IPWAVE Working Group                                       J. Jeong, Ed.
Internet-Draft                                   Sungkyunkwan University
Intended status: Informational                           October 3, 2019                           January 6, 2020
Expires: April 5, July 9, 2020

IP

    IPv6 Wireless Access in Vehicular Environments (IPWAVE): Problem
                        Statement and Use Cases
               draft-ietf-ipwave-vehicular-networking-12
               draft-ietf-ipwave-vehicular-networking-13

Abstract

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

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5   6
     3.1.  V2V . . . . . . . . . . . . . . . . . . . . . . . . . . .   5   7
     3.2.  V2I . . . . . . . . . . . . . . . . . . . . . . . . . . .   6   8
     3.3.  V2X . . . . . . . . . . . . . . . . . . . . . . . . . . .   7   9
   4.  Vehicular Networks  . . . . . . . . . . . . . . . . . . . . .   8   9
     4.1.  Vehicular Network Architecture  . . . . . . . . . . . . .   9  10
     4.2.  V2I-based Internetworking . . . . . . . . . . . . . . . .  11  13
     4.3.  V2V-based Internetworking . . . . . . . . . . . . . . . .  13  15
   5.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .  14  16
     5.1.  Neighbor Discovery  . . . . . . . . . . . . . . . . . . .  15  16
       5.1.1.  Link Model  . . . . . . . . . . . . . . . . . . . . .  16  18
       5.1.2.  MAC Address Pseudonym . . . . . . . . . . . . . . . .  17  19
       5.1.3.  Routing . . . . . . . . . . . . . . . . . . . . . . .  18  20
     5.2.  Mobility Management . . . . . . . . . . . . . . . . . . .  19  20
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  20  21
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  21  23
   Appendix A.  Changes from draft-ietf-ipwave-vehicular-
                networking-11
                networking-12  . . . . . . . . . . . . . . . . . . .  27  29
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  28  29
   Appendix C.  Contributors . . . . . . . . . . . . . . . . . . . .  28  29
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  30  32

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.  The European Union (EU) allocated radio spectrum for
   safety-related and non-safety-related applications of ITS with the
   frequency band of 5.875 - 5.905 GHz, as part of the 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 DSRC
   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.  IEEE 802.11p was first a separate amendment, but was
   later rolled into the base 802.11 standard (IEEE 802.11-2012) as IEEE
   802.11 Outside the Context of a Basic Service Set (OCB) in 2012
   [IEEE-802.11-OCB].

   Along with these WAVE standards, IPv6 [RFC8200] and Mobile IP IPv6
   protocols (e.g., MIPv4 [RFC5944], MIPv6 Mobile IPv6 (MIPv6) [RFC6275], and Proxy MIPv6
   (PMIPv6) [RFC5213][RFC5844]) [RFC5213]) can be applied to vehicular networks.  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 describes use cases and a problem statement about IP-
   based
   IPv6-based vehicular networking for ITS, which is named IP IPv6 Wireless
   Access in Vehicular Environments (IPWAVE).  First, it introduces the
   use cases for using V2V, V2I, and V2X networking in ITS.  Next, it
   makes a problem statement about key aspects in IPWAVE, namely, IPv6
   Neighbor Discovery, Discovery (ND), Mobility Management, Management (MM), and Security & Privacy.
   Privacy (SP).  For each key aspect of the problem statement, this
   document specifies requirements in IP-based for IPv6-based vehicular networking, and proposes the
   direction of solutions fulfilling those requirements. networking.
   This document is intended to motivate development of key protocols
   for IPWAVE.

2.  Terminology

   This document uses the terminology described in [RFC8691].  In
   addition, the following definitions: terms are defined below:

   o  Class-Based Safety Plan: A vehicle can make safety plan by
      classifying the surrounding vehicles into different groups for
      safety purposes according to the geometrical relationship among
      them.  The vehicle groups can be classified as Line-of-Sight
      Unsafe, Non-Line-of-Sight Unsafe, and Safe groups [CASD].

   o  Context-Awareness: A vehicle can be aware of spatial-temporal
      mobility information (e.g., position, speed, direction, and
      acceleration/deceleration) of surrounding vehicles for both safety
      and non-safety uses through sensing or communication [CASD].

   o  LiDAR: "Light Detection  Edge Computing (EC): It is the local computing near an access
      network (i.e., edge network) for the sake of vehicles and Ranging".
      pedestrians.

   o  Edge Computing Device (ECD): It is a scanning computing device to
      measure a distance to an object by emitting pulsed laser light and
      measuring (or server)
      for edge computing for the reflected pulsed light.

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

   o  On-Board Unit (OBU): A node  Edge Network (EN): In is an access network that has physical communication
      devices (e.g., IEEE 802.11-OCB and Cellular V2X (C-V2X)
      [TS-23.285-3GPP]) an IP-RSU for
      wireless communications communication with other OBUs vehicles having an IP-OBU and
      wired communication with other network devices (e.g., routers, IP-
      RSUs, ECDs, servers, and MA).  It may be connected to in-vehicle devices or networks.  An
      OBU is mounted on have a vehicle.

   o  OCB: "Outside radio receiver of
      Global Positioning System (GPS) for its position recognition and
      the Context localization service for the sake of vehicles.

   o  IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a Basic Service Set".
      computer situated in a vehicle such as a car, bicycle, or similar.
      It has at least one IP interface that runs in mode OCB of 802.11
      and has an "OBU" transceiver.  Also, it may have an IP interface
      that runs in Cellular V2X (C-V2X) [TS-23.285-3GPP].  See the
      definition of the term "OBU" in [RFC8691].

   o  IP-RSU: "IP Roadside Unit": An IP-RSU is
      differentiated from situated along the Basic Service Set (BSS) mode road.
      It has at least two distinct IP-enabled interfaces.  The wireless
      PHY/MAC layer of at least one of its IP-enabled interfaces is
      configured to operate in IEEE 802.11-OCB mode.  An IP-RSU communicates
      with the IP-OBU over an 802.11 standard.  A node wireless link operating in OCB mode can directly transmit packets
      mode.  Also, it may have an IP interface that runs in C-V2X along
      with an "RSU" transceiver.  An IP-RSU is similar to other nodes an Access
      Network Router (ANR), defined in [RFC3753], and a Wireless
      Termination Point (WTP), defined in [RFC5415].  See the definition
      of the term "RSU" in [RFC8691].

