First of all, thanks for sharing this - it's a very thorough guide to implementing SIP.

Second, the author says that he has implemented a SIP client in JS as well. But my experience with open-source JS SIP clients (WebRTC) has been that their performance is significantly worse than the free version of xlite. (Both SipML and JSSIP have more frequent packet drops on the same systems than xlite).

Are there better JS implementations that are at least as robust as xlite?