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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 1081, but not defined == Missing Reference: '0xFF' is mentioned on line 1081, 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 Nest Labs 4 Intended status: Standards Track R. Kelsey 5 Expires: December 4, 2015 Silicon Labs 6 June 2, 2015 8 Multicast Protocol for Low power and Lossy Networks (MPL) 9 draft-ietf-roll-trickle-mcast-12 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 a MPL Domain. 19 MPL has two modes of operation. One mode uses the Trickle algorithm 20 to manage control- and data-plane message transmissions, and is 21 applicable for deployments with few multicast sources. The other 22 mode uses classic flooding. By providing both modes and 23 parameterization of the Trickle algorithm, a MPL implementation can 24 be used in a variety of multicast deployments and can trade between 25 dissemination latency and transmission efficiency. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on December 4, 2015. 44 Copyright Notice 46 Copyright (c) 2015 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 63 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 64 4. MPL Protocol Overview . . . . . . . . . . . . . . . . . . . . 6 65 4.1. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . 6 66 4.2. Information Base Overview . . . . . . . . . . . . . . . . 7 67 4.3. Protocol Overview . . . . . . . . . . . . . . . . . . . . 7 68 4.4. Signaling Overview . . . . . . . . . . . . . . . . . . . 9 69 5. MPL Parameters and Constants . . . . . . . . . . . . . . . . 9 70 5.1. MPL Multicast Addresses . . . . . . . . . . . . . . . . . 9 71 5.2. MPL Message Types . . . . . . . . . . . . . . . . . . . . 10 72 5.3. MPL Seed Identifiers . . . . . . . . . . . . . . . . . . 10 73 5.4. MPL Parameters . . . . . . . . . . . . . . . . . . . . . 10 74 6. Protocol Message Formats . . . . . . . . . . . . . . . . . . 12 75 6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . 12 76 6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 14 77 6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 15 78 7. Information Base . . . . . . . . . . . . . . . . . . . . . . 16 79 7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 16 80 7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . 16 81 7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . 16 82 7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . 16 83 8. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 17 84 9. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 17 85 9.1. MPL Data Message Generation . . . . . . . . . . . . . . . 17 86 9.2. MPL Data Message Transmission . . . . . . . . . . . . . . 18 87 9.3. MPL Data Message Processing . . . . . . . . . . . . . . . 19 88 10. MPL Control Messages . . . . . . . . . . . . . . . . . . . . 20 89 10.1. MPL Control Message Generation . . . . . . . . . . . . . 20 90 10.2. MPL Control Message Transmission . . . . . . . . . . . . 20 91 10.3. MPL Control Message Processing . . . . . . . . . . . . . 21 92 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 93 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 94 12.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . 22 95 12.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . 23 96 12.3. Well-known Multicast Addresses . . . . . . . . . . . . . 23 98 13. Security Considerations . . . . . . . . . . . . . . . . . . . 23 99 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 100 14.1. Normative References . . . . . . . . . . . . . . . . . . 24 101 14.2. Informative References . . . . . . . . . . . . . . . . . 25 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 104 1. Introduction 106 Low power and Lossy Networks (LLNs) typically operate with strict 107 resource constraints in communication, computation, memory, and 108 energy. Such resource constraints may preclude the use of existing 109 IPv6 multicast routing and forwarding mechanisms. Traditional IP 110 multicast delivery typically relies on topology maintenance 111 mechanisms to discover and maintain routes to all subscribers of a 112 multicast group (e.g. [RFC3973] [RFC4601]). However, maintaining 113 such topologies in Low power and Lossy Networks is costly and may not 114 be feasible given the available resources. 116 Memory constraints may limit devices to maintaining links/routes to 117 one or a few neighbors. For this reason, the Routing Protocol for 118 LLNs (RPL) specifies both storing and non-storing modes [RFC6550]. 119 The latter allows RPL routers to maintain only one or a few default 120 routes towards a LLN Border Router (LBR) and use source routing to 121 forward messages away from the LBR. For the same reasons, a LLN 122 device may not be able to maintain a multicast routing topology when 123 operating with limited memory. 125 Furthermore, the dynamic properties of wireless networks can make the 126 cost of maintaining a multicast routing topology prohibitively 127 expensive. In wireless environments, topology maintenance may 128 involve selecting a connected dominating set used to forward 129 multicast messages to all nodes in an administrative domain. 130 However, existing mechanisms often require two-hop topology 131 information and the cost of maintaining such information grows 132 polynomially with network density. 134 This document specifies the Multicast Protocol for Low power and 135 Lossy Networks (MPL), which provides IPv6 multicast forwarding in 136 constrained networks. MPL avoids the need to construct or maintain 137 any multicast routing topology, disseminating multicast messages to 138 all MPL Forwarders in a MPL Domain. By using the Trickle algorithm 139 [RFC6206], MPL requires only small, constant state for each MPL 140 device that initiates disseminations. The Trickle algorithm also 141 allows MPL to be density-aware, allowing the communication rate to 142 scale logarithmically with density. 144 2. Terminology 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 148 "OPTIONAL" in this document are to be interpreted as described in 149 [RFC2119]. 151 The following terms are used throughout this document: 153 MPL Forwarder - A router that implements MPL. A MPL Forwarder 154 is equipped with at least one MPL Interface. 156 MPL Interface - A MPL Forwarder's attachment to a 157 communications medium, over which it transmits 158 and receives MPL Data Messages and MPL Control 159 Messages according to this specification. A MPL 160 Interface is assigned one or more unicast 161 addresses and is subscribed to one or more MPL 162 Domain Addresses. 