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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) ** Downref: Normative reference to an Experimental RFC: RFC 3561 ** Downref: Normative reference to an Experimental RFC: RFC 6998 Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ROLL S. Anamalamudi 3 Internet-Draft SRM University-AP 4 Intended status: Standards Track M. Zhang 5 Expires: September 8, 2019 Huawei Technologies 6 C. Perkins 7 Futurewei 8 S.V.R.Anand 9 Indian Institute of Science 10 B. Liu 11 Huawei Technologies 12 March 7, 2019 14 Asymmetric AODV-P2P-RPL in Low-Power and Lossy Networks (LLNs) 15 draft-ietf-roll-aodv-rpl-06 17 Abstract 19 Route discovery for symmetric and asymmetric Point-to-Point (P2P) 20 traffic flows is a desirable feature in Low power and Lossy Networks 21 (LLNs). For that purpose, this document specifies a reactive P2P 22 route discovery mechanism for both hop-by-hop routing and source 23 routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL 24 protocol. Paired Instances are used to construct directional paths, 25 in case some of the links between source and target node are 26 asymmetric. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 8, 2019. 45 Copyright Notice 47 Copyright (c) 2019 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 65 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 7 66 4.1. AODV-RPL DIO RREQ Option . . . . . . . . . . . . . . . . 7 67 4.2. AODV-RPL DIO RREP Option . . . . . . . . . . . . . . . . 9 68 4.3. AODV-RPL DIO Target Option . . . . . . . . . . . . . . . 10 69 5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11 70 6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13 71 6.1. Route Request Generation . . . . . . . . . . . . . . . . 13 72 6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14 73 6.2.1. General Processing . . . . . . . . . . . . . . . . . 14 74 6.2.2. Additional Processing for Multiple Targets . . . . . 15 75 6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 16 76 6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 16 77 6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 16 78 6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 16 79 6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 17 80 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 18 81 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 19 82 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 83 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 19 84 9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 19 85 10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 86 11. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 21 87 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 88 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 89 13.1. Normative References . . . . . . . . . . . . . . . . . . 21 90 13.2. Informative References . . . . . . . . . . . . . . . . . 22 91 Appendix A. Example: ETX/RSSI Values to select S bit . . . . . . 23 92 Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 24 93 B.1. Changes from version 05 to version 06 . . . . . . . . . . 24 94 B.2. Changes from version 04 to version 05 . . . . . . . . . . 24 95 B.3. Changes from version 03 to version 04 . . . . . . . . . . 24 96 B.4. Changes from version 02 to version 03 . . . . . . . . . . 24 97 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 99 1. Introduction 101 RPL[RFC6550] (Routing Protocol for LLNs (Low-Power and Lossy 102 Networks)) is a IPv6 distance vector routing protocol designed to 103 support multiple traffic flows through a root-based Destination- 104 Oriented Directed Acyclic Graph (DODAG). Typically, a router does 105 not have routing information for most other routers. Consequently, 106 for traffic between routers within the DODAG (i.e., Point-to-Point 107 (P2P) traffic) data packets either have to traverse the root in non- 108 storing mode, or traverse a common ancestor in storing mode. Such 109 P2P traffic is thereby likely to traverse longer routes and may 110 suffer severe congestion near the DAG root [RFC6997], [RFC6998]. 112 To discover better paths for P2P traffic flows in RPL, P2P-RPL 113 [RFC6997] specifies a temporary DODAG where the source acts as a 114 temporary root. The source initiates DIOs encapsulating the P2P 115 Route Discovery option (P2P-RDO) with an address vector for both hop- 116 by-hop mode (H=1) and source routing mode (H=0). Subsequently, each 117 intermediate router adds its IP address and multicasts the P2P mode 118 DIOs, until the message reaches the Target Node, which then sends the 119 "Discovery Reply" object. P2P-RPL is efficient for source routing, 120 but much less efficient for hop-by-hop routing due to the extra 121 address vector overhead. However, for symmetric links, when the P2P 122 mode DIO message is being multicast from the source hop-by-hop, 123 receiving nodes can infer a next hop towards the source. When the 124 Target Node subsequently replies to the source along the established 125 forward route, receiving nodes determine the next hop towards the 126 Target Node. For hop-by-hop routes (H=1) over symmetric links, this 127 would allow efficient use of routing tables for P2P-RDO messages 128 instead of the "Address Vector". 