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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL P. Thubert, Ed. 3 Internet-Draft L. Zhao 4 Updates: 8138 (if approved) Cisco Systems 5 Intended status: Standards Track 8 July 2020 6 Expires: 9 January 2021 8 A RPL DODAG Configuration Option for the 6LoWPAN Routing Header 9 draft-ietf-roll-turnon-rfc8138-08 11 Abstract 13 This document updates RFC 8138 and RFC 6550 by defining a bit in the 14 RPL DODAG Configuration Option to indicate whether RFC 8138 15 compression is used within the RPL Instance, and specify the behavior 16 of RFC 8138-capable nodes when the bit is set and reset. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on 9 January 2021. 35 Copyright Notice 37 Copyright (c) 2020 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 42 license-info) in effect on the date of publication of this document. 43 Please review these documents carefully, as they describe your rights 44 and restrictions with respect to this document. Code Components 45 extracted from this document must include Simplified BSD License text 46 as described in Section 4.e of the Trust Legal Provisions and are 47 provided without warranty as described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2.1. References . . . . . . . . . . . . . . . . . . . . . . . 3 54 2.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2.3. Requirements Language . . . . . . . . . . . . . . . . . . 4 56 3. The RPL DODAG Configuration Option . . . . . . . . . . . . . 4 57 4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 5 58 5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 5 59 5.1. Coexistence . . . . . . . . . . . . . . . . . . . . . . . 6 60 5.2. Inconsistent State While Migrating . . . . . . . . . . . 6 61 5.3. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6 62 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 63 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 64 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 65 9. Normative References . . . . . . . . . . . . . . . . . . . . 8 66 10. Informative References . . . . . . . . . . . . . . . . . . . 8 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 69 1. Introduction 71 The packet compression technique defined in [RFC8138] can only be 72 activated in a RPL [RFC6550] network when all the nodes support it. 73 Otherwise, a non-capable node acting as leaf-only would fail to 74 communicate, and acting as a router it would drop the compressed 75 packets and black-hole a portion of the network. 77 The original idea was to use a flag day but that proved impractical 78 in a number of situations such as a large metering network that is 79 used in production and incurs financial losses when interrupted. 81 This specification is designed for the scenario where a live network 82 is upgraded to support [RFC8138]. During the migration, the 83 compression should remain inactive, until all nodes are upgraded. 84 This document complements [RFC8138] and dedicates a flag in the RPL 85 DODAG Configuration Option to indicate whether the [RFC8138] 86 compression should be used within the RPL DODAG. 88 The setting of this new flag is controlled by the Root and propagates 89 as is in the whole network as part of the normal RPL signaling. 91 The idea is to use the flag to maintain the compression inactive 92 during the migration phase. When the migration is complete (e.g., as 93 known by network management and/or inventory), the flag is set and 94 the compression is globally activated in the whole DODAG. 96 2. Terminology 98 2.1. References 100 The Terminology used in this document is consistent with and 101 incorporates that described in "Terms Used in Routing for Low-Power 102 and Lossy Networks (LLNs)" [RFC7102]. Other terms in use in LLNs are 103 found in "Terminology for Constrained-Node Networks" [RFC7228]. 105 "RPL", the "RPL Packet Information" (RPI), "RPL Instance" (indexed by 106 a RPLInstanceID) are defined in "RPL: IPv6 Routing Protocol for 107 Low-Power and Lossy Networks" [RFC6550]. The RPI is the abstract 108 information that RPL defines to be placed in data packets, e.g., as 109 the RPL Option [RFC6553] within the IPv6 Hop-By-Hop Header. By 110 extension the term "RPI" is often used to refer to the RPL Option 111 itself. The DODAG Information Solicitation (DIS), Destination 112 Advertisement Object (DAO) and DODAG Information Object (DIO) 113 messages are also specified in [RFC6550]. 