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Versions: 00 01 02 03 04 05 06 draft-ietf-ipwave-ipv6-over-80211ocb

Network Working Group                                        A. Petrescu
Internet-Draft                                                 CEA, LIST
Intended status: Standards Track                              N. Benamar
Expires: June 3, 2017                           Moulay Ismail University
                                                               J. Haerri
                                                                 Eurecom
                                                              C. Huitema

                                                                  J. Lee
                                                    Sangmyung University
                                                                T. Ernst
                                                                  YoGoKo
                                                                   T. Li
                                                      Peloton Technology
                                                       November 30, 2016


 Transmission of IPv6 Packets over IEEE 802.11 Outside the Context of a
                        Basic Service Set (OCB)
                 draft-petrescu-ipv6-over-80211p-06.txt

Abstract

   In order to transmit IPv6 packets on IEEE 802.11 networks run outside
   the context of a basic service set (OCB, earlier "802.11p") there is
   a need to define a few parameters such as the recommended Maximum
   Transmission Unit size, the header format preceding the IPv6 header,
   the Type value within it, and others.  This document describes these
   parameters for IPv6 and IEEE 802.11 OCB networks; it portrays the
   layering of IPv6 on 802.11 OCB similarly to other known 802.11 and
   Ethernet layers - by using an Ethernet Adaptation Layer.

   In addition, the document attempts to list what is different in
   802.11 OCB (802.11p) compared to more 'traditional' 802.11a/b/g/n
   layers, layers over which IPv6 protocols operates without issues.
   Most notably, the operation outside the context of a BSS (OCB) has
   impact on IPv6 handover behaviour and on IPv6 security.

   An example of an IPv6 packet captured while transmitted over an IEEE
   802.11 OCB link (802.11p) is given.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute



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   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 3, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Communication Scenarios where IEEE 802.11p Links are Used . .   6
   4.  Aspects introduced by the OCB mode to 802.11  . . . . . . . .   6
   5.  Layering of IPv6 over 802.11p as over Ethernet  . . . . . . .   9
     5.1.  Maximum Transmission Unit (MTU) . . . . . . . . . . . . .   9
     5.2.  Frame Format  . . . . . . . . . . . . . . . . . . . . . .  10
       5.2.1.  Ethernet Adaptation Layer . . . . . . . . . . . . . .  11
     5.3.  Link-Local Addresses  . . . . . . . . . . . . . . . . . .  13
     5.4.  Address Mapping . . . . . . . . . . . . . . . . . . . . .  13
       5.4.1.  Address Mapping -- Unicast  . . . . . . . . . . . . .  13
       5.4.2.  Address Mapping -- Multicast  . . . . . . . . . . . .  13
     5.5.  Stateless Autoconfiguration . . . . . . . . . . . . . . .  14
     5.6.  Subnet Structure  . . . . . . . . . . . . . . . . . . . .  15
   6.  Handovers between OCB links . . . . . . . . . . . . . . . . .  15
   7.  Example IPv6 Packet captured over a IEEE 802.11p link . . . .  17
     7.1.  Capture in Monitor Mode . . . . . . . . . . . . . . . . .  18
     7.2.  Capture in Normal Mode  . . . . . . . . . . . . . . . . .  21
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  24
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  24



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   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  24
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     12.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Appendix A.  ChangeLog  . . . . . . . . . . . . . . . . . . . . .  29
   Appendix B.  Explicit Prohibition of IPv6 on Channels
                Related to ITS Scenarios using 802.11p Networks
                - an Analysis  . . . . . . . . . . . . . . . . . . .  31
     B.1.  Interpretation of FCC and ETSI documents             with
           respect to running IP on particular channels  . . . . . .  31
     B.2.  Interpretations of Latencies of IP datagrams  . . . . . .  33
   Appendix C.  Changes Needed on a software driver 802.11a to
                become a                       802.11-OCB driver . .  33
   Appendix D.  Design Considerations  . . . . . . . . . . . . . . .  34
     D.1.  Vehicle ID  . . . . . . . . . . . . . . . . . . . . . . .  34
     D.2.  Non IP Communications . . . . . . . . . . . . . . . . . .  35
     D.3.  Reliability Requirements  . . . . . . . . . . . . . . . .  36
     D.4.  Privacy requirements  . . . . . . . . . . . . . . . . . .  36
     D.5.  Authentication requirements . . . . . . . . . . . . . . .  37
     D.6.  Multiple interfaces . . . . . . . . . . . . . . . . . . .  38
     D.7.  MAC Address Generation  . . . . . . . . . . . . . . . . .  38
     D.8.  Security Certificate Generation . . . . . . . . . . . . .  39
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  39

1.  Introduction

   This document describes the transmission of IPv6 packets on IEEE Std
   802.11 OCB networks (earlier known as 802.11p).  This involves the
   layering of IPv6 networking on top of the IEEE 802.11 MAC layer (with
   an LLC layer).  Compared to running IPv6 over the Ethernet MAC layer,
   there is no modification required to the standards: IPv6 works fine
   directly over 802.11 OCB too (with an LLC layer).

   The term "802.11p" is an earlier definition.  As of year 2012, the
   behaviour of "802.11p" networks has been rolled in the document IEEE
   Std 802.11-2012.  In this document the term 802.11p disappears.
   Instead, each 802.11p feature is conditioned by a flag in the
   Management Information Base.  That flag is named "OCBActivated".
   Whenever OCBActivated is set to true the feature it relates to
   represents an earlier 802.11p feature.  For example, an 802.11
   STAtion operating outside the context of a basic service set has the
   OCBActivated flag set.  Such a station, when it has the flag set, it
   uses a BSS identifier equal to ff:ff:ff:ff:ff:ff.

   In the following text we use the term "802.11p" to mean 802.11-2012
   OCB, and vice-versa.





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   As an overview, we illustrate how an IPv6 stack runs over 802.11p by
   layering different protocols on top of each other.  The IPv6
   Networking is layered on top of the IEEE 802.2 Logical-Link Control
   (LLC) layer; this is itself layered on top of the 802.11p MAC; this
   layering illustration is similar to that of running IPv6 over 802.2
   LLC over the 802.11 MAC, or over Ethernet MAC.


                          +-----------------+      +-----------------+
                          |       ...       |      |       ...       |
                          +-----------------+      +-----------------+
                          | IPv6 Networking |      | IPv6 Networking |
                          +-----------------+      +-----------------+
                          |    802.2 LLC    |  vs. |    802.2 LLC    |
                          +-----------------+      +-----------------+
                          |   802.11p MAC   |      |   802.11b MAC   |
                          +-----------------+      +-----------------+
                          |   802.11p PHY   |      |   802.11b PHY   |
                          +-----------------+      +-----------------+


   However, there are several deployment considerations to optimize the
   performances of running IPv6 over 802.11p (e.g. in the case of
   handovers between 802.11p Access Points, or the consideration of
   using the IP security layer).

   We briefly introduce the vehicular communication scenarios where IEEE
   802.11-OCB links are used.  This is followed by a description of
   differences in specification terms, between 802.11p and 802.11a/b/g/n
   (and the same differences expressed in terms of requirements to
   software implementation are listed in Appendix C.)

   The document then concentrates on the parameters of layering IP over
   802.11p as over Ethernet: MTU, Frame Format, Interface Identifier,
   Address Mapping, State-less Address Auto-configuration.  The values
   of these parameters are precisely the same as IPv6 over Ethernet
   [RFC2464]: the recommended value of MTU to be 1500 octets, the Frame
   Format containing the Type 0x86DD, the rules for forming an Interface
   Identifier, the Address Mapping mechanism and the Stateless Address
   Auto-Configuration.

   As an example, these characteristics of layering IPv6 straight over
   LLC over 802.11p MAC are illustrated by dissecting an IPv6 packet
   captured over a 802.11p link; this is described in the section titled
   "Example of IPv6 Packet captured over an IEEE 802.11p link".

   A couple of points can be considered as different, although they are
   not required in order to have a working implementation of IPv6-over-



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   802.11p.  These points are consequences of the OCB operation which is
   particular to 802.11p (Outside the Context of a BSS).  First, the
   handovers between OCB links need specific behaviour for IP Router
   Advertisements, or otherwise 802.11p's Time Advertisement, or of
   higher layer messages such as the 'Basic Safety Message' (in the US)
   or the 'Cooperative Awareness Message' (in the EU) or the 'WAVE
   Routing Advertisement'; second, the IP security mechanisms are
   necessary, since OCB means that 802.11p is stripped of all 802.11
   link-layer security; a small additional security aspect which is
   shared between 802.11p and other 802.11 links is the privacy concerns
   related to the address formation mechanisms.  The OCB handovers and
   security are described each in section Section 6 and Section 8
   respectively.

   In standards, the operation of IPv6 as a 'data plane' over 802.11p is
   specified at IEEE P1609 in [ieeep1609.3-D9-2010].  For example, it
   mentions that "Networking services also specifies the use of the
   Internet protocol IPv6, and supports transport protocols such as UDP
   and TCP. [...]  A Networking Services implementation shall support
   either IPv6 or WSMP or both." and "IP traffic is sent and received
   through the LLC sublayer as specified in [...]".  The layered stacks
   depicted in the "Architecture" document P1609.0 [ieeep1609.0-D2]
   suggest that WSMP messages may not be transmitted as payload of IPv6
   datagrams; WSMP and IPv6 are parallel (not stacked) layers.

