December 13, 2018

New Net Neutrality Paper

I just released a new paper on net neutrality, called Nuts and Bolts of Network Neutrality. It’s based on several of my earlier blog posts, with some new material.

Quality of Service: A Quality Argument?

One of the standard arguments one hears against network neutrality rules is that network providers need to provide Quality of Service (QoS) guarantees to certain kinds of traffic, such as video. If QoS is necessary, the argument goes, and if net neutrality rules would hamper QoS by requiring all traffic to be treated the same, then net neutrality rules must be harmful. Today, I want to unpack this argument and see how it holds up in light of computer science research and engineering experience.

First, I need to make clear that guaranteeing QoS for an application means more than just giving it lots of bandwidth or prioritizing its traffic above other applications. Those things might be helpful, but they’re not QoS (or at least not the kind I’m talking about today). What QoS mechanisms (try to) do is to make specific performance guarantees to an app over a short window of time.

An example may clarify this point. If you’re loading a web page, and your network connection hiccups so that you get no traffic for (say) half a second, you may notice a short pause but it won’t be a big deal. But if you’re having a voice conversation with somebody, a half-second gap will be very annoying. Web browsing needs decent bandwidth on average, but voice conversations needs better protection against short delays. That protection is QoS.

Careful readers will protest at this point that a good browsing experience depends on more than just average bandwidth. A half-second hiccup might not be a big problem, but a ten-minute pause would be too much, even if performance is really snappy afterward. The difference between voice conversations and browsing is one of degree – voice conversations want guarantees over fractions of seconds, and browsing wants them over fractions of minutes.

The reason we don’t need special QoS mechanisms for browsing is that the broadband Internet already provides performance that is almost always steady enough over the time intervals that matter for browsing.

Sometimes, too, there are simple tricks that can turn an app that cares about short delays into one that cares only about longer delays. For example, watching prerecorded audio or video streams doesn’t need QoS, because you can use buffering. If you’re watching a video, you can download every frame ten seconds before you’re going to watch it; then a hiccup of a few seconds won’t be a problem. This is why streaming audio and video work perfectly well today (when there is enough average bandwidth).

There are two other important cases where QoS isn’t needed. First, if an app needs higher average speed than the Net can provide, than QoS won’t help it – QoS makes the Net’s speed steadier but not faster. Second – and less obvious – if an app needs much less average speed than the Net can provide, then QoS might also be unnecessary. If speed doesn’t drop entirely to zero but fluctuates, with peaks and valleys, then even the valleys may be high enough to give the app what it needs. This is starting to happen for voice conversations – Skype and other VoIP systems seem to work pretty well without any special QoS support in the network.

We can’t say that QoS is never needed, but experience does teach that it’s easy, especially for non-experts, to overestimate the importance of QoS. That’s why I’m not convinced – though I could be, with more evidence – that QoS is a strong argument against net neutrality rules.

AOL, Yahoo Challenge Email Neutrality

AOL and Yahoo will soon start using Goodmail, a system that lets bulk email senders bypass the companies’ spam filters by paying the companies one-fourth of a cent per message, and promising not to send unsolicited messages, according to a New York Times story by Saul Hansell.

Pay-to-send systems are one standard response to spam. The idea is that raising the cost of sending a message will deter the kind of shot-in-the-dark spamming that sends a pitch to everybody in the hope that somebody, somewhere, will respond. The price should be high enough to deter spamming but low enough that legitimate email won’t be deterred. Or so the theory goes.

What’s different here is that senders aren’t paying for delivery, but for an exemption from the email providers’ spam filters. As Eric Rescorla notes, this system creates interesting incentives for the providers. For instance, the providers will have an incentive to make their spam filters overly stringent – so that legitimate messages will be misclassified as spam, and senders will be more likely to pay for an exemption from the filters.

There’s an interesting similarity here to the network neutrality debate. Net neutrality advocates worry that residential ISPs will discriminate against some network traffic so that they can charge web sites and services a fee in exchange for not discriminating against their traffic. In the email case, the worry is that email providers will discriminate against commercial email, so that they can charge email senders a fee in exchange for not discriminating against their messages.

Is this really the same policy problem? If you advocate neutrality regulations on ISPs, does consistency require you to advocate neutrality regulations on email providers? Considering these questions may shed a little light on both issues.

My tentative reaction to the email case is that this may or may not be a smart move by AOL and Yahoo, but they ought to be free to try it. If customers get fewer of the commercial email messages they want (and don’t get enough reduction in spam to make up for it), they’ll be less happy with AOL and Yahoo, and some will take their business elsewhere. The key point, I think, is that customers have realistic alternatives they can switch to. Competition will protect them.

(You may object that switching email providers is costly for a customer who has been using an aol.com or yahoo.com email address – if he switches email providers, his old email address might not work any more. True enough, but a rational email provider will already be exploiting this lock-in, perhaps by charging the customer a slightly higher fee than he would pay elsewhere.)

Competition is a key issue – perhaps the most important one – in the net neutrality debate too. If commercial ISPs face real competition, so that users have realistic alternatives to an ISP who misbehaves, then ISPs will have to heed their customers’ demand for neutral access to sites and services. But if ISPs have monopoly power, their incentives may drive them to behave badly.

To me, the net neutrality issue hinges largely on whether the residential ISP market will be competitive. I can’t make a clear prediction, but I know that there are people who probably can. I’d love to hear what they have to say.

What does seem clear is that regulatory policy can help or hinder the emergence of competition. Enabling competition should be a primary goal of our future telecom regulation.