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Voice Over Ip

What is VOIP?
The term VoIP stands for Voice over Internet Protocol is basically transmission of voice calls across internet and refers to technology that enables routing of voice conversations over the Internet or any other IP network. The voice data flows over Internet, instead of the traditional dedicated, circuit-switched voice transmission lines. Some use the term Internet telephony and IP Telephony to refer making telephone calls over the public internet and also refer to as next generation telephony which is computer telephony integration. In a general point of view VoIP means all multimedia applications that can be supported over IP-derived protocols running on diverse physical media (cable, telephone, wireless, and others) and it includes the technologies, systems, and services that transport voice over the internet protocol (IP).
Figure 1. VoIP Configuration

How It Works?
Basically, VoIP is converting analog voice data into digital packets and the packets are then transported over private or public IP networks and reassembled and decoded on the receiving side. Like conventional telephony, VoIP needs a connection between users, in this case a virtual connection. VoIP architecture involves many components. First, a signaling protocol is needed to set up individual sessions for voice connections between users. Once a session is established, a transport protocol can be used to send the data packets. H.323 protocol that is recommended by International Telecommunication Union (ITU) provides a foundation for audio, video, and data communications across IP based networks, including the Internet.
Figure 2. H.323 Protocol
Voice Application
RTP, RTCP
UDP
IP
Data Link Layer
Physical Layer
Source: Francis Botto, Encylopedia of Wireless Telecommunications, McGraw Hill, 2002.
Advantages and Disadvantages of VoIP
This convergence of data, voice, and video using IP-based networks is delivering advanced services at lower cost across the spectrum,...