IPWAVE Working Group                                       J. Jeong, Ed.
Internet-Draft                                   Sungkyunkwan University
Intended status: Informational                              May 24,                              July 8, 2019
Expires: November 25, 2019 January 9, 2020

IP Wireless Access in Vehicular Environments (IPWAVE): Problem Statement
                             and Use Cases


   This document discusses the problem statement and use cases of IP-
   based vehicular networking for Intelligent Transportation Systems
   (ITS).  The main scenarios of vehicular communications are vehicle-
   to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-
   everything (V2X) communications.  First, this document explains use
   cases using V2V, V2I, and V2X networking.  Next, it makes a problem
   statement about key aspects in IP-based vehicular networking, such as
   IPv6 Neighbor Discovery, Mobility Management, and Security & Privacy.
   For each key aspect, this document specifies requirements in IP-based
   vehicular networking, and suggests the direction of solutions
   satisfying those requirements.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  V2V . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  V2I . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  V2X . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Vehicular Networks  . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Vehicular Network Architecture  . . . . . . . . . . . . .   8
     4.2.  V2I-based Internetworking . . . . . . . . . . . . . . . .   9  10
     4.3.  V2V-based Internetworking . . . . . . . . . . . . . . . .  11  12
   5.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .  13
     5.1.  Neighbor Discovery  . . . . . . . . . . . . . . . . . . .  13
       5.1.1.  Link Model  . . . . . . . . . . . . . . . . . . . . .  14
       5.1.2.  MAC Address Pseudonym . . . . . . . . . . . . . . . .  16
       5.1.3.  Prefix Dissemination/Exchange . . . . . . . . . . . .  16
       5.1.4.  Routing . . . . . . . . . . . . . . . . . . . . . . .  17
     5.2.  Mobility Management . . . . . . . . . . . . . . . . . . .  17
     5.3.  Security and Privacy  . . . . . . . . . . . . . . . . . .  18
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  19  20
   Appendix A.  Changes from draft-ietf-ipwave-vehicular-
                networking-09  . . . . . . . . . . . . . . . . . . .  25  26
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  25  26
   Appendix C.  Contributors . . . . . . . . . . . . . . . . . . . .  25  27
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  27  29

1.  Introduction

   Vehicular networking studies have mainly focused on improving safety
   and efficiency, and also enabling entertainment in vehicular
   networks.  The Federal Communications Commission (FCC) in the US
   allocated wireless channels for Dedicated Short-Range Communications
   (DSRC) [DSRC] in the Intelligent Transportation Systems (ITS) with
   the frequency band of 5.850 - 5.925 GHz (i.e., 5.9 GHz band).  DSRC-
   based wireless communications can support vehicle-to-vehicle (V2V),
   vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X)
   networking.  Also, the European Union (EU) passed a decision to
   allocate a radio spectrum for safety-related and non-safety-related
   applications of ITS with the frequency band of 5.875 - 5.905 GHz,
   which is called Commission Decision 2008/671/EC [EU-2008-671-EC].

   For direct inter-vehicular wireless connectivity, IEEE has amended
   WiFi standard 802.11 to enable driving safety services based on the
   DSRC in terms of standards for the Wireless Access in Vehicular
   Environments (WAVE) system.  The Physical Layer (L1) and Data Link
   Layer (L2) issues are addressed in IEEE 802.11p [IEEE-802.11p] for
   the PHY and MAC of the DSRC, while IEEE 1609.2 [WAVE-1609.2] covers
   security aspects, IEEE 1609.3 [WAVE-1609.3] defines related services
   at network and transport layers, and IEEE 1609.4 [WAVE-1609.4]
   specifies the multi-channel operation.  Note that IEEE 802.11p was a
   separate standard, but was later enrolled into the base 802.11
   standard (IEEE 802.11-2012) as IEEE 802.11 Outside the Context of a
   Basic Service Set in 2012 [IEEE-802.11-OCB].

   Along with these WAVE standards, IPv6 [RFC8200] and Mobile IP
   protocols (e.g., MIPv4 [RFC5944], MIPv6 [RFC6275], and Proxy MIPv6
   (PMIPv6) [RFC5213][RFC5844]) can be applied (or easily modified) to
   vehicular networks.  In Europe, ETSI has standardized a GeoNetworking
   (GN) protocol [ETSI-GeoNetworking] and a protocol adaptation sub-
   layer from GeoNetworking to IPv6 [ETSI-GeoNetwork-IP].  Note that a
   GN protocol is useful to route an event or notification message to
   vehicles around a geographic position, such as an acciendent area in
   a roadway.  In addition, ISO has approved a standard specifying the
   IPv6 network protocols and services to be used for Communications
   Access for Land Mobiles (CALM) [ISO-ITS-IPv6].

   This document explains use cases and a problem statement about IP-
   based vehicular networking for ITS, which is named IP Wireless Access
   in Vehicular Environments (IPWAVE).  First, it introduces the use
   cases for using V2V, V2I, and V2X networking in the ITS.  Next, it
   makes a problem statement about key aspects in IPWAVE, such as IPv6
   Neighbor Discovery, Mobility Management, and Security & Privacy.  For
   each key aspect of the problem statement, this document specifies
   requirements in IP-based vehicular networking, and proposes the
   direction of solutions fulfilling those requirements.  Therefore,
   with the problem statement, this document will open a door to develop
   key protocols for IPWAVE that will be essential to IP-based vehicular
   networks in near future.

2.  Terminology

   This document uses the following definitions:

   o  DMM: Acronym for "Distributed Mobility Management"

   o  LiDAR: Acronym for "Light Detection and Ranging".  It is a
      scanning device to measure a distance to an object by emitting
      pulsed laser light and measuring the reflected pulsed light.

   o  Mobility Anchor (MA): A node that maintains IP addresses and
      mobility information of vehicles in a road network to support
      their address autoconfiguration and mobility management with a
      binding table.  It has end-to-end connections with RSUs under its

   o  On-Board Unit (OBU): A node that has physical communication
      devices (e.g., IEEE 802.11-OCB and Cellular V2X (C-V2X)
      [TS-23.285-3GPP]) for wireless communications with other OBUs and
      RSUs, and may be connected to in-vehicle devices or networks.  An
      OBU is mounted on a vehicle.

   o  OCB: Acronym for "Outside the Context of a Basic Service Set"

   o  Road-Side Unit (RSU): A node that has physical communication
      devices (e.g., IEEE 802.11-OCB and C-V2X) for wireless
      communications with vehicles and is also connected to the Internet
      as a router or switch for packet forwarding.  An RSU is typically
      deployed on the road infrastructure, either at an intersection or
      in a road segment, but may also be located in car parking area.

   o  Traffic Control Center (TCC): A node that maintains road
      infrastructure information (e.g., RSUs, traffic signals, and loop
      detectors), vehicular traffic statistics (e.g., average vehicle
      speed and vehicle inter-arrival time per road segment), and
      vehicle information (e.g., a vehicle's identifier, position,
      direction, speed, and trajectory as a navigation path).  TCC is
      included in a vehicular cloud for vehicular networks.

