Deep packet inspection has come under fire from consumer groups, Net Neutrality proponents and even members of the U.S. Congress. But one U.K. ISP is using DPI in a way intended to improve customer service – with its customers’ permission.

PlusNet is a BT-owned ISP with about 300,000 users that began using Ellacoya’s IP Service Control System – now part of Arbor Networks since its acquisition of Ellacoya – in 2006 to launch a Subscriber Service Portal that allows its customers to monitor their own usage, among other things.

(To see PlusNet’s guide to the tool where customers can see their individual usage, go here: http://www.plus.net/support/broadband/usage/vmbu.shtml.)

“We have been using DPI as part of our overall network management strategy back since 2005,” said Neil Armstrong, products director at PlusNet. “From the beginning, though, we made it very clear and transparent with customers in terms of what we are doing and why we are doing it.”

After first using DPI as a way to inspect and prioritize traffic to protect services such as VoIP and gaming from latency caused by network congestion, PlusNet took things to a new level. The company decided to offer four different classes of service for residential and business customers – or eight classes total – and to further allow customers to customize their particular service when they signed up.

“When we launched this, we gave every one of our customers the chance to walk away from their contracts,” Armstrong said. The vast majority stayed and PlusNet has continued to grow from the 100,000 customers it had in 2006.