The Internet seems infinite -- tens of billions of Web pages and counting -- but the cables that carry the Internet to your home or office are decidedly more limited. That's why no less than the "future of the Internet" is at stake as telecom companies, consumer groups, the Federal Communications Commission and U.S. lawmakers debate whether Internet service providers should be able to choose what content moves, and when it moves, across their networks.

In part, it's a supply-and-demand issue. On the occasions when the demand for Internet bandwidth is high, whose usage should receive priority? Should the Internet be first-come, first-served? Or should Internet service providers be able to interrupt your usage -- as you download a high-resolution movie, songs from iTunes, TV shows from Vuze -- in order to allow speedier correspondence and Web surfing for others?

Then there are privacy issues -- the phone company can't disconnect your phone call based on the content of the message. Should an Internet provider be able to block your service based on the content of the download?

The million-dollar (actually, billions of dollars) question is, "To what extent should your broadband provider be allowed to discriminate in the way it handles your communications?" said Jon Peha, professor of engineering and public policy at Carnegie Mellon University. He's versed on the subject, and in February moderated a debate on "net neutrality" at the William Pitt Union in Oakland.

Now, Congress and the FCC have been called in to referee the fight. In November, Vuze (an Internet platform for sharing big digital files) filed a petition with the FCC, asking the commission for a ruling that would restrict "throttling," the term for when ISPs deliberately block or slow uploads and downloads to preserve bandwidth for other users. Congress, meanwhile, is mulling "neutrality" legislation that could restrict an ISP's ability to manage the very networks that it owns and operates. (A U.S. Senate Committee on Commerce, Science and Transportation hearing on the subject was dramatically titled "the future of the Internet.")

Comcast is one of the villains here -- at least in the eyes of Vuze and other BitTorrent-style file-sharers. Last year, the Associated Press reported that Philadelphia-based Comcast, which provides high-speed Internet to almost 50 million households, was interrupting access to legal file-sharing programs. Vuze did its own experiment, creating a software plug-in that could track how often ISPs interrupt downloads by sending "false reset" messages to the users, telling computers to quit downloading and start over later.

Is it traffic management or is Comcast just being a bully?

At an FCC hearing in February, Comcast Executive Vice President David L. Cohen told the commission that the reset orders were a reasonable method of traffic management during busy usage periods. "Independent research has shown that it takes as few as 15 active BitTorrent users uploading content in a particular geographic area to create congestion sufficient to degrade the experience of the hundreds of other users in that area," he said. "Bandwidth-intensive activities not only degrade other less-intense uses, but also significantly interfere with thousands of Internet companies' businesses."

Free Press, the media reform group that has been vocal on the issue and started a "Save the Internet" petition, says this is tantamount to censorship, and claims that such "network management" techniques are a violation of the FCC dubiously enforceable policy principles (specifically, principle No. 2, "Consumers are entitled to run applications and use services of their choice, subject to the needs of law enforcement.")

But economist Hal Singer, president of Criterion Economics, says Free Press and its ilk are less worried about the traffic delays and more worried about the future -- that Comcast or other dominant ISPs will begin picking favorites, charging some content providers (such as Vuze) a big fee to access the network, but allowing cheap, unfettered access for distributors with favored status.

That hasn't happened yet, says Mr. Singer.

"It's speculative and premature to write nondiscrimination rules" for discrimination yet to occur, he said. If one heavy downloader "ruins the experience [for others], I understand why they want to toggle that down ... most reasonable people would say, let Comcast do what it needs to do."

It seems like a small issue now, but it figures to become a huge deal in the years to come, as ISPs extend the geographic availability of high-speed Internet, and as downloading movies and TV shows, at higher resolution levels, becomes more commonplace. Jim Cicconi, AT&T's vice president of legal affairs, said last month to a group in London that video downloads will increase to the point that all of the Internet's bandwidth will be overrun in two years.

Today, video accounts for less than a third of Internet traffic; by 2010, it could hit 80 percent, he said, according to various published reports. It's a looming "exa-flood," the day when the amount of data humming through the Internet exceeds an exabyte, or 1 billion gigabytes.

"The surge in online content is at the center of the most dramatic changes affecting the Internet," he said. "In three years' time, 20 typical households will generate more traffic than the entire Internet did in 1995."

But bloggers, watchdog groups and many tech experts say ominous speeches like those are just scare tactics to make Congress think twice about regulation. Bandwidth worries can be taken care of with upgrades to the system, especially to the "last mile" of cable that carries phone, cable and Internet traffic from network routing points into homes and businesses.

"They're trying to scare people," said Andrew M. Odlyzko, an Internet professor from the University of Minnesota.

"Of course, the fact that somebody is trying to scare you doesn't mean they're not right. Hurricane Katrina was one of the best-predicted disasters in history."