- | 429 +-------------------+------+-------+------+ 431 Storing: Summary of the use of headers from root to RPL-aware-leaf 433 5.3. Example of Flow from root to not-RPL-aware-leaf 435 In this case the flow comprises: 437 root (6LBR)--> 6LR --> not-RPL-aware-leaf (6LN) 439 The question in this scenario is how the root knows how to address 440 the IPv6-in-IPv6 header. It can not know that the destination isn't 441 RPL aware, so it must insert an IPv6 header that can be removed on 442 the last RPL aware node. Since the root can not know in a storing 443 network where the last RPL aware node is, the IPv6-in-IPv6 header 444 must be added hop-by-hop along the path from root to leaf. 446 The root (6LBR) uses IPv6-in-IPv6 encapsulation to transmit 447 information not related with the RPL domain. In the 6LBR the RPI 448 header is inserted into an IPv6-in-IPv6 header addressed to the last 449 6LR, which removes the header before it passes the packet to the IPv6 450 node (6LN). 452 An alternative option is to add an attribute in the RPL Target Option 453 to indicate that the target is not RPL aware: future work may explore 454 this possibility. 456 +-------------------+---------------+---------------+------+ 457 | Header | 6LBR | 6LR | IPv6 | 458 +-------------------+---------------+---------------+------+ 459 | Inserted headers | IP-in-IP(RPI) | -- | -- | 460 | Removed headers | -- | IP-in-IP(RPI) | -- | 461 | Re-added headers | -- | -- | -- | 462 | Modified headers | -- | -- | -- | 463 | Untouched headers | -- | -- | -- | 464 +-------------------+---------------+---------------+------+ 466 Storing: Summary of the use of headers from root to not-RPL-aware- 467 leaf 469 5.4. Example of Flow from not-RPL-aware-leaf to root 471 In this case the flow comprises: 473 not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) 475 When the packet arrives from IPv6 node to 6LR, the 6LR will insert an 476 RPI header, encapsuladed in a IPv6-in-IPv6 header. The IPv6-in-IPv6 477 header can be addressed to the next hop, or to the root. The root 478 removes the header and processes the packet. 480 +-------------------+------+----------------+---------------+ 481 | Header | IPv6 | 6LR | 6LBR | 482 +-------------------+------+----------------+---------------+ 483 | Inserted headers | -- | IP-in-IP(RPI) | -- | 484 | Removed headers | -- | -- | IP-in-IP(RPI) | 485 | Re-added headers | -- | -- | -- | 486 | Modified headers | -- | -- | -- | 487 | Untouched headers | -- | -- | -- | 488 +-------------------+------+----------------+---------------+ 490 Storing: Summary of the use of headers from not-RPL-aware-leaf to 491 root 493 5.5. Example of Flow from RPL-aware-leaf to Internet 495 RPL information from RFC 6553 should not go out to Internet as it 496 will cause the packet to be discarded at the first non-RPI aware 497 router. The 6LBR must be able to take this information out before 498 sending the packet upwards to the Internet. This requires the RPI 499 header be placed in an IP-in-IP header that the root can remove. 501 In this case the flow comprises: 503 RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet 505 The 6LN will insert the RPI in a IPv6-in-IPv6 in a outer header, 506 which may be addressed to the 6LBR (root), or alternatively, it could 507 be addressed hop-by-hop. 509 +-----------------+---------------+------+---------------+----------+ 510 | Header | 6LN | 6LR | 6LBR | Internet | 511 +-----------------+---------------+------+---------------+----------+ 512 | Inserted | IP-in-IP(RPI) | -- | -- | -- | 513 | headers | | | | | 514 | Removed headers | -- | -- | IP-in-IP(RPI) | -- | 515 | Re-added | -- | -- | -- | -- | 516 | headers | | | | | 517 | Modified | -- | RPI | -- | -- | 518 | headers | | | | | 519 | Untouched | -- | -- | -- | -- | 520 | headers | | | | | 521 +-----------------+---------------+------+---------------+----------+ 523 Storing: Summary of the use of headers from RPL-aware-leaf to 524 Internet 526 5.6. Example of Flow from Internet to RPL-aware-leaf 528 In this case the flow comprises: 530 Internet --> root (6LBR) --> 6LR --> RPL-aware-leaf (6LN) 532 When the packet arrives from Internet to 6LBR the RPI header is added 533 in a outer IPv6-in-IPv6 header and sent to 6LR, which modifies the 534 rank in the RPI. When the packet arrives at 6LN the RPI header is 535 removed and the packet processed. 