Slot time is a concept in computer network

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

ing. It is twice the time it takes for an electronic pulse (OSI

OSI model

The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...

 Layer 1 - Physical

Physical layer

The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....

) to travel the length of
the maximum theoretical distance between two nodes. In CSMA/CD networks such as ethernet

Ethernet

Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

, Network Interface Controllers (NICs) 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

Local collision

A local collision, in CSMA/CD computer networks, is a collision that occurs at the NIC as opposed to on the wire.On UTP cable a local collision is detected on the local segment only when a station detects a signal on the RX pair at the same time it is sending on the TX pair.Since the two signals...

 occurs rather than a late collision

Late collision

Late Collision in computer networking is a type of collision found in the CSMA/CD protocol standard. If a collision error occurs after the first 512 bits of data are transmitted by the transmitting station, a late collision is said to have occurred...

 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 nanoseconds
100 Mbit/s	512 bit times	5.12 nanoseconds
1 Gbit/s	4096 bit times	4.096 nanoseconds
10 Gbit/s	Not applicable	Not applicable

• Slot time is only applicable to half-duplex
  Duplex (telecommunications)
  A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....
  
   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
  Duplex (telecommunications)
  A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....
  
   transmissions. 10 Gbit/s is a full duplex technology, so slot time is not applicable here.

See also: bit time

Bit time

Bit time is a concept in computer networking. It is defined as the time it takes for one bit to be ejected from a Network Interface Card operating at some predefined standard speed, such as 10 Mbit/s. The time is measured between the time the logical link control layer 2 sublayer receives the...