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Versions: 00 01                                                         
NEMO                                                       R. Baldessari
Internet-Draft                                                NEC Europe
Intended status: Informational                                 A. Festag
Expires: August 27, 2007                                     NEC Germany
                                                              M. Lenardi
                                                          Hitachi Europe
                                                       February 23, 2007


       C2C-C Consortium Requirements for Usage of NEMO in VANETs
                   draft-baldessari-c2ccc-nemo-req-00

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on August 27, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   Vehicular ad hoc Networks (VANETs), self-organized networks based on
   short-range wireless technologies, aim at improving road safety and
   providing comfort and entertainment applications.  The Car2Car
   Communication Consortium is defining a European standard for inter-
   vehicle communication that adopts VANETs principles.  This document



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   describes the scope, use cases and requirements for a solution based
   on Network Mobility (NEMO) in VANETs as identified by the Consortium.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Overview of the Car-to-Car Communication Architecture  . . . .  5
     3.1.  Current System Architecture  . . . . . . . . . . . . . . .  6
     3.2.  Current Protocol Architecture  . . . . . . . . . . . . . .  9
     3.3.  Interaction with IPv6  . . . . . . . . . . . . . . . . . . 10
   4.  Scope of NEMO  . . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Example Use Cases  . . . . . . . . . . . . . . . . . . . . . . 12
     5.1.  Notification Services  . . . . . . . . . . . . . . . . . . 12
     5.2.  Peer-to-peer Applications  . . . . . . . . . . . . . . . . 13
     5.3.  Upload and Download Services . . . . . . . . . . . . . . . 13
   6.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 13
     6.1.  V2V and V2I Communication Modes  . . . . . . . . . . . . . 14
     6.2.  Same Identifiers for V2V and V2I . . . . . . . . . . . . . 14
     6.3.  Security . . . . . . . . . . . . . . . . . . . . . . . . . 14
     6.4.  Privacy  . . . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 15
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     10.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
   Intellectual Property and Copyright Statements . . . . . . . . . . 18





















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1.  Introduction

   In Vehicular ad hoc Networks (VANETs), cars are equipped with short-
   range wireless communication devices that operate at frequencies
   dedicated to safety and non-safety vehicular applications.  When
   entering the proximity of each other, vehicles form a self-organized
   network by means of a specialized routing protocol that allows for
   packet exchange through broadcast and unicast communications.
   Further, fixed communication devices are installed along roadsides
   and can either distribute local warnings or offer connectivity with a
   network infrastructure.  Due to its safety-oriented nature and
   extremely dynamic operational environment, this type of communication
   has lead research to consider specialized protocols and algorithms,
   especially concerning information dissemination, geographic
   distribution of packets and privacy/security issues.

   The Car2Car Communication Consortium is an industry consortium of car
   manufacturers and electronics suppliers that focuses on the
   definition of an European standard for vehicular communication
   protocols.  The Consortium gathers results from research projects and
   aims at harmonizing their efforts.  The first technical document [8],
   to be released in the following months, gives an overview of the
   system and protocol architecture, as well as of the applications on
   which the Consortium has agreed so far.  In essence, this document
   defines a C2C-C protocol stack that offers specialized
   functionalities and interfaces to (primarily) safety-oriented
   applications and relies as a communication technology on a modified
   version of [9].  This protocol stack is placed beside a traditional
   TCP/IP stack, exclusively based on IPv6, which is used mainly for
   non-safety applications or potentially by any application that is not
   subject to strict delivery requirements, including Internet-based
   applications.  The interaction between these stacks is currently
   discussed and briefly overviewed in this document.

   As vehicles connecting to the Internet via dedicated access points
   (also termed Road Side Units, see Section 2 for terminology) change
   their attachment point while driving, the Consortium considers IP
   Mobility support as enhancing the system with session continuity and
   global reachability.  When considering that passenger devices can be
   plugged into car communication equipment, therefore turning a vehicle
   into an entire moving network, Network Mobility (NEMO) principles
   have clear benefits in the discussed scenario (i.e. passenger devices
   shielded from mobility, centralized mobility management).