537 +-----------------+----------+---------------+------+---------------+ 538 | Header | Internet | 6LBR | 6LR | 6LN | 539 +-----------------+----------+---------------+------+---------------+ 540 | Inserted | -- | IP-in-IP(RPI) | -- | -- | 541 | headers | | | | | 542 | Removed headers | -- | -- | -- | IP-in-IP(RPI) | 543 | Re-added | -- | -- | -- | -- | 544 | headers | | | | | 545 | Modified | -- | -- | RPI | -- | 546 | headers | | | | | 547 | Untouched | -- | -- | -- | -- | 548 | headers | | | | | 549 +-----------------+----------+---------------+------+---------------+ 551 Storing: Summary of the use of headers from Internet to RPL-aware- 552 leaf 554 5.7. Example of Flow from not-RPL-aware-leaf to Internet 556 In this case the flow comprises: 558 not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet 560 The 6LR node will add an IP-in-IP(RPI) header addressed either to the 561 root, or hop-by-hop such that the root can remove the RPI header 562 before passing upwards. 564 The originating node will ideally leave the IPv6 flow label as zero 565 so that it can be better compressed through the LLN, and the 6LBR 566 will set the flow label to a non-zero value when sending to the 567 Internet. 569 +-----------------+------+---------------+---------------+----------+ 570 | Header | 6LN | 6LR | 6LBR | Internet | 571 +-----------------+------+---------------+---------------+----------+ 572 | Inserted | -- | IP-in-IP(RPI) | -- | -- | 573 | headers | | | | | 574 | Removed headers | -- | -- | IP-in-IP(RPI) | -- | 575 | Re-added | -- | -- | -- | -- | 576 | headers | | | | | 577 | Modified | -- | -- | -- | -- | 578 | headers | | | | | 579 | Untouched | -- | -- | -- | -- | 580 | headers | | | | | 581 +-----------------+------+---------------+---------------+----------+ 583 Storing: Summary of the use of headers from not-RPL-aware-leaf to 584 Internet 586 5.8. Example of Flow from Internet to non-RPL-aware-leaf 588 In this case the flow comprises: 590 Internet --> root (6LBR) --> 6LR --> not-RPL-aware-leaf (6LN) 592 The 6LBR will have to add an RPI header within an IP-in-IP header. 593 The IP-in-IP will need to be addressed hop-by-hop along the path as 594 in storing mode, the 6LBR has no idea if the 6LN is RPL aware or not, 595 nor what the closest attached 6LR node is. 597 The 6LBR MAY set the flow label on the inner IP-in-IP header to zero 598 in order to aid in compression, as the packet will not emerge again 599 from the LLN. 601 +-----------------+----------+---------------+---------------+------+ 602 | Header | Internet | 6LBR | 6LR | IPv6 | 603 +-----------------+----------+---------------+---------------+------+ 604 | Inserted | -- | IP-in-IP(RPI) | -- | -- | 605 | headers | | | | | 606 | Removed headers | -- | -- | IP-in-IP(RPI) | -- | 607 | Re-added | -- | -- | -- | -- | 608 | headers | | | | | 609 | Modified | -- | -- | -- | -- | 610 | headers | | | | | 611 | Untouched | -- | -- | -- | -- | 612 | headers | | | | | 613 +-----------------+----------+---------------+---------------+------+ 615 Storing: Summary of the use of headers from Internet to non-RPL- 616 aware-leaf 618 5.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf 620 In [RFC6550] RPL allows a simple one-hop optimization for both 621 storing and non-storing networks. A node may send a packet destined 622 to a one-hop neighbor directly to that node. Section 9 in [RFC6550]. 624 In this case the flow comprises: 626 6LN --> 6LR --> common parent (6LR) --> 6LR --> 6LN 628 This case is assumed in the same RPL Domain. In the common parent, 629 the direction of RPI is changed (from increasing to decreasing the 630 rank). 632 While the 6LR nodes will update the RPI, no node needs to add or 633 remove the RPI, so no IP-in-IP headers are necessary. The ability to 634 do this depends upon the sending the 6LN to know that the destination 635 is: a) inside the LLN, and b) RPL capable. 637 The sender can determine if the destination is inside the LLN by 638 looking if the destination address is matched by the DIO's PIO 639 option. This check may be modified by the use of backbone routers, 640 but in this case it is assumed that the backbone routers are RPL 641 capable and so can process the RPI header correctly. 643 The other check, that the destination is RPL capable is not currently 644 discernible by the sender. This information is necessary to 645 distinguish this test case from Section 5.10. 