   o  Vehicle: A node that has an OBU for wireless communication with
      other vehicles and RSUs.  It has a radio navigation receiver of
      Global Positioning System (GPS) for efficient navigation.

   o  Vehicular Ad Hoc Network (VANET): A network that consists of
      vehicles interconnected by wireless communication.  Since VANET is
      a connected network component, two vehicles in a VANET can
      communicate with each other through ad hoc routing via other
      vehicles as relays even where they are out of one-hop wireless
      communication range.

   o  Vehicular Cloud: A cloud infrastructure for vehicular networks,
      having compute nodes, storage nodes, and network nodes.

   o  Vehicle Detection Loop (i.e., Loop Detector): An inductive device
      used for detecting vehicles passing or arriving at a certain
      point, for instance, at an intersection with traffic lights or at
      a ramp toward a highway.  The relatively crude nature of the
      loop's structure means that only metal masses above a certain size
      are capable of triggering the detection.

   o  V2I2P: Acronym for "Vehicle to Infrastructure to Pedestrian".

   o  V2I2V: Acronym for "Vehicle to Infrastructure to Vehicle".

   o  WAVE: Acronym for "Wireless Access in Vehicular Environments"

3.  Use Cases

   This section explains use cases of V2V, V2I, and V2X networking.  The
   use cases of the V2X networking exclude the ones of the V2V and V2I
   networking, but include Vehicle-to-Pedestrian (V2P) and Vehicle-to-
   Device (V2D).

3.1.  V2V

   The use cases of V2V networking discussed in this section include

   o  Context-aware navigation for driving safety and collision

   o  Cooperative adaptive cruise control in an urban roadway;

   o  Platooning in a highway;

   o  Cooperative environment sensing.

   These four techniques will be important elements for self-driving

   Context-Aware Safety Driving (CASD) navigator [CASD] can help drivers
   to drive safely by letting the drivers recognize dangerous obstacles
   and situations.  That is, CASD navigator displays obstables or
   neighboring vehicles relevant to possible collisions in real-time
   through V2V networking.  CASD provides vehicles with a class-based
   automatic safety action plan, which considers three situations, such
   as the Line-of-Sight unsafe, Non-Line-of-Sight unsafe, and safe
   situations.  This action plan can be performed among vehicles through
   V2V networking.

   Cooperative Adaptive Cruise Control (CACC) [CA-Cruise-Control] helps
   vehicles to adapt their speed autonomously through V2V communication
   among vehicles according to the mobility of their predecessor and
   successor vehicles in an urban roadway or a highway.  Thus, CACC can
   help adjacent vehicles to efficiently adjust their speed in an
   interactive way through V2V networking in order to avoid collision.

   Platooning [Truck-Platooning] allows a series of vehicles (e.g.,
   trucks) to move together with a very short inter-distance.  Trucks
   can use V2V communication in addition to forward sensors in order to
   maintain constant clearance between two consecutive vehicles at very
   short gaps (from 3 meters to 10 meters).  This platooning can
   maximize the throughput of vehicular traffic in a highway and reduce
   the gas consumption because the leading vehicle can help the
   following vehicles to experience less air resistance.

   Cooperative-environment-sensing use cases suggest that vehicles can
   share environmental information from various vehicle-mounted sensors,
   such as radars, LiDARs, and cameras with other vehicles and
   pedestrians.  [Automotive-Sensing] introduces a millimeter-wave
   vehicular communication for massive automotive sensing.  Data
   generated by those sensors can be substantially large, and these data
   shall be routed to different destinations.  In addition, from the
   perspective of driverless vehicles, it is expected that driverless
   vehicles can be mixed with driver-operated vehicles.  Through the
   cooperative environment sensing, driver-operated vehicles can use
   environmental information sensed by driverless vehicles for better
   interaction with the context.

3.2.  V2I

   The use cases of V2I networking discussed in this section include

   o  Navigation service;

   o  Energy-efficient speed recommendation service;

   o  Accident notification service.

   A navigation service, such as the Self-Adaptive Interactive
   Navigation Tool (called SAINT) [SAINT], using V2I networking
   interacts with TCC for the large-scale/long-range road traffic
   optimization and can guide individual vehicles for appropriate
   navigation paths in real time.  The enhanced version of SAINT
   [SAINTplus] can give the fast moving paths to emergency vehicles
   (e.g., ambulance and fire engine) to let them reach an accident spot
   while providing other vehicles near the accident spot with efficient
   detour paths.

   A TCC can recommend an energy-efficient speed to a vehicle driving in
   different traffic environments.  [Fuel-Efficient] studies fuel-
   efficient route and speed plans for platooned trucks.

   The emergency communication between accident vehicles (or emergency
   vehicles) and TCC can be performed via either RSU or 4G-LTE networks.
   The First Responder Network Authority (FirstNet) [FirstNet] is
   provided by the US government to establish, operate, and maintain an
   interoperable public safety broadband network for safety and security
   network services, such as emergency calls.  The construction of the
   nationwide FirstNet network requires each state in the US to have a
   Radio Access Network (RAN) that will connect to the FirstNet's
   network core.  The current RAN is mainly constructed by 4G-LTE for
   the communication between a vehicle and an infrastructure node (i.e.,
   V2I) [FirstNet-Report], but it is expected that DSRC-based vehicular
   networks [DSRC] will be available for V2I and V2V in near future.

3.3.  V2X

   The use case of V2X networking discussed in this section is
   pedestrian protection service.

   A pedestrian protection service, such as Safety-Aware Navigation
   Application (called SANA) [SANA], using V2I2P networking can reduce
   the collision of a vehicle and a pedestrian carrying a smartphone
   equipped with a network device for wireless communication (e.g.,
   WiFi) with an RSU.  Vehicles and pedestrians can also communicate
   with each other via an RSU that delivers scheduling information for
   wireless communication in order to save the smartphones' battery
   through sleeping mode.

   For Vehicle-to-Pedestrian (V2P), a vehicle and a pedestrian's
   smartphone can directly communicate with each other via V2X without
   the relaying of an RSU as in the V2V scenario that the pedestrian's
   smartphone is regarded as a vehicle with a wireless media interface
   to be able to communicate with another vehicle.  In Vehicle-to-Device
   (V2D), a device can be a mobile node such as bicycle and motorcycle,
   and can communicate directly with a vehicle for collision avoidance.

4.  Vehicular Networks

   This section describes a vehicular network architecture supporting
   V2V, V2I, and V2X communications in vehicular networks.  Also, it
   describes an internal network within a vehicle or RSU, and the
   internetworking between the internal networks via DSRC links.

