Since at least Spring Comcast has been engaged in a very small trial of a network DVR in Boston, where fewer than a dozen people are testing a proof of concept for Comcast's implementation of the technology. The service should be very similar to a network DVR platform deployed by Cablevision, which was delayed repeatedly due to lawsuits from an entertainment industry worried about loss of control and ad revenue. Fierce Cable has noticed that Comcast this week filed for a patent for the as-yet-unannounced technology. "These local hard-drive-based DVRs are well appreciated by users, but there is an ever-present demand for greater flexibility and functionality in how content is offered to, stored and managed for, users," says Comcast in the filing.