647 +-------------+-------+---------------+---------------+-----+-------+ 648 | Header | 6LN | 6LR | 6LR (common | 6LR | 6LN | 649 | | src | | parent) | | dst | 650 +-------------+-------+---------------+---------------+-----+-------+ 651 | Inserted | RPI | -- | -- | -- | -- | 652 | headers | | | | | | 653 | Removed | -- | -- | -- | -- | RPI | 654 | headers | | | | | | 655 | Re-added | -- | -- | -- | -- | -- | 656 | headers | | | | | | 657 | Modified | -- | RPI | RPI | -- | -- | 658 | headers | | (decreasing | (increasing | | | 659 | | | rank) | rank) | | | 660 | Untouched | -- | -- | -- | -- | -- | 661 | headers | | | | | | 662 +-------------+-------+---------------+---------------+-----+-------+ 664 Storing: Summary of the use of headers for RPL-aware-leaf to RPL- 665 aware-leaf 667 5.10. Example of Flow from RPL-aware-leaf to non-RPL-aware-leaf 669 In this case the flow comprises: 671 6LN --> 6LR --> common parent (6LR) --> 6LR --> not-RPL-aware 6LN 673 The sender, being aware out of band, that the receiver is not RPL 674 aware, adds an RPI header inside an IP-in-IP header. The IP-in-IP 675 header needs to be addressed on a hop-by-hop basis so that the last 676 6LR can remove the RPI header. 678 ,---. 679 / \ 680 ( 6LR2 ) IP3,RPI,IP,ULP 681 ,-" . 682 ,-" `---' `. 683 ,' `. 684 ,---. ,-" `,---. 685 / +" / \ 686 ( 6LR1 ) Remove the IP3,RPI( 6LR3 ) 687 \ / \ / 688 /---' `---'| 689 / IP2,RPI,IP,ULP \ 690 / | 691 / \ 692 ,---+-. | 693 / \ +--+----+ 694 ( 6LN ) | | 695 \ / | IPv6 | IP,ULP 696 `-----' | | 697 IP1,RPI,IP,ULP +-------+ 699 Figure 3: Solution IPv6-in-IPv6 in each hop 701 As we mentioned previously, packets with a Hop-by-Hop option which 702 are marked with option type 01 ([RFC2460] section 4.2) must be 703 discarded if received by a host or router which does not understand 704 that option. This means that in general, any packet that leaves the 705 RPL domain of an LLN (or leaves the LLN entirely) is likely to be 706 discarded if it still contains an [RFC6553] RPL Option Header known 707 as the RPI. For this case, if the definition of the Option Type 708 field of RPL Option '01' were changed so that it isn't a "discard if 709 not recognized", then no IP-in-IP header would be necessary. This 710 change is an incompatible on-the-wire change and would require some 711 kind of flag day, possibly a change that is done simultaenously with 712 an updated 6LoRH compress. 714 +--------+------------+------------+------------+------------+------+ 715 | Header | 6LN | 6LR | 6LR | 6LR | IPv6 | 716 | | | | (common | | | 717 | | | | parent) | | | 718 +--------+------------+------------+------------+------------+------+ 719 | Insert | IP-in- | -- | -- | -- | -- | 720 | ed hea | IP(RPI) | | | | | 721 | ders | | | | | | 722 | Remove | -- | -- | -- | IP-in- | -- | 723 | d head | | | | IP(RPI) | | 724 | ers | | | | | | 725 | Re- | -- | -- | -- | -- | -- | 726 | added | | | | | | 727 | header | | | | | | 728 | s | | | | | | 729 | Modifi | -- | IP-in- | IP-in- | -- | -- | 730 | ed hea | | IP(RPI) | IP(RPI) | | | 731 | ders | | | | | | 732 | Untouc | -- | -- | -- | -- | -- | 733 | hed he | | | | | | 734 | aders | | | | | | 735 +--------+------------+------------+------------+------------+------+ 737 Storing: Summary of the use of headers from RPL-aware-leaf to not- 738 RPL-aware-leaf 740 5.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 742 In this case the flow comprises: 744 not-RPL-aware 6LN --> 6LR --> common parent (6LR) --> 6LR --> 6LN 746 The 6LR receives the packet from the the IPv6 node and inserts and 747 the RPI header encapsulated in IPv6-in-IPv6 header. The IP-in-IP 748 header could be addressed to the 6LN if the destination is known to 749 the RPL aware, otherwise it must send the packet using a hop-by-hop 750 IP-in-IP header. Similar considerations apply from section 751 Section 5.10. 753 +--------+------+------------+------------+------------+------------+ 754 | Header | IPv6 | 6LR | common | 6LR | 6LN | 755 | | | | parent | | | 756 | | | | (6LR) | | | 757 +--------+------+------------+------------+------------+------------+ 758 | Insert | -- | IP-in- | -- | -- | -- | 759 | ed hea | | IP(RPI) | | | | 760 | ders | | | | | | 761 | Remove | -- | -- | -- | -- | IP-in- | 762 | d head | | | | | IP(RPI) | 763 | ers | | | | | | 764 | Re- | -- | -- | -- | -- | -- | 765 | added | | | | | | 766 | header | | | | | | 767 | s | | | | | | 768 | Modifi | -- | -- | IP-in- | IP-in- | -- | 769 | ed hea | | | IP(RPI) | IP(RPI) | | 770 | ders | | | | | | 771 | Untouc | -- | -- | -- | -- | -- | 772 | hed he | | | | | | 773 | aders | | | | | | 774 +--------+------+------------+------------+------------+------------+ 776 Storing: Summary of the use of headers from not-RPL-aware-leaf to 777 RPL-aware-leaf 779 5.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-leaf 781 In this case the flow comprises: 783 not-RPL-aware 6LN (IPv6 node)--> 6LR --> root (6LBR) --> 6LR --> not- 784 RPL-aware 6LN (IPv6 node) 786 This flow combines the problems of the two previous sections. There 787 is no choice at the first 6LR: it must insert an RPI, and to do that 788 it must add an IP-in-IP header. That IP-in-IP header must be 789 addressed on a hop-by-hop basis. 