Which label operations does a label edge router perform?

A Label Edge Router (LER) is at the ingress or egress of an MPLS domain. At the ingress, the LER performs a PUSH operation, adding an MPLS label to an incoming IP packet. At the egress, the LER performs a POP operation, removing the MPLS label before forwarding the packet as a standard IP packet. Label Switch Routers (LSRs) within the MPLS domain perform SWAP operations, replacing an incoming label with an outgoing label. PHP (Penultimate Hop Popping) is a specific POP operation performed by the LSR one hop before the egress LER, not directly by the LER itself.