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[Text version]
Network Working Group
Request for Comments: 2911
Obsoletes: 2566
Category: Standards TrackT. Hastings, Editor
R. Herriot
Xerox Corporation
R. deBry
Utah Valley State College
S. Isaacson
Novell, Inc.
P. Powell
Astart Technologies
September 2000
- Status of this Memo
- This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
- Copyright Notice
- Copyright © The Internet Society (2000). 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 describes a simplified model consisting of abstract objects, their attributes, and their operations that is independent of encoding and transport. The model consists of a Printer and a Job object. A Job optionally supports multiple documents. IPP 1.1 semantics allow end-users and operators to query printer capabilities, submit print jobs, inquire about the status of print jobs and printers, cancel, hold, release, and restart print jobs. IPP 1.1 semantics allow operators to pause, resume, and purge (jobs from) Printer objects. This document also addresses security, internationalization, and directory issues.
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/1.1: Model and Semantics (this document) Internet Printing Protocol/1.1: Encoding and Transport [RFC2910] Internet Printing Protocol/1.1: Implementer's Guide [IPP-IIG] Mapping between LPD and IPP Protocols [RFC2569]The "Design Goals for an Internet Printing Protocol" document takes a broad look at distributed printing functionality, and it enumerates real-life scenarios that help to clarify the features that need to be included in a printing protocol for the Internet. It identifies requirements for three types of users: end users, operators, and administrators. It calls out a subset of end user requirements that are satisfied in IPP/1.0. A few OPTIONAL operator operations have been added to IPP/1.1.
The "Rationale for the Structure and Model and Protocol for the Internet Printing Protocol" document describes IPP from a high level view, defines a roadmap for the various documents that form the suite of IPP specification documents, and gives background and rationale for the IETF working group's major decisions.
The "Internet Printing Protocol/1.1: Encoding and Transport" document is a formal mapping of the abstract operations and attributes defined in the model document onto HTTP/1.1 [RFC2616]. It defines the encoding rules for a new Internet MIME media type called "application/ipp". This document also defines the rules for transporting over HTTP a message body whose Content-Type is "application/ipp". This document defines a new scheme named 'ipp' for identifying IPP printers and jobs.
The "Internet Printing Protocol/1.1: Implementer's Guide" document gives insight and advice to implementers of IPP clients and IPP objects. It is intended to help them understand IPP/1.1 and some of the considerations that may assist them in the design of their client and/or IPP object implementations. For example, a typical order of processing requests is given, including error checking. Motivation for some of the specification decisions is also included.
The "Mapping between LPD and IPP Protocols" document gives some advice to implementers of gateways between IPP and LPD (Line Printer Daemon) implementations.
- Table of Contents
3.3.2 Send-URI Operation 66 3.3.3 Cancel-Job Operation 66 3.3.3.1 Cancel-Job Request 67 3.3.3.2 Cancel-Job Response 68 3.3.4 Get-Job-Attributes Operation 69 3.3.4.1 Get-Job-Attributes Request 69 3.3.4.2 Get-Job-Attributes Response 70 3.3.5 Hold-Job Operation 71 3.3.5.1 Hold-Job Request 72 3.3.5.2 Hold-Job Response 73 3.3.6 Release-Job Operation 74 3.3.7 Restart-Job Operation 75 3.3.7.1 Restart-Job Request 76 3.3.7.2 Restart-Job Response 78 4. Object Attributes 78 4.1 Attribute Syntaxes 78 4.1.1 'text' 79 4.1.1.1 'textWithoutLanguage' 80 4.1.1.2 'textWithLanguage' 80 4.1.2 'name' 81 4.1.2.1 'nameWithoutLanguage' 82 4.1.2.2 'nameWithLanguage' 82 4.1.2.3 Matching 'name' attribute values 83 4.1.3 'keyword' 84 4.1.4 'enum' 85 4.1.5 'uri' 85 4.1.6 'uriScheme' 86 4.1.7 'charset' 86 4.1.8 'naturalLanguage' 87 4.1.9 'mimeMediaType' 87 4.1.9.1 Application/octet-stream -- Auto-Sensing 88 the document format 4.1.10 'octetString' 89 4.1.11 'boolean' 89 4.1.12 'integer' 89 4.1.13 'rangeOfInteger' 90 4.1.14 'dateTime' 90 4.1.15 'resolution' 90 4.1.16 '1setOf X' 90 4.2 Job Template Attributes 91 4.2.1 job-priority (integer(1:100)) 94 4.2.2 job-hold-until (type3 keyword | name (MAX)) 95 4.2.3 job-sheets (type3 keyword | name(MAX)) 96 4.2.4 multiple-document-handling (type2 keyword) 96 4.2.5 copies (integer(1:MAX)) 98 4.2.6 finishings (1setOf type2 enum) 98 4.2.7 page-ranges (1setOf rangeOfInteger (1:MAX)) 101 4.2.8 sides (type2 keyword) 1024.4.7 printer-more-info (uri) 130 4.4.8 printer-driver-installer (uri) 130 4.4.9 printer-make-and-model (text(127)) 130 4.4.10 printer-more-info-manufacturer (uri) 130 4.4.11 printer-state (type1 enum) 131 4.4.12 printer-state-reasons (1setOf type2 keyword) 131 4.4.13 printer-state-message (text(MAX)) 134 4.4.14 ipp-versions-supported (1setOf type2 keyword) 134 4.4.15 operations-supported (1setOf type2 enum) 135 4.4.16 multiple-document-jobs-supported (boolean) 136 4.4.17 charset-configured (charset) 136 4.4.18 charset-supported (1setOf charset) 137 4.4.19 natural-language-configured (naturalLanguage) 137 4.4.20 generated-natural-language-supported (1setOf naturalLanguage) 137 4.4.21 document-format-default (mimeMediaType) 138 4.4.22 document-format-supported (1setOf mimeMediaType) 138 4.4.23 printer-is-accepting-jobs (boolean) 138 4.4.24 queued-job-count (integer(0:MAX)) 138 4.4.25 printer-message-from-operator (text(127)) 139 4.4.26 color-supported (boolean) 139 4.4.27 reference-uri-schemes-supported (1setOf uriScheme) 139 4.4.28 pdl-override-supported (type2 keyword) 139 4.4.29 printer-up-time (integer(1:MAX)) 140 4.4.30 printer-current-time (dateTime) 140 4.4.31 multiple-operation-time-out (integer(1:MAX)) 141 4.4.32 compression-supported (1setOf type3 keyword) 141 4.4.33 job-k-octets-supported (rangeOfInteger(0:MAX)) 142 4.4.34 job-impressions-supported (rangeOfInteger(0:MAX)) 142 4.4.35 job-media-sheets-supported (rangeOfInteger(0:MAX)) 142 4.4.36 pages-per-minute (integer(0:MAX)) 142 4.4.37 pages-per-minute-color (integer(0:MAX)) 142 5. Conformance 143 5.1 Client Conformance Requirements 143 5.2 IPP Object Conformance Requirements 145 5.2.1 Objects 145 5.2.2 Operations 145 5.2.3 IPP Object Attributes 146 5.2.4 Versions 146 5.2.5 Extensions 147 5.2.6 Attribute Syntaxes 147 5.2.7 Security 148 5.3 Charset and Natural Language Requirements 148 6. IANA Considerations 148 6.1 Typed 'keyword' and 'enum' Extensions 149 6.2 Attribute Extensibility 151 6.3 Attribute Syntax Extensibility 152 6.4 Operation Extensibility 1526.5 Attribute Group Extensibility 153 6.6 Status Code Extensibility 153 6.7 Out-of-band Attribute Value Extensibility 154 6.8 Registration of MIME types/sub-types for document-formats 154 6.9 Registration of charsets for use in 'charset' attribute values 154 7. Internationalization Considerations 154 8. Security Considerations 158 8.1 Security Scenarios 159 8.1.1 Client and Server in the Same Security Domain 159 8.1.2 Client and Server in Different Security Domains 159 8.1.3 Print by Reference 160 8.2 URIs in Operation, Job, and Printer attributes 160 8.3 URIs for each authentication mechanisms 160 8.4 Restricted Queries 161 8.5 Operations performed by operators and system administrators 161 8.6 Queries on jobs submitted using non-IPP protocols 162 9. References 162 10. Authors' Addresses 166 11. Formats for IPP Registration Proposals 168 11.1 Type2 keyword attribute values registration 169 11.2 Type3 keyword attribute values registration 169 11.3 Type2 enum attribute values registration 169 11.4 Type3 enum attribute values registration 170 11.5 Attribute registration 170 11.6 Attribute Syntax registration 171 11.7 Operation registration 171 11.8 Attribute Group registration 171 11.9 Status code registration 172 11.10 Out-of-band Attribute Value registration 172 12. APPENDIX A: Terminology 173 12.1 Conformance Terminology 173 12.1.1 NEED NOT 173 12.2 Model Terminology 173 12.2.1 Keyword 173 12.2.2 Attributes 173 12.2.2.1 Attribute Name 173 12.2.2.2 Attribute Group Name 174 12.2.2.3 Attribute Value 174 12.2.2.4 Attribute Syntax 174 12.2.3 Supports 174 12.2.4 print-stream page 176 12.2.5 impression 177 13. APPENDIX B: Status Codes and Suggested Status Code Messages 177 13.1 Status Codes 178 13.1.1 Informational 178 13.1.2 Successful Status Codes 17813.1.2.1 successful-ok (0x0000) 178 13.1.2.2 successful-ok-ignored-or-substituted-attributes (0x0001) 179 13.1.2.3 successful-ok-conflicting-attributes (0x0002) 179 13.1.3 