INTERNET-DRAFT Robert Herriot (editor)
<draft-ietf-ipp-notify-get-02.txt> Xerox Corp.
[Target category: standards track] Carl Kugler
IBM, Corp.
Harry Lewis
IBM, Corp.
February 28, 2001
Internet Printing Protocol (IPP):
The 'ippget' Delivery Method for Event 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
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The list of current Internet-Drafts can be accessed at
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Abstract
The notification extension document [ipp-ntfy] defines operations
that a client can perform in order to create Subscription Objects in
a Printer and carry out other operations on them. A Subscription
Object represents a Subscription abstraction. The Subscription Object
specifies that when one of the specified Events occurs, the Printer
sends an asynchronous Event Notification to the specified
Notification Recipient via the specified Delivery Method (i.e.,
protocol).
The notification extension document [ipp-ntfy] specifies that each
Delivery Method is defined in another document. This document is one
such document, and it specifies the 'ippget' delivery method.
The 'ippget' Delivery Method is a 'pull and push' Delivery Method.
That is, the Printer saves Event Notification for a period of time
and expects the Notification Recipient to fetch the Event
Notifications (the pull part). The Printer continues to send Event
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Notifications to the Notification Recipient as Events occur (the push
part) if the client has selected the option to wait for additional
Event Notifications.
When a Printer supports this Delivery Method, it holds each Event
Notification for an amount of time, called the Event Notification
Lease Time.
When a Notification Recipient wants to receive Event Notifications,
it performs an IPP operation called 'Get-Notifications', which this
document defines. This operation causes the Printer to return all
Event Notifications held for the Notification Recipient. If the
Notification Recipient has selected the option to wait for additional
Event Notifications, the Printer continues sending Event
Notifications to the Notification Recipient as additional Events
occur.
The basic 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]
Internet Printing Protocol/1.0 & 1.1: IPP Event Notification
Specification [ipp-ntfy]
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. A few OPTIONAL operator operations have
been added to IPP/1.1.
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 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 that are independent of encoding and transport.
It introduces a Printer and a Job object. The Job object optionally
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supports multiple documents per Job. It also addresses security,
internationalization, and directory issues.
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 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 a new scheme named 'ippget'
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.
The "Event Notification Specification" document describes an
extension to the IPP/1.0, IPP/1.1, and future versions. This
extension allows a client to subscribe to printing related Events.
Subscriptions are modeled as Subscription Objects. The Subscription
Object specifies that when one of the specified Event occurs, the
Printer sends an asynchronous Event Notification to the specified
Notification Recipient via the specified Delivery Method (i.e.,
protocol). A client associates Subscription Objects with a
particular Job by performing the Create-Job-Subscriptions operation
or by submitting a Job with subscription information. A client
associates Subscription Objects with the Printer by performing a
Create-Printer-Subscriptions operation. Four other operations are
defined for Subscription Objects: Get-Subscriptions-Attributes, Get-
Subscriptions, Renew-Subscription, and Cancel-Subscription.
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Table of Contents
1 Introduction....................................................6
2 Terminology.....................................................6
3 Model and Operation.............................................7
4 General Information.............................................8
5 Get-Notifications operation....................................10
5.1 Get-Notifications Request...................................12
5.2 Get-Notifications Response..................................13
6 Subscription Template Attributes...............................18
6.1 Subscription Template Attribute Conformance.................18
6.2 Additional Information about Subscription Template Attributes18
6.2.1 notify-recipient-uri (uri)................................18
6.3 Subscription Description Attribute Conformance..............19
7 Additional Printer Description Attributes......................19
7.1 Printer Description Attribute Conformance...................19
7.2 New Values for Existing Printer Description Attributes......19
7.2.1 notify-schemes-supported (1setOf uriScheme)...............19
7.2.2 operations-supported (1setOf type2 enum)..................19
7.3 begin-to-expire-time-interval (integer(0:MAX))..............20
8 New Status Codes...............................................20
8.1 redirection-other-site (0x300)..............................21
9 The IPPGET URL Scheme..........................................21
9.1 The IPPGET URL Scheme Applicability and Intended Usage......21
9.2 The IPPGET URL Scheme Associated Port.......................21
9.3 The IPPGET URL Scheme Associated MIME Type..................21
9.4 The IPPGET URL Scheme Character Encoding....................22
9.5 The IPPGET URL Scheme Syntax in ABNF........................22
9.5.1 IPPGET URL Examples.......................................23
9.5.2 IPPGET URL Comparisons....................................23
10 Encoding.......................................................24
11 Conformance Requirements.......................................24
11.1 Conformance for IPP Printers................................24
11.2 Conformance for IPP Clients.................................25
12 IANA Considerations............................................25
12.1 Operation Registrations.....................................26
12.2 Additional values of existing attributes....................26
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12.2.1 Additional values for the "notify-schemes-supported" Printer
attribute..............................................26
12.2.2 Additional values for the "operations-supported" Printer
attribute..............................................26
12.3 Attribute Registrations.....................................27
12.4 Status code Registrations...................................27
13 Internationalization Considerations............................27
14 Security Considerations........................................27
15 References.....................................................28
16 Authors' Addresses.............................................29
17 Full Copyright Statement.......................................30
Table of Tables
Table 1 - Information about the Delivery Method....................9
Table 2 - Attributes in Event Notification Content................16
Table 3 - Additional Attributes in Event Notification Content for Job
Events ........................................................17
Table 4 - Combinations of Events and Subscribed Events for "job-
impressions-completed" ........................................17
Table 5 - Additional Attributes in Event Notification Content for
Printer Events ................................................18
Table 6 - Operation-id assignments................................20
Table 7 - The "event-notification-attributes-tag" value...........24
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1 Introduction
The notification extension document [ipp-ntfy] defines operations
that a client can perform in order to create Subscription Objects in
a Printer and carry out other operations on them. A Subscription
Object represents a Subscription abstraction. The Subscription Object
specifies that when one of the specified Events occurs, the Printer
sends an asynchronous Event Notification to the specified
Notification Recipient via the specified Delivery Method (i.e.,
protocol).
