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Jeong, Ed. 3 Internet-Draft Sungkyunkwan University 4 Intended status: Informational 30 March 2022 5 Expires: 1 October 2022 7 IPv6 Wireless Access in Vehicular Environments (IPWAVE): Problem 8 Statement and Use Cases 9 draft-ietf-ipwave-vehicular-networking-28 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 1 October 2022. 42 Copyright Notice 44 Copyright (c) 2022 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 49 license-info) in effect on the date of publication of this document. 50 Please review these documents carefully, as they describe your rights 51 and restrictions with respect to this document. Code Components 52 extracted from this document must include Revised BSD License text as 53 described in Section 4.e of the Trust Legal Provisions and are 54 provided without warranty as described in the Revised BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7 61 3.1. V2V . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 62 3.2. V2I . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 63 3.3. V2X . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 64 4. Vehicular Networks . . . . . . . . . . . . . . . . . . . . . 13 65 4.1. Vehicular Network Architecture . . . . . . . . . . . . . 14 66 4.2. V2I-based Internetworking . . . . . . . . . . . . . . . . 16 67 4.3. V2V-based Internetworking . . . . . . . . . . . . . . . . 19 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 . . . . . . . . . . . . . . . . . . . . . 35 79 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 35 80 8.1. Normative References . . . . . . . . . . . . . . . . . . 35 81 8.2. Informative References . . . . . . . . . . . . . . . . . 40 82 Appendix A. Support of Multiple Radio Technologies for V2V . . . 46 83 Appendix B. Support of Multihop V2X Networking . . . . . . . . . 46 84 Appendix C. Support of Mobility Management for V2I . . . . . . . 48 85 Appendix D. Support of MTU Diversity for IP-based Vehicular 86 Networks . . . . . . . . . . . . . . . . . . . . . . . . 49 87 Appendix E. Acknowledgments . . . . . . . . . . . . . . . . . . 50 88 Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 51 89 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 52 91 1. Introduction 93 Vehicular networking studies have mainly focused on improving safety 94 and efficiency, and also enabling entertainment in vehicular 95 networks. The Federal Communications Commission (FCC) in the US 96 allocated wireless channels for Dedicated Short-Range Communications 97 (DSRC) [DSRC] in the Intelligent Transportation Systems (ITS) with 98 the frequency band of 5.850 - 5.925 GHz (i.e., 5.9 GHz band). DSRC- 99 based wireless communications can support vehicle-to-vehicle (V2V), 100 vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X) 101 networking. The European Union (EU) allocated radio spectrum for 102 safety-related and non-safety-related applications of ITS with the 103 frequency band of 5.875 - 5.905 GHz, as part of the Commission 104 Decision 2008/671/EC [EU-2008-671-EC]. Most countries and regions in 105 the world have adopted the same frequency allocation for vehicular 106 networks. 108 For direct inter-vehicular wireless connectivity, IEEE has amended 109 standard 802.11 (commonly known as Wi-Fi) to enable safe driving 110 services based on DSRC for the Wireless Access in Vehicular 111 Environments (WAVE) system. The Physical Layer (L1) and Data Link 112 Layer (L2) issues are addressed in IEEE 802.11p [IEEE-802.11p] for 113 the PHY and MAC of the DSRC, while IEEE 1609.2 [WAVE-1609.2] covers 114 security aspects, IEEE 1609.3 [WAVE-1609.3] defines related services 115 at network and transport layers, and IEEE 1609.4 [WAVE-1609.4] 116 specifies the multi-channel operation. IEEE 802.11p was first a 117 separate amendment, but was later rolled into the base 802.11 118 standard (IEEE 802.11-2012) as IEEE 802.11 Outside the Context of a 119 Basic Service Set (OCB) in 2012 [IEEE-802.11-OCB]. 121 3GPP has standardized Cellular Vehicle-to-Everything (C-V2X) 122 communications to support V2X in LTE mobile networks (called LTE V2X) 123 and V2X in 5G mobile networks (called 5G V2X) [TS-23.285-3GPP] 124 [TR-22.886-3GPP][TS-23.287-3GPP]. With C-V2X, vehicles can directly 125 communicate with each other without relay nodes (e.g., eNodeB in LTE 126 and gNodeB in 5G). 128 Along with these WAVE standards and C-V2X standards, regardless of a 129 wireless access technology under the IP stack of a vehicle, vehicular 130 networks can operate IP mobility with IPv6 [RFC8200] and Mobile IPv6 131 protocols (e.g., Mobile IPv6 (MIPv6) [RFC6275], Proxy MIPv6 (PMIPv6) 132 [RFC5213], Distributed Mobility Management (DMM) [RFC7333], Network 133 Mobility (NEMO) [RFC3963], Locator/ID Separation Protocol (LISP) 134 [I-D.ietf-lisp-rfc6830bis], and Automatic Extended Route Optimization 135 based on the Overlay Multilink Network Interface (AERO/OMNI) 136 [I-D.templin-6man-aero] [I-D.templin-6man-omni]). In addition, ISO 137 has approved a standard specifying the IPv6 network protocols and 138 services to be used for Communications Access for Land Mobiles (CALM) 139 [ISO-ITS-IPv6][ISO-ITS-IPv6-AMD1]. 141 This document describes use cases and a problem statement about 142 IPv6-based vehicular networking for ITS, which is named IPv6 Wireless 143 Access in Vehicular Environments (IPWAVE). First, it introduces the 144 use cases for using V2V, V2I, and V2X networking in ITS. Next, for 145 IPv6-based vehicular networks, it makes a gap analysis of current 146 IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management, 147 and Security & Privacy), and then enumerates requirements for the 148 extensions of those IPv6 protocols, which are tailored to IPv6-based 149 vehicular networking. Thus, this document is intended to motivate 150 development of key protocols for IPWAVE. 152 2. Terminology 154 This document uses the terminology described in [RFC8691]. In 155 addition, the following terms are defined below: 157 * Class-Based Safety Plan: A vehicle can make a safety plan by 158 classifying the surrounding vehicles into different groups for 159 safety purposes according to the geometrical relationship among 160 them. The vehicle groups can be classified as Line-of-Sight 161 Unsafe, Non-Line-of-Sight Unsafe, and Safe groups [CASD]. 163 * Context-Awareness: A vehicle can be aware of spatial-temporal 164 mobility information (e.g., position, speed, direction, and 165 acceleration/deceleration) of surrounding vehicles for both safety 166 and non-safety uses through sensing or communication [CASD]. 168 * DMM: "Distributed Mobility Management" [RFC7333][RFC7429]. 170 * Edge Computing (EC): It is the local computing near an access 171 network (i.e., edge network) for the sake of vehicles and 172 pedestrians. 174 * Edge Computing Device (ECD): It is a computing device (or server) 175 for edge computing for the sake of vehicles and pedestrians. 177 * Edge Network (EN): It is an access network that has an IP-RSU for 178 wireless communication with other vehicles having an IP-OBU and 179 wired communication with other network devices (e.g., routers, IP- 180 RSUs, ECDs, servers, and MA). It may have a Global Positioning 181 System (GPS) radio receiver for its position recognition and the 182 localization service for the sake of vehicles. 184 * IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a 185 computer situated in a vehicle (e.g., car, bicycle, autobike, 186 motorcycle, and a similar one). It has at least one IP interface 187 that runs in IEEE 802.11-OCB and has an "OBU" transceiver. Also, 188 it may have an IP interface that runs in Cellular V2X (C-V2X) 189 [TS-23.285-3GPP] [TR-22.886-3GPP][TS-23.287-3GPP]. It can play a 190 role of a router connecting multiple computers (or in-vehicle 191 devices) inside a vehicle. See the definition of the term "OBU" 192 in [RFC8691]. 194 * IP-RSU: "IP Roadside Unit": An IP-RSU is situated along the road. 195 It has at least two distinct IP-enabled interfaces. The wireless 196 PHY/MAC layer of at least one of its IP-enabled interfaces is 197 configured to operate in 802.11-OCB mode. An IP-RSU communicates 198 with the IP-OBU over an 802.11 wireless link operating in OCB 199 mode. Also, it may have the third IP-enabled wireless interface 200 running in 3GPP C-V2X in addition to the IP-RSU defined in 201 [RFC8691]. An IP-RSU is similar to an Access Network Router 202 (ANR), defined in [RFC3753], and a Wireless Termination Point 203 (WTP), defined in [RFC5415]. See the definition of the term "RSU" 204 in [RFC8691]. 206 * LiDAR: "Light Detection and Ranging". It is a scanning device to 207 measure a distance to an object by emitting pulsed laser light and 208 measuring the reflected pulsed light. 210 * Mobility Anchor (MA): A node that maintains IPv6 addresses and 211 mobility information of vehicles in a road network to support 212 their IPv6 address autoconfiguration and mobility management with 213 a binding table. An MA has End-to-End (E2E) connections (e.g., 214 tunnels) with IP-RSUs under its control for the address 215 autoconfiguration and mobility management of the vehicles. This 216 MA is similar to a Local Mobility Anchor (LMA) in PMIPv6 [RFC5213] 217 for network-based mobility management. 219 * OCB: "Outside the Context of a Basic Service Set - BSS". It is a 220 mode of operation in which a Station (STA) is not a member of a 221 BSS and does not utilize IEEE Std 802.11 authentication, 222 association, or data confidentiality [IEEE-802.11-OCB]. 224 * 802.11-OCB: It refers to the mode specified in IEEE Std 225 802.11-2016 [IEEE-802.11-OCB] when the MIB attribute 226 dot11OCBActivited is 'true'. 228 * Platooning: Moving vehicles can be grouped together to reduce air- 229 resistance for energy efficiency and reduce the number of drivers 230 such that only the leading vehicle has a driver, and the other 231 vehicles are autonomous vehicles without a driver and closely 232 follow the leading vehicle [Truck-Platooning]. 234 * Traffic Control Center (TCC): A system that manages road 235 infrastructure nodes (e.g., IP-RSUs, MAs, traffic signals, and 236 loop detectors), and also maintains vehicular traffic statistics 237 (e.g., average vehicle speed and vehicle inter-arrival time per 238 road segment) and vehicle information (e.g., a vehicle's 239 identifier, position, direction, speed, and trajectory as a 240 navigation path). TCC is part of a vehicular cloud for vehicular 241 networks. 243 * Vehicle: A Vehicle in this document is a node that has an IP-OBU 244 for wireless communication with other vehicles and IP-RSUs. It 245 has a GPS radio navigation receiver for efficient navigation. Any 246 device having an IP-OBU and a GPS receiver (e.g., smartphone and 247 tablet PC) can be regarded as a vehicle in this document. 249 * Vehicular Ad Hoc Network (VANET): A network that consists of 250 vehicles interconnected by wireless communication. Two vehicles 251 in a VANET can communicate with each other using other vehicles as 252 relays even where they are out of one-hop wireless communication 253 range. 255 * Vehicular Cloud: A cloud infrastructure for vehicular networks, 256 having compute nodes, storage nodes, and network forwarding 257 elements (e.g., switch and router). 259 * V2D: "Vehicle to Device". It is the wireless communication 260 between a vehicle and a device (e.g., smartphone and IoT device). 262 * V2I2D: "Vehicle to Infrastructure to Device". It is the wireless 263 communication between a vehicle and a device (e.g., smartphone and 264 IoT device) via an infrastructure node (e.g., IP-RSU). 266 * V2I2V: "Vehicle to Infrastructure to Vehicle". It is the wireless 267 communication between a vehicle and another vehicle via an 268 infrastructure node (e.g., IP-RSU). 270 * V2I2X: "Vehicle to Infrastructure to Everything". It is the 271 wireless communication between a vehicle and another entity (e.g., 272 vehicle, smartphone, and IoT device) via an infrastructure node 273 (e.g., IP-RSU). 275 * V2X: "Vehicle to Everything". It is the wireless communication 276 between a vehicle and any entity (e.g., vehicle, infrastructure 277 node, smartphone, and IoT device), including V2V, V2I, and V2D. 279 * VIP: "Vehicular Internet Protocol". It is an IPv6 extension for 280 vehicular networks including V2V, V2I, and V2X. 282 * VMM: "Vehicular Mobility Management". It is an IPv6-based 283 mobility management for vehicular networks. 285 * VND: "Vehicular Neighbor Discovery". It is an IPv6 ND extension 286 for vehicular networks. 288 * VSP: "Vehicular Security and Privacy". It is an IPv6-based 289 security and privacy term for vehicular networks. 291 * WAVE: "Wireless Access in Vehicular Environments" [WAVE-1609.0]. 293 3. Use Cases 295 This section explains use cases of V2V, V2I, and V2X networking. The 296 use cases of the V2X networking exclude the ones of the V2V and V2I 297 networking, but include Vehicle-to-Pedestrian (V2P) and Vehicle-to- 298 Device (V2D). 300 IP is widely used among popular end-user devices (e.g., smartphone 301 and tablet) in the Internet. Applications (e.g., navigator 302 application) for those devices can be extended such that the V2V use 303 cases in this section can work with IPv6 as a network layer protocol 304 and IEEE 802.11-OCB as a link layer protocol. In addition, IPv6 305 security needs to be extended to support those V2V use cases in a 306 safe, secure, privacy-preserving way. 308 The use cases presented in this section serve as the description and 309 motivation for the need to augment IPv6 and its protocols to 310 facilitate "Vehicular IPv6". Section 5 summarizes the overall 311 problem statement and IPv6 requirements. Note that the adjective 312 "Vehicular" in this document is used to represent extensions of 313 existing protocols such as IPv6 Neighbor Discovery, IPv6 Mobility 314 Management (e.g., PMIPv6 [RFC5213] and DMM [RFC7429]), and IPv6 315 Security and Privacy Mechanisms rather than new "vehicular-specific" 316 functions. 318 3.1. V2V 320 The use cases of V2V networking discussed in this section include 322 * Context-aware navigation for safe driving and collision avoidance; 324 * Cooperative adaptive cruise control in a roadway; 326 * Platooning in a highway; 328 * Cooperative environment sensing; 330 * Collision avoidance service of end systems of Urban Air Mobility 331 (UAM). 333 These five techniques will be important elements for autonomous 334 vehicles, which may be either terrestrial vehicles or UAM end 335 systems. 