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A Collision Domain is the network segment of ethernet packets which can collide with each other connected by hubs and repeaters.

Let’s see how Collision Domains are created. The CSMA-CD [Carrier Sense Multiple Access - Collision Detect] or IEEE 802.3 protocol standard recognizes that collisions exist. As a result, there is a “Back-off Window” or waiting period of time when all computer devices wait to try sending again.

The back-off, or waiting time before transmitting again, is called the IFS [InterFrame Spacing]. The IFS is a number of bits plus a random number of time spaces called time slots. The purpose of the IFS is to reduce the probability of collision. The IFS period is especially critical in wireless LAN situations where it is difficult to detect collisions. After the back-off period, the next time interval is called the Contention Window as it is the period where any station can attempt to transmit.

Tags: ethernet, ifs, interframe spacing, csma-cd, carrier sense multiple access collision detect