791 +----------+-----+-------------+--------------+--------------+------+ 792 | Header | IPv | 6LR | 6LR (common | 6LR | IPv6 | 793 | | 6 | | parent) | | dst | 794 | | src | | | | | 795 +----------+-----+-------------+--------------+--------------+------+ 796 | Inserted | -- | IP-in- | -- | -- | -- | 797 | headers | | IP(RPI) | | | | 798 | Removed | -- | -- | -- | IP-in- | -- | 799 | headers | | | | IP(RPI) | | 800 | Re-added | -- | IP-in- | IP-in- | IP-in- | -- | 801 | headers | | IP(RPI) | IP(RPI) | IP(RPI) | | 802 | Modified | -- | -- | -- | -- | -- | 803 | headers | | | | | | 804 | Untouche | -- | -- | -- | -- | -- | 805 | d | | | | | | 806 | headers | | | | | | 807 +----------+-----+-------------+--------------+--------------+------+ 809 Storing: Summary of the use of headers from not-RPL-aware-leaf to 810 not-RPL-aware-leaf 812 6. Non Storing mode 814 +--------------+------+------+-----------+---------------+ 815 | Use Case | RPI | RH3 | IP-in-IP | IP-in-IP dst | 816 +--------------+------+------+-----------+---------------+ 817 | Raf to root | Yes | No | No | -- | 818 | root to Raf | Yes | Yes | No | -- | 819 | root to ~Raf | No | Yes | Yes | 6LR | 820 | ~Raf to root | Yes | No | Yes | root | 821 | Raf to Int | Yes | No | Yes | root | 822 | Int to Raf | opt | Yes | Yes | dst | 823 | ~Raf to Int | Yes | No | Yes | root | 824 | Int to ~Raf | opt | Yes | Yes | 6LR | 825 | Raf to Raf | Yes | Yes | Yes | root/dst | 826 | Raf to ~Raf | Yes | Yes | Yes | root/6LR | 827 | ~Raf to Raf | Yes | Yes | Yes | root/6LN | 828 | ~Raf to ~Raf | Yes | Yes | Yes | root/6LR | 829 +--------------+------+------+-----------+---------------+ 831 Table 2: Headers needed in Non-Storing mode: RPI, RH3, IP-in-IP 832 encapsulation 834 6.1. Example of Flow from RPL-aware-leaf to root 836 In non-storing mode the leaf node uses default routing to send 837 traffic to the root. The RPI header must be included to avoid/detect 838 loops. 840 RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) 842 This situation is the same case as storing mode. 844 +-------------------+-----+------+------+ 845 | Header | 6LN | 6LR | 6LBR | 846 +-------------------+-----+------+------+ 847 | Inserted headers | RPI | -- | -- | 848 | Removed headers | -- | -- | RPI | 849 | Re-added headers | -- | RPI | -- | 850 | Modified headers | -- | -- | -- | 851 | Untouched headers | -- | -- | -- | 852 +-------------------+-----+------+------+ 854 Non Storing: Summary of the use of headers from RPL-aware-leaf to 855 root 857 6.2. Example of Flow from root to RPL-aware-leaf 859 In this case the flow comprises: 861 root (6LBR)--> 6LR --> RPL-aware-leaf (6LN) 863 The 6LBR will insert an RH3, and may optionally insert an RPI header. 864 No IP-in-IP header is necessary as the traffic originates with an RPL 865 aware node, the 6LBR. The destination is known to 6LBR because, the 866 root knows the whole topology in non-storing mode. 868 +-------------------+-----------------+------+----------+ 869 | Header | 6LBR | 6LR | 6LN | 870 +-------------------+-----------------+------+----------+ 871 | Inserted headers | (opt: RPI), RH3 | -- | -- | 872 | Removed headers | -- | -- | RH3,RPI | 873 | Re-added headers | -- | -- | -- | 874 | Modified headers | -- | RH3 | -- | 875 | Untouched headers | -- | -- | -- | 876 +-------------------+-----------------+------+----------+ 878 Non Storing: Summary of the use of headers from root to RPL-aware- 879 leaf 881 6.3. Example of Flow from root to not-RPL-aware-leaf 883 In this case the flow comprises: 885 root (6LBR)--> 6LR --> not-RPL-aware-leaf (IPv6 node) 886 In 6LBR the RH3 is added, modified in each intermediate 6LR and it is 887 fully consumed in the last 6LR, but left there. If the RPI is left 888 present, the IPv6 node which does not understand it will drop it, 889 therefore the RPI should be removed before reaching the IPv6-only 890 node. To permit removal, an IP-in-IP header (hop-by-hop) or 891 addressed to the last 6LR is necessary. Due the complete knowledge 892 of the topology at the root, the 6LBR is able to address the IP-in-IP 893 header to the last 6LR. 895 Omitting the RPI entirely is therefore a better solution, as no IP- 896 in-IP header is necessary. 