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Checking references for intended status: Informational ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 4941 (Obsoleted by RFC 8981) == Outdated reference: A later version (-38) exists of draft-ietf-lisp-rfc6830bis-36 == Outdated reference: A later version (-74) exists of draft-templin-6man-omni-41 == Outdated reference: A later version (-15) exists of draft-thubert-6man-ipv6-over-wireless-09 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--).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 2 September 2021 5 Expires: 6 March 2022 7 IPv6 Wireless Access in Vehicular Environments (IPWAVE): Problem 8 Statement and Use Cases 9 draft-ietf-ipwave-vehicular-networking-23 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 6 March 2022. 42 Copyright Notice 44 Copyright (c) 2021 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 Simplified BSD License text 53 as described in Section 4.e of the Trust Legal Provisions and are 54 provided without warranty as described in the Simplified 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 . . . . . . . . . . . . . 14 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 . . . . . . . . . . . . . . . . . 39 82 Appendix A. Support of Multiple Radio Technologies for V2V . . . 44 83 Appendix B. Support of Multihop V2X Networking . . . . . . . . . 45 84 Appendix C. Support of Mobility Management for V2I . . . . . . . 46 85 Appendix D. Acknowledgments . . . . . . . . . . . . . . . . . . 47 86 Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 48 87 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 49 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 [RFC6830BIS], and Asymmetric Extended Route Optimization (AERO) 131 [RFC6706BIS]). In addition, ISO has approved a standard specifying 132 the IPv6 network protocols and services to be used for Communications 133 Access for Land Mobiles (CALM) [ISO-ITS-IPv6][ISO-ITS-IPv6-AMD1]. 135 This document describes use cases and a problem statement about 136 IPv6-based vehicular networking for ITS, which is named IPv6 Wireless 137 Access in Vehicular Environments (IPWAVE). First, it introduces the 138 use cases for using V2V, V2I, and V2X networking in ITS. Next, for 139 IPv6-based vehicular networks, it makes a gap analysis of current 140 IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management, 141 and Security & Privacy), and then enumerates requirements for the 142 extensions of those IPv6 protocols, which are tailored to IPv6-based 143 vehicular networking. Thus, this document is intended to motivate 144 development of key protocols for IPWAVE. 146 2. Terminology 148 This document uses the terminology described in [RFC8691]. In 149 addition, the following terms are defined below: 151 * Class-Based Safety Plan: A vehicle can make a safety plan by 152 classifying the surrounding vehicles into different groups for 153 safety purposes according to the geometrical relationship among 154 them. The vehicle groups can be classified as Line-of-Sight 155 Unsafe, Non-Line-of-Sight Unsafe, and Safe groups [CASD]. 157 * Context-Awareness: A vehicle can be aware of spatial-temporal 158 mobility information (e.g., position, speed, direction, and 159 acceleration/deceleration) of surrounding vehicles for both safety 160 and non-safety uses through sensing or communication [CASD]. 162 * DMM: "Distributed Mobility Management" [RFC7333][RFC7429]. 164 * Edge Computing (EC): It is the local computing near an access 165 network (i.e., edge network) for the sake of vehicles and 166 pedestrians. 168 * Edge Computing Device (ECD): It is a computing device (or server) 169 for edge computing for the sake of vehicles and pedestrians. 171 * Edge Network (EN): It is an access network that has an IP-RSU for 172 wireless communication with other vehicles having an IP-OBU and 173 wired communication with other network devices (e.g., routers, IP- 174 RSUs, ECDs, servers, and MA). It may have a Global Positioning 175 System (GPS) radio receiver for its position recognition and the 176 localization service for the sake of vehicles. 178 * IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a 179 computer situated in a vehicle (e.g., car, bicycle, autobike, 180 motor cycle, and a similar one) and a device (e.g., smartphone and 181 Internet-of-Things (IoT) device). It has at least one IP 182 interface that runs in IEEE 802.11-OCB and has an "OBU" 183 transceiver. Also, it may have an IP interface that runs in 184 Cellular V2X (C-V2X) [TS-23.285-3GPP] 185 [TR-22.886-3GPP][TS-23.287-3GPP]. It can play a role of a router 186 connecting multiple computers (or in-vehicle devices) inside a 187 vehicle. See the definition of the term "OBU" in [RFC8691]. 189 * IP-RSU: "IP Roadside Unit": An IP-RSU is situated along the road. 190 It has at least two distinct IP-enabled interfaces. The wireless 191 PHY/MAC layer of at least one of its IP-enabled interfaces is 192 configured to operate in 802.11-OCB mode. An IP-RSU communicates 193 with the IP-OBU over an 802.11 wireless link operating in OCB 194 mode. Also, it may have an IP interface that runs in C-V2X along 195 with an "RSU" transceiver. An IP-RSU is similar to an Access 196 Network Router (ANR), defined in [RFC3753], and a Wireless 197 Termination Point (WTP), defined in [RFC5415]. See the definition 198 of the term "RSU" in [RFC8691]. 200 * LiDAR: "Light Detection and Ranging". It is a scanning device to 201 measure a distance to an object by emitting pulsed laser light and 202 measuring the reflected pulsed light. 204 * Mobility Anchor (MA): A node that maintains IPv6 addresses and 205 mobility information of vehicles in a road network to support 206 their IPv6 address autoconfiguration and mobility management with 207 a binding table. An MA has End-to-End (E2E) connections (e.g., 208 tunnels) with IP-RSUs under its control for the address 209 autoconfiguration and mobility management of the vehicles. This 210 MA is similar to a Local Mobility Anchor (LMA) in PMIPv6 [RFC5213] 211 for network-based mobility management. 213 * OCB: "Outside the Context of a Basic Service Set - BSS". It is a 214 mode of operation in which a Station (STA) is not a member of a 215 BSS and does not utilize IEEE Std 802.11 authentication, 216 association, or data confidentiality [IEEE-802.11-OCB]. 218 * 802.11-OCB: It refers to the mode specified in IEEE Std 219 802.11-2016 [IEEE-802.11-OCB] when the MIB attribute 220 dot11OCBActivited is 'true'. 222 * Platooning: Moving vehicles can be grouped together to reduce air- 223 resistance for energy efficiency and reduce the number of drivers 224 such that only the leading vehicle has a driver, and the other 225 vehicles are autonomous vehicles without a driver and closely 226 follow the leading vehicle [Truck-Platooning]. 228 * Traffic Control Center (TCC): A system that manages road 229 infrastructure nodes (e.g., IP-RSUs, MAs, traffic signals, and 230 loop detectors), and also maintains vehicular traffic statistics 231 (e.g., average vehicle speed and vehicle inter-arrival time per 232 road segment) and vehicle information (e.g., a vehicle's 233 identifier, position, direction, speed, and trajectory as a 234 navigation path). TCC is part of a vehicular cloud for vehicular 235 networks. 237 * Vehicle: A Vehicle in this document is a node that has an IP-OBU 238 for wireless communication with other vehicles and IP-RSUs. It 239 has a GPS radio navigation receiver for efficient navigation. Any 240 device having an IP-OBU and a GPS receiver (e.g., smartphone and 241 tablet PC) can be regarded as a vehicle in this document. 243 * Vehicular Ad Hoc Network (VANET): A network that consists of 244 vehicles interconnected by wireless communication. Two vehicles 245 in a VANET can communicate with each other using other vehicles as 246 relays even where they are out of one-hop wireless communication 247 range. 249 * Vehicular Cloud: A cloud infrastructure for vehicular networks, 250 having compute nodes, storage nodes, and network forwarding 251 elements (e.g., switch and router). 253 * V2D: "Vehicle to Device". It is the wireless communication 254 between a vehicle and a device (e.g., smartphone and IoT device). 256 * V2I2D: "Vehicle to Infrastructure to Device". It is the wireless 257 communication between a vehicle and a device (e.g., smartphone and 258 IoT device) via an infrastructure node (e.g., IP-RSU). 260 * V2I2V: "Vehicle to Infrastructure to Vehicle". It is the wireless 261 communication between a vehicle and another vehicle via an 262 infrastructure node (e.g., IP-RSU). 264 * V2I2X: "Vehicle to Infrastructure to Everything". It is the 265 wireless communication between a vehicle and another entity (e.g., 266 vehicle, smartphone, and IoT device) via an infrastructure node 267 (e.g., IP-RSU). 269 * V2X: "Vehicle to Everything". It is the wireless communication 270 between a vehicle and any entity (e.g., vehicle, infrastructure 271 node, smartphone, and IoT device), including V2V, V2I, and V2D. 273 * VIP: "Vehicular Internet Protocol". It is an IPv6 extension for 274 vehicular networks including V2V, V2I, and V2X. 276 * VMM: "Vehicular Mobility Management". It is an IPv6-based 277 mobility management for vehicular networks. 279 * VND: "Vehicular Neighbor Discovery". It is an IPv6 ND extension 280 for vehicular networks. 282 * VSP: "Vehicular Security and Privacy". It is an IPv6-based 283 security and privacy for vehicular networks. 285 * WAVE: "Wireless Access in Vehicular Environments" [WAVE-1609.0]. 287 3. Use Cases 289 This section explains use cases of V2V, V2I, and V2X networking. The 290 use cases of the V2X networking exclude the ones of the V2V and V2I 291 networking, but include Vehicle-to-Pedestrian (V2P) and Vehicle-to- 292 Device (V2D). 294 IP is widely used among popular end-user devices (e.g., smartphone 295 and tablet) in the Internet. Applications (e.g., navigator 296 application) for those devices can be extended such that the V2V use 297 cases in this section can work with IPv6 as a network layer protocol 298 and IEEE 802.11-OCB as a link layer protocol. In addition, IPv6 299 security needs to be extended to support those V2V use cases in a 300 safe, secure, privacy-preserving way. 302 The use cases presented in this section serve as the description and 303 motivation for the need to extend IPv6 and its protocols to 304 facilitate "Vehicular IPv6". Section 5 summarizes the overall 305 problem statement and IPv6 requirements. Note that the adjective 306 "Vehicular" in this document is used to represent extensions of 307 existing protocols such as IPv6 Neighbor Discovery, IPv6 Mobility 308 Management (e.g., PMIPv6 [RFC5213] and DMM [RFC7429]), and IPv6 309 Security and Privacy Mechanisms rather than new "vehicular-specific" 310 functions. 312 3.1. V2V 314 The use cases of V2V networking discussed in this section include 316 * Context-aware navigation for safe driving and collision avoidance; 318 * Cooperative adaptive cruise control in a roadway; 320 * Platooning in a highway; 322 * Cooperative environment sensing; 324 * Collision avoidance service of end systems of Urban Air Mobility 325 (UAM) [UAM-ITS]. 327 These five techniques will be important elements for autonomous 328 vehicles, which may be either terrestrial vehicles or UAM end 329 systems. 331 Context-Aware Safety Driving (CASD) navigator [CASD] can help drivers 332 to drive safely by alerting them to dangerous obstacles and 333 situations. That is, a CASD navigator displays obstacles or 334 neighboring vehicles relevant to possible collisions in real-time 335 through V2V networking. CASD provides vehicles with a class-based 336 automatic safety action plan, which considers three situations, 337 namely, the Line-of-Sight unsafe, Non-Line-of-Sight unsafe, and safe 338 situations. This action plan can be put into action among multiple 339 vehicles using V2V networking. 341 Cooperative Adaptive Cruise Control (CACC) [CA-Cruise-Control] helps 342 individual vehicles to adapt their speed autonomously through V2V 343 communication among vehicles according to the mobility of their 344 predecessor and successor vehicles in an urban roadway or a highway. 345 Thus, CACC can help adjacent vehicles to efficiently adjust their 346 speed in an interactive way through V2V networking in order to avoid 347 a collision. 349 Platooning [Truck-Platooning] allows a series (or group) of vehicles 350 (e.g., trucks) to follow each other very closely. Trucks can use V2V 351 communication in addition to forward sensors in order to maintain 352 constant clearance between two consecutive vehicles at very short 353 gaps (from 3 meters to 10 meters). Platooning can maximize the 354 throughput of vehicular traffic in a highway and reduce the gas 355 consumption because the leading vehicle can help the following 356 vehicles to experience less air resistance. 