This document provides an introduction to Multi-Protocol Label Switching (MPLS), including its motivation, basic concepts, components, protocols, operation, advantages, and disadvantages. MPLS combines IP routing with ATM switching to address some of the limitations of IP routing, such as lack of quality of service, while being less complex and expensive than ATM. It works by assigning short, fixed-length labels to IP packets at the edge of the network which are then used for fast packet forwarding within the network core.