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rfc:rfc8010

Internet Engineering Task Force (IETF) M. Sweet Request for Comments: 8010 Apple Inc. Obsoletes: 2910, 3382 I. McDonald Category: Standards Track High North, Inc. ISSN: 2070-1721 January 2017

       Internet Printing Protocol/1.1: Encoding and Transport

Abstract

 The Internet Printing Protocol (IPP) is an application-level protocol
 for distributed printing using Internet tools and technologies.  This
 document defines the rules for encoding IPP operations, attributes,
 and values into the Internet MIME media type called
 "application/ipp".  It also defines the rules for transporting a
 message body whose Content-Type is "application/ipp" over HTTP and/or
 HTTPS.  The IPP data model and operation semantics are described in
 "Internet Printing Protocol/1.1: Model and Semantics" (RFC 8011).
 This document obsoletes RFCs 2910 and 3382.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc8010.

Sweet & McDonald Standards Track [Page 1] RFC 8010 IPP/1.1: Encoding and Transport January 2017

Copyright Notice

 Copyright (c) 2017 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
 2.  Conventions Used in This Document . . . . . . . . . . . . . .   5
   2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.2.  Printing Terminology  . . . . . . . . . . . . . . . . . .   5
   2.3.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   6
 3.  Encoding of the Operation Layer . . . . . . . . . . . . . . .   6
   3.1.  Picture of the Encoding . . . . . . . . . . . . . . . . .   8
     3.1.1.  Request and Response  . . . . . . . . . . . . . . . .   8
     3.1.2.  Attribute Group . . . . . . . . . . . . . . . . . . .   9
     3.1.3.  Attribute . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.4.  Attribute-with-one-value  . . . . . . . . . . . . . .  10
     3.1.5.  Additional-value  . . . . . . . . . . . . . . . . . .  11
     3.1.6.  Collection Attribute  . . . . . . . . . . . . . . . .  12
     3.1.7.  Member Attributes . . . . . . . . . . . . . . . . . .  13
     3.1.8.  Alternative Picture of the Encoding of a Request or a
             Response  . . . . . . . . . . . . . . . . . . . . . .  14
   3.2.  Syntax of Encoding  . . . . . . . . . . . . . . . . . . .  15
   3.3.  Attribute-group . . . . . . . . . . . . . . . . . . . . .  16
   3.4.  Required Parameters . . . . . . . . . . . . . . . . . . .  18
     3.4.1.  "version-number"  . . . . . . . . . . . . . . . . . .  18
     3.4.2.  "operation-id"  . . . . . . . . . . . . . . . . . . .  18
     3.4.3.  "status-code" . . . . . . . . . . . . . . . . . . . .  19
     3.4.4.  "request-id"  . . . . . . . . . . . . . . . . . . . .  19
   3.5.  Tags  . . . . . . . . . . . . . . . . . . . . . . . . . .  19
     3.5.1.  "delimiter-tag" Values  . . . . . . . . . . . . . . .  19
     3.5.2.  "value-tag" Values  . . . . . . . . . . . . . . . . .  20
   3.6.  "name-length" . . . . . . . . . . . . . . . . . . . . . .  23
   3.7.  (Attribute) "name"  . . . . . . . . . . . . . . . . . . .  23
   3.8.  "value-length"  . . . . . . . . . . . . . . . . . . . . .  23
   3.9.  (Attribute) "value" . . . . . . . . . . . . . . . . . . .  24
   3.10. Data  . . . . . . . . . . . . . . . . . . . . . . . . . .  25

Sweet & McDonald Standards Track [Page 2] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 4.  Encoding of Transport Layer . . . . . . . . . . . . . . . . .  26
   4.1.  Printer URI, Job URI, and Job ID  . . . . . . . . . . . .  26
 5.  IPP URI Schemes . . . . . . . . . . . . . . . . . . . . . . .  28
 6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  29
 7.  Internationalization Considerations . . . . . . . . . . . . .  31
 8.  Security Considerations . . . . . . . . . . . . . . . . . . .  31
   8.1.  Security Conformance Requirements . . . . . . . . . . . .  31
     8.1.1.  Digest Authentication . . . . . . . . . . . . . . . .  32
     8.1.2.  Transport Layer Security (TLS)  . . . . . . . . . . .  32
   8.2.  Using IPP with TLS  . . . . . . . . . . . . . . . . . . .  33
 9.  Interoperability with Other IPP Versions  . . . . . . . . . .  33
   9.1.  The "version-number" Parameter  . . . . . . . . . . . . .  34
   9.2.  Security and URI Schemes  . . . . . . . . . . . . . . . .  34
 10. Changes since RFC 2910  . . . . . . . . . . . . . . . . . . .  35
 11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  36
   11.1.  Normative References . . . . . . . . . . . . . . . . . .  36
   11.2.  Informative References . . . . . . . . . . . . . . . . .  38
 Appendix A.  Protocol Examples  . . . . . . . . . . . . . . . . .  40
   A.1.  Print-Job Request . . . . . . . . . . . . . . . . . . . .  40
   A.2.  Print-Job Response (Successful) . . . . . . . . . . . . .  41
   A.3.  Print-Job Response (Failure)  . . . . . . . . . . . . . .  42
   A.4.  Print-Job Response (Success with Attributes Ignored)  . .  43
   A.5.  Print-URI Request . . . . . . . . . . . . . . . . . . . .  45
   A.6.  Create-Job Request  . . . . . . . . . . . . . . . . . . .  46
   A.7.  Create-Job Request with Collection Attributes . . . . . .  46
   A.8.  Get-Jobs Request  . . . . . . . . . . . . . . . . . . . .  48
   A.9.  Get-Jobs Response . . . . . . . . . . . . . . . . . . . .  49
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  51
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  51

Sweet & McDonald Standards Track [Page 3] RFC 8010 IPP/1.1: Encoding and Transport January 2017

1. Introduction

 This document contains the rules for encoding IPP operations and
 describes two layers: the transport layer and the operation layer.
 The transport layer consists of an HTTP request and response.  All
 IPP implementations support HTTP/1.1, the relevant parts of which are
 described in the following RFCs:
 o  Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
    [RFC7230]
 o  Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
    [RFC7231]
 o  Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
    [RFC7232]
 o  Hypertext Transfer Protocol (HTTP/1.1): Caching [RFC7234]
 o  Hypertext Transfer Protocol (HTTP/1.1): Authentication [RFC7235]
 o  The 'Basic' HTTP Authentication Scheme [RFC7617]
 o  HTTP Digest Access Authentication [RFC7616]
 IPP implementations can support HTTP/2, which is described in the
 following RFCs:
 o  Hypertext Transfer Protocol Version 2 (HTTP/2) [RFC7540]
 o  HPACK - Header Compression for HTTP/2 [RFC7541]
 This document specifies the HTTP headers that an IPP implementation
 supports.
 The operation layer consists of a message body in an HTTP request or
 response.  The "Internet Printing Protocol/1.1: Model and Semantics"
 document [RFC8011] and subsequent extensions (collectively known as
 the IPP Model) define the semantics of such a message body and the
 supported values.  This document specifies the encoding of an IPP
 request and response message.

Sweet & McDonald Standards Track [Page 4] RFC 8010 IPP/1.1: Encoding and Transport January 2017

2. Conventions Used in This Document

2.1. Requirements Language

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

2.2. Printing Terminology

 Client: Initiator of outgoing IPP session requests and sender of
 outgoing IPP operation requests (Hypertext Transfer Protocol --
 HTTP/1.1 [RFC7230] User Agent).
 Document: An object created and managed by a Printer that contains
 description, processing, and status information.  A Document object
 may have attached data and is bound to a single Job.
 'ipp' URI: An IPP URI as defined in [RFC3510].
 'ipps' URI: An IPPS URI as defined in [RFC7472].
 Job: An object created and managed by a Printer that contains
 description, processing, and status information.  The Job also
 contains zero or more Document objects.
 Logical Device: A print server, software service, or gateway that
 processes Jobs and either forwards or stores the processed Job or
 uses one or more Physical Devices to render output.
 Model: The semantics of operations, attributes, values, and status-
 codes used in the Internet Printing Protocol as defined in the
 Internet Printing Protocol/1.1: Model and Semantics document
 [RFC8011] and subsequent extensions.
 Output Device: A single Logical or Physical Device.
 Physical Device: A hardware implementation of an endpoint device,
 e.g., a marking engine, a fax modem, etc.
 Printer: Listener for incoming IPP session requests and receiver of
 incoming IPP operation requests (Hypertext Transfer Protocol --
 HTTP/1.1 [RFC7230] Server) that represents one or more Physical
 Devices or a Logical Device.

Sweet & McDonald Standards Track [Page 5] RFC 8010 IPP/1.1: Encoding and Transport January 2017

2.3. Abbreviations

 ABNF: Augmented Backus-Naur Form [RFC5234]
 ASCII: American Standard Code for Information Interchange [RFC20]
 HTTP: Hypertext Transfer Protocol [RFC7230]
 HTTPS: HTTP over TLS [RFC2818]
 IANA: Internet Assigned Numbers Authority
 IEEE: Institute of Electrical and Electronics Engineers
 IESG: Internet Engineering Steering Group
 IPP: Internet Printing Protocol (this document and [PWG5100.12])
 ISTO: IEEE Industry Standards and Technology Organization
 LPD: Line Printer Daemon Protocol [RFC1179]
 PWG: IEEE-ISTO Printer Working Group
 RFC: Request for Comments
 TCP: Transmission Control Protocol [RFC793]
 TLS: Transport Layer Security [RFC5246]
 URI: Uniform Resource Identifier [RFC3986]
 URL: Uniform Resource Locator [RFC3986]
 UTF-8: Unicode Transformation Format - 8-bit [RFC3629]

3. Encoding of the Operation Layer

 The operation layer is the message body part of the HTTP request or
 response and it MUST contain a single IPP operation request or IPP
 operation response.  Each request or response consists of a sequence
 of values and attribute groups.  Attribute groups consist of a
 sequence of attributes each of which is a name and value.  Names and
 values are ultimately sequences of octets.
 The encoding consists of octets as the most primitive type.  There
 are several types built from octets, but three important types are
 integers, character strings, and octet strings, on which most other

Sweet & McDonald Standards Track [Page 6] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 data types are built.  Every character string in this encoding MUST
 be a sequence of characters where the characters are associated with
 some charset [RFC2978] and some natural language.  A character string
 MUST be in "reading order" with the first character in the value
 (according to reading order) being the first character in the
 encoding.  A character string whose associated charset is US-ASCII
 and whose associated natural language is US English is henceforth
 called a US-ASCII-STRING.  A character string whose associated
 charset and natural language are specified in a request or response
 as described in the Model is henceforth called a LOCALIZED-STRING.
 An octet string MUST be in "Model order" with the first octet in the
 value (according to the Model order) being the first octet in the
 encoding.  Every integer in this encoding MUST be encoded as a signed
 integer using two's-complement binary encoding with big-endian format
 (also known as "network order" and "most significant byte first").
 The number of octets for an integer MUST be 1, 2, or 4, depending on
 usage in the protocol.  A one-octet integer, henceforth called a
 SIGNED-BYTE, is used for the version-number and tag fields.  A two-
 byte integer, henceforth called a SIGNED-SHORT, is used for the
 operation-id, status-code, and length fields.  A four-byte integer,
 henceforth called a SIGNED-INTEGER, is used for value fields and the
 request-id.
 The following two sections present the encoding of the operation
 layer in two ways:
 o  informally through pictures and description
 o  formally through Augmented Backus-Naur Form (ABNF), as specified
    by RFC 5234 [RFC5234]
 An operation request or response MUST use the encoding described in
 these two sections.