   o  LiDAR: "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 IPv6 addresses and
      mobility information of vehicles in a road network to support
      their IPv6 address autoconfiguration and mobility management with
      a binding table.  An MA has End-to-End (E2E) connections with IP-
      RSUs under its wireless range without control for the authentication or
      association process defined address autoconfiguration and
      mobility management of the vehicles.  This MA can play a role of a
      Local Mobility Anchor (LMA) in BSS PMIPv6 [RFC5213] for vehicles
      moving in the road network .

   o  OCB: "Outside the Context of a Basic Service Set - BSS".  It is a
      mode of operation in which a Station (STA) is not a member of a
      BSS and does not utilize IEEE Std 802.11 authentication,
      association, or data confidentiality [IEEE-802.11-OCB].

   o  802.11-OCB: It refers to the mode specified in IEEE Std
      802.11-2016 [IEEE-802.11-OCB] when the MIB attribute
      dot11OCBActivited is 'true'.

   o  Platooning: Moving vehicles can be grouped together to reduce air-
      resistance for energy efficiency and reduce the number of drivers
      such that only the leading vehicle has a driver and the other
      vehicles are autonomous vehicles without a driver and closely
      following the leading vehicle [Truck-Platooning].

   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
      through a router or switch for packet forwarding.  An RSU can
      accommodate multiple routers (or switches) and servers (e.g., DNS
      server and edge computing server) in its internal network as an
      edge computing system.  An RSU is typically deployed on the road
      infrastructure, either at an intersection or in a road segment,
      but may also be located in a car parking area.

   o  Traffic Control Center (TCC): A node that maintains road
      infrastructure information (e.g., RSUs, IP-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 Vehicle in this document is a node that has an OBU IP-OBU
      for wireless communication with other vehicles and RSUs. IP-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.  Two vehicles
      in a VANET can communicate with each other using 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 forwarding
      elements (e.g., switch and router).

   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  V2D: "Vehicle to Device".  It is the wireless communication
      between a vehicle and a device (e.g., IoT device).

   o  V2P: "Vehicle to Pedestrian".  It is the wireless communication
      between a vehicle and a pedestrian's mobile device (e.g.,
      smartphone).

   o  V2I2P: "Vehicle to Infrastructure to Pedestrian".  It is the
      wireless communication between a vehicle and a pedestrian's mobile
      device (e.g., smartphone) via an infrastructure node (e.g., IP-
      RSU).

   o  V2I2V: "Vehicle to Infrastructure to Vehicle".  It is the wireless
      communication between a vehicle and another vehicle via an
      infrastructure node (e.g., IP-RSU).

   o  VIP: "Vehicular Internet Protocol".  It is an IPv6 extension for
      vehicular networks including V2V, V2I, and V2X.

   o  VMM: "Vehicular Mobility Management".  It is an IPv6-based
      mobility management for vehicular networks.

   o  V2I2V: "Vehicle to Infrastructure to Vehicle".  VND: "Vehicular Neighbor Discovery".  It is an IPv6 ND extension
      for vehicular networks.

   o  VSP: "Vehicular Security and Privacy".  It is an IPv6-based
      security and privacy for vehicular networks.

   o  WAVE: "Wireless Access in Vehicular Environments" [WAVE-1609.0].

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).

   Since IP is widely used among various computing devices in the
   Internet, it is expected that the use cases in this section need to
   work on top of IPv6 as the network layer protocol.  Thus, the IPv6
   for these use cases should be extended for vehicular IPv6 such that
   the IPv6 can support the functions of the network layer protocol such
   as Vehicular Neighbor Discovery (VND), Vehicular Mobility Management
   (VMM), and Vehicular Security and Privacy (VSP) in vehicular
   networks.  Refer to Section 5 for the problem statement of the
   requirements of the vehicular IPv6.

3.1.  V2V

   The use cases of V2V networking discussed in this section include

   o  Context-aware navigation for driving safety and collision
      avoidance;

   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
   vehicles.

   Context-Aware Safety Driving (CASD) navigator [CASD] can help drivers
   to drive safely by alerting the drivers about dangerous obstacles and
   situations.  That is, CASD navigator displays obstacles 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,
   namely, the Line-of-Sight unsafe, Non-Line-of-Sight unsafe, and safe
   situations.  This action plan can be put into action among multiple
   vehicles using 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 follow each other very closely.  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).  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.  A lot of
   data can be generated by those sensors, and these data typically need
   to 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 other vehicles and environment.

   To support the applications of these V2V use cases, the functions of
   IPv6 such as VND and VSP are prerequisite for the IPv6-based packet
   exchange and the secure, safe communication between two vehicles.

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, for example, the Self-Adaptive Interactive
   Navigation Tool (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 fast moving
   paths to emergency vehicles (e.g., ambulance and fire engine) to let
   them reach an accident spot while redirecting other vehicles near the
   accident spot into efficient detour paths.

   A TCC can recommend an energy-efficient speed to a vehicle that
   depends on its traffic environment.  [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 IP-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, e.g., 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.

   To support the applications of these V2I use cases, the functions of
   IPv6 such as VND, VMM, and VSP are prerequisite for the IPv6-based
   packet exchange, the transport-layer session continuity, and the
   secure, safe communication between a vehicle and a server in the
   vehicular cloud.

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 (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. IP-RSU.  Vehicles and pedestrians can also communicate
   with each other via an RSU that delivers scheduling IP-RSU.  An edge computing device behind the
   IP-RSU can collect the mobility information for from vehicles and
   pedestrians, compute wireless communication in order to scheduling for the sake
   of them.  This scheduling can save the smartphones' battery
   through of each pedestrian's
   smartphone by allowing it to work in sleeping mode. mode before the
   communication with vehicles, considering their mobility.

   For Vehicle-to-Pedestrian (V2P), a vehicle can directly communicate
   with a pedestrian's smartphone by V2X without RSU IP-RSU relaying.  Light-
   weight
   Light-weight mobile nodes such as bicycles may also communicate
   directly with a vehicle for collision avoidance using V2V.

   To support the applications of these V2X use cases, the functions of
   IPv6 such as VND, VMM, and VSP are prerequisite for the IPv6-based
   packet exchange, the transport-layer session continuity, and the
   secure, safe communication between a vehicle and a pedestrian either
   directly or indirectly via an IP-RSU.

4.  Vehicular Networks

   This section describes a an exemplary vehicular network architecture
   supporting V2V, V2I, and V2X communications in vehicular networks.  Also, it
   It describes an internal network within a vehicle or RSU, an edge network
   (called EN).  It explains not only the internetworking between the
   internal networks of a vehicle and an EN via wireless links, but also
   the internetworking between the internal networks of two vehicles via DSRC
   wireless links.