337 Context-Aware Safety Driving (CASD) navigator [CASD] can help drivers 338 to drive safely by alerting them to dangerous obstacles and 339 situations. That is, a CASD navigator displays obstacles or 340 neighboring vehicles relevant to possible collisions in real-time 341 through V2V networking. CASD provides vehicles with a class-based 342 automatic safety action plan, which considers three situations, 343 namely, the Line-of-Sight unsafe, Non-Line-of-Sight unsafe, and safe 344 situations. This action plan can be put into action among multiple 345 vehicles using V2V networking. 347 Cooperative Adaptive Cruise Control (CACC) [CA-Cruise-Control] helps 348 individual vehicles to adapt their speed autonomously through V2V 349 communication among vehicles according to the mobility of their 350 predecessor and successor vehicles in an urban roadway or a highway. 351 Thus, CACC can help adjacent vehicles to efficiently adjust their 352 speed in an interactive way through V2V networking in order to avoid 353 a collision. 355 Platooning [Truck-Platooning] allows a series (or group) of vehicles 356 (e.g., trucks) to follow each other very closely. Trucks can use V2V 357 communication in addition to forward sensors in order to maintain 358 constant clearance between two consecutive vehicles at very short 359 gaps (from 3 meters to 10 meters). Platooning can maximize the 360 throughput of vehicular traffic in a highway and reduce the gas 361 consumption because the leading vehicle can help the following 362 vehicles to experience less air resistance. 364 Cooperative-environment-sensing use cases suggest that vehicles can 365 share environmental information (e.g., air pollution, hazards/ 366 obstacles, slippery areas by snow or rain, road accidents, traffic 367 congestion, and driving behaviors of neighboring vehicles) from 368 various vehicle-mounted sensors, such as radars, LiDARs, and cameras, 369 with other vehicles and pedestrians. [Automotive-Sensing] introduces 370 millimeter-wave vehicular communication for massive automotive 371 sensing. A lot of data can be generated by those sensors, and these 372 data typically need to be routed to different destinations. In 373 addition, from the perspective of driverless vehicles, it is expected 374 that driverless vehicles can be mixed with driver-operated vehicles. 375 Through cooperative environment sensing, driver-operated vehicles can 376 use environmental information sensed by driverless vehicles for 377 better interaction with the other vehicles and environment. Vehicles 378 can also share their intended maneuvering information (e.g., lane 379 change, speed change, ramp in-and-out, cut-in, and abrupt braking) 380 with neighboring vehicles. Thus, this information sharing can help 381 the vehicles behave as more efficient traffic flows and minimize 382 unnecessary acceleration and deceleration to achieve the best ride 383 comfort. 385 A collision avoidance service of UAM end systems in air can be 386 envisioned as a use case in air vehicular environments 387 [I-D.templin-ipwave-uam-its]. This use case is similar to the 388 context-aware navigator for terrestrial vehicles. Through V2V 389 coordination, those UAM end systems (e.g., drones) can avoid a 390 dangerous situation (e.g., collision) in three-dimensional space 391 rather than two-dimensional space for terrestrial vehicles. Also, 392 UAM end systems (e.g., flying car) with only a few meters off the 393 ground can communicate with terrestrial vehicles with wireless 394 communication technologies (e.g., DSRC, LTE, and C-V2X). Thus, V2V 395 means any vehicle to any vehicle, whether the vehicles are ground- 396 level or not. 398 To encourage more vehicles to participate in this cooperative 399 environmental sensing, a reward system will be needed. Sensing 400 activities of each vehicle need to be logged in either a central way 401 through a logging server (e.g., TCC) in the vehicular cloud or a 402 distributed way (e.g., blockchain [Bitcoin]) through other vehicles 403 or infrastructure. In the case of a blockchain, each sensing message 404 from a vehicle can be treated as a transaction and the neighboring 405 vehicles can play the role of peers in a consensus method of a 406 blockchain [Bitcoin][Vehicular-BlockChain]. 408 To support applications of these V2V use cases, the required 409 functions of IPv6 include IPv6-based packet exchange and secure, safe 410 communication between two vehicles. For the support of V2V under 411 multiple radio technologies (e.g., DSRC and 5G V2X), refer to 412 Appendix A. 414 3.2. V2I 416 The use cases of V2I networking discussed in this section include 418 * Navigation service; 420 * Energy-efficient speed recommendation service; 422 * Accident notification service; 424 * Electric vehicle (EV) charging service; 426 * UAM navigation service with efficient battery charging. 428 A navigation service, for example, the Self-Adaptive Interactive 429 Navigation Tool (SAINT) [SAINT], using V2I networking interacts with 430 a TCC for the large-scale/long-range road traffic optimization and 431 can guide individual vehicles along appropriate navigation paths in 432 real time. The enhanced version of SAINT [SAINTplus] can give fast 433 moving paths to emergency vehicles (e.g., ambulance and fire engine) 434 to let them reach an accident spot while redirecting other vehicles 435 near the accident spot into efficient detour paths. 437 Either a TCC or an ECD can recommend an energy-efficient speed to a 438 vehicle that depends on its traffic environment and traffic signal 439 scheduling [SignalGuru]. For example, when a vehicle approaches an 440 intersection area and a red traffic light for the vehicle becomes 441 turned on, it needs to reduce its speed to save fuel consumption. In 442 this case, either a TCC or an ECD, which has the up-to-date 443 trajectory of the vehicle and the traffic light schedule, can notify 444 the vehicle of an appropriate speed for fuel efficiency. 445 [Fuel-Efficient] studies fuel-efficient route and speed plans for 446 platooned trucks. 448 The emergency communication between accident vehicles (or emergency 449 vehicles) and a TCC can be performed via either IP-RSU or 4G-LTE 450 networks. The First Responder Network Authority (FirstNet) 451 [FirstNet] is provided by the US government to establish, operate, 452 and maintain an interoperable public safety broadband network for 453 safety and security network services, e.g., emergency calls. The 454 construction of the nationwide FirstNet network requires each state 455 in the US to have a Radio Access Network (RAN) that will connect to 456 the FirstNet's network core. The current RAN is mainly constructed 457 using 4G-LTE for the communication between a vehicle and an 458 infrastructure node (i.e., V2I) [FirstNet-Report], but it is expected 459 that DSRC-based vehicular networks [DSRC] will be available for V2I 460 and V2V in the near future. An equivalent project in Europe is 461 called Public Safety Communications Europe (PSCE) [PSCE], which is 462 developing a network for emergency communications. 464 An EV charging service with V2I can facilitate the efficient battery 465 charging of EVs. In the case where an EV charging station is 466 connected to an IP-RSU, an EV can be guided toward the deck of the EV 467 charging station or be notified that the charging station is out of 468 service through a battery charging server connected to the IP-RSU. 469 In addition to this EV charging service, other value-added services 470 (e.g., air firmware/software update and media streaming) can be 471 provided to an EV while it is charging its battery at the EV charging 472 station. 474 A UAM navigation service with efficient battery charging can plan the 475 battery charging schedule of UAM end systems (e.g., drone) for long- 476 distance flying [CBDN]. For this battery charging schedule, a UAM 477 end system can communicate with an infrastructure node (e.g., IP-RSU) 478 toward a cloud server via V2I communications. This cloud server can 479 coordinate the battery charging schedules of multiple UAM end systems 480 for their efficient navigation path, considering flight time from 481 their current position to a battery charging station, waiting time in 482 a waiting queue at the station, and battery charging time at the 483 station. 485 In some scenarios such as vehicles moving in highways or staying in 486 parking lots, a V2V2I network is necessary for vehicles to access the 487 Internet since some vehicles may not be covered by an RSU. For those 488 vehicles, a few relay vehicles can help to build the Internet access. 489 For the nested NEMO described in [RFC4888], hosts inside a vehicle 490 shown in Figure 3 for the case of V2V2I may have the same issue in 491 the nested NEMO scenario. 493 To better support these use cases, the existing IPv6 protocol must be 494 augmented either through protocol changes or by including a new 495 adaptation layer in the architecture that efficiently maps IPv6 to a 496 diversity of link layer technologies. Augmentation is necessary to 497 support wireless multihop V2I communications in a highway where RSUs 498 are sparsely deployed, so a vehicle can reach the wireless coverage 499 of an RSU through the multihop data forwarding of intermediate 500 vehicles as packet forwarders. Thus, IPv6 needs to be extended for 501 multihop V2I communications. 503 To support applications of these V2I use cases, the required 504 functions of IPv6 include IPv6 communication enablement with 505 neighborhood discovery and IPv6 address management, reachability with 506 adapted network models and routing methods, transport-layer session 507 continuity, and secure, safe communication between a vehicle and an 508 infrastructure node (e.g., IP-RSU) in the vehicular network. 510 3.3. V2X 512 The use case of V2X networking discussed in this section is for a 513 pedestrian protection service. 515 A pedestrian protection service, such as Safety-Aware Navigation 516 Application (SANA) [SANA], using V2I2P networking can reduce the 517 collision of a vehicle and a pedestrian carrying a smartphone 518 equipped with a network device for wireless communication (e.g., Wi- 519 Fi) with an IP-RSU. Vehicles and pedestrians can also communicate 520 with each other via an IP-RSU. An edge computing device behind the 521 IP-RSU can collect the mobility information from vehicles and 522 pedestrians, compute wireless communication scheduling for the sake 523 of them. This scheduling can save the battery of each pedestrian's 524 smartphone by allowing it to work in sleeping mode before the 525 communication with vehicles, considering their mobility. 527 For Vehicle-to-Pedestrian (V2P), a vehicle can directly communicate 528 with a pedestrian's smartphone by V2X without IP-RSU relaying. 529 Light-weight mobile nodes such as bicycles may also communicate 530 directly with a vehicle for collision avoidance using V2V. Note that 531 it is true that a pedestrian or a cyclist may have a higher risk of 532 being hit by a vehicle if they are not with a smartphone in the 533 current setting. For this case, other human sensing technologies 534 (e.g., moving object detection in images and wireless signal-based 535 human movement detection [LIFS] [DFC]) can be used to provide the 536 motion information of them to vehicles. A vehicle by V2V2I 537 networking can obtain the motion information of a vulnerable road 538 user via an IP-RSU that either employs or connects to a human sensing 539 technology. 541 The existing IPv6 protocol must be augmented through protocol changes 542 in order to support wireless multihop V2X or V2I2X communications in 543 an urban road network where RSUs are deployed at intersections, so a 544 vehicle (or a pedestrian's smartphone) can reach the wireless 545 coverage of an RSU through the multihop data forwarding of 546 intermediate vehicles (or pedestrians' smartphones) as packet 547 forwarders. Thus, IPv6 needs to be extended for multihop V2X or 548 V2I2X communications. 550 To support applications of these V2X use cases, the required 551 functions of IPv6 include IPv6-based packet exchange, transport-layer 552 session continuity, and secure, safe communication between a vehicle 553 and a pedestrian either directly or indirectly via an IP-RSU. 555 4. Vehicular Networks 557 This section describes the context for vehicular networks supporting 558 V2V, V2I, and V2X communications. It describes an internal network 559 within a vehicle or an edge network (called EN). It explains not 560 only the internetworking between the internal networks of a vehicle 561 and an EN via wireless links, but also the internetworking between 562 the internal networks of two vehicles via wireless links. 564 Traffic Control Center in Vehicular Cloud 565 ******************************************* 566 +-------------+ * * 567 |Correspondent| * +-----------------+ * 568 | Node |<->* | Mobility Anchor | * 569 +-------------+ * +-----------------+ * 570 * ^ * 571 * | * 572 * v * 573 ******************************************* 574 ^ ^ ^ 575 | | | 576 | | | 577 v v v 578 +---------+ +---------+ +---------+ 579 | IP-RSU1 |<--------->| IP-RSU2 |<--------->| IP-RSU3 | 580 +---------+ +---------+ +---------+ 581 ^ ^ ^ 582 : : : 583 +-----------------+ +-----------------+ +-----------------+ 584 | : V2I | | : V2I | | : V2I | 585 | v | | v | | v | 586 +--------+ | +--------+ | | +--------+ | | +--------+ | 587 |Vehicle1|===> |Vehicle2|===>| | |Vehicle3|===>| | |Vehicle4|===>| 588 +--------+<...>+--------+<........>+--------+ | | +--------+ | 589 V2V ^ V2V ^ | | ^ | 590 | : V2V | | : V2V | | : V2V | 591 | v | | v | | v | 592 | +--------+ | | +--------+ | | +--------+ | 593 | |Vehicle5|===> | | |Vehicle6|===>| | |Vehicle7|==>| 594 | +--------+ | | +--------+ | | +--------+ | 595 +-----------------+ +-----------------+ +-----------------+ 596 Subnet1 Subnet2 Subnet3 597 (Prefix1) (Prefix2) (Prefix3) 599 <----> Wired Link <....> Wireless Link ===> Moving Direction 601 Figure 1: An Example Vehicular Network Architecture for V2I and V2V 603 4.1. Vehicular Network Architecture 605 Figure 1 shows an example vehicular network architecture for V2I and 606 V2V in a road network. The vehicular network architecture contains 607 vehicles (including IP-OBU), IP-RSUs, Mobility Anchor, Traffic 608 Control Center, and Vehicular Cloud as components. These components 609 are not mandatory, and they can be deployed into vehicular networks 610 in various ways. Some of them (e.g., Mobility Anchor, Traffic 611 Control Center, and Vehicular Cloud) may not be needed for the 612 vehicular networks according to target use cases in Section 3. 