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INTERNET-DRAFT                                   Robert Herriot (editor)
<draft-ietf-ipp-notify-get-02.txt>                           Xerox Corp.
[Target category:  standards track]                          Carl Kugler
                                                              IBM, Corp.
                                                             Harry Lewis
                                                              IBM, Corp.
                                                       February 28, 2001
                     Internet Printing Protocol (IPP):
            The 'ippget' Delivery Method for Event Notifications

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

Status of this Memo:

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [rfc2026].  Internet-Drafts are
   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

   The notification extension document [ipp-ntfy] defines operations
   that a client can perform in order to create Subscription Objects in
   a Printer and carry out other operations on them. A Subscription
   Object represents a Subscription abstraction. The Subscription Object
   specifies that when one of the specified Events occurs, the Printer
   sends an asynchronous Event Notification to the specified
   Notification Recipient via the specified Delivery Method (i.e.,
   protocol).

   The notification extension document [ipp-ntfy] specifies that each
   Delivery Method is defined in another document. This document is one
   such document, and it specifies the 'ippget' delivery method.

   The 'ippget' Delivery Method is a 'pull and push' Delivery Method.
   That is, the Printer saves Event Notification for a period of time
   and expects the Notification Recipient to fetch the Event
   Notifications (the pull part). The Printer continues to send Event

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   Notifications to the Notification Recipient as Events occur (the push
   part) if the client has selected the option to wait for additional
   Event Notifications.

   When a Printer supports this Delivery Method, it holds each Event
   Notification for an amount of time, called the Event Notification
   Lease Time.

   When a Notification Recipient wants to receive Event Notifications,
   it performs an IPP operation called 'Get-Notifications', which this
   document defines. This operation causes the Printer to return all
   Event Notifications held for the Notification Recipient. If the
   Notification Recipient has selected the option to wait for additional
   Event Notifications, the Printer continues sending Event
   Notifications to the Notification Recipient as additional Events
   occur.



   The basic set of IPP documents includes:

     Design Goals for an Internet Printing Protocol [RFC2567]
     Rationale for the Structure and Model and Protocol for the Internet
       Printing Protocol [RFC2568]
     Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
     Internet Printing Protocol/1.1: Encoding and Transport [RFC2910]
     Internet Printing Protocol/1.1: Implementer's Guide [ipp-iig]
     Mapping between LPD and IPP Protocols [RFC2569]
     Internet Printing Protocol/1.0 & 1.1: IPP Event Notification
       Specification [ipp-ntfy]

   The "Design Goals for an Internet Printing Protocol" document takes a
   broad look at distributed printing functionality, and it enumerates
   real-life scenarios that help to clarify the features that need to be
   included in a printing protocol for the Internet.  It identifies
   requirements for three types of users: end users, operators, and
   administrators.  It calls out a subset of end user requirements that
   are satisfied in IPP/1.0.  A few OPTIONAL operator operations have
   been added to IPP/1.1.

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

   The "Internet Printing Protocol/1.1: Model and Semantics" document
   describes a simplified model with abstract objects, their attributes,
   and their operations that are independent of encoding and transport.
   It introduces a Printer and a Job object.  The Job object optionally

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   supports multiple documents per Job.  It also addresses security,
   internationalization, and directory issues.

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

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

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

   The "Event Notification Specification" document describes an
   extension to the IPP/1.0, IPP/1.1, and future versions. This
   extension allows a client to subscribe to printing related Events.
   Subscriptions are modeled as Subscription Objects.  The Subscription
   Object specifies that when one of the specified Event occurs, the
   Printer sends an asynchronous Event Notification to the specified
   Notification Recipient via the specified Delivery Method (i.e.,
   protocol).  A client associates Subscription Objects with a
   particular Job by performing the Create-Job-Subscriptions operation
   or by submitting a Job with subscription information.  A client
   associates Subscription Objects with the Printer by performing a
   Create-Printer-Subscriptions operation.  Four other operations are
   defined for Subscription Objects: Get-Subscriptions-Attributes, Get-
   Subscriptions, Renew-Subscription, and Cancel-Subscription.













