A printing protocol is a protocol for communication between client devices (computers, mobile phones, tablets, etc.)
These protocols put the printer as similar class to remote disks, scanners and multimedia devices.
This is especially true for multi-function printers, that also produce image files (scans and faxes) and send them back through the network.
This kind of protocol is based on one kind of printing protocols plus Zero-configuration networking (zeroconf) mechanisms.
The computer and the printer should be located on the same local area network (LAN) when using all of the above protocols.