Over the past few years, a number of new technologies have been designed to support Carriers and Network Service Providers as they try to keep a step ahead of the explosive growth demand. Multi-Protocol Label Switching (MPLS) is the latest step in the evolution of backbone technology for core network providers. MPLS delivers a solution that seamlessly integrates the control of IP routing with the simplicity of Layer 2 switching (eg X.25, ATM, Frame Relay etc). As background, this paper describes the use of IP-over-ATM as a backbone construction and identifies the key issues and limitations associated with its operation. Against this the MPLS protocol is explained and contrasted including discussion surrounding the key benefits that MPLS aims to deliver, specifically: support for differentiated service, simplified network management, Virtual Private Networking, and the benefits of label swapping and stacking. This paper aims to provided an understanding of the strategic benefits of changing to MPLS; what would drive the need to change, and if so when? Issues of network migration are discussed including integration with existing networks and legacy protocols.