Internet Printing Protocol WG Robert Herriot (editor)
INTERNET-DRAFT Thomas N. Hastings
<draft-ietf-ipp-notify-get-06.txt> Xerox Corp.
Updates: RFC 2911 Carl Kugler
[Target category: standards track] Harry Lewis
Expires: May 19, 2002 IBM, Corp.
November 19, 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
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Abstract
This document describes an extension to the Internet Printing
Protocol/1.0 (IPP) [RFC2566, RFC2565] and IPP/1.1 [RFC2911, RFC2910].
This document specifies the 'ippget' Delivery Method for use with the
"IPP Event Notifications and Subscriptions" specification [ipp-ntfy].
When IPP Notification [ipp-ntfy] is supported, the Delivery Method
defined in this document is one of the RECOMMENDED Delivery Methods
for Printers to support.
The 'ippget' Delivery Method is a Pull Delivery Method. When an Event
occurs, the Printer saves the Event Notification for a period of time
called the Event Life. The Notification Recipient fetches (pulls)
Event Notifications using the Get-Notifications operation. If the
Notification Recipient has selected the Event Wait Mode option to
wait for additional Event Notifications, the Printer continues to
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return Event Notifications to the Notification Recipient as Get-
Notification responses as Events occur using the connection
originated by the Notification Recipient.
Either the Notification Recipient or the Printer can terminate Event
Wait Mode without closing the connection.
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Table of Contents
1 Introduction.....................................................5
2 Terminology......................................................6
3 Model and Operation..............................................7
4 General Information..............................................8
5 Get-Notifications operation......................................9
5.1 Get-Notifications Request.....................................11
5.1.1 notify-subscription-ids (1setOf integer(1:MAX)).............11
5.1.2 notify-sequence-numbers (1setOf integer(1:MAX)).............11
5.1.3 notify-wait (boolean).......................................12
5.2 Get-Notifications Response....................................13
5.2.1 notify-get-interval (integer(0:MAX))........................16
5.2.2 printer-up-time (integer(1:MAX))............................18
5.2.3 redirect-uri (uri)..........................................18
6 Additional Information about Subscription Template Attributes...22
6.1 notify-pull-method (type2 keyword)............................22
7 Subscription Description Attributes.............................23
8 Additional Printer Description Attributes.......................23
8.1 ippget-event-life (integer(15:MAX))...........................23
9 New Values for Existing Printer Description Attributes..........24
9.1 notify-pull-method-supported (1setOf type2 keyword)...........24
9.2 operations-supported (1setOf type2 enum)......................24
10 New Status Codes...............................................25
10.1 successful-ok-events-complete (0x0007).......................25
10.2 redirection-other-site (0x0300)..............................25
11 Encoding and Transport.........................................25
12 Conformance Requirements.......................................27
12.1 Conformance for IPP Printers.................................27
12.2 Conformance for IPP Clients..................................28
13 IANA Considerations............................................28
13.1 Additional attribute value registrations for existing attributes
29
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13.1.1 Additional values for the "notify-pull-method-supported"
Printer attribute......................................29
13.1.2 Additional values for the "operations-supported" Printer
attribute..............................................29
13.2 Operation Registrations......................................30
13.3 Attribute Registrations......................................30
13.4 Status code Registrations....................................30
14 Internationalization Considerations............................31
15 Security Considerations........................................31
16 References.....................................................31
17 Authors' Addresses.............................................33
18 Description of Base IPP documents..............................34
19 Full Copyright Statement.......................................35
Table of Tables
Table 1 - Information about the Delivery Method....................8
Table 2 - Combinations of "notify-wait", "status-code", and "notify-
get-interval" .................................................17
Table 3 - Attributes in Event Notification Content................20
Table 4 - Additional Attributes in Event Notification Content for Job
Events ........................................................21
Table 5 - Combinations of Events and Subscribed Events for "job-
impressions-completed" ........................................22
Table 6 - Additional Attributes in Event Notification Content for
Printer Events ................................................22
Table 7 - Operation-id assignments................................25
Table 8 - The "event-notification-attributes-tag" value...........27
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1 Introduction
The "IPP Event Notifications and Subscriptions" document [ipp-ntfy]
defines an OPTIONAL extension to Internet Printing Protocol/1.0 (IPP)
[RFC2566, RFC2565] and IPP/1.1 [RFC2911, RFC2910]. For a description
of the base IPP documents, see section 18. The [ipp-ntfy] extension
defines operations that a client can perform in order to create
Subscription Objects in a Printer and carry out other operations on
them. A Subscription Object represents a Subscription abstraction.
A client associates Subscription Objects with a particular Job by
performing the Create-Job-Subscriptions operation or by submitting a
Job with subscription information. A client associates Subscription
Objects with the Printer by performing a Create-Printer-Subscriptions
operation. Four other operations are defined for Subscription
Objects: Get-Subscriptions-Attributes, Get-Subscriptions, Renew-
Subscription, and Cancel-Subscription. The Subscription Object
specifies that when one of the specified Events occurs, the Printer
sends an asynchronous Event Notification to the specified
Notification Recipient via the specified Delivery Method (i.e.,
protocol).
The "IPP Event Notifications and Subscriptions" document [ipp-ntfy]
specifies that each Delivery Method is defined in another document.
This document is one such document, and it specifies the 'ippget'
delivery method. When IPP Notification [ipp-ntfy] is supported, the
Delivery Method defined in this document is one of the RECOMMENDED
Delivery Methods for Printers to support.