                     Traffic Control Center in Vehicular Cloud
                    *******************************************
+-------------+    *                                           *
|Corresponding|   *             +-----------------+             *
                 *
|    Node     |<->*             | Mobility Anchor |             *
+-------------+   *             +-----------------+             *
                  *                      ^                      *
                  *                      | Ethernet                      *
                   *                     v                     *
                    *******************************************
                    ^                   ^                     ^
                    | Ethernet                   | Ethernet                     | Ethernet
                    |                   |                     |
                    v                   v                     v
               +--------+ Ethernet +--------+  Ethernet  +--------+
               |  RSU1  |<-------->|  RSU2  |<---------->|  RSU3  |
               +--------+          +--------+            +--------+
              +---------+           +---------+           +---------+
              | IP-RSU1 |<--------->| IP-RSU2 |<--------->| IP-RSU3 |
              +---------+           +---------+           +---------+
                  ^                     ^                    ^
                  :                     :                    :
           +-----------------+ +-----------------+   +-----------------+
           |      : V2I      | |        : V2I    |   |       : V2I     |
           |      v          | |        v        |   |       v         |
+--------+ |   +--------+    | |   +--------+    |   |   +--------+    |
|Vehicle1|===> |Vehicle2|===>| |   |Vehicle3|===>|   |   |Vehicle4|===>|
+--------+<...>+--------+<........>+--------+    |   |   +--------+    |
           V2V     ^         V2V        ^        |   |        ^        |
           |       : V2V     | |        : V2V    |   |        : V2V    |
           |       v         | |        v        |   |        v        |
           |  +--------+     | |   +--------+    |   |    +--------+   |
           |  |Vehicle5|===> | |   |Vehicle6|===>|   |    |Vehicle7|==>|
           |  +--------+     | |   +--------+    |   |    +--------+   |
           +-----------------+ +-----------------+   +-----------------+
                 Subnet1              Subnet2              Subnet3
                (Prefix1)            (Prefix2)            (Prefix3)

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

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

4.1.  Vehicular Network Architecture

   Figure 1 shows an exemplary vehicular network architecture for V2I
   and V2V networking in a road network.  The vehicular network architecture
   contains vehicles, RSUs, IP-RSUs, Vehicular Cloud, Traffic Control Center,
   and Mobility Anchor as components.  However, some components in the
   vehicular network architecture may not be needed for vehicular networking,
   networks, such as Vehicular Cloud, Traffic Control Center, and
   Mobility Anchor.

   As shown in this figure, RSUs IP-RSUs as routers and vehicles with OBU IP-OBU
   have wireless media interfaces for VANET.  Furthermore, 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 IP-
   RSUs.

   For IPv6 packets transported over IEEE 802.11-OCB,
   [IPv6-over-802.11-OCB] [RFC8691]
   specifies several details, including Maximum Transmission Unit (MTU),
   frame format, link-local address, address mapping for unicast and
   multicast, stateless autoconfiguration, and subnet structure.  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 IPv6-based vehicular networks.

   In Figure 1, three RSUs (RSU1, RSU2, IP-RSUs (IP-RSU1, IP-RSU2, and RSU3) IP-RSU3) are
   deployed in the road network and are connected to a Vehicular Cloud with each other
   through the
   Internet. wired networks (e.g., Ethernet), which are part of a
   Vehicular Cloud.  A Traffic Control Center (TCC) is connected to the
   Vehicular Cloud for the management of RSUs IP-RSUs and vehicles in the
   road network.  A Mobility Anchor (MA) can may be located in the TCC as its key
   component a
   mobility management controller, which is a controller for the
   mobility management of vehicles.  Vehicle2, Vehicle3, and Vehicle4
   are wirelessly connected to RSU1, RSU2, IP-RSU1, IP-RSU2, and
   RSU3, IP-RSU3,
   respectively.  The three wireless networks of RSU1, RSU2, IP-RSU1, IP-RSU2, and
   RSU3
   IP-RSU3 can belong to three different subnets (i.e., Subnet1,
   Subnet2, and Subnet3), respectively.  Those three subnets use three
   different prefixes (i.e., Prefix1, Prefix2, and Prefix3).

   A single subnet prefix can span multiple vehicles in VANET.  For
   example, in Figure 1, for Prefix 1, three vehicles (i.e., Vehicle1,
   Vehicle2, and Vehicle5) can construct a connected VANET.  Also, for
   Prefix 2, two vehicles (i.e., Vehicle3 and Vehicle6) can construct
   another connected VANET, and for Prefix 3, two vehicles (i.e.,
   Vehicle4 and Vehicle7) can construct another connected VANET.

   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 IP-RSU2 and IP-
   RSU3) by employing V2I (i.e., V2I2V) communication because they are
   not within the wireless communication range for each other.

   In

   An IPv6 mobility solution is needed in vehicular networks, asymmetric links sometimes exist and must networks so that a
   vehicle's TCP session can be
   considered for continued while it moves from an IP-
   RSU's wireless communications. coverage to another IP-RSU's wireless coverage.  In
   Figure 1, assuming that Vehicle2 has a TCP session with a
   corresponding node in the vehicular cloud, Vehicle2 can move from IP-
   RSU1's wireless coverage to IP-RSU2's wireless coverage.  In this
   case, a handover for Vehicle2 needs to be performed by either a host-
   based mobility management scheme (e.g., MIPv6 [RFC6275]) or a
   network-based mobility management scheme (e.g., PMIPv6 [RFC5213]).
   In the host-based mobility scheme, an IP-RSU plays a role of a home
   agent in a visited network.  On the other hand, in the network-based
   mobility scheme, an MA plays a role of a mobility management
   controller such as a Local Mobility Anchor (LMA) in PMIPv6, and an
   IP-RSU plays a role of an access router such as a Mobile Access
   Gateway (MAG) in PMIPv6 [RFC5213].

   In vehicular networks, the control plane can be separated from the
   data plane for efficient efficient mobility management and data forwarding.
   The separation of the control plane and data plane can be performed
   by the Software-Defined Networking (SDN) [RFC7149].  An MA can
   configure and monitor its IP-RSUs and vehicles for mobility management
   management, location management, and data forwarding. security services in an
   efficient way.

   The mobility information of a GPS receiver mounted in its vehicle
   (e.g., position, speed, and direction) can be used to accommodate
   mobility-aware proactive
   protocols. handover schemes, which can perform the
   handover of a vehicle according to its mobility and the wireless
   signal strength of a vehicle and an IP-RSU in a proactive way.

   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.  IP tunneling over the wireless link should be
   avoided for performance efficiency.  Also, in vehicular networks,
   asymmetric links sometimes exist and must be considered for wireless
   communications such as V2V and V2I.

