Internet Printing Protocol WG Tom Hastings (editor)
INTERNET DRAFT Xerox Corporation
<draft-ietf-ipp-not-06.txt> Roger K deBry
[Target Category: Informational] Utah Valley State College
Expires: January 17, 2002 Harry Lewis
IBM Corporation
July 17, 2001
Internet Printing Protocol (IPP): Requirements for IPP Notifications
Copyright (C) The Internet Society (2001). All Rights Reserved.
STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026]. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ''work in progress.''
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed as
http://www.ietf.org/shadow.html.
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
on the Internet. There are multiple parts to IPP, but the primary
architectural components are the Model, the Protocol and an interface
to Directory Services. This document provides a statement of the
requirements for notifications as an optional part of an IPP Service.
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Table of Contents
1 Scope............................................................3
2 Terminology......................................................3
3 Scenarios........................................................7
4 Requirements....................................................11
5 Security considerations for IPP Notifications requirements......13
6 Internationalization Considerations.............................14
7 IANA Considerations.............................................14
8 References......................................................14
9 Author's Address................................................15
10 Appendix A: Description of the Base IPP Documents..............16
11 Appendix B: Full Copyright Statement...........................17
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1 Scope
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
on the Internet. There are multiple parts to IPP, but the primary
architectural components are the Model, the Protocol and an interface
to Directory Services. This document provides a statement of the
requirements for notifications as an optional part of an IPP Service.
See section 10 for a description of the base IPP documents.
The scope of this requirements document covers functionality used by
the following kinds of IPP Users: End Users, Print Administrators and
Operators. See [ipp-ntfy] for the extensions to the Internet
Printing Protocol/1.0 (IPP) [RFC2565, RFC2566], IPP/1.1 [RFC2911,
RFC2910], and future versions.
2 Terminology
It is necessary to define a set of terms in order to be able to
clearly express the requirements for notification services in an IPP
System.
2.1 Job Submitting End User
A human end user who submits a print job to an IPP Printer. This
person may or may not be within the same security domain as the
Printer. This person may or may not be geographically near the
printer.
2.2 Administrator
A human user who established policy for and configures the print
system.
2.3 Operator
A human user who carries out the policy established by the
Administrator and controls the day to day running of the print
system.
2.4 Job Submitting Application
An application (for example, a batch application), acting on behalf
of a Job Submitting End User, which submits a print job to an IPP
Printer. The application may or may not be within the same security
domain as the Printer. This application may or may not be
geographically near the printer.
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2.5 Security Domain
For the purposes of this discussion, the set of network components
which can communicate without going through a proxy or firewall. A
security domain may be geographically very large, for example -
anyplace within IBM.COM.
2.6 IPP Client
The software component that sends IPP requests to an IPP Printer
object and accepts IPP responses from an IPP Printer.
2.7 Job Recipient
A human who is the ultimate consumer of the print job. In many cases
this will be the same person as the Job Submitting End User, but this
need not always be the case. For example, if I use IPP to print a
document on a printer in a business partner's office, I am the Job
Submitting End User, while the person I intend the document for in my
business partner's office is the Job Recipient. Since one of the
goals of IPP is to be able to print near the Job Recipient of the
printed output, we would normally expect that person to be in the
same security domain as, and geographically near, the Printer.
However, this may not always be the case. For example, I submit a
print job across the Internet to a Kinko's print shop. I am both the
Submitting end User and the Job Recipient, but I am neither near nor
in the same security domain as the Printer.
2.8 Job Recipient Proxy
A person acting on behalf of the Job Recipient. In particular, the
Job Recipient Proxy physically picks up the printed document from the
Printer, if the Job Recipient cannot perform that function. The Proxy
is by definition geographically near and in the same security domain
as the printer. For example, I submit a print job from home to be
printed on a printer at work. I'd like my secretary to pick up the
print job and put it on my desk. In this case, I am acting as both
Job Submitting End User and Job Recipient. My secretary is acting as
a Job Recipient Proxy.
