The advocacy group Public Knowledge has filed a formal petition with the Federal Communications Commission, arguing that Comcast is in violation of its NBC-Universal merger agreement with the regulatory body.

The move was filed Wednesday, and it comes after months of changes that Comcast has made to its data management policies. In March 2012, the company said that Xfinity TV On Demand video played over an Xbox 360 would not count against a 250GB data cap. In May, the company said it would suspend all caps for the moment, but would trial two versions of a 300GB cap model.

"Public Knowledge requests that the Commission move to enforce the conditions it imposed upon Comcast as part of Comcast’s merger with NBC-Universal," the organization wrote in the petition. "Comcast’s decision to exempt its online video service from its own data caps is precisely the type of behavior contemplated and barred by the Commission in the Merger Order. As such, the Commission must move to end the behavior and prevent it from being repeated in the future."

Also in May 2012, many network analysts, including Vint Cerf himself (the co-inventor of TCP/IP!), raised questions about Comcast’s practices after finding the company was not serving its Xfinity TV service through a “private IP network.”

So why wait until now to file a petition to the FCC?

“We wanted to see if Comcast was going to take any steps to see if they would address this on its own, but they didn’t,” said Michael Weinberg, a vice president at Public Knowledge, in an interview with Ars on Wednesday.

“There’s no suggestion that they’re going to get rid of the caps. This is a pressing issue that has a real-world impact today. This is something that is true today, and we know that Comcast is discriminating against every other video competitor.”

In an e-mail sent to Ars, a Comcast spokesperson said the company had no immediate response.

“We generally don’t comment on every press release or petition put out by Public Knowledge,” wrote Sena Fitzmaurice, adding that the 300GB “test approaches” are underway in Nashville.

The FCC did not respond to immediate requests for comment.

UDPATE: FCC spokesperson Mark Wigfield e-mailed Ars later Wednesday morning to say: "We will review the petition."