Network Working Group A. Petrescu
Internet-Draft CEA, LIST
Intended status: Standards Track N. Benamar
Expires: March 14, 2018 Moulay Ismail University
J. Haerri
Eurecom
C. Huitema
Private Octopus Inc.
J. Lee
Sangmyung University
T. Ernst
YoGoKo
T. Li
Peloton Technology
September 10, 2017
Transmission of IPv6 Packets over IEEE 802.11 Networks operating in mode
Outside the Context of a Basic Service Set (IPv6-over-80211-OCB)
draft-ietf-ipwave-ipv6-over-80211ocb-05.txt
Abstract
In order to transmit IPv6 packets on IEEE 802.11 networks run outside
the context of a basic service set (OCB, earlier "802.11p") there is
a need to define a few parameters such as the supported Maximum
Transmission Unit size on the 802.11-OCB link, the header format
preceding the IPv6 header, the Type value within it, and others.
This document describes these parameters for IPv6 and IEEE 802.11-OCB
networks; it portrays the layering of IPv6 on 802.11-OCB similarly to
other known 802.11 and Ethernet layers - by using an Ethernet
Adaptation Layer.
In addition, the document lists what is different in 802.11-OCB
(802.11p) links compared to more 'traditional' 802.11a/b/g/n links,
where IPv6 protocols operate without issues. Most notably, the
operation outside the context of a BSS (OCB) has impact on IPv6
handover behaviour and on IPv6 security.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on March 14, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Communication Scenarios where IEEE 802.11-OCB Links are Used 6
4. Aspects introduced by the OCB mode to 802.11 . . . . . . . . 7
5. Layering of IPv6 over 802.11-OCB as over Ethernet . . . . . . 11
5.1. Maximum Transmission Unit (MTU) . . . . . . . . . . . . . 11
5.2. Frame Format . . . . . . . . . . . . . . . . . . . . . . 11
5.2.1. Ethernet Adaptation Layer . . . . . . . . . . . . . . 13
5.3. Link-Local Addresses . . . . . . . . . . . . . . . . . . 14
5.4. Address Mapping . . . . . . . . . . . . . . . . . . . . . 14
5.4.1. Address Mapping -- Unicast . . . . . . . . . . . . . 14
5.4.2. Address Mapping -- Multicast . . . . . . . . . . . . 15
5.5. Stateless Autoconfiguration . . . . . . . . . . . . . . . 16
5.6. Subnet Structure . . . . . . . . . . . . . . . . . . . . 17
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. ChangeLog . . . . . . . . . . . . . . . . . . . . . 24
Appendix B. Changes Needed on a software driver 802.11a to
become a 802.11-OCB driver . . . 27
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Appendix C. Design Considerations . . . . . . . . . . . . . . . 28
C.1. Vehicle ID . . . . . . . . . . . . . . . . . . . . . . . 28
C.2. Reliability Requirements . . . . . . . . . . . . . . . . 29
C.3. Multiple interfaces . . . . . . . . . . . . . . . . . . . 30
C.4. MAC Address Generation . . . . . . . . . . . . . . . . . 30
Appendix D. IEEE 802.11 Messages Transmitted in OCB mode . . . . 31
Appendix E. Implementation Status . . . . . . . . . . . . . . . 31
E.1. Capture in Monitor Mode . . . . . . . . . . . . . . . . . 32
E.2. Capture in Normal Mode . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction
This document describes the transmission of IPv6 packets on IEEE Std
802.11-OCB networks (earlier known as 802.11p) [IEEE-802.11-2012].
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 that document the term 802.11p disappears.
Instead, each 802.11p feature is conditioned by a flag in the
Management Information Base. That flag is named "OCBActivated".
Whenever OCBActivated is set to true the feature it relates to, or
represents, an earlier 802.11p feature. For example, an 802.11
STAtion operating outside the context of a basic service set has the
OCBActivated flag set. Such a station, when it has the flag set,
uses a BSS identifier equal to ff:ff:ff:ff:ff:ff.
The IPv6 network layer operates on 802.11-OCB in the same manner as
it operates on 802.11 WiFi, with a few particular exceptions. The
IPv6 network layer operates on WiFi by involving an Ethernet
Adaptation Layer; this Ethernet Adaptation Layer maps 802.11 headers
to Ethernet II headers. The operation of IP on Ethernet is described
in [RFC1042], [RFC2464] and [I-D.hinden-6man-rfc2464bis]. The
situation of IPv6 networking layer on Ethernet Adaptation Layer is
illustrated below:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethernet Adaptation Layer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 WiFi MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 WiFi PHY |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(in the above figure, a WiFi profile is represented; this is used
also for OCB profile.)
A more theoretical and detailed view of layer stacking, and
interfaces between the IP layer and 802.11-OCB layers, is illustrated
below. The IP layer operates on top of the EtherType Protocol
Discrimination (EPD); this Discrimination layer is described in IEEE
Std 802.3-2012; the interface between IPv6 and EPD is the LLC_SAP
(Link Layer Control Service Accesss Point).
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 |
+-+-+-+-+-+-{ }+-+-+-+-+-+-+-+
{ LLC_SAP } 802.11-OCB
+-+-+-+-+-+-{ }+-+-+-+-+-+-+-+ Boundary
| EPD | | |
| | MLME | |
+-+-+-{ MAC_SAP }+-+-+-| MLME_SAP |
| MAC Sublayer | | | 802.11-OCB
| and ch. coord. | | SME | Services
+-+-+-{ PHY_SAP }+-+-+-+-+-+-+-| |
| | PLME | |
| PHY Layer | PLME_SAP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In addition to the description of interface between IP and MAC using
"Ethernet Adaptation Layer" and "Ethernet Protocol Discrimination
(EPD)" it is worth mentioning that SNAP [RFC1042] is used to carry
the IPv6 Ethertype.
However, there may be some deployment considerations helping optimize
the performances of running IPv6 over 802.11-OCB (e.g. in the case of
handovers between 802.11-OCB-enabled access routers, or the
consideration of using the IP security architecture [RFC4301]).