358 Cooperative-environment-sensing use cases suggest that vehicles can 359 share environmental information (e.g., air pollution, hazards/ 360 obstacles, slippery areas by snow or rain, road accidents, traffic 361 congestion, and driving behaviors of neighboring vehicles) from 362 various vehicle-mounted sensors, such as radars, LiDARs, and cameras, 363 with other vehicles and pedestrians. [Automotive-Sensing] introduces 364 millimeter-wave vehicular communication for massive automotive 365 sensing. A lot of data can be generated by those sensors, and these 366 data typically need to be routed to different destinations. In 367 addition, from the perspective of driverless vehicles, it is expected 368 that driverless vehicles can be mixed with driver-operated vehicles. 369 Through cooperative environment sensing, driver-operated vehicles can 370 use environmental information sensed by driverless vehicles for 371 better interaction with the other vehicles and environment. Vehicles 372 can also share their intended maneuvering information (e.g., lane 373 change, speed change, ramp in-and-out, cut-in, and abrupt braking) 374 with neighboring vehicles. Thus, this information sharing can help 375 the vehicles behave as more efficient traffic flows and minimize 376 unnecessary acceleration and deceleration to achieve the best ride 377 comfort. 379 A collision avoidance service of UAM end systems in air can be 380 envisioned as a use case in air vehicular environments. This use 381 case is similar to the context-aware navigator for terrestrial 382 vehicles. Through V2V coordination, those UAM end systems (e.g., 383 drones) can avoid a dangerous situation (e.g., collision) in three- 384 dimensional space rather than two-dimensional space for terrestrial 385 vehicles. Also, UAM end systems (e.g., flying car) with only a few 386 meters off the ground can communicate with terrestrial vehicles with 387 wireless communication technologies (e.g., DSRC, LTE, and C-V2X). 388 Thus, V2V means any vehicle to any vehicle, whether the vehicles are 389 ground-level or not. 391 To encourage more vehicles to participate in this cooperative 392 environmental sensing, a reward system will be needed. Sensing 393 activities of each vehicle need to be logged in either a central way 394 through a logging server (e.g., TCC) in the vehicular cloud or a 395 distributed way (e.g., blockchain [Bitcoin]) through other vehicles 396 or infrastructure. In the case of a blockchain, each sensing message 397 from a vehicle can be treated as a transaction and the neighboring 398 vehicles can play the role of peers in a consensus method of a 399 blockchain [Bitcoin][Vehicular-BlockChain]. 401 To support applications of these V2V use cases, the required 402 functions of IPv6 include IPv6-based packet exchange and secure, safe 403 communication between two vehicles. For the support of V2V under 404 multiple radio technologies (e.g., DSRC and 5G V2X), refer to 405 Appendix A. 407 3.2. V2I 409 The use cases of V2I networking discussed in this section include 411 * Navigation service; 413 * Energy-efficient speed recommendation service; 415 * Accident notification service; 417 * Electric vehicle (EV) charging service; 419 * UAM navigation service with efficient battery charging. 421 A navigation service, for example, the Self-Adaptive Interactive 422 Navigation Tool(SAINT) [SAINT], using V2I networking interacts with a 423 TCC for the large-scale/long-range road traffic optimization and can 424 guide individual vehicles along appropriate navigation paths in real 425 time. The enhanced version of SAINT [SAINTplus] can give fast moving 426 paths to emergency vehicles (e.g., ambulance and fire engine) to let 427 them reach an accident spot while redirecting other vehicles near the 428 accident spot into efficient detour paths. 430 Either a TCC or an ECD can recommend an energy-efficient speed to a 431 vehicle that depends on its traffic environment and traffic signal 432 scheduling [SignalGuru]. For example, when a vehicle approaches an 433 intersection area and a red traffic light for the vehicle becomes 434 turned on, it needs to reduce its speed to save fuel consumption. In 435 this case, either a TCC or an ECD, which has the up-to-date 436 trajectory of the vehicle and the traffic light schedule, can notify 437 the vehicle of an appropriate speed for fuel efficiency. 438 [Fuel-Efficient] studies fuel-efficient route and speed plans for 439 platooned trucks. 441 The emergency communication between accident vehicles (or emergency 442 vehicles) and a TCC can be performed via either IP-RSU or 4G-LTE 443 networks. The First Responder Network Authority (FirstNet) 444 [FirstNet] is provided by the US government to establish, operate, 445 and maintain an interoperable public safety broadband network for 446 safety and security network services, e.g., emergency calls. The 447 construction of the nationwide FirstNet network requires each state 448 in the US to have a Radio Access Network (RAN) that will connect to 449 the FirstNet's network core. The current RAN is mainly constructed 450 using 4G-LTE for the communication between a vehicle and an 451 infrastructure node (i.e., V2I) [FirstNet-Report], but it is expected 452 that DSRC-based vehicular networks [DSRC] will be available for V2I 453 and V2V in the near future. 455 An EV charging service with V2I can facilitate the efficient battery 456 charging of EVs. In the case where an EV charging station is 457 connected to an IP-RSU, an EV can be guided toward the deck of the EV 458 charging station through a battery charging server connected to the 459 IP-RSU. In addition to this EV charging service, other value-added 460 services (e.g., air firmware/software update and media streaming) can 461 be provided to an EV while it is charging its battery at the EV 462 charging station. 464 A UAM navigation service with efficient battery charging can plan the 465 battery charging schedule of UAM end systems (e.g., drone) for long- 466 distance flying [CBDN]. For this battery charging schedule, a UAM 467 end system can communicate with an infrastructure node (e.g., IP-RSU) 468 toward a cloud server via V2I communications. This cloud server can 469 coordinate the battery charging schedules of multiple UAM end systems 470 for their efficient navigation path, considering flight time from 471 their current position to a battery charging station, waiting time in 472 a waiting queue at the station, and battery charging time at the 473 station. 475 The existing IPv6 protocol must be augmented through protocol changes 476 in order to support wireless multihop V2I communications in a highway 477 where RSUs are sparsely deployed, so a vehicle can reach the wireless 478 coverage of an RSU through the multihop data forwarding of 479 intermediate vehicles. Thus, IPv6 needs to be extended for multihop 480 V2I communications. 482 To support applications of these V2I use cases, the required 483 functions of IPv6 include IPv6-based packet exchange, transport-layer 484 session continuity, and secure, safe communication between a vehicle 485 and an infrastructure node (e.g., IP-RSU) in the vehicular network. 487 3.3. V2X 489 The use case of V2X networking discussed in this section is for a 490 pedestrian protection service. 492 A pedestrian protection service, such as Safety-Aware Navigation 493 Application (SANA) [SANA], using V2I2P networking can reduce the 494 collision of a vehicle and a pedestrian carrying a smartphone 495 equipped with a network device for wireless communication (e.g., Wi- 496 Fi) with an IP-RSU. Vehicles and pedestrians can also communicate 497 with each other via an IP-RSU. An edge computing device behind the 498 IP-RSU can collect the mobility information from vehicles and 499 pedestrians, compute wireless communication scheduling for the sake 500 of them. This scheduling can save the battery of each pedestrian's 501 smartphone by allowing it to work in sleeping mode before the 502 communication with vehicles, considering their mobility. 504 For Vehicle-to-Pedestrian (V2P), a vehicle can directly communicate 505 with a pedestrian's smartphone by V2X without IP-RSU relaying. 506 Light-weight mobile nodes such as bicycles may also communicate 507 directly with a vehicle for collision avoidance using V2V. 509 The existing IPv6 protocol must be augmented through protocol changes 510 in order to support wireless multihop V2X or V2I2X communications in 511 an urban road network where RSUs are deployed at intersections, so a 512 vehicle (or a pedestrian's smartphone) can reach the wireless 513 coverage of an RSU through the multihop data forwarding of 514 intermediate vehicles (or pedestrians' smartphones) as packet 515 forwarders. Thus, IPv6 needs to be extended for multihop V2X or 516 V2I2X communications. 518 To support applications of these V2X use cases, the required 519 functions of IPv6 include IPv6-based packet exchange, transport-layer 520 session continuity, and secure, safe communication between a vehicle 521 and a pedestrian either directly or indirectly via an IP-RSU. 523 4. Vehicular Networks 525 This section describes the context for vehicular networks supporting 526 V2V, V2I, and V2X communications. It describes an internal network 527 within a vehicle or an edge network (called EN). It explains not 528 only the internetworking between the internal networks of a vehicle 529 and an EN via wireless links, but also the internetworking between 530 the internal networks of two vehicles via wireless links. 532 Traffic Control Center in Vehicular Cloud 533 ******************************************* 534 +-------------+ * * 535 |Corresponding| * +-----------------+ * 536 | Node |<->* | Mobility Anchor | * 537 +-------------+ * +-----------------+ * 538 * ^ * 539 * | * 540 * v * 541 ******************************************* 542 ^ ^ ^ 543 | | | 544 | | | 545 v v v 546 +---------+ +---------+ +---------+ 547 | IP-RSU1 |<--------->| IP-RSU2 |<--------->| IP-RSU3 | 548 +---------+ +---------+ +---------+ 549 ^ ^ ^ 550 : : : 551 +-----------------+ +-----------------+ +-----------------+ 552 | : V2I | | : V2I | | : V2I | 553 | v | | v | | v | 554 +--------+ | +--------+ | | +--------+ | | +--------+ | 555 |Vehicle1|===> |Vehicle2|===>| | |Vehicle3|===>| | |Vehicle4|===>| 556 +--------+<...>+--------+<........>+--------+ | | +--------+ | 557 V2V ^ V2V ^ | | ^ | 558 | : V2V | | : V2V | | : V2V | 559 | v | | v | | v | 560 | +--------+ | | +--------+ | | +--------+ | 561 | |Vehicle5|===> | | |Vehicle6|===>| | |Vehicle7|==>| 562 | +--------+ | | +--------+ | | +--------+ | 563 +-----------------+ +-----------------+ +-----------------+ 564 Subnet1 Subnet2 Subnet3 565 (Prefix1) (Prefix2) (Prefix3) 567 <----> Wired Link <....> Wireless Link ===> Moving Direction 569 Figure 1: An Example Vehicular Network Architecture for V2I and V2V 571 4.1. Vehicular Network Architecture 573 Figure 1 shows an example vehicular network architecture for V2I and 574 V2V in a road network. The vehicular network architecture contains 575 vehicles (including IP-OBU), IP-RSUs, Mobility Anchor, Traffic 576 Control Center, and Vehicular Cloud as components. These components 577 are not mandatory, and they can be deployed into vehicular networks 578 in various ways. Some of them (e.g., Mobility Anchor, Traffic 579 Control Center, and Vehicular Cloud) may not be needed for the 580 vehicular networks according to target use cases in Section 3. 582 Existing network architectures, such as the network architectures of 583 PMIPv6 [RFC5213], RPL (IPv6 Routing Protocol for Low-Power and Lossy 584 Networks) [RFC6550], and OMNI (Overlay Multilink Network Interface) 585 [OMNI], can be extended to a vehicular network architecture for 586 multihop V2V, V2I, and V2X, as shown in Figure 1. Refer to 587 Appendix B for the detailed discussion on multihop V2X networking by 588 RPL and OMNI. 590 As shown in this figure, IP-RSUs as routers and vehicles with IP-OBU 591 have wireless media interfaces for VANET. Furthermore, the wireless 592 media interfaces are autoconfigured with a global IPv6 prefix (e.g., 593 2001:DB8:1:1::/64) to support both V2V and V2I networking. Note that 594 2001:DB8::/32 is a documentation prefix [RFC3849] for example 595 prefixes in this document, and also that any routable IPv6 address 596 needs to be routable in a VANET and a vehicular network including IP- 597 RSUs. 599 In Figure 1, three IP-RSUs (IP-RSU1, IP-RSU2, and IP-RSU3) are 600 deployed in the road network and are connected with each other 601 through the wired networks (e.g., Ethernet). A Traffic Control 602 Center (TCC) is connected to the Vehicular Cloud for the management 603 of IP-RSUs and vehicles in the road network. A Mobility Anchor (MA) 604 may be located in the TCC as a mobility management controller. 605 Vehicle2, Vehicle3, and Vehicle4 are wirelessly connected to IP-RSU1, 606 IP-RSU2, and IP-RSU3, respectively. The three wireless networks of 607 IP-RSU1, IP-RSU2, and IP-RSU3 can belong to three different subnets 608 (i.e., Subnet1, Subnet2, and Subnet3), respectively. Those three 609 subnets use three different prefixes (i.e., Prefix1, Prefix2, and 610 Prefix3). 612 Multiple vehicles under the coverage of an RSU share a prefix just as 613 mobile nodes share a prefix of a Wi-Fi access point in a wireless 614 LAN. This is a natural characteristic in infrastructure-based 615 wireless networks. For example, in Figure 1, two vehicles (i.e., 616 Vehicle2, and Vehicle5) can use Prefix 1 to configure their IPv6 617 global addresses for V2I communication. Alternatively, mobile nodes 618 can employ a "Bring-Your-Own-Addresses (BYOA)" technique using their 619 own IPv6 Unique Local Addresses (ULAs) [RFC4193] over the wireless 620 network, which does not require the messaging (e.g., Duplicate 621 Address Detection (DAD)) of IPv6 Stateless Address Autoconfiguration 622 (SLAAC) [RFC4862]. 