2.1.2.4 System Internal Architecture

The following diagram shows the internal system architecture of the Print Services system.

Print Services system internal system architecture

Figure 9: Print Services system internal system architecture

The Windows print client and Windows administrative client are shown in the preceding diagram as a single client object, contained by a bolded rectangle. Although they are often separate entities, these clients can share many of the same components and are differentiated by whether a client application or the Print Management Console, an administrative application under a user account belonging to the Administrators group, is running.

Within the print client, the Group Policy Service component (GPDPC Service) retrieves Group Policy settings that restrict print client connections to specified print servers. The GPDPC Service also creates print queue connections per computer and per user.

To locate a print queue in a workgroup environment, the print spooler of the print client uses the local computer browser service component, which continually listens for print server announcement messages. In a domain environment, the print spooler of the print client can locate a print queue by various means; it can, for example, access an LDAP server of the Active Directory system. The print spooler then sends a print job to the print spooler that is installed on the print server.

The core protocols of the Print Services system are the Print System Remote Protocol [MS-RPRN], Print System Asynchronous Remote Protocol [MS-PAR], and Print System Asynchronous Notification Protocol [MS-PAN]. The print server contains a print spooler that receives communications from the print client's print spooler by using these protocols.

For print clients that do not use the core protocols, the following three Server Service components provide print server support:

  • The file server service, using SMB/RAP [MS-SMB] [MS-RAP], provides support for the Windows 95 operating system, Windows 98 operating system, and Windows Millennium Edition operating system print clients and for users who are running deprecated print commands.

  • The LPD server service, using the Line Printer Daemon Protocol [RFC1179], provides support for UNIX-based print clients.

  • The Internet Information Server Service, using IPP [RFC2910] [RFC2911] and the Web Point-and-Print Protocol [MS-WPRN], provides support for print clients when the print server is behind a firewall that prevents communications through the core protocols.

In a domain environment, the print server's print spooler publishes shared print queues, which correspond to shared printers, to an LDAP server of the Active Directory system. In a workgroup environment, the print server's print spooler finds other print servers by using the local computer browser service. The print spooler uses the core protocols to announce shared print queues to each print server's local computer browser service.

The print server's print spooler persists system data in a registry component. The print spooler loads print driver, port monitor, print processor, and language monitor modules by using the local file system. The print spooler also uses the local file system of the print server to buffer print jobs.