Network Working Group A. Petrescu
Internet-Draft CEA, LIST
Intended status: Standards Track N. Benamar
Expires: June 4, 2017 Moulay Ismail University
J. Haerri
Eurecom
C. Huitema
J. Lee
Sangmyung University
T. Ernst
YoGoKo
T. Li
Peloton Technology
December 1, 2016
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-00.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
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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-
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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 June 4, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Communication Scenarios where IEEE 802.11p Links are Used . . 6
4. Aspects introduced by the OCB mode to 802.11 . . . . . . . . 6
5. Layering of IPv6 over 802.11p as over Ethernet . . . . . . . 9
5.1. Maximum Transmission Unit (MTU) . . . . . . . . . . . . . 9
5.2. Frame Format . . . . . . . . . . . . . . . . . . . . . . 10
5.2.1. Ethernet Adaptation Layer . . . . . . . . . . . . . . 11
5.3. Link-Local Addresses . . . . . . . . . . . . . . . . . . 13
5.4. Address Mapping . . . . . . . . . . . . . . . . . . . . . 13
5.4.1. Address Mapping -- Unicast . . . . . . . . . . . . . 13
5.4.2. Address Mapping -- Multicast . . . . . . . . . . . . 13
5.5. Stateless Autoconfiguration . . . . . . . . . . . . . . . 14
5.6. Subnet Structure . . . . . . . . . . . . . . . . . . . . 15
6. Handovers between OCB links . . . . . . . . . . . . . . . . . 15
7. Example IPv6 Packet captured over a IEEE 802.11p link . . . . 17
7.1. Capture in Monitor Mode . . . . . . . . . . . . . . . . . 18
7.2. Capture in Normal Mode . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
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11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
12.1. Normative References . . . . . . . . . . . . . . . . . . 25
12.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. ChangeLog . . . . . . . . . . . . . . . . . . . . . 30
Appendix B. Explicit Prohibition of IPv6 on Channels
Related to ITS Scenarios using 802.11p Networks
- an Analysis . . . . . . . . . . . . . . . . . . . 32
B.1. Interpretation of FCC and ETSI documents with
respect to running IP on particular channels . . . . . . 32
B.2. Interpretations of Latencies of IP datagrams . . . . . . 33
Appendix C. Changes Needed on a software driver 802.11a to
become a 802.11-OCB driver . . 33
Appendix D. Design Considerations . . . . . . . . . . . . . . . 34
D.1. Vehicle ID . . . . . . . . . . . . . . . . . . . . . . . 35
D.2. Non IP Communications . . . . . . . . . . . . . . . . . . 35
D.3. Reliability Requirements . . . . . . . . . . . . . . . . 36
D.4. Privacy requirements . . . . . . . . . . . . . . . . . . 37
D.5. Authentication requirements . . . . . . . . . . . . . . . 38
D.6. Multiple interfaces . . . . . . . . . . . . . . . . . . . 38
D.7. MAC Address Generation . . . . . . . . . . . . . . . . . 39
D.8. Security Certificate Generation . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction
This document describes the transmission of IPv6 packets on IEEE Std
802.11 OCB networks (earlier known as 802.11p). This involves the
layering of IPv6 networking on top of the IEEE 802.11 MAC layer (with
an LLC layer). Compared to running IPv6 over the Ethernet MAC layer,
there is no modification required to the standards: IPv6 works fine
directly over 802.11 OCB too (with an LLC layer).
The term "802.11p" is an earlier definition. As of year 2012, the
behaviour of "802.11p" networks has been rolled in the document IEEE
Std 802.11-2012. In this document the term 802.11p disappears.
Instead, each 802.11p feature is conditioned by a flag in the
Management Information Base. That flag is named "OCBActivated".
Whenever OCBActivated is set to true the feature it relates to
represents an earlier 802.11p feature. For example, an 802.11
STAtion operating outside the context of a basic service set has the
OCBActivated flag set. Such a station, when it has the flag set, it
uses a BSS identifier equal to ff:ff:ff:ff:ff:ff.
In the following text we use the term "802.11p" to mean 802.11-2012
OCB, and vice-versa.
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As an overview, we illustrate how an IPv6 stack runs over 802.11p by
layering different protocols on top of each other. The IPv6
Networking is layered on top of the IEEE 802.2 Logical-Link Control
(LLC) layer; this is itself layered on top of the 802.11p MAC; this
layering illustration is similar to that of running IPv6 over 802.2
LLC over the 802.11 MAC, or over Ethernet MAC.
+-----------------+ +-----------------+
| ... | | ... |
+-----------------+ +-----------------+
| IPv6 Networking | | IPv6 Networking |
+-----------------+ +-----------------+
| 802.2 LLC | vs. | 802.2 LLC |
+-----------------+ +-----------------+
| 802.11p MAC | | 802.11b MAC |
+-----------------+ +-----------------+
| 802.11p PHY | | 802.11b PHY |
+-----------------+ +-----------------+
However, there are several deployment considerations to optimize the
performances of running IPv6 over 802.11p (e.g. in the case of
handovers between 802.11p Access Points, or the consideration of
using the IP security layer).
We briefly introduce the vehicular communication scenarios where IEEE
802.11-OCB links are used. This is followed by a description of
differences in specification terms, between 802.11p and 802.11a/b/g/n
(and the same differences expressed in terms of requirements to
software implementation are listed in Appendix C.)
The document then concentrates on the parameters of layering IP over
802.11p as over Ethernet: MTU, Frame Format, Interface Identifier,
Address Mapping, State-less Address Auto-configuration. The values
of these parameters are precisely the same as IPv6 over Ethernet
[RFC2464]: the recommended value of MTU to be 1500 octets, the Frame
Format containing the Type 0x86DD, the rules for forming an Interface
Identifier, the Address Mapping mechanism and the Stateless Address
Auto-Configuration.
As an example, these characteristics of layering IPv6 straight over
LLC over 802.11p MAC are illustrated by dissecting an IPv6 packet
captured over a 802.11p link; this is described in the section titled
"Example of IPv6 Packet captured over an IEEE 802.11p link".
A couple of points can be considered as different, although they are
not required in order to have a working implementation of IPv6-over-
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802.11p. These points are consequences of the OCB operation which is
particular to 802.11p (Outside the Context of a BSS). First, the
handovers between OCB links need specific behaviour for IP Router
Advertisements, or otherwise 802.11p's Time Advertisement, or of
higher layer messages such as the 'Basic Safety Message' (in the US)
or the 'Cooperative Awareness Message' (in the EU) or the 'WAVE
Routing Advertisement'; second, the IP security mechanisms are
necessary, since OCB means that 802.11p is stripped of all 802.11
link-layer security; a small additional security aspect which is
shared between 802.11p and other 802.11 links is the privacy concerns
related to the address formation mechanisms. The OCB handovers and
security are described each in section Section 6 and Section 8
respectively.
In standards, the operation of IPv6 as a 'data plane' over 802.11p is
specified at IEEE P1609 in [ieeep1609.3-D9-2010]. For example, it
mentions that "Networking services also specifies the use of the
Internet protocol IPv6, and supports transport protocols such as UDP
and TCP. [...] A Networking Services implementation shall support
either IPv6 or WSMP or both." and "IP traffic is sent and received
through the LLC sublayer as specified in [...]". The layered stacks
depicted in the "Architecture" document P1609.0 [ieeep1609.0-D2]
suggest that WSMP messages may not be transmitted as payload of IPv6
datagrams; WSMP and IPv6 are parallel (not stacked) layers.
Also, the operation of IPv6 over a GeoNetworking layer and over G5 is
described in [etsi-302663-v1.2.1p-2013].
In the published literature, three documents describe aspects related
to running IPv6 over 802.11p: [vip-wave], [ipv6-80211p-its] and
[ipv6-wave].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
RSU: Road Side Unit.
OCB: Outside the Context of a Basic Service Set identifier.
OCB - Outside the Context of a Basic-Service Set ID (BSSID).
802.11-OCB - IEEE 802.11-2012 text flagged by "dot11OCBActivated".