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There are currently no specifications for handover between OCB links
since these are currently specified as LLC-1 links (i.e.
connectionless). Any handovers must be performed above the Data Link
Layer. To realize handovers between OCB links there is a need of
specific indicators to assist in the handover process. The
indicators may be IP Router Advertisements, or 802.11-OCB's Time
Advertisements, or higher layer messages such as the 'Basic Safety
Message' (in the US), or the 'Cooperative Awareness Message' (in the
EU), or the 'WAVE Routing Advertisement'. However, this document
does not describe handover behaviour.
The OCB operation is stripping off all existing 802.11 link-layer
security mechanisms. There is no encryption applied below the
network layer running on 802.11-OCB. At application layer, the IEEE
1609.2 document [IEEE-1609.2] does provide security services for
certain applications to use. A security mechanism provided at
networking layer, such as IPsec [RFC4301], may provide data security
protection to a wider range of applications. See the section
Security Considerations of this document, Section 6
We briefly introduce the vehicular communication scenarios where IEEE
802.11-OCB links are used. This is followed by a description of
differences in specification terms, between 802.11-OCB and
802.11a/b/g/n - we answer the question of what are the aspects
introduced by OCB mode to 802.11; the same aspects, but expressed in
terms of requirements to implementation, are listed in Appendix B.)
The document then concentrates on the parameters of layering IP over
802.11-OCB as over Ethernet: value of MTU, the Frame Format which
includes a description of an Ethernet Adaptation Layer, the forming
of Link-Local Addresses the rules for forming Interface Identifiers
for Stateless Autoconfiguration, the mechanisms for Address Mapping.
These are precisely the same as IPv6 over Ethernet [RFC2464]. A
reference is made to ad-hoc networking characteristics of the subnet
structure in OCB mode.
As an example, these characteristics of layering IPv6 straight over
LLC over 802.11-OCB MAC are illustrated by dissecting an IPv6 packet
captured over a 802.11-OCB link; this is described in the section
Appendix E.
In the published literature, many documents describe aspects related
to running IPv6 over 802.11-OCB:
[I-D.jeong-ipwave-vehicular-networking-survey].
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
OBU (On-Board Unit): contrary to an RSU, an OBU is almost always
situated in a vehicle; it is a computer with at least two IP
interfaces; also, at least one IP interface runs in OCB mode of
802.11. It may be an IP router.
RSU (Road Side Unit): It is a Wireless Termination Point (WTP), as
defined in [RFC5415], or an Access Point (AP), or an Access Network
Router (ANR) defined in [RFC3753], with one key particularity: the
wireless PHY/MAC layer is configured to operate in 802.11-OCB mode.
The RSU communicates with the On board Unit (OBU) in the vehicle over
802.11 wireless link operating in OCB mode. An RSU MAY be connected
to the Internet, and MAY be an IP router. When it is connected to
the Internet, the term V2I (Vehicle to Internet) is relevant.
OCB (outside the context of a basic service set - BSS): A mode of
operation in which a STA is not a member of a BSS and does not
utilize IEEE Std 802.11 authentication, association, or data
confidentiality.
802.11-OCB, or 802.11-OCB: text in document IEEE 802.11-2012 that is
flagged by "dot11OCBActivated". The text flagged "dot11OCBActivated"
includes IEEE 802.11e for quality of service, 802.11j-2004 for half-
clocked operations and (what was known earlier as) 802.11p for
operation in the 5.9 GHz band and in mode OCB.
3. Communication Scenarios where IEEE 802.11-OCB Links are Used
The IEEE 802.11-OCB Networks are used for vehicular communications,
as 'Wireless Access in Vehicular Environments'. The IP communication
scenarios for these environments have been described in several
documents, among which we refer the reader to one recently updated
[I-D.petrescu-its-scenarios-reqs], about scenarios and requirements
for IP in Intelligent Transportation Systems.
The link model is the following: STA --- 802.11-OCB --- STA. In
vehicular networks, STAs can be RSUs and/or OBUs. While 802.11-OCB
is clearly specified, and the use of IPv6 over such link is not
radically new, the operating environment (vehicular networks) brings
in new perspectives.
The 802.11-OCB links form and terminate; nodes connected to these
links peer, and discover each other; the nodes are mobile. However,
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the precise description of how links discover each other, peer and
manage mobility is not given in this document.
4. Aspects introduced by the OCB mode to 802.11
In the IEEE 802.11-OCB mode, all nodes in the wireless range can
directly communicate with each other without involving authentication
or association procedures. At link layer, it is necessary to set a
same channel number (or frequency) on two stations that need to
communicate with each other. Stations STA1 and STA2 can exchange IP
packets if they are set on the same channel. At IP layer, they then
discover each other by using the IPv6 Neighbor Discovery protocol.
Briefly, the IEEE 802.11-OCB mode has the following properties:
o The use by each node of a 'wildcard' BSSID (i.e., each bit of the
BSSID is set to 1)
o No IEEE 802.11 Beacon frames are transmitted
o No authentication is required in order to be able to communicate
o No association is needed in order to be able to communicate
o No encryption is provided in order to be able to communicate
o Flag dot11OCBActivated is set to true
All the nodes in the radio communication range (OBU and RSU) receive
all the messages transmitted (OBU and RSU) within the radio
communications range. The eventual conflict(s) are resolved by the
MAC CDMA function.
The following message exchange diagram illustrates a comparison
between traditional 802.11 and 802.11 in OCB mode. The 'Data'
messages can be IP packets such as HTTP or others. Other 802.11
management and control frames (non IP) may be transmitted, as
specified in the 802.11 standard. For information, the names of
these messages as currently specified by the 802.11 standard are
listed in Appendix D.
