http://dds6qkxpeiqvogt4y2fd7vtsxq6pvokekb2h4la7jd4iwl4ljuawu5qd.onion/wiki/Dev/Technical_Introduction
For DNS, please refer to the next footnote. ↑ Tor does not depend on, nor use, a functional (system) DNS for most of its operations. IP addresses of Tor directory authorities are hardcoded in the Tor software by Tor developers. (That means Tor knows important addresses in advance and doesn't need to look them up.)