(1) (MultiProtocol Lambda Switching) The earlier name for GMPLS. See GMPLS.

(2) (MultiProtocol Label Switching) A standard from the IETF for including routing information in the packets of an IP network. MPLS is used to ensure that all packets in a particular flow take the same route over a backbone. Deployed by many telcos and service providers, MPLS delivers the quality of service (QoS) required to support real-time voice and video as well as service level agreements (SLAs) that guarantee bandwidth. Large enterprises may also use MPLS in their national networks.

Similar to Cisco's tag switching, an MPLS router attaches labels (tags) containing forwarding information to outgoing IP packets. These "label edge routers" (LERs) sit at the edge of the network and perform the complex packet analysis and classification before the packet enters the core of the network. The routers within the core, known as "label switch routers" (LSRs), quickly examine the label and forward the packet per its directions without having to look up data in tables and compute the forwarding path each time. The edge routers at the receiving end remove the labels.

Following in the tradition of the "dumb network," MPLS enables more decisions to be made at the periphery of the network. See VPLS, GMPLS, dumb network and Diffserv.