1. Automotive Ethernet: How to Handle the difference between the standard and its implementation
6th Ethernet & Automotive Technology Day
Dr.-Ing. Thomas Kirchmeier

2. 01
Motivation.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

3. 01 Motivation. The need of Automotive Ethernet.
Connectivity
Infotainment
Communication relevant for driving
DAS
Proprietary signal based communication
Revolution!
IP based communication
Revolution!
Elec. Signals
CAN
FlexRay
100Base-T1
1000Base-T1
Amount of in-vehicle communication
<1980
<1992
<2007
<2016
future
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

4. 01 Motivation. Benefits of an IP based communication.
Benefits of IP protocols for Automotive.
IP allows an abstraction from Layers 1 and 2 and the use of different technologies, e.g. Ethernet, WiFi, PLC, APIX, …
IP makes the car part of the worldwide network. Connects to the plant, the dealer, the backend, …
IP is the success factor of the Internet.
Further benefits of TCP/IP protocol family.
TCP and UDP are the established transport protocols over IP.
Easier integration and use of IT applications.
Allows the use of a middleware as an abstraction layer to the functions.
Layer 5-7
IEEE 1722
AVB
UDP-NM
HSFZ
SOME/IP SD
DHCP
ICMP
ARP
Layer 4
UDP
TCP / UDP
UDP
Layer 3
IPv4
Layer 1/2
IEEE Ethernet MAC + VLAN (802.1Q)
Automotive Ethernet Physical Layer (BroadR-Reach)
App.
TCP/ IP-Stack
Middleware
Ethernet and IP in car and backend communication
Visible interface and packets
Visible interface and packet
It makes sense to use the TCP/IP protocol family also in automotive.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

5. 02 TCP/IP is a Set of standards, their Interpretation is ambiguous.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

6. Example 1: TCP Zero Window Probing
02 TCP/IP is a Set of standards, their Interpretation is ambiguous. Example for Implementation difference between LWIP and Raspbian.
Example 1: TCP Zero Window Probing
TCP/IP-Stack: lwIP
TCP/IP-Stack: Raspbian
IUT PC
pass
fail
Source: raspberrypi.org 1
TCP-Data 1 2
TCP-win = 0 3
TCP-keep alive 4
TCP-Data 2
UpperTester
Communication channel
Command channel
TCP-win = 0 3 4
TCP-probe
TCP/IP-Stack
TCP connection is established.
IUT sends some data.
PC sends a TCP zero window, which means cannot receive more data.
IwIP sends cyclic TCP-probes to ask the PC if the buffer is free again.
TCP connection is established.
IUT sends some data.
PC sends a TCP zero window, which means cannot receive more data.
Respbian sends cyclic TCP-keep alives to hold the TCP connection open and valid.
TCP_PROBING_WINDOWS_04: Open connection probes ACK
Eth-Driver
TCP/IP
TestSuite
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

7. Example 2: Listen state (TCP_CONTROL_FLAG_09)
02 TCP/IP is a Set of standards, their Interpretation is ambiguous. Example for Implementation difference between LWIP and Raspbian.
Example 2: Listen state (TCP_CONTROL_FLAG_09)
TCP/IP-Stack: lwIP
fail
TCP/IP-Stack: Raspbian
pass 1
IUT PC
IUT PC 2 1 1
TCP-SYN, RST 2
TCP-SYN, RST 2 3
TCP-SYN, ACK 3
IUT is in listen state
PC sends a TCP-SYN with RST-Flag, which doesn’t make sense because a non established TCP connection cannot be reset.
lwIP answers with a TCP-SYN, ACK in order to establish the TCP connection.
IUT is in listen state
PC sends a TCP-SYN with RST-Flag, which doesn’t make sense because a non established TCP connection cannot be reset.
Raspbian does not answer because it isn’t a correct request for TCP connection.
InterfaceUnterTest
TCP_CONTROL_FLAGS_09: To verify that DUT discards a TCP packet with RST flag set when in LISTEN state
TCP can be established independent of a TCP reset flag.
RFC 793
Source:
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

8. 02 TCP/IP is a Set of standards, their Interpretation is ambiguous
02 TCP/IP is a Set of standards, their Interpretation is ambiguous. Example Discussions regrinding the RFC interpretation.
#41494: TCP possibly violates RFC793 open since 2014
What are the consequences?
TCP/IP specifications are not easy to understand.
Their implementations are affected by the different interpretations of the people who develop the stack.
Source:
Many proven TCP/IP stack implementations exist. However, for automotive use, they are often adapted, which causes an additional risk for interpretation errors.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

9. 03 TcP/IP implementations exist, but they have to be adapted.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

