Introduction to Ethernet

Explore the fundamental technology of Local Area Networks (LANs). Understand frame structure, MAC addressing, and the CSMA/CD protocol through interactive simulation.

Learning Objectives

Understand Standards

Identify the IEEE 802.3 standard, data rates (10/100/1000 Mbps), and cabling types (UTP, Fiber).

Frame Structure

Analyze the Ethernet Frame format including Preamble, MAC Addresses, Type/Length, and FCS.

MAC Protocol

Explain the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) mechanism.

Theoretical Background

Ethernet Frame Structure (IEEE 802.3)

Data on an Ethernet network is organized into frames. Hover over the fields below to understand their function.

Hover over a frame field to see details...

CSMA/CD Protocol

Ethernet originally used a mechanism called CSMA/CD to manage access to the shared medium.

  • 1 Carrier Sense: Listen to the wire before transmitting. If busy, wait.
  • 2 Multiple Access: Many devices share the same channel.
  • 3 Collision Detection: If two devices transmit simultaneously (collision), stop and send a jam signal.
  • 4 Backoff: Wait a random amount of time before trying again.

MAC Addressing

Media Access Control addresses are unique 48-bit hardware identifiers burned into Network Interface Cards (NICs).

Example MAC Address
A4:5E:60:F3:9B:12

OUI (First 3 bytes): Identifies the manufacturer (e.g., Cisco, Intel).

Device ID (Last 3 bytes): Unique to the specific device.

Laboratory Procedure

1

Setup Network Topology

Navigate to the Simulation tab. Ensure two hosts (PC-A and PC-B) are connected via a switch. Note the assigned MAC addresses.

2

Construct a Frame

Select PC-A as the source. Enter a payload message (e.g., "Hello"). Observe how the system automatically appends the Source/Destination MAC, Type, and calculates the FCS (Checksum).

3

Transmit and Observe

Click 'Transmit'. Watch the packet travel across the cable. Observe the Switch forwarding logic and the packet arriving at PC-B.

4

Analyze the Log

Check the console log. Verify the integrity of the received data. Check if the FCS matches.

Interactive Simulation

Control Panel

System Log
> System initialized...
> Waiting for user input...
Speed: 1x
PC-A PC-B Switch DATA
Status: IDLE

Report Guidelines

Prepare a formal laboratory report documenting your findings. The report should include the following sections:

Required Sections

  • Aim: State the purpose of the experiment.
  • Theory: Briefly explain Ethernet Frame structure and CSMA/CD.
  • Procedure: Step-by-step actions taken in the simulation.
  • Observation/Screenshots: Include screenshots of the frame transmission and logs.
  • Result: Did the data reach the destination correctly?

Viva Questions

1. What is the size of a standard MAC address?
2. Differentiate between a Hub and a Switch.
3. What is the purpose of the FCS field in the Ethernet frame?
4. Why is CSMA/CD not necessary in Full-Duplex mode?