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Basic Support for IPv6 over IEEE Std 802.11 Networks Operating Outside the Context of a Basic Service Set (IPv6-over-80211-OCB)

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8691.
Authors Nabil Benamar , Jerome Haerri , Jong-Hyouk Lee , Thierry Ernst , Thierry Ernst
Last updated 2019-07-21 (Latest revision 2019-07-08)
Replaces draft-petrescu-ipv6-over-80211p
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Carlos J. Bernardos
Shepherd write-up Show Last changed 2019-07-03
IESG IESG state Became RFC 8691 (Proposed Standard)
Consensus boilerplate Yes
Telechat date (None)
Needs a YES. Needs 7 more YES or NO OBJECTION positions to pass.
Responsible AD Suresh Krishnan
Send notices to Carlos Bernardos <>
IANA IANA review state Version Changed - Review Needed
IPWAVE Working Group                                          N. Benamar
Internet-Draft                        Moulay Ismail University of Meknes
Intended status: Standards Track                               J. Haerri
Expires: January 21, 2020                                        Eurecom
                                                                  J. Lee
                                                    Sangmyung University
                                                                T. Ernst
                                                           July 20, 2019

 Basic Support for IPv6 over IEEE Std 802.11 Networks Operating Outside
        the Context of a Basic Service Set (IPv6-over-80211-OCB)


   This document provides methods and settings, and describes
   limitations, for using IPv6 to communicate among nodes in range of
   one another over a single IEEE 802.11-OCB link.  This support does
   only require minimal changes to existing stacks.  Optimizations and
   usage of IPv6 over more complex scenarios is not covered in this
   specification and is subject of future work.

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

   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 January 21, 2020.

Copyright Notice

   Copyright (c) 2019 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

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   ( 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 . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Communication Scenarios where IEEE 802.11-OCB Links are Used    4
   4.  IPv6 over 802.11-OCB  . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Maximum Transmission Unit (MTU) . . . . . . . . . . . . .   4
     4.2.  Frame Format  . . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  Link-Local Addresses  . . . . . . . . . . . . . . . . . .   5
     4.4.  Stateless Autoconfiguration . . . . . . . . . . . . . . .   5
     4.5.  Address Mapping . . . . . . . . . . . . . . . . . . . . .   6
       4.5.1.  Address Mapping -- Unicast  . . . . . . . . . . . . .   6
       4.5.2.  Address Mapping -- Multicast  . . . . . . . . . . . .   6
     4.6.  Subnet Structure  . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
     5.1.  Privacy Considerations  . . . . . . . . . . . . . . . . .   8
       5.1.1.  Privacy Risks of Meaningful info in Interface IDs . .   9
     5.2.  MAC Address and Interface ID Generation . . . . . . . . .   9
     5.3.  Pseudonym Handling  . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  802.11p  . . . . . . . . . . . . . . . . . . . . . .  16
   Appendix B.  Aspects introduced by the OCB mode to 802.11 . . . .  16
   Appendix C.  Changes Needed on a software driver 802.11a to
                become a 802.11-OCB driver . . . . . . . . . . . . .  21
   Appendix D.  Protocol Layering  . . . . . . . . . . . . . . . . .  22
   Appendix E.  Design Considerations  . . . . . . . . . . . . . . .  23
   Appendix F.  IEEE 802.11 Messages Transmitted in OCB mode . . . .  23
   Appendix G.  Examples of Packet Formats . . . . . . . . . . . . .  23
     G.1.  Capture in Monitor Mode . . . . . . . . . . . . . . . . .  24
     G.2.  Capture in Normal Mode  . . . . . . . . . . . . . . . . .  27
   Appendix H.  Extra Terminology  . . . . . . . . . . . . . . . . .  29
   Appendix I.  Neighbor Discovery (ND) Potential Issues in Wireless
                Links  . . . . . . . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

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1.  Introduction

   This document provides a baseline with limitations for using IPv6 to
   communicate among nodes in range of one another over a single IEEE
   802.11-OCB link [IEEE-802.11-2016] (a.k.a., "802.11p" see Appendix A,
   Appendix B and Appendix C) with minimal changes to existing stacks.
   Moreover, the document identifies limitations of such usage.
   Concretely, the document describes the layering of IPv6 networking on
   top of the IEEE Std 802.11 MAC layer or an IEEE Std 802.3 MAC layer
   with a frame translation underneath.  The resulting stack inherits
   from IPv6 over Ethernet [RFC2464], but operates over 802.11-OCB to
   provide at least P2P (Point to Point) connectivity using IPv6 ND and
   link-local addresses.