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STA AP STA1 STA2
| | | |
|<------ Beacon -------| |<------ Data -------->|
| | | |
|---- Probe Req. ----->| |<------ Data -------->|
|<--- Probe Res. ------| | |
| | |<------ Data -------->|
|---- Auth Req. ------>| | |
|<--- Auth Res. -------| |<------ Data -------->|
| | | |
|---- Asso Req. ------>| |<------ Data -------->|
|<--- Asso Res. -------| | |
| | |<------ Data -------->|
|<------ Data -------->| | |
|<------ Data -------->| |<------ Data -------->|
(a) 802.11 Infrastructure mode (b) 802.11-OCB mode
The link 802.11-OCB was specified in IEEE Std 802.11p (TM) -2010
[IEEE-802.11p-2010] as an amendment to IEEE Std 802.11 (TM) -2007,
titled "Amendment 6: Wireless Access in Vehicular Environments".
Since then, this amendment has been included in IEEE 802.11(TM)-2012
[IEEE-802.11-2012], 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 OCB aspects introduced to 802.11. Note that in
earlier 802.11p documents the term "OCBEnabled" was used instead of
the current "OCBActivated".
In order to delineate the aspects introduced by 802.11-OCB to 802.11,
we refer to the earlier [IEEE-802.11p-2010]. The amendment is
concerned with vehicular communications, where the wireless link is
similar to that of Wireless LAN (using a PHY layer specified by
802.11a/b/g/n), but which needs to cope with the high mobility factor
inherent in scenarios of communications between moving vehicles, and
between vehicles and fixed infrastructure deployed along roads.
While 'p' is a letter just like 'a, b, g' and 'n' are, 'p' is
concerned more with MAC modifications, and a little with PHY
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modifications; the others are mainly about PHY modifications. It is
possible in practice to combine a 'p' MAC with an 'a' PHY by
operating outside the context of a BSS with OFDM at 5.4GHz.
The 802.11-OCB links are specified to be compatible as much as
possible with the behaviour of 802.11a/b/g/n and future generation
IEEE WLAN links. From the IP perspective, an 802.11-OCB MAC layer
offers practically the same interface to IP as the WiFi and Ethernet
layers do (802.11a/b/g/n and 802.3). A packet sent by an OBU may be
received by one or multiple RSUs. The link-layer resolution is
performed by using the IPv6 Neighbor Discovery protocol.
To support this similarity statement (IPv6 is layered on top of LLC
on top of 802.11-OCB, in the same way that IPv6 is layered on top of
LLC on top of 802.11a/b/g/n (for WLAN) or layered on top of LLC on
top of 802.3 (for Ethernet)) it is useful to analyze the differences
between 802.11-OCB and 802.11 specifications. During this analysis,
we note that whereas 802.11-OCB lists relatively complex and numerous
changes to the MAC layer (and very little to the PHY layer), there
are only a few characteristics which may be important for an
implementation transmitting IPv6 packets on 802.11-OCB links.
The most important 802.11-OCB point which influences the IPv6
functioning is the OCB characteristic; an additional, less direct
influence, is the maximum bandwidth afforded by the PHY modulation/
demodulation methods and channel access specified by 802.11-OCB. The
maximum bandwidth possible in 802.11-OCB is 12Mbit/s; this bandwidth
allows the operation of a wide range of protocols relying on IPv6.
o Operation Outside the Context of a BSS (OCB): the (earlier
802.11p) 802.11-OCB links are operated without a Basic Service Set
(BSS). This means that the frames IEEE 802.11 Beacon, Association
Request/Response, Authentication Request/Response, and similar,
are not used. The used identifier of BSS (BSSID) has a
hexadecimal value always 0xffffffffffff (48 '1' bits, represented
as MAC address ff:ff:ff:ff:ff:ff, or otherwise the 'wildcard'
BSSID), as opposed to an arbitrary BSSID value set by
administrator (e.g. 'My-Home-AccessPoint'). The OCB operation -
namely the lack of beacon-based scanning and lack of
authentication - should be taken into account when the Mobile IPv6
protocol [RFC6275] and the protocols for IP layer security
[RFC4301] are used. The way these protocols adapt to OCB is not
described in this document.
o Timing Advertisement: is a new message defined in 802.11-OCB,
which does not exist in 802.11a/b/g/n. This message is used by
stations to inform other stations about the value of time. It is
similar to the time as delivered by a GNSS system (Galileo, GPS,
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...) or by a cellular system. This message is optional for
implementation.
o Frequency range: this is a characteristic of the PHY layer, with
almost no impact to the interface between MAC and IP. However, it
is worth considering that the frequency range is regulated by a
regional authority (ARCEP, ETSI, FCC, etc.); as part of the
regulation process, specific applications are associated with
specific frequency ranges. In the case of 802.11-OCB, the
regulator associates a set of frequency ranges, or slots within a
band, to the use of applications of vehicular communications, in a
band known as "5.9GHz". The 5.9GHz band is different from the
2.4GHz and 5GHz bands used by Wireless LAN. However, as with
Wireless LAN, the operation of 802.11-OCB in "5.9GHz" bands is
exempt from owning a license in EU (in US the 5.9GHz is a licensed
band of spectrum; for the the fixed infrastructure an explicit FCC
autorization is required; for an onboard device a 'licensed-by-
rule' concept applies: rule certification conformity is required);
however technical conditions are different than those of the bands
"2.4GHz" or "5GHz". On one hand, the allowed power levels, and
implicitly the maximum allowed distance between vehicles, is of
33dBm for 802.11-OCB (in Europe), compared to 20 dBm for Wireless
LAN 802.11a/b/g/n; this leads to a maximum distance of
approximately 1km, compared to approximately 50m. On the other
hand, specific conditions related to congestion avoidance, jamming
avoidance, and radar detection are imposed on the use of DSRC (in
US) and on the use of frequencies for Intelligent Transportation
Systems (in EU), compared to Wireless LAN (802.11a/b/g/n).
o Prohibition of IPv6 on some channels relevant for IEEE 802.11-OCB,
as opposed to IPv6 not being prohibited on any channel on which
802.11a/b/g/n runs:
* Some channels are reserved for safety communications; the IPv6
packets should not be sent on these channels.