Sweet & McDonald Standards Track [Page 7] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.1. Picture of the Encoding

3.1.1. Request and Response

 An operation request or response is encoded as follows:
  1. ———————————————-

| version-number | 2 bytes - required

  1. ———————————————-

| operation-id (request) |

 |                      or                     |   2 bytes  - required
 |               status-code (response)        |
 -----------------------------------------------
 |                   request-id                |   4 bytes  - required
 -----------------------------------------------
 |                 attribute-group             |   n bytes - 0 or more
 -----------------------------------------------
 |              end-of-attributes-tag          |   1 byte   - required
 -----------------------------------------------
 |                     data                    |   q bytes  - optional
 -----------------------------------------------
                     Figure 1: IPP Message Format
 The first three fields in the above diagram contain the value of
 attributes described in Section 4.1.1 of the Model and Semantics
 document [RFC8011].
 The fourth field is the "attribute-group" field, and it occurs 0 or
 more times.  Each "attribute-group" field represents a single group
 of attributes, such as an Operation Attributes group or a Job
 Attributes group (see the Model).  The Model specifies the required
 attribute groups and their order for each operation request and
 response.
 The "end-of-attributes-tag" field is always present, even when the
 "data" is not present.  The Model specifies whether the "data" field
 is present for each operation request and response.

Sweet & McDonald Standards Track [Page 8] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.1.2. Attribute Group

 Each "attribute-group" field is encoded as follows:
  1. ———————————————-

| begin-attribute-group-tag | 1 byte

  1. ———————————————————

| attribute | p bytes |- 0 or more

  1. ———————————————————
                  Figure 2: Attribute Group Encoding
 An "attribute-group" field contains zero or more "attribute" fields.
 Note that the values of the "begin-attribute-group-tag" field and the
 "end-of-attributes-tag" field are called "delimiter-tags".

3.1.3. Attribute

 An "attribute" field is encoded as follows:
  1. ———————————————-

| attribute-with-one-value | q bytes

  1. ———————————————————

| additional-value | r bytes |- 0 or more

  1. ———————————————————
                     Figure 3: Attribute Encoding
 When an attribute is single valued (e.g., "copies" with a value of
 10) or multi-valued with one value (e.g., "sides-supported" with just
 the value 'one-sided'), it is encoded with just an "attribute-with-
 one-value" field.  When an attribute is multi-valued with n values
 (e.g., "sides-supported" with the values 'one-sided' and 'two-sided-
 long-edge'), it is encoded with an "attribute-with-one-value" field
 followed by n-1 "additional-value" fields.

Sweet & McDonald Standards Track [Page 9] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.1.4. Attribute-with-one-value

 Each "attribute-with-one-value" field is encoded as follows:
  1. ———————————————-

| value-tag | 1 byte

  1. ———————————————-

| name-length (value is u) | 2 bytes

  1. ———————————————-

| name | u bytes

  1. ———————————————-

| value-length (value is v) | 2 bytes

  1. ———————————————-

| value | v bytes

  1. ———————————————-
               Figure 4: Single Value Attribute Encoding
 An "attribute-with-one-value" field is encoded with five subfields:
 o  The "value-tag" field specifies the attribute syntax, e.g., 0x44
    for the attribute syntax 'keyword'.
 o  The "name-length" field specifies the length of the "name" field
    in bytes, e.g., u in the above diagram or 15 for the name "sides-
    supported".
 o  The "name" field contains the textual name of the attribute, e.g.,
    "sides-supported".
 o  The "value-length" field specifies the length of the "value" field
    in bytes, e.g., v in the above diagram or 9 for the (keyword)
    value 'one-sided'.
 o  The "value" field contains the value of the attribute, e.g., the
    textual value 'one-sided'.

Sweet & McDonald Standards Track [Page 10] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.1.5. Additional-value

 Each "additional-value" field is encoded as follows:
  1. ———————————————-

| value-tag | 1 byte

  1. ———————————————-

| name-length (value is 0x0000) | 2 bytes

  1. ———————————————-

| value-length (value is w) | 2 bytes

  1. ———————————————-

| value | w bytes

  1. ———————————————-
             Figure 5: Additional Attribute Value Encoding
 An "additional-value" is encoded with four subfields:
 o  The "value-tag" field specifies the attribute syntax, e.g., 0x44
    for the attribute syntax 'keyword'.
 o  The "name-length" field has the value of 0 in order to signify
    that it is an "additional-value".  The value of the "name-length"
    field distinguishes an "additional-value" field ("name-length" is
    0) from an "attribute-with-one-value" field ("name-length" is not
    0).
 o  The "value-length" field specifies the length of the "value" field
    in bytes, e.g., w in the above diagram or 19 for the (keyword)
    value 'two-sided-long-edge'.
 o  The "value" field contains the value of the attribute, e.g., the
    textual value 'two-sided-long-edge'.

Sweet & McDonald Standards Track [Page 11] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.1.6. Collection Attribute

 Collection attributes create a named group containing related
 "member" attributes.  The "attribute-with-one-value" field for a
 collection attribute is encoded as follows:
  1. ———————————————-

| value-tag (value is 0x34) | 1 byte

  1. ———————————————-

| name-length (value is u) | 2 bytes

  1. ———————————————-

| name | u bytes

  1. ———————————————-

| value-length (value is 0x0000) | 2 bytes

  1. ———————————————————-

| member-attribute | q bytes |-0 or more

  1. ———————————————————-

| end-value-tag (value is 0x37) | 1 byte

  1. ———————————————-

| end-name-length (value is 0x0000) | 2 bytes

  1. ———————————————-

| end-value-length (value is 0x0000) | 2 bytes

  1. ———————————————-
                Figure 6: Collection Attribute Encoding
 Collection attribute is encoded with eight subfields:
 o  The "value-tag" field specifies the start attribute syntax: 0x34
    for the attribute syntax 'begCollection'.
 o  The "name-length" field specifies the length of the "name" field
    in bytes, e.g., u in the above diagram or 9 for the name "media-
    col".  Additional collection attribute values use a name length of
    0x0000.
 o  The "name" field contains the textual name of the attribute, e.g.,
    "media-col".
 o  The "value-length" field specifies a length of 0x0000.
 o  The "member-attribute" field contains member attributes encoded as
    defined in Section 3.1.7.
 o  The "end-value-tag" field specifies the end attribute syntax: 0x37
    for the attribute syntax 'endCollection'.
 o  The "end-name-length" field specifies a length of 0x0000.

Sweet & McDonald Standards Track [Page 12] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 o  The "end-value-length" field specifies a length of 0x0000.

3.1.7. Member Attributes

 Each "member-attribute" field is encoded as follows:
  1. ———————————————-

| value-tag (value is 0x4a) | 1 byte

  1. ———————————————-

| name-length (value is 0x0000) | 2 bytes

  1. ———————————————-

| value-length (value is w) | 2 bytes

  1. ———————————————-

| value (member-name) | w bytes

  1. ———————————————-

| member-value-tag | 1 byte

  1. ———————————————-

| name-length (value is 0x0000) | 2 bytes

  1. ———————————————-

| member-value-length (value is x) | 2 bytes

  1. ———————————————-

| member-value | x bytes

  1. ———————————————-
                  Figure 7: Member Attribute Encoding
 A "member-attribute" is encoded with eight subfields:
 o  The "value-tag" field specifies 0x4a for the attribute syntax
    'memberAttrName'.
 o  The "name-length" field has the value of 0 in order to signify
    that it is a "member-attribute" contained in the collection.
 o  The "value-length" field specifies the length of the "value" field
    in bytes, e.g., w in the above diagram or 10 for the member
    attribute name 'media-type'.  Additional member attribute values
    are specified using a value length of 0.
 o  The "value" field contains the name of the member attribute, e.g.,
    the textual value 'media-type'.
 o  The "member-value-tag" field specifies the attribute syntax for
    the member attribute, e.g., 0x44 for the attribute syntax
    'keyword'.

Sweet & McDonald Standards Track [Page 13] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 o  The second "name-length" field has the value of 0 in order to
    signify that it is a "member-attribute" contained in the
    collection.
 o  The "member-value-length" field specifies the length of the member
    attribute value, e.g., x in the above diagram or 10 for the value
    'stationery'.
 o  The "member-value" field contains the value of the attribute,
    e.g., the textual value 'stationery'.

