"We found out from most customers that guest access is still the most common test bed for NAC, they're not trying to set up complex policies with these systems yet, they want to restrict Internet access and test rules to see how it works," said Cisco NAC marketing manager Irene Sandler. "From there they can broaden the use cases, but that's not what they're working on yet."

When it comes to Cisco's NAC detractors, Sandler said that users shouldn't "confuse vision with deploy-ability," pointing out that few of the other vendor products she has seen can live up to the guest access piece of the equation, let a lone the rest of the larger concept espoused by Hanna and others.

Many of those companies have only a handful of customers and are trying to make a name for themselves, while Cisco already has well over 2500 users of its NAC appliances, she noted.

Part of the issue, she said, is that so many companies have created different definitions of NAC to fit their products into the space that everyone seems to have adopted their own meaning of the term.

The difference between Cisco's network admission control and the more generic term of network access control may have grown over the last few years, but not as dramatically as some might argue, Sandler defended.

"People can try to expand the definition of NAC if they have a product that fits within that definition," she said. "Some companies are actually selling intrusion protection; it has become in some cases not a question of Cisco having a certain capacity, but whether or not we define NAC as the same thing as some other vendors."

Alan Shimel, the chief strategy officer at NAC software vendor StillSecure -- who also authors a well-read industry blog, admits that part of the problem with people's understanding of where exactly the market stands in terms of its evolution is derived from contrary marketing.

As with any hot IT sector, a number of players who had previously labeled their products otherwise adopted the NAC banner as the niche began to draw interest several years ago, said the expert.

Hanna, he said, is merely trying to drive the NAC sector into the more comprehensive future many hope for, while people like Nevis' Wild are merely trying to align themselves with potential demand.

For customers to embrace the broader vision of NAC will take time, and the many "Johnny Come Lately's" putting pressure on the market aren't helping to foster realistic expectations, Shimel said.

"I'm not saying that these other types of behavior analysis and post-admission technologies aren't important to extending NAC, they are, but let's not lose sight of the fact that the initial NAC functionality was envisioned around access," Shimel said.

"Things have become terribly confusing for end users; any time you have an over-hyped niche like NAC you get a lot of people with business models that have failed jumping on the bandwagon," he said. "This corrupts the message as people try to make it their own, and there's probably no bigger poster child for that sort of problem right now than NAC."