LINK MANAGER
The baseband state machine is controlled largely by the link manager. This firmware, generally provided with the link control hardware, handles link setup, security, and control. Its capabilities include authentication and security services, quality of service monitoring, and baseband state control. The link manager controls paging, changing slave modes, and handling required changes in master/slave roles. It also supervises the link and controls handling of multislot packets.
Link managers communicate with each other using the Link Management Protocol (LMP), which uses the underlying baseband services. LMP packets, which are sent in the ACL payload, are differentiated from logical link control and adaptation protocol (L2CAP) packets by a bit in the ACL header. They are always sent as single-slot packets and are higher priority than L2CAP packets. This helps ensure the integrity of the link under high traffic demand.