One document matched: draft-petrescu-ipv6-over-80211p-00.xml
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<rfc category="info"
docName="draft-petrescu-ipv6-over-80211p-00.txt"
ipr="trust200902">
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<front>
<title abbrev="IPv6-over-80211p">
Transmission of IPv6 Packets over IEEE 802.11p Networks
</title>
<author initials='A.' surname="Petrescu" fullname='Alexandru Petrescu'>
<organization>CEA</organization>
<address>
<postal>
<street>
</street>
<city>
http://www.cea.fr
</city>
<region>
</region>
<code>
</code>
<country>
</country>
</postal>
<phone>
</phone>
<email>
Alexandru.Petrescu@cea.fr
</email>
</address>
</author>
<author initials='R.' surname="Kuntz" fullname='Romain Kuntz'>
<organization>IP Flavors</organization>
<address>
<postal>
<street>
</street>
<city>
http://www.ipflavors.com
</city>
<region>
</region>
<code>
</code>
<country>
</country>
</postal>
<phone>
</phone>
<email>
r.kuntz@ipflavors.com
</email>
</address>
</author>
<author initials='P.' surname="Pfister" fullname='Pierre Pfister'>
<organization>changing</organization>
<address>
<postal>
<street>
</street>
<city>
</city>
<region>
</region>
<code>
</code>
<country>
</country>
</postal>
<phone>
</phone>
<email>
pierre.pfister@polytechnique.org
</email>
</address>
</author>
<author initials='N.' surname="Benamar" fullname='Nabil Benamar'>
<organization>Moulay Ismail University</organization>
<address>
<postal>
<street>
</street>
<city>
</city>
<region>
</region>
<code>
</code>
<country>
Morocco
</country>
</postal>
<phone>
</phone>
<email>
benamar73@gmail.com
</email>
</address>
</author>
<date/>
<!-- Meta-data Declarations -->
<area>Internet</area>
<workgroup>Network Working Group</workgroup>
<!-- WG name at the upperleft corner of the doc, IETF is fine for
individual submissions. If this element is not present, the
default is "Network Working Group", which is used by the RFC
Editor as a nod to the history of the IETF. -->
<keyword>
IPv6 over 802.11p
</keyword>
<!-- Keywords will be incorporated into HTML output files in a
meta tag but they have no effect on text or nroff output. If
you submit your draft to the RFC Editor, the keywords will be
used for the search engine. -->
<abstract>
<t>
In order to transmit IPv6 packets on IEEE 802.11p networks
there is a need to define a few parameters such as the
recommended Maximum Transmission Unit size, the header format
preceding the IPv6 base header, the Type value within it, and
others. This document describes these parameters for IPv6 and
IEEE 802.11p networks; it portrays the layering of IPv6 on
802.11p similarly to other known 802.11 and Ethernet layers,
by using an existing Ethernet Adaptation Layer.
</t>
<t>
In addition, the document attempts to list what is different
in 802.11p compared to more 'traditional' 802.11a/b/g/n
layers, layers over which IPv6 protocols run ok. Most
notably, the operation outside the context of a BSS (OCB) has
impact on IPv6 handover behaviour and on IPv6 security.
</t>
<t>
An example of an IPv6 packet captured while transmitted over
an IEEE 802.11p link is given.
</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>
This document describes the transmission of IPv6 packets on
IEEE 802.11p networks. This involves the layering of IPv6
networking on top of the IEEE 802.11p MAC layer (with an LLC
layer). Compared to running IPv6 over the Ethernet MAC
layer, or over other 802.11 links, there is no modification
required to the standards: IPv6 works fine directly over
802.11p too (with an LLC layer).
</t>
<t>
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.
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
+-----------------+ +-----------------+
| ... | | ... |
+-----------------+ +-----------------+
| IPv6 Networking | | IPv6 Networking |
+-----------------+ +-----------------+
| 802.2 LLC | vs. | 802.2 LLC |
+-----------------+ +-----------------+
| 802.11p MAC | | 802.11b MAC |
+-----------------+ +-----------------+
| 802.11p PHY | | 802.11b PHY |
+-----------------+ +-----------------+
]]>
</artwork>
</figure>
</t>
<t>
But, 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).
