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Network Working Group T. Hastings Request for Comments: 2639 C. Manros Category: Informational Xerox Corporation

                                                             July 1999
        Internet Printing Protocol/1.0: Implementer's Guide

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

 This document is one of a set of documents, which together describe
 all aspects of a new Internet Printing Protocol (IPP).  IPP is an
 application level protocol that can be used for distributed printing
 using Internet tools and technologies.  This document contains
 information that supplements the IPP Model and Semantics [RFC2566]
 and the IPP Transport and Encoding [RFC2565] documents.  It is
 intended to help implementers understand IPP/1.0 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 full 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/1.0: Model and Semantics [RFC2566]
   Internet Printing Protocol/1.0: Encoding and Transport [RFC2565]
   Mapping between LPD and IPP Protocols [RFC2569]
 The document, "Design Goals for an Internet Printing Protocol", 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

Hastings & Manros Informational [Page 1] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 administrators.  The design goals document calls out a subset of end
 user requirements that are satisfied in IPP/1.0.  Operator and
 administrator requirements are out of scope for version 1.0.
 The document, "Rationale for the Structure and Model and Protocol for
 the Internet Printing Protocol", describes IPP from a high level
 view, defines a roadmap for the various documents that form the suite
 of IPP specifications, and gives background and rationale for the
 IETF working group's major decisions.
 The document, "Internet Printing Protocol/1.0: Model and Semantics",
 describes a simplified model with abstract objects, their attributes,
 and their operations.  The model introduces a Printer and a Job.  The
 Job supports multiple documents per Job.  The model document also
 addresses how security, internationalization, and directory issues
 are addressed.
 The document, "Internet Printing Protocol/1.0: Encoding and
 Transport", is a formal mapping of the abstract operations and
 attributes defined in the model document onto HTTP/1.1.  It also
 defines the encoding rules for a new Internet media type called
 "application/ipp".
 The document, "Mapping between LPD and IPP Protocols", gives some
 advice to implementers of gateways between IPP and LPD (Line Printer
 Daemon) implementations.

Table of Contents

1  Introduction......................................................4
 1.1 Conformance language............................................4
 1.2 Other terminology...............................................5
2  Model and Semantics...............................................5
 2.1 Summary of Operation Attributes.................................5
 2.2 Suggested Operation Processing Steps for IPP Objects ..........10
     2.2.1 Suggested Operation Processing Steps for all Operations..11
     2.2.1.1  Validate version number...............................11
     2.2.1.2  Validate operation identifier.........................11
     2.2.1.3  Validate the request identifier.......................11
     2.2.1.4  Validate attribute group and attribute presence and
              order.................................................12
     2.2.1.5  Validate the values of the REQUIRED Operation
              attributes............................................19
     2.2.1.6  Validate the values of the OPTIONAL Operation
              attributes............................................23
   2.2.2 Suggested Additional Processing Steps for Operations that
         Create/Validate Jobs and Add Documents.....................26
     2.2.2.1  Default "ipp-attribute-fidelity" if not supplied......26

Hastings & Manros Informational [Page 2] RFC 2639 IPP/1.0: Implementer's Guide July 1999

     2.2.2.2  Check that the Printer object is accepting jobs.......26
     2.2.2.3  Validate the values of the Job Template attributes....26
   2.2.3 Algorithm for job validation...............................27
     2.2.3.1  Check for conflicting Job Template attributes values..33
     2.2.3.2  Decide whether to REJECT the request..................33
     2.2.3.3  For the Validate-Job operation, RETURN one of the
              success status codes..................................34
     2.2.3.4  Create the Job object with attributes to support......34
     2.2.3.5  Return one of the success status codes................36
     2.2.3.6  Accept appended Document Content......................36
     2.2.3.7  Scheduling and Starting to Process the Job............36
     2.2.3.8  Completing the Job....................................37
     2.2.3.9  Destroying the Job after completion...................37
     2.2.3.10 Interaction with "ipp-attribute-fidelity".............37
 2.3 Status codes returned by operation ............................37
   2.3.1 Printer Operations.........................................38
     2.3.1.1  Print-Job.............................................38
     2.3.1.2  Print-URI.............................................40
     2.3.1.3  Validate-Job..........................................40
     2.3.1.4  Create-Job............................................41
     2.3.1.5  Get-Printer-Attributes................................41
     2.3.1.6  Get-Jobs..............................................42
   2.3.2 Job Operations.............................................43
     2.3.2.1  Send-Document.........................................43
     2.3.2.2  Send-URI..............................................44
     2.3.2.3  Cancel-Job............................................44
     2.3.2.4  Get-Job-Attributes....................................45
 2.4 Validate-Job...................................................46
 2.5 Case Sensitivity in URIs ......................................46
 2.6 Character Sets, natural languages, and internationalization....46
   2.6.1 Character set code conversion support .....................46
   2.6.2 What charset to return when an unsupported charset is
         requested?.................................................48
   2.6.3 Natural Language Override (NLO) ...........................48
 2.7 The "queued-job-count" Printer Description attribute...........50
   2.7.1 Why is "queued-job-count" RECOMMENDED?.....................50
   2.7.2 Is "queued-job-count" a good measure of how busy a printer
         is?........................................................50
 2.8 Sending empty attribute groups ................................50
 2.9 Returning unsupported attributes in Get-Xxxx responses ........51
 2.10 Returning job-state in Print-Job response ....................51
 2.11 Flow controlling the data portion of a Print-Job request .....52
 2.12 Multi-valued attributes ......................................53
 2.13 Querying jobs with IPP that were submitted using other job
      submission protocols .........................................53
 2.14 The 'none' value for empty sets ..............................54
 2.15 Get-Jobs, my-jobs='true', and 'requesting-user-name'?.........54

Hastings & Manros Informational [Page 3] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 2.16 The "multiple-document-handling" Job Template attribute and
      support of multiple document jobs.............................54
3  Encoding and Transport...........................................55
 3.1 General Headers................................................56
 3.2 Request  Headers...............................................57
 3.3 Response Headers...............................................58
 3.4 Entity  Headers................................................59
 3.5 Optional support for HTTP/1.0..................................60
 3.6 HTTP/1.1 Chunking..............................................60
   3.6.1 Disabling IPP Server Response Chunking.....................60
   3.6.2 Warning About the Support of Chunked Requests..............60
4  References.......................................................61
 4.1 Authors' Addresses.............................................62
5  Security Considerations..........................................62
6  Notices..........................................................62
Full Copyright Statement............................................65

1 Introduction

This document contains information that supplements the IPP Model and
Semantics [RFC2566] and the IPP Transport and Encoding [RFC2565]
documents.  As such this information is not part of the formal
specifications.  Instead information is presented to help implementers
understand the specification, including some of the motivation for
decisions taken by the committee in developing the specification.
Some of the implementation considerations are intended to help
implementers design their client and/or IPP object implementations.
If there are any contradictions between this document and [RFC2566] or
[RFC2565], those documents take precedence over this document.

1.1 Conformance language

Usually, this document does not contain the terminology MUST, MUST
NOT, MAY, NEED NOT, SHOULD, SHOULD NOT, REQUIRED, and OPTIONAL.
However, when those terms do appear in this document, their intent is
to repeat what the [RFC2566] and [RFC2565] documents require and
allow, rather than specifying additional conformance requirements.
These terms are defined in section 13 on conformance terminology in
[RFC2566], most of which is taken from RFC 2119 [RFC2119].
Implementers should read section 13 in [RFC2566] in order to
understand these capitalized words.  The words MUST, MUST NOT, and
REQUIRED indicate what implementations are required to support in a
client or IPP object in order to be conformant to [RFC2566] and
[RFC2565].  MAY, NEED NOT, and OPTIONAL indicate was is merely allowed
as an implementer option.  The verbs SHOULD and SHOULD NOT indicate
suggested behavior, but which is not required or disallowed,
respectively, in order to conform to the specification.

Hastings & Manros Informational [Page 4] RFC 2639 IPP/1.0: Implementer's Guide July 1999

1.2 Other terminology

The term "sender" refers to the client that sends a request or an IPP
object that returns a response.  The term "receiver" refers to the IPP
object that receives a request and to a client that receives a
response.

2 Model and Semantics

This section discusses various aspects of IPP/1.0 Model and Semantics
[RFC2566].

2.1 Summary of Operation Attributes

Legend for the following table:
    R indicates a REQUIRED operation or attribute for an
      implementation to support
    O indicates an OPTIONAL operation or attribute for an
      implementation to support

Hastings & Manros Informational [Page 5] RFC 2639 IPP/1.0: Implementer's Guide July 1999

  Table 1.  Summary of operation attributes for Printer operations
                         Printer Operations
                       Requests                         Responses
   Operation           Print-   Pri  Crea Get-     Get- All
   Attributes          Job,     nt-  te-  Printer- Jobs Opera-
                       Validate URI  Job  Attribut      tions
                       -Job     (O)  (O)  es
   Operation parameters--REQUIRED to be supplied by the sender
   operation-id           R      R    R      R      R
   status-code                                            R
   request-id             R      R    R      R      R     R
   version-number         R      R    R      R      R     R
   Operation attributes-REQUIRED to be supplied by the sender
   attributes-charset     R      R    R      R      R     R
   attributes-            R      R    R      R      R     R
   natural-language
   document-uri                   R
   job-id*
   job-uri*
   last-document
   printer-uri            R      R    R      R      R
   Operation attributes-RECOMMENDED to be supplied by the sender
   job-name               R      R    R
   requesting-user-       R      R    R      R      R
   name

Hastings & Manros Informational [Page 6] RFC 2639 IPP/1.0: Implementer's Guide July 1999

                         Printer Operations
                       Requests                        Responses
    Operation          Print-   Pri  Crea Get-    Get-  All
    Attributes         Job,     nt-  te-  Printer Jobs  Opera-
                       Vali-    URI  Job  Attri-        tions
                       date-Job (O)  (O)  butes
    Operation attributes-OPTIONAL to be supplied by the sender
    status-message                                         O
    compression           O     O
    document-format       R     R           O
    document-name         O     O
    document-natural-     O     O
    language
    ipp-attribute-        R     R    R
    fidelity
    job-impressions       O     O    O
    job-k-octets          O     O    O
    job-media-sheets      O     O    O
    limit                                           R
    message
    my-jobs                                         R
    requested-                               R      R
    attributes
    which-jobs                                      R
  • "job-id" is REQUIRED only if used together with

"printer-uri" to identify the target job; otherwise, "job-

    uri" is REQUIRED.

Hastings & Manros Informational [Page 7] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    Table 2.  Summary of operation attributes for Job operations
                       Requests                         Responses
    Operation          Send-    Send-  Cancel  Get-     All
    Attributes         Document URI    -Job    Job-     Opera-
                       (O)      (O)            Attri-   tions
                                               butes
    Operation parameters--REQUIRED to be supplied by the sender
    operation-id          R       R      R       R
    status-code                                          R
    request-id            R       R      R       R       R
    version-number        R       R      R       R       R
    Operation attributes-REQUIRED to be supplied by the sender
    attributes-           R       R      R       R       R
    charset
    attributes-           R       R      R       R       R
    natural-language
    document-uri                   R
    job-id*               R       R      R       R
    job-uri*              R       R      R       R
    last-document         R       R
    printer-uri           R       R      R       R
    Operation attributes-RECOMMENDED to be supplied by the
    sender
    job-name
    requesting-user-      R       R      R       R
    name

Hastings & Manros Informational [Page 8] RFC 2639 IPP/1.0: Implementer's Guide July 1999

                           Job Operations
                         Requests                      Responses
   Operation Attributes  Send-    Send-   Cance Get-    All
                         Document URI     l-Job Job-    Opera-
                         (O)      (O)           Attri-  tions
                                                butes
   Operation attributes.OPTIONAL to be supplied by the sender
   status-message                                       O
   compression               O       O
   document-format           R       R
   document-name             O       O
   document-natural-         O       O
   language
   ipp-attribute-
   fidelity
   job-impressions
   job-k-octets
   job-media-sheets
   limit
   message                                   O
   my-jobs
   requested-attributes                             R
   which-jobs
  • "job-id" is REQUIRED only if used together with "printer-

uri" to identify the target job; otherwise, "job-uri" is

   REQUIRED.

