schmittlauch/hs-pseudonym-schemes-in-v2x
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Trolli Schmittlauch 2018-06-08 13:05:06 +02:00
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@ -155,7 +155,7 @@ This section gives a brief overview of the \ac{ETSI} architecture for Intelligen
A \ac{VANET} consists of different kinds of ITS stations: \\
\acfp{OBU} residing inside vehicles can be divided into the communication and \acl{CCU}, managing the \ac{ITS} specific network communication over the car's wireless interfaces, and \acfp{AU} utilising the network services provided by the \ac{CCU} to communicate transparently over a standard \acs{IPv6} stack. \\
On the stationary infrastructure side, \acfp{RSU} can either just provide some special local services or even be connected to a network operator's infrastructure and thus provide an uplink to the internet.
On the stationary infrastructure side, \acfp{RSU} can either just provide some special local services or even be connected to a network operator's infrastructure and thus provide an uplink to the Internet.
The protocol architecture of \ac{ITS} stations according to the \ac{ETSI} reference architecture \cite{europeantelecommunicationsstandardsinstituteetsiETSI3026652010} is mostly based on the well-known \ac{OSI} layer model.
@ -181,14 +181,14 @@ CALM FAST \cite{TN_libero_mab2} is a non-IP port-mapper protocol designed for si
\subsubsection{GeoNetworking}
\acf{GN} (\cite{europeantelecommunicationsstandardsinstituteetsiETSI30263612014} and following) is an \ac{ETSI}-standardized networking protocol for routing and forwarding packets through \acp{VANET} based on geographical Information. It sits between the link and network layer and provides its services to other networking and transport protocols. The background section of \cite{sandonisVehicleInternetCommunications2016} gives a good high-level overview of the \ac{GN} networking architecture and the rationale behind it.
\acf{GN} (\cite{europeantelecommunicationsstandardsinstituteetsiETSI30263612014} et seq.) is an \ac{ETSI}-standardized networking protocol for routing and forwarding packets through \acp{VANET} based on geographical information. It sits between the link and network layer and provides its services to other networking and transport protocols. The background section of \cite{sandonisVehicleInternetCommunications2016} gives a good high-level overview of the \ac{GN} networking architecture and the rationale behind it.
Every \ac{GN} node has to know its geographical position, e.g. through \acp{GNSS}, for the routing to work. The services provided by \ac{GN} are:
\begin{itemize}
\item geo-unicast: routing a packet to a single node at a specific location
\item geo-multicast: first routing a packet to a specified destination area, then flooding it to all nodes within that area
\item topology-scoped broadcast: broadcast of packet within a a certain depth of neighbouring nodes
\item topology-scoped broadcast: broadcast of packet within a certain numberof neighbour hops
\item single-hop broadcast: sending packets to all neighbouring nodes
\item geo-anycast: routing packet to an arbitrary node within a specified geographical area
\end{itemize}
@ -200,11 +200,11 @@ Security properties of \ac{GN} messages are ensured by signing (authenticity), e
\subsubsection{IPv6}
\acsu{IPv6} \cite{RFC8200} \nocite{baeckerRFCE014IPv6} specifies the 6th version of the Internet Protocol, the routing protocol used in the Networking layer of the internet. Relevant details for \acp{VANET} are the addressing using 128 bit long IP addresses \cite{RFC4291} with the first up to 64 bits specifiying the network part and the last 64 bits specifying the interface ID (node ID) within that subnetwork. Additionally to the globally unique routable address, nodes are also addressable in the scope of the same \ac{OSI} layer 2 link using their link-local address automatically derived from lower-layer identifiers. Together with the huge number of globally unique \ac{IPv6} addresses, this new property makes it usable for vehicular ad-hoc networks. Another improvement in \ac{IPv6} is \textit{neighbour discovery} \cite{RFC4861} using link-local multicast. One application of that is the \textit{\acf{RA}}, where routers just periodically announce their parameters so clients are able to derive an address themselves without further negotiation.
\acsu{IPv6} \cite{RFC8200} \nocite{baeckerRFCE014IPv6} specifies the 6th version of the Internet Protocol, the routing protocol used in the networking layer of the Internet. Relevant details for \acp{VANET} are the addressing using 128 bit long IP addresses \cite{RFC4291} with the first up to 64 bits specifiying the network part and the last 64 bits specifying the interface ID (node ID) within that subnetwork. Additionally to the globally unique routable IPv6 address, nodes are also addressable with their link-local address. This special address is only valid in the scope of the same \ac{OSI} layer 2 link and is automatically derived from lower-layer identifiers. Together with the huge number of globally unique \ac{IPv6} addresses, this new property makes it usable for vehicular ad-hoc networks. Another improvement in \ac{IPv6} is \textit{neighbour discovery} \cite{RFC4861} using link-local multicast. One application of that is the \textit{\acf{RA}}, where routers just periodically announce their parameters so clients are able to derive an address themselves without further negotiation.