* At the time of writing, the prohibition is explicit at higher
layer protocols providing services to the application; these
higher layer protocols are specified in IEEE 1609 documents,
i.e. the "WAVE" stack.
* National or regional specifications and regulations specify the
use of different channels; these regulations must be followed.
o 'Half-rate' encoding: as the frequency range, this parameter is
related to PHY, and thus has not much impact on the interface
between the IP layer and the MAC layer.
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o In vehicular communications using 802.11-OCB links, there are
strong privacy requirements with respect to addressing. While the
802.11-OCB standard does not specify anything in particular with
respect to MAC addresses, in these settings there exists a strong
need for dynamic change of these addresses (as opposed to the non-
vehicular settings - real wall protection - where fixed MAC
addresses do not currently pose some privacy risks). This is
further described in section Section 6. A relevant function is
described in IEEE 1609.3-2016 [IEEE-1609.3], clause 5.5.1 and IEEE
1609.4-2016 [IEEE-1609.4], clause 6.7.
Other aspects particular to 802.11-OCB, which are also particular to
802.11 (e.g. the 'hidden node' operation), may have an influence on
the use of transmission of IPv6 packets on 802.11-OCB networks. The
OCB subnet structure is described in section Section 5.6.
5. Layering of IPv6 over 802.11-OCB as over Ethernet
5.1. Maximum Transmission Unit (MTU)
The default MTU for IP packets on 802.11-OCB is 1500 octets. It is
the same value as IPv6 packets on Ethernet links, as specified in
[RFC2464]. This value of the MTU respects the recommendation that
every link in the Internet must have a minimum MTU of 1280 octets
(stated in [RFC8200], and the recommendations therein, especially
with respect to fragmentation). If IPv6 packets of size larger than
1500 bytes are sent on an 802.11-OCB interface card then the IP stack
will fragment. In case there are IP fragments, the field "Sequence
number" of the 802.11 Data header containing the IP fragment field is
increased.
Non-IP packets such as WAVE Short Message Protocol (WSMP) can be
delivered on 802.11-OCB links. Specifications of these packets are
out of scope of this document, and do not impose any limit on the MTU
size, allowing an arbitrary number of 'containers'. Non-IP packets
such as ETSI GeoNetworking packets have an MTU of 1492 bytes. The
operation of IPv6 over GeoNetworking is specified at
[ETSI-IPv6-GeoNetworking].
5.2. Frame Format
IP packets are transmitted over 802.11-OCB as standard Ethernet
packets. As with all 802.11 frames, an Ethernet adaptation layer is
used with 802.11-OCB as well. This Ethernet Adaptation Layer
performing 802.11-to-Ethernet is described in Section 5.2.1. The
Ethernet Type code (EtherType) for IPv6 is 0x86DD (hexadecimal 86DD,
or otherwise #86DD).
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The Frame format for transmitting IPv6 on 802.11-OCB networks is the
same as transmitting IPv6 on Ethernet networks, and is described in
section 3 of [RFC2464]. The frame format for transmitting IPv6
packets over Ethernet is illustrated below:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination |
+- -+
| Ethernet |
+- -+
| Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source |
+- -+
| Ethernet |
+- -+
| Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 |
+- -+
| header |
+- -+
| and |
+- -+
/ payload ... /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(Each tic mark represents one bit.)
Ethernet II Fields:
Destination Ethernet Address
the MAC destination address.
Source Ethernet Address
the MAC source address.
1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1
binary representation of the EtherType value 0x86DD.
IPv6 header and payload
the IPv6 packet containing IPv6 header and payload.
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5.2.1. Ethernet Adaptation Layer
In general, an 'adaptation' layer is inserted between a MAC layer and
the Networking layer. This is used to transform some parameters
between their form expected by the IP stack and the form provided by
the MAC layer. For example, an 802.15.4 adaptation layer may perform
fragmentation and reassembly operations on a MAC whose maximum Packet
Data Unit size is smaller than the minimum MTU recognized by the IPv6
Networking layer. Other examples involve link-layer address
transformation, packet header insertion/removal, and so on.
An Ethernet Adaptation Layer makes an 802.11 MAC look to IP
Networking layer as a more traditional Ethernet layer. At reception,
this layer takes as input the IEEE 802.11 Data Header and the
Logical-Link Layer Control Header and produces an Ethernet II Header.
At sending, the reverse operation is performed.
+--------------------+------------+-------------+---------+-----------+
| 802.11 Data Header | LLC Header | IPv6 Header | Payload |.11 Trailer|
+--------------------+------------+-------------+---------+-----------+
\ / \ /
----------------------------- --------
^---------------------------------------------/
|
802.11-to-Ethernet Adaptation Layer
|
v
+---------------------+-------------+---------+
| Ethernet II Header | IPv6 Header | Payload |
+---------------------+-------------+---------+
The Receiver and Transmitter Address fields in the 802.11 Data Header
contain the same values as the Destination and the Source Address
fields in the Ethernet II Header, respectively. The value of the
Type field in the LLC Header is the same as the value of the Type
field in the Ethernet II Header.
The ".11 Trailer" contains solely a 4-byte Frame Check Sequence.
The Ethernet Adaptation Layer performs operations in relation to IP
fragmentation and MTU. One of these operations is briefly described
in section Section 5.1.
In OCB mode, IPv6 packets can be transmitted either as "IEEE 802.11
Data" or alternatively as "IEEE 802.11 QoS Data", as illustrated in
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the figure below. Some commercial OCB products use 802.11 Data, and
others 802.11 QoS data. In the future, both could be used.
+--------------------+-------------+-------------+---------+-----------+
| 802.11 Data Header | LLC Header | IPv6 Header | Payload |.11 Trailer|
+--------------------+-------------+-------------+---------+-----------+
or
+--------------------+-------------+-------------+---------+-----------+
| 802.11 QoS Data Hdr| LLC Header | IPv6 Header | Payload |.11 Trailer|
+--------------------+-------------+-------------+---------+-----------+
The distinction between the two formats is given by the value of the
field "Type/Subtype". The value of the field "Type/Subtype" in the
802.11 Data header is 0x0020. The value of the field "Type/Subtype"
in the 802.11 QoS header is 0x0028.
