1. A method for packet classification comprising: determining a matching length of how long each field value of one or more fields in an input packet coincides with a field value of the corresponding field stored in a rule set by performing a field-by-field search on the fields in the input packet, and generating a tuple list made up of combinations of one or more matching lengths by the individual fields; selecting particular tuples existing in the rule set from the tuple list; filtering each of the selected tuples by using a Bloom filter; and searching for a best matching rule as a search pool exclusively within the tuples with the positive result of the filtering.