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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-38) exists of draft-ietf-lisp-rfc6830bis-36 == Outdated reference: A later version (-63) exists of draft-templin-6man-aero-38 == Outdated reference: A later version (-74) exists of draft-templin-6man-omni-52 == Outdated reference: A later version (-15) exists of draft-thubert-6man-ipv6-over-wireless-11 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPWAVE Working Group J. Jeong, Ed. 3 Internet-Draft Sungkyunkwan University 4 Intended status: Informational 22 February 2022 5 Expires: 26 August 2022 7 IPv6 Wireless Access in Vehicular Environments (IPWAVE): Problem 8 Statement and Use Cases 9 draft-ietf-ipwave-vehicular-networking-27 11 Abstract 13 This document discusses the problem statement and use cases of 14 IPv6-based vehicular networking for Intelligent Transportation 15 Systems (ITS). The main scenarios of vehicular communications are 16 vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and 17 vehicle-to-everything (V2X) communications. First, this document 18 explains use cases using V2V, V2I, and V2X networking. Next, for 19 IPv6-based vehicular networks, it makes a gap analysis of current 20 IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management, 21 and Security & Privacy), and then enumerates requirements for the 22 extensions of those IPv6 protocols for IPv6-based vehicular 23 networking. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on 26 August 2022. 42 Copyright Notice 44 Copyright (c) 2022 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 49 license-info) in effect on the date of publication of this document. 50 Please review these documents carefully, as they describe your rights 51 and restrictions with respect to this document. Code Components 52 extracted from this document must include Revised BSD License text as 53 described in Section 4.e of the Trust Legal Provisions and are 54 provided without warranty as described in the Revised BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7 61 3.1. V2V . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 62 3.2. V2I . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 63 3.3. V2X . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 64 4. Vehicular Networks . . . . . . . . . . . . . . . . . . . . . 12 65 4.1. Vehicular Network Architecture . . . . . . . . . . . . . 13 66 4.2. V2I-based Internetworking . . . . . . . . . . . . . . . . 15 67 4.3. V2V-based Internetworking . . . . . . . . . . . . . . . . 18 68 5. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 22 69 5.1. Neighbor Discovery . . . . . . . . . . . . . . . . . . . 23 70 5.1.1. Link Model . . . . . . . . . . . . . . . . . . . . . 25 71 5.1.2. MAC Address Pseudonym . . . . . . . . . . . . . . . . 27 72 5.1.3. Routing . . . . . . . . . . . . . . . . . . . . . . . 27 73 5.2. Mobility Management . . . . . . . . . . . . . . . . . . . 29 74 6. Security Considerations . . . . . . . . . . . . . . . . . . . 31 75 6.1. Security Threats in Neighbor Discovery . . . . . . . . . 32 76 6.2. Security Threats in Mobility Management . . . . . . . . . 33 77 6.3. Other Threats . . . . . . . . . . . . . . . . . . . . . . 33 78 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 79 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 80 8.1. Normative References . . . . . . . . . . . . . . . . . . 35 81 8.2. Informative References . . . . . . . . . . . . . . . . . 40 82 Appendix A. Support of Multiple Radio Technologies for V2V . . . 45 83 Appendix B. Support of Multihop V2X Networking . . . . . . . . . 45 84 Appendix C. Support of Mobility Management for V2I . . . . . . . 47 85 Appendix D. Acknowledgments . . . . . . . . . . . . . . . . . . 48 86 Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 49 87 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 50 89 1. Introduction 91 Vehicular networking studies have mainly focused on improving safety 92 and efficiency, and also enabling entertainment in vehicular 93 networks. The Federal Communications Commission (FCC) in the US 94 allocated wireless channels for Dedicated Short-Range Communications 95 (DSRC) [DSRC] in the Intelligent Transportation Systems (ITS) with 96 the frequency band of 5.850 - 5.925 GHz (i.e., 5.9 GHz band). DSRC- 97 based wireless communications can support vehicle-to-vehicle (V2V), 98 vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X) 99 networking. The European Union (EU) allocated radio spectrum for 100 safety-related and non-safety-related applications of ITS with the 101 frequency band of 5.875 - 5.905 GHz, as part of the Commission 102 Decision 2008/671/EC [EU-2008-671-EC]. 104 For direct inter-vehicular wireless connectivity, IEEE has amended 105 standard 802.11 (commonly known as Wi-Fi) to enable safe driving 106 services based on DSRC for the Wireless Access in Vehicular 107 Environments (WAVE) system. The Physical Layer (L1) and Data Link 108 Layer (L2) issues are addressed in IEEE 802.11p [IEEE-802.11p] for 109 the PHY and MAC of the DSRC, while IEEE 1609.2 [WAVE-1609.2] covers 110 security aspects, IEEE 1609.3 [WAVE-1609.3] defines related services 111 at network and transport layers, and IEEE 1609.4 [WAVE-1609.4] 112 specifies the multi-channel operation. IEEE 802.11p was first a 113 separate amendment, but was later rolled into the base 802.11 114 standard (IEEE 802.11-2012) as IEEE 802.11 Outside the Context of a 115 Basic Service Set (OCB) in 2012 [IEEE-802.11-OCB]. 117 3GPP has standardized Cellular Vehicle-to-Everything (C-V2X) 118 communications to support V2X in LTE mobile networks (called LTE V2X) 119 and V2X in 5G mobile networks (called 5G V2X) [TS-23.285-3GPP] 120 [TR-22.886-3GPP][TS-23.287-3GPP]. With C-V2X, vehicles can directly 121 communicate with each other without relay nodes (e.g., eNodeB in LTE 122 and gNodeB in 5G). 124 Along with these WAVE standards and C-V2X standards, regardless of a 125 wireless access technology under the IP stack of a vehicle, vehicular 126 networks can operate IP mobility with IPv6 [RFC8200] and Mobile IPv6 127 protocols (e.g., Mobile IPv6 (MIPv6) [RFC6275], Proxy MIPv6 (PMIPv6) 128 [RFC5213], Distributed Mobility Management (DMM) [RFC7333], Network 129 Mobility (NEMO) [RFC3963], Locator/ID Separation Protocol (LISP) 130 [I-D.ietf-lisp-rfc6830bis], and Automatic Extended Route Optimization 131 (AERO) [I-D.templin-6man-aero]). In addition, ISO has approved a 132 standard specifying the IPv6 network protocols and services to be 133 used for Communications Access for Land Mobiles (CALM) 134 [ISO-ITS-IPv6][ISO-ITS-IPv6-AMD1]. 136 This document describes use cases and a problem statement about 137 IPv6-based vehicular networking for ITS, which is named IPv6 Wireless 138 Access in Vehicular Environments (IPWAVE). First, it introduces the 139 use cases for using V2V, V2I, and V2X networking in ITS. Next, for 140 IPv6-based vehicular networks, it makes a gap analysis of current 141 IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management, 142 and Security & Privacy), and then enumerates requirements for the 143 extensions of those IPv6 protocols, which are tailored to IPv6-based 144 vehicular networking. Thus, this document is intended to motivate 145 development of key protocols for IPWAVE. 147 2. Terminology 149 This document uses the terminology described in [RFC8691]. In 150 addition, the following terms are defined below: 152 * Class-Based Safety Plan: A vehicle can make a safety plan by 153 classifying the surrounding vehicles into different groups for 154 safety purposes according to the geometrical relationship among 155 them. The vehicle groups can be classified as Line-of-Sight 156 Unsafe, Non-Line-of-Sight Unsafe, and Safe groups [CASD]. 158 * Context-Awareness: A vehicle can be aware of spatial-temporal 159 mobility information (e.g., position, speed, direction, and 160 acceleration/deceleration) of surrounding vehicles for both safety 161 and non-safety uses through sensing or communication [CASD]. 163 * DMM: "Distributed Mobility Management" [RFC7333][RFC7429]. 165 * Edge Computing (EC): It is the local computing near an access 166 network (i.e., edge network) for the sake of vehicles and 167 pedestrians. 169 * Edge Computing Device (ECD): It is a computing device (or server) 170 for edge computing for the sake of vehicles and pedestrians. 172 * Edge Network (EN): It is an access network that has an IP-RSU for 173 wireless communication with other vehicles having an IP-OBU and 174 wired communication with other network devices (e.g., routers, IP- 175 RSUs, ECDs, servers, and MA). It may have a Global Positioning 176 System (GPS) radio receiver for its position recognition and the 177 localization service for the sake of vehicles. 179 * IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a 180 computer situated in a vehicle (e.g., car, bicycle, autobike, 181 motor cycle, and a similar one) and a device (e.g., smartphone and 182 Internet-of-Things (IoT) device). It has at least one IP 183 interface that runs in IEEE 802.11-OCB and has an "OBU" 184 transceiver. Also, it may have an IP interface that runs in 185 Cellular V2X (C-V2X) [TS-23.285-3GPP] 186 [TR-22.886-3GPP][TS-23.287-3GPP]. It can play a role of a router 187 connecting multiple computers (or in-vehicle devices) inside a 188 vehicle. See the definition of the term "OBU" in [RFC8691]. 190 * IP-RSU: "IP Roadside Unit": An IP-RSU is situated along the road. 191 It has at least two distinct IP-enabled interfaces. The wireless 192 PHY/MAC layer of at least one of its IP-enabled interfaces is 193 configured to operate in 802.11-OCB mode. An IP-RSU communicates 194 with the IP-OBU over an 802.11 wireless link operating in OCB 195 mode. Also, it may have an IP interface that runs in C-V2X along 196 with an "RSU" transceiver. An IP-RSU is similar to an Access 197 Network Router (ANR), defined in [RFC3753], and a Wireless 198 Termination Point (WTP), defined in [RFC5415]. See the definition 199 of the term "RSU" in [RFC8691]. 201 * LiDAR: "Light Detection and Ranging". It is a scanning device to 202 measure a distance to an object by emitting pulsed laser light and 203 measuring the reflected pulsed light. 205 * Mobility Anchor (MA): A node that maintains IPv6 addresses and 206 mobility information of vehicles in a road network to support 207 their IPv6 address autoconfiguration and mobility management with 208 a binding table. An MA has End-to-End (E2E) connections (e.g., 209 tunnels) with IP-RSUs under its control for the address 210 autoconfiguration and mobility management of the vehicles. This 211 MA is similar to a Local Mobility Anchor (LMA) in PMIPv6 [RFC5213] 212 for network-based mobility management. 214 * OCB: "Outside the Context of a Basic Service Set - BSS". It is a 215 mode of operation in which a Station (STA) is not a member of a 216 BSS and does not utilize IEEE Std 802.11 authentication, 217 association, or data confidentiality [IEEE-802.11-OCB]. 219 * 802.11-OCB: It refers to the mode specified in IEEE Std 220 802.11-2016 [IEEE-802.11-OCB] when the MIB attribute 221 dot11OCBActivited is 'true'. 223 * Platooning: Moving vehicles can be grouped together to reduce air- 224 resistance for energy efficiency and reduce the number of drivers 225 such that only the leading vehicle has a driver, and the other 226 vehicles are autonomous vehicles without a driver and closely 227 follow the leading vehicle [Truck-Platooning]. 229 * Traffic Control Center (TCC): A system that manages road 230 infrastructure nodes (e.g., IP-RSUs, MAs, traffic signals, and 231 loop detectors), and also maintains vehicular traffic statistics 232 (e.g., average vehicle speed and vehicle inter-arrival time per 233 road segment) and vehicle information (e.g., a vehicle's 234 identifier, position, direction, speed, and trajectory as a 235 navigation path). TCC is part of a vehicular cloud for vehicular 236 networks. 238 * Vehicle: A Vehicle in this document is a node that has an IP-OBU 239 for wireless communication with other vehicles and IP-RSUs. It 240 has a GPS radio navigation receiver for efficient navigation. Any 241 device having an IP-OBU and a GPS receiver (e.g., smartphone and 242 tablet PC) can be regarded as a vehicle in this document. 244 * Vehicular Ad Hoc Network (VANET): A network that consists of 245 vehicles interconnected by wireless communication. Two vehicles 246 in a VANET can communicate with each other using other vehicles as 247 relays even where they are out of one-hop wireless communication 248 range. 250 * Vehicular Cloud: A cloud infrastructure for vehicular networks, 251 having compute nodes, storage nodes, and network forwarding 252 elements (e.g., switch and router). 254 * V2D: "Vehicle to Device". It is the wireless communication 255 between a vehicle and a device (e.g., smartphone and IoT device). 257 * V2I2D: "Vehicle to Infrastructure to Device". It is the wireless 258 communication between a vehicle and a device (e.g., smartphone and 259 IoT device) via an infrastructure node (e.g., IP-RSU). 261 * V2I2V: "Vehicle to Infrastructure to Vehicle". It is the wireless 262 communication between a vehicle and another vehicle via an 263 infrastructure node (e.g., IP-RSU). 265 * V2I2X: "Vehicle to Infrastructure to Everything". It is the 266 wireless communication between a vehicle and another entity (e.g., 267 vehicle, smartphone, and IoT device) via an infrastructure node 268 (e.g., IP-RSU). 270 * V2X: "Vehicle to Everything". It is the wireless communication 271 between a vehicle and any entity (e.g., vehicle, infrastructure 272 node, smartphone, and IoT device), including V2V, V2I, and V2D. 274 * VIP: "Vehicular Internet Protocol". It is an IPv6 extension for 275 vehicular networks including V2V, V2I, and V2X. 277 * VMM: "Vehicular Mobility Management". It is an IPv6-based 278 mobility management for vehicular networks. 280 * VND: "Vehicular Neighbor Discovery". It is an IPv6 ND extension 281 for vehicular networks. 283 * VSP: "Vehicular Security and Privacy". It is an IPv6-based 284 security and privacy for vehicular networks. 