You pick up a handset, dial a number, it rings, and someone answers. How hard can it be?
Actually, a lot goes on behind the scenes with two protocols set into motion—SIP and RTP—to get VoIP to work in a modern network.
For comparison, when you enter www.google.com into a browser, there are two protocols at work: DNS and HTTP. The browser first does a DNS lookup to learn the IP address for the given www.google.com domain name. Once the IP address is learned, it opens an HTTP (or HTTPS) connection to the IP address and begins to download the web page.
A similar mechanism was developed for VoIP where there are two protocols that do the heavy lifting: SIP and RTP.Read More