This means: IEEE 802.11e for quality of service; 802.11j-2004 for
half-clocked operations; and 802.11p for operation in the 5.9 GHz
band and in mode OCB.
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3. Communication Scenarios where IEEE 802.11p Links are Used
The IEEE 802.11p Networks are used for vehicular communications, as
'Wireless Access in Vehicular Environments'. The IP communication
scenarios for these environments have been described in several
documents, among which we refer the reader to one recently updated
[I-D.petrescu-its-scenarios-reqs], about scenarios and requirements
for IP in Intelligent Transportation Systems.
4. Aspects introduced by the OCB mode to 802.11
In the IEEE 802.11 OCB mode, all nodes in the wireless range can
directly communicate with each other without authentication/
association procedures. Briefly, the IEEE 802.11 OCB mode has the
following properties:
o Wildcard BSSID (i.e., all bits are set to 1) used by each node
o No beacons transmitted
o No authentication required
o No association needed
o No encryption provided
o dot11OCBActivated OID set to true
The link 802.11p is specified in IEEE Std 802.11p(TM)-2010
[ieee802.11p-2010] as an amendment to the 802.11 specifications,
titled "Amendment 6: Wireless Access in Vehicular Environments".
Since then, these 802.11p amendments have been included in IEEE
802.11(TM)-2012 [ieee802.11-2012], titled "IEEE Standard for
Information technology--Telecommunications and information exchange
between systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) Specifications"; the modifications are diffused
throughout various sections (e.g. 802.11p's Time Advertisement
message is described in section 'Frame formats', and the operation
outside the context of a BSS described in section 'MLME').
In document 802.11-2012, specifically anything referring
"OCBActivated", or "outside the context of a basic service set" is
actually referring to the 802.11p aspects introduced to 802.11. Note
in earlier 802.11p documents the term "OCBEnabled" was used instead.
In order to delineate the aspects introduced by 802.11p to 802.11, we
refer to the earlier [ieee802.11p-2010]. The amendment is concerned
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with vehicular communications, where the wireless link is similar to
that of Wireless LAN (using a PHY layer specified by 802.11a/b/g/n),
but which needs to cope with the high mobility factor inherent in
scenarios of communications between moving vehicles, and between
vehicles and fixed infrastructure deployed along roads. While 'p' is
a letter just like 'a, b, g' and 'n' are, 'p' is concerned more with
MAC modifications, and a little with PHY modifications; the others
are mainly about PHY modifications. It is possible in practice to
combine a 'p' MAC with an 'a' PHY by operating outside the context of
a BSS with OFDM at 5.4GHz.
The 802.11p links are specified to be compatible as much as possible
with the behaviour of 802.11a/b/g/n and future generation IEEE WLAN
links. From the IP perspective, an 802.11p MAC layer offers
practically the same interface to IP as the WiFi and Ethernet layers
do (802.11a/b/g/n and 802.3).
To support this similarity statement (IPv6 is layered on top of LLC
on top of 802.11p similarly as on top of LLC on top of 802.11a/b/g/n,
and as on top of LLC on top of 802.3) it is useful to analyze the
differences between 802.11p and non-p 802.11 specifications. Whereas
the 802.11p amendment specifies relatively complex and numerous
changes to the MAC layer (and very little to the PHY layer), we note
there are only a few characteristics which may be important for an
implementation transmitting IPv6 packets on 802.11p links.
In the list below, the only 802.11p fundamental points which
influence IPv6 are the OCB operation and the 12Mbit/s maximum which
may be afforded by the IPv6 applications.
o Operation Outside the Context of a BSS (OCB): the 802.11p links
are operated without a Basic Service Set (BSS). This means that
the messages Beacon, Association Request/Response, Authentication
Request/Response, and similar, are not used. The used identifier
of BSS (BSSID) has a hexadecimal value always ff:ff:ff:ff:ff:ff
(48 '1' bits, or the 'wildcard' BSSID), as opposed to an arbitrary
BSSID value set by administrator (e.g. 'My-Home-AccessPoint').
The OCB operation - namely the lack of beacon-based scanning and
lack of authentication - has a potentially strong impact on the
use of the Mobile IPv6 protocol and on the protocols for IP layer
security.
o Timing Advertisement: is a new message defined in 802.11p, which
does not exist in 802.11a/b/g/n. This message is used by stations
to inform other stations about the value of time. It is similar
to the time as delivered by a GNSS system (Galileo, GPS, ...) or
by a cellular system. This message is optional for
implementation. At the date of writing, an experienced reviewer
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considers that currently no field testing has used this message.
Another implementor considers this feature implemented in an
initial manner. In the future, it is speculated that this message
may be useful for very simple devices which may not have their own
hardware source of time (Galileo, GPS, cellular network), or by
vehicular devices situated in areas not covered by such network
(in tunnels, underground, outdoors but shaded by foliage or
buildings, in remote areas, etc.)
o Frequency range: this is a characteristic of the PHY layer, with
almost no impact to the interface between MAC and IP. However, it
is worth considering that the frequency range is regulated by a
regional authority (ARCEP, ETSI, FCC, etc.); as part of the
regulation process, specific applications are associated with
specific frequency ranges. In the case of 802.11p, the regulator
associates a set of frequency ranges, or slots within a band, to
the use of applications of vehicular communications, in a band
known as "5.9GHz". This band is "5.9GHz" which is different from
the bands "2.4GHz" or "5GHz" used by Wireless LAN. However, as
with Wireless LAN, the operation of 802.11p in "5.9GHz" bands is
exempt from owning a license in EU (in US the 5.9GHz is a licensed
band of spectrum; for the the fixed infrastructure an explicit FCC
autorization is required; for an onboard device a 'licensed-by-
rule' concept applies: rule certification conformity is required);
however technical conditions are different than those of the bands
"2.4GHz" or "5GHz". On one hand, the allowed power levels, and
implicitly the maximum allowed distance between vehicles, is of
33dBm for 802.11p (in Europe), compared to 20 dBm for Wireless LAN
802.11a/b/g/n; this leads to a maximum distance of approximately
1km, compared to approximately 50m. On the hand, specific
conditions related to congestion avoidance, jamming avoidance, and
radar detection are imposed on the use of DSRC (in US) and on the
use of frequencies for Intelligent Transportation Systems (in EU),
compared to Wireless LAN (802.11a/b/g/n).
o Explicit prohibition of IPv6 on some channels relevant for the PHY
of IEEE 802.11p, as opposed to IPv6 not being prohibited on any
channel on which 802.11a/b/g/n runs; for example, IPv6 is
prohibited on the 'Control Channel' (number 178 at FCC/IEEE, and
180 at ETSI); for a detailed analysis of IEEE and ETSI prohibition
of IP in particular channels see Appendix B.
o 'Half-rate' encoding: as the frequency range, this parameter is
related to PHY, and thus has not much impact on the interface
between the IP layer and the MAC layer. The standard IEEE 802.11p
uses OFDM encoding at PHY, as other non-b 802.11 variants do.
This considers 20MHz encoding to be 'full-rate' encoding, as the
earlier 20MHz encoding which is used extensively by 802.11b. In
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addition to the full-rate encoding, the OFDM rates also involve
5MHz and 10MHz. The 10MHz encoding is named 'half-rate'. The
encoding dictates the bandwidth and latency characteristics that
can be afforded by the higher-layer applications of IP
communications. The half-rate means that each symbol takes twice
the time to be transmitted; for this to work, all 802.11 software
timer values are doubled. With this, in certain channels of the
"5.9GHz" band, a maximum bandwidth of 12Mbit/s is possible,
whereas in other "5.9GHz" channels a minimal bandwidth of 1Mbit/s
may be used. It is worth mentioning the half-rate encoding is an
optional feature characteristic of OFDM PHY (compared to 802.11b's
full-rate 20MHz), used by 802.11a before 802.11p used it. In
addition to the half-rate (10MHz) used by 802.11p in some
channels, some other 802.11p channels may use full-rate (20MHz) or
quarter-rate(?) (5MHz) encoding instead.
o It is worth mentioning that more precise interpretations of the
'half-rate' term suggest that a maximum throughput be 27Mbit/s
(which is half of 802.11g's 54Mbit/s), whereas 6Mbit/s or 12Mbit/s
throughputs represent effects of further 802.11p-specific PHY
reductions in the throughput necessary to better accommodate
vehicle-class speeds and distance ranges.
o In vehicular communications using 802.11p links, there are strong
privacy concerns with respect to addressing. While the 802.11p
standard does not specify anything in particular with respect to
MAC addresses, in these settings there exists a strong need for
dynamic change of these addresses (as opposed to the non-vehicular
settings - real wall protection - where fixed MAC addresses do not
currently pose some privacy risks). This is further described in
section Section 8.
