PlusNet uses DPI to provide what Armstrong calls “a network heartbeat” every 15 minutes, looking at each individual customer account and updating the customer profile. PlusNet also encourages customers to do their most intensive downloads – such as videos – overnight, but making those downloads free.”

Two-thirds of customers pay a fixed price per month either because they don’t exceed their usage allowance or they choose to not pay more, Armstrong said. Among PlusNet’s more avid users are gamers and users of the BBC’s new iPlayer streaming video service, Armstrong said.

”We certainly have a higher usage profile than most ISPs, but by no means do we attract just heavy downloaders,” he said. “We don’t get the all-you-can-eat crowd, but we do attract a more savvy and sophisticated audience, and what they want is high quality. Because we have been able to manage the network efficient, the service is more attractive to them.”

PlusNet goes to great lengths to explain how it manages its network on its Web site, even though Armstrong admits about 75% of its customers “don’t care and don’t need to care.

“What we have successfully done in the UK is actually express DPI far better as a customer benefit,” Armstrong said. “I think the most important thing is transparency and explaining to the customer why you are doing what you are doing, and why it is in their interests. Our network is actively recommended for people who are looking for a really good gaming service, and as the BBC iPlayer has taken off, we get more and more customers who recognize the benefits of having guaranteed quality. It’s why we are one of the few ISPs in the U.K. that is growing.”

[Note: This is the fourth installment in a series on DPI. Previous installments: Part 1, Part 2, Part 3]