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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 Informational RFC: RFC 5548 ** Downref: Normative reference to an Informational RFC: RFC 5673 ** Downref: Normative reference to an Informational RFC: RFC 5826 ** Downref: Normative reference to an Informational RFC: RFC 5867 ** Downref: Normative reference to an Experimental RFC: RFC 6997 ** Downref: Normative reference to an Experimental RFC: RFC 6998 Summary: 7 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 Huaiyin Institute of Technology 4 Intended status: Standards Track M. Zhang 5 Expires: September 13, 2017 AR. Sangi 6 Huawei Technologies 7 C. Perkins 8 Futurewei 9 S.V.R.Anand 10 Indian Institute of Science 11 March 12, 2017 13 Asymmetric AODV-P2P-RPL in Low-Power and Lossy Networks (LLNs) 14 draft-ietf-roll-aodv-rpl-01 16 Abstract 18 Route discovery for symmetric and asymmetric Point-to-Point (P2P) 19 traffic flows is a desirable feature in Low power and Lossy Networks 20 (LLNs). For that purpose, this document specifies a reactive P2P 21 route discovery mechanism for hop-by-hop routing (storing mode) based 22 on Ad Hoc On-demand Distance Vector Routing (AODV) based RPL 23 protocol. Two separate Instances are used to construct directional 24 paths in case some of the links between source and target node are 25 asymmetric. 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 September 13, 2017. 44 Copyright Notice 46 Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 5 64 4. AODV-RPL Mode of Operation (MoP) . . . . . . . . . . . . . . 5 65 5. RREQ Message . . . . . . . . . . . . . . . . . . . . . . . . 8 66 6. RREP Message . . . . . . . . . . . . . . . . . . . . . . . . 9 67 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 11 68 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 12 69 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 70 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 12 71 9.2. AODV-RPL Options: RREQ and RREP . . . . . . . . . . . . . 12 72 10. Security Considerations . . . . . . . . . . . . . . . . . . . 12 73 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 74 11.1. Normative References . . . . . . . . . . . . . . . . . . 13 75 11.2. Informative References . . . . . . . . . . . . . . . . . 14 76 Appendix A. ETX/RSSI Values to select S bit . . . . . . . . . . 14 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 79 1. Introduction 81 RPL[RFC6550], the IPv6 distance vector routing protocol for Low-power 82 and Lossy Networks (LLNs), is designed to support multiple traffic 83 flows through a root-based Destination-Oriented Directed Acyclic 84 Graph (DODAG). For traffic flows between routers within the DODAG 85 (i.e., Point-to-Point (P2P) traffic), this means that data packets 86 either have to traverse the root in non-storing mode (source 87 routing), or traverse a common ancestor in storing mode (hop-by-hop 88 routing). Such P2P traffic is thereby likely to flow along sub- 89 optimal routes and may suffer severe traffic congestion near the DAG 90 root [RFC6997], [RFC6998]. 92 To discover optimal paths for P2P traffic flows in RPL, P2P-RPL 93 [RFC6997] specifies a temporary DODAG where the source acts as 94 temporary root. The source initiates "P2P Route Discovery mode (P2P- 95 RDO)" with an address vector for both non-storing mode (H=0) and 96 storing mode (H=1). Subsequently, each intermediate router adds its 97 IP address and multicasts the P2P-RDO message, until the message 98 reaches the target node (TargNode). TargNode sends the "Discovery 99 Reply" option. P2P-RPL is efficient for source routing, but much 100 less efficient for hop-by-hop routing due to the extra address vector 101 overhead. In fact, when the P2P-RDO message is being multicast from 102 the source hop-by-hop, receiving nodes are able to determine a next 103 hop towards the source in symmetric links. When TargNode 104 subsequently replies to the source along the established forward 105 route, receiving nodes can determine the next hop towards TargNode. 106 In other words, it is efficient to use only routing tables for P2P- 107 RDO message instead of "Address vector" for hop-by-hop routes (H=1) 108 in symmetric links. 