An xxx-attributes-sequence consists of zero or more compound-
   attributes.

  -----------------------------------------------
  |              compound-attribute             |   s bytes - 0 or more
  -----------------------------------------------

   A compound-attribute consists of an attribute with a single value
   followed by zero or more additional values.

   Note: a 'compound-attribute' represents a single attribute in the
   model document.  The 'additional value' syntax is for attributes with
   2 or more values.

   Each attribute consists of:

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










 
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.




 
RFC 2565            IPP/1.0: Encoding and Transport           April 1999


  ipp-message = ipp-request / ipp-response
  ipp-request = version-number operation-id request-id