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rfc:rfc2910

Network Working Group R. Herriot, Editor Request for Comments: 2910 Xerox Corporation Obsoletes: 2565 S. Butler Category: Standards Track Hewlett-Packard

                                                              P. Moore
                                           Peerless Systems Networking
                                                             R. Turner
                                                             2wire.com
                                                               J. Wenn
                                                     Xerox Corporation
                                                        September 2000
       Internet Printing Protocol/1.1: Encoding and Transport

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

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

Herriot, et al. Standards Track [Page 1] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 The full set of IPP documents includes:
 Design Goals for an Internet Printing Protocol [RFC2567]
 Rationale for the Structure and Model and Protocol for the Internet
 Printing Protocol [RFC2568]
 Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
 Internet Printing Protocol/1.1: Encoding and Transport (this
 document)
 Internet Printing Protocol/1.1: Implementer's Guide [ipp-iig]
 Mapping between LPD and IPP Protocols [RFC2569]
 The document, "Design Goals for an Internet Printing Protocol", takes
 a broad look at distributed printing functionality, and it enumerates
 real-life scenarios that help to clarify the features that need to be
 included in a printing protocol for the Internet. It identifies
 requirements for three types of users: end users, operators, and
 administrators. It calls out a subset of end user requirements that
 are satisfied in IPP/1.1. A few OPTIONAL operator operations have
 been added to IPP/1.1.
 The document, "Rationale for the Structure and Model and Protocol for
 the Internet Printing Protocol", describes IPP from a high level
 view, defines a roadmap for the various documents that form the suite
 of IPP specification documents, and gives background and rationale
 for the IETF working group's major decisions.
 The document, "Internet Printing Protocol/1.1: Model and Semantics",
 describes a simplified model with abstract objects, their attributes,
 and their operations that are independent of encoding and transport.
 It introduces a Printer and a Job object. The Job object optionally
 supports multiple documents per Job. It also addresses security,
 internationalization, and directory issues.
 The document "Internet Printing Protocol/1.1: Implementer's Guide",
 gives advice to implementers of IPP clients and IPP objects.
 The document "Mapping between LPD and IPP Protocols", gives some
 advice to implementers of gateways between IPP and LPD (Line Printer
 Daemon) implementations.

Herriot, et al. Standards Track [Page 2] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Table of Contents

 1. Introduction ...................................................4
 2. Conformance Terminology ........................................4
 3. Encoding of  the Operation Layer ...............................4
    3.1  Picture of the Encoding ...................................6
       3.1.1 Request and Response...................................6
       3.1.2 Attribute Group........................................6
       3.1.3 Attribute..............................................7
       3.1.4 Picture of the Encoding of an Attribute-with-one-value.7
       3.1.5 Additional-value.......................................8
       3.1.6 Alternative Picture of the Encoding of a Request Or a
             Response...............................................9
    3.2  Syntax of Encoding ........................................9
    3.3  Attribute-group ..........................................11
    3.4  Required Parameters ......................................12
       3.4.1 Version-number........................................12
       3.4.2 Operation-id..........................................12
       3.4.3 Status-code...........................................12
       3.4.4 Request-id............................................13
    3.5  Tags .....................................................13
       3.5.1 Delimiter Tags........................................13
       3.5.2 Value Tags............................................14
    3.6  Name-Length ..............................................16
    3.7  (Attribute) Name .........................................16
    3.8  Value Length .............................................16
    3.9  (Attribute) Value ........................................17
    3.10 Data .....................................................18
 4. Encoding of Transport Layer ...................................18
    4.1  Printer-uri and job-uri ..................................19
 5. IPP URL Scheme ................................................20
 6. IANA Considerations ...........................................22
 7. Internationalization Considerations ...........................23
 8. Security Considerations .......................................23
    8.1  Security Conformance Requirements ........................23
       8.1.1 Digest Authentication.................................23
       8.1.2 Transport Layer Security (TLS)........................24
    8.2  Using IPP with TLS .......................................25
 9. Interoperability with IPP/1.0 Implementations .................25
    9.1  The "version-number" Parameter ...........................25
    9.2  Security and URL Schemes .................................26
 10. References ...................................................27
 11. Authors' Addresses ...........................................29
 12. Other Participants: ..........................................31
 13. Appendix A: Protocol Examples ................................33
    13.1 Print-Job Request ........................................33
    13.2 Print-Job Response (successful) ..........................34
    13.3 Print-Job Response (failure) .............................35

Herriot, et al. Standards Track [Page 3] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    13.4 Print-Job Response (success with attributes ignored) .....36
    13.5 Print-URI Request ........................................38
    13.6 Create-Job Request .......................................39
    13.7 Get-Jobs Request .........................................40
    13.8 Get-Jobs Response ........................................41
 14. Appendix B: Registration of MIME Media Type Information for
     "application/ipp".............................................42
 15. Appendix C: Changes from IPP/1.0 .............................44
 16. Full Copyright Statement .....................................45

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/1.1 request or response. RFC
 2616 [RFC2616] describes HTTP/1.1. 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 document "Internet Printing Protocol/1.1: Model and
 Semantics" [RFC2911] defines the semantics of such a message body and
 the supported values. This document specifies the encoding of an IPP
 operation. The aforementioned document [RFC2911] is henceforth
 referred to as the "IPP model document" or simply "model document".
 Note:  the version number of IPP (1.1) and HTTP (1.1) are not linked.
 They both just happen to be 1.1.

2. Conformance Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
 "RECOMMENDED", "MAY", and  "OPTIONAL" in this document are to be
 interpreted as described in RFC 2119 [RFC2119].

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

Herriot, et al. Standards Track [Page 4] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 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 document
 is henceforth called a LOCALIZED-STRING.  An octet string MUST be in
 "IPP model document order" with the first octet in the value
 (according to the IPP model document 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 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:
  1. informally through pictures and description
  2. formally through Augmented Backus-Naur Form (ABNF), as

specified by RFC 2234 [RFC2234]

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

Herriot, et al. Standards Track [Page 5] RFC 2910 IPP/1.1: Encoding and Transport September 2000

3.1 Picture of the Encoding

3.1.1 Request and Response

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

| version-number | 2 bytes - required

  1. ———————————————-

| operation-id (request) |

 |                      or                     |   2 bytes  - required
 |               status-code (response)        |
 -----------------------------------------------
 |                   request-id                |   4 bytes  - required
 -----------------------------------------------
 |                 attribute-group             |   n bytes - 0 or more
 -----------------------------------------------
 |              end-of-attributes-tag          |   1 byte   - required
 -----------------------------------------------
 |                     data                    |   q bytes  - optional
 -----------------------------------------------
 The first three fields in the above diagram contain the value of
 attributes described in section 3.1.1 of the Model document.
 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 document). The IPP model document specifies the
 required attribute groups and their order for each operation request
 and response.
 The "end-of-attributes-tag" field is always present, even when the
 "data" is not present.  The Model document specifies for each
 operation request and response whether the "data" field is present or
 absent.

