(VoIP) uses the Internet Protocol (IP) to transmit voice as packets over an IP network. So VOIP can be achieved on any data network that uses IP, like the Internet, Intranets and Local Area Networks (LAN). Here the voice signal is digitized, compressed and converted to IP packets and then transmitted over the IP network. Signaling protocols are used to set up and tear down calls, carry information required to locate users and negotiate capabilities. One of the main motivations for VoIP telephony is the very low cost involved. Some other motivations are:

• Demand for multimedia communication
  
• Demand for integration of voice and data networks
  
  

Main Issues

For VoIP to become popular, some key issues need to be resolved. Some of these issues stem from the fact that IP was designed for transporting data while some issues have arisen because the vendors are not conforming to the standards.

Voice over IP has a structured network that can lay its foundation on, but it lacks many other important features. One of them is a reliable protocol. But this problem is on the way to being solved. SIP (Session Initiation Protocol) is the name of the protocol that seems to be on the lips of every VoIP products manufacturer.

SIP (Session Initiation Protocol)