IPP> NOT - Agreements on the ISSUES in the IPPGET spec and IP P base sp ec

IPP> NOT - Agreements on the ISSUES in the IPPGET spec and IP P base sp ec

Hastings, Tom N hastings at cp10.es.xerox.com
Wed Jul 18 17:34:05 EDT 2001


I forgot to mention that I added the fourth legal example (d) with the
Printer event first and a statement that (b) and (c) are interleaved; (a)
and (d) are not and may not be appropriate for some Delivery Methods.

Tom

-----Original Message-----
From: Hastings, Tom N [mailto:hastings at cp10.es.xerox.com]
Sent: Wednesday, July 18, 2001 14:17
To: ipp (E-mail)
Subject: IPP> NOT - Agreements on the ISSUES in the IPPGET spec and IPP
base sp ec


We held the telecon, Wednesday, July 18, 2001 and reached the 
following agreements on the Event Notification specs.  This mail note is
also available as a .doc file at:

ftp://ftp.pwg.org/pub/pwg/ipp/new_NOT/notification-clarification-agreements.
doc

Please send any comments on this today to help with my editing so we can
meet the Internet-Drafts deadline of this Friday.  After today, any comments
will be good comments for the Last Call on the IPP GET spec.

Thanks,
Tom

   SUBJECT:  IPP Notification spec ISSUES and agreements 
   Date: 7/18/01 
   File:  notification-clarification-agreements.doc 
    

   We held the telecon, Wednesday, July 18, 2001 and reached the 
   following agreements on the Event Notification specs. 

   Attendees:  Carl Kugler (IBM), Harry Lewis (IBM), Ted Tronson 
   (Novell), Marty Joel (Netreon), Carl-Uno Manros (Xerox), Tom 
   Hastings (Xerox). 

1  Summary of agreements 

   1. Base Event Notifications spec: We agreed to clarify that the 
   Printer MUST send Event Notifications for any given Subscription 
   Object in time stamp order, but MAY interleave Event Notifications 
   from other Subscription Objects.  See explicit text below.  This 
   clarification will be included in the updated Internet-Draft 
   requested by our Area Director, Ned Freed, along with his 
   requested updates. 

   2. IPPGET spec:  We agreed to a number of changes and agreed that 
   this spec needs another WG Last Call which will start next week 
   when the updated Internet-Draft is published and will end the week 
   following the IETF meeting, August 17, 2000.  IPPGET is the only 
   REQUIRED Delivery Method for IPP FAX, so it is worth having the 
   second WG Last Call, now that we are gaining some implementation 
   experience.  The Area Director is still reviewing the previous 
   Internet-Draft we sent last Fall, and we will request that the new 
   version be substituted following the IETF procedures for this, 
   after the Last Call completes.  The IPPGET spec changes are: 

      1.  Change the terminology in IPPGET not to use "push", since 
          the term "push" outside of IPP Notification means create 
          the connection as well as send.  In IPPGET use the term 
          "wait mode" instead. 

      2.  Clarify that a Printer that supports the IPPGET Delivery 
          Method, MUST use HTTP chunking (HTTP/1.1 required feature) 
          in the Get-Notifications response if it keeps the 
          connection open, i.e., honors the client's request for 
          "wait mode". 

      3.  Clarify that "using the Get-Jobs model for returning 
          multiple groups of attributes" means that the Printer 
          returns the 'end-of-attributes' (0x03) tag at the end of 
          the last Get-Notifications Response to indicate that there 
          are no more events that will come. 

      4.  REQUIRE URI matching rules for ippget scheme 

      5.  REQUIRE that a Printer MUST return the "notify-recipient-
          uri" value as submitted by the Subscribing Client. 
      6.  Reduce the length of the "notify-recipient-uri" attribute 
          for ippget to 255 octets (since this doesn't really specify 
          a resource and an implementation may want to keep a 
          canonical form copy as well). 

      7.  In a Get-Notifications response when the client has 
          requested the wait mode, allow a Printer to return the 
          unexpired Notification Events, but also indicate to the 
          client to please disconnect and try again at the indicate 
          interval ("suggested-ask-again-time-interval" renamed to 
          "notify-get-interval").  (IPPGET currently only allows the 
          interval to be returned if the client didn't ask for wait 
          mode or if the Printer is too busy to return any Event 
          Notifications). 

