External Data Representation (XDR) is a
standard data serialization format, for uses such as
computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections ar ...
protocols. It allows data to be transferred between different kinds of 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 which is portable between different
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s and is also independent of the
transport layer
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end ...
.
XDR uses a base unit of 4 bytes, serialized in
big-endian
In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most si ...
order; smaller data types still occupy four bytes each after encoding. Variable-length types such as string and opaque are padded to a total divisible by four bytes.
Floating-point numbers are represented in
IEEE 754
The IEEE Standard for Floating-Point Arithmetic (IEEE 754) is a technical standard for floating-point arithmetic established in 1985 by the Institute of Electrical and Electronics Engineers (IEEE). The standard addressed many problems found i ...
format.
History
XDR was developed in the mid 1980s at
Sun Microsystems
Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, ...
, and first widely published in 1987.
XDR became an
IETF
The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and ...
standard in 1995.
The XDR data format is in use by many systems, including:
*
Network File System (protocol)
Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, l ...
*
ZFS File System
*
NDMP Network Data Management Protocol
*
Open Network Computing Remote Procedure Call
*
Legato NetWorker backup software (later sold by EMC)
*
NetCDF
NetCDF (Network Common Data Form) is a set of software libraries and self-describing, machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. The project homepage is hosted by the Unidata ...
(a scientific data format)
* The
R language and environment for statistical computing
* Th
HTTP-NGBinary Wire Protocol
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two digits (0 and 1)
* Binary function, a function that takes two arguments
* Binary operation, a mathematical operation that ta ...
* The
SpiderMonkey JavaScript engine, to serialize/deserialize compiled JavaScript code
* The
Ganglia
A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympath ...
distributed monitoring system
* The
sFlow
sFlow, short for "sampled flow", is an industry standard for packet export at Layer 2 of the OSI model. sFlow was originally developed by InMon Corp. It provides a means for exporting truncated packets, together with interface counters for the purp ...
network monitoring standard
* The
libvirt virtualization library,
API and
UI
*The
Firebird (database server) for Remote Binary Wire Protocol
*
Stellar Payment Network
XDR data types
*
boolean
Any kind of logic, function, expression, or theory based on the work of George Boole is considered Boolean.
Related to this, "Boolean" may refer to:
* Boolean data type, a form of data with only two possible values (usually "true" and "false" ...
* int – 32-bit
integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...
* unsigned int – unsigned 32-bit
integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...
* hyper – 64-bit
integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...
* unsigned hyper – unsigned 64-bit
integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...
*
IEEE
The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...
float
Float may refer to:
Arts and entertainment Music Albums
* ''Float'' (Aesop Rock album), 2000
* ''Float'' (Flogging Molly album), 2008
* ''Float'' (Styles P album), 2013
Songs
* "Float" (Tim and the Glory Boys song), 2022
* "Float", by Bush ...
* IEEE
double
A double is a look-alike or doppelgänger; one person or being that resembles another.
Double, The Double or Dubble may also refer to:
Film and television
* Double (filmmaking), someone who substitutes for the credited actor of a character
* Th ...
*
quadruple (new in RFC1832)
*
enumeration
An enumeration is a complete, ordered listing of all the items in a collection. The term is commonly used in mathematics and computer science to refer to a listing of all of the elements of a set. The precise requirements for an enumeration ( ...
*
structure
*
string
String or strings may refer to:
*String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects
Arts, entertainment, and media Films
* ''Strings'' (1991 film), a Canadian anim ...
* fixed length
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
* variable length
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
*
union – discriminated union
* fixed length
opaque data
* variable length
opaque data
*
void – zero byte quantity
* optional – optional data is notated similarly to C pointers, but is represented as the data type "pointed to" with a boolean "present or not" flag. Semantically this is
option type
In programming languages (especially functional programming languages) and type theory, an option type or maybe type is a polymorphic type that represents encapsulation of an optional value; e.g., it is used as the return type of functions whic ...
.
See also
* Structured Data eXchange Format (
SDXF SDXF (Structured Data eXchange Format) is a data serialization format defined by RFC 3072. It allows arbitrary structured data of different types to be assembled in one file for data exchange, exchanging between arbitrary computers.
The ability to ...
)
*
Remote Procedure Call
*
Abstract Syntax Notation One
Abstract Syntax Notation One (ASN.1) is a standard interface description language for defining data structures that can be Serialization, serialized and deserialized in a cross-platform way. It is broadly used in telecommunications and computer n ...
*
Data Format Description Language
*
Comparison of data serialization formats
References
External links
The XDR standard exists in three different versions in the following RFCs:
* 2006 This document makes no technical changes to RFC 1832 and is published for the purposes of noting IANA considerations, augmenting security considerations, and distinguishing normative from informative references.
* 1995 version. Added Quadruple precision floating point to .
Cisco's XDR: Technical Notesjsxdrapi.c the main source file of SpiderMonkey that uses XDR
protocol.cppmain xdr source file used in Firebird remote protocol
The GNU Libc implementation of rpcgen, the XDR parser.Mu Dynamics Research Labs racc grammar for XDRIvmaiAsn ASN1/ECN/XDR Tools(a collection of tools containing an XDR/RPC-to-ASN.1 converter)
{{Data Exchange
Networking standards
Internet Standards
Internet protocols
Data modeling languages
Data serialization formats
Data transmission
Sun Microsystems software