Network Working Group A. Petrescu
Internet-Draft CEA, LIST
Intended status: Standards Track N. Benamar
Expires: February 18, 2018 Moulay Ismail University
J. Haerri
Eurecom
C. Huitema
J. Lee
Sangmyung University
T. Ernst
YoGoKo
T. Li
Peloton Technology
August 17, 2017
Transmission of IPv6 Packets over IEEE 802.11 Networks in mode Outside
the Context of a Basic Service Set (IPv6-over-80211ocb)
draft-ietf-ipwave-ipv6-over-80211ocb-04.txt
Abstract
In order to transmit IPv6 packets on IEEE 802.11 networks run outside
the context of a basic service set (OCB, earlier "802.11p") there is
a need to define a few parameters such as the recommended Maximum
Transmission Unit size, the header format preceding the IPv6 header,
the Type value within it, and others. This document describes these
parameters for IPv6 and IEEE 802.11 OCB networks; it portrays the
layering of IPv6 on 802.11 OCB similarly to other known 802.11 and
Ethernet layers - by using an Ethernet Adaptation Layer.
In addition, the document attempts to list what is different in
802.11 OCB (802.11p) compared to more 'traditional' 802.11a/b/g/n
layers, layers over which IPv6 protocols operates without issues.
Most notably, the operation outside the context of a BSS (OCB) has
impact on IPv6 handover behaviour and on IPv6 security.
An example of an IPv6 packet captured while transmitted over an IEEE
802.11 OCB link (802.11p) is given.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 18, 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Communication Scenarios where IEEE 802.11 OCB Links are Used 6
4. Aspects introduced by the OCB mode to 802.11 . . . . . . . . 6
5. Layering of IPv6 over 802.11-OCB as over Ethernet . . . . . . 10
5.1. Maximum Transmission Unit (MTU) . . . . . . . . . . . . . 10
5.2. Frame Format . . . . . . . . . . . . . . . . . . . . . . 11
5.2.1. Ethernet Adaptation Layer . . . . . . . . . . . . . . 12
5.3. Link-Local Addresses . . . . . . . . . . . . . . . . . . 13
5.4. Address Mapping . . . . . . . . . . . . . . . . . . . . . 14
5.4.1. Address Mapping -- Unicast . . . . . . . . . . . . . 14
5.4.2. Address Mapping -- Multicast . . . . . . . . . . . . 14
5.5. Stateless Autoconfiguration . . . . . . . . . . . . . . . 15
5.6. Subnet Structure . . . . . . . . . . . . . . . . . . . . 16
6. Example IPv6 Packet captured over a IEEE 802.11-OCB link . . 16
6.1. Capture in Monitor Mode . . . . . . . . . . . . . . . . . 17
6.2. Capture in Normal Mode . . . . . . . . . . . . . . . . . 19
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
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11. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
11.1. Normative References . . . . . . . . . . . . . . . . . . 23
11.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. ChangeLog . . . . . . . . . . . . . . . . . . . . . 26
Appendix B. Changes Needed on a software driver 802.11a to
become a 802.11-OCB driver . . . 28
Appendix C. Design Considerations . . . . . . . . . . . . . . . 30
C.1. Vehicle ID . . . . . . . . . . . . . . . . . . . . . . . 30
C.2. Reliability Requirements . . . . . . . . . . . . . . . . 30
C.3. Multiple interfaces . . . . . . . . . . . . . . . . . . . 31
C.4. MAC Address Generation . . . . . . . . . . . . . . . . . 32
Appendix D. IEEE 802.11 Messages Transmitted in OCB mode . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
This document describes the transmission of IPv6 packets on IEEE Std
802.11 OCB networks (earlier known as 802.11p). This involves the
layering of IPv6 networking on top of the IEEE 802.11 MAC layer (with
an LLC layer). Compared to running IPv6 over the Ethernet MAC layer,
there is no modification required to the standards: IPv6 works fine
directly over 802.11 OCB too (with an LLC layer).