115 This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware 116 Leaf (RAL) consistently with "Using RPI Option Type, Routing Header 117 for Source Routes and IPv6-in-IPv6 encapsulation in the RPL Data 118 Plane" [USEofRPLinfo]. The term RPL-Aware Node (RAN) refers to a 119 node that is either a RAL or a RPL Router. A RAN manages the 120 reachability of its addresses and prefixes by injecting them in RPL 121 by itself. In contrast, a RUL leverages "Registration Extensions for 122 IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor 123 Discovery" [RFC8505] to obtain reachability services from its parent 124 router(s) as specified in "Routing for RPL Leaves" [UNAWARE-LEAVES]. 126 2.2. Glossary 128 This document often uses the following acronyms: 130 6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network 131 6LoRH: 6LoWPAN Routing Header 132 DIO: DODAG Information Object (a RPL message) 133 DODAG: Destination-Oriented Directed Acyclic Graph 134 LLN: Low-Power and Lossy Network 135 RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks 136 OF: RPL Objective Function 137 OCP: RPL Objective Code Point 138 MOP: RPL Mode of Operation 139 RPI: RPL Packet Information 140 RAL: RPL-Aware Leaf 141 RAN: RPL-Aware Node 142 RUL: RPL-Unaware Leaf 143 SRH: Source Routing Header 145 2.3. Requirements Language 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 149 "OPTIONAL" in this document are to be interpreted as described in BCP 150 14 [RFC2119][RFC8174] when, and only when, they appear in all 151 capitals, as shown here. 153 3. The RPL DODAG Configuration Option 155 The DODAG Configuration Option is defined in Section 6.7.6 of 156 [RFC6550]. 158 The RPL DODAG Configuration Option is typically placed in a DODAG 159 Information Object (DIO) message. The DIO message propagates down 160 the DODAG to form and then maintain its structure. The DODAG 161 Configuration Option is copied unmodified from parents to children. 163 As shown in Figure 1, the DODAG Configuration Option was designed 164 with 4 bit positions reserved for future use as Flags. 166 0 1 2 3 167 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | Type = 0x04 |Opt Length = 14| Flags |A| ... | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 171 | ... | 173 Figure 1: DODAG Configuration Option (Partial View) 175 This specification defines a new flag "Enable RFC8138 Compression" 176 (T). The "T" flag is set to turn-on the use of the compression of 177 RPL artifacts with [RFC8138] within the DODAG. The new "T" flag is 178 encoded in one of the reserved bits in the RPL DODAG Configuration 179 Option. The suggested bit position of the "T" flag is indicated in 180 Section 6. 182 /[RFC6550] states, [RFC6550] states, when referring to the DODAG 183 Configuration Option, that "Nodes other than the DODAG Root MUST NOT 184 modify this information when propagating the DODAG Configuration 185 option". Therefore, even a legacy parent propagates the "T" flag as 186 set by the Root whether it supports this specification or not. So 187 when the "T" flag is set, it is transparently flooded to all the 188 nodes in the DODAG. 190 Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP) 191 in the DIO Base Object. The new "T" flag is defined only for MOP 192 value between 0 to 6. 194 4. Updating RFC 8138 196 A node SHOULD source packets in the compressed form using [RFC8138] 197 if and only if the "T" flag is set. This behaviour can be overridden 198 by e.g., configuration or network management. Overriding may be 199 needed e.g., to cope with a legacy implementations of the Root that 200 supports [RFC8138] but not this specification and cannot set the "T" 201 flag. 203 The decision of using [RFC8138] is made by the originator of the 204 packet depending on its capabilities and its knowledge of the state 205 of the "T" flag. A router that encapsulates a packet is the 206 originator of the resulting packet and is responsible to compress the 207 outer headers with [RFC8138], but it MUST leave the encapsulated 208 packet as is. 210 An external target [USEofRPLinfo] is not expected to support 211 [RFC8138]. In most cases, packets from/to an external target are 212 tunneled back and forth between the RPL border router and the Root 213 regardless of the MOP used in the RPL DODAG. The inner packet is 214 typically not compressed with [RFC8138] so the 6LR just needs to 215 decapsulate the (compressed) outer header and forward the 216 (uncompressed) inner packet towards the external target. 