1. Introduction

**CSMA/CD** is a Media Access Control (MAC) protocol used in early Ethernet networks to manage data transmission on a shared channel (like a coaxial cable). It ensures that multiple computers can share the same wire without garbling each other's data.

2. Working Principle

1. Carrier Sense (Listen before talking): The station listens to the channel. If it is idle, it transmits. If busy, it waits.
2. Multiple Access (Anyone can talk): Multiple stations share the same link.
3. Collision Detection (Stop if interrupted): While transmitting, the station monitors the link. If it detects a signal interference (collision), it stops immediately.
4. Jamming Signal: The detecting station sends a high-frequency jamming signal to inform all other stations of the collision.
5. Backoff: Stations wait for a random amount of time (determined by specific algorithms like Binary Exponential Backoff) before trying again.

3. Mathematical Concept

4. Disadvantages

• Performance degrades heavily as network load increases.
• Not suitable for long-distance networks due to propagation delay limitations.
• Replaced by full-duplex switched Ethernet in modern networks.