   The IPv6 network layer operates on 802.11-OCB in the same manner as
   operating on Ethernet with the following exceptions:

   o  Exceptions due to different operation of IPv6 network layer on
      802.11 than on Ethernet.  The operation of IP on Ethernet is
      described in [RFC1042] and [RFC2464].

   o  Exceptions due to the OCB nature of 802.11-OCB compared to 802.11.
      This has impacts on security, privacy, subnet structure and
      movement detection.  Security and privacy recommendations are
      discussed in Section 5 and Section 4.4.  The subnet structure is
      described in Section 4.6.  The movement detection on OCB links is
      not described in this document.  Likewise, ND Extensions and
      IPWAVE optimizations for vehicular communications are not in
      scope.  The expectation is that further specifications will be
      edited to cover more complex vehicular networking scenarios.

   The reader may refer to [I-D.ietf-ipwave-vehicular-networking] for an
   overview of problems related to running IPv6 over 802.11-OCB.  It is
   out of scope of this document to reiterate those.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The document makes uses of the following terms: IP-OBU (Internet
   Protocol On-Board Unit): an IP-OBU denotes a computer situated in a
   vehicle such as a car, bicycle, or similar.  It has at least one IP
   interface that runs in mode OCB of 802.11, and that has an "OBU"

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   transceiver.  See the definition of the term "OBU" in section
   Appendix H.

   IP-RSU (IP Road-Side Unit): an IP-RSU is situated along the road.  It
   has at least two distinct IP-enabled interfaces.  The wireless PHY/
   MAC layer of at least one of its IP-enabled interfaces is configured
   to operate in 802.11-OCB mode.  An IP-RSU communicates with the IP-
   OBU in the vehicle over 802.11 wireless link operating in OCB mode.
   An IP-RSU is similar to an Access Network Router (ANR) defined in
   [RFC3753], and a Wireless Termination Point (WTP) defined in

   OCB (outside the context of a basic service set - BSS): is 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

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

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'.  In particular, we
   refer the reader to [I-D.ietf-ipwave-vehicular-networking], that
   lists some scenarios and requirements for IP in Intelligent
   Transportation Systems (ITS).

   The link model is the following: STA --- 802.11-OCB --- STA.  In
   vehicular networks, STAs can be IP-RSUs and/or IP-OBUs.  All links
   are assumed to be P2P and multiple links can be on one radio
   interface.  While 802.11-OCB is clearly specified, and a legacy IPv6
   stack can operate on such links, the use of the operating environment
   (vehicular networks) brings in new perspectives.

4.  IPv6 over 802.11-OCB

4.1.  Maximum Transmission Unit (MTU)

   The default MTU for IP packets on 802.11-OCB is inherited from
   [RFC2464] and is, as such, 1500 octets.  This value of the MTU
   respects the recommendation that every link on the Internet must have
   a minimum MTU of 1280 octets (stated in [RFC8200], and the
   recommendations therein, especially with respect to fragmentation).

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4.2.  Frame Format

   IP packets MUST be transmitted over 802.11-OCB media as QoS Data
   frames whose format is specified in IEEE 802.11 spec

   The IPv6 packet transmitted on 802.11-OCB are immediately preceded by
   a Logical Link Control (LLC) header and an 802.11 header.  In the LLC
   header, and in accordance with the EtherType Protocol Discrimination
   (EPD, see Appendix D), the value of the Type field MUST be set to
   0x86DD (IPv6).  The mapping to the 802.11 data service SHOULD use a
   'priority' value of 1 (QoS with a 'Background' user priority),
   reserving higher priority values for safety-critical and time-
   sensitive traffic, including the ones listed in [ETSI-sec-archi].

