1. A method of generating a representation of an access control list, the representation being utilizable in a processor, the method comprising the steps of: determining a plurality of rules of the access control list, each of at least a subset of the rules having a plurality of fields and a corresponding action; and processing the rules to generate a multi-level tree representation of the access control list, each of one or more of the levels of the tree representation being associated with a corresponding one of the fields; wherein at least one level of the tree representation other than a root level of the tree representation comprises a plurality of nodes, with at least two of the nodes at that level each having a separate matching table associated therewith.