3.1.8. Alternative Picture of the Encoding of a Request or a Response

 From the standpoint of a parser that performs an action based on a
 "tag" value, the encoding consists of:
  1. ———————————————-

| version-number | 2 bytes - required

  1. ———————————————-

| operation-id (request) |

 |                      or                     |   2 bytes  - required
 |               status-code (response)        |
 -----------------------------------------------
 |                   request-id                |   4 bytes  - required
 -----------------------------------------------------------
 |        tag (delimiter-tag or value-tag)     |   1 byte  |
 -----------------------------------------------           |-0 or more
 |           empty or rest of attribute        |   x bytes |
 -----------------------------------------------------------
 |              end-of-attributes-tag          |   1 byte   - required
 -----------------------------------------------
 |                     data                    |   y bytes  - optional
 -----------------------------------------------
                Figure 8: Encoding Based on Value Tags
 The following shows what fields the parser would expect after each
 type of "tag":
 o  "begin-attribute-group-tag": expect zero or more "attribute"
    fields
 o  "value-tag": expect the remainder of an "attribute-with-one-value"
    or an "additional-value"
 o  "end-of-attributes-tag": expect that "attribute" fields are
    complete and there is optional "data"

Sweet & McDonald Standards Track [Page 14] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.2. Syntax of Encoding

 The ABNF [RFC5234] syntax for an IPP message is shown in Figure 9.
 ipp-message  = ipp-request / ipp-response
 ipp-request  = version-number operation-id request-id
                *attribute-group end-of-attributes-tag data
 ipp-response = version-number status-code request-id
                *attribute-group end-of-attributes-tag  data
 version-number       = major-version-number minor-version-number
 major-version-number = SIGNED-BYTE
 minor-version-number = SIGNED-BYTE
 operation-id = SIGNED-SHORT     ; mapping from model
 status-code  = SIGNED-SHORT     ; mapping from model
 request-id   = SIGNED-INTEGER   ; whose value is > 0
 attribute-group          = begin-attribute-group-tag *attribute
 attribute                = attribute-with-one-value *additional-value
 attribute-with-one-value = value-tag name-length name
                            value-length value
 additional-value         = value-tag zero-name-length
                            value-length value
 name-length  = SIGNED-SHORT     ; number of octets of 'name'
 name         = LALPHA *( LALPHA / DIGIT / "-" / "_" / "." )
 value-length = SIGNED-SHORT     ; number of octets of 'value'
 value        = OCTET-STRING
 data         = OCTET-STRING
 zero-name-length          = %x00.00           ; name-length of 0
 value-tag                 = %x10-ff           ; see Section 3.5.2
 begin-attribute-group-tag = %x00-02 / %x04-0f ; see Section 3.5.1
 end-of-attributes-tag     = %x03              ; tag of 3
                                               ; see Section 3.5.1
 SIGNED-BYTE    = BYTE
 SIGNED-SHORT   = 2BYTE
 SIGNED-INTEGER = 4BYTE
 DIGIT          = %x30-39        ; "0" to "9"
 LALPHA         = %x61-7A        ; "a" to "z"
 BYTE           = %x00-ff
 OCTET-STRING   = *BYTE
                 Figure 9: ABNF of IPP Message Format

Sweet & McDonald Standards Track [Page 15] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Figure 10 defines additional terms that are referenced in this
 document and provides an alternate grouping of the delimiter tags.
 delimiter-tag = begin-attribute-group-tag /   ; see Section 3.5.1
           end-of-attributes-tag
 begin-attribute-group-tag = %x00 / operation-attributes-tag /
    job-attributes-tag / printer-attributes-tag /
    unsupported-attributes-tag / future-group-tags
 operation-attributes-tag   = %x01             ; tag of 1
 job-attributes-tag         = %x02             ; tag of 2
 end-of-attributes-tag      = %x03             ; tag of 3
 printer-attributes-tag     = %x04             ; tag of 4
 unsupported-attributes-tag = %x05             ; tag of 5
 future-group-tags          = %x06-0f          ; future extensions
               Figure 10: ABNF for Attribute Group Tags

3.3. Attribute-group

 Each "attribute-group" field MUST be encoded with the "begin-
 attribute-group-tag" field followed by zero or more "attribute" sub-
 fields.

Sweet & McDonald Standards Track [Page 16] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Table 1 maps the Model group name to value of the "begin-attribute-
 group-tag" field:
 +----------------+--------------------------------------------------+
 | Model Document | "begin-attribute-group-tag" field values         |
 | Group          |                                                  |
 +----------------+--------------------------------------------------+
 | Operation      | "operations-attributes-tag"                      |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Job Template   | "job-attributes-tag"                             |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Job Object     | "job-attributes-tag"                             |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Unsupported    | "unsupported-attributes-tag"                     |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Requested      | (Get-Job-Attributes) "job-attributes-tag"        |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Requested      | (Get-Printer-Attributes)"printer-attributes-tag" |
 | Attributes     |                                                  |
 +----------------+--------------------------------------------------+
 | Document       | in a special position at the end of the message  |
 | Content        | as described in Section 3.1.1.                   |
 +----------------+--------------------------------------------------+
                         Table 1: Group Values
 For each operation request and response, the Model prescribes the
 required and optional attribute groups, along with their order.
 Within each attribute group, the Model prescribes the required and
 optional attributes, along with their order.
 When the Model requires an attribute group in a request or response
 and the attribute group contains zero attributes, a request or
 response SHOULD encode the attribute group with the "begin-attribute-
 group-tag" field followed by zero "attribute" fields.  For example,
 if the Client requests a single unsupported attribute with the Get-
 Printer-Attributes operation, the Printer MUST return no "attribute"
 fields, and it SHOULD return a "begin-attribute-group-tag" field for
 the Printer Attributes group.  The Unsupported Attributes group is
 not such an example.  According to the Model, the Unsupported
 Attributes group SHOULD be present only if the Unsupported Attributes
 group contains at least one attribute.

Sweet & McDonald Standards Track [Page 17] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 A receiver of a request MUST be able to process the following as
 equivalent empty attribute groups:
 a.  A "begin-attribute-group-tag" field with zero following
     "attribute" fields.
 b.  A missing, but expected, "begin-attribute-group-tag" field.
 When the Model requires a sequence of an unknown number of attribute
 groups, each of the same type, the encoding MUST contain one "begin-
 attribute-group-tag" field for each attribute group, even when an
 "attribute-group" field contains zero "attribute" sub-fields.  For
 example, the Get-Jobs operation may return zero attributes for some
 Jobs and not others.  The "begin-attribute-group-tag" field followed
 by zero "attribute" fields tells the recipient that there is a Job in
 queue for which no information is available except that it is in the
 queue.

3.4. Required Parameters

 Some operation elements are called parameters in the Model.  They
 MUST be encoded in a special position and they MUST NOT appear as
 operation attributes.  These parameters are described in the
 subsections below.

3.4.1. "version-number"

 The "version-number" field consists of a major and minor version-
 number, each of which is represented by a SIGNED-BYTE.  The major
 version-number is the first byte of the encoding and the minor
 version-number is the second byte of the encoding.  The protocol
 described in [RFC8011] has a major version-number of 1 (0x01) and a
 minor version-number of 1 (0x01).  The ABNF for these two bytes is
 %x01.01.
 Note: See Section 9 for more information on the "version-number"
 field and IPP version numbers.

3.4.2. "operation-id"

 The "operation-id" field contains an operation-id value as defined in
 the Model.  The value is encoded as a SIGNED-SHORT and is located in
 the third and fourth bytes of the encoding of an operation request.

Sweet & McDonald Standards Track [Page 18] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.4.3. "status-code"

 The "status-code" field contains a status-code value as defined in
 the Model.  The value is encoded as a SIGNED-SHORT and is located in
 the third and fourth bytes of the encoding of an operation response.
 If an IPP status-code is returned, then the HTTP status-code MUST be
 200 (OK).  With any other HTTP status-code value, the HTTP response
 MUST NOT contain an IPP message body, and thus no IPP status-code is
 returned.

3.4.4. "request-id"

 The "request-id" field contains the request-id value as defined in
 the Model.  The value is encoded as a SIGNED-INTEGER and is located
 in the fifth through eighth bytes of the encoding.

3.5. Tags

 There are two kinds of tags:
 o  delimiter tags: delimit major sections of the protocol, namely
    attribute groups and data
 o  value tags: specify the type of each attribute value
 Tags are part of the IANA IPP registry [IANA-IPP]

3.5.1. "delimiter-tag" Values

 Table 2 specifies the values for the delimiter tags defined in this
 document.  These tags are registered, along with tags defined in
 other documents, in the "Attribute Group Tags" registry.
          +-----------------+------------------------------+
          | Tag Value (Hex) | Meaning                      |
          +-----------------+------------------------------+
          | 0x00            | Reserved                     |
          | 0x01            | "operation-attributes-tag"   |
          | 0x02            | "job-attributes-tag"         |
          | 0x03            | "end-of-attributes-tag"      |
          | 0x04            | "printer-attributes-tag"     |
          | 0x05            | "unsupported-attributes-tag" |
          +-----------------+------------------------------+
                    Table 2: "delimiter-tag" Values

Sweet & McDonald Standards Track [Page 19] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 When a "begin-attribute-group-tag" field occurs in the protocol, it
 means that zero or more following attributes up to the next group tag
 are attributes belonging to the attribute group specified by the
 value of the "begin-attribute-group-tag".  For example, if the value
 of "begin-attribute-group-tag" is 0x01, the following attributes are
 members of the Operations Attributes group.
 The "end-of-attributes-tag" (value 0x03) MUST occur exactly once in
 an operation and MUST be the last "delimiter-tag".  If the operation
 has a document-data group, the Document data in that group follows
 the "end-of-attributes-tag".
 The order and presence of "attribute-group" fields (whose beginning
 is marked by the "begin-attribute-group-tag" subfield) for each
 operation request and each operation response MUST be that defined in
 the Model.
 A Printer MUST treat a "delimiter-tag" (values from 0x00 through
 0x0f) differently from a "value-tag" (values from 0x10 through 0xff)
 so that the Printer knows there is an entire attribute group as
 opposed to a single value.

