Multiprotocol Label Switching (MPLS) began life as a way for routers to short-cut the time-consuming process of treating each packet independently, looking up the target IP address each time and in every router along the path. In an MPLS network, the ingress router does a standard lookup and assigns a numeric label to the packet. Core routers then examine the label and forward the packet according to the label. All packets with the same label are forwarded the same way. This relieves the core routers of much processing, making the overall network more efficient.

Because the labels are just numbers, they can be assigned according to any criteria the router software supports. This feature give MPLS an extraordinary ability to support many networking applications. Some examples of MPLS applications, in addition to basic IP destination-based routing, including:

• VPN membership
• QoS
• Traffic Engineering
• Emulation of any Layer-2 technology

Service providers and enterprises are implementing MPLS to provide their customers with flexible networking services.