There is an inevitable possibility of an LSP forming loops in MPLS networks
and the application of MPLS's loop control mechanisms is restricted by the ATM technological traits.The paper studied different kinds of loop control mechanisms of MPLS networks applied on ATM
including the ATM TTL field survival mechanism
loop detection mechanisms
and two kinds of loop prevention algorithms designed for establishing loop-free state-merging LSPs.These mechanisms were compared in various aspects by theoretical analysis and partial simulation