   To simplify the Application Programming Interface (API) between the
   operating system and the 802.11-OCB media, device drivers MAY
   implement IPv6-over-Ethernet as per [RFC2464] and then a frame
   translation from 802.3 to 802.11 in order to minimize the code

4.3.  Link-Local Addresses

   There are several types of IPv6 addresses [RFC4291], [RFC4193], that
   may be assigned to an 802.11-OCB interface.  Among these types of
   addresses only the IPv6 link-local addresses can be formed using an
   EUI-64 identifier, in particular during transition time.

   If the IPv6 link-local address is formed using an EUI-64 identifier,
   then the mechanism of forming that address is the same mechanism as
   used to form an IPv6 link-local address on Ethernet links.  Moreover,
   whether or not the interface identifier is derived from the EUI-64 A
   identifier, its length is 64 bits as is the case for Ethernet

4.4.  Stateless Autoconfiguration

   The steps a host takes in deciding how to autoconfigure its
   interfaces in IPv6 are described in [RFC4862].  This section
   describes the formation of Interface Identifiers for IPv6 addresses
   of type 'Global' or 'Unique Local'.  Interface Identifiers for IPv6
   address of type 'Link-Local' are discussed in Section 4.3.

   The RECOMMENDED method for forming stable Interface Identifiers
   (IIDs) is described in [RFC8064].  The method of forming IIDs
   described in Section 4 of [RFC2464] MAY be used during transition
   time, in particular for IPv6 link-local addresses.  Regardless of how

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   to form the IID, its length is 64 bits, similarely to IPv6 over
   Ethernet [RFC2464].

   The bits in the IID have no specific 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].

   Semantically opaque IIDs, instead of meaningful IIDs derived from a
   valid and meaningful MAC address ([RFC2464], Section 4), help avoid
   certain privacy risks (see the risks mentioned in Section 5.1.1).  If
   semantically opaque IIDs are needed, they may be generated using the
   method for generating semantically opaque IIDs with IPv6 Stateless
   Address Autoconfiguration given in [RFC7217].  Typically, an opaque
   IID is formed starting from identifiers different than the MAC
   addresses, and from cryptographically strong material.  Thus, privacy
   sensitive information is absent from Interface IDs, because it is
   impossible to calculate back the initial value from which the
   Interface ID was first generated.

   Some applications that use IPv6 packets on 802.11-OCB links (among
   other link types) may benefit from IPv6 addresses whose IIDs don't
   change too often.  It is RECOMMENDED to use the mechanisms described
   in RFC 7217 to permit the use of Stable IIDs that do not change
   within one subnet prefix.  A possible source for the Net-Iface
   Parameter is a virtual interface name, or logical interface name,
   that is decided by a local administrator.

4.5.  Address Mapping

   Unicast and multicast address mapping MUST follow the procedures
   specified for Ethernet interfaces specified in Sections 6 and 7 of

4.5.1.  Address Mapping -- Unicast

   This document is scoped for Address Resolution (AR) and Duplicate
   Address Detection (DAD) per [RFC4862].

4.5.2.  Address Mapping -- Multicast

   The multicast address mapping is performed according to the method
   specified in section 7 of [RFC2464].  The meaning of the value "3333"
   mentioned there is defined in section 2.3.1 of [RFC7042].

   Transmitting IPv6 packets to multicast destinations over 802.11 links
   proved to have some performance issues

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   [I-D.ietf-mboned-ieee802-mcast-problems].  These issues may be
   exacerbated in OCB mode.A  A future improvement to this specification
   should consider solutions for these problems.

4.6.  Subnet Structure

   When vehicles are in close range, a subnet may be formed over
   802.11-OCB interfaces (not by their in-vehicle interfaces).  A Prefix
   List conceptual data structure ([RFC4861] Section 5.1) is maintained
   for each 802.11-OCB interface.

   IPv6 Neighbor Discovery protocol (ND) requires reflexive properties
   (bidirectional connectivity) which is generally, though not always,
   the case for P2P OCB links.  IPv6 ND also requires transitive
   properties for DAD and AR, so an IPv6 subnet can be mapped on an OCB
   network only if all nodes in the network share a single physical
   broadcast domain.  The extension to IPv6 ND operating on a subnet
   that covers multiple OCB links and not fully overlapping (NBMA) is
   not in scope.  Finally, IPv6 ND requires a permanent connectivity of
   all nodes in the subnet to defend their addresses, in other words
   very stable network conditions.

