▁Call ▁Control ▁( B IC C ) ▁is ▁a ▁signal ing ▁protocol ▁based ▁on ▁N - IS UP ▁that ▁is ▁used ▁for ▁supporting ▁narrow band ▁Integr ated ▁Services ▁Digital ▁Network ▁( IS DN ) ▁service ▁over ▁a ▁broad band ▁back bone ▁network . ▁ ▁B IC C ▁is ▁designed ▁to ▁inter work ▁with ▁existing ▁transport ▁techn ologies . ▁B IC C ▁is ▁specified ▁in ▁IT U - T ▁recommendation ▁Q . 1 9 0 1 . ▁ ▁B IC C ▁signal ing ▁messages ▁are ▁nearly ▁identical ▁to ▁those ▁in ▁I SD N ▁User ▁Part ▁( IS UP ); ▁the ▁main ▁difference ▁being ▁that ▁the ▁narrow band ▁circuit ▁identification ▁code ▁( C IC ) ▁has ▁been ▁modified . ▁ ▁The ▁B IC C ▁architecture ▁consists ▁of ▁inter connected ▁serving ▁nodes ▁that ▁provide ▁the ▁call ▁service ▁function ▁and ▁the ▁bear er ▁control ▁function . ▁ ▁The ▁call ▁service ▁function ▁uses ▁B IC C ▁signal ing ▁for ▁call ▁setup ▁and ▁may ▁also ▁inter work ▁with ▁IS UP . ▁ ▁The ▁bear er ▁control ▁function ▁receives ▁direct ives ▁from ▁the ▁call ▁service ▁function ▁via ▁B IC C ▁Bear er ▁Control ▁Pro tocol ▁( IT U - T ▁recommendation ▁Q . 1 9 5 0 ) ▁and ▁is ▁responsible ▁for ▁setup ▁and ▁te ard own ▁of ▁bear er ▁paths ▁on ▁a ▁set ▁of ▁physical ▁transport ▁links . ▁ ▁Transport ▁links ▁are ▁most ▁commonly ▁As ynchronous ▁Transfer ▁Mode ▁( AT M ) ▁or ▁Internet ▁Pro tocol ▁( IP ). ▁▁▁▁ ▁According ▁to ▁the ▁IT U , ▁the ▁completion ▁of