Other aspects particular to 802.11p which are also particular to
802.11 (e.g. the 'hidden node' operation) may have an influence on
the use of transmission of IPv6 packets on 802.11p networks. The
subnet structure which may be assumed in 802.11p networks is strongly
influenced by the mobility of vehicles.
5. Layering of IPv6 over 802.11p as over Ethernet
5.1. Maximum Transmission Unit (MTU)
The default MTU for IP packets on 802.11p is 1500 octets. It is the
same value as IPv6 packets on Ethernet links, as specified in
[RFC2464]. This value of the MTU respects the recommendation that
every link in the Internet must have a minimum MTU of 1280 octets
(stated in [RFC2460], and the recommendations therein, especially
with respect to fragmentation). If IPv6 packets of size larger than
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1500 bytes are sent on an 802.11-OCB interface then the IP stack will
fragment. In case there are IP fragments, the field "Sequence
number" of the 802.11 Data header containing the IP fragment field is
increased.
Non-IP packets such as WAVE Short Message Protocol (WSMP) can be
delivered on 802.11-OCB links. Specifications of these packets are
out of scope of this document, and do not impose any limit on the MTU
size, allowing an arbitrary number of 'containers'. Non-IP packets
such as ETSI 'geonet' packets have an MTU of 1492 bytes.
The Equivalent Transmit Time on Channel is a concept that may be used
as an alternative to the MTU concept. A rate of transmission may be
specified as well. The ETTC, rate and MTU may be in direct
relationship.
5.2. Frame Format
IP packets are transmitted over 802.11p as standard Ethernet packets.
As with all 802.11 frames, an Ethernet adaptation layer is used with
802.11p as well. This Ethernet Adaptation Layer 802.11-to-Ethernet
is described in Section 5.2.1. The Ethernet Type code (EtherType)
for IPv6 is 0x86DD (hexadecimal 86DD, or otherwise #86DD).
The Frame format for transmitting IPv6 on 802.11p networks is the
same as transmitting IPv6 on Ethernet networks, and is described in
section 3 of [RFC2464]. The frame format for transmitting IPv6
packets over Ethernet is illustrated below:
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination |
+- -+
| Ethernet |
+- -+
| Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source |
+- -+
| Ethernet |
+- -+
| Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 |
+- -+
| header |
+- -+
| and |
+- -+
/ payload ... /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(Each tic mark represents one bit.)
5.2.1. Ethernet Adaptation Layer
In general, an 'adaptation' layer is inserted between a MAC layer and
the Networking layer. This is used to transform some parameters
between their form expected by the IP stack and the form provided by
the MAC layer. For example, an 802.15.4 adaptation layer may perform
fragmentation and reassembly operations on a MAC whose maximum Packet
Data Unit size is smaller than the minimum MTU recognized by the IPv6
Networking layer. Other examples involve link-layer address
transformation, packet header insertion/removal, and so on.
An Ethernet Adaptation Layer makes an 802.11 MAC look to IP
Networking layer as a more traditional Ethernet layer. At reception,
this layer takes as input the IEEE 802.11 Data Header and the
Logical-Link Layer Control Header and produces an Ethernet II Header.
At sending, the reverse operation is performed.
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+--------------------+-------------+-------------+---------+
| 802.11 Data Header | LLC Header | IPv6 Header | Payload |
+--------------------+-------------+-------------+---------+
^
|
802.11-to-Ethernet Adaptation Layer
|
v
+---------------------+-------------+---------+
| Ethernet II Header | IPv6 Header | Payload |
+---------------------+-------------+---------+
The Receiver and Transmitter Address fields in the 802.11 Data Header
contain the same values as the Destination and the Source Address
fields in the Ethernet II Header, respectively. The value of the
Type field in the LLC Header is the same as the value of the Type
field in the Ethernet II Header.
When the MTU value is smaller than the size of the IP packet to be
sent, the IP layer fragments the packet into multiple IP fragments.
During this operation, the "Sequence number" field of the 802.11 Data
Header is increased.
In OCB mode, IPv6 packets can be transmitted either as "IEEE 802.11
Data" or alternatively as "IEEE 802.11 QoS Data", as illustrated in
the following figure:
+--------------------+-------------+-------------+---------+
| 802.11 Data Header | LLC Header | IPv6 Header | Payload |
+--------------------+-------------+-------------+---------+
or
+--------------------+-------------+-------------+---------+
| 802.11 QoS Data Hdr| LLC Header | IPv6 Header | Payload |
+--------------------+-------------+-------------+---------+
The distinction between the two formats is given by the value of the
field "Type/Subtype". The value of the field "Type/Subtype" in the
802.11 Data header is 0x0020. The value of the field "Type/Subtype"
in the 802.11 QoS header is 0x0028.
The mapping between qos-related fields in the IPv6 header (e.g.
"Traffic Class", "Flow label") and fields in the "802.11 QoS Data
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Header" (e.g. "QoS Control") are not specified in this document.
Guidance for a potential mapping is provided in
[I-D.ietf-tsvwg-ieee-802-11], although it is not specific to OCB
mode.
5.3. Link-Local Addresses
The link-local address of an 802.11p interface is formed in the same
manner as on an Ethernet interface. This manner is described in
section 5 of [RFC2464].
5.4. Address Mapping
For unicast as for multicast, there is no change from the unicast and
multicast address mapping format of Ethernet interfaces, as defined
by sections 6 and 7 of [RFC2464].
5.4.1. Address Mapping -- Unicast
5.4.2. Address Mapping -- Multicast
IPv6 protocols often make use of IPv6 multicast addresses in the
destination field of IPv6 headers. For example, an ICMPv6 link-
scoped Neighbor Advertisement is sent to the IPv6 address ff02::1
denoted "all-nodes" address. When transmitting these packets on
802.11-OCB links it is necessary to map the IPv6 address to a MAC
address.
The same mapping requirement applies to the link-scoped multicast
addresses of other IPv6 protocols as well. In DHCPv6, the
"All_DHCP_Servers" IPv6 multicast address ff02::1:2, and in OSPF the
"All_SPF_Routers" IPv6 multicast address ff02::5, need to be mapped
on a multicast MAC address.
An IPv6 packet with a multicast destination address DST, consisting
of the sixteen octets DST[1] through DST[16], is transmitted to the
IEEE 802.11-OCB MAC multicast address whose first two octets are the
value 0x3333 and whose last four octets are the last four octets of
DST.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 1 0 0 1 1|0 0 1 1 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[13] | DST[14] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DST[15] | DST[16] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Group ID TBD of length 112bits may be requested from IANA; this
Group ID signifies "All 80211OCB Interfaces Address". Only the least
32 significant bits of this "All 80211OCB Interfaces Address" will be
mapped to and from a MAC multicast address.
Transmitting IPv6 packets to multicast destinations over 802.11 links
proved to have some performance issues
[I-D.perkins-intarea-multicast-ieee802]. These issues may be
exacerbated in OCB mode. Solutions for these problems should
consider the OCB mode of operation.
5.5. Stateless Autoconfiguration
The Interface Identifier for an 802.11p interface is formed using the
same rules as the Interface Identifier for an Ethernet interface;
this is described in section 4 of [RFC2464]. No changes are needed,
but some care must be taken when considering the use of the SLAAC
procedure.
The bits in the the interface identifier have no generic meaning and
the identifier should be treated as an opaque value. The bits
'Universal' and 'Group' in the identifier of an 802.11p interface are
significant, as this is a IEEE link-layer address. The details of
this significance are described in [I-D.ietf-6man-ug].
