NEMO R. Baldessari
Internet-Draft NEC Europe
Intended status: Informational A. Festag
Expires: January 6, 2008 NEC Germany
M. Lenardi
Hitachi Europe
July 05, 2007
C2C-C Consortium Requirements for NEMO Route Optimization
draft-baldessari-c2ccc-nemo-req-01
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Abstract
Vehicular ad hoc Networks (VANETs), self-organized networks based on
short-range wireless technologies, aim at improving road safety and
providing comfort and entertainment applications. The Car2Car
Communication Consortium is defining a European standard for inter-
vehicle communication that adopts VANETs principles. This document
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specifies requirements for Route Optimization techniques for usage of
Network Mobility (NEMO) in VANETs as identified by the Consortium.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. C2C Communication Architecture . . . . . . . . . . . . . . . . 6
3.1. System Architecture . . . . . . . . . . . . . . . . . . . 6
3.2. Protocol Architecture . . . . . . . . . . . . . . . . . . 8
3.3. IPv6 Deployment . . . . . . . . . . . . . . . . . . . . . 9
4. Intended NEMO Deployment . . . . . . . . . . . . . . . . . . . 11
4.1. Scope of NEMO . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Example Use Cases . . . . . . . . . . . . . . . . . . . . 11
4.2.1. Notification Services . . . . . . . . . . . . . . . . 12
4.2.2. Peer-to-peer Applications . . . . . . . . . . . . . . 12
4.2.3. Upload and Download Services . . . . . . . . . . . . . 12
5. NEMO Route Optimization Scenarios . . . . . . . . . . . . . . 13
6. NEMO Route Optimization Requirements . . . . . . . . . . . . . 15
6.1. Req 1 - Separability . . . . . . . . . . . . . . . . . . . 15
6.2. Req 2 - MNN IPsec . . . . . . . . . . . . . . . . . . . . 15
6.3. Req 3 - RO Security . . . . . . . . . . . . . . . . . . . 16
6.4. Req 4 - Privacy Protection . . . . . . . . . . . . . . . . 16
6.5. Req 5 - Multihoming . . . . . . . . . . . . . . . . . . . 17
6.6. Req 6 - Coexistence with Sub-IPv6 RO . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 21
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1. Introduction
In Vehicular ad hoc Networks (VANETs), cars are equipped with short-
range wireless communication devices that operate at frequencies
dedicated to safety and non-safety vehicular applications. When
entering the proximity of each other, vehicles form a self-organized
network by means of a specialized routing protocol that allows for
packet exchange through broadcast and unicast communications.
Further, fixed communication devices are installed along roadsides
and can either distribute local warnings or offer connectivity with a
network infrastructure. Due to its safety-oriented nature and
extremely dynamic operational environment, this type of communication
has lead research to consider specialized protocols and algorithms,
especially concerning information dissemination, geographic
distribution of packets and privacy/security issues.
The Car2Car Communication Consortium [10] is an industry consortium
of car manufacturers and electronics suppliers that focuses on the
definition of an European standard for vehicular communication
protocols. The Consortium gathers results from research projects and
aims at harmonizing their efforts. The first technical document
[11], to be released in the following months, gives an overview of
the system and protocol architecture, as well as of the applications
on which the Consortium has agreed so far. In essence, this document
defines a C2C-C protocol stack that offers specialized
functionalities and interfaces to (primarily) safety-oriented
applications and relies as a communication technology on a modified
version of IEEE 802.11p [12]. This protocol stack is placed beside a
traditional TCP/IP stack, based on IP version 6, which is used mainly
for non-safety applications or potentially by any application that is
not subject to strict delivery requirements, including Internet-based
applications. The interaction between these stacks is currently
discussed and briefly overviewed in this document.
As vehicles connecting to the Internet via dedicated access points
(also termed Road Side Units, see Section 2 for terminology) change
their attachment point while driving, the Consortium considers IP
Mobility support as enhancing the system with session continuity and
global reachability. When considering that passenger devices can be
plugged into car communication equipment, therefore turning a vehicle
into an entire moving network, Network Mobility (NEMO) principles
have clear benefits in the discussed scenario (i.e. passenger devices
shielded from mobility, centralized mobility management).
