rfc2565.txt

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Herriot, et al.               Experimental                      [Page 6]

RFC 2565            IPP/1.0: Encoding and Transport           April 1999


   An additional value consists of:

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

   Note: an additional value is like an attribute whose name-length is 0.

   From the standpoint of a parsing loop, 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          |   2 bytes  - required
  -----------------------------------------------
  |                     data                    |   y bytes  - optional
  -----------------------------------------------

   The value of the tag determines whether the bytes following the
   tag are:

      - attributes
      - data
      - the remainder of a single attribute where the tag specifies the
        type of the value.

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.



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RFC 2565            IPP/1.0: Encoding and Transport           April 1999


  ipp-message = ipp-request / ipp-response
  ipp-request = version-number operation-id request-id
           *(xxx-attributes-tag  xxx-attribute-sequence)
           end-of-attributes-tag data
  ipp-response = version-number status-code request-id
           *(xxx-attributes-tag xxx-attribute-sequence)
           end-of-attributes-tag data
  xxx-attribute-sequence = *compound-attribute

  xxx-attributes-tag = operation-attributes-tag / job-attributes-tag /
        printer-attributes-tag / unsupported-attributes-tag

  version-number = major-version-number minor-version-number
  major-version-number = SIGNED-BYTE  ; initially %d1
  minor-version-number = SIGNED-BYTE  ; initially %d0

  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

  compound-attribute = attribute *additional-values
  attribute = value-tag name-length name value-length value
  additional-values = 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
  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
  end-of-attributes-tag = %x03                 ; tag of 3
  value-tag = %x10-FF

  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





Herriot, et al.               Experimental                      [Page 8]

RFC 2565            IPP/1.0: Encoding and Transport           April 1999


   The syntax allows an xxx-attributes-tag to be present when the xxx-
   attribute-sequence that follows is empty. The syntax is defined this
   way to allow for the response of Get-Jobs where no attributes are
   returned for some job-objects.  Although it is RECOMMENDED that the
   sender not send an xxx-attributes-tag if there are no attributes
   (except in the Get-Jobs response just mentioned), the receiver MUST
   be able to decode such syntax.

3.3 Version-number

   The version-number MUST consist of a major and minor version-number,
   each of which MUST be represented by a SIGNED-BYTE. The protocol
   described in this document MUST have a major version-number of 1
   (0x01) and a minor version-number of  0 (0x00).  The ABNF for these
   two bytes MUST be %x01.00.

3.4 Operation-id

   Operation-ids are defined as enums in the model document. An
   operation-ids enum value MUST be encoded as a SIGNED-SHORT.

   Note: the values 0x4000 to 0xFFFF are reserved for private
   extensions.

3.5 Status-code

   Status-codes are defined as enums in the model document. A status-
   code enum value MUST be encoded as a SIGNED-SHORT.

   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.

3.6 Request-id

   The request-id allows a client to match a response with a request.
   This mechanism is unnecessary in HTTP, but may be useful when
   application/ipp entity bodies are used in another context.

   The request-id in a response MUST be the value of the request-id
   received in the corresponding request.  A client can set the
   request-id in each request to a unique value or a constant value,
   such as 1, depending on what the client does with the request-id



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RFC 2565            IPP/1.0: Encoding and Transport           April 1999


   returned in the response. The value of the request-id MUST be greater
   than zero.

3.7 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

3.7.1 Delimiter Tags

   The following table specifies the values for the delimiter tags:

      Tag Value (Hex)   Delimiter

      0x00              reserved
      0x01              operation-attributes-tag
      0x02              job-attributes-tag
      0x03              end-of-attributes-tag
      0x04              printer-attributes-tag
      0x05              unsupported-attributes-tag
      0x06-0x0e         reserved for future delimiters
      0x0F              reserved for future chunking-end-of-attributes-
                         tag

   When an xxx-attributes-tag occurs in the protocol, it MUST mean that
   zero or more following attributes up to the next delimiter tag are
   attributes belonging to group xxx as defined in the model document,
   where xxx is operation, job, printer, unsupported.

   Doing substitution for xxx in the above paragraph, this means the
   following. When an operation-attributes-tag occurs in the protocol,
   it MUST mean that the zero or more following attributes up to the
   next delimiter tag are operation attributes as defined in the model
   document.  When an job-attributes-tag occurs in the protocol, it MUST
   mean that the zero or more following attributes up to the next
   delimiter tag are job attributes or job template attributes as
   defined in the model document.  When a printer-attributes-tag occurs
   in the protocol, it MUST mean that the zero or more following
   attributes up to the next delimiter tag are printer attributes as
   defined in the model document. When an unsupported-attributes-tag
   occurs in the protocol, it MUST mean that the zero or more following
   attributes up to the next delimiter tag are unsupported attributes as
   defined in the model document.





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RFC 2565            IPP/1.0: Encoding and Transport           April 1999


   The operation-attributes-tag and end-of-attributes-tag MUST each
   occur exactly once in an operation. The operation-attributes-tag MUST
   be the first tag delimiter, and the end-of-attributes-tag MUST be the
   last tag delimiter. If the operation has a document-content group,
   the document data in that group MUST follow the end-of-attributes-
   tag.

   Each of the  other three  xxx-attributes-tags defined above is
   OPTIONAL in an operation and each MUST occur at most once in an
   operation, except for job-attributes-tag in a Get-Jobs response which
   may occur zero or more times.

   The order and presence of delimiter tags for each operation request
   and each operation response MUST be that defined in the model
   document. For further details, see section 3.9 "(Attribute) Name" and
   section 9 "Appendix A: Protocol Examples".

   A Printer MUST treat the reserved delimiter tags differently from
   reserved value tags 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.

3.7.2 Value Tags

   The remaining tables show values for the value-tag, which is the
   first octet of  an attribute. The value-tag specifies the type of the
   value of the attribute. The following table specifies the "out-of-
   band" values for the value-tag.

      Tag Value (Hex) Meaning

      0x10            unsupported
      0x11            reserved for future 'default'
      0x12            unknown
      0x13            no-value

      Tag Value (Hex) Meaning

      0x14-0x1F       reserved for future "out-of-band" values.

   The "unsupported" value MUST be used in the attribute-sequence of an
   error response for those attributes which the printer does not
   support.  The "default" value is reserved for future use of setting
   value back to their default value. The "unknown" value is used for
   the value of a supported attribute when its value is temporarily
   unknown.  The "no-value" value is used for a supported attribute to
   which




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RFC 2565            IPP/1.0: Encoding and Transport           April 1999


   no value has been assigned, e.g. "job-k-octets-supported" has no
   value if an implementation supports this attribute, but an
   administrator has not configured the printer to have a limit.

   The following table specifies the integer values for the value-tag:

      Tag Value (Hex)  Meaning

      0x20             reserved
      0x21             integer
      0x22             boolean
      0x23             enum
      0x24-0x2F        reserved for future integer types

   NOTE: 0x20 is reserved for "generic integer" if it should ever be
   needed.

   The following table specifies the octetString values for the value-
   tag:

      Tag Value (Hex)  Meaning

      0x30             octetString with an  unspecified format
      0x31             dateTime
      0x32             resolution
      0x33             rangeOfInteger
      0x34             reserved for collection (in the future)
      0x35             textWithLanguage
      0x36             nameWithLanguage
      0x37-0x3F        reserved for future octetString types

   The following table specifies the character-string values for the
   value-tag:

      Tag Value (Hex)  Meaning