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rfc:rfc3995

Network Working Group R. Herriot Request for Comments: 3995 Global Workflow Solutions Category: Standards Track T. Hastings Updates: 2911, 2910 Xerox Corporation

                                                            March 2005
                 Internet Printing Protocol (IPP):
               Event Notifications and Subscriptions

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

Abstract

 This document describes an OPTIONAL extension to the Internet
 Printing Protocol/1.1: Model and Semantics (RFC 2911, RFC 2910).
 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 Events
 occurs, the Printer delivers an asynchronous Event Notification to
 the specified Notification Recipient via the specified Push or Pull
 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.

Herriot & Hastings Standards Track [Page 1] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Notification Overview. . . . . . . . . . . . . . . . . .  5
 2.  Models for Notification. . . . . . . . . . . . . . . . . . . .  8
     2.1.  Model for Simple Notification (Normative). . . . . . . .  8
     2.2.  Additional Models for Notification (Informative) . . . .  9
 3.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Conformance Terminology. . . . . . . . . . . . . . . . .  9
     3.2.  Other Terminology. . . . . . . . . . . . . . . . . . . . 10
 4.  Object Relationships . . . . . . . . . . . . . . . . . . . . . 12
     4.1.  Printer and Per-Printer Subscription Objects . . . . . . 13
     4.2.  Printer, Job and Per-Job Subscription Objects. . . . . . 13
 5.  Subscription Object. . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Rules for Support of Subscription Template Attributes. . 14
     5.2.  Rules for Processing Subscription Template Attributes. . 15
     5.3.  Subscription Template Attributes . . . . . . . . . . . . 18
           5.3.1.  notify-recipient-uri (uri) . . . . . . . . . . . 20
           5.3.2.  notify-pull-method (type2 keyword) . . . . . . . 21
           5.3.3.  notify-events (1setOf type2 keyword) . . . . . . 22
           5.3.4.  notify-attributes (1setOf type2 keyword) . . . . 29
           5.3.5.  notify-user-data (octetString(63)) . . . . . . . 30
           5.3.6.  notify-charset (charset) . . . . . . . . . . . . 31
           5.3.7.  notify-natural-language (naturalLanguage). . . . 31
           5.3.8.  notify-lease-duration (integer(0:67108863)). . . 32
           5.3.9.  notify-time-interval (integer(0:MAX)). . . . . . 33
     5.4.  Subscription Description Attributes. . . . . . . . . . . 34
           5.4.1.  notify-subscription-id  (integer (1:MAX)). . . . 35
           5.4.2.  notify-sequence-number (integer (0:MAX)) . . . . 35
           5.4.3.  notify-lease-expiration-time (integer(0:MAX)). . 36
           5.4.4.  notify-printer-up-time (integer(1:MAX)). . . . . 37
           5.4.5.  notify-printer-uri (uri) . . . . . . . . . . . . 37
           5.4.6.  notify-job-id (integer(1:MAX)) . . . . . . . . . 37
           5.4.7.  notify-subscriber-user-name (name(MAX)). . . . . 38
 6.  Printer Description Attributes Related to Notification . . . . 38
     6.1.  printer-state-change-time (integer(1:MAX)) . . . . . . . 39
     6.2.  printer-state-change-date-time (dateTime). . . . . . . . 39
 7.  New Values for Existing Printer Description Attributes . . . . 39
     7.1.  operations-supported (1setOf type2 enum) . . . . . . . . 40
 8.  Attributes Only in Event Notifications . . . . . . . . . . . . 40
     8.1.  notify-subscribed-event (type2 keyword). . . . . . . . . 40
     8.2.  notify-text (text(MAX)). . . . . . . . . . . . . . . . . 41
 9.  Event Notification Content . . . . . . . . . . . . . . . . . . 41
     9.1.  Content of Machine Consumable Event Notifications. . . . 44
           9.1.1.  Event Notification Content Common to All Events. 44
           9.1.2.  Additional Event Notification Content for Job
                   Events . . . . . . . . . . . . . . . . . . . . . 45

Herriot & Hastings Standards Track [Page 2] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

           9.1.3.  Additional Event Notification Content for
                   Printer Events . . . . . . . . . . . . . . . . . 46
     9.2.  Content of Human Consumable Event Notification . . . . . 46
           9.2.1.  Event Notification Content Common to All Events. 47
           9.2.2.  Additional Event Notification Content for Job
                   Events . . . . . . . . . . . . . . . . . . . . . 49
           9.2.3.  Additional Event Notification Content for
                   Printer Events . . . . . . . . . . . . . . . . . 49
 10. Delivery Methods . . . . . . . . . . . . . . . . . . . . . . . 50
 11. Operations for Notification. . . . . . . . . . . . . . . . . . 52
     11.1. Subscription Creation Operations . . . . . . . . . . . . 52
           11.1.1. Create-Job-Subscriptions Operation . . . . . . . 52
           11.1.2. Create-Printer-Subscriptions operation . . . . . 55
           11.1.3. Job Creation Operations - Extensions for
                   Notification . . . . . . . . . . . . . . . . . . 56
     11.2 Other Operations. . . . . . . . . . . . . . . . . . . . . 58
           11.2.1. Restart-Job Operation - Extensions for
                   Notification . . . . . . . . . . . . . . . . . . 58
           11.2.2. Validate-Job Operation - Extensions for
                   Notification . . . . . . . . . . . . . . . . . . 59
           11.2.3. Get-Printer-Attributes - Extensions for
                   Notification . . . . . . . . . . . . . . . . . . 59
           11.2.4. Get-Subscription-Attributes operation. . . . . . 60
           11.2.5. Get-Subscriptions operation. . . . . . . . . . . 63
           11.2.6. Renew-Subscription operation . . . . . . . . . . 66
           11.2.7. Cancel-Subscription operation. . . . . . . . . . 68
 12. Status Codes . . . . . . . . . . . . . . . . . . . . . . . . . 70
     12.1. successful-ok-ignored-subscriptions (0x0003) . . . . . . 70
     12.2. client-error-ignored-all-subscriptions (0x0414). . . . . 71
 13. Status Codes in Subscription Attributes Groups . . . . . . . . 71
     13.1. client-error-uri-scheme-not-supported (0x040C) . . . . . 71
     13.2. client-error-attributes-or-values-not-supported (0x040B) 71
     13.3. client-error-too-many-subscriptions (0x0415) . . . . . . 72
     13.4. successful-ok-too-many-events (0x0005) . . . . . . . . . 72
     13.5. successful-ok-ignored-or-substituted-attributes (0x0001) 72
 14. Encodings of Additional Attribute Tags . . . . . . . . . . . . 72
 15. Conformance Requirements . . . . . . . . . . . . . . . . . . . 72
     15.1. Conformance requirements for clients . . . . . . . . . . 73
     15.2. Conformance requirements for Printers. . . . . . . . . . 73
 16. Model for Notification with Cascading Printers (Informative) . 74
 17. Distributed Model for Notification (Informative) . . . . . . . 75
 18. Extended Notification Recipient (Informative). . . . . . . . . 76
 19. Object Model for Notification (Normative). . . . . . . . . . . 77
     19.1. Object relationships . . . . . . . . . . . . . . . . . . 78
     19.2. Printer Object and Per-Printer Subscription Objects. . . 79
     19.3. Job Object and Per-Job Subscription Objects. . . . . . . 79
 20. Per-Job versus Per-Printer Subscription Objects (Normative). . 79
 21. Normative References . . . . . . . . . . . . . . . . . . . . . 80

Herriot & Hastings Standards Track [Page 3] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 22. Informative References . . . . . . . . . . . . . . . . . . . . 80
 23. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 81
     23.1. Attribute Registrations. . . . . . . . . . . . . . . . . 82
     23.2. Additional Enum Attribute Value Registrations within
           the IPP registry . . . . . . . . . . . . . . . . . . . . 83
     23.3. Operation Registrations. . . . . . . . . . . . . . . . . 83
     23.4. Status code Registrations. . . . . . . . . . . . . . . . 83
     23.5. Attribute Group tag Registrations. . . . . . . . . . . . 84
     23.6. Registration of Events . . . . . . . . . . . . . . . . . 84
     23.7. Registration of Event Notification Delivery Methods. . . 85
           23.7.1. Requirements for Registration of Event
                   Notification Delivery Methods. . . . . . . . . . 85
           23.7.2. Registration Procedure . . . . . . . . . . . . . 86
           23.7.3. Delivery Method Document Registrations . . . . . 87
           23.7.4. Registration Template. . . . . . . . . . . . . . 88
 24. Internationalization Considerations. . . . . . . . . . . . . . 89
 25. Security Considerations. . . . . . . . . . . . . . . . . . . . 89
     25.1. Client access rights . . . . . . . . . . . . . . . . . . 89
     25.2. Printer security threats . . . . . . . . . . . . . . . . 91
     25.3. Notification Recipient security threats. . . . . . . . . 91
 26. Description of the base IPP documents (Informative). . . . . . 92
 27. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 93
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 94
 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 95

Tables

 Table 1  - Subscription Template Attributes. . . . . . . . . . . . 20
 Table 2  - Subscription Description Attributes . . . . . . . . . . 35
 Table 3  - Printer Description Attributes Associated with
            Notification. . . . . . . . . . . . . . . . . . . . . . 39
 Table 4  - Operation-id assignments. . . . . . . . . . . . . . . . 40
 Table 5  - Attributes in Event Notification Content. . . . . . . . 45
 Table 6  - Additional Event Notification Content for Job Events. . 46
 Table 7  - Combinations of Events and Subscribed Events for
            "job-impressions-completed" . . . . . . . . . . . . . . 46
 Table 8  - Additional Event Notification Content for Printer
            Events. . . . . . . . . . . . . . . . . . . . . . . . . 46
 Table 9  - Printer Name in Event Notification Content. . . . . . . 48
 Table 10 - Event Name in Event Notification Content. . . . . . . . 48
 Table 11 - Event Time in Event Notification Content. . . . . . . . 48
 Table 12 - Job Name in Event Notification Content. . . . . . . . . 49
 Table 13 - Job State in Event Notification Content . . . . . . . . 49
 Table 14 - Printer State in Event Notification Content . . . . . . 50
 Table 15 - Information about the Delivery Method . . . . . . . . . 51
 Table 16 - Printer Conformance Requirements for Operations . . . . 74

Herriot & Hastings Standards Track [Page 4] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

Figures

 Figure 1 - Model for Notification. . . . . . . . . . . . . . . . .  9
 Figure 2 - Model for Notification with Cascading Printers. . . . . 75
 Figure 3 - Opaque Use of a Notification Server Transparent to the
            Client. . . . . . . . . . . . . . . . . . . . . . . . . 76
 Figure 4 - Use of an Extended Notification Recipient transparent
            to the Printer. . . . . . . . . . . . . . . . . . . . . 77
 Figure 5 - Object Model for Notification . . . . . . . . . . . . . 78

1. Introduction

 This IPP notification specification is an OPTIONAL extension to
 Internet Printing Protocol/1.1: Model and Semantics [RFC2911,
 RFC2910].  See Appendix 29 for a description of the base IPP
 documents.  This document in combination with the following documents
 is intended to meet the most important notification requirements
 described in [RFC3997]:
    Internet Printing Protocol (IPP):  "Job Progress Attributes"
    [RFC3381]
    Internet Printing Protocol (IPP):  "The 'ippget' Delivery Method
    for Event Notifications" [RFC3996]
 This specification REQUIRES that clients and Printers support the
 'ippget' Pull Delivery Method [RFC3996].  Conforming client and
 Printer implementations MAY support additional Push or Pull Delivery
 Methods as well.  Note: this document does not define any Delivery
 Methods itself, but it does define the rules for conformance for
 Delivery Method Documents and their registration with IANA (see
 section 23.7.3).
 Refer to the Table of Contents for the layout of this document.

1.1. Notification Overview

 This document 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 delivers an asynchronous Event
 Notification to the specified Notification Recipient via the
 specified Delivery Method (i.e., protocol).
 When a client (called a Subscribing Client) performs an operation
 that creates a Subscription Object, the operation contains one or
 more Subscription Template Attributes Groups.  Each such group holds

Herriot & Hastings Standards Track [Page 5] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 information used by the Printer to initialize a newly created
 Subscription Object.  The Printer creates one Subscription Object for
 each Subscription Template Attributes Group in the operation.  This
 group is like the Job Template Attributes group defined in [RFC2911].
 The following is an example of the information included in a
 Subscription Template Attributes Group (see section 5 for details on
 the Subscription Object attributes):
 1. The names of Subscribed Events that are of interest to the
    Notification Recipient.
 2. The address (URL) of one Notification Recipient for a Push
    Delivery Method or the method for a Pull Delivery Method.
 3. The Delivery Method (i.e., the protocol) which the Printer uses to
    deliver the Event Notification.
 4. Some opaque data that the Printer delivers to the Notification
    Recipient in the Event Notification.  For example, the
    Notification Recipient might use this opaque data as a forwarding
    address for the Event Notification.
 5. The charset to use in text fields within an Event Notification
 6. The natural language to use in the text fields of the Event
    Notification
 7. The requested lease time in seconds for the Subscription Object
 An operation that creates a Subscription Object is called a
 Subscription Creation Operation.  These operations include the
 following operations (see section 11.1 for further details):
  1. Job Creation operation: When a client performs such an

operation (Print-Job, Print-URI, and Create-Job), a client can

       include zero or more Subscription Template Attributes Groups in
       the request.  The Printer creates one Subscription Object for
       each Subscription Template Attributes Group in the request, and
       the Printer associates each such Subscription Object with the
       newly created Job.  This document extends these operations'
       definitions in [RFC2911] by adding Subscription Template
       Attributes Groups in the request and Subscription Attributes
       Groups in the response.
  1. Create-Job-Subscriptions operation: A client can include one or

more Subscription Template Attributes Groups in the request.

       The Printer creates one Subscription Object for each

Herriot & Hastings Standards Track [Page 6] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

       Subscription Template Attributes Group and associates each with
       the job that is the target of this operation.
  1. Create-Printer-Subscriptions operation: A client can include

one or more Subscription Template Attributes Groups in the

       request.  The Printer creates one Subscription Object for each
       Subscription Template Attributes Group and associates each with
       the Printer that is the target of this operation.
 For each of the above operations:
  1. the Printer associates a Subscription Object with the Printer

or a specific Job. When a Subscription Object is associated

       with a Job Object, it is called a Per-Job Subscription Object.
       When a Subscription Object is associated with a Printer Object,
       it is called a Per-Printer Subscription Object.
  1. the response contains one Subscription Attributes Group for

each Subscription Template Attributes Group in the request and

       in the same order.  When the Printer successfully creates a
       Subscription Object, its corresponding Subscription Attributes
       Group contains the "notify-subscription-id" attribute.  This
       attribute uniquely identifies the Subscription Object and is
       analogous to a "job-id" for a Job object.  Some operations
       described below use the "notify-subscription-id" to identify
       the target Subscription Object.
 This document defines the following additional operations (see
 section 11.2 for further details):
  1. Restart-Job operation: When a client performs the Restart-Job

operation [RFC2911], the Printer re-uses the same Job and its

    Subscription Objects.
  1. Validate-Job operation: When a client performs this operation, a

client can include zero or more Subscription Template Attributes

    Groups in the request.  The Printer determines if it could create
    one Subscription Object for each Subscription Template Attributes
    Group in the request.  This document extends this operation's
    definition in [RFC2911] by adding Subscription Template Attributes
    Groups in the request and Subscription Attributes Groups in the
    response.
  1. Get-Subscription-Attributes operation: This operation allows a

client to obtain the specified attributes of a target Subscription

    Object.

Herriot & Hastings Standards Track [Page 7] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

  1. Get-Subscriptions operation: This operation allows a client to

obtain the specified attributes of all Subscription Objects

    associated with the Printer or a specified Job.
  1. Renew-Subscription operation: This operation renews the lease on

the target Per-Printer Subscription Object before it expires. A

    newly created Per-Printer Subscription Object receives an initial
    lease.  It is the duty of the client to use this operation
    frequently enough to preserve a Per-Printer Subscription Object.
    The Printer deletes a Per-Printer Subscription Object when its
    lease expires.  A Per-Job Subscription Object last exactly as long
    as its associated Job Object and thus doesn't have a lease.
  1. Cancel-Subscription operation: This operation (1) cancels the

lease on the specified Per-Printer Subscription Object and thereby

    deletes the Per-Printer Subscription Object or (2) deletes the
    Per-Job Subscription Object.
 When an Event occurs, the Printer finds all Subscription Objects
 listening for the Event (see section 9 for details on finding such
 Subscription Objects).  For each such Subscription Object, the
 Printer:
 a) generates an Event Notification with information specified in
    section 9, AND
 b) either:
    i)  If the Delivery Method is a Push Delivery Method as indicated
        by the presence of the Subscription Object's "notify-
        recipient-uri" attribute, delivers the Event Notification
        using the Delivery Method and target address identified in the
        Subscription Object's "notify-recipient-uri" attribute, OR
    ii) If the Delivery Method is a Pull Delivery Method as indicated
        by the presence of the Subscription Object's "notify-pull-
        method" attribute, saves Event Notification for a time period
        called the Event Life defined by the Delivery Method, i.e.,
        the Notification Recipient is expected to fetch the Event
        Notifications.

2. Models for Notification

2.1. Model for Simple Notification (Normative)

 As part of a Subscription Creation Operation, an IPP Printer (i.e.,
 located in an output device or a server) creates one or more
 Subscription Objects.  In a Subscription Creation Operation, the

Herriot & Hastings Standards Track [Page 8] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 client specifies the Notification Recipient to which the Printer is
 to deliver Event Notifications.  A Notification Recipient can be the
 Subscribing Client or a third party.
 Figure 1 shows the Notification model for a simple Client-Printer
 relationship.
 embedded printer:
                                      output device or server
 PDA, desktop, or server                 +---------------+
      +--------+                         |  ###########  |
      | client |-----Subscription ---------># Printer #  |
      +--------+  Creation Operation     |  # Object  #  |
   +------------+                        |  #####|#####  |
   |Notification|                        +-------|-------+
   |Recipient   |<----IPP Event Notifications----+
   +------------+    (Job and/or Printer Events)
                Figure 1 - Model for Notification

2.2. Additional Models for Notification (Informative)

 Additional models have been proposed (see Appendices 16, 17, and 18).

3. Terminology

 This section defines terminology used throughout this document.
 Other terminology is defined in [RFC2911].

3.1. Conformance Terminology

 Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD
 NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to
 conformance as defined in RFC 2119 [RFC2119] and [RFC2911] section
 12.1.  If an implementation supports the extension defined in this
 document, then these terms apply; otherwise, they do not.  These
 terms define conformance to this document only; they do not affect
 conformance to other documents, unless explicitly stated otherwise.
 Note: a feature that is OPTIONAL in this document becomes REQUIRED if
 the Printer implements a Delivery Method that REQUIRES the feature.
 READ-ONLY - an adjective used in an attribute definition to indicate
 that an IPP Printer MUST NOT allow the attribute's value to be
 modified.

