L2CAP (Logical Link Control and Adaptation layer Protocol)

The host of a Bluetooth device uses the L2CAP (Logical Link Control and Adaptation layer Protocol) for the transmission of higher level packets. They are sent to and received from the HCI, via a logical channel. Each end of a L2CAP channel is identified by a 16-bit channel identifier.

A L2CAP packet, or PDU (Packet Data Unit), is transmitted in one or more baseband packets on the ACL link, with the L_CH (Logical Channel) bits of the payload header set to 102 for the initial packet, and 012 for the subsequent packets.