[Docs] [txt|pdf|xml] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: (RFC 2910) 00 01 02 03 04 05 06 07 08 09 10 RFC 8010

IPP WG                                                          M. Sweet
Internet-Draft                                                Apple Inc.
Obsoletes: 2910,3382 (if approved)                           I. McDonald
Intended status: Standards Track                        High North, Inc.
Expires: June 4, 2016                                   December 2, 2015


         Internet Printing Protocol/1.1: Encoding and Transport
                       draft-sweet-rfc2910bis-06

Abstract

   This document is one of a set of documents, which together describe
   all aspects of a new Internet Printing Protocol (IPP).  IPP is an
   application level protocol that can be used for distributed printing
   using Internet tools and technologies.  This document defines the
   rules for encoding IPP operations and IPP attributes into the
   Internet MIME media type called "application/ipp".  This document
   also defines the rules for transporting a message body whose Content-
   Type is "application/ipp" over HTTP.

Editor's Note

   This draft is being submitted as an AD-sponsored replacement of RFCs
   2910 and 3382, with drafts being reviewed and edited by the IEEE-
   ISTO's Printer Working Group IPP WG.  The initial goal is to have an
   clean version of IPP/1.1 as an IETF Proposed Standard.  The long-term
   goal is to advance IPP/1.1 to IETF Internet Standard.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 4, 2016.






Sweet & McDonald          Expires June 4, 2016                  [Page 1]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   4
   2.1.  Requirements Language . . . . . . . . . . . . . . . . . . .   4
   2.2.  Printing Terminology  . . . . . . . . . . . . . . . . . . .   4
   2.3.  Abbreviations . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Encoding of the Operation Layer . . . . . . . . . . . . . . .   6
   3.1.  Picture of the Encoding . . . . . . . . . . . . . . . . . .   7
   3.1.1.  Request and Response  . . . . . . . . . . . . . . . . . .   7
   3.1.2.  Attribute Group . . . . . . . . . . . . . . . . . . . . .   8
   3.1.3.  Attribute . . . . . . . . . . . . . . . . . . . . . . . .   8
   3.1.4.  Attribute-with-one-value  . . . . . . . . . . . . . . . .   8
   3.1.5.  Additional-value  . . . . . . . . . . . . . . . . . . . .   9
   3.1.6.  Collection Attribute  . . . . . . . . . . . . . . . . . .  10
   3.1.7.  Member Attributes . . . . . . . . . . . . . . . . . . . .  11
   3.1.8.  Alternative Picture of the Encoding of a Request Or a
           Response  . . . . . . . . . . . . . . . . . . . . . . . .  12
   3.2.  Syntax of Encoding  . . . . . . . . . . . . . . . . . . . .  13
   3.3.  Attribute-group . . . . . . . . . . . . . . . . . . . . . .  15
   3.4.  Required Parameters . . . . . . . . . . . . . . . . . . . .  17
   3.4.1.  Version-number  . . . . . . . . . . . . . . . . . . . . .  17
   3.4.2.  Operation-id  . . . . . . . . . . . . . . . . . . . . . .  17
   3.4.3.  Status-code . . . . . . . . . . . . . . . . . . . . . . .  17
   3.4.4.  Request-id  . . . . . . . . . . . . . . . . . . . . . . .  18
   3.5.  Tags  . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   3.5.1.  Delimiter Tags  . . . . . . . . . . . . . . . . . . . . .  18
   3.5.2.  Value Tags  . . . . . . . . . . . . . . . . . . . . . . .  19
   3.6.  Name-Length . . . . . . . . . . . . . . . . . . . . . . . .  21
   3.7.  (Attribute) Name  . . . . . . . . . . . . . . . . . . . . .  22
   3.8.  Value Length  . . . . . . . . . . . . . . . . . . . . . . .  22
   3.9.  (Attribute) Value . . . . . . . . . . . . . . . . . . . . .  22
   3.10. Data  . . . . . . . . . . . . . . . . . . . . . . . . . . .  24



Sweet & McDonald          Expires June 4, 2016                  [Page 2]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   4.  Encoding of Transport Layer . . . . . . . . . . . . . . . . .  24
   4.1.  Printer URI, Job URI, and Job ID  . . . . . . . . . . . . .  25
   5.  IPP URI Schemes . . . . . . . . . . . . . . . . . . . . . . .  26
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
   7.  Internationalization Considerations . . . . . . . . . . . . .  28
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   8.1.  Security Conformance Requirements . . . . . . . . . . . . .  28
   8.1.1.  Digest Authentication . . . . . . . . . . . . . . . . . .  29
   8.1.2.  Transport Layer Security (TLS)  . . . . . . . . . . . . .  29
   8.2.  Using IPP with TLS  . . . . . . . . . . . . . . . . . . . .  30
   9.  Interoperability with Other IPP Versions  . . . . . . . . . .  30
   9.1.  The "version-number" Parameter  . . . . . . . . . . . . . .  30
   9.2.  Security and URI Schemes  . . . . . . . . . . . . . . . . .  31
   10. Changes Since RFC 2910  . . . . . . . . . . . . . . . . . . .  31
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  32
   11.1.  Normative References . . . . . . . . . . . . . . . . . . .  32
   11.2.  Informative References . . . . . . . . . . . . . . . . . .  34
   Appendix A.  Protocol Examples  . . . . . . . . . . . . . . . . .  34
   A.1.  Print-Job Request . . . . . . . . . . . . . . . . . . . . .  34
   A.2.  Print-Job Response (successful) . . . . . . . . . . . . . .  36
   A.3.  Print-Job Response (failure)  . . . . . . . . . . . . . . .  38
   A.4.  Print-Job Response (success with attributes ignored)  . . .  39
   A.5.  Print-URI Request . . . . . . . . . . . . . . . . . . . . .  41
   A.6.  Create-Job Request  . . . . . . . . . . . . . . . . . . . .  43
   A.7.  Create-Job Request with Collection Attributes . . . . . . .  43
   A.8.  Get-Jobs Request  . . . . . . . . . . . . . . . . . . . . .  45
   A.9.  Get-Jobs Response . . . . . . . . . . . . . . . . . . . . .  47
   Appendix B.  Registration of MIME Media Type Information for
                "application/ipp"  . . . . . . . . . . . . . . . . .  48
   Appendix C.  Acknowledgements . . . . . . . . . . . . . . . . . .  49
   Appendix D.  Change History . . . . . . . . . . . . . . . . . . .  50
   D.1.  Changes In -06  . . . . . . . . . . . . . . . . . . . . . .  50
   D.2.  Changes In -05  . . . . . . . . . . . . . . . . . . . . . .  51
   D.3.  Changes In -04  . . . . . . . . . . . . . . . . . . . . . .  51
   D.4.  Changes In -03  . . . . . . . . . . . . . . . . . . . . . .  52
   D.5.  Changes In -02  . . . . . . . . . . . . . . . . . . . . . .  52
   D.6.  Changes In -01  . . . . . . . . . . . . . . . . . . . . . .  53
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  53

1.  Introduction

   This document contains the rules for encoding IPP operations and
   describes two layers: the transport layer and the operation layer.

