Image courtesy: GuardKnox
The automotive Ethernet ecosystem is the set of standards and industry groups that bring Ethernet into the car. IEEE 802.3 writes the physical layer standards (100BASE-T1, 1000BASE-T1, 802.3ch multi-gig and the asymmetric camera link project 802.3dm). The OPEN Alliance promotes adoption and writes the test and interoperability specifications. For high-speed camera and display links, two SerDes families compete: the open ASA Motion Link with its Ethernet mode, ASA-MLE, and Analog Devices' GMSL, which is being opened up through the OpenGMSL Association. This post explains each one and how they relate, as of June 2025.
Key takeaways
- Automotive Ethernet replaces or supplements CAN, LIN and FlexRay where bandwidth matters, using a single twisted pair to save weight and cost.
- IEEE 802.3 defines the PHYs; the OPEN Alliance defines how they are tested, woken up, cabled and made interoperable.
- Camera links are asymmetric: gigabits downstream, megabits upstream. That is why 802.3dm, ASA-ML and GMSL exist.
- ASA-MLE puts an Ethernet PHY into the ASA Motion Link specification (v2.0, May 2024).
- GMSL is the incumbent, proprietary SerDes; the OpenGMSL Association, launched in June 2025, aims to make it an open standard.
This post covers, step by step:
- Automotive Ethernet
- IEEE 802.3 standards
- The OPEN Alliance
- ASA-MLE (Automotive SerDes Alliance Motion Link Ethernet)
- GMSL E (Gigabit Multimedia Serial Link with Ethernet)
It ends with a relationship matrix showing how they connect.
Understanding automotive Ethernet
What is automotive Ethernet?
The automotive industry is moving fast toward connected, software-defined vehicles (SDVs) and zonal architectures, which need high-bandwidth, low-latency and interoperable in-vehicle networks (IVNs). Automotive Ethernet is Ethernet adapted for that job. Classic CAN runs at up to 1 Mb/s and FlexRay at 10 Mb/s; automotive Ethernet runs from 10 Mb/s to 10 Gb/s today, with faster grades defined for backbones. Its main uses are:
- Advanced driver assistance systems (ADAS): high-resolution cameras, radar and lidar need multi-gigabit links.
- Infotainment: high-definition displays and media streaming.
- Autonomous driving: real-time data processing and low-latency communication.
- Connected vehicles: over-the-air (OTA) updates, diagnostics and cybersecurity.
Key features
- Single twisted pair: one unshielded twisted pair (UTP) at most rates, or shielded pair and coax at the highest rates, cuts harness weight, cost and complexity.
- Electromagnetic compatibility (EMC): designed for strict automotive emissions and immunity limits.
- Standardisation: built on IEEE 802.3, so parts from different vendors interoperate.
- Zonal architectures: sensors and ECUs connect to zone controllers, and the zones connect to central compute over an Ethernet backbone, replacing many domain-specific networks.
Automotive Ethernet removes the bandwidth bottleneck of legacy buses. Its open standards reduce development cost and vendor lock-in and support the data-heavy applications of SDVs.
IEEE 802.3: the foundation
What is IEEE 802.3?
IEEE 802.3 is the family of standards from the Institute of Electrical and Electronics Engineers that defines the physical layer and the media access control part of the data link layer for wired Ethernet. Originally written for enterprise and consumer networks, it has been extended for cars through amendments aimed at in-vehicle needs.