130 RPL and P2P-RPL both specify the use of a single DODAG in networks of 131 symmetric links, where the two directions of a link MUST both satisfy 132 the constraints of the objective function. This disallows the use of 133 asymmetric links which are qualified in one direction. But, 134 application-specific routing requirements as defined in IETF ROLL 135 Working Group [RFC5548], [RFC5673], [RFC5826] and [RFC5867] may be 136 satisfied by routing paths using bidirectional asymmetric links. For 137 this purpose, [I-D.thubert-roll-asymlink] described bidirectional 138 asymmetric links for RPL [RFC6550] with Paired DODAGs, for which the 139 DAG root (DODAGID) is common for two Instances. This can satisfy 140 application-specific routing requirements for bidirectional 141 asymmetric links in core RPL [RFC6550]. Using P2P-RPL twice with 142 Paired DODAGs, on the other hand, requires two roots: one for the 143 source and another for the target node due to temporary DODAG 144 formation. For networks composed of bidirectional asymmetric links 145 (see Section 5), AODV-RPL specifies P2P route discovery, utilizing 146 RPL with a new MoP. AODV-RPL makes use of two multicast messages to 147 discover possibly asymmetric routes. This provides higher route 148 diversity and can find suitable routes that might otherwise go 149 undetected by RPL. AODV-RPL eliminates the need for address vector 150 overhead in hop-by-hop mode. This significantly reduces the control 151 packet size, which is important for Constrained LLN networks. Both 152 discovered routes (upward and downward) meet the application specific 153 metrics and constraints that are defined in the Objective Function 154 for each Instance [RFC6552]. On the other hand, the point-to-point 155 nature of routes discovered by AODV-RPL can reduce interference near 156 the root nodes and also provide routes with fewer hops, likely 157 improving performance in the network. 159 The route discovery process in AODV-RPL is modeled on the analogous 160 procedure specified in AODV [RFC3561]. The on-demand nature of AODV 161 route discovery is natural for the needs of peer-to-peer routing in 162 RPL-based LLNs. AODV terminology has been adapted for use with AODV- 163 RPL messages, namely RREQ for Route Request, and RREP for Route 164 Reply. AODV-RPL currently omits some features compared to AODV -- in 165 particular, flagging Route Errors, blacklisting unidirectional links, 166 multihoming, and handling unnumbered interfaces. 168 2. Terminology 170 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 171 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 172 "OPTIONAL" in this document are to be interpreted as described in 173 [RFC2119]. This document uses the following terms: 175 AODV 176 Ad Hoc On-demand Distance Vector Routing[RFC3561]. 178 AODV-RPL Instance 179 Either the RREQ-Instance or RREP-Instance 181 Asymmetric Route 182 The route from the OrigNode to the TargNode can traverse different 183 nodes than the route from the TargNode to the OrigNode. An 184 asymmetric route may result from the asymmetry of links, such that 185 only one direction of the series of links fulfills the constraints 186 in route discovery. 188 Bi-directional Asymmetric Link 189 A link that can be used in both directions but with different link 190 characteristics. 192 DIO 193 DODAG Information Object 195 DODAG RREQ-Instance (or simply RREQ-Instance) 196 RPL Instance built using the DIO with RREQ option; used for 197 control message transmission from OrigNode to TargNode, thus 198 enabling data transmission from TargNode to OrigNode. 200 DODAG RREP-Instance (or simply RREP-Instance) 201 RPL Instance built using the DIO with RREP option; used for 202 control message transmission from TargNode to OrigNode thus 203 enabling data transmission from OrigNode to TargNode. 205 Downward Direction 206 The direction from the OrigNode to the TargNode. 208 Downward Route 209 A route in the downward direction. 211 hop-by-hop routing 212 Routing when each node stores routing information about the next 213 hop. 215 on-demand routing 216 Routing in which a route is established only when needed. 218 OrigNode 219 The IPv6 router (Originating Node) initiating the AODV-RPL route 220 discovery to obtain a route to TargNode. 222 Paired DODAGs 223 Two DODAGs for a single route discovery process between OrigNode 224 and TargNode. 226 P2P 227 Point-to-Point -- in other words, not constrained a priori to 228 traverse a common ancestor. 230 reactive routing 231 Same as "on-demand" routing. 233 RREQ-DIO message 234 An AODV-RPL MoP DIO message containing the RREQ option. The 235 RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode. 237 RREP-DIO message 238 An AODV-RPL MoP DIO message containing the RREP option. The 239 RPLInstanceID in RREP-DIO is typically paired to the one in the 240 associated RREQ-DIO message. 242 Source routing 243 A mechanism by which the source supplies the complete route 244 towards the target node along with each data packet [RFC6550]. 246 Symmetric route 247 The upstream and downstream routes traverse the same routers. 249 TargNode 250 The IPv6 router (Target Node) for which OrigNode requires a route 251 and initiates Route Discovery within the LLN network. 253 Upward Direction 254 The direction from the TargNode to the OrigNode. 256 Upward Route 257 A route in the upward direction. 259 ART option 260 AODV-RPL Target option: a target option defined in this document. 262 3. Overview of AODV-RPL 264 With AODV-RPL, routes from OrigNode to TargNode within the LLN 265 network are established "on-demand". In other words, the route 266 discovery mechanism in AODV-RPL is invoked reactively when OrigNode 267 has data for delivery to the TargNode but existing routes do not 268 satisfy the application's requirements. The routes discovered by 269 AODV-RPL are not constrained to traverse a common ancestor. Unlike 270 RPL [RFC6550] and P2P-RPL [RFC6997], AODV-RPL can enable asymmetric 271 communication paths in networks with bidirectional asymmetric links. 272 For this purpose, AODV-RPL enables discovery of two routes: namely, 273 one from OrigNode to TargNode, and another from TargNode to OrigNode. 274 When possible, AODV-RPL also enables symmetric route discovery along 275 Paired DODAGs (see Section 5). 277 In AODV-RPL, routes are discovered by first forming a temporary DAG 278 rooted at the OrigNode. Paired DODAGs (Instances) are constructed 279 according to the AODV-RPL Mode of Operation (MoP) during route 280 formation between the OrigNode and TargNode. The RREQ-Instance is 281 formed by route control messages from OrigNode to TargNode whereas 282 the RREP-Instance is formed by route control messages from TargNode 283 to OrigNode. Intermediate routers join the Paired DODAGs based on 284 the rank as calculated from the DIO message. Henceforth in this 285 document, the RREQ-DIO message means the AODV-RPL mode DIO message 286 from OrigNode to TargNode, containing the RREQ option (see 287 Section 4.1). Similarly, the RREP-DIO message means the AODV-RPL 288 mode DIO message from TargNode to OrigNode, containing the RREP 289 option (see Section 4.2). The route discovered in the RREQ-Instance 290 is used for transmitting data from TargNode to OrigNode, and the 291 route discovered in RREP-Instance is used for transmitting data from 292 OrigNode to TargNode. 