                                                    +-----------------+
                           (*)<........>(*)  +----->| Vehicular Cloud |
          2001:DB8:1:1::/64 |            |   |      +-----------------+
   +------------------------------+  +---------------------------------+
   |                        v     |  |   v   v                         |
   | +-------+ +------+          +-------+ |  | +-------+ +------+          +-------+    |
   | | Host1 |          |IP-OBU1| | DNS1 | |Router1| |  | |Router3| | DNS2  | |IP-RSU1|          | Host3 |    |
   | +-------+ +------+          +-------+ |  | +-------+ +------+          +-------+    |
   |     ^                  ^         ^     |  |     ^                  ^        ^        |
   |        |
   |     |                  |     |  |     |                  |        |
   |     v                  v         v     |  |     v                  v        v        |
   | ---------------------------- |  | ------------------------------- |
   | 2001:DB8:10:1::/64 ^         |  |     ^ 2001:DB8:20:1::/64        |
   |                    |         |  |     |                           |
   |                    v         |  |     v                           |
   | +-------+      +-------+     |  | +-------+ +-------+   +-------+ |
   | | Host2 |      |Router2|      |Router1|     |  | |Router4| |Router2| |Server1|...|ServerN| |
   | +-------+      +-------+     |  | +-------+ +-------+   +-------+ |
   |     ^              ^         |  |     ^         ^           ^     |
   |     |              |         |  |     |         |           |     |
   |     v              v         |  |     v         v           v     |
   | ---------------------------- |  | ------------------------------- |
   |      2001:DB8:10:2::/64      |  |       2001:DB8:20:2::/64        |
   +------------------------------+  +---------------------------------+
      Vehicle1 (Moving Network1)            RSU1            EN1 (Fixed Network1)

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

        Figure 2: Internetworking between Vehicle Network and RSU Edge Network

4.2.  V2I-based Internetworking

   This section discusses the internetworking between a vehicle's
   internal network (i.e., moving network) and an RSU's EN's internal network
   (i.e., fixed network) via V2I communication.  Note that an RSU EN can
   accommodate multiple routers (or switches) and servers (e.g., DNS
   server ECDs,
   navigation server, and edge computing DNS server) in its internal network as an edge
   computing system. network.

   A vehicle's internal network often uses Ethernet to interconnect
   control units
   Electronic Control Units (ECUs) in the vehicle.  The internal network also supports
   can support WiFi and Bluetooth to accommodate a driver's and
   passenger's mobile devices (e.g., smartphone or tablet).  The network
   topology and subnetting depend on each vendor's network configuration
   for a vehicle and an EN.  It is reasonable to consider the
   interaction between the internal network and an external network
   within another vehicle or RSU. an EN.

   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 ND-based prefix discovery,
   network prefixes and parameters should be registered with a vehicle's
   router and an RSU router with an external network interface in
   advance.

   For an IP communication between a vehicle and an RSU or between two
   neighboring vehicles, the network parameter discovery collects
   information relevant to the link layer, MAC layer, and IP layer.  The
   link layer information includes wireless link layer parameters and
   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 2, as internal networks, a vehicle's moving
   network and prefix of an external EN's fixed network interface are self-contained networks having
   multiple subnets and having an edge router (e.g., IP-OBU and IP-RSU)
   for the
   internetworking communication with another vehicle or RSU.

   Once another EN.
   Internetworking between two internal networks via V2I communication
   requires the network parameter discovery and prefix exchange operations
   have been performed, packets can be transmitted between of the vehicle's
   moving network parameters and the RSU's fixed network.  A DNS service should be
   supported for the DNS name resolution of in-vehicle devices within a
   vehicle's internal network as well as for the DNS name resolution
   prefixes of
   those devices from a remote host in the Internet (e.g., a customer's
   web browser and an automotive service center system).  The DNS names
   of in-vehicle devices and their service names can be registered with
   a DNS server in a vehicle or an RSU, as shown in Figure 2. internal networks.

   Figure 2 also shows internetworking between the vehicle's moving
   network and the RSU's EN'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 (IP-OBU1 and Router2). Router1).  There exists another
   internal network (Fixed Network1) inside RSU1.  RSU1 EN1.  EN1 has the DNS Server (DNS2), one host
   (Host3), the two routers (Router3 (IP-RSU1 and Router4), Router2), 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 (a IP-OBU1 (as a mobile router) and RSU1's Router3 (a EN1's IP-RSU1 (as a fixed
   router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for
   V2I networking.  Thus, one a host (Host1) in Vehicle1 can communicate
   with one a server (Server1) in RSU1 EN1 for a vehicular service through
   Vehicle1's moving network, a wireless link between Vehicle1 IP-OBU1 and IP-
   RSU1, and RSU1's EN1's fixed network.

   For an IPv6 communication between an IP-OBU and an IP-RSU or between
   two neighboring IP-OBUs, network parameters need to be shared among
   them, such as MAC layer and IPv6 layer information.  The MAC layer
   information includes wireless link layer parameters, transmission
   power level, the MAC address of an external network interface for the
   internetworking with another IP-OBU or IP-RSU.  The IPv6 layer
   information includes the IPv6 address and network prefix of an
   external network interface for the internetworking with another IP-
   OBU or IP-RSU.

   Through the exchange of network parameters and network prefixes among
   internal networks, packets can be transmitted between the vehicle's
   moving network and the EN's fixed network.  Thus, V2I requires an
   efficient exchange protocol for network parameters and an efficient
   routing protocol for network prefixes.

                           (*)<..........>(*)
          2001:DB8:1:1::/64 |              |
   +------------------------------+  +------------------------------+
   |                        v     |  |     v                        |
   | +-------+ +------+          +-------+ |  | +-------+ +------+          +-------+ |
   | | Host1 |          |IP-OBU1| | DNS1  | |Router1| |  | |Router5| | DNS3 |IP-OBU2|          | | Host4 Host3 | |
   | +-------+ +------+          +-------+ |  | +-------+ +------+          +-------+ |
   |     ^                  ^         ^     |  |     ^                  ^        ^     |     |
   |     |                  |     |  |     |                  |     |
   |
   |     v     v                  v     |  |     v                  v        v     |
   | ---------------------------- |  | ---------------------------- |
   | 2001:DB8:10:1::/64 ^         |  |         ^ 2001:DB8:30:1::/64 |
   |                    |         |  |         |                    |
   |                    v         |  |         v                    |
   | +-------+      +-------+     |  |     +-------+      +-------+ |
   | | Host2 |      |Router2|      |Router1|     |  |     |Router6|     |Router2|      | Host5 Host4 | |
   | +-------+      +-------+     |  |     +-------+      +-------+ |
   |     ^              ^         |  |         ^              ^     |
   |     |              |         |  |         |              |     |
   |     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 Vehicles

