Link, Apple CarPlay, and Android Auto use IP. Current demonstrators of security .... native mobility protocols and locator-iden- tifier split for networked vehicles ...
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INTELLIGENT TRANSPORTATION SYSTEMS AND THE IETF By Alexandre Petrescu and Carlos Pignataro
I
Recent demonstrators featuring vehicle-tovehicle (V2V) use-cases (e.g., platooning), rely on ITS-G5 link-layers and CAM application layers. Within these demonstrators, the platoon size limits (number of cars
NTELLIGENT TRANSPORTATION SYSTEMS (ITS) IS A GENERIC NAME FOR USING
in a platoon) have been exhibited due to
any of a wide range of information technologies to move people, freight, and other
the radio range of ITS-G5. It is believed
devices across roads, waterways, air, and space. Uses may include Internet access in
that the involvement of IP protocols (with
cars, trains, and planes; multimodal itinerary planning across smart cities; high-speed
ETSI ITS applications) featuring IP subnet
multioperator road and park tolling; goods-delivery tracking; traffic supervision and
structures between cars may lead to
management; self-driving cars and car platooning; emergency calls; and highly-improved
arbitrary-size platoons (like the size of the
safety of traffic of automobiles and trucks. To support such a wide range of uses, applica-
Internet can be arbitrary), where packets
tions need reliable communication capabilities across complex systems involving a variety
are IP-forwarded rather than broadcasted.
of mobile and fixed devices with disparate wireless and wired links. To that end, technical committees at the International Standards Organization (ISO) and the European Telecommunications Standards Institute (ETSI), an ITU collaboration effort, and a connectivityfocused US government programme are but a handful of organizations and activities carrying an ITS acronym in their names (e.g., ISO TC204 ITS, ETSI TC ITS, ITU Collabora-
Recent lessons
tion on ITS Communication Standards, USDOT ITS JPO).
learned at a European
Acknowledging that many design require-
stacks are already present in many cars
demonstration event
ments of the early-stage Internet were
that are connected to the Internet with a
related to safety, reliability, and hetero-
cellular modem, typically LTE. In addition,
geneity, and considering the successful
widespread in-car technologies like Mirror-
of sending vehicle
Internet deployments of recent decades,
Link, Apple CarPlay, and Android Auto
position corrections
it is tempting to contemplate the use of
use IP. Current demonstrators of security
the TCP/IP family of protocols to support
mechanisms for out-of-car DSRC2 need
over IPv6.
applications in ITS use-cases. At IETF
an ancillary Internet connection, often LTE
meetings, participants are versed in the
with TCP/IP support, to realize the transfer
design and deployment for such require-
of security material (certificates, revoca-
ments. For example, one illustration of
tion lists, and so on).
illustrated the necessity
reliability is the best-effort nature of IP
Adopting TCP/IP would also help address
packet delivery on a path through a maze
the fact that the pairing operation of
of routers worldwide, with an available
vehicles is independently being develop-
alternative if a known path fails, across
ed by organizations that often overlook
heterogeneous networks.
One illustration of
The communication systems currently
fundamental interoperability requirements. Furthermore, recent lessons learned at a
reliability is the best-
European demonstration event illustrated
some use-cases. For example, multimodal
effort nature of IP
the necessity of sending vehicle position
itinerary ticketing, 50km/h toll passage,
packet delivery on a
corrections over IPv6.
and
path through a maze of
DSRC and ITS-G5 messages, such as
used in transportation are satisfactory in
incumbent
car
platooning
rely
extensively on dedicated communication
BSP or CAM, are broadcast periodically
systems; they are all successful in trial
routers worldwide, with
phases, even though the penetration of
an available alternative
mechanism to allow the sender to learn
the current1 IP family of protocols in these
if a known path fails,
whether or not a message was received
across heterogeneous
with a certain degree of reliability. Using
use-cases is relatively limited, if not outright absent. ITS discussions at the IETF offer hope of
networks.
(IP is not used); there is a need for a
the request-response semantics of some IP protocols may help achieve improved
TCP/IP protocols in vehicular communications in the near future. TCP/IP protocol
Continued on next page
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between vehicles (V2V), for example,
Intelligent Transportation Systems and the IETF, continued
vehicle platooning. Additional use-cases reliability when necessary (e.g., ICMP
The ITS BoF in Buenos Aires
involve communications between a server
Neighbor Solicitation/Advertisement, or
Participants at the IETF have published
situated along or near the road (Road-
TCP SYN/ACK).