                     Traffic Control Center in Vehicular Cloud
                   *                                           *
                  *             +----------------+              *
                 *              | Mobility Anchor|               *
                 *              +----------------+               *
                  *                      ^                      *
                   *                     |                     *
                    ^               ^                        ^
                    |               |                        |
                    |               |                        |
                    v               v                        v
               +--------+ Ethernet +--------+            +--------+
               |  RSU1  |<-------->|  RSU2  |<---------->|  RSU3  |
               +--------+          +--------+            +--------+
                  ^                     ^                    ^
                  :                     :                    :
           +-----------------+ +-----------------+   +-----------------+
           |      : V2I      | |    V2I :        |   |   V2I :         |
           |      v          | |        v        |   |       v         |
+--------+ |   +--------+    | |   +--------+    |   |   +--------+    |
|Vehicle1|===> |Vehicle2|===>| |   |Vehicle3|===>|   |   |Vehicle4|===>|
|        |<...>|        |<........>|        |    |   |   |        |    |
+--------+ V2V +--------+    V2V   +--------+    |   |   +--------+    |
           |                 | |                 |   |                 |
           +-----------------+ +-----------------+   +-----------------+
                 Subnet1              Subnet2              Subnet3

        <----> Wired Link   <....> Wireless Link   ===> Moving Direction

   Figure 1: A Vehicular Network Architecture for V2I and V2V Networking

4.1.  Vehicular Network Architecture

   Figure 1 shows an architecture for V2I and V2V networking in a road
   network.  As shown in this figure, RSUs as routers and vehicles with
   OBU have wireless media interfaces for VANET.  Also, it is assumed
   that such the wireless media interfaces are autoconfigured with a
   global IPv6 prefix (e.g., 2001:DB8:1:1::/64) to support both V2V and
   V2I networking.  Note that 2001:DB8::/32 is a documentation prefix
   [RFC3849] for example prefixes in this document, and also that any
   routable IPv6 address needs to be routable in a VANET and a vehicular
   network including RSUs.

   Especially, for IPv6 packets transporting over IEEE 802.11-OCB,
   [IPv6-over-802.11-OCB] specifies several details, such as Maximum
   Transmission Unit (MTU), frame format, link-local address, address
   mapping for unicast and multicast, stateless autoconfiguration, and
   subnet structure.  Especially, an Ethernet Adaptation (EA) layer is
   in charge of transforming some parameters between IEEE 802.11 MAC
   layer and IPv6 network layer, which is located between IEEE
   802.11-OCB's logical link control layer and IPv6 network layer.  This
   IPv6 over 802.11-OCB can be used for both V2V and V2I in IP-based
   vehicular networks.

   In Figure 1, three RSUs (RSU1, RSU2, and RSU3) are deployed in the
   road network and are connected to a Vehicular Cloud through the
   Internet.  A Traffic Control Center (TCC) is connected to the
   Vehicular Cloud for the management of RSUs and vehicles in the road
   network.  A Mobility Anchor (MA) is located in the TCC as its key
   component for the mobility management of vehicles.  Two vehicles
   (Vehicle1 and Vehicle2) are wirelessly connected to RSU1, and one
   vehicle (Vehicle3) is wirelessly connected to RSU2.  The wireless
   networks of RSU1 and RSU2 belong to two different subnets (denoted as
   Subnet1 and Subnet2), respectively.  Also, another vehicle (Vehicle4)
   is wireless connected to RSU3, belonging to another subnet (denoted
   as Subnet3).

   In wireless subnets in vehicular networks (e.g., Subnet1 and Subnet2
   in Figure 1), vehicles can construct a connected VANET (with an
   arbitrary graph topology) and can communicate with each other via V2V
   communication.  Vehicle1 can communicate with Vehicle2 via V2V
   communication, and Vehicle2 can communicate with Vehicle3 via V2V
   communication because they are within the wireless communication
   range for each other.  On the other hand, Vehicle3 can communicate
   with Vehicle4 via the vehicular infrastructure (i.e., RSU2 and RSU3)
   by employing V2I (i.e., V2I2V) communication because they are not
   within the wireless communication range for each other.

   In vehicular networks, unidirectional links exist and must be
   considered for wireless communications.  Also, in the vehicular
   networks, control plane can be separated from data plane for
   efficient mobility management and data forwarding using Software-
   Defined Networking (SDN) [SDN-DMM].  The mobility information of a
   GPS receiver mounted in its vehicle (e.g., trajectory, position,
   speed, and direction) can be used for the accommodation of mobility-
   aware proactive protocols.  Vehicles can use the TCC as their Home
   Network having a home agent for mobility management as in MIPv6
   [RFC6275] and PMIPv6 [RFC5213], so the TCC maintains the mobility
   information of vehicles for location management.  Also, IP tunneling
   over the wireless link should be avoided for performance efficiency.

4.2.  V2I-based Internetworking

   This section discusses the internetworking between a vehicle's
   internal network (i.e., moving network) and an RSU's internal network
   (i.e., fixed network) via V2I communication.

                           (*)<........>(*)  +----->| Vehicular Cloud |
          2001:DB8:1:1::/64 |            |   |      +-----------------+
   +------------------------------+  +---------------------------------+
   |                        v     |  |   v   v                         |
   | +-------+ +------+ +-------+ |  | +-------+ +------+ +-------+    |
   | | Host1 | | DNS1 | |Router1| |  | |Router3| | DNS2 | | Host3 |    |
   | +-------+ +------+ +-------+ |  | +-------+ +------+ +-------+    |
   |     ^        ^         ^     |  |     ^         ^        ^        |
   |     |        |         |     |  |     |         |        |        |
   |     v        v         v     |  |     v         v        v        |
   | ---------------------------- |  | ------------------------------- |
   | 2001:DB8:10:1::/64 ^         |  |     ^ 2001:DB8:20:1::/64        |
   |                    |         |  |     |                           |
   |                    v         |  |     v                           |
   | +-------+      +-------+     |  | +-------+ +-------+   +-------+ |
   | | Host2 |      |Router2|     |  | |Router4| |Server1|...|ServerN| |
   | +-------+      +-------+     |  | +-------+ +-------+   +-------+ |
   |     ^              ^         |  |     ^         ^           ^     |
   |     |              |         |  |     |         |           |     |
   |     v              v         |  |     v         v           v     |
   | ---------------------------- |  | ------------------------------- |
   |      2001:DB8:10:2::/64      |  |       2001:DB8:20:2::/64        |
   +------------------------------+  +---------------------------------+
      Vehicle1 (Moving Network1)            RSU1 (Fixed Network1)

      <----> Wired Link   <....> Wireless Link   (*) Antenna

     Figure 2: Internetworking between Vehicle Network and RSU Network

   Nowadays, a vehicle's internal network tends to be Ethernet to
   interconnect electronic control units in a vehicle.  It can also
   support WiFi and Bluetooth to accommodate a driver's and passenger's
   mobile devices (e.g., smartphone and tablet).  In this trend, it is
   reasonable to consider a vehicle's internal network (i.e., moving
   network) and also the interaction between the internal network and an
   external network within another vehicle or RSU.

