Multiport MIDI-DIN interfaces became widely used in MIDI systems where more than 16 MIDI channels were required, and these could be used to limit the amount of data sent or received through any one MIDI port. USB and FireWire MIDI protocols allow a particular stream or 'cable' to be identified so that each stream controlling 16 MIDI channels can be routed to a particular physical port or instrument. There are 16 basic MIDI channels, and instruments can usually be set to receive on any specific channel or channels, or to receive on all channels. Two primary classes of message exist: those that relate to specific MIDI channels and those that relate to the system as a whole. The term 'device ID' is now used widely by software as a means of defining one of a number of physical devices in a large MIDI system, rather than defining a MIDI channel number.