294 4. AODV-RPL DIO Options 296 4.1. AODV-RPL DIO RREQ Option 298 OrigNode sets its IPv6 address in the DODAGID field of the RREQ-DIO 299 message. A RREQ-DIO message MUST carry exactly one RREQ option. 301 0 1 2 3 302 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 1 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 | Type | Option Length |S|H|X| Compr | L | MaxRank | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | Orig SeqNo | | 307 +-+-+-+-+-+-+-+-+ | 308 | | 309 | | 310 | Address Vector (Optional, Variable Length) | 311 | | 312 | | 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 Figure 1: DIO RREQ option format for AODV-RPL MoP 317 OrigNode supplies the following information in the RREQ option: 319 Type 320 The type assigned to the RREQ option (see Section 9.2). 322 Option Length 323 The length of the option in octets, excluding the Type and Length 324 fields. Variable due to the presence of the address vector and 325 the number of octets elided according to the Compr value. 327 S 328 Symmetric bit indicating a symmetric route from the OrigNode to 329 the router transmitting this RREQ-DIO. 331 H 332 Set to one for a hop-by-hop route. Set to zero for a source 333 route. This flag controls both the downstream route and upstream 334 route. 336 X 337 Reserved. 339 Compr 340 4-bit unsigned integer. Number of prefix octets that are elided 341 from the Address Vector. The octets elided are shared with the 342 IPv6 address in the DODAGID. This field is only used in source 343 routing mode (H=0). In hop-by-hop mode (H=1), this field MUST be 344 set to zero and ignored upon reception. 346 L 348 2-bit unsigned integer determining the duration that a node is 349 able to belong to the temporary DAG in RREQ-Instance, including 350 the OrigNode and the TargNode. Once the time is reached, a node 351 MUST leave the DAG and stop sending or receiving any more DIOs for 352 the temporary DODAG. The definition for the "L" bit is similar to 353 that found in [RFC6997], except that the values are adjusted to 354 enable arbitrarily long route lifetime. 356 * 0x00: No time limit imposed. 357 * 0x01: 16 seconds 358 * 0x02: 64 seconds 359 * 0x03: 256 seconds 361 L is independent from the route lifetime, which is defined in the 362 DODAG configuration option. The route entries in hop-by-hop 363 routing and states of source routing can still be maintained even 364 after the DAG expires. 366 MaxRank 367 This field indicates the upper limit on the integer portion of the 368 rank (calculated using the DAGRank() macro defined in [RFC6550]). 369 A value of 0 in this field indicates the limit is infinity. 371 Orig SeqNo 372 Sequence Number of OrigNode, defined similarly as in AODV 373 [RFC3561]. 375 Address Vector 376 A vector of IPv6 addresses representing the route that the RREQ- 377 DIO has passed. It is only present when the 'H' bit is set to 0. 378 The prefix of each address is elided according to the Compr field. 380 A node MUST NOT join a RREQ instance if its own rank would equal to 381 or higher than MaxRank. Targnode can join the RREQ instance at a 382 rank whose integer portion is equal to the MaxRank. A router MUST 383 discard a received RREQ if the integer part of the advertised rank 384 equals or exceeds the MaxRank limit. This definition of MaxRank is 385 the same as that found in [RFC6997]. 387 4.2. AODV-RPL DIO RREP Option 389 TargNode sets its IPv6 address in the DODAGID field of the RREP-DIO 390 message. A RREP-DIO message MUST carry exactly one RREP option. 391 TargNode supplies the following information in the RREP option: 393 0 1 2 3 394 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 1 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | Type | Option Length |G|H|X| Compr | L | MaxRank | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 | Shift |Rsv| | 399 +-+-+-+-+-+-+-+-+ | 400 | | 401 | | 402 | Address Vector (Optional, Variable Length) | 403 . . 404 . . 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 Figure 2: DIO RREP option format for AODV-RPL MoP 409 Type 410 The type assigned to the RREP option (see Section 9.2) 412 Option Length 413 The length of the option in octets, excluding the Type and Length 414 fields. Variable due to the presence of the address vector and 415 the number of octets elided according to the Compr value. 417 G 418 Gratuitous route (see Section 7). 420 H 421 Requests either source routing (H=0) or hop-by-hop (H=1) for the 422 downstream route. It MUST be set to be the same as the 'H' bit in 423 RREQ option. 425 X 426 Reserved. 428 Compr 429 4-bit unsigned integer. Same definition as in RREQ option. 431 L 432 2-bit unsigned integer defined as in RREQ option. 434 MaxRank 435 Similarly to MaxRank in the RREQ message, this field indicates the 436 upper limit on the integer portion of the rank. A value of 0 in 437 this field indicates the limit is infinity. 439 Shift 440 6-bit unsigned integer. This field is used to recover the 441 original InstanceID (see Section 6.3.3); 0 indicates that the 442 original InstanceID is used. 444 Rsv 445 MUST be initialized to zero and ignored upon reception. 447 Address Vector 448 Only present when the 'H' bit is set to 0. For an asymmetric 449 route, the Address Vector represents the IPv6 addresses of the 450 route that the RREP-DIO has passed. For a symmetric route, it is 451 the Address Vector when the RREQ-DIO arrives at the TargNode, 452 unchanged during the transmission to the OrigNode. 454 4.3. AODV-RPL DIO Target Option 456 The AODV-RPL Target (ART) Option is defined based on the Target 457 Option in core RPL [RFC6550]: the Destination Sequence Number of the 458 TargNode is added. 