Herriot & Hastings Standards Track [Page 9] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

3.2. Other Terminology

 This document uses the same terminology as [RFC2911], such as
 "client", "Printer", "attribute", "attribute value", "keyword",
 "operation", "request", "response", "administrator", "operator", and
 "support".  In addition, the following terms are defined for use in
 this document and the Delivery Method Documents:
 Compound Event Notification - two or more Event Notifications that a
 Printer delivers together as a single request or response.  The
 Delivery Method Document specifies whether the Delivery Method
 supports Compound Event Notifications.
 Delivery Method - the mechanism by which the Printer delivers an
 Event Notification.
 Delivery Method Document - a document, separate from this document,
 that defines a Delivery Method.
 Event - some occurrence (either expected or unexpected) within the
 printing system of a change of state, condition, or configuration of
 a Job or Printer object.  An Event occurs only at one instant in time
 and does not span the time the physical Event takes place.  For
 example, jam-occurred and jam-cleared are two distinct, instantaneous
 Events, even though the jam may last for a while.
 Event Life - For a Pull Delivery Method, the length of time in
 seconds after an Event occurs during which the Printer will retain
 that Event for delivery in an Event Notification.  After the Event
 Life expires, the Printer will no longer deliver an Event
 Notification for that Event in such a response.
 Event Notification - the information about an Event that the Printer
 delivers when an Event occurs.
 Event Notification Attributes Group - The attributes group which is
 used to deliver an Event Notification in a request (Push Delivery
 Methods) or a response (Pull Delivery Methods).
 Human Consumable Event Notification - localized text for human
 consumption only.  There is no standardized format and thus programs
 should not try to parse this text.
 Job Creation operation - One of the operations that creates a Job
 object:  Print-Job, Print-URI and Create-Job.  The Restart-Job
 operation [RFC2911] is not considered a Job Creation operation, since
 the Printer re-uses the existing Job object.  The Validate-Job
 operation is not considered a Job Creation operation because no Job

Herriot & Hastings Standards Track [Page 10] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 object is created.  Therefore, when a statement also applies to
 either the Restart-Job and/or the Validate-Job operation, they are
 mentioned explicitly.
 Job Event - an Event caused by some change in a particular job on the
 Printer, e.g., 'job-completed'.
 Machine Consumable Event Notification - bytes for program
 consumption.  The bytes are formatted according to the Delivery
 Method document.
 Notification - when not in the phrases 'Event Notification' and
 'Notification Recipient' - the concepts of this specification, i.e.,
 Events, Subscription Objects, and Event Notifications.
 Notification Recipient - the entity to which the Printer delivers an
 Event Notification.  For Push Delivery Methods, the IPP Printer sends
 the Notifications to a Notification Recipient.  For Pull Delivery
 Methods, the Notification Recipient is acting in the role of an IPP
 client and requests Event Notifications and so the terms "client" and
 "Notification Recipient" are used interchangeably with such Delivery
 Methods.  For example, see [RFC3996].
 Per-Job Subscription Object - A Subscription Object that is
 associated with a single Job.  The Create-Job-Subscriptions operation
 and Job Creation operations create such an object.
 Per-Printer Subscription Object - A Subscription Object that is
 associated with the Printer as a whole.  The Create-Printer-
 Subscriptions operation creates such an object.
 Printer Event - an Event caused by some change in the Printer that is
 not specific to a job, e.g., 'printer-state-changed'.
 Pull Delivery Method - The Printer saves Event Notifications for some
 event life time and expects the Notification Recipient to request
 Event Notifications.  The Printer delivers the Event Notifications in
 a response to such a request.
 Push Delivery Method -The Printer delivers the Event Notification
 shortly after an Event occurs.
 Subscribed Event - an Event that the Subscribing Client expresses
 interest in by making it a value of the "notify-events" attribute on
 a Subscription Object.
 Subscribed Job Event - a Subscribed Event that is a Job Event.

Herriot & Hastings Standards Track [Page 11] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Subscribed Printer Event - a Subscribed Event that is a Printer
 Event.
 Subscribing Client - The client that creates the Subscription Object.
 Subscription Attributes Group - The attributes group in a response
 that contains Subscription Object attributes.
 Subscription Creation Operation - An operation that creates a
 Subscription Object:  Job Creation operations, Create-Job-
 Subscriptions operation, Create-Printer-Subscriptions operation.  In
 the context of a Job Creation operation, a Subscription Creation
 Operation is the part of the Job Creation operation that creates one
 or more Subscription objects.  The Restart-Job operation [RFC2911] is
 not considered a Subscription Creation Operation, since the Printer
 re-uses the Job's existing Subscription Objects, rather than creating
 any new Subscription Objects.
 Subscription Creation Request - The request portion of a Subscription
 Creation Operation.
 Subscription Description Attributes - Subscription Object attributes
 that a Printer supplies during a Subscription Creation Operation.
 Subscription Object - An object containing a set of attributes that
 indicate:  the Notification Recipient (for Push Delivery Method
 only), the Delivery Method, the Subscribed Events that cause the
 Printer to deliver an Event Notification, and the information to
 include in an Event Notification.
 Subscription Template Attributes - Subscription Object attributes
 that a client can supply in a Subscription Creation Operation and
 associated Printer Object attributes that specify supported and
 default values for the Subscription Object attributes.
 Subscription Template Attributes Group - The attributes group in a
 request that contains Subscription Object attributes that are
 Subscription Template Attributes.

4. Object Relationships

 This section defines the object relationships between the Printer,
 Job, and Subscription Objects.  It does not define the
 implementation.  For an illustration of these relationships, see
 Appendix 19.

Herriot & Hastings Standards Track [Page 12] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

4.1. Printer and Per-Printer Subscription Objects

 1. A Printer object can be associated with zero or more Per-Printer
    Subscription Objects.
 2. Each Per-Printer Subscription Object is associated with exactly
    one Printer object.

4.2. Printer, Job and Per-Job Subscription Objects

 1. A Printer object is associated with zero or more Job objects.
 2. Each Job object is associated with exactly one Printer object.
 3. A Job object is associated with zero or more Per-Job Subscription
    Objects.
 4. Each Per-Job Subscription Object is associated with exactly one
    Job object.

5. Subscription Object

 A Subscribing Client creates a Subscription Object with a
 Subscription Creation Operation in order to indicate its interest in
 certain Events.  See section 11 for a description of these
 operations.  When an Event occurs, the Subscription Object specifies
 to the Printer where to deliver Event Notifications for Push Delivery
 Methods only, how to deliver them, and what to include in them.  See
 section 9 for details on the contents of an Event Notification.
 Using the IPP Job Template attributes as a model (see [RFC2911]
 section 4.2), the attributes of a Subscription Object are divided
 into two categories: Subscription Template Attributes and
 Subscription Description Attributes.
 Subscription Template attributes are, in turn, like the Job Template
 attributes, divided into
 1. Subscription Object attributes that a client can supply in a
    Subscription Creation Request and
 2. their associated Printer Object attributes that specify supported
    and default values for the Subscription Object attributes
 The remainder of this section specifies general rules for
 Subscription Template Attributes and describes each attribute in a
 Subscription Object.

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5.1. Rules for Support of Subscription Template Attributes

 Subscription Template Attributes are fundamental to the Notification
 model described in this specification.  The client supplies these
 attributes in Subscription Creation Operations and the Printer uses
 these attributes to populate a newly created Subscription Object.
 Subscription Objects attributes that are Subscription Template
 Attributes conform to the following rules:
 1. Each attribute's name starts with the prefix string "notify-" and
    this document calls such attributes "notify-xxx".
 2. For each "notify-xxx" Subscription Object attribute defined in
    column 1 of Table 1 in section 5.3, Table 1 specifies
    corresponding Printer attributes: "notify-xxx-default", "notify-
    xxx-supported", "yyy-supported" and "notify-max-xxx-supported"
    defined in column 2 of Table 1.  Note "xxx" stands for the same
    string in each case and "yyy" stands for some other string.
 3. If a Printer supports "notify-xxx" in column 1 of Table 1, then
    the Printer MUST support all associated attributes specified in
    column 2 of Table 1.  For example, Table 1 shows that if the
    Printer supports "notify-events", it MUST support "notify-events-
    default", "notify-events-supported" and "notify-max-events-
    supported".
 4. If a Printer does not support "notify-xxx" in column 1 of Table 1,
    then the Printer MUST NOT support any associated "notify-yyy"
    attributes specified in column 2 of Table 1.  For example, Table 1
    shows that if the Printer doesn't support "notify-events", it MUST
    NOT support "notify-events-default", "notify-events-supported" and
    "notify-max-events-supported".  Note this rule does not apply to
    attributes whose names do not start with the string "notify-" and
    are thus defined in another object and used by other attributes.
 5. Most "notify-xxx" attributes have a corresponding "yyy-supported"
    attribute that specifies the supported values for "notify-xxx".
    Column 2 of Table 1 specifies the name of each "yyy-supported"
    attribute.  The naming rules of IPP/1.1 (see [RFC2911]) are used
    when "yyy-supported" is "notify-xxx-supported".
 6. Some "notify-xxx" attributes have a corresponding "notify-xxx-
    default" attribute that specifies the value for "notify-xxx" if
    the client does not supply it.  Column 2 of Table 1 specifies the
    name of each "notify-xxx-default" attribute.  The naming rules of
    IPP/1.1 (see [RFC2911]) are used.

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 If a client wishes to present an end user with a list of supported
 values from which to choose, the client SHOULD query the Printer for
 its supported value attributes.  The client SHOULD also query the
 default value attributes.  If the client then limits selectable
 values to only those values that are supported, the client can
 guarantee that the values supplied by the client in the create
 request all fall within the set of supported values at the Printer.
 When querying the Printer, the client MAY enumerate each attribute by
 name in the Get-Printer-Attributes Request, or the client MAY just
 supply the 'subscription-template' group name in order to get the
 complete set of supported attributes (both supported and default
 attributes - see section 11.2.3).

5.2. Rules for Processing Subscription Template Attributes

 This section defines a detailed set of rules that a Printer follows
 when it processes Subscription Template Attributes in a Subscription
 Creation Request.  These rules are similar to the rules for
 processing Operation attributes in [RFC2911].  That is, the Printer
 may or may not support an attribute and a client may or may not
 supply the attribute.  Some combinations of these cases are OK.
 Others return warnings or errors, and perhaps a list of unsupported
 attributes.
 A Printer MUST implement the following behavior for processing
 Subscription Template Attributes in a Subscription Creation Request:
 1. If a client supplies a "notify-xxx" attribute from column 1 of
    Table 1 and the Printer supports it and its value, the Printer
    MUST populate the attribute on the created Subscription Object.
 2. If a client supplies a "notify-xxx" attribute from column 1 of
    Table 1 and the Printer doesn't support it or its value, the
    Printer MUST NOT populate the attribute on the created
    Subscription Object with it.  The Printer MUST do one of the
    following:
    a) If the value of the "notify-xxx" attribute is unsupported, the
       Printer MUST return the attribute with its value in the
       Subscription Attributes Group of the response.
    b) If "notify-xxx" is an unsupported attribute, the Printer MUST
       return the attribute in the Subscription Attributes Group of
       the response with the 'unsupported' out-of-band value.
    Note:  The rules of this step are the same as for Unsupported
    Attributes [RFC2911] section 3.1.7.  except that the unsupported
    attributes are returned in the Subscription Attributes Group

Herriot & Hastings Standards Track [Page 15] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

    rather than the Unsupported Attributes Group because Subscription
    Creation Operations can create more than one Subscription Object).
 3. If a client is REQUIRED to supply a "notify-xxx" attribute from
    column 1 of Table 1 and the Printer doesn't support the supplied
    value, the Printer MUST NOT create a Subscription Object.  The
    rules for Unsupported Attributes in step #2 still apply.
 4. If a client does not supply a "notify-xxx" attribute from column 1
    of Table 1 and the attribute is REQUIRED for the client to supply,
    the Printer MUST reject the Subscription Creation Operation
    (including Job Creation operations) without creating a
    Subscription Object, and MUST return in the response:
    a) the status code 'client-error-bad-request' AND
    b) no Subscription Attribute Groups.
 5. If a client does not supply a "notify-xxx" attribute from column 1
    of Table 1 that is OPTIONAL for the client to supply, and column 2
    of Table 1 either:
    a) specifies a "notify-xxx-default" attribute, the Printer MUST
       behave as if the client had supplied the "notify-xxx-default"
       attribute (see step #1) and populate the Subscription object
       with the value of the "notify-xxx-default" attribute as part of
       the Subscription Creation operation (unlike Job Template
       attributes where the Printer does not populate the Job object
       with defaults - see [RFC2911]) OR
    b) does not specify a "notify-xxx-default" attribute, the Printer
       MUST populate the "notify-xxx" attribute on the Subscription
       Object according to the definition of the "notify-xxx"
       attribute in a section 5.3.  For some attributes, the "notify-
       xxx" is populated with the value of some other attribute, and
       for others, the "notify-xxx" is NOT populated on the
       Subscription object at all.
 6. A Printer MUST create a Subscription Object for each Subscription
    Template Attributes group in a request unless the Printer:
    a) encounters some attributes in a Subscription Template
       Attributes Group that require the Printer not to create the
       Subscription Object OR
    b) would create a Per-Job Subscription Object when it doesn't have
       space for another Per-Job Subscription Object OR

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    c) would create a Per-Printer Subscription Object when it doesn't
       have space for another Per-Printer Subscription Object.
 7. A response MUST contain one Subscription Attributes Group for each
    Subscription Template Attributes Group in the request (and in the
    same order) whether the Printer creates a Subscription Object from
    the Subscription Template Attributes Group or not.  However, the
    attributes in each Subscription Attributes Group can be in any
    order.
 8. The Printer MUST populate each Subscription Attributes Group of
    the response such that each contains:
    a) the "notify-subscription-id" attribute (see section 5.4.1), if
       and only if the Printer creates a Subscription Object.
    b) the "notify-lease-duration" attribute (see section 5.3.8), if
       and only if the Printer creates a Per-Printer Subscription
       Object.  The value of this attribute is the value of the
       Subscription Object's "notify-lease-duration" attribute.  This
       value MAY be different from the client-supplied value (see
       section 5.3.8).  If a client supplies this attribute in the
       creation of a Per-Job Subscription Object, it MUST appear in
       this group with the out-of-band value 'unsupported' to indicate
       that the Printer doesn't support it in this context.
    c) all of the unsupported Subscription Template Attributes from
       step #2.  Note, they are not returned in the Unsupported
       Attributes Group in order to separate the unsupported
       attributes for each Subscription Object.
    d) the "notify-status-code" attribute if the Printer does not
       create the Subscription Object or if there are unsupported
       attributes from step #2.  The possible values of the "notify-
       status-code" attribute are shown below (see section 13 for more
       details).  The Printer returns the first value in the list
       below that describes the status.
       'client-error-uri-scheme-not-supported':  the Subscription
          Object was not created because the scheme of the "notify-
          recipient-uri" attribute is not supported.  See section 13.1
          for more details about this status code.  See step #3 in
          this section for the case that causes this error, and the
          resulting step #6a) that causes the Printer not to create
          the Subscription Object.

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       'client-error-attributes-or-values-not-supported':  the
          Subscription Object was not created because the method of
          the "notify-pull-method" attribute is not supported.  See
          section 13.1 for more details about this status code.  See
          step #3 in this section for the case that causes this error,
          and the resulting step #6a) that causes the Printer not to
          create the Subscription Object.
       'client-error-too-many-subscriptions':  the Subscription
          Object was not created because the Printer has no space for
          additional Subscription Objects.  The client MAY try again
          later.  See section 13.3 for more details about this status
          code.  See steps #6b) and #6c) in this section for the cases
          that causes this error.
       'successful-ok-too-many-events':  the Subscription Object was
          created without the "notify-events" values included in this
          Subscription Attributes Group because the "notify-events"
          attribute contains too many values.  See section 13.4 for
          more details about this status code.  See step #2 in this
          section and section 5.3.3 for the cases that cause this
          status code.
       'successful-ok-ignored-or-substituted-attributes':  the
          Subscription Object was created but some supplied
          Subscription Template Attributes are unsupported.  These
          unsupported attributes are also in the Subscription
          Attributes Group.  See section 13.5 for more details about
          this status code.  See step #2 in this section for the cases
          that cause this status code.
 9. The Printer MUST validate all Subscription Template Attributes and
    MUST return all unsupported attributes and values in the
    corresponding Subscription Attributes Group of the response (see
    step #2) unless it determines that it could not create additional
    Subscription Objects because of condition #6b) or condition #6c).
    Then, the Printer NEED NOT validate these additional Subscription
    Template Attributes and the client MUST NOT expect to find
    unsupported attributes from step #2 in such additional
    Subscription Attribute Groups.

5.3. Subscription Template Attributes

 This section contains the Subscription Template Attributes defined
 for the Subscription and Printer objects.

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 Table 1 below shows the Subscription Template Attributes and has two
 columns:
  1. Attribute in Subscription Object: the name and attribute syntax of

each Subscription Object Attribute that is a Subscription Template

    Attribute
  1. Default and Supported Printer Attributes: the default attribute

and supported Printer attributes that are associated with the

    attribute in column 1.
 The "notify-recipient-uri" attribute is for use with Push Delivery
 Methods.  The "notify-pull-method" attribute is for use with Pull
 Delivery Methods.
 For Push Delivery Methods, a Printer MUST support all attributes in
 Table 1 below except for "notify-pull-method" and "notify-attributes"
 (and "notify-pull-method-supported" and "notify-attributes-
 supported").  For Pull Delivery Methods, a Printer MUST support all
 attributes in Table 1 below except for "notify-recipient-uri" and
 "notify-attributes" (and "notify-schemes-supported" and "notify-
 attributes-supported").  If a Printer supports both Push and Pull
 Delivery Methods, then it MUST support both "notify-recipient-uri"
 and "notify-pull-method" attributes.
 For Pull Delivery Methods, a client MUST supply "notify-recipient-
 uri" and MAY omit any of the rest of the attributes in column 1 of
 Table 1 in a Subscription Creation Request.  For Push Delivery
 Methods, a client MUST supply "notify-pull-method" and MAY omit any
 of the rest of the attributes in column 1 of Table 1 in a
 Subscription Creation Request.  A client MUST NOT supply both
 "notify-recipient-uri" and "notify-pull-method" attributes in the
 same Subscription Creation Request.
 Note:  The Default and Supported Printer attributes listed in column
 2 of Table 1 do not have separate sections in this specification
 defining their semantics.  Instead, the section for the corresponding
 Subscription Object attribute (column 1 of Table 1) contains the
 semantics of these Printer attributes.  This approach follows the
 precedence of the Job Template attributes in section 4.2 of [RFC2911]
 where the corresponding "xxx-default" and "xxx-supported" Printer
 attributes are defined in the same section as the "xxx" Job
 attribute.

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 Table 1 - Subscription Template Attributes
 Attribute in Subscription     Default and Supported Printer
 Object                        Attributes
 notify-recipient-uri (uri) *  notify-schemes-supported  (1setOf
                               uriScheme)
 notify-pull-method (type2     notify-pull-method-supported (1setOf
 keyword) **                   type2 keyword)
 notify-events (1setOf type2   notify-events-default (1setOf type2
 keyword)                      keyword)
                               notify-events-supported (1setOf type2
                               keyword)
                               notify-max-events-supported
                               (integer(2:MAX))
 notify-attributes (1setOf     notify-attributes-supported (1setOf
 type2 keyword)                type2 keyword)
 notify-user-data
 (octetString(63))
 notify-charset (charset)      charset-supported (1setOf charset)
 notify-natural-language       generated-natural-language-supported
 (naturalLanguage)             (1setOf naturalLanguage)
 notify-lease-duration         notify-lease-duration-default
 (integer(0:MAX))              (integer(0:67108863))
                               notify-lease-duration-supported
                               (1setOf (integer(0: 67108863) |
                               rangeOfInteger(0:67108863)))
 notify-time-interval
 (integer(0:MAX))
  • "notify-recipient-uri" is for Push Delivery Methods only.
  • * "notify-pull-method" is for Pull Delivery Methods only.

5.3.1. notify-recipient-uri (uri)

 This attribute's value is a URL, which is a special case of a URI.
 Its value consists of a scheme and an address.  The address specifies
 the Notification Recipient and the scheme specifies the Push Delivery
 Method for each Event Notification associated with this Subscription
 Object.
 If a Printer supports any Push Delivery Methods, a Printer MUST
 support this attribute and return the value as supplied by the client
 (no case conversion or other canonicalization) in any operation
 response that includes this attribute.

Herriot & Hastings Standards Track [Page 20] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 For a Push Delivery Method, a client MUST supply this attribute in a
 Subscription Creation Operation.  Thus there is no need for a default
 Printer attribute.
 The URI scheme of the value of this attribute on a Subscription
 object MUST be a value of the "notify-schemes-supported (1setOf
 uriScheme)" Printer attribute (see section 5.3.1.1).  Note: According
 to [RFC2396] the ":" terminates the scheme and so is not part of the
 scheme.  Therefore, values of the "notify-schemes-supported" Printer
 attribute do not include the ":" character.
 If the client supplies an unsupported scheme in the value of this
 attribute, then the Printer MUST NOT create the Subscription Object
 and MUST return the "notify-status-code" attribute with the 'client-
 error-uri-scheme-not-supported' value in the Subscription Attributes
 Group in the response.

5.3.1.1. notify-schemes-supported (1setOf uriScheme)

 This attribute contains the URI schemes supported in the "notify-
 recipient-uri" Subscription Template attribute.  See sections 5.1 and
 5.2 for the behavior of "xxx-supported" Subscription Template Printer
 attributes.

