Apparatus and method using a register scheme for efficient evaluation of equations in a network switch

摘要

A network switch, configured for performing layer 2 and layer 3 switching in an Ethernet (IEEE 802.3) network includes a network switch port having a filter configured for evaluating an incoming data packet. The filter includes a min term memory configured for storing min term values. Each min term value is stored based on a location of a corresponding selected byte of the incoming data packet for comparison. Each min term is stored as a table entry having an expression portion specifying a corresponding comparison operation and a template identifier field that specifies templates that use the corresponding min term. The template identifier field includes an equation identifier. A min term generator is configured for simultaneously comparing a received byte of the incoming data packet with the min terms that correspond to the received byte and generates respective min term comparison results. An equation core is configured for evaluating equations and generates a frame tag identifying the incoming data packet based on the min term comparison results relative to the templates. The equation core is configured to identify equations which are no longer relevant. An equation reduction module includes a plurality of register arrays. Each register array includes equation identifiers corresponding to the corresponding byte. The equation reduction module includes logic configured to compare the equation identifiers of equations which are no longer relevant to equation identifiers in the register arrays and based on the comparison, to set vectors. A min term controller is configured to read the vectors and based thereon, to send necessary min terms to the min term generator.