diff --git a/figures/GeoNetworking_structure.png b/figures/GeoNetworking_structure.png new file mode 100644 index 0000000..93a6024 Binary files /dev/null and b/figures/GeoNetworking_structure.png differ diff --git a/figures/GeoNetworking_structure_secured.png b/figures/GeoNetworking_structure_secured.png new file mode 100644 index 0000000..04cf43f Binary files /dev/null and b/figures/GeoNetworking_structure_secured.png differ diff --git a/glossary.tex b/glossary.tex index a396ee6..dee1a14 100644 --- a/glossary.tex +++ b/glossary.tex @@ -6,6 +6,8 @@ \acro{BTP}{Basic Transport Protocol} +\acro{CA}{Certificate Authority} + \acro{CCU}{communication \& control unit} \acro{ETSI}{European Telecommunications Standards Institute} @@ -22,8 +24,12 @@ \acro{LS}{GeoNetworking Location Service} +\acro{LLC}{Logical Link Control} + \acro{LT}{GeoNetworking Location Table} +\acro{MAC}{Medium Access Control} + \acro{OBU}{on-board unit} \acro{OSI}{Open Systems Interconnection} diff --git a/main.tex b/main.tex index 8a4ed52..2c2b226 100755 --- a/main.tex +++ b/main.tex @@ -183,7 +183,7 @@ CALM FAST \cite{TN_libero_mab2} is a non-IP port-mapper protocol designed for si \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. -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: +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 @@ -218,16 +218,45 @@ If \ac{IPv6} over \ac{GN} is used at the network layer, transport protocols like \subsection{Identifiers} -There are many different addresses, IDs or other identifying information scattered around the network layers. This sections gives a list of these identifiers and the information encoded in them. +There are many different addresses, IDs or other identifying information scattered around the network layers. This sections gives a list of relevant identifiers and the information encoded in them. Media-dependent additional identifiers are considered out-of-scope. \subsubsection{GeoNetworking} -Each \ac{GN} node is identified by a \ac{GN} address +Each \ac{GN} node is identified by a 64bit GN\_ADDR address \cite{europeantelecommunicationsstandardsinstituteetsiETSI302636412017}, containing information about the \ac{ITS} station type (passenger car, cyclist, pedestrian, \ac{RSU}, …) and 48bit derived from the link-layer address. In case of a pseudonym change, only the latter part is supposed to change. -\ac{GN} packets have a basic, a common and an optional extended header. +\begin{figure} + \includegraphics[width=0.47\textwidth]{figures/GeoNetworking_structure.png} + \caption{structure of an unsecured \ac{GN} packet, source: \cite{hamidaSecurityCooperativeIntelligent2015}} + \label{fig:GNstructure} +\end{figure} + +As shown in fig. \ref{fig:GNstructure}, \ac{GN} packets have a basic, a common and an optional extended header. The \textit{basic header} contains information like the packet's maximum lifetime and the remaining hop limit. These information are non-critical for identification. The \textit{common header} also doesn't contain identifying, only the flag indicating a mobile or stationary \ac{ITS} station could slightly reduce the anonymity set. The \textit{extended header} fields depend on the actual \ac{GN} package type and can contain information like the sequence number (initialized with 0) and position vectors. + +The \ac{LT} is populated with information from beaconing messages and all other messages received by the \ac{ITS} node. \acl{LT} entries also contain identifying data: Additionally to the GN\_ADDR, station type and link-layer address of the peer node it contains a timestamped geographical position (including accuracy), its current speed and its heading. \todo{update position/ reacquire it when changing pseudonym} + +\begin{figure} + \includegraphics[width=0.47\textwidth]{figures/GeoNetworking_structure_secured.png} + \caption{structure of a secured \ac{GN} packet, source: \cite{hamidaSecurityCooperativeIntelligent2015}} + \label{fig:GNstructure_secured} +\end{figure} + +Parts of \ac{GN} packets can be secured by wrapping them into security headers as defined in \cite{europeantelecommunicationsstandardsinstituteetsiETSITS1032017} as shown in fig. \ref{fig:GNstructure_secured}. This service is provided by the vertical security layer in the \ac{ETSI} \ac{ITS} architecture and secures all parts shown in fig. \ref{fig:GNstructure_secured} between security header and trailer according to the chosen security profile. The standard defines security profiles for encrypted, signed, externally signed, and signed encrypted messages. + +The certificates used contain information about signer subject (name, type, keys), validity restrictions and the actual certificate signature from the \ac{CA}. +The signer information can be given in form of a digest, certificate or certificate chain. + +The security trailer contains a signature for verifying authenticity and integrity of the message. + +\todo{sequence number initialized with 0} +\todo{packet buffers: LS, forwarding} \subsubsection{BTP} +The \ac{BTP} header as defined in \cite{europeantelecommunicationsstandardsinstituteetsiETSI302636512017} is only 4 bytes long and has a quite simple structure. \\ +There are 2 modes of operation for BTP: \textit{interactive packet transport} using the BTP-A header, meant for services requiring replies to their messages, and \textit{non-interactive packet transport} using the BTP-B header. +The BTP-A header consists out of 2 16bit numbers denoting the source and destination ports. The BTP-B header contains the 16bit long destination port and 16bit for optional destination port information (depending on the service). +Some of the facility layer services have well-known ports assigned in \cite{europeantelecommunicationsstandardsinstituteetsiETSITS1032016}, so the destination port might identify the service used. + \section{Pseudonym Schemes} \subsection{Pseudonym Schemes for ETSI ITS Systems} diff --git a/mybib.bib b/mybib.bib index b00e0b9..50772d1 100644 --- a/mybib.bib +++ b/mybib.bib @@ -447,4 +447,13 @@ note = {http://www.rfc-editor.org/rfc/rfc4861.txt} } +@misc{europeantelecommunicationsstandardsinstituteetsiETSITS1032016, + title = {{{ETSI TS}} 103 248 {{V1}}.1.1 {{Intelligent Transport Systems}} ( {{ITS}} ); {{GeoNetworking}}; {{Port Numbers}} for the {{Basic Transport Protocol}} ({{BTP}})}, + lccn = {ETSI TS 103 248 V1.1.1}, + author = {{European Telecommunications Standards Institute (ETSI)}}, + month = nov, + year = {2016}, + file = {/home/spiollinux/Zotero/storage/U3RMDZ2I/ts_103248v010101p.pdf} +} +