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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: '0x01' is mentioned on line 1044, but not defined == Missing Reference: '0xFF' is mentioned on line 1044, but not defined ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) -- Obsolete informational reference (is this intentional?): RFC 4601 (Obsoleted by RFC 7761) Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL J. Hui 3 Internet-Draft Cisco 4 Intended status: Standards Track R. Kelsey 5 Expires: May 28, 2015 Silicon Labs 6 November 24, 2014 8 Multicast Protocol for Low power and Lossy Networks (MPL) 9 draft-ietf-roll-trickle-mcast-11 11 Abstract 13 This document specifies the Multicast Protocol for Low power and 14 Lossy Networks (MPL) that provides IPv6 multicast forwarding in 15 constrained networks. MPL avoids the need to construct or maintain 16 any multicast forwarding topology, disseminating messages to all MPL 17 Forwarders in an MPL Domain. MPL uses the Trickle algorithm to 18 manage message transmissions for both control and data-plane 19 messages. Different Trickle parameter configurations allow MPL to 20 trade between dissemination latency and transmission efficiency. 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 May 28, 2015. 39 Copyright Notice 41 Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 59 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 60 4.1. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . 5 61 4.2. Information Base Overview . . . . . . . . . . . . . . . . 6 62 4.3. Protocol Overview . . . . . . . . . . . . . . . . . . . . 6 63 4.4. Signaling Overview . . . . . . . . . . . . . . . . . . . 8 64 5. MPL Parameters and Constants . . . . . . . . . . . . . . . . 9 65 5.1. MPL Multicast Addresses . . . . . . . . . . . . . . . . . 9 66 5.2. MPL Message Types . . . . . . . . . . . . . . . . . . . . 9 67 5.3. MPL Seed Identifiers . . . . . . . . . . . . . . . . . . 9 68 5.4. MPL Parameters . . . . . . . . . . . . . . . . . . . . . 9 69 6. Protocol Message Formats . . . . . . . . . . . . . . . . . . 11 70 6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . 11 71 6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 13 72 6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 14 73 7. Information Base . . . . . . . . . . . . . . . . . . . . . . 15 74 7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 15 75 7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . 15 76 7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . 15 77 7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . 16 78 8. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 16 79 9. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 16 80 9.1. MPL Data Message Generation . . . . . . . . . . . . . . . 17 81 9.2. MPL Data Message Transmission . . . . . . . . . . . . . . 17 82 9.3. MPL Data Message Processing . . . . . . . . . . . . . . . 18 83 10. MPL Control Messages . . . . . . . . . . . . . . . . . . . . 19 84 10.1. MPL Control Message Generation . . . . . . . . . . . . . 19 85 10.2. MPL Control Message Transmission . . . . . . . . . . . . 20 86 10.3. MPL Control Message Processing . . . . . . . . . . . . . 21 87 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 88 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 89 12.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . 22 90 12.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . 22 91 12.3. Well-known Multicast Addresses . . . . . . . . . . . . . 23 92 13. Security Considerations . . . . . . . . . . . . . . . . . . . 23 93 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 94 14.1. Normative References . . . . . . . . . . . . . . . . . . 24 95 14.2. Informative References . . . . . . . . . . . . . . . . . 25 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 98 1. Introduction 100 Low power and Lossy Networks typically operate with strict resource 101 constraints in communication, computation, memory, and energy. Such 102 resource constraints may preclude the use of existing IPv6 multicast 103 routing and forwarding mechanisms. Traditional IP multicast delivery 104 typically relies on topology maintenance mechanisms to discover and 105 maintain routes to all subscribers of a multicast group (e.g. 106 [RFC3973] [RFC4601]). However, maintaining such topologies in Low 107 power and Lossy Networks (LLNs) is costly and may not be feasible 108 given the available resources. 110 Memory constraints may limit devices to maintaining links/routes to 111 one or a few neighbors. For this reason, the Routing Protocol for 112 LLNs (RPL) specifies both storing and non-storing modes [RFC6550]. 113 The latter allows RPL routers to maintain only one or a few default 114 routes towards a LLN Border Router (LBR) and use source routing to 115 forward messages away from the LBR. For the same reasons, a LLN 116 device may not be able to maintain a multicast routing topology when 117 operating with limited memory. 119 Furthermore, the dynamic properties of wireless networks can make the 120 cost of maintaining a multicast routing topology prohibitively 121 expensive. In wireless environments, topology maintenance may 122 involve selecting a connected dominating set used to forward 123 multicast messages to all nodes in an administrative domain. 124 However, existing mechanisms often require two-hop topology 125 information and the cost of maintaining such information grows 126 polynomially with network density. 128 This document specifies the Multicast Protocol for Low power and 129 Lossy Networks (MPL), which provides IPv6 multicast forwarding in 130 constrained networks. MPL avoids the need to construct or maintain 131 any multicast routing topology, disseminating multicast messages to 132 all MPL Forwarders in an MPL Domain. By using the Trickle algorithm 133 [RFC6206], MPL requires only small, constant state for each MPL 134 device that initiates disseminations. The Trickle algorithm also 135 allows MPL to be density-aware, allowing the communication rate to 136 scale logarithmically with density. 138 2. Terminology 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 142 "OPTIONAL" in this document are to be interpreted as described in 143 [RFC2119]. 