Automotive amendments
| Amendment | PHY | Rate | Typical use |
|---|---|---|---|
| 802.3bw (2015) | 100BASE-T1 | 100 Mb/s | Basic ADAS, infotainment, diagnostics; standardised from BroadR-Reach |
| 802.3bp (2016) | 1000BASE-T1 | 1 Gb/s | Multi-camera systems, domain backbones |
| 802.3cg (2019) | 10BASE-T1S / T1L | 10 Mb/s | Multidrop links that can replace CAN in zones |
| 802.3ch (2020) | 2.5/5/10GBASE-T1 | 2.5 to 10 Gb/s | Advanced ADAS, zonal backbones |
| 802.3cy (2023) | 25/50/100GBASE-T1 | 25 to 100 Gb/s | High-end backbones |
| P802.3dm (in development) | Asymmetrical electrical automotive Ethernet | Up to 10 Gb/s one way, lower rate back | Camera and sensor links |
The 802.3dm project focuses on asymmetric, point-to-point, full-duplex links for sensors such as cameras and lidar: a fast downlink from sensor to ECU and a slow uplink for control. Its project authorisation (PAR) was approved on 21 March 2024, and the PAR targets submission to the IEEE standards review committee in November 2026, so at the time of writing it was still a draft.
Goals of IEEE 802.3 in automotive
- Standardisation: define PHYs for fast, reliable Ethernet in the harsh automotive environment.
- Interoperability: PHYs, switches and ECUs from different vendors must work together.
- Scalability: keep raising data rates for new vehicle architectures; 802.3cy already reaches 100 Gb/s.
- Automotive compliance: EMC, low power, light cabling and support for functional safety work under ISO 26262.
The OPEN Alliance: driving adoption
What is the OPEN Alliance?
The OPEN Alliance (One-Pair Ether-Net) Special Interest Group was founded in 2011 by Broadcom, NXP, BMW and others, and has grown to several hundred members (over 400 according to the original version of this post; not re-verified), spanning carmakers, Tier 1 suppliers, chip vendors and tool and test companies. Its aim is to make Ethernet the standard in-vehicle network through open, interoperable solutions.
Goals
- Standardisation: work with IEEE on automotive Ethernet standards such as 100BASE-T1, 1000BASE-T1 and 802.3dm.
- Interoperability: publish test specifications and compliance methods for PHYs, switches and ECUs.
- Automotive-specific additions through technical committees, for example:
- TC10: sleep and wake-up for energy-efficient networks.
- TC9: channel, cable and connector requirements for light, EMC-compliant wiring.
- TC18: remote control protocols for simple edge devices.
- Ecosystem development: reduce reliance on CAN and proprietary SerDes.
Achievements
- Promoted Broadcom's BroadR-Reach as the OPEN 100BASE-T1 specification, which IEEE then standardised as 802.3bw.
- Supported the adoption of 1000BASE-T1 and 802.3ch multi-gig Ethernet.
- Developed compliance tests so parts from different vendors interoperate.
- Expanded membership across the supply chain, driving global adoption.
The OPEN Alliance has sped up deployment and cut network complexity, cabling cost and lock-in. Its work with IEEE helps keep standards like 802.3dm aligned with what carmakers actually need.
Why camera links are different: a worked example
The numbers here are illustrative. A front camera with 3840 x 2160 pixels (8.3 MP), 30 frames a second and 12-bit raw output produces:
8.3 million x 30 x 12 bits = about 3.0 Gb/s, before blanking, protocol overhead and any second exposure for high dynamic range.
The ECU sends back only register writes, trigger signals and perhaps a few diagnostics: well under 100 Mb/s. A symmetric 10 Gb/s link would waste power and cost in the uplink direction. Asymmetric links put the cost where the data is, which is the design idea behind ASA-ML, GMSL and 802.3dm alike.
ASA-MLE: bridging SerDes and Ethernet
What is ASA-MLE?
The Automotive SerDes Alliance (ASA) publishes the ASA Motion Link (ASA-ML) specification, an open, asymmetric SerDes for cameras, radar, lidar and displays. Version 2.0 of the specification, released in May 2024, added an Ethernet physical layer for coax and shielded twisted pair, known as ASA-MLE. It carries Ethernet at up to 10 Gb/s in one direction and a lower rate in the other, so a camera can join the vehicle's Ethernet network directly instead of through a separate video tunnel. Version 2.1 followed in February 2025. ASA has shared its specifications with the IEEE 802.3dm task force as liaison material.