3.1.2 Attribute Group

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

| begin-attribute-group-tag | 1 byte

  1. ———————————————————

| attribute | p bytes |- 0 or more

  1. ———————————————————

Herriot, et al. Standards Track [Page 6] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 The "begin-attribute-group-tag" field marks the beginning of an
 "attribute-group" field and its value identifies the type of
 attribute group, e.g. Operations Attributes group versus a Job
 Attributes group.  The "begin-attribute-group-tag" field also marks
 the end of the previous attribute group except for the "begin-
 attribute-group-tag" field in the first "attribute-group" field of a
 request or response.  The "begin-attribute-group-tag" field acts as
 an "attribute-group" terminator because an "attribute-group" field
 cannot nest inside another "attribute-group" field.
 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:
  1. ———————————————-

| attribute-with-one-value | q bytes

  1. ———————————————————

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

  1. ———————————————————
 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 Picture of the Encoding of an Attribute-with-one-value

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

| value-tag | 1 byte

  1. ———————————————-

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

  1. ———————————————-

| name | u bytes

  1. ———————————————-

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

  1. ———————————————-

| value | v bytes

  1. ———————————————-

Herriot, et al. Standards Track [Page 7] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 An "attribute-with-one-value" field is encoded with five subfields:
    The "value-tag" field specifies the attribute syntax, e.g. 0x44
    for the attribute syntax 'keyword'.
    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".
    The "name" field contains the textual name of the attribute, e.g.
    "sides-supported".
    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'.
    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:
  1. ———————————————-

| value-tag | 1 byte

  1. ———————————————-

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

  1. ———————————————-

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

  1. ———————————————-

| value | w bytes

  1. ———————————————-
 An "additional-value" is encoded with four subfields:
    The "value-tag" field specifies the attribute syntax, e.g. 0x44
    for the attribute syntax 'keyword'.
    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).
    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'.

Herriot, et al. Standards Track [Page 8] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    The "value" field contains the value of the attribute, e.g. the
    textual value 'two-sided-long-edge'.

3.1.6 Alternative Picture of the Encoding of a Request Or a Response

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

| version-number | 2 bytes - required

  1. ———————————————-

| operation-id (request) |

 |                      or                     |   2 bytes  - required
 |               status-code (response)        |
 -----------------------------------------------
 |                   request-id                |   4 bytes  - required
 -----------------------------------------------------------
 |        tag (delimiter-tag or value-tag)     |   1 byte  |
 -----------------------------------------------           |-0 or more
 |           empty or rest of attribute        |   x bytes |
 -----------------------------------------------------------
 |              end-of-attributes-tag          |   1 byte   - required
 -----------------------------------------------
 |                     data                    |   y bytes  - optional
 -----------------------------------------------
 The following show what fields the parser would expect after each
 type of  "tag":
  1. "begin-attribute-group-tag": expect zero or more "attribute"

fields

  1. "value-tag": expect the remainder of an "attribute-with-one-

value" or an "additional-value".

  1. "end-of-attributes-tag": expect that "attribute" fields are

complete and there is optional "data"

3.2 Syntax of Encoding

 The syntax below is ABNF [RFC2234] except 'strings of literals' MUST
 be case sensitive. For example 'a' means lower case  'a' and not
 upper case 'A'.   In addition, SIGNED-BYTE and SIGNED-SHORT fields
 are represented as '%x' values which show their range of values.
    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

Herriot, et al. Standards Track [Page 9] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    attribute-group = begin-attribute-group-tag *attribute
    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 defined below
    status-code = SIGNED-SHORT  ; mapping from model defined below
    request-id = SIGNED-INTEGER ; whose value is > 0
    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 3.7.2
    begin-attribute-group-tag = %x00-02 / %04-0F ; see section 3.7.1
    end-of-attributes-tag = %x03                  ; tag of 3
                                  ; see section 3.7.1
    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
 The syntax below defines additional terms that are referenced in this
 document. This syntax provides an alternate grouping of the delimiter
 tags.
    delimiter-tag = begin-attribute-group-tag  / ; see section 3.7.1
              end-of-attributes-tag
    delimiter-tag = %x00-0F                      ; see section 3.7.1
    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

Herriot, et al. Standards Track [Page 10] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    job-attributes-tag    =  %x02                 ; tag of 2
    printer-attributes-tag =  %x04                ; tag of 4
    unsupported-attributes-tag =  %x05            ; tag of 5

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.
 The table below maps the model document group name to value of the
 "begin-attribute-group-tag" field:
    Model Document Group            "begin-attribute-group-tag" field
                                    values
    Operation Attributes            "operations-attributes-tag"
    Job Template Attributes         "job-attributes-tag"
    Job Object Attributes           "job-attributes-tag"
    Unsupported Attributes          "unsupported-attributes-tag"
    Requested Attributes            "job-attributes-tag"
    (Get-Job-Attributes)
    Requested Attributes            "printer-attributes-tag"
    (Get-Printer-Attributes)
    Document Content                in a special position as
                                    described above
 For each operation request and response, the model document
 prescribes the required and optional attribute groups, along with
 their order.  Within each attribute group, the model document
 prescribes the required and optional attributes, along with their
 order.
 When the Model document 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
 document, 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:

Herriot, et al. Standards Track [Page 11] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    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 document 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, for 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 document
 [RFC2911]. 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 MUST consist of a major and minor
 version-number, each of which MUST be represented by a SIGNED-BYTE.
 The major version-number MUST be the first byte of the encoding and
 the minor version-number MUST be the second byte of the encoding. The
 protocol described in this document MUST have a major version-number
 of 1 (0x01) and a minor version-number of 1 (0x01).  The ABNF for
 these two bytes MUST be %x01.01.

3.4.2 Operation-id

 The "operation-id" field MUST contain an operation-id value defined
 in the model document. The value MUST be encoded as a SIGNED-SHORT
 and it MUST be in the third and fourth bytes of the encoding of an
 operation request.

3.4.3 Status-code

 The "status-code" field MUST contain a status-code value defined in
 the model document. The value MUST be encoded as a SIGNED-SHORT and
 it MUST be in the third and fourth bytes of the encoding of an
 operation response.

