← Go back to Tor Project status

Tor network with congestion control

May 3, 2022 at 4:00 PM

Network Experiments

This experiment is still running

What changed?

We started deploying congestion control on the live Tor network.

Users of Tor versions and above will experience faster performance when using Exits or Onion Services that have upgraded to and above. This faster performance will also increase the Advertised Bandwidth of relays, similar to our previous flooding experiments. Thus, the overall capacity of the network will appear to increase on our network metrics.

As more clients upgrade, particularly after a Tor Browser Stable release with 0.4.7 is made, the consumed bandwidth of the network should also rise. We expect to make this Tor Browser Stable release on May 31st, 2022.

Our performance metrics will remain unchanged until we upgrade those onionperf instances to 0.4.7, which will likely also happen towards the end of May.

When did it start?

At 2022-04-25 19:00:00 UTC.

When did it stop?

It is still ongoing. We will declare this experiment “concluded” once most of our Exit relays have upgraded to Tor 0.4.7 or later, have upgraded the onionperf instances, and released Tor Browser Stable with Tor 0.4.7.

What potential problems to look for, and how to report them?

Relays might see CPU overload in which case operators could consider to rate-limit bandwidth. Additionally, if operators pay for bandwidth by the gigabyte, they could consider hibernation if costs go up.

If you think something has gone wrong with enabling congestion control feel free to start a discussion on the tor-relays mailing list or a topic in our forum.