Hierarchical address translation system for a network switch

Abstract

A network switch routes data transmissions between uniquely addressed network stations connected to input and output ports of the switch. The switch includes a hierarchical address translation system for relating network addresses of stations to receive incoming transmission to the switch ports to which they are connected. The translation system includes a central translation unit having a memory for storing a mapping entry for each network station, the entry mapping the station's network address to its switch port. The system also includes a local translation unit in each input port. Each local translation unit contains a local cache memory for storing a smaller subset of the mapping entries stored by the central translation unit. When a data transmission arrives at an input port directed to a network address, the input port looks for an entry in its cache memory mapping that network address to an output port. Upon finding such an entry in its cache memory, the input port directs the incoming data transmission to that output port. When not finding such an entry in its cache memory, the input port obtains a copy of the appropriate mapping entry from the central translation unit, stores it as a new mapping entry in its cache memory and then directs the data transmission the output port identified by the new mapping entry.