5.3.2. notify-pull-method (type2 keyword)

 This attribute's value is a type2 keyword indicating which Pull
 Delivery Method is to be used.
 Since a Printer MUST support the 'ippget' Pull Delivery Method
 [RFC3996] (see section 15), a Printer MUST support this attribute and
 return the value as supplied by the client in any operation response
 that includes this attribute.
 For a Pull Delivery Method, a client MUST supply this attribute in a
 Subscription Creation Operation.  Thus there is no need for a default
 Printer attribute.
 The keyword value of this attribute on a Subscription object MUST be
 a value of the "notify-pull-method-supported (1setOf type2 keyword)"
 Printer attribute.
 If the client supplies an unsupported method in the value of this
 attribute, then the Printer MUST NOT create the Subscription Object
 and MUST return the "notify-status-code" attribute with the 'client-
 error-attributes-or-values-not-supported' value in the Subscription
 Attributes Group in the response.

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5.3.2.1. notify-pull-method-supported (1setOf type2 keyword)

 See sections 5.1 and 5.2 for the behavior of "xxx-supported"
 Subscription Template Printer attributes.

5.3.3. notify-events (1setOf type2 keyword)

 This attribute contains a set of Subscribed Events.  When an Event
 occurs and it "matches" a value of this attribute, the Printer
 delivers an Event Notification using information in the Subscription
 Object.  The details of "matching" are described subsection 5.3.3.5.
 A Printer MUST support this attribute.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in
 Subscription Creation Operation, the Printer MUST populate this
 attribute on the Subscription Object with its "notify-events-default"
 attribute value.
 Each keyword value of this attribute on a Subscription Object MUST be
 a value of the  "notify-events-supported (1setOf type2 keyword)"
 Printer attribute.
 The number of values of this attribute MUST NOT exceed the value of
 the "notify-max-events-supported" attribute.  A Printer MUST support
 at least 2 values per Subscription Object.  If the number of values
 supplied by a client in a Subscription Creation Operation exceeds the
 value of this attribute, the Printer MUST treat extra values as
 unsupported values and MUST use the value of 'successful-ok-too-
 many-events' for the "notify-status-code" attribute in the
 Subscription Attributes Group of the response.

5.3.3.1. notify-events-default (1setOf type2 keyword)

 See sections 5.1 and 5.2 for the behavior of "xxx-default"
 Subscription Template Printer attributes.

5.3.3.2. notify-events-supported (1setOf type2 keyword)

 See sections 5.1 and 5.2 for the behavior of "xxx-supported"
 Subscription Template Printer attributes.

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5.3.3.3. notify-max-events-supported (integer(2:MAX))

 This attribute specified the maximum number of events that the
 Printer supports for the "notify-events" Subscription Template
 attribute.  See sections 5.1 and 5.2 for the behavior of "xxx-
 supported" Subscription Template Printer attributes.

5.3.3.4. Standard Values for Subscribed Events

 Each value of this attribute is a keyword and it specifies a
 Subscribed Event that represents certain changes.  Some keywords
 represent a subset of changes of another keyword, e.g., 'job-
 completed' is an Event value which is a sub-value of 'job-state-
 change'.  See section 5.3.3.5 for the case where this attribute
 contains both a value and a sub-value.
 The values in this section are divided into three categories: No
 Events, Job Events and Printer Events.
 A Printer MUST support the Events indicated as "REQUIRED" and MAY
 support the Events indicated as "OPTIONAL".

5.3.3.4.1. No Events

 The standard and only keyword value for No Events is:
 'none':  REQUIRED - no Event Notifications for any Events.  As the
    sole value of "notify-events-supported", this value means that the
    Printer does not support the delivery of Event Notifications.  As
    the sole value of "notify-events-default", this value means that a
    client MUST specify the "notify-events" attribute in order for a
    Subscription Creation Operation to succeed.  If the Printer
    receives this value as the sole value of a Subscription Creation
    Operation, it does not create a Subscription Object.  If a Printer
    receives this value with other values of a Subscription Creation
    Operation, the Printer MUST treat this value as an unsupported
    value.

5.3.3.4.2. Subscribed Printer Events

 The standard keyword values for Subscribed Printer Events are:
 'printer-state-changed':  REQUIRED - the Printer changed state from
    any state to any other state.  Specifically, the value of the
    Printer's "printer-state", "printer-state-reasons" or "printer-
    is-accepting-jobs" attributes changed.

Herriot & Hastings Standards Track [Page 23] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

    This Subscribed Event value has the following sub-values:
    'printer-restarted' and 'printer-shutdown'.  A client can listen
    for any of these sub-values if it doesn't want to listen to all
    printer-state changes:
       'printer-restarted':  OPTIONAL - when the printer is powered
          up.
       'printer-shutdown':  OPTIONAL - when the device is being
          powered down.
       'printer-stopped:  REQUIRED - when the printer stops printing,
          i.e., the value of the "printer-state" Printer attribute
          becomes 'stopped'.
 'printer-config-changed':  OPTIONAL - when the configuration of a
    Printer has changed, i.e., the value of the "printer-message-
    from-operator" or any "configuration" Printer attribute has
    changed.  A "configuration" Printer attribute is an attribute
    which can change value because of some human interaction either
    direct or indirect, and which is not covered by one of the other
    Events in this section.  Examples of "configuration" Printer
    attributes are any of the Job Template attributes, such as "xxx-
    supported", "xxx-ready" and "xxx-default".  The client has to
    perform a Get-Printer-Attributes to find out the new values of
    these changed attributes.  This Event is useful for GUI clients
    and drivers to update the available printer capabilities to the
    user.
    This Event value has the following sub-values: 'printer-media-
    changed' and 'printer-finishings-changed'.  A client can listen
    for any of these sub-values if it doesn't want to listen to all
    printer-configuration changes:
       'printer-media-changed':  OPTIONAL - when the media loaded on
          a printer has been changed, i.e., the "media-ready"
          attribute has changed.  This Event includes two cases: an
          input tray that goes empty and an input tray that receives
          additional media of the same type or of a different type.
          The client must check the "media-ready" Printer attribute
          (see [RFC2911] section 4.2.11) separately to find out what
          changed.
       'printer-finishings-changed':  OPTIONAL - when the finisher on
          a printer has been changed, i.e., the "finishings-ready"
          attribute has changed.  This Event includes two cases: a
          finisher that goes empty and a finisher that is refilled
          (even if it is not full).  The client must check the

Herriot & Hastings Standards Track [Page 24] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

          "finishings-ready" Printer attribute separately to find out
          what changed.
 'printer-queue-order-changed': OPTIONAL - the order of jobs in the
    Printer's queue has changed, so that an application that is
    monitoring the queue can perform a Get-Jobs operation to determine
    the new order.  This Event does not include when a job enters the
    queue (the 'job-created' Event covers that) and does not include
    when a job leaves the queue (the 'job-completed' Event covers
    that).

5.3.3.4.3. Subscribed Job Events

 The standard keyword values for Subscribed Job Events are:
 'job-state-changed':  REQUIRED - the job has changed from any state
    to any other state.  Specifically, the Printer delivers this Event
    whenever the value of the "job-state" attribute or "job-state-
    reasons" attribute changes.  When a Job is removed from the Job
    Retention or Job History phases (see [RFC2911] section 4.3.7.1),
    no Event is generated.
    This Event value has the following sub-values: 'job-created',
    'job-completed' and 'job-stopped'.  A client can listen for any of
    these sub-values if it doesn't want to listen to all 'job-state
    changes'.
    'job-created':  REQUIRED - the Printer has accepted a Job
       Creation operation, a Restart-Job operation [RFC2911], or any
       job operation that creates a Job object from an existing Job
       object.  The Printer populates the job's "time-at-creation"
       attribute value (see [RFC2911] section 4.3.14.1).  The Printer
       puts the job in the 'pending', 'pending-held' or 'processing'
       states.
    'job-completed':  REQUIRED - the job has reached one of the
       completed states, i.e., the value of the job's "job-state"
       attribute has changed to: 'completed', 'aborted', or
       'canceled'.  The Job's "time-at-completed" and "date-time-at-
       completed" (if supported) attributes are set (see [RFC2911]
       section 4.3.14).  When a Job completes, a Notification
       Recipient MAY query the Job using the Get-Job-Attributes
       operation.  To allow such a query, the Printer retains the Job
       in the Job Retention and/or the Job History phases (see
       [RFC2911] section 4.3.7.1) for a suitable amount of time that
       depends on implementation and the Delivery Methods supported.
       The Printer also delivers this Event when a Job is removed with
       the Purge-Job operation (see [RFC2911] section 3.2.9).  In this

Herriot & Hastings Standards Track [Page 25] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

       case, the Event Notification MUST report the 'job-state' as
       'canceled' and the Job object is no longer present for query.
    'job-stopped:  OPTIONAL - when the job stops printing, i.e.,
       the value of the "job-state" Job attribute becomes
       'processing-stopped'.
 'job-config-changed':  OPTIONAL - when the configuration of a job has
    changed, i.e., the value of the "job-message-from-operator" or any
    of the "configuration" Job attributes have changed.  A
    "configuration" Job attribute is an attribute that can change
    value because of some human interaction either direct or indirect.
    Examples of "configuration" Job attributes are any of the job
    template attributes and the "job-name" attribute.  The client
    performs a Get-Job-Attributes to find out the new values of the
    changed attributes.  This Event is useful for GUI clients and
    drivers to update the job information to the user.
 'job-progress': OPTIONAL - when the Printer has completed Printing a
    sheet.  See the separate [RFC3381] specification for additional
    attributes that a Printer MAY deliver in an Event Notification
    caused by this Event.  The "notify-time-interval" attribute
    affects this Event by causing the Printer NOT to deliver an Event
    Notification every time a 'job-progress' Events occurs.  See
    section 5.3.9 for full details.

5.3.3.5. Rules for Matching of Subscribed Events

 When an Event occurs, the Printer MUST find each Subscription object
 whose "notify-events" attribute "matches" the Event.  The rules for
 "matching" of Subscribed Events are described separately for Printer
 Events and for Job Events.  This section also describes some special
 cases.

5.3.3.5.1. Rules for Matching of Printer Events

 Given that the Printer causes Printer Event E to occur, for each
 Per-Job or Per-Printer Subscription S in the Printer, if E equals a
 value of this attribute in S or E is a sub-value of a value of this
 attribute in S, the Printer MUST generate an Event Notification.
 Consider the example.  There are three Subscription Objects each with
 the Subscribed Printer Event 'printer-state-changed'.  Subscription
 Object A is a Per-Printer Subscription Object.  Subscription Object B
 is a Per-Job Subscription Object for Job 1, and Subscription Object C
 is a Per-Job Subscription Object for Job 2.  When the Printer enters
 the 'stopped' state, the Printer delivers an Event Notification to
 the Notification Recipients of Subscription Objects A, B, and C

Herriot & Hastings Standards Track [Page 26] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 because this is a Printer Event.  Note if Job 1 has already
 completed, the Printer would not deliver an Event Notification for
 its Subscription Object, even if Job 1 is retained in the Job
 Retention and/or the Job History phases (see [RFC2911] section
 4.3.7.1).

5.3.3.5.2. Rules for Matching of Job Events

 Given that Job J causes Job Event E to occur:
 1. For each Per-Printer Subscription S in the Printer, if E equals a
    value of this attribute in S or E is a sub-value of a value of
    this attribute in S, the Printer MUST generate an Event
    Notification.
 2. For each Per-Job Subscription S associated with Job J, if E equals
    a value of this attribute in S or E is a sub-value of a value of
    this attribute in S, the Printer MUST generate an Event
    Notification.
 3. For each Per-Job Subscription S that is NOT associated Job J, if E
    equals a value of this attribute in S or E is a sub-value of a
    value of this attribute in, the Printer MUST NOT generate an Event
    Notification from S.
 Consider the example: There are three Subscription Objects listening
 for the Job Event 'job-completed'.  Subscription Object A is a Per-
 Printer Subscription Object.  Subscription Object B is a Per-Job
 Subscription Object for Job 1, and Subscription Object C is a Per-Job
 Subscription Object for Job 2.  In addition, Per-Printer Subscription
 Object D is listening for the Job Event 'job-state-changed'.  When
 Job 1 completes, the Printer delivers an Event Notification to the
 Notification Recipient of Subscription Object A (because it is Per-
 Printer) and Subscription Object B because it is a Per-Job
 Subscription Object associated with the Job generating the Event.
 The Printer also delivers an Event Notification to the Notification
 Recipient of Subscription Object D because 'job-completed' is a sub-
 value of 'job-state-changed' - the value that Subscription Object D
 is listening for.  The Printer does not deliver an Event Notification
 to the Notification Recipients of Subscription Object C because it is
 a Per-Job Subscription Object associated with some Job other than the
 Job generating the Event.

5.3.3.5.3. Special Cases for Matching Rules

 This section contains two rules for the special case where a single
 Event produces multiple Event Notifications destined for the same
 Notification Recipient.  These two rules clarify whether a Printer

Herriot & Hastings Standards Track [Page 27] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 should send multiple Event Notifications or consolidate them into a
 single Event Notification.
 If an Event matches Subscribed Events in two different Subscription
 Objects and the Printer would deliver two identical Event
 Notifications (except for the "notify-subscription-id" attribute) to
 the same Notification Recipient using the same Delivery Method, the
 Printer MUST deliver both Event Notifications.  That is, the Printer
 MUST NOT try to consolidate seemingly identical Event Notifications
 that occur in separate Subscription objects.  Incidentally, the
 Printer MUST NOT reject Subscription Creation Operations that would
 create this scenario.
 Consider the example: At the time a Job completes, there are two
 Per-Printer Subscription Objects A and B with the same Notification
 Recipient R.  Subscription Object A has the Subscribed Job Event
 'job-state-changed'.  Subscription Object B has the Subscribed Job
 Event 'job-completed'.  Both Subscription Objects match the Event
 'job-completed'.  The Printer delivers two Event Notifications to the
 Notification Recipient R.  One with the value of  'job-state-changed'
 for the "notify-subscribed-event" attribute and the other with the
 value of  'job-completed' for the "notify-subscribed-event"
 attribute.
 If an Event matches two Subscribed Events in a single Subscription
 object (e.g., a value and its sub-value), a Printer MAY deliver one
 Event Notification for each matched value in the Subscription Object
 or it MAY deliver only a single Event Notification.  The rules in
 sections 5.3.3.5.1 and 5.3.3.5.2 are purposefully flexible about the
 number of Event Notifications sent when Event E matches two or more
 values in a Subscription Object.
 Consider the example: At the time a Job completes, a Subscription
 Object A has two Subscribed Job Events 'job-state-changed' and 'job-
 completed'.  Both Subscribed Job Events match the Event 'job-
 completed'.  The Printer delivers either one or two Event
 Notifications to the Notification Recipient of Subscription Object A,
 depending on implementation.  If it delivers two Event Notifications,
 one has the value of  'job-state-changed' for the "notify-
 subscribed-event" attribute, and the other has the value of 'job-
 completed' for the "notify-subscribed-event" attribute.  If it
 delivers one Event Notification, it has the value of either 'job-
 state-changed' or 'job-completed' for the "notify-subscribed-event"
 attribute, depending on implementation.  The algorithm for choosing
 such a value is implementation dependent.

Herriot & Hastings Standards Track [Page 28] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

5.3.4. notify-attributes (1setOf type2 keyword)

 This attribute contains a set of attribute names.  When a Printer
 delivers a Machine Consumable Event Notification, it includes a fixed
 set of attributes (see section 9.1).  If this attribute is present
 and the Event Notification is Machine Consumable, the Printer also
 includes the attributes specified by this attribute.
 A Printer MAY support this attribute.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in
 Subscription Creation Operation or the Printer does not support this
 attribute, the Subscription Object either (1) MAY contain the
 "notify-attributes" attribute with a 'none' value or (2) NEED NOT
 contain the attribute at all.  There is no "notify-attributes-
 default" Printer attribute.
 Each keyword value of this attribute on a Subscription Object MUST be
 a value of the "notify-attributes-supported (1setOf type2 keyword)"
 Printer attribute (see section 5.3.4.1).  The "notify-attributes-
 supported" MAY contain any Printer attribute, Job attribute or
 Subscription Object attribute that the Printer supports in an Event
 Notification.  It MUST NOT contain any of the attributes in Section
 9.1 that a Printer automatically puts in an Event Notification; it
 would be redundant.  If a client supplies an attribute in Section
 9.1, the Printer MUST treat it as an unsupported attribute value of
 the "notify-attributes" attribute.
 The following rules apply to each keyword value N of the "notify-
 attributes" attribute: If the value N names:
 a) a Subscription attribute, the Printer MUST use the attribute N in
    the Subscription Object that is being used to generate the Event
    Notification.
 b) a Job attribute and the Printer is generating an Event
    Notification from a Per-Job Subscription Object S, the Printer
    MUST use the attribute N in the Job object associated with S.
 c) a Job attribute and the Printer is generating an Event
    Notification from a Per-Printer Subscription Object and the Event
    is:
  1. a Job Event, the Printer MUST use the attribute N in the Job

object that caused the Event.

Herriot & Hastings Standards Track [Page 29] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

  1. a Printer Event, the Printer MUST use the attribute N in the

active Job.

 If a Printer supports this attribute and a Subscription Object
 contains this attribute and the Delivery Method generates a Machine
 Consumable Event Notification, the Printer MUST include in each Event
 Notification:
 a) the attributes specified in section 9.1 and
 b) each attribute named by this attribute.
 The Printer MUST NOT use this attribute to generate a Human
 Consumable Event Notification.

5.3.4.1. notify-attributes-supported (1setOf type2 keyword)

 See sections 5.1 and 5.2 for the behavior of "xxx-supported"
 Subscription Template Printer attributes.

5.3.5. notify-user-data (octetString(63))

 This attribute contains opaque data that some Delivery Methods
 include in each Machine Consumable Event Notification.  The opaque
 data might contain, for example:
  1. the identity of the Subscriber
  1. a path or index to some Subscriber information
  1. a key that identifies to the Notification Recipient the ultimate

recipient of the Event Notification

  1. the id for a Notification Recipient that had previously registered

with an Instant Messaging Service

 A Printer MUST support this attribute.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in the
 Subscription Creation Operation, the Subscription Object either (1)
 MAY contain the "notify-user-data" attribute with a zero length value
 or (2) NEED NOT contain the attribute at all.  There is no "notify-
 user-data-default" Printer attribute.

Herriot & Hastings Standards Track [Page 30] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 There is no "notify-user-data-supported" Printer attribute.  Rather,
 any octetString whose length does not exceed 63 octets is a supported
 value.  If the length exceeds 63 octets, the Printer MUST treat it as
 an unsupported value.

5.3.6. notify-charset (charset)

 This attribute specifies the charset to be used in the Event
 Notification content sent to the Notification Recipient, whether the
 Event Notification content is Machine Consumable or Human Consumable.
 A Printer MUST support this attribute.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in
 Subscription Creation Operation or supplies an unsupported value, the
 Printer MUST populate this attribute in the Subscription Object with
 the value of the "attributes-charset" operation attribute, which is a
 REQUIRED attribute in all IPP requests (see [RFC2911]).  If the value
 of the "attributes-charset" attribute is unsupported, the Printer
 MUST populate this attribute in the Subscription Object with the
 value of the Printer's "charset-configured" attribute.  There is no
 "notify-charset-default" Printer attribute.
 The value of this attribute on a Subscription Object MUST be a value
 of the "charset-supported (1setOf charset)" Printer attribute.

5.3.7. notify-natural-language (naturalLanguage)

 This attribute specifies the natural language to be used in any human
 consumable text in the Event Notification content sent to the
 Notification Recipient, whether the Event Notification content is
 Machine Consumable or Human Consumable.
 A Printer MUST support this attribute.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in
 Subscription Creation Operation or supplies an unsupported value, the
 Printer MUST populate this attribute in the Subscription Object with
 the value of the "attributes-natural-language" operation attribute,
 which is a REQUIRED attribute in all IPP requests (see [RFC2911]
 section 3.1.4).  If the value of the "attributes-natural-language"
 attribute is unsupported, the Printer MUST populate this attribute in
 the Subscription Object with the value of the Printer's "natural-
 language-configured" attribute (see [RFC2911] section 4.4.19).  There
 is no "notify-natural-language-default" Printer attribute.