   Also, the operation of IPv6 over a GeoNetworking layer and over G5 is
   described in [etsi-302663-v1.2.1p-2013].

   In the published literature, three documents describe aspects related
   to running IPv6 over 802.11p: [vip-wave], [ipv6-80211p-its] and
   [ipv6-wave].

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   RSU: Road Side Unit.

   OCB: Outside the Context of a Basic Service Set identifier.

   OCB - Outside the Context of a Basic-Service Set ID (BSSID).

   802.11-OCB - IEEE 802.11-2012 text flagged by "dot11OCBActivated".
   This means: IEEE 802.11e for quality of service; 802.11j-2004 for
   half-clocked operations; and 802.11p for operation in the 5.9 GHz
   band and in mode OCB.



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3.  Communication Scenarios where IEEE 802.11p Links are Used

   The IEEE 802.11p Networks are used for vehicular communications, as
   'Wireless Access in Vehicular Environments'.  The IP communication
   scenarios for these environments have been described in several
   documents, among which we refer the reader to one recently updated
   [I-D.petrescu-its-scenarios-reqs], about scenarios and requirements
   for IP in Intelligent Transportation Systems.

4.  Aspects introduced by the OCB mode to 802.11

   In the IEEE 802.11 OCB mode, all nodes in the wireless range can
   directly communicate with each other without authentication/
   association procedures.  Briefly, the IEEE 802.11 OCB mode has the
   following properties:

   o  Wildcard BSSID (i.e., all bits are set to 1) used by each node

   o  No beacons transmitted

   o  No authentication required

   o  No association needed

   o  No encryption provided

   o  dot11OCBActivated OID set to true

   The link 802.11p is specified in IEEE Std 802.11p(TM)-2010
   [ieee802.11p-2010] as an amendment to the 802.11 specifications,
   titled "Amendment 6: Wireless Access in Vehicular Environments".
   Since then, these 802.11p amendments have been included in IEEE
   802.11(TM)-2012 [ieee802.11-2012], titled "IEEE Standard for
   Information technology--Telecommunications and information exchange
   between systems Local and metropolitan area networks--Specific
   requirements Part 11: Wireless LAN Medium Access Control (MAC) and
   Physical Layer (PHY) Specifications"; the modifications are diffused
   throughout various sections (e.g. 802.11p's Time Advertisement
   message is described in section 'Frame formats', and the operation
   outside the context of a BSS described in section 'MLME').

   In document 802.11-2012, specifically anything referring
   "OCBActivated", or "outside the context of a basic service set" is
   actually referring to the 802.11p aspects introduced to 802.11.  Note
   in earlier 802.11p documents the term "OCBEnabled" was used instead.

   In order to delineate the aspects introduced by 802.11p to 802.11, we
   refer to the earlier [ieee802.11p-2010].  The amendment is concerned



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   with vehicular communications, where the wireless link is similar to
   that of Wireless LAN (using a PHY layer specified by 802.11a/b/g/n),
   but which needs to cope with the high mobility factor inherent in
   scenarios of communications between moving vehicles, and between
   vehicles and fixed infrastructure deployed along roads.  While 'p' is
   a letter just like 'a, b, g' and 'n' are, 'p' is concerned more with
   MAC modifications, and a little with PHY modifications; the others
   are mainly about PHY modifications.  It is possible in practice to
   combine a 'p' MAC with an 'a' PHY by operating outside the context of
   a BSS with OFDM at 5.4GHz.

   The 802.11p links are specified to be compatible as much as possible
   with the behaviour of 802.11a/b/g/n and future generation IEEE WLAN
   links.  From the IP perspective, an 802.11p MAC layer offers
   practically the same interface to IP as the WiFi and Ethernet layers
   do (802.11a/b/g/n and 802.3).

   To support this similarity statement (IPv6 is layered on top of LLC
   on top of 802.11p similarly as on top of LLC on top of 802.11a/b/g/n,
   and as on top of LLC on top of 802.3) it is useful to analyze the
   differences between 802.11p and non-p 802.11 specifications.  Whereas
   the 802.11p amendment specifies relatively complex and numerous
   changes to the MAC layer (and very little to the PHY layer), we note
   there are only a few characteristics which may be important for an
   implementation transmitting IPv6 packets on 802.11p links.

   In the list below, the only 802.11p fundamental points which
   influence IPv6 are the OCB operation and the 12Mbit/s maximum which
   may be afforded by the IPv6 applications.

   o  Operation Outside the Context of a BSS (OCB): the 802.11p links
      are operated without a Basic Service Set (BSS).  This means that
      the messages Beacon, Association Request/Response, Authentication
      Request/Response, and similar, are not used.  The used identifier
      of BSS (BSSID) has a hexadecimal value always ff:ff:ff:ff:ff:ff
      (48 '1' bits, or the 'wildcard' BSSID), as opposed to an arbitrary
      BSSID value set by administrator (e.g.  'My-Home-AccessPoint').
      The OCB operation - namely the lack of beacon-based scanning and
      lack of authentication - has a potentially strong impact on the
      use of the Mobile IPv6 protocol and on the protocols for IP layer
      security.

   o  Timing Advertisement: is a new message defined in 802.11p, which
      does not exist in 802.11a/b/g/n.  This message is used by stations
      to inform other stations about the value of time.  It is similar
      to the time as delivered by a GNSS system (Galileo, GPS, ...) or
      by a cellular system.  This message is optional for
      implementation.  At the date of writing, an experienced reviewer



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      considers that currently no field testing has used this message.
      Another implementor considers this feature implemented in an
      initial manner.  In the future, it is speculated that this message
      may be useful for very simple devices which may not have their own
      hardware source of time (Galileo, GPS, cellular network), or by
      vehicular devices situated in areas not covered by such network
      (in tunnels, underground, outdoors but shaded by foliage or
      buildings, in remote areas, etc.)

   o  Frequency range: this is a characteristic of the PHY layer, with
      almost no impact to the interface between MAC and IP.  However, it
      is worth considering that the frequency range is regulated by a
      regional authority (ARCEP, ETSI, FCC, etc.); as part of the
      regulation process, specific applications are associated with
      specific frequency ranges.  In the case of 802.11p, the regulator
      associates a set of frequency ranges, or slots within a band, to
      the use of applications of vehicular communications, in a band
      known as "5.9GHz".  This band is "5.9GHz" which is different from
      the bands "2.4GHz" or "5GHz" used by Wireless LAN.  However, as
      with Wireless LAN, the operation of 802.11p in "5.9GHz" bands is
      exempt from owning a license in EU (in US the 5.9GHz is a licensed
      band of spectrum; for the the fixed infrastructure an explicit FCC
      autorization is required; for an onboard device a 'licensed-by-
      rule' concept applies: rule certification conformity is required);
      however technical conditions are different than those of the bands
      "2.4GHz" or "5GHz".  On one hand, the allowed power levels, and
      implicitly the maximum allowed distance between vehicles, is of
      33dBm for 802.11p (in Europe), compared to 20 dBm for Wireless LAN
      802.11a/b/g/n; this leads to a maximum distance of approximately
      1km, compared to approximately 50m.  On the hand, specific
      conditions related to congestion avoidance, jamming avoidance, and
      radar detection are imposed on the use of DSRC (in US) and on the
      use of frequencies for Intelligent Transportation Systems (in EU),
      compared to Wireless LAN (802.11a/b/g/n).

   o  Explicit prohibition of IPv6 on some channels relevant for the PHY
      of IEEE 802.11p, as opposed to IPv6 not being prohibited on any
      channel on which 802.11a/b/g/n runs; for example, IPv6 is
      prohibited on the 'Control Channel' (number 178 at FCC/IEEE, and
      180 at ETSI); for a detailed analysis of IEEE and ETSI prohibition
      of IP in particular channels see Appendix B.

   o  'Half-rate' encoding: as the frequency range, this parameter is
      related to PHY, and thus has not much impact on the interface
      between the IP layer and the MAC layer.  The standard IEEE 802.11p
      uses OFDM encoding at PHY, as other non-b 802.11 variants do.
      This considers 20MHz encoding to be 'full-rate' encoding, as the
      earlier 20MHz encoding which is used extensively by 802.11b.  In



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      addition to the full-rate encoding, the OFDM rates also involve
      5MHz and 10MHz.  The 10MHz encoding is named 'half-rate'.  The
      encoding dictates the bandwidth and latency characteristics that
      can be afforded by the higher-layer applications of IP
      communications.  The half-rate means that each symbol takes twice
      the time to be transmitted; for this to work, all 802.11 software
      timer values are doubled.  With this, in certain channels of the
      "5.9GHz" band, a maximum bandwidth of 12Mbit/s is possible,
      whereas in other "5.9GHz" channels a minimal bandwidth of 1Mbit/s
      may be used.  It is worth mentioning the half-rate encoding is an
      optional feature characteristic of OFDM PHY (compared to 802.11b's
      full-rate 20MHz), used by 802.11a before 802.11p used it.  In
      addition to the half-rate (10MHz) used by 802.11p in some
      channels, some other 802.11p channels may use full-rate (20MHz) or
      quarter-rate(?) (5MHz) encoding instead.

   o  It is worth mentioning that more precise interpretations of the
      'half-rate' term suggest that a maximum throughput be 27Mbit/s
      (which is half of 802.11g's 54Mbit/s), whereas 6Mbit/s or 12Mbit/s
      throughputs represent effects of further 802.11p-specific PHY
      reductions in the throughput necessary to better accommodate
      vehicle-class speeds and distance ranges.

   o  In vehicular communications using 802.11p links, there are strong
      privacy concerns with respect to addressing.  While the 802.11p
      standard does not specify anything in particular with respect to
      MAC addresses, in these settings there exists a strong need for
      dynamic change of these addresses (as opposed to the non-vehicular
      settings - real wall protection - where fixed MAC addresses do not
      currently pose some privacy risks).  This is further described in
      section Section 8.

