Which label operations are performed by a label edge router?

SWAP is typically performed by Label Switch Routers (LSRs) in the core of the MPLS network, not edge routers.

SWAP is typically performed by Label Switch Routers (LSRs) in the core of the MPLS network, not edge routers.

While PUSH is an LER function, Penultimate Hop Popping (PHP) is performed by the second-to-last LSR in the path, not the Egress LER itself. The Egress LER might receive an unlabeled packet due to PHP, but it does not perform PHP.

An Ingress Label Edge Router (LER) is responsible for PUSHing an initial MPLS label (or stack of labels) onto an incoming IP packet as it enters the MPLS domain. An Egress LER is responsible for POPping the last MPLS label off a packet before forwarding it as an IP packet to its final destination outside the MPLS domain.