Herriot & Hastings Standards Track [Page 31] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 The value of this attribute on a Subscription Object MUST be a value
 of the "generated-natural-language-supported (1setOf type2
 naturalLanguage)" Printer attribute (see [RFC2911] section 4.4.20).

5.3.8. notify-lease-duration (integer(0:67108863))

 This attribute specifies the duration of the lease (in seconds)
 associated with the Per-Printer Subscription Object at the time the
 Subscription Object was created or the lease was renewed.  The
 duration of the lease is infinite if the value is 0, i.e., the lease
 never expires.  See section 5.4.3 on "notify-lease-expiration-time
 (integer(0:MAX))" for more details.
 This attribute is not present on a Per-Job Subscription Object
 because the Subscription Object lasts exactly as long as the
 associated Job object.  See discussion of the 'job-completed' event
 in section 5.3.3.4.3 about retention of the Job object after
 completion.
 A Printer MUST support this attribute.
 For a Subscription Object Creation operation of a Per-Job
 Subscription Object, the client MUST NOT supply this attribute.  If
 the client does supply this attribute, the Printer MUST treat it as
 an unsupported attribute.
 For a Subscription Creation Operation of a Per-Printer Subscription
 Object or a Renew-Subscription operation, a client MAY supply this
 attribute.  If the client does not supply this attribute, the Printer
 MUST populate this attribute with its "notify-lease-duration-default"
 (0:67108863) attribute value.  If the client supplies this attribute
 with an unsupported value, the Printer MUST populate this attribute
 with a supported value, and this value SHOULD be as close as possible
 to the value requested by the client.  Note: this rule implies that a
 Printer doesn't assign the value of 0 (infinite) unless the client
 requests it.
 After the Printer has populated this attribute with a supported
 value, the value represents the "granted duration" of the lease in
 seconds and the Printer updates the value of the Subscription
 Object's "notify-lease-expiration-time" attribute as specified in
 section 5.4.3.
 The value of this attribute on a Subscription Object MUST be a value
 of the "notify-lease-duration-supported" (1setOf (integer(0:67108863)
 | rangeOfInteger(0:67108863))) Printer attribute.

Herriot & Hastings Standards Track [Page 32] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 A Printer MAY require authentication in order to return the value of
 0 (the lease never expires) as one of the values of "notify-lease-
 duration-supported", and to allow 0 as a value of the "notify-lease-
 duration" attribute.
 Note:  The maximum value 67,108,863 is 2 raised to the 26 power minus
 1 and is about 2 years in seconds.  The value is considerably less
 than MAX so that there is virtually no chance of an overflow when the
 Printer adds it to the Printer's "printer-up-time" attribute value
 (see [RFC2911] section 4.4.29) to produce the "notify-lease-
 expiration-time" Subscription Description attribute value (see
 section 5.4.3).

5.3.8.1. notify-lease-duration-default (integer(0:67108863))

 See sections 5.1 and 5.2 for the behavior of "xxx-default"
 Subscription Template Printer attributes.

5.3.8.2. notify-lease-duration-supported (1setOf (integer(0: 67108863) |

       rangeOfInteger(0:67108863)))
 See sections 5.1 and 5.2 for the behavior of "xxx-supported"
 Subscription Template Printer attributes.

5.3.9. notify-time-interval (integer(0:MAX))

 The 'job-progress' Event occurs each time that a Printer completes a
 sheet.  Some Notification Recipients do not want to receive an Event
 Notification every time this Event occurs.  This attribute allows a
 Subscribing Client to request how often it wants to receive Event
 Notifications for 'job-progress' Events.  The value of this attribute
 MAY be any nonnegative integer (0,MAX) indicating the minimum number
 of seconds between 'job-progress' Event Notifications.
 The Printer MUST support this attribute if and only if the Printer
 supports the 'job-progress' Event.
 A client MAY supply this attribute in a Subscription Creation
 Operation.  If the client does not supply this attribute in the
 Subscription Creation Operation, the Subscription Object either (1)
 MAY contain the "notify-time-interval" attribute with a '0' value or
 (2) NEED NOT contain this attribute at all.  There is no "notify-
 time-interval-default" Printer attribute.
 There is no "notify-time-interval-supported" Printer attribute.

Herriot & Hastings Standards Track [Page 33] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 If the 'job-progress' Event occurs and a Subscription Object contains
 the 'job-progress' Event as a value of the 'notify-events' attribute,
 there are two cases to consider:
 1. This attribute is not present on the Subscription Object or has
    the value of 0.  The Printer MUST generate and deliver an Event
    Notification (as is the case with other Events).
 2. This attribute is present with a nonzero value of N:
    a) If the Printer has not sent an Event Notification for the
       'job-progress' Event for the associated Subscription Object
       within the past N seconds, the Printer MUST deliver an Event
       Notification for the Event that just occurred.  Note when the
       Printer completes the first page of a Job, this rule implies
       that the Printer delivers an Event Notification for a Per-Job
       Subscription Object.
    b) Otherwise, the Printer MUST NOT generate or deliver an Event
       Notification for the associated Subscription Object.  The
       Printer MUST NOT increase the value of the "notify-sequence-
       number" Subscription Object attribute (i.e., the sequence of
       values of the "notify-sequence-number" attribute counts the
       Event Notifications that the Printer sent and not the Events
       that do not cause an Event Notification to be sent).
 It is RECOMMENDED that a Subscribing Client use this attribute when
 it subscribes to the 'job-progress' Event, and that the value be
 sufficiently large to limit the frequency with which the Printer
 delivers Event Notifications requests.
 This attribute MUST NOT effect any Events other than 'job-progress'.

5.4. Subscription Description Attributes

 Subscription Description Attributes are those attributes that a
 Printer adds to a Subscription Object at the time of its creation.
 A Printer MUST support all attributes in this Table 2.
 A client MUST NOT supply the attributes in Table 2 in a Subscription
 Template Attributes Group of a Subscription Creation Operation.
 There are no corresponding default or supported attributes.

Herriot & Hastings Standards Track [Page 34] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Table 2 - Subscription Description Attributes
    Subscription Object attributes:
    notify-subscription-id (integer(1:MAX))
    notify-sequence-number (integer(0:MAX))
    notify-lease-expiration-time (integer(0:MAX))
    notify-printer-up-time (integer(1:MAX))
    notify-printer-uri (uri)
    notify-job-id (integer(1:MAX))
    notify-subscriber-user-name (name(MAX))

5.4.1. notify-subscription-id (integer (1:MAX))

 This attribute identifies a Subscription Object instance with a
 number that is unique within the context of the Printer.  The Printer
 generates this value at the time it creates the Subscription Object.
 A Printer MUST support this attribute.
 The Printer MAY assign the value of this attribute sequentially as it
 creates Subscription Objects.  However, if there is no security on
 Subscription objects, sequential assignment exposes the system to a
 passive traffic monitoring threat.
 The Printer SHOULD avoid re-using recent values of this attribute
 during continuous operation of the Printer as well as across power
 cycles.  Then a Subscribing Client is unlikely to find that a stale
 reference accesses a new Subscription Object.
 The 0 value is not permitted in order to allow for compatibility with
 "job-id" and with MIB table index values, which are recommended not
 to be 0.

5.4.2. notify-sequence-number (integer (0:MAX))

 The value of this attribute indicates the number of times that the
 Printer has generated and attempted to deliver an Event Notification
 for this Subscription object.  When an Event Notification contains
 this attribute, the Notification Recipient can determine whether it
 missed some Event Notifications (i.e., numbers skipped) or received
 duplicates (i.e., same number twice).
 A Printer MUST support this attribute.
 When the Printer creates a Subscription Object, it MUST populate this
 attribute with a value of 0.  This value indicates that the Printer
 has not sent any Event Notifications for this Subscription Object.

Herriot & Hastings Standards Track [Page 35] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Each time the Printer delivers a newly generated Event Notification,
 it MUST increase the value of this attribute by 1.  For some Delivery
 Methods, the Printer MUST include this attribute in each Event
 Notification, and the value MUST be the value after it is increased
 by 1.  That is, the value of this attribute in the first Event
 Notification after Subscription object creation MUST be 1, the second
 MUST be 2, etc.  If a Delivery Method is defined such that the
 Notification Recipient returns a response, the Printer can re-try
 delivering an Event Notification a certain number of times with the
 same sequence number when the Notification Recipient fails to return
 a response.
 If a Subscription Object lasts long enough to reach the value of MAX,
 its next value MUST be 0, i.e., it wraps.

5.4.3. notify-lease-expiration-time (integer(0:MAX))

 This attribute specifies the time in the future when the lease on the
 Per-Printer Subscription Object will expire, i.e., the "printer-up-
 time" value at which the lease will expire.  If the value is 0, the
 lease never expires.
 A Printer MUST support this attribute.
 When the Printer creates a Per-Job Subscription Object, this
 attribute MUST NOT be present - the Subscription Object lasts exactly
 as long as the associated Job object.  See also the discussion of the
 'job-completed' event in section 5.3.3.4.3 about retention of the Job
 object after completion so that a Notification Recipient can query
 the Job object after receiving the 'job-completed' Event
 Notification.
 When the Printer creates a Per-Printer Subscription Object, it
 populates this attribute with a value that is the sum of the values
 of the Printer's "printer-up-time" attribute and the Subscription
 Object's "notify-lease-duration" attribute with the following
 exception.  If the value of the Subscription Object's "notify-lease-
 duration" attribute is 0 (i.e., no expiration time), then the value
 of this attribute MUST be set to 0 (i.e., no expiration time).
 When the Printer powers up, it MUST populate this attribute in each
 persistent Subscription Object with a value using the algorithm in
 the previous paragraph.
 When the "printer-up-time" equals the value of this attribute, the
 Printer MUST delete the Subscription Object.  A client can extend a
 lease of a Per-Printer Subscription Object with the Renew-
 Subscription operation (see section 11.2.6).

Herriot & Hastings Standards Track [Page 36] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Note: In order to compute the number of seconds remaining in a lease
 for a Per-Printer Subscription Object, a client can subtract the
 Subscription's "notify-printer-up-time" attribute (see section 5.4.4)
 from the Subscription's "notify-lease-expiration-time" attribute.

5.4.4. notify-printer-up-time (integer(1:MAX))

 This attribute is an alias for the Printer's "printer-up-time"
 attribute " (see [RFC2911] section 4.4.29).  In other words, when
 this attribute is queried with the Get-Subscriptions or Get-
 Subscription-Attributes operations (see sections 11.2.4 and 11.2.5),
 the value returned is the current value of the Printer's "printer-
 up-time" attribute, rather than the time at which the Subscription
 Object was created.
 A Printer MUST support this attribute.
 When the Printer creates a Per-Job Subscription Object, this
 attribute MUST NOT be present.  When the Printer creates a Per-
 Printer Subscription Object, this attribute MUST be present.
 Note: this attribute exists in a Per-Printer Subscription Object so
 that a client using the Get-Subscription-Attributes or Get-
 Subscription operations can convert the Per-Printer Subscription's
 "notify-lease-expiration-time" attribute to wall clock time with one
 request.  If the value of the "notify-lease-expiration-time"
 attribute is not 0 (i.e., no expiration time), then the difference
 between the "notify-lease-expiration-time" attribute and the
 "notify-printer-up-time" is the remaining number of seconds on the
 lease from the current time.

5.4.5. notify-printer-uri (uri)

 This attribute identifies the Printer object that created this
 Subscription Object.
 A Printer MUST support this attribute.
 During a Subscription Creation Operation, the Printer MUST populate
 this attribute with the value of the "printer-uri" operation
 attribute in the request.  From the Printer URI, the client can, for
 example, determine what security scheme was used.

5.4.6. notify-job-id (integer(1:MAX))

 This attribute specifies whether the containing Subscription Object
 is a Per-Job or Per-Printer Subscription Object, and for Per-Job
 Subscription Objects, it specifies the associated Job.

Herriot & Hastings Standards Track [Page 37] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 A Printer MUST support this attribute.
 If this attribute is not present, the Subscription Object MUST be a
 Per-Printer Subscription.  If this attribute is present, the
 Subscription Object MUST be a Per-Job Subscription Object and this
 attribute MUST identify the Job with which the Subscription Object is
 associated.
 Note: This attribute could be useful to a Notification Recipient that
 receives an Event Notification generated from a Per-Job Subscription
 Object and caused by a Printer Event.  The Event Notification gives
 access to the Printer and the Subscription Object.  The Event
 Notification gives access to the associated Job only via this
 attribute.  See discussion of the 'job-completed' event in section
 5.3.3.4.3 about retention of the Job object after completion so that
 a Notification Recipient can query the Job object after receiving the
 'job-completed' Event Notification.

5.4.7. notify-subscriber-user-name (name(MAX))

 This attribute contains the name of the user who performed the
 Subscription Creation Operation.
 A Printer MUST support this attribute.
 The Printer MUST populates this attribute with the most authenticated
 printable name that it can obtain from the authentication service
 over which the Subscription Creation Operation was received.  The
 Printer uses the same mechanism for determining the value of this
 attribute as it does for a Job's "job-originating-user-name" (see
 [RFC2911] section 4.3.6).
 Note:  To help with authentication, a Subscription Object may have
 additional private attributes about the user, e.g., a credential of a
 principal.  Such private attributes are implementation-dependent and
 not defined in this document.

6. Printer Description Attributes Related to Notification

 This section defines the Printer Description attributes that are
 related to Notification.  Table 3 lists the Printer Description
 attributes, indicates the Printer support required for conformance,
 and whether or not the attribute is READ-ONLY (see section 3.1):

Herriot & Hastings Standards Track [Page 38] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Table 3 - Printer Description Attributes Associated with Notification
 Printer object attributes:                   REQUIRED     READ-ONLY
 printer-state-change-time (integer(1:MAX))   No           Yes
 printer-state-change-date-time (dateTime)    No           Yes

6.1. printer-state-change-time (integer(1:MAX))

 This OPTIONAL attribute records the most recent time at which the
 'printer-state-changed' Printer Event occurred whether or not any
 Subscription objects were listening for this event.  This attribute
 helps a client or operator to determine how long the Printer has been
 in its current state.
 A Printer MAY support this attribute and if so, the attribute MUST be
 READ-ONLY.
 On power-up, the Printer MUST populate this attribute with the value
 of its "printer-up-time" attribute, so that it always has a value.
 Whenever the 'printer-state-changed' Printer Event occurs, the
 Printer MUST update this attribute with the value of the Printer's
 "printer-up-time" attribute.

6.2. printer-state-change-date-time (dateTime)

 This OPTIONAL attribute records the most recent time at which the
 'printer-state-changed' Printer Event occurred whether or not there
 were any Subscription Objects listening for this event.  This
 attribute helps a client or operator to determine how long the
 Printer has been in its current state.
 A Printer MAY support this attribute and if so, the attribute MUST be
 READ-ONLY.
 On power-up, the Printer MUST populate this attribute with the value
 of its "printer-current-time" attribute, so that it always has a
 value (see [RFC2911] section 4.4.30 on "printer-current-time").
 Whenever the 'printer-state-changed' Printer Event occurs, the
 Printer MUST update this attribute with the value of the Printer's
 "printer-current-time" attribute.

7. New Values for Existing Printer Description Attributes

 This section contains those attributes for which additional values
 are added.

Herriot & Hastings Standards Track [Page 39] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

7.1. operations-supported (1setOf type2 enum)

 The following "operation-id" values are added in order to support the
 new operations defined in this document:
 Table 4 - Operation-id assignments
 Value       Operation Name
 0x0016      Create-Printer-Subscriptions
 0x0017      Create-Job-Subscriptions
 0x0018      Get-Subscription-Attributes
 0x0019      Get-Subscriptions
 0x001A      Renew-Subscription
 0x001B      Cancel-Subscription

8. Attributes Only in Event Notifications

 This section contains those attributes that exist only in Event
 Notifications and do not exist in any objects.

8.1. notify-subscribed-event (type2 keyword)

 This attribute indicates the Subscribed Event that caused the Printer
 to deliver this Event Notification.  This attribute exists only in
 Event Notifications.
 This attribute MUST contain one of the values of the "notify-events"
 attribute in the Subscription Object, i.e., one of the Subscribed
 Event values.  Its value is the Subscribed Event that "matches" the
 Event that caused the Printer to deliver this Event Notification.
 This Subscribed Event value may be identical to the Event or the
 Event may be a sub-value of the Subscribed Event.  For example, the
 'job-completed' Event (which is a sub-event of the 'job-state-
 changed' event) would cause the Printer to deliver an Event
 Notification for either the 'job-completed' or 'job-state-changed'
 Subscribed Events and to deliver the 'job-completed' or 'job-state-
 changed' value for this attribute, respectively.  See section 5.3.3.5
 for the "matching" rules of Subscribed Events and for additional
 examples.
 The Delivery Method Document specifies whether the Printer includes
 the value of this attribute in an Event Notification.

Herriot & Hastings Standards Track [Page 40] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

8.2. notify-text (text(MAX))

 This attribute contains a Human Consumable text message (see section
 9.2).  This message describes the Event and is encoded as plain text,
 i.e., 'text/plain' with the charset specified by Subscription
 Object's "notify-charset" attribute.
 Note: this attribute contains a text message only and must not
 contain any encoding information, such as 'text/plain'.  The
 'text/plain' encoding is implicit and thus the charset must be
 specified by an alternate mechanism, namely the "notify-charset"
 attribute.
 The Delivery Method Document specifies whether the Printer includes
 this attribute in an Event Notification.

9. Event Notification Content

 This section defines the Event Notification content that the Printer
 delivers when an Event occurs.
 When an Event occurs, the Printer MUST find each Subscription object
 whose "notify-events" attribute "matches" the Event.  See section
 5.3.3.5 for details on "matching".  For each matched Subscription
 Object, the Printer MUST create an Event Notification with the
 content and format that the Delivery Method Document specifies.  The
 content contains the value of attributes specified by the Delivery
 Method Document.  The Printer obtains the values immediately after
 the Event occurs.  For example, if the "printer-state" attribute
 changes from 'idle' to 'processing', the Event 'printer-state-
 changed' occurs and the Printer puts various attributes into the
 Event Notification, including "printer-up-time" and "printer-state"
 with the values that they have immediately after the Event occurs,
 i.e., the value of  "printer-state" is 'processing'.
 Event Notification Ordering:
 When a Printer delivers Event Notifications, the Event Notifications
 from any given Subscription Object MUST be in time stamp order, i.e.,
 in order of increasing "printer-up-time" attribute value in the Event
 Notification (see Table 5).  These Event Notifications MAY be
 interleaved with those from other Subscription Objects, as long as
 those others are also in time stamp order.  The Printer MUST observe
 these ordering requirements whether delivering multiple pending
 Events as multiple separate Event Notifications or together in a
 single Compound Event Notification.

