The present invention relates to a method for connecting a system (MS; MS1; MS2) utilizing message-based synchronization with an external system (ES). The message-based system comprises a plurality of nodes (1... 6, IN1, IN2) interchanging signals containing synchronization messages with information about the priority of the respective signal in the internal synchronization hierarchy of the system. For the external system to be able to utilize the message-based system as well as possible with respect to timing, synchronization status data in the internal format of the external system is transmitted from the interface node (IN1, IN2) of the system utilizing message-based synchronization to the external system, said synchronization status data being converted from the message-based synchronization signature (18c) transmitted by the interface node in such a manner that the level in the internal synchronization hierarchy of the external system as indicated by the synchronization status transmitted to the external system rises or falls corresponding to the rise and, correspondingly, fall of a predetermined magnitude of the level indicated by the message-based synchronization signature.