rfc2911.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   - Section 17 is an appendix summarizing the additions and changes
     from the IPP/1.0 "Model and Semantics" document [RFC2566] to make
     this IPP/1.1 document.
   - Section 18 is the full copyright notice.

1.1 Simplified Printing Model

   In order to achieve its goal of realizing a workable printing
   protocol for the Internet, the Internet Printing Protocol (IPP) is
   based on a simplified printing model that abstracts the many
   components of real world printing solutions.  The Internet is a
   distributed computing environment where requesters of print services
   (clients, applications, printer drivers, etc.) cooperate and interact
   with print service providers.  This model and semantics document
   describes a simple, abstract model for IPP even though the underlying
   configurations may be complex "n-tier" client/server systems.  An
   important simplifying step in the IPP model is to expose only the key
   objects and interfaces required for printing.  The model described in
   this model document does not include features, interfaces, and
   relationships that are beyond the scope of the first version of IPP
   (IPP/1.1).  IPP/1.1 incorporates many of the relevant ideas and
   lessons learned from other specification and development efforts
   [HTPP] [ISO10175] [LDPA] [P1387.4] [PSIS] [RFC1179] [SWP].  IPP is
   heavily influenced by the printing model introduced in the Document
   Printing Application (DPA) [ISO10175] standard.  Although DPA
   specifies both end user and administrative features, IPP version 1.1
   (IPP/1.1) focuses primarily on end user functionality with a few
   additional OPTIONAL operator operations.

   The IPP/1.1 model encapsulates the important components of
   distributed printing into two object types:

      - Printer (Section 2.1)
      - Job (Section 2.2)

   Each object type has an associated set of operations (see section 3)
   and attributes (see section 4).








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   It is important, however, to understand that in real system
   implementations (which lie underneath the abstracted IPP/1.1 model),
   there are other components of a print service which are not
   explicitly defined in the IPP/1.1 model. The following figure
   illustrates where IPP/1.1 fits with respect to these other
   components.

                                +--------------+
                                |  Application |
                      o         +. . . . . . . |
                     \|/        |   Spooler    |
                     / \        +. . . . . . . |   +---------+
                   End-User     | Print Driver |---|  File   |
         +-----------+ +-----+  +------+-------+   +----+----+
         |  Browser  | | GUI |         |                |
         +-----+-----+ +--+--+         |                |
               |          |            |                |
               |      +---+------------+---+            |
   N   D   S   |      |      IPP Client    |------------+
   O   I   E   |      +---------+----------+
   T   R   C   |                |
   I   E   U   |
   F   C   R   -------------- Transport ------------------
   I   T   I
   C   O   T                    |         --+
   A   R   Y           +--------+--------+  |
   T   Y               |    IPP Server   |  |
   I                   +--------+--------+  |
   O                            |           |
   N                   +-----------------+  | IPP Printer
                       |  Print Service  |  |
                       +-----------------+  |
                                |         --+
                       +-----------------+
                       | Output Device(s)|
                       +-----------------+

   An IPP Printer object encapsulates the functions normally associated
   with physical output devices along with the spooling, scheduling and
   multiple device management functions often associated with a print
   server. Printer objects are optionally registered as entries in a
   directory where end users find and select them based on some sort of
   filtered and context based searching mechanism (see section 16).  The
   directory is used to store relatively static information about the
   Printer, allowing end users to search for and find Printers that
   match their search criteria, for example: name, context, printer
   capabilities, etc.  The more dynamic information, such as state,
   currently loaded and ready media, number of jobs at the Printer,



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   errors, warnings, and so forth, is directly associated with the
   Printer object itself rather than with the entry in the directory
   which only represents the Printer object.

   IPP clients implement the IPP protocol on the client side and give
   end users (or programs running on behalf of end users) the ability to
   query Printer objects and submit and manage print jobs.  An IPP
   server is just that part of the Printer object that implements the
   server-side protocol.  The rest of the Printer object implements (or
   gateways into) the application semantics of the print service itself.
   The Printer objects may be embedded in an output device or may be
   implemented on a host on the network that communicates with an output
   device.

   When a job is submitted to the Printer object and the Printer object
   validates the attributes in the submission request, the Printer
   object creates a new Job object.  The end user then interacts with
   this new Job object to query its status and monitor the progress of
   the job.  An end user can also cancel their print jobs by using the
   Job object's Cancel-Job operation.  An end-user can also hold,
   release, and restart their print jobs using the Job object's OPTIONAL
   Hold-Job, Release-Job, and Restart-Job operations, if implemented.

