Introduction to Ethernet  Study Guide

Master the foundational technology of local area networking. From CSMA/CD to modern switched architectures.

What is Ethernet?

Ethernet is a family of wired computer networking technologies commonly used in local area networks (LANs). Introduced commercially in 1980 and first standardized in 1983 as IEEE 802.3, Ethernet has evolved to support higher bandwidths and improved media access control methods.

48-bit
MAC Address
1500
MTU (Bytes)
10M-400G
Speed Range

Evolution of Ethernet

1973 - Xerox Alto Network

Robert Metcalfe invents Ethernet at Xerox PARC. 2.94 Mbps over coaxial cable.

1980 - DIX Standard

Digital, Intel, Xerox release 10 Mbps Ethernet standard.

1983 - IEEE 802.3

Ethernet becomes IEEE standard. 10BASE5 and 10BASE2 defined.

1990 - 10BASE-T

Twisted pair cabling and hubs revolutionize installation.

1995 - Fast Ethernet

100BASE-TX brings 100 Mbps speeds.

1998-99 - Gigabit Ethernet

1000BASE-X (fiber) and 1000BASE-T (copper) standards.

Ethernet Frame Structure

Click on any field in the diagram below to see detailed information

7 bytes
Sync
1
Start
6 bytes
Destination
6 bytes
Source
2 bytes
Protocol
46-1500 bytes
Data
4 bytes
CRC

Click on a frame field above

Select any field in the Ethernet frame diagram to see detailed information.

CSMA/CD Protocol

How It Works

1
Carrier Sense

Listen to the channel before transmitting. If busy, wait.

2
Multiple Access

Multiple stations share the same medium.

3
Collision Detection

Monitor for collisions while transmitting.

4
Backoff Algorithm

If collision detected, send jam signal and wait random time before retry.

Interactive Simulation

A
B
Click "Normal TX" or "Collision" to simulate

Ethernet Types & Speeds

Standard Speed Media Max Distance Cable
10BASE5 10 Mbps Coax (Thick) 500m RG-8
10BASE2 10 Mbps Coax (Thin) 185m RG-58
10BASE-T 10 Mbps UTP 100m Cat 3/5
100BASE-TX 100 Mbps UTP 100m Cat 5
1000BASE-T 1 Gbps UTP 100m Cat 5e/6
10GBASE-T 10 Gbps UTP 100m Cat 6a/7

Ethernet Switching

Hub (Layer 1)

  • • Physical layer device (repeater)
  • • Broadcasts to all ports
  • • Shared bandwidth
  • • Half-duplex only
  • • CSMA/CD required

Switch (Layer 2)

  • • Data link layer device
  • • Learns MAC addresses
  • • Dedicated bandwidth per port
  • • Full-duplex supported
  • • No CSMA/CD needed

Forwarding Methods

Store-and-Forward

Receives entire frame, checks FCS, then forwards.

Cut-Through

Forwards after reading destination MAC.

Fragment-Free

Forwards after first 64 bytes.

Knowledge Check

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