MPLS typologies

The MPLS protocol architecture has been constructed using the best parts of existing networking typologies.
For example, it includes the packet organization from Frame Relay, the file transmission size from IP, and the QoS goals from ATM. MPLS primarily deals with two important network efficiency aspects.

They are speeding up packet processing and establishing traffic-engineered paths within a network. MPLS uses a label switching technique to forward data through the network. The label-based switching is a technique based on an integration of layer 2 switching and layer 3 routing. This technique has been designed for high speed networks to use in a more efficient way that enhances performances of switching with the scalability and flexibility of IP routing. A small, fixed-format label is inserted in front of each data packet on entry into the MPLS network.

At each hop across the network, the packet is routed based on the value of the incoming interface and label, and dispatched to an outgoing interface with a new label value. The transition in label values defines the network path since the label is swapped at each Label Switched Router (LSR). Since the mapping between labels is constant at each LSR, the complete path is determined by the initial label value. Such a path is called a Label Switched Path(LSP). For efficiency, a Forwarding Equivalence Class (FEC) is defined which is a set of packets that has the same label value on entry to the MPLS network, and they will therefore follow the same LSP.