Hastings & Manros Informational [Page 9] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.2 Suggested Operation Processing Steps for IPP Objects

 This section suggests the steps and error checks that an IPP object
 MAY perform when processing requests and returning responses.  An IPP
 object MAY perform some or all of the error checks.  However, some
 implementations MAY choose to be more forgiving than the error checks
 shown here, in order to be able to accept requests from non-
 conforming clients.  Not performing all of these error checks is a
 so-called "forgiving" implementation.  On the other hand, clients
 that successfully submit requests to IPP objects that do perform all
 the error checks will be more likely to be able to interoperate with
 other IPP object implementations.  Thus an implementer of an IPP
 object needs to decide whether to be a "forgiving" or a "strict"
 implementation.  Therefore, the error status codes returned may
 differ between implementations.   Consequentially, client SHOULD NOT
 expect exactly the error code processing described in this section.
 When an IPP object receives a request, the IPP object either accepts
 or rejects the request. In order to determine whether or not to
 accept or reject the request, the IPP object SHOULD execute the
 following steps.  The order of the steps may be rearranged and/or
 combined, including making one or multiple passes over the request.
 A client MUST supply requests that would pass all of the error checks
 indicated here in order to be a conforming client.  Therefore, a
 client SHOULD supply requests that are conforming, in order to avoid
 being rejected by some IPP object implementations and/or risking
 different semantics by different implementations of forgiving
 implementations.  For example, a forgiving implementation that
 accepts multiple occurrences of the same attribute, rather than
 rejecting the request might use the first occurrences, while another
 might use the last occurrence.  Thus such a non-conforming client
 would get different results from the two forgiving implementations.
 In the following, processing continues step by step until a "RETURNS
 the xxx status code ." statement is encountered.  Error returns are
 indicated by the verb: "REJECTS".  Since clients have difficulty
 getting the status code before sending all of the document data in a
 Print-Job request, clients SHOULD use the Validate-Job operation
 before sending large documents to be printed, in order to validate
 whether the IPP Printer will accept the job or not.
 It is assumed that security authentication and authorization has
 already taken place at a lower layer.

Hastings & Manros Informational [Page 10] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.2.1 Suggested Operation Processing Steps for all Operations

 This section is intended to apply to all operations.  The next
 section contains the additional steps for the Print-Job, Validate-
 Job, Print-URI, Create-Job, Send-Document, and Send-URI operations
 that create jobs, adds documents, and validates jobs.

2.2.1.1 Validate version number

 Every request and every response contains the "version-number"
 attribute.  The value of this attribute is the major and minor
 version number of the syntax and semantics that the client and IPP
 object is using, respectively.  The "version-number" attribute
 remains in a fixed position across all future versions so that all
 clients and IPP object that support future versions can determine
 which version is being used.  The IPP object checks to see if the
 major version number supplied in the request is supported.  If not,
 the Printer object REJECTS the request and RETURNS the 'server-
 error-version-not-supported' status code in the response.  The IPP
 object returns in the "version-number" response attribute the major
 and minor version for the error response.  Thus the client can learn
 at least one major and minor version that the IPP object supports.
 The IPP object is encouraged to return the closest version number to
 the one supplied by the client.
 The checking of the minor version number is implementation dependent,
 however if the client supplied minor version is explicitly supported,
 the IPP object MUST respond using that identical minor version
 number.  If the requested minor version is not supported (the
 requested minor version is either higher or lower) than a supported
 minor version, the IPP object SHOULD return the closest supported
 minor version.

2.2.1.2 Validate operation identifier

 The Printer object checks to see if the "operation-id" attribute
 supplied by the client is supported as indicated in the Printer
 object's "operations-supported" attribute.  If not, the Printer
 REJECTS the request and returns the 'server-error-operation-not-
 supported' status code in the response.

2.2.1.3 Validate the request identifier

 The Printer object SHOULD NOT check to see if the "request-id"
 attribute supplied by the client is in range: between 1 and 2**31 - 1
 (inclusive), but copies all 32 bits.

Hastings & Manros Informational [Page 11] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Note: The "version-number",  "operation-id", and the "request-id"
 parameters are in fixed octet positions in the IPP/1.0 encoding.  The
 "version-number" parameter will be the same fixed octet position in
 all versions of the protocol.  These fields are validated before
 proceeding with the rest of the validation.

2.2.1.4 Validate attribute group and attribute presence and order

 The order of the following validation steps depends on
 implementation.

2.2.1.4.1 Validate the presence and order of attribute groups

 Client requests and IPP object responses contain attribute groups
 that Section 3 requires to be present and in a specified order.  An
 IPP object verifies that the attribute groups are present and in the
 correct order in requests supplied by clients (attribute groups
 without an * in the following tables).
 If an IPP object receives a request with (1) required attribute
 groups missing, or (2) the attributes groups are out of order, or (3)
 the groups are repeated, the IPP object REJECTS the request and
 RETURNS the 'client-error-bad-request' status code.  For example, it
 is an error for the Job Template Attributes group to occur before the
 Operation Attributes group, for the Operation Attributes group to be
 omitted, or for an attribute group to occur more than once, except in
 the Get-Jobs response.
 Since this kind of attribute group error is most likely to be an
 error detected by a client developer rather than by a customer, the
 IPP object NEED NOT return an indication of which attribute group was
 in error in either the Unsupported Attributes group or the Status
 Message.  Also, the IPP object NEED NOT find all attribute group
 errors before returning this error.

2.2.1.4.2 Ignore unknown attribute groups in the expected position

 Future attribute groups may be added to the specification at the end
 of requests just before the Document Content and at the end of
 response, except for the Get-Jobs response, where it maybe there or
 before the first job attributes returned.  If an IPP object receives
 an unknown attribute group in these positions, it ignores the entire
 group, rather than returning an error, since that group may be a new
 group in a later minor version of the protocol that can be ignored.
 (If the new attribute group cannot be ignored without confusing the
 client, the major version number would have been increased in the

Hastings & Manros Informational [Page 12] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 protocol document and in the request).  If the unknown group occurs
 in a different position, the IPP object REJECTS the request and
 RETURNS the 'client-error-bad-request' status code.
 Clients also ignore unknown attribute groups returned in a response.
 Note:  By validating that requests are in the proper form, IPP
 objects force clients to use the proper form which, in turn,
 increases the chances that customers will be able to use such clients
 from multiple vendors with IPP objects from other vendors.

2.2.1.4.3 Validate the presence of a single occurrence of required

        Operation attributes
 Client requests and IPP object responses contain Operation attributes
 that [RFC2566] Section 3 requires to be present.  Attributes within a
 group may be in any order, except for the ordering of target,
 charset, and natural languages attributes.  These attributes MUST be
 first, and MUST be supplied in the following order: charset, natural
 language, and then target. An IPP object verifies that the attributes
 that Section 4 requires to be supplied by the client have been
 supplied in the request (attributes without an * in the following
 tables).  An asterisk (*) indicates groups and Operation attributes
 that the client may omit in a request or an IPP object may omit in a
 response.
 If an IPP object receives a request with required attributes missing
 or repeated from a group or in the wrong position, the behavior of
 the IPP object is IMPLEMENTATION DEPENDENT.  Some of the possible
 implementations are:
    1.REJECTS the request and RETURNS the 'client-error-bad-request'
      status code
    2.accepts the request and uses the first occurrence of the
      attribute no matter where it is
    3.accepts the request and uses the last occurrence of the
      attribute no matter where it is
    4.accept the request and assume some default value for the missing
      attribute
 Therefore, client MUST send conforming requests, if they want to
 receive the same behavior from all IPP object implementations.  For
 example, it is an error for the "attributes-charset" or "attributes-
 natural-language" attribute to be omitted in any operation request,
 or for an Operation attribute to be supplied in a Job Template group

Hastings & Manros Informational [Page 13] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 or a Job Template attribute to be supplied in an Operation Attribute
 group in a create request.  It is also an error to supply the
 "attributes-charset" attribute twice.
 Since these kinds of attribute errors are most likely to be detected
 by a client developer rather than by a customer, the IPP object NEED
 NOT return an indication of which attribute was in error in either
 the Unsupported Attributes group or the Status Message.  Also, the
 IPP object NEED NOT find all attribute errors before returning this
 error.
 The following tables list all the attributes for all the operations
 by attribute group in each request and each response.  The order of
 the groups is the order that the client supplies the groups as
 specified in [RFC2566] Section 3.  The order of the attributes within
 a group is arbitrary, except as noted for some of the special
 operation attributes (charset, natural language, and target).  The
 tables below use the following notation:
   R   indicates a REQUIRED attribute that an IPP object MUST support
   O   indicates an OPTIONAL attribute that an IPP object NEED NOT
             support
   *   indicates that a client MAY omit the attribute in a request
             and that an IPP object MAY omit the attribute in a
             response. The absence of an * means that a client MUST
             supply the attribute in a request and an IPP object MUST
             supply the attribute in a response.
                          Operation Requests
 The tables below show the attributes in their proper attribute groups
 for operation requests:
 Note: All operation requests contain "version-number", "operation-
 id", and "request-id" parameters.
 Print-Job Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)
           requesting-user-name (R*)
           job-name (R*)
           ipp-attribute-fidelity (R*)
           document-name (R*)
           document-format (R*)
           document-natural-language (O*)
           compression (O*)

Hastings & Manros Informational [Page 14] RFC 2639 IPP/1.0: Implementer's Guide July 1999

           job-k-octets (O*)
           job-impressions (O*)
           job-media-sheets (O*)
      Group 2: Job Template Attributes (R*)
           <Job Template attributes> (O*)
                (see [RFC2566] Section 4.2)
      Group 3: Document Content (R)
           <document content>
 Validate-Job Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)
           requesting-user-name (R*)
           job-name (R*)
           ipp-attribute-fidelity (R*)
           document-name (R*)
           document-format (R*)
           document-natural-language (O*)
           compression (O*)
           job-k-octets (O*)
           job-impressions (O*)
           job-media-sheets (O*)
      Group 2: Job Template Attributes (R*)
           <Job Template attributes> (O*)
                (see [RFC2566] Section 4.2)
 Create-Job Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)
           requesting-user-name (R*)
           job-name (R*)
           ipp-attribute-fidelity (R*)
           job-k-octets (O*)
           job-impressions (O*)
           job-media-sheets (O*)
      Group 2: Job Template Attributes (R*)
           <Job Template attributes> (O*) (see
                (see [RFC2566] Section 4.2)
 Print-URI Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)

Hastings & Manros Informational [Page 15] RFC 2639 IPP/1.0: Implementer's Guide July 1999

           document-uri (R)
           requesting-user-name (R*)
           job-name (R*)
           ipp-attribute-fidelity (R*)
           document-name (R*)
           document-format (R*)
           document-natural-language (O*)
           compression (O*)
           job-k-octets (O*)
           job-impressions (O*)
           job-media-sheets (O*)
      Group 2: Job Template Attributes (R*)
           <Job Template attributes> (O*) (see
                (see [RFC2566] Section 4.2)
 Send-Document Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           (printer-uri & job-id) | job-uri (R)
           last-document (R)
           requesting-user-name (R*)
           document-name (R*)
           document-format (R*)
           document-natural-language (O*)
           compression (O*)
      Group 2: Document Content (R*)
           <document content>
 Send-URI Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           (printer-uri & job-id) | job-uri (R)
           last-document (R)
           document-uri (R)
           requesting-user-name (R*)
           document-name (R*)
           document-format (R*)
           document-natural-language (O*)
           compression (O*)

Hastings & Manros Informational [Page 16] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Cancel-Job Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           (printer-uri & job-id) | job-uri (R)
           requesting-user-name (R*)
           message (O*)
 Get-Printer-Attributes Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)
           requesting-user-name (R*)
           requested-attributes (R*)
           document-format (R*)
 Get-Job-Attributes Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           (printer-uri & job-id) | job-uri (R)
           requesting-user-name (R*)
           requested-attributes (R*)
 Get-Jobs Request:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           printer-uri (R)
           requesting-user-name (R*)
           limit (R*)
           requested-attributes (R*)
           which-jobs (R*)
           my-jobs (R*)
                          Operation Responses
 The tables below show the response attributes in their proper
 attribute groups for responses.
 Note: All operation responses contain "version-number", "status-
 code", and "request-id" parameters.
 Print-Job Response:
 Print-URI Response:
 Create-Job Response:

Hastings & Manros Informational [Page 17] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Send-Document Response:
 Send-URI Response:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           status-message (O*)
      Group 2: Unsupported Attributes (R*) (see Note 3)
           <unsupported attributes> (R*)
      Group 3: Job Object Attributes(R*) (see Note 2)
           job-uri (R)
           job-id (R)
           job-state (R)
           job-state-reasons (O*)
           job-state-message (O*)
           number-of-intervening-jobs (O*)
 Validate-Job Response:
 Cancel-Job Response:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           status-message (O*)
      Group 2: Unsupported Attributes (R*) (see Note 3)
           <unsupported attributes> (R*)
 Note 2 - the Job Object Attributes and Printer Object Attributes are
 returned only if the IPP object returns one of the success status
 codes.
 Note 3 - the Unsupported Attributes Group is present only if the
 client included some Operation and/or Job Template attributes or
 values that the Printer doesn't support whether a success or an error
 return.
 Get-Printer-Attributes Response:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           status-message (O*)
      Group 2: Unsupported Attributes (R*) (see Note 4)
           <unsupported attributes> (R*)
      Group 3: Printer Object Attributes(R*) (see Note 2)
           <requested attributes> (R*)
 Note 4 - the Unsupported Attributes Group is present only if the
 client included some Operation attributes that the Printer doesn't
 support whether a success or an error return.

