<pre>Internet Engineering Task Force (IETF)                          M. Sweet
Request for Comments: 8010                                    Apple Inc.
Obsoletes: <a href="./rfc2910">2910</a>, <a href="./rfc3382">3382</a>                                        I. McDonald
Category: Standards Track                               High North, Inc.
ISSN: 2070-1721                                             January 2017


         <span class="h1">Internet Printing Protocol/1.1: Encoding and Transport</span>

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" (<a href="./rfc8011">RFC 8011</a>).

   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 <a href="./rfc7841#section-2">Section&nbsp;2 of RFC 7841</a>.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   <a href="http://www.rfc-editor.org/info/rfc8010">http://www.rfc-editor.org/info/rfc8010</a>.
















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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) 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

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



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   <a href="#section-4">4</a>.  Encoding of Transport Layer . . . . . . . . . . . . . . . . .  <a href="#page-26">26</a>
     <a href="#section-4.1">4.1</a>.  Printer URI, Job URI, and Job ID  . . . . . . . . . . . .  <a href="#page-26">26</a>
   <a href="#section-5">5</a>.  IPP URI Schemes . . . . . . . . . . . . . . . . . . . . . . .  <a href="#page-28">28</a>
   <a href="#section-6">6</a>.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  <a href="#page-29">29</a>
   <a href="#section-7">7</a>.  Internationalization Considerations . . . . . . . . . . . . .  <a href="#page-31">31</a>
   <a href="#section-8">8</a>.  Security Considerations . . . . . . . . . . . . . . . . . . .  <a href="#page-31">31</a>
     <a href="#section-8.1">8.1</a>.  Security Conformance Requirements . . . . . . . . . . . .  <a href="#page-31">31</a>
       <a href="#section-8.1.1">8.1.1</a>.  Digest Authentication . . . . . . . . . . . . . . . .  <a href="#page-32">32</a>
       <a href="#section-8.1.2">8.1.2</a>.  Transport Layer Security (TLS)  . . . . . . . . . . .  <a href="#page-32">32</a>
     <a href="#section-8.2">8.2</a>.  Using IPP with TLS  . . . . . . . . . . . . . . . . . . .  <a href="#page-33">33</a>
   <a href="#section-9">9</a>.  Interoperability with Other IPP Versions  . . . . . . . . . .  <a href="#page-33">33</a>
     <a href="#section-9.1">9.1</a>.  The "version-number" Parameter  . . . . . . . . . . . . .  <a href="#page-34">34</a>
     <a href="#section-9.2">9.2</a>.  Security and URI Schemes  . . . . . . . . . . . . . . . .  <a href="#page-34">34</a>
   <a href="#section-10">10</a>. Changes since <a href="./rfc2910">RFC 2910</a>  . . . . . . . . . . . . . . . . . . .  <a href="#page-35">35</a>
   <a href="#section-11">11</a>. References  . . . . . . . . . . . . . . . . . . . . . . . . .  <a href="#page-36">36</a>
     <a href="#section-11.1">11.1</a>.  Normative References . . . . . . . . . . . . . . . . . .  <a href="#page-36">36</a>
     <a href="#section-11.2">11.2</a>.  Informative References . . . . . . . . . . . . . . . . .  <a href="#page-38">38</a>
   <a href="#appendix-A">Appendix A</a>.  Protocol Examples  . . . . . . . . . . . . . . . . .  <a href="#page-40">40</a>
     <a href="#appendix-A.1">A.1</a>.  Print-Job Request . . . . . . . . . . . . . . . . . . . .  <a href="#page-40">40</a>
     <a href="#appendix-A.2">A.2</a>.  Print-Job Response (Successful) . . . . . . . . . . . . .  <a href="#page-41">41</a>
     <a href="#appendix-A.3">A.3</a>.  Print-Job Response (Failure)  . . . . . . . . . . . . . .  <a href="#page-42">42</a>
     <a href="#appendix-A.4">A.4</a>.  Print-Job Response (Success with Attributes Ignored)  . .  <a href="#page-43">43</a>
     <a href="#appendix-A.5">A.5</a>.  Print-URI Request . . . . . . . . . . . . . . . . . . . .  <a href="#page-45">45</a>
     <a href="#appendix-A.6">A.6</a>.  Create-Job Request  . . . . . . . . . . . . . . . . . . .  <a href="#page-46">46</a>
     <a href="#appendix-A.7">A.7</a>.  Create-Job Request with Collection Attributes . . . . . .  <a href="#page-46">46</a>
     <a href="#appendix-A.8">A.8</a>.  Get-Jobs Request  . . . . . . . . . . . . . . . . . . . .  <a href="#page-48">48</a>
     <a href="#appendix-A.9">A.9</a>.  Get-Jobs Response . . . . . . . . . . . . . . . . . . . .  <a href="#page-49">49</a>
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  <a href="#page-51">51</a>
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  <a href="#page-51">51</a>






