286 * WAVE: "Wireless Access in Vehicular Environments" [WAVE-1609.0]. 288 3. Use Cases 290 This section explains use cases of V2V, V2I, and V2X networking. The 291 use cases of the V2X networking exclude the ones of the V2V and V2I 292 networking, but include Vehicle-to-Pedestrian (V2P) and Vehicle-to- 293 Device (V2D). 295 IP is widely used among popular end-user devices (e.g., smartphone 296 and tablet) in the Internet. Applications (e.g., navigator 297 application) for those devices can be extended such that the V2V use 298 cases in this section can work with IPv6 as a network layer protocol 299 and IEEE 802.11-OCB as a link layer protocol. In addition, IPv6 300 security needs to be extended to support those V2V use cases in a 301 safe, secure, privacy-preserving way. 303 The use cases presented in this section serve as the description and 304 motivation for the need to extend IPv6 and its protocols to 305 facilitate "Vehicular IPv6". Section 5 summarizes the overall 306 problem statement and IPv6 requirements. Note that the adjective 307 "Vehicular" in this document is used to represent extensions of 308 existing protocols such as IPv6 Neighbor Discovery, IPv6 Mobility 309 Management (e.g., PMIPv6 [RFC5213] and DMM [RFC7429]), and IPv6 310 Security and Privacy Mechanisms rather than new "vehicular-specific" 311 functions. 313 3.1. V2V 315 The use cases of V2V networking discussed in this section include 317 * Context-aware navigation for safe driving and collision avoidance; 319 * Cooperative adaptive cruise control in a roadway; 321 * Platooning in a highway; 323 * Cooperative environment sensing; 325 * Collision avoidance service of end systems of Urban Air Mobility 326 (UAM) [I-D.templin-ipwave-uam-its]. 328 These five techniques will be important elements for autonomous 329 vehicles, which may be either terrestrial vehicles or UAM end 330 systems. 332 Context-Aware Safety Driving (CASD) navigator [CASD] can help drivers 333 to drive safely by alerting them to dangerous obstacles and 334 situations. That is, a CASD navigator displays obstacles or 335 neighboring vehicles relevant to possible collisions in real-time 336 through V2V networking. CASD provides vehicles with a class-based 337 automatic safety action plan, which considers three situations, 338 namely, the Line-of-Sight unsafe, Non-Line-of-Sight unsafe, and safe 339 situations. This action plan can be put into action among multiple 340 vehicles using V2V networking. 342 Cooperative Adaptive Cruise Control (CACC) [CA-Cruise-Control] helps 343 individual vehicles to adapt their speed autonomously through V2V 344 communication among vehicles according to the mobility of their 345 predecessor and successor vehicles in an urban roadway or a highway. 346 Thus, CACC can help adjacent vehicles to efficiently adjust their 347 speed in an interactive way through V2V networking in order to avoid 348 a collision. 350 Platooning [Truck-Platooning] allows a series (or group) of vehicles 351 (e.g., trucks) to follow each other very closely. Trucks can use V2V 352 communication in addition to forward sensors in order to maintain 353 constant clearance between two consecutive vehicles at very short 354 gaps (from 3 meters to 10 meters). Platooning can maximize the 355 throughput of vehicular traffic in a highway and reduce the gas 356 consumption because the leading vehicle can help the following 357 vehicles to experience less air resistance. 359 Cooperative-environment-sensing use cases suggest that vehicles can 360 share environmental information (e.g., air pollution, hazards/ 361 obstacles, slippery areas by snow or rain, road accidents, traffic 362 congestion, and driving behaviors of neighboring vehicles) from 363 various vehicle-mounted sensors, such as radars, LiDARs, and cameras, 364 with other vehicles and pedestrians. [Automotive-Sensing] introduces 365 millimeter-wave vehicular communication for massive automotive 366 sensing. A lot of data can be generated by those sensors, and these 367 data typically need to be routed to different destinations. In 368 addition, from the perspective of driverless vehicles, it is expected 369 that driverless vehicles can be mixed with driver-operated vehicles. 370 Through cooperative environment sensing, driver-operated vehicles can 371 use environmental information sensed by driverless vehicles for 372 better interaction with the other vehicles and environment. Vehicles 373 can also share their intended maneuvering information (e.g., lane 374 change, speed change, ramp in-and-out, cut-in, and abrupt braking) 375 with neighboring vehicles. Thus, this information sharing can help 376 the vehicles behave as more efficient traffic flows and minimize 377 unnecessary acceleration and deceleration to achieve the best ride 378 comfort. 380 A collision avoidance service of UAM end systems in air can be 381 envisioned as a use case in air vehicular environments. This use 382 case is similar to the context-aware navigator for terrestrial 383 vehicles. Through V2V coordination, those UAM end systems (e.g., 384 drones) can avoid a dangerous situation (e.g., collision) in three- 385 dimensional space rather than two-dimensional space for terrestrial 386 vehicles. Also, UAM end systems (e.g., flying car) with only a few 387 meters off the ground can communicate with terrestrial vehicles with 388 wireless communication technologies (e.g., DSRC, LTE, and C-V2X). 389 Thus, V2V means any vehicle to any vehicle, whether the vehicles are 390 ground-level or not. 392 To encourage more vehicles to participate in this cooperative 393 environmental sensing, a reward system will be needed. Sensing 394 activities of each vehicle need to be logged in either a central way 395 through a logging server (e.g., TCC) in the vehicular cloud or a 396 distributed way (e.g., blockchain [Bitcoin]) through other vehicles 397 or infrastructure. In the case of a blockchain, each sensing message 398 from a vehicle can be treated as a transaction and the neighboring 399 vehicles can play the role of peers in a consensus method of a 400 blockchain [Bitcoin][Vehicular-BlockChain]. 402 To support applications of these V2V use cases, the required 403 functions of IPv6 include IPv6-based packet exchange and secure, safe 404 communication between two vehicles. For the support of V2V under 405 multiple radio technologies (e.g., DSRC and 5G V2X), refer to 406 Appendix A. 408 3.2. V2I 410 The use cases of V2I networking discussed in this section include 412 * Navigation service; 414 * Energy-efficient speed recommendation service; 416 * Accident notification service; 418 * Electric vehicle (EV) charging service; 420 * UAM navigation service with efficient battery charging. 422 A navigation service, for example, the Self-Adaptive Interactive 423 Navigation Tool (SAINT) [SAINT], using V2I networking interacts with 424 a TCC for the large-scale/long-range road traffic optimization and 425 can guide individual vehicles along appropriate navigation paths in 426 real time. The enhanced version of SAINT [SAINTplus] can give fast 427 moving paths to emergency vehicles (e.g., ambulance and fire engine) 428 to let them reach an accident spot while redirecting other vehicles 429 near the accident spot into efficient detour paths. 431 Either a TCC or an ECD can recommend an energy-efficient speed to a 432 vehicle that depends on its traffic environment and traffic signal 433 scheduling [SignalGuru]. For example, when a vehicle approaches an 434 intersection area and a red traffic light for the vehicle becomes 435 turned on, it needs to reduce its speed to save fuel consumption. In 436 this case, either a TCC or an ECD, which has the up-to-date 437 trajectory of the vehicle and the traffic light schedule, can notify 438 the vehicle of an appropriate speed for fuel efficiency. 439 [Fuel-Efficient] studies fuel-efficient route and speed plans for 440 platooned trucks. 442 The emergency communication between accident vehicles (or emergency 443 vehicles) and a TCC can be performed via either IP-RSU or 4G-LTE 444 networks. The First Responder Network Authority (FirstNet) 445 [FirstNet] is provided by the US government to establish, operate, 446 and maintain an interoperable public safety broadband network for 447 safety and security network services, e.g., emergency calls. The 448 construction of the nationwide FirstNet network requires each state 449 in the US to have a Radio Access Network (RAN) that will connect to 450 the FirstNet's network core. The current RAN is mainly constructed 451 using 4G-LTE for the communication between a vehicle and an 452 infrastructure node (i.e., V2I) [FirstNet-Report], but it is expected 453 that DSRC-based vehicular networks [DSRC] will be available for V2I 454 and V2V in the near future. 456 An EV charging service with V2I can facilitate the efficient battery 457 charging of EVs. In the case where an EV charging station is 458 connected to an IP-RSU, an EV can be guided toward the deck of the EV 459 charging station through a battery charging server connected to the 460 IP-RSU. In addition to this EV charging service, other value-added 461 services (e.g., air firmware/software update and media streaming) can 462 be provided to an EV while it is charging its battery at the EV 463 charging station. 465 A UAM navigation service with efficient battery charging can plan the 466 battery charging schedule of UAM end systems (e.g., drone) for long- 467 distance flying [CBDN]. For this battery charging schedule, a UAM 468 end system can communicate with an infrastructure node (e.g., IP-RSU) 469 toward a cloud server via V2I communications. This cloud server can 470 coordinate the battery charging schedules of multiple UAM end systems 471 for their efficient navigation path, considering flight time from 472 their current position to a battery charging station, waiting time in 473 a waiting queue at the station, and battery charging time at the 474 station. 476 The existing IPv6 protocol must be augmented through protocol changes 477 in order to support wireless multihop V2I communications in a highway 478 where RSUs are sparsely deployed, so a vehicle can reach the wireless 479 coverage of an RSU through the multihop data forwarding of 480 intermediate vehicles. Thus, IPv6 needs to be extended for multihop 481 V2I communications. 483 To support applications of these V2I use cases, the required 484 functions of IPv6 include IPv6-based packet exchange, transport-layer 485 session continuity, and secure, safe communication between a vehicle 486 and an infrastructure node (e.g., IP-RSU) in the vehicular network. 488 3.3. V2X 490 The use case of V2X networking discussed in this section is for a 491 pedestrian protection service. 493 A pedestrian protection service, such as Safety-Aware Navigation 494 Application (SANA) [SANA], using V2I2P networking can reduce the 495 collision of a vehicle and a pedestrian carrying a smartphone 496 equipped with a network device for wireless communication (e.g., Wi- 497 Fi) with an IP-RSU. Vehicles and pedestrians can also communicate 498 with each other via an IP-RSU. An edge computing device behind the 499 IP-RSU can collect the mobility information from vehicles and 500 pedestrians, compute wireless communication scheduling for the sake 501 of them. This scheduling can save the battery of each pedestrian's 502 smartphone by allowing it to work in sleeping mode before the 503 communication with vehicles, considering their mobility. 505 For Vehicle-to-Pedestrian (V2P), a vehicle can directly communicate 506 with a pedestrian's smartphone by V2X without IP-RSU relaying. 507 Light-weight mobile nodes such as bicycles may also communicate 508 directly with a vehicle for collision avoidance using V2V. 510 The existing IPv6 protocol must be augmented through protocol changes 511 in order to support wireless multihop V2X or V2I2X communications in 512 an urban road network where RSUs are deployed at intersections, so a 513 vehicle (or a pedestrian's smartphone) can reach the wireless 514 coverage of an RSU through the multihop data forwarding of 515 intermediate vehicles (or pedestrians' smartphones) as packet 516 forwarders. Thus, IPv6 needs to be extended for multihop V2X or 517 V2I2X communications. 519 To support applications of these V2X use cases, the required 520 functions of IPv6 include IPv6-based packet exchange, transport-layer 521 session continuity, and secure, safe communication between a vehicle 522 and a pedestrian either directly or indirectly via an IP-RSU. 524 4. Vehicular Networks 526 This section describes the context for vehicular networks supporting 527 V2V, V2I, and V2X communications. It describes an internal network 528 within a vehicle or an edge network (called EN). It explains not 529 only the internetworking between the internal networks of a vehicle 530 and an EN via wireless links, but also the internetworking between 531 the internal networks of two vehicles via wireless links. 533 Traffic Control Center in Vehicular Cloud 534 ******************************************* 535 +-------------+ * * 536 |Corresponding| * +-----------------+ * 537 | Node |<->* | Mobility Anchor | * 538 +-------------+ * +-----------------+ * 539 * ^ * 540 * | * 541 * v * 542 ******************************************* 543 ^ ^ ^ 544 | | | 545 | | | 546 v v v 547 +---------+ +---------+ +---------+ 548 | IP-RSU1 |<--------->| IP-RSU2 |<--------->| IP-RSU3 | 549 +---------+ +---------+ +---------+ 550 ^ ^ ^ 551 : : : 552 +-----------------+ +-----------------+ +-----------------+ 553 | : V2I | | : V2I | | : V2I | 554 | v | | v | | v | 555 +--------+ | +--------+ | | +--------+ | | +--------+ | 556 |Vehicle1|===> |Vehicle2|===>| | |Vehicle3|===>| | |Vehicle4|===>| 557 +--------+<...>+--------+<........>+--------+ | | +--------+ | 558 V2V ^ V2V ^ | | ^ | 559 | : V2V | | : V2V | | : V2V | 560 | v | | v | | v | 561 | +--------+ | | +--------+ | | +--------+ | 562 | |Vehicle5|===> | | |Vehicle6|===>| | |Vehicle7|==>| 563 | +--------+ | | +--------+ | | +--------+ | 564 +-----------------+ +-----------------+ +-----------------+ 565 Subnet1 Subnet2 Subnet3 566 (Prefix1) (Prefix2) (Prefix3) 568 <----> Wired Link <....