</t>
<t>
We briefly introduce the vehicular communication scenarios
where IEEE 802.11p 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 <xref
target="software-changes"/>.)
</t>
<t>
The document then concentrates on the parameters of layering
IPv6 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 <xref
target="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.
</t>
<t>
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".
</t>
<t>
A few points can be considered as different, although they
do not seem required in order to have a working
implementation of IPv6-over-802.11p. These points are
consequences of the OCB operation which is particular to
802.11p (Outside the Context of a BSS). 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 should be considered of utmost importance,
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. These two points (OCB handovers and security)
are described each in a section of its own: OCB handovers in
<xref target="ocb-handovers"/> and security in <xref
target="Security"/>.
</t>
<t>
In the published literature, the operation of IPv6 for WAVE
(Wireless Access In Vehicular Environments) was described in
<xref target="ipv6-wave"/>.
</t>
<t>
In standards, the operation of IPv6 as a 'data plane' over
802.11p is specified in <xref
target='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 [...]". Also, the operation of
IPv6 over a GeoNetworking layer and over G5 is described in
<xref target='etsi-302663-v1.2.1p-2013'/>.
</t>
</section>
<section title="Terminology">
<t>
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
<xref target="RFC2119">RFC 2119</xref>.
</t>
<t>
RSU stands for Road Side Unit.
</t>
</section>
<section title="Communication Scenarios where IEEE 802.11p Links are Used">
<t>
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 <xref
target='I-D.petrescu-its-scenarios-reqs'/>, about scenarios
and requirements for IP in Intelligent Transportation Systems.
</t>
</section>
<section title="Aspects introduced by 802.11p to 802.11">
<t>
The link 802.11p is specified in IEEE Std 802.11p(TM)-2010
<xref target="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 <xref target="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').
</t>
<t>
In order to delineate the aspects introduced by 802.11p to
802.11, we refer to the earlier <xref
target="ieee802.11p-2010"/>. The amendment is concerned
with vehicular communications, where the wireless link is
similar to that of Wireless LAN (using a PHY layer
specified by 802.11a/b/g/n), but which needs to cope with
the high mobility factor inherent in scenarios of
communications between moving vehicles, and between
vehicles and fixed infrastructure deployed along roads.
Whereas '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.
</t>
<t>
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).
</t>
<t>
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 802.11p differences
compared to 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 here only a few characteristics which
may be important for an implementation transmitting IPv6
packets on 802.11p links.
</t>
<t>
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.
</t>
<t>
<list style='symbols'>
<t>
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 potentially strong impact on the
use of protocol Mobile IPv6 and protocols for IP layer
security.
</t>
<t>
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 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.)
</t>
<t>
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 than the
bands "2.4GHz" or "5GHz" used for the Wireless LAN.
But, 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 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 maximum
distance of approximately 1km, compared to
approximately 50m. On another 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).
</t>
<t>
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, and 180 at ETSI); for a
detailed analysis of FCC and ETSI prohibition of IP in
particular channels see <xref target='IP-channel'/>.
</t>
<t>
'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 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.
</t>
</list>
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 assumed in 802.11p networks is strongly influenced by
the mobility of vehicles.
</t>
</section>
<section title="Layering of IPv6 over 802.11p as over
Ethernet">
<t>
</t>
<section title="Maximum Transmission Unit (MTU)">
<t>
The default MTU for IPv6 packets on 802.11p is 1500
octets. It is the same value as IPv6 packets on Ethernet
links, as specified in <xref target="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 <xref target="RFC2460"/>, and the
recommendations therein, especially with respect to
fragmentation).
</t>
</section>
<section title="Frame Format">
<t>
IPv6 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 <xref target='aal'/>. The Ethernet Type code
(EtherType) is 0x86DD (hexadecimal 86DD, or otherwise
#86DD).
</t>
<t>
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 <xref target='RFC2464'/>.
For sake of completeness, the frame format for
transmitting IPv6 over Ethernet is illustrated below:
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
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.)