898 +-------------------+------+-----+------+ 899 | Header | 6LBR | 6LR | IPv6 | 900 +-------------------+------+-----+------+ 901 | Inserted headers | RH3 | -- | -- | 902 | Removed headers | -- | -- | -- | 903 | Re-added headers | -- | -- | -- | 904 | Modified headers | -- | RH3 | -- | 905 | Untouched headers | -- | -- | -- | 906 +-------------------+------+-----+------+ 908 Non Storing: Summary of the use of headers from root to not-RPL- 909 aware-leaf 911 6.4. Example of Flow from not-RPL-aware-leaf to root 913 In this case the flow comprises: 915 IPv6-node --> 6LR1 --> 6LR2 --> root (6LBR) 917 In this case the RPI is added by the first 6LR, encapsulated in an 918 IP-in-IP header, and is not modified in the followings 6LRs. The RPI 919 and entire packet is consumed by the root. 921 +-------------------+------+----------------+------+----------------+ 922 | Header | IPv6 | 6LR1 | 6LR2 | 6LBR | 923 +-------------------+------+----------------+------+----------------+ 924 | Inserted headers | -- | IP-in-IP(RPI) | -- | -- | 925 | Removed headers | -- | -- | -- | IP-in-IP(RPI) | 926 | Re-added headers | -- | -- | -- | -- | 927 | Modified headers | -- | -- | -- | -- | 928 | Untouched headers | -- | IP-in-IP(RPI) | -- | -- | 929 +-------------------+------+----------------+------+----------------+ 931 Non Storing: Summary of the use of headers from not-RPL-aware-leaf to 932 root 934 6.5. Example of Flow from RPL-aware-leaf to Internet 936 In this case the flow comprises: 938 RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet 940 This case requires that the RPI be added, but removed by the 6LBR. 941 The 6LN must therefore add the RPI inside an IP-in-IP header, 942 addressed to the root. This case is identical to storing-mode case. 944 The IPv6 flow label should be set to zero to aid in compression, and 945 the 6LBR will set it to a non-zero value when sending towards the 946 Internet. 948 +-----------------+---------------+------+---------------+----------+ 949 | Header | 6LN | 6LR | 6LBR | Internet | 950 +-----------------+---------------+------+---------------+----------+ 951 | Inserted | IP-in-IP(RPI) | -- | -- | -- | 952 | headers | | | | | 953 | Removed headers | -- | -- | IP-in-IP(RPI) | -- | 954 | Re-added | -- | -- | -- | -- | 955 | headers | | | | | 956 | Modified | -- | -- | -- | -- | 957 | headers | | | | | 958 | Untouched | -- | RPI | -- | -- | 959 | headers | | | | | 960 +-----------------+---------------+------+---------------+----------+ 962 Non Storing: Summary of the use of headers from RPL-aware-leaf to 963 Internet 965 6.6. Example of Flow from Internet to RPL-aware-leaf 967 In this case the flow comprises: 969 Internet --> root (6LBR) --> 6LR --> RPL-aware-leaf (6LN) 971 The 6LBR must add an RH3 header. As the 6LBR will know the path and 972 address of the target not, it can address the IP-in-IP header to that 973 node. The 6LBR will zero the flow label upon entry in order to aid 974 compression. 976 The RPI may be added or not. 978 +----------+----------+-----------------------+---------------+-----+ 979 | Header | Internet | 6LBR | 6LR | 6LN | 980 +----------+----------+-----------------------+---------------+-----+ 981 | Inserted | -- | IP-in-IP(RH3,opt:RPI) | -- | -- | 982 | headers | | | | | 983 | Removed | -- | -- | IP-in-IP(RH3) | -- | 984 | headers | | | | | 985 | Re-added | -- | -- | -- | -- | 986 | headers | | | | | 987 | Modified | -- | -- | IP-in-IP(RH3) | -- | 988 | headers | | | | | 989 | Untouche | -- | -- | -- | -- | 990 | d | | | | | 991 | headers | | | | | 992 +----------+----------+-----------------------+---------------+-----+ 994 Non Storing: Summary of the use of headers from Internet to RPL- 995 aware-leaf 997 6.7. Example of Flow from not-RPL-aware-leaf to Internet 999 In this case the flow comprises: 1001 not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet 1003 In this case the flow label is recommended to be zero in the IPv6 1004 node. As RPL headers are added in the IPv6 node, the first 6LN will 1005 add an RPI header inside a new IP-in-IP header. The IP-in-IP header 1006 will be addressed to the root. This case is identical to the 1007 storing-mode case (Section 5.7). 1009 +-----------------+------+---------------+---------------+----------+ 1010 | Header | IPv6 | 6LR | 6LBR | Internet | 1011 +-----------------+------+---------------+---------------+----------+ 1012 | Inserted | -- | IP-in-IP(RPI) | -- | -- | 1013 | headers | | | | | 1014 | Removed headers | -- | -- | IP-in-IP(RPI) | -- | 1015 | Re-added | -- | -- | -- | -- | 1016 | headers | | | | | 1017 | Modified | -- | -- | -- | -- | 1018 | headers | | | | | 1019 | Untouched | -- | -- | -- | -- | 1020 | headers | | | | | 1021 +-----------------+------+---------------+---------------+----------+ 1023 Non Storing: Summary of the use of headers from not-RPL-aware-leaf to 1024 Internet 1026 6.8. Example of Flow from Internet to non-RPL-aware-leaf 1028 In this case the flow comprises: 1030 Internet --> root (6LBR) --> 6LR --> not-RPL-aware-leaf (IPv6 node) 1032 The 6LBR must add an RH3 header inside an IP-in-IP header. The 6LBR 1033 will know the path, and will recognize that the final node is not an 1034 RPL capable node as it will have received the connectivity DAO from 1035 the nearest 6LR. The 6LBR can therefore make the IP-in-IP header 1036 destination be the last 6LR. The 6LBR will set to zero the flow 1037 label upon entry in order to aid compression. 