Key features
- High data rates: ASA-ML supports up to 16 Gb/s per link, with higher aggregate throughput in multi-port parts (up to 64 Gb/s as stated in the original post; not re-verified).
- Low latency: uses time division duplexing (TDD) for the return channel, suited to real-time functions such as adaptive cruise control.
- Interoperability: carries camera interfaces such as MIPI CSI-2 (over C-PHY or D-PHY at the sensor) and, with MLE, native Ethernet frames.
- Power efficiency: asymmetric design keeps power down, which matters in electric vehicles with many cameras.
- Open standard: available to any member, in line with the industry move to open ecosystems.
Goals
- Bridge technologies: connect SerDes-style sensors to Ethernet backbones.
- Support zonal architectures: fast sensor links into central compute.
- Replace proprietary SerDes: offer an open alternative to GMSL and FPD-Link.
- Enable SDVs: provide the bandwidth and latency needed for ADAS, autonomous driving and OTA updates.
ASA-ML is gaining traction for sensor links, with BMW among its prominent backers. Its alignment with IEEE work and OPEN Alliance goals makes it a strong candidate for future in-vehicle networks.
GMSL E: the incumbent SerDes
What is GMSL E?
Gigabit Multimedia Serial Link (GMSL) was developed by Maxim Integrated, now part of Analog Devices (ADI). GMSL2 arrived around 2018 and GMSL3 around 2021. GMSL moves video, control and data over a single coax or shielded twisted pair cable, and can tunnel Ethernet alongside video, which is what this post calls GMSL E. It is widely used for cameras, radar, lidar and displays.
Key features
- Data rates: GMSL2 runs at about 6 Gb/s forward; GMSL3 at about 12 Gb/s forward using PAM4, enabling 4K video and multi-camera aggregation. The reverse channel is about 187.5 Mb/s (the original post said 1.5 Gb/s for GMSL2; corrected).
- Ethernet tunnelling: encapsulates Ethernet traffic over the GMSL link.
- Applications: surround view, rear cameras, displays and sensors, with fault detection designed for ISO 26262 ASIL-rated systems.
- Proprietary until 2025: a single-vendor ecosystem limited interoperability.
Goals
- High-speed connectivity: reliable point-to-point links for cameras and displays.
- Legacy support: serve existing platforms with minimal change.
- Safety compliance: meet functional safety needs for ADAS and autonomous driving.
- Ethernet compatibility: limited integration with Ethernet networks through tunnelling.
GMSL is entrenched because it performs well and is proven in production, but a single source was its weak point. In June 2025 ADI led the launch of the OpenGMSL Association at AutoSens, with founding members reported to include Hyundai Mobis, Geely, Aptiv and Qualcomm, and plans to publish GMSL2 and GMSL3 as open specifications. That is the openGMSL development flagged in the first version of this post.
Goals summary
| Player | Main goal |
|---|---|
| Automotive Ethernet | High-bandwidth, low-latency, scalable networking for ADAS, infotainment, autonomous driving and SDVs |
| IEEE 802.3 | Standard Ethernet physical and data link layers, with automotive amendments such as 802.3dm |
| OPEN Alliance | Adoption through standardisation, interoperability testing and automotive-specific additions |
| ASA-MLE | Bridge SerDes sensors to Ethernet, support zonal architectures and replace proprietary links |
| GMSL E | Proven high-speed SerDes connectivity with Ethernet tunnelling, now moving to an open model |
Relationship matrix
| IEEE 802.3 | OPEN Alliance | ASA-MLE | GMSL E | |
|---|---|---|---|---|
| IEEE 802.3 | Writes the PHY standards | Co-develops; OPEN supplies tests and requirements | Receives ASA liaisons for 802.3dm | No formal link; Ethernet carried by tunnelling |
| OPEN Alliance | Promotes and tests 802.3 PHYs | TC9, TC10, TC18 and others | Shared goal of open standards | Different approach; OpenGMSL is a separate body |
| ASA-MLE | Native Ethernet PHY, candidate input to 802.3dm | Aligned | Open, asymmetric SerDes with Ethernet | Direct competitor for camera links |
| GMSL E | Tunnels Ethernet, does not implement an 802.3 PHY | Outside its ecosystem | Competitor | Incumbent, opening up via OpenGMSL |
Key relationships
- Automotive Ethernet as the core: the unifying technology, enabled by IEEE 802.3, promoted by the OPEN Alliance, extended to sensors by ASA-MLE and connected at the edge by GMSL tunnelling.
