VoIP PSTN Gateway
A gateway is a device used for connecting two different types of networks. In this case, one network is the VoIP network and the other the PSTN. The gateway’s main task is to provide signaling interworking and to transform the information it receives on one side in information compatible with the other side.
Components of a gateway
A gateway can consist of only one piece or it can be distributed into more components. These are:
- Signaling Gateway
- Media Gateway
- Media Gateway Controller.
Let’s talk a little about each part.
The Signaling Gateway provides transparent interworking of signaling between switched circuit, in this case, PSTN, and the VoIP networks.
The Media Gateway is responsible for extracting audio from the PSTN network, encode it and transport it over the Internet. This component carries the data.
The Media Gateway controller is used for controlling the call. It is also known as “Call Agent”.
The only question now is what is PSTN?
PSTN comes from Public Switched Telephony Network. Very much like the Internet, it is composed of many connections between circuit-switched wires. In fact the Internet is modeled upon this architecture. A telephone number references a single telephone, and a public IP address references a computer. The main difference is that VoIP uses the packet-switched network.
Only a little part of the actual PSTN is still using analogue circuits. Most of it has turned into digital. This allowed the appearance of many more services, like ISDN and DSL. These have facilitated the introduction of new telephony services, like: voice mail, caller id, reminder calls, conference calling, Enhanced 911. Some believe that the final purpose of the PSTN network is to be just an Internet application. But, there are a lot of steps to be made until this will happen.
See also