   As shown in Figure 2, the vehicle's moving network and the RSU's
   fixed network are self-contained networks having multiple subnets and
   having an edge router for the communication with another vehicle or
   RSU.  Internetworking between two internal networks via V2I
   communication requires an exchange of network prefix and other
   parameters through a prefix discovery mechanism, such as ND-based
   prefix discovery [ID-Vehicular-ND].  For the ND-based prefix
   discovery, network prefixs and parameters should be registered into a
   vehicle's router and an RSU router with an external network interface
   in advance.

   The network parameter discovery collects networking information for
   an IP communication between a vehicle and an RSU or between two
   neighboring vehicles, such as link layer, MAC layer, and IP layer
   information.  The link layer information includes wireless link layer
   parameters, such as wireless media (e.g., IEEE 802.11-OCB and LTE-
   V2X) and a transmission power level.  The MAC layer information
   includes the MAC address of an external network interface for the
   internetworking with another vehicle or RSU.  The IP layer
   information includes the IP address and prefix of an external network
   interface for the internetworking with another vehicle or RSU.

   Once the network parameter discovery and prefix exchange operations
   have been performed, packets can be transmitted between the vehicle's
   moving network and the RSU's fixed network.  A DNS services service should be
   supported to enable name resolution for hosts or servers residing
   either in the DNS name resolution of in-vehicle devices within a
   vehicle's moving internal network or as well as for the RSU's fixed network. DNS name resolution of
   those devices from a remote host in the Internet for on-line
   diagnosis (e.g., an automotive service center server).  It is assumed
   that the DNS names of in-vehicle devices and their service names are
   registered into a DNS server in a vehicle or an RSU, as shown in
   Figure 2.

   Figure 2 shows internetworking between the vehicle's moving network
   and the RSU's fixed network.  There exists an internal network
   (Moving Network1) inside Vehicle1.  Vehicle1 has the DNS Server
   (DNS1), the two hosts (Host1 and Host2), and the two routers (Router1
   and Router2).  There exists another internal network (Fixed Network1)
   inside RSU1.  RSU1 has the DNS Server (DNS2), one host (Host3), the
   two routers (Router3 and Router4), and the collection of servers
   (Server1 to ServerN) for various services in the road networks, such
   as the emergency notification and navigation.  Vehicle1's Router1
   (called mobile router) and RSU1's Router3 (called fixed router) use
   2001:DB8:1:1::/64 for an external link (e.g., DSRC) for I2V
   networking.  Thus, one host (Host1) in Vehicle1 can communicate with
   one server (Server1) in RSU1 for a vehicular service through
   Vehicle1's moving network, a wireless link between Vehicle1 and RSU1,
   and RSU1's fixed network.

4.3.  V2V-based Internetworking

   This section discusses the internetworking between the moving
   networks of two neighboring vehicles via V2V communication.

          2001:DB8:1:1::/64 |              |
   +------------------------------+  +------------------------------+
   |                        v     |  |     v                        |
   | +-------+ +------+ +-------+ |  | +-------+ +------+ +-------+ |
   | | Host1 | | DNS1 | |Router1| |  | |Router5| | DNS3 | | Host4 | |
   | +-------+ +------+ +-------+ |  | +-------+ +------+ +-------+ |
   |     ^        ^         ^     |  |     ^         ^        ^     |
   |     |        |         |     |  |     |         |        |     |
   |     v        v         v     |  |     v         v        v     |
   | ---------------------------- |  | ---------------------------- |
   | 2001:DB8:10:1::/64 ^         |  |         ^ 2001:DB8:30:1::/64 |
   |                    |         |  |         |                    |
   |                    v         |  |         v                    |
   | +-------+      +-------+     |  |     +-------+      +-------+ |
   | | Host2 |      |Router2|     |  |     |Router6|      | Host5 | |
   | +-------+      +-------+     |  |     +-------+      +-------+ |
   |     ^              ^         |  |         ^              ^     |
   |     |              |         |  |         |              |     |
   |     v              v         |  |         v              v     |
   | ---------------------------- |  | ---------------------------- |
   |      2001:DB8:10:2::/64      |  |       2001:DB8:30:2::/64     |
   +------------------------------+  +------------------------------+
      Vehicle1 (Moving Network1)        Vehicle2 (Moving Network2)

      <----> Wired Link   <....> Wireless Link   (*) Antenna

          Figure 3: Internetworking between Two Vehicle Networks

   Figure 3 shows internetworking between the moving networks of two
   neighboring vehicles.  There exists an internal network (Moving
   Network1) inside Vehicle1.  Vehicle1 has the DNS Server (DNS1), the
   two hosts (Host1 and Host2), and the two routers (Router1 and
   Router2).  There exists another internal network (Moving Network2)
   inside Vehicle2.  Vehicle2 has the DNS Server (DNS3), the two hosts
   (Host4 and Host5), and the two routers (Router5 and Router6).
   Vehicle1's Router1 (called mobile router) and Vehicle2's Router5
   (called mobile router) use 2001:DB8:1:1::/64 for an external link
   (e.g., DSRC) for V2V networking.  Thus, one host (Host1) in Vehicle1
   can communicate with one host (Host4) in Vehicle1 for a vehicular
   service through Vehicle1's moving network, a wireless link between
   Vehicle1 and Vehicle2, and Vehicle2's moving network.

         |                      |                      |
   +-----------+          +-----------+          +-----------+
   |           |          |           |          |           |
   | +-------+ |          | +-------+ |          | +-------+ |
   | |Router1| |          | |Router5| |          | |Router7| |
   | +-------+ |          | +-------+ |          | +-------+ |
   |           |          |           |          |           |
   | +-------+ |          | +-------+ |          | +-------+ |
   | | Host1 | |          | | Host4 | |          | | Host6 | |
   | +-------+ |          | +-------+ |          | +-------+ |
   |           |          |           |          |           |
   +-----------+          +-----------+          +-----------+
      Vehicle1               Vehicle2               Vehicle3

      <....> Wireless Link   (*) Antenna

      Figure 4: Multihop Internetworking between Two Vehicle Networks

   Figure 4 shows multihop internetworking between the moving networks
   of two vehicles in the same VANET.  For example, Host1 in Vehicle1
   can communicate with Host6 in Vehicle3 via Router 5 in Vehicle2 that
   is an intermediate vehicle being connected to Vehicle1 and Vehicle3
   in a linear topology as shown in the figure.

5.  Problem Statement

   This section makes a problem statement about key topics for IPWAVE
   WG, such as neighbor discovery, mobility management, and security &

5.1.  Neighbor Discovery

   IPv6 Neighbor Discovery (IPv6 ND) [RFC4861][RFC4862] is a core part
   of the IPv6 protocol suite.  IPv6 ND is designed for point-to-point
   links and transit links (e.g., Ethernet).  It assumes an efficient
   and reliable support of multicast from the link layer for various
   network operations such as MAC Address Resolution (AR) and Duplicate
   Address Detection (DAD).

