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Internet Printing Protocol WG                    Robert Herriot (editor)
INTERNET-DRAFT                                               Xerox Corp.
<draft-ietf-ipp-notify-get-04.txt>                           Carl Kugler
Updates:  RFC 2911                                           Harry Lewis
[Target category:  standards track]                           IBM, Corp.
Expires:  January 17, 2002                                 July 17, 2001


                     Internet Printing Protocol (IPP):
            The 'ippget' Delivery Method for Event Notifications

      Copyright (C) The Internet Society (2001). All Rights Reserved.

Status of this Memo:

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [rfc2026].  Internet-Drafts are
   working documents of the Internet Engineering Task Force (IETF), its
   areas, and its working groups.  Note that other groups may also
   distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed as
   http://www.ietf.org/shadow.html.

Abstract

   This document describes an extension to the Internet Printing
   Protocol/1.0 (IPP) [RFC2566, RFC2565] and IPP/1.1 [RFC2911, RFC2910].
   This document specifies the 'ippget' Delivery Method for use with the
   "IPP Event Notifications and Subscriptions" specification [ipp-ntfy].
   When IPP Notification [ipp-ntfy] is supported, the Delivery Method
   defined in this document is one of the RECOMMENDED Delivery Methods
   for Printers to support.

   The 'ippget' Delivery Method is a 'pull' Delivery Method with aspects
   of a 'push' method as well. That is, when an Event occurs, the
   Printer saves the Event Notification for a period of time called the
   Event Notification Lease Time.  The Notification Recipient fetches
   (pulls) Event Notifications using the Get-Notifications operation.
   If the Notification Recipient has selected the option to wait for
   additional Event Notifications, the Printer continues to return


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   (similar to push) Event Notifications to the Notification Recipient
   as Get-Notification responses as Events occur.  This push aspect is
   not a true 'push', since the Printer does not open the connect, but
   rather continues to return responses as Events occur using the
   connection originated by the Notification Recipient.












































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Table of Contents


   1 Introduction.....................................................5

   2 Terminology......................................................5

   3 Model and Operation..............................................6

   4 General Information..............................................8

   5 Get-Notifications operation......................................9
   5.1 Get-Notifications Request.....................................11
   5.2 Get-Notifications Response....................................13

   6 Subscription Template Attributes................................18
   6.1 Subscription Template Attribute Conformance...................18
   6.2 Additional Information about Subscription Template Attributes.18
   6.2.1 notify-recipient-uri (uri)..................................18
   6.3 Subscription Description Attribute Conformance................19

   7 Attributes only in Event Notifications..........................19
   7.1 "notify-get-interval" (integer(0:MAX))........................19

   8 Additional Printer Description Attributes.......................20
   8.1 ippget-event-time-to-live (integer(0:MAX))....................20

   9 New Values for Existing Printer Description Attributes..........21
   9.1 notify-schemes-supported (1setOf uriScheme)...................21
   9.2 operations-supported (1setOf type2 enum)......................21

   10 New Status Codes...............................................21
   10.1 redirection-other-site (0x0300)..............................21

   11 The IPPGET URL Scheme..........................................22
   11.1 The IPPGET URL Scheme Applicability and Intended Usage.......22
   11.2 The IPPGET URL Scheme Associated Port........................22
   11.3 The IPPGET URL Scheme Associated MIME Type...................22
   11.4 The IPPGET URL Scheme Character Encoding.....................22
   11.5 The IPPGET URL Scheme Syntax in ABNF.........................23
   11.5.1 IPPGET URL Examples........................................24
   11.5.2 IPPGET URL Comparisons.....................................24

   12 Encoding and Transport.........................................25

   13 Conformance Requirements.......................................26
   13.1 Conformance for IPP Printers.................................26

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   13.2 Conformance for IPP Clients..................................27

   14 IANA Considerations............................................28
   14.1 Operation Registrations......................................28
   14.2 Additional attribute value registrations for existing attributes
         28
   14.2.1 Additional values for the "notify-schemes-supported" Printer
              attribute..............................................28
   14.2.2 Additional values for the "operations-supported" Printer
              attribute..............................................29
   14.3 Attribute Registrations......................................29
   14.4 Status code Registrations....................................29

   15 Internationalization Considerations............................30

   16 Security Considerations........................................30

   17 References.....................................................30

   18 Authors' Addresses.............................................32

   19 Description of Base IPP documents..............................33

   20 Full Copyright Statement.......................................35


Table of Tables

   Table 1 " Information about the Delivery Method....................8
   Table 2 " Attributes in Event Notification Content................16
   Table 3 " Additional Attributes in Event Notification Content for Job
      Events........................................................17
   Table 4 " Combinations of Events and Subscribed Events for "job-
      impressions-completed"........................................17
   Table 5 " Additional Attributes in Event Notification Content for
      Printer Events................................................18
   Table 6 " Operation-id assignments................................21
   Table 7 " The "event-notification-attributes-tag" value...........26











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1 Introduction

   The "IPP Event Notifications and Subscriptions" document [ipp-ntfy]
   defines an OPTIONAL extension to Internet Printing Protocol/1.0 (IPP)
   [RFC2566, RFC2565] and IPP/1.1 [RFC2911, RFC2910].  For a description
   of the base IPP documents, see section 19.  The [ipp-ntfy] extension
   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.
   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.  The Subscription Object
   specifies that when one of the specified Events occurs, the Printer
   sends an asynchronous Event Notification to the specified
   Notification Recipient via the specified Delivery Method (i.e.,
   protocol).

   The "IPP Event Notifications and Subscriptions" document [ipp-ntfy]
   specifies that each Delivery Method is defined in another document.
   This document is one such document, and it specifies the 'ippget'
   delivery method.  When IPP Notification [ipp-ntfy] is supported, the
   Delivery Method defined in this document is one of the RECOMMENDED
   Delivery Methods for Printers to support.

   The 'ippget' Delivery Method is a 'pull' Delivery Method with aspects
   of a 'push' method as well.  That is, when an Event occurs, the
   Printer saves the Event Notification for a period of time called the
   Event Notification Lease Time.  The Notification Recipient fetches
   (pulls) the Event Notifications using the Get-Notifications
   operation.  This operation causes the Printer to return all Event
   Notifications held for the Notification Recipient.  If the
   Notification Recipient has selected the option to wait for additional
   Event Notifications, the Printer continues to return (similar to
   push) Event Notifications to the Notification Recipient as Get-
   Notification responses as Events occur.  This push aspect is not a
   true 'push', since the Printer does not open the connect, but rather
   continues to return responses as Events occur using the connection
   originated by the Notification Recipient.


2 Terminology

   This section defines the following terms that are used throughout
   this document:

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   This document uses the same terminology as [RFC2911], such as
   "client", "Printer", "Job", "attribute", "attribute value",
   "keyword", "operation", "request", "response", and "support".

   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.

