K28.5: A special 10-bit character used to indicate the beginning of a Fibre Channel command.
See also: 8b/10b encoding
The format for Control Character is: Kx.y, where the K comes from an internal joke as in "Kontrol". The control characters only exist within the storage network, i.e., only as 10 bit characters. This makes the characters easy to transmit within the network.