RSSL specs

Hi I'm currently new to the whole topic and see that some people switch from SSL to RSSL. When I understand right the SSL in this context is "Sink Source Library" and not "Secure Socket Layer". I want to understand the security context of RSSL is this sent plaintext over the wire or is a SSL/TLS stack implemented in RSSL or am I totally wrong what RSSL is? The point I'm asking here is, that I can't find any specific Details on the connections.

Thanks for any help