The 16‑kilobyte curtain, confirmed. Cloudflare accuses Russia of throttling its traffic

In a detailed breakdown, Cloudflare has confirmed that Russian internet providers are interfering with web traffic in a way that causes connections to suddenly fail just after they start. The interference affects all major internet protocols, whether a site is using older protocols like TCP or newer ones like HTTP/2 and QUIC. 

“High packet loss is a strong signal but does not on its own indicate throttling, since there might be other explanations”, notes Cloudflare. But in this case, the packet loss lines up with a much more specific and deliberate pattern that they refer to as “resets and timeouts”: say, a user clicks a link, the browser starts loading the page, and then the connection is quietly severed before any real content can be delivered. From the user’s perspective, it might look like the site is just slow or broken. But in reality, the connection is being cut off just after the first few packets (10 to 14), transferring no more than 16 kilobytes of data. That threshold is too small for most modern websites to function. 

“A new tactic that began on June 9 limits the amount of content served to 16 KB, which renders many websites barely usable,” the company wrote in its report. The throttling applies across all major protocols (including older standards like HTTP/1.1 as well as newer, encrypted ones like HTTP/2 and HTTP/3) and affects both traditional connections (TCP/TLS) and modern ones like QUIC. 

Cloudflare reports that widespread connection failures have led to an “overall decrease in traffic” it’s able to serve to users in Russia.

The engineers are not offering a method to circumvent this new blocking method. “As the throttling is being applied by local ISPs, the action is outside of Cloudflare’s control and we are unable, at this time, to restore reliable, high performance access to Cloudflare products and protected websites for Russian users in a lawful manner,” the report states. “Access to a free and open Internet is critical for individual rights and economic development. We condemn any attempt to prevent Russian citizens from accessing it.”