164 MPL Domain Address - A multicast address that identifies the set of 165 MPL Interfaces within a MPL Domain. MPL Data 166 Messages disseminated in a MPL Domain have the 167 associated MPL Domain Address as their 168 destination address. 170 MPL Domain - A scope zone, as defined in [RFC4007], in which 171 MPL Interfaces subscribe to the same MPL Domain 172 Address and participate in disseminating MPL Data 173 Messages. 175 MPL Data Message - A multicast message that is used to communicate 176 a multicast payload between MPL Forwarders within 177 a MPL domain. A MPL Data Message contains a MPL 178 Option in the IPv6 header and has as its 179 destination address the MPL Domain Address 180 corresponding to the MPL Domain. 182 MPL Control Message - A link-local multicast message that is used to 183 communicate information about recently received 184 MPL Data Messages to neighboring MPL Forwarders. 186 MPL Seed - A MPL Forwarder that generates MPL Data 187 Messages and serves as an entry point into a MPL 188 Domain. 190 MPL Seed Identifier - An unsigned integer that uniquely identifies a 191 MPL Seed within a MPL Domain. 193 Node - The term "node" is used within this document to 194 refer to a MPL Forwarder. 196 3. Applicability Statement 198 MPL is an IPv6 multicast forwarding protocol designed for the 199 communication characteristics and resource constraints of Low-Power 200 and Lossy Networks. By implementing controlled disseminations of 201 multicast messages using the Trickle algorithm, MPL is designed for 202 networks that communicate using low-power and lossy links with widely 203 varying topologies in both the space and time dimensions. 205 While designed specifically for Low-Power and Lossy Networks, MPL is 206 not limited to use over such networks. MPL may be applicable to any 207 network where no multicast routing state is desired. MPL may also be 208 used in environments where only a subset of links are considered Low- 209 Power and Lossy links. 211 A host need not be aware that their multicast is supported by MPL as 212 long as its attachment router forwards multicast messages between the 213 MPL Domain and the host. However, a host may choose to implement MPL 214 so that it can take advantage of the broadcast medium inherent in 215 many Low-Power and Lossy Networks and receive multicast messages 216 carried by MPL directly. 218 MPL is parameterized to support different dissemination techniques. 219 In one parameterization, MPL may utilize the classic flooding method 220 that involves having each device receiving a message rebroadcast the 221 message. In another parameterization, MPL may utilize Trickle's 222 [RFC6206] "polite gossip" method that involves transmission 223 suppression and adaptive timing techniques. [Clausen2013] questions 224 the efficiency of Trickle's "polite gossip" mechanism in some 225 multicast scenarios, so by also including a classic flooding mode of 226 operation MPL aims to be able to perform satisfactorily in a variety 227 of situations. 229 To support efficient message delivery in networks that have many poor 230 links, MPL supports a reactive forwarding mode that utilizes MPL 231 Control Messages to summarize the current multicast state. The MPL 232 Control Message size grows linearly with the number of simultaneous 233 MPL Seeds in the MPL Domain - 4 octets per MPL Seed. When reactive 234 forwarding is not enabled, MPL Control Messages are not transmitted 235 and the associated overhead is not incurred. 237 This document does not specify a cryptographic security mechanism for 238 MPL to ensure that MPL messages are not spoofed by anyone with access 239 to the LLN. In general, the basic ability to inject messages into a 240 Low-power and Lossy Network may be used as a denial-of-service attack 241 regardless of what forwarding protocol is used. For these reasons, 242 Low-power and Lossy Networks typically employ link-layer security 243 mechanisms to mitigate an attacker's ability to inject messages. For 244 example, the IEEE 802.15.4 [IEEE802154] standard specifies frame 245 security mechanisms using AES-128 to support access control, message 246 integrity, message confidentiality, and replay protection. However, 247 if the attack vector includes attackers that have access to the LLN, 248 then MPL SHOULD NOT be used. 250 4. MPL Protocol Overview 252 The goal of MPL is to deliver multicast messages to all interfaces 253 that subscribe to the multicast messages' destination address within 254 a MPL Domain. 256 4.1. MPL Domains 258 A MPL Domain is a scope zone, as defined in [RFC4007], in which MPL 259 Interfaces subscribe to the same MPL Domain Address and participate 260 in disseminating MPL Data Messages. 262 When participating in only one MPL Domain, the MPL Domain Address is 263 the ALL_MPL_FORWARDERS multicast address with Realm-Local scope (scop 264 value 3) [RFC7346]. 266 When a MPL Forwarder participates in multiple MPL Domains 267 simultaneously, at most one MPL Domain may be assigned a MPL Domain 268 Address equal to the ALL_MPL_FORWARDERS multicast address. All other 269 MPL Domains MUST be assigned a unique MPL Domain Address that allows 270 the MPL Forwarder to identify each MPL Domain. The MPL Domains 271 SHOULD be configured automatically based on some underlying topology. 272 For example, when using RPL [RFC6550], MPL Domains may be configured 273 based on RPL Instances. 275 When MPL is used in deployments that use administratively defined 276 scopes that cover, for example, multiple subnets based on different 277 underlying network technologies, Admin-Local scope (scop value 4) or 278 Site-Local scope (scop value 5) SHOULD be used. 280 A MPL Forwarder MAY participate in additional MPL Domains identified 281 by other multicast addresses. A MPL Interface MUST subscribe to the 282 MPL Domain Addresses for the MPL Domains that it participates in. 283 The assignment of other multicast addresses is out of scope. 285 For each MPL Domain Address that a MPL Interface subscribes to, the 286 MPL Interface MUST also subscribe to the same MPL Domain Address with 287 Link-Local scope (scop value 2) when reactive forwarding is in use 288 (i.e. when communicating MPL Control Messages). 290 4.2. Information Base Overview 292 A node records necessary protocol state in the following information 293 sets: 295 o The Local Interface Set records the set of local MPL Interfaces 296 and the unicast addresses assigned to those MPL Interfaces. 298 o The Domain Set records the set of MPL Domain Addresses and the 299 local MPL Interfaces that subscribe to those addresses. 