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RFC 2910 - Internet Printing Protocol/1.1: Encoding and Transport


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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.

   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.

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

      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

   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:

      -  informally through pictures and description
      -  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.

3.1 Picture of the Encoding

3.1.1 Request and Response

   An operation request or response is encoded as follows:

   -----------------------------------------------
   |                  version-number             |   2 bytes  - required
   -----------------------------------------------
   |               operation-id (request)        |
   |                      or                     |   2 bytes  - required
   |               status-code (response)        |
   -----------------------------------------------
   |                   request-id                |   4 bytes  - required
   -----------------------------------------------
   |                 attribute-group             |   n bytes - 0 or more
   -----------------------------------------------
   |              end-of-attributes-tag          |   1 byte   - required
   -----------------------------------------------
   |                     data                    |   q bytes  - optional
   -----------------------------------------------

   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:

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

   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:

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

   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:

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

   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:

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

   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'.

      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:

   -----------------------------------------------
   |                  version-number             |   2 bytes  - required
   -----------------------------------------------
   |               operation-id (request)        |
   |                      or                     |   2 bytes  - required
   |               status-code (response)        |
   -----------------------------------------------
   |                   request-id                |   4 bytes  - required
   -----------------------------------------------------------
   |        tag (delimiter-tag or value-tag)     |   1 byte  |
   -----------------------------------------------           |-0 or more
   |           empty or rest of attribute        |   x bytes |
   -----------------------------------------------------------
   |              end-of-attributes-tag          |   1 byte   - required
   -----------------------------------------------
   |                     data                    |   y bytes  - optional
   -----------------------------------------------

   The following show what fields the parser would expect after each
   type of  "tag":

      -  "begin-attribute-group-tag": expect zero or more "attribute"
         fields
      -  "value-tag": expect the remainder of an "attribute-with-one-
         value" or  an "additional-value".
      -  "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

      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

      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:

      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.

   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:

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

   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

   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.

   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.

   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

  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:

      -  the URI of the target job or printer operation
      -  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.

   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

   [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

   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

   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.

   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.

   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.

      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.

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.

   [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.

   [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

   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

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

   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

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

  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

  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

  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

  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

  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

  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

  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

  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

  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

   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.

   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

   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.

Full Copyright Statement

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   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
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   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
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   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.

 

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