      8.  Do not generalize Get-Notifications for use with indp or 
          mailto Delivery Methods.  REQUIRE the Printer to reject the 
          Get-Notifications Request if the scheme is not 'ippget'.  
          But allow a future Delivery Method Document to use the Get-
          Notifications operation if polling makes sense for that 
          Delivery Method 

      9.  Don't change the Get-Notifications operation name and keep 
          it in the ippget spec. 

      10. Change the sense of the Get-Notifications "notify-no-wait" 
          (boolean) operation attribute to a positive "notify-wait" 
          (boolean), so that omitted and 'false' mean the easier non-
          wait operation. 

      11. Rename "notify-ippget-redirect" (uri) to "redirect-uri" 
          (uri), so that it could in principle be used for other 
          operations. 

      12. Rename "suggested-ask-again-time-interval" (integer(0:MAX)) 
          to "notify-get-interval", to shorten it, and indicate that 
          it is for notification, but only events returned by the 
          Get-Notifications operation. 

      13. Rename "begin-to-expire-time-interval" (integer(0:MAX)) to 
          "ippget-event-time-to-live", to shorten it somewhat, use 
          recognized terms for this concept, and indicate that it is 
          for events, but only ippget events. 

      14. Clarify that for Subscriptions that contain Job events, 
          that the Subscription Object that has the ippget scheme 
          MUST stay around for the "ippget-event-time-to-live" value 
          and so MUST the corresponding Job object, so that the 
          Notification Recipient can query the Job after receiving 
          the 'job-completed' Event Notification.  (For the other 
          Delivery Methods, the usual Job History mechanism can be 
          used to retain the Job objects after the job completion, so 
          that the Notification Recipient can query the Job object 
          after receiving the 'job-completed' Event Notification.) 
      15. Clarify that the Cancel-Subscriptions operation does not 
          need to keep the Subscription object after the request, no  
          matter what kind of Delivery Method it contains.  
          Therefore, any events associated with the Subscription 
          object MUST NOT be returned by the Get-Notifications 
          operation after the Cancel-Subscription operation for that 
          Subscription Object. 

2  Clarifications to the ordering that the Printer sends Event 
   Notifications 

   In the Base Event Notifications spec [ipp-ntfy] section 9 after 
   paragraph 2 add the following text: 

   Event Notification Ordering: 

   When a Printer sends Event Notifications, the Event Notifications 
   from any given Subscription Object MUST be in time stamp order, 
   i.e., in order of increasing "printer-up-time" attribute value in 
   the Event Notification (see Table 5).  These Event Notifications 
   MAY be interleaved with those from other Subscription Objects, as 
   long as those others are also in time stamp order.  The Printer 
   MUST observe these ordering requirements whether sending multiple 
   pending Events as multiple separate Event Notifications or 
   together in a single Compound Event Notification.   

   If a Subscribing Client wants the Printer to send certain Event 
   Notifications in time stamp order, the Subscribing Client uses a 
   single Subscription Object.  Even so, depending on the underlying 
   transport, the actual order that a Notification Recipient receives 
   separate Event Notifications may differ from the order sent by the 
   Printer (e.g., email). 

   Example:  Consider two Per-Printer Subscription Objects: SO1 and 
   SO2.  SO1 requests 'job-state-changed' events and SO2 requests 
   'printer-state-changed' events.  The number in parens is the time 
   stamp.  The following Event Notification sequences are the only 
   ones that conform to the ordering requirements for the Printer to 
   send the Event Notifications: 

   (a) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO1: 
   'job-completed' (1009), SO2: 'printer-stopped' (1005) 

   (b) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO2: 
   'printer-stopped' (1005), SO1: 'job-completed' (1009) 

   (c) SO1: 'job-created' (1000), SO2: 'printer-stopped' (1005), SO1: 
   'job-stopped' (1005), SO1: 'job-completed' (1009) 

   (d) SO2: 'printer-stopped (1005), SO1: 'job-created' (1000), SO1: 
   'job-stopped' (1005), SO1: 'job-completed' (1009) 

   Examples (b) and (c) are interleaved; examples (a) and (d) are not 
   and may not be appropriate for some Delivery Methods. 