3.5.2. "value-tag" Values

 The remaining tables show values for the "value-tag" field, which is
 the first octet of an attribute.  The "value-tag" field specifies the
 type of the value of the attribute.
 Table 3 specifies the "out-of-band" values for the "value-tag" field
 defined in this document.  These tags are registered, along with tags
 defined in other documents, in the "Out-of-Band Attribute Value Tags"
 registry.
                   +-----------------+-------------+
                   | Tag Value (Hex) | Meaning     |
                   +-----------------+-------------+
                   | 0x10            | unsupported |
                   | 0x12            | unknown     |
                   | 0x13            | no-value    |
                   +-----------------+-------------+
                      Table 3: Out-of-Band Values

Sweet & McDonald Standards Track [Page 20] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Table 4 specifies the integer values defined in this document for the
 "value-tag" field; they are registered in the "Attribute Syntaxes"
 registry.
 +----------------+--------------------------------------------------+
 | Tag Value      | Meaning                                          |
 | (Hex)          |                                                  |
 +----------------+--------------------------------------------------+
 | 0x20           | Unassigned integer data type (see IANA IPP       |
 |                | registry)                                        |
 | 0x21           | integer                                          |
 | 0x22           | boolean                                          |
 | 0x23           | enum                                             |
 | 0x24-0x2f      | Unassigned integer data types (see IANA IPP      |
 |                | registry)                                        |
 +----------------+--------------------------------------------------+
                         Table 4: Integer Tags
 Table 5 specifies the octetString values defined in this document for
 the "value-tag" field; they are registered in the "Attribute
 Syntaxes" registry.
 +---------------+---------------------------------------------------+
 | Tag Value     | Meaning                                           |
 | (Hex)         |                                                   |
 +---------------+---------------------------------------------------+
 | 0x30          | octetString with an unspecified format            |
 | 0x31          | dateTime                                          |
 | 0x32          | resolution                                        |
 | 0x33          | rangeOfInteger                                    |
 | 0x34          | begCollection                                     |
 | 0x35          | textWithLanguage                                  |
 | 0x36          | nameWithLanguage                                  |
 | 0x37          | endCollection                                     |
 | 0x38-0x3f     | Unassigned octetString data types (see IANA IPP   |
 |               | registry)                                         |
 +---------------+---------------------------------------------------+
                       Table 5: octetString Tags

Sweet & McDonald Standards Track [Page 21] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Table 6 specifies the character-string values defined in this
 document for the "value-tag" field; they are registered in the
 "Attribute Syntaxes" registry.
 +---------------+---------------------------------------------------+
 | Tag Value     | Meaning                                           |
 | (Hex)         |                                                   |
 +---------------+---------------------------------------------------+
 | 0x40          | Unassigned character-string data type (see IANA   |
 |               | IPP registry)                                     |
 | 0x41          | textWithoutLanguage                               |
 | 0x42          | nameWithoutLanguage                               |
 | 0x43          | Unassigned character-string data type (see IANA   |
 |               | IPP registry)                                     |
 | 0x44          | keyword                                           |
 | 0x45          | uri                                               |
 | 0x46          | uriScheme                                         |
 | 0x47          | charset                                           |
 | 0x48          | naturalLanguage                                   |
 | 0x49          | mimeMediaType                                     |
 | 0x4a          | memberAttrName                                    |
 | 0x4b-0x5f     | Unassigned character-string data types (see IANA  |
 |               | IPP registry)                                     |
 +---------------+---------------------------------------------------+
                         Table 6: String Tags
 Note: An attribute value always has a type, which is explicitly
 specified by its tag; one such tag value is "nameWithoutLanguage".
 An attribute's name has an implicit type, which is keyword.
 The values 0x60-0xff are reserved for future type definitions in
 Standards Track documents.
 The tag 0x7f is reserved for extending types beyond the 255 values
 available with a single byte.  A tag value of 0x7f MUST signify that
 the first four bytes of the value field are interpreted as the tag
 value.  Note this future extension doesn't affect parsers that are
 unaware of this special tag.  The tag is like any other unknown tag,
 and the value length specifies the length of a value, which contains
 a value that the parser treats atomically.  Values from 0x00000000 to
 0x3fffffff are reserved for definition in future Standards Track
 documents.  The values 0x40000000 to 0x7fffffff are reserved for
 vendor extensions.

Sweet & McDonald Standards Track [Page 22] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.6. "name-length"

 The "name-length" field consists of a SIGNED-SHORT and specifies the
 number of octets in the immediately following "name" field.  The
 value of this field excludes the two bytes of the "name-length"
 field.  For example, if the "name" field contains 'sides', the value
 of this field is 5.
 If a "name-length" field has a value of zero, the following "name"
 field is empty and the following value is treated as an additional
 value for the attribute encoded in the nearest preceding "attribute-
 with-one-value" field.  Within an attribute group, if two or more
 attributes have the same name, the attribute group is malformed (see
 [RFC8011]).  The zero-length name is the only mechanism for multi-
 valued attributes.

3.7. (Attribute) "name"

 The "name" field contains the name of an attribute.  The Model
 specifies such names.

3.8. "value-length"

 The "value-length" field consists of a SIGNED-SHORT, which specifies
 the number of octets in the immediately following "value" field.  The
 value of this field excludes the two bytes of the "value-length"
 field.  For example, if the "value" field contains the keyword
 (string) value 'one-sided', the value of this field is 9.
 For any of the types represented by binary signed integers, the
 sender MUST encode the value in exactly four octets.
 For any of the types represented by binary signed bytes, e.g., the
 boolean type, the sender MUST encode the value in exactly one octet.
 For any of the types represented by character strings, the sender
 MUST encode the value with all the characters of the string and
 without any padding characters.
 For "out-of-band" values for the "value-tag" field defined in this
 document, such as 'unsupported', the "value-length" MUST be 0 and the
 "value" empty; the "value" has no meaning when the "value-tag" has
 one of these "out-of-band" values.  For future "out-of-band" "value-
 tag" fields, the same rule holds unless the definition explicitly
 states that the "value-length" MAY be non-zero and the "value" non-
 empty

Sweet & McDonald Standards Track [Page 23] RFC 8010 IPP/1.1: Encoding and Transport January 2017

3.9. (Attribute) "value"

 The syntax types (specified by the "value-tag" field) and most of the
 details of the representation of attribute values are defined in the
 Model.  Table 7 augments the information in the Model and defines the
 syntax types from the Model in terms of the five basic types defined
 in Section 3.  The five types are US-ASCII-STRING, LOCALIZED-STRING,
 SIGNED-INTEGER, SIGNED-SHORT, SIGNED-BYTE, and OCTET-STRING.
 +----------------------+--------------------------------------------+
 | Syntax of Attribute  | Encoding                                   |
 | Value                |                                            |
 +----------------------+--------------------------------------------+
 | textWithoutLanguage, | LOCALIZED-STRING                           |
 | nameWithoutLanguage  |                                            |
 +----------------------+--------------------------------------------+
 | textWithLanguage     | OCTET-STRING consisting of four fields: a  |
 |                      | SIGNED-SHORT, which is the number of       |
 |                      | octets in the following field; a value of  |
 |                      | type natural-language; a SIGNED-SHORT,     |
 |                      | which is the number of octets in the       |
 |                      | following field; and a value of type       |
 |                      | textWithoutLanguage.  The length of a      |
 |                      | textWithLanguage value MUST be 4 + the     |
 |                      | value of field a + the value of field c.   |
 +----------------------+--------------------------------------------+
 | nameWithLanguage     | OCTET-STRING consisting of four fields: a  |
 |                      | SIGNED-SHORT, which is the number of       |
 |                      | octets in the following field; a value of  |
 |                      | type natural-language; a SIGNED-SHORT,     |
 |                      | which is the number of octets in the       |
 |                      | following field; and a value of type       |
 |                      | nameWithoutLanguage.  The length of a      |
 |                      | nameWithLanguage value MUST be 4 + the     |
 |                      | value of field a + the value of field c.   |
 +----------------------+--------------------------------------------+
 | charset,             | US-ASCII-STRING                            |
 | naturalLanguage,     |                                            |
 | mimeMediaType,       |                                            |
 | keyword, uri, and    |                                            |
 | uriScheme            |                                            |
 +----------------------+--------------------------------------------+
 | boolean              | SIGNED-BYTE where 0x00 is 'false' and 0x01 |
 |                      | is 'true'                                  |
 +----------------------+--------------------------------------------+
 | integer and enum     | a SIGNED-INTEGER                           |

Sweet & McDonald Standards Track [Page 24] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 +----------------------+--------------------------------------------+
 | dateTime             | OCTET-STRING consisting of eleven octets   |
 |                      | whose contents are defined by              |
 |                      | "DateAndTime" in RFC 2579 [RFC2579]        |
 +----------------------+--------------------------------------------+
 | resolution           | OCTET-STRING consisting of nine octets of  |
 |                      | two SIGNED-INTEGERs followed by a SIGNED-  |
 |                      | BYTE.  The first SIGNED-INTEGER contains   |
 |                      | the value of cross-feed direction          |
 |                      | resolution.  The second SIGNED-INTEGER     |
 |                      | contains the value of feed direction       |
 |                      | resolution.  The SIGNED-BYTE contains the  |
 |                      | units value.                               |
 +----------------------+--------------------------------------------+
 | rangeOfInteger       | Eight octets consisting of two SIGNED-     |
 |                      | INTEGERs.  The first SIGNED-INTEGER        |
 |                      | contains the lower bound and the second    |
 |                      | SIGNED-INTEGER contains the upper bound.   |
 +----------------------+--------------------------------------------+
 | 1setOf X             | Encoding according to the rules for an     |
 |                      | attribute with more than one value.  Each  |
 |                      | value X is encoded according to the rules  |
 |                      | for encoding its type.                     |
 +----------------------+--------------------------------------------+
 | octetString          | OCTET-STRING                               |
 +----------------------+--------------------------------------------+
 | collection           | Encoding as defined in Section 3.1.6.      |
 +----------------------+--------------------------------------------+
                   Table 7: Attribute Value Encoding
 The attribute syntax type of the value determines its encoding and
 the value of its "value-tag".

3.10. Data

 The "data" field MUST include any data required by the operation.

Sweet & McDonald Standards Track [Page 25] RFC 8010 IPP/1.1: Encoding and Transport January 2017

4. Encoding of Transport Layer

 HTTP/1.1 [RFC7230] is the REQUIRED transport layer for this protocol.
 HTTP/2 [RFC7540] is an OPTIONAL transport layer for this protocol.
 The operation layer has been designed with the assumption that the
 transport layer contains the following information:
 o  the target URI for the operation; and
 o  the total length of the data in the operation layer, either as a
    single length or as a sequence of chunks each with a length.
 Printer implementations MUST support HTTP over the IANA-assigned
 well-known port 631 (the IPP default port), although a Printer
 implementation can support HTTP over some other port as well.
 Each HTTP operation MUST use the POST method where the request-target
 is the object target of the operation and where the "Content-Type" of
 the message body in each request and response MUST be "application/
 ipp".  The message body MUST contain the operation layer and MUST
 have the syntax described in Section 3.2, "Syntax of Encoding".  A
 Client implementation MUST adhere to the rules for a Client described
 for HTTP [RFC7230].  A Printer (server) implementation MUST adhere to
 the rules for an origin server described for HTTP [RFC7230].
 An IPP server sends a response for each request that it receives.  If
 an IPP server detects an error, it MAY send a response before it has
 read the entire request.  If the HTTP layer of the IPP server
 completes processing the HTTP headers successfully, it MAY send an
 intermediate response, such as "100 Continue", with no IPP data
 before sending the IPP response.  A Client MUST expect such a variety
 of responses from an IPP server.  For further information on HTTP,
 consult the HTTP documents [RFC7230].
 An HTTP/1.1 server MUST support chunking for IPP requests, and an IPP
 Client MUST support chunking for IPP responses according to HTTP/1.1
 [RFC7230].

