Ethernet Technology

Ethernet is the most widely used local area network (LAN) technology, defining how data is transmitted over wired connections. Developed by Xerox PARC in the 1970s and standardized as IEEE 802.3, Ethernet has evolved from 10 Mbps to modern 400 Gbps standards.

Historical Evolution

  • 1973 Original Ethernet (2.94 Mbps) at Xerox PARC
  • 1980 Ethernet II (DIX) standard - 10 Mbps
  • 1983 IEEE 802.3 standard ratified
  • 1995 Fast Ethernet (802.3u) - 100 Mbps
  • 1998 Gigabit Ethernet (802.3z/ab)
  • 2010+ 10/25/40/100/400 Gigabit Ethernet

Key Technical Concepts

CSMA/CD

Carrier Sense Multiple Access with Collision Detection - The original access method for half-duplex Ethernet where devices listen before transmitting and detect collisions.

Full-Duplex

Modern Ethernet uses switched full-duplex connections, eliminating collisions and allowing simultaneous transmission and reception.

MAC Addressing

48-bit hardware addresses burned into NICs, formatted as six hexadecimal octets (e.g., 00:1A:2B:3C:4D:5E).

Ethernet Frame Structure (IEEE 802.3)

Preamble
7 bytes
SFD
1 byte
Dest MAC
6 bytes
Src MAC
6 bytes
Length/Type
2 bytes
Data/Payload
46-1500 bytes
FCS
4 bytes

Click on any field above to see detailed information

64
Minimum Frame Size (bytes)
Ensures collision detection
1518
Maximum Frame Size (bytes)
Standard MTU + headers
9000
Jumbo Frame (bytes)
Optional for high throughput

Ethernet Topologies

Ethernet Topologies

Star and Bus Topology Comparison

Star Topology (Modern)

All devices connect to a central switch. Most common today due to reliability, scalability, and full-duplex capability.

Bus Topology (Legacy)

All devices share a single coaxial cable. Used 10BASE5 and 10BASE2 standards. Deprecated due to collision issues.

Point-to-Point

Direct connection between two devices. Common for fiber links and switch-to-switch connections.