2.9 Notification Subscriber
A client that requests the IPP Printer to send Event Notifications to
one or more Notification Recipients. A Notification Subscriber may
be a Job Submitting End User or an End User, an Operator, or an
Administrator that is not submitting a job.
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2.10 Notification Source
The entity that sends Event Notifications.
2.11 Notification Recipient
The entity that receives IPP Notifications about Job and/or Printer
events. A Notification Recipient may be a: Job Submitting End User,
Job Submitting Application, Job Recipient, Job Recipient Proxy,
Operator, or Administrator, etc., and their representatives or log
file or usage statistics gathering application or other active or
passive entities.
2.12 Notification Recipient Agent
A program which receives Event Notifications on behalf of the
Notification Recipient. The agent may take some action on behalf of
the recipient, forward the notification to the recipient via some
alternative means (for example, page the recipient), or queue the
notification for later retrieval by the recipient.
2.13 Event
A Event is some occurrence (either expected or unexpected) within the
printing system of a change of state, condition, or configuration of
a Job or Printer object.
2.14 Event Notification
When an event occurs, an Event Notification is generated that fully
describes the event (what the event was, where it occurred, when it
occurred, etc.). Event Notifications are delivered to all the
Notification Recipients that are subscribed to that Event, if any.
The Event Notification is delivered to the address of the
Notification Recipient using the notification delivery method defined
in the subscription. However, an Event Notification is sent ONLY if
there is a corresponding subscription.
2.15 Notification Subscription
A Notification Subscription is a request by a Notification Subscriber
to the IPP Printer to send Event Notifications to specified
Notification Recipient(s) when the event occur.
2.16 Notification Attributes
IPP Objects (for example, a print job) from which notification are
being sent may have attributes associated with them. A user may want
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to have one or more of these associated attributes returned along
with a particular notification. In general, these may include any
attribute associated with the object emitting the notification.
Examples include:
number-of-intervening jobs
job-k-octets
job-k-octets processed
job impressions
job-impressions-interpreted
job-impressions-completed
impressionsCompletedCurrentCopy (job MIB)
sheetCompletedCopyNumber (job MIB)
sheetsCompletedDocumentNumber (job MIB)
Copies-requested
Copy-type
Output-destination
Job-state-reasons
Job ID
Printer URI
Subscription ID (for job independent subscription)
2.17 Notification Delivery Method (or Delivery Method for short)
Event Notifications are delivered using a method, such as email,
TCP/IP, etc.
2.18 Immediate Notification
Notifications sent to the Notification Recipient or the Notification
Recipient's agent in such a way that the notification arrives
immediately , within the limits of common addressing, routing,
network congestion and quality of service.
2.19 Store and Forward Notification
Notifications which are not necessarily delivered to Notification
Recipients immediately, but are queued for delivery by some
intermediate network application, for later retrieval. Email is an
example of a store and forward notification delivery method.
2.20 Reliable Delivery of Notifications
Notifications which are delivered by a reliable delivery of packets
or character stream, with acknowledgment and retry, such that
delivery of the notification is guaranteed within some determinate
time limits. For example, if the Notification Recipient has logged
off and gone home for the day, an immediate notification cannot be
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guaranteed to be delivered, even when sent over a reliable transport,
because there is nothing there to catch it. Guaranteed delivery
requires both store and forward notification and a reliable
transport.
2.21 Notification over Unreliable Transport
Notifications are delivered via the fundamental transport address and
routing framework, but no acknowledgment or retry is required.
Process to process communications, if involved, are unconstrained.
2.22 Human Consumable Notification
Notifications which are intended to be consumed by human end users
only. Email would be an example of a Human consumable notification,
though it could also contain Machine Consumable Notification.
2.23 Machine Consumable Notification
Notifications which are intended for consumption by a program only,
such as an IPP Client. Machine Consumable notifications may not
contain human readable information. Do we need both human and
machine? Machine readable is intended for application to application
only. The Notification Recipient could process the machine readable
Event Notification into human readable format.
2.24 Mixed Notification
A mixed notification contains both Human Consumable and Machine
Consumable information.
