V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

XDR
       eXternal Data Representation (ONC, RPCL, Sun, RFC 1832)


The Free On-line Dictionary of Computing (30 December 2018):

eXternal Data Representation
XDR

   (XDR) A standard for machine independent data structures
   developed by Sun Microsystems for use in remote procedure
   call systems.  It is defined in RFC 1014 and is similar to
   ASN.1.

   (1994-12-13)