4.3.  V2V-based Internetworking

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

   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 (IP-OBU1 and
   Router2). Router1).  There exists another internal
   network (Moving Network2) inside Vehicle2.  Vehicle2 has the DNS Server (DNS3), the two hosts
   (Host4
   (Host3 and Host5), Host4), and the two routers (Router5 (IP-OBU2 and Router6). Router2).  Vehicle1's Router1 (a
   IP-OBU1 (as a mobile router) and Vehicle2's Router5 (a IP-OBU2 (as a mobile
   router) use 2001:DB8:1:1::/64 for an external link (e.g., DSRC) for
   V2V networking.  Thus, one a host (Host1) in Vehicle1 can communicate
   with one another host (Host4) (Host3) in Vehicle1 Vehicle2 for a vehicular service through
   Vehicle1's moving network, a wireless link between Vehicle1 IP-OBU1 and
   Vehicle2, IP-
   OBU2, and Vehicle2's moving network.

        (*)<..................>(*)<..................>(*)
         |                      |                      |
   +-----------+          +-----------+          +-----------+
   |           |          |           |          |           |
   | +-------+ |          | +-------+ |          | +-------+ |
   | |Router1| |IP-OBU1| |          | |Router5| |IP-OBU2| |          | |Router7| |IP-OBU3| |
   | +-------+ |          | +-------+ |          | +-------+ |
   |           |          |           |          |           |
   | +-------+ |          | +-------+ |          | +-------+ |
   | | Host1 | |          | | Host4 Host2 | |          | | Host6 Host3 | |
   | +-------+ |          | +-------+ |          | +-------+ |
   |           |          |           |          |           |
   +-----------+          +-----------+          +-----------+
      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 Host3 in Vehicle3 via Router 5 IP-OBU1 in Vehicle2 that
   is an intermediate vehicle being connected to Vehicle1 Vehicle1, IP-
   OBU2 in Vehicle2, and IP-OBU3 in Vehicle3 in a linear topology as
   shown in the figure.

5.  Problem Statement

   In order to specify protocols using the abovementioned architecture
   for VANETs, IPv6 core protocols have to be adapted to overcome
   certain challenging aspects of vehicular networking.  Since the
   vehicles are likely to be moving at great speed, protocol exchanges
   need to be completed in a time relatively small compared to the
   lifetime of a link between a vehicle and an RSU, IP-RSU, or between two
   vehicles.  This has a major impact on IPv6 neighbor discovery. Neighbor Discovery (ND).
   Mobility management Management (MM) is also vulnerable to disconnections that
   occur before the completion of identity verification and tunnel
   management.  This is especially true given the unreliable nature of
   wireless communications.  Finally, and perhaps most importantly, proper
   authorization for vehicular protocol messages must be assured in
   order to prevent false reports of accidents or other mishaps on the
   road, which would cause horrific misery in modern urban environments.
   This  Thus, this section presents key topics such
   as neighbor discovery and mobility management.

5.1.  Neighbor Discovery

   IPv6 Neighbor Discovery (IPv6 ND) 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).

   DAD and ND-related parameters (e.g., Router Lifetime) need to be
   extended to vehicular networking (e.g., V2V, V2I, and V2X).

   Vehicles move quickly within the communication coverage of any
   particular vehicle or RSU. IP-RSU.  Before the vehicles can exchange
   application messages with each other, they need to be configured with
   a link-
   local link-local IPv6 address or a global IPv6 address, and run 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 partitioning and merging of VANETs makes
   this assumption frequently invalid in vehicular networks.  The
   merging and partitioning of VANETs occurs frequently in vehicular
   networks.  This merging and partitioning should be considered for the
   IPv6 Neighbor Discovery (e.g., SLAAC). ND such as IPv6 Stateless Address Autoconfiguration (SLAAC)
   [RFC4862].  Due to the merging of VANETs, two IPv6 addresses may
   conflict with each other though they were unique before the merging.
   Also, the partitioning of a VANET may make vehicles with the same
   prefix be physically unreachable.  Also, SLAAC should be extended needs to prevent IPv6
   address duplication due to the merging of VANETs.  According to the
   merging and partitioning, a destination vehicle (as an IP IPv6 host) should
   needs to be distinguished as either an on-link host or an off-link
   host even though the source vehicle uses the same prefix with the
   destination vehicle.

   The

   To efficiently prevent the IPv6 address duplication due to the VANET
   partitioning and merging from happing 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 DAD.  In this
   case, two vehicles can communicate with each other when there exists
   a communication path over VANET or a combination of VANETs and IP-
   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.  A vehicular
   infrastructure having RSUs and an MA can participate in the
   vehicular-network-wide DAD for the sake of vehicles [RFC6775].  For
   the vehicle as an IPv6 node, deriving a unique IPv6 address from a
   globally unique MAC address creates a privacy issue.  Refer to
   Section 6 for the discussion about such a privacy issue.

   ND time-related parameters such as router lifetime and Neighbor
   Advertisement (NA) interval should need to 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.

   According to a report from the 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 exchanged
   every 0.5 second.  Thus, if the ND messages (e.g., NS and NA) are
   used as warning messages, they should be exchanged every 0.5 second.

   For IP-based IPv6-based safety applications (e.g., context-aware navigation,
   adaptive cruise control, and platooning) in vehicular network, this
   bounded vehicular networks, the
   delay-bounded data delivery is critical.  Implementations for such
   applications are not available yet.  IPv6 ND needs to efficiently
   work to support IP-
   based IPv6-based safety applications.

5.1.1.  Link Model

   A prefix model for a vehicular network needs to facilitate the
   communication between two vehicles with the same prefix regardless of
   the vehicular network topology as long as there exist bidirectional
   E2E paths between them in the vehicular network including VANETs and
   IP-RSUs.  This prefix model allows vehicles with the same prefix to
   communicate with each other via a combination of multihop V2V and
   multihop V2I with VANETs and IP-RSUs.

   IPv6 protocols work under certain assumptions for the link model that
   do not necessarily hold in a vehicular wireless link [VIP-WAVE]
   [RFC5889].
   [VIP-WAVE][RFC5889].  For instance, some IPv6 protocols assume
   symmetry in the connectivity among neighboring interfaces [RFC6250].
   However, radio interference and different levels of transmission
   power may cause asymmetric links to appear in vehicular wireless
   links.  As a result, a new vehicular link model should needs to consider the
   asymmetry of dynamically changing vehicular wireless links.