3 Scenarios
1.I am sitting in my office and submit a print job to the printer
down the hall. I am in the same security domain as the printer and
of course, geographically near. I want to know immediately when
my print job will be completed (or if there is a problem) because
the document I am working on is urgent. I submit the print job
with the following attributes:
? Notification Recipient - me
? Notification Events - all
? Notification Attributes - job-state-reason
? Notification Type - immediate
2.I am working from home and submit a print job to the same printer
as in the previous example. However, since I am not at work, I
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cannot physically get the print file or do anything with it. It
can wait until I get to work this afternoon. However, I'd like my
secretary to pick up the output and put it on my desk so it
doesn't get lost or miss-filed. I'd also like a store and forward
notification sent to my email so that when I get to work I can
tell if there was a problem with the print job. I submit a print
job with the following attributes:
? Notification Recipient - my secretary
? Notification Events - print complete
? Notification Type - immediate
? Notification Recipient - me
? Notification Events - print complete
? Notification Attributes - impressions completed
? Notification Type - store and forward
3.I am sitting in my office and submit a print job to a client at an
engineering firm we work with on a daily basis. The engineering
firm is in Belgium. I would like my client to know when the print
job is complete, so that she can pick it up from the printer in
her building. It is important that she review it right away and
get her comments back to me. I submit the print job with the
following attributes:
? Notification Recipient - client at engineering firm
? Notification Events - print complete
? Notification Type - immediate
? Notification Language - French
4.I am in a hotel room and send a print job to a Kinko's store in
the town I am working in, in order to get a printed report for the
meeting I am attending in the morning. Since I'm going out to
dinner after I get this job submitted, an immediate notification
won't do me much good. However, I'd like to check in the morning
before I drive to the Kinko's store to see if the file has been
printed. An email notification is sufficient for this purpose. I
submit the print job with the following attributes:
? Notification Recipient - me
? Notification Events - print complete
? Notification Type - store and forward
5.I am printing a large, complex print file. I want to have some
immediate feedback on the progress of the print job as it prints.
I submit the print job with the following attributes:
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? Notification Recipient - me
? Notification Type - immediate
? Notification Events - all state transitions
? Notification Attributes - impression completed
6.I am an operator and my duties is to keep the printer running. I
subscribe independently from a job submission so that my
subscription outlasts any particular job. I subscribe with the
following attributes:
? Notification Recipient - me
? Notification Type - immediate
? Notification Events - all Printer state transitions
? Notification Attributes - Printer state, printer state reasons,
device powering up, device powering down.
7.I am a usage statistics gathering application. I subscribe
independently from a job submission so that my subscription
outlasts any particular job. My subscription may persists across
power cycles. I subscribe with the following attributes:
? Notification Recipient - me
? Notification Type - immediate
? Notification Events - job completion
? Notification Attributes - impression completed, sheets
completed, time submitted, time started, time completed, job
owner, job size in octets, etc.
8.I am a client application program that displays a list of jobs
currently queued for printing on a printer. I display the "job-
name", "job-state", "job-state-reasons", "page-count", and
"intervening-jobs" either for the user's jobs or for all jobs.
The window displaying the job list remains open for an independent
amount of time, and it is desired that it represent the current
state of the queue. It is desired that the application only need
to perform a slow poll in order to recover from any missed
notifications. So the event delivery mechanism provides the means
to update the screen on all needed changes, including querying for
some attributes that may not be delivered in the Notification.
9.I am a client application program that displays a list of
printers. For each Printer I display the current state and
configuration. The window displaying the printer list remains
open for an independent amount of time, and it is desired that it
represent the current state of each printer. It is desired that
the application only need to perform a slow poll in order to
recover from any missed notifications. So the event delivery
mechanism provides the means to update the screen on all needed
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changes, including querying for some attributes that may not be
delivered in the Notification.