As with all Ethernet and 802.11 interface identifiers ([RFC7721]),
the identifier of an 802.11p interface may involve privacy risks. A
vehicle embarking an On-Board Unit whose egress interface is 802.11p
may expose itself to eavesdropping and subsequent correlation of
data; this may reveal data considered private by the vehicle owner.
If stable Interface Identifiers are needed in order to form IPv6
addresses on 802.11-OCB links, it is recommended to follow the
recommendation in [I-D.ietf-6man-default-iids].
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5.6. Subnet Structure
The 802.11 networks in OCB mode may be considered as 'ad-hoc'
networks. The addressing model for such networks is described in
[RFC5889].
6. Handovers between OCB links
A station operating IEEE 802.11p in the 5.9 GHz band in US or EU is
required to send data frames outside the context of a BSS. In this
case, the station does not utilize the IEEE 802.11 authentication,
association, or data confidentiality services. This avoids the
latency associated with establishing a BSS and is particularly suited
to communications between mobile stations or between a mobile station
and a fixed one playing the role of the default router (e.g. a fixed
Road-Side Unit a.k.a RSU acting as an infrastructure router).
The process of movement detection is described in section 11.5.1 of
[RFC6275]. In the context of 802.11p deployments, detecting
movements between two adjacent RSUs becomes harder for the moving
stations: they cannot rely on Layer-2 triggers (such as L2
association/de-association phases) to detect when they leave the
vicinity of an RSU and move within coverage of another RSU. In such
case, the movement detection algorithms require other triggers. We
detail below the potential other indications that can be used by a
moving station in order to detect handovers between OCB ("Outside the
Context of a BSS") links.
A movement detection mechanism may take advantage of positioning data
(latitude and longitude).
Mobile IPv6 [RFC6275] specifies a new Router Advertisement option
called the "Advertisement Interval Option". It can be used by an RSU
to indicate the maximum interval between two consecutive unsolicited
Router Advertisement messages sent by this RSU. With this option, a
moving station can learn when it is supposed to receive the next RA
from the same RSU. This can help movement detection: if the
specified amount of time elapses without the moving station receiving
any RA from that RSU, this means that the RA has been lost. It is up
to the moving node to determine how many lost RAs from that RSU
constitutes a handover trigger.
In addition to the Mobile IPv6 "Advertisement Interval Option", the
Neighbor Unreachability Detection (NUD) [RFC4861] can be used to
determine whether the RSU is still reachable or not. In this
context, reachability confirmation would basically consist in
receiving a Neighbor Advertisement message from a RSU, in response to
a Neighbor Solicitation message sent by the moving station. The RSU
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should also configure a low Reachable Time value in its RA in order
to ensure that a moving station does not assume an RSU to be
reachable for too long.
The Mobile IPv6 "Advertisement Interval Option" as well as the NUD
procedure only help knowing if the RSU is still reachable by the
moving station. It does not provide the moving station with
information about other potential RSUs that might be in range. For
this purpose, it is by increasing the RA frequency that the delay
could be reduced to discover the next RSU. The Neighbor Discovery
protocol [RFC4861] limits the unsolicited multicast RA interval to a
minimum of 3 seconds (the MinRtrAdvInterval variable). This value is
too high for dense deployments of Access Routers deployed along fast
roads. The protocol Mobile IPv6 [RFC6275] allows routers to send
such RA more frequently, with a minimum possible of 0.03 seconds (the
same MinRtrAdvInterval variable): this should be preferred to ensure
a faster detection of the potential RSUs in range.
However, frequent RAs (every 0.03 seconds) may occupy the channel
with too many packets leading to other significant packets being
lost. There is a tradeoff to be established: the more frequent the
RAs the better handover performance but the more risks of packet
loss.
If multiple RSUs are in the vicinity of a moving station at the same
time, the station may not be able to choose the "best" one (i.e. the
one that would afford the moving station spending the longest time in
its vicinity, in order to avoid too frequent handovers). In this
case, it would be helpful to base the decision on the signal quality
(e.g. the RSSI of the received RA provided by the radio driver). A
better signal would probably offer a longer coverage. If, in terms
of RA frequency, it is not possible to adopt the recommendations of
protocol Mobile IPv6 (but only the Neighbor Discovery specification
ones, for whatever reason), then another message than the RA could be
emitted periodically by the Access Router (provided its specification
allows to send it very often), in order to help the Host determine
the signal quality. One such message may be the 802.11p's Time
Advertisement, or higher layer messages such as the "Basic Safety
Message" (in the US) or the "Cooperative Awareness Message " (in the
EU), that are usually sent several times per second. Another
alternative replacement for the IPv6 Router Advertisement may be the
message 'WAVE Routing Advertisement' (WRA), which is part of the WAVE
Service Advertisement and which may contain optionally the
transmitter location; this message is described in section 8.2.5 of
[ieeep1609.3-D9-2010].
Once the choice of the default router has been performed by the
moving node, it can be interesting to use Optimistic DAD [RFC4429] in
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order to speed-up the address auto-configuration and ensure the
fastest possible Layer-3 handover.
To summarize, efficient handovers between OCB links can be performed
by using a combination of existing mechanisms. In order to improve
the default router unreachability detection, the RSU and moving
stations should use the Mobile IPv6 "Advertisement Interval Option"
as well as rely on the NUD mechanism. In order to allow the moving
station to detect potential default router faster, the RSU should
also be able to be configured with a smaller minimum RA interval such
as the one recommended by Mobile IPv6. When multiple RSUs are
available at the same time, the moving station should perform the
handover decision based on the signal quality. Finally, optimistic
DAD can be used to reduce the handover delay.
The Received Frame Power Level (RCPI) defined in IEEE Std
802.11-2012, conditioned by the dotOCBActived flag, is an information
element which contains a value expressing the power level at which
that frame was received. This value may be used in comparing power
levels when triggering IP handovers.
7. Example IPv6 Packet captured over a IEEE 802.11p link
We remind that a main goal of this document is to make the case that
IPv6 works fine over 802.11p networks. Consequently, this section is
an illustration of this concept and thus can help the implementer
when it comes to running IPv6 over IEEE 802.11p. By way of example
we show that there is no modification in the headers when transmitted
over 802.11p networks - they are transmitted like any other 802.11
and Ethernet packets.
We describe an experiment of capturing an IPv6 packet captured on an
802.11p link. In this experiment, the packet is an IPv6 Router
Advertisement. This packet is emitted by a Router on its 802.11p
interface. The packet is captured on the Host, using a network
protocol analyzer (e.g. Wireshark); the capture is performed in two
different modes: direct mode and 'monitor' mode. The topology used
during the capture is depicted below.
+--------+ +-------+
| | 802.11-OCB Link | |
---| Router |--------------------------------| Host |
| | | |
+--------+ +-------+
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During several capture operations running from a few moments to
several hours, no message relevant to the BSSID contexts were
captured (no Association Request/Response, Authentication Req/Resp,
Beacon). This shows that the operation of 802.11p is outside the
context of a BSSID.
Overall, the captured message is identical with a capture of an IPv6
packet emitted on a 802.11b interface. The contents are precisely
similar.
The popular wireshark network protocol analyzer is a free software
tool for Windows and Unix. It includes a dissector for 802.11p
features along with all other 802.11 features (i.e. it displays these
features in a human-readable format).
7.1. Capture in Monitor Mode
The IPv6 RA packet captured in monitor mode is illustrated below.
The radio tap header provides more flexibility for reporting the
characteristics of frames. The Radiotap Header is prepended by this
particular stack and operating system on the Host machine to the RA
packet received from the network (the Radiotap Header is not present
on the air). The implementation-dependent Radiotap Header is useful
for piggybacking PHY information from the chip's registers as data in
a packet understandable by userland applications using Socket
interfaces (the PHY interface can be, for example: power levels, data
rate, ratio of signal to noise).
The packet present on the air is formed by IEEE 802.11 Data Header,
Logical Link Control Header, IPv6 Base Header and ICMPv6 Header.