   The transport layer consists of an HTTP request and response.  All
   IPP implementations MUST support HTTP/1.1, the relevant parts of
   which are described in the following RFCs:




Sweet & McDonald          Expires June 4, 2016                  [Page 3]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
      [RFC7230]

   o  Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
      [RFC7231]

   o  Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
      [RFC7232]

   o  Hypertext Transfer Protocol (HTTP/1.1): Caching [RFC7234]

   o  Hypertext Transfer Protocol (HTTP/1.1): Authentication [RFC7235]

   o  The 'Basic' HTTP Authentication Scheme [RFC7617]

   o  HTTP Digest Access Authentication [RFC7616]

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

   o  Hypertext Transfer Protocol Version 2 (HTTP/2) [RFC7540]

   o  HPACK - Header Compression for HTTP/2 [RFC7541]

   This document specifies the HTTP headers that an IPP implementation
   supports.

   The operation layer consists of a message body in an HTTP request or
   response.  The "Internet Printing Protocol/1.1: Model and Semantics"
   [RFC2911bis] and subsequent extensions (collectively known as the
   IPPP 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.

2.  Conventions Used in This Document

2.1.  Requirements Language

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

2.2.  Printing Terminology

   Client: Initiator of outgoing IPP session requests and sender of
   outgoing IPP operation requests (Hypertext Transfer Protocol --
   HTTP/1.1 [RFC7230] User Agent).




Sweet & McDonald          Expires June 4, 2016                  [Page 4]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   Document: An object created and managed by a Printer that contains
   description, processing, and status information.  A Document object
   may have attached data and is bound to a single Job.

   'ipp' URI: An IPP URI as defined in [RFC3510].

   'ipps' URI: An IPPS URI as defined in [RFC7472].

   Job: An object created and managed by a Printer that contains
   description, processing, and status information.  The Job also
   contains zero or more Document objects.

   Logical Device: A print server, software service, or gateway that
   processes Jobs and either forwards or stores the processed Job or
   uses one or more Physical Devices to render output.

   Model: The semantics of operations, attributes, values, and status
   codes used in the Internet Printing Protocol as defined in the
   Internet Printing Protocol/1.1: Model and Semantics [RFC2911bis] and
   subsequent extensions.

   Output Device: A single Logical or Physical Device.

   Physical Device: A hardware implementation of an endpoint device,
   e.g., a marking engine, a fax modem, etc.

   Printer: Listener for incoming IPP session requests and receiver of
   incoming IPP operation requests (Hypertext Transfer Protocol --
   HTTP/1.1 [RFC7230] Server) that represents one or more Physical
   Devices or a Logical Device.

2.3.  Abbreviations

   ABNF: Augmented Backus-Naur Form [RFC5234]

   ASCII: American Standard Code for Information Interchange [ASCII]

   HTTP: HyperText Transfer Protocol [RFC7230]

   HTTPS: HTTP over TLS [RFC2818]

   IANA: Internet Assigned Numbers Authority

   IEEE: Institute of Electrical and Electronics Engineers

   IESG: Internet Engineering Steering Group

   IPP: Internet Printing Protocol (this document and [PWG5100.12])



Sweet & McDonald          Expires June 4, 2016                  [Page 5]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   ISTO: IEEE Industry Standards and Technology Organization

   LPD: Line Printer Daemon Protocol [RFC1179]

   PWG: IEEE-ISTO Printer Working Group <http://www.pwg.org/>

   RFC: Request for Comments

   TCP: Transmission Control Protocol [RFC793]

   TLS: Transport Layer Security [RFC5246]

   URI: Uniform Resource Identifier [RFC3986]

   URL: Uniform Resource Locator [RFC3986]

   UTF-8: Unicode Transformation Format - 8-bit [RFC3629]

3.  Encoding of the Operation Layer

   The operation layer is the message body part of the HTTP request or
   response and it MUST contain a single IPP operation request or IPP
   operation response.  Each request or response consists of a sequence
   of values and attribute groups.  Attribute groups consist of a
   sequence of attributes each of which is a name and value.  Names and
   values are ultimately sequences of octets.

   The encoding consists of octets as the most primitive type.  There
   are several types built from octets, but three important types are
   integers, character strings and octet strings, on which most other
   data types are built.  Every character string in this encoding MUST
   be a sequence of characters where the characters are associated with
   some charset 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 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.  Such one-octet integers, henceforth called SIGNED-
   BYTE, are used for the version-number and tag fields.  Such two-byte



Sweet & McDonald          Expires June 4, 2016                  [Page 6]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   integers, henceforth called SIGNED-SHORT are used for the operation-
   id, status-code and length fields.  Four byte integers, henceforth
   called SIGNED-INTEGER, are used for value fields and the request-id.

   The following two sections present the encoding of the operation
   layer in two ways:

   o  informally through pictures and description

   o  formally through Augmented Backus-Naur Form (ABNF), as specified
      by RFC 5234 [RFC5234]

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

3.1.  Picture of the Encoding

3.1.1.  Request and Response

   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 Section 3.1.1 of the Model.

   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.



Sweet & McDonald          Expires June 4, 2016                  [Page 7]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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.

3.1.2.  Attribute Group

   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, the values of the "begin-attribute-group-tag" field and the
   "end-of-attributes-tag" field are called "delimiter-tags".

3.1.3.  Attribute

   An "attribute" field is encoded as follows:

   -----------------------------------------------
   |          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 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.

3.1.4.  Attribute-with-one-value

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







Sweet & McDonald          Expires June 4, 2016                  [Page 8]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   -----------------------------------------------
   |                   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'.

3.1.5.  Additional-value

   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



Sweet & McDonald          Expires June 4, 2016                  [Page 9]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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'.

3.1.6.  Collection Attribute

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

   -----------------------------------------------
   |          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'.



Sweet & McDonald          Expires June 4, 2016                 [Page 10]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  The "name-length" field specifies the length of the "name" field
      in bytes, e.g. u in the above diagram or 9 for the name "media-
      col".  Additional collection attribute values use a name length of
      0x0000.

   o  The "name" field contains the textual name of the attribute, e.g.
      "media-col".

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

   o  The "member-attribute" field contains member attributes encoded as
      defined in Section 3.1.7.

   o  The "end-value-tag" field specifies the end attribute syntax: 0x37
      for the attribute syntax 'endCollection'.

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

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

3.1.7.  Member Attributes

   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'.



Sweet & McDonald          Expires June 4, 2016                 [Page 11]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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 specifies 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'.

   o  The second "name-length" field has the value of 0 in order to
      signify that it is a "member-attribute" contained in the
      collection.

   o  The "member-value-length" field specifies the length of the member
      attribute value, e.g. x in the above diagram or 10 for the value
      'stationery'.

   o  The "member-value" field contains the value of the attribute, e.g.
      the textual value 'stationery'.

