In a system (10) for transmitting packets over a link between a compressor and a decompressor, a method is provided for implicit packet type identification. A set of implicit packet transmission characteristics including at least first and second characteristics is selected, and the compressor (18,25) is operated to assign the first and second transmission characteristics to packets of first and second packet types, respectively. The decompressor (16,22) is operated to detect transmission characteristics of packets received by the decompressor (16,22), and to thereby identify a received packetas being either a first or second packet type. Usefully, header free packets (26) 10 comprise one of the packet types.