   The structure of this subnet is ephemeral, in that it is strongly
   influenced by the mobility of vehicles: the hidden terminal effects
   appear; the 802.11 networks in OCB mode may be considered as 'ad-hoc'
   networks with an addressing model as described in [RFC5889].  On
   another hand, the structure of the internal subnets in each vehicle
   is relatively stable.

   As recommended in [RFC5889], when the timing requirements are very
   strict (e.g., fast-drive-through IP-RSU coverage), no on-link subnet
   prefix should be configured on an 802.11-OCB interface.  In such
   cases, the exclusive use of IPv6 link-local addresses is RECOMMENDED.

   Additionally, even if the timing requirements are not very strict
   (e.g., the moving subnet formed by two following vehicles is stable,
   a fixed IP-RSU is absent), the subnet is disconnected from the
   Internet (i.e., a default route is absent), and the addressing peers
   are equally qualified (that is, it is impossible to determine that
   some vehicle owns and distributes addresses to others) the use of
   link-local addresses is RECOMMENDED.

   The baseline ND protocol [RFC4861] MUST be supported over 802.11-OCB
   links.  Transmitting ND packets may prove to have some performance
   issues as mentioned in Section 4.5.2, and Appendix I.  These issues
   may be exacerbated in OCB mode.  Solutions for these problems should
   consider the OCB mode of operation.  Future solutions to OCB should
   consider solutions for avoiding broadcast.  The best of current

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   knowledge indicates the kinds of issues that may arise with ND in OCB
   mode; they are described in Appendix I.

   Protocols like Mobile IPv6 [RFC6275] , [RFC3963] and DNAv6 [RFC6059],
   which depend on a timely movement detection, might need additional
   tuning work to handle the lack of link-layer notifications during
   handover.  This is for further study.

5.  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.

   The OCB operation does not use existing 802.11 link-layer security
   mechanisms.  There is no encryption applied below the network layer
   running on 802.11-OCB.  At the application layer, the IEEE 1609.2
   document [IEEE-1609.2] provides security services for certain
   applications to use; application-layer mechanisms are out of scope of
   this document.  On another hand, a security mechanism provided at
   networking layer, such as IPsec [RFC4301], may provide data security
   protection to a wider range of applications.

   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).  Therefore, an attacker can sniff
   or inject traffic while within range of a vehicle or IP-RSU (by
   setting an interface carda&#128;&#153;s frequency to the proper
   range).  Also, an attacker may not heed to legal limits for radio
   power and can use a very sensitive directional antenna; if attackers
   wishe to attack a given exchange they do not necessarily need to be
   in close physical proximity.  Hence, such a link is less protected
   than commonly used links (wired link or protected 802.11).

   Therefore, any node can join a subnet, directly communicate with any
   nodes on the subset to include potentially impersonating another
   node.A  This design allows for a number of threats outlined in
   Section 3 of [RFC6959].  While not widely deployed, SeND [RFC3971],
   [RFC3972] is a solution that can address Spoof-Based Attack Vectors.

5.1.  Privacy Considerations

   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 hijacking risks.  A vehicle embarking an IP-
   OBU 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 of

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   being tracked.  In outdoors public environments, where vehicles
   typically circulate, the privacy risks are more important than in
   indoors settings.  It is highly likely that attacker sniffers are
   deployed along routes which listen for IEEE frames, including 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 Section 5.2, semantically
   opaque Interface Identifiers and stable Interface Identifiers
   Section 4.4.  An example of change policy is to change the MAC
   address of the OCB interface each time the system boots up.  This may
   help mitigate privacy risks to a certain level.  Futhermore, for
   pricavy concerns, ([RFC8065]) recommends using an address generation
   scheme rather than addresses generated from a fixed link-layer
   address.  However, there are some specificities related to vehicles.
   Since roaming is an important characteristic of moving vehicles, the
   use of the same Link-Local Address over time can indicate the
   presence of the same vehicle in different places and thus leads to
   location tracking.  Hence, a vehicle should get hints about a change
   of environment (e.g. , engine running, GPS, etc..) and renew the IID
   in its LLAs.