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Table of Contents


   1  Introduction....................................................6

   2  Terminology.....................................................6

   3  Model and Operation.............................................7

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

   5  Get-Notifications operation....................................10
   5.1   Get-Notifications Request...................................12
   5.2   Get-Notifications Response..................................13

   6  Subscription Template Attributes...............................18
   6.1   Subscription Template Attribute Conformance.................18
   6.2   Additional Information about Subscription Template Attributes18
   6.2.1   notify-recipient-uri (uri)................................18
   6.3   Subscription Description Attribute Conformance..............19

   7  Additional Printer Description Attributes......................19
   7.1   Printer Description Attribute Conformance...................19
   7.2   New Values for Existing Printer Description Attributes......19
   7.2.1   notify-schemes-supported (1setOf uriScheme)...............19
   7.2.2   operations-supported (1setOf type2 enum)..................19
   7.3   begin-to-expire-time-interval (integer(0:MAX))..............20

   8  New Status Codes...............................................20
   8.1   redirection-other-site (0x300)..............................21

   9  The IPPGET URL Scheme..........................................21
   9.1   The IPPGET URL Scheme Applicability and Intended Usage......21
   9.2   The IPPGET URL Scheme Associated Port.......................21
   9.3   The IPPGET URL Scheme Associated MIME Type..................21
   9.4   The IPPGET URL Scheme Character Encoding....................22
   9.5   The IPPGET URL Scheme Syntax in ABNF........................22
   9.5.1   IPPGET URL Examples.......................................23
   9.5.2   IPPGET URL Comparisons....................................23

   10 Encoding.......................................................24

   11 Conformance Requirements.......................................24
   11.1  Conformance for IPP Printers................................24
   11.2  Conformance for IPP Clients.................................25

   12 IANA Considerations............................................25
   12.1  Operation Registrations.....................................26
   12.2  Additional values of existing attributes....................26

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   12.2.1  Additional values for the "notify-schemes-supported" Printer
              attribute..............................................26
   12.2.2  Additional values for the "operations-supported" Printer
              attribute..............................................26
   12.3  Attribute Registrations.....................................27
   12.4  Status code Registrations...................................27

   13 Internationalization Considerations............................27

   14 Security Considerations........................................27

   15 References.....................................................28

   16 Authors' Addresses.............................................29

   17 Full Copyright Statement.......................................30


Table of Tables

   Table 1 - Information about the Delivery Method....................9

   Table 2 - Attributes in Event Notification Content................16

   Table 3 - Additional Attributes in Event Notification Content for Job

      Events ........................................................17

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

      impressions-completed" ........................................17

   Table 5 - Additional Attributes in Event Notification Content for

      Printer Events ................................................18

   Table 6 - Operation-id assignments................................20

   Table 7 - The "event-notification-attributes-tag" value...........24












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1  Introduction

   The notification extension document [ipp-ntfy] defines operations
   that a client can perform in order to create Subscription Objects in
   a Printer and carry out other operations on them. A Subscription
   Object represents a Subscription abstraction. The Subscription Object
   specifies that when one of the specified Events occurs, the Printer
   sends an asynchronous Event Notification to the specified
   Notification Recipient via the specified Delivery Method (i.e.,
   protocol).

   The notification extension document [ipp-ntfy] specifies that each
   Delivery Method is defined in another document. This document is one
   such document, and it specifies the 'ippget' delivery method.

   The 'ippget' Delivery Method is a 'pull and push' Delivery Method.
   That is, the Printer saves Event Notification for a period of time
   and expects the Notification Recipient to fetch the Event
   Notifications (the pull part). The Printer continues to send Event
   Notifications to the Notification Recipient as Events occur (the push
   part) if the client has selected the option to wait for additional
   Event Notifications.

   When a Printer supports this Delivery Method, it holds each Event
   Notification for an amount of time, called the Event Notification
   Lease Time.

   When a Notification Recipient wants to receive Event Notifications,
   it performs an IPP operation called 'Get-Notifications', which this
   document defines. This operation causes the Printer to return all
   Event Notifications held for the Notification Recipient. If the
   Notification Recipient has selected the option to wait for additional
   Event Notifications, the Printer the Printer continues to send Event
   Notifications to the Notification Recipient as Events occur.


2  Terminology

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

   Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD
   NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to
   conformance to this specification.  These terms are defined in
   [RFC2911 section 13.1 on conformance terminology, most of which is
   taken from RFC 2119 [RFC2119].

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

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

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

   For other capitalized terms that appear in this document, see [ipp-
   ntfy].


3  Model and Operation

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

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

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

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



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


4  General Information

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





































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              Table 1 - Information about the Delivery Method


   Document Method Conformance        Delivery Method Realization
   Requirement


   1.  What is the URL scheme name    ippget
       for the Delivery Method?

   2.  Is the Delivery Method         RECOMMENDED
       REQUIRED, RECOMMENDED or
       OPTIONAL for an IPP Printer
       to support?

