Subject: IPP> Host-to-Printer Protocol Goals

From: [email-masked]
Date: Wed, 18 Feb 1998 13:17:07 -0500

Just to level set us all, I have extracted the scope, purpose
and introduction sections from a late draft of the IEEE
1284-1-1997 Transport Independent Printer System Interface
standard.  Remember, this was originally written 2 or 3 years
ago, mostly before a printer MIB existed.  While things have
changed a little since then, the assumptions and goals
are, I think, still valid.

Try to read this in a printer politics neutral frame-of-mind
(I said TRY) and I think you will agree, there are
significant merits which should be considered.

---------------------

Scope

This project will develop a standard protocol for the control of
printers.  This protocol will be independent of the underlying
data stream or page description language used to create the
printed page.  This protocol will be usable by all classes
of printers.  This project is limited to management and
control of printers and will not include management or
control of printing system or subsystems.

Purpose

There is currently no defined, independent standard for
controlling printers.  Each vendor builds some control into
the underlying page description language or data stream.
Without an independent, openly defined protocol, applications
and operating systems cannot automatically determine the
type of printer being  addressed.  This protocol will
provide a minimum implementation subset which will allow
automatic identification and configuration of printers
and vendor extensibility to provide for growth and product
differentiation.

Introduction

This standard defines a protocol for communications between
a host and printer. Its intent is to provide standard methodology
for software developers, computer vendors, and printer
manufacturers that facilitate the orderly exchange of
information between printers and host computers. The
specification defines a minimum set of functions that permit
meaningful data exchange. Thus, this standard establishes a
foundation upon which compatible applications, computers, and
printers can be developed, without compromising a particular
organization's desire for design innovation.  The following
objectives accompany this specification:

1.   Simplify the printer driver development process by defining
         a standard set of command/response transactions between
         the host computer and printer.
2.   Accelerate the development of communicating printers
         by providing a robust protocol that can be implemented
         in phases ranging from basic to extended functionality.
3.   Ease customers' printing problems (especially over networks)
         by accelerating the availability of communicating
         printers and compatible host software.
4.   Assist software developers in minimizing time to market by
         establishing a base set of functions that insure a
         minimum level of communications between the host and printer.
5.   Facilitate the creation of powerful network print management
         software by defining transactions that work across a wide
         range of printers.
6.   Enable the creation of standard control/communications
         firmware that can be included in many peripheral devices.
7.   Create a standard methodology for host and printer
         communications that is independent of the transport
         mechanism used between devices.
8.   Enhance the management of printers in networks by providing a
         mechanism for printers to readily provide their status
         and configuration to the host application.
9.   Permit design innovation by providing flexibility within the
         specification for printer manufacturers to include
         extensions to the original set of guidelines.
10.  Insure cross-platform host-to-printer communications by creating
         an operating system-independent set of guidelines.
11.  The resultant protocol is PDL independent with the capability of
         a printer to support multiple PDLs, all active at the same
         time, if desired.

The Current Situation

Local area networks are increasingly becoming the most popular
means of interconnecting devices within a corporation. With
costs per connection coming down, this trend shows no sign of
abating. As networks grow larger, more computers and printers
will be interconnected. Any weaknesses in network printing will
only be magnified as more devices are made to communicate.

The absence of feedback from existing printers causes many
problems in today's network environment. For example, a user
could be submitting a job to a remote printer. If that printer
is low on toner, most printers today do not have the capability
to inform users about this condition. Additionally, if the job
is large, the user risks having to wait until the job is finished
before finding out that the output is incorrect. The resulting
waste of paper, toner, and time could be significant when
calculated over a period of time on a large network.

Standardized feedback information from a printer would solve
this problem. By the use of this standard, when a printer
recognizes a condition that would prevent it from accurately
printing a job, it can send a standardized message to a host
computer that is monitoring network printing. Upon receipt
of this message, the host could then send a message to the
user who submitted the job informing him of the error condition.
The user could then redirect a job to a more appropriate
printer or undertake action to correct the defect at the
target printer. When projected over a period of time and a
large number of network users, the resulting monetary savings
could be substantial.

The example shown above is just one of many error conditions
that could occur when printing either on a standalone computer
or over a network. By using this standard format for exchanging
information between the
printer and host, software vendors, network suppliers, and printer
manufacturers will now be able to greatly improve the efficiency
of network printing.

**********************************************
* Don Wright                 [email-masked] *
* Product Manager, Strategic Alliances       *
* Lexmark International                      *
* 740 New Circle Rd                          *
* Lexington, Ky 40550                        *
* 606-232-4808 (phone) 606-232-6740 (fax)    *
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