   Other aspects particular to 802.11p which are also particular to
   802.11 (e.g. the 'hidden node' operation) may have an influence on
   the use of transmission of IPv6 packets on 802.11p networks.  The
   subnet structure which may be assumed in 802.11p networks is strongly
   influenced by the mobility of vehicles.

5.  Layering of IPv6 over 802.11p as over Ethernet

5.1.  Maximum Transmission Unit (MTU)

   The default MTU for IP packets on 802.11p is 1500 octets.  It is the
   same value as IPv6 packets on Ethernet links, as specified in
   [RFC2464].  This value of the MTU respects the recommendation that
   every link in the Internet must have a minimum MTU of 1280 octets
   (stated in [RFC2460], and the recommendations therein, especially
   with respect to fragmentation).  If IPv6 packets of size larger than



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   1500 bytes are sent on an 802.11-OCB interface then the IP stack will
   fragment.  In case there are IP fragments, the field "Sequence
   number" of the 802.11 Data header containing the IP fragment field is
   increased.

   Non-IP packets such as WAVE Short Message Protocol (WSMP) can be
   delivered on 802.11-OCB links.  Specifications of these packets are
   out of scope of this document, and do not impose any limit on the MTU
   size, allowing an arbitrary number of 'containers'.  Non-IP packets
   such as ETSI 'geonet' packets have an MTU of 1492 bytes.

   The Equivalent Transmit Time on Channel is a concept that may be used
   as an alternative to the MTU concept.  A rate of transmission may be
   specified as well.  The ETTC, rate and MTU may be in direct
   relationship.

5.2.  Frame Format

   IP packets are transmitted over 802.11p as standard Ethernet packets.
   As with all 802.11 frames, an Ethernet adaptation layer is used with
   802.11p as well.  This Ethernet Adaptation Layer 802.11-to-Ethernet
   is described in Section 5.2.1.  The Ethernet Type code (EtherType)
   for IPv6 is 0x86DD (hexadecimal 86DD, or otherwise #86DD).

   The Frame format for transmitting IPv6 on 802.11p networks is the
   same as transmitting IPv6 on Ethernet networks, and is described in
   section 3 of [RFC2464].  The frame format for transmitting IPv6
   packets over Ethernet is illustrated below:























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                         0                   1
                         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         |          Destination          |
                         +-                             -+
                         |            Ethernet           |
                         +-                             -+
                         |            Address            |
                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         |             Source            |
                         +-                             -+
                         |            Ethernet           |
                         +-                             -+
                         |            Address            |
                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         |1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1|
                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         |             IPv6              |
                         +-                             -+
                         |            header             |
                         +-                             -+
                         |             and               |
                         +-                             -+
                         /            payload ...        /
                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         (Each tic mark represents one bit.)


5.2.1.  Ethernet Adaptation Layer

   In general, an 'adaptation' layer is inserted between a MAC layer and
   the Networking layer.  This is used to transform some parameters
   between their form expected by the IP stack and the form provided by
   the MAC layer.  For example, an 802.15.4 adaptation layer may perform
   fragmentation and reassembly operations on a MAC whose maximum Packet
   Data Unit size is smaller than the minimum MTU recognized by the IPv6
   Networking layer.  Other examples involve link-layer address
   transformation, packet header insertion/removal, and so on.

   An Ethernet Adaptation Layer makes an 802.11 MAC look to IP
   Networking layer as a more traditional Ethernet layer.  At reception,
   this layer takes as input the IEEE 802.11 Data Header and the
   Logical-Link Layer Control Header and produces an Ethernet II Header.
   At sending, the reverse operation is performed.







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            +--------------------+-------------+-------------+---------+
            | 802.11 Data Header | LLC Header  | IPv6 Header | Payload |
            +--------------------+-------------+-------------+---------+
                                    ^
                                    |
                                    802.11-to-Ethernet Adaptation Layer
                                    |
                                    v

            +---------------------+-------------+---------+
            | Ethernet II Header  | IPv6 Header | Payload |
            +---------------------+-------------+---------+


   The Receiver and Transmitter Address fields in the 802.11 Data Header
   contain the same values as the Destination and the Source Address
   fields in the Ethernet II Header, respectively.  The value of the
   Type field in the LLC Header is the same as the value of the Type
   field in the Ethernet II Header.

   When the MTU value is smaller than the size of the IP packet to be
   sent, the IP layer fragments the packet into multiple IP fragments.
   During this operation, the "Sequence number" field of the 802.11 Data
   Header is increased.

   In OCB mode, IPv6 packets can be transmitted either as "IEEE 802.11
   Data" or alternatively as "IEEE 802.11 QoS Data", as illustrated in
   the following figure:


            +--------------------+-------------+-------------+---------+
            | 802.11 Data Header | LLC Header  | IPv6 Header | Payload |
            +--------------------+-------------+-------------+---------+

                                       or

            +--------------------+-------------+-------------+---------+
            | 802.11 QoS Data Hdr| LLC Header  | IPv6 Header | Payload |
            +--------------------+-------------+-------------+---------+


   The distinction between the two formats is given by the value of the
   field "Type/Subtype".  The value of the field "Type/Subtype" in the
   802.11 Data header is 0x0020.  The value of the field "Type/Subtype"
   in the 802.11 QoS header is 0x0028.

   The mapping between qos-related fields in the IPv6 header (e.g.
   "Traffic Class", "Flow label") and fields in the "802.11 QoS Data



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   Header" (e.g.  "QoS Control") are not specified in this document.
   Guidance for a potential mapping is provided in
   [I-D.ietf-tsvwg-ieee-802-11], although it is not specific to OCB
   mode.

5.3.  Link-Local Addresses

   The link-local address of an 802.11p interface is formed in the same
   manner as on an Ethernet interface.  This manner is described in
   section 5 of [RFC2464].

5.4.  Address Mapping

   For unicast as for multicast, there is no change from the unicast and
   multicast address mapping format of Ethernet interfaces, as defined
   by sections 6 and 7 of [RFC2464].

5.4.1.  Address Mapping -- Unicast

5.4.2.  Address Mapping -- Multicast

   IPv6 protocols often make use of IPv6 multicast addresses in the
   destination field of IPv6 headers.  For example, an ICMPv6 link-
   scoped Neighbor Advertisement is sent to the IPv6 address ff02::1
   denoted "all-nodes" address.  When transmitting these packets on
   802.11-OCB links it is necessary to map the IPv6 address to a MAC
   address.

   The same mapping requirement applies to the link-scoped multicast
   addresses of other IPv6 protocols as well.  In DHCPv6, the
   "All_DHCP_Servers" IPv6 multicast address ff02::1:2, and in OSPF the
   "All_SPF_Routers" IPv6 multicast address ff02::5, need to be mapped
   on a multicast MAC address.

   An IPv6 packet with a multicast destination address DST, consisting
   of the sixteen octets DST[1] through DST[16], is transmitted to the
   IEEE 802.11-OCB MAC multicast address whose first two octets are the
   value 0x3333 and whose last four octets are the last four octets of
   DST.












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                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 |0 0 1 1 0 0 1 1|0 0 1 1 0 0 1 1|
                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 |   DST[13]     |   DST[14]     |
                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 |   DST[15]     |   DST[16]     |
                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   A Group ID TBD of length 112bits may be requested from IANA; this
   Group ID signifies "All 80211OCB Interfaces Address".  Only the least
   32 significant bits of this "All 80211OCB Interfaces Address" will be
   mapped to and from a MAC multicast address.

   Transmitting IPv6 packets to multicast destinations over 802.11 links
   proved to have some performance issues
   [I-D.perkins-intarea-multicast-ieee802].  These issues may be
   exacerbated in OCB mode.  Solutions for these problems should
   consider the OCB mode of operation.

5.5.  Stateless Autoconfiguration

   The Interface Identifier for an 802.11p interface is formed using the
   same rules as the Interface Identifier for an Ethernet interface;
   this is described in section 4 of [RFC2464].  No changes are needed,
   but some care must be taken when considering the use of the SLAAC
   procedure.

   The bits in the the interface identifier have no generic meaning and
   the identifier should be treated as an opaque value.  The bits
   'Universal' and 'Group' in the identifier of an 802.11p interface are
   significant, as this is a IEEE link-layer address.  The details of
   this significance are described in [I-D.ietf-6man-ug].

