RFC2567 - Design Goals for an Internet Printing Protocol

Network Working Group F.D. Wright
Request for Comments: 2567 Lexmark International
Category: EXPerimental April 1999
Design Goals for an Internet Printing Protocol
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
IESG Note
This document defines an Experimental protocol for the Internet
community. The IESG expects that a revised version of this protocol
will be published as Proposed Standard protocol. The Proposed
Standard, when published, is expected to change from the protocol
defined in this memo. In particular, it is expected that the
standards-track version of the protocol will incorporate strong
authentication and privacy features, and that an "ipp:" URL type will
be defined which supports those security measures. Other changes to
the protocol are also possible. Implementers are warned that future
versions of this protocol may not interoperate with the version of
IPP defined in this document, or if they do interoperate, that some
protocol features may not be available.
The IESG encourages experimentation with this protocol, especially in
combination with Transport Layer Security (TLS) [RFC2246], to help
determine how TLS may effectively be used as a security layer for
IPP.
Abstract
This document is one of a set of documents, which together describe
all ASPects of a new Internet Printing Protocol (IPP). IPP is an
application level protocol that can be used for distributed printing
using Internet tools and technologies. This document takes a broad
look at distributed printing functionality, and it enumerates real-
life scenarios that help to clarify the features that need to be
included in a printing protocol for the Internet. It identifies
requirements for three types of users: end users, operators, and
administrators. The design goals document calls out a subset of end
user requirements that are satisfied in IPP/1.0. Operator and
administrator requirements are out of scope for version 1.0.
The full set of IPP documents includes:
Design Goals for an Internet Printing Protocol (this document)
Rationale for the StrUCture and Model and Protocol for the
Internet Printing Protocol [RFC2568]
Internet Printing Protocol/1.0: Model and Semantics [RFC2568]
Internet Printing Protocol/1.0: Encoding and Transport [RFC2565]
Internet Printing Protocol/1.0: Implementer"s Guide [ipp-iig]
Mapping between LPD and IPP Protocols [RFC2569]
The "Rationale for the Structure and Model and Protocol for the
Internet Printing Protocol" document describes IPP from a high level
view, defines a roadmap for the various documents that form the suite
of IPP specifications, and gives background and rationale for the
IETF working group"s major decisions.
The "Internet Printing Protocol/1.0: Model and Semantics" document
describes a simplified model consisting of abstract objects, their
attributes, and their operations that is independent of encoding and
transport. The model consists of a Printer and a Job object. The
Job optionally supports multiple documents. IPP 1.0 semantics allow
end-users and operators to query printer capabilities, submit print
jobs, inquire about the status of print jobs and printers, and cancel
print jobs. This document also addresses security,
internationalization, and Directory issues.
The "Internet Printing Protocol/1.0: Encoding and Transport" document
is a formal mapping of the abstract operations and attributes defined
in the model document onto HTTP/1.1. It defines the encoding rules
for a new Internet media type called "application/ipp".
The "Internet Printing Protocol/1.0: Implementer"s Guide" document
gives insight and advice to implementers of IPP clients and IPP
objects. It is intended to help them understand IPP/1.0 and some of
the considerations that may assist them in the design of their client
and/or IPP object implementations. For example, a typical order of
processing requests is given, including error checking. Motivation
for some of the specification decisions is also included.
The "Mapping between LPD and IPP Protocols" document gives some
advice to implementers of gateways between IPP and LPD (Line Printer
Daemon) implementations.
TABLE OF CONTENTS
1. INTRODUCTION.....................................................4
2. TERMINOLOGY......................................................4
3. DESIGN GOALS.....................................................6
3.1. End-user.......................................................6
3.1.1. Finding or locating a printer................................6
3.1.2. Create an instance of the printer............................7
3.1.3. Viewing the status and capabilities of a printer.............7
3.1.4. Submitting a print job.......................................8
3.1.5. Viewing the status of a submitted print job..................9
3.1.6. Canceling a Print Job........................................9
3.2. Operator (NOT REQUIRED FOR V1.0)...............................9
3.2.1. Alerting.....................................................9
3.2.2. Changing Print and Job Status...............................10
3.3. Administrator (NOT REQUIRED FOR v1.0).........................10
4. OBJECTIVES OF THE PROTOCOL......................................10
4.1. SECURITY CONSIDERATIONS.......................................11
4.2. Interaction with LPD (RFC1179)................................12
4.3. Extensibility.................................................12
4.4. Firewalls.....................................................13
4.5. Internationalization..........................................13
5. IPP SCENARIOS...................................................13
5.1. Printer Discovery.............................................14
5.2. Driver Installation...........................................15
5.3. Submitting a Print Job........................................15
5.4. Getting Status/Capabilities...................................16
5.5. Asynchronous Notification.....................................17
5.6. Job Canceling.................................................17
6. Security Considerations.........................................18
7. REFERENCES......................................................18
8. ACKNOWLEDGMENTS.................................................19
9. AUTHOR"S ADDRESS................................................19
10. APPENDIX - DETAILED SCENARIOS..................................20
10.1. Printer discovery within an enterprise.......................20
10.2. Printer discovery across enterprises.........................21
10.3. Printer discovery on the Internet -logical operations........21
10.4. Printer discovery on the Internet - authentication...........22
10.5. Driver Download..............................................23
10.6. Submitting a print job as a file.............................24
10.7. Submitting a print job with two documents....................24
10.8. Submitting a print job as a file, printing fails.............25
10.9. Submitting a print job with authentication, PRIVACY and
payment......................................................26
10.10. Submitting a print job with decryption error................27
10.11. Submitting a print job with authentication..................28
10.12. Submitting a print job generated dynamically................29
10.13. Submitting a print job with a Printer jam - CANCELED........29
10.14. Submitting a print job with a Printer jam - recovered.......30
10.15. Submitting a print job with server pull.....................31
10.16. Submitting a print job with referenced resources............32
10.17. Getting Capabilities........................................33
10.17.1. Submission Attributes.....................................33
10.17.2. Printer Capabilities......................................33
10.18. Getting Status..............................................34
10.18.1. Printer State/Status......................................34
10.18.2. Job Status................................................34
10.18.3. Status of All My Jobs.....................................34
10.19. Asynchronous Notification...................................35
10.19.1. Job Completion............................................35
10.19.2. Job Complete with Data....................................35
10.19.3. Print Job Fails...........................................35
10.20. Cancel a job................................................36
10.21. End to end Scenario - within an enterprise..................36
10.22. End to end Scenario - across enterprises....................37
10.23. End to End Scenario - on the internet.......................40
11. Full Copyright Statement.......................................43
1. INTRODUCTION
The IPP protocol is heavily influenced by the printing model
introduced in the Document Printing Application (DPA) [ISO10175]
standard. Although DPA specifies both end user and administrative
features, IPP version 1.0 (IPP/1.0) focuses only on end user
functionality.
