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Versions: (draft-petrescu-ipv6-over-80211p) 00 01 02 03 04 05 06

Network Working Group                                        A. Petrescu
Internet-Draft                                                 CEA, LIST
Intended status: Standards Track                              N. Benamar
Expires: March 16, 2018                         Moulay Ismail University
                                                               J. Haerri
                                                                 Eurecom
                                                              C. Huitema
                                                    Private Octopus Inc.
                                                                  J. Lee
                                                    Sangmyung University
                                                                T. Ernst
                                                                  YoGoKo
                                                                   T. Li
                                                      Peloton Technology
                                                      September 12, 2017


Transmission of IPv6 Packets over IEEE 802.11 Networks operating in mode
    Outside the Context of a Basic Service Set (IPv6-over-80211-OCB)
              draft-ietf-ipwave-ipv6-over-80211ocb-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 supported Maximum
   Transmission Unit size on the 802.11-OCB link, 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 lists what is different in 802.11-OCB
   (802.11p) links compared to more 'traditional' 802.11a/b/g/n links,
   where IPv6 protocols operate without issues.  Most notably, the
   operation outside the context of a BSS (OCB) has impact on IPv6
   handover behaviour and on IPv6 security.

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



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   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
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   This Internet-Draft will expire on March 16, 2018.

Copyright Notice

   Copyright (c) 2017 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Communication Scenarios where IEEE 802.11-OCB Links are Used    6
   4.  Aspects introduced by the OCB mode to 802.11  . . . . . . . .   7
   5.  Layering of IPv6 over 802.11-OCB as over Ethernet . . . . . .  11
     5.1.  Maximum Transmission Unit (MTU) . . . . . . . . . . . . .  11
     5.2.  Frame Format  . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  Ethernet Adaptation Layer . . . . . . . . . . . . . .  13
     5.3.  Link-Local Addresses  . . . . . . . . . . . . . . . . . .  14
     5.4.  Address Mapping . . . . . . . . . . . . . . . . . . . . .  14
       5.4.1.  Address Mapping -- Unicast  . . . . . . . . . . . . .  15
       5.4.2.  Address Mapping -- Multicast  . . . . . . . . . . . .  15
     5.5.  Stateless Autoconfiguration . . . . . . . . . . . . . . .  16
     5.6.  Subnet Structure  . . . . . . . . . . . . . . . . . . . .  17
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  18
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  19
     10.2.  Informative References . . . . . . . . . . . . . . . . .  22
   Appendix A.  ChangeLog  . . . . . . . . . . . . . . . . . . . . .  24
   Appendix B.  Changes Needed on a software driver 802.11a to
                become a                     802.11-OCB driver . . .  27



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   Appendix C.  Design Considerations  . . . . . . . . . . . . . . .  29
     C.1.  Vehicle ID  . . . . . . . . . . . . . . . . . . . . . . .  29
     C.2.  Reliability Requirements  . . . . . . . . . . . . . . . .  29
     C.3.  Multiple interfaces . . . . . . . . . . . . . . . . . . .  30
     C.4.  MAC Address Generation  . . . . . . . . . . . . . . . . .  31
   Appendix D.  IEEE 802.11 Messages Transmitted in OCB mode . . . .  31
   Appendix E.  Implementation Status  . . . . . . . . . . . . . . .  32
     E.1.  Capture in Monitor Mode . . . . . . . . . . . . . . . . .  32
     E.2.  Capture in Normal Mode  . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  37

1.  Introduction

   This document describes the transmission of IPv6 packets on IEEE Std
   802.11-OCB networks (earlier known as 802.11p) [IEEE-802.11-2016].
   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.  The behaviour of
   "802.11p" networks is rolled in the document IEEE Std 802.11-2016.
   In that 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, or 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, uses a BSS identifier equal to
   ff:ff:ff:ff:ff:ff.

   The IPv6 network layer operates on 802.11-OCB in the same manner as
   it operates on 802.11 WiFi, with a few particular exceptions.  The
   IPv6 network layer operates on WiFi by involving an Ethernet
   Adaptation Layer; this Ethernet Adaptation Layer maps 802.11 headers
   to Ethernet II headers.  The operation of IP on Ethernet is described
   in [RFC1042], [RFC2464] and [I-D.hinden-6man-rfc2464bis].  The
   situation of IPv6 networking layer on Ethernet Adaptation Layer is
   illustrated below:











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                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 |                 IPv6                  |
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 |       Ethernet Adaptation Layer       |
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 |             802.11 WiFi MAC           |
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 |             802.11 WiFi PHY           |
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   (in the above figure, a WiFi profile is represented; this is used
   also for OCB profile.)