   There is a relationship between a link and a 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 IPv6 link.
   However, the vehicular link model needs to define the relationship
   between a link and a prefix, considering the dynamics of wireless
   links and the characteristics of VANET.

   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.  Suppose 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. connectivity between them.  Thus, in
   this case, the concept of an 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 converge
   to one VANET, the two vehicles can communicate with each other in a
   multihop fashion. fashion, for example, wheh they are Vehicle1 and Vehicle3,
   as shown in Figure 4.

   From the previous observation, a vehicular link model should consider
   the frequent partitioning and merging of VANETs due to vehicle
   mobility.  Therefore, the vehicular link model needs to use an on-
   link prefix and off-link prefix according to the one-hop reachability
   among the network topology of
   vehicles in an appropriate way. such as a one-hop reachable network and a multihop reachable
   network (or partitioned networks).  If the vehicles with the same
   prefix are reachable with each other in one hop, the prefix should be
   on-link.  On the other hand, if some of the vehicles with the same
   prefix are not reachable with each other in one hop due to either the multi-hop
   multihop topology in the VANET or multiple partitions, the prefix
   should be off-link.

   The vehicular link model needs to support the multihop routing in a
   connected VANET where the vehicles with the same global-scope IPv6
   prefix are connected in one hop or multiple hops.  It also needs to
   support the multihop routing in multiple connected VANETs via an RSU
   that has through
   infrastructure nodes (e.g., IP-RSU) where they are connected to the wireless connectivity with each VANET.
   infrastructure.  For example, in Figure 1, suppose that Vehicle1,
   Vehicle2, and Vehicle3 are configured with their IPv6 addresses based
   on the same global-scope IPv6 prefix.  Vehicle1 and Vehicle3 can also
   communicate with each other via either multi-hop multihop V2V or multi-hop multihop
   V2I2V.  When the two vehicles of Vehicle1 and Vehicle3 are connected
   in a VANET, it will be more efficient for them to directly
   communicate with each other via VANET rather than indirectly via IP-
   RSUs.  On the other hand, when the two vehicles of Vehicle1 and
   Vehicle3 are far away from the communication range in separate VANETs
   and under two different RSUs, IP-RSUs, they can communicate with each other
   through the relay of RSUs IP-RSUs via V2I2V.  Thus, two separate VANETs
   can merge into one network via RSU(s). IP-RSU(s).  Also, newly arriving
   vehicles can merge two separate VANETs into one VANET if they can
   play a role of a relay node for those VANETs.

5.1.2.  MAC Address Pseudonym

   For the protection of drivers' privacy, a pseudonym of a MAC address
   of a vehicle's network interface should be used, so that the MAC
   address can be changed periodically.  However, although such a
   pseudonym of a MAC address can protect some extent of privacy of a
   vehicle, it may not be able to resist attacks on vehicle
   identification by other fingerprint information, for example, the
   scrambler seed embedded in IEEE 802.11-OCB frames [Scrambler-Attack].
   The pseudonym of a MAC address affects an IPv6 address based on the
   MAC address, and a transport-layer (e.g., TCP) TCP and and SCTP) 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
   needs to be updated, and the uniqueness of the address should needs to be
   performed
   checked through the DAD procedure.  For vehicular networks with high
   mobility and density, this DAD should needs to be performed efficiently with
   minimum overhead so that the vehicles can exchange warning application
   messages (e.g., collision avoidance and accident notification) with
   each other every 0.5 second [NHTSA-ACAS-Report].

   For the continuity of an end-to-end (E2E) transport-layer (e.g., TCP,
   UDP, and SCTP) session, with a mobility management scheme short interval (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 mobility
   management overhead for pseudonyms should be minimized for efficient
   operations in vehicular networks having lots of vehicles. 0.5 second)
   [NHTSA-ACAS-Report].

5.1.3.  Routing

   For multihop V2V communications in either a VANET or VANETs via IP-
   RSUs, 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 [ID-Multicast-Problems].

   The merging of the IPv6 Neighbor Discovery and a VANET routing
   protocol allows the efficient wireless channel utilization. terms of
   control traffic overhead [ID-Multicast-Problems].

   A routing protocol for VANET may cause redundant wireless frames in
   the air to check the neighborhood of each vehicle and compute the
   routing information in VANET with a dynamic network topology if because
   the IPv6 ND is used to check the neighborhood of each vehicle, and can be
   extended to compute each vehicle's routing table in VANET.

   Vehicular ND can be extended to accommodate vehicle.  Thus,
   the vehicular routing functionality
   with a prefix discovery option.  The ND extension can allow vehicles needs to exchange their prefixes in a multihop fashion [ID-Vehicular-ND].
   With take advantage of the exchanged prefixes, they can compute their routing table (or IPv6 ND's neighbor cache) for the VANETs with a distance-vector
   algorithm [Intro-to-Algorithms]. ND to
   minimize its control overhead.

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.  Note that The GPS receiver may not provide vehicles
   with accurate location information in adverse, local adverse environments such as a
   building area and tunnel.  The location precision can be improved by
   the assistance from the RSUs IP-RSUs or a cellular system with a GPS
   receiver for location information.

   With a GPS navigator, an efficient mobility management will can be
   possible by
   performed with the help of vehicles periodically reporting their
   current position and trajectory (i.e., navigation path) to the
   vehicular infrastructure (having RSUs IP-RSUs and an MA in TCC) [ID-Vehicular-MM]. TCC).  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 IP-RSUs along with mobility information.

   By predicting a vehicle's mobility, the vehicular infrastructure can
   needs to better support RSUs IP-RSUs to perform efficient DAD, SLAAC, data packet routing,
   forwarding, 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
   advance along with the movement of the vehicle [ID-Vehicular-MM]. vehicle.

   For example, as shown in Figure 1, when a vehicle (e.g., Vehicle2) is
   moving from the coverage of an IP-RSU (e.g., IP-RSU1) into the wireless link under
   coverage of another RSU IP-RSU (e.g., IP-RSU2) belonging to a different
   subnet, the RSU IP-RSUs can proactively
   perform support the DAD IPv6 mobility of the
   vehicle, while performing the SLAAC, data forwarding, and handover
   for the sake of the vehicle, reducing IPv6 control
   traffic overhead in vehicle.

   Therefore, for the wireless link.  To prevent a hacker from
   impersonating RSUs as bogus RSUs, RSUs proactive and MA in seamless IPv6 mobility of vehicles,
   the vehicular infrastructure need to have secure channels via IPsec.