   IPv6 ND needs to be extended to vehicular networking (e.g., V2V, V2I,
   and V2X) in terms of DAD and ND-related parameters (e.g., Router
   Lifetime).  The vehicles are moving fast within the communication
   coverage of a vehicular node (e.g., vehicle and RSU).  Before the
   vehicles can exchange application messages with each other, they need
   to be configured with a link-local IPv6 address or a global IPv6
   address, and recognize each other in the aspect of IPv6 ND.

   The legacy DAD assumes that a node with an IPv6 address can reach any
   other node with the scope of its address at the time it claims its
   address, and can hear any future claim for that address by another
   party within the scope of its address for the duration of the address
   ownership.  However, the partioning and merging of VANETs makes this
   assumption frequently invalid in vehicular networks.

   The vehicular networks need to support a vehicular-network-wide DAD
   by defining a scope that is compatible with the legacy DAD, and two
   vehicles can communicate with each other when there exists a
   communication path over VANET or a combination of VANETs and RSUs, as
   shown in Figure 1.  By using the vehicular-network-wide DAD, vehicles
   can assure that their IPv6 addresses are unique in the vehicular
   network whenever they are connected to the vehicular infrastructure
   or become disconnected from it in the form of VANET.  Even though a
   unique IPv6 address can be derived from a globally unique MAC
   address, this derivation yields a privacy issue of a vehicle as an
   IPv6 node.  The vehicular infrastructure having RSUs and an MA can
   participate in the vehicular-network-wide DAD for the sake of
   vehicles [RFC6775][RFC8505].

   ND time-related parameters such as router lifetime and Neighbor
   Advertisement (NA) interval should be adjusted for high-speed
   vehicles and vehicle density.  As vehicles move faster, the NA
   interval should decrease (e.g., from 1 sec to 0.5 sec) for the NA
   messages to reach the neighboring vehicles promptly.  Also, as
   vehicle density is higher, the NA interval should increase (e.g.,
   from 0.5 sec to 1 sec) for the NA messages to reduce collision
   probability with other NA messages.

   When ND is used in vehicular networks,

   According to a report from the communication delay (i.e.,
   latency) between two National Highway Traffic Safety
   Administration (NHTSA) [NHTSA-ACAS-Report], an extra 0.5 second of
   warning time can prevent about 60% of the collisions of vehicles
   moving closely in a roadway.  A warning message should be bounded to a certain
   threshold exchanged
   every 0.5 seconds.  Thus, if the ND messages (e.g., 500 ms) for collision-avoidance message exchange
   [CASD]. NS and NA) are
   used as warning messages, they should be exchanged every 0.5 second.

   For IP-based safety applications (e.g., context-aware navigation,
   adaptive cruise control, and platooning) in vehicular network, this
   bounded data delivery is critical.  The real implementations for such
   applications are not available yet.  Thus, ND needs to appropriately
   operate to support IP-based safety applications.

5.1.1.  Link Model

   IPv6 protocols work under certain assumptions for the link model that
   do not necessarily hold in a vehicular wireless link [VIP-WAVE]
   [RFC5889].  For instance, some IPv6 protocols assume symmetry in the
   connectivity among neighboring interfaces.  However, interference and
   different levels of transmission power may cause unidirectional links
   to appear in vehicular wireless links.  As a result, a new vehicular
   link model is required for a dynamically changing vehicular wireless

   There is a relationship between a link and prefix, besides the
   different scopes that are expected from the link-local and global
   types of IPv6 addresses.  In an IPv6 link, it is assumed that all
   interfaces which are configured with the same subnet prefix and with
   on-link bit set can communicate with each other on an IP link.

   A VANET can have multiple links between pairs of vehicles within
   wireless communication range, as shown in Figure 4.  When two
   vehicles belong to the same VANET, but they are out of wireless
   communication range, they cannot communicate directly with each
   other.  Assume that a global-scope IPv6 prefix is assigned to VANETs
   in vehicular networks.  Even though two vehicles in the same VANET
   configure their IPv6 addresses with the same IPv6 prefix, they may
   not communicate with each other not in a one hop in the same VANET
   because of the multihop network connectivity.  Thus, in this case,
   the concept of a on-link IPv6 prefix does not hold because two
   vehicles with the same on-link IPv6 prefix cannot communicate
   directly with each other.  Also, when two vehicles are located in two
   different VANETs with the same IPv6 prefix, they cannot communicate
   with each other.  When these two VANETs are converged into one VANET,
   the two vehicles can communicate with each other in a multihop
   fashion.  Therefore, a vehicular link model should consider the
   frequent partitioning and merging of VANETs due to vehicle mobility.

   An IPv6 prefix can be used in a multi-link subnet as an extended
   subnet.  IPv6 Stateless Address Autoconfiguration (SLAAC)

   The vehicular link model needs to be
   performed even in support the multiple links multihop routing in a
   connected VANET where all of the links are
   configured vehicles with the same subnet global-scope IPv6
   prefix [RFC4861][RFC4862].  Thus, a
   vehicular link model can consider a multi-hop V2V (or V2I) over a
   multi-link subnet are connected in a vehicular network having one hop or multiple VANETs and
   RSUs, as shown hops.  It also needs to
   support the multhop routing in Figure 1. multiple connected VANETs via an RSU
   that has the wireless connectivity with each VANET.  For example, in this figure, vehicles
   assume that Vehicle1, Vehicle2, and Vehicle3) in Subnet1 Vehicle 2, and Subnet2
   having RSU1 and RSU2, respectively, construct a multi-link subnet Vehicle3 are configured with VANETs and RSUs.
   their IPv6 addresses based on the same global-scope IPv6 prefix.
   Vehicle1 and Vehicle3 can also communicate with each other via either
   multi-hop V2V or multi-hop V2I2V.  When two vehicles (e.g., Vehicle1
   and Vehicle3 in Figure 1) are connected in a VANET, it will be more
   efficient for them to communicate with each other via VANET rather
   than RSUs.  On the other hand, when two vehicles (e.g., Vehicle1 and
   Vehicle3) are far away from the communication range in separate
   VANETs and under two different RSUs, they can communicate with each
   other through the relay of RSUs via V2I2V.

   Therefore, IPv6 ND needs to be extended for an efficient Vehicular
   Neighbor Discovey (VND) to support the concept of an IPv6 link
   corresponding to an IPv6 prefix even in  Thus, two separate VANETs
   can merge into one network via RSU(s).  Also, newly arriving vehicles
   can merge two separate VANETs into one VANET if they can play a multi-link subnet
   consisting role
   of multiple vehicles and RSUs [ID-Vehicular-ND]. a relay node for those VANETs.