   A more theoretical and detailed view of layer stacking, and
   interfaces between the IP layer and 802.11-OCB layers, is illustrated
   below.  The IP layer operates on top of the EtherType Protocol
   Discrimination (EPD); this Discrimination layer is described in IEEE
   Std 802.3-2012; the interface between IPv6 and EPD is the LLC_SAP
   (Link Layer Control Service Accesss Point).


           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |                 IPv6                  |
           +-+-+-+-+-+-{            }+-+-+-+-+-+-+-+
                       {   LLC_SAP  }                 802.11-OCB
           +-+-+-+-+-+-{            }+-+-+-+-+-+-+-+  Boundary
           |            EPD          |       |     |
           |                         | MLME  |     |
           +-+-+-{  MAC_SAP   }+-+-+-|  MLME_SAP   |
           |      MAC Sublayer       |       |     |  802.11-OCB
           |     and ch. coord.      |       | SME |  Services
           +-+-+-{   PHY_SAP  }+-+-+-+-+-+-+-|     |
           |                         | PLME  |     |
           |            PHY Layer    |   PLME_SAP  |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   In addition to the description of interface between IP and MAC using
   "Ethernet Adaptation Layer" and "Ethernet Protocol Discrimination
   (EPD)" it is worth mentioning that SNAP [RFC1042] is used to carry
   the IPv6 Ethertype.

   However, there may be some deployment considerations helping optimize
   the performances of running IPv6 over 802.11-OCB (e.g. in the case of
   handovers between 802.11-OCB-enabled access routers, or the
   consideration of using the IP security architecture [RFC4301]).




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   There are currently no specifications for handover between OCB links
   since these are currently specified as LLC-1 links (i.e.
   connectionless).  Any handovers must be performed above the Data Link
   Layer.  To realize handovers between OCB links there is a need of
   specific indicators to assist in the handover process.  The
   indicators may be IP Router Advertisements, or 802.11-OCB's Time
   Advertisements, or 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'.  However, this document
   does not describe handover behaviour.

   The OCB operation is stripping off all existing 802.11 link-layer
   security mechanisms.  There is no encryption applied below the
   network layer running on 802.11-OCB.  At application layer, the IEEE
   1609.2 document [IEEE-1609.2] does provide security services for
   certain applications to use.  A security mechanism provided at
   networking layer, such as IPsec [RFC4301], may provide data security
   protection to a wider range of applications.  See the section
   Security Considerations of this document, Section 6

   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 802.11-OCB and
   802.11a/b/g/n - we answer the question of what are the aspects
   introduced by OCB mode to 802.11; the same aspects, but expressed in
   terms of requirements to implementation, are listed in Appendix B.)

   The document then concentrates on the parameters of layering IP over
   802.11-OCB as over Ethernet: value of MTU, the Frame Format which
   includes a description of an Ethernet Adaptation Layer, the forming
   of Link-Local Addresses the rules for forming Interface Identifiers
   for Stateless Autoconfiguration, the mechanisms for Address Mapping.
   These are precisely the same as IPv6 over Ethernet [RFC2464].  A
   reference is made to ad-hoc networking characteristics of the subnet
   structure in OCB mode.

   As an example, these characteristics of layering IPv6 straight over
   LLC over 802.11-OCB MAC are illustrated by dissecting an IPv6 packet
   captured over a 802.11-OCB link; this is described in the section
   Appendix E.

   In the published literature, many documents describe aspects related
   to running IPv6 over 802.11-OCB:
   [I-D.jeong-ipwave-vehicular-networking-survey].







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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].

   OBU (On-Board Unit): contrary to an RSU, an OBU is almost always
   situated in a vehicle; it is a computer with at least two IP
   interfaces; also, at least one IP interface runs in OCB mode of
   802.11.  It may be an IP router.

   RSU (Road Side Unit): It is a Wireless Termination Point (WTP), as
   defined in [RFC5415], or an Access Point (AP), or an Access Network
   Router (ANR) defined in [RFC3753], with one key particularity: the
   wireless PHY/MAC layer is configured to operate in 802.11-OCB mode.
   The RSU communicates with the On board Unit (OBU) in the vehicle over
   802.11 wireless link operating in OCB mode.  An RSU MAY be connected
   to the Internet, and MAY be an IP router.  When it is connected to
   the Internet, the term V2I (Vehicle to Internet) is relevant.

   OCB (outside the context of a basic service set - BSS): A mode of
   operation in which a STA is not a member of a BSS and does not
   utilize IEEE Std 802.11 authentication, association, or data
   confidentiality.

   802.11-OCB, or 802.11-OCB: text in document IEEE 802.11-2016 that is
   flagged by "dot11OCBActivated".  The text flagged "dot11OCBActivated"
   includes IEEE 802.11e for quality of service, 802.11j-2004 for half-
   clocked operations and (what was known earlier as) 802.11p for
   operation in the 5.9 GHz band and in mode OCB.