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

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





















Sweet & McDonald          Expires June 4, 2016                 [Page 12]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   -----------------------------------------------
   |                  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 show 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"

3.2.  Syntax of Encoding

   The ABNF [RFC5234] syntax for an IPP message is shown in Figure 9.
















Sweet & McDonald          Expires June 4, 2016                 [Page 13]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   ipp-message  = ipp-request / ipp-response
   ipp-request  = version-number operation-id request-id
                  *attribute-group end-of-attributes-tag data
   ipp-response = version-number status-code request-id
                  *attribute-group end-of-attributes-tag  data

   version-number       = major-version-number minor-version-number
   major-version-number = SIGNED-BYTE
   minor-version-number = SIGNED-BYTE

   operation-id = SIGNED-SHORT     ; mapping from model
   status-code  = SIGNED-SHORT     ; mapping from model
   request-id   = SIGNED-INTEGER   ; whose value is > 0

   attribute-group          = begin-attribute-group-tag *attribute
   attribute                = attribute-with-one-value *additional-value
   attribute-with-one-value = value-tag name-length name
                              value-length value
   additional-value         = value-tag zero-name-length
                              value-length value

   name-length  = SIGNED-SHORT     ; number of octets of 'name'
   name         = LALPHA *( LALPHA / DIGIT / "-" / "_" / "." )
   value-length = SIGNED-SHORT     ; number of octets of 'value'
   value        = OCTET-STRING
   data         = OCTET-STRING

   zero-name-length          = %x00.00           ; name-length of 0
   value-tag                 = %x10-FF           ; see section 3.5.2
   begin-attribute-group-tag = %x00-02 / %04-0F  ; see section 3.5.1
   end-of-attributes-tag     = %x03              ; tag of 3
                                                 ; see section 3.5.1

   SIGNED-BYTE    = BYTE
   SIGNED-SHORT   = 2BYTE
   SIGNED-INTEGER = 4BYTE
   DIGIT          = %x30-39        ; "0" to "9"
   LALPHA         = %x61-7A        ; "a" to "z"
   BYTE           = %x00-FF
   OCTET-STRING   = *BYTE

                   Figure 9: ABNF of IPP Message Format

   Figure 10 defines additional terms that are referenced in this
   document and provides an alternate grouping of the delimiter tags.






Sweet & McDonald          Expires June 4, 2016                 [Page 14]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   delimiter-tag = begin-attribute-group-tag  / ; see section 3.5.1
             end-of-attributes-tag
   delimiter-tag = %x00-0F                      ; see section 3.5.1
   begin-attribute-group-tag = %x00 / operation-attributes-tag /
      job-attributes-tag / printer-attributes-tag /
      unsupported-attributes-tag /  %x06-0F
   operation-attributes-tag =  %x01                ; tag of 1
   job-attributes-tag      =  %x02                 ; tag of 2
   printer-attributes-tag =  %x04                  ; tag of 4
   unsupported-attributes-tag =  %x05      ; tag of 5

                 Figure 10: ABNF for Attribute Group Tags

3.3.  Attribute-group

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

   Table 1 maps the Model group name to value of the "begin-attribute-
   group-tag" field:






























Sweet & McDonald          Expires June 4, 2016                 [Page 15]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   +----------------+--------------------------------------------------+
   | 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 as described above         |
   | Content        |                                                  |
   +----------------+--------------------------------------------------+

                           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.

   A receiver of a request MUST be able to process the following as
   equivalent empty attribute groups:




Sweet & McDonald          Expires June 4, 2016                 [Page 16]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   a.  A "begin-attribute-group-tag" field with zero following
       "attribute" fields.

   b.  An expected but missing "begin-attribute-group-tag" field.

   When the Model requires a sequence of an unknown number of attribute
   groups, each of the same type, the encoding MUST contain one "begin-
   attribute-group-tag" field for each attribute group even when an
   "attribute-group" field contains zero "attribute" sub-fields.  For
   example, the Get-Jobs operation may return zero attributes for some
   jobs and not others.  The "begin-attribute-group-tag" field followed
   by zero "attribute" fields tells the recipient that there is a Job in
   queue for which no information is available except that it is in the
   queue.

3.4.  Required Parameters

   Some operation elements are called parameters in the Model
   [RFC2911bis].  They MUST be encoded in a special position and they
   MUST NOT appear as operation attributes.  These parameters are
   described in the subsections below.

3.4.1.  Version-number

   The "version-number" field consists of a major and minor version-
   number, each of which is represented by a SIGNED-BYTE.  The major
   version-number is the first byte of the encoding and the minor
   version-number is the second byte of the encoding.  The protocol
   described in [RFC2911bis] has a major version-number of 1 (0x01) and
   a minor version-number of 1 (0x01).  The ABNF for these two bytes is
   %x01.01.

   Note: See Section 9 for more information on the "version-number"
   field and IPP version numbers.

3.4.2.  Operation-id

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

3.4.3.  Status-code

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





Sweet & McDonald          Expires June 4, 2016                 [Page 17]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   If an IPP status-code is returned, then the HTTP status-code MUST be
   200 (OK).  With any other HTTP status-code value, the HTTP response
   MUST NOT contain an IPP message body, and thus no IPP status-code is
   returned.

3.4.4.  Request-id

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

3.5.  Tags

   There are two kinds of tags:

   o  delimiter tags: delimit major sections of the protocol, namely
      attributes and data

   o  value tags: specify the type of each attribute value

   Tags are part of the IANA IPP registry [IANA-IPP]

3.5.1.  Delimiter Tags

   Table 2 specifies the values for the delimiter tags defined in this
   document:

   +---------------+---------------------------------------------------+
   | Tag Value     | Meaning                                           |
   | (Hex)         |                                                   |
   +---------------+---------------------------------------------------+
   | 0x00          | reserved for definition in a future standards     |
   |               | track document                                    |
   | 0x01          | "operation-attributes-tag"                        |
   | 0x02          | "job-attributes-tag"                              |
   | 0x03          | "end-of-attributes-tag"                           |
   | 0x04          | "printer-attributes-tag"                          |
   | 0x05          | "unsupported-attributes-tag"                      |
   | 0x06-0x0f     | reserved for future delimiters in standards track |
   |               | documents                                         |
   +---------------+---------------------------------------------------+

                          Table 2: Delimiter Tags

   When a "begin-attribute-group-tag" field occurs in the protocol, it
   means that zero or more following attributes up to the next delimiter
   tag are attributes belonging to the attribute group specified by the
   value of the "begin-attribute-group-tag".  For example, if the value



Sweet & McDonald          Expires June 4, 2016                 [Page 18]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   of "begin-attribute-group-tag" is 0x01, the following attributes are
   members of the Operations Attributes group.

   The "end-of-attributes-tag" (value 0x03) MUST occur exactly once in
   an operation and MUST be the last "delimiter-tag".  If the operation
   has a document-data group, the Document data in that group follows
   the "end-of-attributes-tag".