2. TERMINOLOGY
Internet Printing for the purposes of this document is the
application of Internet tools, programs, servers and networks to
allow end-users to print to a remote printer using, after initial
setup or configuration, the same methods, operations and paradigms as
would be used for a locally attached or a local area network attached
printer. This could include the use of HTTP servers and browsers and
other applications for providing static, dynamic and interactive
printer locating services, user installation, selection,
configuration, print job submission, printer capability inquiry and
status inquiry of remote printers and jobs.
For the purposes of this document, a WEB Browser is software
available from a number of sources including but not limited to the
following: Microsoft Internet Explorer, NCSA Mosaic, Netscape
Navigator, Sun Hot Java!. The major task of these products is to use
the Hypertext Transport Protocol (HTTP) to retrieve, interpret and
display Hypertext Markup Language (Html). These products are often a
part of a complete Internet Printing system because they are often
used as a means of oBTaining the status of or more information about
the printing system; however, they may not be present in all
implementations.
Throughout this document, "printer" shall be interpreted to include
any device which is capable of marking on a piece of media using any
available technology. These design goals do not include support for
multi-tiered printing solutions involving servers (single or
multiple) logically in front of the actual printing device yet all
such configurations shall be supported but shall appear to the end-
user as only a single device.
Throughout this document "driver" refers to the code installed in
some client operating system to generate the print data stream for
the intended printer. Some computing environments may not include a
separate printer driver. Rather, the generation of the proper print
data stream is accomplished in an application on that computer. How
such a computer environment or application is updated to support a
new printer now made available using IPP is outside the scope of IPP.
The actual details for installing a printer driver are operating
system dependent and are also outside the scope of IPP. See also
section 4.1 (SECURITY CONSIDERATIONS) for security implications of
driver download and installation.
The IPP protocol will support the following physical configurations:
- An IPP client talking to an IPP Printer object imbedded in a
single, physical output device.
- An IPP Client talking to a server containing one or more IPP
Printer objects. Each Printer object is associated with exactly one
physical output device supported by the server. The protocol
between the server and the output devices is undefined.
- An IPP Client talking to an IPP Printer object in a server. The
Printer object is associated with one or more physical output
devices, but the client only sees the Printer object, which is an
abstraction and represents all of the associated physical output
devices. The protocol between the server and the physical output
devices is undefined.
Throughout this document, certain design goals will be identified as
not being a part of version 1.0 (or V1.0) of the protocol or as being
satisfied by means outside of IPP. IPP is assumed to be one part, an
enabler, of a complete Internet Printing solution. For example
printer instance creation is not performed by but is enabled by the
protocol. Globally, none of the operator or administrators wants and
needs are included in the design goals for version 1.0. Some of the
end-user wants and needs may also be excluded from version 1.0 and
will be so noted in the description of them. Subsequent versions of
the protocol (e.g. V2.0) may include support for these initially
excluded wants and needs.
3. DESIGN GOALS
The next three sections identify the design goals for an Internet
printing protocol from three roles assumed by humans: end-user,
operator, and administrator. The goals defined here are only those
that need to be addressed by an Internet printing protocol. Other
wants and needs, such as that the operator needs physical Access to
the printer (e.g. to be able to load paper or clear jams) are not
covered by this document. Section 5 contains scenarios which provide
more detailed examples of the entire process including discovery,
status, printing and end-of-job reporting.
3.1. END-USER
An end-user of a printer accepting jobs through the Internet is one
of the roles in which humans act. The end-user is the person that
will submit a job to be printed on the printer.
The wants and needs of the end-user are broken down into six
categories: finding/locating a printer, creating a local instance of
a printer, viewing printer status, viewing printer capabilities,
submitting a print job, viewing print job status, altering the
attributes of a print job.
3.1.1. Finding or locating a printer.
End-users want to be able to find and locate printers to which they
are authorized to print. They want to be able to perform this
function using a standard WEB browser or other application. Multiple
criteria can be applied to find the printers needed. These criteria
include but are not limited to:
- by name (Printer 1, Joes-color-printer, etc.)
- by geographic location (bldg 1, Kentucky, etc.)
