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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-09) exists of draft-ietf-roll-capabilities-06 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL R. Jadhav, Ed. 3 Internet-Draft Huawei Tech 4 Intended status: Standards Track P. Thubert 5 Expires: December 7, 2020 Cisco 6 M. Richardson 7 Sandelman Software Works 8 June 5, 2020 10 Mode of Operation extension 11 draft-ietf-roll-mopex-01 13 Abstract 15 RPL allows different mode of operations which allows nodes to have a 16 consensus on the basic primitives that must be supported to join the 17 network. The MOP field in [RFC6550] is of 3 bits and is fast 18 depleting. This document extends the MOP for future use. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on December 7, 2020. 37 Copyright Notice 39 Copyright (c) 2020 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Requirements Language and Terminology . . . . . . . . . . 3 56 2. Requirements for this document . . . . . . . . . . . . . . . 3 57 3. Extended MOP Control Message Option . . . . . . . . . . . . . 4 58 3.1. Handling MOPex . . . . . . . . . . . . . . . . . . . . . 4 59 3.2. Use of values 0-6 in the MOPex option . . . . . . . . . . 4 60 4. Extending RPL Control Options . . . . . . . . . . . . . . . . 4 61 5. Implementation Considerations . . . . . . . . . . . . . . . . 6 62 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 63 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 64 7.1. Mode of operation: MOPex . . . . . . . . . . . . . . . . 6 65 7.2. New options: MOPex and Capabilities . . . . . . . . . . . 6 66 7.3. New Registry for Extended-MOP-value . . . . . . . . . . . 7 67 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 68 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 69 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 70 9.2. Informative References . . . . . . . . . . . . . . . . . 8 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 73 1. Introduction 75 RPL [RFC6550] specifies a proactive distance-vector based routing 76 scheme. The protocol creates a DAG-like structure which operates 77 with a given "Mode of Operation" (MOP) determining the minimal and 78 mandatory set of primitives to be supported by all the participating 79 nodes. 81 MOP as per [RFC6550] is a 3-bit value carried in DIO messages and is 82 specific to the RPL Instance. The receipient of the DIO message can 83 join the specified network as a router only when it can support the 84 primitives as required by the mode of operation value. For example, 85 in case of MOP=3 (Storing MOP with multicast support) the nodes can 86 join the network as routers only when they can handle the DAO 87 advertisements from the peers and manage routing tables. The 3-bit 88 value is already exhausted and requires replenishment. This document 89 introduces a mechanism to extend mode of operation values. 91 This document further extends the RPL Control Option syntax to handle 92 generic flags. The primary aim of these flags is to define the 93 behaviour of a node not supporting the given control type. If a node 94 does not support a given RPL Control Option, there are three 95 possibilities: 97 REQ1: Strip off the option 99 REQ2: Copy the option as-is 101 REQ3: Ignore the message containing this option 103 REQ4: Let the node join in only as a 6LN to this parent 105 1.1. Requirements Language and Terminology 107 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 108 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 109 document are to be interpreted as described in RFC 2119 [RFC2119]. 111 MOP: Mode of Operation. Identifies the mode of operation of the RPL 112 Instance as administratively provisioned at and distributed by the 113 DODAG root. 115 MOPex: Extended MOP: This document extends the MOP values over a 116 bigger range. This extension of MOP is called MOPex. 118 DAO: DODAG Advertisement Object. An RPL message used to advertise 119 the target information in order to establish routing adjacencies. 121 DIO: DODAG Information Object. An RPL message initiated by the root 122 and is used to advertise the network configuration information. 124 Current parent: Parent 6LR node before switching to the new path. 126 This document uses terminology described in [RFC6550]. For the sake 127 of readability all the known relevant terms are repeated in this 128 section. 130 2. Requirements for this document 132 Following are the requirements considered for this documents: 134 REQ1: MOP extension. Current MOP of 3-bit is fast depleting. An 135 MOP extension needs to extend the possibility of adding new 136 MOPs in the future. 138 REQ2: Backwards compatibility. The new options and new fields in 139 the DIO message should be backward compatible i.e. if there 140 are nodes which support old MOPs they could still operate in 141 their own instances. 143 3. Extended MOP Control Message Option 145 This document reserves existing MOP value 7 to be used as an 146 extender. DIO messages with MOP value of 7 may refer to the Extended 147 MOP (MOPex) option in the DIO message. 149 0 1 2 150 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------------- 152 | Type = TODO | Opt Length | OP-value 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------------- 155 Figure 1: Extended MOP Option 157 The option length value MUST be less than or equal to 2. An option 158 length value of zero is invalid and the implementation MUST silently 159 ignore the DIO on receiving a value of zero. 161 3.1. Handling MOPex 163 The MOPex option MUST be used only if the base DIO MOP is 7. If the 164 base DIO MOP is 7 and if the MOPex option is not present then the DIO 165 MUST be silently ignored. If the base DIO MOP is less than 7 then 166 MOPex MUST NOT be used. In case the base MOP is 7 and if the MOPex 167 option is present, then the implementation MUST use the final MOP 168 value from the MOPex. 170 Note that [RFC6550] allows the node who does not support the received 171 MOP to still join the network as a leaf node. This semantic 172 continues to be true even in case of MOPex. 