Lesson 29: Collision Domains and Broadcast Domains

These two concepts are essential for understanding network efficiency and where Switches and Routers fit in.

1. Collision Domain

A Collision Domain is a network segment where data packets sent by multiple devices can collide with one another, corrupting the data.

• Impact: Collisions force devices to wait and retransmit, wasting bandwidth.
• Device Impact: Hubs create one large collision domain because they broadcast traffic to all ports. Switches break up collision domains—each switch port becomes its own collision domain.
• Goal: Minimize or eliminate collision domains for better performance. Modern full-duplex connections effectively eliminate collisions entirely.

2. Broadcast Domain

A Broadcast Domain is a logical network segment where any device can send a broadcast message that reaches every other device in that segment.

• Impact: Large broadcast domains generate unnecessary traffic (broadcast storm) which consumes CPU resources on every connected device.
• Device Impact: Switches forward broadcasts to all ports, so a switch creates a single, large broadcast domain. Routers stop broadcasts—they do not forward broadcast traffic from one network to another.