> Wireless Link ===> Moving Direction 570 Figure 1: An Example Vehicular Network Architecture for V2I and V2V 572 4.1. Vehicular Network Architecture 574 Figure 1 shows an example vehicular network architecture for V2I and 575 V2V in a road network. The vehicular network architecture contains 576 vehicles (including IP-OBU), IP-RSUs, Mobility Anchor, Traffic 577 Control Center, and Vehicular Cloud as components. These components 578 are not mandatory, and they can be deployed into vehicular networks 579 in various ways. Some of them (e.g., Mobility Anchor, Traffic 580 Control Center, and Vehicular Cloud) may not be needed for the 581 vehicular networks according to target use cases in Section 3. 583 Existing network architectures, such as the network architectures of 584 PMIPv6 [RFC5213], RPL (IPv6 Routing Protocol for Low-Power and Lossy 585 Networks) [RFC6550], and OMNI (Overlay Multilink Network Interface) 586 [I-D.templin-6man-omni], can be extended to a vehicular network 587 architecture for multihop V2V, V2I, and V2X, as shown in Figure 1. 588 Refer to Appendix B for the detailed discussion on multihop V2X 589 networking by RPL and OMNI. Also, refer to Appendix A for the 590 description of how OMNI can support the use of multiple radio 591 technologies in V2X. 593 As shown in this figure, IP-RSUs as routers and vehicles with IP-OBU 594 have wireless media interfaces for VANET. Furthermore, the wireless 595 media interfaces are autoconfigured with a global IPv6 prefix (e.g., 596 2001:DB8:1:1::/64) to support both V2V and V2I networking. Note that 597 2001:DB8::/32 is a documentation prefix [RFC3849] for example 598 prefixes in this document, and also that any routable IPv6 address 599 needs to be routable in a VANET and a vehicular network including IP- 600 RSUs. 602 In Figure 1, three IP-RSUs (IP-RSU1, IP-RSU2, and IP-RSU3) are 603 deployed in the road network and are connected with each other 604 through the wired networks (e.g., Ethernet). A Traffic Control 605 Center (TCC) is connected to the Vehicular Cloud for the management 606 of IP-RSUs and vehicles in the road network. A Mobility Anchor (MA) 607 may be located in the TCC as a mobility management controller. 608 Vehicle2, Vehicle3, and Vehicle4 are wirelessly connected to IP-RSU1, 609 IP-RSU2, and IP-RSU3, respectively. The three wireless networks of 610 IP-RSU1, IP-RSU2, and IP-RSU3 can belong to three different subnets 611 (i.e., Subnet1, Subnet2, and Subnet3), respectively. Those three 612 subnets use three different prefixes (i.e., Prefix1, Prefix2, and 613 Prefix3). 615 Multiple vehicles under the coverage of an RSU share a prefix just as 616 mobile nodes share a prefix of a Wi-Fi access point in a wireless 617 LAN. This is a natural characteristic in infrastructure-based 618 wireless networks. For example, in Figure 1, two vehicles (i.e., 619 Vehicle2, and Vehicle5) can use Prefix 1 to configure their IPv6 620 global addresses for V2I communication. Alternatively, mobile nodes 621 can employ a "Bring-Your-Own-Addresses (BYOA)" technique using their 622 own IPv6 Unique Local Addresses (ULAs) [RFC4193] over the wireless 623 network, which does not require the messaging (e.g., Duplicate 624 Address Detection (DAD)) of IPv6 Stateless Address Autoconfiguration 625 (SLAAC) [RFC4862]. 627 In wireless subnets in vehicular networks (e.g., Subnet1 and Subnet2 628 in Figure 1), vehicles can construct a connected VANET (with an 629 arbitrary graph topology) and can communicate with each other via V2V 630 communication. Vehicle1 can communicate with Vehicle2 via V2V 631 communication, and Vehicle2 can communicate with Vehicle3 via V2V 632 communication because they are within the wireless communication 633 range of each other. On the other hand, Vehicle3 can communicate 634 with Vehicle4 via the vehicular infrastructure (i.e., IP-RSU2 and IP- 635 RSU3) by employing V2I (i.e., V2I2V) communication because they are 636 not within the wireless communication range of each other. 638 As a basic definition for IPv6 packets transported over IEEE 639 802.11-OCB, [RFC8691] specifies several details, including Maximum 640 Transmission Unit (MTU), frame format, link-local address, address 641 mapping for unicast and multicast, stateless autoconfiguration, and 642 subnet structure. 644 An IPv6 mobility solution is needed for the guarantee of 645 communication continuity in vehicular networks so that a vehicle's 646 TCP session can be continued, or UDP packets can be delivered to a 647 vehicle as a destination without loss while it moves from an IP-RSU's 648 wireless coverage to another IP-RSU's wireless coverage. In 649 Figure 1, assuming that Vehicle2 has a TCP session (or a UDP session) 650 with a corresponding node in the vehicular cloud, Vehicle2 can move 651 from IP-RSU1's wireless coverage to IP-RSU2's wireless coverage. In 652 this case, a handover for Vehicle2 needs to be performed by either a 653 host-based mobility management scheme (e.g., MIPv6 [RFC6275]) or a 654 network-based mobility management scheme (e.g., PMIPv6 [RFC5213] and 655 AERO [I-D.templin-6man-aero]). This document describes issues in 656 mobility management for vehicular networks in Section 5.2. 658 4.2. V2I-based Internetworking 660 This section discusses the internetworking between a vehicle's 661 internal network (i.e., moving network) and an EN's internal network 662 (i.e., fixed network) via V2I communication. The internal network of 663 a vehicle is nowadays constructed with Ethernet by many automotive 664 vendors [In-Car-Network]. Note that an EN can accommodate multiple 665 routers (or switches) and servers (e.g., ECDs, navigation server, and 666 DNS server) in its internal network. 668 A vehicle's internal network often uses Ethernet to interconnect 669 Electronic Control Units (ECUs) in the vehicle. The internal network 670 can support Wi-Fi and Bluetooth to accommodate a driver's and 671 passenger's mobile devices (e.g., smartphone or tablet). The network 672 topology and subnetting depend on each vendor's network configuration 673 for a vehicle and an EN. It is reasonable to consider the 674 interaction between the internal network and an external network 675 within another vehicle or an EN. 677 +-----------------+ 678 (*)<........>(*) +----->| Vehicular Cloud | 679 (2001:DB8:1:1::/64) | | | +-----------------+ 680 +------------------------------+ +---------------------------------+ 681 | v | | v v | 682 | +-------+ +-------+ | | +-------+ +-------+ | 683 | | Host1 | |IP-OBU1| | | |IP-RSU1| | Host3 | | 684 | +-------+ +-------+ | | +-------+ +-------+ | 685 | ^ ^ | | ^ ^ | 686 | | | | | | | | 687 | v v | | v v | 688 | ---------------------------- | | ------------------------------- | 689 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:20:1::/64 | 690 | | | | | | 691 | v | | v | 692 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 693 | | Host2 | |Router1| | | |Router2| |Server1|...|ServerN| | 694 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 695 | ^ ^ | | ^ ^ ^ | 696 | | | | | | | | | 697 | v v | | v v v | 698 | ---------------------------- | | ------------------------------- | 699 | 2001:DB8:10:2::/64 | | 2001:DB8:20:2::/64 | 700 +------------------------------+ +---------------------------------+ 701 Vehicle1 (Moving Network1) EN1 (Fixed Network1) 703 <----> Wired Link <....> Wireless Link (*) Antenna 705 Figure 2: Internetworking between Vehicle and Edge Network 707 As shown in Figure 2, as internal networks, a vehicle's moving 708 network and an EN's fixed network are self-contained networks having 709 multiple subnets and having an edge router (e.g., IP-OBU and IP-RSU) 710 for the communication with another vehicle or another EN. The 711 internetworking between two internal networks via V2I communication 712 requires the exchange of the network parameters and the network 713 prefixes of the internal networks. For the efficiency, the network 714 prefixes of the internal networks (as a moving network) in a vehicle 715 need to be delegated and configured automatically. Note that a 716 moving network's network prefix can be called a Mobile Network Prefix 717 (MNP) [RFC3963]. 719 Figure 2 also shows the internetworking between the vehicle's moving 720 network and the EN's fixed network. There exists an internal network 721 (Moving Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and 722 Host2), and two routers (IP-OBU1 and Router1). There exists another 723 internal network (Fixed Network1) inside EN1. EN1 has one host 724 (Host3), two routers (IP-RSU1 and Router2), and the collection of 725 servers (Server1 to ServerN) for various services in the road 726 networks, such as the emergency notification and navigation. 727 Vehicle1's IP-OBU1 (as a mobile router) and EN1's IP-RSU1 (as a fixed 728 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 729 V2I networking. Thus, a host (Host1) in Vehicle1 can communicate 730 with a server (Server1) in EN1 for a vehicular service through 731 Vehicle1's moving network, a wireless link between IP-OBU1 and IP- 732 RSU1, and EN1's fixed network. 734 For the IPv6 communication between an IP-OBU and an IP-RSU or between 735 two neighboring IP-OBUs, they need to know the network parameters, 736 which include MAC layer and IPv6 layer information. The MAC layer 737 information includes wireless link layer parameters, transmission 738 power level, and the MAC address of an external network interface for 739 the internetworking with another IP-OBU or IP-RSU. The IPv6 layer 740 information includes the IPv6 address and network prefix of an 741 external network interface for the internetworking with another IP- 742 OBU or IP-RSU. 744 Through the mutual knowledge of the network parameters of internal 745 networks, packets can be transmitted between the vehicle's moving 746 network and the EN's fixed network. Thus, V2I requires an efficient 747 protocol for the mutual knowledge of network parameters. 749 As shown in Figure 2, the addresses used for IPv6 transmissions over 750 the wireless link interfaces for IP-OBU and IP-RSU can be link-local 751 IPv6 addresses, ULAs, or global IPv6 addresses. When global IPv6 752 addresses are used, wireless interface configuration and control 753 overhead for DAD [RFC4862] and Multicast Listener Discovery (MLD) 754 [RFC2710][RFC3810] should be minimized to support V2I and V2X 755 communications for vehicles moving fast along roadways. 757 Let us consider the upload/download time of a vehicle when it passes 758 through the wireless communication coverage of an IP-RSU. For a 759 given typical setting where 1km is the maximum DSRC communication 760 range [DSRC] and 100km/h is the speed limit in highway, the dwelling 761 time can be calculated to be 72 seconds by dividing the diameter of 762 the 2km (i.e., two times of DSRC communication range where an IP-RSU 763 is located in the center of the circle of wireless communication) by 764 the speed limit of 100km/h (i.e., about 28m/s). For the 72 seconds, 765 a vehicle passing through the coverage of an IP-RSU can upload and 766 download data packets to/from the IP-RSU. 768 4.3. V2V-based Internetworking 770 This section discusses the internetworking between the moving 771 networks of two neighboring vehicles via V2V communication. 773 (*)<..........>(*) 774 (2001:DB8:1:1::/64) | | 775 +------------------------------+ +------------------------------+ 776 | v | | v | 777 | +-------+ +-------+ | | +-------+ +-------+ | 778 | | Host1 | |IP-OBU1| | | |IP-OBU2| | Host3 | | 779 | +-------+ +-------+ | | +-------+ +-------+ | 780 | ^ ^ | | ^ ^ | 781 | | | | | | | | 782 | v v | | v v | 783 | ---------------------------- | | ---------------------------- | 784 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:30:1::/64 | 785 | | | | | | 786 | v | | v | 787 | +-------+ +-------+ | | +-------+ +-------+ | 788 | | Host2 | |Router1| | | |Router2| | Host4 | | 789 | +-------+ +-------+ | | +-------+ +-------+ | 790 | ^ ^ | | ^ ^ | 791 | | | | | | | | 792 | v v | | v v | 793 | ---------------------------- | | ---------------------------- | 794 | 2001:DB8:10:2::/64 | | 2001:DB8:30:2::/64 | 795 +------------------------------+ +------------------------------+ 796 Vehicle1 (Moving Network1) Vehicle2 (Moving Network2) 798 <----> Wired Link <....> Wireless Link (*) Antenna 800 Figure 3: Internetworking between Two Vehicles 802 Figure 3 shows the internetworking between the moving networks of two 803 neighboring vehicles. There exists an internal network (Moving 804 Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and Host2), 805 and two routers (IP-OBU1 and Router1). There exists another internal 806 network (Moving Network2) inside Vehicle2. Vehicle2 has two hosts 807 (Host3 and Host4), and two routers (IP-OBU2 and Router2). Vehicle1's 808 IP-OBU1 (as a mobile router) and Vehicle2's IP-OBU2 (as a mobile 809 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 810 V2V networking. Thus, a host (Host1) in Vehicle1 can communicate 811 with another host (Host3) in Vehicle2 for a vehicular service through 812 Vehicle1's moving network, a wireless link between IP-OBU1 and IP- 813 OBU2, and Vehicle2's moving network. 815 As a V2V use case in Section 3.1, Figure 4 shows the linear network 816 topology of platooning vehicles for V2V communications where Vehicle3 817 is the leading vehicle with a driver, and Vehicle2 and Vehicle1 are 818 the following vehicles without drivers. 820 (*)<..................>(*)<..................>(*) 821 | | | 822 +-----------+ +-----------+ +-----------+ 823 | | | | | | 824 | +-------+ | | +-------+ | | +-------+ | 825 | |IP-OBU1| | | |IP-OBU2| | | |IP-OBU3| | 826 | +-------+ | | +-------+ | | +-------+ | 827 | ^ | | ^ | | ^ | 828 | | |=====> | | |=====> | | |=====> 829 | v | | v | | v | 830 | +-------+ | | +-------+ | | +-------+ | 831 | | Host1 | | | | Host2 | | | | Host3 | | 832 | +-------+ | | +-------+ | | +-------+ | 833 | | | | | | 834 +-----------+ +-----------+ +-----------+ 835 Vehicle1 Vehicle2 Vehicle3 837 <----> Wired Link <....