3.  Communication Scenarios where IEEE 802.11-OCB Links are Used

   The IEEE 802.11-OCB 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.

   The link model is the following: STA --- 802.11-OCB --- STA.  In
   vehicular networks, STAs can be RSUs and/or OBUs.  While 802.11-OCB
   is clearly specified, and the use of IPv6 over such link is not
   radically new, the operating environment (vehicular networks) brings
   in new perspectives.

   The 802.11-OCB links form and terminate; nodes connected to these
   links peer, and discover each other; the nodes are mobile.  However,



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   the precise description of how links discover each other, peer and
   manage mobility is not given in this document.

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 involving authentication
   or association procedures.  At link layer, it is necessary to set a
   same channel number (or frequency) on two stations that need to
   communicate with each other.  Stations STA1 and STA2 can exchange IP
   packets if they are set on the same channel.  At IP layer, they then
   discover each other by using the IPv6 Neighbor Discovery protocol.

   Briefly, the IEEE 802.11-OCB mode has the following properties:

   o  The use by each node of a 'wildcard' BSSID (i.e., each bit of the
      BSSID is set to 1)

   o  No IEEE 802.11 Beacon frames are transmitted

   o  No authentication is required in order to be able to communicate

   o  No association is needed in order to be able to communicate

   o  No encryption is provided in order to be able to communicate

   o  Flag dot11OCBActivated is set to true

   All the nodes in the radio communication range (OBU and RSU) receive
   all the messages transmitted (OBU and RSU) within the radio
   communications range.  The eventual conflict(s) are resolved by the
   MAC CDMA function.

   The following message exchange diagram illustrates a comparison
   between traditional 802.11 and 802.11 in OCB mode.  The 'Data'
   messages can be IP packets such as HTTP or others.  Other 802.11
   management and control frames (non IP) may be transmitted, as
   specified in the 802.11 standard.  For information, the names of
   these messages as currently specified by the 802.11 standard are
   listed in Appendix D.











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     STA                    AP              STA1                   STA2
     |                      |               |                      |
     |<------ Beacon -------|               |<------ Data -------->|
     |                      |               |                      |
     |---- Probe Req. ----->|               |<------ Data -------->|
     |<--- Probe Res. ------|               |                      |
     |                      |               |<------ Data -------->|
     |---- Auth Req. ------>|               |                      |
     |<--- Auth Res. -------|               |<------ Data -------->|
     |                      |               |                      |
     |---- Asso Req. ------>|               |<------ Data -------->|
     |<--- Asso Res. -------|               |                      |
     |                      |               |<------ Data -------->|
     |<------ Data -------->|               |                      |
     |<------ Data -------->|               |<------ Data -------->|

    (a) 802.11 Infrastructure mode         (b) 802.11-OCB mode


   The link 802.11-OCB was specified in IEEE Std 802.11p (TM) -2010
   [IEEE-802.11p-2010] as an amendment to IEEE Std 802.11 (TM) -2007,
   titled "Amendment 6: Wireless Access in Vehicular Environments".
   Since then, this amendment has been included in IEEE 802.11(TM)-2016
   [IEEE-802.11-2016], 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. the Time Advertisement message described in
   the earlier 802.11 (TM) p amendment is now described in section
   'Frame formats', and the operation outside the context of a BSS
   described in section 'MLME').

   In document 802.11-2016, anything qualified specifically as
   "OCBActivated", or "outside the context of a basic service set" is
   actually referring to OCB aspects introduced to 802.11.  Note that in
   earlier 802.11p documents the term "OCBEnabled" was used instead of
   the current "OCBActivated".

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



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   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 802.11-OCB 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 802.11-OCB MAC layer
   offers practically the same interface to IP as the WiFi and Ethernet
   layers do (802.11a/b/g/n and 802.3).  A packet sent by an OBU may be
   received by one or multiple RSUs.  The link-layer resolution is
   performed by using the IPv6 Neighbor Discovery protocol.

   To support this similarity statement (IPv6 is layered on top of LLC
   on top of 802.11-OCB, in the same way that IPv6 is layered on top of
   LLC on top of 802.11a/b/g/n (for WLAN) or layered on top of LLC on
   top of 802.3 (for Ethernet)) it is useful to analyze the differences
   between 802.11-OCB and 802.11 specifications.  During this analysis,
   we note that whereas 802.11-OCB lists relatively complex and numerous
   changes to the MAC layer (and very little to the PHY layer), there
   are only a few characteristics which may be important for an
   implementation transmitting IPv6 packets on 802.11-OCB links.

