By Amir Bar-Niv, VP of Marketing of Automotive Business Unit, Marvell
Ethernet standards comprise a long list of features and solutions that
have been developed over the years to resolve real network needs as well as
resolve security threats. Now, developers of Ethernet In-Vehicle-Networks (IVN)
can easily balance between functionality and cost by choosing the specific
features they would like to have in their car’s network.
The roots of Ethernet technology began in 1973, when Bob Metcalfe, a
researcher at Xerox Research Center (who later founded 3COM), wrote a memo entitled
“Alto Ethernet,” which described how to connect computers over short-distance
copper cable. With the explosion of PC-based Local Area Networks (LAN) in
businesses and corporations in the 1980s, the growth of client/server LAN
architectures continued, and Ethernet started to become the connectivity technology
of choice for these networks. However, the Ethernet advancement that made it
the most successful networking technology ever was when standardization efforts
began for it under the IEEE 802.3
group.
The 10 Mb/s derivative of Ethernet was first approved by the IEEE
Standards Board in 1983, and subsequently published in 1985 as IEEE Std
802.3-1985. The process of
standardization of Ethernet, and the subsequent membership in IEEE 802
standards, has been extremely beneficial to Ethernet’s growth, enabling
multi-vendor support and interoperability as a wide variety of physical layers
have been added. Since the original
Ethernet standard began, data rates from 1 Mb/s to 400 Gb/s have been added on
a wide variety of media and reaches (cable lengths), all under a seamless
architecture in IEEE 802.
Recently, IEEE 802.3 added automotive reaches and rates to its application base, enabling lightweight, high-speed single-pair connectivity for automobiles. Building on the already mature base of LAN technologies in the IT space, automotive networks have rapidly scaled to include speeds from 10 Mb/s to 10 Gb/s and are currently working on reaching speeds beyond 10 Gb/s. These networks are expected to fulfill a variety of applications currently served by mixed networks with proprietary protocols.
Ethernet Advanced Features for Automotive Applications
1)
Switching
The essence of a network is addressing
and switching – the capability to send data between specific nodes that share
the same network. One of the most important attributes of Ethernet
network/switching is the capability to send the traffic between two nodes over
different routes in the network.
Addressing devices and switching
through multiple routes provides redundancy that is critical for the
functionality and reliability of the IVN. The switching architecture of the
Ethernet LAN is based on the IEEE 802.1 standard. It defines the link security,
overall network management, and the higher protocol layers above the Media
Access Control (MAC).
Ethernet switching naturally creates
another very important benefit for the IVN: the ability to support a wide range
of network topologies including mesh, star, ring, daisy-chain, tree and bus (as
shown in Figure 2). This allows system and domain developers to choose the
optimal topology for each domain, while leveraging the same basic components.
Ethernet Advanced Features for Automotive Applications
Figure 2
The payload size of data packets sent over Ethernet is variable,
allowing maximum flexibility for carrying different types of application loads.
In addition, Ethernet’s native support of broadcast and multicast allows high
efficiency, with low latency for each of these topologies.
2)
Ethernet PHY Speeds
The first IEEE standard Automotive Ethernet PHY published was the
100BASE-T1 that was developed under 802.3bw. This standard was ratified in
2015, and specified 100Mbps Ethernet on single-pair, unshielded automotive
cable. Today, 100BASE-T1 has been adopted by many original equipment
manufacturers (OEMs), and most luxury and mid-end cars use 100M Ethernet
networking.
100BASE-T1 specifications were not alone for long, and in 2016, the next
generation of automotive Ethernet, 1000BASE-T1, was published. Developed
simultaneously with 100BASE-T1, the 1000BASE-T1 PHY specification known as
802.3b provided gigabit networking. The 1000BASE-T1 PHY products were
introduced to the market in 2017 and are now getting into mass production.
In 2019 and 2020, Automotive Ethernet added both lower speeds (10 Mb/s)
and multigigabit speeds. The latest Automotive Ethernet PHY standard
development for 2.5 Gbps, 5 Gbps, and 10Gbps, called IEEE 802.3ch, was
completed in early 2020.
Currently, Automotive Ethernet PHY
standards are in progress for speeds higher than 10Gbps. The first effort to
develop a pre-standard set of specifications is done in the NAV (Networking for
Autonomous Vehicles) Alliance(www.nav-alliance.org), under Technical Working Group 1 (TWG1). In addition, a new task
force, called IEEE 802.3cy for “Greater than 10 Gb/s Automotive Ethernet
Electrical PHYs” began its activities in July 2020, with an objective to develop
an automotive PHY for data rates of 25 Gbps, 50 Gbps and 100 Gbps.