460 A RREQ-DIO message MUST carry at least one ART Options. A RREP-DIO 461 message MUST carry exactly one ART Option. 463 OrigNode can include multiple TargNode addresses via multiple AODV- 464 RPL Target Options in the RREQ-DIO, for routes that share the same 465 constraints. This reduces the cost to building only one DODAG. 466 Furthermore, a single Target Option can be used for different 467 TargNode addresses if they share the same prefix; in that case the 468 use of the destination sequence number is not defined in this 469 document. 471 0 1 2 3 472 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 1 473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 474 | Type | Option Length | Dest SeqNo | Prefix Length | 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 | | 477 + | 478 | Target Prefix (Variable Length) | 479 . . 480 . . 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 Figure 3: Target option format for AODV-RPL MoP 485 Type 486 The type assigned to the ART Option 488 Dest SeqNo 490 In RREQ-DIO, if nonzero, it is the last known Sequence Number for 491 TargNode for which a route is desired. In RREP-DIO, it is the 492 destination sequence number associated to the route. 494 5. Symmetric and Asymmetric Routes 496 In Figure 4 and Figure 5, BR is the Border Router, O is the OrigNode, 497 R is an intermediate router, and T is the TargNode. If the RREQ-DIO 498 arrives over an interface that is known to be symmetric, and the 'S' 499 bit is set to 1, then it remains as 1, as illustrated in Figure 4. 500 If an intermediate router sends out RREQ-DIO with the 'S' bit set to 501 1, then all the one-hop links on the route from the OrigNode O to 502 this router meet the requirements of route discovery, and the route 503 can be used symmetrically. 505 BR 506 /----+----\ 507 / | \ 508 / | \ 509 R R R 510 _/ \ | / \ 511 / \ | / \ 512 / \ | / \ 513 R -------- R --- R ----- R -------- R 514 / \ <--S=1--> / \ <--S=1--> / \ 515 <--S=1--> \ / \ / <--S=1--> 516 / \ / \ / \ 517 O ---------- R ------ R------ R ----- R ----------- T 518 / \ / \ / \ / \ 519 / \ / \ / \ / \ 520 / \ / \ / \ / \ 521 R ----- R ----------- R ----- R ----- R ----- R ---- R----- R 523 >---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> 524 <---- RREP-Instance (Control: T-->O; Data: O-->T) -------< 526 Figure 4: AODV-RPL with Symmetric Paired Instances 528 Upon receiving a RREQ-DIO with the 'S' bit set to 1, a node 529 determines whether this one-hop link can be used symmetrically, i.e., 530 both the two directions meet the requirements of data transmission. 531 If the RREQ-DIO arrives over an interface that is not known to be 532 symmetric, or is known to be asymmetric, the 'S' bit is set to 0. If 533 the 'S' bit arrives already set to be '0', it is set to be '0' on 534 retransmission (Figure 5). Therefore, for asymmetric route, there is 535 at least one hop which doesn't fulfill the constraints in the two 536 directions. Based on the 'S' bit received in RREQ-DIO, the TargNode 537 T determines whether or not the route is symmetric before 538 transmitting the RREP-DIO message upstream towards the OrigNode O. 540 The criteria used to determine whether or not each link is symmetric 541 is beyond the scope of the document, and may be implementation- 542 specific. For instance, intermediate routers MAY use local 543 information (e.g., bit rate, bandwidth, number of cells used in 544 6tisch), a priori knowledge (e.g. link quality according to previous 545 communication) or use averaging techniques as appropriate to the 546 application. 548 Appendix A describes an example method using the ETX and RSSI to 549 estimate whether the link is symmetric in terms of link quality is 550 given in using an averaging technique. 552 BR 553 /----+----\ 554 / | \ 555 / | \ 556 R R R 557 / \ | / \ 558 / \ | / \ 559 / \ | / \ 560 R --------- R --- R ---- R --------- R 561 / \ --S=1--> / \ --S=0--> / \ 562 --S=1--> \ / \ / --S=0--> 563 / \ / \ / \ 564 O ---------- R ------ R------ R ----- R ----------- T 565 / \ / \ / \ / \ 566 / <--S=0-- / \ / \ / <--S=0-- 567 / \ / \ / \ / \ 568 R ----- R ----------- R ----- R ----- R ----- R ---- R----- R 569 <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- 571 >---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> 572 <---- RREP-Instance (Control: T-->O; Data: O-->T) -------< 574 Figure 5: AODV-RPL with Asymmetric Paired Instances 576 6. AODV-RPL Operation 578 6.1. Route Request Generation 580 The route discovery process is initiated when an application at the 581 OrigNode has data to be transmitted to the TargNode, but does not 582 have a route for the target that fulfills the requirements of the 583 data transmission. In this case, the OrigNode builds a local 584 RPLInstance and a DODAG rooted at itself. Then it transmits a DIO 585 message containing exactly one RREQ option (see Section 4.1) via 586 link-local multicast. The DIO MUST contain at least one ART Option 587 (see Section 4.3). The 'S' bit in RREQ-DIO sent out by the OrigNode 588 is set to 1. 590 Each node maintains a sequence number, which rolls over like a 591 lollipop counter [Perlman83]; refer to section 7.2 of [RFC6550] for 592 detailed operation. When the OrigNode initiates a route discovery 593 process, it MUST increase its own sequence number to avoid conflicts 594 with previously established routes. The sequence number is carried 595 in the OrigSeqNo field of the RREQ option. 597 The address in the ART Option can be a unicast IPv6 address or a 598 prefix. The OrigNode can initiate the route discovery process for 599 multiple targets simultaneously by including multiple ART Options, 600 and within a RREQ-DIO the requirements for the routes to different 601 TargNodes MUST be the same. 603 OrigNode can maintain different RPLInstances to discover routes with 604 different requirements to the same targets. Using the InstanceID 605 pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for 606 different RPLInstances can be distinguished. 