   The most important 802.11-OCB point which influences the IPv6
   functioning is the OCB characteristic; an additional, less direct
   influence, is the maximum bandwidth afforded by the PHY modulation/
   demodulation methods and channel access specified by 802.11-OCB.  The
   maximum bandwidth possible in 802.11-OCB is 12Mbit/s; this bandwidth
   allows the operation of a wide range of protocols relying on IPv6.

   o  Operation Outside the Context of a BSS (OCB): the (earlier
      802.11p) 802.11-OCB links are operated without a Basic Service Set
      (BSS).  This means that the frames IEEE 802.11 Beacon, Association
      Request/Response, Authentication Request/Response, and similar,
      are not used.  The used identifier of BSS (BSSID) has a
      hexadecimal value always 0xffffffffffff (48 '1' bits, represented
      as MAC address ff:ff:ff:ff:ff:ff, or otherwise 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 - should be taken into account when the Mobile IPv6
      protocol [RFC6275] and the protocols for IP layer security
      [RFC4301] are used.  The way these protocols adapt to OCB is not
      described in this document.

   o  Timing Advertisement: is a new message defined in 802.11-OCB,
      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,



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      ...) or by a cellular system.  This message is optional for
      implementation.

   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 802.11-OCB, 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".  The 5.9GHz band is different from the
      2.4GHz and 5GHz bands used by Wireless LAN.  However, as with
      Wireless LAN, the operation of 802.11-OCB 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 802.11-OCB (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 other
      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  Prohibition of IPv6 on some channels relevant for IEEE 802.11-OCB,
      as opposed to IPv6 not being prohibited on any channel on which
      802.11a/b/g/n runs:

      *  Some channels are reserved for safety communications; the IPv6
         packets should not be sent on these channels.

      *  At the time of writing, the prohibition is explicit at higher
         layer protocols providing services to the application; these
         higher layer protocols are specified in IEEE 1609 documents,
         i.e. the "WAVE" stack.

      *  National or regional specifications and regulations specify the
         use of different channels; these regulations must be followed.

   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.




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   o  In vehicular communications using 802.11-OCB links, there are
      strong privacy requirements with respect to addressing.  While the
      802.11-OCB 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 6.  A relevant function is
      described in IEEE 1609.3-2016 [IEEE-1609.3], clause 5.5.1 and IEEE
      1609.4-2016 [IEEE-1609.4], clause 6.7.

   Other aspects particular to 802.11-OCB, 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 802.11-OCB networks.  The
   OCB subnet structure is described in section Section 5.6.

5.  Layering of IPv6 over 802.11-OCB as over Ethernet

5.1.  Maximum Transmission Unit (MTU)

   The default MTU for IP packets on 802.11-OCB 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 [RFC8200], and the recommendations therein, especially
   with respect to fragmentation).  If IPv6 packets of size larger than
   1500 bytes are sent on an 802.11-OCB interface card 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 GeoNetworking packets have an MTU of 1492 bytes.  The
   operation of IPv6 over GeoNetworking is specified at
   [ETSI-IPv6-GeoNetworking].

5.2.  Frame Format

   IP packets are transmitted over 802.11-OCB as standard Ethernet
   packets.  As with all 802.11 frames, an Ethernet adaptation layer is
   used with 802.11-OCB as well.  This Ethernet Adaptation Layer
   performing 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).




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   The Frame format for transmitting IPv6 on 802.11-OCB 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:


                    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.)


   Ethernet II Fields:

   Destination Ethernet Address
      the MAC destination address.

   Source Ethernet Address
      the MAC source address.

   1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1
      binary representation of the EtherType value 0x86DD.

   IPv6 header and payload
      the IPv6 packet containing IPv6 header and payload.




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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.


 +--------------------+------------+-------------+---------+-----------+
 | 802.11 Data Header | LLC Header | IPv6 Header | Payload |.11 Trailer|
 +--------------------+------------+-------------+---------+-----------+
  \                               /                         \         /
    -----------------------------                             --------
                   ^---------------------------------------------/
                   |
           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.

   The ".11 Trailer" contains solely a 4-byte Frame Check Sequence.

   The Ethernet Adaptation Layer performs operations in relation to IP
   fragmentation and MTU.  One of these operations is briefly described
   in section Section 5.1.

   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




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   the figure below.  Some commercial OCB products use 802.11 Data, and
   others 802.11 QoS data.  In the future, both could be used.


+--------------------+-------------+-------------+---------+-----------+
| 802.11 Data Header | LLC Header  | IPv6 Header | Payload |.11 Trailer|
+--------------------+-------------+-------------+---------+-----------+

or

+--------------------+-------------+-------------+---------+-----------+
| 802.11 QoS Data Hdr| LLC Header  | IPv6 Header | Payload |.11 Trailer|
+--------------------+-------------+-------------+---------+-----------+


   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
   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 802.11-OCB interface is formed in the
   same manner as on an Ethernet interface.  This manner is described in
   section 5 of [RFC2464].  Additionally, if stable identifiers are
   needed, it is recommended to follow the Recommendation on Stable IPv6
   Interface Identifiers [RFC8064].  Additionally, if semantically
   opaque Interface Identifiers are needed, a potential method for
   generating semantically opaque Interface Identifiers with IPv6
   Stateless Address Autoconfiguration is given in [RFC7217].