]]>
</artwork>
</figure>
</t>
<section title='Ethernet Adaptation Layer'
anchor='aal'>
<t>
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.
</t>
<t>
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.
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
+--------------------+-------------+-------------+---------+
| 802.11 Data Header | LLC Header | IPv6 Header | Payload |
+--------------------+-------------+-------------+---------+
^
|
802.11-to-Ethernet Adaptation Layer
|
v
+---------------------+-------------+---------+
| Ethernet II Header | IPv6 Header | Payload |
+---------------------+-------------+---------+
]]>
</artwork>
</figure>
</t>
<t>
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 other fields
in the Data and LLC Headers are not used by the IPv6
stack.
</t>
</section>
</section>
<section title='Link-Local Addresses'>
<t>
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 <xref
target='RFC2464'/>.
</t>
</section>
<section title="Address Mapping">
<t>
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 <xref
target='RFC2464'/>.
</t>
<t>
(however, there is discussion about geography, networking
and IPv6 multicast addresses: geographical dissemination
of IPv6 data over 802.11p may be useful in traffic jams,
for example).
</t>
</section>
<section title='Stateless Autoconfiguration'>
<t>
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 <xref target='RFC2464'/>.
No changes are needed, but some care must be taken when
considering the use of the SLAAC procedure.
</t>
<t>
For example, the Interface Identifier for an 802.11p
interface whose built-in address is, in hexadecimal:
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
30-14-4A-D9-F9-6C
]]>
</artwork>
</figure>
</t>
<t>
would be
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
32-14-4A-FF-FE-D9-F9-6C.
]]>
</artwork>
</figure>
</t>
<t>
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 <xref target="I-D.ietf-6man-ug"/>.
</t>
<t>
As with all Ethernet and 802.11 interface identifiers, 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. The address
generation mechanism should consider these aspects, as
described in <xref
target='I-D.ietf-6man-ipv6-address-generation-privacy'/>.
</t>
</section>
<section title='Subnet Structure'>
<t>
In this section the subnet structure may be described: the
addressing model (are multi-link subnets considered?),
address resolution, multicast handling, packet forwarding
between IP subnets. Alternatively, this section may be
spinned off into a separate documents.
</t>
<t>
The 802.11p networks, much like other 802.11 networks, may
be considered as 'ad-hoc' networks. The addressing model
for such networks is described in <xref
target='RFC5889'/>.
</t>
<t>
The SLAAC procedure makes the assumption that if a packet
is retransmitted a fixed number of times (typically 3, but
it is link dependent), any connected host receives the
packet with high probability. On ad-hoc links (when
802.11p is operated in OCB mode, the link can be
considered as 'ad-hoc'), both the hidden terminal problem
and mobility-range considerations make this assumption
incorrect. Therefore, SLAAC should not be used when
address collisions can induce critical errors in upper
layers.
</t>
<t>
Some aspects of multi-hop ad-hoc wireless communications
which are relevant to the use of 802.11p (e.g. the
'hidden' node) are described in <xref
target="I-D.baccelli-multi-hop-wireless-communication"
/>.
</t>
</section>
</section>
<section title="Handovers between OCB links"
anchor="ocb-handovers">
<t>
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).
</t>
<t>
The process of movement detection is described in section
11.5.1 of <xref target='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.
</t>
<t>
A movement detection mechanism may take advantage of
positioning data (latitude and longitude).
</t>
<t>
Mobile IPv6 <xref target='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.
</t>
<t>
In addition to the Mobile IPv6 "Advertisement Interval
Option", the Neighbor Unreachability Detection (NUD) <xref
target='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
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.
</t>
<t>
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, increasing the RA
frequency could reduce the delay to discover the next RSU.
The Neighbor Discovery protocol <xref target='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 <xref
target="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.
</t>
<t>
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 <xref
target='ieeep1609.3-D9-2010'/>.
</t>
<t>
Once the choice of the default router has been performed by
the moving node, it can be interesting to use Optimistic DAD
<xref target='RFC4429'/> in order to speed-up the address
auto-configuration and ensure the fastest possible Layer-3
handover.
</t>
<t>
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.