301 o A Seed Set records information about received MPL Data Messages 302 received from a MPL Seed within a MPL Domain. Each MPL Domain has 303 an associated Seed Set. A Seed Set maintains the minimum sequence 304 number for MPL Data Messages that the MPL Forwarder is willing to 305 receive or has buffered in its Buffered Message Set from a MPL 306 Seed. MPL uses Seed Sets and Buffered Message Sets to determine 307 when to accept a MPL Data Message, process its payload, and 308 retransmit it. 310 o A Buffered Message Set records recently received MPL Data Messages 311 from a MPL Seed within a MPL Domain. Each MPL Domain has an 312 associated Buffered Message Set. MPL Data Messages resident in a 313 Buffered Message Set have sequence numbers that are greater than 314 or equal to the minimum threshold maintained in the corresponding 315 Seed Set. MPL uses Buffered Message Sets to store MPL Data 316 Messages that may be transmitted by the MPL Forwarder for 317 forwarding. 319 4.3. Protocol Overview 321 MPL achieves its goal by implementing a controlled flood that 322 attempts to disseminate the multicast data message to all interfaces 323 within a MPL Domain. MPL performs the following tasks to disseminate 324 a multicast message: 326 o When having a multicast message to forward into a MPL Domain, the 327 MPL Seed generates a MPL Data Message that includes the MPL Domain 328 Address as the IPv6 Destination Address, the MPL Seed Identifier, 329 a newly generated sequence number, and the multicast message. If 330 the multicast destination address is not the MPL Domain Address, 331 IP-in-IP [RFC2473] is used to encapsulate the multicast message in 332 a MPL Data Message, preserving the original IPv6 Destination 333 Address. 335 o Upon receiving a MPL Data Message, the MPL Forwarder extracts the 336 MPL Seed and sequence number and determines whether or not the MPL 337 Data Message was previously received using the MPL Domain's Seed 338 Set and Buffered Message Set. 340 * If the sequence number is less than the lower-bound sequence 341 number maintained in the Seed Set or a message with the same 342 sequence number exists within the Buffered Message Set, the MPL 343 Forwarder marks the MPL Data Message as old. 345 * Otherwise, the MPL Forwarder marks the MPL Data Message as new. 347 o For each newly received MPL Data Message, a MPL Forwarder updates 348 the Seed Set, adds the MPL Data Message into the Buffered Message 349 Set, processes its payload, and multicasts the MPL Data Message a 350 number of times on all MPL Interfaces participating in the same 351 MPL Domain to forward the message. 353 o Each MPL Forwarder may periodically link-local multicast MPL 354 Control Messages on MPL Interfaces to communicate information 355 contained in a MPL Domain's Seed Set and Buffered Message Set. 357 o Upon receiving a MPL Control Message, a MPL Forwarder determines 358 whether there are any new MPL Data Messages that have yet to be 359 received by the MPL Control Message's source and multicasts those 360 MPL Data Messages. 362 MPL's configuration parameters allow two forwarding strategies for 363 disseminating MPL Data Messages via MPL Interfaces. 365 Proactive Forwarding - With proactive forwarding, a MPL Forwarder 366 schedules transmissions of MPL Data Messages using the Trickle 367 algorithm, without any prior indication that neighboring nodes 368 have yet to receive the message. After transmitting the MPL Data 369 Message a limited number of times, the MPL Forwarder may terminate 370 proactive forwarding for the MPL Data Message. 372 Reactive Forwarding - With reactive forwarding, a MPL Forwarder 373 link-local multicasts MPL Control Messages using the Trickle 374 algorithm [RFC6206]. MPL Forwarders use MPL Control Messages to 375 discover new MPL Data Messages that have not yet been received. 376 When discovering that a neighboring MPL Forwarder has not yet 377 received a MPL Data Message, the MPL Forwarder schedules those MPL 378 Data Messages for transmission using the Trickle algorithm. 380 Note that the use of proactive and reactive forwarding strategies 381 within the same MPL Domain are not mutually exclusive and may be used 382 simultaneously. For example, upon receiving a new MPL Data Message 383 when both proactive and reactive forwarding techniques are enabled, a 384 MPL Forwarder will proactively retransmit the MPL Data Message a 385 limited number of times and schedule further transmissions upon 386 receiving MPL Control Messages. 388 4.4. Signaling Overview 390 MPL generates and processes the following messages: 392 MPL Data Message - Generated by a MPL Seed to deliver a multicast 393 message across a MPL Domain. The MPL Data Message's source is an 394 address in the Local Interface Set of the MPL Seed that generated 395 the message and is valid within the MPL Domain. The MPL Data 396 Message's destination is the MPL Domain Address corresponding to 397 the MPL Domain. A MPL Data Message contains: 399 * The Seed Identifier of the MPL Seed that generated the MPL Data 400 Message. 402 * The sequence number of the MPL Seed that generated the MPL Data 403 Message. 405 * The original multicast message. 407 MPL Control Message - Generated by a MPL Forwarder to communicate 408 information contained in a MPL Domain's Seed Set and Buffered 409 Message Set to neighboring MPL Forwarders. A MPL Control Message 410 contains a list of tuples for each entry in the Seed Set. Each 411 tuple contains: 413 * The minimum sequence number maintained in the Seed Set for the 414 MPL Seed. 416 * A bit-vector indicating the sequence numbers of MPL Data 417 Messages resident in the Buffered Message Set for the MPL Seed, 418 where the first bit represents a sequence number equal to the 419 minimum threshold maintained in the Seed Set. 421 * The length of the bit-vector. 423 5. MPL Parameters and Constants 425 This section describes various program and networking parameters and 426 constants used by MPL. 428 5.1. MPL Multicast Addresses 430 MPL makes use of MPL Domain Addresses to identify MPL Interfaces of a 431 MPL Domain. By default, MPL Forwarders subscribe to the 432 ALL_MPL_FORWARDERS multicast address with Realm-Local scope (scop 433 value 3) [RFC7346]. 435 For each MPL Domain Address that a MPL Interface subscribes to, the 436 MPL Interface MUST also subscribe to the MPL Domain Address with 437 Link-Local scope (scop value 2) when reactive forwarding is in use. 438 MPL Forwarders use the link-scoped MPL Domain Address to communicate 439 MPL Control Messages to neighboring (i.e. on-link) MPL Forwarders. 