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HIGH-PERFORMANCE NETWORKS

Network Front-end
Processors, Yet Again
Mike O’Dell, New Enterprise Associates

“This time for sure, Rocky!” —Bullwinkle J. Moose

The history of the NFE (network front-end) processor, currently best known as a TOE (TCP offload engine), extends all the way back to the Arpanet IMP (interface message processor) and possibly before. The notion is beguilingly simple: partition the work of executing communications protocols from the work of executing the “applications” that require the services of those protocols.

That way, the applications and the network machinery can achieve maximum performance and efficiency, possibly taking advantage of special hardware performance assistance. While this looks utterly compelling on the whiteboard, architectural and implementation realities intrude, often with considerable force.

This article will not attempt to discern whether the NFE is a heavenly gift or a manifestation of evil incarnate. Rather, it will follow the evolution starting from a pure host-based implementation of a network stack and then moving the network stack farther from that initial position, observing the issues that arise. The goal is insight into the tradeoffs that influence the location choice for network stack software in a larger systems context. As such, it is an attempt to prevent old mistakes from being reinvented, while harvesting as much clean grain as possible.