A packet and inspection system for monitoring the performance of one or more flows on a packet network comprises a processor and memory coupled to each other and to a network bus. The memory stores instructions to be executed by the processor and data to be modified by the execution of the instructions. A processor-controlled arbiter is coupled with the processor and the network bus, and upon reception of a packet on the bus or prior to transmission of a packet on the bus for one of said flows, the arbiter requests execution by the processor of selected instructions stored in the memory by providing the processor with the address of the selected instructions in the memory. The memory provides the processor with data associated with the selected instructions, and the processor modifies the data upon execution of the selected instructions.