Comment by GCUMstlyHarmls

It's likely the port open check that's built-in: https://portcheck.transmissionbt.com/443

If people have naïvely configured their BIND client libraries to talk directly to Quad9, instead of via a machine-local forwarding caching proxy DNS server, then libcurl can be sending a re-query out to Quad9 every 60 seconds for domains that it actively needs to map to IP addresses.

* https://curl.se/libcurl/c/CURLOPT_DNS_CACHE_TIMEOUT.html

Excessive DNS traffic and the interaction with libcurl and with not having a machine-local forwarding caching proxy DNS server, is a known and open issue with that software.

* https://github.com/transmission/transmission/issues/1815

Having a machine-local forwarding caching proxy DNS server is in general a good idea. It provides exactly the sort of traffic concentration and redundancy elimination that is required by libcurl's 60 second re-queries, which is otherwise still traffic going out over a gateway even when Quad9 is co-located with one's ISP.

* https://jdebp.uk/FGA/dns-server-roles.html#ChoosingProxy

My guess is that DNS caching in web browsers prevents repeated lookup requests where as maybe the transmission implementation has no caching and does a lookup every time.

Its available for Linux and Windows as well.

No JS:

https://raw.githubusercontent.com/Quad9DNS/quad9-domains-top...