This Recommendation focuses on the functions required for network interworking between ATM and MPLS, specifically the user plane interworking mechanisms and procedures for the AAL type 5 Protocol Data Unit (PDU) and Service Data Unit (SDU) transport modes. In particular, it specifies a list of requirements, interworking scenarios and interworking encapsulation formats and semantics for ATM-MPLS AAL type 5 PDU and SDU mode network interworking.