The term "802.11p" is an earlier definition. As of year 2012, the
behaviour of "802.11p" networks has been rolled in the document IEEE
Std 802.11-2012. In this document the term 802.11p disappears.
Instead, each 802.11p feature is conditioned by a flag in the
Management Information Base. That flag is named "OCBActivated".
Whenever OCBActivated is set to true the feature it relates to
represents an earlier 802.11p feature. For example, an 802.11
STAtion operating outside the context of a basic service set has the
OCBActivated flag set. Such a station, when it has the flag set, it
uses a BSS identifier equal to ff:ff:ff:ff:ff:ff.
In the following text we use the term "802.11p" to mean 802.11-2012
OCB.
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] and [RFC2464]. 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 layer [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. Also, while there is no encryption applied below the network
layer using 802.11p, 1609.2 [ieee1609.2] does provide security
services for applications to use so that there can easily be data
security over the air without invoking IPsec.
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 (and the same differences expressed in terms of
requirements to software 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 contents of Frame
Format, the rules for forming Interface Identifiers, the mechanism
for Address Mapping and for State-less Address Auto-configuration.
These are precisely the same as IPv6 over Ethernet [RFC2464].
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
Section 6.
A couple of points can be considered as different, although they are
not required in order to have a working implementation of IPv6-over-
802.11-OCB. These points are consequences of the OCB operation which
is particular to 802.11 OCB (Outside the Context of a BSS). First,
the handovers between OCB links need specific behaviour for IP Router
Advertisements, or otherwise 802.11 OCB's Time Advertisement, or of
higher layer messages such as the 'Basic Safety Message' (in the US)
or the 'Cooperative Awareness Message' (in the EU) or the 'WAVE
Routing Advertisement'; second, the IP security mechanisms are
necessary, since OCB means that 802.11 is stripped of all 802.11
link-layer security; a small additional security aspect which is
shared between 802.11 OCB and other 802.11 links is the privacy
concerns related to the address formation mechanisms.
In the published literature, many documents describe aspects related
to running IPv6 over 802.11 OCB:
[I-D.jeong-ipwave-vehicular-networking-survey].
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].
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RSU: Road Side Unit. A computer equipped with at least one IEEE
802.11 interface operated in OCB mode. This definition applies to
this document. An RSU may be connected to the Internet, and may be
equipped with additional wired or wireless network interfaces running
IP. An RSU MAY be an IP Router.
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 802.11-2012 that is
flagged by "dot11OCBActivated". This means: 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.
4. Aspects introduced by the OCB mode to 802.11
In the IEEE 802.11 OCB mode, all nodes in the wireless range can
directly communicate with each other without authentication/
association procedures. Briefly, the IEEE 802.11 OCB mode has the
following properties:
o 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 transmitted
o No authentication required
o No association needed
o No encryption provided
o Flag dot11OCBActivated set to true
The following message exchange diagram illustrates a comparison
between traditional 802.11 and 802.11 in OCB mode. The 'Data'
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messages can be IP messages such as the messages used in Stateless or
Stateful Address Auto-Configuration, or other IP messages. 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.
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
[ieee802.11p-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)-2012
[ieee802.11-2012], titled "IEEE Standard for Information technology--
Telecommunications and information exchange between systems Local and
metropolitan area networks--Specific requirements Part 11: Wireless
LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications"; the modifications are diffused throughout various
sections (e.g. 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 802.11-2012, specifically anything referring
"OCBActivated", or "outside the context of a basic service set" is
actually referring to the 802.11p aspects introduced to 802.11. Note
that in earlier 802.11p documents the term "OCBEnabled" was used
instead of te current "OCBActivated".
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In order to delineate the aspects introduced by 802.11 OCB to 802.11,
we refer to the earlier [ieee802.11p-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
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).
