1. A computer-implemented method of data packet classification comprising: receiving a data packet comprising one or more classification properties; determining an interval using a computer, from a non-overlapping interval tree representing applicability of rules to a first data packet classification property that matches the first of the one or more classification properties of the data packet; producing packet classification information by classifying the data packet based on the rules that apply to the determined interval; for each interval for which the number of applicability of rules exceeds a threshold, referring to a second non-overlapping interval tree representing applicability of rules to a second data packet classification property; and for each interval for which the number of applicability of rules does not exceed the threshold, determining the rules that apply for the first property from an ordered list of rules.