Herriot, et al. Standards Track [Page 12] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 The status-code is an operation attribute in the model document. In
 the protocol, the status-code is in a special position, outside of
 the operation attributes.
 If an IPP status-code is returned, then the HTTP Status-Code MUST be
 200 (successful-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 MUST contain a request-id value as defined in
 the model document. The value MUST be encoded as a SIGNED-INTEGER and
 it MUST be in the fifth through eighth bytes of the encoding.

3.5 Tags

 There are two kinds of tags:
  1. delimiter tags: delimit major sections of the protocol, namely

attributes and data

  1. value tags: specify the type of each attribute value

3.5.1 Delimiter Tags

 The following table specifies the values for the delimiter tags:
 Tag Value (Hex)    Meaning
 0x00               reserved for definition in a future IETF
                    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 IETF
                    standards track documents
 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 MUST be attributes belonging to the attribute group specified by
 the value of the "begin-attribute-group-tag". For example, if the
 value of "begin-attribute-group-tag" is 0x01, the following
 attributes MUST be members of the Operations Attributes group.

Herriot, et al. Standards Track [Page 13] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 The "end-of-attributes-tag" (value 0x03) MUST occur exactly once in
 an operation.  It MUST be the last "delimiter-tag". If the operation
 has a document-content group, the document data in that group MUST
 follow 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 document. For further details, see section 3.7 "(Attribute)
 Name" and 13 "Appendix A: Protocol Examples".
 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 that there is an entire attribute group
 that it doesn't understand as opposed to a single value that it
 doesn't understand.

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.
 The following table specifies the "out-of-band" values for the
 "value-tag" field.
 Tag Value (Hex)  Meaning
 0x10             unsupported
 0x11             reserved for 'default' for definition in a future
                  IETF standards track document
 0x12             unknown
 0x13             no-value
 0x14-0x1F        reserved for "out-of-band" values in future IETF
                  standards track documents.
 The following table specifies the integer values for the "value-tag"
 field:
 Tag Value (Hex)   Meaning
 0x20              reserved for definition in a future IETF
                   standards track document
 0x21              integer
 0x22              boolean
 0x23              enum
 0x24-0x2F         reserved for integer types for definition in
                   future IETF standards track documents

Herriot, et al. Standards Track [Page 14] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 NOTE: 0x20 is reserved for "generic integer" if it should ever be
 needed.
 The following table specifies the octetString values for the "value-
 tag" field:
 Tag Value (Hex)   Meaning
 0x30              octetString with an  unspecified format
 0x31              dateTime
 0x32              resolution
 0x33              rangeOfInteger
 0x34              reserved for definition in a future IETF
                   standards track document
 0x35              textWithLanguage
 0x36              nameWithLanguage
 0x37-0x3F         reserved for octetString type definitions in
                   future IETF standards track documents
 The following table specifies the character-string values for the
 "value-tag" field:
 Tag Value (Hex)   Meaning
 0x40              reserved for definition in a future IETF
                   standards track document
 0x41              textWithoutLanguage
 0x42              nameWithoutLanguage
 0x43              reserved for definition in a future IETF
                   standards track document
 0x44              keyword
 0x45              uri
 0x46              uriScheme
 0x47              charset
 0x48              naturalLanguage
 0x49              mimeMediaType
 0x4A-0x5F         reserved for character string type definitions
                   in future IETF standards track documents
 NOTE: 0x40 is reserved for "generic character-string" if it should
 ever be needed.
 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 IETF
 standards track documents.

Herriot, et al. Standards Track [Page 15] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 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 0x00 to
 0x37777777 are reserved for definition in future IETF standard track
 documents.  The values 0x40000000 to 0x7FFFFFFF are reserved for
 vendor extensions.

3.6 Name-Length

 The "name-length" field MUST consist of a SIGNED-SHORT. This field
 MUST specify the number of octets in the immediately following "name"
 field.  The value of this field excludes the two bytes of the "name-
 length" field. For example, if the "name" field contains "sides", the
 value of this field is 5.
 If a "name-length" field has a value of zero, the following "name"
 field MUST be empty, and the following value MUST be 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 mal-
 formed (see [RFC2911] section 3.1.3). The zero-length name is the
 only mechanism for multi-valued attributes.

3.7 (Attribute) Name

 The "name" field MUST contain the name of an attribute. The model
 document [RFC2911] specifies such names.

3.8 Value Length

 The "value-length" field MUST consist of a SIGNED-SHORT. This field
 MUST specify 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 (text) 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 character-strings, the sender
 MUST encode the value with all the characters of the string and
 without any padding characters.

Herriot, et al. Standards Track [Page 16] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 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
 IPP model document. The table below augments the information in the
 model document, and defines the syntax types from the model document
 in terms of the 5 basic types defined in section 3, "Encoding of the
 Operation Layer". The 5 types are US-ASCII-STRING, LOCALIZED-STRING,
 SIGNED-INTEGER, SIGNED-SHORT, SIGNED-BYTE, and OCTET-STRING.
Syntax of Attribute   Encoding
Value
textWithoutLanguage,  LOCALIZED-STRING.
nameWithoutLanguage
textWithLanguage      OCTET-STRING consisting of 4 fields:
                        a. a SIGNED-SHORT which is the number of
                           octets in the following field
                        b. a value of type natural-language,
                        c. a SIGNED-SHORT which is the number of
                           octets in the following field,
                        d. 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. a SIGNED-SHORT which is the number of
                           octets in the following field
                        b. a value of type natural-language,
                        c. a SIGNED-SHORT which is the number of
                           octets in the following field
                        d. 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

Herriot, et al. Standards Track [Page 17] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Syntax of Attribute   Encoding
Value
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 units
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
 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 [RFC2616] is the transport layer for this protocol.
 The operation layer has been designed with the assumption that the
 transport layer contains the following information:

Herriot, et al. Standards Track [Page 18] RFC 2910 IPP/1.1: Encoding and Transport September 2000

  1. the URI of the target job or printer operation
  2. 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 client implementation MUST adhere to the rules for a
 client described for HTTP1.1 [RFC2616].  A printer (server)
 implementation MUST adhere the rules for an origin server described
 for HTTP1.1 [RFC2616].
 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/1.1,
 consult the HTTP documents [RFC2616].
 An HTTP server MUST support chunking for IPP requests, and an IPP
 client MUST support chunking for IPP responses according to  HTTP/1.1
 [RFC2616].  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 and job-uri

 All Printer and Job objects are identified by a Uniform Resource
 Identifier (URI) [RFC2396] so that they can be persistently and
 unambiguously referenced.  Since every URL is a specialized form of a
 URI, even though the more generic term URI is used throughout the
 rest of this document, its usage is intended to cover the more
 specific notion of URL as well.