614 Existing network architectures, such as the network architectures of 615 PMIPv6 [RFC5213], RPL (IPv6 Routing Protocol for Low-Power and Lossy 616 Networks) [RFC6550], and AERO/OMNI 617 [I-D.templin-6man-aero][I-D.templin-6man-omni], can be extended to a 618 vehicular network architecture for multihop V2V, V2I, and V2X, as 619 shown in Figure 1. Refer to Appendix B for the detailed discussion 620 on multihop V2X networking by RPL and OMNI. Also, refer to 621 Appendix A for the description of how OMNI is designed to support the 622 use of multiple radio technologies in V2X. 624 As shown in this figure, IP-RSUs as routers and vehicles with IP-OBU 625 have wireless media interfaces for VANET. Furthermore, the wireless 626 media interfaces are autoconfigured with a global IPv6 prefix (e.g., 627 2001:DB8:1:1::/64) to support both V2V and V2I networking. 629 In Figure 1, three IP-RSUs (IP-RSU1, IP-RSU2, and IP-RSU3) are 630 deployed in the road network and are connected with each other 631 through the wired networks (e.g., Ethernet). A Traffic Control 632 Center (TCC) is connected to the Vehicular Cloud for the management 633 of IP-RSUs and vehicles in the road network. A Mobility Anchor (MA) 634 may be located in the TCC as a mobility management controller. 635 Vehicle2, Vehicle3, and Vehicle4 are wirelessly connected to IP-RSU1, 636 IP-RSU2, and IP-RSU3, respectively. The three wireless networks of 637 IP-RSU1, IP-RSU2, and IP-RSU3 can belong to three different subnets 638 (i.e., Subnet1, Subnet2, and Subnet3), respectively. Those three 639 subnets use three different prefixes (i.e., Prefix1, Prefix2, and 640 Prefix3). 642 Multiple vehicles under the coverage of an RSU share a prefix just as 643 mobile nodes share a prefix of a Wi-Fi access point in a wireless 644 LAN. This is a natural characteristic in infrastructure-based 645 wireless networks. For example, in Figure 1, two vehicles (i.e., 646 Vehicle2, and Vehicle5) can use Prefix 1 to configure their IPv6 647 global addresses for V2I communication. Alternatively, mobile nodes 648 can employ a "Bring-Your-Own-Addresses (BYOA)" (or "Bring-Your-Own- 649 Prefix (BYOP)") technique using their own IPv6 Unique Local Addresses 650 (ULAs) [RFC4193] over the wireless network, which does not require 651 the messaging (e.g., Duplicate Address Detection (DAD)) of IPv6 652 Stateless Address Autoconfiguration (SLAAC) [RFC4862]. 654 In wireless subnets in vehicular networks (e.g., Subnet1 and Subnet2 655 in Figure 1), vehicles can construct a connected VANET (with an 656 arbitrary graph topology) and can communicate with each other via V2V 657 communication. Vehicle1 can communicate with Vehicle2 via V2V 658 communication, and Vehicle2 can communicate with Vehicle3 via V2V 659 communication because they are within the wireless communication 660 range of each other. On the other hand, Vehicle3 can communicate 661 with Vehicle4 via the vehicular infrastructure (i.e., IP-RSU2 and IP- 662 RSU3) by employing V2I (i.e., V2I2V) communication because they are 663 not within the wireless communication range of each other. 665 As a basic definition for IPv6 packets transported over IEEE 666 802.11-OCB, [RFC8691] specifies several details, including Maximum 667 Transmission Unit (MTU), frame format, link-local address, address 668 mapping for unicast and multicast, stateless autoconfiguration, and 669 subnet structure. 671 An IPv6 mobility solution is needed for the guarantee of 672 communication continuity in vehicular networks so that a vehicle's 673 TCP session can be continued, or UDP packets can be delivered to a 674 vehicle as a destination without loss while it moves from an IP-RSU's 675 wireless coverage to another IP-RSU's wireless coverage. In 676 Figure 1, assuming that Vehicle2 has a TCP session (or a UDP session) 677 with a correspondent node in the vehicular cloud, Vehicle2 can move 678 from IP-RSU1's wireless coverage to IP-RSU2's wireless coverage. In 679 this case, a handover for Vehicle2 needs to be performed by either a 680 host-based mobility management scheme (e.g., MIPv6 [RFC6275]) or a 681 network-based mobility management scheme (e.g., PMIPv6 [RFC5213], 682 NEMO [RFC3963][RFC4885] [RFC4888], and AERO [I-D.templin-6man-aero]). 683 This document describes issues in mobility management for vehicular 684 networks in Section 5.2. 686 4.2. V2I-based Internetworking 688 This section discusses the internetworking between a vehicle's 689 internal network (i.e., mobile network) and an EN's internal network 690 (i.e., fixed network) via V2I communication. The internal network of 691 a vehicle is nowadays constructed with Ethernet by many automotive 692 vendors [In-Car-Network]. Note that an EN can accommodate multiple 693 routers (or switches) and servers (e.g., ECDs, navigation server, and 694 DNS server) in its internal network. 696 A vehicle's internal network often uses Ethernet to interconnect 697 Electronic Control Units (ECUs) in the vehicle. The internal network 698 can support Wi-Fi and Bluetooth to accommodate a driver's and 699 passenger's mobile devices (e.g., smartphone or tablet). The network 700 topology and subnetting depend on each vendor's network configuration 701 for a vehicle and an EN. It is reasonable to consider the 702 interaction between the internal network and an external network 703 within another vehicle or an EN. Note that it is dangerous if the 704 internal network of a vehicle is controlled by a malicious party. To 705 minimize this kind of risk, an reinforced identification and 706 verification protocol shall be implemented. 708 +-----------------+ 709 (*)<........>(*) +----->| Vehicular Cloud | 710 (2001:DB8:1:1::/64) | | | +-----------------+ 711 +------------------------------+ +---------------------------------+ 712 | v | | v v | 713 | +-------+ +-------+ | | +-------+ +-------+ | 714 | | Host1 | |IP-OBU1| | | |IP-RSU1| | Host3 | | 715 | +-------+ +-------+ | | +-------+ +-------+ | 716 | ^ ^ | | ^ ^ | 717 | | | | | | | | 718 | v v | | v v | 719 | ---------------------------- | | ------------------------------- | 720 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:20:1::/64 | 721 | | | | | | 722 | v | | v | 723 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 724 | | Host2 | |Router1| | | |Router2| |Server1|...|ServerN| | 725 | +-------+ +-------+ | | +-------+ +-------+ +-------+ | 726 | ^ ^ | | ^ ^ ^ | 727 | | | | | | | | | 728 | v v | | v v v | 729 | ---------------------------- | | ------------------------------- | 730 | 2001:DB8:10:2::/64 | | 2001:DB8:20:2::/64 | 731 +------------------------------+ +---------------------------------+ 732 Vehicle1 (Mobile Network1) EN1 (Fixed Network1) 734 <----> Wired Link <....> Wireless Link (*) Antenna 736 Figure 2: Internetworking between Vehicle and Edge Network 738 As shown in Figure 2, as internal networks, a vehicle's mobile 739 network and an EN's fixed network are self-contained networks having 740 multiple subnets and having an edge router (e.g., IP-OBU and IP-RSU) 741 for the communication with another vehicle or another EN. The 742 internetworking between two internal networks via V2I communication 743 requires the exchange of the network parameters and the network 744 prefixes of the internal networks. For the efficiency, the network 745 prefixes of the internal networks (as a mobile network) in a vehicle 746 need to be delegated and configured automatically. Note that a 747 mobile network's network prefix can be called a Mobile Network Prefix 748 (MNP) [RFC3963]. 750 Figure 2 also shows the internetworking between the vehicle's mobile 751 network and the EN's fixed network. There exists an internal network 752 (Mobile Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and 753 Host2), and two routers (IP-OBU1 and Router1). There exists another 754 internal network (Fixed Network1) inside EN1. EN1 has one host 755 (Host3), two routers (IP-RSU1 and Router2), and the collection of 756 servers (Server1 to ServerN) for various services in the road 757 networks, such as the emergency notification and navigation. 758 Vehicle1's IP-OBU1 (as a mobile router) and EN1's IP-RSU1 (as a fixed 759 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 760 V2I networking. Thus, a host (Host1) in Vehicle1 can communicate 761 with a server (Server1) in EN1 for a vehicular service through 762 Vehicle1's moving network, a wireless link between IP-OBU1 and IP- 763 RSU1, and EN1's fixed network. 765 For the IPv6 communication between an IP-OBU and an IP-RSU or between 766 two neighboring IP-OBUs, they need to know the network parameters, 767 which include MAC layer and IPv6 layer information. The MAC layer 768 information includes wireless link layer parameters, transmission 769 power level, and the MAC address of an external network interface for 770 the internetworking with another IP-OBU or IP-RSU. The IPv6 layer 771 information includes the IPv6 address and network prefix of an 772 external network interface for the internetworking with another IP- 773 OBU or IP-RSU. 775 Through the mutual knowledge of the network parameters of internal 776 networks, packets can be transmitted between the vehicle's moving 777 network and the EN's fixed network. Thus, V2I requires an efficient 778 protocol for the mutual knowledge of network parameters. 780 As shown in Figure 2, the addresses used for IPv6 transmissions over 781 the wireless link interfaces for IP-OBU and IP-RSU can be link-local 782 IPv6 addresses, ULAs, or global IPv6 addresses. When global IPv6 783 addresses are used, wireless interface configuration and control 784 overhead for DAD [RFC4862] and Multicast Listener Discovery (MLD) 785 [RFC2710][RFC3810] should be minimized to support V2I and V2X 786 communications for vehicles moving fast along roadways. 788 Let us consider the upload/download time of a ground vehicle when it 789 passes through the wireless communication coverage of an IP-RSU. For 790 a given typical setting where 1km is the maximum DSRC communication 791 range [DSRC] and 100km/h is the speed limit in highway for ground 792 vehicles, the dwelling time can be calculated to be 72 seconds by 793 dividing the diameter of the 2km (i.e., two times of DSRC 794 communication range where an IP-RSU is located in the center of the 795 circle of wireless communication) by the speed limit of 100km/h 796 (i.e., about 28m/s). For the 72 seconds, a vehicle passing through 797 the coverage of an IP-RSU can upload and download data packets to/ 798 from the IP-RSU. For special cases such as emergency vehicles moving 799 above the speed limit, the dwelling time is relatively shorter than 800 that of other vehicles. For cases of airborne vehicles, considering 801 a higher flying speed and a higher altitude, the dwelling time can be 802 much shorter. 804 4.3. V2V-based Internetworking 806 This section discusses the internetworking between the moving 807 networks of two neighboring vehicles via V2V communication. 809 (*)<..........>(*) 810 (2001:DB8:1:1::/64) | | 811 +------------------------------+ +------------------------------+ 812 | v | | v | 813 | +-------+ +-------+ | | +-------+ +-------+ | 814 | | Host1 | |IP-OBU1| | | |IP-OBU2| | Host3 | | 815 | +-------+ +-------+ | | +-------+ +-------+ | 816 | ^ ^ | | ^ ^ | 817 | | | | | | | | 818 | v v | | v v | 819 | ---------------------------- | | ---------------------------- | 820 | 2001:DB8:10:1::/64 ^ | | ^ 2001:DB8:30:1::/64 | 821 | | | | | | 822 | v | | v | 823 | +-------+ +-------+ | | +-------+ +-------+ | 824 | | Host2 | |Router1| | | |Router2| | Host4 | | 825 | +-------+ +-------+ | | +-------+ +-------+ | 826 | ^ ^ | | ^ ^ | 827 | | | | | | | | 828 | v v | | v v | 829 | ---------------------------- | | ---------------------------- | 830 | 2001:DB8:10:2::/64 | | 2001:DB8:30:2::/64 | 831 +------------------------------+ +------------------------------+ 832 Vehicle1 (Mobile Network1) Vehicle2 (Mobile Network2) 834 <----> Wired Link <....> Wireless Link (*) Antenna 836 Figure 3: Internetworking between Two Vehicles 838 Figure 3 shows the internetworking between the mobile networks of two 839 neighboring vehicles. There exists an internal network (Mobile 840 Network1) inside Vehicle1. Vehicle1 has two hosts (Host1 and Host2), 841 and two routers (IP-OBU1 and Router1). There exists another internal 842 network (Mobile Network2) inside Vehicle2. Vehicle2 has two hosts 843 (Host3 and Host4), and two routers (IP-OBU2 and Router2). Vehicle1's 844 IP-OBU1 (as a mobile router) and Vehicle2's IP-OBU2 (as a mobile 845 router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for 846 V2V networking. Thus, a host (Host1) in Vehicle1 can communicate 847 with another host (Host3) in Vehicle2 for a vehicular service through 848 Vehicle1's mobile network, a wireless link between IP-OBU1 and IP- 849 OBU2, and Vehicle2's mobile network. 851 As a V2V use case in Section 3.1, Figure 4 shows the linear network 852 topology of platooning vehicles for V2V communications where Vehicle3 853 is the leading vehicle with a driver, and Vehicle2 and Vehicle1 are 854 the following vehicles without drivers. 856 (*)<..................>(*)<..................>(*) 857 | | | 858 +-----------+ +-----------+ +-----------+ 859 | | | | | | 860 | +-------+ | | +-------+ | | +-------+ | 861 | |IP-OBU1| | | |IP-OBU2| | | |IP-OBU3| | 862 | +-------+ | | +-------+ | | +-------+ | 863 | ^ | | ^ | | ^ | 864 | | |=====> | | |=====> | | |=====> 865 | v | | v | | v | 866 | +-------+ | | +-------+ | | +-------+ | 867 | | Host1 | | | | Host2 | | | | Host3 | | 868 | +-------+ | | +-------+ | | +-------+ | 869 | | | | | | 870 +-----------+ +-----------+ +-----------+ 871 Vehicle1 Vehicle2 Vehicle3 873 <----> Wired Link <....> Wireless Link ===> Moving Direction 874 (*) Antenna 876 Figure 4: Multihop Internetworking between Two Vehicle Networks 878 As shown in Figure 4, multihop internetworking is feasible among the 879 mobile networks of three vehicles in the same VANET. For example, 880 Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via IP-OBU1 881 in Vehicle1, IP-OBU2 in Vehicle2, and IP-OBU3 in Vehicle3 in the 882 VANET, as shown in the figure. 884 In this section, the link between two vehicles is assumed to be 885 stable for single-hop wireless communication regardless of the sight 886 relationship such as line of sight and non-line of sight, as shown in 887 Figure 3. Even in Figure 4, the three vehicles are connected to each 888 other with a linear topology, however, multihop V2V communication can 889 accommodate any network topology (i.e., an arbitrary graph) over 890 VANET routing protocols. 892 (*)<..................>(*)<..................