Abstract: Methods and arrangements for associating control messages received in the D-channel of an integrated services digital network (ISDN) line with the call control process to which the message relates are disclosed. With ISDN, a single control channel, called the D-channel, can be used concurrently to control a plurality of calls. As each call is initiated, a call control process and data structure including the unique identity of the call, are created. The data structures associated with the same D-channel are linked together. When a control message including a given identity is received, the data structures associated with the D-channel conveying the message are searched in sequence until a data structure having the given identity is found. The contents of this data structure are used to access the control process associated therewith. When the search reveals no matching identity and the message is a call setup message, a new process and data structure are created.