idnits 2.17.1 draft-ietf-roll-turnon-rfc8138-12.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 (2 September 2020) is 1331 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 7102 == Outdated reference: A later version (-30) exists of draft-ietf-roll-unaware-leaves-18 == Outdated reference: A later version (-44) exists of draft-ietf-roll-useofrplinfo-40 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). 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 2 September 2020 6 Expires: 6 March 2021 8 A RPL DODAG Configuration Option for the 6LoWPAN Routing Header 9 draft-ietf-roll-turnon-rfc8138-12 11 Abstract 13 This document updates RFC 8138 by defining a bit in the RPL DODAG 14 Configuration Option to indicate whether compression is used within 15 the RPL Instance, and specify the behavior of RFC 8138-capable nodes 16 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 6 March 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 . . . . . . . . . . . . . . . . . . . 9 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 69 1. Introduction 71 The design of Low Power and Lossy Networks (LLNs) is generally 72 focused on saving energy, which is the most constrained resource of 73 all. The routing optimizations in the "Routing Protocol for Low 74 Power and Lossy Networks" [RFC6550] (RPL) such as routing along a 75 Destination-Oriented Directed Acyclic Graph (DODAG) to a Root Node 76 and the associated packet compression technique [RFC8138] derive from 77 that primary concern. 79 Enabling [RFC8138] requires a Flag Day where the network is upgraded 80 and rebooted. Otherwise, if acting as a Leaf, a node that does not 81 support the compression would fail to communicate; if acting as a 82 router it would drop the compressed packets and black-hole a portion 83 of the network. This specification enables a hot upgrade where a 84 live network is migrated. During the migration, the compression 85 remains inactive, until all nodes are upgraded. 87 This document complements [RFC8138] and dedicates a flag in the RPL 88 DODAG Configuration Option to indicate whether the [RFC8138] 89 compression should be used within the RPL DODAG. The setting of this 90 new flag is controlled by the Root and propagates as is in the whole 91 network as part of the normal RPL signaling. 93 The flag is cleared to maintain the compression inactive during the 94 migration phase. When the migration is complete (e.g., as known by 95 network management and/or inventory), the flag is set and the 96 compression is globally activated in the whole DODAG. 98 2. Terminology 100 2.1. References 102 The terminology used in this document is consistent with and 103 incorporates that described in "Terms Used in Routing for Low-Power 104 and Lossy Networks (LLNs)" [RFC7102]. Other terms in use in LLNs are 105 found in "Terminology for Constrained-Node Networks" [RFC7228]. 107 "RPL", the "RPL Packet Information" (RPI), and "RPL Instance" 108 (indexed by a RPLInstanceID) are defined in "RPL: IPv6 Routing 109 Protocol for Low-Power and Lossy Networks" [RFC6550]. The RPI is the 110 abstract information that RPL defines to be placed in data packets, 111 e.g., as the RPL Option [RFC6553] within the IPv6 Hop-By-Hop Header. 112 By extension the term "RPI" is often used to refer to the RPL Option 113 itself. The DODAG Information Solicitation (DIS), Destination 114 Advertisement Object (DAO) and DODAG Information Object (DIO) 115 messages are also specified in [RFC6550]. 117 This document uses the terms RPL-Unaware Leaf (RUL) and RPL-Aware 118 Leaf (RAL) consistently with "Using RPI Option Type, Routing Header 119 for Source Routes and IPv6-in-IPv6 encapsulation in the RPL Data 120 Plane" [USEofRPLinfo]. The term RPL-Aware Node (RAN) refers to a 121 node that is either a RAL or a RPL Router. A RAN manages the 122 reachability of its addresses and prefixes by injecting them in RPL 123 by itself. In contrast, a RUL leverages "Registration Extensions for 124 IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor 125 Discovery" [RFC8505] to obtain reachability services from its parent 126 router(s) as specified in "Routing for RPL Leaves" [UNAWARE-LEAVES]. 