In NEMO Basic Support protocol [1] all data packets go through the
IPv6-in-IPv6 tunnel established between the Mobile Router (MR) and
the Home Agent (HA). As already pointed out in various documents
([7], [6] and [9]) this can have severe consequences on the
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communication performances, as it causes data packets to follow a
path that can be very far from optimal and requires a double IPv6
header for every packet exchanged with a Correspondent Node (CN) in
the Internet. Compared with a communication that uses the ideal
packet routing and the normal IPv6 header size, these factors results
in an increased delay and a reduced throughput, plus indirect
consequences like increased packet fragmentation and overall less
efficient usage of resources. Even if, as described later, the C2C-C
Consortium intends to adopt NEMO only for non-safety applications, a
Route Optimization (RO) mechanism that alleviates or even eliminates
this inefficiency is highly desirable. Moreover, the actual
deployment of NEMO as default IP mobility support in C2C-C
communication systems strongly depends on the availability of RO
techniques.
The document is organized as follows: Section 2 defines terminology.
Section 3 describes the technical approach of C2C-C Consortium that
allows for usage of NEMO. Section 4 describes the deployment of NEMO
in vehicular applications as intended by the C2C-C Consortium.
Section 5 introduces the RO scenario and finally Section 6 lists the
requirements for NEMO RO.
2. Terminology
The following terms used in this document are defined in the Mobile
IPv6 protocol specification [2]:
o Home Agent (HA)
o Home Address (HoA)
The following terms used in this document are defined in the Mobile
Network terminology document [8]:
o Network Mobility (NEMO)
o Mobile Network
o Mobile Router (MR)
o Mobile Network Prefix (MNP)
o Mobile Network Node (MNN)
The following terms used in this document are defined in the NEMO
Route Optimization Space Analysis document [6]:
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o Correspondent Router (CR)
o Correspondent Entity (CE)
The following new terms are used in this document:
o On Board Unit (OBU): a device installed in vehicles, implementing
the communication protocols and algorithm and equipped with at
least 1) a short-range wireless network interface operating at
dedicated frequencies and 2) a wireless or wired network interface
where Application Units (AU) can be attached to. With respect to
the NEMO terminology, the OBU is the physical machine acting as
MR, 1) is used as egress interface and 2) as ingress.
o Application Unit (AU): a portable or built-in device connected
temporarily or permanently to the vehicle OBU. It is assumed that
AUs support a standard TCP/IPv6 protocol stack, optionally
enhanced with IP Mobility support. With respect to the NEMO
terminology, an AU is a generic MNN.
o Road Side Unit (RSU): a device installed along roadsides
implementing the C2C-C communication protocols and algorithms.
RSUs can either be isolated or connected to a network
infrastructure. In the latter case, RSUs are attachment points
either acting themselves as IPv6 access routers or as network
bridges directly connected to an access router.
o In-vehicle network: the wireless or wired network placed in a
vehicle and composed by (potentially) several AUs and one OBU.
o Vehicle-to-Vehicle (V2V) Communication Mode: a generic
communication mode in which data packets are exchanged between two
vehicles, either directly or by means of multi-hop routing,
without involving any node in the infrastructure.
o Vehicle-to-Infrastructure (V2I) Communication Mode: a generic
communication mode in which data packets sent or received by a
vehicle traverse a network infrastructure.
o Vehicle-to-Infrastructure-to-Vehicle (V2I2V) Communication Mode: a
generic communication mode in which data packets are exchanged
between two vehicles, by means of multi-hop routing involving a
RSU not connected to a network infrastructure.
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3. C2C Communication Architecture
3.1. System Architecture
The current draft reference architecture of the C2C communication
system is shown in Figure 1.