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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>.  Introduction</span>

   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
      [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>]

   o  Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
      [<a href="./rfc7231" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content&quot;">RFC7231</a>]

   o  Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
      [<a href="./rfc7232" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests&quot;">RFC7232</a>]

   o  Hypertext Transfer Protocol (HTTP/1.1): Caching [<a href="./rfc7234" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Caching&quot;">RFC7234</a>]

   o  Hypertext Transfer Protocol (HTTP/1.1): Authentication [<a href="./rfc7235" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Authentication&quot;">RFC7235</a>]

   o  The 'Basic' HTTP Authentication Scheme [<a href="./rfc7617" title="&quot;The 'Basic' HTTP Authentication Scheme&quot;">RFC7617</a>]

   o  HTTP Digest Access Authentication [<a href="./rfc7616" title="&quot;HTTP Digest Access Authentication&quot;">RFC7616</a>]

   IPP implementations can support HTTP/2, which is described in the
   following RFCs:

   o  Hypertext Transfer Protocol Version 2 (HTTP/2) [<a href="./rfc7540" title="&quot;Hypertext Transfer Protocol Version 2 (HTTP/2)&quot;">RFC7540</a>]

   o  HPACK - Header Compression for HTTP/2 [<a href="./rfc7541" title="&quot;HPACK: Header Compression for HTTP/2&quot;">RFC7541</a>]

   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 [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] 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.









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<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>.  Conventions Used in This Document</span>

<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>.  Requirements Language</span>

   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 [<a href="./rfc2119" title="&quot;Key words for use in RFCs to Indicate Requirement Levels&quot;">RFC2119</a>].

<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>.  Printing Terminology</span>

   Client: Initiator of outgoing IPP session requests and sender of
   outgoing IPP operation requests (Hypertext Transfer Protocol --
   HTTP/1.1 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>] 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 [<a href="./rfc3510" title="&quot;Internet Printing Protocol/1.1: IPP URL Scheme&quot;">RFC3510</a>].

   'ipps' URI: An IPPS URI as defined in [<a href="./rfc7472" title="&quot;Internet Printing Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI Scheme&quot;">RFC7472</a>].

   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
   [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] 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 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>] Server) that represents one or more Physical
   Devices or a Logical Device.







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<span class="h3"><a class="selflink" id="section-2.3" href="#section-2.3">2.3</a>.  Abbreviations</span>

   ABNF: Augmented Backus-Naur Form [<a href="./rfc5234" title="&quot;Augmented BNF for Syntax Specifications: ABNF&quot;">RFC5234</a>]

   ASCII: American Standard Code for Information Interchange [<a href="./rfc20" title="&quot;ASCII format for network interchange&quot;">RFC20</a>]

   HTTP: Hypertext Transfer Protocol [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>]

   HTTPS: HTTP over TLS [<a href="./rfc2818" title="&quot;HTTP Over TLS&quot;">RFC2818</a>]

   IANA: Internet Assigned Numbers Authority

   IEEE: Institute of Electrical and Electronics Engineers

   IESG: Internet Engineering Steering Group

   IPP: Internet Printing Protocol (this document and [<a href="#ref-PWG5100.12">PWG5100.12</a>])

   ISTO: IEEE Industry Standards and Technology Organization

   LPD: Line Printer Daemon Protocol [<a href="./rfc1179" title="&quot;Line printer daemon protocol&quot;">RFC1179</a>]

   PWG: IEEE-ISTO Printer Working Group

   RFC: Request for Comments

   TCP: Transmission Control Protocol [<a href="./rfc793" title="&quot;Transmission Control Protocol&quot;">RFC793</a>]

   TLS: Transport Layer Security [<a href="./rfc5246" title="&quot;The Transport Layer Security (TLS) Protocol Version 1.2&quot;">RFC5246</a>]

   URI: Uniform Resource Identifier [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>]

   URL: Uniform Resource Locator [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>]

   UTF-8: Unicode Transformation Format - 8-bit [<a href="./rfc3629" title="&quot;UTF-8, a transformation format of ISO 10646&quot;">RFC3629</a>]

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  Encoding of the Operation Layer</span>

   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



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   data types are built.  Every character string in this encoding MUST
   be a sequence of characters where the characters are associated with
   some charset [<a href="./rfc2978" title="&quot;IANA Charset Registration Procedures&quot;">RFC2978</a>] 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 <a href="./rfc5234">RFC 5234</a> [<a href="./rfc5234" title="&quot;Augmented BNF for Syntax Specifications: ABNF&quot;">RFC5234</a>]

   An operation request or response MUST use the encoding described in
   these two sections.


