10. 03 TcP/IP implementations exist, but they have to be adapted. Why?
Moore’s Law is still valid. e.g. iPhone
Reality for the automotive industry.
Automotive high-end functions need similar performance, like in the IT world.
Everyone is happy!
However, the volumes for specific parts are smaller and therefore cause less economies of scale. In addition automotive qualification adds to the costs.
Source: Apple.com
Engineer: “Marvellous, with this increased power we can build incredible things. Our costumers will be impressed.”
We have to realize more functions on cheaper systems and have to optimize the system use.
Source: Dr. Handel Jones - Why Migration to 20nm Bulk CMOS and 16/14nm FinFETs is Not Best Approach for Semiconductor Industry
Prozessoren werden immer Leistungsfähiger, im Preis-Leistungsverhältnis immer besser, aber Moores-Law ist gebremst, Technologie wird immer Komplexer gerade bei 14nm sind die investitionen höher und im Falle der Automobilindustrie steigen nicht unbedingt die Stückzahlen  Folglich steigen die Chipkosten wieder oder man bleibt bei den größeren Strukturen mit gleichbleibenden Kosten.
Controller: “Marvellous, with this increased power we can buy cheaper. Our shareholder will be impressed.”
Therefore, the TCP/IP stack needs to be optimized.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

11. 03 TcP/IP implementations exist, but they have to be adapted
03 TcP/IP implementations exist, but they have to be adapted. Example of an optimized TCP/IP Stack in Gateway.
Existing TCP/IP implementation from the IT-World
Optimized Automotive TCP/IP implementation HW
Driver
TCP/IP Stack
Routing Core HW
Driver + TCP/IP Stack
Routing Core
DMA
Copy
Copy
DMA
Copy
Segments
PDUs
Segments
PDUs
Ringbuffer
Frames
Ringbuffer
Frames
Datagrams
PDUs
Datagrams
PDUs
Ringbuffer
Frames
Segments
Ringbuffer
Frames
Segments
Ringbuffer
Frames
Datagrams
Ringbuffer
Frames
Datagrams
DMA
Copy
Copy
DMA
Up to 4 copy operations by using a common TCP/IP-Stack
Wasting of RAM and CPU Performance of embedded Systems
Every data list has to be maintained
Driver and TCP/IP-Stack need to be adapted to allow a high performance system.
Application data can be sent via DMA as reference
Implementation is platform dependent
For every embedded controller, the TCP/IP stack has to be optimized to save resources and costs.
Source: As referred to in presentation of Matthias Kessler, 1st Automotive Ethernet Congress, February 04-05, 2015, Munich
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

12. 04
Example Test results.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

13. 04 Example Test results. results of the 1. Testrun (anonymized).
ECU 1
ECU 2
ECU 3
µController Type
Embedded
IT CPU
TCP/IP-Stack
µIP
lwIP
Debian
Stack optimized?
Yes No
TCP (pass / fail)
167 / 73
163 / 77
223 / 17
IP (pass / fail)
28 / 3
32 / 0
UDP (pass / fail)
34 / 14
32 / 16
41 / 1
ARP (pass / fail)
21 / 0
21 / 0
41 / 4
AutoIP (pass / fail)
6 / 12
not needed
Testing is the key to reach a reliable communication between different ECUs in a network.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

14. 04 Example Test results. TC8 Testing process used by BMW.
Testing process of OPEN Alliance TC8.
Benefits.
Single point of truth of TCP/IP test specification with automotive content.
Comparable test results of different TCP/IP stacks.
Harmonization of different TCP/IP stack implementations.
Continuous improvement of the test specification based on the feedback of the Test Houses.
Possibility to adapt or add test cases in order to meet the state of the art of the requirements to the TCP/IP stack in future, e.g. security and/or safety aspects.
OPEN Alliance TC8
ECU test spec.
ECU test spec.
Test House A
Test House B
Feedback
Ethernet ECU test report
Ethernet ECU test report
Tier1 X
Tier1 Y
ECU test
report
ECU test
report
OEM
goal
Network Network
integration tests
reliable communication in network
ECU1
ECU2
We can concentrate on the customer functions.
Source: OPEN Alliance TC8, Document Test Process and ECU Test Specification v1.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

15. 05
Conclusion.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

16. 05 summary.
One of the advantages of using automotive Ethernet is reuse of protocols on higher application layers, like TCP/IP.
However, the devil is in the details:
TCP/IP specifications as such are not unambiguous and despite the years of deployment deviations in interpretations can cause interoperability issues.
The trade off between cost and performance always requires an optimization of all system components. In order to keep the processing units small, the TCP/IP stack implementations are being optimized for the automotive use case.
These optimizations are not standardized and platform dependent and can also result in interoperability issues.
Conformance testing can identify and solve potential interoperability issues.
The OPEN Alliance TC8 developed a respective test process.
The examples of this presentation show the importance of this test process.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day

17. Thank you for your Attention.
Dr.-Ing. Thomas Kirchmeier, BMW Group | | 6th Ethernet & Automotive Technology Day