Slot time


Slot time is a concept in computer networking. It is at least twice the time it takes for an electronic pulse to travel the length of the maximum theoretical distance between two nodes. In CSMA/CD networks such as Ethernet, the slot time is an upper limit on the acquisition of the medium, a limit on the length of a packet fragment generated by a collision, and the scheduling quantum for retransmission.
Since a pulse's runtime will never exceed slot time, the network interface controller, or NIC waits a minimum of slot time before retransmitting after a collision happened, in order to allow any pulse that was initiated at the time that the waiting NIC was requested to send, to reach all other nodes. By allowing the pulse to reach the waiting NIC, a local collision occurs rather than a late collision occurring. By having the collision occur at the NIC and not on the wire CSMA/CD implementation recover the situation by retransmitting later.
Some times for Ethernet slot time include:
See DIFS for information on 802.11x slot times.