145 The following terms are used throughout this document: 147 MPL Forwarder - A router that implements MPL. An MPL Forwarder 148 is equipped with at least one MPL Interface. 150 MPL Interface - An MPL Forwarder's attachment to a 151 communications medium, over which it transmits 152 and receives MPL Data Messages and MPL Control 153 Messages according to this specification. An MPL 154 Interface is assigned one or more unicast 155 addresses and is subscribed to one or more MPL 156 Domain Addresses. 158 MPL Domain Address - A multicast address that identifies the set of 159 MPL Interfaces within an MPL Domain. MPL Data 160 Messages disseminated in an MPL Domain have the 161 associated MPL Domain Address as their 162 destination address. 164 MPL Domain - A scope zone, as defined in [RFC4007], in which 165 MPL Interfaces subscribe to the same MPL Domain 166 Address and participate in disseminating MPL Data 167 Messages. 169 MPL Data Message - A multicast message that is used to communicate 170 a multicast payload between MPL Forwarders within 171 an MPL domain. An MPL Data Message contains an 172 MPL Option in the IPv6 header and has as its 173 destination address the MPL Domain Address 174 corresponding to the MPL Domain. 176 MPL Control Message - A link-local multicast message that is used to 177 communicate information about recently received 178 MPL Data Messages to neighboring MPL Forwarders. 180 MPL Seed - An MPL Forwarder that generates MPL Data 181 Messages and serves as an entry point into an MPL 182 Domain. 184 MPL Seed Identifier - An unsigned integer that uniquely identifies an 185 MPL Seed within an MPL Domain. 187 3. Applicability Statement 189 MPL is an IPv6 multicast forwarding protocol designed for the 190 communication characteristics and resource constraints of Low-Power 191 and Lossy Networks. By implementing controlled disseminations of 192 multicast messages using the Trickle algorithm, MPL is designed for 193 networks that communicate using low-power and lossy links with widely 194 varying topologies in both the space and time dimensions. 196 While designed specifically for Low-Power and Lossy Networks, MPL is 197 not limited to use over such networks. MPL may be applicable to any 198 network where no multicast routing state is desired. MPL may also be 199 used in environments where only a subset of links are considered Low- 200 Power and Lossy links. 202 A host need not be aware that their multicast is supported by MPL as 203 long as its attachment router forwards multicast messages between the 204 MPL Domain and the host. However, a host may choose to implement MPL 205 so that it can take advantage of the broadcast medium inherent in 206 many Low-Power and Lossy Networks and receive multicast messages 207 carried by MPL directly. 209 MPL is parameterized to support different dissemination techniques. 210 In one parameterization, MPL may utilize the classic flooding method 211 that involves having each device receiving a message rebroadcast the 212 message. In another parameterization, MPL may utilize Trickle's 213 [RFC6206] "polite gossip" method that involves transmission 214 suppression and adaptive timing techniques. By supporting both 215 simple flooding and Trickle methods, MPL can be configured to operate 216 well in a variety of situations [Clausen2013]. 218 To support effecient message delievery in networks that have many 219 poor links, MPL supports a reactive forwarding mode that utilizes MPL 220 Control Messages to summarize the current multicast state. The MPL 221 Control Message size grows linearly with the number of simultaneous 222 MPL Seeds in the MPL Domain - 4 octets per MPL Seed. When reactive 223 forwarding is not enabled, MPL Control Messages are not transmitted 224 and the associated overhead is not incurred. 226 4. Protocol Overview 228 The goal of MPL is to deliver multicast messages to all interfaces 229 that subscribe to the multicast messages' destination address within 230 an MPL Domain. 232 4.1. MPL Domains 234 An MPL Domain is a scope zone, as defined in [RFC4007], in which MPL 235 Interfaces subscribe to the same MPL Domain Address and participate 236 in disseminating MPL Data Messages. 238 By default, an MPL Forwarder SHOULD participate in an MPL Domain 239 identified by the ALL_MPL_FORWARDERS multicast address with a scope 240 value of 3 (Realm-Local) [RFC7346]. 242 When MPL is used in deployments that use administratively defined 243 scopes that cover, for example, multiple subnets based on different 244 underlying network technologies, Admin-Local scope (scop value 4) or 245 Site-Local scope (scop value 5) SHOULD be used. 247 An MPL Forwarder MAY participate in additional MPL Domains identified 248 by other multicast addresses. An MPL Interface MUST subscribe to the 249 MPL Domain Addresses for the MPL Domains that it participates in. 250 The assignment of other multicast addresses is out of scope. 252 For each MPL Domain Address that an MPL Interface subscribes to, the 253 MPL Interface MUST also subscribe to the same MPL Domain Address with 254 a scope value of 2 (link-local) when reactive forwarding is in use 255 (i.e. when communicating MPL Control Messages). 257 4.2. Information Base Overview 259 A node records necessary protocol state in the following information 260 sets: 262 o The Local Interface Set records the set of local MPL Interfaces 263 and the unicast addresses assigned to those MPL Interfaces. 265 o The Domain Set records the set of MPL Domain Addresses and the 266 local MPL Interfaces that subscribe to those addresses. 268 o A Seed Set records information about received MPL Data Messages 269 received from an MPL Seed within an MPL Domain. Each MPL Domain 270 has an associated Seed Set. A Seed Set maintains the minimum 271 sequence number for MPL Data Messages that the MPL Forwarder is 272 willing to receive or has buffered in its Buffered Message Set 273 from an MPL Seed. MPL uses Seed Sets and Buffered Message Sets to 274 determine when to accept an MPL Data Message, process its payload, 275 and retransmit it. 277 o A Buffered Message Set records recently received MPL Data Messages 278 from an MPL Seed within an MPL Domain. Each MPL Domain has an 279 associated Buffered Message Set. MPL Data Messages resident in a 280 Buffered Message Set have sequence numbers that are greater than 281 or equal to the minimum threshold maintained in the corresponding 282 Seed Set. MPL uses Buffered Message Sets to store MPL Data 283 Messages that may be transmitted by the MPL Forwarder for 284 forwarding. 