   The order and presence of "attribute-group" fields (whose beginning
   is marked by the "begin-attribute-group-tag" subfield) for each
   operation request and each operation response MUST be that defined in
   the Model.

   A Printer MUST treat a "delimiter-tag" (values from 0x00 through
   0x0F) differently from a "value-tag" (values from 0x10 through 0xFF)
   so that the Printer knows there is an entire attribute group as
   opposed to a single value.

3.5.2.  Value Tags

   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:

   +-------------+-----------------------------------------------------+
   | Tag Value   | Meaning                                             |
   | (Hex)       |                                                     |
   +-------------+-----------------------------------------------------+
   | 0x10        | unsupported                                         |
   | 0x11        | reserved for 'default' for definition in a future   |
   |             | standards track document                            |
   | 0x12        | unknown                                             |
   | 0x13        | no-value                                            |
   | 0x14-0x1F   | reserved for "out-of-band" values in future         |
   |             | standards track documents.                          |
   +-------------+-----------------------------------------------------+

                        Table 3: Out of Band Values

   Table 4 specifies the integer values for the "value-tag" field:








Sweet & McDonald          Expires June 4, 2016                 [Page 19]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   +-------------+-----------------------------------------------------+
   | Tag Value   | Meaning                                             |
   | (Hex)       |                                                     |
   +-------------+-----------------------------------------------------+
   | 0x20        | reserved for definition in a future standards track |
   |             | document                                            |
   | 0x21        | integer                                             |
   | 0x22        | boolean                                             |
   | 0x23        | enum                                                |
   | 0x24-0x2F   | reserved for integer types for definition in future |
   |             | standards track documents                           |
   +-------------+-----------------------------------------------------+

                           Table 4: Integer Tags

   Table 5 specifies the octetString values for the "value-tag" field
   defined in this document:

   +-------------+-----------------------------------------------------+
   | 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   | reserved for octetString type definitions in future |
   |             | standards track documents                           |
   +-------------+-----------------------------------------------------+

                         Table 5: octetString Tags

   Table 6 specifies the character-string values for the "value-tag"
   field defined in this document:













Sweet & McDonald          Expires June 4, 2016                 [Page 20]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   +------------+------------------------------------------------------+
   | Tag Value  | Meaning                                              |
   | (Hex)      |                                                      |
   +------------+------------------------------------------------------+
   | 0x40       | reserved for definition in a future standards track  |
   |            | document                                             |
   | 0x41       | textWithoutLanguage                                  |
   | 0x42       | nameWithoutLanguage                                  |
   | 0x43       | reserved for definition in a future standards track  |
   |            | document                                             |
   | 0x44       | keyword                                              |
   | 0x45       | uri                                                  |
   | 0x46       | uriScheme                                            |
   | 0x47       | charset                                              |
   | 0x48       | naturalLanguage                                      |
   | 0x49       | mimeMediaType                                        |
   | 0x4A       | memberAttrName                                       |
   | 0x4B-0x5F  | reserved for character string type definitions in    |
   |            | future standards track documents                     |
   +------------+------------------------------------------------------+

                           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 4 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.

3.6.  Name-Length

   The "name-length" field consists of a SIGNED-SHORT and specifies the
   number of octets in the immediately following "name" field.  The
   value of this field excludes the two bytes of the "name-length"
   field.  For example, if the "name" field contains 'sides', the value
   of this field is 5.



Sweet & McDonald          Expires June 4, 2016                 [Page 21]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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
   [RFC2911bis]).  The zero-length name is the only mechanism for multi-
   valued attributes.

3.7.  (Attribute) Name

   The "name" field contains the name of an attribute.  The Model
   [RFC2911bis] specifies such names.

3.8.  Value Length

   The "value-length" field consists of a SIGNED-SHORT which specifies
   the number of octets in the immediately following "value" field.  The
   value of this field excludes the two bytes of the "value-length"
   field.  For example, if the "value" field contains the keyword
   (string) value 'one-sided', the value of this field is 9.

   For any of the types represented by binary signed integers, the
   sender MUST encode the value in exactly four octets.

   For any of the types represented by binary signed bytes, 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" "value-tag" fields 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

3.9.  (Attribute) Value

   The syntax types (specified by the "value-tag" field) and most of the
   details of the representation of attribute values are defined in the
   Model.  Table 7 augments the information in the Model and defines the
   syntax types from the Model in terms of the 5 basic types defined in
   Section 3.  The 5 types are US-ASCII-STRING, LOCALIZED-STRING,
   SIGNED-INTEGER, SIGNED-SHORT, SIGNED-BYTE, and OCTET-STRING.

   +----------------------+--------------------------------------------+



Sweet & McDonald          Expires June 4, 2016                 [Page 22]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   | Syntax of Attribute  | Encoding                                   |
   | Value                |                                            |
   +----------------------+--------------------------------------------+
   | textWithoutLanguage, | LOCALIZED-STRING                           |
   | nameWithoutLanguage  |                                            |
   +----------------------+--------------------------------------------+
   | textWithLanguage     | OCTET-STRING consisting of 4 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 4 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                           |
   +----------------------+--------------------------------------------+
   | dateTime             | OCTET-STRING consisting of eleven octets   |
   |                      | whose contents are defined by              |
   |                      | "DateAndTime" in RFC 1903 [RFC1903]        |
   +----------------------+--------------------------------------------+
   | resolution           | OCTET-STRING consisting of nine octets of  |
   |                      | 2 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   |



Sweet & McDonald          Expires June 4, 2016                 [Page 23]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   |                      | units value.                               |
   +----------------------+--------------------------------------------+
   | rangeOfInteger       | Eight octets consisting of 2 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 1 value. Each     |
   |                      | value X is encoded according to the rules  |
   |                      | for encoding its type.                     |
   +----------------------+--------------------------------------------+
   | octetString          | OCTET-STRING                               |
   +----------------------+--------------------------------------------+
   | collection           | Encoding as defined in Section 3.1.6.      |
   +----------------------+--------------------------------------------+

                     Table 7: Attribute Value Encoding

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

3.10.  Data

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

4.  Encoding of Transport Layer

   HTTP/1.1 [RFC7230] is the REQUIRED transport layer for this protocol.
   HTTP/2 [RFC7540] is an OPTIONAL transport layer for this protocol.

   The operation layer has been designed with the assumption that the
   transport layer contains the following information:

   o  the target URI for the operation

   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.

   It is REQUIRED that a Printer implementation support HTTP over the
   IANA assigned Well Known Port 631 (the IPP default port), though a
   Printer implementation may support HTTP over some other port as well.

   Each HTTP operation MUST use the POST method where the request-URI is
   the object target of the operation, and where the "Content-Type" of
   the message body in each request and response MUST be "application/
   ipp".  The message body MUST contain the operation layer and MUST
   have the syntax described in Section 3.2 "Syntax of Encoding".  A



Sweet & McDonald          Expires June 4, 2016                 [Page 24]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   Client implementation MUST adhere to the rules for a Client described
   for HTTP [RFC7230].  A Printer (server) implementation MUST adhere
   the rules for an origin server described for HTTP [RFC7230].

