Dynamically adding application logic and protocol adapters to a programmable network element

Custom or user-defined application program extensions may be loaded into a network infrastructure element such as a router or switch without restarting the device. For example, a network element has program extensibility logic operable for receiving one or more user program extensions that comprise logic operable to interface with the application program and perform message processing functions or protocol processing functions that are not in the application program; installing the one or more user program extensions without restarting the apparatus; receiving one or more packets representing an application message; selecting a particular one of the user program extensions based on a protocol associated with the message; loading the particular one of the user program extensions; executing business logic of the application program associated with the received message; and invoking a function of the particular one of the user program extensions in response to a call in the business logic.