110 RPL and P2P-RPL both specify the use of a single DODAG in networks of 111 symmetric links. But, application-specific routing requirements that 112 are defined in IETF ROLL Working Group [RFC5548], [RFC5673], 113 [RFC5826] and [RFC5867] may need routing metrics and constraints 114 enabling use of asymmetric bidirectional links. For this purpose, 115 [I-D.thubert-roll-asymlink] describes bidirectional asymmetric links 116 for RPL [RFC6550] with Paired DODAGs, for which the DAG root 117 (DODAGID) is common for two Instances. This can satisfy application- 118 specific routing requirements for bidirectional asymmetric links in 119 base RPL [RFC6550]. P2P-RPL for Paired DODAGs, on the other hand, 120 requires two DAG roots: one for the source and another for the target 121 node due to temporary DODAG formation. For networks composed of 122 bidirectional asymmetric links (see Section 4), AODV-RPL specifies 123 P2P route discovery, utilizing RPL with a new MoP. AODV-RPL makes 124 use of two multicast messages to discover possibly asymmetric routes. 125 AODV-RPL eliminates the need for address vector control overhead, 126 significantly reducing the control packet size which is important for 127 Constrained LLN networks. Both discovered routes meet the 128 application specific metrics and constraints that are defined in the 129 Objective Function for each Instance [RFC6552]. 131 2. Terminology 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 135 "OPTIONAL" in this document are to be interpreted as described in 136 [RFC2119]. Additionally, this document uses the following terms: 138 AODV 139 Ad Hoc On-demand Distance Vector Routing[RFC3561]. 141 AODV-Instance 142 Either the RREQ-Instance or RREP-Instance 144 Bi-directional Asymmetric Link 145 A link that can be used in both directions but with different link 146 characteristics (see [I-D.thubert-roll-asymlink]). 148 DODAG RREQ-Instance (or simply RREQ-Instance) 149 AODV Instance built using the RREQ option; used for control 150 transmission from OrigNode to TargNode, thus enabling data 151 transmission from TargNode to OrigNode. 153 DODAG RREP-Instance (or simply RREP-Instance) 154 AODV Instance built using the RREP option; used for control 155 transmission from TargNode to OrigNode thus enabling data 156 transmission from OrigNode to TargNode. 158 downstream 159 Routing along the direction from OrigNode to TargNode. 161 hop-by-hop routing 162 Routing when each node stores routing information about the next 163 hop. 165 OrigNode 166 The IPv6 router (Originating Node) initiating the AODV-RPL route 167 discovery to obtain a route to TargNode. 169 Paired DODAGs 170 Two DODAGs for a single application. 172 P2P 173 Point-to-Point -- in other words, not constrained to traverse a 174 common ancestor. 176 RREQ message 177 An AODV-RPL MoP DIO message containing the RREQ option. The 178 InstanceID in DIO object of RREQ option MUST be always an odd 179 number. 181 RREP message 182 An AODV-RPL MoP DIO message containing the RREP option. The 183 InstanceID in DIO object of RREP option MUST be always an even 184 number (InstanceID of RREQ-Instance+1). 186 source routing 187 The mechanism by which the source supplies the complete route 188 towards the target node along with each data packet. [RFC6997]. 190 TargNode 191 The IPv6 router (Target Node) for which OrigNode requires a route 192 and initiates Route Discovery within the LLN network. 194 upstream 195 Routing along the direction from TargNode to OrigNode. 197 3. Overview of AODV-RPL 199 With AODV-RPL, routes from OrigNode to TargNode within the LLN 200 network established are "on-demand". In other words, the route 201 discovery mechanism in AODV-RPL is invoked reactively when OrigNode 202 has data for delivery to the TargNode but existing routes do not 203 satisfy the application's requirements. The routes discovered by 204 AODV-RPL are point-to-point; in other words the routes are not 205 constrained to traverse a common ancestor. Unlike base RPL [RFC6550] 206 and P2P-RPL [RFC6997], AODV-RPL can enable asymmetric communication 207 paths in networks with bidirectional asymmetric links. For this 208 purpose, AODV-RPL enables discovery of two routes: namely, one from 209 OrigNode to TargNode, and another from TargNode to OrigNode. When 210 possible, AODV-RPL also enables symmetric routing along Paired DODAGs 211 (see Section 4). 213 4. AODV-RPL Mode of Operation (MoP) 215 In AODV-RPL, route discovery is initiated by forming a temporary DAG 216 rooted at the OrigNode. Paired DODAGs (Instances) are constructed 217 according to a new AODV-RPL Mode of Operation (MoP) during route 218 formation between the OrigNode and TargNode. The RREQ-Instance is 219 formed by route control messages from OrigNode to TargNode whereas 220 the RREP-Instance is formed by route control messages from TargNode 221 to OrigNode (as shown in Figure 2). Intermediate routers join the 222 Paired DODAGs based on the rank as calculated from the DIO message. 