441 5.2. MPL Message Types 443 MPL defines an IPv6 Option for carrying a MPL Seed Identifier and a 444 sequence number within a MPL Data Message. The IPv6 Option Type has 445 value 0x6D. 447 MPL defines an ICMPv6 Message (MPL Control Message) for communicating 448 information contained in a MPL Domain's Seed Set and Buffered Message 449 Set to neighboring MPL Forwarders. The MPL Control Message has 450 ICMPv6 Type MPL_ICMP_TYPE. 452 5.3. MPL Seed Identifiers 454 MPL uses MPL Seed Identifiers to uniquely identify MPL Seeds within a 455 MPL Domain. For each MPL Domain that the MPL Forwarder serves as a 456 MPL Seed, the MPL Forwarder MUST have an associated MPL Seed 457 Identifier. A MPL Forwarder MAY use the same MPL Seed Identifier 458 across multiple MPL Domains, but the MPL Seed Identifier MUST be 459 unique within each MPL Domain. The mechanism for assigning and 460 verifying uniqueness of MPL Seed Identifiers is not specified in this 461 document. 463 5.4. MPL Parameters 465 PROACTIVE_FORWARDING A boolean value that indicates whether the MPL 466 Forwarder schedules MPL Data Message transmissions after receiving 467 them for the first time. PROACTIVE_FORWARDING has a default value 468 of TRUE. All MPL interfaces on the same link SHOULD be configured 469 with the same value of PROACTIVE_FORWARDING. An implementation 470 MAY choose to vary the value of PROACTIVE_FORWARDING across 471 interfaces on the same link if reactive forwarding is also in use. 472 The mechanism for setting PROACTIVE_FORWARDING is not specified 473 within this document. 475 SEED_SET_ENTRY_LIFETIME The minimum lifetime for an entry in the 476 Seed Set. SEED_SET_ENTRY_LIFETIME has a default value of 30 477 minutes. It is RECOMMENDED that all MPL Forwarders use the same 478 value for SEED_SET_ENTRY_LIFETIME for a given MPL Domain and use a 479 default value of 30 minutes. Using a value of 480 SEED_SET_ENTRY_LIFETIME that is too small can cause the duplicate 481 detection mechanism to fail, resulting in a MPL Forwarder to 482 receive a given MPL Data Message more than once. The mechanism 483 for setting SEED_SET_ENTRY_LIFETIME is not specified within this 484 document. 486 As specified in [RFC6206], a Trickle timer runs for a defined 487 interval and has three configuration parameters: the minimum interval 488 size Imin, the maximum interval size Imax, and a redundancy constant 489 k. 491 This specification defines a fourth Trickle configuration parameter, 492 TimerExpirations, which indicates the number of Trickle timer 493 expiration events that occur before terminating the Trickle algorithm 494 for a given MPL Data Message or MPL Control Message. 496 Each MPL Interface uses the following Trickle parameters for MPL Data 497 Message and MPL Control Message transmissions. 499 DATA_MESSAGE_IMIN The minimum Trickle timer interval, as defined in 500 [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMIN 501 has a default value of 10 times the expected link-layer latency. 503 DATA MESSAGE_IMAX The maximum Trickle timer interval, as defined in 504 [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMAX 505 has a default value equal to DATA_MESSAGE_IMIN. 507 DATA_MESSAGE_K The redundancy constant, as defined in [RFC6206], for 508 MPL Data Message transmissions. DATA_MESSAGE_K has a default 509 value of 1. 511 DATA_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer 512 expirations that occur before terminating the Trickle algorithm's 513 retransmission of a given MPL Data Message. 514 DATA_MESSAGE_TIMER_EXPIRATIONS has a default value of 3. 516 CONTROL_MESSAGE_IMIN The minimum Trickle timer interval, as defined 517 in [RFC6206], for MPL Control Message transmissions. 518 CONTROL_MESSAGE_IMIN has a default value of 10 times the worst- 519 case link-layer latency. 521 CONTROL_MESSAGE_IMAX The maximum Trickle timer interval, as defined 522 in [RFC6206], for MPL Control Message transmissions. 523 CONTROL_MESSAGE_IMAX has a default value of 5 minutes. 525 CONTROL_MESSAGE_K The redundancy constant, as defined in [RFC6206], 526 for MPL Control Message transmissions. CONTROL_MESSAGE_K has a 527 default value of 1. 529 CONTROL_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer 530 expirations that occur before terminating the Trickle algorithm 531 for MPL Control Message transmissions. 532 CONTROL_MESSAGE_TIMER_EXPIRATIONS has a default value of 10. 534 As described in [RFC6206], if different nodes have different 535 configuration parameters, Trickle may have unintended behaviors. 536 Therefore, it is RECOMMENDED that all MPL Interfaces attached to the 537 same link of a given MPL Domain use the same values for the Trickle 538 Parameters above for a given MPL Domain. The mechanism for setting 539 the Trickle Parameters is not specified within this document. 541 The default MPL parameters specify a forwarding strategy that 542 utilizes both proactive and reactive techniques. Using these default 543 values, a MPL Forwarder proactively transmits any new MPL Data 544 Messages it receives then uses MPL Control Messages to trigger 545 additional MPL Data Message retransmissions where message drops are 546 detected. Setting DATA_MESSAGE_IMAX to the same as DATA_MESSAGE_IMIN 547 in this case is acceptable since subsequent MPL Data Message 548 retransmissions are triggered by MPL Control Messages, where 549 CONTROL_MESSAGE_IMAX is greater than CONTROL_MESSAGE_IMIN. 551 6. Protocol Message Formats 553 Messages generated and processed by a MPL Forwarder are described in 554 this section. 556 6.1. MPL Option 558 The MPL Option is carried in MPL Data Messages in an IPv6 Hop-by-Hop 559 Options header, immediately following the IPv6 header. The MPL 560 Option has the following format: 562 0 1 2 3 563 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 1 564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 565 | Option Type | Opt Data Len | 566 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 567 | S |M|V| rsv | sequence | seed-id (optional) | 568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 Option Type 0x6D. 572 Opt Data Len Length of the Option Data field in octets. 574 S 2-bit unsigned integer. Identifies the length of 575 seed-id. 0 indicates that the seed-id is the 576 IPv6 Source Address and not included in the MPL 577 Option. 1 indicates that the seed-id is a 16-bit 578 unsigned integer. 2 indicates that the seed-id 579 is a 64-bit unsigned integer. 3 indicates that 580 the seed-id is a 128-bit unsigned integer. 