The mapping between qos-related fields in the IPv6 header (e.g.
"Traffic Class", "Flow label") and fields in the "802.11 QoS Data
Header" (e.g. "QoS Control") are not specified in this document.
Guidance for a potential mapping is provided in
[I-D.ietf-tsvwg-ieee-802-11], although it is not specific to OCB
mode.
5.3. Link-Local Addresses
The link-local address of an 802.11-OCB interface is formed in the
same manner as on an Ethernet interface. This manner is described in
section 5 of [RFC2464].
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.
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- Ethernet -+
| |
+- Address -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option fields:
Type
1 for Source Link-layer address.
2 for Target Link-layer address.
Length
1 (in units of 8 octets).
Ethernet Address
The 48 bit Ethernet IEEE 802 address, in canonical bit order.
5.4.2. Address Mapping -- Multicast
IPv6 protocols often make use of IPv6 multicast addresses in the
destination field of IPv6 headers. For example, an ICMPv6 link-
scoped Neighbor Advertisement is sent to the IPv6 address ff02::1
denoted "all-nodes" address. When transmitting these packets on
802.11-OCB links it is necessary to map the IPv6 address to a MAC
address.
The same mapping requirement applies to the link-scoped multicast
addresses of other IPv6 protocols as well. In DHCPv6, the
"All_DHCP_Servers" IPv6 multicast address ff02::1:2, and in OSPF the
"All_SPF_Routers" IPv6 multicast address ff02::5, need to be mapped
on a multicast MAC address.
An IPv6 packet with a multicast destination address DST, consisting
of the sixteen octets DST[1] through DST[16], is transmitted to the
IEEE 802.11-OCB MAC multicast address whose first two octets are the
value 0x3333 and whose last four octets are the last four octets of
DST.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 1 0 0 1 1|0 0 1 1 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[13] | DST[14] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[15] | DST[16] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Group ID named TBD, of length 112bits is requested to IANA; this
Group ID signifies "All 80211OCB Interfaces Address". Only the least
32 significant bits of this "All 80211OCB Interfaces Address" will be
mapped to and from a MAC multicast address.
Transmitting IPv6 packets to multicast destinations over 802.11 links
proved to have some performance issues
[I-D.perkins-intarea-multicast-ieee802]. These issues may be
exacerbated in OCB mode. Solutions for these problems should
consider the OCB mode of operation.
5.5. Stateless Autoconfiguration
The Interface Identifier for an 802.11-OCB interface is formed using
the same rules as the Interface Identifier for an Ethernet interface;
this is described in section 4 of [RFC2464]. No changes are needed,
but some care must be taken when considering the use of the SLAAC
procedure.
The bits in the the interface identifier have no generic meaning and
the identifier should be treated as an opaque value. The bits
'Universal' and 'Group' in the identifier of an 802.11-OCB interface
are significant, as this is an IEEE link-layer address. The details
of this significance are described in [RFC7136].
As with all Ethernet and 802.11 interface identifiers ([RFC7721]),
the identifier of an 802.11-OCB interface may involve privacy, MAC
address spoofing and IP address hijacking risks. A vehicle embarking
an On-Board Unit whose egress interface is 802.11-OCB may expose
itself to eavesdropping and subsequent correlation of data; this may
reveal data considered private by the vehicle owner; there is a risk
of being tracked; see the privacy considerations described in
Appendix C.
If stable Interface Identifiers are needed in order to form IPv6
addresses on 802.11-OCB links, it is recommended to follow the
recommendation in [RFC8064].
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5.6. Subnet Structure
A subnet is formed by the external 802.11-OCB interfaces of vehicles
that are in close range (not their on-board interfaces). This
ephemeral subnet structure is strongly influenced by the mobility of
vehicles: the 802.11 hidden node effects appear. On another hand,
the structure of the internal subnets in each car is relatively
stable.
For routing purposes, a prefix exchange mechanism could be needed
between neighboring vehicles.
The 802.11 networks in OCB mode may be considered as 'ad-hoc'
networks. The addressing model for such networks is described in
[RFC5889].
An addressing model involves several types of addresses, like
Globally-unique Addresses (GUA), Link-Local Addresses (LL) and Unique
Local Addresses (ULA). The subnet structure in 'ad-hoc' networks may
have characteristics that lead to difficulty of using GUAs derived
from a received prefix, but the LL addresses may be easier to use
since the prefix is constant.
6. Security Considerations
Any security mechanism at the IP layer or above that may be carried
out for the general case of IPv6 may also be carried out for IPv6
operating over 802.11-OCB.
802.11-OCB does not provide any cryptographic protection, because it
operates outside the context of a BSS (no Association Request/
Response, no Challenge messages). Any attacker can therefore just
sit in the near range of vehicles, sniff the network (just set the
interface card's frequency to the proper range) and perform attacks
without needing to physically break any wall. Such a link is less
protected than commonly used links (wired link or protected 802.11).
The potential attack vectors are: MAC address spoofing, IP address
and session hijacking and privacy violation.
Within the IPsec Security Architecture [RFC4301], the IPsec AH and
ESP headers [RFC4302] and [RFC4303] respectively, its multicast
extensions [RFC5374], HTTPS [RFC2818] and SeND [RFC3971] protocols
can be used to protect communications. Further, the assistance of
proper Public Key Infrastructure (PKI) protocols [RFC4210] is
necessary to establish credentials. More IETF protocols are
available in the toolbox of the IP security protocol designer.
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Certain ETSI protocols related to security protocols in Intelligent
Transportation Systems are described in [ETSI-sec-archi].
As with all Ethernet and 802.11 interface identifiers, there may
exist privacy risks in the use of 802.11-OCB interface identifiers.