624 In wireless subnets in vehicular networks (e.g., Subnet1 and Subnet2 625 in Figure 1), vehicles can construct a connected VANET (with an 626 arbitrary graph topology) and can communicate with each other via V2V 627 communication. Vehicle1 can communicate with Vehicle2 via V2V 628 communication, and Vehicle2 can communicate with Vehicle3 via V2V 629 communication because they are within the wireless communication 630 range of each other. On the other hand, Vehicle3 can communicate 631 with Vehicle4 via the vehicular infrastructure (i.e., IP-RSU2 and IP- 632 RSU3) by employing V2I (i.e., V2I2V) communication because they are 633 not within the wireless communication range of each other. 635 As a basic definition for IPv6 packets transported over IEEE 636 802.11-OCB, [RFC8691] specifies several details, including Maximum 637 Transmission Unit (MTU), frame format, link-local address, address 638 mapping for unicast and multicast, stateless autoconfiguration, and 639 subnet structure. 641 An IPv6 mobility solution is needed for the guarantee of 642 communication continuity in vehicular networks so that a vehicle's 643 TCP session can be continued, or UDP packets can be delivered to a 644 vehicle as a destination without loss while it moves from an IP-RSU's 645 wireless coverage to another IP-RSU's wireless coverage. In 646 Figure 1, assuming that Vehicle2 has a TCP session (or a UDP session) 647 with a corresponding node in the vehicular cloud, Vehicle2 can move 648 from IP-RSU1's wireless coverage to IP-RSU2's wireless coverage. In 649 this case, a handover for Vehicle2 needs to be performed by either a 650 host-based mobility management scheme (e.g., MIPv6 [RFC6275]) or a 651 network-based mobility management scheme (e.g., PMIPv6 [RFC5213] and 652 AERO [RFC6706BIS]). This document describes issues in mobility 653 management for vehicular networks in Section 5.2. 655 4.2. V2I-based Internetworking 657 This section discusses the internetworking between a vehicle's 658 internal network (i.e., moving network) and an EN's internal network 659 (i.e., fixed network) via V2I communication. The internal network of 660 a vehicle is nowadays constructed with Ethernet by many automotive 661 vendors [In-Car-Network]. Note that an EN can accommodate multiple 662 routers (or switches) and servers (e.g., ECDs, navigation server, and 663 DNS server) in its internal network. 665 A vehicle's internal network often uses Ethernet to interconnect 666 Electronic Control Units (ECUs) in the vehicle. The internal network 667 can support Wi-Fi and Bluetooth to accommodate a driver's and 668 passenger's mobile devices (e.g., smartphone or tablet). The network 669 topology and subnetting depend on each vendor's network configuration 670 for a vehicle and an EN. It is reasonable to consider the 671 interaction between the internal network and an external network 672 within another vehicle or an EN. 674 +-----------------+ 675 (*)<........>(*) +----->| Vehicular Cloud | 676 (2001:DB8:1:1::/64) | | | +-----------------+ 677 +------------------------------+ +---------------------------------+ 678 | v | | v v | 679 | +-------+ +-------+ | | +-------+ +-------+ | 680 | | Host1 | |IP-OBU1| | | |IP-RSU1| | Host3 | | 681 | +-------+ +-------+ | | +-------+ +-------+ | 682 | ^ ^ | | ^ ^ | 683 | | | | | | | | 684 | v v | | v v | 685 | ---------------------------- | | ------------------------------- | 686 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:20:1::/64 | 687 | | | | | | 688 | v | | v | 689 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 690 | | Host2 | |Router1| | | |Router2| |Server1|...|ServerN| | 691 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 692 | ^ ^ | | ^ ^ ^ | 693 | | | | | | | | | 694 | v v | | v v v | 695 | ---------------------------- | | ------------------------------- | 696 | 2001:DB8:10:2::/64 | | 2001:DB8:20:2::/64 | 697 +------------------------------+ +---------------------------------+ 698 Vehicle1 (Moving Network1) EN1 (Fixed Network1) 700 <----> Wired Link <....> Wireless Link (*) Antenna 702 Figure 2: Internetworking between Vehicle and Edge Network 704 As shown in Figure 2, as internal networks, a vehicle's moving 705 network and an EN's fixed network are self-contained networks having 706 multiple subnets and having an edge router (e.g., IP-OBU and IP-RSU) 707 for the communication with another vehicle or another EN. The 708 internetworking between two internal networks via V2I communication 709 requires the exchange of the network parameters and the network 710 prefixes of the internal networks. For the efficiency, the network 711 prefixes of the internal networks (as a moving network) in a vehicle 712 need to be delegated and configured automatically. Note that a 713 moving network's network prefix can be called a Mobile Network Prefix 714 (MNP) [RFC3963]. 716 Figure 2 also shows the internetworking between the vehicle's moving 717 network and the EN's fixed network. There exists an internal network 718 (Moving Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and 719 Host2), and two routers (IP-OBU1 and Router1). There exists another 720 internal network (Fixed Network1) inside EN1. EN1 has one host 721 (Host3), two routers (IP-RSU1 and Router2), and the collection of 722 servers (Server1 to ServerN) for various services in the road 723 networks, such as the emergency notification and navigation. 724 Vehicle1's IP-OBU1 (as a mobile router) and EN1's IP-RSU1 (as a fixed 725 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 726 V2I networking. Thus, a host (Host1) in Vehicle1 can communicate 727 with a server (Server1) in EN1 for a vehicular service through 728 Vehicle1's moving network, a wireless link between IP-OBU1 and IP- 729 RSU1, and EN1's fixed network. 731 For the IPv6 communication between an IP-OBU and an IP-RSU or between 732 two neighboring IP-OBUs, they need to know the network parameters, 733 which include MAC layer and IPv6 layer information. The MAC layer 734 information includes wireless link layer parameters, transmission 735 power level, and the MAC address of an external network interface for 736 the internetworking with another IP-OBU or IP-RSU. The IPv6 layer 737 information includes the IPv6 address and network prefix of an 738 external network interface for the internetworking with another IP- 739 OBU or IP-RSU. 741 Through the mutual knowledge of the network parameters of internal 742 networks, packets can be transmitted between the vehicle's moving 743 network and the EN's fixed network. Thus, V2I requires an efficient 744 protocol for the mutual knowledge of network parameters. 746 As shown in Figure 2, the addresses used for IPv6 transmissions over 747 the wireless link interfaces for IP-OBU and IP-RSU can be link-local 748 IPv6 addresses, ULAs, or global IPv6 addresses. When global IPv6 749 addresses are used, wireless interface configuration and control 750 overhead for DAD [RFC4862] and Multicast Listener Discovery (MLD) 751 [RFC2710][RFC3810] should be minimized to support V2I and V2X 752 communications for vehicles moving fast along roadways. 754 Let us consider the upload/download time of a vehicle when it passes 755 through the wireless communication coverage of an IP-RSU. For a 756 given typical setting where 1km is the maximum DSRC communication 757 range [DSRC] and 100km/h is the speed limit in highway, the dwelling 758 time can be calculated to be 72 seconds by dividing the diameter of 759 the 2km (i.e., two times of DSRC communication range where an IP-RSU 760 is located in the center of the circle of wireless communication) by 761 the speed limit of 100km/h (i.e., about 28m/s). For the 72 seconds, 762 a vehicle passing through the coverage of an IP-RSU can upload and 763 download data packets to/from the IP-RSU. 765 4.3. V2V-based Internetworking 767 This section discusses the internetworking between the moving 768 networks of two neighboring vehicles via V2V communication. 770 (*)<..........>(*) 771 (2001:DB8:1:1::/64) | | 772 +------------------------------+ +------------------------------+ 773 | v | | v | 774 | +-------+ +-------+ | | +-------+ +-------+ | 775 | | Host1 | |IP-OBU1| | | |IP-OBU2| | Host3 | | 776 | +-------+ +-------+ | | +-------+ +-------+ | 777 | ^ ^ | | ^ ^ | 778 | | | | | | | | 779 | v v | | v v | 780 | ---------------------------- | | ---------------------------- | 781 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:30:1::/64 | 782 | | | | | | 783 | v | | v | 784 | +-------+ +-------+ | | +-------+ +-------+ | 785 | | Host2 | |Router1| | | |Router2| | Host4 | | 786 | +-------+ +-------+ | | +-------+ +-------+ | 787 | ^ ^ | | ^ ^ | 788 | | | | | | | | 789 | v v | | v v | 790 | ---------------------------- | | ---------------------------- | 791 | 2001:DB8:10:2::/64 | | 2001:DB8:30:2::/64 | 792 +------------------------------+ +------------------------------+ 793 Vehicle1 (Moving Network1) Vehicle2 (Moving Network2) 795 <----> Wired Link <....> Wireless Link (*) Antenna 797 Figure 3: Internetworking between Two Vehicles 799 Figure 3 shows the internetworking between the moving networks of two 800 neighboring vehicles. There exists an internal network (Moving 801 Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and Host2), 802 and two routers (IP-OBU1 and Router1). There exists another internal 803 network (Moving Network2) inside Vehicle2. Vehicle2 has two hosts 804 (Host3 and Host4), and two routers (IP-OBU2 and Router2). Vehicle1's 805 IP-OBU1 (as a mobile router) and Vehicle2's IP-OBU2 (as a mobile 806 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 807 V2V networking. Thus, a host (Host1) in Vehicle1 can communicate 808 with another host (Host3) in Vehicle2 for a vehicular service through 809 Vehicle1's moving network, a wireless link between IP-OBU1 and IP- 810 OBU2, and Vehicle2's moving network. 812 As a V2V use case in Section 3.1, Figure 4 shows the linear network 813 topology of platooning vehicles for V2V communications where Vehicle3 814 is the leading vehicle with a driver, and Vehicle2 and Vehicle1 are 815 the following vehicles without drivers. 817 (*)<..................>(*)<..................>(*) 818 | | | 819 +-----------+ +-----------+ +-----------+ 820 | | | | | | 821 | +-------+ | | +-------+ | | +-------+ | 822 | |IP-OBU1| | | |IP-OBU2| | | |IP-OBU3| | 823 | +-------+ | | +-------+ | | +-------+ | 824 | ^ | | ^ | | ^ | 825 | | |=====> | | |=====> | | |=====> 826 | v | | v | | v | 827 | +-------+ | | +-------+ | | +-------+ | 828 | | Host1 | | | | Host2 | | | | Host3 | | 829 | +-------+ | | +-------+ | | +-------+ | 830 | | | | | | 831 +-----------+ +-----------+ +-----------+ 832 Vehicle1 Vehicle2 Vehicle3 834 <----> Wired Link <....> Wireless Link ===> Moving Direction 835 (*) Antenna 837 Figure 4: Multihop Internetworking between Two Vehicle Networks 839 As shown in Figure 4, multihop internetworking is feasible among the 840 moving networks of three vehicles in the same VANET. For example, 841 Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via IP-OBU1 842 in Vehicle1, IP-OBU2 in Vehicle2, and IP-OBU3 in Vehicle3 in the 843 VANET, as shown in the figure. 845 In this section, the link between two vehicles is assumed to be 846 stable for single-hop wireless communication regardless of the sight 847 relationship such as line of sight and non-line of sight, as shown in 848 Figure 3. Even in Figure 4, the three vehicles are connected to each 849 other with a linear topology, however, multihop V2V communication can 850 accommodate any network topology (i.e., an arbitrary graph) over 851 VANET routing protocols. 853 (*)<..................>(*)<..................>(*) 854 | | | 855 +-----------+ +-----------+ +-----------+ 856 | | | | | | 857 | +-------+ | | +-------+ | | +-------+ | 858 | |IP-OBU1| | | |IP-RSU1| | | |IP-OBU3| | 859 | +-------+ | | +-------+ | | +-------+ | 860 | ^ | | ^ | | ^ | 861 | | |=====> | | | | | |=====> 862 | v | | v | | v | 863 | +-------+ | | +-------+ | | +-------+ | 864 | | Host1 | | | | Host2 | | | | Host3 | | 865 | +-------+ | | +-------+ | | +-------+ | 866 | | | | | | 867 +-----------+ +-----------+ +-----------+ 868 Vehicle1 EN1 Vehicle3 870 <----> Wired Link <....> Wireless Link ===> Moving Direction 871 (*) Antenna 873 Figure 5: Multihop Internetworking between Two Vehicle Networks 874 via IP-RSU (V2I2V) 876 As shown in Figure 5, multihop internetworking between two vehicles 877 is feasible via an infrastructure node (i.e., IP-RSU) with wireless 878 connectivity among the moving networks of two vehicles and the fixed 879 network of an edge network (denoted as EN1) in the same VANET. For 880 example, Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via 881 IP-OBU1 in Vehicle1, IP-RSU1 in EN1, and IP-OBU3 in Vehicle3 in the 882 VANET, as shown in the figure. 