582 M 1-bit flag. 1 indicates that the value in 583 sequence is known to be the largest sequence 584 number that was received from the MPL Seed. 586 V 1-bit flag. 0 indicates that the MPL Option 587 conforms to this specification. MPL Data 588 Messages with a MPL Option in which this flag is 589 1 MUST be dropped. 591 rsv 4-bit reserved field. MUST be set to 0 on 592 transmission and ignored on reception. 594 sequence 8-bit unsigned integer. Identifies relative 595 ordering of MPL Data Messages from the MPL Seed 596 identified by seed-id. 598 seed-id Uniquely identifies the MPL Seed that initiated 599 dissemination of the MPL Data Message. The size 600 of seed-id is indicated by the S field. 602 The Option Data (specifically the M flag) of the MPL Option is 603 updated by MPL Forwarders as the MPL Data Message is forwarded. 604 Nodes that do not understand the MPL Option MUST discard the MPL Data 605 Message. Thus, according to [RFC2460] the three high order bits of 606 the Option Type are set to '011'. The Option Data length is 607 variable. 609 The seed-id uniquely identifies a MPL Seed. When seed-id is 128 bits 610 (S=3), the MPL Seed MAY use an IPv6 address assigned to one of its 611 interfaces that is unique within the MPL Domain. Managing MPL Seed 612 Identifiers is not within scope of this document. 614 The sequence field establishes a total ordering of MPL Data Messages 615 generated by a MPL Seed for a MPL Domain. The MPL Seed MUST 616 increment the sequence field's value on each new MPL Data Message 617 that it generates for a MPL Domain. Implementations MUST follow the 618 Serial Number Arithmetic as defined in [RFC1982] when incrementing a 619 sequence value or comparing two sequence values. 621 Future updates to this specification may define additional fields 622 following the seed-id field. 624 6.2. MPL Control Message 626 A MPL Forwarder uses ICMPv6 messages to communicate information 627 contained in a MPL Domain's Seed Set and Buffered Message Set to 628 neighboring MPL Forwarders. The MPL Control Message has the 629 following format: 631 0 1 2 3 632 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 1 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 | Type | Code | Checksum | 635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 | | 637 . MPL Seed Info[0..n] . 638 . . 639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 IP Fields: 643 Source Address An IPv6 address in the AddressSet of the 644 corresponding MPL Interface and MUST be valid 645 within the MPL Domain. 647 Destination Address The link-scoped MPL Domain Address corresponding 648 to the MPL Domain. 650 Hop Limit 255 652 ICMPv6 Fields: 654 Type MPL_ICMP_TYPE 656 Code 0 658 Checksum The ICMP checksum. See [RFC4443]. 660 MPL Seed Info[0..n] List of zero or more MPL Seed Info entries. 662 The MPL Control Message indicates the sequence numbers of MPL Data 663 Messages that are within the MPL Domain's Buffered Message Set. The 664 MPL Control Message also indicates the sequence numbers of MPL Data 665 Messages that a MPL Forwarder is willing to receive. The MPL Control 666 Message allows neighboring MPL Forwarders to determine whether there 667 are any new MPL Data Messages to exchange. 669 6.3. MPL Seed Info 671 A MPL Seed Info encodes the minimum sequence number for an MPL Seed 672 maintained in the MPL Domain's Seed Set. The MPL Seed Info also 673 indicates the sequence numbers of MPL Data Messages generated by the 674 MPL Seed that are stored within the MPL Domain's Buffered Message 675 Set. The MPL Seed Info has the following format: 677 0 1 2 3 678 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 1 679 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 680 | min-seqno | bm-len | S | seed-id (0/2/8/16 octets) | 681 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 682 | | 683 . buffered-mpl-messages (variable length) . 684 . . 685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 min-seqno 8-bit unsigned integer. The lower-bound sequence 688 number for the MPL Seed. 690 bm-len 6-bit unsigned integer. The size of buffered- 691 mpl-messages in octets. 693 S 2-bit unsigned integer. Identifies the length of 694 seed-id. 0 indicates that the seed-id value is 695 the IPv6 Source Address and not included in the 696 MPL Seed Info. 1 indicates that the seed-id 697 value is a 16-bit unsigned integer. 2 indicates 698 that the seed-id value is a 64-bit unsigned 699 integer. 3 indicates that the seed-id is a 700 128-bit unsigned integer. 702 seed-id Variable-length unsigned integer. Indicates the 703 MPL Seed associated with this MPL Seed Info. 705 buffered-mpl-messages Variable-length bit vector. Identifies the 706 sequence numbers of MPL Data Messages maintained 707 in the corresponding Buffered Message Set for the 708 MPL Seed. The i'th bit represents a sequence 709 number of min-seqno + i. '0' indicates that the 710 corresponding MPL Data Message does not exist in 711 the Buffered Message Set. '1' indicates that the 712 corresponding MPL Data Message does exist in the 713 Buffered Message Set. 715 The MPL Seed Info does not have any octet alignment requirement. 717 7. Information Base 719 7.1. Local Interface Set 721 The Local Interface Set records the local MPL Interfaces of a MPL 722 Forwarder. The Local Interface Set consists of Local Interface 723 Tuples, one per MPL Interface: (AddressSet). 725 AddressSet - a set of unicast addresses assigned to the MPL 726 Interface. 728 7.2. Domain Set 730 The Domain Set records the MPL Interfaces that subscribe to each MPL 731 Domain Address. The Domain Set consists of MPL Domain Tuples, one 732 per MPL Domain: (MPLInterfaceSet). 734 MPLInterfaceSet - a set of MPL Interfaces that subscribe to the MPL 735 Domain Address that identifies the MPL Domain. 737 7.3. Seed Set 739 A Seed Set records a sliding window used to determine the sequence 740 numbers of MPL Data Messages that a MPL Forwarder is willing to 741 accept generated by the MPL Seed. A MPL Forwarder maintains a Seed 742 Set for each MPL Domain that it participates in. A Seed Set consists 743 of MPL Seed Tuples: (SeedID, MinSequence, Lifetime). 745 SeedID - the identifier for the MPL Seed. 747 MinSequence - a lower-bound sequence number that represents the 748 sequence number of the oldest MPL Data Message the MPL Forwarder 749 is willing to receive or transmit. A MPL Forwarder MUST ignore 750 any MPL Data Message that has sequence value less than than 751 MinSequence. 753 Lifetime - indicates the minimum remaining lifetime of the Seed Set 754 entry. A MPL Forwarder MUST NOT free a Seed Set entry before the 755 remaining lifetime expires. 