128 2.2. Glossary 130 This document often uses the following acronyms: 132 6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network 133 6LoRH: 6LoWPAN Routing Header 134 DIO: DODAG Information Object (a RPL message) 135 DODAG: Destination-Oriented Directed Acyclic Graph 136 LLN: Low-Power and Lossy Network 137 RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks 138 OF: RPL Objective Function 139 OCP: RPL Objective Code Point 140 MOP: RPL Mode of Operation 141 RPI: RPL Packet Information 142 RAL: RPL-Aware Leaf 143 RAN: RPL-Aware Node 144 RUL: RPL-Unaware Leaf 145 SRH: Source Routing Header 147 2.3. Requirements Language 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 151 "OPTIONAL" in this document are to be interpreted as described in BCP 152 14 [RFC2119][RFC8174] when, and only when, they appear in all 153 capitals, as shown here. 155 3. The RPL DODAG Configuration Option 157 The DODAG Configuration Option is defined in Section 6.7.6 of 158 [RFC6550]. 160 The RPL DODAG Configuration Option is typically placed in a DODAG 161 Information Object (DIO) message. The DIO message propagates down 162 the DODAG to form and then maintain its structure. The DODAG 163 Configuration Option is copied unmodified from parents to children. 165 As shown in Figure 1, the DODAG Configuration Option was designed 166 with 4 bit positions reserved for future use as Flags. 168 0 1 2 3 169 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 1 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | Type = 0x04 |Opt Length = 14| | |T| |A| ... | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 173 | <- Flags -> ... | 175 Figure 1: DODAG Configuration Option (Partial View) 177 This specification defines a new flag "Enable RFC8138 Compression" 178 (T). The "T" flag is set to turn-on the use of the compression of 179 RPL artifacts with [RFC8138] within the DODAG. The new "T" flag is 180 encoded in position 2 of the reserved Flags field in the RPL DODAG 181 Configuration Option, and set to 0 in legacy implementations as 182 specified in Section 6.7.6 of [RFC6550]. 184 [RFC6550] states, when referring to the DODAG Configuration Option, 185 that "Nodes other than the DODAG Root MUST NOT modify this 186 information when propagating the DODAG Configuration option". 187 Therefore, a legacy parent propagates the "T" flag as set by the Root 188 whether it supports this specification or not. So when the "T" flag 189 is set, it is transparently flooded to all the nodes in the DODAG. 191 Section 6.3.1 of [RFC6550] defines a 3-bit Mode of Operation (MOP) in 192 the DIO Base Object. This specification applies to MOP values 0 to 193 6. For a MOP value of 7, the compression MUST be used by default 194 regardless of the setting of the "T" flag. 196 4. Updating RFC 8138 198 A node SHOULD generate packets in the compressed form using [RFC8138] 199 if and only if the "T" flag is set. This behavior can be overridden 200 by configuration or network management. Overriding may be needed 201 e.g., to turn on the compression in a network where all nodes support 202 [RFC8138] but the Root does not support this specification and cannot 203 set the "T" flag, or to disable it locally in case of a problem. 205 The decision to use [RFC8138] is made by the originator of the packet 206 depending on its capabilities and its knowledge of the state of the 207 "T" flag. A router encapsulating a packet is the originator of the 208 resulting packet and is responsible for compressing the outer headers 209 with [RFC8138], but it MUST leave the encapsulated packet as is. 211 An external target [USEofRPLinfo] is not expected to support 212 [RFC8138]. In most cases, packets to and from an external target are 213 tunneled back and forth between the border router (referred to as 214 6LR) that serves the external target and the Root, regardless of the 215 MOP used in the RPL DODAG. The inner packet is typically not 216 compressed with [RFC8138], so for outgoing packets, the border router 217 just needs to decapsulate the (compressed) outer header and forward 218 the (uncompressed) inner packet towards the external target. 220 A router MUST uncompress a packet that is to be forwarded to an 221 external target. Otherwise, the router MUST forward the packet in 222 the form that the source used, either compressed or uncompressed. 