Bluetooth Core Specification Addendum 1 adds two additional L2CAP modes to the core specification: Enhanced Retransmission Mode (ERTM) [4] and Streaming Mode (SM) [5]. These modes
effectively deprecate original Retransmission and Flow Control modes.
Reliability in any of these modes is optionally and/or additionally guaranteed by the lower layer Bluetooth BDR/EDR air interface by configuring the number of retransmissions and flush timeout (time after which the radio will flush packets). In-order sequencing is guaranteed by the lower layer.