Recently published research suggests the four major wireless carriers are throttling video traffic and three Senate Democrats want to know what's going on. Senators Edward Markey (Mass.), Richard Blumenthal (Conn.), and Ron Wyden (Ore.) sent letters to AT&T, Sprint, T-Mobile, and Verizon Wireless about the allegations with a demand for a formal explanation from each. "All online traffic should be treated equally, and internet service providers should not discriminate against particular content or applications for competitive advantage purposes or otherwise," said the senators in their letter. The Wehe testing platform showed that AT&T throttled NBC Sports, Netflix, and YouTube; Sprint throttled Amazon Prime, Netflix, Skype Video calls, and YouTube; T-Mobile throttled Amazon Prime, NBC Sports, and Netflix; and Verizon Wireless throttled Amazon Prime, Netflix, and YouTube. T-Mobile also engaged in boosting, which provides unthrottled video streaming for a short time before eventually throttling it. Carriers' usage policies may allow for some throttling or down-graded resolution, and, due to the loss of net neutrality protections, current law does not explicitly prohibit throttling. However, the law does say that carriers have to disclose their throttling policies, if any exist. In this case, it's not clear if any of the carriers have specifically stated that they'll throttle the aforementioned apps and services. AT&T disputed the research and Sprint told Ars Technica that it does not "impose any restrictions on VoIP traffic or VoIP services." The carriers have until December 6 to answer the senators' questions.