>(*) 893 | | | 894 +-----------+ +-----------+ +-----------+ 895 | | | | | | 896 | +-------+ | | +-------+ | | +-------+ | 897 | |IP-OBU1| | | |IP-RSU1| | | |IP-OBU3| | 898 | +-------+ | | +-------+ | | +-------+ | 899 | ^ | | ^ | | ^ | 900 | | |=====> | | | | | |=====> 901 | v | | v | | v | 902 | +-------+ | | +-------+ | | +-------+ | 903 | | Host1 | | | | Host2 | | | | Host3 | | 904 | +-------+ | | +-------+ | | +-------+ | 905 | | | | | | 906 +-----------+ +-----------+ +-----------+ 907 Vehicle1 EN1 Vehicle3 909 <----> Wired Link <....> Wireless Link ===> Moving Direction 910 (*) Antenna 912 Figure 5: Multihop Internetworking between Two Vehicle Networks 913 via IP-RSU (V2I2V) 915 As shown in Figure 5, multihop internetworking between two vehicles 916 is feasible via an infrastructure node (i.e., IP-RSU) with wireless 917 connectivity among the mobile networks of two vehicles and the fixed 918 network of an edge network (denoted as EN1) in the same VANET. For 919 example, Host1 in Vehicle1 can communicate with Host3 in Vehicle3 via 920 IP-OBU1 in Vehicle1, IP-RSU1 in EN1, and IP-OBU3 in Vehicle3 in the 921 VANET, as shown in the figure. 923 For the reliability required in V2V networking, the ND optimization 924 defined in MANET [RFC6130] [RFC7466] improves the classical IPv6 ND 925 in terms of tracking neighbor information with up to two hops and 926 introducing several extensible Information Bases, which serves the 927 MANET routing protocols such as the different versions of Optimized 928 Link State Routing Protocol (OLSR) [RFC3626] [RFC7181], Open Shortest 929 Path First (OSPF) derivatives (e.g., [RFC5614]), and Dynamic Link 930 Exchange Protocol (DLEP) [RFC8175] with its extensions [RFC8629] 931 [RFC8757]. In short, the MANET ND mainly deals with maintaining 932 extended network neighbors to enhance the link reliability. However, 933 an ND protocol in vehicular networks shall consider more about the 934 geographical mobility information of vehicles as an important 935 resource for serving various purposes to improve the reliability, 936 e.g., vehicle driving safety, intelligent transportation 937 implementations, and advanced mobility services. For a more reliable 938 V2V networking, some redundancy mechanisms should be provided in L3 939 in cases of the failure of L2. For different use cases, the optimal 940 solution to improve V2V networking reliability may vary. For 941 example, a group of vehicles in platooning may have stabler neighbors 942 than freely moving vehicles, as described in Section 3.1. 944 5. Problem Statement 946 In order to specify protocols using the architecture mentioned in 947 Section 4.1, IPv6 core protocols have to be adapted to overcome 948 certain challenging aspects of vehicular networking. Since the 949 vehicles are likely to be moving at great speed, protocol exchanges 950 need to be completed in a relatively short time compared to the 951 lifetime of a link between a vehicle and an IP-RSU, or between two 952 vehicles. 954 For safe driving, vehicles need to exchange application messages 955 every 0.5 second [NHTSA-ACAS-Report] to let drivers take an action to 956 avoid a dangerous situation (e.g., vehicle collision), so IPv6 957 protocol exchanges need to support this order of magnitude for 958 application message exchanges. Also, considering the communication 959 range of DSRC (up to 1km) and 100km/h as the speed limit in highway, 960 the lifetime of a link between a vehicle and an IP-RSU is in the 961 order of a minute (e.g., about 72 seconds), and the lifetime of a 962 link between two vehicles is about a half minute. Note that if two 963 vehicles are moving in the opposite directions in a roadway, the 964 relative speed of this case is two times the relative speed of a 965 vehicle passing through an RSU. This relative speed leads the half 966 of the link lifetime between the vehicle and the IP-RSU. In reality, 967 the DSRC communication range is around 500m, so the link lifetime 968 will be a half of the maximum time. The time constraint of a 969 wireless link between two nodes (e.g., vehicle and IP-RSU) needs to 970 be considered because it may affect the lifetime of a session 971 involving the link. The lifetime of a session varies depending on 972 the session's type such as a web surfing, voice call over IP, DNS 973 query, and context-aware navigation (in Section 3.1). Regardless of 974 a session's type, to guide all the IPv6 packets to their destination 975 host(s), IP mobility should be supported for the session. In a V2V 976 scenario (e.g., context-aware navigation), the IPv6 packets of a 977 vehicle should be delivered to relevant vehicles in an efficient way 978 (e.g., multicasting). With this observation, IPv6 protocol exchanges 979 need to be done as short as possible to support the message exchanges 980 of various applications in vehicular networks. 982 Therefore, the time constraint of a wireless link has a major impact 983 on IPv6 Neighbor Discovery (ND). Mobility Management (MM) is also 984 vulnerable to disconnections that occur before the completion of 985 identity verification and tunnel management. This is especially true 986 given the unreliable nature of wireless communication. Meanwhile, 987 the bandwidth of the wireless link determined by the lower layers 988 (i.e., link and PHY layers) can affect the transmission time of 989 control messages of the upper layers (e.g., IPv6) and the continuity 990 of sessions in the higher layers (e.g., IPv6, TCP, and UDP). Hence 991 the bandwidth selection according to Modulation and Coding Scheme 992 (MCS) also affects the vehicular network connectivity. Note that 993 usually the higher bandwidth gives the shorter communication range 994 and the higher packet error rate at the receiving side, which may 995 reduce the reliability of control message exchanges of the higher 996 layers (e.g., IPv6). This section presents key topics such as 997 neighbor discovery and mobility management for links and sessions in 998 IPv6-based vehicular networks. 1000 5.1. Neighbor Discovery 1002 IPv6 ND [RFC4861][RFC4862] is a core part of the IPv6 protocol suite. 1003 IPv6 ND is designed for link types including point-to-point, 1004 multicast-capable (e.g., Ethernet) and Non-Broadcast Multiple Access 1005 (NBMA). It assumes the efficient and reliable support of multicast 1006 and unicast from the link layer for various network operations such 1007 as MAC Address Resolution (AR), DAD, MLD and Neighbor Unreachability 1008 Detection (NUD). 1010 Vehicles move quickly within the communication coverage of any 1011 particular vehicle or IP-RSU. Before the vehicles can exchange 1012 application messages with each other, they need IPv6 addresses to run 1013 IPv6 ND. 1015 The requirements for IPv6 ND for vehicular networks are efficient DAD 1016 and NUD operations. An efficient DAD is required to reduce the 1017 overhead of DAD packets during a vehicle's travel in a road network, 1018 which can guarantee the uniqueness of a vehicle's global IPv6 1019 address. An efficient NUD is required to reduce the overhead of the 1020 NUD packets during a vehicle's travel in a road network, which can 1021 guarantee the accurate neighborhood information of a vehicle in terms 1022 of adjacent vehicles and RSUs. 1024 The legacy DAD assumes that a node with an IPv6 address can reach any 1025 other node with the scope of its address at the time it claims its 1026 address, and can hear any future claim for that address by another 1027 party within the scope of its address for the duration of the address 1028 ownership. However, the partitioning and merging of VANETs makes 1029 this assumption frequently invalid in vehicular networks. The 1030 merging and partitioning of VANETs frequently occurs in vehicular 1031 networks. This merging and partitioning should be considered for the 1032 IPv6 ND such as IPv6 Stateless Address Autoconfiguration (SLAAC) 1033 [RFC4862]. Due to the merging of VANETs, two IPv6 addresses may 1034 conflict with each other though they were unique before the merging. 1035 An address lookup operation may be conducted by an MA or IP-RSU (as 1036 Registrar in RPL) to check the uniqueness of an IPv6 address that 1037 will be configured by a vehicle as DAD. Also, the partitioning of a 1038 VANET may make vehicles with the same prefix be physically 1039 unreachable. An address lookup operation may be conducted by an MA 1040 or IP-RSU (as Registrar in RPL) to check the existence of a vehicle 1041 under the network coverage of the MA or IP-RSU as NUD. Thus, SLAAC 1042 needs to prevent IPv6 address duplication due to the merging of 1043 VANETs, and IPv6 ND needs to detect unreachable neighboring vehicles 1044 due to the partitioning of a VANET. According to the merging and 1045 partitioning, a destination vehicle (as an IPv6 host) needs to be 1046 distinguished as either an on-link host or a not-onlink host even 1047 though the source vehicle can use the same prefix as the destination 1048 vehicle [I-D.ietf-intarea-ippl]. 1050 To efficiently prevent IPv6 address duplication due to the VANET 1051 partitioning and merging from happening in vehicular networks, the 1052 vehicular networks need to support a vehicular-network-wide DAD by 1053 defining a scope that is compatible with the legacy DAD. In this 1054 case, two vehicles can communicate with each other when there exists 1055 a communication path over VANET or a combination of VANETs and IP- 1056 RSUs, as shown in Figure 1. By using the vehicular-network-wide DAD, 1057 vehicles can assure that their IPv6 addresses are unique in the 1058 vehicular network whenever they are connected to the vehicular 1059 infrastructure or become disconnected from it in the form of VANET. 1061 For vehicular networks with high mobility and density, DAD needs to 1062 be performed efficiently with minimum overhead so that the vehicles 1063 can exchange driving safety messages (e.g., collision avoidance and 1064 accident notification) with each other with a short interval 1065 suggested by NHTSA (National Highway Traffic Safety Administration) 1066 [NHTSA-ACAS-Report]. Since the partitioning and merging of vehicular 1067 networks may require re-perform DAD process repeatedly, the link 1068 scope of vehicles may be limited to a small area, which may delay the 1069 exchange of driving safety messages. Driving safety messages can 1070 include a vehicle's mobility information (i.e., position, speed, 1071 direction, and acceleration/deceleration) that is critical to other 1072 vehicles. The exchange interval of this message is recommended to be 1073 less than 0.5 second, which is required for a driver to avoid an 1074 emergency situation, such as a rear-end crash. 1076 ND time-related parameters such as router lifetime and Neighbor 1077 Advertisement (NA) interval need to be adjusted for vehicle speed and 1078 vehicle density. For example, the NA interval needs to be 1079 dynamically adjusted according to a vehicle's speed so that the 1080 vehicle can maintain its neighboring vehicles in a stable way, 1081 considering the collision probability with the NA messages sent by 1082 other vehicles. The ND time-related parameters can be an operational 1083 setting or an optimization point particularly for vehicular networks. 1085 For IPv6-based safety applications (e.g., context-aware navigation, 1086 adaptive cruise control, and platooning) in vehicular networks, the 1087 delay-bounded data delivery is critical. IPv6 ND needs to work to 1088 support those IPv6-based safety applications efficiently. 1090 From the interoperability point of view, in IPv6-based vehicular 1091 networking, IPv6 ND should have minimum changes with the legacy IPv6 1092 ND used in the Internet, including DAD and NUD operations, so that 1093 IPv6-based vehicular networks can be seamlessly connected to other 1094 intelligent transportation elements (e.g., traffic signals, 1095 pedestrian wearable devices, electric scooters, and bus stops) that 1096 use the standard IPv6 network settings. 1098 5.1.1. Link Model 1100 A subnet model for a vehicular network needs to facilitate the 1101 communication between two vehicles with the same prefix regardless of 1102 the vehicular network topology as long as there exist bidirectional 1103 E2E paths between them in the vehicular network including VANETs and 1104 IP-RSUs. This subnet model allows vehicles with the same prefix to 1105 communicate with each other via a combination of multihop V2V and 1106 multihop V2I with VANETs and IP-RSUs. 1107 [I-D.thubert-6man-ipv6-over-wireless] introduces other issues in an 1108 IPv6 subnet model. 1110 IPv6 protocols work under certain assumptions that do not necessarily 1111 hold for vehicular wireless access link types [VIP-WAVE][RFC5889]. 1112 For instance, some IPv6 protocols assume symmetry in the connectivity 1113 among neighboring interfaces [RFC6250]. However, radio interference 1114 and different levels of transmission power may cause asymmetric links 1115 to appear in vehicular wireless links. As a result, a new vehicular 1116 link model needs to consider the asymmetry of dynamically changing 1117 vehicular wireless links. 1119 There is a relationship between a link and a prefix, besides the 1120 different scopes that are expected from the link-local, unique-local, 1121 and global types of IPv6 addresses. In an IPv6 link, it is defined 1122 that all interfaces which are configured with the same subnet prefix 1123 and with on-link bit set can communicate with each other on an IPv6 1124 link. However, the vehicular link model needs to define the 1125 relationship between a link and a prefix, considering the dynamics of 1126 wireless links and the characteristics of VANET. 1128 A VANET can have a single link between each vehicle pair within 1129 wireless communication range, as shown in Figure 4. When two 1130 vehicles belong to the same VANET, but they are out of wireless 1131 communication range, they cannot communicate directly with each 1132 other. Suppose that a global-scope IPv6 prefix (or an IPv6 ULA 1133 prefix) is assigned to VANETs in vehicular networks. Considering 1134 that two vehicles in the same VANET configure their IPv6 addresses 1135 with the same IPv6 prefix, if they are not in one hop (that is, they 1136 have the multihop network connectivity between them), then they may 1137 not be able to communicate with each other. Thus, in this case, the 1138 concept of an on-link IPv6 prefix does not hold because two vehicles 1139 with the same on-link IPv6 prefix cannot communicate directly with 1140 each other. Also, when two vehicles are located in two different 1141 VANETs with the same IPv6 prefix, they cannot communicate with each 1142 other. When these two VANETs converge to one VANET, the two vehicles 1143 can communicate with each other in a multihop fashion, for example, 1144 when they are Vehicle1 and Vehicle3, as shown in Figure 4. 