The 'ippget' Delivery Method is a Pull Delivery Method. When an
Event occurs, the Printer saves the Event Notification for a period
of time called the Event Life. The Notification Recipient fetches
(pulls) the Event Notifications using the Get-Notifications
operation. This operation causes the Printer to return all Event
Notifications held for the specified Subscription object(s). If the
Notification Recipient has selected the Event Wait Mode option to
wait for additional Event Notifications, the Printer continues to
return Event Notifications to the Notification Recipient as Get-
Notification responses as Events occur using the transaction
originated by the Notification Recipient.
The Notification Recipient can terminate Event Wait Mode (without
closing the connection) by supplying the "notify-wait" (boolean)
attribute with a 'false' value in a subsequent Get-Notifications
request. Similarly, the Printer can terminate Event Wait Mode
(without closing the connection) by returning the "notify-get-
interval" (integer) operation attribute in a Get-Notifications
response which tells the Notification Recipient how long to wait
before trying again.
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2 Terminology
This section defines the following terms that are used throughout
this document:
This document uses the same terminology as [RFC2911], such as
"client", "Printer", "Job", "attribute", "attribute value",
"keyword", "operation", "request", "response", and "support".
Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD
NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to
conformance as defined in RFC 2119 [RFC2119] and [RFC2911] section
12.1. If an implementation supports the extension defined in this
document, then these terms apply; otherwise, they do not. These
terms define conformance to this document only; they do not affect
conformance to other documents, unless explicitly stated otherwise.
Event Life: The length of time in seconds after an Event occurs
during which the Printer will return that Event in a Event
Notification in a Get-Notifications response. After the Event
Life expires, the Printer will no longer return an Event
Notification for that Event in a Get-Notifications response.
Event Notification Attributes Group: The attributes group in a
response that contains attributes that are part of an Event
Notification.
Event Wait Mode: The mode requested by a Notification Recipient
client in its Get-Notifications Request and granted by a Printer
to keep the connection open where the Printer sends subsequent
Event Notifications to the Notification Recipient as they occur
as additional Get-Notification Responses.
Other capitalized terms, such as Notification Recipient, Event, Event
Notification, Compound Event Notification, Printer, etc., are
defined in [ipp-ntfy], have the same meanings, and are not
reproduced here. However, for convenience the following key
terms are reproduced here:
Event - some occurrence (either expected or unexpected) within the
printing system of a change of state, condition, or
configuration of a Job or Printer object. An Event occurs only
at one instant in time and does not span the time the physical
Event takes place. For example, jam-occurred and jam-cleared
are two distinct, instantaneous Events, even though the jam may
last for a while.
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Event Notification - the information about an Event that the Printer
sends when an Event occurs.
3 Model and Operation
In a Subscription Creation Operation, when the "notify-pull-method"
attribute is present and has the 'ippget' keyword value, the client
is requesting that the Printer use the 'ippget' Pull Delivery Method
for the Event Notifications associated with the new Subscription
Object.
When an Event occurs, the Printer MUST generate an Event Notification
and MUST assign it the Event Life. The Printer MUST hold an Event
Notification for its assigned Event Life.
When a Notification Recipient wants to receive Event Notifications
for a Subscription object, it performs the Get-Notifications
operation supplying the Subscription object's subscription-id, which
causes the Printer to return all un-expired Event Notifications held
for that Subscription object. If the Notification Recipient has
selected the Event Wait Mode option to wait for additional Event
Notifications, the response to the Get-Notifications request
continues indefinitely as the Printer continues to send Event
Notifications in the response as Events occur for that Subscription
object.
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
MUST save Event Notifications for at least 15 seconds (see section
8.1), the Notification Recipient is unlikely to miss any Event
Notifications that occur between the Subscription Creation and the
Get-Notifications operation.
The 'ippget' Delivery Method is designed primarily for (1) a client
that wants to get Events (from the job's per-Job Subscription object)
for a job that it has submitted and (2) for a privileged client that
wants to get all job or printer Events from a per-Printer
Subscription object. If several groups of users expect to receive
jobs from other users (FAX paradigm) and each group has a different
designated person, say, a secretary, to receive job completion
Events, the Printer should be configured to support multiple URLs,
one for each group. Then the designated (privileged) person can run
an application that gets the events for jobs submitted to that URL
from the per-Printer Subscription object that the application
creates.
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4 General Information
If a Printer supports this Delivery Method, the following are its
characteristics.
Table 1 - Information about the Delivery Method
Document Method Conformance Requirement Delivery Method
Realization
1. What is the URL scheme name for the
Push Delivery Method or the keyword
method name for the Pull Delivery
Method? ippget
2. Is the Delivery Method REQUIRED,
RECOMMENDED or OPTIONAL for an IPP
Printer to support? RECOMMENDED
3. What transport and delivery protocols IPP with one new
does the Printer use to deliver the operation.
Event Notification Content, i.e., what
is the entire network stack?
4. Can several Event Notifications be Yes.
combined into a Compound Event
Notification?
5. Is the Delivery Method initiated by This Delivery Method is
the Notification Recipient (pull), or a pull method with
by the Printer (push)? aspects of a push
method, though the
Printer does not
initiate the connection.
6. Is the Event Notification content Machine Consumable
Machine Consumable or Human
Consumable?
7. What section in this document answers Section 5
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
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ntfy] and the conformance requirements
thereof? For a Human Consumable Event
Notification, what is the
representation and encoding of pieces
of information defined in section 9.2
of [ipp-ntfy] and the conformance
requirements thereof?
8. What are the latency and reliability Same as IPP and the
of the transport and delivery underlying HTTP
protocol? transport
9. What are the security aspects of the Same as IPP and the
transport and delivery protocol, e.g., underlying HTTP
how it is handled in firewalls? transport and in the
same direction, so no
new firewall
considerations.