5.1.1.  Privacy Risks of Meaningful info in Interface IDs

   The privacy risks of using MAC addresses displayed in Interface
   Identifiers are important.  The IPv6 packets can be captured easily
   in the Internet and on-link in public roads.  For this reason, an
   attacker may realize many attacks on privacy.  One such attack on
   802.11-OCB is to capture, store and correlate Company ID information
   present in MAC addresses of many cars (e.g. listen for Router
   Advertisements, or other IPv6 application data packets, and record
   the value of the source address in these packets).  Further
   correlation of this information with other data captured by other
   means, or other visual information (car color, others) may constitute
   privacy risks.

5.2.  MAC Address and Interface ID Generation

   In 802.11-OCB networks, the MAC addresses may change during well
   defined renumbering events.  In the moment the MAC address is changed
   on an 802.11-OCB interface all the Interface Identifiers of IPv6
   addresses assigned to that interface MUST change.

   Implementations should use a policy dictating when the MAC address is
   changed on the 802.11-OCB interface.  For more information on the
   motivation of this policy please refer to the privacy discussion in
   Appendix B.

   A 'randomized' MAC address has the following characteristics:

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

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

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

   To meet the randomization requirements for the 46 remaining bits, a
   hash function may be used.  For example, the SHA256 hash function may
   be used with 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.

   A randomized Interface ID has the same characteristics of a
   randomized MAC address, except the length in bits.

5.3.  Pseudonym Handling

   The demand for privacy protection of vehicles' and drivers'
   identities, which could be granted by using a pseudonym or alias
   identity at the same time, may hamper the required confidentiality of
   messages and trust between participants - especially in safety
   critical vehicular communication.

   o  Particular challenges arise when the pseudonymization mechanism
      used relies on (randomized) re-addressing.

   o  A proper pseudonymization tool operated by a trusted third party
      may be needed to ensure both aspects simultaneously (privacy
      protection on one hand and trust between participants on another

   o  This is discussed in Section 4.4 and Section 5 of this document.

   o  Pseudonymity is also discussed in
      [I-D.ietf-ipwave-vehicular-networking] in its sections 4.2.4 and

6.  IANA Considerations

   No request to IANA.

7.  Contributors

   Christian Huitema, Tony Li.

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

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   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

8.  Acknowledgements

   The authors would like to thank Alexandre Petrescu for initiating
   this work and for being the lead author until the version 43 of this

   The authors would like to thank Pascal Thubert for reviewing,
   proofreading and suggesting modifications of this document.

   The authors would like to thank Mohamed Boucadair for proofreading
   and suggesting modifications of this document.

   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, Abdussalam Baryun,
   Margaret Cullen, Erik Kline, Carlos Jesus Bernardos Cano, Ronald in
   't Velt, Katrin Sjoberg, Roland Bless, Tijink Jasja, Kevin Smith,
   Brian Carpenter, Julian Reschke, Mikael Abrahamsson, Dirk von Hugo,
   Lorenzo Colitti, Pascal Thubert, Ole Troan, Jinmei Tatuya, Joel
   Halpern, Eric Gray and William Whyte.  Their valuable comments
   clarified particular issues and generally helped to improve the

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

   Human Rights Protocol Considerations review by Amelia Andersdotter.

9.  References

9.1.  Normative References

              "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; the document itself is also freely
              available, but with some difficulty (requires
              registration); description and document retrieved on April
              8th, 2019, starting from URL

   [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,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <>.

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   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <>.

   [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,

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,

   [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,

   [RFC6059]  Krishnan, S. and G. Daley, "Simple Procedures for
              Detecting Network Attachment in IPv6", RFC 6059,
              DOI 10.17487/RFC6059, November 2010,

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <>.

   [RFC7042]  Eastlake 3rd, D. and J. Abley, "IANA Considerations and
              IETF Protocol and Documentation Usage for IEEE 802
              Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
              October 2013, <>.

   [RFC7136]  Carpenter, B. and S. Jiang, "Significance of IPv6
              Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
              February 2014, <>.