Hastings & Manros Informational [Page 18] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Get-Job-Attributes Response:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           status-message (O*)
      Group 2: Unsupported Attributes (R*) (see Note 4)
           <unsupported attributes> (R*)
      Group 3: Job Object Attributes(R*) (see Note 2)
           <requested attributes> (R*)
 Get-Jobs Response:
      Group 1: Operation Attributes (R)
           attributes-charset (R)
           attributes-natural-language (R)
           status-message (O*)
      Group 2: Unsupported Attributes (R*) (see Note 4)
           <unsupported attributes> (R*)
      Group 3: Job Object Attributes(R*) (see Note 2, 5)
           <requested attributes> (R*)
 Note 5:  for the Get-Jobs operation the response contains a separate
 Job Object Attributes group 3 to N containing requested-attributes
 for each job object in the response.

2.2.1.5 Validate the values of the REQUIRED Operation attributes

 An IPP object validates the values supplied by the client of the
 REQUIRED Operation attribute that the IPP object MUST support.  The
 next section specifies the validation of the values of the OPTIONAL
 Operation attributes that IPP objects MAY support.
 The IPP object performs the following syntactic validation checks of
 each Operation attribute value:
    a)that the length of each Operation attribute value is correct for
      the attribute syntax tag supplied by the client according to
      [RFC2566] Section 4.1,
    b)that the attribute syntax tag is correct for that Operation
      attribute according to [RFC2566] Section 3,
    c)that the value is in the range specified for that Operation
      attribute according to [RFC2566] Section 3,
    d)that multiple values are supplied by the client only for
      operation attributes that are multi-valued, i.e., that are
      1setOf X according to [RFC2566] Section 3.

Hastings & Manros Informational [Page 19] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 If any of these checks fail, the IPP object REJECTS the request and
 RETURNS the 'client-error-bad-request' or the 'client-error-request-
 value-too-long' status code.  Since such an error is most likely to
 be an error detected by a client developer, rather than by an end-
 user, the IPP object NEED NOT return an indication of which attribute
 had the error in either the Unsupported Attributes Group or the
 Status Message.  The description for each of these syntactic checks
 is explicitly expressed in the first IF statement in the following
 table.
 In addition, the IPP object checks each Operation attribute value
 against some Printer object attribute or some hard-coded value if
 there is no "xxx-supported" Printer object attribute defined. If its
 value is not among those supported or is not in the range supported,
 then the IPP object REJECTS the request and RETURNS the error status
 code indicated in the table by the second IF statement.  If the value
 of the Printer object's "xxx-supported" attribute is 'no-value'
 (because the system administrator hasn't configured a value), the
 check always fails.
 attributes-charset (charset)
    IF NOT a single non-empty 'charset' value, REJECT/RETURN 'client-
       error-bad-request'.
    IF the value length is greater than 63 octets, REJECT/RETURN '
       client-error-request-value-too-long'.
    IF NOT in the Printer object's "charset-supported" attribute,
       REJECT/RETURN "client-error-charset-not-supported".
 attributes-natural-language(naturalLanguage)
    IF NOT a single non-empty 'naturalLanguage' value, REJECT/RETURN
       'client-error-bad-request'.
    IF the value length is greater than 63 octets, REJECT/RETURN '
       client-error-request-value-too-long'.
    ACCEPT the request even if not a member of the set in the Printer
       object's "generated-natural-language-supported" attribute.  If
       the supplied value is not a member of the Printer object's
       "generated-natural-language-supported" attribute, use the
       Printer object's "natural-language-configured" value.

Hastings & Manros Informational [Page 20] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 requesting-user-name
    IF NOT a single 'name' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF the IPP object can obtain a better authenticated name, use it
       instead.
 job-name(name)
    IF NOT a single 'name' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT supplied by the client, the Printer object creates a name
       from the document-name or document-uri.
 document-name (name)
    IF NOT a single 'name' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
 ipp-attribute-fidelity (boolean)
    IF NEITHER a single 'true' NOR a single 'false' 'boolean' value,
       REJECT/RETURN 'client-error-bad-request'.
    IF the value length is NOT equal to 1 octet, REJECT/RETURN '
       client-error-request-value-too-long'
    IF NOT supplied by the client, the IPP object assumes the value
       'false'.
 document-format (mimeMediaType)
    IF NOT a single non-empty 'mimeMediaType' value, REJECT/RETURN
       'client-error-bad-request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT in the Printer object's "document-format-supported"
       attribute, REJECT/RETURN 'client-error-document-format-not-
       supported'

Hastings & Manros Informational [Page 21] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    IF NOT supplied by the client, the IPP object assumes the value of
       the Printer object's "document-format-default" attribute.
 document-uri (uri)
    IF NOT a single non-empty 'uri' value, REJECT/RETURN 'client-
       error-bad-request'.
    IF the value length is greater than 1023 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF the URI syntax is not valid, REJECT/RETURN 'client-error-bad-
       request'.
    IF scheme is NOT in the Printer object's "reference-uri-schemes-
       supported" attribute, REJECT/RETURN 'client-error-uri-scheme-
       not-supported'.
    The Printer object MAY check to see if the document exists and is
       accessible.  If the document is not found or is not accessible,
       REJECT/RETURN 'client-error-not found'.
 last-document (boolean)
    IF NEITHER a single 'true' NOR a single 'false' 'boolean' value,
       REJECT/RETURN 'client-error-bad-request'.
    IF the value length is NOT equal to 1 octet, REJECT/RETURN '
       client-error-request-value-too-long'
 job-id (integer(1:MAX))
    IF NOT an single 'integer' value equal to 4 octets AND in the
       range 1 to MAX, REJECT/RETURN 'client-error-bad-request'.
    IF NOT a job-id of an existing Job object, REJECT/RETURN 'client-
       error-not-found' or 'client-error-gone' status code, if keep
       track of recently deleted jobs.
 requested-attributes (1setOf keyword)
    IF NOT one or more 'keyword' values, REJECT/RETURN 'client-error-
       bad-request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    Ignore unsupported values which are the keyword names of
       unsupported attributes.  Don't bother to copy such requested
       (unsupported) attributes to the Unsupported Attribute response
       group since the response will not return them.

Hastings & Manros Informational [Page 22] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 which-jobs (type2 keyword)
    IF NOT a single 'keyword' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NEITHER 'completed' NOR 'not-completed', copy the attribute and
       the unsupported value to the Unsupported Attributes response
       group and REJECT/RETURN 'client-error-attributes-or-values-
       not-supported'.
    Note: a Printer still supports the 'completed' value even if it
       keeps no completed/canceled/aborted jobs:  by returning no jobs
       when so queried.
    IF NOT supplied by the client, the IPP object assumes the 'not-
       completed' value.
 my-jobs (boolean)
    IF NEITHER a single 'true' NOR a single 'false' 'boolean' value,
       REJECT/RETURN 'client-error-bad-request'.
    IF the value length is NOT equal to 1 octet, REJECT/RETURN '
       client-error-request-value-too-long'
    IF NOT supplied by the client, the IPP object assumes the 'false'
       value.
 limit (integer(1:MAX))
    IF NOT a single 'integer' value equal to 4 octets AND in the range
       1 to MAX, REJECT/RETURN 'client-error-bad-request'.
    IF NOT supplied by the client, the IPP object returns all jobs, no
       matter how many.

2.2.1.6 Validate the values of the OPTIONAL Operation attributes

 OPTIONAL Operation attributes are those that an IPP object MAY or MAY
 NOT support.  An IPP object validates the values of the OPTIONAL
 attributes supplied by the client.  The IPP object performs the same
 syntactic validation checks for each OPTIONAL attribute value as in
 Section 2.2.1.5.  As in Section 2.2.1.5, if any fail, the IPP object
 REJECTS the request and RETURNS the 'client-error-bad-request' or the
 'client-error-request-value-too-long' status code.
 In addition, the IPP object checks each Operation attribute value
 against some Printer attribute or some hard-coded value if there is
 no "xxx-supported" Printer attribute defined. If its value is not
 among those supported or is not in the range supported, then the IPP

Hastings & Manros Informational [Page 23] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 object REJECTS the request and RETURNS the error status code
 indicated in the table.  If the value of the Printer object's "xxx-
 supported" attribute is 'no-value' (because the system administrator
 hasn't configured a value), the check always fails.
 If the IPP object doesn't recognize/support an attribute, the IPP
 object treats the attribute as an unknown or unsupported attribute
 (see the last row in the table below).
 document-natural-language (naturalLanguage)
    IF NOT a single non-empty 'naturalLanguage' value, REJECT/RETURN '
       client-error-bad-request'.
    IF the value length is greater than 63 octets, REJECT/RETURN '
       client-error-request-value-too-long'.
    IF NOT a value that the Printer object supports in document
       formats, (no corresponding "xxx-supported" Printer attribute),
       REJECT/RETURN 'client-error-natural-language-not-supported'.
 compression (type3 keyword)
    IF NOT a single 'keyword' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN '
       client-error-request-value-too-long'.
    IF NOT in the Printer object's "compression-supported" attribute,
       copy the attribute and the unsupported value to the Unsupported
       Attributes response group and REJECT/RETURN 'client-error-
       attributes-or-values-not-supported'.
 job-k-octets (integer(0:MAX))
    IF NOT a single 'integer' value equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the range of the Printer object's "job-k-octets-
       supported" attribute, copy the attribute and the unsupported
       value to the Unsupported Attributes response group and
       REJECT/RETURN 'client-error-attributes-or-values-not-
       supported'.
 job-impressions (integer(0:MAX))
    IF NOT a single 'integer' value equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.

Hastings & Manros Informational [Page 24] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    IF NOT in the range of the Printer object's "job-impressions-
       supported" attribute, copy the attribute and the unsupported
       value to the Unsupported Attributes response group and
       REJECT/RETURN 'client-error-attributes-or-values-not-
       supported'.
 job-media-sheets (integer(0:MAX))
    IF NOT a single 'integer' value equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the range of the Printer object's "job-media-sheets-
       supported" attribute, copy the attribute and the unsupported
       value to the Unsupported Attributes response group and
       REJECT/RETURN 'client-error-attributes-or-values-not-
       supported'.
 message (text(127))
    IF NOT a single 'text' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 127 octets,
    REJECT/RETURN 'client-error-request-value-too-long'.
 unknown or unsupported attribute
    IF the attribute syntax supplied by the client is supported but
       the length is not legal for that attribute syntax,
       REJECT/RETURN 'client-error-request-value-too-long'.
    ELSE copy the attribute and value to the Unsupported Attributes
       response group and change the attribute value to the "out-of-
       band" 'unsupported' value, but otherwise ignore the attribute.
    Note: Future Operation attributes may be added to the protocol
    specification that may occur anywhere in the specified group.
    When the operation is otherwise successful, the IPP object returns
    the 'successful-ok-ignored-or-substituted-attributes' status code.
    Ignoring unsupported Operation attributes in all operations is
    analogous to the handling of unsupported Job Template attributes
    in the create and Validate-Job operations when the client supplies
    the "ipp-attribute-fidelity" Operation attribute with the 'false'
    value.  This last rule is so that we can add OPTIONAL Operation
    attributes to future versions of IPP so that older clients can
    inter-work with new IPP objects and newer clients can inter-work
    with older IPP objects.  (If the new attribute cannot be ignored
    without performing unexpectedly, the major version number would

Hastings & Manros Informational [Page 25] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    have been increased in the protocol document and in the request).
    This rule for Operation attributes is independent of the value of
    the "ipp-attribute-fidelity" attribute.   For example, if an IPP
    object doesn't support the OPTIONAL "job-k-octets" attribute', the
    IPP object treats "job-k-octets" as an unknown attribute and only
    checks the length for the 'integer' attribute syntax supplied by
    the client.  If it is not four octets, the IPP object REJECTS the
    request and RETURNS the 'client-error-bad-request' status code,
    else the IPP object copies the attribute to the Unsupported
    Attribute response group, setting the value to the "out-of-band" '
    unsupported' value, but otherwise ignores the attribute.

2.2.2 Suggested Additional Processing Steps for Operations that

    Create/Validate Jobs and Add Documents
 This section in combination with the previous section recommends the
 processing steps for the Print-Job, Validate-Job, Print-URI, Create-
 Job, Send-Document, and Send-URI operations that IPP objects SHOULD
 use.  These are the operations that create jobs, validate a Print-Job
 request, and add documents to a job.

2.2.2.1 Default "ipp-attribute-fidelity" if not supplied

 The Printer object checks to see if the client supplied an "ipp-
 attribute-fidelity" Operation attribute.  If the attribute is not
 supplied by the client, the IPP object assumes that the value is
 'false'.

2.2.2.2 Check that the Printer object is accepting jobs

 If the value of the Printer object's "printer-is-accepting-jobs" is
 'false', the Printer object REJECTS the request and RETURNS the
 'server-error-not-accepting-jobs' status code.