Radiotap Header v0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Header Revision| Header Pad | Header length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Present flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Rate | Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IEEE 802.11 Data Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type/Subtype and Frame Ctrl | Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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... Receiver Address | Transmitter Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Transmitter Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSS Id...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... BSS Id | Frag Number and Seq Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Logical-Link Control Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSAP |I| SSAP |C| Control field | Org. code...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Organizational Code | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
The value of the Data Rate field in the Radiotap header is set to 6
Mb/s. This indicates the rate at which this RA was received.
The value of the Transmitter address in the IEEE 802.11 Data Header
is set to a 48bit value. The value of the destination address is
33:33:00:00:00:1 (all-nodes multicast address). The value of the BSS
Id field is ff:ff:ff:ff:ff:ff, which is recognized by the network
protocol analyzer as being "broadcast". The Fragment number and
sequence number fields are together set to 0x90C6.
The value of the Organization Code field in the Logical-Link Control
Header is set to 0x0, recognized as "Encapsulated Ethernet". The
value of the Type field is 0x86DD (hexadecimal 86DD, or otherwise
#86DD), recognized as "IPv6".
A Router Advertisement is periodically sent by the router to
multicast group address ff02::1. It is an icmp packet type 134. The
IPv6 Neighbor Discovery's Router Advertisement message contains an
8-bit field reserved for single-bit flags, as described in [RFC4861].
The IPv6 header contains the link local address of the router
(source) configured via EUI-64 algorithm, and destination address set
to ff02::1. Recent versions of network protocol analyzers (e.g.
Wireshark) provide additional informations for an IP address, if a
geolocalization database is present. In this example, the
geolocalization database is absent, and the "GeoIP" information is
set to unknown for both source and destination addresses (although
the IPv6 source and destination addresses are set to useful values).
This "GeoIP" can be a useful information to look up the city,
country, AS number, and other information for an IP address.
The Ethernet Type field in the logical-link control header is set to
0x86dd which indicates that the frame transports an IPv6 packet. In
the IEEE 802.11 data, the destination address is 33:33:00:00:00:01
which is he corresponding multicast MAC address. The BSS id is a
broadcast address of ff:ff:ff:ff:ff:ff. Due to the short link
duration between vehicles and the roadside infrastructure, there is
no need in IEEE 802.11p to wait for the completion of association and
authentication procedures before exchanging data. IEEE 802.11p
enabled nodes use the wildcard BSSID (a value of all 1s) and may
start communicating as soon as they arrive on the communication
channel.
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7.2. Capture in Normal Mode
The same IPv6 Router Advertisement packet described above (monitor
mode) is captured on the Host, in the Normal mode, and depicted
below.
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Ethernet II Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Destination | Source...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
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One notices that the Radiotap Header is not prepended, and that the
IEEE 802.11 Data Header and the Logical-Link Control Headers are not
present. On another hand, a new header named Ethernet II Header is
present.
The Destination and Source addresses in the Ethernet II header
contain the same values as the fields Receiver Address and
Transmitter Address present in the IEEE 802.11 Data Header in the
"monitor" mode capture.
The value of the Type field in the Ethernet II header is 0x86DD
(recognized as "IPv6"); this value is the same value as the value of
the field Type in the Logical-Link Control Header in the "monitor"
mode capture.
The knowledgeable experimenter will no doubt notice the similarity of
this Ethernet II Header with a capture in normal mode on a pure
Ethernet cable interface.
It may be interpreted that an Adaptation layer is inserted in a pure
IEEE 802.11 MAC packets in the air, before delivering to the
applications. In detail, this adaptation layer may consist in
elimination of the Radiotap, 802.11 and LLC headers and insertion of
the Ethernet II header. In this way, it can be stated that IPv6 runs
naturally straight over LLC over the 802.11p MAC layer, as shown by
the use of the Type 0x86DD, and assuming an adaptation layer
(adapting 802.11 LLC/MAC to Ethernet II header).
8. Security Considerations
802.11p does not provide any cryptographic protection, because it
operates outside the context of a BSS (no Association Request/
Response, no Challenge messages). Any attacker can therefore just
sit in the near range of vehicles, sniff the network (just set the
interface card's frequency to the proper range) and perform attacks
without needing to physically break any wall. Such a link is way
less protected than commonly used links (wired link or protected
802.11).
At the IP layer, IPsec can be used to protect unicast communications,
and SeND can be used for multicast communications. If no protection
is used by the IP layer, upper layers should be protected.
Otherwise, the end-user or system should be warned about the risks
they run.
The WAVE protocol stack provides for strong security when using the
WAVE Short Message Protocol and the WAVE Service Advertisement
[ieeep1609.2-D17].
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As with all Ethernet and 802.11 interface identifiers, there may
exist privacy risks in the use of 802.11p interface identifiers.
However, in outdoors vehicular settings, the privacy risks are more
important than in indoors settings. New risks are induced by the
possibility of attacker sniffers deployed along routes which listen
for IP packets of vehicles passing by. For this reason, in the
802.11p deployments, there is a strong necessity to use protection
tools such as dynamically changing MAC addresses. This may help
mitigate privacy risks to a certain level. On another hand, it may
have an impact in the way typical IPv6 address auto-configuration is
performed for vehicles (SLAAC would rely on MAC addresses amd would
hence dynamically change the affected IP address), in the way the
IPv6 Privacy addresses were used, and other effects.
9. IANA Considerations
10. Contributors
Romain Kuntz contributed extensively the concepts described in
Section 6 about IPv6 handovers between links running outside the
context of a BSS (802.11p links).
Tim Leinmueller contributed the idea of the use of IPv6 over
802.11-OCB for distribution of certificates.
Marios Makassikis, Jose Santa Lozano, Albin Severinson and Alexey
Voronov provided significant feedback on the experience of using IP
messages over 802.11-OCB in initial trials.
Michelle Wetterwald contributed extensively the MTU discussion
offering the ETSI ITS perspective, as well as other parts of the
document.
11. Acknowledgements
The authors would like to thank Witold Klaudel, Ryuji Wakikawa,
Emmanuel Baccelli, John Kenney, John Moring, Francois Simon, Dan
Romascanu, Konstantin Khait, Ralph Droms, Richard Roy, Ray Hunter,
Tom Kurihara, Michal Sojka, Jan de Jongh, Suresh Krishnan, Dino
Farinacci, Vincent Park, Jaehoon Paul Jeong and Gloria Gwynne. Their
valuable comments clarified certain issues and generally helped to
improve the document.
Pierre Pfister, Rostislav Lisovy, and others, wrote 802.11-OCB
drivers for linux and described how.
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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.
12. References
12.1. Normative References
[I-D.ietf-6man-default-iids]
Gont, F., Cooper, A., Thaler, D., and S. LIU,
"Recommendation on Stable IPv6 Interface Identifiers",
draft-ietf-6man-default-iids-16 (work in progress),
September 2016.
[I-D.ietf-6man-ug]
Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", draft-ietf-6man-ug-06 (work in
progress), December 2013.
[I-D.ietf-tsvwg-ieee-802-11]
Szigeti, T. and F. Baker, "DiffServ to IEEE 802.11
Mapping", draft-ietf-tsvwg-ieee-802-11-01 (work in
progress), November 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<http://www.rfc-editor.org/info/rfc2464>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
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[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006,
<http://www.rfc-editor.org/info/rfc4429>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
September 2010, <http://www.rfc-editor.org/info/rfc5889>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <http://www.rfc-editor.org/info/rfc6275>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>.
[RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
Considerations for IPv6 Address Generation Mechanisms",
RFC 7721, DOI 10.17487/RFC7721, March 2016,
<http://www.rfc-editor.org/info/rfc7721>.
12.2. Informative References
[etsi-302663-v1.2.1p-2013]
"Intelligent Transport Systems (ITS); Access layer
specification for Intelligent Transport Systems operating
in the 5 GHz frequency band, 2013-07, document
en_302663v010201p.pdf, document freely available at URL
http://www.etsi.org/deliver/etsi_en/302600_302699/302663/
01.02.01_60/en_302663v010201p.pdf downloaded on October
17th, 2013.".