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].








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5.4.1.  Address Mapping -- Unicast

   The procedure for mapping IPv6 unicast addresses into Ethernet link-
   layer addresses is described in [RFC4861].  The Source/Target Link-
   layer Address option has the following form when the link-layer is
   Ethernet.


                     0                   1
                     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     |     Type      |    Length     |
                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     |                               |
                     +-          Ethernet           -+
                     |                               |
                     +-           Address           -+
                     |                               |
                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Option fields:

   Type
      1 for Source Link-layer address.
      2 for Target Link-layer address.

   Length
      1 (in units of 8 octets).

   Ethernet Address
      The 48 bit Ethernet IEEE 802 address, in canonical bit order.

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.




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   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.


                         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         |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 named TBD, of length 112bits is requested to 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 802.11-OCB 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 802.11-OCB interface
   are significant, as this is an IEEE link-layer address.  The details
   of this significance are described in [RFC7136].

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




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   of being tracked; see the privacy considerations described in
   Appendix C.

   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 [RFC8064].  Additionally, if semantically opaque
   Interface Identifiers are needed, a potential method for generating
   semantically opaque Interface Identifiers with IPv6 Stateless Address
   Autoconfiguration is given in [RFC7217].

5.6.  Subnet Structure

   A subnet is formed by the external 802.11-OCB interfaces of vehicles
   that are in close range (not their on-board interfaces).  This
   ephemeral subnet structure is strongly influenced by the mobility of
   vehicles: the 802.11 hidden node effects appear.  On another hand,
   the structure of the internal subnets in each car is relatively
   stable.

   For routing purposes, a prefix exchange mechanism could be needed
   between neighboring vehicles.

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

   An addressing model involves several types of addresses, like
   Globally-unique Addresses (GUA), Link-Local Addresses (LL) and Unique
   Local Addresses (ULA).  The subnet structure in 'ad-hoc' networks may
   have characteristics that lead to difficulty of using GUAs derived
   from a received prefix, but the LL addresses may be easier to use
   since the prefix is constant.

6.  Security Considerations

   Any security mechanism at the IP layer or above that may be carried
   out for the general case of IPv6 may also be carried out for IPv6
   operating over 802.11-OCB.

   802.11-OCB 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 less
   protected than commonly used links (wired link or protected 802.11).





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   The potential attack vectors are: MAC address spoofing, IP address
   and session hijacking and privacy violation.

   Within the IPsec Security Architecture [RFC4301], the IPsec AH and
   ESP headers [RFC4302] and [RFC4303] respectively, its multicast
   extensions [RFC5374], HTTPS [RFC2818] and SeND [RFC3971] protocols
   can be used to protect communications.  Further, the assistance of
   proper Public Key Infrastructure (PKI) protocols [RFC4210] is
   necessary to establish credentials.  More IETF protocols are
   available in the toolbox of the IP security protocol designer.
   Certain ETSI protocols related to security protocols in Intelligent
   Transportation Systems are described in [ETSI-sec-archi].

   As with all Ethernet and 802.11 interface identifiers, there may
   exist privacy risks in the use of 802.11-OCB interface identifiers.
   Moreover, 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
   802.11-OCB 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.

7.  IANA Considerations

   A Group ID named TBD, of length 112bits is requested to IANA; this
   Group ID signifies "All 80211OCB Interfaces Address".

8.  Contributors

   Romain Kuntz contributed extensively about IPv6 handovers between
   links running outside the context of a BSS (802.11-OCB 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.

   Michelle Wetterwald contributed extensively the MTU discussion,
   offered the ETSI ITS perspective, and reviewed other parts of the
   document.




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9.  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 'Dick' Roy, Ray
   Hunter, Tom Kurihara, Michal Sojka, Jan de Jongh, Suresh Krishnan,
   Dino Farinacci, Vincent Park, Jaehoon Paul Jeong, Gloria Gwynne,
   Hans-Joachim Fischer, Russ Housley, Rex Buddenberg, Erik Nordmark,
   Bob Moskowitz, Andrew (Dryden?), Georg Mayer, Dorothy Stanley, Sandra
   Cespedes, Mariano Falcitelli, Sri Gundavelli and William Whyte.
   Their valuable comments clarified particular 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.

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

10.  References

10.1.  Normative References

   [I-D.ietf-tsvwg-ieee-802-11]
              Szigeti, T., Henry, J., and F. Baker, "Diffserv to IEEE
              802.11 Mapping", draft-ietf-tsvwg-ieee-802-11-07 (work in
              progress), September 2017.

