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Ethernet

Ethernet is a reliable, open standard for connecting devices by wire.
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Description

Ethernet is a protocol and hardware used for a wired connection between devices such as computers and networks to deliver data. Ethernet is the physical layer (see Open Systems Interconnection (OSI) communication model) of a network system. In other words, is the physical is means it is the physical connection between devices. It consists of cables, ports, IP, and blocks on chips, depending on the configuration and use. Known for high data rates, Ethernet has the advantage of speed, stability and some security over wireless networks. Ethernet started at 100 Mbps but now higher speed versions are available. See 100GbE Ethernet and 400GbE Ethernet.

Ethernet has been in production for more than 40 years, and it has been well proven under a variety of environmental conditions. Created in the early 1970s by Bob Metcalfe and David Boggs of Xerox’s Palo Alto Research Center (PARC) to network computers together for the first time using a coaxial cable in the ceiling that Metcalfe named the “Ether,” Ethernet has since evolved and continues to evolve. Today, Ethernet is chiefly used for wiring local area networks (LANs) found not only in office spaces and homes but also in data centers, industrial control and automotive. With more deterministic Ethernet, the protocol is now moving into automotive, where its role may expand beyond infotainment to more functional and safety-critical features.

“Today’s Ethernet is a completely different animal that has evolved, changed, adapted, progressed in ways that were never even expected from the original definition of Ethernet,” said Scott Jacobson, director of verification IP marketing, Cadence, in a video explanation of Ethernet. However, Ethernet still boils down to data exchange between computers and other devices.

  • Standards: IEEE 802.3 working group defines the standards for Ethernet. It is an open standard: no proprietary protocols. Ethernet also adheres to the universally-recognized Open Systems Interconnection (OSI) communication model maintained by International Organization for Standardization (ISO).
  • Stacks: Ethernet started with Xerox’s stack protocol XNS (Xerox Networking Standard) standard and evolved to be compliant with ISO’s OSI model.
  • Media: The cable or medium used varies by application and has evolved over the years. “The original definition of Ethernet was around coaxial connections on a bus topology. That was the original intent of Ethernet,” said Cadence’s Jacobson in Part 2 of his video series on Ethernet. “They wanted to go into the office space. In the office space, the existing installation is the phone system. The phone system is a star configuration and it is twisted pair wires.” Ethernet adapted to use twisted pair cables and star topology. Ethernet also adapted to optical systems.
  • Higher performance: Addition of hubs added more ports, and switches and routers added ability to broadcast over subnets and improved performance by managing traffic. Ethernet has also evolved into time sensitive networks (TSN) used for priority control of messaging.
  • Non-deterministic vs deterministic: Ethernet started as a non-deterministic system where a message would wait a random amount of time to send data over the shared system and perhaps it would hit an empty space through which to convey the message. The non-deterministic Ethernet still carries the majority of the traffic and it has improved in speed/bandwidth over the years. A deterministic Ethernet that guarantees messages hit their destination in real time—or at least a guaranteed amount of time—is now possible. “If you have Ethernet in your car and Ethernet is the medium between your foot pedal and your brakes, you don’t want that to be a random amount of time when you step on the brake pedal until when your brakes react. You want to know that it is going to react in a certain amount of time,” said Cadence’s Jacobson in Part 3 of his Ethernet video series. This type of Ethernet, called Time Sensitive Networking (TSN), is used in industrial control and automotive because it gives engineers the tools to design automotive networks with predictable latency and guaranteed bandwidth.

Ethernet for home use

  • Non-deterministic
  • Medium: twisted pair

A common configuration, one that most consumers use for wired access to the Internet, is Ethernet over twisted pair. It consists of an Ethernet cable that plugs into Ethernet ports to connect two devices. Although the Ethernet cable looks like a phone wire, Ethernet has eight pins and wires compared with a phone cable’s four. The cable is a twisted pair cable with modular connectors on either end of the wires that fit into the built-in Ethernet ports. Category 5 Ethernet cables transfer 100 Mbps (megabits per second). Ethernet port speeds have increased by 10X over the last decade.

Ethernet for industrial applications:

  • Deterministic via TSN

Ethernet for data centers:

  • Medium: Optical

Ethernet for back haul:

  • Medium: Optical

Ethernet for automotive:

  • Deterministic via TSN
  • Medium: runs on two up wires on speeds of 2 Gbps.
  • Architecture: Ethernet in automotive could reduce the cacophony of networks in a car because networks vary by domain. “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),” writes Marvell Semiconductor’s Christopher Mash, senior director of automotive applications and architecture. A switch to zonal architecture Ethernet negates the need for all the gateways between network systems. It could also reduce weight by reducing extra wiring.

Ethernet for power delivery:

Power over Ethernet or PoE are systems that pass data and electric power over twisted pair Ethernet cabling.

Thanks to Cadence for video tutorials.