286 4.3. Protocol Overview 288 MPL achieves its goal by implementing a controlled flood that 289 attempts to disseminate the multicast data message to all interfaces 290 within an MPL Domain. MPL performs the following tasks to 291 disseminate a multicast message: 293 o When having a multicast message to forward into an MPL Domain, the 294 MPL Seed generates an MPL Data Message that includes the MPL 295 Domain Address as the IPv6 Destination Address, the MPL Seed 296 Identifier, a newly generated sequence number, and the multicast 297 message. If the multicast destination address is not the MPL 298 Domain Address, IP-in-IP [RFC2473] is used to encapsulate the 299 multicast message in an MPL Data Message, preserving the original 300 IPv6 Destination Address. 302 o Upon receiving an MPL Data Message, the MPL Forwarder extracts the 303 MPL Seed and sequence number and determines whether or not the MPL 304 Data Message was previously received using the MPL Domain's Seed 305 Set and Buffered Message Set. 307 * If the sequence number is less than the lower-bound sequence 308 number maintained in the Seed Set or a message with the same 309 sequence number exists within the Buffered Message Set, the MPL 310 Forwarder marks the MPL Data Message as old. 312 * Otherwise, the MPL Forwarder marks the MPL Data Message as new. 314 o For each newly received MPL Data Message, an MPL Forwarder updates 315 the Seed Set, adds the MPL Data Message into the Buffered Message 316 Set, processes its payload, and multicasts the MPL Data Message a 317 number of times on all MPL Interfaces participating in the same 318 MPL Domain to forward the message. 320 o Each MPL Forwarder may periodically link-local multicast MPL 321 Control Messages on MPL Interfaces to communicate information 322 contained in an MPL Domain's Seed Set and Buffered Message Set. 324 o Upon receiving an MPL Control Message, an MPL Forwarder determines 325 whether there are any new MPL Data Messages that have yet to be 326 received by the MPL Control Message's source and multicasts those 327 MPL Data Messages. 329 MPL's configuration parameters allow two forwarding strategies for 330 disseminating MPL Data Messages via MPL Interfaces. 332 Proactive Forwarding - With proactive forwarding, an MPL Forwarder 333 schedules transmissions of MPL Data Messages using the Trickle 334 algorithm, without any prior indication that neighboring nodes 335 have yet to receive the message. After transmitting the MPL Data 336 Message a limited number of times, the MPL Forwarder may terminate 337 proactive forwarding for the MPL Data Message. 339 Reactive Forwarding - With reactive forwarding, an MPL Forwarder 340 link-local multicasts MPL Control Messages using the Trickle 341 algorithm [RFC6206]. MPL Forwarders use MPL Control Messages to 342 discover new MPL Data Messages that have not yet been received. 343 When discovering that a neighboring MPL Forwarder has not yet 344 received an MPL Data Message, the MPL Forwarder schedules those 345 MPL Data Messages for transmission using the Trickle algorithm. 347 Note that the use of proactive and reactive forwarding strategies 348 within the same MPL Domain are not mutually exclusive and may be used 349 simultaneously. For example, upon receiving a new MPL Data Message 350 when both proactive and reactive forwarding techniques are enabled, 351 an MPL Forwarder will proactively retransmit the MPL Data Message a 352 limited number of times and schedule further transmissions upon 353 receiving MPL Control Messages. 355 4.4. Signaling Overview 357 MPL generates and processes the following messages: 359 MPL Data Message - Generated by an MPL Seed to deliver a multicast 360 message across an MPL Domain. The MPL Data Message's source is an 361 address in the Local Interface Set of the MPL Seed that generated 362 the message and is valid within the MPL Domain. The MPL Data 363 Message's destination is the MPL Domain Address corresponding to 364 the MPL Domain. An MPL Data Message contains: 366 * The Seed Identifier of the MPL Seed that generated the MPL Data 367 Message. 369 * The sequence number of the MPL Seed that generated the MPL Data 370 Message. 372 * The original multicast message. 374 MPL Control Message - Generated by an MPL Forwarder to communicate 375 information contained in an MPL Domain's Seed Set and Buffered 376 Message Set to neighboring MPL Forwarders. An MPL Control Message 377 contains a list of tuples for each entry in the Seed Set. Each 378 tuple contains: 380 * The minimum sequence number maintained in the Seed Set for the 381 MPL Seed. 383 * A bit-vector indicating the sequence numbers of MPL Data 384 Messages resident in the Buffered Message Set for the MPL Seed, 385 where the first bit represents a sequence number equal to the 386 minimum threshold maintained in the Seed Set. 388 * The length of the bit-vector. 390 5. MPL Parameters and Constants 392 This section describes various program and networking parameters and 393 constants used by MPL. 395 5.1. MPL Multicast Addresses 397 MPL makes use of MPL Domain Addresses to identify MPL Interfaces of 398 an MPL Domain. By default, MPL Forwarders subscribe to the 399 ALL_MPL_FORWARDERS multicast address with a scope value of 3 400 [RFC7346]. 402 For each MPL Domain Address that an MPL Interface subscribes to, the 403 MPL Interface MUST also subscribe to the MPL Domain Address with a 404 scope value of 2 (link-local) when reactive forwarding is in use. 405 MPL Forwarders use the link-scoped MPL Domain Address to communicate 406 MPL Control Messages to neighboring (i.e. on-link) MPL Forwarders. 