   In VANETs, wireless multi-hop routing and forwarding are used to
   extend the coverage area of attachment points, allowing vehicles that
   are not in the proximity of a Road Side Unit to exchange packets with
   the infrastructure.  Furthermore, as the coverage of such access



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   points is expected to be (at least short/mid term) very limited
   compared with road extension, direct vehicle-to-vehicle packet
   routing for both kinds of application (safety and non-safety) is
   essential.  These peculiar vehicular use cases require the
   integration of NEMO Basic Support [1] with ad hoc routing in the
   first case, an extension of NEMO to allow isolated vehicles to
   communicate directly in the latter.  Other specific use cases are
   also described in this document.

   This document intends to provide the IETF NEMO work group with an
   overview of the C2C-C Consortium protocol architecture, selected use
   cases and related requirements for the deployment of a vehicular-
   specific solution based on Network Mobility principles.  The document
   is organized as follows: Section 2 defines terminology.  Section 3
   describes the C2C-C Consortium goals and technical approach.
   Section 4 describes the intended scope of NEMO in vehicular
   applications according to the C2C-C Consortium.  Section 5 explains a
   set of selected use cases.  Finally Section 6 lists functional
   requirements.


2.  Terminology

   The following terms used in this document are defined in the Mobile
   IPv6 protocol specification [2]:

      Home Agent (HA)

      Home Address (HoA)

   The following terms used in this document are defined in the Mobile
   Network terminology document [6]:

      Network Mobility (NEMO)

      Mobile Network

      Mobile Router (MR)

      Mobile Network Prefix (MNP)

      Mobile Network Node (MNN)

   The following new terms are used in this document:

   o  On Board Unit (OBU): a device installed in vehicles, implementing
      the communication protocols and algorithm and equipped with at
      least 1) a short-range wireless network interface operating at



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      dedicated frequencies and 2) a wireless or wired network interface
      where Application Units (AU) can be attached to.  With respect to
      the NEMO terminology, the OBU is the physical machine acting as
      MR.

   o  Application Unit (AU): a portable or built-in device connected
      temporarily or permanently to the vehicle OBU.  It is assumed that
      AUs support a standard TCP/IPv6 protocol stack, optionally
      enhanced with IP Mobility support.  With respect to the NEMO
      terminology, an AU is a generic MNN.

   o  Road Side Unit (RSU): a device installed along roadsides
      implementing the same communication protocols and algorithms as an
      OBU.  RSUs can either be isolated or connected to a network
      infrastructure.  In the latter case, RSUs are attachment points
      either acting themselves as IPv6 access routers or as network
      bridges directly connected to an access router.

   o  In-vehicle network: the wireless or wired network placed in a
      vehicle and composed by (potentially) several AUs and one OBU.

   o  Vehicle-to-Vehicle (V2V) Communication Mode: a generic
      communication mode in which data packets are exchanged between two
      vehicles, either directly or by means of multi-hop routing,
      without involving any node in the infrastructure.

   o  Vehicle-to-Infrastructure (V2I) Communication Mode: a generic
      communication mode in which data packets sent or received by a
      vehicle traverse a network infrastructure.

   o  Vehicle-to-Infrastructure-to-Vehicle (V2I2V) Communication Mode: a
      generic communication mode in which data packets are exchanged
      between two vehicles, by means of multi-hop routing involving a
      RSU not connected to a network infrastructure.


3.  Overview of the Car-to-Car Communication Architecture

   The Car2Car Communication Consortium [7] is a non-profit organization
   initiated by European vehicle manufacturers that is open for
   suppliers, research organizations and other partners.  The Car2Car
   Communication Consortium is dedicated to the objective of further
   increasing road traffic safety and efficiency by means of inter-
   vehicle communications.

   The goals of the Car2Car Communication Consortium [8] are:





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   o  Create and establish an open European industry standard for inter-
      vehicle communication systems based on wireless LAN components and
      guarantee European-wide inter-vehicle operability.

   o  Enable the development of active safety applications by
      specifying, prototyping and demonstrating the Car2Car
      Communication system.

   o  Promote the allocation of a royalty free European wide exclusive
      frequency band for Car2Car applications.

   o  Push the harmonization of Car2Car Communication standards
      worldwide.

   o  Develop realistic deployment strategies and business models to
      speed up the market penetration.