   3.  What transport and delivery
       protocols does the Printer
       use to deliver the Event
       Notification Content, i.e.,
       what is the entire network     IPP with one new operation.
       stack?

   4.  Can several Event              Yes.
       Notifications be combined
       into a Compound Event
       Notification?

   5.  Is the Delivery Method         This Delivery Method is a pull
       initiated by the Notification  and a push.
       Recipient (pull), or by the
       Printer (push)?

   6.  Is the Event Notification      Machine Consumable
       content Machine Consumable or
       Human Consumable?

   7.  What section in this document  Section 5
       answers the following
       question? For a Machine
       Consumable Event
       Notification, what is the
       representation and encoding
       of values defined in section
       9.1 of [ipp-ntfy] and the
       conformance requirements
       thereof? For a Human
       Consumable Event
       Notification, what is the
       representation and encoding


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       of pieces of information
       defined in section 9.2 of
       [ipp-ntfy] and the
       conformance requirements
       thereof?

   8.  What are the latency and       Same as IPP and the underlying
       reliability of the transport   HTTP transport
       and delivery protocol?

   9.  What are the security aspects  Same as IPP and the underlying
       of the transport and delivery  HTTP transport
       protocol, e.g., how it is
       handled in firewalls?

   10. What are the content length    None
       restrictions?

   11. What are the additional        None
       values or pieces of
       information that a Printer
       sends in an Event
       Notification content and the
       conformance requirements
       thereof?

   12. What are the additional        None
       Subscription Template and/or
       Subscription Description
       attributes and the
       conformance requirements
       thereof?

   13. What are the additional        None
       Printer Description
       attributes and the
       conformance requirements
       thereof?




5  Get-Notifications operation

   This operation causes the Printer to return all Event Notifications
   held for the Notification Recipient.

   A Printer MUST support this operation.


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

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

     2. Whose associated Subscription Object's "notify-recipient-uri"
        attribute has a scheme value of 'ippget'  AND

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

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

   The Printer MUST respond to this operation immediately with whatever
   Event Notifications it currently holds. If the Notification Recipient
   has selected the option to wait for additional Event Notifications,
   the Printer MUST continue to send Event Notifications as they occur
   until all of the associated Subscription Objects are cancelled.  A
   Subscription Object is cancelled either via the Cancel-Subscription
   operation or by the Printer (e.g. the Subscription Object is
   cancelled when the associated Job completes).

   Note, the Printer terminates the operation in the same way that it
   normally terminates IPP operations. For example, if the Printer is
   sending chunked data, it can send a 0 length chunk to denote the end
   of the operation or it can close the connection.  If the Notification
   Recipient wishes to terminate the Get-Notifications operation, it can
   close the connection.

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

   Access Rights: If the policy of the Printer is to allow all users to
   access all Event Notifications, then the Printer MUST accept this
   operation from any user.  Otherwise, the authenticated user (see
   [RFC2911] section 8.3) performing this operation MUST either be the
   owner of each Subscription Object identified by the "notify-
   recipient-uri" Operation attribute (as determined during a
   Subscription Creation Operation) or an operator or administrator of
   the Printer (see [RFC2911] Sections 1 and 8.5).  Otherwise, the IPP
   object MUST reject the operation and return: 'client-error-
   forbidden', 'client-error-not-authenticated', or 'client-error-not-
   authorized' status code as appropriate.




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5.1  Get-Notifications Request

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

   Group 1: Operation Attributes

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

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

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

      "notify-recipient-uri" (url):
         The client MUST supply this attribute.  The Printer object MUST
         support this attribute. The Printer matches the value of this
         attribute (byte for byte with no case conversion) against the
         value of the "notify-recipient-uri" in each Subscription Object
         in the Printer. If there are no matches, the IPP Printer MUST
         return the 'client-error-not-found' status code.  For each
         matched Subscription Object, the IPP Printer MUST return all
         unexpired Event Notifications associated with it.  The Printer
         MUST send additional Event Notifications as Events occur if and
         only if the value of the "notify-no-wait" attribute is 'false'
         or not supplied by the client (see the next attribute below).

         Note: this attribute allows a subscribing client to pick URLs
         that are unique, e.g. the client's own URL or a friend's URL,
         which in both cases is likely the URL of the person's host. An
         application could make a URL unique for each application.