- by capability or attribute (color, duplex, legal paper, etc.)
Additionally, while it is outside of scope of IPP, end-users want to
be able to limit the scope of their searching to:
- inside a functional sub-domain
- include only a particular domain (lexmark.com)
- exclude specified domains
While an Internet printing protocol may not of itself include this
function, IPP must define and enable a directory schema which will
provide the necessary information for a directory service
implementation to consistently represent printers by their IPP
attributes.
3.1.2. Create an instance of the printer.
After finding the desired printer, an end-user needs to be able to
create a local instance of that printer within the end-user operating
system or desktop. This local instance will vary depending upon the
printing paradigm of the operating system. For example, some UNIX
users will only want a queue or a reference to a remote printer
created on their machine while other UNIX users and Windows NT users
will want the queue and also the necessary icons and registry entries
to be created and initialized. Where required, drivers may need to
be downloaded from some repository and installed on the computer.
All necessary decompressing, unpacking, and other installation
actions should occur without end-user interaction or intervention
excepting initial approval by the end-user. Once the local instance
of the printer has been installed, it shall appear to the end-user of
the operating system and to the applications running there as any
other printer (local, local area network connected, or network
operating system connected) on the end-user desktop or environment.
IPP"s role in this goal is simply to enable the creation of the
printer instance providing information such as where to locate a
printer driver for this printer, as an attribute of an IPP Printer.
3.1.3. Viewing the status and capabilities of a printer.
Before using a selected printer or, in fact at any time, the end-user
needs the ability to verify the characteristics and status of both
printers and jobs queued for that printer. When checking the
characteristics of a printer, the end-user typically wants to be able
to determine the capability of the device, e.g.:
- supported media, commonly paper, by size and type
- paper handling capability, e.g. duplex, collating, finishing
- color capability
When checking the status of the printer and its print jobs, the end-
user typically wants to be able to determine:
- is the printer on-line?
- what are the defaults to be used for printing?
- how many jobs are queued for the printer?
- how are job priorities assigned? (outside the scope of IPP)
3.1.4. Submitting a print job.
Once the desired printer has been located and installed, the end-user
wants to print to that printer from normal applications using
standard methods. These normal applications include such programs as
Word processors, spreadsheets, data-base applications, WEB browsers,
production printing applications, etc. Additionally, the end-user
may want to print a file already existing on the end-user"s computer
-- "simple push". In addition to printing from an application and
simple push, the end-user needs to have the ability to submit a print
job by reference. Printing by reference is defined to mean as
submitting a job by providing a reference to an existing document.
The reference, a URI, will be resolved before the actual print
process occurs. Submitting a job by reference relieves the user from
downloading the document from the remote server and then sending it
via IPP to the printer. This saves both time and network bandwidth.
Some means shall be provided to determine if the format of a job
matches the capability of the printer. This can be done by one of
the following (all of which are outside of scope of the IPP
protocol):
- the end-user selects the correct printer driver
- the printer automatically selects the proper interpreter
- the end-user uses some other manual procedure.
A standard action shall be defined should the job"s requirements not
match the capabilities of the printer.
Because the end-user does not want to know the details of the
underlying printing process, the protocol must support job-to-printer
capability matching (all implementations are not necessarily required
to implement this function.) This matching capability requires
knowing both the printer"s capabilities and attributes and those
capabilities and attributes required by the job. Actions taken when
a print job requires capabilities or attributes that are not
available on the printer vary and can include but are not limited to:
- rejecting the print job
- redirecting the print job to another printer (Not in V1.0)
- printing the job, accepting differences in the appearance
Print jobs will also be submitted by background or batch applications
without human intervention.
End-users need the ability to set certain print job parameters at the
time the job is submitted. These parameters include but are not
limited to:
- number of copies
- single or two sided printing
- finishing
- job priority
3.1.5. Viewing the status of a submitted print job.
After a job has been submitted to a printer, the end-user needs a way
to view the status of that job (i.e. job waiting, job printing, job
done) and to determine where the job is in the print queue.
In addition to the need to inquire about the status of a print job,
automatic notification of the completion of that job is also
required.
Notification means are not defined by the protocol but the protocol
must provide a means of enabling and disabling the notification.
3.1.6. Canceling a Print Job
While a job is waiting to be printed or has been started but not yet
completed, the original creator/submitter of the print job (i.e. the
end-user) shall be able to cancel the job entirely (job is waiting)
or the remaining portion of it (job is printing.) Altering the print
job itself is not a V1.0 design goal.
3.2. OPERATOR (NOT REQUIRED FOR V1.0)
An operator of a printer accepting jobs through the Internet is one
of the roles in which humans act. The operator has the
responsibility of monitoring the status of the printer as well as
managing and controlling the jobs at the device. These
responsibilities include but are not limited to the replenishing of
supplies (ink, toner, paper, etc.), the clearing of minor errors
(paper jams, etc.) and the re-prioritization of end-user jobs.
Operator wants and needs will not be addressed by V1.0 of the
protocol.
The wants and needs of the operator include all those of the end-user
but may include additional privileges. For example, an operator may
be able to view all print jobs on a printer while the end-user might
only be able to see his own jobs.
3.2.1. Alerting.
One of the required operator functions is having the ability to
discover or to be alerted to changes in the status of a printer
particularly those changes that cause a printer to stop printing and
to be able to correct those problems. As such, an Internet printing
protocol shall be able to alert a designated operator or operators to
these conditions such as "out of paper", "out of ink", etc.