Internet-Drafts that are explicitly or impli-
Side Unit) and vehicles passing by. A
smartphone-to-server
citly related to ITS use-cases on many
tutorial on the use of IP in vehicle networks
TCP/IP is the preferred method of mobile
occasions in recent years. In April 2016, at
exposed the advantages of a narrow-waist
interaction, rarely, if ever, does a deployed
the IETF meeting in Buenos Aires, a Birds-
networking layer (compared with network
of-a-Feather (BoF) meeting, chaired by
layer absence or with other link-specific
Arguably,
where
multimodal travel planning application run
or application-specific networking layers),
on IPv6. More importantly, too often appli-
including the support of link layers, such
cation-glued-on-link communication pro-
as 802.11-OCB (also known as DSRC
tocols (i.e., protocols without networking
or 802.11p), with a variety of modulation
layers3) are involved in communications
methods (e.g., WiFi, LTE, and VLC). Other
between automobiles. In this context,
A tutorial on the use of
further involvement of applications relying
IP in vehicle networks
on TCP/IP and of IP forwarding mech-
exposed the advantages
favorably to the use of bouncing-signal
improvements to the security of communi-
of a narrow-waist net-
principles
cations (IPsec), and orders of magnitude
working layer, including
more
the support of link layers,
(Figure 1). These two aspects raised a
such as 802.11-OCB with
number of comments from the audience;
anisms is expected to result in significant
interactions
between
numerous
directly reachable devices in vehicles (IPv6). Applications that are unimaginable today will be possible, when every
a variety of modulation
car can talk to every other car around the
methods.
aspects of using packetised data exchange principles were described as comparing of
communication
between
vehicles, such as when Light Detection And Ranging (LIDAR) or cameras are used
together with previously expressed security and privacy concerns, these comments can be found in the meeting minutes.
world, as computers do via the Internet.
The establishment of a Category A liaison
And since the value of the network grows
between the IETF and the ISO Technical
with the number of connected parties, it
Committee TC204, ITS, was announced
is expected that the Internet’s value and
during the ITS BoF in Buenos Aires. One
reach will increase even more when cars
Carlos Pignataro and Russ Housley, was
liaison statement from ISO/TC204 was
are connected. The potential growth can
held specifically on the topic of ITS. Prob-
announced, with a slide set from the ISO/
be further illustrated by vehicles forming
lem statements were discussed about the
TC204 liaison officer.
an independent network on a road linking
use of IP in vehicle networks: IP for vehicle-
smart cities; to some extent the question
to-vehicle
whether to connect the network of vehicles
communications, IPv6-over-foo, IP path
The initial text of a charter4 for an ITS WG
to the Internet may be turned the other way
establishment, and naming. The presented
was presented in Buenos Aires. In the initial
around.
use-cases involve direct communications
phases of charter writing, a significant
Front car (obstacle)
Car
and
Rear obstacle
Send signalStart timer
vehicle-to-infrastructure
Charter Work and Interim
Car
Front car (obstacle)
Rear obstacle
Request: what is position of front car? Response: position is X. Dist = myposition - X
Stop timer Dist == 10m
Request: can I follow you? Response: yes Regulate
Dist == 4m Local decision: (de/ac)celerate
Bouncing signal principle Figure 1. Vehicle-to-vehicle communication principles
12
Distributed (cooperative) decision
Message exchange principle
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ETSI ITS
IEEE WAVE P1609
IPv6
ISO TC204
IPv6 IPv6
11p among others
ISO 21210:2010 “IPv6 Networking”
workaround?
5GHz among others ?
Opensource at github.com/alexvoronov/geonetworking
Opensource at itsforge.net
Opensource ---
EN 302 636-6-1 V1.2.1 (2014-05) “IPv6 over GeoNetworking”
P1609.3v3/D3 July 2015 “Networking Services”
ISO 21217:2014 “Architecture”
(at IEEE “802.11p” now means “OCBEnabled 802.11-2012”)
(at ISO “802.11p” means “M5” at “5GHz”)
(at ETSI “802.11p” means “ITS-G5”)
Figure 2. Models of Running IPv6 over 802.11p
number of work domains were suggested:
ument, based on “IPv6 over Ethernet”
establishing direct and secure connectivity
communications
between moving networks.
automobiles
RFC 2464. The model of an IPv6-over-
(V2V, V2I), space, airline, and unmanned
802.11p layered stack of protocols can be
aerial
infor-
compared against other models of running
mation- and content-centric networking
IPv6 over 802.11p (DSRC) found at per-
applied in vehicular communications, alter-
tinent Standards Development Organi-
native mobility protocols and locator-iden-
zations. Three such models are illustrated
tifier split for networked vehicles (AERO,
in Figure 2.