Redirection Status Codes 179 13.1.4 Client Error Status Codes 179 13.1.4.1 client-error-bad-request (0x0400) 180 13.1.4.2 client-error-forbidden (0x0401) 180 13.1.4.3 client-error-not-authenticated (0x0402) 180 13.1.4.4 client-error-not-authorized (0x0403) 180 13.1.4.5 client-error-not-possible (0x0404) 180 13.1.4.6 client-error-timeout (0x0405) 181 13.1.4.7 client-error-not-found (0x0406) 181 13.1.4.8 client-error-gone (0x0407) 181 13.1.4.9 client-error-request-entity-too-large (0x0408) 182 13.1.4.10 client-error-request-value-too-long (0x0409) 182 13.1.4.11 client-error-document-format-not-supported (0x040A) 182 13.1.4.12 client-error-attributes-or-values-not-supported (0x040B) 183 13.1.4.13 client-error-uri-scheme-not-supported (0x040C) 183 13.1.4.14 client-error-charset-not-supported (0x040D) 183 13.1.4.15 client-error-conflicting-attributes (0x040E) 183 13.1.4.16 client-error-compression-not-supported (0x040F) 184 13.1.4.17 client-error-compression-error (0x0410) 184 13.1.4.18 client-error-document-format-error (0x0411) 184 13.1.4.19 client-error-document-access-error (0x0412) 184 13.1.5 Server Error Status Codes 185 13.1.5.1 server-error-internal-error (0x0500) 185 13.1.5.2 server-error-operation-not-supported (0x0501) 185 13.1.5.3 server-error-service-unavailable (0x0502) 185 13.1.5.4 server-error-version-not-supported (0x0503) 185 13.1.5.5 server-error-device-error (0x0504) 186 13.1.5.6 server-error-temporary-error (0x0505) 186 13.1.5.7 server-error-not-accepting-jobs (0x0506) 187 13.1.5.8 server-error-busy (0x0507) 187 13.1.5.9 server-error-job-canceled (0x0508) 187 13.1.5.10 server-error-multiple-document-jobs-not-supported (0x0509) 187 13.2 Status Codes for IPP Operations 187 14. APPENDIX C: "media" keyword values 190 15. APPENDIX D: Processing IPP Attributes 208 15.1 Fidelity 209 15.2 Page Description Language (PDL) Override 210 15.3 Using Job Template Attributes During Document Processing 212 16. APPENDIX E: Generic Directory Schema 214 17. APPENDIX F: Differences between the IPP/1.0 and IPP/1.1 "Model and Semantics" Documents 215 18. Full Copyright Statement 224- 1. Introduction
- The Internet Printing Protocol (IPP) is an application level protocol that can be used for distributed printing using Internet tools and technologies. IPP version 1.1 (IPP/1.1) focuses primarily on end user functionality with a few administrative operations included. This document is just one of a suite of documents that fully define IPP. 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/1.1: Model and Semantics (this document) Internet Printing Protocol/1.1: Encoding and Transport [RFC2910] Internet Printing Protocol/1.1: Implementer's Guide [IPP-IIG] Mapping between LPD and IPP Protocols [RFC2569]Anyone reading these documents for the first time is strongly encouraged to read the IPP documents in the above order.
This document is laid out as follows:
- The rest of Section 1 is an introduction to the IPP simplified model for distributed printing. - Section 2 introduces the object types covered in the model with their basic behaviors, attributes, and interactions. - Section 3 defines the operations included in IPP/1.1. IPP operations are synchronous, therefore, for each operation, there is a both request and a response. - Section 4 defines the attributes (and their syntaxes) that are used in the model. - Sections 5 - 6 summarizes the implementation conformance requirements for objects that support the protocol and IANA considerations, respectively. - Sections 7 - 11 cover the Internationalization and Security considerations as well as References, Author contact information, and Formats for Registration Proposals. - Sections 12 - 14 are appendices that cover Terminology, Status Codes and Messages, and "media" keyword values.Note: This document uses terms such as "attributes", "keywords", and "support". These terms have special meaning and are defined in the model terminology section 12.2. Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to conformance. These terms are defined in section 12.1 on conformance terminology, most of which is taken from RFC 2119 [RFC2119].- Section 15 is an appendix that helps to clarify the effects of interactions between related attributes and their values. - Section 16 is an appendix that enumerates the subset of Printer attributes that form a generic directory schema. These attributes are useful when registering a Printer so that a client can find the Printer not just by name, but by filtered searches as well. - Section 17 is an appendix summarizing the additions and changes from the IPP/1.0 "Model and Semantics" document [RFC2566] to make this IPP/1.1 document. - Section 18 is the full copyright notice.- 1.1 Simplified Printing Model
- In order to achieve its goal of realizing a workable printing protocol for the Internet, the Internet Printing Protocol (IPP) is based on a simplified printing model that abstracts the many components of real world printing solutions. The Internet is a distributed computing environment where requesters of print services (clients, applications, printer drivers, etc.) cooperate and interact with print service providers. This model and semantics document describes a simple, abstract model for IPP even though the underlying configurations may be complex "n-tier" client/server systems. An important simplifying step in the IPP model is to expose only the key objects and interfaces required for printing. The model described in this model document does not include features, interfaces, and relationships that are beyond the scope of the first version of IPP (IPP/1.1). IPP/1.1 incorporates many of the relevant ideas and lessons learned from other specification and development efforts [HTPP] [ISO10175] [LDPA] [P1387.4] [PSIS] [RFC1179] [SWP]. IPP is heavily influenced by the printing model introduced in the Document Printing Application (DPA) [ISO10175] standard. Although DPA specifies both end user and administrative features, IPP version 1.1 (IPP/1.1) focuses primarily on end user functionality with a few additional OPTIONAL operator operations.
The IPP/1.1 model encapsulates the important components of distributed printing into two object types:
- Printer (Section 2.1) - Job (Section 2.2)Each object type has an associated set of operations (see section 3) and attributes (see section 4). It is important, however, to understand that in real system implementations (which lie underneath the abstracted IPP/1.1 model), there are other components of a print service which are not explicitly defined in the IPP/1.1 model. The following figure illustrates where IPP/1.1 fits with respect to these other components.
+--------------+ | Application | o +. . . . . . . | \|/ | Spooler | / \ +. . . . . . . | +---------+ End-User | Print Driver |---| File | +-----------+ +-----+ +------+-------+ +----+----+ | Browser | | GUI | | | +-----+-----+ +--+--+ | | | | | | | +---+------------+---+ | N D S | | IPP Client |------------+ O I E | +---------+----------+ T R C | | I E U | F C R -------------- Transport ------------------ I T I C O T | --+ A R Y +--------+--------+ | T Y | IPP Server | | I +--------+--------+ | O | | N +-----------------+ | IPP Printer | Print Service | | +-----------------+ | | --+ +-----------------+ | Output Device(s)| +-----------------+An IPP Printer object encapsulates the functions normally associated with physical output devices along with the spooling, scheduling and multiple device management functions often associated with a print server. Printer objects are optionally registered as entries in a directory where end users find and select them based on some sort of filtered and context based searching mechanism (see section 16). The directory is used to store relatively static information about the Printer, allowing end users to search for and find Printers that match their search criteria, for example: name, context, printer capabilities, etc. The more dynamic information, such as state, currently loaded and ready media, number of jobs at the Printer, errors, warnings, and so forth, is directly associated with the Printer object itself rather than with the entry in the directory which only represents the Printer object.
IPP clients implement the IPP protocol on the client side and give end users (or programs running on behalf of end users) the ability to query Printer objects and submit and manage print jobs. An IPP server is just that part of the Printer object that implements the server-side protocol. The rest of the Printer object implements (or gateways into) the application semantics of the print service itself. The Printer objects may be embedded in an output device or may be implemented on a host on the network that communicates with an output device.