3.1.  Current System Architecture

   The draft reference architecture of the C2C communication system is
   shown in Figure 1.






























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                        |       Internet        |
                        |                       |
                        +---+-----------------+-+
                            |                 |
                 Access  +--+-+            +--+-+  Access
                 Router  | AR |            | AR |  Router
                         +--+-+            +--+-+
                            |                 |
                      --+---+---            --+---+--
                        |                         |
         Road Side   +--+--+                   +--+--+   Public
           Unit      | RSU |                   | PHS |  Hot Spot
                     +---+-+                   +---+-+
                         |                         |
                        /\                        /\

                        \_                         \_
                          \_                         \_
                            \                          \

            Mandatory        \/
          Mod IEEE 802.11p    |       __               \/  Optional IEEE
            Interface     +---+--+      \__      \/     |   802.11a/b/g
                          | OBU1 |                |     |    Interface
                          +--+---+              +-+-----+---+
                   Vehicle1  |                  |   OBU2    |  On-Board
                        -+---+-+-               +--+--------+    Unit
                         |     |                   | Vehicle2
       Application    +--+-+ +-+--+           --+--+--
          Units       | AU | | AU |             |
                      +----+ +----+           +-+--+
                                              | AU |
                                              +----+

                  Figure 1: C2C-CC Reference Architecture

   Vehicles are equipped with networks logically composed of an OBU and
   potentially multiple AUs.  An AU is typically a dedicated device that
   executes a single or a set of applications and utilizes the OBU
   communication capabilities.  An AU can be an integrated part of a
   vehicle and be permanently connected to an OBU.  It can also be a
   portable device such as laptop, PDA or game pad that can dynamically
   attach to (and detach from) an OBU.  AU and OBU are usually connected
   with wired connection, but the connection can also be wireless, such
   as Bluetooth.  The distinction between AU and OBU is logical, they
   can also reside in a single physical unit.

   Vehicles' OBUs and stationary units along the road, termed road-side



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   units (RSUs), form an ad hoc network.  An OBU is at least equipped
   with a (short range) wireless communication device based on draft
   standard IEEE 802.11p [9] (adapted to European conditions and with
   specific C2C-C extensions) primarily dedicated for road safety, and
   potentially with other optional communication devices.  OBUs directly
   communicate if wireless connectivity exist among them.  In case of no
   direct connectivity, multi-hop communication is used, where data is
   forwarded from one OBU to another, until it reaches its destination.
   For example in Figure 1, RSU and OBU1 have direct connectivity,
   whereas OBU2 is out of RSU radio coverage but can communicate with it
   through multi-hop routing.

   The primary role of an RSU is improvement of road safety.  RSUs have
   two possible configuration modes: as isolated nodes, they execute
   applications and/or extend the coverage of the ad hoc network
   implementing routing functionalities.  As attachment point connected
   to an infrastructure network, RSUs distribute information originated
   in the infrastructure and offer connectivity to the vehicles.  As
   result, for example, the latter configuration allows AUs registered
   with an OBU to communicate with any host located in the Internet,
   when at least one RSU connected to a network infrastructure is
   available.

   An OBU may also be equipped with alternative wireless technologies
   for both, safety and non-safety.  For example, an OBU may also
   communicate with Internet nodes or servers via public WLAN hot spots
   (PHS) operated individually or by wireless Internet service
   providers.  While RSUs for Internet access are typically set up with
   a controlled process by a C2C-C key stake holder, such as road
   administrators or other public authorities, public hot spots are
   usually set up in a less controlled environment.  These two types of
   infrastructure access, RSU and PHS, also correspond to different
   applications types.  Other communication technology, such as wide
   coverage/cellular networks (e.g.  UMTS, GPRS) may also be optionally
   installed in OBUs, but their usage is currently considered out of
   scope of the C2C-CC Consortium.

   The C2C-CC commonly refers to two main communication modes:

   o  in Vehicle-to-Vehicle (V2V) mode, data packets are exchanged
      directly between OBUs, either via multi-hop or not, without
      involving any RSU;

   o  in Vehicle-to-Infrastructure mode (V2I), an OBU exchanges data
      packets through a RSU with an arbitrary node connected to the
      infrastructure (potentially another vehicle not attached to the
      same RSU).




