Slot time
Slot time is a concept in
computer networking. It is the time it takes for an electronic pulse (
OSI Layer 1 - Physical) to travel the length ofthe maximum theoretical distance between two nodes. In
CSMA/CD networks such as
ethernet, wait a minimum of the
slot time (which should be a constant, NOT dependent on the individual network -ie, it is a standard across all CSMA/CD networks that use a common NIC) before transmitting, allowing time (the maximum theoretical time - slot time) for the pulse to reach the NIC that intends to send.
Since a pulse will never exceed
slot time(the maximum theoretical time for a frame to travel a network), the NIC waits a minimum of slot time before transmitting, in order to allow any pulse that was initiated at the time that the waiting NIC was requested to send, to reach the waiting NIC. 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 (local) and not on the wire (late) CSMA/CD implementation can take more control over the situation.
Some times for slot time include:
| Speed | Slot time*!Time Interval | | 10 Mbit/s | 512 bit times | 51.2 microseconds |
| 100 Mbit/s | 512 bit times | 5.12 microseconds |
| 1 Gbit/s | 4096 bit times | 4.096 microseconds |
| 10 Gbit/s | Not applicable | Not applicable |
* Slot time is only applicable to
half-duplex transmissions. Since slot time is the time required to wait for the medium to be free from transmissions, there is no time required to wait for
full-duplex transmissions. 10 Gbit/s is a full duplex technology, so slot time is not applicable here.See also:
bit time