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<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>.  Picture of the Encoding</span>

<span class="h4"><a class="selflink" id="section-3.1.1" href="#section-3.1.1">3.1.1</a>.  Request and Response</span>

   An operation request or response is encoded as follows:

   -----------------------------------------------
   |                  version-number             |   2 bytes  - required
   -----------------------------------------------
   |               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 <a href="#section-4.1.1">Section 4.1.1</a> of the Model and Semantics
   document [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>].

   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.













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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-9" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-3.1.2" href="#section-3.1.2">3.1.2</a>.  Attribute Group</span>

   Each "attribute-group" field is encoded as follows:

   -----------------------------------------------
   |           begin-attribute-group-tag         |  1 byte
   ----------------------------------------------------------
   |                   attribute                 |  p bytes |- 0 or more
   ----------------------------------------------------------

                    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".

<span class="h4"><a class="selflink" id="section-3.1.3" href="#section-3.1.3">3.1.3</a>.  Attribute</span>

   An "attribute" field is encoded as follows:

   -----------------------------------------------
   |          attribute-with-one-value           |  q bytes
   ----------------------------------------------------------
   |             additional-value                |  r bytes |- 0 or more
   ----------------------------------------------------------

                       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.















<span class="grey">Sweet &amp; McDonald             Standards Track                    [Page 9]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-10" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-3.1.4" href="#section-3.1.4">3.1.4</a>.  Attribute-with-one-value</span>

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

   -----------------------------------------------
   |                   value-tag                 |   1 byte
   -----------------------------------------------
   |               name-length  (value is u)     |   2 bytes
   -----------------------------------------------
   |                     name                    |   u bytes
   -----------------------------------------------
   |              value-length  (value is v)     |   2 bytes
   -----------------------------------------------
   |                     value                   |   v bytes
   -----------------------------------------------

                 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'.















<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 10]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-3.1.5" href="#section-3.1.5">3.1.5</a>.  Additional-value</span>

   Each "additional-value" field is encoded as follows:

   -----------------------------------------------
   |                   value-tag                 |   1 byte
   -----------------------------------------------
   |            name-length  (value is 0x0000)   |   2 bytes
   -----------------------------------------------
   |              value-length (value is w)      |   2 bytes
   -----------------------------------------------
   |                     value                   |   w bytes
   -----------------------------------------------

               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'.


















<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 11]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-3.1.6" href="#section-3.1.6">3.1.6</a>.  Collection Attribute</span>

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

   -----------------------------------------------
   |          value-tag (value is 0x34)          |   1 byte
   -----------------------------------------------
   |          name-length (value is u)           |   2 bytes
   -----------------------------------------------
   |                     name                    |   u bytes
   -----------------------------------------------
   |        value-length (value is 0x0000)       |   2 bytes
   -----------------------------------------------------------
   |               member-attribute              |   q bytes |-0 or more
   -----------------------------------------------------------
   |        end-value-tag (value is 0x37)        |   1 byte
   -----------------------------------------------
   |      end-name-length (value is 0x0000)      |   2 bytes
   -----------------------------------------------
   |      end-value-length (value is 0x0000)     |   2 bytes
   -----------------------------------------------

                  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 <a href="#section-3.1.7">Section 3.1.7</a>.

   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.



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 12]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


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

<span class="h4"><a class="selflink" id="section-3.1.7" href="#section-3.1.7">3.1.7</a>.  Member Attributes</span>

   Each "member-attribute" field is encoded as follows:

   -----------------------------------------------
   |          value-tag (value is 0x4a)          |   1 byte
   -----------------------------------------------
   |        name-length (value is 0x0000)        |   2 bytes
   -----------------------------------------------
   |          value-length (value is w)          |   2 bytes
   -----------------------------------------------
   |             value (member-name)             |   w bytes
   -----------------------------------------------
   |               member-value-tag              |   1 byte
   -----------------------------------------------
   |        name-length (value is 0x0000)        |   2 bytes
   -----------------------------------------------
   |      member-value-length (value is x)       |   2 bytes
   -----------------------------------------------
   |                member-value                 |   x bytes
   -----------------------------------------------

                    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'.






<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 13]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-14" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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'.