      "notify-no-wait" (boolean):
         The client MAY supply this attribute.  The Printer object MUST
         support this attribute.  If the value of this attribute is
         'false', the Printer MUST send all un-expired Event
         Notifications (as defined in the previous attribute) and it
         MUST continue to send responses for as long as the Subscription
         Objects associated with the specified "notify-recipient-uri"
         continue to exist. If the value of this attribute is 'true',
         the Printer MUST send all un-expired Event Notifications (as
         defined in the previous attribute) and the Printer MUST
         conclude the operation without waiting for any additional
         Events to occur.  If the client doesn't supply this attribute,


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         the Printer MUST behave as if the client had supplied this
         attribute with the value of 'false'.

5.2  Get-Notifications Response

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

   Group 1: Operation Attributes

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

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

            successful-ok: the response contains all Event Notification
               associated with the specified "notify-recipient-uri". If
               the specified Subscription Objects have no associated
               Event Notification, the response MUST contain zero Event
               Notifications.
            client-error-not-found: The Printer has no Subscription
               Object's whose "notify-recipient-uri" attribute equals
               the "notify-recipient-uri" Operation attribute.
            server-error-busy: The Printer is too busy to accept this
               operation. If the "suggested-ask-again-time-interval"
               operation attribute is present in the Operation
               Attributes of the response, then the Notification
               Recipient SHOULD wait for the number of seconds specified
               by the "suggested-ask-again-time-interval" attribute
               before performing this operation again. If the
               "suggested-ask-again-time-interval" Operation Attribute
               is not present, the Notification Recipient should use the
               normal network back-off algorithms for determining when
               to perform this operation again.
            redirection-other-site: The Printer does not handle this
               operation and requests the Notification Recipient to
               perform the operation with the uri specified by the
               "notify-ippget-redirect" Operation Attribute in the
               response.

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

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

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

      "printer-up-time" (integer(0:MAX)):
         The value of this attribute is the Printer's "printer-up-time"
         attribute at the time the Printer sends this response. Because
         each Event Notification also contains the value of this
         attribute when the event occurred, the value of this attribute
         lets a Notification Recipient know when each Event Notification
         occurred relative to the time of this response.

      "suggested-ask-again-time-interval" (integer(0:MAX)):
         The value of this attribute is the number of seconds that the
         Notification Recipient SHOULD wait before trying this operation
         again when
            a) the Printer returns the 'server-error-busy' status code
               OR
            b) the Printer returns the 'successful-ok' status code and
               the client supplied the "notify-no-wait" attribute with a
               value of 'true'.
         This value is intended to help the client be a good network
         citizen.

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

   Group 2: Unsupported Attributes

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



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         If the "subscription-ids" attribute contained subscription-ids
         that do not exist, the Printer returns them in this group as
         value of the "subscription-ids" attribute.

   Group 3 through N: Event Notification Attributes

         The Printer responds with one Event Notification Attributes
         Group per matched Event Notification. The initial matched Event
         Notifications are all un-expired Event Notification associated
         with the matched Subscription Objects.  If the Notification
         Recipient has selected the option to wait for additional Event
         Notifications, the Printer the subsequent Event Notifications
         in the response are Event Notifications associated with the
         matched Subscription Objects as the corresponding Event occurs.

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

         Each Event Notification Group MUST start with an 'event-
         notification-attributes-tag' (see the section "Encodings of
         Additional Attribute Tags" in [ipp-ntfy]).

         Each attribute is encoded using the IPP rules for encoding
         attributes [RFC2910] and may be encoded in any order.  Note:
         the Get-Jobs response in [RFC2911] acts as a model for encoding
         multiple groups of attributes.

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

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

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




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             Table 2 - Attributes in Event Notification Content


     Source Value                               Sends     Source Object


     notify-subscription-id (integer(1:MAX))    MUST      Subscription

     notify-printer-uri (uri)                   MUST      Subscription

     notify-subscribed-event (type2 keyword)    MUST      Event
                                                          Notification

     printer-up-time (integer(MIN:MAX))         MUST      Printer

     printer-current-time (dateTime) *          MUST *    Printer

     notify-sequence-number (integer (0:MAX))   MUST      Subscription

     notify-charset (charset)                   MUST      Subscription

     notify-natural-language (naturalLanguage)  MUST      Subscription

     notify-user-data (octetString(63)) **      MUST      Subscription

     notify-text (text)                         MUST      Event
                                                          Notification

     attributes from the "notify-attributes"    MUST      Printer
     attribute ***

     attributes from the "notify-attributes"    MUST      Job
     attribute ***

     attributes from the "notify-attributes"    MUST      Subscription
     attribute ***


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

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

         *** If the "notify-attributes" attribute is present on the
         Subscription Object, the Printer MUST send all attributes
         specified by the "notify-attributes" attribute.  Note: if the


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         Printer doesn't support the "notify-attributes" attribute, it
         is not present on the associated Subscription Object.