   [RFC1042]  Postel, J. and J. Reynolds, "Standard for the transmission
              of IP datagrams over IEEE 802 networks", STD 43, RFC 1042,
              DOI 10.17487/RFC1042, February 1988,
              <https://www.rfc-editor.org/info/rfc1042>.

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

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





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   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <https://www.rfc-editor.org/info/rfc2818>.

   [RFC3753]  Manner, J., Ed. and M. Kojo, Ed., "Mobility Related
              Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004,
              <https://www.rfc-editor.org/info/rfc3753>.

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, DOI 10.17487/RFC3963, January 2005,
              <https://www.rfc-editor.org/info/rfc3963>.

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <https://www.rfc-editor.org/info/rfc3971>.

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

   [RFC4210]  Adams, C., Farrell, S., Kause, T., and T. Mononen,
              "Internet X.509 Public Key Infrastructure Certificate
              Management Protocol (CMP)", RFC 4210,
              DOI 10.17487/RFC4210, September 2005,
              <https://www.rfc-editor.org/info/rfc4210>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC4429]  Moore, N., "Optimistic Duplicate Address Detection (DAD)
              for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006,
              <https://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,
              <https://www.rfc-editor.org/info/rfc4861>.

   [RFC5374]  Weis, B., Gross, G., and D. Ignjatic, "Multicast
              Extensions to the Security Architecture for the Internet
              Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
              <https://www.rfc-editor.org/info/rfc5374>.

   [RFC5415]  Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
              Ed., "Control And Provisioning of Wireless Access Points
              (CAPWAP) Protocol Specification", RFC 5415,
              DOI 10.17487/RFC5415, March 2009,
              <https://www.rfc-editor.org/info/rfc5415>.

   [RFC5889]  Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
              Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
              September 2010, <https://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, <https://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,
              <https://www.rfc-editor.org/info/rfc6775>.

   [RFC7136]  Carpenter, B. and S. Jiang, "Significance of IPv6
              Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
              February 2014, <https://www.rfc-editor.org/info/rfc7136>.

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,
              <https://www.rfc-editor.org/info/rfc7217>.

   [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,
              <https://www.rfc-editor.org/info/rfc7721>.







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   [RFC8064]  Gont, F., Cooper, A., Thaler, D., and W. Liu,
              "Recommendation on Stable IPv6 Interface Identifiers",
              RFC 8064, DOI 10.17487/RFC8064, February 2017,
              <https://www.rfc-editor.org/info/rfc8064>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

10.2.  Informative References

   [ETSI-IPv6-GeoNetworking]
              "ETSI EN 302 636-6-1 v1.2.1 (2014-05), ETSI, European
              Standard, Intelligent Transportation Systems (ITS);
              Vehicular Communications; Geonetworking; Part 6: Internet
              Integration; Sub-part 1: Transmission of IPv6 Packets over
              Geonetworking Protocols.  Downloaded on September 9th,
              2017, freely available from ETSI website at URL
              http://www.etsi.org/deliver/
              etsi_en/302600_302699/30263601/01.02.01_60/
              en_30263601v010201p.pdf".

   [ETSI-sec-archi]
              "ETSI TS 102 940 V1.2.1 (2016-11), ETSI Technical
              Specification, Intelligent Transport Systems (ITS);
              Security; ITS communications security architecture and
              security management, November 2016.  Dowloaded on
              September 9th, 2017, freely available from ETSI website at
              URL http://www.etsi.org/deliver/
              etsi_ts/102900_102999/102940/01.02.01_60/
              ts_102940v010201p.pdf".

   [I-D.hinden-6man-rfc2464bis]
              Crawford, M. and R. Hinden, "Transmission of IPv6 Packets
              over Ethernet Networks", draft-hinden-6man-rfc2464bis-02
              (work in progress), March 2017.

   [I-D.jeong-ipwave-vehicular-networking-survey]
              Jeong, J., Cespedes, S., Benamar, N., Haerri, J., and M.
              Wetterwald, "Survey on IP-based Vehicular Networking for
              Intelligent Transportation Systems", draft-jeong-ipwave-
              vehicular-networking-survey-03 (work in progress), June
              2017.







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   [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-ieee802-03 (work in
              progress), July 2017.

   [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.

   [IEEE-1609.2]
              "IEEE SA - 1609.2-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Security Services for
              Applications and Management Messages.  Example URL
              http://ieeexplore.ieee.org/document/7426684/ accessed on
              August 17th, 2017.".

   [IEEE-1609.3]
              "IEEE SA - 1609.3-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Networking Services.
              Example URL http://ieeexplore.ieee.org/document/7458115/
              accessed on August 17th, 2017.".

