The Various Steps in a VoIP Conversation

By: Dennis Jaylon

VoIP, in layman terms, is Internet telephone. It is a software that enables the user to use the Internet to call people and converse for a very nominal charge (sometimes for free as well). VoIP phones make use of the packet switching capabilities of the Internet, which allows numerous calls to occupy the space used by a single call in circuit-switched network. It also makes use of the concept of data compression which further reduces the size of the call.

The actual conversation that takes place involves various steps. All these steps combined together enable a smooth VoIP conversation. If both the parties who are conversing have analogue phones linked to the VoIP service provider's ATA (Analogue Telephone Adapter), then the telephone call will start with one of the parties picking up the phone. This transmits a signal to the ATA. The ATA in return sends a dial tone in response to the signal. This is to ensure the Internet connection.

On dialling the desired number, the tones of the analogue phone is converted into digital data by the ATA and stored temporarily. The data related to the phone number is sent to the VoIP service providers call processor that checks the number for a valid format. The next step is mapping the phone number in which the number is converted into an IP address. The devices on both the ends of the call are connected by the soft switch, and the party who has been called receives a signal on their ATA instructing it to ask the connected number to ring.

A session is established between your computer and the called party's system, once the other person answers the call. Both systems expect data from each other and they must use the same protocol to communicate. The packets of data are translated by the ATAs on each end into analogue audio signals, which both parties finally get to hear. Disconnecting the call will close the circuit between the VoIP phones and the ATAs. A signal is then sent to the soft switch by the ATA terminating the session.

Packet switching technology in VoIP enables telephones with the ability to communicate the way computers do.

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