Comcast just can’t get the hang of this network neutrality thing.

Last summer, the FCC chastised Comcast, a cable and Internet provider, for selectively blocking certain kinds of customer Internet traffic – specifically, services that threatened competition to its cable business. We reported on the incident here, and followed up here and here. Going forward, said the FCC, Comcast was free to manage traffic on its network, but not in ways that discriminate based on the customer’s content.

Comcast responded with a reasonable plan. In essence, it gives a customer’s data packets lower priority when the neighborhood system is danger of overloading, and that same customer has been running at near-capacity data rates for at least 15 minutes. The temporary priority shift gives other people’s data a chance to get through. Comcast warned that a customer running voice-over-Internet (VoIP ) along with high-volume traffic runs the risk of “choppy” sounding calls when the voice packets get shunted aside.

The plan seems in line with the FCC’s requirements. A non-story. But for one small detail.

The Comcast website tells customers they can preserve voice quality by subscribing to Comcast’s own VoIP service, while using those other VoIP providers can result in degradation. This looks like the kind of discrimination Comcast promised to avoid. It caught the eye of the FCC, which wants Comcast to justify the disparate treatment. With a touch of sarcasm, the FCC also asks how Comcast’s own VoIP service affects network congestion differently from other Internet traffic.

Comcast made additional trouble for itself by describing its VoIP service as “facilities-based.”   The marketing intern who wrote the copy probably didn’t know it, but this is a code word. Along with other factors, it can trigger a requirement for very expensive payments to other carriers. (Just a reminder, people – show everything to your lawyers.) The FCC invites Comcast to rethink its explanation of how the service works.