Additionally. the operator shall be able to, asynchronous to other
printer activity, inquire as to a printer"s or a job"s status.
3.2.2. Changing Print and Job Status.
Another of the required operator functions is the ability to affect
changes to printer and job status remotely. For example, the
operator will need to be able to re-prioritize or cancel any print
jobs on a printer to which the operator has authority.
3.3. ADMINISTRATOR (NOT REQUIRED FOR V1.0)
An administrator of a printer accepting jobs through the Internet is
one of the roles in which humans act. The administrator has the
responsibility of creating the printer instances and controlling the
authorization of other end-users and operators. Administrator wants
and needs will not be addressed by V1.0 of the protocol.
The wants and needs of the administrator include all those of the
end-user and, in some environments, some or all of those of the
operator. Minimally, the administrator must also have the tools,
programs, utilities and supporting protocols available to be able to:
- create an instance of a printer
- create, edit and maintain the list of authorized end-users
- create, edit and maintain the list of authorized operators
- create, edit and maintain the list of authorized
administrators
- create, customize, change or otherwise alter the manner in
which the status capabilities and other information about printers
and jobs are presented
- create, customize, or change other printer or job features
- administrate billing or other charge-back mechanisms
- create sets of defaults
- create sets of capabilities
The administrator must have the capability to perform all the above
tasks locally or remotely to the printer.
4. OBJECTIVES OF THE PROTOCOL
The protocol to be defined by an Internet printing working group will
address the wants and needs of the end-user (V1.0). It will not, at
least initially, address the operator or administrator wants and
needs (V2.0).
The protocol defined shall be independent of the operating system of
both the client and the server. Generally, any platform capable of
supporting a WEB Browser should be capable of being a client.
Generally, any platform providing a WEB/HTTP server and printing
services should be capable of being a server. Usage of the WEB
Browser and Server is not required for IPP; the operating system,
operating system extensions or other applications may provide IPP
functionality directly.
In many environments such as Windows 95, Windows NT and OS/2, the
print data is created and transmitted to the printer on the fly
rather than being created, spooled and then transmitted to the
printer (a typical UNIX method.) The Internet Printing Protocol must
properly handle either methodology and make this transparent to the
end-user.
4.1. SECURITY CONSIDERATIONS
It is required that the Internet Printing Protocol be able to operate
within a secure environment. Wherever reasonable, IPP ought to make
use of existing security protocols and services. IPP will not invent
new security features when the design goals described in this
document can be met by existing protocols and services. Examples of
such services include Secure Socket Layer Version 3 (SSL3) [SSL] and
HTTP Digest Access Authentication [RFC2069]. Note: SSL3 is not on
the IETF standards track.
Since we cannot anticipate the security levels or the specific
threats that any given IPP print administrator may be concerned with,
IPP must be capable of operating with different security mechanisms
and policies as required by the individual installation. The initial
security needs of IPP are derived from two primary considerations.
First, the printing environments described in this document take into
account that the client, the Printer, and the document to be printed
may each exist in different security domains. When objects are in
different security domains the design goals for authentication and
message protection may be much stronger than when they are all in the
same domain.
Secondly, the sensitivity and value of the content being printed will
vary from one instance of a print job to another. For example, a
publicly available document does not need the same level of
protection as a payroll document does. Message protection design
goals include data origin authentication, privacy, integrity, and
non-repudiation.
In many environments (e.g. Windows, OS/2) a printer driver may be
needed to create the proper datastream for printer. This document
discusses downloading such a new driver from a variety of sources.
Downloading and installing any software, including drivers) on a
computer exposes that computer to a number of security risks
including but not limited to:
- defective software
- malicious software (e.g. Trojan horses)
- inappropriate software (i.e. software doing something
deemed unreasonable by the user.)
As such, proper security considerations and actions need to be taken
by the user and/or a system administrator to prevent the compromising
of the computer. Administrators should configure downloading
mechanism for printer drivers in such a way as to be able to verify
the source of driver software and encrypt or otherwise protect that
software during download.
Examples including security considerations can be found in sections 5
(IPP SCENARIOS) and 10 (APPENDIX - DETAILED SCENARIOS) later in this
document.
4.2. INTERACTION WITH LPD (RFC1179)
Many versions of UNIX and in fact other operating systems provide a
means of printing as described in [RFC1179] (Line Printer Daemon
Protocol.) This document describes the file formats for the control
and data files as well as the messages used by the protocol. Because
of the simplistic approach taken by this protocol, many manufacturers
have include proprietary enhancements and extensions to "lpd."
Because of this divergence and due to other design goals described in
this document, there is no requirement for backward compatibility or
interoperability with "lpd". However, a mapping of LPD functionality
and IPP functionality shall be provided so as to enable a gateway
between LPD and IPP.
4.3. EXTENSIBILITY
The Internet Printing Protocol shall be extensible by several means
that facilitate interoperability and prevent implementation
collisions:
- by providing a process whereby implementers can submit proposals
for registration of new attributes and new enumerated values for
existing attributes.
* that require review and approval. The Internet Assigned
Number Authority (IANA) will be the repository for such
accepted registration proposals after review.
* that do not require review and approval. IANA will be the
repository for such registrations.
- by providing syntax in the protocol so that implementers may add
private (i.e. unregistered) attributes and enumerated attribute
values.
- by providing versioning and negotiation so as to enable future
implementations of IPP to interoperate with implementations of
version 1.0 of IPP.