Herriot & Hastings Standards Track [Page 41] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 If a Subscribing Client wants the Printer to deliver certain Event
 Notifications in time stamp order, the Subscribing Client uses a
 single Subscription Object.  Even so, depending on the underlying
 transport, the actual order that a Notification Recipient receives
 separate Event Notifications may differ from the order sent by the
 Printer (e.g., email).
 Example:  Consider two Per-Printer Subscription Objects: SO1 and SO2.
 SO1 requests 'job-state-changed' events and SO2 requests 'printer-
 state-changed' events.  The number in parens is the time stamp.  The
 following Event Notification sequences are the only ones that conform
 to the ordering requirements for the Printer to deliver the Event
 Notifications:
    (a) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO1:
    'job-completed' (1009), SO2: 'printer-stopped' (1005)
    (b) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO2:
    'printer-stopped' (1005), SO1: 'job-completed' (1009)
    (c) SO1: 'job-created' (1000), SO2: 'printer-stopped' (1005), SO1:
    'job-stopped' (1005), SO1: 'job-completed' (1009)
    (d) SO2: 'printer-stopped (1005), SO1: 'job-created' (1000), SO1:
    'job-stopped' (1005), SO1: 'job-completed' (1009)
 Examples (b) and (c) are interleaved; examples (a) and (d) are not
 interleaved and are not appropriate for some Delivery Methods.
 If two different Events occur simultaneously, or nearly so (e.g.,
 "printer-up-time" has the same value for both), the Printer MUST
 create a separate Event Notification for each Event, even if the
 associated Subscription Object is the same for both Events.  However,
 the Printer MAY combine these distinct Event Notifications into a
 single Compound Event Notification if the Delivery Method supports
 Compound Event Notifications.  For example, suppose that two nearly-
 simultaneously Events represent two successive 'printer-state-
 changed' Events, one from 'idle' to 'processing' and another from
 'processing' to 'stopped'.  These two Events have the same name but
 are different instances of the Event.  Then the Printer MUST create a
 separate Event Notification for each Event and SHOULD accurately
 report the "printer-state" of the first Event as 'processing' and the
 second Event as 'stopped'.
 If a Subscription Object contains more than one Subscribed Event, and
 several Events occur in quick succession each matching a different
 Subscribed Event in the Subscription Object, the Printer MUST NOT
 generate a single Event Notification from several of these Events,

Herriot & Hastings Standards Track [Page 42] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 but MAY combine distinct Event Notifications into a single Compound
 Event Notification if the Delivery Method supports Compound Event
 Notifications.
 After the Printer has created the Event Notification, the Printer
 delivers it via either a:
    Push Delivery Method: The Printer delivers the Event Notification
    shortly after an Event occurs.  For some Push Delivery Methods,
    the Notification Recipient MUST deliver a response; for others it
    MUST NOT deliver a response.
    Pull Delivery Method: The Printer saves Event Notifications for
    some Event Life and expects the Notification Recipient to request
    Event Notifications.  The Printer returns the Event Notifications
    in a response to such a request.
 If an error that meets the following conditions occurs, the Printer
 MUST cancel the Subscription Object.
 a) the error occurs during the delivering of an Event Notification
    generated from Subscription Object S AND
 b) the error would continue to occur every time the Printer delivers
    an Event Notification generated from Subscription Object S in the
    future.
 For example, if the address of the "notify-recipient-uri" of
 Subscription Object A references a non-existent target and the
 Printer determines this fact, it MUST delete Subscription Object A.
 The next two sections describe the values that a Printer delivers in
 the content of Machine Consumable and Human Consumable Event
 Notifications, respectively.
 The tables in the sub-sections of this section contain the following
 columns:
 a) Source Value: the name of the attribute that supplies the value
    for the Event Notification.  Asterisks in this field refer to a
    note below the table.
 b) Delivers: if the Printer supports the value (column 1) on the
    Source Object (column 3) the Delivery Method MUST specify:
       MUST: that the Printer MUST deliver the value.

Herriot & Hastings Standards Track [Page 43] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

       SHOULD: either that the Printer MUST deliver the value or that
       the value is incompatible with the Delivery Method.
       MAY: that the Printer MUST, SHOULD, MAY, MUST NOT, SHOULD NOT,
       or NEED NOT deliver the value.  The Delivery Method specifies
       the level of conformance for the Printer.
 c) Source Object: the object from which the source value comes.  If
    the object is "Event Notification", the Printer fabricates the
    value when it delivers the Event Notification.  See section 8.

9.1. Content of Machine Consumable Event Notifications

 This section defines the attributes that a Delivery Method MUST
 mention in a Delivery Method Document when specifying the Machine
 Consumable Event Notification's contents.
 This document does not define the order of attributes in Event
 Notifications.  However, Delivery Method Documents MAY define the
 order of some or all of the attributes.
 A Delivery Method Document MUST specify additional attributes (if
 any) that a Printer implementation delivers in a Machine Consumable
 Event Notification.
 Notification Recipients MUST be able to accept Event Notifications
 containing attributes they do not recognize.  What a Notification
 Recipient does with an unrecognized attribute is implementation-
 dependent.  Notification Recipients MAY attempt to display
 unrecognized attributes anyway or MAY ignore them.
 The next three sections define the attributes in Event Notification
 Contents that are:
    1. for all Events
    2. for Job Events only
    3. for Printer Events only

9.1.1. Event Notification Content Common to All Events

 This section lists the attributes that a Delivery Method Document
 MUST specify for all Events.
 Table 5 lists potential values in each Event Notification.

Herriot & Hastings Standards Track [Page 44] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Table 5 - Attributes in Event Notification Content
 Source Value                               Delivers   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))   SHOULD     Subscription
 notify-charset (charset)                   SHOULD     Subscription
 notify-natural-language (naturalLanguage)  SHOULD     Subscription
 notify-user-data (octetString(63)) **      SHOULD     Subscription
 notify-text (text)                         SHOULD     Event
                                                       Notification
 attributes from the "notify-attributes"    MAY        Printer
 attribute ***
 attributes from the "notify-attributes"    MAY        Job
 attribute ***
 attributes from the "notify-attributes"    MAY        Subscription
 attribute ***
  • A Printer MUST deliver this value only if and only if it supports

the Printer's "printer-current-time" attribute.

  • * If the Subscription Object does not contain a "notify-user-data"