224 A RUL [UNAWARE-LEAVES] is both a leaf and an external target. A RUL 225 does not participate in RPL and depends on the parent router to 226 obtain connectivity. In the case of a RUL, forwarding towards an 227 external target actually means delivering the packet. 229 5. Transition Scenarios 231 A node that supports [RFC8138] but not this specification can only be 232 used in an homogeneous network. Enabling the [RFC8138] compression 233 without a turn-on signaling method requires a "flag day"; by which 234 time all nodes must be upgraded, and at which point the network can 235 be rebooted with the [RFC8138] compression turned on. 237 The intent for this specification is to perform a migration once and 238 for all without the need for a flag day. In particular it is not the 239 intention to undo the setting of the "T" flag. Though it is possible 240 to roll back (see Section 5.3), adding nodes that do not support 241 [RFC8138] after a roll back may be problematic if the roll back did 242 not fully complete. 244 5.1. Coexistence 246 A node that supports this specification can operate in a network with 247 the [RFC8138] compression turned on or off with the "T" flag set 248 accordingly and in a network in transition from off to on or on to 249 off (see Section 5.2). 251 A node that does not support [RFC8138] can interoperate with nodes 252 that do in a network with [RFC8138] compression turned off. If the 253 compression is turned on, all the RPL-Aware Nodes are expected to be 254 able to handle compressed packets in the compressed form. A node 255 that cannot do so may remain connected to the network as a RUL as 256 described in [UNAWARE-LEAVES]. 258 5.2. Inconsistent State While Migrating 260 When the "T" flag is turned on by the Root, the information slowly 261 percolates through the DODAG as the DIO gets propagated. Some nodes 262 will see the flag and start sourcing packets in the compressed form 263 while other nodes in the same RPL DODAG are still not aware of it. 264 In non-storing mode, the Root will start using [RFC8138] with a 265 Source Routing Header 6LoRH (SRH-6LoRH) that routes all the way to 266 the parent router or to the leaf. 268 To ensure that a packet is forwarded across the RPL DODAG in the form 269 in which it was generated, it is required that all the RPL nodes 270 support [RFC8138] at the time of the switch. 272 Setting the "T" flag is ultimately the responsibility of the Network 273 Administrator. The expectation is that the network management or 274 upgrading tools in place enable the Network Administrator to know 275 when all the nodes that may join a DODAG were migrated. In the case 276 of a RPL instance with multiple Roots, all nodes that participate to 277 the RPL Instance may potentially join any DODAG. The network MUST be 278 operated with the "T" flag reset until all nodes in the RPL Instance 279 are upgraded to support this specification. 281 5.3. Rolling Back 283 When turning [RFC8138] compression off in the network, the Network 284 Administrator MUST wait until all nodes have converged to the "T" 285 flag reset before allowing nodes that do not support the compression 286 in the network. To that effect, whether the compression is active in 287 a node SHOULD be exposed the node's management interface. 289 Nodes that do not support [RFC8138] SHOULD NOT be deployed in a 290 network where the compression is turned on. If that is done, the 291 node can only operate as a RUL. 293 6. IANA Considerations 295 IANA is requested to assign a new option flag from the Registry for 296 the "DODAG Configuration Option Flags" that was created for [RFC6550] 297 as follows: 299 +---------------+---------------------------------+-----------+ 300 | Bit Number | Capability Description | Reference | 301 +---------------+---------------------------------+-----------+ 302 | 2 (suggested) | Turn on RFC8138 Compression (T) | THIS RFC | 303 +---------------+---------------------------------+-----------+ 305 Table 1: New DODAG Configuration Option Flag 307 7. Security Considerations 309 It is worth noting that with RPL [RFC6550], every node in the LLN 310 that is RPL-aware can inject any RPL-based attack in the network. 