4.4. FIREWALLS
As stated in section 3 Design Goals, Internet printing shall, by
definition, support printing from one enterprise to another. As
such, the Internet printing protocol must be capable of passing
through firewalls and/or proxy servers (where enabled by the firewall
administrator) preferably without modification to the existing
firewall technology.
4.5. INTERNATIONALIZATION
Users of Internet printing will come from all over the world. As
such, where appropriate, internationalization and localization will
be enabled for the protocol.
5. IPP SCENARIOS
Each of the scenarios in this section describes a specific IPP
operation, such as submitting a print job. Section 10 contains
several detailed flows for each scenario to provide additional
detail. The examples should not be considered exhaustive, but
illustrative of the functions and features required in the protocol.
Flows are intended to be protocol neutral. It is not assumed that all
of the functions and features described in these scenarios will
necessarily be supported directly by IPP or in version 1.0 of IPP.
See the IPP Model and Semantics document for details on
configurations of clients, servers and firewalls.
5.1. PRINTER DISCOVERY
Client Directory Service
Service
+----------------------------------------------------------- >
give me information on printers with these characteristics
< -----------------------------------------------------------+
Information on Printers matching these characteristics
The objective of printer discovery is to locate printers that meet
the client"s wants and needs. The Directory Service should provide
enough information for the client to make an initial choice. The
client may have to connect to each individual Printer offered to get
more detail. Not all information available from the Directory
Service is obtained using IPP; some information may be
administratively provided.
The actual protocol used between client and Directory or Name Service
is considered outside the scope of IPP. Printer Discover is included
in the scenarios to provide design goals for the directory schema for
IPP Printers and to further define Printer attributes.
Characteristics that might be considered when locating a Printer
include:
- capabilities of the Printer, e.g. PDLs supported
- physical location, e.g. in building 010
- driver required and location
- cost per page to print (outside the scope of IPP)
- whether or not printer is access controlled
- whether or not usage requires client authentication
- whether or not Printer can be authenticated
- whether or not payment is required for printing (outside the scope
of IPP)
- maximum job size (spool size) (outside the scope of IPP)
- whether or not Printer support compression (outside the scope of
IPP)
- whether or not Printer supports encryption
- administrative limits on this Printer
- maximum number of copies per job
- maximum number of pages per job
Responses could additionally include:
- how to get more information
- web page
- telephone number
- help desk
5.2. DRIVER INSTALLATION
Client Printer
+----------------------------------------------------------- >
Where can I find a driver & software to install it?
< -----------------------------------------------------------+
URIs for drivers and install software
Driver here refers to the code installed in some client operating
system to generate the print data stream for the intended printer.
The actual details for installing a printer driver are operating
system dependent and are also outside the scope of IPP. However, an
IPP printer or a directory service advertising an IPP Printer should
be capable of telling a client what drivers are available and/or
required, where they can be found, and provide pointers to
installation instructions, installation code or initialization
strings required to install the driver. See section 4.1 (SECURITY
CONSIDERATIONS) for security implications of driver download and
installation.
5.3. SUBMITTING A PRINT JOB
Client IPP Printer
+----------------------------------------------------------- >
Here is a Print Job
- Job attributes
- Print data
< -----------------------------------------------------------+
Response
The protocol must support these sources of client data:
- Print data is a file submitted with the job
- Print data is generated on the fly by an application
- Print data is a file referenced by a URI
The protocol must handle overrun conditions in the printer and must
support overlapped printing and downloading of the file in devices
that are unable to spool files before printing them.
Every print request will have a response. Responses will indicate
success or failure of the request and provide information on failures
when they occur. Responses would include things like:
- Got the print job and queued it
- Got the print job and am printing it
- Got the print job, started to print it, but printing failed
- why it failed (e.g. unrecoverable PostScript error)
- state of the printer
- how much printed
- Got the print job but couldn"t print it
- why it can"t be printed
- state of the printer
- Got the print job but don"t know what to do with it
- Didn"t get a complete print job (e.g. communication failure)
5.4. GETTING STATUS/CAPABILITIES
Client IPP Printer
+----------------------------------------------------------- >
Get status and/or capabilities of Printer
< -----------------------------------------------------------+
Status/Capabilities
Clients will need to get information about
- Static capabilities of the device
- Dynamic state of the Printer (e.g. out of paper)
- State of a specific job owned by this client
- State of all jobs owned by this client
- queued
- printing
- completed
- Job submission attributes supported/required
- scheduling attributes (e.g. priority)
- production attributes (e.g. number of copies)
5.5. ASYNCHRONOUS NOTIFICATION
Client IPP Printer
+----------------------------------------------------------- >
Use the following method to notify me of Printer events
.
.
.
< -----------------------------------------------------------+
Asynchronous notification of Printer event
Clients must be able to request asynchronous notification for Printer
events such as
- job completion
- a fatal error that requires the job to be resubmitted
- a condition that severely impacts a queued job for this client
e.g. printer is out of paper
Note: end-user notification is a V1.0 design goal while operator
notification is for V2.0.
5.6. JOB CANCELING
Client IPP Printer
+----------------------------------------------------------- >
Cancel the named job as indicated
< -----------------------------------------------------------+
Response (did it or not)
Similarly clients must be able to make changes to jobs which have
been submitted and are queued for printing. Changing of job
attributes should also be supported. Job modifications, holding and
releasing of jobs are not included in the design goals for IPP v1.0.
6. SECURITY CONSIDERATIONS
The security considerations for IPP are described in Section 4.1
above.