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[etsi-draft-102492-2-v1.1.1-2006]
"Electromagnetic compatibility and Radio spectrum Matters
(ERM); Intelligent Transport Systems (ITS); Part 2:
Technical characteristics for pan European harmonized
communications equipment operating in the 5 GHz frequency
range intended for road safety and traffic management, and
for non-safety related ITS applications; System Reference
Document, Draft ETSI TR 102 492-2 V1.1.1, 2006-07,
document tr_10249202v010101p.pdf freely available at URL
http://www.etsi.org/deliver/etsi_tr/102400_102499/
10249202/01.01.01_60/tr_10249202v010101p.pdf downloaded on
October 18th, 2013.".
[fcc-cc] "'Report and Order, Before the Federal Communications
Commission Washington, D.C. 20554', FCC 03-324, Released
on February 10, 2004, document FCC-03-324A1.pdf, document
freely available at URL
http://www.its.dot.gov/exit/fcc_edocs.htm downloaded on
October 17th, 2013.".
[fcc-cc-172-184]
"'Memorandum Opinion and Order, Before the Federal
Communications Commission Washington, D.C. 20554', FCC
06-10, Released on July 26, 2006, document FCC-
06-110A1.pdf, document freely available at URL
http://hraunfoss.fcc.gov/edocs_public/attachmatch/
FCC-06-110A1.pdf downloaded on June 5th, 2014.".
[I-D.baccelli-multi-hop-wireless-communication]
Baccelli, E. and C. Perkins, "Multi-hop Ad Hoc Wireless
Communication", draft-baccelli-multi-hop-wireless-
communication-06 (work in progress), July 2011.
[I-D.perkins-intarea-multicast-ieee802]
Perkins, C., Stanley, D., Kumari, W., and J. Zuniga,
"Multicast Considerations over IEEE 802 Wireless Media",
draft-perkins-intarea-multicast-ieee802-01 (work in
progress), September 2016.
[I-D.petrescu-its-scenarios-reqs]
Petrescu, A., Janneteau, C., Boc, M., and W. Klaudel,
"Scenarios and Requirements for IP in Intelligent
Transportation Systems", draft-petrescu-its-scenarios-
reqs-03 (work in progress), October 2013.
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[ieee16094]
"1609.2-2016 - IEEE Standard for Wireless Access in
Vehicular Environments--Security Services for Applications
and Management Messages; document freely available at URL
https://standards.ieee.org/findstds/
standard/1609.2-2016.html retrieved on July 08th, 2016.".
[ieee802.11-2012]
"802.11-2012 - IEEE Standard for Information technology--
Telecommunications and information exchange between
systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications. Downloaded
on October 17th, 2013, from IEEE Standards, document
freely available at URL
http://standards.ieee.org/findstds/
standard/802.11-2012.html retrieved on October 17th,
2013.".
[ieee802.11p-2010]
"IEEE Std 802.11p(TM)-2010, IEEE Standard for Information
Technology - Telecommunications and information exchange
between systems - Local and metropolitan area networks -
Specific requirements, Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) Specifications,
Amendment 6: Wireless Access in Vehicular Environments;
document freely available at URL
http://standards.ieee.org/getieee802/
download/802.11p-2010.pdf retrieved on September 20th,
2013.".
[ieeep1609.0-D2]
"IEEE P1609.0/D2 Draft Guide for Wireless Access in
Vehicular Environments (WAVE) Architecture. pdf, length
879 Kb. Restrictions apply.".
[ieeep1609.2-D17]
"IEEE P1609.2(tm)/D17 Draft Standard for Wireless Access
in Vehicular Environments - Security Services for
Applications and Management Messages. pdf, length 2558
Kb. Restrictions apply.".
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[ieeep1609.3-D9-2010]
"IEEE P1609.3(tm)/D9, Draft Standard for Wireless Access
in Vehicular Environments (WAVE) - Networking Services,
August 2010. Authorized licensed use limited to: CEA.
Downloaded on June 19, 2013 at 07:32:34 UTC from IEEE
Xplore. Restrictions apply, document at persistent link
http://ieeexplore.ieee.org/servlet/opac?punumber=5562705".
[ieeep1609.4-D9-2010]
"IEEE P1609.4(tm)/D9 Draft Standard for Wireless Access in
Vehicular Environments (WAVE) - Multi-channel Operation.
Authorized licensed use limited to: CEA. Downloaded on
June 19, 2013 at 07:34:48 UTC from IEEE Xplore.
Restrictions apply. Document at persistent link
http://ieeexplore.ieee.org/servlet/opac?punumber=5551097".
[ipv6-80211p-its]
Shagdar, O., Tsukada, M., Kakiuchi, M., Toukabri, T., and
T. Ernst, "Experimentation Towards IPv6 over IEEE 802.11p
with ITS Station Architecture", International Workshop on
IPv6-based Vehicular Networks, (colocated with IEEE
Intelligent Vehicles Symposium), URL:
http://hal.inria.fr/hal-00702923/en, Downloaded on: 24
October 2013, Availability: free at some sites, paying at
others, May 2012.
[ipv6-wave]
Clausen, T., Baccelli, E., and R. Wakikawa, "IPv6
Operation for WAVE - Wireless Access in Vehicular
Environments", Rapport de Recherche INRIA, number 7383,
URL: http://hal.inria.fr/inria-00517909/, Downloaded on:
24 October 2013, Availability: free at some sites,
September 2010.
[TS103097]
"Intelligent Transport Systems (ITS); Security; Security
header and certificate formats; document freely available
at URL http://www.etsi.org/deliver/
etsi_ts/103000_103099/103097/01.01.01_60/
ts_103097v010101p.pdf retrieved on July 08th, 2016.".
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[vip-wave]
Cespedes, S., Lu, N., and X. Shen, "VIP-WAVE: On the
Feasibility of IP Communications in 802.11p Vehicular
Networks", IEEE Transactions on Intelligent Transportation
Systems, Volume 14, Issue 1, URL and Digital Object
Identifier: http://dx.doi.org/10.1109/TITS.2012.2206387,
Downloaded on: 24 October 2013, Availability: free at
some sites, paying at others, March 2013.
Appendix A. ChangeLog
The changes are listed in reverse chronological order, most recent
changes appearing at the top of the list.
From draft-petrescu-ipv6-over-80211p-05.txt to draft-petrescu-ipv6-
over-80211p-06.txt:
o Removed IPv4 text.
o Added text about isues with multicast over 802.11 and OCB mode.
o Shortened the subnet structure section, by referring to an
existing RFC.
o Removed the appendix about distribution of certificates.
o Added text about tradeoff of too frequent RAs, handover
performance and risks of packet loss.
o Removed discussion about other MTU possibilities, kept only the
1500 bytes MTU.
o Keep both header "802.11 Data" and header "802.11 QoS Data".
o Referred to default-iids recommendation of generating stable IIDs.
o Moved the Design Considerations sections to an appendix.
From draft-petrescu-ipv6-over-80211p-02.txt to draft-petrescu-ipv6-
over-80211p-03.txt:
o Added clarification about the "OCBActivated" qualifier in the the
new IEEE 802.11-2012 document; this IEEE document integrates now
all earlier 802.11p features; this also signifies the
dissapearance of an IEEE IEEE 802.11p document altogether.
o Added explanation about FCC not prohibiting IP on channels, and
comments about engineering advice and reliability of IP messages.
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o Added possibility to use 6lowpan adaptation layer when in OCB
mode.
o Added appendix about the distribution of certificates to vehicles
by using IPv6-over-802.11p single-hop communications.
o Refined the explanation of 'half-rate' mode.
o Added the privacy concerns and necessity of and potential effects
of dynamically changing MAC addresses.
From draft-petrescu-ipv6-over-80211p-01.txt to draft-petrescu-ipv6-
over-80211p-02.txt:
o updated authorship.
o added explanation about FCC not prohibiting IP on channels, and
comments about engineering advice and reliability of IP messages.
o added possibility to use 6lowpan adaptation layer when in OCB
mode.
o added appendix about the distribution of certificates to vehicles
by using IPv6-over-802.11p single-hop communications.
o refined the explanation of 'half-rate' mode.
o added the privacy concerns and necessity of and potential effects
of dynamically changing MAC addresses.