> Wireless Link ===> Moving Direction 838 (*) Antenna 840 Figure 4: Multihop Internetworking between Two Vehicle Networks 842 As shown in Figure 4, multihop internetworking is feasible among the 843 moving networks of three vehicles in the same VANET. For example, 844 Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via IP-OBU1 845 in Vehicle1, IP-OBU2 in Vehicle2, and IP-OBU3 in Vehicle3 in the 846 VANET, as shown in the figure. 848 In this section, the link between two vehicles is assumed to be 849 stable for single-hop wireless communication regardless of the sight 850 relationship such as line of sight and non-line of sight, as shown in 851 Figure 3. Even in Figure 4, the three vehicles are connected to each 852 other with a linear topology, however, multihop V2V communication can 853 accommodate any network topology (i.e., an arbitrary graph) over 854 VANET routing protocols. 856 (*)<..................>(*)<..................>(*) 857 | | | 858 +-----------+ +-----------+ +-----------+ 859 | | | | | | 860 | +-------+ | | +-------+ | | +-------+ | 861 | |IP-OBU1| | | |IP-RSU1| | | |IP-OBU3| | 862 | +-------+ | | +-------+ | | +-------+ | 863 | ^ | | ^ | | ^ | 864 | | |=====> | | | | | |=====> 865 | v | | v | | v | 866 | +-------+ | | +-------+ | | +-------+ | 867 | | Host1 | | | | Host2 | | | | Host3 | | 868 | +-------+ | | +-------+ | | +-------+ | 869 | | | | | | 870 +-----------+ +-----------+ +-----------+ 871 Vehicle1 EN1 Vehicle3 873 <----> Wired Link <....> Wireless Link ===> Moving Direction 874 (*) Antenna 876 Figure 5: Multihop Internetworking between Two Vehicle Networks 877 via IP-RSU (V2I2V) 879 As shown in Figure 5, multihop internetworking between two vehicles 880 is feasible via an infrastructure node (i.e., IP-RSU) with wireless 881 connectivity among the moving networks of two vehicles and the fixed 882 network of an edge network (denoted as EN1) in the same VANET. For 883 example, Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via 884 IP-OBU1 in Vehicle1, IP-RSU1 in EN1, and IP-OBU3 in Vehicle3 in the 885 VANET, as shown in the figure. 887 For the reliability required in V2V networking, the ND optimization 888 defined in MANET [RFC6130] [RFC7466] improves the classical IPv6 ND 889 in terms of tracking neighbor information with up to two hops and 890 introducing several extensible Information Bases, which serves the 891 MANET routing protocols such as the difference versions of Optimized 892 Link State Routing Protocol (OLSR) [RFC3626] [RFC7181] [RFC7188] 893 [RFC7722] [RFC7779] [RFC8218] and the Dynamic Link Exchange Protocol 894 (DLEP) with its extensions [RFC8175] [RFC8629] [RFC8651] [RFC8703] 895 [RFC8757]. In short, the MANET ND mainly deals with maintaining 896 extended network neighbors. However, an ND protocol in vehicular 897 networks shall consider more about the geographical mobility 898 information of vehicles as an important resource for serving various 899 purposes to improve the reliability, e.g., vehicle driving safety, 900 intelligent transportation implementations, and advanced mobility 901 services. For a more reliable V2V networking, some redundancy 902 mechanisms should be provided in L3 in the case of the failure of L2. 904 5. Problem Statement 906 In order to specify protocols using the architecture mentioned in 907 Section 4.1, IPv6 core protocols have to be adapted to overcome 908 certain challenging aspects of vehicular networking. Since the 909 vehicles are likely to be moving at great speed, protocol exchanges 910 need to be completed in a time relatively short compared to the 911 lifetime of a link between a vehicle and an IP-RSU, or between two 912 vehicles. 914 For safe driving, vehicles need to exchange application messages 915 every 0.5 second [NHTSA-ACAS-Report] to let drivers take an action to 916 avoid a dangerous situation (e.g., vehicle collision), so IPv6 917 protocol exchanges need to support this order of magnitude for 918 application message exchanges. Also, considering the communication 919 range of DSRC (up to 1km) and 100km/h as the speed limit in highway, 920 the lifetime of a link between a vehicle and an IP-RSU is 72 seconds, 921 and the lifetime of a link between two vehicles is 36 seconds. Note 922 that if two vehicles are moving in the opposite directions in a 923 roadway, the relative speed of this case is two times the relative 924 speed of a vehicle passing through an RSU. This relative speed leads 925 the half of the link lifetime between the vehicle and the IP-RSU. In 926 reality, the DSRC communication range is around 500m, so the link 927 lifetime will be a half of the maximum time. The time constraint of 928 a wireless link between two nodes (e.g., vehicle and IP-RSU) needs to 929 be considered because it may affect the lifetime of a session 930 involving the link. The lifetime of a session varies depending on 931 the session's type such as a web surfing, voice call over IP, DNS 932 query, and context-aware navigation (in Section 3.1). Regardless of 933 a session's type, to guide all the IPv6 packets to their destination 934 host(s), IP mobility should be supported for the session. In a V2V 935 scenario (e.g., context-aware navigation), the IPv6 packets of a 936 vehicle should be delivered to relevant vehicles in an efficient way 937 (e.g., multicasting). With this observation, IPv6 protocol exchanges 938 need to be done as short as possible to support the message exchanges 939 of various applications in vehicular networks. 941 Therefore, the time constraint of a wireless link has a major impact 942 on IPv6 Neighbor Discovery (ND). Mobility Management (MM) is also 943 vulnerable to disconnections that occur before the completion of 944 identity verification and tunnel management. This is especially true 945 given the unreliable nature of wireless communication. Meanwhile, 946 the bandwidth of the wireless link determined by the lower layers 947 (i.e., link and PHY layers) can affect the transmission time of 948 control messages of the upper layers (e.g., IPv6) and the continuity 949 of sessions in the higher layers (e.g., IPv6, TCP, and UDP). Hence 950 the bandwidth selection according to Modulation and Coding Scheme 951 (MCS) also affects the vehicular network connectivity. Note that 952 usually the higher bandwidth gives the shorter communication range 953 and the higher packet error rate at the receiving side, which may 954 reduce the reliability of control message exchanges of the higher 955 layers (e.g., IPv6). This section presents key topics such as 956 neighbor discovery and mobility management for links and sessions in 957 IPv6-based vehicular networks. 959 5.1. Neighbor Discovery 961 IPv6 ND [RFC4861][RFC4862] is a core part of the IPv6 protocol suite. 962 IPv6 ND is designed for link types including point-to-point, 963 multicast-capable (e.g., Ethernet) and Non-Broadcast Multiple Access 964 (NBMA). It assumes the efficient and reliable support of multicast 965 and unicast from the link layer for various network operations such 966 as MAC Address Resolution (AR), DAD, MLD and Neighbor Unreachability 967 Detection (NUD). 969 Vehicles move quickly within the communication coverage of any 970 particular vehicle or IP-RSU. Before the vehicles can exchange 971 application messages with each other, they need to be configured with 972 a link-local IPv6 address or a global IPv6 address, and run IPv6 ND. 974 The requirements for IPv6 ND for vehicular networks are efficient DAD 975 and NUD operations. An efficient DAD is required to reduce the 976 overhead of the DAD packets during a vehicle's travel in a road 977 network, which can guarantee the uniqueness of a vehicle's global 978 IPv6 address. An efficient NUD is required to reduce the overhead of 979 the NUD packets during a vehicle's travel in a road network, which 980 can guarantee the accurate neighborhood information of a vehicle in 981 terms of adjacent vehicles and RSUs. 983 The legacy DAD assumes that a node with an IPv6 address can reach any 984 other node with the scope of its address at the time it claims its 985 address, and can hear any future claim for that address by another 986 party within the scope of its address for the duration of the address 987 ownership. However, the partitioning and merging of VANETs makes 988 this assumption frequently invalid in vehicular networks. The 989 merging and partitioning of VANETs frequently occurs in vehicular 990 networks. This merging and partitioning should be considered for the 991 IPv6 ND such as IPv6 Stateless Address Autoconfiguration (SLAAC) 992 [RFC4862]. Due to the merging of VANETs, two IPv6 addresses may 993 conflict with each other though they were unique before the merging. 994 An address lookup operation may be conducted by an MA or IP-RSU (as 995 Registrar in RPL) to check the uniqueness of an IPv6 address that 996 will be configured by a vehicle as DAD. Also, the partitioning of a 997 VANET may make vehicles with the same prefix be physically 998 unreachable. An address lookup operation may be conducted by an MA 999 or IP-RSU (as Registrar in RPL) to check the existence of a vehicle 1000 under the network coverage of the MA or IP-RSU as NUD. Thus, SLAAC 1001 needs to prevent IPv6 address duplication due to the merging of 1002 VANETs, and IPv6 ND needs to detect unreachable neighboring vehicles 1003 due to the partitioning of a VANET. According to the merging and 1004 partitioning, a destination vehicle (as an IPv6 host) needs to be 1005 distinguished as either an on-link host or an off-link host even 1006 though the source vehicle can use the same prefix as the destination 1007 vehicle [I-D.ietf-intarea-ippl]. 1009 To efficiently prevent IPv6 address duplication due to the VANET 1010 partitioning and merging from happening in vehicular networks, the 1011 vehicular networks need to support a vehicular-network-wide DAD by 1012 defining a scope that is compatible with the legacy DAD. In this 1013 case, two vehicles can communicate with each other when there exists 1014 a communication path over VANET or a combination of VANETs and IP- 1015 RSUs, as shown in Figure 1. By using the vehicular-network-wide DAD, 1016 vehicles can assure that their IPv6 addresses are unique in the 1017 vehicular network whenever they are connected to the vehicular 1018 infrastructure or become disconnected from it in the form of VANET. 1020 For vehicular networks with high mobility and density, the DAD needs 1021 to be performed efficiently with minimum overhead so that the 1022 vehicles can exchange driving safety messages (e.g., collision 1023 avoidance and accident notification) with each other with a short 1024 interval suggested by NHTSA (National Highway Traffic Safety 1025 Administration) [NHTSA-ACAS-Report]. Since the partitioning and 1026 merging of vehicular networks may require re-perform the DAD process 1027 repeatedly, the link scope of vehicles may be limited to a small 1028 area, which may delay the exchange of driving safety messages. 1029 Driving safety messages can include a vehicle's mobility information 1030 (i.e., position, speed, direction, and acceleration/deceleration) 1031 that is critical to other vehicles. The exchange interval of this 1032 message is recommended to be less than 0.5 second, which is required 1033 for a driver to avoid an emergency situation, such as a rear-end 1034 crash. 1036 ND time-related parameters such as router lifetime and Neighbor 1037 Advertisement (NA) interval need to be adjusted for vehicle speed and 1038 vehicle density. For example, the NA interval needs to be 1039 dynamically adjusted according to a vehicle's speed so that the 1040 vehicle can maintain its neighboring vehicles in a stable way, 1041 considering the collision probability with the NA messages sent by 1042 other vehicles. The ND time-related parameters can be an operational 1043 setting or an optimization point particularly for vehicular networks. 1045 For IPv6-based safety applications (e.g., context-aware navigation, 1046 adaptive cruise control, and platooning) in vehicular networks, the 1047 delay-bounded data delivery is critical. IPv6 ND needs to work to 1048 support those IPv6-based safety applications efficiently. 1050 From the interoperability point of view, in IPv6-based vehicular 1051 networking, IPv6 ND should have minimum changes with the legacy IPv6 1052 ND used in the Internet, including the DAD and NUD operations, so 1053 that IPv6-based vehicular networks can be seamlessly connected to 1054 other intelligent transportation elements (e.g., traffic signals, 1055 pedestrian wearable devices, electric scooters, and bus stops) that 1056 use the standard IPv6 network settings. 1058 5.1.1. Link Model 1060 A subnet model for a vehicular network needs to facilitate the 1061 communication between two vehicles with the same prefix regardless of 1062 the vehicular network topology as long as there exist bidirectional 1063 E2E paths between them in the vehicular network including VANETs and 1064 IP-RSUs. This subnet model allows vehicles with the same prefix to 1065 communicate with each other via a combination of multihop V2V and 1066 multihop V2I with VANETs and IP-RSUs. 1067 [I-D.thubert-6man-ipv6-over-wireless] introduces other issues in an 1068 IPv6 subnet model. 1070 IPv6 protocols work under certain assumptions that do not necessarily 1071 hold for vehicular wireless access link types [VIP-WAVE][RFC5889]. 1072 For instance, some IPv6 protocols assume symmetry in the connectivity 1073 among neighboring interfaces [RFC6250]. However, radio interference 1074 and different levels of transmission power may cause asymmetric links 1075 to appear in vehicular wireless links. As a result, a new vehicular 1076 link model needs to consider the asymmetry of dynamically changing 1077 vehicular wireless links. 