<span class="h4"><a class="selflink" id="section-3.1.8" href="#section-3.1.8">3.1.8</a>.  Alternative Picture of the Encoding of a Request or a Response</span>

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

   -----------------------------------------------
   |                  version-number             |   2 bytes  - required
   -----------------------------------------------
   |               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"




<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 14]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>.  Syntax of Encoding</span>

   The ABNF [<a href="./rfc5234" title="&quot;Augmented BNF for Syntax Specifications: ABNF&quot;">RFC5234</a>] 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 &gt; 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 <a href="#section-3.5.2">Section 3.5.2</a>
   begin-attribute-group-tag = %x00-02 / %x04-0f ; see <a href="#section-3.5.1">Section 3.5.1</a>
   end-of-attributes-tag     = %x03              ; tag of 3
                                                 ; see <a href="#section-3.5.1">Section 3.5.1</a>

   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





<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 15]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-16" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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 <a href="#section-3.5.1">Section 3.5.1</a>
             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

<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>.  Attribute-group</span>

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





























<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 16]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-17" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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 <a href="#section-3.1.1">Section 3.1.1</a>.                   |
   +----------------+--------------------------------------------------+

                           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.




<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 17]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-18" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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.

<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>.  Required Parameters</span>

   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.

<span class="h4"><a class="selflink" id="section-3.4.1" href="#section-3.4.1">3.4.1</a>.  "version-number"</span>

   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 [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] 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 <a href="#section-9">Section 9</a> for more information on the "version-number"
   field and IPP version numbers.

<span class="h4"><a class="selflink" id="section-3.4.2" href="#section-3.4.2">3.4.2</a>.  "operation-id"</span>

   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.








<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 18]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-19" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-3.4.3" href="#section-3.4.3">3.4.3</a>.  "status-code"</span>

   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.

<span class="h4"><a class="selflink" id="section-3.4.4" href="#section-3.4.4">3.4.4</a>.  "request-id"</span>

   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.

<span class="h3"><a class="selflink" id="section-3.5" href="#section-3.5">3.5</a>.  Tags</span>

   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 [<a href="#ref-IANA-IPP" title="&quot;Internet Printing Protocol (IPP) Registry&quot;">IANA-IPP</a>]

<span class="h4"><a class="selflink" id="section-3.5.1" href="#section-3.5.1">3.5.1</a>.  "delimiter-tag" Values</span>

   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





<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 19]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-20" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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.

<span class="h4"><a class="selflink" id="section-3.5.2" href="#section-3.5.2">3.5.2</a>.  "value-tag" Values</span>

   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









<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 20]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-21" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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











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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-22" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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.







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-23" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h3"><a class="selflink" id="section-3.6" href="#section-3.6">3.6</a>.  "name-length"</span>

   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
   [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>]).  The zero-length name is the only mechanism for multi-
   valued attributes.

<span class="h3"><a class="selflink" id="section-3.7" href="#section-3.7">3.7</a>.  (Attribute) "name"</span>

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

<span class="h3"><a class="selflink" id="section-3.8" href="#section-3.8">3.8</a>.  "value-length"</span>

   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





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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-24" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h3"><a class="selflink" id="section-3.9" href="#section-3.9">3.9</a>.  (Attribute) "value"</span>

   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 <a href="#section-3">Section 3</a>.  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                           |





<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 24]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-25" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   +----------------------+--------------------------------------------+
   | dateTime             | OCTET-STRING consisting of eleven octets   |
   |                      | whose contents are defined by              |
   |                      | "DateAndTime" in <a href="./rfc2579">RFC 2579</a> [<a href="./rfc2579" title="&quot;Textual Conventions for SMIv2&quot;">RFC2579</a>]        |
   +----------------------+--------------------------------------------+
   | 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 <a href="#section-3.1.6">Section 3.1.6</a>.      |
   +----------------------+--------------------------------------------+

                     Table 7: Attribute Value Encoding

   The attribute syntax type of the value determines its encoding and
   the value of its "value-tag".

<span class="h3"><a class="selflink" id="section-3.10" href="#section-3.10">3.10</a>.  Data</span>

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














<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 25]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-26" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>.  Encoding of Transport Layer</span>

   HTTP/1.1 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>] is the REQUIRED transport layer for this protocol.
   HTTP/2 [<a href="./rfc7540" title="&quot;Hypertext Transfer Protocol Version 2 (HTTP/2)&quot;">RFC7540</a>] 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 <a href="#section-3.2">Section 3.2</a>, "Syntax of Encoding".  A
   Client implementation MUST adhere to the rules for a Client described
   for HTTP [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].  A Printer (server) implementation MUST adhere to
   the rules for an origin server described for HTTP [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].

   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 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].

   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
   [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].

<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>.  Printer URI, Job URI, and Job ID</span>

   All Printer and Job objects are identified by a Uniform Resource
   Identifier (URI) [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>] so that they can be persistently and
   unambiguously referenced.  Jobs can also be identified by a
   combination of Printer URI and Job ID.






<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 26]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-27" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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.