   Therefore, with a proactive handover (including IP-RSUs and a multihop DAD in vehicular
   networks, RSUs MA) needs to
   efficiently forward data packets from perform the
   wired network (or mobility management of the wireless network) to a moving destination
   vehicle along its trajectory. vehicles with
   their mobility information and link-layer information.

6.  Security Considerations

   This section discusses security and privacy for IP-based IPv6-based vehicular
   networking.  The security and privacy are one of key components privacy is one of key components in
   IPv6-based vehicular networking along with neighbor discovery and
   mobility management.

   Security and privacy are paramount in the V2I, V2V, and V2X
   networking.  Only authorized vehicles need to be allowed to use the
   vehicular networking.  Also, in-vehicle devices (e.g., ECU) and
   mobile devices (e.g., smartphone) in a vehicle need to communicate
   with other in-vehicle devices and mobile devices in
   IP-based vehicular networking, such as neighbor discovery another vehicle,
   and
   mobility management, so they need other servers in an IP-RSU in a secure way.  Even a perfectly
   authorized and legitimate vehicle may be hacked to run malicious
   applications to track and collect its and other vehicles'
   information.  For this case, an attack mitigation process may be analyzed in depth.
   required to reduce the aftermath of the malicious behaviors.

   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.

   For example, Sybil attack, which tries to confuse a vehicle with
   multiple false identities, disturbs a vehicle in taking a safe
   maneuver.  This sybil attack should needs to be prevented through the
   cooperation between good vehicles and RSUs. IP-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
   cloud.  However, applications on
   IP-based IPv6-based vehicular networking,
   which are resilient to such a sybil attack, are not developed and
   tested yet.

   Security and privacy are paramount in

   To identify the V2I, V2V, and V2X
   networking in vehicular networks.  Only authorized genuineness of 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.  Even a perfectly authorized and legitimate
   vehicle may be hacked to run against malicious applications to track and
   collect other vehicles' information.  For this case, vehicles,
   an attack
   mitigation process may be required to reduce the aftermath of the
   malicious behaviors. authentication method is required.  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) IP-RSU)
   connected to an authentication server in the vehicular cloud.  Also,
   Transport Layer Security (TLS) certificates can be used for the
   vehicle authentication to allow secure E2E vehicle communications.
   To identify the genuineness of vehicles against malicious vehicles,
   an authentication method is required.  For vehicle authentication,
   information available from a vehicle or a driver (e.g., Vehicle
   Identification Number (VIN) and Transport Layer Security (TLS)
   certificate [RFC8446]) needs to be used to efficiently authenticate a
   vehicle or a user with the help of a road infrastructure node (e.g.,
   IP-RSU) connected to an authentication server in TCC.  Also, Transport Layer Security (TLS) certificates can be
   used for secure E2E vehicle communications. the vehicular cloud.

   For secure V2I communication, a secure channel between a mobile
   router (i.e., IP-OBU) in a vehicle and a fixed router (i.e., IP-RSU)
   in an RSU should EN needs to be established, as shown in Figure 2.  Also, for
   secure V2V communication, a secure channel between a mobile router
   (i.e., IP-OBU) in a vehicle and a mobile router (i.e., IP-OBU) in
   another vehicle should needs to 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 needs to be provided to the
   vehicle; that is, each vehicle should periodically update updates 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 vehicles (or between a vehicle and an IP-
   RSU) in terms of transport layer for a long-
   living higher-layer long-living transport-layer session.  However, if this
   pseudonym is performed without strong E2E confidentiality, there will
   be no privacy benefit from changing MAC and IP IPv6 addresses, because
   an adversary can see observe the change of the MAC and IP IPv6 addresses and
   track the vehicle with those addresses.

   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 or vehicular network
   including the RSUs and networks.  Thus, the MA.  The
   vehicles and RSUs IP-RSUs need to filter out suspicious ND traffic in
   advance.

   For the mobility management, a malicious vehicle can construct
   multiple virtual bogus vehicles, and register them with the RSU IP-RSUs and
   the
   MA.  This registration makes the RSU IP-RSUs and MA waste their
   resources.  The RSU IP-RSUs and MA need to determine whether a vehicle is
   genuine or bogus in the mobility management.  Also, the
   confidentiality of control packets and data packets among IP-RSUs and
   MA, the E2E paths (e.g., tunnels) need to be protected by secure
   communication channels.  In addition, to prevent bogus IP-RSUs and MA
   from interfering IPv6 mobility of vehicles, the mutual authentication
   among them needs to be performed by certificates (e.g., TLS
   certificate).

7.  Informative References

   [Automotive-Sensing]
              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.

   [CA-Cruise-Control]
              California Partners for Advanced Transportation Technology
              (PATH), "Cooperative Adaptive Cruise Control", [Online]
              Available:
              http://www.path.berkeley.edu/research/automated-and-
              connected-vehicles/cooperative-adaptive-cruise-control,
              2017.

   [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.

   [EU-2008-671-EC]
              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.

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

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

   [Fuel-Efficient]
              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.

   [ID-Multicast-Problems]
              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.

   [ID-Vehicular-MM]
              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), July 2019.

   [ID-Vehicular-ND]
              Jeong, J., Ed., Shen, Y., and Z. Xiang, "Vehicular
              Neighbor Discovery for IP-Based Vehicular Networks",
              draft-jeong-ipwave-vehicular-neighbor-discovery-07 draft-ietf-mboned-ieee802-mcast-problems-11 (work
              in progress), July December 2019.

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

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

   [IEEE-802.11p]
              "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.

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

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

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

   [NHTSA-ACAS-Report]
              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
              2003.

   [RFC3753]  Manner, J. and M. Kojo, "Mobility Related Terminology",
              RFC 3753, June 2004.

   [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
              2005.

   [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.

   [RFC5415]  Calhoun, P., Montemurro, M., and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", D. Stanley, "Control And
              Provisioning of Wireless Access Points (CAPWAP) Protocol
              Specification", RFC 5844, May 2010. 5415, March 2009.

   [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.

   [RFC6250]  Thaler, D., "Evolution of the IP Model", RFC 6250, May
              2011.

   [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.

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, March 2014.

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

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

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, August 2018.

   [RFC8691]  Benamar, N., Haerri, J., Lee, J., and T. Ernst, "Basic
              Support for IPv6 Networks Operating Outside the Context of
              a Basic Service Set over IEEE Std 802.11", RFC 8691,
              December 2019.

   [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.

   [SAINTplus]
              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.

