▁In ▁Sun ▁Java ▁System ▁Directory ▁Server ▁and ▁Microsoft ▁Active ▁Directory ▁( AD ), ▁an ▁organiz ational ▁unit ▁( OU ) ▁can ▁contain ▁any ▁other ▁unit , ▁including ▁other ▁O Us , ▁users , ▁groups , ▁and ▁computers . ▁Organ iz ational ▁units ▁in ▁separate ▁domains ▁may ▁have ▁identical ▁names ▁but ▁are ▁independent ▁of ▁each ▁other . ▁▁ ▁O Us ▁let ▁an ▁administrator ▁group ▁computers ▁and ▁users ▁so ▁as ▁to ▁apply ▁a ▁common ▁policy ▁to ▁them . ▁Organ iz ational ▁Units ▁give ▁a ▁hier arch ical ▁structure , ▁and ▁when ▁properly ▁designed ▁can ▁ease ▁administration . ▁ ▁Orig ins ▁with ▁X . 5 0 0 , ▁Nov ell , ▁and ▁Lot us ▁software ▁ ▁Nov ell ▁and ▁Lot us ▁supplied ▁the ▁two ▁largest ▁software ▁directory ▁systems . ▁ ▁Each ▁of ▁these ▁companies ▁started ▁with ▁flat ▁account ▁and ▁directory ▁structures , ▁and ▁encountered ▁the ▁support ▁and ▁name - conf lict ▁limitations ▁inher ent ▁in ▁their ▁flat ▁structures . ▁ ▁They ▁adopted ▁the ▁X . 5 0 0 ▁O U ▁concept ▁into ▁their ▁next - gener ation ▁software ▁around ▁ 1 9 9 3 ▁– ▁Nov ell ▁with ▁the ▁release ▁of ▁Nov ell ▁Directory ▁Services ▁( sub sequently ▁known ▁as ▁e Directory ), ▁and ▁Lot us ▁with ▁the ▁release ▁of ▁the ▁third ▁version ▁of ▁Lot us ▁Notes . ▁ ▁Microsoft ▁alleg edly ▁used ▁Nov ell ' s ▁directory ▁as ▁a ▁blue print ▁for ▁the ▁first ▁released ▁versions ▁of ▁AD , ▁but ▁this ▁claim ▁appears ▁suspect , ▁given ▁that ▁X . 5 0 0 ▁served ▁as ▁the