10.What are the content length None
restrictions?
11.What are the additional values or None
pieces of information that a Printer
sends in an Event Notification content
and the conformance requirements
thereof?
12.What are the additional Subscription None
Template and/or Subscription
Description attributes and the
conformance requirements thereof?
13.What are the additional Printer "ipp-event-life"
Description attributes and the (integer (15: MAX))
conformance requirements thereof?
5 Get-Notifications operation
This operation is issued by a client acting in the role of a
Notification Recipient requesting the Printer to return all Event
Notifications held for the identified Subscription object(s).
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-subscription-id"
Subscription Description attribute equals one of the values of
the "notify-subscription-ids" (1setOf integer(1:MAX)) operation
attribute AND
2. Whose associated Subscription Object's contains the "notify-
pull-method" attribute and it has the 'ippget' keyword value AND
3. Whose "notify-sequence-number" is equal to or greater than the
corresponding value of the "notify-sequence-numbers (1setOf
integer(1:MAX)) operation attribute, if supplied AND
4. Whose Event Life has not yet expired AND
5. Where the Notification Recipient is the owner of or has read-
access rights to the identified Subscription Object.
The Notification Recipient client can request Event Wait Mode by
supplying the "notify-wait" operation attribute with a 'true' value.
The Notification Recipient client can terminate Event Wait Mode
(without closing the connection) by supplying the "notify-wait"
attribute with a 'false' value in a subsequent Get-Notifications
request. Similarly, the Printer can terminate Event Wait Mode
(without closing the connection) by returning the "notify-get-
interval" operation attribute in a Get-Notifications response which
tells the Notification Recipient how long to wait before trying
again.
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 be the owner of
each Subscription Object identified by the "notify-subscription-ids"
operation attribute (as returned 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.
5.1.1 notify-subscription-ids (1setOf integer(1:MAX))
This attribute identifies one or more Subscription objects for
which Events are requested. The client MUST supply this
attribute with at least one value. The Printer object MUST
support this attribute with multiple values.
If no Subscription Object exists with the supplied identifier
or the identified Subscription Object does not contain the
"notify-pull-method" attribute with the 'ippget' keyword value,
the Printer MUST return the 'client-error-not-found' status
code.
Note: The name of both the "notify-subscription-ids" and
"notify-sequence-numbers" end in 's', since they are
multi-valued. However, there are other occurrences of
these attribute names without the 's' that are single
valued.
5.1.2 notify-sequence-numbers (1setOf integer(1:MAX))
This attribute specifies one or more lowest Event Notification
sequence number values for the Subscription objects identified
by the corresponding values of the "notify-subscription-ids"
operation attribute. The Notification Recipient SHOULD supply
this attribute and the number of values SHOULD be the same as
the number of values of the "notify-subscriptions-ids"
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attribute. The Printer MUST support this attribute with
multiple values.
The Printer MUST NOT return Notification Events with lower
sequence numbers for the corresponding Subscription object.
Therefore, by supplying the proper values for this attribute
the Notification Recipient can prevent getting the same Event
Notifications from a Subscription object that were returned on
a previous Get-Notifications request. The Notification
Recipient SHOULD remember the highest "notify-sequence-number"
value returned for each Subscription object requested and
SHOULD pass that value for each requested Subscription object
on the next Get-Notifications request.
If the Notification Recipient supplies fewer values for this
attribute (including omitting this attribute) than for the
"notify-subscription-ids" operation attribute, the Printer
assumes a '1' value for each missing value. A value of '1'
causes the Printer to return any un-expired Event Notification
for that Subscription object, since '1' is the lowest possible
sequence number. If the Notification Recipient supplies more
values for this attribute than the number of values for the
"notify-subscription-ids" operation attribute, the Printer
ignores the extra values.
Note: If a Notification Recipient performs two consecutive Get-
Notifications operations with the same value for "notify-
sequence-number" (or omits the attribute), 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 with a sequence number equal or higher 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.
5.1.3 notify-wait (boolean)
This value indicates whether or not the Notification Recipient
wants Event Wait Mode. The client MAY supply this attribute.
The Printer object MUST support both values of this attribute.
If the client supplies the 'false' value or omits this
attribute, the client is not requesting Event Wait Mode. If
the value is 'true', the client is requesting Event Wait Mode.
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See the beginning of section 5.2 for the rules for Event Wait
Mode.
5.2 Get-Notifications Response
The Printer has the following options for responding to a Get-
Notifications Request:
1. The Printer can reject the request and return the 'server-error-
busy' status code, if the Printer is too busy to accept this
operation at this time. In this case, the Printer MUST return
the "get-notify-interval" operation attribute to indicate when
the client SHOULD try again.
2. If the Notification Recipient did not request Event Wait Mode
("notify-wait-mode" = 'false' or omitted), the Printer MUST
return immediately whatever Event Notifications it currently
holds in the requested Subscription object(s) and MUST return
the "notify-get-interval" operation attribute with number of
seconds from now at which the Notification Recipient SHOULD
repeat the Get-Notifications Request to get future Event
Notifications.
3. If the Notification Recipient requested Event Wait Mode
("notify-wait-mode" = 'true'), the Printer MUST return
immediately whatever Event Notifications it currently holds in
the requested Subscription object(s) and MUST continue to return
Event Notifications as they occur until all of the requested
Subscription Objects are canceled. A Subscription Object is
canceled either via the Cancel-Subscription operation or by the
Printer (e.g., the Subscription Object is canceled when the
associated Job completes and is no longer in the Job Retention
or Job History phase - see the "ippget-event-life
(integer(15:MAX))" attribute discussion in section 8.1).