218 A router MUST uncompress a packet that is to be forwarded to an 219 external target. Otherwise, the router MUST forward the packet in 220 the form that the source used, either compressed or uncompressed. 222 A RUL [UNAWARE-LEAVES] is both a leaf and an external target . A RUL 223 does not participate in RPL and depends on the parent router to 224 obtain connectivity. In the case of a RUL, forwarding towards an 225 external target actually means delivering the packet. 227 5. Transition Scenarios 229 A node that supports [RFC8138] but not this specification can only be 230 used in an homogeneous network. Enabling the [RFC8138] compression 231 requires a "flag day"; all nodes must be upgraded, and then the 232 network can be rebooted with the [RFC8138] compression turned on. 234 The intent for this specification is to perform a migration once and 235 for all without the need for a flag day. In particular it is not the 236 intention to undo the setting of the "T" flag. Though it is possible 237 to roll back (see Section 5.3), adding nodes that do not support 238 [RFC8138] after a roll back may be problematic if the roll back did 239 not fully complete. 241 5.1. Coexistence 243 A node that supports this specification can operate in a network with 244 the [RFC8138] compression turned on or off with the "T" flag set 245 accordingly and in a network in transition from off to on or on to 246 off (see Section 5.2). 248 A node that does not support [RFC8138] can interoperate with nodes 249 that do in a network with [RFC8138] compression turned off. If the 250 compression is turned on, all the RPL-Aware Nodes are expected to be 251 able to handle compressed packets in the compressed form. A node 252 that cannot do so may remain connected to the network as a RUL, but 253 how the node is modified to turn into a RUL is out of scope. 255 5.2. Inconsistent State While Migrating 257 When the "T" flag is turned on by the Root, the information slowly 258 percolates through the DODAG as the DIO gets propagated. Some nodes 259 will see the flag and start sourcing packets in the compressed form 260 while other nodes in the same RPL DODAG are still not aware of it. 261 Conversely, in non-storing mode, the Root will start using [RFC8138] 262 with a Source Routing Header 6LoRH (SRH-6LoRH) that routes all the 263 way to the parent router or to the leaf. 265 To ensure that a packet is forwarded across the RPL DODAG in the form 266 in which it was generated, it is required that all the RPL nodes 267 support [RFC8138] at the time of the switch. 269 Setting the "T" flag is ultimately the responsibility of the Network 270 Administrator. The expectation is that the network management or 271 upgrading tools in place enable the Network Administrator to know 272 when all the nodes that may join a DODAG were migrated. In the case 273 of a RPL instance with multiple Roots, all nodes that participate to 274 the RPL Instance may potentially join any DODAG. The network MUST be 275 operated with the "T" flag reset until all nodes in the RPL Instance 276 are upgraded to support this specification. 278 5.3. Rolling Back 280 When turning [RFC8138] compression off in the network, the Network 281 Administrator MUST wait until all nodes have converged to the "T" 282 flag reset before allowing nodes that do not support the compression 283 in the network. 285 It is RECOMMENDED to only deploy nodes that support [RFC8138] in a 286 network where the compression is turned on. A node that does not 287 support [RFC8138] MUST only be used as a RUL. 289 6. IANA Considerations 291 IANA is requested to assign a new option flag from the Registry for 292 the "DODAG Configuration Option Flags" that was created for [RFC6550] 293 as follows: 295 +---------------+---------------------------------+-----------+ 296 | Bit Number | Capability Description | Reference | 297 +---------------+---------------------------------+-----------+ 298 | 2 (suggested) | Turn on RFC8138 Compression (T) | THIS RFC | 299 +---------------+---------------------------------+-----------+ 301 Table 1: New DODAG Configuration Option Flag 303 The DODAG Configuration Option Flags defined so far will be obsolete 304 for RPL Mode of Operation (MOP) above and including 7. 