From draft-petrescu-ipv6-over-80211p-00.txt to draft-petrescu-ipv6-
over-80211p-01.txt:
o updated one author's affiliation detail.
o added 2 more references to published literature about IPv6 over
802.11p.
From draft-petrescu-ipv6-over-80211p-00.txt to draft-petrescu-ipv6-
over-80211p-00.txt:
o first version.
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Appendix B. Explicit Prohibition of IPv6 on Channels Related to ITS
Scenarios using 802.11p Networks - an Analysis
B.1. Interpretation of FCC and ETSI documents with respect to running
IP on particular channels
o The FCC created the term "Control Channel" [fcc-cc]. For it, it
defines the channel number to be 178 decimal, and positions it
with a 10MHz width from 5885MHz to 5895MHz. The FCC rules point
to standards document ASTM-E2213 (not freely available at the time
of writing of this draft); in an interpretation of a reviewer of
this document, this means not making any restrictions to the use
of IP on the control channel.
o The FCC created two more terms for particular channels
[fcc-cc-172-184], among others. The channel 172 (5855MHz to
5865MHz)) is designated "exclusively for [V2V] safety
communications for accident avoidance and mitigation, and safety
of life and property applications", and the channel 184 (5915MHz
to 5925MHz) is designated "exclusively for high-power, longer-
distance communications to be used for public-safety applications
involving safety of life and property, including road-intersection
collision mitigation". However, they are not named "control"
channels, and the document does not mention any particular
restriction on the use of IP on either of these channels.
o On another hand, at IEEE, IPv6 is explicitely prohibited on
channel number 178 decimal - the FCC's 'Control Channel'. The
document [ieeep1609.4-D9-2010] prohibits upfront the use of IPv6
traffic on the Control Channel: 'data frames containing IP
datagrams are only allowed on service channels'. Other 'Service
Channels' are allowed to use IP, but the Control Channel is not.
o In Europe, basically ETSI considers FCC's "Control Channel" to be
a "Service Channel", and defines a "Control Channel" to be in a
slot considered by FCC as a "Service Channel". In detail, FCC's
"Control Channel" number 178 decimal with 10MHz width (5885MHz to
5895MHz) is defined by ETSI to be a "Service Channel", and is
named 'G5-SCH2' [etsi-302663-v1.2.1p-2013]. This channel is
dedicated to 'ITS Road Safety' by ETSI. Other channels are
dedicated to 'ITS road traffic efficiency' by ETSI. The ETSI's
"Control Channel" - the "G5-CCH" - number 180 decimal (not 178) is
reserved as a 10MHz-width centered on 5900MHz (5895MHz to 5905MHz)
(the 5895MHz-5905MHz channel is a Service Channel for FCC).
Compared to IEEE, ETSI makes no upfront statement with respect to
IP and particular channels; yet it relates the 'In car Internet'
applications ('When nearby a stationary public internet access
point (hotspot), application can use standard IP services for
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applications.') to the 'Non-safety-related ITS application'
[etsi-draft-102492-2-v1.1.1-2006]. Under an interpretation of an
author of this Internet Draft, this may mean ETSI may forbid IP on
the 'ITS Road Safety' channels, but may allow IP on 'ITS road
traffic efficiency' channels, or on other 5GHz channels re-used
from BRAN (also dedicated to Broadband Radio Access Networks).
o At EU level in ETSI (but not some countries in EU with varying
adoption levels) the highest power of transmission of 33 dBm is
allowed, but only on two separate 10Mhz-width channels centered on
5900MHz and 5880MHz respectively. It may be that IPv6 is not
allowed on these channels (in the other 'ITS' channels where IP
may be allowed, the levels vary between 20dBm, 23 dBm and 30 dBm;
in some of these channels IP is allowed). A high-power of
transmission means that vehicles may be distanced more
(intuitively, for 33 dBm approximately 2km is possible, and for 20
dBm approximately 50meter).
B.2. Interpretations of Latencies of IP datagrams
IPv6 may be "allowed" on any channel. Certain interpretations
consider that communicating IP datagrams may involve longer latencies
than non-IP datagrams; this may make them little adapted for safety
applications which require fast reaction. Certain other views
disagree with this, arguing that IP datagrams are transmitted at the
same speed as any other non-IP datagram and may thus offer same level
of reactivity for safety applications.
Appendix C. Changes Needed on a software driver 802.11a to become a
802.11-OCB driver
The 802.11p amendment modifies both the 802.11 stack's physical and
MAC layers but all the induced modifications can be quite easily
obtained by modifying an existing 802.11a ad-hoc stack.
Conditions for a 802.11a hardware to be 802.11p compliant:
o The chip must support the frequency bands on which the regulator
recommends the use of ITS communications, for example using IEEE
802.11p layer, in France: 5875MHz to 5925MHz.
o The chip must support the half-rate mode (the internal clock
should be able to be divided by two).
o The chip transmit spectrum mask must be compliant to the "Transmit
spectrum mask" from the IEEE 802.11p amendment (but experimental
environments tolerate otherwise).
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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).
* Timing Advertisement frames, defined in the amendment, should
be supported. The upper layer should be able to trigger such
frames emission and to retrieve information contained in
received Timing Advertisements.
Appendix D. Design Considerations
The networks defined by 802.11-OCB are in many ways similar to other
networks of the 802.11 family. In theory, the encapsulation of IPv6
over 802.11-OCB could be very similar to the operation of IPv6 over
other networks of the 802.11 family. However, the high mobility,
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strong link asymetry and very short connection makes the 802.11-OCB
link significantly different from other 802.11 networks. Also, the
automotive applications have specific requirements for reliability,
security and privacy, which further add to the particularity of the
802.11-OCB link.
This section does not address safety-related applications, which are
done on non-IP communications. However, this section will consider
the transmission of such non IP communication in the design
specification of IPv6 over IEEE 802.11-OCB.
D.1. Vehicle ID
Automotive networks require the unique representation of each of
their node. Accordingly, a vehicle must be identified by at least
one unique ID. The current specification at ETSI and at IEEE 1609
identifies a vehicle by its MAC address uniquely obtained from the
802.11-OCB NIC.
A MAC address uniquely obtained from a IEEE 802.11-OCB NIC
implicitely generates multiple vehicle IDs in case of multiple
802.11-OCB NICs. A mechanims to uniquely identify a vehicle
irrespectively to the different NICs and/or technologies is required.
D.2. Non IP Communications
In IEEE 1609 and ETSI ITS, safety-related communications CANNOT be
used with IP datagrams. For example, Basic Safety Message (BSM, an
IEEE 1609 datagram) and Cooperative Awareness Message (CAM, an ETSI
ITS-G5 datagram), are each transmitted as a payload that is preceded
by link-layer headers, without an IP header.
Each vehicle taking part of traffic (i.e. having its engine turned on
and being located on a road) MUST use Non IP communication to
periodically broadcast its status information (ID, GPS position,
speed,..) in its immediate neighborhood. Using these mechanisms,
vehicles become 'aware' of the presence of other vehicles in their
immediate vicinity. Therefore, IP communication being transmitted by
vehicles taking part of traffic MUST co-exist with Non IP
communication and SHOULD NOT break any Non IP mechanism, including
'harmful' interference on the channel.
The ID of the vehicle transmitting Non IP communication is
transmitted in the src MAC address of the IEEE 1609 / ETSI-ITS-G5
datagrams. Accordingly, non-IP communications expose the ID of each
vehicle, which may be considered as a privacy breach.
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IEEE 802.11-OCB bypasses the authentication mechanisms of IEEE 802.11
networks, in order to transmit non IP communications to without any
delay. This may be considered as a security breach.
IEEE 1609 and ETSI ITS provided strong security and privacy
mechanisms for Non IP Communications. Security (authentication,
encryption) is done by asymetric cryptography, where each vehicle
attaches its public key and its certificate to all of its non IP
messages. Privacy is enforced through the use of Pseudonymes. Each
vehicle will be pre-loaded with a large number (>1000s) of
pseudonymes generated by a PKI, which will uniquely assign a
pseudonyme to a certificate (and thus to a public/private key pair).