However, the Printer MAY decide to terminate Event Wait Mode at
any time, including in the first response. In this case the
Printer MUST return the "notify-get-interval" operation
attribute. This attribute indicates that the Printer wishes to
leave Event Wait Mode and the number of seconds in the future
that the Notification Recipient SHOULD try the Get-Notifications
operation again. The Notification Recipient MUST accept this
response and MUST disconnect. If the Notification Recipient
does not disconnect, the Printer SHOULD do so.
From the Notification Recipient's view, the response appears as an
initial burst of data, which includes the Operation Attributes Group
and one Event Notification Attributes Group per Event Notification
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that the Printer is holding. After the initial burst of data, if the
Notification Recipient has selected the Event Wait Mode option to
wait for additional Event Notifications, the Notification Recipient
receives occasional Event Notification Attribute Groups. Proxy
servers may delay some Event Notifications or cause time-outs to
occur. The client MUST be prepared to perform the Get-Notifications
operation again when time-outs occur.
Each attribute is encoded using the IPP rules for encoding attributes
[RFC2910] and MAY be encoded in any order. Note: the Get-Jobs
response in [RFC2911] acts as a model for encoding multiple groups of
attributes. See section 11 for the encoding and transport rules.
The following groups of attributes are part of the Get-Notifications
Response:
Group 1: Operation Attributes
Status Message:
In addition to the REQUIRED status code returned in every
response, the response OPTIONALLY includes a "status-message"
(text(255)) and/or a "detailed-status-message" (text(MAX))
operation attribute as described in [RFC2911] sections 13 and
3.1.6.
The Printer can return any status codes defined in [RFC2911].
If the status code is not 'successful-xxx', the Printer MUST
NOT return any Event Notification Attribute groups. The
following is a description of the important status codes:
successful-ok: the response contains all Event Notification
associated with the specified subscription-ids that had
been supplied in the "notify-subscription-ids" operation
attribute in the request. If the requested Subscription
Objects have no associated Event Notification, the
response MUST contain zero Event Notifications.
successful-ok-events-complete: indicate when this return
is the last return for all Subscription objects that
match the request, whether or not there are Event
Notifications being returned. This condition occurs for
Event Wait Mode with Notification Recipients waiting for
responses when the Subscription Object is: (1) canceled
with a Cancel-Subscription operation, (2) deleted when
the Per-Printer Subscription lease time expires, or (3)
when the 'job-completed' event occurs for a Per-Job
Subscription. This condition also occurs for a Get-
Notifications request that a Notification Recipient makes
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after the job completes, but before the Event Life
expires. See section 10.1.
client-error-not-found: The Printer has no Subscription
Object's whose "notify-subscription-id" attribute equals
any of the values of the "notify-subscription-ids"
operation attribute supplied or the identified
Subscription Object does not contain the "notify-pull-
method" attribute with the 'ippget' keyword value.
server-error-busy: The Printer is too busy to accept this
operation. The Printer SHOULD return the "notify-get-
interval" operation attribute in the Operation Attributes
of the response, then the Notification Recipient SHOULD
wait for the number of seconds specified by the "notify-
get-interval" operation attribute before performing this
operation again. If the "notify-get-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 again with the uri specified by the
"redirect-uri" Operation Attribute in the response. See
section 10.2.
Natural Language and Character Set:
The "attributes-charset" and "attributes-natural-language"
attributes as described in [RFC2911] section 3.1.4.2.
The Printer MUST use the values of "notify-charset" and
"notify-natural-language", respectively, from one Subscription
Object associated with the Event Notifications in this
response.
Normally, there is only one matched Subscription Object, or the
value of the "notify-charset" and "notify-natural-language"
attributes is the same in all Subscription Objects. If not, the
Printer MUST pick one Subscription Object from which to obtain
the value of these attributes. The algorithm for picking the
Subscription Object is implementation dependent. The choice of
natural language is not critical because 'text' and 'name'
values can override the "attributes-natural-language" operation
attribute. The Printer's choice of charset is critical because
a bad choice may leave it unable to send some 'text' and 'name'
values accurately.
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5.2.1 notify-get-interval (integer(0:MAX))
The value of this operation attribute is the number of seconds
that the Notification Recipient SHOULD wait before trying the
Get-Notifications operation again. The Printer MUST return
this operation attribute if: (1) it is too busy to return
events, (2) the Notification Recipient client did not request
Event Wait Mode, or (3) the Printer is terminating Event Wait
Mode. The client MUST accept this attribute and SHOULD re-
issue the Get-Notifications operation (with or without "notify-
wait" = 'true') the indicated number of seconds in the future
in order to get more Event Notifications This value is
intended to help the client be a good network citizen.
The value of this attribute MUST be at least as large as the
value of the Printer's "ippget-event-life" Printer Description
attribute (see section 8.1). The Printer MAY return a value
that is larger than the value of the "ippget-event-life"
Printer Description attribute provided that the Printer
increases the Event Life for this Subscription object, so that
Notification Recipients taking account of the larger value and
polling with a longer interval will not miss events. Note;
implementing such an algorithm requires some hidden attributes
in the Subscription object that are IMPLEMENTATION DEPENDENT.
If the Printer wants to remain in Event Wait Mode, then the
Printer MUST NOT return this attribute in the response.
