The Common Unix Printing System (CUPS) is another project aimed at improving, and ultimately superceding, the traditional printing subsystems. CUPS is distinguished by the fact that it was designed to address printing within a networking environment from the beginning, rather than being focused on printing within a single system. Accordingly, it has features designed to support both local and remote printing, as well as printers directly attached to the network. We will take a brief look at CUPS in this section. The homepage for the project is http://www.cups.org.
CUPS is implemented via the Internet Printing Protocol (IPP). This protocol is supported by most current printer manufacturers and operating systems. IPP is implemented as a layer on top of HTTP, and it includes support for security-related features such as access control, user authentication, and encryption. Given this structure, CUPS requires a web server on printer server systems.
Architecturally, CUPS separates the print job handling and device spooling functions into distinct modules. Print jobs are given a identifier number and also have a number of associated attributes: their destination, priority, media type, number of copies, and so on. As with other spooling subsystems, filters may be specified for print queues and/or devices in order to process print jobs. TheCUPS system provides many of them. Finally, backend programs are responsible for sending print jobs to the actual printing devices.
CUPS also supports ...