Method and arrangement of arranging traffic in telecommunications system

A method for arranging traffic in a telecommunications system comprising a data transmission path and devices using the data transmission path for data transmission, data being transmitted on the data transmission path between the devices in messages cyclically according to at least one cycle having a substantially constant cycle time, the method comprising:

• monitoring by one or more of the devices in turns during one or more first turns, respectively, the cyclic traffic of the data transmission path in the telecommunications system;
• setting by one or more of the devices, during the respective one or more first turns the timing of the devices' own cyclic traffic on the data transmission path between cyclic traffic detected based on the monitoring by the device;
• and
• determining by one or more of the devices, during a second turn, on the basis of the monitoring and the cycle time of the at least one cycle of the cyclic traffic at least one expected occurrence time slot of the cyclic traffic;
• and
• transmitting by one or more of the devices during the second turn one or more non-cyclic messages that do not belong to the cyclic traffic from one or more devices to the data transmission path on the basis of at least one determined occurrence time slot of the cyclic traffic such that the messages do not collide with one or more messages of the cyclic traffic which occur in the determined at least one occurrence time slot and the periodic nature of the cyclic traffic is maintained.