2.2.2.3 Validate the values of the Job Template attributes

 An IPP object validates the values of all Job Template attribute
 supplied by the client.  The IPP object performs the analogous
 syntactic validation checks of each Job Template attribute value that
 it performs for Operation attributes (see Section 2.2.1.5.):
    a)that the length of each value is correct for the attribute
      syntax tag supplied by the client according to [RFC2566] Section
      4.1.
    b)that the attribute syntax tag is correct for that attribute
      according to [RFC2566] Sections 4.2 to 4.4.

Hastings & Manros Informational [Page 26] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    c)that multiple values are supplied only for multi-valued
      attributes, i.e., that are 1setOf  X according to [RFC2566]
      Sections 4.2 to 4.4.
 As in Section 2.2.1.5, if any of these syntactic checks fail, the IPP
 object REJECTS the request and RETURNS the 'client-error-bad-request'
 or 'client-error-request-value-too-long' status code as appropriate,
 independent of the value of the "ipp-attribute-fidelity".  Since such
 an error is most likely to be an error detected by a client
 developer, rather than by an end-user, the IPP object NEED NOT return
 an indication of which attribute had the error in either the
 Unsupported Attributes Group or the Status Message.  The description
 for each of these syntactic checks is explicitly expressed in the
 first IF statement in the following table.
 Each Job Template attribute MUST occur no more than once.  If an IPP
 Printer receives a create request with multiple occurrences of a Job
 Template attribute, it MAY:
    1.reject the operation and return the 'client-error-bad syntax'
      error status code
    2.accept the operation and use the first occurrence of the
      attribute
    3.accept the operation and use the last occurrence of the
      attribute
 depending on implementation.  Therefore, clients MUST NOT supply
 multiple occurrences of the same Job Template attribute in the Job
 Attributes group in the request.

2.2.3 Algorithm for job validation

 The process of validating a Job-Template attribute "xxx" against a
 Printer attribute "xxx-supported" can use the following validation
 algorithm (see section 3.2.1.2 in [RFC2566]).
 To validate the value U of Job-Template attribute "xxx" against the
 value V of Printer "xxx-supported", perform the following algorithm:
    1.If U is multi-valued, validate each value X of U by performing
      the algorithm in Table 3 with each value X. Each validation is
      separate from the standpoint of returning unsupported values.
      Example: If U is "finishings" that the client supplies with
      'staple', 'bind' values, then X takes on the successive values:
      'staple', then 'bind'

Hastings & Manros Informational [Page 27] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    2.If V is multi-valued, validate X against each Z of V by
      performing the algorithm in Table 3 with each value Z.  If a
      value Z validates, the validation for the attribute value X
      succeeds. If it fails, the algorithm is applied to the next
      value Z of V. If there are no more values Z of V, validation
      fails.
      Example: If V is "sides-supported" with values: 'one-sided',
      'two-sided-long', and 'two-sided-short', then Z takes on the
      successive values: 'one-sided', 'two-sided-long', and
      'two-sided-short'.  If the client supplies "sides" with 'two-
      sided-long', the first comparison fails ('one-sided' is not
      equal to 'two-sided-long'), the second comparison succeeds
      ('two-sided-long' is equal to 'two-sided-long"), and the third
      comparison ('two-sided-short' with 'two-sided-long') is not even
      performed.
    3.If both U and V are single-valued, let X be U and Z be V and use
      the validation rules in Table 3.
          Table 3 - Rules for validating single values X against Z
   attribute    attribute       validated if:
   syntax of X  syntax of Z
   integer      rangeOfInteger  X is within the range of
                                 Z
   uri          uriScheme       the uri scheme in X is
                                 equal to Z
   any          boolean         the value of Z is TRUE
   any          any             X and Z are of the same
                                 type and are equal.
 If the value of the Printer object's "xxx-supported" attribute is '
 no-value' (because the system administrator hasn't configured a
 value), the check always fails.  If the check fails, the IPP object
 copies the attribute to the Unsupported Attributes response group
 with its unsupported value.  If the attribute contains more than one
 value, each value is checked and each unsupported value is separately
 copied, while supported values are not copied.  If an IPP object
 doesn't recognize/support a Job Template attribute, i.e., there is no
 corresponding Printer object "xxx-supported" attribute, the IPP
 object treats the attribute as an unknown or unsupported attribute
 (see the last row in the table below).

Hastings & Manros Informational [Page 28] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 If some Job Template attributes are supported for some document
 formats and not for others or the values are different for different
 document formats, the IPP object SHOULD take that into account in
 this validation using the value of the "document-format" supplied by
 the client (or defaulted to the value of the Printer's "document-
 format-default" attribute, if not supplied by the client).  For
 example, if "number-up" is supported for the 'text/plain' document
 format, but not for the 'application/postscript' document format, the
 check SHOULD (though it NEED NOT) depend on the value of the
 "document-format" operation attribute.  See "document-format" in
 [RFC2566] section 3.2.1.1 and 3.2.5.1.
 Note: whether the request is accepted or rejected is determined by
 the value of the "ipp-attribute-fidelity" attribute in a subsequent
 step, so that all Job Template attribute supplied are examined and
 all unsupported attributes and/or values are copied to the
 Unsupported Attributes response group.
 job-priority (integer(1:100))
    IF NOT a single 'integer' value with a length equal to 4 octets,
       REJECT/RETURN 'client-error-bad-request'.
    IF NOT supplied by the client, use the value of the Printer
       object's "job-priority-default" attribute at job submission
       time.
    IF NOT in the range 1 to 100, inclusive, copy the attribute and
       the unsupported value to the Unsupported Attributes response
       group.
    Map the value to the nearest supported value in the range 1:100 as
       specified by the number of discrete values indicated by the
       value of the Printer's "job-priority-supported" attribute.  See
       the formula in [RFC2566] Section 4.2.1.
 job-hold-until (type3 keyword | name)
    IF NOT a single 'keyword' or 'name' value, REJECT/RETURN 'client-
       error-bad-request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT supplied by the client, use the value of the Printer
       object's "job-hold-until" attribute at job submission time.
    IF NOT in the Printer object's "job-hold-until-supported"
       attribute, copy the attribute and the unsupported value to the
       Unsupported Attributes response group.

Hastings & Manros Informational [Page 29] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 job-sheets (type3 keyword | name)
    IF NOT a single 'keyword' or 'name' value, REJECT/RETURN 'client-
       error-bad-request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT in the Printer object's "job-sheets-supported" attribute,
       copy the attribute and the unsupported value to the Unsupported
       Attributes response group.
 multiple-document-handling (type2 keyword)
    IF NOT a single 'keyword' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT in the Printer object's "multiple-document-handling-
       supported" attribute, copy the attribute and the unsupported
       value to the Unsupported Attributes response group.
 copies (integer(1:MAX))
    IF NOT a single 'integer' value with a length equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in range of the Printer object's "copies-supported"
       attribute copy the attribute and the unsupported value to the
       Unsupported
       Attributes response group.
 finishings (1setOf type2 enum)
    IF NOT an 'enum' value(s) each with a length equal to 4 octets,
       REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the Printer object's "finishings-supported" attribute,
       copy the attribute and the unsupported value(s), but not any
       supported values, to the Unsupported Attributes response group.
 page-ranges (1setOf  rangeOfInteger(1:MAX))
    IF NOT a 'rangeOfInteger' value(s) each with a length equal to 8
       octets, REJECT/RETURN 'client-error-bad-request'.
    IF first value is greater than second value in any range, the
       ranges are not in ascending order, or ranges overlap,
       REJECT/RETURN 'client-error-bad-request'.
    IF the value of the Printer object's "page-ranges-supported"
       attribute is 'false', copy the attribute to the Unsupported
       Attributes response group and set the value to the "out-of-
       band" 'unsupported' value.

Hastings & Manros Informational [Page 30] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 sides (type2 keyword)
    IF NOT a single 'keyword' value, REJECT/RETURN 'client-error-bad-
       request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT in the Printer object's "sides-supported" attribute, copy
       the attribute and the unsupported value to the Unsupported
       Attributes response group.
 number-up (integer(1:MAX))
    IF NOT a single 'integer' value with a length equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT a value or in the range of one of the values of the Printer
       object's "number-up-supported" attribute, copy the attribute
       and value to the Unsupported Attribute response group.
 orientation-requested (type2 enum)
    IF NOT a single 'enum' value with a length equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the Printer object's "orientation-requested-supported"
       attribute, copy the attribute and the unsupported value to the
       Unsupported Attributes response group.
 media (type3 keyword | name)
    IF NOT a single 'keyword' or 'name' value, REJECT/RETURN 'client-
       error-bad-request'.
    IF the value length is greater than 255 octets, REJECT/RETURN
       'client-error-request-value-too-long'.
    IF NOT in the Printer object's "media-supported" attribute, copy
       the attribute and the unsupported value to the Unsupported
       Attributes response group.
 printer-resolution (resolution)
    IF NOT a single 'resolution' value with a length equal to 9
       octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the Printer object's "printer-resolution-supported"
       attribute, copy the attribute and the unsupported value to the
       Unsupported Attributes response group.

Hastings & Manros Informational [Page 31] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 print-quality (type2 enum)
    IF NOT a single 'enum' value with a length equal to 4 octets,
    REJECT/RETURN 'client-error-bad-request'.
    IF NOT in the Printer object's "print-quality-supported"
       attribute, copy the attribute and the unsupported value to the
       Unsupported Attributes response group.
 unknown or unsupported attribute (i.e., there is no corresponding
 Printer object "xxx-supported" attribute)
    IF the attribute syntax supplied by the client is supported but
       the length is not legal for that attribute syntax,
    REJECT/RETURN 'client-error-bad-request' if the length of the
       attribute syntax is fixed or 'client-error-request-value-too-
       long' if the length of the attribute syntax is variable.
    ELSE copy the attribute and value to the Unsupported Attributes
       response group and change the attribute value to the "out-of-
       band" 'unsupported' value.  Any remaining Job Template
       Attributes are either unknown or unsupported Job Template
       attributes and are validated algorithmically according to their
       attribute syntax for proper length (see below).
       If the attribute syntax is supported AND the length check
       fails, the IPP object REJECTS the request and RETURNS the '
       client-error-bad-request' if the length of the attribute syntax
       is fixed or the 'client-error-request-value-too-long' status
       code if the length of the attribute syntax is variable.
       Otherwise, the IPP object copies the unsupported Job Template
       attribute to the Unsupported Attributes response group and
       changes the attribute value to the "out-of-band" 'unsupported'
       value.  The following table shows the length checks for all
       attribute syntaxes.  In the following table:  "<=" means less
       than or equal, "=" means equal to:
 Name              Octet length check for read-write attributes
 -----------       --------------------------------------------
 'textWithLanguage    <= 1023 AND 'naturalLanguage'  <= 63
 'textWithoutLanguage' <= 1023
 'nameWithLanguage'    <= 255 AND 'naturalLanguage'  <= 63
 'nameWithoutLanguage' <= 255
 'keyword'             <= 255
 'enum'                = 4
 'uri'                 <= 1023
 'uriScheme'           <= 63
 'charset'             <= 63
 'naturalLanguage'     <= 63
 'mimeMediaType'       <= 255

Hastings & Manros Informational [Page 32] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 'octetString'         <= 1023
 'boolean'             = 1
 'integer'             = 4
 'rangeOfInteger'      = 8
 'dateTime'            = 11
 'resolution'          = 9
 '1setOf  X'

2.2.3.1 Check for conflicting Job Template attributes values

 Once all the Operation and Job Template attributes have been checked
 individually, the Printer object SHOULD check for any conflicting
 values among all the supported values supplied by the client.  For
 example, a Printer object might be able to staple and to print on
 transparencies, however due to physical stapling constraints, the
 Printer object might not be able to staple transparencies. The IPP
 object copies the supported attributes and their conflicting
 attribute values to the Unsupported Attributes response group.  The
 Printer object only copies over those attributes that the Printer
 object either ignores or substitutes in order to resolve the
 conflict, and it returns the original values which were supplied by
 the client.  For example suppose the client supplies "finishings"
 equals 'staple' and "media" equals 'transparency', but the Printer
 object does not support stapling transparencies.  If the Printer
 chooses to ignore the stapling request in order to resolve the
 conflict, the Printer objects returns "finishings" equal to 'staple'
 in the Unsupported Attributes response group.  If any attributes are
 multi-valued, only the conflicting values of the attributes are
 copied.
 Note: The decisions made to resolve the conflict (if there is a
 choice) is implementation dependent.

2.2.3.2 Decide whether to REJECT the request

 If there were any unsupported Job Template attributes or
 unsupported/conflicting Job Template attribute values and the client
 supplied the "ipp-attribute-fidelity" attribute with the 'true'
 value, the Printer object REJECTS the request and return the status
 code:
    (1) 'client-error-conflicting-attributes' status code, if there
        were any conflicts between attributes supplied by the client.
    (2) 'client-error-attributes-or-values-not-supported' status code,
        otherwise.

Hastings & Manros Informational [Page 33] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Note:  Unsupported Operation attributes or values that are returned
 do not affect the status returned in this step.  If the unsupported
 Operation attribute was a serious error, the above already rejected
 the request in a previous step.  If control gets to this step with
 unsupported Operation attributes being returned, they are not serious
 errors.