223 Henceforth in this document, the RREQ-Instance message means the 224 AODV-RPL DIO message from OrigNode to TargNode, containing the RREQ 225 option. Similarly, the RREP-Instance means the AODV-RPL DIO message 226 from TargNode to OrigNode, containing the RREP option. Subsequently, 227 the RREQ-Instance is used for data transmission from TargNode to 228 OrigNode and RREP-Instance is used for Data transmission from 229 OrigNode to TargNode. 231 The AODV-RPL Mode of Operation defines a new bit, the Symmetric bit 232 ('S'), which is added to the base DIO message as illustrated in 233 Figure 1. OrigNode sets the the 'S' bit to 1 in the RREQ-Instance 234 message when initiating route discovery. 236 0 1 2 3 237 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 1 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 239 | RPLInstanceID |Version Number | Rank | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 |G|0| MOP | Prf | DTSN |S| Flags | Reserved | 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | | 244 + + 245 | | 246 + DODAGID + 247 | | 248 + + 249 | | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | Option(s)... 253 Figure 1: DIO modification to support asymmetric route discovery 255 A device originating a AODV-RPL message supplies the following 256 information in the DIO header of the message: 258 'S' bit 260 Symmetric bit in the DIO base object 262 MOP 264 MOP operation in the DIO object MUST be set to "5(TBD1)" for AODV- 265 RPL DIO messages 267 RPLInstanceID 269 RPLInstanceID in the DIO object MUST be the InstanceID of AODV- 270 Instance(RREQ-Instance). The InstanceID for RREQ-Instance MUST be 271 always an odd number. 273 DODAGID 275 For RREQ-Instance : 277 DODAGID in the DIO object MUST be the IPv6 address of the device 278 that initiates the RREQ-Instance. 280 For RREP-Instance 282 DODAGID in the DIO object MUST be the IPv6 address of the device 283 that initiates the RREP-Instance. 285 Rank 287 Rank in the DIO object MUST be the the rank of the AODV-Instance 288 (RREQ-Instance). 290 Metric Container Options 292 AODV-Instance(RREQ-Instance) messages MAY carry one or more Metric 293 Container options to indicate the relevant routing metrics. 295 The 'S' bit is set to mean that the route is symmetric. If the RREQ- 296 Instance arrives over an interface that is known to be symmetric, and 297 the 'S' bit is set to 1, then it remains set at 1, as illustrated in 298 Figure 2. 300 In this figure: 301 S := OrigNode; R := Intermediate nodes; D := TargNode 303 R---------R---------R---------R 304 |<--S=1-->|<--S=1-->|<--S=1-->| 305 | | | | 306 <--S=1--> | | <--S=1--> 307 | | | | 308 | | | | 309 S---------R---------R---------R---------R---------R---------D 310 <--S=1-->| | | |<--S=1-->|<--S=1-->| 311 | | | | | | 312 | | | | | | 313 R---------R---------R---------R---------R---------R 315 >---- RREQ-Instance (Control: S-->D; Data: D-->S) -------> 316 <---- RREP-Instance (Control: D-->S; Data: S-->D) -------< 318 Figure 2: AODV-RPL with Symmetric Paired Instances 320 If the RREQ-Instance arrives over an interface that is not known to 321 be symmetric, or is known to be asymmetric, the 'S' bit is set to be 322 0. Moreover, if the 'S' bit arrives already set to be '0', it is set 323 to be '0' on retransmission (Figure 3). Based on the 'S' bit 324 received in RREQ-Instance, the TargNode decides whether or not the 325 route is symmetric before transmitting the RREP-Instance message 326 upstream towards the OrigNode. The metric used to determine symmetry 327 (i.e., set the "S" bit to be "1" (Symmetric) or "0" (asymmetric)) is 328 implementation specific. We used ETX/RSSI to verify the feasibility 329 of the protocol operations in this draft, as discussed in Appendix A. 331 R---------R--------R--------R 332 | --S=1-->|--S=1-->|--S=0-->| 333 | | | | 334 --S=1--> | | --S=0--> 335 | | | | 336 --S=1-->| | | | 337 S--------R---------R--------R--------R--------R---------D 338 <--S=0--| | | |--S=0-->| --S=0-->| 339 | | | | | | 340 <--S=0-- | | | | <--S=0-- 341 | | | | | | 342 | <--S=0--|<--S=0--|<--S=0--|<--S=0--|<--S=0-- | 343 R---------R--------R--------R--------R---------R 345 >---- RREQ-Instance (Control: S-->D; Data: D-->S) -------> 