he Link Manager and Baseband layers, allowing the protocol stack to Wireless PAN Standards be divided between two pieces of hardware - for example, a processor hosting higher layer software and a Bluetooth module. The host device performs upper layer functions and is able to interface with the second device performing LMP, Baseband and PHY layer functions. The two are connected through the Host Controller Transport layer, that can be either a UART, RS232 or USB interface. Logical Link Control and Adaptation (L2CAP) The logical link control and adaptation protocol (L2CAP) creates the logical connections between the upper layer protocols and the Baseband channels, assigning a channel identifier (CID) to each end-point of a channel. The process of establishing connections includes the exchange of information on the expected QoS between devices, and L2CAP monitors resource usage to ensure that QoS guarantees are met. L2CAP also manages the segmentation and re-assembly of data packets for higher layer protocols that use data packets larger than the Baseband's maximum transmission unit (MTU) of 341 bytes. RFCOMM The Bluetooth RFCOMM protocol is based on a subset of the ETSI TS 07.10 standard, and provides serial port emulation over the L2CAP protocol for cable replacement applications. RFCOMM assembles serial bit streams into bytes and data packets and provides reliable sequenced transport of the serial bit stream, using request to send/clear to send (RTS/CTS) and data terminal ready/data set ready (DTR/DSR) control signals. One adaptation of the ETSI standard implemented in RFCOMM is a credit-based flow control mechanism that limits frame transmission rate to ensure that the receiving device's input buffer does not overflow. If the credit counter for a connection reaches zero, RFCOMM will stop and wait until it receives more credit from the receiving device, indicating that the input buffer is able to receive data. The service discovery protocol (SDP) enables applications to discover what services are available on dev