Last week, Nevis Networks announced that upgrades to its gear would cut the time it took for the equipment to scan end-user machines before they are allowed network access.

The reduction was significant, down from 30 seconds to less than 10 seconds. Which raises the point that security takes time, and raises the question how much time are end users willing to spend being safe?

With NAC, it’s not just the time it takes to scan. Consider the case of a remote user whose job calls for making presentations to customers that include the latest sales figures. In preparing for a meeting, the worker tries to access the network for updated numbers but can’t get on because somewhere along the line the machine being used has fallen shy of security policies.

Let's assume the NAC gear being used is integrated with a means for updating machines so they come into compliance. Great, but reconfiguring or downloading and installing updates and patches also takes time - time that the remote user might not have.

The problem might be less specific - NAC takes long enough that workers avoid using network resources because they consider it too much trouble. Productivity can be affected.

The lesson for potential NAC customers; check out the performance data of the NAC gear that you're considering. Customers should also test the gear with end users in various departments to find out whether the technology eats up too much time for some users, and whether some dispensation from NAC should be allowed in critical cases.

Tim Greene is senior editor at Network World.