In Multiprotocol Label Switching (MPLS), short, fixed-length labels are attached to packets as they enter the network. These labels identify the forwarding path to the next node, streamlining packet routing. As the packet traverses the network, each MPLS node removes the old label and replaces it with a new one based on its internal forwarding table. This process continues until the packet reaches its destination, where the final label is removed, and the original packet is delivered. As a pre-requisite, existing routing protocol (e.g., OSPF, IS-IS etc.) is used to establish reachability and distribute labels among the network nodes.
MPLS and its extension provide several advantages such as reduced latency and traffic engineering to balance loads across different paths, Quality of Service (QoS) policy implementation and simplified network management.