7. REFERENCES
[ipp-iig] Hastings, T. and C. Manros, "Internet Printing
Protocol/1.0: Implementer"s Guide", Work in Progress.
[RFC2569] Herriot, R., Hastings, T., Jacobs, N. and J. Martin,
"Mapping between LPD and IPP Protocols", RFC2569, April
1999.
[RFC2566] deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P.
Powell, "Internet Printing Protocol/1.0: Model and
Semantics", RFC2568, April 1999.
[RFC2565] Herriot, R., Butler, S., Moore, P. and R. Tuner, "Internet
Printing Protocol/1.0: Encoding and Transport", RFC2565,
April 1999.
[RFC2568] Zilles, S., "Rationale for the Structure and Model and
Protocol for the Internet Printing Protocol", RFC2568,
April 1999.
[ISO10175] ISO/IEC 10175, Document Printing Application, June 1996.
[RFC1179] McLaughlin, L., "Line Printer Daemon Protocol" RFC1179,
August 1990.
[SSL] Netscape, The SSL Protocol, Version 3, (Text version
3.02), November 1996.
8. ACKNOWLEDGMENTS
This document draws heavily from preliminary work done by others
especially in the Printer Working Group (PWG). The author gratefully
acknowledges the specific contributions of:
Scott Isaacson Roger deBry
Novell Utah Valley State College
sisaacson@novell.com debryro@uvsc.edu
Carl-Uno Manros Robert Herriot
Xerox Sun
manros@cp10.es.xerox.com Robert.Herrior@pahv.xerox.xom
Tom Hastings Peter Zehler
Xerox Xerox
hastings@cp10.es.xerox.com Peter.Zehler@usa.xerox.com
9. AUTHOR"S ADDRESS
F.D. (Don) Wright
Lexmark International
C14/035-3
740 New Circle Rd
Lexington, KY 40550
Phone: 606-232-4808
Fax: 606-232-6740
EMail: don@lexmark.com
10. APPENDIX - DETAILED SCENARIOS
The following are more detailed scenarios illustrating how the
Internet Printing Protocol is expected to be used as a part of a
complete Internet Printing system. Some parts of the scenarios
include concepts, functions and information that may be outside of
the scope of version 1.0 of IPP (e.g. cost per page, payments means
available, etc.) The information contained herein is meant to be
generic. There may not be an exact wording or terminology match
between these scenarios and the implementation documents.
10.1. PRINTER DISCOVERY WITHIN AN ENTERPRISE
A user wants to find a color Postscript printer in his/her enterprise
which will print transparencies. The client, directory service, and
printer are all behind the same corporate firewall. Because color
foils are expensive, printers of this type are access controlled and
require an account to be established so that printing can be billed
back to the using department. Note the request to find a printer
usable by Dept. J15. Drivers for all supported printers are
available from the server they are associated with. A help desk is
provided for end user support. The printer is unattended.
Client Directory Service
+---------------------------------------------------------- >
Find a printer with these characteristics
- prints color, prints transparencies
- prints Postscript
- is in building 003
- accessible by the client
< ----------------------------------------------------------+
Printer "Color-A"
- prints color, prints transparencies
- prints Postscript
- in room H-6, building 003
- driver ABC-Postscript-V1.3 required, here is URI
- cost is $.45 per page for color transparencies
- limit is 10 pages per job
- authentication required to use printer
- printer is unattended
- help desk at x5001
Printer "Color-B"
- prints color, prints transparencies
- prints Postscript
- in room J-10, building 003
- driver XYZ-Postscript-V2.4 required, here is URI
- cost is $1.25 page for color transparencies
- limit is 5 pages per job
- authentication is required to use printer
- printer is unattended
- help desk at x5001
10.2. PRINTER DISCOVERY ACROSS ENTERPRISES
A user in Company A wants to find a public printer in a business
partner"s enterprise (Company B) on which to print a purchase order.
The client is behind one corporate firewall and the directory service
and the printer are behind a different corporate firewall. Drivers
for all supported printers are available from the server they are
associated with. A web page is provided for end user support for
public printers.
Client Company B Directory Service
+---------------------------------------------------------- >
Find a printer with these characteristics
- prints black and white
- is in El Segundo, building A
- is a public printer
< ----------------------------------------------------------+
Printer "Public-A"
- prints black and white
- prints Postscript
- in El Segundo, room H-6, building A
- driver ABC-Postscript-V1.3 required, here is URI
- printer is public
- help available at http://xerox/elSegundo/publicPrinters
Printer "Public-B"
- prints black and white
- prints PCL/5e
- is in El Segundo, room J-10, building A
- driver XYZ-PCL-V2.4 required, here is URI
- printer is public
- help available at http://xerox/elSegundo/publicPrinters
10.3. PRINTER DISCOVERY ON THE INTERNET -LOGICAL OPERATIONS
A student wants to print a paper on a printer at his neighborhood
Ink-o"s print shop. The report was written using Microsoft Word. The
student is interested in the cost of printing since his budget is
limited. Note the use of logical operators to find this information.
