A method of controlling a transmission of data units arranged in accordance with a predetermined communication protocol over a plurality of network entities, said network entities operating according to said predetermined communication protocol, from a sending network entity to a receiving network entity over one or more forwarding network entities, comprising providing in a data unit a first data field arranged to contain network entity identification information, said first data field being different from a forwarding data field designated by said communication protocol to contain information to be used by forwarding network entities for forwarding said data unit to the receiving network entity, said first data field being defined such that a given network entity that reads the first data field can at least make a decision on the basis thereof whether said given network entity is identified or not, and in said one or more forwarding network entities, performing a data unit processing operation after receiving said data unit, which comprises reading said first data field and making an identification decision on the basis thereof whether the forwarding network entity performing said data unit processing operation is identified or not.