174 3.2. Use of values 0-6 in the MOPex option 176 The MOPex option could also be allowed to re-use the values 0-6, 177 which have been used for MOP so far. The use of current MOPs in 178 MOPex indicates that the MOP is supported with extended set of 179 semantics for e.g., the capability options 180 [I-D.ietf-roll-capabilities]. 182 4. Extending RPL Control Options 184 Section 6.7.1 of RFC6550 explains the RPL Control Message Option 185 Generic Format. This document extends this format to following: 187 0 1 2 188 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+----------- 190 | |X| OptionType| Option Length |Opt Flags|J|I|C| Option Data 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+----------- 193 Figure 2: Extended RPL Option Format 195 New fields in extended RPL Control Message Option Format: 197 'X' bit in Option Type: Value 1 indicates that this is an extended 198 option. If the 'X' flag is set, a 1 byte Option Flags follows the 199 Option Length field. 201 Option Length: 8-bit unsigned integer, representing the length in 202 octets of the option, not including the Option Type and Length 203 fields. Option Flags and variable length Option Data fields are 204 included in the length. 206 'J' (Join) bit in Option Flags: A node MUST join only as a 6LN if 207 the Option Type is not understood. 209 'C' (Copy) bit in Option Flags: A node which does not understand 210 the Option Type MUST copy the Option while generating the 211 corresponding message. For e.g., if a 6LR receives a DIO message 212 with an unknown Option with 'C' bit set and if the 6LR choses to 213 accept this node as the preferred parent then the node MUST copy 214 this option in the subsequent DIO message it generates. 215 Alternatively, if the 'C' flag is unset the node MUST strip off 216 the option and process the message. 218 'I' (Ignore) bit in Option Flags: A node which does not understand 219 the Option Type MUST ignore this whole message if the 'I' bit is 220 set. If 'I' bit is set than the value of 'J' and 'C' bits are 221 irrelevant and the message MUST be ignored. 223 Note that this format does not deprecate the previous format, it 224 simply extends it and the new format is applicable only when 2nd bit 225 ('X' flag) of the Option Type is set. Option Type 0x40 to 0x7F are 226 thus applicable only as extended options. 228 +---------+---------+-----------------------------------------------+ 229 | 'J' bit | 'C' bit | Handling | 230 +---------+---------+-----------------------------------------------+ 231 | 0 | 0 | Strip off the option, and the node can join | 232 | | | as 6LR | 233 | 0 | 1 | Copy the option, and the node can join as 6LR | 234 | 1 | NA | Join as 6LN | 235 +---------+---------+-----------------------------------------------+ 237 Table 1: Option Flags handling 239 If a node receives an unknown Option without 'X' flag set then the 240 node MUST ignore the option and process the message. The option MUST 241 be treated as if J=0, C=0, I=0. 243 5. Implementation Considerations 245 [RFC6550], it was possible to discard an unsupported DIO-MOP just by 246 inspecting the base message. With this document, the MOPex is a 247 different control message option and thus the discarding of the DIO 248 message could happen after inspecting the message options. 250 6. Acknowledgements 252 Using 'I' bit was Pascal Thubert's idea. 254 7. IANA Considerations 256 7.1. Mode of operation: MOPex 258 IANA is requested to assign a new Mode of Operation, named "MOPex" 259 for MOP extension under the RPL registry. The value of 7 is to be 260 assigned from the "Mode of Operation" space [RFC6550] 262 +-------+-------------+---------------+ 263 | Value | Description | Reference | 264 +-------+-------------+---------------+ 265 | 7 | MOPex | This document | 266 +-------+-------------+---------------+ 268 Mode of Operation 270 7.2. New options: MOPex and Capabilities 272 A new entry is required for supporting new option "MOPex" in the "RPL 273 Control Message Options" space [RFC6550]. 275 +-------+---------+---------------+ 276 | Value | Meaning | Reference | 277 +-------+---------+---------------+ 278 | TBD1 | MOPex | This document | 279 +-------+---------+---------------+ 281 New options 283 7.3. New Registry for Extended-MOP-value 285 IANA is requested to create a registry for the extended-MOP-value 286 (MOPex). This registry should be located in TODO. New MOPex values 287 may be allocated only by an IETF review. Currently no values are 288 defined by this document. Each value is tracked with the following 289 qualities: 291 o MOPex value 293 o Description 295 o Defining RFC 297 8. Security Considerations 299 The options defined in this document are carried in the base message 300 objects as defined in [RFC6550]. The RPL control message options are 301 protected by the same security mechanisms that protect the base 302 messages. 304 Capabilities flag can reveal that the node has been upgraded or is 305 running a old feature set. This document assumes that the base 306 messages that carry these options are protected by RPL security 307 mechanisms and thus are not visible to a malicious node. 309 9. References 311 9.1. Normative References 313 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 314 Requirement Levels", BCP 14, RFC 2119, 315 DOI 10.17487/RFC2119, March 1997, 316 . 318 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 319 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 320 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 321 Low-Power and Lossy Networks", RFC 6550, 322 DOI 10.17487/RFC6550, March 2012, 323 . 325 9.2. Informative References 327 [I-D.ietf-roll-capabilities] 328 Jadhav, R., Thubert, P., Richardson, M., and R. Sahoo, 329 "RPL Capabilities", draft-ietf-roll-capabilities-06 (work 330 in progress), June 2020. 332 Authors' Addresses 334 Rahul Arvind Jadhav (editor) 335 Huawei Tech 336 Kundalahalli Village, Whitefield, 337 Bangalore, Karnataka 560037 338 India 340 Phone: +91-080-49160700 341 Email: rahul.ietf@gmail.com 343 Pascal Thubert 344 Cisco Systems, Inc 345 Building D 346 45 Allee des Ormes - BP1200 347 MOUGINS - Sophia Antipolis 06254 348 France 350 Phone: +33 497 23 26 34 351 Email: pthubert@cisco.com 353 Michael Richardson 354 Sandelman Software Works 356 Email: mcr+ietf@sandelman.ca