▁can ▁then ▁choose ▁from ▁the ▁returned ▁results ▁the ▁most ▁appropriate ▁rep lica ▁to ▁use . ▁This ▁service ▁is ▁usually ▁provided ▁as ▁part ▁of ▁a ▁management ▁system ▁known ▁as ▁a ▁Storage ▁Resource ▁Bro ker ▁( SR B ). ▁Information ▁about ▁the ▁locations ▁of ▁files ▁and ▁ma ppings ▁between ▁the ▁L F N s ▁and ▁P F N s ▁may ▁be ▁stored ▁in ▁a ▁metadata ▁or ▁rep lica ▁catalog ue . ▁The ▁rep lica ▁catalog ue ▁would ▁contain ▁information ▁about ▁L F N s ▁that ▁map ▁to ▁multiple ▁rep lica ▁P F N s . ▁ ▁Data ▁transport ▁service ▁Another ▁middle ware ▁service ▁is ▁that ▁of ▁providing ▁for ▁data ▁transport ▁or ▁data ▁transfer . ▁Data ▁transport ▁will ▁en comp ass ▁multiple ▁functions ▁that ▁are ▁not ▁just ▁limited ▁to ▁the ▁transfer ▁of ▁bits , ▁to ▁include ▁such ▁items ▁as ▁fault ▁toler ance ▁and ▁data ▁access . ▁F ault ▁toler ance ▁can ▁be ▁achieved ▁in ▁a ▁data ▁grid ▁by ▁providing ▁mechan isms ▁that ▁ens ures ▁data ▁transfer ▁will ▁res ume ▁after ▁each ▁inter ruption ▁until ▁all ▁requested ▁data ▁is ▁received . ▁There ▁are ▁multiple ▁possible ▁methods ▁that ▁might ▁be ▁used ▁to ▁include ▁starting ▁the ▁entire ▁transmission ▁over ▁from ▁the ▁beginning ▁of ▁the ▁data ▁to ▁res uming ▁from ▁where ▁the ▁transfer ▁was ▁interrupted . ▁As ▁an ▁example , ▁Grid F TP ▁provides ▁for ▁fault ▁toler ance ▁by ▁sending ▁data ▁from ▁the ▁last ▁acknowled ged ▁byte ▁without ▁starting ▁the ▁entire ▁transfer ▁from ▁the ▁beginning . ▁ ▁The ▁data ▁transport ▁service ▁also ▁provides ▁for ▁the ▁low - level ▁access ▁and