5.1.2.  MAC Address Pseudonym

   For the protection of drivers' privacy, the pseudonym of a MAC
   address of a vehicle's network interface should be used, with the
   help of which the MAC address can be changed periodically.  The
   pseudonym of a MAC address affects an IPv6 address based on the MAC
   address, and a transport-layer (e.g., TCP) session with an IPv6
   address pair.  However, the pseudonym handling is not implemented and
   tested yet for applications on IP-based vehicular networking.

   In the ETSI standards, for the sake of security and privacy, an ITS
   station (e.g., vehicle) can use pseudonyms for its network interface
   identities (e.g., MAC address) and the corresponding IPv6 addresses
   [Identity-Management].  Whenever the network interface identifier
   changes, the IPv6 address based on the network interface identifier
   should be updated, and the uniqueness of the address should be
   performed through the DAD procedure.  For vehicular networks with
   high-mobility, this DAD should be performed efficiently with minimum

   For the continuity of an end-to-end (E2E) transport-layer (e.g., TCP,
   UDP, and SCTP) session, with a mobility management scheme (e.g.,
   MIPv6 and PMIPv6), the new IP address for the transport-layer session
   can be notified to an appropriate end point, and the packets of the
   session should be forwarded to their destinations with the changed
   network interface identifier and IPv6 address.  This mobiliy
   management overhead for pseudonyms should be minimized for efficient
   operations in vehicular networks having lots of vehicles.

5.1.3.  Prefix Dissemination/Exchange

   A vehicle and an RSU can have their internal network, as shown in
   Figure 2 and Figure 3.  In this case, nodes in within the internal
   networks of two vehicular nodes (e.g., vehicle and RSU) want to
   communicate with each other.  For this communication on the wireless
   link, the network prefix dissemination or exchange is required.  It
   is assumed that a vehicular node has an external network interface
   and its internal network, as shown in Figure 2 and Figure 3.  The
   vehicular ND (VND) [ID-Vehicular-ND] can support the communication
   between the internal-network nodes (e.g., an in-vehicle device in a
   vehicle and a server in an RSU) of vehicular nodes with a vehicular
   prefix information option.  Thus, this ND extension for routing
   functionality can reduce control traffic for routing in vehicular
   networks without a vehicular ad hoc routing protocol (e.g., AODV
   [RFC3561] and OLSRv2 [RFC7181]).

5.1.4.  Routing

   For multihop V2V communications in a VANET (or a multi-link subnet),
   a vehicular ad hoc routing protocol (e.g., AODV and OLSRv2) may be
   required to support both unicast and multicast in the links of the
   subnet with the same IPv6 prefix.  However, it will be costly to run
   both vehicular ND and a vehicular ad hoc routing protocol in terms of
   control traffic overhead. overhead [ID-Multicast-Problems].  As a feasible
   approach, Vehicular ND can be extended to accommodate routing
   functionality with a prefix discovery option.  In this case, there is
   no need to run a separate vehicular ad hoc routing protocol in
   VANETs.  The ND extension can allow vehicles to exchange their
   prefixes in a multihop fashion [ID-Vehicular-ND].  With the exchanged
   prefixes, they can compute their routing table (or IPv6 ND's neighbor
   cache) for the multi-link subnet with a distance-vector algorithm

   Also, an efficient, rapid DAD needs to be supported in a vehicular
   network having multiple VANETs (or a multi-link subnet) to prevent or
   reduce IPv6 address conflicts in such a subnet.  A feasible approach
   is to use a multi-hop DAD optimization for the efficient vehicular-
   network-wide DAD [RFC6775][RFC8505].

5.2.  Mobility Management

   The seamless connectivity and timely data exchange between two end
   points requires an efficient mobility management including location
   management and handover.  Most of vehicles are equipped with a GPS
   receiver as part of a dedicated navigation system or a corresponding
   smartphone App.  The GPS receiver may not provide vehicles with
   accurate location information in adverse, local environments such as
   building area and tunnel.  The location precision can be improved by
   the assistance from the RSUs or a cellular system with a GPS receiver
   for location information.

   With a GPS navigator, an efficient mobility management will be
   possible by vehicles periodically reporting their current position
   and trajectory (i.e., navigation path) to the vehicular
   infrastructure (having RSUs and an MA in TCC) [ID-Vehicular-MM].
   This vehicular infrastructure can predict the future positions of the
   vehicles with their mobility information (i.e., the current position,
   speed, direction, and trajectory) for the efficient mobility
   management (e.g., proactive handover).  For a better proactive
   handover, link-layer parameters, such as the signal strength of a
   link-layer frame (e.g., Received Channel Power Indicator (RCPI)
   [VIP-WAVE]), can be used to determine the moment of a handover
   between RSUs along with mobility information.

   With the prediction of the vehicle mobility, the vehicular
   infrastructure needs to support RSUs to perform efficient DAD, data
   packet routing, horizontal handover (i.e., handover in wireless links
   using a homogeneous radio technology), and vertical handover (i.e.,
   handover in wireless links using heterogeneous radio technologies) in
   a proactive manner [ID-Vehicular-MM].  For example, when a vehicle is
   moving into the wireless link under another RSU belonging to a
   different subnet, the RSU can proactively perform the DAD for the
   sake of the vehicle, reducing IPv6 control traffic overhead in the
   wireless link.  To prevent a hacker from impersonating RSUs as bogus
   RSUs, RSUs and MA in the vehicular infrastructure need to have secure
   channels via IPsec.

   Therefore, with a proactive handover and a multihop DAD in vehicular
   networks, RSUs needs to efficiently forward data packets from the
   wired network (or the wireless network) to a moving destination
   vehicle along its trajectory.  As a result, a moving vehicle can
   communicate with its corresponding vehicle in the vehicular network
   or a host/server in the Internet along its trajectory.

5.3.  Security and Privacy

   Strong security measures shall protect vehicles roaming in road
   networks from the attacks of malicious nodes, which are controlled by
   hackers.  For safety applications, the cooperation among vehicles is
   assumed.  Malicious nodes may disseminate wrong driving information
   (e.g., location, speed, and direction) to make driving be unsafe.
   Sybil attack, which tries to illude a vehicle with multiple false
   identities, disturbs a vehicle in taking a safe maneuver.  This sybil
   attack should be prevented through the cooperation between good
   vehicles and RSUs.  Note that good vehicles are ones with valid
   certificates that are determined by the authentication process with
   an authentication server in the vehicular network.  Applications on
   IP-based vehicular networking, which are resilient to such a sybil
   attack, are not developed and tested yet.

   Security and privacy are paramount in the V2I, V2V, and V2X
   networking in vehicular networks.  Only authorized vehicles should be
   allowed to use vehicular networking.  Also, in-vehicle devices and
   mobile devices in a vehicle need to communicate with other in-vehicle
   devices and mobile devices in another vehicle, and other servers in
   an RSU in a secure way.

