Hosted pbx is a term which contains different meaning and definition. And it is widely used in the different business fields and also in various purposes with interpretations and definitions. On SIP Hosted PBX is a link which is mainly used for the business communication web services, which get delivered over a data connection. It is maintain their unique features that maintain their web services with no PBX hardware to manage at any part of the system communication. There will no single point of connection will get failed and make the single point of physical connection to fail in the physical connection. The PBX maintains or manages a large amount of customer s on a single platform that will be completely redundant databases, servers, routers and the internet connections. But it cannot run on a single box that may get fail on the screeching halt. SIP is defined as Session Initiation protocol by which the internet telephony services provider deliver their services to communicate to the equipped customer with the private branch exchange. The Sip trunking is a voice over internet protocol based services. The architecture will provide the network may be divided into two kinds of domains such as public domain and private domain.