Herriot, et al. Standards Track [Page 19] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 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 URI 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 NEED NOT be literally
 identical. One can be a relative URI and the other can be an absolute
 URI.  HTTP/1.1 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 URLs should be
 used in the mapping of IPP onto HTTP/1.1:
    1. Although potentially redundant, a client MUST supply the target
       of the operation both as an operation attribute and as a URI at
       the HTTP layer.  The rationale for this decision is to maintain
       a consistent set of rules for mapping application/ipp to
       possibly many communication layers, even where URLs are not
       used as the addressing mechanism in the transport layer.
    2. Even though these two URLs might not be literally identical
       (one being relative and the other being absolute), they MUST
       both reference the same IPP object. However, a Printer NEED NOT
       verify that the two URLs reference the same IPP object, and
       NEED NOT take any action if it determines the two URLs to be
       different.
    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.  The HTTP server
       need not be aware of the URI within the operation request.
    4. Once the HTTP server resource begins to process the HTTP
       request, it might get the reference to the appropriate IPP
       Printer object from either the HTTP URI (using to the context
       of the HTTP server for relative URLs) 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 operation MUST be an absolute URI.

5. IPP URL Scheme

 The IPP/1.1 document defines a new scheme 'ipp' as the value of a URL
 that identifies either an IPP printer object or an IPP job object.
 The IPP attributes using the 'ipp' scheme are specified below.
 Because the HTTP layer does not support the 'ipp' scheme, a client
 MUST map 'ipp' URLs to 'http' URLs, and then follows the HTTP
 [RFC2616][RFC2617] rules for constructing a Request-Line and HTTP
 headers.  The mapping is simple because the 'ipp' scheme implies all
 of the same protocol semantics as that of the 'http' scheme

Herriot, et al. Standards Track [Page 20] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 [RFC2616], except that it represents a print service and the implicit
 (default) port number that clients use to connect to a server is port
 631.
 In the remainder of this section the term 'ipp-URL' means a URL whose
 scheme is 'ipp' and whose implicit (default) port is 631. The term
 'http-URL' means a URL whose scheme is 'http', and the term 'https-
 URL' means a URL whose scheme is 'https',
 A client and an IPP object (i.e. the server) MUST support the ipp-URL
 value in the following IPP attributes.
     job attributes:
         job-uri
         job-printer-uri
     printer attributes:
         printer-uri-supported
     operation attributes:
         job-uri
         printer-uri
 Each of the above attributes identifies a printer or job object. The
 ipp-URL is intended as the value of the attributes in this list, and
 for no other attributes. All of these attributes have a syntax type
 of 'uri', but there are attributes with a syntax type of 'uri' that
 do not use the 'ipp' scheme, e.g. 'job-more-info'.
 If a printer registers its URL with a directory service, the printer
 MUST register an ipp-URL.
 User interfaces are beyond the scope of this document. But if
 software exposes the ipp-URL values of any of the above five
 attributes to a human user, it is REQUIRED that the human see the
 ipp-URL as is.
 When a client sends a request, it MUST convert a target ipp-URL to a
 target http-URL for the HTTP layer according to the following rules:
    1. change the 'ipp' scheme to 'http'
    2. add an explicit port 631 if the URL does not contain an
       explicit port. Note: port 631 is the IANA assigned Well Known
       Port for the 'ipp' scheme.
 The client  MUST use the target http-URL in both the HTTP Request-
 Line and HTTP headers, as specified by HTTP [RFC2616] [RFC2617] .
 However, the client MUST use the target ipp-URL 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-URL

Herriot, et al. Standards Track [Page 21] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 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-URL "ipp://myhost.com/myprinter/myqueue", it opens a
 TCP connection to port 631 (the ipp implicit port) on the host
 "myhost.com" and sends the following data:
  POST /myprinter/myqueue HTTP/1.1
  Host: myhost.com:631
  Content-type: application/ipp
  Transfer-Encoding: chunked
  ...
  "printer-uri" "ipp://myhost.com/myprinter/myqueue"
            (encoded in application/ipp message body)
  ...
 As another example, when an IPP client sends the same request as
 above via a proxy "myproxy.com", it opens a TCP connection to the
 proxy port 8080 on the proxy host "myproxy.com" and sends the
 following data:
  POST http://myhost.com:631/myprinter/myqueue   HTTP/1.1
  Host: myhost.com:631
  Content-type: application/ipp
  Transfer-Encoding: chunked
  ...
  "printer-uri" "ipp://myhost.com/myprinter/myqueue"
            (encoded in application/ipp message body)
  ...
 The proxy then connects to the IPP origin server with headers that
 are the same as the "no-proxy" example above.

6. IANA Considerations

 This section describes the procedures for allocating encoding for the
 following IETF standards track extensions and vendor extensions to
 the IPP/1.1 Encoding and Transport document:
    1. attribute syntaxes - see [RFC2911] section 6.3
    2. attribute groups - see [RFC2911] section 6.5
    3. out-of-band attribute values - see [RFC2911] section 6.7

Herriot, et al. Standards Track [Page 22] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 These extensions follow the "type2" registration procedures defined
 in [RFC2911] section 6.  Extensions registered for use with IPP/1.1
 are OPTIONAL for client and IPP object conformance to the IPP/1.1
 Encoding and Transport document.
 These extension procedures are aligned with the guidelines as set
 forth by the IESG [IANA-CON].  The [RFC2911] Section 11 describes how
 to propose new registrations for consideration.  IANA will reject
 registration proposals that leave out required information or do not
 follow the appropriate format described in [RFC2911] Section 11.  The
 IPP/1.1 Encoding and Transport document may also be extended by an
 appropriate RFC that specifies any of the above extensions.

7. Internationalization Considerations

 See the section on "Internationalization Considerations" in the
 document "Internet Printing Protocol/1.1: Model and Semantics"
 [RFC2911] for information on internationalization. This document adds
 no additional issues.

8. Security Considerations

 The IPP Model and Semantics document [RFC2911] 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.

8.1.1 Digest Authentication

 IPP clients MUST support:
    Digest Authentication [RFC2617].
       MD5 and MD5-sess MUST be implemented and supported.
       The Message Integrity feature NEED NOT be used.