The notification extension document [ipp-ntfy] specifies that each
Delivery Method is defined in another document. This document is one
such document, and it specifies the 'ippget' delivery method.
The 'ippget' Delivery Method is a 'pull and push' Delivery Method.
That is, the Printer saves Event Notification for a period of time
and expects the Notification Recipient to fetch the Event
Notifications (the pull part). The Printer continues to send Event
Notifications to the Notification Recipient as Events occur (the push
part) if the client has selected the option to wait for additional
Event Notifications.
When a Printer supports this Delivery Method, it holds each Event
Notification for an amount of time, called the Event Notification
Lease Time.
When a Notification Recipient wants to receive Event Notifications,
it performs an IPP operation called 'Get-Notifications', which this
document defines. This operation causes the Printer to return all
Event Notifications held for the Notification Recipient. If the
Notification Recipient has selected the option to wait for additional
Event Notifications, the Printer the Printer continues to send Event
Notifications to the Notification Recipient as Events occur.
2 Terminology
This section defines the following terms that are used throughout
this document:
Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD
NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to
conformance to this specification. These terms are defined in
[RFC2911 section 13.1 on conformance terminology, most of which is
taken from RFC 2119 [RFC2119].
Event Notification Lease: The lease that is associated with an Event
Notification. When the lease expires, the Printer discards the
associated Event Notification.
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Event Notification Lease Time: The expiration time assigned to a
lease that is associated with an Event Notification.
Event Notification Attributes Group: The attributes group in a
response that contains attributes that are part of an Event
Notification.
For other capitalized terms that appear in this document, see [ipp-
ntfy].
3 Model and Operation
In a Subscription Creation Operation, when the value of the "notify-
recipient-uri" attribute has the scheme 'ippget', the client is
requesting that the Printer use the 'ippget' Delivery Method for the
Event Notifications associated with the new Subscription Object. The
client SHOULD choose a value for the address part of the "notify-
recipient-uri" attribute that uniquely identifies the Notification
Recipient.
When an Event occurs, the Printer MUST generate an Event Notification
and MUST assign it the Event Notification Lease Time. The Printer
MUST hold an Event Notification for its assigned Event Notification
Lease Time. The Printer MUST assign the same Event Notification
Lease Time to each Event Notification.
When a Notification Recipient wants to receive Event Notifications,
it performs the Get-Notifications operation, which causes the Printer
to return all un-expired Event Notifications held for the
Notification Recipient. If the Notification Recipient has selected
the option to wait for additional Event Notifications, the response
to the Get-Notifications request continues indefinitely as the
Printer continues to send Event Notifications in the response as
Events occur. For the Get-Notification operation, the Printer sends
only those Event Notifications that are generated from Subscription
Objects whose "notify-recipient-uri" attribute value equals the value
of the "notify-recipient-uri" Operation Attribute in the Get-
Notifications operation.
If a Notification Recipient performs the Get-Notifications operation
twice in quick succession, it will receive nearly the same Event
Notification both times because most of the Event Notifications are
those that the Printer saves for a few seconds after the Event
occurs. There are two possible differences. Some old Event
Notifications may not be present in the second response because their
Event Notification Leases have expired. Some new Event Notifications
may be present in the second response but not the first response.
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When the Notification Recipient requests Event Notifications for per-
Job Subscription Objects, the Notification Recipient typically
performs the Get-Notifications operation within a second of
performing the Subscription Creation operation. Because the Printer
is likely to save Event Notifications for several seconds, the
Notification Recipient is unlikely to miss any Event Notifications
that occur between the Subscription Creation and the Get-
Notifications operation.
4 General Information
If a Printer supports this Delivery Method, the following are its
characteristics.
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Table 1 - Information about the Delivery Method
Document Method Conformance Delivery Method Realization
Requirement
1. What is the URL scheme name ippget
for the Delivery Method?
2. Is the Delivery Method RECOMMENDED
REQUIRED, RECOMMENDED or
OPTIONAL for an IPP Printer
to support?
3. What transport and delivery
protocols does the Printer
use to deliver the Event
Notification Content, i.e.,
what is the entire network IPP with one new operation.
stack?