884 For the reliability required in V2V networking, the ND optimization 885 defined in MANET [RFC6130] [RFC7466] improves the classical IPv6 ND 886 in terms of tracking neighbor information with up to two hops and 887 introducing several extensible Information Bases, which serves the 888 MANET routing protocols such as the difference versions of Optimized 889 Link State Routing Protocol (OLSR) [RFC3626] [RFC7181] [RFC7188] 890 [RFC7722] [RFC7779] [RFC8218] and the Dynamic Link Exchange Protocol 891 (DLEP) with its extensions [RFC8175] [RFC8629] [RFC8651] [RFC8703] 892 [RFC8757]. In short, the MANET ND mainly deals with maintaining 893 extended network neighbors. However, an ND protocol in vehicular 894 networks shall consider more about the geographical mobility 895 information of vehicles as an important resource for serving various 896 purposes to improve the reliability, e.g., vehicle driving safety, 897 intelligent transportation implementations, and advanced mobility 898 services. For a more reliable V2V networking, some redundancy 899 mechanisms should be provided in L3 in the case of the failure of L2. 901 5. Problem Statement 903 In order to specify protocols using the architecture mentioned in 904 Section 4.1, IPv6 core protocols have to be adapted to overcome 905 certain challenging aspects of vehicular networking. Since the 906 vehicles are likely to be moving at great speed, protocol exchanges 907 need to be completed in a time relatively short compared to the 908 lifetime of a link between a vehicle and an IP-RSU, or between two 909 vehicles. 911 For safe driving, vehicles need to exchange application messages 912 every 0.5 second [NHTSA-ACAS-Report] to let drivers take an action to 913 avoid a dangerous situation (e.g., vehicle collision), so IPv6 914 protocol exchanges need to support this order of magnitude for 915 application message exchanges. Also, considering the communication 916 range of DSRC (up to 1km) and 100km/h as the speed limit in highway, 917 the lifetime of a link between a vehicle and an IP-RSU is 72 seconds, 918 and the lifetime of a link between two vehicles is 36 seconds. Note 919 that if two vehicles are moving in the opposite directions in a 920 roadway, the relative speed of this case is two times the relative 921 speed of a vehicle passing through an RSU. This relative speed leads 922 the half of the link lifetime between the vehicle and the IP-RSU. In 923 reality, the DSRC communication range is around 500m, so the link 924 lifetime will be a half of the maximum time. The time constraint of 925 a wireless link between two nodes (e.g., vehicle and IP-RSU) needs to 926 be considered because it may affect the lifetime of a session 927 involving the link. The lifetime of a session varies depending on 928 the session's type such as a web surfing, voice call over IP, DNS 929 query, and context-aware navigation (in Section 3.1). Regardless of 930 a session's type, to guide all the IPv6 packets to their destination 931 host(s), IP mobility should be supported for the session. In a V2V 932 scenario (e.g., context-aware navigation), the IPv6 packets of a 933 vehicle should be delivered to relevant vehicles in an efficient way 934 (e.g., multicasting). With this observation, IPv6 protocol exchanges 935 need to be done as short as possible to support the message exchanges 936 of various applications in vehicular networks. 938 Therefore, the time constraint of a wireless link has a major impact 939 on IPv6 Neighbor Discovery (ND). Mobility Management (MM) is also 940 vulnerable to disconnections that occur before the completion of 941 identity verification and tunnel management. This is especially true 942 given the unreliable nature of wireless communication. Meanwhile, 943 the bandwidth of the wireless link determined by the lower layers 944 (i.e., link and PHY layers) can affect the transmission time of 945 control messages of the upper layers (e.g., IPv6) and the continuity 946 of sessions in the higher layers (e.g., IPv6, TCP, and UDP). Hence 947 the bandwidth selection according to Modulation and Coding Scheme 948 (MCS) also affects the vehicular network connectivity. Note that 949 usually the higher bandwidth gives the shorter communication range 950 and the higher packet error rate at the receiving side, which may 951 reduce the reliability of control message exchanges of the higher 952 layers (e.g., IPv6). This section presents key topics such as 953 neighbor discovery and mobility management for links and sessions in 954 IPv6-based vehicular networks. 956 5.1. Neighbor Discovery 958 IPv6 ND [RFC4861][RFC4862] is a core part of the IPv6 protocol suite. 959 IPv6 ND is designed for link types including point-to-point, 960 multicast-capable (e.g., Ethernet) and Non-Broadcast Multiple Access 961 (NBMA). It assumes the efficient and reliable support of multicast 962 and unicast from the link layer for various network operations such 963 as MAC Address Resolution (AR), DAD, MLD and Neighbor Unreachability 964 Detection (NUD). 966 Vehicles move quickly within the communication coverage of any 967 particular vehicle or IP-RSU. Before the vehicles can exchange 968 application messages with each other, they need to be configured with 969 a link-local IPv6 address or a global IPv6 address, and run IPv6 ND. 971 The requirements for IPv6 ND for vehicular networks are efficient DAD 972 and NUD operations. An efficient DAD is required to reduce the 973 overhead of the DAD packets during a vehicle's travel in a road 974 network, which can guarantee the uniqueness of a vehicle's global 975 IPv6 address. An efficient NUD is required to reduce the overhead of 976 the NUD packets during a vehicle's travel in a road network, which 977 can guarantee the accurate neighborhood information of a vehicle in 978 terms of adjacent vehicles and RSUs. 980 The legacy DAD assumes that a node with an IPv6 address can reach any 981 other node with the scope of its address at the time it claims its 982 address, and can hear any future claim for that address by another 983 party within the scope of its address for the duration of the address 984 ownership. However, the partitioning and merging of VANETs makes 985 this assumption frequently invalid in vehicular networks. The 986 merging and partitioning of VANETs frequently occurs in vehicular 987 networks. This merging and partitioning should be considered for the 988 IPv6 ND such as IPv6 Stateless Address Autoconfiguration (SLAAC) 989 [RFC4862]. Due to the merging of VANETs, two IPv6 addresses may 990 conflict with each other though they were unique before the merging. 991 An address lookup operation may be conducted by an MA or IP-RSU (as 992 Registrar in RPL) to check the uniqueness of an IPv6 address that 993 will be configured by a vehicle as DAD. Also, the partitioning of a 994 VANET may make vehicles with the same prefix be physically 995 unreachable. An address lookup operation may be conducted by an MA 996 or IP-RSU (as Registrar in RPL) to check the existence of a vehicle 997 under the network coverage of the MA or IP-RSU as NUD. Thus, SLAAC 998 needs to prevent IPv6 address duplication due to the merging of 999 VANETs, and IPv6 ND needs to detect unreachable neighboring vehicles 1000 due to the partitioning of a VANET. According to the merging and 1001 partitioning, a destination vehicle (as an IPv6 host) needs to be 1002 distinguished as either an on-link host or an off-link host even 1003 though the source vehicle can use the same prefix as the destination 1004 vehicle [ID-IPPL]. 1006 To efficiently prevent IPv6 address duplication due to the VANET 1007 partitioning and merging from happening in vehicular networks, the 1008 vehicular networks need to support a vehicular-network-wide DAD by 1009 defining a scope that is compatible with the legacy DAD. In this 1010 case, two vehicles can communicate with each other when there exists 1011 a communication path over VANET or a combination of VANETs and IP- 1012 RSUs, as shown in Figure 1. By using the vehicular-network-wide DAD, 1013 vehicles can assure that their IPv6 addresses are unique in the 1014 vehicular network whenever they are connected to the vehicular 1015 infrastructure or become disconnected from it in the form of VANET. 1017 For vehicular networks with high mobility and density, the DAD needs 1018 to be performed efficiently with minimum overhead so that the 1019 vehicles can exchange driving safety messages (e.g., collision 1020 avoidance and accident notification) with each other with a short 1021 interval suggested by NHTSA (National Highway Traffic Safety 1022 Administration) [NHTSA-ACAS-Report]. Since the partitioning and 1023 merging of vehicular networks may require re-perform the DAD process 1024 repeatedly, the link scope of vehicles may be limited to a small 1025 area, which may delay the exchange of driving safety messages. 1026 Driving safety messages can include a vehicle's mobility information 1027 (i.e., position, speed, direction, and acceleration/deceleration) 1028 that is critical to other vehicles. The exchange interval of this 1029 message is recommended to be less than 0.5 second, which is required 1030 for a driver to avoid an emergency situation, such as a rear-end 1031 crash. 1033 ND time-related parameters such as router lifetime and Neighbor 1034 Advertisement (NA) interval need to be adjusted for vehicle speed and 1035 vehicle density. For example, the NA interval needs to be 1036 dynamically adjusted according to a vehicle's speed so that the 1037 vehicle can maintain its neighboring vehicles in a stable way, 1038 considering the collision probability with the NA messages sent by 1039 other vehicles. The ND time-related parameters can be an operational 1040 setting or an optimization point particularly for vehicular networks. 1042 For IPv6-based safety applications (e.g., context-aware navigation, 1043 adaptive cruise control, and platooning) in vehicular networks, the 1044 delay-bounded data delivery is critical. IPv6 ND needs to work to 1045 support those IPv6-based safety applications efficiently. 1047 From the interoperability point of view, in IPv6-based vehicular 1048 networking, IPv6 ND should have minimum changes with the legacy IPv6 1049 ND used in the Internet, including the DAD and NUD operations, so 1050 that IPv6-based vehicular networks can be seamlessly connected to 1051 other intelligent transportation elements (e.g., traffic signals, 1052 pedestrian wearable devices, electric scooters, and bus stops) that 1053 use the standard IPv6 network settings. 1055 5.1.1. Link Model 1057 A subnet model for a vehicular network needs to facilitate the 1058 communication between two vehicles with the same prefix regardless of 1059 the vehicular network topology as long as there exist bidirectional 1060 E2E paths between them in the vehicular network including VANETs and 1061 IP-RSUs. This subnet model allows vehicles with the same prefix to 1062 communicate with each other via a combination of multihop V2V and 1063 multihop V2I with VANETs and IP-RSUs. [IPoWIRELESS] introduces other 1064 issues in an IPv6 subnet model. 1066 IPv6 protocols work under certain assumptions that do not necessarily 1067 hold for vehicular wireless access link types [VIP-WAVE][RFC5889]. 1068 For instance, some IPv6 protocols assume symmetry in the connectivity 1069 among neighboring interfaces [RFC6250]. However, radio interference 1070 and different levels of transmission power may cause asymmetric links 1071 to appear in vehicular wireless links. As a result, a new vehicular 1072 link model needs to consider the asymmetry of dynamically changing 1073 vehicular wireless links. 1075 There is a relationship between a link and a prefix, besides the 1076 different scopes that are expected from the link-local and global 1077 types of IPv6 addresses. In an IPv6 link, it is defined that all 1078 interfaces which are configured with the same subnet prefix and with 1079 on-link bit set can communicate with each other on an IPv6 link. 1080 However, the vehicular link model needs to define the relationship 1081 between a link and a prefix, considering the dynamics of wireless 1082 links and the characteristics of VANET. 1084 A VANET can have a single link between each vehicle pair within 1085 wireless communication range, as shown in Figure 4. When two 1086 vehicles belong to the same VANET, but they are out of wireless 1087 communication range, they cannot communicate directly with each 1088 other. Suppose that a global-scope IPv6 prefix (or an IPv6 ULA 1089 prefix) is assigned to VANETs in vehicular networks. Even though two 1090 vehicles in the same VANET configure their IPv6 addresses with the 1091 same IPv6 prefix, they may not communicate with each other not in one 1092 hop in the same VANET because of the multihop network connectivity 1093 between them. Thus, in this case, the concept of an on-link IPv6 1094 prefix does not hold because two vehicles with the same on-link IPv6 1095 prefix cannot communicate directly with each other. Also, when two 1096 vehicles are located in two different VANETs with the same IPv6 1097 prefix, they cannot communicate with each other. When these two 1098 VANETs converge to one VANET, the two vehicles can communicate with 1099 each other in a multihop fashion, for example, when they are Vehicle1 1100 and Vehicle3, as shown in Figure 4. 