Formally termed IrBus, now called IrDA. The specification defines the physical (PHY), Media Access Control (MAC), and Logical Link Control (LLC) layers. The physical layer only defines the optical portion of the transmission.
IrDA uses the same (asynchronous) data rates as RS-232. Normal data transfers start at 9600 until the transfer rate of the device can be determined. The transfer then moves to the new higher rate. Possible data rates are: 2400, 9600, 19200, 38400, 57600, 115200, 576000, 1152000, and 4000000 bits per second. The transmission uses RZI, and includes bit stuffing to allow devices to remain synchronized for all speeds other than 4Mb/s. At 4Mbps Pulse Position Modulation (PPM) is used. The higher the data rate the smaller the bit time / pulse duration.

Uses the standard serial data transmission; 1 start bit, 8 data bits, 0 parity bits, 1 stop bit. Data is transmitted LSB first. CRC is included; 8 bits (CRC-8) for a short packet, or 16 bits (CRC-16) for a long packet.