data link connection identifier

{{Short description|Network protocol}}

A data link connection identifier (DLCI) is a Frame Relay 10-bit-wide link-local virtual circuit identifier used to assign frames to a specific PVC or SVC. Frame Relay networks use DLCIs to statistically multiplex frames. DLCIs are preloaded into each switch and act as road signs to the traveling frames.{{cite web|title=DLCI's|url=http://www.infocellar.com/networks/frame-relay/dlci.htm|accessdate=22 March 2011}}

The standard allows the existence of 1024 DLCIs. DLCI 0 is reserved for the ANSI/q993a LMI standard—only numbers 16 to 976 are usable for end-user equipment. DLCI 1023 is reserved for Cisco LMI, however, numbers 16 to 1007 are usable.{{cite web|url=http://communitystring.com/2009/10/frame-relay-lmi/|title=Frame Relay LMI|accessdate=2014-04-24|url-status=dead|archiveurl=https://web.archive.org/web/20160401071013/http://communitystring.com/2009/10/frame-relay-lmi/|archivedate=2016-04-01}}

In summary, if using Cisco LMI, numbers from 16 to 1007 are available for end-user equipment. The rest are reserved for various management purposes.{{cite web |url=http://www.dcbnet.com/notes/framerly.html|title=What is Frame Relay|accessdate=2007-09-18}}

DLCI are Layer 2 Addresses that are locally significant. No two devices have the same DLCI mapped to its interface in one frame relay cloud.