   As with all Ethernet and 802.11 interface identifiers ([RFC7721]),
   the identifier of an 802.11p interface may involve privacy risks.  A
   vehicle embarking an On-Board Unit whose egress interface is 802.11p
   may expose itself to eavesdropping and subsequent correlation of
   data; this may reveal data considered private by the vehicle owner.

   If stable Interface Identifiers are needed in order to form IPv6
   addresses on 802.11-OCB links, it is recommended to follow the
   recommendation in [I-D.ietf-6man-default-iids].








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5.6.  Subnet Structure

   The 802.11 networks in OCB mode may be considered as 'ad-hoc'
   networks.  The addressing model for such networks is described in
   [RFC5889].

6.  Handovers between OCB links

   A station operating IEEE 802.11p in the 5.9 GHz band in US or EU is
   required to send data frames outside the context of a BSS.  In this
   case, the station does not utilize the IEEE 802.11 authentication,
   association, or data confidentiality services.  This avoids the
   latency associated with establishing a BSS and is particularly suited
   to communications between mobile stations or between a mobile station
   and a fixed one playing the role of the default router (e.g. a fixed
   Road-Side Unit a.k.a RSU acting as an infrastructure router).

   The process of movement detection is described in section 11.5.1 of
   [RFC6275].  In the context of 802.11p deployments, detecting
   movements between two adjacent RSUs becomes harder for the moving
   stations: they cannot rely on Layer-2 triggers (such as L2
   association/de-association phases) to detect when they leave the
   vicinity of an RSU and move within coverage of another RSU.  In such
   case, the movement detection algorithms require other triggers.  We
   detail below the potential other indications that can be used by a
   moving station in order to detect handovers between OCB ("Outside the
   Context of a BSS") links.

   A movement detection mechanism may take advantage of positioning data
   (latitude and longitude).

   Mobile IPv6 [RFC6275] specifies a new Router Advertisement option
   called the "Advertisement Interval Option".  It can be used by an RSU
   to indicate the maximum interval between two consecutive unsolicited
   Router Advertisement messages sent by this RSU.  With this option, a
   moving station can learn when it is supposed to receive the next RA
   from the same RSU.  This can help movement detection: if the
   specified amount of time elapses without the moving station receiving
   any RA from that RSU, this means that the RA has been lost.  It is up
   to the moving node to determine how many lost RAs from that RSU
   constitutes a handover trigger.

   In addition to the Mobile IPv6 "Advertisement Interval Option", the
   Neighbor Unreachability Detection (NUD) [RFC4861] can be used to
   determine whether the RSU is still reachable or not.  In this
   context, reachability confirmation would basically consist in
   receiving a Neighbor Advertisement message from a RSU, in response to
   a Neighbor Solicitation message sent by the moving station.  The RSU



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   should also configure a low Reachable Time value in its RA in order
   to ensure that a moving station does not assume an RSU to be
   reachable for too long.

   The Mobile IPv6 "Advertisement Interval Option" as well as the NUD
   procedure only help knowing if the RSU is still reachable by the
   moving station.  It does not provide the moving station with
   information about other potential RSUs that might be in range.  For
   this purpose, it is by increasing the RA frequency that the delay
   could be reduced to discover the next RSU.  The Neighbor Discovery
   protocol [RFC4861] limits the unsolicited multicast RA interval to a
   minimum of 3 seconds (the MinRtrAdvInterval variable).  This value is
   too high for dense deployments of Access Routers deployed along fast
   roads.  The protocol Mobile IPv6 [RFC6275] allows routers to send
   such RA more frequently, with a minimum possible of 0.03 seconds (the
   same MinRtrAdvInterval variable): this should be preferred to ensure
   a faster detection of the potential RSUs in range.

   However, frequent RAs (every 0.03 seconds) may occupy the channel
   with too many packets leading to other significant packets being
   lost.  There is a tradeoff to be established: the more frequent the
   RAs the better handover performance but the more risks of packet
   loss.

   If multiple RSUs are in the vicinity of a moving station at the same
   time, the station may not be able to choose the "best" one (i.e. the
   one that would afford the moving station spending the longest time in
   its vicinity, in order to avoid too frequent handovers).  In this
   case, it would be helpful to base the decision on the signal quality
   (e.g.  the RSSI of the received RA provided by the radio driver).  A
   better signal would probably offer a longer coverage.  If, in terms
   of RA frequency, it is not possible to adopt the recommendations of
   protocol Mobile IPv6 (but only the Neighbor Discovery specification
   ones, for whatever reason), then another message than the RA could be
   emitted periodically by the Access Router (provided its specification
   allows to send it very often), in order to help the Host determine
   the signal quality.  One such message may be the 802.11p's Time
   Advertisement, or higher layer messages such as the "Basic Safety
   Message" (in the US) or the "Cooperative Awareness Message " (in the
   EU), that are usually sent several times per second.  Another
   alternative replacement for the IPv6 Router Advertisement may be the
   message 'WAVE Routing Advertisement' (WRA), which is part of the WAVE
   Service Advertisement and which may contain optionally the
   transmitter location; this message is described in section 8.2.5 of
   [ieeep1609.3-D9-2010].

   Once the choice of the default router has been performed by the
   moving node, it can be interesting to use Optimistic DAD [RFC4429] in



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   order to speed-up the address auto-configuration and ensure the
   fastest possible Layer-3 handover.

   To summarize, efficient handovers between OCB links can be performed
   by using a combination of existing mechanisms.  In order to improve
   the default router unreachability detection, the RSU and moving
   stations should use the Mobile IPv6 "Advertisement Interval Option"
   as well as rely on the NUD mechanism.  In order to allow the moving
   station to detect potential default router faster, the RSU should
   also be able to be configured with a smaller minimum RA interval such
   as the one recommended by Mobile IPv6.  When multiple RSUs are
   available at the same time, the moving station should perform the
   handover decision based on the signal quality.  Finally, optimistic
   DAD can be used to reduce the handover delay.

   The Received Frame Power Level (RCPI) defined in IEEE Std
   802.11-2012, conditioned by the dotOCBActived flag, is an information
   element which contains a value expressing the power level at which
   that frame was received.  This value may be used in comparing power
   levels when triggering IP handovers.

7.  Example IPv6 Packet captured over a IEEE 802.11p link

   We remind that a main goal of this document is to make the case that
   IPv6 works fine over 802.11p networks.  Consequently, this section is
   an illustration of this concept and thus can help the implementer
   when it comes to running IPv6 over IEEE 802.11p.  By way of example
   we show that there is no modification in the headers when transmitted
   over 802.11p networks - they are transmitted like any other 802.11
   and Ethernet packets.

   We describe an experiment of capturing an IPv6 packet captured on an
   802.11p link.  In this experiment, the packet is an IPv6 Router
   Advertisement.  This packet is emitted by a Router on its 802.11p
   interface.  The packet is captured on the Host, using a network
   protocol analyzer (e.g.  Wireshark); the capture is performed in two
   different modes: direct mode and 'monitor' mode.  The topology used
   during the capture is depicted below.


                 +--------+                                +-------+
                 |        |        802.11-OCB Link         |       |
              ---| Router |--------------------------------| Host  |
                 |        |                                |       |
                 +--------+                                +-------+






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   During several capture operations running from a few moments to
   several hours, no message relevant to the BSSID contexts were
   captured (no Association Request/Response, Authentication Req/Resp,
   Beacon).  This shows that the operation of 802.11p is outside the
   context of a BSSID.

   Overall, the captured message is identical with a capture of an IPv6
   packet emitted on a 802.11b interface.  The contents are precisely
   similar.

   The popular wireshark network protocol analyzer is a free software
   tool for Windows and Unix.  It includes a dissector for 802.11p
   features along with all other 802.11 features (i.e. it displays these
   features in a human-readable format).

7.1.  Capture in Monitor Mode

   The IPv6 RA packet captured in monitor mode is illustrated below.
   The radio tap header provides more flexibility for reporting the
   characteristics of frames.  The Radiotap Header is prepended by this
   particular stack and operating system on the Host machine to the RA
   packet received from the network (the Radiotap Header is not present
   on the air).  The implementation-dependent Radiotap Header is useful
   for piggybacking PHY information from the chip's registers as data in
   a packet understandable by userland applications using Socket
   interfaces (the PHY interface can be, for example: power levels, data
   rate, ratio of signal to noise).

   The packet present on the air is formed by IEEE 802.11 Data Header,
   Logical Link Control Header, IPv6 Base Header and ICMPv6 Header.



     Radiotap Header v0
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Header Revision|  Header Pad   |    Header length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Present flags                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Data Rate     |             Pad                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     IEEE 802.11 Data Header
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Type/Subtype and Frame Ctrl  |          Duration             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Receiver Address...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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     ... Receiver Address           |      Transmitter Address...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ... Transmitter Address                                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            BSS Id...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ... BSS Id                     |  Frag Number and Seq Number   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Logical-Link Control Header
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      DSAP   |I|     SSAP    |C| Control field | Org. code...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ... Organizational Code        |             Type              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     IPv6 Base Header
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Version| Traffic Class |           Flow Label                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Payload Length        |  Next Header  |   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                         Source Address                        +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                      Destination Address                      +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Router Advertisement
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Cur Hop Limit |M|O|  Reserved |       Router Lifetime         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Reachable Time                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Retrans Timer                        |



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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...
     +-+-+-+-+-+-+-+-+-+-+-+-


   The value of the Data Rate field in the Radiotap header is set to 6
   Mb/s.  This indicates the rate at which this RA was received.

