Collision/Broadcast Domains

All stations on an Ethernet segment are connected to the same segment. Therefore, all signals are received by all the devices. When devices sent signals at the same time, a collision occurs. A scheme is need to detect and compensate for collisions.

• Collision domain  -  A group of devices connected to the same physical medium so that if two devices access the medium at the same time, a collision results. This is a Layer 1 domain.

• Broadcast domain -  A group of devices on the network that receive on another’s broadcast messages. This is a layer 2 domain.

• Ethernet Hubs -  Device that allow the concentration of many devices into a single segment. They have the following characteristics.

1.  
   1. Physical layer devices.
   2. Do no manipulate or view traffic.
   3. Do not create separate collision domains.
   4. Use carrier sense multiple access collision detect (CSMA/CD).
   5. When a collision occurs, both stations resent the signal after a random period.
   6. Collisions increase with the number of the stations.
   7. Regenerate the signal, allowing traffic to travel longer distances.

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• Collision Domains