idnits 2.17.1 draft-ietf-roll-turnon-rfc8138-09.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 (27 July 2020) is 1367 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references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 7102 == Outdated reference: A later version (-30) exists of draft-ietf-roll-unaware-leaves-18 == Outdated reference: A later version (-44) exists of draft-ietf-roll-useofrplinfo-40 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--).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 27 July 2020 6 Expires: 28 January 2021 8 A RPL DODAG Configuration Option for the 6LoWPAN Routing Header 9 draft-ietf-roll-turnon-rfc8138-09 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 28 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 . . . . . . . . . . . . . . . . . . . . . . . 7 65 9. Normative References . . . . . . . . . . . . . . . . . . . . 7 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 the Flags field in the RPL DODAG Configuration Option. 179 The suggested bit position of the "T" flag is indicated in Section 6. 181 [RFC6550] states, when referring to the DODAG Configuration Option, 182 that "Nodes other than the DODAG Root MUST NOT modify this 183 information when propagating the DODAG Configuration option". 184 Therefore, a legacy parent propagates the "T" flag as set by the Root 185 whether it supports this specification or not. So when the "T" flag 186 is set, it is transparently flooded to all the nodes in the DODAG. 188 Section 6.3.1 of [RFC6550] defines a 3-bit Mode of Operation (MOP) in 189 the DIO Base Object. For MOP values 0 to 6, the use of compression 190 depends on the "T" flag as specified in this document. A MOP value 191 of 7 and above MUST use compression by default and ignore the setting 192 of the "T" flag. 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 In non-storing mode, the Root will start using [RFC8138] with a 262 Source Routing Header 6LoRH (SRH-6LoRH) that routes all the way to 263 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 7. Security Considerations 305 First of all, it is worth noting that with [RFC6550], every node in 306 the LLN that is RPL-aware can inject any RPL-based attack in the 307 network. A trust model has to be put in place in an effort to 308 exclude rogue nodes from participating to the RPL and the 6LoWPAN 309 signaling, as well as from the data packet exchange. This trust 310 model could be at a minimum based on a Layer-2 Secure joining and the 311 Link-Layer security. This is a generic RPL and 6LoWPAN requirement, 312 see Req5.1 in Appendix of [RFC8505]. 314 Setting the "T" flag before all routers are upgraded may cause a loss 315 of packets. The new bit is protected as the rest of the 316 configuration so this is just one of the many attacks that can happen 317 if an attacker manages to inject a corrupted configuration. 319 Setting and resetting the "T" flag may create inconsistencies in the 320 network but as long as all nodes are upgraded to [RFC8138] support 321 they will be able to forward both forms. The source is responsible 322 for selecting whether the packet is compressed or not, and all 323 routers must use the format that the source selected. So the result 324 of an inconsistency is merely that both forms will be present in the 325 network, at an additional cost of bandwidth for packets in the 326 uncompressed form. 328 8. Acknowledgments 330 The authors wish to thank Alvaro Retana, Dominique Barthel and Rahul 331 Jadhav for their in-depth reviews and constructive suggestions. 333 Also many thanks to Michael Richardson for being always helpful and 334 responsive when need comes. 336 9. Normative References 338 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 339 Requirement Levels", BCP 14, RFC 2119, 340 DOI 10.17487/RFC2119, March 1997, 341 . 343 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 344 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 345 May 2017, . 347 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 348 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 349 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 350 Low-Power and Lossy Networks", RFC 6550, 351 DOI 10.17487/RFC6550, March 2012, 352 . 354 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 355 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 356 2014, . 358 [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, 359 "IPv6 over Low-Power Wireless Personal Area Network 360 (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, 361 April 2017, . 363 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 364 Perkins, "Registration Extensions for IPv6 over Low-Power 365 Wireless Personal Area Network (6LoWPAN) Neighbor 366 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 367 . 369 [UNAWARE-LEAVES] 370 Thubert, P. and M. Richardson, "Routing for RPL Leaves", 371 Work in Progress, Internet-Draft, draft-ietf-roll-unaware- 372 leaves-18, 12 June 2020, . 375 10. Informative References 377 [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- 378 Power and Lossy Networks (RPL) Option for Carrying RPL 379 Information in Data-Plane Datagrams", RFC 6553, 380 DOI 10.17487/RFC6553, March 2012, 381 . 383 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 384 Constrained-Node Networks", RFC 7228, 385 DOI 10.17487/RFC7228, May 2014, 386 . 388 [USEofRPLinfo] 389 Robles, I., Richardson, M., and P. Thubert, "Using RPI 390 Option Type, Routing Header for Source Routes and IPv6-in- 391 IPv6 encapsulation in the RPL Data Plane", Work in 392 Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-40, 393 25 June 2020, . 396 Authors' Addresses 398 Pascal Thubert (editor) 399 Cisco Systems, Inc 400 Building D 401 45 Allee des Ormes - BP1200 402 06254 MOUGINS - Sophia Antipolis 403 France 405 Phone: +33 497 23 26 34 406 Email: pthubert@cisco.com 408 Li Zhao 409 Cisco Systems, Inc 410 Xinsi Building 411 No. 926 Yi Shan Rd 412 SHANGHAI 413 200233 414 China 416 Email: liz3@cisco.com