346 <---- RREP-Instance (Control: D-->S; Data: S-->D) -------< 348 Figure 3: AODV-RPL with Asymmetric Paired Instances 350 5. RREQ Message 352 0 1 2 3 353 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 1 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 | Type | Orig SeqNo | Dest SeqNo | 356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 357 | | 358 | TargNode IPv6 Address | 359 | | 360 | | 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 Figure 4: DIO RREQ option format for AODV-RPL MoP 365 OrigNode supplies the following information in the RREQ option of the 366 RREQ-Instance message: 368 Type 370 The type of the RREQ option(see Section 9.2). 372 Orig SeqNo 374 Sequence Number of OrigNode. 376 Dest SeqNo 377 If nonzero, the last known Sequence Number for TargNode for which 378 a route is desired. 380 TargNode IPv6 Address 382 IPv6 address of the TargNode that receives RREQ-Instance message. 383 This address MUST be in the RREQ option (see Figure 4) of AODV- 384 RPL. 386 In order to establish the upstream route from TargNode to OrigNode, 387 OrigNode multicasts the RREQ-Instance message (see Figure 4) to its 388 one-hop neighbours. In order to enable intermediate nodes R_i to 389 associate a future RREP message to an incoming RREQ message, the 390 InstanceID of RREQ-Instance MUST assign an odd number. 392 Each intermediate node R_i computes the rank for RREQ-Instance and 393 creates a routing table entry for the upstream route towards the 394 source if the routing metrics/constraints are satisfied. For this 395 purpose R_i must use the asymmetric link metric measured in the 396 upstream direction, from R_i to its upstream neighbor that 397 multicasted the RREQ-Instance message. 399 When an intermediate node R_i receives a RREQ message in storing 400 mode, it MUST store the OrigNode's InstanceID (RREQ-Instance) along 401 with the other routing information needed to establish the route back 402 to the OrigNode. This will enable R_i to determine that a future 403 RREP message (containing a paired InstanceID for the TargNode) must 404 be transmitted back to the OrigNode's IP address. 406 If the paths to and from TargNode are not known, the intermediate 407 node multicasts the RREQ-Instance message with updated rank to its 408 next-hop neighbors until the message reaches TargNode (Figure 2). 409 Based on the 'S' bit in the received RREQ message, the TargNode will 410 decide whether to unicast or multicast the RREP message back to 411 OrigNode. 413 As described in Section 7, in certain circumstances R_i MAY unicast a 414 Gratuitous RREP towards OrigNode, thereby helping to minimize 415 multicast overhead during the Route Discovery process. 417 6. RREP Message 419 The TargNode supplies the following information in the RREP message: 421 0 1 2 3 422 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 1 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 424 | Type | Dest SeqNo | Prefix Sz |T|G| Rsvd | 425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 426 | | 427 | TargNode IPv6 Address (when present) | 428 | | 429 | | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 Figure 5: DIO RREP option format for AODV-RPL MoP 434 Type 436 The type of the RREP option (see Section 9.2) 438 Dest SeqNo 440 The Sequence Number for the TargNode for which a route is 441 established. 443 Prefix Sz 445 The size of the prefix which the route to the TargNode is 446 available. This allows routing to other nodes on the same subnet 447 as the TargNode. 449 'T' bit 451 'T' is set to true to indicate that the TargNode IPv6 Address 452 field is present 454 'G' bit 456 (see Section 7) 458 TargNode IPv6 Address (when present) 460 IPv6 address of the TargNode that receives RREP-Instance message. 462 In order to reduce the need for the TargNode IPv6 Address to be 463 included with the RREP message, the InstanceID of the RREP-Instance 464 is paired, whenever possible, with the InstanceID from the RREQ 465 message, which is always an odd number. The pairing is accomplished 466 by adding one to the InstanceID from the RREQ message and using that, 467 whenever possible, as the InstanceID for the RREP message. If this 468 is not possible (for instance because the incremented InstanceID is 469 still a valid InstanceID for another route to the TargNode from an 470 earlier Route Discovery operation), then the 'T' bit is set and an 471 alternative even number is chosen for the InstanceID of RREP from 472 TargNode. 