(Data Link Connection Identifier) The number of a private or switched virtual circuit in a frame relay network. Located in the frame header, the DLCI field identifies which logical circuit the data travels over, and each DLCI has a committed information rate (CIR) associated with it. The DLCI number is local to the FRAD and frame relay switch it connects to, and it is generally changed by the switch within the network, because the receiving switch uses a different DLCI for the same connection. See CIR, PVC, SVC and frame relay.