1146 From the previous observation, a vehicular link model should consider 1147 the frequent partitioning and merging of VANETs due to vehicle 1148 mobility. Therefore, the vehicular link model needs to use an on- 1149 link prefix and not-onlink prefix according to the network topology 1150 of vehicles such as a one-hop reachable network and a multihop 1151 reachable network (or partitioned networks). If the vehicles with 1152 the same prefix are reachable from each other in one hop, the prefix 1153 should be on-link. On the other hand, if some of the vehicles with 1154 the same prefix are not reachable from each other in one hop due to 1155 either the multihop topology in the VANET or multiple partitions, the 1156 prefix should be not-onlink. In most cases in vehicular networks, 1157 due to the partitioning and merging of VANETs, and the multihop 1158 network topology of VANETS, not-onlink prefixes will be used for 1159 vehicles as default. 1161 The vehicular link model needs to support multihop routing in a 1162 connected VANET where the vehicles with the same global-scope IPv6 1163 prefix (or the same IPv6 ULA prefix) are connected in one hop or 1164 multiple hops. It also needs to support the multihop routing in 1165 multiple connected VANETs through infrastructure nodes (e.g., IP-RSU) 1166 where they are connected to the infrastructure. For example, in 1167 Figure 1, suppose that Vehicle1, Vehicle2, and Vehicle3 are 1168 configured with their IPv6 addresses based on the same global-scope 1169 IPv6 prefix. Vehicle1 and Vehicle3 can also communicate with each 1170 other via either multihop V2V or multihop V2I2V. When Vehicle1 and 1171 Vehicle3 are connected in a VANET, it will be more efficient for them 1172 to communicate with each other directly via VANET rather than 1173 indirectly via IP-RSUs. On the other hand, when Vehicle1 and 1174 Vehicle3 are far away from direct communication range in separate 1175 VANETs and under two different IP-RSUs, they can communicate with 1176 each other through the relay of IP-RSUs via V2I2V. Thus, two 1177 separate VANETs can merge into one network via IP-RSU(s). Also, 1178 newly arriving vehicles can merge two separate VANETs into one VANET 1179 if they can play the role of a relay node for those VANETs. 1181 Thus, in IPv6-based vehicular networking, the vehicular link model 1182 should have minimum changes for interoperability with standard IPv6 1183 links in an efficient fashion to support IPv6 DAD, MLD and NUD 1184 operations. 1186 5.1.2. MAC Address Pseudonym 1188 For the protection of drivers' privacy, a pseudonym of a MAC address 1189 of a vehicle's network interface should be used, so that the MAC 1190 address can be changed periodically. However, although such a 1191 pseudonym of a MAC address can protect to some extent the privacy of 1192 a vehicle, it may not be able to resist attacks on vehicle 1193 identification by other fingerprint information, for example, the 1194 scrambler seed embedded in IEEE 802.11-OCB frames [Scrambler-Attack]. 1195 The pseudonym of a MAC address affects an IPv6 address based on the 1196 MAC address, and a transport-layer (e.g., TCP and SCTP) session with 1197 an IPv6 address pair. However, the pseudonym handling is not 1198 implemented and tested yet for applications on IP-based vehicular 1199 networking. 1201 In the ETSI standards, for the sake of security and privacy, an ITS 1202 station (e.g., vehicle) can use pseudonyms for its network interface 1203 identities (e.g., MAC address) and the corresponding IPv6 addresses 1204 [Identity-Management]. Whenever the network interface identifier 1205 changes, the IPv6 address based on the network interface identifier 1206 needs to be updated, and the uniqueness of the address needs to be 1207 checked through DAD procedure. 1209 5.1.3. Routing 1211 For multihop V2V communications in either a VANET or VANETs via IP- 1212 RSUs, a vehicular Mobile Ad Hoc Networks (MANET) routing protocol may 1213 be required to support both unicast and multicast in the links of the 1214 subnet with the same IPv6 prefix. However, it will be costly to run 1215 both vehicular ND and a vehicular ad hoc routing protocol in terms of 1216 control traffic overhead [RFC9119]. 1218 A routing protocol for a VANET may cause redundant wireless frames in 1219 the air to check the neighborhood of each vehicle and compute the 1220 routing information in a VANET with a dynamic network topology 1221 because the IPv6 ND is used to check the neighborhood of each 1222 vehicle. Thus, the vehicular routing needs to take advantage of the 1223 IPv6 ND to minimize its control overhead. 1225 RPL [RFC6550] defines a routing protocol for low-power and lossy 1226 networks, which constructs and maintains Destination-Oriented 1227 Directed Acyclic Graphs (DODAGs) optimized by an Objective Function 1228 (OF). A defined OF provides route selection and optimization within 1229 an RPL topology. The RPL nodes use an anisotropic Distance Vector 1230 (DV) approach to form a DODAG by discovering and aggressively 1231 maintaining the upward default route toward the root of the DODAG. 1232 Downward routes follow the same DODAG, with lazy maintenance and 1233 stretched Peer-to-Peer (P2P) routing in the so-called storing mode. 1234 It is well-designed to reduce the topological knowledge and routing 1235 state that needs to be exchanged. As a result, the routing protocol 1236 overhead is minimized, which allows either highly constrained stable 1237 networks or less constrained, highly dynamic networks. Refer to 1238 Appendix B for the detailed description of RPL for multihop V2X 1239 networking. 1241 An address registration extension for 6LoWPAN (IPv6 over Low-Power 1242 Wireless Personal Area Network) in [RFC8505] can support light-weight 1243 mobility for nodes moving through different parents. [RFC8505], as 1244 opposed to [RFC4861], is stateful and proactively installs the ND 1245 cache entries, which saves broadcasts and provides a deterministic 1246 presence information for IPv6 addresses. Mainly it updates the 1247 Address Registration Option (ARO) of ND defined in [RFC6775] to 1248 include a status field that can indicate the movement of a node and 1249 optionally a Transaction ID (TID) field, i.e., a sequence number that 1250 can be used to determine the most recent location of a node. Thus, 1251 RPL can use the information provided by the Extended ARO (EARO) 1252 defined in [RFC8505] to deal with a certain level of node mobility. 1253 When a leaf node moves to the coverage of another parent node, it 1254 should de-register its addresses to the previous parent node and 1255 register itself with a new parent node along with an incremented TID. 1257 RPL can be used in IPv6-based vehicular networks, but it is primarily 1258 designed for lossy networks, which puts energy efficiency first. For 1259 using it in IPv6-based vehicular networks, there have not been actual 1260 experiences and practical implementations for vehicular networks, 1261 though it was tested in IoT low-power and lossy networks (LLN) 1262 scenarios. 1264 Moreover, due to bandwidth and energy constraints, RPL does not 1265 suggest to use a proactive mechanism (e.g., keepalive) to maintain 1266 accurate routing adjacencies such as Bidirectional Forwarding 1267 Detection [RFC5881] and MANET Neighborhood Discovery Protocol 1268 [RFC6130]. As a result, due to the mobility of vehicles, network 1269 fragmentation may not be detected quickly and the routing of packets 1270 between vehicles or between a vehicle and an infrastructure node may 1271 fail. 1273 5.2. Mobility Management 1275 The seamless connectivity and timely data exchange between two end 1276 points requires efficient mobility management including location 1277 management and handover. Most vehicles are equipped with a GPS 1278 receiver as part of a dedicated navigation system or a corresponding 1279 smartphone App. Note that the GPS receiver may not provide vehicles 1280 with accurate location information in adverse environments such as a 1281 building area or a tunnel. The location precision can be improved 1282 with assistance of the IP-RSUs or a cellular system with a GPS 1283 receiver for location information. 1285 With a GPS navigator, efficient mobility management can be performed 1286 with the help of vehicles periodically reporting their current 1287 position and trajectory (i.e., navigation path) to the vehicular 1288 infrastructure (having IP-RSUs and an MA in TCC). This vehicular 1289 infrastructure can predict the future positions of the vehicles from 1290 their mobility information (i.e., the current position, speed, 1291 direction, and trajectory) for efficient mobility management (e.g., 1292 proactive handover). For a better proactive handover, link-layer 1293 parameters, such as the signal strength of a link-layer frame (e.g., 1294 Received Channel Power Indicator (RCPI) [VIP-WAVE]), can be used to 1295 determine the moment of a handover between IP-RSUs along with 1296 mobility information. 1298 By predicting a vehicle's mobility, the vehicular infrastructure 1299 needs to better support IP-RSUs to perform efficient SLAAC, data 1300 forwarding, horizontal handover (i.e., handover in wireless links 1301 using a homogeneous radio technology), and vertical handover (i.e., 1302 handover in wireless links using heterogeneous radio technologies) in 1303 advance along with the movement of the vehicle. 1305 For example, as shown in Figure 1, when a vehicle (e.g., Vehicle2) is 1306 moving from the coverage of an IP-RSU (e.g., IP-RSU1) into the 1307 coverage of another IP-RSU (e.g., IP-RSU2) belonging to a different 1308 subnet, the IP-RSUs can proactively support the IPv6 mobility of the 1309 vehicle, while performing the SLAAC, data forwarding, and handover 1310 for the sake of the vehicle. 1312 For a mobility management scheme in a domain, where the wireless 1313 subnets of multiple IP-RSUs share the same prefix, an efficient 1314 vehicular-network-wide DAD is required. If DHCPv6 is used to assign 1315 a unique IPv6 address to each vehicle in this shared link, DAD is not 1316 required. On the other hand, for a mobility management scheme with a 1317 unique prefix per mobile node (e.g., PMIPv6 [RFC5213]), DAD is not 1318 required because the IPv6 address of a vehicle's external wireless 1319 interface is guaranteed to be unique. There is a tradeoff between 1320 the prefix usage efficiency and DAD overhead. Thus, the IPv6 address 1321 autoconfiguration for vehicular networks needs to consider this 1322 tradeoff to support efficient mobility management. 1324 Even though the SLAAC with classic ND costs a DAD during mobility 1325 management, the SLAAC with [RFC8505] and/or AERO/OMNI do not cost a 1326 DAD. SLAAC for vehicular networks needs to consider the minimization 1327 of the cost of DAD with the help of an infrastructure node (e.g., IP- 1328 RSU and MA). Using an infrastructure prefix over VANET allows direct 1329 routability to the Internet through the multihop V2I toward an IP- 1330 RSU. On the other hand, a BYOA does not allow such direct 1331 routability to the Internet since the BYOA is not topologically 1332 correct, that is, not routable in the Internet. In addition, a 1333 vehicle configured with a BYOA needs a tunnel home (e.g., IP-RSU) 1334 connected to the Internet, and the vehicle needs to know which 1335 neighboring vehicle is reachable inside the VANET toward the tunnel 1336 home. There is nonnegligible control overhead to set up and maintain 1337 routes to such a tunnel home [RFC4888] over the VANET. 1339 For the case of a multihomed network, a vehicle can follow the first- 1340 hop router selection rule described in [RFC8028]. For example, an 1341 IP-OBU inside a vehicle may connect to an IP-RSU that has multiple 1342 routers behind. In this scenario, because the IP-OBU can have 1343 multiple prefixes from those routers, the default router selection, 1344 source address selection, and packet redirect process should follow 1345 the guidelines in [RFC8028]. That is, the vehicle should select its 1346 default router for each prefix by preferring the router that 1347 advertised the prefix. 1349 Vehicles can use the TCC as their Home Network having a home agent 1350 for mobility management as in MIPv6 [RFC6275], PMIPv6 [RFC5213], and 1351 NEMO [RFC3963], so the TCC (or an MA inside the TCC) maintains the 1352 mobility information of vehicles for location management. Also, in 1353 vehicular networks, asymmetric links sometimes exist and must be 1354 considered for wireless communications such as V2V and V2I. 1356 Therefore, for the proactive and seamless IPv6 mobility of vehicles, 1357 the vehicular infrastructure (including IP-RSUs and MA) needs to 1358 efficiently perform the mobility management of the vehicles with 1359 their mobility information and link-layer information. Also, in 1360 IPv6-based vehicular networking, IPv6 mobility management should have 1361 minimum changes for the interoperability with the legacy IPv6 1362 mobility management schemes such as PMIPv6, DMM, LISP, and AERO. 1364 6. Security Considerations 1366 This section discusses security and privacy for IPv6-based vehicular 1367 networking. Security and privacy are paramount in V2I, V2V, and V2X 1368 networking along with neighbor discovery and mobility management. 1370 Vehicles and infrastructure must be authenticated in order to 1371 participate in vehicular networking. For the authentication in 1372 vehicular networks, vehicular cloud needs to support a kind of Public 1373 Key Infrastructure (PKI) in an efficient way. To provide safe 1374 interaction between vehicles or between a vehicle and infrastructure, 1375 only authenticated nodes (i.e., vehicle and infrastructure node) can 1376 participate in vehicular networks. Also, in-vehicle devices (e.g., 1377 ECU) and a driver/passenger's mobile devices (e.g., smartphone and 1378 tablet PC) in a vehicle need to communicate with other in-vehicle 1379 devices and another driver/passenger's mobile devices in another 1380 vehicle, or other servers behind an IP-RSU in a secure way. Even 1381 though a vehicle is perfectly authenticated and legitimate, it may be 1382 hacked for running malicious applications to track and collect its 1383 and other vehicles' information. In this case, an attack mitigation 1384 process may be required to reduce the aftermath of malicious 1385 behaviors. Note that when driver/passenger's mobile devices are 1386 connected to a vehicle's internal network, the vehicle may be more 1387 vulnerable to possible attacks from external networks. 