When a job is submitted to the Printer object and the Printer object validates the attributes in the submission request, the Printer object creates a new Job object. The end user then interacts with this new Job object to query its status and monitor the progress of the job. An end user can also cancel their print jobs by using the Job object's Cancel-Job operation. An end-user can also hold, release, and restart their print jobs using the Job object's OPTIONAL Hold-Job, Release-Job, and Restart-Job operations, if implemented.
A privileged operator or administrator of a Printer object can cancel, hold, release, and restart any user's job using the REQUIRED Cancel-Job and the OPTIONAL Hold-Job, Release-Job, and Restart-Job operations. In additional privileged operator or administrator of a Printer object can pause, resume, or purge (jobs from) a Printer object using the OPTIONAL Pause-Printer, Resume-Printer, and Purge- Jobs operations, if implemented.
The notification service is out of scope for this IPP/1.1 document, but using such a notification service, the end user is able to register for and receive Printer specific and Job specific events. An end user can query the status of Printer objects and can follow the progress of Job objects by polling using the Get-Printer- Attributes, Get-Jobs, and Get-Job-Attributes operations.
- 2. IPP Objects
- The IPP/1.1 model introduces objects of type Printer and Job. Each type of object models relevant aspects of a real-world entity such as a real printer or real print job. Each object type is defined as a set of possible attributes that may be supported by instances of that object type. For each object (instance), the actual set of supported attributes and values describe a specific implementation. The object's attributes and values describe its state, capabilities, realizable features, job processing functions, and default behaviors
and characteristics. For example, the Printer object type is defined as a set of attributes that each Printer object potentially supports. In the same manner, the Job object type is defined as a set of attributes that are potentially supported by each Job object.Each attribute included in the set of attributes defining an object type is labeled as:
- "REQUIRED": each object MUST support the attribute. - "RECOMMENDED": each object SHOULD support the attribute. - "OPTIONAL": each object MAY support the attribute.
Some definitions of attribute values indicate that an object MUST or SHOULD support the value; otherwise, support of the value is OPTIONAL.
However, if an implementation supports an attribute, it MUST support at least one of the possible values for that attribute.
- 2.1 Printer Object
- The major component of the IPP/1.1 model is the Printer object. A Printer object implements the server-side of the IPP/1.1 protocol. Using the protocol, end users may query the attributes of the Printer object and submit print jobs to the Printer object. The actual implementation components behind the Printer abstraction may take on different forms and different configurations. However, the model abstraction allows the details of the configuration of real components to remain opaque to the end user. Section 3 describes each of the Printer operations in detail.
The capabilities and state of a Printer object are described by its attributes. Printer attributes are divided into two groups:
- "job-template" attributes: These attributes describe supported job processing capabilities and defaults for the Printer object. (See section 4.2) - "printer-description" attributes: These attributes describe the Printer object's identification, state, location, references to other sources of information about the Printer object, etc. (see section 4.4)Since a Printer object is an abstraction of a generic document output device and print service provider, a Printer object could be used to represent any real or virtual device with semantics consistent with the Printer object, such as a fax device, an imager, or even a CD writer. Some examples of configurations supporting a Printer object include:
1) An output device with no spooling capabilities 2) An output device with a built-in spooler 3) A print server supporting IPP with one or more associated output devices 3a) The associated output devices may or may not be capable of spooling jobs 3b) The associated output devices may or may not support IPPThe following figures show some examples of how Printer objects can be realized on top of various distributed printing configurations. The embedded case below represents configurations 1 and 2. The hosted and fan-out figures below represent configurations 3a and 3b.
In this document the term "client" refers to a software entity that sends IPP operation requests to an IPP Printer object and accepts IPP operation responses. A client MAY be:
1. contained within software controlled by an end user, e.g. activated by the "Print" menu item in an application or2. the print server component that sends IPP requests to either an output device or another "downstream" print server.The term "IPP Printer" is a network entity that accepts IPP operation requests and returns IPP operation responses. As such, an IPP object MAY be:
1. an (embedded) device component that accepts IPP requests and controls the device or2. a component of a print server that accepts IPP requests (where the print server controls one or more networked devices using IPP or other protocols).Legend:
##### indicates a Printer object which is either embedded in an output device or is hosted in a server. The Printer object might or might not be capable of queuing/spooling.any indicates any network protocol or direct connect, including IPPembedded printer: output device +---------------+ O +--------+ | ########### | /|\ | client |------------IPP------------># Printer # | / \ +--------+ | # Object # | | ########### | +---------------+hosted printer: +---------------+ O +--------+ ########### | | /|\ | client |--IPP--># Printer #-any->| output device | / \ +--------+ # Object # | | ########### +---------------++---------------+ fan out: | | +-->| output device | any/ | | O +--------+ ########### / +---------------+ /|\ | client |-IPP-># Printer #--* / \ +--------+ # Object # \ +---------------+ ########### any\ | | +-->| output device | | | +---------------+- 2.2 Job Object
- A Job object is used to model a print job. A Job object contains documents. The information required to create a Job object is sent in a create request from the end user via an IPP Client to the Printer object. The Printer object validates the create request, and if the Printer object accepts the request, the Printer object creates the new Job object. Section 3 describes each of the Job operations in detail.
The characteristics and state of a Job object are described by its attributes. Job attributes are grouped into two groups as follows:
- "job-template" attributes: These attributes can be supplied by the client or end user and include job processing instructions which are intended to override any Printer object defaults and/or instructions embedded within the document data. (See section 4.2)- "job-description" attributes: These attributes describe the Job object's identification, state, size, etc. The client supplies some of these attributes, and the Printer object generates others. (See section 4.3)An implementation MUST support at least one document per Job object. An implementation MAY support multiple documents per Job object. A document is either:
- a stream of document data in a format supported by the Printer object (typically a Page Description Language - PDL), or - a reference to such a stream of document dataIn IPP/1.1, a document is not modeled as an IPP object, therefore it has no object identifier or associated attributes. All job processing instructions are modeled as Job object attributes. These attributes are called Job Template attributes and they apply equally to all documents within a Job object.
- 2.3 Object Relationships
- IPP objects have relationships that are maintained persistently along with the persistent storage of the object attributes.
A Printer object can represent either one or more physical output devices or a logical device which "processes" jobs but never actually uses a physical output device to put marks on paper. Examples of logical devices include a Web page publisher or a gateway into an online document archive or repository. A Printer object contains zero or more Job objects.
A Job object is contained by exactly one Printer object, however the identical document data associated with a Job object could be sent to either the same or a different Printer object. In this case, a second Job object would be created which would be almost identical to the first Job object, however it would have new (different) Job object identifiers (see section 2.4).
A Job object is either empty (before any documents have been added) or contains one or more documents. If the contained document is a stream of document data, that stream can be contained in only one document. However, there can be identical copies of the stream in other documents in the same or different Job objects. If the contained document is just a reference to a stream of document data, other documents (in the same or different Job object(s)) may contain the same reference.
- 2.4 Object Identity
- All Printer and Job objects are identified by a Uniform Resource Identifier (URI) [RFC2396] so that they can be persistently and unambiguously referenced. Since every URL is a specialized form of a URI, even though the more generic term URI is used throughout the rest of this document, its usage is intended to cover the more specific notion of URL as well.
An administrator configures Printer objects to either support or not support authentication and/or message privacy using Transport Layer Security (TLS) [RFC2246] (the mechanism for security configuration is outside the scope of this IPP/1.1 document). In some situations, both types of connections (both authenticated and unauthenticated) can be established using a single communication channel that has some sort of negotiation mechanism. In other situations, multiple communication channels are used, one for each type of security configuration. Section 8 provides a full description of all security considerations and configurations.
If a Printer object supports more than one communication channel, some or all of those channels might support and/or require different security mechanisms. In such cases, an administrator could expose the simultaneous support for these multiple communication channels as multiple URIs for a single Printer object where each URI represents one of the communication channels to the Printer object. To support this flexibility, the IPP Printer object type defines a multi-valued identification attribute called the "printer-uri-supported" attribute. It MUST contain at least one URI. It MAY contain more than one URI. That is, every Printer object will have at least one URI that identifies at least one communication channel to the Printer object, but it may have more than one URI where each URI identifies a different communication channel to the Printer object. The "printer-uri-supported" attribute has two companion attributes, the "uri-security-supported" attribute and the "uri-authentication- supported". Both have the same cardinality as "printer-uri- supported". The purpose of the "uri-security-supported" attribute is to indicate the security mechanisms (if any) used for each URI listed in "printer-uri-supported". The purpose of the "uri-authentication- supported" attribute is to indicate the authentication mechanisms (if any) used for each URI listed in "printer-uri-supported". These three attributes are fully described in sections 4.4.1, 4.4.2, and 4.4.3.
