Question about expected recursive resolver behavior

[Chuck Aurora]

On 2020-04-23 14:16, Sarah Newman wrote:
> What should happen when for a given domain:
> 
> - The domain resolves via TCP but not UDP - UDP for this domain had no
> response at all.
> - That authoritative nameserver hosts other domains, and those domains
> resolve via UDP.

Do you have an example for this?  I don't get the "no response on UDP"
part.  If the same nameserver is answering other queries on UDP, why
wouldn't at least send a REFUSED reply?

Perhaps REFUSED has been disabled somehow; that could be tested by
querying it for other non-hosted zones,

dig @<that-NS> ns isc.org.