Time Sensitive Networks approaches the car
A work in progress at the IEEE standards association, TSN features represent a set of extensions to be added to existing 802.1 and 802.3 Ethernet standards in order to ensure a deterministic performance of the network. The so-called automotive Ethernet that all car OEMs are longing for will be in fact a TSN-enabled implementation of 802.3 Ethernet, with new PHY standards 100BASE-T1 and gigabit PHY allowing the use of a light unshielded twisted pair of copper wires for the automotive Ethernet backbone.
The TSN features undergoing a standardization process include, Timing and Synchronization, Frame Pre-emption, Scheduled Traffic, enhancements to the Stream Reservation Protocol (SRP), Per-Stream Filtering and Policing, and Frame Replication and Elimination for Reliability.
Timing and Synchronization (IEEE P802.1AS-REV) is a revision of the existing Audio-Visual Bridging (AVB) standard to add support for multiple time domains.
Frame Pre-emption (IEEE P802.3br) allows critical data packets to have priority over non-critical data packets by breaking-up the interfering frames into smaller “fragments” should there be data in transit. This means the critical data doesn’t have to wait until the full frame of non-critical data has been transmitted, ensuring a faster routing.
The Scheduled Traffic (IEEE 802.1Qbv) option divides Ethernet traffic into different classes each with reserved access to the network at specific times, creating class-specific protected “channels”.
The SRP enhancements & performance improvements under TSN option IEEE 802.1Qcc add a User Network Interface (UNI) allowing for a remote centralized network configuration.
The Per-Stream Filtering and Policing option (IEEE 802.1Qci), also known as ingress policing, is used to prevent traffic overload conditions (that could be due to software bugs on endpoints or switches) from affecting the receiving node or port. Ingress policing could also be used against hostile devices or attacks.
The TSN option IEEE P802.1CB described as “Frame Replication and Elimination for Reliability” is to enforce robust and reliable communication regardless of link failures, cable breakage and other faults. This option ensures that duplicate copies of critical traffic are sent across disjoint paths in the network, only keeping whatever packet reaches its destination first for a seamless redundancy.
Eventually, once stabilized, these new deterministic features would turn Ethernet as a viable option to replace all existing legacy networks in the car, such as CAN, LIN, MOST and FlexRay, becoming the car’s core network backbone.
In the exhibition hall, several companies were demonstrating TSN-ready automotive Ethernet, typically showing real-time control tasks running across an Ethernet network, unfazed by other non-critical data (such as synchronized streams of passenger entertainment audio and video or an end-node going wrong) competing for bandwidth.
Chip vendor Innovasic who has been offering deterministic industrial networking solutions for over ten years was running a demonstration with two Ethernet network segments running side by side, one TSN-enabled, the other for non-critical data. For the TSN gateway boards, the demonstration was using its fido5000 Real-time Ethernet Multi-protocol (REM) Switch, a configurable device the company released nearly three years ago.
At the show, Innovasic was also launching a TSN evaluation kit pre-installed with the most mature TSN features (802.1AS and 802.1Qbv) while promising software updates to support the other options as they would stabilize.
Innovasic’s COO Jordon Woods was quite upbeat about automotive Ethernet. “We’ve been doing deterministic networking for ten years, we’ve got all the know-how in house to integrate our switch with other IP and deliver a complete TSN SoC” he boasted. According to Woods, with the right partner, the automotive sector could drive Innovasic’s business (automotive customers only represent 10 to 15% of the company’s business today).
On Bosch’s stand, a ball was kept in balance in the centre of an actuated plate controlled through real-time vision-processing. You could nudge the ball and see how the plate would immediately compensate for the deviation and centre the ball back in place. The TSN network was setup in such a way that the camera feed linking to the real-time image processing unit would compete for bandwidth with data from a network traffic generator. Different switches would activate some TSN features while at the same time adding traffic on the network, illustrating how without the pre-emptive option, the ball would no longer be kept in the centre of the plate when disturbed.
Bosch’s TSN gateway demonstration was built around Marvell’s 7-port automotive qualified 88EA6321 Audio/Video Bridging switch (with 2 integrated PHYs). The guys at the Bosch stand hinted that Marvell would release engineering samples of a TSN chip for the automotive market before the end of the year. Marvell’s Director for the Automotive Solution Group, Alexander Tan who was present as one of the conference speakers on PHY solutions declined to comment on the specific features and IP blocks that would be integrated on the upcoming chip.
Renesas Electronics too was running an Ethernet TSN demonstration, alongside a large poster comparing current and future car network architectures, around 2020. The car network of the future was illustrated with an Ethernet backbone connecting different domains, each with its TSN control unit, maybe in the shape of master MCUs integrating Ethernet PHYs and TSN switch functionalities together with security modules and various protocol converters for local legacy serial networks.
The FPGA-based TSN gateways in the demo were demonstrating all the conceivable TSN features. A real-time control loop linking a flash-light and a position sensor aside an encoded rotating wheel was ensuring a perfectly static stroboscopic effect. When uncontrolled traffic was fed into the network by a “babbling idiot” board, the stroboscopic effect was only maintained if ingress policing was performed through a TSN gateway, while a live video feed in AVB mode would be pre-empted when needed.
So when will Renesas’ first TSN-ready automotive MCUs hit the market?
Principal Engineer for Automotive Network Communication Protocols, Tobias Belitz remained evasive, only accepting the possibility that Renesas could produce “intelligent TSN switches” depending on customer demand. The poster mentioned the 2020s, so surely parts would be needed before such architectures would be built, but among the Renesas engineers at the booth, none would agree on a specific time frame.
On the Avnu Alliance booth, Ixia, Renesas and the InterOperability Laboratory from the University of New Hampshire (UNH-IOL) showed the results of Avnu’s first Plug-fest for the pre-emption TSN feature, enabling different solution providers to check for the AVB/TSN interoperability of their solutions. Here, they were running an IEEE 802.3br Pre-emption interoperability and performance demo.
Product specialist for automotive Ethernet at network test equipment provider Ixia and a member of the Avnu Alliance (an industry consortium driving open, standards-based deterministic networking based on IEEE 802 AVB/TSN), Bogdan Tenea told eeNews Europe that a certification program for automotive AVB devices would be launching soon, with a pilot currently in progress. Mid-September, the Avnu Alliance announced the availability of its Automotive Ethernet AVB Functional and Interoperability Specification (derived from the Avnu Automotive Profile). The document defines a common baseline among multiple standard options within the Ethernet AVB set of standards, with additional functionality required by automotive devices. The Avnu Automotive certification program is the logical next step.
Visit Innovasic at www.innovasic.com
Visit Bosch at www.bosch.com
Visit Marvell Technology at www.marvell.com
Visit Renesas Electronics at www.renesas.com
Visit Ixia at www.ixiacom.com
Visit Avnu at https://avnu.org/
Visit IEEE’s Time-Sensitive Networking Task Group at www.ieee802.org/1/pages/tsn.html
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Automotive Ethernet needed for adaptive headlights, says Porsche
Innovasic demonstrates TSN-ready Deterministic Ethernet for automotive
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