608 The transmission of RREQ-DIO obeys the Trickle timer. If the 609 duration specified by the "L" bit has elapsed, the OrigNode MUST 610 leave the DODAG and stop sending RREQ-DIOs in the related 611 RPLInstance. 613 6.2. Receiving and Forwarding RREQ messages 615 6.2.1. General Processing 617 Upon receiving a RREQ-DIO, a router which does not belong to the 618 RREQ-instance goes through the following steps: 620 Step 1: 622 If the 'S' bit in the received RREQ-DIO is set to 1, the router 623 MUST check the two directions of the link by which the RREQ-DIO is 624 received. In case that the downward (i.e. towards the TargNode) 625 direction of the link can't fulfill the requirements, the link 626 can't be used symmetrically, thus the 'S' bit of the RREQ-DIO to 627 be sent out MUST be set as 0. If the 'S' bit in the received 628 RREQ-DIO is set to 0, the router only checks into the upward 629 direction (towards the OrigNode) of the link. 631 If the upward direction of the link can fulfill the requirements 632 indicated in the constraint option, and the router's rank would 633 not exceed the MaxRank limit, the router joins the DODAG of the 634 RREQ-Instance. The router that transmitted the received RREQ-DIO 635 is selected as the preferred parent. Later, other RREQ-DIO 636 messages might be received. How to maintain the parent set, 637 select the preferred parent, and update the router's rank obeys 638 the core RPL and the OFs defined in ROLL WG. In case that the 639 constraint or the MaxRank limit is not fulfilled, the router MUST 640 discard the received RREQ-DIO and MUST NOT join the DODAG. 642 Step 2: 644 Then the router checks if one of its addresses is included in one 645 of the ART Options. If so, this router is one of the TargNodes. 646 Otherwise, it is an intermediate router. 648 Step 3: 650 If the 'H' bit is set to 1, then the router (TargNode or 651 intermediate) MUST build the upward route entry accordingly. The 652 route entry MUST include at least the following items: Source 653 Address, InstanceID, Destination Address, Next Hop, Lifetime, and 654 Sequence Number. The Destination Address and the InstanceID can 655 be respectively learned from the DODAGID and the RPLInstanceID of 656 the RREQ-DIO, and the Source Address is copied from the ART 657 Option. The next hop is the preferred parent. The lifetime is 658 set according to DODAG configuration and can be extended when the 659 route is actually used. The sequence number represents the 660 freshness of the route entry, and it is copied from the Orig SeqNo 661 field of the RREQ option. A route entry with same source and 662 destination address, same InstanceID, but stale sequence number, 663 SHOULD be deleted. 665 If the 'H' bit is set to 0, an intermediate router MUST include 666 the address of the interface receiving the RREQ-DIO into the 667 address vector. 669 Step 4: 671 An intermediate router transmits a RREQ-DIO via link-local 672 multicast. TargNode prepares a RREP-DIO. 674 6.2.2. Additional Processing for Multiple Targets 676 If the OrigNode tries to reach multiple TargNodes in a single RREQ- 677 instance, one of the TargNodes can be an intermediate router to the 678 others, therefore it SHOULD continue sending RREQ-DIO to reach other 679 targets. In this case, before rebroadcasting the RREQ-DIO, a 680 TargNode MUST delete the Target Option encapsulating its own address, 681 so that downstream routers with higher ranks do not try to create a 682 route to this TargetNode. 684 An intermediate router could receive several RREQ-DIOs from routers 685 with lower ranks in the same RREQ-instance but have different lists 686 of Target Options. When rebroadcasting the RREQ-DIO, the 687 intersection of these lists SHOULD be included. For example, suppose 688 two RREQ-DIOs are received with the same RPLInstance and OrigNode. 689 Suppose further that the first RREQ has (T1, T2) as the targets, and 690 the second one has (T2, T4) as targets. Then only T2 needs to be 691 included in the generated RREQ-DIO. If the intersection is empty, it 692 means that all the targets have been reached, and the router SHOULD 693 NOT send out any RREQ-DIO. Any RREQ-DIO message with different ART 694 Options coming from a router with higher rank is ignored. 696 6.3. Generating Route Reply (RREP) at TargNode 698 6.3.1. RREP-DIO for Symmetric route 700 If a RREQ-DIO arrives at TargNode with the 'S' bit set to 1, there is 701 a symmetric route along which both directions can fulfill the 702 requirements. Other RREQ-DIOs might later provide asymmetric upward 703 routes (i.e. S=0). Selection between a qualified symmetric route 704 and an asymmetric route that might have better performance is 705 implementation-specific and out of scope. If the implementation uses 706 the symmetric route, the TargNode MAY delay transmitting the RREP-DIO 707 for duration RREP_WAIT_TIME to await a better symmetric route. 709 For a symmetric route, the RREP-DIO message is unicast to the next 710 hop according to the accumulated address vector (H=0) or the route 711 entry (H=1). Thus the DODAG in RREP-Instance does not need to be 712 built. The RPLInstanceID in the RREP-Instance is paired as defined 713 in Section 6.3.3. In case the 'H' bit is set to 0, the address 714 vector received in the RREQ-DIO MUST be included in the RREP-DIO. 715 TargNode increments its current sequence number and uses the 716 incremented result in the Dest SeqNo in the ART option of the RREQ- 717 DIO. The address of the OrigNode MUST be encapsulated in the ART 718 Option and included in this RREP-DIO message. 720 6.3.2. RREP-DIO for Asymmetric Route 722 When a RREQ-DIO arrives at a TargNode with the 'S' bit set to 0, the 723 TargNode MUST build a DODAG in the RREP-Instance rooted at itself in 724 order to discover the downstream route from the OrigNode to the 725 TargNode. The RREP-DIO message MUST be re-transmitted via link-local 726 multicast until the OrigNode is reached or MaxRank is exceeded. 