   An IPP server sends a response for each request that it receives.  If
   an IPP server detects an error, it MAY send a response before it has
   read the entire request.  If the HTTP layer of the IPP server
   completes processing the HTTP headers successfully, it MAY send an
   intermediate response, such as "100 Continue", with no IPP data
   before sending the IPP response.  A Client MUST expect such a variety
   of responses from an IPP server.  For further information on HTTP,
   consult the HTTP documents [RFC7230].

   An HTTP/1.1 server MUST support chunking for IPP requests, and an IPP
   Client MUST support chunking for IPP responses according to HTTP/1.1
   [RFC7230].

   Note: this rule causes a conflict with non-compliant implementations
   of HTTP/1.1 that don't support chunking for POST methods, and this
   rule may cause a conflict with non-compliant implementations of
   HTTP/1.1 that don't support chunking for CGI scripts

4.1.  Printer URI, Job URI, and Job ID

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

   Some operation elements are encoded twice, once as the request-URI 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 URI can be relative while the IPP request URI MUST
   be 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



Sweet & McDonald          Expires June 4, 2016                 [Page 25]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


       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.

5.  IPP URI Schemes

   The IPP URI schemes are 'ipp' [RFC3510] and 'ipps' [RFC7472].
   Clients and Printers MUST support the ipp-URI value in the following
   IPP attributes:

   o  Job attributes:

      *  job-uri

      *  job-printer-uri

   o  Printer attributes:

      *  printer-uri-supported

   o  Operation attributes:

      *  job-uri

      *  printer-uri

   Each of the above attributes identifies a Printer or Job. The ipp-URI
   is 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".



Sweet & McDonald          Expires June 4, 2016                 [Page 26]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   If a Printer registers its URI with a directory service, the Printer
   MUST register an ipp-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 rules:

   1.  change the 'ipp' scheme to 'http' or 'ipps' scheme to 'https'

   2.  add an explicit port 631 if the http-URL or https-URL does not
       contain an explicit port.  Note: port 631 is the IANA assigned
       Well Known Port for the 'ipp' and 'ipps' schemes.

   The Client MUST use the target http-URL or https-URL in both the HTTP
   Request-Line and HTTP headers, as specified by HTTP [RFC7230].
   However, the Client MUST use the target ipp-URI or ipps-URI for the
   value of the "printer-uri" or "job-uri" operation attribute within
   the application/ipp body of the request.  The server MUST use the
   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:









Sweet & McDonald          Expires June 4, 2016                 [Page 27]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


     POST http://printer.example.com:631/ipp/print/myqueue HTTP/1.1
     Host: printer.example.com:631
     Content-type: application/ipp
     Transfer-Encoding: chunked
     ...
     "printer-uri" 'ipp://printer.example.com/ipp/print/myqueue'
            (encoded in application/ipp message body)
     ...

                      Figure 12: Proxied IPP Request

   The proxy then connects to the IPP origin server with headers that
   are the same as the "no-proxy" example above.

6.  IANA Considerations

   See the section on "IANA Considerations" in the document "Internet
   Printing Protocol/1.1: Model and Semantics" [RFC2911bis] for
   information on IANA considerations.  This document adds no additional
   considerations.

7.  Internationalization Considerations

   See the section on "Internationalization Considerations" in the
   document "Internet Printing Protocol/1.1: Model and Semantics"
   [RFC2911bis] for information on internationalization.  This document
   adds no additional issues.

8.  Security Considerations

   The IPP Model and Semantics document [RFC2911bis] 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.

8.1.  Security Conformance Requirements

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








Sweet & McDonald          Expires June 4, 2016                 [Page 28]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


8.1.1.  Digest Authentication

   IPP Clients and Printers SHOULD support Digest Authentication
   [RFC7616].  If supported, MD5 and MD5-sess MUST be implemented and
   supported.  Use of the Message Integrity feature (qop="auth-int") is
   OPTIONAL.

   The reasons that IPP Clients and Printers SHOULD (rather than MUST)
   support Digest Authentication are:

   1.  While Client Authentication is important, 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.

   2.  Print devices that have high-volume throughput and have available
       ROM space are more likely to provide support for Client
       Authentication that safeguards the device from unauthorized
       access.  These devices are prone to a high loss of consumables
       and paper if unauthorized access occurs.

8.1.2.  Transport Layer Security (TLS)

   IPP Clients and Printers SHOULD support Transport Layer Security
   (TLS) [RFC5246] [RFC7525] for Server Authentication and Operation
   Privacy.  IPP Printers MAY also support TLS for Client
   Authentication.  IPP Clients and Printers MAY support Basic
   Authentication [RFC7617] for User Authentication if the channel is
   secure.

   The IPP Model and Semantics document [RFC2911bis] 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 protocol itself.







Sweet & McDonald          Expires June 4, 2016                 [Page 29]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


8.2.  Using IPP with TLS

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

   IPP uses the "HTTPS: HTTP over TLS" mechanism [RFC2818] for 'ipps'
   URIs.  The Client and server negotiate a secure TLS connection
   immediately and unconditionally.

9.  Interoperability with Other IPP Versions

   It is beyond the scope of this specification to mandate conformance
   with versions of IPP other than 1.1.  IPP was deliberately designed,
   however, to make supporting other versions easy.  IPP Printer
   implementations SHOULD:

   o  understand any valid request in the format of IPP/1.x or 2.x;

   o  respond appropriately with a response containing the same
      "version-number" parameter value used by the Client in the
      request.

   IPP Clients SHOULD:

   o  understand any valid response in the format of IPP/1.1, 2.0, 2.1,
      or 2.2.

9.1.  The "version-number" Parameter

   The following are rules regarding the "version-number" parameter (see
   Section 3.3):

   1.  Clients MUST send requests containing a "version-number"
       parameter with the highest supported value, e.g., '1.1', '2.0',
       etc., and SHOULD try supplying alternate version numbers if they
       receive a 'server-error-version-not-supported' error return in a
       response.

   2.  IPP objects 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').





Sweet & McDonald          Expires June 4, 2016                 [Page 30]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   3.  IPP objects SHOULD accept any request with the major version '1'
       or '2', or reject the request for reasons other than 'server-
       error-version-not-supported'.  See [RFC2911bis] "Versions" sub-
       section.

   4.  In any case, security MUST NOT be compromised when a Client
       supplies a lower "version-number" parameter in a request.  For
       example, if an IPP/2.0 conforming Printer accepts version '1.1'
       requests and is configured to enforce Digest Authentication, it
       MUST do the same for a version '1.1' request.

9.2.  Security and URI Schemes

   The following are rules regarding security, the "version-number"
   parameter, and the URI scheme supplied in target attributes and
   responses:

   1.  When a Client supplies a request, the "printer-uri" or "job-uri"
       target operation attribute MUST have the same scheme as that
       indicated in one of the values of the "printer-uri-supported"
       Printer attribute.