   Event Notification Lease: The lease that is associated with an Event
   Notification. When the lease expires, the Printer discards the
   associated Event Notification.

   Event Notification Lease Time: The expiration time assigned to a
   lease that is associated with an Event Notification.

   Event Notification Attributes Group: The attributes group in a
   response that contains attributes that are part of an Event
   Notification.

   Event Wait Mode: The mode requested by a Notification Recipient
   client in its Get-Notifications Request and granted by a Printer to
   keep the connection open where the Printer sends subsequent Event
   Notifications to the Notification Recipient as they occur as
   additional Get-Notification Responses.

   Other capitalized terms, such as Notification Recipient, Event
   Notification, Compound Event Notification, Printer, etc.,  are
   defined in [ipp-ntfy], have the same meanings, and are not reproduced
   here.




3 Model and Operation

   In a Subscription Creation Operation, when the value of the "notify-
   recipient-uri" attribute has the scheme 'ippget', the client is
   requesting that the Printer use the 'ippget' Delivery Method for the
   Event Notifications associated with the new Subscription Object.  The
   client SHOULD choose a value for the address part of the "notify-
   recipient-uri" attribute that uniquely identifies the Notification
   Recipient.



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   When an Event occurs, the Printer MUST generate an Event Notification
   and MUST assign it the Event Notification Lease Time.  The Printer
   MUST hold an Event Notification for its assigned Event Notification
   Lease Time.  The Printer MUST assign the same Event Notification
   Lease Time to each Event Notification.

   When a Notification Recipient wants to receive Event Notifications,
   it performs the Get-Notifications operation, which causes the Printer
   to return all un-expired Event Notifications held for the
   Notification Recipient.  If the Notification Recipient has selected
   the Event Wait Mode option to wait for additional Event
   Notifications, the response to the Get-Notifications request
   continues indefinitely as the Printer continues to send Event
   Notifications in the response as Events occur.  For the Get-
   Notification operation, the Printer sends only those Event
   Notifications that are generated from Subscription Objects whose
   "notify-recipient-uri" attribute value equals the value of the
   "notify-recipient-uri" Operation Attribute in the Get-Notifications
   operation.

   If a Notification Recipient performs the Get-Notifications operation
   twice in quick succession, it will receive nearly the same Event
   Notification both times because most of the Event Notifications are
   those that the Printer saves for a few seconds after the Event
   occurs.  There are two possible differences. Some old Event
   Notifications may not be present in the second response because their
   Event Notification Leases have expired.  Some new Event Notifications
   may be present in the second response but not the first response,
   because they occurred after the first response.

   When the Notification Recipient requests Event Notifications for per-
   Job Subscription Objects, the Notification Recipient typically
   performs the Get-Notifications operation within a second of
   performing the Subscription Creation operation.  Because the Printer
   is likely to save Event Notifications for several seconds, the
   Notification Recipient is unlikely to miss any Event Notifications
   that occur between the Subscription Creation and the Get-
   Notifications operation.











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4 General Information

   If a Printer supports this Delivery Method, the following are its
   characteristics.


              Table 1 " Information about the Delivery Method

    Document Method Conformance Requirement       Delivery Method
                                                   Realization

    1.  What is the URL scheme name for the       ippget
        Delivery Method?
    2.  Is the Delivery Method REQUIRED,          RECOMMENDED
        RECOMMENDED or OPTIONAL for an IPP
        Printer to support?
    3.  What transport and delivery protocols     IPP with one new
        does the Printer use to deliver the Event operation.
        Notification Content, i.e., what is the
        entire network stack?
    4.  Can several Event Notifications be        Yes.
        combined into a Compound Event
        Notification?
    5.  Is the Delivery Method initiated by the   This Delivery Method
        Notification Recipient (pull), or by the  is a pull method
        Printer (push)?                           with aspects of a
                                                   push method, though
                                                   the Printer does not
                                                   initiate the
                                                   connection.
    6.  Is the Event Notification content Machine Machine Consumable
        Consumable or Human Consumable?
    7.  What section in this document answers the Section 5
        following question? For a Machine
        Consumable Event Notification, what is
        the representation and encoding of values
        defined in section 9.1 of [ipp-ntfy] and
        the conformance requirements thereof? For
        a Human Consumable Event Notification,
        what is the representation and encoding
        of pieces of information defined in
        section 9.2 of [ipp-ntfy] and the
        conformance requirements thereof?
    8.  What are the latency and reliability of   Same as IPP and the
        the transport and delivery protocol?      underlying HTTP
                                                   transport
    9.  What are the security aspects of the      Same as IPP and the
        transport and delivery protocol, e.g.,    underlying HTTP


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        how it is handled in firewalls?           transport
    10. What are the content length restrictions? None
    11. What are the additional values or pieces  None
        of information that a Printer sends in an
        Event Notification content and the
        conformance requirements thereof?
    12. What are the additional Subscription      None
        Template and/or Subscription Description
        attributes and the conformance
        requirements thereof?
    13. What are the additional Printer           None
        Description attributes and the
        conformance requirements thereof?



5 Get-Notifications operation

   This operation is issued by a client acting in the role of a
   Notification Recipient and causes the Printer to return all Event
   Notifications held for the Notification Recipient.

   A Printer MUST support this operation.

   When a Printer performs this operation, it MUST return all and only
   those Event Notifications:

      1. Whose associated Subscription Object's "notify-subscription-id"
        attribute equals the "notify-subscription-id" Operation
        attribute if supplied AND

      2. Whose associated Subscription Object's "notify-recipient-uri"
        attribute equals the "notify-recipient-uri" Operation attribute
        AND

      3. Whose associated Subscription Object's "notify-recipient-uri"
        attribute matches the scheme value of 'ippget' using the
        matching rules in section 11.5.2 AND

      4. Whose Event Notification Lease Time has not yet expired AND

      5. Where the Notification Recipient is the owner of or has read-
        access rights to the associated Subscription Object.

   The Printer has the following options for responding to a Get-
   Notifications Request:




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      1. The Printer can reject the request and return the 'server-error-
        busy' status code, if the Printer is too busy to accept this
        operation at this time.  In this case, the Printer MUST return
        the "get-notify-interval" attribute to indicate when the client
        should try again.

      2. If the Notification Recipient did not request Event Wait Mode,
        the Printer MUST respond to this operation immediately with
        whatever Event Notifications it currently holds and return the
        "notify-get-interval" attribute with number of seconds from now
        at which the Notification Recipient MAY repeat the Get-
        Notifications Request to get future Event Notifications.