   A privileged operator or administrator of a Printer object can
   cancel, hold, release, and restart any user's job using the REQUIRED
   Cancel-Job and the OPTIONAL Hold-Job, Release-Job, and Restart-Job
   operations.  In additional privileged operator or administrator of a
   Printer object can pause, resume, or purge (jobs from) a Printer
   object using the OPTIONAL Pause-Printer, Resume-Printer, and Purge-
   Jobs operations, if implemented.

   The notification service is out of scope for this IPP/1.1 document,
   but using such a notification service, the end user is able to
   register for and receive Printer specific and Job specific events.
   An end user can query the status of Printer objects and can follow
   the progress of Job objects by polling using the Get-Printer-
   Attributes, Get-Jobs, and Get-Job-Attributes operations.

2. IPP Objects

   The IPP/1.1 model introduces objects of type Printer and Job.  Each
   type of object models relevant aspects of a real-world entity such as
   a real printer or real print job.  Each object type is defined as a
   set of possible attributes that may be supported by instances of that
   object type.  For each object (instance), the actual set of supported
   attributes and values describe a specific implementation.  The
   object's attributes and values describe its state, capabilities,
   realizable features, job processing functions, and default behaviors



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   and characteristics.  For example, the Printer object type is defined
   as a set of attributes that each Printer object potentially supports.
   In the same manner, the Job object type is defined as a set of
   attributes that are potentially supported by each Job object.

   Each attribute included in the set of attributes defining an object
   type is labeled as:

   - "REQUIRED": each object MUST support the attribute.
   - "RECOMMENDED": each object SHOULD support the attribute.
   - "OPTIONAL": each object MAY support the attribute.

   Some definitions of attribute values indicate that an object MUST or
   SHOULD support the value; otherwise, support of the value is
   OPTIONAL.

   However, if an implementation supports an attribute, it MUST support
   at least one of the possible values for that attribute.

2.1 Printer Object

   The major component of the IPP/1.1 model is the Printer object.  A
   Printer object implements the server-side of the IPP/1.1 protocol.
   Using the protocol, end users may query the attributes of the Printer
   object and submit print jobs to the Printer object.  The actual
   implementation components behind the Printer abstraction may take on
   different forms and different configurations.  However, the model
   abstraction allows the details of the configuration of real
   components to remain opaque to the end user.  Section 3 describes
   each of the Printer operations in detail.

   The capabilities and state of a Printer object are described by its
   attributes.  Printer attributes are divided into two groups:

   - "job-template" attributes: These attributes describe supported job
     processing capabilities and defaults for the Printer object. (See
     section 4.2)
   - "printer-description" attributes: These attributes describe the
     Printer object's identification, state, location, references to
     other sources of information about the Printer object, etc. (see
     section 4.4)

   Since a Printer object is an abstraction of a generic document output
   device and print service provider, a Printer object could be used to
   represent any real or virtual device with semantics consistent with
   the Printer object, such as a fax device, an imager, or even a CD
   writer.




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   Some examples of configurations supporting a Printer object include:

      1) An output device with no spooling capabilities
      2) An output device with a built-in spooler
      3) A print server supporting IPP with one or more associated
         output devices
         3a) The associated output devices may or may not be capable of
             spooling jobs
         3b) The associated output devices may or may not support IPP

   The following figures show some examples of how Printer objects can
   be realized on top of various distributed printing configurations.
   The embedded case below represents configurations 1 and 2. The hosted
   and fan-out figures below represent configurations 3a and 3b.

   In this document the term "client" refers to a software entity that
   sends IPP operation requests to an IPP Printer object and accepts IPP
   operation responses.  A client MAY be:

      1. contained within software controlled by an end user, e.g.
         activated by the "Print" menu item in an application or

      2. the print server component that sends IPP requests to either an
         output device or another "downstream" print server.

   The term "IPP Printer" is a network entity that accepts IPP operation
   requests and returns IPP operation responses.  As such, an IPP object
   MAY be:

      1. an (embedded) device component that accepts IPP requests and
         controls the device or

      2. a component of a print server that accepts IPP requests (where
         the print server controls one or more networked devices using
         IPP or other protocols).

   Legend:

   ##### indicates a Printer object which is
         either embedded in an output device or is