1079 There is a relationship between a link and a prefix, besides the 1080 different scopes that are expected from the link-local and global 1081 types of IPv6 addresses. In an IPv6 link, it is defined that all 1082 interfaces which are configured with the same subnet prefix and with 1083 on-link bit set can communicate with each other on an IPv6 link. 1084 However, the vehicular link model needs to define the relationship 1085 between a link and a prefix, considering the dynamics of wireless 1086 links and the characteristics of VANET. 1088 A VANET can have a single link between each vehicle pair within 1089 wireless communication range, as shown in Figure 4. When two 1090 vehicles belong to the same VANET, but they are out of wireless 1091 communication range, they cannot communicate directly with each 1092 other. Suppose that a global-scope IPv6 prefix (or an IPv6 ULA 1093 prefix) is assigned to VANETs in vehicular networks. Even though two 1094 vehicles in the same VANET configure their IPv6 addresses with the 1095 same IPv6 prefix, they may not communicate with each other not in one 1096 hop in the same VANET because of the multihop network connectivity 1097 between them. Thus, in this case, the concept of an on-link IPv6 1098 prefix does not hold because two vehicles with the same on-link IPv6 1099 prefix cannot communicate directly with each other. Also, when two 1100 vehicles are located in two different VANETs with the same IPv6 1101 prefix, they cannot communicate with each other. When these two 1102 VANETs converge to one VANET, the two vehicles can communicate with 1103 each other in a multihop fashion, for example, when they are Vehicle1 1104 and Vehicle3, as shown in Figure 4. 1106 From the previous observation, a vehicular link model should consider 1107 the frequent partitioning and merging of VANETs due to vehicle 1108 mobility. Therefore, the vehicular link model needs to use an on- 1109 link prefix and off-link prefix according to the network topology of 1110 vehicles such as a one-hop reachable network and a multihop reachable 1111 network (or partitioned networks). If the vehicles with the same 1112 prefix are reachable from each other in one hop, the prefix should be 1113 on-link. On the other hand, if some of the vehicles with the same 1114 prefix are not reachable from each other in one hop due to either the 1115 multihop topology in the VANET or multiple partitions, the prefix 1116 should be off-link. In most cases in vehicular networks, due to the 1117 partitioning and merging of VANETs, and the multihop network topology 1118 of VANETS, off-link prefixes will be used for vehicles as default. 1120 The vehicular link model needs to support multihop routing in a 1121 connected VANET where the vehicles with the same global-scope IPv6 1122 prefix (or the same IPv6 ULA prefix) are connected in one hop or 1123 multiple hops. It also needs to support the multihop routing in 1124 multiple connected VANETs through infrastructure nodes (e.g., IP-RSU) 1125 where they are connected to the infrastructure. For example, in 1126 Figure 1, suppose that Vehicle1, Vehicle2, and Vehicle3 are 1127 configured with their IPv6 addresses based on the same global-scope 1128 IPv6 prefix. Vehicle1 and Vehicle3 can also communicate with each 1129 other via either multihop V2V or multihop V2I2V. When Vehicle1 and 1130 Vehicle3 are connected in a VANET, it will be more efficient for them 1131 to communicate with each other directly via VANET rather than 1132 indirectly via IP-RSUs. On the other hand, when Vehicle1 and 1133 Vehicle3 are far away from direct communication range in separate 1134 VANETs and under two different IP-RSUs, they can communicate with 1135 each other through the relay of IP-RSUs via V2I2V. Thus, two 1136 separate VANETs can merge into one network via IP-RSU(s). Also, 1137 newly arriving vehicles can merge two separate VANETs into one VANET 1138 if they can play the role of a relay node for those VANETs. 1140 Thus, in IPv6-based vehicular networking, the vehicular link model 1141 should have minimum changes for interoperability with standard IPv6 1142 links in an efficient fashion to support IPv6 DAD, MLD and NUD 1143 operations. 1145 5.1.2. MAC Address Pseudonym 1147 For the protection of drivers' privacy, a pseudonym of a MAC address 1148 of a vehicle's network interface should be used, so that the MAC 1149 address can be changed periodically. However, although such a 1150 pseudonym of a MAC address can protect to some extent the privacy of 1151 a vehicle, it may not be able to resist attacks on vehicle 1152 identification by other fingerprint information, for example, the 1153 scrambler seed embedded in IEEE 802.11-OCB frames [Scrambler-Attack]. 1154 The pseudonym of a MAC address affects an IPv6 address based on the 1155 MAC address, and a transport-layer (e.g., TCP and SCTP) session with 1156 an IPv6 address pair. However, the pseudonym handling is not 1157 implemented and tested yet for applications on IP-based vehicular 1158 networking. 1160 In the ETSI standards, for the sake of security and privacy, an ITS 1161 station (e.g., vehicle) can use pseudonyms for its network interface 1162 identities (e.g., MAC address) and the corresponding IPv6 addresses 1163 [Identity-Management]. Whenever the network interface identifier 1164 changes, the IPv6 address based on the network interface identifier 1165 needs to be updated, and the uniqueness of the address needs to be 1166 checked through the DAD procedure. 1168 5.1.3. Routing 1170 For multihop V2V communications in either a VANET or VANETs via IP- 1171 RSUs, a vehicular Mobile Ad Hoc Networks (MANET) routing protocol may 1172 be required to support both unicast and multicast in the links of the 1173 subnet with the same IPv6 prefix. However, it will be costly to run 1174 both vehicular ND and a vehicular ad hoc routing protocol in terms of 1175 control traffic overhead [RFC9119]. 1177 A routing protocol for a VANET may cause redundant wireless frames in 1178 the air to check the neighborhood of each vehicle and compute the 1179 routing information in a VANET with a dynamic network topology 1180 because the IPv6 ND is used to check the neighborhood of each 1181 vehicle. Thus, the vehicular routing needs to take advantage of the 1182 IPv6 ND to minimize its control overhead. 1184 RPL [RFC6550] defines a routing protocol for low-power and lossy 1185 networks, which constructs and maintains Destination-Oriented 1186 Directed Acyclic Graphs (DODAGs) optimized by an Objective Function 1187 (OF). A defined OF provides route selection and optimization within 1188 an RPL topology. The RPL nodes use an anisotropic Distance Vector 1189 (DV) approach to form a DODAG by discovering and aggressively 1190 maintaining the upward default route toward the root of the DODAG. 1191 Downward routes follow the same DODAG, with lazy maintenance and 1192 stretched Peer-to-Peer (P2P) routing in the so-called storing mode. 1193 It is well-designed to reduce the topological knowledge and routing 1194 state that needs to be exchanged. As a result, the routing protocol 1195 overhead is minimized, which allows either highly constrained stable 1196 networks or less constrained, highly dynamic networks. Refer to 1197 Appendix B for the detailed description of RPL for multihop V2X 1198 networking. 1200 An address registration extension for 6LoWPAN (IPv6 over Low-Power 1201 Wireless Personal Area Network) in [RFC8505] can support light-weight 1202 mobility for nodes moving through different parents. [RFC8505], as 1203 opposed to [RFC4861], is stateful and proactively installs the ND 1204 cache entries, which saves broadcasts and provides a deterministic 1205 presence information for IPv6 addresses. Mainly it updates the 1206 Address Registration Option (ARO) of ND defined in [RFC6775] to 1207 include a status field that can indicate the movement of a node and 1208 optionally a Transaction ID (TID) field, i.e., a sequence number that 1209 can be used to determine the most recent location of a node. Thus, 1210 RPL can use the information provided by the Extended ARO (EARO) 1211 defined in [RFC8505] to deal with a certain level of node mobility. 1212 When a leaf node moves to the coverage of another parent node, it 1213 should de-register its addresses to the previous parent node and 1214 register itself with a new parent node along with an incremented TID. 1216 RPL can be used in IPv6-based vehicular networks, but it is primarily 1217 designed for lossy networks, which puts energy efficiency first. For 1218 using it in IPv6-based vehicular networks, there have not been actual 1219 experiences and practical implementations for vehicular networks, 1220 though it was tested in IoT low-power and lossy networks (LLN) 1221 scenarios. 1223 Moreover, due to bandwidth and energy constraints, RPL does not 1224 suggest to use a proactive mechanism (e.g., keepalive) to maintain 1225 accurate routing adjacencies such as Bidirectional Forwarding 1226 Detection [RFC5881] and MANET Neighborhood Discovery Protocol 1227 [RFC6130]. As a result, due to the mobility of vehicles, network 1228 fragmentation may not be detected quickly and the routing of packets 1229 between vehicles or between a vehicle and an infrastructure node may 1230 fail. 1232 5.2. Mobility Management 1234 The seamless connectivity and timely data exchange between two end 1235 points requires efficient mobility management including location 1236 management and handover. Most vehicles are equipped with a GPS 1237 receiver as part of a dedicated navigation system or a corresponding 1238 smartphone App. Note that the GPS receiver may not provide vehicles 1239 with accurate location information in adverse environments such as a 1240 building area or a tunnel. The location precision can be improved 1241 with assistance of the IP-RSUs or a cellular system with a GPS 1242 receiver for location information. 1244 With a GPS navigator, efficient mobility management can be performed 1245 with the help of vehicles periodically reporting their current 1246 position and trajectory (i.e., navigation path) to the vehicular 1247 infrastructure (having IP-RSUs and an MA in TCC). This vehicular 1248 infrastructure can predict the future positions of the vehicles from 1249 their mobility information (i.e., the current position, speed, 1250 direction, and trajectory) for efficient mobility management (e.g., 1251 proactive handover). For a better proactive handover, link-layer 1252 parameters, such as the signal strength of a link-layer frame (e.g., 1253 Received Channel Power Indicator (RCPI) [VIP-WAVE]), can be used to 1254 determine the moment of a handover between IP-RSUs along with 1255 mobility information. 1257 By predicting a vehicle's mobility, the vehicular infrastructure 1258 needs to better support IP-RSUs to perform efficient SLAAC, data 1259 forwarding, horizontal handover (i.e., handover in wireless links 1260 using a homogeneous radio technology), and vertical handover (i.e., 1261 handover in wireless links using heterogeneous radio technologies) in 1262 advance along with the movement of the vehicle. 1264 For example, as shown in Figure 1, when a vehicle (e.g., Vehicle2) is 1265 moving from the coverage of an IP-RSU (e.g., IP-RSU1) into the 1266 coverage of another IP-RSU (e.g., IP-RSU2) belonging to a different 1267 subnet, the IP-RSUs can proactively support the IPv6 mobility of the 1268 vehicle, while performing the SLAAC, data forwarding, and handover 1269 for the sake of the vehicle. 1271 For a mobility management scheme in a domain, where the wireless 1272 subnets of multiple IP-RSUs share the same prefix, an efficient 1273 vehicular-network-wide DAD is required. If DHCPv6 is used to assign 1274 a unique IPv6 address to each vehicle in this shared link, the DAD is 1275 not required. On the other hand, for a mobility management scheme 1276 with a unique prefix per mobile node (e.g., PMIPv6 [RFC5213]), DAD is 1277 not required because the IPv6 address of a vehicle's external 1278 wireless interface is guaranteed to be unique. There is a tradeoff 1279 between the prefix usage efficiency and DAD overhead. Thus, the IPv6 1280 address autoconfiguration for vehicular networks needs to consider 1281 this tradeoff to support efficient mobility management. 1283 Even though the SLAAC with classic ND costs a DAD during mobility 1284 management, the SLAAC with [RFC8505] does not cost a DAD. SLAAC for 1285 vehicular networks needs to consider the minimization of the cost of 1286 DAD with the help of an infrastructure node (e.g., IP-RSU and MA). 1287 Using an infrastructure prefix over VANET allows direct routability 1288 to the Internet through the multihop V2I toward an IP-RSU. On the 1289 other hand, a BYOA does not allow such direct routability to the 1290 Internet since the BYOA is not topologically correct, that is, not 1291 routable in the Internet. In addition, a vehicle configured with a 1292 BYOA needs a tunnel home (e.g., IP-RSU) connected to the Internet, 1293 and the vehicle needs to know which neighboring vehicle is reachable 1294 inside the VANET toward the tunnel home. There is nonnegligible 1295 control overhead to set up and maintain routes to such a tunnel home 1296 over the VANET. 1298 For the case of a multihomed network, a vehicle can follow the first- 1299 hop router selection rule described in [RFC8028]. For example, an 1300 IP-OBU inside a vehicle may connect to an IP-RSU that has multiple 1301 routers behind. In this scenario, because the IP-OBU can have 1302 multiple prefixes from those routers, the default router selection, 1303 source address selection, and packet redirect process should follow 1304 the guidelines in [RFC8028]. That is, the vehicle should select its 1305 default router for each prefix by preferring the router that 1306 advertised the prefix. 1308 Vehicles can use the TCC as their Home Network having a home agent 1309 for mobility management as in MIPv6 [RFC6275] and PMIPv6 [RFC5213], 1310 so the TCC (or an MA inside the TCC) maintains the mobility 1311 information of vehicles for location management. IP tunneling over 1312 the wireless link should be avoided for performance efficiency. 