<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 27]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-28" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  IPP URI Schemes</span>

   The IPP URI schemes are 'ipp' [<a href="./rfc3510" title="&quot;Internet Printing Protocol/1.1: IPP URL Scheme&quot;">RFC3510</a>] and 'ipps' [<a href="./rfc7472" title="&quot;Internet Printing Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI Scheme&quot;">RFC7472</a>].
   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 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].
   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




<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 28]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-29" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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 <a href="http://printer.example.com:631/ipp/print/myqueue">http://printer.example.com:631/ipp/print/myqueue</a> 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.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  IANA Considerations</span>

   The IANA-PRINTER-MIB [<a href="./rfc3805">RFC3805</a>] has been updated to reference this
   document; the current version is available from
   &lt;<a href="http://www.iana.org">http://www.iana.org</a>&gt;.

   See the IANA Considerations in the document "Internet Printing
   Protocol/1.1: Model and Semantics" [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] for information on IANA
   considerations for IPP extensions.  IANA has updated the existing



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 29]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-30" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   'application/ipp' media type registration (whose contents are defined
   in <a href="#section-3">Section 3</a> "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 [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] as
   well as protocol-encoding rules in this document are complete and
   unambiguous.  See also the security considerations in this document
   and [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>].

   Interoperability considerations: IPP requests (generated by Clients)
   and responses (generated by servers) MUST comply with all conformance
   requirements imposed by the normative specifications [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] and
   this document.  Protocol-encoding rules specified in <a href="./rfc8010">RFC 8010</a> 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







<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 30]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-31" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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 &amp; email address to contact for further information:

      ISTO PWG IPP Workgroup &lt;ipp@pwg.org&gt;

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: ISTO PWG IPP Workgroup &lt;ipp@pwg.org&gt;

   Change controller: ISTO PWG IPP Workgroup &lt;ipp@pwg.org&gt;

   Provisional registration? (standards tree only): No

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  Internationalization Considerations</span>

   See the section on "Internationalization Considerations" in the
   document "Internet Printing Protocol/1.1: Model and Semantics"
   [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] for information on internationalization.  This document
   adds no additional issues.

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>.  Security Considerations</span>

   The IPP Model and Semantics document [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] 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" [<a href="./rfc7472" title="&quot;Internet Printing Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI Scheme&quot;">RFC7472</a>].

<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>.  Security Conformance Requirements</span>

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




<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 31]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-32" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h4"><a class="selflink" id="section-8.1.1" href="#section-8.1.1">8.1.1</a>.  Digest Authentication</span>

   IPP Clients and Printers SHOULD support Digest Authentication
   [<a href="./rfc7616" title="&quot;HTTP Digest Access Authentication&quot;">RFC7616</a>].  Use of the Message Integrity feature (qop="auth-int") is
   OPTIONAL.

   Note: Previous versions of this specification required support for
   the MD5 algorithms; however, [<a href="./rfc7616" title="&quot;HTTP Digest Access Authentication&quot;">RFC7616</a>] 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.

<span class="h4"><a class="selflink" id="section-8.1.2" href="#section-8.1.2">8.1.2</a>.  Transport Layer Security (TLS)</span>

   IPP Clients and Printers SHOULD support Transport Layer Security
   (TLS) [<a href="./rfc5246" title="&quot;The Transport Layer Security (TLS) Protocol Version 1.2&quot;">RFC5246</a>] [<a href="./rfc7525" title="&quot;Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)&quot;">RFC7525</a>] for Server Authentication and Operation
   Privacy.  IPP Printers MAY also support TLS for Client
   Authentication.  IPP Clients and Printers MAY support Basic
   Authentication [<a href="./rfc7617" title="&quot;The 'Basic' HTTP Authentication Scheme&quot;">RFC7617</a>] for User Authentication if the channel is
   secure, e.g., IPP over HTTPS [<a href="./rfc7472" title="&quot;Internet Printing Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI Scheme&quot;">RFC7472</a>].  IPP Clients and Printers
   SHOULD NOT support Basic Authentication over insecure channels.

   The IPP Model and Semantics document [<a href="./rfc8011" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC8011</a>] 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.





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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-33" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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 ([<a href="./rfc7258" title="&quot;Pervasive Monitoring Is an Attack&quot;">RFC7258</a>]),
   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 [<a href="./rfc7435" title="&quot;Opportunistic Security: Some Protection Most of the Time&quot;">RFC7435</a>]) in addition to traditional X.509 certificate
   validation.

<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>.  Using IPP with TLS</span>

   IPP uses the "Upgrading to TLS Within HTTP/1.1" mechanism [<a href="./rfc2817" title="&quot;Upgrading to TLS Within HTTP/1.1&quot;">RFC2817</a>]
   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 [<a href="./rfc2818" title="&quot;HTTP Over TLS&quot;">RFC2818</a>] for 'ipps'
   URIs.  The Client and server negotiate a secure TLS connection
   immediately and unconditionally.

