V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

MPLS
       Multi-Protocol Label Switching (RFC 3031)


The Free On-line Dictionary of Computing (30 December 2018):

Multiprotocol Label Switching
MPLS

    (MPLS) A packet switching protocol developed
   by the IETF.  Initially developed to improve switching
   speed, other benefits are now seen as being more important.

   MPLS adds a 32-bit label to each packet to improve
   network efficiency and to enable routers to direct
   packets along predefined routes in accordance with the
   required quality of service.  The label is added when the
   packet enters the MPLS network, and is based on an
   analysis of the packet header.  The label contains
   information on the route along which the packet may travel,
   and the forwarding equivalence class (FEC) of the packet.
   Packets with the same FEC are routed through the network
   in the same way.

   Routers make forwarding decisions based purely on the contents
   of the label.  This simplifies the work done by the router,
   leading to an increase in speed.  At each router, the label
   is replaced with a new label, which tells the next router
   how to forward the packet.  The label is removed when the
   packet leaves the MPLS network.

   Modern ASIC-based routers can look up routes fast enough to
   make the speed increase less important.  However, MPLS still
   has some benefits.  The use of FECs allows QoS levels to
   be guaranteed, and MPLS allows IP tunnels to be created
   through a network, so that VPNs can be implemented without
   encryption.

   MPLS Resource Center (http://mplsrc.com/).

   [RFC 3031]

   (2002-04-14)