When a job is submitted to the Printer object via a create request, the client supplies only a single Printer object URI. The client supplied Printer object URI MUST be one of the values in the "printer-uri-supported" Printer attribute. IPP/1.1 does not specify how the client obtains the client supplied URI, but it is RECOMMENDED that a Printer object be registered as an entry in a directory service. End-users and programs can then interrogate the directory searching for Printers. Section 16 defines a generic schema for Printer object entries in the directory service and describes how the entry acts as a bridge to the actual IPP Printer object. The entry in the directory that represents the IPP Printer object includes the possibly many URIs for that Printer object as values in one its attributes.
When a client submits a create request to the Printer object, the Printer object validates the request and creates a new Job object. The Printer object assigns the new Job object a URI which is stored in the "job-uri" Job attribute. This URI is then used by clients as the target for subsequent Job operations. The Printer object generates a Job URI based on its configured security policy and the URI used by the client in the create request.
For example, consider a Printer object that supports both a communication channel secured by the use of SSL3 (using HTTP over SSL3 with an "https" schemed URI) and another open communication channel that is not secured with SSL3 (using a simple "http" schemed URI). If a client were to submit a job using the secure URI, the Printer object would assign the new Job object a secure URI as well. If a client were to submit a job using the open-channel URI, the Printer would assign the new Job object an open-channel URI.
In addition, the Printer object also populates the Job object's "job-printer-uri" attribute. This is a reference back to the Printer object that created the Job object. If a client only has access to a Job object's "job-uri" identifier, the client can query the Job's "job-printer-uri" attribute in order to determine which Printer object created the Job object. If the Printer object supports more than one URI, the Printer object picks the one URI supplied by the client when creating the job to build the value for and to populate the Job's "job-printer-uri" attribute.
Allowing Job objects to have URIs allows for flexibility and scalability. For example, in some implementations, the Printer object might create Jobs that are processed in the same local environment as the Printer object itself. In this case, the Job URI might just be a composition of the Printer's URI and some unique component for the Job object, such as the unique 32-bit positive integer mentioned later in this paragraph. In other implementations, the Printer object might be a central clearing-house for validating all Job object creation requests, but the Job object itself might be created in some environment that is remote from the Printer object. In this case, the Job object's URI may have no physical-location relationship at all to the Printer object's URI. Again, the fact that Job objects have URIs allows for flexibility and scalability, however, many existing printing systems have local models or interface constraints that force print jobs to be identified using only a 32-bit positive integer rather than an independent URI. This numeric Job ID is only unique within the context of the Printer object to which the create request was originally submitted. Therefore, in order to allow both types of client access to IPP Job objects (either by Job URI or by numeric Job ID), when the Printer object successfully processes a create request and creates a new Job object, the Printer object MUST generate both a Job URI and a Job ID. The Job ID (stored in the "job-id" attribute) only has meaning in the context of the Printer object to which the create request was originally submitted. This requirement to support both Job URIs and Job IDs allows all types of clients to access Printer objects and Job objects no matter the local constraints imposed on the client implementation.
In addition to identifiers, Printer objects and Job objects have names ("printer-name" and "job-name"). An object name NEED NOT be unique across all instances of all objects. A Printer object's name is chosen and set by an administrator through some mechanism outside the scope of this IPP/1.1 document. A Job object's name is optionally chosen and supplied by the IPP client submitting the job. If the client does not supply a Job object name, the Printer object generates a name for the new Job object. In all cases, the name only has local meaning.
To summarize:
- Each Printer object is identified with one or more URIs. The Printer's "printer-uri-supported" attribute contains the URI(s). - The Printer object's "uri-security-supported" attribute identifies the communication channel security protocols that may or may not have been configured for the various Printer object URIs (e.g., 'tls' or 'none'). - The Printer object's "uri-authentication-supported" attribute identifies the authentication mechanisms that may or may not have been configured for the various Printer object URIs (e.g., 'digest' or 'none'). - Each Job object is identified with a Job URI. The Job's "job- uri" attribute contains the URI. - Each Job object is also identified with Job ID which is a 32- bit, positive integer. The Job's "job-id" attribute contains the Job ID. The Job ID is only unique within the context of the Printer object which created the Job object.- Each Job object has a "job-printer-uri" attribute which contains the URI of the Printer object that was used to create the Job object. This attribute is used to determine the Printer object that created a Job object when given only the URI for the Job object. This linkage is necessary to determine the languages, charsets, and operations which are supported on that Job (the basis for such support comes from the creating Printer object). - Each Printer object has a name (which is not necessarily unique). The administrator chooses and sets this name through some mechanism outside the scope of this IPP/1.1 document. The Printer object's "printer-name" attribute contains the name. - Each Job object has a name (which is not necessarily unique). The client optionally supplies this name in the create request. If the client does not supply this name, the Printer object generates a name for the Job object. The Job object's "job-name" attribute contains the name.- 3. IPP Operations
- IPP objects support operations. An operation consists of a request and a response. When a client communicates with an IPP object, the client issues an operation request to the URI for that object. Operation requests and responses have parameters that identify the operation. Operations also have attributes that affect the run-time characteristics of the operation (the intended target, localization information, etc.). These operation-specific attributes are called operation attributes (as compared to object attributes such as Printer object attributes or Job object attributes). Each request carries along with it any operation attributes, object attributes, and/or document data required to perform the operation. Each request requires a response from the object. Each response indicates success or failure of the operation with a status code as a response parameter. The response contains any operation attributes, object attributes, and/or status messages generated during the execution of the operation request.
This section describes the semantics of the IPP operations, both requests and responses, in terms of the parameters, attributes, and other data associated with each operation. The IPP/1.1 Printer operations are:
Print-Job (section 3.2.1) Print-URI (section 3.2.2) Validate-Job (section 3.2.3) Create-Job (section 3.2.4) Get-Printer-Attributes (section 3.2.5) Get-Jobs (section 3.2.6) Pause-Printer (section 3.3.5) Resume-Printer (section 3.3.6) Purge-Jobs (section 3.3.7)The Job operations are:
Send-Document (section 3.3.1) Send-URI (section 3.3.2) Cancel-Job (section 3.3.3) Get-Job-Attributes (section 3.3.4) Hold-Job (section 3.3.5) Release-Job (section 3.3.6) Restart-Job (section 3.3.7)The Send-Document and Send-URI Job operations are used to add a new document to an existing multi-document Job object created using the Create-Job operation.
- 3.1 Common Semantics
- All IPP operations require some common parameters and operation attributes. These common elements and their semantic characteristics are defined and described in more detail in the following sections.
- 3.1.1 Required Parameters
- Every operation request contains the following REQUIRED parameters:
- a "version-number", - an "operation-id", - a "request-id", and - the attributes that are REQUIRED for that type of request.Every operation response contains the following REQUIRED parameters:
- The "Encoding and Transport" document [RFC2910] defines special rules for the encoding of these parameters. All other operation elements are represented using the more generic encoding rules for attributes and groups of attributes.
- a "version-number", - a "status-code", - the "request-id" that was supplied in the corresponding request, and - the attributes that are REQUIRED for that type of response.- 3.1.2 Operation IDs and Request IDs
- Each IPP operation request includes an identifying "operation-id" value. Valid values are defined in the "operations-supported" Printer attribute section (see section 4.4.15). The client specifies which operation is being requested by supplying the correct "operation-id" value.
In addition, every invocation of an operation is identified by a "request-id" value. For each request, the client chooses the "request-id" which MUST be an integer (possibly unique depending on client requirements) in the range from 1 to 2**31 - 1 (inclusive). This "request-id" allows clients to manage multiple outstanding requests. The receiving IPP object copies all 32-bits of the client- supplied "request-id" attribute into the response so that the client can match the response with the correct outstanding request, even if the "request-id" is out of range. If the request is terminated before the complete "request-id" is received, the IPP object rejects the request and returns a response with a "request-id" of 0.
Note: In some cases, the transport protocol underneath IPP might be a connection oriented protocol that would make it impossible for a client to receive responses in any order other than the order in which the corresponding requests were sent. In such cases, the "request-id" attribute would not be essential for correct protocol operation. However, in other mappings, the operation responses can come back in any order. In these cases, the "request-id" would be essential.