<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>.  Interoperability with Other IPP Versions</span>

   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.





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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>.  The "version-number" Parameter</span>

   The following are rules regarding the "version-number" parameter (see
   <a href="#section-3.3">Section 3.3</a>):

   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 <a href="./rfc8011#section-4.1.8">Section&nbsp;4.1.8 of
       [RFC8011]</a>.

   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.

<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>.  Security and URI Schemes</span>

   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



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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


       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.

<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>.  Changes since <a href="./rfc2910">RFC 2910</a></span>

   The following changes have been made since the publication of
   <a href="./rfc2910">RFC 2910</a>:

   o  Added references to current IPP extension specifications.

   o  Added optional support for HTTP/2.

   o  Added collection attribute syntax from <a href="./rfc3382">RFC 3382</a>.

   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 <a href="./rfc7472">RFC 7472</a>.

   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.















<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 35]</span></pre>
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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h2"><a class="selflink" id="section-11" href="#section-11">11</a>.  References</span>

<span class="h3"><a class="selflink" id="section-11.1" href="#section-11.1">11.1</a>.  Normative References</span>

   [<a id="ref-PWG5100.12">PWG5100.12</a>]
              Sweet, M. and I. McDonald, "IPP Version 2.0, 2.1, and
              2.2", October 2015, &lt;<a href="http://ftp.pwg.org/pub/pwg/standards/std-ipp20-20151030-5100.12.pdf">http://ftp.pwg.org/pub/pwg/standards/</a>
              <a href="http://ftp.pwg.org/pub/pwg/standards/std-ipp20-20151030-5100.12.pdf">std-ipp20-20151030-5100.12.pdf</a>&gt;.

   [<a id="ref-RFC20">RFC20</a>]    Cerf, V., "ASCII format for network interchange", STD 80,
              <a href="./rfc20">RFC 20</a>, DOI 10.17487/RFC0020, October 1969,
              &lt;<a href="http://www.rfc-editor.org/info/rfc20">http://www.rfc-editor.org/info/rfc20</a>&gt;.

   [<a id="ref-RFC793">RFC793</a>]   Postel, J., "Transmission Control Protocol", STD 7,
              <a href="./rfc793">RFC 793</a>, DOI 10.17487/RFC0793, September 1981,
              &lt;<a href="http://www.rfc-editor.org/info/rfc793">http://www.rfc-editor.org/info/rfc793</a>&gt;.

   [<a id="ref-RFC2119">RFC2119</a>]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>,
              DOI 10.17487/RFC2119, March 1997,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2119">http://www.rfc-editor.org/info/rfc2119</a>&gt;.

   [<a id="ref-RFC2579">RFC2579</a>]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2",
              STD 58, <a href="./rfc2579">RFC 2579</a>, DOI 10.17487/RFC2579, April 1999,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2579">http://www.rfc-editor.org/info/rfc2579</a>&gt;.

   [<a id="ref-RFC2817">RFC2817</a>]  Khare, R. and S. Lawrence, "Upgrading to TLS Within
              HTTP/1.1", <a href="./rfc2817">RFC 2817</a>, DOI 10.17487/RFC2817, May 2000,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2817">http://www.rfc-editor.org/info/rfc2817</a>&gt;.

   [<a id="ref-RFC2818">RFC2818</a>]  Rescorla, E., "HTTP Over TLS", <a href="./rfc2818">RFC 2818</a>,
              DOI 10.17487/RFC2818, May 2000,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2818">http://www.rfc-editor.org/info/rfc2818</a>&gt;.

   [<a id="ref-RFC2978">RFC2978</a>]  Freed, N. and J. Postel, "IANA Charset Registration
              Procedures", <a href="https://www.rfc-editor.org/bcp/bcp19">BCP 19</a>, <a href="./rfc2978">RFC 2978</a>, DOI 10.17487/RFC2978,
              October 2000, &lt;<a href="http://www.rfc-editor.org/info/rfc2978">http://www.rfc-editor.org/info/rfc2978</a>&gt;.

   [<a id="ref-RFC3510">RFC3510</a>]  Herriot, R. and I. McDonald, "Internet Printing
              Protocol/1.1: IPP URL Scheme", <a href="./rfc3510">RFC 3510</a>,
              DOI 10.17487/RFC3510, April 2003,
              &lt;<a href="http://www.rfc-editor.org/info/rfc3510">http://www.rfc-editor.org/info/rfc3510</a>&gt;.

