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What is Ethernet?

The family of standards (IEEE 802.3) for wired LANs. Data is placed in frames that are addressed by MAC address. It runs over twisted-pair cable and optical fiber at speeds from 10 Mbit/s to hundreds of Gbit/s. Each frame ends with a CRC-32 error-detection code, the frame check sequence (FCS). Today devices are normally connected to switches in full duplex, so the old CSMA/CD collision handling is no longer used.

Japanese name: イーサネット

Ethernet appears in 12 practice questions across 4 topics, including Computer Networking Basics, Automotive Semiconductors and Functional Safety, I/O Interfaces & Buses.

Field: Computer Networking Basics

Try it: questions about Ethernet

Which correctly describes a feature of automotive Ethernet (100BASE-T1, 1000BASE-T1, etc.)?

  1. AIt communicates full-duplex over a single twisted pair, providing 100 Mbit/s or 1 Gbit/s of bandwidth while keeping wiring light
  2. BThe standard mandates the same four-pair cables and RJ45 connectors as office LANs, making the wiring heavier than in offices
  3. CIts communication speed is about the same as LIN, but because it is robust against noise it is used only for safety-critical control
Show answer and explanation

Answer: A. It communicates full-duplex over a single twisted pair, providing 100 Mbit/s or 1 Gbit/s of bandwidth while keeping wiring light

Automotive Ethernet standards such as 100BASE-T1 and 1000BASE-T1 communicate full-duplex over just a single twisted pair, are lighter than the four-pair cables used in offices, and also cope with harsh automotive noise conditions. With far greater bandwidth than CAN, they are used for camera and display data, the backbone network linking ECUs, software reprogramming and more. Time synchronization and latency guarantees are achieved by combining TSN (Time-Sensitive Networking) technologies.

High-speed links such as 100-gigabit Ethernet are sometimes built by bundling, for example, four 25 Gb/s lanes. Which describes this approach?

  1. AThree of the four are spares; data actually travels on just one
  2. BThe same data is sent on all four and errors are fixed by majority vote
  3. CBecause per-lane speed is limited, data is spread across several SerDes lanes to reach the total bandwidth
Show answer and explanation

Answer: C. Because per-lane speed is limited, data is spread across several SerDes lanes to reach the total bandwidth

The speed of one SerDes lane is limited by circuit and channel technology. Spreading data across several lanes and realigning it in order at the receiver yields large total bandwidth. As per-lane speeds rise, the same bandwidth needs fewer lanes; for example, a single 100 Gb/s PAM4 lane can carry 100-gigabit traffic.

Ethernet in the explanations

Questions that mention Ethernet (12)

  1. Which correctly describes a feature of automotive Ethernet (100BASE-T1, 1000BASE-T1, etc.)?
  2. High-speed links such as 100-gigabit Ethernet are sometimes built by bundling, for example, four 25 Gb/s lanes. Which describes this approach?
  3. On 1 Gbps Ethernet, TCP data is sent continuously with IP packets filling the 1500-byte MTU. Taking the IPv4 header as 20 bytes, the TCP header as 20 bytes, the Ethernet header and FCS together as 18 bytes, and the preamble and inter-frame gap together as 20 bytes, which is closest to the upper limit on application-data throughput?
  4. What is the main reason wireless LAN uses CSMA/CA rather than CSMA/CD, which has been used in wired Ethernet?
  5. What is a typical use of a linear feedback shift register (LFSR), which feeds the XOR of some outputs of a shift register back to its input?
  6. In CAN, what happens when two nodes start transmitting frames at the same time?
  7. Which correctly describes a feature of the in-vehicle network LIN?
  8. Which correctly describes a feature of the in-vehicle network FlexRay?
  9. What is the role of a SerDes (serializer/deserializer) in high-speed serial links?
  10. When a web page's data is sent, what happens on the sending side each time the data is passed from an upper layer to a lower layer?
  11. Which statement about MAC addresses is correct?
  12. Which correctly describes the role of ARP?

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Comparisons that include this term

Related terms

IP (Internet Protocol) Packet Wi-Fi SerDes TCP (Transmission Control Protocol) IPv4 MAC address DHCP IP address PAM4

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