Encapsulation Methods for Transport of Ethernet over MPLS Network
This IETF Request For Comments (RFC) provides useful background information on the transport of Carrier Ethernet services over MPLS networks.
" An Ethernet pseudowire (PW) is used to carry Ethernet/802.3 Protocol Data Units (PDUs) over an MPLS network. This enables service providers to offer "emulated" Ethernet services over existing MPLS networks. This document specifies the encapsulation of Ethernet/802.3 PDUs within a pseudowire. It also specifies the procedures for using a PW to provide a "point-to-point Ethernet" service."
More links relating to Ethernet pseudowires over MPLS can be found at the Wikipedia page on this topic.