      3. If the Notification Recipient requested Event Wait Mode, the
        Printer MUST respond to this operation immediately with whatever
        Event Notifications it currently holds  MUST continue to send
        Event Notifications as they occur until all of the associated
        Subscription Objects are cancelled.  A Subscription Object is
        cancelled either via the Cancel-Subscription operation or by the
        Printer (e.g., the Subscription Object is cancelled when the
        associated Job completes and is no longer in the Job Retention
        or Job History phase - see the "ippget-event-time-to-live
        (integer(0:MAX))" attribute discussion in section 8.1).
        However, the Printer MAY decide to terminate Event Wait Mode at
        any time, including in the first response.  In this case the
        Printer MUST return an additional Event Notification Attributes
        Group that contains the single "notify-get-interval" attribute.
        This attribute indicates that the Printer wishes to leave Event
        Wait Mode and the number of seconds in the future that the
        Notification Recipient SHOULD try the Get-Notifications
        operation again.  The Notification Recipient MUST accept this
        response and MUST disconnect.  If the Notification Recipient
        does not disconnect, the Printer SHOULD do so.

   If the Notification Recipient wishes to terminate the Get-
   Notifications operation, it can close the connection.  See section 12
   for the encoding and transport rules for the Get-Notifications
   Response for the Event Wait Mode.

   The Printer MUST accept the request in any state (see [RFC2911]
   "printer-state" and "printer-state-reasons" attributes) and MUST
   remain in the same state with the same "printer-state-reasons"
   values.

   Access Rights: If the policy of the Printer is to allow all users to
   access all Event Notifications, then the Printer MUST accept this
   operation from any user.  Otherwise, the authenticated user (see
   [RFC2911] section 8.3) performing this operation MUST either be the

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   owner of each Subscription Object identified by the "notify-
   recipient-uri" Operation attribute (as determined during a
   Subscription Creation Operation) or an operator or administrator of
   the Printer (see [RFC2911] Sections 1 and 8.5).  Otherwise, the IPP
   object MUST reject the operation and return: 'client-error-
   forbidden', 'client-error-not-authenticated', or 'client-error-not-
   authorized' status code as appropriate.


5.1 Get-Notifications Request

   The following groups of attributes are part of the Get-Notifications
   Request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.1.

      Target:
         The "printer-uri" (uri) operation attribute which is the target
         for this operation as described in [RFC2911] section 3.1.5.

      Requesting User Name:
         The "requesting-user-name" (name(MAX)) attribute SHOULD be
         supplied by the client as described in [RFC2911] section 8.3.

      "notify-subscription-id" (integer(1:MAX)):
         The client SHOULD supply this attribute, if known, and the
         client is only monitoring a single Subscription object.  The
         Printer object MUST support this attribute.  If supplied, but
         no Subscription Object exists with this identifier, the Printer
         MUST return the 'client-error-not-found' status code.

         If supplied and the identified Subscription Object exists, the
         Printer MUST check that the Subscription Object's "notify-
         recipients-uri" attribute scheme is 'ippget' (case insensitive-
         match - see section 11.5.2).  If the scheme does not match
         'ippget', the Printer MUST reject the request and return the
         'client-error-uri-scheme-not-supported' status code.

         Note: If Notification Recipients supplies this attribute, if
         known, then the Event Notifications will be sent in time stamp
         order since only one Subscription object is involved (see
         "Event Notification Ordering" requirements in [ipp-ntfy]
         section 9).  Supplying this attribute also reduces the Event
         processing time on the Printer since the Printer doesn't have


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         to search all of the Subscription Objects in order to match the
         "notify-recipient-uri" operation attribute (see next
         attribute).

      "notify-recipient-uri" (uri(255)):
         The client MAY supply this attribute whether or not it also
         supplies the "notify-subscription-id" operation attribute.  The
         Printer object MUST support this attribute.  If the client
         supplies neither the "notify-subscription-id" nor the "notify-
         recipient-uri", the Printer MUST reject the request and return
         the 'client-error-bad-request' status code.

         If the supplied scheme is not ippget (case insensitive-match -
         see section 11.5.2), the Printer MUST reject the request and
         return the 'client-error-uri-scheme-not-supported' status code.

         If the client also supplied the "notify-subscription-id"
         attribute, then the value of this attribute MUST match the
         "notify-recipient-uri" Subscription Description attribute for
         the identified Subscription object.  If they do not match, the
         Printer MUST return the 'client-error-not-found' status code.

         If the client did not supply the "notify-subscription-id"
         operation attribute, the Printer matches the value of this
         "notify-recipient-uri" attribute against the value of the
         "notify-recipient-uri" Subscription Description attribute in
         each Subscription Object in the Printer using the URI matching
         rules specified in section 11.5.2. If there are no matches, the
         IPP Printer MUST return the 'client-error-not-found' status
         code.

         The value of this attribute is defined to be shorter (255
         octets) than the 'uri' attribute syntax (1023 octets) in
         [RFC2911], since this uri is used for identification, not for
         locating a network resource.

         The [ipp-ntfy] specification REQUIRES that Subscription
         Object's "notify-recipient-uri" attribute be returned in any
         operation with the identical representation as supplied by the
         original Subscribing Client in the Subscription Creation
         Request.  Therefore the Printer implementation MUST use other
         means to perform the URI match than changing the Subscription
         Object's original "notify-recipient-uri" value to a canonical
         form.

         Note: this attribute allows a subscribing client to pick URLs
         that are unique, e.g. the client's own URL or a friend's URL,


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         which in both cases is likely the URL of the person's host. An
         application could make a URL unique for each application.

      "notify-wait" (boolean):
         The client MAY supply this attribute.  The Printer object MUST
         support both values of this attribute.  If the value is 'true',
         the client is requesting Event Wait Mode.  See the beginning of
         section 5 for the rules for Event Wait Mode.

5.2 Get-Notifications Response

   The following groups of attributes are part of the Get-Notifications
   Response:

   Group 1: Operation Attributes

      Status Message:
         In addition to the REQUIRED status code returned in every
         response, the response OPTIONALLY includes a "status-message"
         (text(255)) and/or a "detailed-status-message" (text(MAX))
         operation attribute as described in [RFC2911] sections 13 and
         3.1.6.

         The Printer can return any status codes defined in [RFC2911].
         If the status code is not 'successful-xxx', the Printer MUST
         NOT return any Event Notification Attribute groups. The
         following is a description of the important status codes:

             successful-ok: the response contains all Event Notification
               associated with the specified "notify-recipient-uri". If
               the specified Subscription Objects have no associated
               Event Notification, the response MUST contain zero Event
               Notifications.
             client-error-not-found: The Printer has no Subscription
               Object's whose "notify-recipient-uri" attribute equals
               the "notify-recipient-uri" Operation attribute, if
               supplied or whose "notify-subscription-id" attribute
               equals the "notify-subscription-id" Operation attribute,
               if supplied.
             server-error-busy: The Printer is too busy to accept this
               operation. If the "notify-get-interval" operation
               attribute is present in the Operation Attributes of the
               response, then the Notification Recipient SHOULD wait for
               the number of seconds specified by the "notify-get-
               interval" attribute before performing this operation
               again. If the "notify-get-interval" Operation Attribute
               is not present, the Notification Recipient SHOULD use the



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               normal network back-off algorithms for determining when
               to perform this operation again.
             redirection-other-site: The Printer does not handle this
               operation and requests the Notification Recipient to
               perform the operation again with the uri specified by the
               "redirect-uri" Operation Attribute in the response.

