1. A system for providing a service to a packet based network, the service applying classifications that use arbitrary combinations of extracted packet header information, the system comprising: a processor having instructions to extract predetermined header information from a packet and further having instructions to perform table look-ups with the header information; a first data structure that provides a longest match value for processor table look-ups; a second data structure that provides a first match value for processor table look-ups of combinations of longest match values, the first match value determining a classification for the packet.