Understand what SIP is, how it works, demystify jargon like proxy server and location server, understand how SIP fits in with softswitches and call managers, and trace the establishment of an IP phone call step by step. Covers connecting to carriers using traditional DS0 PBX trunks and PRIs, how Megaco fits in to the story, plus IP interconnect, co-existence with legacy systems, integrated messaging and more.