1313 Also, in vehicular networks, asymmetric links sometimes exist and 1314 must be considered for wireless communications such as V2V and V2I. 1316 Therefore, for the proactive and seamless IPv6 mobility of vehicles, 1317 the vehicular infrastructure (including IP-RSUs and MA) needs to 1318 efficiently perform the mobility management of the vehicles with 1319 their mobility information and link-layer information. Also, in 1320 IPv6-based vehicular networking, IPv6 mobility management should have 1321 minimum changes for the interoperability with the legacy IPv6 1322 mobility management schemes such as PMIPv6, DMM, LISP, and AERO. 1324 6. Security Considerations 1326 This section discusses security and privacy for IPv6-based vehicular 1327 networking. Security and privacy are paramount in V2I, V2V, and V2X 1328 networking along with neighbor discovery and mobility management. 1330 Vehicles and infrastructure must be authenticated in order to 1331 participate in vehicular networking. For the authentication in 1332 vehicular networks, vehicular cloud needs to support a kind of Public 1333 Key Infrastructure (PKI) in an efficient way. To provide safe 1334 interaction between vehicles or between a vehicle and infrastructure, 1335 only authenticated nodes (i.e., vehicle and infrastructure node) can 1336 participate in vehicular networks. Also, in-vehicle devices (e.g., 1337 ECU) and a driver/passenger's mobile devices (e.g., smartphone and 1338 tablet PC) in a vehicle need to communicate with other in-vehicle 1339 devices and another driver/passenger's mobile devices in another 1340 vehicle, or other servers behind an IP-RSU in a secure way. Even 1341 though a vehicle is perfectly authenticated and legitimate, it may be 1342 hacked for running malicious applications to track and collect its 1343 and other vehicles' information. In this case, an attack mitigation 1344 process may be required to reduce the aftermath of malicious 1345 behaviors. 1347 For secure V2I communication, a secure channel (e.g., IPsec) between 1348 a mobile router (i.e., IP-OBU) in a vehicle and a fixed router (i.e., 1349 IP-RSU) in an EN needs to be established, as shown in Figure 2 1350 [RFC4301][RFC4302] [RFC4303][RFC4308] [RFC7296]. Also, for secure 1351 V2V communication, a secure channel (e.g., IPsec) between a mobile 1352 router (i.e., IP-OBU) in a vehicle and a mobile router (i.e., IP-OBU) 1353 in another vehicle needs to be established, as shown in Figure 3. 1354 For secure communication, an element in a vehicle (e.g., an in- 1355 vehicle device and a driver/passenger's mobile device) needs to 1356 establish a secure connection (e.g., TLS) with another element in 1357 another vehicle or another element in a vehicular cloud (e.g., a 1358 server). IEEE 1609.2 [WAVE-1609.2] specifies security services for 1359 applications and management messages, but this WAVE specification is 1360 optional. Thus, if the link layer does not support the security of a 1361 WAVE frame, either the network layer or the transport layer needs to 1362 support security services for the WAVE frames. 1364 6.1. Security Threats in Neighbor Discovery 1366 For the classical IPv6 ND, the DAD is required to ensure the 1367 uniqueness of the IPv6 address of a vehicle's wireless interface. 1368 This DAD can be used as a flooding attack that uses the DAD-related 1369 ND packets disseminated over the VANET or vehicular networks. 1370 [RFC6959] introduces threats enabled by IP source address spoofing. 1371 This possibility indicates that vehicles and IP-RSUs need to filter 1372 out suspicious ND traffic in advance. [RFC8928] introduces a 1373 mechanism that protects the ownership of an address for 6loWPAN ND 1374 from address theft and impersonation attacks. Based on the SEND 1375 [RFC3971] mechanism, the authentication for routers (i.e., IP-RSUs) 1376 can be conducted by only selecting an IP-RSU that has a certification 1377 path toward trusted parties. For authenticating other vehicles, the 1378 cryptographically generated address (CGA) can be used to verify the 1379 true owner of a received ND message, which requires to use the CGA ND 1380 option in the ND protocols. For a general protection of the ND 1381 mechanism, the RSA Signature ND option can also be used to protect 1382 the integrity of the messages by public key signatures. For a more 1383 advanced authentication mechanism, a distributed blockchain-based 1384 approach [Vehicular-BlockChain] can be used. However, for a scenario 1385 where a trustable router or an authentication path cannot be 1386 obtained, it is desirable to find a solution in which vehicles and 1387 infrastructures can authenticate each other without any support from 1388 a third party. 1390 When applying the classical IPv6 ND process to VANET, one of the 1391 security issues is that an IP-RSU (or an IP-OBU) as a router may 1392 receive deliberate or accidental DoS attacks from network scans that 1393 probe devices on a VANET. In this scenario, the IP-RSU can be 1394 overwhelmed for processing the network scan requests so that the 1395 capacity and resources of IP-RSU are exhausted, causing the failure 1396 of receiving normal ND messages from other hosts for network address 1397 resolution. [RFC6583] describes more about the operational problems 1398 in the classical IPv6 ND mechanism that can be vulnerable to 1399 deliberate or accidental DoS attacks and suggests several 1400 implementation guidelines and operational mitigation techniques for 1401 those problems. Nevertheless, for running IPv6 ND in VANET, those 1402 issues can be more acute since the movements of vehicles can be so 1403 diverse that it leaves a large room for rogue behaviors, and the 1404 failure of networking among vehicles may cause grave consequences. 1406 Strong security measures shall protect vehicles roaming in road 1407 networks from the attacks of malicious nodes, which are controlled by 1408 hackers. For safe driving applications (e.g., context-aware 1409 navigation, cooperative adaptive cruise control, and platooning), as 1410 explained in Section 3.1, the cooperative action among vehicles is 1411 assumed. Malicious nodes may disseminate wrong driving information 1412 (e.g., location, speed, and direction) for disturbing safe driving. 1413 For example, a Sybil attack, which tries to confuse a vehicle with 1414 multiple false identities, may disturb a vehicle from taking a safe 1415 maneuver. 1417 To identify malicious vehicles among vehicles, an authentication 1418 method may be required. A Vehicle Identification Number (VIN) and a 1419 user certificate (e.g., X.509 certificate [RFC5280]) along with an 1420 in-vehicle device's identifier generation can be used to efficiently 1421 authenticate a vehicle or its driver (having a user certificate) 1422 through a road infrastructure node (e.g., IP-RSU) connected to an 1423 authentication server in the vehicular cloud. This authentication 1424 can be used to identify the vehicle that will communicate with an 1425 infrastructure node or another vehicle. In the case where a vehicle 1426 has an internal network (called Moving Network) and elements in the 1427 network (e.g., in-vehicle devices and a user's mobile devices), as 1428 shown in Figure 2, the elements in the network need to be 1429 authenticated individually for safe authentication. Also, Transport 1430 Layer Security (TLS) certificates [RFC8446][RFC5280] can be used for 1431 an element's authentication to allow secure E2E vehicular 1432 communications between an element in a vehicle and another element in 1433 a server in a vehicular cloud, or between an element in a vehicle and 1434 another element in another vehicle. 1436 6.2. Security Threats in Mobility Management 1438 For mobility management, a malicious vehicle can construct multiple 1439 virtual bogus vehicles, and register them with IP-RSUs and MA. This 1440 registration makes the IP-RSUs and MA waste their resources. The IP- 1441 RSUs and MA need to determine whether a vehicle is genuine or bogus 1442 in mobility management. Also, the confidentiality of control packets 1443 and data packets among IP-RSUs and MA, the E2E paths (e.g., tunnels) 1444 need to be protected by secure communication channels. In addition, 1445 to prevent bogus IP-RSUs and MA from interfering with the IPv6 1446 mobility of vehicles, mutual authentication among them needs to be 1447 performed by certificates (e.g., TLS certificate). 1449 6.3. Other Threats 1451 For the setup of a secure channel over IPsec or TLS, the multihop V2I 1452 communications over DSRC or 5G V2X (or LTE V2X) is required in a 1453 highway. In this case, multiple intermediate vehicles as relay nodes 1454 can help forward association and authentication messages toward an 1455 IP-RSU (gNodeB, or eNodeB) connected to an authentication server in 1456 the vehicular cloud. In this kind of process, the authentication 1457 messages forwarded by each vehicle can be delayed or lost, which may 1458 increase the construction time of a connection or some vehicles may 1459 not be able to be authenticated. 1461 Even though vehicles can be authenticated with valid certificates by 1462 an authentication server in the vehicular cloud, the authenticated 1463 vehicles may harm other vehicles. To deal with this kind of security 1464 issue, for monitoring suspicious behaviors, vehicles' communication 1465 activities can be recorded in either a central way through a logging 1466 server (e.g., TCC) in the vehicular cloud or a distributed way (e.g., 1467 blockchain [Bitcoin]) along with other vehicles or infrastructure. 1468 To solve the issue ultimately, we need a solution where, without 1469 privacy breakage, vehicles may observe activities of each other to 1470 identify any misbehavior. Once identifying a misbehavior, a vehicle 1471 shall have a way to either isolate itself from others or isolate a 1472 suspicious vehicle by informing other vehicles. Alternatively, for 1473 completely secure vehicular networks, we shall embrace the concept of 1474 "zero-trust" for vehicles in which no vehicle is trustable and 1475 verifying every message is necessary. For doing so, we shall have an 1476 efficient zero-trust framework or mechanism for vehicular networks. 1478 For the non-repudiation of the harmful activities of malicious nodes, 1479 a blockchain technology can be used [Bitcoin]. Each message from a 1480 vehicle can be treated as a transaction and the neighboring vehicles 1481 can play the role of peers in a consensus method of a blockchain 1482 [Bitcoin] [Vehicular-BlockChain]. For a blockchain's efficient 1483 consensus in vehicular networks having fast moving vehicles, a new 1484 consensus algorithm needs to be developed or an existing consensus 1485 algorithm needs to be enhanced. 1487 To prevent an adversary from tracking a vehicle with its MAC address 1488 or IPv6 address, especially for a long-living transport-layer session 1489 (e.g., voice call over IP and video streaming service), a MAC address 1490 pseudonym needs to be provided to each vehicle; that is, each vehicle 1491 periodically updates its MAC address and its IPv6 address needs to be 1492 updated accordingly by the MAC address change [RFC4086][RFC8981]. 1493 Such an update of the MAC and IPv6 addresses should not interrupt the 1494 E2E communications between two vehicles (or between a vehicle and an 1495 IP-RSU) for a long-living transport-layer session. However, if this 1496 pseudonym is performed without strong E2E confidentiality (using 1497 either IPsec or TLS), there will be no privacy benefit from changing 1498 MAC and IPv6 addresses, because an adversary can observe the change 1499 of the MAC and IPv6 addresses and track the vehicle with those 1500 addresses. Thus, the MAC address pseudonym and the IPv6 address 1501 update should be performed with strong E2E confidentiality. 1503 7. IANA Considerations 1505 This document does not require any IANA actions. 1507 8. References 1508 8.1. Normative References 1510 [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast 1511 Listener Discovery (MLD) for IPv6", RFC 2710, 1512 DOI 10.17487/RFC2710, October 1999, 1513 . 1515 [RFC3626] Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link 1516 State Routing Protocol (OLSR)", RFC 3626, 1517 DOI 10.17487/RFC3626, October 2003, 1518 . 1520 [RFC3753] Manner, J., Ed. and M. Kojo, Ed., "Mobility Related 1521 Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004, 1522 . 1524 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1525 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1526 DOI 10.17487/RFC3810, June 2004, 1527 . 1529 [RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix 1530 Reserved for Documentation", RFC 3849, 1531 DOI 10.17487/RFC3849, July 2004, 1532 . 1534 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1535 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 1536 RFC 3963, DOI 10.17487/RFC3963, January 2005, 1537 . 1539 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1540 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1541 DOI 10.17487/RFC3971, March 2005, 1542 . 1544 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1545 "Randomness Requirements for Security", BCP 106, RFC 4086, 1546 DOI 10.17487/RFC4086, June 2005, 1547 . 1549 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1550 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1551 . 1553 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1554 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 1555 December 2005, . 1557 [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, 1558 DOI 10.17487/RFC4302, December 2005, 1559 . 1561 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 1562 RFC 4303, DOI 10.17487/RFC4303, December 2005, 1563 . 1565 [RFC4308] Hoffman, P., "Cryptographic Suites for IPsec", RFC 4308, 1566 DOI 10.17487/RFC4308, December 2005, 1567 . 1569 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1570 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1571 DOI 10.17487/RFC4861, September 2007, 1572 . 