408 5.2. MPL Message Types 410 MPL defines an IPv6 Option for carrying an MPL Seed Identifier and a 411 sequence number within an MPL Data Message. The IPv6 Option Type has 412 value 0x6D. 414 MPL defines an ICMPv6 Message (MPL Control Message) for communicating 415 information contained in an MPL Domain's Seed Set and Buffered 416 Message Set to neighboring MPL Forwarders. The MPL Control Message 417 has ICMPv6 Type MPL_ICMP_TYPE. 419 5.3. MPL Seed Identifiers 421 MPL uses MPL Seed Identifiers to uniquely identify MPL Seeds within 422 an MPL Domain. For each MPL Domain that the MPL Forwarder serves as 423 an MPL Seed, the MPL Forwarder MUST have an associated MPL Seed 424 Identifier. An MPL Forwarder MAY use the same MPL Seed Identifier 425 across multiple MPL Domains, but the MPL Seed Identifier MUST be 426 unique within each MPL Domain. The mechanism for assigning and 427 verifying uniqueness of MPL Seed Identifiers is not specified in this 428 document. 430 5.4. MPL Parameters 432 PROACTIVE_FORWARDING A boolean value that indicates whether the MPL 433 Forwarder schedules MPL Data Message transmissions after receiving 434 them for the first time. PROACTIVE_FORWARDING has a default value 435 of TRUE. The mechanism for setting PROACTIVE_FORWARDING is not 436 specified within this document. 438 SEED_SET_ENTRY_LIFETIME The minimum lifetime for an entry in the 439 Seed Set. SEED_SET_ENTRY_LIFETIME has a default value of 30 440 minutes. It is RECOMMENDED that all MPL Forwarders use the same 441 value for SEED_SET_ENTRY_LIFETIME for a given MPL Domain and use a 442 default value of 30 minutes. Using a value of 443 SEED_SET_ENTRY_LIFETIME that is too small can cause the duplicate 444 detection mechanism to fail, resulting in a MPL Forwarder to 445 receive a given MPL Data Message more than once. The mechanism 446 for setting SEED_SET_ENTRY_LIFETIME is not specified within this 447 document. 449 As specified in [RFC6206], a Trickle timer runs for a defined 450 interval and has three configuration parameters: the minimum interval 451 size Imin, the maximum interval size Imax, and a redundancy constant 452 k. 454 This specification defines a fourth Trickle configuration parameter, 455 TimerExpirations, which indicates the number of Trickle timer 456 expiration events that occur before terminating the Trickle algorithm 457 for a given MPL Data Message or MPL Control Message. 459 Each MPL Interface uses the following Trickle parameters for MPL Data 460 Message and MPL Control Message transmissions. 462 DATA_MESSAGE_IMIN The minimum Trickle timer interval, as defined in 463 [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMIN 464 has a default value of 10 times the expected link-layer latency. 466 DATA MESSAGE_IMAX The maximum Trickle timer interval, as defined in 467 [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMAX 468 has a default value equal to DATA_MESSAGE_IMIN. 470 DATA_MESSAGE_K The redundancy constant, as defined in [RFC6206], for 471 MPL Data Message transmissions. DATA_MESSAGE_K has a default 472 value of 1. 474 DATA_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer 475 expirations that occur before terminating the Trickle algorithm's 476 retransmission of a given MPL Data Message. 477 DATA_MESSAGE_TIMER_EXPIRATIONS has a default value of 3. 479 CONTROL_MESSAGE_IMIN The minimum Trickle timer interval, as defined 480 in [RFC6206], for MPL Control Message transmissions. 481 CONTROL_MESSAGE_IMIN has a default value of 10 times the worst- 482 case link-layer latency. 484 CONTROL_MESSAGE_IMAX The maximum Trickle timer interval, as defined 485 in [RFC6206], for MPL Control Message transmissions. 486 CONTROL_MESSAGE_IMAX has a default value of 5 minutes. 488 CONTROL_MESSAGE_K The redundancy constant, as defined in [RFC6206], 489 for MPL Control Message transmissions. CONTROL_MESSAGE_K has a 490 default value of 1. 492 CONTROL_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer 493 expirations that occur before terminating the Trickle algorithm 494 for MPL Control Message transmissions. 495 CONTROL_MESSAGE_TIMER_EXPIRATIONS has a default value of 10. 497 As described in [RFC6206], if different nodes have different 498 configuration parameters, Trickle may have unintended behaviors. 499 Therefore, it is RECOMMENDED that all MPL Interfaces attached to the 500 same link of a given MPL Domain use the same values for the Trickle 501 Parameters above for a given MPL Domain. The mechanism for setting 502 the Trickle Parameters is not specified within this document. 504 The default MPL parameters specify a forwarding strategy that 505 utilizes both proactive and reactive techniques. Using these default 506 values, an MPL Forwarder proactively transmits any new MPL Data 507 Messages it receives then uses MPL Control Messages to trigger 508 additional MPL Data Message retransmissions where message drops are 509 detected. Setting DATA_MESSAGE_IMAX to the same as DATA_MESSAGE_IMIN 510 in this case is acceptable since subsequent MPL Data Message 511 retransmissions are triggered by MPL Control Messages, where 512 CONTROL_MESSAGE_IMAX is greater than CONTROL_MESSAGE_IMIN. 514 6. Protocol Message Formats 516 The protocol messages generated and processed by an MPL Forwarder are 517 described in this section. 519 6.1. MPL Option 521 The MPL Option is carried in MPL Data Messages in an IPv6 Hop-by-Hop 522 Options header, immediately following the IPv6 header. The MPL 523 Option has the following format: 525 0 1 2 3 526 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 1 527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 | Option Type | Opt Data Len | 529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 530 | S |M|V| rsv | sequence | seed-id (optional) | 531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 533 Option Type 0x6D. 535 Opt Data Len Length of the Option Data field in octets. 537 S 2-bit unsigned integer. Identifies the length of 538 seed-id. 0 indicates that the seed-id is the 539 IPv6 Source Address and not included in the MPL 540 Option. 1 indicates that the seed-id is a 16-bit 541 unsigned integer. 2 indicates that the seed-id 542 is a 64-bit unsigned integer. 3 indicates that 543 the seed-id is a 128-bit unsigned integer. 545 M 1-bit flag. 1 indicates that the value in 546 sequence is known to be the largest sequence 547 number that was received from the MPL Seed. 549 V 1-bit flag. 0 indicates that the MPL Option 550 conforms to this specification. MPL Data 551 Messages with an MPL Option in which this flag is 552 1 MUST be dropped. 554 rsv 4-bit reserved field. MUST be set to 0 on 555 transmission and ignored on reception. 