1039 +----------+---------+-----------------------+---------------+------+ 1040 | Header | Interne | 6LBR | 6LR | IPv6 | 1041 | | t | | | | 1042 +----------+---------+-----------------------+---------------+------+ 1043 | Inserted | -- | IP-in-IP(RH3,opt:RPI) | -- | -- | 1044 | headers | | | | | 1045 | Removed | -- | -- | IP-in-IP(RH3, | -- | 1046 | headers | | | RPI) | | 1047 | Re-added | -- | -- | -- | -- | 1048 | headers | | | | | 1049 | Modified | -- | -- | -- | -- | 1050 | headers | | | | | 1051 | Untouche | -- | -- | -- | -- | 1052 | d | | | | | 1053 | headers | | | | | 1054 +----------+---------+-----------------------+---------------+------+ 1056 NonStoring: Summary of the use of headers from Internet to non-RPL- 1057 aware-leaf 1059 6.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf 1061 In this case the flow comprises: 1063 6LN --> 6LR --> root (6LBR) --> 6LR --> 6LN 1065 This case involves only nodes in same RPL Domain. The originating 1066 node will add an RPI header to the original packet, and send the 1067 packet upwards. 1069 The originating node could put the RPI into an IP-in-IP header 1070 addressed to the root, so that the 6LBR can remove that header. 1072 The 6LBR will need to insert an RH3 header, which requires that it 1073 add an IP-in-IP header. It may be able to remove the RPI if it was 1074 contained in an IP-in-IP header addressed to it. Otherwise, there 1075 may be an RPI header buried inside the inner IP header, which should 1076 get ignored. 1078 Networks that use the RPL P2P extension [RFC6997] are essentially 1079 non-storing DODAGs and fall into this scenario. 1081 +----------+---------------+--------------+-----+-------------------+ 1082 | Header | 6LN src | 6LBR | 6LR | 6LN dst | 1083 +----------+---------------+--------------+-----+-------------------+ 1084 | Inserted | IP-in-IP(RPI) | IP-in-IP(RH3 | -- | -- | 1085 | headers | | to 6LN,RPI) | | | 1086 | Removed | -- | -- | -- | IP-in-IP(RH3,RPI) | 1087 | headers | | | | | 1088 | Re-added | -- | -- | -- | -- | 1089 | headers | | | | | 1090 | Modified | -- | -- | -- | -- | 1091 | headers | | | | | 1092 | Untouche | -- | -- | -- | -- | 1093 | d | | | | | 1094 | headers | | | | | 1095 +----------+---------------+--------------+-----+-------------------+ 1097 Non Storing: Summary of the use of headers for RPL-aware-leaf to RPL- 1098 aware-leaf 1100 6.10. Example of Flow from RPL-aware-leaf to not-RPL-aware-leaf 1102 In this case the flow comprises: 1104 6LN --> 6LR --> root (6LBR) --> 6LR --> not-RPL-aware (IPv6 node) 1106 As in the previous case, the 6LN will insert an RPI header which MUST 1107 be in an IP-in-IP header addressed to the root so that the 6LBR can 1108 remove this RPI. The 6LBR will then insert an RH3 inside a new IP- 1109 in-IP header addressed to the 6LN above the destination node. 1111 +-----------+---------------+---------------+----------------+------+ 1112 | Header | 6LN | 6LBR | 6LR | IPv6 | 1113 +-----------+---------------+---------------+----------------+------+ 1114 | Inserted | IP-in-IP(RPI) | IP-in-IP(RH3, | -- | -- | 1115 | headers | | opt RPI) | | | 1116 | Removed | -- | IP-in-IP(RPI) | IP-in-IP(RH3, | -- | 1117 | headers | | | opt RPI) | | 1118 | Re-added | -- | -- | -- | -- | 1119 | headers | | | | | 1120 | Modified | -- | -- | -- | -- | 1121 | headers | | | | | 1122 | Untouched | -- | -- | -- | -- | 1123 | headers | | | | | 1124 +-----------+---------------+---------------+----------------+------+ 1126 Non Storing: Summary of the use of headers from RPL-aware-leaf to 1127 not-RPL-aware-leaf 1129 6.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 1131 In this case the flow comprises: 1133 not-RPL-aware 6LN --> 6LR --> root (6LBR) --> 6LR --> 6LN 1135 This scenario is mostly identical to the previous one. The RPI is 1136 added by the first 6LR inside an IP-in-IP header addressed to the 1137 root. The 6LBR will remove this RPI, and add it's own IP-in-IP 1138 header containing an RH3 header. 