an egress packet modifier includes a script parser and a pipeline of processing stages . rather than performing egress modifications using a processor that fetches and decodes and executes instructions in a classic processor fashion , and rather than storing a packet in memory and reading it out and modifying it and writing it back , the packet modifier pipeline processes the packet by passing parts of the packet through the pipeline . a processor identifies particular egress modifications to be performed by placing a script code at the beginning of the packet . the script parser then uses the code to identify a specific script of opcodes , where each opcode defines a modification . as a part passes through a stage , the stage can carry out the modification of such an opcode . as realized using current semiconductor fabrication process , the packet modifier can modify 200m packets / second at a sustained rate of up to 100 gigabits / second .