Moreover, in outdoors vehicular settings, the privacy risks are more
important than in indoors settings. New risks are induced by the
possibility of attacker sniffers deployed along routes which listen
for IP packets of vehicles passing by. For this reason, in the
802.11-OCB deployments, there is a strong necessity to use protection
tools such as dynamically changing MAC addresses. This may help
mitigate privacy risks to a certain level. On another hand, it may
have an impact in the way typical IPv6 address auto-configuration is
performed for vehicles (SLAAC would rely on MAC addresses amd would
hence dynamically change the affected IP address), in the way the
IPv6 Privacy addresses were used, and other effects.
7. IANA Considerations
A Group ID named TBD, of length 112bits is requested to IANA; this
Group ID signifies "All 80211OCB Interfaces Address".
8. Contributors
Romain Kuntz contributed extensively about IPv6 handovers between
links running outside the context of a BSS (802.11-OCB links).
Tim Leinmueller contributed the idea of the use of IPv6 over
802.11-OCB for distribution of certificates.
Marios Makassikis, Jose Santa Lozano, Albin Severinson and Alexey
Voronov provided significant feedback on the experience of using IP
messages over 802.11-OCB in initial trials.
Michelle Wetterwald contributed extensively the MTU discussion,
offered the ETSI ITS perspective, and reviewed other parts of the
document.
9. Acknowledgements
The authors would like to thank Witold Klaudel, Ryuji Wakikawa,
Emmanuel Baccelli, John Kenney, John Moring, Francois Simon, Dan
Romascanu, Konstantin Khait, Ralph Droms, Richard 'Dick' Roy, Ray
Hunter, Tom Kurihara, Michal Sojka, Jan de Jongh, Suresh Krishnan,
Dino Farinacci, Vincent Park, Jaehoon Paul Jeong, Gloria Gwynne,
Hans-Joachim Fischer, Russ Housley, Rex Buddenberg, Erik Nordmark,
Bob Moskowitz, Andrew (Dryden?), Georg Mayer, Dorothy Stanley, Sandra
Cespedes, Mariano Falcitelli, Sri Gundavelli and William Whyte.
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Their valuable comments clarified particular issues and generally
helped to improve the document.
Pierre Pfister, Rostislav Lisovy, and others, wrote 802.11-OCB
drivers for linux and described how.
For the multicast discussion, the authors would like to thank Owen
DeLong, Joe Touch, Jen Linkova, Erik Kline, Brian Haberman and
participants to discussions in network working groups.
The authours would like to thank participants to the Birds-of-
a-Feather "Intelligent Transportation Systems" meetings held at IETF
in 2016.
10. References
10.1. Normative References
[I-D.ietf-tsvwg-ieee-802-11]
Szigeti, T., Henry, J., and F. Baker, "Diffserv to IEEE
802.11 Mapping", draft-ietf-tsvwg-ieee-802-11-07 (work in
progress), September 2017.
[RFC1042] Postel, J. and J. Reynolds, "Standard for the transmission
of IP datagrams over IEEE 802 networks", STD 43, RFC 1042,
DOI 10.17487/RFC1042, February 1988,
<https://www.rfc-editor.org/info/rfc1042>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<https://www.rfc-editor.org/info/rfc2464>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC3753] Manner, J., Ed. and M. Kojo, Ed., "Mobility Related
Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004,
<https://www.rfc-editor.org/info/rfc3753>.
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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>.
[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971,
DOI 10.17487/RFC3971, March 2005,
<https://www.rfc-editor.org/info/rfc3971>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen,
"Internet X.509 Public Key Infrastructure Certificate
Management Protocol (CMP)", RFC 4210,
DOI 10.17487/RFC4210, September 2005,
<https://www.rfc-editor.org/info/rfc4210>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/info/rfc4303>.
[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006,
<https://www.rfc-editor.org/info/rfc4429>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast
Extensions to the Security Architecture for the Internet
Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
<https://www.rfc-editor.org/info/rfc5374>.
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[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>.
[RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
September 2010, <https://www.rfc-editor.org/info/rfc5889>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
February 2014, <https://www.rfc-editor.org/info/rfc7136>.
[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>.
[RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu,
"Recommendation on Stable IPv6 Interface Identifiers",
RFC 8064, DOI 10.17487/RFC8064, February 2017,
<https://www.rfc-editor.org/info/rfc8064>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
10.2. Informative References
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[ETSI-IPv6-GeoNetworking]
"ETSI EN 302 636-6-1 v1.2.1 (2014-05), ETSI, European
Standard, Intelligent Transportation Systems (ITS);
Vehicular Communications; Geonetworking; Part 6: Internet
Integration; Sub-part 1: Transmission of IPv6 Packets over
Geonetworking Protocols. Downloaded on September 9th,
2017, freely available from ETSI website at URL
http://www.etsi.org/deliver/
etsi_en/302600_302699/30263601/01.02.01_60/
en_30263601v010201p.pdf".
[ETSI-sec-archi]
"ETSI TS 102 940 V1.2.1 (2016-11), ETSI Technical
Specification, Intelligent Transport Systems (ITS);
Security; ITS communications security architecture and
security management, November 2016. Dowloaded on
September 9th, 2017, freely available from ETSI website at
URL http://www.etsi.org/deliver/
etsi_ts/102900_102999/102940/01.02.01_60/
ts_102940v010201p.pdf".
[I-D.hinden-6man-rfc2464bis]
Crawford, M. and R. Hinden, "Transmission of IPv6 Packets
over Ethernet Networks", draft-hinden-6man-rfc2464bis-02
(work in progress), March 2017.
[I-D.jeong-ipwave-vehicular-networking-survey]
Jeong, J., Cespedes, S., Benamar, N., Haerri, J., and M.
Wetterwald, "Survey on IP-based Vehicular Networking for
Intelligent Transportation Systems", draft-jeong-ipwave-
vehicular-networking-survey-03 (work in progress), June
2017.
[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.
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[IEEE-1609.2]
"IEEE SA - 1609.2-2016 - IEEE Standard for Wireless Access
in Vehicular Environments (WAVE) -- Security Services for
Applications and Management Messages. Example URL
http://ieeexplore.ieee.org/document/7426684/ accessed on
August 17th, 2017.".