1102 From the previous observation, a vehicular link model should consider 1103 the frequent partitioning and merging of VANETs due to vehicle 1104 mobility. Therefore, the vehicular link model needs to use an on- 1105 link prefix and off-link prefix according to the network topology of 1106 vehicles such as a one-hop reachable network and a multihop reachable 1107 network (or partitioned networks). If the vehicles with the same 1108 prefix are reachable from each other in one hop, the prefix should be 1109 on-link. On the other hand, if some of the vehicles with the same 1110 prefix are not reachable from each other in one hop due to either the 1111 multihop topology in the VANET or multiple partitions, the prefix 1112 should be off-link. In most cases in vehicular networks, due to the 1113 partitioning and merging of VANETs, and the multihop network topology 1114 of VANETS, off-link prefixes will be used for vehicles as default. 1116 The vehicular link model needs to support multihop routing in a 1117 connected VANET where the vehicles with the same global-scope IPv6 1118 prefix (or the same IPv6 ULA prefix) are connected in one hop or 1119 multiple hops. It also needs to support the multihop routing in 1120 multiple connected VANETs through infrastructure nodes (e.g., IP-RSU) 1121 where they are connected to the infrastructure. For example, in 1122 Figure 1, suppose that Vehicle1, Vehicle2, and Vehicle3 are 1123 configured with their IPv6 addresses based on the same global-scope 1124 IPv6 prefix. Vehicle1 and Vehicle3 can also communicate with each 1125 other via either multihop V2V or multihop V2I2V. When Vehicle1 and 1126 Vehicle3 are connected in a VANET, it will be more efficient for them 1127 to communicate with each other directly via VANET rather than 1128 indirectly via IP-RSUs. On the other hand, when Vehicle1 and 1129 Vehicle3 are far away from direct communication range in separate 1130 VANETs and under two different IP-RSUs, they can communicate with 1131 each other through the relay of IP-RSUs via V2I2V. Thus, two 1132 separate VANETs can merge into one network via IP-RSU(s). Also, 1133 newly arriving vehicles can merge two separate VANETs into one VANET 1134 if they can play the role of a relay node for those VANETs. 1136 Thus, in IPv6-based vehicular networking, the vehicular link model 1137 should have minimum changes for interoperability with standard IPv6 1138 links in an efficient fashion to support IPv6 DAD, MLD and NUD 1139 operations. 1141 5.1.2. MAC Address Pseudonym 1143 For the protection of drivers' privacy, a pseudonym of a MAC address 1144 of a vehicle's network interface should be used, so that the MAC 1145 address can be changed periodically. However, although such a 1146 pseudonym of a MAC address can protect to some extent the privacy of 1147 a vehicle, it may not be able to resist attacks on vehicle 1148 identification by other fingerprint information, for example, the 1149 scrambler seed embedded in IEEE 802.11-OCB frames [Scrambler-Attack]. 1150 The pseudonym of a MAC address affects an IPv6 address based on the 1151 MAC address, and a transport-layer (e.g., TCP and SCTP) session with 1152 an IPv6 address pair. However, the pseudonym handling is not 1153 implemented and tested yet for applications on IP-based vehicular 1154 networking. 1156 In the ETSI standards, for the sake of security and privacy, an ITS 1157 station (e.g., vehicle) can use pseudonyms for its network interface 1158 identities (e.g., MAC address) and the corresponding IPv6 addresses 1159 [Identity-Management]. Whenever the network interface identifier 1160 changes, the IPv6 address based on the network interface identifier 1161 needs to be updated, and the uniqueness of the address needs to be 1162 checked through the DAD procedure. 1164 5.1.3. Routing 1166 For multihop V2V communications in either a VANET or VANETs via IP- 1167 RSUs, a vehicular Mobile Ad Hoc Networks (MANET) routing protocol may 1168 be required to support both unicast and multicast in the links of the 1169 subnet with the same IPv6 prefix. However, it will be costly to run 1170 both vehicular ND and a vehicular ad hoc routing protocol in terms of 1171 control traffic overhead [ID-Multicast-Problems]. 1173 A routing protocol for a VANET may cause redundant wireless frames in 1174 the air to check the neighborhood of each vehicle and compute the 1175 routing information in a VANET with a dynamic network topology 1176 because the IPv6 ND is used to check the neighborhood of each 1177 vehicle. Thus, the vehicular routing needs to take advantage of the 1178 IPv6 ND to minimize its control overhead. 1180 RPL [RFC6550] defines a routing protocol for low-power and lossy 1181 networks, which constructs and maintains Destination-Oriented 1182 Directed Acyclic Graphs (DODAGs) optimized by an Objective Function 1183 (OF). A defined OF provides route selection and optimization within 1184 an RPL topology. A node in a DODAG discovers and maintains the 1185 upward routes toward the root node of the DODAG. RPL uses a Distance 1186 Vector (DV) approach, with lazy maintenance and stretched anisotropic 1187 routing. It is well-designed to reduce the topological knowledge and 1188 routing state that needs to be exchanged. As a result, the routing 1189 protocol overhead is minimized, which allows either highly 1190 constrained stable networks or less constrained, highly dynamic 1191 networks. Refer to Appendix B for the detailed description of RPL 1192 for multihop V2X networking. 1194 An address registration extension for 6LoWPAN (IPv6 over Low-Power 1195 Wireless Personal Area Network) in [RFC8505] can support light-weight 1196 mobility for nodes moving through different parents. [RFC8505], as 1197 opposed to [RFC4861], is stateful and proactively installs the ND 1198 cache entries, which saves broadcasts and provides a deterministic 1199 presence information for IPv6 addresses. Mainly it updates the 1200 Address Registration Option (ARO) of ND defined in [RFC6775] to 1201 include a status field that can indicate the movement of a node and 1202 optionally a Transaction ID (TID) field, i.e., a sequence number that 1203 can be used to determine the most recent location of a node. Thus, 1204 RPL can use the information provided by the Extended ARO (EARO) 1205 defined in [RFC8505] to deal with a certain level of node mobility. 1206 When a leaf node moves to the coverage of another parent node, it 1207 should de-register its addresses to the previous parent node and 1208 register itself with a new parent node along with an incremented TID. 1210 RPL can be used in IPv6-based vehicular networks, but it is primarily 1211 designed for lossy networks, which puts energy efficiency first. For 1212 using it in IPv6-based vehicular networks, there have not been actual 1213 experiences and practical implementations for vehicular networks, 1214 though it was tested in IoT low-power and lossy networks (LLN) 1215 scenarios. 1217 Moreover, due to bandwidth and energy constraints, RPL does not 1218 suggest to use a proactive mechanism (e.g., keepalive) to maintain 1219 accurate routing adjacencies such as Bidirectional Forwarding 1220 Detection [RFC5881] and MANET Neighborhood Discovery Protocol 1221 [RFC6130]. As a result, due to the mobility of vehicles, network 1222 fragmentation may not be detected quickly and the routing of packets 1223 between vehicles or between a vehicle and an infrastructure node may 1224 fail. 1226 5.2. Mobility Management 1228 The seamless connectivity and timely data exchange between two end 1229 points requires efficient mobility management including location 1230 management and handover. Most vehicles are equipped with a GPS 1231 receiver as part of a dedicated navigation system or a corresponding 1232 smartphone App. Note that the GPS receiver may not provide vehicles 1233 with accurate location information in adverse environments such as a 1234 building area or a tunnel. The location precision can be improved 1235 with assistance of the IP-RSUs or a cellular system with a GPS 1236 receiver for location information. 1238 With a GPS navigator, efficient mobility management can be performed 1239 with the help of vehicles periodically reporting their current 1240 position and trajectory (i.e., navigation path) to the vehicular 1241 infrastructure (having IP-RSUs and an MA in TCC). This vehicular 1242 infrastructure can predict the future positions of the vehicles from 1243 their mobility information (i.e., the current position, speed, 1244 direction, and trajectory) for efficient mobility management (e.g., 1245 proactive handover). For a better proactive handover, link-layer 1246 parameters, such as the signal strength of a link-layer frame (e.g., 1247 Received Channel Power Indicator (RCPI) [VIP-WAVE]), can be used to 1248 determine the moment of a handover between IP-RSUs along with 1249 mobility information. 1251 By predicting a vehicle's mobility, the vehicular infrastructure 1252 needs to better support IP-RSUs to perform efficient SLAAC, data 1253 forwarding, horizontal handover (i.e., handover in wireless links 1254 using a homogeneous radio technology), and vertical handover (i.e., 1255 handover in wireless links using heterogeneous radio technologies) in 1256 advance along with the movement of the vehicle. 1258 For example, as shown in Figure 1, when a vehicle (e.g., Vehicle2) is 1259 moving from the coverage of an IP-RSU (e.g., IP-RSU1) into the 1260 coverage of another IP-RSU (e.g., IP-RSU2) belonging to a different 1261 subnet, the IP-RSUs can proactively support the IPv6 mobility of the 1262 vehicle, while performing the SLAAC, data forwarding, and handover 1263 for the sake of the vehicle. 1265 For a mobility management scheme in a domain, where the wireless 1266 subnets of multiple IP-RSUs share the same prefix, an efficient 1267 vehicular-network-wide DAD is required. If DHCPv6 is used to assign 1268 a unique IPv6 address to each vehicle in this shared link, the DAD is 1269 not required. On the other hand, for a mobility management scheme 1270 with a unique prefix per mobile node (e.g., PMIPv6 [RFC5213]), DAD is 1271 not required because the IPv6 address of a vehicle's external 1272 wireless interface is guaranteed to be unique. There is a tradeoff 1273 between the prefix usage efficiency and DAD overhead. Thus, the IPv6 1274 address autoconfiguration for vehicular networks needs to consider 1275 this tradeoff to support efficient mobility management. 1277 Even though the SLAAC with classic ND costs a DAD during mobility 1278 management, the SLAAC with [RFC8505] does not cost a DAD. SLAAC for 1279 vehicular networks needs to consider the minimization of the cost of 1280 DAD with the help of an infrastructure node (e.g., IP-RSU and MA). 1281 Using an infrastructure prefix over VANET allows direct routability 1282 to the Internet through the multihop V2I toward an IP-RSU. On the 1283 other hand, a BYOA does not allow such direct routability to the 1284 Internet since the BYOA is not topologically correct, that is, not 1285 routable in the Internet. In addition, a vehicle configured with a 1286 BYOA needs a tunnel home (e.g., IP-RSU) connected to the Internet, 1287 and the vehicle needs to know which neighboring vehicle is reachable 1288 inside the VANET toward the tunnel home. There is nonnegligible 1289 control overhead to set up and maintain routes to such a tunnel home 1290 over the VANET. 1292 For the case of a multihomed network, a vehicle can follow the first- 1293 hop router selection rule described in [RFC8028]. For example, an 1294 IP-OBU inside a vehicle may connect to an IP-RSU that has multiple 1295 routers behind. In this scenario, because the IP-OBU can have 1296 multiple prefixes from those routers, the default router selection, 1297 source address selection, and packet redirect process should follow 1298 the guidelines in [RFC8028]. That is, the vehicle should select its 1299 default router for each prefix by preferring the router that 1300 advertised the prefix. 1302 Vehicles can use the TCC as their Home Network having a home agent 1303 for mobility management as in MIPv6 [RFC6275] and PMIPv6 [RFC5213], 1304 so the TCC (or an MA inside the TCC) maintains the mobility 1305 information of vehicles for location management. IP tunneling over 1306 the wireless link should be avoided for performance efficiency. 1307 Also, in vehicular networks, asymmetric links sometimes exist and 1308 must be considered for wireless communications such as V2V and V2I. 1310 Therefore, for the proactive and seamless IPv6 mobility of vehicles, 1311 the vehicular infrastructure (including IP-RSUs and MA) needs to 1312 efficiently perform the mobility management of the vehicles with 1313 their mobility information and link-layer information. Also, in 1314 IPv6-based vehicular networking, IPv6 mobility management should have 1315 minimum changes for the interoperability with the legacy IPv6 1316 mobility management schemes such as PMIPv6, DMM, LISP, and AERO. 1318 6. Security Considerations 1320 This section discusses security and privacy for IPv6-based vehicular 1321 networking. Security and privacy are paramount in V2I, V2V, and V2X 1322 networking along with neighbor discovery and mobility management. 