4.1. Printer URI, Job URI, and Job ID

 All Printer and Job objects are identified by a Uniform Resource
 Identifier (URI) [RFC3986] so that they can be persistently and
 unambiguously referenced.  Jobs can also be identified by a
 combination of Printer URI and Job ID.

Sweet & McDonald Standards Track [Page 26] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Some operation elements are encoded twice, once as the request-target
 on the HTTP request-line and a second time as a REQUIRED operation
 attribute in the application/ipp entity.  These attributes are the
 target for the operation and are called "printer-uri" and "job-uri".
 Note: The target URI is included twice in an operation referencing
 the same IPP object, but the two URIs can be different.  For example,
 the HTTP request-target can be relative while the IPP request URI is
 absolute.
 HTTP allows Clients to generate and send a relative URI rather than
 an absolute URI.  A relative URI identifies a resource with the scope
 of the HTTP server but does not include scheme, host, or port.  The
 following statements characterize how URIs are used in the mapping of
 IPP onto HTTP:
 1.  Although potentially redundant, a Client MUST supply the target
     of the operation both as an operation attribute and as a URI at
     the HTTP layer.  The rationale for this decision is to maintain a
     consistent set of rules for mapping "application/ipp" to possibly
     many communication layers, even where URIs are not used as the
     addressing mechanism in the transport layer.
 2.  Even though these two URIs might not be literally identical (one
     being relative and the other being absolute), they MUST both
     reference the same IPP object.
 3.  The URI in the HTTP layer is either relative or absolute and is
     used by the HTTP server to route the HTTP request to the correct
     resource relative to that HTTP server.
 4.  Once the HTTP server resource begins to process the HTTP request,
     it can get the reference to the appropriate IPP Printer object
     from either the HTTP URI (using to the context of the HTTP server
     for relative URIs) or from the URI within the operation request;
     the choice is up to the implementation.
 5.  HTTP URIs can be relative or absolute, but the target URI in the
     IPP operation attribute MUST be an absolute URI.

Sweet & McDonald Standards Track [Page 27] RFC 8010 IPP/1.1: Encoding and Transport January 2017

5. IPP URI Schemes

 The IPP URI schemes are 'ipp' [RFC3510] and 'ipps' [RFC7472].
 Clients and Printers MUST support the ipp-URI value in the following
 IPP attributes:
 o  Job attributes:
  • job-uri
  • job-printer-uri
 o  Printer attributes:
  • printer-uri-supported
 o  Operation attributes:
  • job-uri
  • printer-uri
 Each of the above attributes identifies a Printer or Job.  The
 ipp-URI and ipps-URI are intended as the value of the attributes in
 this list.  All of these attributes have a syntax type of 'uri', but
 there are attributes with a syntax type of 'uri' that do not use the
 'ipp' scheme, e.g., "job-more-info".
 If a Printer registers its URI with a directory service, the Printer
 MUST register an ipp-URI or ipps-URI.
 When a Client sends a request, it MUST convert a target ipp-URI to a
 target http-URL (or ipps-URI to a target https-URI) for the HTTP
 layer according to the following steps:
 1.  change the 'ipp' scheme to 'http' or 'ipps' scheme to 'https';
     and
 2.  add an explicit port 631 if the ipp-URL or ipps-URL does not
     contain an explicit port.  Note that port 631 is the IANA-
     assigned well-known port for the 'ipp' and 'ipps' schemes.
 The Client MUST use the target http-URL or https-URL in both the HTTP
 request-line and HTTP headers, as specified by HTTP [RFC7230].
 However, the Client MUST use the target ipp-URI or ipps-URI for the
 value of the "printer-uri" or "job-uri" operation attribute within
 the application/ipp body of the request.  The server MUST use the

Sweet & McDonald Standards Track [Page 28] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 ipp-URI or ipps-URI for the value of the "printer-uri", "job-uri", or
 "printer-uri-supported" attributes within the application/ipp body of
 the response.
 For example, when an IPP Client sends a request directly, i.e., no
 proxy, to an ipp-URI "ipp://printer.example.com/ipp/print/myqueue",
 it opens a TCP connection to port 631 (the IPP implicit port) on the
 host "printer.example.com" and sends the following data:
   POST /ipp/print/myqueue HTTP/1.1
   Host: printer.example.com:631
   Content-type: application/ipp
   Transfer-Encoding: chunked
   ...
   "printer-uri" 'ipp://printer.example.com/ipp/print/myqueue'
          (encoded in application/ipp message body)
   ...
                     Figure 11: Direct IPP Request
 As another example, when an IPP Client sends the same request as
 above via a proxy "myproxy.example.com", it opens a TCP connection to
 the proxy port 8080 on the proxy host "myproxy.example.com" and sends
 the following data:
   POST http://printer.example.com:631/ipp/print/myqueue HTTP/1.1
   Host: printer.example.com:631
   Content-type: application/ipp
   Transfer-Encoding: chunked
   ...
   "printer-uri" 'ipp://printer.example.com/ipp/print/myqueue'
          (encoded in application/ipp message body)
   ...
                    Figure 12: Proxied IPP Request
 The proxy then connects to the IPP origin server with headers that
 are the same as the "no-proxy" example above.

6. IANA Considerations

 The IANA-PRINTER-MIB [RFC3805] has been updated to reference this
 document; the current version is available from
 <http://www.iana.org>.
 See the IANA Considerations in the document "Internet Printing
 Protocol/1.1: Model and Semantics" [RFC8011] for information on IANA
 considerations for IPP extensions.  IANA has updated the existing

Sweet & McDonald Standards Track [Page 29] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 'application/ipp' media type registration (whose contents are defined
 in Section 3 "Encoding of the Operation Layer") with the following
 information.
 Type name: application
 Subtype name: ipp
 Required parameters: N/A
 Optional parameters: N/A
 Encoding considerations: IPP requests/responses MAY contain long
 lines and ALWAYS contain binary data (for example, attribute value
 lengths).
 Security considerations: IPP requests/responses do not introduce any
 security risks not already inherent in the underlying transport
 protocols.  Protocol mixed-version interworking rules in [RFC8011] as
 well as protocol-encoding rules in this document are complete and
 unambiguous.  See also the security considerations in this document
 and [RFC8011].
 Interoperability considerations: IPP requests (generated by Clients)
 and responses (generated by servers) MUST comply with all conformance
 requirements imposed by the normative specifications [RFC8011] and
 this document.  Protocol-encoding rules specified in RFC 8010 are
 comprehensive so that interoperability between conforming
 implementations is guaranteed (although support for specific optional
 features is not ensured).  Both the "charset" and "natural-language"
 of all IPP attribute values that are a LOCALIZED-STRING are explicit
 within IPP requests/responses (without recourse to any external
 information in HTTP, SMTP, or other message transport headers).
 Published specifications: RFCs 8010 and 8011
 Applications that use this media type: Internet Printing Protocol
 (IPP) print clients and print servers that communicate using HTTP/
 HTTPS or other transport protocols.  Messages of type "application/
 ipp" are self-contained and transport independent, including
 "charset" and "natural-language" context for any LOCALIZED-STRING
 value.
 Fragment identifier considerations: N/A

Sweet & McDonald Standards Track [Page 30] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Additional information:
    Deprecated alias names for this type: N/A
    Magic number(s): N/A
    File extension(s): N/A
    Macintosh file type code(s): N/A
 Person & email address to contact for further information:
    ISTO PWG IPP Workgroup <ipp@pwg.org>
 Intended usage: COMMON
 Restrictions on usage: N/A
 Author: ISTO PWG IPP Workgroup <ipp@pwg.org>
 Change controller: ISTO PWG IPP Workgroup <ipp@pwg.org>
 Provisional registration? (standards tree only): No

7. Internationalization Considerations

 See the section on "Internationalization Considerations" in the
 document "Internet Printing Protocol/1.1: Model and Semantics"
 [RFC8011] for information on internationalization.  This document
 adds no additional issues.

8. Security Considerations

 The IPP Model and Semantics document [RFC8011] discusses high-level
 security requirements (Client Authentication, Server Authentication,
 and Operation Privacy).  Client Authentication is the mechanism by
 which the Client proves its identity to the server in a secure
 manner.  Server Authentication is the mechanism by which the server
 proves its identity to the Client in a secure manner.  Operation
 Privacy is defined as a mechanism for protecting operations from
 eavesdropping.
 Message Integrity is addressed in the document "Internet Printing
 Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI
 Scheme" [RFC7472].

8.1. Security Conformance Requirements

 This section defines the security requirements for IPP Clients and
 IPP objects.

Sweet & McDonald Standards Track [Page 31] RFC 8010 IPP/1.1: Encoding and Transport January 2017

8.1.1. Digest Authentication

 IPP Clients and Printers SHOULD support Digest Authentication
 [RFC7616].  Use of the Message Integrity feature (qop="auth-int") is
 OPTIONAL.
 Note: Previous versions of this specification required support for
 the MD5 algorithms; however, [RFC7616] makes SHA2-256 mandatory to
 implement and deprecates MD5, only allowing its use for backwards
 compatibility reasons.  IPP implementations that support Digest
 Authentication MUST support SHA2-256 and SHOULD support MD5 for
 backwards compatibility.
 Note: The reason that IPP Clients and Printers SHOULD (rather than
 MUST) support Digest Authentication is that there is a certain class
 of Output Devices where it does not make sense.  Specifically, a low-
 end device with limited ROM space and low paper throughput may not
 need Client Authentication.  This class of device typically requires
 firmware designers to make trade-offs between protocols and
 functionality to arrive at the lowest-cost solution possible.
 Factored into the designer's decisions is not just the size of the
 code, but also the testing, maintenance, usefulness, and time-to-
 market impact for each feature delivered to the customer.  Forcing
 such low-end devices to provide security in order to claim IPP/1.1
 conformance would not make business sense.  Print devices that have
 high-volume throughput and have available ROM space will typically
 provide support for Client Authentication that safeguards the device
 from unauthorized access because these devices are prone to a high
 loss of consumables and paper if unauthorized access occurs.