474 The OrigNode IP address for RREQ-Instance is available as the DODAGID 475 in the DIO base message (see Figure 1). When TargNode receives a 476 RREQ message with the 'S' bit set to 1 (as illustrated in Figure 2), 477 it unicasts the RREP message with the 'S' bit set to 1. In this 478 case, route control messages and application data between OrigNode 479 and TargNode for both RREQ-Instance and RREP-Instance are transmitted 480 along symmetric links. When 'T' bit set is to "1" in the RREP- 481 Instance, then TargNode IPv6 Address is transmitted in RREP option. 482 Otherwise, the TargNode IPv6 Address is elided in RREP option. 484 When (as illustrated in Figure 3) the TargNode receives RREQ message 485 with the 'S' bit set to 0, it also multicasts the RREP message with 486 the 'S' bit set to 0. Intermediate nodes create a routing table 487 entry for the path towards the TargNode while processing the RREP 488 message to OrigNode. Once OrigNode receives the RREP message, it 489 starts transmitting the application data to TargNode along the path 490 as discovered through RREP messages. Similarly, application data 491 from TargNode to OrigNode is transmitted through the path that is 492 discovered from RREQ message. 494 7. Gratuitous RREP 496 Under some circumstances, an Intermediate Node that receives a RREQ 497 message MAY transmit a "Gratuitous" RREP message back to OrigNode 498 instead of continuing to multicast the RREQ message towards TargNode. 499 For these circumstances, the 'G' bit of the RREP option is provided 500 to distinguish the Gratuitous RREP sent by the Intermediate node from 501 the RREP sent by TargNode. 503 When an Intermediate node R receives a RREQ message and has recent 504 information about the cost of an upstream route from TargNode to R, 505 then R MAY unicast the Gratuitous RREP (GRREP) message to OrigNode. 506 R determines whether its information is sufficiently recent by 507 comparing the value it has stored for the Sequence Number of TargNode 508 against the DestSeqno in the incoming RREQ message. R also must have 509 information about the metric information of the upstream route from 510 TargNode. The GRREP message MUST have PrefixSz == 0 and the 'G' bit 511 set to 1. R SHOULD also unicast the RREQ message to TargNode, to 512 make sure that TargNode will have a route to OrigNode. 514 8. Operation of Trickle Timer 516 The trickle timer operation to control RREQ-Instance/RREP-Instance 517 multicast is similar to that in P2P-RPL [RFC6997]. 519 9. IANA Considerations 521 9.1. New Mode of Operation: AODV-RPL 523 IANA is required to assign a new Mode of Operation, named "AODV-RPL" 524 for Point-to-Point(P2P) hop-by-hop routing under the RPL registry. 525 The value of TBD1 is assigned from the "Mode of Operation" space 526 [RFC6550]. 528 +-------------+---------------+---------------+ 529 | Value | Description | Reference | 530 +-------------+---------------+---------------+ 531 | TBD1 (5) | AODV-RPL | This document | 532 +-------------+---------------+---------------+ 534 Figure 6: Mode of Operation 536 9.2. AODV-RPL Options: RREQ and RREP 538 Two entries are required for new AODV-RPL options "RREQ-Instance" and 539 "RREQ-Instance", with values of TBD2 (0x0A) and TBD3 (0x0B) from the 540 "RPL Control Message Options" space [RFC6550]. 542 +-------------+---------------------+---------------+ 543 | Value | Meaning | Reference | 544 +-------------+---------------------+---------------+ 545 | TBD2 (0x0A) | RREQ Option | This document | 546 +-------------+---------------------+---------------+ 547 | TBD3 (0x0B) | RREP Option | This document | 548 +-------------+---------------------+---------------+ 550 Figure 7: AODV-RPL Options 552 10. Security Considerations 554 This document does not introduce additional security issues compared 555 to base RPL. For general RPL security considerations, see [RFC6550]. 557 11. References 558 11.1. Normative References 560 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 561 Requirement Levels", BCP 14, RFC 2119, 562 DOI 10.17487/RFC2119, March 1997, 563 . 565 [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- 566 Demand Distance Vector (AODV) Routing", RFC 3561, 567 DOI 10.17487/RFC3561, July 2003, 568 . 570 [RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and 571 D. Barthel, Ed., "Routing Requirements for Urban Low-Power 572 and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May 573 2009, . 