In a networked control system(NCS), a message must be
processed before and after it travels through the network
channel. These processing times are dependent on network
devices and can be constant or stochastic. For different types of
networks the amount of time it takes for a message to reach its
destination, called the transmission time, is a function of the
communication rate and protocol used. In some cases, such as
in token-passing protocols, transmission times are bounded; for
other protocols like Ethernet with collision detection,
transmission time can be unbounded. Thus, system
performance is not only dependent on the performance on
individual devices, but also on their impact on the network
medium. In some cases, the network protocols are more
important to performances of networked control systems than
other aspects.