Data messages such as data packets in an IPv4 or IPv6 format are processed with a view to compression/decompression, using information obtained from sources other than the data packet itself, or the stream to which it belongs. This may involve additional dynamic processing defined in specifications identified by a shared marker, or obtained from an additional data source such as a static file, database application or the like. Embodiments described herein enhance this approach with a dynamic determination of data components.