   [IEEE-1609.4]
              "IEEE SA - 1609.4-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Multi-Channel
              Operation.  Example URL
              http://ieeexplore.ieee.org/document/7435228/ accessed on
              August 17th, 2017.".

   [IEEE-802.11-2016]
              "IEEE Standard 802.11-2016 - 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. Status - Active Standard.  Description
              retrieved freely on September 12th, 2017, at URL
              https://standards.ieee.org/findstds/
              standard/802.11-2016.html".









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   [IEEE-802.11p-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.".

Appendix A.  ChangeLog

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

   From draft-ietf-ipwave-ipv6-over-80211ocb-05 to draft-ietf-ipwave-
   ipv6-over-80211ocb-06

   o  Updated references of 802.11-OCB document from -2012 to the IEEE
      802.11-2016.

   o  In the LL address section, and in SLAAC section, added references
      to 7217 opaque IIDs and 8064 stable IIDs.

   From draft-ietf-ipwave-ipv6-over-80211ocb-04 to draft-ietf-ipwave-
   ipv6-over-80211ocb-05

   o  Lengthened the title and cleanded the abstract.

   o  Added text suggesting LLs may be easy to use on OCB, rather than
      GUAs based on received prefix.

   o  Added the risks of spoofing and hijacking.

   o  Removed the text speculation on adoption of the TSA message.

   o  Clarified that the ND protocol is used.

   o  Clarified what it means "No association needed".

   o  Added some text about how two STAs discover each other.

   o  Added mention of external (OCB) and internal network (stable), in
      the subnet structure section.





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   o  Added phrase explaining that both .11 Data and .11 QoS Data
      headers are currently being used, and may be used in the future.

   o  Moved the packet capture example into an Appendix Implementation
      Status.

   o  Suggested moving the reliability requirements appendix out into
      another document.

   o  Added a IANA Consiserations section, with content, requesting for
      a new multicast group "all OCB interfaces".

   o  Added new OBU term, improved the RSU term definition, removed the
      ETTC term, replaced more occurences of 802.11p, 802.11 OCB with
      802.11-OCB.

   o  References:

      *  Added an informational reference to ETSI's IPv6-over-
         GeoNetworking.

      *  Added more references to IETF and ETSI security protocols.

      *  Updated some references from I-D to RFC, and from old RFC to
         new RFC numbers.

      *  Added reference to multicast extensions to IPsec architecture
         RFC.

      *  Added a reference to 2464-bis.

      *  Removed FCC informative references, because not used.

   o  Updated the affiliation of one author.

   o  Reformulation of some phrases for better readability, and
      correction of typographical errors.

   From draft-ietf-ipwave-ipv6-over-80211ocb-03 to draft-ietf-ipwave-
   ipv6-over-80211ocb-04

   o  Removed a few informative references pointing to Dx draft IEEE
      1609 documents.

   o  Removed outdated informative references to ETSI documents.

   o  Added citations to IEEE 1609.2, .3 and .4-2016.




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   o  Minor textual issues.

   From draft-ietf-ipwave-ipv6-over-80211ocb-02 to draft-ietf-ipwave-
   ipv6-over-80211ocb-03

   o  Keep the previous text on multiple addresses, so remove talk about
      MIP6, NEMOv6 and MCoA.

   o  Clarified that a 'Beacon' is an IEEE 802.11 frame Beacon.

   o  Clarified the figure showing Infrastructure mode and OCB mode side
      by side.

   o  Added a reference to the IP Security Architecture RFC.

   o  Detailed the IPv6-per-channel prohibition paragraph which reflects
      the discussion at the last IETF IPWAVE WG meeting.

   o  Added section "Address Mapping -- Unicast".

   o  Added the ".11 Trailer" to pictures of 802.11 frames.

   o  Added text about SNAP carrying the Ethertype.

   o  New RSU definition allowing for it be both a Router and not
      necessarily a Router some times.

   o  Minor textual issues.

   From draft-ietf-ipwave-ipv6-over-80211ocb-01 to draft-ietf-ipwave-
   ipv6-over-80211ocb-02

   o  Replaced almost all occurences of 802.11p with 802.11-OCB, leaving
      only when explanation of evolution was necessary.

   o  Shortened by removing parameter details from a paragraph in the
      Introduction.

   o  Moved a reference from Normative to Informative.

   o  Added text in intro clarifying there is no handover spec at IEEE,
      and that 1609.2 does provide security services.

   o  Named the contents the fields of the EthernetII header (including
      the Ethertype bitstring).






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   o  Improved relationship between two paragraphs describing the
      increase of the Sequence Number in 802.11 header upon IP
      fragmentation.

   o  Added brief clarification of "tracking".