Herriot, et al. Standards Track [Page 23] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 IPP Printers SHOULD support:
    Digest Authentication [RFC2617].
       MD5 and MD5-sess MUST be implemented and supported.
       The Message Integrity feature NEED NOT be used.
 The reasons that IPP Printers SHOULD (rather than MUST) support
 Digest Authentication are:
 1. While Client Authentication is important, there is a certain class
    of printer 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 and could potentially
    stall the adoption of the standard.
 2. Print devices that have high-volume throughput and have available
    ROM space have a compelling argument 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 should occur.

8.1.2 Transport Layer Security (TLS)

 IPP Printers SHOULD support Transport Layer Security (TLS) [RFC2246]
 for Server Authentication and Operation Privacy. IPP Printers MAY
 also support TLS for Client Authentication.  If an IPP Printer
 supports TLS, it MUST support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
 cipher suite as mandated by RFC 2246 [RFC2246].  All other cipher
 suites are OPTIONAL.  An IPP Printer MAY support Basic Authentication
 (described in HTTP/1.1 [RFC2617])  for Client Authentication if the
 channel is secure. TLS with the above mandated cipher suite can
 provide such a secure channel.
 If a IPP client supports TLS, it MUST support the
 TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite as mandated by RFC
 2246 [RFC2246].  All other cipher suites are OPTIONAL.

Herriot, et al. Standards Track [Page 24] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 The IPP Model and Semantics document 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
 should be the primary reference for security implications with regard
 to the IPP protocol itself.  For backward compatibility with IPP
 version 1.0, IPP clients and printers may also support SSL3 [ssl].
 This is in addition to the security required in this document.

8.2 Using IPP with TLS

 IPP/1.1 uses the "Upgrading to TLS Within HTTP/1.1" mechanism
 [RFC2817].  An initial IPP request never uses TLS.  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.

9. Interoperability with IPP/1.0 Implementations

 It is beyond the scope of this specification to mandate conformance
 with previous versions.  IPP/1.1 was deliberately designed, however,
 to make supporting previous versions easy.  It is worth noting that,
 at the time of composing this specification (1999), we would expect
 IPP/1.1 Printer implementations to:
    understand any valid request in the format of IPP/1.0, or 1.1;
    respond appropriately with a response containing the same
    "version-number" parameter value used by the client in the
    request.
 And we would expect IPP/1.1 clients to:
    understand any valid response in the format of IPP/1.0, or 1.1.

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 a '1.1' value and SHOULD try supplying alternate
       version numbers if they receive a 'server-error-version-not-
       supported' error return in a response.

Herriot, et al. Standards Track [Page 25] RFC 2910 IPP/1.1: Encoding and Transport September 2000

    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').
    3. It is recommended that IPP objects accept any request with the
       major version '1' (or reject the request for reasons other than
       'server-error-version-not-supported').  See [RFC2911]
       "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/1.1 conforming Printer object accepts
       version '1.0' requests and is configured to enforce Digest
       Authentication, it MUST do the same for a version '1.0'
       request.

9.2 Security and URL Schemes

 The following are rules regarding security, the "version-number"
 parameter, and the URL 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 server returns the "job-printer-uri" or "job-uri" Job
       Description attributes, it SHOULD return the same scheme
       ('ipp', 'https', 'http', 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 server 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. It is recommended that if a server registers a non-secure ipp-
       URL with a directory service (see [RFC2911] "Generic Directory
       Schema" Appendix), then it also register an http-URL for
       interoperability with IPP/1.0 clients (see section 9).
    4. In any case, security MUST NOT be compromised when a client
       supplies an 'http' or other non-secure URL scheme in the target
       "printer-uri" and "job-uri" operation attributes in a request.

Herriot, et al. Standards Track [Page 26] RFC 2910 IPP/1.1: Encoding and Transport September 2000

10. References

 [dpa]      ISO/IEC 10175 Document Printing Application (DPA), June
            1996.
 [iana]     IANA Registry of Coded Character Sets:
            ftp://ftp.isi.edu/in-notes/iana/assignments/character-
            sets.
 [IANA-CON] Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 2434,
            October 1998.
 [ipp-iig]  Hastings, Tom, et al., "Internet Printing Protocol/1.1:
            Implementer's Guide", Work in Progress.
 [RFC822]   Crocker, D., "Standard for the Format of ARPA Internet
            Text Messages", STD 11, RFC 822, August 1982.
 [RFC1123]  Braden, S., "Requirements for Internet Hosts - Application
            and Support", STD 3, RFC 1123, October, 1989.
 [RFC1179]  McLaughlin, L. III, (editor), "Line Printer Daemon
            Protocol", RFC 1179, August 1990.
 [RFC2223]  Postel, J. and J. Reynolds, "Instructions to RFC Authors",
            RFC 2223, October 1997.
 [RFC1738]  Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
            Resource Locators (URL)", RFC 1738, December 1994.
 [RFC1759]  Smith, R., Wright, F., Hastings, T., Zilles, S. and J.
            Gyllenskog, "Printer MIB", RFC 1759, March 1995.
 [RFC1766]  Alvestrand, H., "Tags for the Identification of
            Languages", RFC 1766, March 1995.
 [RFC1808]  Fielding, R., "Relative Uniform Resource Locators", RFC
            1808, June 1995.
 [RFC1903]  Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
            "Textual Conventions for Version 2 of the Simple Network
            Management Protocol (SNMPv2)", RFC 1903, January 1996.
 [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
            Extensions (MIME) Part Two: Media Types", RFC 2046,
            November 1996.

Herriot, et al. Standards Track [Page 27] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 [RFC2048]  Freed, N., Klensin, J. and J. Postel, "Multipurpose
            Internet Mail Extension (MIME) Part Four: Registration
            Procedures", BCP 13, RFC 2048, November 1996.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2184]  Freed, N. and K. Moore, "MIME Parameter Value and Encoded
            Word Extensions: Character Sets, Languages, and
            Continuations", RFC 2184, August 1997.
 [RFC2234]  Crocker, D. and P. Overall, "Augmented BNF for Syntax
            Specifications: ABNF", RFC 2234, November 1997.
 [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol", RFC 2246.
            January 1999.
 [RFC2396]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
            Resource Identifiers (URI): Generic Syntax", RFC 2396,
            August 1998.
 [RFC2565]  Herriot, R., Butler, S., Moore, P. and R. Turner,
            "Internet Printing Protocol/1.0: Encoding and Transport",
            RFC 2565, April 1999.
 [RFC2566]  deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P.
            Powell, "Internet Printing Protocol/1.0: Model and
            Semantics", RFC 2566, April 1999.
 [RFC2567]  Wright, D., "Design Goals for an Internet Printing
            Protocol", RFC2567, April 1999.
 [RFC2568]  Zilles, S., "Rationale for the Structure and Model and
            Protocol for the Internet Printing Protocol", RFC 2568,
            April 1999.
 [RFC2569]  Herriot, R., Hastings, T., Jacobs, N. and J. Martin,
            "Mapping between LPD and IPP Protocols", RFC 2569, April
            1999.
 [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
            Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext
            Transfer Protocol - HTTP/1.1", RFC 2616, June 1999.
 [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
            Leach, P., Luotonen, A. and L. Stewart, "HTTP
            Authentication: Basic and Digest Access Authentication",
            RFC 2617, June 1999.

