Method for operating an industrial automation system communication network comprising a plurality of communication devices, in which - a plurality of control units each control functions of a plurality of associated communication devices , wherein a predefinable share of system resources of an associated communication device is made available for each control unit for a predefinable resource usage duration, - during the resource usage duration, the control units each determine communication network paths between selected communication devices via associated communication devices on the basis of a quality measure taking into account respective available system resources and control routing or switching functions of the associated communication devices according to the communication network paths which have been determined, - the control units synchronously capture state variables of the communication devices when predefinable synchronization events occur and compare said state variables with one another, wherein the synchronization events comprise predefinable synchronization intervals and the resource usage duration is limited by successive synchronization events, - the control units determine , for at least one past resource usage duration, which quality measure changes result for communication network paths to be determined on the basis of a determination time available for path determination and determine a first correction value for the synchronization events on the basis of the quality measure changes, - the control units determine inconsistent state variables when comparing the state variables with one another and determine a second correction value for the synchronization events on the basis of inconsistent state variables, - changed synchronization events are specified for the control units on the basis of the first and second correction values. - a plurality of control units each control functions of a plurality of associated communication devices , wherein a predefinable share of system resources of an associated communication device is made available for each control unit for a predefinable resource usage duration, - during the resource usage duration, the control units each determine communication network paths between selected communication devices via associated communication devices on the basis of a quality measure taking into account respective available system resources and control routing or switching functions of the associated communication devices according to the communication network paths which have been determined, - the control units synchronously capture state variables of the communication devices when predefinable synchronization events occur and compare said state variables with one another, wherein the synchronization events comprise predefinable synchronization intervals and the resource usage duration is limited by successive synchronization events, - the control units determine , for at least one past resource usage duration, which quality measure changes result for communication network paths to be determined on the basis of a determination time available for path determination and determine a first correction value for the synchronization events on the basis of the quality measure changes, - the control units determine inconsistent state variables when comparing the state variables with one another and determine a second correction value for the synchronization events on the basis of inconsistent state variables, - changed synchronization events are specified for the control units on the basis of the first and second correction values. <EOS>