ISDN D CHANNEL RESTORATION WITHOUT LOSS OF SIGNALING OR PACKET DATA

A communication switching system has a plurality of switch nodes with each of the switch nodes responsive to a failure of the primary signaling channel that is providing the common signaling channel in a facility access service (FAS) group to immediately switch to the secondary signaling channel of the FAS group. This switching occurs quickly so that no calls are dropped within the FAS group. Any logical links being communicated on the primary signaling channel are transferred to the secondary signaling channel with no data packets being irreplaceable lost. A first physical object is established to control a physical protocol on the primary signaling channel, and a second physical object is established to control the physical protocol on the secondary signaling channel. Further, a single software object is established to always control the first layer of software protocol on the common signaling channel whether that is the primary signaling channel or secondary signaling channel. When failure of the primary signaling channel is detected, information for the common signaling channel is routed from the second physical object to the software object, thereby preserving the common signaling channel.