10. I am an IPP Server that controls one or more devices and
implements an IPP Printer object to represent each device. I want
to support IPP Notification for each of the IPP Printer objects
that I implement. Many of these devices do not support
notification (or IPP). So I need to support the IPP Notification
semantics specified for each IPP Printer object myself on behalf
of each of the devices that each of the IPP Printer objects
represent. When I accept IPP job creation requests, I convert the
request to what the device will accept. In some cases, I must
poll the devices in order to be informed of their job and device
state and state changes in order to be able to send IPP
Notifications to subscribed Notification Recipients.
11. I am an IPP Server that controls one or more devices and
implements an IPP Printer object to represent each device. I want
to support IPP Notification for each of the IPP Printer objects
that I implement. These devices all support IPP, including IPP
Notification. I would like the design choice for supporting IPP
Notification for these IPP Printer objects that I implement either
(1) by forwarding the notification to the IPP Printers that I
alone control and have them send the notifications to the intended
Notification Recipients without my involvement or (2) replace the
notification submitted with the Job to indicate me as the
Notification Recipient and I will in turn forward Notifications to
the Notification Recipients requested by my clients. Most of the
rest of the contents of the IPP Job that I send to the IPP
Printers that I control will be the same as the IPP Job that I
receive from my IPP clients.
12. I am an IPP Server that controls one or more devices and
implements an IPP Printer object to represent each device. I want
to support IPP Notification for each of the IPP Printer objects
that I implement. These devices all support IPP, including IPP
Notification. Because these IPP Printers MAY also be being
controlled by other servers (using IPP or other protocols), I only
want job events for the jobs that I send, but do want Printer
events all the time, so that I can show proper Printer state to my
clients. So I subscribe to these IPP Printers for Printer events
with a long standing subscription with myself to as the
Notification Recipient. When I get a Job Creation request, I
decide to which IPP Printer to send the job. When I do so, I also
add a job subscription for Job events with me as the Notification
Recipient to the job's job subscriptions supplied by my clients
(this usage is called "piggy-backing"). These IPP Printers
automatically remove their job subscriptions when the job
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completes as for all job subscriptions so that I no longer get Job
events when my jobs are completed.
4 Requirements
The following requirements are intended to be met by the IPP
Notification specification (not the implementation). The resulting
IPP Notification Specification document:
1.must indicate which of these requirements are REQUIRED and which
are OPTIONAL for a conforming implementation to support. See
[RFC2911] section 12.1 for the definition of these important
conformance terms.
2.must be designed to that an IPP Printer can transparently support
the IPP Notification semantics using third party notification
services that exist today or that may be standardized in the
future.
3.must define means for a Job Submitting End User to specify zero or
more Notification Recipients when submitting a print job. A
Submitter will not be able to prevent out of band subscriptions
from authorized persons, such as Operators.
4.must define means when specifying a Notification Recipient, for a
Notification Subscriber to be able to specify one or more
notification events for that Notification Recipient, subject to
administrative and security policy restrictions. Any of the
following constitute Job or Printer Events that a Job Submitting
End User can specify notifications be sent for:
? Any standard Printer MIB alert (i.e. device alerts) (critical
and warning?) (state change notifications)?
? Job Received (transition from Unknown to Pending)
? Job Started (Transition from Pending to Processing)
? Page Complete (Page is stacked)
? Collated Copy Complete (last sheet of collated copy is
stacked)
? Job Complete (transition from Processing or Processing-
stopped to Completed)
? Job aborted (transition from Pending, Pending-held,
Processing, or Processing-stopped to Aborted)
? Job canceled (transition from Pending, Pending-held,
Processing, or Processing-held to Canceled)
? Other job state changes like 'paused', purged?
? Device problems for which the job is destined
? Job (interpreter) issues
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5.must define how an End User or Operator subscribes for:
? Any set of Job Events for a specific job.
? Any set of Printer Events while a specific job is not
complete.
6.must define how an End User or Operator subscribes for the
following without having to submit a Job:
? Any set of Printer Events for a defined period.
? Any set of Job Events for all jobs with no control over which
jobs.
7.must define how the Notification Subscriber is able to specify
either immediate or store and forward notification independently
for each Notification Recipient. The means may be explicit, or
implied by the method of delivery chosen by the Job Submitting End
User.