Client Ink-o"s Directory Service
+---------------------------------------------------------- >
Find a Printer with these characteristics
- prints color or black and white
- costs less than $.50 per page
- tell me about resolution and marking technology
< ----------------------------------------------------------+
Printer "Color-A"
- prints color
- 600 dpi laser printer
- prints Postscript
- driver ABC-Postscript-V1.3 required, here is URI
- cost is $.50 per page for color
- payment required prior to submitting print job
- here is URI for more information on Ink-o"s
Printer "Mono-B"
- prints black and white
- 300 dpi inkjet printer
- prints Postscript
- driver XYZ-Postscript-V2.4 required, here is URI
- cost is $0.35 page for black and white
- payment required prior to submitting print job
- here is URI for more information on Ink-o"s
10.4. PRINTER DISCOVERY ON THE INTERNET - AUTHENTICATION
An executive in her hotel room is finishing an important presentation
on her laptop computer. She connects to a local print shop through
the web to get a copy of her charts printed for tomorrow"s
presentation. She must find a print shop that is convenient to her
hotel and can print color transparencies. She wants to be sure that
the printer can be authenticated and can accept encrypted data.
Client SirZippy Directory Service
+---------------------------------------------------------- >
Find a Printer with these characteristics
- prints color transparencies
- is in Boulder, Colorado
- Printer can be authenticated
- Printer supports encryption
Tell me when you are open for business
< ----------------------------------------------------------+
Printer "Color-A"
- prints color transparencies
- prints Postscript
- driver ABC-Postscript-V1.3 required, here is URI
- payment required prior to submitting print job
- Printer can be authenticated
- Data can be encrypted
- Located at 1670 Pearl Street, Boulder, CO
- This Branch is open 24 hours a day
Printer "Color-B"
- prints color transparencies
- prints Postscript
- driver ABC-Postscript-V1.3 required, here is URI
- payment required prior to submitting print job
- Printer can be authenticated
- Data can be encrypted
- Located at 1220 Arapahoe, Boulder, CO
- This Branch is open from 9:00 am to 6:30 pm
10.5. DRIVER DOWNLOAD
An end user in an enterprise wants to print a lengthy report on a
newly installed high speed PostScript printer. Since she will likely
use this printer often, she would like to download a driver and
install it on her workstation. She is running Windows 95. Note:
Driver download is not a V1.0 design goal.
Client IPP Printer
+---------------------------------------------------------- >
Tell me where to find print drivers for you
< ----------------------------------------------------------+
Driver install file is at
http://www.ibm.com/drivers/NP12a/Win95
10.6. SUBMITTING A PRINT JOB AS A FILE
An end-user wants to submit a print job. The print file already
exists on his workstation. The client and printer are behind the same
corporate firewall. The printer is available to anyone behind the
firewall and no authorization or authentication is required. The data
is pushed to the printer. The printer is capable of spooling the
output. No errors occur.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print job accepted and spooled
- job id = #12345
- current state of print job = spooled
- submission time = 02/12/97, 15:35
- printer state = printing
10.7. SUBMITTING A PRINT JOB WITH TWO DOCUMENTS
An end-user wants to submit a print job. The print file already
exists on his workstation. The client and printer are behind the same
corporate firewall. The printer is available to anyone behind the
firewall and no authorization or authentication is required. The data
is pushed to the printer. The job consists of two separate documents.
The printer is capable of spooling the output. No errors occur.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
< ----------------------------------------------------------+
Print job accepted and spooled
- job id = #12345
- submission time = 02/12/97, 15:35
+---------------------------------------------------------- >
- here is the document to print
< ----------------------------------------------------------+
- OK
+---------------------------------------------------------- >
- here is the document to print, it is the last document.
< ----------------------------------------------------------+
- OK
10.8. SUBMITTING A PRINT JOB AS A FILE, PRINTING FAILS
An end-user wants to submit a print job. The print file already
exists on his workstation. The client and printer are behind the same
corporate firewall. The printer is available to anyone behind the
firewall and no authorization or authentication is required. The data
is pushed to the printer. The printer is not capable of spooling the
output so it begins printing while still receiving the file. An error
occurs and the printer cannot complete printing (in this case the
user requires A4 paper and that paper size is not available on the
printer.)
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print job accepted
- printing failed
- current state of print job = canceled (A4 not available)
- submission time = 02/12/97, 15:35
- printer state = ready
10.9. SUBMITTING A PRINT JOB WITH AUTHENTICATION, PRIVACY AND PAYMENT
A traveling executive needs to print a set of transparencies for an
important business meeting. The charts are in Lotus Freelance format
on his notebook computer. He has located a SirZippy print shop near
his hotel that will print color transparencies. Because the
information on the charts is sensitive, he wants to be sure that his
data is sent to the Printer in an encrypted format. He also wants to
authenticate the Printer. The Printer also authenticates the user.
Payment occurs across the Internet.
Client IPP Printer
+---------------------------------------------------------- >
< ----------------------------------------------------------+
Mutual authentication and exchange of secret keys
+---------------------------------------------------------- >
Here is a print job (encrypted)
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- tell me where to pick up output
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print job accepted and spooled (encrypted)
- job id = #12345
- current state of print job = spooled
- submission time = 02/12/97, 15:35
- printer state = printing
- payment required to proceed with job
- pick up at 230 East Main after 3:30 pm today
+---------------------------------------------------------- >
< ----------------------------------------------------------+
Payment transaction
10.10. SUBMITTING A PRINT JOB WITH DECRYPTION ERROR
A traveling executive needs to print a set of transparencies for an
important business meeting. The charts are in Lotus Freelance format
on his notebook computer. He has located a SirZippy print shop near
his hotel that will print color transparencies. Because the
information on the charts is sensitive, he wants to be sure that his
data is sent to the printer in an encrypted format. He also wants to
authenticate the printer. The printer also authenticates the user.
Payment occurs across the Internet. An error occurs during
decryption.