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3.2.  Current Protocol Architecture

   The protocol stack currently considered by C2C-CC for OBUs is
   depicted in Figure 2.

               +--------------------+------------------+
               |                    |                  |
               |       C2C-CC       |     IP-based     |
               |    Applications    |   Applications   |
               |                    |                  |
               +--------------------+------------------+
               |                    |    TCP/UDP/...   |
               |  C2C-CC Transport  +------------------+
               |                    |                  |
               +--------------------+-----+    IPv6    |
               |                          |            |
               |      C2C-CC Network      |            |
               |                          |            |
               +--------------------+-----+------------+
               |      Modified      |  Standard WLAN   |
               |    IEEE 802.11p    | IEEE 802.11a/b/g |
               +--------------------+------------------+

                       Figure 2: OBU Protocol Stack

   Protocol blocks are explained in the following list:

   o  Modified IEEE 802.11p: this block represents MAC and PHY layers of
      a wireless technology based upon current draft standard IEEE
      802.11p [9] but modified for usage in Europe.  In Europe,
      allocation of dedicated frequencies around 5.9 GHz for safety and
      non-safety applications is in progress.  Expected communication
      range in line of sight is around 500m.  This network interface is
      mandatory.

   o  IEEE 802.11a/b/g: this block represents MAC and PHY layers
      provided by one ore more IEEE 802.11a/b/g network interfaces.
      This network interface is optional but C2C-C Consortium encourages
      its installation.

   o  C2C-CC Network: this block represents the network layer protocol
      currently defined by C2C-CC.  The protocol provides secure ad hoc
      routing and forwarding, as well as addressing, error handling,
      packet sequencing, congestion control and efficient information
      dissemination.  The specification of this protocol is currently
      under discussion.  Only the C2C-CC Network protocol can access the
      Modified IEEE 802.11p network interface.  The C2C-CC Network
      protocol can also access the IEEE 802.11a/b/g interface.  The



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      C2C-CC Network protocol offers an interface to the IPv6 protocol.
      This interface allows IPv6 headers and payload to be encapsulated
      into C2C-CC Network datagrams and sent over the Modified IEEE
      802.11p or IEEE 802.11a/b/g network interface.  The specification
      of this interface is currently under discussion.  A primary goal
      of the C2C-CC Network layer is to provide geographic routing and
      addressing functionalities for cooperative safety applications.
      Through the mentioned interface to the IPv6 protocol, these
      functionalities are also available for IP-based applications.

   o  C2C-CC Transport: this block represents the transport layer
      protocol currently defined by C2C-CC.  This protocol provides a
      selected set of traditional transport layer functionalities (e.g.
      application data multiplexing/demultiplexing, connection
      establishment, reliability etc.).  The specification of this
      protocol is currently under discussion.

   o  C2C-CC Applications: this block represents the application layer
      protocol currently defined by C2C-CC and concerns Active Safety
      and Traffic Efficiency Applications.

3.3.  Interaction with IPv6

   As described in Section 3.2, the C2C-CC includes IPv6 as mandatory
   part of its specified protocol architecture.  Currently, three
   methods are discussed for transmission of IPv6 headers and their
   payload:

   o  On the Modified IEEE 802.11p interface via the C2C-CC Network
      layer: in this method, IPv6 headers are encapsulated into C2C-CC
      Network headers and sent using dedicated frequencies for inter-
      vehicle communications.  As the C2C-CC Network layer transparently
      provides ad hoc routing, from the IPv6 layer perspective other
      nodes (OBUs and RSU) are attached to the same link.  With respect
      to a currently adopted terminology, introduced in [10], the C2C-C
      Consortium approach for usage of NEMO on the Modified IEEE 802.11p
      is fully MANET-Centric, in the sense that the protocol layer below
      IPv6 provides routing and forwarding in the ad hoc network, with
      the result that the ad hoc nature of VANETs is hidden from upper
      layers.  A comparison of approaches for VANETs can be found in
      [11].  The deployability of this method strongly depends on the
      future availability of dedicated frequencies for non-safety
      purposes in inter-vehicle communications.  If frequencies for this
      purpose will not be allocated, only the left part of the protocol
      stack of Figure 2 can access the Modified IEEE 802.11p interface.