vehicle
between
communications,
LISP) and more. Facing this potentially enormous scope, extensive discussions led to more than just improving the text, it helped narrow down the number of deliverables: two Informational documents on the context and the problem statement for the use of IP in vehicular communications, and one Standards Track document on “IPv6-over-802.11p”. This charter structure was further finalized during the virtual interim ITS BoF held on 31 May 2016 via audio-conference with remote slide presentation. The details are described in the
Definitions The Working Group defines the terms V2V, V2I, and V2X as follows: V2V (vehicle-to-vehicle communications). The communications can be direct (without requiring an access point or relay by the
Prior to the BoF in Buenos Aires, the topic
road-side), or indirect (relying on one or
of vehicular networks was presented at
multiple relays along the road-side).
the IETF 93 technical plenary in Prague, Czech Republic. Presentations from academic and industry experts in vehicle networks, security, and standardization were discussed. For more on the plenary, see “Vehicular Networks Are Expected to Save Lives But Carry Privacy Risks,” IETF Journal, Vol. 11, Issue 2 (https://www.
V2I (vehicle-to-infrastructure communications). Data flows happen between a mobile vehicle and a server in the fixed infrastructure
nearby.
Sometimes
V2I
stands for vehicle-to-Internet communications, referring to a server anywhere in the Internet.
internetsociety.org/publications/ietf-journal-
V2X
november-2015/vehicular-networks).
cations). In some contexts it is a handy
(vehicle-to-‘any
other’
communi-
term to mean both V2V and V2I at the
minutes of the virtual interim meeting.
A Proposal for an ITS WG
The item “IPv6 over 802.11p” is regarded
The goal of the proposed ITS WG is to
as a typical IETF “IPv6 over foo” doc-
standardize and/or profile IP protocols for
same time, e.g., “V2X technology enables Continued on next page
13
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Draft targeting one of the three proposed
Intelligent Transportation Systems and the IETF, continued
work items: ITS General Problem Area, IPv6 over 802.11p, or Problem Statement. You are also invited to read the existing Internet-Drafts in this group, review them, and make comments.
Footnotes What is your IP address?
Sense neighbor
1. Ahead of general thinking, the IETF considers the current version of the IP family of protocols to be IPv6. Work is being considered to declare IPv4 as “Historic”, or “Restricted Standard”, and, simultaneously, work is ongoing to promote IPv6 as “Internet Standard”. See page 1.
This is my IP address
IP is in front of me (camera-based)
What is your position/speed/heading? This is my position/speed/heading
[de/ac]celerate Can I follow you? Yes but I usually overcome speedlimits (no, I don’t like people following me)
Don’t follow
Figure 3. Example Application Using IP Messages for C-ACC
a vehicle to stay connected to both the
Looking Forward
Internet and other cars”. In other contexts
The charter text is now stable, and work
it means vehicle-to-‘something other than
has started on the initial work items. Four
vehicle or infrastructure, most notably
Internet-Drafts have been identified as
a human’ communications, e.g., V2P
good candidates for the first three work
(vehicle-to-pedestrian),
(vehicle-
items. More people have joined the email
to-nomadic pedestrian), and V2D (vehicle-
list and some of those have expressed
to-device of pedestrian).
interest in submitting Internet-Drafts to
Models and Use-Cases
address the goals in the current proposed
Two use-cases were discussed at the
charter.
BoF: cooperative adaptive cruise-control
If you are interested in the use of IP proto-
(C-ACC) and platooning. These communi-
cols in vehicular communications, please
cation models are illustrated in Figures 3
subscribe to the email list https://ietf.org/
and 4.
mailman/listinfo/its and submit an Internet-
V2N
2. The term Dedicated Short-Range Communications (DSRC) is used with multiple meanings. An earlier IETF Journal article defines DSRC as “802.11e for quality of service; 802.11j-2004 for half-clocked operations, which are a more robust form of communication; and 802.11p for operation in the 5.9 GHz band and a new mode called OCB for Outside the Context of a Basic Service Set.” Also, DSRC MAC and PHY layers are defined by ASTM E2213 - 03(2010), which may refer to IEEE documents. The DSRC application layer is defined by SAE J2735_201603. In Europe, DSRC is defined by CEN/TC278. An additional standard used in Europe for 5 gigahertz, in lieu and place of DSRC, is defined by ETSI as “ITS-G5”. 3. An early example of an application protocol glued onto the link layer (without a network layer) is the Wireless Application Protocol (WAP). It was used in the initial deployments of interactive applications in the first smartphones, only to be phased out by the arrival of TCP/IP. Today, WAP has largely disappeared, yet similar tendencies persist to develop such protocols within and outside ITS. 4. See the latest proposed charter at https:// tools.ietf.org/wg/its/trac/.
unreachable 802.11p max range
Scalability and interoperability issue of initial non-IP platooning demonstrators
Figure 4. Scalability and Interoperability Issue of Initial Non-IP Platooning Demonstrators
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