- 3.1.3 Attributes
- Operation requests and responses are both composed of groups of attributes and/or document data. The attributes groups are:
- Operation Attributes: These attributes are passed in the operation and affect the IPP object's behavior while processing the operation request and may affect other attributes or groups of attributes. Some operation attributes describe the document data associated with the print job and are associated with new Job objects, however most operation attributes do not persist beyond the life of the operation. The description of each operation attribute includes conformance statements indicating which operation attributes are REQUIRED and which are OPTIONALfor an IPP object to support and which attributes a client MUST supply in a request and an IPP object MUST supply in a response. - Job Template Attributes: These attributes affect the processing of a job. A client OPTIONALLY supplies Job Template Attributes in a create request, and the receiving object MUST be prepared to receive all supported attributes. The Job object can later be queried to find out what Job Template attributes were originally requested in the create request, and such attributes are returned in the response as Job Object Attributes. The Printer object can be queried about its Job Template attributes to find out what type of job processing capabilities are supported and/or what the default job processing behaviors are, though such attributes are returned in the response as Printer Object Attributes. The "ipp-attribute-fidelity" operation attribute affects processing of all client-supplied Job Template attributes (see sections 3.2.1.2 and 15 for a full description of "ipp-attribute-fidelity" and its relationship to other attributes). - Job Object Attributes: These attributes are returned in response to a query operation directed at a Job object. - Printer Object Attributes: These attributes are returned in response to a query operation directed at a Printer object. - Unsupported Attributes: In a create request, the client supplies a set of Operation and Job Template attributes. If any of these attributes or their values is unsupported by the Printer object, the Printer object returns the set of unsupported attributes in the response. Sections 3.1.7, 3.2.1.2, and 15 give a full description of how Job Template attributes supplied by the client in a create request are processed by the Printer object and how unsupported attributes are returned to the client. Because of extensibility, any IPP object might receive a request that contains new or unknown attributes or values for which it has no support. In such cases, the IPP object processes what it can and returns the unsupported attributes in the response. The Unsupported Attribute group is defined for all operation responses for returning unsupported attributes that the client supplied in the request.Later in this section, each operation is formally defined by identifying the allowed and expected groups of attributes for each request and response. The model identifies a specific order for each group in each request or response, but the attributes within each group may be in any order, unless specified otherwise.
The attributes within a group MUST be unique; if an attribute with the same name occurs more than once, the group is mal-formed. Clients MUST NOT submit such malformed requests and Printers MUST NOT return such malformed responses. If such a malformed request is submitted to a Printer, the Printer MUST either (1) reject the request with the 'client-error-bad-request' status code (see section 13.1.4.1) or (2) process the request normally after selecting only one of the attribute instances, depending on implementation. Which attribute is selected when there are duplicate attributes depends on implementation. The IPP Printer MUST NOT use the values from more than one such duplicate attribute instance.
Each attribute definition includes the attribute's name followed by the name of its attribute syntax(es) in parenthesizes. In addition, each 'integer' attribute is followed by the allowed range in parentheses, (m:n), for values of that attribute. Each 'text' or 'name' attribute is followed by the maximum size in octets in parentheses, (size), for values of that attribute. For more details on attribute syntax notation, see the descriptions of these attributes syntaxes in section 4.1.
Note: Document data included in the operation is not strictly an attribute, but it is treated as a special attribute group for ordering purposes. The only operations that support supplying the document data within an operation request are Print-Job and Send- Document. There are no operation responses that include document data.
Some operations are REQUIRED for IPP objects to support; the others are OPTIONAL (see section 5.2.2). Therefore, before using an OPTIONAL operation, a client SHOULD first use the REQUIRED Get- Printer-Attributes operation to query the Printer's "operations- supported" attribute in order to determine which OPTIONAL Printer and Job operations are actually supported. The client SHOULD NOT use an OPTIONAL operation that is not supported. When an IPP object receives a request to perform an operation it does not support, it returns the 'server-error-operation-not-supported' status code (see section 13.1.5.2). An IPP object is non-conformant if it does not support a REQUIRED operation.
- 3.1.4 Character Set and Natural Language Operation Attributes
- Some Job and Printer attributes have values that are text strings and names intended for human understanding rather than machine understanding (see the 'text' and 'name' attribute syntax descriptions in section 4.1). The following sections describe two special Operation Attributes called "attributes-charset" and "attributes-natural-language". These attributes are always part of the Operation Attributes group. For most attribute groups, the order of the attributes within the group is not important. However, for these two attributes within the Operation Attributes group, the order is critical. The "attributes-charset" attribute MUST be the first
attribute in the group and the "attributes-natural-language" attribute MUST be the second attribute in the group. In other words, these attributes MUST be supplied in every IPP request and response, they MUST come first in the group, and MUST come in the specified order. For job creation operations, the IPP Printer implementation saves these two attributes with the new Job object as Job Description attributes. For the sake of brevity in this document, these operation attribute descriptions are not repeated with every operation request and response, but have a reference back to this section instead.- 3.1.4.1 Request Operation Attributes
- The client MUST supply and the Printer object MUST support the following REQUIRED operation attributes in every IPP/1.1 operation request:
"attributes-charset" (charset): This operation attribute identifies the charset (coded character set and encoding method) used by any 'text' and 'name' attributes that the client is supplying in this request. It also identifies the charset that the Printer object MUST use (if supported) for all 'text' and 'name' attributes and status messages that the Printer object returns in the response to this request. See Sections 4.1.1 and 4.1.2 for the definition of the 'text' and 'name' attribute syntaxes.All clients and IPP objects MUST support the 'utf-8' charset [RFC2279] 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. The Printer NEED NOT return any attributes in the Unsupported Attributes Group (See sections 3.1.7 and 3.2.1.2). The Printer object MUST indicate the charset(s) supported as the values of the "charset-supported" Printer attribute (see Section 4.4.18), so that the client can query to determine which charset(s) are supported.Note to client implementers: Since IPP objects are only required to support the 'utf-8' charset, in order to maximize interoperability with multiple IPP object implementations, a client may want to supply 'utf-8' in the "attributes-charset" operation attribute, even though the client is only passing and able to present a simpler charset, such as US-ASCII [ASCII] or ISO-8859-1 [ISO8859-1]. Then the client will have to filterout (or charset convert) those characters that are returned in the response that it cannot present to its user. On the other hand, if both the client and the IPP objects also support a charset in common besides utf-8, the client may want to use that charset in order to avoid charset conversion or data loss.See the 'charset' attribute syntax description in Section 4.1.7 for the syntax and semantic interpretation of the values of this attribute and for example values."attributes-natural-language" (naturalLanguage): This operation attribute identifies the natural language used by any 'text' and 'name' attributes that the client is supplying in this request. This attribute also identifies the natural language that the Printer object SHOULD use for all 'text' and 'name' attributes and status messages that the Printer object returns in the response to this request. See the 'naturalLanguage' attribute syntax description in section 4.1.8 for the syntax and semantic interpretation of the values of this attribute and for example values.There are no REQUIRED natural languages required for the Printer object to support. However, the Printer object's "generated-natural-language-supported" attribute identifies the natural languages supported by the Printer object and any contained Job objects for all text strings generated by the IPP object. A client MAY query this attribute to determine which natural language(s) are supported for generated messages.For any of the attributes for which the Printer object generates text, i.e., for the "job-state-message", "printer- state-message", and status messages (see Section 3.1.6), the Printer object MUST be able to generate these text strings in any of its supported natural languages. If the client requests a natural language that is not supported, the Printer object MUST return these generated messages in the Printer's configured natural language as specified by the Printer's "natural-language-configured" attribute" (see Section 4.4.19).For other 'text' and 'name' attributes supplied by the client, authentication system, operator, system administrator, or manufacturer (i.e., for "job-originating-user-name", "printer- name" (name), "printer-location" (text), "printer-info" (text), and "printer-make-and-model" (text)), the Printer object is only required to support the configured natural language of thePrinter identified by the Printer object's "natural-language- configured" attribute, though support of additional natural languages for these attributes is permitted.For any 'text' or 'name' attribute in the request that is in a different natural language than the value supplied in the "attributes-natural-language" operation attribute, the client MUST use the Natural Language Override mechanism (see sections 4.1.1.2 and 4.1.2.2) for each such attribute value supplied. The client MAY use the Natural Language Override mechanism redundantly, i.e., use it even when the value is in the same natural language as the value supplied in the "attributes- natural-language" operation attribute of the request.The IPP object MUST accept any natural language and any Natural Language Override, whether the IPP object supports that natural language or not (and independent of the value of the "ipp- attribute-fidelity" Operation attribute). That is the IPP object accepts all client supplied values no matter what the values are in the Printer object's "generated-natural- language-supported" attribute. That attribute, "generated- natural-language-supported", only applies to generated messages, not client supplied messages. The IPP object MUST remember that natural language for all client-supplied attributes, and when returning those attributes in response to a query, the IPP object MUST indicate that natural language.Each value whose attribute syntax type is 'text' or 'name' (see sections 4.1.1 and 4.1.2) has an Associated Natural-Language. This document does not specify how this association is stored in a Printer or Job object. When such a value is encoded in a request or response, the natural language is either implicit or explicit:- In the implicit case, the value contains only the text/name value, and the language is specified by the "attributes- natural-language" operation attribute in the request or response (see sections 4.1.1.1 textWithoutLanguage and 4.1.2.1 nameWithoutLanguage).- In the explicit case (also known as the Natural-Language Override case), the value contains both the language and the text/name value (see sections 4.1.1.2 textWithLanguage and 4.1.2.2 nameWithLanguage).For example, the "job-name" attribute MAY be supplied by the client in a create request. The text value for this attribute will be in the natural language identified by the "attribute-natural-language" attribute, or if different, as identified by the Natural Language Override mechanism. If supplied, the IPP object will use the value of the "job-name" attribute to populate the Job object's "job-name" attribute. Whenever any client queries the Job object's "job-name" attribute, the IPP object returns the attribute as stored and uses the Natural Language Override mechanism to specify the natural language, if it is different from that reported in the "attributes-natural- language" operation attribute of the response. The IPP object MAY use the Natural Language Override mechanism redundantly, i.e., use it even when the value is in the same natural language as the value supplied in the "attributes-natural- language" operation attribute of the response.An IPP object MUST NOT reject a request based on a supplied natural language in an "attributes-natural-language" Operation attribute or in any attribute that uses the Natural Language Override.Clients SHOULD NOT supply 'text' or 'name' attributes that use an illegal combination of natural language and charset. For example, suppose a Printer object supports charsets 'utf-8', 'iso-8859-1', and 'iso-8859-7'. Suppose also, that it supports natural languages 'en' (English), 'fr' (French), and 'el' (Greek). Although the Printer object supports the charset 'iso-8859-1' and natural language 'el', it probably does not support the combination of Greek text strings using the 'iso-8859-1' charset. The Printer object handles this apparent incompatibility differently depending on the context in which it occurs:
- In a create request: If the client supplies a text or name attribute (for example, the "job-name" operation attribute) that uses an apparently incompatible combination, it is a client choice that does not affect the Printer object or its correct operation. Therefore, the Printer object simply accepts the client supplied value, stores it with the Job object, and responds back with the same combination whenever the client (or any client) queries for that attribute. - In a query-type operation, like Get-Printer-Attributes: If the client requests an apparently incompatible combination, the Printer object responds (as described in section 3.1.4.2) using the Printer's configured natural language rather than the natural language requested by the client.In either case, the Printer object does not reject the request because of the apparent incompatibility. The potential incompatible combination of charset and natural language can occur either at the global operation level or at the Natural Language Override attribute-by-attribute level. In addition, since the response always includes explicit charset and natural language information, there is never any question or ambiguity in how the client interprets the response.
