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

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

Hastings, Tom N hastings at cp10.es.xerox.com
Thu Jul 19 18:13:23 EDT 2001


Marty,

Thanks for the feedback.  See my relies preceded by TH>

You bring up a significant issue:

      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.
MJ> end-of-attributes after each blast of returned events?  That's what I
hope it is,
    although I don't think we got done discussing how this would be used.
TH> ISSUE:  You are right that we didn't discuss how the Printer indicates
that it is finished for now in wait mode.  The problem with it indicating
this using the 'end-of-attributes' tag, is that this tag is supposed to come
only once at the very end when there will never be any more Event
Notifications, i.e., after the Subscription object is gone.

TH> Anyone have any thoughts?

TH> One possibility would be to add a "notify-status-code" attribute that
can be returned in an Event Notification Attributes group along with Event
Notification attributes.  The value would indicate that this is the last
group for now.  We've done a similar status code in a Group thing for INDP
Send-Notifications Attribute Groups.

Tom

-----Original Message-----
From: mjoel at netreon.com [mailto:mjoel at netreon.com]
Sent: Thursday, July 19, 2001 09:50
To: ipp at pwg.org
Subject: Re: IPP> NOT - Agreements on the ISSUES in the IPPGET spec and
IPP base spec



Hi Tom,

I only had a few comments, marked below with MJ>

Marty






"Hastings, Tom N" <hastings at cp10.es.xerox.com>@pwg.org on 07/18/2001
02:17:22 PM

Sent by:  owner-ipp at pwg.org


To:   "ipp (E-mail)" <ipp at pwg.org>
cc:

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".
MJ> Didn't we also agree to mention that HTTP's "Connection: close" cannot
be used?
    Maybe it's just obvious (but the need to use chunking probably is too).
TH> Yes, I'll include.


      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.
MJ> end-of-attributes after each blast of returned events?  That's what I
hope it is,
    although I don't think we got done discussing how this would be used.
TH> ISSUE:  You are right that we didn't discuss how the Printer indicates
that it is finished for now in wait mode.  The problem with it indicating
this using the 'end-of-attributes' tag, is that this tag is supposed to come
only once at the very end when there will never be any more Event
Notifications, i.e., after the Subscription object is gone.

TH> Anyone have any thoughts?



      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}
MJ>  should say:  (the "notify-wait" attribute was set to 'true')
MJ>  why is sends in {} ?
TH> Thanks, this was the text before changing the attribute sense.

   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)
MJ>  should be:  "notify-wait" was false or omitted
TH> yes
            OR
          c) the Printer returns the 'successful-ok' status code and
            the client supplied the "notify-no-wait" attribute with
MJ>  should be:  the client supplied the "notify-wait" attribute with
     a 'true' value and the Printer wants th eclient to disconnect...
TH> yes
            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).








More information about the Ipp mailing list