| Internet |
| |
+---+-----------------+-+
| |
Access +--+-+ +--+-+ Access
Router | AR | | AR | Router
+--+-+ +--+-+
| |
--+---+--- --+---+--
| |
Road Side +--+--+ +--+--+ Public
Unit | RSU | | PHS | Hot Spot
+---+-+ +---+-+
| |
/\ /\
\_ \_
\_ \_
\ \
Mandatory \/
Mod IEEE 802.11p | __ \/ Optional IEEE
Interface +---+--+ \__ \/ | 802.11a/b/g
| OBU1 | | | Interface
+--+---+ +-+-----+---+
Vehicle1 | | OBU2 | On-Board
-+---+-+- +--+--------+ Unit
| | | Vehicle2
Application +--+-+ +-+--+ --+--+--
Units | AU | | AU | |
+----+ +----+ +-+--+
| AU |
+----+
Figure 1: C2C-CC Reference Architecture
Vehicles are equipped with networks logically composed of an OBU and
potentially multiple AUs. An AU is typically a dedicated device that
executes a single or a set of applications and utilizes the OBU
communication capabilities. An AU can be an integrated part of a
vehicle and be permanently connected to an OBU. It can also be a
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portable device such as laptop, PDA or game pad that can dynamically
attach to (and detach from) an OBU. AU and OBU are usually connected
with wired connection, but the connection can also be wireless, such
as Bluetooth. The distinction between AU and OBU is logical, they
can also reside in a single physical unit.
Vehicles' OBUs and stationary units along the road, termed road-side
units (RSUs), form an ad hoc network. An OBU is at least equipped
with a (short range) wireless communication device based on draft
standard IEEE 802.11p [12] (adapted to European conditions and with
specific C2C-C extensions) primarily dedicated for road safety, and
potentially with other optional communication devices. OBUs directly
communicate if wireless connectivity exist among them. In case of no
direct connectivity, multi-hop communication is used, where data is
forwarded from one OBU to another, until it reaches its destination.
For example in Figure 1, RSU and OBU1 have direct connectivity,
whereas OBU2 is out of RSU radio coverage but can communicate with it
through multi-hop routing.
The primary role of an RSU is improvement of road safety. RSUs have
two possible configuration modes: as isolated nodes, they execute
applications and/or extend the coverage of the ad hoc network
implementing routing functionalities. As attachment point connected
to an infrastructure network, RSUs distribute information originated
in the infrastructure and offer connectivity to the vehicles. As
result, for example, the latter configuration allows AUs registered
with an OBU to communicate with any host located in the Internet,
when at least one RSU connected to a network infrastructure is
available.
An OBU may also be equipped with alternative wireless technologies
for both, safety and non-safety. For example, an OBU may also
communicate with Internet nodes or servers via public wireless LAN
hot spots (PHS) operated individually or by wireless Internet service
providers. While RSUs for Internet access are typically set up with
a controlled process by a C2C-C key stake holder, such as road
administrators or other public authorities, public hot spots are
usually set up in a less controlled environment. These two types of
infrastructure access, RSU and PHS, also correspond to different
applications types. Other communication technology, such as wide
coverage/cellular networks (e.g. UMTS, GPRS) may also be optionally
installed in OBUs, but their usage is currently considered out of
scope of the C2C-CC Consortium.
The C2C-CC commonly refers to two main communication modes:
o in Vehicle-to-Vehicle (V2V) mode, data packets are exchanged
directly between OBUs, either via multi-hop or not, without
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involving any RSU;
o in Vehicle-to-Infrastructure mode (V2I), an OBU exchanges data
packets through a RSU with an arbitrary node connected to the
infrastructure (potentially another vehicle not attached to the
same RSU).
3.2. Protocol Architecture
The protocol stack currently considered by C2C-CC for OBUs is
depicted in Figure 2.
+--------------------+------------------+
| | |
| C2C-CC | IP-based |
| Applications | Applications |
| | |
+--------------------+------------------+
| | TCP/UDP/... |
| C2C-CC Transport +------------------+
| | |
+--------------------+-----+ IPv6 |
| | |
| C2C-CC Network | |
| | |
+--------------------+-----+------------+
| Modified | Standard WLAN |
| IEEE 802.11p | IEEE 802.11a/b/g |
+--------------------+------------------+
Figure 2: OBU Protocol Stack
Protocol blocks are explained in the following list:
o Modified IEEE 802.11p: this block represents MAC and PHY layers of
a wireless technology based upon current draft standard IEEE
802.11p [12] but modified for usage in Europe. In Europe,
allocation of dedicated frequencies around 5.9 GHz for safety and
non-safety applications is in progress. Expected communication
range in line of sight is around 500m. This network interface is
mandatory.
o IEEE 802.11a/b/g: this block represents MAC and PHY layers
provided by one ore more IEEE 802.11a/b/g network interfaces.
This network interface is optional but C2C-C Consortium encourages
its installation.
