▁real m ▁can ▁either ▁be ▁hosted ▁by ▁a ▁Ker ber os ▁key ▁distribution ▁center ▁( K DC ) ▁running ▁on ▁the ▁server ▁system , ▁or ▁the ▁server ▁can ▁particip ate ▁in ▁an ▁existing ▁Ker ber os ▁real m . ▁ ▁For ▁services ▁that ▁are ▁not ▁Ker ber ized , ▁the ▁Password ▁Server ▁provides ▁the ▁following ▁Simple ▁Authentication ▁and ▁Security ▁L ayer - based ▁authentication ▁methods : ▁▁▁ ▁AP OP ▁▁ ▁C RAM - MD 5 ▁▁ ▁D iff ie – H ell man ▁key ▁exchange ▁▁ ▁Dig est - MD 5 ▁▁ ▁MS - CH AP v 2 ▁▁ ▁N TL M ▁v 1 ▁and ▁v 2 ▁▁ ▁Lan ▁Manager ▁▁ ▁Web D AV - Dig est ▁ ▁Any ▁Mac ▁OS ▁X ▁Server ▁system ▁prior ▁to ▁ 1 0 . 7 ▁( L ion ) ▁configured ▁as ▁an ▁Active ▁Directory ▁Master ▁can ▁act ▁as ▁a ▁Windows ▁Primary ▁Domain ▁Controller ▁( P DC ), ▁providing ▁domain ▁authentication ▁services ▁to ▁Microsoft ▁Windows ▁clients . ▁ ▁Directory ▁services ▁framework ▁In ▁a ▁more ▁general ▁sense , ▁Open ▁Directory ▁can ▁describe ▁the ▁plugins ▁model ▁used ▁by ▁Directory ▁Util ity ▁and ▁the ▁directory ▁services ▁framework ▁in ▁mac OS ▁and ▁mac OS ▁Server . ▁ ▁This ▁could ▁be ▁thought ▁of ▁as ▁analog ous ▁to ▁the ▁Name ▁Service ▁Switch ▁systems ▁of ▁some ▁other ▁Unix - like ▁operating ▁systems . ▁When ▁connected ▁to ▁a ▁directory ▁system , ▁a ▁mac OS ▁client ▁or ▁Server ▁can ▁authentic ate ▁users , ▁lookup ▁contacts , ▁perform ▁service ▁discovery ▁and ▁name ▁resolution ▁with ▁the ▁following ▁types ▁of