 Alternatively, under penultimate hop popping this function may instead be performed by the LSR directly connected to the LER.When forwarding an IP datagram into the MPLS domain, a LER uses routing information to determine the appropriate label to be affixed, labels the packet accordingly, and then forwards the labeled packet into the MPLS domain.Likewise, upon receiving a labeled packet which is destined to exit the MPLS domain, the LER strips off the label and forwards the resulting IP packet using normal IP forwarding rules.