757 7.4. Buffered Message Set 759 A Buffered Message Set records recently received MPL Data Messages 760 from a MPL Seed within a MPL Domain. A MPL Forwarder uses a Buffered 761 Message Set to buffer MPL Data Messages while the MPL Forwarder is 762 forwarding the MPL Data Messages. A MPL Forwarder maintains a 763 Buffered Message Set for each MPL Domain that it participates in. A 764 Buffered Message Set consists of Buffered Message Tuples: (SeedID, 765 SequenceNumber, DataMessage). 767 SeedID - the identifier for the MPL Seed that generated the MPL Data 768 Message. 770 SequenceNumber - the sequence number for the MPL Data Message. 772 DataMessage - the MPL Data Message. 774 All MPL Data Messages within a Buffered Message Set MUST have a 775 sequence number greater than or equal to MinSequence for the 776 corresponding SeedID. When increasing MinSequence for a MPL Seed, 777 the MPL Forwarder MUST delete any MPL Data Messages from the 778 corresponding Buffered Message Set that have sequence numbers less 779 than MinSequence. 781 8. MPL Seed Sequence Numbers 783 Each MPL Seed maintains a sequence number for each MPL Domain that it 784 serves. The sequence numbers are included in MPL Data Messages 785 generated by the MPL Seed. The MPL Seed MUST increment the sequence 786 number for each MPL Data Message that it generates for a MPL Domain. 787 Implementations MUST follow the Serial Number Arithmetic as defined 788 in [RFC1982] when incrementing a sequence value or comparing two 789 sequence values. This sequence number is used to establish a total 790 ordering of MPL Data Messages generated by a MPL Seed for a MPL 791 Domain. 793 9. MPL Data Messages 795 9.1. MPL Data Message Generation 797 MPL Data Messages are generated by MPL Seeds when these messages 798 enter the MPL Domain. All MPL Data messages have the following 799 properties: 801 o The IPv6 Source Address MUST be an address in the AddressSet of a 802 corresponding MPL Interface and MUST be valid within the MPL 803 Domain. 805 o The IPv6 Destination Address MUST be set to the MPL Domain Address 806 corresponding to the MPL Domain. 808 o A MPL Data Message MUST contain a MPL Option in its IPv6 Header to 809 identify the MPL Seed that generated the message and the ordering 810 relative to other MPL Data Messages generated by the MPL Seed. 812 When the destination address is a MPL Domain Address and the source 813 address is in the AddressLIst of a MPL Interface that belongs to that 814 MPL Domain Address, the application message and the MPL Data Message 815 MAY be identical. In other words, the MPL Data Message may contain a 816 single IPv6 header that includes the MPL Option. 818 Otherwise, IPv6-in-IPv6 encapsulation MUST be used to satisfy the MPL 819 Data Message requirements listed above [RFC2473]. The complete IPv6- 820 in-IPv6 message forms a MPL Data Message. The outer IPv6 header 821 conforms to the MPL Data Message requirements listed above. The 822 encapsulated IPv6 datagram encodes the multicast data message that is 823 communicated beyond the MPL Domain. 825 9.2. MPL Data Message Transmission 827 A MPL Forwarder manages transmission of MPL Data Messages in its 828 Buffered Message Sets using the Trickle algorithm [RFC6206]. A MPL 829 Forwarder MUST use a separate Trickle timer for each MPL Data Message 830 that it is actively forwarding. In accordance with Section 5 of RFC 831 6206 [RFC6206], this document defines the following: 833 o This document defines a "consistent" transmission as receiving a 834 MPL Data Message that has the same MPL Domain Address, seed-id, 835 and sequence value as the MPL Data Message managed by the Trickle 836 timer. 838 o This document defines an "inconsistent" transmission as receiving 839 a MPL Data Message that has the same MPL Domain Address, seed-id 840 value, and the M flag set, but has a sequence value less than MPL 841 Data Message managed by the Trickle timer. 843 o This document does not define any external "events". 845 o This document defines MPL Data Messages as Trickle messages. 847 o The actions outside the Trickle algorithm that MPL takes involve 848 managing the MPL Domain's Seed Set and Buffered Message Set. 850 As specified in [RFC6206], a Trickle timer has three variables: the 851 current interval size I, a time within the current interval t, and a 852 counter c. MPL defines a fourth variable, e, which counts the number 853 of Trickle timer expiration events since the Trickle timer was last 854 reset. 856 After DATA_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, the MPL 857 Forwarder MUST disable the Trickle timer. When a buffered MPL Data 858 Message does not have an associated Trickle timer, the MPL Forwarder 859 MAY delete the message from the Buffered Message Set by advancing 860 MinSequence of the corresponding MPL Seed in the Seed Set. When the 861 MPL Forwarder no longer buffers any messages for a MPL Seed, the MPL 862 Forwarder MUST NOT increment MinSequence for that MPL Seed. 864 When transmitting a MPL Data Message, the MPL Forwarder MUST either 865 set the M flag to zero or set it to a level that indicates whether or 866 not the message's sequence number is the largest value that has been 867 received from the MPL Seed. 869 9.3. MPL Data Message Processing 871 Upon receiving a MPL Data Message, the MPL Forwarder first processes 872 the MPL Option and updates the Trickle timer associated with the MPL 873 Data Message if one exists. 875 Upon receiving a MPL Data Message, a MPL Forwarder MUST perform one 876 of the following actions: 878 o Accept the message and enter the MPL Data Message in the MPL 879 Domain's Buffered Message Set. 881 o Accept the message and update the corresponding MinSequence in the 882 MPL Domain's Seed Set to 1 greater than the message's sequence 883 number. 885 o Discard the message without any change to the MPL Information 886 Base. 888 If a Seed Set entry exists for the MPL Seed, the MPL Forwarder MUST 889 discard the MPL Data Message if its sequence number is less than 890 MinSequence or exists in the Buffered Message Set. 892 If a Seed Set entry does not exist for the MPL Seed, the MPL 893 Forwarder MUST create a new entry for the MPL Seed before accepting 894 the MPL Data Message. 896 If memory is limited, a MPL Forwarder SHOULD reclaim memory resources 897 by: 899 o Incrementing MinSequence entries in a Seed Set and deleting MPL 900 Data Messages in the corresponding Buffered Message Set that fall 901 below the MinSequence value. 