External Data Representation | StudentB Wikipedia Search

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages)

This article includes a list of general references, but it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations. (February 2017) (Learn how and when to remove this message)

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "External Data Representation" – news · newspapers · books · scholar · JSTOR (February 2017) (Learn how and when to remove this message)

(Learn how and when to remove this message)

OSI model by layer
7. Application layer NNTP SIP SSI DNS FTP Gopher HTTP (HTTP/3) NFS NTP SMPP SSH SMTP SNMP Telnet DHCP NETCONF more....
6. Presentation layer MIME XDR ASN.1 ASCII TLS PGP
5. Session layer Named pipe NetBIOS SAP PPTP RTP SOCKS X.225^[1]
4. Transport layer TCP UDP SCTP DCCP QUIC SPX
3. Network layer IP IPv4 IPv6 ICMP (ICMPv6) IPsec IGMP IPX IS-IS AppleTalk X.25 PLP
2. Data link layer ATM ARP SDLC HDLC CSLIP SLIP GFP PLIP IEEE 802.2 LLC MAC L2TP IEEE 802.3 Frame Relay ITU-T G.hn DLL PPP X.25 LAPB Q.922 LAPF IEEE 802.11
1. Physical layer RS-232 RS-449 ITU-T V-Series I.430 I.431 PDH SONET/SDH PON OTN DSL IEEE 802.3 IEEE 802.11 IEEE 802.15 IEEE 802.16 IEEE 1394 ITU-T G.hn PHY USB Bluetooth
v t e

External Data Representation (XDR) is a standard data serialization format, for uses such as computer network 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 systems and is also independent of the transport layer.

XDR uses a base unit of 4 bytes, serialized in big-endian 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 format.

^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.