|
|
TITLE
|
Article ID:
Created:
Modified:
|
24512
7/28/98
7/28/98
|
|
TOPIC
- What is LPR? Someone told me it is a printing
protocol. Is that so? Do Apple systems use LPR?
DISCUSSION
Definition of LPR/LPD
LPR/LPD is a platform-independent printing protocol that
runs over TCP/IP. Originally implemented for BSD unix,
its use has spread into the desktop world and is a de
facto industry standard. The specification for LPR is
defined in Request for Comment (RFC) 1179.
Terminology
LPR: Line Printer Remote. Refers to the process
that sends jobs to the printer or print queue. This is
analogous to the print client software and is often
called the 'LPR client'.
Apple has included an LPR client starting with the
LaserWriter 8.5.1 printer driver, which shipped with Mac
OS 8.1. It is also available separately. This software
enables you to send print jobs to any LPD printer or
print server.
LPD: Line Printer Daemon. Refers to the process
that accepts print job from the line printer daemon
client (the LPR client). This is analogous to the printer
or the print server software and is often called the 'LPD
server'.
The print server waits for the client to send it jobs. A
print server may be capable of handling multiple printers
and print queues at once. Since it (usually) has only a
single IP address, the queue name must be used to specify
the intended print queue.
LPR and LPD also refer to the protocol defined by the
LPR/LPD specification (RFC 1179).
How LPR Works
LPR is a lot like sending a file, except you're sending a
print job instead. Also, there are two parts to each
print job: the data file (the data to be printed) and the
control file (instructions that describe the data file
and specify what to do with the data file).
When you click the 'Print' button in the print dialog,
the computer spools the print job to disk and generates
the PostScript data (the data file). It then sends the
data file and control file to the IP address specified in
the LPR desktop printer. Since there may be more than one
queue at the destination IP address, the queue name is
sent at the very beginning to identify the intended
queue.
If the destination is a printer, the printer prints the
job. If the destination is a print server, it may do some
additional processing (for example, security checking)
and then forward the job to the next destination in the
path (usually the printer).
Advantages Of Using LPR
Migration to single-protocol environments
More cross-platform; platform-independent
Accessible via the Internet
Advantages Of Using PAP (Printer Access Protocol, the
Appletalk protocol for printing )
- Better status info (idle, busy, and so forth)
- Better error info (out of paper, tray out)
- Easier to set up (autodiscovery versus manual
entry/selection)
Apple LaserWriter Printers With Built-in LPD
- LaserWriter 8500
- LaserWriter 12/640PS
- Color LaserWriter 12/660PS
- Color LaserWriter 12/600PS
- LaserWriter 16/600PS
- LaserWriter Pro 810
Since these printers support LPD, you can print from any
LPR client (for example, LaserWriter 8.5.1) directly to
the printer. In essence, the printer itself is an LPD
print server.
Other LPR clients and LPD servers
LPR and LPD have been widely adopted by other
communities, including:
- Many flavors of unix.
- Windows NT: LPR client included in NT Workstation
and Server. LPD server only included in NT
Server.
- Windows 3.1x/95/98: LPR and LPD not included but
available by third parties.
For more information on LaserWriter driver 8.5.1 and LPR
printing, please see the following Tech Info Library
article:
Article 24409: "LaserWriter
8.5.1: Configuring For IP Printing (LPR)"
|