   [<a id="ref-RFC3629">RFC3629</a>]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, <a href="./rfc3629">RFC 3629</a>, DOI 10.17487/RFC3629, November
              2003, &lt;<a href="http://www.rfc-editor.org/info/rfc3629">http://www.rfc-editor.org/info/rfc3629</a>&gt;.




<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 36]</span></pre>
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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   [<a id="ref-RFC3986">RFC3986</a>]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              <a href="./rfc3986">RFC 3986</a>, DOI 10.17487/RFC3986, January 2005,
              &lt;<a href="http://www.rfc-editor.org/info/rfc3986">http://www.rfc-editor.org/info/rfc3986</a>&gt;.

   [<a id="ref-RFC5234">RFC5234</a>]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, <a href="./rfc5234">RFC 5234</a>,
              DOI 10.17487/RFC5234, January 2008,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5234">http://www.rfc-editor.org/info/rfc5234</a>&gt;.

   [<a id="ref-RFC5246">RFC5246</a>]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", <a href="./rfc5246">RFC 5246</a>,
              DOI 10.17487/RFC5246, August 2008,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5246">http://www.rfc-editor.org/info/rfc5246</a>&gt;.

   [<a id="ref-RFC7230">RFC7230</a>]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              <a href="./rfc7230">RFC 7230</a>, DOI 10.17487/RFC7230, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7230">http://www.rfc-editor.org/info/rfc7230</a>&gt;.

   [<a id="ref-RFC7231">RFC7231</a>]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", <a href="./rfc7231">RFC 7231</a>,
              DOI 10.17487/RFC7231, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7231">http://www.rfc-editor.org/info/rfc7231</a>&gt;.

   [<a id="ref-RFC7232">RFC7232</a>]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Conditional Requests", <a href="./rfc7232">RFC 7232</a>,
              DOI 10.17487/RFC7232, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7232">http://www.rfc-editor.org/info/rfc7232</a>&gt;.

   [<a id="ref-RFC7234">RFC7234</a>]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              <a href="./rfc7234">RFC 7234</a>, DOI 10.17487/RFC7234, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7234">http://www.rfc-editor.org/info/rfc7234</a>&gt;.

   [<a id="ref-RFC7235">RFC7235</a>]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", <a href="./rfc7235">RFC 7235</a>,
              DOI 10.17487/RFC7235, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7235">http://www.rfc-editor.org/info/rfc7235</a>&gt;.

   [<a id="ref-RFC7472">RFC7472</a>]  McDonald, I. and M. Sweet, "Internet Printing Protocol
              (IPP) over HTTPS Transport Binding and the 'ipps' URI
              Scheme", <a href="./rfc7472">RFC 7472</a>, DOI 10.17487/RFC7472, March 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7472">http://www.rfc-editor.org/info/rfc7472</a>&gt;.







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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   [<a id="ref-RFC7540">RFC7540</a>]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", <a href="./rfc7540">RFC 7540</a>,
              DOI 10.17487/RFC7540, May 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7540">http://www.rfc-editor.org/info/rfc7540</a>&gt;.

   [<a id="ref-RFC7541">RFC7541</a>]  Peon, R. and H. Ruellan, "HPACK: Header Compression for
              HTTP/2", <a href="./rfc7541">RFC 7541</a>, DOI 10.17487/RFC7541, May 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7541">http://www.rfc-editor.org/info/rfc7541</a>&gt;.

   [<a id="ref-RFC7616">RFC7616</a>]  Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
              Digest Access Authentication", <a href="./rfc7616">RFC 7616</a>,
              DOI 10.17487/RFC7616, September 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7616">http://www.rfc-editor.org/info/rfc7616</a>&gt;.

   [<a id="ref-RFC7617">RFC7617</a>]  Reschke, J., "The 'Basic' HTTP Authentication Scheme",
              <a href="./rfc7617">RFC 7617</a>, DOI 10.17487/RFC7617, September 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7617">http://www.rfc-editor.org/info/rfc7617</a>&gt;.

   [<a id="ref-RFC8011">RFC8011</a>]  Sweet, M. and I. McDonald, "Internet Printing
              Protocol/1.1: Model and Semantics", <a href="./rfc8011">RFC 8011</a>,
              DOI 10.17487/RFC8011, January 2017,
              &lt;<a href="http://www.rfc-editor.org/info/rfc8011">http://www.rfc-editor.org/info/rfc8011</a>&gt;.

<span class="h3"><a class="selflink" id="section-11.2" href="#section-11.2">11.2</a>.  Informative References</span>

   [<a id="ref-IANA-IPP">IANA-IPP</a>] IANA, "Internet Printing Protocol (IPP) Registry",
              &lt;<a href="http://www.iana.org/assignments/ipp-registrations/">http://www.iana.org/assignments/ipp-registrations/</a>&gt;.