   The value of the Transmitter address in the IEEE 802.11 Data Header
   is set to a 48bit value.  The value of the destination address is
   33:33:00:00:00:1 (all-nodes multicast address).  The value of the BSS
   Id field is ff:ff:ff:ff:ff:ff, which is recognized by the network
   protocol analyzer as being "broadcast".  The Fragment number and
   sequence number fields are together set to 0x90C6.

   The value of the Organization Code field in the Logical-Link Control
   Header is set to 0x0, recognized as "Encapsulated Ethernet".  The
   value of the Type field is 0x86DD (hexadecimal 86DD, or otherwise
   #86DD), recognized as "IPv6".

   A Router Advertisement is periodically sent by the router to
   multicast group address ff02::1.  It is an icmp packet type 134.  The
   IPv6 Neighbor Discovery's Router Advertisement message contains an
   8-bit field reserved for single-bit flags, as described in [RFC4861].

   The IPv6 header contains the link local address of the router
   (source) configured via EUI-64 algorithm, and destination address set
   to ff02::1.  Recent versions of network protocol analyzers (e.g.
   Wireshark) provide additional informations for an IP address, if a
   geolocalization database is present.  In this example, the
   geolocalization database is absent, and the "GeoIP" information is
   set to unknown for both source and destination addresses (although
   the IPv6 source and destination addresses are set to useful values).
   This "GeoIP" can be a useful information to look up the city,
   country, AS number, and other information for an IP address.

   The Ethernet Type field in the logical-link control header is set to
   0x86dd which indicates that the frame transports an IPv6 packet.  In
   the IEEE 802.11 data, the destination address is 33:33:00:00:00:01
   which is he corresponding multicast MAC address.  The BSS id is a
   broadcast address of ff:ff:ff:ff:ff:ff.  Due to the short link
   duration between vehicles and the roadside infrastructure, there is
   no need in IEEE 802.11p to wait for the completion of association and
   authentication procedures before exchanging data.  IEEE 802.11p
   enabled nodes use the wildcard BSSID (a value of all 1s) and may
   start communicating as soon as they arrive on the communication
   channel.




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7.2.  Capture in Normal Mode

   The same IPv6 Router Advertisement packet described above (monitor
   mode) is captured on the Host, in the Normal mode, and depicted
   below.














































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     Ethernet II Header
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Destination...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...Destination                 |           Source...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...Source                                                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Type                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     IPv6 Base Header
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Version| Traffic Class |           Flow Label                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Payload Length        |  Next Header  |   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                         Source Address                        +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                      Destination Address                      +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Router Advertisement
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Cur Hop Limit |M|O|  Reserved |       Router Lifetime         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Reachable Time                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Retrans Timer                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...
     +-+-+-+-+-+-+-+-+-+-+-+-





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   One notices that the Radiotap Header is not prepended, and that the
   IEEE 802.11 Data Header and the Logical-Link Control Headers are not
   present.  On another hand, a new header named Ethernet II Header is
   present.

   The Destination and Source addresses in the Ethernet II header
   contain the same values as the fields Receiver Address and
   Transmitter Address present in the IEEE 802.11 Data Header in the
   "monitor" mode capture.

   The value of the Type field in the Ethernet II header is 0x86DD
   (recognized as "IPv6"); this value is the same value as the value of
   the field Type in the Logical-Link Control Header in the "monitor"
   mode capture.

   The knowledgeable experimenter will no doubt notice the similarity of
   this Ethernet II Header with a capture in normal mode on a pure
   Ethernet cable interface.

   It may be interpreted that an Adaptation layer is inserted in a pure
   IEEE 802.11 MAC packets in the air, before delivering to the
   applications.  In detail, this adaptation layer may consist in
   elimination of the Radiotap, 802.11 and LLC headers and insertion of
   the Ethernet II header.  In this way, it can be stated that IPv6 runs
   naturally straight over LLC over the 802.11p MAC layer, as shown by
   the use of the Type 0x86DD, and assuming an adaptation layer
   (adapting 802.11 LLC/MAC to Ethernet II header).

8.  Security Considerations

   802.11p does not provide any cryptographic protection, because it
   operates outside the context of a BSS (no Association Request/
   Response, no Challenge messages).  Any attacker can therefore just
   sit in the near range of vehicles, sniff the network (just set the
   interface card's frequency to the proper range) and perform attacks
   without needing to physically break any wall.  Such a link is way
   less protected than commonly used links (wired link or protected
   802.11).

   At the IP layer, IPsec can be used to protect unicast communications,
   and SeND can be used for multicast communications.  If no protection
   is used by the IP layer, upper layers should be protected.
   Otherwise, the end-user or system should be warned about the risks
   they run.

   The WAVE protocol stack provides for strong security when using the
   WAVE Short Message Protocol and the WAVE Service Advertisement
   [ieeep1609.2-D17].



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   As with all Ethernet and 802.11 interface identifiers, there may
   exist privacy risks in the use of 802.11p interface identifiers.
   However, in outdoors vehicular settings, the privacy risks are more
   important than in indoors settings.  New risks are induced by the
   possibility of attacker sniffers deployed along routes which listen
   for IP packets of vehicles passing by.  For this reason, in the
   802.11p deployments, there is a strong necessity to use protection
   tools such as dynamically changing MAC addresses.  This may help
   mitigate privacy risks to a certain level.  On another hand, it may
   have an impact in the way typical IPv6 address auto-configuration is
   performed for vehicles (SLAAC would rely on MAC addresses amd would
   hence dynamically change the affected IP address), in the way the
   IPv6 Privacy addresses were used, and other effects.

9.  IANA Considerations

10.  Contributors

   Romain Kuntz contributed extensively the concepts described in
   Section 6 about IPv6 handovers between links running outside the
   context of a BSS (802.11p links).

   Tim Leinmueller contributed the idea of the use of IPv6 over
   802.11-OCB for distribution of certificates.

   Marios Makassikis, Jose Santa Lozano, Albin Severinson and Alexey
   Voronov provided significant feedback on the experience of using IP
   messages over 802.11-OCB in initial trials.

11.  Acknowledgements

   The authors would like to thank Witold Klaudel, Ryuji Wakikawa,
   Emmanuel Baccelli, John Kenney, John Moring, Francois Simon, Dan
   Romascanu, Konstantin Khait, Ralph Droms, Richard Roy, Ray Hunter,
   Tom Kurihara, Michelle Wetterwald, Michal Sojka, Jan de Jongh, Suresh
   Krishnan, Dino Farinacci, Vincent Park, Jaehoon Paul Jeong and Gloria
   Gwynne.  Their valuable comments clarified certain issues and
   generally helped to improve the document.

   Pierre Pfister, Rostislav Lisovy, and others, wrote 802.11-OCB
   drivers for linux and described how.

   For the multicast discussion, the authors would like to thank Owen
   DeLong, Joe Touch, Jen Linkova, Erik Kline, Brian Haberman and
   participants to discussions in network working groups.






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   The authours would like to thank participants to the Birds-of-
   a-Feather "Intelligent Transportation Systems" meetings held at IETF
   in 2016.

12.  References

12.1.  Normative References

   [I-D.ietf-6man-default-iids]
              Gont, F., Cooper, A., Thaler, D., and S. LIU,
              "Recommendation on Stable IPv6 Interface Identifiers",
              draft-ietf-6man-default-iids-16 (work in progress),
              September 2016.

   [I-D.ietf-6man-ug]
              Carpenter, B. and S. Jiang, "Significance of IPv6
              Interface Identifiers", draft-ietf-6man-ug-06 (work in
              progress), December 2013.

   [I-D.ietf-tsvwg-ieee-802-11]
              Szigeti, T. and F. Baker, "DiffServ to IEEE 802.11
              Mapping", draft-ietf-tsvwg-ieee-802-11-01 (work in
              progress), November 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
              <http://www.rfc-editor.org/info/rfc2464>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <http://www.rfc-editor.org/info/rfc4086>.

   [RFC4429]  Moore, N., "Optimistic Duplicate Address Detection (DAD)
              for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006,
              <http://www.rfc-editor.org/info/rfc4429>.






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   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC5889]  Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
              Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
              September 2010, <http://www.rfc-editor.org/info/rfc5889>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <http://www.rfc-editor.org/info/rfc6275>.

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <http://www.rfc-editor.org/info/rfc6775>.

   [RFC7721]  Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              RFC 7721, DOI 10.17487/RFC7721, March 2016,
              <http://www.rfc-editor.org/info/rfc7721>.

12.2.  Informative References

   [etsi-302663-v1.2.1p-2013]
              "Intelligent Transport Systems (ITS); Access layer
              specification for Intelligent Transport Systems operating
              in the 5 GHz frequency band, 2013-07, document
              en_302663v010201p.pdf, document freely available at URL
              http://www.etsi.org/deliver/etsi_en/302600_302699/302663/
              01.02.01_60/en_302663v010201p.pdf downloaded on October
              17th, 2013.".