728 The settings of the fields in RREP option and ART option are the same 729 as for the symmetric route, except for the 'S' bit. 731 6.3.3. RPLInstanceID Pairing 733 Since the RPLInstanceID is assigned locally (i.e., there is no 734 coordination between routers in the assignment of RPLInstanceID), the 735 tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely 736 identify a discovered route. The upper layer applications may have 737 different requirements and they can initiate the route discoveries 738 simultaneously. Thus between the same pair of OrigNode and TargNode, 739 there can be multiple AODV-RPL instances. To avoid any mismatch, the 740 RREQ-Instance and the RREP-Instance in the same route discovery MUST 741 be paired somehow, e.g. using the RPLInstanceID. 743 When preparing the RREP-DIO, a TargNode could find the RPLInstanceID 744 to be used for the RREP-Instance is already occupied by another RPL 745 Instance from an earlier route discovery operation which is still 746 active. In other words, it might happen that two distinct OrigNodes 747 need routes to the same TargNode, and they happen to use the same 748 RPLInstanceID for RREQ-Instance. In this case, the occupied 749 RPLInstanceID MUST NOT be used again. Then the second RPLInstanceID 750 MUST be shifted into another integer so that the two RREP-instances 751 can be distinguished. In RREP option, the Shift field indicates the 752 shift to be applied to original RPLInstanceID. When the new 753 InstanceID after shifting exceeds 63, it rolls over starting at 0. 754 For example, the original InstanceID is 60, and shifted by 6, the new 755 InstanceID will be 2. Related operations can be found in 756 Section 6.4. 758 6.4. Receiving and Forwarding Route Reply 760 Upon receiving a RREP-DIO, a router which does not belong to the 761 RREQ-instance goes through the following steps: 763 Step 1: 765 If the 'S' bit is set to 1, the router proceeds to step 2. 767 If the 'S' bit of the RREP-DIO is set to 0, the router MUST check 768 the downward direction of the link (towards the TargNode) over 769 which the RREP-DIO is received. If the downward direction of the 770 link can fulfill the requirements indicated in the constraint 771 option, and the router's rank would not exceed the MaxRank limit, 772 the router joins the DODAG of the RREP-Instance. The router that 773 transmitted the received RREP-DIO is selected as the preferred 774 parent. Afterwards, other RREP-DIO messages can be received. How 775 to maintain the parent set, select the preferred parent, and 776 update the router's rank obeys the core RPL and the OFs defined in 777 ROLL WG. 779 If the constraints are not fulfilled, the router MUST NOT join the 780 DODAG; the router MUST discard the RREQ-DIO, and does not execute 781 the remaining steps in this section. 783 Step 2: 785 The router next checks if one of its addresses is included in the 786 ART Option. If so, this router is the OrigNode of the route 787 discovery. Otherwise, it is an intermediate router. 789 Step 3: 791 If the 'H' bit is set to 1, then the router (OrigNode or 792 intermediate) MUST build a downward route entry. The route entry 793 SHOULD include at least the following items: OrigNode Address, 794 InstanceID, TargNode Address as destination, Next Hop, Lifetime 795 and Sequence Number. For a symmetric route, the next hop in the 796 route entry is the router from which the RREP-DIO is received. 797 For an asymmetric route, the next hop is the preferred parent in 798 the DODAG of RREQ-Instance. The InstanceID in the route entry 799 MUST be the original RPLInstanceID (after subtracting the Shift 800 field value). The source address is learned from the ART Option, 801 and the destination address is learned from the DODAGID. The 802 lifetime is set according to DODAG configuration and can be 803 extended when the route is actually used. The sequence number 804 represents the freshness of the route entry, and is copied from 805 the Dest SeqNo field of the ART option of the RREP-DIO. A route 806 entry with same source and destination address, same InstanceID, 807 but stale sequence number, SHOULD be deleted. 809 If the 'H' bit is set to 0, for an asymmetric route, an 810 intermediate router MUST include the address of the interface 811 receiving the RREP-DIO into the address vector; for a symmetric 812 route, there is nothing to do in this step. 814 Step 4: 816 If the receiver is the OrigNode, it can start transmitting the 817 application data to TargNode along the path as provided in RREP- 818 Instance, and processing for the RREP-DIO is complete. Otherwise, 819 in case of an asymmetric route, the intermediate router transmits 820 the RREP-DIO via link-local multicast. In case of a symmetric 821 route, the RREP-DIO message is unicast to the next hop according 822 to the address vector in the RREP-DIO (H=0) or the local route 823 entry (H=1). The RPLInstanceID in the transmitted RREP-DIO is the 824 same as the value in the received RREP-DIO. The local knowledge 825 for the TargNode's sequence number SHOULD be updated. 827 7. Gratuitous RREP 829 In some cases, an Intermediate router that receives a RREQ-DIO 830 message MAY transmit a "Gratuitous" RREP-DIO message back to OrigNode 831 instead of continuing to multicast the RREQ-DIO towards TargNode. 832 The intermediate router effectively builds the RREP-Instance on 833 behalf of the actual TargNode. The 'G' bit of the RREP option is 834 provided to distinguish the Gratuitous RREP-DIO (G=1) sent by the 835 Intermediate node from the RREP-DIO sent by TargNode (G=0). 837 The gratuitous RREP-DIO can be sent out when an intermediate router R 838 receives a RREQ-DIO for a TargNode T, and R happens to have a more 839 recent (larger destination sequence number) pair of downward and 840 upward routes to T which also fulfill the requirements. 