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o C2C-CC Network: this block represents the network layer protocol
currently defined by C2C-CC. The protocol provides secure ad hoc
routing and forwarding, as well as addressing, error handling,
packet sequencing, congestion control and efficient information
dissemination. The specification of this protocol is currently
under discussion. Only the C2C-CC Network protocol can access the
Modified IEEE 802.11p network interface. The C2C-CC Network
protocol can also access the IEEE 802.11a/b/g interface. The
C2C-CC Network protocol offers an interface to the IPv6 protocol.
This interface allows IPv6 headers and payload to be encapsulated
into C2C-CC Network datagrams and sent over the Modified IEEE
802.11p or IEEE 802.11a/b/g network interface. The specification
of this interface is currently under discussion. A primary goal
of the C2C-CC Network layer is to provide geographic routing and
addressing functionalities for cooperative safety applications.
Through the mentioned interface to the IPv6 protocol, these
functionalities are also available for IP-based applications.
o C2C-CC Transport: this block represents the transport layer
protocol currently defined by C2C-CC. This protocol provides a
selected set of traditional transport layer functionalities (e.g.
application data multiplexing/demultiplexing, connection
establishment, reliability etc.). The specification of this
protocol is currently under discussion.
o C2C-CC Applications: this block represents the application layer
protocol currently defined by C2C-CC and concerns Active Safety
and Traffic Efficiency Applications.
3.3. IPv6 Deployment
As described in Section 3.2, the C2C-CC includes IPv6 as mandatory
part of its specified protocol architecture. Currently, three
methods are discussed for transmission of IPv6 headers and their
payload:
o On the Modified IEEE 802.11p interface via the C2C-CC Network
layer: in this method, IPv6 headers are encapsulated into C2C-CC
Network headers and sent using dedicated frequencies for inter-
vehicle communications. As the C2C-CC Network layer transparently
provides ad hoc routing, from the IPv6 layer perspective other
nodes (OBUs and RSU) are attached to the same link. The real
broadcast domain, where IPv6 multicast headers are distributed to,
is chosen by the C2C-CC Network layer according to the packet
type. In particular, C2C-CC Network layer provides efficient
flooding and geographically scoped broadcast mechanisms. With
respect to a currently adopted terminology, introduced in [13],
the C2C-C Consortium approach for usage of NEMO on the Modified
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IEEE 802.11p is fully MANET-Centric, in the sense that the sub-
IPv6 protocol layer provides routing and forwarding in the ad hoc
network. This results in the ad hoc nature of VANETs being hidden
from IPv6 layer. A comparison of approaches for VANETs can be
found in [14]. The deployability of this method strongly depends
on the future availability of dedicated frequencies for non-safety
purposes in inter-vehicle communications. If frequencies for this
purpose will not be allocated, only the left part of the protocol
stack of Figure 2 can access the Modified IEEE 802.11p interface.
o On the IEEE 802.11a/b/g interface via the C2C-CC Network layer: in
this method, IPv6 headers are encapsulated into C2C-CC Network
headers and sent using license-free ISM frequency bands (wireless
LAN). Except the network interface, this method is equivalent to
the previous one.
o On the IEEE 802.11a/b/g interface directly: in this method, IPv6
headers are sent directly to the wireless LAN interface as
specified by [5].
The following informational list briefly summarizes currently
discussed design concepts:
o vehicles use only IPv6 addresses with as host part an EUI-64
identifier derived from the MAC address. Privacy issues described
in [4] are strongly alleviated through the use of temporary,
changing MAC addresses, which are assigned in a set to every
vehicle (as part of their assigned "pseudonyms");
o when a RSU connected to a network infrastructure is available, an
OBU configures a globally routable Care-of Address using stateless
address configuration;
o when infrastructure access is not available, OBUs use addresses
with as prefix part a predefined IPv6 prefix (either reserved for
C2C-C communications or a general purpose one);
o RSU can either act as IPv6 Access Routers or as network bridges
connected to external IPv6 Access Routers. Different Access
Routers are responsible for announcing different network prefixes
with global validity. As a consequence, when roaming between
different Access Routers, vehicles experience layer 3 handovers.
In all the methods for use of IPv6 in C2C-CC systems as described
above, the IPv6 layer is meant to be enhanced with Mobility Support.