   [etsi-draft-102492-2-v1.1.1-2006]
              "Electromagnetic compatibility and Radio spectrum Matters
              (ERM); Intelligent Transport Systems (ITS); Part 2:
              Technical characteristics for pan European harmonized
              communications equipment operating in the 5 GHz frequency
              range intended for road safety and traffic management, and
              for non-safety related ITS applications; System Reference
              Document, Draft ETSI TR 102 492-2 V1.1.1, 2006-07,
              document tr_10249202v010101p.pdf freely available at URL
              http://www.etsi.org/deliver/etsi_tr/102400_102499/
              10249202/01.01.01_60/tr_10249202v010101p.pdf downloaded on
              October 18th, 2013.".




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   [fcc-cc]   "'Report and Order, Before the Federal Communications
              Commission Washington, D.C. 20554', FCC 03-324, Released
              on February 10, 2004, document FCC-03-324A1.pdf, document
              freely available at URL
              http://www.its.dot.gov/exit/fcc_edocs.htm downloaded on
              October 17th, 2013.".

   [fcc-cc-172-184]
              "'Memorandum Opinion and Order, Before the Federal
              Communications Commission Washington, D.C. 20554', FCC
              06-10, Released on July 26, 2006, document FCC-
              06-110A1.pdf, document freely available at URL
              http://hraunfoss.fcc.gov/edocs_public/attachmatch/
              FCC-06-110A1.pdf downloaded on June 5th, 2014.".

   [I-D.baccelli-multi-hop-wireless-communication]
              Baccelli, E. and C. Perkins, "Multi-hop Ad Hoc Wireless
              Communication", draft-baccelli-multi-hop-wireless-
              communication-06 (work in progress), July 2011.

   [I-D.perkins-intarea-multicast-ieee802]
              Perkins, C., Stanley, D., Kumari, W., and J. Zuniga,
              "Multicast Considerations over IEEE 802 Wireless Media",
              draft-perkins-intarea-multicast-ieee802-01 (work in
              progress), September 2016.

   [I-D.petrescu-its-scenarios-reqs]
              Petrescu, A., Janneteau, C., Boc, M., and W. Klaudel,
              "Scenarios and Requirements for IP in Intelligent
              Transportation Systems", draft-petrescu-its-scenarios-
              reqs-03 (work in progress), October 2013.

   [ieee16094]
              "1609.2-2016 - IEEE Standard for Wireless Access in
              Vehicular Environments--Security Services for Applications
              and Management Messages; document freely available at URL
              https://standards.ieee.org/findstds/
              standard/1609.2-2016.html retrieved on July 08th, 2016.".













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   [ieee802.11-2012]
              "802.11-2012 - IEEE Standard for Information technology--
              Telecommunications and information exchange between
              systems Local and metropolitan area networks--Specific
              requirements Part 11: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) Specifications.  Downloaded
              on October 17th, 2013, from IEEE Standards, document
              freely available at URL
              http://standards.ieee.org/findstds/
              standard/802.11-2012.html retrieved on October 17th,
              2013.".

   [ieee802.11p-2010]
              "IEEE Std 802.11p(TM)-2010, IEEE Standard for Information
              Technology - Telecommunications and information exchange
              between systems - Local and metropolitan area networks -
              Specific requirements, Part 11: Wireless LAN Medium Access
              Control (MAC) and Physical Layer (PHY) Specifications,
              Amendment 6: Wireless Access in Vehicular Environments;
              document freely available at URL
              http://standards.ieee.org/getieee802/
              download/802.11p-2010.pdf retrieved on September 20th,
              2013.".

   [ieeep1609.0-D2]
              "IEEE P1609.0/D2 Draft Guide for Wireless Access in
              Vehicular Environments (WAVE) Architecture.  pdf, length
              879 Kb.  Restrictions apply.".

   [ieeep1609.2-D17]
              "IEEE P1609.2(tm)/D17 Draft Standard for Wireless Access
              in Vehicular Environments - Security Services for
              Applications and Management Messages.  pdf, length 2558
              Kb.  Restrictions apply.".

   [ieeep1609.3-D9-2010]
              "IEEE P1609.3(tm)/D9, Draft Standard for Wireless Access
              in Vehicular Environments (WAVE) - Networking Services,
              August 2010.  Authorized licensed use limited to: CEA.
              Downloaded on June 19, 2013 at 07:32:34 UTC from IEEE
              Xplore. Restrictions apply, document at persistent link
              http://ieeexplore.ieee.org/servlet/opac?punumber=5562705".









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   [ieeep1609.4-D9-2010]
              "IEEE P1609.4(tm)/D9 Draft Standard for Wireless Access in
              Vehicular Environments (WAVE) - Multi-channel Operation.
              Authorized licensed use limited to: CEA. Downloaded on
              June 19, 2013 at 07:34:48 UTC from IEEE Xplore.
              Restrictions apply.  Document at persistent link
              http://ieeexplore.ieee.org/servlet/opac?punumber=5551097".

   [ipv6-80211p-its]
              Shagdar, O., Tsukada, M., Kakiuchi, M., Toukabri, T., and
              T. Ernst, "Experimentation Towards IPv6 over IEEE 802.11p
              with ITS Station Architecture", International Workshop on
              IPv6-based Vehicular Networks, (colocated with IEEE
              Intelligent Vehicles Symposium), URL:
               http://hal.inria.fr/hal-00702923/en, Downloaded on:  24
              October 2013, Availability: free at some sites, paying at
              others, May 2012.

   [ipv6-wave]
              Clausen, T., Baccelli, E., and R. Wakikawa, "IPv6
              Operation for WAVE - Wireless Access in Vehicular
              Environments", Rapport de Recherche INRIA, number 7383,
              URL:  http://hal.inria.fr/inria-00517909/, Downloaded on:
               24 October 2013, Availability: free at some sites,
              September 2010.

   [TS103097]
              "Intelligent Transport Systems (ITS); Security; Security
              header and certificate formats; document freely available
              at URL http://www.etsi.org/deliver/
              etsi_ts/103000_103099/103097/01.01.01_60/
              ts_103097v010101p.pdf retrieved on July 08th, 2016.".

   [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, Volume 14, Issue 1, URL and Digital Object
              Identifier:  http://dx.doi.org/10.1109/TITS.2012.2206387,
              Downloaded on:  24 October 2013, Availability: free at
              some sites, paying at others, March 2013.

Appendix A.  ChangeLog

   The changes are listed in reverse chronological order, most recent
   changes appearing at the top of the list.





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   From draft-petrescu-ipv6-over-80211p-05.txt to draft-petrescu-ipv6-
   over-80211p-06.txt:

   o  Removed IPv4 text.

   o  Added text about isues with multicast over 802.11 and OCB mode.

   o  Shortened the subnet structure section, by referring to an
      existing RFC.

   o  Removed the appendix about distribution of certificates.

   o  Added text about tradeoff of too frequent RAs, handover
      performance and risks of packet loss.

   o  Removed discussion about other MTU possibilities, kept only the
      1500 bytes MTU.

   o  Keep both header "802.11 Data" and header "802.11 QoS Data".

   o  Referred to default-iids recommendation of generating stable IIDs.

   o  Moved the Design Considerations sections to an appendix.

   From draft-petrescu-ipv6-over-80211p-02.txt to draft-petrescu-ipv6-
   over-80211p-03.txt:

   o  Added clarification about the "OCBActivated" qualifier in the the
      new IEEE 802.11-2012 document; this IEEE document integrates now
      all earlier 802.11p features; this also signifies the
      dissapearance of an IEEE IEEE 802.11p document altogether.

   o  Added explanation about FCC not prohibiting IP on channels, and
      comments about engineering advice and reliability of IP messages.

   o  Added possibility to use 6lowpan adaptation layer when in OCB
      mode.

   o  Added appendix about the distribution of certificates to vehicles
      by using IPv6-over-802.11p single-hop communications.

   o  Refined the explanation of 'half-rate' mode.

   o  Added the privacy concerns and necessity of and potential effects
      of dynamically changing MAC addresses.

   From draft-petrescu-ipv6-over-80211p-01.txt to draft-petrescu-ipv6-
   over-80211p-02.txt:



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   o  updated authorship.

   o  added explanation about FCC not prohibiting IP on channels, and
      comments about engineering advice and reliability of IP messages.

   o  added possibility to use 6lowpan adaptation layer when in OCB
      mode.

   o  added appendix about the distribution of certificates to vehicles
      by using IPv6-over-802.11p single-hop communications.

   o  refined the explanation of 'half-rate' mode.

   o  added the privacy concerns and necessity of and potential effects
      of dynamically changing MAC addresses.

   From draft-petrescu-ipv6-over-80211p-00.txt to draft-petrescu-ipv6-
   over-80211p-01.txt:

   o  updated one author's affiliation detail.

   o  added 2 more references to published literature about IPv6 over
      802.11p.

   From draft-petrescu-ipv6-over-80211p-00.txt to draft-petrescu-ipv6-
   over-80211p-00.txt:

   o  first version.

