The Common Printer Access Protocol

The concept of a "Printer Access Protocol" or "PAP" was introduced during the mid-1980s to provide for comprehensive access to the new generation of more capable, networked printers. The design goals for a PAP need to consider the variety of data presentation protocols in use and the heterogeneous nature of distributed interconnection methods. A Digital printing architecture team adopted an existing prototype, the Reid-Kent Print Server Protocol, as the basis for a proposed "Common Printer Access Protocol," or CPAP. Digital's first server instantiation of the CPAP, PrintServer Supporting Host Software version 4.0, also needed to address implementation practicalities to ensure interoperability and backwards compatibility. The solutions selected are applicable to a broad range of client-server systems where clients and servers may be independently developed, and where such components may be installed and upgraded asynchronously from one another. CPAP is being considered for adoption as an Internet standard, and is an element of the Palladium Printing System, which has been accepted as the printing systems component of OSF/1. [Protocol paper starts here.]