As a vehicle includes a set of attached devices (AUs), Network
Mobility seems the most appropriate solution, allowing for a
centralized management of mobility to be executed in OBUs.
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4. Intended NEMO Deployment
4.1. Scope of NEMO
In VANETs based on IEEE 802.11 family, a limited amount of bandwidth
is shared among a potentially high number of vehicles. Additionally
applications for safety purposes have strict requirements in terms of
delay, information dissemination and aggregation and secure ad hoc
routing. This conflicting conditions have led research activities to
consider different approaches compared with traditional, packet-
centric network engineering. In particular, only through a more
information-centric approach it seems possible to achieve
functionalities like geographic distribution, information
dissemination according to relevance, information aggregation using
cross-layer analysis, plausibility checks at different protocol
layers.
Taking these aspects into consideration, the C2C-C Consortium is
defining a protocol stack mainly dedicated for vehicular safety
communications. Applications that are not subject to these
particular requirements must use the right part of the protocol stack
of Figure 2. This implies that the usage of NEMO in vehicular
communications does not target safety-of-life applications but rather
less restrictive, non-safety applications.
Another important aspect for deployability is related to costs. A
primary goal of the C2C-C Consortium is to achieve a spread diffusion
in terms of vehicles equipped with communication devices and
protocols. This implies that vehicles of different brands and
classes should be equipped by default with a basic communication
system, whereas differentiation of products can be achieved by
offering additional services. NEMO, like any other solution based on
IP Mobility support, relies on a service provider that guarantees
global reachability at the Home Network Prefix by maintaining an Home
Agent. As it does not seem realistic that every car owner will also
subscribe for such a service, a set of limited applications based on
IPv6 should be available even without Mobility Support. Therefore,
NEMO modularity and interoperability with non-NEMO equipped vehicles
has to be guaranteed.
4.2. Example Use Cases
In this section, the main use cases are listed that have been
identified by the C2C-CC for usage of NEMO in inter-vehicle
communications: notification services, peer-to-peer applications and
upload/download services.
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4.2.1. Notification Services
A generic notification service delivers information to subscribers by
means of the Internet. After subscribing the service with a
provider, a user is notified when updates are available. Example
services are weather, traffic or news reports, as well as commercial
and technical information from the car producer or other companies.
As the network address of a vehicle changes while the vehicle moves
among different points of attachment, without NEMO each application
should register the new address in order to receive information at
the correct location. Service providers would need to update
continuously the subscription data and would be able to track the
users. Adopting NEMO, which provides global reachability at a
reasonably constant identifier (e.g. Mobile Network Prefix),
efficiency and location privacy improve considerably.
4.2.2. Peer-to-peer Applications
A generic peer-to-peer application exchanges data directly between
vehicles, without contacting any application server. Data traffic
goes through a network infrastructure (V2I or V2I2V) or directly
between cars when the infrastructure is not available (V2V). Example
applications are vehicle-to-vehicle instant messaging (chat) and off-
line messaging (peer-to-peer email), vehicle-to-vehicle voice over IP
and file exchange.
In this set of use cases, the same applications should be able to run
in V2V and V2I mode. As applications should not be aware of routing
nor addressing issues, they should use the same identifier for
sessions and users (e.g. cars/drivers/passengers) independently of
the communications mode. Possible approaches are either to adopt
resolution mechanisms or actually maintain the same network
identifier in both V2V and V2I modes. This could be achieved for
example generalizing the concept of Mobile Network Prefix (MNP) and
allowing a Mobile Router (OBU) to use it for V2V communications in
absence of attachment points. By means of enforcing limited lifetime
for IPv6 prefixes and due to the isolation of VANET clusters from the
infrastructure (in V2V), this use of MNP should not introduce routing
inconsistencies.
4.2.3. Upload and Download Services
A generic upload/download service via the Internet consists in simple
file exchange procedures with servers located in the Internet.
As in vehicular scenarios the connectivity to the infrastructure is
highly intermittent, network address' changes cause applications to
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re-establish sessions in order to resume the exchange, which implies
considerable overhead. Session re-establishment can be avoided
adopting NEMO.
5. NEMO Route Optimization Scenarios
In this section, operational characteristics of the intended NEMO
deployment are described that are relevant for the design of Route
Optimization techniques. In particular a restriction of the general
solution space for RO and motivations for RO requirements described
in Section 6 are provided.