1324 Vehicles and infrastructure must be authenticated in order to 1325 participate in vehicular networking. For the authentication in 1326 vehicular networks, vehicular cloud needs to support a kind of Public 1327 Key Infrastructure (PKI) in an efficient way. To provide safe 1328 interaction between vehicles or between a vehicle and infrastructure, 1329 only authenticated nodes (i.e., vehicle and infrastructure node) can 1330 participate in vehicular networks. Also, in-vehicle devices (e.g., 1331 ECU) and a driver/passenger's mobile devices (e.g., smartphone and 1332 tablet PC) in a vehicle need to communicate with other in-vehicle 1333 devices and another driver/passenger's mobile devices in another 1334 vehicle, or other servers behind an IP-RSU in a secure way. Even 1335 though a vehicle is perfectly authenticated and legitimate, it may be 1336 hacked for running malicious applications to track and collect its 1337 and other vehicles' information. In this case, an attack mitigation 1338 process may be required to reduce the aftermath of malicious 1339 behaviors. 1341 For secure V2I communication, a secure channel (e.g., IPsec) between 1342 a mobile router (i.e., IP-OBU) in a vehicle and a fixed router (i.e., 1343 IP-RSU) in an EN needs to be established, as shown in Figure 2 1344 [RFC4301][RFC4302] [RFC4303][RFC4308] [RFC7296]. Also, for secure 1345 V2V communication, a secure channel (e.g., IPsec) between a mobile 1346 router (i.e., IP-OBU) in a vehicle and a mobile router (i.e., IP-OBU) 1347 in another vehicle needs to be established, as shown in Figure 3. 1348 For secure communication, an element in a vehicle (e.g., an in- 1349 vehicle device and a driver/passenger's mobile device) needs to 1350 establish a secure connection (e.g., TLS) with another element in 1351 another vehicle or another element in a vehicular cloud (e.g., a 1352 server). IEEE 1609.2 [WAVE-1609.2] specifies security services for 1353 applications and management messages, but this WAVE specification is 1354 optional. Thus, if the link layer does not support the security of a 1355 WAVE frame, either the network layer or the transport layer needs to 1356 support security services for the WAVE frames. 1358 6.1. Security Threats in Neighbor Discovery 1360 For the classical IPv6 ND, the DAD is required to ensure the 1361 uniqueness of the IPv6 address of a vehicle's wireless interface. 1362 This DAD can be used as a flooding attack that uses the DAD-related 1363 ND packets disseminated over the VANET or vehicular networks. 1364 [RFC6959] introduces threats enabled by IP source address spoofing. 1365 This possibility indicates that vehicles and IP-RSUs need to filter 1366 out suspicious ND traffic in advance. [RFC8928] introduces a 1367 mechanism that protects the ownership of an address for 6loWPAN ND 1368 from address theft and impersonation attacks. Based on the SEND 1369 [RFC3971] mechanism, the authentication for routers (i.e., IP-RSUs) 1370 can be conducted by only selecting an IP-RSU that has a certification 1371 path toward trusted parties. For authenticating other vehicles, the 1372 cryptographically generated address (CGA) can be used to verify the 1373 true owner of a received ND message, which requires to use the CGA ND 1374 option in the ND protocols. For a general protection of the ND 1375 mechanism, the RSA Signature ND option can also be used to protect 1376 the integrity of the messages by public key signatures. For a more 1377 advanced authentication mechanism, a distributed blockchain-based 1378 approach [Vehicular-BlockChain] can be used. However, for a scenario 1379 where a trustable router or an authentication path cannot be 1380 obtained, it is desirable to find a solution in which vehicles and 1381 infrastructures can authenticate each other without any support from 1382 a third party. 1384 When applying the classical IPv6 ND process to VANET, one of the 1385 security issues is that an IP-RSU (or an IP-OBU) as a router may 1386 receive deliberate or accidental DoS attacks from network scans that 1387 probe devices on a VANET. In this scenario, the IP-RSU can be 1388 overwhelmed for processing the network scan requests so that the 1389 capacity and resources of IP-RSU are exhausted, causing the failure 1390 of receiving normal ND messages from other hosts for network address 1391 resolution. [RFC6583] describes more about the operational problems 1392 in the classical IPv6 ND mechanism that can be vulnerable to 1393 deliberate or accidental DoS attacks and suggests several 1394 implementation guidelines and operational mitigation techniques for 1395 those problems. Nevertheless, for running IPv6 ND in VANET, those 1396 issues can be more acute since the movements of vehicles can be so 1397 diverse that it leaves a large room for rogue behaviors, and the 1398 failure of networking among vehicles may cause grave consequences. 1400 Strong security measures shall protect vehicles roaming in road 1401 networks from the attacks of malicious nodes, which are controlled by 1402 hackers. For safe driving applications (e.g., context-aware 1403 navigation, cooperative adaptive cruise control, and platooning), as 1404 explained in Section 3.1, the cooperative action among vehicles is 1405 assumed. Malicious nodes may disseminate wrong driving information 1406 (e.g., location, speed, and direction) for disturbing safe driving. 1407 For example, a Sybil attack, which tries to confuse a vehicle with 1408 multiple false identities, may disturb a vehicle from taking a safe 1409 maneuver. 1411 To identify malicious vehicles among vehicles, an authentication 1412 method may be required. A Vehicle Identification Number (VIN) and a 1413 user certificate (e.g., X.509 certificate [RFC5280]) along with an 1414 in-vehicle device's identifier generation can be used to efficiently 1415 authenticate a vehicle or its driver (having a user certificate) 1416 through a road infrastructure node (e.g., IP-RSU) connected to an 1417 authentication server in the vehicular cloud. This authentication 1418 can be used to identify the vehicle that will communicate with an 1419 infrastructure node or another vehicle. In the case where a vehicle 1420 has an internal network (called Moving Network) and elements in the 1421 network (e.g., in-vehicle devices and a user's mobile devices), as 1422 shown in Figure 2, the elements in the network need to be 1423 authenticated individually for safe authentication. Also, Transport 1424 Layer Security (TLS) certificates [RFC8446][RFC5280] can be used for 1425 an element's authentication to allow secure E2E vehicular 1426 communications between an element in a vehicle and another element in 1427 a server in a vehicular cloud, or between an element in a vehicle and 1428 another element in another vehicle. 1430 6.2. Security Threats in Mobility Management 1432 For mobility management, a malicious vehicle can construct multiple 1433 virtual bogus vehicles, and register them with IP-RSUs and MA. This 1434 registration makes the IP-RSUs and MA waste their resources. The IP- 1435 RSUs and MA need to determine whether a vehicle is genuine or bogus 1436 in mobility management. Also, the confidentiality of control packets 1437 and data packets among IP-RSUs and MA, the E2E paths (e.g., tunnels) 1438 need to be protected by secure communication channels. In addition, 1439 to prevent bogus IP-RSUs and MA from interfering with the IPv6 1440 mobility of vehicles, mutual authentication among them needs to be 1441 performed by certificates (e.g., TLS certificate). 1443 6.3. Other Threats 1445 For the setup of a secure channel over IPsec or TLS, the multihop V2I 1446 communications over DSRC or 5G V2X (or LTE V2X) is required in a 1447 highway. In this case, multiple intermediate vehicles as relay nodes 1448 can help forward association and authentication messages toward an 1449 IP-RSU (gNodeB, or eNodeB) connected to an authentication server in 1450 the vehicular cloud. In this kind of process, the authentication 1451 messages forwarded by each vehicle can be delayed or lost, which may 1452 increase the construction time of a connection or some vehicles may 1453 not be able to be authenticated. 1455 Even though vehicles can be authenticated with valid certificates by 1456 an authentication server in the vehicular cloud, the authenticated 1457 vehicles may harm other vehicles. To deal with this kind of security 1458 issue, for monitoring suspicious behaviors, vehicles' communication 1459 activities can be recorded in either a central way through a logging 1460 server (e.g., TCC) in the vehicular cloud or a distributed way (e.g., 1461 blockchain [Bitcoin]) along with other vehicles or infrastructure. 1462 To solve the issue ultimately, we need a solution where, without 1463 privacy breakage, vehicles may observe activities of each other to 1464 identify any misbehavior. Once identifying a misbehavior, a vehicle 1465 shall have a way to either isolate itself from others or isolate a 1466 suspicious vehicle by informing other vehicles. Alternatively, for 1467 completely secure vehicular networks, we shall embrace the concept of 1468 "zero-trust" for vehicles in which no vehicle is trustable and 1469 verifying every message is necessary. For doing so, we shall have an 1470 efficient zero-trust framework or mechanism for vehicular networks. 1472 For the non-repudiation of the harmful activities of malicious nodes, 1473 a blockchain technology can be used [Bitcoin]. Each message from a 1474 vehicle can be treated as a transaction and the neighboring vehicles 1475 can play the role of peers in a consensus method of a blockchain 1476 [Bitcoin] [Vehicular-BlockChain]. For a blockchain's efficient 1477 consensus in vehicular networks having fast moving vehicles, a new 1478 consensus algorithm needs to be developed or an existing consensus 1479 algorithm needs to be enhanced. 1481 To prevent an adversary from tracking a vehicle with its MAC address 1482 or IPv6 address, especially for a long-living transport-layer session 1483 (e.g., voice call over IP and video streaming service), a MAC address 1484 pseudonym needs to be provided to each vehicle; that is, each vehicle 1485 periodically updates its MAC address and its IPv6 address needs to be 1486 updated accordingly by the MAC address change [RFC4086][RFC4941]. 1487 Such an update of the MAC and IPv6 addresses should not interrupt the 1488 E2E communications between two vehicles (or between a vehicle and an 1489 IP-RSU) for a long-living transport-layer session. However, if this 1490 pseudonym is performed without strong E2E confidentiality (using 1491 either IPsec or TLS), there will be no privacy benefit from changing 1492 MAC and IPv6 addresses, because an adversary can observe the change 1493 of the MAC and IPv6 addresses and track the vehicle with those 1494 addresses. Thus, the MAC address pseudonym and the IPv6 address 1495 update should be performed with strong E2E confidentiality. 1497 7. IANA Considerations 1499 This document does not require any IANA actions. 1501 8. References 1502 8.1. Normative References 1504 [RFC8691] Benamar, N., Haerri, J., Lee, J., and T. Ernst, "Basic 1505 Support for IPv6 Networks Operating Outside the Context of 1506 a Basic Service Set over IEEE Std 802.11", RFC 8691, 1507 December 2019, . 1509 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1510 (IPv6) Specification", RFC 8200, July 2017, 1511 . 1513 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1514 Support in IPv6", RFC 6275, July 2011, 1515 . 1517 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1518 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1519 RFC 5213, August 2008, 1520 . 1522 [RFC7333] Chan, H., Liu, D., Seite, P., Yokota, H., and J. Korhonen, 1523 "Requirements for Distributed Mobility Management", 1524 RFC 7333, August 2014, 1525 . 1527 [RFC7429] Liu, D., Zuniga, JC., Seite, P., Chan, H., and CJ. 1528 Bernardos, "Distributed Mobility Management: Current 1529 Practices and Gap Analysis", RFC 7429, January 2015, 1530 . 1532 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1533 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 1534 RFC 3963, January 2005, 1535 . 1537 [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., 1538 Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. 1539 Alexander, "RPL: IPv6 Routing Protocol for Low-Power and 1540 Lossy Networks", RFC 6550, March 2012, 1541 . 1543 [RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology", 1544 RFC 3753, June 2004, 1545 . 1547 [RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And 1548 Provisioning of Wireless Access Points (CAPWAP) Protocol 1549 Specification", RFC 5415, March 2009, 1550 . 1552 [RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined 1553 Networking: A Perspective from within a Service Provider 1554 Environment", RFC 7149, March 2014, 1555 . 1557 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1558 "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, 1559 September 2007, . 1561 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1562 Address Autoconfiguration", RFC 4862, September 2007, 1563 . 