MultiProtocolLabelSwitching(MPLS)isadata-carryingmechanismthatbelongstothefamilyofpacket-switchednetworks.ForanMPLSlabel,ifthestackbitissetto1,whichoptionistrue?()
A.ThestackbitwillonlybeusedwhenLDPisthelabeldistributionprotocol
B.Thelabelisthelastentryinthelabelstack.
C.ThestackbitisforCiscoimplementationsexclusivelyandwillonlybeusedwhenTDPisthelabeldistributionprotocol.
D.Thestackbitisreservedforfutureuse.
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