   2.  When the Printer returns the "job-printer-uri" or "job-uri" Job
       Description attributes, it SHOULD return the same scheme ('ipp',
       'ipps', etc.) that the Client supplied in the "printer-uri" or
       "job-uri" target operation attributes in the Get-Job-Attributes
       or Get-Jobs request, rather than the scheme used when the Job was
       created.  However, when a Client requests Job attributes using
       the Get-Job-Attributes or Get-Jobs operations, the Jobs and Job
       attributes that the Printer returns depends on: (1) the security
       in effect when the Job was created, (2) the security in effect in
       the query request, and (3) the security policy in force.

   3.  The Printer MUST enforce its security and privacy policies based
       on the owner of the IPP object and the URI scheme and/or
       credentials supplied by the Client in the current request.

10.  Changes Since RFC 2910

   The following changes have been made since the publication of RFC
   2910:

   o  Added references to current IPP extension specifications.

   o  Added optional support for HTTP/2.

   o  Added collection attribute syntax from RFC 3382.




Sweet & McDonald          Expires June 4, 2016                 [Page 31]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  Fixed typographical errors.

   o  Now reference TLS/1.2 and no longer mandate the TLS/1.0 MTI cipher
      suites.

   o  Updated all references.

   o  Updated document organization to follow current style.

   o  Updated example ipp: URIs to follow RFC 7472 guidelines.

   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.

11.  References

11.1.  Normative References

   [ASCII]    ANSI, "Information Systems - Coded Character Sets - 7-Bit
              American National Standard Code for Information
              Interchange (7-Bit ASCII)", June 2007.

   [PWG5100.12]
              Sweet, M. and I. McDonald, "IPP/2.0, 2.1, and 2.2",
              October 2015, <http://ftp.pwg.org/pub/pwg/standards/
              std-ipp20-20151030-5100.12.pdf>.

   [RFC1903]  McCloghrie, K., Case, J., Rose, M., and S. Waldbusser,
              "Textual Conventions for Version 2 of the Simple Network
              Management Protocol (SNMPv2)", RFC 1903, January 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2817]  Khare, R. and S. Lawrence, "Upgrading to TLS Within
              HTTP/1.1", RFC 2817, May 2000.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC2911bis]
              Sweet, M. and I. McDonald, "Internet Printing
              Protocol/1.1: Model and Semantics", December 2015,
              <https://tools.ietf.org/html/draft-sweet-rfc2911bis>.




Sweet & McDonald          Expires June 4, 2016                 [Page 32]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   [RFC3510]  Herriot, R. and I. McDonald, "Internet Printing
              Protocol/1.1: IPP URL Scheme", RFC 3510, April 2003.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC7230]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Message Syntax and Routing", RFC 7230, June
              2014.

   [RFC7231]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content", RFC 7231, June 2014.

   [RFC7232]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Conditional Requests", RFC 7232, June 2014.

   [RFC7234]  Fielding, R., Nottingham, M., and J. Reschke, "Hypertext
              Transfer Protocol (HTTP/1.1): Caching", RFC 7234, June
              2014.

   [RFC7235]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Authentication", RFC 7235, June 2014.

   [RFC7472]  McDonald, I. and M. Sweet, "Internet Printing Protocol
              (IPP) over HTTPS Transport Binding and the 'ipps' URI
              Scheme", RFC 7472, March 2015.

   [RFC7540]  Belshe, M., Peon, R., and M. Thompson, "Hypertext Transfer
              Protocol Version 2 (HTTP/2)", May 2015,
              <https://tools.ietf.org/html/rfc7540>.

   [RFC7541]  Peon, R. and H. Ruellan, "HPACK - Header Compression for
              HTTP/2", May 2015, <https://tools.ietf.org/html/rfc7541>.

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



Sweet & McDonald          Expires June 4, 2016                 [Page 33]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   [RFC7617]  Reschke, J., "The 'Basic' HTTP Authentication Scheme",
              RFC 7617, DOI 10.17487/RFC7617, September 2015,
              <http://www.rfc-editor.org/info/rfc7617>.

   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

11.2.  Informative References

   [IANA-CON]
              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [IANA-IPP]
              "IANA IPP Registry",
              <http://www.iana.org/assignments/ipp-registrations/>.

   [PWG5100.3]
              Ocke, K. and T. Hastings, "IPP Production Printing
              Attributes Set 1", February 2001,
              <http://ftp.pwg.org/pub/pwg/candidates/
              cs-ippprodprint10-20010212-5100.3.pdf>.

   [RFC1179]  McLaughlin, L., "Line printer daemon protocol", RFC 1179,
              August 1990.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, May 2015.

Appendix A.  Protocol Examples

A.1.  Print-Job Request

   The following is an example of a Print-Job request with "job-name",
   "copies", and "sides" specified.  The "ipp-attribute-fidelity"
   attribute is set to 'true' so that the print request will fail if the
   "copies" or the "sides" attribute are 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-



Sweet & McDonald          Expires June 4, 2016                 [Page 34]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


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





Sweet & McDonald          Expires June 4, 2016                 [Page 35]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


A.2.  Print-Job Response (successful)

   Here is an example of a successful Print-Job response to the previous
   Print-Job request.  The Printer supported the "copies" and "sides"
   attributes and their supplied values.  The status code returned is
   'successful-ok'.













































Sweet & McDonald          Expires June 4, 2016                 [Page 36]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


    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-
                                     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






Sweet & McDonald          Expires June 4, 2016                 [Page 37]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


A.3.  Print-Job Response (failure)

   Here is an example of an unsuccessful Print-Job response to the
   previous Print-Job request.  It fails because, in this case, the
   Printer does not support the "sides" attribute and because the value
   '20' for the "copies" attribute is not supported.  Therefore, no Job
   is created, and neither a "job-id" nor a "job-uri" operation
   attribute is returned.  The error code returned is 'client-error-
   attributes-or-values-not-supported' (0x040B).










































Sweet & McDonald          Expires June 4, 2016                 [Page 38]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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
   attributes-natural-language attributes-natural-language name
   0x0005                                                  value-length
   en-us                       en-US                       value
   0x41                        textWithoutLanguage type    value-tag
   0x000E                                                  name-length
   status-message              status-message              name
   0x002F                                                  value-length
   client-error-attributes-or- client-error-attributes-or- value
   values-not-supported        values-not-supported
   0x05                        start unsupported-          unsupported-
                               attributes                  attributes
                                                           tag
   0x21                        integer type                value-tag
   0x0006                                                  name-length
   copies                      copies                      name
   0x0004                                                  value-length
   0x00000014                  20                          value
   0x10                        unsupported (type)          value-tag
   0x0005                                                  name-length
   sides                       sides                       name
   0x0000                                                  value-length
   0x03                        end-of-attributes           end-of-
                                                           attributes-
                                                           tag

A.4.  Print-Job Response (success with attributes ignored)