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.

         The Printer MUST use the values of "notify-charset" and
         "notify-natural-language", respectively, from one Subscription
         Object associated with the Event Notifications in this
         response.

         Normally, there is only one matched Subscription Object, or the
         value of the "notify-charset" and "notify-natural-language"
         attributes is the same in all Subscription Objects. If not, the
         Printer MUST pick one Subscription Object from which to obtain
         the value of these attributes. The algorithm for picking the
         Subscription Object is implementation dependent. The choice of
         natural language is not critical because 'text' and 'name'
         values can override the "attributes-natural-language" Operation
         attribute. The Printer's choice of charset is critical because
         a bad choice may leave it unable to send some 'text' and 'name'
         values accurately.

      "printer-up-time" (integer(1:MAX)):
         The value of this attribute is the Printer's "printer-up-time"
         attribute at the time the Printer sends this response. Because
         each Event Notification also contains the value of this
         attribute when the event occurred, the value of this attribute
         lets a Notification Recipient know when each Event Notification
         occurred relative to the time of this response.


      "redirect-uri" (uri):
         The value of this attribute is the uri that the Notification
         Recipient MUST use for a subsequent Get-Notifications
         operation. This attribute is returned in the Operation
         Attributes Group if and only if the status code has the value
         'redirection-other-site'.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 for details on returning
         Unsupported Attributes.


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   Group 3 through N: Event Notification Attributes

         The Printer responds with one Event Notification Attributes
         Group per matched Event Notification.  The entire response is
         considered a single Compound Event Notification (see [ipp-
         ntfy]).  The last Event Notification Attributes Group MAY
         contain a single "notify-get-interval" (see section 7.1 and
         12), in which case the Printer will return no future responses.
         The initial matched Event Notifications are all un-expired
         Event Notification associated with the matched Subscription
         Objects and MUST follow the "Event Notification Ordering"
         requirements for Event Notifications within a Compound Event
         Notification specified in [ipp-ntfy] section 9.

         If the Notification Recipient has selected the Event Wait Mode
         option to wait for additional Event Notifications (the "notify-
         wait" attribute was set to 'true'), the Printer sends
         subsequent Event Notifications in the response each time it
         processes additional Events.  Each time the Printer sends such
         Event Notifications, their ordering MUST follow the "Event
         Notification Ordering" requirements in [ipp-ntfy] section 9.

         Note: If a Notification Recipient performs two consecutive Get-
         Notifications operations, the time stamp of the first Event
         Notification in the second Get-Notifications Response may be
         less than the time stamp of the last Event Notification in the
         first Get-Notification Response.  This happens because the
         Printer sends all unexpired Event Notification according to the
         ordering specified in [ipp-ntfy] and some Event Notifications
         from the first Get-Notifications operation may not have expired
         by the time the second Get-Notifications operation occurs.

         From the Notification Recipient's view, the response appears as
         an initial burst of data, which includes the Operation
         Attributes Group and one Event Notification Attributes Group
         per Event Notification that the Printer is holding.  After the
         initial burst of data, if the Notification Recipient has
         selected the Event Wait Mode option to wait for additional
         Event Notifications, the Notification Recipient receives
         occasional Event Notification Attribute Groups. Proxy servers
         may delay some Event Notifications or cause time-outs to occur.
         The client MUST be prepared to perform the Get-Notifications
         operation again when time-outs occur.

         Each attribute is encoded using the IPP rules for encoding
         attributes [RFC2910] and MAY be encoded in any order.  Note:


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         the Get-Jobs response in [RFC2911] acts as a model for encoding
         multiple groups of attributes.  See section 12 for the encoding
         and transport rules.

         Each Event Notification Group MUST contain all of attributes
         specified in section 9.1 ("Content of Machine Consumable Event
         Notifications") of [ipp-ntfy] with exceptions denoted by
         asterisks in the tables below.

         The tables below are copies of the tables in section 9.1
         ("Content of Machine Consumable Event Notifications") of [ipp-
         ntfy] except that each cell in the "Sends" column is a  "MUST".

         For an Event Notification for all Events, the Printer includes
         the attributes shown in Table 2.

              Table 2 " Attributes in Event Notification Content

      Source Value                              Sends     Source Object

      notify-subscription-id (integer(1:MAX))   MUST      Subscription
      notify-printer-uri (uri)                  MUST      Subscription
      notify-subscribed-event (type2 keyword)   MUST      Event
                                                           Notification
      printer-up-time (integer(1:MAX))          MUST      Printer
      printer-current-time (dateTime)           MUST *    Printer
      notify-sequence-number (integer (0:MAX))  MUST      Subscription
      notify-charset (charset)                  MUST      Subscription
      notify-natural-language (naturalLanguage) MUST      Subscription
      notify-user-data (octetString(63))        MUST **   Subscription
      notify-text (text)                        MUST      Event
                                                           Notification
      attributes from the "notify-attributes"   MUST ***  Printer
      attribute
      attributes from the "notify-attributes"   MUST ***  Job
      attribute
      attributes from the "notify-attributes"   MUST ***  Subscription
      attribute

         * The Printer MUST send the "printer-current-time" attribute if
         and only if it supports the "printer-current-time" attribute on
         the Printer object.

         ** If the associated Subscription Object does not contain a
         "notify-user-data" attribute, the Printer MUST send an octet-
         string of length 0.



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         *** If the "notify-attributes" attribute is present on the
         Subscription Object, the Printer MUST send all attributes
         specified by the "notify-attributes" attribute.  Note: if the
         Printer doesn't support the "notify-attributes" attribute, it
         is not present on the associated Subscription Object.

         For Event Notifications for Job Events, the Printer includes
         the additional attributes shown in Table 3.

      Table 3 " Additional Attributes in Event Notification Content for
                                  Job Events

      Source Value                                  Sends  Source
                                                            Object

      job-id (integer(1:MAX))                       MUST   Job
      job-state (type1 enum)                        MUST   Job
      job-state-reasons (1setOf type2 keyword)      MUST   Job
      job-impressions-completed (integer(0:MAX))    MUST * Job

         *  The Printer MUST send the "job-impressions-completed"
         attribute in an Event Notification only for the combinations of
         Events and Subscribed Events shown in Table 4.


       Table 4 " Combinations of Events and Subscribed Events for "job-
                            impressions-completed"

      Job Event                 Subscribed Job Event

      'job-progress'            'job-progress'
      'job-completed'           'job-completed'
      'job-completed'           'job-state-changed'


         For Event Notification for Printer Events, the Printer includes
         the additional attributes shown in Table 5.












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      Table 5 " Additional Attributes in Event Notification Content for
                                Printer Events

      Source Value                                  Sends   Source
                                                             Object

      printer-state (type1 enum)                    MUST    Printer
      printer-state-reasons (1setOf type2 keyword)  MUST    Printer
      printer-is-accepting-jobs (boolean)           MUST    Printer

6 Subscription Template Attributes

   This section defines the Subscription object conformance requirements
   for Printers.


