▁P ▁router ▁is ▁significantly ▁easier ▁than ▁that ▁of ▁a ▁P E ▁router , ▁so ▁they ▁can ▁be ▁less ▁complex ▁and ▁may ▁be ▁more ▁depend able ▁because ▁of ▁this . ▁ ▁Label ▁Distribution ▁Pro tocol ▁Label s ▁are ▁distributed ▁between ▁L ER s ▁and ▁L SR s ▁using ▁the ▁Label ▁Distribution ▁Pro tocol ▁( LD P ). ▁L SR s ▁in ▁an ▁M PL S ▁network ▁regularly ▁exchange ▁label ▁and ▁reach ability ▁information ▁with ▁each ▁other ▁using ▁standard ized ▁procedures ▁in ▁order ▁to ▁build ▁a ▁complete ▁picture ▁of ▁the ▁network ▁so ▁they ▁can ▁then ▁use ▁to ▁forward ▁packets . ▁ ▁Label - switch ed ▁paths ▁Label - switch ed ▁paths ▁( L SP s ) ▁are ▁established ▁by ▁the ▁network ▁operator ▁for ▁a ▁variety ▁of ▁purposes , ▁such ▁as ▁to ▁create ▁network - based ▁IP ▁virtual ▁private ▁networks ▁or ▁to ▁route ▁traffic ▁along ▁specified ▁paths ▁through ▁the ▁network . ▁In ▁many ▁respect s , ▁L SP s ▁are ▁not ▁different ▁from ▁permanent ▁virtual ▁circ uits ▁( P VC s ) ▁in ▁AT M ▁or ▁Frame ▁Rel ay ▁networks , ▁except ▁that ▁they ▁are ▁not ▁dependent ▁on ▁a ▁particular ▁layer - 2 ▁technology . ▁ ▁Rout ing ▁When ▁an ▁un l abeled ▁packet ▁enters ▁the ▁ing ress ▁router ▁and ▁needs ▁to ▁be ▁passed ▁on ▁to ▁an ▁M PL S ▁tunnel , ▁the ▁router ▁first ▁determ ines ▁the ▁forward ing ▁equivalence ▁class ▁( F EC ) ▁for ▁the ▁packet ▁and ▁then ▁inser ts ▁one ▁or ▁more ▁labels ▁in ▁the ▁packet ' s ▁newly ▁created ▁M PL