attribute and the Delivery Method Document REQUIRES the Printer to

 deliver the "notify-user-data" source value in the Event
 Notification, the Printer MUST deliver an octet-string of length 0.
  • The last three rows represent additional attributes that a client MAY request via the "notify-attributes" attribute. A Printer MAY support the "notify-attributes" attribute. The Delivery Method MUST say that the Printer MUST, SHOULD, MAY, MUST NOT, SHOULD NOT, or NEED NOT support the "notify-attributes" attribute and specific values of this attribute. The Delivery Method MAY say that support for the "notify-attributes" is conditioned on support of the attribute by the Printer or it MAY say that Printer MUST support the "notify- attributes" attribute if the Printer supports the Delivery Method. 9.1.2. Additional Event Notification Content for Job Events This section lists the additional attributes that a Delivery Method Document MUST specify for Job Events. See Table 6. Herriot & Hastings Standards Track [Page 45] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Table 6 - Additional Event Notification Content for Job Events Source Value Delivers 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 deliver the "job-impressions-completed" attribute in an Event Notification only for the combinations of Events and Subscribed Events shown in Table 7. Table 7 - 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' 9.1.3. Additional Event Notification Content for Printer Events This section lists the additional attributes that a Delivery Method Document MUST specify for Printer Events. See Table 8. Table 8 - Additional Event Notification Content for Printer Events Source Value Delivers Source Object printer-state (type1 enum) MUST Printer printer-state-reasons (1setOf type2 MUST Printer keyword) printer-is-accepting-jobs (boolean) MUST Printer 9.2. Content of Human Consumable Event Notification This section defines the information that a Delivery Method MUST mention in a Delivery Method Document when specifying the Human Consumable Event Notifications contents or the value of the "notify- text" attribute. Such a Delivery Method MUST specify the following information and a Printer SHOULD deliver it: a) the Printer name (see Table 9) Herriot & Hastings Standards Track [Page 46] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 b) the time of the Event (see Table 11) c) for Printer Events only: i) the Event (see Table 10) and/or Printer state information (see Table 14) d) for Job Events only: i) the job identity (see Table 12) ii) the Event (see Table 10) and/or Job state information (see Table 13) The subsections of this section specify the attributes that a Printer MUST use to obtain this information. A Delivery Method Document MUST specify additional information (if any) that a Printer implementation delivers in a Human Consumable Event Notification or in the "notify-text" attribute. A client MUST NOT request additional attributes via the "notify- attributes" attribute because this attribute works only for Machine Consumable Event Notifications. Notification Recipients MUST NOT expect to be able to parse the Human Consumable Event Notification contents or the value of the "notify- text" attribute. The next three sections define the attributes in Event Notification Contents that are: a) for all Events b) for Job Events only c) for Printer Events only 9.2.1. Event Notification Content Common to All Events This section lists the source of the information that a Delivery Method MUST specify for all Events. There is a separate table for each piece of information. Each row in the table represents a source value for the information and the values are listed in order of preference, with the first one being the preferred one. An implementation SHOULD use the source value from the earliest row in each table. It MAY use the source value Herriot & Hastings Standards Track [Page 47] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 from another row instead, or it MAY combine the source values from several rows. An implementation is free to determine the best way to present this information. In all tables of this section, all rows contain a "MAY" in order to state that the Delivery Method specifies the conformance. Table 9 lists the source of the information for the Printer Name. The "printer-name" is more user-friendly unless the Notification Recipient is in a place where the Printer name is not meaningful. For example, an implementation could have the intelligence to deliver the value of the "printer-name" attribute to a Notification Recipient that can access the Printer via value of the "printer-name" attribute and otherwise deliver the value of the "notify-printer-uri" attribute. Table 9 - Printer Name in Event Notification Content Source Value Delivers Source Object printer-name (name(127)) MAY Printer notify-printer-uri (uri) MAY Subscription Table 10 lists the source of the information for the Event name. A Printer MAY combine this information with state information described for Jobs in Table 13 or for Printers in Table 14. Table 10 - Event Name in Event Notification Content Source Value Delivers Source Object notify-subscribed-event (type2 keyword) MAY Subscription Table 11 lists the source of the information for the time that the Event occurred. A Printer can deliver this value only if it supports the Printer's "printer-current-time" attribute. If a Printer does not support the "printer-current-time" attribute, it MUST NOT deliver the "printer-up-time" value instead, since it is not an allowed option for human consumable information. Table 11 - Event Time in Event Notification Content Source Value Delivers Source Object printer-current-time (dateTime) MAY Printer Herriot & Hastings Standards Track [Page 48] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 9.2.2. Additional Event Notification Content for Job Events This section lists the source of the additional information that a Delivery Method MUST specify for Job Events. Table 12 lists the source of the information for the job name. The "job-name" is likely more meaningful to a user than "job-id". Table 12 - Job Name in Event Notification Content Source Value Delivers Source Object job-name (name(MAX)) MAY Job job-id (integer(1:MAX)) MAY Job Table 13 lists the source of the information for the job state. If a Printer supports the "job-state-message" and "job-detailed-state- message" attributes, it SHOULD use those attributes for the job state information, otherwise, it should fabricate such information from the "job-state" and "job-state-reasons". For some Events, a Printer MAY combine this information with Event information. Table 13 - Job State in Event Notification Content Source Value Delivers Source Object job-state-message (text(MAX)) MAY Job job-detailed-status-messages (1setOf text(MAX)) MAY Job job-state (type1 enum) MAY Job job-state-reasons (1setOf type2 keyword) MAY Job 9.2.3. Additional Event Notification Content for Printer Events This section lists the source of the additional information that a Delivery Method MUST specify for Printer Events. Table 14 lists the source of the information for the printer state. If a Printer supports the "printer-state-message", it SHOULD use that attribute for the job state information, otherwise it SHOULD fabricate such information from the "printer-state" and "printer- state-reasons". For some Events, a Printer MAY combine this information with Event information. Herriot & Hastings Standards Track [Page 49] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Table 14 - Printer State in Event Notification Content Source Value Delivers Source Object printer-state-message (text(MAX)) MAY Printer printer-state (type1 enum) MAY Printer printer-state-reasons (1setOf type2 keyword) MAY Printer printer-is-accepting-jobs (boolean) MAY Printer 10. Delivery Methods A Delivery Method is the mechanism, i.e., protocol, by which the Printer delivers an Event Notification to a Notification Recipient. There are several potential Delivery Methods for Event Notifications, standardized, as well as proprietary. This specification REQUIRES that the 'ippget' Pull Delivery Method [RFC3996] be supported. Conforming implementations MAY support additional Push or Pull Delivery Methods as well. This document does not define any of these delivery mechanisms. Each Delivery Method MUST be defined in a Delivery Method Document that is separate from this document. New Delivery Methods will be created as needed using an extension to the registration procedures defined in [RFC2911]. Such documents are registered with IANA (see section 23.7.3). The following sorts of Delivery Methods are possible: - The Notification Recipient polls for Event Notifications at intervals directed by the Printer - The Printer delivers Event Notifications to the Notification Recipient using http as the transport. - The Printer delivers an email message. This section specifies how to define a Delivery Method Document and what to put in such a document. A Delivery Method Document MUST contain an exact copy of the following paragraph, caption and table. In addition, column 2 of the table in the Delivery Method Document MUST contain answers to questions in column 1 for the Delivery Method. Also, the Delivery Method document MUST contain a reference to this document and call that reference [RFC3995] because the table contains an [RFC3995] reference. If a Printer supports this Delivery Method, the following are its characteristics. Herriot & Hastings Standards Track [Page 50] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Table 15 - Information about the Delivery Method Document Method Conformance Requirement Delivery Method Realization 1. What is the URL scheme name for the Push Delivery Method or the keyword method name for the Pull Delivery Method? 2. Is the Delivery Method 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 stack? 4. Can several Event Notifications be combined into a Compound Event Notification? 5. Is the Delivery Method initiated by the Notification Recipient (pull), or by the Printer (push)? 6. Is the Event Notification content Machine Consumable or Human Consumable? 7. What section in this document answers the following question? For a Machine Consumable Event Notification, what is the representation and encoding of values defined in section 9.1 of [RFC3995] 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 [RFC3995] and the conformance requirements thereof? 8. What are the latency and reliability of the transport and delivery protocol? 9. What are the security aspects of the transport and delivery protocol, e.g., how it is handled in firewalls? 10. What are the content length restrictions? 11. What are the additional values or pieces of information that a Printer delivers in an Event Notification content and the conformance requirements thereof? 12. What are the additional Subscription Template and/or Subscription Description attributes and the conformance requirements thereof? Herriot & Hastings Standards Track [Page 51] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 13. What are the additional Printer Description attributes and the conformance requirements thereof? 11. Operations for Notification This section defines all of the operations for Notification. Section 7.1 assigns the "operation-id" for each operation. The following two sub-sections define Subscription Creation Operations, and other operations. 11.1. Subscription Creation Operations This section defines the Subscription Creation Operations. The first section on Create-Job-Subscriptions gives most of the information. The other Subscription Creation Operations refer to the section on Create-Job-Subscriptions, even though the Create-Job-Subscriptions operation is the only OPTIONAL operation in this document (see section 12). A Printer MUST support Create-Printer-Subscriptions and the Subscription Template Attributes Group in Job Creation operations. It MAY support Create-Job-Subscriptions operations. 11.1.1. Create-Job-Subscriptions Operation The operation creates one or more Per-Job Subscription Objects. The client supplies one or more Subscription Template Attributes Groups each containing one or more of Subscription Template Attributes (defined in section 5.3). Except for errors, the Printer MUST create exactly one Per-Job Subscription Object from each Subscription Template Attributes Group in the request, even if the newly created Subscription Object would have identical behavior to some existing Subscription Object. The Printer MUST associate each newly created Per-Job Subscription Object with the target Job, which is specified by the "notify-job-id" operation attribute. The Printer MUST accept the request in any of the target job's 'not- completed' states, i.e., 'pending', 'pending-held', 'processing', or 'processing-stopped'. The Printer MUST NOT change the job's "job- state" attribute because of this operation. If the target job is in any of the 'completed' states, i.e., 'completed', 'canceled', or 'aborted, then the Printer MUST reject the request and return the 'client-error-not-possible' status code; the response MUST NOT contain any Subscription Attribute Groups. Herriot & Hastings Standards Track [Page 52] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Access Rights: To create Per-Job Subscription Objects, the authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) be the job owner, (2) have Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by the Printer's administrator-configured security policy to create Per-Job Subscription Objects for the target job. Otherwise the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not-authenticated', or 'client-error-not-authorized' status code as appropriate. 11.1.1.1. Create-Job-Subscriptions Request The following groups of attributes are part of the Create-Job- Subscriptions 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" attribute which defines the target for this operation as described in [RFC2911] section 3.1.5. Requesting User Name: The "requesting-user-name" attribute SHOULD be supplied by the client as described in [RFC2911] section 8.3. 11.1.1.1.1. notify-job-id (integer(1:MAX)) The client MUST supply this attribute and it MUST specify the Job object to associate the Per-Job Subscription with. The value of "notify-job-id" MUST be the value of the "job-id" of the associated Job object. If the client does not supply this attribute, the Printer MUST reject this request with a 'client-error-bad-request' status code. Group 2-N: Subscription Template Attributes For each occurrence of this group: The client MUST supply one or more Subscription Template Attributes in any order. See section 5.3 for a description of each such attribute. See section 5.2 for details on processing these attributes. Herriot & Hastings Standards Track [Page 53] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.1.1.2. Create-Job-Subscriptions Response The Printer MUST return to the client the following sets of attributes as part of a Create-Job-Subscriptions 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. In this group, the Printer can return any status codes defined in [RFC2911] and section 12. The following is a description of the important status codes: successful-ok: the Printer created all Subscription Objects requested (see [RFC2911]). successful-ok-ignored-subscriptions: the Printer created some Subscription Objects requested but some failed. The Subscription Attributes Groups with a "notify-status-code" attribute are the ones that failed (see section 12.1). client-error-ignored-all-subscriptions: the Printer created no Subscription Objects requested and all failed. The Subscription Attributes Groups with a "notify-status-code" attribute are the ones that failed (see section 12.2). client-error-not-possible: For this operation and other Per-Job Subscription operations, this error can occur because the specified Job has already completed (see [RFC2911], whether or not the Job is retained in the Job Retention and/or Job History phases (see [RFC2911] section 4.3.7.1). Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. Group 2: Unsupported Attributes See [RFC2911] section 3.1.7 for details on returning Unsupported Attributes. This group does not contain any unsupported Subscription Template Attributes; they are returned in the Subscription Attributes Group (see below). Herriot & Hastings Standards Track [Page 54] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Group 3-N: Subscription Attributes These groups MUST be returned unless the Printer is unable to interpret the entire request, e.g., the "status-code" parameter returned in Group 1 has the value: 'client-error-bad-request'. "notify-status-code" (type2 enum): Indicates the status of this subscription (see section 13 for the status code definitions). Section 5.2 defines when this attribute MUST be present in this group. See section 5.2 for details on the contents of each occurrence of this group. 11.1.2. Create-Printer-Subscriptions operation The operation is identical to Create-Job-Subscriptions with exceptions noted in this section. The operation creates Per-Printer Subscription Objects instead of Per-Job Subscription Objects, and associates each newly created Per- Printer Subscription Object with the Printer specified by the operation target rather than with a specific Job. The Printer MUST accept the request in any of its states, i.e., 'idle', 'processing', or 'stopped'. The Printer MUST NOT change its "printer-state" attribute because of this operation. Access Rights: To create Per-Printer Subscription Objects, the authenticated user (see [RFC2911] section 8.3) performing this operation MUST have (1) Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5), or (2) be otherwise authorized by the Printer's administrator-configured security policy to create Per-Printer Subscription Objects for this Printer. Otherwise, the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not-authenticated', or 'client-error-not-authorized' status code as appropriate. 11.1.2.1. Create-Printer-Subscriptions Request The groups are identical to the Create-Job-Subscriptions (see section 11.1.1.1) except that the Operation Attributes group MUST NOT contain the "notify-job-id" attribute. If the client does supply the "notify-job-id" attribute, then the Printer MUST treat it as any other unsupported Operation attribute and MUST return it in the Unsupported Attributes group. Herriot & Hastings Standards Track [Page 55] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.1.2.2. Create-Printer-Subscriptions Response The groups are identical to the Create-Job-Subscriptions (see section 11.1.1.2). 11.1.3. Job Creation Operations - Extensions for Notification This document extends the Job Creation operations (see section 3.2) to create Subscription Objects as a part of the operation. The Job Creation operations are identical to Create-Job-Subscriptions operation with exceptions noted in this section. Unlike the Create-Job-Subscriptions operation, a Job Creation operation associates the newly created Subscription Objects with the Job object created by this operation. The operation succeeds if and only if the Job creation succeeds. If the Printer does not create some or all of the requested Subscription Objects, the Printer MUST return a 'successful-ok-ignored-subscriptions' status-code instead of a 'successful-ok' status-code, but the Printer MUST NOT reject the operation because of a failure to create Subscription Objects. If the Job Creation operation includes a Job Template group, the client MUST supply it after the Operation Attributes group and before the first Subscription Template Attributes Group. If a Printer does not support this Notification specification, then it MUST treat the Subscription Attributes Group like an unknown group and ignore it (see [RFC2911] section 5.2.2). Because the Printer ignores the Subscription Attributes Group, it doesn't return them in the response either, thus indicating to the client that the Printer doesn't support Notification. After completion of a successful Job Creation operation, the Printer generates a 'job-created' event (see section 5.3.3.4.3). Access Rights: To create Per-Job Subscription Objects, the authenticated user (see [RFC2911] section 8.3) performing this operation MUST either have permission to create Jobs on the Printer or have Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5). Otherwise the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error- not-authenticated', or 'client-error-not-authorized' status code as appropriate. Herriot & Hastings Standards Track [Page 56] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.1.3.1. Job Creation Request The groups for this operation are sufficiently different from the Create-Job-Subscriptions operation that they are all presented here. The following groups of attributes are supplied as part of a Job Creation Request: Group 1: Operation Attributes Same as defined in [RFC2911] for Print-Job, Print-URI, and Create-Job requests. Group 2: Job Template Attributes The client OPTIONALLY supplies a set of Job Template attributes as defined in [RFC2911] section 4.2. Group 3 to N: Subscription Template Attributes The same as Group 2-N in Create-Job-Subscriptions. See section 11.1.1.1. Group N+1: Document Content (Print-Job only) The client MUST supply the document data to be processed. 11.1.3.2. Job Creation Response The Printer MUST return to the client the following sets of attributes as part of a Print-Job, Print-URI, and Create-Job Response: Group 1: Operation Attributes Status Message: As defined in [RFC2911] for Print-Job, Print-URI, and Create- Job requests. In this group, the Printer can return any status codes defined in [RFC2911] and section 12. The following is a description of the important status codes: successful-ok: the Printer created the Job and all Subscription Objects requested (see [RFC2911]. successful-ok-ignored-subscriptions: the Printer created the Job and not all of the Subscription Objects requested Herriot & Hastings Standards Track [Page 57] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 (see section 12.1). This status-code hides 'successful-ok- xxx' status-codes that could reveal problems in Job creation. The Printer MUST NOT return the 'client-error- ignored-all-subscriptions' status code for Job Creation operations because the Printer returns an error status-code only when it fails to create a Job. Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. Group 2: Unsupported Attributes See [RFC2911] section 3.1.7 for details on returning Unsupported Attributes. This group does not contain any unsupported Subscription Template Attributes; they are returned in the Subscription Attributes Group (see below). Group 3: Job Object Attributes The "job-id" of the Job Object just created, etc., as defined in [RFC2911] for Print-Job, Print-URI, and Create-Job requests. Group 4 to N: Subscription Attributes These groups MUST be returned if and only if the client supplied Subscription Template Attributes and the operation was accepted. See section 5.2 for details on the contents of each occurrence of this group. 11.2. Other Operations This section defines other operations on Subscription objects. 11.2.1. Restart-Job Operation - Extensions for Notification The Restart-Job operation [RFC2911] is neither a Job Creation operation nor a Subscription Creation operation (see section 3.2). For the Restart-Job operation, the client MUST NOT supply any Job Subscription Attributes Groups. The Printer MUST treat any supplied Job Subscription Attributes as unsupported attributes. For this operation, the Printer does not return a job-id or any Subscription Attributes groups because the Printer reuses the existing Job object with the same job-id and the existing Per-Job Subscription Objects with the same subscription-ids. However, after Herriot & Hastings Standards Track [Page 58] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 successful completion of this operation, the Printer generates a 'job-created' event (see section 5.3.3.4.3). 11.2.2. Validate-Job Operation - Extensions for Notification A client can test whether one or more Subscription Objects could be created using the Validate-Job operation. The client supplies one or more Subscription Template Attributes Groups (defined in section 5.3), just as in a Job Creation request. A Printer MUST support this extension to this operation. The Printer MUST accept requests that are identical to the Job Creation request defined in section 11.1.3.1, except that the request MUST NOT contain document data. The Printer MUST return the same groups and attributes as the Print- Job operation (section 11.1.3.1) with the following exceptions. The Printer MUST NOT return a Job Object Attributes Group because no Job is created. The Printer MUST NOT return the "notify-subscription-id" attribute in any Subscription Attribute Group because no Subscription Object is created. If the Printer would succeed in creating a Subscription Object, the corresponding Subscription Attributes Group either has no 'status- code' attribute or a 'status-code' attribute with a value of 'successful-ok-too-many-events' or 'successful-ok-ignored-or- substituted-attributes' (see sections 5.2 and 13). The status-codes have the same meaning as in Job Creation except the results state what "would happen". The Printer MUST validate Subscription Template Attributes Groups in the same manner as the Job Creation operations. 11.2.3. Get-Printer-Attributes - Extensions for Notification This operation is extended so that it returns Printer attributes defined in this document. A Printer MUST support this extension to this operation. In addition to the requirements of [RFC2911] section 3.2.5, a Printer MUST support the following additional values for the "requested- attributes" Operation attribute in this operation and return such attributes in the Printer Object Attributes group of its response. 1. Subscription Template Attributes: Each supported attribute in column 2 of Table 1. Herriot & Hastings Standards Track [Page 59] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 2. New Printer Description Attributes: Each supported attribute in section 6. 3. New Group Name: The 'subscription-template' group name, which names all supported Subscription Template Attribute in column 2 of Table 1. This group name is also used in the Get-Subscription- Attributes and Get-Subscriptions operation with an analogous meaning. 4. Extended Group Name: The 'all' group name, which names all Printer attributes according to [RFC2911] section 3.2.5. In this extension 'all' names all attributes specified in [RFC2911] plus those named in items 1 and 2 of this list. 11.2.4. Get-Subscription-Attributes operation This operation allows a client to request the values of the attributes of a Subscription Object. A Printer MUST support this operation. This operation is almost identical to the Get-Job-Attributes operation (see [RFC2911] section 3.3.4). The only differences are that the operation is directed at a Subscription Object rather than a Job object, and the returned attribute group contains Subscription Object attributes rather than Job object attributes. Access Rights: The authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) be the Subscription Object owner, (2) have Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by the Printer's administrator-configured security policy to query the Subscription Object for the target job. Otherwise the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not-authenticated', or 'client-error-not-authorized' status code as appropriate. Furthermore, the Printer's security policy MAY limit which attributes are returned, in a manner similar to the Get-Job-Attributes operation (see [RFC2911] end of section 3.3.4.2). 11.2.4.1. Get-Subscription-Attributes Request The following groups of attributes are part of the Get-Subscription- Attributes request: Group 1: Operation Attributes Natural Language and Character Set: Herriot & Hastings Standards Track [Page 60] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 The "attributes-charset" and "attributes-natural-language" attributes as described in section [RFC2911] 3.1.4.1. Target: The "printer-uri" attribute which defines the target for this operation as described in [RFC2911] section 3.1.5. Requesting User Name: The "requesting-user-name" attribute SHOULD be supplied by the client as described in [RFC2911] section 8.3. 11.2.4.1.1. "notify-subscription-id" (integer (1:MAX)) The client MUST supply this attribute. The Printer MUST support this attribute. This attribute specifies the Subscription Object from which the client is requesting attributes. If the client omits this attribute, the Printer MUST reject this request with the 'client- error-bad-request' status code. 11.2.4.1.2. "requested-attributes" (1setOf keyword) The client OPTIONALLY supplies this attribute. The Printer MUST support this attribute. This attribute specifies the attributes of the specified Subscription Object that the Printer MUST return in the response. Each value of this attribute is either an attribute name (defined in sections 5.3 and 5.4) or an attribute group name. The attribute group names are: - 'subscription-template': all attributes that are both defined in section 5.3 and present on the specified Subscription Object (column 1 of Table 1). - 'subscription-description': all attributes that are both defined in section 5.4 and present on the specified Subscription Object (Table 2). - 'all': all attributes that are present on the specified Subscription Object. A Printer MUST support all these group names. If the client omits this attribute, the Printer MUST respond as if this attribute had been supplied with a value of 'all'. 11.2.4.2. Get-Subscription-Attributes Response The Printer returns the following sets of attributes as part of the Get-Subscription-Attributes Response: Herriot & Hastings Standards Track [Page 61] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Group 1: Operation Attributes Status Message: Same as [RFC2911]. Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. The "attributes-natural-language" MAY be the natural language of the Subscription Object, rather than the one requested. Group 2: Unsupported Attributes See [RFC2911] section 3.1.7 and section 3.2.5.2 for details on returning Unsupported Attributes. The response NEED NOT contain the "requested-attributes" operation attribute with any supplied keyword values that were requested by the client but are not supported by the IPP object. If the Printer object does return unsupported attributes referenced in the "requested-attributes" operation attribute, the values of the "requested-attributes" attribute returned MUST include only the unsupported keywords that were requested by the client. If the client had requested a group name, such as 'all', the resulting unsupported attributes returned MUST NOT include attribute keyword names described in the standard but not supported by the implementation. Group 3: Subscription Attributes This group contains a set of attributes with their current values. Each attribute returned in this group: a) MUST be specified by the "requested-attributes" attribute in the request, AND b) MUST be present on the specified Subscription Object AND c) MUST NOT be restricted by the security policy in force. For example, a Printer MAY prohibit a client who is not the creator of a Subscription Object from seeing some or all of its attributes. See [RFC2911] end of section 3.3.4.2 and section 8. The Printer can return the attributes of the Subscription Object in any order. The client MUST accept the attributes in any order. Herriot & Hastings Standards Track [Page 62] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.2.5. Get-Subscriptions operation This operation allows a client to retrieve the values of attributes of all Subscription Objects belonging to a Job or Printer. A Printer MUST supported this operation. This operation is similar to the Get-Subscription-Attributes operation, except that this Get-Subscriptions operation returns attributes from possibly more than one object. This operation is similar to the Get-Jobs operation (see [RFC2911] section 3.2.6), except that the operation returns Subscription Objects rather than Job objects. Access Rights: To query Per-Job Subscription Objects of the specified job (client supplied the "notify-job-id" operation attribute - see section 11.2.5.1.1), the authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) be the Subscription Object owner, (2) have Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by the Printer's administrator-configured security policy to query the Subscription Object for the target job. To query Per-Printer Subscription Objects of the Printer (client omits the "notify-job-id" operation attribute - see section 11.2.5.1.1), the authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) have Operator or Administrator access rights for this Printer (see [RFC2911] sections 1 and 8.5), or (2) be otherwise authorized by the Printer's administrator-configured security policy to query Per-Printer Subscription Objects for the target Printer. Otherwise the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not- authenticated', or 'client-error-not-authorized' status code as appropriate. Furthermore, the Printer's security policy MAY limit which attributes are returned, in a manner similar to the Get-Jobs and Get-Printer-Attributes operations (see [RFC2911] end of sections 3.2.6.2 and 3.2.5.2). 11.2.5.1. Get-Subscriptions Request The following groups of attributes are part of the Get-Subscriptions 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. Herriot & Hastings Standards Track [Page 63] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Target: The "printer-uri" attribute which defines the target for this operation as described in [RFC2911] section 3.1.5. Requesting User Name: The "requesting-user-name" attribute SHOULD be supplied by the client as described in [RFC2911] section 8.3. 11.2.5.1.1. "notify-job-id" (integer(1:MAX)) If the client specifies this attribute, the Printer returns the specified attributes of all Per-Job Subscription Objects associated with the Job whose "job-id" attribute value equals the value of this attribute. If the client does not specify this attribute, the Printer returns the specified attributes of all Per-Printer Subscription Objects. Note: there is no way to get all Per-Job Subscriptions known to the Printer in a single operation. A Get-Jobs operation followed by a Get-Subscriptions operation for each Job will return all Per-Job Subscriptions. 11.2.5.1.2. "limit" (integer(1:MAX)) The client OPTIONALLY supplies this attribute. The Printer MUST support this attribute. It is an integer value that determines the maximum number of Subscription Objects that a client will receive from the Printer even if the "my-subscriptions" attribute constrains which Subscription Objects are returned. The limit is a "stateless limit" in that if the value supplied by the client is 'N', then only the first 'N' Subscription Objects are returned in the Get- Subscriptions Response. There is no mechanism to allow for the next 'M' Subscription Objects after the first 'N' Subscription Objects. If the client does not supply this attribute, the Printer responds with all applicable Subscription Objects. 11.2.5.1.3. "requested-attributes" (1setOf type2 keyword) The client OPTIONALLY supplies this attribute. The Printer MUST support this attribute. This attribute specifies the attributes of the specified Subscription Objects that the Printer MUST return in the response. Each value of this attribute is either an attribute name (defined in sections 5.3 and 5.4) or an attribute group name (defined in section 11.2.4.1). If the client omits this attribute, the Printer MUST respond as if the client had supplied this attribute with the one value: 'notify-subscription-id'. Herriot & Hastings Standards Track [Page 64] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.2.5.1.4. "my-subscriptions" (boolean) The client OPTIONALLY supplies this attribute. The Printer MUST support this attribute. If the value is 'false', the Printer MUST consider the Subscription Objects from all users as candidates. If the value is 'true', the Printer MUST return the Subscription Objects created by the requesting user of this request. If the client does not supply this attribute, the Printer MUST respond as if the client had supplied the attribute with a value of 'false'. The means for authenticating the requesting user and matching the Subscription Objects is similar to that for Jobs which is described in [RFC2911] section 8. 11.2.5.2 Get-Subscriptions Response The Printer returns the following sets of attributes as part of the Get-Subscriptions Response: Group 1: Operation Attributes Status Message: Same as [RFC2911]. Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. Group 2: Unsupported Attributes Same as for Get-Subscription-Attributes. Groups 3 to N: Subscription Attributes The Printer responds with one Subscription Attributes Group for each requested Subscription Object (see the "notify-job-id" attribute in the Operation Attributes Group of this operation). The Printer returns Subscription Objects in any order. If the "limit" attribute is present in the Operation Attributes group of the request, the number of Subscription Attributes Groups in the response MUST NOT exceed the value of the "limit" attribute. It there are no Subscription Objects associated with the specified Job or Printer, the Printer MUST return zero Subscription Attributes Groups and it MUST NOT treat this case as an error, Herriot & Hastings Standards Track [Page 65] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 i.e., the status-code MUST be 'successful-ok' unless something else causes the status code to have some other value. See the Group 3 response (Subscription Attributes Group) of the Get-Subscription-Attributes operation (section 11.2.4.2) for the attributes that a Printer returns in this group. 11.2.6. Renew-Subscription operation This operation allows a client to request the Printer to extend the lease on a Per-Printer Subscription Object. The Printer MUST support this operation. The Printer MUST accept this request for a Per-Printer Subscription Object in any of the target Printer's states, i.e., 'idle', 'processing', or 'stopped', but MUST NOT change the Printer's "printer-state" attribute. The Printer MUST reject this request for a Per-Job Subscription Object because it has no lease (see section 5.4.3). The status code returned MUST be 'client-error-not-possible'. Access Rights: The authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) be the owner of the Per-Printer Subscription Object, (2) have Operator or Administrator access rights for the Printer (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by the Printer's administrator-configured security policy to renew Per-Printer Subscription Objects for the target Printer. Otherwise, the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not- authenticated', or 'client-error-not-authorized' status code as appropriate. 11.2.6.1. Renew-Subscription Request The following groups of attributes are part of the Renew-Subscription 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" attribute which defines the target for this operation as described in [RFC2911] section 3.1.5. Herriot & Hastings Standards Track [Page 66] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Requesting User Name: The "requesting-user-name" (name(MAX)) attribute SHOULD be supplied by the client as described in [RFC2911] section 8.3. 11.2.6.1.1. "notify-subscription-id" (integer (1:MAX)) The client MUST supply this attribute. The Printer MUST support this attribute. This attribute specifies the Per-Printer Subscription Object whose lease the Printer MUST renew. If the client omits this attribute, the Printer MUST reject this request with the 'client- error-bad-request' status code. Group 2: Subscription Template Attributes 11.2.6.1.2. "notify-lease-duration" (integer(0:MAX)) The client MAY supply this attribute. It indicates the number of seconds to renew the lease for the specified Subscription Object. A value of 0 requests an infinite lease (which MAY require Operator access rights). If the client omits this attribute, the Printer MUST use the value of the Printer's "notify-lease-duration-default" attribute. See section 5.3.8 for more details. 11.2.6.2. Renew-Subscription Response The Printer returns the following sets of attributes as part of the Renew-Subscription Response: Group 1: Operation Attributes Status Message: Same as [RFC2911]. The following are some of the status codes returned (see [RFC2911]: successful-ok: The operation successfully renewed the lease on the Subscription Object for the requested duration. successful-ok-ignored-or-substituted-attributes: The operation successfully renewed the lease on the Subscription Object for some duration other than the amount requested. client-error-not-possible: The operation failed because the "notify-subscription-id" Operation attribute identified a Per-Job Subscription Object. Herriot & Hastings Standards Track [Page 67] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 client-error-not-found: The operation failed because the "notify-subscription-id" Operation attribute identified a non-existent Subscription Object. Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. The "attributes-natural-language" MAY be the natural language of the Subscription Object, rather than the one requested. Group 2: Unsupported Attributes See [RFC2911] section 3.1.7 for details on returning Unsupported Attributes. Group 3: Subscription Attributes The Printer MUST return the following Subscription Attribute: 11.2.6.2.1. "notify-lease-duration" (integer(0:MAX)) The value of this attribute MUST be the number of seconds that the Printer has granted for the lease of the Subscription Object (see section 5.3.8 for details, such as the value of this attribute when the Printer doesn't support the requested value). 11.2.7. Cancel-Subscription operation This operation allows a client to delete a Subscription Object and stop the Printer from delivering more Event Notifications. Once performed, there is no way to reference the Subscription Object. A Printer MUST supported this operation. The Printer MUST accept this request in any of the target Printer's states, i.e., 'idle', 'processing', or 'stopped', but MUST NOT change the Printer's "printer-state" attribute. If the specified Subscription Object is a Per-Job Subscription Object, the Printer MUST accept this request in any of the target Job's states, but MUST NOT change the Job's "job-state" attribute or affect the Job. Note: There is no way to change any attributes on a Subscription Object, except the "notify-lease-duration" attribute (using the Renew-Subscription operation). In order to change other attributes, a client performs a Subscription Creation Operation and Cancel- Subscription operation on the old Subscription Object. If the client Herriot & Hastings Standards Track [Page 68] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 wants to avoid missing Event Notifications, it performs the Subscription Creation Operation first. If this order would create too many Subscription Objects on the Printer, the client reverses the order. Access Rights: The authenticated user (see [RFC2911] section 8.3) performing this operation MUST (1) be the owner of the Subscription Object, (2) have Operator or Administrator access rights for the Printer (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by the Printer's administrator-configured security policy to cancel the target Subscription Object. Otherwise, the Printer MUST reject the operation and return: the 'client-error-forbidden', 'client-error-not-authenticated', or 'client-error-not-authorized' status code as appropriate. 11.2.7.1. Cancel-Subscription Request The following groups of attributes are part of the Cancel- Subscription 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" attribute which defines the target for this operation as described in [RFC2911] section 3.1.5. Requesting User Name: The "requesting-user-name" attribute SHOULD be supplied by the client as described in [RFC2911] section 8.3. 11.2.7.1.1. "notify-subscription-id" (integer (1:MAX)) The client MUST supply this attribute. The Printer MUST support this attribute. This attribute specifies the Subscription Object that the Printer MUST cancel. If the client omits this attribute, the Printer MUST reject this request with the 'client-error-bad-request' status code. Herriot & Hastings Standards Track [Page 69] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 11.2.7.2. Cancel-Subscription Response The Printer returns the following sets of attributes as part of the Cancel-Subscription Response: Group 1: Operation Attributes Status Message: Same as [RFC2911]. The following are some of the status codes returned (see [RFC2911]: successful-ok: The operation successfully canceled (deleted) the Subscription Object. client-error-not-found: The operation failed because the "notify-subscription-id" Operation attribute identified a non-existent Subscription Object. Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in [RFC2911] section 3.1.4.2. The "attributes-natural-language" MAY be the natural language of the Subscription Object, rather than the one requested. Group 2: Unsupported Attributes See [RFC2911] section 3.1.7 for details on returning Unsupported Attributes. 12. Status Codes The following status codes are defined as extensions for Notification and are returned as the value of the "status-code" parameter in the Operation Attributes Group of a response (see [RFC2911] section 3.1.6.1). Operations in this document can also return the status codes defined in section 13 of [RFC2911]. The 'successful-ok' status code is an example of such a status code. 12.1. successful-ok-ignored-subscriptions (0x0003) The Subscription Creation Operation was unable to create all requested Subscription Objects. For a Create-Job-Subscriptions or Create-Printer-Subscriptions operation, this status code means that the Printer created one or Herriot & Hastings Standards Track [Page 70] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 more Subscription Objects, but not all requested Subscription Objects. For a Job Creation operation, this status code means that the Printer created the Job along with zero or more Subscription Objects. The Printer returns this status code even if other job attributes are unsupported or in conflict. That is, if an IPP Printer finds a warning that would allow it to return 'successful-ok-ignored- subscriptions' and either 'successful-ok-ignored-or-substituted- attributes' and/or 'successful-ok-conflicting-attributes', it MUST return 'successful-ok-ignored-subscriptions'. 12.2. client-error-ignored-all-subscriptions (0x0414) This status code is the same as 'successful-ok-ignored-subscriptions' except that only the Create-Job-Subscriptions and Create-Printer- Subscriptions operation return it. They return this status code only when the Printer creates zero Subscription Objects. 13. Status Codes in Subscription Attributes Groups This section contains values of the "notify-status-code" (type2 enum) attribute that the Printer returns in a Subscription Attributes Group in a response when the corresponding Subscription Object: 1. is not created or 2. is created and some of the client-supplied attributes are not supported. The following sections are ordered in decreasing order of importance of the status-codes. 13.1. client-error-uri-scheme-not-supported (0x040C) This status code is defined in [RFC2911]. This document extends its meaning and allows it to be in a Subscription Attributes Group of a response. The scheme of the client-supplied URI in a "notify-recipient-uri" Subscription Template Attribute in a Subscription Creation Operation is not supported. See section 5.3.1. 13.2. client-error-attributes-or-values-not-supported (0x040B) This status code is defined in [RFC2911]. This document extends its meaning and allows it to be in a Subscription Attributes Group of a response. Herriot & Hastings Standards Track [Page 71] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 The method of the client-supplied keyword in a "notify-pull-method" Subscription Template Attribute in a Subscription Creation Operation is not supported. See section 5.3.2. 13.3. client-error-too-many-subscriptions (0x0415) The number of Subscription Objects supported by the Printer would be exceeded if this Subscription Object were created (see section 5.2). 13.4. successful-ok-too-many-events (0x0005) The client supplied more Events in the "notify-events" operation attribute of a Subscription Creation Operation than the Printer supports, as indicated in its "notify-max-events-supported" Printer attribute (see section 5.3.3). 13.5. successful-ok-ignored-or-substituted-attributes (0x0001) This status code is defined in [RFC2911]. This document extends its meaning to include unsupported Subscription Template Attributes and it can appear in a Subscription Attributes Group. 14. Encodings of Additional Attribute Tags This section assigns values to two attributes tags as extensions to the encoding defined in [RFC2910]). The "subscription-attributes-tag" delimits Subscription Template Attributes Groups in requests and Subscription Attributes Groups in responses. The "event-notification-attributes-tag" delimits Event Notifications in Delivery Methods that use an IPP-like encoding. The following table specifies the values for the delimiter tags: Tag Value (Hex) Meaning 0x06 "subscription-attributes-tag" 0x07 "event-notification-attributes-tag" 15. Conformance Requirements It is OPTIONAL for IPP clients and Printers to implement this Event Notification specification. Herriot & Hastings Standards Track [Page 72] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 15.1. Conformance requirements for clients If this Event Notification specification is implemented by a client, the client MUST support the 'ippget' Pull Delivery Method and meet the conformance requirements as defined in [RFC3996] for clients. A client MAY support additional Delivery Methods. 15.2. Conformance requirements for Printers If this Event Notification specification is implemented by a Printer, the Printer MUST: - meet the Conformance Requirements detailed in section 5 of [RFC2911]. - support the Subscription Template Attributes Group in requests and the Subscription Attributes Group in responses. - support all of the following attributes: a. REQUIRED Subscription Object attributes in section 5. b. REQUIRED Printer Description object attributes in section 6. c. REQUIRED attributes in Event Notification content in section 8. - support the 'ippget' Pull Delivery Method and meet the conformance requirements as defined in [RFC3996] for Printers. The Printer MAY support additional Push and Pull Delivery Methods. - deliver Event Notifications that conform to the requirements of section 9 and the requirements of the Delivery Method Document for each supported Delivery Method (the conformance requirements for Delivery Method Documents is specified in section 10). - for all of the Job Creation Operations that the Printer supports, MUST support the REQUIRED extensions for notification defined in section 11.1.3. - meet the conformance requirements for operations as described in Table 16 and meet the requirements for Printers as specified in the indicated sub-sections of section 11: Herriot & Hastings Standards Track [Page 73] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Table 16 - Printer Conformance Requirements for Operations Operation Printer Conformance Requirements Create-Printer-Subscriptions (section 11.1.2) REQUIRED Create-Job-Subscriptions (section 11.1.1) OPTIONAL Get-Subscription-Attributes (section 11.2.3) REQUIRED Get-Subscriptions (section 11.2.5) REQUIRED Renew-Subscription (section 11.2.6) REQUIRED Cancel-Subscription (section 11.2.7) REQUIRED 16. Model for Notification with Cascading Printers (Informative) With this model (see Figure 2 below), there is an intervening Print server between the human user and the output-device. So the system effectively has two Printer objects. There are two cases to consider. 1. When the Printer 1 (in the server) generates Events, the system behaves like the client and Printer in Figure 1. In this case, Printer 1 delivers Event Notifications that are shown as Event Notifications (A) of Figure 2. 2. When the Printer 2 (in the output-device) generates Events, there are two possible system configurations: a) Printer 1 forwards the client-supplied Subscription Creation Operations to the downstream Printer 2 and lets Printer 2 deliver the Event Notifications directly to the Notification Recipients supplied by the Client (Event Notifications(C) in the diagram). b) Printer 1 performs the client-supplied Subscription Creation Operations and also forwards the Subscription Creation Operations to Printer 2 with the Notification Recipient changed to be the Printer 1. When an Event occurs in Printer 2, Printer 2 delivers the Event Notification (B) to Notification Recipient of Printer 1, which relays the received Event Notification (B) to the client-supplied Notification Recipient (as Event Notifications(A) in the diagram). Note, when a client performs a Subscription Creation Operation, Printer 1 need not forward the Subscription Creation Operation to Printer 2 if it would create a duplicate Subscription Object on Printer 2. Herriot & Hastings Standards Track [Page 74] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 Note: when Printer 1 is forwarding Subscription Creation Operations to Printer 2, it may request Printer 2 to create additional Subscription Objects (called "piggy-backing"). Piggy-backing is useful when: - Device A is configured to accept (IPP or non-IPP) requests from other servers. - Server S wants to receive Job Events that the client didn't request and Server S wants these Events for jobs it submits and not for other jobs. server S device A +————+ +————+ | | | | +——–+ Subscription | ###########| | ###########| | client |–Creation —→# Printer #| Subscription | # Printer #| +——–+ Operation | # Object 1#|—Creation——|># Object 2#| | ###|#######| Operation | ####|#|####| +—-|—^—+ +—–|-|—-+ +——–+ Event | | | | |Notific-|←Notifications(A)-+ +– Event Notifications(B)–+ | |ation Re|←————Event Notifications(C)—————–+ |cipient | +——–+ Figure 2 - Model for Notification with Cascading Printers 17. Distributed Model for Notification (Informative) A Printer implementation could use some other remote notification server to provide some or most of the service. For example, the remote notification server could deliver Event Notifications using Delivery Methods that are not directly supported by the output device or Printer object. Or, the remote notification server could store Subscription Objects (passed to it from the output device in response to Subscription Creation requests), accept Events, format the Event Notification in the natural language of the Notification Recipient, and deliver the Event Notifications to the Notification Recipient(s). Figure 3 shows this partitioning. The interface between the output device (or Printer object) and the remote notification server is outside the scope of this document and is intended to be transparent to the client and this document. Herriot & Hastings Standards Track [Page 75] RFC 3995 IPP: Event Notifications and Subscriptions March 2005 *
    • Printer in combination
    • with the distributed
    • Notification Server)
    • output device or server
    • +—————+

