The Internet was designed to treat all traffic with equal priority. Web pages from Google or Bank of America are transmitted via the same network nodes at the same speeds (and with the same occasional logjams) as the latest updates from Mom and Pop's RV Park.

But this tradition of "network neutrality" has never had the force of law. Now a movement is afoot in Congress to codify this egalitarian idea, as part of upcoming revisions to the Telecommunications Act, which was last updated in 1996.

Meanwhile, lobbyists for phone and cable companies have launched an all-out campaign to keep network neutrality requirements out of the legislation -- claiming they're ready to offer premium services to their largest customers, and that they need to do so to recoup the billions they've invested in faster Internet backbone connections and fiber-optic links to private homes.

In such a world -- where companies who can afford to pay will reach consumers faster -- websites owned by organizations or individuals who can't pay the fees would be relegated to second-class status. And that might ultimately shrink the range of resources and viewpoints available to average Net users, according to proponents of network neutrality.

"The Internet has been an unrivaled medium for free speech," says Craig Aaron, communications director for Free Press, a nonpartisan Internet policy think tank in Washington, DC. "With network neutrality, any little website can grow into the equivalent of a TV network and attract a mass audience. But if we give the network to the operators, then we have something that looks a lot more like cable TV, where there are 'choices' -- but they're all pre-selected by the programmers and the channels that get favored are the ones they own."

Millions of dollars are being spent to sway members of Congress on this issue, and lawmakers are likely to settle it within the next year. If regulations limiting tiered Internet services become law, nothing much will change for consumers. If the principle isn't codified, however, the decks will be clear for the nation's largest Internet service providers -- the cable and telephone companies -- to create a "pay for play" Internet.

What might this two-tiered model look like? The cable and telephone companies haven't been explicit about their plans for offering faster access to higher-paying customers; but using documents from network hardware and software makers, such as Cisco Systems, it's possible to construct a snapshot of how a tiered Internet would work -- and what it would be like to use it.

For one thing, a next-generation Internet with premium toll "roadways" would be fundamentally unlike the current network, which was not engineered to separate traffic into faster and slower pathways.

Under the standard Internet Protocol, information hops across the Web from node to node in small bundles, called packets, each bearing the address of its destination. And these nodes are indifferent about the content of packets; packets that belong to an instant message between two love-struck 14-year-olds are handled with the same care and swiftness as a video conference between two multi-national corporations.