Method for the transmission of time-critical data within a communication system, in which - selected datagrams are assigned to data streams and are transmitted from first communication devices to second communication devices via third communication devices comprising paths, - the first communication devices send first datagrams comprising a data stream identifier in each case for notification of subscribable data streams and specify quality-of-service parameters in the first datagrams for the respective data stream, - the second communication devices send, in each case, second datagrams for reserving resources to be provided by the third communication devices for a transmission of the data streams and specify in these the respective data stream identifier, - a higher-level communication control facility determines a path on the first and second datagrams in each case for the respective data stream and, if sufficient resources are available, reserves resources for the transmission of the respective data stream via the third communication devices, - if sufficient resources are available, the higher-level communication control facility configures at least third communication devices (101, 102) connected to a first or second communication device, in each case, such that datagrams assigned to data streams are placed in send queues (111-112, 121-122) reserved for data streams, - the data streams are identified in each case for a send queue assignment of their datagrams by their data stream identifier and their assignment to a virtual local network, - if there is a lack or uncertainty of availability of sufficient resources, the higher-level communication control facility at least temporarily configures at least the third communication devices connected to a first or second communication device in each case, such that datagrams assigned to selected data streams are placed in a send queue (113, 123) for data traffic in each case, which data traffic is not covered by specific quality of service assurance. - selected datagrams are assigned to data streams and are transmitted from first communication devices to second communication devices via third communication devices comprising paths, - the first communication devices send first datagrams comprising a data stream identifier in each case for notification of subscribable data streams and specify quality-of-service parameters in the first datagrams for the respective data stream, - the second communication devices send, in each case, second datagrams for reserving resources to be provided by the third communication devices for a transmission of the data streams and specify in these the respective data stream identifier, - a higher-level communication control facility determines a path on the first and second datagrams in each case for the respective data stream and, if sufficient resources are available, reserves resources for the transmission of the respective data stream via the third communication devices, - if sufficient resources are available, the higher-level communication control facility configures at least third communication devices (101, 102) connected to a first or second communication device, in each case, such that datagrams assigned to data streams are placed in send queues (111-112, 121-122) reserved for data streams, - the data streams are identified in each case for a send queue assignment of their datagrams by their data stream identifier and their assignment to a virtual local network, - if there is a lack or uncertainty of availability of sufficient resources, the higher-level communication control facility at least temporarily configures at least the third communication devices connected to a first or second communication device in each case, such that datagrams assigned to selected data streams are placed in a send queue (113, 123) for data traffic in each case, which data traffic is not covered by specific quality of service assurance.