A device for operating a parking brake of a motor vehicle, wherein the parking lock includes an actuatable actuator element for disengaging the parking lock counter to a restoring pressure, and an actuatable holding device for holding the parking lock when the latter is disengaged. Congestion sensing heuristics are used to adaptively route traffic across links. The duplex mismatch circuit declares a duplex mismatch when the communication channel was established without attempting auto-negotiation, the port is in a half-duplex mode, and the collision detect circuit detects a very late collision involving one of the first frames.