8.must define common delivery methods, e.g. email, must be defined.
9.must define how an IPP Printer validates its ability to deliver an
Event using the specified delivery scheme. If it does not support
the specified scheme, or the specified scheme is invalid for some
reason, then the IPP Printer accepts and performs the request
anyway and responds indicating the unsupported attribute values.
There is no requirement for the IPP Printer receiving the print
request to validate the identity of an Notification Recipient, nor
the ability of the system to deliver an event to that recipient as
requested (for example, if the Notification Recipient is not at
work today).
10. must define a class of IPP event notification delivery methods
which can flow through corporate firewalls. However, an IPP
printer need not test to guarantee delivery of the notification
through a firewall before accepting a print job.
11. may define means for delivering a notification to the
submitting client when the delivery of an event notification to a
specified Notification Recipient fails. Fall back means of
subscribers determining if notifications have failed, i.e.
polling, may be provided.
12. must define a mechanism for localizing Human Consumable
notifications by the Notification Source.
13. may define a way to specify whether or not event delivery
requires acknowledgement back to the Notification Source.
14. There must be a mechanism defined so that job independent
subscriptions do not become stale and do not require human
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intervention to remove stale subscriptions. However, stale must
not be the inability to deliver an Event Notification , since
temporary Notification delivery problems must be tolerated.
15. A mechanism must be defined so that an Event Subscriber is
able to add an Event Subscription to a Job after the Job has been
submitted.
16. A mechanism must be defined so that a client is able to cancel
an Event Subscription on a job or printer after the job has been
submitted.
17. A mechanism must be defined so that a client can obtain the
set of current Subscriptions.
5 Security considerations for IPP Notifications requirements
By far the biggest security concern is the abuse of notification:
sending unwanted notifications to third parties (i.e., spam). The
problem is made worse by notification addresses that may be
redistributed to multiple parties (e.g. mailing lists). There exist
scenarios where third party notification is required (see Scenario #2
and #3). The fully secure solution would require active agreement of
all recipients before sending out anything. However, requirement #9
("There is no requirement for IPP Printer receiving the print request
to validate the identity of an event recipient") argues against this.
Certain systems may decide to disallow third party notifications (a
traditional fax model).
Clients submitting notification requests to the IPP Printer has the
same security issues as submitting an IPP/1.1 print job request. The
same mechanisms used by IPP/1.1 can therefore be used by the client
notification submission. Operations that require authentication can
use the HTTP authentication. Operations that require privacy can use
the HTTP/TLS privacy.
The notification access control model should be similar to the IPP
access control model. Creating a notification subscription is
associated with a user. Only the creator or an operator can cancel
the subscription. The system may limit the listing of items to only
those items owned by the user. Some subscriptions (e.g. those that
have a lifetime longer than a job) can be done only by privileged
users (operators and/or administrators), if that is the authorization
policy.
The standard security concerns (delivery to the right user, privacy
of content, tamper proof content) apply to the notification delivery.
IPP should use the security mechanism of the delivery method used.
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Some delivery mechanisms are more secure than others. Therefore,
sensitive notifications should use the delivery method that has the
strongest security.
6 Internationalization Considerations
The Human Consumable notification must be localized to the natural
language and charset that Notification Subscriber specifies within
the choice of natural languages and charsets that the IPP Printer
supports.
The Machine Consumable notification data uses the 'application/ipp'
MIME media type. It contains some attributes whose text values are
required to be in the natural language and charset that the
Notification Subscriber specifies within the choice of natural
languages and charsets that the IPP Printer supports. See [RFC2566].
7 IANA Considerations
There will be some notification delivery methods registered with IANA
for use in URLs. These will be defined in other documents.
8 References
[ipp-ntfy]
Isaacson, S., Martin, J., deBry, R., Hastings, T., Shepherd, M.,
Bergman, R., " IPP Event Notification Specification", <draft-ietf-
ipp-not-spec-07.txt>, work in progress, July 17, 2001.
[RFC2565]
Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet Printing
Protocol/1.0: Encoding and Transport", RFC 2565, April 1999.