903 o Deleting other Seed Set entries that have expired and the 904 corresponding MPL Data Messages in the Buffered Message Set. 906 If the MPL Forwarder accepts the MPL Data Message, the MPL Forwarder 907 MUST perform the following actions: 909 o Reset the Lifetime of the corresponding Seed Set entry to 910 SEED_SET_ENTRY_LIFETIME. 912 o If PROACTIVE_FORWARDING is true, the MPL Forwarder MUST initialize 913 and start a Trickle timer for the MPL Data Message. 915 o If the MPL Control Message Trickle timer is not running and 916 CONTROL_MESSAGE_TIMER_EXPIRATIONS is non-zero, the MPL Forwarder 917 MUST initialize and start the MPL Control Message Trickle timer. 919 o If the MPL Control Message Trickle timer is running, the MPL 920 Forwarder MUST reset the MPL Control Message Trickle timer. 922 10. MPL Control Messages 924 10.1. MPL Control Message Generation 926 A MPL Forwarder generates MPL Control Messages to communicate a MPL 927 Domain's Seed Set and Buffered Message Set to neighboring MPL 928 Forwarders. Each MPL Control Message is generated according to 929 Section 6.2, with a MPL Seed Info for each entry in the MPL Domain's 930 Seed Set. Each MPL Seed Info entry has the following content: 932 o S set to the size of the seed-id field in the MPL Seed Info entry. 934 o min-seqno set to MinSequence of the MPL Seed. 936 o bm-len set to the size of buffered-mpl-messages in octets. 938 o seed-id set to the MPL seed identifier. 940 o buffered-mpl-messages with each bit representing whether or not a 941 MPL Data Message with the corresponding sequence number exists in 942 the Buffered Message Set. The i'th bit represents a sequence 943 number of min-seqno + i. '0' indicates that the corresponding MPL 944 Data Message does not exist in the Buffered Message Set. '1' 945 indicates that the corresponding MPL Data Message does exist in 946 the Buffered Message Set. 948 10.2. MPL Control Message Transmission 950 A MPL Forwarder transmits MPL Control Messages using the Trickle 951 algorithm. A MPL Forwarder maintains a single Trickle timer for each 952 MPL Domain. When CONTROL_MESSAGE_TIMER_EXPIRATIONS is 0, the MPL 953 Forwarder does not execute the Trickle algorithm and does not 954 transmit MPL Control Messages. In accordance with Section 5 of RFC 955 6206 [RFC6206], this document defines the following: 957 o This document defines a "consistent" transmission as receiving a 958 MPL Control Message that results in a determination that neither 959 the receiving nor transmitting node has any new MPL Data Messages 960 to offer. 962 o This document defines an "inconsistent" transmission as receiving 963 a MPL Control Message that results in a determination that either 964 the receiving or transmitting node has at least one new MPL Data 965 Message to offer. 967 o The Trickle timer is reset in response to external "events." This 968 document defines an "event" as increasing MinSequence of any entry 969 in the corresponding Seed Set or adding a message to the 970 corresponding Buffered Message Set. 972 o This document defines a MPL Control Message as a Trickle message. 974 As specified in [RFC6206], a Trickle timer has three variables: the 975 current interval size I, a time within the current interval t, and a 976 counter c. MPL defines a fourth variable, e, which counts the number 977 of Trickle timer expiration events since the Trickle timer was last 978 reset. After CONTROL_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, 979 the MPL Forwarder MUST disable the Trickle timer. 981 10.3. MPL Control Message Processing 983 A MPL Forwarder processes each MPL Control Message that it receives 984 to determine if it has any new MPL Data Messages to receive or offer. 986 A MPL Forwarder determines if a new MPL Data Message has not been 987 received from a neighboring node if any of the following conditions 988 hold true: 990 o The MPL Control Message includes a MPL Seed that does not exist in 991 the MPL Domain's Seed Set. 993 o The MPL Control Message indicates that the neighbor has a MPL Data 994 Message in its Buffered Message Set with sequence number greater 995 than MinSequence (i.e. the i-th bit is set to 1 and min-seqno + i 996 > MinSequence) and is not included in the MPL Domain's Buffered 997 Message Set. 999 When a MPL Forwarder determines that it has not yet received a MPL 1000 Data Message buffered by a neighboring device, the MPL Forwarder MUST 1001 reset its Trickle timer associated with MPL Control Message 1002 transmissions. If a MPL Control Message Trickle timer is not 1003 running, the MPL Forwarder MUST initialize and start a new Trickle 1004 timer. 1006 A MPL Forwarder determines if a MPL Data Message in the Buffered 1007 Message Set has not yet been received by a neighboring MPL Forwarder 1008 if any of the following conditions hold true: 1010 o The MPL Control Message does not include a MPL Seed for the MPL 1011 Data Message. 1013 o The MPL Data Message's sequence number is greater than or equal to 1014 min-seqno and not included in the neighbor's corresponding 1015 Buffered Message Set (i.e. the MPL Data Message's sequence number 1016 does not have a corresponding bit in buffered-mpl-messages set to 1017 1). 1019 When a MPL Forwarder determines that it has at least one MPL Data 1020 Message in its corresponding Buffered Message Set that has not yet 1021 been received by a neighbor, the MPL Forwarder MUST reset the MPL 1022 Control Message Trickle timer. Additionally, for each of those 1023 entries in the Buffered Message Set, the MPL Forwarder MUST reset the 1024 Trickle timer and reset e to 0. If a Trickle timer is not associated 1025 with the MPL Data Message, the MPL Forwarder MUST initialize and 1026 start a new Trickle timer. 1028 11. Acknowledgements 1030 The authors would like to acknowledge the helpful comments of Robert 1031 Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Adrian Farrel, Ulrich 1032 Herberg, Owen Kirby, Philip Levis, Kerry Lynn, Joseph Reddy, Michael 1033 Richardson, Ines Robles, Don Sturek, Dario Tedeschi, and Peter van 1034 der Stok, which greatly improved the document. 1036 12. IANA Considerations 1038 This document defines one IPv6 Option, a type that must be allocated 1039 from the IPv6 "Destination Options and Hop-by-Hop Options" registry 1040 of [RFC2780]. 1042 This document defines one ICMPv6 Message, a type that must be 1043 allocated from the "ICMPv6 "type" Numbers" registry of [RFC4443]. 1045 This document registers a well-known multicast address from the 1046 Variable Scope Multicast Address registry. 