10BASE-T Ethernet and Fast Ethernet use a star topology, in which access is controlled by a central computer. Generally a computer is located at one end of the segment, and the other end is terminated in central location with a hub. Because UTP is often run in conjunction with telephone cabling, this central location can be a telephone closet or other area where it is convenient to connect the UTP segment to a backbone. Other computer users on the network continue to operate as if that segment were nonexistent. Collisions Ethernet is a shared media, so there are rules for sending packets of data to avoid conflicts and protect data integrity.
Nodes determine when the network is available for sending packets.
It is possible that two nodes at different locations attempt to send data at the same time. When both PCs are transferring a packet to the network at the same time, a collision will result. Minimizing collisions is a crucial element in the design and operation of networks. Increased collisions are often the result of too many users on the network, which results in a lot of contention for network bandwidth. This can slow the performance of the network from the user's point of view.