A useful website if you’re learning about voice over IP is VoIP-Info.org.
Telos Systems mentions it in its latest newsletter. “More and more radio engineers are jumping into the world of VoIP telephony,” the company’s Clark Novak writes. “It’s no easy task, sorting the the jumble of acronyms and alphabet soup that make up the VoIP lexicon. What’s an FXO, and will it work with my DID setup? Where do I find a list of SIP response codes? And do I need to worry about IAX, or not?”
Joe Talbot at Telos pointed out the useful site.