\subsubsection{IPv6 over GeoNetworking}
Transparently exposing IP networking to higher layers allows re-using existing services based on the classical internet TCP/IP stack without modification. The \acf{GN6ASL} \cite{europeantelecommunicationsstandardsinstituteetsiETSI302636612014} specifies a mechanism for sending \ac{IPv6} packets over the GN protocol by using it as a sub-IP coupling layer. \ac{GN} takes care of encapsulating and routing the IP packet to its final destination node, so that the whole underlying \ac{VANET} looks like a flat layer 2 network to IP services.
Transparently exposing IP networking to higher layers allows re-using existing services based on the classical Internet TCP/IP stack without modification. The \acf{GN6ASL} \cite{europeantelecommunicationsstandardsinstituteetsiETSI302636612014} specifies a mechanism for sending \ac{IPv6} packets over the GN protocol by using it as a sub-IP coupling layer. \ac{GN} takes care of encapsulating and routing the IP packets to its final destination node, so that the whole underlying \ac{VANET} looks like a flat layer 2 network to IP services.
\ac{GN6ASL} specifies how to derive a \ac{GN} address from an \ac{IPv6} address and extends \ac{IPv6} with some \acl{GN} specific extensions like geographic multicast, Geographically
Scoped stateless Address Configuration or (un)reachability detection.
@ -212,7 +212,7 @@ Scoped stateless Address Configuration or (un)reachability detection.
The transport layer protocol above \acl{GN} is the \acf{BTP} \cite{europeantelecommunicationsstandardsinstituteetsiETSI302636512017}. It provides a connectionless multiplexing/ demultiplexing of datagrams to the layers above, adding minimal overhead while providing an unreliable packet transport comparable to UDP.
If \ac{IPv6} over \ac{GN} is used at the network layer, transport protocols like TCP and UDP from the standard internet protocol suite can of course be used, too.
If \ac{IPv6} over \ac{GN} is used at the network layer, transport protocols like TCP and UDP from the standard Internet protocol suite can of course be used, too.
The \textbf{Facilities Layer} unifies the three upper \ac{OSI} layers (application, presentation, session layer) and provides different support tasks to services and applications like time management, position management, database management and session management. It is also responsible to manage service priorities when passing down data to the Network and Transport Layer.
@ -267,7 +267,7 @@ Some of the facility layer services have well-known ports assigned in \cite{euro
While each IPv6-capable network interface can have multiple addresses, it has at least one link-local address with the interface ID (the lower 64bits) uniquely derived from its data-link layer address. The mapping of IPv6 link-local address and GN\_ADDR is straight-forward, as both addresses are deterministically derived from the same 48bit link layer address. Additionally to the IPv6 address, the IPv6 header can also contain a 20bit \textit{flow label} \cite{RFC6437} which could lead to partial linkability of packets even after an address change: Although a flow shall be identified by the triplet of flow label, source and destination address, an equal flow label could indicate the resumption of a connection even after an address change.
There exists a static mapping between IPv6 multicast groups and geographical areas (relative to the station). That means it is possible to contact IPv6-based services within a node's surrounding. But as this mapping is static and relative, it shouldn't help reidentifying hosts.
\acfp{GVL} are another important concept for understanding the visibility scope of IPv6 packets to other nodes. These virtual links are defined as non-overlapping, restricted geographical areas wherein all IPv6 multicasts within the same subnet are forwarded via \ac{GN} to all nodes of that \ac{GVL}. Usually this is a zone around a specific \ac{RSU} serving as an internet uplink and thus managing the whole subnet and its addresses. Globally routable IPv6 addresses are usually obtained via the stateless autoconfiguration with the help of \acp{RA}. So changing the \ac{GVL} means getting another IPv6 prefix announced via \ac{RA} and thus implies a change in the node's global IPv6 address.
\acfp{GVL} are another important concept for understanding the visibility scope of IPv6 packets to other nodes. These virtual links are defined as non-overlapping, restricted geographical areas wherein all IPv6 multicasts within the same subnet are forwarded via \ac{GN} to all nodes of that \ac{GVL}. Usually this is a zone around a specific \ac{RSU} serving as an Internet uplink and thus managing the whole subnet and its addresses. Globally routable IPv6 addresses are usually obtained via the stateless autoconfiguration with the help of \acp{RA}. So changing the \ac{GVL} means getting another IPv6 prefix announced via \ac{RA} and thus implies a change in the node's global IPv6 address.
There are no obvious identifiers specified in the Facilities layer, though some might be introduced in real-world implementations.