1389 For secure V2I communication, a secure channel (e.g., IPsec) between 1390 a mobile router (i.e., IP-OBU) in a vehicle and a fixed router (i.e., 1391 IP-RSU) in an EN needs to be established, as shown in Figure 2 1392 [RFC4301][RFC4302] [RFC4303][RFC4308] [RFC7296]. Also, for secure 1393 V2V communication, a secure channel (e.g., IPsec) between a mobile 1394 router (i.e., IP-OBU) in a vehicle and a mobile router (i.e., IP-OBU) 1395 in another vehicle needs to be established, as shown in Figure 3. 1396 For secure communication, an element in a vehicle (e.g., an in- 1397 vehicle device and a driver/passenger's mobile device) needs to 1398 establish a secure connection (e.g., TLS) with another element in 1399 another vehicle or another element in a vehicular cloud (e.g., a 1400 server). IEEE 1609.2 [WAVE-1609.2] specifies security services for 1401 applications and management messages, but this WAVE specification is 1402 optional. Thus, if the link layer does not support the security of a 1403 WAVE frame, either the network layer or the transport layer needs to 1404 support security services for the WAVE frames. 1406 6.1. Security Threats in Neighbor Discovery 1408 For the classical IPv6 ND, DAD is required to ensure the uniqueness 1409 of the IPv6 address of a vehicle's wireless interface. This DAD can 1410 be used as a flooding attack that uses the DAD-related ND packets 1411 disseminated over the VANET or vehicular networks. [RFC6959] 1412 introduces threats enabled by IP source address spoofing. This 1413 possibility indicates that vehicles and IP-RSUs need to filter out 1414 suspicious ND traffic in advance. [RFC8928] introduces a mechanism 1415 that protects the ownership of an address for 6loWPAN ND from address 1416 theft and impersonation attacks. Based on the SEND [RFC3971] 1417 mechanism, the authentication for routers (i.e., IP-RSUs) can be 1418 conducted by only selecting an IP-RSU that has a certification path 1419 toward trusted parties. For authenticating other vehicles, the 1420 cryptographically generated address (CGA) can be used to verify the 1421 true owner of a received ND message, which requires to use the CGA ND 1422 option in the ND protocols. For a general protection of the ND 1423 mechanism, the RSA Signature ND option can also be used to protect 1424 the integrity of the messages by public key signatures. For a more 1425 advanced authentication mechanism, a distributed blockchain-based 1426 approach [Vehicular-BlockChain] can be used. However, for a scenario 1427 where a trustable router or an authentication path cannot be 1428 obtained, it is desirable to find a solution in which vehicles and 1429 infrastructures can authenticate each other without any support from 1430 a third party. 1432 When applying the classical IPv6 ND process to VANET, one of the 1433 security issues is that an IP-RSU (or an IP-OBU) as a router may 1434 receive deliberate or accidental DoS attacks from network scans that 1435 probe devices on a VANET. In this scenario, the IP-RSU can be 1436 overwhelmed for processing the network scan requests so that the 1437 capacity and resources of IP-RSU are exhausted, causing the failure 1438 of receiving normal ND messages from other hosts for network address 1439 resolution. [RFC6583] describes more about the operational problems 1440 in the classical IPv6 ND mechanism that can be vulnerable to 1441 deliberate or accidental DoS attacks and suggests several 1442 implementation guidelines and operational mitigation techniques for 1443 those problems. Nevertheless, for running IPv6 ND in VANET, those 1444 issues can be more acute since the movements of vehicles can be so 1445 diverse that it leaves a large room for rogue behaviors, and the 1446 failure of networking among vehicles may cause grave consequences. 1448 Strong security measures shall protect vehicles roaming in road 1449 networks from the attacks of malicious nodes, which are controlled by 1450 hackers. For safe driving applications (e.g., context-aware 1451 navigation, cooperative adaptive cruise control, and platooning), as 1452 explained in Section 3.1, the cooperative action among vehicles is 1453 assumed. Malicious nodes may disseminate wrong driving information 1454 (e.g., location, speed, and direction) for disturbing safe driving. 1455 For example, a Sybil attack, which tries to confuse a vehicle with 1456 multiple false identities, may disturb a vehicle from taking a safe 1457 maneuver. Since cyber security issues in vehicular networks may 1458 cause physical vehicle safety issues, it may be necessary to consider 1459 those physical security concerns when designing protocols in IPWAVE. 1461 To identify malicious vehicles among vehicles, an authentication 1462 method may be required. A Vehicle Identification Number (VIN) and a 1463 user certificate (e.g., X.509 certificate [RFC5280]) along with an 1464 in-vehicle device's identifier generation can be used to efficiently 1465 authenticate a vehicle or its driver (having a user certificate) 1466 through a road infrastructure node (e.g., IP-RSU) connected to an 1467 authentication server in the vehicular cloud. This authentication 1468 can be used to identify the vehicle that will communicate with an 1469 infrastructure node or another vehicle. In the case where a vehicle 1470 has an internal network (called Moving Network) and elements in the 1471 network (e.g., in-vehicle devices and a user's mobile devices), as 1472 shown in Figure 2, the elements in the network need to be 1473 authenticated individually for safe authentication. Also, Transport 1474 Layer Security (TLS) certificates [RFC8446][RFC5280] can be used for 1475 an element's authentication to allow secure E2E vehicular 1476 communications between an element in a vehicle and another element in 1477 a server in a vehicular cloud, or between an element in a vehicle and 1478 another element in another vehicle. 1480 6.2. Security Threats in Mobility Management 1482 For mobility management, a malicious vehicle can construct multiple 1483 virtual bogus vehicles, and register them with IP-RSUs and MA. This 1484 registration makes the IP-RSUs and MA waste their resources. The IP- 1485 RSUs and MA need to determine whether a vehicle is genuine or bogus 1486 in mobility management. Also, the confidentiality of control packets 1487 and data packets among IP-RSUs and MA, the E2E paths (e.g., tunnels) 1488 need to be protected by secure communication channels. In addition, 1489 to prevent bogus IP-RSUs and MA from interfering with the IPv6 1490 mobility of vehicles, mutual authentication among them needs to be 1491 performed by certificates (e.g., TLS certificate). 1493 6.3. Other Threats 1495 For the setup of a secure channel over IPsec or TLS, the multihop V2I 1496 communications over DSRC or 5G V2X (or LTE V2X) is required in a 1497 highway. In this case, multiple intermediate vehicles as relay nodes 1498 can help forward association and authentication messages toward an 1499 IP-RSU (gNodeB, or eNodeB) connected to an authentication server in 1500 the vehicular cloud. In this kind of process, the authentication 1501 messages forwarded by each vehicle can be delayed or lost, which may 1502 increase the construction time of a connection or some vehicles may 1503 not be able to be authenticated. 1505 Even though vehicles can be authenticated with valid certificates by 1506 an authentication server in the vehicular cloud, the authenticated 1507 vehicles may harm other vehicles. To deal with this kind of security 1508 issue, for monitoring suspicious behaviors, vehicles' communication 1509 activities can be recorded in either a central way through a logging 1510 server (e.g., TCC) in the vehicular cloud or a distributed way (e.g., 1511 blockchain [Bitcoin]) along with other vehicles or infrastructure. 1512 To solve the issue ultimately, we need a solution where, without 1513 privacy breakage, vehicles may observe activities of each other to 1514 identify any misbehavior. Once identifying a misbehavior, a vehicle 1515 shall have a way to either isolate itself from others or isolate a 1516 suspicious vehicle by informing other vehicles. Alternatively, for 1517 completely secure vehicular networks, we shall embrace the concept of 1518 "zero-trust" for vehicles in which no vehicle is trustable and 1519 verifying every message is necessary. For doing so, we shall have an 1520 efficient zero-trust framework or mechanism for vehicular networks. 1522 For the non-repudiation of the harmful activities of malicious nodes, 1523 a blockchain technology can be used [Bitcoin]. Each message from a 1524 vehicle can be treated as a transaction and the neighboring vehicles 1525 can play the role of peers in a consensus method of a blockchain 1526 [Bitcoin] [Vehicular-BlockChain]. For a blockchain's efficient 1527 consensus in vehicular networks having fast moving vehicles, a new 1528 consensus algorithm needs to be developed or an existing consensus 1529 algorithm needs to be enhanced. 1531 To prevent an adversary from tracking a vehicle with its MAC address 1532 or IPv6 address, especially for a long-living transport-layer session 1533 (e.g., voice call over IP and video streaming service), a MAC address 1534 pseudonym needs to be provided to each vehicle; that is, each vehicle 1535 periodically updates its MAC address and its IPv6 address needs to be 1536 updated accordingly by the MAC address change [RFC4086][RFC8981]. 1537 Such an update of the MAC and IPv6 addresses should not interrupt the 1538 E2E communications between two vehicles (or between a vehicle and an 1539 IP-RSU) for a long-living transport-layer session. However, if this 1540 pseudonym is performed without strong E2E confidentiality (using 1541 either IPsec or TLS), there will be no privacy benefit from changing 1542 MAC and IPv6 addresses, because an adversary can observe the change 1543 of the MAC and IPv6 addresses and track the vehicle with those 1544 addresses. Thus, the MAC address pseudonym and the IPv6 address 1545 update should be performed with strong E2E confidentiality. Privacy 1546 concerns for excessively collecting vehicle activities from roadway 1547 operators such as public transportation administrators and private 1548 contractors may also pose threats on violating privacy rights of 1549 vehicles. It might be interesting to find a solution from a 1550 technology point of view along with public policy development for the 1551 issue. 1553 7. IANA Considerations 1555 This document does not require any IANA actions. 1557 8. References 1559 8.1. Normative References 1561 [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast 1562 Listener Discovery (MLD) for IPv6", RFC 2710, 1563 DOI 10.17487/RFC2710, October 1999, 1564 . 1566 [RFC3626] Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link 1567 State Routing Protocol (OLSR)", RFC 3626, 1568 DOI 10.17487/RFC3626, October 2003, 1569 . 1571 [RFC3753] Manner, J., Ed. and M. Kojo, Ed., "Mobility Related 1572 Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004, 1573 . 1575 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1576 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1577 DOI 10.17487/RFC3810, June 2004, 1578 . 1580 [RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix 1581 Reserved for Documentation", RFC 3849, 1582 DOI 10.17487/RFC3849, July 2004, 1583 . 1585 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1586 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 1587 RFC 3963, DOI 10.17487/RFC3963, January 2005, 1588 . 1590 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1591 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1592 DOI 10.17487/RFC3971, March 2005, 1593 . 1595 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1596 "Randomness Requirements for Security", BCP 106, RFC 4086, 1597 DOI 10.17487/RFC4086, June 2005, 1598 . 1600 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1601 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1602 . 1604 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1605 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 1606 December 2005, . 1608 [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, 1609 DOI 10.17487/RFC4302, December 2005, 1610 . 1612 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 1613 RFC 4303, DOI 10.17487/RFC4303, December 2005, 1614 . 1616 [RFC4308] Hoffman, P., "Cryptographic Suites for IPsec", RFC 4308, 1617 DOI 10.17487/RFC4308, December 2005, 1618 . 1620 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1621 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1622 DOI 10.17487/RFC4861, September 2007, 1623 . 1625 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1626 Address Autoconfiguration", RFC 4862, 1627 DOI 10.17487/RFC4862, September 2007, 1628 . 1630 [RFC4885] Ernst, T. and H-Y. Lach, "Network Mobility Support 1631 Terminology", RFC 4885, DOI 10.17487/RFC4885, July 2007, 1632 . 1634 [RFC4888] Ng, C., Thubert, P., Watari, M., and F. Zhao, "Network 1635 Mobility Route Optimization Problem Statement", RFC 4888, 1636 DOI 10.17487/RFC4888, July 2007, 1637 . 1639 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1640 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1641 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1642 . 1644 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1645 Housley, R., and W. Polk, "Internet X.509 Public Key 1646 Infrastructure Certificate and Certificate Revocation List 1647 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1648 . 1650 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1651 Ed., "Control And Provisioning of Wireless Access Points 1652 (CAPWAP) Protocol Specification", RFC 5415, 1653 DOI 10.17487/RFC5415, March 2009, 1654 . 1656 [RFC5614] Ogier, R. and P. Spagnolo, "Mobile Ad Hoc Network (MANET) 1657 Extension of OSPF Using Connected Dominating Set (CDS) 1658 Flooding", RFC 5614, DOI 10.17487/RFC5614, August 2009, 1659 . 1661 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1662 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 1663 DOI 10.17487/RFC5881, June 2010, 1664 . 1666 [RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing 1667 Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889, 1668 September 2010, . 1670 [RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc 1671 Network (MANET) Neighborhood Discovery Protocol (NHDP)", 1672 RFC 6130, DOI 10.17487/RFC6130, April 2011, 1673 . 1675 [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, 1676 DOI 10.17487/RFC6250, May 2011, 1677 . 1679 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1680 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1681 2011, . 1683 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 1684 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 1685 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 1686 Low-Power and Lossy Networks", RFC 6550, 1687 DOI 10.17487/RFC6550, March 2012, 1688 . 