mediasoup (server side, so the Node + C++ component you mean) does not implement "RTCPeerConnection". That's just needed for browsers. In mediasoup we don't use SDP but specific RTP parameters as defined here:

https://mediasoup.org/documentation/v3/mediasoup/rtp-paramet...

If you want to know why we don't use SDP (as communication means between client and server) here a good reading: https://webrtchacks.com/webrtc-sdp-inaki-baz-castillo/