I ) ▁are ▁both ▁carried ▁together ▁in ▁the ▁cell ▁header , ▁limit ing ▁AT M ▁to ▁a ▁single ▁level ▁of ▁t unn eling . ▁ ▁The ▁biggest ▁advantage ▁that ▁M PL S ▁has ▁over ▁AT M ▁is ▁that ▁it ▁was ▁designed ▁from ▁the ▁start ▁to ▁be ▁complement ary ▁to ▁IP . ▁Modern ▁rou ters ▁are ▁able ▁to ▁support ▁both ▁M PL S ▁and ▁IP ▁n atively ▁across ▁a ▁common ▁interface ▁allowing ▁network ▁operators ▁great ▁flex ibility ▁in ▁network ▁design ▁and ▁operation . ▁AT M ' s ▁in compat ib ilities ▁with ▁IP ▁require ▁complex ▁adaptation , ▁making ▁it ▁compar atively ▁less ▁suitable ▁for ▁today ' s ▁pre domin antly ▁IP ▁networks . ▁ ▁Dep loyment ▁M PL S ▁is ▁currently ▁( as ▁of ▁March ▁ 2 0 1 2 ) ▁in ▁use ▁in ▁IP - only ▁networks ▁and ▁is ▁standard ized ▁by ▁the ▁I ET F ▁in ▁. ▁It ▁is ▁deployed ▁to ▁connect ▁as ▁few ▁as ▁two ▁facilities ▁to ▁very ▁large ▁deploy ments . ▁ ▁In ▁practice , ▁M PL S ▁is ▁mainly ▁used ▁to ▁forward ▁IP ▁protocol ▁data ▁units ▁( P DU s ) ▁and ▁Virtual ▁Private ▁L AN ▁Service ▁( V PL S ) ▁E ther net ▁traffic . ▁Major ▁applications ▁of ▁M PL S ▁are ▁tele communic ations ▁traffic ▁engineering , ▁and ▁M PL S ▁V PN . ▁ ▁E volution ▁ ▁M PL S ▁has ▁been ▁originally ▁proposed ▁to ▁allow ▁high - per formance ▁traffic ▁forward ing ▁and ▁traffic ▁engineering ▁in ▁IP ▁networks . ▁However ▁it ▁evol ved ▁in