1140 +------------+------+---------------+---------------+---------------+ 1141 | Header | IPv6 | 6LR | 6LBR | 6LN | 1142 +------------+------+---------------+---------------+---------------+ 1143 | Inserted | -- | IP-in-IP(RPI) | IP-in-IP(RH3) | -- | 1144 | headers | | | | | 1145 | Removed | -- | IP-in-IP(RPI) | -- | IP-in-IP(RH3) | 1146 | headers | | | | | 1147 | Re-added | -- | -- | -- | -- | 1148 | headers | | | | | 1149 | Modified | -- | -- | -- | -- | 1150 | headers | | | | | 1151 | Untouched | -- | -- | -- | -- | 1152 | headers | | | | | 1153 +------------+------+---------------+---------------+---------------+ 1155 Non Storing: Summary of the use of headers from not-RPL-aware-leaf to 1156 RPL-aware-leaf 1158 6.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-leaf 1160 In this case the flow comprises: 1162 not-RPL-aware 6LN --> 6LR --> root (6LBR) --> 6LR --> not-RPL-aware 1163 (IPv6 node) 1165 This scenario is the combination of the previous two cases. 1167 +----------+-----+-------------+--------------+--------------+------+ 1168 | Header | IPv | 6LR | 6LBR | 6LR | IPv6 | 1169 | | 6 | | | | | 1170 +----------+-----+-------------+--------------+--------------+------+ 1171 | Inserted | -- | IP-in- | IP-in- | -- | -- | 1172 | headers | | IP(RPI) | IP(RH3) | | | 1173 | Removed | -- | -- | IP-in- | IP-in- | -- | 1174 | headers | | | IP(RPI) | IP(RH3, opt | | 1175 | | | | | RPI) | | 1176 | Re-added | -- | -- | -- | -- | -- | 1177 | headers | | | | | | 1178 | Modified | -- | -- | -- | -- | -- | 1179 | headers | | | | | | 1180 | Untouche | -- | -- | -- | -- | -- | 1181 | d | | | | | | 1182 | headers | | | | | | 1183 +----------+-----+-------------+--------------+--------------+------+ 1185 Non Storing: Summary of the use of headers from not-RPL-aware-leaf to 1186 not-RPL-aware-leaf 1188 7. Observations about the problem 1190 7.1. Storing mode 1192 In the completely general storing case, which includes not-RPL aware 1193 leaf nodes, it is not possible for a sending node to know if the 1194 destination is RPL aware, and therefore it must always use hop-by-hop 1195 IP-in-IP encapsulation, and it can never omit the IP-in-IP 1196 encapsulation. See table Table 1 1198 The simplest fully general approach for storing mode is to always put 1199 in hop-by-hop IP-in-IP headers. [I-D.ietf-roll-routing-dispatch] 1200 shows that this hop-by-hop IP-in-IP header can be compressed down to 1201 {TBD} bytes. 1203 There are potential significant advantages to having a single code 1204 path that always processes IP-in-IP headers with no options. 1206 If all RPL aware nodes can be told/configured that there are no non- 1207 RPL aware leaf nodes, then the only case where an IP-in-IP header is 1208 needed is when communicating outside the LLN. The 6LBR knows well 1209 when the communication is from the outside, and the 6LN can tell by 1210 comparing the destination address to the prefix provided in the PIO. 1211 If it is known that there are no communications outside the RPL 1212 domain (noting that the RPL domain may well extend to outside the 1213 LLN), then RPI headers can be included in all packets, and IP-in-IP 1214 headers are *never* needed. This may be significantly advantageous 1215 in relatively closed systems such as in building or industrial 1216 automation. Again, there are advantages to having a single code 1217 path. 1219 In order to support the above two cases with full generality, the 1220 different situations (always do IP-in-IP vs never use IP-in-IP) 1221 should be signaled in the RPL protocol itself. 1223 7.2. Non-Storing mode 1225 In the non-storing case, dealing with non-RPL aware leaf nodes is 1226 much easier as the 6LBR (DODAG root) has complete knowledge about the 1227 connectivity of all DODAG nodes, and all traffic flows through the 1228 root node. 1230 The 6LBR can recognize non-RPL aware leaf nodes because it will 1231 receive a DAO about that node from the 6LN immediately above that 1232 node. This means that the non-storing mode case can avoid ever using 1233 hop-by-hop IP-in-IP headers. 1235 It is unclear what it would mean for an RH3 header to be present in a 1236 hop-by-hop IP-in-IP header. The receiving node ought to consume the 1237 IP-in-IP header, and therefore consume the RH3 as well, and then 1238 attempt to send the packet again. But intermediate 6LN nodes would 1239 not know how to forward the packet (because they do not save the 1240 sate), so the RH3 would need to be retained. This is a new kind of 1241 IPv6 packet processing. Therefore it may be that on the outbound leg 1242 of non-storing RPL networks, that hop-by-hop IP-in-IP header can NOT 1243 be used. 1245 [I-D.ietf-roll-routing-dispatch] shows how the destination=root, and 1246 destination=6LN IP-in-IP header can be compressed down to {TBD} 1247 bytes. 