1048 12.1. MPL Option Type 1050 IANA is requested to allocate an IPv6 Option Type from the IPv6 1051 "Destination Options and Hop-by-Hop Options" registry of [RFC2780], 1052 as specified in Table 1 below: 1054 +-----------+-----+-----+-------+-------------+---------------+ 1055 | Hex Value | act | chg | rest | Description | Reference | 1056 +-----------+-----+-----+-------+-------------+---------------+ 1057 | 0x6D | 01 | 1 | 01101 | MPL Option | This Document | 1058 +-----------+-----+-----+-------+-------------+---------------+ 1060 Table 1: IPv6 Option Type Allocation 1062 12.2. MPL ICMPv6 Type 1064 IANA is requested to allocate an ICMPv6 Type from the "ICMPv6 "type" 1065 Numbers" registry of [RFC4443], as specified in Table 2 below: 1067 +------+---------------------+---------------+ 1068 | Type | Name | Reference | 1069 +------+---------------------+---------------+ 1070 | TBD | MPL Control Message | This Document | 1071 +------+---------------------+---------------+ 1073 Table 2: IPv6 Option Type Allocation 1075 In this document, the mnemonic MPL_ICMP_TYPE was used to refer to the 1076 ICMPv6 Type above, which is TBD by IANA. 1078 12.3. Well-known Multicast Addresses 1080 IANA is requested to allocate an IPv6 multicast address, with Group 1081 ID in the range [0x01,0xFF] for 6LoWPAN compression [RFC6282], 1082 "ALL_MPL_FORWARDERS" from the "Variable Scope Multicast Addresses" 1083 sub-registry of the "IPv6 Multicast Address Space" registry [RFC3307] 1084 as specified in Table 3 below: 1086 +---------------------+--------------------+-----------+------------+ 1087 | Address(s) | Description | Reference | Date | 1088 | | | | Registered | 1089 +---------------------+--------------------+-----------+------------+ 1090 | FF0X:0:0:0:0:0:0:FC | ALL_MPL_FORWARDERS | This | 2013-04-10 | 1091 | | | Document | | 1092 +---------------------+--------------------+-----------+------------+ 1094 Table 3: Variable Scope Multicast Address Allocation 1096 13. Security Considerations 1098 MPL uses sequence numbers to maintain a total ordering of MPL Data 1099 Messages from a MPL Seed. The use of sequence numbers allows a 1100 denial-of-service attack where an attacker can spoof a message with a 1101 sufficiently large sequence number to: (i) flush messages from the 1102 Buffered Message List and (ii) increase the MinSequence value for a 1103 MPL Seed in the corresponding Seed Set. In both cases, the side 1104 effect allows an attacker to halt the forwarding process of any MPL 1105 Data Messages being disseminated and prevents MPL Forwarders from 1106 accepting new MPL Data Messages that a MPL Seed generates while the 1107 sequence number is less than MinSequence or until the corresponding 1108 Seed Set Entry expires. The net effect applies to both proactive and 1109 reactive forwarding modes. 1111 In general, the basic ability to inject messages into a Low-power and 1112 Lossy Network may be used as a denial-of-service attack regardless of 1113 what forwarding protocol is used. Because MPL is a dissemination 1114 protocol, the ability to spoof MPL messages allows an attacker to 1115 affect an entire MPL Domain. For these reasons, Low-power and Lossy 1116 Networks typically employ link-layer security mechanisms to mitigate 1117 an attacker's ability to inject messages. For example, the IEEE 1118 802.15.4 [IEEE802154] standard specifies frame security mechanisms 1119 using AES-128 to support access control, message integrity, message 1120 confidentiality, and replay protection. However, if the attack 1121 vector includes attackers that have access to the LLN, then MPL 1122 SHOULD NOT be used. 1124 To prevent attackers from injecting packets through a MPL Forwarder, 1125 the MPL Forwarder MUST NOT accept or forward MPL Data Messages from a 1126 communication interface that does not subscribe to the MPL Domain 1127 Address identified in message's destination address. 1129 MPL uses the Trickle algorithm to manage message transmissions and 1130 the security considerations described in [RFC6206] apply. 1132 14. References 1134 14.1. Normative References 1136 [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, 1137 August 1996. 1139 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1140 Requirement Levels", BCP 14, RFC 2119, March 1997. 1142 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1143 (IPv6) Specification", RFC 2460, December 1998. 1145 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1146 IPv6 Specification", RFC 2473, December 1998. 1148 [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For 1149 Values In the Internet Protocol and Related Headers", BCP 1150 37, RFC 2780, March 2000. 1152 [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast 1153 Addresses", RFC 3307, August 2002. 1155 [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and 1156 B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, 1157 March 2005. 1159 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 1160 Message Protocol (ICMPv6) for the Internet Protocol 1161 Version 6 (IPv6) Specification", RFC 4443, March 2006. 1163 [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, 1164 "The Trickle Algorithm", RFC 6206, March 2011. 1166 [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 1167 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1168 September 2011. 1170 [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., 1171 Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. 1172 Alexander, "RPL: IPv6 Routing Protocol for Low-Power and 1173 Lossy Networks", RFC 6550, March 2012. 1175 [RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346, 1176 August 2014. 1178 14.2. Informative References 1180 [Clausen2013] 1181 Clausen, T., Colin de Verdiere, A., and J. Yi, 1182 "Performance Analysis of Trickle as a Flooding Mechanism", 1183 The 5th IEEE International Conference on Communication 1184 Technology (ICCT2013), November 2013. 1186 [IEEE802154] 1187 "IEEE Std. 802.15.4-2006", October 2006. 1189 [RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol 1190 Independent Multicast - Dense Mode (PIM-DM): Protocol 1191 Specification (Revised)", RFC 3973, January 2005. 1193 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 1194 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 1195 Protocol Specification (Revised)", RFC 4601, August 2006. 1197 Authors' Addresses 1199 Jonathan W. Hui 1200 Nest Labs 1201 3400 Hillview Ave 1202 Palo Alto, California 94304 1203 USA 1205 Phone: +650 253 2770 1206 Email: jonhui@nestlabs.com 1208 Richard Kelsey 1209 Silicon Labs 1210 25 Thomson Place 1211 Boston, Massachusetts 02210 1212 USA 1214 Phone: +617 951 1225 1215 Email: richard.kelsey@silabs.com