557 sequence 8-bit unsigned integer. Identifies relative 558 ordering of MPL Data Messages from the MPL Seed 559 identified by seed-id. 561 seed-id Uniquely identifies the MPL Seed that initiated 562 dissemination of the MPL Data Message. The size 563 of seed-id is indicated by the S field. 565 The Option Data (in particular the M flag) of the MPL Option is 566 updated by MPL Forwarders as the MPL Data Message is forwarded. 567 Nodes that do not understand the MPL Option MUST discard the MPL Data 568 Message. Thus, according to [RFC2460] the three high order bits of 569 the Option Type are set to '011'. The Option Data length is 570 variable. 572 The seed-id uniquely identifies an MPL Seed. When seed-id is 128 573 bits (S=3), the MPL Seed MAY use an IPv6 address assigned to one of 574 its interfaces that is unique within the MPL Domain. Managing MPL 575 Seed Identifiers is not within scope of this document. 577 The sequence field establishes a total ordering of MPL Data Messages 578 generated by an MPL Seed for an MPL Domain. The MPL Seed MUST 579 increment the sequence field's value on each new MPL Data Message 580 that it generates for an MPL Domain. Implementations MUST follow the 581 Serial Number Arithmetic as defined in [RFC1982] when incrementing a 582 sequence value or comparing two sequence values. 584 Future updates to this specification may define additional fields 585 following the seed-id field. 587 6.2. MPL Control Message 589 An MPL Forwarder uses ICMPv6 messages to communicate information 590 contained in an MPL Domain's Seed Set and Buffered Message Set to 591 neighboring MPL Forwarders. The MPL Control Message has the 592 following format: 594 0 1 2 3 595 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 1 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | Type | Code | Checksum | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | | 600 . MPL Seed Info[0..n] . 601 . . 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 604 IP Fields: 606 Source Address An IPv6 address in the AddressSet of the 607 corresponding MPL Interface and MUST be valid 608 within the MPL Domain. 610 Destination Address The link-scoped MPL Domain Address corresponding 611 to the MPL Domain. 613 Hop Limit 255 615 ICMPv6 Fields: 617 Type MPL_ICMP_TYPE 618 Code 0 620 Checksum The ICMP checksum. See [RFC4443]. 622 MPL Seed Info[0..n] List of zero or more MPL Seed Info entries. 624 The MPL Control Message indicates the sequence numbers of MPL Data 625 Messages that are within the MPL Domain's Buffered Message Set. The 626 MPL Control Message also indicates the sequence numbers of MPL Data 627 Messages that an MPL Forwarder is willing to receive. The MPL 628 Control Message allows neighboring MPL Forwarders to determine 629 whether there are any new MPL Data Messages to exchange. 631 6.3. MPL Seed Info 633 An MPL Seed Info encodes the minimum sequence number for an MPL Seed 634 maintained in the MPL Domain's Seed Set. The MPL Seed Info also 635 indicates the sequence numbers of MPL Data Messages generated by the 636 MPL Seed that are stored within the MPL Domain's Buffered Message 637 Set. The MPL Seed Info has the following format: 639 0 1 2 3 640 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 1 641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 | min-seqno | bm-len | S | seed-id (0/2/8/16 octets) | 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | | 645 . buffered-mpl-messages (variable length) . 646 . . 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 min-seqno 8-bit unsigned integer. The lower-bound sequence 650 number for the MPL Seed. 652 bm-len 6-bit unsigned integer. The size of buffered- 653 mpl-messages in octets. 655 S 2-bit unsigned integer. Identifies the length of 656 seed-id. 0 indicates that the seed-id value is 657 the IPv6 Source Address and not included in the 658 MPL Seed Info. 1 indicates that the seed-id 659 value is a 16-bit unsigned integer. 2 indicates 660 that the seed-id value is a 64-bit unsigned 661 integer. 3 indicates that the seed-id is a 662 128-bit unsigned integer. 664 seed-id Variable-length unsigned integer. Indicates the 665 MPL Seed associated with this MPL Seed Info. 667 buffered-mpl-messages Variable-length bit vector. Identifies the 668 sequence numbers of MPL Data Messages maintained 669 in the corresponding Buffered Message Set for the 670 MPL Seed. The i'th bit represents a sequence 671 number of min-seqno + i. '0' indicates that the 672 corresponding MPL Data Message does not exist in 673 the Buffered Message Set. '1' indicates that the 674 corresponding MPL Data Message does exist in the 675 Buffered Message Set. 677 The MPL Seed Info does not have any octet alignment requirement. 679 7. Information Base 681 7.1. Local Interface Set 683 The Local Interface Set records the local MPL Interfaces of an MPL 684 Forwarder. The Local Interface Set consists of Local Interface 685 Tuples, one per MPL Interface: (AddressSet). 687 AddressSet - a set of unicast addresses assigned to the MPL 688 Interface. 690 7.2. Domain Set 692 The Domain Set records the MPL Interfaces that subscribe to each MPL 693 Domain Address. The Domain Set consists of MPL Domain Tuples, one 694 per MPL Domain: (MPLInterfaceSet). 696 MPLInterfaceSet - a set of MPL Interfaces that subscribe to the MPL 697 Domain Address that identifies the MPL Domain. 699 7.3. Seed Set 701 A Seed Set records a sliding window used to determine the sequence 702 numbers of MPL Data Messages that an MPL Forwarder is willing to 703 accept generated by the MPL Seed. An MPL Forwarder maintains a Seed 704 Set for each MPL Domain that it participates in. A Seed Set consists 705 of MPL Seed Tuples: (SeedID, MinSequence, Lifetime). 707 SeedID - the identifier for the MPL Seed. 709 MinSequence - a lower-bound sequence number that represents the 710 sequence number of the oldest MPL Data Message the MPL Forwarder 711 is willing to receive or transmit. An MPL Forwarder MUST ignore 712 any MPL Data Message that has sequence value less than than 713 MinSequence. 715 Lifetime - indicates the minimum remaining lifetime of the Seed Set 716 entry. An MPL Forwarder MUST NOT free a Seed Set entry before the 717 remaining lifetime expires. 