Is quality of service necessary? AT&T drives to control net via technology but AT&T Labs researcher finds simpler is better

Is quality of service necessary? AT&T drives to control net via technology but AT&T Labs researcher finds simpler is better

David S. Isenberg

A T&T carries the burdens of incumbency in a world exploding with disruptive technology. My concept of a Stupid Network tries to explain the disruptions that telcos must face, but AT&T still doesn’t seem to get it.

Recently, Dan Sheinbein, AT&T’s vice president of network architecture & development, told the Star-Ledger (Newark, N.J.) that the Stupid Network has “not been a particularly active area of discussion” at AT&T lately. Even more recently, Sheinbein told me, “On balance, AT&T’s network is getting smarter.”

To me, the Stupid Network – the dumb transport component of people’s applications, designed simply to “deliver the bits, stupid” – is a consequence of the new abundance created by technology’s headlong spurt. It’s enabled by the Internet Protocol (IP). (See for details.)

AT&T Chairman Mike Armstrong says he’s embraced IP, but the strategy he articulates for AT&T is clearly “intelligent.” He says that if AT&T controls the interfaces, specifications, protocols, standards and platforms of the network, it can weave them into a set of seamless services. If AT&T could pull this off, it would be able to hold back the rising tide of commoditization and reglue the delaminating value proposition. But to do that, Armstrong somehow would have to get AT&T back into the equipment game, stamp out IP and repeal Moore’s Law.


At the edge of Armstrong’s awareness, AT&T Labs’ mathematician Andrew Odlyzko is researching the economics of networks. He is no Stupid Network ideologue. In fact, he used to believe that the Internet needed such “intelligent” complications as Quality of Service (QoS) and differential pricing. Both of these make networks treat different kinds of data differently.

But now Odlyzko’s research has led him to the conclusion that simpler is better. Odlyzko, who came to Bell Labs Research 23 years ago straight from his MIT doctorate, has convinced himself that simply adding bandwidth could “turn out to be the cheapest approach when one considers the costs of QoS solutions for the entire information technologies industry.”

Internet telephony, introduced in 1995, made the apparent need for QoS acute. Until then, Internet traffic consisted of email and file transfers, and then Web page information. For these applications, fast transmission is nice, but delays do not make them unusable. Not so with Internet telephony – people just can’t have conversations when there’s more than a few hundred milliseconds of delay.

Differential pricing is the first cousin of QoS. If you have different levels of service, you need some motivation for people to use the lower-grade service. Otherwise, the argument goes, people will always use the best service whether they need to or not.

Odlyzko now thinks that even simple QoS schemes may be too complex. Two years ago, he proposed a simple QoS plan that used only differential pricing. He called it Paris Metro Pricing (PMP), after the Parisian subway system of letting people who pay more ride in “first class” cars. These cars are physically identical, but less crowded only because they cost more. In Odlyzko’s vision, a PMP Internet would have two identical, parallel channels, and one would be designated “first class.” It would cost more, so it’d have less traffic and provide better service. But Odlyzko now says that administering parallel channels would add more complexity than users or service providers desire.


Lightly loaded networks don’t need QoS. They’re adequate even for Internet telephony. Odlyzko found that on most data nets, traffic is surprisingly light. (His analogy for the typical corporate Intranet is “a 100-lane highway [for] a few fast cars.”) Also, he says, other work showed only 40% of Internet congestion is due to transmission bottlenecks, and only a very few choke points are to blame. These, he says, are relatively cheap to replace.

As intelligence migrates to the edges of the Internet, so does network administration, Odlyzko says, “where it is wastefully duplicated,” at great expense because it requires human expertise. He concludes that “The complexity of the entire Internet is so great, that the greatest imperative should be to keep the system as simple as possible. The costs of QoS or pricing schemes are high, and should be avoided … we should seek the simplest scheme that works.”

And that simplest scheme, Odlyzko says, involves flat-rate pricing and overprovisioned, lightly loaded networks with a single grade of best-effort service. This scheme takes advantage of rapidly improving routing and transmission technologies, and it doesn’t mess with any of the properties that made the Internet great. But it’ll be a hard one for AT&T to control.

Andrew Odlyzko’s work is at David S. Isenberg ( thanks Jock Gill for comments on an earlier draft. Readers may send comments to anrespond@ameri

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