Which of the following devices performs a label swap operation?

A Label Switch Router (LSR) is designed to perform label swapping operations in a Multiprotocol Label Switching (MPLS) network. In the context of MPLS, an LSR receives a data packet with an incoming label and swaps it for a new outgoing label before forwarding the packet to the appropriate next hop. This process is critical for maintaining efficient data forwarding within MPLS networks, as it relies on the label rather than the network layer address to route packets.

The other devices listed serve different functions within the network. For example, Edge Label Routers (iLER and eLER) are involved in label edge operations, which handle the labeling process as packets enter or exit the MPLS network, but they are not the ones that perform the swapping of labels in transit. Customer Edge devices (CE) typically connect to the provider network and do not engage in any label operations, as they operate at the edge and primarily deal with customer traffic without performing MPLS functions.

In summary, the LSR is the only device mentioned that actively handles the label swapping operation necessary for packet forwarding in an MPLS environment.