FRAME FORMATS
The Bluetooth core protocols consist of baseband, LMP, L2CAP, and SDP. The baseband and link control layer enables the physical RF link between Bluetooth units forming a piconet. As the Bluetooth RF system is a frequency hopping spread-spectrum system in which packets are transmitted in defined time slots on defined frequencies, this layer uses inquiry and paging procedures to synchronize the transmission hopping frequency and clock of different Bluetooth devices (see box this page).
The link manager protocol is responsible for link setup between Bluetooth devices. This includes security aspects like authentication and encryption by generating, exchanging, and checking link and encryption keys, and the control and negotiation of baseband packet sizes.
L2CAP provides connection-oriented and connectionless data services to the upper-layer protocols with protocol multiplexing capability, segmentation and reassembly, and group abstractions. Discovery services are crucial to the Bluetooth framework. These services provide the basis for all the usage models.