[RFC2566]
R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell,
"Internet Printing Protocol/1.0: Model and Semantics", RFC 2566,
April 1999.
[RFC2567]
Wright, D., "Design Goals for an Internet Printing Protocol", RFC
2567, April 1999.
[RFC2568]
Zilles, S., "Rationale for the Structure and Model and Protocol for
the Internet Printing Protocol", RFC 2568, April 1999.
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[RFC2569]
Herriot, R., Hastings, T., Jacobs, N., Martin, J., "Mapping between
LPD and IPP Protocols", RFC 2569, April 1999.
[RFC2639]
T. Hastings, C. Manros. "Internet Printing Protocol/1.0:
Implementer's Guide", RFC 2639, July 1999.
[RFC2910]
Herriot, R., Butler, S., Moore, P., Turner, R., "Internet Printing
Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.
[RFC2911]
deBry, R., , Hastings, T., Herriot, R., Isaacson, S., Powell, P.,
"Internet Printing Protocol/1.1: Model and Semantics", RFC 2911,
September 2000.
9 Author's Address
Harry Lewis
HUC/003G
IBM Corporation
P.O. Box 1900
Boulder, CO 80301-9191
Phone: (303) 924-5337
Fax: (303) 924-9889
e-mail:
[email protected]
Roger deBry
Utah Valley State College
Orem, UT 84058
Phone: (801) 222-8000
e-mail:
[email protected]
Tom Hastings (editor)
Xerox Corporation
737 Hawaii St. ESAE 231
El Segundo, CA 90245
Phone: 310-333-6413
Fax: 310-333-5514
e-mail:
[email protected]
IPP Web Page:
http://www.pwg.org/ipp/
IPP Mailing List:
[email protected]
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To subscribe to the ipp mailing list, send the following email:
1) send it to
[email protected]
2) leave the subject line blank
3) put the following two lines in the message body:
subscribe ipp
end
Implementers of this specification document are encouraged to join
the IPP Mailing List in order to participate in any discussions of
clarification issues and review of registration proposals for
additional attributes and values. In order to reduce spam the
mailing list rejects mail from non-subscribers, so you must subscribe
to the mailing list in order to send a question or comment to the
mailing list.
10 Appendix A: Description of the Base IPP Documents
The base set of IPP documents includes:
Design Goals for an Internet Printing Protocol [RFC2567]
Rationale for the Structure and Model and Protocol for the Internet
Printing Protocol [RFC2568]
Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
Internet Printing Protocol/1.1: Encoding and Transport [RFC2910]
Internet Printing Protocol/1.1: Implementer's Guide [IPP-IIG]
Mapping between LPD and IPP Protocols [RFC2569]
The "Design Goals for an Internet Printing Protocol" 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. It calls out a subset of end user requirements that
are satisfied in IPP/1.0 [RFC2566, RFC2565]. A few OPTIONAL operator
operations have been added to IPP/1.1 [RFC2911, RFC2910].
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 specification documents, and gives background and rationale
for the IETF IPP working group's major decisions.
The "Internet Printing Protocol/1.1: Model and Semantics" document
describes a simplified model with abstract objects, their attributes,
and their operations. The model introduces a Printer and a Job. The
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Job supports multiple documents per Job. The model document also
addresses how security, internationalization, and directory issues
are addressed.
The "Internet Printing Protocol/1.1: Encoding and Transport" document
is a formal mapping of the abstract operations and attributes defined
in the model document onto HTTP/1.1 [RFC2616]. It also defines the
encoding rules for a new Internet MIME media type called
"application/ipp". This document also defines the rules for
transporting over HTTP a message body whose Content-Type is
"application/ipp". This document defines the 'ipp' scheme for
identifying IPP printers and jobs.
The "Internet Printing Protocol/1.1: Implementer's Guide" document
gives insight and advice to implementers of IPP clients and IPP
objects. It is intended to help them understand IPP/1.1 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.
11 Appendix B: Full Copyright Statement
Copyright (C) The Internet Society (1998,1999,2000,2001). All Rights
Reserved
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
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The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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