   A Vehicle Identification Number (VIN) and a user certificate along
   with in-vehicle device's identifier generation can be used to
   efficiently authenticate a vehicle or a user through a road
   infrastructure node (e.g., RSU) connected to an authentication server
   in TCC.  Also, Transport Layer Security (TLS) certificates can be
   used for secure E2E vehicle communications.

   For secure V2I communication, a secure channel between a mobile
   router in a vehicle and a fixed router in an RSU should be
   established, as shown in Figure 2.  Also, for secure V2V
   communication, a secure channel between a mobile router in a vehicle
   and a mobile router in another vehicle should be established, as
   shown in Figure 3.

   To prevent an adversary from tracking a vehicle with its MAC address
   or IPv6 address, MAC address pseudonym should be provided to the
   vehicle; that is, each vehicle should periodically update its MAC
   address and the corresponding IPv6 address as suggested in
   [RFC4086][RFC4941].  Such an update of the MAC and IPv6 addresses
   should not interrupt the E2E communications between two vehicular
   nodes (e.g., vehicle and RSU) in terms of transport layer for a long-
   living higher-layer session.  However, if this pseudonym is performed
   without strong E2E confidentiality, there will be no privacy benefit
   from changing MAC and IP addresses, because an adversary can see the
   change of the MAC and IP addresses and track the vehicle with those

   For the IPv6 ND, the vehicular-network-wide DAD is required for the
   uniqueness of the IPv6 address of a vehicle's wireless interface.
   This DAD can be used as a flooding attack that makes the DAD-related
   ND packets are disseminated over the VANET and vehicular network
   including the RSU and the MA.  The vehicles and RSUs need to filter
   out suspicious ND traffic in advance.

   For the mobility management, a malicious vehicle constructs multiple
   virtual bogus vehicles, and register them with the RSU and the MA.
   This registration makes the RSU and MA waste their resources.  The
   RSU and MA need to determine whether a vehicle is genuine or bogus in
   the mobility management.

6.  Security Considerations

   This document discussed security and privacy for IP-based vehicular

   The security and privacy for key components in IP-based vehicular
   networking, such as neighbor discovery and mobility management, need
   to be analyzed in depth.

7.  Informative References

              Choi, J., Va, V., Gonzalez-Prelcic, N., Daniels, R., R.
              Bhat, C., and R. W. Heath, "Millimeter-Wave Vehicular
              Communication to Support Massive Automotive Sensing",
              IEEE Communications Magazine, December 2016.

              California Partners for Advanced Transportation Technology
              (PATH), "Cooperative Adaptive Cruise Control", [Online]

   [CASD]     Shen, Y., Jeong, J., Oh, T., and S. Son, "CASD: A
              Framework of Context-Awareness Safety Driving in Vehicular
              Networks", International Workshop on Device Centric Cloud
              (DC2), March 2016.

   [DSRC]     ASTM International, "Standard Specification for
              Telecommunications and Information Exchange Between
              Roadside and Vehicle Systems - 5 GHz Band Dedicated Short
              Range Communications (DSRC) Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications",
              ASTM E2213-03(2010), October 2010.

              ETSI Technical Committee Intelligent Transport Systems,
              "Intelligent Transport Systems (ITS); Vehicular
              Communications; GeoNetworking; Part 6: Internet
              Integration; Sub-part 1: Transmission of IPv6 Packets over
              GeoNetworking Protocols", ETSI EN 302 636-6-1, October

              ETSI Technical Committee Intelligent Transport Systems,
              "Intelligent Transport Systems (ITS); Vehicular
              Communications; GeoNetworking; Part 4: Geographical
              addressing and forwarding for point-to-point and point-to-
              multipoint communications; Sub-part 1: Media-Independent
              Functionality", ETSI EN 302 636-4-1, May 2014.

              European Union, "Commission Decision of 5 August 2008 on
              the Harmonised Use of Radio Spectrum in the 5875 - 5905
              MHz Frequency Band for Safety-related Applications of
              Intelligent Transport Systems (ITS)", EU 2008/671/EC,
              August 2008.

              U.S. National Telecommunications and Information
              Administration (NTIA), "First Responder Network Authority
              (FirstNet)", [Online]
              Available: https://www.firstnet.gov/, 2012.

              First Responder Network Authority, "FY 2017: ANNUAL REPORT
              TO CONGRESS, Advancing Public Safety Broadband
              Communications", FirstNet FY 2017, December 2017.

              van de Hoef, S., H. Johansson, K., and D. V. Dimarogonas,
              "Fuel-Efficient En Route Formation of Truck Platoons",
              IEEE Transactions on Intelligent Transportation Systems,
              January 2018.

              Perkins, C., McBride, M., Stanley, D., Kumari, W., and JC.
              Zuniga, "Multicast Considerations over IEEE 802 Wireless
              Media", draft-ietf-mboned-ieee802-mcast-problems-06 (work
              in progress), July 2019.

              Jeong, J., Ed., Shen, Y., and Z. Xiang, "Vehicular
              Mobility Management for IP-Based Vehicular Networks",
              draft-jeong-ipwave-vehicular-mobility-management-01 (work
              in progress), March July 2019.

              Jeong, J., Ed., Shen, Y., and Z. Xiang, "IPv6 "Vehicular
              Neighbor Discovery for IP-Based Vehicular Networks", draft-jeong-
              draft-jeong-ipwave-vehicular-neighbor-discovery-07 (work
              in progress),
              March July 2019.

              Wetterwald, M., Hrizi, F., and P. Cataldi, "Cross-layer
              Identities Management in ITS Stations", The 10th
              International Conference on ITS Telecommunications,
              November 2010.

              "Part 11: Wireless LAN Medium Access Control (MAC) and
              Physical Layer (PHY) Specifications", IEEE Std
              802.11-2016, December 2016.

              "Part 11: Wireless LAN Medium Access Control (MAC) and
              Physical Layer (PHY) Specifications - Amendment 6:
              Wireless Access in Vehicular Environments", IEEE Std
              802.11p-2010, June 2010.

              H. Cormen, T., E. Leiserson, C., L. Rivest, R., and C.
              Stein, "Introduction to Algorithms, 3rd ed.", The
              MIT Press, July 2009.

              Benamar, N., Haerri, J., Lee, J., and T. Ernst,
              "Transmission of "Basic
              Support for IPv6 Packets over IEEE Std 802.11 Networks
              operating in mode Operating
              Outside the Context of a Basic Service Set (IPv6-over-80211-OCB)", draft-ietf-ipwave-ipv6-over-
              80211ocb-45 (IPv6-over-
              80211-OCB)", draft-ietf-ipwave-ipv6-over-80211ocb-49 (work
              in progress), April July 2019.

              ISO/TC 204, "Intelligent Transport Systems -
              Communications Access for Land Mobiles (CALM) - IPv6
              Networking", ISO 21210:2012, June 2012.

              National Highway Traffic Safety Administration (NHTSA),
              "Final Report of Automotive Collision Avoidance Systems
              (ACAS) Program", DOT HS 809 080, August 2000.

