Big news last week in the ongoing network neutrality debate. Over the holidays, AT&T (T) hashed out an agreement with the FCC for its merger with BellSouth in which AT&T agrees to abide by some of the principles of network neutrality (The primary document). This is a major development for an issue that's pitted Internet companies (Google (GOOG), Yahoo (YHOO), et al) against the telcos. And the Internet companies seem to have won this latest round.

First, a quick primer on network neutrality. Network neutrality is the idea that internet service providers can't discriminate between data packets based on their content. For instance, Google's data has to be treated the same as Yahoo's, and telco companies can't create tiers of service in which some sites can pay to have their content delivered faster and with greater reliability than others. (FORTUNE ran a 60 Second Briefing on this last year. And if that's still too reductive, see Wikipedia for more.)

There were bills floating around Washington in the last Congressional session that sought to put some of these principles in writing, but none got passed. This FCC agreement is in essence the first time the government will be trying to enforce net neutrality, and AT&T gets to be the guinea pig. The FCC agreement prevents AT&T from discriminating between where data comes from—but leaves room for AT&T to prioritize certain kinds of data (for instance, delivering video faster). This seems like a win for consumers.

But the Browser has a question: how will the FCC detect discrimination and enforce this policy? Edward Felten, head of the Center for Information Technology Policy at Princeton, raised just this point in a paper last year, following a scenario in which consumers discover they're having jitter problems with their VoIP services:

The most challenging possibility, from a policy standpoint, is that TelCo didn't take any obvious steps to cause the problem but is happy that it exists, and is subtly managing its network in a way that fosters jitter. Network management is complicated, and many management decisions could impact jitter one way or the other. A network provider who wants to cause high jitter can do so, and might have pretextual excuses for all of the steps it takes. Can regulators distinguish this kind of stratagem from the case of fair and justified engineering decisions that happen to cause a little temporary jitter?

Surely some discriminatory strategies are so obvious, and the offered engineering pretexts so weak, that we could block or punish them without worrying about being wrong. But there would be hard cases too. Net neutrality regulation, even if justified, will inevitably lead to some difficult line-drawing.

Maybe the Browser is missing the nitty gritty technicalities here, but it seems like decisions about how to priotize data—conscious or otherwise—have to be made all the time when managing a network. One might imagine a circumstance where one network provider has an infrastructure that favors data packets from one VoIP provider over others just by virtue of the engineering. Does AT&T have to rectify that on behalf of the other VoIP companies? How can we tell the difference between pernicious discrimination and the types of network failings that are just the price of doing business?