   [<a id="ref-PWG5100.3">PWG5100.3</a>]
              Ocke, K. and T. Hastings, "Internet Printing Protocol
              (IPP): Production Printing Attributes - Set1", Candidate
              Standard 5100.3-2001, February 2001,
              &lt;<a href="http://ftp.pwg.org/pub/pwg/candidates/cs-ippprodprint10-20010212-5100.3.pdf">http://ftp.pwg.org/pub/pwg/candidates/</a>
              <a href="http://ftp.pwg.org/pub/pwg/candidates/cs-ippprodprint10-20010212-5100.3.pdf">cs-ippprodprint10-20010212-5100.3.pdf</a>&gt;.

   [<a id="ref-RFC1179">RFC1179</a>]  McLaughlin, L., "Line printer daemon protocol", <a href="./rfc1179">RFC 1179</a>,
              DOI 10.17487/RFC1179, August 1990,
              &lt;<a href="http://www.rfc-editor.org/info/rfc1179">http://www.rfc-editor.org/info/rfc1179</a>&gt;.

   [<a id="ref-RFC7258">RFC7258</a>]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", <a href="https://www.rfc-editor.org/bcp/bcp188">BCP 188</a>, <a href="./rfc7258">RFC 7258</a>, DOI 10.17487/RFC7258, May
              2014, &lt;<a href="http://www.rfc-editor.org/info/rfc7258">http://www.rfc-editor.org/info/rfc7258</a>&gt;.

   [<a id="ref-RFC7435">RFC7435</a>]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", <a href="./rfc7435">RFC 7435</a>, DOI 10.17487/RFC7435,
              December 2014, &lt;<a href="http://www.rfc-editor.org/info/rfc7435">http://www.rfc-editor.org/info/rfc7435</a>&gt;.





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<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   [<a id="ref-RFC7525">RFC7525</a>]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", <a href="https://www.rfc-editor.org/bcp/bcp195">BCP 195</a>, <a href="./rfc7525">RFC 7525</a>, DOI 10.17487/RFC7525, May
              2015, &lt;<a href="http://www.rfc-editor.org/info/rfc7525">http://www.rfc-editor.org/info/rfc7525</a>&gt;.














































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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-40" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>.  Protocol Examples</span>

<span class="h3"><a class="selflink" id="appendix-A.1" href="#appendix-A.1">A.1</a>.  Print-Job Request</span>

   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-



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 40]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-41" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


                                                        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...                       &lt;PDF Document&gt;       data

<span class="h3"><a class="selflink" id="appendix-A.2" href="#appendix-A.2">A.2</a>.  Print-Job Response (Successful)</span>

   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-



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 41]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-42" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


                                     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

<span class="h3"><a class="selflink" id="appendix-A.3" href="#appendix-A.3">A.3</a>.  Print-Job Response (Failure)</span>

   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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 42]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-43" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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

<span class="h3"><a class="selflink" id="appendix-A.4" href="#appendix-A.4">A.4</a>.  Print-Job Response (Success with Attributes Ignored)</span>

   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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 43]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-44" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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






<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 44]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-45" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


<span class="h3"><a class="selflink" id="appendix-A.5" href="#appendix-A.5">A.5</a>.  Print-URI Request</span>

   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      <a href="ftp://foo.example.co">ftp://foo.example.co</a> 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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 45]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-46" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


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

<span class="h3"><a class="selflink" id="appendix-A.6" href="#appendix-A.6">A.6</a>.  Create-Job Request</span>

   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

<span class="h3"><a class="selflink" id="appendix-A.7" href="#appendix-A.7">A.7</a>.  Create-Job Request with Collection Attributes</span>

   The following is an example of Create-Job request with the "media-
   col" collection attribute [<a href="#ref-PWG5100.3">PWG5100.3</a>] 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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 46]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-47" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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)



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 47]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-48" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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

<span class="h3"><a class="selflink" id="appendix-A.8" href="#appendix-A.8">A.8</a>.  Get-Jobs Request</span>

   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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 48]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-49" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


    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

<span class="h3"><a class="selflink" id="appendix-A.9" href="#appendix-A.9">A.9</a>.  Get-Jobs Response</span>

   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



<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 49]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-50" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


   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








<span class="grey">Sweet &amp; McDonald             Standards Track                   [Page 50]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-51" ></span>
<span class="grey"><a href="./rfc8010">RFC 8010</a>             IPP/1.1: Encoding and Transport        January 2017</span>


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 <a href="./rfc2910">RFC 2910</a>), 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 &amp; McDonald             Standards Track                   [Page 51]
</pre>