• by Wendy Davis , Staff Writer @wendyndavis, January 19, 2009

Last year, faced with an irate Federal Communications Commission, Comcast said it would stop blocking peer-to-peer visits to manage congestion on its network. Instead, the company promised to control traffic without regard to the type of content or application.

But it's not clear that Comcast is keeping that promise. DSLReports.com, says the FCC is now questioning Comcast about its policies for Voice over Internet Protocol telephone service. Specifically, the FCC wants to know why the company says some VoIP phone calls might occasionally sound "choppy" -- but not those placed through Comcast's own digital phone service.

In a Jan. 18 letter to Comcast vice president for regulatory affairs Kathryn Zachem, the FCC demanded "a detailed justification for Comcast's disparate treatment of its own VoIP service as compared to that offered by other competitors on its network."

"To the extent that Comcast maintains that its VoIP offering is a telephone service ... it would appear that the fee Comcast assesses its customers for VoIP service pays in part for the privileged transmission of information of the customer's choosing across Comcast's network," states the letter, which was signed by Dana Shaffer, chief of the FCC's wireline competition bureau, and general counsel Matthew Berry.

Last year, Comcast said it would manage its network by slowing down a small portion of traffic during periods of heavy use. The new system involves two classes of traffic -- a "priority best effort" category and the potentially slower "best effort" category. Comcast downgrades subscribers to the "best effort" bucket if they have used a high amount of bandwidth in a 15-minute period. When those users decrease bandwidth use for a 15-minute period, they're returned to the "priority best effort" state.

But Comcast says on its Web site that it's excluding its own digital voice services from this two-tiered system.

"Comcast Digital Voice is a separate facilities-based IP phone service that is not affected by this technique," the company writes. "Comcast customers who use VoIP providers that rely on delivering calls over the public Internet who are also using a disproportionate amount of bandwidth during a period when this network management technique goes into effect may experience a degradation of their call quality at times of network congestion."

At the same time, Comcast also indicates that the difference in treatment might not affect users. "VoIP calling in and of itself does not use a significant amount of bandwidth," the company wrote. "Furthermore, our real-world testing of this technique did not indicate any significant change in the quality of VoIP calls, even for managed customer traffic during periods of congestion."

A Comcast spokesperson tells MediaPost that the company is reviewing the letter. "We have fully complied with the FCC's order regarding our congestion management practices," the spokesperson says.

The FCC gave Comcast until Jan. 30 to respond.