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

label switching

    A routing technique that uses information from
   existing IP routing protocols to identify IP datagrams
   with labels and forwards them to a modified switch or
   router, which then uses the labels to switch the datagrams
   through the network.

   Label switching combines the best attributes of data link
   layer (layer two) switching (as in ATM and Frame Relay)
   with the best attributes of network layer (layer three)
   routing (as in IP).

   Prior to the formation of the MPLS Working Group in 1997, a
   number of vendors had announced and/or implemented proprietary
   label switching.

   (2007-10-17)