Functional separation of internal and external controls in network devices

This invention relates to network devices, and more particularly, to network devices such as data switches and routers. The present invention provides a network device, such as a network switch or a router, having a high degree of modularity and reliability. The network device includes a data plane and a control plane. The data plane relays datagrams between a pair of receive and transmit network interface ports. The control plane runs management and control operations, such as routing and policing algorithms which provide the data plane with instructions on how to relay cell/packets/frames. Further, the control plane includes an internal control device that is primarily responsible for managing the internal resources of the network device, and a separate external control device that is primarily responsible for operations relating to the interfacing of the network device with an external environment.