[IEEE-1609.3]
"IEEE SA - 1609.3-2016 - IEEE Standard for Wireless Access
in Vehicular Environments (WAVE) -- Networking Services.
Example URL http://ieeexplore.ieee.org/document/7458115/
accessed on August 17th, 2017.".
[IEEE-1609.4]
"IEEE SA - 1609.4-2016 - IEEE Standard for Wireless Access
in Vehicular Environments (WAVE) -- Multi-Channel
Operation. Example URL
http://ieeexplore.ieee.org/document/7435228/ accessed on
August 17th, 2017.".
[IEEE-802.11-2012]
"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.".
[IEEE-802.11p-2010]
"IEEE Std 802.11p (TM)-2010, IEEE Standard for Information
Technology - Telecommunications and information exchange
between systems - Local and metropolitan area networks -
Specific requirements, Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) Specifications,
Amendment 6: Wireless Access in Vehicular Environments;
document freely available at URL
http://standards.ieee.org/getieee802/
download/802.11p-2010.pdf retrieved on September 20th,
2013.".
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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-04 to draft-ietf-ipwave-
ipv6-over-80211ocb-05
o Lengthened the title and cleanded the abstract.
o Added text suggesting LLs may be easy to use on OCB, rather than
GUAs based on received prefix.
o Added the risks of spoofing and hijacking.
o Removed the text speculation on adoption of the TSA message.
o Clarified that the ND protocol is used.
o Clarified what it means "No association needed".
o Added some text about how two STAs discover each other.
o Added mention of external (OCB) and internal network (stable), in
the subnet structure section.
o Added phrase explaining that both .11 Data and .11 QoS Data
headers are currently being used, and may be used in the future.
o Moved the packet capture example into an Appendix Implementation
Status.
o Suggested moving the reliability requirements appendix out into
another document.
o Added a IANA Consiserations section, with content, requesting for
a new multicast group "all OCB interfaces".
o Added new OBU term, improved the RSU term definition, removed the
ETTC term, replaced more occurences of 802.11p, 802.11 OCB with
802.11-OCB.
o References:
* Added an informational reference to ETSI's IPv6-over-
GeoNetworking.
* Added more references to IETF and ETSI security protocols.
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* Updated some references from I-D to RFC, and from old RFC to
new RFC numbers.
* Added reference to multicast extensions to IPsec architecture
RFC.
* Added a reference to 2464-bis.
* Removed FCC informative references, because not used.
o Updated the affiliation of one author.
o Reformulation of some phrases for better readability, and
correction of typographical errors.
From draft-ietf-ipwave-ipv6-over-80211ocb-03 to draft-ietf-ipwave-
ipv6-over-80211ocb-04
o Removed a few informative references pointing to Dx draft IEEE
1609 documents.
o Removed outdated informative references to ETSI documents.
o Added citations to IEEE 1609.2, .3 and .4-2016.
o Minor textual issues.
From draft-ietf-ipwave-ipv6-over-80211ocb-02 to draft-ietf-ipwave-
ipv6-over-80211ocb-03
o Keep the previous text on multiple addresses, so remove talk about
MIP6, NEMOv6 and MCoA.
o Clarified that a 'Beacon' is an IEEE 802.11 frame Beacon.
o Clarified the figure showing Infrastructure mode and OCB mode side
by side.
o Added a reference to the IP Security Architecture RFC.
o Detailed the IPv6-per-channel prohibition paragraph which reflects
the discussion at the last IETF IPWAVE WG meeting.
o Added section "Address Mapping -- Unicast".
o Added the ".11 Trailer" to pictures of 802.11 frames.
o Added text about SNAP carrying the Ethertype.
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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.
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.
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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:
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).
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* 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).
* Timing Advertisement frames, defined in the amendment, should
be supported. The upper layer should be able to trigger such
frames emission and to retrieve information contained in
received Timing Advertisements.
Appendix C. Design Considerations
The networks defined by 802.11-OCB are in many ways similar to other
networks of the 802.11 family. In theory, the encapsulation of IPv6
over 802.11-OCB could be very similar to the operation of IPv6 over
other networks of the 802.11 family. However, the high mobility,
strong link asymmetry and very short connection makes the 802.11-OCB
link significantly different from other 802.11 networks. Also, the
automotive applications have specific requirements for reliability,
security and privacy, which further add to the particularity of the
802.11-OCB link.
C.1. Vehicle ID
In automotive networks it is required that each node is represented
uniquely. Accordingly, a vehicle must be identified by at least one
unique identifier. The current specification at ETSI and at IEEE
1609 identifies a vehicle by its MAC address, which is obtained from
the 802.11-OCB Network Interface Card (NIC).
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In case multiple 802.11-OCB NICs are present in one car, implicitely
multiple vehicle IDs will be generated. Additionally, some software
generates a random MAC address each time the computer boots; this
constitutes an additional difficulty.
A mechanim to uniquely identify a vehicle irrespectively to the
multiplicity of NICs, or frequent MAC address generation, is
necessary.
C.2. Reliability Requirements
This section may need to be moved out into a separate requirements
document.
The dynamically changing topology, short connectivity, mobile
transmitter and receivers, different antenna heights, and many-to-
many communication types, make IEEE 802.11-OCB links significantly
different from other IEEE 802.11 links. Any IPv6 mechanism operating
on IEEE 802.11-OCB link MUST support strong link asymmetry, spatio-
temporal link quality, fast address resolution and transmission.
IEEE 802.11-OCB strongly differs from other 802.11 systems to operate
outside of the context of a Basic Service Set. This means in
practice that IEEE 802.11-OCB does not rely on a Base Station for all
Basic Service Set management. In particular, IEEE 802.11-OCB SHALL
NOT use beacons. Any IPv6 mechanism requiring L2 services from IEEE
802.11 beacons MUST support an alternative service.
Channel scanning being disabled, IPv6 over IEEE 802.11-OCB MUST
implement a mechanism for transmitter and receiver to converge to a
common channel.