   o  On the IEEE 802.11a/b/g interface via the C2C-CC Network layer: in
      this method, IPv6 headers are encapsulated into C2C-CC Network



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      headers and sent using license-free ISM frequency bands (wireless
      LAN).  Except the network interface, this method is equivalent to
      the previous one.

   o  On the IEEE 802.11a/b/g interface directly: in this method, IPv6
      headers are sent directly to the wireless LAN interface as
      specified by [5].

   The following informational list briefly summarizes currently
   discussed design concepts:

   o  vehicles use only IPv6 addresses with as host part an EUI-64
      identifier derived from the MAC address.  Privacy issues described
      in [4] are strongly alleviated through the use of temporary,
      changing MAC addresses, which are assigned in a set to every
      vehicle (as part of their assigned "pseudonyms");

   o  when a RSU connected to a network infrastructure is available, an
      OBU configures a globally routable Care-of Address using stateless
      address configuration;

   o  when infrastructure access is not available, OBUs use addresses
      with as prefix part a predefined IPv6 prefix reserved for C2C-C
      communications (TBD);

   o  RSU can either act as IPv6 Access Routers or as network bridges
      connected to external IPv6 Access Routers.  Different Access
      Routers are responsible for announcing different network prefixes
      with global validity.  As a consequence, when roaming between
      different Access Routers, vehicles experience layer 3 handovers.

   In all the methods for use of IPv6 in C2C-C systems as described
   above, the IPv6 layer is meant to be enhanced with Mobility Support.
   As a vehicle includes a set of attached devices (AUs), Network
   Mobility seems the most appropriate solution, allowing for a
   centralized management of mobility to be executed in OBUs.


4.  Scope of NEMO

   In VANETs based on IEEE 802.11 family, a limited amount of bandwidth
   is shared among a potentially high number of vehicles.  Additionally
   applications for safety purposes have strict requirements in terms of
   delay, information dissemination and aggregation and secure ad hoc
   routing.  This conflicting conditions have led research activities to
   consider different approaches compared with traditional, packet-
   centric network engineering.  In particular, only through a more
   information-centric approach it seems possible to achieve



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   functionalities like geographic distribution, information
   dissemination according to relevance, information aggregation using
   cross-layer analysis, plausibility checks at different protocol
   layers.

   Taking these aspects into consideration, the C2C-C Consortium is
   defining a protocol stack mainly dedicated for vehicular safety
   communications.  Applications that are not subject to these
   particular requirements must use the right part of the protocol stack
   of Figure 2.  This implies that the usage of NEMO in vehicular
   communications does not target safety-of-life applications but rather
   less restrictive, non-safety applications.

   Another important aspect for deployability is related to costs.  A
   primary goal of the C2C-C Consortium is to achieve a spread diffusion
   in terms of vehicles equipped with communication devices and
   protocols.  This implies that vehicles of different brands and
   classes should be equipped by default with a basic communication
   system, whereas differentiation of products can be achieved by
   offering additional services.  NEMO, like any other solution based on
   IP Mobility support, relies on a service provider that guarantees
   global reachability at the Home Network Prefix by maintaining an Home
   Agent.  As it does not seem realistic that every car owner will also
   subscribe for such a service, a set of limited applications based on
   IPv6 should be available even without Mobility Support.  Therefore,
   NEMO modularity and interoperability with non-NEMO equipped vehicles
   has to be guaranteed.


5.  Example Use Cases

   In this section, the main use cases are listed that have been
   identified by the C2C-CC for usage of NEMO in inter-vehicle
   communications: notification services, peer-to-peer applications and
   upload/download services.

5.1.  Notification Services

   A generic notification service delivers information to subscribers by
   means of the Internet.  After subscribing the service with a
   provider, a user is notified when updates are available.  Example
   services are weather, traffic or news reports, as well as commercial
   and technical information from the car producer or other companies.

