Back long ago, we added a feature to allow torrc to list a bunch of FallbackDir entries. These tell a client where to look for consensus directory documents, so that the clients don't just load the authorities down. It would be good if we shipped with such a list. One idea has been to identify directories that have: * a stable IP:Port over a long time, * reasonably good uptime (as a fraction) * good bandwidth * a contact address. Then, contact the admins of these directory caches and ask them for permission to put them on a list. (See also legacy/trac#8374)