719 7.4. Buffered Message Set 721 A Buffered Message Set records recently received MPL Data Messages 722 from an MPL Seed within an MPL Domain. An MPL Forwarder uses a 723 Buffered Message Set to buffer MPL Data Messages while the MPL 724 Forwarder is forwarding the MPL Data Messages. An MPL Forwarder 725 maintains a Buffered Message Set for each MPL Domain that it 726 participates in. A Buffered Message Set consists of Buffered Message 727 Tuples: (SeedID, SequenceNumber, DataMessage). 729 SeedID - the identifier for the MPL Seed that generated the MPL Data 730 Message. 732 SequenceNumber - the sequence number for the MPL Data Message. 734 DataMessage - the MPL Data Message. 736 All MPL Data Messages within a Buffered Message Set MUST have a 737 sequence number greater than or equal to MinSequence for the 738 corresponding SeedID. When increasing MinSequence for an MPL Seed, 739 the MPL Forwarder MUST delete any MPL Data Messages from the 740 corresponding Buffered Message Set that have sequence numbers less 741 than MinSequence. 743 8. MPL Seed Sequence Numbers 745 Each MPL Seed maintains a sequence number for each MPL Domain that it 746 serves. The sequence numbers are included in MPL Data Messages 747 generated by the MPL Seed. The MPL Seed MUST increment the sequence 748 number for each MPL Data Message that it generates for an MPL Domain. 749 Implementations MUST follow the Serial Number Arithmetic as defined 750 in [RFC1982] when incrementing a sequence value or comparing two 751 sequence values. This sequence number is used to establish a total 752 ordering of MPL Data Messages generated by an MPL Seed for an MPL 753 Domain. 755 9. MPL Data Messages 756 9.1. MPL Data Message Generation 758 MPL Data Messages are generated by MPL Seeds when these messages 759 enter the MPL Domain. All MPL Data messages have the following 760 properties: 762 o The IPv6 Source Address MUST be an address in the AddressSet of a 763 corresponding MPL Interface and MUST be valid within the MPL 764 Domain. 766 o The IPv6 Destination Address MUST be set to the MPL Domain Address 767 corresponding to the MPL Domain. 769 o An MPL Data Message MUST contain an MPL Option in its IPv6 Header 770 to identify the MPL Seed that generated the message and the 771 ordering relative to other MPL Data Messages generated by the MPL 772 Seed. 774 When the destination address is an MPL Domain Address and the source 775 address is in the AddressLIst of an MPL Interface that belongs to 776 that MPL Domain Address, the application message and the MPL Data 777 Message MAY be identical. In other words, the MPL Data Message may 778 contain a single IPv6 header that includes the MPL Option. 780 Otherwise, IPv6-in-IPv6 encapsulation MUST be used to satisfy the MPL 781 Data Message requirements listed above [RFC2473]. The complete IPv6- 782 in-IPv6 message forms an MPL Data Message. The outer IPv6 header 783 conforms to the MPL Data Message requirements listed above. The 784 encapsulated IPv6 datagram encodes the multicast data message that is 785 communicated beyond the MPL Domain. 787 9.2. MPL Data Message Transmission 789 An MPL Forwarder manages transmission of MPL Data Messages in its 790 Buffered Message Sets using the Trickle algorithm [RFC6206]. An MPL 791 Forwarder MUST use a separate Trickle timer for each MPL Data Message 792 that it is actively forwarding. In accordance with Section 5 of RFC 793 6206 [RFC6206], this document defines the following: 795 o This document defines a "consistent" transmission as receiving an 796 MPL Data Message that has the same MPL Domain Address, seed-id, 797 and sequence value as the MPL Data Message managed by the Trickle 798 timer. 800 o This document defines an "inconsistent" transmission as receiving 801 an MPL Data Message that has the same MPL Domain Address, seed-id 802 value, and the M flag set, but has a sequence value less than MPL 803 Data Message managed by the Trickle timer. 805 o This document does not define any external "events". 807 o This document defines MPL Data Messages as Trickle messages. 809 o The actions outside the Trickle algorithm that the protocol takes 810 involve managing the MPL Domain's Seed Set and Buffered Message 811 Set. 813 As specified in [RFC6206], a Trickle timer has three variables: the 814 current interval size I, a time within the current interval t, and a 815 counter c. MPL defines a fourth variable, e, which counts the number 816 of Trickle timer expiration events since the Trickle timer was last 817 reset. 819 After DATA_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, the MPL 820 Forwarder MUST disable the Trickle timer. When a buffered MPL Data 821 Message does not have an associated Trickle timer, the MPL Forwarder 822 MAY delete the message from the Buffered Message Set by advancing 823 MinSequence of the corresponding MPL Seed in the Seed Set. When the 824 MPL Forwarder no longer buffers any messages for an MPL Seed, the MPL 825 Forwarder MUST NOT increment MinSequence for that MPL Seed. 827 When transmitting an MPL Data Message, the MPL Forwarder MUST either 828 set the M flag to zero or set it to a level that indicates whether or 829 not the message's sequence number is the largest value that has been 830 received from the MPL Seed. 832 9.3. MPL Data Message Processing 834 Upon receiving an MPL Data Message, the MPL Forwarder first processes 835 the MPL Option and updates the Trickle timer associated with the MPL 836 Data Message if one exists. 838 Upon receiving an MPL Data Message, an MPL Forwarder MUST perform one 839 of the following actions: 841 o Accept the message and enter the MPL Data Message in the MPL 842 Domain's Buffered Message Set. 844 o Accept the message and update the corresponding MinSequence in the 845 MPL Domain's Seed Set to 1 greater than the message's sequence 846 number. 848 o Discard the message without any change to the MPL Information 849 Base. 851 If a Seed Set entry exists for the MPL Seed, the MPL Forwarder MUST 852 discard the MPL Data Message if its sequence number is less than 853 MinSequence or exists in the Buffered Message Set. 855 If a Seed Set entry does not exist for the MPL Seed, the MPL 856 Forwarder MUST create a new entry for the MPL Seed before accepting 857 the MPL Data Message. 859 If memory is limited, an MPL Forwarder SHOULD reclaim memory 860 resources by: 862 o Incrementing MinSequence entries in a Seed Set and deleting MPL 863 Data Messages in the corresponding Buffered Message Set that fall 864 below the MinSequence value. 