Here is a complete table of combinations of "notify-wait",
"status-code", "notify-get-interval", and Event Notification
Attributes Groups for Get-Notification initial (Wait and No
Wait) Responses and subsequent Event Wait Mode Responses (which
may be staying in Event Wait Mode or may be requesting the
Notification Recipient to leave Event Wait Mode):
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Table 2 - Combinations of "notify-wait", "status-code", and "notify-
get-interval"
client sends: Printer returns: Printer Event
returns: Notification
"notify-wait" "status-code" "notify-get- Attribute
interval" Groups
1. 'false'* 'successful-ok' MUST return N maybe
2. 'false'* 'not-found' MUST NOT MUST NOT
3. 'false'* 'busy' MUST return N MUST NOT
4. 'false'* 'events- 'job-
complete' MUST NOT completed'
5. 'true' 'successful-ok' MUST NOT MUST
6. 'true' 'successful-ok' MUST return N maybe
7. 'true' 'not-found' MUST NOT MUST NOT
8. 'true' 'busy' MUST return N MUST NOT
9. 'true' 'events- MUST NOT 'job-
complete' completed' or
maybe other
* 'false' or client omits the "notify-wait" attribute.
Explanation:
1-4: client does not request Event Wait Mode
5-9: client requests Event Wait Mode
2,7: Subscription object not found, or was canceled earlier;
client should NOT try again.
3,8: server busy, tells client to try later; client should try
again in N seconds.
4: client polled after job completed, but before Event Life
expired, and got the 'job-completed' event, so the client
shouldn't bother trying again; client should NOT try again
later.
5: Printer returns one or more Event Notifications and is OK
to stay in Event Wait Mode; the client waits for more Event
Notifications to be returned.
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6: Printer wants to leave Event Wait mode. Can happen on the
first response (with or without Event Notifications) or happen
on a subsequent response with or without Event Notifications;
the client SHOULD try again in N seconds.
9: Printer either (1) returns 'job-completed' event or (2) the
Subscription Object was canceled by either a Cancel-Job or a
Per-Printer Subscription expired without being renewed. For
case (1), at least one Event Notification MUST be returned,
while for case (2), it is unlikely that any Event Notifications
are returned; the client should NOT try again.
5.2.2 printer-up-time (integer(1:MAX))
The value of this attribute is the Printer's "printer-up-time"
attribute at the time the Printer sends this response. The
Printer MUST return this attribute. 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.
5.2.3 redirect-uri (uri)
The value of this attribute is the uri that the Notification
Recipient MUST use for a subsequent Get-Notifications
operation. The Printer MAY support this attribute. This
attribute MUST be returned in the Operation Attributes Group if
and only if the Printer returns the 'redirection-other-site'
status code (see section 10.2).
Group 2: Unsupported Attributes
See [RFC2911] section 3.1.7 for details on returning
Unsupported Attributes.
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 matched Event Notifications are all un-expired
Event Notification associated with the matched Subscription
Objects and MUST follow the "Event Notification Ordering"
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requirements for Event Notifications within a Compound Event
Notification specified in [ipp-ntfy] section 9. In other
words, the Printer MUST order these Event Notification groups
in ascending time stamp (and sequence number) order for a
Subscription object. If Event Notifications for multiple
Subscription objects are being returned, the Notification
Events for the next Subscription object follow in ascending
time stamp order, etc.
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".
If more than one Event Notification is being returned and the
status of each is not the same, then the Printer MUST return a
"notify-status-code" attribute in each Event Notification
Attributes group to indicate the differing status values.
For an Event Notification for all Events, the Printer includes
the attributes shown in Table 3.
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Table 3 - Attributes in Event Notification Content
Source Value Sends Source
Object
notify-subscription-id (integer(1:MAX)) MUST Subscription
notify-printer-uri (uri) MUST Subscription
notify-subscribed-event (type2 keyword) MUST Event
Notification
printer-up-time (integer(1:MAX)) * MUST Printer
printer-current-time (dateTime) MUST ** Printer
notify-sequence-number (integer (0:MAX)) MUST Subscription
notify-charset (charset) MUST Subscription
notify-natural-language (naturalLanguage) MUST Subscription
notify-user-data (octetString(63)) MUST *** Subscription
notify-text (text) MUST Event
Notification
attributes from the "notify-attributes" MUST **** Printer
attribute
attributes from the "notify-attributes" MUST **** Job
attribute
attributes from the "notify-attributes" MUST **** Subscription
attribute
* As specified in [ipp-ntfy] section 9, the value of the
"printer-up-time" attribute sent in each Event Notification
MUST be the time at which the Event occurred, not the time at
which the Event Notification was sent.
** The Printer MUST send the "printer-current-time" attribute
if and only if it supports the "printer-current-time" attribute
on the Printer object.
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*** 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
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 4.
Table 4 - 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 5.
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Table 5 - 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 6.
Table 6 - 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 Additional Information about Subscription Template Attributes
The 'ippget' Delivery Method does not define any addition
Subscription Template attributes. The 'ippget' Delivery Method has
the same conformance requirements for Subscription Template
attributes as defined in [ipp-ntfy]. This section defines additional
information about Subscription Template attributes defined in [ipp-
ntfy].
6.1 notify-pull-method (type2 keyword)
This Subscription Template attribute identifies the Pull Delivery
Method to be used for the Subscription Object (see [ipp-ntfy]). In
order to support the 'ippget' Pull Delivery Method defined in this
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document, the Printer MUST support this attribute with the following
keyword value:
'ippget': indicates that the IPPGET Pull Delivery Method is to be
used for this Subscription Object.
7 Subscription Description Attributes
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.
8 Additional Printer Description Attributes
This section defines additional Printer Description attributes for
use with the 'ippget' Delivery Method.
