What is VOIP || How does it work?

What is VOIP?

VoIP stands for voice over internet protocol l. Is also called Internet telephony. it used to speak to other users over the internet. VoIP uses the internet instead of a telephone network to connect a user to another user. it requires a high-speed Internet connection like Dsl.

VOIP Gateways

VoIP technology used voice calls originated and terminated at standard telephones supported by the Public Switched Telephone Network to be conveyed over internet protocol networks. Voice over internet protocol “gateways” provide the bridge between the local and the Internet protocol network for both the originating and termina Public Switched Telephone Network ting sides of a call.

To originate a call, the calling party will access the nearest gateway either by a direct connection or by placing a call over the local Public Switched Telephone Network and entering the desired destination phone number. 

 

The VoIP technology translates the destination telephone number into the data network address (“Internet protocol address”) link with a corresponding terminating gateway nearest to the destination number. 

Using the appropriate protocol and packet transmission over the internet protocol network, the terminating gateway will then initiate a call to the destination phone number over the local Public Switched Telephone Network to establish end-to-end 2-way communications. 

Despite the additional connections required, the overall call set-up time is not significantly longer than with a call fully supported by the Public Switched Telephone network. 

 

 

The gateways must use a common protocol—for example, the H.323 or MGCP or a proprietary protocol—to support standard telephony signaling. 

The gateways emulate the functions of the PSTN in responding to the telephone’s on-hook or off-hook state, receiving or generating DTMF digits, and receiving or generating call progress tones. 

Recommended signals are interpreted and mapped to the appropriate message for relay to the communicating gateway to support call set-up, maintenance, billing, and call tear-down.

The translation of a destination telephone number into the IP address of the correct terminating gateway is a primary VOIP “gatekeeper” function. The routing table maintained by the gatekeeper resolves which gateway corresponds to the destination telephone number to complete

 

VOIP Gatekeepers

Gatekeeper functionality can be distributed among all the gateways of the VOIP network or can be centralized at one or several locations. 

When gatekeeper functions are embedded in each gateway, all gateways of the overall VOIP network act autonomously to coordinate their actions. 

With a centralized gatekeeper, all gateways of the network coordinate their actions concerning the centralized gatekeeper rather than acting independently.[7]

VOIP Cost Structure

Long distance and especially international voice calls can be significantly low cost when supported by an Internet Protocol network rather than by the Public Switched Telephone network. 

Calls supported by Voice over internet protocol technology are not subject to the same cost structure of access charges, transmission costs, and settlement charges. 

 

Access charges are imposed by the local telephone company to allow long-distance carriers to originate or terminate the local portion of each telephone call. In the United States, however, the Federal Communications Commission has ruled that such access charges do not apply to VoIP calls.

 Transmission costs associated with the actual long-distance transmission are typically much fewer thanks to the reduced bandwidth required by the data packets associated with the call. And, finally, the settlement charges associated with international calls are not present when the international transmission is carried by an internet protocol network.

A call supported by the Public Switched Telephone network involves the establishment and cost of an end-to-end circuit that is maintained for the duration of the call. A call supported by Voice Over Internet Protocol technology, by contrast, involves the transmission of many individual packets over an Internet Protocol network. 

 

The cost of a Voice Over Internet Protocol call thus depends in part on the number and length of the packets that must be transmitted; i.e., the bandwidth required. The use of speech compression algorithms can reduce the required bandwidth by a factor of 8 or more. 

Further bandwidth reductions can be obtained by recognizing and not explicitly transmitting the silences that naturally occur in human speech. These reductions in bandwidth directly translate to a reduction in cost. 

 

The total cost per voice over internet protocol call is thus due to the costs associated with access to the gateways at both ends and the cost of transmission over the internet protocol network. 

If originating calls access the Voice over internet protocol gateway through the Public Switched Telephone Network, access costs at the originating end may include the costs of local or long-distance connections or the monthly cost of a toll-free access number. 

Access costs at the terminating end may include the costs of the local or long-distance connections associated with terminating a call from the nearest gateway to the destination number. 

 

The cost of transmission over the IP network depends on what Internet Protocol network is employed. If the Internet is employed as the underlying Internet Protocol network, then the just cost is the cost of Internet access at every gateway. 

Costs are higher if a proprietary or leased IP network is employed, but, in return, the network can provide enhanced reliability and assured Quality of Service.