3)
Ethernet MAC speeds
IEEE 802.3 developed standards for MAC at rates ranging from 10Mbps all
the way up to 100Gbps (200Gbps and 400Gbps were also developed, but these rates
today require multiple channels of 100Gbps). These standards had previously
been developed and proven for LAN and data center applications, and today they
also find applications in automotive networking.
Specifically, Ethernet supports rates of 10Mbps, 100Mbps, 1Gbps,
2.5Gbps, 5Gbps, 10Gbps, 25Gbps, 50Gbps and 100Gbps. These MAC rates open the
door for future automotive network speeds beyond 10Gbps, for high speed
backbone.
4)
Asymmetrical Ethernet
Automotive Ethernet is capable of symmetric traffic rates, meaning it
transports data at the same speed in both directions on a single-pair
automotive cable. This capability makes it the preferred technology for the
network backbone. However, Ethernet can also operate in an asymmetrical mode
when needed. In 2009, the Ethernet standards group developed a set of protocols
for efficiently handling asymmetric and time-varying traffic loads known as
Energy Efficient Ethernet (EEE).
EEE provides a method to reduce power consumption during periods of low
data activity. In its normal mode of operation, an Ethernet link consumes power
in both directions, even when a link is idle and no data is being transmitted. Based
on the IEEE 802.3az standard, EEE uses a Low Power Idle (LPI) mode to reduce
the energy consumption of a link when no packets/data are being sent.
The standard specifies a signaling protocol to achieve power saving
during idle time by exchanging LPI indications to signal the transition to
low-power mode when there is no traffic. LPI indicates when a link can go idle,
and when the link needs to resume after a predefined delay.
The asymmetrical mode is useful for camera and sensors links. On these
links, data (video) is sent at high speed (multi gigabits per second) from the
camera to the SoC/GPU. On the other direction (from SoC to camera), there are
only control signals that need to be sent at much lower speeds (megabit per
second) – these can leverage the EEE mode for power saving.
The 100BASE-T1 automotive Ethernet PHY did not specify a low-power mode,
and it was added in 1000BASE-T1. As it
became clear that supporting energy efficient asymmetric traffic would be
important in the automotive networking world, 2.5G, 5G, and 10Gb/s Ethernet
improved the concepts of energy efficiency in 802.3ch by allowing a slow wake.
This mode works with a longer delay to re-establish traffic, and is especially
useful on asymmetric links.
5)
Virtual Local Area Network (VLAN)
VLANs work by applying identifiers (known as 802.1Q tags) to network
packets and handling these tags at switching nodes, creating the appearance and
functionality of network traffic that is physically on a single network but that
acts as if it is split between separate networks. This way, VLANs keep traffic
from different applications separate, despite being connected to the same
physical network. VLANs also allow grouping of nodes and data sources together,
even if they are not directly connected to the same switch. Because VLANs can
be easily configured, system design and data source deployment are greatly
simplified. In Automotive, VLAN is used to isolate traffic from different
applications or domains, and can route video from different sources over the
same physical link and/or isolate traffic that requires higher priority.
VLAN traffic can be routed, multicast and broadcast. In addition, VLANs
also support Quality of Service and traffic prioritization using the 802.1P
standard, allowing for efficient bandwidth utilization, which can be utilized
in advanced IVN.
6)
Precision Time Protocol
The vision analysis algorithm in a car requires either simultaneous
sampling of multiple sensors or knowing the time that a measurement was taken.
As these measurements are taken by different sensors and cameras, and carried
through different routes, (cables, repeaters, hubs and switches), time
synchronization needs to be done between all the nodes in the car down to very
short intervals.
The IEEE 802.1AS (Timing and Synchronization for Time-Sensitive
Applications in Bridged Local Area Networks) standard allows for
synchronization of timing. This standard leverages the IEEE 1588 v2 and uses a
special profile called “PTP Profile” to select the best clock source in the
system as the master clock for all nodes. Additionally, clock redundancy and
rapid failover is easily supported using these protocols.