311 This document applies typically to an existing deployment and does 312 not change its security requirements and operations. It is assumed 313 that the security mechanisms as defined for RPL are followed. 315 Setting the "T" flag before all routers are upgraded may cause a loss 316 of packets. The new bit is protected as the rest of the 317 configuration so this is just one of the many attacks that can happen 318 if an attacker manages to inject a corrupted configuration. 320 Setting and resetting the "T" flag may create inconsistencies in the 321 network but as long as all nodes are upgraded to [RFC8138] support 322 they will be able to forward both forms. The source is responsible 323 for selecting whether the packet is compressed or not, and all 324 routers must use the format that the source selected. So the result 325 of an inconsistency is merely that both forms will be present in the 326 network, at an additional cost of bandwidth for packets in the 327 uncompressed form. 329 An attacker in the middle of the network may reset the "T" flag to 330 cause extra energy spending in its subDAG. Conversely it may set the 331 "T" flag, so that nodes located downstream would compress when that 332 it is not desired, potentially resulting in the loss of packets. In 333 a tree structure, the attacker would be in position to drop the 334 packets from and to the attacked nodes. So the attacks above would 335 be more complex and more visible than simply dropping selected 336 packets. The downstream node may have other parents and see both 337 settings, which could raise attention. 339 8. Acknowledgments 341 The authors wish to thank Meral Shirazipour, Barry Leiba, Nagendra 342 Kumar Nainar, Stewart Bryant, Carles Gomez, Alvaro Retana, Dominique 343 Barthel and Rahul Jadhav for their in-depth reviews and constructive 344 suggestions. 346 Also many thanks to Michael Richardson for being always helpful and 347 responsive when need comes. 349 9. Normative References 351 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 352 Requirement Levels", BCP 14, RFC 2119, 353 DOI 10.17487/RFC2119, March 1997, 354 . 356 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 357 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 358 May 2017, . 360 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 361 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 362 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 363 Low-Power and Lossy Networks", RFC 6550, 364 DOI 10.17487/RFC6550, March 2012, 365 . 367 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 368 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 369 2014, . 371 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 372 "IPv6 over Low-Power Wireless Personal Area Network 373 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 374 April 2017, . 376 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 377 Perkins, "Registration Extensions for IPv6 over Low-Power 378 Wireless Personal Area Network (6LoWPAN) Neighbor 379 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 380 . 382 [UNAWARE-LEAVES] 383 Thubert, P. and M. Richardson, "Routing for RPL Leaves", 384 Work in Progress, Internet-Draft, draft-ietf-roll-unaware- 385 leaves-18, 12 June 2020, . 388 10. Informative References 390 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 391 Power and Lossy Networks (RPL) Option for Carrying RPL 392 Information in Data-Plane Datagrams", RFC 6553, 393 DOI 10.17487/RFC6553, March 2012, 394 . 396 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 397 Constrained-Node Networks", RFC 7228, 398 DOI 10.17487/RFC7228, May 2014, 399 . 401 [USEofRPLinfo] 402 Robles, I., Richardson, M., and P. Thubert, "Using RPI 403 Option Type, Routing Header for Source Routes and IPv6-in- 404 IPv6 encapsulation in the RPL Data Plane", Work in 405 Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-40, 406 25 June 2020, . 409 Authors' Addresses 411 Pascal Thubert (editor) 412 Cisco Systems, Inc 413 Building D 414 45 Allee des Ormes - BP1200 415 06254 MOUGINS - Sophia Antipolis 416 France 418 Phone: +33 497 23 26 34 419 Email: pthubert@cisco.com 421 Li Zhao 422 Cisco Systems, Inc 423 Xinsi Building 424 No. 926 Yi Shan Rd 425 SHANGHAI 426 200233 427 China 429 Email: liz3@cisco.com