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

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


     Source Value                                   Sends  Source
                                                           Object


     job-id (integer(1:MAX))                        MUST   Job

     job-state (type1 enum)                         MUST   Job

     job-state-reasons (1setOf type2 keyword)       MUST   Job

     job-impressions-completed (integer(0:MAX)) *   MUST   Job


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


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


     Job Event                  Subscribed Job Event


     'job-progress'             'job-progress'

     'job-completed'            'job-completed'

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



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






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


     Source Value                                   Sends   Source
                                                            Object


     printer-state (type1 enum)                     MUST    Printer

     printer-state-reasons (1setOf type2 keyword)   MUST    Printer

     printer-is-accepting-jobs (boolean)            MUST    Printer


6  Subscription Template Attributes

   This section defines the Subscription object conformance requirements
   for Printers.


6.1  Subscription Template Attribute Conformance

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


6.2  Additional Information about Subscription Template Attributes

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


6.2.1  notify-recipient-uri (uri)

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

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

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

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6.3  Subscription Description Attribute Conformance

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


7  Additional Printer Description Attributes

   This section defines the Printer Description Attributes conformance
   requirements for Printers.


7.1  Printer Description Attribute Conformance

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


7.2  New Values for Existing Printer Description Attributes

   This section defines additional values for existing Printer
   Description attributes.


7.2.1  notify-schemes-supported (1setOf uriScheme)

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

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

7.2.2  operations-supported (1setOf type2 enum)

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










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                    Table 6 - Operation-id assignments


     Value        Operation Name


     0x001C       Get-Notifications




7.3  begin-to-expire-time-interval (integer(0:MAX))

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

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

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

   For example, assume the following:

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

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

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

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


8  New Status Codes

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



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8.1  redirection-other-site (0x300)

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


9  The IPPGET URL Scheme

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


9.1  The IPPGET URL Scheme Applicability and Intended Usage

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

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


9.2  The IPPGET URL Scheme Associated Port

   None.

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

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


9.3  The IPPGET URL Scheme Associated MIME Type

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

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






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9.4  The IPPGET URL Scheme Character Encoding

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


9.5  The IPPGET URL Scheme Syntax in ABNF

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

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

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

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

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

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

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

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      hostport   = host [ ":" port ]
      abs_path   = "/"  path_segments

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

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


9.5.1  IPPGET URL Examples

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

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

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

   The choice of 'userinfo@hostport' versus the simpler 'hostport'
   production in an 'ippget' URL may be influenced by the intended
   usage.

   If a given IPP Client creates an IPP Subscription object for event
   notifications intended for retrieval by the same IPP Client, then the
   simple 'hostport' production may be most appropriate.

   On the other hand, if a given IPP Client creates an IPP Subscription
   object for event notifications intended for retrieval by a different
   IPP Client, then the 'userinfo@hostport' production (using, for
   example, the right-hand side of a 'mailto:' URL, see [RFC2368]) may
   be most appropriate.


9.5.2  IPPGET URL Comparisons

   When comparing two 'ippget' URLs to decide if they match or not, an
   IPP Client or IPP Printer SHOULD use a case-sensitive octet-by-octet
   comparison of the entire URLs, with these exceptions:

        - Comparisons of host names MUST be case-insensitive;

        - Comparisons of scheme names MUST be case-insensitive;

        - An empty 'abs_path' is equivalent to an 'abs_path' of "/".

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   Characters other than those in the "reserved" and "unsafe" sets (see
   [RFC2396] and [RFC2732]) are equivalent to their ""%" HEX HEX"
   encoding.