4. Can several Event Yes.
Notifications be combined
into a Compound Event
Notification?
5. Is the Delivery Method This Delivery Method is a pull
initiated by the Notification and a push.
Recipient (pull), or by the
Printer (push)?
6. Is the Event Notification Machine Consumable
content Machine Consumable or
Human Consumable?
7. What section in this document Section 5
answers the following
question? For a Machine
Consumable Event
Notification, what is the
representation and encoding
of values defined in section
9.1 of [ipp-ntfy] and the
conformance requirements
thereof? For a Human
Consumable Event
Notification, what is the
representation and encoding
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of pieces of information
defined in section 9.2 of
[ipp-ntfy] and the
conformance requirements
thereof?
8. What are the latency and Same as IPP and the underlying
reliability of the transport HTTP transport
and delivery protocol?
9. What are the security aspects Same as IPP and the underlying
of the transport and delivery HTTP transport
protocol, e.g., how it is
handled in firewalls?
10. What are the content length None
restrictions?
11. What are the additional None
values or pieces of
information that a Printer
sends in an Event
Notification content and the
conformance requirements
thereof?
12. What are the additional None
Subscription Template and/or
Subscription Description
attributes and the
conformance requirements
thereof?
13. What are the additional None
Printer Description
attributes and the
conformance requirements
thereof?
5 Get-Notifications operation
This operation causes the Printer to return all Event Notifications
held for the Notification Recipient.
A Printer MUST support this operation.
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When a Printer performs this operation, it MUST return all and only
those Event Notifications:
1. Whose associated Subscription Object's "notify-recipient-uri"
attribute equals the "notify-recipient-uri" Operation attribute
AND
2. Whose associated Subscription Object's "notify-recipient-uri"
attribute has a scheme value of 'ippget' AND
3. Whose Event Notification Lease Time has not yet expired AND
4. Where the Notification Recipient is the owner of or has read-
access rights to the associated Subscription Object.
The Printer MUST respond to this operation immediately with whatever
Event Notifications it currently holds. If the Notification Recipient
has selected the option to wait for additional Event Notifications,
the Printer MUST continue to send Event Notifications as they occur
until all of the associated Subscription Objects are cancelled. A
Subscription Object is cancelled either via the Cancel-Subscription
operation or by the Printer (e.g. the Subscription Object is
cancelled when the associated Job completes).
Note, the Printer terminates the operation in the same way that it
normally terminates IPP operations. For example, if the Printer is
sending chunked data, it can send a 0 length chunk to denote the end
of the operation or it can close the connection. If the Notification
Recipient wishes to terminate the Get-Notifications operation, it can
close the connection.
The Printer MUST accept the request in any state (see [RFC2911]
"printer-state" and "printer-state-reasons" attributes) and MUST
remain in the same state with the same "printer-state-reasons"
values.
Access Rights: If the policy of the Printer is to allow all users to
access all Event Notifications, then the Printer MUST accept this
operation from any user. Otherwise, the authenticated user (see
[RFC2911] section 8.3) performing this operation MUST either be the
owner of each Subscription Object identified by the "notify-
recipient-uri" Operation attribute (as determined during a
Subscription Creation Operation) or an operator or administrator of
the Printer (see [RFC2911] Sections 1 and 8.5). Otherwise, the IPP
object MUST reject the operation and return: 'client-error-
forbidden', 'client-error-not-authenticated', or 'client-error-not-
authorized' status code as appropriate.
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5.1 Get-Notifications Request
The following groups of attributes are part of the Get-Notifications
Request:
Group 1: Operation Attributes
Natural Language and Character Set:
The "attributes-charset" and "attributes-natural-language"
attributes as described in [RFC2911] section 3.1.4.1.
Target:
The "printer-uri" (uri) operation attribute which is the target
for this operation as described in [RFC2911] section 3.1.5.
Requesting User Name:
The "requesting-user-name" (name(MAX)) attribute SHOULD be
supplied by the client as described in [RFC2911] section 8.3.
"notify-recipient-uri" (url):
The client MUST supply this attribute. The Printer object MUST
support this attribute. The Printer matches the value of this
attribute (byte for byte with no case conversion) against the
value of the "notify-recipient-uri" in each Subscription Object
in the Printer. If there are no matches, the IPP Printer MUST
return the 'client-error-not-found' status code. For each
matched Subscription Object, the IPP Printer MUST return all
unexpired Event Notifications associated with it. The Printer
MUST send additional Event Notifications as Events occur if and
only if the value of the "notify-no-wait" attribute is 'false'
or not supplied by the client (see the next attribute below).
Note: this attribute allows a subscribing client to pick URLs
that are unique, e.g. the client's own URL or a friend's URL,
which in both cases is likely the URL of the person's host. An
application could make a URL unique for each application.
"notify-no-wait" (boolean):
The client MAY supply this attribute. The Printer object MUST
support this attribute. If the value of this attribute is
'false', the Printer MUST send all un-expired Event
Notifications (as defined in the previous attribute) and it
MUST continue to send responses for as long as the Subscription
Objects associated with the specified "notify-recipient-uri"
continue to exist. If the value of this attribute is 'true',
the Printer MUST send all un-expired Event Notifications (as
defined in the previous attribute) and the Printer MUST
conclude the operation without waiting for any additional
Events to occur. If the client doesn't supply this attribute,
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the Printer MUST behave as if the client had supplied this
attribute with the value of 'false'.