842 In case of source routing, the intermediate router R MUST unicast the 843 received RREQ-DIO to TargNode T including the address vector between 844 the OrigNode O and the router R. Thus T can have a complete upward 845 route address vector from itself to O. Then R MUST send out the 846 gratuitous RREP-DIO including the address vector from R to T. 848 In case of hop-by-hop routing, R MUST unicast the received RREQ-DIO 849 hop-by-hop to T. The routers along the route SHOULD build new route 850 entries with the related RPLInstanceID and DODAGID in the downward 851 direction. Then T MUST unicast the RREP-DIO hop-by-hop to R, and the 852 routers along the route SHOULD build new route entries in the upward 853 direction. Upon receiving the unicast RREP-DIO, R sends the 854 gratuitous RREP-DIO to the OrigNode as defined in Section 6.3. 856 8. Operation of Trickle Timer 858 The trickle timer operation to control RREQ-Instance/RREP-Instance 859 multicast is similar to that in P2P-RPL [RFC6997]. 861 9. IANA Considerations 863 9.1. New Mode of Operation: AODV-RPL 865 IANA is required to assign a new Mode of Operation, named "AODV-RPL" 866 for Point-to-Point(P2P) hop-by-hop routing under the RPL registry. 867 The value of TBD1 is assigned from the "Mode of Operation" space 868 [RFC6550]. 870 +-------------+---------------+---------------+ 871 | Value | Description | Reference | 872 +-------------+---------------+---------------+ 873 | TBD1 (5) | AODV-RPL | This document | 874 +-------------+---------------+---------------+ 876 Figure 6: Mode of Operation 878 9.2. AODV-RPL Options: RREQ, RREP, and Target 880 Three entries are required for new AODV-RPL options "RREQ", "RREP" 881 and "ART" with values of TBD2 (0x0A), TBD3 (0x0B) and TBD4 (0x0C) 882 from the "RPL Control Message Options" space [RFC6550]. 884 +-------------+------------------------+---------------+ 885 | Value | Meaning | Reference | 886 +-------------+------------------------+---------------+ 887 | TBD2 (0x0A) | RREQ Option | This document | 888 +-------------+------------------------+---------------+ 889 | TBD3 (0x0B) | RREP Option | This document | 890 +-------------+------------------------+---------------+ 891 | TBD3 (0x0C) | ART Option | This document | 892 +-------------+------------------------+---------------+ 894 Figure 7: AODV-RPL Options 896 10. Security Considerations 898 The security mechanisms defined in section 10 of [RFC6550] and 899 section 11 of [RFC6997] can also be applied to the control messages 900 defined in this specification. The RREQ-DIO and RREP-DIO both have a 901 secure variant, which provide integrity and replay protection as well 902 as optional confidentiality and delay protection. 904 AODV-RPL can operate in the three security modes defined in 905 [RFC6550]. AODV-RPL messages SHOULD use a security mode at least as 906 strong as the security mode used in RPL. 908 o Unsecured. In this mode, RREQ-DIO and RREP-DIO are used without 909 any security fields as defined in section 6.1 of [RFC6550]. The 910 control messages can be protected by other security mechanisms, 911 e.g. link-layer security. This mode SHOULD NOT be used when RPL 912 is using Preinstalled mode or Authenticated mode (see below). 914 o Preinstalled. In this mode, AODV-RPL uses secure RREQ-DIO and 915 RREP-DIO messages, and a node wishing to join a secured network 916 will have been pre-configured with a shared key. A node can use 917 that key to join the AODV-RPL DODAG as a host or a router. 918 Unsecured messages MUST be dropped. This mode SHOULD NOT be used 919 when RPL is using Authenticated mode. 921 o Authenticated. In this mode, besides the preinstalled shared key, 922 a node MUST obtain a second key from a key authority. The 923 interaction between a node and the key authority is out of scope 924 for this specification. Authenticated mode may be useful, for 925 instance, to protect against a malicious rogue router advertising 926 false information in RREQ-DIO or RREP-DIO to include itself in the 927 discovered route. This mode would also prevent a malicious router 928 from initiating route discovery operations or launching denial-of- 929 service attacks to impair the performance of the LLN. AODV-RPL 930 can use the keys established with the Authenticated mode RPL 931 instance. Once a router or a host has been authenticated in the 932 RPL instance, it can join the AODV-RPL instance without any 933 further authentication. The authentication in AODV-RPL can also 934 be independent to RPL if, before joining the AODV-RPL instance, 935 the node obtains another key from the key authority. 937 11. Future Work 939 There has been some discussion about how to determine the initial 940 state of a link after an AODV-RPL-based network has begun operation. 941 The current draft operates as if the links are symmetric until 942 additional metric information is collected. The means for making 943 link metric information is considered out of scope for AODV-RPL. In 944 the future, RREQ and RREP messages could be equipped with new fields 945 for use in verifying link metrics. In particular, it is possible to 946 identify unidirectional links; an RREQ received across a 947 unidirectional link has to be dropped, since the destination node 948 cannot make use of the received DODAG to route packets back to the 949 source node that originated the route discovery operation. This is 950 roughly the same as considering a unidirectional link to present an 951 infinite cost metric that automatically disqualifies it for use in 952 the reverse direction. 954 12. Contributors 956 Abdur Rashid Sangi 957 Huaiyin Institute of Technology 958 No.89 North Beijing Road, Qinghe District 959 Huaian 223001 960 P.R. China 961 Email: sangi_bahrian@yahoo.com 963 13. References 965 13.1. Normative References 967 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 968 Requirement Levels", BCP 14, RFC 2119, 969 DOI 10.17487/RFC2119, March 1997, 970 . 972 [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- 973 Demand Distance Vector (AODV) Routing", RFC 3561, 974 DOI 10.17487/RFC3561, July 2003, 975 . 977 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 978 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 979 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 980 Low-Power and Lossy Networks", RFC 6550, 981 DOI 10.17487/RFC6550, March 2012, 982 . 