It is used on the control plane. Netconf (rfc6241) operations un most routers (not just Cisco) are handled from an Erlang application. Some years ago the best

It is used on the control plane. Netconf (rfc6241) operations un most routers (not just Cisco) are handled from an Erlang application. Some years ago the best netconf implementation was from tail-f systems. Cisco and Juniper licensed the software from them... ... And Cisco bought the company for the Netconf and orchestation/automation part.