   Here is an example of a successful Print-Job response to a Print-Job
   request like the previous Print-Job request, except that the value of
   "ipp-attribute-fidelity" is 'false'.  The print request succeeds,



Sweet & McDonald          Expires June 4, 2016                 [Page 39]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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
   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



Sweet & McDonald          Expires June 4, 2016                 [Page 40]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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

A.5.  Print-URI Request

   The following is an example of Print-URI request with "copies" and
   "job-name" parameters:































Sweet & McDonald          Expires June 4, 2016                 [Page 41]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


    Octets                         Symbolic Value       Protocol field

    0x0101                         1.1                  version-number
    0x0003                         Print-URI            operation-id
    0x00000001                     1                    request-id
    0x01                           start operation-     operation-
                                   attributes           attributes-tag
    0x47                           charset type         value-tag
    0x0012                                              name-length
    attributes-charset             attributes-charset   name
    0x0005                                              value-length
    utf-8                          UTF-8                value
    0x48                           natural-language     value-tag
                                   type
    0x001B                                              name-length
    attributes-natural-language    attributes-natural-  name
                                   language
    0x0005                                              value-length
    en-us                          en-US                value
    0x45                           uri type             value-tag
    0x000B                                              name-length
    printer-uri                    printer-uri          name
    0x002C                                              value-length
    ipp://printer.example.com/ipp/ printer pinetree     value
    print/pinetree
    0x45                           uri type             value-tag
    0x000C                                              name-length
    document-uri                   document-uri         name
    0x0019                                              value-length
    ftp://foo.example.com/foo      ftp://foo.example.co value
                                   m/foo
    0x42                           nameWithoutLanguage  value-tag
                                   type
    0x0008                                              name-length
    job-name                       job-name             name
    0x0006                                              value-length
    foobar                         foobar               value
    0x02                           start job-attributes job-attributes-
                                                        tag
    0x21                           integer type         value-tag
    0x0006                                              name-length
    copies                         copies               name
    0x0004                                              value-length
    0x00000001                     1                    value
    0x03                           end-of-attributes    end-of-
                                                        attributes-tag





Sweet & McDonald          Expires June 4, 2016                 [Page 42]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


A.6.  Create-Job Request

   The following is an example of Create-Job request with no parameters
   and no attributes:

    Octets                         Symbolic Value       Protocol field

    0x0101                         1.1                  version-number
    0x0005                         Create-Job           operation-id
    0x00000001                     1                    request-id
    0x01                           start operation-     operation-
                                   attributes           attributes-tag
    0x47                           charset type         value-tag
    0x0012                                              name-length
    attributes-charset             attributes-charset   name
    0x0005                                              value-length
    utf-8                          UTF-8                value
    0x48                           natural-language     value-tag
                                   type
    0x001B                                              name-length
    attributes-natural-language    attributes-natural-  name
                                   language
    0x0005                                              value-length
    en-us                          en-US                value
    0x45                           uri type             value-tag
    0x000B                                              name-length
    printer-uri                    printer-uri          name
    0x002C                                              value-length
    ipp://printer.example.com/ipp/ printer pinetree     value
    print/pinetree
    0x03                           end-of-attributes    end-of-
                                                        attributes-tag

A.7.  Create-Job Request with Collection Attributes

   The following is an example of Create-Job request with the "media-
   col" collection attribute [PWG5100.3] with the value "media-
   size={x-dimension=21000 y-dimension=29700} media-type='stationery'":

   Octets                         Symbolic Value       Protocol field

   0x0101                         1.1                  version-number
   0x0005                         Create-Job           operation-id
   0x00000001                     1                    request-id
   0x01                           start operation-     operation-
                                  attributes           attributes-tag
   0x47                           charset type         value-tag
   0x0012                                              name-length



Sweet & McDonald          Expires June 4, 2016                 [Page 43]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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)
   0x21                           integer              member-value-tag
   0x0000                         0                    name-length
   0x0004                         4                    member-value-
                                                       length



Sweet & McDonald          Expires June 4, 2016                 [Page 44]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   0x00007404                     29700                member-value
   0x37                           endCollection        end-value-tag
   0x0000                         0                    end-name-length
   0x0000                         0                    end-value-length
   0x4A                           memberAttrName       value-tag
   0x0000                         0                    name-length
   0x000A                         10                   value-length
   media-type                     media-type           value (member-
                                                       name)
   0x44                           keyword              member-value-tag
   0x0000                         0                    name-length
   0x000A                         10                   member-value-
                                                       length
   stationery                     stationery           member-value
   0x37                           endCollection        end-value-tag
   0x0000                         0                    end-name-length
   0x0000                         0                    end-value-length
   0x03                           end-of-attributes    end-of-
                                                       attributes-tag

A.8.  Get-Jobs Request

   The following is an example of Get-Jobs request with parameters but
   no attributes:



























Sweet & McDonald          Expires June 4, 2016                 [Page 45]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


    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
    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






Sweet & McDonald          Expires June 4, 2016                 [Page 46]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


A.9.  Get-Jobs Response

   The following is an of Get-Jobs response from previous request with 3
   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
   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)



Sweet & McDonald          Expires June 4, 2016                 [Page 47]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   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

Appendix B.  Registration of MIME Media Type Information for
             "application/ipp"

   This section is strictly informative.  The MIME media type listed in
   this section should not be re-registered by IANA when this document
   is published.

   This appendix contains the information that IANA requires for
   registering a MIME media type.  The information following this
   paragraph will be forwarded to IANA to register application/ipp whose
   contents are defined in Section 3 "Encoding of the Operation Layer"
   in this document:

   MIME type name: application

   MIME subtype name: ipp

   A Content-Type of "application/ipp" indicates an Internet Printing
   Protocol message body (request or response) whose syntax is described
   in Section 3 "Encoding of the Operation Layer" of [RFC2910bis], and
   whose semantics are described in [RFC2911bis].

   Required parameters: none

   Optional parameters: none

   Encoding considerations:

   IPP protocol requests/responses MAY contain long lines and ALWAYS
   contain binary data (for example attribute value lengths).




Sweet & McDonald          Expires June 4, 2016                 [Page 48]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   Security considerations:

   IPP protocol requests/responses do not introduce any security risks
   not already inherent in the underlying transport protocols.  Protocol
   mixed-version interworking rules in [RFC2911bis] as well as protocol
   encoding rules in [RFC2910bis] are complete and unambiguous.

   Interoperability considerations:

   IPP requests (generated by clients) and responses (generated by
   servers) MUST comply with all conformance requirements imposed by the
   normative specifications [RFC2911bis] and [RFC2910bis].  Protocol
   encoding rules specified in [RFC2910bis] 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
   which are a LOCALIZED-STRING are explicit within IPP protocol
   requests/responses (without recourse to any external information in
   HTTP, SMTP, or other message transport headers).

   Published specifications:

   [RFC2911bis] Sweet, M., McDonald, I., "Internet Printing
   Protocol/1.1: Model and Semantics" draft-sweet-rfc2911bis-06.txt,
   December, 2015.