   For example, the following three URIs are equivalent:

        ippget://abc.com/~smith/listener

        ippget://ABC.com/%7Esmith/listener

        ippget://ABC.com:/%7esmith/listener


10 Encoding

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


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


   Tag Value (Hex)    Meaning


   0x07               "event-notification-attributes-tag"



11 Conformance Requirements


11.1 Conformance for IPP Printers

   IPP Printers that conform to this specification:

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

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

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

     4. MUST support the additional values for IPP/1.1 Printer
        Description attributes defined in section 7.2;

     5. MUST support the "begin-to-expire-time-interval" Printer
        Description attribute defined in section 7.3;

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     6. MUST support the "redirection-other-site" status code defined
        8.1;

     7. SHOULD reject received 'ippget' URLs in 'application/ipp'
        request bodies (e.g., in the "notify-recipient-uri" attribute in
        a Get-Notifications request) that do not conform to the ABNF for
        'ippget' URLs specified in section 9.5 of this document;

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

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


11.2 Conformance for IPP Clients

   IPP Clients that conform to this specification:

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

     2.MUST send 'ippget' URLs (e.g., in the "notify-recipient-uri"
       attribute in a Get-Notifications request) that conform to the
       ABNF specified in section 9.5 of this document;

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

     4.MUST convert the associated 'ipp' URLs to their corresponding
       'http' URL forms according to the rules in section 5 "IPP URL
       Scheme" in [RFC2910].

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


12 IANA Considerations

   IANA is requested to register the 'ippget' URL scheme as defined in
   section 9 according to the procedures of [RFC2717].

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




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


12.1 Operation Registrations

   The operations defined in this document will be published by IANA
   according to the procedures in RFC 2911 [RFC2911] section 6.4 with
   the following path:

       ftp.isi.edu/iana/assignments/ipp/operations/

   The registry entry will contain the following information:

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


12.2 Additional values of existing attributes


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

   The "notify-schemes-supported" 'uriScheme' attribute value defined in
   this document will be published by IANA according to the procedures
   in RFC 2911 [RFC2911] section 6.1 with the following path:

     ftp.isi.edu/iana/assignments/ipp/attribute-values/notify-schemes-
     supported/

   The registry entry will contain the following information:

                                                  Ref.      Section:
   ippget                                         RFC NNNN    7.2.1


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

   The "operations-supported" type2 enum attribute value defined in this
   document will be published by IANA according to the procedures in RFC
   2911 [RFC2911] section 6.1 with the following path:

     ftp.isi.edu/iana/assignments/ipp/attribute-values/operations-
     supported/

   The registry entry will contain the following information:


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                                        Value     Ref.      Section:
   Get-Notifications                    0x001C    RFC NNNN    7.2.2


12.3 Attribute Registrations

   The attributes defined in this document will be published by IANA
   according to the procedures in RFC 2911 [RFC2911] section 6.2 with
   the following path:

     ftp.isi.edu/iana/assignments/ipp/attributes/

   The registry entry will contain the following information:

   Printer Description attributes:                Ref.      Section:
   begin-to-expire-time-interval (integer(0:MAX)) RFC NNNN     7.3

12.4 Status code Registrations

   The status codes defined in this document will be published by IANA
   according to the procedures in RFC 2911 [RFC2911] section 6.6 with
   the following path:

     ftp.isi.edu/iana/assignments/ipp/status-codes/

   The registry entry will contain the following information:

   Status codes:                                  Ref.      Section:
   redirection-other-site (0x300)                 RFC NNNN    8.1


13 Internationalization Considerations

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

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


14 Security Considerations

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

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   Privacy is defined as a mechanism for protecting operations from
   eavesdropping.

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


15 References

   [ipp-iig]
     Hastings, T., Manros, C., Kugler, K, Holst H., Zehler, P.,
     "Internet Printing Protocol/1.1:  draft-ietf-ipp-implementers-
     guide-v11-02.txt, work in progress, January 25, 2001

   [ipp-ntfy]
     R. Herriot, Hastings, T., Isaacson, S., Martin, J., deBry, R.,
     Shepherd, M., Bergman, R., "Internet Printing Protocol/1.1: IPP
     Event Notification Specification", <draft-ietf-ipp-not-spec-
     06.txt>, February 24, 2001.

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

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

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

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

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

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



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   [RFC2567]
     Wright, D., "Design Goals for an Internet Printing Protocol", RFC
     2567, April 1999.

   [RFC2568]
     Zilles, S., "Rationale for the Structure and Model and Protocol for
     the Internet Printing Protocol", RFC 2568, April 1999.

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

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

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

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

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

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


16 Authors' Addresses


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

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


   Carl Kugler
   IBM

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   P.O. Box 1900
   Boulder, CO 80301-9191

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

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

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


17 Full Copyright Statement

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

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

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

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

Acknowledgement

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


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