What is an Internet Telephony Service Provider and How to Set up your ITSP?

ITSPs provide digital telecommunications services over the Internet using Voice over Internet Protocol (VoIP). In many cases, ITSPs provide services directly to end users or as wholesaling suppliers to other ITSPs. Many ITSPs use signaling and multimedia protocols, such as the Session Initiation Protocol (SIP), the Media Gateway Control Protocol (MGCP), Megaco, and the H.323 protocol. One of the earliest VoIP protocols, H.323 is slowly declining in popularity and is rarely used in consumer products.