866 o Deleting other Seed Set entries that have expired and the 867 corresponding MPL Data Messages in the Buffered Message Set. 869 If the MPL Forwarder accepts the MPL Data Message, the MPL Forwarder 870 MUST perform the following actions: 872 o Reset the Lifetime of the corresponding Seed Set entry to 873 SEED_SET_ENTRY_LIFETIME. 875 o If PROACTIVE_FORWARDING is true, the MPL Forwarder MUST initialize 876 and start a Trickle timer for the MPL Data Message. 878 o If the MPL Control Message Trickle timer is not running and 879 CONTROL_MESSAGE_TIMER_EXPIRATIONS is non-zero, the MPL Forwarder 880 MUST initialize and start the MPL Control Message Trickle timer. 882 o If the MPL Control Message Trickle timer is running, the MPL 883 Forwarder MUST reset the MPL Control Message Trickle timer. 885 10. MPL Control Messages 887 10.1. MPL Control Message Generation 889 An MPL Forwarder generates MPL Control Messages to communicate an MPL 890 Domain's Seed Set and Buffered Message Set to neighboring MPL 891 Forwarders. Each MPL Control Message is generated according to 892 Section 6.2, with an MPL Seed Info for each entry in the MPL Domain's 893 Seed Set. Each MPL Seed Info entry has the following content: 895 o S set to the size of the seed-id field in the MPL Seed Info entry. 897 o min-seqno set to MinSequence of the MPL Seed. 899 o bm-len set to the size of buffered-mpl-messages in octets. 901 o seed-id set to the MPL seed identifier. 903 o buffered-mpl-messages with each bit representing whether or not an 904 MPL Data Message with the corresponding sequence number exists in 905 the Buffered Message Set. The i'th bit represents a sequence 906 number of min-seqno + i. '0' indicates that the corresponding MPL 907 Data Message does not exist in the Buffered Message Set. '1' 908 indicates that the corresponding MPL Data Message does exist in 909 the Buffered Message Set. 911 10.2. MPL Control Message Transmission 913 An MPL Forwarder transmits MPL Control Messages using the Trickle 914 algorithm. An MPL Forwarder maintains a single Trickle timer for 915 each MPL Domain. When CONTROL_MESSAGE_TIMER_EXPIRATIONS is 0, the 916 MPL Forwarder does not execute the Trickle algorithm and does not 917 transmit MPL Control Messages. In accordance with Section 5 of RFC 918 6206 [RFC6206], this document defines the following: 920 o This document defines a "consistent" transmission as receiving an 921 MPL Control Message that results in a determination that neither 922 the receiving nor transmitting node has any new MPL Data Messages 923 to offer. 925 o This document defines an "inconsistent" transmission as receiving 926 an MPL Control Message that results in a determination that either 927 the receiving or transmitting node has at least one new MPL Data 928 Message to offer. 930 o The Trickle timer is reset in response to external "events." This 931 document defines an "event" as increasing MinSequence of any entry 932 in the corresponding Seed Set or adding a message to the 933 corresponding Buffered Message Set. 935 o This document defines an MPL Control Message as a Trickle message. 937 As specified in [RFC6206], a Trickle timer has three variables: the 938 current interval size I, a time within the current interval t, and a 939 counter c. MPL defines a fourth variable, e, which counts the number 940 of Trickle timer expiration events since the Trickle timer was last 941 reset. After CONTROL_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, 942 the MPL Forwarder MUST disable the Trickle timer. 944 10.3. MPL Control Message Processing 946 An MPL Forwarder processes each MPL Control Message that it receives 947 to determine if it has any new MPL Data Messages to receive or offer. 949 An MPL Forwarder determines if a new MPL Data Message has not been 950 received from a neighboring node if any of the following conditions 951 hold true: 953 o The MPL Control Message includes an MPL Seed that does not exist 954 in the MPL Domain's Seed Set. 956 o The MPL Control Message indicates that the neighbor has an MPL 957 Data Message in its Buffered Message Set with sequence number 958 greater than MinSequence (i.e. the i-th bit is set to 1 and min- 959 seqno + i > MinSequence) and is not included in the MPL Domain's 960 Buffered Message Set. 962 When an MPL Forwarder determines that it has not yet received an MPL 963 Data Message buffered by a neighboring device, the MPL Forwarder MUST 964 reset its Trickle timer associated with MPL Control Message 965 transmissions. If an MPL Control Message Trickle timer is not 966 running, the MPL Forwarder MUST initialize and start a new Trickle 967 timer. 969 An MPL Forwarder determines if an MPL Data Message in the Buffered 970 Message Set has not yet been received by a neighboring MPL Forwarder 971 if any of the following conditions hold true: 973 o The MPL Control Message does not include an MPL Seed for the MPL 974 Data Message. 976 o The MPL Data Message's sequence number is greater than or equal to 977 min-seqno and not included in the neighbor's corresponding 978 Buffered Message Set (i.e. the MPL Data Message's sequence number 979 does not have a corresponding bit in buffered-mpl-messages set to 980 1). 982 When an MPL Forwarder determines that it has at least one MPL Data 983 Message in its corresponding Buffered Message Set that has not yet 984 been received by a neighbor, the MPL Forwarder MUST reset the MPL 985 Control Message Trickle timer. Additionally, for each of those 986 entries in the Buffered Message Set, the MPL Forwarder MUST reset the 987 Trickle timer and reset e to 0. If a Trickle timer is not associated 988 with the MPL Data Message, the MPL Forwarder MUST initialize and 989 start a new Trickle timer. 991 11. Acknowledgements 993 The authors would like to acknowledge the helpful comments of Robert 994 Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Adrian Farrel, Ulrich 995 Herberg, Owen Kirby, Philip Levis, Kerry Lynn, Joseph Reddy, Michael 996 Richardson, Ines Robles, Don Sturek, Dario Tedeschi, and Peter van 997 der Stok, which greatly improved the document. 999 12. IANA Considerations 1001 This document defines one IPv6 Option, a type that must be allocated 1002 from the IPv6 "Destination Options and Hop-by-Hop Options" registry 1003 of [RFC2780]. 