Huawei Contrail Systems Huawei Cisco China Telecom Existing technologies to encapsulate Multi-Protocol Label Switching (MPLS) over IP are not adequate for efficient load balancing of MPLS application traffic, such as MPLS-based Layer2 Virtual Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN) traffic across IP networks. This document specifies additional IP-based encapsulation technology, referred to as MPLS-in-User Datagram Protocol (UDP), which can facilitate the load balancing of MPLS application traffic across IP networks.