- 3.1.4.2 Response Operation Attributes
- The Printer object MUST supply and the client MUST support the following REQUIRED operation attributes in every IPP/1.1 operation response:
"attributes-charset" (charset): This operation attribute identifies the charset used by any 'text' and 'name' attributes that the Printer object is returning in this response. The value in this response MUST be the same value as the "attributes-charset" operation attribute supplied by the client in the request. If this is not possible (i.e., the charset requested is not supported), the request would have been rejected. See "attributes-charset" described in Section 3.1.4.1 above.If the Printer object supports more than just the 'utf-8' charset, the Printer object MUST be able to code convert between each of the charsets supported on a highest fidelity possible basis in order to return the 'text' and 'name' attributes in the charset requested by the client. However, some information loss MAY occur during the charset conversion depending on the charsets involved. For example, the Printer object may convert from a UTF-8 'a' to a US-ASCII 'a' (with no loss of information), from an ISO Latin 1 CAPITAL LETTER A WITH ACUTE ACCENT to US-ASCII 'A' (losing the accent), or from a UTF-8 Japanese Kanji character to some ISO Latin 1 error character indication such as '?', decimal code equivalent, or to the absence of a character, depending on implementation.Whether an implementation that supports more than one charset stores the data in the charset supplied by the client or code converts to one of the other supported charsets, depends on implementation. The strategy should try to minimize loss of information during code conversion. On each response, such an implementation converts from its internal charset to that requested."attributes-natural-language" (naturalLanguage): This operation attribute identifies the natural language used by any 'text' and 'name' attributes that the IPP object is returning in this response. Unlike the "attributes-charset" operation attribute, the IPP object NEED NOT return the samevalue as that supplied by the client in the request. The IPP object MAY return the natural language of the Job object or the Printer's configured natural language as identified by the Printer object's "natural-language-configured" attribute, rather than the natural language supplied by the client. For any 'text' or 'name' attribute or status message in the response that is in a different natural language than the value returned in the "attributes-natural-language" operation attribute, the IPP object MUST use the Natural Language Override mechanism (see sections 4.1.1.2 and 4.1.2.2) on each attribute value returned. The IPP object MAY use the Natural Language Override mechanism redundantly, i.e., use it even when the value is in the same natural language as the value supplied in the "attributes-natural-language" operation attribute of the response.- 3.1.5 Operation Targets
- All IPP operations are directed at IPP objects. For Printer operations, the operation is always directed at a Printer object using one of its URIs (i.e., one of the values in the Printer object's "printer-uri-supported" attribute). Even if the Printer object supports more than one URI, the client supplies only one URI as the target of the operation. The client identifies the target object by supplying the correct URI in the "printer-uri (uri)" operation attribute.
For Job operations, the operation is directed at either:
- The Job object itself using the Job object's URI. In this case, the client identifies the target object by supplying the correct URI in the "job-uri (uri)" operation attribute. - The Printer object that created the Job object using both the Printer objects URI and the Job object's Job ID. Since the Printer object that created the Job object generated the Job ID, it MUST be able to correctly associate the client supplied Job ID with the correct Job object. The client supplies the Printer object's URI in the "printer-uri (uri)" operation attribute and the Job object's Job ID in the "job-id (integer(1:MAX))" operation attribute.If the operation is directed at the Job object directly using the Job object's URI, the client MUST NOT include the redundant "job-id" operation attribute. The operation target attributes are REQUIRED operation attributes that MUST be included in every operation request. Like the charset and natural language attributes (see section 3.1.4), the operation target attributes are specially ordered operation attributes. In all cases, the operation target attributes immediately follow the "attributes-charset" and "attributes-natural-language" attributes within the operation attribute group, however the specific ordering rules are:
- In the case where there is only one operation target attribute (i.e., either only the "printer-uri" attribute or only the "job-uri" attribute), that attribute MUST be the third attribute in the operation attributes group. - In the case where Job operations use two operation target attributes (i.e., the "printer-uri" and "job-id" attributes), the "printer-uri" attribute MUST be the third attribute and the "job-id" attribute MUST be the fourth attribute.In all cases, the target URIs contained within the body of IPP operation requests and responses must be in absolute format rather than relative format (a relative URL identifies a resource with the scope of the HTTP server, but does not include scheme, host or port).
The following rules apply to the use of port numbers in URIs that identify IPP objects:
1. If the URI scheme allows the port number to be explicitly included in the URI string, and a port number is specified within the URI, then that port number MUST be used by the client to contact the IPP object.2. If the URI scheme allows the port number to be explicitly included in the URI string, and a port number is not specified within the URI, then default port number implied by that URI scheme MUST be used by the client to contact the IPP object.3. If the URI scheme does not allow an explicit port number to be specified within the URI, then the default port number implied by that URI MUST be used by the client to contact the IPP object.Note: The IPP "Encoding and Transport document [RFC2910] shows a mapping of IPP onto HTTP/1.1 [RFC2616] and defines a new default port number for using IPP over HTTP/1.1.
- 3.1.6 Operation Response Status Codes and Status Messages
- Every operation response includes a REQUIRED "status-code" parameter and an OPTIONAL "status-message" operation attribute, and an OPTIONAL "detailed-status-message" operation attribute. The Print-URI and Send-URI response MAY include an OPTIONAL "document-access-error" operation attribute.
- 3.1.6.1 "status-code" (type2 enum)
- The REQUIRED "status-code" parameter provides information on the processing of a request.
The status code is intended for use by automata. A client implementation of IPP SHOULD convert status code values into any localized message that has semantic meaning to the end user.
The "status-code" value is a numeric value that has semantic meaning. The "status-code" syntax is similar to a "type2 enum" (see section 4.1 on "Attribute Syntaxes") except that values can range only from 0x0000 to 0x7FFF. Section 13 describes the status codes, assigns the numeric values, and suggests a corresponding status message for each status code for use by the client when the user's natural language is English.
If the Printer performs an operation with no errors and it encounters no problems, it MUST return the status code 'successful-ok' in the response. See section 13.
If the client supplies unsupported values for the following parameters or Operation attributes, the Printer object MUST reject the operation, NEED NOT return the unsupported attribute value in the Unsupported Attributes group, and MUST return the indicated status code:
version-number server-error-version-not-supported operation-id server-error-operation-not-supported attributes-charset client-error-charset-not-supported compression client-error-compression-not-supported document-format client-error-document-format-not-supported document-uri client-error-uri-scheme-not-supported, client-error-document-access-errorIf the client supplies unsupported values for other attributes, or unsupported attributes, the Printer returns the status code defined in section 3.1.7 on Unsupported Attributes.