306 IANA is requested to update the name of the Registry from "DODAG 307 Configuration Option Flags" to "DODAG Configuration Option Flags for 308 RPL MOP 0..6". 310 When MOP values of 7 and more are defined, a new registry will be 311 needed. 313 7. Security Considerations 315 First of all, it is worth noting that with [RFC6550], every node in 316 the LLN that is RPL-aware can inject any RPL-based attack in the 317 network. A trust model has to be put in place in an effort to 318 exclude rogue nodes from participating to the RPL and the 6LoWPAN 319 signaling, as well as from the data packet exchange. This trust 320 model could be at a minimum based on a Layer-2 Secure joining and the 321 Link-Layer security. This is a generic RPL and 6LoWPAN requirement, 322 see Req5.1 in Appendix of [RFC8505]. 324 Setting the "T" flag before all routers are upgraded may cause a loss 325 of packets. The new bit is protected as the rest of the 326 configuration so this is just one of the many attacks that can happen 327 if an attacker manages to inject a corrupted configuration. 329 Setting and resetting the "T" flag may create inconsistencies in the 330 network but as long as all nodes are upgraded to [RFC8138] support 331 they will be able to forward both forms. The source is responsible 332 for selecting whether the packet is compressed or not, and all 333 routers must use the format that the source selected. So the result 334 of an inconsistency is merely that both forms will be present in the 335 network, at an additional cost of bandwidth for packets in the 336 uncompressed form. 338 8. Acknowledgments 340 The authors wish to thank Alvaro Retana, Dominique Barthel and Rahul 341 Jadhav for their in-depth reviews and constructive suggestions. 343 Also many thanks to Michael Richardson for being always helpful and 344 responsive when need comes. 346 9. Normative References 348 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 349 Requirement Levels", BCP 14, RFC 2119, 350 DOI 10.17487/RFC2119, March 1997, 351 . 353 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 354 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 355 May 2017, . 357 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 358 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 359 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 360 Low-Power and Lossy Networks", RFC 6550, 361 DOI 10.17487/RFC6550, March 2012, 362 . 364 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 365 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 366 2014, . 368 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 369 "IPv6 over Low-Power Wireless Personal Area Network 370 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 371 April 2017, . 373 10. Informative References 375 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 376 Power and Lossy Networks (RPL) Option for Carrying RPL 377 Information in Data-Plane Datagrams", RFC 6553, 378 DOI 10.17487/RFC6553, March 2012, 379 . 381 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 382 Constrained-Node Networks", RFC 7228, 383 DOI 10.17487/RFC7228, May 2014, 384 . 386 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 387 Perkins, "Registration Extensions for IPv6 over Low-Power 388 Wireless Personal Area Network (6LoWPAN) Neighbor 389 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 390 . 392 [UNAWARE-LEAVES] 393 Thubert, P. and M. Richardson, "Routing for RPL Leaves", 394 Work in Progress, Internet-Draft, draft-ietf-roll-unaware- 395 leaves-18, 12 June 2020, . 398 [USEofRPLinfo] 399 Robles, I., Richardson, M., and P. Thubert, "Using RPI 400 Option Type, Routing Header for Source Routes and IPv6-in- 401 IPv6 encapsulation in the RPL Data Plane", Work in 402 Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-40, 403 25 June 2020, . 406 Authors' Addresses 408 Pascal Thubert (editor) 409 Cisco Systems, Inc 410 Building D 411 45 Allee des Ormes - BP1200 412 06254 MOUGINS - Sophia Antipolis 413 France 415 Phone: +33 497 23 26 34 416 Email: pthubert@cisco.com 418 Li Zhao 419 Cisco Systems, Inc 420 Xinsi Building 421 No. 926 Yi Shan Rd 422 SHANGHAI 423 200233 424 China 426 Email: liz3@cisco.com