</t>
<!-- <t> -->
<!-- The minimum time separating sending two Router Advertisements -->
<!-- is limited by the value of the MinRtrAdvInterval router -->
<!-- configuration variable, as specified by <xref -->
<!-- target="RFC4861"/>. This value is 3 seconds. This value is -->
<!-- too high for dense deployments of Access Routers deployed -->
<!-- along fast roads. The Mobile IPv6 specification <xref -->
<!-- target="RFC6275"/> allows for a minimum time separating -->
<!-- sending two Router Advertisements to 0.03 seconds (the -->
<!-- MinRtrAdvInterval variable.) -->
<!-- </t> -->
<!-- <t> -->
<!-- If it is not possible to implement the Mobile IPv6 -->
<!-- specification (and must stick to the ND specification only, -->
<!-- for whatever reason), then another message than the Router -->
<!-- Advertisement, 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 power levels. -->
<!-- In some stack implementations and some versions of particular -->
<!-- operating systems, the Host is able to attach a RadioTap -->
<!-- header to any message it receives. This header contains the -->
<!-- value of the strength of the signal received. One such -->
<!-- message may be the 802.11p's Time Advertisement (even though -->
<!-- itself does not contain that value). -->
<!-- </t> -->
</section>
<!-- Possibly a 'Contributors' section ... -->
<section title="Example IPv6 Packet captured over a IEEE 802.11p
link">
<t>
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.
</t>
<t>
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.
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
########## ########
# # # #
# Router #--------------------# Host #
# # 802.11p Link # #
########## ########
/ \ o o
]]>
</artwork>
</figure>
</t>
<t>
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.
</t>
<t>
Overall, the captured message is precisely similar with a
capture of an IPv6 packet emitted on a 802.11b interface. The
contents are precisely similar.
</t>
<section title="Capture in Monitor Mode">
<t>
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).
</t>
<t>
The packet present on the air is formed by IEEE 802.11 Data
Header, Logical Link Control Header, IPv6 Base Header and
ICMPv6 Header.
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
Radiotap Header v0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Header Revision| Header Pad | Header length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Present flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Rate | Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IEEE 802.11 Data Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type/Subtype and Frame Ctrl | Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Receiver Address | Transmitter Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Transmitter Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSS Id...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... BSS Id | Frag Number and Seq Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Logical-Link Control Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSAP |I| SSAP |C| Control field | Org. code...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Organizational Code | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Base Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Advertisement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
]]>
</artwork>
</figure>
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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".
</t>
<t>
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 <xref target="RFC4861"/>.
</t>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="Capture in Normal Mode">
<t>
The same IPv6 Router Advertisement packet described above
(monitor mode) is captured on the Host, in the Normal mode,
and depicted below.
</t>
<t>
<figure align="center">
<artwork align="center">
<![CDATA[
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 ...
+-+-+-+-+-+-+-+-+-+-+-+-
]]>
</artwork>
</figure>
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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).
</t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>
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).
</t>
<t>
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.
</t>
<t>
The WAVE protocol stack provides for strong security when
using the WAVE Short Message Protocol and the WAVE Service
Advertisement <xref target='ieeep1609.2-D17'/>.
</t>
<t>
As with all Ethernet and 802.11 interface identifiers, there
may exist privacy risks in the use of 802.11p interface
identifiers.
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>
</t>
</section>
<section anchor="Acknowledgements"
title="Acknowledgements">
<t>
The authors would like to acknowledge Witold Klaudel, Ryuji
Wakikawa, Emmanuel Baccelli, John Kenney, John Moring,
Francois Simon, Dan Romascanu, Konstantin Khait and Ralph
Droms. Their supportive comments at the early stages
enlightened and helped improve the document. More comments
from more persons are expected.
</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<references title="Normative References">
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2460"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2464"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4861"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4429"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.5889"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.6275"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-6man-ug"
?>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-6man-ipv6-address-generation-privacy"
?>
</references>
<references title="Informative References">
<reference anchor="ieee802.11p-2010" >
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="ieeep1609.2-D17">
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="ieeep1609.3-D9-2010">
<front>
<title>
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
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="ieeep1609.4-D9-2010">
<front>
<title>
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
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="ieee802.11-2012" >
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="fcc-cc" >
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="etsi-302663-v1.2.1p-2013" >
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="etsi-draft-102492-2-v1.1.1-2006" >
<front>
<title>
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.