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   [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,

   [RFC8064]  Gont, F., Cooper, A., Thaler, D., and W. Liu,
              "Recommendation on Stable IPv6 Interface Identifiers",
              RFC 8064, DOI 10.17487/RFC8064, February 2017,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,

9.2.  Informative References

              "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.  Downloaded on
              September 9th, 2017, freely available from ETSI website at

              Jeong, J., "IP Wireless Access in Vehicular Environments
              (IPWAVE): Problem Statement and Use Cases", draft-ietf-
              ipwave-vehicular-networking-11 (work in progress), July

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

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              "IEEE SA - 1609.2-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Security Services for
              Applications and Management Messages.  Example URL
     accessed on
              August 17th, 2017.".

              "IEEE SA - 1609.3-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Networking Services.
              Example URL
              accessed on August 17th, 2017.".

              "IEEE SA - 1609.4-2016 - IEEE Standard for Wireless Access
              in Vehicular Environments (WAVE) -- Multi-Channel
              Operation.  Example URL
     accessed on
              August 17th, 2017.".

              "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
              download/802.11p-2010.pdf retrieved on September 20th,

   [RFC3753]  Manner, J., Ed. and M. Kojo, Ed., "Mobility Related
              Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004,

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, DOI 10.17487/RFC3963, January 2005,

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,

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   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, DOI 10.17487/RFC3972, March 2005,

   [RFC5889]  Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
              Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
              September 2010, <>.

   [RFC6959]  McPherson, D., Baker, F., and J. Halpern, "Source Address
              Validation Improvement (SAVI) Threat Scope", RFC 6959,
              DOI 10.17487/RFC6959, May 2013,

   [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,

   [RFC8065]  Thaler, D., "Privacy Considerations for IPv6 Adaptation-
              Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065,
              February 2017, <>.

Appendix A.  802.11p

   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 the IEEE Management Information Base (MIB)
   attribute "OCBActivated" [IEEE-802.11-2016].  Whenever OCBActivated
   is set to true the IEEE Std 802.11-OCB state is activated.  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.

Appendix B.  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.  In OCB mode, the manner in which channels
   are selected and used is simplified compared to when in BSS mode.
   Contrary to BSS mode, at link layer, it is necessary to set
   statically the same channel number (or frequency) on two stations
   that need to communicate with each other (in BSS mode this channel
   set operation is performed automatically during 'scanning').  The
   manner in which stations set their channel number in OCB mode is not
   specified in this document.  Stations STA1 and STA2 can exchange IP
   packets only if they are set on the same channel.  At IP layer, they
   then discover each other by using the IPv6 Neighbor Discovery

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   protocol.  The allocation of a particular channel for a particular
   use is defined statically in standards authored by ETSI (in Europe),
   FCC in America, and similar organisations in South Korea, Japan and
   other parts of the world.

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

   The message exchange diagram in Figure 1 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 F.

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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 -------->|

         (i) 802.11 Infrastructure mode         (ii) 802.11-OCB mode

   Figure 1: Difference between messages exchanged on 802.11 (left) and
                            802.11-OCB (right)

   The interface 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 integrated in IEEE 802.11(TM)
   -2012 and -2016 [IEEE-802.11-2016].

   In document 802.11-2016, anything qualified specifically as
   "OCBActivated", or "outside the context of a basic service" set to be
   true, then it is actually referring to OCB aspects introduced to

   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 identifying the Amendment, 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 and 5.9GHz.

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   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 802.11a/b/g/n and
   802.3.  A packet sent by an IP-OBU may be received by one or multiple
   IP-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 theoretically possible in 802.11-OCB is 54 Mbit/s
   (when using, for example, the following parameters: 20 MHz channel;
   modulation 64-QAM; coding rate R is 3/4); in practice of IP-over-
   802.11-OCB a commonly observed figure 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

   o  Frequency range: this is a characteristic of the PHY layer, with
      almost no impact on the interface between MAC and IP.  However, it
      is worth considering that the frequency range is regulated by a
      regional authority (ARCEP, ECC/CEPT based on ENs from 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 fixed
      infrastructure an explicit FCC authorization is required; for an
      on-board device a 'licensed-by-rule' concept applies: rule
      certification conformity is required.)  Technical conditions are
      different than those of the bands "2.4GHz" or "5GHz".  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.
      Additionally, 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

   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.