Authentication not being possible, IPv6 over IEEE 802.11-OCB MUST
implement an distributed mechanism to authenticate transmitters and
receivers without the support of a DHCP server.
Time synchronization not being available, IPv6 over IEEE 802.11-OCB
MUST implement a higher layer mechanism for time synchronization
between transmitters and receivers without the support of a NTP
server.
The IEEE 802.11-OCB link being asymmetric, IPv6 over IEEE 802.11-OCB
MUST disable management mechanisms requesting acknowledgements or
replies.
The IEEE 802.11-OCB link having a short duration time, IPv6 over IEEE
802.11-OCB SHOULD implement fast IPv6 mobility management mechanisms.
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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.
Certain privacy requirements imply that if these multiple interfaces
are represented by many network interface, a single renumbering event
SHALL cause renumbering of all these interfaces. If one MAC changed
and another stayed constant, external observers would be able to
correlate old and new values, and the privacy benefits of
randomization would be lost.
The privacy requirements of Non IP safety-critical communications
imply that if a change of pseudonyme occurs, renumbering of all other
interfaces SHALL also occur.
C.4. MAC Address Generation
When designing the IPv6 over 802.11-OCB address mapping, we will
assume that the MAC Addresses will change during well defined
"renumbering events". The 48 bits randomized MAC addresses will have
the following characteristics:
o Bit "Local/Global" set to "locally admninistered".
o Bit "Unicast/Multicast" set to "Unicast".
o 46 remaining bits set to a random value, using a random number
generator that meets the requirements of [RFC4086].
The way to meet the randomization requirements is to retain 46 bits
from the output of a strong hash function, such as SHA256, taking as
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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.
Appendix E. Implementation Status
This section describese an example of an IPv6 Packet captured over a
IEEE 802.11-OCB link.
By way of example we show that there is no modification in the
headers when transmitted over 802.11-OCB networks - they are
transmitted like any other 802.11 and Ethernet packets.
We describe an experiment of capturing an IPv6 packet on an
802.11-OCB link. In this experiment, the packet is an IPv6 Router
Advertisement. This packet is emitted by a Router on its 802.11-OCB
interface. The packet is captured on the Host, using a network
protocol analyzer (e.g. Wireshark); the capture is performed in two
different modes: direct mode and 'monitor' mode. The topology used
during the capture is depicted below.
+--------+ +-------+
| | 802.11-OCB Link | |
---| Router |--------------------------------| Host |
| | | |
+--------+ +-------+
During several capture operations running from a few moments to
several hours, no message relevant to the BSSID contexts were
captured (no Association Request/Response, Authentication Req/Resp,
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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.
E.1. Capture in Monitor Mode
The IPv6 RA packet captured in monitor mode is illustrated below.
The radio tap header provides more flexibility for reporting the
characteristics of frames. The Radiotap Header is prepended by this
particular stack and operating system on the Host machine to the RA
packet received from the network (the Radiotap Header is not present
on the air). The implementation-dependent Radiotap Header is useful
for piggybacking PHY information from the chip's registers as data in
a packet understandable by userland applications using Socket
interfaces (the PHY interface can be, for example: power levels, data
rate, ratio of signal to noise).
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 the corresponding multicast MAC address. The BSS id is a
broadcast address of ff:ff:ff:ff:ff:ff. Due to the short link
duration between vehicles and the roadside infrastructure, there is
no need in IEEE 802.11-OCB to wait for the completion of association
and authentication procedures before exchanging data. IEEE
802.11-OCB enabled nodes use the wildcard BSSID (a value of all 1s)
and may start communicating as soon as they arrive on the
communication channel.
E.2. Capture in Normal Mode
The same IPv6 Router Advertisement packet described above (monitor
mode) is captured on the Host, in the Normal mode, and depicted
below.
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Ethernet II Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Destination | Source...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
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One notices that the Radiotap Header, the IEEE 802.11 Data Header and
the Logical-Link Control Headers are not present. On the other hand,
a new header named Ethernet II Header is present.
The Destination and Source addresses in the Ethernet II header
contain the same values as the fields Receiver Address and
Transmitter Address present in the IEEE 802.11 Data Header in the
"monitor" mode capture.
The value of the Type field in the Ethernet II header is 0x86DD
(recognized as "IPv6"); this value is the same value as the value of
the field Type in the Logical-Link Control Header in the "monitor"
mode capture.
The knowledgeable experimenter will no doubt notice the similarity of
this Ethernet II Header with a capture in normal mode on a pure
Ethernet cable interface.
An Adaptation layer is inserted on top of a pure IEEE 802.11 MAC
layer, in order to adapt packets, before delivering the payload data
to the applications. It adapts 802.11 LLC/MAC headers to Ethernet II
headers. In further detail, this adaptation consists in the
elimination of the Radiotap, 802.11 and LLC headers, and in the
insertion of the Ethernet II header. In this way, IPv6 runs straight
over LLC over the 802.11-OCB MAC layer; this is further confirmed by
the use of the unique Type 0x86DD.
Authors' Addresses
Alexandre Petrescu
CEA, LIST
CEA Saclay
Gif-sur-Yvette , Ile-de-France 91190
France
Phone: +33169089223
Email: Alexandre.Petrescu@cea.fr
Nabil Benamar
Moulay Ismail University
Morocco
Phone: +212670832236
Email: benamar73@gmail.com
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Jerome Haerri
Eurecom
Sophia-Antipolis 06904
France
Phone: +33493008134
Email: Jerome.Haerri@eurecom.fr
Christian Huitema
Private Octopus Inc.
Friday Harbor, WA 98250
U.S.A.
Email: huitema@huitema.net
Jong-Hyouk Lee
Sangmyung University
31, Sangmyeongdae-gil, Dongnam-gu
Cheonan 31066
Republic of Korea
Email: jonghyouk@smu.ac.kr
Thierry Ernst
YoGoKo
France
Email: thierry.ernst@yogoko.fr
Tony Li
Peloton Technology
1060 La Avenida St.
Mountain View, California 94043
United States
Phone: +16503957356
Email: tony.li@tony.li
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