2.2.3.3 For the Validate-Job operation, RETURN one of the success

        status codes
 If the requested operation is the Validate-Job operation, the Printer
 object returns:
    (1) the "successful-ok" status code, if there are no unsupported
        or conflicting Job Template attributes or values.
    (2) the "successful-ok-conflicting-attributes, if there are any
        conflicting Job Template attribute or values.
    (3) the "successful-ok-ignored-or-substituted-attributes, if there
        are only unsupported Job Template attributes or values.
 Note:  Unsupported Operation attributes or values that are returned
 do not affect the status returned in this step.  If the unsupported
 Operation attribute was a serious error, the above already rejected
 the request in a previous step.  If control gets to this step with
 unsupported Operation attributes being returned, they are not serious
 errors.

2.2.3.4 Create the Job object with attributes to support

 If "ipp-attribute-fidelity" is set to 'false' (or it was not supplied
 by the client), the Printer object:
    (1) creates a Job object, assigns a unique value to the job's
        "job-uri" and "job-id" attributes, and initializes all of the
        job's other supported Job Description attributes.
    (2) removes all unsupported attributes from the Job object.
    (3) for each unsupported value, removes either the unsupported
        value or substitutes the unsupported attribute value with some
        supported value.  If an attribute has no values after removing
        unsupported values from it, the attribute is removed from the
        Job object (so that the normal default behavior at job
        processing time will take place for that attribute).
    (4) for each conflicting value, removes either the conflicting
        value or substitutes the conflicting attribute value with some
        other supported value.  If an attribute has no values after
        removing conflicting values from it, the attribute is removed
        from the Job object (so that the normal default behavior at
        job processing time will take place for that attribute).

Hastings & Manros Informational [Page 34] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 If there were no attributes or values flagged as unsupported, or the
 value of 'ipp-attribute-fidelity" was 'false', the Printer object is
 able to accept the create request and create a new Job object.  If
 the "ipp-attribute-fidelity" attribute is set to 'true', the Job
 Template attributes that populate the new Job object are necessarily
 all the Job Template attributes supplied in the create request.  If
 the "ipp-attribute-fidelity" attribute is set to 'false', the Job
 Template attributes that populate the new Job object are all the
 client supplied Job Template attributes that are supported or that
 have value substitution.  Thus, some of the requested Job Template
 attributes may not appear in the Job object because the Printer
 object did not support those attributes.  The attributes that
 populate the Job object are persistently stored with the Job object
 for that Job.  A Get-Job-Attributes operation on that Job object will
 return only those attributes that are persistently stored with the
 Job object.
 Note: All Job Template attributes that are persistently stored with
 the Job object are intended to be "override values"; that is, they
 that take precedence over whatever other embedded instructions might
 be in the document data itself.  However, it is not possible for all
 Printer objects to realize the semantics of "override".  End users
 may query the Printer's "pdl-override-supported" attribute to
 determine if the Printer either attempts or does not attempt to
 override document data instructions with IPP attributes.
 There are some cases, where a Printer supports a Job Template
 attribute and has an associated default value set for that attribute.
 In the case where a client does not supply the corresponding
 attribute, the Printer does not use its default values to populate
 Job attributes when creating the new Job object; only Job Template
 attributes actually in the create request are used to populate the
 Job object. The Printer's default values are only used later at Job
 processing time if no other IPP attribute or instruction embedded in
 the document data is present.
 Note: If the default values associated with Job Template attributes
 that the client did not supply were to be used to populate the Job
 object, then these values would become "override values" rather than
 defaults.  If the Printer supports the 'attempted' value of the
 "pdl-override-supported" attribute, then these override values could
 replace values specified within the document data.  This is not the
 intent of the default value mechanism. A default value for an
 attribute is used only if the create request did not specify that
 attribute (or it was ignored when allowed by "ipp-attribute-fidelity"
 being 'false') and no value was provided within the content of the
 document data.

Hastings & Manros Informational [Page 35] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 If the client does not supply a value for some Job Template
 attribute, and the Printer does not support that attribute, as far as
 IPP is concerned, the result of processing that Job (with respect to
 the missing attribute) is undefined.

2.2.3.5 Return one of the success status codes

 Once the Job object has been created, the Printer object accepts the
 request and returns to the client:
    (1) the 'successful-ok' status code, if there are no unsupported
        or conflicting Job Template attributes or values.
    (2) the 'successful-ok-conflicting-attributes' status code, if
        there are any conflicting Job Template attribute or values.
    (3) the 'successful-ok-ignored-or-substituted-attributes' status
        code, if there are only unsupported Job Template attributes or
        values.
 Note:  Unsupported Operation attributes or values that are returned
 do not affect the status returned in this step.  If the unsupported
 Operation attribute was a serious error, the above already rejected
 the request in a previous step.  If control gets to this step with
 unsupported Operation attributes being returned, they are not serious
 errors.
 The Printer object also returns Job status attributes that indicate
 the initial state of the Job ('pending', 'pending-held', '
 processing', etc.), etc.  See Print-Job Response, [RFC2566] section
 3.2.1.2.

2.2.3.6 Accept appended Document Content

 The Printer object accepts the appended Document Content data and
 either starts it printing, or spools it for later processing.

2.2.3.7 Scheduling and Starting to Process the Job

 The Printer object uses its own configuration and implementation
 specific algorithms for scheduling the Job in the correct processing
 order.  Once the Printer object begins processing the Job, the
 Printer changes the Job's state to 'processing'. If the Printer
 object supports PDL override (the "pdl-override-supported" attribute
 set to 'attempted'), the implementation does its best to see that IPP
 attributes take precedence over embedded instructions in the document
 data.

Hastings & Manros Informational [Page 36] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.2.3.8 Completing the Job

 The Printer object continues to process the Job until it can move the
 Job into the 'completed' state.  If an Cancel-Job operation is
 received, the implementation eventually moves the Job into the '
 canceled' state.  If the system encounters errors during processing
 that do not allow it to progress the Job into a completed state, the
 implementation halts all processing, cleans up any resources, and
 moves the Job into the 'aborted' state.

2.2.3.9 Destroying the Job after completion

 Once the Job moves to the 'completed', 'aborted', or 'canceled'
 state, it is an implementation decision as to when to destroy the Job
 object and release all associated resources.  Once the Job has been
 destroyed, the Printer would return either the "client-error-not-
 found" or "client-error-gone" status codes for operations directed at
 that Job.
 Note:  the Printer object SHOULD NOT re-use a "job-uri" or "job-id"
 value for a sufficiently long time after a job has been destroyed, so
 that stale references kept by clients are less likely to access the
 wrong (newer) job.

2.2.3.10 Interaction with "ipp-attribute-fidelity"

 Some Printer object implementations may support "ipp-attribute-
 fidelity" set to 'true' and "pdl-override-supported" set to '
 attempted' and yet still not be able to realize exactly what the
 client specifies in the create request.  This is due to legacy
 decisions and assumptions that have been made about the role of job
 instructions embedded within the document data and external job
 instructions that accompany the document data and how to handle
 conflicts between such instructions.  The inability to be 100%
 precise about how a given implementation will behave is also
 compounded by the fact that the two special attributes, "ipp-
 attribute-fidelity" and "pdl-override-supported", apply to the whole
 job rather than specific values for each attribute. For example, some
 implementations may be able to override almost all Job Template
 attributes except for "number-up".

2.3 Status codes returned by operation

 This section lists all status codes once in the first operation
 (Print-Job).  Then it lists the status codes that are different or
 specialized for subsequent operations under each operation.

Hastings & Manros Informational [Page 37] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.3.1 Printer Operations

2.3.1.1 Print-Job

 The Printer object MUST return one of the following "status-code"
 values for the indicated reason.  Whether all of the document data
 has been accepted or not before returning the success or error
 response depends on implementation.  See Section 14 for a more
 complete description of each status code.
 For the following success status codes, the Job object has been
 created and the "job-id", and "job-uri" assigned and returned in the
 response:
    successful-ok:  no request attributes were substituted or ignored.
    successful-ok-ignored-or-substituted-attributes:  some supplied
       (1) attributes were ignored or (2) unsupported attribute
       syntaxes or values were substituted with supported values or
       were ignored.  Unsupported attributes, attribute syntaxes, or
       values MUST be returned in the Unsupported Attributes group of
       the response.
    successful-ok-conflicting-attributes:  some supplied attribute
       values conflicted with the values of other supplied attributes
       and were either substituted or ignored.  Attributes or values
       which conflict with other attributes and have been substituted
       or ignored MUST be returned in the Unsupported Attributes group
       of the response as supplied by the client.
 [RFC2566] section 3.1.6 Operation Status Codes and Messages states:
       If the Printer object supports the "status-message" operation
       attribute, it SHOULD use the REQUIRED 'utf-8' charset to return
       a status message for the following error status codes (see
       section 14):  'client-error-bad-request', 'client-error-
       charset-not-supported', 'server-error-internal-error', '
       server-error-operation-not-supported', and 'server-error-
       version-not-supported'.  In this case, it MUST set the value of
       the "attributes-charset" operation attribute to 'utf-8' in the
       error response.
 For the following error status codes, no job is created and no "job-
 id" or "job-uri" is returned:
    client-error-bad-request:  The request syntax does not conform to
       the specification.

Hastings & Manros Informational [Page 38] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    client-error-forbidden:  The request is being refused for
       authorization or authentication reasons.  The implementation
       security policy is to not reveal whether the failure is one of
       authentication or authorization.
    client-error-not-authenticated:  Either the request requires
       authentication information to be supplied or the authentication
       information is not sufficient for authorization.
    client-error-not-authorized:  The requester is not authorized to
       perform the request on the target object.
    client-error-not-possible:  The request cannot be carried out
       because of the state of the system.  See also 'server-error-
       not-accepting-jobs' status code which MUST take precedence if
       the Printer object's "printer-accepting-jobs" attribute is '
       false'.
    client-error-timeout:  not applicable.
    client-error-not-found:  the target object does not exist.
    client-error-gone:  the target object no longer exists and no
       forwarding address is known.
    client-error-request-entity-too-large:  the size of the request
       and/or print data exceeds the capacity of the IPP Printer to
       process it.
    client-error-request-value-too-long:  the size of request variable
       length attribute values, such as 'text' and 'name' attribute
       syntaxes, exceed the maximum length specified in [RFC2566] for
       the attribute and MUST be returned in the Unsupported
       Attributes Group.
    client-error-document-format-not-supported:  the document format
       supplied is not supported.  The "document-format" attribute
       with the unsupported value MUST be returned in the Unsupported
       Attributes Group.  This error SHOULD take precedence over any
       other 'xxx-not-supported' error, except 'client-error-charset-
       not-supported'.
    client-error-attributes-or-values-not-supported:  one or more
       supplied attributes, attribute syntaxes, or values are not
       supported and the client supplied the "ipp-attributes-fidelity"
       operation attribute with a 'true' value.  They MUST be returned
       in the Unsupported Attributes Group as explained below.
    client-error-uri-scheme-not-supported:  not applicable.
    client-error-charset-not-supported:  the charset supplied in the
       "attributes-charset" operation attribute is not supported.  The
       Printer's "configured-charset" MUST be returned in the response
       as the value of the "attributes-charset" operation attribute
       and used for any 'text' and 'name' attributes returned in the
       error response.  This error SHOULD take precedence over any
       other error, unless the request syntax is so bad that the
       client's supplied "attributes-charset" cannot be determined.

Hastings & Manros Informational [Page 39] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    client-error-conflicting-attributes:  one or more supplied
       attribute va attribute values conflicted with each other and
       the client supplied the "ipp-attributes-fidelity" operation
       attribute with a 'true' value.  They MUST be returned in the
       Unsupported Attributes Group as explained below.
    server-error-internal-error:  an unexpected condition prevents the
       request from being fulfilled.
    server-error-operation-not-supported:  not applicable (since
       Print-Job is REQUIRED).
    server-error-service-unavailable:  the service is temporarily
       overloaded.
    server-error-version-not-supported:  the version in the request is
       not supported.  The "closest" version number supported MUST be
       returned in the response.
    server-error-device-error:  a device error occurred while
       receiving or spooling the request or document data or the IPP
       Printer object can only accept one job at a time.
    server-error-temporary-error:  a temporary error such as a buffer
       full write error, a memory overflow, or a disk full condition
       occurred while receiving the request and/or the document data.
    server-error-not-accepting-jobs:  the Printer object's "printer-
       is-not-accepting-jobs" attribute is 'false'.
    server-error-busy:  the Printer is too busy processing jobs to
       accept another job at this time.
    server-error-job-canceled:  the job has been canceled by an
       operator or the system while the client was transmitting the
       document data.

2.3.1.2 Print-URI

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to Print-URI with the following
 specializations and differences.  See Section 14 for a more complete
 description of each status code.
    server-error-uri-scheme-not-supported:  the URI scheme supplied in
       the "document-uri" operation attribute is not supported and is
       returned in the Unsupported Attributes group.

