Abstract: The present invention provides methods and apparatus for abstracting network processors using a virtual machine. The virtual machine approach substantially abstracts the network processor, letting the application developer focus all attention on packet processing. In accordance with the present invention, the NPU-based virtual machine provides the functionality of a pipelined engine, N-way parallelism, or both. The present invention provides a high-level functional language for expressing a wide variety of packet processing applications. The high-level functional language provides primitives in the form of instructions such as, but not limited to, tracking a connection or session, removing an outer header, translating an IP address, encrypting a packet, and scanning the payload for a regular expression.