8.1 ippget-event-life (integer(15:MAX))
This Printer Description attribute specifies the Event Life value
that the Printer assigns to each Event, i.e., the number of seconds
after an Event occurs during which a Printer will return that Event
in an Event Notification in a Get-Notifications response. After the
Event Life expires for the Event, the Printer MAY no longer return an
Event Notification for that Event in a Get-Notifications response.
The Printer MUST support this attribute if it supports the 'ippget'
Delivery Method. The value MUST be 15 or more (at least 15 seconds)
and 60 (seconds) is the RECOMMENDED value to align with the PWG Job
Monitoring MIB [RFC2707] jmGeneralJobPersistence and
jmGeneralAttributePersistence objects.
For example, assume the following:
1.a client performs a Job Creation operation that creates a
Subscription Object associated with the 'ippget' 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 such that the client is connected N
seconds after the Job Creation operation.
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Then, if N is less than the value of this attribute, the client(s)
performing the Get-Notifications operations can expect not to miss
any Event-Notifications, barring some unforeseen lack of memory space
in the Printer. Note: The client MUST initiate the Get-
Notifications a time that is sufficiently less that N seconds to
account for network latency so that it is connected to the Printer
before N seconds elapses.
If a Printer supports the 'ippget' Delivery Method, it MUST keep
'completed', 'canceled', or 'aborted' Job objects in the Job
Retention and/or Job History phases for at least as long as this
attribute's value. The Printer MAY retain jobs longer that this
value. See [RFC2911] section 4.3.7.1 and the discussion in [ipp-
ntfy] 'job-completed' event) that explains that a Notification
Recipients can query the Job after receiving a 'job-completed' Event
Notification in order to find out other information about the job
that is 'completed', 'aborted', or 'canceled'. However, this
attribute has no effect on the Cancel-Subscription operation which
deletes the Subscription object immediately, whether or not it
contain the "notify-pull-method" attribute with the 'ippget' keyword
value. Immediately thereafter, subsequent Get-Notifications
Responses MUST NOT contain Event Notifications associated with the
canceled Subscription object.
9 New Values for Existing Printer Description Attributes
This section defines additional values for existing Printer
Description attributes defined in [ipp-ntfy].
9.1 notify-pull-method-supported (1setOf type2 keyword)
The following keyword value for the "notify-pull-method-supported"
attribute is added in order to support the new Delivery Method
defined in this document:
'ippget' - The IPP Notification Pull Delivery Method defined in
this document.
9.2 operations-supported (1setOf type2 enum)
Table 7 lists the "operation-id" value defined in order to support
the new Get-Notifications operation defined in this document.
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Table 7 - Operation-id assignments
Value Operation Name
0x001C Get-Notifications
10 New Status Codes
The following status codes are defined as extensions for this
Delivery Method and are returned as the status code of the Get-
Notifications operation in Group 1 or Group 3 to N.
10.1 successful-ok-events-complete (0x0007)
The Printer MUST return the 'successful-ok-events-complete' status
code to indicate when this Get-Notifications response is the last
response for a Subscription object, whether or not there are Event
Notifications being returned. This condition occurs for Event Wait
Mode with Notification Recipients waiting for responses when the
Subscription Object is: (1) canceled with a Cancel-Subscription
operation, (2) deleted when the Per-Printer Subscription lease time
expires, or (3) when the 'job-completed' event occurs for a Per-Job
Subscription. This condition also occurs for a Get-Notifications
request that a Notification Recipient makes after the job completes,
but before the Event Life expires.
10.2 redirection-other-site (0x0300)
This status code means that the Printer doesn't perform that Get-
Notifications operation and that the "redirect-uri" operation
attribute in the response contains the uri that the Notification
Recipient MUST use for performing the Get-Notifications operation.
If the client issues subsequent Get-Notifications operations, it MUST
use the value of the "redirect-uri" operation attribute returned by
the Printer as the target of the operation.
11 Encoding and Transport
This section defines the encoding and transport considerations for
this Delivery Method based on [RFC2910].
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The encoding of a Get-Notifications Response is modeled the Get-Jobs
Response (see [RFC2911]). In a Get-Notifications Response, each
Event Notification Attributes Group MUST start with an 'event-
notification-attributes-tag' (see the section "Encodings of
Additional Attribute Tags" in [ipp-ntfy]), and end with an 'end-of-
attributes-tag'. In addition, for Event Wait Mode the multi-
part/related is used to separate each multiple response (in time) to
a single Get-Notifications Request.
The Printer returns Get-Notification Response as follows:
1. If the Notification Recipient client did not request Event Wait
Mode ("notify-wait" = 'false' or omitted), the Printer ends the
response with an 'end-of-attributes-tag' (see [RFC2911] Get-Jobs
encoding) as with any operation response.
2. If the Notification Recipient client requests Event Wait Mode
("notify-wait" = 'true') and the Printer wishes to honor the
request, the Printer MUST return the response as an
application/ipp part inside a multi-part/related MIME media
type. When one or more additional Events occur, the Printer
returns each as an additional Event Notification Group using a
separate application/ipp part under the multi-part/related type.
3. If the client requested Event Wait Mode ("notify-wait" =
'true'), but the Printer does not wish to honor the request in
the initial response but wants the client explicitly poll for
Event Notifications, the Printer MUST return the "notify-get-
interval" operation attribute (see section 5.2.1). The Printer
returns the response as an application/ipp part which MAY be
inside an multi-part/related type. The client MUST accept this
response and re-issue the Get-Notifications request in the
future indicated by the value of the "notify-get-interval"
attribute value..