   As the network address of a vehicle changes while the vehicle moves
   among different points of attachment, each application should
   register the new address in order to receive information at the
   correct location.  Service providers need to update continuously the



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   subscription data and are able to track the users.  Adopting global
   reachability at a reasonably constant identifier (e.g.  Mobile
   Network Prefix), efficiency and location privacy improve
   considerably.

5.2.  Peer-to-peer Applications

   A generic peer-to-peer application exchanges data directly between
   vehicles, without contacting any application server.  Data traffic
   goes through a network infrastructure (V2I) or directly between cars
   when the infrastructure is not available (V2V).  Example applications
   are vehicle-to-vehicle instant messaging (chat) and off-line
   messaging (peer-to-peer email), vehicle-to-vehicle voice over IP and
   file exchange.

   In this set of use cases, the same applications should be able to run
   in V2V and V2I mode.  As applications should not be aware of routing
   nor addressing issues, they should use the same identifier for
   sessions and users (e.g. cars/drivers/passengers) independently of
   the communications mode.  Possible approaches are either to adopt
   resolution mechanisms or actually maintain the same network
   identifier in both V2V and V2I modes.  This could be achieved for
   example generalizing the concept of Mobile Network Prefix (MNP) and
   allowing a Mobile Router (OBU) to use it for V2V communications in
   absence of attachment points.  By means of enforcing limited lifetime
   for IPv6 prefixes and due to the isolation of VANET clusters from the
   infrastructure (in V2V), this use of MNP should not introduce routing
   inconsistencies.

5.3.  Upload and Download Services

   A generic upload/download service via the Internet consists in simple
   file exchange procedures with servers located in the Internet.

   As in vehicular scenarios the connectivity to the infrastructure is
   highly intermittent, network address' changes cause applications to
   re-establish sessions in order to resume the exchange, which implies
   considerable overhead.  Session re-establishment can be avoided
   adopting NEMO.


6.  Requirements

   The C2C-C Consortium has identified the following requirements for a
   NEMO solution for vehicular communications, with respect to the
   referred use cases.





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6.1.  V2V and V2I Communication Modes

   A vehicle equipped only with a Modified IEEE 802.11p interface can
   use V2V and V2I communication modes for IP-based applications running
   in an OBU or in attached AUs.  In other words, an OBU and the AUs
   attached to it are able to exchange IP packets with a node in the
   Internet (when a RSU connected to a network infrastructure is
   available), indirectly via a not connected RSU, or directly with
   other OBUs and AUs, even if a RSU is not available.

6.2.  Same Identifiers for V2V and V2I

   Vehicles and in-vehicle networks attached to are reachable at
   identifiers (e.g.  Mobile Network Prefix) that do not change
   frequently and can be used both when the infrastructure is available
   (V2I, e.g. through an Home Agent) and to communicate directly when
   infrastructure is not available (V2V).

6.3.  Security

   As data security is mandatory for safety applications targeted by the
   C2C-C Consortium and implemented in the left part of the protocol
   stack depicted in Figure 2, any IP-based application must not
   introduce new security leaks for the C2C-CC applications or render
   their security measures ineffective.  Further details can not be
   provided at this point of time because solutions for security in the
   C2C-CC protocol stack are still under discussion.  As informational
   references, see [13], [14] and [15].

6.4.  Privacy

   Privacy of drivers and passengers is mandatory for safety
   applications targeted by the C2C-C Consortium.  Mechanisms to
   implement privacy in the left part of the protocol stack depicted in
   Figure 2 are currently discussed (e.g. "revocable pseudonimity",
   where pre-assigned, quasi-random and changing pseudonyms are used as
   layer 2 and 2.5 identifiers).  Therefore any IP-based application
   must not allow for linking changed pseudonyms by sending constant
   identifiers as clear text.  In particular, encryption of Home Address
   and Mobile Network Prefix in NEMO signaling should be mandatory in
   VANETs and not optional as described in [3].  Furthermore, direct V2V
   communication mode without the infrastructure using a constant MNP
   might introduce the possibility to track vehicles.  Further details
   can not be provided at this point of time because solutions for
   privacy in the C2C-CC protocol stack are still under discussion.  As
   informational reference, see [12].





