, ▁constraints ▁such ▁as ▁the ▁R SV P ▁band width ▁of ▁the ▁travers ed ▁links ▁can ▁also ▁be ▁considered , ▁such ▁that ▁the ▁short est ▁path ▁with ▁available ▁band width ▁will ▁be ▁chosen . ▁M PL S ▁Tra ffic ▁Engineering ▁re lies ▁upon ▁the ▁use ▁of ▁TE ▁extensions ▁to ▁Open ▁Short est ▁Path ▁First ▁( OS PF ) ▁or ▁Inter mediate ▁System ▁To ▁Inter mediate ▁System ▁( IS - IS ) ▁and ▁R SV P . ▁In ▁addition ▁to ▁the ▁constraint ▁of ▁R SV P ▁band width , ▁users ▁can ▁also ▁define ▁their ▁own ▁constraints ▁by ▁specifying ▁link ▁attributes ▁and ▁special ▁requirements ▁for ▁t unn els ▁to ▁route ▁( or ▁not ▁to ▁route ) ▁over ▁links ▁with ▁certain ▁attributes . ▁ ▁For ▁end - users ▁the ▁use ▁of ▁M PL S ▁is ▁not ▁visible ▁directly , ▁but ▁can ▁be ▁assumed ▁when ▁doing ▁a ▁trac er oute : ▁only ▁nodes ▁that ▁do ▁full ▁IP ▁routing ▁are ▁shown ▁as ▁h ops ▁in ▁the ▁path , ▁thus ▁not ▁the ▁M PL S ▁nodes ▁used ▁in ▁between , ▁therefore ▁when ▁you ▁see ▁that ▁a ▁packet ▁h ops ▁between ▁two ▁very ▁distant ▁nodes ▁and ▁hardly ▁any ▁other ▁' h op ' ▁is ▁seen ▁in ▁that ▁provider ' s ▁network ▁( or ▁AS ) ▁it ▁is ▁very ▁likely ▁that ▁network ▁uses ▁M PL S . ▁ ▁M PL S ▁local ▁protection ▁( fast ▁r er oute ) ▁▁ ▁In ▁the ▁event ▁of ▁a ▁network ▁element ▁failure ▁when ▁recovery ▁mechan isms ▁are ▁employed ▁at ▁the ▁IP ▁layer , ▁rest oration