A bridge–an unlisted relay–will not host much traffic. It is the kind of connection most needed now.

~~Rhona

The Tor software in client mode, which is what you use when you are surfing the web reasonably “anonymously”, is much, much less intensive, with a few updates every 10 minutes or so.

Even though there are faster , fibre optic to the local street cabinet infrastructures being rolled out “soon”,
most residential or small business broadband internet customers only have access to ADSL where the download speed is, say up to a theoretical 8 Mega bits per second, several times that of the uplink speed, perhaps a theoretical 512 kilo bits per second, half a Mega bit per second.

Tor relay servers, like web servers or peer to peer file sharing nodes, on average send out as much data as they receive, so the minimum 160 Kbs is quite a fraction of the available 512 Kbs maximum, and is consumed at the same time both on the downlink and, crucially, on the uplink.

If you run your Tor server at , say, 50 Kbs i.e. 400 kilo bits per second (leaving you enough upstream bandwidth for sending web browsing commands and Voice over IP and emails etc.) and you leave it running 24 / 7, then you will probably consume around 2 to 3 Gigabytes a day, which will probably bring your monthly bandwidth total to between 70 to 100 Gigabytes.

Many “cheap” broadband deals and almost all mobile phone based ones, have explicit monthly bandwidth caps or “fair usage” policies, even on allegedly “unlimited” broadband deals, perhaps capped at only 20 Gigabytes per month.

However,with care, even this can be used to run a part time Tor server node, especially a lightly used (because it is not widely advertised) one in Bridge mode

The Tor server settings do also allow you to allocate say 1 Gigabyte of bandwidth per day, or during a particular time period , perhaps at night, which when used up, the Tor server node will automatically go offline until the next accounting period.

If, as hundreds of thousands of people do, you make use of the Tor anonymity cloud for your own web browsing or other purposes, it is morally right for you to contribute something back to the project – either Tor server bandwidth, or money to support the project, or publicity to tell your friends about it.