# A Perspective on Ethernet in Automotive Communications--Current Status and Future Trends
## 5 Car Architecture Evolution and Relevant Challenges
### Insights on Automotive Ethernet Testing  
The introduction of Automotive Ethernet as the car backbone or as a replacement for some of the traditional in-car networks represents a major shift that also has an impact on system testing. In fact, with the increasing degree of system integration in the car, fewer ECUs perform more functions. On the one hand, this integration reduces costs and weight, on the other hand it causes a proportional increase in software complexity. As novel Automotive Ethernet protocols continue to be developed to meet the increasing software requirements, it is essential to also adapt the test methodology to the growing complexities in order to ensure the continued reliable functioning of systems interconnected via Automotive Ethernet.  
Automotive testing has several benefits, as it checks the compliance with global regulations, allows the early discovery of faults (thus preventing costly recalls), and helps to ensure safety from the early stage of development. Automotive testing consists of different phases [23]. First, the Component test, which evaluates the functionality of an ECU as a standalone component. Second, the Network test, which is performed by connecting the ECUs and testing networking functions such as start-up, shut-down, sleep, restart, etc. Third, the System test, which evaluates the functionality of the integrated system against the requirement specifications. Finally, the last testing phase consists of the In-Vehicle acceptance test, when all required functions have to pass the final in-vehicle acceptance test with all ECUs integrated into the vehicle.  
Figure 3: Example of zonal architecture.  
While the System-level tests and In-Vehicle tests are independent of the networking technology, and are therefore not affected, the introduction of Automotive Ethernet has an impact on the Component test, Network test, and on maintenance throughout the lifetime of the car [23]. In fact, in the Component test, as Ethernet is a point-to-point network, the device under test (DUT), i.e., the ECU, can only be connected to the testing device, while in a shared bus, e.g., CAN, multiple devices can be connected together as well as with the test tool on the same network. Moreover, for Automotive Ethernet, a media converter is needed to simulate the vehicle network traffic. In the Network test, the introduction of Automotive Ethernet, i.e., a point-to-point switched network, changes the way the test is performed compared to a shared bus network. In fact, the traffic flows on every link of the switch can be different, so it is not possible to simply connect a tool that will receive and transmit all network traffic. Instead, to track all communications, either a transparent logger (often called a TAP, i.e., Test Access Point) is inserted in each link or the switch has to provide an extra port for mirroring all communications to the data logger. The first solution, i.e., TAP, has the drawback that its insertion introduces some latency, while the mirroring port has a few more drawbacks, because the data logger attached to the mirroring port will not receive bad frames that are dropped by the switch. Moreover, the extra port raises the hardware cost of the switch. Multi-Active TAPs are also available and offer the ability to monitor and time-align frames from multiple ports of an Ethernet switch. Finally, the introduction of Automotive Ethernet has an impact on maintenance because, upon a reported malfunctioning, the in-vehicle network traffic in the customer's cars should be accessible to the diagnostic tools, and therefore, such tools should be able to decode Ethernet traffic.  
To support testing, a broad set of test specifications is made available by the OPEN Alliance [55], and several companies offer suitable tools that are available on the market.