575 [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. 576 Phinney, "Industrial Routing Requirements in Low-Power and 577 Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October 578 2009, . 580 [RFC5826] Brandt, A., Buron, J., and G. Porcu, "Home Automation 581 Routing Requirements in Low-Power and Lossy Networks", 582 RFC 5826, DOI 10.17487/RFC5826, April 2010, 583 . 585 [RFC5867] Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen, 586 "Building Automation Routing Requirements in Low-Power and 587 Lossy Networks", RFC 5867, DOI 10.17487/RFC5867, June 588 2010, . 590 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 591 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 592 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 593 Low-Power and Lossy Networks", RFC 6550, 594 DOI 10.17487/RFC6550, March 2012, 595 . 597 [RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing 598 Protocol for Low-Power and Lossy Networks (RPL)", 599 RFC 6552, DOI 10.17487/RFC6552, March 2012, 600 . 602 [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and 603 J. Martocci, "Reactive Discovery of Point-to-Point Routes 604 in Low-Power and Lossy Networks", RFC 6997, 605 DOI 10.17487/RFC6997, August 2013, 606 . 608 [RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci, 609 "A Mechanism to Measure the Routing Metrics along a Point- 610 to-Point Route in a Low-Power and Lossy Network", 611 RFC 6998, DOI 10.17487/RFC6998, August 2013, 612 . 614 11.2. Informative References 616 [I-D.thubert-roll-asymlink] 617 Thubert, P., "RPL adaptation for asymmetrical links", 618 draft-thubert-roll-asymlink-02 (work in progress), 619 December 2011. 621 Appendix A. ETX/RSSI Values to select S bit 623 We have tested the combination of "RSSI(downstream)" and "ETX 624 (upstream)" to decide whether the link is symmetric or asymmetric at 625 the intermediate nodes. The example of how the ETX and RSSI values 626 are used in conjuction is explained below: 628 Source---------->NodeA---------->NodeB------->Destination 630 Figure 8: Communication link from Source to Destination 632 +-------------------------+----------------------------------------+ 633 | RSSI at NodeA for NodeB | Expected ETX at NodeA for nodeB->nodeA | 634 +-------------------------+----------------------------------------+ 635 | > -15 | 150 | 636 | -25 to -15 | 192 | 637 | -35 to -25 | 226 | 638 | -45 to -35 | 662 | 639 | -55 to -45 | 993 | 640 +-------------------------+----------------------------------------+ 642 Table 1: Selection of 'S' bit based on Expected ETX value 644 We tested the operations in this specification by making the 645 following experiment, using the above parameters. In our experiment, 646 a communication link is considered as symmetric if the ETX value of 647 NodeA->NodeB and NodeB->NodeA (See Figure.8) are, say, within 1:3 648 ratio. This ratio should be taken as a notional metric for deciding 649 link symmetric/asymmetric nature, and precise definition of the ratio 650 is beyond the scope of the draft. In general, NodeA can only know 651 the ETX value in the direction of NodeA -> NodeB but it has no direct 652 way of knowing the value of ETX from NodeB->NodeA. Using physical 653 testbed experiments and realistic wireless channel propagation 654 models, one can come up with a relationship between RSSI and ETX that 655 can be represented as an expression or a mapping table. Such a 656 relationship in turn can be used to estimate ETX value at nodeA for 657 link NodeB--->NodeA from the received RSSI from NodeB. Whenever 658 nodeA determines that the link towards the nodeB is bi-directional 659 asymmetric then the "S" bit is set to "S=0". Later on, link from 660 NodeA to Destination is asymmetric with "S" bit remains to "0". 662 Authors' Addresses 664 Satish Anamalamudi 665 Huaiyin Institute of Technology 666 No.89 North Beijing Road, Qinghe District 667 Huaian 223001 668 China 670 Email: satishnaidu80@gmail.com 672 Mingui Zhang 673 Huawei Technologies 674 No. 156 Beiqing Rd. Haidian District 675 Beijing 100095 676 China 678 Email: zhangmingui@huawei.com 680 Abdur Rashid Sangi 681 Huawei Technologies 682 No.156 Beiqing Rd. Haidian District 683 Beijing 100095 684 P.R. China 686 Email: sangi_bahrian@yahoo.com 688 Charles E. Perkins 689 Futurewei 690 2330 Central Expressway 691 Santa Clara 95050 692 Unites States 694 Email: charliep@computer.org 695 S.V.R Anand 696 Indian Institute of Science 697 Bangalore 560012 698 India 700 Email: anand@ece.iisc.ernet.in