Header compression system for compressing the header of the data packets of a flow transmitted from an ingress node to an egress node through a data transmission network comprising template creating means, in both ingress node and egress node, adapted for creating the same compression template from a predetermined number of uncompressed data packets at the beginning of the flow respectively transmitted by the ingress node and received by the egress node, and header compression means, in the ingress node, adapted for compressing the header of each packet following the predetermined number of uncompressed data packets before transmitting it through the data transmission network, the compression being achieved by using the compression template.