In most NEMO deployment scenarios, MRs have permanent connectivity to
the infrastructure and Route Optimization techniques are mainly
intended as extensions of MIPv6 RO, where communication assumes to
take place always through a point of attachment (infrastructure-based
RO). In VANETs based on wireless LAN technologies, the connectivity
of moving vehicles to the infrastructure is intermittent due to
limited coverage of access points. Nevertheless, direct
communication among vehicles should be supported even when
infrastructure access is not available. Because this case is
strictly a peculiarity of the considered scenario, a technique to
allow direct communication (single- and multi-hop) by exposing the
MNP associated to vehicles will be studied by the C2C-CC as part of
the sub-IPv6 C2C-CC Network layer. Once such a mechanism is
available, it MAY also be used as RO technique between MRs located in
their vicinity (infrastructure-less RO). The sub-IPv6 layer is
responsible for making sure that this mechanism is scalable,
reasonably secure (i.e. compared with current Internet level of
security) and protects users' privacy. More details about
infrastructure-less RO are out of the scope of this document.
A C2C-CC OBU MUST be capable of both infrastructure-based and
infrastructure-less NEMO RO. When both techniques are simultaneously
possible (e.g. two MRs that are reachable both via the infrastructure
and directly in the ad hoc domain) the OBU should apply appropriate
policies to choose one. The definition of such policies is out of
scope of this document. Furthermore, the scope of this document is
restricted to the specification of requirements for infrastructure-
based NEMO RO techniques.
With respect to the classification of NEMO Route Optimization
scenarios described in [6], the non-nested NEMO RO case (Section 3.1)
is considered as the most important for the C2C-CC deployment. In
fact, MIPv6-enabled AUs (i.e. VMNs) and nested Network Mobility are
not considered in the C2C-CC use cases.
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The requirements defined in this document refer to RO between MR and
CR (Correspondent Router). According to C2C-CC use cases, the CR can
be:
o a NEMO MR. For example the MR running on another vehicle or
another mobile device connected to the Internet;
o a RO-enabled router, i.e. a router static or mobile that does not
act as NEMO MR but is capable of establishing RO sessions with
NEMO MRs. For example the access router serving a CN in the
infrastructure that offers services to vehicles, or the access
router serving RSUs installed along the road;
o a RO-enabled router collapsed into the CN, i.e. performing
internal routing. For example RSUs installed along the road.
As consequence of the fact that connectivity to the infrastructure
strongly depends on vehicles' mobility, two opposite situations are
here considered as RO scenarios: vehicles passing by points of
attachment while driving and vehicles connecting to the
infrastructure while stopped or parked.
In the first case, the connectivity to the infrastructure is
available only for short time intervals. Vehicles' applications
exchange data packets with nodes in the infrastructure in form of
short bursts, containing for example traffic updates or information
about local points of interests. In this situation, providing prompt
and reliable communication is more important than achieving optimal
routing or highest available throughput. In particular, the
additional delay for RO establishment with every CRs can have a
considerable negative impact. Furthermore, in some situations the
path through MR-HA tunnel might be considered more reliable and
trustworthy than a direct one to the CR. In particular, the tunnel
allows the MR to hide its CoA from the CR which results in a location
privacy protection. Therefore:
o vehicles should be able to decide whether or not to switch to RO
according to various criteria (e.g. speed, density and geographic
location of attachment points, trustworthiness of CR etc.);
o a lightweight RO scheme providing some degree of optimization
(e.g. direct MR-CR routing but with the same packet overhead due
to tunneling) and requiring short establishment times is more
likely to be selected.
Another aspect of the vehicular dynamic scenario is that
communication involving the infrastructure takes place mostly with
nodes dedicated for vehicular communications, like control centers,
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notification points, infotainment service providers. In all of these
cases, the Correspondent Router is a newly deployed device.
Consequently, RO techniques for this scenario are not strictly
required to be compatible with CNs implementing legacy MIPv6 RO.
In the case of low mobile or static vehicles, the characteristics of
the connectivity allow for classical internet-based applications,
involving multiple nodes in the infrastructure. This scenario
presents less peculiarities than the dynamic one when compared with
other NEMO deployments (considering that the sub-IPv6 C2C-CC layer
presents a flat topology to NEMO).
