In IP-based networks

VoIP has become the representative technology of the next generation voice system

but its QoS is limited by the IP network capacity.Now MPLS is regarded as a most promising technology for high-speed backbone networks.By MPLS

layer 3 routing can be well complemented by layer 2 switching

which guarantees the point-to-point QoS.Network performance can be further optimized by the combination of DiffServ and QoS of MPLS.