- 3.1.6.2 "status-message" (text(255))
- The OPTIONAL "status-message" operation attribute provides a short textual description of the status of the operation. The "status- message" attribute's syntax is "text(255)", so the maximum length is 255 octets (see section 4.1.1). The status message is intended for the human end user. If a response does include a "status-message" attribute, an IPP client NEED NOT examine or display the messages, however it SHOULD do so in some implementation specific manner. The "status-message" is especially useful for a later version of a Printer object to return as supplemental information for the human user to accompany a status code that an earlier version of a client might not understand.
If the Printer object supports the "status-message" operation attribute, the Printer object MUST be able to generate this message in any of the natural languages identified by the Printer object's "generated-natural-language-supported" attribute (see the "attributes-natural-language" operation attribute specified in section 3.1.4.1. Section 13 suggests the text for the status message returned by the Printer for use with the English natural language.
As described in section 3.1.4.1 for any returned 'text' attribute, if there is a choice for generating this message, the Printer object uses the natural language indicated by the value of the "attributes- natural-language" in the client request if supported, otherwise the Printer object uses the value in the Printer object's own "natural- language-configured" attribute.
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 13): '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.
- 3.1.6.3 "detailed-status-message" (text(MAX))
- might obscure the technical meaning of such messages. Clients MUST NOT attempt to parse the value of this attribute. See the "document-access-error" operation attribute (section 3.1.6.4) for additional errors that a program can process.
The OPTIONAL "detailed-status-message" operation attribute provides additional more detailed technical and implementation-specific information about the operation. The "detailed-status-message" attribute's syntax is "text(MAX)", so the maximum length is 1023 octets (see section 4.1.1). If the Printer objects supports the "detailed-status-message" operation attribute, the Printer NEED NOT localize the message, since it is intended for use by the system administrator or other experienced technical persons. Localization- 3.1.6.4 "document-access-error" (text(MAX))
- This OPTIONAL operation attribute provides additional information about any document access errors encountered by the Printer before it returned a response to the Print-URI (section 3.2.2) or Send-URI (section 3.3.1) operation. For errors in the protocol identified by the URI scheme in the "document-uri" operation attribute, such as 'http:' or 'ftp:', the error code is returned in parentheses, followed by the URI. For example:
Most Internet protocols use decimal error codes (unlike IPP), so the ASCII error code representation is in decimal.
- 3.1.7 Unsupported Attributes
- The Unsupported Attributes group contains attributes that are not supported by the operation. This group is primarily for the job creation operations, but all operations can return this group.
A Printer object MUST include an Unsupported Attributes group in a response if the status code is one of the following: 'successful- ok-ignored-or-substituted-attributes', 'successful-ok-conflicting- attributes', 'client-error-attributes-or-values-not-supported' or 'client-error-conflicting-attributes'.
If the status code is one of the four specified in the preceding paragraph, the Unsupported Attributes group MUST contain all of those attributes and only those attributes that are:
a. an Operation or Job Template attribute supplied in the request, andb. unsupported by the printer. See below for details on the three categories "unsupported" attributes.If the status code is one of those in the table in section 3.1.6.1, the Unsupported Attributes group NEED NOT contain the unsupported parameter or attribute indicated in that table. If the Printer object is not returning any Unsupported Attributes in the response, the Printer object SHOULD omit Group 2 rather than sending an empty group. However, a client MUST be able to accept an empty group.
Unsupported attributes fall into three categories:
1. The Printer object does not support the supplied attribute (no matter what the attribute syntax or value).2. The Printer object does support the attribute, but does not support some or all of the particular attribute syntaxes or values supplied by the client (i.e., the Printer object does not have those attribute syntaxes or values in its corresponding "xxx-supported" attribute).3. The Printer object does support the attributes and values supplied, but the particular values are in conflict with one another, because they violate a constraint, such as not being able to staple transparencies.In the case of an unsupported attribute name, the Printer object returns the client-supplied attribute with a substituted value of 'unsupported'. This value's syntax type is "out-of-band" and its encoding is defined by special rules for "out-of-band" values in the "Encoding and Transport" document [RFC2910]. Its value indicates no support for the attribute itself (see the beginning of section 4.1).
In the case of a supported attribute with one or more unsupported attribute syntaxes or values, the Printer object simply returns the client-supplied attribute with the unsupported attribute syntaxes or values as supplied by the client. This indicates support for the attribute, but no support for that particular attribute syntax or value. If the client supplies a multi-valued attribute with more than one value and the Printer object supports the attribute but only supports a subset of the client-supplied attribute syntaxes or values, the Printer object
MUST return only those attribute syntaxes or values that are unsupported.
In the case of two (or more) supported attribute values that are in conflict with one another (although each is supported independently, the values conflict when requested together within the same job), the Printer object MUST return all the values that it ignores or substitutes to resolve the conflict, but not any of the values that it is still using. The choice for exactly how to resolve the conflict is implementation dependent. See sections 3.2.1.2 and 15. See The Implementer's Guide [IPP-IIG] for an example.
- 3.1.8 Versions
- Each operation request and response carries with it a "version- number" parameter. Each value of the "version-number" is in the form "X.Y" where X is the major version number and Y is the minor version number. By including a version number in the client request, it allows the client to identify which version of IPP it is interested in using, i.e., the version whose conformance requirements the client may be depending upon the Printer to meet.
If the IPP object does not support that major version number supplied by the client, i.e., the major version field of the "version-number" parameter does not match any of the values of the Printer's "ipp- versions-supported" (see section 4.4.14), the object MUST respond with a status code of 'server-error-version-not-supported' along with the closest version number that is supported (see section 13.1.5.4). If the major version number is supported, but the minor version number is not, the IPP object SHOULD accept and attempt to perform the request (or reject the request if the operation is not supported), else it rejects the request and returns the 'server- error-version-not-supported' status code. In all cases, the IPP object MUST return the "version-number" that it supports that is closest to the version number supplied by the client in the request.
There is no version negotiation per se. However, if after receiving a 'server-error-version-not-supported' status code from an IPP object, a client SHOULD try again with a different version number. A client MAY also determine the versions supported either from a directory that conforms to Appendix E (see section 16) or by querying the Printer object's "ipp-versions-supported" attribute (see section 4.4.14) to determine which versions are supported.
An IPP object implementation MUST support version '1.1', i.e., meet the conformance requirements for IPP/1.1 as specified in this document and [RFC2910]. It is recommended that IPP object implementations accept any request with the major version '1' (or reject the request if the operation is not supported).
There is only one notion of "version number" that covers both IPP Model and IPP Protocol changes. Thus the version number MUST change when introducing a new version of the Model and Semantics document (this document) or a new version of the "Encoding and Transport" document [RFC2910]. Changes to the major version number of the Model and Semantics document indicate structural or syntactic changes that make it impossible for older version of IPP clients and Printer objects to correctly parse and correctly process the new or changed attributes, operations and responses. If the major version number changes, the minor version numbers is set to zero. As an example, adding the REQUIRED "ipp-attribute-fidelity" attribute to version '1.1' (if it had not been part of version '1.0'), would have required a change to the major version number, since an IPP/1.0 Printer would not have processed a request with the correct semantics that contained the "ipp-attribute-fidelity" attribute that it did not know about. Items that might affect the changing of the major version number include any changes to the Model and Semantics document (this document) or the "Encoding and Transport" document [RFC2910] itself, such as:
- reordering of ordered attributes or attribute sets - changes to the syntax of existing attributes - adding REQUIRED (for an IPP object to support) operation attribute groups - adding values to existing REQUIRED operation attributes - adding REQUIRED operationsChanges to the minor version number indicate the addition of new features, attributes and attribute values that may not be understood by all IPP objects, but which can be ignored if not understood. Items that might affect the changing of the minor version number include any changes to the model objects and attributes but not the encoding and transport rules [RFC2910] (except adding attribute syntaxes). Examples of such changes are:
- grouping all extensions not included in a previous version into a new version - adding new attribute values - adding new object attributes - adding OPTIONAL (for an IPP object to support) operation attributes (i.e., those attributes that an IPP object can ignore without confusing clients) - adding OPTIONAL (for an IPP object to support) operation attribute groups (i.e., those attributes that an IPP object can ignore without confusing clients) - adding new attribute syntaxes - adding OPTIONAL operations - changing Job Description attributes or Printer Description attributes from OPTIONAL to REQUIRED or vice versa. - adding OPTIONAL attribute syntaxes to an existing attribute.The encoding of the "version-number" MUST NOT change over any version number (either major or minor). This rule guarantees that all future versions will be backwards compatible with all previous versions (at least for checking the "version-number"). In addition, any protocol elements (attributes, error codes, tags, etc.) that are not carried forward from one version to the next are deprecated so that they can never be reused with new semantics.
