Thirteen senators called on Federal Communications Commission chairman Tom Wheeler to reclassify Internet service providers as common carriers in order to protect net neutrality.

The lawmakers, led by Sen. Edward Markey, D-Mass., submitted a letter directing the FCC to classify the providers under Title II of the Communications Act, the same law used to regulate telecommunications services. The senators said broadband provides an “essential function” comparable to telephone services, and they believed such a change would prevent discriminatory practices that would allow some content to be delivered faster than other content.

The letter also denounced paid prioritization, or the creation of Internet “fast lanes” that the FCC is considering implementing. The senators said such practices would leave small businesses in the “slow lane.”

“An open Internet has become the world’s most successful platform for innovation, job-creation and entrepreneurialism,” the senators wrote. “An open Internet enables freedom of expression and the sharing of ideas around the world.”

The letter is signed by Sens. Al Franken (D-Minn.), Bernie Sanders (I-Vt.), Charles Schumer (D-N.Y.), Ron Wyden (D-Ore.), Richard Blumenthal (D-Conn.), Jeff Merkley (D-Ore.), Elizabeth Warren (D-Mass.), Sheldon Whitehouse (D-R.I.), Ben Cardin (D-Md.), Kirsten Gillibrand (D-N.Y.) and Corey Booker (D-N.J.).

Markey and a handful of the signers joined representatives from Etsy, Public Knowledge and Free Press on Tuesday morning to discuss net neutrality at a press conference.

The first FCC comment period was set to close at 9 p.m. PST Tuesday, but the FCC decided to extend the comment period to July 18 on Tuesday morning after an influx of comments crashed its site. The FCC had received more than 650,000 comments on its website as of Monday.

The Telecommunications Industry Association (TIA) also submitted comments to the FCC on Tuesday, arguing against classifying broadband under Title II.

“The Commission has considered Title II classification for broadband ISP services several times over the last dozen years – and each time, whether under Democratic or Republican leadership, has rejected it,” the TIA said in its comment. “Recreating a common carrier regime for broadband ISP service now, years after the Commission set a different regulatory course, would thwart the operation of the ‘virtuous cycle’ of investment, competition, and innovation […] and throw the industry into disarray.”

AT&T has argued that reclassifying broadband under Title II would not make paid prioritization illegal, but Y Combinator released a letter debunking that claim yesterday. In it, the tech accelerator argued the FCC can only impose a nondiscrimination rule on the providers if they are reclassified.

After the first comment period closes, the FCC will begin its reply commenting period that is slated to extend until Sept. 10. A spokesman from the FCC tells me citizens may continue to submit comments that are not replies to other comments during this period.