   [RFC2910bis] Sweet, M., McDonald, I., "Internet Printing
   Protocol/1.1: Encoding and Transport", draft-sweet-rfc2910bis-06.txt,
   December, 2015.

   Applications which use this media type:

   Internet Printing Protocol (IPP) print clients and print servers,
   communicating using HTTP (see [RFC2910bis]), SMTP/ESMTP, FTP, or
   other transport protocol.  Messages of type "application/ipp" are
   self-contained and transport-independent, including "charset" and
   "natural-language" context for any LOCALIZED-STRING value.

Appendix C.  Acknowledgements

   The authors would like to acknowledge the following individuals for
   their contributions to the original IPP/1.1 specification:

   Robert Herriot (original RFC 2910 editor), Paul Moore, Sylvan Butler,
   Randy Turner, and John Wenn






Sweet & McDonald          Expires June 4, 2016                 [Page 49]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


Appendix D.  Change History

D.1.  Changes In -06

   The following changes are in draft-sweet-rfc2910bis-06:

   o  Global: "Model" changed to just "Model".

   o  Global: "message-body" changed to "message body".

   o  Abstract: "MIME" instead of "mime" plus some minor rewording.

   o  Section 1: Updated references to HTTP Basic and Digest, clarify
      that the semantics/model are defined in both the Model and
      subsequent extensions.

   o  Section 2.2: Fixed some typos and added a definition of Model.

   o  Section 3.1.1: Reworded paragraph about the data field.

   o  Section 3.2: Reworded and now use figure references, and fixed
      section references in figures.

   o  Section 3.3: Added table reference, fix typo.

   o  Section 3.4.1: Replace "this document" with reference to 2911bis.

   o  Section 3.4.3: HTTP status-code (to be consistent with RFC 7230).

   o  Section 3.5.1: Add table references, capitalize Document, reword
      ordering requirements, reword printer requirements.

   o  Section 3.5.2: Add table references, dropped notes (15 years
      without needing it, we don't need the note...)

   o  Section 3.6: "mal-formed" changed to "malformed", fix RFC2911bis
      reference, single quotes around value.

   o  Section 3.8: "string" instead of "text", use single quotes for
      values.

   o  Section 3.9: Add table reference.

   o  Section 4: Fix HTTP references and put Note in a separate
      paragraph.

   o  Section 4.1: Mention the Job ID, clean up Note and get rid of
      "NEED NOT" language.



Sweet & McDonald          Expires June 4, 2016                 [Page 50]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  Section 5: Clients and Printers MUST support, drop "object", use
      double quotes around attribute names, drop discussion of UI, fix
      typos.

   o  Section 6: Point to RFC2911bis.

   o  Section 8.1.1: Update references to HTTP Basic and Digest RFCs.

   o  Section 9: Allow 1.x and 2.x, fix typos.

   o  Section 11.1: Updated 5100.12, HTTP Basic and Digest references

   o  Appendix A: Examples now use UTF-8, fix job-uri to be consistent
      with job-id.

   o

D.2.  Changes In -05

   The following changes are in draft-sweet-rfc2910bis-05:

   o  Submission type is now IETF (AD-sponsored), clarify goals.

   o  Abstract: This document does not define the 'ipp' URI scheme.

   o  Section 5: drop reference to RFC 2617

   o  Section 8.1.1: combine identical Client and Printer requirements

   o  Section 8.1.2: also applies to clients, HTTP Basic is User
      authentication, not Client authentication.

   o  References to RFC 2617 are updated to the updated drafts in the
      RFC editor's queue

   o  Global: Client, Printer, and Job are defined terms, capitalize

D.3.  Changes In -04

   The following changes are in draft-sweet-rfc2910bis-04:

   o  Removed more references to IPP/1.0.

   o  Section 5: Be explicit about ipp/s-URI and http/s-URL

   o  Section 9.1: Reword SHOULD recommendation (avoid passive voice)





Sweet & McDonald          Expires June 4, 2016                 [Page 51]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  Section 9.2: Reword item 3: the server MUST NOT compromise
      security...

   o  Make sure to use URI for generic schemes and URL for HTTP/HTTPS.

   o  Fixed incorrect usage of lowercase conformance words.

D.4.  Changes In -03

   The following changes are in draft-sweet-rfc2910bis-03:

   o  New HTTP/2 RFCs: 7540, 7541

   o  Added informative reference to UTA BCP (RFC 7525)

   o  Culled list of people in acknowledgements to the original RFC 2910
      editors, per IPP F2F.

D.5.  Changes In -02

   The following changes are in draft-sweet-rfc2910bis-02:

   o  Sections 3.1.x: Dropped "Picture of the encoding of" from titles

   o  Section 3.4.1: Added reference to IPP version interoperability
      section.

   o  Section 3.4.2: Removed paragraph on status-code as operation
      attribute (already covered in 3.4 intro) and updated HTTP status
      code 200 name (OK)

   o  Section 3.5: Added reference to IANA IPP registry for tags.

   o  Section 3.8: Mention SIGNED-BYTE is 1 octet.

   o  Section 4.1: Drop mention of URIs not being widely implemented,
      and that implementations will pass around URLs (not true).  Also
      remove more "need not" text.

   o  Section 6: Fixed references.

   o  Section 8.1.1: Make Digest authentication a SHOULD for clients.

   o  Section 9: Reworked for generic IPP version compatibility.

   o  Section 9.1: Reworked for IPP 2.x compatibility.

   o  Section 9.2: Drop reference to IPP/1.0 and http/https URI schemes.



Sweet & McDonald          Expires June 4, 2016                 [Page 52]


Internet-Draft       IPP/1.1: Encoding and Transport       December 2015


   o  Appendix A: Updated example URIs to follow IETF and IPP/IPPS URI
      examples

   o  Global: ipp-URL tp ipp-URI, URL to URI

   o  Global: Don't use conformance language for statements of fact.

   o  Global: Change "NOTE:" to "Note:" for consistency.

D.6.  Changes In -01

   The following changes are in draft-sweet-rfc2910bis-01:

   o  Errata ID 4100: Cleaned up TLS references and recommendations - no
      longer include cipher suites.

   o  Errata ID 4172: Fixed range of standards-track value tags (to
      0x3ffffff not 0x37777777)

   o  Updated RFC references.

   o  Added HTTP/2 references, made it clear that only HTTP/1.1 is
      required and HTTP/2 is optional.

   o  Added collection attribute encoding from RFC 3382.

Authors' Addresses

   Michael Sweet
   Apple Inc.
   1 Infinite Loop
   MS 111-HOMC
   Cupertino, CA  95014
   US

   Email: msweet@apple.com


   Ira McDonald
   High North, Inc.
   PO Box 221
   Grand Marais, MI  49839
   US

   Phone: +1 906-494-2434
   Email: blueroofmusic@gmail.com





Sweet & McDonald          Expires June 4, 2016                 [Page 53]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/