Other requirements for RO pointed out in Section 6 like multihoming,
security and privacy, are fundamental and not related to the dynamics
of the scenario.
6. NEMO Route Optimization Requirements
The C2C-C Consortium has identified the following requirements for
NEMO RO techniques.
6.1. Req 1 - Separability
A RO technique, including its establishment procedure, MUST have the
ability to be bypassed by applications that desire to use
bidirectional tunnels through the HA.
As explained in Section 5, in some scenarios due to the intermittent
connectivity, it might not be beneficial to activate RO. Therefore,
applications or other management instances in the OBU should be able
to trigger the switching to RO according to appropriate criteria.
This requirement is also specified in [9].
6.2. Req 2 - MNN IPsec
A RO technique SHOULD allow MNNs connected to the MR to use IPsec as
if they were connected to a regular access router.
This requirement comes from the fact that no assumption can be made
on pre-existing trust relationships between passenger devices and the
OBU. Therefore, passenger devices (assumed to run IPv6 without
Mobility Support) should be able to use full IPsec functionalities
when connecting to the infrastructure via a MR.
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6.3. Req 3 - RO Security
A RO technique MUST prevent malicious nodes to claim false MNP
ownership. In order to achieve this, a RO technique MAY make use of
security features provided by the sub-IPv6 C2C-CC Network layer (e.g.
cryptographic protection), but it MUST NOT introduce new security
leaks for the C2C-CC applications or render their security measures
ineffective.
It is required that the security level of a RO scheme is comparable
with today's Internet, which is the same goal of MIPv6 Return
Routability procedure. In addition to that, as data security is
mandatory for safety applications targeted by the C2C-C Consortium
and implemented in the left part of the protocol stack depicted in
Figure 2, security features will be already implemented in a C2C-CC
compliant OBU. The presence of this features might facilitate the
design of a lightweight, yet secure, RO technique.
C2C-CC security mechanisms are currently discussed and further
details are out of scope of this document. As informational
references, see [16], [17] and [18].
6.4. Req 4 - Privacy Protection
A RO technique MUST not require that the MNP is revealed to all nodes
in the visited network. Instead, a RO technique MUST allow for
revealing the MNP only to selected nodes in the visited network.
Furthermore, a RO technique SHOULD allow that MNP and HoA are not
exchanged as clear text.
Privacy of drivers and passengers is mandatory for safety
applications targeted by the C2C-C Consortium. Mechanisms to
implement privacy in the left part of the protocol stack depicted in
Figure 2 are currently discussed (e.g. "revocable pseudonimity",
where pre-assigned, quasi-random and changing pseudonyms are used as
MAC and sub-IPv6 layer identifiers).
When using the right part of the stack depicted in Figure 2 to access
the Internet using IPv6, users will be aware that the level of
privacy protection is decreased. Nevertheless, clear text
information that could allow for linking changed pseudonyms by
sending constant identifiers should be minimized or even prohibited.
In particular, encryption of Home Address and Mobile Network Prefix
in NEMO signaling should be considered (e.g. specified as optional
mechanism in [3]).
C2C-CC privacy protection mechanisms are currently discussed and
further details are out of scope of this document. As informational
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reference, see [15].
6.5. Req 5 - Multihoming
A RO technique MUST allow a MR to be simultaneously connected to
multiple access networks, having multiple prefixes and Care-Of
Addresses in a MONAMI6 context.
In other words, it is required that a RO technique can be used on
multiple communication technologies. Assuming that mechanisms for
registering and handling multiple CoAs are provided from the MONAMI6
work, NEMO RO should be usable for every available CoA.
This requirement is also specified in [9].
6.6. Req 6 - Coexistence with Sub-IPv6 RO
A RO technique MUST allow for coexistence in the same OBU with a RO
technique offered by the sub-IPv6 C2C-CC Network layer. The OBU MUST
be able to choose which technique to use when both are simultaneously
available.
The here mentioned sub-IPv6 RO technique is supposed to inject routes
into the IPv6 routing table as result of a sub-IPv6 signaling between
cars, without involving the infrastructure. A NEMO RO technique
should not be disturbed by the sub-IPv6 RO technique.
7. IANA Considerations
This document does not require any IANA action.
