example.net.
IN NAPTR 100 10 "" DOTS-CALL-HOME:signal.udp "" signal.example.net.
IN NAPTR 200 10 "" DOTS-CALL-HOME:signal.tcp "" signal.example.net.

signal.example.net.
IN NAPTR 100 10 "s" DOTS-CALL-HOME:signal.udp "" 
            _dots-call-home._udp.example.net.
IN NAPTR 200 10 "s" DOTS-CALL-HOME:signal.tcp "" 
            _dots-call-home._tcp.example.net.

_dots-call-home._udp.example.net.
IN SRV   0 0 6000 b.example.net.

_dots-call-home._tcp.example.net.
IN SRV   0 0 6001 b.example.net.

b.example.net.
IN AAAA  2001:db8::2