4. If the client requested Event Wait Mode ("notify-wait" =
'true'), and the Printer initially honored the request, but
later wishes to leave Event Wait Mode, the Printer MUST return
the "notify-get-interval" operation attribute (see section
5.2.1). The Printer returns the response as an application/ipp
part which MUST be inside an multi-part/related type.
Note: All of the above is without either the Printer or the
Notification Recipient closing the connection. In fact, the
connection SHOULD remain open for any subsequent IPP operations.
However, either the Notification Recipient or the Printer can
abnormally terminate by closing the connection. But, if the Printer
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closes the connection too soon after returning the response, the
client may not receive the response.
The Printer MAY chunk the responses, but this has no significance to
the IPP semantics.
Note: While HTTP/1.1 allows a proxy to collect chunked responses
over a period of time and return them back as a single un-chunked
response (with a Content Length instead). However, in practice no
proxy wants to have an infinite buffer. Also no proxy want to hold
up responses, since user would be furious.
This notification delivery method uses the IPP transport and encoding
[RFC2910] for the Get-Notifications operation with the following
extension allocated in [ipp-ntfy]:
Table 8 - The "event-notification-attributes-tag" value
Tag Value (Hex) Meaning
0x07 "event-notification-attributes-tag"
12 Conformance Requirements
The 'ippget' Delivery Method is RECOMMEND for Printers to support.
12.1 Conformance for IPP Printers
IPP Printers that conform to this specification:
1. MUST meet the conformance requirements defined in [ipp-ntfy] for
a Pull Delivery Method;
2. MUST support the Get-Notifications operation defined in section
5, including Event Wait Mode;
3. MUST support the Subscription Template object attributes as
defined in section 6;
4. MUST support the Subscription Description object attributes as
defined in section 7;
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5. MUST support the "ippget-event-life" Printer Description
attribute defined in section 8.1, including retaining jobs in
the Job Retention and/or Job History phases for at least as long
as the value specified by the Printer's "ippget-event-life";
6. MUST support the additional values for IPP/1.1 Printer
Description attributes defined in section 9;
7. MUST support the 'successful-ok-events-complete' status code as
described in section 10.1;
8. MUST support the "redirection-other-site" status code defined
10.2, if it redirects Get-Notifications operations;
9. 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;
10. SHOULD NOT listen for IPP Get-Notifications operation requests
on any other port, unless explicitly configured by system
administrators or site policies.
12.2 Conformance for IPP Clients
IPP Clients that conform to this specification:
1.MUST create Subscription Objects containing the "notify-pull-
method" attribute (as opposed to the "notify-recipient-uri"
attribute) using the 'ippget' keyword value;
2.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;
3.MUST convert the associated 'ipp' URLs for use in IPP Get-
Notifications operation to their corresponding 'http' URL forms
for use in the HTTP layer according to the rules in section 5
"IPP URL Scheme" in [RFC2910].
13 IANA Considerations
This section contains the exact information for IANA to add to the
IPP Registries according to the procedures defined in RFC 2911
[RFC2911] section 6.
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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.
13.1 Additional attribute value registrations for existing attributes
This section lists additional attribute value registrations for use
with existing attributes defined in other documents.
13.1.1 Additional values for the "notify-pull-method-supported" Printer
attribute
The following table lists the keyword value defined in this document
as an additional keyword value for use with the "notify-pull-method-
supported" Printer attribute defined in [ipp-ntfy]. This is to be
registered according to the procedures in RFC 2911 [RFC2911] section
6.1.
keyword Attribute Values: Ref. Section:
ippget RFC NNNN 9.1
The resulting keyword method attribute value registrations will be
published in the
ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
values/notify-pull-method-supported/
area.
13.1.2 Additional values for the "operations-supported" Printer
attribute
The following table lists the enum attribute value defined in this
document as an additional type2 enum value for use with the
"operations-supported" Printer attribute defined in [RFC2911]. This
is to be registered according to the procedures in RFC 2911 [RFC2911]
section 6.1.
type2 enum Attribute Values: Value Ref. Section:
Get-Notifications 0x001C RFC NNNN 9.2
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The resulting enum attribute value registration will be published in
the
ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
values/operations-supported/
area.
13.2 Operation Registrations
The following table lists the operation defined in this document.
This is to be registered according to the procedures in RFC 2911
[RFC2911] section 6.4.
Operations: Ref. Section:
Get-Notifications operation RFC NNNN 5
The resulting operation registration will be published in the
ftp://ftp.iana.org/in-notes/iana/assignments/ipp/operations/
area.
13.3 Attribute Registrations
The following table lists the attribute defined in this document.
This is to be registered according to the procedures in RFC 2911
[RFC2911] section 6.2.
Printer Description attributes: Ref. Section:
ippget-event-life (integer(15:MAX)) RFC NNNN 8.1
The resulting attribute registration will be published in the
ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attributes/
area.
13.4 Status code Registrations
The following table lists the status code defined in this document.
This is to be registered according to the procedures in RFC 2911
[RFC2911] section 6.6.
Status codes: Ref. Section:
successful-ok-events-complete (0x0007) RFC NNNN 10.1
redirection-other-site (0x0300) RFC NNNN 10.2
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The resulting status code registration will be published in the
ftp://ftp.iana.org/in-notes/iana/assignments/ipp/status-codes/
area.
14 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.
15 Security Considerations
The IPP Model and Semantics document [RFC2911] discusses high-level
security requirements (Client Authentication, Server Authentication
and Operation Privacy). Client Authentication is the mechanism by
which the client proves its identity to the server in a secure
manner. Server Authentication is the mechanism by which the server
proves its identity to the client in a secure manner. Operation
Privacy is defined as a mechanism for protecting operations from
eavesdropping.