   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 5.  A relevant function is described
      in documents IEEE 1609.3-2016 [IEEE-1609.3] and IEEE 1609.4-2016

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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 802.11-OCB compliant:

   o  The PHY entity shall be an orthogonal frequency division
      multiplexing (OFDM) system.  It 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

   o  The OFDM system must provide a "half-clocked" operation using 10
      MHz channel spacings.

   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 local computer file that describes regulatory domains
         rules, if used by the kernel to enforce local specific
         restrictions.  Such modifications to the local computer file
         must respect the location-specific regulatory rules.

      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).

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      *  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.  Protocol Layering

   A more theoretical and detailed view of layer stacking, and
   interfaces between the IP layer and 802.11-OCB layers, is illustrated
   in Figure 2.  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 Access 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  |

                Figure 2: EtherType Protocol Discrimination

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Appendix E.  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 transportation 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.

Appendix F.  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 MUST send data frames of subtype QoS Data.

Appendix G.  Examples of Packet Formats

   This section describes 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 topology depicted in Figure 3, 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.

   The packet is captured on the Host.  The Host is an IP-OBU containing
   an 802.11 interface in format PCI express (an ITRI product).  The
   kernel runs the ath5k software driver with modifications for OCB
   mode.  The capture tool is Wireshark.  The file format for save and

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   analyze is 'pcap'.  The packet is generated by the Router.  The
   Router is an IP-RSU (ITRI product).

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

         Figure 3: Topology for capturing IP packets on 802.11-OCB

   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

G.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                               |

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

     Router Advertisement

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     |     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.

   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.

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G.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

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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.

   A frame translation 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.

Appendix H.  Extra Terminology

   The following terms are defined outside the IETF.  They are used to
   define the main terms in the main terminology section Section 2.

   DSRC (Dedicated Short Range Communication): a term defined outside
   the IETF.  The US Federal Communications Commission (FCC) Dedicated
   Short Range Communication (DSRC) is defined in the Code of Federal
   Regulations (CFR) 47, Parts 90 and 95.  This Code is referred in the
   definitions below.  At the time of the writing of this Internet
   Draft, the last update of this Code was dated October 1st, 2010.

   DSRCS (Dedicated Short-Range Communications Services): a term defined
   outside the IETF.  The use of radio techniques to transfer data over
   short distances between roadside and mobile units, between mobile
   units, and between portable and mobile units to perform operations
   related to the improvement of traffic flow, traffic safety, and other
   intelligent transportation service applications in a variety of
   environments.  DSRCS systems may also transmit status and
   instructional messages related to the units involve.  [Ref. 47 CFR
   90.7 - Definitions]

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   OBU (On-Board Unit): a term defined outside the IETF.  An On-Board
   Unit is a DSRCS transceiver that is normally mounted in or on a
   vehicle, or which in some instances may be a portable unit.  An OBU
   can be operational while a vehicle or person is either mobile or
   stationary.  The OBUs receive and contend for time to transmit on one
   or more radio frequency (RF) channels.  Except where specifically
   excluded, OBU operation is permitted wherever vehicle operation or
   human passage is permitted.  The OBUs mounted in vehicles are
   licensed by rule under part 95 of the respective chapter and
   communicate with Roadside Units (RSUs) and other OBUs.  Portable OBUs
   are also licensed by rule under part 95 of the respective chapter.
   OBU operations in the Unlicensed National Information Infrastructure
   (UNII) Bands follow the rules in those bands. - [CFR 90.7 -

   RSU (Road-Side Unit): a term defined outside of IETF.  A Roadside
   Unit is a DSRC transceiver that is mounted along a road or pedestrian
   passageway.  An RSU may also be mounted on a vehicle or is hand
   carried, but it may only operate when the vehicle or hand- carried
   unit is stationary.  Furthermore, an RSU operating under the
   respectgive part is restricted to the location where it is licensed
   to operate.  However, portable or hand-held RSUs are permitted to
   operate where they do not interfere with a site-licensed operation.
   A RSU broadcasts data to OBUs or exchanges data with OBUs in its
   communications zone.  An RSU also provides channel assignments and
   operating instructions to OBUs in its communications zone, when
   required. - [CFR 90.7 - Definitions].