Client IPP Printer
+---------------------------------------------------------- >
< ----------------------------------------------------------+
Mutual authentication and exchange of secret keys
+---------------------------------------------------------- >
Here is a print job (encrypted)
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- tell me where to pick up output
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print job accepted and spooled (encrypted)
- job id = #12345
- current state of print job = spooled
- submission time = 02/12/97, 15:35
- printer state = printing
- payment required to proceed with job
- pick up at 230 East Main after 3:30 pm today
+---------------------------------------------------------- >
< ----------------------------------------------------------+
Payment transaction
.
.
.
< ----------------------------------------------------------+
Asynchronous response (email in this case)
- decryption failed on job #12345
- no pages printed
- current state of job = aborted
10.11. SUBMITTING A PRINT JOB WITH AUTHENTICATION
An end-user wants to submit a print job. The print file already
exists on his workstation. The client and printer are behind the same
corporate firewall. The printer is available to anyone behind the
firewall but authentication and authorization is required.
Authorization takes place using the authenticated end-user"s name.
The data is pushed to the printer. The printer is capable of spooling
the output.
Client IPP Printer
+---------------------------------------------------------- >
< ----------------------------------------------------------+
Authentication
Note: An authentication failure would end the transaction at
this point.
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- tell me where to pick up output
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print job accepted and spooled
- job id = #12345
- current state of print job = spooled
- submission time = 02/12/97, 15:35
- printer state = printing
10.12. SUBMITTING A PRINT JOB GENERATED DYNAMICALLY
An end-user wants to submit a print job. The print data is generated
dynamically and is being transmitted by a printer driver on the
client workstation as available. The client and printer are behind
the same corporate firewall. The printer is available to anyone
behind the firewall and no authentication and authorization is
required. The data is pushed to the printer. The printer is capable
of spooling the output. No error occurs.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- document is in Postscript format
- here is the print job
< ----------------------------------------------------------+
Print data accepted and spooling started
- job id = #12345
- current job state = spooled
- submission time = 02/12/97, 15:35
- printer state = printing
10.13. SUBMITTING A PRINT JOB WITH A PRINTER JAM - CANCELED
An end-user wants to submit a print job. The print data is generated
dynamically and is being transmitted by a printer driver on the
client workstation as available. The client and printer are behind
the same corporate firewall. The printer is available to anyone
behind the firewall and no authentication and authorization is
required. The data is pushed to the printer. The printer is not
capable of spooling the output. The printer jams notifies the user
and the user chooses to cancel the job.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print data accepted and printing started
- job id = #12345
+---------------------------------------------------------- >
- What is the status of print job #12345?
< --------------------------------------------------------- +
- Job #12345 accepted but printer jammed, cannot continue
+---------------------------------------------------------- >
- Cancel job #12345
* Printer flushes remaining data
< ----------------------------------------------------------+
Print job terminated
- current job state = canceled
- submission time = 02/12/97, 15:35
- printer state = jammed
10.14. SUBMITTING A PRINT JOB WITH A PRINTER JAM - RECOVERED
An end-user wants to submit a print job. The print data is generated
dynamically and is being transmitted by a printer driver on the
client workstation as available. The client and printer are behind
the same corporate firewall. The printer is available to anyone
behind the firewall and no authentication and authorization is
required. The data is pushed to the printer. The printer is not
capable of spooling the output. The printer jams, notifies the user
and the user clears the jam and elects to continue.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- document is in Postscript format
- here is the document to print
< ----------------------------------------------------------+
Print data accepted and printing started
- job id = #12345
< --------------------------------------------------------- +
- Notification: printer jammed, cannot continue
* Jam is clear by human intervention, printing continues
+---------------------------------------------------------- >
Here is the last part of the document to print
< ----------------------------------------------------------+
Print job received
- current job state = printing
- submission time = 02/12/97, 15:35
- printer state = printing
10.15. SUBMITTING A PRINT JOB WITH SERVER PULL
An end-user wants to submit a print job. The print data is in a file
and is publicly available. It is pulled by the printer. The client
and printer are behind the same corporate firewall. The printer is
available to anyone behind the firewall and no authentication and
authorization is required. The printer is capable of spooling the
output. Printing may start before the entire job has been pulled.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
- here is a reference to the data to be printed
< ----------------------------------------------------------+
Print data accepted and printing started
- job id = #12345
- current state of job = spooled
- submission time = 02/12/97, 13:15
- printer state = printing
.
.
< ----------------------------------------------------------+
Get the file to be printed
+---------------------------------------------------------- >
Here it is
Note: Failure to find the file, would end the transaction
with an error at this point and an asynchronous
notification would be send to the Client.
< ----------------------------------------------------------+
Data received
10.16. SUBMITTING A PRINT JOB WITH REFERENCED RESOURCES
An end-user wants to submit a print job. Part of the print data is
on a file on the user"s workstation. It is pushed by the client, but
the print job requires some resource not included in the print file.
The client and printer are behind the same corporate firewall. The
printer is available to anyone behind the firewall and no
authentication and authorization is required. The printer is capable
of spooling the output. No errors occur.
Client IPP Printer
+---------------------------------------------------------- >
Here is a print job
- job name = MyJob
- notify me by email when done printing
- print on iso-a4-white paper
- print on both sides of the paper
- return status of the printer in response
< ----------------------------------------------------------+
Print job accepted and spooled
- job id = #12345
- submission time = 02/12/97, 15:35
+---------------------------------------------------------- >
- here is the document to print
< ----------------------------------------------------------+
- OK
+---------------------------------------------------------- >
- here is the URI to print, it is the last document.