5.2 Get-Notifications Response
The following groups of attributes are part of the Get-Notifications
Response:
Group 1: Operation Attributes
Status Message:
In addition to the REQUIRED status code returned in every
response, the response OPTIONALLY includes a "status-message"
(text(255)) and/or a "detailed-status-message" (text(MAX))
operation attribute as described in [RFC2911] sections 13 and
3.1.6.
The Printer can return any status codes defined in [RFC2911].
If the status code is not 'successful-', the Printer MUST NOT
return any Event Notification Attribute groups. The following
is a description of the important status codes:
successful-ok: the response contains all Event Notification
associated with the specified "notify-recipient-uri". If
the specified Subscription Objects have no associated
Event Notification, the response MUST contain zero Event
Notifications.
client-error-not-found: The Printer has no Subscription
Object's whose "notify-recipient-uri" attribute equals
the "notify-recipient-uri" Operation attribute.
server-error-busy: The Printer is too busy to accept this
operation. If the "suggested-ask-again-time-interval"
operation attribute is present in the Operation
Attributes of the response, then the Notification
Recipient SHOULD wait for the number of seconds specified
by the "suggested-ask-again-time-interval" attribute
before performing this operation again. If the
"suggested-ask-again-time-interval" Operation Attribute
is not present, the Notification Recipient should use the
normal network back-off algorithms for determining when
to perform this operation again.
redirection-other-site: The Printer does not handle this
operation and requests the Notification Recipient to
perform the operation with the uri specified by the
"notify-ippget-redirect" Operation Attribute in the
response.
Natural Language and Character Set:
The "attributes-charset" and "attributes-natural-language"
attributes as described in [RFC2911] section 3.1.4.2.
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The Printer MUST use the values of "notify-charset" and
"notify-natural-language", respectively, from one Subscription
Object associated with the Event Notifications in this
response.
Normally, there is only one matched Subscription Object, or the
value of the "notify-charset" and "notify-natural-language"
attributes is the same in all Subscription Objects. If not, the
Printer MUST pick one Subscription Object from which to obtain
the value of these attributes. The algorithm for picking the
Subscription Object is implementation dependent. The choice of
natural language is not critical because 'text' and 'name'
values can override the "attributes-natural-language" Operation
attribute. The Printer's choice of charset is critical because
a bad choice may leave it unable to send some 'text' and 'name'
values accurately.
"printer-up-time" (integer(0:MAX)):
The value of this attribute is the Printer's "printer-up-time"
attribute at the time the Printer sends this response. Because
each Event Notification also contains the value of this
attribute when the event occurred, the value of this attribute
lets a Notification Recipient know when each Event Notification
occurred relative to the time of this response.
"suggested-ask-again-time-interval" (integer(0:MAX)):
The value of this attribute is the number of seconds that the
Notification Recipient SHOULD wait before trying this operation
again when
a) the Printer returns the 'server-error-busy' status code
OR
b) the Printer returns the 'successful-ok' status code and
the client supplied the "notify-no-wait" attribute with a
value of 'true'.
This value is intended to help the client be a good network
citizen.
"notify-ippget-redirect" (uri):
The value of this attribute is uri that the Notification
Recipient MUST use for the Get-Notifications operation. This
attribute is present in the Operation Attributes if and only if
the status code has the value 'redirection-other-site'.
Group 2: Unsupported Attributes
See [RFC2911] section 3.1.7 for details on returning
Unsupported Attributes.
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If the "subscription-ids" attribute contained subscription-ids
that do not exist, the Printer returns them in this group as
value of the "subscription-ids" attribute.
Group 3 through N: Event Notification Attributes
The Printer responds with one Event Notification Attributes
Group per matched Event Notification. The initial matched Event
Notifications are all un-expired Event Notification associated
with the matched Subscription Objects. If the Notification
Recipient has selected the option to wait for additional Event
Notifications, the Printer the subsequent Event Notifications
in the response are Event Notifications associated with the
matched Subscription Objects as the corresponding Event occurs.
From the Notification Recipient's view, the response appears as
an initial burst of data, which includes the Operation
Attributes Group and one Event Notification Attributes Groups
per Event Notification that the Printer is holding. After the
initial burst of data, if the Notification Recipient has
selected the option to wait for additional Event Notifications,
the Notification Recipient receives occasional Event
Notification Attribute Groups. Proxy servers may delay some
Event Notifications or cause time-outs to occur. The client
MUST be prepared to perform the Get-Notifications operation
again when time-outs occur.
Each Event Notification Group MUST start with an 'event-
notification-attributes-tag' (see the section "Encodings of
Additional Attribute Tags" in [ipp-ntfy]).
Each attribute is encoded using the IPP rules for encoding
attributes [RFC2910] and may be encoded in any order. Note:
the Get-Jobs response in [RFC2911] acts as a model for encoding
multiple groups of attributes.