- IEEE 802.3 and OPEN Alliance: the OPEN Alliance works with IEEE on automotive standards (802.3bw, 802.3bp, 802.3ch, 802.3dm), and its technical committees cover EMC, sleep and wake, and power efficiency.
- ASA-MLE alignment: brings SerDes sensors into automotive Ethernet and has been shared with the 802.3dm task force, so it is likely to complement or influence 802.3dm.
- GMSL E position: it competes with the open standards. It tunnels Ethernet but is not an IEEE 802.3 PHY, which limited its role until the OpenGMSL move.
- 802.3dm's emerging role: an IEEE asymmetric Ethernet standard for camera links, aimed at replacing proprietary SerDes with standard Ethernet links.
Evolution in 2025 and beyond
Industry trends
- Centralised compute: Ethernet backbones connect zones and sensors to central ECUs; 802.3dm and ASA-MLE support this move.
- Software-defined vehicles: Ethernet's scalability enables OTA updates, cybersecurity and real-time processing.
- Standardisation push: carmakers such as BMW and Tesla were reported to favour IEEE 802.3 and OPEN Alliance solutions to cut cost and avoid lock-in, which puts pressure on proprietary SerDes and explains the move to OpenGMSL.
Current state (June 2025)
- Automotive Ethernet is in production for ADAS, infotainment and driver assistance, and multi-gig rates are becoming common.
- IEEE 802.3 keeps evolving, with 802.3dm in development for asymmetric camera links.
- The OPEN Alliance continues to expand, supporting 802.3dm and work on higher rates and time synchronisation (IEEE 802.1AS).
- ASA-ML and ASA-MLE are gaining traction as the open sensor link, with BMW a prominent supporter.
- GMSL remains the installed base and is now being opened through OpenGMSL, which is worth watching.
Future outlook
The view of this blog: by 2030, automotive Ethernet will probably absorb most proprietary SerDes, with 802.3dm and ASA-MLE leading new sensor designs. ASA-MLE's openness and data rates position it well for SDVs. GMSL is likely to hold legacy and existing platforms, and OpenGMSL could extend its life if carmakers accept it as an open alternative. Once published, 802.3dm will formalise asymmetric Ethernet and speed up the shift to standard in-vehicle networks.
Common mistakes
- Treating "automotive Ethernet" as one PHY. It is a family, from 10BASE-T1S multidrop to 100 Gb/s backbones.
- Assuming tunnelled Ethernet is the same as an 802.3 PHY. Tunnelling carries frames but does not give PHY-level interoperability between vendors.
- Sizing camera links on frame rate and pixels alone. Blanking, embedded data, HDR and protocol overhead can add a large margin.
FAQ
Is 802.3dm a finished standard?
Not as of June 2025. The task force was formed in March 2024 and its PAR targets completion in late 2026.
What is the difference between ASA-ML and ASA-MLE?
ASA-ML is the SerDes link that tunnels camera and display protocols. ASA-MLE, added in specification v2.0, provides an Ethernet physical layer over the same kind of asymmetric link.
Will automotive Ethernet replace CAN completely?
Not soon. CAN and LIN remain cheap and adequate for many low-rate functions, though 10BASE-T1S is aimed at some of those jobs inside zones.
Why do carmakers want open SerDes?
A second source lowers cost and supply risk, and a common standard makes test, validation and tooling reusable across programmes.
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