Bit time is a concept in
computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
ing. It is defined as the time it takes for one bit to be ejected from a
network interface controller
A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network.
Ear ...
(NIC) operating at some predefined standard speed, such as 10 Mbit/s. The time is measured between the time the
logical link control
In the IEEE 802 reference model of computer networking, the logical link control (LLC) data communication protocol layer is the upper sublayer of the data link layer (layer 2) of the seven-layer OSI model. The LLC sublayer acts as an interface ...
sublayer receives the instruction from the
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
until the bit actually leaves the NIC. The bit time has nothing to do with the time it takes for a bit to travel on the network medium but has to do with the internals of the NIC.
To calculate the bit time at which a NIC ejects bits, use the following:
bit time = 1 / NIC speed
To calculate the bit time for a 10 Mbit/s NIC, use the formula as follows:
bit time = 1 / (10 * 10^6)
= 10^-7
= 100 * 10^-9
= 100 nanoseconds
The bit time for a 10 Mbit/s NIC is 100 nanoseconds. That is, a 10 Mbit/s NIC can eject 1 bit every 0.1 microsecond (100 nanoseconds = 0.1 microseconds).
Bit time is distinctively different from
slot time
Slot time is a concept in computer networking. It is at least twice the time it takes for an electronic pulse ( OSI Layer 1 - Physical) to travel the length of the maximum theoretical distance between two nodes. In CSMA/CD networks such as Ethe ...
, which is the time taken for a pulse to travel through the longest permitted length of network medium.
Ethernet
Computer network analysis
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