Implementations that support a certain version NEED NOT support ALL previous versions. As each new version is defined (through the release of a new IPP specification document), that version will specify which previous versions MUST and which versions SHOULD be supported in compliant implementations.
- 3.1.9 Job Creation Operations
- In order to "submit a print job" and create a new Job object, a client issues a create request. A create request is any one of following three operation requests:
- The Print-Job Request: A client that wants to submit a print job with only a single document uses the Print-Job operation. The operation allows for the client to "push" the document data to the Printer object by including the document data in the request itself.- The Print-URI Request: A client that wants to submit a print job with only a single document (where the Printer object "pulls" the document data instead of the client "pushing" the data to the Printer object) uses the Print-URI operation. In this case, the client includes in the request only a URI reference to the document data (not the document data itself).- The Create-Job Request: A client that wants to submit a print job with multiple documents uses the Create-Job operation. This operation is followed by an arbitrary number (one or more) of Send-Document and/or Send-URI operations (each creating another document for the newly create Job object). The Send-Document operation includes the document data in the request (the client "pushes" the document data to the printer), and the Send-URI operation includes only a URI reference to the document data in the request (the Printer "pulls" the document data from the referenced location). The last Send-Document or Send-URI request for a given Job object includes a "last-document" operation attribute set to 'true' indicating that this is the last request.Throughout this model document, the term "create request" is used to refer to any of these three operation requests. A Create-Job operation followed by only one Send-Document operation is semantically equivalent to a Print-Job operation, however, for performance reasons, the client SHOULD use the Print-Job operation for all single document jobs. Also, Print-Job is a REQUIRED operation (all implementations MUST support it) whereas Create-Job is an OPTIONAL operation, hence some implementations might not support it.
Job submission time is the point in time when a client issues a create request. The initial state of every Job object is the 'pending', 'pending-held', or 'processing' state (see section 4.3.7). When the Printer object begins processing the print job, the Job object's state moves to 'processing'. This is known as job processing time. There are validation checks that must be done at job submission time and others that must be performed at job processing time.
At job submission time and at the time a Validate-Job operation is received, the Printer MUST do the following:
1. Process the client supplied attributes and either accept or reject the request 2. Validate the syntax of and support for the scheme of any client supplied URIAt job submission time the Printer object MUST validate whether or not the supplied attributes, attribute syntaxes, and values are supported by matching them with the Printer object's corresponding "xxx-supported" attributes. See section 3.1.7 for details. [IPP- IIG] presents suggested steps for an IPP object to either accept or reject any request and additional steps for processing create requests.
At job submission time the Printer object NEED NOT perform the validation checks reserved for job processing time such as:
1. Validating the document data 2. Validating the actual contents of any client supplied URI (resolve the reference and follow the link to the document data)At job submission time, these additional job processing time validation checks are essentially useless, since they require actually parsing and interpreting the document data, are not guaranteed to be 100% accurate, and MUST be done, yet again, at job processing time. Also, in the case of a URI, checking for availability at job submission time does not guarantee availability at job processing time. In addition, at job processing time, the Printer object might discover any of the following conditions that were not detectable at job submission time:
- runtime errors in the document data, - nested document data that is in an unsupported format, - the URI reference is no longer valid (i.e., the server hosting the document might be down), or - any other job processing errorAt job submission time, a Printer object, especially a non-spooling Printer, MAY accept jobs that it does not have enough space for. In such a situation, a Printer object MAY stop reading data from a client for an indefinite period of time. A client MUST be prepared for a write operation to block for an indefinite period of time (see section 5.1 on client conformance).
When a Printer object has too little space for starting a new job, it MAY reject a new create request. In this case, a Printer object MUST return a response (in reply to the rejected request) with a status- code of 'server-error-busy' (see section 14.1.5.8) and it MAY close the connection before receiving all bytes of the operation. A Printer SHOULD indicate that it is temporarily unable to accept jobs by setting the 'spool-space-full' value in its "printer-state- reasons" attribute and removing the value when it can accept another job (see section 4.4.12).
When receiving a 'server-error-busy' status-code in an operation response, a client MUST be prepared for the Printer object to close the connection before the client has sent all of the data (especially for the Print-Job operation). A client MUST be prepared to keep submitting a create request until the IPP Printer object accepts the create request.
At job processing time, since the Printer object has already responded with a successful status code in the response to the create request, if the Printer object detects an error, the Printer object is unable to inform the end user of the error with an operation status code. In this case, the Printer, depending on the error, can set the job object's "job-state", "job-state-reasons", or "job- state-message" attributes to the appropriate value(s) so that later queries can report the correct job status.
Note: Asynchronous notification of events is outside the scope of this IPP/1.1 document.
- 3.2 Printer Operations
- All Printer operations are directed at Printer objects. A client MUST always supply the "printer-uri" operation attribute in order to identify the correct target of the operation.
- 3.2.1 Print-Job Operation
- This REQUIRED operation allows a client to submit a print job with only one document and supply the document data (rather than just a reference to the data). See Section 15 for the suggested steps for processing create operations and their Operation and Job Template attributes.
- 3.2.1.1 Print-Job Request
- The following groups of attributes are supplied as part of the Print-Job Request:
Natural Language and Character Set: The "attributes-charset" and "attributes-natural-language" attributes as described in section 3.1.4.1. The Printer object MUST copy these values to the corresponding Job Description attributes described in sections 4.3.19 and 4.3.20.Target: The "printer-uri" (uri) operation attribute which is the target for this operation as described in section 3.1.5.Requesting User Name: The "requesting-user-name" (name(MAX)) attribute SHOULD be supplied by the client as described in section 8.3."job-name" (name(MAX)): The client OPTIONALLY supplies this attribute. The Printer object MUST support this attribute. It contains the client supplied Job name. If this attribute is supplied by the client, its value is used for the "job-name" attribute of the newly created Job object. The client MAY automatically include any information that will help the end-user distinguish amongst his/her jobs, such as the name of the application program along with information from the document, such as the document name, document subject, or source file name. If this attribute is not supplied by the client, the Printer generates a name to use in the "job-name" attribute of the newly created Job object (see Section 4.3.5)."ipp-attribute-fidelity" (boolean): The client OPTIONALLY supplies this attribute. The Printer object MUST support this attribute. The value 'true' indicates that total fidelity to client supplied Job Template attributes and values is required, else the Printer object MUST reject the Print-Job request. The value 'false' indicates that a reasonable attempt to print the Job object is acceptable and the Printer object MUST accept the Print-Job request. If not supplied, the Printer object assumes the value is 'false'. All Printer objects MUST support both types of job processing. See section 15 for a full description of "ipp-attribute-fidelity" and its relationship to other attributes, especially the Printer object's "pdl-override-supported" attribute."document-name" (name(MAX)): The client OPTIONALLY supplies this attribute. The Printer object MUST support this attribute. It contains the client supplied document name. The document name MAY be different than the Job name. Typically, the client software automatically supplies the document name on behalf of the end user by using a file name or an application generated name. If this attribute is supplied, its value can be used in a manner defined by each implementation. Examples include: printed along with the Job (job start sheet, page adornments, etc.), used by accounting or resource tracking management tools, or even stored along with the document as a document level attribute. IPP/1.1 does not support the concept of document level attributes."compression" (type3 keyword): The client OPTIONALLY supplies this attribute. The Printer object MUST support this attribute and the "compression- supported" attribute (see section 4.4.32). The client supplied "compression" operation attribute identifies the compression algorithm used on the document data. The following cases exist:a) If the client omits this attribute, the Printer object MUST assume that the data is not compressed (i.e. the Printer follows the rules below as if the client supplied the "compression" attribute with a value of 'none'). b) If the client supplies this attribute, but the value is not supported by the Printer object, i.e., the value is not one of the values of the Printer object's "compression- supported" attribute, the Printer object MUST reject the request, and return the 'client-error-compression-not- supported' status code. See section 3.1.7 for returning unsupported attributes and values.c) If the client supplies the attribute and the Printer object supports the attribute value, the Printer object uses the corresponding decompression algorithm on the document data. d) If the decompression algorithm fails before the Printer returns an operation response, the Printer object MUST reject the request and return the 'client-error- compression-error' status code. e) If the decompression algorithm fails after the Printer returns an operation response, the Printer object MUST abort the job and add the 'compression-error' value to the job's "job-state-reasons" attribute. f) If the decompression algorithm succeeds, the document data MUST then have the format specified by the job's "document- format" attribute, if supplied (see "document-format" operation attribute definition below)."document-format" (mimeMediaType): The client OPTIONALLY supplies this attribute. The Printer object MUST support this attribute. The value of this attribute identifies the format of the supplied document data. The following cases exist: