Browse Prior Art Database

Protocol for Reliable Printer Sharing Among Multiple Servers

IP.com Disclosure Number: IPCOM000118425D
Original Publication Date: 1997-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 107K

Publishing Venue

IBM

Related People

Airola, JT: AUTHOR [+4]

Abstract

This disclosure defines a set of functions that support the reliable sharing of a printer by print servers. These functions guarantee that: o print-job boundaries are preserved o sharing is transparent to end-users o private print resources, such as logos and signatures, which were loaded into the printer by one print server are not accessible to any other print server.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Protocol for Reliable Printer Sharing Among Multiple Servers

      This disclosure defines a set of functions that support the
reliable sharing of a printer by print servers.  These functions
guarantee that:
  o  print-job boundaries are preserved
  o  sharing is transparent to end-users
  o  private print resources, such as logos and signatures,
      which were loaded into the printer by one print server
      are not accessible to any other print server.

      An example of a system configuration is shown in the Figure
where a printer control unit supports connections to three different
servers on interfaces A, B, and C.  Note that, in general, the number
of servers and interfaces is not limited to three.  The interfaces
may be distinct physical interfaces or they may be logical interfaces
mapped to one physical interface.  The control unit attaches multiple
printers that can be accessed independently by the servers.

      The printer sharing protocol is defined on the transmission
protocol that acts as the carrier for a print data stream.  An
example of a transmission protocol is the IBM S/390* Channel
protocol, and an example of a print data stream is the IBM
Intelligent Printer Data Stream (IPDS).  The sharing protocol
consists of a set of commands, responses, and interrupts that are
implemented in the print server and the printer.  The commands are
based on a protocol that is used by IBM tape drives.
  o  Assign command
       The Assign is issued when a print server requires use of
      the printer, i.e., when it has at least one job to print.  The
      command is accepted by the printer if it is not assigned to
      another server or rejected by the printer if it is assigned
      to another server.  If rejected, the printer generates sense
      information that indicates that the printer is 'assigned
      elsewhere'.  Once the Assign command is accepted, the print
      server has established sole access to the printer and may
      begin to send print data streams.
  o  Unassign command
       The Unassign command is issued by the print server when it
      no longer requires use of the printer.  It is issued based on
      an algorithm that takes the following into account:
       -  the printer is at a print job boundary
       -  the print queue in the server is empty
       -  the printer has indicated, via sense data, that another
           server has attempted to issue an Assign to the printer.
  When the Unassign command is accepted by the printer, the server
   has lost its access to that printer.
  o  No-longer-assigned interrupt
       When an Unassign command is processed by the printer, the
      printer generates a unique interrupt to those servers that
      previously had an Assign command rejected with an 'assigned
      else...