Broadcast Domain vs Collision Domain - ayosecu/security-terms GitHub Wiki

Broadcast Domain:

A broadcast domain refers to a segment of a network where any device within that domain can directly receive broadcast messages from other devices in the same domain. In a broadcast domain, a message sent to the broadcast address (such as 255.255.255.255 for IPv4) is delivered to all devices within that network segment.

1. Key Points

• Broadcasts are sent to all devices within the same domain. This is used for tasks like device discovery, ARP requests, and DHCP.
• Routers create separate broadcast domains because routers do not forward broadcast traffic. Each router interface creates a new broadcast domain.
• Switches and hubs do not break broadcast domains; devices connected through a switch or hub belong to the same broadcast domain.

2. Example In a typical network with several switches but no routers, all devices connected to the same switch or interconnected switches will belong to the same broadcast domain. A broadcast packet sent by any device will be received by all other devices within that broadcast domain.

Collision Domain:

A collision domain is a network segment where data packets can collide with one another during transmission, especially in environments where devices share the same transmission medium. This concept is primarily relevant to half-duplex Ethernet networks where multiple devices attempt to send data simultaneously over the same medium.

1. Key Points

• Collisions occur when two or more devices send data at the same time, causing the data packets to interfere with each other, which leads to a collision. In such cases, the data has to be resent.
• Hubs and coaxial cables (used in older Ethernet networks) create a single collision domain because all devices share the same communication channel.
• Switches break up collision domains. Each port on a switch creates its own collision domain, meaning that devices connected to different ports on a switch can transmit data simultaneously without collisions.

2. Example In a hub-based network, all devices are part of the same collision domain, meaning if two devices attempt to send data simultaneously, a collision occurs. In a switch-based network, each device connected to a different port has its own collision domain, reducing the chances of collisions and improving network efficiency.

Differences Between Broadcast and Collision Domains:

1. Broadcast Domain

• Affects devices that can receive broadcast traffic.
• Separated by routers.
• Switches and hubs do not divide broadcast domains.

2. Collision Domain

• Affects devices that share the same physical transmission medium, where data collisions can occur.
• Separated by switches (each port creates its own collision domain).
• Hubs and older technologies create a single, shared collision domain.

Summary:

• A broadcast domain is where all devices receive broadcast messages from any device in the same domain, and it is defined by routers.
• A collision domain is where data collisions can occur, primarily in older or half-duplex networks. Switches break up collision domains, improving efficiency by allowing devices to communicate without interference.