   [RFC3561]  Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
              Demand Distance Vector (AODV) Routing", RFC 3561, July

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", RFC 4086, June

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007.

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, August 2008.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, May 2010.

   [RFC5889]  Baccelli, E. and M. Townsley, "IP Addressing Model in Ad
              Hoc Networks", RFC 5889, September 2010.

   [RFC5944]  Perkins, C., Ed., "IP Mobility Support in IPv4, Revised",
              RFC 5944, November 2010.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, July 2011.

   [RFC6775]  Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
              "Neighbor Discovery Optimization for IPv6 over Low-Power
              Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
              November 2012.

   [RFC7181]  Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
              "The Optimized Link State Routing Protocol Version 2",
              RFC 7181, April 2014.

   [RFC7333]  Chan, H., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
              "Requirements for Distributed Mobility Management",
              RFC 7333, August 2014.

   [RFC7429]  Liu, D., Zuniga, JC., Seite, P., Chan, H., and CJ.
              Bernardos, "Distributed Mobility Management: Current
              Practices and Gap Analysis", RFC 7429, January 2015.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 8200, July 2017.

   [RFC8505]  Thubert, P., Nordmark, E., Chakrabarti, S., and C.
              Perkins, "Registration Extensions for IPv6 over Low-Power
              Wireless Personal Area Network (6LoWPAN) Neighbor
              Discovery", RFC 8505, November 2018.

   [SAINT]    Jeong, J., Jeong, H., Lee, E., Oh, T., and D. Du, "SAINT:
              Self-Adaptive Interactive Navigation Tool for Cloud-Based
              Vehicular Traffic Optimization", IEEE Transactions on
              Vehicular Technology, Vol. 65, No. 6, June 2016.

              Shen, Y., Lee, J., Jeong, H., Jeong, J., Lee, E., and D.
              Du, "SAINT+: Self-Adaptive Interactive Navigation Tool+
              for Emergency Service Delivery Optimization",
              IEEE Transactions on Intelligent Transportation Systems,
              June 2017.

   [SANA]     Hwang, T. and J. Jeong, "SANA: Safety-Aware Navigation
              Application for Pedestrian Protection in Vehicular
              Networks", Springer Lecture Notes in Computer Science
              (LNCS), Vol. 9502, December 2015.

   [SDN-DMM]  Nguyen, T., Bonnet, C., and J. Harri, "SDN-based
              Distributed Mobility Management for 5G Networks",
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Appendix A.  Changes from draft-ietf-ipwave-vehicular-networking-08 draft-ietf-ipwave-vehicular-networking-09

   The following changes are made from draft-ietf-ipwave-vehicular-

   o  This version is revised based on the comments from Charlie Perkins
      and Sri Gundavelli.

   o  This version focuses  For the question on the problem statement about IP-based preference on a multi-link subnet model,
      the revision does not suggest the multi-link subnet model as a
      possible solution, focusing on the characteristics and
      requirements for a vehicular networking, link model.

   o  The motivation about DNS in a vehicle network is addressed

   o  The timing importance of ND is addressed with a reference to

   o  The Security Considerations are expanded with cross references to
      other parts of the document such as IPv6 neighbor discovery, ND and mobility

   o  2001:DB8::/32 is a reserved prefix for use in documentation
      [RFC3849].  Any routable IPv6 address needs to be routable in a
      VANET and security & privacy. a vehicular network including RSUs.

   o  With an example in Figure 1, it is suggested that two separate
      VANETs can merge into one network.

   o  A suggestion is made about how to distinguish good nodes from bad
      nodes with an authentication process.

Appendix B.  Acknowledgments

   This work was supported by Basic Science Research Program through the
   National Research Foundation of Korea (NRF) funded by the Ministry of
   Education (2017R1D1A1B03035885).

   This work was supported in part by the MSIT (Ministry of Science and
   ICT), Korea, under the ITRC (Information Technology Research Center)
   support program (IITP-2019-2017-0-01633) supervised by the IITP
   (Institute for Information & communications Technology Promotion).

   This work was supported in part by the French research project
   DataTweet (ANR-13-INFR-0008) and in part by the HIGHTS project funded
   by the European Commission I (636537-H2020).

Appendix C.  Contributors

   This document is a group work of IPWAVE working group, greatly
   benefiting from inputs and texts by Rex Buddenberg (Naval
   Postgraduate School), Thierry Ernst (YoGoKo), Bokor Laszlo (Budapest
   University of Technology and Economics), Jose Santa Lozanoi
   (Universidad of Murcia), Richard Roy (MIT), Francois Simon (Pilot),
   Sri Gundavelli (Cisco), Erik Nordmark, Dirk von Hugo (Deutsche
   Telekom), and Pascal Thubert (Cisco).  The authors sincerely
   appreciate their contributions.

   The following are co-authors of this document:

   Nabil Benamar
   Department of Computer Sciences
   High School of Technology of Meknes
   Moulay Ismail University

   Phone: +212 6 70 83 22 36
   EMail: benamar73@gmail.com

   Sandra Cespedes
   NIC Chile Research Labs
   Universidad de Chile
   Av.  Blanco Encalada 1975

   Phone: +56 2 29784093
   EMail: scespede@niclabs.cl

   Jerome Haerri
   Communication Systems Department

   Phone: +33 4 93 00 81 34
   EMail: jerome.haerri@eurecom.fr

   Dapeng Liu
   Beijing, Beijing 100022

   Phone: +86 13911788933
   EMail: max.ldp@alibaba-inc.com

   Tae (Tom) Oh
   Department of Information Sciences and Technologies
   Rochester Institute of Technology
   One Lomb Memorial Drive
   Rochester, NY 14623-5603

   Phone: +1 585 475 7642
   EMail: Tom.Oh@rit.edu

   Charles E.  Perkins
   Futurewei Inc.
   2330 Central Expressway
   Santa Clara, CA 95050

   Phone: +1 408 330 4586
   EMail: charliep@computer.org

   Alexandre Petrescu
   CEA Saclay
   Gif-sur-Yvette, Ile-de-France 91190

   Phone: +33169089223
   EMail: Alexandre.Petrescu@cea.fr

   Yiwen Chris Shen
   Department of Computer Science & Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do 16419
   Republic of Korea

   Phone: +82 31 299 4106
   Fax: +82 31 290 7996
   EMail: chrisshen@skku.edu
   URI: http://iotlab.skku.edu/people-chris-shen.php
   Michelle Wetterwald
   21, Route de Luxembourg
   Wasserbillig, Luxembourg L-6633

   EMail: Michelle.Wetterwald@gmail.com

Author's Address

   Jaehoon Paul Jeong (editor)
   Department of Software
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do  16419
   Republic of Korea

   Phone: +82 31 299 4957
   Fax:   +82 31 290 7996
   EMail: pauljeong@skku.edu
   URI:   http://iotlab.skku.edu/people-jaehoon-jeong.php