On a traditional IP network, routing lookups are performed at every router a packet passes through. Each router in the network makes an independent decision when forwarding packets.
MPLS helps reduce the number of routing lookups and can forward based on criteria other than the default destination network. This capability eliminates the need to run a particular routing protocol on all the devices. To accomplish this, MPLS imposes labels; each packet gets an additional header. The labels are simply numbers that are used to make forwarding decisions. They are assigned on the edge of the MPLS of the network, and forwarding within the MPLS network is based on solely labels.
Labels usually correspond to a path to Layer 3 destination addresses; ...