8.1.2. Transport Layer Security (TLS)

 IPP Clients and Printers SHOULD support Transport Layer Security
 (TLS) [RFC5246] [RFC7525] for Server Authentication and Operation
 Privacy.  IPP Printers MAY also support TLS for Client
 Authentication.  IPP Clients and Printers MAY support Basic
 Authentication [RFC7617] for User Authentication if the channel is
 secure, e.g., IPP over HTTPS [RFC7472].  IPP Clients and Printers
 SHOULD NOT support Basic Authentication over insecure channels.
 The IPP Model and Semantics document [RFC8011] defines two Printer
 attributes ("uri-authentication-supported" and "uri-security-
 supported") that the Client can use to discover the security policy
 of a Printer.  That document also outlines IPP-specific security
 considerations and is the primary reference for security implications
 with regard to the IPP itself.

Sweet & McDonald Standards Track [Page 32] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 Note: Because previous versions of this specification did not require
 TLS support, this version cannot require it for IPP/1.1.  However,
 since printing often involves a great deal of sensitive or private
 information (medical reports, performance reviews, banking
 information, etc.) and network monitoring is pervasive ([RFC7258]),
 implementors are strongly encouraged to include TLS support.
 Note: Because IPP Printers typically use self-signed X.509
 certificates, IPP Clients SHOULD support Trust On First Use (defined
 in [RFC7435]) in addition to traditional X.509 certificate
 validation.

8.2. Using IPP with TLS

 IPP uses the "Upgrading to TLS Within HTTP/1.1" mechanism [RFC2817]
 for 'ipp' URIs.  The Client requests a secure TLS connection by using
 the HTTP "Upgrade" header while the server agrees in the HTTP
 response.  The switch to TLS occurs either because the server grants
 the Client's request to upgrade to TLS or a server asks to switch to
 TLS in its response.  Secure communication begins with a server's
 response to switch to TLS.
 IPP uses the "HTTPS: HTTP over TLS" mechanism [RFC2818] for 'ipps'
 URIs.  The Client and server negotiate a secure TLS connection
 immediately and unconditionally.

9. Interoperability with Other IPP Versions

 It is beyond the scope of this specification to mandate conformance
 with versions of IPP other than 1.1.  IPP was deliberately designed,
 however, to make supporting other versions easy.  IPP objects
 (Printers, Jobs, etc.) SHOULD:
 o  understand any valid request whose major "version-number" is
    greater than 0; and
 o  respond appropriately with a response containing the same
    "version-number" parameter value used by the Client in the request
    (if the Client-supplied "version-number" is supported) or the
    highest "version-number" supported by the Printer (if the Client-
    supplied "version-number" is not supported).
 IPP Clients SHOULD:
 o  understand any valid response whose major "version-number" is
    greater than 0.

Sweet & McDonald Standards Track [Page 33] RFC 8010 IPP/1.1: Encoding and Transport January 2017

9.1. The "version-number" Parameter

 The following are rules regarding the "version-number" parameter (see
 Section 3.3):
 1.  Clients MUST send requests containing a "version-number"
     parameter with the highest supported value, e.g., '1.1', '2.0',
     etc., and SHOULD try supplying alternate version numbers if they
     receive a 'server-error-version-not-supported' error return in a
     response.  For example, if a Client sends an IPP/2.0 request that
     is rejected with the 'server-error-version-not-supported' error
     and an IPP/1.1 "version-number", it SHOULD retry by sending an
     IPP/1.1 request.
 2.  IPP objects (Printers, Jobs, etc.)  MUST accept requests
     containing a "version-number" parameter with a '1.1' value (or
     reject the request for reasons other than 'server-error-version-
     not-supported').
 3.  IPP objects SHOULD either accept requests whose major version is
     greater than 0 or reject such requests with the 'server-error-
     version-not-supported' status-code.  See Section 4.1.8 of
     [RFC8011].
 4.  In any case, security MUST NOT be compromised when a Client
     supplies a lower "version-number" parameter in a request.  For
     example, if an IPP/2.0 conforming Printer accepts version '1.1'
     requests and is configured to enforce Digest Authentication, it
     MUST do the same for a version '1.1' request.

9.2. Security and URI Schemes

 The following are rules regarding security, the "version-number"
 parameter, and the URI scheme supplied in target attributes and
 responses:
 1.  When a Client supplies a request, the "printer-uri" or "job-uri"
     target operation attribute MUST have the same scheme as that
     indicated in one of the values of the "printer-uri-supported"
     Printer attribute.
 2.  When the Printer returns the "job-printer-uri" or "job-uri" Job
     Description attributes, it SHOULD return the same scheme ('ipp',
     'ipps', etc.) that the Client supplied in the "printer-uri" or
     "job-uri" target operation attributes in the Get-Job-Attributes
     or Get-Jobs request, rather than the scheme used when the Job was
     created.  However, when a Client requests Job attributes using
     the Get-Job-Attributes or Get-Jobs operations, the Jobs and Job

Sweet & McDonald Standards Track [Page 34] RFC 8010 IPP/1.1: Encoding and Transport January 2017

     attributes that the Printer returns depends on: (1) the security
     in effect when the Job was created, (2) the security in effect in
     the query request, and (3) the security policy in force.
 3.  The Printer MUST enforce its security and privacy policies based
     on the owner of the IPP object and the URI scheme and/or
     credentials supplied by the Client in the current request.

10. Changes since RFC 2910

 The following changes have been made since the publication of
 RFC 2910:
 o  Added references to current IPP extension specifications.
 o  Added optional support for HTTP/2.
 o  Added collection attribute syntax from RFC 3382.
 o  Fixed typographical errors.
 o  Now reference TLS/1.2 and no longer mandate the TLS/1.0 MTI
    ciphersuites.
 o  Updated all references.
 o  Updated document organization to follow current style.
 o  Updated example ipp: URIs to follow guidelines in RFC 7472.
 o  Updated version compatibility for all versions of IPP.
 o  Updated HTTP Digest Authentication to optional for Clients.
 o  Removed references to (Experimental) IPP/1.0 and usage of
    http:/https: URLs.

Sweet & McDonald Standards Track [Page 35] RFC 8010 IPP/1.1: Encoding and Transport January 2017

11. References

11.1. Normative References

 [PWG5100.12]
            Sweet, M. and I. McDonald, "IPP Version 2.0, 2.1, and
            2.2", October 2015, <http://ftp.pwg.org/pub/pwg/standards/
            std-ipp20-20151030-5100.12.pdf>.
 [RFC20]    Cerf, V., "ASCII format for network interchange", STD 80,
            RFC 20, DOI 10.17487/RFC0020, October 1969,
            <http://www.rfc-editor.org/info/rfc20>.
 [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
            RFC 793, DOI 10.17487/RFC0793, September 1981,
            <http://www.rfc-editor.org/info/rfc793>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
            Schoenwaelder, Ed., "Textual Conventions for SMIv2",
            STD 58, RFC 2579, DOI 10.17487/RFC2579, April 1999,
            <http://www.rfc-editor.org/info/rfc2579>.
 [RFC2817]  Khare, R. and S. Lawrence, "Upgrading to TLS Within
            HTTP/1.1", RFC 2817, DOI 10.17487/RFC2817, May 2000,
            <http://www.rfc-editor.org/info/rfc2817>.
 [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
            DOI 10.17487/RFC2818, May 2000,
            <http://www.rfc-editor.org/info/rfc2818>.
 [RFC2978]  Freed, N. and J. Postel, "IANA Charset Registration
            Procedures", BCP 19, RFC 2978, DOI 10.17487/RFC2978,
            October 2000, <http://www.rfc-editor.org/info/rfc2978>.
 [RFC3510]  Herriot, R. and I. McDonald, "Internet Printing
            Protocol/1.1: IPP URL Scheme", RFC 3510,
            DOI 10.17487/RFC3510, April 2003,
            <http://www.rfc-editor.org/info/rfc3510>.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
            2003, <http://www.rfc-editor.org/info/rfc3629>.

Sweet & McDonald Standards Track [Page 36] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
            Resource Identifier (URI): Generic Syntax", STD 66,
            RFC 3986, DOI 10.17487/RFC3986, January 2005,
            <http://www.rfc-editor.org/info/rfc3986>.
 [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", STD 68, RFC 5234,
            DOI 10.17487/RFC5234, January 2008,
            <http://www.rfc-editor.org/info/rfc5234>.
 [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
            (TLS) Protocol Version 1.2", RFC 5246,
            DOI 10.17487/RFC5246, August 2008,
            <http://www.rfc-editor.org/info/rfc5246>.
 [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Message Syntax and Routing",
            RFC 7230, DOI 10.17487/RFC7230, June 2014,
            <http://www.rfc-editor.org/info/rfc7230>.
 [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
            DOI 10.17487/RFC7231, June 2014,
            <http://www.rfc-editor.org/info/rfc7231>.
 [RFC7232]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
            DOI 10.17487/RFC7232, June 2014,
            <http://www.rfc-editor.org/info/rfc7232>.
 [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
            Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
            RFC 7234, DOI 10.17487/RFC7234, June 2014,
            <http://www.rfc-editor.org/info/rfc7234>.
 [RFC7235]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Authentication", RFC 7235,
            DOI 10.17487/RFC7235, June 2014,
            <http://www.rfc-editor.org/info/rfc7235>.
 [RFC7472]  McDonald, I. and M. Sweet, "Internet Printing Protocol
            (IPP) over HTTPS Transport Binding and the 'ipps' URI
            Scheme", RFC 7472, DOI 10.17487/RFC7472, March 2015,
            <http://www.rfc-editor.org/info/rfc7472>.

Sweet & McDonald Standards Track [Page 37] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
            Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
            DOI 10.17487/RFC7540, May 2015,
            <http://www.rfc-editor.org/info/rfc7540>.
 [RFC7541]  Peon, R. and H. Ruellan, "HPACK: Header Compression for
            HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
            <http://www.rfc-editor.org/info/rfc7541>.
 [RFC7616]  Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
            Digest Access Authentication", RFC 7616,
            DOI 10.17487/RFC7616, September 2015,
            <http://www.rfc-editor.org/info/rfc7616>.
 [RFC7617]  Reschke, J., "The 'Basic' HTTP Authentication Scheme",
            RFC 7617, DOI 10.17487/RFC7617, September 2015,
            <http://www.rfc-editor.org/info/rfc7617>.
 [RFC8011]  Sweet, M. and I. McDonald, "Internet Printing
            Protocol/1.1: Model and Semantics", RFC 8011,
            DOI 10.17487/RFC8011, January 2017,
            <http://www.rfc-editor.org/info/rfc8011>.