1249 Unlike in the storing mode case, there is no need for all nodes to 1250 know about the existence of non-RPL aware nodes. Only the 6LBR needs 1251 to change when there are non-RPL aware nodes. Further, in the non- 1252 storing case, the 6LBR is informed by the DAOs when there are non-RPL 1253 aware nodes. 1255 8. 6LoRH Compression cases 1257 The [I-D.ietf-roll-routing-dispatch] proposes a compression method 1258 for RPI, RH3 and IPv6-in-IPv6. 1260 In Storing Mode, for the examples of Flow from RPL-aware-leaf to non- 1261 RPL-aware-leaf and non-RPL-aware-leaf to non-RPL-aware-leaf comprise 1262 an IP-in-IP and RPI compression headers. The type of this case is 1263 critical since IP-in-IP is encapsulating a RPI header. 1265 +--+-----+---+--------------+-----------+-------------+-------------+ 1266 |1 | 0|0 |TSE| 6LoRH Type 6 | Hop Limit | RPI - 6LoRH | LOWPAN IPHC | 1267 +--+-----+---+--------------+-----------+-------------+-------------+ 1269 Figure 4: Critical IP-in-IP (RPI). 1271 9. IANA Considerations 1273 There are no IANA considerations related to this document. 1275 10. Security Considerations 1277 The security considerations covering of [RFC6553] and [RFC6554] apply 1278 when the packets get into RPL Domain. 1280 11. Acknowledgments 1282 This work is partially funded by the FP7 Marie Curie Initial Training 1283 Network (ITN) METRICS project (grant agreement No. 607728). 1285 The authors would like to acknowledge the review, feedback, and 1286 comments of Robert Cragie, Simon Duquennoy, Cenk Guendogan, Peter van 1287 der Stok, Xavier Vilajosana and Thomas Watteyne. 1289 12. References 1291 12.1. Normative References 1293 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1294 Requirement Levels", BCP 14, RFC 2119, 1295 DOI 10.17487/RFC2119, March 1997, 1296 . 1298 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1299 (IPv6) Specification", RFC 2460, December 1998. 1301 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1302 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1303 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1304 Low-Power and Lossy Networks", RFC 6550, 1305 DOI 10.17487/RFC6550, March 2012, 1306 . 1308 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 1309 Power and Lossy Networks (RPL) Option for Carrying RPL 1310 Information in Data-Plane Datagrams", RFC 6553, 1311 DOI 10.17487/RFC6553, March 2012, 1312 . 1314 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 1315 Routing Header for Source Routes with the Routing Protocol 1316 for Low-Power and Lossy Networks (RPL)", RFC 6554, 1317 DOI 10.17487/RFC6554, March 2012, 1318 . 1320 12.2. Informative References 1322 [I-D.ietf-6man-rfc2460bis] 1323 Deering, D. and R. Hinden, "Internet Protocol, Version 6 1324 (IPv6) Specification", draft-ietf-6man-rfc2460bis-05 (work 1325 in progress), June 2016. 1327 [I-D.ietf-6tisch-architecture] 1328 Thubert, P., "An Architecture for IPv6 over the TSCH mode 1329 of IEEE 802.15.4", draft-ietf-6tisch-architecture-10 (work 1330 in progress), June 2016. 1332 [I-D.ietf-roll-routing-dispatch] 1333 Thubert, P., Bormann, C., Toutain, L., and R. Cragie, 1334 "6LoWPAN Routing Header", draft-ietf-roll-routing- 1335 dispatch-00 (work in progress), March 2016. 1337 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1338 Control Message Protocol (ICMPv6) for the Internet 1339 Protocol Version 6 (IPv6) Specification", RFC 4443, 1340 DOI 10.17487/RFC4443, March 2006, 1341 . 1343 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1344 Bormann, "Neighbor Discovery Optimization for IPv6 over 1345 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1346 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1347 . 1349 [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and 1350 J. Martocci, "Reactive Discovery of Point-to-Point Routes 1351 in Low-Power and Lossy Networks", RFC 6997, 1352 DOI 10.17487/RFC6997, August 2013, 1353 . 1355 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 1356 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 1357 2014, . 1359 [Second6TischPlugtest] 1360 "2nd 6Tisch Plugtest", . 1363 Authors' Addresses 1365 Maria Ines Robles 1366 Ericsson 1367 Hirsalantie 11 1368 Jorvas 02420 1369 Finland 1371 Email: maria.ines.robles@ericsson.com 1373 Michael C. Richardson 1374 Sandelman Software Works 1375 470 Dawson Avenue 1376 Ottawa, ON K1Z 5V7 1377 CA 1379 Email: mcr+ietf@sandelman.ca 1380 URI: http://www.sandelman.ca/ 1382 Pascal Thubert 1383 Cisco Systems, Inc 1384 Village d'Entreprises Green Side 400, Avenue de Roumanille 1385 Batiment T3, Biot - Sophia Antipolis 06410 1386 France 1388 Email: pthubert@cisco.com