There are libraries to do SIP signaling over WS/WSS with WebRTC from a browser (or whatever) that theoretically allow for interop with other SIP devices. In pr

There are libraries to do SIP signaling over WS/WSS with WebRTC from a browser (or whatever) that theoretically allow for interop with other SIP devices. In practice the fundamentals of WebRTC rely on things like ICE, STUN, and TURN for media so they're not going to be compatible with almost all existing SIP implementations - many of which can't even do interop with bog-standard vanilla SIP over UDP with standard codecs properly. As is often the case with SIP you're back to using some Session Border Controller or equivalent architectural component to make interop actually work reliably.