984 [RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing 985 Protocol for Low-Power and Lossy Networks (RPL)", 986 RFC 6552, DOI 10.17487/RFC6552, March 2012, 987 . 989 [RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci, 990 "A Mechanism to Measure the Routing Metrics along a Point- 991 to-Point Route in a Low-Power and Lossy Network", 992 RFC 6998, DOI 10.17487/RFC6998, August 2013, 993 . 995 13.2. Informative References 997 [I-D.thubert-roll-asymlink] 998 Thubert, P., "RPL adaptation for asymmetrical links", 999 draft-thubert-roll-asymlink-02 (work in progress), 1000 December 2011. 1002 [Perlman83] 1003 Perlman, R., "Fault-Tolerant Broadcast of Routing 1004 Information", December 1983. 1006 [RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and 1007 D. Barthel, Ed., "Routing Requirements for Urban Low-Power 1008 and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May 1009 2009, . 1011 [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. 1012 Phinney, "Industrial Routing Requirements in Low-Power and 1013 Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October 1014 2009, . 1016 [RFC5826] Brandt, A., Buron, J., and G. Porcu, "Home Automation 1017 Routing Requirements in Low-Power and Lossy Networks", 1018 RFC 5826, DOI 10.17487/RFC5826, April 2010, 1019 . 1021 [RFC5867] Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen, 1022 "Building Automation Routing Requirements in Low-Power and 1023 Lossy Networks", RFC 5867, DOI 10.17487/RFC5867, June 1024 2010, . 1026 [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and 1027 J. Martocci, "Reactive Discovery of Point-to-Point Routes 1028 in Low-Power and Lossy Networks", RFC 6997, 1029 DOI 10.17487/RFC6997, August 2013, 1030 . 1032 Appendix A. Example: ETX/RSSI Values to select S bit 1034 We have tested the combination of "RSSI(downstream)" and "ETX 1035 (upstream)" to determine whether the link is symmetric or asymmetric 1036 at the intermediate nodes. The example of how the ETX and RSSI 1037 values are used in conjuction is explained below: 1039 Source---------->NodeA---------->NodeB------->Destination 1041 Figure 8: Communication link from Source to Destination 1043 +-------------------------+----------------------------------------+ 1044 | RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA | 1045 +-------------------------+----------------------------------------+ 1046 | > -60 | 150 | 1047 | -70 to -60 | 192 | 1048 | -80 to -70 | 226 | 1049 | -90 to -80 | 662 | 1050 | -100 to -90 | 993 | 1051 +-------------------------+----------------------------------------+ 1053 Table 1: Selection of 'S' bit based on Expected ETX value 1055 We tested the operations in this specification by making the 1056 following experiment, using the above parameters. In our experiment, 1057 a communication link is considered as symmetric if the ETX value of 1058 NodeA->NodeB and NodeB->NodeA (See Figure.8) are, say, within 1:3 1059 ratio. This ratio should be taken as a notional metric for deciding 1060 link symmetric/asymmetric nature, and precise definition of the ratio 1061 is beyond the scope of the draft. In general, NodeA can only know 1062 the ETX value in the direction of NodeA -> NodeB but it has no direct 1063 way of knowing the value of ETX from NodeB->NodeA. Using physical 1064 testbed experiments and realistic wireless channel propagation 1065 models, one can determine a relationship between RSSI and ETX 1066 representable as an expression or a mapping table. Such a 1067 relationship in turn can be used to estimate ETX value at nodeA for 1068 link NodeB--->NodeA from the received RSSI from NodeB. Whenever 1069 nodeA determines that the link towards the nodeB is bi-directional 1070 asymmetric then the "S" bit is set to "S=0". Later on, the link from 1071 NodeA to Destination is asymmetric with "S" bit remains to "0". 1073 Appendix B. Changelog 1075 B.1. Changes from version 05 to version 06 1077 o Added Security Considerations based on the security mechanisms 1078 defined in RFC 6550. 1080 o Clarified the nature of improvements due to P2P route discovery 1081 versus bidirectional asymmetric route discovery. 1083 o Editorial improvements and corrections. 1085 B.2. Changes from version 04 to version 05 1087 o Add description for sequence number operations. 1089 o Extend the residence duration L in section 4.1. 1091 o Change AODV-RPL Target option to ART option. 1093 B.3. Changes from version 03 to version 04 1095 o Updated RREP option format. Remove the 'T' bit in RREP option. 1097 o Using the same RPLInstanceID for RREQ and RREP, no need to update 1098 [RFC6550]. 1100 o Explanation of Shift field in RREP. 1102 o Multiple target options handling during transmission. 1104 B.4. Changes from version 02 to version 03 1106 o Include the support for source routing. 1108 o Import some features from [RFC6997], e.g., choice between hop-by- 1109 hop and source routing, the "L" bit which determines the duration 1110 of residence in the DAG, MaxRank, etc. 1112 o Define new target option for AODV-RPL, including the Destination 1113 Sequence Number in it. Move the TargNode address in RREQ option 1114 and the OrigNode address in RREP option into ADOV-RPL Target 1115 Option. 1117 o Support route discovery for multiple targets in one RREQ-DIO. 1119 o New InstanceID pairing mechanism. 1121 Authors' Addresses 1123 Satish Anamalamudi 1124 SRM University-AP 1125 Amaravati Campus 1126 Amaravati, Andhra Pradesh 522 502 1127 India 1129 Email: satishnaidu80@gmail.com 1131 Mingui Zhang 1132 Huawei Technologies 1133 No. 156 Beiqing Rd. Haidian District 1134 Beijing 100095 1135 China 1137 Email: zhangmingui@huawei.com 1139 Charles E. Perkins 1140 Futurewei 1141 2330 Central Expressway 1142 Santa Clara 95050 1143 United States 1145 Email: charliep@computer.org 1147 S.V.R Anand 1148 Indian Institute of Science 1149 Bangalore 560012 1150 India 1152 Email: anand@ece.iisc.ernet.in 1154 Bing Liu 1155 Huawei Technologies 1156 No. 156 Beiqing Rd. Haidian District 1157 Beijing 100095 1158 China 1160 Email: remy.liubing@huawei.com