systems don’t have enough network “go-fast” to deliver the performance required, so just add a dedicated processor to the network interface to make up for it. The economics of that are fleeting at best, however. Between chip design and system-integration complexity, an NFE will need to be an economically attractive solution for quite some time to recoup the development costs. Unfortunately, the relentless improvements in processor, memory system, and system interconnect in the base PC platform make that window of advantage a shrinking, fast-moving target. Does anyone remember the HiFN file compression processor chip? It got built into PC systems for a very short time. Processors quickly improved enough to do compression/decompression on the fly, and that was the end of HiFN’s dream—well before the dropping cost of disk storage would have killed it.

“BU T NOT EVERY TIME”

The previous section questioning the efficacy of NFEs should include a caveat for one particular case that merits a special mention because it indeed makes a compelling case for a particular style of NFE.

The proliferation of microcontrollers in devices such as thermostats, light switches, toasters, and almost everything else with more than a simple on/off switch has created a real opportunity for NFEs. Almost all of these microcontroller applications are typified by intense cost pressure, which usually translates into extreme limitations on available computing resources. It is simply out of the question to put a network stack in the vast majority of these systems, but the desirability of remote management of these devices increases daily.

This has created a new breed of NFE: the NCA ( network communications adapter), which specializes in the simplicity of the protocol between the microcontroller host and the NFE—serial ASCII. Most microcontrollers have some serial port ability, so by looking like a terminal, the NCA can play the role of translator, speaking serial out one side and TCP/IP out the other. The NCA appears as a host on the TCP network, often containing a simple Web server that vends state information and may provide certain other management functions that get translated into simple ASCII exchanges with the microcontroller system.

An NCA is usually implemented in one of the more powerful microcontrollers designed to provide an Ethernet interface and support enough RAM and ROM to contain a simplified network stack. The NCA is now available as an off-the-shelf module designed for integration no more difficult than a modem on a serial port.

The question of which is the tail and which is the dog comes to mind in many of these applications. From the TCP network’s point of view, the NCA is the host and the microcontroller is being managed. From the point of view of the lighting controller, the NCA looks like just one more switch, albeit a chatty one. This distinction is usually irrelevant—it just makes hash of pedantic layering diagrams. There’s something quite satisfying about that.

CONCLUSION

Rather than debate the religious propriety of NFEs, particularly the TOE variety, this article has examined the architectural issues that have produced their recurring rise and fall. The TOE-style NFE is best viewed as a tactical tool with a limited expected lifetime of economic viability, not an enduring architectural approach.

This is just another example of the recurring ebb and flow of functions between specialized peripherals and the system CPU(s), as the economics slosh back and forth interacting with system requirements. The limited lifetime of the NFE’s advantages makes it difficult to justify the significant development costs for any but the highest-value applications.

That said, the inexpensive NCA is likely to be an approach that does endure. It literally transforms network communication into an inexpensive, pluggable physical component. By doing so, it provides an avenue for dealing with the extreme cost pressure inherent in microcontroller applications, while providing an incremental option of genuine network citizenship when the customer will pay for it. Q

 

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MIKE O’DELL is a venture partner at New Enterprise Associates (NEA). His primary interest is the structure and behavioral dynamics of large, complex systems. He works with NEA’s technology team to identify early-stage information technology, communications, and energy opportunities. Odell came to NEA from UUNET Technologies, where he was chief scientist, responsible for network and product architecture during the emergence of the commercial Internet. He has also held positions at Bellcore (now Telcordia), a GaAs Sparc supercomputer startup, and a U.S. government contractor. He was founding editor of Computing Systems, an international refereed scholarly journal. He received his B.S. and M.S. in computer science from the University of Oklahoma. © 2009 ACM 1542-7730 /09/0200 $5.00