6.1 Subscription Template Attribute Conformance

   The 'ippget' Delivery Method has the same conformance requirements
   for Subscription Template attributes as defined in [ipp-ntfy].  The
   'ippget' Delivery Method does not define any addition Subscription
   Template attributes.


6.2 Additional Information about Subscription Template Attributes

   This section defines additional information about Subscription
   Template attributes defined in [ipp-ntfy].


6.2.1 notify-recipient-uri (uri)

   This section describes the syntax of the value of this attribute for
   the 'ippget' Delivery Method.  The syntax for values of this
   attribute for other Delivery Method is defined in other Delivery
   Method Documents.

   In order to support the 'ippget' Delivery Method and Protocol, the
   Printer MUST support the following syntax:

     The 'ippget://' URI scheme.  The remainder of the URI indicates
     something unique about the Notification Recipient, such as its host
     name or host address (and optional path) that the Printer uses to
     match the "notify-recipient-uri" Operation attribute supplied in
     the Get-Notifications request.  See section 11 for a complete
     definition of the syntax of the IPPGET URL.




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6.3 Subscription Description Attribute Conformance

   The 'ippget' Delivery Method has the same conformance requirements
   for Subscription Description attributes as defined in [ipp-ntfy].
   The 'ippget' Delivery Method does not define any addition
   Subscription Description attributes.


7 Attributes only in Event Notifications

   This section defines attributes that exist only in Event
   Notifications and do no exist in any IPP-defined objects.


7.1 "notify-get-interval" (integer(0:MAX))

   The Printer returns this attribute to give the client an indication
   of when to try another Get-Notifications request in the future.  The
   value of this attribute is the number of seconds that the
   Notification Recipient SHOULD wait before trying the Get-
   Notifications operation again.  This value is intended to help the
   client be a good network citizen.

   The Printer MUST return this attribute by itself in a separate Event
   Notification Attributes Group.  The Printer MUST return this
   attribute if and only if:

      1. Printer busy case:  the Printer returns the 'server-error-busy'
        status code OR

      2. No wait case:  the Printer returns the 'successful-ok' status
        code and the client either (1) supplied the "notify-wait"
        attribute with a value of 'false' or (2) omitted the attribute
        entirely OR

      3. Printer leaves Event Wait Mode:  the Printer returns the
        'successful-ok' status code and the client supplied the "notify-
        wait" attribute with the 'true value (Event Wait Mode) but the
        Printer wants the client to disconnect (no wait), instead of
        staying connected.  The client MUST accept this response and
        MUST disconnect.  If the client does not disconnect, the Printer
        SHOULD do so.  The Printer returns this attribute for this case
        only if the implementation does not want to keep the connection
        open at this time.  If the Printer wants the client to keep the
        connection open and remain in Event Wait Mode, then the Printer
        MUST NOT return this attribute in the response.





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8 Additional Printer Description Attributes

   This section defines additional Printer Description attributes for
   use with the 'ippget' Delivery Method.


8.1 ippget-event-time-to-live (integer(0:MAX))

   This Printer Description attribute specifies the number of seconds
   that a Printer keeps an Event Notification that is associated with
   the 'ippget' Delivery Method.

   The Printer MUST support this attribute if it supports the 'ippget'
   Delivery Method.

   The value of this attribute is the minimum number of seconds that
   MUST elapse between the time the Printer creates an Event
   Notification object for the 'ippget' Delivery Method and the time the
   Printer discards the same Event Notification.

   For example, assume the following:

     1. a client performs a Job Creation operation that creates a
        Subscription Object associated with this Delivery Method, AND

     2. an Event associated with the new Job occurs immediately after
        the Subscription Object is created, AND

     3. the same client or some other client performs a Get-
        Notifications operation N seconds after the Job Creation
        operation.

   Then, if N is less than the value of this attribute, the client(s)
   performing the Get-Notifications operations can expect not to miss
   any Event-Notifications, barring some unforeseen lack of memory space
   in the Printer.

   The value of this attribute also specifies the minimum number of
   seconds that the Printer, if supporting the ippget Delivery Method,
   MUST keep 'completed', 'canceled', or 'aborted' Job objects in the
   Job Retention and/or Job History phases.  See [RFC2911] section
   4.3.7.1 and the discussion in [ipp-ntfy] 'job-completed' event) that
   explains that a Notification Recipients can query the Job after
   receiving a 'job-completed' Event Notification in order to find out
   other information about the job that is completing.  However, this
   attribute has no effect on the Cancel-Subscription operation which
   deletes the object  immediately, whether or not it contain the ippget
   scheme.  Immediately thereafter, subsequent Get-Notifications

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   Responses MUST NOT contain Event Notifications associated with the
   cancelled Subscription object.


9 New Values for Existing Printer Description Attributes

   This section defines additional values for existing Printer
   Description attributes define in [ipp-ntfy].


9.1 notify-schemes-supported (1setOf uriScheme)

   The following value for the "notify-schemes-supported" attribute is
   added in order to support the new Delivery Method defined in this
   document:

      'ippget'  - The IPP Notification Delivery Method defined in this
         document.

9.2 operations-supported (1setOf type2 enum)

   Table 6 lists the "operation-id" value defined in order to support
   the new Get-Notifications operation defined in this document.


                     Table 6 " Operation-id assignments

      Value       Operation Name

      0x001C      Get-Notifications



10 New Status Codes

   The following status codes are defined as extensions for this
   Delivery Method and are returned as the status code of the Get-
   Notifications operation.


10.1 redirection-other-site (0x0300)

   This status code means that the Printer doesn't perform that Get-
   Notifications operation and that the "redirect-uri" Operation
   Attribute in the response contains the uri that the Notification
   Recipient MUST use for performing the Get-Notifications operation.




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11 The IPPGET URL Scheme

   This section defines the 'ippget' URL and the conformance
   requirements for using it.


11.1 The IPPGET URL Scheme Applicability and Intended Usage

   This section is intended for use in registering the 'ippget' URL
   scheme with IANA and fully conforms to the requirements in [RFC2717].
   This document defines the 'ippget'" URL (Uniform Resource Locator)
   scheme for specifying a unique identifier for an IPP Client which
   implements the IPP Get-Notifications operation specified in this
   document (see section 5).

   The intended usage of the 'ippget' URL scheme is COMMON.


11.2 The IPPGET URL Scheme Associated Port

   None.

   An 'ippget' URL behaves as a unique identifier for IPP Clients and is
   NOT used to initiate any over-the-wire protocol associations.

   See:  IANA Port Numbers Registry [IANA-PORTREG].


11.3 The IPPGET URL Scheme Associated MIME Type

   All IPP Get-Notifications operations (requests and responses) MUST be
   conveyed in an 'application/ipp' MIME media type as registered in
   [IANA-MIMEREG].  An 'ippget' URL MUST uniquely identify an IPP Client
   that support this 'application/ipp' MIME media type.