Herriot, et al. Standards Track [Page 28] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 [RFC2817]  Khare, R. and S. Lawrence, "Upgrading to TLS Within
            HTTP/1.1", RFC 2817, May 2000.
 [RFC2910]  Herriot, R., Butler, S., Moore, P., Turner, R. and J.
            Wenn, "Internet Printing Protocol/1.1: Encoding and
            Transport", RFC 2910, September 2000.
 [RFC2911]  Hastings, T., Herriot, R., deBry, R., Isaacson, S. and P.
            Powell, "Internet Printing Protocol/1.1: Model and
            Semantics", RFC 2911, September 2000.
 [SSL]      Netscape, The SSL Protocol, Version 3, (Text version
            3.02), November 1996.

11. Authors' Addresses

 Robert Herriot, Editor
 Xerox Corporation
 3400 Hillview Ave., Bldg #1
 Palo Alto, CA 94304
 Phone: 650-813-7696
 Fax:   650-813-6860
 EMail: robert.herriot@pahv.xerox.com
 Sylvan Butler
 Hewlett-Packard
 11311 Chinden Blvd.
 Boise, ID 83714
 Phone: 208-396-6000
 Fax: 208-396-3457
 EMail: sbutler@boi.hp.com
 Paul Moore
 Peerless Systems Networking
 10900 NE 8th St #900
 Bellevue, WA 98004
 Phone: 425-462-5852
 EMail: pmoore@peerless.com

Herriot, et al. Standards Track [Page 29] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 Randy Turner
 2Wire, Inc.
 694 Tasman Dr.
 Milpitas, CA 95035
 Phone: 408-546-1273
 John Wenn
 Xerox Corporation
 737 Hawaii St
 El Segundo, CA  90245
 Phone: 310-333-5764
 Fax: 310-333-5514
 EMail: jwenn@cp10.es.xerox.com
 IPP Web Page: http://www.pwg.org/ipp/
 IPP Mailing List: ipp@pwg.org
 To subscribe to the ipp mailing list, send the following email:
    1) send it to majordomo@pwg.org
    2) leave the subject line blank
    3) put the following two lines in the message body:
            subscribe ipp
            end

Herriot, et al. Standards Track [Page 30] RFC 2910 IPP/1.1: Encoding and Transport September 2000

12. Other Participants:

 Chuck Adams - Tektronix             Shivaun Albright - HP
 Stefan Andersson - Axis             Jeff Barnett - IBM
 Ron Bergman - Hitachi Koki Imaging  Dennis Carney - IBM
 Systems
 Keith Carter - IBM                  Angelo Caruso - Xerox
 Rajesh Chawla - TR Computing        Nancy Chen - Okidata
 Solutions
 Josh Cohen - Microsoft              Jeff Copeland - QMS
 Andy Davidson - Tektronix           Roger deBry - IBM
 Maulik Desai - Auco                 Mabry Dozier - QMS
 Lee Farrell - Canon Information     Satoshi Fujitami - Ricoh
 Systems
 Steve Gebert - IBM                  Sue Gleeson - Digital
 Charles Gordon - Osicom             Brian Grimshaw - Apple
 Jerry Hadsell - IBM                 Richard Hart - Digital
 Tom Hastings - Xerox                Henrik Holst - I-data
 Stephen Holmstead                   Zhi-Hong Huang - Zenographics
 Scott Isaacson - Novell             Babek Jahromi - Microsoft
 Swen Johnson - Xerox                David Kellerman - Northlake
                                     Software
 Robert Kline - TrueSpectra          Charles Kong - Panasonic
 Carl Kugler - IBM                   Dave Kuntz - Hewlett-Packard
 Takami Kurono - Brother             Rick Landau - Digital
 Scott Lawrence - Agranot Systems    Greg LeClair - Epson
 Dwight Lewis - Lexmark              Harry Lewis - IBM
 Tony Liao - Vivid Image             Roy Lomicka - Digital
 Pete Loya - HP                      Ray Lutz - Cognisys
 Mike MacKay - Novell, Inc.          David Manchala - Xerox
 Carl-Uno Manros - Xerox             Jay Martin - Underscore
 Stan McConnell - Xerox              Larry Masinter - Xerox
 Sandra Matts - Hewlett Packard      Peter Michalek - Shinesoft
 Ira McDonald - High North Inc.      Mike Moldovan - G3 Nova
 Tetsuya Morita - Ricoh              Yuichi Niwa - Ricoh
 Pat Nogay - IBM                     Ron Norton - Printronics
 Hugo Parra, Novell                  Bob Pentecost - Hewlett-Packard
 Patrick Powell - Astart             Jeff Rackowitz - Intermec
 Technologies
 Eric Random - Peerless              Rob Rhoads - Intel
 Xavier Riley - Xerox                Gary Roberts - Ricoh
 David Roach - Unisys                Stuart Rowley - Kyocera
 Yuji Sasaki - Japan Computer        Richard Schneider - Epson
 Industry
 Kris Schoff - HP                    Katsuaki Sekiguchi - Canon
                                     Information Systems

Herriot, et al. Standards Track [Page 31] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 Bob Setterbo - Adobe                Gail Songer - Peerless
 Hideki Tanaka - Cannon Information  Devon Taylor - Novell, Inc.
 Systems
 Mike Timperman - Lexmark            Atsushi Uchino - Epson
 Shigeru Ueda - Canon                Bob Von Andel - Allegro Software
 William Wagner - NetSilicon/DPI     Jim Walker - DAZEL
 Chris Wellens - Interworking Labs   Trevor Wells - Hewlett Packard
 Craig Whittle - Sharp Labs          Rob Whittle - Novell, Inc.
 Jasper Wong - Xionics               Don Wright - Lexmark
 Michael Wu - Heidelberg Digital     Rick Yardumian - Xerox
 Michael Yeung - Canon Information   Lloyd Young - Lexmark
 Systems
 Atsushi Yuki - Kyocera              Peter Zehler - Xerox
 William Zhang - Canon Information   Frank Zhao - Panasonic
 Systems
 Steve Zilles - Adobe                Rob Zirnstein - Canon Information
                                     Systems

