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

Data Link Connection Identifier

    (DLCI) A channel number which is attached to
   data frames to tell a Frame Relay network how to route the
   data.  In Frame Relay, multiple logical channels are
   multiplexed over a single physical channel.  The DLCI says
   which of these logical channels a particular data frame
   belongs to.

   (http://etinc.com/frmain.htm#whatsadlci).

   (2000-02-13)