2.3.1.3 Validate-Job

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to Validate-Job.  See Section 14
 for a more complete description of each status code.

Hastings & Manros Informational [Page 40] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.3.1.4 Create-Job

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to Create-Job with the following
 specializations and differences.  See Section 14 for a more complete
 description of each status code.
    server-error-operation-not-supported:  the Create-Job operation is
       not supported.

2.3.1.5 Get-Printer-Attributes

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to the Get-Printer-Attributes
 operation with the following specializations and differences.   See
 Section 14 for a more complete description of each status code.
 For the following success status codes, the requested attributes are
 returned in Group 3 in the response:
    successful-ok:  no request attributes were substituted or ignored
       (same as Print-Job) and no requested attributes were
       unsupported.
    successful-ok-ignored-or-substituted-attributes:   same as Print-
       Job, except the "requested-attributes" operation attribute MAY,
       but NEED NOT, be returned with the unsupported values.
    successful-ok-conflicting-attributes:  same as Print-Job.
 For the error status codes, Group 3 is returned containing no
 attributes or is not returned at all:
    client-error-not-possible:  Same as Print-Job, in addition the
       Printer object is not accepting any requests.
    client-error-request-entity-too-large:  same as Print-job, except
       that no print data is involved.
    client-error-attributes-or-values-not-supported:  not applicable,
       since unsupported operation attributes MUST be ignored and '
       successful-ok-ignored-or-substituted-attributes' returned.
    client-error-conflicting-attributes:  same as Print-Job, except
       that "ipp-attribute-fidelity" is not involved.
    server-error-operation-not-supported:  not applicable (since Get-
       Printer-Attributes is REQUIRED).
    server-error-device-error:  same as Print-Job, except that no
       document data is involved.
    server-error-temporary-error:  same as Print-Job, except that no
       document data is involved.
    server-error-not-accepting-jobs:  not applicable.

Hastings & Manros Informational [Page 41] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    server-error-busy:  same as Print-Job, except the IPP object is
       too busy to accept even query requests.
    server-error-job-canceled:  not applicable.

2.3.1.6 Get-Jobs

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to the Get-Jobs operation with the
 following specializations and differences.   See Section 14 for a
 more complete description of each status code.
 For the following success status codes, the requested attributes are
 returned in Group 3 in the response:
    successful-ok:  no request attributes were substituted or ignored
       (same as Print-Job) and no requested attributes were
       unsupported.
    successful-ok-ignored-or-substituted-attributes:   same as Print-
       Job, except the "requested-attributes" operation attribute MAY,
       but NEED NOT, be returned with the unsupported values.
    successful-ok-conflicting-attributes:  same as Print-Job.
 For any error status codes, Group 3 is returned containing no
 attributes or is not returned at all.  The following brief error
 status code descriptions contain unique information for use with
 Get-Jobs operation.  See section 14 for the other error status codes
 that apply uniformly to all operations:
    client-error-not-possible:  Same as Print-Job, in addition the
       Printer object is not accepting any requests.
    client-error-request-entity-too-large:  same as Print-job, except
       that no print data is involved.
    client-error-document-format-not-supported:  not applicable.
    client-error-attributes-or-values-not-supported:  not applicable,
       since unsupported operation attributes MUST be ignored and '
       successful-ok-ignored-or-substituted-attributes' returned.
    client-error-conflicting-attributes:  same as Print-Job, except
       that "ipp-attribute-fidelity" is not involved.
    server-error-operation-not-supported:  not applicable (since Get-
       Jobs is REQUIRED).
    server-error-device-error:  same as Print-Job, except that no
       document data is involved.
    server-error-temporary-error:  same as Print-Job, except that no
       document data is involved.
    server-error-not-accepting-jobs:  not applicable.
    server-error-job-canceled:  not applicable.

Hastings & Manros Informational [Page 42] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.3.2 Job Operations

2.3.2.1 Send-Document

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to the Get-Printer-Attributes
 operation with the following specializations and differences.   See
 Section 14 for a more complete description of each status code.
 For the following success status codes, the document has been added
 to the specified Job object and the job's "number-of-documents"
 attribute has been incremented:
    successful-ok:  no request attributes were substituted or ignored
       (same as Print-Job).
    successful-ok-ignored-or-substituted-attributes:  same as Print-
       Job.
    successful-ok-conflicting-attributes:  same as Print-Job.
 For the error status codes, no document has been added to the Job
 object and the job's "number-of-documents" attribute has not been
 incremented:
    client-error-not-possible: Same as Print-Job, except that the
       Printer's "printer-is-accepting-jobs" attribute is not
       involved, so that the client is able to finish submitting a
       multi-document job after this attribute has been set to 'true'.
       Another condition is that the state of the job precludes Send-
       Document, i.e., the job has already been closed out by the
       client.  However, if the IPP Printer closed out the job due to
       timeout, the 'client-error-timeout' error status SHOULD  be
       returned instead.
    client-error-timeout:  This request was sent after the Printer
       closed the job, because it has not received a Send-Document or
       Send-URI operation within the Printer's "multiple-operation-
       time-out" period.
    client-error-request-entity-too-large:  same as Print-Job.
    client-error-conflicting-attributes:  same as Print-Job, except
       that "ipp-attributes-fidelity" operation attribute is not
       involved.
    server-error-operation-not-supported:  the Send-Document request
       is not supported.
    server-error-not-accepting-jobs:  not applicable.
    server-error-job-canceled:  the job has been canceled by an
       operator or the system while the client was transmitting the
       data.

Hastings & Manros Informational [Page 43] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.3.2.2 Send-URI

 All of the Print-Job status code descriptions in Section 3.2.1.2
 Print-Job Response with the specializations described for Send-
 Document are applicable to Send-URI.  See Section 14 for a more
 complete description of each status code.
    server-error-uri-scheme-not-supported:  the URI scheme supplied in
       the "document-uri" operation attribute is not supported and the
       "document-uri" attribute MUST be returned in the Unsupported
       Attributes group.

2.3.2.3 Cancel-Job

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to Cancel-Job with the following
 specializations and differences.  See Section 14 for a more complete
 description of each status code.
 For the following success status codes, the Job object is being
 canceled or has been canceled:
    successful-ok:  no request attributes were substituted or ignored
       (same as Print-Job).
    successful-ok-ignored-or-substituted-attributes:   same as Print-
       Job.
    successful-ok-conflicting-attributes:  same as Print-Job.
 For any of the error status codes, the Job object has not been
 canceled or was previously canceled.
    client-error-not-possible:  The request cannot be carried out
       because of the state of the Job object ('completed', '
       canceled', or 'aborted') or the state of the system.
    client-error-not-found:  the target Printer and/or Job object does
       not exist.
    client-error-gone:  the target Printer and/or Job object no longer
       exists and no forwarding address is known.
    client-error-request-entity-too-large:  same as Print-Job, except
       no document data is involved.
    client-error-document-format-not-supported:  not applicable.
    client-error-attributes-or-values-not-supported:  not applicable,
       since unsupported operation attributes and values MUST be
       ignored.
    client-error-conflicting-attributes:  same as Print-Job, except
       that the Printer's "printer-is-accepting-jobs" attribute is not
       involved.

Hastings & Manros Informational [Page 44] RFC 2639 IPP/1.0: Implementer's Guide July 1999

    server-error-operation-not-supported:  not applicable (Cancel-Job
       is REQUIRED).
    server-error-device-error:  same as Print-Job, except no document
       data is involved.
    server-error-temporary-error:  same as Print-Job, except no
       document data is involved.
    server-error-not-accepting-jobs:  not applicable.
    server-error-job-canceled:  not applicable.

2.3.2.4 Get-Job-Attributes

 All of the Print-Job status codes described in Section 3.2.1.2
 Print-Job Response are applicable to Get-Job-Attributes with the
 following specializations and differences.  See Section 14 for a more
 complete description of each status code.
 For the following success status codes, the requested attributes are
 returned in Group 3 in the response:
    successful-ok:  no request attributes were substituted or ignored
       (same as Print-Job) and no requested attributes were
       unsupported.
    successful-ok-ignored-or-substituted-attributes:   same as Print-
       Job, except the "requested-attributes" operation attribute MAY,
       but NEED NOT, be returned with the unsupported values.
    successful-ok-conflicting-attributes:  same as Print-Job.
 For the error status codes, Group 3 is returned containing no
 attributes or is not returned at all.
    client-error-not-possible:  Same as Print-Job, in addition the
       Printer object is not accepting any requests.
    client-error-document-format-not-supported:  not applicable.
    client-error-attributes-or-values-not-supported:  not applicable.
    client-error-uri-scheme-not-supported:  not applicable.
    client-error-conflicting-attributes:  not applicable
    server-error-operation-not-supported:  not applicable (since Get-
       Job-Attributes is REQUIRED).
    server-error-device-error:  same as Print-Job, except no document
       data is involved.
    server-error-temporary-error:  sane as Print-Job, except no
       document data is involved.
    server-error-not-accepting-jobs:  not applicable.  server-error-
    job-canceled:  not applicable.

Hastings & Manros Informational [Page 45] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.4 Validate-Job

 The Validate-Job operation has been designed so that its
 implementation may be a part of the Print-Job operation.  Therefore,
 requiring Validate-Job is not a burden on implementers.  Also it is
 useful for client's to be able to count on its presence in all
 conformance implementations, so that the client can determine before
 sending a long document, whether the job will be accepted by the IPP
 Printer or not.

2.5 Case Sensitivity in URIs

 IPP client and server implementations must be aware of the diverse
 uppercase/lowercase nature of URIs.  RFC 2396 defines URL schemes and
 Host names as case insensitive but reminds us that the rest of the
 URL may well demonstrate case sensitivity.  When creating URL's for
 fields where the choice is completely arbitrary, it is probably best
 to select lower case.  However, this cannot be guaranteed and
 implementations MUST NOT rely on any fields being case-sensitive or
 case-insensitive in the URL beyond the URL scheme and host name
 fields.
 The reason that the IPP specification does not make any restrictions
 on URIs, is so that implementations of IPP may use off-the-shelf
 components that conform to the standards that define URIs, such as
 RFC 2396 and the HTTP/1.1 specifications [RFC2068].  See these
 specifications for rules of matching, comparison, and case-
 sensitivity.
 It is also recommended that System Administrators and implementations
 avoid creating URLs for different printers that differ only in their
 case.  For example, don't have Printer1 and printer1 as two different
 IPP Printers.
 The HTTP/1.1 specification [RFC2068] contains more details on
 comparing URLs.

2.6 Character Sets, natural languages, and internationalization

 This section discusses character set support, natural language
 support and internationalization.

2.6.1 Character set code conversion support

 IPP clients and IPP objects are REQUIRED to support UTF-8.  They MAY
 support additional charsets.  It is RECOMMENDED that an IPP object
 also support US-ASCII, since many clients support US-ASCII, and
 indicate that UTF-8 and US-ASCII are supported by populating the

Hastings & Manros Informational [Page 46] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Printer's "charset-supported" with 'utf-8' and 'us-ascii' values.  An
 IPP object is required to code covert with as little loss as possible
 between the charsets that it supports, as indicated in the Printer's
 "charsets-supported" attribute.
 How should the server handle the situation where the "attributes-
 charset" of the response itself is "us-ascii", but one or more
 attributes in that response is in the "utf-8" format?
 Example:  Consider a case where a client sends a Print-Job request
 with "utf-8" as the value of "attributes-charset" and with the "job-
 name" attribute supplied.  Later another client submits a Get-Job-
 Attribute or Get-Jobs request.  This second request contains the
 "attributes-charset" with value "us-ascii" and "requested-attributes"
 attribute with exactly one value "job-name".
 According to the RFC2566 document (section 3.1.4.2), the value of the
 "attributes-charset" for the response of the second request must be
 "us-ascii" since that is the charset specified in the request.  The
 "job-name" value, however, is in "utf-8" format.  Should the request
 be rejected even though both "utf-8" and "us-ascii" charsets are
 supported by the server? or should the "job-name" value be converted
 to "us-ascii" and return "successful-ok-conflicting-attributes"
 (0x0002) as the status code?
 Answer:  An IPP object that supports both utf-8 (REQUIRED) and us-
 ascii, the second paragraph of section 3.1.4.2 applies so that the
 IPP object MUST accept the request, perform code set conversion
 between these two charsets with "the highest fidelity possible" and
 return 'successful-ok', rather than a warning 'successful-ok-
 conflicting-attributes, or an error.  The printer will do the best it
 can to convert between each of the character sets that it supports--
 even if that means providing a string of question marks because none
 of the characters are representable in US ASCII.  If it can't perform
 such conversion, it MUST NOT advertise us-ascii as a value of its
 "attributes-charset-supported" and MUST reject any request that
 requests 'us-ascii'.
 One IPP object implementation strategy is to convert all request text
 and name values to a Unicode internal representation.  This is 16-bit
 and virtually universal.  Then convert to the specified operation
 attributes-charset on output.
 Also it would be smarter for a client to ask for 'utf-8', rather than
 'us-ascii' and throw away characters that it doesn't understand,
 rather than depending on the code conversion of the IPP object.