PDA, desktop, or server * + ########### +

         +--------+                       * |  #         #  |
         | client |---IPP Subscription--------># Printer #  |
         +--------+   Creation operation  * |  # Object  #  |
                                          * |  #####|#####  |
                                          * +-------|-------+
                                          *         | Subscriptions
                                          *         | OR Event
      +------------+                      *         | Notifications
      |Notification|   IPP-defined        *  +------v--------+
      |Recipient   |<--Event Notifications---| Notification  |
      +------------+                      *  | Server        |
                                          *  +---------------+
                                          *
                                          *************************
 *** = Implementation configuration opaque boundary
   Figure 3 - Opaque Use of a Notification Server Transparent to the
                                Client

18. Extended Notification Recipient (Informative)

 The model allows for an extended Notification Recipient that is
 itself a notification server that forwards each Event Notification to
 another recipient (called the Ultimate Notification Recipient in this
 section).  The Delivery Method to the Ultimate Recipient is probably
 different from the Delivery Method used by the Printer to the
 extended Notification Recipient.
 This extended Notification Recipient is transparent to the Printer
 but not to the client.
 When a client performs a Subscription Creation Operation, it
 specifies the extended Notification Recipient as it would any
 Notification Recipient.  In addition, the client specifies the
 Ultimate Notification Recipient in the Subscription Creation
 Operation in a manner specified by the extended Notification
 Recipient.  Typically, it is either some bytes in the value of
 "notify-user-data" or some additional parameter in the value of
 "notify-recipient-uri".  The client also subscribes directly with the

Herriot & Hastings Standards Track [Page 76] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 extended Notification Recipient (by means outside this document),
 since it is a notification server in its own right.
 The IPP Printer treats the extended Notification Recipient like any
 other Notification Recipient and the IPP Printer is not aware of the
 forwarding.  The Delivery Method that the extended Notification
 Recipient uses for delivering the Event Notification to the Ultimate
 Notification Recipient is beyond the scope of this document and is
 transparent to the IPP Printer.
 Examples of this extended Notification Recipient are paging,
 immediate messaging services, general notification services, and NOS
 vendors' infrastructure.  Figure 4 shows this approach.
    PDA, desktop, or server                    server or output device
                                                    +---------------+
        +--------+                                  |  ###########  |
        | client |---Subscription Creation -----------># Printer #  |
        +--------+       Operation                  |  # Object  #  |
                                                    |  #####|#####  |
 +------------+     +------------+   IPP-defined    +-------|-------+
 |Ultimate    | any |Notification|<--Event Notifications----+
 |Notification|<----|Recipient   |
 |Recipient   |     +------------+
 +------------+     (Notification Server)
  Figure 4 - Use of an Extended Notification Recipient transparent to
                              the Printer

19. Object Model for Notification (Normative)

 This section describes the Notification object model that adds a
 Subscription Object which together with the Job and Printer object
 provide the complete Notification semantics.

Herriot & Hastings Standards Track [Page 77] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 The object relationships can be seen pictorially as:
 Subscription Objects (Per-Printer Subscriptions)     Printer object
 +----+                                               +------------+
 | s1 |<--------------------------------------------->|            |
 +----++                                              |            |
  | s2 |<-------------------------------------------->|     p1     |
  +----++                                             |            |
   | s3 |<------------------------------------------->|            |
   +----+                                             +------------+
                  Job objects
                  +---------+
                  |         |
   +----+         |   j1    |
   | s4 |<------->|         |
   +----+         |         |
                  |         |    s4 is a Per-Job Subscription Object
                  ++--------++
                   |         |
     +----+        |   j2    |
     | s5 |<------>|         |
     +----++       |         |
      | s6 |<----->|         |    s5 and s6 are Per-Job Subscription
      +----+       ++--------++                  Objects
                    |         |
                    |   j3    |
                    |         |
                    |         |         <----> indicates association
                    +---------+
             Figure 5 - Object Model for Notification
 s1, s2, and s3 are Per-Printer Subscription Objects and can identify
 Printer and/or Job Events.
 s4, s5, and s6 are Per-Job Subscription Objects and can identify
 Printer and/or Job Events.

19.1. Object relationships

 This sub-section defines the object relationships between the
 Printer, Job, and Subscription Objects by example.  Whether Per-
 Printer Subscription Objects are actually contained in a Printer
 object or are just bi-directionally associated with them in some way
 is IMPLEMENTATION DEPENDENT and is transparent to the client.
 Similarly, whether Per-Job Subscription Objects are actually

Herriot & Hastings Standards Track [Page 78] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 contained in a Job object or are just bi-directionally associated
 with them in some way is IMPLEMENTATION DEPENDENT and is transparent
 to the client.  The object relationships are defined as follows:

19.2. Printer Object and Per-Printer Subscription Objects

 1. The Printer object contains (is associated with) zero or more
    Per-Printer Subscription Objects (p1 contains s1-s3 Per-Printer
    Subscription Objects).
 2. Each Per-Printer Subscription Object (s1, s2, and s3) is contained
    in (or is associated with) exactly one Printer object (p1).

19.3. Job Object and Per-Job Subscription Objects

 1. A Job object (j1, j2, j3) is associated with zero or more Per-Job
    Subscription Objects (s4-s6).  Job j1 is associated with Per-Job
    Subscription Object s4, Job j2 is associated with Per-Job
    Subscription Objects s5 and s6, and Job j3 is not associated with
    any Per-Job Subscription Object.
 2. Each Per-Job Subscription Object is associated with exactly one
    Job object.

20. Per-Job versus Per-Printer Subscription Objects (Normative)

 Per-Job and Per-Printer Subscription Objects are quite similar.
 Either type of Subscription Object can subscribe to Job Events,
 Printer Events, or both.  Both types of Subscription Objects can be
 queried using the Get-Subscriptions and Get-Subscription-Attributes
 operations and canceled using the Cancel-Subscription operation.
 Both types of Subscription Objects create Subscription Objects which
 have the same Subscription Object attributes defined.  However, there
 are some semantic differences between Per-Job Subscription Objects
 and Per-Printer Subscription Objects.  A Per-Job Subscription Object
 is established by the client when submitting a job and after creating
 the job using the Create-Job-Subscriptions operation by specifying
 the "job-id" of the Job with the "notify-job-id" attribute.  A Per-
 Printer Subscription Object is established between a client and a
 Printer using the Create-Printer-Subscriptions operation.  Some
 specific differences are:
 1. A client usually creates one or more Per-Job Subscription Objects
    as part of the Job Creation operations (Create-Job, Print-Job, and
    Print-URI), rather than using the OPTIONAL Create-Job-
    Subscriptions operation, especially since Printer implementations
    NEED NOT support the Create-Job-Subscriptions operation, since it
    is OPTIONAL.

Herriot & Hastings Standards Track [Page 79] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 2. For Per-Job Subscription Objects, the Subscription Object is only
    valid while the job is "not-complete" (see sections 5.4.3) while
    for the Per-Printer Subscription Objects, the Subscription Object
    is valid until the time (in seconds) that the Printer returned in
    the "notify-lease-expiration-time" operation attribute.
 3. Job Events in a Per-Job Subscription Object apply only to "one
    job" (the Job created by the Job Creation operation or references
    by the Create-Job-Subscriptions operation) while Job Events in a
    Per-Printer Subscription Object apply to ALL jobs contained in the
    IPP Printer.

21. Normative References

 [RFC2119]         Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119 , March 1997.
 [RFC2396]         Berners-Lee, T., Fielding, R., and L. Masinter,
                   "Uniform Resource Identifiers (URI): Generic
                   Syntax", RFC 2396, August 1998.
 [RFC2717]         Petke, R. and I. King, "Registration Procedures for
                   URL Scheme Names", RFC 2717, November 1999.
 [RFC2910]         Herriot, R., Butler, S., Moore, P., and R. Turner,
                   "Internet Printing Protocol/1.1: Encoding and
                   Transport", RFC 2910, September 2000.
 [RFC2911]         deBry, R., Hastings, T., Herriot, R., Isaacson, S.,
                   and P. Powell, "Internet Printing Protocol/1.1:
                   Model and Semantics", RFC 2911, September 2000.
 [RFC3381]         Hastings, T., Lewis, H., and R. Bergman, "IPP: Job
                   Progress Attributes", RFC 3381,  September 2002.
 [RFC3996]         Herriot, R., Hastings, T., and H. Lewis, "Internet
                   Printing Protocol (IPP): The 'ippget' Delivery
                   Method for Event Notifications", RFC 3996, March
                   2005.

22. Informative References

 [IANA-CON]        Narten, T. and H. Alvestrand, "Guidelines for
                   Writing an IANA Considerations Section in RFCs",
                   BCP 26, RFC 2434, October 1998.

Herriot & Hastings Standards Track [Page 80] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 [RFC2565]         Herriot, R., Butler, S., Moore, P., and R. Turner,
                   "Internet Printing Protocol/1.0: Encoding and
                   Transport", RFC 2565, April 1999.
 [RFC2566]         deBry, R., Hastings, T., Herriot, R., Isaacson, S.,
                   and 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.
 [RFC2569]         Herriot, R., Hastings, T., Jacobs, N., and J.
                   Martin, "Mapping between LPD and IPP Protocols",
                   RFC 2569, April 1999.
 [RFC2616]         Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
                   Masinter, L., Leach, P., and T. Berners-Lee,
                   "Hypertext Transfer Protocol - HTTP/1.1", RFC 2616,
                   June 1999.
 [RFC3196]         Hastings, T., Manros, C., Zehler, P., Kugler, C.,
                   and H. Holst, "Internet Printing Protocol/1.1:
                   Implementer's Guide", RFC 3196, November 2001.
 [RFC3997]         Hastings, T., Editor, deBry, R., and H. Lewis,
                   "Internet Printing Protocol (IPP): Requirements for
                   IPP Notifications", RFC 3997, March 2005.

23. IANA Considerations

 This section contains the registration information that IANA added to
 the IPP Registry according to the procedures defined in RFC 2911
 [RFC2911] section 6 to cover the definitions in this document.  In
 addition, this section defines how Events and Delivery Methods will
 be registered when they are defined in other documents.  The
 resulting registrations have been published in the
 http://www.iana.org/assignments/ipp-registrations registry.

Herriot & Hastings Standards Track [Page 81] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

23.1. Attribute Registrations

 The following table lists all the attributes defined in this
 document.  These have been registered according to the procedures in
 RFC 2911 [RFC2911] section 6.2.
 Subscription Template attributes:                 Reference  Section
 ---------------------------------                 ---------  -------
 notify-attributes (1setOf type2 keyword)          [RFC3995]  5.3.4
 notify-attributes-supported (1setOf type2 keyword)
                                                   [RFC3995]  5.3.4.1
 notify-charset (charset)                          [RFC3995]  5.3.6
 notify-events (1setOf type2 keyword)              [RFC3995]  5.3.3
 notify-events-default (1setOf type2 keyword)      [RFC3995]  5.3.3.1
 notify-events-supported (1setOf type2 keyword)    [RFC3995]  5.3.3.2
 notify-lease-duration (integer(0:67108863))       [RFC3995]  5.3.8
 notify-lease-duration-default (integer(0:67108863))
                                                   [RFC3995]  5.3.8.1
 notify-lease-duration-supported (1setOf (integer(0: 67108863) |
        rangeOfInteger(0:67108863)))               [RFC3995]  5.3.8.2
 notify-max-events-supported (integer(2:MAX))      [RFC3995]  5.3.3.3
 notify-natural-language (naturalLanguage)         [RFC3995]  5.3.7
 notify-pull-method (type2 keyword)                [RFC3995]  5.3.2
 notify-pull-method-supported (1setOf type2 keyword)
                                                   [RFC3995]  5.3.2.1
 notify-recipient-uri (uri)                        [RFC3995]  5.3.1
 notify-schemes-supported  (1setOf uriScheme)      [RFC3995]  5.3.1.1
 notify-time-interval (integer(0:MAX))             [RFC3995]  5.3.9
 notify-user-data (octetString(63))                [RFC3995]  5.3.5
 Subscription Description Attributes:
 notify-job-id (integer(1:MAX))                    [RFC3995]  5.4.6
 notify-lease-expiration-time (integer(0:MAX))     [RFC3995]  5.4.3
 notify-printer-up-time (integer(1:MAX))           [RFC3995]  5.4.4
 notify-printer-uri (uri)                          [RFC3995]  5.4.5
 notify-sequence-number (integer (0:MAX))          [RFC3995]  5.4.2
 notify-subscriber-user-name (name(MAX))           [RFC3995]  5.4.7
 notify-subscription-id  (integer (1:MAX))         [RFC3995]  5.4.1
 Printer Description Attributes:
 printer-state-change-date-time (dateTime)         [RFC3995]  6.2
 printer-state-change-time (integer(1:MAX))        [RFC3995]  6.1
 Attributes Only in Event Notifications
 notify-subscribed-event (type2 keyword)           [RFC3995]  8.1
 notify-text (text(MAX))                           [RFC3995]  8.2

Herriot & Hastings Standards Track [Page 82] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

23.2. Additional Enum Attribute Value Registrations within the IPP

     registry
 The following table lists all the new enum attribute values defined
 in this document.  These have been registered within the IPP registry
 according to the procedures in RFC 2911 [RFC2911] section 6.1.
 Attribute
   Value      Name                                 Reference   Section
   ------     -----------------------------        ---------   -------
 operations-supported (1setOf type2 enum)          [RFC2911]   4.4.15
   0x0016     Create-Printer-Subscriptions         [RFC3995]   7.1
   0x0017     Create-Job-Subscriptions             [RFC3995]   7.1
   0x0018     Get-Subscription-Attributes          [RFC3995]   7.1
   0x0019     Get-Subscriptions                    [RFC3995]   7.1
   0x001A     Renew-Subscription                   [RFC3995]   7.1
   0x001B     Cancel-Subscription                  [RFC3995]   7.1

23.3. Operation Registrations

 The following table lists all of the operations defined in this
 document.  These have been registered according to the procedures in
 RFC 2911 [RFC2911] section 6.4.
 Operation Name                                    Reference   Section
 ---------------------------------                 ---------   -------
 Cancel-Subscription                               [RFC3995]   11.2.7
 Create-Job - Extensions                           [RFC3995]   11.1.3
 Create-Job-Subscriptions                          [RFC3995]   11.1.1
 Create-Printer-Subscriptions                      [RFC3995]   11.1.2
 Get-Printer-Attributes - Extensions               [RFC3995]   11.2.3
 Get-Subscription-Attributes                       [RFC3995]   11.2.4
 Get-Subscriptions                                 [RFC3995]   11.2.5
 Print-Job - Extensions                            [RFC3995]   11.1.3
 Print-URI - Extensions                            [RFC3995]   11.1.3
 Renew-Subscription                                [RFC3995]   11.2.6
 Validate-Job Operation - Extensions               [RFC3995]   11.2.2

23.4. Status code Registrations

 The following table lists all the status codes defined in this
 document.  These have been registered according to the procedures in
 RFC 2911 [RFC2911] section 6.6.