1005 This document defines one ICMPv6 Message, a type that must be 1006 allocated from the "ICMPv6 "type" Numbers" registry of [RFC4443]. 1008 This document registers a well-known multicast address from the 1009 Variable Scope Multicast Address registry. 1011 12.1. MPL Option Type 1013 IANA is requested to allocate an IPv6 Option Type from the IPv6 1014 "Destination Options and Hop-by-Hop Options" registry of [RFC2780], 1015 as specified in Table 1 below: 1017 +-----------+-----+-----+-------+-------------+---------------+ 1018 | Hex Value | act | chg | rest | Description | Reference | 1019 +-----------+-----+-----+-------+-------------+---------------+ 1020 | 0x6D | 01 | 1 | 01101 | MPL Option | This Document | 1021 +-----------+-----+-----+-------+-------------+---------------+ 1023 Table 1: IPv6 Option Type Allocation 1025 12.2. MPL ICMPv6 Type 1027 IANA is requested to allocate an ICMPv6 Type from the "ICMPv6 "type" 1028 Numbers" registry of [RFC4443], as specified in Table 2 below: 1030 +------+---------------------+---------------+ 1031 | Type | Name | Reference | 1032 +------+---------------------+---------------+ 1033 | TBD | MPL Control Message | This Document | 1034 +------+---------------------+---------------+ 1036 Table 2: IPv6 Option Type Allocation 1038 In this document, the mnemonic MPL_ICMP_TYPE was used to refer to the 1039 ICMPv6 Type above, which is TBD by IANA. 1041 12.3. Well-known Multicast Addresses 1043 IANA is requested to allocate an IPv6 multicast address, with Group 1044 ID in the range [0x01,0xFF] for 6LoWPAN compression [RFC6282], 1045 "ALL_MPL_FORWARDERS" from the "Variable Scope Multicast Addresses" 1046 sub-registry of the "IPv6 Multicast Address Space" registry [RFC3307] 1047 as specified in Table 3 below: 1049 +---------------------+--------------------+-----------+------------+ 1050 | Address(s) | Description | Reference | Date | 1051 | | | | Registered | 1052 +---------------------+--------------------+-----------+------------+ 1053 | FF0X:0:0:0:0:0:0:FC | ALL_MPL_FORWARDERS | This | 2013-04-10 | 1054 | | | Document | | 1055 +---------------------+--------------------+-----------+------------+ 1057 Table 3: Variable Scope Multicast Address Allocation 1059 13. Security Considerations 1061 MPL uses sequence numbers to maintain a total ordering of MPL Data 1062 Messages from an MPL Seed. The use of sequence numbers allows a 1063 denial-of-service attack where an attacker can spoof a message with a 1064 sufficiently large sequence number to: (i) flush messages from the 1065 Buffered Message List and (ii) increase the MinSequence value for an 1066 MPL Seed in the corresponding Seed Set. The former side effect 1067 allows an attacker to halt the forwarding process of any MPL Data 1068 Messages being disseminated. The latter side effect allows an 1069 attacker to prevent MPL Forwarders from accepting new MPL Data 1070 Messages that an MPL Seed generates while the sequence number is less 1071 than MinSequence. 1073 More generally, the basic ability to inject messages into a Low-power 1074 and Lossy Network can be used as a denial-of-service attack 1075 regardless of what forwarding protocol is used. For these reasons, 1076 Low-power and Lossy Networks typically employ link-layer security 1077 mechanisms to disable an attacker's ability to inject messages. 1079 To prevent attackers from injecting packets through an MPL Forwarder, 1080 the MPL Forwarder MUST NOT accept or forward MPL Data Messages from a 1081 communication interface that does not subscribe to the MPL Domain 1082 Address identified in message's destination address. 1084 MPL uses the Trickle algorithm to manage message transmissions and 1085 the security considerations described in [RFC6206] apply. 1087 14. References 1089 14.1. Normative References 1091 [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, 1092 August 1996. 1094 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1095 Requirement Levels", BCP 14, RFC 2119, March 1997. 1097 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1098 (IPv6) Specification", RFC 2460, December 1998. 1100 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1101 IPv6 Specification", RFC 2473, December 1998. 1103 [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For 1104 Values In the Internet Protocol and Related Headers", BCP 1105 37, RFC 2780, March 2000. 1107 [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast 1108 Addresses", RFC 3307, August 2002. 1110 [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and 1111 B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, 1112 March 2005. 1114 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 1115 Message Protocol (ICMPv6) for the Internet Protocol 1116 Version 6 (IPv6) Specification", RFC 4443, March 2006. 1118 [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, 1119 "The Trickle Algorithm", RFC 6206, March 2011. 1121 [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 1122 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1123 September 2011. 1125 [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., 1126 Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. 1127 Alexander, "RPL: IPv6 Routing Protocol for Low-Power and 1128 Lossy Networks", RFC 6550, March 2012. 1130 [RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346, 1131 August 2014. 1133 14.2. Informative References 1135 [Clausen2013] 1136 Clausen, T., Colin de Verdiere, A., and J. Yi, 1137 "Performance Analysis of Trickle as a Flooding Mechanism", 1138 November 2013. 1140 [RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol 1141 Independent Multicast - Dense Mode (PIM-DM): Protocol 1142 Specification (Revised)", RFC 3973, January 2005. 1144 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 1145 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 1146 Protocol Specification (Revised)", RFC 4601, August 2006. 1148 Authors' Addresses 1150 Jonathan W. Hui 1151 Cisco 1152 170 West Tasman Drive 1153 San Jose, California 95134 1154 USA 1156 Phone: +408 424 1547 1157 Email: jonhui@cisco.com 1159 Richard Kelsey 1160 Silicon Labs 1161 25 Thomson Place 1162 Boston, Massachusetts 02210 1163 USA 1165 Phone: +617 951 1225 1166 Email: richard.kelsey@silabs.com