   See:  IANA MIME Media Types Registry [IANA-MIMEREG].


11.4 The IPPGET URL Scheme Character Encoding

   The 'ippget' URL scheme defined in this document is based on the ABNF
   for the URI Generic Syntax [RFC2396] and further updated by [RFC2732]
   and [RFC2373] (for IPv6 addresses in URLs).  The 'ippget' URL scheme
   is case-insensitive in the scheme and 'authority' part; however, the
   'abs_path' part is case-sensitive, as in [RFC2396].  Code points
   outside [US-ASCII] MUST be hex escaped by the mechanism specified in
   [RFC2396].


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11.5 The IPPGET URL Scheme Syntax in ABNF

   This document is intended for use in registering the 'ippget' URL
   scheme with IANA and fully conforms to the requirements in [RFC2717].
   This document defines the 'ippget' URL (Uniform Resource Locator)
   scheme for specifying a unique identifier for an IPP Client which
   implements IPP 'Get-Notifications' operation specified in this
   document.

   The intended usage of the 'ippget' URL scheme is COMMON.

   The IPP protocol places a limit of 1023 octets (NOT characters) on
   the length of a URI (see section 4.1.5 'uri' in [RFC2911]).  An IPP
   Printer MUST return the 'client-error-request-value-too-long' status
   code (see section 13.1.4.10 in [RFC2911]) when a URI received in a
   request is too long.

     Note:  IPP Clients and IPP Printers ought to be cautious about
     depending on URI lengths above 255 bytes, because some older client
     or proxy implementations might not properly support these lengths.

   An 'ippget' URL MUST be represented in absolute form.  Absolute URLs
   always begin with a scheme name followed by a colon.  For definitive
   information on URL syntax and semantics, see "Uniform Resource
   Identifiers (URI): Generic Syntax and Semantics" [RFC2396].  This
   specification adopts the definitions of "authority", "abs_path",
   "query", "reg_name", "server", "userinfo", and "hostport" from
   [RFC2396], as updated by [RFC2732] and [RFC2373] (for IPv6 addresses
   in URLs).

   The 'ippget' URL scheme syntax in ABNF is as follows:

      ippget_URL = "ippget:" "//" authority [ abs_path [ "?" query ]]
      authority  = server | reg_name
      reg_name   = 1*( unreserved | escaped | "$" | "," |
                       ";" | ":" | "@" | "&" | "=" | "+" )
      server     = [ [ userinfo "@" ] hostport ]
      userinfo   = *( unreserved | escaped |
                      ";" | ":" | "&" | "=" | "+" | "$" | "," )
      hostport   = host [ ":" port ]
      abs_path   = "/"  path_segments

   If the port is empty or not given, then no port is assumed.  The
   semantics are that the 'ippget' URL is a unique identifier for an IPP
   Client that will retrieve IPP event notifications via the IPP Get-
   Notifications operation.



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   Note:  The use of IP addresses in URLs SHOULD be avoided whenever
   possible (see [RFC1900]).


11.5.1 IPPGET URL Examples

   The following are examples of valid 'ippget' URLs for IPP Clients
   (using DNS host names):

          ippget://abc.com
          ippget://abc.com/listener
          ippget://bob@abc.com/listener/1232

   Note:  The use of IP addresses in URLs SHOULD be avoided whenever
   possible (see [RFC1900]).

   The IPP Client that creates the Subscription object and the
   Notification Recipient have to agree on a unique IPPGET URL value in
   order for the Get-Notifications operations to retrieve the proper
   Event Notifications.  Therefore, the choice of 'userinfo@hostport'
   versus the simpler 'hostport' production in an 'ippget' URL may be
   influenced by the intended usage.

   If a given IPP Client creates an IPP Subscription object for event
   notifications intended for retrieval by the same IPP Client, then the
   simple 'hostport' production may be most appropriate.  In this case,
   the IPP Client and the Notification Recipient both know the
   'hostport' of the client.

   On the other hand, if a given IPP Client creates an IPP Subscription
   object for event notifications intended for retrieval by a different
   IPP Client, then the 'userinfo@hostport' production (using, for
   example, the right-hand side of a 'mailto:' URL, see [RFC2368]) may
   be most appropriate.  For this case, a mail address serves as the
   prior agreement on the IPPGET URL value between the IPP Client and
   the Notification Recipient.


11.5.2 IPPGET URL Comparisons

        When comparing two 'ippget' URLs to decide if they match or not,
           an IPP Client or IPP Printer MUST use the same rules as those
           defined for HTTP URI comparisons in [RFC2616].






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12 Encoding and Transport

   This section defines the encoding and transport considerations for
   this Delivery Method based on [RFC2910].

   The encoding of a Get-Notifications Response is modeled the Get-Jobs
   Response (see [RFC2911]).  In a Get-Notifications Response, each
   Event Notification Attributes Group MUST start with an 'event-
   notification-attributes-tag' (see the section "Encodings of
   Additional Attribute Tags" in [ipp-ntfy]), but only the last group
   ends with an 'end-of-attributes-tag'.  In addition, for Event Wait
   Mode the multi-part/related is used to separate each multiple
   response (in time) to a single Get-Notifications Request.

   The Printer returns Get-Notification Response as follows:

      1. If the Notification Recipient client did not request Event Wait
        Mode ("notify-wait" = 'false' or omitted), the Printer ends the
        response with an 'end-of-attributes-tag' (see [RFC2911] Get-Jobs
        encoding) as with any operation response.  The Notification
        Recipient is expected to close the connection.

      2. If the Notification Recipient client requests Event Wait Mode
        ("notify-wait" = 'true') and the Printer wishes to honor the
        request, the Printer ends the Response without an 'end-of-
        attributes-tag' and MUST return the response as an
        application/ipp part inside a multi-part/related MIME media
        type.  Neither the Notification Recipient nor the Printer close
        the connection.  When one or more additional Events occur, the
        Printer returns each as an additional Event Notification Group
        using a separate application/ipp part under the multi-
        part/related type.

      3. If the client requested Event Wait Mode ("notify-wait" =
        'true'), but the Printer does not wish to honor the request in
        the initial response but wants the client to disconnect, the
        Printer MUST return the "notify-get-interval" attribute (see
        section 7.1) as the last Event Notifications Attributes Group -
        see section 5.2), the Printer ends the Response with an 'end-of-
        attributes-tag'.  The Printer returns the response as an
        application/ipp part which MAY be inside an multi-part/related
        type.  The client MUST accept this response and MUST disconnect.
        If the client does not disconnect, the Printer SHOULD do so.

      4. If the client requested Event Wait Mode ("notify-wait" =
        'true'), and the Printer initially honored the request, but
        later wishes to leave Event Wait Mode,  the Printer MUST return
        the "notify-get-interval" attribute (see section 7.1) as the

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        last Event Notifications Attributes Group - see section 5.2),
        the Printer ends the Response with an 'end-of-attributes-tag'.
        The Printer returns the response as an application/ipp part
        which MUST be inside an multi-part/related type.