Hastings & Manros Informational [Page 47] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.6.2 What charset to return when an unsupported charset is requested?

 Section 3.1.4.1 Request Operation attributes was clarified in
 November 1998 as follows:
    All clients and IPP objects MUST support the 'utf-8' charset
    [RFC2044] and MAY support additional charsets provided that they
    are registered with IANA [IANA-CS].  If the Printer object does
    not support the client supplied charset value, the Printer object
    MUST reject the request, set the "attributes-charset" to 'utf-8'
    in the response, and return the 'client-error-charset-not-
    supported' status code and any 'text' or 'name' attributes using
    the 'utf-8' charset.
 Since the client and IPP object MUST support UTF-8, returning any
 text or name attributes in UTF-8 when the client requests a charset
 that is not supported should allow the client to display the text or
 name.
 Since such an error is a client error, rather than a user error, the
 client should check the status code first so that it can avoid
 displaying any other returned 'text' and 'name' attributes that are
 not in the charset requested.
 Furthermore, [RFC2566] section 14.1.4.14 client-error-charset-not-
 supported (0x040D) was clarified in November 1998 as follows:
    For any operation, if the IPP Printer does not support the charset
    supplied by the client in the "attributes-charset" operation
    attribute, the Printer MUST reject the operation and return this
    status and any 'text' or 'name' attributes using the 'utf-8'
    charset (see Section 3.1.4.1).

2.6.3 Natural Language Override (NLO)

 The 'text' and 'name' attributes each have two forms.  One has an
 implicit natural language, and the other has an explicit natural
 language.  The 'textWithoutLanguage' and 'textWithoutLanguage' are
 the two 'text' forms.  The 'nameWithoutLanguage" and '
 nameWithLanguage are the two 'name' forms.  If a receiver (IPP object
 or IPP client) supports an attribute with attribute syntax 'text', it
 MUST support both forms in a request and a response.  A sender (IPP
 client or IPP object) MAY send either form for any such attribute.
 When a sender sends a WithoutLanguage form, the implicit natural
 language is specified in the "attributes-natural-language" operation
 attribute which all senders MUST include in every request and
 response.

Hastings & Manros Informational [Page 48] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 When a sender sends a WithLanguage form, it MAY be different from the
 implicit natural language supplied by the sender or it MAY be the
 same.  The receiver MUST treat either form equivalently.
 There is an implementation decision for senders, whether to always
 send the WithLanguage forms or use the WithoutLanguage form when the
 attribute's natural language is the same as the request or response.
 The former approach makes the sender implementation simpler.  The
 latter approach is more efficient on the wire and allows inter-
 working with non-conforming receivers that fail to support the
 WithLanguage forms.  As each approach have advantages, the choice is
 completely up to the implementer of the sender.
 Furthermore, when a client receives a 'text' or 'name' job attribute
 that it had previously supplied, that client MUST NOT expect to see
 the attribute in the same form, i.e., in the same WithoutLanguage or
 WithLanguage form as the client supplied when it created the job.
 The IPP object is free to transform the attribute from the
 WithLanguage form to the WithoutLanguage form and vice versa, as long
 as the natural language is preserved.  However, in order to meet this
 latter requirement, it is usually simpler for the IPP object
 implementation to store the natural language explicitly with the
 attribute value, i.e., to store using an internal representation that
 resembles the WithLanguage form.
 The IPP Printer MUST copy the natural language of a job, i.e., the
 value of the "attributes-natural-language" operation attribute
 supplied by the client in the create operation, to the Job object as
 a Job Description attribute, so that a client is able to query it.
 In returning a Get-Job-Attributes response, the IPP object MAY return
 one of three natural language values in the response's "attributes-
 natural-language" operation attribute: (1) that requested by the
 requester, (2) the natural language of the job, or (3) the configured
 natural language of the IPP Printer, if the requested language is not
 supported by the IPP Printer.
 This "attributes-natural-language" Job Description attribute is
 useful for an IPP object implementation that prints start sheets in
 the language of the user who submitted the job.  This same Job
 Description attribute is useful to a multi-lingual operator who has
 to communicate with different job submitters in different natural
 languages.  This same Job Description attribute is expected to be
 used in the future to generate notification messages in the natural
 language of the job submitter.
 Early drafts of [RFC2566] contained a job-level natural language
 override (NLO) for the Get-Jobs response.  A job-level (NLO) is an
 (unrequested) Job Attribute which then specified the implicit natural

Hastings & Manros Informational [Page 49] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 language for any other WithoutLanguage job attributes returned in the
 response for that job.  Interoperability testing of early
 implementations showed that no one was implementing the job-level NLO
 in Get-Job responses.  So the job-level NLO was eliminated from the
 Get- Jobs response.  This simplification makes all requests and
 responses consistent in that the implicit natural language for any
 WithoutLanguage 'text' or 'name' form is always supplied in the
 request's or response's "attributes-natural-language" operation
 attribute.

2.7 The "queued-job-count" Printer Description attribute

2.7.1 Why is "queued-job-count" RECOMMENDED?

 The reason that "queued-job-count" is RECOMMENDED, is that some
 clients look at that attribute alone when summarizing the status of a
 list of printers, instead of doing a Get-Jobs to determine the number
 of jobs in the queue.  Implementations that fail to support the
 "queued-job-count" will cause that client to display 0 jobs when
 there are actually queued jobs.
 We would have made it a REQUIRED Printer attribute, but some
 implementations had already been completed before the issue was
 raised, so making it a SHOULD was a compromise.

2.7.2 Is "queued-job-count" a good measure of how busy a printer is?

 The "queued-job-count" is not a good measure of how busy the printer
 is when there are held jobs.  A future registration could be to add a
 "held-job-count" (or an "active-job-count") Printer Description
 attribute if experience shows that such an attribute (combination) is
 needed to quickly indicate how busy a printer really is.

2.8 Sending empty attribute groups

 The [RFC2566] and [RFC2565] specifications RECOMMEND that a sender
 not send an empty attribute group in a request or a response.
 However, they REQUIRE a receiver to accept an empty attribute group
 as equivalent to the omission of that group.  So a client SHOULD omit
 the Job Template Attributes group entirely in a create operation that
 is not supplying any Job Template attributes.  Similarly, an IPP
 object SHOULD omit an empty Unsupported Attributes group if there are
 no unsupported attributes to be returned in a response.

Hastings & Manros Informational [Page 50] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 The [RFC2565] specification REQUIRES a receiver to be able to receive
 either an empty attribute group or an omitted attribute group and
 treat them equivalently.  The term "receiver" means an IPP object for
 a request and a client for a response.  The term "sender' means a
 client for a request and an IPP object for a response.
 There is an exception to the rule for Get-Jobs when there are no
 attributes to be returned.  [RFC2565] contains the following
 paragraph:
    The syntax allows an xxx-attributes-tag to be present when the
    xxx-attribute-sequence that follows is empty. The syntax is
    defined this way to allow for the response of Get-Jobs where no
    attributes are returned for some job-objects.  Although it is
    RECOMMENDED that the sender not send an xxx-attributes-tag if
    there are no attributes (except in the Get-Jobs response just
    mentioned), the receiver MUST be able to decode such syntax.

2.9 Returning unsupported attributes in Get-Xxxx responses

 In the Get-Printer-Attributes, Get-Jobs, or Get-Job-Attributes
 responses, the client cannot depend on getting unsupported attributes
 returned in the Unsupported Attributes group that the client
 requested, but are not supported by the IPP object.  However, such
 unsupported requested attributes will not be returned in the Job
 Attributes or Printer Attributes group (since they are unsupported).
 Furthermore, the IPP object is REQUIRED to return the 'successful-
 ok-ignored-or-substituted-attributes' status code, so that the client
 knows that not all that was requested has been returned.

2.10 Returning job-state in Print-Job response

 An IPP client submits a small job via Print-Job.  By the time the IPP
 printer/print server is putting together a response to the operation,
 the job has finished printing and been removed as an object from the
 print system.  What should the job-state be in the response?
 The Model suggests that the Printer return a response before it even
 accepts the document content.  The Job Object Attributes are returned
 only if the IPP object returns one of the success status codes. Then
 the job-state would always be "pending" or "pending-held".
 This issue comes up for the implementation of an IPP Printer object
 as a server that forwards jobs to devices that do not provide job
 status back to the server.  If the server is reasonably certain that
 the job completed successfully, then it should return the job-state
 as 'completed'.  Also the server can keep the job in its "job
 history" long after the job is no longer in the device.  Then a user

Hastings & Manros Informational [Page 51] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 could query the server and see that the job was in the 'completed'
 state and completed as specified by the job's "time-at-completed"
 time which would be the same as the server submitted the job to the
 device.
 An alternative is for the server to respond to the client before or
 while sending the job to the device, instead of waiting until the
 server has finished sending the job to the device.  In this case, the
 server can return the job's state as 'pending' with the 'job-
 outgoing' value in the job's "job-state-reasons" attribute.
 If the server doesn't know for sure whether the job completed
 successfully (or at all), it could return the (out-of-band) 'unknown'
 value.
 On the other hand, if the server is able to query the device and/or
 setup some sort of event notification that the device initiates when
 the job makes state transitions, then the server can return the
 current job state in the Print-Job response and in subsequent queries
 because the server knows what the job state is in the device (or can
 query the device).
 All of these alternatives depend on implementation of the server and
 the device.

2.11 Flow controlling the data portion of a Print-Job request

 A paused printer (or one that is stopped due to paper out or jam or
 spool space full or buffer space full, may flow control the data of a
 Print-Job operation (at the TCP/IP layer), so that the client is not
 able to send all the document data.  Consequently, the Printer will
 not return a response until the condition is changed.
 The Printer should not return a Print-Job response with an error code
 in any of these conditions, since either the printer will be resumed
 and/or the condition will be freed either by human intervention or as
 jobs print.
 In writing test scripts to test IPP Printers, the script must also be
 written not to expect a response, if the printer has been paused,
 until the printer is resumed, in order to work with all possible
 implementations.

2.12 Multi-valued attributes

 What is the attribute syntax for a multi-valued attribute?  Since
 some attributes support values in more than one data type, such as
 "media", "job-hold-until", and "job-sheets", IPP semantics associate

Hastings & Manros Informational [Page 52] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 the attribute syntax with each value, not with the attribute as a
 whole.  The protocol associates the attribute syntax tag with each
 value.  Don't be fooled, just because the attribute syntax tag comes
 before the attribute keyword.  All attribute values after the first
 have a zero length attribute keyword as the indication of a
 subsequent value of the same attribute.

2.13 Querying jobs with IPP that were submitted using other job

   submission protocols
 The following clarification was added to [RFC2566] section 8.5:
    8.5 Queries on jobs submitted using non-IPP protocols
    If the device that an IPP Printer is representing is able to
    accept jobs using other job submission protocols in addition to
    IPP, it is RECOMMEND that such an implementation at least allow
    such "foreign" jobs to be queried using Get-Jobs returning "job-
    id" and "job-uri" as 'unknown'.  Such an implementation NEED NOT
    support all of the same IPP job attributes as for IPP jobs.  The
    IPP object returns the 'unknown' out-of-band value for any
    requested attribute of a foreign job that is supported for IPP
    jobs, but not for foreign jobs.
    It is further RECOMMENDED, that the IPP Printer generate "job-id"
    and "job-uri" values for such "foreign jobs", if possible, so that
    they may be targets of other IPP operations, such as Get-Job-
    Attributes and Cancel-Job.  Such an implementation also needs to
    deal with the problem of authentication of such foreign jobs.  One
    approach would be to treat all such foreign jobs as belonging to
    users other than the user of the IPP client.  Another approach
    would be for the foreign job to belong to 'anonymous'.  Only if
    the IPP client has been authenticated as an operator or
    administrator of the IPP Printer object, could the foreign jobs be
    queried by an IPP request.  Alternatively, if the security policy
    is to allow users to query other users' jobs, then the foreign
    jobs would also be visible to an end-user IPP client using Get-
    Jobs and Get-Job-Attributes.
 Thus IPP MAY be implemented as a "universal" protocol that provides
 access to jobs submitted with any job submission protocol.  As IPP
 becomes widely implemented, providing a more universal access makes
 sense.

Hastings & Manros Informational [Page 53] RFC 2639 IPP/1.0: Implementer's Guide July 1999

2.14 The 'none' value for empty sets

 [RFC2566] states that the 'none' value should be used as the value of
 a 1SetOf when the set is empty. In most cases, sets that are
 potentially empty contain keywords so the keyword 'none' is used, but
 for the 3 finishings attributes, the values are enums and thus the
 empty set is represented by the enum 3.  Currently there are no other
 attributes with 1SetOf values which can be empty and can contain
 values that are not keywords.  This exception requires special code
 and is a potential place for bugs.  It would have been better if we
 had chosen an out-of-band value, either "no-value" or some new value,
 such as 'none'.  Since we didn't, implementations have to deal with
 the different representations of 'none', depending on the attribute
 syntax.