Herriot, et al. Standards Track [Page 32] RFC 2910 IPP/1.1: Encoding and Transport September 2000

13. Appendix A: Protocol Examples

13.1 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-attributes    operation-attributes-tag
0x47            charset type                  value-tag
0x0012                                        name-length
attributes-     attributes-charset            name
charset
0x0008                                        value-length
us-ascii        US-ASCII                      value
0x48            natural-language type         value-tag
0x001B                                        name-length
attributes-                                   name
natural-        attributes-natural-language
language
0x0005                                        value-length
en-us           en-US                         value
0x45            uri type                      value-tag
0x000B                                        name-length
printer-uri     printer-uri                   name
0x0015                                        value-length
ipp://forest/   printer pinetree              value
  pinetree
0x42            nameWithoutLanguage type      value-tag
0x0008                                        name-length
job-name        job-name                      name
0x0006                                        value-length
foobar          foobar                        value
0x22            boolean type                  value-tag
0x0016                                        name-length
ipp-attribute-  ipp-attribute-fidelity        name
fidelity
0x0001                                        value-length
0x01            true                          value

Herriot, et al. Standards Track [Page 33] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets          Symbolic Value                Protocol field
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-      two-sided-long-edge           value
long-edge
0x03            end-of-attributes             end-of-attributes-tag
%!PS...         <PostScript>                  data

13.2 Print-Job Response (successful)

 Here is an example of a successful Print-Job response to the previous
 Print-Job request.  The printer supported the "copies" and "sides"
 attributes and their supplied values.  The status code returned is
 'successful-ok'.
Octets            Symbolic Value              Protocol field
0x0101            1.1                         version-number
0x0000            successful-ok               status-code
0x00000001        1                           request-id
0x01              start operation-attributes  operation-attributes-tag
0x47              charset type                value-tag
0x0012                                        name-length
attributes-       attributes-charset          name
charset
0x0008                                        value-length
us-ascii          US-ASCII                    value
0x48              natural-language type       value-tag
0x001B                                        name-length
attributes-       attributes-natural-         name
natural-language  language
0x0005                                        value-length
en-us             en-US                       value
0x41              textWithoutLanguage type    value-tag
0x000E                                        name-length
status-message    status-message              name
0x000D                                        value-length

Herriot, et al. Standards Track [Page 34] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets            Symbolic Value              Protocol field
successful-ok     successful-ok               value
0x02              start job-attributes        job-attributes-tag
0x21              integer                     value-tag
0x0006                                        name-length
job-id            job-id                      name
0x0004                                        value-length
147               147                         value
0x45              uri type                    value-tag
0x0007                                        name-length
job-uri           job-uri                     name
0x0019                                        value-length
ipp://forest/     job 123 on pinetree         value
  pinetree/123
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

13.3 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).
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-   attributes-charset            name
charset
0x0008                                      value-length
us-ascii      US-ASCII                      value

Herriot, et al. Standards Track [Page 35] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets        Symbolic Value                Protocol field
0x48          natural-language type         value-tag
0x001B                                      name-length
attributes-   attributes-natural-language   name
natural-
language
0x0005                                      value-length
en-us         en-US                         value
0x41          textWithoutLanguage type      value-tag
0x000E                                      name-length
status-       status-message                name
message
0x002F                                      value-length
client-error-                               value
attributes-   values-not-supported
or-values-    client-error-attributes-or-
not-supported
0x05          start unsupported-attributes  unsupported-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

13.4 Print-Job Response (success with attributes ignored)

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

Herriot, et al. Standards Track [Page 36] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets            Symbolic Value              Protocol field
                  substituted-attributes
0x00000001        1                           request-id
0x01              start operation-attributes  operation-attributes-tag
0x47              charset type                value-tag
0x0012                                        name-length
attributes-       attributes-charset          name
charset
0x0008                                        value-length
us-ascii          US-ASCII                    value
0x48              natural-language type       value-tag
0x001B                                        name-length
attributes-       attributes-natural-         name
natural-language  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-    successful-ok-ignored-or-   value
ignored-or-       substituted-attributes
substituted-
attributes
0x05              start unsupported-          unsupported-attributes
                  attributes                  tag
0x21              integer type                value-tag
0x0006                                        name-length
copies            copies                      name
0x0004                                        value-length
0x00000014        20                          value
0x10              unsupported  (type)         value-tag
0x0005                                        name-length
sides             sides                       name
0x0000                                        value-length
0x02              start job-attributes        job-attributes-tag
0x21              integer                     value-tag
0x0006                                        name-length
job-id            job-id                      name
0x0004                                        value-length
147               147                         value
0x45              uri type                    value-tag
0x0007                                        name-length
job-uri           job-uri                     name
0x0019                                        value-length
ipp://forest/     job 123 on pinetree         value
  pinetree/123

Herriot, et al. Standards Track [Page 37] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets           Symbolic Value               Protocol field
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

13.5 Print-URI Request

 The following is an example of Print-URI request with copies and
 job-name parameters:
Octets         Symbolic Value               Protocol field
0x0101         1.1                          version-number
0x0003         Print-URI                    operation-id
0x00000001     1                            request-id
0x01           start operation-attributes   operation-attributes-tag
0x47           charset type                 value-tag
0x0012                                      name-length
attributes-    attributes-charset           name
charset
0x0008                                      value-length
us-ascii       US-ASCII                     value
0x48           natural-language type        value-tag
0x001B                                      name-length
attributes-    attributes-natural-language  name
natural-
language
0x0005                                      value-length
en-us          en-US                        value
0x45           uri type                     value-tag
0x000B                                      name-length
printer-uri    printer-uri                  name
0x0015                                      value-length
ipp://forest/  printer pinetree             value
  pinetree
0x45           uri type                     value-tag
0x000C                                      name-length
document-uri   document-uri                 name
0x0011                                      value-length
ftp://foo.com  ftp://foo.com/foo            value

Herriot, et al. Standards Track [Page 38] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets         Symbolic Value               Protocol field
/foo
0x42           nameWithoutLanguage type     value-tag
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

