TLD Survey:Open Recursive/Caching?
- For each zone & server, do
- Query server for obvious out-of-zone data with recursion off
- Repeat query with recursion on
- Repeat query with recursion off again
- If 1st response is referral, and 2nd and 3rd responses have the “ra” bit set (and are the same, modulo TTL differences), then the server is open recursive/caching