1565 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1566 Addresses", RFC 4193, October 2005, 1567 . 1569 [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast 1570 Listener Discovery (MLD) for IPv6", RFC 2710, October 1571 1999, . 1573 [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery 1574 Version 2 (MLDv2) for IPv6", RFC 3810, June 2004, 1575 . 1577 [RFC5889] Baccelli, E. and M. Townsley, "IP Addressing Model in Ad 1578 Hoc Networks", RFC 5889, September 2010, 1579 . 1581 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1582 "Randomness Requirements for Security", RFC 4086, June 1583 2005, . 1585 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 1586 Extensions for Stateless Address Autoconfiguration in 1587 IPv6", RFC 4941, September 2007, 1588 . 1590 [RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix 1591 Reserved for Documentation", RFC 3849, July 2004, 1592 . 1594 [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, May 1595 2011, . 1597 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1598 Version 1.3", RFC 8446, August 2018, 1599 . 1601 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1602 Housley, R., and W. Polk, "Internet X.509 Public Key 1603 Infrastructure Certificate and Certificate Revocation List 1604 (CRL) Profile", RFC 5280, May 2008, 1605 . 1607 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1608 Internet Protocol", RFC 4301, December 2005, 1609 . 1611 [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December 1612 2005, . 1614 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 1615 RFC 4303, December 2005, 1616 . 1618 [RFC4308] Hoffman, P., "Cryptographic Suites for IPsec", RFC 4308, 1619 December 2005, . 1621 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 1622 Kivinen, "Internet Key Exchange Protocol Version 2 1623 (IKEv2)", RFC 7296, October 2014, 1624 . 1626 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1627 Hosts in a Multi-Prefix Network", RFC 8028, November 2016, 1628 . 1630 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 1631 Neighbor Discovery (SEND)", RFC 3971, March 2005, 1632 . 1634 [RFC8505] Thubert, P., Nordmark, E., Chakrabarti, S., and C. 1635 Perkins, "Registration Extensions for IPv6 over Low-Power 1636 Wireless Personal Area Network (6LoWPAN) Neighbor 1637 Discovery", RFC 8505, November 2018, 1638 . 1640 [RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann, 1641 "Neighbor Discovery Optimization for IPv6 over Low-Power 1642 Wireless Personal Area Networks (6LoWPANs)", RFC 6775, 1643 November 2012, . 1645 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1646 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 1647 2010, . 1649 [RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc 1650 Network (MANET) Neighborhood Discovery Protocol (NHDP)", 1651 RFC 6130, April 2011, 1652 . 1654 [RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational 1655 Neighbor Discovery Problems", RFC 6583, March 2012, 1656 . 1658 [RFC8928] Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, 1659 "Address-Protected Neighbor Discovery for Low-Power and 1660 Lossy Networks", RFC 8928, November 2020, 1661 . 1663 [RFC3626] Clausen, T. and P. Jacquet, "Optimized Link State Routing 1664 Protocol (OLSR)", RFC 3626, October 2003, 1665 . 1667 [RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg, 1668 "The Optimized Link State Routing Protocol Version 2", 1669 RFC 7181, April 2014, 1670 . 1672 [RFC7188] Dearlove, C. and T. Clausen, "Optimized Link State Routing 1673 Protocol Version 2 (OLSRv2) and MANET Neighborhood 1674 Discovery Protocol (NHDP) Extension TLVs", RFC 7188, April 1675 2014, . 1677 [RFC7722] Dearlove, C. and T. Clausen, "Multi-Topology Extension for 1678 the Optimized Link State Routing Protocol Version 2 1679 (OLSRv2)", RFC 7722, December 2015, 1680 . 1682 [RFC7779] Rogge, H. and E. Baccelli, "Directional Airtime Metric 1683 Based on Packet Sequence Numbers for Optimized Link State 1684 Routing Version 2 (OLSRv2)", RFC 7779, April 2016, 1685 . 1687 [RFC8218] Yi, J. and B. Parrein, "Multipath Extension for the 1688 Optimized Link State Routing Protocol Version 2 (OLSRv2)", 1689 RFC 8218, August 2017, 1690 . 1692 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 1693 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 1694 June 2017, . 1696 [RFC8629] Cheng, B. and L. Berger, "Dynamic Link Exchange Protocol 1697 (DLEP) Multi-Hop Forwarding Extension", RFC 8629, July 1698 2019, . 1700 [RFC8651] Cheng, B., Wiggins, D., and L. Berger, "Dynamic Link 1701 Exchange Protocol (DLEP) Control-Plane-Based Pause 1702 Extension", RFC 8651, October 2019, 1703 . 1705 [RFC8703] Taylor, R. and S. Ratliff, "Dynamic Link Exchange Protocol 1706 (DLEP) Link Identifier Extension", RFC 8703, February 1707 2020, . 1709 [RFC8757] Cheng, B. and L. Berger, "Dynamic Link Exchange Protocol 1710 (DLEP) Latency Range Extension", RFC 8757, March 2020, 1711 . 1713 [RFC7466] Dearlove, C. and T. Clausen, "An Optimization for the 1714 Mobile Ad Hoc Network (MANET) Neighborhood Discovery 1715 Protocol (NHDP)", RFC 7466, March 2015, 1716 . 1718 8.2. Informative References 1720 [ID-IPPL] Nordmark, E., "IP over Intentionally Partially Partitioned 1721 Links", Work in Progress, Internet-Draft, draft-ietf- 1722 intarea-ippl-00, March 2017, 1723 . 1726 [RFC6830BIS] 1727 Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. 1728 Cabellos, "The Locator/ID Separation Protocol (LISP)", 1729 Work in Progress, Internet-Draft, draft-ietf-lisp- 1730 rfc6830bis-36, November 2020, 1731 . 1734 [RFC6706BIS] 1735 Templin, F., "Automatic Extended Route Optimization 1736 (AERO)", Work in Progress, Internet-Draft, draft-templin- 1737 intarea-6706bis-99, March 2021, 1738 . 1741 [OMNI] Templin, F. and A. Whyman, "Transmission of IP Packets 1742 over Overlay Multilink Network (OMNI) Interfaces", Work in 1743 Progress, Internet-Draft, draft-templin-6man-omni-41, 1744 August 2021, . 1747 [UAM-ITS] Templin, F., "Urban Air Mobility Implications for 1748 Intelligent Transportation Systems", Work in Progress, 1749 Internet-Draft, draft-templin-ipwave-uam-its-04, January 1750 2021, . 1753 [DMM-FPC] Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S., 1754 Moses, D., and C. Perkins, "Protocol for Forwarding Policy 1755 Configuration (FPC) in DMM", Work in Progress, Internet- 1756 Draft, draft-ietf-dmm-fpc-cpdp-14, September 2020, 1757 . 1760 [ID-Multicast-Problems] 1761 Perkins, C., McBride, M., Stanley, D., Kumari, W., and JC. 1762 Zuniga, "Multicast Considerations over IEEE 802 Wireless 1763 Media", Work in Progress, Internet-Draft, draft-ietf- 1764 mboned-ieee802-mcast-problems-15, July 2021, 1765 . 1768 [DSRC] ASTM International, "Standard Specification for 1769 Telecommunications and Information Exchange Between 1770 Roadside and Vehicle Systems - 5 GHz Band Dedicated Short 1771 Range Communications (DSRC) Medium Access Control (MAC) 1772 and Physical Layer (PHY) Specifications", 1773 ASTM E2213-03(2010), October 2010. 1775 [EU-2008-671-EC] 1776 European Union, "Commission Decision of 5 August 2008 on 1777 the Harmonised Use of Radio Spectrum in the 5875 - 5905 1778 MHz Frequency Band for Safety-related Applications of 1779 Intelligent Transport Systems (ITS)", EU 2008/671/EC, 1780 August 2008. 1782 [IEEE-802.11p] 1783 "Part 11: Wireless LAN Medium Access Control (MAC) and 1784 Physical Layer (PHY) Specifications - Amendment 6: 1785 Wireless Access in Vehicular Environments", IEEE Std 1786 802.11p-2010, June 2010. 1788 [IEEE-802.11-OCB] 1789 "Part 11: Wireless LAN Medium Access Control (MAC) and 1790 Physical Layer (PHY) Specifications", IEEE Std 1791 802.11-2016, December 2016. 1793 [WAVE-1609.0] 1794 IEEE 1609 Working Group, "IEEE Guide for Wireless Access 1795 in Vehicular Environments (WAVE) - Architecture", IEEE Std 1796 1609.0-2013, March 2014. 1798 [WAVE-1609.2] 1799 IEEE 1609 Working Group, "IEEE Standard for Wireless 1800 Access in Vehicular Environments - Security Services for 1801 Applications and Management Messages", IEEE Std 1802 1609.2-2016, March 2016. 1804 [WAVE-1609.3] 1805 IEEE 1609 Working Group, "IEEE Standard for Wireless 1806 Access in Vehicular Environments (WAVE) - Networking 1807 Services", IEEE Std 1609.3-2016, April 2016. 1809 [WAVE-1609.4] 1810 IEEE 1609 Working Group, "IEEE Standard for Wireless 1811 Access in Vehicular Environments (WAVE) - Multi-Channel 1812 Operation", IEEE Std 1609.4-2016, March 2016. 1814 [ISO-ITS-IPv6] 1815 ISO/TC 204, "Intelligent Transport Systems - 1816 Communications Access for Land Mobiles (CALM) - IPv6 1817 Networking", ISO 21210:2012, June 2012. 1819 [ISO-ITS-IPv6-AMD1] 1820 ISO/TC 204, "Intelligent Transport Systems - 1821 Communications Access for Land Mobiles (CALM) - IPv6 1822 Networking - Amendment 1", ISO 21210:2012/AMD 1:2017, 1823 September 2017. 1825 [TS-23.285-3GPP] 1826 3GPP, "Architecture Enhancements for V2X Services", 3GPP 1827 TS 23.285/Version 16.2.0, December 2019. 1829 [TR-22.886-3GPP] 1830 3GPP, "Study on Enhancement of 3GPP Support for 5G V2X 1831 Services", 3GPP TR 22.886/Version 16.2.0, December 2018. 1833 [TS-23.287-3GPP] 1834 3GPP, "Architecture Enhancements for 5G System (5GS) to 1835 Support Vehicle-to-Everything (V2X) Services", 3GPP 1836 TS 23.287/Version 16.2.0, March 2020. 1838 [VIP-WAVE] Cespedes, S., Lu, N., and X. Shen, "VIP-WAVE: On the 1839 Feasibility of IP Communications in 802.11p Vehicular 1840 Networks", IEEE Transactions on Intelligent Transportation 1841 Systems, vol. 14, no. 1, March 2013. 1843 [Identity-Management] 1844 Wetterwald, M., Hrizi, F., and P. Cataldi, "Cross-layer 1845 Identities Management in ITS Stations", The 10th 1846 International Conference on ITS Telecommunications, 1847 November 2010. 1849 [SAINT] Jeong, J., Jeong, H., Lee, E., Oh, T., and D. Du, "SAINT: 1850 Self-Adaptive Interactive Navigation Tool for Cloud-Based 1851 Vehicular Traffic Optimization", IEEE Transactions on 1852 Vehicular Technology, Vol. 65, No. 6, June 2016. 1854 [SAINTplus] 1855 Shen, Y., Lee, J., Jeong, H., Jeong, J., Lee, E., and D. 1856 Du, "SAINT+: Self-Adaptive Interactive Navigation Tool+ 1857 for Emergency Service Delivery Optimization", 1858 IEEE Transactions on Intelligent Transportation Systems, 1859 June 2017. 1861 [SANA] Hwang, T. and J. Jeong, "SANA: Safety-Aware Navigation 1862 Application for Pedestrian Protection in Vehicular 1863 Networks", Springer Lecture Notes in Computer Science 1864 (LNCS), Vol. 9502, December 2015. 1866 [CASD] Shen, Y., Jeong, J., Oh, T., and S. Son, "CASD: A 1867 Framework of Context-Awareness Safety Driving in Vehicular 1868 Networks", International Workshop on Device Centric Cloud 1869 (DC2), March 2016. 1871 [CA-Cruise-Control] 1872 California Partners for Advanced Transportation Technology 1873 (PATH), "Cooperative Adaptive Cruise Control", Available: 1874 http://www.path.berkeley.edu/research/automated-and- 1875 connected-vehicles/cooperative-adaptive-cruise-control, 1876 2017. 1878 [Truck-Platooning] 1879 California Partners for Advanced Transportation Technology 1880 (PATH), "Automated Truck Platooning", Available: 1881 http://www.path.berkeley.edu/research/automated-and- 1882 connected-vehicles/truck-platooning, 2017. 1884 [FirstNet] U.S. National Telecommunications and Information 1885 Administration (NTIA), "First Responder Network Authority 1886 (FirstNet)", Available: https://www.firstnet.gov/, 2012. 1888 [FirstNet-Report] 1889 First Responder Network Authority, "FY 2017: ANNUAL REPORT 1890 TO CONGRESS, Advancing Public Safety Broadband 1891 Communications", FirstNet FY 2017, December 2017. 1893 [SignalGuru] 1894 Koukoumidis, E., Peh, L., and M. Martonosi, "SignalGuru: 1895 Leveraging Mobile Phones for Collaborative Traffic Signal 1896 Schedule Advisory", ACM MobiSys, June 2011. 1898 [Fuel-Efficient] 1899 van de Hoef, S., H. Johansson, K., and D. V. Dimarogonas, 1900 "Fuel-Efficient En Route Formation of Truck Platoons", 1901 IEEE Transactions on Intelligent Transportation Systems, 1902 January 2018. 1904 [Automotive-Sensing] 1905 Choi, J., Va, V., Gonzalez-Prelcic, N., Daniels, R., R. 1906 Bhat, C., and R. W. Heath, "Millimeter-Wave Vehicular 1907 Communication to Support Massive Automotive Sensing", 1908 IEEE Communications Magazine, December 2016. 1910 [NHTSA-ACAS-Report] 1911 National Highway Traffic Safety Administration (NHTSA), 1912 "Final Report of Automotive Collision Avoidance Systems 1913 (ACAS) Program", DOT HS 809 080, August 2000. 1915 [CBDN] Kim, J., Kim, S., Jeong, J., Kim, H., Park, J., and T. 1916 Kim, "CBDN: Cloud-Based Drone Navigation for Efficient 1917 Battery Charging in Drone Networks", IEEE Transactions on 1918 Intelligent Transportation Systems, November 2019. 1920 [In-Car-Network] 1921 Lim, H., Volker, L., and D. Herrscher, "Challenges in a 1922 Future IP/Ethernet-based In-Car Network for Real-Time 1923 Applications", ACM/EDAC/IEEE Design Automation Conference 1924 (DAC), June 2011. 1926 [Scrambler-Attack] 1927 Bloessl, B., Sommer, C., Dressier, F., and D. Eckhoff, 1928 "The Scrambler Attack: A Robust Physical Layer Attack on 1929 Location Privacy in Vehicular Networks", IEEE 2015 1930 International Conference on Computing, Networking and 1931 Communications (ICNC), February 2015. 