Each Event Notification Group MUST contain all of attributes
specified in section 9.1 ("Content of Machine Consumable Event
Notifications") of [ipp-ntfy] with exceptions denoted by
asterisks in the tables below.
The tables below are copies of the tables in section 9.1
("Content of Machine Consumable Event Notifications") of [ipp-
ntfy] except that each cell in the "Sends" column is a "MUST".
For an Event Notification for all Events, the Printer includes
the attributes shown in Table 2.
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Table 2 - Attributes in Event Notification Content
Source Value Sends Source Object
notify-subscription-id (integer(1:MAX)) MUST Subscription
notify-printer-uri (uri) MUST Subscription
notify-subscribed-event (type2 keyword) MUST Event
Notification
printer-up-time (integer(MIN:MAX)) MUST Printer
printer-current-time (dateTime) * MUST * Printer
notify-sequence-number (integer (0:MAX)) MUST Subscription
notify-charset (charset) MUST Subscription
notify-natural-language (naturalLanguage) MUST Subscription
notify-user-data (octetString(63)) ** MUST Subscription
notify-text (text) MUST Event
Notification
attributes from the "notify-attributes" MUST Printer
attribute ***
attributes from the "notify-attributes" MUST Job
attribute ***
attributes from the "notify-attributes" MUST Subscription
attribute ***
* The Printer MUST send the "printer-current-time" attribute if
and only if it supports the "printer-current-time" attribute on
the Printer object.
** If the associated Subscription Object does not contain a
"notify-user-data" attribute, the Printer MUST send an octet-
string of length 0.
*** If the "notify-attributes" attribute is present on the
Subscription Object, the Printer MUST send all attributes
specified by the "notify-attributes" attribute. Note: if the
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Printer doesn't support the "notify-attributes" attribute, it
is not present on the associated Subscription Object.
For Event Notifications for Job Events, the Printer includes
the additional attributes shown in Table 3.
Table 3 - Additional Attributes in Event Notification Content for
Job Events
Source Value Sends Source
Object
job-id (integer(1:MAX)) MUST Job
job-state (type1 enum) MUST Job
job-state-reasons (1setOf type2 keyword) MUST Job
job-impressions-completed (integer(0:MAX)) * MUST Job
* The Printer MUST send the "job-impressions-completed"
attribute in an Event Notification only for the combinations of
Events and Subscribed Events shown in Table 4.
Table 4 - Combinations of Events and Subscribed Events for "job-
impressions-completed"
Job Event Subscribed Job Event
'job-progress' 'job-progress'
'job-completed' 'job-completed'
'job-completed' 'job-state-changed'
For Event Notification for Printer Events, the Printer includes
the additional attributes shown in Table 5.
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Table 5 - Additional Attributes in Event Notification Content for
Printer Events
Source Value Sends Source
Object
printer-state (type1 enum) MUST Printer
printer-state-reasons (1setOf type2 keyword) MUST Printer
printer-is-accepting-jobs (boolean) MUST Printer
6 Subscription Template Attributes
This section defines the Subscription object conformance requirements
for Printers.
6.1 Subscription Template Attribute Conformance
The 'ippget' Delivery Method has the same conformance requirements
for Subscription Template attributes as defined in [ipp-ntfy]. The
'ippget' Delivery Method does not define any addition Subscription
Template attributes.
6.2 Additional Information about Subscription Template Attributes
This section defines additional information about Subscription
Template attributes defined in [ipp-ntfy].
6.2.1 notify-recipient-uri (uri)
This section describes the syntax of the value of this attribute for
the 'ippget' Delivery Method. The syntax for values of this
attribute for other Delivery Method is defined in other Delivery
Method Documents.
In order to support the 'ippget' Delivery Method and Protocol, the
Printer MUST support the following syntax:
The 'ippget://' URI scheme. The remainder of the URI indicates
something unique about the Notification Recipient, such as its host
name or host address (and optional path) that the Printer uses to
match the "notify-recipient-uri" Operation attribute supplied in
the Get-Notifications request.
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6.3 Subscription Description Attribute Conformance
The 'ippget' Delivery Method has the same conformance requirements
for Subscription Description attributes as defined in [ipp-ntfy].
The 'ippget' Delivery Method does not define any addition
Subscription Description attributes.
7 Additional Printer Description Attributes
This section defines the Printer Description Attributes conformance
requirements for Printers.
7.1 Printer Description Attribute Conformance
The 'ippget' Delivery Method has the same conformance requirements
for Printer Description attributes as defined in [ipp-ntfy]. The
'ippget' Delivery Method does not define any addition Printer
Description attributes.
7.2 New Values for Existing Printer Description Attributes
This section defines additional values for existing Printer
Description attributes.
7.2.1 notify-schemes-supported (1setOf uriScheme)
The following value for the "notify-schemes-supported" attribute is
added in order to support the new Delivery Method defined in this
document:
'ippget' - The IPP Notification Delivery Method defined in this
document.
7.2.2 operations-supported (1setOf type2 enum)
Table 6 lists the "operation-id" value defined in order to support
the new Get-Notifications operation defined in this document.