1574 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1575 Address Autoconfiguration", RFC 4862, 1576 DOI 10.17487/RFC4862, September 2007, 1577 . 1579 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1580 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1581 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1582 . 1584 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1585 Housley, R., and W. Polk, "Internet X.509 Public Key 1586 Infrastructure Certificate and Certificate Revocation List 1587 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1588 . 1590 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1591 Ed., "Control And Provisioning of Wireless Access Points 1592 (CAPWAP) Protocol Specification", RFC 5415, 1593 DOI 10.17487/RFC5415, March 2009, 1594 . 1596 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1597 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 1598 DOI 10.17487/RFC5881, June 2010, 1599 . 1601 [RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing 1602 Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889, 1603 September 2010, . 1605 [RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc 1606 Network (MANET) Neighborhood Discovery Protocol (NHDP)", 1607 RFC 6130, DOI 10.17487/RFC6130, April 2011, 1608 . 1610 [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, 1611 DOI 10.17487/RFC6250, May 2011, 1612 . 1614 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1615 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1616 2011, . 1618 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1619 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1620 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1621 Low-Power and Lossy Networks", RFC 6550, 1622 DOI 10.17487/RFC6550, March 2012, 1623 . 1625 [RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational 1626 Neighbor Discovery Problems", RFC 6583, 1627 DOI 10.17487/RFC6583, March 2012, 1628 . 1630 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1631 Bormann, "Neighbor Discovery Optimization for IPv6 over 1632 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1633 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1634 . 1636 [RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined 1637 Networking: A Perspective from within a Service Provider 1638 Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014, 1639 . 1641 [RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg, 1642 "The Optimized Link State Routing Protocol Version 2", 1643 RFC 7181, DOI 10.17487/RFC7181, April 2014, 1644 . 1646 [RFC7188] Dearlove, C. and T. Clausen, "Optimized Link State Routing 1647 Protocol Version 2 (OLSRv2) and MANET Neighborhood 1648 Discovery Protocol (NHDP) Extension TLVs", RFC 7188, 1649 DOI 10.17487/RFC7188, April 2014, 1650 . 1652 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 1653 Kivinen, "Internet Key Exchange Protocol Version 2 1654 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 1655 2014, . 1657 [RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J. 1658 Korhonen, "Requirements for Distributed Mobility 1659 Management", RFC 7333, DOI 10.17487/RFC7333, August 2014, 1660 . 1662 [RFC7429] Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and 1663 CJ. Bernardos, "Distributed Mobility Management: Current 1664 Practices and Gap Analysis", RFC 7429, 1665 DOI 10.17487/RFC7429, January 2015, 1666 . 1668 [RFC7466] Dearlove, C. and T. Clausen, "An Optimization for the 1669 Mobile Ad Hoc Network (MANET) Neighborhood Discovery 1670 Protocol (NHDP)", RFC 7466, DOI 10.17487/RFC7466, March 1671 2015, . 1673 [RFC7722] Dearlove, C. and T. Clausen, "Multi-Topology Extension for 1674 the Optimized Link State Routing Protocol Version 2 1675 (OLSRv2)", RFC 7722, DOI 10.17487/RFC7722, December 2015, 1676 . 1678 [RFC7779] Rogge, H. and E. Baccelli, "Directional Airtime Metric 1679 Based on Packet Sequence Numbers for Optimized Link State 1680 Routing Version 2 (OLSRv2)", RFC 7779, 1681 DOI 10.17487/RFC7779, April 2016, 1682 . 1684 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1685 Hosts in a Multi-Prefix Network", RFC 8028, 1686 DOI 10.17487/RFC8028, November 2016, 1687 . 1689 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 1690 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 1691 DOI 10.17487/RFC8175, June 2017, 1692 . 1694 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1695 (IPv6) Specification", STD 86, RFC 8200, 1696 DOI 10.17487/RFC8200, July 2017, 1697 . 1699 [RFC8218] Yi, J. and B. Parrein, "Multipath Extension for the 1700 Optimized Link State Routing Protocol Version 2 (OLSRv2)", 1701 RFC 8218, DOI 10.17487/RFC8218, August 2017, 1702 . 1704 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1705 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1706 . 1708 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1709 Perkins, "Registration Extensions for IPv6 over Low-Power 1710 Wireless Personal Area Network (6LoWPAN) Neighbor 1711 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1712 . 1714 [RFC8629] Cheng, B. and L. Berger, Ed., "Dynamic Link Exchange 1715 Protocol (DLEP) Multi-Hop Forwarding Extension", RFC 8629, 1716 DOI 10.17487/RFC8629, July 2019, 1717 . 1719 [RFC8651] Cheng, B., Wiggins, D., and L. Berger, Ed., "Dynamic Link 1720 Exchange Protocol (DLEP) Control-Plane-Based Pause 1721 Extension", RFC 8651, DOI 10.17487/RFC8651, October 2019, 1722 . 1724 [RFC8691] Benamar, N., Härri, J., Lee, J., and T. Ernst, "Basic 1725 Support for IPv6 Networks Operating Outside the Context of 1726 a Basic Service Set over IEEE Std 802.11", RFC 8691, 1727 DOI 10.17487/RFC8691, December 2019, 1728 . 1730 [RFC8703] Taylor, R. and S. Ratliff, "Dynamic Link Exchange Protocol 1731 (DLEP) Link Identifier Extension", RFC 8703, 1732 DOI 10.17487/RFC8703, February 2020, 1733 . 1735 [RFC8757] Cheng, B. and L. Berger, Ed., "Dynamic Link Exchange 1736 Protocol (DLEP) Latency Range Extension", RFC 8757, 1737 DOI 10.17487/RFC8757, March 2020, 1738 . 1740 [RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik, 1741 "Address-Protected Neighbor Discovery for Low-Power and 1742 Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November 1743 2020, . 1745 [RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves, 1746 "Temporary Address Extensions for Stateless Address 1747 Autoconfiguration in IPv6", RFC 8981, 1748 DOI 10.17487/RFC8981, February 2021, 1749 . 1751 [RFC9119] Perkins, C., McBride, M., Stanley, D., Kumari, W., and JC. 1752 Zúñiga, "Multicast Considerations over IEEE 802 Wireless 1753 Media", RFC 9119, DOI 10.17487/RFC9119, October 2021, 1754 . 1756 8.2. Informative References 1758 [RFC6959] McPherson, D., Baker, F., and J. Halpern, "Source Address 1759 Validation Improvement (SAVI) Threat Scope", RFC 6959, 1760 DOI 10.17487/RFC6959, May 2013, 1761 . 1763 [I-D.ietf-intarea-ippl] 1764 Nordmark, E., "IP over Intentionally Partially Partitioned 1765 Links", Work in Progress, Internet-Draft, draft-ietf- 1766 intarea-ippl-00, 30 March 2017, 1767 . 1770 [I-D.ietf-lisp-rfc6830bis] 1771 Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. 1772 Cabellos, "The Locator/ID Separation Protocol (LISP)", 1773 Work in Progress, Internet-Draft, draft-ietf-lisp- 1774 rfc6830bis-36, 18 November 2020, 1775 . 1778 [I-D.templin-6man-aero] 1779 Templin, F. L., "Automatic Extended Route Optimization 1780 (AERO)", Work in Progress, Internet-Draft, draft-templin- 1781 6man-aero-38, 31 December 2021, 1782 . 1785 [I-D.templin-6man-omni] 1786 Templin, F. L. and T. Whyman, "Transmission of IP Packets 1787 over Overlay Multilink Network (OMNI) Interfaces", Work in 1788 Progress, Internet-Draft, draft-templin-6man-omni-52, 31 1789 December 2021, . 1792 [I-D.templin-ipwave-uam-its] 1793 Templin, F. L., "Urban Air Mobility Implications for 1794 Intelligent Transportation Systems", Work in Progress, 1795 Internet-Draft, draft-templin-ipwave-uam-its-04, 4 January 1796 2021, . 1799 [I-D.ietf-dmm-fpc-cpdp] 1800 Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S., 1801 Moses, D., and C. E. Perkins, "Protocol for Forwarding 1802 Policy Configuration (FPC) in DMM", Work in Progress, 1803 Internet-Draft, draft-ietf-dmm-fpc-cpdp-14, 22 September 1804 2020, . 1807 [I-D.thubert-6man-ipv6-over-wireless] 1808 Thubert, P., "IPv6 Neighbor Discovery on Wireless 1809 Networks", Work in Progress, Internet-Draft, draft- 1810 thubert-6man-ipv6-over-wireless-11, 15 December 2021, 1811 . 1814 [DSRC] ASTM International, "Standard Specification for 1815 Telecommunications and Information Exchange Between 1816 Roadside and Vehicle Systems - 5 GHz Band Dedicated Short 1817 Range Communications (DSRC) Medium Access Control (MAC) 1818 and Physical Layer (PHY) Specifications", 1819 ASTM E2213-03(2010), October 2010. 1821 [EU-2008-671-EC] 1822 European Union, "Commission Decision of 5 August 2008 on 1823 the Harmonised Use of Radio Spectrum in the 5875 - 5905 1824 MHz Frequency Band for Safety-related Applications of 1825 Intelligent Transport Systems (ITS)", EU 2008/671/EC, 1826 August 2008. 1828 [IEEE-802.11p] 1829 "Part 11: Wireless LAN Medium Access Control (MAC) and 1830 Physical Layer (PHY) Specifications - Amendment 6: 1831 Wireless Access in Vehicular Environments", IEEE Std 1832 802.11p-2010, June 2010. 1834 [IEEE-802.11-OCB] 1835 "Part 11: Wireless LAN Medium Access Control (MAC) and 1836 Physical Layer (PHY) Specifications", IEEE Std 1837 802.11-2016, December 2016. 1839 [WAVE-1609.0] 1840 IEEE 1609 Working Group, "IEEE Guide for Wireless Access 1841 in Vehicular Environments (WAVE) - Architecture", IEEE Std 1842 1609.0-2013, March 2014. 1844 [WAVE-1609.2] 1845 IEEE 1609 Working Group, "IEEE Standard for Wireless 1846 Access in Vehicular Environments - Security Services for 1847 Applications and Management Messages", IEEE Std 1848 1609.2-2016, March 2016. 1850 [WAVE-1609.3] 1851 IEEE 1609 Working Group, "IEEE Standard for Wireless 1852 Access in Vehicular Environments (WAVE) - Networking 1853 Services", IEEE Std 1609.3-2016, April 2016. 1855 [WAVE-1609.4] 1856 IEEE 1609 Working Group, "IEEE Standard for Wireless 1857 Access in Vehicular Environments (WAVE) - Multi-Channel 1858 Operation", IEEE Std 1609.4-2016, March 2016. 1860 [ISO-ITS-IPv6] 1861 ISO/TC 204, "Intelligent Transport Systems - 1862 Communications Access for Land Mobiles (CALM) - IPv6 1863 Networking", ISO 21210:2012, June 2012. 1865 [ISO-ITS-IPv6-AMD1] 1866 ISO/TC 204, "Intelligent Transport Systems - 1867 Communications Access for Land Mobiles (CALM) - IPv6 1868 Networking - Amendment 1", ISO 21210:2012/AMD 1:2017, 1869 September 2017. 1871 [TS-23.285-3GPP] 1872 3GPP, "Architecture Enhancements for V2X Services", 3GPP 1873 TS 23.285/Version 16.2.0, December 2019. 1875 [TR-22.886-3GPP] 1876 3GPP, "Study on Enhancement of 3GPP Support for 5G V2X 1877 Services", 3GPP TR 22.886/Version 16.2.0, December 2018. 1879 [TS-23.287-3GPP] 1880 3GPP, "Architecture Enhancements for 5G System (5GS) to 1881 Support Vehicle-to-Everything (V2X) Services", 3GPP 1882 TS 23.287/Version 16.2.0, March 2020. 1884 [VIP-WAVE] Cespedes, S., Lu, N., and X. Shen, "VIP-WAVE: On the 1885 Feasibility of IP Communications in 802.11p Vehicular 1886 Networks", IEEE Transactions on Intelligent Transportation 1887 Systems, vol. 14, no. 1, March 2013. 1889 [Identity-Management] 1890 Wetterwald, M., Hrizi, F., and P. Cataldi, "Cross-layer 1891 Identities Management in ITS Stations", The 10th 1892 International Conference on ITS Telecommunications, 1893 November 2010. 1895 [SAINT] Jeong, J., Jeong, H., Lee, E., Oh, T., and D. Du, "SAINT: 1896 Self-Adaptive Interactive Navigation Tool for Cloud-Based 1897 Vehicular Traffic Optimization", IEEE Transactions on 1898 Vehicular Technology, Vol. 65, No. 6, June 2016. 1900 [SAINTplus] 1901 Shen, Y., Lee, J., Jeong, H., Jeong, J., Lee, E., and D. 1902 Du, "SAINT+: Self-Adaptive Interactive Navigation Tool+ 1903 for Emergency Service Delivery Optimization", 1904 IEEE Transactions on Intelligent Transportation Systems, 1905 June 2017. 1907 [SANA] Hwang, T. and J. Jeong, "SANA: Safety-Aware Navigation 1908 Application for Pedestrian Protection in Vehicular 1909 Networks", Springer Lecture Notes in Computer Science 1910 (LNCS), Vol. 9502, December 2015. 1912 [CASD] Shen, Y., Jeong, J., Oh, T., and S. Son, "CASD: A 1913 Framework of Context-Awareness Safety Driving in Vehicular 1914 Networks", International Workshop on Device Centric Cloud 1915 (DC2), March 2016. 1917 [CA-Cruise-Control] 1918 California Partners for Advanced Transportation Technology 1919 (PATH), "Cooperative Adaptive Cruise Control", Available: 1920 https://path.berkeley.edu/research/connected-and- 1921 automated-vehicles/cooperative-adaptive-cruise-control, 1922 2022. 1924 [Truck-Platooning] 1925 California Partners for Advanced Transportation Technology 1926 (PATH), "Automated Truck Platooning", Available: 1927 https://path.berkeley.edu/research/connected-and- 1928 automated-vehicles/truck-platooning, 2022. 1930 [FirstNet] U.S. National Telecommunications and Information 1931 Administration (NTIA), "First Responder Network Authority 1932 (FirstNet)", Available: https://www.firstnet.gov/, 2022. 1934 [FirstNet-Report] 1935 First Responder Network Authority, "FY 2017: ANNUAL REPORT 1936 TO CONGRESS, Advancing Public Safety Broadband 1937 Communications", FirstNet FY 2017, December 2017. 1939 [SignalGuru] 1940 Koukoumidis, E., Peh, L., and M. Martonosi, "SignalGuru: 1941 Leveraging Mobile Phones for Collaborative Traffic Signal 1942 Schedule Advisory", ACM MobiSys, June 2011. 1944 [Fuel-Efficient] 1945 van de Hoef, S., H. Johansson, K., and D. V. Dimarogonas, 1946 "Fuel-Efficient En Route Formation of Truck Platoons", 1947 IEEE Transactions on Intelligent Transportation Systems, 1948 January 2018. 1950 [Automotive-Sensing] 1951 Choi, J., Va, V., Gonzalez-Prelcic, N., Daniels, R., R. 1952 Bhat, C., and R. W. Heath, "Millimeter-Wave Vehicular 1953 Communication to Support Massive Automotive Sensing", 1954 IEEE Communications Magazine, December 2016. 