DatexII or ETSI for C-ITS
Should you use the DatexII or the ETSI protocol for C-ITS use cases? Even though DatexII and ETSI support the same type of use cases,
they are developed for different purposes and have significant distinctions.
Even though DatexII and ETSI standards both can support many use cases in present connected mobility services, they are developed for different scenarios and therefor, both from a logical and technical perspective, have significant distinctions. In this report we have assessed the technical capabilities of the standards to explain these distinctions.
The DatexII standard is a data exchange standard for exchanging traffic information between traffic management centers, traffic service providers, traffic operators, and media partners. It contains information about traffic incidents, current roadworks, and other traffic-related events. The primary objective of the DatexII standard is to create a common view of the state of the road network among stakeholders. This enables more efficient traffic management and a more effective traffic information channel to road users, from traffic management centers via service providers and media partners. This not only improves road efficiency by reducing traffic congestion but also enhances road safety by informing drivers of potential obstacles in the lane ahead.
The ETSI standard is a data exchange standard for exchanging traffic notifications between vehicles and roadside equipment. It encompasses information about traffic incidents, ongoing road works, and other relevant events, while also facilitating the provision of sensor and actuator data. Its primary goal is to enhance situational awareness for both vehicles and roadside equipment, thereby
enabling advanced algorithms for driving assistance services and traffic control systems. This not only improves road safety but also enhances overall road efficiency.
When comparing these standards, four essential capabilities stand out for present and future V2X (vehicle-to-everything) connected mobility use cases. These capabilities include:
Performance
In the realm of future V2X connected mobility services, low latency stands out as a critical factor. Many of the present use cases, such as those seen in Day 1 services, heavily depend on swift data provisioning with latency requirements below 100ms. Anticipated future applications, particularly those involving bi-directional communication like platooning, are likely to impose even stricter demands on low latency. Therefore, the question arises: which protocol offers superior performance in terms of provision speed and latency?
The ETSI standard is engineered around package-based uPer encoded binary data provisioning. Each message typically occupies less than 64 bytes, ensuring minimal latency in data provision, thus enabling remarkably fast provisioning. In contrast, the DatexII standard relies on XML-based data packed into TCP/IP packets. When comparing the two, the same information provided in 64 bytes under the ETSI standard would require at least one TCP packet with a size of 1480 bytes under the DatexII standard—an increase of over 20 times in size. Assuming both standards have similar overhead and bit speed in the transmission and datalink layers, the DatexII standard exhibits more than 20 times the latency compared to the ETSI standard.
In conclusion, the comparison highlights a significant difference in latency performance, with ETSI demonstrating a clear advantage.
Interoperability
Firstly, both standards are platform and technology independent, laying a solid foundation for interoperability. However, notable discrepancies exist in how they handle use case-specific data, impacting interoperability.
The DatexII standard relies on a single extensive data model that must be streamlined into a subset of classes and properties via profiling to ensure practical and effective data provisioning. Unfortunately, the standard lacks predefined profiles for most specific use cases, leaving the task to individual data producers. Consequently, data consumers must establish relationships with each producer and implement the corresponding profile before consuming DatexII data. This constraint diminishes interoperability in DatexII implementations, hindering the scalability of the connected mobility ecosystem.
In contrast, the ETSI standard adopts only six distinct message profiles with stringent conventions. A data consumer adhering to the standard can readily consume data from a producer once it’s provisioned. This seamless interaction is not coincidental but a deliberate outcome of the standard’s focus on connecting vehicles and roadside equipment. Given the potential diversity in vehicle and equipment manufacturers and their global distribution, the standard operates under the assumption that there may be no prior contract or tuning between data producers and consumers before the data is available, unlike in DatexII implementations.
In essence, while both standards offer interoperability benefits, the ETSI standard’s more straightforward approach to data provisioning and consumption presents a compelling advantage.
Information Security
Both DatexII and ETSI standards recognize the critical importance of security in facilitating safe and reliable data exchange within transportation networks. However, they approach security in slightly different ways.
DatexII emphasizes security measures at the TCP-session level, leveraging protocols like TLS 1.3 to ensure secure communication channels. While this provides a solid foundation for data integrity and confidentiality, DatexII may face challenges in environments where multiple datalinks and transmission layers beyond TCP/IP are utilized, as it lacks specific provisions for additional transmission layer security.
On the other hand, ETSI addresses this challenge by extending its security framework to encompass various transmission layers, including those beyond TCP/IP, through standards like IEEE 1609. This approach enables not only secure communication at the TCP-session level but also additional transmission-level security, such as message signing and encryption. This ensures that data integrity and confidentiality are maintained regardless of the transmission medium, enhancing the overall security posture of the system.
While both standards prioritize security, ETSI offers a more comprehensive approach by incorporating transmission-level security measures, making it better equipped to address the evolving security needs of connected mobility environments.
Accessibility
Both DatexII and ETSI standards recognize the critical importance of security in facilitating safe and reliable data exchange within transportation networks. However, they approach security in slightly different ways.
DatexII emphasizes security measures at the TCP-session level, leveraging protocols like TLS 1.3 to ensure secure communication channels. While this provides a solid foundation for data integrity and confidentiality, DatexII may face challenges in environments where multiple datalinks and transmission layers beyond TCP/IP are utilized, as it lacks specific provisions for additional transmission layer security.
On the other hand, ETSI addresses this challenge by extending its security framework to encompass various transmission layers, including those beyond TCP/IP, through standards like IEEE 1609. This approach enables not only secure communication at the TCP-session level but also additional transmission-level security, such as message signing and encryption. This ensures that data integrity and confidentiality are maintained regardless of the transmission medium, enhancing the overall security posture of the system.
While both standards prioritize security, ETSI offers a more comprehensive approach by incorporating transmission-level security measures, making it better equipped to address the evolving security needs of connected mobility environments.
Summary
In summary, while both standards serve essential roles in traffic data exchange, DatexII offers superior usability and accessibility compared to ETSI. The combination of established integration patterns, abundant resources, and centralized documentation makes DatexII a more user-friendly and accessible option for organizations seeking straightforward and efficient solutions for traffic management and data exchange.
However, it’s crucial to consider the performance, security and interoperability asptect, particularly when evaluating ETSI versus DatexII. ETSI excels in scenarios where low latency is critical, as its architecture and protocols are optimized for rapid data transmission. IT´s also important to weight in the interoperability and security advantages ETSI has. This makes ETSI particularly suitable for applications where real-time communication and response are essential, and were there has to be a trust fundation between many stakeholders such as in connected vehicle environments or for time-sensitive traffic management operations.
From our opinion, ETSI is is in most cases the better choice for C-ITS compared to Datex.
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