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Table 6 - Operation-id assignments
Value Operation Name
0x001C Get-Notifications
7.3 begin-to-expire-time-interval (integer(0:MAX))
This Printer Description attribute specifies the number of seconds
that a Printer keeps an Event Notification that is associated with
the 'ippget' Delivery Method.
The Printer MUST support this attribute if it supports the 'ippget'
Delivery Method.
The value of this attribute is the minimum number of seconds that
MUST elapse between the time the Printer creates an Event
Notification object for the 'ippget' Delivery Method and the time the
Printer discards the same Event Notification.
For example, assume the following:
1.a client performs a Job Creation operation that creates a
Subscription Object associated with this Delivery Method, AND
2.an Event associated with the new Job occurs immediately after
the Subscription Object is created, AND
3.the same client or some other client performs a Get-
Notifications operation N seconds after the Job Creation
operation.
Then, if N is less than the value of this attribute, the client
performing the Get-Notifications operations can expect not miss any
Event-Notifications, barring some unforeseen lack of memory space in
the Printer.
8 New Status Codes
The following status codes are defined as extensions for this
Delivery Method and are returned as the status code of the Get-
Notifications operation.
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8.1 redirection-other-site (0x300)
This status code means that the Printer doesn't perform that Get-
Notifications operation and that the "notify-ippget-redirect"
Operation Attribute in the response contains the uri that the
Notification Recipient MUST use for performing the Get-Notifications
operation.
9 The IPPGET URL Scheme
This section defines the 'ippget' URL and the conformance
requirements for using it.
9.1 The IPPGET URL Scheme Applicability and Intended Usage
This section is intended for use in registering the 'ippget' URL
scheme with IANA and fully conforms to the requirements in [RFC2717].
This document defines the 'ippget'" URL (Uniform Resource Locator)
scheme for specifying a unique identifier for an IPP Client which
implements the IPP Get-Notifications operation specified in this
document (see section 5).
The intended usage of the 'ippget' URL scheme is COMMON.
9.2 The IPPGET URL Scheme Associated Port
None.
An 'ippget' URL behaves as a unique identifier for IPP Clients and is
NOT used to initiate any over-the-wire protocol associations.
See: IANA Port Numbers Registry [IANA-PORTREG].
9.3 The IPPGET URL Scheme Associated MIME Type
All IPP Get-Notifications operations (requests and responses) MUST be
conveyed in an 'application/ipp' MIME media type as registered in
[IANA-MIMEREG]. An 'ippget' URL MUST uniquely identify an IPP Client
that support this 'application/ipp' MIME media type.
See: IANA MIME Media Types Registry [IANA-MIMEREG].
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9.4 The IPPGET URL Scheme Character Encoding
The 'ippget' URL scheme defined in this document is based on the ABNF
for the URI Generic Syntax [RFC2396] and further updated by [RFC2732]
and [RFC2373] (for IPv6 addresses in URLs). The 'ippget' URL scheme
is case-insensitive in the host name or host address part; however,
the path part is case-sensitive, as in [RFC2396]. Code points
outside [US-ASCII] MUST be hex escaped by the mechanism specified in
[RFC2396].
9.5 The IPPGET URL Scheme Syntax in ABNF
This document is intended for use in registering the 'ippget' URL
scheme with IANA and fully conforms to the requirements in [RFC2717].
This document defines the 'ippget' URL (Uniform Resource Locator)
scheme for specifying a unique identifier for an IPP Client which
implements IPP 'Get-Notifications' operation specified in this
document.
The intended usage of the 'ippget' URL scheme is COMMON.
The IPP protocol places a limit of 1023 octets (NOT characters) on
the length of a URI (see section 4.1.5 'uri' in [RFC2911]). An IPP
Printer MUST return the 'client-error-request-value-too-long' status
code (see section 13.1.4.10 in [RFC2911]) when a URI received in a
request is too long.
Note: IPP Clients and IPP Printers ought to be cautious about
depending on URI lengths above 255 bytes, because some older client
or proxy implementations might not properly support these lengths.
An 'ippget' URL MUST be represented in absolute form. Absolute URLs
always begin with a scheme name followed by a colon. For definitive
information on URL syntax and semantics, see "Uniform Resource
Identifiers (URI): Generic Syntax and Semantics" [RFC2396]. This
specification adopts the definitions of "authority", "abs_path",
"query", "reg_name", "server", "userinfo", and "hostport" from
[RFC2396], as updated by [RFC2732] and [RFC2373] (for IPv6 addresses
in URLs).
The 'ippget' URL scheme syntax in ABNF is as follows:
ippget_URL = "ippget:" "//" authority [ abs_path [ "?" query ]]
authority = server | reg_name
reg_name = 1*( unreserved | escaped | "$" | "," |
";" | ":" | "@" | "&" | "=" | "+" )
server = [ [ userinfo "@" ] hostport ]
userinfo = *( unreserved | escaped |
";" | ":" | "&" | "=" | "+" | "$" | "," )
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hostport = host [ ":" port ]
abs_path = "/" path_segments
If the port is empty or not given, then no port is assumed. The
semantics are that the 'ippget' URL is a unique identifier for an IPP
Client that will retrieve IPP event notifications via the IPP Get-
Notifications operation.