1933 [Bitcoin] Nakamoto, S., "Bitcoin: A Peer-to-Peer Electronic Cash 1934 System", URL: https://bitcoin.org/bitcoin.pdf, May 2009. 1936 [Vehicular-BlockChain] 1937 Dorri, A., Steger, M., Kanhere, S., and R. Jurdak, 1938 "BlockChain: A Distributed Solution to Automotive Security 1939 and Privacy", IEEE Communications Magazine, Vol. 55, No. 1940 12, December 2017. 1942 [IPoWIRELESS] 1943 Thubert, P., "IPv6 Neighbor Discovery on Wireless 1944 Networks", Work in Progress, Internet-Draft, draft- 1945 thubert-6man-ipv6-over-wireless-09, May 2021, 1946 . 1949 [RFC6959] McPherson, D., Baker, F., and J. Halpern, "Source Address 1950 Validation Improvement (SAVI) Threat Scope", RFC 6959, May 1951 2013, . 1953 Appendix A. Support of Multiple Radio Technologies for V2V 1955 Vehicular networks may consist of multiple radio technologies such as 1956 DSRC and 5G V2X. Although a Layer-2 solution can provide a support 1957 for multihop communications in vehicular networks, the scalability 1958 issue related to multihop forwarding still remains when vehicles need 1959 to disseminate or forward packets toward multihop-away destinations. 1960 In addition, the IPv6-based approach for V2V as a network layer 1961 protocol can accommodate multiple radio technologies as MAC 1962 protocols, such as DSRC and 5G V2X. Therefore, the existing IPv6 1963 protocol can be augmented through the addition of a virtual interface 1964 (e.g., Overlay Multilink Network (OMNI) Interface [OMNI]) and/or 1965 protocol changes in order to support both wireless single-hop/ 1966 multihop V2V communications and multiple radio technologies in 1967 vehicular networks. In such a way, vehicles can communicate with 1968 each other by V2V communications to share either an emergency 1969 situation or road hazard information in a highway having multiple 1970 kinds of radio technologies. 1972 Appendix B. Support of Multihop V2X Networking 1974 The multihop V2X networking can be supported by RPL (IPv6 Routing 1975 Protocol for Low-Power and Lossy Networks) [RFC6550] and Overlay 1976 Multilink Network Interface (OMNI) [OMNI]. 1978 RPL defines an IPv6 routing protocol for low-power and lossy networks 1979 (LLN), mostly designed for home automation routing, building 1980 automation routing, industrial routing, and urban LLN routing. It 1981 uses a Destination-Oriented Directed Acyclic Graph (DODAG) to 1982 construct routing paths for hosts (e.g., IoT devices) in a network. 1983 The DODAG uses an objective function (OF) for route selection and 1984 optimization within the network. A user can use different routing 1985 metrics to define an OF for a specific scenario. RPL supports 1986 multipoint-to-point, point-to-multipoint, and point-to-point traffic, 1987 and the major traffic flow is the multipoint-to-point traffic. For 1988 example, in a highway scenario, a vehicle may not access an RSU 1989 directly because of the distance of the DSRC coverage (up to 1 km). 1990 In this case, the RPL can be extended to support a multihop V2I since 1991 a vehicle can take advantage of other vehicles as relay nodes to 1992 reach the RSU. Also, RPL can be extended to support both multihop 1993 V2V and V2X in the similar way. 1995 RPL is primarily designed to minimize the control plane activity, 1996 which is the relative amount of routing protocol exchanges versus 1997 data traffic; this approach is beneficial for situations where the 1998 power and bandwidth are scarce (e.g., an IoT LLN where RPL is 1999 typically used today), but also in situations of high relative 2000 mobility between the nodes in the network (also known as swarming, 2001 e.g., within a variable set of vehicles with a similar global motion, 2002 or a variable set of drones flying toward the same direction). 2004 To reduce the routing exchanges, RPL leverages a Distance Vector (DV) 2005 approach, which does not need a global knowledge of the topology, and 2006 only optimizes the routes to and from the root, allowing Peer-to-Peer 2007 (P2P) paths to be stretched. Although RPL installs its routes 2008 proactively, it only maintains them lazily, that is, in reaction to 2009 actual traffic, or as a slow background activity. Additionally, RPL 2010 leverages the concept of an objective function (called OF), which 2011 allows to adapt the activity of the routing protocol to use cases, 2012 e.g., type, speed, and quality of the radios. RPL does not need 2013 converge, and provides connectivity to most nodes most of the time. 2014 The default route toward the root is maintained aggressively and may 2015 change while a packet progresses without causing loops, so the packet 2016 will still reach the root. There are two modes for routing in RPL 2017 such as non-storing mode and storing mode. In non-storing mode, a 2018 node inside the mesh/swarm that changes its point(s) of attachment to 2019 the graph informs the root with a single unicast packet flowing along 2020 the default route, and the connectivity is restored immediately; this 2021 mode is preferable for use cases where Internet connectivity is 2022 dominant. On the other hand, in storing mode, the routing stretch is 2023 reduced, for a better P2P connectivity, while the Internet 2024 connectivity is restored more slowly, during the time for the DV 2025 operation to operate hop-by-hop. While an RPL topology can quickly 2026 scale up and down and fits the needs of mobility of vehicles, the 2027 total performance of the system will also depend on how quickly a 2028 node can form an address, join the mesh (including Authentication, 2029 Authorization, and Accounting (AAA)), and manage its global mobility 2030 to become reachable from another node outside the mesh. 2032 OMNI defines a protocol for the transmission of IPv6 packets over 2033 Overlay Multilink Network Interfaces that are virtual interfaces 2034 governing multiple physical network interfaces. OMNI supports 2035 multihop V2V communication between vehicles in multiple forwarding 2036 hops via intermediate vehicles with OMNI links. It also supports 2037 multihop V2I communication between a vehicle and an infrastructure 2038 access point by multihop V2V communication. The OMNI interface 2039 supports an NBMA link model where multihop V2V and V2I communications 2040 use each mobile node's ULAs without need for any DAD or MLD 2041 Messaging. 2043 Appendix C. Support of Mobility Management for V2I 2045 The seamless application communication between two vehicles or 2046 between a vehicle and an infrastructure node requires mobility 2047 management in vehicular networks. The mobility management schemes 2048 include a host-based mobility scheme, network-based mobility scheme, 2049 and software-defined networking scheme. 2051 In the host-based mobility scheme (e.g., MIPv6), an IP-RSU plays a 2052 role of a home agent. On the other hand, in the network-based 2053 mobility scheme (e.g., PMIPv6, an MA plays a role of a mobility 2054 management controller such as a Local Mobility Anchor (LMA) in 2055 PMIPv6, which also serves vehicles as a home agent, and an IP-RSU 2056 plays a role of an access router such as a Mobile Access Gateway 2057 (MAG) in PMIPv6 [RFC5213]. The host-based mobility scheme needs 2058 client functionality in IPv6 stack of a vehicle as a mobile node for 2059 mobility signaling message exchange between the vehicle and home 2060 agent. On the other hand, the network-based mobility scheme does not 2061 need such a client functionality for a vehicle because the network 2062 infrastructure node (e.g., MAG in PMIPv6) as a proxy mobility agent 2063 handles the mobility signaling message exchange with the home agent 2064 (e.g., LMA in PMIPv6) for the sake of the vehicle. 2066 There are a scalability issue and a route optimization issue in the 2067 network-based mobility scheme (e.g., PMIPv6) when an MA covers a 2068 large vehicular network governing many IP-RSUs. In this case, a 2069 distributed mobility scheme (e.g., DMM [RFC7429]) can mitigate the 2070 scalability issue by distributing multiple MAs in the vehicular 2071 network such that they are positioned closer to vehicles for route 2072 optimization and bottleneck mitigation in a central MA in the 2073 network-based mobility scheme. All these mobility approaches (i.e., 2074 a host-based mobility scheme, network-based mobility scheme, and 2075 distributed mobility scheme) and a hybrid approach of a combination 2076 of them need to provide an efficient mobility service to vehicles 2077 moving fast and moving along with the relatively predictable 2078 trajectories along the roadways. 2080 In vehicular networks, the control plane can be separated from the 2081 data plane for efficient mobility management and data forwarding by 2082 using the concept of Software-Defined Networking (SDN) 2083 [RFC7149][DMM-FPC]. Note that Forwarding Policy Configuration (FPC) 2084 in [DMM-FPC], which is a flexible mobility management system, can 2085 manage the separation of data-plane and control-plane in DMM. In 2086 SDN, the control plane and data plane are separated for the efficient 2087 management of forwarding elements (e.g., switches and routers) where 2088 an SDN controller configures the forwarding elements in a centralized 2089 way and they perform packet forwarding according to their forwarding 2090 tables that are configured by the SDN controller. An MA as an SDN 2091 controller needs to efficiently configure and monitor its IP-RSUs and 2092 vehicles for mobility management, location management, and security 2093 services. 2095 Appendix D. Acknowledgments 2097 This work was supported by Institute of Information & Communications 2098 Technology Planning & Evaluation (IITP) grant funded by the Korea 2099 MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based 2100 Security Intelligence Technology Development for the Customized 2101 Security Service Provisioning). 2103 This work was supported in part by the MSIT, Korea, under the ITRC 2104 (Information Technology Research Center) support program (IITP- 2105 2021-2017-0-01633) supervised by the IITP. 2107 This work was supported in part by the French research project 2108 DataTweet (ANR-13-INFR-0008) and in part by the HIGHTS project funded 2109 by the European Commission I (636537-H2020). 2111 This work was supported in part by the Cisco University Research 2112 Program Fund, Grant # 2019-199458 (3696), and by ANID Chile Basal 2113 Project FB0008. 2115 Appendix E. Contributors 2117 This document is a group work of IPWAVE working group, greatly 2118 benefiting from inputs and texts by Rex Buddenberg (Naval 2119 Postgraduate School), Thierry Ernst (YoGoKo), Bokor Laszlo (Budapest 2120 University of Technology and Economics), Jose Santa Lozanoi 2121 (Universidad of Murcia), Richard Roy (MIT), Francois Simon (Pilot), 2122 Sri Gundavelli (Cisco), Erik Nordmark, Dirk von Hugo (Deutsche 2123 Telekom), Pascal Thubert (Cisco), Carlos Bernardos (UC3M), Russ 2124 Housley (Vigil Security), Suresh Krishnan (Kaloom), Nancy Cam-Winget 2125 (Cisco), Fred L. Templin (The Boeing Company), Jung-Soo Park (ETRI), 2126 Zeungil (Ben) Kim (Hyundai Motors), Kyoungjae Sun (Soongsil 2127 University), Zhiwei Yan (CNNIC), YongJoon Joe (LSware), Peter E. Yee 2128 (Akayla), and Erik Kline. The authors sincerely appreciate their 2129 contributions. 2131 The following are co-authors of this document: 2133 Nabil Benamar 2135 Department of Computer Sciences, High School of Technology of Meknes, 2136 Moulay Ismail University, Morocco, Phone: +212 6 70 83 22 36, EMail: 2137 benamar73@gmail.com 2139 Sandra Cespedes 2141 NIC Chile Research Labs, Universidad de Chile, Av. Blanco Encalada 2142 1975, Santiago, Chile, Phone: +56 2 29784093, EMail: 2143 scespede@niclabs.cl 2145 Jerome Haerri 2147 Communication Systems Department, EURECOM, Sophia-Antipolis, France, 2148 Phone: +33 4 93 00 81 34, EMail: jerome.haerri@eurecom.fr 2150 Dapeng Liu 2152 Alibaba, Beijing, Beijing 100022, China, Phone: +86 13911788933, 2153 EMail: max.ldp@alibaba-inc.com 2155 Tae (Tom) Oh 2157 Department of Information Sciences and Technologies, Rochester 2158 Institute of Technology, One Lomb Memorial Drive, Rochester, NY 2159 14623-5603, USA, Phone: +1 585 475 7642, EMail: Tom.Oh@rit.edu 2161 Charles E. Perkins 2162 Futurewei Inc., 2330 Central Expressway, Santa Clara, CA 95050, USA, 2163 Phone: +1 408 330 4586, EMail: charliep@computer.org 2165 Alexandre Petrescu 2167 CEA, LIST, CEA Saclay, Gif-sur-Yvette, Ile-de-France 91190, France, 2168 Phone: +33169089223, EMail: Alexandre.Petrescu@cea.fr 2170 Yiwen Chris Shen 2172 Department of Computer Science & Engineering, Sungkyunkwan 2173 University, 2066 Seobu-Ro, Jangan-Gu, Suwon, Gyeonggi-Do 16419, 2174 Republic of Korea, Phone: +82 31 299 4106, Fax: +82 31 290 7996, 2175 EMail: chrisshen@skku.edu, URI: https://chrisshen.github.io 2177 Michelle Wetterwald 2179 FBConsulting, 21, Route de Luxembourg, Wasserbillig, Luxembourg 2180 L-6633, Luxembourg, EMail: Michelle.Wetterwald@gmail.com 2182 Author's Address 2184 Jaehoon (Paul) Jeong (editor) 2185 Department of Computer Science and Engineering 2186 Sungkyunkwan University 2187 2066 Seobu-Ro, Jangan-Gu 2188 Suwon 2189 Gyeonggi-Do 2190 16419 2191 Republic of Korea 2193 Phone: +82 31 299 4957 2194 Email: pauljeong@skku.edu 2195 URI: http://iotlab.skku.edu/people-jaehoon-jeong.php