Abstract: In a packet-based communications system where each packet includes a header and an associated data portion, message packets are communicated between entities on a radio communications network through a data gateway. The other network uses a standard internetwork protocol (IP). Predetermined fields in the standard (IP) header of each message packet are eliminated to obtain a modified radio network layer header before transmitting message packets over the radio network. Conversely, one or more predetermined fields are added to the modified header to convert that modified header into a corresponding standard IP header before transmission over the other network. Short and long versions of the modified radio network layer header are used with the short header version being used by radios to support network layer communications with minimal impact to the radios. Enough information is preserved in the reduced IP network header so that the standard IP header may be reassembled/reconstructed.