Appendix B.  Explicit Prohibition of IPv6 on Channels Related to ITS
             Scenarios using 802.11p Networks - an Analysis

B.1.  Interpretation of FCC and ETSI documents with respect to running
      IP on particular channels

   o  The FCC created the term "Control Channel" [fcc-cc].  For it, it
      defines the channel number to be 178 decimal, and positions it
      with a 10MHz width from 5885MHz to 5895MHz.  The FCC rules point
      to standards document ASTM-E2213 (not freely available at the time
      of writing of this draft); in an interpretation of a reviewer of
      this document, this means not making any restrictions to the use
      of IP on the control channel.

   o  The FCC created two more terms for particular channels
      [fcc-cc-172-184], among others.  The channel 172 (5855MHz to
      5865MHz)) is designated "exclusively for [V2V] safety
      communications for accident avoidance and mitigation, and safety
      of life and property applications", and the channel 184 (5915MHz



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      to 5925MHz) is designated "exclusively for high-power, longer-
      distance communications to be used for public-safety applications
      involving safety of life and property, including road-intersection
      collision mitigation".  However, they are not named "control"
      channels, and the document does not mention any particular
      restriction on the use of IP on either of these channels.

   o  On another hand, at IEEE, IPv6 is explicitely prohibited on
      channel number 178 decimal - the FCC's 'Control Channel'.  The
      document [ieeep1609.4-D9-2010] prohibits upfront the use of IPv6
      traffic on the Control Channel: 'data frames containing IP
      datagrams are only allowed on service channels'.  Other 'Service
      Channels' are allowed to use IP, but the Control Channel is not.

   o  In Europe, basically ETSI considers FCC's "Control Channel" to be
      a "Service Channel", and defines a "Control Channel" to be in a
      slot considered by FCC as a "Service Channel".  In detail, FCC's
      "Control Channel" number 178 decimal with 10MHz width (5885MHz to
      5895MHz) is defined by ETSI to be a "Service Channel", and is
      named 'G5-SCH2' [etsi-302663-v1.2.1p-2013].  This channel is
      dedicated to 'ITS Road Safety' by ETSI.  Other channels are
      dedicated to 'ITS road traffic efficiency' by ETSI.  The ETSI's
      "Control Channel" - the "G5-CCH" - number 180 decimal (not 178) is
      reserved as a 10MHz-width centered on 5900MHz (5895MHz to 5905MHz)
      (the 5895MHz-5905MHz channel is a Service Channel for FCC).
      Compared to IEEE, ETSI makes no upfront statement with respect to
      IP and particular channels; yet it relates the 'In car Internet'
      applications ('When nearby a stationary public internet access
      point (hotspot), application can use standard IP services for
      applications.') to the 'Non-safety-related ITS application'
      [etsi-draft-102492-2-v1.1.1-2006].  Under an interpretation of an
      author of this Internet Draft, this may mean ETSI may forbid IP on
      the 'ITS Road Safety' channels, but may allow IP on 'ITS road
      traffic efficiency' channels, or on other 5GHz channels re-used
      from BRAN (also dedicated to Broadband Radio Access Networks).

   o  At EU level in ETSI (but not some countries in EU with varying
      adoption levels) the highest power of transmission of 33 dBm is
      allowed, but only on two separate 10Mhz-width channels centered on
      5900MHz and 5880MHz respectively.  It may be that IPv6 is not
      allowed on these channels (in the other 'ITS' channels where IP
      may be allowed, the levels vary between 20dBm, 23 dBm and 30 dBm;
      in some of these channels IP is allowed).  A high-power of
      transmission means that vehicles may be distanced more
      (intuitively, for 33 dBm approximately 2km is possible, and for 20
      dBm approximately 50meter).





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B.2.  Interpretations of Latencies of IP datagrams

   IPv6 may be "allowed" on any channel.  Certain interpretations
   consider that communicating IP datagrams may involve longer latencies
   than non-IP datagrams; this may make them little adapted for safety
   applications which require fast reaction.  Certain other views
   disagree with this, arguing that IP datagrams are transmitted at the
   same speed as any other non-IP datagram and may thus offer same level
   of reactivity for safety applications.

Appendix C.  Changes Needed on a software driver 802.11a to become a
             802.11-OCB driver

   The 802.11p amendment modifies both the 802.11 stack's physical and
   MAC layers but all the induced modifications can be quite easily
   obtained by modifying an existing 802.11a ad-hoc stack.

   Conditions for a 802.11a hardware to be 802.11p compliant:

   o  The chip must support the frequency bands on which the regulator
      recommends the use of ITS communications, for example using IEEE
      802.11p layer, in France: 5875MHz to 5925MHz.

   o  The chip must support the half-rate mode (the internal clock
      should be able to be divided by two).

   o  The chip transmit spectrum mask must be compliant to the "Transmit
      spectrum mask" from the IEEE 802.11p amendment (but experimental
      environments tolerate otherwise).

   o  The chip should be able to transmit up to 44.8 dBm when used by
      the US government in the United States, and up to 33 dBm in
      Europe; other regional conditions apply.

   Changes needed on the network stack in OCB mode:

   o  Physical layer:

      *  The chip must use the Orthogonal Frequency Multiple Access
         (OFDM) encoding mode.

      *  The chip must be set in half-mode rate mode (the internal clock
         frequency is divided by two).

      *  The chip must use dedicated channels and should allow the use
         of higher emission powers.  This may require modifications to
         the regulatory domains rules, if used by the kernel to enforce




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         local specific restrictions.  Such modifications must respect
         the location-specific laws.

      MAC layer:

      *  All management frames (beacons, join, leave, and others)
         emission and reception must be disabled except for frames of
         subtype Action and Timing Advertisement (defined below).

      *  No encryption key or method must be used.

      *  Packet emission and reception must be performed as in ad-hoc
         mode, using the wildcard BSSID (ff:ff:ff:ff:ff:ff).

      *  The functions related to joining a BSS (Association Request/
         Response) and for authentication (Authentication Request/Reply,
         Challenge) are not called.

      *  The beacon interval is always set to 0 (zero).

      *  Timing Advertisement frames, defined in the amendment, should
         be supported.  The upper layer should be able to trigger such
         frames emission and to retrieve information contained in
         received Timing Advertisements.

Appendix D.  Design Considerations

   The networks defined by 802.11-OCB are in many ways similar to other
   networks of the 802.11 family.  In theory, the encapsulation of IPv6
   over 802.11-OCB could be very similar to the operation of IPv6 over
   other networks of the 802.11 family.  However, the high mobility,
   strong link asymetry and very short connection makes the 802.11-OCB
   link significantly different from other 802.11 networks.  Also, the
   automotive applications have specific requirements for reliability,
   security and privacy, which further add to the particularity of the
   802.11-OCB link.

   This section does not address safety-related applications, which are
   done on non-IP communications.  However, this section will consider
   the transmission of such non IP communication in the design
   specification of IPv6 over IEEE 802.11-OCB.

D.1.  Vehicle ID

   Automotive networks require the unique representation of each of
   their node.  Accordingly, a vehicle must be identified by at least
   one unique ID.  The current specification at ETSI and at IEEE 1609




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   identifies a vehicle by its MAC address uniquely obtained from the
   802.11-OCB NIC.

   A MAC address uniquely obtained from a IEEE 802.11-OCB NIC
   implicitely generates multiple vehicle IDs in case of multiple
   802.11-OCB NICs.  A mechanims to uniquely identify a vehicle
   irrespectively to the different NICs and/or technologies is required.

D.2.  Non IP Communications

   In IEEE 1609 and ETSI ITS, safety-related communications CANNOT be
   used with IP datagrams.  For example, Basic Safety Message (BSM, an
   IEEE 1609 datagram) and Cooperative Awareness Message (CAM, an ETSI
   ITS-G5 datagram), are each transmitted as a payload that is preceded
   by link-layer headers, without an IP header.

   Each vehicle taking part of traffic (i.e. having its engine turned on
   and being located on a road) MUST use Non IP communication to
   periodically broadcast its status information (ID, GPS position,
   speed,..) in its immediate neighborhood.  Using these mechanisms,
   vehicles become 'aware' of the presence of other vehicles in their
   immediate vicinity.  Therefore, IP communication being transmitted by
   vehicles taking part of traffic MUST co-exist with Non IP
   communication and SHOULD NOT break any Non IP mechanism, including
   'harmful' interference on the channel.

   The ID of the vehicle transmitting Non IP communication is
   transmitted in the src MAC address of the IEEE 1609 / ETSI-ITS-G5
   datagrams.  Accordingly, non-IP communications expose the ID of each
   vehicle, which may be considered as a privacy breach.

   IEEE 802.11-OCB bypasses the authentication mechanisms of IEEE 802.11
   networks, in order to transmit non IP communications to without any
   delay.  This may be considered as a security breach.

   IEEE 1609 and ETSI ITS provided strong security and privacy
   mechanisms for Non IP Communications.  Security (authentication,
   encryption) is done by asymetric cryptography, where each vehicle
   attaches its public key and its certificate to all of its non IP
   messages.  Privacy is enforced through the use of Pseudonymes.  Each
   vehicle will be pre-loaded with a large number (>1000s) of
   pseudonymes generated by a PKI, which will uniquely assign a
   pseudonyme to a certificate (and thus to a public/private key pair).

