What does VoIP need to be the Best Solution?

It must offer the same functions or something better, and the same quality of the current PSTN, of course at a lower cost.
The main functions are:

Signaling

Database services

Call connect and disconnect

Codec operations.


Signaling

All devices must communicate in the Network and for doing so they need to cohordinate their components in order to make a call.
In the PSTN for doing so, we use Switches, in the VoIP world the messages are exchanged using standard protocols (SIP, H323, MGCP...)

Database Services

Under this name we list all the features related to regulation of the funcionality of the endpoints.
This can include the billing services, the network security, the calls control.
In the H323 enviroment this is done by a so called Gatekeeper.

Call Connect and disconnect

In the PSTN Network, switches connect the two endpoints in a dedicated channel.
In the VoIP world this connection is a multimedia stream (can be audio, video or both) transported in real time.
The voice is packetized and follows the stream of the Internet passively, sharing a channel.
Every packet has a target and an address and in the case of H323 has a prioritation on the data packets.

Codec Operations

The Network needs a way to convert the voice in a format that can be transported and streamed.
The process to convert voice waves into packets is done with a coder-decoder.