   [Scrambler-Attack]
              Bloessl, B., Sommer, C., Dressier, F., and D. Eckhoff,
              "The Scrambler Attack: A Robust Physical Layer Attack on
              Location Privacy in Vehicular Networks", IEEE 2015
              International Conference on Computing, Networking and
              Communications (ICNC), February 2015.

   [Timing-Attack]
              Matte, C., Cunche, M., Rousseau, F., and M. Vanhoef,
              "Defeating MAC Address Randomization Through Timing
              Attacks", ACM the 9th ACM Conference on Security & Privacy
              in Wireless and Mobile Networks (WiSec '16), July 2016.

   [Truck-Platooning]
              California Partners for Advanced Transportation Technology
              (PATH), "Automated Truck Platooning", [Online] Available:
              http://www.path.berkeley.edu/research/automated-and-
              connected-vehicles/truck-platooning, 2017.

   [TS-23.285-3GPP]
              3GPP, "Architecture Enhancements for V2X Services", 3GPP
              TS 23.285, June 2018.

   [VIP-WAVE]
              Cespedes, S., Lu, N., and X. Shen, "VIP-WAVE: On the
              Feasibility of IP Communications in 802.11p Vehicular
              Networks", IEEE Transactions on Intelligent Transportation
              Systems, vol. 14, no. 1, March 2013.

   [WAVE-1609.0]
              IEEE 1609 Working Group, "IEEE Guide for Wireless Access
              in Vehicular Environments (WAVE) - Architecture", IEEE Std
              1609.0-2013, March 2014.

   [WAVE-1609.2]
              IEEE 1609 Working Group, "IEEE Standard for Wireless
              Access in Vehicular Environments - Security Services for
              Applications and Management Messages", IEEE Std
              1609.2-2016, March 2016.

   [WAVE-1609.3]
              IEEE 1609 Working Group, "IEEE Standard for Wireless
              Access in Vehicular Environments (WAVE) - Networking
              Services", IEEE Std 1609.3-2016, April 2016.

   [WAVE-1609.4]
              IEEE 1609 Working Group, "IEEE Standard for Wireless
              Access in Vehicular Environments (WAVE) - Multi-Channel
              Operation", IEEE Std 1609.4-2016, March 2016.

Appendix A.  Changes from draft-ietf-ipwave-vehicular-networking-11

   The following changes are made from draft-ietf-ipwave-vehicular-
   networking-11:

   o  This version is revised based on the comments from Charlie Perkins
      and Sandra Cespedes.

   o  In Section 5, the problem statement is revisd with easily
      identifiable problems.

   o  In Section 1, the description of GeoNetworking (GN) protocols
      (i.e., geographic routing) is removed because the GN protocols are
      not relevant to the IPWAVE's use cases.

   o  In Section 2, the terms of OCB, Context-Awareness, Platooning, and
      Class-Based Safety Plan are clarified.

   o  In Section 2, the definition of an RSU is revised so that it can
      accommodate multiple routers (or switches) and servers (including
      DNS server and edge computing server) as an edge computing system
      because the RSU is regularly a router or switch.

   o  In Section 4.1, a general vehicular network architecture is
      proposed for the problem statement along with Figure 1.  This
      figure clarifies that a single subnet prefix can span multiple
      vehicles that construct a subnet.  Also, some components in the
      vehicular network architecture may not be needed such as Vehicular
      Cloud, Traffic Control Center, and Mobility Anchor.

   o  In Section 5.1.1, the motivation of a new link model as a
      vehicular link model is added.  The "on-link" and "off-link"
              IEEE 1609 Working Group, "IEEE Standard for
      prefixes are classified according to the subnet topology of VANET.

   o  In Section 5.1.1, the merging and partitioning of VANETs is
      described, and the requirements of the IPv6 ND are addressed Wireless
              Access in Vehicular Environments - Security Services for
      the merging
              Applications and partitioning as a problem statement.

   o  In Section 5.1.2, a citation of [Scrambler-Attack], which uses the
      scrambler seed Management Messages", IEEE Std
              1609.2-2016, March 2016.

   [WAVE-1609.3]
              IEEE 1609 Working Group, "IEEE Standard for Wireless
              Access in the Vehicular Environments (WAVE) - Networking
              Services", IEEE 802.11-OCB frames as fingerprint
      information, is added to show the insufficiency of the MAC address
      pseudonym Std 1609.3-2016, April 2016.

   [WAVE-1609.4]
              IEEE 1609 Working Group, "IEEE Standard for privacy. Wireless
              Access in Vehicular Environments (WAVE) - Multi-Channel
              Operation", IEEE Std 1609.4-2016, March 2016.

Appendix A.  Changes from draft-ietf-ipwave-vehicular-networking-12

   The following changes are made from draft-ietf-ipwave-vehicular-
   networking-12:

   o  In Section 5.1, the subsection of Prefix Dissemination/Exchange  This version is
      removed because revised based on the Prefix Dissemination/Exchange subsection
      discusses a solution comments from Carlos
      Bernardos.

   o  This version focuses on problems rather than a problem or requirement.

   o  In Section 5.1.3, solutions for IPWAVE.
      Also, this version addresses the motivation requirements of merging the IPv6 ND and a
      VANET routing protocol is explained to improve wireless channel
      utilization by removing redundant neighbor information exchange.

   o  The text of the problems
      discovery, mobility management, and requirements of security and privacy
      in vehicular networks are moved to Section 6. privacy.

   o  In Section 6, the compromise 2, IP-OBU and IP-RSU are used instead of a perfectly authorized OBU and
      legitimate vehicle is described as a security problem to be
      considered. RSU,
      respectively.

   o  In Section 3.3, the description of Vehicle-to-Pedestrian (V2P) 4.1, an exemplary vehicular network architecture is
      concised to deliver the clear concept of
      illustrated for the direct communication
      between a vehicle and a pedestrian. problem statement as Figure 1.

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). (Cisco), Carlos Bernardos (UC3M), Russ
   Housley (Vigil Security), and Suresh Krishnan (Kaloom).  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
   Morocco

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

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

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

   Jerome Haerri
   Communication Systems Department
   EURECOM
   Sophia-Antipolis
   France

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

   Dapeng Liu
   Alibaba
   Beijing, Beijing 100022
   China

   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
   USA

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

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

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

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

   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
   FBConsulting
   21, Route de Luxembourg
   Wasserbillig, Luxembourg L-6633
   Luxembourg

   EMail: Michelle.Wetterwald@gmail.com

Author's Address

   Jaehoon Paul Jeong (editor)
   Department of Computer Science and Engineering
   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