11.2. Informative References

 [IANA-IPP] IANA, "Internet Printing Protocol (IPP) Registry",
            <http://www.iana.org/assignments/ipp-registrations/>.
 [PWG5100.3]
            Ocke, K. and T. Hastings, "Internet Printing Protocol
            (IPP): Production Printing Attributes - Set1", Candidate
            Standard 5100.3-2001, February 2001,
            <http://ftp.pwg.org/pub/pwg/candidates/
            cs-ippprodprint10-20010212-5100.3.pdf>.
 [RFC1179]  McLaughlin, L., "Line printer daemon protocol", RFC 1179,
            DOI 10.17487/RFC1179, August 1990,
            <http://www.rfc-editor.org/info/rfc1179>.
 [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
            Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
            2014, <http://www.rfc-editor.org/info/rfc7258>.
 [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
            Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
            December 2014, <http://www.rfc-editor.org/info/rfc7435>.

Sweet & McDonald Standards Track [Page 38] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
            "Recommendations for Secure Use of Transport Layer
            Security (TLS) and Datagram Transport Layer Security
            (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
            2015, <http://www.rfc-editor.org/info/rfc7525>.

Sweet & McDonald Standards Track [Page 39] RFC 8010 IPP/1.1: Encoding and Transport January 2017

Appendix A. Protocol Examples

A.1. Print-Job Request

 The following is an example of a Print-Job request with "job-name",
 "copies", and "sides" specified.  The "ipp-attribute-fidelity"
 attribute is set to 'true' so that the print request will fail if the
 "copies" or the "sides" attribute is not supported or their values
 are not supported.
  Octets                         Symbolic Value       Protocol field
  0x0101                         1.1                  version-number
  0x0002                         Print-Job            operation-id
  0x00000001                     1                    request-id
  0x01                           start operation-     operation-
                                 attributes           attributes-tag
  0x47                           charset type         value-tag
  0x0012                                              name-length
  attributes-charset             attributes-charset   name
  0x0005                                              value-length
  utf-8                          UTF-8                value
  0x48                           natural-language     value-tag
                                 type
  0x001b                                              name-length
  attributes-natural-language    attributes-natural-  name
                                 language
  0x0005                                              value-length
  en-us                          en-US                value
  0x45                           uri type             value-tag
  0x000b                                              name-length
  printer-uri                    printer-uri          name
  0x002c                                              value-length
  ipp://printer.example.com/ipp/ printer pinetree     value
  print/pinetree
  0x42                           nameWithoutLanguage  value-tag
                                 type
  0x0008                                              name-length
  job-name                       job-name             name
  0x0006                                              value-length
  foobar                         foobar               value
  0x22                           boolean type         value-tag
  0x0016                                              name-length
  ipp-attribute-fidelity         ipp-attribute-       name
                                 fidelity
  0x0001                                              value-length
  0x01                           true                 value
  0x02                           start job-attributes job-attributes-

Sweet & McDonald Standards Track [Page 40] RFC 8010 IPP/1.1: Encoding and Transport January 2017

                                                      tag
  0x21                           integer type         value-tag
  0x0006                                              name-length
  copies                         copies               name
  0x0004                                              value-length
  0x00000014                     20                   value
  0x44                           keyword type         value-tag
  0x0005                                              name-length
  sides                          sides                name
  0x0013                                              value-length
  two-sided-long-edge            two-sided-long-edge  value
  0x03                           end-of-attributes    end-of-
                                                      attributes-tag
  %!PDF...                       <PDF Document>       data

A.2. Print-Job Response (Successful)

 Here is an example of a successful Print-Job response to the previous
 Print-Job request.  The Printer supported the "copies" and "sides"
 attributes and their supplied values.  The status-code returned is
 'successful-ok'.
  Octets                           Symbolic Value     Protocol field
  0x0101                           1.1                version-number
  0x0000                           successful-ok      status-code
  0x00000001                       1                  request-id
  0x01                             start operation-   operation-
                                   attributes         attributes-tag
  0x47                             charset type       value-tag
  0x0012                                              name-length
  attributes-charset               attributes-charset name
  0x0005                                              value-length
  utf-8                            UTF-8              value
  0x48                             natural-language   value-tag
                                   type
  0x001b                                              name-length
  attributes-natural-language      attributes-        name
                                   natural-language
  0x0005                                              value-length
  en-us                            en-US              value
  0x41                             textWithoutLanguag value-tag
                                   e type
  0x000e                                              name-length
  status-message                   status-message     name
  0x000d                                              value-length
  successful-ok                    successful-ok      value
  0x02                             start job-         job-attributes-

Sweet & McDonald Standards Track [Page 41] RFC 8010 IPP/1.1: Encoding and Transport January 2017

                                   attributes         tag
  0x21                             integer            value-tag
  0x0006                                              name-length
  job-id                           job-id             name
  0x0004                                              value-length
  147                              147                value
  0x45                             uri type           value-tag
  0x0007                                              name-length
  job-uri                          job-uri            name
  0x0030                                              value-length
  ipp://printer.example.com/ipp/pr job 147 on         value
  int/pinetree/147                 pinetree
  0x23                             enum type          value-tag
  0x0009                                              name-length
  job-state                        job-state          name
  0x0004                                              value-length
  0x0003                           pending            value
  0x03                             end-of-attributes  end-of-
                                                      attributes-tag

A.3. Print-Job Response (Failure)

 Here is an example of an unsuccessful Print-Job response to the
 previous Print-Job request.  It fails because, in this case, the
 Printer does not support the "sides" attribute and because the value
 '20' for the "copies" attribute is not supported.  Therefore, no Job
 is created, and neither a "job-id" nor a "job-uri" operation
 attribute is returned.  The error code returned is 'client-error-
 attributes-or-values-not-supported' (0x040b).
 Octets                      Symbolic Value              Protocol
                                                         field
 0x0101                      1.1                         version-
                                                         number
 0x040b                      client-error-attributes-or- status-code
                             values-not-supported
 0x00000001                  1                           request-id
 0x01                        start operation-attributes  operation-
                                                         attributes
                                                         tag
 0x47                        charset type                value-tag
 0x0012                                                  name-length
 attributes-charset          attributes-charset          name
 0x0005                                                  value-length
 utf-8                       UTF-8                       value
 0x48                        natural-language type       value-tag
 0x001b                                                  name-length

Sweet & McDonald Standards Track [Page 42] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 attributes-natural-language attributes-natural-language name
 0x0005                                                  value-length
 en-us                       en-US                       value
 0x41                        textWithoutLanguage type    value-tag
 0x000e                                                  name-length
 status-message              status-message              name
 0x002f                                                  value-length
 client-error-attributes-or- client-error-attributes-or- value
 values-not-supported        values-not-supported
 0x05                        start unsupported-          unsupported-
                             attributes                  attributes
                                                         tag
 0x21                        integer type                value-tag
 0x0006                                                  name-length
 copies                      copies                      name
 0x0004                                                  value-length
 0x00000014                  20                          value
 0x10                        unsupported (type)          value-tag
 0x0005                                                  name-length
 sides                       sides                       name
 0x0000                                                  value-length
 0x03                        end-of-attributes           end-of-
                                                         attributes-
                                                         tag

A.4. Print-Job Response (Success with Attributes Ignored)

 Here is an example of a successful Print-Job response to a Print-Job
 request like the previous Print-Job request, except that the value of
 "ipp-attribute-fidelity" is 'false'.  The print request succeeds,
 even though, in this case, the Printer supports neither the "sides"
 attribute nor the value '20' for the "copies" attribute.  Therefore,
 a Job is created and both a "job-id" and a "job-uri" operation
 attribute are returned.  The unsupported attributes are also returned
 in an Unsupported Attributes group.  The error code returned is
 'successful-ok-ignored-or-substituted-attributes' (0x0001).
 Octets                     Symbolic Value              Protocol field
 0x0101                     1.1                         version-number
 0x0001                     successful-ok-ignored-or-   status-code
                            substituted-attributes
 0x00000001                 1                           request-id
 0x01                       start operation-attributes  operation-
                                                        attributes-tag
 0x47                       charset type                value-tag
 0x0012                                                 name-length
 attributes-charset         attributes-charset          name

Sweet & McDonald Standards Track [Page 43] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 0x0005                                                 value-length
 utf-8                      UTF-8                       value
 0x48                       natural-language type       value-tag
 0x001b                                                 name-length
 attributes-natural-        attributes-natural-language name
 language
 0x0005                                                 value-length
 en-us                      en-US                       value
 0x41                       textWithoutLanguage type    value-tag
 0x000e                                                 name-length
 status-message             status-message              name
 0x002f                                                 value-length
 successful-ok-ignored-or-  successful-ok-ignored-or-   value
 substituted-attributes     substituted-attributes
 0x05                       start unsupported-          unsupported-
                            attributes                  attributes tag
 0x21                       integer type                value-tag
 0x0006                                                 name-length
 copies                     copies                      name
 0x0004                                                 value-length
 0x00000014                 20                          value
 0x10                       unsupported  (type)         value-tag
 0x0005                                                 name-length
 sides                      sides                       name
 0x0000                                                 value-length
 0x02                       start job-attributes        job-
                                                        attributes-tag
 0x21                       integer                     value-tag
 0x0006                                                 name-length
 job-id                     job-id                      name
 0x0004                                                 value-length
 147                        147                         value
 0x45                       uri type                    value-tag
 0x0007                                                 name-length
 job-uri                    job-uri                     name
 0x0030                                                 value-length
 ipp://printer.example.com/ job 147 on pinetree         value
 ipp/print/pinetree/147
 0x23                       enum  type                  value-tag
 0x0009                                                 name-length
 job-state                  job-state                   name
 0x0004                                                 value-length
 0x0003                     pending                     value
 0x03                       end-of-attributes           end-of-
                                                        attributes-tag

Sweet & McDonald Standards Track [Page 44] RFC 8010 IPP/1.1: Encoding and Transport January 2017

