Digit is our DNS client side tool that can perform DNS queries via different protocols such as UDP, TCP, TLS. This tool is primarily designed to evaluate the client side latency of using DNS over TCP/TLS.
IANA has allocated port 853 to use TLS/DTLS for DNS temporarily in the most recent version of Internet draft “DNS over TLS: Initiation and Performance Considerations” (draft-ietf-dprive-dns-over-tls-01).
To track the current specification, we have updated Digit to do direct TLS on port 853 by default, with TCP. STARTTLS and other protocols as options for comparison.
These changes are available as Digit-1.4.1 at https://ant.isi.edu/software/tdns/index.html.