1690 [RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational 1691 Neighbor Discovery Problems", RFC 6583, 1692 DOI 10.17487/RFC6583, March 2012, 1693 . 1695 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1696 Bormann, "Neighbor Discovery Optimization for IPv6 over 1697 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1698 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1699 . 1701 [RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined 1702 Networking: A Perspective from within a Service Provider 1703 Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014, 1704 . 1706 [RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg, 1707 "The Optimized Link State Routing Protocol Version 2", 1708 RFC 7181, DOI 10.17487/RFC7181, April 2014, 1709 . 1711 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 1712 Kivinen, "Internet Key Exchange Protocol Version 2 1713 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 1714 2014, . 1716 [RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J. 1717 Korhonen, "Requirements for Distributed Mobility 1718 Management", RFC 7333, DOI 10.17487/RFC7333, August 2014, 1719 . 1721 [RFC7429] Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and 1722 CJ. Bernardos, "Distributed Mobility Management: Current 1723 Practices and Gap Analysis", RFC 7429, 1724 DOI 10.17487/RFC7429, January 2015, 1725 . 1727 [RFC7466] Dearlove, C. and T. Clausen, "An Optimization for the 1728 Mobile Ad Hoc Network (MANET) Neighborhood Discovery 1729 Protocol (NHDP)", RFC 7466, DOI 10.17487/RFC7466, March 1730 2015, . 1732 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1733 Hosts in a Multi-Prefix Network", RFC 8028, 1734 DOI 10.17487/RFC8028, November 2016, 1735 . 1737 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 1738 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 1739 DOI 10.17487/RFC8175, June 2017, 1740 . 1742 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1743 (IPv6) Specification", STD 86, RFC 8200, 1744 DOI 10.17487/RFC8200, July 2017, 1745 . 1747 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1748 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1749 . 1751 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1752 Perkins, "Registration Extensions for IPv6 over Low-Power 1753 Wireless Personal Area Network (6LoWPAN) Neighbor 1754 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1755 . 1757 [RFC8629] Cheng, B. and L. Berger, Ed., "Dynamic Link Exchange 1758 Protocol (DLEP) Multi-Hop Forwarding Extension", RFC 8629, 1759 DOI 10.17487/RFC8629, July 2019, 1760 . 1762 [RFC8691] Benamar, N., Härri, J., Lee, J., and T. Ernst, "Basic 1763 Support for IPv6 Networks Operating Outside the Context of 1764 a Basic Service Set over IEEE Std 802.11", RFC 8691, 1765 DOI 10.17487/RFC8691, December 2019, 1766 . 1768 [RFC8757] Cheng, B. and L. Berger, Ed., "Dynamic Link Exchange 1769 Protocol (DLEP) Latency Range Extension", RFC 8757, 1770 DOI 10.17487/RFC8757, March 2020, 1771 . 1773 [RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik, 1774 "Address-Protected Neighbor Discovery for Low-Power and 1775 Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November 1776 2020, . 1778 [RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves, 1779 "Temporary Address Extensions for Stateless Address 1780 Autoconfiguration in IPv6", RFC 8981, 1781 DOI 10.17487/RFC8981, February 2021, 1782 . 1784 [RFC9119] Perkins, C., McBride, M., Stanley, D., Kumari, W., and JC. 1785 Zúñiga, "Multicast Considerations over IEEE 802 Wireless 1786 Media", RFC 9119, DOI 10.17487/RFC9119, October 2021, 1787 . 1789 8.2. Informative References 1791 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 1792 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 1793 . 1795 [RFC6959] McPherson, D., Baker, F., and J. Halpern, "Source Address 1796 Validation Improvement (SAVI) Threat Scope", RFC 6959, 1797 DOI 10.17487/RFC6959, May 2013, 1798 . 1800 [RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T. 1801 Völker, "Packetization Layer Path MTU Discovery for 1802 Datagram Transports", RFC 8899, DOI 10.17487/RFC8899, 1803 September 2020, . 1805 [I-D.ietf-intarea-ippl] 1806 Nordmark, E., "IP over Intentionally Partially Partitioned 1807 Links", Work in Progress, Internet-Draft, draft-ietf- 1808 intarea-ippl-00, 30 March 2017, 1809 . 1812 [I-D.ietf-lisp-rfc6830bis] 1813 Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. 1814 Cabellos, "The Locator/ID Separation Protocol (LISP)", 1815 Work in Progress, Internet-Draft, draft-ietf-lisp- 1816 rfc6830bis-36, 18 November 2020, 1817 . 1820 [I-D.templin-6man-aero] 1821 Templin, F. L., "Automatic Extended Route Optimization 1822 (AERO)", Work in Progress, Internet-Draft, draft-templin- 1823 6man-aero-40, 7 March 2022, 1824 . 1827 [I-D.templin-6man-omni] 1828 Templin, F. L., "Transmission of IP Packets over Overlay 1829 Multilink Network (OMNI) Interfaces", Work in Progress, 1830 Internet-Draft, draft-templin-6man-omni-55, 7 March 2022, 1831 . 1834 [I-D.templin-ipwave-uam-its] 1835 Templin, F. L., "Urban Air Mobility Implications for 1836 Intelligent Transportation Systems", Work in Progress, 1837 Internet-Draft, draft-templin-ipwave-uam-its-04, 4 January 1838 2021, . 1841 [I-D.templin-intarea-parcels] 1842 Templin, F. L., "IP Parcels", Work in Progress, Internet- 1843 Draft, draft-templin-intarea-parcels-09, 10 February 2022, 1844 . 1847 [I-D.ietf-dmm-fpc-cpdp] 1848 Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S., 1849 Moses, D., and C. E. Perkins, "Protocol for Forwarding 1850 Policy Configuration (FPC) in DMM", Work in Progress, 1851 Internet-Draft, draft-ietf-dmm-fpc-cpdp-14, 22 September 1852 2020, . 1855 [I-D.thubert-6man-ipv6-over-wireless] 1856 Thubert, P., "IPv6 Neighbor Discovery on Wireless 1857 Networks", Work in Progress, Internet-Draft, draft- 1858 thubert-6man-ipv6-over-wireless-11, 15 December 2021, 1859 . 1862 [DSRC] ASTM International, "Standard Specification for 1863 Telecommunications and Information Exchange Between 1864 Roadside and Vehicle Systems - 5 GHz Band Dedicated Short 1865 Range Communications (DSRC) Medium Access Control (MAC) 1866 and Physical Layer (PHY) Specifications", 1867 ASTM E2213-03(2010), October 2010. 1869 [EU-2008-671-EC] 1870 European Union, "Commission Decision of 5 August 2008 on 1871 the Harmonised Use of Radio Spectrum in the 5875 - 5905 1872 MHz Frequency Band for Safety-related Applications of 1873 Intelligent Transport Systems (ITS)", EU 2008/671/EC, 1874 August 2008. 1876 [IEEE-802.11p] 1877 "Part 11: Wireless LAN Medium Access Control (MAC) and 1878 Physical Layer (PHY) Specifications - Amendment 6: 1879 Wireless Access in Vehicular Environments", IEEE Std 1880 802.11p-2010, June 2010. 1882 [IEEE-802.11-OCB] 1883 "Part 11: Wireless LAN Medium Access Control (MAC) and 1884 Physical Layer (PHY) Specifications", IEEE Std 1885 802.11-2016, December 2016. 1887 [WAVE-1609.0] 1888 IEEE 1609 Working Group, "IEEE Guide for Wireless Access 1889 in Vehicular Environments (WAVE) - Architecture", IEEE Std 1890 1609.0-2013, March 2014. 1892 [WAVE-1609.2] 1893 IEEE 1609 Working Group, "IEEE Standard for Wireless 1894 Access in Vehicular Environments - Security Services for 1895 Applications and Management Messages", IEEE Std 1896 1609.2-2016, March 2016. 1898 [WAVE-1609.3] 1899 IEEE 1609 Working Group, "IEEE Standard for Wireless 1900 Access in Vehicular Environments (WAVE) - Networking 1901 Services", IEEE Std 1609.3-2016, April 2016. 1903 [WAVE-1609.4] 1904 IEEE 1609 Working Group, "IEEE Standard for Wireless 1905 Access in Vehicular Environments (WAVE) - Multi-Channel 1906 Operation", IEEE Std 1609.4-2016, March 2016. 1908 [ISO-ITS-IPv6] 1909 ISO/TC 204, "Intelligent Transport Systems - 1910 Communications Access for Land Mobiles (CALM) - IPv6 1911 Networking", ISO 21210:2012, June 2012. 1913 [ISO-ITS-IPv6-AMD1] 1914 ISO/TC 204, "Intelligent Transport Systems - 1915 Communications Access for Land Mobiles (CALM) - IPv6 1916 Networking - Amendment 1", ISO 21210:2012/AMD 1:2017, 1917 September 2017. 1919 [TS-23.285-3GPP] 1920 3GPP, "Architecture Enhancements for V2X Services", 3GPP 1921 TS 23.285/Version 16.2.0, December 2019. 1923 [TR-22.886-3GPP] 1924 3GPP, "Study on Enhancement of 3GPP Support for 5G V2X 1925 Services", 3GPP TR 22.886/Version 16.2.0, December 2018. 1927 [TS-23.287-3GPP] 1928 3GPP, "Architecture Enhancements for 5G System (5GS) to 1929 Support Vehicle-to-Everything (V2X) Services", 3GPP 1930 TS 23.287/Version 16.2.0, March 2020. 1932 [VIP-WAVE] Cespedes, S., Lu, N., and X. Shen, "VIP-WAVE: On the 1933 Feasibility of IP Communications in 802.11p Vehicular 1934 Networks", IEEE Transactions on Intelligent Transportation 1935 Systems, vol. 14, no. 1, March 2013. 1937 [Identity-Management] 1938 Wetterwald, M., Hrizi, F., and P. Cataldi, "Cross-layer 1939 Identities Management in ITS Stations", The 10th 1940 International Conference on ITS Telecommunications, 1941 November 2010. 1943 [SAINT] Jeong, J., Jeong, H., Lee, E., Oh, T., and D. Du, "SAINT: 1944 Self-Adaptive Interactive Navigation Tool for Cloud-Based 1945 Vehicular Traffic Optimization", IEEE Transactions on 1946 Vehicular Technology, Vol. 65, No. 6, June 2016. 1948 [SAINTplus] 1949 Shen, Y., Lee, J., Jeong, H., Jeong, J., Lee, E., and D. 1950 Du, "SAINT+: Self-Adaptive Interactive Navigation Tool+ 1951 for Emergency Service Delivery Optimization", 1952 IEEE Transactions on Intelligent Transportation Systems, 1953 June 2017. 1955 [SANA] Hwang, T. and J. Jeong, "SANA: Safety-Aware Navigation 1956 Application for Pedestrian Protection in Vehicular 1957 Networks", Springer Lecture Notes in Computer Science 1958 (LNCS), Vol. 9502, December 2015. 1960 [CASD] Shen, Y., Jeong, J., Oh, T., and S. Son, "CASD: A 1961 Framework of Context-Awareness Safety Driving in Vehicular 1962 Networks", International Workshop on Device Centric Cloud 1963 (DC2), March 2016. 1965 [CA-Cruise-Control] 1966 California Partners for Advanced Transportation Technology 1967 (PATH), "Cooperative Adaptive Cruise Control", Available: 1968 https://path.berkeley.edu/research/connected-and- 1969 automated-vehicles/cooperative-adaptive-cruise-control, 1970 2022. 1972 [Truck-Platooning] 1973 California Partners for Advanced Transportation Technology 1974 (PATH), "Automated Truck Platooning", Available: 1975 https://path.berkeley.edu/research/connected-and- 1976 automated-vehicles/truck-platooning, 2022. 1978 [FirstNet] U.S. National Telecommunications and Information 1979 Administration (NTIA), "First Responder Network Authority 1980 (FirstNet)", Available: https://www.firstnet.gov/, 2022. 1982 [PSCE] European Commission, "Public Safety Communications Europe 1983 (PSCE)", Available: https://www.psc-europe.eu/, 2022. 1985 [FirstNet-Report] 1986 First Responder Network Authority, "FY 2017: ANNUAL REPORT 1987 TO CONGRESS, Advancing Public Safety Broadband 1988 Communications", FirstNet FY 2017, December 2017. 1990 [SignalGuru] 1991 Koukoumidis, E., Peh, L., and M. Martonosi, "SignalGuru: 1992 Leveraging Mobile Phones for Collaborative Traffic Signal 1993 Schedule Advisory", ACM MobiSys, June 2011. 1995 [Fuel-Efficient] 1996 van de Hoef, S., H. Johansson, K., and D. V. Dimarogonas, 1997 "Fuel-Efficient En Route Formation of Truck Platoons", 1998 IEEE Transactions on Intelligent Transportation Systems, 1999 January 2018. 2001 [Automotive-Sensing] 2002 Choi, J., Va, V., Gonzalez-Prelcic, N., Daniels, R., R. 2003 Bhat, C., and R. W. Heath, "Millimeter-Wave Vehicular 2004 Communication to Support Massive Automotive Sensing", 2005 IEEE Communications Magazine, December 2016. 2007 [NHTSA-ACAS-Report] 2008 National Highway Traffic Safety Administration (NHTSA), 2009 "Final Report of Automotive Collision Avoidance Systems 2010 (ACAS) Program", DOT HS 809 080, August 2000. 2012 [CBDN] Kim, J., Kim, S., Jeong, J., Kim, H., Park, J., and T. 2013 Kim, "CBDN: Cloud-Based Drone Navigation for Efficient 2014 Battery Charging in Drone Networks", IEEE Transactions on 2015 Intelligent Transportation Systems, November 2019. 2017 [LIFS] Wang, J., Xiong, J., Jiang, H., Jamieson, K., Chen, X., 2018 Fang, D., and C. Wang, "Low Human-Effort, Device-Free 2019 Localization with Fine-Grained Subcarrier Information", 2020 IEEE Transactions on Mobile Computing, November 2018. 2022 [DFC] Jeong, J., Shen, Y., Kim, S., Choe, D., Lee, K., and Y. 2023 Kim, "DFC: Device-free human counting through WiFi fine- 2024 grained subcarrier information", IET Communications, 2025 January 2021. 2027 [In-Car-Network] 2028 Lim, H., Volker, L., and D. Herrscher, "Challenges in a 2029 Future IP/Ethernet-based In-Car Network for Real-Time 2030 Applications", ACM/EDAC/IEEE Design Automation Conference 2031 (DAC), June 2011. 2033 [Scrambler-Attack] 2034 Bloessl, B., Sommer, C., Dressier, F., and D. Eckhoff, 2035 "The Scrambler Attack: A Robust Physical Layer Attack on 2036 Location Privacy in Vehicular Networks", IEEE 2015 2037 International Conference on Computing, Networking and 2038 Communications (ICNC), February 2015. 2040 [Bitcoin] Nakamoto, S., "Bitcoin: A Peer-to-Peer Electronic Cash 2041 System", URL: https://bitcoin.org/bitcoin.pdf, May 2009. 2043 [Vehicular-BlockChain] 2044 Dorri, A., Steger, M., Kanhere, S., and R. Jurdak, 2045 "BlockChain: A Distributed Solution to Automotive Security 2046 and Privacy", IEEE Communications Magazine, Vol. 55, No. 2047 12, December 2017. 2049 Appendix A. Support of Multiple Radio Technologies for V2V 2051 Vehicular networks may consist of multiple radio technologies such as 2052 DSRC and 5G V2X. Although a Layer-2 solution can provide support for 2053 multihop communications in vehicular networks, the scalability issue 2054 related to multihop forwarding still remains when vehicles need to 2055 disseminate or forward packets toward multihop-away destinations. In 2056 addition, the IPv6-based approach for V2V as a network layer protocol 2057 can accommodate multiple radio technologies as MAC protocols, such as 2058 DSRC and 5G V2X. Therefore, the existing IPv6 protocol can be 2059 augmented through the addition of a virtual interface (e.g., OMNI 2060 [I-D.templin-6man-omni] and DLEP [RFC8175]) and/or protocol changes 2061 in order to support both wireless single-hop/multihop V2V 2062 communications and multiple radio technologies in vehicular networks. 2063 In such a way, vehicles can communicate with each other by V2V 2064 communications to share either an emergency situation or road hazard 2065 information in a highway having multiple kinds of radio technologies. 