Note: The use of IP addresses in URLs SHOULD be avoided whenever
possible (see [RFC1900]).
9.5.1 IPPGET URL Examples
The following are examples of valid 'ippget' URLs for IPP Clients
(using DNS host names):
ippget://abc.com
ippget://abc.com/listener
ippget://bob@abc.com/listener/1232
Note: The use of IP addresses in URLs SHOULD be avoided whenever
possible (see [RFC1900]).
The choice of 'userinfo@hostport' versus the simpler 'hostport'
production in an 'ippget' URL may be influenced by the intended
usage.
If a given IPP Client creates an IPP Subscription object for event
notifications intended for retrieval by the same IPP Client, then the
simple 'hostport' production may be most appropriate.
On the other hand, if a given IPP Client creates an IPP Subscription
object for event notifications intended for retrieval by a different
IPP Client, then the 'userinfo@hostport' production (using, for
example, the right-hand side of a 'mailto:' URL, see [RFC2368]) may
be most appropriate.
9.5.2 IPPGET URL Comparisons
When comparing two 'ippget' URLs to decide if they match or not, an
IPP Client or IPP Printer SHOULD use a case-sensitive octet-by-octet
comparison of the entire URLs, with these exceptions:
- Comparisons of host names MUST be case-insensitive;
- Comparisons of scheme names MUST be case-insensitive;
- An empty 'abs_path' is equivalent to an 'abs_path' of "/".
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Characters other than those in the "reserved" and "unsafe" sets (see
[RFC2396] and [RFC2732]) are equivalent to their ""%" HEX HEX"
encoding.
For example, the following three URIs are equivalent:
ippget://abc.com/~smith/listener
ippget://ABC.com/%7Esmith/listener
ippget://ABC.com:/%7esmith/listener
10 Encoding
This notification delivery method uses the IPP transport and encoding
[RFC2910] for the Get-Notifications operation with one extension
allocated in [ipp-ntfy]:
Table 7 - The "event-notification-attributes-tag" value
Tag Value (Hex) Meaning
0x07 "event-notification-attributes-tag"
11 Conformance Requirements
11.1 Conformance for IPP Printers
IPP Printers that conform to this specification:
1. MUST meet the conformance requirements defined in [ipp-ntfy];
2. MUST support the Get-Notifications operation defined in section
5;
3. MUST support the Subscription object attributes as defined in
section 6;
4. MUST support the additional values for IPP/1.1 Printer
Description attributes defined in section 7.2;
5. MUST support the "begin-to-expire-time-interval" Printer
Description attribute defined in section 7.3;
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6. MUST support the "redirection-other-site" status code defined
8.1;
7. SHOULD reject received 'ippget' URLs in 'application/ipp'
request bodies (e.g., in the "notify-recipient-uri" attribute in
a Get-Notifications request) that do not conform to the ABNF for
'ippget' URLs specified in section 9.5 of this document;
8. MUST listen for the IPP Get-Notifications operation requests on
IANA-assigned well-known port 631, unless explicitly configured
by system administrators or site policies;
9. SHOULD NOT listen for IPP Get-Notifications operation requests
on any other port, unless explicitly configured by system
administrators or site policies.
11.2 Conformance for IPP Clients
IPP Clients that conform to this specification:
1.MUST create unambiguously unique 'ippget' URLs in all cases;
2.MUST send 'ippget' URLs (e.g., in the "notify-recipient-uri"
attribute in a Get-Notifications request) that conform to the
ABNF specified in section 9.5 of this document;
3.MUST send IPP Get-Notifications operation requests via the port
specified in the associated 'ipp' URL (if present) or otherwise
via IANA assigned well-known port 631;
4.MUST convert the associated 'ipp' URLs to their corresponding
'http' URL forms according to the rules in section 5 "IPP URL
Scheme" in [RFC2910].
Note: The use of ambiguous 'ippget' URLs is NOT an optional feature
for IPP Clients; it is a non-conformant implementation error.
12 IANA Considerations
IANA is requested to register the 'ippget' URL scheme as defined in
section 9 according to the procedures of [RFC2717].
The rest of this section contains the exact information for
additional IPP entities for IANA to add to the IPP Registries
according to the procedures defined in RFC 2911 [RFC2911] section 6.
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Note to RFC Editors: Replace RFC NNNN below with the RFC number
for this document, so that it accurately reflects the content of
the information for the IANA Registry.