To support this similarity statement (IPv6 is layered on top of LLC
on top of 802.11 OCB similarly as on top of LLC on top of
802.11a/b/g/n, and as on top of LLC on top of 802.3) it is useful to
analyze the differences between 802.11 OCB and 802.11 specifications.
Whereas the 802.11p amendment specifies relatively complex and
numerous changes to the MAC layer (and very little to the PHY layer),
we note there are only a few characteristics which may be important
for an implementation transmitting IPv6 packets on 802.11 OCB links.
In the list below, the only 802.11 OCB fundamental points which
influence IPv6 are the OCB operation and the 12Mbit/s maximum which
may be afforded by the IPv6 applications.
o Operation Outside the Context of a BSS (OCB): the (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 - has a potentially strong impact on the use of the
Mobile IPv6 protocol [RFC6275] and on the protocols for IP layer
security [RFC4301].
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
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stations to inform other stations about the value of time. It is
similar to the time as delivered by a GNSS system (Galileo, GPS,
...) or by a cellular system. This message is optional for
implementation. At the date of writing, an experienced reviewer
considers that currently no field testing has used this message.
Another implementor considers this feature implemented in an
initial manner. In the future, it is speculated that this message
may be useful for very simple devices which may not have their own
hardware source of time (Galileo, GPS, cellular network), or by
vehicular devices situated in areas not covered by such network
(in tunnels, underground, outdoors but shaded by foliage or
buildings, in remote areas, etc.)
o Frequency range: this is a characteristic of the PHY layer, with
almost no impact to the interface between MAC and IP. However, it
is worth considering that the frequency range is regulated by a
regional authority (ARCEP, ETSI, FCC, etc.); as part of the
regulation process, specific applications are associated with
specific frequency ranges. In the case of 802.11-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". This band is "5.9GHz" which is different
from the bands "2.4GHz" or "5GHz" used by Wireless LAN. However,
as with Wireless LAN, the operation of 802.11-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.
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* 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.
* 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.
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 7. A relevant function is
described in IEEE 1609.3-2016 [ieee1609.3], clause 5.5.1 and IEEE
1609.4-2016 [ieee1609.4], 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
subnet structure which may be assumed in 802.11-OCB networks is
strongly influenced by the mobility of vehicles.
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 [RFC2460], 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 'geonet' packets have an MTU of 1492 bytes.
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The Equivalent Transmit Time on Channel is a concept that may be used
as an alternative to the MTU concept. A rate of transmission may be
specified as well. The ETTC, rate and MTU may be in direct
relationship.
5.2. Frame Format
IP packets are transmitted over 802.11-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).
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.)
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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.
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 |
+---------------------+-------------+---------+
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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
the following figure:
+--------------------+-------------+-------------+---------+-----------+
| 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].
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5.4. Address Mapping
For unicast as for multicast, there is no change from the unicast and
multicast address mapping format of Ethernet interfaces, as defined
by sections 6 and 7 of [RFC2464].
5.4.1. Address Mapping -- Unicast
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.
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The same mapping requirement applies to the link-scoped multicast
addresses of other IPv6 protocols as well. In DHCPv6, the
"All_DHCP_Servers" IPv6 multicast address ff02::1:2, and in OSPF the
"All_SPF_Routers" IPv6 multicast address ff02::5, need to be mapped
on a multicast MAC address.
An IPv6 packet with a multicast destination address DST, consisting
of the sixteen octets DST[1] through DST[16], is transmitted to the
IEEE 802.11-OCB MAC multicast address whose first two octets are the
value 0x3333 and whose last four octets are the last four octets of
DST.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 1 0 0 1 1|0 0 1 1 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[13] | DST[14] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[15] | DST[16] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Group ID TBD of length 112bits may be requested from IANA; this
Group ID signifies "All 80211OCB Interfaces Address". Only the least
32 significant bits of this "All 80211OCB Interfaces Address" will be
mapped to and from a MAC multicast address.
