The Logical Link Control and Adaptation Protocol (L2CAP) is a Bluetooth core protocol that handles multiplexing and Segmentation and Reassembly( SAR) functions in Bluetooth.
The L2CAP protocol connects the higher layers of the Bluetooth protocol stack with the Link Manager Protocol( LMP) and in parallel with the baseband protocol. The L2CAP protocol can provide connectionless and connection-oriented services via RF Communication( RFCOMM) and the transport protocols above it, and forms the core protocol for the Bluetooth profiles.
The L2CAP layer is only about data packet transmission, not voice data. In L2CAP, Quality of Service( QoS) can be specified concerning the data flow according to RFC 1363, its delay and distortions.