13.6 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-attributes   operation-attributes-tag
0x47           charset type                 value-tag
0x0012                                      name-length
attributes-    attributes-charset           name
charset
0x0008                                      value-length
us-ascii       US-ASCII                     value
0x48           natural-language type        value-tag
0x001B                                      name-length
attributes-    attributes-natural-language  name
natural-
language
0x0005                                      value-length
en-us          en-US                        value
0x45           uri type                     value-tag
0x000B                                      name-length
printer-uri    printer-uri                  name
0x0015                                      value-length
ipp://forest/  printer pinetree             value
  pinetree

Herriot, et al. Standards Track [Page 39] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets         Symbolic Value               Protocol field
inetree
0x03           end-of-attributes            end-of-attributes-tag

13.7 Get-Jobs Request

 The following is an example of Get-Jobs request with parameters but
 no attributes:
Octets           Symbolic Value               Protocol field
0x0101           1.1                          version-number
0x000A           Get-Jobs                     operation-id
0x00000123       0x123                        request-id
0x01             start operation-attributes   operation-attributes-tag
0x47             charset type                 value-tag
0x0012                                        name-length
attributes-      attributes-charset           name
charset
0x0008                                        value-length
us-ascii         US-ASCII                     value
0x48             natural-language type        value-tag
0x001B                                        name-length
attributes-      attributes-natural-language  name
natural-
language
0x0005                                        value-length
en-us            en-US                        value
0x45             uri type                     value-tag
0x000B                                        name-length
printer-uri      printer-uri                  name
0x0015                                        value-length
ipp://forest/    printer pinetree             value
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-       requested-attributes         name
attributes
0x0006                                        value-length

Herriot, et al. Standards Track [Page 40] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets           Symbolic Value               Protocol field
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

13.8 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
0x00000123       0x123                         request-id (echoed
                                               back)
0x01             start operation-attributes    operation-attributes-tag
0x47             charset type                  value-tag
0x0012                                         name-length
attributes-      attributes-charset            name
charset
0x000A                                         value-length
ISO-8859-1       ISO-8859-1                    value
0x48             natural-language type         value-tag
0x001B                                         name-length
attributes-      attributes-natural-language   name
natural-
language
0x0005                                         value-length
en-us            en-US                         value
0x41             textWithoutLanguage type      value-tag
0x000E                                         name-length
status-message   status-message                name
0x000D                                         value-length
successful-ok    successful-ok                 value
0x02             start job-attributes (1st     job-attributes-tag

Herriot, et al. Standards Track [Page 41] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Octets           Symbolic Value                Protocol field
                 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 (2nd     job-attributes-tag
                 object)
0x02             start job-attributes (3rd     job-attributes-tag
                 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

14. Appendix B: Registration of MIME Media Type Information for

 "application/ipp"
 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

Herriot, et al. Standards Track [Page 42] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 A Content-Type of "application/ipp" indicates an Internet Printing
 Protocol message body (request or response). Currently there is one
 version: IPP/1.1, whose syntax is described in Section 3 "Encoding of
 the Operation Layer" of [RFC2910], and whose semantics are described
 in [RFC2911].
 Required parameters:  none
 Optional parameters:  none
 Encoding considerations:
 IPP/1.1 protocol requests/responses MAY contain long lines and ALWAYS
 contain binary data (for example attribute value lengths).
 Security considerations:
 IPP/1.1 protocol requests/responses do not introduce any security
 risks not already inherent in the underlying transport protocols.
 Protocol mixed-version interworking rules in [RFC2911] as well as
 protocol encoding rules in [RFC2910] are complete and unambiguous.
 Interoperability considerations:
 IPP/1.1 requests (generated by clients) and responses (generated by
 servers) MUST comply with all conformance requirements imposed by the
 normative specifications [RFC2911] and [RFC2910]. Protocol encoding
 rules specified in [RFC2910] 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/1.1 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:
 [RFC2911] Hastings, T., Herriot, R., deBry, R., Isaacson, S.  and P.
           Powell, "Internet Printing Protocol/1.1: Model and
           Semantics", RFC 2911, September 2000.
 [RFC2910] Herriot, R., Butler, S., Moore, P., Turner, R.  and J.
           Wenn, "Internet Printing Protocol/1.1: Encoding and
           Transport", RFC 2910, September 2000.

Herriot, et al. Standards Track [Page 43] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 Applications which use this media type:
 Internet Printing Protocol (IPP) print clients and print servers,
 communicating using HTTP/1.1 (see [RFC2910]), 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.
 Person & email address to contact for further information:
 Tom Hastings
 Xerox Corporation
 737 Hawaii St. ESAE-231
 El Segundo, CA
 Phone: 310-333-6413
 Fax: 310-333-5514
 EMail: hastings@cp10.es.xerox.com
 or
 Robert Herriot
 Xerox Corporation
 3400 Hillview Ave., Bldg #1
 Palo Alto, CA 94304
 Phone: 650-813-7696
 Fax: 650-813-6860
 EMail: robert.herriot@pahv.xerox.com
 Intended usage:
 COMMON

15. Appendix C: Changes from IPP/1.0

 IPP/1.1 is identical to IPP/1.0 [RFC2565] with the follow changes:
 1. Attributes values that identify a printer or job object use a new
    'ipp' scheme.  The 'http' and 'https' schemes are supported only
    for backward compatibility.  See section 5.
 2. Clients MUST support of Digest Authentication, IPP Printers SHOULD
    support Digest Authentication.  See Section 8.1.1
 3. TLS is recommended for channel security.  In addition, SSL3 may be
    supported for backward compatibility.  See Section 8.1.2

Herriot, et al. Standards Track [Page 44] RFC 2910 IPP/1.1: Encoding and Transport September 2000

 4. It is recommended that IPP/1.1 objects accept any request with
    major version number '1'.  See section 9.1.
 5. IPP objects SHOULD return the URL scheme requested for "job-
    printer-uri" and "job-uri" Job Attributes, rather than the URL
    scheme used to create the job.   See section 9.2.
 6. The IANA and Internationalization sections have been added.  The
    terms "private use" and "experimental" have been changed to
    "vendor extension".  The reserved allocations for attribute group
    tags, attribute syntax tags, and out-of-band attribute values have
    been clarified as to which are reserved to future IETF standards
    track documents and which are reserved to vendor extension.   Both
    kinds of extensions use the type2 registration procedures as
    defined in [RFC2911].
 7. Clarified that future "out-of-band" value definitions may use the
    value field if additional information is needed.

Herriot, et al. Standards Track [Page 45] RFC 2910 IPP/1.1: Encoding and Transport September 2000

Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

Herriot, et al. Standards Track [Page 46]

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