Transmitting IPv6 packets to multicast destinations over 802.11 links
proved to have some performance issues
[I-D.perkins-intarea-multicast-ieee802]. These issues may be
exacerbated in OCB mode. Solutions for these problems should
consider the OCB mode of operation.
5.5. Stateless Autoconfiguration
The Interface Identifier for an 802.11-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 [I-D.ietf-6man-ug].
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As with all Ethernet and 802.11 interface identifiers ([RFC7721]),
the identifier of an 802.11-OCB interface may involve privacy 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 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 [I-D.ietf-6man-default-iids].
5.6. Subnet Structure
The 802.11 networks in OCB mode may be considered as 'ad-hoc'
networks. The addressing model for such networks is described in
[RFC5889].
6. Example IPv6 Packet captured over a IEEE 802.11-OCB link
We remind that a main goal of this document is to make the case that
IPv6 works fine over 802.11-OCB networks. Consequently, this section
is an illustration of this concept and thus can help the implementer
when it comes to running IPv6 over IEEE 802.11-OCB. 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,
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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.
6.1. Capture in Monitor Mode
The IPv6 RA packet captured in monitor mode is illustrated below.
The radio tap header provides more flexibility for reporting the
characteristics of frames. The Radiotap Header is prepended by this
particular stack and operating system on the Host machine to the RA
packet received from the network (the Radiotap Header is not present
on the air). The implementation-dependent Radiotap Header is useful
for piggybacking PHY information from the chip's registers as data in
a packet understandable by userland applications using Socket
interfaces (the PHY interface can be, for example: power levels, data
rate, ratio of signal to noise).
The packet present on the air is formed by IEEE 802.11 Data Header,
Logical Link Control Header, IPv6 Base Header and ICMPv6 Header.
Radiotap Header v0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Header Revision| Header Pad | Header length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Present flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Rate | Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IEEE 802.11 Data Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type/Subtype and Frame Ctrl | Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Receiver Address | Transmitter Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Transmitter Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSS Id...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... BSS Id | Frag Number and Seq Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Logical-Link Control Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSAP |I| SSAP |C| Control field | Org. code...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Organizational Code | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
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The value of the Transmitter address in the IEEE 802.11 Data Header
is set to a 48bit value. The value of the destination address is
33:33:00:00:00:1 (all-nodes multicast address). The value of the BSS
Id field is ff:ff:ff:ff:ff:ff, which is recognized by the network
protocol analyzer as being "broadcast". The Fragment number and
sequence number fields are together set to 0x90C6.
The value of the Organization Code field in the Logical-Link Control
Header is set to 0x0, recognized as "Encapsulated Ethernet". The
value of the Type field is 0x86DD (hexadecimal 86DD, or otherwise
#86DD), recognized as "IPv6".
A Router Advertisement is periodically sent by the router to
multicast group address ff02::1. It is an icmp packet type 134. The
IPv6 Neighbor Discovery's Router Advertisement message contains an
8-bit field reserved for single-bit flags, as described in [RFC4861].
The IPv6 header contains the link local address of the router
(source) configured via EUI-64 algorithm, and destination address set
to ff02::1. Recent versions of network protocol analyzers (e.g.
Wireshark) provide additional informations for an IP address, if a
geolocalization database is present. In this example, the
geolocalization database is absent, and the "GeoIP" information is
set to unknown for both source and destination addresses (although
the IPv6 source and destination addresses are set to useful values).
This "GeoIP" can be a useful information to look up the city,
country, AS number, and other information for an IP address.
The Ethernet Type field in the logical-link control header is set to
0x86dd which indicates that the frame transports an IPv6 packet. In
the IEEE 802.11 data, the destination address is 33:33:00:00:00:01
which is he corresponding multicast MAC address. The BSS id is a
broadcast address of ff:ff:ff:ff:ff:ff. Due to the short link
duration between vehicles and the roadside infrastructure, there is
no need in IEEE 802.11-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.
