IR

Infrared

Not strictly speaking a bus, it allows the transmission of data as Invisible light, similar to a remote control for a house hold appliance.

the core IrDA protocol layers including:
• The infrared physical layer
• Controllers, drivers and framers
• IrLAP: The IrDA Link Access Protocol ([Linux])
• IrLMP: The IrDA Link Management Protocol
• TinyTP: The IrDA Tiny Transport Protocol
• IAS: The IrDA Information Access Service
• IrDA Lite strategies
A description of important session layer protocols including:
• IrCOMM and IrLPT: Legacy support for serial and parallel communications ([Linux] modules)
• IrOBEX: IrDA Object Exchange ([Linux] applications)
• IrFM: Infrared Financial Message exchange

Good explanation of IR can be found at gnokii-IrDA-Linux