INTERNET-DRAFT Robert Herriot (editor)
<draft-ietf-ipp-notify-get-01.txt> Xerox Corp.
Carl Kugler
IBM, Corp.
Harry Lewis
IBM, Corp.
November 16, 2000
Internet Printing Protocol (IPP):
The 'ippget' Delivery Method for Event Notifications
Copyright (C) The Internet Society (2000). 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
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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 Notifications to
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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.
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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
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
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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......................................................7
2 Terminology.......................................................7
3 Model and Operation...............................................8
4 General Information...............................................9
5 Get-Notifications operation......................................11
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 Attributes.18
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)................................20
9 Encoding.........................................................20
10 Conformance Requirements.........................................21
11 IANA Considerations..............................................21
12 Internationalization Considerations..............................21
13 Security Considerations..........................................21
14 References.......................................................22
15 Authors' Addresses...............................................22
16 Full Copyright Statement.........................................23
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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...................................19
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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].
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Event Notification Lease: The lease that is associated with an Event
Notification. When the lease expires, the Printer discards the
associated Event Notification.
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" attributes 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 unexpired 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" equals 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
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Leases have expired. Some new Event Notifications may be present in
the second response but not the first response.
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.
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 IPP with one new operation.
protocols does the Printer use
to deliver the Event
Notification Content, i.e.,
what is the entire network
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 and
initiated by the Notification a push.
Recipient (pull), or by the
Printer (push)?
6.Is the Event Notification Machine Consumable
content Machine Consumable or
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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 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 HTTP
reliability of the transport transport
and delivery protocol?
9.What are the security aspects Same as IPP and the underlying HTTP
of the transport and delivery 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
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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.
When a Printer performs this operation, it MUST return all and only
those Event Notifications:
a)Whose associated Subscription Object's "notify-recipient-uri"
attribute equals the "notify-recipient-uri" Operation attribute
AND
b)Whose associated Subscription Object's "notify-recipient-uri"
attribute has a scheme value of 'ippget' AND
c)Whose Event Notification Lease Time has not yet expired AND
d)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".
Access Rights: If the policy of the Printer is to allow all users to
access all Event Notifications, then the Printer MUST accept this
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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' as appropriate.
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.
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"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, 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
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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.
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.
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"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.
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
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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
following attributes.
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 "printer-current-time" if and only if it
supports the "printer-current-time" attribute on the Printer
object.
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** 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
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
following additional attributes.
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 MUST Job
(integer(0:MAX)) *
* 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 following additional attributes.
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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 MUST Printer
keyword)
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].
6.2.1notify-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
and address 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.
7.2.1notify-schemes-supported (1setOf uriScheme)
The following "notify-schemes-supported" value is added in order to
support the new Delivery Method defined in this document:
'ippget' - The IPP Notification Delivery Method defined in this
document.
7.2.2operations-supported (1setOf type2 enum)
Table 6 lists the "operation-id" value added in order to support the
new operation defined in this document.
Table 6 - Operation-id assignments
Value Operation Name
0x001C Get-Notifications
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7.3 begin-to-expire-time-interval (integer(0:MAX))
This attribute specifies the number of seconds that a Printer keeps an
Event Notification that is associated with this Delivery Method.
The Printer MUST support this attribute if it supports this 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 this 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.
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 Encoding
This notification delivery method uses the IPP transport and encoding
[RFC2910] for the Get-Notifications operation with one extension:
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notification-attributes-tag = %x07 ; tag of
7
10 Conformance Requirements
If the Printer supports the 'ippget' Delivery Method, the Printer MUST:
1.meet the conformance requirements defined in [ipp-ntfy].
2.support the Get-Notifications operation defined in section 5.
3.support the Subscription object attributes as defined in section 6.
4.support the additional values for IPP/1.1 Printer Description
attributes defined in section 7.2.
5.support the "begin-to-expire-time-interval" Printer Description
attribute defined in section 7.3.
6.support the "redirection-other-site" status code defined 8.1
11 IANA Considerations
The 'ippget' URL scheme for the 'ippget' Delivery Method will be
registered with IANA according to the procedures of [RFC2717].
12 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.
13 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 Privacy is
defined as a mechanism for protecting operations from eavesdropping.
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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.
14 References
[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-
04.txt>, June 30, 2000.
[rfc2026]
S. Bradner, "The Internet Standards Process -- Revision 3", RFC
2026, October 1996.
[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.
[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.
15 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
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IBM
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
16 Full Copyright Statement
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The limited permissions granted above are perpetual and will not be
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NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
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