In its broadest definition, VoIP can be described as the ‘‘conveyance of voice, fax and unrelated services publicly or wholly over packet switched IP-based networks including peer-to-peer VoIP and VoIP services connected to PSTN’’. This section presents a broad overview of the technology involved in both internet voice and data transactions. It discusses, in a non-technical manner, how VoIP transmits voice communications over the internet. VoIP is a technology by which oral communications can be transferred from circuit-switched networks to or over Internet Protocol networks, and vice versa. VoIP transforms standard oral telephone signals into compressed data packets that are sent over the Internet Protocol. The audio signal at this point is captured either by way of a microphone or received from line input. This analogue representation is then converted to a digital representation at the audio input device. The resulting digital samples are copied into a memory buffer in blocks of frame length. Here, a silence detector decides whether the block is silence or a portion of speech. Prior to transmission over the internet, the block itself is written to a socket. Once this is completed, the communication is transmitted to another VoIP terminal. This terminal parses the header information and the block of audio is decoded applying the same codec and the samples written into a buffer. Once this step is complete, the block of samples is copied from the buffer to the audio output device. The audio output device makes the digital to analogue conversion and outputs the signal. VoIP can be used with either a telephone or a PC as the user terminal. This gives different modes of operation: PC to PC, PC to telephone, telephone to PC and telephone to telephone (via the internet), all VoIP protocols are application layer protocols.
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