   Non IP Communication being developped for safety-critical
   applications, complex mechanisms have been provided for their
   support.  These mechanisms are OPTIONAL for IP Communication, but
   SHOULD be used whenever possible.



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D.3.  Reliability Requirements

   The dynamically changing topology, short connectivity, mobile
   transmitter and receivers, different antenna heights, and many-to-
   many communication types, make IEEE 802.11-OCB links significantly
   different from other IEEE 802.11 links.  Any IPv6 mechanism operating
   on IEEE 802.11-OCB link MUST support strong link asymetry, spatio-
   temporal link quality, fast address resolution and transmission.

   IEEE 802.11-OCB strongly differs from other 802.11 systems to operate
   outside of the context of a Basic Service Set.  This means in
   practice that IEEE 802.11-OCB does not rely on a Base Station for all
   Basic Service Set management.  In particular, IEEE 802.11-OCB SHALL
   NOT use beacons.  Any IPv6 mechanism requiring L2 services from IEEE
   802.11 beacons MUST support an alternative service.

   Channel scanning being disabled, IPv6 over IEEE 802.11-OCB MUST
   implement a mechanism for transmitter and receiver to converge to a
   common channel.

   Authentication not being possible, IPv6 over IEEE 802.11-OCB MUST
   implement an distributed mechanism to authenticate transmitters and
   receivers without the support of a DHCP server.

   Time synchronization not being available, IPv6 over IEEE 802.11-OCB
   MUST implement a higher layer mechanism for time synchronization
   between transmitters and receivers without the support of a NTP
   server.

   The IEEE 802.11-OCB link being asymetic, IPv6 over IEEE 802.11-OCB
   MUST disable management mechanisms requesting acknowledgements or
   replies.

   The IEEE 802.11-OCB link having a short duration time, IPv6 over IEEE
   802.11-OCB MUST implement fast IPv6 mobility management mechanisms.

D.4.  Privacy requirements

   Vehicles will move.  As each vehicle moves, it needs to regularly
   announce its network interface and reconfigure its local and global
   view of its network.  L2 mechanisms of IEEE 802.11-OCB MAY be
   employed to assist IPv6 in discovering new network interfaces.  L3
   mechanisms over IEEE 802.11-OCB SHOULD be used to assist IPv6 in
   discovering new network interfaces.

   The headers of the L2 mechanisms of IEEE 802.11-OCB and L3 management
   mechanisms of IPv6 are not encrypted, and as such expose at least the
   src MAC address of the sender.  In the absence of mitigations,



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   adversaries could monitor the L2 or L3 management headers, track the
   MAC Addresses, and through that track the position of vehicles over
   time; in some cases, it is possible to deduce the vehicle
   manufacturer name from the OUI of the MAC address of the interface
   (with help of additional databases).  It is important that sniffers
   along roads not be able to easily identify private information of
   automobiles passing by.

   Similary to Non IP safety-critical communications, the obvious
   mitigation is to use some form of MAC Address Randomization.  We can
   assume that there will be "renumbering events" causing the MAC
   Addresses to change.  Clearly, a change of MAC Address should induce
   a simultaneous change of IPv6 Addresses, to prevent linkage of the
   old and new MAC Addresses through continuous use of the same IP
   Addresses.

   The change of an IPv6 address also implies the change of the network
   prefix.  Prefix delegation mechanisms should be available to vehicles
   to obtain new prefixes during "renumbering events".

   Changing MAC and IPv6 addresses will disrupt communications, which
   goes against the reliability requirements expressed in [TS103097].
   We will assume that the renumbering events happen only during "safe"
   periods, e.g.  when the vehicle has come to a full stop.  The
   determination of such safe periods is the responsibility of
   implementors.  In automobile settings it is common to decide that
   certain operations (e.g. software update, or map update) must happen
   only during safe periods.

   MAC Address randomization will not prevent tracking if the addresses
   stay constant for long intervals.  Suppose for example that a vehicle
   only renumbers the addresses of its interface when leaving the
   vehicle owner's garage in the morning.  It would be trivial to
   observe the "number of the day" at the known garage location, and to
   associate that with the vehicle's identity.  There is clearly a
   tension there.  If renumbering events are too infrequent, they will
   not protect privacy, but if their are too frequent they will affect
   reliability.  We expect that implementors will eventually find the
   right balance.

D.5.  Authentication requirements

   IEEE 802.11-OCB does not have L2 authentication mechanisms.
   Accordingly, a vehicle receiving a IPv6 over IEEE 802.11-OCB packet
   cannot check or be sure the legitimacy of the src MAC (and associated
   ID).  This is a significant breach of security.





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   Similarly to Non IP safety-critical communications, IPv6 over
   802.11-OCB packets must contain a certificate, including at least the
   public key of the sender, that will allow the receiver to
   authenticate the packet, and guarantee its legitimacy.

   To satisfy the privacy requiremrents of Appendix D.4, the certificate
   SHALL be changed at each 'renumbering event'.

D.6.  Multiple interfaces

   There are considerations for 2 or more IEEE 802.11-OCB interface
   cards per vehicle.  For each vehicle taking part in road traffic, one
   IEEE 802.11-OCB interface card MUST be fully allocated for Non IP
   safety-critical communication.  Any other IEEE 802.11-OCB may be used
   for other type of traffic.

   The mode of operation of these other wireless interfaces is not
   clearly defined yet.  One possibility is to consider each card as an
   independent network interface, with a specific MAC Address and a set
   of IPv6 addresses.  Another possibility is to consider the set of
   these wireless interfaces as a single network interface (not
   including the IEEE 802.11-OCB interface used by Non IP safety
   critical communications).  This will require specific logic to
   ensure, for example, that packets meant for a vehicle in front are
   actually sent by the radio in the front, or that multiple copies of
   the same packet received by multiple interfaces are treated as a
   single packet.  Treating each wireless interface as a separate
   network interface pushes such issues to the application layer.

   The privacy requirements of Appendix D.4 imply that if these multiple
   interfaces are represented by many network interface, a single
   renumbering event SHALL cause renumbering of all these interfaces.
   If one MAC changed and another stayed constant, external observers
   would be able to correlate old and new values, and the privacy
   benefits of randomization would be lost.

   The privacy requirements of Non IP safety-critical communications
   imply that if a change of pseudonyme occurs, renumbering of all other
   interfaces SHALL also occur.

D.7.  MAC Address Generation

   When designing the IPv6 over 802.11-OCB address mapping, we will
   assume that the MAC Addresses will change during well defined
   "renumbering events".  The 48 bits randomized MAC addresses will have
   the following characteristics:

   o  Bit "Local/Global" set to "locally admninistered".



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   o  Bit "Unicast/Multicast" set to "Unicast".

   o  46 remaining bits set to a random value, using a random number
      generator that meets the requirements of [RFC4086].

   The way to meet the randomization requirements is to retain 46 bits
   from the output of a strong hash function, such as SHA256, taking as
   input a 256 bit local secret, the "nominal" MAC Address of the
   interface, and a representation of the date and time of the
   renumbering event.

D.8.  Security Certificate Generation

   When designing the IPv6 over 802.11-OCB address mapping, we will
   assume that the MAC Addresses will change during well defined
   "renumbering events".  So MUST also the Security Certificates.
   Unless unavailable, the Security Certificate Generation mechanisms
   SHOULD follow the specification in IEEE 1609.2 [ieee16094] or ETSI TS
   103 097 [TS103097].  These security mechanisms have the following
   characteristics:

   o  Authentication - Elliptic Curve Digital Signature Algorithm
      (ECDSA) - A Secured Hash Function (SHA-256) will sign the message
      with the public key of the sender.

   o  Encryption - Elliptic Curve Integrated Encryption Scheme (ECIES) -
      A Key Derivation Function (KDF) between the sender's public key
      and the receiver's private key will generate a symetric key used
      to encrypt a packet.

   If the mechanisms described in IEEE 1609.2 [ieee16094] or ETSI TS 103
   097 [TS103097] are either not supported or not capable of running on
   the hardware, an alternative approach based on Pretty-Good-Privacy
   (PGP) MAY be used as an alternative.

Authors' Addresses

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

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






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   Nabil Benamar
   Moulay Ismail University
   Morocco

   Phone: +212670832236
   Email: benamar73@gmail.com


   Jerome Haerri
   Eurecom
   Sophia-Antipolis   06904
   France

   Phone: +33493008134
   Email: Jerome.Haerri@eurecom.fr


   Christian Huitema
   Friday Harbor, WA  98250
   U.S.A.

   Email: huitema@huitema.net


   Jong-Hyouk Lee
   Sangmyung University
   31, Sangmyeongdae-gil, Dongnam-gu
   Cheonan   31066
   Republic of Korea

   Email: jonghyouk@smu.ac.kr


   Thierry Ernst
   YoGoKo
   France

   Email: thierry.ernst@yogoko.fr


   Tony Li
   Peloton Technology
   1060 La Avenida St.
   Mountain View, California   94043
   United States

   Phone: +16503957356
   Email: tony.li@tony.li



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