Herriot & Hastings Standards Track [Page 83] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Value    Status Code Name                        Reference  Section
 -----    ----------------------------            ---------  -------
 0x0000:0x00FF - Successful:
 0x0003   successful-ok-ignored-subscriptions     [RFC3995]  12.1
 0x0005   successful-ok-too-many-events           [RFC3995]  13.4
 0x0400:0x04FF - Client Error:
 0x0414   client-error-ignored-all-subscriptions  [RFC3995]  12.2
 0x0415   client-error-too-many-subscriptions     [RFC3995]  13.3

23.5. Attribute Group tag Registrations

 The following table lists all the attribute group tags defined in
 this document.  These have been registered according to the
 procedures in RFC 2911 [RFC2911] section 6.5.
 Value    Attribute Group Tag Name                 Reference  Section
 -----    --------------------------------         --------   -------
 0x06     subscription-attributes-tag              [RFC3995]  14
 0x07     event-notification-attributes-tag        [RFC3995]  14

23.6. Registration of Events

 The following table lists all the Events defined in this document as
 type2 keywords to be used with the "notify-events", "notify-events-
 default", and "notify-events-supported" Subscription Template
 attributes (see section 5.3.3)).  Rather than creating a separate
 section in the IPP Registry for Events, these event keywords have
 been registered according to the procedures of [RFC2911] section 7.1
 as additional keyword attribute values for use with the "notify-
 events" Subscription Template attribute (see section 5.3.3), i.e.,
 registered as keyword values for the "notify-events", "notify-
 events-default", and "notify-events-supported" attributes:
 Attribute (attribute syntax)
   Value                                          Reference  Section
   ---------------------                          ---------  -------
 notify-events (1setOf type2 keyword)             [RFC3995]  5.3.3
 notify-events-default (1setOf type2 keyword)     [RFC3995]  5.3.3.1
 notify-events-supported (1setOf type2 keyword)   [RFC3995]  5.3.3.2
 notify-subscribed-event (type2 keyword)          [RFC3995]  8.1
   No Events:
     none                                         [RFC3995]  5.3.3.4.1
   Printer Events:
     printer-state-changed                        [RFC3995]  5.3.3.4.2
     printer-restarted                            [RFC3995]  5.3.3.4.2
     printer-shutdown                             [RFC3995]  5.3.3.4.2
     printer-stopped                              [RFC3995]  5.3.3.4.2

Herriot & Hastings Standards Track [Page 84] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

     printer-config-changed                       [RFC3995]  5.3.3.4.2
     printer-media-changed                        [RFC3995]  5.3.3.4.2
     printer-finishings-changed                   [RFC3995]  5.3.3.4.2
     printer-queue-order-changed                  [RFC3995]  5.3.3.4.2
   Job Events:
     job-state-changed                            [RFC3995]  5.3.3.4.3
     job-created                                  [RFC3995]  5.3.3.4.3
     job-completed                                [RFC3995]  5.3.3.4.3
     job-stopped                                  [RFC3995]  5.3.3.4.3
     job-config-changed                           [RFC3995]  5.3.3.4.3
     job-progress                                 [RFC3995]  5.3.3.4.3

23.7. Registration of Event Notification Delivery Methods

 This section describes the requirements and procedures for
 registration and publication of Event Notification Delivery Methods
 and for the submission of such proposals.

23.7.1. Requirements for Registration of Event Notification Delivery

       Methods
 Registered IPP Event Notification Delivery Methods are expected to
 follow a number of requirements described below.

23.7.1.1. Required Characteristics

 A Delivery Method Document MUST either (1) contain all of the
 semantics of the Delivery Method or (2) contain the IPP Delivery
 Method registration requirements and a profile of some other protocol
 that in combination is the Delivery Method (e.g., mailto).  The
 Delivery Method Document (and any documents it requires) MUST define
 either (1) a URL for a Push Delivery Method that the meets the
 requirements of [RFC2717].  or (2) a keyword for a Pull Delivery
 method.
 IPP Event Notification Delivery Method Documents MUST meet the
 requirements of this document (see sections 9 and 10).
 In addition, a Delivery Method Document MUST contain the following
 information:
    Type of registration:  IPP Event Notification Delivery Method
    Name of this delivery method:
    Proposed URL scheme name of this Push Delivery Method or the
    keyword name of this Pull Delivery Method:
    Name of proposer:
    Address of proposer:

Herriot & Hastings Standards Track [Page 85] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

    Email address of proposer:
    Is this delivery method REQUIRED or OPTIONAL for conformance to
    the IPP Event Notification and Subscriptions document:
    Is this delivery method defining Machine Consumable and/or Human
    Consumable content:

23.7.1.2. Naming Requirements

 Exactly one (URL scheme or keyword) name MUST be assigned to each
 Delivery Method.
 Each assigned name MUST uniquely identify a single Delivery Method.
 All Push Delivery Method names MUST conform to the rules for URL
 scheme names, according to [RFC2396] and [RFC2717] for schemes in the
 IETF tree.  All Pull Delivery Method names MUST conform to the rules
 for keywords according to [RFC2911].

23.7.1.3. Functionality Requirements

 Delivery Methods MUST function as a protocol that is capable of
 delivering (push or pull) IPP Event Notifications to Notification
 Recipients.

23.7.1.4. Usage and Implementation Requirements

 Use of a large number of Delivery Methods may hamper
 interoperability.  However, the use of a large number of undocumented
 and/or unlabeled Delivery Methods hampers interoperability even more.
 A Delivery Method should therefore be registered ONLY if it adds
 significant functionality that is valuable to a large community, OR
 if it documents existing practice in a large community.  Note that
 Delivery Methods registered for the second reason should be
 explicitly marked as being of limited or specialized use and should
 only be used with prior bilateral agreement.

23.7.1.5. Publication Requirements

 Delivery Method Documents MUST be published in a standards track,
 informational, or experimental RFCs.

23.7.2. Registration Procedure

 The IPP WG is developing a small number of Delivery Methods which are
 intended to be published as standards track RFCs.  However, some
 parties may wish to register additional Delivery Methods in the
 future.  This section describes the procedures for these additional
 Delivery Methods.

Herriot & Hastings Standards Track [Page 86] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

23.7.2.1. Present the proposal to the Community

 First the Delivery Method Document MUST be an Internet-Draft with a
 target category of standards track, informational, or experimental.
 The same MUST be true for any documents that it references.
 Deliver the proposed Delivery Method Document proposal to the
 "ipp@pwg.org" mailing list.  This mailing list has been established
 by [RFC2911] for reviewing proposed registrations and discussing
 other IPP matters.  Proposed Delivery Method Documents are not
 formally registered and MUST NOT be used until approved.
 The intent of the public posting is to solicit comments and feedback
 on the definition and suitability of the Delivery Method and the name
 chosen for it over a four week period.

23.7.2.2. Delivery Method Reviewer

 The Delivery Method Reviewer is the same person who has been
 appointed by the IETF Application Area Director(s) as the IPP
 Designated Expert according to [RFC2911] and [IANA-CON].  When the
 four week period is over and the IPP Designated Expert is convinced
 that consensus has been achieved, the IPP Designated Expert either
 approves the request for registration or rejects it.  Rejection may
 occur because of significant objections raised on the list or
 objections raised externally.
 Decisions made by the Reviewer must be posted to the ipp@pwg.org
 mailing list within 14 days.  Decisions made by the Reviewer may be
 appealed to the IESG.

23.7.2.3. IANA Registration

 Provided that the Delivery Method registration proposal has either
 passed review or has been successfully appealed to the IESG, the IANA
 will be notified by the delivery method reviewer and asked to
 register the Delivery Method and make it available to the community.

23.7.3. Delivery Method Document Registrations

 Each Push Delivery Method Document defines a URI scheme.  Such a URI
 scheme is used in a URI value of the "notification-recipient" (uri)
 Subscription Template attribute (see section 5.3.1) and the uriScheme
 value of the "notify-schemes-supported" (1setOf uriScheme 5.3.1.1)
 Printer attribute(see section ).  Rather than creating a separate
 section in the IPP Registry for Delivery Methods, Push Delivery
 Methods will be registered as an additional value of the "notify-
 schemes-supported" Printer attribute.  These uriScheme values will be

Herriot & Hastings Standards Track [Page 87] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 registered according to the procedures of [RFC2911] section 7.1 for
 additional attribute values.  Therefore, the IPP Registry entry for a
 Push Delivery Method will be of the form:
 Attribute
   Value                                        Ref.       Section
   ---------------------                        --------   -------
 notify-schemes-supported (1setOf uriScheme)    [RFC3995]  5.3.1.1
   <scheme name>                                RFC xxxx   m.n
 Each Pull Delivery Method Document defines a keyword method which is
 registered as an additional value of the "notify-pull-method" and
 "notify-pull-method-supported" Printer attributes.  These keyword
 values will be registered according to the procedures of [RFC2911]
 section 7.1 for additional attribute values.  Therefore, the IPP
 Registry entry for a Pull Delivery Method will be of the form:
 Attribute
   Value                                        Ref.       Section
   ---------------------                        --------   -------
 notify-pull-method (type2 keyword)             [RFC3995]  5.3.2
 notify-pull-method-supported (1setOf type2 keyword)
                                                [RFC3995]  5.3.2.1
   <method keyword name>                        RFC xxxx    m.n

23.7.4. Registration Template

 To: ipp@pwg.org
 Subject: Registration of a new Delivery Method
 Delivery Method name:
 (All Push Delivery Method names must be suitable for use as the value
 of a URL scheme in the IETF tree and all Pull Delivery Method names
 must be suitable IPP keywords according to [RFC2911])
 Published specification(s):
 (A specification for the Delivery Method must be openly available
 that accurately describes what is being registered.)
 Person & email address to contact for further information:

Herriot & Hastings Standards Track [Page 88] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

24. Internationalization Considerations

 This IPP Notification specification continues support for the
 internationalization of [RFC2911] of attributes containing text
 strings and names.  Allowing a Subscribing Client to specify a
 different natural language and charset for each Subscription Object
 increases the internationalization support.
 The Printer MUST be able to localize the content of Human Consumable
 Event Notifications and to localize the value of "notify-text"
 attribute in Machine Consumable Event Notifications that it delivers
 to Notification Recipients.  For localization, the Printer MUST use
 the value of the "notify-charset" attribute and the "notify-natural-
 language" attribute in the Subscription Object supplied by the
 Subscribing Client.

25. Security Considerations

 Clients submitting Notification requests to the IPP Printer have the
 same security issues as submitting an IPP/1.1 print job request (see
 [RFC2911] section 3.2.1 and section 8).  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.  As with IPP/1.1 Print Job Objects, if there is no security
 on Subscription Objects, sequential assignment of subscription-ids
 exposes the system to a passive traffic monitoring threat.

25.1. Client access rights

 The Subscription Object access control model is the same as the
 access control model for Job objects.  The client MUST have the
 following access rights for the indicated Subscription operations:
 1. Create-Job-Subscriptions (see section 11.1.1):  A Per-Job
    Subscription object is associated with a Job.  To create Per-Job
    Subscription Objects, the authenticated user (see [RFC2911]
    section 8.3) performing this operation MUST (1) be the job owner,
    (2) have Operator or Administrator access rights for this Printer
    (see [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized
    by the Printer's administrator-configured security policy to
    create Per-Job Subscription Objects for the target job.
 2. Create-Printer-Subscriptions (see section 11.1.2):  A Per-Printer
    Subscription object is associated with the Printer.  To create
    Per-Printer Subscription Objects, the authenticated user (see
    [RFC2911] section 8.3) performing this operation MUST (1) have
    Operator or Administrator access rights for this Printer (see

Herriot & Hastings Standards Track [Page 89] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

    [RFC2911] sections 1 and 8.5) or (2) be otherwise authorized by
    the Printer's administrator-configured security policy to create
    Per-Printer Subscription Objects for this Printer.
 3. Get-Subscription-Attributes (see section 11.2.4):  The access
    control model for this operation is the same as that of the Get-
    Job-Attributes operation (see [RFC2911] section 3.3.4).  The
    primary difference is that a Get-Subscription-Attributes operation
    is directed at a Subscription Object rather than at a Job object,
    and a returned attribute group contains Subscription Object
    attributes rather than Job object attributes.  To query the
    specified Subscription Object, the authenticated user (see
    [RFC2911] section 8.3) performing this operation MUST (1) be the
    Subscription Object owner, (2) have Operator or Administrator
    access rights for this Printer (see [RFC2911] sections 1 and 8.5),
    or (3) be otherwise authorized by the Printer's administrator-
    configured security policy to query the Subscription Object for
    the target job.  Furthermore, the Printer's security policy MAY
    limit which attributes are returned, in a manner similar to the
    Get-Job-Attributes operation (see [RFC2911] end of section
    3.3.4.2).
 4. Get-Subscriptions (see section 11.2.5):  The access control model
    for this operation is the same as that of the Get-Jobs operation
    (see [RFC2911] section 3.2.6).  The primary difference is that the
    operation is directed at Subscription Objects rather than at Job
    objects, and the returned attribute groups contain Subscription
    Object attributes rather than Job object attributes.  To query
    Per-Job Subscription Objects of the specified job (client supplied
    the "notify-job-id" operation attribute - see section 11.2.5.1.1),
    the authenticated user (see [RFC2911] section 8.3) performing this
    operation MUST (1) be the Subscription Object owner, (2) have
    Operator or Administrator access rights for this Printer (see
    [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by
    the Printer's administrator-configured security policy to query
    the Subscription Object for the target job.  To query Per-Printer
    Subscription Objects of the Printer (client omits the "notify-
    job-id" operation attribute - see section 11.2.5.1.1), the
    authenticated user (see [RFC2911] section 8.3) performing this
    operation MUST (1) have Operator or Administrator access rights
    for this Printer (see [RFC2911] sections 1 and 8.5), or (2) be
    otherwise authorized by the Printer's administrator-configured
    security policy to query Per-Printer Subscription Objects for the
    target Printer.  Furthermore, the Printer's security policy MAY
    limit which attributes are returned, in a manner similar to the
    Get-Job-Attributes operation (see [RFC2911] end of section
    3.2.6.2).

Herriot & Hastings Standards Track [Page 90] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 5. Renew-Subscriptions (see section 11.2.6):  The authenticated user
    (see [RFC2911] section 8.3) performing this operation MUST (1) be
    the owner of the Per-Printer Subscription Object, (2) have
    Operator or Administrator access rights for the Printer (see
    [RFC2911] sections 1 and 8.5), or (3) be otherwise authorized by
    the Printer's administrator-configured security policy to renew
    Per-Printer Subscription Objects for the target Printer
 6. Cancel-Subscription (see section 11.2.7):  The authenticated user
    (see [RFC2911] section 8.3) performing this operation MUST (1) be
    the owner of the Subscription Object, (2) have Operator or
    Administrator access rights for the Printer (see [RFC2911]
    sections 1 and 8.5), or (3) be otherwise authorized by the
    Printer's administrator-configured security policy to cancel the
    target Subscription Object.
 The standard security concerns (delivery to the right user, privacy
 of content, tamper proof content) apply to each Delivery Method.
 Some Delivery Methods are more secure than others.  Each Delivery
 Method Document MUST discuss its Security Considerations.

25.2. Printer security threats

 Notification trap door:  If a Printer supports the OPTIONAL "notify-
 attributes" Subscription Template attribute (see section 5.3.4) where
 the client can request that the Printer return any specified Job,
 Printer, and Subscription object attributes, the Printer MUST apply
 the same security policy to these requested attributes in the Get-
 Notifications request as it does for the Get-Jobs, Get-Job-
 Attributes, Get-Printer-Attributes, and Get-Subscription-Attributes
 requests.

25.3. Notification Recipient security threats

 Unwanted Events Notifications (spam):  For any Push Delivery Method,
 by far the biggest security concern is the abuse of notification:
 delivering unwanted Event Notifications to third parties (i.e.,
 spam).  The problem is made worse by notification addresses that may
 be redistributed to multiple parties.  There exist scenarios where
 third party notification is used (see Scenario #2 and #3 in
 [RFC3997]).  Any fully secure solution would require active agreement
 of all recipients before delivering anything.

Herriot & Hastings Standards Track [Page 91] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

26. Description of the base IPP documents (Informative)

 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 [RFC3196]
 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
 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

Herriot & Hastings Standards Track [Page 92] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 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.

27. Contributors

 The following people made significant contributions to the design and
 review of this specification:
 Scott A.  Isaacson
 Novell, Inc.
 122 E 1700 S
 Provo, UT  84606
 Phone: 801-861-7366
 Fax:   801-861-2517
 EMail: sisaacson@novell.com
 Roger deBry
 Utah Valley State College
 Orem, UT 84058
 Phone: 801-863-8848
 EMail: debryro@uvsc.edu
 Jay Martin
 Underscore Inc.
 9 Jacqueline St.
 Hudson, NH 03051-5308
 Phone: 603-889-7000
 Fax:   775-414-0245
 EMail: jkm@underscore.com
 Michael Shepherd
 Xerox Corporation
 800 Phillips Road  MS 128-51E
 Webster, NY  14450
 Phone: 716-422-2338
 Fax:   716-265-8871
 EMail: mshepherd@usa.xerox.com

Herriot & Hastings Standards Track [Page 93] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

 Ron Bergman
 Ricoh Printing Systems America
 1757 Tapo Canyon Road
 Simi Valley, CA 93063-3394
 Phone: 805-578-4421
 Fax:   805-578-4001
 EMail: ron.bergman@rpsa.ricoh.com

Authors' Addresses

 Robert Herriot
 Global Workflow Solutions
 706 Colorado Ave.
 Palo Alto, CA 94303
 Phone:  650-324-4000
 EMail:  bob@herriot.com
 Tom Hastings
 Xerox Corporation
 701 S Aviation Blvd, ESAE 242
 El Segundo, CA  90245
 Phone: 310-333-6413
 Fax:   310-333-6342
 EMail: hastings@cp10.es.xerox.com

Herriot & Hastings Standards Track [Page 94] RFC 3995 IPP: Event Notifications and Subscriptions March 2005

Full Copyright Statement

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 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Herriot & Hastings Standards Track [Page 95]

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