The telephone network is the most common of today’s voice communication facilities. However a silent revolution that is taking place on telephone networks; that revolution a voice over IP. That enable us to voice communication over the internet protocol, which is cheaper than voice communication through telephone network. In general VOIP refers to transport of new time media such as voice and video over the Internet to provide interactive communication among the Internet. Basic differences in technology used in VOIP and conventional telephone network is that, in VOIP packet switching is used but in telephone network, circuit switching is used. But quality of voice over IP is poor. Voice traveling over congested data network is a good as no voice at W1. The quality can be improved by having more bandwidth and providing primary voice in the various results on the net.
INTRODUCTION
The public telephone network and the equipment that makes it possible are taken for granted in most parts of the world. Availability of a telephone and access to a low cost ,high quality worldwide network is considered to be essential in modern society .Anything that would jeopardize this is usually since more and more communication is in digital format and transported via packet networks such as IP,ATM cells etc. Since data traffic is growing much faster than telephone traffic, there has been considerable interest in transporting voice over data networks.
Support for voice communication using the Internet Protocol (IP), which is usually just called “voice over IP” or VoIP, has been become especially attractive given the cost, flat rate pricing of the public internet. In fact, toll quality telephone over IP has now become one of the key steps leading to the convergence of the voice, video, and data communication industries. The feasibility carrying voice and call signaling messages over the Internet has already been demonstrated but delivering high quality commercial products, establishing public services, and convincing users to buy in to the vision are just beginning.
VoIP can be defined as the ability make telephone calls and to send facsimiles or IP based data networks with suitable quality of service (QoS) and much superior cost / benefit. Equipments producers see VoIP as a new opportunity to innovate compete. The challenge for them is turning this vision in to reality by quickly developing new VoIP enabled equipments. For Internet service providers the possibility of introducing usage based pricing and increasing their traffic volumes is very attractive. Users are seeking new types of integrated voice / data application as well as cost benefits.