1956 [NHTSA-ACAS-Report] 1957 National Highway Traffic Safety Administration (NHTSA), 1958 "Final Report of Automotive Collision Avoidance Systems 1959 (ACAS) Program", DOT HS 809 080, August 2000. 1961 [CBDN] Kim, J., Kim, S., Jeong, J., Kim, H., Park, J., and T. 1962 Kim, "CBDN: Cloud-Based Drone Navigation for Efficient 1963 Battery Charging in Drone Networks", IEEE Transactions on 1964 Intelligent Transportation Systems, November 2019. 1966 [In-Car-Network] 1967 Lim, H., Volker, L., and D. Herrscher, "Challenges in a 1968 Future IP/Ethernet-based In-Car Network for Real-Time 1969 Applications", ACM/EDAC/IEEE Design Automation Conference 1970 (DAC), June 2011. 1972 [Scrambler-Attack] 1973 Bloessl, B., Sommer, C., Dressier, F., and D. Eckhoff, 1974 "The Scrambler Attack: A Robust Physical Layer Attack on 1975 Location Privacy in Vehicular Networks", IEEE 2015 1976 International Conference on Computing, Networking and 1977 Communications (ICNC), February 2015. 1979 [Bitcoin] Nakamoto, S., "Bitcoin: A Peer-to-Peer Electronic Cash 1980 System", URL: https://bitcoin.org/bitcoin.pdf, May 2009. 1982 [Vehicular-BlockChain] 1983 Dorri, A., Steger, M., Kanhere, S., and R. Jurdak, 1984 "BlockChain: A Distributed Solution to Automotive Security 1985 and Privacy", IEEE Communications Magazine, Vol. 55, No. 1986 12, December 2017. 1988 Appendix A. Support of Multiple Radio Technologies for V2V 1990 Vehicular networks may consist of multiple radio technologies such as 1991 DSRC and 5G V2X. Although a Layer-2 solution can provide a support 1992 for multihop communications in vehicular networks, the scalability 1993 issue related to multihop forwarding still remains when vehicles need 1994 to disseminate or forward packets toward multihop-away destinations. 1995 In addition, the IPv6-based approach for V2V as a network layer 1996 protocol can accommodate multiple radio technologies as MAC 1997 protocols, such as DSRC and 5G V2X. Therefore, the existing IPv6 1998 protocol can be augmented through the addition of a virtual interface 1999 (e.g., Overlay Multilink Network (OMNI) Interface 2000 [I-D.templin-6man-omni]) and/or protocol changes in order to support 2001 both wireless single-hop/multihop V2V communications and multiple 2002 radio technologies in vehicular networks. In such a way, vehicles 2003 can communicate with each other by V2V communications to share either 2004 an emergency situation or road hazard information in a highway having 2005 multiple kinds of radio technologies. 2007 Appendix B. Support of Multihop V2X Networking 2009 The multihop V2X networking can be supported by RPL (IPv6 Routing 2010 Protocol for Low-Power and Lossy Networks) [RFC6550] and Overlay 2011 Multilink Network Interface (OMNI) [I-D.templin-6man-omni]. 2013 RPL defines an IPv6 routing protocol for low-power and lossy networks 2014 (LLN), mostly designed for home automation routing, building 2015 automation routing, industrial routing, and urban LLN routing. It 2016 uses a Destination-Oriented Directed Acyclic Graph (DODAG) to 2017 construct routing paths for hosts (e.g., IoT devices) in a network. 2018 The DODAG uses an objective function (OF) for route selection and 2019 optimization within the network. A user can use different routing 2020 metrics to define an OF for a specific scenario. RPL supports 2021 multipoint-to-point, point-to-multipoint, and point-to-point traffic, 2022 and the major traffic flow is the multipoint-to-point traffic. For 2023 example, in a highway scenario, a vehicle may not access an RSU 2024 directly because of the distance of the DSRC coverage (up to 1 km). 2025 In this case, the RPL can be extended to support a multihop V2I since 2026 a vehicle can take advantage of other vehicles as relay nodes to 2027 reach the RSU. Also, RPL can be extended to support both multihop 2028 V2V and V2X in the similar way. 2030 RPL is primarily designed to minimize the control plane activity, 2031 which is the relative amount of routing protocol exchanges versus 2032 data traffic; this approach is beneficial for situations where the 2033 power and bandwidth are scarce (e.g., an IoT LLN where RPL is 2034 typically used today), but also in situations of high relative 2035 mobility between the nodes in the network (also known as swarming, 2036 e.g., within a variable set of vehicles with a similar global motion, 2037 or a variable set of drones flying toward the same direction). 2039 To reduce the routing exchanges, RPL leverages a Distance Vector (DV) 2040 approach, which does not need a global knowledge of the topology, and 2041 only optimizes the routes to and from the root, allowing Peer-to-Peer 2042 (P2P) paths to be stretched. Although RPL installs its routes 2043 proactively, it only maintains them lazily, that is, in reaction to 2044 actual traffic, or as a slow background activity. Additionally, RPL 2045 leverages the concept of an objective function (called OF), which 2046 allows to adapt the activity of the routing protocol to use cases, 2047 e.g., type, speed, and quality of the radios. RPL does not need 2048 converge, and provides connectivity to most nodes most of the time. 2049 The default route toward the root is maintained aggressively and may 2050 change while a packet progresses without causing loops, so the packet 2051 will still reach the root. There are two modes for routing in RPL 2052 such as non-storing mode and storing mode. In non-storing mode, a 2053 node inside the mesh/swarm that changes its point(s) of attachment to 2054 the graph informs the root with a single unicast packet flowing along 2055 the default route, and the connectivity is restored immediately; this 2056 mode is preferable for use cases where Internet connectivity is 2057 dominant. On the other hand, in storing mode, the routing stretch is 2058 reduced, for a better P2P connectivity, while the Internet 2059 connectivity is restored more slowly, during the time for the DV 2060 operation to operate hop-by-hop. While an RPL topology can quickly 2061 scale up and down and fits the needs of mobility of vehicles, the 2062 total performance of the system will also depend on how quickly a 2063 node can form an address, join the mesh (including Authentication, 2064 Authorization, and Accounting (AAA)), and manage its global mobility 2065 to become reachable from another node outside the mesh. 2067 OMNI defines a protocol for the transmission of IPv6 packets over 2068 Overlay Multilink Network Interfaces that are virtual interfaces 2069 governing multiple physical network interfaces. OMNI supports 2070 multihop V2V communication between vehicles in multiple forwarding 2071 hops via intermediate vehicles with OMNI links. It also supports 2072 multihop V2I communication between a vehicle and an infrastructure 2073 access point by multihop V2V communication. The OMNI interface 2074 supports an NBMA link model where multihop V2V and V2I communications 2075 use each mobile node's ULAs without need for any DAD or MLD 2076 Messaging. 2078 Appendix C. Support of Mobility Management for V2I 2080 The seamless application communication between two vehicles or 2081 between a vehicle and an infrastructure node requires mobility 2082 management in vehicular networks. The mobility management schemes 2083 include a host-based mobility scheme, network-based mobility scheme, 2084 and software-defined networking scheme. 2086 In the host-based mobility scheme (e.g., MIPv6), an IP-RSU plays a 2087 role of a home agent. On the other hand, in the network-based 2088 mobility scheme (e.g., PMIPv6, an MA plays a role of a mobility 2089 management controller such as a Local Mobility Anchor (LMA) in 2090 PMIPv6, which also serves vehicles as a home agent, and an IP-RSU 2091 plays a role of an access router such as a Mobile Access Gateway 2092 (MAG) in PMIPv6 [RFC5213]. The host-based mobility scheme needs 2093 client functionality in IPv6 stack of a vehicle as a mobile node for 2094 mobility signaling message exchange between the vehicle and home 2095 agent. On the other hand, the network-based mobility scheme does not 2096 need such a client functionality for a vehicle because the network 2097 infrastructure node (e.g., MAG in PMIPv6) as a proxy mobility agent 2098 handles the mobility signaling message exchange with the home agent 2099 (e.g., LMA in PMIPv6) for the sake of the vehicle. 2101 There are a scalability issue and a route optimization issue in the 2102 network-based mobility scheme (e.g., PMIPv6) when an MA covers a 2103 large vehicular network governing many IP-RSUs. In this case, a 2104 distributed mobility scheme (e.g., DMM [RFC7429]) can mitigate the 2105 scalability issue by distributing multiple MAs in the vehicular 2106 network such that they are positioned closer to vehicles for route 2107 optimization and bottleneck mitigation in a central MA in the 2108 network-based mobility scheme. All these mobility approaches (i.e., 2109 a host-based mobility scheme, network-based mobility scheme, and 2110 distributed mobility scheme) and a hybrid approach of a combination 2111 of them need to provide an efficient mobility service to vehicles 2112 moving fast and moving along with the relatively predictable 2113 trajectories along the roadways. 2115 In vehicular networks, the control plane can be separated from the 2116 data plane for efficient mobility management and data forwarding by 2117 using the concept of Software-Defined Networking (SDN) 2118 [RFC7149][I-D.ietf-dmm-fpc-cpdp]. Note that Forwarding Policy 2119 Configuration (FPC) in [I-D.ietf-dmm-fpc-cpdp], which is a flexible 2120 mobility management system, can manage the separation of data-plane 2121 and control-plane in DMM. In SDN, the control plane and data plane 2122 are separated for the efficient management of forwarding elements 2123 (e.g., switches and routers) where an SDN controller configures the 2124 forwarding elements in a centralized way and they perform packet 2125 forwarding according to their forwarding tables that are configured 2126 by the SDN controller. An MA as an SDN controller needs to 2127 efficiently configure and monitor its IP-RSUs and vehicles for 2128 mobility management, location management, and security services. 2130 Appendix D. Acknowledgments 2132 This work was supported by Institute of Information & Communications 2133 Technology Planning & Evaluation (IITP) grant funded by the Korea 2134 MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based 2135 Security Intelligence Technology Development for the Customized 2136 Security Service Provisioning). 2138 This work was supported in part by the MSIT, Korea, under the ITRC 2139 (Information Technology Research Center) support program (IITP- 2140 2021-2017-0-01633) supervised by the IITP. 2142 This work was supported in part by the IITP (2020-0-00395, Standard 2143 Development of Blockchain based Network Management Automation 2144 Technology). 2146 This work was supported in part by the French research project 2147 DataTweet (ANR-13-INFR-0008) and in part by the HIGHTS project funded 2148 by the European Commission I (636537-H2020). 2150 This work was supported in part by the Cisco University Research 2151 Program Fund, Grant # 2019-199458 (3696), and by ANID Chile Basal 2152 Project FB0008. 2154 Appendix E. Contributors 2156 This document is a group work of IPWAVE working group, greatly 2157 benefiting from inputs and texts by Rex Buddenberg (Naval 2158 Postgraduate School), Thierry Ernst (YoGoKo), Bokor Laszlo (Budapest 2159 University of Technology and Economics), Jose Santa Lozanoi 2160 (Universidad of Murcia), Richard Roy (MIT), Francois Simon (Pilot), 2161 Sri Gundavelli (Cisco), Erik Nordmark, Dirk von Hugo (Deutsche 2162 Telekom), Pascal Thubert (Cisco), Carlos Bernardos (UC3M), Russ 2163 Housley (Vigil Security), Suresh Krishnan (Kaloom), Nancy Cam-Winget 2164 (Cisco), Fred L. Templin (The Boeing Company), Jung-Soo Park (ETRI), 2165 Zeungil (Ben) Kim (Hyundai Motors), Kyoungjae Sun (Soongsil 2166 University), Zhiwei Yan (CNNIC), YongJoon Joe (LSware), Peter E. Yee 2167 (Akayla), and Erik Kline. The authors sincerely appreciate their 2168 contributions. 2170 The following are co-authors of this document: 2172 Nabil Benamar - 2174 Department of Computer Sciences, High School of Technology of Meknes, 2175 Moulay Ismail University, Morocco, Phone: +212 6 70 83 22 36, EMail: 2176 benamar73@gmail.com 2178 Sandra Cespedes - 2180 NIC Chile Research Labs, Universidad de Chile, Av. Blanco Encalada 2181 1975, Santiago, Chile, Phone: +56 2 29784093, EMail: 2182 scespede@niclabs.cl 2184 Jerome Haerri - 2186 Communication Systems Department, EURECOM, Sophia-Antipolis, France, 2187 Phone: +33 4 93 00 81 34, EMail: jerome.haerri@eurecom.fr 2189 Dapeng Liu - 2191 Alibaba, Beijing, Beijing 100022, China, Phone: +86 13911788933, 2192 EMail: max.ldp@alibaba-inc.com 2194 Tae (Tom) Oh - 2196 Department of Information Sciences and Technologies, Rochester 2197 Institute of Technology, One Lomb Memorial Drive, Rochester, NY 2198 14623-5603, USA, Phone: +1 585 475 7642, EMail: Tom.Oh@rit.edu 2200 Charles E. Perkins - 2201 Futurewei Inc., 2330 Central Expressway, Santa Clara, CA 95050, USA, 2202 Phone: +1 408 330 4586, EMail: charliep@computer.org 2204 Alexandre Petrescu - 2206 CEA, LIST, CEA Saclay, Gif-sur-Yvette, Ile-de-France 91190, France, 2207 Phone: +33169089223, EMail: Alexandre.Petrescu@cea.fr 2209 Yiwen Chris Shen - 2211 Department of Computer Science & Engineering, Sungkyunkwan 2212 University, 2066 Seobu-Ro, Jangan-Gu, Suwon, Gyeonggi-Do 16419, 2213 Republic of Korea, Phone: +82 31 299 4106, Fax: +82 31 290 7996, 2214 EMail: chrisshen@skku.edu, URI: https://chrisshen.github.io 2216 Michelle Wetterwald - 2218 FBConsulting, 21, Route de Luxembourg, Wasserbillig, Luxembourg 2219 L-6633, Luxembourg, EMail: Michelle.Wetterwald@gmail.com 2221 Author's Address 2223 Jaehoon (Paul) Jeong (editor) 2224 Department of Computer Science and Engineering 2225 Sungkyunkwan University 2226 2066 Seobu-Ro, Jangan-Gu 2227 Suwon 2228 Gyeonggi-Do 2229 16419 2230 Republic of Korea 2231 Phone: +82 31 299 4957 2232 Email: pauljeong@skku.edu 2233 URI: http://iotlab.skku.edu/people-jaehoon-jeong.php