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7.  IANA Considerations

   This document does not require any IANA action.


8.  Security Considerations

   This document defines requirements and therefore does not create any
   security threat.  However, it mentions security and privacy issues in
   VANETs as currently discussed in the C2C-C Consortium.


9.  Acknowledgments

   The authors would like to thank the members of the work groups PHY/
   MAC/NET and APP of the C2C-C Consortium and in particular Andras
   Kovacs, Bernd Bochow and Matthias Roeckl for supporting and
   commenting this document.


10.  References

10.1.  Normative References

   [1]   Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
         "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
         January 2005.

   [2]   Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

   [3]   Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
         Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
         Agents", RFC 3776, June 2004.

   [4]   Narten, T. and R. Draves, "Privacy Extensions for Stateless
         Address Autoconfiguration in IPv6", RFC 3041, January 2001.

   [5]   Crawford, M., "Transmission of IPv6 Packets over Ethernet
         Networks", RFC 2464, December 1998.

   [6]   Ernst, T. and H. Lach, "Network Mobility Support Terminology",
         draft-ietf-nemo-terminology-06 (work in progress),
         November 2006.







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10.2.  Informative References

   [7]   "Car2Car Communication Consortium Official Website",
         http://www.car-2-car.org/ .

   [8]   "Car2Car Communication Consortium Handbook", work in progress,
         February 2007.

   [9]   "Draft Amendment to Standard for Information Technology .
         Telecommunications and information exchange between systems .
         Local and Metropolitan networks . specific requirements - Part
         11: Wireless LAN Medium Access Control (MAC) and Physical Layer
         (PHY) specifications: Amendment 3: Wireless Access in Vehicular
         Environments (WAVE)", IEEE P802.11p/D1.0, February 2006.

   [10]  McCarthy, B., Edwards, C., Dunmore, M., and R. Aguiar, "The
         Integration of Ad-hoc (MANET) and Mobile Networking (NEMO):
         Principles to Support Rescue Team Communication", Proc. of
         International Conference on Mobile Computing and Ubiquitous
         Networking (ICMU 2006), October 2006.

   [11]  Baldessari, R., Festag, A., and J. Abeille, "NEMO meets VANET:
         A Deployability Analysis of Network Mobility in Vehicular
         Communication", Under submission, February 2007.

   [12]  Fonseca, E., Festag, A., Baldessari, R., and R. Aguiar,
         "Support of Anonymity in VANETs - Putting Pseudonymity into
         Practice", To appear in Proc.of IEEE Wireless Communication and
         Networking  Conference (WCNC2007), March 2007.

   [13]  Raya, M. and J. Hubaux, "The Security of Vehicular Ad Hoc
         Networks", Proc.of Workshop on Security of Ad Hoc and Sensor
         Networks (SASN2005), November 2005.

   [14]  Aijaz, A., Bochow, B., Doetzer, F., Festag, A., Gerlach, M.,
         Leinmueller, T., and R. Kroh, "Attacks on Inter Vehicle
         Communication Systems - an Analysis", Proc.of International
         Workshop on  Intelligent Transportation (WIT2006), March 2006.

   [15]  Fonseca, E. and A. Festag, "A Survey of Existing Approaches for
         Secure Ad Hoc Routing and Their Applicability to VANETS", NEC
         Technical Report NLE-PR-2006-19, March 2006.









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Authors' Addresses

   Roberto Baldessari
   NEC Europe Network Laboratories
   Kurfuersten-anlage 36
   Heidelberg  69115
   Germany

   Phone: +49 6221 4342167
   Email: roberto.baldessari@netlab.nec.de


   Andreas Festag
   NEC Deutschland GmbH
   Kurfuersten-anlage 36
   Heidelberg  69115
   Germany

   Phone: +49 6221 4342147
   Email: andreas.festag@netlab.nec.de


   Massimiliano Lenardi
   Hitachi Europe SAS Sophia Antipolis Laboratory
   Immeuble Le Theleme
   1503 Route des Dolines
   Valbonne  F-06560
   France

   Phone: +33 489 874168
   Email: massimiliano.lenardi@hitachi-eu.com




















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