A.5. Print-URI Request

 The following is an example of Print-URI request with "copies" and
 "job-name" parameters:
  Octets                         Symbolic Value       Protocol field
  0x0101                         1.1                  version-number
  0x0003                         Print-URI            operation-id
  0x00000001                     1                    request-id
  0x01                           start operation-     operation-
                                 attributes           attributes-tag
  0x47                           charset type         value-tag
  0x0012                                              name-length
  attributes-charset             attributes-charset   name
  0x0005                                              value-length
  utf-8                          UTF-8                value
  0x48                           natural-language     value-tag
                                 type
  0x001b                                              name-length
  attributes-natural-language    attributes-natural-  name
                                 language
  0x0005                                              value-length
  en-us                          en-US                value
  0x45                           uri type             value-tag
  0x000b                                              name-length
  printer-uri                    printer-uri          name
  0x002c                                              value-length
  ipp://printer.example.com/ipp/ printer pinetree     value
  print/pinetree
  0x45                           uri type             value-tag
  0x000c                                              name-length
  document-uri                   document-uri         name
  0x0019                                              value-length
  ftp://foo.example.com/foo      ftp://foo.example.co value
                                 m/foo
  0x42                           nameWithoutLanguage  value-tag
                                 type
  0x0008                                              name-length
  job-name                       job-name             name
  0x0006                                              value-length
  foobar                         foobar               value
  0x02                           start job-attributes job-attributes-
                                                      tag
  0x21                           integer type         value-tag
  0x0006                                              name-length
  copies                         copies               name
  0x0004                                              value-length

Sweet & McDonald Standards Track [Page 45] RFC 8010 IPP/1.1: Encoding and Transport January 2017

  0x00000001                     1                    value
  0x03                           end-of-attributes    end-of-
                                                      attributes-tag

A.6. Create-Job Request

 The following is an example of Create-Job request with no parameters
 and no attributes:
  Octets                         Symbolic Value       Protocol field
  0x0101                         1.1                  version-number
  0x0005                         Create-Job           operation-id
  0x00000001                     1                    request-id
  0x01                           start operation-     operation-
                                 attributes           attributes-tag
  0x47                           charset type         value-tag
  0x0012                                              name-length
  attributes-charset             attributes-charset   name
  0x0005                                              value-length
  utf-8                          UTF-8                value
  0x48                           natural-language     value-tag
                                 type
  0x001b                                              name-length
  attributes-natural-language    attributes-natural-  name
                                 language
  0x0005                                              value-length
  en-us                          en-US                value
  0x45                           uri type             value-tag
  0x000b                                              name-length
  printer-uri                    printer-uri          name
  0x002c                                              value-length
  ipp://printer.example.com/ipp/ printer pinetree     value
  print/pinetree
  0x03                           end-of-attributes    end-of-
                                                      attributes-tag

A.7. Create-Job Request with Collection Attributes

 The following is an example of Create-Job request with the "media-
 col" collection attribute [PWG5100.3] with the value "media-
 size={x-dimension=21000 y-dimension=29700} media-type='stationery'":
 Octets                         Symbolic Value       Protocol field
 0x0101                         1.1                  version-number
 0x0005                         Create-Job           operation-id
 0x00000001                     1                    request-id

Sweet & McDonald Standards Track [Page 46] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 0x01                           start operation-     operation-
                                attributes           attributes-tag
 0x47                           charset type         value-tag
 0x0012                                              name-length
 attributes-charset             attributes-charset   name
 0x0005                                              value-length
 utf-8                          UTF-8                value
 0x48                           natural-language     value-tag
                                type
 0x001b                                              name-length
 attributes-natural-language    attributes-natural-  name
                                language
 0x0005                                              value-length
 en-us                          en-US                value
 0x45                           uri type             value-tag
 0x000b                                              name-length
 printer-uri                    printer-uri          name
 0x002c                                              value-length
 ipp://printer.example.com/ipp/ printer pinetree     value
 print/pinetree
 0x34                           begCollection        value-tag
 0x0009                         9                    name-length
 media-col                      media-col            name
 0x0000                         0                    value-length
 0x4a                           memberAttrName       value-tag
 0x0000                         0                    name-length
 0x000a                         10                   value-length
 media-size                     media-size           value (member-
                                                     name)
 0x34                           begCollection        member-value-tag
 0x0000                         0                    name-length
 0x0000                         0                    member-value-
                                                     length
 0x4a                           memberAttrName       value-tag
 0x0000                         0                    name-length
 0x000b                         11                   value-length
 x-dimension                    x-dimension          value (member-
                                                     name)
 0x21                           integer              member-value-tag
 0x0000                         0                    name-length
 0x0004                         4                    member-value-
                                                     length
 0x00005208                     21000                member-value
 0x4a                           memberAttrName       value-tag
 0x0000                         0                    name-length
 0x000b                         11                   value-length
 y-dimension                    y-dimension          value (member-
                                                     name)

Sweet & McDonald Standards Track [Page 47] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 0x21                           integer              member-value-tag
 0x0000                         0                    name-length
 0x0004                         4                    member-value-
                                                     length
 0x00007404                     29700                member-value
 0x37                           endCollection        end-value-tag
 0x0000                         0                    end-name-length
 0x0000                         0                    end-value-length
 0x4a                           memberAttrName       value-tag
 0x0000                         0                    name-length
 0x000a                         10                   value-length
 media-type                     media-type           value (member-
                                                     name)
 0x44                           keyword              member-value-tag
 0x0000                         0                    name-length
 0x000a                         10                   member-value-
                                                     length
 stationery                     stationery           member-value
 0x37                           endCollection        end-value-tag
 0x0000                         0                    end-name-length
 0x0000                         0                    end-value-length
 0x03                           end-of-attributes    end-of-
                                                     attributes-tag

A.8. Get-Jobs Request

 The following is an example of Get-Jobs request with parameters but
 no attributes:
  Octets                         Symbolic Value       Protocol field
  0x0101                         1.1                  version-number
  0x000a                         Get-Jobs             operation-id
  0x0000007b                     123                  request-id
  0x01                           start operation-     operation-
                                 attributes           attributes-tag
  0x47                           charset type         value-tag
  0x0012                                              name-length
  attributes-charset             attributes-charset   name
  0x0005                                              value-length
  utf-8                          UTF-8                value
  0x48                           natural-language     value-tag
                                 type
  0x001b                                              name-length
  attributes-natural-language    attributes-natural-  name
                                 language
  0x0005                                              value-length
  en-us                          en-US                value

Sweet & McDonald Standards Track [Page 48] RFC 8010 IPP/1.1: Encoding and Transport January 2017

  0x45                           uri type             value-tag
  0x000b                                              name-length
  printer-uri                    printer-uri          name
  0x002c                                              value-length
  ipp://printer.example.com/ipp/ printer pinetree     value
  print/pinetree
  0x21                           integer type         value-tag
  0x0005                                              name-length
  limit                          limit                name
  0x0004                                              value-length
  0x00000032                     50                   value
  0x44                           keyword type         value-tag
  0x0014                                              name-length
  requested-attributes           requested-attributes name
  0x0006                                              value-length
  job-id                         job-id               value
  0x44                           keyword type         value-tag
  0x0000                         additional value     name-length
  0x0008                                              value-length
  job-name                       job-name             value
  0x44                           keyword type         value-tag
  0x0000                         additional value     name-length
  0x000f                                              value-length
  document-format                document-format      value
  0x03                           end-of-attributes    end-of-
                                                      attributes-tag

A.9. Get-Jobs Response

 The following is an example of a Get-Jobs response from a previous
 request with three Jobs.  The Printer returns no information about
 the second Job (because of security reasons):
 Octets                  Symbolic Value          Protocol field
 0x0101                  1.1                     version-number
 0x0000                  successful-ok           status-code
 0x0000007b              123                     request-id (echoed
                                                 back)
 0x01                    start operation-        operation-attributes-
                         attributes              tag
 0x47                    charset type            value-tag
 0x0012                                          name-length
 attributes-charset      attributes-charset      name
 0x0005                                          value-length
 utf-8                   UTF-8                   value
 0x48                    natural-language type   value-tag
 0x001b                                          name-length

Sweet & McDonald Standards Track [Page 49] RFC 8010 IPP/1.1: Encoding and Transport January 2017

 attributes-natural-     attributes-natural-     name
 language                language
 0x0005                                          value-length
 en-us                   en-US                   value
 0x41                    textWithoutLanguage     value-tag
                         type
 0x000e                                          name-length
 status-message          status-message          name
 0x000d                                          value-length
 successful-ok           successful-ok           value
 0x02                    start job-attributes    job-attributes-tag
                         (1st  object)
 0x21                    integer type            value-tag
 0x0006                                          name-length
 job-id                  job-id                  name
 0x0004                                          value-length
 147                     147                     value
 0x36                    nameWithLanguage        value-tag
 0x0008                                          name-length
 job-name                job-name                name
 0x000c                                          value-length
 0x0005                                          sub-value-length
 fr-ca                   fr-CA                   value
 0x0003                                          sub-value-length
 fou                     fou                     name
 0x02                    start job-attributes    job-attributes-tag
                         (2nd object)
 0x02                    start job-attributes    job-attributes-tag
                         (3rd object)
 0x21                    integer type            value-tag
 0x0006                                          name-length
 job-id                  job-id                  name
 0x0004                                          value-length
 148                     149                     value
 0x36                    nameWithLanguage        value-tag
 0x0008                                          name-length
 job-name                job-name                name
 0x0012                                          value-length
 0x0005                                          sub-value-length
 de-CH                   de-CH                   value
 0x0009                                          sub-value-length
 isch guet               isch guet               name
 0x03                    end-of-attributes       end-of-attributes-tag

Sweet & McDonald Standards Track [Page 50] RFC 8010 IPP/1.1: Encoding and Transport January 2017

Acknowledgements

 The authors would like to acknowledge the following individuals for
 their contributions to the original IPP/1.1 specifications:
 Sylvan Butler, Roger deBry, Tom Hastings, Robert Herriot (the
 original editor of RFC 2910), Paul Moore, Kirk Ocke, Randy Turner,
 John Wenn, and Peter Zehler.

Authors' Addresses

 Michael Sweet
 Apple Inc.
 1 Infinite Loop
 MS 111-HOMC
 Cupertino, CA  95014
 United States of America
 Email: msweet@apple.com
 Ira McDonald
 High North, Inc.
 PO Box 221
 Grand Marais, MI  49839
 United States of America
 Phone: +1 906-494-2434
 Email: blueroofmusic@gmail.com

Sweet & McDonald Standards Track [Page 51]

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