NETWORK TELEPHONY –VOICE OVER INTERNET PROTOCOL(VoIP)
VoIP is a set of technologies that enable voice calls to be carried over the internet (or other networks designed for data), rather than the traditional telephone landline system-the Public Switched Telephone Networks(PSTN). VoIP uses IP protocols, originally designed for the internet, to break voice calls up into digital ‘packets’. In order for a call to take place the separate packets travel over an IP network and are reassembled at the far end. The breakthrough was in being able to transmit voice calls, which are much more sensitive to any time delays or problems on the network, in the same way as data. Packetised voice also enables much more efficient use of the network because bandwidth is only used when something is actually being transmitted. Also, the network can handle connection from many applications and many users at the same time, unlike the dedicated circuit-switch approach. The basic process involved in a VoIP calls is as follows:
Conversion of the callers analogue voice signal into a digital format. Compression and translation of the digital signal into discrete Internet Protocol packets. Transmission of the packets over Internet or other IP-based network. Reverse translation of packets into an analogue voice signal for the call recipient.
The digitisation and transmission of the analogue voice as a stream of packets is carried out over a digital data network that can carry data packets using IP and other, related Internet protocols. This network may be an organisation’s internal LAN, a leased network, the PSTN or the open Internet. The compression process is carried out by a codec, a voice-encoding algorithm, which allows the call to be transmitted over the IP network within the network’s available bandwidth. To make a VoIP call, the consumer user requires VoIP software and a broadband connection to the Internet. The software will handle the call...
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