   IPPGET: 

   Make the following changes to the first paragraph in the Get-
   Notifications Response, section 5.2 (I put [] around new text, but 
   deleted old text without indication): 

   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 initial matched Event Notifications are all un-expired Event 
   Notifications associated with the matched Subscription Objects 
   [and MUST follow the ordering requirements for Event Notifications 
   within a Compound Event Notification specified for the "Event 
   Notification Ordering" in [ipp-ntfy] section 9].   

   If the Notification Recipient has selected the option to wait for 
   additional Event Notifications [(the "notify-no-wait" attribute 
   was set to 'false' or was omitted)], 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 be the ordering specified 
   for the "Event Notification Ordering" 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. ] 

    

   INDP: 

   In INDP section 8.1 Send-Notifications Request, 2nd paragraph (I 
   put [] around the new text): 

   The Printer composes the information defined for an IPP 
   Notification [ipp-ntfy] and sends it using the Send-Notifications 
   operation to the Notification Recipient supplied in the 
   Subscription object.  [The ordering of separate Send-Notifications 
   operations that a Printer sends MUST be the ordering specified for 
   the "Event Notification Ordering" in [ipp-ntfy] section 9.] 

    

   In INDP section 8.1.1 Send-Notifications Request (I put [] around 
   the new text): 
   Group 2 to N: Event Notification Attributes 

   In each group 2 to N, each attribute is encoded using the IPP 
   rules for encoding attributes [RFC2910] and [the attributes within 
   a group] MAY be encoded in any order.  [The entire request is 
   considered a single Compound Event Notification and MUST follow 
   the ordering requirements for Event Notifications within a 
   Compound Event Notification specified for the "Event Notification 
   Ordering" in [ipp-ntfy] section 9.]  Note: the Get-Jobs response 
   in [RFC2911] acts as a model for encoding multiple groups of 
   attributes.    

    

   MAILTO: 

   MAILTO section 6, add the following after the existing 2nd 
   paragraph: 

   While the "Event Notification Ordering" in [ipp-ntfy] section 9 
   specifies ordering requirements for Printers when sending separate 
   Event Notifications, email messages are not guaranteed to arrive 
   in the order sent so that the Notification Recipient may not 
   receive them in the same order. 

    

   MAILTO section 6 Event Notification Content, right before section 
   6.1 (I put [] around the new text): 

   The Event Notification content has two parts, the headers and the 
   message body. The headers precede the message body and are 
   separated by a blank line (see [RFC 822]). 

   [A Printer implementation MAY combine several Event Notifications 
   into a single email message body.  Such an email message is 
   considered a single Compound Event Notification and MUST follow 
   the ordering requirements for Event Notifications within a 
   Compound Event Notification specified for the "Event Notification 
   Ordering" in [ipp-ntfy] section 9.]   

    

3  Some of the text changes for the IPPGET Delivery Method 


Here are some of the text changes for the agreed changes to the 
IPPGET Delivery Method spec: 

3.1 IPPGET: Matching "notify-recipient-uri" 

   Change IPPGET Section 5.1 from: 
      "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.   

        to: 

      "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 against the value of the "notify-
        recipient-uri" in each Subscription Object in the Printer 
        following the normal URI comparison rules (see section 
        9.5.2). If the scheme is not the ippget scheme, the Printer 
        MUST reject the request and return the 'client-error-uri-
        scheme-not-supported' status code.  If there are no matches, 
        the IPP Printer MUST reject the request and return the 
        'client-error-not-found' status code.   

         

3.2 IPPGET: Allow the Printer to request the client to disconnect 

   Change section 5.2: 

      "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.  
   to: 

      "notify-get-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' (the no wait case)
            OR 
          c) the Printer returns the 'successful-ok' status code and 
            the client supplied the "notify-no-wait" attribute with 
            either 'false' value or omitted the attribute all
together (the wait case) and the Printer wants the 
            client to disconnect, 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, then the Printer 
            MUST NOT return this attribute in the response. 

         This value is intended to help the client be a good network 
         citizen. 
    

    

3.3 Change the sense of the "notify-no-wait" operation attribute to 
    "notify-wait" 

   Change section 5.1, "notify-no-wait" (boolean) from: 

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

   to: 

      "notify-wait" (boolean): 
         The client MAY supply this attribute.  The Printer object 
         MUST support this attribute.  If the value of this attribute 
         is 'false' or omitted, 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 value of this 
         attribute is 'true', 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 or return the "notify-get-
         interval" attribute in the response (see section 5.2).  
          
    



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