Abstract: All the information sections of a processed data structure, including pre-header, tail and extra section, header and payload, can be selectively copied in a node of a communication network by means of a copy mask (12) associated with a copy block (11). A combination of an insert block (14) and an insert mask (15) is used for selectively writing to all the information sections in the data structure. In order to increase the capacity of the data structure, the length of the pre-header or tail can be increased. In the path between an input interface (10) and the insert block (14) there is an adjustable delay block (13) into which the data structure can be copied as a whole. A microprocessor (25) is coupled to all the processing units (10)-(17) and (22)-(24) of the system and serves for presetting the two masks for selecting the information to be copied and inserted.