8. Security Considerations
This document does not specify any protocol therefore does not create
any security threat. However, it specifies requirements for a
protocol that include security and privacy issues in VANETs as
currently discussed in the C2C-C Consortium.
9. Acknowledgments
The authors would like to thank the members of the work groups PHY/
MAC/NET and APP of the C2C-C Consortium and in particular Tim
Leinmueller, Bernd Bochow, Andras Kovacs and Matthias Roeckl.
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10. References
10.1. Normative References
[1] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
[2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[3] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
Agents", RFC 3776, June 2004.
[4] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[5] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[6] Ng, C., Zhao, F., Watari, M., and P. Thubert, "Network Mobility
Route Optimization Solution Space Analysis",
draft-ietf-nemo-ro-space-analysis (work in progress),
September 2006.
[7] Ng, C., "Network Mobility Route Optimization Problem
Statement", draft-ietf-nemo-ro-problem-statement-03 (work in
progress), September 2006.
10.2. Informative References
[8] Ernst, T. and H. Lach, "Network Mobility Support Terminology",
draft-ietf-nemo-terminology-06 (work in progress),
November 2006.
[9] Eddy, W., Ivancic, W., and T. Davis, "NEMO Route Optimization
Requirements for Operational Use in Aeronautics and Space
Exploration Mobile Networks", draft-eddy-nemo-aero-reqs-00
(work in progress), April 2007.
[10] "Car2Car Communication Consortium Official Website",
http://www.car-2-car.org/ .
[11] "Car2Car Communication Consortium Manifesto",
http://www.car-2-car.org/index.php?id=570 , May 2007.
[12] "Draft Amendment to Standard for Information Technology .
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Telecommunications and information exchange between systems .
Local and Metropolitan networks . Specific requirements - Part
11: Wireless LAN Medium Access Control (MAC) and Physical Layer
(PHY) specifications: Amendment 3: Wireless Access in Vehicular
Environments (WAVE)", IEEE P802.11p/D1.0, February 2006.
[13] McCarthy, B., Edwards, C., Dunmore, M., and R. Aguiar, "The
Integration of Ad-hoc (MANET) and Mobile Networking (NEMO):
Principles to Support Rescue Team Communication", Proc. of
International Conference on Mobile Computing and
Ubiquitous Networking (ICMU 2006), October 2006.
[14] Baldessari, R., Festag, A., and J. Abeille, "NEMO meets VANET:
A Deployability Analysis of Network Mobility in Vehicular
Communication", Proc.of 7th International Conference on ITS
Telecommunications (ITST2007), June 2007.
[15] Fonseca, E., Festag, A., Baldessari, R., and R. Aguiar,
"Support of Anonymity in VANETs - Putting Pseudonymity into
Practice", Proc.of IEEE Wireless Communication and Networking
Conference (WCNC2007), March 2007.
[16] Raya, M. and J. Hubaux, "The Security of Vehicular Ad Hoc
Networks", Proc.of Workshop on Security of Ad Hoc and
Sensor Networks (SASN2005), November 2005.
[17] Aijaz, A., Bochow, B., Doetzer, F., Festag, A., Gerlach, M.,
Leinmueller, T., and R. Kroh, "Attacks on Inter Vehicle
Communication Systems - an Analysis", Proc.of International
Workshop on Intelligent Transportation (WIT2006),
March 2006.
[18] Fonseca, E. and A. Festag, "A Survey of Existing Approaches for
Secure Ad Hoc Routing and Their Applicability to VANETS", NEC
Technical Report NLE-PR-2006-19, March 2006.
Authors' Addresses
Roberto Baldessari
NEC Europe Network Laboratories
Kurfuersten-anlage 36
Heidelberg 69115
Germany
Phone: +49 6221 4342167
Email: roberto.baldessari@netlab.nec.de
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Andreas Festag
NEC Deutschland GmbH
Kurfuersten-anlage 36
Heidelberg 69115
Germany
Phone: +49 6221 4342147
Email: andreas.festag@netlab.nec.de
Massimiliano Lenardi
Hitachi Europe SAS Sophia Antipolis Laboratory
Immeuble Le Theleme
1503 Route des Dolines
Valbonne F-06560
France
Phone: +33 489 874168
Email: massimiliano.lenardi@hitachi-eu.com
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