6.2. Capture in Normal Mode
The same IPv6 Router Advertisement packet described above (monitor
mode) is captured on the Host, in the Normal mode, and depicted
below.
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Ethernet II Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Destination | Source...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
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One notices that the Radiotap Header is not prepended, and that the
IEEE 802.11 Data Header and the Logical-Link Control Headers are not
present. On another hand, a new header named Ethernet II Header is
present.
The Destination and Source addresses in the Ethernet II header
contain the same values as the fields Receiver Address and
Transmitter Address present in the IEEE 802.11 Data Header in the
"monitor" mode capture.
The value of the Type field in the Ethernet II header is 0x86DD
(recognized as "IPv6"); this value is the same value as the value of
the field Type in the Logical-Link Control Header in the "monitor"
mode capture.
The knowledgeable experimenter will no doubt notice the similarity of
this Ethernet II Header with a capture in normal mode on a pure
Ethernet cable interface.
It may be interpreted that an Adaptation layer is inserted in a pure
IEEE 802.11 MAC packets in the air, before delivering to the
applications. In detail, this adaptation layer may consist in
elimination of the Radiotap, 802.11 and LLC headers and insertion of
the Ethernet II header. In this way, it can be stated that IPv6 runs
naturally straight over LLC over the 802.11-OCB MAC layer, as shown
by the use of the Type 0x86DD, and assuming an adaptation layer
(adapting 802.11 LLC/MAC to Ethernet II header).
7. 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 way
less protected than commonly used links (wired link or protected
802.11).
At the IP layer, IPsec can be used to protect unicast communications,
and SeND can be used for multicast communications. If no protection
is used by the IP layer, upper layers should be protected.
Otherwise, the end-user or system should be warned about the risks
they run.
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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.
8. IANA Considerations
9. 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.
10. 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 and
William Whyte. Their valuable comments clarified certain issues and
generally helped to improve the document.
Pierre Pfister, Rostislav Lisovy, and others, wrote 802.11-OCB
drivers for linux and described how.
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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.
11. References
11.1. Normative References
[I-D.ietf-6man-default-iids]
Gont, F., Cooper, A., Thaler, D., and S. LIU,
"Recommendation on Stable IPv6 Interface Identifiers",
draft-ietf-6man-default-iids-16 (work in progress),
September 2016.
[I-D.ietf-6man-ug]
Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", draft-ietf-6man-ug-06 (work in
progress), December 2013.
[I-D.ietf-tsvwg-ieee-802-11]
Szigeti, T., Henry, J., and F. Baker, "Diffserv to IEEE
802.11 Mapping", draft-ietf-tsvwg-ieee-802-11-06 (work in
progress), August 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>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[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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[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
11.2. Informative References
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[fcc-cc] "'Report and Order, Before the Federal Communications
Commission Washington, D.C. 20554', FCC 03-324, Released
on February 10, 2004, document FCC-03-324A1.pdf, document
freely available at URL
http://www.its.dot.gov/exit/fcc_edocs.htm downloaded on
October 17th, 2013.".
[fcc-cc-172-184]
"'Memorandum Opinion and Order, Before the Federal
Communications Commission Washington, D.C. 20554', FCC
06-10, Released on July 26, 2006, document FCC-
06-110A1.pdf, document freely available at URL
http://hraunfoss.fcc.gov/edocs_public/attachmatch/
FCC-06-110A1.pdf downloaded on June 5th, 2014.".
[I-D.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.
[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.
[ieee1609.2]
"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.".
[ieee1609.3]
"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.".
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[ieee1609.4]
"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.".
[ieee802.11-2012]
"802.11-2012 - IEEE Standard for Information technology--
Telecommunications and information exchange between
systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications. Downloaded
on October 17th, 2013, from IEEE Standards, document
freely available at URL
http://standards.ieee.org/findstds/
standard/802.11-2012.html retrieved on October 17th,
2013.".
