Automotive Ethernet—Full-Stack Conformance Testing
Ethernet is the evolved communication layer for automobiles
To overcome in-car network speed challenges, next-generation automobiles are moving to Ethernet as the physical layer for the communication system. The market trends indicate that a significant majority of car manufacturers are planning to move to Ethernet for all classes of cars. While BMW is the frontrunner in terms of adopting this technology, most car makers are making headway in this direction. This is evidenced by Hyundai using automotive Ethernet for infotainment systems in upcoming cars, and Volkswagen using automotive Ethernet for driver-assist systems.
According to a Strategy Analytics presentation, the total number of ethernet ports in an automotive network is expected to be nearly 600 million in automotive networks by 2023.
The automotive ethernet ecosystem
Ethernet was not initially designed to support the low latency and determinism that a time-critical automotive application requires. A new set of technologies have evolved to ensure existing applications run on new Ethernet-based communication systems. New technologies like audio/video bridging (AVB) and time-sensitive networking (TSN) have matured and secured their place in the car network. The Layer 2 – 7 stack of an automotive electronic control unit (ECU) may need to implement some or all of the below-mentioned protocols.
What changes with ethernet?
Because Ethernet is a switched network, it opens a lot of flexibility compared to traditional automotive busses when it comes to network design. Most of the automotive ECUs in production have multiple ports, which allows them to connect to other ECUs. For such an ECU, it’s very important to validate that incoming frames are forwarded on the correct ports under all conditions.
And besides testing the switching capabilities, one needs to ensure that ECUs properly implement the higher layers that traditionally run over Ethernet (the TCP/IP stack), new protocols that have been adapted for automotive use such as AVB and TSN, as well as new automotive-specific protocols like SOME/IP.
Validation Strategies and Techniques
With so many new technologies playing a role – conformance testing of each component is extremely critical. In automotive Ethernet, there are four high-level areas to validate:
- PHY or physical layer – signal integrity of the new automotive PHY
- Multiple PHYs in an ECU – an implementation of classic Ethernet switch
- Implementation for the various protocols used in the ECU
- Deployed networks
Testing the TCP/IP stack is a difficult task
Testing a protocol like TCP is much more complex than other automotive protocols such as CAN or FlexRay. This cannot be fully tested using a “black-box only” approach. It needs to be able to cause the device under test (DUT) protocol implementation to move to certain states. A validation tool needs to use a specialized technique called an upper tester to instruct the DUT protocol stack to respond in synchronization with test steps.
Industry leading conformance solutions like Ixia’s IxANVL has this approach integrated into the tool and provides sample upper tester code for ready use by the DUT.
Automakers implementing a best-of-breed approach use components from different suppliers, so they must ensure that all ECUs speak the exact same language. Therefore, an effort was made within consortiums like AUTOSAR and OPEN Alliance to standardize the test cases. Ixia has been contributing most of the now-standardized test cases from its huge library of test packages being used by top the NEMs in the traditional networking domain.
IxANVL provides an extensive coverage of the latest Automotive Ethernet standardized conformance test cases. These tests are field-proven and have been used to validate numerous devices in the past 20 years.
Need for specialized hardware for testing AVB automotive profile
On the other hand, AVB was introduced to allow switches to provide guarantees regarding throughput and latency for A/V traffic. Validating the AVB ecosystem protocols – gPTP, 1722 traffic – requires accurate measurement capabilities of time synchronization, specific configuration and traffic patterns in which the switch network will operate. Because of the nature of the specialized techniques required for validation, the car manufacturers and ECU suppliers use Ixia’s IxNetwork, which has all the capabilities build into the high performance hardware.
The Avnu Alliance has defined an interoperability and functional specification for automotive Ethernet AVB devices. The goal of the specification is to provide a baseline specification of Ethernet AVB functionality on automotive AVB devices. The Avnu test plan for certification is an excellent guide for conformance testing of the AVB stack of the ECU.
Ixia’s time-tested IxNetwork platform simplifies preparation for Avnu certification with a pre-packaged Avnu AVB Conformance Test Library. This tool provides summary reporting with graphical representations of the test results, along with debugging capabilities at the bits and bytes level.
Ixia’s automotive test solutions are being used by the leading car manufactures to ensure robustness and compliance of their ECUs. Using Ixia’s IxNetwork and IxANVL products, customers like the BMW Group are successful in validating their automotive Ethernet toolchain, getting visibility into the performance and robustness of the switches integrated in ECUs. Ixia’s L2-3 test solutions helped the BMW Group ensure delivery of the premium-quality vehicle communications that their car owners expect from the BMW brand. Read more to know about the validation tools and techniques used by BMW and BYD.
Note: This blog is based on my article originally published in German magazine Hanser Automotive.