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Ethernet Standards (802.3)

Networking Fundamentals: The 0 to Hero Guide

Lesson 28: Ethernet Standards (802.3)

Ethernet, governed primarily by the IEEE 802.3 standards, is the dominant wired LAN technology worldwide. It defines the physical and Data Link layer standards for communication.

Ethernet Frame Structure

Before data (the packet) can be sent over Ethernet, it must be framed. An Ethernet frame contains crucial fields:

  • Preamble: Synchronization signal.
  • Destination MAC Address: The MAC address of the receiver (6 bytes).
  • Source MAC Address: The MAC address of the sender (6 bytes).
  • EtherType/Length: Identifies the Network Layer protocol (e.g., IP).
  • Data (Payload): The Layer 3 packet.
  • Frame Check Sequence (FCS): A trailer that contains a Cyclical Redundancy Check (CRC) used for error detection.

Naming Conventions

Ethernet standards use a specific naming structure that indicates speed, transmission type, and medium:

  • 10BASE-T: 10 Mbps (speed), Baseband signaling, Twisted-pair copper (T) cable.
  • 100BASE-TX: 100 Mbps, Baseband, Twisted-pair (Fast Ethernet).
  • 1000BASE-T (Gigabit Ethernet): 1 Gbps, Baseband, Twisted-pair.
  • 10GBASE-SR: 10 Gbps, Baseband, Short Reach (Fiber Optic).

Note: The progression from 10BASE-T to 1000BASE-T required manufacturers to develop new techniques (like using all four twisted pairs instead of two) while maintaining backward compatibility.