[ieee802.11p-2010]
"IEEE Std 802.11p (TM)-2010, IEEE Standard for Information
Technology - Telecommunications and information exchange
between systems - Local and metropolitan area networks -
Specific requirements, Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) Specifications,
Amendment 6: Wireless Access in Vehicular Environments;
document freely available at URL
http://standards.ieee.org/getieee802/
download/802.11p-2010.pdf retrieved on September 20th,
2013.".
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-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.
o Minor textual issues.
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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).
o Improved relationship between two paragraphs describing the
increase of the Sequence Number in 802.11 header upon IP
fragmentation.
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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.
Conditions for a 802.11a hardware to be 802.11-OCB compliant:
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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.
* The beacon interval is always set to 0 (zero).
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* 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 asymetry and very short connection makes the 802.11-OCB
link significantly different from other 802.11 networks. Also, the
automotive applications have specific requirements for reliability,
security and privacy, which further add to the particularity of the
802.11-OCB link.
C.1. Vehicle ID
Automotive networks require the unique representation of each of
their node. Accordingly, a vehicle must be identified by at least
one unique identifier. The current specification at ETSI and at IEEE
1609 identifies a vehicle by its MAC address uniquely obtained from
the 802.11-OCB NIC.
A MAC address uniquely obtained from a IEEE 802.11-OCB NIC
implicitely generates multiple vehicle IDs in case of multiple
802.11-OCB NICs. A mechanims to uniquely identify a vehicle
irrespectively to the different NICs and/or technologies is required.
C.2. Reliability Requirements
The dynamically changing topology, short connectivity, mobile
transmitter and receivers, different antenna heights, and many-to-
many communication types, make IEEE 802.11-OCB links significantly
different from other IEEE 802.11 links. Any IPv6 mechanism operating
on IEEE 802.11-OCB link MUST support strong link asymetry, spatio-
temporal link quality, fast address resolution and transmission.
IEEE 802.11-OCB strongly differs from other 802.11 systems to operate
outside of the context of a Basic Service Set. This means in
practice that IEEE 802.11-OCB does not rely on a Base Station for all
Basic Service Set management. In particular, IEEE 802.11-OCB SHALL
NOT use beacons. Any IPv6 mechanism requiring L2 services from IEEE
802.11 beacons MUST support an alternative service.
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Channel scanning being disabled, IPv6 over IEEE 802.11-OCB MUST
implement a mechanism for transmitter and receiver to converge to a
common channel.
Authentication not being possible, IPv6 over IEEE 802.11-OCB MUST
implement an distributed mechanism to authenticate transmitters and
receivers without the support of a DHCP server.
Time synchronization not being available, IPv6 over IEEE 802.11-OCB
MUST implement a higher layer mechanism for time synchronization
between transmitters and receivers without the support of a NTP
server.
The IEEE 802.11-OCB link being asymetic, IPv6 over IEEE 802.11-OCB
MUST disable management mechanisms requesting acknowledgements or
replies.
The IEEE 802.11-OCB link having a short duration time, IPv6 over IEEE
802.11-OCB MUST implement fast IPv6 mobility management mechanisms.
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.
The privacy requirements of [] 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.
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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.
Authors' Addresses
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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
Jerome Haerri
Eurecom
Sophia-Antipolis 06904
France
Phone: +33493008134
Email: Jerome.Haerri@eurecom.fr
Christian Huitema
Friday Harbor, WA 98250
U.S.A.
Email: huitema@huitema.net
Jong-Hyouk Lee
Sangmyung University
31, Sangmyeongdae-gil, Dongnam-gu
Cheonan 31066
Republic of Korea
Email: jonghyouk@smu.ac.kr
Thierry Ernst
YoGoKo
France
Email: thierry.ernst@yogoko.fr
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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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