Why are our Internet lines in danger of jamming up?
One way of looking at it is this: Internet service providers have been serving us an all-you-can-eat buffet for years. That has worked great, because they've had more food than they knew what to do with and we've enjoyed the simplicity of a flat price and our pick of the dishes.
But every year, our appetites have been growing. Some of us have turned into real gluttons, taking advantage of the pricing to eat 10 times as much as the majority of customers. The food is running out, and diners are starting to get in each other's way at the table.
Now, Internet service providers are starting to limit the availability of dishes that are popular with the big eaters (controlling traffic). They're also considering telling us to stick to two helpings per person (limiting monthly downloads). They might end up doing both.
The consumer ISPs at the forefront of these trends are cable providers. Comcast Corp. has become the poster case for traffic control by hampering some file sharing, and Time Warner Cable Inc. is testing monthly bandwidth caps.
This is hardly an accident, because congestion is a greater threat to cable companies.
In the basic configuration, each cable serves about 500 households, which share about 40 megabits per second of download capacity. If each household gets Internet service with a maximum download speed of 10 mbps, that means four of them downloading at full speed can saturate the connection.
"Fundamentally, the cable companies have come at this from kind of a disadvantage," said Rob Malan, chief technology officer of Arbor Networks, which provides traffic-management equipment. "One greedy person on that network knocks the whole neighborhood offline."
Cable companies can employ various tricks to increase capacity. For instance, they can devote additional channels to data, or they can "split the node" to reduce the number of households on each cable. A new modem technology called Docsis 3.0 that is starting to roll out this year can increase download capacity on a cable to 160 mbps.
But these solutions cost money. Stan Schatt, an analyst at ABI Research, estimates that cable providers need to spend $24 billion through 2012 to upgrade their networks.
Phone companies like AT&T Inc. and Verizon Communications Inc., which operate digital subscriber lines, aren't immune to congestion. But since phone lines aren't shared, bottlenecks for DSL service are deeper in the system, on routers and fiber-optic links that are easier to upgrade.
It's nothing new that cable and phone companies have sold more bandwidth than they can provide to everyone at the same time. The practice of "oversubscription" is as old as telecommunications, and it's the only way to build a network consumers can afford. The phone network, after all, has never been able to handle everyone trying to call at once.
Meanwhile, Internet use keeps climbing, with video being the big driver in recent years. Google Inc.'s YouTube, which started up in 2005, already accounts for about 10 percent of Internet traffic, according to Ellacoya Networks (which is being acquired by Arbor Networks).
"If you want to think of video, think of it as the cholesterol that has the potential to clog the arteries of the Internet," said ABI's Schatt.