   From draft-ietf-ipwave-ipv6-over-80211ocb-00 to draft-ietf-ipwave-
   ipv6-over-80211ocb-01

   o  Introduced message exchange diagram illustrating differences
      between 802.11 and 802.11 in OCB mode.

   o  Introduced an appendix listing for information the set of 802.11
      messages that may be transmitted in OCB mode.

   o  Removed appendix sections "Privacy Requirements", "Authentication
      Requirements" and "Security Certificate Generation".

   o  Removed appendix section "Non IP Communications".

   o  Introductory phrase in the Security Considerations section.

   o  Improved the definition of "OCB".

   o  Introduced theoretical stacked layers about IPv6 and IEEE layers
      including EPD.

   o  Removed the appendix describing the details of prohibiting IPv6 on
      certain channels relevant to 802.11-OCB.

   o  Added a brief reference in the privacy text about a precise clause
      in IEEE 1609.3 and .4.

   o  Clarified the definition of a Road Side Unit.

   o  Removed the discussion about security of WSA (because is non-IP).

   o  Removed mentioning of the GeoNetworking discussion.

   o  Moved references to scientific articles to a separate 'overview'
      draft, and referred to it.

Appendix B.  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.



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   Conditions for a 802.11a hardware to be 802.11-OCB compliant:

   o  The chip must support the frequency bands on which the regulator
      recommends the use of ITS communications, for example using IEEE
      802.11-OCB 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
         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.




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      *  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 C.  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 asymmetry 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.

C.1.  Vehicle ID

   In automotive networks it is required that each node is represented
   uniquely.  Accordingly, a vehicle must be identified by at least one
   unique identifier.  The current specification at ETSI and at IEEE
   1609 identifies a vehicle by its MAC address, which is obtained from
   the 802.11-OCB Network Interface Card (NIC).

   In case multiple 802.11-OCB NICs are present in one car, implicitely
   multiple vehicle IDs will be generated.  Additionally, some software
   generates a random MAC address each time the computer boots; this
   constitutes an additional difficulty.

   A mechanim to uniquely identify a vehicle irrespectively to the
   multiplicity of NICs, or frequent MAC address generation, is
   necessary.

C.2.  Reliability Requirements

   This section may need to be moved out into a separate requirements
   document.

   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 asymmetry, spatio-
   temporal link quality, fast address resolution and transmission.




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   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 asymmetric, 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 SHOULD implement fast IPv6 mobility management mechanisms.

C.3.  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 could 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.




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   Certain privacy requirements 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.

C.4.  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".

   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.

Appendix D.  IEEE 802.11 Messages Transmitted in OCB mode

   For information, at the time of writing, this is the list of IEEE
   802.11 messages that may be transmitted in OCB mode, i.e. when
   dot11OCBActivated is true in a STA:

   o  The STA may send management frames of subtype Action and, if the
      STA maintains a TSF Timer, subtype Timing Advertisement;

   o  The STA may send control frames, except those of subtype PS-Poll,
      CF-End, and CF-End plus CFAck;

   o  The STA may send data frames of subtype Data, Null, QoS Data, and
      QoS Null.






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Appendix E.  Implementation Status

   This section describese an example of an IPv6 Packet captured over a
   IEEE 802.11-OCB link.

   By way of example we show that there is no modification in the
   headers when transmitted over 802.11-OCB networks - they are
   transmitted like any other 802.11 and Ethernet packets.

   We describe an experiment of capturing an IPv6 packet on an
   802.11-OCB link.  In this experiment, the packet is an IPv6 Router
   Advertisement.  This packet is emitted by a Router on its 802.11-OCB
   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  |
                     |        |                                |       |
                     +--------+                                +-------+


   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 802.11-OCB 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.

E.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).




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



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     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                      Destination Address                      +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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



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   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 the 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 802.11-OCB to wait for the completion of association
   and authentication procedures before exchanging data.  IEEE
   802.11-OCB enabled nodes use the wildcard BSSID (a value of all 1s)
   and may start communicating as soon as they arrive on the
   communication channel.

E.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, the IEEE 802.11 Data Header and
   the Logical-Link Control Headers are not present.  On the other 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.

   An Adaptation layer is inserted on top of a pure IEEE 802.11 MAC
   layer, in order to adapt packets, before delivering the payload data
   to the applications.  It adapts 802.11 LLC/MAC headers to Ethernet II
   headers.  In further detail, this adaptation consists in the
   elimination of the Radiotap, 802.11 and LLC headers, and in the
   insertion of the Ethernet II header.  In this way, IPv6 runs straight
   over LLC over the 802.11-OCB MAC layer; this is further confirmed by
   the use of the unique Type 0x86DD.

Authors' Addresses

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

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


   Nabil Benamar
   Moulay Ismail University
   Morocco

   Phone: +212670832236
   Email: benamar73@gmail.com






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   Jerome Haerri
   Eurecom
   Sophia-Antipolis   06904
   France

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


   Christian Huitema
   Private Octopus Inc.
   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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