2.15 Get-Jobs, my-jobs='true', and 'requesting-user-name'?

 In [RFC2566] section 3.2.6.1 'Get-Jobs Request', if the attribute '
 my-jobs' is present and set to TRUE, MUST the 'requesting-user-name'
 attribute be there to, and if it's not present what should the IPP
 printer do?
 [RFC2566] Section 8.3 describes the various cases of "requesting-
 user-name" being present or not for any operation.  If the client
 does not supply a value for "requesting-user-name", the printer MUST
 assume that the client is supplying some anonymous name, such as
 "anonymous".

2.16 The "multiple-document-handling" Job Template attribute and support

   of multiple document jobs
 ISSUE:  IPP/1.0 is silent on which of the four effects an
 implementation would perform if it supports Create-Job, but does not
 support "multiple-document-handling".
 A fix to IPP/1.0 would be to require implementing all four values of
 "multiple-document-handling" if Create-Job is supported at all.  Or
 at least 'single-document-new-sheet' and 'separate-documents-
 uncollated-copies'.  In any case, an implementation that supports
 Create-Job SHOULD also support "multiple-document-handling".  Support
 for all four values is RECOMMENDED, but at least the 'single-
 document-new-sheet' and 'separate-documents-uncollated-copies'
 values, along with the "multiple-document-handling-default"
 indicating the default behavior and "multiple-document-handling-
 supported" values.  If an implementation spools the data, it should
 also support the 'separate-documents-collated-copies' value as well.

Hastings & Manros Informational [Page 54] RFC 2639 IPP/1.0: Implementer's Guide July 1999

3 Encoding and Transport

 This section discusses various aspects of IPP/1.0 Encoding and
 Transport [RFC2565].
 A server is not required to send a response until after it has
 received the client.s entire request.  Hence, a client must not
 expect a response until after it has sent the entire request.
 However, we recommend that the server return a response as soon as
 possible if an error is detected while the client is still sending
 the data, rather than waiting until all of the data is received.
 Therefore, we also recommend that a client listen for an error
 response that an IPP server MAY send before it receives all the data.
 In this case a client, if chunking the data, can send a premature
 zero-length chunk to end the request before sending all the data (and
 so the client can keep the connection open for other requests, rather
 than closing it). If the request is blocked for some reason, a client
 MAY determine the reason by opening another connection to query the
 server using Get-Printer-Attributes.
 In the following sections, there are a tables of all HTTP headers
 which describe their use in an IPP client or server.  The following
 is an explanation of each column in these tables.
  1. the .header. column contains the name of a header.
  2. the .request/client. column indicates whether a client sends the

header.

  1. the .request/ server. column indicates whether a server supports

the header when received.

  1. the .response/ server. column indicates whether a server sends

the header.

  1. the .response /client. column indicates whether a client

supports the header when received.

  1. the .values and conditions. column specifies the allowed header

values and the conditions for the header to be present in a

      request/response.
 The table for .request headers. does not have columns for responses,
 and the table for .response headers. does not have columns for
 requests.
 The following is an explanation of the values in the .request/client.
 and .response/ server. columns.
  1. must: the client or server MUST send the header,
  2. must-if: the client or server MUST send the header when the

condition described in the .values and conditions. column is

      met,

Hastings & Manros Informational [Page 55] RFC 2639 IPP/1.0: Implementer's Guide July 1999

  1. may: the client or server MAY send the header
  2. not: the client or server SHOULD NOT send the header. It is not

relevant to an IPP implementation.

 The following is an explanation of the values in the
 .response/client.  and .request/ server. columns.
  1. must: the client or server MUST support the header,
  2. may: the client or server MAY support the header
  3. not: the client or server SHOULD NOT support the header. It is

not relevant to an IPP implementation.

3.1 General Headers

 The following is a table for the general headers.
 General-     Request         Response       Values and Conditions
 Header
              Client  Server Server Client
 Cache-       must    not    must   not     .no-cache. only
 Control
 Connection   must-if must   must-  must    .close. only. Both
                              if             client and server
                                              SHOULD keep a
                                              connection for the
                                              duration of a sequence
                                              of operations. The
                                              client and server MUST
                                              include this header
                                              for the last operation
                                              in such a sequence.
 Date         may     may    must   may     per RFC 1123 [RFC1123]
                                              from RFC 2068
                                              [RFC2068]
 Pragma       must    not    must   not     .no-cache. only
 Transfer-    must-if must   must-  must    .chunked. only .
 Encoding                     if             Header MUST be present
                                              if Content-Length is
                                              absent.

Hastings & Manros Informational [Page 56] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Upgrade      not     not    not    not
 Via          not     not    not    not

3.2 Request Headers

 The following is a table for the request headers.
 Request-Header   Client   Server  Request Values and Conditions
 Accept           may      must    .application/ipp. only.  This
                                    value is the default if the
 Request-Header   Client   Server  Request Values and Conditions
                                    client omits it
 Accept-Charset   not      not      Charset information is within
                                    the application/ipp entity
 Accept-Encoding  may      must    empty and per RFC 2068 [RFC2068]
                                    and IANA registry for content-
                                    codings
 Accept-Language  not      not     language information is within
                                    the application/ipp entity
 Authorization    must-if  must    per RFC 2068. A client MUST send
                                    this header when it receives a
                                    401 .Unauthorized. response and
                                    does not receive a  .Proxy-
                                    Authenticate. header.
 From             not      not     per RFC 2068. Because RFC
                                    recommends sending this header
                                    only with the user.s approval, it
                                    is not very useful
 Host             must     must    per RFC 2068
 If-Match         not      not
 If-Modified-     not      not
 Since
 If-None-Match    not      not

Hastings & Manros Informational [Page 57] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 If-Range         not      not
 If-Unmodified-   not      not
 Since
 Max-Forwards     not      not
 Proxy-           must-if  not     per RFC 2068. A client MUST send
 Authorization                      this header when it receives a
                                    401 .Unauthorized. response and a
                                    .Proxy-Authenticate. header.
 Range            not      not
 Referer          not      not
 User-Agent       not      not

3.3 Response Headers

 The following is a table for the request headers.
 Response-      Server  Client  Response Values and Conditions
 Header
 Accept-Ranges  not     not
 Age            not     not
 Location       must-if may     per RFC 2068. When URI needs
                                 redirection.
 Proxy-         not     must    per RFC 2068
 Authenticate
 Public         may     may     per RFC 2068
 Retry-After    may     may     per RFC 2068
 Server         not     not
 Vary           not     not
 Warning        may     may     per RFC 2068

Hastings & Manros Informational [Page 58] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 WWW-           must-if must    per RFC 2068. When a server needs to
 Authenticate                    authenticate a client.

3.4 Entity Headers

 The following is a table for the entity headers.
 Entity-Header  Request         Response        Values and Conditions
                Client  Server Server  Client
 Allow          not     not    not     not
 Content-Base   not     not    not     not
 Content-       may     must   must    must   per RFC 2068 and IANA
 Encoding                                       registry for content
                                                codings.
 Content-       not     not    not     not    Application/ipp
 Language                                       handles language
 Content-       must-if must   must-if must   the length of the
 Length                                         message-body per RFC
                                                2068. Header MUST be
                                                present if Transfer-
 Entity-Header  Request         Response        Values and Conditions
                Client  Server Server  Client
                                                Encoding is absent.
 Content-       not     not    not     not
 Location
 Content-MD5    may     may    may     may    per RFC 2068
 Content-Range  not     not    not     not
 Content-Type   must    must   must    must   .application/ipp.
                                                only
 ETag           not     not    not     not
 Expires        not     not    not     not

Hastings & Manros Informational [Page 59] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Last-Modified  not     not    not     not

3.5 Optional support for HTTP/1.0

 IPP implementations consist of an HTTP layer and an IPP layer.  In
 the following discussion, the term "client" refers to the HTTP client
 layer and the term "server" refers to the HTTP server layer.  The
 Encoding and Transport document [RFC2565] requires that HTTP 1.1 MUST
 be supported by all clients and all servers.  However, a client
 and/or a server implementation may choose to also support HTTP 1.0.
  1. This option means that a server may choose to communicate with a

(non-conforming) client that only supports HTTP 1.0. In such cases

   the server should not use any HTTP 1.1 specific parameters or
   features and should respond using HTTP version number 1.0.
  1. This option also means that a client may choose to communicate with

a (non-conforming) server that only supports HTTP 1.0. In such

   cases, if the server responds with an HTTP .unsupported version
   number. to an HTTP 1.1 request, the client should retry using HTTP
   version number 1.0.

3.6 HTTP/1.1 Chunking

3.6.1 Disabling IPP Server Response Chunking

 Clients MUST anticipate that the HTTP/1.1 server may chunk responses
 and MUST accept them in responses.  However, a (non-conforming) HTTP
 client that is unable to accept chunked responses may attempt to
 request an HTTP 1.1 server not to use chunking in its response to an
 operation by using the following HTTP header:
      TE: identity
 This mechanism should not be used by a server to disable a client
 from chunking a request, since chunking of document data is an
 important feature for clients to send long documents.

3.6.2 Warning About the Support of Chunked Requests

 This section describes some problems with the use of chunked requests
 and HTTP/1.1 servers.
 The HTTP/1.1 standard [HTTP] requires that conforming servers support
 chunked requests for any method.  However, in spite of this
 requirement, some HTTP/1.1 implementations support chunked responses
 in the GET method, but do not support chunked POST method requests.

Hastings & Manros Informational [Page 60] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 Some HTTP/1.1 implementations that support CGI scripts [CGI] and/or
 servlets [Servlet] require that the client supply a Content-Length.
 These implementations might reject a chunked POST method and return a
 411 status code (Length Required), might attempt to buffer the
 request and run out of room returning a 413 status code (Request
 Entity Too Large), or might successfully accept the chunked request.
 Because of this lack of conformance of HTTP servers to the HTTP/1.1
 standard, the IPP standard [RFC2565] REQUIRES that a conforming IPP
 Printer object implementation support chunked requests and that
 conforming clients accept chunked responses.  Therefore, IPP object
 implementers are warned to seek HTTP server implementations that
 support chunked POST requests in order to conform to the IPP standard
 and/or use implementation techniques that support chunked POST
 requests.

4 References

 [CGI]     Coar, K. and D. Robinson, "The WWW Common Gateway Interface
           Version 1.1 (CGI/1.1)", Work in Progress.
 [HTTP]    Fielding, R., Gettys,J., Mogul, J., Frystyk,, H., Masinter,
           L., Leach, P. and T. Berners-Lee, "Hypertext Transfer
           Protocol -- HTTP/1.1", RFC 2616, June 1999.
 [RFC2569] Herriot, R., Hastings, T., Jacobs, N. and J. Martin,
           "Mapping between LPD and IPP Protocols", RFC 2569, April
           1999.
 [RFC2566] deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P.
           Powell, "Internet Printing Protocol/1.0: Model and
           Semantics", RFC 2566, April 1999.
 [RFC2565] Herriot, R., Butler, S., Moore, P. and R. Tuner, "Internet
           Printing Protocol/1.0: Encoding and Transport", RFC 2565,
           April 1999.
 [RFC2568] Zilles, S., "Rationale for the Structure and Model and
           Protocol for the Internet Printing Protocol", RFC 2568,
           April 1999.
 [RFC2567] Wright, D., "Design Goals for an Internet Printing
           Protocol", RFC 2567, April 1999.
 [RFC1123] Braden, S., "Requirements for Internet Hosts - Application
           and Support", STD 3, RFC 1123, October 1989.

Hastings & Manros Informational [Page 61] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
           3", BCP 9, RFC 2026, October 1996.
 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T.
           Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC
           2068, January 1997.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
           Resource Identifiers (URI): Generic Syntax", RFC 2396,
           August 1998.
 [Servlet] Servlet Specification Version 2.1
           (http://java.sun.com/products/servlet/2.1/index.html).
 [SSL]     Netscape, The SSL Protocol, Version 3, (Text version 3.02),
           November 1996.

4.1 Authors' Addresses

 Thomas N. Hastings
 Xerox Corporation
 701 Aviation Blvd.
 El Segundo, CA 90245
 EMail: hastings@cp10.es.xerox.com
 Carl-Uno Manros
 Xerox Corporation
 701 Aviation Blvd.
 El Segundo, CA 90245
 EMail: manros@cp10.es.xerox.com

5 Security Considerations

 Security issues are discussed in sections 2.2, 2.3.1, and 8.5.

6 Notices

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it

Hastings & Manros Informational [Page 62] RFC 2639 IPP/1.0: Implementer's Guide July 1999

 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11 [BCP-11].
 Copies of claims of rights made available for publication and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

Hastings & Manros Informational [Page 63] RFC 2639 IPP/1.0: Implementer's Guide July 1999

Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

Hastings & Manros Informational [Page 64]

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