Multiprotocol Label Switching (MPLS) is a network protocol for speeding up and shaping wide area network (WAN) traffic flows. MPLS directs data from one WAN node to the next based on short path labels as opposed to long network addresses. MPLS supports a variety of WAN technologies, including Frame Relay and DSL. MPLS WANs are private networks sold BT large carries such as AT&T, Verizon, and BT, where bandwidth is extremely expensive and so most enterprises can only afford Limited Bandwidth at most locations. Many businesses are using SD-WAN technology to augment or even replace their expensive MPLS connections with lower-cost, high-bandwidth Internet links.

Multiprotocol Label Switching (MPLS) is a switching technology that forwards data from one source to its destination using labels rather than IP addresses. The MPLS protocol speeds up and influences traffic flows. In a legacy MPLS network, the first router to receive a packet governs the packet's entire route. The identity of that packet is then transported to the following routers using a label in the packet header. MPLS compresses packets of several network protocols, which is why it is known as a multiprotocol. MPLS supports a wide variety of access technologies, including Frame Relay and DSL.

Is MPLS Layer 2 or Layer 3?
A common question is whether MPLS is Layer 2 or Layer 3 service. The truth is MPLS doesn’t really fit into the OSI seven-layer hierarchy. One of the key benefits of MPLS is the ability to separate forwarding mechanisms from the underlying data-link service. Essentially, MPLS creates forwarding tables for any underlying protocol.