Unlike other Event Notification delivery methods in which the IPP
Printer initiates the Event Notification, with the method defined in
this document, the Notification Recipient is the client who initiates
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.
Because the Get-Notifications operation is sent in the same direction
as Job Creation operations, this Event Notification Delivery Method
poses no additional firewall or port assignment issues.
16 References
[ipp-iig]
Hastings, T., Manros, C., Kugler, K, Holst H., Zehler, P.,
"Internet Printing Protocol/1.1: draft-ietf-ipp-implementers-
guide-v11-03.txt, work in progress, July 17, 2001
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[ipp-ntfy]
R. Herriot, Hastings, T., Isaacson, S., Martin, J., deBry, R.,
Shepherd, M., Bergman, R., "Internet Printing Protocol/1.1: IPP
Event Notifications and Subscriptions", <draft-ietf-ipp-not-spec-
08.txt>, November 19, 2001.
[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
[RFC2565]
Herriot, R., Butler, S., Moore, P., and R. Turner, "Internet
Printing Protocol/1.0: Encoding and Transport", RFC 2565, April
1999.
[RFC2566]
R. deBry, T. Hastings, R. Herriot, S. Isaacson, and P. Powell,
"Internet Printing Protocol/1.0: Model and Semantics", RFC 2566,
April 1999.
[RFC2567]
Wright, D., "Design Goals for an Internet Printing Protocol", RFC
2567, April 1999.
[RFC2568]
Zilles, S., "Rationale for the Structure and Model and Protocol for
the Internet Printing Protocol", RFC 2568, April 1999.
[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.
[RFC2707]
Bergman, R., Hastings, T., Isaacson, S., and H. Lewis, "Job
Monitoring MIB - V1.0", November 1999.
[RFC2910]
Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet Printing
Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.
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[RFC2911]
R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell,
"Internet Printing Protocol/1.1: Model and Semantics", RFC 2911,
September 2000.
17 Authors' Addresses
Robert Herriot
706 Colorado Ave.
Palo Alto, CA 94303
Phone: 650-327-4466
Fax: 650-327-4466
email:
[email protected]
Thomas N. Hastings
Xerox Corporation
737 Hawaii St. ESAE 231
El Segundo CA 90245
Phone: 310-333-6413
Fax: 310-333-5514
email:
[email protected]
Carl Kugler
IBM
P.O. Box 1900
Boulder, CO 80301-9191
Phone:
Fax:
e-mail:
[email protected]
Harry Lewis
IBM
P.O. Box 1900
Boulder, CO 80301-9191
Phone: 303-924-5337
FAX:
e-mail:
[email protected]
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IPP Web Page:
http://www.pwg.org/ipp/
IPP Mailing List:
[email protected]
To subscribe to the ipp mailing list, send the following email:
1) send it to
[email protected]
2) leave the subject line blank
3) put the following two lines in the message body:
subscribe ipp
end
Implementers of this specification document are encouraged to join
the IPP Mailing List in order to participate in any discussions of
clarification issues and review of registration proposals for
additional attributes and values. In order to reduce spam the
mailing list rejects mail from non-subscribers, so you must subscribe
to the mailing list in order to send a question or comment to the
mailing list.
18 Description of Base IPP documents
The base set of IPP documents includes:
Design Goals for an Internet Printing Protocol [RFC2567]
Rationale for the Structure and Model and Protocol for the Internet
Printing Protocol [RFC2568]
Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
Internet Printing Protocol/1.1: Encoding and Transport [RFC2910]
Internet Printing Protocol/1.1: Implementer's Guide [ipp-iig]
Mapping between LPD and IPP Protocols [RFC2569]
Internet Printing Protocol (IPP): IPP Event Notifications and
Subscriptions [ipp-ntfy]
The "Design Goals for an Internet Printing Protocol" document takes a
broad look at distributed printing functionality, and it enumerates
real-life scenarios that help to clarify the features that need to be
included in a printing protocol for the Internet. It identifies
requirements for three types of users: end users, operators, and
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.
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The "Internet Printing Protocol/1.1: Model and Semantics" document
describes a simplified model with abstract objects, their attributes,
and their operations that are independent of encoding and transport.
It introduces a Printer and a Job object. The Job object optionally
supports multiple documents per Job. It also addresses security,
internationalization, and directory issues.
The "Internet Printing Protocol/1.1: Encoding and Transport" document
is a formal mapping of the abstract operations and attributes defined
in the model document onto HTTP/1.1 [RFC2616]. It defines the
encoding rules for a new Internet MIME media type called
"application/ipp". This document also defines the rules for
transporting over HTTP a message body whose Content-Type is
"application/ipp". This document defines the 'ipp' scheme for
identifying IPP printers and jobs.
The "Internet Printing Protocol/1.1: Implementer's Guide" document
gives insight and advice to implementers of IPP clients and IPP
objects. It is intended to help them understand IPP/1.1 and some of
the considerations that may assist them in the design of their client
and/or IPP object implementations. For example, a typical order of
processing requests is given, including error checking. Motivation
for some of the specification decisions is also included.
The "Mapping between LPD and IPP Protocols" document gives some
advice to implementers of gateways between IPP and LPD (Line Printer
Daemon) implementations.
The "IPP Event Notifications and Subscriptions" document defines an
extension to IPP/1.0 [RFC2566, RFC2565] and IPP/1.1 [RFC2911,
RFC2910]. This extension allows a client to subscribe to printing
related Events and defines the semantics for delivering asynchronous
Event Notifications to the specified Notification Recipient via a
specified Delivery Method (i.e., protocols) defined in (separate)
Delivery Method documents.
19 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
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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
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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