This doc also claims that:
" The SRV record allows
DNS resolvers to search for particular applications and underlying
transports (for example, HTTP running over TLS, see [RFC2818]) and to
learn the domain name and port where that service resides in a given
administrative domain. "
The transports should be TCP, UDP, or (arguably or not) other transport
protocols. TLS is not a transport.
Currently http is distinguished from https using the service names
string, not the transport. I.e., IMO, in SRV records:
service name = layers 5-7
transport = layer 4
TLS is above layer 4.
Additionally, it's useful to distinguish The DNS (i.e., with the
existing well-know roots) from A DNS -- the latter using the same
protocols and records, but not sharing the same initial roots.
Ietf mailing list