7)
Audio Video Bridging (AVB/TSN)
Audio Video Bridging (AVB) is a method to transport audio and video (AV)
streams over Ethernet-based networks, to ensure the highest Quality-of-Service
(QoS). QoS guarantees the ability to dependably run high-priority
applications and traffic on a network with a limited capacity. This is handled by the 802.1 suite of
standards originally known as AVB, and now known as Time Sensitive Networking
(TSN). The Advance Driver Assistance Systems (ADAS) rely on AVB to get data
from cameras and sensors in a timely manner at a low, controlled latency with
guaranteed bandwidth. The IEEE 802.1 AVB Task Group is working on standards to
meet these requirements, including 802.1Qat Stream Reservation, as well as
802.1Qav Queuing and Forwarding for AV Bridges.
AVB IEEE standards define signaling, transport, and synchronization of
the audio and video streams. In essence, AVB works by reserving a fraction of
the available Ethernet bandwidth for AVB traffic. Its main attributes for
Ethernet networks include:
Precise
timing of streaming in conjunction with PTP. Support of low-jitter media clocks
and accurate synchronization of multiple streams.
A
reservation protocol that enables the endpoint device to notify the various
network elements to reserve resources necessary to support its stream.
Queuing-and-forwarding
defined rules to ensure that an AV stream will pass through the network within
the delay specified in the reservation.
In November 2012, AVB was renamed “Time-Sensitive Networking Task Group”
(TSN), which is an enhancement of AVB that added specifications to expand the
range, functionality and applications of the standard.
The TSN suite of standards also rely on IEEE standards outside of the
802 family, such as IEEE 1722. IEEE 1722
– Layer 2 Audio/Video Transport Protocol (AVTP) for Time Sensitive Applications
in a Bridged Local Area Network – sets the presentation time (time-stamping)
for each AV stream and manages latencies.
The AVnu Alliance(www.avnu.org ) is an industry forum dedicated to
the advancement of AV transport through the adoption of IEEE 802.1 AVB/TSN and
the related IEEE 1722 standard. The Alliance is used by most OEM and Tier-1
companies to define a complete Ethernet-based solution for audio and video in
IVNs.
8)
MAC-PHY Security
Media Access Control Security (MACSec) is an 802.1AE IEEE industry
standard security technology that secures data transmissions over Ethernet
networks. MACSec is used for authentication, encryption and validation of the
integrity of packets that are sent between peer nodes and provides
point-to-point security on Ethernet links.
MACSec is capable of identifying and preventing security threats, such
as intrusion, man-in-the-middle, masquerading, passive wiretapping and playback
attacks in the IVN.
Additionally, an Ethernet MACSec root node can be used as the security
center for all domains in the car, including lower-speed CAN, LIN, USB, and
others. This can be achieved by using one or more trunking ports from an
Ethernet switch to an Ethernet supporting gateway, bridging those legacy
networks.
9)
Power Over Cable
One great advantage of copper-cabled Ethernet for automotive networking
is the ability to deliver power over the same wires as data, which in turn
saves weight in the vehicle. This is especially important in the case of
cameras and sensors that are mounted all around the vehicle.
The IEEE 802.3bu standard, which was ratified in 2016, defines specifications and parameters for adding standardized power to single-pair cabling. The standard defines a power delivery protocol that supports multiple voltages and classes of power delivery for each voltage. It includes assured fault protection and detection capabilities for identifying device signatures, as well as direct communication with devices to determine accurate and safe power delivery. Total power delivery over the automotive cable ranges from 0.5W up to 50W.
Marvell’s
automotive Ethernet products roadmap for IVN includes the most comprehensive
set of solutions in the market, which enable our customers to build vehicle
networks for low, mid and high-end cars, all the way to fully autonomous cars. This
roadmap includes a broad range of switches, PHYs, controllers and bridges (at
Ethernet speeds from 10Mbps up to 10Gbps and higher), advanced security
features, and the support for the latest industry requirements for AVB/TSN
features in IVN.
The
latest addition to the Marvell Ethernet PHY roadmap is the 88Q2220 and 88Q2221,
the first 1000BASE-T1 Automotive PHY family of products for secured network, with
the support of IEEE 802.1AE MACSec. In addition, these ultra-low power Gigabit PHY
products support the latest TC10 standard of OPEN Alliance for 1000BASE-T1 Sleep
and Wake-up modes.
In
our next blog, we will discuss Ethernet QoS for IVN, the related standards and
features, as well as the AvNU certification of Marvell Automotive Switch
products.