12.1 Operation Registrations
The operations defined in this document will be published by IANA
according to the procedures in RFC 2911 [RFC2911] section 6.4 with
the following path:
ftp.isi.edu/iana/assignments/ipp/operations/
The registry entry will contain the following information:
Operations: Ref. Section:
Get-Notifications operation RFC NNNN 5
12.2 Additional values of existing attributes
12.2.1 Additional values for the "notify-schemes-supported" Printer
attribute
The "notify-schemes-supported" 'uriScheme' attribute value defined in
this document will be published by IANA according to the procedures
in RFC 2911 [RFC2911] section 6.1 with the following path:
ftp.isi.edu/iana/assignments/ipp/attribute-values/notify-schemes-
supported/
The registry entry will contain the following information:
Ref. Section:
ippget RFC NNNN 7.2.1
12.2.2 Additional values for the "operations-supported" Printer
attribute
The "operations-supported" type2 enum attribute value defined in this
document will be published by IANA according to the procedures in RFC
2911 [RFC2911] section 6.1 with the following path:
ftp.isi.edu/iana/assignments/ipp/attribute-values/operations-
supported/
The registry entry will contain the following information:
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Value Ref. Section:
Get-Notifications 0x001C RFC NNNN 7.2.2
12.3 Attribute Registrations
The attributes defined in this document will be published by IANA
according to the procedures in RFC 2911 [RFC2911] section 6.2 with
the following path:
ftp.isi.edu/iana/assignments/ipp/attributes/
The registry entry will contain the following information:
Printer Description attributes: Ref. Section:
begin-to-expire-time-interval (integer(0:MAX)) RFC NNNN 7.3
12.4 Status code Registrations
The status codes defined in this document will be published by IANA
according to the procedures in RFC 2911 [RFC2911] section 6.6 with
the following path:
ftp.isi.edu/iana/assignments/ipp/status-codes/
The registry entry will contain the following information:
Status codes: Ref. Section:
redirection-other-site (0x300) RFC NNNN 8.1
13 Internationalization Considerations
The IPP Printer MUST localize the "notify-text" attribute as
specified in section 14 of [ipp-ntfy].
In addition, when the client receives the Get-Notifications response,
it is expected to localize the attributes that have the 'keyword'
attribute syntax according to the charset and natural language
requested in the Get-Notifications request.
14 Security Considerations
The IPP Model and Semantics document [RFC2911] discusses high-level
security requirements (Client Authentication, Server Authentication
and Operation Privacy). Client Authentication is the mechanism by
which the client proves its identity to the server in a secure
manner. Server Authentication is the mechanism by which the server
proves its identity to the client in a secure manner. Operation
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Privacy is defined as a mechanism for protecting operations from
eavesdropping.
Unlike other Event Notification delivery methods in which the IPP
Printer initiates the Event Notification, with the method defined in
this document, the Notification Recipient is the client who s the
Get-Notifications operation. Therefore, there is no chance of "spam"
notifications with this method. Furthermore, such a client can close
down the HTTP channel at any time, and so can avoid future unwanted
Event Notifications at any time.
15 References
[ipp-iig]
Hastings, T., Manros, C., Kugler, K, Holst H., Zehler, P.,
"Internet Printing Protocol/1.1: draft-ietf-ipp-implementers-
guide-v11-02.txt, work in progress, January 25, 2001
[ipp-ntfy]
R. Herriot, Hastings, T., Isaacson, S., Martin, J., deBry, R.,
Shepherd, M., Bergman, R., "Internet Printing Protocol/1.1: IPP
Event Notification Specification", <draft-ietf-ipp-not-spec-
06.txt>, February 24, 2001.
[RFC1900]
B. Carpenter, Y. Rekhter. Renumbering Needs Work, RFC 1900,
February 1996.
[RFC2026]
S. Bradner, "The Internet Standards Process -- Revision 3", RFC
2026, October 1996.
[RFC2119]
S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119 , March 1997
[RFC2368]
P. Hoffman, L. Masinter, J. Zawinski. The "mailto" URL Scheme, RFC
2368, July 1998.
[RFC2373]
R. Hinden, S. Deering. IP Version 6 Addressing Architecture, RFC
2373, July 1998.
[RFC2396]
Berners-Lee, T. et al. Uniform Resource Identifiers (URI): Generic
Syntax, RFC 2396, August 1998
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[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.
[RFC2569]
Herriot, R., Hastings, T., Jacobs, N., Martin, J., "Mapping between
LPD and IPP Protocols", RFC 2569, April 1999.
[RFC2616]
R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P.
Leach, T. Berners-Lee, "Hypertext Transfer Protocol - HTTP/1.1",
RFC 2616, June 1999.
[RFC2717]
R. Petke and I. King, "Registration Procedures for URL Scheme
Names", RFC 2717, November 1999.
[RFC2732]
R. Hinden, B. Carpenter, L. Masinter. Format for Literal IPv6
Addresses in URL's, RFC 2732, December 1999.
[RFC2910]
Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet Printing
Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.
[RFC2911]
R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell,
"Internet Printing Protocol/1.1: Model and Semantics", RFC 2911,
September 2000.
16 Authors' Addresses
Robert Herriot
Xerox Corp.
3400 Hill View Ave, Building 1
Palo Alto, CA 94304
Phone: 650-813-7696
Fax: 650-813-6860
e-mail: robert.herriot@pahv.xerox.com
Carl Kugler
IBM
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P.O. Box 1900
Boulder, CO 80301-9191
Phone:
Fax:
e-mail: kugler@us.ibm.com
Harry Lewis
IBM
P.O. Box 1900
Boulder, CO 80301-9191
Phone: 303-924-5337
FAX:
e-mail: harryl@us.ibm.com
17 Full Copyright Statement
Copyright (C) The Internet Society (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.
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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