Optimizing the use of network resources for data transmission over an IP-network

A method for optimizing the use of network resources for the transmission of data frames, preferably voice frames, between network units (3,4) in an Internet protocol IP-supporting network (1). The data frames are obtained by means of codecs (5A, 5B) from data samples, e.g. voice samples, that are formatted and to which a data frame header is added, and the codecs have different mouth-to-ear transmission delay budgets. The method comprises the steps of: attributing codec categories to each of the data or voice frames according to the codecs by means of which the data samples are generated, each codec category corresponding to a different mouth-to-ear delay budget range for the data frames; sorting out the data frames according to their codec categories; generating multiplexed cells from data frames of a same codec category, each multiplexed cell being obtained by multiplex aggregation of a predetermined number of voice samples; and transporting the multiplexed cells from an ingress router (3) to an egress router (4) in the IP-network (1).