By Christopher Mash, Senior Director of Automotive Applications & Architecture, Marvell
The in-vehicle networks currently used in automobiles are based on a combination of several different data networking protocols, some of which have been in place for decades. There is the controller area network (CAN), which takes care of the powertrain and related functions; the local interconnect network (LIN), which is predominantly used for passenger/driver comfort purposes that are not time sensitive (such as climate control, ambient lighting, seat adjustment, etc.); the media oriented system transport (MOST), developed for infotainment; and FlexRay™ for anti-lock braking (ABS), electronic power steering (EPS) and vehicle stability functions.
As a result of using different protocols, gateways are needed to transfer data within the infrastructure. The resulting complexity is costly for car manufacturers. It also affects vehicle fuel economy, since the wire harnessing needed for each respective network adds extra weight to the vehicle. The wire harness represents the third heaviest element of the vehicle (after the engine and chassis) and the third most expensive, too. Furthermore, these gateways have latency issues, something that will impact safety-critical applications where rapid response is required.
The number of electronic control units (ECUs) incorporated into cars is continuously increasing, with luxury models now often having 150 or more ECUs, and even standard models are now approaching 80-90 ECUs. At the same time, data intensive applications are emerging to support advanced driver assistance system (ADAS) implementation, as we move toward greater levels of vehicle autonomy. All this is causing a significant ramp in data rates and overall bandwidth, with the increasing deployment of HD cameras and LiDAR technology on the horizon.
As a consequence, the entire approach in which in-vehicle networking is deployed needs to fundamentally change, first in terms of the topology used and, second, with regard to the underlying technology on which it relies.
Currently, the networking infrastructure found inside a car is a domain-based architecture. There are different domains for each key function – one for body control, one for infotainment, one for telematics, one for powertrain, and so on. Often these domains employ a mix of different network protocols (e.g., with CAN, LIN and others being involved).
As network complexity increases, it is now becoming clear to automotive engineers that this domain-based approach is becoming less and less efficient. Consequently, in the coming years, there will need to be a migration away from the current domain-based architecture to a zonal one.
A zonal arrangement means data from different traditional domains is connected to the same ECU, based on the location (zone) of that ECU in the vehicle. This arrangement will greatly reduce the wire harnessing required, thereby lowering weight and cost – which in turn will translate into better fuel efficiency. Ethernet technology will be pivotal in moving to zonal-based, in-vehicle networks.
In addition to the high data rates that Ethernet technology can support, Ethernet adheres to the universally-recognized OSI communication model. Ethernet is a stable, long-established and well-understood technology that has already seen widespread deployment in the data communication and industrial automation sectors. Unlike other in-vehicle networking protocols, Ethernet has a well-defined development roadmap that is targeting additional speed grades, whereas protocols – like CAN, LIN and others – are already reaching a stage where applications are starting to exceed their capabilities, with no clear upgrade path to alleviate the problem.
Future expectations are that Ethernet will form the foundation upon which all data transfer around the car will occur, providing a common protocol stack that reduces the need for gateways between different protocols (along with the hardware costs and the accompanying software overhead). The result will be a single homogeneous network throughout the vehicle in which all the protocols and data formats are consistent. It will mean that the in-vehicle network will be scalable, allowing functions that require higher speeds (10G for example) and ultra-low latency to be attended to, while also addressing the needs of lower speed functions. Ethernet PHYs will be selected according to the particular application and bandwidth demands – whether it is a 1Gbps device for transporting imaging sensing data, or one for 10Mbps operation, as required for the new class of low data rate sensors that will be used in autonomous driving.
Each Ethernet switch in a zonal architecture will be able to carry data for all the different domain activities. All the different data domains would be connected to local switches and the Ethernet backbone would then aggregate the data, resulting in a more effective use of the available resources and allowing different speeds to be supported, as required, while using the same core protocols. This homogenous network will provide ‘any data, anywhere’ in the car, supporting new applications through combining data from different domains available through the network.
Marvell is leading the way when it comes to the progression of Ethernet-based, in-vehicle networking and zonal architectures by launching, back in the summer of 2017, the AEC-Q100-compliant 88Q5050 secure Gigabit Ethernet switch for use in automobiles. This device not only deals with OSI Layers 1-2 (the physical layer and data layer) functions associated with standard Ethernet implementations, it also has functions located at OSI Layers 3,4 and beyond (the network layer, transport layer and higher), such as deep packet inspection (DPI). This, in combination with Trusted Boot functionality, provides automotive network architects with key features vital in ensuring network security.