Appendix I.  Neighbor Discovery (ND) Potential Issues in Wireless Links

   IPv6 Neighbor Discovery (IPv6 ND) [RFC4861][RFC4862] was designed for
   point-to-point and transit links such as Ethernet, with the
   expectation of a cheap and reliable support for multicast from the
   lower layer.  Section 3.2 of RFC 4861 indicates that the operation on
   Shared Media and on non-broadcast multi-access (NBMA) networks
   require additional support, e.g., for Address Resolution (AR) and
   duplicate address detection (DAD), which depend on multicast.  An
   infrastructureless radio network such as OCB shares properties with
   both Shared Media and NBMA networks, and then adds its own
   complexity, e.g., from movement and interference that allow only
   transient and non-transitive reachability between any set of peers.

   The uniqueness of an address within a scoped domain is a key pillar
   of IPv6 and the base for unicast IP communication.  RFC 4861 details
   the DAD method to avoid that an address is duplicated.  For a link
   local address, the scope is the link, whereas for a Globally
   Reachable address the scope is much larger.  The underlying
   assumption for DAD to operate correctly is that the node that owns an

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   IPv6 address can reach any other node within the scope at the time it
   claims its address, which is done by sending a NS multicast message,
   and can hear any future claim for that address by another party
   within the scope for the duration of the address ownership.

   In the case of OCB, there is a potentially a need to define a scope
   that is compatible with DAD, and that cannot be the set of nodes that
   a transmitter can reach at a particular time, because that set varies
   all the time and does not meet the DAD requirements for a link local
   address that could possibly be used anytime, anywhere.  The generic
   expectation of a reliable multicast is not ensured, and the operation
   of DAD and AR (Address Resolution) as specified by RFC 4861 cannot be
   guaranteed.  Moreover, multicast transmissions that rely on broadcast
   are not only unreliable but are also often detrimental to unicast
   traffic (see [draft-ietf-mboned-ieee802-mcast-problems]).

   Early experience indicates that it should be possible to exchange
   IPv6 packets over OCB while relying on IPv6 ND alone for DAD and AR
   (Address Resolution) in good conditions.  In the absence of a correct
   DAD operation, a node that relies only on IPv6 ND for AR and DAD over
   OCB should ensure that the addresses that it uses are unique by means
   others than DAD.  It must be noted that deriving an IPv6 address from
   a globally unique MAC address has this property but may yield privacy

   RFC 8505 provides a more recent approach to IPv6 ND and in particular
   DAD.  RFC 8505 is designed to fit wireless and otherwise constrained
   networks whereby multicast and/or continuous access to the medium may
   not be guaranteed.  RFC 8505 Section 5.6 "Link-Local Addresses and
   Registration" indicates that the scope of uniqueness for a link local
   address is restricted to a pair of nodes that use it to communicate,
   and provides a method to assert the uniqueness and resolve the link-
   Layer address using a unicast exchange.

   RFC 8505 also enables a router (acting as a 6LR) to own a prefix and
   act as a registrar (acting as a 6LBR) for addresses within the
   associated subnet.  A peer host (acting as a 6LN) registers an
   address derived from that prefix and can use it for the lifetime of
   the registration.  The prefix is advertised as not onlink, which
   means that the 6LN uses the 6LR to relay its packets within the
   subnet, and participation to the subnet is constrained to the time of
   reachability to the 6LR.  Note that RSU that provides internet
   connectivity MAY announce a default router preference [RFC4191],
   whereas a car that does not provide that connectivity MUST NOT do so.
   This operation presents similarities with that of an access point,
   but at Layer-3.  This is why RFC 8505 well-suited for wireless in

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   Support of RFC 8505 may be implemented on OCB.  OCB nodes that
   support RFC 8505 SHOULD support the 6LN operation in order to act as
   a host, and may support the 6LR and 6LBR operations in order to act
   as a router and in particular own a prefix that can be used by RFC
   8505-compliant hosts for address autoconfiguration and registration.

Authors' Addresses

   Nabil Benamar
   Moulay Ismail University of Meknes

   Phone: +212670832236

   Jerome Haerri
   Sophia-Antipolis   06904

   Phone: +33493008134

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


   Thierry Ernst


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