   ISSUE:  Should we use application/multiplexed (draft-herriot-
   application-multiplexed-03.txt) which can chunk mime types using
   content lengths, instead of multi-part/related, which uses boundary
   strings?

   Note: either the Notification Recipient or the Printer can abnormally
   terminate by closing the connection.  However, if the Printer closes
   the connection too soon after returning the response, the client may
   not receive the response.

   The Printer MAY chunk the responses, but this has no significance to
   the IPP semantics.

   This notification delivery method uses the IPP transport and encoding
   [RFC2910] for the Get-Notifications operation with one extension
   allocated in [ipp-ntfy]:


          Table 7 " The "event-notification-attributes-tag" value

    Tag Value (Hex)   Meaning

    0x07              "event-notification-attributes-tag"


13 Conformance Requirements

   The 'ippget' Delivery Method is RECOMMEND for Printers to support.


13.1 Conformance for IPP Printers

   IPP Printers that conform to this specification:

      1. MUST meet the conformance requirements defined in [ipp-ntfy];

      2. MUST support the Get-Notifications operation defined in section
        5;

      3. MUST support the Subscription object attributes as defined in
        section 6;



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      4. MUST support the additional values for IPP/1.1 Printer
        Description attributes defined in section 9;

#@# next line is > 72 characters: 73
      5. MUST support the "ippget-event-time-to-live" Printer Description
        attribute defined in section 8.1;

      6. MUST support the "redirection-other-site" status code defined
        10.1, if it redirects Get-Notifications operations;

      7. SHOULD reject received 'ippget' URLs in 'application/ipp'
        request bodies (e.g., in the "notify-recipient-uri" attribute in
        a Get-Notifications request) that do not conform to the ABNF for
        'ippget' URLs specified in section 11.5 of this document;

      8. MUST listen for the IPP Get-Notifications operation requests on
        IANA-assigned well-known port 631, unless explicitly configured
        by system administrators or site policies;

      9. SHOULD NOT listen for IPP Get-Notifications operation requests
        on any other port, unless explicitly configured by system
        administrators or site policies.


13.2 Conformance for IPP Clients

   IPP Clients that conform to this specification:

     1. MUST create unambiguously unique 'ippget' URLs in all cases;

     2. MUST send 'ippget' URLs (e.g., in the "notify-recipient-uri"
        attribute in a Get-Notifications request) that conform to the
        ABNF specified in section 11.5 of this document;

     3. MUST send IPP Get-Notifications operation requests via the port
        specified in the associated 'ipp' URL (if present) or otherwise
        via IANA assigned well-known port 631;

     4. MUST convert the associated 'ipp' URLs for use in IPP Get-
        Notifications operation to their corresponding 'http' URL forms
        for use in the HTTP layer according to the rules in section 5
        "IPP URL Scheme" in [RFC2910].

   Note:  The use of ambiguous 'ippget' URLs is NOT an optional feature
   for IPP Clients; it is a non-conformant implementation error.





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14 IANA Considerations

   IANA shall register the 'ippget' URL scheme as defined in section 11
   according to the procedures of [RFC2717].

   The rest of this section contains the exact information for IANA to
   add to the IPP Registries according to the procedures defined in RFC
   2911 [RFC2911] section 6.

     Note to RFC Editors:  Replace RFC NNNN below with the RFC number
     for this document, so that it accurately reflects the content of
     the information for the IANA Registry.


14.1 Operation Registrations

   The following table lists the operation defined in this document.
   This is to be registered according to the procedures in RFC 2911
   [RFC2911] section 6.4.

   Operations:                                    Ref.      Section:
   Get-Notifications operation                    RFC NNNN     5

   The resulting operation registration will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/operations/
   area.


14.2 Additional attribute value registrations for existing attributes

   This section lists additional attribute value registrations for use
   with existing attributes defined in other documents.


14.2.1 Additional values for the "notify-schemes-supported" Printer
     attribute

   The following table lists the uriScheme value defined in this
   document as an additional uriScheme value for use with the "notify-
   schemes-supported"  Printer attribute defined in [ipp-ntfy].   This
   is to be registered according to the procedures in RFC 2911 [RFC2911]
   section 6.1.

   uriScheme Attribute Values:                    Ref.      Section:
   ippget                                         RFC NNNN    9.1




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   The resulting URI scheme attribute value registrations will be
                       published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
                       values/notify-schemes-supported/
   area.


14.2.2 Additional values for the "operations-supported" Printer
     attribute

   The following table lists the enum attribute value defined in this
   document as an additional type2 enum value for use with the
   "operations-supported" Printer attribute defined in [RFC2911]. This
   is to be registered according to the procedures in RFC 2911 [RFC2911]
   section 6.1.

   type2 enum Attribute Values:         Value     Ref.      Section:
   Get-Notifications                    0x001C    RFC NNNN    9.2

   The resulting enum attribute value registration will be published in
                       the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
                       values/operations-supported/
   area.


14.3 Attribute Registrations

   The following table lists the attribute defined in this document.
   This is to be registered according to the procedures in RFC 2911
   [RFC2911] section 6.2.

   Printer Description attributes:                Ref.      Section:
   ippget-event-time-to-live (integer(0:MAX))     RFC NNNN     8.1

   The resulting attribute registration will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attributes/
   area.


14.4 Status code Registrations

   The following table lists the status code defined in this document.
   This is to be registered according to the procedures in RFC 2911
   [RFC2911] section 6.6.

   Status codes:                                  Ref.      Section:
   redirection-other-site (0x0300)                 RFC NNNN    10.1

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   The resulting status code registration will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/status-codes/
   area.


15 Internationalization Considerations

   The IPP Printer MUST localize the "notify-text" attribute as
   specified in section 14 of [ipp-ntfy].

   In addition, when the client receives the Get-Notifications response,
   it is expected to localize the attributes that have the 'keyword'
   attribute syntax according to the charset and natural language
   requested in the Get-Notifications request.


16 Security Considerations

   The IPP Model and Semantics document [RFC2911] discusses high-level
   security requirements (Client Authentication, Server Authentication
   and Operation Privacy).  Client Authentication is the mechanism by
   which the client proves its identity to the server in a secure
   manner.  Server Authentication is the mechanism by which the server
   proves its identity to the client in a secure manner.  Operation
   Privacy is defined as a mechanism for protecting operations from
   eavesdropping.

   Unlike other Event Notification delivery methods in which the IPP
   Printer initiates the Event Notification, with the method defined in
   this document, the Notification Recipient is the client who   s the
   Get-Notifications operation.  Therefore, there is no chance of "spam"
   notifications with this method.  Furthermore, such a client can close
   down the HTTP channel at any time, and so can avoid future unwanted
   Event Notifications at any time.


