Token bus is a type of LAN technology that based on Bus topology. Token Bus is standardized in IEEE 802.4 standard. This technology is usually designed for large organizations. A token is passed to the node over the virtual ring within the bus network.
The fields used in the Token Bus LAN frame format are:
Permeable: Contains one to three octet (a unit of digital information that used in computing and Telecommunications) patterns that enable bit synchronization.
Start Delimiter (SD): Contains one octet unique bit pattern, which marks the start of the frame.
Frame Control (FC): Contains one octet bit pattern, which indicates the type of frame, data frame, or control frame
Destination Address (DA): Contains two to six octet bit patterns, which define the destination address.
Source Address (SA): Contains two to six octets, which define the source address.
Data: Contains the Logical Link Control (LLC) frame and the size of this frame is up to 8191 octets.
Frame Check Sequence (FCS): Uses four bytes to store the calculation value of Cyclic Redundancy Check (CRC is an error detecting code that identifies accidental changes in the data) that is used for error detection.
End Delimiter (ED): Contains 1 octet unique, bit pattern, which marks the end of the frame.