2067 Appendix B. Support of Multihop V2X Networking 2069 The multihop V2X networking can be supported by RPL (IPv6 Routing 2070 Protocol for Low-Power and Lossy Networks) [RFC6550] and Overlay 2071 Multilink Network Interface (OMNI) [I-D.templin-6man-omni]. 2073 RPL defines an IPv6 routing protocol for low-power and lossy networks 2074 (LLN), mostly designed for home automation routing, building 2075 automation routing, industrial routing, and urban LLN routing. It 2076 uses a Destination-Oriented Directed Acyclic Graph (DODAG) to 2077 construct routing paths for hosts (e.g., IoT devices) in a network. 2078 The DODAG uses an objective function (OF) for route selection and 2079 optimization within the network. A user can use different routing 2080 metrics to define an OF for a specific scenario. RPL supports 2081 multipoint-to-point, point-to-multipoint, and point-to-point traffic, 2082 and the major traffic flow is the multipoint-to-point traffic. For 2083 example, in a highway scenario, a vehicle may not access an RSU 2084 directly because of the distance of the DSRC coverage (up to 1 km). 2085 In this case, the RPL can be extended to support a multihop V2I since 2086 a vehicle can take advantage of other vehicles as relay nodes to 2087 reach the RSU. Also, RPL can be extended to support both multihop 2088 V2V and V2X in the similar way. 2090 RPL is primarily designed to minimize the control plane activity, 2091 which is the relative amount of routing protocol exchanges versus 2092 data traffic; this approach is beneficial for situations where the 2093 power and bandwidth are scarce (e.g., an IoT LLN where RPL is 2094 typically used today), but also in situations of high relative 2095 mobility between the nodes in the network (also known as swarming, 2096 e.g., within a variable set of vehicles with a similar global motion, 2097 or a variable set of drones flying toward the same direction). 2099 To reduce the routing exchanges, RPL leverages a Distance Vector (DV) 2100 approach, which does not need a global knowledge of the topology, and 2101 only optimizes the routes to and from the root, allowing Peer-to-Peer 2102 (P2P) paths to be stretched. Although RPL installs its routes 2103 proactively, it only maintains them lazily, that is, in reaction to 2104 actual traffic, or as a slow background activity. Additionally, RPL 2105 leverages the concept of an objective function (called OF), which 2106 allows to adapt the activity of the routing protocol to use cases, 2107 e.g., type, speed, and quality of the radios. RPL does not need 2108 converge, and provides connectivity to most nodes most of the time. 2109 The default route toward the root is maintained aggressively and may 2110 change while a packet progresses without causing loops, so the packet 2111 will still reach the root. There are two modes for routing in RPL 2112 such as non-storing mode and storing mode. In non-storing mode, a 2113 node inside the mesh/swarm that changes its point(s) of attachment to 2114 the graph informs the root with a single unicast packet flowing along 2115 the default route, and the connectivity is restored immediately; this 2116 mode is preferable for use cases where Internet connectivity is 2117 dominant. On the other hand, in storing mode, the routing stretch is 2118 reduced, for a better P2P connectivity, while the Internet 2119 connectivity is restored more slowly, during the time for the DV 2120 operation to operate hop-by-hop. While an RPL topology can quickly 2121 scale up and down and fits the needs of mobility of vehicles, the 2122 total performance of the system will also depend on how quickly a 2123 node can form an address, join the mesh (including Authentication, 2124 Authorization, and Accounting (AAA)), and manage its global mobility 2125 to become reachable from another node outside the mesh. 2127 OMNI defines a protocol for the transmission of IPv6 packets over 2128 Overlay Multilink Network Interfaces that are virtual interfaces 2129 governing multiple physical network interfaces. OMNI supports 2130 multihop V2V communication between vehicles in multiple forwarding 2131 hops via intermediate vehicles with OMNI links. It also supports 2132 multihop V2I communication between a vehicle and an infrastructure 2133 access point by multihop V2V communication. The OMNI interface 2134 supports an NBMA link model where multihop V2V and V2I communications 2135 use each mobile node's ULAs without need for any DAD or MLD 2136 Messaging. 2138 In OMNI protocol, each wireless media interface is configured with an 2139 IPv6 Unique Local Address (ULA) [RFC4193] that is assured unique 2140 within the vehicular network according to AERO/OMNI and [RFC5889]. 2141 The ULA supports both V2V and V2I multihop forwarding within the 2142 vehicular network (e.g., via a VANET routing protocol) while each 2143 vehicle can communicate with Internet correspondents using global 2144 IPv6 addresses via OMNI interface encapsulation over the wireless 2145 interface. 2147 For the control traffic overhead for running both vehicular ND and a 2148 VANET routing protocol, the AERO/OMNI approach may avoid this issue 2149 by using MANET routing protocols only (i.e., no multicast of IPv6 ND 2150 messaging) in the wireless underlay network while applying efficient 2151 unicast IPv6 ND messaging in the OMNI overlay on an as-needed basis 2152 for router discovery and NUD. This greatly reduces the overhead for 2153 VANET-wide multicasting while providing agile accommodation for 2154 dynamic topology changes. 2156 Appendix C. Support of Mobility Management for V2I 2158 The seamless application communication between two vehicles or 2159 between a vehicle and an infrastructure node requires mobility 2160 management in vehicular networks. The mobility management schemes 2161 include a host-based mobility scheme, network-based mobility scheme, 2162 and software-defined networking scheme. 2164 In the host-based mobility scheme (e.g., MIPv6), an IP-RSU plays a 2165 role of a home agent. On the other hand, in the network-based 2166 mobility scheme (e.g., PMIPv6, an MA plays a role of a mobility 2167 management controller such as a Local Mobility Anchor (LMA) in 2168 PMIPv6, which also serves vehicles as a home agent, and an IP-RSU 2169 plays a role of an access router such as a Mobile Access Gateway 2170 (MAG) in PMIPv6 [RFC5213]. The host-based mobility scheme needs 2171 client functionality in IPv6 stack of a vehicle as a mobile node for 2172 mobility signaling message exchange between the vehicle and home 2173 agent. On the other hand, the network-based mobility scheme does not 2174 need such a client functionality for a vehicle because the network 2175 infrastructure node (e.g., MAG in PMIPv6) as a proxy mobility agent 2176 handles the mobility signaling message exchange with the home agent 2177 (e.g., LMA in PMIPv6) for the sake of the vehicle. 2179 There are a scalability issue and a route optimization issue in the 2180 network-based mobility scheme (e.g., PMIPv6) when an MA covers a 2181 large vehicular network governing many IP-RSUs. In this case, a 2182 distributed mobility scheme (e.g., DMM [RFC7429]) can mitigate the 2183 scalability issue by distributing multiple MAs in the vehicular 2184 network such that they are positioned closer to vehicles for route 2185 optimization and bottleneck mitigation in a central MA in the 2186 network-based mobility scheme. All these mobility approaches (i.e., 2187 a host-based mobility scheme, network-based mobility scheme, and 2188 distributed mobility scheme) and a hybrid approach of a combination 2189 of them need to provide an efficient mobility service to vehicles 2190 moving fast and moving along with the relatively predictable 2191 trajectories along the roadways. 2193 In vehicular networks, the control plane can be separated from the 2194 data plane for efficient mobility management and data forwarding by 2195 using the concept of Software-Defined Networking (SDN) 2196 [RFC7149][I-D.ietf-dmm-fpc-cpdp]. Note that Forwarding Policy 2197 Configuration (FPC) in [I-D.ietf-dmm-fpc-cpdp], which is a flexible 2198 mobility management system, can manage the separation of data-plane 2199 and control-plane in DMM. In SDN, the control plane and data plane 2200 are separated for the efficient management of forwarding elements 2201 (e.g., switches and routers) where an SDN controller configures the 2202 forwarding elements in a centralized way and they perform packet 2203 forwarding according to their forwarding tables that are configured 2204 by the SDN controller. An MA as an SDN controller needs to 2205 efficiently configure and monitor its IP-RSUs and vehicles for 2206 mobility management, location management, and security services. 2208 Appendix D. Support of MTU Diversity for IP-based Vehicular Networks 2210 The wireless and/or wired-line links in paths between both mobile 2211 nodes and fixed network correspondents may configure a variety of 2212 Maximum Transmission Units (MTUs), where all IPv6 links are required 2213 to support a minimum MTU of 1280 octets and may support larger MTUs. 2214 Unfortunately, determining the path MTU (i.e., the minimum link MTU 2215 in the path) has proven to be inefficient and unreliable due to the 2216 uncertain nature of the loss-oriented ICMPv6 messaging service used 2217 for path MTU discovery. Recent developments have produced a more 2218 reliable path MTU determination service for TCP [RFC4821] and UDP 2219 [RFC8899] however the MTUs discovered are always limited by the most 2220 restrictive link MTU in the path (often 1500 octets or smaller). 2222 The AERO/OMNI service addresses the MTU issue by introducing a new 2223 layer in the Internet architecture known as the "OMNI Adaptation 2224 Layer (OAL)". The OAL allows end systems that configure an OMNI 2225 interface to utilize a full 65535 octet MTU by leveraging the IPv6 2226 fragmentation and reassembly service during encapsulation to produce 2227 fragment sizes that are assured of traversing the path without loss 2228 due to a size restriction. (This allows end systems to send packets 2229 that are often much larger than the actual path MTU.) 2231 Performance studies over the course of many decades have proven that 2232 applications will see greater performance by sending smaller numbers 2233 of large packets (as opposed to larger numbers of small packets) even 2234 if fragmentation is needed. The OAL further supports even larger 2235 packet sizes through the IP Parcels construct 2236 [I-D.templin-intarea-parcels] which provides "packets-in-packet" 2237 encapsulation for a total size up to 4MB. Together, the OAL and IP 2238 Parcels will provide a revolutionary new capability for greater 2239 efficiency in both mobile and fixed networks. 2241 Appendix E. Acknowledgments 2243 This work was supported by Institute of Information & Communications 2244 Technology Planning & Evaluation (IITP) grant funded by the Korea 2245 MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based 2246 Security Intelligence Technology Development for the Customized 2247 Security Service Provisioning). 2249 This work was supported in part by the MSIT, Korea, under the ITRC 2250 (Information Technology Research Center) support program (IITP- 2251 2021-2017-0-01633) supervised by the IITP. 2253 This work was supported in part by the IITP (2020-0-00395, Standard 2254 Development of Blockchain based Network Management Automation 2255 Technology). 2257 This work was supported in part by the French research project 2258 DataTweet (ANR-13-INFR-0008) and in part by the HIGHTS project funded 2259 by the European Commission I (636537-H2020). 2261 This work was supported in part by the Cisco University Research 2262 Program Fund, Grant # 2019-199458 (3696), and by ANID Chile Basal 2263 Project FB0008. 2265 Appendix F. Contributors 2267 This document is a group work of IPWAVE working group, greatly 2268 benefiting from inputs and texts by Rex Buddenberg (Naval 2269 Postgraduate School), Thierry Ernst (YoGoKo), Bokor Laszlo (Budapest 2270 University of Technology and Economics), Jose Santa Lozanoi 2271 (Universidad of Murcia), Richard Roy (MIT), Francois Simon (Pilot), 2272 Sri Gundavelli (Cisco), Erik Nordmark, Dirk von Hugo (Deutsche 2273 Telekom), Pascal Thubert (Cisco), Carlos Bernardos (UC3M), Russ 2274 Housley (Vigil Security), Suresh Krishnan (Kaloom), Nancy Cam-Winget 2275 (Cisco), Fred L. Templin (The Boeing Company), Jung-Soo Park (ETRI), 2276 Zeungil (Ben) Kim (Hyundai Motors), Kyoungjae Sun (Soongsil 2277 University), Zhiwei Yan (CNNIC), YongJoon Joe (LSware), Peter E. Yee 2278 (Akayla), and Erik Kline. The authors sincerely appreciate their 2279 contributions. 2281 The following are co-authors of this document: 2283 Nabil Benamar - 2285 Department of Computer Sciences, High School of Technology of Meknes, 2286 Moulay Ismail University, Morocco, Phone: +212 6 70 83 22 36, EMail: 2287 benamar73@gmail.com 2289 Sandra Cespedes - 2291 NIC Chile Research Labs, Universidad de Chile, Av. Blanco Encalada 2292 1975, Santiago, Chile, Phone: +56 2 29784093, EMail: 2293 scespede@niclabs.cl 2295 Jerome Haerri - 2297 Communication Systems Department, EURECOM, Sophia-Antipolis, France, 2298 Phone: +33 4 93 00 81 34, EMail: jerome.haerri@eurecom.fr 2300 Dapeng Liu - 2302 Alibaba, Beijing, Beijing 100022, China, Phone: +86 13911788933, 2303 EMail: max.ldp@alibaba-inc.com 2305 Tae (Tom) Oh - 2307 Department of Information Sciences and Technologies, Rochester 2308 Institute of Technology, One Lomb Memorial Drive, Rochester, NY 2309 14623-5603, USA, Phone: +1 585 475 7642, EMail: Tom.Oh@rit.edu 2311 Charles E. Perkins - 2312 Futurewei Inc., 2330 Central Expressway, Santa Clara, CA 95050, USA, 2313 Phone: +1 408 330 4586, EMail: charliep@computer.org 2315 Alexandre Petrescu - 2317 CEA, LIST, CEA Saclay, Gif-sur-Yvette, Ile-de-France 91190, France, 2318 Phone: +33169089223, EMail: Alexandre.Petrescu@cea.fr 2320 Yiwen Chris Shen - 2322 Department of Computer Science & Engineering, Sungkyunkwan 2323 University, 2066 Seobu-Ro, Jangan-Gu, Suwon, Gyeonggi-Do 16419, 2324 Republic of Korea, Phone: +82 31 299 4106, Fax: +82 31 290 7996, 2325 EMail: chrisshen@skku.edu, URI: https://chrisshen.github.io 2327 Michelle Wetterwald - 2329 FBConsulting, 21, Route de Luxembourg, Wasserbillig, Luxembourg 2330 L-6633, Luxembourg, EMail: Michelle.Wetterwald@gmail.com 2332 Author's Address 2334 Jaehoon (Paul) Jeong (editor) 2335 Department of Computer Science and Engineering 2336 Sungkyunkwan University 2337 2066 Seobu-Ro, Jangan-Gu 2338 Suwon 2339 Gyeonggi-Do 2340 16419 2341 Republic of Korea 2342 Phone: +82 31 299 4957 2343 Email: pauljeong@skku.edu 2344 URI: http://iotlab.skku.edu/people-jaehoon-jeong.php