External Data Representation

External Data Representation

eXternal Data Representation (XDR) is an IETF standard from 1995 of the presentation layer in the OSI model. XDR allows data to be wrapped in an architecture independent manner so data can be transferred between heterogeneous computer systems. Converting from the local representation to XDR is called encoding. Converting from XDR to the local representation is called decoding. XDR is implemented as a software library of functions that is portable between different operating systems and is also independent of the transport layer.

The XDR data format is in use by many systems, including:

XDR data types

  • boolean
  • char (8 bit integer/character)
  • int (32 bit integer)
  • hyper (64 bit integer)
  • float
  • double
  • quadruple (new in RFC1832)
  • enumeration
  • structure
  • string
  • fixed length array
  • variable length array
  • union
  • opaque data
  • Optional data. It is notated similarly to C pointers, but is represented as the data type "pointed to" with a boolean "present or not" flag.

See also

External links

The XDR standard exists in three different versions in the following RFC's...

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