Station address 0xFF is reserved for broadcast communication. Any packets received with address 0xFF are passed to a single active link station for subsequent response on a port. Any additional active link stations on that port do not receive the packet. All communication between the local and remote stations is accomplished by the transmission of frames. Information frames transport sequenced user data between the local and remote stations.
Supervisory frames carry control parameters relative to the sequenced data transfer.
Unnumbered frames transport the controls relative to nonsequenced transfers. Once operating in NRM, information frames containing user data can be transferred. The secondary station's address can be any value from 1 through 254. Once contact has been made, the secondary station's returned address is used exclusively for the remainder of the session. All commands are generated by the primary station for the secondary station.