17 References

   [ipp-iig]
     Hastings, T., Manros, C., Kugler, K, Holst H., Zehler, P.,
     "Internet Printing Protocol/1.1:  draft-ietf-ipp-implementers-
     guide-v11-03.txt, work in progress, July 17, 2001






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   [ipp-ntfy]
     R. Herriot, Hastings, T., Isaacson, S., Martin, J., deBry, R.,
     Shepherd, M., Bergman, R., "Internet Printing Protocol/1.1: IPP
     Event Notifications and Subscriptions", <draft-ietf-ipp-not-spec-
     07.txt>, July 17, 2001.

   [RFC1900]
     B. Carpenter, Y. Rekhter.  Renumbering Needs Work, RFC 1900,
     February 1996.

   [RFC2026]
     S. Bradner, "The Internet Standards Process -- Revision 3", RFC
     2026, October 1996.

   [RFC2119]
     S. Bradner, "Key words for use in RFCs to Indicate Requirement
     Levels", RFC 2119 , March 1997

   [RFC2368]
     P. Hoffman, L. Masinter, J. Zawinski.  The "mailto" URL Scheme, RFC
     2368, July 1998.

   [RFC2373]
     R. Hinden, S. Deering.  IP Version 6 Addressing Architecture, RFC
     2373, July 1998.

   [RFC2396]
     Berners-Lee, T. et al.  Uniform Resource Identifiers (URI): Generic
     Syntax, RFC 2396, August 1998

   [RFC2565]
     Herriot, R., Butler, S., Moore, P., and R. Turner, "Internet
     Printing Protocol/1.0: Encoding and Transport", RFC 2565, April
     1999.

   [RFC2566]
     R. deBry, T. Hastings, R. Herriot, S. Isaacson, 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.


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   [RFC2569]
     Herriot, R., Hastings, T., Jacobs, N., Martin, J., "Mapping between
     LPD and IPP Protocols", RFC 2569, April 1999.

   [RFC2616]
     R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P.
     Leach, T. Berners-Lee, "Hypertext Transfer Protocol - HTTP/1.1",
     RFC 2616, June 1999.

   [RFC2717]
     R. Petke and I. King, "Registration Procedures for URL Scheme
     Names", RFC 2717, November 1999.

   [RFC2732]
     R. Hinden, B. Carpenter, L. Masinter.  Format for Literal IPv6
     Addresses in URL's, RFC 2732, December 1999.

   [RFC2910]
     Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet Printing
     Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.

   [RFC2911]
     R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell,
     "Internet Printing Protocol/1.1: Model and Semantics", RFC 2911,
     September 2000.


18 Authors' Addresses


   Robert Herriot
   Xerox Corp.
   3400 Hill View Ave, Building 1
   Palo Alto, CA 94304

   Phone: 650-813-7696
   Fax:  650-813-6860
   e-mail: robert.herriot@pahv.xerox.com

   Carl Kugler
   IBM
   P.O. Box 1900
   Boulder, CO 80301-9191

   Phone:
   Fax:
   e-mail: kugler@us.ibm.com


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   Harry Lewis
   IBM
   P.O. Box 1900
   Boulder, CO 80301-9191

   Phone: 303-924-5337
   FAX:
   e-mail:  harryl@us.ibm.com


   IPP Web Page:  http://www.pwg.org/ipp/
   IPP Mailing List:  ipp@pwg.org

   To subscribe to the ipp mailing list, send the following email:
     1) send it to majordomo@pwg.org
     2) leave the subject line blank
     3) put the following two lines in the message body:
          subscribe ipp
          end

   Implementers of this specification document are encouraged to join
   the IPP Mailing List in order to participate in any discussions of
   clarification issues and review of registration proposals for
   additional attributes and values.  In order to reduce spam the
   mailing list rejects mail from non-subscribers, so you must subscribe
   to the mailing list in order to send a question or comment to the
   mailing list.


19 Description of Base IPP documents

   The base set of IPP documents includes:

     Design Goals for an Internet Printing Protocol [RFC2567]
     Rationale for the Structure and Model and Protocol for the Internet
        Printing Protocol [RFC2568]
     Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
     Internet Printing Protocol/1.1: Encoding and Transport [RFC2910]
     Internet Printing Protocol/1.1: Implementer's Guide [ipp-iig]
     Mapping between LPD and IPP Protocols [RFC2569]
     Internet Printing Protocol (IPP): IPP Event Notifications and
        Subscriptions [ipp-ntfy]

   The "Design Goals for an Internet Printing Protocol" document takes a
   broad look at distributed printing functionality, and it enumerates
   real-life scenarios that help to clarify the features that need to be
   included in a printing protocol for the Internet.  It identifies
   requirements for three types of users: end users, operators, and

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   administrators.  It calls out a subset of end user requirements that
   are satisfied in IPP/1.0.  A few OPTIONAL operator operations have
   been added to IPP/1.1.

   The "Rationale for the Structure and Model and Protocol for the
   Internet Printing Protocol" document describes IPP from a high level
   view, defines a roadmap for the various documents that form the suite
   of IPP specification documents, and gives background and rationale
   for the IETF working group's major decisions.

   The "Internet Printing Protocol/1.1: Model and Semantics" document
   describes a simplified model with abstract objects, their attributes,
   and their operations that are independent of encoding and transport.
   It introduces a Printer and a Job object.  The Job object optionally
   supports multiple documents per Job.  It also addresses security,
   internationalization, and directory issues.

   The "Internet Printing Protocol/1.1: Encoding and Transport" document
   is a formal mapping of the abstract operations and attributes defined
   in the model document onto HTTP/1.1 [RFC2616].  It defines the
   encoding rules for a new Internet MIME media type called
   "application/ipp".  This document also defines the rules for
   transporting over HTTP a message body whose Content-Type is
   "application/ipp".  This document defines the 'ippget' scheme for
   identifying IPP printers and jobs.

   The "Internet Printing Protocol/1.1: Implementer's Guide" document
   gives insight and advice to implementers of IPP clients and IPP
   objects.  It is intended to help them understand IPP/1.1 and some of
   the considerations that may assist them in the design of their client
   and/or IPP object implementations.  For example, a typical order of
   processing requests is given, including error checking.  Motivation
   for some of the specification decisions is also included.

   The "Mapping between LPD and IPP Protocols" document gives some
   advice to implementers of gateways between IPP and LPD (Line Printer
   Daemon) implementations.

   The "IPP Event Notifications and Subscriptions" document defines an
   extension to IPP/1.0 [RFC2566, RFC2565] and IPP/1.1 [RFC2911,
   RFC2910].  This extension allows a client to subscribe to printing
   related Events and defines the semantics for delivering asynchronous
   Event Notifications to the specified Notification Recipient via a
   specified Delivery Method (i.e., protocols) defined in (separate)
   Delivery Method documents.






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20 Full Copyright Statement

   Copyright (C) The Internet Society (2001). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the  purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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



















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