It enables devices at the edge of a network to apply labels to packets and devices at the core of a network to switch packets according to the labels with minimum lookup overhead.
Labels indicate both routes and service attributes.
As shown in Figure 1, incoming packets are processed and labels are selected and applied on the ingress edge. The core reads labels, applies appropriate services, and forwards packets based on the label. Processor-intensive analysis, classification, and filtering happen only once, at the ingress edge. At the egress edge, labels are stripped, and packets are forwarded to their final destination using normal routing mechanisms. Hence MPLS combines the benefits of connectionless Layer 3 routing and forwarding with connection-oriented Layer 2 forwarding.