What is MPLS-based IP VPN?

It is a IP VPN deploying MPLS technology to mark, classify, and monitor IP packets. At the ingress side of MPLS network, LER examines and determines whether the incoming packets should be labeled. LER classifies incoming IP traffic with MPLS label. The LER converts IP packets into MPLS packets. When the MPLS packets leave the LER, they are examined by LSR for the presence of labels. LSR will then swap labels according to label instructions. At the egress of the network, the LER removes the MPLS header, reconverts MPLS packet into IP packet and forward it to the destined IP network.