The L2CAP protocol ( Logical Link Control and Adaptation Protocol ) provides data services, both connection-oriented and non-connection oriented, to higher-level protocols with multiplexing capabilities and support for segmentation and reassembly operations. L2CAP in basic mode allows higher-level protocols and applications to send and receive L2CAP data packets up to 64 Kbytes in length with standard MTU 672 bytes. The minimum supported MTU is 48 bytes.
L2CAP is based on the concept of channels. A channel is a logical connection over a connection over a radio channel. Each channel is tied to a certain protocol on a many-to-one basis. Multiple channels can be bound to the same protocol, but a channel cannot be bound to multiple protocols. Each L2CAP packet received by the channel is redirected to the corresponding higher-level protocol. Multiple channels can share the same radio connection.
One netgraph node of type l2cap is created for one Bluetooth device . The L2CAP host usually connects to the HCI Bluetooth host (downstream) and the Bluetooth socket hosts (upstream).