</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="ipv6-wave" >
<front>
<title>
Clausen, T., Baccelli, E. and R. Wakikawa, "IPv6 Operation
for WAVE - Wireless Access in Vehicular Environments",
Rapport de recherche, INRIA, numero 7383, September 2010.
</title>
<author/>
<date/>
</front>
</reference>
<?rfc
include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.baccelli-multi-hop-wireless-communication"
?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.petrescu-its-scenarios-reqs" ?>
</references>
<section anchor='changelog'
title='ChangeLog'>
<t>
The changes are listed in reverse chronological order, most
recent changes appearing at the top of the list.
</t>
<t>
From draft-authors-ipv6-over-80211p-00.txt to
draft-authors-ipv6-over-80211p-00.txt:
<list style='symbols'>
<t>
first version.
</t>
</list>
</t>
</section>
<section title='Explicit Prohibition of IPv6 on Channels
Related to ITS Scenarios using 802.11p Networks
- an Analysis'
anchor='IP-channel'>
<t>
<list style='symbols'>
<t>
IPv6 is prohibited on channel number 178 decimal, named
'Control Channel' at IEEE and FCC. The document <xref
target='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'. The FCC names the Control Channel as being the
channel number 178 decimal, and positions it with a 10MHz
width from 5885MHz to 5895MHz <xref
target='fcc-cc'/>. Other 'Service Channels' are allowed to
use IP, but the Control Channel is not.
</t>
<t>
The same channel number 178 decimal with 10MHz
width (5885MHz to 5895MHz) is considered to be a
Service Channel by ETSI and is named 'G5-SCH2'
<xref target='etsi-302663-v1.2.1p-2013'/>. This
channel is dedicated to 'ITS Road Safety'. Other
channels are dedicated to 'ITS road traffic
efficiency'. Also, a 'Control Channel G5-CCH'
number 180 decimal (not 178) is reserved by ETSI
to be 10MHz-width centered on 5900MHz. Compared
to FCC, the 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 applications.') to the
'Non-safety-related ITS application' <xref
target='etsi-draft-102492-2-v1.1.1-2006'/>. This
means 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).
</t>
<t>
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
appears 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).
</t>
</list>
</t>
</section>
<section title="Changes Needed on a software driver 802.11a to become a
802.11p driver"
anchor="software-changes">
<t>
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.
</t>
<t>
Conditions for a 802.11a hardware to be 802.11p compliant:
<list style='symbols'>
<t>
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.
</t>
<t>
The chip must support the half-rate mode (the internal
clock can divided by two).
</t>
<t>
The chip transmit spectrum mask must be compliant to the
"Transmit spectrum mask" from the IEEE 802.11p amendment
(but experimental environments tolerate otherwise).
</t>
<t>
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.
</t>
</list>
</t>
<t>
Changes needed on the network stack in OCB mode:
<list style='symbols'>
<t>
Physical layer:
<list style='symbols'>
<t>
The chip must use the Orthogonal Frequency Multiple
Access (OFDM) encoding mode.
</t>
<t>
The chip must be set in half-mode rate mode (the
internal clock frequency is divided by two).
</t>
<t>
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.
</t>
</list>
MAC layer:
<list style='symbols'>
<t>
All management frames (beacons, join, leave, etc...)
emission and reception must be disabled except for
frames of subtype Action and Timing Advertisement
(defined below).
</t>
<t>
No encryption key or method must be used.
</t>
<t>
Packet emission and reception must be performed as in
ad-hoc mode, using the wildcard BSSID
(ff:ff:ff:ff:ff:ff).
</t>
<t>
The functions related to joining a BSS (Association
Request/Response) and for authentication
(Authentication Request/Reply, Challenge) are not
called.
</t>
<t>
The beacon interval is always set to 0 (zero).
</t>
<t>
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.
</t>
</list>
</t>
</list>
</t>
</section>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 23:36:23 |