Non IP Communication being developped for safety-critical
applications, complex mechanisms have been provided for their
support. These mechanisms are OPTIONAL for IP Communication, but
SHOULD be used whenever possible.
D.3. Reliability Requirements
The dynamically changing topology, short connectivity, mobile
transmitter and receivers, different antenna heights, and many-to-
many communication types, make IEEE 802.11-OCB links significantly
different from other IEEE 802.11 links. Any IPv6 mechanism operating
on IEEE 802.11-OCB link MUST support strong link asymetry, spatio-
temporal link quality, fast address resolution and transmission.
IEEE 802.11-OCB strongly differs from other 802.11 systems to operate
outside of the context of a Basic Service Set. This means in
practice that IEEE 802.11-OCB does not rely on a Base Station for all
Basic Service Set management. In particular, IEEE 802.11-OCB SHALL
NOT use beacons. Any IPv6 mechanism requiring L2 services from IEEE
802.11 beacons MUST support an alternative service.
Channel scanning being disabled, IPv6 over IEEE 802.11-OCB MUST
implement a mechanism for transmitter and receiver to converge to a
common channel.
Authentication not being possible, IPv6 over IEEE 802.11-OCB MUST
implement an distributed mechanism to authenticate transmitters and
receivers without the support of a DHCP server.
Time synchronization not being available, IPv6 over IEEE 802.11-OCB
MUST implement a higher layer mechanism for time synchronization
between transmitters and receivers without the support of a NTP
server.
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The IEEE 802.11-OCB link being asymetic, IPv6 over IEEE 802.11-OCB
MUST disable management mechanisms requesting acknowledgements or
replies.
The IEEE 802.11-OCB link having a short duration time, IPv6 over IEEE
802.11-OCB MUST implement fast IPv6 mobility management mechanisms.
D.4. Privacy requirements
Vehicles will move. As each vehicle moves, it needs to regularly
announce its network interface and reconfigure its local and global
view of its network. L2 mechanisms of IEEE 802.11-OCB MAY be
employed to assist IPv6 in discovering new network interfaces. L3
mechanisms over IEEE 802.11-OCB SHOULD be used to assist IPv6 in
discovering new network interfaces.
The headers of the L2 mechanisms of IEEE 802.11-OCB and L3 management
mechanisms of IPv6 are not encrypted, and as such expose at least the
src MAC address of the sender. In the absence of mitigations,
adversaries could monitor the L2 or L3 management headers, track the
MAC Addresses, and through that track the position of vehicles over
time; in some cases, it is possible to deduce the vehicle
manufacturer name from the OUI of the MAC address of the interface
(with help of additional databases). It is important that sniffers
along roads not be able to easily identify private information of
automobiles passing by.
Similary to Non IP safety-critical communications, the obvious
mitigation is to use some form of MAC Address Randomization. We can
assume that there will be "renumbering events" causing the MAC
Addresses to change. Clearly, a change of MAC Address should induce
a simultaneous change of IPv6 Addresses, to prevent linkage of the
old and new MAC Addresses through continuous use of the same IP
Addresses.
The change of an IPv6 address also implies the change of the network
prefix. Prefix delegation mechanisms should be available to vehicles
to obtain new prefixes during "renumbering events".
Changing MAC and IPv6 addresses will disrupt communications, which
goes against the reliability requirements expressed in [TS103097].
We will assume that the renumbering events happen only during "safe"
periods, e.g. when the vehicle has come to a full stop. The
determination of such safe periods is the responsibility of
implementors. In automobile settings it is common to decide that
certain operations (e.g. software update, or map update) must happen
only during safe periods.
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MAC Address randomization will not prevent tracking if the addresses
stay constant for long intervals. Suppose for example that a vehicle
only renumbers the addresses of its interface when leaving the
vehicle owner's garage in the morning. It would be trivial to
observe the "number of the day" at the known garage location, and to
associate that with the vehicle's identity. There is clearly a
tension there. If renumbering events are too infrequent, they will
not protect privacy, but if their are too frequent they will affect
reliability. We expect that implementors will eventually find the
right balance.
D.5. Authentication requirements
IEEE 802.11-OCB does not have L2 authentication mechanisms.
Accordingly, a vehicle receiving a IPv6 over IEEE 802.11-OCB packet
cannot check or be sure the legitimacy of the src MAC (and associated
ID). This is a significant breach of security.
Similarly to Non IP safety-critical communications, IPv6 over
802.11-OCB packets must contain a certificate, including at least the
public key of the sender, that will allow the receiver to
authenticate the packet, and guarantee its legitimacy.
To satisfy the privacy requiremrents of Appendix D.4, the certificate
SHALL be changed at each 'renumbering event'.
D.6. Multiple interfaces
There are considerations for 2 or more IEEE 802.11-OCB interface
cards per vehicle. For each vehicle taking part in road traffic, one
IEEE 802.11-OCB interface card MUST be fully allocated for Non IP
safety-critical communication. Any other IEEE 802.11-OCB may be used
for other type of traffic.
The mode of operation of these other wireless interfaces is not
clearly defined yet. One possibility is to consider each card as an
independent network interface, with a specific MAC Address and a set
of IPv6 addresses. Another possibility is to consider the set of
these wireless interfaces as a single network interface (not
including the IEEE 802.11-OCB interface used by Non IP safety
critical communications). This will require specific logic to
ensure, for example, that packets meant for a vehicle in front are
actually sent by the radio in the front, or that multiple copies of
the same packet received by multiple interfaces are treated as a
single packet. Treating each wireless interface as a separate
network interface pushes such issues to the application layer.
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The privacy requirements of Appendix D.4 imply that if these multiple
interfaces are represented by many network interface, a single
renumbering event SHALL cause renumbering of all these interfaces.
If one MAC changed and another stayed constant, external observers
would be able to correlate old and new values, and the privacy
benefits of randomization would be lost.
The privacy requirements of Non IP safety-critical communications
imply that if a change of pseudonyme occurs, renumbering of all other
interfaces SHALL also occur.
D.7. MAC Address Generation
When designing the IPv6 over 802.11-OCB address mapping, we will
assume that the MAC Addresses will change during well defined
"renumbering events". The 48 bits randomized MAC addresses will have
the following characteristics:
o Bit "Local/Global" set to "locally admninistered".
o Bit "Unicast/Multicast" set to "Unicast".
o 46 remaining bits set to a random value, using a random number
generator that meets the requirements of [RFC4086].
The way to meet the randomization requirements is to retain 46 bits
from the output of a strong hash function, such as SHA256, taking as
input a 256 bit local secret, the "nominal" MAC Address of the
interface, and a representation of the date and time of the
renumbering event.
D.8. Security Certificate Generation
When designing the IPv6 over 802.11-OCB address mapping, we will
assume that the MAC Addresses will change during well defined
"renumbering events". So MUST also the Security Certificates.
Unless unavailable, the Security Certificate Generation mechanisms
SHOULD follow the specification in IEEE 1609.2 [ieee16094] or ETSI TS
103 097 [TS103097]. These security mechanisms have the following
characteristics:
o Authentication - Elliptic Curve Digital Signature Algorithm
(ECDSA) - A Secured Hash Function (SHA-256) will sign the message
with the public key of the sender.
o Encryption - Elliptic Curve Integrated Encryption Scheme (ECIES) -
A Key Derivation Function (KDF) between the sender's public key
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and the receiver's private key will generate a symetric key used
to encrypt a packet.
If the mechanisms described in IEEE 1609.2 [ieee16094] or ETSI TS 103
097 [TS103097] are either not supported or not capable of running on
the hardware, an alternative approach based on Pretty-Good-Privacy
(PGP) MAY be used as an alternative.
Authors' Addresses
Alexandre Petrescu
CEA, LIST
CEA Saclay
Gif-sur-Yvette , Ile-de-France 91190
France
Phone: +33169089223
Email: Alexandre.Petrescu@cea.fr
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
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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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